JPS5835136B2 - Embossed film Seizouhouhou - Google Patents

Description

Detailed Description of the Invention The present invention relates to polypropylene biaxially oriented (hereinafter referred to as PP-BO)
P P - which maintains the excellent properties of the film (abbreviated as ) and has an excellent transfer rate and form retention rate of the embossed pattern.
Regarding the manufacturing method of BO composite embossed film, conventionally, polypropylene, polyester, nylon,
Biaxially stretched films made of polystyrene, vinyl chloride, etc.
Compared to paper, it has superior mechanical strength such as tensile strength and flexibility, and electrical properties such as withstand voltage and dielectric constant, so attempts have been made to develop various uses to take advantage of these characteristics. The disadvantages of plastic film compared to paper are that the surface is smooth, so if two or more sheets are stacked, they may block, and particles may get into the space between the stacked layers. -: J, There are problems such as a slimy feeling and poor feeling of '2, and as a countermeasure, attempts have been made to create unevenness by embossing, and polyester film 1" Lupa or hinyl chloride film is used as a countermeasure. The L0 nimbos film has been put into practical use as an electrical insulator, heat insulator, book cover, etc.

Shikaruni PP-B O film, Techi-ite,
5- Even if you change the embossing conditions, such as embossing humidity, pressure, pattern, etc., the embossed pattern is not transferred (poor transfer rate), and the pattern transferred to the surface is also long. PP-BO film has a major problem of poor shape retention, with the pattern almost disappearing when exposed to a load or heated to around 100°C. Utilizing its electrical properties such as excellent voltage resistance and low dielectric loss (tano), it can be used, for example, as an interlayer insulator for wires, coils, etc., in an insulating oil. Even if it is not used, the insulating oil will be prevented from penetrating between the layers, so it will be useless.
-BO embossed film has not been put into practical use.

The present invention solves this problem, and conventionally only P
Even when the P-BO film was embossed, the transfer rate of the embossed pattern was poor, and the form retention rate of the transferred pattern was also poor, whereas at least one side of the P-BO film layer was better than the KM film. A composite film formed by combining a polymer composite layer with a low melting point is
By stacking two or more 4L seams where the layers touch each other and integrally embossing all the layers at a temperature lower than the melting point of the composite layer] - Surprisingly, the PP with two or more stacked layers -
It has been discovered that an embossed film can be obtained in which the BO composite film is firmly laminated and bonded, the transfer rate of the embossed pattern is improved, and the form retention rate of the transferred embossed pattern is also very good.

However, even if two or more regular PP-BO films were stacked together and embossed under the same conditions, they would not adhere at all, and each embossed film obtained had poor transfer rate and morphology. Retention encyclopedia very poor.

Furthermore, even if two or more PP-BO composite films used in the present invention are stacked and thermocompressed under the same conditions at a temperature lower than the melting point of the composite layer using a normal calendar roll, no adhesion occurs, and the above structure of the present invention does not adhere. It has been discovered that an embossed film having the above-mentioned surprising effects can be obtained for the first time by employing this method.

In addition, as an effect other than the above, conventional PP-BO film has the following effects:
Cooling of unstretched film is only industrially produced with a thickness of about 60μ at most, but according to the present invention, by stacking two or more films, P with a base thickness of 120μ or more can be obtained. P-BO embossed film can be easily obtained, and the method of the present invention can be used to increase the thickness, especially in applications where P-BO is not used because it is less stiff (softer) than polyester film. My lower back has improved and I can now use it.

In that case, by setting the outermost layer as a P P -B 0 layer as necessary, there is an advantage that the polymer having a low melting point of the composite layer can be prevented from coming out to the outermost layer.

The composition of the P P -B O composite film used to achieve the present invention is a composite of a polypropimen biaxially oriented film layer and a polymer film having a melting point lower than that of the film layer on at least one side of the film layer. The composite layer is not particularly limited as long as it can be composited with the polypropylene film layer, but ethylene propylene copolymer, polyethylene, ethylene vinyl acetate copolymer, etc. can be used with the polypropylene film layer. It is particularly preferable that the composite film has good adhesion and that the edge portion can be recovered and remelted and extruded when the composite film is formed.
It may be uniaxially stretched or unstretched.

Here, the embossing in the present invention does not mean giving uneven deformation to only some layers of the composite film as shown in FIG. This provides an integral embossing deformation over the layers.

1. The transfer rate of the embossed pattern in the present invention is 1.
The depth and height of the unevenness of the pair of embossing rolls is D, the thickness of the film before embossing is A as shown in Figure 3,
Assuming that the apparent thickness of the embossed film formed by stacking n sheets and being embossed is B as shown in FIG. 4, it is defined as follows.

In addition, the form retention rate of the embossed pattern in the present invention is
The apparent thickness of the embossed film after applying some kind of treatment such as applying a load Ji or heating to the embossed film having an apparent thickness B which has been embossed by stacking n sheets is given as C as shown in Fig. 5. Then, it is defined as .

Note that a conventional embossing method can be used, but in this case, it is important to use a temperature higher than the glass transition point of the composite layer and lower than the melting point as the second embossing temperature.

By adopting such conditions for the composite film of the present invention, problems such as protrusion and outflow from the edge portion of the composite layer will not occur, and therefore the embossing roll will not be soiled and the efficiency will be improved without causing clogging etc. It can be used in a uniform manner, and since the composite layer does not shrink, a homogeneous embossed pattern can be obtained, and it has excellent adhesive strength.

As the emboss pattern (emboss shape), any appropriate one can be used depending on the application, and the one shown in Example 2 is only a part of the example, and the present invention is not limited thereto.

The adhesive strength of the embossed film is ASTM-()903-
It was measured by the 180 degree peeling method according to No. 49.

Note that the melting point in the present invention refers to 10 mg of Sanflu placed in a scanning calorimeter (DSC) at 5°C/m in a N2 stream.
This is the melting peak temperature when the temperature is increased at a temperature increase rate of in.

Example 1 Isotactic polypropylene with an intrinsic viscosity of 2.3 and a melting point of 161°C in a 135°C tetragonal solution was extruded and cast using a melt extrusion method, and stretched 5 times in the vertical direction to obtain a uniaxially stretched sheet with a thickness of 280μ. Then, from another extruder, a crystalline ethylene propylene copolymer having an intrinsic viscosity of 1.6, an ethylene content of 2.1% by weight, and a melting point of 147° C. is melt-extruded to obtain the uniaxially stretched polypropylene sheet. This composite film is laminated with a thickness of 40μ on top.
After stretching 8 times in the horizontal direction in hot air at 50°C, heat centrifuge.
A polypropylene composite film having a total thickness of 40 μm, including a PP-BO base layer of 35 μm and a uniaxially oriented ethylene propylene copolymer layer of 5 μm, was obtained.

Next, two of the composite films were stacked so that the ethylene propylene copolymer composite layer was on the inside, and the height was 0.66.
Cabinet, width 0.66 rrrm, depth and height) 0.2y+
Using a pair of embossing rolls consisting of a metal roll and a paper roll, each having 225 piramint-shaped irregularities of +m, embossing was carried out at a pressure of 30 kq/cm and a temperature of 130°C. An embossed composite film having a thickness of 168 μm and laminated and bonded together was obtained.

The transfer rate of this embossed pattern was excellent at 44%, and the adhesive strength was excellent at 116 f/cm.

The embossed film was left in hot air at 120°C for 24 hours to dehumidify it, then cooled in a room temperature cabinet and its apparent thickness was measured to be 166μ, with an excellent form retention rate of 98. .

Comparative Example 1 Isotactic polypropylene, which is the same raw material as in Example 1, was melt-extruded in a normal manner without any compounding and
Biaxially stretched by 8 times in the horizontal direction and 8 times in the horizontal direction, and heated to a thickness of 40
A single ordinary P P -BO film of μ was obtained.

When two sheets of the film were stacked and embossed under the same conditions as in Example 1, an embossed film with a thickness of 146 μm was obtained, but the transfer rate was as low as 33%, and the sample was cut into strips to measure the adhesive strength. When it was cut into pieces, it separated into two pieces and could not be measured, resulting in Of/cm.

Also, when it was left in hot air at 120°C for 24 hours under the same conditions as in Example 1, it naturally peeled off into two films.
The apparent thickness of each is 52μ, and the shape retention rate is 37
It was low compared to the person in charge.

On the other hand, when a single ethylene propylene copolymer film with a thickness of 40 μm was embossed in the same manner and the shape retention rate was determined, it was as low as 42%.

In addition, in Example 1, when the embossing temperature was 152'Cf-[- which was 5°C higher than the melting point of the ethylene propylene copolymer, the embossed 1llK pattern returned, the transfer rate was as low as 27, and furthermore, during embossing, A drawback occurred in that the ethylene propylene copolymer flowed out from the edge portion and stained the embossing roll.

Also, two sheets of the composite film obtained in Example 1 were stacked together in the same manner as in Example 1, and a calender roll made of a smooth metal roll and a paper roll with the same circumferential speed was used.
Although calendering was carried out at the same pressure of 30 hy/cm and temperature of 130° C. as in Example 1, the two composite films did not adhere at all.

Example 2 Low-density polyethylene with a melting point of 100° C. is extrusion laminated on a regular PP-BO film with a thickness of 40μ by a conventional method to form a PP-BO base layer of 40μ and a composite unstretched polyethylene layer. A composite film having a total thickness of 50μ and consisting of 10μ was obtained.

The composite film was stacked so that the polyethylene composite layer was on the inside, one side of the base was 1 mm, and the height was 0.
An embossing roll consisting of a pair of metal rolls and a paper roll with a 45mm hexagonal pattern, 35kq/
Embossing was carried out under a pressure of cm and a temperature of 90°C to obtain a single laminated and bonded embossed composite film with an apparent thickness of 293μ.

The transfer rate of the film was 43%, and the adhesive strength was 270%.
y/cm, which was excellent.

As a result of leaving the embossed composite film in hot air at 80°C for 24 hours, the apparent thickness was 285μ, and the shape retention rate was 96.
I was on good terms with the person in charge.

Comparative Example 2 A single low-density polyethylene film having a thickness of 50 μm was embossed in the same manner as in Example 2, and the shape retention rate was determined to be as low as 38.

Furthermore, in Example 2, when embossing was carried out at only the embossing temperature of 120°C, which is 20°C higher than the melting point of low-density polyethylene, the transfer rate was as low as 29 degrees, and the low-density polyethylene flowed out from the edge portion, staining the embossing roll. A problem arose.

Furthermore, in Example 2, the embossing roll was replaced with a smooth calender roll and calendering was carried out at the same pressure and temperature as in Example 2, but the two composite films did not adhere.

Example 3 An ethylene-vinyl acetate copolymer (vinyl acetate content: 12% by weight) film with a melting point of 86°C was laminated as a composite layer on one side of a normal unstretched polypropylene film using a heat press, and then stretched 5x using a film stretcher. 8 times biaxial stretching, P P -BO base layer is 25μ, ethylene vinyl acetate BO
A composite film with a composite layer of 5μ and a total thickness of 30μ was obtained.

Two of the composite films were stacked so that the ethylene vinyl acetate copolymer composite layer was on the inside, and embossing was performed using the same embossing roll as in Example 1 at a pressure of 35 kV/cm and a temperature of 80°C. An embossed composite film having a thickness of 144 μm and laminated and bonded together was obtained.

The transfer rate is excellent at 42%, and the adhesive strength is 28497 cm.
It was excellent.

Next, when the embossed film was left in hot air at 70° C. for 24 hours, the apparent thickness was 140 μm, and the shape retention rate was good at 95%.

Comparative Example 3 Contrary to Example 3, a single film of ethylene/vinyl acetate copolymer with a thickness of 30 μm was embossed in the same manner as in Example 3, and the transfer rate and form retention rate were determined. 31 each
The price was as low as 35 yen.

As described above, according to the present invention, a PP-BO film with a low transfer rate and poor shape retention of an emboss pattern is coated with a PP-BO film having a lower melting point than PP-BO, which also has a poor transfer rate and shape retention. Composite other polymers on at least one side, stack two or more composite films so that the composite layers with low melting points are in contact with each other, and perform embossing over the entire layer at a temperature lower than the melting point of the composite layer. Surprisingly, it was discovered that a PP-BO composite embossed film laminated into a single sheet with good transfer rate and shape retention can be easily obtained, especially when the outermost layer is made of PP-B
By using the O base layer, the composite layer is completely covered with the PP-BO layer, resulting in an excellent embossed film that retains the excellent mechanical, electrical, and chemical properties of the PP-BO film. It is particularly suitable for interlayer materials in electrical equipment such as transformers in which insulating fluid circulates.Furthermore, the PP-BO film, which could only be industrially produced in the past with a thickness of 60 μm, has been improved by the present invention. According to this method, an embossed film having an arbitrary thickness can be obtained, and its practical effects are extremely large.

[Brief explanation of drawings]

FIG. 1 is an example of a cross-sectional view of an embossed film, which is outside the scope of the present invention, in which there is a composite layer on only one side of the P P -BO base layer, and only the composite layer is embossed. FIG. 2 is a cross-sectional view of an embossed film, which is outside the scope of the present invention, in which there is a composite layer on both sides of the PP-BO layer, and only the composite layer is embossed. FIG. 3 is an example of a composite film having a composite layer on one side of a P P -BO substrate layer. FIG. 4 is a cross-sectional view of the embossed composite film of the present invention in which two composite films of FIG. This is one example. FIG. 5 is an example of a cross-sectional view of the embossed composite film shown in FIG. 4 after being processed. 1: PP-BO base layer, 2: composite layer.

Claims (1)

[Claims] 1. On at least one side of a biaxially stretched polypropylene film, two or more biaxially stretched polypropylene composite films made of a polymer having a lower melting point than that of the film are stacked so that the composite layers are in contact with each other, A method for producing an embossed film, characterized in that the entire layer is integrally embossed at a temperature lower than the melting point of the composite layer.