JP3099999B2 - Metal laminating film and metal laminating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for metal laminating, and more particularly to a film having good adhesiveness, formability and slipperiness when drawing and ironing after lamination with a metal plate and after lamination. The present invention relates to a polyester film for metal lamination exhibiting the following.

[0002]

2. Description of the Related Art Conventionally, thermosetting paints are often applied to prevent corrosion of the inner and outer surfaces of metal beverage cans. On the other hand, it has been proposed that a thermoplastic resin film is heat-laminated on a metal plate and then formed into a can shape by drawing or ironing. As the thermoplastic resin film, a polyolefin film, a copolymerized polyester film, a polyester film with an adhesive and the like have been proposed. Japanese Patent Publication No. 2-58094 discloses a method for producing a film-coated metal plate in which a polyethylene terephthalate (PET) film is heat-laminated and then quenched to leave a non-oriented metal-laminated side and a biaxial orientation on the opposite side. Have been.

[0003]

However, the heat resistance and corrosion resistance of the polyolefin film are poor, and the film sticks to the plug at the time of drawing or ironing of the copolymerized polyester film, so that the plug does not easily come off, and the forming speed does not increase.
Laminating with an adhesive increases the cost, and there are problems with the drawability and ironability of the adhesive layer. Also P
In the method of heat laminating ET film, it is necessary to set the lamination temperature high, so that the metal plate is damaged,
Especially, the plating layer such as tin plate is greatly damaged, and PE
Since T alone has poor moldability itself, there has been a major problem in coping with deep drawing like a general beverage can.

On the other hand, when laminating a metal plate using a copolymerized polyester film, slippage between the heated metal plate and the film is poor, and air bubbles are often caught or wrinkled, resulting in poor lamination. However, this has caused coating defects such as film cracking during drawing and ironing.

[0005] The present invention improves the suitability of the film for metal lamination and the metal plate in the heat lamination, especially the slipperiness, and further improves the adhesiveness and formability in the forming in the drawing or ironing of the film-coated metal plate. It is an object of the present invention to provide a metal laminating film which can improve the film quality.

[0006]

According to the present invention, at least A
A film comprising a layer A and a layer B,
Consists biaxially oriented polyester in both layers, in the range crystallinity (chi _A) is 25-50% of the A layer, crystallinity of the B layer (chi _B) is. 15 to (chi _A -5) %, And the average surface roughness of the surface opposite to the layer A side of the layer B is 0.01%.
The present invention relates to a metal laminating film characterized by being in a range of from 1.0 to 1.0 μm and a metal laminated film comprising a metal plate laminated on the surface of the layer B opposite to the layer A side.

The polyester in the polyester film used in the present invention is obtained by polycondensation of a dicarboxylic acid and a diol, wherein the dicarboxylic acid is terephthalic acid, isophthalic acid, adipic acid, sebacic acid, azelaic acid, 2,6 -Naphthalenedicarboxylic acid, aromatic, aliphatic, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and diols such as ethylene glycol, butanediol, hexanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol; And a copolymer of two or more dicarboxylic acids or diols, or a mixture of two or more polymers. Further, copolymers with monomers or polymers such as diethylene glycol, triethylene glycol, and polyethylene glycol are also used.

Among these polyesters, those containing polyethylene terephthalate as a main component are preferred.
Those containing about 30 mol% of a copolymer component are preferred.
As the copolymerization component, isophthalic acid, sebacic acid, cyclohexanedimethanol and the like are preferable. As for the thermal properties of these polyesters, the melting point of the polyester in layer A on which the metal plate is not laminated is preferably from 210 to 280 ° C. Further, it is not preferable in that the production conditions become severe. The melting point of the polyester in layer B on which the metal plate is laminated is 170-250 ° C.
And the melting point of the polyester in the layer A is preferably 5 to 40 ° C. lower. If the melting point is too low, it is difficult to balance the layer with the layer A when forming a film, and if the melting point is too high, there is a problem in adhesion and moldability with a metal plate, which is not preferable. . However, in the present invention, as will be described later, it is important that the crystallinity of the A layer and the B layer are each in a specific range. For example, even if a polymer having a low melting point is used, the crystallinity is very high Such a film is not preferable because of poor adhesion.

Also, additives such as antioxidants, heat stabilizers, ultraviolet absorbers, inorganic particles, organic particles, pigments, antistatic agents and the like are added to the polyester as required without impairing the object of the present invention. May be.

[0010] One of the objects of the present invention is to improve the smoothness of the lamination of a film and a metal plate and to prevent poor lamination caused by bubble entrapment and generation of wrinkles. Although it is conceivable to improve the slip by roughening, the slip alone cannot be improved, and it has been confirmed that various problems occur in the formability and the like, and the present invention has been reached.
The reason is that a high temperature slip property of a heat lamination is required.

The film for metal lamination of the present invention comprises at least an A layer and a B layer, and the A layer on which the metal plate is not laminated is used for preventing adhesion with a nip roll or the like at the time of laminating the film and the metal plate, or for drawing or forming. It has the meaning of preventing sticking to the plug during ironing. On the other hand, the layer B on which the metal plate is laminated has a role of bonding (fusing) to the metal plate and ensuring the formability of the film. As is clear from this, the required characteristics are exactly opposite between the layer on which the metal plate is not laminated and the layer on which the metal plate is laminated, and it is possible to easily satisfy the requirements by adopting a two-layer structure.

[0012] The film after the metal plate is laminated needs to be in a state where biaxial orientation remains in order to maintain properties such as impact resistance and hydrolysis resistance.
Therefore, Japanese Patent Publication No. 2-58094 described above discloses that this can be achieved by a method of laminating a metal plate. However, it is very difficult to control the lamination method, and strict requirements are imposed on the accuracy of the thickness of the film. I have to be 2
With the layer structure, the degree of orientation or crystallinity can be easily controlled.

In the present invention, the crystallinity (χ _A ) of the layer _A is 25% to 50%, and the crystallinity (χ _B ) of the layer _B is 15%.
_{A% ~ (χ A -5)%} . When the crystallinity of the layer A is less than 25%, the plug adheres during molding and the plug is hardly removed, and when it is more than 50%, the stress at the time of molding is large and it is easy to crack, resulting in a problem in moldability. Crystallinity of B layer is 1
If it is less than 5%, the film is almost unoriented, and the physical properties of the film are unfavorably changed with time due to the volume relaxation phenomenon after production.
If it is not less than a small value, sufficient adhesive strength and moldability at the time of drawing are not obtained, which is not preferable. Further, the crystallinity of the layer B is also important for the coefficient of friction of the surface of the layer B with a metal at a high temperature. If the crystallinity is low, the slipperiness during lamination with a metal plate is unfavorable.

The average surface roughness of the layer opposite to the layer A side of the layer B of the metal laminating film of the present invention is 0.01 to 1.0.
μm, preferably 0.05 to 0.5 μm. 0.0
If it is less than 1 μm, there is a problem that wrinkles are easily formed due to poor slippage during lamination with the metal plate, and air is easily trapped between the film and the metal plate. It is not preferable because it becomes easy. However, a good lamination state is achieved only when the crystallinity of the layer B is in the range of the present invention. When the degree of crystallinity is low, wrinkles due to adhesion are likely to occur even if the surface roughness is appropriate, and when the degree of crystallinity is too high, air bubbles are trapped because the film surface does not soften and does not follow the irregularities on the metal plate surface This tends to cause film coating defects during molding after lamination.

The thickness of the metal laminating film of the present invention is 5 to 250 μm, and the most frequently used range is 10 to 50 μm.
m, more preferably 15 to 35 μm. Among them, the layer A on which the metal plate is not laminated is preferably thinner than the layer B on which the metal plate is laminated, and the more preferable thickness ratio is such that the layer A is thinner than 1: 5. It is preferable that the layer B is thick because the moldability, in particular, the laminated film follows the metal plate to be stretched easily and the adhesiveness is improved. On the other hand, the layer A is preferably at least about 5 μm or more. If it is too thin, it is not preferable because sufficient coating cannot be obtained on the side surface of the can which is drawn by drawing or ironing.

Next, a method for producing the film of the present invention will be described, but the present invention is not limited thereto.

The polyester A of the layer A on which the metal plate is not laminated and the polyester B of the layer B on which the metal plate is laminated are melt-extruded by separate extruders, and they are combined by a feed block system or a multi-manifold type die. Cast from a die onto a cooling drum. The unstretched film solidified by cooling is stretched in the longitudinal direction and the width direction, and is heat-treated as necessary. The stretching ratio in one direction is 2 to 6 times, preferably 3 to 5 times, and the heat treatment is appropriately selected according to the type and melting point of the polymer.

In order to control the crystallinity of each layer of the film among the above manufacturing steps, a combination of a cooling drum temperature, stretching conditions and heat treatment conditions is appropriately selected according to the characteristics of the selected polyester. is important.

The film thus obtained may be subjected to a general surface treatment such as a corona treatment, a plasma treatment or a chemical treatment, if necessary.

The film for metal lamination of the present invention can be suitably used for coating the inner and outer surfaces of a metal can produced by drawing or ironing. Also, it can be preferably used for covering the lid portion of a two-piece can or the body, lid, and bottom of a three-piece can because of its good metal adhesion and moldability.

[0021]

[Method of measuring characteristics and method of evaluating effects] The characteristic values of the present invention are determined by the following methods.

(1) Crystallinity The density of the fine pieces cut out from each layer was measured by a density gradient tube, and the crystallinity was determined by calculating the crystallinity from the densities of the amorphous state and the crystalline state of the polyester. In addition, the cross section of the sheet is cut out, the half width of the detected intensity measured by the laser Raman emission method of each layer in the sheet is determined, and the crystallinity is calculated from the half width in the amorphous state and the crystalline state of the polyester. Was.

(2) Average surface roughness A stylus type surface roughness meter HOMM specified by DIN4768
EL TESTERT10 type, cutoff 0.25m
The center line average surface roughness in m was measured.

(3) With respect to a sample film having a coefficient of friction of 80 × 150 mm, a chromium-plated steel sheet heated to 100 ° C. is superimposed on the surface of the layer B on which the metal plate is to be laminated, and 200 g is placed on the film.
And the value obtained by dividing the tension when the lower steel plate was pulled at a speed of 200 mm / min with the load of 200 g by the load of 200 g was defined as the friction coefficient.

(4) Formability A polyester film and a metal plate are laminated, molded by a press molding machine (VAS-33P type, manufactured by Senba Iron Works Co., Ltd.) at a pressure of 100 kg / cm ² , and a diameter of 100 m
m, a cup having a depth of 70 mm was obtained. The state of cracks in the film on the inner surface of the cup was visually observed and observed with a microscope.

[0026]

EXAMPLES The present invention will be described with reference to examples.

Example 1 10 mol% of isophthalic acid was used as the polyester for the layer A.
Using a polyethylene terephthalate (PET) resin copolymerized (relative to the acid component equivalent) and a PET resin copolymerized with isophthalic acid of 30 mol% (relative to the acid component equivalent) as the polyester for the B layer, each using a different extruder. After being melt-extruded and merged with a composite pipe, it was extruded from a T-type die onto a cooling drum kept at 40 ° C. and cooled to obtain an unstretched film. At this time, 0.5% by weight of silica particles having an average particle size of 0.01 μm was added to each of the polyester in the layer A and the polyester in the layer B, and melt extrusion was performed. Next, the unstretched film is
After stretching 3.3 times in the longitudinal direction at 100 ° C. and 3.3 times in the transverse direction at 100 ° C., heat treatment was performed at 200 ° C. for 5 seconds to obtain a film for metal lamination. The total film thickness is 30 μm,
The A layer was 5 μm and the B layer was 25 μm.

The degree of crystallinity of the obtained film was A layer 35.
%, B layer 22%, average surface roughness of B layer is 0.03 μm,
The coefficient of friction at 100 ° C. was 2.4.

The B layer surface of this film was superimposed on a tin plate having a thickness of 0.3 mm, and laminated between a metal roll and a nip roll at 220 ° C. at a linear pressure of 20 kg / cm and a speed of 5 m / min. It was confirmed that lamination could be performed smoothly without generation of wrinkles, and that even when reheated to 250 ° C., no swelling or the like occurred in the film and no air bubbles were caught. .

The metal plate after lamination was subjected to a molding test and found to be in a good molded state without cracking of the film.

Example 2 10 mol% of isophthalic acid was used as the polyester for the layer A.
Polyethylene terephthalate (PET) copolymerized (with respect to the acid component equivalent) is used as the polyester of the B layer. Isophthalic acid is 12 mol% (relative to the acid component equivalent) and cyclohexanedimethanol is 12 mol% (relative to the glycol component equivalent). Using the copolymerized PET, under the same film forming conditions as in Example 1, the total film thickness was 30 μm, the A layer was 5 μm,
A film for metal lamination having a layer B of 25 μm was obtained.

The degree of crystallinity of the obtained film was A layer 37.
%, B layer 21%, average surface roughness of the B layer is 0.04 μm,
The coefficient of friction at 100 ° C. was 1.9.

When this film was subjected to a laminating and forming test in the same manner as in Example 1, good laminating properties and moldability were confirmed.

Example 3 Polyester terephthalate (PET) obtained by copolymerizing 20 mol% of sebacic acid (based on the equivalent of the acid component) was used as the polyester of the layer A, and 15 mol% of isophthalic acid was used as the polyester of the layer B (based on the equivalent of the acid component). On the other hand) copolymerized PET
And a film for metal lamination having a total film thickness of 30 μm, an A layer of 5 μm, and a B layer of 25 μm under the same film forming conditions as in Example 1.

The degree of crystallinity of the obtained film was A layer 34.
%, B layer 27%, average surface roughness of the B layer is 0.04 μm,
The coefficient of friction at 100 ° C. was 1.9.

When this film was subjected to a laminating and forming test in the same manner as in Example 1, good laminating properties and moldability were confirmed.

Comparative Example 1 Isophthalic acid of 20 mol% was used as the polyester of the layer A.
Stretching in a film-forming process using polyethylene terephthalate (PET) resin copolymerized (relative to acid component equivalent) and PET copolymerized with 25 mol% (relative to acid component equivalent) of isophthalic acid as polyester B of layer B A film was formed in the same manner as in Example 1 except that the magnification was set to 2.6 times in the vertical direction and 2.8 times in the horizontal direction, and a lamination and molding test were performed.

The degree of crystallinity of the obtained film was A layer 15
%, B layer 13%, average surface roughness of the B layer is 0.03 μm,
The coefficient of friction at 100 ° C. was 6.5. In the lamination test, the surface of the layer B and the tin plate were slightly tacky, and the surface of the layer A and the nip roll were slightly tacky. Next, when a molding test was performed, cracking of the film was confirmed at the portion where the bubbles were caught, and both the molding plugs were slightly sticky and the moldability was poor.

Comparative Example 2 A film was formed in the same manner as in Example 1 except that the addition amount of the silica particles was 0.05% by weight. The crystallinity of the obtained film was 29% for the A layer, 20% for the B layer, the average surface roughness of the B layer was 0.005 μm, and the friction coefficient at 100 ° C. was 5.4. In the lamination test, slippage between the surface of layer B and the tin plate was poor, wrinkles were easily formed, and some air bubbles were caught in the interface of the laminate. Next, when a molding test was performed, it was confirmed that the film was cracked at a wrinkled portion or a portion where a bubble was caught.

Comparative Example 3 Polyester terephthalate (PET) copolymerized with 5 mol% of isophthalic acid (based on acid component equivalent) was used as the polyester for layer A, and 5 mol% isophthalic acid (based on acid component equivalent) was used as the polyester for layer B. On the other hand, using a PET resin obtained by copolymerizing cyclohexanedimethanol with 5 mol% (based on the equivalent of the glycol component) and the same film-forming conditions as in Example 1, the total film thickness was 30 μm, the A layer was 5 μm, and the B layer was 25 μm. A film for metal lamination was obtained.

The degree of crystallinity of the obtained film was A layer 37.
%, Layer B 33%, average surface roughness of layer B is 0.05 μm,
The coefficient of friction at 100 ° C. was 1.6.

When this film was subjected to a laminating and molding test in the same manner as in Example 1, the laminating property was good, but the film cracked on the side surface of the can during molding and the coating was poor.

Comparative Example 4 A film was produced in the same manner as in Example 1 except that the same polyester as that in Example 1 was used as the polyester in the layer A and the polyester in the layer B, and the heat treatment temperature in the film forming step was 160 ° C. Was formed into a film, and further subjected to a lamination and molding test.

The degree of crystallinity of the obtained film was A layer 22.
%, B layer 18%, average surface roughness of B layer 0.02 μm,
The coefficient of friction at 100 ° C. was 4.8.

In the lamination test, the surface of the layer B and the tin plate were sticky, and the surface of the layer A and the nip roll were also sticky, and air bubbles were slightly caught in the interface of the laminate. Next, when a molding test was performed, cracking of the film was confirmed at the portion where the bubbles were caught, and the molding plug was poor in moldability due to stickiness.

[0046]

[Table 1]

[0047]

The crystallinity of the layer A on which the metal plate is not laminated is in a high range, the crystallinity of the layer B on which the metal plate is laminated is in a relatively low range, and the layer B is lower than the layer A, By setting the average surface roughness of the B layer surface to a specific range, the slip property at the time of lamination with a metal plate is improved to reduce lamination defects, and the adhesiveness to the metal plate, the metal is stretched following the metal. In addition to the moldability, drawability and ironing can be made compatible with dies and punches and heat resistance.

Therefore, the film for metal lamination of the present invention can be used as a can for beverages by drawing,
It is suitably used for side-seamless containers by ironing.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FIB29L 9:00 (56) References JP-A-2-81630 (JP, A) JP-A-59-168927 (JP, A) Table Hei 2-501638 (JP, A) Special Table Hei 2-501640 (JP, A) Special Table Hei 2-501644 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B32B 1 / 00-35/00

Claims (2)

(57) [Claims] 1. A film comprising at least an A layer and a B layer, wherein both the A layer and the B layer are made of biaxially oriented polyester, and the crystallinity (χ _A ) of the A layer is 25 to
And the crystallinity (χ _B ) of the B layer is 15 to
(Chi _A -5) ranges% of the metal laminate film, wherein an average surface roughness of the opposite surface and the layer A side of the B layer is in the range of 0.01 to 1.0 [mu] m. 2. A metal laminated film comprising a metal plate laminated on a surface of the layer B opposite to the layer A side according to claim 1.