JP6980452B2 - Hollow container and its manufacturing method, and polypropylene resin composition for blow fill seal - Google Patents

Description

The present invention relates to a hollow container, a method for producing the same, and a polypropylene resin composition for blow-fill sealing.

As a food container or a medical container, a hollow container having a layer made of a polypropylene-based resin composition is known (Patent Document 1).

Japanese Unexamined Patent Publication No. 2006-225536

When forming a hollow molded body, it may be necessary for the formed molded body to solidify in a very short time. For example, a hollow molded body having a mouth portion is formed in a mold by direct blow molding, and then the hollow molded body is filled with a liquid product in the mold and then liquid-filled by a blow fill sealing method in which the mouth portion is sealed. When manufacturing a container, the hollow molded body formed in the mold is immediately filled with the liquid product, so that the hollow molded body needs to be solidified in a very short time. When a hollow molded body of a polypropylene resin composition is formed by a molding method that requires such a molded body to solidify in a short time, it is possible to form a hollow molded body having a desired shape with high accuracy. It became clear that it tended to be difficult.

Therefore, an object of one aspect of the present invention is to suppress the occurrence of defects in the hollow molded body with respect to the hollow container having the hollow molded body of the polypropylene resin composition.

One aspect of the present invention relates to a hollow container containing a hollow molded body of a polypropylene resin composition. The polypropylene resin composition is
(A1) A crystalline propylene-based polymer A1 containing a monomer unit derived from propylene, and
(A2) A crystalline propylene-based polymer A2 containing a monomer unit derived from propylene, and
(B) Ethylene-α-olefin copolymer and
(C) Nuclear agent and
Contains.
The crystalline propylene-based polymer A1 is a copolymer in which the content of a monomer unit derived from a comonomer other than propylene is 2 to 8% by mass based on the mass of the crystalline propylene-based polymer A1.
The crystalline propylene-based polymer A2 has a monomer unit content derived from a comonomer other than propylene of 0 to 1% by mass based on the mass of the crystalline propylene-based polymer A2, and has a differential scanning calorimetry of 50 to 180 ° C. A homopolymer or copolymer having a maximum crystallinity peak temperature observed in the range of 150 ° C. or higher.
The comonomer in the crystalline propylene-based polymer A1 and the crystalline propylene-based polymer A2 is at least one olefin among ethylene and α-olefin.
The density of the ethylene-α-olefin copolymer is 856-920 kg / m ³ .
Based on the total amount of the crystalline propylene-based polymer A1, the crystalline propylene-based polymer A2, and the ethylene-α-olefin copolymer, the content of the crystalline propylene-based polymer A1 is 35 to 93% by mass. The content of the crystalline propylene-based polymer A2 is 1 to 35% by mass, and the content of the ethylene-α-olefin copolymer is 5 to 30% by mass.
The semi-crystallization time of the polypropylene resin composition measured at 115 ° C. is 70 seconds or less.

The hollow container according to one aspect of the present invention can be manufactured while suppressing shape defects by a molding method such as a blow fill sealing method in which the formed molded body needs to be solidified in a short time. be able to.

Another aspect of the present invention is a sealed container comprising the hollow container and a liquid product housed in the hollow container, and the hollow molded body has a sealed mouth portion, and the inside of the sealed container. The present invention relates to a liquid-encapsulated container in which the liquid product is sealed. Since this liquid-filled container has a hollow molded body of a polypropylene resin composition, it can be efficiently manufactured by the blow-fill sealing method while suppressing shape defects.

In yet another aspect of the present invention, a polypropylene resin composition is molded by direct blow molding to form a hollow molded body having a mouth portion in a mold, and the hollow molded body is filled with a liquid product in the mold. The present invention relates to a method for manufacturing a liquid-encapsulated container, which comprises a step of forming a liquid-encapsulated container by a blow-fill sealing method for sealing the mouth portion. According to this method, a liquid-filled container can be efficiently manufactured while suppressing defects in the shape of the hollow molded product.

Yet another aspect of the present invention relates to a polypropylene resin composition for blow-fill sealing used for forming the liquid-filled container by the blow-fill sealing method. The polypropylene resin composition here is the same as that described above.

According to the present invention, with respect to a hollow container having a hollow molded body of a polypropylene resin composition formed by a molding method that requires the molded body to solidify in a short time, the occurrence of defects in the hollow molded body is suppressed. can do. The hollow container according to the present invention is excellent in transparency, flexibility, impact strength at low temperature, and can also have high surface smoothness.

It is a graph which shows the example of the method of determining a semi-crystallization time.

Hereinafter, some embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

The hollow container according to one embodiment includes a hollow molded body of a polypropylene resin composition. This polypropylene resin composition is
(A1) A crystalline propylene-based polymer A1 containing a monomer unit derived from propylene, and
(A2) A crystalline propylene-based polymer A2 containing a monomer unit derived from propylene, and
(B) Ethylene-α-olefin copolymer and
(C) Nuclear agent and
Contains.
The crystalline propylene-based polymer A1 is a copolymer in which the content of the monomer unit derived from a comonomer other than propylene is 2 to 8% by mass based on the mass of the crystalline propylene-based polymer A1. The crystalline propylene-based polymer A2 is a homopolymer or a copolymer in which the content of the monomer unit derived from a comonomer other than propylene is 0 to 1% by mass based on the mass of the crystalline propylene-based polymer A2. Is. The portion of the crystalline propylene-based polymers A1 and A2 other than the monomer unit derived from the comonomer is composed of the monomer unit derived from propylene.

Here, in the present specification, the "crystalline propylene-based polymer" means a propylene-based polymer in which a peak of crystal melting with a calorific value of 20 J / g or more is observed in differential scanning calorimetry. The amount of heat of fusion of the crystals of the crystalline propylene-based polymer A1 is usually 20 to 75 J / g, and may be 30 to 75 J / g from the viewpoint of transparency, flexibility, and impact strength of the hollow molded product. The heat of fusion of the crystals of the crystalline propylene-based polymer A2 is usually 82 J / g or more, and may be 85 J / g or more, and 130 J / g or less, from the viewpoint of the transparency of the hollow molded body after the heat treatment. May be.

The differential scanning calorimetry referred to herein is the following (i), (ii), (iii), (iv), (v), (vi) and (vi) under a nitrogen atmosphere, unless otherwise specified. It is performed under the condition that the heat history is added to the test piece in the order of (vii).
(I) Raise from 24 ° C to 220 ° C at a rate of 300 ° C / min (ii) Hold at 220 for 5 minutes (iii) Decrease to 150 ° C at a rate of 300 ° C / min (iv) Hold at 150 ° C for 1 minute (ii) v) From the crystal melting peak obtained from the step of lowering to 50 ° C. at a rate of 5 ° C./min (vi), holding at 50 ° C. for 1 minute (vii) and raising to 180 ° C. at a rate of 5 ° C./min (vii). The maximum crystal melting peak temperature observed in the range of 50 to 180 ° C. and the amount of heat of melting (J / g) at the crystal melting peak indicating the maximum crystal melting peak temperature are calculated. The maximum crystal melting peak temperature is usually considered to be the melting point of the polymer. The amount of heat of melting of a crystal is a value calculated from the area of the region surrounded by the line extending the baselines on both sides of the crystal melting peak and the crystal melting peak.

The comonomer other than propylene constituting the crystalline propylene-based polymer A1 or A2 is ethylene, α-olefin, or a combination thereof. The α-olefin may be, for example, at least one selected from the group consisting of butene-1, hexene-1, 4-methylpentene-1, and octene-1. The type of comonomer may be the same or different between the crystalline propylene-based polymer A1 and the crystalline propylene-based polymer A2.

The content of the monomer unit derived from the comonomer in the crystalline propylene-based polymer A1 is usually 2 to 8% by mass, 2 to 7% by mass, or 3 to 3 to 8% by mass based on the mass of the crystalline propylene-based polymer A1. It may be 6% by mass.

The crystalline propylene-based polymer A1 may be a propylene-ethylene copolymer, a propylene-ethylene-butene-1 copolymer, or a propylene-butene-1 copolymer.

The temperature of the maximum crystal melting peak observed in the range of 50 to 180 ° C. in the differential scanning calorimetry of the crystalline propylene polymer A1 is 100 to 145 ° C., 110 to 145 ° C., or 120 to 140 ° C. May be good.

The melt flow rate of the crystalline propylene-based polymer A1 may be 0.5 to 10 g / 10 minutes, 1.0 to 8 g / 10 minutes, or 1.0 to 6 g / 10 minutes. Here, the melt flow rate is a value measured under the conditions of a temperature of 230 ° C. and a load of 2.16 kgf. When measuring the melt flow rate, a small amount of an antioxidant (for example, about 0.5 part by mass with respect to 100 parts by mass of the crystalline propylene-based polymer) may be blended with the crystalline propylene-based polymer. Hereinafter, the melt flow rate measured under this condition is referred to as MFR (230 ° C., 2.16 kgf).

The crystalline propylene-based polymer A2 is a propylene homopolymer or a copolymer containing a very small amount of a monomer unit derived from a comonomer. The crystalline propylene-based polymer A2, together with the nucleating agent, contributes to accelerating the crystallization of the polypropylene resin composition.

The crystalline propylene-based polymer A2 may be a propylene homopolymer, a propylene-ethylene copolymer, a propylene-ethylene-butene-1 copolymer, or a propylene-butene-1 copolymer.

The temperature of the maximum crystal melting peak (peak top temperature) observed in the range of 50 to 180 ° C. in the differential scanning calorimetry of the crystalline propylene-based polymer A2 is 150 ° C. or higher. When the temperature of the crystal melting peak of the crystalline propylene-based polymer A2 is lower than 150 ° C., the transparency of the hollow molded body after the heat treatment tends to decrease. From the same viewpoint, the temperature of the crystal melting peak of the crystalline propylene-based polymer A2 may be 155 ° C. or higher, or 170 ° C. or lower.

From the viewpoint of surface smoothness and transparency of the hollow molded product, the MFR (230 ° C., 2.16 kgf) of the crystalline propylene polymer A2 is 1 to 200 g / 10 minutes, 2 to 100 g / 10 minutes, or 3 to 3 to. It may be 20 g / 10 minutes.

The ethylene-α-olefin copolymer is a copolymer containing ethylene as a main monomer unit. The monomer unit derived from ethylene may be 50% by mass or more based on the mass of the ethylene-α-olefin copolymer, and 55% by mass or more from the viewpoint of flexibility and impact strength of the hollow molded body. It may be 60% by mass or more, or 65% by mass or more.

The α-olefin constituting the ethylene-α-olefin copolymer may have 4 to 12 carbon atoms. The α-olefin may be, for example, at least one selected from the group consisting of butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, and decene-1. From the viewpoint of the impact strength of the hollow molded product at a low temperature, the α-olefin may be butene-1, hexene-1, or a combination thereof.

The density of the ethylene-α-olefin copolymer is usually 856 to 920 kg / m ³ , and may be 868 to 910 kg / m ³ , or 870 to 900 kg / m ^3.

The MFR (190 ° C., 2.16 kgf) of the ethylene-α-olefin copolymer is 0.1 to 50 g / 10 minutes, 0.5 to 40 g / 10 minutes, 1 to 30 g / 10 minutes, or 2 to 20 g. It may be / 10 minutes.

Based on the total amount of the crystalline propylene-based polymer A1, the crystalline propylene-based polymer A2, and the ethylene-α-olefin copolymer, the content of the crystalline propylene-based polymer A1 is 35 to 93% by mass. The content of the crystalline propylene-based polymer A2 is 1 to 35% by mass, and the content of the ethylene-α-olefin copolymer is 5 to 30% by mass. From the viewpoint of flexibility, transparency, impact strength at low temperature, and transparency after heat treatment of the hollow molded product, the content of the crystalline propylene-based polymer A1 is 60 to 90% by mass, and the crystalline propylene-based polymer is a crystalline propylene-based polymer. The content of A2 may be 3 to 20% by mass, and the content of the ethylene-α-olefin copolymer may be 5 to 20% by mass. In order to particularly increase the crystallization rate of the polypropylene resin composition and enable a faster molding cycle, the content of the crystalline propylene-based polymer A1 is 70 to 92% by mass, and the content of the crystalline propylene-based polymer A2 is contained. The amount is 3 to 18% by mass, the content of the ethylene-α-olefin copolymer may be 5 to 12% by mass, and the content of the crystalline propylene-based polymer A1 is 74 to 90% by mass. The content of the crystalline propylene-based polymer A2 may be 4 to 15% by mass, and the content of the ethylene-α-olefin copolymer may be 6 to 11% by mass. Regarding the polypropylene resin composition, regarding the crystalline propylene-based polymer A1, the crystalline propylene-based polymer A2 and the ethylene-α-olefin copolymer, when two or more kinds are contained in the polypropylene resin composition, the total amount thereof is It may be within the above content range.

The nucleating agent is a component that promotes crystallization of the polypropylene resin composition. By combining this nucleating agent with the crystalline propylene-based polymer A1, the crystalline propylene-based polymer A2, and the ethylene-α-olefin copolymer, the semi-crystallization time of the polypropylene resin composition at 115 ° C. is 70 seconds. It can be as follows. In the case of a molding method in which it is required to solidify the formed molded product in a short time by using a polypropylene resin composition showing a semi-crystallization time of 70 seconds or less at 115 ° C., especially in the case of a blow fill sealing method. Even if there is, it is possible to suppress the occurrence of defects in the hollow molded body. From the viewpoint of suppressing defects in the hollow molded product, the semi-crystallization time of the polypropylene resin composition at 115 ° C. may be 50 seconds or less, 40 seconds or less, 5 seconds or more, or 10 seconds or more. good. A polypropylene resin composition exhibiting such a short semi-crystallization time is useful, for example, as a polypropylene resin composition for blow-fill sealing.

The nucleating agent can be selected without particular limitation from those used as nucleating agents in the art. Examples of nucleating agents include aromatic phosphate ester metal salts, sorbitol-based nucleating agents, rosin-based nucleating agents, and polymer-based nucleating agents such as high-density polyethylene and polyvinylcycloalkane. The polypropylene resin composition may contain two or more nucleating agents.

The content of the nucleating agent is 10,000 ppm or less, 5000 ppm or less, or 2000 ppm or less based on the total amount of the crystalline propylene-based polymer A1, the crystalline propylene-based polymer A2, and the ethylene-α-olefin copolymer. It may be 50 ppm or more, 100 ppm or more, or 150 ppm or more. When the content of the nucleating agent is within these ranges, a polypropylene resin composition exhibiting a semi-crystallization time of 70 seconds or less can be particularly easily obtained. Here, "ppm" in the present specification is a value based on mass (mass ppm).

The polypropylene resin composition may further contain other components in addition to the components described above, as long as the gist of the present invention is not deviated. Other ingredients include, for example, neutralizing agents, antioxidants, heat stabilizers, weathering agents, UV absorbers, antistatic agents, dispersants, antibacterial agents, optical brighteners, dyes, pigments, and fillers. Can be mentioned.

The polypropylene resin composition can be obtained as pellets of the melt-kneaded product, for example, by melt-kneading the mixture containing each component. The temperature of melt kneading may be, for example, 160 to 300 ° C. Alternatively, a mixture containing each component before melt kneading may be supplied to a molding machine for molding a hollow molded product. Devices used for mixing the components include, for example, Henschel mixers, V-blenders, ribbon blenders, and tumbler blenders. Devices used for melt kneading include, for example, single-screw extruders, twin-screw extruders, kneader kneaders, Banbury mixers, and roll mills.

The thickness of the hollow molded product is not particularly limited, but may be, for example, 0.1 to 2.0 mm.

The hollow container may be a single-layer product composed of only the hollow molded body, or may be a multi-layer product further having another layer provided on the inner surface or the outer surface of the hollow molded body. The other layer may be, for example, a resin layer containing a resin selected from an ethylene-vinyl alcohol copolymer, a polyamide resin, and a polyethylene terephthalate resin. The ratio of the thickness of the hollow molded product of the polypropylene resin composition to the thickness of the hollow container may be 30% or more, 40% or more, or 50% or more.

Hollow containers usually have a mouth for loading and unloading the contents. The mouth may form an opening, in which case a removable lid may be attached to the mouth. Alternatively, the hollow container may be a sealed container having a sealed mouth. A hollow container or a hollow molded body can constitute a liquid-filled container including a hollow container and a liquid product housed in the hollow container. In this case, the hollow molded body may be a sealed container formed by the blow fill sealing method. A liquid product is enclosed in this sealed container. The liquid product may be a viscous body as long as it has a fluidity that allows it to be taken in and out of the mouth.

If the surface of the hollow container or the hollow molded body of the polypropylene resin composition is smooth, the hollow container can have a good appearance with high transparency. From this point of view, the average surface roughness SRa of the hollow molded product of the polypropylene resin composition may be 0.01 μm or more, 0.12 μm or less, or 0.10 μm or less.

The hollow container can be manufactured, for example, by direct blow molding using an extrusion hollow molding machine. In direct blow molding, for example, a polypropylene resin composition is extruded from a die to form a tubular parison, and the parison is sandwiched between molds having cavities having a shape corresponding to the hollow molded body, and then pressure is applied to the inside of the parison. Includes blowing gas. The pressure of the pressurized gas shapes the parison into a shape along the cavity of the mold and cools it. After that, the mold is opened and the hollow molded body (or hollow container) is discharged.

When the liquid-filled container is manufactured by the blow fill sealing method, the polypropylene resin composition is molded by the above direct blow molding to form a hollow molded body having a mouth portion in a mold, and then in the same mold. The hollow molded product is filled with a liquid product and then the mouth is sealed. In this way, even when the hollow molded body is filled with the liquid component in a short time in the same mold after molding, the polypropylene resin composition is rapidly solidified, so that defects in the shape of the hollow molded body are suppressed. be able to.

The use of the hollow container is not particularly limited, but the hollow container is particularly useful as a food container or a medical container. The food container may be, for example, a container containing a liquid product selected from mayonnaise, ketchup, sauces, dressings, honey, jam, soft drinks, and popsicles. The medical container may be a container that contains any drug solution such as blood component, physiological saline, electrolyte, dextran preparation, mannitol preparation, sugar preparation, amino acid preparation, fat emulsion, eye drops, or liquid food as a liquid product. can.

1. 1. The polymers used in the raw material examples and comparative examples are as follows.
(A1) Crystalline propylene-based polymer A1
Crystalline Propylene Polymer A1-1: 1:
A solid polymerization catalyst for α-olefin polymerization was prepared by the method described in Example 1 of JP-A-7-216017. In the presence of this solid polymerization catalyst, propylene and ethylene were subjected to gas phase polymerization to obtain a powdery propylene-based polymer A1-1 which is a propylene-ethylene random copolymer. When the characteristics of the obtained crystalline propylene-based polymer A1-1 were measured by the method described later, the melt flow rate was 1.4 g / 10 minutes, the ethylene content was 5.6% by mass, and the melting point was 133 ° C. The amount of heat of fusion was 62 J / g.

Crystalline propylene polymer A1-2
Similar to the synthesis of propylene-based polymer A1-1 except that the amount of ethylene was changed, powdery crystalline propylene-based polymer A1-2 (melt flow rate: 1), which is a propylene-ethylene random copolymer. .3 g / 10 minutes, ethylene content: 4.0% by mass, melting point: 142 ° C., heat of fusion: 69 J / g) was obtained.

(A2) Crystalline propylene polymer A2
Crystalline propylene polymer A2-1 (melt flow rate: 8 g / 10 minutes, ethylene content: 0% by mass, similar to the synthesis of propylene polymer A1-1 except that ethylene was not used. Melting point: 166 ° C., heat of fusion: 120 J / g) was obtained.

(B) Ethylene-α-olefin copolymer Ethylene-hexene-1 copolymer manufactured by Sumitomo Chemical Co., Ltd. (trade name: Excelene FX FX301, MFR (190 ° C., 2.18N): 3.5 g / 10 minutes , Density: 898 kg / m ³ ) was prepared.

(C) Nucleating agent C1: Aromatic phosphate ester metal salt (ADEKASTAB NA-18, manufactured by ADEKA Corporation)
C2: Aromatic phosphate metal salt (ADEKASTAB NA-21, manufactured by ADEKA Corporation)

(D) Neutralizer / Magnesium / Aluminum / Hydroxide / Carbonate (DHT-4C, manufactured by Kyowa Chemical Industry Co., Ltd.)

(E) Antioxidant E1: Phenolic antioxidant (pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], Irganox 1010, manufactured by BASF Japan Ltd.)
E2: Phosphorus-based antioxidant (Tris (2,4-di-tert-butylphenyl) phosphite, Irgafos 168, manufactured by BASF Japan Ltd.)

2. 2. Test method 2-1. Melt flow rate (MFR)
100 parts by mass of the powder of the crystalline propylene-based polymer A1 or A2 was blended with 0.5 part by mass of the antioxidant dibutylhydroxytoluene (BHT), respectively. Using the obtained powder mixture, the MFR of the crystalline propylene-based polymers A1 and A2 was measured at 230 ° C. according to the method of condition 14 of JIS K7210. The MFR of the ethylene-α-olefin copolymer was measured at 190 ° C. according to JIS K6760.

2-2. Density (d)
The density of the ethylene-α-olefin copolymer (kg / m ³ ) was measured according to JIS K6760-1981.

2-3. Content of monomer unit derived from ethylene (ethylene content)
The IR spectrum of the crystalline propylene-based polymer was measured. From the obtained IR spectrum data, the content (unit: mass%) of the monomer unit derived from ethylene is described in page 616 of the Polymer Analysis Handbook (published by Kii Kuniya Bookstore in 1995). ) Method for random copolymers ”.

2-4. Melting point Tm (unit: ° C), heat of fusion (unit: J / g)
The crystalline propylene-based polymer was heat-press molded to prepare a sheet having a thickness of 0.5 mm. The hot press molding was carried out under the condition that after preheating at 230 ° C. for 5 minutes, the pressure was increased to 5.0 MPa over 1 minute, the pressure was held for 2 minutes, and then the mixture was cooled at 30 ° C. and 5.0 MPa for 5 minutes. The sample collected from the obtained sheet was measured for differential scanning calorimetry using a differential scanning calorimeter (Diamond DSC, manufactured by PerkinElmer) under the following conditions, and the melting point and the amount of heat for melting were determined.

<Measurement conditions>
Thermal history was added to the test pieces in the order of (i), (ii), (iii), (iv), (v), (vi) and (vii) below.
(I) Raise from 24 ° C to 220 ° C at a rate of 300 ° C / min (ii) Hold at 220 for 5 minutes (iii) Decrease to 150 ° C at a rate of 300 ° C / min (iv) Hold at 150 ° C for 1 minute (ii) v) From the crystal melting peak obtained from the step of lowering to 50 ° C. at a rate of 5 ° C./min (vi), holding at 50 ° C. for 1 minute (vii) and raising to 180 ° C. at a rate of 5 ° C./min (vii). The maximum crystal melting peak temperature observed in the range of 50-180 ° C. was recorded as the melting point. Further, the calorific value of melting (J / g) of the crystal was calculated from the area of the crystal melting peak showing the maximum crystal melting peak. The amount of heat of melting of a crystal is a value calculated from the area of the region surrounded by the line extending the baselines on both sides of the crystal melting peak and the crystal melting peak.

2-5. Semi-crystallization time t _1/2 (unit: seconds)
The semi-crystallization time (t _1/2 ) indicating the crystallization rate was measured by the depolarization intensity method. In the depolarization intensity method, a molten sample is placed between two polarizing plates installed so that the axes of polarization are orthogonal to each other, crystallized at a constant temperature, and the crystallization process is tracked by the transmitted light intensity of light. The method. The longer the semi-crystallization time, the slower the crystallization.
The pellet of the polypropylene resin composition was molded by a hot press at 190 ° C. to obtain a resin sheet having a thickness of 100 μm. This resin sheet was cut to obtain a sample of a resin sheet of 1.5 cm square. This sample was sandwiched between cover glasses and heated in a melting furnace at 230 ° C. to melt the resin sheet. Then, the cover glass sandwiching the molten resin sheet was placed in an oil bath at 115 ° C. to start crystallization of the resin. Two polarizing plates are installed in advance so that the polarization axes are orthogonal to each other with an oil bath in between, and a cover glass sandwiching a molten resin sheet is provided with two main surfaces. It was fixed at a position between the two polarizing plates in an oil bath so as to be parallel to the polarizing plate. The time at which the transmitted light intensity is halved with respect to the transmitted light intensity of the resin sheet in which crystallization has progressed sufficiently by detecting the transmitted light that increases with the progress of crystallization is defined as the semi-crystallization time t _1/2 . did. FIG. 1 is a graph showing an example of a method of determining a semi-crystallization time from a time change of transmitted light intensity. The vertical axis of FIG. 1 indicates the intensity of the incident light transmitted through the resin sheet, and a large value on the vertical axis means that the transmitted light intensity is high. As shown in FIG. 1, the transmitted light intensity changes sharply from the initial value as the crystallization progresses, and becomes a constant value when the crystallization progresses sufficiently. When the difference between the initial value of the transmitted light intensity and the transmitted light intensity after the crystallization has progressed sufficiently is L, the time _thalf until the transmitted light intensity reaches the initial value + L / 2 and the crystallization start. The difference ( _thalf −t ₀ ) from the time (time when the change in transmitted light intensity started) t ₀ is the semi-crystallization time t _1/2 .

3. 3. Molding of polypropylene resin composition 3-1. Preparation of Pellets The raw materials having the compositions (parts by mass or ppm) shown in Table 1 were dry-blended in a nitrogen atmosphere using a Henschel mixer. The obtained mixture is melt-kneaded by a single-screw extruder (manufactured by Tanabe Plastics Machinery Co., Ltd., screw diameter 40 mmφ, VS40-28 type) at 230 ° C. and a rotation speed of 80 rpm in a nitrogen atmosphere to prepare a polypropylene resin composition. Pellets were obtained.

3-2. Hollow molding 3-1. The pellet obtained in the above section is extruded into a cylindrical shape by an NB3B type hollow molding machine manufactured by Japan Steel Works, Ltd., which is a full flight type and has a screw with a diameter of 50 mm, at an extrusion rate of 5 kg / hour and a die and core temperature of 195 ° C. Formed a hot parison. Immediately sandwich the hot parison with a mold whose temperature has been adjusted to 35 ° C., and blow compressed air at a pressure of 0.1 to 0.15 MPa into the hot parison for 11 seconds to form a hollow molded product as a single-layer hollow container having a mouth portion. Weight: 35 g, volume: 600 ml, side wall thickness: about 0.5 mm) was formed.

4. Evaluation of hollow container 4-1. Surface roughness of the hollow container The central part of the side wall of the hollow container was cut out as a test piece. Use a three-dimensional surface roughness measuring instrument Surfcoder SE-30K (manufactured by Kosaka Laboratory Co., Ltd.) to measure the average surface roughness of this test piece in the MD direction (vertical direction of the container) with a stylus. The average surface roughness (SRa) μm was determined by the vertical movement of the stylus caused by the unevenness of the surface. The moving speed of the stylus was 0.2 mm / sec, and the surface in the range of 1 mm × 1 mm was traced at intervals of 10 μm in the TD direction perpendicular to the MD direction.

4-2. Moldability Water was put into a hollow container and the mouth was covered. After that, the hollow container was held with the mouth facing down, and the presence or absence of liquid leakage was confirmed from the mouth. If the shape of the mouth is defective, liquid leakage will occur. If there is no liquid leakage, it is regarded as "good", and if liquid leakage occurs, it is regarded as "bad". The moldability was evaluated.

As shown in Table 1, the hollow container formed from the polypropylene resin composition of the example had a mouth portion having a normal shape. In addition, the surface of the side wall of the hollow container was sufficiently smooth. On the other hand, the hollow container formed from the polypropylene resin composition of the comparative example had a defect in the shape of the mouth portion, so that liquid leakage occurred. The hollow container of Comparative Example 1 had low smoothness on the surface of the side wall portion.

Claims (2)

A sealed container having a hollow container containing a hollow molded body of a polypropylene resin composition and a liquid product housed in the hollow container, and the hollow molded body has a sealed mouth, and the inside of the sealed container. A method for manufacturing a liquid-filled container, comprising a step of forming a liquid-filled container in which the liquid product is sealed by a blow-fill sealing method.
The polypropylene resin composition is
(A1) A crystalline propylene-based polymer A1 containing a monomer unit derived from propylene, and
(A2) A crystalline propylene-based polymer A2 containing a monomer unit derived from propylene, and
(B) Ethylene-α-olefin copolymer and
(C) Nuclear agent and
Contains,
The crystalline propylene-based polymer A1 is a copolymer in which the content of a monomer unit derived from a comonomer other than propylene is 2 to 8% by mass based on the mass of the crystalline propylene-based polymer A1.
The content of the monomer unit derived from the comonomer other than propylene in the crystalline propylene-based polymer A2 is 0 to 1% by mass based on the mass of the crystalline propylene-based polymer A2, and 50 to 1 in the differential scanning calorimetry. A homopolymer or copolymer having a maximum crystallinity peak temperature observed in the 180 ° C range of 150 ° C or higher.
The comonomer in the crystalline propylene-based polymer A1 and the crystalline propylene-based polymer A2 is at least one olefin among ethylene and α-olefin.
The density of the ethylene-α-olefin copolymer is 856-920 kg / m ³ .
The content of the crystalline propylene-based polymer A1 is 35 to 93 based on the total amount of the crystalline propylene-based polymer A1, the crystalline propylene-based polymer A2, and the ethylene-α-olefin copolymer. By mass%, the content of the crystalline propylene-based polymer A2 is 1 to 35% by mass, and the content of the ethylene-α-olefin copolymer is 5 to 30% by mass.
A method in which the semi-crystallization time of the polypropylene resin composition measured at 115 ° C. is 70 seconds or less. A sealed container having a hollow container containing a hollow molded body of a polypropylene resin composition and a liquid product housed in the hollow container, and the hollow molded body has a sealed mouth, and the inside of the sealed container. A polypropylene resin composition for blow-fill sealing used for forming a liquid-filled container in which the liquid product is sealed by a blow-fill sealing method.
The polypropylene resin composition is
(A1) A crystalline propylene-based polymer A1 containing a monomer unit derived from propylene, and
(A2) A crystalline propylene-based polymer A2 containing a monomer unit derived from propylene, and
(B) Ethylene-α-olefin copolymer and
(C) Nuclear agent and
Contains,
The crystalline propylene-based polymer A1 is a copolymer in which the content of a monomer unit derived from a comonomer other than propylene is 2 to 8% by mass based on the mass of the crystalline propylene-based polymer A1.
The content of the monomer unit derived from the comonomer other than propylene in the crystalline propylene-based polymer A2 is 0 to 1% by mass based on the mass of the crystalline propylene-based polymer A2, and 50 to 1 in the differential scanning calorimetry. A homopolymer or copolymer having a maximum crystallinity peak temperature observed in the 180 ° C range of 150 ° C or higher.
The comonomer in the crystalline propylene-based polymer A1 and the crystalline propylene-based polymer A2 is at least one olefin among ethylene and α-olefin.
The density of the ethylene-α-olefin copolymer is 856-920 kg / m ³ .
The content of the crystalline propylene-based polymer A1 is 35 to 93 based on the total amount of the crystalline propylene-based polymer A1, the crystalline propylene-based polymer A2, and the ethylene-α-olefin copolymer. By mass%, the content of the crystalline propylene-based polymer A2 is 1 to 35% by mass, and the content of the ethylene-α-olefin copolymer is 5 to 30% by mass.
A polypropylene resin composition for blow-fill sealing, wherein the semi-crystallization time measured at 115 ° C. of the polypropylene resin composition is 70 seconds or less.

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