JP3429386B2 - Easy adhesion polyamide film - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an easily adhesive film. More specifically, the present invention relates to an easily adhering polyamide film having improved printing ink, lamination with other films, and adhesion with other coating agents, especially adhesion under wet conditions, and suitable for boil sterilization and retort sterilization packaging applications.

[0002]

2. Description of the Related Art Plastic films are excellent in transparency, physical strength, chemical stability, mechanical suitability, moisture resistance and gas barrier property and are widely used for packaging and the like. However, plastic film is rarely used without any surface treatment, usually printing, metallization,
It is used as a composite such as a laminate with another film or coating with a coating agent. Conventionally, surface treatments such as corona discharge treatment, low temperature plasma treatment, flame treatment, and chromium mixed acid treatment have been performed to improve adhesion.

[0003]

Even when the surface treatment for improving the adhesion is applied as described above, printing ink, metal vapor deposition,
Lamination with other films and adhesion with other coating agents, especially adhesion under wet conditions, were insufficient.

For example, in Japanese Unexamined Patent Publication No. 1-244847, a biaxially stretched polyamide film (hereinafter abbreviated as BOPA) having a surface tension in a specific range is provided with an adhesion-modifying layer on the surface thereof to adhere to a printing ink layer or a sealant layer. A method for improving the force has been proposed, and it is described that the higher the surface tension of the biaxially stretched polyamide film before the provision of the adhesion-modifying layer, the lower the adhesion force when wet. However, in general, BOPA has a high degree of crystallinity due to heat treatment after stretching, and free polar groups (NH, CO, OH groups) are hydrogen-bonded between molecules in the resin, and the surface tension is also low.
For this reason, the number of free polar groups on the film surface, which greatly affects the adhesiveness with the adhesion-modified layer, is reduced, and a film having a high degree of crystallinity after heat treatment does not have sufficient adhesive force. In particular, the adhesive strength is remarkably reduced when wet. Further, this method is a so-called off-line method in which coating is performed after stretching, which is expensive.

In order to solve these drawbacks, the present inventors apply a water-soluble coating agent containing a specific water-soluble (meth) acrylic acid ester and a water-soluble epoxy compound as a main component to one side of the film. As a result, a method for improving the adhesiveness especially under wet condition has been proposed (Japanese Patent Laid-Open No. 2-3432). However, as the use of polyamide film expands, for example, when a laminated composite film is made into a bag and filled with food or the like and sterilized by boil or retort, the adhesive strength decreases and the bag is broken in a boil tank or a retort kettle. There are problems such as frequent accidents, and stronger adhesive force, especially adhesiveness at the time of boiling and retorting, has been demanded.

[0006]

[Means for Solving the Problems] As a result of intensive investigations by the present inventors in order to solve the above problems, the contact angle of water droplets on the surface was 4
After coating a specific amount of a specific coating agent on a polyamide film having a temperature of 5 to 60 degrees, the film is stretched in at least one direction and subjected to a heat treatment, and the coated surface of the film is surface-treated so that the wettability index of the coated surface is 4
By setting it to 0 to 52 dyn / cm, the adhesiveness is improved, and the adhesiveness to the printing ink, the laminated film and the coating agent, etc., is particularly improved without lowering the transparency, slipperiness and blocking resistance of the original film. The inventors have found that the adhesiveness under wet conditions during boiling can be greatly improved, and have completed the present invention.

That is, the present invention is a polyamide film which is unstretched or stretched only in the uniaxial direction and is not heat-treated, and the surface of the film having a water droplet contact angle of 45 to 60 degrees is crosslinked with A: an epoxy group. 98 to 30 parts by weight of a water-soluble acrylic acid ester copolymer or a water-soluble methacrylic acid ester copolymer having a functional group contributing to the reaction and having a glass transition point of 40 ° C. or higher, B: water-soluble polyepoxy compound 2 to 70 parts by weight, C: average particle size of 0.005
A coating amount after stretching of an aqueous coating liquid containing 0.1 to 10 parts by weight of 1.0 μm fine particles as a main component is 0.001 to 0.00.
After coating so as to be 8 g / m ² , stretching in at least one direction, heat treatment, and then surface treatment of the coated surface of the film,
The present invention relates to an easily-adhesive polyamide film having a wettability index of 40 to 52 dyn / cm on a coated surface, and a composite film having another coated film and a printing layer on the coated surface.

The polyamide film used in the present invention, which is unstretched or stretched only in the uniaxial direction and is not heat-treated, generally has many free polar groups on the surface of the film, which greatly affects the adhesiveness, and further, after coating, stretching and heat treatment. As a result, more heat is applied, the adhesion between the polyamide film and the coated surface becomes stronger, and there is an advantage that the adhesion becomes stronger than in the off-line coating.

Further, the above polyamide film has adhesiveness,
The surface tension must be controlled within a certain range in order to improve the adhesion, especially under wet conditions. However, according to JIS K6768, which is conventionally used as a method for determining the degree of surface treatment of a film, a polyamide film as used in the present invention, which is not stretched immediately after film formation or is stretched only in a uniaxial direction and is not heat-treated. Is 56
Since it is around dyn / cm, it is difficult to serve as a guideline for controlling the surface tension for the purpose of the present invention. In the present invention, the range of surface tension can be effectively controlled by using the method of measuring the water droplet contact angle on the film surface. That is, the water droplet contact angle is in the range of 45 to 60 degrees. When the water droplet contact angle is 60 degrees or more, there are few free polar groups on the film surface, and the adhesive force with the adhesion modifying layer is low. Also, 45
If it is less than 100 ° C., the surface of the polyamide film becomes too rough and brittle, leading to a decrease in adhesive strength. Cause the destruction of.
Corona discharge treatment, etc. is effective to set the contact angle of water droplets to 45 to 60 degrees, and the strength of the treatment is 30 W · min / m ²
The following are appropriate:

The (meth) acrylic acid ester copolymer used in the present invention must have a glass transition point of 40 ° C. or higher. If the glass transition point is less than 40 ° C, it is wound into a roll after coating in order to crosslink and cure with a water-soluble polyepoxy compound, blocking occurs when it is aged at 30 to 60 ° C, and the trace of adhesion remains transparent. If the film becomes uneven, it cannot be rewound if it is more severe, and if the film is forcibly rewound, the film is broken, which is not preferable.

The (meth) acrylic acid ester copolymer used in the present invention comprises a main monomer composed of acrylic acid esters and / or methacrylic acid esters and the like, and a comonomer having an epoxy group and a functional group contributing to a crosslinking reaction. It can be obtained by copolymerizing an essential component and, in addition, a neutral monomer which is copolymerizable with the above-mentioned monomer, if desired.

Among the above-mentioned main monomers, examples of acrylates include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, etc.
Further, as the methacrylic acid esters, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate,
Isopropyl methacrylate, n-butyl methacrylate,
Examples thereof include isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate and the like.

Examples of the above-mentioned comonomers include α, β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, maleic acid monoester and fumaric acid monoester, and methacrylic acid. Hydroxy compounds such as 2-hydroxyethyl and polyethylene glycol monomethacrylate, epoxy compounds such as glycidyl methacrylate and allyl glycidyl ether, amines such as allylamine, N, N-dimethylaminoethyl acrylate and N, N-dimethylaminopropylacrylamide, N Examples thereof include, but are not limited to, amides such as methylacrylamide and acid anhydrides such as maleic anhydride. The functional groups of these monomers contribute to cross-linking with the polyepoxy compound, adhesion with the plastic film, and the like.

The above-mentioned copolymerizable neutral monomers include styrene, styrenes such as α-methylstyrene, acrylonitriles such as acrylonitrile and methacrylonitrile, and aliphatic vinyl esters such as vinyl acetate and vinyl propionate. Examples thereof include, but are not limited to, vinyl alkyl ethers such as vinyl methyl ether and vinyl ethyl ether, α-olefins such as ethylene, propylene and 1-butene, vinyl chloride and vinylidene chloride.

The (meth) acrylic acid ester copolymer used in the present invention must be water-soluble as its limitation. The organic solvent solution has a risk of flammable explosion, acute and chronic poisoning, and problems such as cost increase due to the use of an expensive organic solvent. The present invention is characterized by using an aqueous coating agent. However, the minimum necessary organic solvent may be used to impart water solubility.

When the above-mentioned copolymer is an aqueous dispersion, it is inferior in film forming property to an aqueous solution and has problems in adhesion, water resistance and solvent resistance. Therefore, it is solubilized by adding an acid or a base. It is preferable to use afterwards. At this time, the aqueous dispersion used is preferably emulsified without using an emulsifier. Further, a solution-polymerized product using a small amount of a water-soluble organic solvent can also be used by solubilizing it by adding an acid or a base to an organic solvent solution, but the method of water solubilization is not limited to these. Absent.

The molecular weight of the (meth) acrylic acid ester copolymer used in the present invention is preferably 5,000 or more and 100,000 or less. If the molecular weight is less than 5,000, the water resistance, solvent resistance and scratch resistance are poor, and the molecular weight is 100,000.
If it exceeds 0, it becomes difficult to solubilize the water, and the viscosity increases, which makes the handling difficult. The molecular weight as used herein refers to a weight average molecular weight in terms of polymethylmethacrylate homopolymer calculated by GPC (gel permeation chromatography).

The water-soluble polyepoxy compound B used in the present invention is a compound which is soluble in water and has two or more epoxy groups, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol. , A diepoxy compound obtained by etherification of 1 mol of glycols such as dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and 2 mol of epichlorohydrin, glycerin Polyepoxidation obtained by etherification of 1 mol of polyhydric alcohols such as polyglycerin, trimethylolpropane, pentaerythritol and sorbitol with 2 mol or more of epichlorohydrin Things, phthalic acid terephthalic acid, oxalic acid, a diepoxy compound obtained by esterification of a dicarboxylic acid 1 mol of epichlorohydrin 2 moles, and the like are not limited to these, such as adipic acid.

These polyepoxy compounds crosslink with the crosslinkable functional groups of the (meth) acrylic acid ester copolymer used in the present invention to improve the water resistance and solvent resistance of the coating film, and further to form a plastic film. Also contributes to the adhesiveness of.

As the fine particles used in the present invention, fine particles having an average particle diameter of 0.005 to 1.0 μm are used, and preferably fine spherical particles are used. The true spherical particles mean that the minor axis / major axis is 0.90 or more in the electron micrograph. It is preferable that the fine particles have a spherical shape, because they have an excellent effect on blocking resistance and slipperiness, and a decrease in transparency is small. The average particle size is 0.005
If it is less than μm, there is no effect on blocking resistance and slipperiness. If the average particle size exceeds 1.0 μm, the printability deteriorates. In particular, in the case of photolithographic printing, ink loss occurs in the highlight area. The fine particles may be inorganic or organic, but they are required to have heat resistance so that they are not deformed during the manufacturing process and lose their effect.

These fine particles are wound in a roll form after coating in order to accelerate the crosslinking between the (meth) acrylic acid ester copolymer used in the present invention and the polyepoxy compound, and are aged at 30 to 60 ° C. It has the function of an anti-blocking agent and a slip agent that imparts appropriate slip properties in post-processing steps such as winding, printing, laminating and coating. For example, true spherical silica fine particles “Seahoster” KE-P30 (average particle diameter 0.3 μm) manufactured by Nippon Shokubai Chemical Co., Ltd.,
Examples include colloidal silica “Snowtex” ST-20 (average particle size 10 to 20 nm) manufactured by Nissan Chemical Industries, Ltd., but are not limited thereto.

The compounding ratio A / B of the (meth) acrylic acid ester copolymer (A) used in the present invention described above and the water-soluble polyepoxy compound (B) is 98/2 to 98.
It is preferably 30/70. A / B ratio is 98
If it is larger than / 2, the crosslink density is reduced and the water resistance, solvent resistance and adhesiveness are poor. On the contrary, if the A / B ratio is less than 30/70, blocking during aging remains a problem.

The amount of the fine particles (C) blended is the total amount (A + B) of the (meth) acrylic acid ester copolymer (A) and the water-soluble polyepoxy compound (B) used in the present invention. C / (A + B) is 0.1 / 1 as a ratio
It is preferably from 00 to 10/100. If this ratio is less than 0.1 / 100, the effect on blocking resistance and slipperiness is insufficient, and conversely, if it is more than 10/100, the effect remains unchanged and it is economically disadvantageous.

As described above, the coating amount of the (meth) acrylic acid ester copolymer used in the present invention, the water-soluble polyepoxy compound, and the aqueous coating agent containing fine particles as the main component is 0.001 in dry weight after stretching. preferably ~0.05g / m ^2, 0.
More preferably, it is 001 to 0.008 g / m ² .
If it is less than 0.001, the water resistance and adhesiveness are insufficient even when the method of the present invention is used. On the contrary, even if the coating amount is 0.05 g / m ² or more, no further improvement in performance is observed, the adhesive force is decreased, and the cost is increased, which is not preferable.

Known coater heads may be used for coating on the polyamide film, and examples thereof include a gravure coater, a squeeze coater, a Mayer bar coater, a kiss coater and a reverse roll coater.

Further, after coating, the coated surface of the polyamide film stretched and heat-treated is subjected to a surface treatment, and JIS is applied.
Wetting index according to K 6768, 40-52 dyn / c
By setting m, the adhesiveness with printing ink is also improved. When it is 40 dyn / cm or less, the number of free polar groups on the coated surface is small and the adhesive force with the adhesion-modified layer is low. Also,
If it is more than 52 dyn / cm, the coating surface becomes too rough and becomes brittle, leading to a decrease in adhesive strength, and if it is used in a composite such as printing or laminating with another film, it may cause interface destruction or coating. It causes the destruction of things.

Corona discharge treatment or the like is effective for setting the wetting index to 40 to 52 dyn / cm, and the treatment strength is suitably 15 to 60 W · min / m ² . Further, the surface treatment on the coated surface is not effective unless the coating agent is cured to some extent because the coating agent is heated. In the case of in-line coating, the coated surface is cured to some extent by stretching and heat treatment after coating. Therefore, even on the coated surface before being completely cured before aging, the surface treatment also improves the adhesion to the printing ink. The surface treatment can also be performed after the aging described below.

After the drawing, in order to complete the crosslinking reaction with the polyepoxy compound, the film is wound into a roll at 30 to 60 ° C.
It is preferable to age at. If the temperature is lower than 30 ° C, it takes a long time for the effects to be exhibited, which is not practical. If it exceeds 60 ° C, problems such as blocking and deterioration of the flatness of the film occur.

[0029]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. The evaluation method in this example is as follows. 1. The laminate strength test surface and the 60 μm-thick CPP corona discharge treated surface were treated with a dry laminating adhesive AD-590 / CAT-56 manufactured by Toyo Morton Co., Ltd. at a solid content of 4 g / m ²
After coating and dry lamination, it was aged at 45 ° C. for 72 hours. After sampling to a width of 15 mm, peeling was performed at a speed of 100 mm / min by a tensile tester, and the value during the progress of peeling was read. When wet, after boiling, when wet, the measurement was performed while water was attached to the peeling port.

2. Heat seal strength A laminate sample is prepared in the same manner as the laminate strength, and a heat seal sample is prepared on the same CPP surface. 15
After sampling to a width of mm, 1
The maximum strength was read after peeling at a speed of 00 mm / min. When wet, and after boiling, when wet, measurement was performed while water was applied to the seal portion.

3. Blocking resistance The coated samples before aging are overlaid so that the coated surface and the non-coated surface face each other, and they are placed at 40 ° C. for 48 hours and 25 mm × 25 m.
A load of 10 kg is applied to the area of m. After cooling to room temperature, a tensile tester was used to perform shear peeling at a speed of 100 mm / min, and the maximum strength was read.

4. The coefficient of static friction between the coated surface and the non-coated surface in the slip property ASTM D1894.

5. Wetting index Wetting index of coated surface according to JIS K 6768.

6. Ink Adhesion Toyo Ink Mfg. Co., Ltd. Gravure printing ink NEW Ramipack Super R162 Red was applied with a Mayer bar to a dryness of 1 g / m ² and dried at 60 ° C. for 10 seconds. To this sample, Nichiban Co., Ltd. Cellotape CT-1
After pressure-bonding the pressure-sensitive adhesive surface of No. 8 well, it was peeled off rapidly by holding one end, and the peeling rate of the ink was evaluated according to the following criteria. Ink peeling rate (%) Rating 0 ○ 0 to 10 ○ Δ 10 to 30 Δ 30 to 80 × 80 to 100 × ×

Comparative Example 1 A 6-nylon resin having a relative viscosity of 3.5 was melt extruded from a ring die and cooled by an inner and outer water-cooled mandrel to have a thickness of 150 μm.
A tubular film of was obtained. The tube film was biaxially stretched simultaneously in MD and TD by the speed difference between the low speed nip roll and the high speed nip roll and the air pressure existing therebetween. After that, the tube was folded and heat-treated at 210 ° C for 10 seconds in a tenter oven to obtain a film with a thickness of 15 µm, both ears were cut off to make a flat film, and corona discharge treatment was performed on one side to form two rolls. I wound up. The laminate strength and heat seal strength of this corona discharge treated surface were measured. As shown in Table 1 and Table 2, the adhesiveness of the obtained film was poor.

Reference Example 1 A 6 nylon resin having a relative viscosity of 3.5 was melt extruded from a ring die and cooled with an inner and outer water cooling mandrel to have a thickness of 150 μm.
A tubular film of was obtained. On the outer surface of the tubular film, a water-soluble methyl methacrylate copolymer “Ricabond” SA-R615A (Tg67 manufactured by Chuo Rika Kogyo Co., Ltd.
(° C.) water-soluble polyepoxy compound “Denacol” EX-521 (polyglycerol polyglycidyl ether) manufactured by Nagase Chemical Industries Co., Ltd. and true spherical silica fine particles “Seahoster” KE-P30 (manufactured by Nippon Shokubai Kagaku Co., Ltd.) (Average particle size 0.3 μm) was added at a compounding ratio of 75/25 / 0.5, and the aqueous coating agent prepared by diluting with water to have a nonvolatile content of 7% was applied with a dip coater to give a coating amount of 0.1. 05 g / m
^It was coated in-line so as to be ² and dried. The tube film was biaxially stretched simultaneously in MD and TD by the speed difference between the low speed nip roll and the high speed nip roll and the air pressure existing therebetween. Then fold the tube and heat it in a tenter oven at 210 ° C for 10 seconds to obtain a thickness of 1
A 5 μm film is obtained, both ears are cut off to form a flat film, and the corona discharge treatment is applied to the coated surface with a processing power of 30 W · m.
in / m ² (wetting index 44 dyn / cm),
It was wound into two rolls. Then, it was aged at 50 ° C. for 48 hours. The laminate strength and heat seal strength of this in-line coated surface were measured. Table 1 shows the manufacturing conditions, and Table 2 shows the evaluation results. As shown in Table 2, the resulting film exhibited superior adhesive strength to the off-line coated product.

Comparative Example 2 Reference Example 1 was applied to the corona discharge treated surface of the film obtained in Comparative Example 1.
The water-based coating agent used in 1. was diluted with water to have a nonvolatile content of 3%, and the coating was applied with a Mayer bar and then dried at 140 ° C. for 15 seconds. Then, it was aged at 50 ° C. for 48 hours. Coating amount 0.0
It was 5 g / m ² . Although the adhesiveness of the obtained film was improved as compared with Comparative Example 1, the adhesive strength was not sufficient.

Comparative Example 3 The laminate strength and heat seal strength of the coated surface were measured in the same manner as in Comparative Example 2 except that the film used in Comparative Example 1 was not subjected to corona discharge treatment before coating. Although the adhesive strength of the obtained film was improved as compared with Comparative Example 1, it was inferior to Comparative Example 2 because no corona discharge treatment was performed.

Reference Example 2 The surface of the tubular nylon resin before being coated with the aqueous coating agent used in Reference Example 1 was subjected to corona discharge treatment with a treatment power of 15
Laminate strength and heat seal strength were measured in the same manner as in Reference Example 1 except that the application was performed at W · min / m ² (water drop contact angle 50 °). Table 1 shows the manufacturing conditions, and Table 2 shows the evaluation results. As shown in Table 2, the resulting film showed good adhesive strength.

Comparative Example 4 Laminate strength and heat seal strength were measured in the same manner as in Reference Example 2 except that the coating amount of the aqueous coating agent used in Reference Example 2 was changed. The adhesive strength of the obtained film is
It was inferior to Reference Example 2. Further, as shown in Table 2, the blocking resistance and the slip resistance were poor.

Reference Example 3 The surface of the tubular nylon resin before being coated with the aqueous coating agent used in Reference Example 1 was subjected to corona discharge treatment with a treatment power of 30.
Laminate strength and heat seal strength were measured in the same manner as in Reference Example 2 except that the application was performed at W · min / m ² (water droplet contact angle 45 degrees). Table 1 shows the manufacturing conditions, and Table 2 shows the evaluation results. As shown in Table 2, the resulting film showed good adhesive strength.

Comparative Example 5 The surface of the tubular nylon resin before being coated with the water-based coating agent used in Reference Example 1 was subjected to corona discharge treatment at a treatment power of 50.
Laminate strength and heat seal strength were measured in the same manner as in Reference Example 2 except that W · min / m ² (water droplet contact angle 40 degrees) was applied. The adhesive strength of the obtained film was inferior to that of Reference Example 3.

Examples 1 and 2 Laminate strength and heat seal strength were measured in the same manner as in Reference Example 1 except that the coating amount of the water-based coating agent used in Reference Example 1 was changed. Table 1 shows the manufacturing conditions, and Table 2 shows the evaluation results. As shown in Table 2, the resulting film showed good adhesive strength.

Comparative Examples 6 and 7 Laminate strength and heat seal strength were measured in the same manner as in Reference Example 1 except that the coating amount of the water-based coating agent used in Reference Example 1 was changed. The adhesive strength of the obtained film is
It was inferior to Reference Example 3.

Comparative Example 8 The characteristics of the film were evaluated in the same manner as in Example 2 except that the fine particles used in Reference Example 1 were not added. As can be seen from the results in Table 2, the blocking resistance and the slip resistance were poor.

Comparative Example 9 and Examples 3 and 4 The fine particles used in Reference Example 1 were colloidal silica "Snowtex" ST-0 (average particle size 1 manufactured by Nissan Chemical Industries, Ltd.).
The film characteristics were evaluated in the same manner as in Example 2 except that the composition ratio was changed to 0 to 20 nm). Table 1 shows the manufacturing conditions, and Table 2 shows the evaluation results. As shown in Table 2, a film having good blocking resistance, slip resistance, and adhesive strength was obtained.

Reference Example 4 Laminate strength and heat seal strength were the same as in Reference Example 1 except that the surface of the coated surface used in Reference Example 1 was subjected to a corona discharge treatment and then a treatment power of 30 W · min / m ^{2 was} applied. Was measured. Table 1 shows the manufacturing conditions, and Table 2 shows the evaluation results. As shown in Table 2, the resulting film showed good adhesive strength. The ink adhesion was also good.

Comparative Example 10 Laminate strength and heat seal strength were measured in the same manner as in Reference Example 1 except that the surface on the coated surface used in Reference Example 1 was not subjected to corona discharge treatment. The resulting film showed good adhesive strength. However, the ink adhesion was inferior to that of Reference Example 1.

Comparative Example 11 Laminate strength and heat seal strength were measured in the same manner as in Reference Example 1 except that the surface of the coated surface used in Reference Example 1 was subjected to corona discharge treatment and the treatment power was changed. The ink adhesion of the obtained film is good, but the adhesive strength is
It was inferior to Reference Example 1.

[0050]

[Table 1]

[0052]

[Table 1]

[0053]

The easily-adhesive polyamide film of the present invention has blocking resistance, slipperiness, transparency, adhesiveness with printing inks, laminates and other coating agents, especially adhesiveness under wet conditions during boiling and retorting. Is excellent and is a polyamide film most suitable for boil sterilization, retort sterilization, and water product packaging applications. Furthermore, the present invention is inexpensive because it is an in-line coating, and is safe because it uses a water-based coating agent, and since the surface tension of the film before coating is controlled by the water droplet contact angle, it is easy with a small amount of coating agent. Moreover, a film having excellent adhesive strength can be obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI B29L 9:00 B29L 9:00 (56) Reference JP-A-2-3432 (JP, A) JP-A-2-202929 (JP , A) Japanese Patent Laid-Open No. 3-133639 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 7/04

Claims (3)

(57) [Claims] 1. An unstretched or uniaxially stretched,
A polyamide film which has not been heat-treated and has a surface water drop contact angle of 45 to 60 degrees,
A: Having a functional group that contributes to a crosslinking reaction with an epoxy group,
98 to 30 parts by weight of water-soluble acrylic acid ester copolymer or water-soluble methacrylic acid ester copolymer having a glass transition point of 40 ° C. or higher, B: water-soluble polyepoxy compound 2 to
70 parts by weight, C: average particle size 0.005-1.0 μm
The coating amount of the aqueous coating solution containing 0.1 to 10 parts by weight of the fine particles of 0.001 to 0.008 g / m ² after stretching
After coating so that the coating surface of the film is stretched in at least one direction, and then the coating surface of the film is surface-treated, and the wettability index of the coating surface is 40 to 52 dyn / cm. 2. A composite film in which the easily adhesive coated surface of the easily adhesive polyamide film according to claim 1 and another layer are laminated. 3. The composite film according to claim 2, wherein the other layer is another plastic film.