JPH0254783B2 - - Google Patents

Description

[Detailed description of the invention]

It is an object of the present invention to provide a particularly translucent polypropylene biaxially oriented laminated film. Currently, semitransparent films with rough surfaces mainly composed of polypropylene resin are being actively developed as films for medical, industrial, and food packaging applications. Methods for producing such a translucent polypropylene film having a rough surface include a method of adding other polyolefins such as polyethylene to polypropylene, a method of adding a blowing agent to polypropylene,
Proposed methods include adding a special nucleating agent such as a quinacridone derivative to polypropylene, melt-molding it to create a polypropylene sheet having a β-type crystal structure, and stretching this, or adding inorganic fine particles. These methods have problems such as the range of optimal conditions for obtaining the desired rough surface is narrow, special molding conditions are required, the degree of roughening is low, or the balance with other physical properties is inappropriate. Also, there are problems such as the inorganic fine particles appearing to flicker, and considerable improvement is required. The present inventors conducted intensive studies on a method for producing a translucent film by roughening the surface of a biaxially stretched polypropylene film. As a result, the present inventors discovered a laminated film having a layer containing a specific polyethylene component on at least one side of the polypropylene layer. The present invention was achieved by discovering that the degree of haze, which is a measure of translucency, of an axially stretched polypropylene film increases significantly, and that the degree of haze does not change easily depending on the molding conditions. That is, the present invention is a laminated biaxially stretched film comprising a layer (A) made of polypropylene and a roughened layer (B) made of a propylene-ethylene block copolymer resin composition on at least one side,
Thickness of layer (B) / thickness of layer (A) + thickness of layer (B) = α, and the laminated biaxially stretched film is eluted and separated by a column fractional elution method, and the ethylene content is 85 When the content of the polyethylene component which is % by weight or more is w% by weight, the value of w/α is 8% by weight or more and the average intrinsic viscosity of the polyethylene component [η] _w
(measured in tetralin at 135℃) is 1.5 to 10.0 dl/g
This is a roughened biaxially oriented polypropylene film characterized by the following. Layer made of polypropylene used in the present invention
In (A), polypropylene is a copolymer of propylene with a small amount of other α-olefins (one or more of ethylene, butene-1, hexene-1, etc.) in addition to crystalline propylene homopolymer. It also includes crystalline copolymers. In the present invention, the resin composition forming the roughened layer (B) made of an ethylene-propylene block copolymer composition can be produced by various methods.
An example is a propylene-ethylene block copolymer obtained by polymerization using a catalyst system consisting of a known titanium trichloride catalyst and an organoaluminum compound. At this time, the resin used in the present invention can be produced by appropriately selecting the polymerization design and the hydrogen concentration in the polymerization tank. Furthermore, a blend of the propylene-ethylene block copolymer with polyethylene or a propylene-ethylene random copolymer can also be used as the resin for layer (B). When these resins are blended, their content in the resin composition is preferably less than 50% by weight, preferably less than 30% by weight. Next, a method for specifying a laminated biaxially stretched polypropylene film in the present invention will be described in detail. In the present invention, the proportion of the thickness of the roughened layer (B) forming the laminated biaxially stretched film (thickness of layer (B)/thickness of layer (A) + thickness of layer (B)) is α When the content of the polyethylene component having an ethylene content of 85% by weight or more obtained by elution and separation of the laminated biaxially stretched film by the column fractional elution method described below is defined as w% by weight, w/α is The polyethylene component must have an average intrinsic viscosity [η] _w (measured in tetralin at 135°C) of 1.5 to 10.0 dl/g. It is. If the value of w/α is less than 8% by weight, the degree of haze will be low, and if it is greater than 50% by weight, the degree of haze will not increase much, but the heat resistance will decrease, which is not preferable. Also, if the value of [η] _w is smaller than 1.5 dl/g,
The degree of haze is low, and if it is greater than 10.0 dl/g, it will cause uneven film formation, which is not preferable. In order to reduce the surface unevenness of the roughened layer, [η] _w is preferably 1.5 dl/g or more and less than 5.0 dl/g, and in order to increase the surface unevenness of the roughened layer, [η] _w is 5.0. ~10.0dl/g is good. The layer (B) in the present invention has a surface roughness Ra (center line average roughness, value measured at a cutoff value of 0.25 mm, JIS
B 0601) is preferably 0.2 μ or more, preferably 0.2 to 1.5 μ. In addition, layer (B) has a haze level (JIS K
6714) is 50% or more, and layer (B) has a gloss level (GS-
60°, JIS Z 8741 method 2) is more preferably 30 or less. Next, the column fractional elution method in the present invention will be described. Diatomaceous earth (Celite manufactured by Wako Pure Chemical Industries, Ltd.) as a carrier
No. 535), but also tetralin/
An ethyl carbitol mixed solvent is used. (1) 4g of sample and stabilizer 2,6-di-t-butyl-
45g of p-cresol with 800ml of tetralin
Pour into a 2000 ml flask and heat while stirring under a nitrogen stream to completely dissolve at 150°C. Next, 90 g of Celite was added, and after stirring at 150°C for 30 minutes, the temperature was lowered to 110°C at a rate of 0.5°C/min while stirring. Then similarly 0.167℃/min
The temperature is lowered to 90℃, and then further lowered at a rate of 0.33℃/min to 50℃. (2) After thoroughly mixing the supported sample obtained in (1) above with 500 ml of ethyl carbitol, it is packed into a column. There are no particular limitations on the structure of the column, but it should have an inner diameter of 2 to 5 cm and a height of 1 to 2 m.
The column can be kept at a temperature of 170°C or higher in some way. After filling the column, most of the tetralin is removed by flowing ethyl carbitol. (3) Perform fractional elution of the loaded sample with a tetralin/ethyl carbitol mixed solvent. At this time, the column temperature should be 170℃ or higher, for example 175℃ and ±
Fractional elution is performed by maintaining the temperature to an accuracy of 0.2°C and charging the mixed solvent after bringing it to 175°C. At this time, 8 g of 2,6-di-t-butyl-p-cresol was added to 400 ml of the mixed solvent. The eluted polymer is precipitated with a large amount of methanol, separated, and then dried. Regarding the ratio of tetralin/ethyl carbitol mixed solvent, the appropriate ratio will vary depending on the sample to be separated, but the appropriate ratio will be 0.2 to 0.4 g of polymer distilled with 400 ml of mixed solvent. Carbitol volume ratio should be varied from 18% to 100% and fractionated into approximately 10-20 parts. (4) Measure the intrinsic viscosity and ethylene content of the n parts separated by the above procedure. Intrinsic viscosity is 135℃ as a tetralin solution.
It is measured in Ethylene content can be determined by infrared absorption spectrum,
Measured by a known method such as NMR. Let W _i be the weight of the i-th separated portion, and i
Let the intrinsic viscosity of the ith fractionated portion be [η] _i and the ethylene content of the ith fractionated portion be EL _i . EL _i
Assuming that the fractionated portion containing 85 to 100% by weight is the (n-j)th to nth, the content w (wt%) of the polyethylene component with an ethylene content of 85 to 100% by weight in the present invention and its average limit Viscosity [η] _w is calculated using the following formula. In the present invention, various commonly used additives such as stabilizers, antistatic agents, and lubricants may be used in the resin compositions forming layer (A) and layer (B) as necessary. . In the present invention, the resin composition forming the layer (A) and the resin composition forming the layer (B) are simultaneously extruded using separate extruders to form the layer (B) on one or both sides of the layer (A). After forming a layer or three-layer sheet, it may be biaxially stretched, or the resin composition forming the layer (B) may be laminated on one or both sides of an unstretched film of the resin composition forming the layer (A). After that, this may be biaxially stretched. The translucent biaxially stretched laminated film obtained by the present invention can be used in a wide range of applications as follows. (1) By pasting this film on printed matter, photographs, etc., the shiny appearance can be changed to a soft and calm appearance. (2) When this film is printed, the finished print has a smooth and calm appearance. (3) By laminating this film with metal foil such as aluminum, the glittering effect of the metal foil can be removed. (4) When a metal such as aluminum is vapor-deposited on this film, a vapor-deposited film with no glitter can be created. (5) This film has good impregnability with oils such as electrical insulating oil, so it is also excellent as an insulating layer for electrical equipment that requires oil impregnation (such as capacitors and transformers). (6) Since this film has excellent mold release properties, it can be used as a mold release film when molding unsaturated polyester resins, melamine resins, etc. (7) Since this film can be heat-sealed, it can be used to make bags as is or to be placed in an automatic packaging machine. Furthermore, when heat is applied to the rough side, only that part becomes transparent, and this can be used to create a patterned film with a mixture of transparent and semi-transparent parts. This transparency can also be achieved by printing on the rough side with colorless ink. (8) If an adhesive tape or adhesive sheet is made by applying an adhesive to one side of this film, the adhesive part will be inconspicuous even when attached to an article. Furthermore, even if you use this tape to repair a torn part of a document, etc. and copy it, the tape will hardly come out on the copying surface, resulting in clean copies. As described above, the biaxially stretched laminated film of the present invention has a very wide range of uses and is very useful. The present invention will be explained in more detail by the following examples, but these examples are not intended to limit the invention. Example 1 Polypropylene homopolymer ([η]
^* = 2.25 dl/g) (*intrinsic viscosity measured in tetralin at 135°C, the same applies hereinafter) was supplied to one extruder, and the other extruder was supplied with a propylene-ethylene block for layer (B). Copolymer ([η] = 3.03dl/
g, ethylene content 23.1% by weight, block copolymerization part [η] = 9.37 dl/g), merged in a short pipe section, and melt-extruded at 260 ° C. to form a sheet with a two-layer structure. This was wrapped around a cooling drum at 40°C and cooled and solidified. This sheet was preheated to 120° C., and then stretched 5.0 times in the longitudinal direction while being locally heated with an infrared heater. After feeding this uniaxially stretched sheet into a tenter and preheating it to 155℃,
It was stretched 9 times in the width direction at 160°C. Next, heat treatment was applied at 160° C. for 2 seconds while the film was kept under tension, and then air-cooled to obtain a two-layer laminated biaxially stretched film having a thickness of 20 μm. The thickness structure of the obtained film is that layer (A) is
The thickness of the layer (B) was controlled to be 16 μm, and the thickness of layer (B) was 4 μm. The haze of this film was measured. (Measurement of haze is
One film was measured using the method of ASTM D 1003-61. ) Next, using the laminated biaxially stretched film described above, fractionation was performed by a column fractional elution method. Put 4g of the above film and 45g of 2,6-di-t-butyl-p-cresol into flask 2 together with 800ml of tetralin, and after bubbling nitrogen thoroughly, heat in a nitrogen atmosphere and stir at 150℃ to completely Dissolved. Next, 90g of Celite No. 535 was added, and the mixture was kept at 150°C for 30 minutes while stirring thoroughly. Then, while stirring, the temperature is lowered at a rate of 0.5°C/min to 110°C. Next, the temperature was lowered at a rate of 0.167°C/min to 80°C, and then
The temperature was lowered to 50°C at a rate of 0.33°C/min. After the temperature was lowered to room temperature, the mixture was thoroughly mixed with 500 ml of ethyl carbitol. All of the above operations were performed under a nitrogen atmosphere. Prepare a column with a jacket attached to the bottom of the column and a glass filter. The column has a height of 1 m and an internal diameter of 4 cm. The above sample is loaded into this column, and most of the tetralin is washed out and removed by opening the column and allowing ethyl carbitol to flow from the top while the liquid is flowing. Next, the kettle was closed and 175°C silicone oil was passed through the jacket to maintain the internal temperature at 175°C. Next, Tetralin/(Tetralin + Ethyl Carbitol) is 18
%, 22%, 25%, 27.5%, 29.5%, 31%, 32%,
33%, 34%, 35.5%, 37%, 39%, 43%, 50%,
Elution operations were performed sequentially using 400 ml of each 100% developing solvent. Note that 8 g of 2,6-di-t-butyl-p-cresol was added to each developing solvent. Each fraction separated by the above operation was precipitated with a large amount of methanol, thoroughly dried, and the weight, intrinsic viscosity, and ethylene content of each fraction were measured, and w, w/α, [η] were determined according to the definitions described above. _w was calculated.
The results are shown in Table 1. Example 2 For layer (B), propylene-ethylene block copolymer ([η] = 2.17 dl/g, ethylene content 18.5
Weight%, [η] of block copolymerized part = 2.17 dl/g)
Everything was carried out in the same manner as in Example 1 except that . The results are shown in Table 1. Example 3 For layer (B), a propylene-ethylene block copolymer ([η] = 2.25 dl/g, ethylene content 23.0
Weight%, [η] of block copolymerized part = 3.10 dl/g)
Everything was carried out in the same manner as in Example 1 except that .
The results are shown in Table 1. Example 4 For layer (B), a propylene-ethylene block copolymer ([η] = 3.22 dl/g, ethylene content 25% by weight, [η] of the block copolymer portion 8.52 dl/g) is used. Everything else was the same as in Example 1. The results are shown in Table 1. Comparative Example 1 For layer (B), propylene-ethylene block copolymer ([η] = 2.25 dl/g, ethylene content 6.0
Weight %, [η] of block copolymerized portion = 2.78 dl/g)
Everything was carried out in the same manner as in Example 1 except that . The results are shown in Table 1. Comparative Example 2 For layer (B), propylene-ethylene block copolymer ([η] = 1.93 dl/g, ethylene content 18.5
Weight%, [η] of block copolymerized portion = 1.50 dl/g)
Everything was carried out in the same manner as in Example 1 except that . The results are shown in Table 1. Comparative Example 3 Propylene-ethylene block copolymer for layer (B) ([η] = 3.42 dl/g, ethylene content 18.0% by weight, [η] of block copolymer portion = 16.3 dl/g)
Everything was carried out in the same manner as in Example 1 except that . The results are shown in Table 1. It can be seen from Table 1 that the laminated biaxially stretched polypropylene film of the present invention has no uneven film formation and a good degree of surface roughening. Comparative Example 4 For layer (B), a block copolymer having the same composition as in Example 2 was used to obtain a laminated unstretched film having a polypropylene layer of 16 μm and a block copolymer layer of 4 μm. The results are shown in Table 1. Comparative Example 5 For layer (B), a normal injection molding high impact resistant block copolymer Noblen BJS-G (manufactured by Mitsui Toatsu Chemical Co., Ltd.) ([η] = 2.30, ethylene content 9.0% by weight, block copolymerization Comparative Example 4 using [η] = 3.8)
A laminated unstretched film was obtained in the same manner. Results first
Shown in the table. Comparative Example 6 The same procedure as in Example 1 was carried out except that a block copolymer having the same composition as in Comparative Example 5 was used for layer (B). The results are shown in Table 1.

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Claims (1)

[Scope of Claims] 1 A laminated biaxially stretched film comprising a layer (A) made of polypropylene and a roughened layer (B) made of a propylene-ethylene block copolymer resin composition on at least one side, Thickness of layer (B) / thickness of layer (A) + layer (B)
) = α, and the content of the polyethylene component with an ethylene content of 85% by weight or more, which is obtained by eluating and separating the laminated biaxially stretched film by a column fractional elution method, is w% by weight. , the value of w/α is 8
% by weight or more, and the average intrinsic viscosity of the polyethylene component [η] _w (measured in tetralin at 135°C)
A roughened biaxially oriented polypropylene film having a surface roughening of 1.5 to 10.0 dl/g.