KR20010068578A - A co-extrusion polyester film for metal plate bonding, and a process of preparing for the same - Google Patents

Abstract

PURPOSE: A coextruded polyester film for adhering metal plates is provided, which has excellent adhesibility to the metal plate and draw molding property and improves heat-proof property and shock-resistance of a metal can. And a method for preparing thereof is also provided. CONSTITUTION: The method comprises steps of: (i) surface-fractionating a copolymer polyester chip(A) containing 12-30 mol of isophthalic acid based on the total acid components and 3-10 mol of neopentyl glycol based on the total glycol components with a surface-fractionating device under a condition of the following formula (I): 1/70*PH/lr¬2 ; and (ii) after two-layer coextruding a copolymer polyester chip(B), which has an ethylene terephthalate as a main repeating unit, as a first layer and the surface-frictionated copolymer polyester chip as a second layer, biaxially orienting it. In the formula (I), P is a distance(millimeter) between screw pitches, H is a height(millimeter) of a screw peak, l is an average length(millimeter) of a chip, r is an average diameter(millimeter) of a chip and Q is a rotating speed(revolution per minute) of a surface-fractionating machine. The coextruded polyester film for adhering metal plates comprises a first layer of copolymer polyester having an ethylene terephthalate as a main repeating unit and a second layer of copolymer polyester containing 12-30 mol of isophthalic acid based on the total acid components and 3-10 mol of neopentyl glycol based on the total glycol components.

Description

A co-extrusion polyester film for metal plate bonding, and a process of preparing for the same}

The present invention relates to a coextruded polyester film for metal plate bonding and a method for producing the same.

Until now, in order to prevent corrosion of the inner and outer surfaces, various methods of dissolving or dispersing various thermosetting resins such as epoxy and phenol in organic solvents and coating them on metal surfaces have been widely performed. Recently, metal plate coating using a thermoplastic resin film has been attempted without using an organic solvent for the purpose of process simplification, hygiene and environmental pollution prevention. Many studies have been made on a method of manufacturing a can by drawing a thermoplastic resin film after bonding a thermoplastic resin film to a metal plate such as tin plated steel sheet, chromium plated steel sheet, or aluminum. Polyolefins, polyamides, and the like have been attempted as raw materials for such thermoplastic resin films, but these films did not satisfy all of the moldability and heat resistance of the product cans and the steering properties.

Meanwhile, polyethylene terephthalate in polyester is widely used for food packaging because it is chemically and physically stable, and has excellent mechanical strength, heat resistance, chemical resistance, and gas barrier property. In order to use the polyethylene terephthalate film on the surface of the metal can, the adhesion with the metal plate, no defects during bonding, no defects during drawing molding, and no defects such as pinholes after drawing molding And other characteristics are required.

As a conventional method for satisfying such characteristics, Japanese Laid-Open Patent Publication No. 56-10451 proposes a method of laminating a biaxially oriented polyethylene terephthalate film on a metal plate through a copolyester adhesive layer having a low melting point.

As a method of manufacturing the two-layer metal bonding film, there are a method of laminating an adhesive layer and a method by coextrusion. The method of manufacturing a two-layer film by using double coextrusion has an advantage of not requiring an additional process such as lamination because it imparts thermal adhesiveness during the manufacturing process of the film.

However, the technical scope is limited because the polyethylene terephthalate layer and the copolyester adhesive layer undergo the same thermal history and stretching process in the biaxial stretching process, which is a conventional polyester film manufacturing process. In particular, the resin selection of the polyethylene terephthalate layer and the copolyester adhesive layer to satisfy the characteristics such as heat adhesion, heat resistance, water resistance, etc. is important, and the setting of suitable processing conditions for the evenly formed interface between the two layers is important.

In particular, an amorphous resin is used as the copolyester resin forming the adhesive layer. In order to satisfy the characteristics of the metal bonding film, the extrusion amount of the amorphous resin as the adhesive layer should be uniform. However, the amorphous copolyester resin does not have a crystal part in comparison with the low glass transition temperature, so that the extrusion amount may be uneven due to excessive deformation of chips or fusion between chips in the extruder feeding zone during extrusion. This is a problem that the final produced film causes poor results when bonding the metal plate.

The present invention solves these problems of the prior art, and the bonding with the metal plate is good, excellent drawing moldability during the metal can manufacturing process, and can improve the heat resistance, impact resistance and steering properties of the metal can. The present invention provides a coextruded polyester film for joining a metal plate and a method of manufacturing the same.

1 is a cross-sectional view of the surface friction apparatus used in the present invention.

※ Explanation of Codes on Major Parts of Drawings

1 chip inlet 2 screw 3 cylinder

4 chip outlet 5 drive 6 screw pitch

L: Cylinder length C: Cylinder and screw clearance

H: acid height of screw

The present invention relates to a coextruded polyester film for metal plate bonding and a method for producing the same. More specifically, in the present invention, the first layer is a copolyester with ethylene terephthalate as the main repeating unit, and the second layer (adhesive layer) contains 12 to 30 moles of isophthalic acid components with respect to the total acid component, and neopentyl It is the co-extruded polyester film for metal plate joining which is a co-polyester containing 3-10 mol of glycol components.

Hereinafter, the manufacturing method of the present invention will be described in detail.

The present invention is characterized in that it is subjected to surface friction treatment before coextrusion for uniform extrusion of the copolyester forming the adhesive layer (second layer).

Specifically, the copolyester polyester chip (A) containing 12 to 30 moles of isophthalic acid component with respect to all acid components and 3 to 10 moles of neopentyl glycol component with respect to all glycol components is used in the surface friction apparatus of FIG. Surface friction treatment is performed under the conditions of the following formula (I).

≤ Q ≤ (I)

Where P is the distance between the screw pitches (mm), H is the height of the screw threads (mm), l is the average length of the chip (mm), r is the average diameter of the chip (mm), and Q is the rotation of the surface friction machine. Speed (rpm).

It is preferable to use the friction type precrystallization apparatus as shown in FIG. 1 as the surface friction apparatus.

Since the copolyester chip (A) is amorphous, if excessive heat is generated in the friction machine, fusion between the chips occurs in the friction machine, so the frictional heat should be adjusted to an appropriate level or less. If the operating speed is too slow, it is not desirable because not enough friction is applied to the chip surface. Therefore, it is preferable to impart friction under the conditions of the above formula (I), and more preferably, to impart friction under the conditions of the following formula (II).

≤ Q ≤ (Ⅱ)

Where P is the distance between the screw pitches (mm), H is the height of the screw threads (mm), l is the average length of the chip (mm), r is the average diameter of the chip (mm), and Q is the rotation of the surface friction machine. Speed (rpm).

The copolyester chip (A) surface friction under the above conditions is generated irregularities in more than 0.5 of the total surface area. The surface friction effectively reduces the fusion between the chips in the feeding zone (Feeding Zone) inside the extruder and gives the lubricity between the chips to prevent the deformation of the chip to enable uniform extrusion thereof.

Next, co-extrusion of the copolymerized polyester chip (B) having ethylene terephthalate as the main repeating unit as the first layer and the surface-polished copolymerized polyester chip (A) to the second layer (adhesive layer), followed by biaxial orientation To produce a coextruded polyester film for joining a metal plate of the present invention.

The copolyester resin of the first layer is prepared by polycondensation of an aromatic dicarboxylic acid component and a glycol component. Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, and the like. Ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentylglycol, etc. are mentioned. Especially, it is preferable to make terephthalic acid and ethylene glycol into 97 mol or more with respect to each dicarboxylic acid component and glycol component.

As a copolyester resin of the 2nd layer which is an adhesive layer, an aromatic dicarboxylic acid component and a glycol component are manufactured by polycondensation. Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, and the like. Isophthalic acid is preferred. Ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentylglycol, etc. are mentioned as a glycol component, Among these, ethylene glycol and neopentylglycol are preferable.

The adhesive layer copolyester of the present invention contains 12 to 30 moles of isophthalic acid component with respect to all acid components, and 3 to 10 moles of neopentyl glycol component with respect to all glycol components. If the isophthalic acid component is less than 12 moles, the adhesive force is lowered, and if the isophthalic acid component is more than 30 moles, the problem of deterioration in heat resistance occurs. In addition, when the neopentyl glycol component is less than 3 moles, the adhesive force is lowered, and when it exceeds 10 moles, the glass transition temperature is lowered and the heat resistance is lowered.

In the preparation of the copolyester resin of the first layer and the second layer, a known additive such as a polycondensation catalyst, a dispersant, a crystallization accelerator, an antiblocking agent, or the like may be added, and the inorganic substance may also have the effect of the present invention. You may add in the range which does not damage. Examples of the inorganic substance that can be added include titanium dioxide, silicon dioxide, calcium carbonate, and the like, and may be used by mixing two or more kinds.

In the present invention, the physical properties of the copolyester chip and the film are evaluated by the following method.

Surface friction degree (surface irregularity area ratio)

The chip surface was captured at 400x magnification using the high-speed KII 2200 model from Compact Micro Vision System. The chip was randomly sampled 20 times at a 5-minute interval from the surface friction machine and photographed randomly three times, and the average was calculated by calculating the area ratio of the unevenness to friction on the entire area.

Uniformity evaluation of coextrusion interface

Co-extruded 200 µm unstretched film 20 times at 5 minute intervals using a Colin company's 45- and 30-pi single screw extruders and co-extrusion dies to determine the thickness of the first layer or the second layer. Measurement was made using a Hi-Scope. At this time, the conditions were set such that the first layer had a thickness of 150 µm and the second layer had a thickness of 50 µm.

◎: difference between maximum and minimum thickness of the second layer <2 μm

○: difference between the maximum value and the minimum value of the thickness of the second layer <5 μm

X: difference between the maximum value and the minimum value of the thickness of the second layer> 5 µm

Thermal adhesive evaluation

After heating the tin free steel to 200-220 degreeC, the film produced in the Example was crimped | bonded using the rubber roll. At this time, the crimping pressure was set to 30 kg / m 2 speed 100 m / min. The film was then subjected to an adhesion test using Instron.

It looks at in more detail through the following examples and comparative examples. However, the present invention is not limited only to the following examples.

Example 1

A polyester resin having an intrinsic viscosity of 0.6 dl / g polycondensed using only 98 moles of acid component terephthalic acid and 2 moles of isophthalic acid as the first layer resin and only ethylene glycol as the glycol component is prepared. As the second layer adhesive resin, a polyester resin having an intrinsic viscosity of 0.69 dl / g polycondensed with 87 moles of acid component terephthalic acid and 13 moles of isophthalic acid and 95 moles of ethylene glycol and 5 moles of neopentyl glycol as a glycol component is prepared. At this time, the shape of the second layer co-polyester resin is in the form of a rod having an average diameter of 2.6 mm and a length of 3.2 mm. The second layer co-polyester resin chip is subjected to surface friction treatment with a surface friction machine having a screw rotational speed of 30 rpm, a pitch interval of 120 mm, and a screw height of 120 mm. The first layer and the second layer resin thus prepared are coextruded using a coextrusion die to prepare a film, and then biaxially stretched by a conventional method to produce the film of the present invention. Table 2 shows the results of evaluating the uneven surface area ratio of the surface friction treatment chip and the properties of the film.

Example 2

The coextruded polyester film was prepared in the same process and conditions as in Example 1, except that the isophthalic acid and neopentyl glycol content of the second layer (adhesive layer) and the clouding condition (rpm) of the surface friction machine were changed as shown in Table 1. Manufacture. Table 2 shows the results of evaluating the uneven surface area ratio of the surface friction treatment chip and the properties of the film.

<Table 1> Manufacturing Conditions

division Composition of the second layer (adhesive layer) Surface Friction Operating Condition (rpm) Isophthalic acid content (mol compared to total acid component) Neopentylglycol content (mole relative to the total glycol component) Example 1 13 5 30 Example 2 20 3 30 Example 3 10 8 40 Example 4 13 5 50 Example 5 13 5 15 Example 6 13 5 10 Comparative Example 1 7 2 30 Comparative Example 2 35 15 50 Comparative Example 3 13 5 85

<Table 2> Property Evaluation Results

division Area of unevenness generation of chip subjected to surface friction treatment () Properties of the film Uniformity of coextrusion interface Thermal adhesiveness (g / cm) Example 1 66 ◎ 559 Example 2 57 ◎ 605 Example 3 68 ◎ 571 Example 4 89 ○ 521 Example 5 26 ○ 511 Example 6 14 ○ 485 Comparative Example 1 65 ○ 215 Comparative Example 2 - -Fusion occurs during surface friction -Fusion occurs during surface friction Comparative Example 3 - -Fusion occurs during surface friction -Fusion occurs during surface friction

In the present invention, since the surface friction-based amorphous adhesive layer resin is used during the co-extrusion, it is possible to uniformly extrude the adhesive layer, so that the bonding between the metal plate and the adhesive layer is very good.

In addition, the drawing moldability during the can manufacturing process is excellent, and the heat resistance, impact resistance and steering properties of the manufactured metal cans are improved.

Claims (4)

(Iii) The surface friction apparatus shown in FIG. 1 is a co-polyester chip (A) containing 12 to 30 moles of isophthalic acid component relative to the total acid component and 3 to 10 moles of neopentyl glycol component relative to the total glycol component. Surface friction under the condition of the following formula (I), and then (ii) the copolymer polyester chip (B) having ethylene terephthalate as the main repeating unit as the first layer, and the surface friction copolymer polyester chip (A) Biaxially oriented after coextrusion with a 2nd layer (adhesive layer), The manufacturing method of the co-extrusion polyester film for metal plate joining characterized by the above-mentioned. ≤ Q ≤ (I) Where P is the distance between the screw pitches (mm), H is the height of the screw threads (mm), l is the average length of the chip (mm), r is the average diameter of the chip (mm), and Q is the rotation of the surface friction machine. Speed (rpm). The method for producing a co-extruded polyester film for joining a metal plate according to claim 1, wherein surface rubbing is performed such that unevenness occurs in 0.5 or more of the total surface area of the surface friction copolymerized polyester chip (A). The first layer is a copolyester with ethylene terephthalate as the main repeating unit, and the second layer contains 12 to 30 moles of isophthalic acid component and 3 to 10 moles of neopentyl glycol component with respect to all acid components. The co-extruded polyester film for metal plate joining which is co-polyester which is present. The coextruded polyester fiber for joining a metal sheet according to claim 3, wherein the content of the first layer is 50 to 90 weights and the content of the second layer is 10 to 50 weights relative to the total weight of the coextruded polyester film.