JPH04453B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an ultra-thin polyethylene terephthalate film, particularly a film having a thickness of 4 μm or less, more specifically, a thickness of 2 μm.
The present invention relates to a method for producing a polyethylene terephthalate film having a particle size of 1.0 m or less.

[Prior art and its drawbacks]

A method for producing ultra-thin polyethylene terephthalate film by coextruding and laminating polyethylene terephthalate and polypropylene, stretching this, and then peeling off the polyethylene terephthalate film is described in JP-A-57-176125, 58-
5226, 58-136417, etc.,
It is publicly known.

However, such conventional methods have three drawbacks: frequent film tearing during stretching, large film thickness unevenness, and poor peelability when peeling the polyethylene terephthalate film from the polypropylene layer.

[Purpose of the invention]

An object of the present invention is to provide a method for producing an ultra-thin polyethylene terephthalate film that has less tearing during stretching, less uneven film thickness, and excellent peelability.

[Structure of the invention]

In order to achieve the above object, the present invention has the following composition: polyethylene terephthalate with an intrinsic viscosity of 0.55 to 0.75 dl/g, and polyethylene terephthalate with an intrinsic viscosity of 1.0 to 2.0 dl/g.
dl/g, and a propylene copolymer with a melting point of 100 to 150°C is coextruded to form a laminated sheet, which is uniaxially or biaxially stretched. The outline of the method for producing an ultrathin polyethylene terephthalate film is to heat treat it at a lower temperature, cool it to room temperature, and then peel the polyethylene terephthalate film from the propylene copolymer layer.

Polyethylene terephthalate in the present invention is a polymer in which 90 mol% or more of the molecular structure consists of ethylene terephthalate units, and its intrinsic viscosity is 0.55 to 0.75 dl/g, preferably 0.58 to 0.70.
It is in the range of dl/g. If the intrinsic viscosity is larger or smaller than the above range, the film will have a large thickness unevenness, which will not meet the purpose of the present invention.
Of course, the present invention also includes copolymerization of known copolymerized molecular units such as ethylene isophthalate, butylene terephthalate, ethylene adipate, ethylene sebacate, polyethylene glycol, etc., as long as the ethylene terephthalate unit does not become less than 90 mol%. It is included in polyethylene terephthalate.

In addition, this polyethylene terephthalate has
Known additives such as organic or inorganic fine particles, pigments, plasticizers, waxes, antioxidants, ultraviolet absorbers, antistatic agents, etc. may be added depending on the purpose. (In the following explanation, polyethylene terephthalate will be abbreviated as PET.) Propylene copolymer is a polymer consisting of a copolymer of 80 to 97 mol% of propylene and 3 to 20 mol% of olefin other than propylene. Specific examples include propylene/ethylene copolymer, propylene/butene copolymer, propylene/hexene copolymer, propylene/ethylene/butene terpolymer, or a mixture thereof. As for the copolymerization mode, a random copolymer is preferable, but a block copolymer can also be used.
It can be used depending on the degree of blocking. Note that even if it is a mixture of propylene copolymer and other polyolefins (e.g. polyethylene, polybutene, etc.), if the propylene copolymer accounts for 50% by weight or more, preferably 75% by weight or more of the mixture, It can be included in the scope of the propylene copolymer referred to in the present invention.

The intrinsic viscosity of the propylene copolymer used in the present invention needs to be in the range of 1.0 to 2.0 dl/g, preferably 1.2 to 1.8 dl/g. If it deviates from this range, the film will have poor thickness unevenness and will no longer meet the purpose of the present invention.

In addition, the melting point of propylene copolymer is 100 to 150
℃, preferably 105-140℃, more preferably
It is necessary that the temperature is in the range of 110 to 135°C. Outside this range, the frequency of film tearing during stretching increases, which is not preferable. (In the following explanation, the propylene copolymer will be abbreviated as PPC.) In the present invention, PET and PPC are supplied to separate extruders and melt-extruded at an extrusion temperature of 200 to 300°C, so that the molten copolymer are merged inside the polymer tube or inside the nozzle to form a laminated state, and extruded from the nozzle as a laminated sheet (this is called coextrusion). This laminated sheet may have two layers of PET/PPC, or PET/PPC/
Three layers of PET or PET/PPC/
It may be five layers like PET/PPC/PET. In any case, it is desirable that a PET layer be present on at least one side of the outermost layer. Otherwise, in the heat treatment after stretching, the film tends to be distorted and thickness unevenness tends to worsen. The coextruded molten laminated sheet is wound around a cooling drum with a surface temperature of 10 to 60°C, and cooled to 20 to 70°C to solidify to form an unstretched laminated sheet. During this cooling and solidification, a wire to which a DC high voltage of 1 to 15 KV is applied is placed on the top surface of the molten sheet, and the molten sheet is pressed against the drum by this electric charge, resulting in an unstretched laminated sheet with less uneven thickness. can get. This sheet is heated to 80 to 130°C, preferably 90 to 120°C, and uniaxially stretched 3 to 5 times. This stretching is 2~
It may be done in three stages. Next, in the case of biaxial stretching, the above-mentioned uniaxially stretched film is stretched in a direction perpendicular to the front direction at a stretching speed of 1000 to 10000%/min for 3.5 to 6
Stretch twice. The stretching temperature in this case is preferably 5 to 20°C higher than the temperature during the previous -axis stretching. Alternatively, the unstretched laminated sheet may be biaxially stretched by heating it to 80 to 130°C, preferably 90 to 120°C, and simultaneously stretching it in both directions 3 to 5 times. Further, the biaxially stretched film may be stretched again by 1.1 to 2.0 times in any direction.

Next, this stretched laminated film is made into PPC
By heating to a temperature above the melting point of PET and below the melting point of PET,
Heat treatment is performed for 1 to 20 seconds, preferably 2 to 10 seconds.
This heat treatment may be carried out while the film is held in tension, but it is better to perform the heat treatment while giving an area relaxation rate of 2 to 15% based on the area after stretching, so that the PET film can be peeled off later. It is preferable because it improves the peelability when stretching (calculation example of area relaxation rate: film area 100 cm ² after stretching is
During the heat treatment, it undergoes slight relaxation and shrinkage in one or two axial directions, and if the area after the heat treatment is 96 cm ² , the area relaxation rate is 4%).
Furthermore, if this heat treatment temperature is lower than the melting point of PPC,
This is not preferable because the peelability when peeling off the PET film later becomes worse, and conversely, if the temperature is higher than the melting point of PET, the PET film becomes cloudy and brittle.
This is also not preferable since it will not be possible to peel it off.

Next, the heat-treated laminated film is slowly cooled to room temperature, typically 20 to 40°C. Cooling may be performed with air or water, or may be cooled by contacting with a cooling roll. Note that the cooled film may be kept at that temperature or may be heated again to 50 to 90°C with a heating roll to perform corona discharge treatment on one or both sides of the film. This treatment may make it easier to peel off the PET film later. The PET film is peeled off from the laminated film thus obtained, and the normal thickness is
Ultra-thin PET with a thickness of 0.2-4μm, preferably 0.2-2μm
Get the film. This peeling method is not particularly limited, but the laminated film is nipped between a set of nip rolls, and the surface of one roll is
Continuous peeling is easy if the PET film is peeled along the line. In addition, laminated film PET
After the surface has been printed, laminated, coated or vapor deposited, the PET film may be peeled off. In either case, it is important to remove static electricity on the surface of the PET film to be peeled using a static eliminator to facilitate peeling.

The present invention is characterized by the method described above, but in the PPC layer, 0.001 to 1% by weight,
By preferably containing 0.005 to 0.5% by weight of a non-particulate lubricant, the releasability of the PET film can be further improved. A non-particulate lubricant is a substance that is liquid or molten at the melt extrusion temperature of PPC, and its addition can improve the lubricity of PPC film. Specific examples include: It is a substance like. In addition, when two or more of these substances are contained in the film, the total amount thereof may be within the above content range.

A. Aliphatic hydrocarbons Liquid paraffin, microcrystalline wax, natural paraffin, synthetic paraffin, polyethylene wax, polypropylene wax, etc.

B Higher fatty acids or their metal salts Stearic acid, calcium stearate, hydroxystearic acid, hydrogenated oil, sodium montanate, etc.

C Fatty acid amide Stearamide, oleic acid amide, erucic acid amide, ricinoleic acid amide, behenamide, methylene bisstearamide, etc.

D Fatty acid ester n-butyl stearate, methyl hydroxystearate, myricyl serotinate, polyhydric alcohol fatty acid ester, ester wax, etc.

E Fatty acid ketone Ketone wax etc.

F Fatty Alcohols Lauryl alcohol, stearyl alcohol, myristyl alcohol, cetyl alcohol, etc.

G Partial esters of fatty acids and polyhydric alcohols Glycerin fatty acid esters, hydroxystearic acid triglyceride, sorbitan fatty acid esters, etc.

H Nonionic surfactant Polyoxyethylene alkyl ether, polyoxyethylene phenyl ether, polyoxyethylene alkylamide, polyoxyethylene fatty acid ester, etc.

I Silicone oil Linear methyl silicone oil, methylphenyl silicone oil, modified silicone oil, etc.

J Fluorine surfactant Fluoroalkylcarboxylic acid, perfluoroalkylcarboxylic acid, monoperfluoroalkyl ethyl phosphate, perfluoroalkyl sulfonate, etc.

In addition, in combination with the above-mentioned non-particulate lubricant, inorganic fine particles with an average particle size of 0.001 to 2 μm, such as dry silica, wet silica, zeolite, calcium carbonate,
Particulate lubricants such as calcium phosphate, kaolin, kaolinite, clay, talc, titanium oxide, alumina, zirconia, and aluminum hydroxide,
When it is contained in the PPC film in an amount of 0.01 to 0.5% by weight, the effect of the non-particulate lubricant can often be enhanced synergistically.

〔Effect of the invention〕

The present invention has specific physical properties as described above.
PET and PPC are coextruded, stretched, heat treated at a specific temperature range, and then the PET film is peeled off.
Since this method was used to manufacture ultra-thin PET film,
The effects of reducing the frequency of film tearing during stretching, reducing film thickness unevenness, and improving peelability when peeling the PET film are achieved, making it possible to improve the
It became possible to produce film stably. The ultrathin PTE film thus obtained can be used for many purposes, such as a dielectric for capacitors, base paper for stencil printing, and base film for typewriter ribbons.

[Measurement method and evaluation criteria for physical properties]

The methods for measuring physical properties and the evaluation criteria for each property used in the present invention are as follows.

(1) Intrinsic viscosity of PET PET was dissolved in orthochlorophenol at 25°C, and the intrinsic viscosity was measured by a conventional method.

(2) Intrinsic viscosity of PPC The intrinsic viscosity of ASTM-D1601 was used.

(3) Melting point Using DSC, the temperature was increased at a rate of 20°C/min, and the melting point was defined as the temperature corresponding to the top of the endothermic peak accompanying melting (sample amount: 10 mg).
In addition, when there were two or more melting point peaks, the temperature at the top of the higher peak was taken as the melting point.

(4) Frequency of film tearing It was expressed as the number of times film tearing occurred during continuous biaxial stretching film formation for 8 hours. Therefore, the unit is times/8 hours. Usually, unless this value is 2 times/8 hours or less, it is difficult to put it into practical use.

(5) Film thickness unevenness The thickness of the heat-treated and cooled laminated film in the film width direction is continuously measured using an electronic film thickness gauge (film width 1 m). Divide the difference between the thickness of the thickest part and the thickness of the thinnest part by the average thickness, and multiply this by 100.
Thickness unevenness (%). Generally, if this value is less than 10%, it is considered impractical.

(6) Peelability of PET film The PET film was continuously peeled from the obtained laminated film at a peeling speed of 10 m/min, and evaluated using the following three evaluation criteria.

“Good”: No film cut or tear, 500
Items that can be peeled off continuously for more than m.

“Normal”: Continuous peeling is possible for a distance of about 100 to 300 meters, but the film breaks or tears after that distance.

“Poor”: Continuous peeling is only possible for about 10 to 90 meters.

Of course, it can be said that if the releasability is not "good", it is impractical.

[Examples and comparative examples]

Hereinafter, one embodiment of the present invention will be described with reference to Examples and Comparative Examples.

Example 1 The following two types of raw materials (pellets) were prepared.

PET: Homopolymer of polyethylene terephthalate. Intrinsic viscosity 0.62dl/g. Melting point 259℃.

PPC: Propylene with 6% ethylene content by weight.
Ethylene random copolymer. Intrinsic viscosity 1.65
dl/g. Melting point: 120℃. Erucic acid amide 0.3% by weight
and 0.3% by weight of calcium carbonate with an average particle size of 0.9 μm.

These two types of raw materials are each supplied to separate extruders, and PET is melt-extruded at 280℃ and PPC at 260℃.
The respective melts are brought together in a T-shaped nozzle,
It had a two-layer structure of PET/PPC, which was wound around a cooling drum at 30°C, and cooled and solidified while applying a DC high voltage of 8KV to form a two-layer laminated sheet.
After heating this sheet to 90℃, 3.4
It was stretched twice and immediately cooled to 30°C. Then,
Heat again to 100℃ and stretch at a speed of 2500 in the width direction.
The film was stretched 5.0 times at a rate of 5.0%/min, then the temperature was raised to 215°C and heat treated for 5 seconds. Within this heat treatment section, relaxation treatment was performed with an area relaxation rate of 5%. This film was slowly cooled to room temperature and wound up while removing static electricity using a static eliminator. The thus obtained laminated film had a PET layer of 1.0 μm and a PPC layer of 10 μm. When this film was continuously formed, the film tear frequency was 0 times/8 hours, and the film thickness unevenness was 5%, both of which were good. Next, when we tried peeling off the PET film from this laminated film, we were able to peel it off continuously for over 500 meters.
The peelability was "good".

Comparative example 1 In relation to the PPC of Example 1, the intrinsic viscosity was 2.3.
I tried using PPC of dl/g (other characteristics of PPC are
Same as Example 1). When the film was formed in the same manner as in Example 1, the thickness unevenness of the film was 25%.
It became extremely inferior.

Comparative Example 2 Contrary to Comparative Example 1, PPC with an intrinsic viscosity of 0.8 dl/g
When a film was formed using the same method as Comparative Example 1 (Example 1), the thickness unevenness of the film was 32%.
Moreover, the frequency of film tearing increased to 6 times/8 hours.

Comparative Example 3 By changing the ethylene content of PPC in Example 1,
Films were formed using PPC with a melting point of 155°C and a melting point of 95°C, but in the same manner as in Example 1.
Even with PPC, the film tear frequency is 20 times/8
It was extremely easy to tear over time and was of little practical use.

Comparative Example 4 PET with an intrinsic viscosity of 0.50 and 0.80 dl/g was used instead of PET in Example 1, and the other conditions were as in Example 1.
When I tried forming a film in the same manner as above, I found that both
Even when PET was used, the thickness unevenness of the film was extremely poor, exceeding 20%.

Comparative Example 5 In Example 1, the heat treatment temperature after stretching was changed to 110
℃, and film formation was performed with other conditions unchanged. When the peelability of the obtained laminated film was evaluated, it was found to be "average" and somewhat lacking in practicality.

Claims (1)

[Claims] 1 Polyethylene terephthalate with an intrinsic viscosity of 0.55 to 0.75 dl/g, an intrinsic viscosity of 1.0 to 2.0 dl/g, and a melting point
A laminated sheet is coextruded with a propylene copolymer at 100 to 150°C, stretched uniaxially or biaxially, and then heat treated at a temperature higher than the melting point of the propylene copolymer and lower than the melting point of polyethylene terephthalate. After that, the polyethylene terephthalate film is cooled to room temperature, and then the polyethylene terephthalate film is peeled from the propylene copolymer layer.