JP3275625B2 - Seal film for lid material, lid material and container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to seal strength, sealability,
The present invention relates to a seal film comprising a styrene-based resin composition, which has a good balance between easy-opening properties and oil resistance, and thus is most suitable for use as a seal layer, a lid material using the seal film, and a container using the lid material. .

[0002]

2. Description of the Related Art Containers for foods, medicines, cosmetics, and the like are used by covering a main body portion into which the contents are put. A polystyrene resin is generally used for the main body, and after the contents to be filled are stored in the main body, a lid having heat sealing properties is heat-welded and sealed. Conditions required in such a case include high sealing strength, excellent sealing properties, excellent easy-opening properties, and excellent oil resistance. Note that the easy opening property means that the lid material can be easily peeled off from the container body when the food is used.

[0003] The lid material is usually made of a single-layer or multi-layer film of aluminum, polyolefin-based resin, polystyrene-based resin, polyamide-based resin, polyester-based resin, or the like, and a resin film having heat sealability is formed on the base material. Are laminated, and then the laminated film is processed into a predetermined shape to form a cover material.

[0004] Japanese Patent Publication No. 47-34808 discloses a sealing material comprising a rubber-modified polystyrene resin and a styrene-butadiene block copolymer rubber. E
P (Europe) 215333 discloses a sealing material comprising a rubber-modified polystyrene resin, a styrene-butadiene block copolymer rubber, and a mineral oil. Further, Japanese Patent Application Laid-Open No. 4-144744 discloses a sealing material comprising a rubber-modified polystyrene resin, a styrene-butadiene block copolymer rubber, and a polyolefin resin. However, these sealing materials are insufficient from the viewpoint of improving the sealing strength, sealing properties, easy-openability, and oil resistance in a well-balanced manner.

[0005]

In view of such circumstances, the problems to be solved by the present invention are sealing strength, sealing performance,
The present invention provides a sheet film made of a styrene-based resin composition, which has a good balance between easy-opening properties and oil resistance, and thus is optimal for use as a sealing material, a lid material using the sealing film, and a container using the lid material. Exists.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and have reached the present invention.

That is, one aspect of the present invention is to provide a seal film comprising a styrene resin composition containing the following components (A) to (C). Component (A): 50 to 80% by weight of a rubber-modified styrene resin having a soft component particle content of 5 to 25% by weight Component (B): 10 to 45% by weight of a polyolefin resin (C) Component: Styrene-isoprene Hydrogenated block copolymer rubber 3 to 20% by weight

[0008] A second aspect of the present invention is to provide a lid member using the above-mentioned sealing film as a sealing layer.

According to a third aspect of the present invention, there is provided a container using the above-mentioned lid material.

Hereinafter, the present invention will be described in detail. The component (A) of the present invention has a content of the soft component particles of 5 to 25% by weight.
Is a rubber-modified styrenic resin.

Here, the rubber-modified styrenic resin is obtained from a styrenic polymer and a rubbery polymer, and comprises a polystyrene-based polymer forming a matrix and soft component particles dispersed and present in the polymer. So-called high impact polystyrene (High Impact)
Polystyrene (HIPS).

As the styrene monomer constituting the styrene polymer, styrene is generally used, but alkyl-substituted styrenes such as o-methylstyrene, m-methylstyrene and p-methylstyrene can also be used.

As the rubbery polymer, a butadiene polymer, a styrene-butadiene copolymer, an isoprene polymer, a styrene-isoprene copolymer and the like can be used. Further, a styrene-butadiene copolymer and a butadiene polymer can be used in combination. As the butadiene polymer, either so-called high cis polybutadiene having a high cis content or so-called middle cis polybutadiene having a cis content of about 35% can be used.

The component (A) of the present invention has a soft component particle content of 5 to 25% by weight, preferably 10 to 20% by weight. If the content is too small, the easy-opening property will be poor, while if the content is too large, the sealing strength will be low.

Here, the content of the soft component particles in the component (A) is measured by the following method. Specifically, about 0.5 g of the sample (A) component was precisely weighed (weight: W ₁ ), and the sample was taken at room temperature (about 23 ° C.) in a mixed solvent of methyl ethyl ketone / methanol (methyl ethyl ketone / methanol volume ratio = 10/1). ) Dissolve in 50 ml. Next, the insoluble matter during the dissolution is isolated by centrifugation and decantation, and the insoluble matter is dried and its weight (W ₂ ) is measured. The content of the soft component particles is W ₂ / W ₁ × 100
It is determined by weight%.

In the present invention, the soft component particles are constituted by a core portion, which is a single continuous phase composed of only a styrene-based polymer, and a shell portion composed of a rubber-like polymer containing the core portion (occlude). In addition, those having a so-called single occlusion structure (also referred to as a core / shell structure or a capsule structure), and a plurality of small particles of a styrene-based polymer dispersed in a continuous phase composed of a rubber-like polymer are present. Any of those having a so-called salami structure can be used.

As the component (A), commercially available products can be used.

The component (B) of the present invention is a polyolefin resin. Specific examples of the polyolefin resin include:
Examples include ethylene homopolymer, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, propylene homopolymer, block or random polypropylene, or a mixture thereof.

The component (C) of the present invention is a hydrogenated product of a styrene-isoprene block copolymer rubber.

The ratio between styrene and isoprene before hydrogenation is usually 40/60 to 80/20 (weight ratio).
If the proportion of styrene is too small or too large, the compatibility is poor and the sealing strength may be poor.

The component (C) is obtained by hydrogenating (hydrogenating) the styrene-isoprene block copolymer described above, and preferably has 70% or more of the double bonds in the isoprene block portion hydrogenated. More preferably 90% or more is hydrogenated. If the hydrogenation rate is too low, the compatibility is poor and the sealing strength may be poor.

As the component (C), a corresponding commercially available product can be used.

The content ratio of each of the components (A) to (C) in the present invention is 50 to 80% by weight, preferably 50 to 70% by weight of the component (A).
0 to 45% by weight, preferably 20 to 40% by weight;
(C) Component 3 to 20% by weight, preferably 5 to 10% by weight
(Note that (A) component + (B) component + (C) component =
100% by weight. ).

When the amount of the component (A) is too small, the sealing strength and the sealing property are poor. On the other hand, when the amount of the component (A) is too large, the easy opening property is poor. If the amount of the component (B) is too small, the easy-opening properties and oil resistance are poor. On the other hand, if the amount of the component (B) is too large, the sealing strength and the sealing properties are poor. If the amount of the component (C) is too small, the sealing strength and the sealing property are inferior. On the other hand, if the amount of the component (C) is too large, the sealing strength and the sealing property are inferior and the cost is increased.

The method for obtaining the seal film of the present invention is not particularly limited, and examples thereof include the following method. That is, the components (A) to (C) and, if necessary, additives such as a stabilizer, a plasticizer, a colorant, and an antistatic agent are added, and the mixture is melt-kneaded by a single-screw extruder or a twin-screw extruder. A method of extruding from a T-die after melt-kneading with a machine, a method of extruding a sheet from an extruder, and then biaxially stretching by a tenter method, or a method of biaxially stretching by an inflation method. In addition, a styrene-butadiene block copolymer rubber may be added to adjust the sealing temperature of the seal film within a range that does not impair the effects of the present invention.

As a method for obtaining the cover material of the present invention, for example, a single-layer or multi-layer film base such as aluminum, polyolefin resin, polystyrene resin, polyamide resin, polyester resin, etc. is obtained by a coextrusion method or a lamination method. Above, there is a method of laminating the seal film of the present invention, and then processing the laminated film into a predetermined shape.

As a method for obtaining the container of the present invention, for example, there is a method in which a container body is filled with contents and a lid material is thermally welded to the container body. In addition, as a material of the container main body, a polystyrene resin, a composite material containing 50% by weight or more of the polystyrene resin, or the like is used.

The styrenic resin composition of the present invention is optimally used for seal film applications, but can be used in fields other than seal films by taking advantage of the above-mentioned characteristics of the styrenic resin composition.

[0029]

Next, the present invention will be described with reference to examples, but the present invention is not limited to the examples. Example 1 and Comparative Examples 1 to 4 The blends shown in Table 1 were melt-kneaded at a temperature of 220 ° C. using a twin-screw extruder (Model 2S25 manufactured by Toyo Seiki Seisaku-sho, Ltd.) to obtain pellets. The pellets were press-molded at 220 ° C. to form a sample film (100 μm in thickness).
Heat sealability and oil resistance were evaluated by the following methods. Table 1 shows the results.

(1) Heat Sealability The sample film was heat-sealed with a 300 μm HIPS sheet (M583 manufactured by Sumitomo Chemical Co., Ltd.) at 2 kg / cm ² × 3 seconds. At this time, the heat sealing temperature was changed, and the heat sealing strength at each temperature was measured. The measurement of the seal strength was performed in accordance with JIS K6854. However, the peeling angle is 180 ° (bending the film to 180 °)
And the peeling speed was 300 mm / min. When the seal strength is less than 500 g / 25 mm, the sealing property is poor, while when the seal strength is 1000 g / 25 mm or more, the easy-open property is poor.

(2) Oil resistance The sample film was cut out into a circle having a diameter of 15 cm, folded in four, expanded in a conical shape, and set on a funnel set in a beaker. 3 cc of coconut oil was poured therein, the beaker and the funnel were placed in a constant temperature chamber at 100 ° C., and left for 1 hour, and the presence or absence of oil leakage was observed. The test was repeated three times, and the case where no oil leakage occurred was represented by “○”, and the case where oil leakage occurred even once was represented by “×”.

Here, it can be seen from the results that in Example 1, which satisfies the conditions of the present invention, favorable seal strength was obtained in a wide temperature range and oil resistance was excellent. on the other hand,
Comparative Examples 1 and 2 lacking the component (C) are inferior in seal strength,
Poor sealing performance. In Comparative Examples 3 and 4 lacking the component (B), the seal strength is greatly changed due to the temperature change, and it is difficult to perform optimal control. When the seal temperature is low, the sealability is poor, and when the seal temperature is high, the easy-opening property is sharp. And poor oil resistance.

[0033]

[Table 1] Example Comparative Example 1 1 2 3 4配合 Formula * 1 (A) component wt% 60 60 60 100 70 (B) component wt% 30 40 30 0 0 (C) component wt% 10 0 0 0 0 (D) component wt% 0 0 10 0 30 Evaluation Seal strength g / 25mm Seal temperature 140 ℃ 500 <10 350 <10 150 150 ℃ 600 <10 400 250 900 160 ℃ 700 <10 400 1500 2000 Oil resistance ○ × ○ × × ────────────────────────────────

* 1 Component (A): Rubber-modified styrene resin having a soft component particle content of 19% by weight (Sumibrite M583 manufactured by Sumitomo Chemical Co., Ltd .; styrene monomer = styrene; rubbery polymer = butadiene) Polymer; structure of soft component particles = salami structure) (B) component: low-density polyethylene (Sumikasen G401 manufactured by Sumitomo Chemical Co., Ltd .; melt flow rate = 4 g / 10 minutes;
(Density = 0.925 g / cm ³ ) Component (C): Styrene-isoprene block copolymer (Septon 2104 manufactured by Kuraray Co., Ltd .; ratio of styrene and isoprene before hydrogenation = 65/35 (weight ratio); (Hydrogenation rate of double bond = 97% or more) (D) Component: Styrene-butadiene block copolymer rubber (Taphrene A manufactured by Asahi Kasei Corporation; ratio of styrene and butadiene = 40/60 (weight ratio)) (A) component -Amount of component (D):% by weight of each component (provided that component (A) + component (B) + component (C) + component (D) = 100% by weight).

[0035]

As described above, according to the present invention, the seal strength, the sealability, the ease of opening and the oil resistance are improved in a well-balanced manner. And a container using the lid material.

Claims (5)

(57) [Claims] 1. A sealing film for a cover material comprising a styrene resin composition containing the following components (A) to (C). Component (A): 50 to 80% by weight of a rubber-modified styrene resin having a soft component particle content of 5 to 25% by weight Component (B): 10 to 45% by weight of a polyolefin resin (C) Component: Styrene-isoprene Hydrogenated block copolymer rubber 3 to 20% by weight 2. The sealing film for a lid material according to claim 1, wherein the ratio of styrene to isoprene before hydrogenation of the component (C) is 40/60 to 80/20 (weight ratio). 3. The seal for a lid material according to claim 1, wherein the component (C) is one in which 70% or more of the double bonds in the isoprene block portion before hydrogenation are hydrogenated. the film. 4. A cover material comprising the seal film for a cover material according to claim 1 as a seal layer. 5. A container using the lid material according to claim 4 .