JP2001071432A - Multilayered stretched polypropylene film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered stretched polypropylene film excellent in transparency, slip properties, blocking resistance, scratch resistance and drop out properties and suitable for overlap-packaging having high speed auto matic packaging properties. SOLUTION: A polypropylene film is formed by laminating a skin layer formed from a polypropylene resin compsn., which is prepared by compounding 0.05-0.5 pts.wt. of three-dimensional calcite type calcium carbonate particle having a vol. mean particle size of 1.5-5 μm, a ratio (D90/D10) of a 90% cumulated particle size (D90) and 10% cumulated particle size (D10) of 5.0 or less and containing no particles with a particle size of 10 μm or more with 100 pts.wt. of a propylene random copolymer with an MFR of 1-30 g/10 min, to at least the single surface of a substrate layer formed from a crystalline propylene polymer and stretched at least uniaxially to obtain a multilayered stretched polypropylene film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer stretched polypropylene film having a heat seal layer laminated thereon.
More specifically, it relates to a multilayer stretched polypropylene film having excellent transparency, slipperiness, blocking resistance, scratch resistance, and falling resistance, and significantly reduced contamination in a film processing step, and excellent in automatic packaging suitability. .

[0002]

2. Description of the Related Art A multilayer stretched polypropylene film such as a biaxially stretched polypropylene film having a heat seal layer laminated thereon is widely used as an overlap packaging film for food, tobacco, cassette tape and the like. In such a film, due to the recent development of a high-speed automatic packaging machine, the quality required for automatic packaging suitability has been higher than ever.

[0003] For example, one of the important characteristics of an overlap packaging film is low-temperature heat-sealing property. This low-temperature heat-sealing property is not suitable for a resin material forming a heat-sealing layer. A method has been proposed in which a resin such as an excellent propylene / ethylene random copolymer or propylene / ethylene / butene-1 copolymer is added as a second component.

On the other hand, another important property is anti-blocking property. Blocking refers to a phenomenon in which, when films are stacked, the films that come into contact with each other are in close contact with each other and are hardly peeled off. If the blocking resistance is poor, the packaging operation is hindered. As a measure for improving the suitability of a film for a packaging machine for speeding up an automatic packaging machine in recent years, it is important to improve the blocking resistance.

As a means for improving the blocking resistance, a method of adding silicas such as amorphous silica and synthetic silica and inorganic fine particles such as calcium carbonate as an anti-blocking agent to a resin material forming a heat seal layer. (Japanese Patent Publication No. 4-30347) or a method of adding organic fine particles such as cross-linked polymethyl methacrylate (PMMA) and spherical silicone resin powder (Japanese Patent Application Laid-Open No. 62-233248). Has been
A great improvement effect has been obtained for speeding up the automatic packaging machine.

However, in the method using amorphous silica or synthetic silica, the affinity with the polypropylene resin is insufficient, so that voids are generated at the time of stretching the film, the transparency is deteriorated, and the antiblocking agent is dropped off. This causes problems such as contamination of the packaging machine. In addition, the projection shape on the film surface and the scratch resistance derived from the hardness become poor. Even in the method using organic fine particles, the affinity with the polypropylene resin was insufficient, so that the transparency and falling resistance were insufficient.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been developed in consideration of the above-mentioned circumstances, and has a high speed which is excellent in transparency, slip resistance, blocking resistance, scratch resistance, and anti-dropping resistance of an anti-blocking agent. To provide a multilayer stretched polypropylene film suitable for automatic packaging

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have used a resin composition in which specific properties of calcium carbonate particles are blended as an antiblocking agent with a propylene-based random copolymer for a skin layer. By making a multilayer film, we found that the above problems could be solved,
The present invention has been reached.

That is, the present invention provides a multilayer stretched polypropylene film having a layer [1] and a layer [2] shown below, which is a polypropylene film stretched in at least one direction.

[1] A base material layer formed of a polypropylene resin material containing a crystalline propylene polymer as a main component. [2] A layer provided on at least one side of the base material layer, wherein the volume average particle diameter is 1.5 with respect to 100 parts by weight of the propylene random copolymer having an MFR of 1 to 30 g / 10 min.
μm to 5 μm, the ratio (D90 / D10) of 90% cumulative particle size (D90) to 10% cumulative particle size (D10) is 5.0 or less,
A skin layer formed of a polypropylene resin composition containing 0.05 to 0.5 parts by weight of cubic calcite-type calcium carbonate particles having no particles having a particle size of 10 μm or more.

Further, the present invention provides the multilayer stretched polypropylene film, wherein the propylene random copolymer is a propylene / α-olefin random copolymer.

[0012]

Hereinafter, an actual embodiment of the present invention will be described. The multilayer stretched polypropylene film of the present invention,
The layer structure has at least the following base material layer and skin layer.

(1) Base Material Layer The base material layer is formed of a polypropylene resin material containing a crystalline propylene polymer as a main component.

Crystalline propylene-based polymer The crystalline propylene-based polymer used in the base material layer of the present invention may be a propylene homopolymer or a propylene having a majority polymerization ratio and another α-olefin (ethylene, butene, hexene). , 4-methylpentene, octene, etc.), unsaturated carboxylic acids or derivatives thereof (acrylic acid, maleic anhydride, etc.), aromatic vinyl monomers (styrene, etc.), random, block or graft copolymers. .

The isotactic index (II) of such a crystalline propylene polymer is at least 40%,
Among them, those having 60% or more, particularly 80% or more are preferable.
Therefore, it is most preferable to use a propylene homopolymer. I is 90% or more, especially 9
It is preferable to use 5% or more, particularly 98% or more, from the viewpoints of the stiffness of the film, the paper dropping property of the film feeding portion, and the suitability for high-speed automatic packaging.

Further, the MFR of the crystalline propylene polymer
(Melt flow rate: a value measured at 230 ° C. under a load of 2.16 kg in accordance with JIS-K6758) is 0.5
It is preferably 10 to 10 g / 10 min, particularly preferably 1 to 5 g / 10 min. When the MFR is in this range, the operability is good, so that it is preferable.

These crystalline propylene polymers may be used alone or as a mixture of plural kinds of polymers. Further, a resin containing a crystalline propylene-based polymer as a main component may be used.

Other Compounding Components The polypropylene resin material forming the base material layer contains the above-mentioned crystalline propylene polymer as a main component. In addition to the polymer, a range not impairing the effects of the present invention is provided. The other compounding material can be added arbitrarily. Examples of such compounding materials include other thermoplastic polymers such as ethylene polymers, butene polymers, and hydrocarbon polymers (including hydrogenated products thereof) such as petroleum resins, terpene resins, and styrene resins. be able to. Such another thermoplastic polymer can be blended, for example, in a range of 30% by weight or less.

Further, stabilizers such as antioxidants and weathering agents,
It may contain additives such as processing aids, coloring agents, antistatic agents and lubricants. Among these additives, those containing an antistatic agent are particularly preferable. Preferred examples of the antistatic agent include fatty acid esters of glycerin, alkylamines, ethylene oxide adducts of alkylamines, and fatty acid esters thereof. In the case of a film to which good antistatic performance has not been imparted, static electricity may accumulate during running of the film, resulting in poor paper dropping properties.

(2) Skin Layer The skin layer is formed on at least one surface of the substrate layer, and may be formed on only one surface or both surfaces of the substrate layer. . The skin layer is formed of a polypropylene-based resin composition obtained by blending calcium carbonate particles having specific properties as an antiblocking agent with a propylene-based random copolymer.

Propylene random copolymer The propylene random copolymer used for the skin layer includes a propylene / α-olefin random copolymer.

The α-olefin which is a comonomer in the propylene / α-olefin random copolymer preferably has 2 or 4 to 10 carbon atoms. Specifically, ethylene, butene-1, pentene-1, Hexene-1, octene-1, 4-methylpentene-1 and the like.

Specific examples of the propylene / α-olefin random copolymer include a propylene / ethylene random copolymer and a propylene / ethylene / butene-1 random copolymer. More specifically, the propylene / ethylene random copolymer has an ethylene content of 2 to 10% by weight, preferably 3 to 8% by weight, particularly preferably 3 to 6% by weight. When the ethylene content in the propylene / ethylene random copolymer is less than the above range, the heat sealability tends to be reduced.
If the ethylene content exceeds the above range, the film tends to be sticky, and the blocking resistance tends to decrease and the scratch resistance tends to decrease.

The propylene / ethylene / butene-1 random copolymer has an ethylene content of 0.3.
-6% by weight, preferably 0.5-5% by weight, particularly preferably 1-4% by weight, and a butene-1 content of 2-30% by weight, preferably 3-25% by weight, particularly preferred. Is from 4 to 20% by weight. If the ethylene content or the butene-1 content in the propylene / ethylene / butene-1 random copolymer exceeds the above range, the film becomes sticky, the blocking resistance decreases, or the scratch resistance tends to decrease. is there.

MF of the propylene random copolymer
R is 1 to 30 g / 10 min, preferably 1 to 20 g / 1.
0 minutes, more preferably 2 to 20 g / 10 minutes, particularly preferably 2 to 10 g / 10 minutes. If the MFR is less than the above range, the extrusion moldability deteriorates and the productivity decreases, which is not preferable. If the MFR exceeds the above range, the thickness accuracy of the skin layer becomes unfavorable.

Calcium Carbonate Particles In the present invention, a specific property antiblocking agent is blended in the skin layer as an antiblocking agent. The calcium carbonate particles used here are cubic calcite-type calcium carbonate particles having a volume average particle size of 1.5 to
It is 5 μm, preferably 2.0 to 4.0 μm. When the volume average particle size is less than the above range, the blocking resistance is insufficient, and when the volume average particle size exceeds the above range, transparency, printability, and falling resistance are undesirably reduced. The volume average particle size is
The average particle diameter is defined as the particle diameter of 50% of the total volume calculated from the small particle side in the particle size distribution measured using a laser type particle size distribution analyzer.

Regarding the particle size distribution, the ratio (D90) of the 90% cumulative particle size (D90) to the 10% cumulative particle size (D10)
90 / D10) is 5.0 or less, preferably 3.0 or less. When D90 / D10 exceeds 5.0, the balance between transparency and blocking resistance deteriorates, which is not preferable. The 90% cumulative particle size means a particle size of 90% of the volume cumulative from the smaller particle side in the particle size distribution measured using the laser type particle size distribution analyzer, and 10%
Similarly, the cumulative particle size means a particle size of 10% by volume in total.

The calcium carbonate particles have a particle size of 1
It is characterized in that particles having a size of 0 μm or more do not exist. 10
If coarse particles having a size of μm or more are present, fish eyes are generated and the appearance of the film is deteriorated. In addition, print omission is likely to occur during film printing.

The mixing amount of the calcium carbonate particles is 0.1 to 100 parts by weight of the propylene-based random copolymer.
It is 0.5 to 0.5 part by weight, preferably 0.1 to 0.3 part by weight. If the amount of the calcium carbonate particles is less than the above range, the blocking resistance is insufficient, and if the amount exceeds the above range, the transparency is undesirably reduced.

In the present invention, since the calcium carbonate particle concentration in the skin layer may be finally within the above range, the calcium carbonate particles may be compounded, for example, by preparing a polypropylene resin composition having a predetermined concentration. Instead of forming the film afterwards, a method of preparing a high-concentration master batch in advance and performing after blending at the time of forming the film may be adopted. The method for producing the calcium carbonate particles is not particularly limited, and commercially available ones can be used. For example, CUBE series manufactured by Maruo Calcium Co., Ltd. may be mentioned.

Other Ingredients The polypropylene resin composition for forming the skin layer of the present invention does not impair the effects of the present invention in addition to the above essential components (namely, the propylene random copolymer and calcium carbonate particles). Within the range, auxiliary additives generally used in polypropylene resin materials can be arbitrarily compounded. Such auxiliary components include antioxidants,
Examples include weathering agents, antistatic agents, neutralizing agents, lubricants and the like.

In addition to the above essential components, additional components other than the above essential components can be added for further improvement or for other purposes. Examples of the additional component include an acid-modified polyolefin resin, a crystalline butene-1 polymer, and propylene / butene-
Transparency, resistance to falling off, and low-temperature heat sealability can be further improved by adding 1 copolymer or the like to the propylene-based random copolymer.

The acid-modified polyolefin resin is a polyolefin resin in which at least a part of the terminal is acid-modified, and has an acid value defined by JIS-K0070 of 1.0 to 100 mgKOH / g, preferably 5 to 100 mgKOH / g. 60m
Those having gKOH / g are preferred.
When the acid value is less than the above range, the effect of further improving the transparency and the effect of preventing the calcium carbonate particles from falling off may not be expected. On the other hand, if it exceeds the above range, the operability deteriorates. Polyolefins include propylene, ethylene, butene-1, hexene-1, 4-
A homopolymer or copolymer such as methylpentene-1 or a mixture of these polymers is exemplified, and among them, low molecular weight polypropylene is preferably used.

The acid-modified polyolefin resin using the above low molecular weight polypropylene includes a number average molecular weight of 800
~ 20,000, preferably 1,000 ~ 18,000
(Hereinafter, may be simply abbreviated as “acid-modified low-molecular-weight PP”). The acid-modified low molecular weight PP is obtained by chemically adding an unsaturated carboxylic acid and / or an anhydride thereof described below to a low molecular weight polypropylene having a terminal double bond,
Alternatively, it is synthesized by reducing the molecular weight of ordinary acid-modified polypropylene, and at least a part thereof is acid-modified at its terminal. The acid-modified polypropylene obtained by the acid modification generally has a softening point of 13
It indicates a temperature of 0 to 170C, preferably 140 to 160C.

Preferred low molecular weight polypropylene having a terminal double bond is 1 to 1 per 1,000 carbons.
It has 0, preferably 2 to 7 terminal double bonds, and has a number average molecular weight of 800 to 20,000, preferably 1,000 to
18,000. If the terminal double bond is less than the above range, desired acid modification may not be performed. If the terminal double bond exceeds the above range, the heat resistance of the acid-modified low molecular weight PP tends to decrease. . Further, when the number average molecular weight exceeds the above range, there is a tendency that a further improvement effect of transparency and a further improvement effect of preventing dropping of calcium carbonate particles cannot be expected.

The above acid modification is carried out by a melt grafting method or a solution grafting method. In the melt grafting method, the reaction temperature is usually 100 to 270 ° C., preferably 130 to 240 ° C., usually 0.5 to 30 hours. It is preferably carried out under the conditions of a reaction time of 1 to 20 hours. In the solution grafting method, after completely dissolved in xylene, a peroxide is used in combination, and the reaction with an unsaturated carboxylic acid and / or an anhydride thereof is usually performed at 120 to 180 ° C., preferably 140 ° C.
The reaction is carried out at a reaction temperature of １６０160 ° C., usually for a reaction time of 1 to 20 hours, preferably 3 to 15 hours.
Then, a precipitate is obtained using a large amount of acetone or the like. Those obtained by the acid modification generally contain 0.01 to 20% by weight, preferably 0.05 to 15% by weight, particularly preferably 0.1 to 20% by weight of unsaturated carboxylic acid and / or anhydride thereof.
Desirably, it is contained at a ratio of 10% by weight.

The unsaturated carboxylic acid as a modifier includes:
Examples include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and nadic acid. Further, as the unsaturated carboxylic anhydride,
Maleic anhydride, itaconic anhydride, citraconic anhydride,
Allyl succinic anhydride, nadic anhydride and the like can be mentioned. Among these, it is preferable to use maleic anhydride.

Such an acid-modified polyolefin may be a directly modified one diluted with an unmodified one, or may be appropriately selected from commercially available ones. As a commercially available product, a maleic anhydride-modified polypropylene such as Umex series (manufactured by Sanyo Chemical Industries, Ltd.) can be used.

The preferred compounding amount of the acid-modified polyolefin resin is 0.01 to 5 parts by weight based on 100 parts by weight of the propylene random copolymer. If the compounding amount is less than the above range, a further improvement effect of transparency or a further improvement effect of preventing calcium carbonate particles from falling off may not be expected. On the other hand, if the amount exceeds the above range,
This is not preferable because the appearance of the film tends to deteriorate and the heat sealability tends to deteriorate, and the cost increases.

In addition to the above-mentioned crystalline butene-1 polymer as an additional component that can be used, butene-1
And copolymers of butene-1 with other α-olefins such as ethylene and propylene. Further, the MFR of these copolymers is 180 to 300.
At the same temperature in the range of ° C., the use of a propylene-based random copolymer having an MFR equal to or greater than that of the propylene-based random copolymer is advantageous in that transparency and low-temperature heat sealability can be further improved. preferable.

In order to improve the suitability for high-speed packaging, it is preferable to add an organic lubricant such as various silicone oils and silicone gums. Particularly preferred lubricants include polydiorganosiloxane gums having a polymerization degree n of 3,500 to 8,000, or a viscosity of 100 to 10
000 centistokes silicone oil, and the like.
It is preferable to add about 0.1 to 1 part by weight based on parts by weight.

Polypropylene Resin Composition The polypropylene resin composition for forming the skin layer of the present invention comprises the essential components of the above-mentioned propylene random copolymer, calcium carbonate particles, and, if necessary, an acid-modified polyolefin resin. And the like, and then mixed by a mixer such as a Henschel mixer, a V blender, a ribbon blender or the like, and then kneaded with a kneader such as a single screw or twin screw extruder. The calcium carbonate particles may be prepared by blending a masterbatch blended in a larger amount than a predetermined amount, and diluting the masterbatch during molding.

MFR of the polypropylene resin composition
Is 1 to 30 g / 10 min, preferably 1 to 20 g / 10
Min, more preferably 2 to 20 g / 10 min, particularly preferably 2 to 10 g / 10 min. If the MFR is less than the above range, the extrusion moldability deteriorates and the productivity decreases, which is not preferable. If the MFR exceeds the above range, the thickness accuracy of the skin layer becomes unfavorable.

(3) Multilayer stretched polypropylene film The multilayer stretched polypropylene film of the present invention is a multilayer film having at least the above-mentioned substrate layer [1] and skin layer [2] in its layer structure. The skin layer,
It may be formed on at least one surface of the substrate layer, and may be formed on only one surface of the substrate layer, or may be formed on both surfaces.
Further, in addition to the base layer and the skin layer, a layer having various functions such as an adhesive layer and a gas barrier layer can be appropriately provided between the base layer and the skin layer as needed.

The multilayer stretched polypropylene-based film of the present invention having such a layer constitution only needs to be stretched in at least one uniaxial direction.
It may be a biaxially stretched film.

The thickness of the multilayer stretched polypropylene-based film is appropriately determined depending on its use.
It is in the range of 100 μm, preferably 10 to 60 μm.
The ratio of the skin layer to the base material layer is usually 1 to 20%, preferably 1.5 to 10%. More specifically, the thickness of the skin layer is generally 0.2 to 3 μm, preferably 0.3 to 2 μm. If the thickness of the skin layer exceeds the above range, transparency may be poor. If the thickness is less than the above range, uniform heat sealing strength may not be provided.

(4) Method for Producing Multilayer Stretched Polypropylene Film The multilayer stretched polypropylene film of the present invention is obtained by coating the surface of a base material layer formed of a polypropylene resin material containing a crystalline propylene polymer as a main component. It is manufactured by laminating and stretching a skin layer formed of the polypropylene resin composition for a skin layer.

Lamination As a method of lamination, for example, a polypropylene resin composition for a skin layer is melt-coextruded on one or both sides of a polypropylene resin material for a base material layer to form a sheet, and this is uniaxially formed. Alternatively, a biaxial stretching method is preferable because the skin layer can be easily and uniformly and thinly laminated. In addition, the unstretched base layer sheet is formed in advance,
After melt-extruding and coating the polypropylene resin composition for the skin layer, a method of uniaxially or biaxially stretching, or after melt-extruding and coating the polypropylene resin composition for the skin layer on the uniaxially stretched base layer sheet. Alternatively, a method of stretching in a direction perpendicular to the stretching direction of the base material layer to form biaxial stretching can also be adopted.

Stretching In the case of uniaxial stretching, for example, a method utilizing a difference in roll peripheral speed may be mentioned.
It is stretched 3 to 8 times, preferably 4 to 6 times at ~ 135 ° C.

The method of biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching. In the case of sequential biaxial stretching, the stretching is carried out in a tenter oven in the transverse direction following the longitudinal stretching in a tenter oven.
Stretching, preferably 6 to 11 times. In addition, in order to prevent heat shrinkage at the time of heat sealing, to prevent shrinkage with time, and to prevent heat shrinkage at the time of secondary processing, 120 to 1 after the above stretching step.
It is preferred to heat set at a temperature of 70 ° C.

Other Treatments In the present invention, known surface treatments such as corona discharge treatment and flame treatment are applied to the obtained multilayer stretched film for the purpose of further imparting printability and promoting bleeding of an antistatic agent. Can be applied.

(5) Applications The multilayer stretched polypropylene film of the present invention has good blocking resistance and the antiblocking agent does not easily fall off, so that it has good suitability for high-speed automatic packaging and has no contamination to packaging machines. Since it has good transparency, low-temperature heat sealability, and scratch resistance, it is suitable for high-speed automatic packaging and can be suitably used as a film for overlapping packaging of foods, cigarettes, cassette tapes, and the like.

[0053]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, the measured value of each item in the examples was measured by the following method.

(1) MFR (unit: g / 10 min) Measured according to the melt flow rate (condition: 230 ° C., load: 2.16 kgf) according to JIS-K6758 polypropylene test method.

(2) Haze (unit:%) Measured according to JIS-K7105 and used as a measure of transparency. The smaller the value, the better the transparency.

(3) Blocking property (unit: g / 10c)
m ² ) From the obtained film, a corona-treated surface of a sample film of 2 cm (width) × 15 cm (length) is overlapped over a length of 5 cm, and under a load of 100 g / cm ² under an atmosphere of 40 ° C. for 24 hours. After the standing, the load was removed, the temperature was sufficiently adjusted to 23 ° C., and the force required for shearing and peeling the sample was measured at a speed of 200 mm / min using a tensile tester. The smaller the value, the better.

(4) Slipperiness In accordance with ASTM-D1894, the obtained film was measured for a coefficient of static friction (μs) and a coefficient of dynamic friction (μd) by a slip tester method. The smaller the value, the better the slipperiness.

(5) Scratch Resistance A 100 × 300 mm film (film A) was sagged on a wooden plate on which a felt cloth was stuck, and was fixed with the corona treated surface facing upward without wrinkling. 50 × 150mm
Is placed on the film A so that the corona-treated surfaces are in contact with each other, and 3 kg is placed on the center of the film B.
Was placed so as to make contact with an area of 5 × 5 cm. Next, by moving the film B horizontally,
The space between 300 mm was rubbed three times in one direction. Haze (“four-layer haze”) was measured by stacking four films A rubbed in this way, and “Δ4-layer haze” which was the difference from “four-layer haze” of film A before rubbing was measured. Was determined as a measure of the scratch resistance of the film. The smaller the value, the better.

(6) Drop-off resistance A 100 × 300 mm film was fixed on a glass plate with the corona-treated surface facing up, without sagging and without wrinkling. In addition, a 100 × 50 mm black paper was wound around a bar having a contact area of 100 × 10 mm around which gauze was wound three times and fixed. Both have an amplitude of 200 mm and a shaking speed of 72
Rubbing was performed for 10 minutes under the condition of times / minute. The adhesion of the antiblocking agent to the black paper was visually observed and evaluated according to the following criteria. ：: Almost no adhesion was observed. Δ: Slight adhesion is observed. X: Adhesion is observed. XX: Vigorous adhesion is observed.

(7) Particle size measurement (volume average particle size, 90% cumulative particle size, and 10% cumulative particle size) A laser type particle size distribution analyzer (Ultrasonic dispersion using a dispersion medium of methanol for 120 seconds in advance) was used. `` SK LASER MICRON SIZER PRO-7000S '': SEISHIN ENTE
RPRISE CO. LTD) was used to measure the particle size distribution, and the particle size of 50% of the total volume calculated from the small particle side in the obtained particle size distribution was defined as the volume average particle size, and the total volume of 10%
10% cumulative particle size (D10), 90% cumulative volume
Was determined as the 90% cumulative particle size (D90).

(8) Heat Sealability (Unit: ° C.) Using a heat seal bar of 5 mm × 200 mm, a heat seal pressure of 1 kg / cm ² and a heat seal time of 10 seconds were used to measure 15 m from a sample sealed at each temperature setting.
A sample having a width of m was peeled off at a tensile speed of 500 mm / min using a shopper type tester, and the load was read. The heat sealability was evaluated at a sealing temperature (° C.) at which a load of 300 g was reached. The smaller this value is, the better the heat sealing property is.

[0062]

Example 1 (1) Production of anti-blocking agent master batch MFR 5.0 g / 10 min, ethylene content 4.0% by weight propylene / ethylene random copolymer powder 94% by weight, "CUBE18BHS" manufactured by Maruo Calcium Co., Ltd. "
(Cubic calcite-type calcium carbonate particles: volume average particle size = 1.8 μm, D90 / D10 = 2.0, particle size 10
1% by weight), and an acid-modified polypropylene resin ("UMEX 100" manufactured by Sanyo Chemical Industries, Ltd.).
1 ", acid value = 26 mgKOH / g) 0.05 part by weight of calcium stearate and 0.2 part by weight of BHT (2,6-di-tert-butylhydroxytoluene) per 100 parts by weight of a resin composition consisting of 5% by weight. , Irgano
After mixing 0.05 parts by weight of x1010 (manufactured by Ciba Geigy) with a Henschel mixer, the mixture was granulated with a 30 mm single screw extruder and pelletized to obtain an antiblocking agent master batch.

(2) Preparation of Resin Composition for Skin Layer Ethylene content 2% by weight, butene-1 content 12% by weight, M
Propylene ethylene butene-1 random copolymer powder having an FR of 5.5 g / 10 min; 100 parts by weight, calcium stearate; 0.05 parts by weight, BHT; 0.2
After mixing with a Henschel mixer, 0.05 parts by weight of Irganox 1010 by weight was granulated with a 50 mm single screw extruder to obtain propylene / ethylene / butene-1 random copolymer pellets. 80% by weight of the obtained propylene / ethylene / butene-1 random copolymer pellets,
The anti-blocking agent master batch obtained in the above (1) was mixed with 20% by weight of a master batch using a ribbon mixer, and a pellet mixture (resin composition for a skin layer of a multilayer stretched polypropylene film: anti-blocking agent concentration: 0.2% by weight) Equivalent).

(3) Preparation of resin material for base layer MFR 2.3 g / 10 min polypropylene powder (propylene homopolymer); 100 parts by weight; calcium stearate; 0.05 parts by weight; BHT; 0.2 parts by weight , I
rganox1010; 0.05 parts by weight and 0.9 parts by weight of a fatty acid ester of polyoxyethylene alkylamine were mixed with a Henschel mixer, and the mixture was granulated with a 50 mm single screw extruder to form polypropylene pellets (based on a multilayer stretched polypropylene-based film). (Resin material for material layer).

(4) Production of Multilayer Stretched Polypropylene Film The pellet mixture obtained in the above (2) was used as a skin layer,
The polypropylene pellet obtained in the above (3) is used as a core layer, and is co-extruded from a T-die so that a two-layer sheet of a skin layer / core layer is formed, and rapidly cooled by a cooling roll to obtain a sheet having a thickness of about 1 mm. I got The sheet is stretched in a tenter-type sequential biaxial stretching apparatus at 140 ° C. in the longitudinal direction at a stretch ratio of 5 times, and then preheated to 164 ° C. in a tenter furnace, and then stretched in the transverse direction at 160 ° C. by 8 times in the transverse direction. It was stretched at a magnification and the skin layer surface was subjected to corona discharge treatment. In this way, a biaxially oriented polypropylene film of two kinds and two layers having a total film thickness of 25 μm (of which the skin layer thickness was 2 μm) was obtained. Table 1 shows the evaluation results.

[0066]

Example 2 In the production of the anti-blocking agent masterbatch of Example 1, "CUBE18BHS" was replaced with CUBE25BHS (cubic calcite-type calcium carbonate particles manufactured by Maruo Calcium Co., Ltd .: volume average particle size: 2.5 μm).
m, D90 / D10 = 1.9, and no particles having a particle size of 10 μm or more). Table 1 shows the evaluation results.

[0067]

Comparative Example 1 In the production of the anti-blocking agent masterbatch of Example 1, "CUBE18BHS" was replaced by Fuji Silysia Co., Ltd., Silicia 350 (amorphous silica fine particles: volume average particle diameter 1.8 μm, D90 / D10 = 4.
Except having changed to 1), it carried out similarly to Example 1. Table 1 shows the evaluation results. This was inferior to the examples in blocking resistance, slipperiness, and scratch resistance.

[0068]

Comparative Example 2 In the production of the anti-blocking agent masterbatch of Example 1, "CUBE18BHS" was replaced with Art Pearl F4P manufactured by Negami Kogyo Co., Ltd. (crosslinked PMMA fine particles: volume average particle diameter 1.8 μm, D90 / D10 = 2). .
The procedure was performed in the same manner as in Example 1 except that the procedure was changed to 0). Table 1 shows the evaluation results. This was inferior in drop-out resistance as compared with the example.

[0069]

Comparative Example 3 In the production of the anti-blocking agent master batch of Example 1, "CUBE18BHS" was replaced with Tospearl 120 (spherical synthetic silica fine particles: volume average particle diameter 2.0 μm, D90 / D10 = 1.
Except having changed to 9), it carried out similarly to Example 1. Table 1 shows the evaluation results. This was inferior to the examples in scratch resistance and shedding resistance.

[0070]

Comparative Example 4 The procedure of Example 1 was repeated except that the propylene / ethylene / butene-1 random copolymer was replaced with a polypropylene homopolymer having an MFR of 2.3 g / 10 min in the preparation of the skin layer resin composition of Example 1. Performed similarly to 1. Table 1 shows the evaluation results. This was inferior to the examples in heat sealability.

[0071]

[Table 1]

[0072]

The multilayer stretched polypropylene film of the present invention contains a specific amount of calcium carbonate particles having a specific structure as an anti-blocking agent in the skin layer, and has high blocking resistance and the anti-blocking agent does not easily fall off. For this reason, it has good high-speed automatic packaging suitability, and there is no contamination to the packaging machine. Further, it has excellent transparency, low-temperature heat sealability, and scratch resistance. Therefore, it is suitable for high-speed automatic packaging and can be suitably used as an overlap packaging film for foods, cigarettes, cassette tapes and the like.

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 4F100 AA08B AA08C AK04 AK04J AK07 AK07A AK07B AK07C AK07J AK09 AK09J AK64 AK66B AK66C AK80 AL03 AL03B AL03C AL07 AT00A BA02 BA03 BA06 BA10B01B01B18 BA10BBABBAE JK16 JL00 JL06 JL12 JN01 YY00B YY00C 4F210 AA03H AA11 AA11H AB07 AB16 AG03 AH54 QA02 QC06 QG01 QG15 QG18

Claims (2)

[Claims] 1. A multilayer stretched polypropylene film having a layer [1] and [2] shown below, which is a polypropylene film stretched in at least one direction. [1] A substrate layer formed of a polypropylene resin material containing a crystalline propylene polymer as a main component. [2] A layer provided on at least one side of the base material layer, wherein the volume average particle diameter is 1.5 with respect to 100 parts by weight of the propylene random copolymer having an MFR of 1 to 30 g / 10 min.
μm to 5 μm, the ratio (D90 / D10) of 90% cumulative particle size (D90) to 10% cumulative particle size (D10) is 5.0 or less,
A skin layer formed of a polypropylene resin composition containing 0.05 to 0.5 parts by weight of cubic calcite-type calcium carbonate particles having no particles having a particle size of 10 μm or more. 2. The propylene random copolymer,
A propylene / α-olefin random copolymer,
The multilayer stretched polypropylene-based film according to claim 1.