KR0175612B1 - White polyester film for joining metal forming process - Google Patents

Abstract

The present invention relates to a polyester film used for covering the outer surface of a metal tube for metal tube, and in particular, it is easy to thermally adhere and has excellent mobility for forming a pipe after bonding, does not require a primer by white paint during printing, It is an object of the present invention to provide a white polyester film for electrodeposition exhibiting excellent impact resistance.

In order to achieve the above-mentioned object, the present invention provides a polyester film obtained by melt-extruding, casting, biaxially stretching and thermoforming a white copolymer polyester obtained by adding a white inorganic pigment and other additives to a copolymer polyester, And a melting point of 210 to 235 DEG C, wherein a white inorganic pigment is added between the content of the white inorganic pigment and the thickness of the film so as to satisfy the following relational expression: do.

150 / d? Xp? 300 / d

(Where d is the film thickness and Xp is the weight% of the inorganic pigment)

Description

White polyester film for metal plate joint molding

FIG. 1 is an illustration of a metal plate lamination process of a polyester film. FIG.

DESCRIPTION OF THE REFERENCE NUMERALS

1: metal plate 2: film

3: guide roll 4: squeeze roll

5: heat treatment apparatus 6: cooling apparatus

More particularly, the present invention relates to a polyester film which is used for covering the outer surface of a metal tube for metal tube, more specifically, it is easy to thermally adhere and has excellent afterglow molding processability and does not require a base due to white paint during printing, And has excellent heat resistance and impact resistance after molding.

Heretofore, various methods have been widely used for dissolving or dispersing various thermosetting resins such as an epoxy resin, a phenol clock, etc. in a solvent to coat the surface of the metal in order to prevent corrosion on the outer surface of the metal tube. However, in such a method of coating the thermosetting resin, usually, the inner surface of the tube is repeatedly applied twice, and drying of the applied coating at 180 ° C to 220 ° C for 10 minutes to 20 minutes is required every time, It is not preferable because it is relatively low in productivity because it is printed at 7 degrees including final vanishing, and it involves environmental pollution caused by the use of a large amount of organic solvent and a large amount of wastewater generated during carbon dioxide washing and drying.

In order to solve this problem, a thermoplastic resin film such as a polyolefin or a polyamide is laminated on a metal plate which has been subjected to various surface treatments such as plating on the surface of a steel plate, an aluminum plate or each metal plate, However, in the case of polyolefin or polyamide, molding processability, heat resistance and impact resistance are not completely satisfied.

On the other hand, thermoplastic polyesters widely used as food containers such as beverage and cooking oil, especially polyethylene terephthalate, have excellent moldability, heat resistance, retort resistance and mechanical strength and have been proposed to use them. Specifically, For example, a biaxially oriented polyethylene terephthalate film may be produced by introducing a low-melting-point polyester adhesive layer and thermally adhered to a metal plate to use the biaxially oriented polyethylene terephthalate film as a pipe material (Japanese Patent Application Laid-Open No. 56-10451, Japanese Patent Application Laid- ), A method in which an amorphous or extremely low crystalline aromatic polyester film is thermally adhered to a metal plate and used as a pipe material (JP-A-1-192545, JP-A-2-22530) , A method of bonding a co-polyester film having a heat shrinkage ratio and density (JP-A-3-86729 ) And the like.

However, the biaxially oriented polyethylene terephthalate film is excellent in heat resistance and preservation of fragrance but is poor in elongation of the film due to insufficient forming workability, so that in the case of a tube processing with a stretching ratio of more than a certain level, cracking or breakage occurs in the film, there is a problem. In addition, when an amorphous or low-crystalline aromatic polyester film is laminated on a metal plate, the film is excellent in molding processability, but is not easily peeled off by heat treatment such as printing after printing, retort treatment, or the like . ≪ / RTI > It is difficult to produce a lowly oriented film applicable to pipe processing because the lowly oriented polyethylene terephthalate film can not secure the isotropy of the film surface and thus can not be sufficient in the shaping workability in a specific direction. In addition, polyethylene terephthalate has a high melting point When the heat is adhered, the steel sheet must also be heated to a high temperature, which leads to a large loss. On the other hand, when the low melting point polyester resin is laminated on the cross section of the polyethylene terephthalate film to improve the adhesive property, if the draw ratio is increased to a certain level or more by stretching such as drawing during the pipe making process, There is a problem that interlayer peeling or cracking occurs due to the decrease of the interfacial adhesion force due to the difference of the interlayer adhesion. In addition, in the case of a metal tube using the above polyester film, a white film is coated on the outer side thereof to reduce the number of times of printing in the tubing process and make the appearance more beautiful (Japanese Patent Application Laid-Open No. 5-287090, 49234). However, it is not suitable for satisfying not only appearance such as light-shielding property, whiteness, printing ink generation property, etc., but also the properties of molding processability, heat resistance, and low temperature impact resistance. Particularly, when the dispersion state of the white pigment is not good, the yield of film production is greatly lowered, and scratch patches and cracks are likely to occur in the film during thermal bonding and tube forming. When a shock is applied at a low temperature, It is easy to get out of this metal pipe. Also, if the coated white film has a low heat resistance, it can not withstand the heat received during printing after post-processing or in the retort sterilization treatment, and is liable to be deformed.

It is an object of the present invention to provide a process for producing a film having excellent intrinsic viscosity at the time of pulverization after the intrinsic viscosity of the final film is close to the level of the inner film and the crystallization degree, Heat resistance and low temperature impact resistance as well as exhibiting excellent light shielding properties, thereby providing a white printing effect which is not affected by the dark color of the metal sheet and which has a good print ink generating property, thereby shortening the printing process at the time of metal tube manufacturing, The present invention is to provide a white polyester film which can be produced in a fine manner.

In order to achieve the above object, the present invention provides a method for producing a white polyester copolymer, which comprises mixing 5 to 30% by weight of a white inorganic pigment such as oxidized tartrate, a dispersant such as strontium acid and a fluorescent whitening agent, The final film has an intrinsic viscosity of from 0.60 to 0.70 and a melting point of from 210 to 235 ° C when the film is extruded, cast, biaxially stretched and thermally fixed, and the content of the inorganic pigment is adjusted according to the thickness of the film, Ester film.

Hereinafter, the present invention will be described in detail.

The copolymerized polyester used in the present invention has a main chain of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and polycyclohexanedimethylene terephthalate, which are copolymerized to achieve the object of the present invention As the dicarboxylic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphthalene dicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, sebacic acid and maleic acid, among which terephthalic acid, isophthalic acid, naphthalene dicarboxylic 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 cyclohexanedimethanol, aromatic glycols such as hydroquinone and bisphenol A, and the like, The dicarboxylic acid and diol components listed above may be used alone or in combination of two or more.

The copolyester used in the present invention is preferably a polyethylene terephthalate, polyethylene naphthalate or the like as a main chain thereof, and a copolyester component of isophthalic acid as a copolymerization component is most suitable for the purpose of the present invention. As the dicarboxylic acid copolymerization component, Phthalic acid as a copolymer component is most suitable for the purpose of the present invention, and the content of the dicarboxylic acid copolymer component is 5 to 20 mol%, preferably 7 to 15 mol%, more preferably 10 to 12 mol% Mol% is preferable in view of molding processability, retort resistance, heat resistance and the like.

Diethylene glycol or the like may be used as a copolymer component of the diol component within a range that does not impair the characteristics of the copolymer polyester, but it is effective in the present invention that the diol component does not exceed 10 mol% with respect to the total diol component.

The melting point of the copolyester used in the present invention is most suitable for the purpose of the present invention within the range of 210 ° C to 235 ° C (preferably 215 ° C to 230 ° C). When the melting point is lower than 210 ° C, And retort resistance are deteriorated, which is undesirable. On the other hand, when the temperature is higher than 240 ° C, the heat resistance and retort resistance are improved, but the crystallinity of the polymer is increased and the thermal adhesive strength is lowered. As a result, the film is peeled off during production of the laminate after the laminating on the metal plate, It does not work. In addition, since a high temperature is required in the preheating of the metal plate, excessive energy consumption is required, resulting in an increase in manufacturing cost.

In addition, the intrinsic viscosity of the polyester suitable for the purpose of the present invention is 0.55 to 0.80, more preferably 0.60 to 0.75, and particularly preferably 0.62 to 0.70. That is, if the amount is too small, heat resistance, formability and impact resistance are lowered, and if the amount is too high, the productivity is lowered.

The copolymerized polyester used in the present invention is obtained by subjecting a reaction product obtained by subjecting terephthalic acid, ethylene glycol and isophthalic acid or a copolymerization component to an esterification reaction or an ester exchange reaction, by a polycondensation reaction.

Reaction catalysts which can be used in the transesterification reaction include manganese acetate, magnesium acetate, calcium acetate, potassium acetate and the like, and they are added at the initial stage or at any stage of the reaction. The polycondensation catalyst to be added to the polycondensation reaction step includes antimony trioxide or a germanium compound, which is mainly added at the beginning of the polycondensation reaction. If necessary, lubricants, antioxidants, heat stabilizers, ultraviolet absorbers, antistatic agents and the like may be added.

As a white colorant necessary for producing a white film, any of inorganic, organic, dye and pigment is preferable, but it is more preferable that it has heat resistance and weather resistance.

The amount of the colorant to be added is limited to a level that satisfies the light transmittance and color tone of the film. In the case of the inorganic pigment, 5 to 30% by weight (more preferably 10 to 25% by weight) And it is suitable to reduce the breakage caused by the drawing process in the tube making process. In addition, the amount of addition thereof should be appropriately adjusted according to the thickness of the final film to obtain desired light transmittance and white color. The present invention is characterized in that the following relationship is satisfied between the content of the inorganic pigment and the thickness.

150 / d? Xp? 300 / d

(Where d is the film thickness and Xp is the weight% of the inorganic pigment)

As shown in the above equation, the thinner the film, the more the addition amount should be increased. In this case, the film should not be fixed or cracked or broken.

Of the white colorants, those suitable for the purpose of the present invention are white pigments such as titanium oxide, alumina, silica, calcium carbonate and barium sulfate. Particularly suitable are titanium oxide, which is classified into an anatase type and a rutile type, Although the mold is excellent in hiding power and light shielding property, its surface is treated with a compound such as silicon, aluminum or zinc or various kinds of organic substances for the purpose of improving the dispersibility due to a slight dispersibility in the polymer resin. However, These surface treatment agents have a problem of decomposing the polyester and lowering the molecular weight. Therefore, anatase-type titanium oxide is mainly used when high-concentration titanium oxide is added.

In the present invention, any of them may be used, and the dispersibility can be remarkably improved by using a dispersant such as strontium acid. Titanium oxide suitable for the production of the polyester film is preferably 0.1-0.5 micron. If it is less than 0.1 micron, it is difficult to uniformly disperse the titanium oxide. If it is larger than 0.5 micron, coarse particles are contained in a large amount. When titanium oxide is used as a white colorant, it is effective to add a fluorescent whitening agent to improve whiteness.

There are various methods for adding titanium oxide to the copolyester in the present invention, but typical examples thereof include 1) a method of adding the titanium oxide before the transesterification reaction or the esterification reaction at the time of the copolymerization polyester polymerization or before the initiation of the polycondensation reaction (3) a master batch chip in which a large amount (40 to 60% by weight) of titanium oxide is added, and then kneaded with a copolymerized polyester in which the particles are not mixed, There is a method in which a predetermined amount of titanium oxide is contained.

Among them, a method using a master batch chip of 3) is used in particular, but when a master batch chip containing a high concentration of an inorganic pigment is manufactured, due to the high temperature and stress applied at the time of manufacture, There is a drawback that the molecular weight of the polyester is remarkably lowered. Therefore, even if it is kneaded with the graphene copolymerized polyester again, the average molecular weight or viscosity of the mixture may not be enough to be used for a metal plate laminate or a steel pipe.

That is, when a polyester having a low molecular weight is used for a tube, there are drawbacks that all properties such as heat resistance, stretching property, and impact resistance are lowered. However, in the production of masterbatches, molecular weight reduction is considered to be inevitable in the process. Therefore, in the present invention, the non-particulate polyester kneaded with the masterbatch is used in a relatively high A method of increasing the average molecular weight of the final white film by using a polyester of viscosity is used.

The white film of the present invention is obtained by mixing an appropriate amount of a copolymer polyester master chip to which a large amount of a white inorganic pigment is added and a high viscosity nonparticle copolymerized polyester chip so as to have a predetermined inorganic pigment content, Extrusion, cooling and solidification through a die, and then adjusting the conditions such as temperature and stretch ratio of coarse stretching and drawing, and the temperature of the heat setting step. The final finish of the produced film is preferably about 10 to 40 占 퐉 (more preferably 12 to 30 占 퐉). If the finish of the film is less than 10 占 퐉, the film tends to be broken during the tube processing, If it exceeds 40 탆, it is uneconomical due to overuse.

In the present invention, a metal plate for laminating a copolymer polyester film is preferably a tin-plated steel plate, a chrome-plated steel plate, a chromium oxide-plated steel plate, an aluminum plate, or the like. A method of laminating a film on a metal plate is as follows. First, when the film is laminated on the metal plate after cleaning the lubricant or the like on the metal plate, the lamination process as shown in FIG. 1 is carried out. That is, the metal plate 1 is heated to the melting point or more of the film 2 , And then laminated using a compression ratio (4) on one or both sides of the metal sheet, if necessary.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The properties of each copolymer polyester and film evaluated here were measured by the following methods.

* Intrinsic viscosity

2.0 g of each copolymer polyester was dissolved in a mixed solvent of 1,1,2,2-tetrachloroethane / phenol (60/40 weight percent) and measured at 25 캜.

* Glass transition temperature and melting point

A sample of 6.0 mg of copolymerized polyester was obtained using a DuPont 9100 differential scanning calorimeter at a heating rate of 20 ° C / min and a maximum endothermic park temperature in the case of melting point.

* Film properties

The longitudinal and transverse strength and elongation of the film were measured using an intrinsic tensile strength tester.

* Thermal adhesion

The co-extruded polyester film was sandwiched between the coated steel sheets and heat-pressed at a constant pressure using a hot press, and then the size of the adhesive force was evaluated by the ASM T-1876 method.

* Stretch adhesion

The co-extruded polyester film was thermally bonded to a metal plate, and the metal plate was cut into a tensile strength test piece, and the degree of peeling of the film with respect to the tensile strength of the tensile strength tester was observed. The surface of the test piece was scratched with a spiral test machine according to the print ratio, and then peeled off with a 3 M tape. The tensile ratio at the time when the peeling of the film started to take place was expressed by the stretching adhesion of the film.

* Stretch forming processability

The laminated metal plate was cut into a circular shape having a diameter of 187 mm, and then a single-piece pipe having a cup diameter of 66 mm and a cup height of 140 mm was formed through punching and draw processes, and the formability was evaluated by observing the breaking or peeling degree of the film.

No peeling or peeling of the film, Partially peeled off,

* Hue of film

A model 1001DP colorimeter of Tensho Kusa Co., Ltd. was used, and L, a, and b values of one film were determined using standard plates Y = 94.41 and Z = 111.22.

* Light transmittance

The light transmittance per film of the film was measured using a Model NDH-1001DP haze meter of Tensho Corp., Japan.

* Shading

A black line having a length of 50 mm, a width of 0.1 mm, and a width of 1 mm was drawn on the plated steel sheet before the lamination, and then the black line after the lamination and neutralization of the film was observed and evaluated.

○ All black lines of 0.1mm and 1mm are not visible, only black lines of △ 1mm are visible, and all black lines of × 0.1mm and 1mm are visible.

* Dispersibility of Inorganic Pigments

The copolymer polyester melt was passed through a filter having a size of 30 mu m using a measuring device of Kilion Co., USA, and the increase of the filtration pressure at the passage of 1 kg was measured and evaluated.

* My Retort Castle

The processed can is filled with water, retorted at 120 ° C for 1 hour in a steam sterilizer, and then held at 50 ° C for 30 days. Next, each group consisting of 10 cans was dropped on a polyvinyl chloride tile floor at a height of 1 m, and the appearance was observed and evaluated.

○ All 10 cans were good, △ 1 to 5 cans cracked on film, × 6 cans cracked or broken

* Low temperature impact resistance

The processed tube was filled with water, cooled to 10 ° C, and then dropped at a height of 30 cm at a height of 10 cm for each composition. Subsequently, the tube was immersed in 1% saline solution and allowed to stand at 80 ° C for 24 hours. Were observed and evaluated.

○ No generation of rust, △ Less than 1 mm of rust occurred within 3, × Multiple rusts

[Example 1]

5.34 kg of dimethyl terephthalate, 0.73 kg of dimethyl isophthalate and 3 L of ethylene glycol were charged into a reaction tube, and after the temperature of the reaction tube reached 145 캜, 0.03 wt% of manganese acetate, 0.07 wt% of potassium acetate %, And the transesterification reaction is carried out until the temperature of the reaction product reaches 235 캜. When the temperature of the reaction reached 235 ° C, 0.03% by weight of antimony trioxide and 0.03% by weight of trimethyl phosphate were added. Then, the temperature of the reaction product was raised to 245 ° C to remove excess ethylene glycol from the reaction product, The pressure is reduced to 0.5 torr.

On the other hand, the temperature of the reaction tube is raised at the same time as the pressure is reduced, the temperature of the reaction product is elevated to 285 ° C, and then the polycondensation reaction is carried out. The above-mentioned copolymerized polyesters having an intrinsic viscosity of 0.71 and a melting point of 225 ° C were preliminarily dried at 80 ° C for 60 minutes and then dried at 120 ° C for 90 minutes and at 150 ° C for 280 minutes to prepare a particleless copolyester chip . Further, 50% by weight of rutile type titanium triacetate having an average particle diameter of 0.24 탆 was dispersed and added with a small amount of strontium acid to a co-polyester having the same composition as the above-mentioned copolymerization component to prepare a master batch chip having an intrinsic viscosity of 0.38. Then, the above non-particle chip and master chip were mixed at a weight ratio of 76:24, respectively, so that the concentration of titanium oxide became 12 wt%, melt-extruded at a melting temperature of 275 ° C, and cooled and solidified to prepare an unstretched film . This unstretched film was stretched 3.1 times in the longitudinal direction at 90 DEG C and 3.2 times in the transverse direction at 105 DEG C and then heat set at 190 DEG C to prepare a biaxially stretched white film having a final thickness of 20 mu m. The biaxially stretched film thus prepared was pressed on both sides of a metal plate having a thickness of 0.21 mu m plated with chromium oxide preheated at 240 DEG C and then quenched with cooling water at 50 DEG C to prepare a laminated metal plate From these, a single-piece tube having a diameter of 66 mm and a cup height of 140 mm was produced, and the properties thereof were evaluated and shown in Tables 1 and 2 below.

[Example 2]

A copolymer polyester having an intrinsic viscosity of 0.71 was prepared in the same manner as in Example 1 and then mixed with a master chip containing 50 wt% of rutile-type titanium oxide having an average particle diameter of 0.3 mu m at a ratio of 70:30 to prepare a 15 wt% , And then melt-extruded to prepare a biaxially stretched film having a longitudinal stretching ratio of 3.5 times, a transverse stretching ratio of 3.3 times, and a heat fixing temperature of 190 占 폚 to form a biaxially stretched film having a thickness of 15 占 퐉. The plated metal plate was laminated and subjected to tube forming, and its physical properties were evaluated and shown in Tables 1 and 2.

[Example 3]

A copolymer polyester having an intrinsic viscosity of 0.71 was prepared in the same manner as in Example 1 and then mixed with a master chip containing 50 wt% of rutile-type titanium oxide having an average particle diameter of 0.3 mu m at a ratio of 80:20 to prepare a 10 wt% And then melt-extruded to prepare a biaxially stretched film having a longitudinal stretching ratio of 2.9 times, a transverse stretching ratio of 3.1 times, and a heat-setting temperature of 190 占 폚 to form a biaxially stretched film having a thickness of 25 占 퐉. The plated metal plate was laminated and subjected to tube forming, and its physical properties were evaluated and shown in Tables 1 and 2.

[Example 4]

A copolymerized polyester having an intrinsic viscosity of 0.72 having an isophthalic acid component of 10 mol% based on the total acid components and a diethylene glycol content of 1.8 mol% based on the total diol component was prepared in the same manner as in Example 1, And a master chip containing 50 wt% of rutile-type titanium oxide at a ratio of 76:24 to make 12 wt% of titanium oxide, and then melt-extruded, and the longitudinal stretching ratio was 3.1 times, the heat setting temperature was 190 DEG C To prepare a biaxially oriented copolymerized polyester film having an afterglow of 20 mu m. The resultant laminate was laminated on a plated metal plate of chromium and chromium oxide layers, and the properties thereof were evaluated and shown in Tables 1 and 2. [

[Comparative Example 1]

6.06 kg of dimethyl terephthalate and 3 L of ethylene glycol were placed in a reaction tube similar to that of Example 1 and polycondensation was carried out by the same method to obtain polyethylene terephthalate having an intrinsic viscosity of 0.62 and a melting point of 255 DEG C and then the polyesters having the same composition as the above- 50 wt% of rutile-type titanium oxide having an average particle diameter of 0.3 탆 was dispersed and added with a small amount of strontium acid to prepare a master chip having an intrinsic viscosity of 0.39. Then, the above non-particle needle and the master chip were mixed at a weight ratio of 76:24 to obtain 12 wt% of titanium oxide, melt-extruded at a melting temperature of 285 ° C, and cooled and solidified to prepare an unoriented film. Using this, a film having a longitudinal draw ratio of 3.1 times, a draw ratio of 3.5 in the transverse direction, and a heat setting temperature of 215 占 폚 and a film finish of 20 占 퐉 was obtained. The prepared film was laminated on a chromium oxide plated metal sheet preheated to 265 DEG C using a press roll, and the properties thereof were evaluated and shown in Tables 1 and 2. [

[Comparative Example 2]

A copolymerized polyester having an intrinsic viscosity of 0.62 and an inherent viscosity of 0.62 and a melting point of 223 ° C was produced by polycondensation using the same composition and method as in Example 1, and then stretched 3.1 times in the machine direction and 3.2 times in the machine direction, To obtain a copolymer polyester film having a haze of 20 mu m. The prepared film was laminated on a chromium oxide plated metal plate preheated to 240 DEG C, and physical properties thereof are shown in Tables 1 and 2. [

[Comparative Example 3]

A polyester film prepared without using a dispersing agent such as strontium acid was used in the production of a film and lamination to a metal plate in the same manner as in Comparative Example 2. The properties of the polyester film were evaluated, Respectively.

[Comparative Example 4]

A polyester film prepared without using a dispersing agent such as strontium acid was used for the production of a film and lamination to a metal plate in the same manner as in Comparative Example 2 except that dispersion of titanium oxide in a white film was added. Are shown in Tables 1 and 2.

[Comparative Example 5]

A film was produced and laminated to a metal plate in the same manner as in Comparative Example 2, except that a film prepared so that the thickness of the film was 15 μm, the content of titanium oxide in the white film being equal to 12 wt% The results are shown in Tables 1 and 2.

Claims (5)

The final film obtained by melt extrusion, casting, biaxial stretching and thermosetting a white copolymer polyester obtained by adding a white inorganic pigment and other additives to a copolymerized polyester is blended with a white polyester having an intrinsic viscosity of 0.6 to 0.7 and a melting point of 210 to 235 캜 Wherein a white inorganic pigment is added between the content of the white inorganic pigment and the thickness of the film in the film so as to satisfy the following relational expression. 150 / d? Xp? 300 / d (Where d is the film thickness and Xp is the weight% of the inorganic pigment) 2. The polyester resin composition according to claim 1, wherein the copolymer polyester comprises terephthalic acid and ethylene glycol as the main component and a dicarboxylic acid component in an amount of 5 to 20 mol% of the total acid components as the dicarboxylic acid and glycol component, Wherein the white polyester film has an average particle diameter of not more than 50 占 퐉. The white polyester film according to claim 1, wherein the white inorganic pigment is used in an amount of 5 to 30% by weight based on the polyester. The white polyester film for joining metal sheet processing according to claim 1, wherein the white inorganic pigment is selected from titanium oxide, alumina, silica, barium carbonate, and barium sulfate. The white polyester film for bonding and metal sheet processing according to claim 1, wherein the final finish of the produced film is in the range of 10 to 40 mu m.