JP4122873B2 - Container molding film - Google Patents

Description

表中の略号は次の通り。
【００３７】
ＰＥＴ：ポリエチレンテレフタレート
ＰＢＴ：ポリブチレンテレフタレート
変性ＰＢＴ（ポリアルキレングリコールブロック共重合ポリブチレンテレフタレート）：東レ・デュポン（株）製エラストマー“ハイトレル”（登録商標）７２７７
ＰＥＴ／Ｉ^１８：イソフタル酸１８モル％共重合ポリエチレンテレフタレート
ＰＥＴ−Ｇ：イーストマンケミカル社製“イースター”（登録商標）６７６３
表１の評価結果から、実施例では本発明のポリマーＡとポリマーＢを交互に配置してなる積層フィルムにおいて、少なくとも５層以上の積層フィルムを満足していることから、優れた特性を有していた。また、実施例３では積層数が９層と少なく、１層当りの平均厚みも厚いため、実用上は問題ないものの特性が若干低下した。
【００３８】
一方、本発明の要件を満足していない比較例では、耐衝撃性が大幅に低下し、実際に商品として使用できないレベルであった。
【００３９】
【発明の効果】
フィルム単独でもしくは金属板などの基材にラミネートした後、容器に成形する際に割れが発生することなく容易に成形可能であり、さらに成形後に落下などの衝撃が加わった際にもクラックが入ったりせず、耐衝撃性に優れた容器成形用フィルムを提供できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a container forming film. Specifically, the film according to the present invention alone or bonded to a base material such as a metal plate, plastic or paper can be easily formed into a container, and further, a container formed with excellent taste characteristics and impact resistance. It is related with the film.
[0002]
[Prior art]
Examples of the thermoplastic resin used for the packaging container include polystyrene, polycarbonate, polyethylene, polypropylene, nylon, polyethylene terephthalate, and polyvinyl chloride. When these thermoplastic resins are used alone, the container is usually obtained by pouring the resin into a mold to obtain a molded product or molding an unstretched sheet. However, in molding using an unstretched sheet, it is difficult to impart impact resistance, and in the case of an amorphous resin, heat resistance is poor, and conversely, in the case of a crystalline resin, whitening occurs during molding. It was.
[0003]
In addition, when the resin is formed into a film and bonded to a substrate such as a metal plate and then molded into a container, the film must have the following characteristics.
[0004]
(1) Excellent laminating properties on metal plates
(2) Excellent adhesion to the metal plate,
(3) Excellent moldability and no defects such as pinholes after molding,
(4) Due to the impact on the metal can, the polyester film does not peel off, cracks or pinholes occur,
(5) The scent component of the contents of the can is adsorbed to the film, and the flavor of the contents is not impaired by the eluate from the film (hereinafter referred to as taste characteristics).
[0005]
Many proposals have been made to solve these requirements. For example, JP-A-9-194604 discloses a film blended with a polyester having a specific intrinsic viscosity, and JP-A-2000-313755 discloses a film having a specific temperature rising crystallization temperature. Has been. Furthermore, Japanese Patent No. 2851468, Japanese Patent No. 2908160, Japanese Patent No. 2908191, Japanese Patent No. 2908192, Japanese Patent No. 2908195, Japanese Patent No. 2908196, Japanese Patent No. 3016936, Japanese Patent No. 3016943 Japanese Patent No. 3048725 discloses a blend film of a copolymerized polyester having a melting point of 245 ° C. or less and polybutylene terephthalate, or a laminated film obtained by laminating the copolymerized polyester on the film. However, these proposals do not necessarily satisfy the wide variety of required characteristics as described above, and it is not possible to achieve both taste characteristics and impact resistance in applications that require particularly excellent moldability. It was difficult.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to eliminate the above-mentioned problems of the prior art, and to provide a container molding film suitable for a packaging container excellent in molding processability, taste characteristics and impact resistance.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the container-forming film of the present invention mainly has the following configuration. That is,
Polymer A and polymer B are alternately laminated and the number of laminated layers is at least 5 or more. The polymer A is polyethylene terephthalate, and the polymer B is polybutylene terephthalate or a polybutylene terephthalate and a polyalkylene glycol block. A container-forming film comprising polymerized polybutylene terephthalate .
[0008]
In the present invention, it is necessary that the polymer A is polyethylene terephthalate and the polymer B is made of polybutylene terephthalate or polybutylene terephthalate and polyalkylene glycol block copolymer polybutylene terephthalate .
[0009]
Heat resistance, impact resistance, moldability, etc. This is because the most well-balanced good.
[0010]
The polymer A and the polymer B are preferably compatible from the viewpoint of affinity at the interlayer interface. For example, it is a very preferable embodiment that polyethylene terephthalate and polybutylene terephthalate, which are polyesters, are polymer A and polymer B. When the polymers A and B are incompatible, they may be separated at the lamination interface, resulting in an extremely thin single layer film.
[0011]
Furthermore, it is preferable that the difference between the glass transition points of the polymer A and the polymer B used in the container molding film of the present invention is 20 to 200 ° C, more preferably 30 to 150 ° C. If the difference in the glass transition point is within such a preferable range, the interlayer difference in the thermal mobility of the amorphous region in the film is sufficient and the impact resistance is improved, while the interlayer difference in the mobility of the amorphous region is large. It is not too difficult to form a film.
[0012]
The container molding film of the present invention is a laminated film in which polymer A and polymer B are alternately arranged from the viewpoint of impact resistance, and needs to be a laminated film of 5 or more layers. If it is 4 layers or less, the impact resistance is poor. In the same thickness film, increasing the number of layers means reducing the thickness per layer, and if the thickness per layer is reduced, the free volume for the polymer can be reduced, and It is considered that impact resistance is improved because energy absorption occurs between the interfaces by increasing the number of interfaces. From the viewpoint of impact resistance, the number of laminated layers is more preferably 100 layers or more.
[0013]
The average thickness per layer is preferably 1 nm to 1 μm from the viewpoint of improving impact resistance, and more preferably 1 to 500 nm. If it is 1-50 nm, since impact resistance improves remarkably, it is especially preferable.
[0014]
When the container forming film of the present invention is used alone, the film thickness is preferably 1000 to 50 μm, more preferably 250 to 100 μm. On the other hand, when it is used for an application in which it is bonded to a base material such as a metal plate, it is preferably 38 to 5 μm, more preferably 25 to 10 μm.
[0015]
The film of the present invention preferably has a melting point of 205 to 270 ° C. from the viewpoint of heat resistance. When it is within such a preferable range, it is not necessary to provide a use restriction when used as a container. More preferably, the melting point of the film is 220-270 ° C.
[0016]
The film of the present invention contains 0.01 to 3 wt% of known internal particles, inorganic particles and / or organic particles having an average particle diameter of 0.01 to 10 [mu] m in order to improve the handleability and processability. Is preferred. The particle concentration is more preferably 0.05 to 3% by weight, more preferably 0.1 to 3% by weight, and still more preferably 0.3 to 3% by weight. As a method for depositing the internal particles, known techniques can be used. For example, JP-A 48-61556, JP-A 51-12860, JP-A 53-41355, and JP-A Techniques described in, for example, 54-90397 can be employed. Further, other particles described in Japanese Patent Publication No. 55-20496 and Japanese Patent Publication No. 59-204617 can be used in combination. If the average particle diameter is within the above preferred range, no defects will occur in the film.
[0017]
Examples of such inorganic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, aluminum oxide, mica, kaolin, and clay, and organic particles include styrene, silicone, and acrylic. Particles containing as constituents acids, methacrylic acids, polyesters, divinyl compounds and the like can be used. Among them, it is preferable to use inorganic particles such as wet and dry silica and alumina, and particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components. Furthermore, these internal particles, inorganic particles, and organic particles may be used in combination of two or more.
[0018]
The container-forming film in the present invention is required to be a laminated film of 5 layers or more, but since the production method needs to alternately arrange the polymer A and the polymer B, two or more melt extruders are used. It is possible to preferably use a method of supplying a polymer to each of the extruders, performing melt extrusion, and laminating using a feed block, a static mixer, a multi-manifold or the like installed on the top of the T die. As a particularly preferred method, there is a method in which polymer A and polymer B are laminated in a feed block in three or more layers, and then the number of laminations is increased using a static mixer, and discharged from a T die into a sheet to obtain an unstretched sheet. Can be mentioned.
[0019]
Next, regarding the method for producing a container-forming film of the present invention, a preferred production method for the case where polyethylene terephthalate is used for polymer A and polybutylene terephthalate is used for polymer B will be specifically described.
[0020]
As a method for preparing polyethylene terephthalate used as the polymer A, for example, the following may be performed. To a mixture of 100% by weight of dimethyl terephthalate and 60% by weight of ethylene glycol, 0.09% by weight of magnesium acetate and 0.03% by weight of antimony trioxide are added to the amount of dimethyl terephthalate, and the temperature is raised by a conventional method. Then, a transesterification reaction is performed. Next, after adding 0.020% by weight of 85% aqueous solution of phosphoric acid to the amount of dimethyl terephthalate, the transesterification reaction product is transferred to the polycondensation reaction layer. Further, the reaction system is gradually depressurized while being heated and heated, and a polycondensation reaction is performed at 290 ° C. under a reduced pressure of 1 mmHg by a conventional method to obtain a polyethylene terephthalate resin having a desired intrinsic viscosity.
[0021]
Moreover, what is necessary is just to perform as a manufacturing method of the polybutylene terephthalate used as the polymer B as follows, for example. A mixture of 100% by weight of terephthalic acid and 110% by weight of 1,4-butanediol was heated to 140 ° C. in a nitrogen atmosphere to obtain a homogeneous solution, and then tetra-n-butyl orthotitanate was added to terephthalic acid in an amount of 0.1%. 054% by weight and 0.054% by weight of monohydroxybutyltin oxide are added, and an esterification reaction is carried out by a conventional method. Next, 0.066 wt% of tetra-n-butyl orthotitanate is added and a polycondensation reaction is performed under reduced pressure to obtain a polybutylene terephthalate resin having a desired intrinsic viscosity.
[0022]
Both polyethylene terephthalate and polybutylene terephthalate may be subjected to solid phase polymerization as necessary.
[0023]
The polyester obtained as described above is dried in a nitrogen atmosphere, a vacuum atmosphere, etc., for example, at 150 ° C. for 5 hours, and then supplied to an individual extruder and melted. Subsequently, the foreign matter is removed and the amount of extrusion is leveled through a filter and a gear pump in different paths, and the feed blocks are stacked. Next, after increasing the number of stacked layers to a desired number using a static mixer, the sheet is discharged in a sheet form from a T die onto a cooling drum. In that case, for example, a method of applying static electricity using a wire-like electrode or a tape-like electrode, a casting method in which a water film is provided between a casting drum and an extruded polymer sheet, and the casting drum temperature is changed from the glass transition point of polyester to ( The sheet-like polymer is brought into close contact with the casting drum and cooled and solidified by a method of adhering the extruded polymer at a glass transition point of -20 ° C. or a combination of these methods to obtain an unstretched film. Among these casting methods, when using polyester, a method of applying an electrostatic force is preferably used from the viewpoint of productivity flatness. Moreover, when using polyolefin, the air knife method pressed against a cooling drum with compressed air is preferable. Using such an unstretched film, the film is stretched in the longitudinal direction and then stretched in the width direction, or the stretched film is stretched in the width direction and then stretched in the longitudinal direction, and the longitudinal direction and the width direction of the film are stretched almost simultaneously. Stretching is performed by the simultaneous biaxial stretching method.
[0024]
In such a stretching method, the stretching ratio employed is preferably 1.6 to 4.2 times in each direction, and more preferably 1.7 to 4.0 times. The stretching speed is desirably 1,000 to 200,000% / min. In the case of polyester, the stretching temperature is set to an arbitrary temperature as long as it is in the temperature range of glass transition point to (glass transition point + 100 ° C.). However, the stretching temperature is preferably 80 to 140 ° C., particularly preferably 90 to 125 ° C. in the longitudinal direction and 80 to 130 ° C. in the width direction. Further, the stretching may be performed a plurality of times in each direction.
[0025]
Further, the film is heat-treated after biaxial stretching, and this heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. The heat treatment temperature can be any temperature between 120 ° C. and the melting point of the polyester, but it is preferably a heat treatment temperature of 120 to 230 ° C. from the viewpoint of moldability and impact resistance. At such a preferable temperature, the impact resistance is good, while the moldability is not deteriorated. From the point of impact resistance after molding, it is more preferably 150 to 220 ° C, and even more preferably 170 to 210 ° C. Moreover, although heat processing time can be made arbitrary in the range which does not deteriorate another characteristic, Usually, it is preferable to carry out for 1 to 60 seconds. Further, the heat treatment may be performed by relaxing the film in the longitudinal direction and / or the width direction.
[0026]
The film for forming a container of the present invention not only has excellent moldability and taste characteristics, but also has a very excellent impact resistance. It can also be preferably used for a metal container manufactured by drawing or ironing after being bonded to a metal plate such as a steel plate or an aluminum plate after being bonded to plastic.
[0027]
【Example】
Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.
(1) Melting point and glass transition point About 10 mg of polymer or film is precisely weighed and measured with a differential scanning calorimeter (DSC2 type, manufactured by Perkin Elmer Co., Ltd.) at a heating rate of 20 ° C./min. From the point, the melting point was determined from the peak position of the endothermic peak accompanying melting of the glass transition point. The measurement was performed at a low temperature by using liquid nitrogen as necessary.
(2) Number of laminated layers and average layer thickness The number of laminated layers was determined by a feed block and a static mixer installed on the upper part of the T die as described in Examples and Comparative Examples described below. Whether or not the number of laminated layers was actually set was confirmed by observing a cross section of an arbitrary place of the film with a transmission electron microscope. At that time, the average layer thickness per layer was determined.
(3) Formability A film was bonded to an aluminum plate (thickness 0.2 mm) heated to 220 ° C. at 30 m / min, and then rapidly cooled in a 40 ° C. water bath. Thereafter, the film-laminated steel sheet was heat-treated at the melting point of the film + 15 ° C. and then rapidly cooled again in a water bath. The laminated steel sheet thus obtained was molded with a drawing machine (molding ratio (maximum thickness / minimum thickness) = 2.0)) to obtain a can. 1% sodium chloride aqueous solution was put into the obtained can and left for 1 day, then a voltage of 6 V was applied to the electrode and metal can in the sodium chloride aqueous solution, the current value after 3 seconds was read, and the average after 10 cans measurement The value was evaluated according to the following criteria.
[0028]
Class A: less than 0.0001 mA Class B: 0.0001 to 0.001 mA
Class C: 0.001 to 0.01 mA
Class D: 0.01 mA or more (4) Impact resistance The above aluminum can was filled with water, cooled to 5 ° C., and dropped from a height of 1.3 m onto a vinyl chloride tile floor. Thereafter, a voltage of 6 V was applied to the electrode in water and the aluminum can, the current value after 3 seconds was read, 10 cans were measured, and the average value was evaluated according to the following criteria.
[0029]
Class A: less than 0.001 mA Class B: 0.001 to 0.005 mA
Class C: 0.005 to 0.01 mA
Class D: 0.01 mA or more (5) Pinhole resistance According to ASTM F-392, a film cut into a size of 297 × 210 mm was subjected to 500 repeated bending tests at 0 ° C. using a gel bot tester. Carried out. The test was performed 10 times, the number of pinholes was measured, and the average value was calculated.
(Example 1)
Polyethylene terephthalate was used as polymer A, and polybutylene terephthalate was used as polymer B. The preparation method of each polymer is as follows.
[Method for preparing polymer A]
To 100% by weight of dimethyl terephthalate as an acid component, 67% by weight of ethylene glycol as a glycol component was added, and 0.04% by weight of manganese acetate was added as a transesterification catalyst, and a transesterification reaction was performed by a conventional method. Next, 0.025% by weight of 85% phosphoric acid aqueous solution and 0.02% by weight of germanium dioxide were added, and the temperature was gradually raised and depressurized. Finally, the temperature was raised to 290 ° C. and 0.5 mmHg, and the polycondensation reaction was performed. And polyethylene terephthalate having an intrinsic viscosity of 0.68 and a melting point of 253 ° C. was obtained.
[Method for preparing polymer B]
A mixture of 100% by weight of terephthalic acid and 110% by weight of 1,4-butanediol was heated to 140 ° C. in a nitrogen atmosphere to obtain a homogeneous solution, and then tetra-n-butyl orthotitanate was added to terephthalic acid in an amount of 0.1%. 054% by weight and 0.054% by weight of monohydroxybutyltin oxide were added, and an esterification reaction was carried out by a conventional method. Subsequently, 0.066 wt% of tetra-n-butyl orthotitanate was added and a polycondensation reaction was performed under reduced pressure to obtain a polybutylene terephthalate resin having an intrinsic viscosity of 0.88. Thereafter, crystallization was performed at 140 ° C. in a nitrogen atmosphere, followed by solid phase polymerization at 200 ° C. for 6 hours in a nitrogen atmosphere to obtain a polybutylene terephthalate resin having an intrinsic viscosity of 1.2.
[0030]
Polymers A and B obtained as described above were separately vacuum-dried at 180 ° C. for 3 hours, then supplied to separate 45 mm single screw extruders (L / D = 28), melt extruded at 280 ° C. Three layers of A / B / A are laminated in the feed block installed in the A, B / A / B /.../ A / B / A 129 using a square mixer which is a kind of static mixer. The layer was laminated. This was extruded while electrostatically applied to a cooling drum cooled to 20 ° C. from a T die to obtain an unstretched sheet.
[0031]
Next, the film is heated to 85 ° C. and stretched 3.5 times in the longitudinal direction of the film, once cooled, introduced into a tenter type stretching machine, stretched in the width direction 3.5 times at 100 ° C., and 5% in the width direction as it is. Heat treatment was performed at 190 ° C. while relaxing, and after gradually cooling to room temperature, a wound film was obtained on a roll. The thickness of the obtained film was 25 μm, the average thickness per layer of the polymer A layer was 250 nm, and the average thickness per layer of the polymer B layer was 130 nm.
(Example 2)
As polymer A, PET resin “J120” manufactured by Mitsui Chemicals, Inc. was used. Further, as polymer B, 5% by weight of PBT resin “Toraycon” (registered trademark) 1200S 95% by weight manufactured by Toray Industries, Inc. was mixed with 5% by weight of elastomer “Hytrel” (registered trademark) 7277 manufactured by Toray DuPont.
[0032]
25 μm biaxially oriented film in the same manner as in Example 1 except that the number of layers in the feed block was 9 layers with A / B / A /./ B / A and then 513 layers were formed with a square mixer. Got.
(Example 3)
Except not using a square mixer, it formed into a film like Example 2 and obtained the 9-layer lamination biaxially oriented film.
( Comparative Example 4 )
“Easter” (registered trademark) 6763 manufactured by Eastman Chemical Co., which is isophthalic acid copolymerized polyethylene terephthalate as polymer A and cyclohexanedimethanol copolymerized polyethylene terephthalate as polymer B was used. The preparation method of the polymer A is as follows.
[Method for preparing polymer A]
To a mixture of 82% by weight of dimethyl terephthalate as an acid component and 18% by weight of dimethyl isophthalate, 67% by weight of ethylene glycol is added as a glycol component, and 0.04% by weight of manganese acetate is added as a transesterification catalyst. A transesterification reaction was performed. Next, 0.025% by weight of 85% phosphoric acid aqueous solution and 0.03% by weight of antimony trioxide were added, and the temperature was gradually raised and depressurized. Finally, the temperature was raised to 290 ° C. and 0.5 mmHg, and the polycondensation was performed. Reaction was performed to obtain 18 mol% copolymerized polyethylene terephthalate having an intrinsic viscosity of 0.70 and a melting point of 220 ° C.
[0033]
Polymer A (isophthalic acid copolymerized polyethylene terephthalate) prepared as described above was vacuum dried at 170 ° C. for 3.5 hours, polymer B was dried at 80 ° C. for 5 hours, and then a separate 45 mm single screw extruder (L / D). = 28), melt extruded at 280 ° C., three layers of A / B / A are laminated in a feed block installed on the top of the T-die, and then A / B / It was set as the lamination | stacking state of 65 layers of A / B /.../ A / B / A. This was extruded while electrostatically applied to a cooling drum cooled to 20 ° C. from a T die to obtain an unstretched sheet.
[0034]
Next, the film was heated to 80 ° C. and stretched 3.4 times in the longitudinal direction of the film, and after cooling, it was introduced into a tenter type stretching machine and stretched in the width direction 3.6 times at 100 ° C. Heat treatment was performed at 200 ° C. while relaxing, and the film was gradually cooled to room temperature and wound on a roll to obtain a biaxially oriented film having a thickness of 25 μm.
(Comparative Example 1)
A single layer sheet was extruded from a T-die using only Mitsui Chemicals Co., Ltd. PET resin “J120”, and a film was formed under the same stretching conditions as in Example 1.
(Comparative Example 2)
Except not using a square mixer, it formed into a film like Example 2 and the three-layer lamination biaxially oriented film was obtained.
(Comparative Example 3)
Polymer A and polymer B used in Example 1 were blended so as to have a weight ratio of 7: 3, supplied to a 45 mm single screw extruder (L / D = 28), extruded from a T die, and cooled to 20 ° C. An extruded single layer unstretched sheet was obtained while applying electrostatic force to the cooled drum.
[0035]
Next, the film is heated to 80 ° C. and stretched by 3.2 times in the longitudinal direction of the film, once cooled, introduced into a tenter type stretching machine, stretched in the width direction by 3.0 times at 100 ° C., and 3% in the width direction as it is. Heat treatment was performed at 210 ° C. while relaxing, and the film was gradually cooled to room temperature and wound on a roll to obtain a biaxially oriented film having a thickness of 20 μm.
[0036]
[Table 1]

The abbreviations in the table are as follows.
[0037]
PET: Polyethylene terephthalate PBT: Polybutylene terephthalate modified PBT (Polyalkylene glycol block copolymerized polybutylene terephthalate) : Elastomer “Hytrel” (registered trademark) 7277 manufactured by Toray DuPont Co., Ltd.
PET / I ¹⁸ : Isophthalic acid 18 mol% copolymerized polyethylene terephthalate PET-G: “Easter” (registered trademark) 6763 manufactured by Eastman Chemical Co.
From the evaluation results of Table 1, in the examples, the laminated film formed by alternately arranging the polymer A and the polymer B of the present invention has at least five laminated films, and thus has excellent characteristics. It was. In Example 3, the number of laminated layers was as small as 9 layers, and the average thickness per layer was thick.
[0038]
On the other hand, in the comparative example that does not satisfy the requirements of the present invention, the impact resistance was greatly reduced, and it was at a level where it could not be actually used as a product.
[0039]
【The invention's effect】
It can be easily formed without cracking when it is molded into a container after it has been laminated on a base material such as a film or a metal plate, and cracks also occur when impacts such as dropping are applied after molding. Therefore, it is possible to provide a container molding film having excellent impact resistance.

Claims (4)

Polymer A and polymer B are alternately laminated and the number of laminated layers is at least 5 or more. The polymer A is polyethylene terephthalate, and the polymer B is polybutylene terephthalate or a polybutylene terephthalate and a polyalkylene glycol block. A container-forming film comprising polymerized polybutylene terephthalate . The container-forming film according to claim 1, wherein the average thickness per layer is 1 nm to 1 μm. The film for container molding according to claim 1 or 2, wherein the number of layers is 100 or more. The container-forming film according to claim 1, wherein the polyethylene terephthalate has a melting point of 252 ° C. or higher.