KR0170073B1 - Preparation of copolymer polyester film for metal plate laminate - Google Patents

Abstract

The present invention improves the stretch adhesive strength of the film during the production process by saving the elongation of the film within a certain range in order to give excellent molding processability when laminating a co-polyester film on a metal plate subjected to various electroplating, such as tin or chromium The present invention relates to a method for producing a copolyester film having excellent crack resistance and peeling resistance. The method of preparing a coaxial polyester film having a melting point in the range of 210 to 235 ° C is obtained by liquid or liquid polymerization and solid phase polymerization. The longitudinal elongation of the obtained film is 120 to 180%, and the transverse elongation is 90 to 110% of the longitudinal elongation.

Description

Method for producing copolyester film for metal plate laminate

The present invention relates to a method for producing a copolyester film for metal plate laminate, and more particularly, to a method for producing a copolyester film that can be heat-bonded to a metal plate subjected to various electroplating such as tin or chromium. In order to give excellent molding processability during steelmaking after lamination, the elongation of the film is controlled within a certain range to improve the stretch adhesion of the film during the steelmaking, and to prepare a co-polyester film for metal plate laminate having excellent crack resistance and peeling resistance. It is about a method.

Conventionally, a method of coating a metal surface by dissolving or dispersing various thermosetting resins such as an anode clock and a phenol-based solvent in order to prevent corrosion on inner and outer surfaces of a metal tube is widely used. However, since the method of coating the thermosetting resin requires a long time of about 10 to 20 minutes at 180 to 220 ° C. for drying the coated paint, the productivity is relatively low, and carbon dioxide generated during the use and drying of a large amount of organic solvent, It is not good because it is accompanied by environmental pollution by a large amount of waste water generated during washing.

In order to solve this problem, a method of laminating thermoplastic resin films such as polyolefins and polyamides on steel sheets and aluminum plates, which are materials of metal pipes, has been proposed. Processability, heat resistance and impact resistance are not completely satisfied.

On the other hand, thermoplastic polyesters, especially polyethylene terephthalate (PET), which are widely used in food containers such as drinking water and cooking oil, have excellent moldability, heat resistance, retort resistance, and mechanical strength, so that the PET is biaxially oriented and laminated on a metal plate. This has been proposed.

That is, a biaxially oriented PET film is thermally bonded to a metal plate using a low melting point polyester adhesive layer to be used as a material for manufacturing (Japanese Patent Publication No. 56-10451, Japanese Patent Publication No. H1-11-1546), A method of thermally bonding an amorphous or extremely low crystalline aromatic polyester film to a metal plate to use as a pipe material (Japanese Patent Laid-Open Publication No. Hei 1-192545 and 2-57339), biaxially fixed to have a low orientation The method (The Japanese Unexamined-Japanese-Patent No. 64-22530) etc. are mentioned by heat-bonding an oriented polyethylene terephthalate film to a metal plate, and using it as a piping manufacturing material.

However, biaxially oriented PET film has excellent toughness, heat resistance, and fragrance preservation, but the film has low elongation and insufficient molding processability. There is an easy problem. In addition, when the amorphous or low-crystalline aromatic polyester film is laminated on a metal plate, the molding processability is excellent, but it is fragile and damaged by the impact on the outside of the tube during long-term preservation or printing after tube making, printing after tube making, retort treatment, etc. There is a problem of deterioration with an easy film. On the other hand, when the polyester resin of low melting point is to be extracted to the end surface of PET film and the adhesiveness is improved, when the draw ratio becomes larger than a certain level by drawing such as draw during the manufacturing process, the strength and crystallinity of each layer, etc. There is a problem that delamination or cracking occurs due to the decrease in the interfacial adhesion force due to the difference of

The present invention has been made to solve these problems, the cohesive polyester having a certain level of melting point by using a conventional biaxial stretching method to ensure that the elongation of the film to an appropriate range by the heat-bonded to the metal plate after the stretchability during the tube It is to provide a method for producing a co-polyester film that is excellent in the formation and to reduce the deterioration of the adhesive force due to stretching to reduce the problems such as peeling and cracking of the film during the tube forming.

For the purposes of the present invention described above, after the copolymerized polyester having a melting point in the range of 210 to 235 ° C. is obtained by liquid phase or liquid phase polymerization and solid phase polymerization, the elongation of the final film is longitudinally oriented using a conventional biaxially oriented film production method. A biaxially oriented co-polyester film was prepared that satisfies 120 to 180% and 90 to 110% of longitudinal elongation in the transverse direction, and the copolyester film was heated to the melting point or higher of the copolyester. Laminated to prepare a steel sheet for canning used in the production of food, beverages and miscellaneous goods tube, it was possible to produce a beverage and food pipes through a conventional canning process using this.

On the other hand, as the metal plate used for thermal fusion, a surface-treated steel plate and an aluminum plate, which were plated with chromium or tin on steel or steel surfaces, were used.

The copolyester used in the present invention has a main chain of polyethylene terephthalate or polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, polycyclohexanedimethylene terephthalate, and the like. Examples of the copolymerized components include dicarboxylic acids such as aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid and maleic acid, among which terephthalic acid. , Isophthalic acid, naphthalenedicarboxylic acid and the like are suitable for the purpose of the present invention.

Examples of the diol component in the copolymerization component include aliphatic glycols such as ethylene glycol, diethylene glycol, butylene glycol, and cyclohexane dimethanol, aromatic glycols such as hydroquinone and bisphenol A, and the like. The dicarboxylic acid and diol component enumerated above can also be used individually or in combination of 2 or more in the range which does not carry out.

In particular, the copolyester used in the present invention is polyethylene terephthalate, polyethylene naphthalate, and the like as its main chain, and isophthalic acid as the copolymerization component is most suitable for the purpose of the present invention. The component satisfies 5 to 20 mol%, preferably 7 to 15 mol%, more preferably 10 to 12 mol% with respect to the total acid component in terms of molding processability, retort resistance, heat resistance and the like. Moreover, although diethylene glycol etc. may be used as a copolymerization component of a diol component in the range which does not impair the characteristic of copolyester, it is preferable that it does not exceed 10 mol% with respect to all the diol components.

Melting point of the copolyester used in the present invention is 210 ~ 235 ℃, preferably in the range of 215 ~ 230 ℃ is most suitable for the purpose according to the present invention, when the melting point is less than 210 ℃ processability during steelmaking process is improved but heat resistance and heat resistance Retort properties deteriorate and are not a preferred method. On the other hand, if it exceeds 240 ℃, the heat resistance and retort resistance are improved, but the crystallinity of the polymer is increased, and the heat adhesive strength is lowered. Therefore, the film is peeled off during lamination on the metal plate, and the moldability is deteriorated. There is no way. In addition, since excessive energy consumption is required, such as requiring a high temperature during preheating of the metal plate, an increase in manufacturing cost is caused. In addition, it is most suitable for the purpose of the present invention that the copolymer polyester has a range of 120 to 180% in the longitudinal direction and 90 to 110% in the longitudinal direction in the transverse direction using a conventional biaxial stretching method. It is suitable, and more preferably, the case where the longitudinal elongation is 130 to 170% and the transverse elongation is 95 to 105% of the longitudinal elongation is most suitable for the purpose of the present invention. If the longitudinal elongation is less than 120% or the transverse elongation is less than 90% of the longitudinal elongation, the film's stretch adhesive strength decreases when heat-bonding the film to the metal plate. On the contrary, when the film exceeds 180% or the transverse elongation exceeds 110% of the longitudinal elongation, the peeling or cracking of the film is considerably reduced, but it is difficult to maintain the thickness of the film uniformly.

The copolyester used in the present invention was polycondensed the reaction product obtained by esterifying or exchanging terephthalic acid, ethylene glycol and isophthalic acid or copolymerized components to obtain isophthalic acid copolyester or copolyester polymer.

Reaction catalysts used in the transesterification reaction include manganese acetate, magnesium acetate, calcium acetate, potassium acetate, and the like, and were added at the initial or arbitrary stage of the reaction. In the polycondensation reaction step, antimony trioxide or germanium compound was added at the beginning of the polycondensation reaction as a polycondensation catalyst.

On the other hand, if necessary, a lubricant, a fluorescent brightener, an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent, or the like may be added.

The copolyester film used in the present invention is melted to a temperature above the melting point in the compressor, and then extruded, cooled, and solidified through a die, followed by the conditions such as the temperature and draw ratio of longitudinal stretching and transverse stretching, and the temperature of the heat setting process. It could be prepared by adjusting. 12-40 micrometers is preferable for the final aftercoat of the produced film, More preferably, 15-30 micrometers is advantageous for the objective of this invention. When the thickness of the film is 12 μm or less, breakage of the film is likely to occur during the steelmaking process. On the contrary, when the thickness of the film exceeds 40 μm, the film has excessive quality characteristics, which is uneconomical.

In the present invention, as the metal plate for laminating the copolyester film, in particular, the metal plate for steel making, tin plated steel plate, chromium plated steel plate, chromium oxide plated steel plate, aluminum plate and the like are suitable. In the method of laminating a film on a metal plate, the lubricant or the like deposited on the metal plate is first washed, and then heated to the melting point or higher of the film to be laminated, and then laminated using one or more of the metal plates using a compression ratio as necessary.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

The properties of each copolyester and film were measured by the following method.

Unique viscosity

2.0 g of each copolyester was dissolved in a 1,1,2,2-tetrachloroethane / phenol (60/40 wt%) mixed solvent and measured at 25 ° C.

Melting Point

A 6.0 mg sample of copolyester was measured at a heating rate of 20 ° C./min using a DuPont 9100 differential scanning calorimetry, and the melting point was taken as the maximum endothermic peak temperature.

Film Shinto

The longitudinal stretch of the film was measured using the Instron Co., Ltd. tensile strength tester.

Thermal adhesion

The copolyester film was sandwiched between plated steel sheets and heated and pressed at a constant pressure using a heating press, and then the size of the adhesive force was evaluated by ASTM D1876.

Stretch adhesive force

After the co-polyester film was thermally bonded to the metal plate, the metal plate was cut with a tensile strength test piece, and the peeling degree of the film different from the tensile rate of the tensile strength tester was observed.

The tensile strength at the time point at which the peeling of the film started by peeling off the surface of the film with a spiral tester after peeling the test piece according to the tensile rate was indicated by the stretch adhesive force of the film.

Stretch forming processability

The laminated metal plate was cut into a circular shape with a diameter of 187 mm, and then a punched and drawn process was made to produce an integral tube having a diameter of 66 mm and a cup height of 140 mm, and then observed the degree of breakage or peeling of the film. Evaluated.

○: No breakage or peeling phenomenon of the film, △: Partial peeling, ×: Breakage of the film

Example 1

5.34 kg of dimethyl terephthalate, 0.73 kg of dimethyl isophthalate and 3 liters of ethylene glycol were added to the reaction tube, and after the temperature of the reaction tube reached 145 ° C, 0.03 weight% of manganese acetate and 0.007 weight of potassium acetate based on 100 parts by weight of the resulting polymer. % Is added and the transesterification reaction is carried out until the temperature of the reactant reaches 235 ° C.

When the temperature of the reaction reaches 235 ° C, 0.03% by weight of antimony trioxide and 0.03% by weight of trimethylphosphate are added, and then the temperature of the reaction is raised to 245 ° C to remove excess ethylene glycol in the reaction, and then slowly reacted for 45 minutes. Reduce the pressure to 0.5torr. On the other hand, at the same time as the pressure reduction, the temperature of the reaction tube is raised, the temperature of the reactant is raised to 285 ° C, and then the polycondensation reaction is performed.

In this way, the copolymer polyester having an intrinsic viscosity of 0.67 and a melting point of 223 ° C. was preliminarily dried at 80 ° C. for 60 minutes, and then dried at 120 ° C./90 minutes and 150 ° C./280 minutes to melt extrusion at a melting temperature of 275 ° C. After cooling, the unstretched film was prepared.

The unstretched film is stretched 3.1 times in the longitudinal direction at 90 ° C. and 3.2 times in the transverse direction at 105 ° C., and then heat-set at 190 ° C. to give the final elongation of 151.5% in the longitudinal direction and 150.1% in the transverse elongation. A biaxially oriented film of 25 mu m was prepared.

The biaxially oriented film was pressed on both sides of a chromium oxide plated metal plate preheated to 230 ° C. using a compression rate, and then quenched in 50 ° C. cooling water to prepare a metal plate laminated with co-polyester film. The molding processability was evaluated and the results showed excellent molding processability and peeling resistance as shown in Tables 1 and 2.

Example 2

After preparing the copolyester of intrinsic viscosity 0.70 by the same method as in Example 1, the longitudinal draw ratio was 3.5 times, the transverse draw ratio was 3.3 times, and the heat setting temperature was 195 ° C. A biaxially oriented film was prepared, and the characteristics were compared after laminating on a metal plate plated with chromium and chromium oxide layers using the same, and the results are shown in Tables 1 and 2 below.

Example 3

In the same manner as in Example 1, a copolyester polyester having an intrinsic viscosity of 0.65 having an isophthalic acid component of 10 mol% based on the total acid component and diethylene glycol of 1.8 mol% based on the total diol component was prepared. The biaxially stretched copolyester polyester film having a thickness of 20 μm was prepared using a draw ratio of 3.3 times in a direction, 3.4 times in a lateral direction, and a heat setting temperature of 190 ° C., which was plated with chromium and chromium oxide layers. It was laminated on a metal plate to compare the properties, and the results are shown in Tables 1 and 2 below.

Example 4

In the same manner as in Example 1, a co-polyester having an intrinsic viscosity of 0.65 having 7 mole% of isophthalic acid component and 3.0 mole% of total diol content of diethylene glycol was prepared, and then A biaxially stretched copolyester polyester film having a film thickness of 20 μm was prepared at a draw ratio of 3.4 times, a draw ratio of 3.4 times in a lateral direction and a heat setting temperature of 195 ° C., which was plated with chromium and chromium oxide layers. It was laminated on a metal plate to compare the properties, and the results are shown in Tables 1 and 2 below.

Comparative Example 1

6.06 kg of dimethyl terephthalate and 3 liters of ethylene glycol were placed in the same reaction tube as in Example 1, and the polycondensation was carried out in the same manner to obtain polyethylene terephthalate having an intrinsic viscosity of 0.62 and a melting point of 255 ° C. The film whose thickness was 20 micrometers was obtained with the draw ratio of the lateral direction 3.5 times and heat setting temperature being 235 degreeC.

The prepared film was laminated on a chromium oxide plated metal plate preheated to 260 ° C. using a compression ratio, and then its properties were evaluated. The results are shown in Tables 1 and 2 below.

Comparative Example 2

4.55 kg of dimethyl terephthalate, 1.51 kg of dimethyl isophthalate, and 3 l of ethylene glycol were polycondensed in the same manner as in Example 1 to prepare a copolymer polyester having an intrinsic viscosity of 0.70 and a melting point of 190 ° C., and then using it 3.5 times in the longitudinal direction and in the transverse direction. The film was stretched 3.8 times to give a copolymer polyester film having a final thickness of 25 µm.

The film was laminated on a chromium oxide plated metal plate preheated to 200 ° C., and then its properties were compared. The results are shown in Tables 1 and 2 below.

Comparative Example 3

5.34 kg of dimethyl terephthalate, 0.73 kg of dimethyl isophthalate and 3 liters of ethylene glycol were added to the reaction tube, and the copolymerized polyester having an intrinsic viscosity of 0.65 and melting point of 223 ° C. was prepared by polycondensation in the same manner as in Example 1. The film was stretched 4.0 times in the longitudinal direction and 4.5 times in the lateral direction to obtain a copolyester film having a thickness of 20 µm in the final film.

The prepared film was laminated on a chromium oxide plated metal plate preheated to 230 ° C., and then its properties were compared. The results are shown in Tables 1 and 2 below.

Comparative Example 4

5.34 kg of dimethyl terephthalate, 0.73 kg of dimethyl isophthalate and 3 liters of ethylene glycol were added to the reaction tube, and then a copolymerized polyester having an intrinsic viscosity of 0.67 and a melting point of 223 ° C. obtained by polycondensation was prepared in the same manner as in Example. The film was stretched 4.5 times in the longitudinal direction and 4.5 times in the lateral direction to obtain a hollow polyester film having a thickness of 20 µm.

The prepared film was laminated on a chromium oxide plated metal plate preheated to 230 ° C., and then its properties were compared. The results are shown in Tables 1 and 2 below.

Claims (3)

After the copolymerization polyester having a melting point in the range of 210 to 235 ° C. is obtained by liquid or liquid polymerization and solid phase polymerization, the longitudinal elongation of the film obtained using the biaxially oriented film production method is 120 to 180% and the transverse elongation is longitudinally elongated. 90-110% of the manufacturing method of the copolymer polyester film for metal plate laminates characterized by the above-mentioned. The method for producing a co-polyester film for metal plate laminate according to claim 1, wherein dicarboxylic acid is contained in an amount of 5 to 20 mol% based on the total acid component. The thickness of the polyester film produced by copolymerization is 12-40 micrometers, The manufacturing method of the copolymer polyester film for metal plate laminates of Claim 1 characterized by the above-mentioned.