JP3314823B2 - Easy-to-adhesive void-containing polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when used in labels, posters, recording paper, packaging materials, etc., contains a large amount of fine cavities inside a film with improved surface peel strength, opacity, whiteness, etc. And a polyester film having good adhesion to both hydrophilic and hydrophobic resins.

[0002]

2. Description of the Related Art Synthetic paper, which is a paper substitute made of synthetic resin as a main raw material, has a higher water resistance, a greater moisture absorption dimensional stability, and a higher stability than natural paper.
Excellent in surface stability, gloss and sharpness of printing, mechanical strength, etc. In recent years, application development utilizing these advantages has been promoted. As a method for obtaining a film having a function similar to paper made of polyester as a main raw material, a method of containing a large amount of fine cavities inside the film can provide a point that the film itself can be reduced in weight and impart appropriate flexibility. ,
There is an advantage that clear printing and transfer become possible.

[0003] As a method of forming fine cavities inside a film, conventionally, a polymer incompatible with polyester is melt-kneaded with an extruder, and a sheet in which the polymer is dispersed in fine particles in polyester is obtained. A method of generating a cavity around fine particles by stretching is disclosed. Examples of the polymer incompatible with the polyester used for the cavity (hereinafter, referred to as a cavity developing agent) include polyolefin resins (for example, JP-A-49-13).
No. 4755) and polystyrene resins (for example, JP-B-49-2016 and JP-B-54-29550) are preferable.

Conventional void-containing polyester films have excellent properties such as lightness, concealment, and stiffness. However, the void-containing polyester film has good adhesiveness to both hydrophilic and hydrophobic resins. There was no polyester film contained.

[0005]

[SUMMARY OF THE INVENTION The present invention, the disadvantages, i.e., by suitability of the distribution cavity, printing or printing, copying, etc. There are vivid and durable, concealing property and whiteness, It is an object of the present invention to provide a substrate having excellent surface strength and good adhesion to both hydrophilic and hydrophobic resins.

[0006]

That is, the present invention provides a polyester layer containing fine cavities formed by at least uniaxially orienting a polymer mixture of a polyester and a thermoplastic resin incompatible with the polyester. on at least one surface of (a), the thermoplastic layer of the resin (B) void-containing polyester film having a (C), further, its
An easily adhesive void-containing polyester film obtained by laminating a mixture of a water-soluble resin and a water-insoluble polyester copolymer on at least one side of
the void content contained up to 8 μm is 8% by volume or less;
The present invention relates to an easily-adhesive void-containing polyester film, wherein the average void content of the film (C) is 10% by volume or more and 50% by volume or less.

The polyester of the present invention and a polymer mixture obtained by mixing the polyester with an incompatible thermoplastic resin may be obtained, for example, by mixing chips of each resin, melt-kneading in an extruder, and then extruding and solidifying. A method obtained by kneading both resins with a kneading machine in advance, and a method of solidifying by extruding the mixture further by an extruder, or adding a thermoplastic resin incompatible with polyester in a polyester polymerization step, stirring and dispersing. It can also be obtained by a method of melt-extruding the chips obtained and solidifying them.

[0008] To the polymer mixture, a coloring agent, a light-proofing agent, a fluorescent agent, an antistatic agent and the like can be added according to the use. The obtained polymer mixture is further stretched between rolls having different speeds (roll stretching), stretched by gripping and spreading with a clip (tenter stretching), or stretched by air pressure (inflation stretching). At least one axis orientation treatment is performed by such as. By the orientation treatment, peeling occurs at the interface between the polyester and the cavity developing agent, and cavities are developed.

Therefore, the amount of the thermoplastic resin which is incompatible with the polyester and which is mixed with the polyester depends on the amount of the target cavity, but is preferably 3% by weight to 35% by weight based on the whole polymer mixture. . If the content is less than 3% by weight, there is a limit in increasing the amount of cavities formed, and the desired flexibility, lightness and drawing property cannot be obtained. Conversely, 40
If the amount is more than the weight percentage, the heat resistance and strength of the polyester film are significantly impaired.

The conditions for orienting the polymer mixture are closely related to the formation of cavities. Therefore, the conditions for achieving this object are, for example, the most commonly performed sequential biaxial stretching step, for example, taking a continuous sheet of the polymer mixture as a roll in the longitudinal direction and then stretching in the width direction. In the case of the sequential biaxial stretching method in which tenter stretching is performed, the following is performed. In the roll stretching, it is preferable that the temperature is not higher than the biaxial stretching temperature of the polyester + 30 ° C. and the magnification is 1.2 to 5 times in order to generate many cavities. In tenter stretching, the temperature is set to 80 to 140 for stable film formation without breaking.
It is preferable that the temperature and the magnification are 1.2 to 5 times.

[0011] The void-containing film subjected to the stretching orientation treatment is
When heat setting is performed at 30 degrees or more, preferably 180 degrees or more, dimensional stability at high temperatures can be improved. In the present invention, a so-called composite film in which a surface layer and a center layer are laminated must be used. The method is not particularly limited. However, in consideration of productivity, the raw materials of the surface layer and the center layer are extruded from separate extruders, guided to one die to obtain an unstretched sheet, and then oriented at least uniaxially.
Lamination by the so-called coextrusion method is most preferred.

The void-containing polyester film thus obtained has a void content of not more than 8% by volume in the layer from the surface of the layer A to a depth of 3 μm, and an average void content of the entire layer of 10% by volume. It is necessary to be above. When the thermoplastic resin B layer is not provided, or when the surface layer from the surface of the layer A to the depth of 3 μm contains more than 8% by volume of cavities, a material having particularly good surface strength cannot be obtained. The thickness of the surface layer portion of the cavity ratio A layer be not more than 8% by volume 3
When the thickness is smaller than μm , a material having particularly good surface strength cannot be obtained. If the average porosity of the entire film layer is less than 10% by volume , the flexibility inherent in the void-containing polyester film becomes insufficient, and the drawing properties and cushioning properties also become insufficient.

In order to reduce the amount of cavities only in the surface layer of the layer A, it is effective to make the dispersed particles of the thermoplastic resin in the polymer mixture finer near the surface of the layer A than at the center. It can be obtained by selecting the melt viscosity characteristics of the polyester and the thermoplastic resin and the conditions for melt extrusion from an extruder. Examples of the water-soluble polymer used in the present invention include polyvinyl alcohol, polyvinyl methyl ether, vinyl methyl ether / cobolimer maleic anhydride, polyvinyl pyrrolidone, polyvinyl sulfone, polyacrylic acid, polyacrylamide, polyethylene oxide, gelatin, casein, methyl cellulose, ethyl cellulose, Carboxymethylcellulose,
Examples include, but are not limited to, alginic acid-modified starch and starch. These water-soluble polymers can be arbitrarily selected according to the requirements of various adhesive properties and other properties.

[0015] The polyester copolymer of the present invention, 0.5 to 15 mol% of a dicarbonic acid containing a metal sulfonate, and 85 to 9 mol% of a dicarponic acid containing no metal sulfonate.
A substantially water-insoluble polyester copolymer obtained by reacting a mixed dicarponic acid with 9.5 mol% with a glycol component. Examples of the sulfonic acid metal base-containing dicarponic acid include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2.7-dicarponic acid, and 5 [4-sulfophenoxy] isophthalic acid. Metal salts, and particularly preferred is 5
-Sodium sulfoisophthalic acid and sodium sulfoterephthalic acid.

As the dicarponic acid containing no sulfonic acid metal base, aromatic, aliphatic and alicyclic dicarponic acids can be used. Examples of aromatic dicarponic acids include terephthalic acid, isophthalic acid, orthophthalic acid, and 2.6 naphthalenedicarponic acid. Examples of aliphatic and alicyclic dicarponic acids include succinic acid, adipic acid, sebacic acid, and 1.3.
-Cyclopentanedicarboxylic acid, 1.2-cyclohexanedicarboxylic acid, 1.4-cyclohexanedicarboxylic acid and the like.

The glycol components to be reacted with the mixed dicarponic acid include ethylene glycol, 1.2-propylene glycol, 1.3-propanediol, and 1.4.
Heptanediol, neopentyl glycol, 1.6-hexanediol, 1.2-cyclohexanedimethanol, 1.3-cyclohexanedimethanol, 1.4-cyclohexanedimethanol, p-xylylene glycol, diethylene glycol, triethylene glycol, etc. is there. Examples of the polyether include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like.

In order to obtain an aqueous dispersion of the polyester copolymer, it is necessary to disperse the polyester copolymer in water together with a water-soluble organic compound. The water-soluble organic compound is, for example, methanol,
1 such as ethanol, isopropanol, n-butanol
Polyhydric alcohols, glycols such as ethylene glycol and propylene glycol, glycol derivatives such as methyl cellosolve, ethyl cellosolp, n-butyl cellosolve, dioxane, ethers such as tetrahydrofuran,
Esters such as ethyl acetate and ketones such as methyl ethyl ketone. These water-soluble organic compounds can be used alone or in combination of two or more.

These raw materials and methods are not limited to the above-mentioned methods, and known ones (for example, JP-A-61-270153) can be used.

[0019]

In the present invention, polyester is used for
This is for satisfying the heat resistance and mechanical strength of the void-containing polyester film. In the present invention, mixing a thermoplastic resin incompatible with the polyester to the polyester, to obtain a polymer mixture, by dispersing fine particles of the thermoplastic resin incompatible with the polyester in the polyester, This is because the nuclei of the cavities generated by the next alignment treatment are formed.

In the present invention, the reason why the thermoplastic resin B layer is provided and the amount of cavities contained in the surface layer portion 3 μm of the A layer is set to 8% by volume or less is that the surface strength is further increased. On the other hand, the reason why the average void content of the entire layer is set to 10% by volume or more is to provide appropriate drawing properties and cushioning properties. In the present invention, to use a water-soluble resin and water insoluble polyester copolymer is order to improve the adhesion of both hydrophilic resin and a hydrophobic resin.

The void-containing polyester film thus obtained satisfies the surface strength required for applications such as posters, labels, thermal transfer papers, printing papers, and image receiving papers and the adhesiveness to hydrophilic resins and hydrophobic resins. Obtained.

[0022]

Next, examples of the present invention will be described. 1) Intrinsic viscosity of polyester The polyester was dissolved in a mixed solvent of phenol (6 parts by weight) and tetrachloroethane (4 parts by weight) and measured at 30 ° C. 2) Melt flow index of polystyrene resin Measured at 200 ° C. under a load of 5 kg according to JIS-K7210. 3) Apparent specific gravity of the film The film was accurately cut into a square of 5.00 cm × 5.00 cm, the thickness was measured at 50 points, and the average thickness was tμ.
m, its weight is measured to 0.1 mg and wg,
The apparent density of the film was calculated by the following equation. Apparent density (g / cm ³ ) = w / (5 × 5 × t) × 10000 The specific gravity of the solid is the density of the solid and the density of water at 4 ° C.
(0.999973 g / cm ³ ) and generally defined as
It is the density of water and substantially 1.00 g / cm ³ Minaseruko
From the apparent density of the film divided by the density of water
And the apparent specific gravity of the film is calculated as follows.

Apparent specific gravity (−) = w / (5 × 5 × t) × 10000

4) Average porosity of film Calculated by the following equation. Cavity content (volume%) = 100 × (1-true specific volume / apparent specific volume)

Where true specific volume = x1 / d1 + x2 / d2 + x3 / d3 +... + Xi / di +.

Apparent specific volume = 1 / apparent specific gravity of film In the above formula, xi represents the weight fraction of the i component, and di represents the true specific gravity of the i component. The values of the true specific gravity used in the calculations in the examples were polyethylene terephthalate 1.40, general-purpose polystyrene 1.05, and anatase-type titanium dioxide 3.9.
Was used.

5) Porosity of Surface Layer of Void-Containing Film A photograph of the vicinity of the surface layer in the cross section of the film taken with a scanning electron microscope, and then tracing the cavities in the region from the surface layer to a depth of 3 μm on the tracing film to fill it out. Was subjected to image processing by an image analyzer, and the porosity was obtained as an area ratio, and this value was directly displayed as volume%. -Scanning electron microscope used Hitachi-S-510 scanning electron microscope-Image analysis processing equipment used Luzex IID (Nireco Corporation)

6) Light transmittance According to JIS-K6714, a Poick integrating sphere formula T.
The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Kogaku). The smaller the value, the higher the concealment property.

7) Surface Peeling Strength Using a cellophane tape (18 mm width, made by Nichiban), the surface peeling strength was evaluated by a cellophane tape peeling test. The peel angle was performed in the direction of about 150 degrees while the cavity-containing film was kept flat. The area was differentiated from the area of the peeled void-containing film as follows. Class 5: The whole has peeled off Class 4: Almost peeled off Class 3 ... About half the peeled off Class 2 ... Almost no peeling Class 1 ... No peeling off at all

Example 1 As a raw material, 80% by weight of a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 was added to a melt flow index of 2.0.
g / 10 minutes Polystyrene for general use 15% by weight, 5% by weight of anatase type titanium dioxide having an average particle diameter of 0.3 μm is used as a raw material of the layer A, and 95% by weight of a polyethylene terephthalate resin and an average particle diameter of 0.3 μm are used as a raw material of the layer B. 5 wt% of rutile-type titanium dioxide is melt-extruded from a T-die at 290 ° C. by another twin screw extruder, and solidified electrostatically on a cooling rotary roll, and each layer is B / A / B
= 30/440/30 µm to obtain an unstretched sheet of a polymer mixture. At this time, the T-die slit interval is 1.0 mm
The average flow rate of the melt of the polymer mixture in that portion is 8.
8 m / sec. Subsequently, the unstretched sheet was longitudinally stretched 3.5 times at 83 ° C. by a roll stretching machine, and then transversely stretched 3.5 times at 130 ° C. by a tenter.
Heat treatment was carried out while relaxing, to obtain a polyester film containing many cavities inside. The thickness is B / A / B = 3 /
44/3 μm. The porosity of the surface layer of layer A of the obtained film was 2% by volume, and the whole was 21% by volume. In addition, a portion with few cavities was present from the surface to a depth of about 3 μm. The surface strength of the void-containing film obtained in this example was class 1.

The cross section of the unstretched sheet of the polymer mixture of the present example was observed with a scanning electron microscope. The average particle size was 0.7 μm. The apparent specific gravity is 1.10, and the porosity of the surface layer of the A layer is 2
The volume%, the total average porosity was 21% by volume, the light transmittance was 13%, and the thickness was 50 μm.

Dimethyl terephthalate was added to this film.
117 parts (49 mol%), dimethyl isophthalate 11
7 parts (49 mol%), diethylene glycol 103 parts (50 mol%), diethylene glycol 58 parts (50 mol%), zinc acetate 0.08 part, antimony trioxide 0.1 part.
08 parts was heated to 40 to 220 ° C. in a reactor and subjected to transesterification for 3 hours, and then 9 parts (2 mol%) of 5-sodium sulfoisophthalic acid was added to add 220 to 260
C. for 1 hour, and then under reduced pressure (10 to 10
A polycondensation reaction was performed at 0.2 mmHg) for 2 hours to obtain a polyester copolymer having an average molecular weight of 18,000 and a softening point of 140 ° C. 300 parts of this polyester copolymer and 140 parts of n-butyl cellosolp were placed in a container at 150 to 170 parts.
C. for about 3 hours to obtain a uniform melt, 560 parts of water was gradually added to the melt, and after about 1 hour, a uniform pale white aqueous dispersion having a solid concentration of 30% was obtained. Further, syloid 150 is added to the polyester copolymer at 500
Dilution by adding 3% by weight of acrylic acid grafted polyethylene glycol having a molecular weight of 20,000 (graft ratio: 20%), 1% of sodium dodecylbenzenesulfonate, 5% of sodium hypophosphite, 4500 parts of water, and 4500 parts of ethyl alcohol Then, after obtaining a coating solution having a solid concentration of 3%, the solution was applied to the above-mentioned void-containing film.

As the PVA and PVC, those obtained by dissolving 10% in water and DMF (dimethylformamide) were colored with a red dye soluble in each solvent. These were printed so as to have a coating amount of 2 g / m ² , and a tape peeling test was performed. In the tape peeling test, a cellophane tape (trade name: L-Pack, manufactured by Nichiban Co., Ltd.) was uniformly applied to the ink printing surface, and then immediately pulled in the 180 ° or 360 ° direction, and the portion where the ink remained remained. 95% or more of the entire seat is indicated by ◎, 50 to 95% is indicated by 、, 10 to 50% is indicated by Δ, and 10% or less is indicated by X. In the examples, PVA and PVC are both excellent in ◎, and the applied film is wound 1000 m.
After being left for 24 hours at 20 ° C. and 65 RH% ↓, rewinding did not result in blocking.

[0034]

The void-containing polyester film of the present invention has the same light weight, flexibility, concealing properties, matting properties, and drawing properties as the conventional void-containing polyester film obtained using polystyrene or polyolefin as a void-generating agent. In addition to having the properties, compared to the conventional void-containing polyester film , excellent opacity, whiteness, surface strength,
In addition, there is an effect that it has good adhesiveness to both hydrophilic and hydrophobic resins. Therefore, the void-containing polyester film of the present invention can be used for labels, posters, recording paper,
Packaging materials, heat-sensitive recording material, can be used in a very wide range of fields, such as photographic paper.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 9/00

Claims (1)

(57) [Claims] At least one surface of a polyester layer (A) containing fine cavities formed by at least uniaxially orienting a polymer mixture of a polyester and a thermoplastic resin incompatible with the polyester. , the void containing polyester film in which a layer (B) comprising a thermoplastic resin (C), further, easy adhesion formed by laminating a mixture of at least one surface in a water-soluble resin and water insoluble polyester copolymer A polyester film having a void content, wherein the void content from the surface of the layer A to 3 μm is 8% by volume or less, and the average void content of the entire film (C) is 10% by volume or more and 50% by volume or less. An easily-adhesive void-containing polyester film, characterized in that: