JP2009149109A - Multilayered resin film, resin coated metal sheet, production process of multilayered resin film and production process of resin coated metal sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayered resin film with small surface irregularity, a resin coated metal sheet made by laminating the multilayered resin film onto a metal sheet, a production process of the multilayered resin film which produces the multilayered resin film by laminating a plurality of molten resins different in melt viscocity with high-speed without making irregularity on the film surface, and a production process of the resin coated metal sheet which laminates the multilayered resin film onto the metal sheet in the multilayered film comprising a plurality of resin layers mutually different in melt viscosity. <P>SOLUTION: A non-oriented multilayered resin film comprises at least a polyester resin containing a coloring component and a polyester resin without coloring component. In addition, melting tension Tm under extrusion temperature of the polyester resin without coloring component fulfills 1.0g ≤Tm, and thickness of the film comprising the polyester resin without coloring component is one third or more of the total thickness. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a multilayer resin film having a small surface irregularity composed of a plurality of resin layers having different melt tension and melt viscosity, a resin-coated metal plate coated with the multilayer resin film, a method for producing the multilayer resin film, and The present invention relates to a method for producing a resin-coated metal plate. In particular, the present invention relates to a manufacturing method capable of high-speed production with a resin film forming speed of 100 m / min or more.

  In the field of beverage cans and the like, a can obtained by drawing or squeezing and squeezing a resin film-coated metal plate is frequently used. This is because the resin film has excellent adhesion to the metal plate during processing and excellent permeation resistance to the contents. In recent years, the cans formed by molding these resin film-coated metal plates have a processing degree for diversifying the contents to be filled in the cans and further reducing the weight of the cans for the purpose of reducing can costs. Along with the rise, it has become difficult to achieve both excellent permeation resistance and excellent work adhesion with a single-layer resin film. For this reason, by using a single-layer resin film having excellent properties and processing adhesion and permeation resistance separately, and by coating a metal plate with a film obtained by multilayering those individual single-layer films. Attempts have been made to apply it as a resin film used for a resin film-coated metal plate, which has even better work adhesion and permeation resistance than before.

  However, when resin films having different physical properties are used in multiple layers as described above, resins having different melting points and different melt viscosities when heated and melted at the same temperature are heated and melted and coextruded to form a film. However, when resins having different melting points are heated and melted, if they are heated and melted at the same temperature, the melt viscosity of a resin having a high melting temperature is high, and the melt viscosity of a resin having a low melting temperature is often low. And when multi-manifold dies are used to laminate and laminate a resin in which such resins are heated and melted at the same temperature, if the melt viscosity of adjacent resins is different, individual heated and melted resins that have passed through individual manifolds When the materials are joined together as a multilayer resin, the flow of the heated molten resin may be disturbed at the interface between the resin layers, resulting in uneven thickness (unevenness) on the film surface. The uneven thickness on the film surface is called a flow mark and is not only visually defective, but also draw processing and drawing ironing to form a can body, neck-in (small diameter) processing of the upper opening of the can When carrying out the process, uniform processing becomes impossible, which may cause broken bodies. Also, if the molten resin is extruded at a high speed in order to improve the production speed, the difference in dimensions in the width direction, that is, the generation of ears will increase, or the resin extruded from the die lip will fall without pulsating uniformly. Thus, a film having a uniform thickness cannot be obtained. Moreover, when the pigment which is a coloring component enters into a film, these will generate | occur | produce easily. In order to suppress the occurrence of such unevenness of the ears and film (unevenness, flow mark), the method disclosed in the following publication has been tried.

  Patent Document 1 discloses a method for preventing the occurrence of a flow mark by selecting and using a resin having a small difference in melting point and viscosity at the time of heating and melting. However, physical properties required for a resin film are disclosed. Depending on the case, it is often necessary to select resins having mutually different melting points or viscosities when heated and melted, and the method disclosed in this publication can be applied only to extremely limited applications.

  Patent Document 2 uses a feed block method in which a plurality of heat-melted resin layers are joined in front of a T die, and a multilayer extrusion that combines a feed block and a T die that is connected to the feed block to form a multilayer resin film. In the molding method, a method is disclosed in which the temperature of a heater provided in a feed block is controlled to reduce a defective phenomenon such as a shift (flow mark) at a laminated boundary surface joining multiple layers. FIG. 2 shows an outline of an example of the multilayer extrusion molding apparatus. The multilayer extrusion molding apparatus is composed of a feed block 10 having a plurality of manifolds 14a to 14g, and a T die 12 provided below the junction 16 of the resin from the manifolds 14a to 14g and connected to the feed block 10. ing. Around the junction of the resin passages from the manifolds 14a to 14g, for example, the heaters 20b and 22b, the thermometer 28b, etc. in the resin passage on the outlet side of the manifold 14b (for the sake of simplicity, only the manifold 14b is mentioned) And controlling the temperature / viscosity of each molten resin material supplied from each manifold to equalize the temperature / viscosity, thereby reducing the defective phenomenon at the laminated interface joining the multilayer resin.

  However, in the feed block method, the inside of the T die into which the resin flows after joining the multilayers has a single layer structure, and the joined and multilayered resin reaches from the joining part 16 to the outlet opening 34 of the die lip 32. Since the T die is only heated as a whole while the distance increases and the molten resin moves through the distance, the heating temperature of each resin layer immediately after merging is increased. Since it is impossible to keep the difference and the heating temperature of each resin layer is changed at the outlet opening 34, the melt viscosity of each resin layer cannot be kept the same. It becomes difficult to prevent. As described above, the method according to this publication can be applied only to a limited use such as using a resin that does not differ so much in melting point that the same melt viscosity is obtained. Also, in the methods disclosed in these publications, the film forming speed cannot be increased when the tension of the molten resin is small.

Japanese Patent Application Laid-Open No. 08-290532 Japanese Patent Laid-Open No. 11-309770

  The present invention relates to a multilayer film composed of a plurality of resin layers having different melt viscosities, a multilayer resin film having small surface irregularities, a resin-coated metal plate obtained by laminating a multilayer resin film on a metal plate, and a melt viscosity of each other A method for producing a multilayer resin film by laminating a plurality of different molten resins at high speed without forming irregularities on the film surface, and a resin-coated metal plate for laminating a multilayer resin film on a metal plate An object is to provide a manufacturing method. In particular, the present invention relates to a manufacturing method capable of high-speed production with a resin film forming speed of 100 m / min or more.

According to the present invention, in a multilayer resin film composed of a polyester resin containing at least a coloring component and a polyester resin not containing a coloring component, the polyester resin not containing the coloring component has a melt tension Tm of 1. There is provided an unstretched multilayer resin film characterized in that 0 g ≦ Tm and the thickness of the film made of a polyester resin not containing the coloring component is one third or more of the total thickness .
In the multilayer resin film of the present invention, the thickness unevenness represented by a difference between the maximum thickness and the minimum thickness was measured in the length direction of the full width direction is less than or equal to 5.0 .mu.m.
Moreover , according to this invention, the resin-coated metal plate formed by laminating | stacking the said multilayer resin film on a metal plate is provided .

According to the present invention, two or more kinds of polyester resins containing at least a polyester resin containing no coloring component and a polyester resin containing a coloring component having a melt tension Tm at an extrusion temperature of 1.0 g ≦ Tm Using a die, an extruder provided continuously in each manifold, each manifold, and an extruder through which a resin having a high melt viscosity passes, controlling the temperature of each manifold and the portion of the die adjacent to each manifold, Polyester resin that does not contain coloring components by maintaining the temperature of the manifold and the portion of the die adjacent to the manifold higher than the temperature of the extruder through which the low melt viscosity resin passes, the manifold, and the portion of the die adjacent to the manifold The thickness of the film will be more than one third of the total thickness Thus, there is provided a method for producing a multilayer resin film, wherein each molten resin is laminated to form a multilayer film.
In the method for producing a multilayer resin film of the present invention, it is preferable to control the temperature so that the difference in melt viscosity between adjacent resin layers is 3000 poise or less at a shear rate of 20 to 500 sec- ¹ .

According to the present invention, two or more kinds of polyester resins including at least a polyester resin not containing a coloring component having a melt tension Tm at an extrusion temperature of 1.0 g ≦ Tm and a polyester resin containing a coloring component are added to a multi-manifold die. Are used to control the temperature of each of the extruders continuously provided in each manifold, each manifold, and the portion of the die adjacent to each manifold, and the extruder through which the resin having a high melt viscosity passes. And the temperature of the die portion adjacent to the manifold is higher than the temperature of the extruder, manifold, and die portion adjacent to the manifold through which the low melt viscosity resin passes, and from the polyester resin containing no coloring component The thickness of the film to be more than one third of the total thickness Thus, a method for producing a resin-coated metal sheet is provided , wherein each molten resin is laminated and multilayered and then extruded onto the metal sheet.
In the method for producing a resin-coated metal sheet of the present invention, it is preferable to control the temperature so that the difference in melt viscosity between adjacent resin layers is 3000 poise or less at a shear rate of 20 to 500 sec- ^1. is there.

In the present invention, two or more kinds of resins containing at least one kind of resin containing a coloring component and having a difference in melt viscosity of 3000 to 20000 poise at a shear rate of 20 to 500 sec- ^{1 at} the same heating and melting temperature. Using a multi-manifold die, the temperature of the extruder provided continuously in each manifold, each manifold, and the portion of the die adjacent to each manifold is controlled, and a resin with a high melt viscosity is obtained. The temperature of the extruder, manifold, and die part adjacent to the manifold passing through is kept higher than the temperature of the extruder, manifold, and die part adjacent to the manifold through which the low melt viscosity resin passes. the difference in melt viscosities of the layers, and 3000 poises at a shear rate of 20 to 500 sec ^-1 And then, as the thickness of the resin melting tension does not contain coloring component is at least 1g becomes one third or more of the total thickness, in which a multilayer film by laminating each molten resin There is no increase in pulsation or ear generation even when the film is formed at high speed, and the thickness unevenness of the obtained resin film is extremely small. Moreover, since the multilayer film obtained in this way has a thickness unevenness of 5 μm or less on the surface, it is not only excellent in visual smoothness but also based on the melt viscosity as in a normal multilayer film in a resin film. Since no stress is generated, when a multilayer resin film is laminated and coated on a metal plate to form a multilayer resin film-coated metal plate, the resin film will roll up and peel off from the metal plate even if the resin film has wrinkles. There is no.

Schematic which shows an example of the manufacturing method of the multilayer film of this invention. Schematic which shows an example of the manufacturing method of the conventional multilayer film.

  The present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an example of a method for producing a multilayer film of the present invention comprising a plurality of resin layers having different melt viscosities. In order to simplify the explanation, a case of using for forming a two-layer resin film is illustrated. The multi-manifold die 1 having two manifolds 2a and 2b includes an extruder 6a that heats and melts a resin having a higher melt viscosity and an extruder 6b that heats and melts a resin having a lower melt viscosity. Are respectively connected to 2a and 2b via resin passages. The manifolds 2a and 2b are combined below the multi-manifold die 1 to form a lip land 5, and are connected to a discharge port 7 provided in the lowermost die lip of the multi-manifold die 1.

  The multi-manifold die 1 includes a heater 11a for heating the side through which the higher melt viscosity of the die body passes, a heater 11b for heating the side through which the lower melt viscosity passes, a manifold 2a, Heaters 3a and 3b provided adjacent to the respective manifolds for heating 2b, and heaters 4a and 4b are provided, and the extruder 6a and the extruder 6b are connected to the multi-manifolds 2a and 2b, respectively. Heaters 10a and 10b for heating the passage are provided. A temperature measuring means such as a thermocouple (not shown) is provided in the vicinity of the portion where each of these heaters is provided, and the heating temperature is controlled to be constant while measuring the temperature of each portion, and each of the manifolds 2a and 2b is controlled. The temperature of each heater is individually controlled so that the difference in viscosity of the heated molten resin is within a certain range.

  The two types of resins melted and melted by the extruder 6a and the extruder 6b and having a difference in melt viscosity at the same heating and melting temperature of 3000 to 20000 poise at a shear rate of 20 to 500 sec-1 are respectively multi-manifold dies. 1 through the manifolds 2a and 2b provided in the die 1, stacked at the inlet of the lip land 5 combined below the multi-manifold die 1, and from the outlet 7 provided in the lowermost die lip of the die 1 to the outlet 7 Winding of a coiler or the like which is discharged onto a cooling roll 9 configured to circulate a coolant such as water in the interior provided below and becomes a cooled and solidified multilayer resin film 8 and continuously wound in a coil shape It is wound up on the means 12.

Using the multilayer resin film manufacturing apparatus configured as described above, the multilayer resin film of the present invention can be formed as follows.
Although it does not specifically limit as said applicable resin film, For example, the following polyester resin is applicable. Examples of the acid component from which the polyester resin is derived include terephthalic acid, isophthalic acid, orthophthalic acid, P-β-oxyethoxybenzoic acid, naphthalene-2,6-dicarboxylic acid, diphenoxyethane-4,4′-dicarboxylic acid, Dibasic aromatic dicarboxylic acids such as 5-sodiumsulfoisophthalic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid and cyclohexanediacetic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid and dimer acid, trimet acid, Pyromellitic acid, hemimellitic acid, 1,1,2,2-ethanetetracarboxylic acid, 1,1,2-ethanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid, 1,2,3,4-cyclo And polybasic acids such as pentanetetracarboxylic acid and biphenyl-3,4,3 ′, 4′-tetracarboxylic acid. Of course, these may be used alone or in combination of two or more. Examples of the alcohol component from which the polyester is derived include diols such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol, and cyclohexanedimethanol. And polyhydric alcohols such as pentaerythritol, glycerol, trimethylolpropane, 1,2,6-hexanetriol, sorbitol, 1,1,4,4-tetrakis (hydroxymethyl) cyclohexane, and the like. Of course, these can be used alone or in combination of two or more.

As the coloring component used in the multilayer resin film of the present invention, all the coloring agents conventionally used for coloring a resin film can be used. For example, the following can be exemplified.
Black pigment: carbon black, magnetite, acetylene black, run black, aniline black.
Yellow pigments: yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow Rake, Permanent Yellow NCG, Tartrazine Rake.
Orange pigments: reddish yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK.
Red pigment: Bengala, cadmium red, red lead, mercury cadmium sulfide, permanent red 4R, risor red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant Carmine 3B.
Purple pigment: Manganese purple, fast violet B, methyl violet lake.
Blue pigments: ultramarine blue, bituminous blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, indanthrene blue BC.
Green pigments: chrome green, chrome oxide, pigment green B, malachite green lake, fanal yellow green G.
White pigments: rutile or anatase titanium dioxide, zinc white, gloss white, perlite, sulfate precipitated perlite, calcium carbonate, gypsum, precipitated silica, aerosil, talc, calcined or uncalcined clay, barium carbonate, alumina white, Synthetic or natural mica, synthetic calcium silicate, magnesium carbonate.

The particle size of the colorant is generally in the range of 0.05 to 2 μm, particularly 0.1 to 0.5 μm. This makes it possible to combine both excellent processability and hiding power. A particularly suitable colorant for the purposes of the present invention is titanium dioxide, which is white and has great hiding power.
The blending amount of the colorant to the resin is not particularly limited as long as the melt viscosity and melt tension of the color component-containing resin can be within the above-described ranges, and can be appropriately determined according to the application.

Resins having different melt viscosities at the same heating and melting temperature in the range of 3000 to 20000 poises at a shear rate of 20 to 500 seconds- ¹ as described above, and containing one coloring component (in the case of FIG. 1) Are two types, and for ease of explanation, the pellets of the extruder 6a will be described below assuming that the resin to be heated and melted by the extruder 6b shown in FIG. 1 contains a coloring component). And 6b are led to the manifolds 2a and 2b connected via the respective resin passages in the multi-manifold die 1 provided below the respective extruders, and proceed toward the combined portion. At this time, the respective resins have a difference in melt viscosity of 3000 poise at a shear rate of 20 to 500 seconds −1 by the heaters 10a and 10b, the heaters 11a and 11b, the heaters 3a and 3b, and the heaters 4a and 4b. As described below, the heating temperature of each heater is controlled while being measured by temperature measuring means such as a thermocouple provided in the vicinity of each heater.

Next, the molten resin having a difference in melt viscosity of 3000 poise or less at a shear rate of 20 to 500 seconds ⁻¹ as described above is laminated at the entrance of the lip land 5 merged at the merged portion of the manifolds 2a and 2b. Then, it is discharged from the discharge port 7 onto the cooling roll 9 and solidified to form a multilayer (two-layer) film 8. Especially when the molten resin is extruded at a high speed, the resin containing the coloring component at the extrusion temperature is melted. When the tension is less than 0.5 g, or the melt tension of the resin containing no coloring component is less than 1 g, the extruded film-like molten resin pulsates and the longitudinal thickness becomes nonuniform or the width direction Ears are generated. Using a resin having a color component containing a melt tension Tm of 0.5 g ≦ Tm <1.0 g, the melt tension of 0.5 g ≦ Tm <1.0 g is applied to the total thickness of the extruded multilayer film. A resin layer having a resin layer having a melt tension of 0.5 g ≦ Tm <1.0 g is used with respect to the total thickness of the extruded multilayer film. Use a resin with a melt tension of 1 g or more so that the resin does not contain a coloring component so that the melt tension is 1 g or more with respect to the total thickness of the extruded multilayer film. By controlling the amount of extrusion so that the thickness becomes one third or more, the occurrence of pulsation and ears can be prevented. Therefore, the film can be formed at a higher speed.

  As described above, after adjusting the difference in melt viscosity and adjusting the discharge amount using a resin containing a coloring component in at least one of the resins, the resin is discharged from the discharge port 7 onto the cooling roll 9. The solidified multilayer (two-layer) film 8 is wound around the winding means 12. In this way, the multilayer resin film of the present invention is produced.

  The multilayer resin film of the present invention obtained as described above preferably has a difference in unevenness on the surface of the multilayer resin film of 5 μm or less. When the unevenness difference exceeds 5 μm, it is not only visually inferior, but also after the multilayer resin film is laminated and coated on a metal plate to form a multilayer resin film-coated metal plate, the multilayer resin film-coated metal plate is applied to a can body. Drawing or ironing to form, or the resin film peels off from the metal plate when performing neck-in processing of the opening at the top of the can. Can not be formed into a can body due to breaking in processing and drawing ironing and crashing in neck-in processing.

Further, the multilayer resin film of the present invention is a multilayer resin film in which the multilayer resin heated and melted from the discharge part of the die lip using the above-described method for producing a multilayer resin film is directly discharged onto a metal plate in a film form and coated. It can be a coated metal plate. In addition, a multilayer resin film prepared using the above-described multilayer resin film production method is laminated on a metal plate directly or via an adhesive to form a multilayer resin film-coated metal plate using a known lamination method. You can also. In addition, when the multilayer resin melted by heating is directly discharged onto a metal plate in the form of a film, the difference in unevenness on the surface of the multilayer resin film after the layer coating is 5 μm or less for the same reason as described above. Is preferred.
In the above description, the case where a two-layer resin film using two kinds of resins is formed has been described. However, a multi-manifold die provided with three or more manifolds and an extruder 3 connected to each manifold. Needless to say, it is possible to form a resin film having three or more layers by providing more than one.

EXAMPLES Hereinafter, an Example is shown and this invention is demonstrated in detail.
(Comparative Example 1)
Polyester resin A (ethylene terephthalate / ethylene isophthalate copolymer (10 mol% ethylene isophthalate) excellent in permeation resistance, melting point: 220 ° C., intrinsic viscosity: 0.85, 260 ° C., shear rate: 100 sec ⁻¹ Melt viscosity: 7500 poise, melt tension: 0.7 g (hereinafter simply referred to as Resin A. Melt tension is Capillograph 3A (trade name: manufactured by Toyo Seiki Co., Ltd.), resin temperature: 260 ° C., extrusion Speed: 10 mm / min, winding speed: 10 m / min, nozzle diameter: 1 mm, nozzle length: measured at 10 mm) and polyester resin B (ethylene terephthalate / ethylene isophthalate copolymer) excellent in work adhesion Coalescence (ethylene isophthalate 15 mol%), melting point: 215 ° C, intrinsic viscosity: 0.9, melting point: 215 ° C, temperature 260 ° C Melt viscosity at 100 sec ^-1: shear rate 9000 poises, melt tension: 0.7 g) (hereinafter, briefly resin TiO ₂ as coloring component in) that the resin B was added 27 wt% (260 ° C., shear rate: 100 The melt viscosity at second ⁻¹ : 4000 poise and melt tension: 0.4 g) were melted by heating Resin A at 265 ° C. and Resin B (27 wt% of TiO ₂ added) at 260 ° C. using an extruder, respectively. . Next, two manifolds are connected to the two extruders via resin passages, and two-layer film is produced on each manifold of the multi-manifold die provided with heaters for individually controlling the temperature adjacent to the manifolds. The molten resin A and the molten resin B are led by adjusting the discharge amount so that the ratio of the thickness of the resin A and the thickness of the resin B after the film formation is 1: 3 and the thickness of the two-layer resin film is 16 μm. It was. The side of the multi-manifold die through which the molten resin A passes and the resin passage and manifold through which the molten resin A passes, and the side of the multi-manifold die through which the molten resin B passes and the resin passage through which the molten resin B passes and the manifold are respectively adjacent to the heater. Was previously heated to 260 ° C., and the molten resin A and the molten resin B were passed through the respective manifolds. At this time, the resin temperature immediately before the T-die and the resin viscosity at a shear rate of 100 seconds ⁻¹ are resin A: 265 ° C., about 6500 poise, and resin B + TiO ₂ : 260 ° C., 4000 poise. After the molten resin A and the molten resin B are heated in this way, the molten resin A and the molten resin B are united and laminated at the united portion of the manifold, and at a speed of 70 m / min through the lip land from the united point of the manifold. When the two-layer resin was discharged from the discharge port, the discharge resin generated ear shaking and pulsation, and the film thickness accuracy in the longitudinal direction became 7 μm or more. After discharging, it was dropped on a cooling roll in which water was circulated inside the discharge port and solidified by cooling, and wound around a coiler as a two-layer resin film having a width of about 1 m.

Example 1
Resin A and polyester resin C (ethylene terephthalate / ethylene isophthalate copolymer (15 mol% ethylene isophthalate) modified with trimellitic acid (0.3 mol%), melting point: 215 ° C., intrinsic viscosity: 0.8 wt. Temperature, 260 ° C. and shear rate: 100 sec- ¹ melt viscosity: 8000 poise, melt tension: 1.2 g) (hereinafter simply referred to as “resin C”) 27 wt% of TiO ₂ added as a coloring component The resin (260 ° C., shear rate: 100 seconds ⁻¹ melt viscosity: 4500 poise, melt tension: 0.65 g) was added to resin A at 265 ° C. and resin C (TiO ₂ at 27 wt%, respectively) using an extruder. ) Was heated to 260 ° C. and melted. Next, two manifolds are connected to the two extruders via resin passages, and two-layer film is produced on each manifold of the multi-manifold die provided with heaters for individually controlling the temperature adjacent to the manifolds. After the film is formed, the ratio of the thickness of the resin A to the thickness of the resin C (containing 27 wt% of TiO ₂ ) is 1: 3, and the discharge amount is adjusted so that the thickness of the two-layer resin film is 16 μm. Resin A and molten resin C were led. The side of the multi-manifold die through which the molten resin A passes and the resin passage and manifold through which the molten resin A pass are heated to 260 ° C. by the heater adjacent to the side, and the side of the multi-manifold die through which the molten resin A passes and the resin passage through which the molten resin C passes. Were preheated to 250 ° C. with heaters adjacent to each, and the molten resin A and the molten resin C were passed through the respective manifolds. At this time, the resin temperature immediately before the T-die and the resin viscosity at a shear rate of 100 seconds ⁻¹ are resin A: 265 ° C., about 6500 poise, and resin C + TiO ₂ : 250 ° C., about 5000 poise. In this way, after the molten resin A and the molten resin C are heated, the molten resin A and the molten resin C are combined and laminated at the united portion of the manifold, and at a speed of 100 m / min through the lip land from the united point of the manifold. When the two-layer resin was discharged from the discharge port, the discharge resin did not pulsate and no ears were generated in the width direction of the film. After discharging, it was dropped on a cooling roll in which water was circulated inside the discharge port and solidified by cooling, and wound around a coiler as a two-layer resin film having a width of about 1 m.

(Example 2)
Resin B with 27% by weight of TiO ₂ added as a coloring component (260 ° C., shear rate: 100 ps- ¹ melt viscosity: 4000 poise, melt tension: 0.4 g) and resin C, respectively, Resin B (27 wt% of TiO ₂ added) was heated at 260 ° C. and Resin C was heated at 270 ° C. to be melted. Next, two manifolds are connected to the two extruders via resin passages, and two-layer film is produced on each manifold of the multi-manifold die provided with heaters for individually controlling the temperature adjacent to the manifolds. After the film is formed, the ratio of the thickness of the resin C to the thickness of the resin B (containing 27 wt% of TiO ₂ ) is 1: 2, and the discharge amount is adjusted so that the thickness of the two-layer resin film is 16 μm. Resin C and molten resin B were led. The resin passage and manifold through which the molten resin C of the multi-manifold die passes and the resin passage and manifold through which the molten resin B pass are heated to 260 ° C. by the heater adjacent thereto, and the resin passage and manifold through which the molten resin C passes through the side of the multi-manifold die. Were preheated to 260 ° C. with heaters adjacent to each, and the molten resin C and the molten resin B were passed through the respective manifolds. At this time, the resin temperature immediately before the T-die and the resin viscosity at a shear rate of 100 seconds ⁻¹ are resin C: 268 ° C., about 6300 poise, and resin B + TiO ₂ : 260 ° C., about 4000 poise. After the molten resin C and the molten resin B are heated in this way, the molten resin C and the molten resin B are united and laminated at the united portion of the manifold, and at a speed of 100 m / min through the lip land from the united point of the manifold. When the two-layer resin was discharged from the discharge port, the discharge resin did not pulsate, and no ears were generated in the width direction of the film. After discharging, it was dropped on a cooling roll in which water was circulated inside the discharge port and solidified by cooling, and wound around a coiler as a two-layer resin film having a width of about 1 m.

[Characteristic evaluation]
The characteristics of the resin films of Examples 1-2 and Comparative Example 1 prepared as described above were evaluated as follows.
<Thickness unevenness>
For the resin films of Examples 1 and 2 and Comparative Example 1, the thickness in the full width direction (about 1 m) was continuously measured every 1 m (16 places) at the 15 m portion in the longitudinal direction of the resin film 5 minutes after the start of film formation. And the difference of the maximum thickness of all the measured values measured in the full width direction of 16 length directions and the minimum thickness was calculated | required as thickness nonuniformity.
The evaluation results are shown in Table 1.

  As shown in Table 1, the melt tension of the resin containing the coloring component of the film including at least one coloring component: Tm is 0.5 g ≦ Tm <1.0 g and the thickness is 2 minutes. 1 or more, or Tm ≧ 1.0 g and the thickness is 1/3 or more of the total thickness, or the melt tension of the film containing no coloring component is 1 g or more and the thickness is the total thickness. When a multilayer resin film having a thickness of 1/3 or more is formed, even if the film is formed at a high speed, pulsation and ear generation do not increase, and the thickness unevenness of the obtained resin film is extremely small.

  The resin-coated metal plate obtained by laminating the multilayer resin film of the present invention on a metal plate is suitable for forming into a drawn can and a drawn and ironed can. Even if the neck-in processing is performed, the resin film does not peel from the metal plate, and there are no parts with locally different processing degrees. Can be stably formed into a can without crashing.

Claims (7)

In a multilayer resin film composed of a polyester resin containing at least a coloring component and a polyester resin not containing a coloring component, the polyester resin not containing the coloring component has a melt tension Tm at an extrusion temperature of 1.0 g ≦ Tm, An unstretched multilayer resin film, wherein the thickness of the film made of a polyester resin not containing the coloring component is at least one third of the total thickness . The multilayer resin film according to claim 1 , wherein the thickness unevenness represented by the difference between the maximum thickness and the minimum thickness measured in the full width direction in the length direction is 5.0 µm or less.   A resin-coated metal plate obtained by laminating the multilayer resin film according to claim 1 or 2 on a metal plate. Two or more kinds of polyester resins including at least a polyester resin not containing a coloring component and a polyester resin containing a coloring component having a melt tension Tm of 1.0 g ≦ Tm at an extrusion temperature are obtained using a multi-manifold die. Adjacent to the extruder, manifold, and manifold through which the high melt melt resin passes, controlling the temperature of each extruder continuously provided in the manifold, each manifold, and the portion of the die adjacent to each manifold The temperature of the die part is kept higher than the temperature of the extruder, manifold, and die part adjacent to the manifold through which the low-viscosity resin passes, so that the thickness of the film made of polyester resin containing no coloring component is increased. Each thickness should be at least one third of the total thickness. A method for producing a multilayer resin film, comprising laminating a molten resin to form a multilayer film. Difference in melt viscosity between adjacent resin layers is 20 to 500 seconds ^-1 The method for producing a multilayer resin film according to claim 4, wherein the temperature is controlled so that the shear rate is 3000 poise or less. Two or more kinds of polyester resins including at least a polyester resin not containing a coloring component and a polyester resin containing a coloring component having a melt tension Tm of 1.0 g ≦ Tm at an extrusion temperature are obtained using a multi-manifold die. Adjacent to the extruder, manifold, and manifold through which the high melt melt resin passes, controlling the temperature of each extruder continuously provided in the manifold, each manifold, and the portion of the die adjacent to each manifold The temperature of the die part is kept higher than the temperature of the extruder, manifold, and die part adjacent to the manifold through which the low-viscosity resin passes, so that the thickness of the film made of polyester resin containing no coloring component is increased. Each thickness should be at least one third of the total thickness. A method for producing a resin-coated metal plate, comprising: laminating a molten resin to form a multilayer, and then extruding the molten resin onto a metal plate. Difference in melt viscosity between adjacent resin layers is 20 to 500 seconds ^-1 The method for producing a resin-coated metal sheet according to claim 6, wherein the temperature is controlled so that the shear rate is 3000 poise or less.

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