JP3019394B2 - Void-containing polyester film laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention, when used for labels, posters, recording paper, packaging materials, etc., is applied to the inside of a film with improved wettability and adhesion such as ink and coating agent. The present invention relates to a drawable polyester film containing a large amount of fine cavities.

(Prior art) Synthetic paper, which is a paper substitute made of synthetic resin as a main raw material, is more water-resistant, has greater moisture absorption dimensional stability, better surface smoothness than natural paper.
Excellent printing gloss, sharpness, mechanical strength, etc.

In recent years, application development utilizing these advantages has been promoted.

Polyethylene, polypropylene, polyester, etc. are used as the main raw materials of synthetic paper. Among them, polyester represented by polyethylene terephthalate is excellent in terms of high heat resistance and strong rigidity, and Application development is possible.

As a method for obtaining a film having a function similar to that of paper using polyester as a main raw material, there have been conventionally (1) a method in which fine cavities are contained in a large amount in the film, or (2) sandblasting of a normal flat polyester film. Treatment, (2-2) chemical etching treatment, and (2-3) matting treatment (method of laminating a matting agent together with a binder)
For example, a method of roughening the surface by the method is disclosed.

Among them, the method of (1), in which a large amount of fine cavities are contained in the film, allows the film itself to be reduced in weight and imparts appropriate flexibility, thereby enabling clear printing and transfer. There is an advantage.

As a method to generate fine cavities inside the film,
Conventionally, a thermoplastic resin that is incompatible with polyester is melt-kneaded with an extruder to obtain a sheet in which the polymer is dispersed in fine particles in polyester, and the sheet is further stretched to generate cavities around the fine particles. A method is disclosed.

Examples of the thermoplastic resin that is incompatible with polyester used for generating cavities (hereinafter referred to as a cavitation developing agent) include polyolefin-based resins (for example, JP-A-49-134755) and polystyrene-based resins (for example, JP-B-49-134). Many proposals have been made, such as Japanese Patent Publication No. 2016, Japanese Patent Publication No. 54-29550, and polyarylate resin (for example, Japanese Patent Publication No. 58-28097).

Certainly, this method is a useful method for generating fine cavities inside the film, but it depends on the thermal decomposition product of the thermoplastic resin used as the cavity developing agent and the additives added to the thermoplastic resin. The resulting void-containing polyester film has a drawback that when performing post-processing such as printing and printing, repelling and unevenness of the ink and the coating liquid occur. Further, there is a disadvantage that the adhesive of the ink and the coating agent is insufficient.

(Problems to be Solved by the Invention) The present invention improves printing, printing, copying and the like by improving the above-mentioned drawbacks, that is, poor wetting and poor bonding of ink and coating agent on the surface of the void-containing polyester film. It is an object of the present invention to provide a clear and durable base material suitable for labels, posters, recording paper, and the like.

(Means for Solving the Problems) That is, the object is to provide a fine cavity produced by orienting at least uniaxially a composition mainly composed of polyester and a thermoplastic resin insoluble in polyester. In a polyester film having a large number of voids, at least one side of a non-oriented polyester film or a uniaxially oriented polyester film extruded by melt extrusion is subjected to an active energy irradiation treatment excluding a corona discharge treatment to reduce the contact angle of the film surface with water. It can be achieved by a void-containing polyester film laminate obtained by forming a coating layer on the treated surface at 90 ° or less, and further biaxially or uniaxially stretching this coating film.

The polyester referred to in the present invention is terephthalic acid, isophthalic acid, an aromatic dicarboxylic acid such as naphthalenedicarboxylic acid or an ester thereof and ethylene glycol, diethylene glycol, 1,4-butanediol, polycondensed with a glycol such as neopentyl glycol. It is a manufactured polyester. These polyesters are produced by directly reacting an aromatic dicarboxylic acid and a glycol, and are also subjected to a transesterification reaction between an alkyl ester of an aromatic dicarboxylic acid and a glycol followed by polycondensation or a dicondensation of an aromatic dicarboxylic acid. It is produced by a method such as polycondensation of a glycol ester. Representative examples of such polyesters include polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate. This polyester may be a homopolymer or a copolymer of the third component. In any case, in the present invention, a polyester having ethylene terephthalate unit, butylene terephthalate unit or ethylene-1,4-naphthalate unit of 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is preferable. .

The thermoplastic resin (B) insoluble in the polyester used in the present invention can be used without limitation as long as it is insoluble in the polyester described above. Those having good stability are preferred.

Specifically, polyethylene, polypropylene, polyolefin resins such as polymethylpentene, copolymerized polyolefin resins such as ionomer resin EP rubber, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer and the like Polystyrene resins, polyarylate resins, polycarbonate resins, polyacrylonitrile resins and the like can be mentioned. Among these, polyolefin-based resins and polystyrene-based resins are particularly preferred.

A polymer mixture obtained by mixing the polyester of the present invention and a thermoplastic resin insoluble in the polyester is, for example,
It is obtained by mixing and melting and kneading each resin chip in an extruder, and then extruding and solidifying. In addition to this, the mixture obtained by kneading both resins with a kneading machine in advance is further melt-extruded from an extruder and solidified, or a thermoplastic resin insoluble in polyester is added in the polyester polymerization step, and the mixture is stirred and dispersed. It can also be obtained by, for example, a method of melt-extruding the chips obtained and solidifying them. The polymer obtained by solidification is usually in a non-oriented or weakly oriented state. Further, a thermoplastic resin insoluble in the polyester is dispersed in the polyester in various shapes such as a spherical shape, an elliptical spherical shape, and a thread shape. The dispersion diameter is spherical and 0.1 to 30 μm in diameter. Pigments, colorants, light stabilizers, fluorescers, antistatic agents and the like can be added to the polymer mixture depending on the application. The polymer mixture thus obtained is further stretched between rolls having different speeds (roll stretching), stretched by gripping and expanding with clips (tenter stretching), or stretched by air pressure (inflation stretching). At least one axis orientation treatment is performed by such as. At this time, separation occurs at the interface between the dispersed polyester-insoluble thermoplastic resin and the polyester, and a large number of cavities are generated in the polymer mixture.

Therefore, although the amount of the thermoplastic resin insoluble in the polyester to be mixed with the polyester varies depending on the amount of the target cavity, the amount of the thermoplastic resin is 1 to the entire polymer mixture.
% By weight to 35% by weight is preferred. If the amount is less than 1% by weight, there is a limit in increasing the amount of voids generated, and the desired flexibility, lightness and drawing property cannot be obtained. Conversely, if the content is 40% by weight or more, the heat resistance and strength of the polyester film are significantly impaired.

The conditions for orienting the polymer mixture are also closely related to the formation of cavities. For example, the most commonly performed sequential biaxial stretching step is exemplified by a sequential biaxial stretching method in which a continuous sheet of the polymer mixture is roll-stretched in the longitudinal direction and then tenter-stretched in the width direction. The stretching temperature is
The stretching ratio is preferably from 50 to 140 ° C. and 1.2 to 5 times, and the tenter stretching temperature is preferably from 60 to 150 ° C. and the scaling ratio is preferably from 1.2 to 5 times. Further, the cavity-containing film subjected to the stretching orientation treatment is 130 ° C. or more, preferably 1 ° C.
Performing heat setting at 80 ° C. or higher can improve dimensional stability at high temperatures.

In addition, the film containing cavities oriented only in the uniaxial direction,
It is useful for shrinkable films and easily tearable films.

Since the present invention relates to a void-containing polyester film in which voids are generated by an orientation treatment, it is necessary to orient at least one axis.

In the present invention, at least one side of the unoriented polyester film or the uniaxially oriented polyester film melt-extruded in the above method is subjected to an active energy irradiation treatment, and the contact angle of the film surface with water to 90 ° or less,
It is necessary to provide a coating layer on the treated surface, and to further biaxially or uniaxially stretch this coating film.

If the contact angle with water exceeds 90 °, the coating layer will be repelled during the coating process, making uniform coating difficult.In addition, in the final product, a void-containing polyester film laminate, adhesion to printing inks and coating agents, etc. It is not preferable because the property is lowered.

The active energy irradiation treatment, which is a means for reducing the contact angle with water to 90 ° C. or less, includes an ultraviolet irradiation treatment, a plasma treatment, an electron beam irradiation treatment, and the like. Irradiation processing, electron beam irradiation processing and the like are easy to perform continuous processing. In particular, the UV irradiation treatment is continuous,
This is advantageous in terms of economic efficiency such as productivity. The ultraviolet irradiation treatment can be performed not only in ordinary air but also in a specific atmosphere such as nitrogen gas or carbon dioxide gas. Depending on the type of the coating layer, the treatment under another gas atmosphere such as nitrogen gas may be preferable.

In the present invention, as the compound constituting the coating layer, a polyester-based resin is more preferable because the recovery layer can be reused.In addition, a polyurethane-based resin, a polyester-urethane-based resin, and an ordinary polyester film such as an acrylic-based resin can be used. The compounds disclosed as means for improving the adhesiveness can be applied. In particular, use of a water-soluble resin, a water-emulsifiable resin and a water-dispersible resin is preferred. As the method for providing the coating layer, a method generally used such as a gravure coating method, a kiss coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, a reverse roll coating method, or the like can be applied. . The thickness of the coating layer varies depending on the intended level, but is usually 0.01 to 10 μm. A coloring agent, a matting agent, an antistatic agent, an ultraviolet absorber, a cross-linking agent, and the like can be appropriately added to the coating layer according to the purpose.

The void-containing polyester film thus obtained and the laminate thereof have significantly improved wettability and adhesive properties such as ink as compared with the conventionally proposed void-containing polyester film using polystyrene or polypropylene as a void developing agent. When the void-containing polyester film of the present invention is used as a base material, labels, posters, recording paper, packaging materials, etc. can be printed, printed and copied, and have excellent durability and laminate strength. Can be

(Examples) Next, examples and comparative examples of the present invention will be described.

 The measurement / evaluation method used in the present invention will be described below.

1) Intrinsic viscosity of polyester 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) Amount of n-hexane extractables in polystyrene resin 10 g of polystyrene resin was extracted with n-hexane for 24 hours using a Soxhlet extractor, then n-hexane was evaporated to dryness and extracted from the remaining amount. % By weight was determined.

3) Melt flow index of polystyrene resin Measured at 200 ° C under a load of 5 kg according to JIS K-7210.

4) Melt flow index of crystalline polypropylene resin Measured at 230 ° C under a load of 2.16 kg according to JI K-6758.

5) Apparent specific gravity of the film The film is accurately cut out into a square of 5.00 cm × 5.00 cm, its thickness is measured at 50 points, the average thickness is tμm, the weight is measured up to 0.1 mg, and it is defined as wg. Calculated.

 Apparent specific gravity (-) = W / 5 x 5 x t x 10000 6) Cavity content of film Film was calculated by the following formula.

Void content (vol%) = 100 × (1-true specific volume / apparent specific volume) wherein True specific volume _{= x 1 / d 1 + x} 2 / d 2 + x 3 / d 3 + ... + x 1 / d ₁ +… Apparent specific volume = 1 / In the apparent specific gravity equation of film
x ₁ is the weight fraction of the i component, d ₁ represents the true specific gravity of component i.

The value of the true specific gravity used in the calculations in the examples is polyethylene terephthalate 1.40, anatase type titanium dioxide.
3.90, a general-purpose polystyrene resin 1.05, and a crystalline polypropylene resin 0.91 were used.

7) Concealment of Film Containing Cavities The light transmittance of the film was measured using a Poic integrating sphere HTR meter (manufactured by Nippon Seimitsu Kogaku) in accordance with JIS K6714. The smaller this value is, the higher the concealment property is. When a commonly used electrostatic copying valve paper was measured, it was 27%.

8) Surface roughness Using a Surfcom 300A type surface roughness meter (manufactured by Tokyo Seimitsu), stylus diameter 2 μm, stylus pressure 30 mg, measurement length 2.5 mm, cutoff 0.8.
The center line average thickness was measured in mm.

If this value is too small, the surface is smooth and the drawing property is lost, resulting in a glossy film. Conversely, if it is too large, the surface will be too rough, causing drawbacks such as printing and missing prints.

9) Drawability by Pencil A hand-drawn drawing of the film containing cavities was judged using a mechanical pencil using a uni-pen 100-100HB mechanical pencil (manufactured by Mitsubishi Pencil).

10) Contact angle measuring instrument in an atmosphere with a water contact angle of 20 ° C and 60% relative temperature
The contact angle of water was measured using CA-A (manufactured by Kyowa Kagaku). The smaller the value, the better the wettability of the surface of the cavity-containing film with the aqueous ink and the polar solvent-based ink.

11) Repelling after applying water-based ink Water-based ink Aqua Color 39 indigo (manufactured by Toyo Ink Manufacturing Co., Ltd.)
With a gravure coater, the thickness of the ink layer after drying is 3μ.
Was applied on the film containing cavities and dried, and then the repelling of the ink was visually observed to determine the presence or absence of the repelling.

12) Water-based ink cellophane stripping test Using the water-containing ink obtained in the above step 11) and drying the void-containing film, the adhesiveness between the water-based ink and the void-containing film was examined by a cellophane stripping test.

The cutting angle was set at about 150 degrees while the cavity-containing film was kept flat.

After peeling, the remaining area of the ink was measured with an image processing apparatus Luzex IID (manufactured by NIRECO), and the surface was expressed in%. It is considered that the larger this value is, the stronger the adhesive force between the hollow film and the ink is.

Production Example 1 A) Preparation of Coating Solution The dicarboxylic acid unit is composed of 50 mol% of terephthalic acid, 45 mol% of isophthalic acid and 5 mol% of 5-sodium sulfoisophthalic acid, and the glycol unit is composed of 80 mol% of ethylene glycol. And a sulfonic acid-modified polyester (molecular weight: about 20,000) composed of 20% by mole of neopentyl glycol. This polyester was dispersed in water at a ratio of 10% by weight to prepare a coating liquid.

B) Preparation of laminated film As raw materials, (1) 82% by weight of polyethylene terephthalate resin having an intrinsic viscosity of 0.62, (2) 8% by weight of anatase type titanium dioxide and (3) n-hexane extractable at a melt flow index of 3.0 g / 10 minutes. 10 wt% of general-purpose polystyrene having an amount of 4.5 wt% is melt-extruded from a T-die at 285 ° C. by a twin screw extruder, solidified electrostatically on a cooling rotating roll, and subsequently heated to 80 ° C. by a roll stretching machine. To stretch 3.0 times. The surface of the stretched film is subjected to corona discharge treatment, and the coating liquid prepared in A) is applied to the corona discharge treated surface by an air knife method, dried with hot air at 70 ° C., and then 3.2 times at 130 ° C. with a tenter. The film was stretched and heat-set at 220 ° C. to obtain a white polyester film having a thickness of 57 μm (resin composition layer: 0.20 μm).

Comparative Example 1 Table 1 shows the properties of the polyester film obtained by the same method as in Production Example 1 except that the corona discharge treatment was canceled in the method of Production Example 1.

In this comparative example, it was difficult to obtain a uniform coating film due to poor wettability of the coating liquid. Further, the obtained film had extremely poor adhesive strength.

Comparative Example 2 Table 1 shows the properties of the polyester film obtained by the same method as in Production Example 1 except that the application of the coating liquid was stopped by the method of Production Example 1.

The film obtained in this comparative example had extremely poor adhesive strength.

Comparative Example 3 Table 1 shows the properties of the polyester film obtained by the same method as in Production Example 1, except that the blending of polystyrene was stopped by the method of Production Example 1, and the blending amount of polyethylene terephthalate was increased accordingly.

The film obtained in this comparative example had good adhesive strength, but had a low void content of 1%, and could not be drawn with a pencil.

Example 1 A) Preparation of Coating Liquid In the same manner as in Production Example 1, the reaction time was shortened.
A 10% aqueous dispersion of a sulfonic acid-modified polyester having a molecular weight of 4000 was prepared. After 100 parts by weight of this polyester is dissolved in 72 parts by weight of methyl ethyl ketone and 72 parts by weight of toluene, 21 parts by weight of 4,4'-diphenylmethane diisocyanate and 0.05 parts by weight of dibutyltin dilaurate are added to the solution, and the mixture is heated to 70 to 80 ° C. For 3 hours. The solvent was evaporated to obtain an aqueous dispersion containing the polyester polyurethane.

The dispersion was diluted with a water-ethanol mixture to obtain a solid component concentration of 8%.
A coating solution of weight% was obtained.

B) Preparation of Laminated Film The method of Production Example 1 was changed to use crystalline polypropylene having a melt flow index of 2.5 g / 10 minutes instead of polystyrene, and to perform ultraviolet irradiation treatment instead of corona discharge treatment. Table 1 shows the characteristics of the film obtained in the same manner as in Production Example 1 except for the above.

 Table 1 shows the properties of the obtained film.

The film obtained in this example was of high quality.

Comparative Example 4 The characteristics of the film obtained by the same method as in Example 1 except that the ultraviolet irradiation treatment was canceled in the method of Example 1 are shown in Table 1.
Shown in

In this comparative example, it was difficult to obtain a uniform coating film due to poor wettability of the coating liquid. Further, the obtained film had extremely poor adhesion.

Production Example 2 A) Preparation of coating liquid In an autoclave equipped with a thermometer and a stirrer, 485 parts by weight of dimethyl terephthalate, 485 parts by weight of dimethyl isophthalate, 409 parts by weight of ethylene glycol, 485 parts by weight of neopentyl glycol, and tetrabutoxy were used. 0.68 parts by weight of titanate was charged, and the mixture was heated at 150 to 230 ° C. for 120 minutes to perform transesterification. Then, 50.1 parts by weight of the phosphorus-containing compound ((III) -2-2) described in this specification was added, and
The reaction was carried out at 0 ° C. for another hour. The temperature of the reaction system was raised to 250 ° C. in 30 minutes, the pressure of the system was gradually reduced to 10 mmHg after 45 minutes, and the reaction was continued under these conditions for another 60 minutes.
The molecular weight of the obtained polyester diol A was 2500 and the phosphorus content was 1600 ppm.

Next, 100 parts by weight of the polyester diol A was dissolved in 72 parts by weight of toluene and 72 parts by weight of methyl ethyl ketone, and 21 parts by weight of 4,4'-diphenylmethane diisocyanate and 0.05 part by weight of dibutyltin dilaurate were added, and 70 parts by weight were added.
The mixture was reacted at -80 ° C for 3 hours to obtain a phosphorus-containing polyurethane.

300 parts by weight of the phosphorus-containing polyurethane and 140 parts by weight of n-butyl cellosolve were stirred in a vessel at 150 to 170 ° C. for about 3 hours to obtain a uniform and viscous melt. 560
Parts by weight were gradually added, and after about 1 hour, a uniform pale white aqueous dispersion (solid content: 30%) was obtained.

The aqueous dispersion was diluted with a water-isopropanol mixture to obtain a coating liquid having a solid content of 7.5% by weight.

B) Preparation of laminated film In the method of Production Example 1, except that the blending of the anatase type titanium dioxide was stopped, the blending ratio of the polyethylene terephthalate resin was increased accordingly, and the coating liquid was changed to that prepared in the above A). A film was obtained in the same manner as in Production Example 1.

Comparative Example 5 Table 1 shows the properties of the polyester film obtained by the same method as in Production Example 1 except that the corona discharge treatment was canceled in the method of Production Example 2.

The film obtained in this comparative example had extremely poor adhesive strength.

Production Example 3 A) Preparation of coating liquid In a 2 liter four-necked flask equipped with a reflux condenser, 650 g of water and, among the monomers shown in the above table (350 g in total), the total amount of sodium vinyl sulfonate and each one-fifth of the other monomers , 0.85 g of dodecyl mercaptan and a quarter of potassium persulfate (solvent: 0.2 g in total) were charged. The temperature was raised to 80 ° C. while stirring under a nitrogen stream, and the remaining monomer and solvent were gradually added at the same temperature over 1 hour and 30 minutes. Stirring was continued for another hour at the same temperature to complete the reaction. A milky liquid, homogeneous and stable non-emulsifier latex was obtained. The latex was diluted with water, and the solid content concentration was 7.
A coating solution of 0% by weight was obtained.

B) Preparation of Laminated Film A film was obtained in the same manner as in Production Example 1, except that the coating solution was changed to that prepared in A) above.

(Effect of the Invention) The void-containing polyester film laminate of the present invention is similar to a void-containing polyester film obtained by using a conventional polystyrene or polypropylene as a void developing agent, and is not present in a polyester film containing no ordinary air bubbles. It has lightness, flexibility, hiding properties, matting properties, drawing properties, etc., and has excellent surface wettability compared to conventional void-containing polyester films obtained using conventional polystyrene or polypropylene as a void generating agent. And has adhesiveness. Therefore, the void-containing polyester film laminate of the present invention can be used in a very wide range of fields such as labels, posters, recording paper, and packaging materials, and the resulting products can be expected to be clear and durable.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI // (C08L 67/00 23:00 25:04) (72) Inventor Katsufumi Kumano 2-1-1 Katada, Otsu City, Shiga Prefecture Yoko Nakajima, Examiner at Toyobo Co., Ltd. (56) References JP-A-4-107127 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35 / 00 C08J 7/00-9/00

Claims (1)

(57) [Claims] 1. A composition comprising a polyester and a thermoplastic resin insoluble in the polyester as a main component.
On a cavity-containing polyester film having a large number of fine cavities produced by orienting in an axial direction, at least one surface of a melt-extruded unoriented polyester film or a uniaxially oriented polyester film except for corona discharge treatment is irradiated with active energy. A void-containing polyester film laminate obtained by subjecting the film surface to a contact angle of 90 ° or less with water, providing a coating layer on the treated surface, and further biaxially or uniaxially stretching the applied film.