JP4441844B2 - Film roll for squeezing and ironing can coating and manufacturing method thereof - Google Patents

Description

【００６５】
【発明の効果】
本発明の絞りしごき缶被覆用フィルムは、特に２ピース缶用のラミネートフィルムとして使用した場合、製缶加工性に優れ、外観特性や耐衝撃性にも優れる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermoplastic resin film suitable for a resin-coated metal plate. In particular, the present invention relates to a thermoplastic resin film that is suitably used for surface coating of a drawn iron can. More specifically, the present invention relates to a thermoplastic resin film roll for metal plate laminating and molding excellent in can manufacturing process such as drawing and ironing.
[0002]
[Prior art]
As a method for preventing corrosion of the inner wall surface and the outer wall surface of a metal can, there is a method of laminating a thermoplastic resin film. For example, there is a polyester film for laminating a metal material for food canning (see, for example, Patent Document 1).
[0003]
This polyester film has excellent scratch resistance. For example, in a can manufacturing process in which a metal plate is formed into a cylinder and a lid is wound around the upper and lower openings of the cylinder, , "Film laminate metal plate"), and when the laminate metal plate is processed by winding or the like, the scratch on the film surface does not occur and the commercial value is not reduced. That's it.
[0004]
In addition, this film has excellent resistance at the time of squeezing, and after the can is filled with food, the amount of oligomer elution is small when heated hot water treatment such as retort treatment is performed, so it is laminated on the inner wall surface of the metal container. Excellent as a polyester film.
[0005]
By the way, for food cans, in addition to the so-called three-piece cans, which are formed by cylindrically forming a metal plate, a lid is attached to the upper and lower openings of the metal cylinder, and a metal plate is deep-drawn to form a container part. In addition, there is a so-called two-piece can formed by winding a lid on the upper surface opening of the container.
[0006]
In the case of a three-piece can, the film-laminated metal plate is simply formed into a cylindrical shape, but in the case of a two-piece can, the film-laminated metal plate is formed by squeezing and ironing.
Therefore, in order to be applicable to a two-piece can, it is necessary to have good formability of being formed following the formation of a metal plate and to have excellent adhesion to the metal plate. If the formability is insufficient or the film has insufficient adhesion to the metal plate, a so-called delaminating phenomenon occurs in which the film is peeled off from the metal plate, or the film is produced during the production of the container part of a two-piece can. It is because it is torn.
[0007]
Furthermore, in the drawing process, the film laminate metal plate is processed into a container shape while repeatedly raising and lowering the punch, so that in the case of a film laminated on the inner wall surface side of the container, the releasability from the punch, as well as the container In the case of the outer wall surface, releasability from the die is required, but this releasability depends on the melting point of the film.
In the can making process, the film is rewound from the film roll and continuously laminated to the metal plate, but when the melting point of each part of the roll film is greatly different, the releasability from the die under the same conditions is different, In order to maintain releasability, there was a problem that the conditions had to be changed.
[0008]
[Patent Document 1]
JP-A-7-227946
[Problems to be solved by the invention]
The object of the present invention has been made in view of such circumstances, and a film roll for laminating excellent in can manufacturing stability, a film laminated metal plate using the roll, a film laminated metal container, and so-called 2 The object is to provide a coating film roll applicable to a piece.
[0010]
[Means to solve the problem]
The film roll for covering a squeezed iron can according to the present invention that has achieved the above object is composed of two or more kinds of polyester resins. Samples are cut out at intervals of 100 m, and the high-temperature side melting point of 250 cut out samples is 248 ± 3. It is characterized by entering the range of ° C.
The film roll can be achieved by setting the raw material chip particle size within a range of ± 20%.
[0011]
In this case, it is preferable that the film roll has a two-layer structure of A / B.
[0012]
Furthermore, in this case, it is preferable that 5 to 15 mol% of the total acid component in the B layer is an aliphatic dicarboxylic acid having 10 or more carbon atoms.
[0013]
Furthermore, in this case, in the method for producing the film roll for covering a squeezed iron can, the average major axis (mm) of the polyester raw material chips other than the most used polyester raw material chips is used. It is preferable that the average minor diameter (mm) and the average chip length (mm) are included within a range of ± 20%.
[0014]
Furthermore, in this case, it is preferable that the film is coated on a metal plate and used as a metal plate for a squeezed iron.
[0015]
Furthermore, in this case, it is preferable to make the film-coated metal plate and use it as a squeezed iron.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The thermoplastic resin material used for the film roll for covering the drawn iron can according to the present invention is not particularly limited, but it is preferable to use a thermoplastic polyester resin from the viewpoint of heat resistance and fragrance retention. More specifically, it is preferable that the crystalline polyethylene terephthalate / polybutylene terephthalate is composed of 20 to 80/80 to 20% by weight, particularly 40 to 60/60 to 40% by weight. If the polybutylene terephthalate ratio is less than 20% by weight, the coating film is whitened unevenly by hot water treatment in the food and beverage filling process, and if it exceeds 80% by weight, the above functions are saturated, and This is because it is not economical in terms of productivity and raw material costs.
[0017]
In addition, the production method of the film is as follows. When the polyester of the most used amount is mixed with one or more other polyesters having a different composition from the polyester, the polyester other than the most used polyester is used. It is assumed that the raw material chips are included within a range of ± 20% with respect to the average major axis (mm), average minor axis (mm) and average chip length (mm) of the polyester raw material chip having the largest use amount. preferable. This is because when the chip size exceeds ± 20%, the variation in the raw material blend ratio increases in the film-forming process, and so-called raw material segregation occurs. When this phenomenon occurs, the high temperature melting point of the film varies, which is not preferable.
[0018]
In the said thermoplastic polyester, it is preferable that a melting peak exists in the range of 200 to 260 degreeC. If the melting peak is less than 200 ° C., the can-making property and heat resistance are impaired, and if it exceeds 260 ° C., the film-forming property of the film is lowered. More preferably, it is 220 degreeC-260 degreeC. This is because when the can-making speed is increased, the yield decreases near 200 ° C. A plurality of melting peaks may be present, which is achieved by controlling the resin temperature during melt extrusion and suppressing the transesterification reaction.
[0019]
The amount of lubricant in the squeezed iron can coating film of the present invention is not particularly limited, but is preferably in the range of 0.01 to 1% by weight. This is because a lubricant amount of 0.01% by weight or more is preferable so that the film can be smoothly released from punches and dies during drawing. On the other hand, even if it contains an amount exceeding 1% by weight, the effect of releasability does not change and only the cost becomes disadvantageous.
[0020]
Here, it is preferable to use inert inorganic particles, crosslinked polymer particles, or the like as the lubricant.
[0021]
Examples of the inert inorganic particles include silica, alumina, kaolin, clay, titanium oxide, calcium phosphate, calcium carbonate, lithium fluoride, barium sulfate, and carbon black.
[0022]
Examples of the crosslinked polymer particles include acrylic monomers such as acrylic acid, methacrylic acid, acrylic acid esters and methacrylic acid esters, styrene monomers such as styrene and alkyl-substituted styrene, and divinylbenzene. , Divinyl sulfone, ethylene glycol dimethacrylate, trimethylolpropane trimethyl acrylate, copolymers with crosslinkable monomers such as pentaerythritol tetramethyl acrylate; melamine resin; benzoguanamine resin; phenol resin; silicon-containing resin Etc. can be illustrated.
[0023]
The average particle diameter of the particulate lubricant is preferably 1 to 3 μm. This is because if it is less than 1 μm, the effect of improving punch releasability cannot be exhibited. On the other hand, if the thickness exceeds 3 μm, the effect of improving punch releasability is saturated. On the other hand, the lubricant is likely to fall off due to wear, or the film may break when laminated with a metal plate.
[0024]
In the squeezed and ironed can coating film of the present invention, it is preferable that the content of the low molecular weight compound is smaller from the standpoint of antifouling property of the can manufacturing line and aroma retention in the case of the inner surface of the can. For example, in the case of a polyester film, the content of oligomeric cyclic trimers including ethylene terephthalate cyclic trimer is preferably 0.7% by weight or less. This is for suppressing oligomer precipitation from a film and making a can-making line hard to be contaminated. In addition, when used on the inner surface of a can, when food products such as beverages are filled and heat treatment such as retort treatment is performed, a large amount of oligomers are eluted, and the oligomers migrate to foods, resulting in the taste of food. This is to prevent adverse effects on flavors and flavors.
[0025]
The method for reducing the oligomer cyclic trimer content to 0.7% by weight or less is not particularly limited. (1) A method of extracting and removing the cyclic trimer from the film with water or an organic solvent after film formation, {Circle around (2)} A method using a polyester having a small amount of a cyclic trimer. Of these, the method (2) is more economical and preferable.
[0026]
In the above method (2), the method for producing a polyester having a low cyclic trimer content is not limited, and the solid phase polymerization method; after polymerization, by heat treatment under reduced pressure or by extraction with water or an organic solvent, And a method for extracting and removing the polymer; and a method combining these methods. In particular, after producing a polyester having a low cyclic trimer content by solid phase polymerization, the method of extracting the obtained polyester with water to further reduce the cyclic trimer is the cyclic trimer in the film forming step. It is most preferable because the amount of body produced can be reduced.
[0027]
The polyester used in the present invention is synthesized by a conventionally known method such as a direct esterification method in which a dicarboxylic acid and a diol are directly reacted; a transesterification method in which a dimethyl ester of a dicarboxylic acid is reacted with a diol. Each of these methods may be performed by either a batch method or a continuous method. Alternatively, a solid phase polymerization method may be used to increase the molecular weight. The solid phase polymerization method is also preferable from the viewpoint of reducing the content of the cyclic trimer as described above. The polyester synthesized in this manner may be included in the film in a single type or in a mixture of two or more types.
[0028]
In addition to the above compounds, the polyester includes inorganic fine particles, incompatible thermoplastic resins, antioxidants, thermal stabilizers, ultraviolet absorbers, plasticizers, pigments, antistatic agents, lubricants, if necessary. Additives such as crystal nucleating agents may be included. There are various types of heat stabilizers such as hindered phenols and phosphorus, and it is a particularly preferred embodiment that these are contained alone or in combination in an amount of 0.01 to 10% by weight.
[0029]
Moreover, it is preferable that the said polyester exists in the range whose crystallization peak temperature at the time of temperature rising is 70-100 degreeC. This is because when the crystallization peak exceeds 100 ° C., crystal whitening is likely to occur during hot water treatment, and when it is less than 70 ° C., the film forming property is deteriorated.
[0030]
The intrinsic viscosity of the polyester when the various components are mixed is preferably in the range of 0.6 to 1.2. If the intrinsic viscosity is less than 0.6, the mechanical properties of the resulting film may be deteriorated. If the intrinsic viscosity exceeds 1.2, the effect of the mechanical properties will not change, and the productivity of the raw material polyester will also decrease. So it's not economical.
[0031]
The polyester-based film of the present invention is not limited to use by laminating another layer, in addition to being used as a single layer film having the above-described configuration. The lamination method is not particularly limited, and may be manufactured by a multilayer extrusion method, or may be manufactured by an extrusion lamination method or the like. In particular, it is a preferred embodiment to treat another layer as an adhesive layer with the metal plate.
[0032]
For example, as the dicarboxylic acid component constituting the other layer, terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, In addition, oxycarboxylic acid, long chain aliphatic dicarboxylic acid, and alicyclic dicarboxylic acid can be used.
[0033]
Examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, pentanediol, hexanediol, and neopentyl glycol, alicyclic glycols such as cyclohexane dimethanol, and aromatic glycols such as bisfenal A and bisphenol S. Can be used.
[0034]
It should be noted that a conventional method can be used as a method for synthesizing the polyester constituting this other layer, and that other additives can be contained in the polyester composition as necessary within the range satisfying the above requirements, the polyester composition The intrinsic viscosity is the same as described above.
[0035]
The film of the present invention may be a biaxially stretched film or an unstretched film. Here, the biaxial stretching method may be any of sequential biaxial stretching, simultaneous biaxial stretching, or a combination thereof. In the case of successive biaxial stretching, generally, a method of stretching in the longitudinal direction and then stretching in the transverse direction is adopted, but a method of stretching in the reverse order may be employed. In addition, it is preferable to fix the orientation of the polyester by heat treatment after biaxial stretching, but after biaxial stretching, re-stretching may be performed in the longitudinal direction and / or the width direction before the heat treatment step. Furthermore, the corona discharge treatment or the predetermined coating treatment is not limited at all on one side or both sides of the film before or after the stretching step.
[0036]
The method for laminating the film of the present invention with a metal plate is not particularly limited, and for example, a dry laminating method, a thermal laminating method, or the like can be employed. Specifically, the metal plate is heated to a temperature equal to or higher than the melting point of the laminate surface of the film, and the film is brought into contact with the surface of the metal plate. Subsequently, it laminates by making it quench-harden at 10-40 degreeC. After passing through the nip roll, if necessary, it may be remelted above the melting point of the film.
[0037]
Moreover, the lamination of the film may be performed only on one side of the metal plate or on both sides. In the case of double-sided lamination, it may be laminated at the same time or sequentially.
[0038]
In the present invention, when the film to be used is a biaxially stretched film and the film laminated metal plate is applied to a two-piece can, heating is performed at a temperature equal to or higher than the melting point of the polyester constituting the film in order to remove the molecular orientation of the polyester after lamination. It is preferable to perform a remelt (remelting) treatment. Immediately after remelting, it is preferable to perform rapid cooling by using cooling water or the like. This is because, after remelting, crystallization occurs in the process of cooling and solidifying the polyester in the case of decooling, for example, allowing it to cool to the atmosphere, and when the polyester is subjected to drawing and ironing in the subsequent can manufacturing process, the polyester is This is because it cannot follow the deformation, and as a result, it cannot be made.
[0039]
The degree of molecular orientation by X-ray observation after the remelt treatment is 10% or less, which can be said to be substantially non-oriented. In other words, a biaxially stretched film in which the polyester is in an oriented state is difficult to be plastically deformed or stretched, making it difficult to perform a drawing process for forming the container portion. The delaminating phenomenon of peeling off occurs, tears, or scrapes. On the other hand, if it is substantially non-oriented, it can follow the deformation of the laminated metal plate, so that it can be molded with plastic deformation of the metal like a two-piece can without delaminating or tearing. be able to.
[0040]
The film laminated metal container of the present invention is a metal container formed by appropriately forming the biaxially stretched or non-oriented type film laminated metal plate of the present invention, and the shape of the container, the method of forming the metal container, There is no particular limitation. Specifically, a so-called three-piece can in which the top cover is wound and filled with the contents, as well as a two-piece can that is formed by drawing a metal plate to form a container portion can be used.
[0041]
In the metal container of the present invention, the polyester film of the present invention may be molded so as to be on the inner wall surface side of the metal container, or may be molded so as to be on the outer wall surface side.
[0042]
In addition, when carrying out drawing ironing, you may apply | coat a lubricant to the film surface which a punch contacts as needed.
[0043]
The film-laminated metal container of the present invention may be subjected to printing or the like as necessary, and may be subjected to a re-melt process after a can making process or a printing process.
[0044]
In the present invention, a surface-treated steel plate such as tin-free steel, an aluminum plate, an aluminum alloy plate, or a surface-treated aluminum plate or aluminum alloy plate can be used as the metal plate to be used.
[0045]
In the present invention, the thickness of the resin film on the metal plate is not particularly limited, but 10 to 50 μm is a preferred embodiment from the viewpoint of coating effect (rust prevention), impact resistance, and economical efficiency. If the thickness of the resin film is less than 10 μm, impact resistance cannot be obtained, and if it exceeds 50 μm, the quality is excessive, which is economically undesirable.
[0046]
【Example】
Hereinafter, the present invention will be described based on examples.
[0047]
Various evaluation methods in the present invention are shown below.
[0048]
(1) Thermal characteristics of polyester After heating and melting a polyester composition at 300 ° C. for 5 minutes, 10 mg of a sample obtained by quenching with liquid nitrogen was used, and a differential scanning calorimeter (DSC) was used in a nitrogen stream. When the exothermic / endothermic curve (DSC curve) is measured at a heating rate of ° C / min, the peak temperature of the endothermic peak accompanying melting is the melting point Tm (° C), and the peak temperature during temperature rising crystallization is TC (° C) It was.
[0049]
(2) Removable remelt aluminum plate of can inner surface resin and processing punch was made at n = 10, and the degree of buckling occurring at the upper part of the molded can was visually observed. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Buckling has not occurred at the can opening Δ: Buckling has occurred at about 1/3 of the circumference of the can opening ×: Buckling has occurred at 1/3 or more of the circumference of the can opening
(3) A can was obtained by making an impact-resistant remelt aluminum plate, and a 7 cm square sample was cut out from the center of the body wall of the can that was heated at 280 ° C. for 40 seconds and then quenched in water. A weight (600 g) having a tip diameter of 10 mm is dropped from a height of 10 cm to the surface where the sample is not evaluated, and an impact is applied. Next, the impacted part and the surface to be evaluated were immersed in 7% dilute hydrochloric acid, and the corrosion state of the part was visually observed after 3 days. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: No corrosion occurred ×: Corrosion occurred
(4) About whitening after warm water treatment A can obtained by making a remelt aluminum plate can be further heated at 270 ° C. for 40 seconds and then rapidly quenched in water. After immersing this sample in warm water at 80 ° C. for 10 minutes, the can obtained by quenching in water was visually observed. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Whitening is inconspicuous Δ: Clearly whitened, but the color of the aluminum alloy plate is visible ×: The color of the aluminum alloy plate is not visible due to whitening [0052]
(Example-1)
[Production of polyester film]
Base resin in which polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) are blended at a weight ratio of 40/60% by weight, agglomerated silica particles (average particle size 1.5 μm) 0.3% by weight, and a heat stabilizer A polyester composition containing 3% by weight, having an intrinsic viscosity of 0.7 and an ethylene terephthalate cyclic trimer of 0.4% by weight was used. The raw material chip size was within the range of ± 10% with respect to the average major axis (mm), average minor axis (mm), and average chip length (mm) of the most frequently used raw material chips.
[0053]
The composition was melted with an extruder, and the melt was extruded and rapidly cooled to obtain an unstretched sheet. This unstretched sheet was stretched 3.3 times in the machine direction at a preheating temperature of 65 ° C. and a stretching temperature of 100 ° C., and further stretched by 4.0 times in the transverse direction at a preheating temperature of 65 ° C. and a stretching temperature of 90 ° C. Then, heat treatment was performed at 160 ° C. for 8 seconds, and 4% relaxation treatment was performed at 160 ° C. to obtain a biaxially stretched film having a thickness of 20 μm.
[0054]
[Production of film-laminated metal plate]
The polyester film is laminated on both sides of a preheated aluminum plate while passing between nip rolls and pressed, and then heat-treated. Immediately after that, the film is rapidly cooled in a 10-40 ° C. water bath. A laminated aluminum plate was obtained. At the time of laminating, the initial adhesiveness was good, and there were no problems such as fluctuations in tension and winding around the nip roll, and the film of this example had good laminating properties. Thereafter, the film-laminated aluminum plate was heated and remelted at 275 ° C. and then quenched in water to prepare a remelt aluminum plate.
[0055]
[Production of film-laminated metal container]
The remelt aluminum plate produced above was drawn and ironed so that the thickness reduction rate was 30% to form a film laminated metal container. At the time of molding, there was no peeling or tearing of the film, and the releasability from the mold was good, which was very good. Thereafter, the film-laminated metal container was heated and re-melted as described above, and then rapidly cooled in water. Even at this time, the film portion was not defective due to whitening and was good. Furthermore, after printing the outer surface, a varnish was applied, and after heat-curing, it was quenched with cold air.
[0056]
The container formed in this way was filled with a beverage, and the lid with the tabs was wound and joined, followed by hot water treatment at 100 ° C. for 30 minutes to produce a two-piece beverage can. The resulting beverage can was free of whitening and whitening spots due to hot water treatment, and was free from oligomer elution and precipitation from the film. Further, there was no decrease in adhesion over time. (See Table-1)
[0057]
(Example-2)
The same polyester composition A as Example-1 is used as the polyester A layer, and the raw material chip size is based on the average major axis (mm), average minor axis (mm), and average chip length (mm) of the most used raw material chip. Each within the range of ± 10% was used.
As the polyester B layer, the dicarboxylic acid component is composed of 90 mol% of terephthalic acid units, 10 mol% of dimer acid units having 36 carbon atoms, and 60% by weight of dimer acid copolymerized PET having a diol component of 100 mol% of ethylene glycol units. Polyester composition B mixed with 40% by weight of PET was used. The subsequent film forming process, can manufacturing process, and evaluation were performed in the same manner as in Example 1, and the polyester B layer side was set to the metal plate side.
[0058]
The can thus produced has very good can-making processability as in Example-1 and there is no whitening or whitening spots caused by hot water treatment, and no elution of oligomers into beverages or precipitation from films. It was. Furthermore, the adhesiveness did not deteriorate with the lapse of time, and the film was not torn against the external impact expected at the distribution stage or during low-temperature storage. Various measurement results are shown in Table 1. [0059]
(Comparative Example-1)
Other compositions, film-forming processes, can-making processes, and evaluations were performed in the same manner as in Example 1 except that the raw material chip sizes were ± 30%.
[0060]
The can thus produced was inferior in can-making processability and lower in yield than Example-1. Moreover, the whitening by the warm water process and the whitening spot also fell with respect to Example-1, and the variation became large.
[0061]
(Comparative Example-2)
The composition, film-forming process, can-making process, and evaluation were performed in the same manner as in Example 2 except that each of the raw material chip sizes was ± 30%.
[0062]
The can thus produced was inferior in can-making processability as in Comparative Example-1, and the yield was poor. Moreover, the whitening by the warm water process and the whitening spot also decreased with respect to Example-2, and the variation became large. There was no tearing of the film in response to external impacts expected at the distribution stage or during low-temperature storage.
[0063]
The results are shown in Table 1.
[0064]
[Table 1]

[0065]
【The invention's effect】
The drawn and ironed can coating film of the present invention is excellent in can-making processability and in appearance characteristics and impact resistance, particularly when used as a laminate film for a two-piece can.

Claims (6)

  A film roll for squeezing and squeezing cans, wherein the film comprises a mixture of polyethylene terephthalate / polybutylene terephthalate in an amount of 20-80 / 80-20% by weight and a hint phenolic or phosphorus thermal stabilizer, and has a melting peak. A plurality of samples 250 exist in the range of 220 ° C. to 260 ° C., the crystallization peak temperature at the time of temperature increase is in the range of 70 to 100 ° C., and the film is cut out at 100 m intervals and cut out. A film roll for covering a squeezed iron can, characterized in that the high-temperature melting point of the point falls within a range of 248 ± 3 ° C.   2. The film roll for covering a drawn iron can according to claim 1, wherein another layer is laminated on the film.   The film roll according to claim 2, wherein 5 to 15 mol% of the total acid component in the further layer is an aliphatic dicarboxylic acid having 10 or more carbon atoms. . A method for producing a film roll for covering a squeezed iron can according to claim 1, wherein the film roll is used in a step of performing melt extrusion by mixing polyethylene terephthalate, polybutylene terephthalate and a hint phenolic / phosphorus heat stabilizer. The raw material chips of polyester other than the polyester having the largest amount are within ± 20% of the average major axis (mm), average minor axis (mm) and average chip length (mm) of the polyester raw material chip having the largest amount of use. A method for producing a film roll for covering a squeezed iron can, characterized by being included in a range .   A metal plate for a drawn and ironed can, wherein the film according to claim 1 is coated on a metal plate.   6. A squeezed and ironed can made from the film-coated metal plate according to claim 5.