JP2001071431A - Multilayered stretched polypropylene film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered stretched polypropylene film for overlap having high transparency, slip properties, blocking resistance scratch resistance, drop out resistance and heat seal characteristics in good balance and suitable for high speed automatic packaging. SOLUTION: A polypropylene film is formed by laminating a skin layer formed from a resin compsn., which is prepared by compounding 0.05-0.5 pts.wt. of three-dimensional calcite type calcium carbonate particles with a vol. mean particle size of 1.5-5 μm, a ratio of a 90% cumulated particle size and a 10% cumulated particle size of 5 or less and containing no particles with a particle size of 10 μm or more with 100 pts.wt. of a propylene polymer with an MFR of 1-30, Me of 0.9-1.4, Tp of DSC of 100-140 deg.C and an orthodichlorobenzene extraction amt. of 2 wt.% or less, 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.
Specifically, it has excellent transparency, slipperiness, blocking resistance, scratch resistance, falling resistance and heat sealing properties, less stickiness, less deterioration in film storage and quality after transportation, and contamination in the film processing process. The present invention relates to a multilayer stretched polypropylene-based film excellent in suitability for automatic packaging, in which is significantly reduced.

[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 properties of the film for overlap packaging is heat sealing properties such as low-temperature heat sealing properties. As a method for improving low-temperature heat sealability, a resin such as propylene / ethylene random copolymer or propylene / ethylene / butene-1 copolymer having excellent heat sealability is used as a resin material for forming a heat seal layer. A method of adding as a component has been proposed.

[0004] Another important characteristic is blocking resistance. Blocking refers to a phenomenon in which when the films are sticky and the films are stacked, they are in close contact with each other and are difficult to peel 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). Have been.

However, the conventionally known biaxially stretched polypropylene film having a heat-sealing layer laminated thereon still has insufficient heat-sealing properties at a low temperature and insufficient heat-sealing properties. Even if the copolymerization amount of α-olefin such as ethylene is increased, the low-temperature heat sealability is improved, but the stickiness and the slipperiness of the film, particularly the film storage in summer, the slipperiness after transport, and the transparency over time. This causes problems such as deterioration of the quality.

Further, in a multilayer stretched film in which a low-temperature heat-sealing resin in which inorganic or organic fine particles are added to the surface layer of the film is laminated, the added fine particles easily fall off and fall off in various processes for processing the film. It has been found that they have disadvantages such as contamination by fine particles or deterioration in transparency and scratch resistance. That is, in the method using amorphous silica or synthetic silica,
Since the affinity with the polypropylene resin is insufficient, voids are generated at the time of stretching the film, the transparency is deteriorated, and problems such as the antiblocking agent falling off are caused. 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. These tendencies become more pronounced in films with better low-temperature heat sealability and transparency.

Therefore, it is excellent in transparency, slipperiness, blocking resistance, scratch resistance, and shedding resistance, and is also excellent in heat sealing properties such as low-temperature heat sealing properties, has little stickiness of a film, and is high-speed automatic. Development of a multilayer stretched polypropylene film suitable for packaging has been desired.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has good transparency, good slipperiness,
It is an object of the present invention to provide a multilayer stretched polypropylene film having a good balance of blocking resistance, scratch resistance, dropout resistance and heat sealing properties and suitable for high-speed automatic packaging with little stickiness of the film.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by using specific calcium carbonate particles as an anti-blocking agent in a propylene polymer having a specific property. And arrived at the present invention.

That is, the present invention provides a multi-layer stretched polypropylene film which is a polypropylene-based film stretched at least uniaxially and has the following layers [1] and [2].

[1] A substrate layer formed of a polypropylene resin material (A) containing a crystalline propylene polymer as a main component. [2] A polypropylene resin material (B), which is a layer provided on at least one side of the base material layer and mainly contains a propylene polymer satisfying the following conditions (a) to (d).
For 100 parts by weight, the volume average particle size is 1.5 μm to 5 μm.
m, 90% cumulative particle size (D90) and 10% cumulative particle size (D1
0) (D90 / D10) is 5.0 or less and the particle size is 1
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 of 0 μm or more.

(A) The melt flow rate is 1 to 30 g /
10 minutes. (B) The memory effect is 0.9 to 1.4. (C) a differential scanning calorimeter at the determined primary melting peak temperature _{(T P)} is in the range of 100 to 140 ° C.. (D) The amount of extraction when extracting at 40 ° C. using orthodichlorobenzene as a solvent is 2% by weight or less.

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

Further, in the present invention, the propylene-based resin material (B) may be such that the propylene-based polymer 80 to 100
The present invention provides the multilayer stretched polypropylene-based film, characterized by comprising 0 to 20% by weight of a polypropylene-based resin other than the propylene-based polymer.

[0016]

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

Crystalline propylene-based polymer The crystalline propylene-based polymer used in the substrate layer of the present invention may be a propylene homopolymer or a propylene having a polymerization ratio of more than half 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 crystalline propylene polymer has an isotactic index (II) of 40% or more,
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.

The melt flow rate of the crystalline propylene polymer (MFR: a value measured at 230 ° C. and 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 (A) forming the base material layer is
The main component is the above-mentioned crystalline propylene-based polymer, and other compounding materials can be arbitrarily added in addition to the polymer, as long as the effects of the present invention are not impaired. Such compounding materials include ethylene polymer, butene polymer,
Other thermoplastic polymers such as hydrocarbon polymers (including their hydrogenated products) such as petroleum resins, terpene resins and styrene resins can be mentioned. Such other thermoplastic polymers are:
For example, it can be blended 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 comprising a polypropylene-based resin material (B) containing a propylene-based polymer as a main component and calcium carbonate particles having specific properties as an anti-blocking agent.

Propylene Polymer The polypropylene resin material (B) used for the skin layer contains a propylene polymer as a main component. The propylene-based polymer satisfies the following conditions (a) to (d).

(A) MFR MFR of the propylene polymer (JIS-K6758)
Value measured at 230 ° C and 2.16 kg load according to
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.

(B) Memory Effect The propylene polymer has a memory effect (ME) of 0.9 to 1.4, preferably 1.0 to 1.3.
It is. If the ME exceeds the above range, the polymer contains a large amount of a high molecular weight component, and if the ME is less than the above range, the melt viscosity is too small, so that the thickness accuracy of the skin layer becomes poor in any case. The ME was measured by extruding the resin through an orifice having an inner diameter of 1.0 mm, an outer diameter of 9.5 mm, and a length of 8.0 mm at a measurement temperature of 190 ° C. at an extrusion speed of 0.1 g / min, and then collecting a strand. The diameter of this strand is determined by using a micrometer to two decimal places.

(C) Melting peak temperature (T _P ) The propylene-based polymer is a differential scanning calorimeter (Differ
ential Scanning Calorimeter: DSC) in the obtained primary melting peak temperature _{(T P)} is 100 to 140 ° C., preferably in the range of 110 to 135 ° C.. T _P is generated sticky feeling on the film is less than 100 ° C., the commercial value lowers. On the other hand, when the temperature exceeds 140 ° C., the heat sealing characteristics become poor.

(D) Orthodichlorobenzene Extraction Amount The propylene-based polymer has an extraction amount of 2% by weight or less, preferably 1.5% by weight or less when extracted at 40 ° C. using orthodichlorobenzene as a solvent. is there.
If the amount of extraction exceeds 2% by weight, the stickiness of the film will deteriorate.

The propylene-based polymer of the present invention satisfying the above conditions (a) to (d) is preferably a propylene / α-olefin random copolymer containing propylene as a main component. The α-olefin which is a comonomer in the propylene / α-olefin random copolymer preferably has 2 or 4 to 10 carbon atoms, and specifically includes ethylene, butene-1, pentene-1 and 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 4 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 becomes sticky, and problems such as deterioration of blocking resistance, slipperiness, transparency over time, and the like are likely to occur.

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 5 to 20% by weight. If the propylene / ethylene / butene-1 random copolymer has an ethylene content or butene-1 content exceeding the above range, the film tends to be sticky and the scratch resistance tends to decrease.

The propylene polymer of the present invention can be produced, for example, by a polymerization method using a metallocene catalyst.

Polypropylene Resin Material (B) The polypropylene resin material (B) used in the present invention may contain a polypropylene resin other than the propylene polymer. Specific examples of such a polypropylene resin include a propylene homopolymer and a propylene / ethylene random copolymer.

The polypropylene resin material (B) of the present invention
Is 80 to 100.
% By weight, the proportion of polypropylene resin is 0 to 20% by weight
It is. If the proportion of the propylene-based polymer is less than 80% by weight, the heat sealing properties deteriorate, which is not preferable.

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 1.5 to 4 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. In addition, the volume average particle diameter is a particle diameter of 50% of the volume cumulative from the small particle side in the particle size distribution measured by using a laser-type particle size distribution analyzer, as the average particle diameter.

As for 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 amount of the calcium carbonate particles is 0.05 to 0.5 part by weight, preferably 0.1 to 0.4 part by weight, based on 100 parts by weight of the polypropylene resin material (B). 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 In addition to the above essential components, the polypropylene resin composition for forming the skin layer of the present invention is generally used as a polypropylene resin material as long as the effects of the present invention are not impaired. Auxiliary components can be optionally added. Such auxiliary additives include antioxidants, 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, falling-off resistance, and low-temperature heat sealability can be further improved by adding a copolymer or the like to the polypropylene resin material (B).

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 specified 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. Examples of the polyolefin include propylene, ethylene, butene-1, hexene-1, and a homopolymer or a copolymer of 4-methylpentene-1 or a mixture of these polymers, and among them, low-molecular-weight polypropylene is preferably used. .

As the acid-modified polyolefin resin using the low molecular weight polypropylene, 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.

The 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 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 modifying agent 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 amount of the acid-modified polyolefin resin is 0.01 to 5 parts by weight based on 100 parts by weight of the polypropylene resin material (B). If the amount 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 the compounding amount exceeds the above range, the film appearance tends to deteriorate and the heat sealability tends to deteriorate, and the cost increases, which is not preferable.

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.
The use of a polypropylene resin material (B) having an MFR equal to or larger than that of the polypropylene resin material (B) at the same temperature in the range of ° C. can further improve transparency and low-temperature heat sealability. It is preferable because it can be performed.

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 of silicone oil and the like, and these are the above-mentioned polypropylene resin material (B) 10
It is preferable to add about 0.1 to 1 part by weight to 0 part by weight.

Polypropylene Resin Composition The polypropylene resin composition for forming the skin layer of the present invention may be any of the above-mentioned polypropylene resin material (B), calcium carbonate particles, and an optional acid-modified polyolefin resin used if necessary. Ingredients, Henschel mixer, V
It is preferable that the mixture is mixed by a mixer such as a blender or a ribbon blender, and then kneaded by 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 according to 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 a surface of a substrate 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, the polypropylene resin composition for the skin layer is melt-coextruded on one or both sides of the polypropylene resin material for the 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 using 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 a 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, shrinkage prevention with time, and heat shrinkage at the time of secondary processing, 120 to 170 following the above stretching step.
It is preferred to heat set at a temperature of ° 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 multi-layer stretched polypropylene film of the present invention has good blocking resistance and the anti-blocking agent does not easily fall off, so that it has good suitability for high-speed automatic packaging and no contamination to packaging machines. Excellent low-temperature heat sealability and heat seal start-up properties, and excellent heat seal properties.
Since it has good scratch resistance and transparency, 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.

[0063]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement method and evaluation method for each item in the examples are as follows.

(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) Memory Effect (ME) The temperature in the cylinder of the melt indexer was set to 190 ° C., the inner diameter was 1.0 mm, the outer diameter was 9.5 mm, and the length was 8.0 m.
An orifice with m / L / D = 8 was used. Also, place a measuring cylinder filled with ethyl alcohol directly below the orifice, and set the distance between the level immediately below the orifice and the liquid level
0 ± 2 mm. In this state, the sample is put into the cylinder, and the amount of the extrudate per minute is 0.10 ± 0.03 g.
The extrudate after 6 to 7 minutes was dropped into ethanol and solidified and collected after 6 to 7 minutes. The diameter of the extruded strand-shaped sample was measured with a micrometer at three places: 1 cm from the top, 1 cm from the bottom, and the center, and the maximum and minimum values were determined for each. The average value of the diameters obtained was defined as a memory effect (ME) value.

(3) Melting peak temperature and melting end temperature by DSC (unit: ° C.) Using a Seiko DSC, a sample amount of 5.0 mg was taken and kept at 200 ° C. for 5 minutes, then 10 ° C./40° C.
The crystal was crystallized at a temperature lowering speed of 10 minutes, and was further melted at a temperature increasing speed of 10 ° C./minute, and the melting peak temperature at this time was determined.

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

(5) 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 the blocking resistance.

(6) Slipperiness According to ASTM-D1894, the obtained film was measured for a static friction coefficient (μs) and a dynamic friction coefficient (μd) by a slip tester method. The smaller the number,
It means that the slipperiness is excellent. However, the sample used for this measurement had been previously conditioned for 14 days at 40 ° C. and 50% RH. This is because the effect of film storage and transport is taken into consideration, and the slipperiness during actual film processing is checked.

(7) 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.

(8) Extraction amount of orthodichlorobenzene at 40 ° C. The extraction amount at 40 ° C. was measured by the cross fractionation method using the following apparatus. Equipment: Mitsubishi Chemical Corporation, CFC / T150A type Column: Showa Denko KK, AD80M / S-3 Concentration: 40 mg / 10 ml Solvent: orthodichlorobenzene

(9) Drop-off resistance A 100 × 300 mm film was fixed on a glass plate with the corona-treated surface facing up and without wrinkles. 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.

(10) Heat sealability (unit: ° C.) Using a 5 mm × 200 mm heat seal bar, 15 m from a sample sealed under the conditions of a heat seal pressure of 1 kg / cm ² and a heat seal time of 10 seconds 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. Seal temperature at which load becomes 300g [THS]
The heat sealability was evaluated at (° C.). The smaller this value is, the better the heat sealing property is. Further, to evaluate the heat sealability of the melting peak temperature commensurate with the difference between the melting peak temperature T _P and THS. The larger the difference, the better the low-temperature heat-sealing properties in proportion to the melting peak temperature.

(11) Particle size measurement (volume average particle size, 90%
Cumulative particle size and 10% cumulative particle size) For particles that have been ultrasonically dispersed in methanol for 120 seconds in advance, use a laser type particle size distribution analyzer (“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).

[0075]

Example 1 (1) Production of anti-blocking agent masterbatch 85% by weight of propylene homopolymer powder with MFR of 5.0 g / 10 min, CUBE18 manufactured by Maruo Calcium Co., Ltd.
BHS (cubic calcite-type calcium carbonate particles: volume average particle size = 1.8 μm, D90 / D10 = 2.0, no particles having a particle size of 10 μm or more) 10% by weight, and acid-modified polypropylene resin (Sanyo Chemical Co., Ltd. ) Made "UMEX 1
001 ", acid value = 26 mgKOH / g) 5 parts by weight of a resin composition composed of 5 parts by weight, 0.05 parts by weight of calcium stearate and 0.2 parts by weight of BHT (2,6-ditert-butylhydroxytoluene) , Irga
After mixing 0.05 part by weight of nox1010 (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 Polypropylene powder (PP-
1); 100 parts by weight, calcium stearate; 0.0
5 parts by weight, BHT; 0.2 parts by weight, Irganox10
After mixing 0.05 parts by weight with a Henschel mixer, the mixture was granulated with a 50 mm single screw extruder to obtain polypropylene pellets. The obtained polypropylene pellets (98% by weight) and the anti-blocking agent master batch (2% by weight) obtained in the above (1) were mixed with a ribbon mixer, and the resulting mixture was mixed with a pellet mixture (resin composition for skin layer of multilayer stretched polypropylene film). An antiblocking agent concentration of 0.2
Wt%).

(3) Preparation of Resin Material for Base Material Layer Propylene homopolymer powder having an MFR of 2.3 g / 10 min; 100 parts by weight, calcium stearate; 0.05
Parts by weight, BHT; 0.2 parts by weight, Irganox 101
0: 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 then 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.

[0079]

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.

[0080]

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.

[0081]

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.

[0082]

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.

[0083]

Comparative Example 3 The polypropylene powder used for the skin layer in Example 1 was replaced with the PP powder obtained in Production Example 2 above.
Except having changed to 2, it carried out similarly to Example 1. Table 1 shows the evaluation results. This was inferior to the examples in low-temperature heat sealability.

[0084]

Comparative Example 4 In the preparation of the resin composition for a skin layer of Example 1, PP-1 was replaced with PP-2 (ethylene content 2% by weight, butene content 12% by weight, MFR 5.9) as shown in Table 2 below.
g / 10 minutes of propylene / ethylene / butene-1 random copolymer powder). Table 1 shows the evaluation results. This was more sticky and inferior in blocking resistance and slipperiness as compared with the examples.

[0085]

Comparative Example 5 In the preparation of the resin composition for a skin layer of Example 1, PP-1 shown in Table 2 below was used as PP-3 (propylene content: 5.6% by weight, MFR: 5.9 g / 10 min. -Ethylene random copolymer powder) was carried out in the same manner as in Example 1. Table 1 shows the evaluation results.
This product was more sticky and inferior in blocking resistance, slipperiness, and heat sealing properties as compared with the examples.

[0086]

[Table 1]

[0087]

[Table 2]

[0088]

The multilayer stretched polypropylene film of the present invention uses a propylene polymer having a specific property produced by a metallocene catalyst for a skin layer, and contains a specific amount of calcium carbonate particles having a specific structure as an antiblocking agent. The anti-blocking agent has high blocking resistance and does not easily fall off. Also, it has excellent heat sealing properties. For this reason, it has good high-speed automatic packaging suitability, and there is no contamination to the packaging machine. Also, it has excellent low-temperature heat sealability and low stickiness. Furthermore, it is excellent in transparency 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 Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08K 7/18 C08K 7/18 C08L 23/10 C08L 23/10 23/16 23/16 // B29C 55 / 02 B29C 55/02 B29K 23:00 B29L 9:00 F term (reference) 3E086 AD01 BA04 BA15 BA33 BA35 BB22 BB51 BB55 BB90 CA01 CA40 4F071 AA14X AA20 AA20X AA32X AA36X AA75 AA76 AA01 BB03 AF06 4F100 AA08B AK07A AK07B AK66B BA02 CA17B EJ37A GB15 JA04B JA06B JA11A JA20B JK20 JL01 JL06 YY00B 4F210 AA11E AB07 AB16 AE01 AG01 QC01 QC05 QC06 QG01 QG15 QG18 BB121 BB121 BB121 BB121 BB121 BB121 BB121 BB121 BB141

Claims (3)

[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 base material layer formed of a polypropylene resin material (A) containing a crystalline propylene polymer as a main component. [2] A polypropylene resin material (B), which is a layer provided on at least one side of the base material layer and mainly contains a propylene polymer satisfying the following conditions (a) to (d).
For 100 parts by weight, the volume average particle size is 1.5 μm to 5 μm.
m, 90% cumulative particle size (D90) and 10% cumulative particle size (D1
0) (D90 / D10) is 5.0 or less and the particle size is 1
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 of 0 μm or more. (A) The melt flow rate is 1 to 30 g / 10 minutes. (B) The memory effect is 0.9 to 1.4. (C) a differential scanning calorimeter at the determined primary melting peak temperature _{(T P)} is in the range of 100 to 140 ° C.. (D) The amount of extraction when extracting at 40 ° C. using orthodichlorobenzene as a solvent is 2% by weight or less. 2. The multilayer stretched polypropylene film according to claim 1, wherein the propylene polymer is a propylene / α-olefin random copolymer containing propylene as a main component. 3. The polypropylene resin material (B)
Is 80 to 100% by weight of the propylene polymer and 0 to 2 of a polypropylene resin other than the propylene polymer.
2. The composition according to claim 1, wherein the composition contains 0% by weight.
Or the multilayer stretched polypropylene-based film according to 2.