JP2004256807A - Resin composition and its application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a resin composition capable of forming a molding with homogenous thickness in TD (width) direction in filming such as inflation molding to give films or sheets, and to provide a mono or multilayered structure using the resin composition. <P>SOLUTION: The present invention provides the multilayered structure containing the resin composition or its layers composed of (A) a copolymerized saponified product of ethylene, vinyl acetate and a vinyl silane compound and (B) magnesium acetate or a bivalent higher fatty acid metal salt. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a resin composition containing a saponified copolymer of ethylene, vinyl acetate and a vinylsilane compound and a multilayer structure using the same, and more particularly, to a TD (width) direction during film formation such as inflation molding. The present invention relates to a resin composition of the above-mentioned saponified copolymer in which variation in thickness is suppressed, and a multilayer structure having a layer of the composition.

  Conventionally, saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) is excellent in transparency, gas barrier properties, fragrance retention, solvent resistance, oil resistance, and the like. It is used by being formed into films and sheets of food packaging materials, pharmaceutical packaging materials, industrial chemical packaging materials, agricultural chemical packaging materials, and the like, or containers such as bottles.

  In the above-mentioned molding, it is general that EVOH is extruded in a molten state from a device such as an extruder (die or the like) with a constant thickness to form a film. However, unevenness of cooling and flow of molten resin are not uniform. The thickness of the extruded film or sheet may be uneven due to uniformity, neck-in, or the like. In particular, thickness variations are often observed in the TD (width) direction, and such variations cause poor appearance of a formed film or sheet, poor adhesion (lamination) with another film or sheet, poor printing on the surface, and the like. Inconvenience.

Therefore, in order to prevent such variations, the present applicant added EVOH to boron compounds, peroxides, polyacids, polyamide compounds, copper compounds, aluminum compounds, titanium compounds, zinc compounds, tin compounds, vanadium. It has been proposed that EVOH be prepared by reacting at least one compound selected from a compound and a chromium compound (see Patent Document 1) and that EVOH contain a specific oxide (see Patent Document 2).
JP-A-9-165483 JP 2000-351811 A

  However, according to the technology disclosed in Patent Document 1, although a film having excellent transparency can be obtained, it is difficult to suppress a variation in the film thickness in the TD direction at the time of film formation by an inflation molding machine, and there are many gels. Although the film can be easily formed, and the technique disclosed in Patent Document 2 can improve the swaying and meandering of the film at the time of high-speed film formation, when a die having a long flow path is used at the time of inflation molding, or when the outermost or innermost layer is EVOH. In the case of a laminated body in which layers are arranged, the thickness in the TD direction may not be stable, and a resin composition in which the variation in the thickness in the TD direction is suppressed during film formation is desired.

  The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that a copolymer saponified product of ethylene, vinyl acetate and vinyl silane compound (A), magnesium acetate or a higher fatty acid of a divalent metal The present inventors have found that the resin composition containing the salt (B) meets the above object, and have completed the present invention.

  The resin composition of the present invention can suppress thickness variations in the TD (width) direction at the time of film formation such as inflation molding, and can obtain a molded product such as a film or sheet having a uniform thickness. The multilayer structure including the formed layer is useful for packaging of foods, pharmaceuticals and the like.

Hereinafter, the present invention will be described in detail.
The saponified copolymer (A) used in the resin composition of the present invention is obtained by saponifying a copolymer of ethylene, vinyl acetate and a vinylsilane-based compound. Examples of the vinylsilane-based compound include vinyltrimethoxysilane and vinyl Methyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, vinylisobutyldimethoxysilane, vinylethyldimethoxysilane, vinylmethoxydibutoxysilane, vinyldimethoxybutoxysilane, vinyltributoxysilane , Vinylmethoxydihexyloxysilane, vinyldimethoxyhexyloxysilane, vinyltrihexyloxysilane, vinylmethoxydioctyloxysilane, vinyldimethoxyoctyloxysilane, vinyl Trioctyloxysilane, vinylmethoxy dilauroxy silane, vinyl dimethoxy lauryloxy silane, vinyl methoxy dioleoxy silane, vinyl dimethoxy oleyloxy silane, and the like, among which vinyl methoxy silane and vinyl triethoxy silane are preferred. Used.

In order to obtain such a copolymer, vinyl acetate and the above-mentioned vinylsilane compound are dissolved in a solvent such as methanol, and 2,2'-azobis is dissolved under pressure with ethylene (about 30 to 60 kg / cm ² ). The desired copolymer can be obtained by performing a copolymerization reaction in the presence of a polymerization initiator such as isobutyronitrile (AIBN).

  Thus, a copolymer comprising ethylene, vinyl acetate and a vinylsilane compound is obtained, and the ethylene content in the copolymer is 5 to 60 mol% (further 25 to 58 mol%, particularly 25 to 58 mol%). If the ethylene content is less than 5 mol%, the gas barrier properties and melt moldability of the finally obtained saponified copolymer (A) at high humidity are reduced, and conversely 70 mol%. %, It is not preferable because sufficient gas barrier properties cannot be obtained.

  The content of silicon derived from vinylsilane groups in the copolymer is 0.001 to 0.1% by weight (furthermore, 0.005 to 0.05% by weight, particularly 0.005 to 0.03% by weight). %) Is preferred, and if the content is less than 0.001% by weight, the function and effect of the present invention may not be sufficiently obtained. Conversely, if the content exceeds 0.1% by weight, gel may be generated in a molded film. Is not preferred.

  In the present invention, a copolymerizable ethylenically unsaturated monomer may be further copolymerized as long as the effects of the present invention are not impaired. Examples of such a monomer include propylene, 1-butene, Olefins such as isobutene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid or salts thereof, or mono- or dialkyl having 1 to 18 carbon atoms Acrylamides such as esters, acrylamide, N-alkylacrylamide having 1 to 18 carbon atoms, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or a salt thereof, acrylamidopropyldimethylamine or an acid salt or a quaternary salt thereof , Methacrylamide, C-C18 N-alkyl methacrylamide, Methacrylamides such as N, N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or a salt thereof, methacrylamidopropyldimethylamine or an acid salt or a quaternary salt thereof, N-vinylpyrrolidone, N-vinylformamide, N- N-vinylamides such as vinylacetamide, vinyl cyanides such as acrylonitrile and methacrylonitrile, vinyl ethers such as alkyl vinyl ether having 1 to 18 carbon atoms, hydroxyalkyl vinyl ether and alkoxyalkyl vinyl ether, vinyl chloride, vinylidene chloride, fluoride Vinyl halides such as vinyl, vinylidene fluoride and vinyl bromide, vinyl silanes such as trimethoxy vinyl silane, allyl acetate, allyl chloride, allyl alcohol, dimethyl allyl alcohol Trimethyl - (3-acrylamido-3-dimethylpropyl) - ammonium chloride, and the like acrylamido-2-methylpropanesulfonic acid. Further, the saponified copolymer may be post-modified such as urethane, acetal, cyanoethyl, etc. within a range not to impair the purpose of the present invention.

  The copolymer obtained above is then saponified, and a known method can be employed for the saponification. For example, after saponifying the copolymer with an alkali such as sodium hydroxide, potassium hydroxide, sodium methylate and potassium methylate in a methanol solvent, the copolymer is saponified by neutralizing with an acid such as acetic acid. (A) is obtained.

  The saponification degree of the vinyl acetate component of the obtained saponified copolymer (A) is preferably at least 90 mol% (more preferably at least 95 mol%, particularly preferably at least 99 mol%). If it is less than 90 mol%, the gas barrier properties, thermal stability, moisture resistance, etc. are undesirably reduced.

  Further, the saponified copolymer (A) has a melt flow rate (MFR) (210 ° C., load 2160 g) of 0.5 to 100 g / 10 min (further 1 to 50 g / 10 min, particularly 3 to 35 g). / 10 min) is preferred, and if the melt flow rate is less than 0.5 g / 10 min, the inside of the extruder will be in a high torque state during molding, making extrusion difficult, and conversely, exceeding 100 g / 10 min. In such a case, the thickness accuracy of the obtained film or sheet may decrease, which is not preferable.

  Further, as the saponified copolymer EVOH (A), two or more different kinds of saponified copolymers can be used. In this case, the ethylene content is 5 mol% or more (further 5 to 25%). Mol%, especially 8 to 20 mol%), and / or the degree of saponification is 1 mol% or more (further 1 to 15 mol%, especially 2 to 10 mol%), and / or the ratio of MFR is different. It is preferably 2 or more (more preferably 3 to 20, especially 4 to 15).

  The resin composition of the present invention contains the above saponified copolymer (A) and a higher fatty acid salt of magnesium acetate or a divalent metal (B). Examples include fatty acid salts of several or more, specifically, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, oleic acid, capric acid, behenic acid, In addition to alkaline earth metal salts such as magnesium salts, calcium salts and barium salts of higher fatty acids such as linoleic acid, zinc metal salts and the like can be mentioned. Among these, stearic acid, oleic acid and alkaline earth metal laurate can be mentioned. Salts (magnesium salts, calcium salts) are preferably used.

  The resin composition of the present invention contains the above (A) and (B), and the content ratio is not particularly limited, but (B) is 100 parts by weight of (A) in metal conversion. 0.001 to 0.05 parts by weight (more preferably 0.001 to 0.03 parts by weight, particularly 0.001 to 0.02 parts by weight) is contained, and such a content is less than 0.001 part by weight. In such a case, it is difficult to sufficiently obtain the operation and effect of the present invention. Conversely, if the content exceeds 0.05 part by weight, the appearance of the obtained film or sheet becomes poor, which is not preferable.

  In order to obtain the resin composition of the present invention, the above-mentioned (A) and (B) may be blended. Specifically, a) saponified copolymer (A) powder and pellets are prepared by adding magnesium acetate Or a method of externally adding a fatty acid metal salt (B), a) a method of melt-mixing a saponified copolymer (A) with magnesium acetate or a fatty acid metal salt (B), c) a solution of the resin composition (A) (water) / Alcohol solution), and then mixing the fatty acid metal salt (B) with a coagulating liquid and extruding the mixture into strands to form pellets. A method (a) is preferably employed.

  In the present invention, it is also preferable to further include a boron compound (C) in the resin composition in that the effects of the present invention can be more remarkably obtained. Acid or a metal salt thereof, for example, calcium borate, cobalt borate, zinc borate (zinc tetraborate, zinc metaborate, etc.), aluminum potassium potassium, ammonium borate (ammonium metaborate, ammonium tetraborate, Ammonium borate, ammonium octaborate, etc.), cadmium borate (cadmium orthoborate, cadmium tetraborate, etc.), potassium borate (potassium metaborate, potassium tetraborate, potassium pentaborate, potassium hexaborate, potassium hexaborate) Potassium borate, etc.), silver borate (silver metaborate, silver tetraborate, etc.), copper borate (secondary boric acid) , Copper metaborate, copper tetraborate, etc.), sodium borate (sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate, sodium octaborate, etc.), lead borate (Lead metaborate, lead hexaborate, etc.), nickel borate (nickel orthoborate, nickel diborate, nickel tetraborate, nickel octaborate, etc.), barium borate (barium orthoborate, barium metaborate, Barium borate, barium tetraborate, etc.), bismuth borate, magnesium borate (magnesium orthoborate, magnesium diborate, magnesium metaborate, trimagnesium tetraborate, pentamagnesium tetraborate, etc.), manganese borate ( Manganese borate, manganese metaborate, manganese tetraborate, etc.), lithium borate ( And other borate minerals such as borax, carnite, inyoite, dwarf stone, syanite, and Zeyberite, and the like. Sand, boric acid, sodium borate (sodium metaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate, sodium octaborate, etc.) are used.

  The content of the boron compound (C) is not particularly limited, but is 0.001 to 1.0 parts by weight (furthermore, 0.001 to 0 parts by weight) in terms of boron based on 100 parts by weight of the saponified copolymer (A). 0.5 parts by weight, particularly 0.001 to 0.2 parts by weight). When the content is less than 0.001 parts by weight, it is difficult to obtain the effect of the content. Exceeding the parts by weight is not preferred because the appearance of molded products such as films and sheets tends to deteriorate.

  When the boron compound (C) is contained in the resin composition, there is no particular limitation, and a method of adding the boron compound (C) to the resin composition containing the above (A) and (B) may be employed. However, in consideration of uniformly dispersing the boron compound (C), it is preferable that the boron compound (C) is previously contained in the saponified copolymer (A), and particularly preferable methods include 1) a water content of 20 to 80% by weight of the porous precipitate of the saponified copolymer was prepared by reducing the content of the boron compound in the aqueous boron compound solution to 100% of the total amount of water contained in the saponified copolymer and water contained in the aqueous boron compound solution. After contacting with a boron compound aqueous solution adjusted to be 0.001 to 1.0 parts by weight with respect to parts by weight to contain the boron compound, drying is performed by further combining fluidized drying and standing drying. Method 2) A method in which a saponified copolymer is brought into contact with an aqueous solution of a boron compound to contain the boron compound, dried to a water content of 0.001 to 2% by weight, and then contacted with water. The combined saponified pellet is brought into contact with an aqueous solution of a boron compound to contain the boron compound, and then dried to a water content of 0.001 to 10% by weight, and the resulting copolymer saponified pellet is melt-kneaded and pelletized again. 4) After a boron compound is contained in a homogeneous solution (water / alcohol solution or the like) of a saponified copolymer, the mixture is extruded into a coagulating solution in the form of a strand, and then the obtained strand is cut into pellets. And a drying method.

  Thus, the resin composition of the present invention containing (A) and (B) or (A) to (C) as described above can be obtained. As long as the object of the invention is not impaired, saturated aliphatic amides (eg, stearic acid amide, etc.), unsaturated fatty acid amides (eg, oleic acid amide, etc.), bisfatty acid amides (eg, ethylene bisstearic acid amide, etc.), low molecular weight polyolefins (eg, For example, lubricants such as low molecular weight polyethylene having a molecular weight of about 500 to 10,000 or low molecular weight polypropylene, etc., organic acids (eg, acetic acid, propionic acid, stearic acid, etc.), inorganic acids (eg, boric acid, phosphoric acid, etc.), inorganics Salts (eg, hydrotalcite), plasticizers (eg, aliphatic glycols such as ethylene glycol, glycerin, and hexanediol) Polyhydric alcohols), oxygen absorbers (eg, reduced iron powder, potassium sulfite, ascorbic acid, hydroquinone, gallic acid, etc.), heat stabilizers, light stabilizers, antioxidants containing no amide group, ultraviolet absorbers, Coloring agents, antistatic agents, surfactants, antibacterial agents, antiblocking agents, slip agents, fillers (eg, inorganic fillers, etc.), and other resins (eg, polyolefins, polyesters, etc.) may be added.

  The resin composition of the present invention is useful for various packaging materials and the like, and can be directly used for melt molding and used for such applications, but the workability during melt molding and the discharge stability of an extruder and the like are also possible. In consideration of the above, it is preferable to knead the mixture once in a molten state and then cool and solidify the mixture to form a pellet or the like. As such means, for example, a known kneading apparatus such as a kneader-ruder, an extruder, a mixing roll, a Banbury mixer, and a blast mill can be used, but usually, a single-screw or twin-screw extruder is used. It is industrially preferable, and if necessary, it is also preferable to provide a vent suction device, a gear pump device, a screen device, and the like. In particular, in order to remove moisture and by-products (such as low-molecular weight pyrolysis products), the extruder is provided with one or more vent holes to prevent suction under reduced pressure and prevent oxygen from being mixed into the extruder. By continuously supplying an inert gas such as nitrogen into the hopper, a resin composition of excellent quality with reduced thermal coloring and thermal deterioration can be obtained.

  Such a resin composition is formed into films, sheets, containers, fibers, rods, pipes, and various other molded products by melt molding, and these crushed products (such as when reused collected products are reused) are again melt-molded. It can also be used for As the melt molding method, an extrusion molding method (T-die extrusion, inflation extrusion, blow molding, melt spinning, profile extrusion, etc.) or an injection molding method is mainly employed, and the melting temperature is selected from a range of 150 to 300 ° C. Often.

In particular, the resin composition of the present invention can remarkably exert its function and effect in an inflation molding method, and such a molding method will be described.
The inflation molding method is to introduce a resin or a resin composition melted by an extruder into a cylindrical die (a spider die, a spiral mandrel die, etc.) and blow air into a cylindrical film extruded from the die. It is a method of expanding, cooling with an apparatus such as an air ring, and winding the obtained film.In applying the resin composition of the present invention to such a method, a conventionally known air-cooled multilayer inflation film is formed. Inflation molding can be performed using an apparatus or the like, and molding conditions at this time can employ conventionally known conditions. For example, the blow-up ratio is 0.75 to 1.0, and the take-off speed is 15 to 30 m / min, the film folding width may be about 200 to 350 mm, and the melting temperature of the resin composition of the present invention is 150 to 250 ° C. (further 18 ° C.). To 230 ° C.) may be selected from the range of about.

  Such a molded article can of course be used as a single layer for various uses, but is also useful as a laminate (multilayer structure), and in particular, a thermoplastic resin layer is formed on at least one surface of a layer made of the resin composition. It is preferable to use as a laminated body obtained by laminating, and a laminated body suitable for practical use having water resistance, mechanical properties, heat sealability and the like is obtained.

Hereinafter, such a laminate will be described.
In producing the laminate, another substrate (such as a thermoplastic resin) is laminated on one or both sides of the resin composition of the present invention. The laminating method includes, for example, the resin composition of the present invention. A method of melt-extruding and laminating another substrate on a molded film or a sheet of a resin, a method of melt-extruding and laminating the resin composition on another substrate, and co-extrusion of the resin composition with another substrate And a method of dry laminating a molded film or sheet of the resin composition with another substrate using an adhesive such as an organic titanium compound, an isocyanate compound, a polyester-based compound, or a polyurethane compound. The melt molding temperature during the above melt extrusion is often selected from the range of 150 to 300 ° C.

  As such another substrate, a thermoplastic resin is useful. Specifically, linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer Coalesce, ionomer, ethylene-propylene (block or random) copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, Polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, homo- or copolymer of olefin such as polybutene, polypentene, polymethylpentene, or homo- or copolymer of these olefins Graft-modified with unsaturated carboxylic acids or their esters Any broadly defined polyolefin resin, polyester resin, polyamide resin (including copolymerized polyamide), polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, chlorine Polyethylene, chlorinated polypropylene, aromatic or aliphatic polyketones, polyalcohols obtained by reducing them, and other EVOH, etc., but practical use such as properties (particularly strength and appearance) of the laminate. From the viewpoint of properties, polypropylene, ethylene-propylene (block or random) copolymer, polyamide, polyethylene, ethylene-vinyl acetate copolymer, polystyrene, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN) are preferred. Used, in particular stretchability, transparency, excellent polypropylene flexible, ethylene - propylene (block or random) copolymer, polyethylene.

  Furthermore, when a molded product such as a film or sheet of the resin composition of the present invention is extrusion-coated with another substrate, or when a film or sheet of another substrate is laminated with an adhesive, such a substrate is used. Can be used any substrate (paper, metal foil, uniaxially or biaxially stretched plastic film or sheet and its inorganic deposit, woven fabric, nonwoven fabric, metal flocculent, woody, etc.) other than the thermoplastic resin. is there.

  The layer structure of the laminate is such that the layer of the resin composition of the present invention is a (a1, a2,...), And another base material, for example, a thermoplastic resin layer is b (b1, b2,...). In the case of a film, sheet, or bottle, not only the two-layer structure of a / b but also b / a / b, a / b / a, a1 / a2 / b, a / b1 / b2, b2 / b1 Any combination such as / a / b1 / b2 and b2 / b1 / a / b1 / a / b1 / b2 is possible. Further, at least a regrind layer comprising a mixture of a resin composition and a thermoplastic resin is referred to as R. B / R / a, b / R / a / b, b / R / a / R / b, b / a / R / a / b, b / R / a / R / a / R / b In the filament form, a and b may be any type such as a bimetal type, a core (a) -sheath (b) type, a core (b) -sheath (a) type, or an eccentric core-sheath type. Together is possible.

  In the present invention, in the above-described laminated structure, a laminated structure in which a layer of the resin composition of the present invention is the outermost layer is particularly preferable, and more specifically, a layer of the resin composition of the present invention / adhesive resin. Layer / polyolefin-based resin (preferably polyethylene) layer, layer of the resin composition of the present invention / polyamide-based resin layer / polyolefin-based resin (preferably polyethylene) layer, and the like. Sometimes, a better film appearance can be obtained, and advantages such as excellent uniformity of the film thickness can be obtained.

  In the above-described various layer configurations, an adhesive resin layer can be provided between the respective layers as necessary, and various types of such adhesive resins can be used. The addition of an unsaturated carboxylic acid or an anhydride thereof to an olefin polymer (homopolymer or copolymer of the above-mentioned olefins) is preferred in that a laminated body can be obtained. And a modified olefin polymer containing a carboxyl group obtained by chemically bonding them by a graft reaction or the like.Specifically, maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, anhydride Maleic acid graft modified ethylene-propylene (block or random) copolymer, maleic anhydride graft modified ethylene Ethyl acrylate copolymer, maleic anhydride graft-modified ethylene anhydride - one or a mixture of two or more species selected from vinyl acetate copolymers and the like as preferred. At this time, the amount of the unsaturated carboxylic acid or anhydride thereof contained in the thermoplastic resin is preferably 0.001 to 3% by weight, more preferably 0.01 to 1% by weight, and particularly preferably 0.03% by weight. ~ 0.5% by weight. If the amount of modification in the modified product is small, the adhesiveness may be insufficient, while if it is large, a crosslinking reaction may occur, and moldability may deteriorate, which is not preferable. These adhesive resins may be blended with the resin composition of the present invention, other rubber / elastomer components such as EVOH, polyisobutylene, and ethylene-propylene rubber, as well as the resin of layer b. In particular, by blending a polyolefin resin different from the base polyolefin resin of the adhesive resin, the adhesiveness may be improved, which is useful.

  The thickness of each layer of the laminate cannot be unconditionally determined depending on the layer constitution, the type of b, the use and the form of the container, the required physical properties, and the like. The layer is selected from a range of about 10 to 5000 μm (further 30 to 1000 μm), and the adhesive resin layer is selected from a range of about 5 to 400 μm (further 10 to 150 μm). If the thickness of the layer a is less than 5 μm, the gas barrier properties are insufficient, and the thickness control becomes unstable. On the other hand, if the thickness exceeds 500 μm, the impact resistance and the like are inferior, and it is not economical. On the contrary, if the thickness exceeds 5000 μm, the weight becomes large and it is not economical and is not preferable. If the adhesive resin layer is less than 5 μm, the interlayer adhesion becomes insufficient, and the thickness control becomes unstable. Exceeding the weight increases the weight and is not economical and is not preferable.

  The laminate is used as it is in various shapes. However, in order to further improve the physical properties of the laminate and to form a desired container shape, it is preferable to perform a heat stretching treatment. Here, the heat-stretching treatment means to heat a film, a sheet, and a parison-like laminate that are uniformly heated by a chuck, a plug, a vacuum force, a pneumatic force, a blow, or the like to form a cup, tray, tube, bottle, or film. This stretching operation may be uniaxial stretching or biaxial stretching, and it is better to perform stretching at the highest possible magnification in terms of physical properties, such as pinholes and cracks during stretching. Thus, a stretch-formed product excellent in gas barrier properties, free from stretch unevenness, uneven thickness, delamination, etc. is obtained.

  As the stretching method, a roll stretching method, a tenter stretching method, a tubular stretching method, a stretch blow method, a vacuum forming, a press forming, a vacuum press forming, or the like having a high draw ratio can be employed. In the case of biaxial stretching, any of a simultaneous biaxial stretching method and a sequential biaxial stretching method can be adopted. The stretching temperature is selected from the range of 60 to 170 ° C, preferably about 80 to 160 ° C.

After the stretching is completed, it is also preferable to perform heat setting. The heat setting can be performed by a well-known means, and heat treatment is performed at 80 to 170 ° C., preferably 100 to 160 ° C. for about 2 to 600 seconds while keeping the stretched film in a tensioned state.
In addition, when used for heat shrink packaging of raw meat, processed meat, cheese, etc., the product film is not heat-set after stretching, and the raw meat, processed meat, cheese, etc. are stored in the film, The film is subjected to a heat treatment at 50 to 130 ° C., preferably 70 to 120 ° C. for about 2 to 300 seconds to thermally shrink the film and to perform tight packaging.

  The shape of the thus obtained laminate may be any shape, and examples thereof include a film, a sheet, a tape, a cup, a tray, a tube, a bottle, a pipe, a filament, and an extrudate having a modified cross section. The obtained laminate may be subjected to heat treatment, cooling treatment, rolling treatment, printing treatment, dry lamination treatment, solution or melt coating treatment, bag making, deep drawing, box processing, tube processing, split processing, etc., as necessary. It can be carried out.

  Containers made of cups, trays, tubes, bottles, pouches, bags, etc., and bags and lids made of stretched films obtained as described above are not only general foods, but also seasonings such as mayonnaise and dressings, fermentation of miso, etc. Foods, oils and fats such as salad oils, beverages, cosmetics, pharmaceuticals, detergents, cosmetics, industrial chemicals, agricultural chemicals, fuels, and various other containers are useful. In the present invention, a film with particularly excellent appearance is obtained. Therefore, it is useful for packaging of foods, pharmaceuticals and the like that show beautiful contents.

Hereinafter, the present invention will be specifically described with reference to examples.
In the examples, “parts” and “%” mean on a weight basis unless otherwise specified.

Regarding the measurement of the content of the boron compound in the saponified copolymer (A) and the resin composition, the saponified copolymer (A) and the resin composition are alkali-melted, and the amount of boron is determined by ICP emission spectroscopy. It was done by doing.
For the measurement of the alkali (earth) metal content, the saponified copolymer (A) and the resin composition are ashed, then dissolved in an aqueous hydrochloric acid solution, and the alkali (earth) metal is analyzed by atomic absorption spectrometry. Performed by quantification.

[Production of saponified copolymer (A)]
Vinyl acetate and vinyltrimethoxysilane were dissolved in a methanol solvent, and under ethylene pressure (55 kg / cm ² ), 2,2′-azobisisobutyronitrile (AIBN) was used as an initiator at a reaction temperature of 60 ° C. The reaction was carried out until the concentration reached 50% to obtain a silane-containing copolymer.
Sodium hydroxide was added to the obtained copolymer in an amount equivalent to 0.02% based on the vinyl acetate component, and a saponification reaction was carried out to obtain an ethylene content of 44 mol% and a saponification degree of the vinyl acetate component of 99.5 mol. %, A vinylsilane modified amount of 0.04 mol% (silicon content 0.03%), and a copolymer saponified product (A) having an MFR of 3.2 g / 10 min (210 ° C., load 2160 g).

Example 1
100 parts of the above saponified copolymer (A), 0.01 parts of magnesium acetate (B) (0.002 parts in terms of magnesium) and 0.01 part of boric acid (C) (0.0015 parts in terms of boron). Was melt-kneaded under the following conditions using a twin-screw extruder to obtain a resin composition (pellet) of the present invention.

[Melting pelletization conditions by twin screw extruder]
Screw inner diameter 30mm (L / D = 30)
Screw shape Screen mesh having a 100 mm kneading disk in the compression part 90/90 mesh
Screw rotation speed 150rpm
Vent hole Decompression suction is performed. Nitrogen gas is supplied in the hopper and replaced. Extrusion temperature C1: 120 ° C
C2: 170 ° C
C3: 210 ° C
C4: 220 ° C
C5: 220 ° C
AD: 210 ° C
D: 210 ° C

  The resin composition (pellet) obtained above was charged into an inflation molding machine, and inflation film formation was performed under the following conditions.

[Inflation film forming conditions]
Die diameter 150mm
Pickup speed 15m / min
Layer configuration [Outside] EVOH / adhesive resin / LDPE = 10 μm / 10 μm / 30 μm [Inside]
Film fold width 200mm

  The thickness of the obtained film in the TD (width) direction was measured, and the average thickness and the difference between the maximum thickness and the minimum thickness were determined. The measurement was performed at intervals of about 1 cm in the TD direction and over about 1 m in the MD (longitudinal) direction.

Example 2
Example 1 is the same as Example 1 except that magnesium acetate (B) was changed to 0.005 part (0.001 part in terms of magnesium) and boric acid (C) was changed to 0.02 part (0.003 part in terms of boron). To obtain a resin composition, which was similarly evaluated.

Example 3
A resin composition was obtained in the same manner as in Example 1 except that magnesium stearate (B) was used in place of magnesium acetate (B) in an amount of 0.025 part (0.001 part in terms of magnesium). Was done.

Example 4
A resin composition was obtained in the same manner as in Example 1, except that 0.02 part of zinc stearate (B) (0.002 part in terms of zinc) was used instead of magnesium acetate (B), and evaluated similarly. Was done.

Example 5
A resin composition was obtained in the same manner as in Example 1, except that 0.02 part of calcium stearate (B) (0.0013 part in terms of calcium) was used instead of magnesium acetate (B). went.

Example 6
A resin composition was obtained in the same manner as in Example 1 except that 0.08 part (0.003 part in terms of boron) of potassium borate (C) was used instead of boric acid (C), and evaluation was similarly performed. went.

Example 7
A resin composition was obtained in the same manner as in Example 1 except that boric acid (C) was not contained, and was similarly evaluated.

Comparative Example 1
In Example 1, inflation molding was performed using only the saponified copolymer (A), and the evaluation was performed in the same manner.

Table 1 shows the evaluation results of the examples and the comparative examples.
[Table 1]
Average thickness Maximum thickness Minimum thickness Difference between maximum thickness and minimum thickness
Example 1 47.0 52.5 41.5 11.0
〃 247.7 54.5 42.5 11.0
〃 347.1 53.8 41.9 11.9
４ 4 48.0 54.2 43.3 11.9
５ 5 47.9 53.1 42.4 10.7
〃 6 48.3 54.2 43.3 10.9
〃 7 50.2 56.9 43.8 13.1
Comparative Example 1 47.4 57.0 39.5 17.5
Unit: μm

  The resin composition of the present invention can suppress thickness variations in the TD (width) direction at the time of film formation such as inflation molding, and can obtain a molded product such as a film or sheet having a uniform thickness. The multilayer structure including the formed layer is useful for packaging of foods, pharmaceuticals and the like.

Claims (9)

  A resin composition comprising a saponified copolymer of ethylene, vinyl acetate and a vinylsilane compound (A), a higher fatty acid salt of magnesium acetate or a divalent metal (B).   The resin composition according to claim 1, wherein the content of silicon in the saponified copolymer (A) is 0.001 to 0.1% by weight.   The content of the higher fatty acid salt (B) of magnesium acetate or a divalent metal is 0.001 to 0.05 parts by weight in terms of metal based on 100 parts by weight of the saponified copolymer (A). The resin composition according to claim 1.   The ethylene content in a saponified copolymer (A) is 5 to 60 mol%, and the saponification degree of a vinyl acetate component is 90 mol% or more, The Claims 1-3 characterized by the above-mentioned. Resin composition.   The resin composition according to any one of claims 1 to 4, further comprising a boron compound (C).   The resin composition according to claim 5, wherein the content of the boron compound (C) is 0.001 to 1 part by weight in terms of boron based on 100 parts by weight of the saponified copolymer (A).   A multilayer structure comprising at least one layer of the resin composition according to claim 1.   The multilayer structure according to claim 7, wherein a multilayer film in which a layer of the resin composition is disposed as an outermost layer is bonded to another film.   9. The multilayer structure according to claim 7, which is manufactured by an inflation molding method.