JP2951093B2 - Polyester film for metal plate lamination processing - 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 film for laminating and forming a metal plate, and more particularly, it shows excellent formability when laminating a metal plate and performing can making such as drawing. The present invention relates to a polyester film for laminating and forming a metal plate that is resistant to cracking even when subjected to an impact from the outside of the can after the can is made.

[0002]

2. Description of the Related Art Metal cans are generally coated to prevent corrosion of the inner and outer surfaces. Recently, for the purpose of simplifying the process, improving hygiene, and preventing pollution, rust prevention is performed without using an organic solvent. Development of a method for obtaining the property has been advanced, and as one of the methods, coating with a thermoplastic resin film has been attempted. That is,
Studies have been made on a method of laminating a thermoplastic resin film on a metal plate such as tinplate, tin-free steel, or aluminum, and then forming the can by drawing or the like. Polyolefin films and polyamide films have been tried as the thermoplastic resin film, but they do not satisfy molding workability, heat resistance and impact resistance.

On the other hand, polyester films, particularly polyethylene terephthalate films, have attracted attention as having balanced properties, and several proposals based on them have been made. That is, (A) a biaxially oriented polyethylene terephthalate film is laminated on a metal plate via a low-melting-point polyester adhesive layer and used as a can-making material (JP-A-56-10451).
No. JP-A-1-192546). (B) Amorphous or extremely low-crystalline aromatic polyester film is laminated on a metal plate and used as a material for can production (Japanese Patent Application Laid-Open Nos. 1-192545 and 2-573).
No. 39). (C) A low-orientation, heat-fixed, biaxially oriented polyethylene terephthalate film is laminated on a metal plate and used as a can-making material (Japanese Patent Laid-Open No. 64-22530).

[0004]

However, none of these methods can provide sufficient characteristics, and it has been found that each of the methods has the following problems. Regarding (A), the biaxially oriented polyethylene terephthalate film is excellent in heat resistance, but is insufficient in moldability, and causes whitening (generation of minute cracks) and breakage of the film in canning with large deformation. . (B) is an amorphous or extremely low-crystalline aromatic polyester film and thus has good moldability, but is easily embrittled by post-processing such as printing after can-making and retort sterilization. Transforms into a fragile film due to external impact. (C)
Is not effective in the intermediate region between the above (A) and (B), however, since the isotropy of the film surface is not guaranteed, the omnidirectional When the deformation is performed, the formability in a specific direction of the film may be insufficient.

The present inventors have further studied to develop a polyester film for can-making without these problems, and as a result, by using a specific copolymerized polyester as a raw material of the film, the moldability and can-making were improved. The present inventors have found that a polyester film for can processing excellent in later impact resistance can be obtained, and arrived at the present invention.

[0006]

That is, the present invention is directed to a method for producing a terephthalic acid according to the present invention, wherein the main acid component is composed of terephthalic acid, and the glycol component is composed of 5 to 30 mol% of pentamethylene glycol and 95 to 70 mol% of ethylene glycol.
A polyester film for laminating a metal plate, comprising a copolymerized polyester having a secondary transition point of 245 ° C. or less and a lubricant having an average particle diameter of 2.5 μm or less.

The acid component constituting the copolymerized polyester in the present invention mainly comprises a terephthalic acid component. Here, “mainly” means that 80% by mole or more of the acid component is a terephthalic acid component. Even if a small amount of another acid component such as isophthalic acid or adipic acid is copolymerized at a ratio of 20% by mole or less. Good. However, usually, the desired copolymerized polyester can be obtained solely from the terephthalic acid component alone, and the melting point may be too low due to the copolymerization of the other acid component. Therefore, it is preferable not to use the other acid component. On the other hand, the glycol component is 5 to 30 mol%, preferably 10 to 2 mol%.
5 mol% is a pentamethylene glycol component, 95 to 70
Mole%, preferably 90-75 mol%, must be the ethylene glycol component. If the pentamethylene glycol component is less than 5 mol%, the moldability and impact resistance of the resulting polyester film will be insufficient, and if it exceeds 30 mol%, the heat resistance will be insufficient and all will be satisfactory. No good product is obtained. When a glycol component other than pentamethylene glycol, for example, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, or the like is used, a polyester film having good moldability and impact resistance cannot be obtained.

[0008] The copolymerized polyester in the present invention must have a melting point in the range of 210 to 245 ° C.
When the melting point of the polymer is less than 210 ° C., the heat resistance is inferior, so that the heating in printing after can-making cannot be continued. On the other hand, when the melting point of the polymer exceeds 245 ° C., the crystallinity of the polymer is too high and the moldability is deteriorated. Here, the melting point of the polyester was measured by Du Pont Instrument.
s 910 DSC, a method of obtaining a melting peak at a heating rate of 20 ° C./min. The sample amount is about 20mg
And

The secondary transition point of the copolymerized polyester must be 80 ° C. or lower. Secondary transition point is 80
If the temperature is higher than ℃, the moldability and impact resistance of the polyester film will be insufficient. The secondary transition point described here is defined as the temperature distribution and t as measured by the “Vibron direct-reading dynamic viscoelasticity meter DDV-II type” manufactured by Toyo Baldwin.
The value of an δ is measured, the dynamic loss modulus (E ″) is determined based on the measured value of tan δ, and the temperature at which the value of E ″ becomes the maximum is defined as the secondary transition point. The measurement condition at this time is the driving frequency 1
The heating is performed at 10 cps, and the temperature is raised from room temperature at a rate of 1 ° C./min. The measurement sample is prepared by preparing a thin film having a width of 5 mm, a length of 20 mm and a thickness of 0.2 mm from the molten polymer, cooling the film immediately after forming the film, and leaving it at room temperature for 3 days or more. At this time, if there is unevenness in the thickness of the film, the measured values may vary slightly.
Each of the measurement films is measured, and an average value of the five measurement values is defined as a secondary transition point.

The copolymerized polyester in the present invention contains a lubricant having an average particle size of 2.5 μm or less. The lubricant may be inorganic or organic, but inorganic is preferred. As the inorganic lubricant, silica, alumina, titanium dioxide,
Calcium carbonate, barium sulfate and the like can be exemplified, and as the organic lubricant, silicone particles and the like can be exemplified. In any case, the average particle size needs to be 2.5 μm or less. When the average particle size of the lubricant exceeds 2.5 μm, coarse lubricant particles (for example, 10 μm) of a portion deformed by processing such as a deep drawing can are manufactured.
m or more) as a starting point, causing a pinhole,
In some cases, it is not preferable because it breaks.

The amount of the lubricant in the copolymerized polyester may be determined according to the winding property in the film production process. Generally, it is preferable to add a small amount of particles having a large particle diameter and a large amount of particles having a small particle diameter. For example, it is preferable to add about 0.05% by weight in the case of silica having an average particle diameter of 2.0 μm, and about 0.3% by weight in the case of titanium dioxide having an average particle diameter of 0.3 μm. By intentionally adjusting the content of the lubricant, the film can be made opaque. For example, titanium dioxide
By adding 0 to 15% by weight, a white film can be obtained.

The copolyester in the present invention can be produced by a conventionally known method. For example, a terephthalic acid component and an ethylene glycol or pentamethylene glycol component are subjected to an esterification reaction or a transesterification reaction in the presence or absence of a catalyst to obtain a bisglycol ester and / or a precondensate thereof. Then, it can be easily obtained by a polycondensation reaction in the presence of a polycondensation catalyst. In the production of the copolymerized polyester, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, and an antistatic agent can be added as necessary.

The polyester film of the present invention is obtained by melting the above-mentioned lubricant-containing copolymerized polyester, discharging it from a die, forming it into a film, biaxially stretching and heat setting. This polyester film preferably has a thickness of 6 to 75 μm. 10 to 75 μm, especially 15
It is preferably from 50 μm to 50 μm. If the thickness is less than 6 μm, breakage or the like is likely to occur during processing, while if it exceeds 75 μm, the quality is excessive and uneconomical.

As the metal plate for cans to which the polyester film of the present invention is bonded, a plate of tin, tin-free steel, aluminum or the like is suitable. The lamination of the polyester film to the metal plate is performed, for example, in the following (1),
It can be performed by the method of (2).

(1) A metal plate is heated to a temperature not lower than the melting point of the film, the film is bonded and then rapidly cooled, and the surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered.

(2) The film is previously coated with an adhesive layer with a primer, and this surface is bonded to a metal plate. As the adhesive layer, a known resin adhesive such as an epoxy-based adhesive,
Epoxy-ester adhesives, alkyd adhesives and the like can be used.

[0017]

The present invention will be further described with reference to the following examples.
However, parts in the examples mean parts by weight. In addition, the moldability and impact resistance of the film were evaluated by the following methods.

The obtained film is bonded to both sides of a tin-free steel sheet having a thickness of 0.25 mm heated to 260 ° C., cooled with water, cut into a disk having a diameter of 150 mm, and drawn in two stages using a drawing die and a punch. To form a 55 mm-diameter side seamless container (hereinafter abbreviated as can). The following observations and tests were performed on the cans, and each was evaluated according to the following criteria.

Formability--1 Good: Both inner and outer surfaces are processed into films without any abnormality, and no whitening or breakage is observed on the film on the inner and outer surfaces of the can. Some of the film on the inside and outside of the can is broken

Formability -2 ○: The inner and outer surfaces were processed without any abnormality, and the rust prevention test of the film surface in the can was carried out (1% NaCl water was put in the can, the electrode was inserted, the can was used as the anode, and 6 V was applied. Is measured when a voltage of 0.1 mA is applied.
×: The film has no abnormality on both the inner and outer surfaces, but the current value is 0.1 mA or more in the ERV test, and pinhole-shaped cracks starting from the coarse lubricant of the film are observed when the energized portion is enlarged and observed.

Impact resistance The cans having good moldability were filled with water, and 10 pieces of each test were dropped on a PVC tile floor from a height of 1 m for each test, and the ERV test was performed in the cans. , ０．１: 0.1 mA or less for all 10 pieces Δ: 0.1 mA or more for 1 to 5 pieces ×: 0.1 mA or more for 6 or more pieces, or cracks in the film are already observed after dropping

Heat Embrittlement Resistance The can having good moldability was heated and held at 210 ° C. for 5 minutes, and the above-mentioned impact resistance was evaluated. C: 0.1 mA or more for 1 to 5 pieces X: 0.1 mA or more for 6 or more pieces, or after heating at 210 ° C. for 5 minutes, cracks of the film are already observed

[0023]

Example 1 Production of copolymerized polyester: dimethyl terephthalate 97
0 parts, 583 parts of ethylene glycol (EG), 63 parts of pentamethylene glycol (PMG), and 1.23 parts of manganese acetate as a transesterification catalyst.
Then, the mixture was charged into a reactor provided with a methanol distilling condenser, and heated while gradually raising the temperature from 130 ° C. to 240 ° C., and methanol produced as a result of the reaction was distilled out of the system to carry out a transesterification reaction. Three hours after the start of the reaction, the internal temperature reached 240 ° C., and 320 parts of methanol were distilled off.
Here, 0.77 of trimethyl phosphate is used as a stabilizer.
Parts, 1.94 parts of spherical monodispersed silica having an average particle size of 1.5 μm as a lubricant, and 0.44 parts of antimony trioxide as a polycondensation catalyst were added. The reaction mixture was transferred to a reactor equipped with a stirrer and glycol distillation condenser,
The temperature was raised from 0 ° C. to 290 ° C., and the polycondensation reaction was carried out while reducing the pressure from normal pressure to a high vacuum of 1 mmHg. After a total polycondensation reaction time of 3 hours, a polymer having an intrinsic viscosity ([η]: measured at 30 ° C. using orthochlorophenol) of 0.651 was obtained. This polymer has a second transition point of 77 ° C. and a melting point of 23.
8 ° C. The molar ratio of the glycol component in the polymer was EG / PMG = 90/10. Production of polyester film: The copolymerized polyester obtained as described above was melt-extruded at 280 ° C. and solidified rapidly to obtain an unstretched film. Next, the unstretched film is stretched longitudinally at 100 ° C. by 3.0 times, and further stretched by 3.2 times while increasing the temperature from 110 ° C. to 160 ° C .;
The film was heat-set at 00 ° C. to obtain a 25 μm-thick biaxially oriented film. Table 1 shows the evaluation results of the film.

[0024]

Example 2 Production of copolymerized polyester: ethylene glycol was added to 53
6 parts and 141 parts of pentamethylene glycol were used, and 0.9% spherical monodispersed silica having an average particle diameter of 2.0 μm was used as a lubricant.
The same procedure as in Example 1 was carried out except that 7 parts were used, and [η]
A polymer of 0.648 was obtained. This polymer had a secondary transition point of 70 ° C. and a melting point of 216 ° C. The molar ratio of the glycol component in the polymer was EG / PMG = 75/2.
It was 5.

Production of polyester film: A biaxially oriented film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the temperature of the heat setting treatment was changed to 190 ° C. Table 1 shows the evaluation results of the film.

[0026]

Example 3 Production of copolymerized polyester: The same procedure as in Example 1 was carried out except that 922 parts of dimethyl terephthalate and 49 parts of dimethyl isophthalate were used as dicarboxylic acid components.
A polymer having [η] of 0.662 was obtained. This polymer had a secondary transition point of 75 ° C. and a melting point of 227 ° C.

Production of polyester film: A biaxially oriented film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the temperature of the heat setting treatment was changed to 190 ° C. Table 1 shows the evaluation results of the film.

[0028]

Comparative Example 1 Production of copolymerized polyester: 192 parts of dimethyl terephthalate and 58 parts of dimethyl isophthalate as a dicarboxylic acid component, and ethylene glycol 60 as a glycol component
Except for using 8 parts and 21 parts of pentamethylene glycol, the same procedure as in Example 1 was carried out to obtain a polymer having [η] of 0.653. This polymer had a secondary transition point of 78 ° C and a melting point of 240 ° C. The molar ratio of the glycol component in the polymer was EG / PMG = 98/2.

Production of polyester film: The same procedure as in Example 1 was carried out to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of the film.

[0030]

Comparative Example 2 Production of Copolyester: Ethylene glycol was added to 50
The same procedure as in Example 1 was carried out except that 5 parts and 193 parts of pentamethylene glycol were used, to obtain a polymer having an [η] of 0.660. This polymer had a secondary transition point of 51 ° C. and a melting point of 202 ° C. The molar ratio of the glycol component in the polymer was EG / PMG = 65/35.

Production of polyester film: A biaxially oriented film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the melt extrusion temperature was 270 ° C. and the temperature of the heat setting treatment was 180 ° C. Table 1 shows the evaluation results of the film.

[0032]

Comparative Example 3 A biaxially oriented film having a thickness of 25 μm was obtained in the same manner as in Example 1, except that 0.97 parts of spherical monodispersed silica having an average particle size of 2.8 μm was used as a lubricant. Table 1 shows the evaluation results of the film.

[0033]

Comparative Example 4 Production of Copolymerized Polyester: Performed in the same manner as in Example 1 except that 552 parts of ethylene glycol and 99 parts of tetramethylene glycol (TMG) were used as a glycol component to obtain a polymer having a [η] of 0.650. Was. This polymer had a secondary transition point of 78 ° C and a melting point of 231 ° C. The molar ratio of the glycol component in the polymer is EG / TM
G = 80/20.

Production of polyester film: The same procedure as in Example 1 was carried out to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of the film.

[0035]

Comparative Example 5 Production of copolymerized polyester: The same procedure as in Example 1 was carried out except that 552 parts of ethylene glycol and 130 parts of hexamethylene glycol (HMG) were used as a glycol component to obtain a polymer having an [η] of 0.654. Was. This polymer had a secondary transition point of 66 ° C. and a melting point of 233 ° C.
The molar ratio of the glycol component in the polymer is EG / H
MG = 80/20.

Production of polyester film: The same operation as in Example 1 was carried out to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of the film.

[0037]

Comparative Example 6 Production of copolymerized polyester: The same procedure as in Example 1 was carried out except that 854 parts of dimethyl terephthalate and 116 parts of dimethyl isophthalate were used as the dicarboxylic acid component, and 620 parts of ethylene glycol was used as the glycol component. [Η] A polymer of 0.653 was obtained. This polymer had a secondary transition point of 78 ° C and a melting point of 228 ° C.

Production of polyester film: The same procedure as in Example 1 was carried out to obtain a biaxially oriented film having a thickness of 25 μm. Table 1 shows the evaluation results of the film.

[0039]

[Table 1]

[0040]

According to the present invention, when forming cans such as drawing by laminating with a metal plate, it exhibits excellent formability.
Further, it is possible to provide a polyester film for metal plate laminating and forming, which is hard to be broken even when receiving an impact from the outside of the can after the can is made.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-52-127940 (JP, A) JP-A-54-95634 (JP, A) JP-A-57-70172 (JP, A) 210421 (JP, A) JP-A-2-305827 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08G 63/00-63/91 C08L 67/00-67/08 C09J 167/00-167/08 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] (1) a main acid component comprising terephthalic acid;
And the glycol component is pentamethylene glycol 5 to 3
0 mol% and 95-70 mol% ethylene glycol, consisting of a copolyester having a melting point of 210-245 ° C. and a secondary transition point of 80 ° C. or less, and an average particle size of 2.5 μm
A polyester film for laminating a metal plate, comprising the following lubricant: