JPH06182941A - Manufacture of heat sealable laminate - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] It has both antistatic ability and strong heat-sealing strength, and it has good paper feeding / discharging property in the printing machine. Provided is a laminate 2 which is used as a bag-forming material for pillow packaging, a heat-sealing lid material for containers, and an in-mold label, which prevents deterioration of heat-sealing strength and appearance due to adhesion of dust and the like. [Structure] A heat-sealable resin layer of a laminate 2 obtained by using a paper or plastic film layer as a base material layer, and providing a heat-sealable resin layer having a melting point lower than that of the base material layer on one or both surfaces thereof. 20-80% of the surface area of the heat-sealable resin layer is covered with 0.1-4 kw / m ²
The method for producing a heat-sealable laminate, which comprises forming an antistatic layer by applying a water-soluble antistatic agent to the corona discharge treated surface after the corona discharge treatment with the discharge amount of 1 and then drying.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to blow molding, injection molding,
A heat seal used as a heat-sealable lid material for a container such as an in-mold label and a bag forming material for pillow packaging, which is attached to the container as a label at the same time as forming the container by differential pressure molding, a cup noodle, yogurt, etc. To a method for producing a flexible laminate.

[0002]

2. Description of the Related Art Conventionally, it has been used as an in-mold label that is attached to a container as a label at the same time as molding the container, a bag forming material for pillow packaging, a heat-sealable lid material for containers such as cup noodles and yogurt. As a packaging material, pulp paper, polyethylene terephthalate, polyamide, polypropylene, etc. high melting point resin substrate surface is subjected to corona discharge treatment, ethylene / vinyl acetate copolymer, ethylene / methyl acrylate A laminate obtained by laminating a heat-sealable resin such as a copolymer or Surlyn (metal salt of ethylene / acrylic acid copolymer) is used (Japanese Patent Publication No. 46-14552 and Japanese Patent Publication No. 62-6096).
No. 9, Japanese Patent Publication No. 63-12792, Japanese Patent Publication No. 2-8890
See each bulletin of the issue). Further, in the above-mentioned method for producing the packaging material, a method is also used in which an antistatic agent such as an oil-soluble (non-water-soluble) fatty acid amine or fatty acid monoglyceride is kneaded.

[0003]

When the former packaging material is applied to a printing machine for printing, it does not have antistatic ability, so the paper feeding / discharging property of the printing machine is poor, and static electricity generated during printing causes Dust, dust, dust, etc. may adhere to the packaging material,
There are problems such as a decrease in heat seal strength and a decrease in appearance. In order to solve such a problem, the heat-sealable resin layer side of the packaging material is coated with a water-soluble antistatic agent and dried to provide an antistatic layer, which solves the above problem, This time, there was a defect that the heat seal strength was reduced. In the latter method of kneading the antistatic material, since it depends on the antistatic function by bleeding out the antistatic material to the surface of the heat-sealable resin, the antistatic function can be fully exerted in the initial stage immediately after the production. I couldn't do that. However, after a long period of time, the antistatic ability comes to be sufficiently exerted, but this time, there is a problem that the film members block each other and the heat seal strength is lowered during bag formation. Therefore, it is an object of the present invention to provide a packaging material which is excellent in antistatic ability and is less likely to cause a decrease in heat-sealing strength over time.

[0004]

[Means for Solving the Problems]

[Summary of the Invention] The present inventors have conducted intensive studies in view of the above problems, and as a result, the laminate subjected to a specific treatment has an excellent antistatic ability and a heat seal strength of The present invention has been completed based on the finding that it is a packaging material that does not easily deteriorate. That is, the method for producing a heat-sealable laminate of the present invention is obtained by using a paper or plastic film layer as a base material layer, and providing a heat-sealable resin layer having a lower melting point than the base material layer on one or both surfaces thereof. The surface of the heat-sealing resin layer of the obtained laminated body is covered with 20 to 80% of the surface area of the heat-sealing resin layer by 0.1
The antistatic layer is formed by applying a water-soluble antistatic agent to the corona discharge treated surface after a corona discharge treatment with a discharge amount of ˜4 kw / m ² and drying.

[Detailed Description of the Invention] [I] Laminate (1) Layer Constitution (a) Base Layer The material used as the base layer in the method for producing the heat-sealable laminate of the present invention is pulp paper. , Coated paper, synthetic paper made of stretched film of resin containing inorganic filler, polyethylene terephthalate, polyamide, polypropylene,
Polycarbonate, saponified ethylene / vinyl acetate copolymer, aluminum foil, etc., or laminated products of these materials,
Alternatively, those obtained by subjecting these base materials to aluminum vapor deposition or silicon oxide vapor deposition can be mentioned. The thickness of the base material layer is generally 8 to 200 μm, preferably 10 to 150 μm.
m.

(B) Heat-sealable resin layer One or both surfaces of the base material layer has a melting point lower than that of the material used for the base material layer, and preferably higher than that of the material used for the base material layer. A melting point lower than 10 ° C., particularly preferably 15 to 150 than the melting point of the material used for the base material layer.
A heat-sealable resin having a melting point lower than ℃ is used. Such heat-sealable resins include high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene / propylene copolymer,
Ethylene / vinyl acetate copolymer, ethylene / (meth) acrylic acid copolymer, ethylene / (meth) acrylic acid alkyl ester copolymer (where the carbon number of the alkyl group is 1 to
8), a metal salt of ethylene / (meth) acrylic acid copolymer (Zn, Al, Li, K, Na) or the like having a melting point of 80 to 13
An ethylene resin having a temperature of 8 ° C. may be mentioned. The heat seal resin layer may be a transparent film and may be unstretched or stretched. Further, it may be in a smooth state or a state in which embossing or the like is applied. The thickness of the heat seal resin layer is generally 0.1 to 40 μm, preferably 0.5 to 30 μm.

(2) Manufacture of Laminated Product Regarding the method for manufacturing the above laminated product, the following method can be mentioned as a preferred method. A method of extruding and laminating the heat-sealable resin film on the surface of the base material layer. A method of applying the emulsion of the heat-sealable resin or a solution dissolved in a solvent to the surface of the base material layer and drying. A method of co-extruding a base layer forming resin and a heat sealable resin. In the method for producing these laminates, corona discharge treatment, ozone treatment, plasma treatment or anchor coating agent treatment may be applied to the surface of the base material layer in order to improve the adhesion to the heat-sealable resin. The thickness of the laminate is generally 8 to 240 μm, preferably 10 to 180 μm.

[II] Corona Discharge Treatment (1) Treatment Conditions In the present invention, the above-mentioned laminate is used in an amount of 20 to 80%, preferably 3% of the total surface area of the heat-sealing resin layer of the laminate.
0 to 70% is 0.1 to 4 kw / m ² , preferably 0.
It is important that the corona discharge treatment is performed with a discharge amount of 5 to 2.5 kw / m ² . Such a corona discharge treatment can achieve its purpose by performing only on the heat-sealing resin layer on the heat-sealing side when the heat-sealing resin layer is provided on both sides of the base material layer. Therefore, when the heat-sealable resin layer is provided on both sides of the base material layer, the ratio of the treatment area and the treatment amount are based on only the heat-sealable resin layer on the heat-sealing side. . In the above corona discharge treatment, if the surface area of the heat-sealing resin layer of the laminate is too narrower than the above range, there will be a portion where the antistatic agent described later is not applied, and the antistatic ability cannot be sufficiently exhibited. On the other hand, if it is wider than the above range, the heat-sealing strength is lowered and blocking between the films is likely to occur, which makes it difficult to feed and discharge the paper. On the other hand, if the discharge amount is less than the above range, a portion where the antistatic agent described below is not applied is generated, the antistatic ability is lowered, dust is attached, and the paper feeding / discharging property is deteriorated. If the amount is too large, the antistatic agent is applied too much, the heat seal strength is lowered, blocking is likely to occur, and it becomes difficult to feed and discharge the paper.

(2) Treatment device As the corona discharge electrode used in the corona discharge treatment in the present invention, various shapes can be adopted, but in particular, the discharge protrusions are formed at the tip portion at a constant interval. It is preferable to perform the corona discharge treatment using a corona discharge electrode which is provided and has an area of the discharge convex portion of 5 to 70%, preferably 10 to 65% of the electrode tip area.

A specific example of such a corona discharge treatment machine is a discharge treatment machine having a shape as shown in FIGS. 1 and 2. FIG. 1 is a perspective view showing a state in which the laminate 2 is subjected to corona discharge treatment using the discharge treatment machine 1. 2 (a) is a partially cutaway front view of the shape of the tip of the discharge electrode of the discharge processor of FIG.
(B) and It is a side view. In FIG. 2, 3 is a corona discharge electrode, and 4 is a corona discharge protrusion provided at the tip of the electrode. The corona discharge protrusions 4 and 4'are formed with a constant size and at regular intervals, and are arranged such that the ratio of the entire discharge treatment tip portion falls within the above range. Specifically, the size of the convex portion 4 is such that the height (h) is 0.5 mm or more, preferably 1 to 10 mm, and the width (w) is 0.5 to 5 mm, preferably 1 to 4 mm. The interval (L) between 4,4 'is 1.5 to 20 mm, preferably 2 to 15 mm. Further, it is preferable that the protrusions 4 are provided so that the relationship between the width (w) and the interval (L) can satisfy 1.5w ≦ L ≦ 20. The shape of the electrode is not limited to a straight line, and may be divided into two or more. Any shape may be used as long as it can satisfy the range of the ratio of the discharge treatment tip portion. 20-80% of the area of the heat-sealing resin layer surface of the laminated body 2 guided by the treater roll 5 is treated by corona discharged from the convex portion 4 of the discharge electrode 3 attached to the corona treatment device 1. .
The distance between the convex portion 4 at the tip of the corona discharge treated electrode and the laminate film 2 is generally 0.1 to 5 mm, particularly 0.5 to 3 mm.
It is preferably mm.

[III] Formation of Antistatic Layer (1) Antistatic Agent As the water-soluble antistatic agent used in the present invention, various known ones can be used. You can list the following. Specific examples include those selected from quaternary nitrogen-containing acrylic polymers selected from polyethyleneimine, poly (ethyleneimine-urea) polyamine polyamide ethyleneimine adducts, polyamine polyamide epichlorohydrin adducts, acrylic resins, and the like. You can Examples of these water-soluble antistatic agents include SAFTMER 1000, 1100, 1300 (acrylic resin) manufactured by Mitsubishi Petrochemical Co., Ltd., Chemistat 2019 manufactured by Sanyo Kasei Co., Ltd., Electrostriper QN manufactured by Kao Corporation, and Lion Corporation. It is commercially available as Lipomin LIT manufactured by San Nopco Ltd. and Nopcostat HS manufactured by San Nopco Co., Ltd. The composition of the antistatic agent is not particularly limited as long as the surface tension of the antistatic agent is 38 to 50 dynes / cm. When the surface tension of the antistatic agent is less than 38 dynes / cm, the primer is wetted and dried even in the part which is not subjected to corona discharge treatment. Therefore, the part which is not subjected to corona treatment is also subjected to corona treatment. Similarly, it becomes impossible to distinguish, and a coating film is formed over the entire surface to be heat-sealed, so that it is difficult to obtain the adhesive strength originally required at the time of heat-sealing. On the other hand, when the surface tension exceeds 50 dynes / cm, the antistatic agent does not continuously wet the portion subjected to the corona discharge treatment, and it is difficult to obtain sufficient antistatic performance.

(2) Application of Antistatic Agent The above water-soluble antistatic agent is applied to the corona discharge treated surface and dried to form an antistatic layer. The amount of the antistatic agent applied is generally 0.05 to 10 g / m ² ,
It is preferably 0.1 to 5 g / m ² . The drying is generally carried out at a temperature of 30 to 90 ° C, preferably 50 to 80 ° C.

(3) Treatment effect In the case of a laminate obtained by laminating low density polyethylene (melting point 110 ° C.) on the surface of a stretched polypropylene film without corona discharge treatment, the surface of the low density polyethylene (heat sealable resin layer) surface The tension is 32 dynes / cm, but when the surface of this polypropylene stretched film is subjected to corona discharge treatment, the surface tension of the low density polyethylene surface is 4
It rises to 0 dynes / cm. Then 4 on this surface
When a water-soluble antistatic agent having a surface tension of 2 dynes / cm is applied to the entire surface of low-density polyethylene (heat-sealable resin layer), the antistatic agent is well wetted by the corona discharge-treated portion and charged. Since the antistatic layer is formed, the antistatic ability can be sufficiently exhibited. Therefore, when this heat-sealable laminate is used for printing, it is easy to feed and discharge the paper and prevent blocking. However, the antistatic agent applied to the part that is not subjected to corona discharge treatment is repelled because the surface tension of this part of the low density polyethylene (heat-sealable resin layer) is small, and there are parts where the antistatic agent is not applied. It is possible to prevent the heat seal strength from being lowered when the bag is formed.

In general, in order for the coating type antistatic agent to lower the potential charged on the surface to enable antistatic treatment,
If a certain amount of the antistatic agent is continuously connected, a sufficient effect can be exhibited, and it is not necessary that the low-density polyethylene (heat-sealable resin layer) is entirely applied. On the contrary, the area of the corona discharge treated area is 80%
If it exceeds, the heat-sealing property is deteriorated and practical heat-sealing strength cannot be obtained. Therefore, the surface area of the heat-sealable resin layer of the heat-sealable laminate of the present invention is 20 to 80
By performing a corona discharge treatment of%, the antistatic function of the antistatic agent can be exhibited. On the other hand, the surface of the heat-sealable resin layer of 80 to 20% which has not been subjected to corona discharge treatment is repelled because the surface tension of this portion is small, and the antistatic agent removes the antistatic agent from the heat-sealable resin layer surface. As a result, the heel seal strength is less likely to decrease and sufficient heel seal strength can be maintained.

[IV] Application The heat-sealing laminate formed as described above is
As such, it can be used as a bag-forming material as a packaging material for pillow packaging machines, or as a heat-sealable lid material for containers such as cup noodles and yogurt. Further, if necessary, printing is performed on the heat seal surface or the base material layer surface using a gravure printing machine or an offset printing machine, and hollow molding, injection molding,
It can be used as an in-mold label which is attached to the container as a label at the same time as molding the container by differential pressure molding.

[0016]

EXAMPLES In order to describe the method for producing a heat-sealing laminate of the present invention in more detail, examples and comparative examples will be specifically described below. Example 1 (1) Production of Laminated Body Synthetic paper made of polypropylene stretched film containing an inorganic filler used as a base material layer (YUPO FP manufactured by Oji Yuka Co., Ltd.)
G60: trade name), on one side of which a low-density polyethylene (Yukaron LM40 manufactured by Mitsubishi Petrochemical Co., Ltd .: trade name) used as a heat-sealable resin layer is extruded with a thickness of 15 μm from an extruder to be laminated, Thickness 75μ
A laminated body having an m and a width of 150 cm was obtained.

(2) Corona discharge treatment In place of the discharge electrode 3 of the corona discharge processor (made by Kasuga Denki Co., Ltd.), the width of the projections 4 and 4'at the tip 3a of the discharge electrode 3 (perpendicular to the processing direction Surface: w) is 1 mm, the number of convex portions 4 (n) is 51, the distance (L) between the convex portions 4 and 4'is 2 mm, and the convex portion 4 is
Of the electrode bar 1 processed to have a height (h) of 1.5 mm, the electrode bar 3 is treated as a treater roll (insulating roll).
5 and the tip convex portion 4 of the electrode 3 were set to have a gap (t) of 2 mm. In the gap (t) between the protrusion 4 of the electrode bar 3 and the treater roll 5 of the corona discharge treatment machine 1, the surface on the side where the laminated body 2 is laminated with low density polyethylene is the side of the discharge electrode bar 3. The corona discharge treatment was performed by the corona discharge generated by the corona generator 6 while passing through the above-mentioned arrangement. The corona discharge treatment was performed on the surface of the low density polyethylene (heat-sealable resin layer) at a discharge rate of 1.5 kw / m ² and a treatment speed of 50 m / min.

(3) Formation of Antistatic Layer Next, a water-solubilized acrylic resin antistatic agent having a surface tension of 45 (dyne / cm) was applied to the surface of the corona-treated laminate film 2 (Mitsubishi Oil Chemical Co., Ltd.). Saftomer 1300 (trade name) manufactured by Co., Ltd. is applied with a # 6 wire bar at an application amount of 1
After coating so as to be 0 g / m ² , it was sufficiently dried in a dryer at 50 ° C. for 5 minutes.

(4) Evaluation An aqueous solution containing 2.5% of a dye (for example, bromphenol blue) which reacts with the oxide of the antistatic agent to color the surface of the obtained laminate coated with the antistatic agent. By immersing it in a dye and measuring the area of the dyed part and the entire area by this, the application area ratio of the antistatic agent was determined, and the area ratio of the antistatic agent applied was It was 55%. Furthermore, the antistatic ability of the surface coated with this antistatic agent (the side on which low density polyethylene is laminated) is JI.
When the surface specific resistance value was obtained by a method conforming to S-C21222, a good value of 2 × 10 ¹¹ Ω was obtained. Then
The surfaces of the laminated body coated with the antistatic agent were overlaid, and the heat sealing temperature was 130 ° C. and the sealing pressure was 1.5 kg using a Toyo Seiki Co., Ltd. (Type HG-100) heat gradient tester.
/ Cm ² , and the sealing time was 2 seconds, and heat sealing was performed. The heat-sealing strength (T-shaped peeling strength) of this product was measured using a universal tensile tester manufactured by Orion Tech Co.
When measured at 00 mm / min, a heat seal strength of 380 g / 15 mm width, which was high enough to cause material destruction of the synthetic paper YUPO as the base material, was obtained. Next, the obtained laminate was cut into a size of half a chrysanthemum size, and offset printing was performed at a speed of 7,000 sheets / hour on the surface opposite to the surface subjected to this surface treatment (the surface of the synthetic paper). Paper feeding / discharging property and 1.00
The blocking state when stacking 0 sheets was observed. The results are shown in Table 1.

Further, this printed matter was punched into a size of 60 mm × 90 mm to prepare an in-mold label.
This label is mounted in advance in a mold by a vacuum action so that the printing surface comes into contact with the mold surface, and then polypropylene (Mitsubishi Polypro MA-7) is melted at 200 ° C. and supplied into the parison, and the parison is Compressed air was blown into the container to expand it to form a container, and the container was fused with the label previously mounted in the mold. Then, the mold was cooled, and then the mold was opened to take out the hollow container. This hollow container can shrink the label,
No blister was found. Further, although 100 labels were continuously supplied to the blow molding die by the automatic label feeding device, there was never a mistake (such as inserting two labels due to electrification). Further, the adhesive strength of the attached label to the hollow container was measured and found to be 390 g /
A strength of 15 mm was obtained. In this case as well, the material was destroyed from the synthetic paper as the base material.

Examples 2 to 5 and Comparative Examples 1 to 4 The same procedure as in Example 1 was carried out except that the shape of the electrode tip of the corona discharge treatment machine and the discharge amount were as shown in Table 1. The results obtained are shown in Table 1.

[0022]

[Table 1]

[0023]

The heat-sealable laminate obtained by the method for producing a heat-sealable laminate of the present invention as described above has both antistatic ability and strong heat-seal strength, so that it can be used in a printing machine. It has good paper feeding / discharging properties, and static electricity generated during printing causes dust, dirt, etc. to adhere,
Without lowering heat-sealing strength or appearance, heat-sealable lid materials for pillow packaging bag forming materials, cup noodles, yogurt, etc. and containers by hollow molding, injection molding, or differential pressure molding. It can be used as an in-mold label or the like that is attached to the container as a label upon molding.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state in which a laminate is subjected to corona discharge treatment using the discharge treatment apparatus according to the embodiment of the present invention.

2 (a) is a partial front view of a tip portion of a discharge electrode of the discharge processor of FIG. 1, and FIG. 2 (b) shows a side view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Corona treatment device 2 Laminated body 3 Discharge electrode, electrode bar 3a Discharge electrode tip part 4 Convex part 5 Treater roll (insulating roll) 6 Corona generator w Width of convex part 2 (surface perpendicular to the processing direction) h Convex part Height n Number of convex portions 2 L Distance between convex portions 2 and 2 ′ t Gap between convex portion of electrode bar and treater roll

Claims (1)

[Claims] 1. A heat-sealable resin layer of a laminate obtained by using a paper or plastic film layer as a base material layer, and providing a heat-sealable resin layer having a melting point lower than that of the base material layer on one or both sides thereof. Of the surface of the heat-sealable resin layer is subjected to corona discharge treatment at a discharge amount of 0.1 to 4 kw / m ² , and then a water-soluble antistatic agent is applied to the corona discharge treated surface. A method for producing a heat-sealable laminate, comprising forming an antistatic layer by drying and drying.