JP2699681B2 - Liner for metal screw cap - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is excellent in preservability of contents,
Also, the present invention relates to a cap liner that facilitates opening in practical use, and particularly to a screw-type metal cap liner. More specifically, the excellent flexibility of ethylene resin, food hygiene,
Threaded metal cap liner with markedly improved sealing, storage and opening performance in practical use for beverages, especially soft drinks, beer, and other contents with internal pressure without impairing characteristics such as moldability. About.

[0002]

2. Description of the Related Art Conventionally, cork, soft PVC, olefin-based resins, especially ethylene-based resins, etc. have been used as materials for bottle cap liners. Of these, cork liners are preferred for their rebound resilience and are a natural material that has been used for a long time.However, the quality difference is large and the quality is unstable, and the generation of cork dust and the relatively high cost For this reason, in recent years, it has been giving up its position to liners such as soft PVC and olefin-based resins.

On the other hand, although a soft PVC liner is also flexible and has excellent sealing properties, in recent years, it has been changed to an olefin resin having excellent hygiene due to a hygiene problem caused by a plasticizer, a vinyl chloride monomer and the like. Ethylene resin, which has inherently soft properties, is widely used in the olefin resin liner, but it has sufficient sealing properties against bottle shape defects, scratches, or chipping of the bottle. Is not obtained, or the internal pressure indicated by the contents during long-term storage decreases,
Furthermore, even if sufficient sealing properties are obtained, there is a problem that the screw-type cap is difficult to open, and improvement has been desired.

On the other hand, the present inventors have previously described Japanese Patent Application No.
No. 270260 describes the solution. However, even in the method of the prior application, the slipperiness of the sheet material serving as a liner that provides easy opening can cause upset of the sheet material during manufacture of the screw-type cap, or the flexibility of the sheet material that provides good sealing performance. However, it has been found that there is a problem to be solved in manufacturing that the holding, transfer and processing of the sheet material in other processes during manufacturing are unstable.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems in the production, that is, the same excellent molding processability and food hygiene of the ethylene resin as in the prior application invention, It is an object of the present invention to improve the properties of ethylene-based resin, particularly the sealing property, storage property and openability which cannot be solved only by flexibility, and to provide a high-quality metal screw-type cap liner by stable production. .

[0006]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve such problems, and as a result, have found that the problems can be solved by using a liner made of a specific ethylene polymer composition. Completed the invention.

That is, the present invention relates to (A) an ethylene resin 6
0 to 80% by weight (hereinafter referred to as "wt%"), (B) 40 to 20% by weight of a hydrogenated block copolymer elastomer,
(C) The higher fatty acid amide has a total amount of (A) and (B) of 100
A composition comprising 0.1 to 0.5 parts by weight per part by weight, (A) component low-density polyethylene and / or ethylene - consists vinyl acetate copolymer, and ethylene
In the case of containing a vinyl acetate-vinyl acetate copolymer, the component (A) has a vinyl acetate content of 3 to 10% by weight, and the component (B) mainly contains a styrene-based polymer block and hydrogenated butadiene. A surface layer composed of a composition in which the component (C) is an amide compound of a fatty acid having 8 to 22 carbon atoms;
The back layer is composed of the component ( A) or the component (A) and the component (A).
0.1% by weight or less of the component (C) , the thickness of which is 1/2 or less and 1/10 or more of the total thickness. Liner. And / or a multilayer sheet having an intermediate layer between the two surface layers and having a composition between the two compositions and having a thickness of 1/2 or less of the total thickness. Is to supply.

The low-density polyethylene used for each layer constituting the multilayer sheet of the present invention has a density of 0.910 or more and less than 0.930 specified in JIS: K6748.
Those having a density of 0.920 or less are preferred in terms of flexibility for imparting sealing properties. Further, in the ethylene resin (A) comprising the polyethylene and / or the ethylene-vinyl acetate copolymer, vinyl acetate contains 3 to 10% by weight, preferably 4 to 4% by weight.
-8% by weight.

When the content exceeds 10% by weight, the odor of some contents is disliked, and although the contents are rich, the load resistance is poor and the deformation is large, so that the sealing property is insufficient and the long-term storage property is reduced. It is not preferable because it easily occurs. On the other hand, if the content is less than 3% by weight, it is difficult to obtain the desired performance.

The hydrogenated styrene-butadiene block copolymer has a styrene content of 10 to 45% by weight and a hydrogenation rate of 80% or more, preferably 90% or more. Mixing ratio is 20-40wt%
It is. If it exceeds 40% by weight, the rubber elasticity is high, and this is a preferable direction because of long-term storage properties. However, shear deformation increases, and it becomes difficult to open the screw cap. On the other hand, 20wt
%, It is difficult to obtain a sufficient sealing property.

[0011] The higher fatty acid amide is preferably a C8-C8 compound.
22 or more preferably comprise at least one amide compound of an unsaturated fatty acid having 16 to 22 carbon atoms, and more preferably 100 parts by weight of a mixture of the polymers (A) and (B). 0.1 to 0.5 part by weight, preferably 0.2 to 0.4 part by weight is added. 0.
If the amount is less than 1 part by weight, sufficient slippage cannot be obtained and the opening property tends to be insufficient. If the amount exceeds 0.5 part by weight, bleeding to the surface of the liner becomes remarkable, which may cause a problem such as mixing into contents. Is not preferred. In the above composition,
Additives such as commonly used colorants, stabilizers, modifiers, and processability improvers may be added within a range that does not impair the properties of the polymer composition of the present invention.

In order to obtain the polymer composition used in the liner of the present invention, (A) an ethylene resin, (B) a hydrogenated styrene-butadiene block copolymer, and (C) a higher fatty acid amide are uniformly mixed. I just need. The mixing method is a general mixer such as a Henschel mixer, a drum blender, etc., and an extruder, a Banbury mixer,
A method of uniformly mixing using a melt kneader such as a roll mill can be used.

The liner is generally formed into a plate shape by a sheet forming apparatus such as an extruder. A plurality of extruders equal in number to the number of layers constituting the sheet are used to form a target multilayer sheet. Molding. The thickness is selected according to the function of the cap, but ranges from 0.5 to 2 mm.

The back layer constituting the thickness is composed of (A) an ethylene-based resin and does not contain (C) a higher fatty acid amide, or 0.1 wt% which does not provide substantially slipperiness even if it is contained.
It is preferable that the thickness is not more than 1/2 and the thickness does not exceed 1/2 of the whole. If it exceeds this, the influence of the back surface on the liner surface in contact with the bottle mouth tends to appear, and sufficient sealing performance may not be obtained. On the other hand, if the thickness is 1/10 or less of the total thickness, the original function of forming a multi-layered structure, that is, the stable feeding at the time of manufacturing the screw cap, cannot be sufficiently obtained. More preferably, it is 1/5 or more and 1/3 or less of the entire thickness.

When an intermediate layer is added to the construction, it is preferred that the thickness of this layer does not exceed one half of the total thickness. If this layer having the composition between the front layer and the back layer exceeds this, the effect on both surface layers may not be negligible,
The sealing effect is exerted on the surface layer. More preferably, it is 1/3 or less of the entire thickness. The multilayer sheet is cut or punched according to the size and shape of the metal screw cap, and is provided inside the cap.

[0016]

By using the liner of the present invention,
Without impairing the excellent moldability and food hygiene of ethylene-based resin, the performance of excellent sealing and preservability of beverages with internal pressure such as carbon dioxide is exhibited, and easy to open in practical use. Stable production has made it possible to provide high-quality metal screw caps.

[0017]

The present invention will be described below in detail with reference to examples. Examples 1 to 4 and Comparative Examples 1 to 14 Using the polymers and additives shown in Table 3, the following (1) to
By the method shown in (3), a sheet material having the composition shown in Table 3 was prepared using the compositions shown in Tables 1 and 2, and then a liner was prepared using the sheet material and attached to the cap. This was evaluated by the method shown in (4) below. Table 4 shows the results.

(1) Preparation of Composition Each composition shown in Tables 1 and 2 was premixed, melt-kneaded in an extruder, and extruded into pellets (3 ^φ × 3 ^L mm) to prepare. The pre-mixing was performed at room temperature with a drum blender for 15 minutes.
Minutes. The melt kneading was performed with a 60 mm ^φ extruder (L / D28, full flight screw) for 200 minutes.
It was performed by melt extrusion at ℃.

(2) Preparation of Liner The above composition (pellet) was extruded into a 60 mm ^φ extruder (L / D2).
A sheet having a thickness of 0.8 mm was formed at 200 ° C. by a sheet forming apparatus including two extruders (8, full flight screw) and 40 mm ^φ extruder (L / D28, full flight screw). Next, this was punched out with a 33 mm ^φ cutting blade.

(3) Cap (33 mm ^φ , 20 mm ^H ) Al screw type cap) Heat at 200 ° C. for 1 minute so that the surface layer of the liner is in contact with the bottle, and the back layer is in contact with the top surface of the cap. It was attached by crimping. The portion corresponding to the inner surface of the cap was previously provided with adhesiveness. A cap coated with an ethylene oxide-modified epoxy-based hot melt material for imparting adhesiveness in advance was used for a portion corresponding to the inner surface of the cap.

(4) Evaluation method (a) Cap processing test The sheet material is loaded into a metal screw cap production apparatus, and the sheet is automatically fed, punched, cut and mounted (adhered) continuously on a production line. A machining test was performed. Evaluation: ○: Continuous processing is possible ×: Continuous processing is impossible due to uneven feeding, poor cutting, etc. △: Difficult to finish cut surface, and continuous processing requires fine adjustment by hand .

(B) Preservation sensory test A “Asahi Beer” was filled in a clean glass container, and a liner made of a polymer composition shown in Tables 1 and 2 was attached.
1 Close the container with a screw cap, and store at 25 ° C with the container inverted. The bottle was opened 14 days after storage, and the presence or absence of a difference from "Asahi Beer" (using a low-density polyethylene liner) that was simultaneously stored by 12 panelists was examined by a discrimination test. The test result is indicated by "x" for "significant difference", "o" for "no significant difference", and "△" for "not significant difference, but some difference".

(C) Sealing and storage test (a) Using a cap equipped with a liner made of a polymer composition shown in Tables 1 and 2 with 100 cc left in a 2 liter glass bottle filled with carbon dioxide gas water. , Top load 270kgf
, Seal with side pressure torque 38kgf-cm. As the carbon dioxide gas water, used was one in which 2.5 times the volume of carbon dioxide gas was dissolved in the same amount of water at 23 ° C.

(B) The glass container sample in the state of (a) was kept at 60 ° C.
And heat for 10 minutes and inspect for gas leakage. Further 40
Leave at 7 ° C for 7 days and inspect for gas leakage. (c) The above glass bottle is assumed to have a shape defect of the bottle, which is unavoidable in practical use, and to be damaged or chipped at the same portion. A total of ten glass bottles with a chip in the range of 1-2 mm were selected and used for the evaluation.

(D) The results of the evaluation are shown below. ：: All or most do not leak (leakage rate: 0/10 to 1/10) ×: All or most leak (leakage rate: 6 to 10/10) △: Intermediate between the above two (leakage rate: 2 to 5 / 10).

(D) Opening test (c) The glass bottle sample of (a) was heated at 60 ° C. for 10 minutes, then cooled to room temperature and stored at 5 ° C. for 1, 3, 7, 14 days. Thereafter, each is opened with a torque meter, and the opening torque at that time is measured. Preferred torque is 5-20 kgf-cm
If it is less than 5 kgf-cm, it may not be possible to maintain sufficient sealing properties in practical use, and if the torque exceeds 20 kgf-cm, it becomes difficult to open the plug in proportion to the magnitude.

The evaluation results are shown as follows: ：: A torque indicating 10 to 16 kgf-cm ×: Torque of less than 5 kgf-cm and exceeding 20 kgf-cm △: Torque of 5 kgf-cm or more and less than 10 kgf-cm or 1
6kgf-cm or more and 20kgf-cm or less

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Haruo Hayashi Asahi Breweries, Inc. 1-2-1 Azumabashi, Sumida-ku, Tokyo (72) Inventor Hajime Takayama 1-3-1 Tajiri, Ichikawa-shi, Chiba Prefecture Shibasaki Co., Ltd. (56) References JP-A-58-183458 (JP, A) JP-A-55-45739 (JP, A)

Claims (2)

(57) [Claims] (1) 60 to 80% by weight of an ethylene resin, (B) hydrogenated block copolymer elastomer 40 to 2
0% by weight, and 0.1 to 0.5 part by weight of (C) higher fatty acid amide based on 100 parts by weight of the total of components (A) and (B), wherein component (A) has a low density. Made of polyethylene and / or ethylene-vinyl acetate copolymer, and ethylene-vinegar
When an acid vinyl copolymer is contained, the component (A) has a vinyl acetate content of 3 to 10% by weight, and the component (B) mainly contains a styrene-based polymer block and hydrogenated butadiene. to a hydrogenated block copolymer comprising a polymer, and component (C) consists of the composition is an amide compound of a fatty acid having 8 to 22 carbon atoms surface (surface layer), (a) component or
Component (A) and component (C) of not more than 0.1% by weight of component (A)
And the thickness is not more than 1/2 of the total thickness1
A liner provided in a metal screw-type cap, wherein a multi-layer sheet comprising at least another surface layer (back surface layer) having a ratio of / 10 or more is used. 2. An intermediate layer between the two surface layers described in claim 1 having a composition between the compositions used for both layers, wherein the thickness of the intermediate layer is 1 / th of the total thickness. A liner provided inside a metal screw-type cap, wherein a multi-layered sheet of 2 or less is used.