JPS6045056B2 - Method for producing polyester film with excellent flatness and processed products thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for eliminating seaweed-like flatness defects at the edges of thick products, particularly polyester films of 50 μm or more in thickness, and rolled products of processed products thereof, which occur due to moisture expansion.

When polyester films of 50 μm or more and processed products thereof manufactured under normal conditions are left in rolled products or laminates for a long period of time, when they are made into sheets, seaweed-like flatness defects always occur at the edges.

This wakame-like defect refers to the film 1 as shown in FIG.
The end of the film is partially raised, and this raised portion 2 is deformed into a semi-conical shape in the width direction of the film with the end as the bottom. This seaweed-like defect at the edge causes meandering, misalignment, etc. during post-processing such as printing, coaching, matting, and forming such as drilling and cutting, which prevents sufficient processing and reduces the yield and quality of processed products. cause Furthermore, when these processed products are used for drafting purposes, the presence of this wakame-like defect causes misalignment of printed and molded parts, resulting in a decrease in quality. This seaweed-like defect at the edge is seen in thick polyester films of 50μ or more and processed products thereof.
It is hardly seen in polyester films of 0μ or less and processed products thereof. In addition, the surface layer 1 of the rolled product and the laminate
It is hardly seen in the 27wt part, and the inner layer 2~3wr
It is seen in areas larger than m. Moreover, this wakame-like defect disappears when the sheet is left for a long time. The inventors
As a result of intensive research to eliminate seaweed-like defects that occur at the edges of rolled products and laminates made of polyester film and its processed products, we have found that the adsorption state of moisture at the edges and in the width direction of rolled products and laminates has been determined. The authors discovered that this wakame-like defect can be eliminated by reducing the difference in moisture content between the edges and the center to 5 x 10% or less. This led to an invention.

The gist of the present invention is to heat-treat thick polyester films and processed products thereof that have wakame-like defects due to moisture expansion at any temperature in the range of 50*c to 130°C (film surface temperature). The difference in moisture content between the edges and the center is 5 x 10-0% or less without causing distortion,
This method does not cause any deterioration in flatness and eliminates seaweed-like defects.

First, to explain the details of wakame-like defects, in the film forming process of polyester chill film, approximately 150 to 2
When a temperature of 500C is applied and the film is in an absolutely dry state, and when it is finished into a rolled product by slitting after film formation, the adsorbed moisture at the edges and center of the film is at most 0.2 times the equilibrium moisture content. It is. (The moisture content of the polyester film at 100% RH is 0.70% as the equilibrium moisture content) Furthermore, there is almost no difference in the adsorption state between the edges and the center.

Therefore, no seaweed-like defects at the edges are observed in the rolled product immediately after film formation and slitting. However, if the rolled product is left for a long period of time, moisture from the outside air will enter from the ends of the rolled product, and only the ends will reach an equilibrium state with the humidity of the outside air, increasing the moisture content in that area. On the other hand, the adsorption state in the central part is close to the state in which the product is rolled into a rolled product immediately after the film forming slit, and the moisture content is small. As a result, seaweed-like defects occur at the ends due to the difference in moisture expansion between the ends and the center of the rolled product, where the suction state is different. The size of this seaweed-like defect extends from the edges to the center where the adsorption state is constant (moisture content is constant). This relationship is shown in FIG. Figure 2a shows the size of the seaweed-like defect, which corresponds to the moisture content in b, and a higher moisture content indicates a larger defect. Further, depending on the humidity of the atmosphere in which the rolled product is left, the speed at which the difference in adhesion between the ends and the center occurs differs. i.e. 50-80
Several hours (2 to 10 hours) in a humid atmosphere with %RH
, for several days (1~
7 days). Surface layer 1-2 of rolled product? Partly because the winding pressure is low in this part, there is little difference in the suction state between the ends and the center because there is contact with the moisture in the outside air, so seaweed-like defects at the ends are less likely to occur. The above-mentioned relationship also applies to polyester film processed and wound products of 50 μm or more and laminates. These polyester films and their processing. In order to prevent the occurrence of this seaweed-like defect in the product, a sealed package is required that maintains the difference in moisture content between the ends and the center of the product to 0-2% or less. In the case of a rolled product laminate made of ordinary polyester film and its processed products, the seaweed-like defect described above occurs! There is. The present invention was developed through further intensive research into a method for removing this seaweed-like defect during processing. That is, the wakame-like defects can be eliminated by controlling the difference in moisture content between the edges and the center of polyester films having wakame-like defects and processed products thereof to 5×10 -2% or less.

As a means for this purpose, application of heat can generally be applied. However, in applying this heat, it is necessary to perform the treatment at a temperature near the glass transition temperature Tg (about 70 to 80°C) of the polyester film. That is, when the surface temperature of the polyester film is 50° C. or lower, the water adsorbed on the polyester film is not sufficiently volatilized, so that the wakame-like defect does not disappear. On the other hand, when the film surface temperature is 130° C. or higher, moisture is sufficiently volatilized and seaweed-like defects are eliminated, but on the other hand, flatness defects such as sagging and sagging occur due to thermal distortion. This poor flatness is different from the seaweed-like defect due to moisture expansion mentioned earlier, and is a planar defect that is not affected by the difference in moisture content between the edges and the center, and will not disappear even if the sheet is left for a long time. . Therefore, by heat-treating the film at any temperature in the range of 50°C to 130°C, preferably 60°C to 110°C, moisture 1 is sufficiently volatilized, and flatness does not deteriorate due to thermal distortion. , it can erase wakame-like defects. This relationship is shown in FIG. Figure 3 shows
It shows the relationship between film temperature, strain (shrinkage rate), and film defects; A shows the film defects; B
indicates the strain'' (shrinkage rate). In the figure, when the film temperature is in the a range (130 is C or higher), the film strain (shrinkage rate) becomes large, and many products with defective flatness occur.

On the other hand, it can be seen that in the c region (50° C. or lower), there is almost no distortion, but the wakame-like defect does not disappear. in this way,
In order to eliminate the seaweed-like defects of polyester films and processed products that have seaweed-like defects caused by moisture expansion, it is necessary to sufficiently volatilize the adsorbed moisture of the polyester film and heat the polyester film in region b (50 to 130℃) without thermal distortion. ) and reduce the difference in moisture content between the edges and the width by 5 x 10-2.
The goal can be achieved by keeping the amount below %. This method for eliminating wakame-like defects can be applied to polyester films having wakame-like defects, during the processing thereof, and during the manufacturing process of processed products. The polyester film used in the present invention refers to an unstretched, multiaxially stretched film of 50μ or more made of 80% or more polyethylene terephthalate, and polyester film processed products include printing, coating, sand matting, etc. on polyester film. Refers to products that have undergone processing such as drilling.

Note that the shape includes all laminated products in addition to rolled products. Examples will be described below. Example (1) A biaxially stretched polyester film #125 (125 μm) was formed and then finished with slits into a rolled product having a width of 50 m and a length of 300 m.

Cut off the surface layer 5 inner layer part of this rolled product, and divide this part into 3
7n. Take out a long sheet, place it on a cork plate with a thickness of 2 Cym, and check the flatness. The moisture content in the center was measured. As a result, the moisture content at the edges was 0.02%, and the moisture content at the center was 0.
．． 01%, this raw sheet had good flatness and no seaweed-like defects were observed at the edges. (2) After leaving the rolled product without seaweed-like defects on the edges of item (1) in an atmosphere of 40°C and 90% RH for one week, the surface layer 5 of the rolled product is left in an atmosphere of 40°C and 90% RH. The inner layer portion was cut off, and this portion was taken out in the form of a 3 m long sheet, made into a flat plate, and its flatness was examined, and the moisture content at the edges and center was measured using a DuPont model 26-321 solid moisture meter.

As a result, the difference in moisture content between the edges and the center was as large as 0.17%, with the edges being 0.22% and the center being 0.05%. 10 wakame-like defects
Ke/3TrL. It was occurring. (3) While unwinding the rolled product with the seaweed-like defect at the end of item (2), use a hot air dryer (zone length 5m) to reduce the tension to 4.8k9/500wrm.
Constant width, processing temperature 50-170°C, processing speed 5-2
0Tr1. The heat treatment was performed at different times per minute.

During this heat treatment, A.
LEVERMORECO. Ltd. heat label ゜“
HermeV was attached, and the film surface temperature during heat treatment was measured. Furthermore, the heat-treated film was made into a flat plate to examine flatness and width shrinkage. These results are shown in Table 1. Furthermore, the NO. of the original film before heat treatment and the heat treated film in Table 1. 3, NO. The temperature-dependent heat shrinkage stress in the longitudinal direction and the width direction of each of No. 6 was measured. As a result, NO.
It can be seen that the sample No. 3 in which the seaweed-like defect has disappeared shows the same temperature-dependent heat shrinkage stress as the original fabric before heat treatment, and there is no thermal strain. On the other hand, NO. It can be seen that in the case where the flatness of No. 6 deteriorated, the heat shrinkage stress decreased significantly in the heat shrinkage stress measurement temperature range of 70 to 150°C, and thermal distortion occurred. From these results, heat treatment at a film temperature of 50°C or lower does not sufficiently volatilize the moisture in the original film and the seaweed-like defects do not disappear, but heat treatment at a film temperature of 50°C or higher
After heat treatment at 30℃, the difference in moisture content between the edges and center is 0.05%.
As described above, the water in the original film was sufficiently volatilized and the seaweed-like defects disappeared, and a polyester film with good flatness and no thermal distortion was obtained.

Heat treatment at 130'C or higher results in zero moisture content difference between the edges and center.
．． Although the volatilization of moisture was sufficient at 0.05% or less, it did not disappear when left on a flat plate, resulting in thermal distortion and deterioration of flatness such as sagging.

[Brief explanation of the drawing]

Figure 1 shows the seaweed-like flatness defect of the film, Figure 2
The figure shows the size of seaweed-like defects in the film width direction,
FIG. 3 is a diagram showing the relationship between film temperature and film distortion (shrinkage rate) and film defects. 1: film, 2: raised part.

Claims (1)

[Claims] 1 Thick polyester films and processed products thereof that have seaweed-like defects that have occurred at the edges due to moisture expansion are heat-treated at any film surface temperature in the range of 50°C to 130°C to remove the seaweed-like defects. A method for producing a polyester film with excellent flatness and a processed product thereof.