JP2006305883A - Metal vapor deposited biaxially oriented film for twist packaging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal vapor deposited biaxially oriented polyethylene terephthalate resin film which maintains practical characteristics without losing the excellent characteristics of a biaxially oriented polyester resin film, has good twisting properties and bending properties, and is excellent in gas-barrier properties and beauty and useful as a twist packaging film good in practicality, economical efficiency, and productivity. <P>SOLUTION: The metal vapor deposited biaxially oriented polyethylene terephthalate resin film for twist packaging is made of a resin containing polyethylene terephthalate as a substantially main component. The refractive index Nx in the longitudinal direction of the film is larger than the refractive index Ny in the width direction, and the density of the film is 1.34-1.375 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a biaxially stretched polyethylene terephthalate resin film for metal vapor deposition twist packaging. More specifically, while maintaining the excellent properties of the biaxially stretched polyethylene terephthalate resin film, it has good twisting and folding properties, and also has high commercial value barrier properties and aesthetics for twist packaging applications. The present invention relates to a film for metallized twist packaging excellent in practicality, economy, and productivity.

  Conventionally, cellophane is known as a film excellent in twistability and bendability. Metal-deposited cellophane is used for various packaging materials such as twisted packaging and adhesive tapes due to its excellent transparency, easy cutting properties, twisting properties and the like. However, since cellophane has hygroscopicity, its characteristics fluctuate depending on the season, and it is difficult to supply it while maintaining a constant quality. Further, a packaging material using polyethylene terephthalate as a base film has been suitably used in various applications due to excellent properties such as toughness, heat resistance, water resistance, and transparency of the stretched polyethylene terephthalate film. On the other hand, there are drawbacks in terms of cutability, tearability in the packaging bag, and difficulty in tearing with the adhesive tape. Further, in applications that require bendability, there is a drawback in that the shape cannot be maintained after folding because of its firmness. Further, in the twist packaging application, there are drawbacks such as poor twist retention such as poor shape maintenance after twisting, and it has been difficult to use as a cellophane substitute.

  As a polyethylene terephthalate stretched film which is advantageous in terms of cost and has good productivity, there is a uniaxially stretched film in the longitudinal direction or the width direction. However, in the case of the uniaxially stretched film in the longitudinal direction, the refractive index Nx in the longitudinal direction is larger than the refractive index Ny in the width direction, and a film having a relatively good twist or bendability can be obtained. There is a problem that productivity is deteriorated because the width when pulled by a casting roll during resin extrusion is restricted.

  In addition, in the case of a uniaxially stretched film in the width direction, the speed taken up by a casting roll at the time of resin extrusion becomes a limit, which is also unproductive. Further, each of the uniaxially stretched films has a problem that thickness unevenness easily occurs, and there is a problem in productivity that knitted meat and sagging occur in a roll shape.

  In other words, in consideration of economy and productivity, the current situation is that a stretched film with high yield and profitability is required, and in a twist packaging film substantially composed of a resin mainly composed of polyethylene terephthalate, In order to develop foldability and twistability, there is no film orientation and / or low orientation and / or no crystallization or low crystallinity, so there is no film orientation and the film does not crystallize. As described above, this has a problem that it is disadvantageous for productivity.

As a method for solving the above drawbacks, when the stress-strain curve has a yield point and the average refractive index of the unstretched film of the copolymer is N0 and the average refractive index of the biaxially stretched film is N1, 0 An easily bendable polyester film (for example, see Patent Document 1) characterized by satisfying .003 ≦ N1-N0 ≦ 0.021 has been reported.
Japanese Patent No. 2505474

However, in the above prior art, a biaxially stretched film made of a copolymer of polyethylene terephthalate, which has a yield point in the stress-strain curve, and the average refractive index of the unstretched film of the copolymer is N ₀ , When the average refractive index of the biaxially stretched film is N ₁ , the method of 0.003 ≦ N ₁ −N ₀ ≦ 0.021 is such that the refractive index Ny in the width direction of the film is larger than the refractive index Nx in the longitudinal direction. Thus, the present invention is not sufficient to obtain the desired bendability and shape maintenance after twisting required for twist packaging applications. Although it has been described that the thermal shrinkage rate is reduced in the use of a copolymer such as isophthalic acid and the heat treatment step after biaxial stretching, the use of the copolymer increases the cost and is preferable for productivity. It also had the problem of not being.

Further, the film is made of polyethylene terephthalate, the density is in the range of 1.35 to 1.375 g / cm ³ , the thermal shrinkage at 120 ° C. is at least 10%, and the film thickness is 6 to 30 μm. A food film for twist packaging (for example, refer to Patent Document 2) has been proposed.
Japanese Patent Publication No.59-12544

  However, even in the above prior art, the return angle after twisting is large, and as in the above prior art, it is not sufficient to obtain the shape maintenance after twisting that is necessary for twist packaging applications, and the contents appear and many defects are produced. It was not practical because of the problem of rate.

  In recent years, the use of metal cell-wrapped packaging cellophane films has been diversified as solid packaging films found in twist packaging and folding packaging. The purpose of this is to improve the product value of twist-wrapped and folded-wrapped by improving the gas barrier property by metal vapor deposition and its excellent beauty, and it is one of the effective packaging means for expanding sales. . Accordingly, although there is a great demand for twist packaging and folding packaging using metal-deposited polyethylene terephthalate as a base film, development is desired, but it is not sufficient.

  The present invention has a good twist and foldability while maintaining the excellent properties of a biaxially stretched polyethylene terephthalate resin film, and also has a high commercial value barrier property and beautiful appearance for twist packaging applications. The object is to provide a metal-deposited twist packaging film which is excellent in economic efficiency and productivity.

  In view of the above-described problems of the prior art, the present inventors have provided a twist packaging film made of a resin composed mainly of polyethylene terephthalate, which has practicality and is advantageous in terms of cost and good productivity. As a result of earnest research for the purpose of obtaining the above, the present invention has been achieved.

  The present invention is a film composed of a resin mainly composed of polyethylene terephthalate in which the orientation (here, referred to as refractive index) and crystallinity (here, referred to as film density) of a biaxially stretched film is controlled. is there.

That is, the present invention is a film substantially made of a resin mainly composed of polyethylene terephthalate, wherein the refractive index Nx in the longitudinal direction of the film is larger than the refractive index Ny in the width direction, and the film density is 1. It is to provide a biaxially stretched polyethylene terephthalate resin film for metal vapor deposition twist packaging characterized by being 34 to 1.375 g / cm ³ . The refractive index here refers to a sample condition adjustment and measurement temperature of 30 ° C., measured with an Abbe refractometer according to JIS-K-7142 with NaD ray light, using methylene iodide as the mounting liquid, and in the longitudinal direction. It means a value obtained as a refractive index (Nx) and a refractive index (Ny) in the width direction. The film density means a value measured at 25 ° C. by means of a density gradient tube method (for example, a solution of calcium nitrate) or a flotation method. Thus, using polyester having a specific composition, making the refractive index Nx in the longitudinal direction of the film and the refractive index Ny in the width direction have the above specific relationship, and further making the film density in the above specific range, It is preferable for obtaining excellent twistability and bendability while satisfying economic efficiency and productivity, and is useful as a metal vapor deposition twist packaging film.

  In this case, the refractive index Nx in the longitudinal direction of the film is preferably 1.60 ≦ Nx ≦ 1.68 and the refractive index Ny in the width direction is 1.59 ≦ Ny ≦ 1.64. When the refractive index Nx in the longitudinal direction is less than 1.60 and / or the refractive index Ny in the width direction is less than 1.59, unevenness in thickness due to low draw ratio occurs. On the other hand, if the refractive index Nx in the longitudinal direction exceeds 1.68 and / or if the refractive index Ny in the width direction exceeds 1.64, the degree of orientation of the film becomes high and the twistability and bending property deteriorate.

  In this case, it is preferable that the thermal shrinkage rate in the longitudinal direction of the film at 120 ° C. is 20% or more. When the thermal shrinkage rate in the longitudinal direction at 120 ° C. of the film is less than 20%, the film density is increased and the twistability and the folding property are deteriorated.

  In addition, since the refractive index Nx in the longitudinal direction and the refractive index Ny in the width direction of the biaxially stretched polyethylene terephthalate resin film for metal vapor deposition twist packaging of the present invention can be easily collected from the manufacturing process, the sample In order to measure the refractive index of a metal-deposited biaxially-stretched polyethylene terephthalate resin film for metallized wrapping, the metal-deposited film is removed by, for example, hydrochloric acid treatment. The refractive index of the film can be measured and determined.

The present invention is a film consisting essentially of a resin mainly composed of polyethylene terephthalate, wherein the refractive index Nx in the longitudinal direction of the film is larger than the refractive index Ny in the width direction, and the film density is 1.34 to By setting it as 1.375 g / cm < ³ >, the biaxially-stretched polyethylene terephthalate resin film for metal vapor deposition twist packaging which has favorable twist property and bendability, and also has favorable productivity can be provided.

The resin essentially comprising polyethylene terephthalate constituting the present invention is a resin obtained by directly esterifying terephthalic acid and ethylene glycol, and as a by-product, diethylene glycol, oligomer, cyclic oligomer, etc. Linear monomers and oligomers may be included as reactants. Further, the intrinsic viscosity of the resin having polyethylene terephthalate as a main component is preferably 0.55 to 1.30 dl / g, more preferably 0.60 to 1.20 dl / g. At this time, the resin density is preferably 1.350 to 1.450 g / cm ³ .
As used herein, the resin having substantially polyethylene terephthalate as a main component means a resin in which 70 mol% or more of constituent components are preferably composed of ethylene terephthalate units, and more preferably 80 mol% or more.

  The resin having substantially polyethylene terephthalate as a main component can be produced by a conventional method. Examples include a direct esterification method in which an acidic component and a glycol component are directly reacted, and a transesterification method in which an ester as an acid component is reacted with a glycol component, but are not particularly limited.

  In the said composition, various additives may be contained as needed besides the resin which has polyethylene terephthalate as a main component. Additives include titanium dioxide, fine particle silica, kaolin, calcium carbonate, and other inorganic lubricants, and fine particle materials made of acrylic cross-linked polymers, such as acrylic acid, methacrylic acid, acrylic ester, and methacrylic ester. Examples thereof include organic lubricants such as cross-linked polymers made of monomers. Moreover, an antistatic agent, an anti-aging agent, an ultraviolet light inhibitor, a colorant, a dye and the like may be contained alone, or two or more kinds may be used in combination.

The additive used in the present invention is preferably fine particle silica, but is not particularly limited. The composition of the fine-particle silica is mainly composed of silicon dioxide (SiO ₂ ), and the shape may be any shape such as indefinite shape, spherical shape, and agglomerated shape, but in the present invention, the indefinite shape having no crystal structure. Is preferred. Furthermore, the average particle size (Coulter counter method) is preferably 1.4 to 4.5 μm, more preferably 1.8 to 3.0 μm. If the average particle size is less than 1.4 μm, blocking between films occurs, which becomes a problem. On the other hand, when the average particle size is larger than 4.5 μm, there arises a problem that fine particle silica is dropped during film processing and a problem that scratch resistance is deteriorated. In the present invention, silicia manufactured by Fuji Silysia Co., Ltd. (grade: 310P, shape: amorphous, average particle size: 2.7 μm) was used.

  The resin film essentially comprising polyethylene terephthalate of the present invention can be formed by a known film forming method. As a film forming method, for example, an unstretched film is obtained by casting a resin melt-kneaded by an extruder. Thereafter, a method of performing biaxial stretching such as simultaneous biaxial stretching or sequential biaxial stretching and then heat setting is used. Extrusion conditions, film forming methods, stretching conditions, and the like can be appropriately selected and are not particularly limited. Preferably, the above stretching conditions can be performed in the following steps. For example, preheating is performed at a temperature not lower than the melting point and not higher than the melting point of the polymer composition constituting the resin composition. As the stretching ratio, in the case of biaxial stretching, the area ratio after stretching is 2 to 30 times, preferably 9 to 16 times the area before stretching. More preferably, in the sequential biaxial stretching method, the film is first stretched in the width direction and then stretched in the longitudinal direction.

  In the sequential biaxial stretching method, the film is first stretched in the width direction, and then stretched in the longitudinal direction, so that the refractive index Nx in the longitudinal direction can be made larger than the refractive index Ny in the width direction, which is a good twist. And bendability can be achieved.

  In the present invention, in order to make the film density within a preferable range, the biaxial stretching method such as the simultaneous biaxial stretching method or the sequential biaxial stretching method is performed and then heat-set, and then the stretched film is under tension or in the width direction. A method of heat treatment while relaxing is used. In this case, the heat treatment temperature is preferably 60 ° C to 120 ° C, more preferably 80 ° C to 100 ° C, and the time is preferably 0.5 seconds to 30 seconds. Furthermore, relaxation treatment is performed in the range of 0.1% to 10% in the longitudinal direction and / or preferably in the width direction during the cooling process from the heat treatment temperature. The relaxation process may be performed in one stage, may be performed in multiple stages, and a change in temperature distribution may be provided.

  The resin film essentially comprising polyethylene terephthalate of the present invention may be subjected to surface treatment by a conventionally known method such as corona discharge treatment, plasma treatment, ozone treatment, chemical treatment, etc., or a known anchor treatment depending on the purpose. An anchor treatment using an agent may be performed. The antistatic coating agent is not particularly limited as long as it is an alkylsulfonic acid, glycerin ester, polyglycene ester, or the like, and can impart antistatic properties. The coating method is not particularly limited as long as it is a conventionally known method such as a berth roll coating method, a roll knife coating method, a die coating method, or a gravure coating method. Furthermore, it may be a coating by in-line coating.

  The biaxially stretched polyethylene terephthalate resin film of the present invention preferably has a heat shrinkage rate of 120% or more at 120 ° C.

  The biaxially stretched polyethylene terephthalate resin film for metal vapor deposition twist packaging of the present invention is obtained by forming a metal vapor deposition layer on at least one surface of a biaxially stretched polyethylene terephthalate resin film. Examples of the metal used for forming the metal vapor deposition layer include Al, Zn, Mg, Sn, Ti, In, Cr, Ni, Cu, Pb, and Fe. Among these, Al, Zn, and Mg are preferable as a metal vapor deposition layer formed on the metal vapor deposition biaxially stretched polyethylene terephthalate resin film of the present invention. In particular, Al is a preferable metal from the viewpoint of productivity.

  The film thickness of the said metal vapor deposition layer of this invention is 1-500 nm normally, Preferably it is 5-200 nm. If the film thickness is less than 1 nm, it is difficult to obtain a good appearance necessary as a packaging material. On the other hand, if the film thickness is excessively increased beyond 500 nm, it is disadvantageous in terms of flatness, productivity and economy of the film after metal deposition. Further, the adhesion strength between the biaxially stretched polyethylene terephthalate resin film and the metal vapor deposition layer is preferably a strength at which the metal vapor deposition layer does not peel in the tape peeling evaluation. If the metal vapor deposition layer is peeled off in this adhesion strength evaluation, there is a problem that when the tape is peeled off after the package is taped, the metal vapor deposition layer is taken to the tape side and the appearance is impaired. The tape peeling evaluation mentioned here is to perform tape peeling instantaneously at a peeling angle of 90 degrees after using a Nichiban Co., Ltd. cello tape (registered trademark) (15 mm width) and adhering a length of 50 mm to the metal deposition layer side. It can be determined by visually observing the presence or absence of a metal vapor deposition layer taken on the peeled tape side. In order to increase the adhesion strength between the biaxially stretched polyethylene terephthalate resin film and the metal deposition layer, for example, surface treatment by a conventionally known method such as corona discharge treatment, plasma treatment, ozone treatment, chemical treatment, or a known anchor treatment agent was used. There is anchor processing, but there is no particular limitation.

  Formation of the metal vapor deposition layer of the present invention includes a physical vapor deposition method such as a vacuum vapor deposition method, a sputtering method, and an ion plating method, or a chemical vapor deposition method such as CVD, which can be used as appropriate, but is not particularly limited. .

As a method for forming the metal vapor deposition layer of the present invention, for example, the following steps can be performed. The film was set on the unwinding side of the take-up vacuum deposition apparatus, the pressure in the chamber was reduced to 4 × 10 ⁻³ Pa, and aluminum was evaporated by high-frequency induction overheating to form an aluminum deposition layer having a thickness of 50 nm. At this time, the film supply rate was 40 m / min, the chill roll temperature was −15 ° C., and the biaxially stretched polyethylene terephthalate resin film for metal vapor deposition twist packaging of the present invention was obtained, but it is not particularly limited.

  The present invention can be used as a twist package in which packages to be packaged made of solid materials such as various foods, stationery, and industrial parts are individually packaged due to its excellent twistability and bendability, and various packaging forms of the package It can be.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited by these Examples. In addition, the measuring method of the physical property of the film obtained by the Example and the comparative example is as follows.

Test Method (1) Twistability Twist packaging was performed at a rate of 200 pieces / minute using a twist packaging machine TA300 type manufactured by Tenchi. The film is twisted 1.5 turns (540 degrees) into individual packages. Then measure the angle at which the twist was held after a slight return. (Hereafter referred to as “Twist holding angle”)
The twisting property is better as the holding angle is larger, and the evaluation is classified as follows.
○: Twist holding angle is 240 degrees or more Δ: Twist holding angle is 180 degrees or more and less than 240 degrees X: Twist holding angle is less than 180 degrees

(2) Refractive index It measured with the NaD ray light with the Abbe refractometer according to JIS-K-7142 except having adjusted the state of the sample and the measurement temperature to 30 degreeC. The mounting liquid was methylene iodide, and the refractive index in the longitudinal direction (Nx), the refractive index in the width direction (Ny), and the refractive index in the thickness direction (Nz) were measured.

(3) Tm (melting point)
The measurement was performed by connecting a TA60WS disk station (manufactured by Shimadzu Corporation) to a robot DSC (differential scanning calorimeter) DSC-60 (manufactured by Shimadzu Corporation). After adjusting 10 mg of the sample to an aluminum pan, it is set in a DSC apparatus (reference: aluminum pan of the same type without a sample). After heating, it was quenched with liquid nitrogen. The sample was then reheated at a rate of 10 ° C./min, and the melting point (Tm) was measured from the DSC chart.

(4) Thermal shrinkage rate The thermal shrinkage rate was measured according to JIS C-2318 except that the shrinkage condition was 120 ° C. and 15 minutes.

(5) Intrinsic viscosity 0.1 g of the chip sample was precisely weighed, dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 6/4 (mass ratio), and measured at 30 ° C. using an Ostwald viscometer. The measurement was performed three times and the average value was obtained.

(6) Film density The film density was measured at 25 ° C. with a density gradient tube obtained by adjusting the concentration of a solution of calcium nitrate.

(7) Average particle diameter The volume median diameter of the aqueous dispersion of the sample was measured using a Coulter Counter Multisizer II (Beckman Coulter, Inc.).

(8) Formation method of metal vapor deposition layer The film is set on the unwinding side of the wind-up type vacuum vapor deposition apparatus, the inside of the chamber is depressurized to 4 × 10 ⁻³ Pa, aluminum is evaporated by high frequency induction overheating, and the thickness is 50 nm. An aluminum vapor deposition layer was formed. At this time, the film supply rate was 40 m / min, and the chill roll temperature was −15 ° C.

Example 1
Silica (Silicia manufactured by Fuji Silysia Co., Ltd. (grade: 310P, shape: amorphous, average particle size: 2.7 μm) is added so as to be 0.03% by weight with respect to polyethylene terephthalate (inherent viscosity is 0.63 dl / g). A polyethylene terephthalate resin composition was obtained as an additive, melted and kneaded with an extruder, and the melted and kneaded product was supplied to a T die so that the resin temperature was 285 ° C. from the inside of the T die. Then, the film was cast with a casting roll at a temperature of 25 ° C., and then the film was stretched 3.2 times in one direction (lateral direction) at 90 ° C. to obtain a uniaxially stretched polyester film. The film is stretched 4.0 times at 80 ° C. in the direction perpendicular to the stretching direction (longitudinal direction), heat-treated at 80 ° C. with a relaxation rate of 3% for 10 seconds, A biaxially stretched polyester resin film having a thickness of 16 μm was obtained, and then a 50 nm thick aluminum vapor deposition layer was formed on one side of the film by using a winding vacuum vapor deposition apparatus, and a metal vapor deposited biaxially stretched polyethylene terephthalate resin film was obtained. Obtained.

(Example 2)
The film was stretched 3.5 times in one direction (lateral direction) at 90 ° C. to obtain a uniaxially stretched polyester film. Then, the film was stretched 3.8 times at 80 ° C. in the direction perpendicular to the stretching direction (longitudinal direction), and heat treated at 100 ° C. with a relaxation rate of 5% for 11 seconds. Similarly, a metal-deposited biaxially stretched polyethylene terephthalate resin film was obtained.

(Comparative Example 1)
The film was stretched 4.0 times in one direction (lateral direction) at 90 ° C. to obtain a uniaxially stretched polyester film. Subsequently, it heat-processed at 80 degreeC, and obtained the metal vapor deposition uniaxial stretching polyethylene terephthalate resin film like Example 1 except having set it as the horizontal uniaxial stretching film.

(Comparative Example 2)
The film was stretched 3.5 times in one direction (longitudinal direction) at 80 ° C. to obtain a uniaxially stretched polyester film. Subsequently, it heat-processed at 90 degreeC, and obtained the metal vapor deposition uniaxially stretched polyethylene terephthalate resin film like Example 1 except having set it as the longitudinally uniaxially stretched film.

(Comparative Example 3)
The film was stretched 3.5 times in one direction (longitudinal direction) at 80 ° C. to obtain a uniaxially stretched polyester film. Then, the film was stretched 4.0 times at 90 ° C. in the direction perpendicular to the stretching direction (transverse direction), and heat-treated at 100 ° C. with a relaxation rate of 8% for 12 seconds. Similarly, a metal-deposited biaxially stretched polyethylene terephthalate resin film was obtained.

(Comparative Example 4)
The film was stretched 3.5 times in one direction (longitudinal direction) at 80 ° C. to obtain a uniaxially stretched polyester film. Next, the film was stretched 4.0 times at 90 ° C. in the direction perpendicular to the stretching direction (transverse direction), and heat-treated at 160 ° C. with a relaxation rate of 10% for 12 seconds. Similarly, a metal-deposited biaxially stretched polyethylene terephthalate resin film was obtained.

  The biaxially stretched polyethylene terephthalate resin film for metal vapor deposition twist wrapping of the present invention has good twistability and bendability suitable for twist wrapping and folding wrapping while maintaining the excellent properties of the biaxially stretched polyethylene terephthalate resin film, In addition, it has high barrier properties and beautiful appearance as commercial value, is excellent in practicality, economy, and productivity, can be used in the field of twist packaging, and contributes to the industry of twist packaging. .

Claims (4)

A film consisting essentially of a resin mainly composed of polyethylene terephthalate, wherein the refractive index Nx in the longitudinal direction of the film is larger than the refractive index Ny in the width direction, and the film density is 1.34 to 1.375 g / A biaxially stretched polyethylene terephthalate resin film for metal vapor deposition twist packaging, characterized in that it is cm ³ .   2. The film according to claim 1, wherein the refractive index Nx in the longitudinal direction of the film is 1.60 ≦ Nx ≦ 1.68, and the refractive index Ny in the width direction is 1.59 ≦ Ny ≦ 1.64. A biaxially oriented polyethylene terephthalate resin film for metal vapor deposition twist packaging.   3. A biaxially stretched polyethylene terephthalate resin film for metal vapor deposition twist packaging, wherein the film has a thermal shrinkage rate in the longitudinal direction at 120 [deg.] C. of 20% or more.   4. A twist package according to claim 1, wherein the film is obtained by twist-wrapping and / or folding-wrapping an object to be packaged.