JP2008080687A - Manufacturing method of polyamide stretched film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyamide stretched film excellent in gas barrier properties, pinhole resistance, flexibility and impact resistance, prevented from mutual sticking at the time of manufacture and capable of being stably produced. <P>SOLUTION: When a multilayered film, which is composed of a layer based on a polyamide resin obtained using meta-xylylenediamine and a 6-12C α, ω-aliphatic dicarboxylic acid as main raw material and a layer based on an aliphatic polyamide resin, is manufactured by a roll/tenter type sequential biaxially stretching method, the temperature of a cooling roll after casting is controlled to a specific range. A biaxially stretched film obtained by this manufacturing method is also disclosed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing 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).

Regarding the production of films composed of these two types of polyamides, methods for improving physical properties using additives (see Patent Documents 3 to 10) have been proposed. However, when trying to stretch a multilayer structure composed of these two types of polyamides, the glass transition temperatures of nylon MXD6 and aliphatic polyamide are different, so that the optimum stretching conditions are different and it is difficult to stretch the combined multilayer structure. Become. In particular, when a film such as a B layer (aliphatic polyamide) / A layer (nylon MXD6) / B layer structure having excellent gas barrier properties, pinhole properties, flexibility, and impact resistance is stretched longitudinally with a roll, A At 80 ° C. or higher, which is the temperature at which the layer can be stretched, the resin of the B layer adheres to the roll, causing appearance defects and winding problems, making long-term stable production difficult.
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

  The object of the present invention is to obtain a stretched polyamide film that is excellent in gas barrier properties, pinhole resistance, flexibility, impact resistance, and prevents sticking during film production and can be stably produced in view of the above-mentioned actual situation. is there.

The inventors of the present invention control the temperature of the chill roll after casting to a specific range when manufacturing a multilayer film composed of a layer mainly composed of nylon MXD6 and a layer mainly composed of aliphatic polyamide resin. Thus, it was found that sticking and winding to the roll during longitudinal stretching using the subsequent roll was prevented, and stable production became possible, and the present invention was completed.
That is, in the present invention, 70 mol% or more of the structural units derived from diamine are derived from metaxylylenediamine, and 70 mol% or more of the structural units derived from dicarboxylic acid are α, C 6-12. An unstretched laminated film comprising a layer (A) mainly comprising a polyamide resin (X) derived from ω-aliphatic dicarboxylic acid and a layer (B) mainly comprising an aliphatic polyamide resin (Y) When a biaxially stretched film is produced by stretching the film by a roll / tenter type sequential biaxial stretching method, the temperature of the cooling roll after casting the unstretched laminated film is set to 30 to 60 ° C, and then 80 to 110 ° C. The present invention relates to a biaxially stretched film produced by the production method, characterized in that it is longitudinally stretched using a roll and is then subjected to a tenter transverse stretch at 80 to 160 ° C. That.

  By the method for producing a biaxially stretched film of the present invention, transparency, impact resistance, pinhole resistance, gas barrier properties are excellent, and a stretched film that can be boiled or retorted can be stably produced. The obtained stretched film can be suitably used as a packaging material for foods, pharmaceuticals, industrial chemicals, cosmetics, inks and the like. Since the biaxially stretched film of the present invention is particularly excellent in gas barrier properties, the biaxially stretched film is excellent in food storage stability and can be suitably used particularly as food packaging.

  The biaxially stretched film of the present invention comprises at least two layers of a layer (A) mainly composed of a polyamide resin (X) and a layer (B) mainly composed of an aliphatic polyamide resin (Y). Configurations such as / B, B / A, B / A / B / A / B, and B / A / B / A 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.

  In the present invention, it is also possible to recycle and use the cut end material of the film for each layer. 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. These parts called ear trims can be reused for each layer. 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.

  The thickness of the biaxially 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) having the polyamide resin (X) as a main component in the biaxially 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 biaxially 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 successive biaxial stretching by the following method.

  First, an unstretched laminated film that is substantially amorphous and not oriented is produced from the raw material polyamide resin (X) and aliphatic polyamide resin (Y). 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 die, and then cooled to obtain a flat unstretched laminated film. By setting the temperature of the cooling roll at this time to 30 to 60 ° C., it is possible to prevent sticking and winding of the roll during longitudinal stretching using the subsequent roll, and stable production becomes possible. If the temperature of this cooling roll is less than 30 ° C., adhesion and winding to the roll during longitudinal stretching using the subsequent roll occur, resulting in poor appearance and reduced physical properties, and stable production cannot be achieved. If the temperature of the cooling roll exceeds 60 ° C., crystallization of the polyamide resin proceeds, and stretching failure or whitening occurs during longitudinal stretching using the subsequent roll.

  Next, longitudinal stretching of the unstretched laminated film is performed. In the longitudinal stretching step using a roll, the unstretched laminated film is heated using a roll of 80 to 110 ° C. and stretched 2.5 to 5 times in the vertical axis direction. When the roll temperature is less than 80 ° C., it is not preferable because breakage or appearance failure occurs due to poor drawing due to insufficient heating. When the roll temperature exceeds 110 ° C., crystallization proceeds and poor stretching or whitening occurs, which is not preferable. When the longitudinal stretching ratio is less than 2.5 times, the mechanical properties are deteriorated, and when it exceeds 5 times, breakage, whitening and poor appearance occur.

  The film after longitudinal stretching can be produced by stretching it 2.5 to 5 times in the transverse axis direction within a temperature range of 80 to 160 ° C. by a tenter-type lateral stretching machine. If the transverse stretching temperature is less than 80 ° C., it is not preferable because breakage due to insufficient heating due to insufficient heating causes breakage or poor appearance. If this transverse stretching temperature exceeds 160 ° C., crystallization proceeds and poor stretching or whitening occurs, which is not preferable. When the transverse stretching ratio is less than 2.5 times, the mechanical properties are deteriorated, and when it exceeds 5 times, breakage, whitening, and poor appearance occur.

  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.

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%. A predetermined number (500 times) of bending was performed, 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

<Example 1>
Nylon MXD6 (equivalent to polyamide resin (X). Made by 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., Ube nylon 1022FDX04) (aliphatic polyamide (Y)) was melted separately using three 65 mmφ extruders, and T It is laminated in a die and extruded as a laminated film with a three-layer structure (Y / X / Y). It is closely cooled with a 30 ° C cast roll using a pinning device, and Y / X / Y = 50/50 / 50μm multilayer A raw film (unstretched laminated film) was obtained. The obtained unstretched laminated 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 evaluation results of the obtained stretched film are shown in Table 1.

<Example 2>
In Example 1, a film was produced in the same manner as in Example 1 except that the cast roll temperature was 40 ° C. and the longitudinal stretching roll temperature was 95 ° C., 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, a film was produced in the same manner as in Example 1 except that the temperature of the cast roll was 20 ° C., and a product stretched film was obtained. Adhesion to the longitudinal stretching roll occurred during production, resulting in poor film appearance and uneven thickness. The evaluation results of the obtained stretched film are shown in Table 2.

<Comparative example 2>
In Example 1, a film was produced in the same manner as in Example 1 except that the cast roll temperature was 30 ° C. and the longitudinal roll temperature was 60 ° C., to obtain a stretched product film. Although the sticking to the longitudinal stretching roll did not occur during production, the stretching failure occurred because the longitudinal stretching temperature was low, resulting in poor film appearance and uneven thickness. The evaluation results of the obtained stretched film are shown in Table 2.

Claims (3)

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 an α, ω-aliphatic dicarboxylic acid having 6 to 12 carbon atoms. An unstretched laminated film comprising a layer (A) mainly composed of an acid-derived polyamide resin (X) and a layer (B) mainly composed of an aliphatic polyamide resin (Y) is a roll / tenter type. When producing a biaxially stretched film by stretching by the sequential biaxial stretching method, the temperature of the cooling roll after casting the unstretched laminated film is set to 30 to 60 ° C, and then the roll is stretched vertically using a roll of 80 to 110 ° C. A method for producing a biaxially stretched film, characterized in that after stretching, a tenter-type transverse stretching is performed at 80 to 160 ° C. The manufacturing method according to claim 1, wherein a layer configuration of the unstretched laminated film is layer (B) / layer (A) / layer (B). The biaxially stretched film obtained by the manufacturing method of Claim 1 or 2.