JP3221532B2 - Polyester composite film for metal lamination - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester composite film for laminating a metal, and more particularly to a metal can having a long can wall (for example, a beer can, a carbonated beverage can, a juice can, an aerosol can, etc.). The present invention relates to a polyester composite film suitable as a constituent material of a laminated steel sheet.

[0002]

2. Description of the Related Art Conventionally, a metal can is coated to prevent a metal odor from migrating to its contents and preventing the contents from corroding the inner surface of the metal can.
For the purpose of simplifying the process, improving hygiene, preventing pollution, etc., after laminating the polyester film by heating and pressure bonding to a metal plate such as tin, tin-free steel, aluminum, etc. without using an organic solvent, Investigation of a method for making cans by drawing or the like is in progress.

For example, JP-B-57-23584, JP-B-59-34580, and JP-B-62-61.
No. 427 discloses the technical contents thereof. However, in this technique, when laminated with a steel plate at a temperature equal to or higher than the melting point of the polymer constituting the film and sufficiently adhered to the steel plate, an impact during can making, that is, a local impact on the bottom of the can due to an impact applied to the stopper at a high speed. Film tears (cracks) occur. In order to avoid such drawbacks, when trying to improve the flexibility of the film to secure deformation resistance and impact resistance, the film sticks to the punch due to the heat generated by the processing by the die and punch in the can making process. Often, the film on the can wall is torn and torn. further,
Traces of the transfer pins are likely to be formed during transfer in a heat treatment step or the like after the can making process. That is, various problems due to insufficient heat resistance occur. Further, the polyester having improved flexibility has a disadvantage that the property of adsorbing the fragrance component in the can filling is deteriorated, that is, the flavor resistance is poor. From the above, it is not satisfactory as a metal can inner protective layer.

In order to avoid such a disadvantage, Japanese Patent Laid-Open Publication No.
No. 1630 discloses a method using two types and two layers of a composite polyester film. However, it has been difficult to achieve a balance between moldability and heat resistance to a level that satisfies market requirements.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and has a deformability, an impact resistance and an adhesion during a can-making process, and has excellent heat resistance. There is no punch adhesion and no trace of transfer pins during processing.
Provided is a polyester composite film for metal lamination having good flavor resistance.

[0006]

According to the present invention, there are provided an A layer, a B layer,
A polyester composite film comprising an A layer, wherein the A layer is made of a copolymer of polyethylene terephthalate and isophthalate having a melting point of 210 to 230 ° C,
The layer contains 50 mol% or more of terephthalic acid residues, 5 to 50 mol% of aliphatic dicarboxylic acid residues having 10 or more carbon atoms in all dicarboxylic acid components, and 50 mol% of all alcohol components.
The above is a polyester composite film for metal bonding, characterized by being made of a polyester resin having a glass transition point of 1,4 butanediol residue and having a glass transition point of 40 ° C. or less.

[0007] The polyester resin constituting the layer A in the present invention must be a copolymer of polyethylene terephthalate and isophthalate having a melting point of 210 to 230 ° C. Such a polyester resin is allowed to contain a diethylene glycol residue by-produced in the production process.
Further, other copolymer components may be contained within the above melting point range, but it is better not to contain other copolymer components from the viewpoint of flavor resistance. From the viewpoint of flavor resistance, the content of the diethylene glycol residue is preferably as small as possible.
The copolymerization ratio of isophthalate varies depending on the amount of diethylene glycol residue by-produced in the polyester production process, but is generally in the range of 8 to 18 mol%. Melting point 210
If the temperature is lower than ℃, the heat resistance is low and punch sticking occurs during the can-making process, the operability of the can-making process is lowered, and the film of the can wall is torn, which is not preferable because it causes problems such as tearing. . On the other hand, when the temperature exceeds 230 ° C., the adhesiveness at the time of heat lamination with a metal plate is reduced, and the film tearing (crack) starting from local film peeling at the can wall portion at the time of can making is preferable, which is preferable. Absent.

The A layer has two layers, an upper layer and a lower layer. The thickness of each layer may be the same, but the function differs between the side laminated with the metal plate and the opposite layer. It is a more preferable practice to respond by changing the thickness. A on the side to be laminated with the metal plate
Layer (A ₂ layer) adhesiveness imparting to the metal plate, whereas the opposite layer (A ₁ layer), confer heat resistance and flavor retention is its primary function. When each is called an adhesive layer and a protective layer and classified, the thickness of the adhesive layer is preferably 1 to 15 μm. 2 to 10 μm is more preferred. When the thickness is less than 1 μm, the adhesion to the metal plate becomes insufficient, which is not preferable. Conversely, if it exceeds 15 μm, the adhesion to the metal plate is saturated, and the deformability and impact resistance are undesirably reduced. On the other hand, the thickness of the protective layer is preferably 1 to 20 μm.
-15 μm is more preferable. If it is less than 1 μm, the effect of improving heat resistance and flavor resistance is not sufficient, which is not preferable. Conversely, if it exceeds 20 μm, the effect of improving heat resistance and flavor resistance is saturated, and at the same time, deformability and impact resistance are undesirably reduced.

In the polyester resin constituting the layer B in the present invention, 50 mol% or more of the total acid component contains terephthalic acid residues, and 5 to 50 mol% contains aliphatic dicarboxylic acid residues having 10 or more carbon atoms. A glass transition point in which at least 50 mol% of all alcohol components are composed of 1,4 butanediol residues is 4
It must be less than 0 ° C. If the amount of terephthalic acid is less than 50 mol%, heat resistance is insufficient, so that it is not preferable. Examples of the aliphatic dicarboxylic acid having 10 or more carbon atoms include sebacic acid, eicoic acid, dodecanedicarboxylic acid, and dimer acid. Dimer acid is obtained by a dimerization reaction of a higher unsaturated fatty acid such as oleic acid and generally has an unsaturated bond in the molecule. Hydrogenation is more preferable because heat resistance and flexibility are improved. In the course of the dimerization reaction, a linear branched structure, an alicyclic structure, and an aromatic nucleus structure are generated, but these structures and amounts are not particularly limited. 1 carbon
An aliphatic dicarboxylic acid residue of less than 0 is not preferable because deformation and impact resistance are not sufficiently imparted. The content of the aliphatic dicarboxylic acid residue needs to be 5 to 50 mol% based on the total acid component. If it is less than 5 mol%, it is not preferable because imparting of deformability and impact resistance becomes insufficient. Conversely, if it exceeds 50 mol%, the deformability and the impact resistance are saturated, and the heat resistance is undesirably reduced.

[0010] The polyester resin constituting the layer B is not particularly limited to include dicarboxylic acid residues other than terephthalic acid and an aliphatic dicarboxylic acid having 10 or more carbon atoms as an acid component as long as the above range is satisfied. In addition, carbon number 1
The aliphatic dicarboxylic acid residue of 0 or more may be one kind,
Two or more kinds may be used in combination. In the polyester resin constituting the layer B, 50 mol% or more of the total alcohol component is 1,4.
It must be a butanediol residue. If the amount is less than 50 mol%, the crystallinity of the resin is reduced, and the handleability of the resin is deteriorated. More preferably, 90 mol% or more are 1,4 butanediol residues. Other glycol components include ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, 1,4 cyclohexane dimethanol, and the like. It is a preferred embodiment that the total amount is a 1,4 butanediol residue. The polyester resin constituting the B layer needs to have a glass transition point of 40 ° C. or lower. 30
C. or lower is more preferable. If the glass transition point exceeds 40 ° C., it is not preferable because deformation and impact resistance are not sufficiently imparted.

The structure of the polyester resin constituting the layer B can be arbitrarily set within the above range. The thickness of the layer B is preferably from 10 to 60 μm. 15-4
0 μm is more preferred. If it is less than 10 μm, it is not preferable because deformation and impact resistance are not sufficiently imparted. Conversely 6
If it exceeds 0 μm, it is not preferable because imparting of deformability and impact resistance is saturated and heat resistance is lowered. It is also disadvantageous in terms of cost.

It is preferable that both polyester resins constituting the layer A and the layer B have an intrinsic viscosity of 0.5 or more. More than 0.7 is more preferable. Also,
One type of polyester resin constituting each layer may be used, or two or more types may be blended and used. Further, if necessary, these polyester resins may contain an antioxidant, a heat stabilizer, an ultraviolet absorber, a plasticizer, a pigment, an antistatic agent, a lubricant, a crystal nucleating agent, a lubricant comprising inorganic or organic particles, and the like. The compounding is not restricted at all. There is no limitation on the method for producing the polyester resin described above,
Any of those produced by a transesterification method or a direct polymerization method can be used. Further, those produced by a solid-phase polymerization method to increase the molecular weight may be used. The polyester resin constituting the layer A is a polyester resin having a low oligomer content produced by a vacuum solid-phase polymerization method in that the precipitation of oligomers from the polyester resin during retort treatment or the like after filling the contents in the can is reduced. Is a particularly preferred embodiment.

As described above, the composite film of the present invention
As long as the layer, the layer B, and the layer A are arranged in this order, either an unstretched film or a stretched film may be used. The film having the layer structure is preferably produced by a multilayer extrusion method. Uniaxial stretching and 2 for stretched film
Any of axial stretching may be used, but a biaxially stretched film is preferred from the viewpoint of isotropy. The method for producing the composite film is not limited at all. For example, in the case of a stretched film, any of the T-die method and the tubular method can be applied. When the composite polyester film of the present invention is used for laminating a metal, it is necessary to use the A2 layer surface as a metal plate side. The bonding method is not particularly limited, but the most preferred embodiment is a method in which the composite polyester film is pressure-bonded to a metal plate heated by an electric current method and thermally bonded.

The present invention will be described below based on embodiments.
The measuring method used in the examples is as follows. (1) Melting point (Tm), glass transition point (Tg) Determined using a differential scanning calorimeter. Sample at 300 ° C
And then quenched with liquid nitrogen for 10 minutes.
Was heated at a heating rate of 10 ° C./min, a specific heat change based on a transition from a glassy state to a rubbery state was read, and this temperature was taken as a glass transition point (Tg). The endothermic peak temperature based on crystal melting was defined as the melting point (Tm).

(2) Adhesiveness A composite polyester film and a tin plate having a thickness of 0.29 mm are overlapped between a metal roll and a rubber roll heated to 230 ° C. (the surface of the A2 layer of the composite polyester is brought into contact with the tin plate), and pressure is applied. Passed at 20 kg / cm. The adhesive strength (lamination strength) of the film and tin laminate after passing was measured by Tensilon. ：: Laminate strength of 200 g / cm or more ×: Laminate strength of less than 200 g / cm

(3) Stick temperature The film surface of the laminated film laminated on the tin plate by the method of (2) is adhered to a metal roll heated to a predetermined temperature, and the resistance is sharply increased by hand-holding adhesion. Measure. Evaluation was performed at a 5 ° C. pitch, and finally, evaluation was performed at a 1 ° C. pitch to determine the stick temperature. If the stick temperature is less than 80 ° C., the sticking of the punch occurs in the can making process, and the operability of the can is reduced, which is not preferable.

(4) Heat resistance The laminated film laminated on a tin plate by the method of (2) is cut into a size of 5 cm × 5 cm.
After a weight of 100 g was placed and heated at 200 ° C. for 5 minutes, the appearance of traces of the weight was visually evaluated. (5) Impact resistance A film having a tip diameter of 4 mm and a weight of 0.4 kg is applied to the film surface of the laminated film laminated on the tin plate by the method of (2).
Was vertically dropped from a height of 30 cm and deformed to make a model of a can. The can-made model laminated film was 220
After heat treatment at 10 ° C. for 10 minutes, the mixture was placed in a water-laden autoclave and heated at 120 ° C. for 30 minutes to perform a retort model treatment. A weight having a flat bottom and a weight of 0.4 kg was dropped vertically from a height of 24 cm from the tin plate side to a portion deformed by the can-made model of the retort model-processed laminated film to give an impact. A pipe made of polyvinyl chloride was bonded to the film side of the laminated film subjected to the impact with an adhesive, 1% saline was inserted into the pipe, an electrode was inserted, and a voltage of 6 V was applied using a tin plate as an anode, and after 30 seconds, Current value (m
A) was measured. It is preferably 0.2 mA or less.

(6) Wrinkles after heat treatment A laminate film laminated on a tin plate by the method of (2) was press-formed with a press at a pressure of 100 kg / cm ² to obtain a cup. After the cup was heated at 200 ° C. for 5 minutes, the state of wrinkling of the film was visually evaluated.

(7) Flavor resistance A 10 cm square film is sealed three-sided with an impulse sealer with the A1 layer side as the inner surface. D-
Fill with 30 cm of limonene and seal the opening with an impulse sealer. The sealed bag is allowed to stand in a constant temperature room at 40 ° C. for 10 days to adsorb d-limonene. After the suction bag is opened and d-limonene is discharged, the film of the unsealed portion is cut out to a size of 4 cm square, and d-limonene adheres to the surface.
- to measure the weight W ₁ of the film wipe clean the limonene in the Kimwipe. After vacuum drying the film at 60 ° C. for 24 hours, the weight W ₂ of the film is measured again. d
-The amount of limonene adsorbed was determined by the following formula and expressed in terms of% by weight. The amount of adsorbed d-limonene (%) = W ₁ -W ₂ / W ₂ It is practical that the amount of adsorbed d-limonene is 2% or less.

Example 1 Spherical silica 200 having an average particle diameter of 3 μm as a layer A resin
Terephthalic acid / isophthalic acid containing 0 ppm (molar ratio 8
8/12) and ethylene glycol (Tm 225 ° C.) [Polyester A], terephthalic acid containing 0.2% by weight of Irganoc / 330 as a B-layer resin / dimer acid having 36 carbon atoms (molar ratio) 90 /
10) and a copolymerized polyester (Tm 204 ° C., Tg 4 ° C.) from 1,4 butanediol (polyester B) are melted by separate extruders, and the melts are combined and separated in a die, and then cooled. Extruded on a drum and cooled to form a three-layer structure consisting of A / B / A layers.
(A1 layer thickness 8 μm, B layer thickness 20 μm, A2 layer thickness 4
μm). Table 1 shows the properties of the obtained film and the laminated film with the tin plate (the A2 layer side was laminated, and in the following Examples and Comparative Examples, the A2 layer side was laminated). The composite film obtained in this example is excellent in adhesiveness, operability in can-making, heat resistance, impact resistance, and flavor resistance, and is highly practical as a film for bonding metal. there were.

Comparative Example 1 Copolymerized polyester (Tm245) of terephthalic acid / isophthalic acid (molar ratio: 95/5) containing 2000 ppm of spherical silica having an average particle diameter of 3 μm and ethylene glycol instead of polyester A as the resin for layer A. ° C) The properties of the unstretched film and the laminate film with the tin plate obtained by the same method as in Example 1 except that [Polyester C] was used are shown in Table 1. The composite film obtained in this comparative example was inferior in adhesiveness and low in practicability as a metal bonding film.

Comparative Example 2 Copolymerized polyester (Tm170) of terephthalic acid / isophthalic acid (molar ratio 67/33) containing 2000 ppm of spherical silica having an average particle diameter of 3 μm and ethylene glycol instead of polyester A as the resin for layer A. C., measured with a Mettler melting point apparatus).
Table 1 shows the properties of the unstretched film and the laminate film with the tin plate obtained by the same method as described above. The composite film obtained in this comparative example had a low stick temperature, was poor in heat resistance, was inferior in can-making operability, etc., and was of low practicality as a film for metal bonding.

Comparative Example 3 Polybutylene terephthalate (Tm2
Table 1 shows the properties of the unstretched film and the laminate film with the tin plate obtained by the same method as in Example 1 except for [Polyester E]. The film obtained in this comparative example was inferior in impact resistance, and was of low practicality as a film for metal bonding.

Comparative Example 4 The properties of an unstretched film and a laminate film with a tin plate obtained by the same method as in Example 1 except that polyester A is used for both the A layer resin and the B layer resin are shown in Table 1. The composite film obtained in this comparative example was inferior in impact resistance and was of low practicality as a film for bonding metal.

Comparative Example 5 The properties of an unstretched film and a laminate film with a tin plate obtained by the same method as in Example 1 except that polyester B is used for both the A layer resin and the B layer resin are shown in Table 1. The composite film obtained in this comparative example was inferior in heat resistance and flavor resistance and was of low practicality as a film for bonding metal.

Example 2 As a layer A resin. Copolymerized polyester (Tm 215 ° C.) [polyester F] of terephthalic acid / isophthalic acid (molar ratio 83/17) containing 700 ppm of amorphous silica having an average particle size of 2.5 μm and ethylene glycol [Polyester F]
Polyester B is melted in a separate extruder as a layer resin, and the melts are joined and merged in a die, and then extruded on a cooling drum and cooled to form a three-layer A / B / A layer. A stretched film was obtained. The unstretched film is first stretched 3.3 times in the longitudinal direction at 85 ° C., then 3.4 times in the transverse direction at 100 ° C., and then heat-set at 170 ° C. to a total thickness of 32 μm [A1 layer 7 μm, B layer 20μ
m, A2 layer 5 μm). Table 1 shows the properties of the obtained film and the laminate film with the tin plate. The composite film obtained in this example was excellent in all the properties and was highly practical as a film for bonding metal.

Comparative Example 6 Table 1 shows the properties of a biaxially stretched film and a laminate film with a tin plate obtained in the same manner as in Example 2, except that polyester C was used in place of polyester F as the resin for layer A. The composite film obtained in this comparative example was inferior in adhesiveness and low in practicability as a metal bonding film.

Comparative Example 7 Copolymerized polyester (Tm 200 ° C.) of terephthalic acid (molar ratio 80/20) containing 700 ppm of amorphous silica having an average particle diameter of 2.5 μm and ethylene glycol instead of polyester F as the resin for layer A Table 1 shows the properties of the biaxially stretched film obtained by the same method as in Example 2 except that [Polyester G] was used and the film laminated with a metal plate. The composite film obtained in this comparative example had a low stick temperature, was poor in heat resistance, was inferior in can-making operability, and had low practicality as a film for bonding metal.

Comparative Example 8 The properties of a biaxially stretched film and a laminate film with a tin plate obtained in the same manner as in Example 2 except that polyester E was used instead of polyester B as the B layer resin are shown in Table 1. The composite film obtained in this comparative example was inferior in impact resistance and was of low practicality as a film for bonding metal.

Comparative Example 9 The properties of a biaxially stretched film and a laminate film with a tin plate obtained in the same manner as in Example 2 except that polyester F was used for both the A-layer resin and the B-layer resin are shown in Table 1.
The composite film obtained in this comparative example was inferior in impact resistance and low in practicability as a film for bonding metal.

Comparative Example 10 The properties of a biaxially stretched film and a laminate film with a tin plate obtained in the same manner as in Example 2 except that polyester B was used for both the A-layer resin and the B-layer resin are shown in Table 1.
The composite polyester film obtained in this comparative example was inferior in heat resistance and flavor resistance and was of low practicality as a film for metal bonding.

Example 3 Copolymerized polyester (Tm 220 ° C.) of terephthalic acid / isophthalic acid (molar ratio 85/15) containing 2000 ppm of crosslinked polymethyl methacrylate-based beads having an average particle size of 3 μm as layer A resin and ethylene glycol )
[Polyester H] was used as a B-layer resin to prepare a copolymerized polyester (Tm 195 ° C., Tg) of terephthalic acid / sebacic acid (molar ratio 80/20) and 1,4 butanediol.
(10 ° C.) [Polyester I] was used to obtain an unstretched film having a total thickness of 32 μm (A1 layer: 7 μm, B layer: 20 μm, C layer: 5 μm) in the same manner as in Example 1. Table 1 shows the properties of the unstretched film and the laminate film with the tin plate. The composite film obtained in this example was excellent in all the properties and was highly practical as a film for bonding metal.

Example 4 Copolymerized polyester (Tm205) of terephthalic acid / dodecanedicarboxylic acid (molar ratio: 89/11) and ethylene glycol in place of polyester B as the B layer resin
Table 1 shows the properties of the biaxially stretched film and the laminate film with the tin plate obtained by the same method as in Example 2 except that [Polyester J] was used. The composite film obtained in this example was excellent in all properties and highly practical.

[0034]

The polyester composite film for metal lamination of the present invention has a three-layer structure and the characteristics of the polyester resin constituting each layer are controlled to a specific range. When applied to the production of metal cans with a long can wall after joining, they are excellent in heat adhesion to metal plates and in can processing, and have excellent heat resistance. It is very useful because it has good operability in the process and excellent impact resistance and flavor resistance after can making.

[0035]

[Table 1]

──────────────────────────────────────────────────続 き Continuing on the front page (72) Kuniharu Mori 344 Maebata, Kizu, Inuyama-shi, Aichi Prefecture Toyo Boseki, Ltd. Yurika Ashihara Examiner, Headquarters Co., Ltd. (56) References JP-A-5-154971 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (1)

(57) [Claims] 1. A polyester composite film comprising an A layer, a B layer and an A layer, wherein the A layer has a melting point of 210 to 2
The layer B is composed of a copolymer of polyethylene terephthalate and isophthalate at 30 ° C.
Glass in which 0 mol% or more contains terephthalic acid residues, 5 to 50 mol% contains aliphatic dicarboxylic acid residues having 10 or more carbon atoms, and 50 mol% or more of all alcohol components are 1,4 butanediol residues. A polyester composite film for bonding metal, comprising a polyester resin having a transition point of 40 ° C. or lower.