JP2008080686A - Polyamide stretched film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide based laminated biaxially stretched film having excellent oxygen gas barrier properties, excellent bending pinhole resistance and toughness. <P>SOLUTION: The polyamide based laminated biaxially stretched film is a multilayered stretched film containing at least two layers, that is, a layer based on a polyamide resin (X) and a layer (B) comprising a resin Z which contains an aliphatic polyamide resin (Y) and the polyamide resin (X). The polyamide resin (X) is obtained using meta-xylylenediamine and a 6-12C α, ω-aliphatic dicarboxylic acid as main raw materials and the resin (Z) is based on the aliphatic polyamide resin (Y) and a cut waste material at the time of production of the film is mixed with the aliphatic polyamide resin (Y). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a stretched polyamide film excellent in flexibility, impact resistance, pinhole resistance, transparency, and gas barrier properties that can be boiled or retorted.

  As a packaging material having gas barrier properties, a multilayer film using polyvinylidene chloride (PVDC), ethylene-vinyl alcohol copolymer (EVOH), polyamide or the like as a gas barrier layer is used. Among polyamides, metaxylylene group-containing polyamides obtained by polycondensation of metaxylylenediamine and α, ω-aliphatic dicarboxylic acids having 6 to 12 carbon atoms are boiled or retorted against other gas barrier resins. When performing the above, there is a feature that the gas barrier property is hardly lowered and the gas barrier property is rapidly recovered. In particular, polymetaxylylene adipamide (hereinafter sometimes referred to as nylon MXD6) using adipic acid as an α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms has recently been used in the packaging field by taking advantage of this feature. Is progressing.

  Nylon MXD6 has the disadvantages of low impact resistance, flexibility, and pinhole resistance in a non-stretched state, but it can improve impact resistance, flexibility, and pinhole resistance to some extent by stretching. However, nylon MXD6 alone cannot be sufficiently improved, and a method of producing a laminated biaxially stretched film by an inflation method by separately melt-extruding two kinds of polyamide-based polymers has been proposed (Patent Document 1). reference). In addition, a laminated film having a structure in which a layer mainly composed of an aromatic polyamide polymer is sandwiched between layers composed mainly of an aliphatic polyamide polymer has also been proposed (see Patent Document 2).

In the case of producing a laminated biaxially stretched film using different types of polyamide polymers as raw materials, it is inevitable to produce a mixture of different polyamide polymers. For example, after starting production of a laminated biaxially stretched film and before reaching a steady state where a product within the standard is achieved, even if a non-standard film is produced or a steady state is reached, The cutting cutting material that is called is made. Since these nonstandard films and ear trims are a mixture of different polyamide polymers, it is virtually impossible to separate and collect them separately and use them as virgin raw materials. There is a problem that the yield of raw materials decreases and the product cost increases. Regarding the reuse of these nonstandard films, ear trims, etc., a method using additives (see Patent Documents 3 to 10) has been proposed for measures to reduce physical properties when reused. Although these methods can prevent deterioration of mechanical properties and pinhole resistance, the barrier properties are not improved. No effective method has been proposed for improving barrier properties when reusing ear trims and the like.
JP-A-57-51427 JP-A-56-155762 Japanese Patent No. 3021851 Japanese Unexamined Patent Publication No. 7-117198 JP-A-7-276591 Japanese Patent No. 2666663 Japanese Patent No. 3021854 Japanese Patent No. 3074883 Japanese Patent No. 3136789 Japanese Patent No. 3395474

  In view of the above circumstances, the present invention has been conventionally discarded as scrap when producing a polyamide-based laminated biaxially stretched film having excellent oxygen gas barrier properties, excellent bending pinhole properties, toughness, and the like. A laminated biaxially stretched film that effectively utilizes a non-standard film produced during production and a mixture of raw material polyamide-based polymers such as ear trims, and does not deteriorate physical properties, including gas barrier properties, by reusing them. The purpose is to provide.

  As a result of examining the barrier properties and mechanical properties of a mixture of a metaxylylene group-containing polyamide and an aliphatic polyamide, the present inventors have found that when the proportion of the metaxylylene group-containing polyamide in the mixture exceeds 50%, both of them are repeatedly heated and melted. When the resin undergoes an amide exchange reaction and becomes compatible, mechanical properties and gas barrier properties, and transparency after boiling and retort treatment are drastically reduced. On the other hand, when the proportion of the polyamide containing metaxylylene groups in the mixture is 50% or less Found that there was almost no decrease in physical properties due to the above-mentioned compatibilization, and the present invention was completed.

That is, the present invention relates to the following inventions (1) to (4).
(1) A multilayer including two layers of a layer (B) composed of a resin (Z) containing at least a polyamide resin (X) as a main component (A), an aliphatic polyamide resin (Y) and a polyamide resin (X) In the stretched film, the polyamide resin (X) is such that 70 mol% or more of the structural unit derived from diamine is derived from metaxylylenediamine, and 70 mol% or more of the structural unit derived from dicarboxylic acid is present. It is derived from an α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms, and the resin (Z) is mainly composed of an aliphatic polyamide resin (Y), and a cut end material at the time of production of the film is added thereto. A multilayer stretched film formed by mixing.
(2) The multilayer stretched film according to (1), wherein the weight of the polyamide resin (X) in the layer (B) is 3 to 50%.
(3) The multilayer stretched film according to (1), wherein the oxygen permeability at 23 ° C. and a relative humidity of 60% is 20 to 150 (ml / (m ² · day · MPa)).
(4) The film which laminated the multilayer stretched film as described in (1) with polyolefin.

  The stretched polyamide film of the present invention uses a polyamide resin (X) as a gas barrier layer, and has excellent transparency, impact resistance, pinhole resistance, and gas barrier properties by adding a cut end material to the aliphatic polyamide resin. In addition, since it can be boiled or retorted, it can be suitably used as a packaging material for foods, pharmaceuticals, industrial chemicals, cosmetics, inks and the like. Since the stretched polyamide film of the present invention is particularly excellent in gas barrier properties, it is excellent in food preservability and can be suitably used particularly as food packaging.

  The multilayer stretched film of the present invention is a resin (Z) in which at least a (A) layer composed of a polyamide resin (X) and an aliphatic polyamide resin (Y) are the main components, and a cut end material at the time of film production is mixed therewith. The (C) layer made of the aliphatic polyamide resin (Y) may be added as necessary. Specifically, B / A / B, B / A / C, B / C / A, B / A / B / A / B, C / A / B / A / C, C / A / B / A Configurations such as / B are possible, but are not limited thereto. Among these, the B / A / B configuration is practical and preferable.

  In the polyamide resin (X) used in the present invention, 70 mol% or more of the structural unit derived from diamine is derived from metaxylylenediamine, and 70 mol% or more of the structural unit derived from dicarboxylic acid is carbon. It is derived from α, ω-aliphatic dicarboxylic acid of formula 6-12. The polyamide resin (X) uses, for example, a diamine component containing 70 mol% or more of metaxylylenediamine and a dicarboxylic acid component containing 70 mol% or more of an α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms. These are obtained by polycondensation. The structural unit derived from metaxylylenediamine is preferably 90 mol% or more, and more preferably 100 mol%. When the structural unit derived from metaxylylenediamine is within the above range, a predetermined gas barrier property can be maintained.

For polycondensation, diamines other than metaxylylenediamine, paraxylylenediamine, orthoxylylenediamine, bis (aminomethyl) cyclohexane, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine Nonamethylenediamine, orthophenylenediamine, metaphenylenediamine, paraphenylenediamine, and the like can be used.
Moreover, when the structural unit derived from the α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms is 70 mol% or more, it is possible to obtain practical physical properties of the polyamide resin. Examples of the α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms include adipic acid and sebacic acid. These dicarboxylic acids can be used alone or in combination of two or more. Among these, it is particularly desirable to use adipic acid as the dicarboxylic acid component from the viewpoint of gas barrier properties of the polyamide resin (X). An aromatic carboxylic acid or the like can be used as a dicarboxylic acid other than an α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms, and examples thereof include isophthalic acid and terephthalic acid.

  The aliphatic polyamide resin (Y) may be a chain polyamide having an amide bond, and specific examples include ε-caprolactam homopolymer, polyhexamethylene azamide, and ε-caprolactam or hexamethylene. And a copolymer comprising 2 to 10% by mole of a compound having azamide as a main component and copolymerizable therewith. Examples of the compound copolymerizable with ε-caprolactam or hexamethylene adipamide include nylon salts of aliphatic diamines and aliphatic dicarboxylic acids. Specific examples of the aliphatic diamines include ethylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, octamethylene diamine, decamethylene diamine and the like. Specific examples of the aliphatic dicarboxylic acids include adipic acid, sebacic acid, corkic acid, glutaric acid, azelaic acid, β-methyladipic acid, decamethylene dicarboxylic acid, dodecamethylene dicarboxylic acid, pimelic acid and the like. Among these polymers, nylon-6, which is a homopolymer of ε-caprolactam, or polyhexamethylene adipamide called nylon 66 can be obtained at a low cost and can smoothly perform a biaxial stretching operation. This is preferable. Furthermore, nylon 6,66 copolymerized with these can also be used suitably.

  The cut end material as referred to in the present invention is a general term for a product that does not become a product generated during film production, and can be reused by mixing with an aliphatic polyamide resin (Y) to form a resin (Z). In the stretching by the tenter method, the sequential stretching method is generally used in which the film is stretched in the longitudinal direction using a roll, then the film is gripped with a chuck or clip and then laterally stretched.However, the product is not stretched in the vicinity of the grip. Rather, it is common to cut this part with a slitter. The same is true for the simultaneous biaxial stretching method, and the film is gripped with a chuck or clip and biaxially stretched at the same time, but the area near the grip is not stretched, so it is not a product, and it is normal to cut this part with a slitter. It is. The present invention reuses these so-called ear trims. In general, when producing stretched film, the production of the film starts at a low speed and then gradually increases to the normal production speed. It becomes the object of use. The width of the film obtained by the machine is several times the width when printing or laminating, and it is usually cut into an appropriate width. Due to the film width, at this time, there is inevitably a remainder left after cutting. This surplus is also subject to reuse. When there is a trouble in the longitudinal stretching process, the lateral stretching process, etc., it may be dealt with while winding the film in the previous process, but the film wound up at that time is also subject to reuse. In addition, the purged product at the start of extrusion is also the object of reuse.

  The polyamide resin (X), the aliphatic polyamide resin (Y), the resulting film, the cut end material, etc. are all highly hygroscopic. In order to prevent film formation, it is preferable to store and transport in dry air or nitrogen so as not to absorb moisture, or to dry in advance so that the moisture content is 0.5% by weight or less.

  When the ratio of the metaxylylene group-containing polyamide in the layer (B) composed of the mixture of the cut end materials is 50% or more, both the polyamide resin (X) and the aliphatic polyamide resin (Y) are obtained by repeated heating and melting. Since the resin undergoes an amide exchange reaction and becomes compatible, mechanical properties, gas barrier properties, and transparency after boil and retort treatment are drastically reduced. The proportion of the metaxylylene group-containing polyamide in the layer (B) is preferably 50% or less in order to control so that the physical property deterioration due to the compatibilization hardly occurs.

  Immediately after the start of reuse, since the material to be recycled has received only one thermal history, even if the proportion of the polyamide containing metaxylylene groups in the layer (B) exceeds 50%, the physical properties do not deteriorate so much. If the process is continued, the reused resin will be subjected to a thermal history many times, and the compatibilization proceeds and the physical properties decrease. When the proportion of the metaxylylene group-containing polyamide in the layer (B) is 50% or less, the compatibilization hardly proceeds even when the thermal history is repeatedly received, and there is almost no deterioration in physical properties. Accordingly, even if the production is continued, the physical properties are not deteriorated, and the same quality product can be stably produced.

  Since the cut end material may not be supplied to the extruder as it is, it is preferably pulverized and pulverized, compressed and granulated, pelletized, or melted and re-extruded to be pelletized. From the viewpoint of supply stability and discharge stability in an extruder, pelletization by melt re-extrusion is particularly preferred.

  At the time of melt pelletization, a pulverized cut end material is supplied to a hopper using a single-screw extruder or a twin-screw extruder, melt-extruded, and the resulting strand is cut with a pelletizer to be pelletized. Pelletization is preferably carried out using a vented extruder while removing moisture under vacuum. During extrusion, in order to prevent compatibilization of both resins, the extrusion temperature is preferably 270 ° C. or less and the residence time is preferably 10 minutes or less. When the extrusion temperature exceeds 270 ° C., or when the residence time exceeds 10 minutes, both resins are compatibilized, which is preferable because mechanical properties, pinhole resistance, impact resistance, and transparency after heat treatment deteriorate. Absent.

  The thickness of the multilayer stretched film of the present invention is preferably 10 μm or more and 40 μm or less. When the total thickness is less than 10 μm, the balance between oxygen gas barrier property and bending pinhole property is poor, and the wear resistance is also poor, so that a satisfactory film for packaging use cannot be obtained. On the other hand, when the thickness exceeds 40 μm, the film becomes hard, and when the sealant layer is laminated, the whole film becomes very thick and is not suitable for soft packaging applications.

When there are a plurality of layers (A) containing the polyamide resin (X) as a main component in the multilayer stretched film of the present invention, 3 to 20 μm is appropriate. Thereby, the oxygen permeability as a multilayer film can be 20 to 150 (ml / (m ² · day · MPa)). If the thickness of the layer (A) is thinner than this, the barrier property is deteriorated, and if it is thick, the pinhole resistance, impact resistance and flexibility are lowered, which is not preferable.

  In order to improve impact resistance, pinhole resistance and flexibility, an impact resistance improving material may be added to the layer (A) or the layer (B). Examples of impact resistance improvers include polyolefins, polyamide elastomers, hydrogenated products of styrene-butadiene copolymer resins, ionomers, ethylene-ethyl acrylate copolymer resins, ethylene-ethyl acrylate copolymer resins modified with maleic anhydride, ethylene -Methacrylic acid copolymer resin, nylon 12, ethylene-propylene copolymer elastomer, polyester elastomer, etc. can be added. The addition amount of the impact resistance improving material is preferably 1 to 10% by weight, more preferably 1 to 5% by weight, and particularly preferably 2 to 3% by weight. When the amount added is large, transparency and gas barrier properties are lowered. If the amount added is small, impact resistance, pinhole resistance and flexibility are not improved so much.

  Various additives such as lubricants, antistatic agents, antioxidants, antiblocking agents, stabilizers, dyes, pigments, inorganic fine particles, and clay minerals are added to the layer (A) and layer (B) to affect the properties of the film. It can be added within the range not given.

  The multilayer stretched film obtained in the present invention can be used by laminating with a thermoplastic resin. Examples of thermoplastic resins that can be used include low density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, polybutene, copolymers thereof, ionomer resins, ethylene-acrylic acid copolymers, ethylene-vinyl acetate. Copolymers, modified polyolefin resins, and mixtures thereof can be used. Among these, low density polyethylene, high density polyethylene, linear low density polyethylene, and polypropylene are preferable.

The film according to the present invention can be produced by the following method.
First, a multilayer film made of polyamide resin (X) and aliphatic polyamide resin (Y) is manufactured, and ear trims and the like are secured. Next, cut end materials such as ear trims are crushed and melted into pellets to obtain recycled pellets. The obtained pellets are blended with the aliphatic polyamide resin (Y) to form a resin (Z), and reuse is started.
Next, an unstretched laminated film that is substantially amorphous and not oriented is produced from the raw material. The thickness of the unstretched laminated film is appropriately selected according to the use of the film and the stretching ratio, but is usually in the range of 60 to 1000 μm. In the production method by the co-extrusion method, the raw material is melted by 2 to 3 extruders, extruded from a flat tie or an annular tie, and then rapidly cooled to obtain a flat or annular unstretched laminated film. The unstretched laminated film is biaxially stretched 2.5 to 5 times in the film flow (vertical axis) direction and in the direction perpendicular to it (horizontal axis). If the draw ratio is less than 2.5 times each in the longitudinal direction and the transverse direction of the film, there is no effect of stretching, the strength of the film is inferior, and if it is more than 5 times in each axial direction, The film tends to tear during stretching, which is not preferable. As the biaxial stretching method, conventionally known stretching methods such as tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, tubular simultaneous biaxial stretching, and the like can be adopted.

  For example, in the case of the tenter-type sequential biaxial stretching method, the unstretched laminated film is heated to a temperature range of 60 to 100 ° C., and stretched 2.5 to 5 times in the vertical axis direction by a roll type longitudinal stretching machine, Subsequently, it can be produced by stretching 2.5 to 5 times in the transverse axis direction within a temperature range of 80 to 140 ° C. by a tenter type transverse stretching machine. On the other hand, in the case of the tenter type simultaneous biaxial stretching method or the tubular type simultaneous biaxial stretching method, for example, in the temperature range of 60 to 110 ° C., the film is stretched by 2.5 to 5 times in the axial direction at the same time in the longitudinal and lateral directions. Can be manufactured. The film stretched by the above method is preferably subjected to a heat treatment thereafter. By performing heat treatment, a stretched film having excellent dimensional stability can be obtained. The heat treatment temperature can be arbitrarily set in addition to a stretched film having excellent dimensional stability by selecting a range in which the upper limit is 110 ° C and 5 ° C lower than the melting point of the lowest melting point among the constituent components. A stretched film having a heat shrinkage rate can also be obtained.

The multilayer stretched film of the present invention has excellent gas barrier properties, and preferably has an oxygen permeability of 20 to 150 (ml / (m ² · day · MPa)) at 23 ° C. and a relative humidity of 60%. .

Hereinafter, the features of the present invention will be described more specifically with reference to Examples and Comparative Examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Accordingly, the scope of the present invention should not be construed as being limited by the specific examples shown below.
In the examples and comparative examples, the following measurement methods and evaluation methods were employed.
(1) Cloudiness value The measurement was carried out at 23 ° C. and a relative humidity of 60% according to ASTM D1003.
The measuring instrument used is a difference / turbidity measuring instrument (model: COH-300A) manufactured by Nippon Denshoku Industries Co., Ltd. Similarly, the cloudiness value after retorting at 121 ° C. for 30 minutes was also measured.
(2) Oxygen permeability The measurement was performed according to ASTM D3985.
The measuring instrument used is an oxygen permeability measuring device (model: OX-TRAN 10 / 50A) manufactured by Modern Controls, and the measurement conditions are 23 ° C. and relative humidity 60%.
(3) Impact drilling strength The measurement was performed according to ASTM D781.
The measuring instrument used is a film impact tester (model: ITF-60) manufactured by Toko Precision Industry Co., Ltd., and the measurement conditions are 23 ° C. and relative humidity 50%.
(4) Flexibility test (pinhole resistance test)
The measuring instrument used was a gel bow flex tester manufactured by Rigaku Kogyo Co., Ltd., and the measurement conditions were 23 ° C. and relative humidity 50%. Bending was performed a predetermined number of times, and the number of pinholes / per 624 cm ² was counted with a pinhole tester.
(5) Tensile strength test The measurement was performed according to ASTM D882.
The measuring instrument used was Strograph V1-C manufactured by Toyo Seiki Co., Ltd., and the measurement conditions were 23 ° C. and relative humidity 50%.
(6) Thickness measurement The thickness of each layer of a multilayer structure was measured using the following thickness measuring machine.
Measuring equipment: Gunze multilayer film thickness measuring device DC-8200

<Reference example>
Nylon MXD6 (corresponding to polyamide resin (X). Mitsubishi Gas Chemical Co., Ltd., trade name: MX nylon 6011. The structural unit derived from diamine is derived from metaxylylenediamine, and the structural unit derived from dicarboxylic acid is carbon number. 6), poly-ε-caproamide (Ube Kosan Co., Ltd., Ubenylon 1022FDX04) (aliphatic polyamide resin (Y)) was melted separately using three 65 mmφ extruders, It is laminated in a T-die and extruded as a laminated film with a three-layer structure (Y / X / Y). It is tightly cooled with a 30 ° C cast roll using a pinning device. Y / X / Y = 50/50 / 50μm A multilayer raw film was obtained. The obtained laminated unstretched film was stretched 3 times in the vertical axis direction by a roll-type stretching machine under the condition of 85 ° C., and then the end of this film was held with a tenter clip, Under the condition of ˜120 ° C., the film was stretched 3.3 times in the horizontal axis direction, and then heat-fixed at 215 ° C. for 10 seconds. The film after the heat treatment was used as a raw material for reuse by cutting out both ends of the film held by clips at 10% width. The product film part was wound up by a winder to obtain a stretched product film having a thickness composition of X / Y / X = 5/5/5 μm.

<Example 1>
The film ear portion obtained in the reference example was pulverized with a pulverizer, melted at 260 ° C. using a 37 mm twin screw extruder, extruded in a strand shape, and then cut with a pelletizer to obtain recycled pellets. The resulting pellet was mixed with poly-ε-caproamide (Ube Kosan Co., Ltd., Ube Nylon 1022FDX04) (aliphatic polyamide resin (Y)) so that the weight of nylon MXD 6 was 10 wt%. Except that it was used in place of the polyamide resin (Y), extrusion was performed in the same manner as in the reference example, and longitudinal stretching and transverse stretching were performed to obtain a stretched product film. The evaluation results of the obtained stretched film are shown in Table 1.

<Example 2>
The product stretched film obtained in Example 1 was slit by surplus film for printing / laminating using a pulverizer, melted at 260 ° C. using a 37 mm twin screw extruder, extruded in a strand, and then pelletized. To obtain recycled pellets. The resulting pellet was mixed with poly-ε-caproamide (Ube Kosan Co., Ltd., Ube Nylon 1022FDX04) (aliphatic polyamide resin (Y)) so that the weight of nylon MXD 6 was 15 wt%. Except that it was used in place of the polyamide resin (Y), extrusion was performed in the same manner as in the reference example, and longitudinal stretching and transverse stretching were performed to obtain a stretched product film. The evaluation results of the obtained stretched film are shown in Table 1.

<Comparative Example 1>
In Example 1, the product obtained by melting and pelletizing the film edge pulverized product was added to the polyamide resin (X) instead of the aliphatic polyamide resin (Y) so that the recycling rate was the same as in Example 1. Obtained a stretched film in the same manner as in Example 1. The evaluation results of the obtained stretched film are shown in Table 2.

Claims (5)

A multilayer stretched film comprising two layers of a layer (B) comprising at least a layer (A) comprising a polyamide resin (X) as a main component and an aliphatic polyamide resin (Y) and a resin (Z) containing a polyamide resin (X). In the polyamide resin (X), 70 mol% or more of the structural unit derived from diamine is derived from metaxylylenediamine, and 70 mol% or more of the structural unit derived from dicarboxylic acid has 6 carbon atoms. ~ 12 derived from α, ω-aliphatic dicarboxylic acid, and resin (Z) is mainly composed of aliphatic polyamide resin (Y), and this is mixed with cutting end material during production of the film. A multilayer stretched film. The multilayer stretched film according to claim 1, wherein the layer structure is layer (B) / layer (A) / layer (B). The multilayer stretched film according to claim 1, wherein the weight of the polyamide resin (X) in the layer (B) is 3 to 50%. ^2. The multilayer stretched film according to claim 1, which has an oxygen permeability of 20 to 150 (ml / (m ² · day · MPa)) at 23 ° C. and a relative humidity of 60%. The film which laminated the multilayer stretched film of Claim 1 with polyolefin.