JPH05262900A - Nonstretched polypropylene film - Google Patents

Abstract

PURPOSE:To provide a nonstretched polypropylene film excellent in heat- sealability at low temps. and retorting resistance. CONSTITUTION:A nonstretched polypropylene film is formed from a compsn. comprsising a polypropylene copolymer and a polyethylene copolymer. The polypropylene copoymer to be used is a propylene-ethylene copolymer having an ethylene unit content of 1.5 to 3.5wt.%, a melt flow rate of at least 5g/10min, and an extractable component content of at most 20wt.% as measured according to the cross fractionation method which is conducted using o-dichlorobenzene as the solvent at 80 deg.C. The ethylene copolymer to be used is a copolymer having a density of at most 0.91g/cm<3>. The amt. of the ethylene copolymer to be blended in the compsn. is 2 to 20 pts.wt. per 100 pts.wt. of the polypropylene copolymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene non-stretched film, and more particularly to a polypropylene non-stretched film which is particularly excellent in low temperature heat sealability and retort resistance when used for food packaging. is there.

[0002]

2. Description of the Related Art As a method for improving the low temperature heat-sealing property of polypropylene unstretched film, a relatively large amount of ethylene (for example, 3.5% by weight or more) relative to propylene is used.
There is known a method of copolymerizing Also proposed is a method of blending an ethylene copolymer such as an elastomer with a copolymer of propylene and a relatively small amount of ethylene.

[0003]

However, in the former method described above, the retort resistance becomes poor, and moreover,
The blocking property also becomes poor. Also, in the latter method,
Inevitably, the low temperature heat sealability is not good, and the retort resistance is insufficient.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have blended a specific polypropylene copolymer with a specific amount of a specific ethylene-based copolymer. The present invention has been completed based on the finding that a film having excellent low-temperature heat-sealing properties and improved retort resistance can be obtained by using the composition. That is, the gist of the present invention is a polypropylene unstretched film composed of a composition of a polypropylene copolymer and an ethylene copolymer, wherein the content of the ethylene component is 1.5 to 3. Propylene-ethylene copolymer having 5% by weight, a melt flow rate of 5 g / 10 min or more, ortho-di-glorbenzene as a solvent, and an amount of an extractable component of 20% by weight or less by a cross fractionation method at a temperature of 80 ° C. And a copolymer having a density of 0.91 g / cm ³ or less is used as the ethylene copolymer, and the blending amount of the ethylene copolymer in the composition is 2 with respect to 100 parts by weight of the polypropylene copolymer. It exists in a polypropylene unstretched film characterized by being ˜20 parts by weight.

The present invention will be described in detail below. In the present invention, the propylene copolymer has an ethylene component content of 1.5 to 3.5% by weight, preferably 2 to 3% by weight, and a melt flow rate of 5 g / 10 minutes or more, preferably 6 to 15 g. / 10 minutes, ortho-di- gloylbenzene is used as a solvent, and the amount of the extraction component by the cross fractionation method under the condition of a temperature of 80 ° C. is 20% by weight or less, preferably 2 to 20.
% Propylene-ethylene copolymer is used. A particularly preferred propylene copolymer is propylene-
It is an ethylene random copolymer. The melt flow rate is a value measured in accordance with JIS K 7210 under the conditions of a temperature of 230 ° C. and a load of 2.16 kg (hereinafter the same).

When the content of the ethylene component is smaller than the above range, the impact strength and tear strength of the film and the low temperature heat sealability are deteriorated, and when the content of the copolymer is larger than the above range. , The heat resistance and retort resistance of the film are deteriorated. Further, in the case of a copolymer having a melt flow rate smaller than the above range, it is difficult to uniformly cool the film, and the moldability is deteriorated. Furthermore, in the case of a copolymer in which the amount of components extracted by the cross fractionation method is larger than the above range, the low temperature heat sealability of the film is deteriorated.

In the present invention, the ethylene copolymer has a density of 0.91 g / cm ³ or less, preferably 0.8
An ethylene-based copolymer of 5 to 0.90 g / cm ³ is used. The above-mentioned density is a value measured according to JIS K 6760. In the case of an ethylene-based copolymer having a density higher than the above range, the heat sealability of the film is insufficiently improved. In the present invention, further, 0.
Ethylene-based copolymers having a melt flow rate of 5-10 g / 10 min are suitable.

The ethylene-based copolymer is usually a copolymer of ethylene and an α-olefin having 3 or more carbon atoms.
Examples of the olefin include propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1 and the like, and a copolymer with propylene or butene-1 is preferable. The ethylene copolymer in the present invention also includes a terpolymer obtained by copolymerizing ethylene, an α-olefin having 3 or more carbon atoms and a non-conjugated diene. Examples of non-conjugated dienes include 1,4-hexadiene, dicyclopentadiene and ethylidene norbornene.

The above ethylene copolymer uses a Ziegler-Natta catalyst, particularly a catalyst composed of a vanadium compound such as vanadium oxytrichloride, vanadium tetrachloride and the like, and an organoaluminum compound. Can be produced by copolymerizing with a non-conjugated diene. The ethylene content of the ethylene copolymer used in the present invention is 40 to
It is preferably in the range of 90 mol%, and the content of the α-olefin having 3 or more carbon atoms is preferably in the range of 10 to 60 mol%.

Examples of the ethylene-based copolymer as described above include CdF Chimie E. P. Company "NORSO
FLEX "(FW1600, FW1900, MW192
0, SMW2440, LW2220, LW2500, L
W2550), "Flex Resin" by Nippon Unicar Co., Ltd.
(DFDA1137, DEDA1138, DEFD12
10, DEFD9042), "TAFUMA" (A4085, A4090, P0180, P048) of Mitsui Petrochemical Co., Ltd.
0, P0680), "JSR-EP" by Japan Synthetic Rubber Co., Ltd.
Commercially available products such as (EP02P, EP07P, EP57P) can be used.

In the present invention, the ethylene-based copolymer is
2 to 20 relative to 100 parts by weight of the polypropylene copolymer
It is used in parts by weight, preferably 5 to 15 parts by weight.
When the blending amount of the ethylene-based copolymer is less than the above range, the improvement of the low temperature heat sealability of the film is insufficient, and when it exceeds the above range, the heat resistance and transparency of the film decrease. To do.

The raw material composition of the unstretched film of the present invention is
It can be obtained by dry blending the above copolymers, or by melt kneading at a temperature of 190 to 300 ° C. and pelletizing. A Henschel type mixer, a V type mixer, a ribbon type blender or the like can be used for dry blending, and a Banbury mixer, a continuous mixer, a mixing roll, an extruder or the like can be used for melt kneading. I can. If necessary, various known additives used for polypropylene such as heat stabilizers, antioxidants, ultraviolet absorbers, lubricants, and other additives can be added to the above resin composition.

The unstretched film of the present invention can be obtained by extrusion molding the above resin composition. The molding can be carried out according to a usual film forming method. For example, an inflation molding method using a circular die,
A T-die molding method using a T-die is adopted. In the case of inflation molding, the blow-up ratio is 0.5-2.
0, draft rate 1 to 50, resin temperature 200 to 270
It is preferably selected from the range of ° C. When performing T-die molding, the draft rate is 1 to 10 and the resin temperature is 190 to 30.
It is preferable to select from the range of 0 ° C. The draft rate is defined by the following mathematical formula [Equation 1].

[0014]

[Equation 1]

The meaning of each symbol in the above equations is as follows. G: Width of die slit t: Thickness of film obtained ρm: Density of resin extruded from die slit ρf: Density of film BUR: Blow-up ratio (BUR = in case of T die molding)
Represented as 1)

[0016]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In the following examples, a T-die casting molding machine in which a T-die having a slit width of 450 mm and a lip clearance of 1.0 mm, a cooling roll and a take-up roll were attached to a 40 mmφ extruder was used.
Resin temperature 250 ° C, extrusion rate 12 kg / hr, take-up speed 6.0
The film was formed under the condition of m / min.

The physical properties of the obtained film were measured by the following methods. (1) Drop impact strength (g) According to ASTM D-1709 (2) Transparency Measure haze (%) according to ASTM D-1003 (3) Heat seal strength (g / 15 mm) According to JIS Z 1526 Retort The heat seal strength after the treatment was measured after the film was allowed to stand in an autoclave and steam sterilized at 120 ° C. for 30 minutes.

Example 1 As a raw material, a resin composition prepared by dry blending 95 parts by weight of the following polypropylene copolymer with 5 parts by weight of the following ethylene copolymer was used and was subjected to T-die casting to obtain an 80 μm thick non-coated resin composition. A stretched film was obtained, and its physical property values are shown in Table 1.
It was shown to. [Polypropylene copolymer] Content of ethylene component is 2.5% by weight, melt flow rate is 7.0 g / 10
And the amount of the extracted component by the cross fractionation method under the condition of using orthodiglobenzene as the solvent and the temperature of 80 ° C.
8 wt%, a density of 0.89 g / cm ³ propylene - ethylene copolymer [ethylene copolymer] density 0.88 g / cm ^3, melt flow rate of 6.7 g / 10 min ethylene - butene - 1 copolymer (manufactured by Mitsui Petrochemical Co., Ltd. under the trade name "Tufmer A"
4085 ")

Examples 2 and 3 In the same manner as in Example 1, except that the mixing ratio of the ethylene-based copolymer was changed to 7.5% by weight and 10% by weight, respectively. A stretched film was obtained. The physical properties of the obtained film are shown in Table 1.

Example 4 In Example 1, 92.5 parts by weight of the polypropylene copolymer and 7.5 parts by weight of the ethylene copolymer were dry blended, and the temperature of the resin was 250 ° C. in a twin-screw kneader having a screw diameter of 40 mmφ. An 80 μm-thick unstretched film was obtained in the same manner as in Example 1 except that the melt-blended resin composition was used. The physical properties of the obtained film are shown in Table 1.

Comparative Examples 1 and 2 An unstretched film having a thickness of 80 μm was obtained in the same manner as in Example 1 except that the mixing ratio of the ethylene copolymer was changed to 25% by weight and 0% by weight, respectively. Got
The physical properties of the obtained film are shown in Table 1.

Comparative Example 3 In Example 3, as the ethylene-based copolymer, ortho-di-g-roylbenzene was used as the solvent, and the propylene-ethylene random copolymer containing 25% of the amount of the extracted component by the cross fractionation method at the temperature of 80 ° C. was used. An unstretched film having a thickness of 80 μm was obtained in the same manner as in Example 3 except that the polymer was used. The physical properties of the obtained film are shown in Table 1.

[0023]

[Table 1]Example Comparative example 1 2 3 4 1 2 3 Drop impact strength 1050 ＞ 1120 ＞ 1120 ＞ 1120 ＞ 1120 760 ＞ 1120 (g) Haze (%) 1.9 2.6 3.5 2.4 8.0 1.7 2.7 Heat seal strength (g / 15mm) Before retort treatment 1700 1800 1400 1800 900 600 1100 After retort treatment 1700 1700 1200 2100 700 400 1000

[0024]

According to the present invention described above, a polypropylene unstretched film having excellent low temperature heat sealability and retort resistance is provided. Therefore, the industrial value of the present invention is great.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yu Wada 3-10 Shiodori, Kurashiki City, Okayama Prefecture Mitsubishi Kasei Co., Ltd. Mizushima Plant

Claims (1)

[Claims] 1. A polypropylene unstretched film comprising a composition of a polypropylene copolymer and an ethylene copolymer, wherein the content of the ethylene component as the polypropylene copolymer is 1.5 to 3.5% by weight. Propylene-having a melt flow rate of 5 g / 10 min or more, using orthodiglobenzene as a solvent, and an extraction component amount of 20% by weight or less by a cross fractionation method under the condition of a temperature of 80 ° C.
An ethylene copolymer is used, a density of 0.91 g / cm ³ or less is used as the ethylene copolymer, and the blending amount of the ethylene copolymer in the composition is 100 parts by weight of the polypropylene copolymer. 2 to 20 parts by weight with respect to the polypropylene unstretched film.