JP3224358B2 - White laminated 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 white laminated polyester film for laminating a metal plate, and more particularly to a metal useful for laminating a metal plate so that the film becomes the outer surface of a container. The present invention relates to a white laminated polyester film for plate forming.

[0002]

2. Description of the Related Art Metal cans are generally coated to prevent corrosion of the inner and outer surfaces. Recently, coating with a thermoplastic resin film has been attempted as a method for imparting rust prevention without using an organic solvent for the purpose of simplifying the process, improving hygiene, and preventing pollution. That is, a method of laminating a thermoplastic resin film on a metal plate of tin, tin-free steel, aluminum, or the like, followed by drawing, etc., has been studied.

[0003] Polyolefin films and polyamide films have been tried as the thermoplastic resin film.
It does not satisfy all of moldability, heat resistance and fragrance retention.

Therefore, attention has been paid to polyester films, especially polyethylene terephthalate films, as having balanced properties, and several proposals based on these have been made. That is, (A) a biaxially oriented polyethylene terephthalate film is laminated on a metal plate and used as a material for can production (JP-A-56-10451, JP-A-1-192546). (B) An amorphous or extremely low-crystalline aromatic polyester film is laminated on a metal plate and used as a material for producing a can (JP-A-1-192545, JP-A-2-5-5).
No. 7339). (C) A biaxially oriented polyethylene terephthalate film, which is heat-set with low orientation, is laminated on a metal plate and used as a can-making material (JP-A-64-22530).

[0005] However, in the investigations of the present inventors, no sufficient characteristics were obtained, and it was found that each had the following problems. Regarding (A), the biaxially oriented polyethylene terephthalate film is excellent in heat resistance and fragrance retention, but the molding processability is insufficient, and in the can-making process involving large deformation, minute cracks are generated in the film, In such cases, breakage occurs. About (B), since it is an amorphous or extremely low-crystalline aromatic polyester film, the moldability is good, but the fragrance retention is inferior, and post-processing such as printing after can-making, retort sterilization, Furthermore, there is a possibility that the film may be easily embrittled by long-term storage and be easily broken by an impact from the outside of the can. As for (C), the effect is not exerted in the intermediate region between the above (A) and (B), but it has not yet reached the low orientation applicable to can processing.

In general, printing is performed on the outer surface of the metal container. When printing, a white paint is preliminarily coated for the purpose of shading before printing. By setting the thermoplastic resin film to be laminated on the metal plate to a white light-shielding film, the undercoating of the white paint can be omitted. However, in the methods (A), (B) and (C), the white pigment In the case of a white film produced by adding, the respective disadvantages are not solved and the purpose of the outer surface of the can is not achieved. Furthermore, in the case of a white film containing titanium oxide at a high concentration for improving the concealing property, the film itself becomes brittle and frequently breaks during stretching, thereby deteriorating the film-forming property, and abrasion of the roll used at the time of film formation is a problem. Becomes

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a metal can which is excellent in film forming properties and roll abrasion, and is formed by laminating with a metal plate and then forming the metal can by, for example, deep drawing. Another object of the present invention is to provide a polyester film for metal plate laminating and forming which is excellent in lamination suitability, abrasion resistance, deep drawability, impact resistance after can production, heat resistance, and whiteness of the outer surface of the can.

[0008]

According to the present invention, a rutile type titanium oxide having an average particle size of 0.1 to 0.5 .mu.m is used for 10 to 50 days.
% Of a copolymerized polyester layer (B layer) having a melting point of 210 to 245 ° C. and an intrinsic viscosity of the polymer portion of 0.46 to 0.66, and an average particle size laminated on one surface of the B layer. 0.1 to 0.5 μm rutile type titanium oxide
Rutile-type titanium oxide having an average particle diameter of 0.1 to 0.5 μm, which is laminated on the other surface of a copolymer polyester layer (A layer) having a melting point of 210 to 245 ° C. 0-15% by weight, melting point 210-24
A laminated polyester film comprising a copolymerized polyester layer (C layer) at 5 ° C., wherein the intrinsic viscosity of the polymer portion of each copolymerized polyester film layer is (1) to (3).
A metal plate, wherein the X-ray diffraction intensity and the apparent density of the laminated film satisfy the expressions (4) and (5), respectively, and the MOR value is in the range of 1.5 or less. It is a white laminated polyester film for lamination processing.

[0009]

(Equation 2)

In the present invention, examples of the copolymerized polyester constituting the layer A, layer B and layer C include polyethylene terephthalate copolymer, polyethylene isophthalate copolymer, polyethylene-2,6-naphthalate copolymer and polybutylene. A terephthalate copolymer is exemplified. Among these, a polyethylene terephthalate copolymer is preferred.

The copolymer component of the copolymerized polyester may be an acid component or an alcohol component. Examples of the acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid, adipic acid, and the like.
Azelaic acid, sebacic acid, aliphatic carboxylic acids such as 1,10-decanedicarboxylic acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, and the like. Examples thereof include aliphatic diols such as 4-butanediol and 1,6-hexanediol, and alicyclic diols such as 1,4-cyclohexanedimethanol. These can be used alone or in combination of two or more. Of these, isophthalic acid and sebacic acid are preferred, and isophthalic acid is more preferred.

The types and proportions of the copolymerization components of the copolymerized polyester constituting the layer A, layer B and layer C may be the same or different.

The proportion of such a copolymer component depends on the type of the copolymer, but is a proportion that results in a polymer melting point of 210 to 245 ° C., preferably 215 to 235 ° C. When the melting point of the polymer is less than 210 ° C., the heat resistance is inferior. On the other hand, when the melting point of the polymer exceeds 245 ° C., the crystallinity of the polymer is increased, and the moldability is impaired.

Here, the melting point of the copolyester was measured by Du Pont Instruments 910.
A method in which a melting peak is determined at a heating rate of 20 ° C./min using DSC. The sample amount is about 20 mg.

The copolymerized polyester in the present invention can be produced by a known method. For example, as a method for producing copolymerized polyethylene terephthalate, terephthalic acid,
Ethylene glycol and a copolymerization component are subjected to an esterification reaction, and then the resulting reaction product is subjected to a polycondensation reaction to obtain a copolymerized polyethylene terephthalate, or dimethyl terephthalate, an ethylene glycol and a copolymerization component are subjected to a transesterification reaction, and then obtained. A preferred example is a method of subjecting the resulting reaction product to a polycondensation reaction to obtain a copolymerized polyethylene terephthalate. In the production of the copolymerized polyester, other additives such as a fluorescent whitening agent, an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent and the like can be added as required. In particular, when the whiteness is to be improved, the addition of a fluorescent whitening agent is effective.

In the present invention, the intrinsic viscosity of the polymer portion constituting the layer B is from 0.46 to 0.66, preferably from 0.48 to 0.64. This intrinsic viscosity is 0.
When it is less than 46, the film breakage during film stretching increases, and when the obtained film is laminated on a metal plate and then molded into a container, the film is likely to break. Also, 0.6
If it exceeds 6, it is uneconomical because the quality is excessive and the productivity of the raw material polymer decreases.

Further, the intrinsic viscosity (η _A ) of the polymer portion constituting the A layer and the intrinsic viscosity (η _C ) of the polymer portion constituting the C layer are related to each other and the intrinsic viscosity of the polymer portion constituting the B layer. In relation to the viscosity (η _B ), it is necessary to satisfy the above equations (1) to (3). Difference between the intrinsic viscosities of the polymer portions of these layers (the above-mentioned (1) to
(Left-hand side of the expression (3)) must all be less than 0.15, and all are preferably less than 0.12.
More preferably, all are less than 0.10. When at least one of the differences in the intrinsic viscosity of the polymer portion of each layer is 0.15 or more, a large orientation difference occurs in each layer of the laminated film, handling becomes difficult when laminating the film, and further, wrinkles and the like are generated. It is not preferable.

Here, the intrinsic viscosities of the polymer portions of the layer A, layer B and layer C were measured after dissolving in O-chlorophenol.
Remove filler such as titanium oxide by centrifugal separator 3
It was measured in a 5 ° C. solution.

In the present invention, the rutile type titanium oxide contained in the copolymerized polyester of the layer A, the layer B and the layer C is a rutile type titanium oxide having an average particle size of 0.1 to 0.5 μm. This average particle size is preferably from 0.2 to 0.4 μm. When the average particle size is less than 0.1 μm, it is difficult to uniformly disperse the copolymer in the copolymerized polyester, and the white concealing property becomes poor. It is difficult to produce rutile-type titanium oxide having an average particle size of more than 0.5 μm, and the produced product is also not preferable because it has many coarse particles.

The rutile titanium preferably has a purity of 95% or more. If it is less than 95%, when added at a high concentration, the dispersibility is poor, and the molecular weight of the copolymerized polyester is remarkably reduced.

In the present invention, the content of the rutile-type titanium oxide added to the copolymerized polyester constituting the layer B is 10%.
５０50% by weight, preferably 15-40% by weight. If the content is less than 10% by weight, the white concealing property of the film is not sufficient, while if it exceeds 50% by weight, the white concealing property is saturated, and the effect is not further improved. Becomes brittle and there are many film breaks during film stretching, and after laminating the obtained film to a metal plate,
When molded into a container, it tends to break.

The content of the rutile-type titanium oxide in the copolymerized polyester constituting the layers A and C is 0 to 15% by weight, preferably 0 to 10% by weight, more preferably 0 to 10% by weight, respectively. 6% by weight. If the content exceeds 15%, roll abrasion occurs in the film forming process, which is not preferable.

In the present invention, other white pigments such as alumina, calcium carbonate,
Silica, barium sulfate, zinc sulfide, anatase type titanium oxide and the like can be used.

Before adding the rutile-type titanium oxide in the present invention to the copolymerized polyester, it is preferable to adjust the particle size and remove coarse particles using a purification process. As an industrial means of the purification process, a pulverizing means includes, for example, a dry or wet centrifuge. These means may be used in combination of two or more, and may be purified stepwise.

Various methods can be used for incorporating the rutile type titanium oxide into the copolymerized polyester. A typical method is as follows. (A) A method of adding before the end of transesterification or esterification reaction at the time of synthesizing the copolyester, or adding before the start of the polycondensation reaction. (A) A method of adding to the copolymerized polyester and melt-kneading. (C) In the above methods (a) and (b), a method in which a master pellet containing a large amount of titanium oxide is produced, kneaded with a copolyester containing no particles, and a predetermined amount of rutile-type titanium oxide is contained. .

When the method (a) of adding rutile-type titanium oxide at the time of polyester synthesis is used, it is desirable to add the rutile-type titanium oxide to a reaction system as a slurry in which glycol is dispersed in glycol.

The apparent density (ρ) of the white laminated polyester film for laminating a metal plate of the present invention must satisfy the above-mentioned formula (5). By satisfying the expression (5), the film-forming property of the film can be improved. On the other hand, the ratio (ρ / ρ ₀ ) between the apparent density and the calculated density is 0.
If it is less than 75, the number of voids in the film increases, and the film becomes brittle, so that the film breaks during stretching and the productivity decreases. In addition, when the obtained film is bonded to a metal plate and then molded into a container, breaks, cracks, and minute defects are likely to occur. In addition, the density of the film was measured using the density gradient tube.

The white laminated polyester film for laminating a metal plate of the present invention must have an X-ray diffraction intensity ratio satisfying the above-mentioned formula (4). If the X-ray diffraction intensity ratio is less than 0.22, a large number of voids are generated due to titanium oxide in the film, causing film breakage during film formation and lowering of moldability, and furthermore, the above-mentioned formula (5). Cannot be satisfied, which is not preferable. Conversely, when the X-ray diffraction intensity ratio exceeds 0.4, thickness unevenness tends to occur during film formation, which is not preferable.

Here, the X diffraction intensity was measured by the following method. Using CuK-α as an X-ray source, measurement was performed under the conditions of a divergence slit of 1/2 °, a scattering slit of 1/2 °, a light receiving slit of 0.15 mm, and a scan speed of 1.000 ° / min, and a Pseudo Voice peel model was used. The following X-ray diffraction intensity was measured by the multiple peel separation method used, and the X-ray diffraction intensity ratio was calculated.

[0030]

[Outside 1]

However, the X-ray diffraction intensity was obtained by calculating the area of the diffraction peak on each crystal plane, and this area was defined as the X-ray diffraction intensity. Further, the reflection peaks (anatase (101) and rutile (110)) due to pigments such as titanium oxide are near the (100) plane, but the area was determined excluding this.

The white laminated polyester film for laminating a metal plate of the present invention must have an MOR value of 1.5 or less, preferably 1.45 or less. If the MOR value is more than 1.5, the in-plane anisotropy of the film becomes large, and it is not preferable because microcracks and cracks occur when the film is molded into a container after being bonded to a metal plate.

Here, the MOR value was measured using a molecular orientation meter MOA-2001A manufactured by Kanzaki Paper Co., Ltd., and the maximum value (X _MAX ) and the minimum value (X _MAX ) of the transmission intensity when microwaves were transmitted.
_MIN ) (formula (7) below) was taken as the MOR value.

[0034]

## EQU3 ## MOR value = X _MAX / X _MIN --- (7)

As an example of a method for producing such a film satisfying the requirements, a method using biaxial stretching, particularly sequential biaxial stretching will be described below, but the present invention is not limited to this method alone. .

The white laminated polyester film of the present invention for metal plate lamination processing is prepared by melting the polyester constituting each layer separately, coextruding from a die, laminating and fusion before solidifying, and immediately quenching to substantially cool. To obtain an amorphous copolyester sheet. Next, the sheet is heated by roll heating, infrared heating or the like and stretched in the machine direction. At this time, the stretching temperature is set to the glass transition point (T
g) at a temperature higher by 20 to 50 ° C., and a draw ratio of 2.5
It is preferable to set it to 3.6 times. When the film is stretched in the longitudinal direction, a method in which the film is divided into two or more times and stretched in the longitudinal direction is particularly preferable. The transverse stretching is the Tg of the copolymerized polyester.
It is preferable to start at a temperature 20 ° C. or more higher and to raise the temperature to a temperature 100 to 130 ° C. lower than the melting point (Tm) of the polyester. The magnification of the transverse stretching is preferably 2.6 to 3.7 times. The heat setting temperature is 150 ℃
It is preferable to select a temperature in the range of -230 ° C to adjust the film quality according to the melting point of the copolyester polymer. In addition, each copolymerized polyester can be separately melted, extruded to form a film, stretched by an unstretched state or stretched by the stretching method, and then laminated and fused.

The white laminated polyester film for laminating a metal plate of the present invention preferably has a thickness of 6 to 75 μm.
m. 10 to 75 μm, especially 15 to 50 μm
It is preferred that If the thickness is less than 6 μm, cracks and the like are likely to occur during processing, while if it exceeds 75 μm, the quality is excessive and uneconomical.

The white laminated polyester film for laminating and forming a metal plate of the present invention has a layer B as a core layer, a layer A on one surface of the layer B, and a layer C on the other surface of the layer B. It is a laminated film having a three-layer structure.

In the above white laminated polyester film for laminating and forming a metal plate, the ratio (X _A / X _B ) of the thickness (X _A ) of the layer A to the thickness (X _B ) of the layer _B and the thickness of the layer C ( X _C ) and the thickness ratio (X _C / X _B ) of the layer _B are each 0.1.
It is preferably from 0.5 to 1.0, and more preferably from 0.1 to 0.7.

As the metal plate to which the white laminated polyester film for metal plate lamination processing of the present invention is bonded, in particular, a metal plate for can making, a plate of tinplate, tin-free steel, aluminum or the like is suitable. The bonding of the polyester film to the metal plate can be performed, for example, by the following method. The metal plate is heated to a temperature equal to or higher than the melting point of the film, the film is laminated, and then cooled. The surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered. An adhesive layer is primer-coated on the film in advance, 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-based adhesives, alkyd-based adhesives, and the like can be used.

[0041]

The present invention will be further described below with reference to examples. The properties of the film were measured and evaluated by the following methods.

(1) Film-forming property The film-forming property of the film was evaluated according to the following criteria. ：: Stable film formation is possible with almost no film breakage. ×: Many film breaks occurred, resulting in poor film-forming properties.

(2) Abrasion A film cut into a half-inch width is bladed (UK G
The blade of a KI industrial razor testing machine) was placed vertically and pressed further in for 1.5 mm to bring it into contact with
The vehicle was driven at an entrance tension of 60 g at a speed of 60 m / min in an environment of 60 ° C. and a humidity of 60%. The amount of wear (W μm ³ ) of the blade after running the film for 50 m was measured with a scanning electron microscope (SEM) and evaluated according to the following criteria. 〇: W <4.0 × 10 ⁴ μm ³ ×: W ≧ 4.0 × 10 ⁴ μm ³

The films obtained in Examples and Comparative Examples were laminated on 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, drawn with a die and a punch. Deep-drawing in three stages using a 50mm diameter side seam (hereinafter abbreviated as can)
It was created.

(3) Suitability for lamination The film bonded to tin-free steel was observed and evaluated according to the following criteria. ○: Laminable without wrinkles ×: Wrinkles generated during lamination

Further, the following observations and tests were performed on these containers, and each was evaluated according to the following criteria.

(4) Deep drawing workability -1 ○: Both inner and outer surfaces are processed into a film without any excess, and fine cracks and breaks are not recognized in the film on the inner and outer surfaces of the can. X: Film breakage is observed in a part of the film on the inner and outer surfaces of the can.

(5) Deep drawing workability-2 ○: The inner and outer surfaces were processed without any abnormality, and the rust prevention test of the film surface on the inner surface of the can (1% NaCl water was placed in the can, the electrode was inserted, and the can was The current value is measured when a voltage of 6 V is applied to the anode, and the current value is 0.2 mA at ERV.
The following is shown. ×: There is no abnormality on the inner and outer surfaces, but the current value exceeds 0.2 mA in the ERV test, and when the energized portion is observed under magnification, pinhole-shaped cracks starting from the coarse lubricant are observed in the film.

(6) Impact cracking resistance For cans with good drawability, pour water thoroughly, drop 10 pieces for each test from a height of 30 cm onto a PVC tile floor, and conduct an ERV test in the can. As a result, ○: 0.2 mA or less for all 10 samples. Δ: More than 0.2 mA for 1 to 5 pieces. ×: Exceeding 0.2 mA for 6 or more pieces, or cracking of the film was already observed after dropping.

(7) Heat Embrittlement Resistance The can which had been subjected to good deep drawing was heated at 210 ° C. for 5 minutes and then subjected to impact cracking resistance evaluation described in (6). It is 0.2 mA or less per unit. Δ: More than 0.2 mA for 1 to 5 pieces. ×: Exceeding 0.2 mA for 6 or more, or 21
After heating at 0 ° C. for 5 minutes, cracks are already observed.

(8) Whiteness of can outer surface Before laminating the film and tin-free steel, the tin-free steel surface, which becomes the outer surface of the can after the can is made, has a length of 50 mm and a width of 0.2 mm, .4m
After the black line of m was filled in and the can was made, the black line was observed through a film and evaluated according to the following criteria. ：: Neither black line is visible. Δ: One black line looks faint, but the other black line is not visible. ×: One black line is visible, and the other black line is also faint.

[Examples 1 to 7, Comparative Examples 1 to 8] Rutile-type titanium oxide having an average particle size shown in Table 1 was added to a copolymerized polyethylene terephthalate obtained by copolymerizing the components shown in Table 1 in an amount shown in the table. Thus, copolymerized polyesters for the A layer, the B layer, and the C layer were obtained. Under the film-forming conditions shown in Table 3, these copolymerized polyesters were separately melted, co-pressed from dies adjacent to each other, laminated and fused, quenched and solidified to form an unstretched film, and then the unstretched film was cured. The film was stretched longitudinally and transversely under the conditions shown in Table 3 and then heat-set to obtain a biaxially oriented film having a thickness of 20 μm. Table 4 shows the properties of these films.
Shown in In addition, about Example 1, Example 3, and Example 4, when extending | stretching longitudinally, extending | stretching was performed twice by the draw ratio 1.7 times.

Comparative Example 9 Rutile-type titanium oxide and calcium carbonate having an average particle diameter shown in Table 2 were added to a polyethylene terephthalate copolymer obtained by copolymerizing 12% by mole of isophthalic acid, as shown in Table 3. It was melt-extruded under the film forming conditions shown, quenched and solidified to obtain an unstretched film, and then the unstretched film was stretched longitudinally, stretched horizontally, and then heat-set to obtain a biaxially oriented film having a thickness of 20 μm. Table 4 shows the properties of this film. In addition, the intrinsic viscosity of each layer in Table 4 is
It is the value of the unstretched film obtained by extruding the copolymerized polyester of each layer alone.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

[Table 3]

[0057]

[Table 4]

From the results shown in Table 4, the white laminated polyester film for laminating and forming a metal plate of Example was found to have film forming properties, abrasion resistance, suitability for lamination, deep drawability, impact cracking resistance,
It turns out that it is excellent in all of heat resistance and can outer surface whiteness.

[0059]

The white laminated polyester film of the present invention for laminating a metal plate has excellent film-forming properties and abrasion resistance, and after laminating to a metal plate, can forming, for example, deep drawing. In forming metal cans, suitable for lamination,
Abrasion resistance, deep drawing workability, impact resistance after can making, heat resistance,
It has excellent whiteness on the outer surface of the can and is extremely useful for coating metal containers.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B29K 105: 16 B29K 105: 16 B29L 7:00 B29L 7:00 9:00 9:00 (72) Inventor Tetsuo Yoshida Sagamihara, Kanagawa 3-37-19 Ichikoyama, Sagamihara Research Center, Teijin Limited (56) References JP-A-10-338755 (JP, A) JP-A-10-175279 (JP, A) (58) Fields studied (Int .Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] A rutile-type titanium oxide having an average particle size of 0.1 to 0.5 μm is contained in an amount of 10 to 50% by weight, and has a melting point of 210%.
２245 ° C. and the intrinsic viscosity of the polymer part is 0.4
6 to 0.66 copolymerized polyester layer (layer B), 0 to 15% by weight of rutile type titanium oxide having an average particle size of 0.1 to 0.5 μm laminated on one surface of layer B, Is 2
The average particle size laminated on the other surface of the copolymerized polyester layer (layer A) and layer B at 10 to 245 ° C. is 0.1
A laminated polyester film comprising a copolymerized polyester layer (C layer) containing 0 to 15% by weight of rutile type titanium oxide of 0.5 to 0.5 μm and having a melting point of 210 to 245 ° C. The intrinsic viscosity of the polymer portion satisfies the formulas (1) to (3), and the X-ray diffraction intensity and apparent density of the laminated film are expressed by the formula (4), respectively.
A white laminated polyester film for a metal plate laminating process, which satisfies the formula (5) and further has an MOR value in a range of 1.5 or less. (Equation 1) 2. The white laminated polyester film for laminating a metal plate according to claim 1, wherein the film is laminated on a surface of the metal plate to be an outer surface of the container.