JPH09207294A - Low temperature heat-sealable polypropylene multilayered film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent low temp. heat sealing strength, no blocking property and possibility of high speed packaging at afterprocessing by constituting a film of a multi-layer film consisting of a polypropylene layer and a heat seal layer wherein at least one outermost layer consists of a linear low density polyethylene with specified physical properties and constitution. SOLUTION: This low temp. heat-sealable polypropylene multilayered film consists of a polypropylene layer and a multi-layer film wherein at least one outermost layer consists of a linear low density polyethylene heat seal layer with a density of 0.893-0.905g/cc, a melt index (at 190 deg.C and under a loading of 2.16kg of 0.1-10g/10min, a m.p. of 90-100 deg.C and a ratio of wt. average mol.wt./ no. average mol.wt. of 2.0-3.0 and contg. at most 20wt.% 4-8C α-olefin comonomer. The skin layer of polypropylene consists of a homopolypropylene, a propylene-ethylene random copolymer or a compsn. of a propylene-ethylene random copolymer and an ethylene-butene copolymer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a low-temperature heat-sealing polypropylene multilayer film, and more particularly to a low-temperature heat-sealing polypropylene multilayer film having a specific linear low-density polyethylene as a heat-sealing layer.

[0002]

2. Description of the Related Art Conventionally, polypropylene unstretched films have a polypropylene random copolymer, such as an ethylene-propylene copolymer rubber, an ethylene-butene copolymer rubber, and a polypropylene random copolymer, in order to lower the heat-sealing temperature. Propylene-butene copolymer rubber, ethylene-propylene-butene copolymer rubber and the like are generally added. However, the heat seal temperature is 1
This is still insufficient to obtain a practical seal strength (300 g / 15 mm width or more) at 00 ° C. or lower, and it can be achieved by adding polybutene-1. JP-A-7-109389
Issue.

Further, conventionally known low-density polyethylene or linear low-density polyethylene can be used for the heat-sealing layer, but these do not necessarily have sufficient compatibility with polypropylene, and thus the sealing layers are the same. In heat sealing, there remains a problem that delamination between the seal layer and other layers occurs.

[0004]

However, with polybutene-1, polybutene-1 deteriorates in heat sealability due to the phase transition after molding, and in order to stabilize this, polybutene-1 is required.
It was necessary to increase the amount of the compound and to combine high-density polyethylene, a polyolefin-based copolymer or the like as a stabilizer. In addition, polybutene-1 has a remarkably slow crystallization rate and is wound around a roll during practical film production,
Because the film roll of the product may block,
There was a problem that it was difficult to secure a sufficient production rate. Therefore, it has been desired to develop an unstretched polypropylene film having excellent productivity and low temperature heat sealability.

Therefore, it is an object of the present invention to provide a low-temperature heat-sealing polypropylene multilayer film which is excellent in low-temperature heat-sealing strength, has good productivity without causing blocking, and is capable of high-speed packaging in post-processing. To do.

[0006]

Means for Solving the Problems As a result of intensive research to solve the above-mentioned problems, the present inventors have found that productivity can be improved by using a specific linear low-density polyethylene as a heat-sealing layer of a polypropylene film. The present invention has been completed based on the finding that it is improved and excellent in low-temperature heat sealability and that high-speed packaging in post-processing is possible.

That is, in the low temperature heat-sealable polypropylene multilayer film of the present invention, the polypropylene layer and at least the outermost layer have a density of 0.893 to 0.905 g /
cc, melt index (190 ° C, load 2.16k
g, hereinafter referred to as MI) 0.1 to 10 g / 10 minutes, melting point 9
0 to 100 ° C, weight average molecular weight / number average molecular weight (hereinafter M
w / Mn) 2.0 to 3.0 and a heat-sealing layer of linear low-density polyethylene containing 20% by weight or less of an α-olefin comonomer having 4 to 8 carbon atoms.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

The low-temperature heat-sealable polypropylene multilayer film of the present invention comprises a polypropylene layer and a heat-sealing layer of linear low-density polyethylene (hereinafter also referred to as L-LDPE) having at least one outermost layer having specific physical properties. The basic structure of the multilayer film is, but a multilayer film having a three-layer structure of a polypropylene laminate layer (hereinafter referred to as a skin layer) / a polypropylene intermediate layer (hereinafter referred to as a core layer) / L-LDPE heat seal has a surface property. It is preferable in terms of transparency, high-speed packaging property, and the like.

As the skin layer of polypropylene in the polypropylene multilayer film, homopolypropylene,
A propylene-ethylene random copolymer having an ethylene content of 0.2 to 5% by weight, or various polypropylene and polyolefin copolymer rubbers such as ethylene-
Propylene copolymer rubber, ethylene-butene copolymer rubber, propylene-butene copolymer rubber, ethylene-propylene-butene copolymer rubber, and the like, or a composition containing 5 to 20% by weight of one or more of them. There is one consisting of. Among these, homopolypropylene, a propylene-ethylene random copolymer or a composition of a propylene-ethylene random copolymer and an ethylene-butene copolymer rubber is preferable from the viewpoint of surface gloss and transparency.

As the polypropylene core layer in the polypropylene multilayer film, homopolypropylene, propylene having an ethylene content of 0.2 to 5% by weight is used.
Ethylene random copolymer, ethylene content 2-15
Examples thereof include those composed of propylene-ethylene block copolymer in a weight percentage.

Further, L-LDPE constituting the outermost layer of the low temperature heat-sealable polypropylene multilayer film.
Has a density of 0.893 to 0.905 g / cm ³ , preferably 0.895 to 0.900 g / cc, and an MI of 0.1.
-10 g / 10 min, preferably 1-5 g / 10 min, melting point 90-100 ° C, preferably 95-100 ° C, M
It has a w / Mn of 2.0 to 3.0. The α-olefin comonomer to be copolymerized with ethylene has 4 to 8 carbon atoms, and is preferably 1-octene having 8 carbon atoms. The amount of comonomer to be copolymerized with ethylene is 20% by weight or less, preferably 10 to 20% by weight. L-LDPE having the above physical properties is preferable from the viewpoint of low-temperature heat-sealing property and blocking prevention during film production.

The L-LDPE heat-sealing layer contains an antiblocking agent, for example, one of inorganic fillers such as silica, zeolite, and talc in order to further improve film-forming property and high-speed wrapping property. 0.1 to 1.0 for 2 parts or more based on 100 parts by weight of L-LDPE.
It is preferable to add parts by weight. Further, a lubricant, for example, one or two of amides such as oleic acid amide, erucic acid amide, stearic acid amide, and behenic acid amide.
0.1 to 100 parts by weight of L-LDPE
It is preferable to add 1.0 part by weight.

The addition of these antiblocking agents and lubricants may be directly blended with L-LDPE, or a masterbatch may be prepared in advance in order to further enhance the blending effect, which is preferably 1 to 20% by weight. , And more preferably 5 to 10% by weight. As the masterbatch, it is preferable to use a resin such as L-LDPE mixed with the antiblocking agent and the lubricant and melt-kneaded in advance.

The L-LDPE used in the heat-sealing layer of the present invention uses a metallocene catalyst having a small Mw / Mn, which is a measure of the molecular weight distribution among the specific physical properties, that is, a metallocene catalyst capable of narrowing the width of the molecular weight distribution. Polymerized ones are preferred.

The metallocene catalyst is a metallocene having a structure in which a transition metal such as titanium, zirconium or hafnium is sandwiched between unsaturated cyclic compounds such as a π-electron cyclopentadinyl or substituted cyclopentadienyl group, It is a combination with a promoter such as an aluminum compound.

The L-LDPE used in the present invention comprises ethylene and a comonomer in the presence of a metatheron catalyst obtained by activating a metallocene such as titanocene or zirconocene with an aluminum compound such as an alkylaluminoxane, an aluminum alkyl, an aluminum halide or an aluminum alkyl halide. Solution polymerization of an α-olefin having 4 to 8 carbon atoms, preferably 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, etc., particularly preferably 1-octene. Can be obtained by doing.

The low-temperature heat-sealable polypropylene multilayer film of the present invention may be added with other layers or the thickness composition ratio of each layer may be adjusted as necessary within the range not impairing the object of the present invention.

Next, the low temperature heat-sealable polypropylene multi-layer film of the present invention can be produced by multi-layering the film layers forming each of the above layers. From the viewpoint of productivity, co-extrusion molding capable of forming a multi-layer film at the same time is preferred for this multi-layering. In particular, the L-LDPE is heated to, for example, 150 to 250 ° C. using three or more extruders, and the core layer polypropylene and the skin layer polypropylene are heated to, for example, 180 to 270 ° C. to melt each, The functionality of a multilayer film obtained by bringing the above materials into contact with each other within the die or in the die opening and extruding a polypropylene skin layer / polypropylene core layer / L-LDPE heat seal layer as a single product. It is preferable in terms of productivity. Further, the total thickness of the multilayer film is preferably 15 to 50 μm, and the thickness of each layer at this time is as follows: polypropylene skin layer / polypropylene core layer / L-LDPE seal layer = 1 / 1-1 to 1/8 / 1 is preferable.

The obtained coextruded unstretched polypropylene film (also referred to as CPP) may be used alone as a packaging material, and a stretched film of polypropylene, polyethylene terephthalate, polyamide or the like may be used as a base material and an adhesive or You may use it by pasting together through a molten polyethylene resin.

As described above, the low-temperature heat-sealable polypropylene multilayer film of the present invention has sufficient strength by low-temperature heat-sealing and does not cause blocking, so that high-speed packaging in various fields can be realized.

The reason why such an effect is obtained is that L-L
It is considered that DPE has a low melting point and a high crystallization rate from a molten state to cooling and solidification. In addition, the L-LDPE of the present invention has a particularly small Mw / Mn and a very narrow molecular weight distribution, and therefore has a low temperature sealability as a sealant, high hot tack strength, odorlessness, hygiene, bag breakage resistance, and high-speed packaging. It is considered that characteristics excellent in properties such as sex can be obtained. In particular, L-LDPE polymerized with a metallocene catalyst having 1-octene as a comonomer has a long-chain branch in the main chain, and therefore has a high melt strength in addition to the above-mentioned characteristics and can be easily coextruded with polypropylene. Therefore, it is considered that coextrusion molding of the polypropylene multilayer film can be easily performed.

[0023]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to the following examples. The following resins and additives were used as raw materials. (1) Homopolypropylene (HPP): Melt flow rate (MFR, 230 ° C., 2.16 kg load) 9 g / 1
0 minutes (2) Propylene-ethylene random copolymer (RP
P): Melt flow rate (MFR, 230 ° C., 2.1
6 kg load) 9 g / 10 minutes, ethylene content 3.6 wt% (3) L-LDPE-1 (metallocene catalyst polymerized product):
[AFFINITY POP made by Dow Chemical Japan Co., Ltd.
s PF1140 (trade name), density 0.895g / c
c, MI 1.6 g / 10 min, melting point 94 ° C., comomer: 1
-Octene 14% by weight, Mw / Mn2.04] (4) L-LDPE-2 (metallocene catalyst polymerized product):
[AFFINITY POP made by Dow Chemical Japan Co., Ltd.
s PL1845 (trade name), density 0.910 g / c
c, MI 3.5 g / 10 minutes, melting point 103 ° C., comonomer: 1-octene 9.0 wt%, Mw / Mn 2.05] (5) Antiblocking agent (AB agent): talc [Hayashi Kasei Co., Ltd., Micron White # 5000S (trade name)] (6) Lubricant: Erucamide [Diamid L-200 (trade name) manufactured by Nippon Kasei Co., Ltd.] (7) Ethylene-butene copolymer rubber (EBR): [ Mitsui Petrochemical Industry Co., Ltd., Tuffmer A4085 (trade name), density 0.880 g / cc, MFR 3.6 g / 10
Min] (8) Polybutene-1 (PB-1): [Mitsui Petrochemical Industrial Co., Ltd., Buron M2481 (trade name), density 0.900 g / cc, MFR 4.0 g / 10 min] (9) High density Polyethylene (HDPE): [Tonen Kagaku KK, Tonen Polyethylene S6211 (trade name), density 0.956 g / cc, MI 12 g / 10 min] (10) Low density polyethylene (LDPE): Nippon Unicar Co., Ltd., NUCDFD0148 (trade name) [density 0.922 g / cc, MI 10 g / 10 min, melting point 105
C, Mw / Mn 3.3] (11) L-LDPE-3: [manufactured by Nippon Unicar Co., Ltd.,
NUCG-5471 (trade name), density 0.925g / c
c, MI 10.0 g / 10 minutes, melting point 106 ° C., Mw / M
n3.5]

The test methods in Examples and Comparative Examples are as follows. (1) Film-forming property: (A) Judgment 1: The effective width of 400 mm after neck-in that passed through the chill roll at a film-forming take-off speed of 25 m / min was cut off by 30 mm at both ends, and the cut ears were No. One that does not wrap around one drive roll (mirror surface) is marked with ◯, one that wraps once in 10 to 30 minutes is marked with Δ, and one that wraps frequently is marked with X.

(B) Judgment 2: The film itself from which the ears were cut off had the following No. 2 The drive roll (mirror surface) has no sticking, and the one with sticking is △.
Marks and sticking and noise when peeling off were marked with X. (2) Haze: Measured according to JIS K6714. (3) Coefficient of dynamic friction (COF): Measured according to JIS K7125 (measured with the skin layer surface and the seal layer surface or the seal layer surface and the seal layer surface in contact with each other). (4) Heat seal strength (H / S strength): The seal layer surfaces of the three-layer film are the same as the heat sealer No. manufactured by Yasuda Seiki Seisakusho. 138, using a base temperature of 50 ℃,
It was heat-sealed by applying a pressure of 1.0 kg / cm ² for 1 second at a predetermined temperature. The heat seal strength of this product is JIS Z
Measured by the test method of 1707. (5) Melting point: measured with a differential scanning calorimeter.

Examples 1 to 5 and Comparative Examples 1 to 6 Seal layers were prepared by dry blending with the compositions shown in Table 1. Next, each resin component constituting the skin layer, core layer and seal layer shown in Table 1 was supplied to a three-layer coextrusion film-forming machine (manufactured by Placo Co., 45 mmφ × 3, three-layer multi-manifold) to form three layers. A film was formed by coextrusion. The film forming conditions are as follows.

Film forming conditions: C ₁ C ₂ C ₃ AD J D Extruder rotation speed (° C.) (° C.) (° C.) (° C.) (° C.) (° C.) (rpm) Seal layer 190 210 230 230 230 10 core Layer 210 230 250 250 250 240 50 Skin layer 210 230 250 250 250 10 However, only in Example 5, rpm is sealed Layer = 10 / Core layer =
40 / skin layer = 10. The take-off speed is 25m.
/ Min.

Here, C _{1 to} C ₃ are the resin temperature of the cylinder, AD is the resin temperature of the adapter, J is the resin temperature of the joint portion, and D is the resin temperature when coextruded by the die.

Table 2 shows the film-forming properties and the evaluation results of the haze and the coefficient of dynamic friction (COF) after aging the formed film in an oven at 40 ° C for 1 day. Further, Table 3 shows the evaluation results of the heat seal strength (H / S strength) after aging for 1 day and 7 days in an oven at 40 ° C.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

From the above results, the polypropylene multilayer film using the specific linear low-density polyethylene of the present invention for the heat-sealing layer is excellent in film forming property, haze and heat-sealing strength at low temperature. I understand. Also, the coefficient of dynamic friction shows a good value. On the other hand, linear low-density polyethylene outside the scope of the present invention,
When the composition of low density polyethylene, propylene-ethylene random copolymer and polybutene-1 is used for the heat-sealing layer, the one having excellent heat-sealing property has poor film-forming property, haze, dynamic friction coefficient, etc. It can be seen that those having good properties, haze, and dynamic friction coefficient have remarkably inferior heat seal strength.

[0034]

As described above, according to the present invention, it is possible to obtain a polypropylene multilayer film which has a low-temperature heat-sealing property, has a good haze and a coefficient of dynamic friction, and can be packaged at high speed. In addition, since the film is not blocked, the productivity is good.

Therefore, it is suitable for use in various packaging fields of unstretched polypropylene which are required to have surface properties and transparency.

Claims (4)

[Claims] 1. A polypropylene layer and at least one outermost layer having a density of 0.893 to 0.905 g / cc and a melt index (190 ° C., load 2.16 kg) of 0.1 to 1.
0 g / 10 minutes, melting point 90 to 100 ° C., weight average molecular weight /
Α- having a number average molecular weight of 2.0 to 3.0 and a carbon number of 4 to 8
A low temperature heat-sealable polypropylene multi-layer film comprising a heat-seal layer composed of a linear low-density polyethylene containing 20% by weight or less of an olefin comonomer. 2. The heat seal layer comprises 0.1 to 1.0 parts by weight of an antiblocking agent and 0.1 to 1.0 parts by weight of a lubricant with respect to 100 parts by weight of the linear low-density polyethylene. The low-temperature heat-sealable polypropylene multilayer film according to claim 1, which contains. 3. The low-temperature heat-sealable polypropylene multilayer film according to claim 1, wherein the α-olefin comonomer of the linear low-density polyethylene is 1-octene. 4. The unstretched film obtained by coextrusion molding, wherein the multilayer comprises a laminated layer of polypropylene / an intermediate layer of polypropylene / the heat seal layer of the linear low-density polyethylene. Low temperature heat sealable polypropylene multi-layer film.