JPH08224834A - Polypropylene laminate - Google Patents

Abstract

PURPOSE: To provide a laminate consisting of a polypropylene film and a polyvinylidene chloride layer having excellent peel strength and clear cut property suitable for packaging foods by a simple and low-cost means. CONSTITUTION: This polypropylene laminate consists of a polypropylene film and a polyvinylidene chloride layer. The polypropylene film is obtained by extruding a polypropylene resin at 290-320 deg.C and stretching it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene laminate, and more particularly to a laminate having a polypropylene film and a polyvinylidene chloride layer as constituent units, which is used for packaging foods and the like.

[0002]

2. Description of the Related Art Films for packaging foods such as confectionery, meats, fresh fish and pickles, especially packaging bags using the films, are moisture-proof because they are directly provided to consumers together with their contents. It is necessary to have gas barrier properties and cosmetic appearance, but in addition to these, it is also a major requirement to have a clear cut property.

In order to satisfy the above-mentioned required functions, these packaging bags have, for example, a polyethylene terephthalate film or a biaxially oriented polypropylene film (OP) laminated with polyvinylidene chloride (PVDC) as a surface layer.
P), an unstretched polypropylene film (CPP), and a laminate using a low density polyethylene film as an inner layer are known.

However, the packaging bag using the laminated body having the above-mentioned structure has a problem that when the contents such as confectionery are taken out, the adhesive surface of the laminated body is peeled off and clear cutting cannot be performed.

In order to prevent the peeling on the adhesive surface, it is necessary to improve the peel strength between the films of the laminate, especially between the OPP which is the surface layer and the laminated PVDC layer. Usually, the peel strength is improved by activating the surface of the film by corona discharge treatment, but sufficient peel strength was not obtained.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a laminate comprising a polypropylene film and a polyvinylidene chloride layer as constituent units, which are excellent in peel strength by a simple and inexpensive means and exhibit good clear cut properties. With the goal.

[0007]

Means for Solving the Problems The present inventor has conducted extensive studies on a laminate comprising a polypropylene film and a polyvinylidene chloride layer, and as a result, after extruding a polypropylene resin as a polypropylene film in a specific temperature range. The present invention has been completed by finding that the object of the present invention can be achieved by using a film obtained by stretching in at least a uniaxial direction.

That is, the present invention is a laminate obtained by laminating at least a polypropylene film and a polyvinylidene chloride layer, the polypropylene film being extruded at 290 to 320 ° C. and then stretched in at least uniaxial direction. The gist is a polypropylene laminate consisting of one.

The polypropylene resin used in the present invention is crystalline, particularly 80% by weight of boiling n-heptane insoluble matter.
Highly crystalline ones containing the above are preferable, and they are ethylene, 1-butene, and 4 in addition to propylene homopolymer.
Copolymers with other olefins such as -methyl-1-pentene, 1-hexene and 1-octene can also be used. The content of other olefins in the copolymer is such that the crystallinity of the copolymer is not impaired, which is usually 3
It is 0% by weight or less.

Polypropylene resin has a melt flow rate (MFR; JIS K) from the viewpoint of film moldability.
7210; load 2.16 kg, measured at 230 ° C.) is 0.
Those having 1 to 100 g / 10 minutes, particularly 1 to 10 g / 10 minutes are preferable.

Further, the polypropylene resin may be blended with additives such as an antioxidant, a light stabilizer and an ultraviolet absorber in order to prevent deterioration of the resin during molding or after molding.

Polyvinylidene chloride (hereinafter abbreviated as PVDC) used in the present invention comprises vinylidene chloride homopolymer and vinylidene chloride, and a monomer having an unsaturated bond copolymerizable therewith. It is a copolymer.

Examples of the monomer include vinyl chloride, acrylonitrile, acrylic acid, methacrylic acid, alkyl acrylates having an alkyl group having 1 to 18 carbon atoms, and methacrylic acid having an alkyl group having 1 to 18 carbon atoms. Alkyl ester, maleic anhydride, maleic acid, maleic acid alkyl ester, itaconic acid, itaconic acid alkyl ester, vinyl acetate, ethylene, propylene, isobutylene, butadiene, etc. can be exemplified, and these can be used alone or in combination of two or more. You can

The laminate of the present invention uses a polypropylene film obtained by extruding a polypropylene resin at 290 to 320 ° C., preferably 300 to 318 ° C., and then stretching it at least uniaxially, preferably biaxially. However, the most preferable embodiment is to use a polypropylene film obtained by extruding a polypropylene resin at 300 to 318 ° C. and then biaxially stretching it.

Extrusion of polypropylene resin is carried out through a T die, an annular die, a coat hanger die, etc. attached to an extruder. If the extrusion temperature is less than 290 ° C, the peel strength between the polypropylene film and the PVDC layer is insufficient and the clear cut property is not exhibited, and if it exceeds 320 ° C, the transparency of the polypropylene film is lost and whitening occurs.

The laminate of the present invention is a final laminate of a polypropylene film and a PVDC layer, as long as the polypropylene film is stretched at least uniaxially. The polypropylene film can be stretched by using a polypropylene resin and a PVDC resin. It is preferable to carry out before laminating polypropylene and PVDC due to the difference in physical properties, the difference in thickness between the polypropylene film and PVDC layer before stretching, and the like.

The sheet-shaped polypropylene extruded in the above temperature range can be stretched by a method generally used in industry, such as roll stretching, tenter stretching or inflation stretching. Stretching is performed in at least a uniaxial direction, but it is particularly preferable that the stretching is performed in a biaxial direction. Further, it is desirable that the stretching is usually carried out at a temperature not lower than the softening point and not higher than the melting point of the polypropylene resin and at a magnification of 3 times or more in one direction.

The method of laminating the polypropylene film and PVDC includes (1) a method of simply laminating a stretched or unstretched polypropylene film and PVDC, and (2) a urethane type adhesive coated on the stretched polypropylene film surface. After drying, a method of applying a dispersion or solution of PVDC to form a film layer of PVDC can be mentioned.

In the above method (1) or (2), in order to enhance the adhesion between the polypropylene film layer and the PVDC layer, an anchor coating agent such as urethane-based, isocyanate-based, titanate-based, etc. is previously formed on the polypropylene film. It is preferable to apply a coating composition of about 0.2 to 4 g / m ² after curing and dry cure.

Of the above methods, the method (2) is particularly desirable.

The above method (2) will be described in more detail. The above dispersion was subjected to a reverse roll coating method, an air knife coating method, a doctor roll coating method, etc., and the above solution was subjected to a dipping method, a gravure coating method, etc. The PVDC layer can be formed on the polypropylene film by coating and drying on one side or both sides of the polypropylene film, if necessary.

Thus, the laminate of the present invention can be manufactured. The thickness of each film in the laminate is not particularly limited, but is usually 1 to 100 μm for a polypropylene film and 0.5 for a PVDC layer.
˜100 μm. As described above, the laminate of the present invention has at least the polypropylene film and the PVDC layer as constituent unit layers. The constituent unit layer, the constituent unit layer and / or another film layer, and a metal thin film layer. It is also possible to make a laminated body by combining and.

[0023]

The present invention will be described in more detail with reference to the following examples.

The physical properties of the laminate were measured according to the following test methods.

Peel strength Adhesive tape (peel strength 600 g / 15 mm) was attached to the PVDC surface of a laminate having a width of 15 mm to form a sample having a width of 15 mm, and a gap between the polypropylene film and the adhesive tape was measured using an autograph type tensile tester. The film was pulled in the direction of ° at a pulling speed of 500 m / min, and the force when the two films peeled off was shown.

Whitening resistance After the extruded polypropylene film was stretched in the machine direction, the transparency of the film was visually observed and evaluated according to the following criteria.

Totally transparent: ○ Partially or wholly lacking transparency: × Easy-tear laminate and a non-stretched polypropylene film having a thickness of 25 μm with an adhesive When dry laminating and tearing this by hand, the following criteria were evaluated.

Good peeling without peeling on the laminated surface: ○ Peeling on the laminated surface and difficult to tear: × (Examples 1 to 4) Melt flow rate (MFR) 4.0
After dry blending an antioxidant with a polypropylene resin of g / 10 minutes, it was extruded from a T-die at the extrusion temperature shown in Table 1 and rapidly cooled with a cooling roll to give a thickness of 0.6.
mm film.

This film was stretched by a tenter type sequential biaxial stretching device at a stretching ratio of 5 times in the longitudinal direction at 140 ° C. and 8 times in the lateral direction at 155 ° C., and then corona discharge treated to obtain a thickness of 2
It was a 0 μm biaxially stretched film.

On this film surface, an isocyanate-based anchor coating agent (manufactured by Toyo Moroton Co., Ltd., trade name EL220 and CAT200 mixed and diluted) was cured and then 0.2
It was applied so as to be g / m ² and dried and cured at 80 ° C. for 1 minute.

On the film surface treated with this anchor coating agent, a PVDC emulsion (trade name Saran Latex L-501 manufactured by Asahi Kasei Co., Ltd.), which is a copolymer of vinylidene chloride and vinyl chloride, has a thickness after drying. It was applied so as to have a thickness of 3 μm and dried at 100 ° C. for 1 minute and 50 ° C. for 24 hours to obtain a laminate of the present invention. The physical properties of the obtained laminate were measured and are shown in Table 1.

Comparative Examples 1 to 4 Examples 1 to 4 except that the extrusion temperature of the polypropylene resin was set as shown in Table 1.
A laminate was obtained in the same manner as above, and its physical properties are shown in Table 1.

[0033]

[Table 1]

[0034]

The laminate of the present invention having the above-mentioned constitution is
It has the transparency of the polypropylene film, the gas barrier property of the PVDC layer, and the moisture proof property, and the peel strength between both layers is strong, and it shows a good clear cut property. Moreover, such a laminate has an advantage that it can be produced by a simple means of simply setting the extrusion temperature of the resin in molding a polypropylene film within a specific range.

The laminate of the present invention having the above-mentioned characteristics is useful as a packaging material for the above foods, disposable body warmers, etc., especially as a packaging bag material using the same.

Claims (2)

[Claims] 1. A polypropylene resin is 290 to 320 ° C.
A polypropylene laminate obtained by laminating polyvinylidene chloride on a polypropylene film obtained by extruding at 1, then stretching in at least one uniaxial direction. 2. The polypropylene laminate according to claim 1, wherein the polypropylene film is laminated with polyvinylidene chloride by coating.