JP2002355889A - Heat-shrinkable polyamide film and packaging bag comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially stretched polyamide film having good easy adhesiveness and heat shrinkability, a lamination film excellent in lamination strength and suppressed in delamination and lower expansion deformation due to boiling treatment, and a packaging bag. SOLUTION: The heat-shrinkable polyamide film has an easily adhesive film on at least the single surface thereof. The hot water shrinkage factor in the MD and TD directions of the heat-shrinakable polyamide film, after the film is allowed to stand for 24h under an environment of a temperature of 20 deg.C and a relative humidity RH of 65% and subsequently immersed in hot water at 100 deg.C for 30 min, is 23-26% and the hot water shrink stress in the MD and TD directions of the film is 46-85 mN/cm per a thickness of 1 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a biaxially stretched polyamide film having excellent adhesion, heat shrinkage, pinhole resistance, transparency and tensile strength, and a packaging bag using the same. These can be used as packaging materials for foods, medicines, industrial products and the like.

[0002]

2. Description of the Related Art Biaxially stretched polyamide films have excellent mechanical, optical, thermal and gas barrier properties, as well as abrasion resistance, impact resistance, and pinhole resistance. It has been widely used mainly. In addition, shrink type biaxially stretched polyamide film having high heat shrinkability is used for fish meat such as ham and sausage,
It is widely used for shrink packaging of processed meat products, water products such as wild vegetables and seasonal vegetables, viscous foods such as creams and jams, processed agricultural products such as tofu, and daily necessities.

[0003]

As a technique for imparting high heat shrinkage to a biaxially stretched polyamide film, it is generally known to lower the heat setting treatment temperature during film production. However, in this case, there is a problem that the lower the heat setting temperature, the lower the lamination strength of the film. In the case of a packaging bag using a heat-shrinkable film, when the shrinkage and the shrinkage stress are high,
Delamination with the sealant layer occurs, and when it is low, the commercial value is significantly reduced.

[0004]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve such problems, and as a result, coated an easily adhesive primer on at least one surface of a biaxially stretched polyamide film having heat shrinkability. , The hot water shrinkage rate is 23 to 26
%, Hot water shrinkage stress is 46 to 85 mN per 1 μm thickness
The present inventors have found that the above-mentioned problems can be solved by using a biaxially stretched polyamide film having a thickness of / cm and have reached the present invention.

That is, the gist of the present invention is as follows. The biaxially stretched polyamide film has an easy-adhesion film on at least one side, is left for 24 hours in an environment of a temperature of 20 ° C. and a humidity of 65% RH, and then immersed in hot water of 100 ° C. for 30 minutes to obtain MD and TD. Direction of hot water shrinkage
Both are 23 to 26%, and the hot water shrinkage stress in the MD and TD directions is 46 to 85 mN / c per 1 μm in thickness.
m, a biaxially stretched polyamide film having excellent adhesiveness and heat shrinkability, characterized in that the laminated film containing at least one layer of the biaxially stretched polyamide film is bonded through an easily adhesive film. A laminate film having a laminate strength of 2 N / cm or more with another film, and a packaging bag using the same.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As the polyamide in the present invention, nylon 6, nylon 66, nylon 46, nylon 610, nylon 612, nylon 12, nylon 1
1, a copolymerized polyamide thereof, and a mixed polyamide resin. Nylon 6 is particularly preferred. As a method for stretching a biaxially stretched polyamide film,
Sequential biaxial stretching, or simultaneous biaxial stretching is common,
The present invention is not limited to these production methods, and any biaxially stretched film can be used. The thickness is preferably from 12 to 25 μm.

In the present invention, examples of the easy-adhesion primer for forming the easy-adhesion film of the film include a polyurethane resin or a copolyester resin.

[0008] The polyurethane resin is not particularly limited, and examples thereof include a polyester polyurethane, a polyether polyurethane, and a polyurethane polyurea resin. The polyurethane resin may be a solvent type or an aqueous dispersion type, but the water-dispersion type polyurethane resin is preferable because the degree of crosslinking of the polyurethane resin film is easily adjusted and the environment at the production site is problematic. As the water-dispersed polyurethane resin, a carboxylic acid salt (such as —COONa) and a sulfonic acid salt (—SO
₃ Na, etc.) self-emulsifying polyurethane resin obtained by introducing a hydrophilic group such as is desirable.

Both water-dispersible and solvent-based polyurethane resins include melanin resins, epoxy resins, imine resins,
Isocyanate resin or the like may be added as a crosslinking agent,
Addition of a melanin-based resin is preferred. The addition amount is preferably about 3 to 10% by mass based on the polyurethane resin. The crosslinking agent not only improves the water resistance and solvent resistance of the easily adhesive film, but also contributes to the adhesion. In addition, the polyurethane resin has a solid content of 60 to
It is 95% by mass, more preferably 70 to 90% by mass.

[0010] Further, as a primer layer for forming an easily adhesive film, a copolymerized polyester resin may be mentioned. 80 mol% as an acid component of the copolymerized polyester resin
The above is an aromatic dicarboxylic acid, preferably 90 to 1
00 mol%. When the proportion of the aromatic dicarboxylic acid is less than 80 mol%, the glass transition point of the copolymerized polyester resin decreases, and the heat resistance and the blocking resistance deteriorate. The proportion of terephthalic acid in the aromatic dicarboxylic acid is from 20 to 95 mol%, preferably from 30 to 90 mol%. When the proportion of terephthalic acid exceeds 95 mol%, the solubility of the copolymerized polyester resin in an organic solvent decreases, and the copolymerized polyester resin tends to be hard and brittle. On the other hand, when it is less than 20 mol, the glass transition point becomes low, and the heat resistance and the blocking resistance deteriorate. Next, as the glycol component of the copolymerized polyester resin, an aliphatic glycol having a straight chain or a side chain having 1 or more carbon atoms is used.

Further, an isocyanate resin, an epoxy resin, a melamine resin, or an acid anhydride resin may be added as a crosslinking agent to the copolymerized polyester resin. These resins act as curing agents, but epoxy resins are most preferred for improving adhesive strength, but isocyanate resins, melamine, etc., depending on other properties, ease of handling or price. Resins, acid anhydride resins, or two or more of these resins may be suitable. The mixing ratio of the copolyester resin and the crosslinking agent is 5 to 50% by mass, preferably 20 to 40% by mass, based on the copolyester resin. Incidentally, the copolymerized polyester resin is preferably 60 to 95% by mass, more preferably 7% by mass, based on the primer layer.
0 to 90% by mass.

The amount of the easy-adhesive primer layer is 0.04 to 0.1 g /
m ² , more preferably 0.05 to 0.08 g / m ² . If the coating amount is less than 0.04 g / m ² , the adhesion and water resistance are insufficient, and the coating amount is 0.1 g.
Even if the coating is carried out in excess of / m ² , no further improvement in performance is recognized, and not only blocking occurs, but also cost increases.

The biaxially stretched polyamide film having easy adhesion and heat shrinkability in the present invention has a temperature of 20.degree.
After being left for 24 hours in a 5% RH environment and then immersed in 100 ° C. hot water for 30 minutes, it is necessary that both the hot water shrinkage in the MD and TD directions are 23 to 26%. If the performance is less than the lower limit value under the above conditions, the degree of adhesion to the contents is reduced, or the tension is insufficient, and the commercial value is significantly reduced. In the case of a performance exceeding the upper limit value under the above-described conditions, delamination with the sealant film occurs at a required sterilizing temperature due to the heat shrinking treatment that proceeds simultaneously with the sterilizing treatment. In the sterilization treatment at a temperature at which delamination does not occur, there is a problem that the contents are spoiled.

Further, the biaxially stretched polyamide film of the present invention is allowed to stand for 24 hours in an environment of a temperature of 20 ° C. and a humidity of 65% RH, and then immersed in hot water of 100 ° C. for 30 minutes. Are required to be 46 to 85 mN / cm per 1 μm of thickness. In the case of performance below the lower limit under the above conditions, not only is the tension on the contents insufficient, for example,
In sausages, etc., at the time of high temperature during sterilization treatment or immediately after sterilization treatment, downward swelling deformation occurs due to the weight of the contents, resulting in defective products, and in filling, increase the filling rate to make the packaging bag tighter It is necessary and the cost increases. In the case of a performance exceeding the upper limit value under the above-described conditions, delamination with the sealant film occurs at a required sterilizing temperature due to the heat shrinking treatment that proceeds simultaneously with the sterilizing treatment. In the sterilization treatment at a temperature at which delamination does not occur, there is a problem that the contents are spoiled.

Next, a method for producing the biaxially stretched polyamide film of the present invention will be described. The biaxially stretched polyamide film of the present invention can be produced, for example, by the following method. The polyamide resin composition is usually 260 to 300
After being heated and melted at a temperature of 0 ° C., it is extruded from a T-die and is cooled by contact with a cooling drum to prepare an unstretched sheet. The cooling at this time is preferably performed by rapid cooling and solidification. If the quenching and solidification are insufficient, the crystallization of the film proceeds and whitens, which may result in poor transparency or difficulty in stretching.

Next, the obtained unstretched film is stretched by sequential biaxial stretching or simultaneous biaxial stretching to obtain a biaxially oriented film. As the stretching conditions, it is appropriate that the stretching temperature is equal to or higher than the glass transition point of the polyamide resin composition and equal to or lower than the melting point, and the stretching ratio is suitably 8 to 12 times, more preferably 9 to 11 times. After the stretching, it is appropriate to carry out a heat setting treatment at 100 ° C. to 180 ° C., more preferably at 130 ° C. to 150 ° C. However, the present invention is not limited to these production methods, and it is sufficient that the film is a biaxially stretch-oriented film and has the shrinkage performance of the present invention.

Regarding the method of forming the easily adhesive film,
Although not particularly limited, in-line coating is preferred in terms of productivity and cost. For example, in the case of the sequential biaxial stretching method of T-die extrusion, an easy-adhesion primer is applied after vertical stretching, and in the case of the simultaneous biaxial stretching method of T-die extrusion, the easy-adhesion primer is applied before stretching. In the case of the simultaneous biaxial stretching method of the annular die, it is preferable to apply an easy-adhesion primer after stretching and before heat-setting.

The biaxially stretched polyamide film having easy adhesion and heat shrinkability according to the present invention may be an oxygen barrier, a water vapor barrier, or the like, as long as the effects of the present invention are not impaired.
Performances such as slipperiness, antistatic and anti-fog may be provided.

The biaxially stretched polyamide film of the present invention comprises:
Can be laminated with other films. As the configuration of the laminate film, the biaxially stretched polyamide film of the present invention is NS, the polyethylene film is PE,
When the polypropylene film is PP, NS /
PE, PE / NS / PE, NS / PP, PP / NS / P
P and the like. Although there is no particular limitation on the lamination method, the lamination strength of the laminate film needs to be 2.0 N / cm or more. When the lamination strength is less than 2.0 N / cm, the resulting packaging bag may be broken or may be delaminated during the hot water sterilization treatment due to insufficient compressive strength or insufficient dropping strength. is there.

The packaging form of the packaging bag in the present invention is not particularly limited. For example, a three-sided bag, a four-sided bag, a self-standing bag, a pillow bag, a gusset bag, a stick bag, a rocket packaging bag, a drawn container and a cup And a cover material.

[0021]

Next, the present invention will be specifically described with reference to examples and comparative examples. The measuring method used in the present invention is as follows.

Hot water shrinkage; sample width 10 mm, sample length 1
A film cut into 5 cm is subjected to a temperature of 20 ° C and a humidity of 65.
% RH environment for 24 hours.
After marking the 0 cm mark, the sample was immersed in hot water at 100 ° C. for 30 minutes, the gap between the treated marks was read, and the hot water shrinkage was determined by the following formula. Hot water shrinkage rate (%) = (10-length between reference points after treatment (cm)) × 100/10

Hot water shrinkage stress: temperature 20 ° C., humidity 65%
A sample having a sample width of 10 mm and a sample length of 15 cm left for 24 hours in an RH environment was subjected to a tensile tester (Shimadzu AG-
500B) with a crosshead distance of 10 cm
The sample was immersed in hot water at 00 ° C. for 30 minutes, the maximum load was read, and the value per unit thickness of the sample was defined as the hot water shrinkage stress.

Boil resistance; laminate film width 3
A rocket packaging bag having a diameter of 10 cm and a distance of 23 cm between base clips was prepared by cutting out a piece of 5 cm x length 40 cm and filling with 2 kg of water, immersing it in hot water at 100 ° C for 2 hours, and then performing delamination at the back seal. The presence or absence was checked. The judgment was “X” when the bag was broken, “破” when the bag was not broken but delamination occurred, and “な け れ ば” when no delamination occurred.

Retort resistance: A laminate film was cut out to a width of 35 cm × length of 40 cm, and a rocket packaging bag filled with 2 kg of water and having a diameter of 10 cm and a distance between base clips of 23 cm was prepared and subjected to hot water retort treatment at 120 ° C.
After the application for minutes, the presence or absence of delamination at the back seal was checked. The judgment was “X” when the bag was broken, “破” when the bag was not broken but delamination occurred, and “な け れ ば” when no delamination occurred.

Deformation degree of lower swelling: A laminate film was cut out to a width of 35 cm and a length of 40 cm, and a rocket packaging bag filled with 2 kg of water and having a diameter of 10 cm and a distance between base clips of 23 cm was prepared, and heated in hot water at 90 ° C. for 2 hours. Dipped.
Immediately after the treatment, using a compression tester (Model 3800, manufactured by AIKO ENGINEERING CO., LTD.), The distance between the base clips is reduced to 18 cm. 5c
The measurement was performed at a total of three points at the position m. The judgment was x when any one of the three points had a diameter of less than 9 cm or more than 11 cm, and when the diameter of all three points was 9 cm or more and 11 cm or less.

Laminating strength: A laminated film was cut into a width of 15 mm and a length of 70 mm, and the interface between the biaxially stretched polyamide film of the present invention and another bonded film was peeled off, and a tensile tester (AG- manufactured by Shimadzu Corporation) was used. 1
00) using the T-peel method and a tensile speed of 300 mm /
Minutes, and the load was measured.

After the packaging bag subjected to the boil resistance and retort resistance evaluation was left under an environment of a temperature of 20 ° C. and a humidity of 65% RH for 24 hours, a three-level evaluation by five panelists (poor appearance: 0) Point, normal: 1 point, good looking:
2 points), the total points are 0 to 3 points x, 4 to 6 points are △,
7 to 10 points were evaluated as ○.

Comprehensive evaluation; boiling resistance, retort resistance,
Each evaluation of the degree of deformation of the lower swelling and the appearance, and the evaluation of laminate strength (2 N / cm or more: 、 １, 1 N / cm or more, 2
Less than N / cm: Δ, less than 1 N / cm: x), the worst evaluation result was taken as the comprehensive evaluation.

Example 1-1 Nylon 6 (melting point: 220 ° C.) at 260 ° C. and a width of 600
After being melt-extruded into a sheet shape from a T-die having a thickness of 25 mm, the mixture was brought into close contact with a rotating drum at 25 ° C. and rapidly cooled by an air knife casting method to obtain a substantially amorphous, non-oriented, unstretched film having a thickness of 155 μm. Next, this unstretched film is stretched by a longitudinal stretching machine composed of a group of heating rollers having different peripheral speeds.
The film was longitudinally stretched 2.8 times to obtain a longitudinally stretched film. continue,
One side of the longitudinally stretched film is coated with a self-emulsifiable polyurethane polyurea resin (100% by mass) and an easy-adhesion primer obtained by mixing a melamine-based crosslinking agent (6% by mass). did. 130 ° C-1 after stretching
A heat setting treatment was performed at 50 ° C. to obtain a biaxially stretched polyamide film (A) having a thickness of 15 μm. The easy-adhesion primer layer of the obtained biaxially stretched polyamide film (A) was 0.07.
g / m ² , and after standing for 24 hours in an environment at a temperature of 20 ° C. and a humidity of 65% RH, the hot water shrinkage in the MD and TD directions when immersed in 100 ° C. hot water for 30 minutes is 2
3% and 25%, and the hot water shrinkage stress in the MD and TD directions was 52 mN / c per 1 μm thickness.
m and 72 mN / cm.

Biaxially stretched polyamide film (A), sealant film (G) (PE; TUX-F manufactured by Tosero Corporation)
CS thickness: 50 μm), and an aromatic ester adhesive (Takeda A manufactured by Takeda Pharmaceutical Co., Ltd.) was used as the adhesive.
A laminated film was produced by dry lamination (adhesive application amount 4 g / m ² ) using -515 / A-50 two-pack type. Using the obtained laminate film, evaluation of boil resistance, retort resistance, lower blister deformation, and lamination strength was performed. Table 1 shows the results.

Example 1-2 Biaxially stretched polyamide film (A), sealant film (H) (PP; RXC-18 manufactured by Tosello Co., Ltd., thickness 50)
μm), a laminate film was prepared and evaluated in the same manner as in Example 1-1.

Comparative Examples 1-1 and 1-2 A biaxially stretched polyamide film (B) was produced in the same manner as in the above biaxially stretched polyamide film (A) except that the primer for easy adhesion was not applied. Biaxially stretched polyamide film (B), sealant film (G),
Using (H), a laminate film was prepared and evaluated in the same manner as in Example 1-1.

Comparative Example 2 A biaxially stretched polyamide film (C) was produced in the same manner as in the above biaxially stretched polyamide film (A), except that the film was heat-set at 160 ° C. after stretching. The obtained film (C) was treated at a temperature of 20 ° C. and a humidity of 65% RH for 24 hours.
MD after immersion in hot water at 100 ° C for 30 minutes
Hot water shrinkage in the TD and TD directions is 21%, 2
2%, and the hot water shrinkage stress in the MD and TD directions is 49 mN / cm and 69 mN / c per 1 μm, respectively.
m. Using a biaxially stretched polyamide film (C) and a sealant film (G), a laminate film was prepared and evaluated in the same manner as in Example 1-1.

Comparative Examples 3 to 5 Biaxially stretched film (D) (Emblem U manufactured by Unitika Ltd.)
S thickness 15 μm), biaxially stretched film (E) (Emblem NK thickness 15 μm manufactured by Unitika), biaxially stretched film (F) (Emblem ONU thickness 15 μm manufactured by Unitika), sealant film (G), (H) used Then, with the configuration shown in Table 1, a laminate film was prepared and evaluated in the same manner as in Example 1-1.

[0036]

[Table 1]

[0037]

According to the present invention, a biaxially stretched polyamide film having good adhesiveness and heat shrinkability, and excellent lamination strength, delamination by hot water treatment,
It is possible to obtain a lamination film and a packaging bag with good tightness in which the bag breakage and the downward swelling deformation are suppressed.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) // B29K 77:00 B29K 77:00 (72) Inventor Tatsui Fukayuki 31-3 Uji Hinojiri Uji City, Kyoto Prefecture Unitika Stock A term A in the Uji Plastics Factory (reference) BB51 BB52 BB67 BB90 CA04 CA17 CA35 4F100 AK43G AK46A AK51G AR00B AR00C BA02 BA03 BA06 BA07 EJ38A EJ65 GB23 JK02 JL11 JL11B JL11C JN01 4F210 AA29 AE01 AG01 AG03 RA01 RC02 RG02 RG04 RG02 RG04 RG02

Claims (3)

[Claims] 1. A biaxially stretched polyamide film having an easy-adhesion film on at least one surface, a temperature of 20 ° C. and a humidity of 65% R.
After standing in an H environment for 24 hours and then immersing in 100 ° C. hot water for 30 minutes, the hot water shrinkage in the MD and TD directions is 23 to 26%, and the hot water shrinkage in the MD and TD directions The contraction stress is 46 to 8 per 1 μm in thickness.
A biaxially stretched polyamide film having an adhesive property and heat shrinkability of 5 mN / cm. 2. A laminated film comprising at least one layer of the biaxially stretched polyamide film according to claim 1, wherein the lamination strength with another film adhered through an easy-adhesion film is 2 N / cm or more. Laminate film. 3. A packaging bag using the laminated film according to claim 2.