JP2979660B2 - Stretched laminated film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretched laminated film having a polypropylene resin composition layer and a polyamide resin layer. More specifically, the present invention relates to a stretched laminated film suitable for a packaging film, particularly a wrapping film, which is excellent in heat resistance, adhesiveness, water vapor barrier property, cutability and food safety.

[0002]

2. Description of the Related Art Hitherto, as a so-called wrapping film used for food packaging, a film mainly comprising polyvinylidene chloride, polyethylene or polyvinyl chloride has been known. However, the polyvinylidene chloride film has a disadvantage that shrinkage upon heating is large,
Films made of polyethylene have the drawback that if the film is heated due to contact with an oily substance (such as meat or tempura), the film will melt, and if the film made of polyvinyl chloride comes in contact with boiling hot water, There is a problem of causing a whitening phenomenon.

On the other hand, aliphatic polyamide resins are known as heat-resistant resins for packaging films. However, even though the aliphatic polyamide resin has excellent heat resistance and mechanical strength, it is difficult to maintain its original physical properties because of its high hygroscopicity. In particular, nylon 6 and nylon 6 / 6-6, nylon 6 /
Copolymerized nylons such as 6-10 have a problem in food safety because ε-caprolactam, which is a monomer component thereof, bleeds to the film surface, and their use in food packaging applications is restricted.

Further, such a wrapping film has the following problems in cutability (easiness of cutting).
In other words, the wrapping film is usually stored in a case such as a paper tube, and the film is cut off to an appropriate length by pulling the film against a cutting blade called a “saw blade” attached to the case, Due to the adhesiveness of the above, the opening of the food storage container and the cut end of the food are sealed. As a "saw blade" used for cutting a film, a simple blade which is generally only punched into a saw-shaped 0.2 mm thick iron plate is used, and supports the "saw blade". Also for the case, a paper box made of coated cardboard of about 350 to 700 g / m ² is used, and the rigidity is extremely low. This kind of film is required to be easily cut according to the user's will even with such a simple cutting mechanism, but in reality, the case and the "saw blade" are only deformed. Instead, the film may be deformed, or cutting may occur at a position outside the “saw blade”. Specifically, a film made of conventional polyvinylidene chloride, when a tear is formed in a part of the film at the time of cutting, the tear spreads and the "saw blade"
It cuts diagonally without being cut along. Further, a conventional polyethylene film requires a considerable tensile force at the time of cutting, so that not only the case is bent but also the film is changed.

[0005]

In view of the above problems of the conventional wrapping film, the present inventors have made intensive studies to produce a good wrapping film. By uniaxially stretching a specific polypropylene-based resin composition laminated by a co-extrusion method in the film take-off direction, the above problems are solved, and the inherent properties (heat resistance and mechanical strength) of the polyamide resin are improved. The present inventors have found that a heat-resistant wrap film excellent in adhesiveness, cut properties, water vapor barrier properties and food safety can be obtained without impairment, and completed the present invention.

That is, the gist of the present invention is to provide at least an outer layer,
An outer layer and an inner layer each comprising (A) 100 parts by weight of a polypropylene resin, (B) 5 to 40 parts by weight of polybutene or polyisobutylene, and (C) acyl having 2 to 6 carbon atoms. A laminated film comprising a polypropylene resin composition comprising 0.1 to 10 parts by weight of a glyceride having a group and an acyl group having 8 to 22 carbon atoms, wherein the intermediate layer is made of an aliphatic polyamide resin (D); Stretch ratio of 2 in the film take-up direction (longitudinal direction)
A stretched laminated film characterized by being stretched by a factor of 4.5.

Hereinafter, the present invention will be described specifically.

[0008] The stretched laminated film of the present invention comprises at least three resin layers, an outer layer, an intermediate layer and an inner layer. The outer layer and the inner layer of the stretched laminated film are (A)
Glyceride 0.1 having 100 parts by weight of a polypropylene resin, 5 to 40 parts by weight of (B) polybutene, and (C) an acyl group having 2 to 6 carbon atoms and an acyl group having 8 to 22 carbon atoms.
It is a polypropylene resin composition comprising from 10 to 10 parts by weight. The intermediate layer is (D) an aliphatic polyamide resin.

The polypropylene resin as the component (A) of the composition of the present invention is blended in a larger amount than the other components (B) and (C), and is used as a base material of the composition. It is. The polypropylene resin that can be used here may be a propylene homopolymer or a copolymer of propylene and a small amount of another copolymer component (eg, ethylene, butene, etc.). Examples of the propylene homopolymer include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene, but for film forming, isotactic polypropylene is preferable. Further, the copolymer of propylene and another copolymer component such as ethylene may be either a random copolymer or a block copolymer. The physical properties of the polypropylene resin as the component (A) may be appropriately selected according to various applications and conditions, and usually, the melt flow rate (MFR) is 0.5 to 10 g / 1.
0 minutes (230 ° C., based on JIS K 6758, 2.
Value measured under a load of 16 kg), density 0.89 to 0.91
g / cm ³ are preferred.

[0010] The component (B) of the composition of the present invention, polybutene or polyisobutylene, acts as a thickener and imparts excellent tackiness to the film. The amount of the polybutene or polyisobutylene is usually 5 to 40 parts by weight, preferably 10 to 30 parts by weight, per 100 parts by weight of the polypropylene resin as the component (A). The amount is 5
If the amount is less than 10 parts by weight, sufficient tackiness is not exhibited.
Exceeding the weight part is not preferred because stickiness due to a large amount of bleed occurs and the heat resistance decreases. In addition,
The physical properties of the polybutene or polyisobutylene used here can be appropriately determined according to the blending amount, the type of the other components, the intended use of the composition, and the like. There is no particular limitation, but usually the number average molecular weight is 550 to 550. Those having a range of 3000, preferably 1000 to 2500 are preferred. The glyceride having an acyl group having 2 to 6 carbon atoms and an acyl group having 8 to 22 carbon atoms, which is the component (C) of the composition of the present invention, means that one of three hydroxyl groups of glycerin has 2 to 2 carbon atoms. 6 lower fatty acids, the other one must be esterified with a higher fatty acid having 8 to 22 carbon atoms, and the other 1
The diacetin compound is a hydroxyl group or a diacetin compound or a triacetin compound esterified with a lower fatty acid having 2 to 6 carbon atoms or a higher fatty acid having 8 to 22 carbon atoms (hereinafter, referred to as “hybrid glyceride”). Of course, the acyl groups of the triacetin compound may all be different. The higher fatty acid may be saturated or unsaturated as long as it is a fatty acid having 8 to 22 carbon atoms, and is usually preferably a fatty acid having 10 to 18 carbon atoms. The lower fatty acid has 2 to 2 carbon atoms.
Any of six types may be used.

Examples of the glycerides of the present invention include, for example, diacetyl monolauryl glycerin, diacetyl monopalmityl glycerin, diacetyl monooleyl glycerin, monoacetyl dilauryl glycerin, monoacetyl monopalmityl glycerin, monoacetyl dioleyl glycerin, monoacetyl Monolauryl glycerin, monoacetyl monooleyl glycerin, dipropionyl monolauryl glycerin, dicaproyl monolauryl glycerin, dicaproyl monopalmityl glycerin, monoacetyl monocapryl glycerin, monoacetyl monobrush glycerin, monopropionyl monobrush glycerin , Monoacetylmonoerucylglycerin and the like. Of course, two or more of these hybrid glycerides may be used in combination.

The film molded from the glyceride-containing polypropylene-based resin composition of the present invention has good adhesiveness and can easily adhere to an object without pressure bonding. The compounding amount of the glyceride of the present invention is usually 0.1 to 10 parts by weight, preferably 1.0 to 5.0 parts by weight based on 100 parts by weight of the polypropylene resin as the component (A). When the amount is less than 0.1 part by weight, the effect of imparting tackiness is not sufficient. On the other hand, when the amount exceeds 10 parts by weight, stickiness and remarkable slippage occur in the obtained film, thereby reducing workability. On the other hand, as the aliphatic polyamide which is the component (D) of the intermediate layer of the stretched laminated film of the present invention,
Nylon 6, nylon 6-6, nylon 6-10, nylon 6 / 6-6 copolymer, nylon 6 / 6-10 copolymer and the like can be exemplified. However, the use of nylon 6, nylon 6 / 6-6 copolymer, nylon 6 / 6-10 copolymer or the like containing ε-caprolactam as a monomer component has good thermal stability and moldability and is easy to form a film. Is preferred.

The polypropylene resin composition used in the present invention can be obtained by adding the above components (A), (B) and (C) and mixing them sufficiently. The mixing at this time may be a conventional method, for example, dry blending, or pelletizing with a Banbury mixer or a pelletizer after the dry blending is considered. Stretched laminated film of the present invention, first by any lamination method, the outer layer and the inner layer are composed of the polypropylene resin composition,
The intermediate layer is formed by forming an unstretched laminated film made of the aliphatic polyamide resin, and then uniaxially stretching the unstretched laminated film in a film take-up direction (longitudinal direction).

The production method (lamination method) of the unstretched laminated film includes a heat bonding method, an extrusion or dry lamination method,
Coextrusion and the like can be mentioned, and particularly preferred is molding by coextrusion. The coextrusion molding uses a cylindrical round die, and the molten polymer is formed into a tube by, for example, co-extrusion of two types and three layers, and at the same time, air is fed into the tube to a predetermined width. After natural expansion, or by blowing air, it is cooled and sandwiched between nip rolls of a take-up machine.

The unstretched multilayer film obtained by the above-mentioned coextrusion molding is then uniaxially stretched at a stretching ratio of 2 to 4.5 times, preferably 2.5 to 4 times, in the film take-up direction (longitudinal direction). If the draw ratio is less than 2 times, the cuttability of the film is insufficient, and if it is more than 4.5 times, the drawability is reduced and the film may be stretched unevenly. The stretching treatment is performed by heating the unstretched film as it is or by slitting it to a predetermined width, for example, by changing the peripheral speed of a stretching roll,
That is, it is performed by a method of stretching in the longitudinal direction or the like. The stretching temperature in the stretching treatment is usually at least 20 ° C. lower than the melting point of the polypropylene resin, specifically 60 to
It is preferable to carry out in the range of 120 ° C.

The thickness of the stretched laminated film of the present invention is usually 50 μm or less, preferably 2 to 30 μm, more preferably 3 to 20 μm, and the thickness of the intermediate layer is 50 to 90% with respect to the total thickness of the film. % Range. If the thickness of the film is larger than 50 μm, the tear strength at the time of cutting the film becomes too large, which is not suitable for wrap film applications. If the thickness of the intermediate layer is less than 50% of the total thickness of the film, the inherent heat resistance and mechanical strength of the polyamide resin will be impaired, and if it is more than 90%, the polypropylene resin composition layer forming the outer layer and the inner layer Is too thin, and it becomes difficult to wear the intermediate layer uniformly by coextrusion molding or the like, which is not preferable.

The layer structure of the stretched laminated film of the present invention is essentially composed of at least three resin layers of an outer layer / intermediate layer / inner layer, but may further include other resin layers without departing from the gist of the present invention. It is possible to add four resin layers to form a structure having four or more layers. Such a structure having four or more layers includes, for example, a structure having an adhesive layer between an outer layer and an intermediate layer, or an inner layer and an intermediate layer, or a structure having a resin layer outside the outer layer or the inner layer. Can be considered.

[0018]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Examples 1-2, Comparative Examples 1-4 Isotactic polypropylene-based resin (propylene-ethylene random copolymer; MFR) as component (A)
= 9.0, d = 0.89; manufactured by Mitsubishi Kasei Corporation), (B)
Polybutene (molecular weight 1450; manufactured by Idemitsu Petrochemical Co., Ltd.) as a component and diacetylmonolauryl glycerin (manufactured by Riken Vitamin Oil Co., Ltd.) as a component (C) were mixed in a blender shown in Table 1, respectively, and then mixed with a blender to a diameter of 30 mm. Was pelletized under the extrusion conditions of 220 ° C. using a twin-screw pelletizer described above to produce a polypropylene-based resin composition. Next, the above-mentioned polypropylene-based resin composition was extruded into an extruder having a diameter of 40 mm by using an air-cooled two- and three-layer coextrusion inflation apparatus, and nylon 6 / 6-6-6 was used as a component (D).
Copolymer (manufactured by Mitsubishi Kasei Corporation; copolymerization ratio (6: 6-6))
= 85: 15 (weight ratio)) into an extruder with a diameter of 50 mm.
Each was charged and an unstretched film was molded at a molding temperature of 230 ° C. Next, the film is uniaxially stretched in the film take-up direction (longitudinal direction) at a stretching temperature of 100 ° C. and a predetermined magnification to a thickness of 10 μm.
m, a stretched film having a layer thickness ratio of 1: 8: 1 was obtained. Table 1 shows the conditions at this time, and Table 2 shows the evaluation results.

[0019]

[Table 1]

[0020]

[Table 2]

The evaluation of the laminated film was performed as follows. Adhesive strength Lightly stack two films,
The film is pressed three times at a linear pressure of 0.3 kg / cm ² with a roll having a diameter of 25 mm and a width of 150 mm.
The force required when the films were sheared and peeled in the direction of 180 ° C. was measured using an Instron type tensile tester under the conditions shown in Table 3.

[0022]

[Table 3]

A film having a heat-resistant temperature width of 30 mm and a length of 150 mm was subjected to a tensile load of 10 g, and the maximum atmosphere temperature at which the film did not break even after being left in an air oven for 1 hour was measured.

According to JIS Z 0208, the moisture permeability is 40
It measured on conditions of 90 degreeC and 90% RH.

Using a saw blade for a wrap film, the cutting performance of the saw blade was evaluated on a four-point scale (good, normal, slightly poor, and poor) in a tactile test by hand tearing. As a criterion for evaluation, the cutability level of a commercially available wrap film was evaluated as normal.

The poor cuttability of Comparative Example 1 was due to the fact that the film was stretched and it was very difficult to cut. Comparative Example 3 was frequently broken because the film was frequently broken and a satisfactory film was not obtained. Film evaluation failed.

[0027]

According to the present invention, the stretch laminated film of the present invention maintains the excellent heat resistance and mechanical properties inherently possessed by the polyamide resin, and has good adhesiveness, cutting properties, water vapor barrier properties, and food safety. It is an adhesive film having properties. Moreover, since this adhesive film does not contain harmful additives, it is particularly suitable for stretch films, wrap films and the like for food packaging. From the viewpoint of practicality when used as a stretch film or a wrap film, as the values measured in the examples, the adhesive strength was 0.40 kg / cm ² or more for shear peeling and 4.0 g / 180 ° peel strength. It is preferably 50 mm or less.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI B29L 9:00 (58) Field surveyed (Int.Cl. ⁶ , DB name) B32B 1/00-35/00 B65D 65/00 -65/46 B29C 55/00-55/30

Claims (1)

(57) [Claims] The present invention has at least three layers, an outer layer, an intermediate layer and an inner layer, wherein the outer layer and the inner layer are (A) 100 parts by weight of a polypropylene resin, (B) 5 to 40 parts by weight of polybutene or polyisobutylene, and (C) A) a polypropylene resin composition comprising 0.1 to 10 parts by weight of a glyceride having an acyl group having 2 to 6 carbon atoms and an acyl group having 8 to 22 carbon atoms, wherein the intermediate layer is made of (D) an aliphatic polyamide resin; A stretched laminated film, characterized in that the stretched film is stretched at a stretching ratio of 2 to 4.5 times in a take-up direction (longitudinal direction) of the film.