JPH06136157A - Stretched polyamide resin film - Google Patents

Abstract

PURPOSE:To obtain a stretched polyamide resin film excellent in oxygen gas barrier properties and prevention of pinhole formation due to flexure stretching a polyamide resin composition obtained by melt-mixing an aliphatic polyamide with a specified modified polyolefin composition under specified conditions. CONSTITUTION:The film is obtained by stretching a polyamide resin composition obtained by melt-mixing 99.7-90.0wt.% aliphatic polyamide (e.g. poly-epsilon-capramide) with 0.3-10wt.% modified polyolefin composition comprising 100-5wt.% modified polyolefin prepared by grafting an unsaturated carboxylic acid (e.g. maleic anhydride) onto a polyolefin (e.g. ethylene/propylene copolymer) and 0-95wt.% polyolefin (e.g. ethylene/vinyl acetate copolymer) at least monoaxially at a stretch ratio of 2-8.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a stretched film containing an aliphatic polyamide as a main component. More specifically, it relates to a polyamide resin stretched film comprising an aliphatic polyamide and a specific modified polyolefin composition and having improved bending pinhole resistance.

[0002]

2. Description of the Related Art Heretofore, polyamide resin films have been used in various packaging fields either alone or laminated with other films. However, although a stretched polyamide film containing an aliphatic polyamide as a main component has excellent mechanical properties such as tensile strength and impact strength, and an oxygen gas barrier property, it has a high degree of gas barrier property due to its difficulty in bending pinhole resistance. Required foods, medicines,
The packaging of chemicals etc. was not always satisfactory.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, that is, a stretched film, that is, an aliphatic polyamide, which retains the excellent mechanical properties and gas barrier properties inherently possessed by the polyamide, and is resistant to bending pinholes. It is an object of the present invention to provide a stretched polyamide-based resin film having improved properties.

[0004]

Means for Solving the Problems As a result of intensive studies made by the present inventors to solve the above-mentioned conventional technical problems,
The present invention has been completed. Therefore, the gist of the present invention is that the aliphatic polyamide (A) 99.
Modified polyolefin (Pa) 100 in which 7 to 90.0% by weight and polyolefin are grafted with unsaturated carboxylic acid
Modified polyolefin composition (P) 0.3 to 10 consisting of 5 to 5% by weight and polyolefin (Pb) 0 to 95% by weight
A stretched film made of a polyamide resin composition obtained by melt-mixing with a resin by weight, wherein the stretched polyamide resin film is stretched at least uniaxially at a stretch ratio of 2 to 8 times. Exist.

The present invention will be described in detail below. In the present invention, the aliphatic polyamide (A) means (1) homopolymer of ε-caprolactam, (2) polyhexamethylene adipamide, (3) ε-caprolactam or nylon composed of hexamethylene diamine and adipic acid. A copolymer containing a salt as a main component and 2 to 10 mol% of a compound copolymerizable therewith, (4) these homopolymers and / or copolymers, and other heavy compounds compatible with them. 5 to 2
It means a mixture of 0% by weight.

Examples of the compound copolymerizable with the nylon salt of ε-caprolactam or hexamethylenediamine and adipic acid include nylon salts of aliphatic diamines and aliphatic dicarboxylic acids. Aliphatic diamines Representative examples of ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, decamethylenediamine, and the like, representative examples of the aliphatic dicarboxylic acids, adipic acid, sebacic acid, cork acid, Examples thereof include glutaric acid, azelaic acid, β-methyladipic acid, decamethylenedicarboxylic acid, dodecamethylenedicarboxylic acid and pimelic acid.

Among these aliphatic polyamides, a homopolymer of ε-caprolactam called nylon-6,
Polyhexamethylene adipamide called nylon-6,6 is particularly advantageous as a film raw material because it is easily available and inexpensive. When these polyamides have a large hygroscopicity and absorb moisture, water vapor is generated when the raw material is melt-extruded, which causes a problem in the film forming step, so that the water content is 0.1% by weight. It is better to use the one of about 10% or less.

In the present invention, the modified polyolefin composition (P) is a modified polyolefin (Pa) obtained by grafting an unsaturated carboxylic acid onto a polyolefin, or an unmodified non-modified with the modified polyolefin (Pa). Of a polyolefin (Pb). As the polyolefin modified by grafting an unsaturated carboxylic acid, high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, polypropylene and the like can be used. On the other hand, specific examples of the unsaturated carboxylic acid grafted to these polyolefins include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, etc., and maleic anhydride, citraconic acid anhydride, itaconic acid anhydride, etc. Examples thereof include acid anhydrides and metal salts such as potassium acrylate and potassium methacrylate. Of these, maleic anhydride is particularly preferable.

Here, the modified polyolefin (Pa) is
The unsaturated carboxylic acid content is preferably in the range of 0.01 to 5% by weight, and particularly preferably in the range of 0.1 to 3% by weight. The unsaturated carboxylic acid content is 0.
When less than 1% by weight is used, the stretched film finally obtained tends to be hazy, and 0.01% by weight
This is because this tendency becomes more prominent when less than 1 is used. Further, those having an unsaturated carboxylic acid content of more than 3% by weight not only have a high manufacturing cost but also tend to saturate the effect of improving the bending pinhole resistance of the stretched film obtained by using this. If the amount exceeds 5% by weight, the tendency is more remarkable. Therefore, the unsaturated carboxylic acid content in the modified polyolefin (Pa) is 5% by weight.
Those that do not exceed are practical.

The above-mentioned modified polyolefin (Pa) is reacted in a solution state by a conventionally known production method, for example, a method of reacting a polyolefin with an unsaturated carboxylic acid in a molten state (see, for example, Japanese Patent Publication No. 27421/43). A method (see, for example, Japanese Patent Publication No. 44-15422),
It can be produced by either a method of reacting in a slurry state (see, for example, JP-B-43-18144), a method of reacting in a gas phase state (see, for example, JP-A-50-77493), or the like.

The polyolefin (Pb) that can be used as a mixture with the modified polyolefin (Pa) is a polyolefin that is the same or different from the polyolefin component that constitutes the modified polyolefin (Pa), and is, for example, low density polyethylene or linear. Low density polyethylene, polypropylene, ethylene-vinyl acetate copolymer and the like are preferable.

The modified polyolefin composition (P) used in the present invention includes the above-mentioned modified polyolefin (P
a) 100 to 5% by weight and the above polyolefin (Pb) 0
˜95% by weight. In this modified polyolefin composition (P), the polyolefin (P
When the proportion of b) exceeds 95% by weight, the effect of improving the bending pinhole resistance of the finally obtained stretched film is insufficient.

The stretched polyamide resin film according to the present invention comprises the aliphatic polyamide (A) 99.7 to 90.0.
% By weight and the above modified polyolefin composition (P) 0.3 to
It is manufactured from a polyamide resin composition obtained by melt-mixing with 10% by weight. When the proportion of the modified polyolefin composition (P) is less than 0.3% by weight, the effect of improving the bending pinhole resistance of the obtained stretched film is weakened, while when it exceeds 10% by weight, the transparency of the obtained stretched film is high. Is damaged. And modified polyolefin composition (P) for aliphatic polyamide (A)
When the ratio of the modified polyolefin composition (P) was decreased, the modified polyolefin composition (P) with a large amount of the modified polyolefin (Pa) within the above range was used, while the ratio of the modified polyolefin composition (P) was increased. In this case, as the modified polyolefin composition (P), it is preferable to use a modified polyolefin (Pa) having a small amount within the above range.

Further, the raw material resin composition of the stretched polyamide resin film according to the present invention contains various additives such as a lubricant, an antistatic agent, an antioxidant, an antiblocking agent, a stabilizer, a dye, a pigment and inorganic fine particles. The film may be added in a small amount as long as it does not adversely affect the properties of the film.

The stretched polyamide-based resin film according to the present invention is made of the above-mentioned polyamide-based resin having a specific composition and stretched at least in a uniaxial direction at a draw ratio of 2 to 8 times. If it is less than 2 times, the stretching effect is small and the strength of the film is poor, and if it exceeds 8 times, the film tends to be broken during the stretching operation and the long-run property tends to be poor in practical use.
Difficult to manufacture.

The thickness of the stretched polyamide-based resin film according to the present invention is not particularly limited as long as it can be appropriately determined depending on the application, but in general, a thickness in the range of 3 to 40 μm is practical.

As described above, the stretched polyamide resin film according to the present invention is a raw material resin composition obtained by melting and mixing the aliphatic polyamide (A) and the modified polyolefin composition (P) in a specific ratio. Manufactured from things. As the method for preparing the above-mentioned raw material resin composition, the modified polyolefin composition (P) containing the specified amount of the modified polyolefin (Pa) is necessarily prepared in advance and melt-mixed with the aliphatic polyamide (A). There is no need, and if the three ratios of the aliphatic polyamide (A), the modified polyolefin (Pa) and the unmodified polyolefin (Pb) are finally within the specific range, they are added separately and melt mixed. It goes without saying that it is also good. That is, modified polyolefin (Pa) and unmodified polyolefin (Pb)
And the ratio of the total of the two and the aliphatic polyamide (A) are within the above specific range.

The stretched polyamide resin film according to the present invention can be produced using the above-mentioned raw material resin composition by a conventionally known general method. First, a modified polyolefin composition (P) containing a modified polyolefin (Pa) in a predetermined amount is mixed with an aliphatic polyamide (A), or an aliphatic polyamide (A), a modified polyolefin (Pa), and necessary According to the above, the unmodified polyolefin (Pb) is mixed separately, and the raw material resin composition is melted by an extruder and extruded from a flat die or an annular die, followed by quenching to obtain a flat or annular shape. A substantially unoriented unstretched film is produced.

Then, the above unstretched film is stretched at a draw ratio of 2 in the uniaxial direction of the flow (longitudinal) direction or in the (transverse) direction perpendicular thereto or in the biaxial direction of the longitudinal direction and the transverse direction.
-8 times, preferably 2.5-5 times. If it is less than 2 times, the stretching effect is small and the strength of the film is poor, and if it is more than 8 times, the film is often broken during the stretching operation and the long-run property tends to be poor in practical use. As the uniaxial stretching, usually, longitudinal stretching with a roll is preferably used, but any stretching means may be adopted as long as the gist of the present invention is not changed. In the case of stretching in the machine direction by a roll, the unstretched film may be heated to a temperature range of 45 to 100 ° C. and stretched 2 to 8 times.

The stretching ratio of biaxial stretching is 2.5 in each axial direction.
~ 5 times is desirable. If it is less than 2.5 times, the effect of stretching is small and the strength of the film is poor, and if the stretching ratio is more than 5 times, the film tends to break during stretching and the long-run property tends to be poor in practical use. Examples of the biaxial stretching method include tenter sequential biaxial stretching, tenter simultaneous biaxial stretching, tubular simultaneous biaxial stretching and the like, but any stretching method may be adopted unless the gist of the present invention is changed. In the case of tenter sequential biaxial stretching, for example, an unstretched film is first drawn at 45 ° C to 11 ° C.
It is heated to a temperature range of 0 ° C. and stretched 2.5 to 5 times in the longitudinal direction by a roll type longitudinal stretching machine, and then 60 ° C. to 120 ° C.
It may be heated to a temperature range of ° C and stretched 2.5 to 5 times by a tenter type transverse stretching machine. In the case of simultaneous tenter biaxial stretching and tubular simultaneous biaxial stretching, for example, 60
It may be heated in the temperature range of ℃ to 120 ℃ and stretched 2.5 to 5 times in each direction at the same time in the longitudinal and transverse directions.

By heat-setting after stretching, a stretched film having excellent dimensional stability can be obtained. By adjusting the heat treatment temperature within the range of 110 ° C. as the lower limit and 5 ° C. lower than the melting point of the raw material polyamide (A) as the upper limit, the heat treatment temperature has dimensional stability and any hot water shrinkage. A stretched film having a ratio is obtained. Surprisingly, the polyamide resin stretched film according to the present invention thus obtained has almost no pinholes even when it is subjected to a repeated bending test (gelbo flex test). In addition, the oxygen gas permeability is hardly reduced as compared with a stretched film made of a conventional aliphatic polyamide resin which does not contain a modified polyolefin.

The stretched polyamide resin film according to the present invention can be further processed. By providing a coating layer of vinylidene chloride resin on this film, a film having further improved gas barrier properties and excellent flex pinhole resistance can be obtained. In addition, by laminating with various conventionally known single-layer or laminated films by a dry laminating method, a wet laminating method, an extrusion laminating method or the like, the obtained laminated body has excellent bending pinhole resistance.

[0023]

INDUSTRIAL APPLICABILITY The present invention has particularly remarkable effects as follows, and its industrial utility value is extremely large. 1. The stretched polyamide-based resin film according to the present invention has excellent oxygen gas barrier properties, and also has excellent bending pinhole resistance. 2. Since the polyamide-based resin stretched film according to the present invention is excellent in its properties, it can be suitably used as a gas barrier packaging material such as foods, pharmaceuticals, and chemicals that do not like alteration of the contents by oxygen gas. it can.

[0024]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In the following examples, the obtained film was evaluated by the following method. The resin composition of the film and the evaluation results are shown in Table 1. <Bending pinhole resistance (piece / 77 inch2)> Temperature 2
A film that has been conditioned for 24 hours or more at 3 ° C. and a relative humidity of 50% is cut into an 8 inch × 11 inch rectangular film, and the rectangular film is made by Rigaku Kogyo Gelboflex. Tester (No. 1 type) 440 in 3.5 inches straight ahead
Rotate ゜, go straight for 2.5 inches, and then count as one movement to return to the original position in the reverse stroke, 300
A flexion test was performed 0 times. With respect to the test film after completion of the bending test, the number of pinholes generated was measured by applying a voltage of 1 KV with a pinhole tester TRD type manufactured by Sanko Electronic Research Laboratory. The number of pinholes measured in this way (measurement area: 77 inch2) was used as a measure of resistance to bending pinholes.

Example 1 (1) Preparation of modified polyolefin composition (P) 100 parts by weight of an ethylene-propylene copolymer having an ethylene content of 83 mol% and a melt flow index of 1.0 gr / 10 minutes, and a small amount. Α dissolved in a quantity of acetone,
0.025 parts by weight of α'-bis-t-butylperoxy-p-diisopropylbenzene and 0.8 parts by weight of maleic anhydride were mixed in a Henschel mixer to obtain granules. This granular material is extruded at 230 ° C. using an extruder having an inner diameter of 40 mmφ and L / D = 28, pelletized, and a modified polyolefin of ethylene-propylene copolymer system (P
a) was obtained. Next, this modified polyolefin (Pa) 2
0 parts by weight, ethylene having a vinyl acetate content of 8% by weight and a melt flow index of 1.5 gr / 10 minutes
After mixing with 80 parts by weight of a vinyl acetate copolymer (Pb), this mixture was extruded at 200 ° C. using an extruder having an inner diameter of 40 mmφ and L / D = 28, and pelletized to obtain a modified polyolefin composition (P). Got (2) Production of Stretched Film Poly-ε-caproamide (Novamid 1022, manufactured by Mitsubishi Kasei Co., Ltd.) and the modified polyolefin composition (P) prepared by the method described in the preceding paragraph were mixed at a ratio of 95/5 by weight as a raw material. The resin composition was melt extruded at a resin temperature of 250 ° C. using a 65 mmφ extruder equipped with a coat hanger T die, and was rapidly cooled by closely adhering to a cast roll adjusted to 25 ° C. to form an unstretched film having a thickness of about 135 μm. Obtained. The obtained unstretched film was heated to 50 ° C. and then stretched 3 times in the machine direction by a roll-type machine, and then the end portion of this film was held by a tenter clip and placed in a tenter oven for 8 hours.
After being stretched three times in the transverse direction under the condition of 0 ° C., heat treatment was performed at 210 ° C. for 4 seconds to obtain a stretched film having a thickness of about 15 μ. (3) Evaluation of Stretched Film With respect to the stretched film produced by the method described in the preceding paragraph, the flex pinhole resistance was measured according to the method described above. The results are shown in Table 1 below, together with the mixing ratio (weight ratio) of the raw material resins and the type of modified polyolefin used. In Table 1, the abbreviations for the raw material resins have the following meanings. A: Poly-ε-caproamide (Mitsubishi Kasei Co., Ltd.)
Manufactured by Novamid 1022) P: Modified polyolefin composition (P) Pa: Modified polyolefin Pb: Unmodified polyolefin Et-Pr: Modified polyolefin (Pa) EVA: ethylene-acetic acid grafted with ethylene-propylene copolymer. Vinyl copolymer (Pb) LDPE: Low density polyethylene (Pb) PP: Polypropylene (Pb)

Example 2 (1) Preparation of modified polyolefin composition (P) In the example described in Example 1, the ethylene-vinyl acetate copolymer (Pb) used in the same example was melt flow indexed to 1.5 gr. A modified polyolefin composition (P) in the form of pellets was obtained in the same manner as in the example except that the low density polyethylene (Pb) was changed to / 10 minutes. (2) Manufacture of Stretched Film In the example described in Example 1, the modified polyolefin composition (P) used in the same example was added to the modified polyolefin composition (P) prepared by the method described in the preceding paragraph to obtain the resin temperature at the time of melt extrusion. To 270 ° C. and the temperature of the film during longitudinal stretching is 60 ° C.
Further, a stretched film having a thickness of about 15 μm was obtained in the same manner as in the same example except that the film temperature during transverse stretching was changed to 90 ° C. (3) Evaluation of Stretched Film With respect to the stretched film produced by the method described in the preceding paragraph, the flex pinhole resistance was measured according to the method described above. The results are also shown in Table 1 below.

Example 3 (1) Preparation of modified polyolefin composition (P) 100 parts by weight of an ethylene-propylene copolymer having an ethylene content of 2.0% by weight and a melt flow index of 0.6 gr / 10 minutes. 2,5-dimethyl-2,5di (t-butylperoxy) dissolved in a small amount of acetone
0.12 parts by weight of hexane and 2 parts by weight of maleic anhydride were mixed in a Henschel mixer to obtain granules. This granular material was extruded at 230 ° C. using an extruder having an inner diameter of 40 mmφ and L / D = 28, pelletized, and ethylene-
A modified polyolefin (Pa) of propylene copolymer system was obtained. Next, 20 parts by weight of the modified polyolefin (Pa) and 80 parts by weight of polypropylene (Pb) having a melt flow index of 4.0 gr / 10 minutes were mixed, and then the mixture was mixed with an inner diameter of 40 mmφ and L / D = The modified polyolefin composition (P) was obtained by extruding using an No. 28 extruder at 220 ° C. and pelletizing. (2) Manufacture of Stretched Film Poly-ε-caproamide (Novamid 1022, manufactured by Mitsubishi Kasei Co., Ltd.) and the modified polyolefin composition (P) prepared by the method described in the preceding paragraph were mixed at a ratio of 95/5 by weight as a raw material. The resin composition was melt-extruded at a resin temperature of 270 ° C. using a 65 mmφ extruder equipped with a coat hanger T die, and was rapidly cooled by closely adhering to a cast roll adjusted to 25 ° C. to form an unstretched film having a thickness of about 135 μm. Obtained. The obtained unstretched film was heated to 60 ° C. and then stretched 3 times in the longitudinal direction by a roll type longitudinal stretching machine. Then, the end portion of this film was held by a tenter clip, and the film was placed in a tenter oven for 9 days.
After being stretched three times in the transverse direction under the condition of 0 ° C., heat treatment was performed at 210 ° C. for 4 seconds to obtain a stretched film having a thickness of about 15 μ. (3) Evaluation of Stretched Film With respect to the stretched film produced by the method described in the preceding paragraph, the flex pinhole resistance was measured according to the method described above. The results are also shown in Table 1 below.

Examples 4 to 8 In the example described in Example 1, (a) the modified polyolefin (P) in the preparation of the modified polyolefin composition (P)
Ratio of a) to unmodified polyolefin (Pb), (b)
The thickness of poly-ε-caproamide (Novamid 1022, manufactured by Mitsubishi Kasei Co., Ltd.) and the modified polyolefin composition (P) were changed as shown in Table 1, respectively, and the thickness was about A stretched film of 15μ was obtained. The flexural pinhole resistance of the obtained stretched film was measured according to the method described above. The results are also shown in Table 1 below.

Comparative Example 1 In the example described in Example 1, the modified polyolefin composition (P) was not prepared, but poly-ε-caproamide (Novamid 1022 manufactured by Mitsubishi Kasei Co., Ltd.) and an ethylene-vinyl acetate copolymer ( An attempt was made to produce a stretched film in the same manner as in the same example, using a resin composition in which Pb) was mixed at a ratio of 95/5 on a weight basis as a raw material. However,
Since the dispersibility of the ethylene-vinyl acetate copolymer (Pb) was poor, stretching was unstable and a good product could not be obtained.

Comparative Example 2 In the example described in Example 1, neither modified polyolefin nor unmodified polyolefin was blended, and only poly-ε-caproamide (Novamid 1022 manufactured by Mitsubishi Kasei Co., Ltd.) was used as a raw material. In the same manner, a stretched film having a thickness of about 15μ was obtained. Regarding the obtained stretched film,
The bending pinhole resistance was measured according to the above method. The results are also shown in Table 1 below.

Example 9 A polyurethane adhesive (Takelac A310 / A-3 manufactured by Takeda Pharmaceutical Co., Ltd.) was applied to one side of the stretched film having a thickness of about 15 μm produced in the example described in Example 1. 5
It is applied to a thickness of gr / m2, dried, and then polyvinylidene chloride (abbreviated as "PVDC", the same applies hereinafter) latex liquid concentrate (Kureha Chemical Co., Ltd., Kureharon DO-8).
21S) was applied to a thickness of 5 gr / m 2. Then 8
After drying for 30 seconds in an oven at 0 ° C, aging treatment was performed at 40 ° C for 40 hours. The flexural pinhole resistance of the obtained PVDC-coated stretched film was measured according to the method described above. The results are also shown in Table 1 below.

Comparative Example 3 In the same manner as in Example 9, except that the stretched film produced by the method described in Example 1 was replaced with the stretched film produced by the method described in Comparative Example 2. A PVDC-coated stretched film was obtained in the same manner as. Obtained P
The bending resistance of the VDC-coated stretched film was measured according to the method described above. The results are also shown in Table 1 below.

[0033]

[Table 1]

From Table 1, the polyamide resin stretched film according to the present invention is excellent in bending pinhole resistance,
It can be seen that the film of Comparative Example is inferior in resistance to bending pinholes. This effect is also noticeable when the stretched polyamide resin film according to the present invention is coated with PVDC.

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display area B29K 77:00 4F B29L 7:00 4F

Claims (1)

[Claims] 1. Aliphatic polyamide (A) 99.7-9
Modified polyolefin composition (P) 0.3 to 0.0% by weight, modified polyolefin (Pa) 100 to 5% by weight obtained by grafting unsaturated carboxylic acid on polyolefin, and polyolefin (Pb) 0 to 95% by weight 10% by weight
A stretched film comprising a polyamide resin composition obtained by melt-mixing
A polyamide-based resin stretched film, which is stretched at a stretch ratio of 8 times.