WO2006129379A1

WO2006129379A1 - Gas barrier polymer material, production method thereof, and packaging material using the gas barrier polymer material

Info

Publication number: WO2006129379A1
Application number: PCT/JP2005/010438
Authority: WO
Inventors: Kikuo Arimoto; Keisuke Morikawa; Nobuhiro Moriguchi; Hiroyuki Ohgi
Original assignee: Kuraray Co., Ltd.
Priority date: 2005-05-31
Filing date: 2005-05-31
Publication date: 2006-12-07

Abstract

Provision of a gas barrier polymer material capable of expressing sufficiently high oxygen barrier property even without addition of a nucleating agent and the like, and a production method capable of producing the same with high reproducibility, as well as a packaging material using such a gas barrier polymer material.The gas barrier polymer material of the present invention comprises a hydroxyl group-containing gas barrier polymer mainly comprising a structural unit represented by the following formula (I): wherein m and n are each an integer of 0 to 10; X1 and X2 are each a hydrogen atom, a hydroxyl group or a functional group convertible to a hydroxyl group, provided that the total of m and n is not less than 1 and at least one of X1 and X2 is a hydroxyl group or a functional group convertible to a hydroxyl group; R1, R2 and R3 are each a hydrogen atom, a hydroxyl group, a functional group convertible to a hydroxyl group, an alkyl group, an aryl group, an aralkyl group or a heteroaryl group; and R1, R2, R3, X1 and X2 present in plurality are optionally the same as or different from each other, and shows a crystal-amorphous structure period of not less than 1 m as determined by a light scattering method.

Description

GAS BARRIER POLYMER MATERIAL, PRODUCTION METHOD THEREOF, AND PACKAGING MATERIAL USING THE GAS BARRIER POLYMER MATERIAL

Technical Field The present invention relates to a gas barrier polymer material, a production method thereof and a packaging material. More particularly, the present invention relates to a gas barrier polymer material showing extremely high gas barrier property conventionally unattainable, a production method thereof, and a packaging material using the gas barrier polymer material.

Background Art

A polymer having a functional group such as hydroxyl group and the like in a molecule shows various properties derived from the functional group, such as hydrophilicity, adhesion property, gas barrier property and the like and, depending on the properties, can be used as a constituent component of various functional packaging materials, various functional molding materials, various sheets, films, fibers, various coatings, various functional alloys and blends, and the like. As such polymer, various types are known and, in recent years, as one of such polymers, a polymer is known, which is obtained by hydrogenation, in the presence of a hydrogenation catalyst such as palladium carbon and the like, of a polymer represented by the formula (II) :

(ID wherein X and Y are each a hydroxyl group, a carboxyl group, a carboxylic acid ester group, an amido group, a nitrile group or a carbonyl group, R is an alkyl group having 1 to 5 carbon atoms or the above-mentioned X, a and b are each an integer of 0 to 6 and a+b is 2-7, which is obtained by ring-opening matathesis polymerization of C7-C12 cycloalkene having a functional group, such as 5-cyclooctene-l,2-diol and the like. Particularly, it is known that, when X and Y in the formula are both hydroxyl groups, the polymer is useful as a constituent component of packaging materials having high oxygen barrier property (WO99/50331 and WO00/18579) .

Basically, the gas barrier property of polymer shows values specific to each chemical species such as polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), ethylene-vinyl alcohol copolymer (EVOH) and the like. In the case of polymers belonging to the same chemical species (having the same molecular weight, molecular weight distribution, branch degree and the like) , crystalline polymers are superior to noncrystalline polymers in the gas barrier property. However, due to tangles characteristic of polymers, a single crystal material having homogeneous property in the entirety thereof cannot be obtained, and polymers generally show a high order structure wherein a crystal phase, an amorphous phase and an intermediate phase are entangled. Heretofore, for the purpose of improving mechanical strength of polymers, a technique for controlling high order structures of a crystal phase, an amorphous phase and an intermediate phase has been proposed (JP-A-2000-248128) . As the situation stands, as a technique for modifying a polymer itself for the purpose of improving gas barrier property of the polymer, the proportion of crystal phase is increased, namely, a nucleating agent and the like are added to improve the degree of crystallinity (JP-A-2002-69320) . However, use of additives such as nucleating agent and the like is not desirable in view of the environmental problems and extra steps that become necessary, and, what is more, the modification effect afforded thereby is not entirely sufficient.

Disclosure of the Invention A material used as a constituent component of packaging materials for various foods, beverages, pharmaceutical products and the like is required to have particularly high oxygen barrier property. The problem of the present invention is to provide a gas barrier polymer material capable of expressing sufficiently high oxygen barrier property even without addition of a nucleating agent and the like, and a production method capable of producing the same with high reproducibility, as well as a packaging material using such a gas barrier polymer material.

The present inventors have conducted intensive studies in an attempt to solve the above-mentioned problem and found that a heat treatment of a molten product of a hydroxyl group-containing gas barrier polymer under given temperature conditions markedly extends its crystal-amorphous structure period, which in turn strikingly improves the gas barrier property thereof, and further studied based on the findings, which resulted in the completion of the present invention.

Accordingly, the present invention relates to

(1) a gas barrier polymer material comprising a hydroxyl group- containing gas barrier polymer mainly comprising a structural unit represented by the following formula (I) :

wherein m and n are each an integer of 0 to 10; X¹ and X² are each a hydrogen atom, a hydroxyl group or a functional group convertible to a hydroxyl group, provided that the total of m and n is not less than 1 and at least one of X¹ and X² is a hydroxyl group or a functional group convertible to a hydroxyl group;

R- ^■, R² and R^{3 '} are each a hydrogen atom, a hydroxyl group, a functional group convertible to a hydroxyl group, an alkyl group, an aryl group, an aralkyl group or a heteroaryl group; and R¹/ R², R³, X¹ and X² present in plurality are optionally the same as or different from each other, which material shows a crystal-amorphous structure period of not less than 1 μm as determined by a light scattering method,

(2) the gas barrier polymer material of the above-mentioned (1) , wherein the amount of oxygen permeation at 20⁰C, 90%RH is not more than 1 cc*20 μm/ m^2>dayatm,

(3) a packaging material comprising a gas barrier polymer material of the above-mentioned (1) or (2),

(4) a production method of a gas barrier polymer material comprising a hydroxyl group-containing gas barrier polymer, which comprises Step A comprising cooling a molten product of the hydroxyl group-containing gas barrier polymer or a resin composition comprising the hydroxyl group-containing gas barrier polymer to a temperature within the range of from a temperature lower than the melting point of the hydroxyl group-containing gas barrier polymer by 100⁰C (Tm-IOO⁰C) to the melting point (Tm⁰C) and retaining the molten product within the aforementioned temperature range for not less than 2 minutes, wherein the hydroxyl group-containing gas barrier polymer mainly comprises a structural unit represented by the following formula (I) :

wherein m and n are each an integer of 0 to 10;

X¹ and X² are each a hydrogen atom, a hydroxyl group or a functional group convertible to a hydroxyl group, provided that the total of m and n is not less than 1 and at least one of X¹ and X² is a hydroxyl group or a functional group convertible to a hydroxyl group; R¹, R² and R³ are each a hydrogen atom, a hydroxyl group, a functional group convertible to a hydroxyl group, an alkyl group, an aryl group, an aralkyl group or a heteroaryl group; and R¹, R², R³, X¹ and X² present in plurality are optionally the same as or different from each other, and

(5) the production method of the above-mentioned (4), which further comprises, after Step A, performing crystallization at any temperature (Step B) . Since the gas barrier polymer material of the present invention has a specific high order structure with markedly large crystal-amorphous structure period, it shows high gas barrier property that conventional gas barrier polymer materials of the same chemical species (gas barrier polymer materials substantially the same in polymer species thereof (the kind of structural unit (monomer) ) , composition, molecular weight, molecular weight distribution, branch degree and the like) have failed to achieve.

According to the production method of a gas barrier polymer material of the present invention, a gas barrier polymer material having sufficiently high gas barrier property can be easily produced.

Conventionally, for example, when a polymer material of a packaging material shows insufficient gas barrier property by itself, a gas barrier layer, such as an aluminum foil, an aluminum vapor deposition layer, a silicon oxide vapor deposition layer and the like, has been formed. Since the gas barrier polymer material of the present invention shows extremely high gas barrier property, the present invention can solve the defect that lamination of an aluminum foil, an aluminum vapor deposition layer, a silicon oxide vapor deposition layer and the like conceals the contents of packages and a problem of lower disposability of packaging materials and the like.

Brief Description of the Drawings

Fig. 1 shows the results of light scattering measurement of the hydrogenated poly (5-cyclooctene-l,2-diol) of Examples 1, 2 and Comparative Examples 1 - 3. Fig. 2 shows the results of light scattering measurement of ethylene-vinyl alcohol copolymers (EVMJ-G) of Comparative Examples 4 - 6.

Best Mode for Embodying the Invention

The present invention is explained in more detail in the following.

The gas barrier polymer material of the present invention mainly comprises a hydroxyl group-containing gas barrier polymer and is characterized by a crystal-amorphous structure period of not less than 1 μm as determined by a light scattering method. The hydroxyl group-containing gas barrier polymer to be used in the present invention comprises a main structural unit represented by the following formula (I) :

wherein m and n are each an integer of 0 to 10;

X¹ and X² are each a hydrogen atom, a hydroxyl group or a functional group convertible to a hydroxyl group, provided that the total of m and n is not less than 1 and at least one of X¹ and X² is a hydroxyl group or a functional group convertible to a hydroxyl group/ R¹, R² and R³ are each a hydrogen atom, a hydroxyl group, a functional group convertible to a hydroxyl group, an alkyl group, an aryl group, an aralkyl group or a heteroaryl group; and

R¹, R², R³, X¹ and X² present in plurality are optionally the same as or different from each other.

In the above-mentioned formula (I) , X¹ and X² are each a hydrogen atom, a hydroxyl group or a functional group convertible to a hydroxyl group. However, at least one of X¹ and X² is a hydroxyl group or a functional group convertible to a hydroxyl group. When X¹ and X² are present in plurality, they may be the same as or different from each other. As the above-mentioned functional group convertible to a hydroxyl group, for example, an epoxy group, a hydroxyl group protected by a protecting group and the like can be mentioned. As the epoxy group, a 3-membered ring structure consisting of a carbon atom bonded to X¹, a carbon atom bonded to X² and an oxygen atom can be mentioned.

As the above-mentioned hydroxyl-protecting group, for example, alkyl groups such as methyl group, ethyl group, t-butyl group and the like; alkenyl groups such as allyl group and the like; aralkyl groups such as benzyl group and the like; aryl groups such as phenyl group and the like; alkoxyalkyl groups such as methoxymethyl group, methoxyethyl group, ethoxyethyl group and the like; acyl groups such as acetyl group, propionyl group, benzoyl group and the like; alkoxycarbonyl groups such as methoxycarbonyl group, ethoxycarbonyl group, t-butoxy carbonyl group, phenyloxycarbonyl group, benzyloxycarbonyl group and the like; silyl groups such as trimethylsilyl group, t- butyldimethylsilyl group and the like; and the like can be mentioned. .

Of these, alkoxyalkyl groups such as iαethoxymethyl group, methoxyethyl group, ethoxyethyl group and the like; acyl groups such as acetyl group, propionyl group, benzoyl group and the like; alkoxycarbonyl groups such as methoxycarbonyl group, ethoxycarbonyl group, t-butoxycarbonyl group, phenyloxycarbonyl group, benzyloxycarbonyl group and the like; hydroxyl group protected by silyl group, such as trimethylsilyl group, t- butyldimethylsilyl group and the like; and the like can be preferably used, because protection and deprotection are easy. Particularly, since economical industrial preparation is available, acyl groups such as acetyl group, propionyl group, benzoyl group and the like are more preferable.

In the above-mentioned formula (I) , X¹ and X² are each preferably a hydroxyl group and/or a functional group convertible to a hydroxyl group.

In the above-mentioned formula (I) , R¹, R² and R³ are each a hydrogen atom, a hydroxyl group, a functional group convertible to a hydroxyl group, an alkyl group, an aryl group, an aralkyl group or a heteroaryl group. When R¹, R² and R³ are present in plurality, they may be the same as or different from each other.

As the functional group convertible to a hydroxyl group for R¹, R² or R³, for example, those exemplified as the functional group convertible to a hydroxyl group for the above-mentioned X¹ or X² can be mentioned. As the alkyl group for R¹, R² or R³, an alkyl group having

1 to 5 carbon atoms is preferable. As such alkyl group, for example, fatty chain alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, n-pentyl group and the like; alicyclic alkyl groups such as cyclopentyl group and the like; and the like can be mentioned.

As the aryl group for R¹, R² or R³, for example, phenyl group, naphthyl group, biphenyl group, phenanthryl group, anthryl group, triphenylenyl group, pyrenyl group and the like can be mentioned.

As the aralkyl group for R¹, R² or R³, for example, benzyl group, phenethyl group, naphthylmethyl group, biphenylmethyl group and the like can be mentioned. As the heteroaryl group for R¹, R² or R³, for example, pyridyl group, quinolyl group, isoquinolyl group, pyrrolyl group, indolyl group, furyl group, benzofuranyl group, thienyl group, benzothiophenyl group and the like can be mentioned.

The hydroxyl group-containing gas barrier polymer to be used in the present invention preferably comprises a hydroxyl group or a functional group convertible to a hydroxyl group in a proportion of 1-500 mol%, more preferably 1-300 mol%, relative to the total mol amount of the repeat unit constituting the polymer.

Furthermore, the hydroxyl group-containing gas barrier polymer to be used in the present invention may consist only of a structural unit represented by the above-mentioned formula (I) or may comprise a structural unit other than the structural unit represented by the above-mentioned formula (I) . As the structural unit other than the structural unit represented by the above-mentioned formula (I) , for example, straight chain alkylene groups such as tetramethylene-l,4-diyl group, pentamethylene-1, 5- diyl group, heptamethylene-l,7-diyl group, octamethylene-1, 8-diyl group and the like; branched chain alkylene groups such as 2- methylpentane-l,5-diyl group, 3-methylpentane-l,5-diyl group and the like; alkylene groups having a ring structure such as cyclopentane-l,3-dimethylenediyl group and the like; and the like can be mentioned.

While the content of the structural unit represented by the above-mentioned formula (I) in the hydroxyl-containing gas barrier polymer to be used in the present invention is not particularly limited, it is preferably not less than 50 mol%, more preferably not less than 70 mol%, particularly preferably not less than 80 mol%, relative to the entire structural units constituting the polymer.

While the molecular weight of the hydroxyl group- containing gas barrier polymer to be used in the present invention is not particularly limited, the number average molecular weight (Mn) is preferably within the range of 1,000- 1,000,000, more preferably 1,000-200,000, still more preferably 1,000-80,000. When the number average molecular weight (Mn) is not more than 1,000,000, the polymer has suitable melt moldability. When the number average molecular weight (Mn) is less than 1,000, the mecanical strength becomes poor and film forming tends to be unattainable. As used herein, by the average molecular weight (Mn) is meant a value obtained by dissolving a hydroxyl group-containing gas barrier polymer in a solvent capable of dissolving the polymer, analyzing by gel permeation chromatography (GPC) and converting with poly(methyl methacrylate) as a standard substance.

The hydroxyl group-containing gas barrier polymer to be used in the present invention can be produced by a known production method. As examples thereof, a method according to a method comprising subjecting cyclic olefins containing at least one kind of cyclic olefin having a hydroxyl group or a functional group convertible to a hydroxyl group, to ring-opening polymerization in the presence of a metal alkylidene complex having a ligand with an imidazolidine structure (WO00/71554) , and subjecting the obtained unsaturated polymer to hydrogenation and the like can be mentioned (JP-A-2002-338621) .

The gas barrier polymer material of the present invention comprises the above-mentioned hydroxyl group-containing gas barrier polymer. The content of the hydroxyl group-containing gas barrier polymer in the gas barrier polymer material of the present invention is preferably within the range of 80-100 wt%, more preferably within the range of 90-100 wt%, still more preferably within the range of 95-100 wt%.

The gas barrier polymer material of the present invention can contain components other than the hydroxyl group-containing gas barrier polymer as long as the effect of the invention is not impaired. That is, the material can be a composition (resin composition) containing a hydroxyl group-containing gas barrier polymer and components other than the hydroxyl group-containing gas barrier polymer. As such components, for example, conventionally known additives such as heat stabilizer, antioxidant, UV absorber, weather stabilizer, plasticizer, coloring agent, mold releasing agent, lubricant, flavoring, filler, surfactant and the like, and the like can be mentioned. The content of these components in the composition (resin composition) is preferably not more than 20 wt%, more preferably not more than 10 wt%, and still more preferably not more than 5 wt%.

As mentioned above, the gas barrier polymer material of the present invention essentially has a crystal-amorphous structure period as determined by a light scattering method of not less than 1 μm. Due to the specific high order structure, the material effectively blocks or extends a gas diffusion path and the gas barrier property of a hydroxyl group-containing gas barrier polymer is further enhanced to a higher level . The crystal-amorphous structure period as determined by a light scattering method is preferably not less than 2 μm, more preferably not less than 3 μm.

The gas barrier polymer material of the present invention can be produced by Step A comprising cooling a molten product of a hydroxyl group-containing gas barrier polymer having a main structural unit represented by the above-mentioned formula (I), or a molten product of a resin composition comprising the hydroxyl group-containing gas barrier polymer (i.e., a composition comprising the hydroxyl group-containing gas barrier polymer and a component other than the hydroxyl group-containing gas barrier polymer) to a temperature within the range of from a temperature lower than the melting point of the hydroxyl group- containing gas barrier polymer by 100°C (Tm-IOO⁰C) to the melting point (Tm⁰C) of the hydroxyl group-containing gas barrier polymer and maintaining the product within this temperature range for not less than 2 min.

Since the crystal-amorphous structure period becomes large by Step A and a gas diffusion path can be effectively blocked or extended, the gas barrier property thereof is further enhanced to a higher level and a gas barrier polymer material showing extremely high gas barrier property can be obtained.

When the treatment temperature in Step A of the present invention is lower than a temperature lower by 100⁰C than the melting point of the hydroxyl group-containing gas barrier polymer (Tm-IOO)⁰C (when temperature in Step A is too low), the crystal-amorphous periodic structure does not easily grow large, and when it is higher than the melting point (Tm⁰C) of the hydroxyl group-containing gas barrier polymer, (when temperature in Step A is too high) , a crystal-amorphous periodic structure is not formed. Therefore, the temperature range in Step A is preferably between a temperature lower by 100⁰C than the melting point of the hydroxyl group-containing gas barrier polymer (Tm-

100⁰C) and the melting point (Tm⁰C) of the hydroxyl group- containing gas barrier polymer, and a temperature between a temperature lower by 70⁰C than the melting point of the hydroxyl group-containing gas barrier polymer (Tm-70°C) and the melting point (Tm⁰C) of the hydroxyl group-containing gas barrier polymer is more preferable. The treatment temperature in Step A may be constant or may vary as long as it is within the above-mentioned temperature range. In addition, Step A preferably includes a step of retaining at a temperature within the range of [any temperature selected from the above-mentioned temperature range] +10⁰C for not less than 1 min, from the aspects of operability and reproducibility of properties.

In the present invention, the crystal-amorphous structure period is measured by Hv light scattering measurement. The detail is explained in the Examples to be mentioned later.

In the present invention, the melting point is measured by a differential scanning calorimeter (DSC) .

In the present invention, the treatment time (retention time) in Step A needs to be not less than 2 min. With this treatment time, the crystal-amorphous structure period of a hydroxyl group-containing gas barrier polymer becomes large, and the obtained gas barrier polymer material shows sufficiently improved gas barrier property. This treatment time is preferably not less than 4 min. In the production method of the gas barrier polymer material of the present invention, a step (step B) for enhancing progress of the crystallization of a gas barrier polymer at any temperature is preferably performed after the above-mentioned Step A. To be specific, for the progress of crystallization of the gas barrier polymer, Step B comprising cooling a hydroxyl group-containing gas barrier polymer after the above-mentioned Step A or a resin composition containing the hydroxyl group- containing gas barrier polymer to Tm - (Tm-IOO)⁰C, preferably Tm - (Tm-70)°C, and retaining for about 1 - 30 min, preferably 1 - 15 min is preferably performed, which is followed by cooling to room temperature. Step B may be omitted when the crystal- amorphous structure period has become sufficiently large in Step A. Concrete operation of Step B includes, for example, after Step A, once cooling to a temperature lower than (Tm-IOO)⁰C and then heating to a temperature range of Tm - (Tm-IOO)⁰C and the like.

When a gas barrier polymer material containing the aforementioned conventionally known additives (e.g., heat stabilizer, antioxidant, UV absorber, weather stabilizer, plasticizer, coloring agent, mold releasing agent, lubricant, flavoring, filler, surfactant etc.) is to be obtained, such can be obtained by melting a resin composition containing a hydroxyl group-containing gas barrier polymer and conventionally known additives and subjecting the composition to Step A. In this case, the conventionally known additives may be added during Step A, or partially added before Step A and the rest may be added during Step A. While the facility (apparatus) to be used for the production of the gas barrier polymer material of the present invention is not particularly limited, one capable of maintaining a gas barrier polymer material, which is equipped with a heat source, a control means to control the amount of heat from the heat source, a cooling means, a control means to control the amount of cooling by the cooling means and the like, and which can control the temperature of the gas barrier polymer material, is preferable.

The gas barrier polymer material of the present invention shows high gas barrier property, which is conventionally unattainable, and shows extremely high gas barrier property as evidenced by an amount of oxygen permeation of preferably not more than 1 cc*20 μm/m²*dayatm, more preferably not more than 0.5 cc*20 μm/m^2#dayatm, under high humidity (90%RH) . The gas barrier polymer material of the present invention can be used in the form of various molded products such as a film, a sheet, a container and the like by known forming methods for polymer materials, such as injection forming, blow molding, extrusion molding, inflation molding and the like. In addition, after processing into a film, a sheet and the like, it can be processed into various molded products by methods comprising deep draw molding such as vacuum molding, air pressure forming, vacuum air pressure forming and the like, and the like. While the use of the gas barrier polymer material of the present invention is not particularly limited as long as its extremely high gas barrier property can be effectively used, packaging materials for various products, particularly, packaging materials for food, beverage, pharmaceutical product and the like, specifically packaging materials for food. In this case, the packaging material may be in various forms such as a film, a sheet, a box, a container and the like can be mentioned. When a film or a sheet is formed, the thickness thereof is generally about 1-200 μm, preferably about 10-50 μm.

The present invention is explained in detail below by referring to Examples, which are not to be construed as limitative. The measurements in the following Examples and Comparative Examples followed the methods below. <measurement of crystal-amorphous structure period by light scattering method>

The hydroxyl group-containing gas barrier polymer materials (films) obtained in Examples and Comparative Examples were sandwiched between cover glasses, and Hv scattering was measured using a light scattering measurement apparatus LS-6012 manufactured by Optic Technology Limited and laser beam at wavelength λ=632.8 (unit: run) . The scattering intensity was corrected based on the thickness, and a crystal-amorphous structure period (Λm, unit: μm) was calculated from the scattering angle (θ, unit:⁰) of the top peak by the following formula (1) , wherein n is an refractive index of the film.

Formula (1): Λm=(λ/n) / (2xl000xsin(θ/2) ) <measurement of melting point>

Using differential scanning calorimeter DSC-7 manufactured by PerkinElmer, the temperature and melting enthalpy were corrected with lead and indium. After melting at 200°C for 5 min, the temperature was lowered to -50°C at 10°C/min and raised to 200°C at 10°C/min to determine the melting point (Tm) . <measurement of amount of oxygen permeation>

The amount of oxygen permeation of the films obtained in the following Examples and Comparative Examples was measured to evaluate the gas barrier property. MOCON OX-TRAN2/20 manufactured by Modern Control was used for the measurement of the amount of oxygen permeation, and the amount of oxygen permeation was measured under the conditions of 90%RH at 20°C according to the method described in JIS K 7126 (equal pressure method) . As used herein, the "amount of oxygen permeation" is a value of an amount of oxygen permeation (unit: cc/m²'dayatm) obtained by converting said amount measured at any membrane thickness, based on a membrane thickness of 20 μm. (cc20 μm/m^2# day*atm) . A smaller amount of oxygen permeation means more superior oxygen barrier property. <measurement of degree of crystallinity>

The degree of crystallinity was measured according to the method described in Cerrada et al., Macromolecules, 31, 2259(1998) . <Reference Example 1> (a) [preparation of poly (5-cyclooctene-l,2-diol) ]

In a separable flask (inner volume 3L) equipped with a thermometer, a dropping funnel, a refluxing tube and a stirrer were placed under an argon atmosphere 5-cyclooctene-l, 2-diol (320 g, 2.25 mol) , 3-cis-hexen-l-ol (2.O g, 0.02 mol) as a chain transfer agent and tetrahydrofuran (1280 g) , and the mixture was retained at 55°C. To this solution was added dropwise with stirring a solution of 1, 3-bis (2, 4, 6-trimethylphenyl) -4, 5- dihydroimidazol-2-ylidene (tricyclohexylphosphine) benzylidene ruthenium dichloride (0.127 g, 0.15 mmol) in tetrahydrofuran (5 ml) . After 30 min, a solution of ethyl vinyl ether (2 g, 0.028 mol) in a mixed solvent of methanol (500 g) and tetrahydrofuran (250 g) was added as a terminator, and the mixture was stirred at room temperature. The reaction solution was added to hexane (20 L) , the precipitate was collected by filtration and the solvent was removed under reduced pressure to give 300 g of poly (5- cyclooctene-1, 2-diol) .

(b) [hydrogenation of poly (5-cyclooctene-l, 2-diol) ] A solution of poly (5-cyclooctene-l, 2-diol) (300 g) obtained in the above-mentioned (a) in a mixed solvent of tetrahydrofuran (1470 g) and methanol (1230 g) was placed in an autoclave (inner volume 5 L, manufactured by Hastelloy-C) equipped with a pressure gauge, a pop valve, a hydrogen gas introduction tube, a thermometer, a sampling tube and a stirrer under a nitrogen atmosphere, and chlorotris (triphenylphosphine) rhodium (7 g, 7.6 mmol) was added. Then, the atmosphere in the autoclave was substituted 3 times with hydrogen gas, the temperature in the autoclave was raised from room temperature to 60⁰C over 30 min by an outside heating furnace with stirring at a hydrogen pressure of 5.9 MPa, and the mixture was maintained at the same temperature for 5 hr, during which time hydrogen was supplied to the autoclave to maintain the hydrogen pressure at 5.9 MPa. After cooling to room temperature, the reaction mixture was taken out, added to methanol (3 L) , the precipitated polymer was recovered and the solvent was evaporated under reduced pressure to give hydrogenated poly (5-cyclooctene- 1, 2-diol) (290 g) .

The molecular weight of the above-mentioned hydrogenated poly (5-cyclooctene-l, 2-diol) was measured using a GPC apparatus (150ALC/GPC manufactured by Waters), a column (HFIP806M manufactured by SHODEX) and a developing solvent of hexafluoroisopropanol, and converted based on standard polymethyl methacrylate . As a result, the number average molecular weight (Mn) was 9,800, and the weight average molecular weight (Mw) was 26,800. It was also found that the hydrogenation degree of the polymer as obtained by 500 MHz ¹H-NMR spectrum (DMSO-dβ solution, measurement temperature 85°C) was 99.9%. The melting point was 147°C and the refractive index (n) was 1.55. <Example 1>

The hydrogenated poly (δ-cyclooctene-l^-diol) obtained in Reference Example 1 (b) was melted at 190°C on a temperature- controlable hot plate, cooled to 100°C at a rate of 90°C/min, maintained at the same temperature for 10 min, and cooled to 25⁰C at a rate of 90°C/min. The obtained sample (film of membrane thickness: 200 μm) was subjected to the measurements of light scattering and degree of crystallinity. The results are shown in Table 1. In addition, the amount of oxygen permeation of the sample was measured and found to be less than 0.3 cc*20 μm/m^2#day atm.

The hydrogenated poly (5-cyclooctene-l,2-diol) obtained in Reference Example 1 (b) was melted at 190°C on a temperature- controlable hot plate, cooled to 100°C at a rate of 90°C/min, maintained at the same temperature for 5 min, further cooled to

40°C at a rate of 90°C/min, maintained for 5 min, then raised to 100°C at a rate of 90°C/min, maintained at the same temperature for 10 min, and cooled to 25°C. The obtained sample (film of membrane thickness: 200 μm) was subjected to the measurements of light scattering and degree of crystallinity. The results are shown in Table 1. In addition, the amount of oxygen permeation of the sample was measured and found to be less than 0.3 cc20 μm/m^2#dayatm.

The hydrogenated poly (5-cyclooctene-l,2-diol) obtained in Reference Example 1 (b) was melted at 190°C on a temperature- controlable hot plate, cooled to 40°C at a rate of 90°C/min, maintained at the same temperature for 5 min, raised to 100°C at a rate of 90°C/min, maintained at the same temperature for 10 min, and cooled to 25°C. The obtained sample (film of membrane thickness: 200 μm) was subjected to the measurements of light scattering and degree of crystallinity. The results are shown in Table 1. The amount of oxygen permeation of the sample was measured and found to be 6 cc*20 μm/m^2#dayatm. Comparative Example 2> The hydrogenated poly (5-cyclooctene-l_/2-diol) obtained in

Reference Example 1 (b) was melted at 190°C on a temperature- controlable hot plate, cooled to -50⁰C at a rate of 90°C/min, maintained at the same temperature for 5 min, raised to 100°C at a rate of 90°C/min, maintained at the same temperature for 10 min, and cooled to 25°C. The obtained sample (film of membrane thickness: 200 μm) was subjected to the measurements of light scattering and degree of crystallinity. The results are shown in Table 1. The amount of oxygen permeation of the sample was measured and found to be 6.3 cc*20 μm/m^2>dayatm. <Comparative Example 3>

The hydrogenated poly (5-cyclooctene-l,2-diol) obtained in Reference Example 1 (b) was melted at 190⁰C on a temperature- controlable hot plate, cooled to 100⁰C at a rate of 90°C/min, maintained at the same temperature for 0.5 min, further cooled to 40⁰C at a rate of 90°C/min, maintained for 5 min, then raised to 100⁰C at a rate of 90°C/min, maintained at the same temperature for 10 min, and cooled to 25°C. The obtained sample (film of membrane thickness: 200 μm) was subjected to the measurements of light scattering and degree of crystallinity. The results are shown in Table 1. In addition, the amount of oxygen permeation of the sample was measured and found to be 6.2 cc20 μm/m^2#dayatm.

Fig. 1 shows the results of light scattering measurement using the samples of Examples 1, 2 and Comparative Examples 1 - 3.

In Fig. 1, the transverse axis shows scattering angle (°) and the vertical axis shows strength (intensity) . A scattering angle of the maximum scattering intensity was calculated from Fig. 1, and the crystal-amorphous structure period was calculated. <Comparative Example 4> An ethylene-vinyl alcohol copolymer manufactured by KURARAY CO., LTD. (EVAL-G: ethylene content: 47 mol%, Tm=ISe⁰C, refractive index (n)=1.51) was melted at 190°C on a temperature- controlable hot plate, cooled to 100°C at a rate of 90°C/min, maintained at the same temperature for 10 min, cooled to 25°C at a rate of 90°C/min. The obtained sample (film of membrane thickness: 200 μm) was subjected to the measurements of light scattering and degree of crystallinity. The results are shown in Table 1. The amount of oxygen permeation of the sample was measured and found to be 9.3 cc*20 μm/m^2>dayatm. <Comparative Example 5>

An ethylene-vinyl alcohol copolymer (EVAL-G: ethylene content: 47 mol%, Tm=156°C, refractive index . (n) =1.51) manufactured by KURARAY CO., LTD. was melted at 190°C on a temperature-controlable hot plate, cooled to 40°C at a rate of

90°C/min, maintained at the same temperature for 5 min, raised to 100°C at a rate of 90°C/min, maintained at the same temperature for 10 min, and cooled to 25°C. The obtained sample (film of membrane thickness: 200 μm) was subjected to the measurements of light scattering and degree of crystallinity. The results are shown in Table 1. The amount of oxygen permeation of the sample was measured and found to be 9.1 cc*20 μm/m²*dayatm. <Comparative Example 6>

An ethylene-vinyl alcohol copolymer (EVAL-G: ethylene content: 47 mol%, Tm=156°C, refractive index (n)=1.51) manufactured by KURARAY CO., LTD. was melted at 190⁰C on a temperature-controlable hot plate, cooled to -5O⁰C at a rate of 90°C/min, maintained at the same temperature for 5 min, raised to 100⁰C at a rate of 90°C/min, maintained at the same temperature for 10 min, and cooled to 25°C. The obtained sample (film of membrane thickness: 200 μm) was subjected to the measurements of light scattering and degree of crystallinity. The results are shown in Table 1. The amount of oxygen permeation of the sample was measured and found to be 9.1 cc*20 μm/m^2#dayatm.

Fig. 2 shows the results of light scattering measurement using the samples of Comparative Examples 4 - 6. In Fig. 2, the transverse axis shows scattering angle (°) and the vertical axis shows strength (intensity) . A scattering angle of the maximum scattering intensity was calculated from Fig. 2, and the crystal- amorphous structure period was calculated.

The crystal-amorphous structure period, degree of crystallinity and amount of oxygen permeation obtained under the heat treatment conditions of Examples 1, 2 and Comparative Examples 1 -6 are shown in the following Table 1.

Table 1

From these results, it was observed that, when hydrogenated poly(5-cyclooctene-l,2-diol) , which is a hydroxyl group-containing gas barrier polymer mainly comprising the structural unit represented by the above-mentioned formula (I), was used, the particular heat treatment conditions induced remarkable growth of crystal-amorphous structure period without markedly changing the degree of crystallinity. As a result, it was found that the diffusion path was blocked or extended and the oxygen barrier property was strikingly improved. Industrial Applicability

As is clear from the foregoing explanation, a gas barrier polymer material showing extremely high gas barrier property can be obtained according to the present invention. In addition, such a gas barrier polymer material can be produced by a relatively simple step. The gas barrier polymer material obtained by the present invention has extremely high gas barrier property and fine moldability. Therefore, the material can be used as a packaging material for various products by, for example, forming into a film, a sheet or a container. Particularly, since the material shows extremely high oxygen barrier property over a wide range of from low humidity to high humidity, a gas barrier layer of a metal, a vapor deposition film of silicon oxide and the like is not necessary, whereby a packaging material for food with fine visual observability of the contents can be provided.

Claims

1. A gas barrier polymer material comprising a hydroxyl group- containing gas barrier polymer mainly comprising a structural unit represented by the following formula (I) :

wherein m and n are each an integer of 0 to 10;

X¹ and X² are each a hydrogen atom, a hydroxyl group or a functional group convertible to a hydroxyl group, provided that the total of m and n is not less than 1 and at least one of X¹ and X² is a hydroxyl group or a functional group convertible to a hydroxyl group; R¹, R² and R³ are each a hydrogen atom, a hydroxyl group, a functional group convertible to a hydroxyl group, an alkyl group, an aryl group, an aralkyl group or a heteroaryl group; and R¹, R², R³, X¹ and X² present in plurality are optionally the same as or different from each other, which material shows a crystal-amorphous structure period of not less than 1 μm as determined by a light scattering method.

2. The gas barrier polymer material of claim 1, wherein the amount of oxygen permeation at 20°C, 90%RH is not more than 1 cc 20 μm/atπrm^2#day.

3. A packaging material comprising a gas barrier polymer material of claim 1 or 2.

4. A production method of a gas barrier polymer material comprising a hydroxyl group-containing gas barrier polymer, which comprises Step A comprising cooling a molten product of the hydroxyl group-containing gas barrier polymer or a resin composition comprising the hydroxyl group-containing gas barrier polymer to a temperature within the range of from a temperature lower than the melting point of the hydroxyl group-containing gas barrier polymer by 100°C (Tm-IOO⁰C) to the melting point (Tm⁰C) and retaining the molten product within the aforementioned temperature range for not less than 2 minutes, wherein the hydroxyl group-containing gas barrier polymer mainly comprises a structural unit represented by the following formula (I) :

wherein m and n are each an integer of 0 to 10; X¹ and X² are each a hydrogen atom, a hydroxyl group or a functional group convertible to a hydroxyl group, provided that the total of m and n is not less than 1 and at least one of X¹ and X² is a hydroxyl group or a functional group convertible to a hydroxyl group; R¹, R² and R³ are each a hydrogen atom, a hydroxyl group, a functional group convertible to a hydroxyl group, an alkyl group, an aryl group, an aralkyl group or a heteroaryl group; and R¹, R², R³, X¹ and X² present in plurality are optionally the same as or different from each other.

5. The production method of claim 4, which further comprises, after Step A, performing crystallization at any temperature (Step B).