JPS5828838Y2 - Three layer laminated film - Google Patents

Description

[Detailed description of the invention] This invention is based on isophthalic acid and/or terephthalic acid.
, 6 structural units consisting of ω-aliphatic diamine in the molecular chain.
Three layers are directly laminated: a polyamide layer A containing 0 mol% or more, a modified polyolefin layer B having an ethylenically unsaturated carboxylic acid unit concentration of 0.01 to 10% by weight, and a biaxially oriented polypropylene layer C. The present invention provides a laminated film consisting of:

That is, in the present invention, as shown in FIG. 1, A is a specific polyamide layer, B is a specific modified polyolefin layer, and C is a specific polyamide layer.
is a laminated film consisting of biaxially oriented polypropylene layers.

The laminated film of the present invention combines excellent transparency and mechanical properties, and has extremely excellent oxygen and water vapor barrier properties, making it ideal for packaging foods that are susceptible to deterioration.

Polypropylene layer, modified polyolefin layer and aliphatic polyamide (e.g. nylon 6 or nylon 66)
Films made of three laminated layers are already known and are in practical use on the market, albeit in small quantities.

However, such known films have the following defects compared to the film of the present invention.

(1) Water vapor and oxygen barrier properties are poor.

(2) Since the stretching behavior of the polypropylene layer and the aliphatic polyamide layer is different, each layer must be made into a film separately and then laminated by bonding with an adhesive or the like.

Therefore, manufacturing costs become high. (3) Since defective films or film scraps cannot be reused, manufacturing costs are high and waste disposal problems arise.

Each of the above items (1) to (3), which is a simplified comparison between the known film and the film of the present invention, will be explained in more detail.

First, a film (total thickness 20μ) was made by a known inflation method.

(consisting of 9μ of polypropylene, 10μ of nylon 6, and 1μ of modified polyolefin intervening) and a film of the present invention made by the method described below (same thickness, but with a specific polyamide layer containing terephthalic acid and isophthalic acid instead of nylon 6). The water vapor permeability and oxygen permeability are compared and shown below.

Water vapor transmission rate Oxygen transmission rate (g/m2・24 hrs) (cc/m2°24 hrs)
rs) Known Film 30 150 Inventive Film 1510 As is clear from this comparison, the oxygen and water vapor barrier properties of the inventive film are significantly superior to the known film.

It goes without saying that such blocking performance is effective in preventing deterioration of the contents of the package.

Next, in the manufacturing method of the laminated film of the present invention,
Much more advantageous than known films.

In other words, with the film of this invention, 3
The layers are superimposed and stretched as they are to produce a laminated film.

In other words, since the stretching conditions for polypropylene and those for the specific polyamide are almost the same, they can be stretched simultaneously in a laminated state.

On the other hand, in known films, the stretching behavior of nylon 6 or nylon 66 and polypropylene is completely different, so it is impossible to laminate them and stretch them, particularly to sequentially biaxially stretch them.

In other words, if nylon 6 and polypropylene were laminated in a molten state and this was sequentially biaxially stretched at 150°C, it would not be possible to obtain a laminated film because even though the polypropylene was stretched, nylon 6 would tear easily. .

This problem occurs not only with aliphatic nylons such as nylon 6 and nylon 66, but also with polyamides containing metaxylylene diamine components, such as those described in Patent Publication No. 1156/1980.

In other words, since polyamide and polypropylene have completely different stretching behaviors, it is extremely difficult to stretch them after laminating them, and practically impossible.

In the laminated film of the present invention, since the stretching behavior of polypropylene and the specific polyamide are similar, the laminated film can be stretched in a laminated state, and therefore a laminated film can be obtained all at once in one process.

Comparing this with a known film manufacturing process, in which polypropylene and polyamide films are made separately and then bonded together using an adhesive, etc.
It is clear that the method for producing the film of the present invention is simple and economical.

Another advantage of the film of the present invention is that defective films and trimming waste can be crushed and mixed into the original polypropylene raw material for reuse.

If this was done with a known film, the polypropylene layer would become cloudy due to lack of compatibility, so it could hardly be reused.

The specific polyamide used in the present invention has some compatibility with polypropylene, so that if it is mixed into the polypropylene layer in small amounts, it will not cause any harmful effects.

This compatibility is further improved by the presence of specific modified polyolefins used as the intermediate layer of the film of the invention.

In other words, the clouding of the polypropylene layer due to the contamination of the specific polyamide is caused by the coexistence of the specific modified polyolefin.
It is greatly suppressed.

In this way, the ability to reuse film scraps is not only economically advantageous, but it also eliminates the problem of waste disposal, which is a very advantageous feature from an industrial perspective. That's why.

The specific polyamide constituting layer A of the present invention is one containing 60 mol% or more of a structural unit consisting of isophthalic acid and/or terephthalic acid and α,ω-aliphatic diamine in its molecular chain.

The dicarboxylic acid component may be only isophthalic acid and terephthalic acid, but for the purpose of facilitating polymerization, a small amount of other dicarboxylic acids such as succinic acid, glutaric acid,
Adipic acid, pimelic acid, speric acid, azenic acid, sebacic acid, etc. may be used in combination.

The molar ratio of isophthalic acid and terephthalic acid is 100.
: 0-50 : The range of about 5 layers is preferable.

If the ratio of terephthalic acid exceeds the ratio of isophthalic acid, troubles during polymerization will increase and the stretching behavior will deviate from that of polypropylene, making lamination stretching difficult.

On the other hand, if the ratio of terephthalic acid becomes extremely small, the water resistance, mechanical toughness, impact strength, etc. of the polyamide layer will decrease.

The most preferred range is the isophthalic acid/terephthalic acid molar ratio of 80/20 to 55/45.

Next, the α,ω-aliphatic diamine used in the present invention is 0
2 to C20 can be used, such as ethylenediamine, propylene diamine, butylene diamine, hexamethylene diamine, octamethylene diamine, thecamethylene diamine, the thicamethylene diamine, or alkyl substituted products thereof, such as 2, 2.4 or 2 ,4.
4-trimethylhexamethylene diamine or a mixture thereof can be used.

In addition, a small amount of aromatic diamine such as meta- or para-xylylene diamine (1 to 1 molar ratio to the total diamine) is added.
(approximately 30 mol%) may be used in combination.

In addition to the dicarboxylic acids and diamines mentioned above, aminocarboxylic acids 9, such as ε-aminocaproic acid, para-aminobenzoic acid, or meta-aminomethylbenzoic acid, are added in an amount of 0 to 40% by weight based on the total weight of the polyamide, preferably 0. ~20% by weight may be used in combination or ring-closed lactams, such as butyrolactam.

Valerolactam, caprolactam, enantlactam, laurolactam, etc. may be used in combination.

Therefore, the molar ratio of isophthalic acid, terephthalic acid, hexamethylene diamine, and ε-caprolactam is 25/20.
A polyamide consisting of /45/10 is also within the scope of the present invention.

Polyamides of this composition can be produced by copolymerization, but can also be produced by blending in other ways.

In other words, a polyamide with the above composition can be obtained by separately preparing 6-nylon, which is a polymer of ε-caprolactam, and polyhexamethylene isophthalamide/terephthalamide, and then mixing and melt-molding them. .

The polyamide used in the present invention must contain at least 60 mol%, preferably at least 70 mol%, of a structural unit consisting of isophthalic acid and/or terephthalic acid and α,ω-aliphatic diamine in its molecular chain. be.

60. If the content is preferably 70 mol% or less, oxygen barrier properties, water resistance, co-stretching with polypropylene, and reusability of film scraps are all deteriorated, which is not preferable.

The manufacturing method of the specific polyamide used in the present invention is as follows:
No. 19712, No. 45-21116, No. 46-846
No. 50-39689.

However, these only mention the manufacturing method, and do not mention that these polyamides have high oxygen barrier properties, co-stretchability with polypropylene, or that film waste can be collected and reused. This was discovered for the first time as a result of research conducted by the inventors.

Next, the modified polyolefin layer constituting layer B of the film of the present invention refers to polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, or copolymers thereof (propylene/ethylene copolymer, propylene/butene-1 copolymer, etc.). ) is copolymerized or graft-polymerized with 0.01 to 10% by weight of ethylenically unsaturated carboxylic acid or its anhydride.

As the ethylenically unsaturated carboxylic acid or its anhydride,
Acrylic acid, methacrylic acid, maleic acid, itaconic acid,
Himic acid or an airless substance thereof, particularly maleic anhydride, acrylic acid, etc., are preferably used.

Copolymerization or graft polymerization of these ethylenically unsaturated carboxylic acids and olefins can be carried out by various known methods, such as those described in Japanese Patent Publication Nos. 38-23494, 43-18393, and 44-9908. It can be done in a certain way.

Graft polymerization can be carried out by irradiation with ionizing radiation or ultraviolet rays, by using a radical initiator, by peroxidation by the action of oxygen, ozone, or heat, or by using heat and shear force in an extruder or kneader. It can be done by etc.

Of course, these methods can be carried out in a solution state, slurry state, or melt state.

The acid portion of the copolymerized or grafted unsaturated carboxylic acid may be substituted with a metal such as sodium or zinc.

Modified polyolefins that can be particularly preferably used in the present invention include:
Polyethylene, polypropylene or propylene/ethylene copolymer modified with maleic anhydride.

The concentration of ethylenically unsaturated carboxylic acid or its anhydride in the modified polyolefin constituting layer B is 0.01 to 1.
It should be 0% by weight, preferably 0.1-6% by weight.

When the content is 0.01% or less, preferably 0.1% or less, sufficient adhesion between the specific polyamide layer and the polypropylene layer can be achieved, and when film scraps are collected and reused in polypropylene, the adhesiveness between the polypropylene and the specific polyamide layer can be sufficiently achieved. The effect of improving the compatibility of is also insufficient.

On the other hand, if it exceeds 10%, preferably 6%, melt extrusion becomes unstable and discoloration is likely to occur.
It becomes extremely impractical.

Therefore, the concentration of ethylenically unsaturated carboxylic acid in the modified polyolefin constituting layer B is 0.01 to 10% by weight,
Preferably, it needs to be in the range of 0.1 to 6% by weight.

Examples of commercially available modified polyolefins include Atmer (manufactured by Mitsui Petrochemicals) and Surlyn (manufactured by DuPont).

Next, the zero layer of the film of the present invention is a biaxially oriented polypropylene layer.

Of course, not only propylene homopolymers but also propylene-ethylene copolymers containing a small amount of ethylene (e.g. 0.1-2% by weight) or a small amount of butene 1 (
For example, propylene-butene-1 copolymers containing 0.1 to 6% by weight) are also included within the expression polypropylene herein.

Polypropylene also contains small amounts of other polyolefins and known additives (stabilizers, antistatic agents, lubricants, inorganic or organic fine particles, ultraviolet absorbers, nucleation inhibitors, clarifying agents, pigments, dyes, etc.). It is also free to mix and add.

In addition, one of the features of the present invention is that defective products and trimming waste of the laminated film of the present invention can be crushed and returned to the polypropylene raw material for recovery and reuse. Of course, a mixture of polyolefins can be used as the zero layer.

Biaxial orientation of this layer is achieved by various methods known as methods for biaxially stretching polypropylene, such as sequential biaxially stretching or simultaneous biaxially stretching.

The adhesion between each layer of the laminated film of the present invention is strengthened by stretching, so that the lamination between each layer can be performed before or during stretching (that is, after being stretched in the -axis direction, but not yet stretched in the other uniaxial direction). It is highly desirable that this be done at a stage where the

For example, three-layer polymers A, B, and C are laminated in a molten state to form a three-layer unstretched film, which is then biaxially stretched, or a two-layer unstretched film consisting of B and 0 layers is first laminated. The most suitable process for producing the laminated film of the present invention is to prepare a film in advance, stretch it in the -axial direction, then melt-laminate layer A on layer B, and then stretch it in the other uniaxial direction. It is something that

In either case, a step is included in which the specific boamide of layer A and the polypropylene of layer 0 are simultaneously stretched.
The property that both polymers can be stretched under the same conditions (co-stretchability) is extremely important in achieving the present invention.

The three-layer laminated film of the present invention may be provided with various known coating layers (polyvinyl chloride, polyacrylate, etc.) or laminate layers (polyethylene, polypropylene, propylene/ethylene copolymer, etc.) on one or both sides. .

In addition, propylene/ethylene copolymer or propylene/butene-1 copolymer is laminated on layer A.
It may be in the form of a 4-layer laminate, with no layers, -axially or biaxially stretched.

In this way, by laminating other layers on top of the three layers by some method, good heat-sealability can be achieved, making the film extremely easy to process and use.

Before laminating other layers on top of the three layers, one or both surfaces of the three layers are subjected to known surface activation methods (such as corona discharge treatment).
Alternatively, a known anchor coating agent can be applied.

The present invention will be described below with reference to Examples, but the present invention is not limited thereto.

Example 1 Isotactic bopp propylene with a melt index of 2.0 was fed into an extruder with a diameter of 90 mm and melt-extruded at 280°C. 2 containing 0.80% by weight of maleic acid).
Melt extrusion was carried out at 40° C., and the molten polymers flowing from both extruders were superimposed in two layers in a die, and in this state, they were extruded from the die into a sheet shape, and cooled and solidified.

This sheet consists of a polypropylene layer of 760μ and a modified polyethylene layer of 40μ.

It is an unstretched laminated sheet with a total thickness of 800μ.

This was heated to 120° C. and stretched 5.0 times in the longitudinal direction while heating the polypropylene side with an infrared heater.

On the modified polyethylene layer of this -axially stretched film, an aromatic polyamide having the following composition was melt-extruded and laminated at 290°C.

Molar ratio (%) Terephthalic acid 15 Isophthalic acid 25 Adipic acid 10 Hexamethylene diamine: 50 This three-layer laminated sheet was fed into a stenter and stretched 8 times in the width direction (stretching temperature 155°C), then at 155°C 5 times
Tension heat treated for seconds and further heated to 5% of the total width in the width direction at 150℃
It was heat-treated while allowing shrinkage by an amount equivalent to , and then, after cooling, it was wound up.

The obtained film was transparent and had the following three-layer structure.

Polypropylene layer: 19μ modified polyethylene layer: 1μ polyamide layer
: 5μ The physical properties of this film are shown below.

Tensile strength (kg/mm2) (longitudinal direction): 12.3 (
Width direction): 20.1 Tensile elongation (%) (Longitudinal direction): 148
(Width direction) Near 2 Haze (%): 3.0 Oxygen permeability (cc (NTP) 7m2-24 hours): 2
3.2 Water vapor transmission rate (27m2/24 hours):
7.3 Example 2 A transparent three-layer laminate film was obtained by using a polyamide having the following composition in place of the polyamide in Example 1, and using the same conditions as in Example 1 except for the following conditions.

Molar ratio (%) Terephthalic acid 20 Isophthalic acid °30 Hexamethylene diamine: 50 The physical properties of this film also showed values similar to those of Example 1.

Example 3 A film was made that had the same three-layer structure as Example 2, but the thickness structure of each layer was as follows.

Polypropylene layer ° 19μ Modified polyethylene layer ° 1μ Aromatic polyamide layer ゛ 2μ This film was finely cut and crushed, and 1.0 parts by weight of the crushed product and polypropylene 9
0 parts by weight.

This mixture was used as a raw material for the polypropylene layer to produce a three-layer laminate film having the same structure as above.

When the haze of both films was measured, there was almost no difference in transparency between 3.0% and 3.1%.

This fact indicates that defective film products and film waste should be collected and reused.

Example 4 The following three layers were laminated during melt extrusion to create an unstretched three-layer laminate sheet.

A layer: hexamethylene terephthalamide/isophthalamide (molar ratio of terephthalic acid and isophthalic acid is 40:6
0° Relative viscosity in 98% concentrated sulfuric acid 2.30) 90 parts by weight and 6
Mixture with 10 parts by weight of nylon.

B layer: modified polypropylene containing 1.2% by weight of maleic anhydride.

Melt index 3.5°0 layer: Isotactic polypropylene with melt index 2.4.

This three-layer laminated sheet was heated to 150° C. and simultaneously biaxially stretched 5 times by 4 times in two axial directions.

The thickness structure of the obtained film is A: B: C=
The ratio was 2.5:1.0:19 (μ).

The oxygen permeability of this film is 42cc (NTP) 7m2
・24-hour Tea Tsuta.

Example 5 A three-layer laminate film was produced in the same manner as in Example 4 except that polypropylene grafted with acrylic acid (grafting rate: 3.0% by weight) was used as layer B in Example 4.

The oxygen permeability of this film is 40cc (NTP) 7m2
・24-hour Tea Tsuta.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the laminated film of the present invention. A... Specific aromatic polyamide layer, B...
- Specific modified polyolefin layer, C...biaxially oriented polypropylene layer.

Claims (1)

[Scope of utility model registration request] isophthalic acid and/or terephthalic acid, α, ω-
60 structural units consisting of aliphatic diamine in the molecular chain
Three layers are directly laminated: a polyamide layer A containing mol% or more, a modified polyolefin layer B having an ethylenically unsaturated carboxylic acid unit concentration of 0.01 to 10% by weight, and a biaxially oriented polypropylene layer C. A laminated film with excellent oxygen and water vapor barrier properties.