JP2001106803A - Gas-permeability controlled film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an oriented polypropylene film having gas permeability necessary for keeping freshness of the content and used as a packaging material and capable of controlling the ratio of gas permeability according to necessity. SOLUTION: This film comprises a monolayer or multilayer film having a thickness [D1] of 10-100 μm containing at least one layer of a film obtained by stretching a propylene resin composition in one axis direction and composed of a propylene/α-olefin randam copolymer (A) comprising 99.4-99.9 wt.% propylene content and a propylene/α-olefin randam copolymer (B) comprising 45-70 wt.% propylene content. The copolymer B has an intrinsic viscosity [η]B of at most 2.0 dl/g and contains at least 80 wt.% xylene soluble component at 20 deg.C based on the weight of B. The intrinsic viscosity ratio of B to A, [η]B/[η]A, is 0.3-1.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film having good gas permeability. More specifically, the present invention relates to a film that can be used as a packaging material for fruits and vegetables such as vegetables and fruits, which is required to have a capability of suitably transmitting gas such as water vapor, oxygen, and ethylene.

[0002]

BACKGROUND ART In recent years, plastic films have been widely used for food packaging, textile packaging and the like. In particular, as a representative of polyolefin films, at least a uniaxially stretched polypropylene film (hereinafter sometimes abbreviated as a stretched PP film) has high transparency and gloss, and further has high mechanical strength. It is widely used as a packaging material because of its excellent printing processability, bag making processability and filling workability. Generally, in a stretched PP film, the regularity of molecular orientation is increased by stretching, and the permeability of a gas such as water vapor or oxygen is reduced by increasing the density of the film. When such a film is used for packaging fruits and vegetables such as vegetables and fruits, the supply of oxygen to the inclusions is insufficient, and the freshness of the inclusions is reduced. On the other hand, it is said that fruits and vegetables lose their commercial value if they lose 5% or more of water, and it is necessary to moderately suppress the evaporation of water to maintain their freshness. Conversely, excessive humidification and condensation can also cause spoilage of packaged fruits and vegetables. Furthermore, a decrease in the permeability of ethylene gas causes a problem of promoting ripening and decay of the fruits and vegetables due to accumulation of the ethylene gas generated by the fruits and vegetables themselves. In order to cope with the generation of ethylene gas, a film into which a porous structure such as activated carbon or Oya stone is kneaded has been studied or partially used. These are intended to maintain the freshness of the fruits and vegetables by absorbing the ethylene gas generated by the fruits and vegetables into the porous structure and fixing them in the film. However, these porous structures have a limited adsorption capacity.For example, if water is adsorbed to near the saturation of the adsorption capacity of the structure, the ethylene removal ability is greatly reduced, and once the ethylene is removed. The adsorbed porous structure re-releases a portion of the adsorbed ethylene in an environment of excessive moisture. Therefore, these films cannot be said to have sufficiently satisfactory freshness-retaining ability as a packaging film for fruits and vegetables generally stored and distributed under high humidity conditions. In addition, packaging films include:
Transparency is important for promoting the quality of inclusions such as freshness to buyers. However, the inclusion of a porous structure inevitably reduces transparency. Currently, the stretched PP film that is distributed for the packaging of fruits and vegetables can prevent dew condensation by mixing a drip-proof agent with the film without properly controlling the evaporation of water vapor, or can prevent water vapor, oxygen, carbon dioxide In the process leading to packaging,
The reality is that the film is used by physically perforating it.

[0003]

SUMMARY OF THE INVENTION The present invention relates to the stretching P
The present invention has been made in view of the drawbacks of P film, and has as its object to provide a film suitable for packaging of fruits and vegetables, which can control gas related to the physiological action of fruits and vegetables and moderately suppress transpiration. It is in. More specifically, the permeability of gas such as water vapor, oxygen, and ethylene can be controlled to a value suitable for packaging of fruits and vegetables, and has high transparency, gloss, excellent transparency, and It is an object of the present invention to provide a film which maintains the excellent mechanical strength of a stretched PP film and has improved productivity and profitability by omitting a conventional drilling step, and is particularly suitable for packaging fruits and vegetables. I do.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, a film produced under specific conditions using a specific propylene-based resin composition has been obtained. They have found that they have gas permeability and are suitable as films for packaging fruits and vegetables, and have completed the present invention.

That is, the present invention relates to a propylene-α having a propylene unit content of 99.4 to 99.9% by weight.
-10 to 60% by weight of the olefin random copolymer (A) with respect to the composition, and the content of propylene units is 45 to 45;
70 to 40% by weight of the propylene-α-olefin random copolymer (B) with respect to the composition, and the intrinsic viscosity [η] _{B of the} propylene-α-olefin random copolymer (B) Is 2.0 dl / g or less,
The propylene-α-olefin random copolymer (B) is at 20 ° C. at 80% by weight or more based on the weight of the copolymer (B).
It contains a xylene-soluble component, and the intrinsic viscosity ratio [η] _B / [η] _A of the propylene-α-olefin random copolymer (B) and the propylene-α-olefin random copolymer (A) is 0.3. A film obtained by processing a propylene-based resin composition of at least 1.2 and stretching at least in a uniaxial direction as at least one layer, and having a thickness [D ₁ ] of 10 to 10.
A single-layer or multilayer film having a thickness of 100 μm, (1) water vapor permeability [T _H2O ] (according to JIS Z0208), (2) oxygen gas permeability [T _O2 ] (JIS K)
7126-A), and (3) Permeability of ethylene gas [T _ethylene ] (based on JIS K 7126-A)
Are gas permeable films in the following ranges, respectively. _{(1) [T H2O] =} 9~50 ( ^{Unit: g / m 2 · 24h)} (2) [T O2] = 600~12500 ( Unit: nmol
/ M ² · s · 100 kPa) (3) [T _ethylene ] = 600 to 22,500 (unit: nmo)
^{l / m 2 · s · 100kPa} )

The gas permeable film of the present invention has a thickness [D ₁ ] of 10 to 100 μm.
(1) Water vapor permeability [ _TH2O ] (JIS Z-0208), (2)
Permeability of oxygen gas [T _O2] (conforming to JIS K-7126A), and (3) permeability of ethylene gas [T _ethylene] (JIS K-7126
A)), each of which satisfies the following numerical ranges. _{(1) [T H2O] =} 9~50 ( ^{Unit: g / m 2 · 24Hr)} (2) [T O2] = 600~12500 ( ^{Unit: nmol / m 2 · s ·} 100
kPa) (3) [T _ethylene ] = 600 to 22,500 (unit: nm)
ol / m ² · s · 100 kPa) The thickness of the gas-permeable film of the present invention is 10 to 100 μm.
m means film formability and workability (package)
It is preferable from the point of view. If the thickness of the film is less than 10 μm, it is difficult to form a uniform thickness,
If the thickness is larger than m, the gas permeability is undesirably small. It is preferable that the thickness of the film is 15 to 70 μm, since the freshness of the fruits and vegetables can be maintained well. If the water vapor permeability of the film is less than 9 g / m ² · 24Hr, rot is likely to be promoted due to excessive moisture, and 50 g / m ² ·
If it is greater than 24 hours, fruits and vegetables, especially vegetables, etc., are apt to dry and wither, which is not preferable. More preferably 10-4
It is in the range of 5 g / m ² · 24Hr. Oxygen gas permeability is 6
If it is less than 00 nmol / m ² · s · 100 kPa, the respiratory rate of the fruits and vegetables is reduced, and the freshness of the fruits and vegetables is easily lost, and 12,500 nmol / m ²
-If it is larger than s · 100 kPa, it is not preferable because the accompanying water vapor permeability becomes too large. The oxygen gas permeability is preferably 600 to 12,500 nmol / m ² · s · 100 kPa
, Preferably 1000 to 9000 nmol / m ² · s · 100 kPa
Range. Further, the permeability of ethylene gas is 600
and nmol / m ² · s · 100kPa smaller, easily promotes ripening and corruption of vegetables and fruits, larger than ^{22500nmol / m 2 · s · 100kPa} , concomitant undesirable because the permeability of water vapor becomes too large. Ethylene gas permeability is 600 ~
22,500 nmol / m ² · s · 100 kPa, preferably 600 to
15000 nmol / m ² · s · 100 kPa, more preferably 60
The range is from 0 to 9000 nmol / m ² · s · 100 kPa.

[0007] The propylene-based resin composition of the present invention comprises 90 parts by weight of the propylene-α-olefin copolymer (A) (hereinafter sometimes simply referred to as the copolymer (A)) based on the weight of the composition. Propylene-α-olefin copolymer (B) (hereinafter sometimes simply referred to as copolymer (B)) at a ratio of 10 to 60% by weight. When the content of the copolymer (A) is large and the content of the copolymer (B) is small, the gas permeability becomes small, the content of the copolymer (A) is small, and the content of the copolymer (B) is reduced. When the content is large, rigidity and transparency are reduced. The propylene-based resin composition of the present invention has a copolymer (A) of 80 to 80% based on the weight of the composition.
50% by weight, and 20 to 50% by weight of the copolymer (B)
It is preferable to include them in the ratio of

[0008] The propylene-α-olefin random copolymer (A) of the propylene-based resin composition of the present invention has a propylene unit content in the range of 99.4 to 99.9% by weight, other than propylene and propylene. It is a random copolymer with an α-olefin. When the propylene unit content is small, the heat resistance decreases, and when the propylene unit content is large, the transparency decreases. The propylene-based resin composition of the present invention has a propylene unit content of 99.4 to 99.9% by weight in the copolymer (A), and is used for performing secondary processing such as multicolor printing and extrusion lamination. It can be suitably used without impairing the commercial value, even when high transparency is required depending on the contents to be packaged due to its excellent transparency. As the α-olefin component of the copolymer (A), ethylene, 1-butene, 1-pentene, 1-hexene, 1
-Octene, 1-decene, 1-dodecene, 4-methyl-
Examples thereof include 1-pentene and 3-methyl-1-pentene, and one or more of these are used. Among them, ethylene and 1-
Butene is preferred.

The propylene-α-olefin random copolymer (B) of the propylene-based resin composition of the present invention is a copolymer of propylene and an α-olefin other than propylene containing propylene units in the range of 45 to 70% by weight. It is a random copolymer. When the propylene unit content of the copolymer (B) is too large, gas permeability becomes insufficient, while when it is too small, transparency and transparency deteriorate. More preferable propylene content of the copolymer (B) is 60 to 7
0% by weight. As the α-olefin component of the copolymer (B), the same compounds as those of the copolymer (A) can be mentioned. Here, ethylene and 1-butene are preferable.

The copolymer (B) has an intrinsic viscosity [η] _B measured in tetralin at 135 ° C. of 2.0 dl / g or less, more preferably 0.5 to 2.0 dl / g, and an intrinsic viscosity [eta] _a copolymer was measured under the same conditions (a)
The intrinsic viscosity ratio [η] _B / [η] _A is 0.3 to 1.2, preferably 0.5 to 1.0.

The intrinsic viscosity [η] _B of the copolymer (B) affects the rigidity and transparency of the film, and the intrinsic viscosity ratio [η] _B /
[η] _A affects the dispersibility of the copolymer (B) in the copolymer (A). As the intrinsic viscosity [η] _B of the copolymer (B) increases, the transparency of the film decreases, and when it is too low, the rigidity of the film decreases. In addition, the limiting viscosity ratio ([η] _B /
If [η] _A ) is too large, the transparency of the film will be reduced, and if it is too small, the rigidity of the film will be reduced and the desired properties cannot be achieved.

The propylene-α-olefin random copolymer (B) component contains at least 80% by weight, preferably at least 85% by weight, of a xylene-soluble component at 20 ° C. based on the weight of the copolymer (B) component. I do.

The intrinsic viscosity of the propylene-based resin composition is from 1.6 to 3.6 d from the viewpoint of moldability during film formation.
1 / g is preferable, and 1.8 to 2.5 dl / g is more preferable.

The gas-permeable film of the present invention obtained by using the composition satisfying the constitution specified in the present invention has excellent film strength, fusing seal strength and the like even in a single layer. A very suitable performance for packaging of fruits and vegetables, in which the gas permeability can be controlled by adjusting the content of the propylene-α-olefin random copolymer (B) component in the composition, and further by adjusting the stretching ratio. It is a film having.

As a means for imparting gas permeability to polyolefin films, a method including a chemical species having a polar group as one component of the composition constituting the film has been proposed in the past. In addition, there is a possibility that there may be restrictions on use in cutting the polyolefin film and recycling it as a polyolefin raw material. In such a case, it is necessary to select a film composed of a component having an affinity for this as another laminated component, and the design of a multilayer film is also restricted by the restriction. The film of the present invention,
The industrial significance is extremely large in that a polyolefin film substantially composed of olefin units is used, and even a single-layer film has excellent suitability as a film for packaging of fruits and vegetables.

The film of the present invention is obtained by molding the propylene-based resin composition used in the present invention by a usual T-die method or inflation method to obtain a sheet, and then forming the sheet in a uniaxial or biaxial direction. It can be manufactured by stretching. Examples of the stretching method include a sequential biaxial stretching method using a tenter method and a simultaneous biaxial stretching method using a tubular method. The stretching ratio is preferably 3 to 60 times in order to maintain the transparency, strength, and gas passage of the film. If the stretching ratio is less than 3 times, the thickness of the film tends to be non-uniform, and if it is more than 60 times, the film itself becomes difficult to form, which is not preferable. Preferably it is 10 to 60 times, more preferably 20 to 50 times.

[0017] In order to impart film strength and straight cut properties required for packaging materials, polypropylene films are particularly stretched and used, but in general, polypropylene films have regularity of molecular orientation by stretching. As the film density increases and the density of the film increases, there is a property that gas such as water vapor and oxygen hardly permeates the film. However, the propylene-based resin composition suitably used in the present invention has a feature that the gas permeation performance is less reduced even when stretched, and further has excellent transparency and transparency, so that the use environment can be improved. This is advantageous when designing a thicker film as required.

The multilayer film of the present invention is a multilayer film containing a stretched film obtained by using the propylene-based resin composition used in the present invention and another film. Any material can be used as long as it satisfies various characteristics. In the multilayer film,
It is preferable that the thickness of the stretched film using the propylene-based resin composition specified in the present invention be 50% or more based on the thickness of the multilayer film in order to maintain an appropriate gas permeation amount. If the thickness is less than 50%, the amount of gas permeation tends to be insufficient, which is not preferable. The method for producing the multilayer film is not particularly limited, and examples thereof include a multilayer extrusion molding method, a dry lamination method, and an extrusion lamination method.

The propylene resin composition used in the present invention may be produced by any method as long as the above conditions are satisfied. However, it is preferably produced by employing a two-stage continuous polymerization method using a gas phase method. be able to. In this two-stage continuous polymerization method, propylene and an α-olefin other than propylene are copolymerized in the gas phase in the presence of an olefin polymerization catalyst to obtain a propylene-α-olefin random having a predetermined amount and a predetermined composition ratio. A first polymerization step for producing the copolymer (A), and then propylene and α other than propylene
-A second polymerization step of copolymerizing olefins with varying their composition ratios to produce the remaining propylene-α-olefin random copolymer (B), in that order. When such a multi-stage continuous polymerization method is employed, the weight percentage (W _A , W _B ) of the copolymer A and the copolymer B occupying in the propylene-based resin composition is determined as a component of the catalyst, respectively. By focusing on, for example,
It can be calculated based on the following equations (1) to (4). (1) CY _A (g-powder / g-catalyst) = 10000 ×
Mg content in catalyst (wt%) / Mg content in powder extracted in first polymerization step (wtppm) (2) CY _WHOLE (g-powder / g-catalyst) = 1000
0 × Mg content in the catalyst (wt%) / Mg content of the final steps in the extracted in powder _{(wtppm) (3) W B} = (CY WHOLE -CY A) / CY WHOLE (4) W A = 1 -W _B Furthermore, the intrinsic viscosity of the intrinsic viscosity [eta] _B has an intrinsic viscosity [eta] _a, and a propylene-based resin composition as a final product of the copolymer was measured directly (a) of the copolymer (B) [η] _{WHO LE} ,
Further, the content can be determined from the content W _B (% by weight) of the copolymer (B) in the propylene-based resin composition by the following formula (5). (5) [η] _B = ｛[η] _WHOLE − (1−W _B / 100)
_{[η] A} / (W} B / 100) In addition, the copolymer (B) 20 ° C. xylene-soluble component wt% of component (CXS _B) is 20 to the copolymer (A) in component
Xylene-soluble component weight% (CXS _A ) of the propylene-based resin composition at 20 ° C. xylene-soluble component weight% (CXS
_WHOLE), and copolymers occupying the propylene resin composition from (content W _B (% by weight of B)), can be determined by the following equation (6). _{(6) CXS B = {CXS} WHOLE - (1-W B / 100)
_{CXS A} / (W B /} 100) olefin polymerization catalyst used in the above production method is not particularly limited, can be produced by using a catalyst such as a titanium catalyst or a metallocene catalyst. Among them, a titanium-based catalyst is preferable in terms of cost.

The propylene resin composition used in the present invention may contain known additives such as an antioxidant, an antiblocking agent, an antifogging agent, and a surfactant, as long as the effects of the present invention are not impaired. Can be. As a method for adding the above-mentioned additives to the propylene-based resin composition, any method may be used as long as they can be uniformly mixed. However, the mixture is mixed with a ribbon blender, a Henschel mixer (trade name) or the like, and the mixture is extruded. A method of melt-kneading with a machine or the like is preferred. Conventionally, when a film is used as a packaging material for fruits and vegetables, it has been necessary to form a hole for gas permeation in the film because the film has insufficient gas permeability. However, in such a film, the ethylene gas emitted from the inclusions and the oxygen gas necessary for breathing the fruits and vegetables are sufficiently absorbed, but at the same time, the evaporation of water vapor from the fruits and vegetables causes the fruits and vegetables to evaporate. However, it has the disadvantage that it is dried and its freshness is lost. In addition, there is a serious drawback that the bacteria enter the hole and cause the contents to be spoiled by the bacteria. In contrast, in the gas-permeable film of the present invention, the uptake of oxygen gas and the emission of ethylene gas are sufficiently maintained, and the transpiration of water vapor can be appropriately suppressed. The effect that it can be maintained can be exerted. The film of the present invention provides high productivity and profitability by eliminating the conventional step of physically piercing in the packaging step.

In the present specification, "vegetables" refers to vegetables, root vegetables, fruits, flowers, and mushrooms. The following are examples of fruits and vegetables suitable for packaging using the film of the present invention. For example, artichoke, asagi, red beans, asparagus, avocado, aloe, apricot, strawberry,
Fig fruit, iyokan, udo, plum, shallot, edamame, enoki mushroom, okra, olive, orange, kaiware radish, persimmon, turnip, pumpkin, cauliflower, kiwi, chrysanthemum,
Jellyfish, cabbage, cucumber, kumquat, ginkgo, chestnut, green peas, walnut, grapefruit, watercress, gogo, lingonberry, burdock, komatsuna, koriansa, cherry, pomegranate, sweet potato, taro, pomelo, green bean, snow peas, saladana, shiitake mushroom, shiso , Shimeji, potato, shanzei, spring chrysanthemum, ginger, watermelon, sweetie, suzushiro, suzuna, starfruit, zucchini, plum, seri, celery, spring, broad bean, taro, radish, soy, takanotsume, bamboo shoot, onion, taranome,
Bok choy, horsetail, tecopon, winter melon, corn, tomato, durian, truffle, yam, leek,
Eggplant, Nazuna, summer tangerine, rape, nameko, Nagauri,
Japanese pear, chive, carrot, carrot, pineapple, Chinese cabbage, chickweed, parsley, hassaku, banana, papaya, vampire, peppers, loquat, butterbur, fukinotou, kurotake,
Grapes, plums, blueberries, prunes, broccoli, spinach, photokenosa, ponkan, maitake, muscat, mushroom, matsutake, mango, mangosteen, mandarin orange, honeybee, mioga, melon, peach, bean sprouts, moroheiya, yamatoimo, yuzu, pear, mugwort , Lychee, raspberry, radish, apple, lettuce, lemon, lotus root, scallion, wasabi and the like.

[0022]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The methods for measuring physical properties and the evaluation criteria shown in the examples and comparative examples are as follows. (1) Transparency: Haze value (unit:%) Measured according to the method described in ASTM D1003. The smaller the value, the better the transparency. (2) Transparency: (unit: sheets) A black frame square (20 mm × 20 mm, line width: 1.0 mm) drawn on a white paper at a position 3 m away from the naked eye immediately before the naked eye with the sample film (25 μm) Is seen through at a room illuminance of about 800 to 1000 lux. Observation is performed while increasing the number of superimposed sample films, and the maximum number of superimposed images in which a square can be clearly seen is used as a measure of transparency. The greater the number, the better the transparency. (3) Rigidity: Young's modulus (unit: MPa) Measured according to the method described in ASTM D882.
The larger the value, the higher the rigidity of the film. (4) Water vapor permeability: T _H2O (unit: g / m ² · 24)
h) Measured according to JIS Z-0208. Temperature 40
Measured under the conditions of ° C and 90% RH. (5) Oxygen permeability: T _O2 (unit: nmol / m ² · s)
-100 kPa) It measured based on JISK-7126A. (6) Permeability of ethylene gas: T _ethylene (unit: nmol)
/ M ² · s · 100 kPa) It was measured in accordance with JIS K-7126A. Note that [D
₁ ] indicates the thickness (μm) of the film used in the examples. (7) Intrinsic viscosity (unit: dl / g) Using a tetralin (tetrahydronaphthalene) as a solvent, an automatic viscosity measurement device (AVS) under a temperature condition of 135 ° C.
The measurement was performed using Model 2 (manufactured by Mitsui Toatsu Co., Ltd.). (8) α-Olefin polymerization unit content (unit: wt%) It was measured by an infrared absorption spectrum method. (9) Amount of xylene-soluble component at 20 ° C. (unit:% by weight) Measured in accordance with ISO / DIS1873-1.

Table 1 shows the polymer properties of the various propylene resin compositions (PP-1 to PP-7) used in the examples and comparative examples. For PP-8, a propylene homopolymer having an intrinsic viscosity [η] _WHOLE of 2.1 dl / g was used.

[0024]

[Table 1]

The PP-1 used in Example 1 was produced as follows. <1> Preparation of Titanium-Containing Solid Catalyst Component (α) Anhydrous Mg was placed in a nitrogen-purged stainless steel autoclave.
953 g of Cl ₂ and 3.52 liters of dry EtOH were added and the mixture was heated to 105 ° C. with stirring to dissolve. After stirring for 1 hour, pressurized nitrogen heated to 105 ° C. (1.
This solution was sprayed from a two-fluid spray nozzle into the spray tower at 1 MPa). The flow rate of the nitrogen gas was 38 l / min. The inside of the spray tower was maintained at -15 ° C by introducing liquid nitrogen. The composition of the powder (2730 g) collected in the cooled hexane introduced into the bottom of the column was MgC
l was ₂ · 6EtOH. The obtained powder was sieved to obtain 2180 g of a spherical carrier having a particle size of 45 to 212 µm. The obtained carrier was subjected to aeration drying at room temperature for 200 hours using nitrogen at a flow rate of 30 L / min.
To obtain a dry carrier of ₂ · 1.7EtOH. 4.8 liters of purified 1,2-dichloroethane, 400 g of a dry carrier, and 3.2 liters of titanium tetrachloride were placed in a stainless steel reactor, and heated to 100 ° C. with stirring.
0.136 liter of butyl and further added at 100 ° C. for 2 hours.
After heating for an hour, the liquid layer was removed by hot filtration. To the remaining solid, 6.4 liters of purified 1,2-dichloroethane and 3.2 liters of titanium tetrachloride were added again, and 100
After heating at ℃ for 1 hour, the liquid layer was removed by hot filtration.
The obtained solid is washed with purified hexane until free titanium is no longer detected in the washing liquid, and dried, and a titanium-containing solid catalyst component (α) containing an average particle diameter of 115 μm and containing 1.6% by weight of titanium (α). I got

<2> Preliminary polymerization of titanium-containing solid catalyst component (α) After replacing a stainless steel reactor (internal volume: 20 liters) with inclined stirring blades with nitrogen gas, the kinematic viscosity at 40 ° C was 7.
1.7 liters of 3 centistoke saturated hydrocarbon solvent (CRYSTOL-52, manufactured by Esso Oil Co., Ltd.), n-
Hexane 16 liters, triethylaluminum 129
mmol, diisopropyldimethoxysilane 19 mmo
l, and 140 g of the titanium-containing solid catalyst component (α) prepared in the preceding section was added at room temperature, and the mixture was heated to 30 ° C. and supplied with 280 g of propylene over 7 hours to cause a reaction, thereby performing prepolymerization. As a result of the analysis, 1.8 g of polypropylene was produced per 1 g of the titanium-containing solid catalyst component (α).

<3> First Polymerization Step A horizontal polymerization vessel having stirring blades (L / D = 6, internal volume 10
0 liter), 0.4 g / h of the preactivated polyolefin polymerization catalyst component, triethylaluminum as an organic aluminum compound and diisopropyldimethoxysilane as an organosilicon compound having an Al / Mg molar ratio of 6 and an Al / Si molar ratio of 6; It was continuously supplied as much as possible.
A mixed gas of ethylene and propylene is continuously supplied while maintaining the conditions of a reaction temperature of 60 ° C., a reaction pressure of 2.1 MPa, and a stirring speed of 35 rpm. Further, the ethylene / propylene molar ratio in the gas phase of the reactor is 0.002, and the hydrogen / The propylene molar ratio was adjusted to 0.008 to obtain a produced polymer, that is, a propylene-ethylene copolymer (A).

The propylene-ethylene random copolymer (A) obtained had a polymer holding level of 50% of the reaction volume.
The solution was continuously withdrawn from the polymerization vessel in the first polymerization step so as to have a volume%, and supplied to the polymerization vessel in the second polymerization step. At this time, a part of the propylene-ethylene random copolymer (A) was intermittently extracted to prepare a sample for obtaining the ethylene content, the intrinsic viscosity [η] _A and the polymer yield per unit weight of the catalyst. Polymer yield per unit weight of catalyst
Inductively coupled plasma emission spectroscopy (ICP method).

<4> Second polymerization step A horizontal polymerization vessel having stirring blades (L / D = 6, internal volume 10
(0 liter), the propylene-ethylene random copolymer (A) and the ethylene-propylene mixed gas from the first polymerization step were continuously supplied to copolymerize ethylene and propylene. The reaction conditions were agitation speed 25 rpm, temperature 5
The temperature was 5 ° C., the pressure was 1.9 MPa, and the gas composition in the gas phase was adjusted to an ethylene / propylene molar ratio of 0.33 and a hydrogen / ethylene molar ratio of 0.54. Carbon monoxide as a polymerization activity inhibitor for adjusting the polymerization amount of the propylene-ethylene random copolymer (B), and hydrogen gas for adjusting the molecular weight of the propylene-ethylene random copolymer (B). Each supplied.

The propylene-based resin composition obtained through the second polymerization step was continuously withdrawn from the polymerization vessel such that the level of the retained polymer was 50% by volume of the reaction volume. The production rate of the propylene-based resin composition was 8 to 15 kg / hr. The unreacted monomer is removed from the extracted propylene-based resin composition, and a part of the propylene-based resin composition is measured for intrinsic viscosity ([η] _WHOLE ), ethylene content is measured by infrared absorption spectrum analysis, and polymer is measured by ICP method. Medium M
Propylene by g min measured - were subjected to measurement of the ethylene random copolymer component (B) polymerization ratio (W _B). PP
-2 to PP-7 were produced using the same method, with the production conditions changed.

Examples 1 to 6, Comparative Examples 1 to 5 <Production of Film> PP-1 to PP-4 and PP-6 to
100 parts each of PP-8 propylene resin composition and the like
0.15 parts by weight of tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane as an antioxidant, and a neutralizing agent And 0.1% by weight of calcium stearate, and Henschel Mixer (trade name)
The resulting mixture was melt-kneaded with an extruder to obtain a pellet-shaped composition.

With respect to the propylene resin composition of PP-5, tetrakis- [methylene-3- (3 ′, 5′-di-tert-butyl) was used as an antioxidant with respect to 100 parts by weight.
0.15 parts by weight of 4'-hydroxyphenyl) propionate] methane, 0.10 part by weight of calcium stearate as a neutralizing agent and 2,5-dimethyl-2,5-di (t-butyl) as a molecular weight regulator Peroxy) hexane in a mixing ratio of 0.02 parts by weight,
(Trade name), and the resulting mixture was melt-kneaded with an extruder to obtain a pellet-shaped composition. Each of the obtained compositions was supplied to an extruder having a diameter of 65 mm,
After melting at 0 ° C., it was extruded from a T-die and cooled with a cooling roll at 30 ° C. to obtain a sheet. Next, the sheet was sequentially biaxially stretched using a pantograph-type biaxial stretching tester,
A biaxially stretched film as shown in Table 2 was obtained. Sequential biaxial stretching is performed using a sheet obtained from the composition of PP-1 to PP-7.
After preheating at 156 ° C for 150 seconds,
The sheet obtained from the PP-8 composition was successively stretched by 4.2 times in the machine direction and then by 8.2 times in the transverse direction.
After preheating at 158 ° C for 120 seconds, it is 4.2 times longer in the longitudinal direction,
The film was successively stretched 8.2 times in the transverse direction. A predetermined test piece was prepared from each of the films thus obtained, and transparency, transparency, rigidity, and gas permeability were measured in accordance with a predetermined test method. The results are shown in Table 2. In addition, as shown in Table 2, PP-1 to PP-4 correspond to Examples 1 to 4, and PP-5 to PP-8 correspond to Comparative Examples 1 to 4, respectively. In Examples 5 and 6, the composition [PP-1] used in Example 1 was used.

[0033]

[Table 2]

<Packaging of fruits and vegetables> 50 g of cut Chinese cabbage was packaged in a 20 x 30 cm side fusing seal bag prepared using each film, and stored at a temperature of 23 ° C and a humidity of 50%. Table 3 shows an example of observation of the storage state when
It was shown to. In addition, 15 × 2 prepared using each film
Table 4 shows an example of observation of the storage state when 50 g of broccoli were packaged in a 0 cm side fusing seal bag and stored at a temperature of 10 ° C. and a humidity of 50%. In addition, Tables 3 and 4 show Comparative Example 5 as Comparative Example 5.
An example using a film obtained by forming a hole having a diameter of 3 mm at a density of 3 pieces / (15 × 15 cm) was also described.

[0035]

[Table 3]

[0036]

[Table 4]

From the data shown in Tables 3 and 4, the packaging bag using the film of the present invention (Examples 1 to 6) having good gas permeability is different from the packaging bag with perforated processing (Comparative Example 5). In comparison, the freshness of fruits and vegetables was better maintained,
It can be seen that the freshness retention period has been extended as compared with the conventional polypropylene packaging bag without perforation processing (Comparative Example 4).

[0038]

The film of the present invention comprises propylene-α-
By adjusting the kind and content% of the α-olefin of the olefin random copolymer (A) and the kind and content% of the α-olefin of the propylene-α-olefin random copolymer (B), As a result of keeping the intake of ethylene gas and the emission of ethylene gas sufficiently, the emission of water vapor can be moderately suppressed, and the effect that the freshness of fruits and vegetables can be maintained for a long time is exhibited, and further, high transparency, gloss, excellent Thus, a film having excellent transparency and mechanical properties (such as rigidity) can be obtained. Furthermore, the obtained film is excellent in productivity and profitability in which the step of physically forming a hole in the packaging step can be omitted. Therefore, the gas permeable film of the present invention can be widely used for packaging fruits and vegetables.

Continued on the front page F-term (reference) 4F071 AA15X AA20 AA20X AA81 AA88 AF08Y AH04 BB07 BC01 4F100 AK07A AK64A AK66A AL05A BA01 EH17 EJ37A EJ38 GB01 GB23 JA06A JB08A JD02A JD03J01B02J01B02

Claims (4)

[Claims] 1. A single-layer or multilayer film having a thickness [D ₁ ] of 10 to 100 μm, comprising at least one film obtained by processing a propylene-based resin composition and stretching it in at least one axial direction. The propylene resin composition has a propylene unit content of 99.4 to 9;
9.9% by weight of the propylene-α-olefin random copolymer (A) is 90 to 40% by weight based on the weight of the composition, and the propylene unit content is 45 to 70% by weight. Olefin random copolymer (B)
And the intrinsic viscosity of the propylene-α-olefin random copolymer (B) is 10 to 60% by weight based on the weight of the composition.
[η] _B is 2.0 dl / g or less, and the propylene-α-olefin random copolymer (B) contains at least 80% by weight of a xylene-soluble component at 20 ° C based on the weight of the copolymer (B). The intrinsic viscosity ratio [η] _B / [η] _{A of} the propylene-α-olefin random copolymer (B) and the propylene-α-olefin random copolymer (A) is 0.3 to 1.2. Using a propylene-based resin composition, the obtained film has (1) water vapor permeability [T _H2O ] (JIS Z 02
08), (2) Oxygen gas permeability [T _O2 ] (JI
(3) A gas-permeable film having a permeability of ethylene gas [T _ethylene ] (based on JIS K 7126-A) in the following ranges. _{(1) [T H2O] =} 9~50 ( Unit: g /
^{m 2 · 24h) (2)} [T O2] = 600~12500 ( unit: nmol
/ M ² · s · 100 kPa) (3) [T _ethylene ] = 600 to 22,500 (unit: nmo)
^{l / m 2 · s · 100kPa} ) 2. A propylene resin composition comprising:
The gas-permeable film according to claim 1, wherein the content of the α-olefin random copolymer (B) is 15 to 50% by weight based on the weight of the propylene-based resin composition. 3. The gas-permeable film according to claim 1, wherein the gas-permeable film is obtained by processing a propylene-based resin composition and stretching the film at least in a uniaxial direction at a stretching ratio of 3 to 60 times as at least one layer. 4. The gas-permeable film according to claim 1, wherein the gas-permeable film is a film for packaging fruits and vegetables.