JP3504912B2 - Heat sealable film - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat-sealable film which is excellent in hand-cutting property and dead-hold property as a constituent material for packaging materials such as foods, and particularly suitable as a film for stick packaging forms such as chewing gum and candy. Heat sealable film.

[0002]

2. Description of the Related Art Conventionally, cellophane has been used as a base material as a constituent material of a packaging material for packaging foods, especially confectionery and tea leaves,
So-called moisture-proof cellophane coated with vinyl chloride-vinyl acetate copolymer or a film (K-coated cellophane) having vinylidene chloride as a base material and using cellophane as a base material has been used. For example, as a packaging material for stick-wrapping chewing gum, candy, etc., a laminated body having a structure such as moisture-proof cellophane / adhesive layer / aluminum foil / adhesive layer / hot-melt adhesive layer is used. Dead-hold property (folding property), hand-cutting property, and heat-sealing property for fixing the packaging material have been required. In addition, as a packaging material for storing tea leaves, a laminated body having a structure such as moisture-proof cellophane / polyethylene / aluminum foil / polyethylene is formed into a bag shape. Heat sealability was required.

Moisture-proof cellophane and K-coated cellophane have excellent dead-holding property, hand-cutting property, and heat-sealing property, but the cellophane base material is expensive and there is a concern about supply in the future. Therefore, there is a demand for a film that replaces moisture-proof cellophane or K-coated cellophane, and in particular, a film that has a base material that replaces cellophane, but hitherto no film satisfying both the dead hold property and the hand tearability has been obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sealable film which is excellent in dead-holding property and hand-cutting property and which does not use cellophane as a substrate.

According to the present invention, the film is pre-notched.
Tear strength, which indicates hand tearability, measured without
00g or more and 1000g or less, and dead hold
With a bending angle of 90 ° or less that shows
And heat-sealing film with excellent dead hold
The substrate is a polyester film having a thickness of 4 μm or more and 10 μm or less, and a thickness of at least one surface of the substrate is
It is characterized in that it has a heat-sealing layer of 0.3 μm or more and 5 μm or less .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a polyester film as a base material is mainly composed of a polyester resin. The polyester as the main component of the polyester resin is not particularly limited, and polyalkylene terephthalate resins such as polyethylene terephthalate, polybutylene terephthalate, poly 1,4-cyclohexyl dimethylene terephthalate, polyethylene-2,6-naphthalate, Examples thereof include polyalkylene naphthalate resins such as polybutylene-2,6-naphthalate. These are not limited to homopolymers, and may be dicarboxylic acids and / or diols, which are constituent components of polyester, with a part of the dicarboxylic acids and / or other diols substituted. Further, other components may be contained in addition to the polyester as long as the action of the present invention is not impaired.

In the present invention, the thickness of the polyester film as the base material is preferably 3 μm or more and less than 12 μm, more preferably 3 μm or more and 10 μm or less,
Particularly preferably, it is 4 μm or more and 10 μm or less. When the thickness is less than 3 μm, the strength is lowered, and the step of forming the heat seal layer, and further the step of printing on the heat seal film of the present invention when forming the packaging material using the heat seal film of the present invention. Also, when laminated with other materials, the film is likely to be broken or it is difficult to wind the film. Further, when the thickness is 12 μm or more, the hand-cutting property and the dead hold property are deteriorated.

In the present invention, the material constituting the heat-sealing layer is not particularly limited as long as it is a material exhibiting adhesion to the polyester film as the base material. Examples of such a material include a thermoplastic copolyester resin. As such a thermoplastic copolyester resin, specifically, dicarboxylic acids such as terephthalic acid and isophthalic acid, aliphatic carboxylic acids such as adipic acid and sebacic acid, ethylene glycol, 1,4-butanediol, Examples thereof include copolymers with diols such as diethylene glycol and neopentyl glycol.
These may be used alone or in combination of two or more.

The material constituting the heat seal layer is
It may be crosslinked with a curing agent such as isocyanate in order to improve the adhesion to the substrate. The curing agent may be used alone or in combination of two or more. The mixing amount of the curing agent is not particularly limited,
It is preferably 1 part by weight to 20 parts by weight, and more preferably 2 parts by weight to 10 parts by weight with respect to 100 parts by weight of the resin which is the main constituent of the material constituting the heat seal layer. If the compounding amount of the curing agent is less than 1 part by weight, the effect of compounding the curing agent cannot be obtained, and if it is more than 20 parts by weight, the heat-sealing start temperature becomes high.

As the material constituting the heat-sealing layer, an acrylic resin or the like can be used in addition to the above-mentioned thermoplastic copolyester resin. As the acrylic resin, a polyester film which is a base film,
Any material can be used as long as it exhibits sufficient adhesion during heat sealing. For example, as the constituent monomer of the acrylic resin, for example, styrene, ethyl methacrylate, methyl methacrylate, acrylonitrile, methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, hydroxy. Examples thereof include ethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate and the like. These may be used alone or in combination of two or more.

When the above acrylic resin is used as the material for the heat seal layer, a curing agent may be used in combination to improve the adhesion to the polyester film as the base material. Examples of the curing agent include an aqueous emulsion of a polycarbodiimide resin containing a carbodiimide group.

As the material for the heat-sealing layer, in addition to the resin as the main constituent material as described above, it is preferable to add fine particles as an anti-blocking agent for preventing blocking. The fine particles include PMM
At least one kind of fine particles selected from A resin fine particles, silica fine particles, acrylic resin fine particles, and colloidal silica is preferable. The amount of the fine particles to be compounded is not particularly limited, but is preferably 0.1 to 1 part by weight, and more preferably 0.2 to 100 parts by weight of the resin as the main constituent material.
˜0.8 parts by weight, particularly preferably 0.4 to 0.6 parts by weight. If the amount of the fine particles is less than 0.1 part by weight, the effect of the compounding is insufficient, and if it exceeds 1 part by weight, the transparency of the film tends to decrease. The above antiblocking agents may be used alone or in combination of two or more.

The material constituting the heat seal layer may contain waxes in order to improve the slip property of the surface of the heat seal layer. Examples of the waxes include plant waxes typified by carnauba wax, animal waxes typified by lanolin, mineral oil waxes typified by ozokerite, artificial waxes including peat wax, and aliphatic typified by stearyl alcohol. It is selected from alcohol. The blending amount of the above waxes is not particularly limited, but it is preferably 0.2 to 2 parts by weight with respect to 100 parts by weight of the resin which is the main constituent material. If the compounding amount of waxes is less than 0.2 parts by weight, the effect of compounding is insufficient, and if it exceeds 2 parts by weight, heat sealability may be impaired.

The glass transition temperature or melting point of the material mainly constituting the heat seal layer is preferably 40 ° C. or higher 1
20 ° C. or lower, and more preferably 50 ° C. or higher and 100 ° C. or lower. Glass transition temperature or melting point is 4
When the temperature is lower than 0 ° C, a film blocking phenomenon is apt to occur when the heat-sealing films of the present invention are stacked or formed into a roll, and when higher than 120 ° C, the temperature range in which heat sealing is possible is high. Become.

In the present invention, the thickness of the heat seal layer is not particularly limited, but is preferably 0.3 μm or more and 5 μm or more.
Hereafter, it is more preferable that the thickness is 1 μm or more and 3 μm or less. If the heat-sealing layer is less than 0.3 μm, it is difficult to obtain sufficient sealing strength, and if it exceeds 5 μm, the cost tends to be disadvantageous.

The method for producing the heat-sealable film of the present invention is not particularly limited, and even if the polyester film as the base material and the heat-sealing layer are simultaneously formed, the base material is separately molded and the heat-resistant film is heat-treated on the base material. A seal layer may be formed. Specifically, a method of simultaneously forming a heat-sealing layer by a co-extrusion method or the like at the time of molding a polyester film of a substrate, a method of forming a heat-sealing layer by hot-melt coating on a substrate previously formed into a film shape, Examples include a method of providing a heat-sealing layer by coating a film-shaped substrate with a coating liquid in which the constituent components of the heat-sealing layer are dissolved and dispersed in a solvent. For example, the components of the heat seal layer may be coated on the substrate as an emulsion. The solvent for dissolving / dispersing the constituent components of the heat seal layer may be appropriately selected depending on the material used, and examples thereof include organic solvents and water, and a mixture thereof may be used. In addition, the molding conditions of the heat seal layer such as the base material and co-extrusion,
The molding method and the coating method and coating conditions for separately forming the heat-sealing layer are not particularly limited, and the methods and conditions generally used in general can be used. Further, the surface of the polyester film of the substrate may be subjected to a surface treatment before forming the heat seal layer.

In the present invention, the heat-sealing layer may be formed on only one side of the substrate or on both sides.

In the present invention, the heat seal layer is preferably formed on the entire surface of one side or both sides of the base material, but it may be formed only on a portion necessary for suitability as a packaging material. When the heat seal layer is partially formed, a method such as gravure printing using a general gravure printing machine can be used as a method for forming the heat seal layer.

The heat seal layer preferably has a heat seal strength of 20 g / 15 mm width or more.
When the heat seal strength is less than 20 g / 15 mm width,
The packaging suitability of the packaging material using the heat-sealable film of the present invention decreases.

The heat-sealable film of the present invention can be used alone as a packaging material, but can also be laminated with other materials and used as a packaging material. Other materials include paper, metals such as aluminum, resin films,
Materials that are generally used for packaging materials, such as adhesives, can be used, and the configuration and the stacking method are not particularly limited. Also,
The heat-sealable film of the present invention may be subjected to coloring treatment or image forming treatment by printing or the like.

As a packaging material using the heat-sealable film of the present invention, a packaging material having a multilayer structure having at least a layer made of the heat-sealable film of the present invention, a layer made of paper and a layer made of aluminum foil. Examples thereof include a packaging material having at least another layer structure formed by sequentially laminating the heat-sealable film of the present invention, an aluminum foil, and paper.

In the case of having the above-mentioned multilayer structure, it is preferable that the paper has a basis weight of 25 g / m ² or more and 100 g / m ² or less. Further, the thickness of the aluminum foil is preferably 5 μm or more and 10 μm or less.

The present invention will be described in more detail below with reference to test examples and examples, but the present invention is not limited thereto. Test Example Test Method (1) Hand-cutability (tear strength) The films of Examples 1 to 3, Comparative Examples 1 and 2 and Reference Examples 1 and 2 were 10 cm (a in FIG. 1) × 7 cm (b in FIG. 1). Cut into small pieces, and as shown in FIG. 1, width 5 cm (c in FIG. 1),
An adhesive tape having a length of 10 cm (d in FIG. 1) (polyester adhesive tape 6200, manufactured by Sliontech Co., Ltd. 6200: indicated by 2 in the figure) was attached to the small piece (indicated by 1 in the figure) in the MD direction (arrow MD in FIG. 1) 5 cm (e in FIG. 1) so that it overlaps, and put a notch (indicated by 3 in the figure) on the adhesive tape of the part that does not overlap with the small piece parallel to the MD direction of the small piece (the notch does not enter the film) Test piece was prepared. Using a tensile tester, the adhesive tape on both sides of the notch was pulled in opposite directions at a crosshead speed of 30 mm / min, and the maximum strength (tear strength) when the film was torn was measured to evaluate hand tearability. did. As for the hand-cutting property, a tear strength of less than 100 g or a value of more than 1000 g was regarded as unacceptable. When the film is torn, the relationship between the strength and the moving distance of the crosshead is shown in FIG. 2, and the point (f) in FIG. 2 is the strength when the film starts to be torn. "Tear strength" in indicates the strength at point (f).

(2) Dead Hold Property (Bending Angle) The films of Examples 1 to 3, Comparative Examples 1 and 2 and Reference Examples 1 and 2 were 60 mm (f in FIG. 3) × 70 mm (g + h in FIG. 3).
After being cut into small pieces of 10 mm and folding back the end portion 10 mm in the length direction (h in FIG. 3) as shown in FIG. 3 (a), as shown in FIG. 3 (b), glass having a size of 60 mm × 60 mm and a thickness of 2 mm A plate (indicated by 5 in FIG. 3 (b)) is placed on a small piece (indicated by 4 in FIG. 3), and a 2 kg weight (indicated by 6 in FIG. 3 (b)) is placed on the glass plate. Is placed and the load F is 6
It took 0 seconds. After removing the weight and the glass plate, the rebound angle (bending angle, D in FIG. 3 (c)) of the folded back portion after 10 seconds was measured and used as the value of the dead hold property.

(3) Heat Seal Strength The films of Examples 1 to 3, Comparative Examples 1 and 2 and Reference Examples 1 and 2 were cut into two pieces (width 60 mm × length 80 mm), and each of the pieces was cut. Cellophane adhesive tape for packaging (cellophane tape No. 405, made by Nichiban) on the non-heat-sealed surface (the surface of the base material opposite to the surface on which the seat heel layer is formed)
Was adhered to each other, the heat-sealing layers of the small pieces were adhered to each other, heat-sealed for 1 second under the condition of 1 kg / cm ² , and 150 ° C., and then cut into a width of 15 mm to prepare a test piece. Each end of the two films of the test piece was moved in the opposite direction by a tensile tester at a crosshead speed of 30.
It was pulled at a speed of 0 mm / min, and the maximum peel strength was taken as the heat seal strength. In addition, the measurement was performed on three test pieces, and the measured value was the average value.

(4) Blocking resistance With respect to the films of Examples 1 to 3, Comparative Examples 1 and 2, and Reference Examples 1 and 2, rolls having a width of 200 mm and a length of 4000 m were prepared, and the rolls were kept at 40 ° C. and 30% RH. Save for 1 month,
The blocking resistance when the roll was unwound was evaluated based on the following criteria. [Evaluation Criteria] O : No blocking was observed even when the core was unwound. Δ : Blocking was observed when unwound to the vicinity of the core. X: Blocking was observed from the beginning of winding.

Test results Table 1 shows the results of the above tests (1) to (4).

[0028]

Example 1 Saturated copolymerized thermoplastic polyester resin (manufactured by Unitika,
Elitel 3201: Resin glass transition temperature = 65 ° C)
Is a mixed solvent of toluene and MEK (weight ratio: toluene /
MEK = 1/1) was dissolved in a mixed solvent to a solid content concentration of 10 wt%, and isocyanate (Coronate L, manufactured by Nippon Polyurethane) was added to 5 parts by weight with respect to 100 parts by weight of the polyester resin. A coating liquid was prepared by adding acrylic resin fine particles having an average particle diameter of 1.5 μm as an anti-blocking agent so as to be 0.4 parts by weight with respect to 100 parts by weight of the polyester resin. Using a polyester film (film thickness 6 μm, K200 manufactured by Mitsubishi Kagaku Polyester Film Co., Ltd.) as a base material, one side of the base material is coated with the coating liquid so that the coating amount when dried is 1.0 g / m ^2. Then, it dried and formed the heat seal layer and obtained the heat sealable film.

Example 2 A polyester film (film thickness 9 μm as a substrate
m, Mitsubishi Kagaku Polyester Film Co., Ltd., M16
0) was used, and a heat-sealing film was obtained in the same manner as in Example 1 except that the thickness of the heat-sealing layer was 2 g / m ² in terms of the coating amount when dried.

Example 3 The thickness of the heat-sealing layer was 0.5 g / m in terms of coating amount when dried.
^A heat-sealable film was obtained in the same manner as in Example 1 except that the number was changed to ² .

Comparative Example 1 A polyester film (film thickness 12 μm as a base material
A film was obtained in the same manner as in Example 1 except that m) was used.

Comparative Example 2 A film was obtained in the same manner as in Example 1 except that a transparent polypropylene film (film thickness 20 μm) was used as the substrate.

Reference Example 1 A film was obtained in the same manner as in Example 1 except that the resin constituting the heat seal layer was a polyester resin (manufactured by Unitika, Elitel 3230: resin glass transition temperature = 35 ° C.).

Reference Example 2 The thickness of the heat-sealing layer was 0.1 g / m in terms of coating amount when dried.
^A heat-sealable film was obtained in the same manner as in Example 1 except that the number was changed to ² .

[0035]

[Table 1]

[0036]

EFFECTS OF THE INVENTION The heat-sealing film of the present invention is excellent in dead-holding property and hand-cutting property, is advantageous in cost, and can be stably supplied, even though cellophane is not used as a substrate. .

[Brief description of drawings]

FIG. 1 (a) is a view showing the configuration of a test piece for measuring tear strength from the front direction, and FIG. 1 (b) is FIG. 1 (a).
It is a figure which shows the test piece of FIG.

FIG. 2 is a diagram showing a relationship between a film strength and a moving distance of a cross head in tear strength measurement.

FIG. 3 (a) is a view showing a structure of a test piece for measuring a bending angle showing a dead hold property, FIG. 3 (b).
FIG. 3 is a diagram showing a method for measuring a bending angle, and FIG. 3C is a diagram showing measurement points for the bending angle.

[Explanation of symbols]

1,4 film 2 Adhesive tape 3 notches 5 glass plates 6 weights

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 10-305868 (JP, A) JP 11-70607 (JP, A) JP 5-294056 (JP, A) JP 58- 147354 (JP, A) JP-A-2-43047 (JP, A) JP-A-50-14731 (JP, A) JP-A-8-224846 (JP, A) JP-A-10-510771 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 7/04

Claims (5)

(57) [Claims] 1. A state in which a notch is not previously formed in a film
Tear strength indicating hand tearability measured is 100g or more
Folds less than 1000g and showing dead hold
Hand bendability and deadness with a bending angle of 90 ° or less
A heat-sealing film having an excellent hold property, wherein a polyester film having a thickness of 4 μm or more and 10 μm or less is used as a base material, and the thickness is 0.3 or more on at least one surface of the base material.
A heat-sealing film having a heat-sealing layer having a thickness of not less than μm and not more than 5 μm . 2. The heat-sealable film according to claim 1, wherein the material mainly constituting the heat-sealing layer has a glass transition temperature or a melting point of 40 ° C. or higher and 120 ° C. or lower. 3. The heat seal layer is anti-blocking
Polymethylmethacrylate (PMMA) resin
Particles, silica particles, acrylic resin particles or colloiders
Contains at least one type of fine particles selected from rusilica
Heat seam according to claim 1 or 2, characterized in that
Film. 4. A consists heat sealable film according to any one of claims 1 to 3 layers, a layer made of paper,
A packaging material having a multilayer structure having at least a layer made of aluminum foil. 5. A packaging material having at least a multi-layer structure in which the heat-sealable film according to any one of claims 1 to 3 , an aluminum foil, and paper are sequentially laminated.