ETHYLENIC COPOLYMER MOLDING STRUCTURE AND ETHYLENIC COPOLYMER COMPOSITION

Abstract: A first molding structure is made from an ethylenic copolymer composition comprising 50 to 80 wt% of an ethylene/unsaturated ester copolymer (A) and 50 to 20 wt% of an ethylene/vinyl alcohol copolymer (B) having a melt viscosity 300 to 1,000 Pa.s smaller than that of the copolymer (A) at the temperature of 220°C and the shear rate of 100 sec⁻¹, and has a layered structure wherein the copolymer (B) is dispersed in the form of a thin layer. A first ethylenic copolymer composition is one prepared by replacing part of the copolymer (A) by a grafted ethylene/α-olefin copolymer and excellent in thermal stability in molding, moldability into film, and kneadability in extrusion. A second molding structure is made from this ethylene copolymer composition and has a layered structure like the first molding structure. Both the molding structures are excellent in gas barrier properties and resistance to pinhole formation.

Description: This invention relates to ethylene copolymer molded structures and ethylene copolymer compositions and more particularly to molded structures comprising ethylene copolymer excellent in gas barrier properties and pinhole-free properties, and to ethylene copolymer compositions excellent in drawing properties at the time of molding, film-forming properties and heat stability. When molded into film or the like, ethylene/vinyl alcohol copolymers containing vinyl alcohol structural units in a high proportion exhibit excellent gas barrier properties, and hence they are used widely as packaging material. However, the ethylene/vinyl alcohol copolymers have such problems that they are liable to water absorption, poor in drawability as well as in heat resistance, and are difficult to mold at high temperature. In the molded articles obtained from the above-mentioned copolymers, there are such problems that they deteriorate in gas barrier properties on account of the water absorption properties of said copolymers, they are insufficient in impact resistance in a dry state and, moreover, they are poor in pinhole resistance. On that account, the ethylene/vinyl alcohol copolymers as mentioned above are used singly rarely if ever and are used usually in combination with other materials. As an example of the combination use referred to above, there may be mentioned a multi-ply laminates prepared by laminating an interlayer composed of the ethylene/vinyl alcohol copolymer with other materials. Further, there have been proposed numbers of methods intended to obtain modified compositions by blending the above-mentioned copolymers and other resins. In the blending methods as mentioned above, however, it is difficult to obtain ethylene/vinyl alcohol copolymer compositions in which the defect of said copolymer has been removed markedly when the ethylene/vinyl alcohol is used as a main component of the resulting blend. On the other hand, when the resin other than the ethylene/vinyl alcohol copolymer is used as a main component of the resulting blend, it has heretofore been difficult to obtain compositions excellent in gas barrier properties owing to the ethylene/vinyl alcohol copolymer. In recent years, there have been proposed molded articles excellent in gas barrier properties, said molded articles being obtained from ethylene/vinyl alcohol copolymer compositions prepared by blending ethylene/vinyl alcohol copolymers and other resins. For example, Japanese Patent Publn. No. 30104/1976 proposes molded structures having a stratiform structure and different in content of an ethylene/vinyl alcohol copolymer in the direction of thickness, said structures being obtained by molding a composition comprising polyolefin and ethylene/vinyl alcohol copolymers into a desired shape under specific conditions. Further, Japanese Patent L-O-P Publn. No. 121017/1980 discloses a stratiform molded article of polymer composition containing 60-95% by weight of polyolefin, vinyl alcohol (co)polymer and alkylcarboxyl-substituted polyolefin. The copolymers of polyolefin and ethylene/vinyl alcohol copolymers as disclosed in the publications cited above, however, are poor in compatibility and tend to become poor in moldability, and it is therefore not always easy to mold these polymers into thin-layer films, and the thin-layer films obtained, if any, are required to show a further improvement in gas barrier properties. The present invention is intended to solve such problems involved in the prior art as mentioned above, and an object of the invention is to provide ethylene copolymer molded structures excellent in gas barrier properties, pinhole resistance and the like. A further object of the invention is to provide ethylene copolymer compositions excellent in drawing properties, film-forming properties and heat stability at the time of molding thereof and, at the same time, excellent in gas barrier properties and pinhole resistance. The first ethylene copolymer molded structure of the present invention comprises an ethylene copolymer composition comprising [A] 50-80% by weight of an ethylene/unsaturated ester copolymer having 85-65% by weight of ethylene structural units, 15-35% by weight of unsaturated ester structural units, and a melt flow rate of 0.5-20 g/10 min as measured at 190°C under a load of 2160 g, and [B] 45-20% by weight of an ethylene/vinyl alcohol copolymer having 50-20 mol% of ethylene structural units, 50-80 mol% of vinyl alcohol structural units, and a melt flow rate of 0.5-30 g/10 min, said ethylene/vinyl alcohol copolymer [B] having an apparent melt viscosity, as measured at 220°C and a rate of shear of 100 sec -1 , smaller by 300-1000 Pa·s than that of said ethylene/unsaturated ester copolymer [A], and said ethylene/vinyl alcohol copolymer [B] being dispersed into said molded structure in the form of thin layers. The first ethylene copolymer composition of the invention comprises [A] 30-75% by weight of an ethylene/unsaturated ester copolymer having 85-65% by weight of ethylene structural units, 15-35% by weight of unsaturated ester structural units, and a melt flow rate, as measured at 190°C under a load of 2160 g, of 0.5-20 g/10 min, [B] 45-20% by weight of an ethylene/vinyl alcohol copolymer having ethylene structural units of 50-20 mol%, 50-80 mol% of vinyl alcohol structural units, and a melt flow rate, as measured at 210°C under a load of 2160 g, of 0.5-30 g/10 min, and [C] 1-40% by weight of a graft-modified product of a non-crystalline or low crystalline ethylene/α-olefin copolymer having 60-90 mol% of ethylene structural units with an unsaturated carboxylic acid or its anhydride, said ethylene/vinyl alcohol copolymer [B] having an apparent melt viscosity, as measured at 220°C and a rate of shear of 100 sec -1 , smaller by 300-1000 Pa·s than that of said ethylene/unsaturated ester copolymer [A]. The second molded structure of the invention comprises the ethylene copolymer compositions as mentioned above, said ethylene/vinyl alcohol copolymer [B] being dispersed into said molded structure in the form of thin layers. In the accompanying drawings: Fig. 1 is a photograph of an electron microscope of the section of the molded structure according to the present invention. This electron microscope was obtained by taking a photograph of the section of the first molded structure of the present invention by means of a scanning type electron microscope, said molded structure being obtained as a film of 50 µm in thickness and dyed with osmic acid and ruthenium. In Fig. 1, black portions represent the ethylene/unsaturated ester copolymer [A] present as a matrix layer, and the ethylene/vinyl alcohol copolymer [B] is dispersed along the film surface in the form of thin layers, without uneven distribution, and is observed as a portion surrounded by discontinuous white lines. The molded structures of the invention have such a stratiform structure as mentioned above. The molded structures obtained from the ethylene copolymer compositions of the present invention, and said ethylene copolymer compositions are illustrated below in detail. The term "polymer" used in the present invention is intended sometimes to designate not only homopolymer but also copolymer. First, the ethylene copolymer compositions from which the molded structures of the present invention are formed are illustrated hereinafter. Molded structure The ethylene copolymer compositions of the invention comprises [A] an ethylene/unsaturated ester copolymer and [B] an ethylene/vinyl alcohol copolymer. The ethylene/unsaturated ester copolymer [A] used in the ethylene copolymer compositions of the invention comprises 85-65% by weight, preferably 85-72% by weight of ethylene structural units and 15-35% by weight, preferably 15-28% by weight of unsaturated ester structural units. If the ethylene copolymer composition contains less than 15% by weight of the unsaturated ester structural units, said composition tends to decrease in gas barrier properties and, on the contrary, if said composition contains the unsaturated ester structural units in an amount exceeding 35% by weight, the molded structure resulting therefrom tends to decrease in strength. The ethylene/unsaturated ester copolymer [A] has a melt flow rate of 0.5-20 g/10 min, preferably 1-15 g/10 min as measured at 190°C under a load of 2160 g. The ethylene/unsaturated ester copolymer [A] as illustrated above may be obtained by copolymerization of ethylene and unsaturated ester. In this case, the unsaturated ester used may be either carboxylic acid unsaturated ester or unsaturated carboxylic acid ester. Concretely, these unsaturated esters include, for example, vinyl acetate, acrylic ester and methacrylic ester. Ester components of acrylic ester or methacrylic ester are, for example, alkyl esters of 1 to 8 carbon atoms. Of these alkyl esters, preferred are methyl esters or ethyl esters. The ethylene/vinyl alcohol copolymer [B] used in the ethylene copolymer compositions of the invention comprises 50-20 mol%, preferably 45-25 mol% of ethylene structural units and 50-80 mol%, preferably 55-75 mol% of vinyl alcohol structural units. Such copolymers [B] as mentioned above may be obtained by saponifying the corresponding ethylene/vinyl acetate copolymer in such a proportion that the saponification value becomes not less than 95%, preferably not less than 99%. The ethylene/vinyl alcohol copolymers [B] have a melt flow rate of 0.5-30 g/10 min, preferably 1-20 g/10 min as measured at 210°C under a load of 2160 g. The ethylene/vinyl alcohol copolymers [B] have an apparent melt viscosity, as measured at 220°C and a rate of shear of 100 sec -1 , smaller by 300-1000 Pa·s, preferably smaller by 400-900 Pa·s than that of the ethylene/unsaturated ester copolymers [A]. By virtue of the fact that the ethylene copolymer composition is formed from the ethylene/unsaturated ester copolymer [A] and ethylene vinyl alcohol copolymer [B] having a such difference in apparent melt viscosity between them as shown above, said ethylene copolymer composition comes to be capable of forming a molded structure in which the ethylene/vinyl alcohol copolymer [B] has been dispersed in the form of thin layers without uneven distribution. The ethylene copolymer composition from which the first molded structure of the present invention is formed comprises the above-mentioned ethylene/unsaturated ester copolymer [A] and ethylene/vinyl alcohol copolymer [B], said copolymer [A] being present in an amount of 55-80% by weight, preferably 55-70% by weight, and said copolymer [B] being present in an amount of 20-45% by weight, preferably 30-45% by weight. The ethylene copolymer compositions having such constituents as mentioned above are excellent in heat stability, drawing properties and film-forming properties at the time of molding thereof. The first molded structures of the invention are formed from the ethylene copolymer compositions as illustrated above. The molded structures of the invention have such a structure in which the above-mentioned ethylene/vinyl alcohol copolymer [B] has been dispersed in the form of thin layers without uneven distribution. More particularly, the copolymer [B] forms discontinuous thin layer along the direction of surface of the molded structure, and the resulting molded structure has in its main portion a stratiform structure in which the copolymer [B] has been dispersed substantially without uneven distribution. Such a structure as mentioned above is shown in the aforementioned electron microscope of Fig. 1. Because of their stratiform structure as mentioned above, the molded structures of the invention are excellent in gas barrier properties though they have been formed from the compositions containing 50-20% by weight of the ethylene/vinyl alcohol copolymer [B]. The molded structures of the invention are preferably those having a broad area and a relatively small thickness, and they may be of various shapes such as film, sheet, hollow container or the like. The molded structures of the invention have a thickness of usually 5-1000 µm, preferably 20-500 µm, and they exhibit excellent gas barrier properties even when they are thin layers having a thickness of 30-50 µm. The molded structures as illustrated above may be molded out of the above-mentioned ethylene copolymer compositions of the invention. In that case, the molding operation is preferably carried out by kneading together the above-mentioned components [A] and [B] of the ethylene copolymer composition and then feeding the resulting kneaded product to a molding machine, though said molding operation may be carried out by continuously kneading and feeding said components [A] and [B]. The kneading operation is preferably carried out usually under the conditions of a kneading temperature of 170-235°C, a rate of shear of 10-2000 sec -1 , and a retention time of 10 sec to 5 min. The molding operation may be carried out by such a method that the molten ethylene copolymer composition flows in the direction of the face of the resulting molded structure. Concretely speaking, the molding of the ethylene copolymer compositions can be carried out by such a method as extrusion, blow molding, injection molding, injection-blow molding and vacuum forming. In preparing the molded structures from the ethylene copolymer compositions as illustrated above, said copolymer compositions may be incorporated with various additives according to the purpose for which the compositions are used. Such additives as may be used for the purpose include, for example, antioxidants, heat stabilizers, drying agents, nucleating agents, antistatic agents and in addition thereto barrier properties imparting fillers such as mica. The addition to the ethylene copolymer compositions of the drying agent is preferred, because a tendency that the ethylene/vinyl alcohol copolymer [B] component of the ethylene copolymer composition absorbs water to decrease the resulting molded structure in gas barrier properties can be relaxed. Further, the resulting molded structure can be further improved in gas barrier properties by loading the ethylene copolymer composition with mica. In the ethylene copolymer compositions of the invention used for forming the molded structures, it is presumed that because the apparent melt viscosity of the above-mentioned ethylene/vinyl alcohol copolymer [B] is smaller by 300-1000 Pa·s than that of the ethylene/unsaturated ester copolymer [A], the ethylene/vinyl alcohol copolymer is dispersed at the time of molding in the form of thin layers along the direction of the surface of the molded structure. The first molded structures of the invention are excellent in gas barrier properties and pinhole resistance and, moreover, they are markedly superior in water absorbing properties to the molded structures obtained from the ethylene copolymer compositions containing only the ethylene/vinyl alcohol copolymer [B]. The first molded structures of the invention may be laminated with layers composed of other materials. Such materials as may be used herein include, for example, polyolefins such as high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene and poly-4-methyl-1-pentene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, thermoplastic resins represented by polyamides such as nylon-6 and nylon-6,6, thermosetting resins such as polyurethane, various elastomers, metallic materials such as aluminum foil, and paper. In the laminated structures mentioned above, one or two or more of the molded structure layer of the invention may be contained as a surface layer or interlayer of the laminated structure. Ethylene copolymer composition The first ethylene copolymer compositions of the present invention are illustrated hereinafter. The ethylene copolymer composition of the invention comprises the aforementioned ethylene/unsaturated ester copolymer [A], ethylene/vinyl alcohol copolymer [B] and the following graft-modified product of an ethylene/α-olefin copolymer [C]. The graft modified product [C] of ethylene/α-olefin copolymer used in the invention may be obtained by modification of the ethylene/α-olefin copolymer with unsaturated carboxylic acid or its anhydride. The ethylene/α-olefin copolymer used herein comprises 60-90 mol%, preferably 70-85 mol% of ethylene structural units and 40-10 mol%, preferably 30-15 mol% of structural units derived from α-olefin other than ethylene. The α-olefin used herein includes concretely those having about 3-8 carbon atoms, preferably propylene, 1-butene, 1-pentene and 4-methyl-1-pentene. The ethylene/α-olefin copolymers used in the present invention are low crystalline or non-crystalline, and concretely have a crystallinity index, as measured by the X-ray diffractometry, of usually not more than 30%, preferably not more than 20%. This ethylene/α-olefin copolymers desirably have a melt flow rate at 190°C and a load of 2160 g of usually 0.3-50 g/10 min, preferably 0.5-20 g/10 min. The unsaturated carboxylic acid or its anhydride used in graft modifying the above-mentioned ethylene/α-olefin copolymer includes concretely acrylic acid, methacrylic acid, fumaric acid, maleic acid, nadic acid, maleic anhydride, itaconic anhydride and nadic anhydride. Of the acids and anhydrides thereof, particularly preferred is maleic acid or maleic anhydride. The graft-modified product [C] of the ethylene/α-olefin copolymer is preferably modified so that the grafted amount becomes usually 0.03-7% by weight, preferably 0.05-5% by weight. Besides the graft modified product of the ethylene/α-olefin copolymer used in the ethylene copolymer compositions of the invention, graft modified products, for example, an ethylene/vinyl acetate copolymer graft-modified product are known. However, when graft modified products other than those of the ethylene/α-olefin copolymer are used as the graft modified products [C] in the invention, the gas barrier properties of the resulting molded structure sometimes decrease greatly depending upon the amount of the other graft modified product used in the ethylene copolymer composition. In contrast thereto, practically no decrease in gas barrier properties is observed in the resulting molded structure even when the graft modified product [C] of the ethylene/α-olefin copolymer of the invention is used in a relatively large amount in the ethylene copolymer composition of the invention. The ethylene copolymer compositions of the invention comprise the above-mentioned ethylene/unsaturated ester copolymer [A] in amounts of 30-75 % by weight, preferably 40-65 % by weight, ethylene/vinyl alcohol copolymer [B] in amounts of 20-50 % by weight, preferably 30-45 % by weight and graft modified product [C] in amounts of 1-40 % by weight, preferably 5-30 % by weight. The ethylene copolymer compositions of the invention having such composition as mentioned above are excellent in heat stability, drawing properties and film forming properties at the time of molding thereof, and are capable of forming molded structures excellent in gas barrier properties and pinhole resistance. Since the ethylene copolymer compositions of the invention contain the graft modified product [C] of the ethylene/α-olefin copolymer in an amount as defined above, the ethylene copolymer compositions have been improved further in extrusion kneading properties and film forming properties. When the ethylene copolymer compositions contain large amounts of the graft modified product [C], the molded structure resulting therefrom sometimes decreases in gas barrier properties. In the case of the ethylene copolymer compositions of the invention containing the graft modified product [C] in such an amount as defined above, practically no decrease in gas barrier properties is observed in the molded structure resulting therefrom. The second molded structures of the invention are formed from the above-mentioned first ethylene copolymer as mentioned above. The second molded structures of the invention have a stratiform structure similar to that of the first molded structures of the invention as mentioned above. The second molded structures may take the same shapes as those of the first molded structures as mentioned above, and may be molded in the same manner as in the case of the first molded structures of the invention. The second molded structures may be obtained by using extruders having usual kneading functions, and it is not necessary to employ such extrusion conditions under which a laminar flow is formed. Further, a sheet-like molded structure obtained may be formed into a container of the desired shape by fabrication technique such as vacuum or air-pressure forming. In the first ethylene copolymer molded structures provided according to the present invention, the ethylene/vinyl alcohol copolymer [B] is dispersed in the form of thin layers without uneven distribution, hence the molded structures are excellent in gas barrier properties. Because of low water absorption properties, the first ethylene copolymer molded structures are small in dependence on humidity. Furthermore, the molded structures obtained as films and the like are excellent in pinhole resistance as well, and are useful as various packaging materials such as food wrap films. The first ethylene copolymer compositions of the invention comprise an ethylene/unsaturated ester copolymer [A] containing a specific amount of unsaturated ester structural units, an ethylene/vinyl alcohol copolymer [B] having an apparent melt viscosity varying by a specific value from that of said copolymer [A], and a graft modified product [C] of an ethylene/α-olefin copolymer, and hence the ethylene copolymer compositions are excellent in heat stability and drawing properties at the time of molding thereof and, at the same time, exhibit further improved extrusion-kneadability and film forming properties at the time of molding thereof. The second molded structures provided according to the invention are formed from the above-mentioned ethylene copolymer compositions, and have a stratiform structure similar to that of the first molded structures of the invention, and hence are excellent in gas barrier properties and also in pinhole resistance. EXAMPLE The present invention is illustrated below more in detail with reference to examples. In this connection, the kneading method, molding-processing method, evaluation and analytical method employed for the resins used in the examples and comparative examples were conducted by the following procedures under the conditions mentioned below. (1) MFR (melt flow rate) The measurement was conducted in accordance with JIS K-6760. Temperature: 190°C or 210°C (190°C in the measurement of the composition) Load: 2160 g (2) Apparent melt viscosity Using Instron (U.S.A.) capillary rheometer 3211, the shearing stress was detected at a melting temperature and shearing rate as prescribed to calculate an apparent melt viscosity therefrom. Particulars of this measurement are as follows: Specification of the capillary rheometer 3211 (3) Method for kneading resin The resins were melt kneaded in the prescribed proportion under the following conditions. Kneader ... Single screw extruder, 30 mm Screw ... Plunger head type single flight screw L/D = 33 Barrel Temperature (°C) C 1 C 2 C 3 C 4 C 5 D 80 150 180 200 200 180 Screw speed ... 40 rpm (4) Extrusion kneadability The extrusion kneadability was judged by visual observation of the state of strand of the molten resin extruded through the die at the time of kneading the resin in (3) above. (5) Method for forming film and evaluation of formability Blown films were formed by means of a blown film machine comprising a single screw full flight extruder of 30 mm under the following conditions. C 1 C 2 C 3 C 4 H D 150 200 200 200 200 200 The film formability was judged by observation of the stable state of bubbles at the time of molding the blown films. In Examples 2 and 8, the films were formed by changing the discharging rate of the molten resin from the extruder. In this connection, the above-mentioned molding conditions are those employed in ordinary blown film forming method, and no particular procedure such as control of dispersion or flowing state of the ethylene/vinyl alcohol resin. (6) Measurement of the amount of oxygen gas permeated Using a gas permeability tester (differential pressure method) manufactured and sold by Toyo Seiki K.K., the amount of oxygen gas permeated through a film of 50 µm in thickness obtained by the method shown in the (5) above in an atmosphere of 23°C x 50% RH was measured. The resins used in the examples and comparative examples are shown in Table 1. Examples 1-6 The ethylene/vinyl acetate copolymer [A] and the ethylene/vinyl alcohol copolymer [B] shown in Table 1 were kneaded in the proportion as indicated in Table 2 by the method as described in the aforementioned (3) to prepare an ethylene copolymer composition. MFR of the ethylene copolymer composition thus obtained and the amount of oxygen permeated through a film obtained from said composition were measured. Results obtained are shown in Table 2. A photograph of the section of the film of Example 1 taken by electron microscope is shown in Fig. 1. Comparative Examples 1-6 The ethylene copolymer [A] and the ethylene/vinyl alcohol copolymer [B] shown in Table 1 were kneaded in the proportion as indicated in Table 3 by the method as described in the aforementioned (3) to prepare an ethylene copolymer composition. MFR of the ethylene copolymer composition thus obtained and the amount of oxygen permeated through a film obtained from said composition were measured. Results obtained are shown in Table 3. Example Ethylene copolymer composition (wt%) Screw speed at the time of molding film rpm MFR dg/min Difference in apparent melt viscosity A-B [Pa·S] (220°C, 100 sec -1 ) Amount of oxygen permeated 50 µm cm 3 /m 2 ·24hr· atm 1 A-(1)/B-(1) = 60/40 45 3.6 448 8.6 2 A-(1)/B(1) = 60/40 60 3.6 448 10.0 3 A-(1)/B-(1) = 70/30 45 3.3 448 54.0 4 A-(1)/B-(2) = 70/30 45 2.1 446 22.0 5 A-(4)/B-(1) = 60/40 45 2.8 558 6.8 6 A-(5)/B-(1) = 60/40 45 3.2 483 9.4 Comp. Example Ethylene copolymer composition (wt%) Screw speed at the time of molding film rpm MFR dg/min Difference in apparent melt viscosity A-B [Pa·S] (220°C, 100 sec -1 ) Amount of oxygen permeated 50 µm cm 3 /m 2 ·24hr· atm 1 A-(2)/B-(1) = 70/30 45 4.4 364 1300 2 A-(3)/B-(3) = 60/40 45 12.3 97 7560 3 A-(9)/B-(1) = 70/30 45 4.2 386 2330 4 A-(6)/B-(1) = 60/40 45 10.9 176 896 5 A-(1) 45 2.5 - 7550 6 A-(3) 45 15 - 7930 Examples 7-18 The three components, i.e. the ethylene/vinyl acetate copolymer [A], ethylene/vinyl alcohol copolymer [B] and ethylene/α-olefin copolymer graft-molded product [C] shown in Table 1 were kneaded in the proportions as indicated in Table 4 by the method as described in the aforementioned (3) to prepare an ethylene copolymer composition. The performance of the resulted composition and the molded structure obtained therefrom, such as extrusion kneadability, film-forming properties and the amount of oxygen permeated through the blown film, was evaluated. Results obtained are shown in Table 4. Example Ethylene copolymer composition (wt%) Extrusion kneadability Film forming properties Difference in apparent melt viscosity A-B [Pa·S] (220°C, 100 sec -1 ) Amount of oxygen permeated 50 µm cm 3 /m 2 ·24hr· atm 7 A-(1)/B-(1)/C-(1) 42/40/18 good ○ 448 20 8 A-(1)/B-(1)/C-(1) 42/40/18 good ○ 448 22 9 A-(1)/B-(1)/C-(1) 63/30/7 good ○ 448 97 10 A-(1)/B-(1)/C-(1) 50/40/10 good ○ 448 15 11 A-(1)/B-(1)/C-(1) 35/30/35 good Δ 448 152 12 A-(1)/B-(1)/C-(1) 55/30/15 good ○ 448 42 13 A-(4)/B-(1)/C-(1) 50/40/10 good ○ 588 10 14 A-(4)/B-(2)/C-(1) 50/40/10 good ○ 588 18 15 A-(4)/B-(3)/C-(1) 50/40/10 good ○ 577 78 16 A-(5) /B-(1)/C-(1) 50/40/10 good ○ 483 8 17 A-(7) /B-(2)/C-(1) 50/40/10 good ○ 580 21 18 A-(7)/B-(3)/C-(1) 50/40/10 good ○ 571 73 * ○: good Δ: unstable X: failed in film forming Comparative Examples 7-13 The three components, i.e. the ethylene/vinyl acetate copolymer [A], ethylene/vinyl alcohol polymer [B] and the ethylene/α-olefin copolymer graft-modified product [C] shown in Table 1 were kneaded in the proportions as indicated in Table 5 by the method as described in the aforementioned (3) to prepare an ethylene copolymer composition. The performance of the resulted composition and the molded structure obtained therefrom, such as extrusion kneadability, film forming properties and the amount of oxygen permeated through the blown film, was evaluated. Results obtained are shown in Table 5. Comp. Example Ethylene copolymer composition (wt%) Extrusion kneadability Film forming properties Difference in apparent melt viscosity A-B [Pa·S] (220°C, 100 sec -1 ) Amount of oxygen permeated 50 µm cm 3 /m 2 ·24hr· atm 7 A-(1)/B-(1)/C-(1) 20/30/50 Melt fracture X 448 264 8 A-(1)/B-(1)/C-(2) 42/40/18 good Δ 448 3260 9 A-(8) /B-(1)/C-(1) 50/30/20 good ○ 94 2013 10 A-(9)/B-(1)/C-(1) 63/30/7 good ○ 386 2020 11 A-(9)/B-(1)-/C-(2) 63/30/7 good Δ 386 2080 12 A-(10)/B-(1)/C-(1) 49/30/21 good Δ 368 6340 13 A-(3)/B-(1)/C-(2) 50/40/10 good ○ 108 7330 * ○:good Δ:unstable X: failed in film forming

Claims: An ethylene copolymer molded structure comprising an ethylene copolymer composition comprising [A] 55-80% by weight of an ethylene/unsaturated ester copolymer having 85-65% by weight of ethylene structural units, 15-35% by weight of unsaturated ester structural units, and a melt flow rate of 0.5-20 g/10 min as measured at 190°C under a load of 2160 g, and [B] 45-20% by weight of an ethylene/vinyl alcohol copolymer having 50-20 mol% of ethylene structural units, 50-80% mol% of vinyl alcohol structural units, and a melt flow rate of 0.5-30 g/10 min as measured at 210°C under a load of 2160 g, said ethylene/vinyl alcohol copolymer [B] having an apparent melt viscosity, as measured at 220°C and a rate of shear of 100 sec -1 , which is 300-1000 Pas lower than that of said ethylene/unsaturated ester copolymer [A], and said ethylene/vinyl alcohol copolymer [B] being dispersed into said molded structure in the form of thin layers. A process for preparing a molded structure as claimed in claim 1, comprising kneading together components [A] and [B] and moulding the resultant product. An ethylene copolymer composition comprising [A] 30-75% by weight of an ethylene/unsaturated ester copolymer having 85-65% by weight of ethylene structural units, 15-35% by weight of unsaturated ester structural units, and a melt flow rate, as measured at 190°C under a load of 2160 g, of 0.5-20 g/10 min [B] 45-20% by weight of an ethylene/vinyl alcohol copolymer having 50-20 mol% of ethylene structural units, 50-80 mol% of vinyl alcohol structural units, and a melt flow rate, as measured at 210°C under a load of 2160 g, of 0.5-30 g/10 min, and [C] 1-40% by weight of a graft modified product of a non-crystalline or low crystalline ethylene/α-olefin copolymer having 60-90 mol% of ethylene structural units with an unsaturated carboxylic acid or its anhydride, said ethylene/vinyl alcohol copolymer [B] having an apparent melt viscosity, as measured at 220°C and a rate of shear of 100 sec -1 , which is 300-1000 Pas lower than that of said ethylene/unsaturated ester copolymer [A]. An ethylene copolymer molded structure formed from an ethylene copolymer composition as claimed in claim 3, wherein said ethylene/vinyl alcohol copolymer [B] of said composition is dispersed in said structure in the form of thin layers.

Inventors: FUKADA TORU, ITO HIROSHI, FUKADA, TORU, ITO, HIROSHI
Applicants: MITSUI DU PONT POLYCHEMICAL, DU PONT-MITSUI POLYCHEMICALS CO., LTD.
Application year: 1991
Main classification: C08L23
IPC codes: C08L51, C08L23, C08L29