KR19990008986A - Method for producing copolyester film for metal plate laminate - Google Patents

Abstract

The present invention relates to a method for producing a co-polyester film for metal plate outer surface laminates having excellent heat-resistance and printing characteristics for a metal plate subjected to electroplating such as tin or chromium, and the present invention relates to polyethylene, terephthalate, and polyethylene. Naphthalate, polybutylene terephthalate and the like are copolymerized polyesters having a main chain, and aromatic carboxylic acid or aliphatic dicarboxylic acid is used as a copolymerization component. It is a method for producing copolyester for metal plate outer laminates containing 50.0 wt% and having a combat rate of 30% or less and a melting point of 210 to 245 ° C.

The polyester film for metal sheet laminate according to the present invention has a melting point difference of -1.0 to 10.0 ° C. and a light hiding power of 30% or less with a polyester film for inner surface lamination, and is excellent in heat adhesiveness preventing peeling and scratching. Industrially useful invention with excellent printing characteristics.

Description

Method for producing copolyester film for metal plate laminate

The present invention relates to a method for producing a co-polyester film used in metal sheet laminates for canning, and more particularly, has excellent heat adhesiveness for an electroplated metal plate such as tin or chromium, and has excellent white hiding power and post-coating. The present invention relates to a method for producing a co-polyester film for metal tube outer surface laminates having excellent printing properties in outer printing.

Conventionally, a metal plate coating method using a thermosetting resin paint such as epoxy or phenol is widely used to prevent corrosion of inner and outer surfaces of a metal tube. However, since the method of applying the thermosetting resin paint requires a high temperature dryer for drying the paint after application, the productivity is relatively low, and a large amount of harmful gas due to the use of an organic solvent and carbon dioxide generation and a large amount due to cleaning after drying In recent years, the thermoplastic resin film is laminated on the inner and outer surfaces of tin plated steel sheet, chrome plated steel sheet, and aluminum such as aluminum for the purpose of streamlining the process, improving hygiene and preventing pollution. A method for producing a tube by punching, draw processing or the like has been proposed.

However, in the method of laminating the thermoplastic resin film, a co-polyester film capable of satisfying properties such as heat adhesion, molding processability, and heat resistance should be selected. In particular, the film laminated on the outer surface of the thermoplastic resin film exhibits excellent light hiding power for printing. The use of a white film containing a white pigment is required, and the components of the film for tube outer lamination satisfying this requirement are different in structure from the polyester film for inner layer laminate not containing white pigment and thus show a large difference in melting temperature.

As such, when the difference (ΔT) of the melting temperature of the co-polyester laminated on the inner and outer surfaces of the metal plate is out of a certain range, a large difference occurs in the thermal adhesiveness between the inner and outer surfaces of the film and the metal plate, and thus during the molding process of the laminated metal plate. Due to the difference in thermal adhesiveness between inner and outer films, peeling phenomenon of the polyester film laminated on the outer surface or inner surface of the tube occurs during molding processing or retort treatment or by external impact, and also there is a high possibility of scratching on each film. This phenomenon is particularly remarkable in the fuselage portion of the tube which undergoes many deformations during the tube forming.

Therefore, an object of the present invention is to minimize the melting point temperature difference (ΔT) according to the difference in the composition of the co-polyester laminated on the inner and outer surfaces of the tube, the same thermal adhesive properties when laminating the copolyester film on the inner and outer surfaces of the metal plate The present invention also provides a method for producing a co-polyester film used in the outer laminate of a metal plate for canning that does not peel off or scratch from the metal tube even when forming a metal plate.

It is still another object of the present invention to provide a method for producing a copolymer polyester film for metal plate outer surface laminates in which a melting point temperature difference of the inner and outer surfaces of the copolymerized polyester is within a certain range and has excellent light hiding power.

In order to achieve the above object of the present invention, the melting point difference (ΔT = outer copolymer polyester film melting point-inner copolymer polyester film melting point) of the outer copolymer polyester film melting point and the inner copolymer polyester film is -1.0 It is preferable that the melting point temperature is in the range of 210 to 245 ° C, and the present inventors have studied the method of producing a copolymerized polyester that satisfies this temperature range. The present invention was completed by finding that the melting temperature difference of the polyester produced was kept constant by keeping the mole% of the components and the weight% of the added white pigment.

In the present invention, the melting point difference (ΔT = outer copolymer polyester film melting point-inner copolymer polyester film melting point) of the outer copolymer polyester film melting point and the inner copolymer polyester film satisfies the range of -1.0 to 10.0 ° C. After the copolymerization polyester in the range of 210 ~ 245 ℃ obtained by the liquid phase polymerization or liquid phase polymerization after the solid phase polymerization was continuously prepared through the conventional biaxially stretched PET film manufacturing method to prepare a final copolymerized polyester film.

If the melting point of the film is less than 210 ℃ heat resistance is insufficient, if the heat drying during printing after the tube can not be damaged the film, if it exceeds 245 ℃ the crystallinity is increased and the tube can be formed poor, the present invention Not suitable for the purpose of

The copolyester used in the present invention has a main chain of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, polycyclohexanedimethylene terephthalate and the like and copolymerization for achieving the object of the present invention. Examples of the dicarboxylic acid include aromatic carboxylic acids such as terephthalic acid, isophthalic acid and naphthalene dacarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid and maleic acid, among which terephthalic acid and isophthalic acid. And naphthalene dicarboxylic acid are suitable for the purpose of the present invention.

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

The copolyester used in the present invention is most suited for the purpose of the present invention using polyethylene terephthalate, polyethylene naphthalate and the like as its main chain and polyethylene isophthalate as the copolymerization component. In particular, the dicarboxylic acid copolymer component preferably satisfies the range of 1 to 20 mol%, preferably 7 to 15 mol%, based on the total acid component. Moreover, although diethylene glycol may be used as a copolymerization component of a diol component in the range which does not impair the characteristic of co-polyester, it is effective for this invention not to exceed 10 mol% with respect to the whole diol component.

In the present invention, the melting point of the outer surface of the co-polyester film for the metal tube is -1.0 ° C to 10.0 ° C, preferably 0 ° C to 5.0 ° C, and more preferably 0.5 ° C to 3.0 ° C. It is suitable for the object of the present invention to be about ℃. If the melting point difference is less than -1.0 ℃ the heat resistance is insufficient to cause yellowing during printing, if it exceeds 10.1 ℃ the adhesive strength is insufficient to peel off the film during the tube making.

In the present invention, the copolyester film is added to 5.0 to 50.0wt% of the final film with a white pigment having an average particle diameter of 3.0㎛ or less for the light hiding power so that the film has a combat rate of 30% or less, preferably 20% or less It was. If the amount of white pigment particles is less than 5.0wt%, sufficient light hiding power cannot be obtained. On the contrary, when excess amount of more than 50.0wt% is added, the light hiding power is excellent, but breakage of the film occurs easily and film adhesion decreases during film formation. This is not preferable because of high possibility of peeling of the film during the tube forming. On the other hand, when the average particle diameter of the white pigment exceeds 3.0㎛, it is not preferable because the pinhole or film breakage due to coarse particles occurs during the manufacturing process such as punching, draw.

The above-mentioned white pigments may be inorganic or organic, but the use of inorganic white pigments is suitable for the purpose of the present invention. Examples of the inorganic white pigments include alumina, titanium dioxide, potassium carbonate, barium sulfate and the like. The above-mentioned white pigment may be used singly or in plural kinds, and it is preferable to use rutile titanium dioxide in view of cost and light hiding power.

In the present invention, there may be various methods for adding the white pigment into the copolyester film, but the following two methods are suitable for the purpose of the present invention.

A) A method in which a certain amount of white pigment is added before the end of the transesterification reaction or the esterification reaction or the start of the polycondensation reaction in the synthesis of the copolyester.

B) A method of producing a white film containing a certain amount of white pigment by mixing a copolyester masterbatch containing a high concentration of white pigment with a copolyester that does not contain a white pigment when forming a film.

The copolyester used in the present invention is a terephthalic acid, ethylene glycol and copolymerized components using isophthalic acid or other copolymerized components to carry out polycondensation of the reaction product obtained through esterification or transesterification. Got it. For the transesterification reaction, manganese acetate, magnesium acetate, potassium acetate, or the like was used alone or as a reaction catalyst, and as the polycondensation catalyst, antimony trioxide or germanium compound was added at the end of the transesterification reaction, the esterification reaction or the initial polycondensation reaction. Polycondensation was performed. On the other hand, fluorescent whitening agent, antioxidant, heat stabilizer, ultraviolet absorber, antistatic agent, etc. can also be added as needed. In particular, in order to improve the whiteness, it is also good to add a fluorescent brightener.

The copolyester film used in the present invention is a co-polyester or a copolyester polyester containing a white pigment and a copolyester masterbatch containing a high concentration of white pigment is first mixed in a dryer and then melt-extruded to a temperature above the melting point in an extruder Then, the sheet is formed in an amorphous state, and the sheet is heated in the longitudinal direction by a roll heating method or an infrared heater heating method. At this time, the stretching ratio is preferably 2.5 to 4.5 times. The transverse stretching is preferably carried out by gradually increasing the temperature starting at a temperature at least 20 ° C. or higher than the glass transition temperature of the copolyester, and the stretching ratio is preferably 2.5 to 4.5 times. In addition, the heat setting temperature is selected in consideration of the melting point of the copolymer polyester and the physical properties of the film in the range of 150 ℃ to 210 ℃. As for the thickness of the polyester film for outer tube laminates of this invention, 5-50 micrometers is suitable for the objective of this invention, It is more preferable that it is 10-30 micrometers especially.

If the thickness is less than 5㎛, a large amount of white pigment is required for light hiding power, and the film is easily damaged during the tube forming. If it exceeds 50㎛, it is advantageous in terms of hiding power, but it is uneconomical. .

As the metal plate used to laminate the co-polyester film according to the present invention, tin-plated plate, chromium-plated steel plate, aluminum, etc. are suitable. In the lamination method between the metal plate and the film, the metal plate is first heated above the melting point of the co-polyester film. Then, using a pressing roll, the film is laminated on the inner and outer surfaces of the metal plate at the same time, and then cooled to prepare a laminated steel sheet for canning, followed by punching or draw forming to form a final metal tube.

In the polyester film for metal plate outer surface laminate according to the present invention, the melting point of the polyester film laminated with a melting point difference of -1.0 ° C to 10.0 ° C with a melting point difference of the inner surface copolymerized polyester film in the range of 210 to 240 ° C. It is a useful invention that facilitates printing and the like by exhibiting excellent light hiding power while sufficiently suppressing scratching and scratching.

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

The characteristics and tube forming moldability of each co-polyester film were measured by the following method.

EXAMPLES 1-4

High concentration of 50% by weight of rutile titanium dioxide having an average particle diameter of 0.30 µm in copolyester polyester having the same composition as copolymerized polyethylene terephthalate (intrinsic viscosity 0.70) containing no white pigment prepared by copolymerizing the components shown in Table 1. The masterbatch was mixed, melt-extruded, cooled and solidified under the film forming conditions shown in Table 1 to form an unstretched sheet, which was stretched under each stretching condition and then heat-set to obtain a final copolymerized polyester film. Melting points, combat yield and laminate properties, and moldability of these films are shown in Table 3 to be measured by the following method.

Glass transition temperature and melting point

A sample of 6.0 mg of copolyester was analyzed using a DuPont 910 differential scanning calorimeter under conditions of a temperature increase rate of 20 ° C / min.

Light hiding power

The battle transient rate for the copolyester film was measured using a 300A haze meter from Nippon Electric Corporation.

○ Battle rate 30% or less × Battle rate 30% or more

Metal plate laminate properties

After the melting point of the copolyester was preheated to the gold plate by using a pressing roll to laminate the inner and outer surfaces of the metal plate at the same time and observed the surface damage by heat.

○ Good film surface condition × Damage to film surface occurs.

Moldability

The metal plate laminated with the co-polyester film was molded through a conventional draw process, and then the film was classified according to the following criteria by observing whether the film was damaged or not.

○ No peeling or breaking of film, no peeling or breaking of part of film

Inner surface polyester film: Melt-extruded copolymerized polyethylene terephthalate containing 12 mol% of isophthalic acid (high viscosity of 0.70, containing 0.25 wt% of spherical silica particles with an average particle diameter of 0.5 μm and melting point of 223 ° C copolymerized polyester) at 270 ° C. It cooled and solidified and the unstretched sheet was shape | molded. The film was stretched at 3.15 times in the longitudinal direction and 3.40 times in the transverse direction and then heat-set at the maximum heat setting temperature of 205 ° C. to obtain a film for an inner surface laminate having a thickness of 25 μm.

Comparative Examples 1 to 3

Copolymerized polyester films of the components shown in Table 2 were obtained in the same manner as in Example, and their melting point, combat yield, laminate properties, molding processability, and the like are shown in Table 3.

TABLE 1

TABLE 2

TABLE 3

As shown in the above Examples and Comparative Examples, the polyester film for outer surface laminates prepared according to the present invention has a very small melting point difference of 1 to 5 ° C. with an inner surface film, and a combat rate and a rate of 20% or less. It is an industrially useful invention that exhibits no peeling phenomenon due to thermal adhesion during processing of laminated metal sheets, and is excellent in light hiding power and printing characteristics.

Claims (4)

In the manufacture of the polyester film for metal plate outer surface laminate, 5.0 to 50.0% by weight of white pigment having an average particle diameter of 3.0 μm or less is contained so that the combat rate is 30% or less and the melting point is within the range of 210 ° C to 245 ° C. Method for producing a copolymer polyester film for metal plate outer surface laminate, characterized in that the difference between the film and the melting point to satisfy the range -1 ℃ ~ 10 ℃. The method according to claim 1, A method for producing a copolyester film for metal plate outer surface laminate, characterized in that the white pigment is particularly rutile titanium dioxide. The method according to claim 1, The copolymerization component is isophthalic acid, The manufacturing method of the copolymer polyester film for metal plate outer surface laminates characterized by the above-mentioned. The use of the co-polyester film for exterior laminate, characterized in that the polyester film for the inner surface laminate with a melting point of the copolyester of the range of 210 ~ 230 ℃ and the polyester film for outer surface laminate prepared according to claim 1 at the same time laminated Way.