JPH05178361A - Liner for crown cap - Google Patents

Abstract

PURPOSE:To improve the sealing properties, shelf stability and impact resistance by forming a liner for crown cap by in-shell molding with a plastic material which consists of a specified ethylene resin and a specified hydrogenated block copolymer elastomer. CONSTITUTION:For a liner for crown cap, which seals the bottle mouth of a bottle containing a content with inner pressure such as carbonated beverage or beer, etc., a composition of which MI is 1-20g/min is prepared with 50-90wt.% ethylene resin consisting of a low density polyethylene of which the vinyl acetate content is 12wt.% or lower and/or an ethylene-vinyl acetate copolymer, and 50-10wt.% hydrogenated block copolymer elastomer consisting of a polymer block of which the major component is styrene, and a polymer block of which the major component is hydrogenated butadiene. By forming this composition by in-shell molding, a line for crown cap with superior sealing properties, shelf stability and impact resistance is obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is excellent in storage stability, aroma retention and hygiene of the contents, and can sufficiently withstand external force such as impact on the bottle mouth at the time of practical use such as load handling, transportation and storage. sex,
The present invention relates to a load bearing crown liner. More specifically, the excellent flexibility of the ethylene resin, food hygiene, without compromising the characteristics such as moldability, beverages, especially soft drinks,
The present invention relates to a crown liner having remarkably improved sealing property, storability, and durability against external force during practical use of contents having internal pressure such as beer.

[0002]

2. Description of the Related Art Conventionally, cork, soft PVC, olefin resins, especially ethylene resins have been used as materials for crown liners. Of these, the cork surface liner is a natural material that has been used for a long time because of its favorable impact resilience, but due to the large quality difference and unstable quality, the generation of cork dust, and the relatively high cost, In recent years, its position is being handed over to liners such as soft PVC and olefin resins.

On the other hand, a soft PVC surface liner is also flexible and excellent in sealing property, but in recent years, due to the problem of hygiene caused by a plasticizer, a vinyl chloride monomer, etc., it is being changed to an olefin resin excellent in hygiene. As the olefin-based resin surface liner, an ethylene-based resin originally having a flexible property is widely used.

On the other hand, a method for processing a liner has been developed, and a method in which a polymer sol found in soft PVC in addition to cork is applied and dried, or a sheet material is formed, which is cut and attached to a crown ( Hereinafter, this will be referred to as a sheet method) and an in-shell molding method (see JP-A-52-110176 and JP-A-53-89583).

Among them, the method by in-shell molding is more effective and efficient than the method by sheet, because the thickness and shape of the liner portion facing the bottle mouth requiring sealing can be selectively selected. It has the feature that a unique seal design can be added to the liner. Therefore, the liner manufactured by in-shell molding is excellent in economical efficiency because it can save the resources used, and the process is shortened because it is processed in the state of being directly installed inside the crown, and the production speed is excellent. In particular, it is becoming the mainstream of the crown liner processing method for containers such as carbonated drinks and beer whose production numbers are enormous.

[0006] By the way, even with the ethylene resin which is widely used at present, it is not possible to obtain a sufficient sealing property for a shape defect of the bottle mouth, a scratch or a chip at the same portion, or a long-term storage property. There was a problem in terms of performance and quality. As a solution to this problem, the inventors previously disclosed in JP-A-3-134085 a liner for a cap with a screw, which is different from the crown method by the sheet method, but in the method by in-shell molding, the melt extrudate is disclosed. Continuously stable cutability, stability of supply to the crown, shapeability of the detailed shape by embossing in the molten state, reliable adhesion of the liner to the crown, high pressure resistance of the liner seal part, etc. However, it is still technically inadequate to deal with these problems, and a solution to these problems has been demanded.

[0007]

The object of the present invention is to solve the above-mentioned problems, that is, various properties of the ethylene-based resin, especially flexibility, without impairing the excellent processability and food hygiene of the ethylene-based resin. The purpose of the present invention is to provide a crown liner with improved sealability, storability, and impact resistance that cannot be solved only by the properties.

[0008]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have found that a liner made by in-shell molding using a polymer composition mainly composed of an ethylene resin. The inventors have found that the problem can be solved by using it, and completed the present invention.

That is, according to the present invention, (A) 50 to 90% by weight of an ethylene-based resin composed of low-density polyethylene having a vinyl acetate content of 12% by weight or less and / or an ethylene / vinyl acetate copolymer, and (B) 50 to 10% by weight of a hydrogenated block copolymer elastomer composed of a polymer block mainly composed of styrene and a polymer block mainly composed of hydrogenated butadiene, and having an MI of 1 to 20 g / 10 min. The present invention provides a crown liner produced by molding and processing a composition by in-shell molding.

The low density polyethylene used in the present invention is J
IS: K6748 has a density of 0.910 g / cm
^The content is ³ or more and less than 0.930 g / cm ³ , but a density of 0.920 or less is preferable from the viewpoint of flexibility that imparts sealing property. Further, an ethylene resin (A) comprising the polyethylene and / or ethylene-vinyl acetate copolymer
Vinyl acetate is 0 to 12 wt%, preferably 4 to 10
wt% is contained. When the content exceeds 15 wt%, the odor is disliked depending on the content and the flexibility is high, but the load resistance is poor and the deformation is large, which easily causes deterioration of sealing property and long-term storage stability, which is not preferable. ..

On the other hand, if the content is less than 2 wt%, it is difficult to obtain the desired performance. The hydrogenated product of the styrene-butadiene block copolymer has a styrene content of 10 to 45 wt% and a hydrogenation rate of 80% or more, preferably 90% or more, and the blending ratio in the polymer composition is 10-50
wt%. If the content exceeds 50 wt%, rubber elasticity is high and impact resistance is in a more preferable direction, but the deformation of the liner at the time of capping the crown becomes large, which makes capping unstable, and the in-shell of the crown liner Difficulty also appears in the molding process of molding. On the other hand, 10 wt
If it is less than%, it is difficult to obtain sufficient sealing performance.

The fluidity of the polymer composition used in the present invention is
JIS: K7210, MI specified in condition 4 is 1 g / 1
0 minutes or more is preferable, and if it is less than this, the viscous resistance at the time of heating and melting increases, and it is not preferable for uniform plasticization required for in-shell molding and stable extrusion of the melt. On the other hand, when the amount is 20 g / 10 min or more, it is difficult to cut the melt and supply the predetermined amount into the shell (crown), the supply becomes unstable, and a liner with stable quality is obtained. It will be difficult. More preferably, the MI of the polymer composition is in the range of 2.5 to 15 g / 10 minutes.

In the above composition, additives such as commonly used colorants, stabilizers, modifiers, processability improvers, etc., which are necessary for molding and practical use of the liner, are added to the polymer composition of the present invention. You may add it in the range which does not impair the characteristic of the thing. In order to obtain the polymer composition used for the liner of the present invention, the ethylene resin (A) and the hydrogenated styrene-butadiene block copolymer (B) may be uniformly mixed.

As a method of mixing, there is a method of mixing with a commonly used mixer such as a Henschel mixer, a drum blender and the like, and using a melt-kneader such as an extruder, a Banbury mixer, a roll mill and the like to perform uniform mixing. The liner is made by in-shell molding. That is,
The above-mentioned polymer composition is uniformly plasticized by an extruder, and is extruded, cut, and then supplied to the inner surface of the crown, and the die is extruded and shaped in a molten state, followed by cooling.

[0015]

By using the liner of the present invention,
Excellent processability of ethylene resin, without impairing food hygiene, performance of excellent sealing performance and preservability of beverages with internal pressure such as carbon dioxide gas, etc. It has become possible to provide a crown with excellent impact resistance.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples. Examples 1 to 11 and Comparative Examples 1 to 7 Using the polymers and additives shown in Table 3, the following (1) to
By the method shown in (2), the liner to be installed in the cap was prepared using the compositions shown in Tables 1 and 2. This was evaluated by the method shown in (3) below.

(1) Preparation of Compositions The compositions shown in Tables 1 and 2 were premixed, melt-mixed with an extruder and extruded into pellets ( ^3φ × 3 ^l mm). In addition, the pre-mixing is performed at room temperature with a drum blender for 15 minutes.
The mixing was carried out for minutes. In addition, melt kneading is performed with a 60 mm ^φ extruder (L / D28, full flight screw) at 200
It was carried out by melt extrusion at ° C.

(2) Preparation of Liner The liner was prepared by in-shell molding. That is, the above composition (pellets) was applied to a 17 mm by a 40 mm ^φ extruder (L / D28, full flight screw).
It is melted uniformly at 0 ° C., extruded, and this melt is continuously cut by a rotary blade that is in contact with the extrusion outlet. The adjustment of the volume is determined by the extrusion area and the number of times of the rotary blades of the opening area of the extrusion port, and is confirmed by separately weighing the cut product.

The melt thus cut is supplied by being dropped onto the inner surface of the crown immediately adjacent to it, sent, pressed by the liner mold, cooled, and the liner is directly formed on the inner surface of the crown. .. The following cutting, crown feeding, and pressing of the liner mold are all mechanically and electrically synchronized and continuously operated to produce the liner. 1000 liners /
Molded at a speed of minutes.

(3) Evaluation method (b) Hygiene A sensory test for preservation was conducted as follows. A clean glass container was filled with Asahi Breweries (registered trademark), sealed with a crown (hereinafter referred to as a sample crown) equipped with a liner made of the polymer composition shown in Tables 1 and 2, and the container was placed at 25 ° C. Save upside down.

After 14 days of storage, the bottles were opened and examined by a discrimination test for the difference from Asahi Breweries (registered trademark: using a liner made of low density polyethylene) simultaneously stored by 12 panelists. The test result is x, "significantly different",
“No significant difference” is indicated by ◯, “what is not significantly different, but something that feels some difference” is indicated by Δ.

(B) Storability (short time) In accordance with JIS S-9017-1976, Table 1 and Table 2
The sample crown consisting of was capped into the bottle mouth of the glass container and connected to a water pressure tester, the pressure inside the container was gradually increased, and the pressure at which leakage started to occur from the bottle mouth was measured as the instantaneous pressure resistance. The number of samples was 10, respectively. The test results are displayed as shown below.

[0023] × the moment breakdown voltage 10~17kgf / cm ² a moment withstand 18kgf / cm ² or more ○ moment withstand 10kgf / cm less than ² △

(C) Storability (long time) In accordance with JIS S-9017, a glass container (large beer bottle) was filled with 3.0 Vol. Carbon dioxide gas water, and the sample crown was stoppered (capping force 380 kg). , The same below) and seal. Immerse this container in warm water at 50 ° C, raise the water temperature in 5 ° C increments,
Holding for 30 minutes is repeated to bring the temperature inside the container to 65 ° C. In this state, it is stored for 60 minutes and observed for gas leakage from the sample crown.

After that, the water temperature is gradually lowered, and the mixture is allowed to stand overnight at room temperature, and on the next day, the gas pressure in the container at 20 ° C. is measured as a continuous withstand pressure, and is compared and evaluated with the same gas pressure of the untreated stored product. The number of samples was 40 each.

The test results are: -No gas leakage (visual inspection), no significant difference in continuous pressure resistance from untreated products (2.1 to 2.4 kg / cm ² )-○ -No gas leakage (visual inspection) Inspection), withstanding pressure lower than untreated product (2.0 kg / cm ² or less) …… △ ・ Gas leakage …… ×

(D) Impact resistance (drop impact test) Asahi Breweries (registered trademark) is added to a glass container (large beer bottle).
The sample crowns shown in Tables 1 and 2 are capped and sealed. Impact the impact on the sample crown and the bottle mouth by tilting the bottle mouth upside down onto an iron sloping base with an angle of 10 ° and 20 ° to the floor surface and free fall from a height of 19.0 mm from the drop point. give. Immediately after the test, inspect the sample crown for leaks. The number of samples was 20 each.

The test was first carried out in the above manner from a 10 ° tilt table and then on a 20 ° tilt table using a new test vessel. After the test container that had been subjected to the drop impact was left standing upright at 20 ° C. for 24 hours, the gas pressure in the container was measured and compared with the same gas pressure of the unprocessed stored product for evaluation.

The test results are displayed as follows. No leakage due to drop impact (visual inspection), and gas pressure after 24 hours is not significantly different from comparative untreated product
…… ○ There is no leakage due to drop impact (visual inspection), and the gas pressure after 24 hours is different from the untreated product (2.0 kg / cm).
⁽² or less) …… △ Leakage caused by drop impact …… ×

(E) Workability A liner molding test was carried out using the polymer compositions (pellets) shown in Tables 1 and 2 under the equipment, method and conditions shown in the item (2). The test results are displayed as follows. Processing of sample liner is possible ... ○ Processing of sample liner is not possible ... × Although sample liner can be processed, instability such as lack of smoothness of the cut surface of the melt is observed.
.. (F) MI Measured in accordance with Condition 4 of JIS: K7210.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

Claims (1)

[Claims] 1. The content of (A) vinyl acetate is 12% by weight.
50 to 90% by weight of an ethylene-based resin comprising the following low-density polyethylene and / or ethylene-vinyl acetate copolymer, and (B) a polymer block mainly composed of styrene and a polymer mainly composed of hydrogenated butadiene Hydrogenated block copolymer elastomer 50 composed of blocks
-10 wt% and its MI is 1-20 g / 1
A liner for a crown produced by molding and processing a composition of 0 minutes by in-shell molding.