JPH0776360A - Composition for cap liner - Google Patents

Abstract

(57) [Summary] [Purpose] An object of the present invention is to provide a cap liner material capable of preventing the occurrence of the wax float phenomenon due to the outflow of wax from the liner material. [Structure] Hydrogenated styrene / butadiene block copolymer 10 to 60% by weight, liquid paraffin 5 to 35% by weight, polypropylene 5 to 50% by weight, polyethylene 5 to 5%
A composition for a cap liner containing 45% by weight. [Effect] This composition prevents the wax float phenomenon, has a good opening torque value under high temperature storage, and is suitably used as a liner material for synthetic resin caps.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for a cap liner suitable as a packing material for a synthetic resin cap, and particularly, it has excellent heat resistance and prevents the occurrence of the wax float phenomenon due to the outflow of wax from the liner material. To obtain a cap liner material.

[0002]

2. Description of the Related Art As one of recent environmental measures, it has been suggested to use synthetic resin caps instead of aluminum caps for recycling plastic bottles. One of the uses of such synthetic resin caps is in container caps for mineral water products and the like.
Since these products are extremely dislike of off-flavor and off-flavor, hygienic synthetic resin caps without deterioration are particularly preferable.

Conventionally, as a liner material for a synthetic resin cap, for example, a liner material described in Japanese Patent Application Laid-Open No. 2-57569 is known. This liner material contains 10 to 6 hydrogenated styrene-butadiene block copolymer.
A composition comprising three components of 0% by weight, liquid paraffin of 20 to 80% by weight, and polypropylene of 5 to 60% by weight, the composition of which the heat resistance effect was recognized in the examples of the specification of the publication is In the examples of the publication, a composition containing 20 to 55% by weight of hydrogenated styrene-butadiene block copolymer, 35 to 65% by weight of liquid paraffin, and 5 to 45% by weight of polypropylene is disclosed. As a liner material for synthetic resin caps of this kind, the inclusion of polypropylene, which is the same as that of the cap body, is inevitable in order to give adhesiveness, and accordingly, in order to give the liner elasticity, hydrogenated styrene / Butadiene block copolymer and liquid paraffin are required. In addition, addition of liquid paraffin is indispensable in order to improve the processability of hydrogenated styrene / butadiene block copolymer.

However, in the above-mentioned conventional cap liner material, if a container is filled with a liquid, the cap is wound, sealed and manufactured into a product, it is left in an environment of about 40 ° C. In some cases, an oily substance, which is considered to be liquid paraffin, was separated from the liner material and floated in the form of droplets on the surface of the content liquid, or an oil film was formed (hereinafter referred to as wax float). Further, the conventional liner material has a phenomenon that the opening torque value is too low in the 60 ° C. storage test assuming a high temperature environment in summer, and there is a concern about the sealing property of the container.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a cap liner material having excellent heat resistance and capable of preventing the occurrence of a wax float phenomenon due to the outflow of wax from the liner material. Has an aim.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have (remarkably) reduced the ratio of liquid paraffin in the conventional liner material composition, and newly added polyethylene. By doing so, it was found that the wax float phenomenon, which is a drawback of conventional products, can be prevented, and the opening torque value at high temperature storage is improved, and the present invention has been completed. That is, the present invention includes (a) hydrogenated styrene / butadiene block copolymer 10 to 60% by weight, (b) liquid paraffin 5 to 35% by weight, (c) polypropylene 5
To 50% by weight, and (d) polyethylene 5 to 45% by weight, the present invention relates to a composition for a cap liner. Hereinafter, the present invention will be described in detail.

The hydrogenated styrene / butadiene block copolymer used as the component (a) of the cap liner composition of the present invention is a hydrogenated product of a block copolymer having a polystyrene / polybutadiene / polystyrene structure. For example, it is produced by hydrogenating a block copolymer in the presence of a catalyst such as Raney nickel, as described in JP-B-43-6636. By this hydrogenation, at least 50% or more, preferably 90% or more, of the olefinic double bonds in the polybutadiene block are hydrogenated. The amount of polystyrene block in the hydrogenated block copolymer is 8
˜55 wt%, preferably 10-40 wt%. The melt index (200 ° C., load 5 kg) is not particularly limited, but it is preferably 1 g / 10 minutes or less from the viewpoint of elasticity and flexibility at high temperature. These hydrogenated styrene / butadiene block copolymers are manufactured and sold as, for example, Kraton G (trade name, manufactured by Shell Japan Co., Ltd.).

The liquid paraffin used as the component (b) of the cap liner composition of the present invention is also called white oil, and contains impurities such as aromatic hydrocarbons and sulfur compounds contained in the lubricating oil fraction of petroleum. It consists of saturated hydrocarbons removed and purified. The viscosity is not particularly limited, but one having 30 to 400 centistokes at 37.8 ° C. is preferable from the viewpoint of heat resistance.

The polypropylene used as the component (c) of the composition for a cap liner of the present invention is a homopolymer of propylene or a small amount of other 1
Melt flow rate (hereinafter sometimes abbreviated as "MFR". A copolymer of one or more kinds of α-olefins. JI
SK6758, 230 ℃, 2.16kgf) 1g /
It is 10 minutes or more, preferably 5 g / 10 minutes or more. If the MFR is out of the range, the workability is poor. Examples of the α-olefin which is a copolymerization comonomer include ethylene, 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene. Specific examples of the propylene copolymer, a propylene-ethylene copolymer containing 0.1 to 6 mol% ethylene, 0.1 to 6 mol%
Propylene / 1-butene copolymer containing 1-butene, 0.1 to 6 mol% ethylene and 0.1 to 6 mol% 1
Examples include butene-containing propylene / ethylene / 1-butene copolymers.

The polyethylene used as the component (d) of the cap liner composition of the present invention has a density (JIS K6760) of 0.850 to 0.940 g / c.
m ³ , maximum peak temperature (T measured by differential scanning calorimetry)
m) is a homopolymer of ethylene having a temperature of 100 ° C. or higher and / or a copolymer of ethylene and α-olefin. α
- The olefin of the general formula R-CH = CH ₂ (. Wherein R is an alkyl group having 2 to 14 carbon atoms) one represented by, if specific examples, 1-butene, 1- Hexen, 4
-Methyl-1-pentene, 1-octene, 1-decene, 1-nonene, 4-methyl-1-hexene and the like. If the density is less than 0.850 g / cm ³ , industrial production becomes difficult and blocking occurs in the composition pellets, which is not preferable. When the density exceeds 0.940 g / cm ³ , the composition becomes hard and lacks flexibility and elasticity, resulting in poor liner sealing performance. Maximum peak temperature (T
When m) is less than 100 ° C., the heat resistance is lowered, which is not preferable. The measuring method of Tm by the differential scanning calorimeter is as follows.

[Method of Measuring Tm by Differential Scanning Calorimeter] About 5 mg of sample was weighed from a hot press-formed film having a thickness of about 100 μm and heated from 80 ° C. to 80 ° C./min up to 230 ° C. Heat up and hold for 5 minutes. 10 ° C
The temperature is decreased to −10 ° C. at a rate of / minute. The temperature is held at −10 ° C. for 5 minutes, then again raised to 230 ° C. at a rate of 10 ° C./min, and the temperature at the apex of the maximum peak among the peaks appearing during the temperature rise is Tm.

In the composition containing each of the components (a) to (d), if the composition ratio of the hydrogenated styrene / butadiene block copolymer is less than 10% by weight, the elasticity of the composition becomes insufficient and the liner. The sealing performance of the will deteriorate. On the other hand, if the composition ratio thereof is more than 60% by weight, the melt fluidity of the composition is too high and the liner processability is deteriorated, which is not preferable. When the composition ratio of liquid paraffin is less than 5% by weight, the flexibility and elasticity of the composition are insufficient and the processability is deteriorated. When it is more than 35% by weight, wax float is generated, which is not preferable. Further, if the composition ratio of polypropylene is less than 5% by weight, the adhesion of the composition to a generally used polypropylene resin cap is deteriorated, and as a result, the adhesion between the cap and the liner becomes insufficient, resulting in 50% by weight. When it is more than 0.1%, the composition becomes hard and the flexibility and elasticity become insufficient, so that the sealing property of the liner deteriorates. When the composition ratio of polyethylene is less than 5% by weight, the composition ratio of hydrogenated styrene-butadiene copolymer and polypropylene becomes high and the composition becomes hard, resulting in poor elasticity and flexibility, which is not preferable. Increasing the amount of paraffin causes wax float. On the other hand, if the composition ratio of polyethylene is more than 45% by weight, the heat resistance of the liner becomes poor, which is not preferable.

The preparation of the resin composition of the present invention is carried out from (a) to
Various known methods such as a Henschel mixer, a V blender, and a tumbler blender are used to mechanically mix the solid component (d), or after mixing, a single-screw extruder, a twin-screw extruder, a Banbury mixer, a kneader, etc. may be used. It can be obtained by a method of granulating or pulverizing after melt-kneading. Among them, the method of melt kneading using a single-screw extruder or a twin-screw extruder is generally used from the viewpoint of productivity.

The resin composition of the present invention contains, if necessary, an antioxidant, an antistatic agent, an antiblocking agent, a lubricant, a light stabilizer, an ultraviolet absorber, within a range not impairing the effects of the present invention. Additives generally used for thermoplastics such as colorants, fillers, nucleating agents, clarifying agents, organic peroxides and catalyst neutralizing agents may be used. For example, to prevent thermal deterioration during sterilization, use antioxidants such as phenol and phosphorus to adjust the liner, and colorants such as titanium dioxide and phthalocyanine blue to adjust the liner torque. For this purpose, a lubricant such as higher fatty acid, wax, silicone oil, higher fatty acid amide or the like can be added.

The resin composition of the present invention is closely molded in a cap shell made of synthetic resin by a known liner forming method. Examples of the liner forming method include a method in which a resin composition is formed into a sheet having a thickness of 0.5 to 1.0 mm, which is then punched into a cap having a diameter suitable for the shape of the cap and is then adhered in the cap, and is extruded by an extruder. Another example is an in-shell molding method in which a certain amount of molten resin is dropped inside the cap and the liner shape is formed by embossing under cooling. Examples of synthetic resin caps include polypropylene caps and high-density polyethylene caps.
Of these, polypropylene caps are preferably used because of their excellent adhesion to the resin composition of the present invention.

[0016]

【Example】

・ Polypropylene (J5350A manufactured by Tosoh Corporation; P
Abbreviated as P), low-density polyethylene (Tosoh Corporation 248; LD
Abbreviated as PE), hydrogenated styrene / butadiene block copolymer (G1650 manufactured by Shell Japan Co., abbreviated as SEBS), liquid paraffin (PW-90 manufactured by Idemitsu Kosan Co., abbreviated as liquid para), And other additives (lubricants, pigments, etc.) were mixed in the proportions shown in Table 1.

Next, these compositions were molded by the in-shell molding method in a polypropylene cap shell having a nominal diameter of 28 mm and a liner was formed to prepare various test caps. A PET bottle with a capacity of 1.5 liters was filled with Miranel water at 85 ° C., and various test caps produced using a Magna torque head of Alcoa capping machine were tightened with a tightening torque of 11.0 kg · cm. The following test was performed using the sealed sample.

1. Confirmation of Presence or Absence of Wax Float The sample after winding the cap is laid sideways and stored in a constant temperature bath at 40 ° C. for 48 hours, then returned to room temperature, and the presence or absence of wax float on the liquid surface is visually confirmed. 2. Opening performance test Samples after tightening the cap were placed in a constant temperature bath at 60 ° C and 5
The sample is stored in a refrigerator at 1 ° C for 1 week, after which the opening torque value is measured, and the measured torque value is evaluated according to the following criteria. ○: One showing all suitable torque values (10 to 20 kg / cm), △ One or more showing intermediate torque values (5 to 10 kg / cm or 20 to 25 kg / cm), ×: Inappropriate torque value (less than 5 kg / cm or 25 kg / cm or more)
There was one or more of the above. 3. Workability Each composition was molded into a liner in the cap shell by the in-shell molding method, and the liner of the obtained cap was visually inspected and evaluated according to the following criteria. ○ …… No liner molding failure × …… 1% or more liner molding failure

[0019]

[Table 1]

From the results of Table 1, sample 2 according to the present invention
Each of the compositions (1) to (6) can completely prevent wax float while maintaining good liner characteristics such as openability and processability. In particular, the compositions of Samples 3, 4 and 5 were found to be suitable as liner materials for synthetic resin caps because they have excellent openability and workability and can completely prevent wax float.

[0021]

INDUSTRIAL APPLICABILITY The resin composition of the present invention prevents the wax float phenomenon, has a good opening torque value under high temperature storage, and is suitably used as a liner material for synthetic resin caps.

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Claims (1)

[Claims] 1. The following components: (a) hydrogenated styrene / butadiene copolymer 10 to 60% by weight, (b) liquid paraffin 5 to 35% by weight, (c) polypropylene 5 to 50% by weight, (d). A composition for a cap liner, comprising 5 to 45% by weight of polyethylene.