JPS6210192B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a matted polyolefin laminated film that has hand-tearability in any direction, practical strength, and excellent drawability and copyability.

For example, office adhesive tape is often used to bond printed or handwritten papers together. In this case, it is necessary to cut the tape to an appropriate length, but it is desirable that the tape be easily cut by hand or with a dispenser, rather than a sharp knife. on the other hand,
A certain level of practical strength is also required to prevent the bonded papers from separating easily. In addition, writing with a pencil, pen, etc. is carried out over the adhesive tape, or type printing or printing ink is sometimes placed on the tape, and drawing performance has become required. Further, printed matter to which tape is attached is often copied as is, and in this case, it is desirable that the shadow of the tape not be visible.

In this way, the ideal tape is easy to cut by hand,
It is necessary to use a film that has practical strength, drawability, and copyability, but at present no film has been found that satisfies all of these requirements.

For example, in order to improve the hand-tearability of the film, there are known methods such as irradiating the film with electron beams to make it brittle, or using brittle materials such as polystyrene. I haven't found anything that has both. In addition, drawability,
Attempts have been made to physically roughen the film surface in order to improve the copying properties, but these methods have had drawbacks such as loss of transparency and extremely low strength.

SUMMARY OF THE INVENTION It is an object of the present invention to meet the above-mentioned needs and provide a film that satisfies all of the requirements of hand-tearability, practical strength, drawability, and copyability.

The structure of the present invention is made of a crystalline low molecular weight polyolefin with an intrinsic viscosity of 0.5 to 1.5 and has a thickness of 5 to 50%.
A 50 μm thick layer is used as the center layer (A), and a layer of crystalline polyolefin with a higher melting point is formed on both sides.
Thin film layers (B) and (B') of 0.5 to 8 μm are laminated to form a three-layer laminated structure, and at least one of the thin film layers (B) and (B') has a surface roughness of 3 to 20 μm. This is a matted biaxially oriented polyolefin laminate film.

The crystalline low molecular weight polyolefin used as the center layer (A) of the laminated film of the present invention is a copolymer of propylene and other olefins (having 2 and 4 to 10 carbon atoms) (propylene content 70 to 99.5% by weight); Copolymers of ethylene and other olefins (3 to 10 carbon atoms) (ethylene content 70 to 99.5% by weight), butene-1 and other olefins (2, 3, and 5 to 5 carbon atoms)
10) (butene-1 content 70 to 99.5% by weight), copolymers of 4-methylpentene-1 and other olefins (carbon number 2 to 10) (4-methylpentene-1 content 70%) ~99.5% by weight) and other olefin copolymers (including not only binary copolymers but also tertiary or more copolymers; the copolymerization mode may be either random copolymerization or block copolymerization), and propylene, ethylene, butene
2 to 10 carbon atoms, such as 1,4-methylpentene-1
It is a homopolymer of olefin with an intrinsic viscosity of
It is in the range of 0.5 to 1.5, preferably in the range of 0.7 to 1.2. Particularly preferred is an intrinsic viscosity of 0.5
The above olefin copolymer in the range of ~1.5;
More preferably, the intrinsic viscosity is 0.5 to 1.5.
The above olefin copolymer has an intrinsic viscosity in the range of
This is a mixed composition containing 0.5 to 1.5 of the above olefin homopolymers (based on the weight of the mixture, the amount of olefin homopolymer is 2 to 40%). The intrinsic viscosity of such a crystalline low molecular weight polyolefin is
It is necessary for the purpose of the present invention to be in the range of 0.5 to 1.5, preferably 0.7 to 1.2. If the intrinsic viscosity is lower than this range, the film will become too brittle and will lack practical strength. Conversely, if the intrinsic viscosity is higher than this range, it will not be easy to cut by hand in any direction. Next, the thickness of the center layer (A) made of this crystalline low molecular weight polyolefin is 5 to 50 μm,
Preferably, it needs to be in the range of 10 to 40 μm. If it is thinner than this range, it will lack practical strength and will be too thin, resulting in poor handling and workability. On the other hand, if it is thicker than this range, the ability to cut it by hand in any direction becomes insufficient.

Next, thin film layers (B) are laminated on both sides of this central layer (A),
(B′) will be explained.

The thin film layer is made of crystalline polyolefin with a higher melting point than the central layer polymer, has a thickness of 0.5 to 8 μm, and has a surface roughness of at least 3 to 20 μm.
It needs to be in μm. The preferable melting point difference between the center layer polymer and the thin film layer polymer is in the range of 1 to 50°C, more preferably 5 to 30°C. If the melting point of the thin film layer polymer is not higher than the melting point of the central layer polymer, it will be extremely difficult to combine the object of the present invention of manual tearability in any direction and practical strength. The crystalline polyolefin used for this thin film layer may be propylene, ethylene, butene-1,4-methylpentene-1, or other materials with a carbon number of 10
It is a homopolymer, copolymer or block copolymer of the following olefins. Intrinsic viscosity is 0.5~
2.0, preferably in the range of 0.7 to 1.5. The thickness of one of this thin film layer needs to be in the range of 0.5 to 8 μm, preferably 1 to 5 μm.
If it is thinner than this range, the film will lack practical strength; conversely, if it is thicker than this range,
The ability to cut by hand in any direction is eliminated.

Furthermore, the surface of at least one of the thin film layers of the present invention must have a surface roughness of 3 to 20 μm. The standard for surface roughness is JIS B 0601, which will be described later.
Maximum height Rmax value measured according to 1976.
If the surface roughness is smaller than 3 μm, there will be no matting effect and the drawing performance will be improved because light is reflected without scattering, but the copyability will be affected due to the difference in light reflectance between the paper and the film of the present invention. It has the disadvantage that the revised portion is noticeable when

The following methods can be used to roughen the surface of the thin film layer.

(1) The polyolefin constituting the thin film layer has a particle size
Inorganic particles of 0.1 to 10 μm, preferably 0.5 to 5 μm, are added and mixed in an amount of 1 to 25% based on the polymer. Examples of suitable inorganic particles include calcium carbonate,
Examples include magnesium carbonate, magnesium oxide, alumina, silica, aluminum silicate, kaolin, kaolinite, talc, clay, diatomaceous earth, doromanite, titanium oxide, and zeolite.
If the amount of these inorganic fine particles added is less than the above range, there will be almost no effect of the addition. On the other hand, if the amount is greater than the above range, the copying suitability will be poor.

(2) Other polymers in polyolefin, such as polyethylene, polybutene-1, poly4-methyl-pentene-1, propylene/ethylene rubber,
Propylene/ethylene/diene ternary copolymer rubber, polybutadiene, polystyrene, polyethylene terephthalate, poly(ε-caprolactam), etc. are added in an amount of 1 to 25% based on the polymer.

(3) A block copolymer of uniaxially or biaxially stretched propylene and another olefin is used as the polyolefin constituting the thin film layer.
When this block copolymer is stretched, its surface becomes rough and it becomes drawable. As the other olefin, ethylene is most preferred, and the copolymerization ratio of propylene and olefin is preferably in the range of 95:5 to 65:35 (by weight). When using a propylene/ethylene block copolymer, the presence or absence of infrared absorption spectra at 720 cm ^-1 and 731 cm ^-1 can be used to distinguish between block copolymer and random copolymer. The absorption at 720 cm ^-1 is due to ethylene, and the absorption at 731 cm ^-1 is due to propylene chains, but in reality both types of absorption appear. The block copolymer suitable for the present invention is
The ratio A/B of absorbance A at 720 cm ^-1 and absorbance B at 731 cm ^-1 is in the range of 0.4 to 3.0, preferably 0.6 to 2.0.

(4) In addition to the block copolymer described in (3) above, (1)
The inorganic particles and/or other types of polymers mentioned in (2) are added and mixed.

(5) Perform mechanical processing such as embossing or sandblasting on the surface of the thin film layer.

The film of the present invention is a biaxially stretched laminated film. Biaxial stretching can improve practical strength and hand tearability. Note that the biaxial stretching method may be any method such as sequential biaxial stretching, simultaneous biaxial stretching, tubular method, etc.

In addition, since the heat treatment made the surface roughness of at least one side of the thin film layer (B) 3 to 20 μm, the hand tearability was improved, probably because cracks were generated from the surface unevenness and propagated compared to a smooth surface film. However, it is not necessary because the heat treatment temperature can be set to A.
It is preferable to carry out the treatment at a temperature higher than the melting point of the layer polymer and lower than the melting point of the B layer polymer, since this further improves the hand-cutting property.

The objective of the present invention, which is the range in which the film can be easily cut by hand in any direction and has practical strength, can be well expressed by the falling ball impact strength of the laminated film. In other words, in order to have the ability to cut by hand in any direction, within the thickness range of the film of the present invention, that is, within the thickness range of 6 to 66 μm, preferably 12 to 50 μm, the falling ball impact strength must be 25 kg cm or less. , preferably 20Kg・
It is highly desirable that the thickness be less than cm.
On the other hand, in order to have practical strength, it is extremely desirable that the falling ball impact strength be 2 Kg·cm or more, preferably 5 Kg·cm or more. Therefore, the purpose of the present invention, which is to have both hand cutability in any direction and practical strength, can be expressed numerically by having a falling ball impact strength in the range of 2 to 25 kg/cm, preferably 5 to 20 kg/cm. It can also be expressed as a three-layer laminated polypropylene film with a value of .

Next, a general example of the method for manufacturing the film of the present invention will be described. First, 1 to 25 inorganic particles with a particle size of 0.1 to 10 μm are
A three-layer laminate sheet in the form of B/A/B is produced by a known coextrusion method, with a crystalline low molecular weight polyolefin added as layer A and a crystalline polyolefin with a higher melting point as layer B. In this case, the intrinsic viscosity of the A layer polymer is such that the intrinsic viscosity of the A layer after film production is within the range of 0.5 to 1.5, preferably 0.7 to 1.2. Further, the intrinsic viscosity of the B layer polymer is such that the intrinsic viscosity of the B layer after film production is within the range of 0.5 to 2.0, preferably 0.7 to 1.5. In order to facilitate coextrusion etc., the intrinsic viscosity of layer B should be within the above range,
It is desirable that the intrinsic viscosity of layer A be within ±20%, preferably within ±10%. The thickness of layer A and layer B of this three-layer laminated sheet is such that the thickness of layer A after film production is 5 to 50 μm, preferably
The thickness of the B layer is preferably 0.5 to 8 μm, preferably 1 to 5 μm. In addition, the melting point of the polymer of layer B is 1 to 50°C, preferably 5 to 50°C, than that of layer A.
Keep the temperature 30℃ higher.

Such a three-layer laminated sheet is biaxially stretched 1.5 times, preferably 2 to 10 times, in each of the longitudinal direction and the width direction by a known biaxial stretching method such as simultaneous biaxial stretching or sequential biaxial stretching. The stretching temperature at this time is preferably in the range of (melting point of layer A polymer - 10) C. or higher and lower than or equal to the melting point of layer B polymer. Next, if necessary, this biaxially stretched film is heated for 1 to 100 seconds, preferably for 3 to 100 seconds, at a temperature range of not less than the melting point of the A-layer polymer and not more than the melting point of the B-layer polymer.
Heat treat for 30 seconds. This heat treatment may be a tension heat treatment in which the film is kept under tension, or a relaxation heat treatment in which the film is allowed to relax by 1 to 20% of its original length in the longitudinal and/or width directions; A combination of these may also be used. Next, if necessary, one or both sides of this film are subjected to a known surface activation treatment such as corona discharge treatment to reduce the wetting tension of the treated surface to 35~35.
50 dynes/cm. In the thus obtained three-layer laminated film, the thickness of the A layer is in the range of 5 to 50 μm, preferably 10 to 40 μm, and the thickness of the B layer is in the range of 5 to 50 μm, preferably 10 to 40 μm.
It is in the range of 0.5 to 8 μm, preferably 1 to 5 μm, so the total thickness is 6 to 66 μm,
Preferably it is in the range of 12 to 50 μm.
Further, inorganic fine particles are dispersed in the B layer, and the surface roughness thereof is in the range of 3 to 20 μm.

The present invention will be specifically described below with reference to Examples. In the Examples, the intrinsic viscosity, melting point, falling ball impact strength, and surface roughness are values measured as follows.

(1) Intrinsic viscosity 0.1 g of polymer is completely dissolved in 100 ml of tetralin at 135°C, and the specific viscosity S is determined by measuring this solution with a Fitz-Simmons viscometer in a constant temperature bath at 135±0.05°C. From this, the intrinsic viscosity is calculated using the following formula.

Intrinsic viscosity = S / [0.1 (1 + 0.22S)] In the present invention, the center layer (A layer) of the film
Alternatively, the intrinsic viscosity of the polymer of the surface layer (layer B) is a value measured by the method described above after sampling 0.1 g of the polymer constituting the layer. Therefore, even if the layer is made of a mixture of polymers, the value measured using 0.1 g of the polymer mixture is taken as the intrinsic viscosity of each layer of the film.

(2) Melting point 5 mg of polymer was set in a scanning thermal analyzer (DSC-type manufactured by Perkin Elmer), heated in a nitrogen atmosphere, and raised to 290°C (heating rate 20°C/min). ). After holding this temperature for 60 seconds, the sample is removed and immediately placed in liquid nitrogen for quenching. This sample is again set in the measurement cell, and the temperature is raised at a rate of 20° C./min, and the temperature at the endothermic peak caused by melting of the crystals is taken as the melting point of the polymer.
In addition, when two or more peaks appear because the polymer is composed of a mixture or a block copolymer, the temperature at the peak portion of the peak with the highest peak height is regarded as the melting point of the polymer.

(3) Falling ball impact strength The film is placed in a constant temperature room at 20±0.5°C overnight and measured in that state. Fix the film taut in a 5cm diameter frame. A steel ball (diameter 38.1 mm) is dropped from a height of 2 m directly above it.
Immediately after the steel ball breaks the film, the falling speed of the steel ball is measured with a phototube, and this speed is expressed as V (cm/sec).
shall be. Also, let V ₀ (cm/sec) be the falling speed at the relevant part when there is no film. Then,
The energy required to break the film (this is referred to as the falling ball impact strength) can be calculated using the following formula.

Falling ball impact strength (Kg・cm) = M (V ₀ ² - V ² )/2g However, M: Weight of steel ball (Kg) g: Gravitational acceleration (980cm/sec ² ) (4) Surface roughness (Rmax ) is determined from a chart of a specified length measured by the stylus method as described in JIS B0601-1976.

Example 1 The following two types of polymers were prepared.

Polymer A: Propylene-butene-1 random copolymer. Butene-1 content 6% by weight. Intrinsic viscosity 0.90. Melting point: 150℃. As an antioxidant, 2,6-di-t-butyl-p
- Contains 0.2% by weight of cresol and 0.6% by weight of stearic acid monoglyceride with a purity of 99% or more as an antistatic agent.

Polymer B: Propylene, ethylene block copolymer. Ethylene content 23%. 720 cm ^-1 and 731 cm in the infrared absorption spectrum
^-1 and absorbance ratio 1.36. Intrinsic viscosity 0.90.
Melting point 160℃. The following were added as a surface roughening agent, antioxidant and plasticizer.

Calcium carbonate: Calcium carbonate 20
% “Irganox 1010” (Ciba Geigy): 0.05% Calcium stearate: 0.20% These two polymers were fed into two separate extruders and melt extruded at 200°C to form a three-layer stack with three manifolds. The melts were merged together in a die to form a three-layer laminated sheet with a center layer made of Polymer A and both surface layers made of Polymer B.
This was taken out from the nozzle and immediately brought into contact with a cooling drum whose surface temperature was 35° C. while applying an electrostatic charge, to cool and solidify. This three-layer laminated sheet
After sufficiently preheating by contacting with a 145°C preheating roll, the film was stretched 6.5 times in the longitudinal direction while being rapidly heated with an infrared heater, and immediately brought into contact with a 20°C cooling roll to be rapidly cooled. This uniaxially stretched sheet is
After sufficiently preheating with hot air at 150°C, the film is stretched 8 times in the width direction, then heat treated in hot air at 155°C for 5 seconds while maintaining the tension, and then stretched to 6 times its original width in the same hot air. A relaxation heat treatment was performed for 3 seconds while allowing % relaxation, and then a tension heat treatment was performed again in the same hot air for 3 seconds, and then slowly cooled to room temperature (average cooling rate 30° C./sec). The thickness of the center layer of the film thus obtained was 29 μm, the thickness of both surface layers was 3 μm each, and the total thickness was 35 μm, making it a three-layer laminated film. The surface of this film is cloudy, and the surface roughness (Rmax) measured by the method described in JIS B0601-1976 is 6.
It was μm. On this surface, characters could be written on with a pencil or ballpoint pen, and the characters could also be clearly copied using a diazo copying machine. Furthermore, even if the film was pasted onto a printed matter with the surface of the film in contact with the printed material and a copy was made through the film, the film did not interfere with the copying process and a clear copy could be made. In addition, the falling ball impact strength of this film is 17Kg.
cm and could be easily cut by hand.

Example 2 Using exactly the same polymer as in Example 1, extrusion casting was performed under the same conditions to obtain an unstretched sheet. After sufficiently preheating this three-layer laminated sheet in a hot air oven at 143°C, it was stretched 5.5 times in the longitudinal direction and immediately heated to 25°C.
It was cooled by contacting it with a cooling roll. A three-layer laminated film was produced in the same manner as in Example 1, except that this uniaxially stretched sheet was stretched 8 times in the width direction in a tenter kept at 150°C, and then the film was formed while relaxing 10% at room temperature. Obtained. The surface of the film thus obtained was cloudy, and the surface roughness (Rmax) was 6 μm. This surface had good drawing properties and was excellent in copyability. The falling ball impact strength of this film was 18 kg cm, and it could be easily cut by hand.

Comparative Example 1 A three-layer laminated film with a thickness of 35 μm was obtained in the same manner as in Example 2, except that polymer B was homopolypropylene with an intrinsic viscosity of 1.4 (melting point: 160° C.). The film thus obtained was transparent and had a surface roughness (Rmax) of 1.0 μm. If you cannot write with a pencil or ballpoint pen, or if you paste a film onto a printed matter with the film side touching the printed matter and make a copy through the film, there will be lines at the edges and you will not be able to make a clean copy. Ta.

In addition, this film has a falling ball impact strength of 26 km/cm.
Therefore, it could not be easily cut by hand.

Comparative Example 2 Polymer A: Propylene/ethylene random copolymer, ethylene content 3.0wt/%, intrinsic viscosity 1.7, melting point 145°C, Polymer B: Example except that the intrinsic viscosity of the propylene/ethylene block copolymer was 1.7. A 35 μm three-layer laminated film was obtained in the same manner as in Example 1.

The surface of this film was cloudy and had a surface roughness of 7 μm. This surface had drawing properties and was excellent for copying, but the impact strength of falling balls was 29 kg·cm, and it was impossible to cut by hand.

Claims (1)

[Claims] 1. The center layer (A) is a 5-50 μm thick layer made of crystalline low molecular weight polyolefin with an intrinsic viscosity of 0.5-1.5, and on both sides are thin film layers of 0.5-8 μm thick made of crystalline polyolefin with a higher melting point. (B),
(B') is laminated to form a three-layer laminated structure, and at least one of the thin film layers (B) and (B') has a roughness of 3 to 20 μm. .