JPH09164640A - Polypropylene composite film for packing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extrusion coated polypropylene composite film excellent in transparency and high in the adhesive strength and heat sealing strength of a base material layer and a seal layer. SOLUTION: This film is obtained by extruding a resin compsn. (B) consisting of a polypropylene resin (c) and a low density polyethylene and/or a polyethylenic resin (d) composed of an amorphous or low crystalline ethylene/α- olefin copolymer to coat the resin layer (a) of a two-layered co-extrusion stretched film (A) consisting of a polypropylene resin layer (a) with low heat sealing temp. of 110-130 deg.C and a crystalline polypropylene layer (b).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polypropylene composite film for packaging.

[0002]

2. Description of the Related Art Conventionally, as a packaging material for foods and general articles, a direct lamination composite film is known in which a stretched polypropylene film is used as a base material and a polypropylene resin as a sealing layer is extruded and coated on the base material.

However, the composite film obtained by this method does not have sufficient adhesive strength between the base film layer and the seal layer and is inferior in transparency, and this composite film is used to make a bag by heat sealing. In this case, there is a problem that the heat seal strength is low. In order to improve these problems, many attempts have been made from the resin surface to be extrusion coated, but they are still insufficient.

On the other hand, a dry lamination method in which a stretched polypropylene film as a substrate and a polypropylene resin film are made into a composite film via an adhesive is also used. The composite film obtained by this method has good adhesive strength and transparency between both films,
Depending on the intended use of the composite film, it is necessary to use an adhesive or its solvent, which is not desirable depending on the purpose of use, or a new process needs to be provided, which is disadvantageous in terms of equipment and workability as compared with the extrusion coating method. Is.

[0005]

DISCLOSURE OF THE INVENTION The present invention uses a stretched polypropylene film as a base material, and when a composite film obtained by extrusion-coating a polypropylene resin as a sealing layer on the base material is used for packaging, the base material layer and the sealing material are sealed. An object of the present invention is to provide a polypropylene composite film for packaging, which has a high heat-sealing strength and has good transparency without delamination between layers.

[0006]

Means for Solving the Problems As a result of intensive investigations, the inventors of the present invention co-extruded two layers of a base material polypropylene and a low temperature heat sealable polypropylene resin,
The present invention was completed by finding that a composite film obtained by extrusion-coating a stretched film with a specific resin composition can achieve the object of the present invention.

That is, the present invention relates to a resin layer of a two-layer coextruded stretched film (A) comprising a polypropylene resin layer (a) having a heat sealing temperature of 110 to 130 ° C. and a crystalline polypropylene layer (b) ( On the a) side, a polypropylene resin composition (B) comprising a polypropylene resin (c) and a low density polyethylene and / or a polyethylene resin (d) comprising an amorphous or low crystalline ethylene-α-olefin copolymer is provided. The gist is a polypropylene composite film for packaging formed by extrusion coating.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The resin to be the polypropylene resin layer (a) used in the present invention (hereinafter referred to as resin (a)) is a resin having a heat sealing temperature of 110 to 130 ° C. In addition, having a heat sealing temperature of 110 to 130 ° C. means that heat sealing can be performed at a temperature of 110 to 130 ° C.

The resin (a) is preferably a propylene-olefin random copolymer or a mixture of the random copolymer and an olefin copolymer rubber. Propylene-
Examples of the olefin of the olefin random copolymer include ethylene and α-olefins having 4 or more carbon atoms,
Examples of the α-olefin include 1-butene and 3-methyl-
Examples include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene and the like. Among these olefins, ethylene is particularly desirable.

The random copolymer of propylene and ethylene preferably used has an ethylene content of 6
It is desirable that the amount is less than 1% by weight, especially 3 to 6% by weight.
The melt flow rate (MFR: JIS K721
0; load 2.16 kg / 10 min, measured at 230 ° C.) is 0.5 to 9.0 g / 10 min, especially 1.0 to 6.0 g / 1
0 minute is desirable. When the ethylene content is out of the above range, the low temperature heat seal property of 110 to 130 ° C. may not be exhibited.

The olefin copolymer rubber which may be used in combination with the propylene-olefin random copolymer includes ethylene and propylene, 1-butene, 3-methyl-1-butene, 1-hexene, 4-methyl-. Examples thereof include rubbers obtained by copolymerizing two or three or more olefins selected from α-olefins such as 1-pentene, and specifically, ethylene-propylene copolymer rubber (EP
R), ethylene-1-butene copolymer rubber (EBR),
Examples include propylene-1-butene copolymer rubber (PBR).

As the resin (a), it is desirable to use a propylene-olefin random copolymer and an olefin-based copolymer rubber in combination. Particularly, when the proportion of the propylene-olefin random copolymer is 40 to 90% by weight. ,
The resulting film has better transparency and heat seal strength.

The crystalline polypropylene of the crystalline polypropylene layer (b) used in the present invention (hereinafter referred to as resin (b)) is a polypropylene having a boiling n-heptane insoluble content of 70% by weight or more. As the resin (b). In addition to propylene homopolymer, propylene and ethylene or 1
-Butene, 1-hexene, 4-methyl-1-pentene,
Examples thereof include random copolymers and block copolymers with α-olefins such as 1-octene.

Polypropylene resin (c) which is one component of the polypropylene resin composition (B) used in the present invention
As the (hereinafter, referred to as resin (c)), any polypropylene resin can be used, but particularly, the melt flow rate (MFR: the measuring method is the same as the above) is 0.1 to 0.1.
MFR obtained by degrading 3.0 g / 10 minutes of crystalline polypropylene resin in the presence of organic peroxide is 7 to 30 g / 1.
It is desirable to use 0 minute polypropylene resin (e) (hereinafter referred to as resin (e)).

The crystalline polypropylene resin, which is the raw material of the resin (e), has the above-mentioned MFR and is selected from the above-mentioned resins (b), and particularly has an ethylene content of 2.0 to 5.0.
A weight percentage of propylene-ethylene random copolymer is desirable.

In the present invention, this crystalline polypropylene resin is degraded in the presence of an organic peroxide so that its MFR is 7%.
It is desirable to use the one set to be about 30 g / 10 minutes. M
When FR is less than 7 g / 10 minutes, the film thickness may not be constant due to generation of surging during extrusion coating,
When it exceeds 30 g / 10 minutes, the mechanical strength of the extrusion-coated film may be insufficient.

The organic peroxide used for degrading the crystalline polypropylene resin is benzoylperoxide, di-t-butylperoxide, dicumylperoxide, t-butylcumylperoxide, 1,1-bis- ( t-butylperoxy))-3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis (t-butylperoxy).
(Oxy) octane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,5-dimethyl-2,
5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) -3 -Hexyne, 1,3-bis (t-butylper)
Oxyisopropyl) benzene, α, α′-bis (t-
Butylper-oxyisopropyl) benzene, t-butyl-hydroper-oxide, cumene hydroper-oxide, lauroyl-peroxide, di-t-butyl-
Dipa-oxyphthalate, t-butylperoxymaleic acid, t-butylperoxypropyl carbonate
And isopropyl percarbonate.

These are not limited to one type, and two or more types can be used in combination. Among these, 2,5-
Dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) -3-hexyne, 1,3-bis (t-butylperoxy)
Oxyisopropyl) benzene, α, α′-bis (t-
Butylpa-oxyisopropyl) benzene is particularly preferred.

The degrading method is carried out by adding an organic peroxide in an amount of 0.005 to 0. per 100 parts by weight of the crystalline polypropylene resin.
01 parts by weight may be used to heat and knead both at a temperature equal to or higher than the melting temperature of the resin, for example, 180 to 300 ° C.,
Although any method can be adopted as the method, it is particularly preferable to carry out in an extruder. In order to uniformly disperse the organic peroxide in the crystalline polypropylene resin, both should be mixed in advance with a Henschel mixer before heating and kneading them.
The mixing may be sufficiently performed using a mixer such as a ribbon blender or Brabender Plastograph (registered trademark). Furthermore, in order to improve the dispersibility of the organic peroxide, it is possible to use a mixture of the organic peroxide and a suitable medium. By doing so, the resin (e) can be produced.

The polyethylene resin (d) (hereinafter referred to as resin (d)) used in the present invention is low density polyethylene and / or amorphous or low crystalline ethylene-α-.
It consists of an olefin copolymer.

The low-density polyethylene used as the resin (d) preferably has a density of 0.925 g / cm ³ or less. If a density of more than 0.925 g / cm ³ is used, high-speed moldability is poor. It will be. Such low density polyethylene is produced by a known method, particularly a high pressure method.

The amorphous or low crystalline ethylene-α-olefin copolymer used as the resin (d) is as follows:
Ethylene and propylene, 1-butene, 1-hexene,
Copolymers with one or more α-olefins such as 4-methyl-1-pentene and 1-octene, and ethylene and α-olefins (preferably propylene) and 1,
Examples thereof include copolymers with diolefins such as 3-butadiene, isoprene, (di) cyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene norbornene and ethylidene norbornene. Among these, a copolymer of ethylene and propylene or 1-butene, particularly a copolymer of ethylene and 1-butene is preferable.

The above copolymer has a density of 0.86 to 0.9.
0 g / cm ³ , especially 0.870 to 0.890 g / cm ³
Those having a melt index (MI: J
ISK 7210; load 2.16 kg, measured at 190 ° C.) of 0.5 to 30 g / 10 minutes, particularly preferably 1 to 7 g / 10 minutes.

The use of the above low density polyethylene in the resin (d) further improves the high speed extrusion coating processability of the polypropylene resin composition (B), and the amorphous or low crystalline ethylene-α-olefin copolymerization The use of coalescence lowers the heat seal temperature. Also, the use of both exerts their synergistic effect. When both are used, the low density polyethylene and the amorphous or low crystalline ethylene-
The weight ratio of the α-olefin copolymer used is 1:
It is preferable that the ratio is 0.5 to 1: 2.0.

The proportion of the resin (c) and the resin (d) used is preferably 70 to 90% by weight for the former and 30 to 10% by weight for the latter. The method of mixing the resin (c) and the resin (d) is not particularly limited, but a method of kneading the both under melting is particularly preferable because both are uniformly mixed. It is preferable to use an extruder for the melt kneading. In particular, when the stretched film (A) is extrusion-coated with the resin (c) and the resin (d), it is desirable to mix the two as described above.

The polypropylene resin composition (B) is prepared as described above. The resin composition (B) is
Known additives such as an antioxidant, a neutralizing agent, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a lubricant, and a coloring agent may be added as necessary. Further, these additives can be added to the resin (a) and / or the resin (b).

The composite film of the present invention comprises the resin (c) on the resin layer (a) side of the two-layer coextruded stretched film (A) consisting of the resin layer (a) and the crystalline polypropylene layer (b). And a polypropylene resin composition (B) comprising the resin (d) and the resin (d) are extrusion-coated.

The stretched film (A) is obtained by coextruding the resin (a) and the resin (b) into a film having two layers, and then stretching. The coextrusion of the resin (a) and the resin (b) may be carried out according to a commonly used method. As a method of stretching the film-shaped molded product, the molded product may be uniaxially or biaxially stretched by a usual method, but biaxial stretching is particularly preferable.

Stretching of the molded article is carried out at a stretch ratio such that the thickness of the stretched film (A) is 1 to 100 μm, preferably 5 to 50 μm, and the stretch ratio is usually 4 to 1
5 times. Regarding the thickness of the resin layer (a) and the crystalline polypropylene layer (b) in the stretched film (A), the crystalline polypropylene layer (b) is thicker than the resin layer (a). Is desirable.

The resin film (A) side of the stretched film (A) obtained as described above is extrusion-coated with the above resin composition (B) to obtain a composite film of the present invention.

The method of extrusion coating is a usual method, typically, the above resin composition (B) is melted on the above stretched film (A), extruded from a T-die, and both are pressure-bonded when hot and molded. It is done by doing. The thickness of the coating layer made of the resin composition (B) is arbitrary, but is usually 5 to 50 μm.
m.

As described above, the composite film of the present invention is produced, and the composite film can have other members laminated on one side or both sides thereof. Other members include polypropylene, polyester, polyamide, saponified ethylene-vinyl acetate copolymer, resin film or sheet such as polyvinylidene chloride, metal such as aluminum, iron and copper, foil such as alloy of these metals, or Examples include plates, cellophane, paper, cloth, non-woven fabrics and the like.

[0033]

The present invention will be described below in detail with reference to examples.
The percentages (%) in the examples are based on weight except haze, and the physical properties of the composite film were measured according to the following test methods.

Haze ASTM D1003 Heat-sealing temperature of resin layer (a) The resin layer (a) surface of the two-layer coextruded stretched film (A) was sealed with a sealing time of 1.0 second and a sealing surface pressure of 2.0 kgf / c.
Heat sealing was performed at m ² at each sealing temperature, and a test piece having a width of 15 mm was cut out from the obtained laminate, and a pulling speed was 3
The heat-sealed portion was peeled off at 00 mm / min, and the heat-sealing temperature corresponding to the peeling strength at this time of 300 gf / 15 mm was determined.

A laminate obtained by heat-sealing the extruded coating layers (B) of the heat-sealable composite film at a sealing time of 1.0 second and a sealing surface pressure of 2.0 kgf / cm ² at each sealing temperature. From 15m
The strength when the heat-sealed part was peeled off at a pulling speed of 300 mm / min was shown.

Lamination Peel Strength The adhesive strength between the resin layer (a) and the extrusion coating layer (B) of the two-layer coextruded stretched film (A) of the composite film with a width of 15 mm was measured at an angle of 180 ° and a pulling speed. The strength when peeled at 300 mm / min is shown.

(Examples 1 to 3) (Comparative Examples 1 and 2) Propylene-ethylene random copolymer (RCP) as resin (a) (ethylene content 3.8%, MFR 1.8)
g / 10 minutes) and propylene-butene copolymer rubber (PB
R) (1-butene content 30.0%, density 0.89 g /
cm ³ , MI 3.2 g / 10 min) in a ratio shown in Table 1 and a homopolypropylene having an MFR of 2.5 g / 10 min as the crystalline polypropylene (b) were mixed with T of an extruder. After co-extruding from a die to obtain a film-shaped molded product, it is stretched by a biaxial stretching machine to have a thickness of 25 μm.
A two-layer coextruded stretched film (A) of m ((a) layer 3 μm) was obtained.

Ethylene content of 3.8 as resin (c)
%, MFR 0.2 g / 10 min RCP 100 parts (parts by weight; the same applies hereinafter), antioxidant 0.15 parts, neutralizer 0.
05 parts, 0.3 parts of anti-blocking agent, 0.1 parts of lubricant and a mixture of 20% of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 80% of liquid paraffin was mixed with an organic peroxide. After adding 0.16 parts each as an oxide and mixing with a Heschel mixer, the mixture was supplied to an extruder,
Extruded at an extrusion temperature of 240 ° C to produce pellets (MFR 25g
/ 10 minutes) and 80% of the pellets of this degraded RCP and low density polyethylene (LDPE) (density 0.925 g / cm ³ , MI 6.7 g / 10 minutes) as resin (d) 20.
% Of the resin composition (B)
Was obtained.

65 mmφ extruder, die width 1,200 mm
Of the resin composition (B) obtained above on the layer (a) of the two-layer film obtained above using the T-die type extrusion coating processing apparatus of Was extrusion-coated at 300 ° C. so that the thicknesses shown in Table 1 were obtained to obtain the composite film of the present invention. The physical properties of the obtained film were measured, and the results are shown in Table 1.

In Comparative Example 1, the two-layer coextruded stretched film (A) could not be formed. (Example 4) A composite film was obtained in the same manner as in Examples 1 to 3 except that only RCP (ethylene content 5.2%, MFR 3.0 g / 10 min) was used as the resin (a). The physical properties of the obtained film were measured, and the results are shown in Table 2.

Example 5 As resin (a), RCP (ethylene content 3.8%, MFR 1.8 g / 10 minutes) and ethylene-butene copolymer rubber (EBR) (1-butene content 20.0). %, Density 0.88 g / cm ³ , MI 3.6
g / 10 minutes) was used in the proportions shown in Table 2, and a composite film was obtained in the same manner as in Examples 1 to 3 except that the resin composition obtained was used. The physical properties of the obtained film were measured, and the results are shown in Table 2.

(Comparative Example 3) LDPE as resin (d)
Composite films were obtained in the same manner as in Examples 1 to 3 except that high density polyethylene (HDPE) was used instead of. The physical properties of the obtained film were measured, and the results are shown in Table 2.

Comparative Example 4 As the resin composition (B), HDPE and EB were used instead of LDPE as the resin (d).
R (1-butene content 20.0%, density 0.88 g / c
m ^3, was obtained using MI3.6g / 10 min), except for using a resin composition having the composition ratio shown in Table 2 (B), a composite film was obtained in the same manner as in Example 1-3. The physical properties of the obtained film were measured, and the results are shown in Table 2.

(Comparative Example 5) As the resin composition (B), the undegraded R was used instead of the degraded RCP as the resin (c).
CP is used, and HDPE and EBR (1-butene content 20.0%, instead of LDPE as the resin (d),
A composite was prepared in the same manner as in Examples 1 to 3 except that the resin composition (B) having a compounding ratio shown in Table 2 was used, which was obtained by using a density of 0.88 g / cm ³ and MI of 3.6 g / 10 min. I got a film. The physical properties of the obtained film were measured, and the results are shown in Table 2.

Comparative Example 6 Instead of the bilayer coextruded stretched film (A), homopolypropylene (MFR 2.5 g) was used.
/ 10 min) single layer stretched film (OPP) (thickness 25μ
Composite films were obtained in the same manner as in Examples 1 to 3 except that m) was used. The physical properties of the obtained film were measured, and the results are shown in Table 2.

(Comparative Example 7) Homopolypropylene (MFR
3.0 g / 10 min) OPP (thickness 20 μm) and homo-polypropylene (MFR 9.0 g / 10 min) unstretched film (thickness 20 μm) using a polyether-urethane adhesive (coating amount). 3 g / m ² ) Dry lamination was performed to obtain a laminated film. The physical properties of the obtained film were measured, and the results are shown in Table 2.

[0047]

[Table 1]

[Table 2]

[0048]

INDUSTRIAL APPLICABILITY The composite film of the present invention, when used for packaging, has no delamination between the base material layer and the seal layer, has a large heat seal strength, and has good transparency.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area B29K 23:00 B29L 7:00 9:00 C08K 5:14

Claims (3)

[Claims] 1. A two-layer coextruded stretched film (A) having a polypropylene resin layer (a) having a heat sealing temperature of 110 to 130 ° C. and a crystalline polypropylene layer (b) on the resin layer (a) side. , Polypropylene resin (c)
A polypropylene composite film for packaging obtained by extrusion-coating a polypropylene resin composition (B) consisting of a low-density polyethylene and / or a polyethylene resin (d) consisting of an amorphous or low-crystalline ethylene-α-olefin copolymer . 2. The polypropylene resin layer (a) comprises a propylene-olefin random copolymer or the random copolymer and an olefin copolymer rubber.
The polypropylene composite film for packaging described in. 3. The polypropylene resin composition (B) has a melt flow rate (MFR) of 0.1 to 3.0 g / 10.
70% to 90% by weight of a polypropylene resin (e) having a MFR of 7 to 30 g / 10 min and a low density polyethylene and / or an amorphous or low amount. Crystalline ethylene-α-
Polyethylene resin (d) consisting of olefin copolymer
The polypropylene composite film for packaging according to claim 1 or 2, which is a resin composition comprising 30 to 10% by weight.