JP3370220B2 - Black polyester film for lamination in metal cans - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black polyester film for laminating in a metal can. [0002] At present, as cans for beverage cans, food cans and the like,
A method of laminating a thermoplastic resin film on a metal plate of tin, tin-free steel, aluminum or the like, and then processing the laminated metal plate to produce a can has been performed. For example, a laminated steel sheet is prepared by, for example, pressing a polyester film on a steel sheet via an adhesive or directly pressing a polyester film on a heated steel sheet, and cutting the laminated steel sheet into blank plates for can bodies. . Next, this plate is cylindrically formed and a side seam is formed using an adhesive or the like. Next, a series of can-making processes such as flanging, lid bottom seaming, can inspection, and palletizing are exemplified. Compared to the method of manufacturing a can by painting a metal plate, which is another method, since no organic solvent is used, simplification of the process, improvement of safety and health, prevention of pollution and the like can be obtained,
This is a method that can obtain rust prevention on the inner and outer surfaces of the metal can.
For example, biaxially oriented polyethylene terephthalate which is heat-set with low orientation, such as JP-A-1-192545 and JP-A-2-57339, which are examples using an amorphous or extremely low-crystalline polyester film. JP-A-64-22530, which is an example using a film, and JP-A-5-339393, which is an example using a copolymerized polyester. [0003] However, the laminated metal plate using the inner-coated film produced by these methods, whether or not laminated even after lamination to a steel plate, or the state of lamination due to the transparency of the film. It was difficult to easily visually inspect pinholes and pinholes. When a poorly laminated steel sheet is filled with food, drinking water, or the like after can production, there may be a problem with the content retention property and the like. [0004] The object of the present invention is to enable easy inspection of lamination failure of laminated steel sheets, pinholes and the like, and that food and drinking water and the like after canning are manufactured. An object of the present invention is to provide a laminating metal can-inside-film which has good content retention even after being filled and stored for a long period of time. Means for Solving the Problems The inventors of the present invention have made intensive studies in view of the above-mentioned circumstances, and as a result, it has been found that the above problems can be solved by including certain particles in a specified amount in a polyester film. And completed the present invention. That is, the gist of the present invention is to provide a biaxially oriented polyester film having a primary particle size of 15 to 1
It contains 0.01 to 15% by weight of carbon black particles of 00 nm, and a thermosetting resin-based adhesive is applied on one side of the film.
The present invention is characterized in that it is a black polyester film for being laminated inside a laminated metal can, which is characterized by being woven. Hereinafter, the present invention will be described in more detail. The polyester film referred to in the present invention is a film extruded by a so-called extrusion method, which is melt-extruded from an extrusion die, and is a film which is later oriented in two axial directions of a longitudinal direction and a lateral direction. In the present invention, the polyester is obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. A typical polyester is polyethylene terephthalate (P
ET), polyethylene-2,6-naphthalenedicarboxylate (PEN) and the like. [0008] The polyester used in the present invention may be a copolymer containing a third component. Examples of the dicarboxylic acid component of the copolymerized polyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and
Oxycarboxylic acid (for example, P-oxybenzoic acid, etc.)
And glycol components include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like. In the present invention, examples of the carbon black particles contained in the biaxially oriented polyester film include channel black, thermal black, and furnace black. The primary particle size of the carbon black particles is 15 to 100 nm,
Preferably from 20 to 70 nm, more preferably from 20 to 5
0 nm. The primary particle size of carbon black particles is 15
When the particle size is less than nm, the particles are likely to agglomerate, so that the filter life in the extruder is shortened and productivity is deteriorated, which is not preferable. Further, when the primary particle size of the carbon black particles exceeds 100 nm, the degree of surface roughening of the film becomes large, and a method such as pressing the polyester film directly onto the heated steel plate via an adhesive or by a method such as pressing. However, it is not preferable because the adhesiveness between the steel sheet and the film when the laminated steel sheet is formed is reduced. The method of blending particles with the polyester in the present invention is not particularly limited, and a known method can be employed. For example, it can be added at any stage of producing the polyester, but is preferably added as a slurry dispersed in ethylene glycol or the like at the esterification stage or at the stage after the end of the transesterification reaction and before the start of the polycondensation reaction. The condensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a polyester raw material using a kneading extruder with a vent, or a method of blending dried particles with a polyester raw material using a kneading extruder, etc. Done by In the present invention, the content of the carbon black particles contained in the biaxially oriented polyester film is preferably 0.01 to 15% by weight,
0.05 to 7.5% by weight, more preferably 0.1 to 5% by weight
% By weight is preferred. When the content of the particles is less than 0.01% by weight, the slipperiness of the film is poor, and the workability is poor when winding the film or forming a laminated steel sheet, which is not preferable. When the content of the particles exceeds 15% by weight,
Since the blackness required for identification is saturated and uneconomical, and the surface roughness increases, the polyester film is pressed on the steel plate with an adhesive or directly on the heated steel plate. When the laminated steel sheet is prepared by the method described in the above, the adhesiveness between the steel sheet and the polyester film deteriorates, which is not preferable. The polyester film of the present invention may have any thickness as long as it can be formed as a film.
0 μm, preferably 5 to 50 μm, more preferably 8 μm
In the case of a film having a thickness of ２５25 μm, an excellent effect is exhibited. Next, the method for producing a biaxially stretched polyester film in the present invention will be specifically described, but the film of the present invention is not limited to the following production examples.
In the present invention, a method in which the polyester raw material described above is used, the polyester is melt-extruded from a die using an extruder, and cooled and solidified by a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum, and the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed. Next, the obtained unstretched film is stretched biaxially to be biaxially oriented. That is, first, the unstretched sheet is stretched in one direction by a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120
° C, preferably 80 to 110 ° C, and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, stretching is performed in a direction orthogonal to the stretching direction of the first stage. The stretching temperature is usually 70 to 120 ° C, preferably 80 to 11 ° C.
The stretching ratio is usually 3.0 to 7 times, and preferably 3.5 to 6 times. And, continuously, 170-2
Heat treatment is performed at a temperature of 50 ° C. under tension or relaxation within 30% to obtain a biaxially oriented film. A so-called in-line coating for treating the film surface during the stretching step can be applied. Although it is not limited to the following, in particular, after the first-stage stretching is completed, before the second-stage stretching, an improvement in antistatic properties, slipperiness, adhesion, etc. For the purpose, the coating treatment such as water-soluble, water-based emulsion, water-based slurry or the like can be performed. [0012] In the above stretching, the stretching in one direction is 2
It is also possible to use a method of performing the above steps. In that case,
It is preferable that the stretching is performed so that the stretching ratio in the two directions finally falls within the above range. It is also possible to simultaneously biaxially stretch the unstretched sheet so that the area magnification becomes 10 to 40 times. Further, if necessary, the film may be stretched in the longitudinal and / or transverse directions again before or after the heat treatment. In the present invention, a thermosetting resin-based adhesive is applied to one surface of a biaxially oriented polyester film.
There is a need. The thermosetting resin-based adhesive is not particularly limited, but has a number average molecular weight of 5,000 to 2,000.
0 / epoxy resin and acid anhydride-based curing agent at 70 / 30-
An adhesive made of a resin containing 99/1 by weight, or a polyester resin and an aminoplast resin in a ratio of 70/30 to
One selected from adhesives made of resin containing 90/10 by weight. The epoxy resin forming the adhesive is preferably a bisphenol-type epoxy resin obtained by reacting bisphenol with epichlorohydrin. The acid anhydride-based curing agent is preferably selected from trimellitic anhydride-based curing agents including trimellitic anhydride, glycerol tristrimellitate anhydride, and trimellitic anhydride derivatives. Further, in addition to the acid anhydride-based curing agent, another curing agent such as a phenol resin may be included. As the polyester resin in the adhesive comprising the polyester resin and the aminoplast resin, a known polyester resin may be used alone, or an epoxy resin-modified polyester resin modified with an epoxy resin or the like may be used. As the aminoplast resin, a melamine resin, a benzoguanamine resin, or the like can be used.
In the present invention, the method for applying the adhesive to the polyester film is not particularly limited, but an air doctor coating method, a flexible blade coating method, a rod coating method, a floating knife coating method,
Knife over blanket coating, knife over roll coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss roll coating, bead coating, cast coating, spray coating It can be applied by a known method such as a curtain coating method, a fountain coating method, and a calendar coating method. The applied thickness of the adhesive is usually 0.3 to 30 μm after drying.
m, preferably 0.6 to 20 μm, more preferably
One or two or more solvents such as MEK, toluene, ethyl acetate, xylene, and butyl cellosolve are mixed to dilute the adhesive so as to have a thickness of 1 to 10 μm. If the thickness of the adhesive applied is less than 0.3 μm, the adhesive strength when bonded to a steel sheet tends to be low, and if it exceeds 30 μm, the solvent may be insufficiently dried. EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the examples and comparative examples, “parts” means “parts by weight”. The measuring method used in the present invention is as follows. (1) After fixing a sample film piece of the primary particle size of the particles with epoxy resin,
The film was cut with a microtome, and the cross section of the film was observed with a transmission electron microscope. The maximum diameter (a) of the particles observed in the cross section of the film and the maximum diameter (b) orthogonal thereto are measured, the primary particle diameter of one particle is obtained from the following equation, and the measurement is performed on 500 particles. The arithmetic mean was defined as the primary particle size of the particles. ## EQU1 ## Primary particle size of one particle = (a + b) / 2 (2) Identification of laminated steel sheet A sample film was bonded to a steel sheet via an adhesive to prepare a laminated steel sheet. A total of 100 sheets were randomly judged within 5 seconds by visual observation, 50 sheets of steel sheets and 50 sheets of steel sheets not bonded to each other, and the number of correct answers was used as the discriminability of the laminated steel sheet. (3) 250 ml of mineral water in 300 ml Erlenmeyer flask
1 and a sample film of 80 square centimeters.
After storage at 0 ° C. for 90 days, a sensory test of taste was conducted. The results of the sensory test were classified as follows. ：: No change in taste. ×: Change in taste. <Production of Polyester> Production Example 1 (Polyester A) 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were placed in a reactor. Then, the mixture was heated and heated, and methanol was distilled off to carry out a transesterification reaction. The temperature was raised to 230 ° C. over 4 hours from the start of the reaction, thereby substantially terminating the transesterification reaction. Next, an ethylene glycol slurry containing 0.1 part of wet-process silica particles having a primary particle diameter of 35 nm was added to the reaction system, and ethyl acid phosphate 0.1% was added.
10 parts after adding 04 parts and 0.01 parts of germanium oxide
At 0 minutes, the temperature was set to 280 ° C. and the pressure was set to 15 mmHg. Thereafter, the pressure was gradually reduced and finally set to 0.3 mmHg.
After 4 hours, the pressure in the system was returned to normal pressure, and polyester A was obtained.
The content of the wet-process silica particles of the polyester A was 0.1% by weight. Production Example 2 (Polyester B) In the same manner as in Production Example 1, except that an ethylene glycol slurry containing 0.1 part of wet-processed silica particles having a primary particle size of 35 nm is not added to the reaction system. And polyester B. Production Example 3 (Polyester C) In Production Example 1, ethylene containing 0.5 parts of fine alumina particles having a primary particle diameter of 20 nm was used instead of ethylene glycol slurry containing 0.1 parts of wet-processed silica particles having a primary particle diameter of 35 nm. A polyester C was obtained in the same manner as in Production Example 1 except that the glycol slurry was used. The content of the fine alumina particles in the polyester C was 0.5% by weight. Production Example 4 (Polyester D) 98.6 parts of polyester B produced in Production Example 2 and 1.4 parts of carbon black particles having a primary particle size of 13 nm were dry-blended and extruded using a twin-screw kneading extruder. Polyester D was obtained. Production Example 5 (Polyester E) 98.6 parts of polyester B produced in Production Example 2 and 1.4 parts of carbon black particles having a primary particle size of 20 nm are dry-blended, and the mixture is extruded using a twin-screw extruder. And extruded to obtain a polyester E. Production Example 6 (Polyester F) 99.3 parts of polyester B produced in Production Example 2 and 0.7 parts of carbon black particles having a primary particle diameter of 20 nm are dry-blended and extruded using a twin-screw kneading extruder. Polyester F was obtained. Production Example 7 (Polyester G) 92.5 parts of the polyester B produced in Production Example 2 and 7.5 parts of carbon black particles having a primary particle size of 20 nm were dry-blended and extruded using a twin-screw kneading extruder. Polyester G was obtained. Production Example 8 (Polyester H) 98.6 parts of the polyester B produced in Production Example 2 and 1.4 parts of carbon black particles having a primary particle size of 24 nm are dry-blended, and the mixture is extruded using a twin-screw extruder. And extruded to obtain a polyester H. Production Example 9 (Polyester I) In Production Example 2, 98.6 of the produced polyester B was used.
Parts and carbon black particles 1.4 having a primary particle size of 40 μm.
And the mixture was extruded using a twin-screw kneading extruder to obtain a polyester I. Production Example 10 (Polyester J) 99 parts of the polyester B produced in Production Example 2 and 1 part of the polyester F produced in Production Example 6 were dry-blended to obtain Polyester J. Production Example 11 (Polyester K) 80 parts of the polyester B produced in Production Example 2 and 20 parts of carbon black particles having a primary particle size of 20 nm were dry-blended and extruded using a twin-screw kneading extruder to obtain polyester K. Production Example 12 (Polyester L) 98.6 parts of the polyester B produced in Production Example 2 and 1.4 parts of carbon black particles having a primary particle size of 150 nm were dry-blended and extruded using a twin-screw extruder kneading extruder. L was obtained. Example 1 Polyester E was dried at 180 ° C. for 4 hours in an inert gas atmosphere, melt-extruded at 290 ° C. by a melt extruder, and cooled at a surface temperature of 40 ° C. using an electrostatic application contact method. It was cooled and solidified on a roll to obtain an unstretched sheet. The obtained sheet was stretched 3.5 times in the longitudinal direction at 85 ° C. Then
The film was guided to a tenter, stretched 3.7 times in the transverse direction at 100 ° C., and then heat-set at 230 ° C. to a thickness of 12 μm.
m was obtained. The obtained film, 80 parts of bisphenol type epoxy resin having an average molecular weight of 10,000,
A thermosetting resin-based adhesive comprising an acid anhydride-based curing agent and trimellitic anhydride 20 parts is dried and diluted with a solvent so as to have a thickness of 1 μm after coating, and a thermosetting resin-based adhesive coating film is formed. Obtained. Example 2 In the same manner as in Example 1, a coating film was obtained using polyester F. Example 3 In the same manner as in Example 1, a coating film was obtained using polyester G. Example 4 In the same manner as in Example 1, a coating film was obtained using polyester H. Example 5 A coating film was obtained using Polyester I in the same manner as in Example 1. Comparative Example 1 In the same manner as in Example 1, a coating film was obtained using polyester A. Comparative Example 2 In the same manner as in Example 1, a coating film was obtained using polyester C. Comparative Example 3 When extrusion was performed using polyester D in the same manner as in Example 1, the filter pressure was increased, and extrusion was impossible. Comparative Example 4 When a film was formed using polyester J in the same manner as in Example 1, the film was poorly wound by a winder.
The film was wrinkled and could not be put to practical use. Comparative Examples 5 to 6 Coating films were obtained using polyester K (Comparative Example 5) and polyester L (Comparative Example 6) in the same manner as in Example 1. Although the obtained coating film and the steel plate were heated and pressed, they were easily peeled off with a finger and could not be put to practical use. The results obtained are summarized in Tables 1 and 2 below. [Table 1] In Table 1, CB means carbon black. [Table 2] According to the present invention described above, when a polyester film is bonded to a steel plate for a can body of a laminated metal can, it is easy to confirm whether or not the polyester film has been bonded. Inspection of defective bonding of laminated steel sheets and laminated steel sheets, pinholes, etc. can be easily performed, and after the cans are filled with food and drinking water, etc., the content retention property is good even when stored for a long time. Therefore, it can be applied to fields such as food cans and beverage cans, and its industrial value is high.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI B32B 27/36 B32B 27/36 C08K 3/04 C08K 3/04 C08L 67/02 C08L 67/02 C09C 1/48 C09C 1/48 // B29K 67:00 B29K 67:00 105: 16 105: 16 (56) References JP-A-6-116486 (JP, A) JP-A-7-238176 (JP, A) JP-A-63-139786 (JP, A) JP-A-61-228061 (JP, A) JP-A-61-20736 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/00-5/24 C08L 1 / 00-101/16 B32B 1/00-35/00

Claims (1)

(57) Claims 1. A biaxially oriented polyester film containing 0.01 to 15% by weight of carbon black particles having a primary particle size of 15 to 100 nm, and one side of the film.
A black polyester film for sticking in a laminated metal can, characterized in that a thermosetting resin-based adhesive is applied to the laminate.