JPH0825597A - White polyester film - Google Patents

Abstract

PURPOSE:To obtain a white polyester film that has a flexibility and heat-sealing properties as well as superior masking properties and can be used in the application to a decorative laminate and other building materials requiring masking properties. CONSTITUTION:In a white polyester film, a heat-sealing layer is provided on at least one surface of a polyester film, a tension modulus is 1-150-kg/mm<2> an optical density is from 0.7 to and including 1.6, and the film is substantially unoriented.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a white polyester film. More specifically, the present invention relates to a white polyester film having flexibility and heat-sealing properties and excellent concealing properties, which is used in fields where concealing properties are required such as building materials.

[0002]

It is well known that a white polyester film can be obtained by adding a large amount of titanium dioxide or calcium carbonate to polyester. It is also well known to add propylene to polyester to obtain a white polyester film. However, these films are very hard and stiff. Therefore, there is one (for example, Japanese Patent Laid-Open No. 3-76727) that has improved cushioning properties by generating fine bubbles inside to reduce the density.

[0003]

However, although these films have cushioning properties, they are still insufficient in terms of flexibility. Therefore, there is a problem that it is difficult to process a corner portion or a curved portion when it is used as a building material. Further, the sealing property due to heat was weak and it could not be processed as a concealing layer for a printing film or the like.

An object of the present invention is to eliminate the above-mentioned conventional problems, and to provide a white polyester film having flexibility and heat sealing properties and excellent concealing properties.

[0005]

In order to achieve the above object, the present invention has a heat seal layer on at least one side of a polyester film and has a tensile modulus of 1 to 150 k.
A white polyester film having a g / mm ² and an optical density of 0.7 or more and 1.6 or less and being substantially non-oriented.

In the present invention, the polyester is a polyester having an aromatic dibasic acid and a glycol as main constituents, and examples of the aromatic dibasic acid include terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid. ,
Diphenyl sulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, cyclohexane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl thioether dicarboxylic acid, diphenyl ketone dicarboxylic acid, phenylindane dicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid Examples thereof include acids and aromatic dicarboxylic acids having a metal sulfonate such as 4-sodium sulfo-2,6-naphthalenedicarboxylic acid. Furthermore, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, aliphatic dicarboxylic acids such as dimer acid, polyethyleneoxydicarboxylic acid, polyether dicarboxylic acid such as polytetramethyleneoxydicarboxylic acid, etc. may be copolymerized. . Preferable aromatic dibasic acids are mainly terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid, and terephthalic acid is particularly preferable.

As the glycol, ethylene glycol, propylene glycol, butylene glycol,
Cyclohexanedimethanol, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, bis (hydroxyphenyl) sulfone, diethylene glycol, neopentyl glycol, hydroquinone, cyclohexanediol, polyethylene Examples thereof include glycol, polypropylene glycol, polytetramethylene glycol, and polyalkylene glycol such as ethylene glycol-propylene glycol copolymer. A preferred glycol is butylene glycol.

Of course, it may be a copolymer composed of a plurality of dibasic acids and a plurality of glycols. From the viewpoint of mechanical strength and the like, those having butylene terephthalate as a main repeating unit are preferable, and at least 60 of the repeating units are included.
A polyester having a mol% or more of butylene terephthalate is preferable. The remaining less than 40 mol% of repeating units is preferably composed of a unit obtained by copolymerizing an aliphatic dicarboxylic acid, particularly a long-chain aliphatic dicarboxylic acid such as sebacic acid, dodecanedioic acid or dimer acid.

The intrinsic viscosity of the polyester of the present invention is preferably 0.3 to 2.0 dl / g, more preferably 0.5 to 1.5 dl / g.

The melting point (Tm) of the polyester of the present invention is
The temperature is preferably 130 to 260 ° C, more preferably 150 to 240 ° C.

The glass transition temperature (Tg) is 30 ° C.
The following is preferable, and 10 ° C. or less is more preferable.

The thickness of the polyester film of the present invention is not particularly limited, but it is preferably 1 to 1000 μm, more preferably 5 to 700 μm, and still more preferably 10 to 500 μm.

The polyester film of the present invention needs to be substantially non-oriented. Substantially non-oriented means that
The state in which the film is not stretched and is not uniaxially or biaxially stretched. For example, the degree of plane orientation is preferably 0.10 or less, more preferably 0.05 or less. Here, the plane orientation degree ΔP is given by ΔP = (nβ + nγ) / 2−nα, where nα is the refractive index in the thickness direction, nβ is the refractive index in the longitudinal direction, and nγ is the refractive index in the width direction.

The polyester film of the present invention has a tensile elastic modulus of 1 to 150 kg / mm ² , and preferably 5 to 5.
It is 120 kg / mm ² . Tensile elastic modulus is 1 kg / mm
^When it is less than ² , the stiffness is too weak and the handleability is deteriorated, which is not preferable. On the other hand, if it exceeds 150 kg / mm ² , the flexibility is deteriorated, which is not preferable.

The optical density of the white polyester film in the present invention is 0.7 or more and 1.6 or less, preferably 0.8 or more and 1.6 or less. If the optical density is less than 0.7, the back side can be seen through because the hiding property of the film is small, which is not preferable. On the other hand, if the optical density exceeds 1.6, the mechanical properties such as the strength of the film are greatly deteriorated, which is not preferable.

The polyester film of the present invention preferably contains white inorganic particles. As the white inorganic particles, titanium oxide, zinc oxide, zinc sulfate, lithopone, lead white,
White pigments such as basic lead sulfate, basic lead silicate, and lead-zinc white can be mentioned. Among them, titanium oxide with a high refractive index, especially rutile type titanium oxide, zinc white, zinc sulfate,
Ritopon and the like can be preferably used. The average particle size of the white inorganic particles is preferably in the range of 0.01 to 8 μm, but is preferably in the range of 0.1 to 0.5 μm because more excellent hiding property can be obtained.

The heat seal layer constituting the polyester film of the present invention has a melting point of 12 in terms of heat sealability.
It is preferably 0 to 240 ° C, particularly 140 to 220 ° C.
Is preferable because not only the self-heat adhesiveness but also the heat adhesiveness to other materials becomes good.

The thickness of the heat-sealing layer is preferably 1/500 to 1/3, more preferably 1/300 to 1/5, based on the total thickness. The heat seal layer may be either a single area layer or a double sided laminate.

The heat seal layer is preferably composed of polyester, and the composition of the polyester is
As acid components, aromatic dicarboxylic acid components such as terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, benzophenone dicarboxylic acid, and fats such as sebacic acid and dimer acid Group dicarboxylic acid components and ester-forming derivatives thereof, and the like. As the glycol component, one or more glycol components selected from aliphatic, alicyclic and aromatic diols having 10 or less carbon atoms, preferably Are 1,4-butanediol and ethylene glycol. For example, isophthalic acid-copolymerized polybutylene terephthalate and dimer acid-copolymerized polybutylene terephthalate can be preferably used.

Particularly, in order to improve aging and heat sealability, the polyester contains a long chain aliphatic dicarboxylic acid unit having an alkylene group having 8 or more carbon atoms in an amount of 5 to 30 mol% based on the total acid component. It is preferable that the 1,4-butanediol unit is contained in an amount of 80 mol% or more based on all diol components. The long-chain aliphatic dicarboxylic acid having an alkylene group having 8 or more carbon atoms is, for example, sebacic acid, dodecanedioic acid, hexadecadioic acid, octadecadioic acid, nonadecadionic acid, eicosandioic acid, heneicosandioic acid. , Docosandionate, tricosandionate, tetracosandionate, pentacosandionate, hexacosandionate, heptacosandionate, octacosandionate, nonacosandionate, triacontandionate and their ester-forming derivatives Examples thereof include dimer acid obtained by dimerizing an unsaturated fatty acid having 8 to 25 carbon atoms, a hydrogenated product thereof, and an ester-forming derivative thereof. In particular, those containing a dimer acid component are preferable because of their excellent transparency and heat sealability.

The elongation at break of the polyester film of the present invention is preferably 50% or more, more preferably 100%.
That is all.

Further, the polyester film of the present invention is a crystal nucleating agent, an antioxidant, an anti-coloring agent, a pigment, a dye, an ultraviolet absorber, a releasing agent, an easy-to-use agent, depending on the use, as long as the purpose is not impaired. Lubricants, flame retardants, antistatic agents, inorganic and / or organic particles and the like can be added. The average particle size of the film is 0.
Inorganic particles such as silicon oxide, calcium carbonate, and alumina having a diameter of about 01 to 10 μm are added to the polyester in an amount of 0.01 to
It is preferable to contain 5% by weight.

Next, the method for producing the polyester film of the present invention will be described.

First, the method for producing polyester is well known in the art, and any method can be adopted. For example, a direct esterification reaction between a dicarboxylic acid component and a glycol component, or, when using a dialkyl ester of a dicarboxylic acid component, a transesterification reaction with a glycol component, this is heated under reduced pressure to excess glycol component A polyester can be obtained by removing. At this time, if necessary, a transesterification catalyst or a polymerization reaction catalyst may be used, or a stabilizer such as a phosphorus compound may be added. of course,
An anti-coloring agent, an antioxidant, a crystal nucleating agent, a lubricant, a stabilizer, an ultraviolet absorber, an antistatic agent and the like may be added.

The polyester film as in the present invention is
It may be produced by any method within the range specified in the present invention, but is most preferably produced by coextrusion. For example, in the case of a two-layer structure, that is, a layer A and a layer B, the respective polyesters are merged and laminated in the polymer channel between the melt extruder and the die, but are merged and laminated upstream of the die (for example, a manifold). Preferably. That is, the polyesters constituting the A layer and the B layer, which are supplied after drying to separate melt extruders and heated to a temperature higher than the melting point of each polyester, and melted, are produced by a merging device provided between the extruder and the outlet of the die. In a molten state, they are laminated so as to have a predetermined thickness ratio, and are extruded from a slit-shaped mouthpiece outlet. The molten laminate is cooled on a rotary cooling drum to obtain a substantially amorphous unstretched film. When cooling on a rotary cooling drum, from the point of uniformity of thickness, the electrostatic cast method and Japanese Patent Publication No. 5-83063 are used.
It is preferable to adopt the liquid casting method described in the publication. A known apparatus can be applied to the melt extrusion apparatus, but an extruder is preferable because it is simple.

Here, the base layer is extruded containing a colorant together with the polyester. The film obtained as described above, if necessary, corona discharge treatment, chemical treatment, flame treatment, ultraviolet treatment, plasma treatment,
You may perform various surface treatments, such as coating.

[0027]

[Characteristic Evaluation Method and Measuring Method] The characteristics of the polyester film were measured and evaluated by the following methods.

(1) Intrinsic viscosity O-chloroferrol was used as a solvent and measured at 25 ° C. The unit is dl / g.

(2) Melting point (Tm), glass transition temperature (T
g) Differential scanning calorimeter DSC-2 (manufactured by Perkin Elmer)
It measured using. The mixture was melted and maintained at 280 ° C. for 5 minutes under a nitrogen stream, and then cooled using liquid nitrogen. When the sample thus obtained was heated at a heating rate of 10 ° C./min, the change in specific heat based on the transition from the glass state to the rubber state was read, and this temperature was measured as the glass transition temperature (T
g). In addition, the endothermic peak temperature based on crystal melting was defined as the melting point (Tm).

(3) Mechanical Properties Regarding tensile modulus and elongation at break, ASTM D-88
It measured according to the 2-81 (A) method.

(4) Film Haze The film was measured according to JIS-K-6714 and converted to a thickness of 100 μm by the following formula.

H ₁₀₀ (%) = (H / d) × 100 where H is the measured haze value (%), and d is the film thickness (μm) of the haze measurement portion.

(5) Optical density films are piled up so as to have a thickness near 150 μm,
The transmission density is measured by an optical densitometer (TR927 manufactured by Macbeth Co.). Plot thickness and optical density, 150μ
The optical density corresponding to the thickness of m was determined.

(6) Concealability The film was placed on a paper on which characters were written, and the appearance of the characters was judged according to the following criteria.

◎: The character is not visible at all ○: Something is slightly visible △: The character cannot be read, but something like the character is visible ×: The character is clearly visible

(7) Heat-sealability Films are kept at 180 ° C., 3 kg / mm ² , heating time 5
The sealing force when sealing in seconds was judged according to the following criteria.
The sealing force was measured at a sample width of 10 mm and a pulling speed of 200 mm / min.

◯: Sealing force 1.0 kg / cm or more Δ: Sealing force 0.6 kg / cm or more but less than 1.0 kg / cm ×: Sealing force less than 0.6 kg / cm

[0038]

The present invention will be described in detail below with reference to examples.

Example 1 Polybutylene terephthalate / dodecanedicarboxylic acid (hereinafter abbreviated as D) copolymer (D component amount = 13 mol%, melting point = 210 ° C., IV = 0.80) Resin 5 kg 150
After vacuum drying at ℃ for 3 hours, add 5 kg of rutile-type titanium oxide (average particle size 0.25 μm), supply to a counter-rotating twin-screw extruder, melt at 300 ° C., extrude from a 3 mmφ die, and quench. It was cut into pellets to obtain a polyester containing a colorant.

The polyester thus obtained is used as a core layer (A
Layer) and a polybutylene terephthalate / hydrogenated dimer acid (hereinafter abbreviated as DA) copolymer (DA component amount = 17 mol%, melting point = 190 ° C., IV = 0.80) on the surface layer (B layer).
Melt and extrude the resin using different extruders, and adjust to B / A / B (stacking ratio 1: 60: 1) in the die.
Laminated in layers and extruded into 150 μm sheets.

The film thus obtained was flexible with a tensile modulus of elasticity of 90 kg / mm ² , as shown in Table 1, and had good concealing properties and heat sealing properties.

Comparative Example 1 The colorant-containing polyester obtained in the same manner as in Example 1 was melt-extruded by itself to obtain a 150 μm single-film film. As shown in Table 2, the obtained film had no heat-sealing property and was poor in processability.

Examples 2 to 4 and Comparative Examples 2 to 4 As shown in Table 1, Table 2 and Table 3, except that the thickness of the film, the composition ratio and the addition amount of the colorant were changed. A film was prepared in the same manner as in Example 1.

As is clear from Tables 1, 2 and 3, the polyester film of the present invention is excellent in all of hiding power, flexibility and heat sealability.

Comparative Example 5 Polyethylene terephthalate polymer and polypropylene polymer were blended in a ratio of 8: 2 and melt extruded 150 μm.
I got a film. The obtained film was extremely hard as shown in Table 3 and had poor workability and handleability.

Example 5 In Example 1, the heat-sealable polyester was a polybutylene terephthalate / isophthalic acid (hereinafter abbreviated as I) copolymer (component I = 35 mol%, melting point 160 ° C., I).
V = 0.78) A film was obtained in the same manner as in Example 1 except that the resin was used. The obtained film had good flexibility, hiding power and heat sealability as shown in Table 2.

[0047]

[Table 1]

[Table 2]

[Table 3]

[0048]

The white polyester film of the present invention is
Not only it has flexibility and heat sealability, but also has excellent concealing properties, so that it can be used in applications requiring concealing properties such as decorative films and other construction material films.

Claims (4)

[Claims] 1. A polyester film having a heat-sealing layer on at least one side, and a tensile elastic modulus of 1 to 150 kg.
/ Mm ² , the optical density is 0.7 or more and 1.6 or less, and is substantially non-oriented, a white polyester film. 2. The white polyester film according to claim 1, wherein at least 60 mol% or more of the repeating units of the polyester film are constituted by butylene terephthalate units. 3. The white polyester film according to claim 1, wherein the polyester film contains white inorganic particles selected from titanium oxide, zinc oxide, zinc sulfate and lithopone. 4. The heat-sealing layer comprises a long-chain aliphatic dicarboxylic acid unit having an alkylene group having 8 or more carbon atoms in an amount of 5 to 30 mol% with respect to the total acid component, and a 1,4-butanediol unit in the total diol component. The white polyester film according to claim 1, wherein the white polyester film contains 80 mol% or more.