Polyamide resin composition and film therefrom.

Detailed Description of the Invention

0001The present invention relates to a polyamide resin composition and a film produced therefrom. More specifically, it relates to a polyamide resin composition which is excellent in gas-barrier properties, liquid-barrier properties and transparency, and a film which is suitably usable as a packing film for foods, drugs, cosmetics, etc.

0002Polyamide produced by a melt-polycondensation reaction between m-xylylenediamine and adipic acid (to be referred to as "nylon MXD6" hereinafter) has excellent gas-barrier properties, and it also has excellent thermal stability when melted. Further, nylon MXD6 is co-extrudable or co-injection moldable with various thermoplastic resins such as polyethylene terephthalate, nylon 6, polypropylene, etc. Therefore, the utilization thereof in multi-layer structure articles having gas-barrier properties is actively under way.

0003However, nylon MXD6 in an unstretched state or in a state of being stretched at a low stretch ratio has a defect in that it is whitened or crystallized to show a decrease in transparency when used as a film produced therefrom, when heated beyond the glass transition temperature at a molding time, when stored under high humidity or when treated with water vapor or hot water for sterilization.

0004U.S. Patent 4,908,272 proposes a polyamide mixture containing nylon MXD6 and a noncrystalline polyamide obtained from an aliphatic dicarboxylic acid, isophthalic acid and terephthalic acid as a di-carboxylic acid component and m-xylylenediamine as a diamine component. Further, U.S. Patent Application Serial No. 277,244 proposes a polyamide mixture containing nylon MXD6 and a copolyamide obtained from isophthalic acid and terephthalic acid as a dicarboxylic acid component and hexamethylenediamine as a diamine component.

0005However, both of the above polyamide mixtures are noncrystalline, and yet they are whitened due to hot water treatment or water absorption for a long period of time, although the whitening degree is small. Therefore, a film produced from any one of the above mixtures, too, shows an increase in haze due to hot water treatment or water absorption for a long period of time.

0006For this reason, nylon MXD6 in an unstretched state or in a state of being stretched at a low stretch ratio has been rarely used for a film or a packaging material produced from such a film.

0007It is an object of the present invention to provide a novel polyamide resin composition.

0008It is another object of the present invention to provide a polyamide resin composition which retains excellent transparency even in an unstretched state or a state of being stretched at a low stretch ratio and which has excellent gas-barrier properties.

0009It is still another object of the present invention to provide a polyamide resin composition which, even in an unstretched state or a state of being stretched at a low stretch ratio, retains excellent transparency even when processed after formed into a film, when stored under highly humid conditions, or when treated with water vapor or hot water for sterilization, and which is excellent in gas-barrier properties and is usable as an outer layer of a multilayer structure article which is directly exposed under highly humid atmosphere.

0010It is further another object of the present invention to provide an unstretched film, a biaxially stretched film and a multi-layer film, which are obtained from the polyamide resin composition of the present invention and have excellent properties described above.

0011The above and other objects and advantages of the present invention will be apparent from the following description.

0012According to the present invention, the above objects and advantages of the present invention are achieved, first, by a polyamide resin composition obtained by melting and kneading <ul id="ul0001" list-style="none"><li>(A) a first polyamide containing not less than 90 mol%, based on the total recurring units, of a m-xylylene adipamide unit of the formula, <chemistry id="chem0001" num="0001"><img file="EP0475720A2_D0001.tif" /></chemistry> and</li><li>(B) a second polyamide showing a semicrystallization time of not more than 30 seconds in a constant-temperature crystallization at 160°C and having a solubility parameter in the range of 13 ± 1.5</li><li>(C) under the conditions where the following relationship is satisfied,<maths id="math0001" num="(1)"><math display="block"><mrow><mtext>(0.025C-2.2) ≦ log R ≦ (0.025C-0.5)</mtext></mrow></math><img file="EP0475720A2_D0002.tif" /></maths> wherein C is a proportion (wt.%) of the first polyamide based on the total weight of the first and second polyamides, and R is a ratio of the melt viscosity of the first polyamide to the melt viscosity of the second polyamide at a temperature higher by 20°C than the melting point of that one of the first and second polyamides which has a higher melting point than the other, provided that C is in the range of 20 to 95 (wt.%).</li></ul>

0013The first polyamide (A) used in the present invention contains not less than 90 mol% of the m-xylylene adipamide unit of the above formula based on the total recurring units.

0014When the content of the structural unit of the above formula, produced from m-xylylene diamine and adipic acid, in the polyamide is smaller than 90 mol%, the resultant polyamide shows an increase in gas permeability and an extreme decrease in crystallization, and no material meeting the objects of the present invention can be obtained.

0015The first polyamide (A) preferably contains not less than 95 mol% of the m-xylylene adipamide unit based on the total recurring units.

0016The first polyamide (A) may contain other amide unit(s) in an amount of less than 10 mol%, preferably less than 5 mol% in addition to the m-xylylene adipamide unit.

0017The diamine and dicarboxylic acid to constitute the "other amide unit(s)" are as follows. For example, the diamine preferably includes aliphatic diamines having 4 to 12 carbon atoms such as hexamethylenediamine, tetramethylenediamine, etc.; alicyclic diamines such as 1,3-bisaminomethyl-cyclohexane, etc; and p-xylylene diamine. The dicarboxylic acid preferably includes aliphatic dicarboxylic acids having 4 to 12 carbon atoms such as succinic acid, sebacic acid, dodecanedioic acid and aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, etc.

0018The first polyamide (A) may have terminal(s) blocked with, e.g. a monoamine, a monocarboxylic acid, or the like, which has been added as a molecular weight regulator when the polycondensation has been carried out.

0019The first polyamide (A) is usually produced by a melt-polycondensation method, in which, for example, a material composed mainly of a nylon salt formed of m-xylylene diamine and adipic acid is heated in the presence of a water solvent under pressure and polymerized in a molten state while water added and water formed during the polycondensation are removed.

0020Alternatively, the first polyamide (A) can be produced by adding a diamine mainly containing m-xylylene diamine to a dicarboxylic acid which mainly contains adipic acid and is in a molten state, and polycondensing these components at an atmospheric pressure.

0021In the latter method, the reaction system is maintained in a uniform liquid state without adding water as a solvent. For this purpose, the polycondensation is carried out by continuously adding m-xylylene diamine to the reaction system and elevating the temperature of the reaction system such that the reaction temperature does not drop below the melting points of oligoamide and polyamide being formed. A polymer having a higher molecular weight formed by solid-phase polymerization of the resultant polymer may be used as a first polyamide (A) as well.

0022The second polyamide (B) used in the present invention is a polyamide showing a semicrystallization time (according to a depolarized light intensity method ) of not more than 30 seconds in a constant-temperature crystallization at 160°C, and has a solubility parameter in the range of 13 ± 1.5.

0023When the semicrystallization time of the second polyamide (B) is not more than 30 seconds as described above, the second polyamide (B) undergoes crystallization when melt-mixed with the first polyamide (A) and formed into a film, and the resultant crystal of the second polyamide (B) effectively works as a nucleating agent for crystallization of the first polyamide (A). As a result, the first polyamide (A) does not form too large spherulites.

0024On the other hand, when the above semicrystallization time of the second polyamide (B) exceeds 30 seconds, the crystallization rate of the second polyamide (B) is low, so that it does not arrive at crystallization when melt-mixed with the first polyamide (A) and formed into a film. Thus, the second polyamide (B) does not work as a nucleating agent for the crystallization of the first polyamide (A), and hence, the first polyamide (A) forms too large spherulites. As a result, no film having excellent transparency can be obtained.

0025The first polyamide (A) used in the present invention, by its nature, tends to form a large size of spherulites due to water absorption and moisture absorption after formed into a film or during the crystallization under heat at a temperature higher than the glass transition temperature, when no nucleating material is present. The so-formed large spherulites cause light scattering and increases the degree of haze, which results in a decrease in the transparency of the film. Furthermore, when the second polyamide (B) used in the present invention is not crystallized at a film-forming time, it is impossible to expect the crystallization of the first polyamide (A) which is induced by the crystallization of the second polyamide (B), and as a result, the resultant film cannot have improved gas-barrier properties.

0026The semicrystallization time of the second polyamide (B) refers not only to the semicrystallization time of the polyamide alone but also to the crystallization time of the polyamide containing a nucleating agent. Therefore, even a polyamide which shows a semicrystallization time of more than 30 seconds may be used as a second polyamide (B) in the present invention if the semicrystallization time of the polyamide is decreased to not more than 30 seconds by the incorporation of a nucleating agent.

0027The second polyamide (B) preferably shows a semicrystallization time of not more than 20 seconds.

0028The second polyamide (B) used in the present invention has a solubility parameter of 13 ± 1.5. The solubility parameter used in the present specification refers to the constants of Small described in Table on page 97 of "The Technology of Plasticizers", by J. Kern Sears and Joseph R. Darby, issued in 1982.

0029When a polyamide having a solubility parameter outside the above range is used, the resultant polyamide composition exhibits higher haze, and it is impossible to obtain such a material for a packaging material having excellent transparency as is intended in the present invention.

0030The second polyamide (B) is specifically selected, for example, from nylon 6, nylon 66 and a blend or copolymer of one or both of nylon 6 and nylon 66 with any one(s) of nylon 46, nylon 610, nylon 612, nylon 11, nylon 12, etc. Further, as far as the afore-described conditions on the semicrystallization time and the solubility parameter are fulfilled, there may be used a copolymer composed of at least two amide units out of amide units which constitute a variety of the above nylons.

0031In the polyamide resin composition of the present invention, the amount of the first polyamide (A) is in the range of 20 to 95 % by weight based on the total weight of the first polyamide (A) and the second polyamide (B).

0032The polyamide resin composition of the present invention is obtained by melt-kneading the first polyamide (A) and the second polyamide (B) of which the amounts are in the above range under the conditions where the following relationship is fulfilled.<maths id="math0002" num=""><math display="block"><mrow><mtext>(0.025C-2.2) ≦ log R ≦ (0.025C-0.5)</mtext></mrow></math><img file="EP0475720A2_D0003.tif" /></maths>

0033In the above relationship, C is the value for a weight percentage of the first polyamide (A) based on the total weight of the first polyamide (A) and the second polyamide (B), and R is a ratio of the melt viscosity of the first polyamide (A) to the melt viscosity of the second polyamide (B) at a temperature higher by 20°C than the melting point of that one of the first and second polyamides (A) and (B) which has a higher melting point than the other.

0034To qualitatively explain the above relationship, the above relationship shows that with an increase in the ratio R, the proportion of the first polyamide (A) should be increased and that with a decrease in the ratio R, the proportion of the first polyamide (A) should be decreased.

0035In the present invention, it is preferred to adjust one of the polyamide A or the polyamide B which has a smaller mixing ratio (volumetric ratio) than the other to have a comparatively low melt viscosity in order to obtain a transparent film. Specifically, when the mixing ratio of the polyamide A is smaller (when C is less than about 50 %), R is required to be set in the range which does not exceed the upper limit. When the R exceeds the upper limit, the polyamide A of which the mixing ratio is smaller has too high a melt viscosity, and no film having a low haze can be obtained. The reason for this is considered to be as follows. Since the polyamide A has too high a melt viscosity, the polyamide A is not fully dispersed in the polyamide B, and the polyamide B as a nucleating agent does not work on the polyamide A effectively. The lower limit of R is determined in view of moldability. When R is lower than the lower limit, the flowability of the resin mixture becomes unstable (the rate of outflow from a die is not uniform in the width direction of the die) due to a large difference in melt viscosity between the two polyamides although the resultant film shows low haze. Thus, it is difficult to stably produce a film having a uniform thickness.

0036On the other hand, when the mixing ratio of the polyamide B is smaller (when C is more than about 50 %), R is required to be set in the range which is not lower than the lower limit. When the R is lower than the lower limit, the polyamide B of which the mixing ratio is smaller has too high a melt viscosity, and no film having a low haze can be obtained. The reason for this is considered to be as follows. Since the polyamide B has too high a melt viscosity, the polyamide B is not fully dispersed in the polyamide A, and the effect of the polyamide B as a nucleating agent does not work on the entirety of the mixture. The upper limit of R is determined in view of moldability. When R exceeds the upper limit, the flowability of the resin mixture becomes unstable (the rate of outflow from a die is not uniform in the width direction of the die) due to a large difference in melt viscosity between the two polyamides although the resultant film shows low haze. As a result, it is difficult to stably produce a film having a uniform thickness.

0037In the present invention, the first polyamide (A) preferably shows a relative viscosity between 1.9 and 3.7, and the second polyamide (B) preferably shows a relative viscosity between 2.0 and 4.2. Further, the first polyamide (A) preferably shows a melt viscosity of about 600 to about 30,000 poise at a temperature higher by 20°C than the melting point thereof, and the second polyamide (B) preferably shows a melt viscosity of about 400 to about 17,000 at a temperature which is similarly higher by 20°C than the melting point thereof.

0038The polyamide resin composition of the present invention can give a film having excellent gas-barrier properties, liquid-barrier properties and transparency. Owing to these excellent properties, such a film is suitably usable as a packaging film.

0039Therefore, according to the present invention, there are provided an unstretched film and a biaxially stretched film produced from the polyamide resin composition of the present invention.

0040The above unstretched film of the present invention has its characteristic feature in that the unstretched film as a film having a thickness of 50 µm shows a haze value of not more than 7 %.

0041The unstretched film of the present invention preferably has a thickness of 10 to 100 µm, and more preferably has a thickness of 15 to 80 µm.

0042In this invention, the conversion between the film thickness and the haze value can be made by the following relational equation on the assumption that the Lambert-Beer's law is effected between the quantity of transmission light and the thickness.<maths id="math0003" num=""><math display="block"><mrow><mtext>(log </mtext><mfrac><mrow><mtext>1</mtext></mrow><mrow><mtext>1 - haze value/100</mtext></mrow></mfrac><mtext>)/d = k</mtext></mrow></math><img file="EP0475720A2_D0004.tif" /></maths>    wherein d is the thickness of a film, and k is a constant.

0043That is, the above relational equation is derived from the following two relational equations.<maths id="math0004" num=""><math display="block"><mrow><mtext>Haze value = </mtext><mfrac><mrow><mtext>D</mtext></mrow><mrow><mtext>T</mtext></mrow></mfrac><mtext> x 100 (%)</mtext></mrow></math><img file="EP0475720A2_D0005.tif" /></maths>    wherein D is a quantity of diffuse transmission light, and T is a total quantity of transmission light.<maths id="math0005" num=""><math display="block"><mrow><mtext>log </mtext><mfrac><mrow><mtext>T</mtext></mrow><mrow><mtext>PT</mtext></mrow></mfrac><mtext> = k·d</mtext></mrow></math><img file="EP0475720A2_D0006.tif" /></maths>    wherein T, k and d are as defined above, and PT is a quantity of parallel transmission light and equals a value of T-D.

0044It should be understood that the above conversion between the film thickness and the haze value can apply to that of the biaxially stretched film of the present invention to be described later.

0045The unstretched film of the present invention is obtained from the polyamide resin composition preferably containing 60 to 95 % by weight of the first polyamide (A), provided by the present invention. The unstretched film obtained from this preferred embodiment of the polyamide resin composition also has a haze value of not more than 7 % when it is converted to a film having a thickness of 50 µm.

0046The above unstretched film of the present invention can be produced from the polyamide resin composition of the present invention by a known film-forming method such as a T-die extrusion method, a cylindrical die extrusion method (inflation method), a co-extrusion method, an injection method, a co-injection method, a blow molding method or a combination of these methods.

0047The molding temperature for forming the film is preferably 235 to 300°C, more preferably 245 to 285°C.

0048When the molding temperature exceeds 300°C, the resultant polyamide film is whitened due to water absorption, treatment with hot water or treatment under heat at a temperature equal to or higher than the glass transition temperature, and therefore, the film having excellent transparency intended in the present invention cannot be obtained.

0049When the molding temperature is lower than 235°C, it is difficult to mold the polyamide resin composition into a film since the first polyamide (A) cannot be sufficiently melted.

0050The molding temperature for forming the polyamide film of the present invention refers to a temperature of the polyamide measured at the terminal outlet of a film-forming machine such as an extruder, an injection molding machine or the like, or the temperature of the polyamide measured at the outlet of a die located at the terminal end of a film-forming machine.

0051The residence time for forming the film is preferably not more than 7 minutes, more preferably 0.7 to 5 minutes.

0052The residence time for forming the film in the present invention refers to a period of time from a point of time when a material containing a polyamide mixture is charged into the heat-melting cylinder of a film-forming machine such as an extruder, an injection molding machine or the like through the feed port to a point of time when the polyamide mixture is discharged through the terminal end of a film-producing apparatus.

0053When the residence time exceeds 7 minutes, the resultant polyamide mixture film is liable to be whitened due to water absorption, treatment with hot water or treatment under heat at a temperature equal to or higher than the glass transition temperature, and therefore, the film having excellent transparency intended in the present invention cannot be obtained.

0054When the residence time is less than 0.5 minutes, the mixing of the first polyamide (A) and the second polyamide (B) is sometimes insufficient, although it depends on a film-forming machine used. When the mixing is insufficient, the resultant film shows a high haze value, and moreover, the haze value increases further due to water absorption, treatment with hot water or treatment under heat.

0055The biaxially stretched film of the present invention has a characteristic feature in that it as a film having a thickness of 25 µm has a haze value of not more than 3.5 %.

0056The biaxially stretched film of the present invention preferably has a thickness of 10 to 50 µm, and more preferably has a thickness of 15 to 40 µm.

0057The biaxially stretched film of the present invention is obtained from the polyamide resin composition preferably containing 20 to 60 % by weight of the first polyamide (A), provided by the present invention. The biaxially stretched film obtained from this preferred embodiment of the polyamide resin composition also has a haze value of not more than 3.5 % when it is converted to a film having a thickness of 25 µm.

0058The above biaxially stretched film of the present invention can be produced by any one of known stretching methods such as a tenter method, a double bubble method, a roll stretching method, a rolling method, etc.

0059The unstretched film and stretched film of the present invention can be also used as a constituent of a multi-layer film or a multi-layer structure, which are formed by a laminating method such as an extrusion laminating method, a dry laminating method, etc.

0060Therefore, according to the present invention, there is provided an unstretched multi-layer film and a biaxially stretched multi-layer film, each of which is composed of layer(s) of the polyamide resin composition of the present invention and layer(s) of other thermoplastic resin(s).

0061The unstretched multi-layer film of the present invention preferably has a layer composed of the polyamide resin composition of the present invention which contains 60 to 95 % by weight of the first polyamide (A).

0062The "other thermoplastic resin(s)" described above is preferably selected, for example, from polyolefins, polycarbonates, polyesters, styrene polymers and polyamides. Preferred as a polyolefin are, for example, polyethylene and polypropylene. Preferred as a polycarbonate is a bisphenol A type polycarbonate. Preferred as a polyester is polyethylene terephthalate. Preferred as a styrene polymer is polystyrene, and preferred as a polyamide are those which are usable as a second polyamide (B) in the composition of the present invention. Of the above thermoplastic resins, particularly preferred are the polyolefin, polycarbonate, polyethylene terephthalate and polyamide usable as a second polyamide (B).

0063The above unstretched multi-layer film of the present invention can be produced by co-extruding the polyamide resin composition of the present invention and other thermoplastic resin with a known apparatus, or it can be also produced by separately preparing unstretched film(s) produced from the polyamide resin composition of the present invention and unstretched film(s) produced from other thermoplastic resin, and adhering these films to each other via an adhesive layer.

0064The biaxially stretched multi-layer film of the present invention preferably has a layer composed of the polyamide resin composition of the present invention which contains 20 to 60 % by weight of the first polyamide (A).

0065The biaxially stretched multi-layer film can be produced, for example, by biaxially stretching the above-produced unstretched multi-layer film, i.e. one obtained by co-extruding the above resins or adhering the above films via an adhesive layer.

0066The present invention is more specifically described hereinbelow by reference to Examples.

0067The evaluation methods used in Examples and Comparative Examples are as follows.

(1) Melt viscosity:

0068Measured with a capillary rheometer (flow tester CFT-50, supplied by Shimadzu Corporation).

0069Capillary dimension: diameter 1 mm⌀, length 10 mm, pressure 10 kg/cm².

0070Relative viscosity:    1 Gram of a sample was dissolved in 100 ml of 96 % sulfuric acid, and the measurement was conducted at 25°C with a Cannon-Fenske type viscometer. The relative viscosity was calculated on the basis of the following equation.<maths id="math0006" num=""><math display="block"><mrow><mtext>Relative viscosity = </mtext><mfrac><mrow><mtext>Time (second) required for dropping of sulfuric acid solution of polymer</mtext></mrow><mrow><mtext>Time (second) required for dropping of sulfuric acid</mtext></mrow></mfrac></mrow></math><img file="EP0475720A2_D0007.tif" /></maths>

(2) Semicrystallization time:

0071Measured according to a depolarized light intensity method with a crystallization rate measuring apparatus (MK701, supplied by Kotaki Seisakusho) under the following conditions.

0072Temperature for melting a sample: temperature by 15°C higher than the melting point

0073Time for melting a sample: 3 minutes

0074Temperature of a crystallizing bath: 160°C

(3) Solubility parameter (SP)

0075Calculated from the following equation, on the basis of Small's constant described on "The Technology of Plasticizers", p.97 (written by J. Kern Sears and Joseph R. Darby and issued in 1982).<maths id="math0007" num=""><math display="block"><mrow><mtext>SP = </mtext><mfrac><mrow><mtext>ΣF</mtext></mrow><mrow><mtext>V</mtext></mrow></mfrac></mrow></math><img file="EP0475720A2_D0008.tif" /></maths><dl id="dl0001"><dt>F:</dt><dd>Small's molar-attraction constant</dd><dt>V:</dt><dd>Molar volume (cm³/mol)</dd></dl>

(4) Oxygen permeability

0076Measured according to ASTM D3985 with an oxygen permeability measuring apparatus (model: OX-TRAN 10/50A, supplied by Modern Controls Co., Ltd.) under the following conditions.

0077Temperature: 23°C, Relative humidity (RH) 60 % or 100 %.

(5) Haze:

0078Measured according to ASTM D1003 with a color-difference meter (Z- Σ80, supplied by Nippon Denshoku Kogyo K.K.) under the following conditions.

0079Conditions for hot water treatment: Immersion in boiling water for 30 minutes.

Example 1

0080Pellets of nylon MXD6 (hereinafter sometimes simply abbreviated as N-MXD6) (relative viscosity: 3.6) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 80/20 (by weight) (melt viscosity ratio: 1.7, measured at 260°C). This pellet mixture was melted and kneaded at 260°C with a single-screw extruder (screw diameter: 90 mm⌀, L/D: 35, a screw type: full flighted), and then extruded onto a running metal belt. The extrudate was cooled in a strand form, and cut with a rotary cutter to obtain pellets of the polyamide mixture.

0081Then, this polyamide mixture was extruded with a single-screw extruder (screw diameter: 20 mm⌀, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C, at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0082Table 1 shows the performances of the resultant film. The composition of the starting materials is also shown in Table 1.

Examples 2 and 3, and Comparative Examples 1 and 2

0083A combination of pellets of nylon MXD6 and nylon 6 of which the melt viscosity ratio was different from that in Example 1 was processed in the same manner as in Example 1 to prepare pellets of a polyamide mixture of which the mixing ratio is shown in Table 1 (Examples) and in Table 2 (Comparative Examples). That is, the nylon MXD6 used was one having a relative viscosity of 3.6, which was the same as that used in Example 1, or nylon MXD6 having a relative viscosity of 2.6. The nylon 6 used was the one having a relative viscosity of 4.1, which was the same as that used in Example 1, the one having a relative viscosity of 2.2, or the one having a relative viscosity of 3.5. Then, films were produced from the pelletized polyamide mixtures in the same manner as in Example 1.

0084Tables 1 and 2 show also the performances of the above-obtained films.

Comparative Example 3

0085A film having a width of about 120 mm and a thickness of 0.05 mm was prepared from the same nylon MXD6 as that used in Example 1 in the same manner as in Example 1 with a single-screw extruder (screw diameter 20 mm⌀, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C, at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C. Table 2 shows the performances of the film and composition of the starting materials.

Examples 4 - 6 and Comparative Example 4

0086Pellets of the same nylon MXD6 as that used in Example 1 and pellets of the same nylon 6 as that used in Example 1 were mixed with a tumbler in the mixing ratio shown in Table 1 or Table 2 to prepare pellet mixtures.

0087Then, these polyamide mixtures were separately extruded with a single-screw extruder (screw diameter: 20 mm⌀, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C, at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C, whereby films having a width of about 120 mm and a thickness of about 0.05 mm were obtained. Table 1 shows the performances of the films (obtained in Examples) and compositions of the materials, and Table 2 shows the performances of the film (obtained in Comparative Example) and composition of the materials. <tables id="tabl0001" num="0001"><img file="EP0475720A2_D0009.tif" /></tables><tables id="tabl0002" num="0002"><img file="EP0475720A2_D0010.tif" /></tables>

Example 7

0088Pellets of nylon MXD6 (relative viscosity: 3.0) and pellets of nylon 66 (relative viscosity: 2.4) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 66 blend ratio of 90/10 (by weight) (melt viscosity ratio: 27.4, measured at 285°C).

0089Then, this polyamide pellet mixture was extruded with a single-screw extruder (screw diameter : 20 mm⌀, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C, at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 120 mm and a thickness of about 53 µm was obtained.

0090The above-obtained film showed a haze value of 1.1 %, and it was treated with hot water to show a haze value of 5.9 %. Thus, it retained the initial excellent transparency. Table 3 shows the composition of the starting materials and the results.

Comparative Example 5

0091A film having a thickness of 30 µm was obtained from the same nylon MXD6 as that used in Example 7 in the same manner as in Example 7. The so-obtained film showed a haze value of 2.3 %, and was treated with hot water to show a haze value of 46.8 %, and a clear whitening was observed. Table 4 shows the composition of the starting material and the results.

Example 8

0092Pellets of nylon MXD6 (relative viscosity: 2.6) and pellets of nylon 66 (relative viscosity: 3.3) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 66 blend ratio of 40/60 (by weight) (melt viscosity ratio: 0.7, measured at 285°C).

0093Then, this pellet mixture was melted and kneaded with a single-screw extruder (screw diameter : 20 mm, L/D: 25, screw type: full flighted) at a temperature of 275°C, and extruded according to T-die method to give a sheet having a thickness of 225 µm.

0094In the above process, the resin temperature at an outlet of the die was 273°C, and the residence time was 1.8 minutes.

0095The above-obtained sheet (90 mm x 90 mm) was heated at 100°C for 5 seconds and then simultaneously biaxially stretched at a stretch ratio of 3 x 3 at a stretch rate of 3 m/minute with a biaxially stretching machine (according to a tenter method, supplied by Toyo Seiki K.K.).

0096The resultant stretched film had a thickness of 25 µm, and showed a haze value of 3.0 %.

0097Further, the above stretched film was thermoset in an atmosphere at 260°C for 5 seconds. The thermoset film was subjected to a hot water treatment (30 minutes/immersion in boiling water) to show a haze value of 3.2 %.

0098Thus, the stretched film had excellent transparency. Table 3 shows the composition of the starting materials and the results.

Comparative Example 6

0099Pellets of nylon MXD6 (relative viscosity: 3.6) and pellets of nylon 66 (relative viscosity: 2.8) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 66 blend ratio of 40/60 (by weight) (melt viscosity ratio: 10.0, measured at 285°C).

0100Then, this pellet mixture was melted and mixed with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) at a temperature of 275°C, and extruded according to T-die method to give a sheet having a thickness of 220 µm.

0101In the above process, the resin temperature at an outlet of the die was 275°C, and the residence time was 1.8 minutes. The above-obtained sheet (90 mm x 90 mm) was heated at 100°C for 5 seconds and then simultaneously biaxially stretched at a stretch ratio of 3 x 3 at a stretch rate of 3 m/minute with a biaxially stretching machine (according to a tenter method, supplied by Toyo Seiki K.K.).

0102The resultant stretched film having a thickness of 25 µm showed a haze value of 5.3 %, which was inferior in transparency to that of the film obtained in Example 8. Table 4 shows the composition of the starting material and the results.

Example 9

0103Pellets of nylon MXD6 (relative viscosity: 3.6) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 40/60 (by weight) (melt viscosity ratio: 1.7, measured at 260°C).

0104Then, this pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C at a T-die temperature of 260°C at a screw revolution rate of 60 rpm and at a cooling roll temperature of 60°C, whereby a sheet having a width of 120 cm and a thickness of 230 µm was obtained.

0105In the above process, the resin temperature at an outlet of the die was 269°C, and the residence time was 2.3 minutes.

0106Then, the above-obtained sheet (90 mm x 90 mm) was heated at 85°C for 20 seconds and then simultaneously biaxially stretched at a stretch ratio of 3 x 3 at a stretch rate of 3 m/minute with a biaxially stretching machine (according to a tenter method, supplied by Toyo Seiki K.K.).

0107The resultant stretched film had a thickness of 25 µm, and showed a haze value of 3.0 %.

0108Further, the above stretched film was thermoset in an atmosphere at 250°C for 5 seconds. The thermoset film was subjected to a hot water treatment (30 minutes/immersion in boiling water) to show a haze value of 2.8 %. Thus, the stretched film had excellent transparency. Table 3 shows the composition of the starting materials and the results.

Example 10

0109Pellets of nylon MXD6 (relative viscosity: 3.6) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 80/20 (by weight) (melt viscosity ratio: 1.7, measured at 260°C).

0110This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 260°C and 270°C at a T-die temperature of 260°C at a screw revolution rate of 90 rpm and at a cooling roll temperature of 60°C, whereby a sheet having a width of 120 cm and a thickness of 230 µm was obtained.

0111In the above process, the resin temperature at an outlet of the die was 269°C, and the residence time was 1.8 minutes.

0112Then, the above-obtained sheet (90 mm x 90 mm) was heated at 85°C for 20 seconds and then simultaneously biaxially stretched at a stretch ratio of 3 x 3 at a stretch rate of 3 m/minute with a biaxially stretching machine (according to a tenter method, supplied by Toyo Seiki K.K.).

0113The resultant stretched film had a thickness of 25 µm, and showed a haze value of 3.2 %.

0114Further, the above stretched film was thermoset in an atmosphere at 250°C for 5 seconds. The thermoset film was subjected to a hot water treatment (30 minutes/immersion in boiling water) to show a haze value of 3.3 %. Thus, the stretched film had excellent transparency. Table 3 shows the composition of the starting materials and the results.

Comparative Example 7

0115Pellets of nylon MXD6 (relative viscosity: 2.6) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 80/20 (by weight) (melt viscosity ratio: 0.4, measured at 260°C).

0116This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 260°C and 270°C at a T-die temperature of 260°C at a screw revolution rate of 90 rpm and at a cooling roll temperature of 60°C, whereby a sheet having a width of 120 cm and a thickness of 500 µm was obtained.

0117In the above process, the resin temperature at an outlet of the die was 260°C, and the residence time was 1.8 minutes.

0118Then, the above-obtained sheet (90 mm x 90 mm) was heated at 85°C for 20 seconds and then simultaneously biaxially stretched at a stretch ratio of 3 x 3 at a stretch rate of 3 m/minute with a biaxially stretching machine (according to a tenter method, supplied by Toyo Seiki K.K.).

0119The resultant stretched film having a thickness of 45 µm showed a haze value of 16.3 % and it was inferior in transparency to that of the film obtained in Example 10. Table 4 shows the composition of the starting materials and the results. <tables id="tabl0003" num="0003"><img file="EP0475720A2_D0011.tif" /></tables><tables id="tabl0004" num="0004"><img file="EP0475720A2_D0012.tif" /></tables>

Example 11

0120Pellets of nylon MXD6 (relative viscosity: 3.56) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 80/20 (by weight) (melt viscosity ratio: 1.7).

0121This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0122In the above process, the resin temperature at an outlet of the die was 270°C, and the residence time was 3 minutes.

0123The above-obtained film had excellent transparency.

0124Table 5 shows the composition of the starting materials, the film-forming conditions and the results.

Example 12

0125Pellets of nylon MXD6 (relative viscosity: 3.56) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 80/20 (by weight) (melt viscosity ratio: 1.7).

0126This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 270°C and 290°C at a T-die temperature of 290°C at a screw revolution rate of 42 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0127In the above process, the resin temperature at an outlet of the die was 288°C, and the residence time was 2.8 minutes.

0128The above-obtained film had excellent transparency.

0129Table 5 shows the composition of the starting materials, the film-forming conditions and the results.

Comparative Example 8

0130Pellets of nylon MXD6 (relative viscosity: 3.56) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 80/20 (by weight) (melt viscosity ratio: 1.7).

0131This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 270°C and 290°C at a T-die temperature of 290°C at a screw revolution rate of 42 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 125 mm and a thickness of about 0.10 mm was obtained.

0132In the above process, the resin temperature at an outlet of the die was 288°C, and the residence time was 2.8 minutes.

0133In order to prepare a film sample obtained under a longer residence time, the above-obtained film was crushed to such small pieces that they could be fed to an extruder, and extruded with the same extruder under the same conditions to form a film.

0134This film was again crushed into small pieces, and extruded for the third time to form a film.

0135Upon the third extrusion, the total residence time was 8.2 minutes. Table 6 shows the haze value and oxygen permeability of the film obtained by the third extrusion together with the composition of the starting materials and the film-forming conditions.

Comparative Example 9

0136Pellets of nylon MXD6 (relative viscosity: 2.64) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 80/20 (by weight) (melt viscosity ratio: 0.39).

0137This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0138In the above process, the resin temperature at an outlet of the die was 268°C, and the residence time was 3 minutes.

0139The above-obtained film had a higher haze value than that obtained in Example 12, and it was also treated with hot water to show a higher haze than that treated with hot water in Example 12.

0140Table 6 shows the composition of the starting materials and the film-forming conditions.

Example 13

0141Pellets of nylon MXD6 (relative viscosity: 3.56) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 40/60 (by weight) (melt viscosity ratio: 1.7).

0142This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0143In the above process, the resin temperature at an outlet of the die was 269°C, and the residence time was 3 minutes.

0144The above-obtained film had excellent transparency.

0145Table 5 shows the composition of the starting materials, the film-forming conditions and the results.

Example 14

0146Pellets of nylon MXD6 (relative viscosity: 2.64) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 40/60 (by weight) (melt viscosity ratio: 0.39).

0147This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0148In the above process, the resin temperature at an outlet of the die was 270°C, and the residence time was 3 minutes.

0149The above-obtained film had excellent transparency, and the degree of the increase in the haze value after the hot water treatment was small.

0150Table 5 shows the composition of the starting materials, the film-forming conditions and the results.

Example 15

0151Pellets of nylon MXD6 (relative viscosity: 3.56) and pellets of nylon 6 (relative viscosity: 3.5) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 60/40 (by weight) (melt viscosity ratio: 3.1).

0152This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0153In the above process, the resin temperature at an outlet of the die was 269°C, and the residence time was 3 minutes.

0154The above-obtained film had excellent transparency, and the degree of an increase in the haze value after the hot water treatment was small.

0155Table 5 shows the composition of the starting materials, the film-forming conditions and the results.

Comparative Example 10

0156Pellets of nylon MXD6 (relative viscosity: 2.10) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 60/40 (by weight) (melt viscosity ratio: 1.7).

0157It was attempted to form a film from the above pellet mixture with the same extruder as that used in Example 15 under the same conditions as those in Example 15. However, no film having a uniform thickness could be formed.

0158In the above process, the resin temperature at an outlet of the die was 268°C, and the residence time was 3 minutes.

0159Table 6 shows the composition of the starting materials, the film-forming conditions and the results.

Comparative Example 11

0160Pellets of nylon MXD6 (relative viscosity: 2.64) and pellets of nylon 6 (relative viscosity: 2.22) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 40/60 (by weight) (melt viscosity ratio: 10).

0161This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 75°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0162In the above process, the resin temperature at an outlet of the die was 270°C, and the residence time was 3 minutes.

0163The above-obtained film had a higher haze value than that obtained in Example 1, and the degree of an increase in the haze value after the hot water treatment was larger.

0164Table 6 shows the composition of the starting materials, the film-forming conditions and the results.

Example 16

0165Pellets of nylon MXD6 (relative viscosity: 2.64) and pellets of nylon 6 (relative viscosity: 3.5) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 20/80 (by weight) (melt viscosity ratio: 0.77).

0166This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 245°C and 260°C at a T-die temperature of 260°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 65°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0167In the above process, the resin temperature at an outlet of the die was 258°C, and the residence time was 3 minutes.

0168The above-obtained film had excellent transparency.

0169Table 5 shows the composition of the starting materials, the film-forming conditions and the results.

Example 17

0170Pellets of nylon MXD6 (relative viscosity : 2.64) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 20/80 (by weight) (melt viscosity ratio: 0.39).

0171This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 265°C and 270°C at a T-die temperature of 270°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 65°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0172In the above process, the resin temperature at an outlet of the die was 269°C, and the residence time was 3 minutes.

0173The above-obtained film had excellent transparency, and the degree of an increase in the haze value after the hot water treatment was small.

0174Table 5 shows the composition of the starting materials, the film-forming conditions and the results.

Comparative Example 12

0175Pellets of nylon MXD6 (relative viscoslty: 3.56) and pellets of nylon 6 (relative viscosity: 4.1) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 6 blend ratio of 20/80 (by weight) (melt viscosity ratio: 1.7).

0176This pellet mixture was extruded with a single-screw extruder (screw diameter: 20 mm, L/D: 25, screw type: full flighted) according to a T-die method at a cylinder temperature between 245°C and 260°C at a T-die temperature of 260°C at a screw revolution rate of 40 rpm and at a cooling roll temperature of 65°C, whereby a film having a width of about 120 mm and a thickness of about 0.05 mm was obtained.

0177In the above process, the resin temperature at an outlet of the die was 259°C, and the residence time was 3 minutes.

0178The above-obtained film had a higher haze value than those obtained in Examples 10 and 11, and it was treated with hot water to show a higher haze value than those obtained in Examples 10 and 11.

0179Table 6 shows the composition of the starting materials, the film-forming conditions and the results.

Example 18

0180Pellets of nylon MXD6 (relative viscosity : 3.56) and pellets of nylon 66 (relative viscosity: 3.31) were mixed with a tumbler to prepare a pellet mixture having a nylon MXD6/nylon 66 blend ratio of 85/15 (by weight) (melt viscosity ratio: 2.70).

0181This pellet mixture was mixed and melted at 275°C with a single-screw extruder (screw diameter: 40 mm, L/D: 22, screw type: full flighted), and formed into a film having a thickness of 32 µm through a ring die according to an air-cooling inflation method.

0182In the above process, the resin temperature at the outlet of the die was 273°C, and the residence time was 2.5 minutes.

0183The above-obtained film showed a haze value of 2.5 %, and it was immersed in boiling water for 30 minutes to show a haze value of 4.9 %. Thus, the initial good transparency was well retained.

0184A film having a thickness of 30 µm was formed from nylon MXD6 (relative viscosity 3.56) in the same manner as above. This film showed a haze value of 2.3 %, and it was treated with hot water to show a haze value of 46.8 %. Thus, a whitening was clearly observed.

0185Table 5 shows the composition of the starting materials, the film-forming conditions and the results. <tables id="tabl0005" num="0005"><img file="EP0475720A2_D0013.tif" /></tables><tables id="tabl0006" num="0006"><img file="EP0475720A2_D0014.tif" /></tables><tables id="tabl0007" num="0007"><img file="EP0475720A2_D0015.tif" /></tables>