JP3217506B2 - Method for producing heat-sealable laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to hollow molding, injection molding,
A heat seal used as a heat sealable lid material for containers such as in-mold labels and pillow packaging bags, cup noodles, yogurt, etc., which are formed on the container at the same time as the container is formed by differential pressure molding. The present invention relates to a method for producing a functional laminate.

[0002]

2. Description of the Related Art Conventionally, it has been used as an in-mold label and a bag forming material for pillow packaging, a heat-sealing lid material for containers such as cup noodles, yogurt, etc., which are simultaneously attached to the container as a label at the same time as the container is molded. As a packaging material, corona discharge treatment is applied to the surface of a base material of a high melting point resin such as pulp paper, polyethylene terephthalate, polyamide, and polypropylene, and the corona discharge treated surface is treated with an ethylene-vinyl acetate copolymer, ethylene-methyl acrylate. Laminated heat-sealable resins such as copolymers and Surlyn (metal salts of ethylene-acrylic acid copolymers) are used (JP-B-46-14552, JP-B-62-6096).
No. 9, Japanese Patent Publication No. 63-12792, Japanese Patent Publication No. 2-8890
No.). In the method of manufacturing the packaging material, a method of kneading an antistatic agent such as an oil-soluble (water-insoluble) fatty acid amine or fatty acid monoglyceride is also used.

[0003]

When printing on the former packaging material and applying it to a printing machine, the paper feeding / discharging property of the printing machine is poor due to lack of antistatic ability. Dust, dust, dirt, etc. adhere to the packaging material,
There were problems such as a decrease in heat seal strength and a decrease in appearance. In order to solve such problems, a water-soluble antistatic agent is applied to the heat-sealable resin layer side of the packaging material, and when the antistatic layer is provided by drying, the above problem is solved. This time, there was a disadvantage that the heat seal strength was reduced. In the latter method of kneading the antistatic material, since the antistatic material relies on the antistatic function by bleeding out to the heat-sealable resin surface, the antistatic function is sufficiently exerted in the initial stage immediately after production. I couldn't do that. However, after a long period of time, the antistatic ability is sufficiently exhibited, but this time, there is a problem that the films are blocked or the heat seal strength is reduced when forming the bag. Therefore, the method for producing a heat-sealing laminate of the present invention provides a packaging material which has excellent antistatic ability, hardly causes blocking, is easy to feed, and hardly causes a decrease in heat-sealing strength even after a lapse of time. It is intended to do so.

[0004]

Means for Solving the Problems [Summary of the Invention] The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, a laminated body which has been subjected to a specific treatment has an excellent antistatic ability and a high blocking ability. It has been found that the present invention has been found to be a packaging material in which the heat sealing strength does not easily occur, the paper feeding is easy, and the heat seal strength does not easily decrease even after a lapse of time. That is, the method for producing a heat-sealable laminate of the present invention is obtained by providing a paper or plastic film layer as a base layer and providing a heat-sealable resin layer having a lower melting point than the base layer on one or both sides thereof. Discharge projections are provided at regular intervals on the surface of the heat-sealing resin layer of the laminated body, and the area of the discharge projections accounts for 5 to 70% of the electrode tip area. Using a corona discharge electrode, 20 to 80 of the total surface area of the heat-sealable resin layer
% Of corona discharge treatment at a discharge amount of 0.1 to 4 kW / m ^{2 on} the area of the surface, and then applying a water-soluble antistatic agent to the corona discharge treated surface and drying to form an antistatic layer. It is characterized by the following.

[I] Laminate (1) Layer configuration (a) Base layer The material used as the base layer in the method for producing a heat-sealable laminate of the present invention is pulp paper. , Coated paper, synthetic paper consisting of stretched film of resin containing inorganic filler, polyethylene terephthalate, polyamide, polypropylene,
Polycarbonate, saponified ethylene / vinyl acetate copolymer, aluminum foil, etc., or a laminate of these materials,
Alternatively, those obtained by subjecting these substrates to aluminum evaporation or silicon oxide evaporation can be given. 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 have a melting point lower than the melting point of the material used for the base material layer, preferably a melting point of the material used for the base material layer. A melting point lower than 10 ° C. or more, particularly preferably 15 to 150 than the melting point of the material used for the base material layer.
A heat-sealing resin having a melting point lower by 0 ° C. is used. Such heat-sealing 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 (the alkyl group has 1 to 1 carbon atoms)
8) the melting point of a metal salt of an ethylene / (meth) acrylic acid copolymer (Zn, Al, Li, K, Na) is 80 to 13;
An ethylene-based resin at 8 ° C. can be used. The heat seal resin layer may be a transparent film, and may be unstretched or stretched. Further, a smooth state or an embossed state may be 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 laminate The following method can be cited as a preferable method of manufacturing the laminate. A method of extruding and laminating the heat-sealing resin film on the surface of a base material layer. A method in which an emulsion of the heat-sealable resin or a solution dissolved in a solvent is applied to the surface of the base material layer and dried. A method of co-extruding a resin for forming a base material layer and a heat-sealing resin. In the production method of these laminates, a corona discharge treatment, an ozone treatment, a plasma treatment, or an anchor coat agent treatment may be performed to improve the adhesion of the surface of the base material layer to the heat sealing resin. The thickness of the laminate is generally from 8 to 240 μm, preferably from 10 to 180 μm.

[II] Corona Discharge Treatment (1) Treatment Conditions In the present invention, the laminate is used in an amount of 20 to 80%, preferably 3 to 80% of the total surface area of the heat-sealable resin layer of the laminate.
0 to 70%, 0.1 to 4 kw / m ² , preferably 0.1 to 4 kw / m ² .
It is important that the corona discharge treatment is performed at a discharge amount of 5 to 2.5 kw / m ² . Such a corona discharge treatment achieves its purpose by performing only the heat-sealing resin layer on the side to be heat-sealed when the heat-sealing resin layer is provided on both surfaces of the base material layer. Therefore, when the heat-sealing resin layer is provided on both surfaces of the base material layer, the ratio of the processing area and the processing amount are based on only the heat-sealing resin layer on the side to be heat-sealed. . In the above-mentioned corona discharge treatment, if the surface area of the heat-sealable resin layer of the laminate is too narrower than the above range, a portion to which the antistatic agent is not applied will be formed, and the antistatic ability cannot be sufficiently exhibited. On the other hand, if the width is larger than the above range, the heat sealing strength is reduced, and at the same time, blocking between the films is apt to occur. On the other hand, if the discharge amount is less than the above range, a portion to which the antistatic agent is not applied will be formed, and the antistatic ability will be reduced, and dust will adhere and the paper feeding / discharging property will be reduced. If the amount is too large, the anti-static agent is applied too much, and the heat seal strength is reduced, and at the same time, blocking tends to occur, making it difficult to feed and discharge the paper.

(2) Treatment Apparatus As the corona discharge electrode used in the corona discharge treatment of the present invention, those having various shapes can be adopted. It is preferable that the corona discharge treatment is performed using a corona discharge electrode provided so that the area of the discharge projection occupies 5 to 70%, preferably 10 to 65% of the electrode tip area.

As a specific example of such a corona discharge treatment machine, a discharge treatment machine having a shape as shown in FIGS. 1 and 2 can be mentioned. FIG. 1 is a perspective view showing a state in which a laminate 2 is subjected to corona discharge treatment using a discharge treatment machine 1. FIG. 2A is a partially cutaway front view of the distal end shape of the discharge electrode of the discharge treatment machine of FIG.
(B) and its side view. In FIG. 2, reference numeral 3 denotes a corona discharge electrode, and reference numeral 4 denotes a corona discharge projection provided at the tip of the electrode. The corona discharge projections 4 and 4 'are formed at a constant size and at regular intervals, and are arranged so that the ratio of the entire distal end portion of the discharge treatment falls within the above range. Specifically, the size of the projection 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 distance (L) between 4, 4 'is 1.5 to 20 mm, preferably 2 to 15 mm. Further, it is preferable that the projection 4 be 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 front end portion. The surface of the heat-sealable resin layer of the laminate 2 guided by the treater roll 5 is treated by corona discharged from the projections 4 of the discharge electrodes 3 attached to the corona treatment device 1 to 20 to 80% of its area. .
The distance between the convex portion 4 at the tip of the corona discharge treatment electrode and the laminated film 2 is generally 0.1 to 5 mm, particularly 0.5 to 3 mm.
mm.

[III] Formation of antistatic layer (1) Antistatic agent As the water-soluble antistatic agent used in the present invention, various known water-soluble antistatic agents can be used. Can be mentioned. Specifically, quaternary nitrogen-containing acrylic polymers selected from polyethyleneimine, an ethyleneimine adduct of a poly (ethyleneimine-urea) polyamine polyamide, an epichlorohydrin adduct of a polyamine polyamide, an acrylic resin, and the like. Can be. Examples of these water-soluble antistatic agents include Saftomer 1000, 1100, 1300 (acrylic resin) manufactured by Mitsubishi Yuka Co., Ltd., Chemistat 2019 manufactured by Sanyo Kasei Co., Ltd., Electrostripper QN manufactured by Kao Corporation, and Lion Corporation. It is commercially available as Lipomin LIT manufactured by San Nopco Co., Ltd. and Nopcostat HS manufactured by San Nopco. 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 that has not been subjected to the corona discharge treatment is also wet and dried, so that the part that is not subjected to the corona treatment is also subjected to the corona treatment. In the same manner as in the above, it is difficult to distinguish, and a 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. Conversely, if the surface tension exceeds 50 dynes / cm, the antistatic agent does not continuously wet the corona discharge-treated portion, 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 coating amount of the antistatic agent is generally 0.05 to 10 g / m ² ,
Preferably it is 0.1-5 g / m < ² >. Drying is generally carried out at a temperature of 30 to 90C, preferably 50 to 80C.

(3) Treatment Effect In the case of a laminate in which low-density polyethylene (melting point 110 ° C.) is laminated on the surface of a stretched polypropylene film without corona discharge treatment, the surface of the low-density polyethylene (heat-sealing resin layer) surface Although the tension is 32 dynes / cm, when the surface of the stretched polypropylene film is subjected to corona discharge treatment, the surface tension of the low-density polyethylene surface becomes 4 dynes / cm.
It rises to 0 dynes / cm. After that, 4
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 above-mentioned corona-discharge treated portion is well wetted by the antistatic agent and charged. Since the antistatic layer is formed, the antistatic ability can be sufficiently exhibited. Accordingly, when the heat-sealing laminate is used for printing, paper feeding and discharging is facilitated and blocking is also prevented. However, the antistatic agent applied to the portion not subjected to the corona discharge treatment is repelled because the surface tension of this portion of the low-density polyethylene (heat-sealable resin layer) is small, and a portion to which the antistatic agent is not applied is generated. In addition, it is possible to prevent a decrease in heat sealing strength when forming a bag.

Generally, in order to reduce the potential charged on the surface of a coating type antistatic agent to enable antistatic,
If a certain amount of the antistatic agent is continuously connected, a sufficient effect can be exerted, and it is not necessary to apply the antistatic agent over the entire surface of the low-density polyethylene (heat-sealing resin layer). Conversely, the area of the corona discharge treated portion is 80%
If it exceeds 2,000, the heat sealability is reduced, and practical heat seal strength cannot be obtained. Therefore, the surface area of the heat-sealing resin layer of the heat-sealing laminate of the present invention is 20 to 80.
%, The antistatic function of the antistatic agent can be exhibited. On the other hand, the surface of the 80 to 20% heat-sealing resin layer that has not been subjected to the 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-sealing resin layer surface. Therefore, the decrease in heel seal strength is small, and sufficient heel seal strength can be maintained.

[IV] Applications 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 a pillow packaging machine, or as a heat sealable lid material for containers such as cup noodles and yogurt. In addition, if necessary, printing is performed on the heat sealing surface or the substrate layer surface using a gravure printing machine or an offset printing machine, hollow molding, injection molding,
It can be used as an in-mold label attached to the container at the same time as the container is formed 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, specific examples will be given below with reference to examples and comparative examples. Example 1 (1) Production of laminated body Synthetic paper made of a stretched polypropylene film containing an inorganic filler used as a base material layer (YUPO FP manufactured by Oji Yuka Co., Ltd.)
G60: trade name), a low-density polyethylene (Mitsubishi Yuka Co., Ltd. Yucalon LM40: trade name) used as a heat-sealing resin layer was extruded with a thickness of 15 μm from an extruder and laminated. 75μ thickness
m and a laminate having a width of 150 cm were obtained.

(2) Corona Discharge Treatment In place of the discharge electrode 3 of the corona discharge treatment machine (made by Kasuga Electric) 1, the width of the projections 4 and 4 'is formed at the tip 3a of the discharge electrode 3 (at right angles to the treatment direction). Surface: w) is 1 mm, the number (n) of the projections 4 is 51, the distance (L) between the projections 4 and 4 'is 2 mm, and the projections 4
Using an electrode bar 1 having a height (h) of 1.5 mm, the electrode bar 3 is treated with a treater roll (insulating roll).
5 and the tip 3 of the electrode 3 were set so that the gap (t) was 2 mm. In the gap (t) between the protrusion 4 of the electrode bar 3 of the corona discharge treatment machine 1 and the treater roll 5, the surface of the laminate 2 on which the low-density polyethylene is laminated is the discharge electrode bar 3 side. A corona discharge treatment was performed by corona discharge generated by the corona generator 6 while passing through while being arranged as described above. The corona discharge treatment was performed on the surface of the low-density polyethylene (heat-sealing 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-soluble acrylic resin antistatic agent having a surface tension of 45 (dynes / cm) was applied to the surface of the corona-treated laminated film 2 (Mitsubishi Yuka Kagaku). Coat of Saftomer 1300 (trade name) manufactured by Co., Ltd. with a # 6 wire bar and 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 The surface of the obtained laminate coated with an antistatic agent is coated with an aqueous solution containing 2.5% of a dye (eg, bromophenol blue) which reacts with and colors the oxide of the antistatic agent. It was immersed and dyed in it, and the area of the part dyed by this and the whole area were measured to determine the application area ratio of the antistatic agent. 55%. Furthermore, the antistatic ability of the surface to which the antistatic agent was applied (the side on which low density polyethylene was laminated) was determined by JI.
When the surface resistivity was determined by a method based on S-C22222, a good value of 2 × 10 ¹¹ Ω was obtained. Then
The surfaces of the laminates each coated with an antistatic agent are overlapped with each other, and a heat sealing temperature of 130 ° C. and a sealing pressure of 1.5 kg are measured using a thermal gradient tester (Type HG-100) manufactured by Toyo Seiki Co., Ltd.
/ Cm ² and a sealing time of 2 seconds. The heat-sealing strength (T-peel strength) of this product was measured using a universal tensile tester manufactured by Orion Tech Co., Ltd. at a tensile speed of 2
When measured at 00 mm / min, a material having a heat seal strength as high as 380 g / 15 mm wide enough to cause material destruction of the synthetic paper YUPO as a base material was obtained. Next, the obtained laminate was cut into chrysanthemum half-sized pieces, and offset printing was performed at a speed of 7,000 sheets / hour on the surface opposite to the surface treated (synthetic paper), Paper feeding and discharging properties and 1,00
The state of blocking when 0 sheets were stacked was observed. Table 1 shows the results.

The printed matter was punched out to a size of 60 mm × 90 mm to prepare an in-mold label.
After mounting this label in a mold in advance by vacuum so that the printing surface is in contact with the mold surface, polypropylene (Mitsubishi Polypropylene MA-7) is melted at 200 ° C. and supplied into the parison. Compressed air was blown to expand to form a container, and the container was fused to the label previously mounted in the mold. After cooling the mold, the mold was opened and the hollow container was taken out. This hollow container shrinks the label,
No blistering was observed. In addition, 100 labels were continuously supplied to the blow molding die by the automatic label feeder, but there was no mistake (such as inserting two labels by charging). Furthermore, when the adhesive strength of the attached label to the hollow container was measured, it was 390 g /
A strength of 15 mm was obtained. Also in this case, the material was destroyed from the synthetic paper portion as the base material.

Examples 2 to 5 and Comparative Examples 1 to 6 The procedure of Example 1 was repeated except that the shape of the electrode tip of the corona discharge treatment machine, the discharge amount and the ratio of the area of application of the antistatic agent were as shown in Table 1. The procedure was performed in the same manner as described above. Table 1 shows the obtained results.

[0022]

[Table 1]

[0023]

As described above, the heat-sealing laminate obtained by the method for producing a heat-sealing laminate of the present invention has both an antistatic property and a high heat-sealing strength. Blocking does not easily occur, the paper feeding and discharging properties are good, and the static electricity generated during printing does not cause dust, dirt, dust, etc. to adhere, lowering the heat seal strength or reducing the appearance, and it is suitable for pillow packaging. Heat-sealing lid material for containers such as bag-forming materials, cup noodles, and yogurt, and use as an in-mold label or the like that is molded as a container by hollow molding, injection molding, or differential pressure molding, and is simultaneously attached to the container as a label. Can be.

[Brief description of the drawings]

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

2 (a) is a partial front view of a distal end portion of a discharge electrode of the discharge processing machine of FIG. 1, and FIG. 2 (b) and a side view thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Corona processing apparatus 2 Laminated body 3 Discharge electrode, electrode bar 3a Discharge electrode tip 4 Convex part 5 Treator roll (insulating roll) 6 Corona generator w Width of convex part 2 (plane perpendicular to processing direction) h Convex part N The number of the convex portions 2 L The distance between the convex portions 2 and 2 't The gap between the convex portion of the electrode bar and the treater roll

Claims (1)

(57) [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 surfaces thereof. the surface of a predetermined distance at the tip portion
A discharge protrusion is provided, and the area of the discharge protrusion is
Corona discharge occupies 5 to 70% of the tip area
With pole 20 of the total surface area of the heat sealable resin layer
After corona discharge treatment with a discharge amount of 0.1~4kw / m ² to 80% of the area to form an antistatic layer followed by drying by applying a water-soluble antistatic agent to the corona discharge treated surface A method for producing a heat-sealing laminate , comprising the steps of :