JPH09151284A - Seal film, cover material and container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal film improved in sealing strength, sealability, easy openability and oil resistance while keeping a good balance among them, a cover material using this seal film and a container using this cover material. SOLUTION: A seal film made from a polystyrene resin composition comprising 100 pts.wt. polystyrene resin and above 10 to 250 pts.wt. polymer having a solubility parameter (SP) of 8.45-8.70 and freed from any aromatic vinyl units, a cover material having a seal layer made of this film and a container having a cover made of this cover material are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a seal strength, a sealing property,
A sealing film comprising a styrene-based resin composition most suitable for use as a sealing layer, in which easy-opening property and oil resistance are improved in a well-balanced manner, a lid material using the sealing film, and a container using the lid material Is.

[0002]

2. Description of the Related Art For example, containers for foods, medicines, cosmetics, etc., are used with a main body for containing contents covered with a lid.
Polystyrene resin is generally used for the main body, and after the contents to be filled in the main body are stored, a heat-sealable lid is heat-welded and sealed. Conditions required in such a case include high sealing strength, excellent sealing property, easy opening property, and excellent oil resistance. The easy-open property means that the lid member can be easily peeled off from the container main body when using food or the like. By the way, the lid material is usually a single-layer or multi-layer film of aluminum, a polyolefin resin, a polystyrene resin, a polyamide resin, a polyester resin or the like as a base material, and a resin film having heat sealability is laminated on the base material. Then, the laminated film is processed into a predetermined shape to obtain a lid material. Japanese Patent Publication No. 47-34808 discloses a sealing material composed of a rubber-modified styrene resin and a styrene-butadiene block copolymer rubber. EP (European Patent) 215333 discloses a sealing material composed of rubber-modified styrene resin, styrene-butadiene block copolymer rubber and mineral oil. Further, JP-A-4-144744 discloses a sealing material composed of a rubber-modified styrene resin, a styrene-butadiene block copolymer rubber and an olefin resin. However, these sealing materials have been insufficient from the viewpoint of improving the balance of sealing strength, sealing property, easy-opening property and oil resistance in a well-balanced manner.

[0003]

In view of the above situation, the problems to be solved by the present invention include sealing strength, sealing property,
Another object is to provide a sealing film in which the easy-open property and the oil resistance are improved in a well-balanced manner, a lid material using the sealing film, and a container using the lid material.

[0004]

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 of the inventions is for sealing using a polystyrene resin composition containing more than 10 parts by weight and 250 parts by weight or less of the component (B) with respect to 100 parts by weight of the following component (A). It provides a film. (A): Polystyrene resin (B): Solubility parameter (SP) is 8.45 to 8.7.
0, and the polymer does not contain an aromatic vinyl compound unit in the polymer. Further, of the present invention, the second invention provides a lid material using the above-mentioned sealing film as a sealing layer. The third invention of the present invention provides a container using the above-mentioned lid member. The details will be described below.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As the polystyrene resin as the component (A) used in the present invention, so-called general-purpose polystyrene resins, rubber-modified polystyrene resins and mixtures thereof can be used. Here, general-purpose polystyrene resin means GPPS (general purpose).
Also referred to as polystyrene), the rubber-modified polystyrene-based resin is obtained by polymerizing a styrene-based monomer in the presence of a rubber-like polymer, and has a high impact polystyrene (HIPS: high impact porosity).
It is also called lystherene). Examples of the styrene-based monomer include styrene, α-alkyl-substituted styrene such as α-methylstyrene, and nuclear-substituted alkylstyrene such as p-methylstyrene. Examples of the compound copolymerizable with the styrene-based monomer include vinyl monomers such as acrylonitrile, methacrylonitrile, methacrylic acid and methyl methacrylate, maleic anhydride, maleimide, and nucleus-substituted maleimide. Further, as the rubber-like polymer, for example, polybutadiene, styrene-butadiene copolymers, terpolymers of ethylene-propylene-non-conjugated diene and the like are used. Among them, polybutadiene and styrene-butadiene copolymers are used. Coalescents are preferred.
As the polybutadiene, both high cis polybutadiene having a high cis content and low cis polybutadiene having a low cis content can be used. In the present invention, (A)
When a rubber-modified styrene-based resin is used as the component polystyrene-based resin, the soft component particles in the resin include, for example, a core portion that is a single continuous phase composed of only the styrene-based resin and an inclusion (occlude occlude) of the core portion.
Having a single occlusion structure (also referred to as a core / shell structure or a capsule structure) composed of a shell portion made of a rubbery polymer, or a plurality of styrenic resins in a continuous phase made of a rubbery polymer. Examples thereof include those having a so-called salami structure in which small particles exist in a dispersed state, but the structure is not particularly limited.
The structure of the soft component particles can be observed by making an ultrathin section of the rubber-modified polystyrene-based resin and taking a transmission electron micrograph thereof.

As the method for producing the polystyrene resin as the component (A) used in the present invention, a bulk polymerization method or a bulk / suspension two-stage polymerization is used. Then, the polystyrene-based resin satisfying the conditions of the present invention can be obtained by adjusting the concentration of the rubber-like polymer, the stirring speed, the temperature and the like during the polymerization reaction. Next, in the present invention, (B) a polymer having a solubility parameter (SP) of 8.45 to 8.70 and containing no aromatic vinyl compound unit in the composition is (A) 100 parts by weight of a polystyrene resin. However, if the content is 10 parts by weight or less, the sealing strength is not sufficient, and if the content is more than 250 parts by weight, the sealing strength is not sufficient. The content of the component (B) in the composition of the present invention is converted from the area ratio of the component (B) occupying in the photograph by making an ultrathin section of the composition and taking a transmission electron micrograph of the composition. You can ask. In addition, a method of obtaining from the absorption peak using a spectroscope such as NMR or IR, a method of performing fractionation using a solvent, and the like can be used. Further, the solubility parameter (SP) of the component (B) of the present invention is 8.45 to 8.70,
If it is smaller than 8.45 or larger than 8.70, the seal strength is poor. The solubility parameter here means Hil
The attraction between molecules is defined by the debrand-Scatchard theory. For detailed explanations, refer to general textbooks on polymer science, such as "Polymer Blend, Saburo Akimoto et al., CMC, 4th edition, 12".
5 to 144 (1991) ”, etc. However, this solubility parameter can be obtained by experiments such as the viscosity method or the swelling method, or by calculation from the molecular structure. Is slightly different, so S
The method of calculating from the molecular structure proposed by mall was used here. This method and theory is described in "Journal of Applied Chemistry".
al of Applied Chemistry),
3, p. 71-80 (1953) ". Solubility parameters were calculated using the following equation.

[0007]

(Equation 1) Fi represents a molar attraction force of a constituent group such as an atom or an atomic group constituting a molecule and a bond type, V represents a molar volume, and ρ represents a density. M represents a molecular weight, and in the case of a polymer, represents a molecular weight of a repeating unit (that is, a monomer unit). As the value of Fi, the value of Small described in the above two documents was used. For ρ, ΣFi or M of the copolymer, ρ, ΣF of each homopolymer of the monomer units constituting the copolymer
The sum of the values of i or M multiplied by the mole fraction of monomer units was calculated and used. The component (B) of the present invention is a polymer containing no aromatic vinyl compound unit in the polymer. A composition using a polymer containing an aromatic vinyl compound unit has poor seal strength. Examples of aromatic vinyl compounds include styrene, α-alkyl-substituted styrenes such as α-methylstyrene, and nuclear-substituted alkylstyrenes such as p-methylstyrene. Further, the polymer having a solubility parameter (SP) of the component (B) used in the present invention of 8.45 to 8.70 is at least one of unsaturated carboxylic acid, unsaturated carboxylic acid ester or vinyl acetate. And a copolymer of ethylene and vinyl monomer. Examples thereof include ethylene-unsaturated carboxylic acid copolymers, ethylene-unsaturated carboxylic acid ester copolymers, ethylene-vinyl acetate copolymers, ethylene-unsaturated carboxylic acid ester-vinyl acetate terpolymers, ethylene. And a multi-component copolymer composed of two or more kinds of unsaturated carboxylic acid esters. Specific examples of the unsaturated carboxylic acid include acrylic acid and methacrylic acid. Further, as a specific example of the unsaturated carboxylic acid ester, ethyl acrylate,
Methyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, 2
-Ethylhexyl methacrylate, stearyl methacrylate, glycidyl methacrylate and the like can be mentioned.

Preferred examples of the copolymer of one or more vinyl monomers of unsaturated carboxylic acid, unsaturated carboxylic acid ester or vinyl acetate used in the present invention and ethylene are ethylene-acrylic acid copolymer and ethylene. -Methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl Acrylate-glycidyl methacrylate copolymer, ethylene-methyl methacrylate-glycidyl methacrylate copolymer, ethylene-
Examples thereof include vinyl acetate-glycidyl methacrylate copolymer. The ratio of the vinyl monomer to ethylene in the copolymer is determined by the solubility parameter (SP) 8.45 to 8.7.
It can be appropriately determined within a range that gives a copolymer of 0. The ratio of the vinyl monomer in the copolymer is 5 to 60.
% By weight is preferred. Further, there is no limitation on the binding mode (for example, random, block, alternating) between the vinyl monomer and ethylene in the copolymer. The melt flow rate of the copolymer is not particularly limited (based on JIS K7210, temperature 190 ° C., load 2.16 kgf), but is preferably about 1 to 500 g / 10 minutes.

The method for obtaining the sheet film of the present invention is not particularly limited, but the following method can be used, for example. That is, the components (A) and (B) and, if necessary, additives such as stabilizers, plasticizers, colorants and antistatic agents are added, and melt-kneading using a single-screw extruder, a twin-screw extruder or the like. A method of melt-kneading with a machine and then extruding from a T-die, a method of extruding into a sheet from an extruder and then biaxially stretching with a tenter method, or a method of biaxially stretching with an inflation method. Further, in order to adjust the strength of the seal film, a styrene-butadiene block copolymer rubber may be added within a range that does not impair the effects of the present invention.

As a method for obtaining the lid material of the present invention, for example, a single layer or multi-layer film substrate of aluminum, polyolefin resin, polystyrene resin, polyamide resin, polyester resin or the like is prepared by a coextrusion method or a laminating method. There is a method of laminating the seal film of the present invention on a material and then processing the laminated film into a predetermined shape.

As a method for obtaining the container of the present invention, for example, a method of filling the container main body with the contents and then thermally welding a lid member to the container main body can be mentioned. As the material of the container body, a polystyrene resin, a composite material containing 50% by weight or more of a polystyrene resin, or the like is used.

[0012]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples. Examples 1 to 5 and Comparative Examples 1 to 4 The compositions shown in Tables 1 and 2 were combined with a twin screw extruder (manufactured by Toyo Seiki Seisakusho,
Melt kneading using a model 2S25) at a temperature of 220 ° C.,
Pellets were obtained. The pellets were press-molded at 220 ° C. to obtain a sample film (thickness 50 μm). The heat sealability and oil resistance were evaluated by the following methods. The results are shown in Tables 1 and 2. (1) Heat-sealing property A sample film is a HIPS sheet of 300 μm (manufactured by Sumitomo Chemical Co., Ltd., trade name Sumibrite M583) and 2 kg / cm.
Heat seal for ² × 3 seconds. At this time, the heat sealing temperature was changed and the heat sealing strength at each temperature was measured.
The seal strength was measured according to JIS K6854. However, the peeling angle is 180 degrees (1 film
It was bent to 80 degrees) and the peeling speed was 300 mm / min. If the sealing strength is less than 500 g / 25 mm, the sealing performance is poor, while the sealing strength is 1000 g / 25 mm.
In the above cases, the ease of opening is poor. (2) Oil resistance A sample film was cut out into a circle with a diameter of 15 cm, folded in four, spread in a conical shape, and set on a funnel standing in a beaker. 3 ml of coconut oil was poured therein, the beaker and the funnel were placed in a thermostatic 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 once was marked with "O", and the case where oil leakage occurred even once was marked with "X". The (A) polystyrene resin used was A1: rubber-modified polystyrene resin,
Sumitomo Chemical Co., Ltd., trade name Sumibright M583 (soft component particle amount is 19% by weight, soft component particle structure is salami structure), A2: rubber modified polystyrene resin, Sumitomo Chemical Co., Ltd., trade name Sumibright M540 (soft component Particle amount is 1
6% by weight, the structure of the soft component particles is a salami structure). Also,
The component (B) used is B1: ethylene-methyl methacrylate copolymer, manufactured by Sumitomo Chemical Co., Ltd., trade name Acryft WM.
403 (methyl methacrylate content 38% by weight, melt flow rate 15 g / 10 min), B2: ethylene-vinyl acetate copolymer, Sumitomo Chemical Co., Ltd., trade name Summitate R
B-11 (vinyl acetate content 41% by weight, melt flow rate 60 g / 10 min), B3: polypropylene, manufactured by Sumitomo Chemical Co., Ltd., trade name Noblene AD571 (melt flow rate 0.2 g / 10 min), B4: polyethylene, Sumitomo Chemical industry, trade name Sumikasen α FZ103-0 (melt flow rate 0.9 g / 10 min). The melt flow rate was measured according to JIS K7210 at a temperature of 190 ° C. and a load of 2.16 kgf. Table 2 shows the solubility parameter SP of these components (B). The results show the following. The examples of the present invention have excellent seal strength and oil resistance. On the other hand, Comparative Example 1 in which the amount of the component (B) is small is inferior in oil resistance and seal strength. Comparative Examples 2 and 3 containing as the component (B) a polymer in which SP is out of the specified range have poor seal strength. Comparative Example 4 containing no component (A) is inferior in seal strength.

[0013]

[Table 1] * 1: (A) polystyrene resin * 2: (B) polymer shown in Table 2

[0014]

[Table 2] * 1: (A) polystyrene resin * 2: (B) polymer shown in Table 3

[0015]

[Table 3]

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area C08L 23/04 LCK C08L 23/04 LCK 33/12 LJB 33/12 LJB

Claims (6)

[Claims] 1. To 100 parts by weight of the following component (A),
A sealing film using a polystyrene resin composition containing the component (B) in an amount of more than 10 parts by weight and 250 parts by weight or less. (A): Polystyrene resin (B): Solubility parameter (SP) is 8.45 to 8.7.
A polymer which is 0 and does not contain an aromatic vinyl compound unit in the polymer. 2. The sealing film according to claim 1, wherein the component (B) is a copolymer composed of ethylene and at least one vinyl monomer selected from unsaturated carboxylic acids, unsaturated carboxylic acid esters or vinyl acetate. 3. The sealing film according to claim 1, wherein the component (B) is an ethylene-unsaturated carboxylic acid ester copolymer. 4. The sealing film according to claim 1, wherein the component (B) is an ethylene-methyl methacrylate copolymer. 5. A lid member comprising the sealing film according to claim 1, claim 2, claim 3 or claim 4 as a seal layer. 6. A container using the lid member according to claim 5.