JPH07119296B2 - White roughened polyester film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a white surface-roughened polyester film and a method for producing the same, more specifically, a polyester resin composition containing a polypropylene resin containing a white inorganic pigment. The present invention relates to a white roughened biaxially stretched polyester film having a Japanese paper-like surface and having improved writing properties and adhesiveness with a wax ink, and a method for producing the same.

<Prior Art> Conventionally, a polyester whitened by adding an inorganic pigment or another kind of polymer has been used in various fields. However, since these polyester films are hard and have a high density, they have the drawback of being poorly handled as a copying material as compared with paper. The surface was also glossy, giving a very low-grade image. In addition, because of its flatness and surface chemistry, the adhesiveness with wax-based ink is insufficient, and if a special treatment is not applied to the surface, printing by a computer, word processor, printer, etc. will easily come off. However, it has a drawback that it is not easy to write with a pencil or ballpoint pen.

On the other hand, the paper that has been widely used as a copy material until now is
It had poor water resistance and mechanical strength, and could not withstand hard use. Further, the surface smoothness and the dimensional stability are poor, and it is unsuitable for the fields demanding more precise and sharp printing such as today. Further, there is also a problem that the fibers on the surface peel off due to peeling with a cellophane tape or the like and the appearance is remarkably impaired. Contamination by the suspension of paper fibers in the air resulting from the fate of being made of fine fibers has prevented the use of paper in places where dust is highly disliked. Although polypropylene synthetic paper is mentioned as a supplement to this aspect, it has a problem of poor heat resistance.

<Object of the Invention> An object of the present invention is to provide a white roughened polyester film having a Japanese paper-like pattern which is suitable as a copying material and which overcomes these drawbacks of conventional white polyester films and papers, and a method for producing the same. Especially.

<Structure / Effect of Invention> According to the present invention, a polyester resin composition containing a white inorganic pigment and a polypropylene resin having a melt flow index of 0.5 to 50 in an amount of 2 to 40% by weight is first described. It is achieved by a white roughened biaxially stretched polyester film which is made of a material and has a Japanese paper pattern.

The polyester referred to in the present invention, an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid or an ester-forming derivative thereof, and a glycol such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol. Is an aromatic polyester produced by polycondensation reaction of

These polyesters are produced by directly reacting an aromatic dicarboxylic acid and a glycol, or by subjecting an alkyl ester of an aromatic dicarboxylic acid and a glycol to transesterification and then polycondensation, or an aromatic dicarboxylic acid. It can also be produced by a method such as polycondensing a bisglycol ester. Typical examples of such polyesters include polyethylene terephthalate and polyethylene-
2,6-naphthalate, polybutylene terephthalate, etc. may be mentioned.

This polyester may be a homopolymer or a copolymer of a third component. In any case, in the present invention, a polyester having an ethylene terephthalate unit and / or an ethylene-2,6-naphthalate unit and / or a butylene terephthalate unit in an amount of 70 mol% or more, preferably 80 mol% or more, and more preferably 90 mol% or more. Is preferred.

Further, in the present invention, if the polymerization degree of the polyester is too low, the mechanical strength is lowered, so that the intrinsic viscosity (orthochlorophenol, 35 ° C.) is 0.4 or more, preferably 0.5 to
It is preferably 1.2, more preferably 0.55 to 0.85.

The polypropylene resin referred to in the present invention may be a homopolymer or a copolymer as long as it has a melt flow index of 0.5 to 50, preferably 0.5 to 15. Of these, homopolymers are preferred. When the melt flow index is out of the above range, the Japanese paper-like pattern is broken or the film-forming property is deteriorated, which is not preferable.

In the present invention, the polypropylene resin is blended with the polyester, but before this, it is necessary to previously contain (for example, kneading) the white inorganic pigment in the polypropylene resin. Typical examples of the white inorganic pigment include titanium oxide, barium sulfate, silicon oxide, talc, calcium carbonate, magnesium oxide and the like. The average particle size of these inorganic pigments is preferably 0.3 μm to 6 μm.

The polypropylene resin containing a white inorganic pigment is mixed with the polyester in an amount of 2 to 40% by weight, preferably 5 to 35% by weight, based on the total amount of the polyester. When the amount of polypropylene resin is less than 2% by weight, the expression of Japanese paper pattern is not sufficient, while when it exceeds 40% by weight, the film-forming property is significantly impaired. The polyester and the polypropylene resin can be mixed with each other, and the white inorganic pigment and the polypropylene resin can be mixed with each other by a known mixing method, but it is preferable that the mixing is performed by a melt kneading method.

The polyester resin composition thus obtained is subjected to film formation to obtain the polyester film of the present invention. The film formation is preferably carried out by the following method.

First, polypropylene resin and white inorganic pigment are melt-kneaded by a uniaxial or biaxial extruder. The concentration of the inorganic pigment at this time varies depending on the type of the inorganic pigment, but is usually 2 to 80.
It is selected from the range of weight%, and more specifically, it is desirable to be 5 to 80 weight% for barium sulfate and 2 to 60 weight% for calcium carbonate. Further, the polypropylene resin obtained by kneading the white inorganic pigment is melt-kneaded with polyester by a uniaxial or biaxial extruder to obtain a master chip.
At this time, the concentration of polypropylene resin is preferably about 20 to 40% by weight. The master chip and polyester are dry blended in a predetermined ratio, and the resulting mixture is subjected to a melt extruder having a slit at the tip. The sheet-like material melt-extruded from the slit is rapidly cooled and solidified to obtain an unstretched film. As a means for rapid solidification, a method known in the art or a method accumulated in the art can be used, and a combination of a rotary cooling drum and an electrostatic load contact method is particularly preferable. The unstretched film is further biaxially stretched,
This biaxial stretching can be performed using a method known in the art or accumulated in the art. To further describe these specific examples, a polyester resin composition as a raw material is melt-kneaded at a temperature of 250 to 300 ° C. in an extruder, extruded in a sheet form from a die, and cooled to a temperature of about 70 ° C. or less to be substantially cooled. Amorphous sheet. Then, the sheet is stretched in the longitudinal and transverse directions by an area ratio of 4 times or more, preferably 9 times or more, and further heat-treated at a temperature of 120 to 250 ° C. to produce the sheet. The thickness of the film is preferably 25 to 250 μ, and the surface roughness Ra is preferably 0.3 to 0.6.

Thus, a white roughened biaxially stretched polyester film having a Japanese paper pattern is obtained. This polyester film improves the shortcomings of conventional white film, and is easy to write on.
It has excellent adhesiveness to wax-based ink and exhibits excellent properties as a writing material.

<Examples> Hereinafter, the present invention will be specifically described with reference to Examples. The various characteristic values in the present invention are obtained by the following measuring methods.

(1) Stiffness (g / 0.5 inch) Measurement was performed using a loop stiffener tester manufactured by Toyo Seiki Co., Ltd. The film was formed into a loop having a width of 0.5 inch and a length of 10 cm, and the load required to crush the loop to 1.0 cm was measured. At that time, the loop was installed horizontally so that the influence of gravity would not appear. The number of measurements n = 3, and the average value was used as the measured value.

(2) Vickers hardness (Kg / mm ² ) Taiyo Tester Co., Ltd. Type MM-2 type, JIS B
The measurement was performed according to the method of 7734. The number of measurements n = 5, and the average value was used as the measured value.

(3) Heat shrinkage rate (%) Heat shrinkage was performed for 30 minutes in a 150 ° C. atmosphere in a tensionless state, and the lengths of the samples before and after the heat treatment were measured to calculate by the following formula.

Heat shrinkage (%) = [(sample length before heat treatment) mm- (sample length after heat treatment) mm] x 100 / sample length before heat treatment) mm (4) Haze (%) Nippon Denshoku Industries Co., Ltd. Using NHD-2 type, JIS B7734
The measurement was performed according to the method of. The number of measurements n = 3, and the average value was used as the measured value.

(5) Surface roughness Ra (μm) It was measured according to the method of JIS B-0601-1976 using a surface roughness measuring instrument SE-30C manufactured by Kosaka Laboratory Ltd. The number of measurements was n = 5, and the average value of n = 4 excluding the maximum value was taken as the centerline average roughness Ra value.

(6) Density (g / cm ³ ) 10 cm x 10 cm was cut from any part of the obtained film, the average thickness of 9 points was measured with a micrometer, and the weight was measured to determine the weight per unit volume. I calculated. The number of measurements was n = 5, and the average value was used as the measured value.

(7) Washi Patterns Washi patterns were compared with each other and ranked by visual sensory inspection.

Rank ◯: A Japanese paper-like pattern having a high-class feeling is exhibited.

Rank Δ: Too large or too small as a Japanese paper pattern. Or, it is glossy and has no sense of quality.

Rank x: No Japanese paper pattern is shown.

(8) Writability A writing test was performed with a pencil and a ballpoint pen, and the writing quality and the paste of ink and the like were compared with paper (Toshiba Japanese word processor thermal transfer paper JW-Z103) and evaluated by a sensory test.

Rank ◯: The writing quality is equal to or better than that of paper, and the paste such as ink is also good.

Rank Δ: Writing is possible, but writing quality and ink paste are clearly inferior to paper.

Rank x: Can not be written at all.

(9) Printability Printing was carried out with a portable word processor Toshiba JW-70F, and the printed portion was rubbed with the pad of the finger, and the flaking off of the printing was evaluated by visual inspection.

Rank ◯: Adhesiveness of ink is equal to or better than that of paper.

Rank Δ: It is clearly inferior to paper, but it does not reach the point where it completely falls off.

Rank x: The print is completely peeled off.

Example 1 Calcium carbonate was added to a polypropylene resin (PP resin) having a melt flow index of 0.5, and the mixture was kneaded and extruded with a uniaxial extruder. The weight ratio of calcium carbonate to polypropylene at this time was 30:70. Intrinsic viscosity [η] =
It was mixed with 0.66 polyethylene terephthalate resin. The weight ratio of calcium carbonate: polypropylene: polyethylene terephthalate at this time was 8.6: 20: 71.4. This was extruded with a uniaxial extruder at 280 ° C. and rapidly cooled on a cooling drum to obtain an amorphous sheet. Then, the film was stretched 3.3 times in the machine direction and 3.3 in the cross direction and then heat-treated at 200 ° C. for 1 minute to finally obtain a biaxially stretched film having a film thickness of 50 μm.

Table 1 shows the characteristics of the finally obtained film. As shown in Table-1, the finally obtained film is
It was a white roughened biaxially stretched polyester film with a low density of 0.95 g / cm ³ and ranks ○ in all of the washi-like patterns, writing properties and printability, and had excellent properties as a writing material. .

Example 2 Instead of the calcium carbonate used in Example 1, barium sulfate was used. The same polypropylene resin and polyethylene terephthalate as in Example 1 were used. So that the final weight ratio of barium sulfate: polypropylene: polyethylene terephthalate is 10:20:70,
Formulated in a manner similar to Example 1. Then, Example 1
A biaxially stretched film was obtained in the same manner as.

As shown in Table 1, the obtained film had almost the same characteristics as in Example 1, and was a white roughened biaxially stretched polyester excellent as a writing material having a rank ○ in all of washi-like patterns, writability and printability. It was a film.

Comparative Example 1 The polypropylene and polyethylene terephthalate used in Example 1 were used. A biaxially stretched film was obtained in the same manner as in Example 1, except that the white inorganic pigment was not added and the weight ratio of polypropylene: polyethylene terephthalate was 20:80.

The obtained film has a Japanese paper-like pattern, as shown in Table 1.
The writability and the printability were both ranked Δ, and the film was not suitable as a writing material. Also, the haze was as low as 95%, and the film had the drawback that the print was clearly visible from the back side.

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Claims (3)

[Claims] 1. A white roughened biaxially stretched polyester comprising a polyester resin composition containing a white inorganic pigment and a polypropylene resin having a melt flow index of 0.5 to 50 and having a melt flow index of 2 to 40% by weight. Film. 2. The polyester film according to claim 1, wherein the polypropylene resin has a melt flow index of 0.5 to 15. 3. A polyester resin composition containing a white inorganic pigment and containing 2 to 40% by weight of a polypropylene resin having a melt flow index of 0.5 to 50 is melt-extruded and rapidly solidified to form an unstretched film. Is biaxially stretched so as to give a Japanese paper-like pattern, and further heat-fixed if desired, to produce a white roughened biaxially stretched polyester film.