JPH03155944A - Laminated polyester film - Google Patents

Abstract

PURPOSE:To enhance close adhesive strength under a high humidity condition at the time of the vapor deposition of a metal by a method wherein a polyester layer having an m.p. lower than that of a polyolefin-containing polyester layer is laminated to the single surface of the polyolefin-containing polyester layer and both layers is heat-treated at temp. between both melting points to be brought to specific density. CONSTITUTION:To at least the single surface of an oriented layer composed of polyester A containing 0.1-10wt.% of polyolefin, a layer composed of polyester B having an m.p. lower than that of polyester A is laminated in thickness of 0.01-1mum and the obtained laminate is heat-treated at temp. between the m.p. of polyester B and that of polyester A to be brought to density of 1.25g/cm<3> or more. Herein, polyester A is polyethylene terephthalate and has intrinsic viscosity(IV) of 0.7dl/g or more and polyolefin is at least one resin selected from polyethylene, polypropylene, polybutene and a copolymer thereof. A metal vapor deposition layer and/or a metal oxide vapor deposition layer are formed on the layer composed of at least one polyester B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyester film with improved adhesion of metal and/or metal oxide vapor deposited layers;
In particular, the present invention relates to a polyester film with improved vapor deposition adhesion under high humidity conditions.

[Prior Art] Polyester films have superior metal vapor deposition suitability over polyolefins, but have the disadvantage of reduced adhesion under high humidity.Corona discharge treatment is a method of improving adhesion. method, method of mixing low-crystalline polyester and high-crystalline polyester (Japanese Patent Publication No. 64-10
No. 188, etc.) have been proposed.

[Problems to be Solved by the Invention] However, the method of applying corona discharge treatment has a small effect on improving adhesion, and the method of mixing low-crystalline polyester and high-crystalline polyester may cause transesterification depending on the extrusion conditions. However, it is difficult to control and the uniformity of quality obtained is poor.

Furthermore, with the conventionally proposed techniques, the improvement of vapor deposition adhesion in high humidity conditions is insufficient, and the vapor deposition adhesion is still insufficient, especially for boil and retort packaging. An object of the present invention is to provide a polyester film that exhibits excellent adhesion under high humidity when metal-deposited.

[Means for Solving the Problems] As a result of intensive studies on vapor deposition properties and physical properties of polyester films, the present invention has found that excellent adhesion properties under high humidity can be obtained by adding the following constituent requirements. .

That is, in the present invention, a layer made of polyester B having a lower melting point than polyester A is laminated to a thickness of 0.01 to 1 μm on at least one side of an oriented layer made of polyester A containing 0.1 to 10% by weight of polyolefin. The film is heat-treated at a temperature higher than the melting point of polyester B and lower than the melting point of polyester, and has a density of 1.
The present invention provides a laminated polyester film characterized in that it has a weight of 25 g/cm3 or more.

In the present invention, polyester A refers to a polymer consisting of an aromatic dicarboxylic acid and a diol, and specifically includes resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene 2.6 naphthalene carboxylate 1. Although it is a blend or a copolymer, the present invention particularly uses polyethylene terephthalate whose composition is ethylene terephthalate in 90 mol% or more, more preferably 95 mol% or more, and has durability against heat load during processing. From the point of view, its crystal melting energy (ΔT-1u) is 7 cal/g
It is preferably 10ca or more, more preferably 10ca
It is good if it is 1/ or more.

In addition, it has good dispersibility with the polyolefin described below,
From the viewpoint of improving vapor deposition adhesion, the polyethylene terephthalate preferably has an intrinsic viscosity (TV) of 0.7 dl/g or more, more preferably 0.7 dl/g or more. 8-1.
Preferably it is 2 dl/g. In particular, when the TV is within the above range, the mechanical properties will be good, and the pinhole resistance and impact resistance will also be good, which is desirable as a packaging material.

Next, the polyolefins contained in the polyester A include ethylene, propylene, 1-butene, pentene,
hexene, 3-methyl-1-butene, 4-methyl-1゜-
It is at least one selected from polymers or copolymers of α-olefins such as pentene. Furthermore, copolymerization components include acrylic acid, methacrylic acid, and these metals (sodium, potassium, cesium, zinc,
Examples include neutralized products of magnesium, calcium, etc.

Furthermore, a graft component may be added to these (co)polymers (1. Examples of the graft component include acid anhydrides such as phthalic anhydride, styrene, etc.

In particular, preferred polyolefins in the present invention are (co)polymers whose main skeleton is selected from ethylene, propylene, and butene, as they have good heat resistance and mechanical properties. Examples include polyethylene, polypropylene, polybutene-1, ethylene propylene copolymer, propylene butene copolymer, ethylene methacrylic acid copolymer, and metal neutralized ethylene methacrylic acid copolymer.

Among these, resins having a melting point of 60 to 180°C and a glass transition temperature of 10°C or less are preferably used because they have good vapor deposition suitability.

In the present invention, the polyolefin content in the layer made of polyester A (hereinafter abbreviated as A layer) is 0.1 to 1.
0% by weight, preferably 0.5% by weight.
~5% by weight. If the polyolefin content is too low, vapor deposition adhesion and moisture resistance will be poor.

On the other hand, if the amount of polyolefin added is too large, not only the haze of the film increases, but also voids occur frequently, resulting in a film with poor mechanical strength, heat resistance, and flatness.

Next, polyester B, which has a lower melting point than polyester A (
(hereinafter abbreviated as polyester B) means polyester A
The temperature is preferably 10° C. or more lower than that, more preferably 1-5 to 70° C., in order to improve vapor deposition adhesion.

For example, when polyethylene terephthalate is used as polyester A, the main skeleton is ethylene terephthalate,
Alternatively, butylene terephthalate may be used as a copolymerization component such as isophthalic acid, adipic acid, sebacic acid, dimer acid, 2,6-naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, diethylene glycol, cyclohexane dimetatool, 1,4-butanediol, etc. Examples include copolymerized thermoplastic polyesters, but are not limited thereto.

Here, in order to obtain good adhesion as polyester B, a particularly preferable structure is an ester bond (-0-C
The number of carbon atoms between -) is preferably 2 to 10, preferably 2 to 8.

Furthermore, from the viewpoint of improving vapor deposition properties, polyester B
ΔI-T u is preferably in the range of 6 cal/g or less, and more preferably 0.1 to 5 cal/g.
It is preferable that it is in the range of g.

The laminated thickness of such a layer made of polyester B (hereinafter referred to as layer B) needs to be in the range of 0.01 to 1 μm, preferably 0.01 to 0.3 μm.
It is. If the lamination thickness is too thin, the vapor deposition adhesion will be low, causing a practical problem. On the other hand, if the lamination thickness is too thick, the slippage during vapor deposition will deteriorate, and the glossiness of the vapor-deposited surface will be poor.

Further, although it is permissible for the B layer to contain particles, it is preferable that the average particle size (R) is 3/2 or more of the laminated thickness (d), and more preferably, R
, /d is preferably in the range of 2 to 200, particularly preferably 10 to 100. In addition, the amount added is 0.001
A range of 1% to 1% by weight, more preferably 0.01% to 0.5% by weight is preferred since the gloss after vapor deposition will not decrease.

The density of the laminated polyester film of the present invention is 1°25
g/cm3 or more, preferably 1
, 30 g/cm3 or more. If the density is too low, problems such as a decrease in the uniformity of the deposited film and a decrease in adhesion under high humidity will occur.

In addition, in terms of heat resistance and mechanical properties, it is necessary that at least the A layer among the A layer/B layer constituting the film of the present invention is stretched and oriented along the -axis, and preferably it is oriented biaxially. It is preferable that the

Further, the B layer or another layer may be laminated on the other surface of the A layer. Specifically, other layers include:
Examples include an antistatic layer, a matte layer, a hard coat layer, an easy-slip coat layer, an easy-adhesion layer, and an adhesive layer.

In addition, the six layers may contain well-known antioxidants, heat stabilizers, antistatic agents, weathering agents, flame retardants, UV
Absorbents, lubricants, crystal nucleating agents, etc. may be added.

The laminated polyester film of the present invention is used by vapor depositing on at least one 8-layer surface, and examples of vapor deposits that can be used in the present invention include aluminum, zinc, magnesium, tin, iron, copper, and alloys thereof. , and oxides thereof, and the structure of the deposited film is a single film or a multilayer film selected from the above-mentioned single metals, alloys, and oxides.

The deposition thickness is appropriately selected depending on the purpose, but is usually 10
~5,000 people, preferably 50-1,000 people. In particular, if the vapor deposition thickness is too thick, it tends to increase internal stress generated in the vapor deposited film and increase thermal strain in the polyester film, which often results in a decrease in vapor deposition adhesion.

The film of the present invention is particularly suitable for boiling and retort packaging used under high temperature and high humidity conditions. In such applications, the vapor deposited material is preferably selected from aluminum or tin and oxides thereof, and the vapor deposition thickness is ,
The number is preferably in the range of 50 to 1000 people in order to achieve both barrier properties and vapor deposition adhesion.

Next, a method for producing the film of the present invention will be described, but the method is not limited thereto.

Polyester No. 8 to which polyolefin has been added and Polyester B are melt-extruded using separate extruders, and are laminated in a manifold part of a die or a polymer tube entering the die.

As described above, the laminated body having the basic structure of polyester A and polyester B added with polyolefin is melt-extruded into a sheet or cylinder shape, and then rapidly cooled and cast to a temperature below the glass transition temperature of polyester A. Next, the film is preheated to a temperature higher than the glass transition temperature of polyester and stretched at least uniaxially to obtain a stretched film. The stretching ratio is preferably in the range of 2 to 5 times in the uniaxial direction,
In the case of biaxial stretching, it is preferable that the area magnification is in the range of 4 to 20 times, since both mechanical properties and flatness will be good.

Next, the stretched film is heat-treated, but in order to obtain the film of the present invention, the heat treatment temperature needs to be higher than the melting point of polyester B and lower than the melting point of polyester, preferably higher than the melting point of polyester B. The melting point of A is -10°C or lower. here,
The heat treatment temperature in the present invention refers to the melting peak of metacrystals associated with thermal crystallization remaining as the heat history during the heat treatment of polyester A, which is observed using a differential scanning calorimeter to be described later. Therefore, it does not match the atmospheric temperature in the heat treatment roll or oven during film formation. In general, by allowing a sufficient heat treatment time, the ambient temperature during heat treatment and the heat treatment temperature in the present invention almost match.

The film obtained as described above is subjected to surface treatments such as corona discharge treatment, low-temperature plasma treatment, flame treatment, and the aforementioned coating treatment, as required. Note that it is preferable that the surface of the polyester 8 used for vapor deposition is not subjected to surface treatment as much as possible in order to improve the adhesion with the vapor deposition layer.

[Effects and Applications of the Invention] Due to the above structure, the laminated polyester film of the present invention has high vapor deposition adhesion 1 2 and good adhesion strength under humidity, and is preferable for boiling and retort use. However, as a secondary effect, it is preferable that the film of the present invention uses a polyester having a particularly high intrinsic viscosity as the A layer, since pinhole resistance and impact resistance will be improved.

[Property evaluation method and effect evaluation method] The evaluation and measurement of effects used in the present invention will be summarized below.

(1) Melting energy (△ITu), melting point (Tm).

Glass transition temperature (Tg) Determined using a differential scanning calorimeter DSC2 (manufactured by PerkinElmer).

Measurement was carried out using 10 mg of sample at 280°C in a nitrogen stream.
Hold molten for ×5 minutes, then cool at a cooling rate of 320°C/min.

When the sample thus obtained was heated at a heating rate of 10°C/min, the change in specific heat due to the transition from the glass state to the rubber state was measured and this temperature was determined as the glass transition temperature (
Tg). Furthermore, the endothermic peak temperature based on crystal melting is defined as the melting point (Tm).

The melting energy (ΔTTu) was determined from the peak area. Note that the correction was made using the melting energy of indium.

(2) Heat treatment temperature A differential scanning calorimeter is used as in (1).

The temperature of 1.0 mg of sample was raised from room temperature at a heating rate of 10°C/min under a nitrogen stream, and among the peaks attributed to crystal melting of polyester A, the melting peak temperature corresponding to metacrystal was determined as the heat treatment temperature. shall be.

Usually, it appears as a broader peak that is smaller than the melting point peak observed in (1).

(3) Polyolefin content Remove layer B from the sample to leave only layer A, and
Vacuum dry for 24 hours and measure the weight W1. Next, using the hydrolysis method, the polyester part was decomposed/water-solubilized and removed from the sample, and the remaining material was vacuum-dried for 24 hours at 80°C to remove water, and the remaining polyolefin amount W2
Measure.

As a result, polyolefin content=W 2 /W 1.
Calculate by xloo (%).

(4) Polyolefin [η] Based on ASTM D 1601, test FI
Measurement is performed by completely dissolving 1 g of O in 100 ml of tetralin at 1-35°C. Unit: 617 g
For example, the particles are removed using Yamato Kagaku PR-503 model) to expose the particles. The processing conditions are selected so that the polyester is incinerated but the particles are not damaged. Observe this with a SEM, process the image of the particles with an image analyzer (for example, QTM900 manufactured by Cambridge Instruments), and calculate the number average diameter obtained using the following formula for 1000 or more observed particles. The diameter shall be the diameter.

D-ΣD i/N Here, Di is the circular diameter of the particle, and N is the number of particles.

(6) Content of particles A sample is dissolved using a solvent (such as 0-chlorophenol) that dissolves polyester but does not dissolve particles.The particles are centrifuged from the solution, and the amount of particles relative to the total weight of the sample is The weight ratio (wt%) is defined as the particle content.

(7) Thickness of layer B The following two methods are used depending on the thickness of layer B.

(T) method (thickness of layer B is less than 0.2 μm) by ellipsometry method. An automatic ellipsometer (DVA-36L manufactured by Mizojiri Optical Industry Co., Ltd.) was used.

(II) Method (B layer thickness is 0.2 μm or more) The thickness (T1) of the sample is measured with an electronic micrometer. Next, using a solvent that dissolves layer B but not layer A, remove layer B from the measurement area and measure the thickness (T2) of the same area again.

From this result, the thickness of layer B - T 1. −T 2.

In each case, measurements were taken at 20 points at different locations, and the average value of 16 points, 2 points from the largest value and 2 points from the smallest value, was taken as the thickness of layer B.

-5 6 (8) Intrinsic viscosity (IV) Measured at 25°C using 0-chlorophenol as a solvent. The unit is dl/g.

(9) Vapor deposition adhesion A1 metal was deposited using an electron beam heating vapor deposition machine to a thickness of 500 evaporation ports, and then an unstretched polypropylene film [CPP] (manufactured by Toshi Gosei Film Co., Ltd.) using a polyester adhesive. T3501-150 μm) was laminated and left in an atmosphere of 290% relative humidity at 40° C. for 120 hours, and then the CPP was peeled off. The peeling state was determined using a 90° C. peeling method, and the results were ranked as follows. In addition, the peeling force was determined for a method in which water is dropped onto the peeling interface during peeling (Wet) and a method in which water is not dripped (Dry).

Rank C: The deposited metal completely remains on the polyester film side.

Rank C: 50% or more of the deposited metal remains on the polyester film side.

Rank C: Less than 50% of the deposited metal remains on the polyester film side.

Rank D: Vapor deposited metal is completely peeled off.

Practically speaking, in the case of the dry peeling method, a problem will occur if the rank is not A, but in the case of the wet peeling method, if the rank is 8 or higher, the problem heat (can be used).

(G) Glossiness of vapor deposition surface J 11Z8741. (60°-60°). Note that the measurement was performed on the vapor-deposited surface of the vapor-deposited film.

(11) Film density Measure using the density gradient tube method. Measurement temperature is 25°C0 [Example] The present invention will be specifically explained using examples.

Example 1 Polypropylene (manufactured by Mitsui Toatsu Chemical Co., Ltd., [η] 1.85 dl/
g, melting point = 165 ° C.) to which 2.5% by weight was added,
Polyester B contains terephthalic acid (TP) as an acid component.
A) Resin consisting of 85 mol%, isophthalic acid (TPA) 15 mol%, and ethylene glycol (EG) as a diol component (TV-0,62 dl/g, Tm = 21-5°
C1Tg=69°C) with 0 silicate particles with an average particle size of 3 μm.
゜08% by weight was added and melt extruded using separate extruders to form a sheet in which 8 layers of polyester were laminated on one side of a layer of polyester A and polyolefin by laminating with 1'' gold and white. .

The thus obtained sheet was heated at 85°C in the longitudinal direction for 3.3
The film was stretched twice, then introduced into a stenter, heated to 100°C, stretched 3.3 times in the width direction, heat-treated at 220°C, and then subjected to low-temperature heat treatment at 120°C for 10 seconds and wound.

The film thus obtained had a total thickness of 12 μm,
B layer measured by ellipsometry is 0°05 tt m
Met.

In the evaluation of vapor deposition adhesion, the adhesion was excellent with rank A in both dry and wet conditions.

Comparative Example 1 - A film was formed in the same manner as in Example 1 except that the heat treatment temperature was 190°C.

The adhesion strength was ranked C for dry and rank D for wet.

Comparative Example 2 A film was formed in the same manner as in Example 1, except that 1 to 5% by weight of the polypropylene used in Example 1 was added to polyethylene terephthalate (melting point: 256° C.) with an IV of 0.62 dl/g as polyester A.

The film density thus obtained is ], -20g/cm
It was as low as 3.

The gloss of the aluminum vapor-deposited surface was low at 550% (and the vapor deposition adhesion was also poor at rank C in the wet evaluation).

Example 2 Polyethylene terephthalate having a TV value of 0.76 dl/g was used as polyester A, and high-density polyethylene was added as a polyolefin at 1.5% by weight.

In addition, as polyester B, polybutylene terephthalate/isophthalate (IPA copolymerization amount 35 mol%, melting point 1
Silica particles (average particle size 27 zm) were added to 50°C). 1
The weight was 90% added.

Each resin was melt-extruded at 280°C using a separate extruder, laminated in the die in the same manner as in Example 1, and biaxially stretched to 230°C.
It was heat treated at °C and rolled up.

The polyester B lamination thickness of the thus obtained film was 0.09 μm and a film density of 1.35 g/cm', the gloss of the vapor deposition surface was as high as 730%, and the vapor deposition adhesion was excellent with rank A in both dry and wet conditions. .

Japanese Patent Publication No. 3 155944 (7) solid buy a lot Suke Apocalypse Δ To To To h

Claims (4)

[Claims] (1) A film in which a layer made of polyester B having a lower melting point than polyester A is laminated to a thickness of 0.01 to 1 μm on at least one side of an oriented layer made of polyester A containing 0.1 to 10% by weight of polyolefin. A laminated polyester film characterized in that it is heat-treated at a temperature higher than the melting point of polyester B and lower than the melting point of polyester A, and has a density of 1.25 g/cm^3 or higher. (2) The laminated polyester film according to claim (1), wherein the polyester A is polyethylene terephthalate and has an intrinsic viscosity (IV) of 0.7 dl/g or more. (3) Claim (1) characterized in that the polyolefin is at least one resin selected from polyethylene, polypropylene, polybutene, and copolymers thereof.
Or the laminated polyester film described in (2). (4) The laminated polyester film according to any one of claims (1) to (3), wherein a metal and/or metal oxide vapor deposition layer is formed on at least one layer made of polyester B.