JPH04294754A - Liner for metal screw caps - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention has excellent preservability of contents,
The present invention also relates to a cap liner that facilitates opening during practical use, particularly to a threaded metal cap liner. For more details, please see the excellent flexibility of ethylene resin, food hygiene,
A liner for screw-type metal caps that has significantly improved sealing properties, storage stability, and opening performance for beverages, especially those with internal pressure such as soft drinks and beer, without sacrificing characteristics such as moldability. Regarding.

0002

2. Description of the Related Art Cork, soft PVC, olefin resins, especially ethylene resins, and the like have been used as materials for liners for bottle caps. Among these, cork liners are preferred for their rebound resilience and are a natural material that has been used for a long time, but there are large differences in quality, making the quality unstable, producing cork dust, and being relatively expensive. In recent years, liners such as soft PVC and olefin resins have been giving up their position.

On the other hand, although soft PVC liners are also flexible and have excellent sealing properties, in recent years, due to hygienic problems caused by plasticizers, vinyl chloride monomers, etc., olefin resins, which have excellent hygienic properties, are being replaced. Ethylene resin is widely used for the olefin resin liner, which is naturally flexible, but it has sufficient sealing performance against defects in the shape of the bottle mouth, scratches or chips in the same area, etc. or the internal pressure of the contents decreases during long-term storage.
Furthermore, even if sufficient sealing performance is obtained, there is a problem in that the screw cap is difficult to open, and an improvement has been desired.

[0004] In response to these, the present inventors previously filed a patent application for patent application No.
A solution to this problem is shown in the specification of No.-270260. However, even with the method of this prior invention, the slipperiness of the sheet material that serves as the liner that provides easy opening may disrupt the feeding of the sheet material during the manufacture of the screw-type cap, and the flexibility of the sheet material that provides good sealing performance. However, it was discovered that there was a manufacturing issue that needed to be resolved in that it made holding, transporting, and processing of sheet materials unstable in other processes during manufacturing.

[0005]

[Problems to be Solved by the Invention] The object of the present invention is to solve the above-mentioned manufacturing problems, that is, to solve the above-mentioned manufacturing problems, without impairing the excellent moldability and food hygiene of ethylene resin, as in the prior invention. Our goal is to improve the properties of ethylene resin, especially its sealing performance, storage stability, and opening performance, which cannot be solved by flexibility alone, and to provide liners for high-quality metal screw caps through stable production. .

[0006]

[Means for Solving the Problem] As a result of repeated studies to solve the problem, the present inventors discovered that the problem could be solved by using a liner made of a specific ethylene polymer composition. Completed the invention.

That is, the present invention provides (A) ethylene resin 6
0 to 80 wt% (hereinafter referred to as wt%), (B) hydrogenated block copolymer elastomer 40 to 20 wt%,
(C) Total amount of higher fatty acid amide of (A) and (B) 100
A composition consisting of 0.1 to 0.5 parts by weight based on the weight part, wherein the (A) component consists of low density polyethylene and/or ethylene-vinyl acetate copolymer, and (A)
The vinyl acetate content in the component is 3 to 10 wt%, and (B
) is a hydrogenated block copolymer consisting of a polymer block mainly composed of styrene and a polymer block mainly composed of hydrogenated butadiene, and the component (C) is an amide of a fatty acid having 8 to 22 carbon atoms. A multilayer sheet is used in which the surface layer is made of a composition that is a compound and the back layer is made of an ethylene resin and the component (A) above, and the thickness thereof is 1/2 or more and 1/10 or more of the total thickness. A liner installed inside the characteristic metal screw cap. and/or
The above-mentioned liner is provided using a multilayer sheet having an intermediate layer having a composition between the two surface layers and having a thickness of 1/2 or less of the total thickness. It is.

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 as specified in JIS: K6748.
A material having a density of 0.920 or less is preferable from the viewpoint of flexibility that provides sealing performance. Furthermore, ethylene resin (A
) contains 3 to 10 wt% vinyl acetate, preferably 4 to 10 wt%.
Contains 8wt%.

[0009] If the content exceeds 10 wt%, the odor may be disliked depending on the content, and although the content is highly flexible,
It is undesirable because it has poor load resistance and large deformation, which tends to cause insufficient sealing performance and deterioration in long-term storage stability. On the other hand, if the content is less than 3 wt%, it is difficult to obtain the desired performance.

[0010] The hydrogenated 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 in the present polymer composition, The blending ratio is 20-40wt
%. If it exceeds 40 wt%, it will have high rubber elasticity, which is preferable for long-term storage stability, but shear deformation will also increase and it will be difficult to open the screw-type cap. On the other hand, 2
If it is less than 0 wt%, it is difficult to obtain sufficient sealing performance.

[0011] The higher fatty acid amide preferably has 8 to 8 carbon atoms.
consisting of one or more amide compounds of 22 fatty acids, more preferably one or more amide compounds of unsaturated fatty acids having 16 to 22 carbon atoms, in 100 parts by weight of the mixture of polymers (A) and (B). It is added in an amount of 0.1 to 0.5 part by weight, preferably 0.2 to 0.4 part by weight. 0.
If it is less than 1 part by weight, sufficient slippage may not be obtained and the opening performance is likely to be insufficient. If it exceeds 0.5 part by weight, bleeding onto the liner surface becomes noticeable and may cause problems such as contamination with the contents. This is not desirable. In addition, in the above composition,
Additives such as commonly used colorants, stabilizers, modifiers, processability improvers, etc. may be added to the extent that the properties of the polymer composition of the present invention are not impaired.

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. Bye. The mixing method is to use a commonly used mixer such as a Henschel mixer or a drum blender, and an extruder, Banbury mixer, or
A method of homogeneous mixing using a melt kneader such as a roll mill is exemplified.

Liners are generally formed into a plate shape using a sheet forming device such as an extruder, but the desired multilayer sheet is formed using a plurality of extruders equal to the number of layers constituting the sheet. Shape. The thickness is selected depending on the function of the cap, but ranges from 0.5 to 2 mm.

The back layer constituting the thickness is (A) made of ethylene resin, and (C) does not contain higher fatty acid amide, or contains 0.1 wt% which does not substantially provide slipperiness.
or less, and the thickness preferably does not exceed 1/2 of the total thickness. If this value is exceeded, 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 less than 1/10 of the total thickness, the original function of multi-layering, ie, stable feeding during manufacturing of screw-type caps, etc. cannot be sufficiently achieved. More preferably, the thickness is 1/5 or more and 1/3 or less of the total thickness.

[0015] If an intermediate layer is added to the arrangement, it is preferred that the thickness of this layer does not exceed 1/2 of the total thickness. If this layer, which has a composition between that of the surface layer and the back layer, exceeds this, the influence on both surface layers may become unignorable, and in particular,
It affects the sealing performance of the surface layer. More preferably, it is ⅓ or less of the total thickness. The multilayer sheet is cut or punched according to the size and shape of the metal screw cap, and is installed inside the cap.

[0016]

[Effects of the invention] By using the liner of the present invention,
It exhibits excellent performance in sealing and preserving beverages with internal pressure such as carbon dioxide gas without sacrificing the excellent moldability and food hygiene of ethylene resin, and is easy to open during practical use. Stable manufacturing has made it possible to provide high quality metal screw caps.

[0017]

[Examples] The present invention will be specifically explained below with reference to Examples. Examples 1 to 5, Comparative Examples 1 to 13 Using the polymers and additives shown in Table 3, the following (1) to (
A sheet material having the structure shown in Table 3 was produced using the composition shown in Tables 1 and 2 by the method shown in 3), and then a liner was made using this and attached to a cap. This product was evaluated by the method shown in (4) below. The results are shown in Table 4.

(1) Preparation of composition The compositions shown in Tables 1 and 2 were premixed, melt-kneaded using an extruder, and extruded into pellets (3φ×3L mm) to prepare them. The preliminary mixing was performed at room temperature using a drum blender for 15 minutes. In addition, melt kneading was performed using a 60 mmφ extruder (L/D28, full-flight screw).
Melt extrusion was carried out at 00°C.

(2) Production of liner The above composition (pellets) was transferred to a 60 mmφ extruder (L/D2
A sheet with a thickness of 0.8 mm was molded at 200° C. using a sheet molding device consisting of two extruders (L/D 28, full flight screw) and a 40 mmφ extruder (L/D 28, full flight screw). Next, this was punched out using a cutting blade of 33 mmφ.

(3) Cap (33mmφ, 20mmH
) Al screw-type cap) The liner was heat-pressed at 200° C. for 1 minute and attached so that the surface layer of the liner was in contact with the bottle mouth and the back layer was in contact with the inner top surface of the cap. Adhesive was applied to the corresponding part of the inner surface of the cap in advance. A cap was used in which an ethylene oxide-modified epoxy hot-melt material that imparted adhesiveness was applied in advance to the corresponding inner surface of the cap.

(4) Evaluation method (a) Cap processing test The sheet material is loaded into a metal screw type cap production device, and the sheet is automatically fed, punched and cut, and attached (glued).
Processing tests were conducted continuously on the production line. The evaluation is as follows: ○: Can be processed continuously ×: Cannot be processed continuously due to uneven feed, poor cutting, etc. △: Difficult to finish the cut surface, and manual fine adjustment is required for continuous processing .

(b) Storage sensory test A clean glass container was filled with "Asahi Beer" and fitted with a liner made of the polymer composition shown in Tables 1 and 2.
Seal the container tightly using a screw-type cap made by L and store it at 25°C with the container inverted. After 14 days of storage, the beer was opened, and 12 panelists conducted a discrimination test to determine whether there was any difference from "Asahi Beer" (using a low-density polyethylene liner) that had been stored at the same time. The test results are displayed as × for ``significant difference'', ○ for ``no significant difference'', and △ for ``although it cannot be said that there is a significant difference, there is some sense of difference.''

(c) Sealing and storage stability test (a) Fill a 2L glass bottle with carbonated water, leaving 100cc, and use a cap fitted with a liner made of the polymer composition shown in Tables 1 and 2. , Top Road 27
0kgf, side pressure torque 38kgf-
Seal with cm. The carbonated water used was one that dissolved 2.5 times the volume of carbon dioxide per the same amount of water at 23°C.

(b) The glass container sample in the state of (a) is heated in hot water at 60° C. for 10 minutes and inspected for gas leakage. Further, leave it at 40°C for 7 days and check for gas leaks. (c) The above-mentioned glass bottle is designed to have a width of 2 to 3 mm in the circumferential direction and a depth of 2 to 3 mm in the radial direction on the outer edge of the bottle mouth, assuming defects in the shape of the bottle mouth and scratches and chips in the same part that are unavoidable in practical use. A total of 10 glass bottles with chips in the range of 1 to 2 mm in diameter were selected and used for this evaluation.

(d) The results of the evaluation were displayed as follows. ○: All or most of the leaks do not occur. (Leakage rate 0/10 to 1/10) ×: All or most of it leaks (Leakage rate 6-10/10) △: Between the above two (Leak rate 2-5/10).

(d) Openability test The glass bottle sample from (c) (a) above was heated in hot water at 60°C for 10 minutes, then cooled to room temperature and stored at 5°C for 1, 3, 7, and 14 days. After that, open each cap using a torque meter and measure the opening torque at that time. Preferable torque is 5-20kgf
If the torque is less than 5 kgf-cm, sufficient sealing performance may not be maintained in practical use, and if the torque exceeds 20 kgf-cm, opening becomes difficult in proportion to the torque.

[0027] The results of this evaluation are displayed as follows: ○: Indicating a torque of 10 to 16 kgf-cm ×: Torque less than 5 kgf-cm and exceeding 20 kgf-cm △
: Torque of 5 kgf-cm or more and less than 10 kgf-cm or 16 kgf-cm or more and 20 kgf-cm or less

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

Claims (2)

[Claims] Claim 1: (A) ethylene resin 60 to 80% by weight, (B) hydrogenated block copolymer elastomer 40
~20% by weight, and (C) higher fatty acid amide in an amount of 0.1~0.0% per 100 parts by weight of the total amount of components (A) and (B).
5 parts by weight, wherein component (A) consists of low density polyethylene and/or ethylene-vinyl acetate copolymer, and the vinyl acetate content in component (A) is 3 parts by weight.
~10% by weight, component (B) is a hydrogenated block copolymer consisting of a polymer block mainly composed of styrene and a polymer mainly composed of hydrogenated butadiene,
C) A surface layer consisting of a composition in which the component is an amide compound of a fatty acid having 8 to 22 carbon atoms, and the above-mentioned (A) component, and the thickness thereof is 1/2 or less of the total thickness.
A liner installed inside a metal cap, characterized by using a multilayer sheet consisting of at least one surface layer (back layer) of 0 or more. 2. Between the two surface layers described in ``Claim 1,'' there is an intermediate layer having a composition between the compositions used in both layers, and the thickness of the intermediate layer is 1/1/2 of the total thickness. A liner installed inside a metal cap, characterized by using a multilayer sheet having a thickness of 2 or less.