JP2020084016A - Film, production method thereof, packaging material, and vacuum packaging bag - Google Patents

Abstract

To provide a film excellent in film formability, stretchability and impact resistance at a low temperature and a production method thereof and to provide a packaging material and a vacuum packaging bag each using the film.SOLUTION: The film is formed from a resin composition containing (A) an ethylene/vinyl alcohol copolymer having an ethylene unit content of 20 to 60 mol% and (B) a boron compound. The boron compound (B) includes (C) free boric acid; the content of the boron compound (B) based on the ethylene/vinyl alcohol copolymer (A) in the resin composition is 100 ppm to 5,000 ppm in terms of orthoboric acid; and the proportion of the free boric acid (C) in the boron compound (B) is 0.1 mass% to 10 mass% in terms of orthoboric acid.SELECTED DRAWING: None

Description

The present invention relates to a film, a manufacturing method thereof, a packaging material, and a vacuum packaging bag.

Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH") is a polymer material having excellent gas barrier properties, oil resistance, antistatic properties, mechanical strength, etc., and various packaging materials such as films and containers. Is widely used as. When using EVOH as various packaging materials, an EVOH resin composition that is relatively easy to melt-mold has been proposed.

In Patent Document 1, in producing a resin composition containing a specific amount of EVOH and a boron compound, EVOH having a water content of 20 to 80 mass% is brought into contact with an aqueous solution of a boron compound, and the content of the boron compound in the aqueous solution of the boron compound. Is 0.001 to 0.5 parts by mass based on 100 parts by mass of the total amount of water contained in the EVOH and the water contained in the aqueous solution of the boron compound, whereby the melt moldability is excellent, and particularly, the production of a multilayer laminate. It is described that it is possible to obtain an EVOH resin composition which can suppress the generation of fish eyes and the like and has good long-run moldability.

Patent Document 2, 100 to 5000 ppm boron compound orthoboric acid _(H 3 BO ₃₎ in terms of carboxylic acid and / or 100~1000ppm a salt thereof with a carboxylic acid in terms of, and an alkali metal salt in terms of a metal 50~300ppm Disclosed is a multi-layer structure obtained by co-extruding a melted multi-layered body comprising an EVOH resin composition layer and a carboxylic acid-modified polyolefin resin layer adjacent to the EVOH resin composition layer. It is stated that extrusion film forming stability is improved.

JP, 11-293078, A International Publication No. 2000/020211

However, it cannot be said that the conventional EVOH resin composition has sufficient film-forming properties. Specifically, during film formation of the EVOH resin composition, neck-in, fish eyes, etc. may be a problem. Neck-in is a phenomenon in which the width of the extruded film is smaller than the effective width of the die in the film formation by the T-die. In addition, the fish eye is a crosslinked structure in which boric acid crosslinking locally progresses and the viscosity thereof is partially increased, and this is a factor that deteriorates performance such as appearance and gas barrier property.

Further, the film obtained by forming the EVOH resin composition may be stretched to improve the strength and the like, but streak-like unevenness may occur in the film during stretching. Such stretching unevenness is a factor that deteriorates the appearance and performance such as gas barrier properties. In particular, the above-mentioned fish eye and stretching unevenness tend to occur easily when the film is formed at a relatively high temperature and a high speed and continuously for a long time.

Further, in order to maintain the freshness of the contents, etc., the contents may be stored or transported at low temperature in a state of being wrapped with a packaging material. However, the packaging material molded from the EVOH resin composition has a disadvantage that it becomes hard at a low temperature and cracks and the like easily occur upon impact. When a crack or the like occurs, the gas barrier property or the like is deteriorated. Therefore, packaging materials such as films are required to have good impact resistance even in a low temperature environment.

The present invention has been made based on the above circumstances, and an object thereof is a film excellent in film-forming property, stretchability, and impact resistance at low temperature, a method for manufacturing the film, and such a film. It is to provide a used packaging material and a vacuum packaging bag.

That is, the present invention relates to [1] an ethylene-vinyl alcohol copolymer (A) having an ethylene unit content of 20 to 60 mol% (hereinafter sometimes abbreviated as "EVOH (A)") and a boron compound (B). A film formed from a resin composition containing, wherein the boron compound (B) contains free boric acid (C), and the content of the boron compound (B) with respect to EVOH (A) in the resin composition is ortho-boror. A film having an acid conversion of 100 ppm or more and 5000 ppm or less and a ratio of free boric acid (C) in the boron compound (B) of 0.1 mass% or more and 10 mass% or less in terms of orthoboric acid;
[2] The film of [1], wherein the resin composition contains a phosphate compound in an amount of 1 ppm to 500 ppm in terms of phosphate radicals;
[3] The film of [1] or [2], wherein the resin composition contains a carboxylic acid and/or a carboxylate ion in terms of carboxylic acid radicals in an amount of 0.01 μmol/g or more and 20 μmol/g or less;
[4] The film according to any one of [1] to [3], which has a melt index of 0.1 to 15 g/10 minutes measured according to ASTM D1238 under a load of 2160 g at 190° C. in the resin composition;
[5] The film of any one of [1] to [4], which is a stretched film;
[6] A method for producing a film according to [5], comprising a step of stretching the film according to any one of [1] to [4];
[7] A packaging material including the film according to any one of [1] to [5];
[8] A vacuum packaging bag provided with the film according to any one of [1] to [5];
Is achieved by providing.

ADVANTAGE OF THE INVENTION According to this invention, the film excellent in film forming property, stretchability, and impact resistance in low temperature, its manufacturing method, and the packaging material and vacuum packaging bag using such a film can be provided.

It is a side surface transparent explanatory view which shows the hot cutter used in the Example.

<Film>
The film of the present invention is a film formed from a resin composition containing EVOH (A) and a boron compound (B), wherein the boron compound (B) contains free boric acid (C). The content of the boron compound (B) with respect to the EVOH (A) is 100 ppm or more and 5000 ppm or less in terms of orthoboric acid, and the ratio of the free boric acid (C) in the boron compound (B) is 0.1 mass in terms of orthoboric acid. % To 10% by mass.

Since the film of the present invention is formed from a resin composition containing a predetermined amount of a boron compound (B) and a predetermined ratio of free boric acid (C), film-forming property, stretchability, and low temperature Excellent impact resistance. The "impact resistance at low temperature" means the resistance to impact in a low temperature environment. In the production of the film of the present invention, neck-in during film formation is suppressed, and generation of fish eyes is suppressed even during continuous film formation for a long time. Therefore, the film of the present invention is excellent in appearance, performance and the like. Further, in the production of the film of the present invention, the excellent film formability is maintained over a relatively high temperature and high speed, or over a long period of continuous film formation, so that the productivity is high. Further, the film of the present invention is less likely to cause streak-like unevenness due to stretching even when stretched, and is excellent in appearance, performance and the like. Furthermore, since the film of the present invention is excellent in impact resistance at low temperature, good gas barrier property is maintained even when impact is applied at low temperature. Hereinafter, first, the resin composition forming the film of the present invention will be described in detail.

(Resin composition)
The resin composition contains EVOH (A) and a boron compound (B), and the boron compound (B) contains free boric acid (C). Hereinafter, each component of the resin composition will be described.

(EVOH(A))
EVOH (A) is a copolymer having ethylene units and vinyl alcohol units and having an ethylene unit content of 20 to 60 mol %. EVOH (A) is usually obtained by saponification of an ethylene-vinyl ester copolymer, and the ethylene-vinyl ester copolymer can be produced and saponified by a known method. Vinyl acetate is a typical vinyl ester, but other aliphatics such as vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate and vinyl versatate. It may be a carboxylic acid vinyl ester.

The ethylene unit content of EVOH (A) is 20 mol% or more, preferably 25 mol% or more, and more preferably 27 mol% or more. The ethylene unit content of EVOH (A) is 60 mol% or less, preferably 55 mol% or less, and more preferably 50 mol% or less. If the ethylene unit content is less than 20 mol %, the thermal stability at the time of melt extrusion decreases, gelation tends to occur, and streaks and fish eyes tend to occur. This is particularly noticeable when operating at high temperature or high speed for a long time under general conditions. When the ethylene unit content exceeds 60 mol %, the gas barrier property tends to deteriorate.

The degree of saponification of EVOH (A) is preferably 90 mol% or more, more preferably 95 mol% or more, still more preferably 99 mol% or more. When the degree of saponification of EVOH (A) is 90 mol% or more, the gas barrier property, heat stability and moisture resistance of the resin composition or film tend to be good. The saponification degree may be 100 mol% or less, 99.97 mol% or less, or 99.94 mol% or less.

The EVOH (A) may have a unit derived from a monomer other than ethylene, vinyl ester and its saponified product, as long as the object of the present invention is not impaired. When EVOH (A) has a unit derived from the other monomer, the content of the unit derived from the other monomer with respect to all the structural units of EVOH (A) is preferably 30 mol% or less, and 20 mol% The following is more preferable, 10 mol% or less is further preferable, 5 mol% or less is still more preferable, and 1 mol% or less is even more preferable. When EVOH (A) has a unit derived from the other monomer, the content thereof may be 0.05 mol% or more, or 0.10 mol% or more. The other monomers include, for example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid or the like, their anhydrides, salts, or mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; Amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid or salts thereof; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxy-ethoxy)silane, γ -Vinylsilane compounds such as methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketones, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride and the like.

The unit derived from the other monomer is represented by the structural unit (I) represented by the following formula (I), the structural unit (II) represented by the following formula (II), and the following formula (III). The structural unit (III) may be at least one kind.

In the structural unit (I), structural unit (II) and structural unit (III), R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ is independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, an aromatic hydrocarbon group having 6 to 10 carbon atoms, or a hydroxyl group. Represents. Also, a pair of R ¹ , R ² and R ³ , R ⁴ and R ⁵ , and R ⁶ and R ⁷ may be bonded. Part or all of the hydrogen atoms contained in the aliphatic hydrocarbon group having 1 to 10 carbon atoms, the alicyclic hydrocarbon group having 3 to 10 carbon atoms and the aromatic hydrocarbon group having 6 to 10 carbon atoms are hydroxyl groups, It may be substituted with an alkoxy group, a carboxyl group or a halogen atom. In the structural unit (III), R ¹² and R ¹³ each independently represent a hydrogen atom, a formyl group or an alkanoyl group having 2 to 10 carbon atoms.

When the EVOH (A) has the structural unit (I), (II) or (III), the flexibility and processing characteristics of the resin composition are improved, and the stretchability and thermoformability of the resulting film or the like are good. Tends to become.

In the structural unit (I), (II) or (III), examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include an alkyl group and an alkenyl group, and an alicyclic carbon group having 3 to 10 carbon atoms. Examples of the hydrogen group include a cycloalkyl group and a cycloalkenyl group, and examples of the aromatic hydrocarbon group having 6 to 10 carbon atoms include a phenyl group.

In the structural unit (I), R ¹ , R ² and R ³ are preferably each independently a hydrogen atom, a methyl group, an ethyl group, a hydroxyl group, a hydroxymethyl group or a hydroxyethyl group, and among them, it is obtained. From the viewpoint that the stretchability and thermoformability of the multilayer structure and the like can be further improved, it is more preferable that they are each independently a hydrogen atom, a methyl group, a hydroxyl group and a hydroxymethyl group.

The method of incorporating the structural unit (I) into the EVOH (A) is not particularly limited, and for example, in the polymerization of ethylene and vinyl ester, a monomer derived from the structural unit (I) is copolymerized. Methods and the like. Examples of the monomer derived from the structural unit (I) include alkenes such as propylene, butylene, pentene, and hexene; 3-hydroxy-1-propene, 3-acyloxy-1-propene, 3-acyloxy-1-butene. , 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-hydroxy-1-butene, 4-acyloxy-3-hydroxy-1-butene, 3-acyloxy-4-methyl -1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy-3-methyl-1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-hydroxy-1-pentene , 5-hydroxy-1-pentene, 4,5-dihydroxy-1-pentene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-hydroxy-3 -Methyl-1-pentene, 5-hydroxy-3-methyl-1-pentene, 4,5-dihydroxy-3-methyl-1-pentene, 5,6-dihydroxy-1-hexene, 4-hydroxy-1-hexene 5-hydroxy-1-hexene, 6-hydroxy-1-hexene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene Alkenes having a hydroxyl group or an ester group such as Among them, propylene, 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, and 3 from the viewpoint of copolymerization reactivity, processability of the obtained film, and gas barrier property. ,4-diacyloxy-1-butene is preferred. In addition, "acyloxy" is preferably acetoxy, specifically, 3-acetoxy-1-propene, 3-acetoxy-1-butene, 4-acetoxy-1-butene and 3,4-diacetoxy-1-butene. Is preferred. In the case of an alkene having an ester, the structural unit (I) is derived during the saponification reaction.

In the structural unit (II), R ⁴ and R ⁵ are preferably both hydrogen atoms. More preferably, both R ⁴ and R ⁵ are hydrogen atoms, one of R ⁶ and R ⁷ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and the other is a hydrogen atom. The aliphatic hydrocarbon group is preferably an alkyl group or an alkenyl group. From the viewpoint of particularly emphasizing the gas barrier property in the obtained multilayer structure, it is more preferable that one of R ⁶ and R ⁷ is a methyl group or an ethyl group and the other is a hydrogen atom. Further, it is more preferable that one of R ⁶ and R ⁷ is a substituent represented by (CH ₂ ) _h OH (where h is an integer of 1 to 8) and the other is a hydrogen atom. In the substituent represented by (CH ₂ ) _h OH, h is preferably an integer of 1 to 4, more preferably 1 or 2, and even more preferably 1.

The method of incorporating the structural unit (II) into EVOH (A) is not particularly limited, and a method of incorporating the monovalent epoxy compound into EVOH (A) obtained by the saponification reaction and the like are included. Used. As the monovalent epoxy compound, compounds represented by the following formulas (IV) to (X) are preferably used.

In the formulas (IV) to (X), R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ are each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 10 carbon atoms (alkyl group, And an alicyclic hydrocarbon group having 3 to 10 carbon atoms (such as a cycloalkyl group and a cycloalkenyl group) or an aliphatic hydrocarbon group having 6 to 10 carbon atoms (such as a phenyl group). Further, i, j, k, p and q each independently represent an integer of 1 to 8. However, when R ¹⁷ is a hydrogen atom, R ¹⁸ has a substituent other than a hydrogen atom.

Examples of the monovalent epoxy compound represented by the formula (IV) include epoxyethane (ethylene oxide), epoxypropane, 1,2-epoxybutane, 2,3-epoxybutane, and 3-methyl-1,2-epoxy. Butane, 1,2-epoxypentane, 3-methyl-1,2-epoxypentane, 1,2-epoxyhexane, 2,3-epoxyhexane, 3,4-epoxyhexane, 3-methyl-1,2-epoxy Hexane, 3-methyl-1,2-epoxyheptane, 4-methyl-1,2-epoxyheptane, 1,2-epoxyoctane, 2,3-epoxyoctane, 1,2-epoxynonane, 2,3-epoxy Nonane, 1,2-epoxydecane, 1,2-epoxydodecane, epoxyethylbenzene, 1-phenyl-1,2-epoxypropane, 3-phenyl-1,2-epoxypropane and the like can be mentioned. Examples of the monovalent epoxy compound represented by the formula (V) include various alkyl glycidyl ethers. Examples of the monovalent epoxy compound represented by the formula (VI) include various alkylene glycol monoglycidyl ethers. Examples of the monovalent epoxy compound represented by the formula (VII) include various alkenyl glycidyl ethers. Examples of the monovalent epoxy compound represented by the formula (VIII) include various epoxy alkanols such as glycidol. Examples of the monovalent epoxy compound represented by the formula (IX) include various epoxy cycloalkanes. Examples of the monovalent epoxy compound represented by the formula (X) include various epoxy cycloalkenes.

Among the monovalent epoxy compounds, epoxy compounds having 2 to 8 carbon atoms are preferable. Particularly, from the viewpoint of easy handling of the compound and reactivity, the carbon number of the monovalent epoxy compound is more preferably 2 to 6, and further preferably 2 to 4. Further, the monovalent epoxy compound is particularly preferably the compound represented by the formula (IV) or the formula (V). Specifically, from the viewpoints of reactivity with EVOH (A), processability of the obtained film and the like, gas barrier property, etc., 1,2-epoxybutane, 2,3-epoxybutane, epoxypropane, epoxyethane or Glycidol is preferable, and among them, epoxypropane or glycidol is more preferable.

In the structural unit (III), R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are preferably a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms, and the aliphatic hydrocarbon group is a methyl group. , Ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group or n-pentyl group are preferred.

The method for incorporating the structural unit (III) into EVOH (A) is not particularly limited, and examples thereof include the method described in JP-A-2014-034647.

EVOH (A) may be used alone or in combination of two or more. From the viewpoint of gas barrier properties and the like, the proportion of EVOH (A) in the resin composition is preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more. On the other hand, the proportion of EVOH (A) in the resin composition may be, for example, 99.9% by mass or less, or 99% by mass or less.

(Boron compound (B))
The resin composition contains a boron compound (B) containing free boric acid (C) described below in an amount of 100 ppm or more and 5000 ppm or less in terms of orthoboric acid (H ₃ BO ₃ ). The orthoboric acid equivalent content of the boron compound (B) is synonymous with the orthoboric acid equivalent content of all the boron atoms contained in the resin composition. The quantification of the boron compound (B) can be performed by a known method such as ICP emission analysis, and specifically, it can be measured by the method described in the examples. In addition, ppm is based on mass.

Examples of the boron compound (B) include boric acid such as orthoboric acid (H ₃ BO ₃ ), metaboric acid, and tetraboric acid; sodium metaborate, sodium tetraborate, sodium pentaborate, borax, lithium borate, and the like. Examples thereof include borates such as potassium borate; borate esters such as triethyl borate and trimethyl borate, and the boron compound (B) reacts with a component other than the boron compound (B) (for example, EVOH (A)). The compound described above is also included in the boron compound (B). Among them, orthoboric acid, borax and derivatives thereof are preferably used from the viewpoint of cost and improvement of melt moldability. The derivative means a compound obtained by reacting with orthoboric acid or the like such as its ester or amide.

The content of the boron compound (B) with respect to EVOH (A) is 100 ppm or more in terms of orthoboric acid, preferably 500 ppm or more, more preferably 700 ppm or more, and even more preferably 1000 ppm or more. If the content of the boron compound (B) is less than 100 ppm, neck-in tends to occur during film formation.

On the other hand, the content of the boron compound (B) is 5000 ppm or less in terms of orthoboric acid, preferably 2500 ppm or less, and more preferably 1500 ppm or less. When the content of the boron compound (B) exceeds 5000 ppm, the stretchability tends to decrease.

(Free boric acid (C))
The boron compound (B) contains free boric acid (C) which is “unreacted boric acid or a salt thereof”. Usually, in the boron compound (B), most of the boron compound (B) other than free boric acid (C) is cross-linked boric acid. On the other hand, free boric acid (C) is present in the resin composition of the present invention in a non-crosslinked state. The amount of free boric acid (C) in the resin composition of the present invention is determined by a coordination compound capable of forming a complex ion with boric acid, such as 2-ethyl-1,3-hexanediol and free boric acid (C). ) And the reaction product, the reaction product can be quantified and calculated, and specifically can be quantified by the method described in Examples.

The ratio of free boric acid (C) in the boron compound (B) is 0.1% by mass or more in terms of orthoboric acid with respect to the boron compound (B), preferably 0.3% by mass or more, and 0.5 It is more preferably at least mass%. Even if the content of the boron compound (B) is the same, if the ratio of the free boric acid (C) to the boron compound (B) is less than 0.1% by mass, the impact resistance at low temperature decreases, and at low temperature The gas barrier property after impact is liable to decrease. The reason for this is not clear, but it is presumed that the presence of a predetermined amount of free boric acid (C) suppresses the embrittlement of the film at low temperatures.

Moreover, the ratio of the free boric acid (C) in the boron compound (B) is 10 mass% or less in terms of orthoboric acid with respect to the boron compound (B), preferably 7 mass% or less, and 3 mass% or less. It is more preferably 1.5% by mass or less or 1% by mass or less in some cases. If the ratio of the free boric acid (C) to the boron compound (B) exceeds 10% by mass, the local cross-linking reaction due to the free boric acid (C) proceeds, and fish eyes are likely to occur during film formation, Stretchability also tends to decrease. These become remarkable when the film is continuously formed for a long time. Further, when the ratio of free boric acid (C) in the boron compound (B) is more than 10% by mass, neck-in tends to occur during film formation, and gel-like particles generated by local crosslinking increase. The impact resistance at low temperatures may decrease. The ratio of free boric acid (C) in the boron compound (B) can be adjusted by the method for producing a resin composition described below.

The upper limit of the content of free boric acid (C) with respect to EVOH (A) is 500 ppm (10% of 5000 ppm) in terms of orthoboric acid, but 200 ppm is preferable, 100 ppm is more preferable, and 20 ppm or 10 ppm is even more preferable. is there. By setting the content of free boric acid (C) to the above upper limit or less, the film forming property and the stretchability are further improved. On the other hand, the lower limit of the content of this free boric acid (C) is 0.1 ppm (0.1% of 100 ppm), but 0.5 ppm is preferable, 1 ppm is more preferable, and 3 ppm or 5 ppm is even more preferable. is there. When the content of free boric acid (C) is at least the above lower limit, impact resistance at low temperatures tends to increase.

(Other optional ingredients)
The resin composition may contain, as other components, a resin other than EVOH (A) and an additive other than the boron compound (B) within a range that does not impair the effects of the present invention.

Examples of the other resin include thermoplastic resins such as polyolefin. When the resin composition contains the other resin, the content of the other resin in the resin composition is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 3% by mass or less.

Examples of other additives include known additives such as antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, fillers, antiblocking agents, and desiccants. The method of incorporating these additives into the resin composition is not particularly limited, for example, a method of melting the resin composition and mixing the additives, a method of melt blending the resin composition and the additive in the extruder, a resin Examples thereof include a method of impregnating or spreading the resin composition by mixing powder, granular, spherical, cylindrical chip-shaped pellets of the composition with a solid, liquid or solution of these additives. These methods can be appropriately selected in consideration of the physical properties of the additive and the permeability of the resin composition. When the other additive is contained, its content is preferably 5% by mass or less, and more preferably 3% by mass or less, based on the resin composition.

Examples of the antioxidant include 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4′-thiobis-(6-t-butylphenol, 2,2′methylene. -Bis(4-methyl-6-t-butylphenol, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, octadecyl-3-(3' , 5'-di-t-butyl-4'-hydroxyphenyl)propionate, 4,4'-thiobis-(6-t-butylphenol), etc. As the ultraviolet absorber, ethyl-2-cyano-3 is used. , 3-diphenyl acrylate, 2-(2'-hydroxy-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5 -Chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, etc. Examples of the plasticizer include dimethyl phthalate and phthalate. Examples thereof include diethyl acid, dioctyl phthalate, wax, liquid paraffin, phosphoric acid ester, etc. Antistatic agents include pentaerythritol monostearate, sorbitan monopalmitate, sulfated oleic acid, polyethylene oxide, carbowax and the like. Lubricants include ethylenebisstearylamide, butyl stearate, calcium stearate, zinc stearate, etc. Colorants include carbon black, phthalocyanine, quinacridone, indoline, azo pigments, titanium oxide, red iron oxide, etc. Examples of the filler include glass fiber, mica, ballastonite and the like.

Examples of the antiblocking agent include synthetic silica, calcium carbide, amorphous aluminosilicate, zeolite, diatomaceous earth, talc, feldspar, crosslinked polymethylmethacrylate and the like. The average particle size of the antiblocking agent is preferably, for example, 0.5 to 10 μm, more preferably 1 to 5 μm. Moreover, as content of the antiblocking agent in the said resin composition, 0.005-0.5 mass% is preferable, for example, and 0.01-0.1 mass% is more preferable.

Further, the resin composition may contain various acids, metal salts and the like from the viewpoint of thermal stability or viscosity adjustment. Examples of the various acids include carboxylic acids and phosphoric acid compounds, and examples of the various metal salts include alkali metal salts and alkaline earth metal salts. In addition, you may mix and use these acids, a metal salt, etc. with EVOH (A) beforehand.

(Carboxylic acid and/or carboxylate ion)
When the resin composition contains a carboxylic acid and/or a carboxylate ion, the coloring resistance during melt molding tends to be improved. Carboxylic acid is a compound having one or more carboxy groups in the molecule. The carboxylate ion is a hydrogen ion of the carboxy group of carboxylic acid desorbed. The carboxylic acid may be a monocarboxylic acid, a polyvalent carboxylic acid compound having two or more carboxyl groups in the molecule, or a combination thereof. The polyvalent carboxylic acid does not contain a polymer. Further, the polyvalent carboxylate ion is one in which at least one hydrogen ion of the carboxy group of the polyvalent carboxylic acid is eliminated. The carboxy group of the carboxylic acid may have an ester structure, and the carboxylic acid ion may form a salt with a metal.

The monocarboxylic acid is not particularly limited, and examples thereof include formic acid, acetic acid, propionic acid, butyric acid, caproic acid, capric acid, acrylic acid, methacrylic acid, benzoic acid and 2-naphthoic acid. These carboxylic acids may have a hydroxy group or a halogen atom. Further, examples of the carboxylate ion include those in which the hydrogen ion of the carboxy group of each of the above-mentioned carboxylic acids is eliminated. The pKa of the monocarboxylic acid (including the monocarboxylic acid that gives a monocarboxylic acid ion) is preferably 3.5 or more, more preferably 4 or more from the viewpoint of the pH adjusting ability and melt moldability of the resin composition of the present invention. preferable. Examples of such monocarboxylic acids include formic acid (pKa=3.68), acetic acid (pKa=4.74), propionic acid (pKa=4.85), butyric acid (pKa=4.80), and the like. Acetic acid is preferred from the standpoint of ease of use.

The polycarboxylic acid is not particularly limited as long as it has two or more carboxy groups in the molecule, and examples thereof include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, and adipine. Acids, aliphatic dicarboxylic acids such as pimelic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid; tricarboxylic acids such as aconitic acid; 1,2,3,4-butanetetracarboxylic acid, ethylenediaminetetraacetic acid, etc. A carboxylic acid having 4 or more carboxyl groups; a hydroxycarboxylic acid such as tartaric acid, citric acid, isocitric acid, malic acid, mutic acid, tartronic acid, citramalic acid; oxaloacetic acid, mesooxalic acid, 2-ketoglutaric acid, 3-ketoglutaric acid Examples thereof include ketocarboxylic acids such as acids; amino acids such as glutamic acid, aspartic acid, and 2-aminoadipic acid. Incidentally, examples of the polyvalent carboxylate ion include these anions. Among them, succinic acid, malic acid, tartaric acid, and citric acid are particularly preferable because they are easily available.

When the resin composition contains a carboxylic acid and/or a carboxylate ion, the content thereof is 0.01 μmol/g or more in terms of carboxylic acid radicals in the resin composition from the viewpoint of coloring resistance during melt molding. It is preferably 0.05 μmol/g or more, more preferably 0.5 μmol/g or more. In addition, it is preferably 20 μmol/g or less, more preferably 15 μmol/g or less, still more preferably 10 μmol/g or less in terms of carboxylic acid radical.

(Phosphate compound)
When the resin composition contains a phosphoric acid compound, long-run property during melt molding tends to be improved.

The phosphoric acid compound is not particularly limited, and examples thereof include various phosphorus oxygen acids such as phosphoric acid and phosphorous acid, and salts thereof. The phosphate may be contained in any form of, for example, a first phosphate, a second phosphate and a third phosphate, and its counter cation species is not particularly limited, and examples thereof include alkali metal salts. Alternatively, an alkaline earth metal salt is preferable, and an alkali metal salt is more preferable. Specifically, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate or dipotassium hydrogen phosphate is preferable from the viewpoint of improving long-run property during melt molding.

When the resin composition contains a phosphoric acid compound, the content thereof is preferably 1 ppm or more, more preferably 5 ppm or more, and further preferably 8 ppm or more in terms of phosphate radical. Further, it is preferably 500 ppm or less, more preferably 200 ppm or less, and further preferably 50 ppm or less in terms of phosphate radical conversion. When the content of the phosphoric acid compound is within the above range, the long-run property during melt molding can be further improved.

(Alkali metal salt)
When the resin composition contains an alkali metal salt, the long-run property and the interlayer adhesive force when forming a multilayer structure are improved. Examples of the alkali metal that constitutes the alkali metal salt include lithium, sodium, potassium, rubidium, and cesium, but sodium and potassium are more preferable from the viewpoint of industrial availability.

The alkali metal salt is not particularly limited, and examples thereof include aliphatic carboxylic acid salts of lithium, sodium, potassium, etc., aromatic carboxylic acid salts, phosphoric acid salts included in the aforementioned phosphoric acid compounds, metal complexes, and the like. Be done. Specifically, sodium acetate, potassium acetate, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, lithium dihydrogen phosphate. , Trilithium phosphate, sodium stearate, potassium stearate, sodium salt of ethylenediaminetetraacetic acid, and the like. Among these, sodium acetate, potassium acetate and sodium dihydrogen phosphate are particularly preferable because they are easily available.

When the resin composition contains an alkali metal salt, the content of the alkali metal salt in the resin composition is preferably 2.5 μmol/g or more, more preferably 3.5 μmol/g or more, and 4.5 μmol/g or more. Is more preferable. The content of the alkali metal salt is preferably 22 μmol/g or less, more preferably 16 μmol/g or less, still more preferably 10 μmol/g or less. When the content of the alkali metal salt is 2.5 μmol/g or more, the interlayer adhesion of the obtained multilayer structure is more excellent. Further, when the content of the alkali metal salt is 22 μmol/g or less, the appearance of the film tends to be better.

(Alkaline earth metal salt)
When the resin composition contains an alkaline earth metal salt, scrap recovery of a film containing the resin composition is improved. Examples of the alkaline earth metal composing the alkaline earth metal salt include beryllium, magnesium, calcium, strontium, barium, etc. From the viewpoint of industrial availability, magnesium or calcium is preferable.

The resin composition has a melt index (hereinafter, may be abbreviated as “MI”) measured according to ASTM D1238 at 190° C. under a load of 2160 g of 0.1 to 15 g/10 minutes. preferable. When the MI is 50 g/10 minutes or less, the mechanical strength of the film is increased and the practicality is increased. In addition, since the melt viscosity does not become too low at the time of melt molding at high temperature, the occurrence of neck-in is reduced and the film forming property is further enhanced. MI at 190° C. under a load of 2160 g is preferably 15 g/10 minutes or less, more preferably 10 g/10 minutes or less, even more preferably 6.6 g/10 minutes or less, still more preferably 6 g/10 minutes or less, 2 g/10 Minutes or less are particularly preferred. Further, when the MI is 0.1 g/10 minutes or more, even if the take-up speed at the time of melt molding is high, the film breaks or the resin pressure increases during resin extrusion, which makes melt film formation difficult. Can be suppressed. Furthermore, when MI is 0.1 g/10 minutes or more, the generation of fish eyes and streaks when operating at high temperature for a long time is further suppressed, and the output, that is, the amount of resin that can be ejected when the same energy is applied and extruded. Can be increased. From these viewpoints, MI at 190° C. under a load of 2160 g is preferably 0.2 g/10 minutes or more, more preferably 0.5 g/10 minutes or more.

(Method for producing resin composition)
The resin composition can be produced, for example, by the following steps.
(1) Step of polymerizing ethylene and vinyl ester to obtain ethylene-vinyl ester copolymer (EVAc) (polymerization step)
(2) A step of saponifying the EVAc to obtain EVOH (A) (saponification step)
(3) Step of obtaining pellets containing EVOH(A) from the solution or paste containing EVOH(A) (pelletizing step)
(4) Step of washing the pellet (washing step)
(5) Step of dehydrating the pellet (dehydration step)
(6) Step of drying the pellets (drying step)

(1) Polymerization step The method of copolymerizing ethylene and vinyl ester is not particularly limited, and may be, for example, solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization, or the like, and may be continuous or batch type.

As the vinyl ester used for the polymerization, those mentioned above can be mentioned. In the case of copolymerizing a monomer other than ethylene and vinyl ester, the other monomer may be the one described above.

The solvent used for the polymerization is not particularly limited as long as it is an organic solvent capable of dissolving ethylene, vinyl ester and ethylene-vinyl ester copolymer, and examples thereof include methanol, ethanol, propanol, n-butanol, tert-butanol and the like. Alcohol; dimethyl sulfoxide and the like can be used. Of these, methanol is preferable because it can be easily removed and separated after the reaction.

Examples of the catalyst used for the polymerization include 2,2′-azobisisobutyronitrile, 2,2′-azobis-(2,4-dimethylvaleronitrile), 2,2′-azobis-(4-methoxy-). Azonitrile initiators such as 2,4-dimethylvaleronitrile) and 2,2′-azobis-(2-cyclopropylpropionitrile); isobutyryl peroxide, cumylperoxyneodecanoate, diisopropylperoxycarbonate, Examples thereof include organic peroxide-based initiators such as di-n-propylperoxydicarbonate, t-butylperoxy neodecanoate, lauroyl peroxide, benzoyl peroxide, and t-butyl hydroperoxide.

The polymerization temperature is, for example, preferably 20 to 90°C, more preferably 40 to 70°C. The polymerization time is preferably 2 to 15 hours, more preferably 3 to 11 hours. The polymerization rate is preferably 10 to 90%, more preferably 30 to 80%, based on the charged vinyl ester. The resin content in the solution after polymerization is preferably 5 to 85% by mass, more preferably 20 to 70% by mass.

Usually, after polymerization for a predetermined period of time or after reaching a predetermined polymerization rate, a polymerization inhibitor is added as necessary to remove unreacted ethylene and then unreacted vinyl ester. As a method for removing unreacted vinyl ester, for example, the reaction solution is continuously supplied at a constant rate from the upper part of the column filled with a filler such as Raschig ring, and an organic solvent such as methanol is blown as vapor from the lower part of the column, Examples include a method of distilling a mixed vapor of an organic solvent such as methanol and unreacted vinyl ester from the top of the column and taking out a copolymer solution from which the unreacted vinyl ester is removed from the bottom of the column.

(2) Saponification step Next, the EVAc obtained in the above step is saponified. The saponification method may be either continuous or batch. The saponification catalyst is not particularly limited, but an alkali catalyst is preferable, and for example, sodium hydroxide, potassium hydroxide, alkali metal alcoholate, etc. are used.

As the saponification conditions, for example, in the case of a batch system, the concentration in the EVAc solution is preferably 10 to 50% by mass, the reaction temperature is preferably 30 to 60° C., and the amount of the catalyst used is 0. It is preferably from 02 to 0.6 mol, and the saponification time is preferably from 1 to 6 hours. In the case of the continuous system, the methyl acetate produced by the saponification can be removed more efficiently, so that a resin having a high degree of saponification can be obtained with a smaller amount of catalyst than in the case of the batch system, while the EVOH produced by the saponification can be obtained. In order to prevent precipitation of (A), it is necessary to saponify at a higher temperature. Therefore, in the case of the continuous system, for example, the concentration in the EVAc solution is 10% by mass or more and 50% by mass or less, the reaction temperature is 70°C or more and 150°C or less, and the amount of the catalyst used is 0.005 mol or more per mol of vinyl ester structural unit 0.1 mol or less, and the saponification time can be 1 hour or more and 6 hours or less.

The saponification step gives a solution or paste containing EVOH (A). EVOH (A) after the saponification reaction contains an alkali catalyst, by-product salts such as sodium acetate and potassium acetate, and other impurities, and therefore may be removed by neutralizing and washing them as necessary. .. Here, when the EVOH (A) after the saponification reaction is washed with ion-exchanged water containing almost no metal ions, chloride ions, etc., the EVOH (A) is partially left with sodium acetate, potassium acetate, etc. May be.

(3) Pelletizing Step and (4) Cleaning Step Next, the obtained EVOH (A) solution or paste is pelletized. The method of pelletizing is not particularly limited, and examples thereof include a method of cooling and solidifying an EVOH (A) solution and cutting, a method of melting and kneading EVOH (A) in an extruder, and then discharging and cutting. As the cutting method of EVOH (A), a method of extruding EVOH (A) into a strand shape and then cutting with a pelletizer, a method of cutting EVOH (A) discharged from a die by a center hot cut method or an underwater cut method, etc. Etc. are given as specific examples.

Method (i)
When the EVOH(A) solution is extruded into a strand and pelletized, the coagulating liquid for precipitating the EVOH(A) is water or a water/alcohol mixed solvent, aromatic hydrocarbons such as benzene, ketones such as acetone and methyl ethyl ketone. Examples thereof include ethers such as dipropyl ether, organic acid esters such as methyl acetate, ethyl acetate and methyl propionate, and water or a water/alcohol mixed solvent is preferable from the viewpoint of easy handling. As the alcohol, alcohols such as methanol, ethanol and propanol are used, but methanol is industrially preferable. The mass ratio (coagulating liquid/strand of EVOH(A)) of the coagulating liquid in the coagulating liquid and the strand of EVOH(A) is preferably 50 to 10,000. By setting the mass ratio within the above range, EVOH(A) pellets having a uniform size distribution can be obtained.

The temperature at which the EVOH (A) solution is brought into contact with the coagulating liquid (bath temperature during pelletizing) is preferably -10°C or higher, more preferably 0°C or higher. The bath temperature during pelletizing is preferably 40°C or lower, more preferably 20°C or lower, further preferably 15°C or lower, and particularly preferably 10°C or lower. When the bath temperature during pelletizing is −10° C. or higher, precipitation of low molecular weight components tends to be suppressed, and when it is 40° C. or lower, thermal deterioration of EVOH (A) tends to be suppressed.

The EVOH (A) solution is extruded into a coagulating liquid in a strand shape by a nozzle having an arbitrary shape. The shape of the nozzle is not particularly limited, and for example, a cylindrical shape is preferable. The number of strands is not necessarily one, and can be extruded in any number between several and several hundreds.

Next, the EVOH (A) extruded in the form of strands is sufficiently solidified and then cut, pelletized, and then washed with water. The size of such pellets can be, for example, a diameter of 1 mm or more and 10 mm or less, a length of 1 mm or more and 10 mm or less in the case of a cylindrical shape, and a diameter of 1 mm or more and 10 mm or less in the case of a spherical shape.

Subsequently, a washing step of washing the EVOH (A) pellets with water in a water tank is performed. By this washing treatment, oligomers and impurities in the EVOH(A) pellets are removed. The water temperature during washing is preferably 5°C or higher, and preferably 80°C or lower. An aqueous acetic acid solution or ion-exchanged water can be used for washing, but it is preferable to finally wash with ion-exchanged water. The washing with ion-exchanged water is preferably performed twice or more for one hour or more. The water temperature of the ion-exchanged water at this time is preferably in the range of 5 to 60° C., and the bath ratio of the ion-exchanged water to the EVOH(A) pellets is preferably 2 or more.

After the washing step, the pellets are immersed in a solution containing the boron compound (B) (hereinafter sometimes abbreviated as “immersion solution”) to contain the boron compound (B) in the pellets. At this time, the solution may contain other components (for example, an acid component and a metal salt), so that the other components may be contained in the pellet.

The concentration of the boron compound (B) in the dipping solution is 0.01 to 2 g/L in terms of orthoboric acid, and an appropriate amount of the boron compound (B) can be contained in the dry resin composition pellets. It is suitable. The lower limit of the concentration of the boron compound (B) in the immersion solution is more preferably 0.05 g/L, and even more preferably 0.2 g/L. When it is 0.01 g/L or more, the MI of the resin composition becomes sufficient due to a sufficient crosslinking effect, and neck-in tends to occur more easily. The upper limit of the concentration of the boron compound (B) is more preferably 1.5 g/L, and even more preferably 0.8 g/L. When it is 2 g/L or less, gelation of the resin composition is suppressed, and the appearance of the film tends to be further enhanced.

Method (ii)
When performing pelletization by melt-kneading using an extruder, the shape of EVOH (A) before being charged into the extruder is not particularly limited, and the pellets are obtained by cutting the molten resin extruded in the air. It is also possible to use a solution of EVOH (A) after polymerization/saponification, or a precipitate on crumb where the paste is solidified in an irregular shape.

The water content of EVOH (A) before being charged into the extruder is preferably 0.5% by mass or more, more preferably 5% by mass or more, and further preferably 7% by mass or more. Further, the water content of EVOH (A) before being charged into the extruder is preferably 70% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less.

In pelletizing by melt-kneading using an extruder, the boron compound (B) can be added to EVOH (A) in the extruder. When adding the boron compound (B) to the EVOH (A) in the extruder, the feed position of the boron compound (B) is preferably added at a position where the EVOH (A) is melted in the extruder. Is more preferable. In particular, it is preferable to add the boron compound (B) to EVOH (A) which is in a water-containing and molten state. The boron compound (B) can be added to the extruder at one location or at two or more locations, and at this time, other components (for example, an acid component and a metal salt) may be added at the same time.

When the boron compound (B) is added in the extruder, the amount supplied in the extruder is the content in the resin composition. The addition form of the boron compound (B) is not particularly limited, and it may be added as a dry powder in the extruder, as a paste impregnated with a solvent, as a suspension in a liquid, or as a solvent. Examples of the method include dissolving and adding as a solution. From the viewpoint of controlling the addition amount and uniformly dispersing the boron compound (B) in EVOH (A), the boron compound (B) is dissolved in a solvent. The method of adding as a solution is particularly preferable. The solvent is not particularly limited, and water is preferable from the viewpoint of solubility of the boron compound (B), economy, ease of handling, safety of working environment, and the like.

When adding the boron compound (B) as a solution to EVOH (A), the addition amount of the solution is preferably 1 part by mass or more based on 100 parts by mass of dry mass of EVOH (A), and preferably 3 parts by mass. More preferably, it is more preferably 5 parts by mass or more. Further, the addition amount of the solution is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and particularly preferably 20 parts by mass or less, based on 100 parts by mass of dry mass of EVOH (A). If the amount of the solution added is less than 1 part by mass, the concentration of the solution generally increases, and the dispersibility of the boron compound (B) tends to decrease. If it exceeds 50 parts by mass, the control of the water content of EVOH (A) tends to be difficult, and the resin and water contained in the resin tend to undergo phase separation in the extruder. The concentration of orthoboric acid in the solution is in the range of 0.2 g/L to 57 g/L, and is appropriately adjusted depending on the amount of orthoboric acid to be contained with respect to the dry weight of EVOH (A) and the addition amount of the solution.

The resin temperature in the extruder is preferably 70 to 170°C. When the resin temperature is lower than 70°C, EVOH (A) may not be completely melted, and the dispersibility of the added boron compound (B) may be insufficient. The resin temperature is more preferably 80°C or higher, still more preferably 90°C or higher. When the resin temperature exceeds 170° C., EVOH (A) tends to be easily deteriorated by heat. Furthermore, when the boron compound (B) is added as an aqueous solution, it becomes difficult to mix the EVOH (A) with the aqueous solution at a suitable aqueous solution concentration because the water evaporation becomes violent when the resin temperature exceeds 170° C. Tends to be. The resin temperature in the extruder is more preferably 150°C or lower, further preferably 130°C or lower. The method of adjusting the resin temperature is not particularly limited, and a method of suitably setting the temperature of the cylinder in the extruder is particularly preferable. In the present invention, the resin temperature means a temperature detected by a temperature sensor installed in the cylinder in the extruder, and the detection point indicates the temperature near the discharge port at the tip of the extruder.

The water content of the resin composition immediately after being discharged from the extruder is preferably 5 to 40% by mass, more preferably 5 to 35% by mass. When the water content of the resin composition immediately after being discharged from the extruder exceeds 40% by mass, the resin and water contained in the resin tend to undergo phase separation, and as a result, the strands after being discharged from the extruder foam. Tends to be easier to do. When the water content of the resin composition immediately after being discharged from the extruder is less than 5% by mass, the deterioration of EVOH (A) due to heating tends to be insufficiently suppressed, resulting in poor coloration resistance of the obtained pellets. Tend.

The method of pelletizing the resin composition discharged from the extruder is not particularly limited, and a method of extruding the resin composition into air from a die and cutting the resin composition to an appropriate length is exemplified. From the viewpoint of easy handling of pellets, the diameter of the die is preferably 2 to 5 mmφ (φ is the diameter. The same applies below), and the strand is preferably cut into a length of about 1 to 5 mm.

When pelletizing by melt-kneading using an extruder, the washing step may be the same as the method (i), but a step of washing in the extruder may be provided. When washing is performed in the extruder, a method of injecting the washing liquid into the extruder to wash the resin and then discharging the washing liquid from the downstream side of the extruder can be mentioned.

(5) Dehydration step The proportion of free boric acid (C) in the boron compound (B) in the resin composition is, for example, water removed by physical means without heating the hydrous pellets containing the boron compound (B). After that, it can be adjusted by drying. Examples of the method for removing water include centrifugal dehydration (separation) method, reduced pressure sieve (hydro sieve), gas flow, etc., and it is preferable to remove water adhering to the pellet preferentially. The centrifugal dehydration method is preferably used industrially.

The centrifugal dehydration method may be either a batch method or a continuous method, and the continuous method is preferably used industrially. Both batch type and continuous type have a bucket-shaped rotating body with perforated holes or slits, and the continuous type is a centrifugal dehydrator (centrifugal dewatering device if it has a structure that allows continuous discharge without changing the shape of pellets). The separation device) is not limited. The water content to be removed is adjusted by the diameter of the perforated plate, the number of rotations, the amount of treatment (processing time), etc. The diameter of the perforated plate should be smaller than the diameter of the pellet, preferably about 0.1 to 3 mm. If the diameter of the perforated plate is less than 0.1 mm, the water removing ability is insufficient, and further, clogging by fine powder is likely to occur, while if it exceeds 3 mm, it is difficult to adjust the water removing ability. The rotation speed varies depending on the device, but is preferably 500 to 20,000 rpm, and the processing time is preferably 10 seconds or more and 15 minutes or less. If the rotation speed is too low, the proportion of the remaining free boric acid (C) tends to increase. On the other hand, if the number of rotations is too high, the proportion of residual free boric acid (C) tends to be low. Similarly, if the treatment time is less than 10 seconds, it causes an increase in the proportion of free boric acid (C) remaining in the obtained resin composition. The treatment time is preferably 45 seconds or longer, more preferably 1 minute or longer. If the treatment time exceeds 15 minutes, the ratio of free boric acid (C) in the obtained resin composition tends to decrease. The treatment time is preferably 13 minutes or less, more preferably 10 minutes or less.

(6) Drying process The pellets that have undergone the dehydration process are subjected to the drying process. For the drying, the water content of the EVOH(A) pellets after drying is preferably 0.08 mass% or less. If the water content exceeds 0.08% by mass, the amount of cross-linked boric acid tends to decrease and the amount of free boric acid (C) tends to increase. The water content is preferably 0.05% by mass or less. The drying method is not particularly limited, and examples thereof include a static drying method combined with air drying or nitrogen drying, a fluidized drying method, a vacuum drying method, and the like, but a multi-stage drying method in which several drying methods are combined is preferable, More preferably, it is multistage drying including preliminary drying and main drying. The term "preliminary drying" as used herein refers to drying from a relatively high water content to a water content of about 10% by mass in order to suppress heat fusion between resin compositions having a high water content during drying. By comparison, it means drying at a lower temperature. On the other hand, the main drying is used to reduce the water content of the resin composition having a relatively low water content after the preliminary drying, and means drying performed at a higher temperature than the preliminary drying. For the preliminary drying, heating gas (hot air or the like), infrared rays, microwaves, or the like can be used. The temperature and time of the preliminary drying are not particularly limited, and for example, by subjecting to a drying time of 1 hour or more and 12 hours or less at 60° C. or more and 100° C. or less, a resin composition having a target water content can be obtained. For the main drying, the above-mentioned general drying means can be used, but among them, vacuum drying is suitable for setting the free boric acid (C) to a specific amount. With methods other than vacuum drying, controlling the specific amount of free boric acid (C) tends to be somewhat difficult.

The lower limit of the main drying temperature (atmosphere temperature) is preferably 70°C, more preferably 100°C, further preferably 110°C, particularly preferably 120°C. On the other hand, the upper limit is preferably 160°C, more preferably 150°C, and further preferably 130°C. When the temperature of the main drying is equal to or higher than the lower limit, sufficient main drying can be efficiently performed, and the time of the main drying can be shortened. On the other hand, when the main drying temperature is set to the upper limit or lower, the thermal deterioration of EVOH (A) can be suppressed. Further, when the temperature of the main drying is within the above range, it becomes easy to adjust the free boric acid (C) to an appropriate amount. For example, by lowering the main drying temperature, the proportion of free boric acid (C) tends to decrease. Further, the drying time at a specific main drying temperature is not particularly limited, but is, for example, 80° C. for 30 hours or more and 160 hours or less, 120° C. for 15 hours or more and 100 hours or less, and 150° C. for 0.5 hours or more and 20 hours or less. Then, a resin composition having a desired water content is obtained.

(Film shape, etc.)
The film of the present invention is formed from the resin composition by melt molding or the like. The film of the present invention may be a single layer film consisting of only the resin composition layer or a multilayer film. The average thickness of the film of the present invention is, for example, 1 μm or more and less than 300 μm, and preferably 5 μm or more and less than 100 μm. The film of the present invention can be suitably used as various packaging materials.

The arithmetic average roughness (Ra) of at least one surface of the film of the present invention measured according to JIS B0601 is preferably 1.0 μm or less, more preferably 0.8 μm or less, and further preferably 0.6 μm or less. , 0.4 μm or less is particularly preferable. The arithmetic mean roughness (Ra) of at least one surface of the film of the present invention is preferably 0.05 μm or more, more preferably 0.10 μm or more, further preferably 0.15 μm or more, and particularly preferably 0.20 μm or more. When the arithmetic mean roughness (Ra) of at least one surface of the film of the present invention is in the above range, the break resistance is more excellent.

The average length (RSm) of the contour curve element on at least one surface of the film of the present invention measured according to JIS B0601 is preferably 1000 μm or less, more preferably 800 μm or less, further preferably 600 μm or less, and 400 μm or less. Is particularly preferable. The average length (RSm) of the contour curve element on at least one surface of the film of the present invention is preferably 50 μm or more, more preferably 100 μm or more, further preferably 150 μm or more, particularly preferably 200 μm or more. When the average length (RSm) of the contour curve element on at least one surface of the film of the present invention is within the above range, the break resistance is more excellent. The above-mentioned JIS B0601 represents, for example, JIS B0601:2001.

The film of the present invention may be an unstretched film, but is preferably stretched. Stretching improves the strength and the like. Furthermore, when the film of the present invention is a stretched film, the occurrence of streak-like unevenness that may occur during stretching is small, and therefore the appearance and gas barrier properties are also good.

<Film manufacturing method>
The film of the present invention can be produced by a known method. The film forming method is not particularly limited, and examples thereof include a melting method, a solution method, and a calender method, and the melting method is preferable. Examples of the melting method include a T-die method (casting method) and an inflation method, and the casting method is preferable. In particular, it is preferably produced by a method including a cast molding step of melt-extruding the resin composition constituting the film of the present invention onto a casting roll, and a step of stretching an unstretched film obtained from the resin composition. The melting temperature in the melting method varies depending on the melting point of EVOH (A) and the like, but is preferably about 150 to 300°C.

The stretching may be uniaxial stretching or biaxial stretching, with biaxial stretching being preferred. The biaxial stretching may be either sequential biaxial stretching or simultaneous biaxial stretching. The lower limit of the draw ratio in terms of area is preferably 6 times, and more preferably 8 times. The upper limit of the draw ratio is preferably 15 times, more preferably 12 times. When the stretching ratio is in the above range, the film thickness uniformity, gas barrier property and mechanical strength can be improved. The stretching temperature may be, for example, 60°C or higher and 120°C or lower.

The method for producing a film of the present invention may include a step of heat-treating the stretched film after the stretching step. The heat treatment temperature is usually set to a temperature higher than the stretching temperature, and can be set to, for example, more than 120°C and 200°C or less.

<Packaging material>
The packaging material of the present invention comprises the film of the present invention. Since the packaging material of the present invention comprises the film of the present invention, it has excellent appearance and impact resistance at low temperatures. Therefore, the gas barrier property is maintained for a long period of time even when stored at a low temperature in an impact environment. Moreover, since the film of the present invention having excellent film-forming properties is used, the packaging material of the present invention is also excellent in productivity.

The packaging material of the present invention may be a single layer film or a multilayer structure containing the film of the present invention. The multilayer structure can be composed of the layer of the film of the present invention and the layer containing other components. The number of layers of the multilayer structure may be two or more. On the other hand, the upper limit of the number of layers may be 1000 layers, 100 layers, or 10 layers. In addition, the multilayer structure may further have a layer formed of a material other than resin, such as a paper layer or a metal layer.

As the layer composed of the other component, for example, a thermoplastic resin layer formed of a thermoplastic resin is preferable. The layer structure of the multilayer structure is not particularly limited, and when the layer of the film of the present invention is represented by E, the layer obtained from the adhesive resin is represented by Ad, and the layer obtained from the thermoplastic resin is represented by T, T/E/T, Examples include structures such as E/Ad/T and T/Ad/E/Ad/T. Each of these layers may be a single layer or a multilayer. The layer Ad obtained from the adhesive resin may be included in the thermoplastic resin layer formed from the thermoplastic resin. The film of the present invention in the multilayer structure is preferably a monolayer film.

The method for producing a multilayer structure is not particularly limited, for example, a method of melt-extruding a thermoplastic resin into the film of the present invention, an organic titanium compound, an isocyanate compound, a polyester-based compound of the film of the present invention and another thermoplastic resin layer. Examples include a method of laminating using a known adhesive such as a compound.

The thermoplastic resin may be linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, propylene-α-olefin (having 4 carbon atoms). .About.20 α-olefins) copolymers, homopolymers or copolymers of olefins such as polybutene and polypentene, polyesters such as polyethylene terephthalate, polyester elastomers, polyamides such as nylon-6 and nylon-66, polystyrene, polyvinyl chloride. , Polyvinylidene chloride, acrylic resin, vinyl ester resin, polyurethane elastomer, polycarbonate, chlorinated polyethylene, chlorinated polypropylene and the like. Among them, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyamide, polystyrene and polyester are preferably used.

The adhesive resin is not particularly limited as long as it has adhesiveness with the gas barrier layer and other thermoplastic resin layers, and an adhesive resin containing a carboxylic acid-modified polyolefin is preferable. As the carboxylic acid-modified polyolefin, it is preferable to use a modified olefin-based polymer containing a carboxyl group obtained by chemically bonding an ethylenically unsaturated carboxylic acid, an ester thereof or an anhydride thereof to an olefin-based polymer. it can. Here, the olefin polymer means a polyolefin such as polyethylene, linear low-density polyethylene, polypropylene and polybutene, and a copolymer of olefin and another monomer. Among them, linear low-density polyethylene, ethylene-vinyl acetate copolymer and ethylene-acrylic acid ethyl ester copolymer are preferable, and linear low-density polyethylene and ethylene-vinyl acetate copolymer are particularly preferable.

The packaging material of the present invention may be in the form of a film as it is, or may be a film or a multilayer structure which is secondarily processed. Examples of the packaging material obtained by secondary processing include (1) a tray cup-shaped container obtained by thermoforming a film or a multilayer structure such as vacuum forming, pressure forming, vacuum pressure forming, and the like, (2) Examples thereof include bottles and cup-shaped containers obtained by performing stretch blow molding or the like on the film or the multilayer structure, and (3) bag-shaped containers obtained by heat-sealing the film or the multilayer structure. The secondary processing method is not limited to the above-exemplified methods, and for example, a known secondary processing method other than the above, such as blow molding, can be appropriately used.

The packaging material of the present invention is used for packaging, for example, foods, beverages, chemicals such as agricultural chemicals and medicines, medical equipments, machine parts, industrial materials such as precision materials, clothing and the like. In particular, the packaging material of the present invention is preferably used for applications requiring a barrier property against oxygen, and applications where the inside of the packaging material is replaced with various functional gases. The packaging material of the present invention is formed in various forms depending on the application, for example, vertical bag-making filling seal bag, vacuum packaging bag, spout-equipped pouch, laminated tube container, container lid material, and the like.

<Vacuum packaging bag>
The vacuum packaging bag of the present invention comprises the film of the present invention. Since the vacuum packaging bag of the present invention comprises the film of the present invention, it has excellent appearance and impact resistance at low temperatures. Therefore, the gas barrier property is maintained for a long period of time even when stored at a low temperature in an impact environment. Moreover, since the film of the present invention having excellent film-forming properties is used, the vacuum packaging bag of the present invention also has excellent productivity.

An example of the vacuum packaging bag of the present invention is a bag-shaped container that is provided with the film of the present invention as a partition wall that separates the inside into which the contents are packaged and the outside, and the inside of which is depressurized. In the vacuum packaging bag of the present invention, for example, the two films of the present invention are overlapped with each other, and the peripheral portions of the two films are sealed to each other. In the vacuum packaging bag of the present invention, a multilayer structure containing the film of the present invention as the partition wall is preferably used. Specific examples of the multilayer structure include the examples of the multilayer structure described above. The vacuum packaging bag can be manufactured using a nozzle type or chamber type vacuum packaging machine.

The vacuum packaging bag of the present invention is used for applications where it is desired to package in a vacuum state, for example, for storing foods, beverages and the like. Further, the vacuum packaging bag of the present invention can be used as an outer packaging material for a vacuum heat insulator.

Hereinafter, the present invention will be described in detail with reference to Examples and the like, but the present invention is not limited to these Examples. The obtained resin composition was evaluated as follows.

(1) Quantification of Boron Compound (B) in Resin Composition The dried resin composition pellets obtained in Production Example were pulverized by freeze pulverization. To 0.5 g of the obtained powder, 5 mL of nitric acid for precision analysis manufactured by Wako Pure Chemical Industries, Ltd. was added and wet-decomposed with Speedwave MWS-2 (manufactured by Berghof). The obtained liquid was diluted with ion-exchanged water to prepare a sample solution with a total liquid volume of 50 mL, and an elemental boron was quantified using an ICP emission spectrophotometer (“Optima 4300 DV”, manufactured by Perkin Elmer Japan Co., Ltd.). Analysis was performed and the amount of the boron compound (B) was calculated as an orthoboric acid conversion value (B1). For the quantification, a calibration curve prepared using an atomic absorption spectrophotometric standard stock solution of boron (1000 ppm) (manufactured by Kanto Chemical Co., Inc.) was used.

(2) Quantification of free boric acid (C) in resin composition (i) Preparation of sample solution The dried resin composition pellets obtained in Production Examples were pulverized by freeze pulverization. The obtained powder was sieved with a sieve having a nominal size of 1 mm (standard sieve standard JIS Z-8801 compliant), and a measurement sample of 1000 mg of the powder of the resin composition which passed through the sieve was taken as 2-ethyl-1,3-hexanediol. /Chloroform mixed solution (volume ratio: 10/90) (3.5 mL) was mixed, the mixture was allowed to stand at room temperature for 24 hours and then filtered using a 0.2 μm filter to obtain a filtrate.
(Ii) Quantitative measurement device for free boric acid (C): ICP emission spectrometer iCAP6300 (manufactured by Thermo Fisher Scientific)
Measurement wavelength: 208.893 nm, 208.959 nm, 249.773 nm
Calibration curve: For atomic absorption analysis: Boron standard stock solution (1000 ppm) prepared using Kanto Chemical Co., Inc. Measurement sample: 0.6 g of filtrate was weighed and made up to 10 mL with ethanol.
All the obtained boron contents were considered to be derived from free boric acid (C), and were calculated as orthoboric acid conversion values (B2).
(Iii) Calculation of ratio of free boric acid (C) Calculated by the following formula using the measurement result (B1) of the boron compound (B) and the measurement result (B2) of the free boric acid (C) obtained by the above measurement. did.
Ratio (% by mass) of free boric acid (C)=measurement result of free boric acid (C) (B2)/measurement result of boron compound (B) (B1)×100

(3) Melt index (MI) of resin composition
According to ASTM-D1238, a melt indexer was used, and the measurement was performed under the conditions of a temperature of 190° C. and a load of 2160 g.

(4) Quantification of metal salt and acid component in resin composition (quantification of phosphate compound/metal ion)
A sample solution was prepared in the same manner as in (1), and quantitatively analyzed at each of the following observation wavelengths using an ICP optical emission spectroscopic analyzer Optima 4300 DV manufactured by Perkin Elmer Japan Co., Ltd. to quantify the amounts of metal ions and phosphate compounds. did. The amount of the phosphoric acid compound was determined by quantifying the elemental phosphorus and calculating the equivalent value of phosphate radical. A calibration curve prepared by diluting various standard solutions was used for the quantification.
Na: 589.592 nm
K: 766.490 nm
P: 214.914 nm
(Quantification of carboxylic acid and carboxylate ion)
The dry resin composition obtained in Production Example was pulverized by freeze pulverization. The obtained pulverized resin composition is sieved with a sieve having a nominal size of 1 mm (standard sieving standard JIS Z8801-1 to 3), and 10 g of the resin composition powder that has passed through the sieve and 50 mL of ion-exchanged water with a stopper are 100 mL. The mixture was placed in an Erlenmeyer flask, a cooling condenser was attached, and the mixture was stirred at 95°C for 10 hours. 2 mL of the obtained solution was taken and diluted with 8 mL of ion-exchanged water. The diluted solution was subjected to quantification of carboxylic acid and carboxylate ion using an ion chromatography "ICS-1500" manufactured by Yokogawa Electric Co., Ltd. according to the following measurement conditions. For the quantification, a calibration curve prepared using a monocarboxylic acid or a polycarboxylic acid was used.
Measurement condition column: “IONPAC ICE-AS1 (9φ×250 mm, electric conductivity detector)” manufactured by DIONEX
Eluent: 1.0 mmol/L octanesulfonic acid aqueous solution Measurement temperature: 35°C
Eluent flow rate: 1 mL/min Analytical amount: 50 μL

Production example 1
A polymerization tank having a pressure resistance of 100 kg/cm ² was charged with 19600 parts of vinyl acetate, 2180 parts of methanol, and 7.5 parts of AIBN (2,2′-azobisisobutyronitrile). Then, the internal temperature was adjusted to 60° C. and the ethylene pressure was adjusted to 35.5 kg/cm ² . After maintaining the temperature and pressure for 3.5 hours for polymerization, 5 parts of hydroquinone was added, the polymerization tank was returned to normal pressure, and ethylene was removed by evaporation. Subsequently, this methanol solution was continuously flown down from the upper part of the Raschig ring-filled expelling column, while methanol vapor was blown from the bottom of the column to release unreacted vinyl acetate monomer from the top of the column together with methanol vapor. By removing through ethylene to obtain a 45% methanol solution of unreacted vinyl acetate 0.01% or less ethylene-vinyl acetate copolymer. At this time, the polymerization rate was 47% based on the charged vinyl acetate, and the ethylene content rate was 32 mol %. Next, a methanol solution of ethylene-vinyl acetate copolymer was charged into a saponification reactor, and sodium hydroxide/methanol solution (80 g/L) was added in an amount of 0.4 equivalent to the vinyl acetate component in the copolymer. As described above, methanol was added to adjust the copolymer concentration to 20%. The temperature was raised to 60° C. and the reaction was carried out for about 4 hours while blowing nitrogen gas into the reactor. Then, it was neutralized with acetic acid to stop the reaction, extruded into water from a metal plate having a circular opening to cause precipitation, and cut to obtain a pellet having a diameter of about 3 mm and a length of about 5 mm. The obtained pellets were deliquored with a centrifuge, and then washing and deliquoring were repeated by adding a large amount of water to obtain washed hydrated pellets. The degree of saponification of the obtained EVOH was 99.7 mol %. The washed water-containing pellets (300 g) were dispersed in an immersion liquid (0.5 L) containing orthoboric acid (0.06 g/L), acetic acid (0.1 g/L) and potassium dihydrogen phosphate (0.3 g/L), and the mixture was stirred for 4 hours. Then, the obtained pellets were taken out, dehydrated by a centrifuge (mesh diameter 1 mm, rotation speed 4000 rpm, processing time 15 minutes), and then preliminarily dried with a hot air dryer at 80° C. in an air atmosphere. It was dried for 3 hours. The water content of the pellets before centrifugation was 200 mass% on a dry mass basis, the water content after centrifugal dehydration for 15 minutes was 78 mass%, and the water content after preliminary air drying was 10 mass%. Then, using a vacuum dryer as main drying, it was dried at 80° C. for 142 hours under vacuum conditions. Vacuum drying was carried out until the water content in the pellets after the main drying became 0.08% by mass or less, to obtain a resin composition 1. Regarding the resin composition 1, the metal component and the acid component were quantified according to the method described in (4) above. As a result of the measurement, the acetic acid and its salt contained in the resin composition were 600 ppm (10 μmol/g) in terms of acetate, the alkali metal salt was 150 ppm in terms of metal, and the phosphate compound was 35 ppm in terms of phosphate.

Production Examples 2 to 24, Production Examples C1 to C14
Table showing the ethylene unit content (Et) of the EVOH used, the concentration of orthoboric acid in the immersion liquid in which the water-containing pellets after washing are immersed, the centrifugal dehydration conditions (treatment time and water content after centrifugal dehydration), and the treatment temperature of the main drying Resin compositions 2 to 24 and resin compositions C1 to C14 were produced in the same manner as in Production Example 1 except that the changes were made as shown in 1. In each of the production examples, main drying was performed for the treatment time shown in Table 1 until the water content in the pellets became 0.08 mass% or less. In addition, in the manufacturing example which did not perform centrifugal dehydration, the value described in the column of water content after centrifugal dehydration is the water content before performing predrying (the same applies hereinafter).

Production Examples C15 to C17
The orthoboric acid concentration of the immersion liquid for immersing the water-containing pellets after washing and the centrifugal dehydration conditions (treatment time, and water content after centrifugal dehydration) are as shown in Table 2, and the main drying was performed in a hot air dryer under an air atmosphere. Resin compositions C15 to C17 were produced in the same manner as in Production Example 1 except that air was dried under the conditions shown in Table 2 until the water content in the pellets became 0.08% by mass or less.

Production Examples C18 to C20
The concentration of orthoboric acid in the immersion liquid in which the water-containing pellets after washing are immersed and the centrifugal dehydration conditions (treatment time and water content after centrifugal dehydration) are as shown in Table 3, and as a main drying, a hot air dryer under a nitrogen atmosphere ( Resin compositions C18 to C20 were produced in the same manner as in Production Example 1 except that the oxygen content in the machine was 200 ppm) and the temperature was set to the conditions shown in Table 3 until the moisture content in the pellets was nitrogen-dried to 0.08 mass% or less. Manufactured.

Production Example 25
Up to the saponification step, the same procedure as in Production Example 1 was carried out to obtain a 20% EVOH methanol solution. Subsequently, a methanol solution of EVOH was introduced from the upper part of the tower type tray reaction vessel, steam was introduced from the bottom of the reaction vessel, and methanol was added with water under the conditions of a tower internal temperature of 130° C. and a tower internal pressure of 3 kg/cm ^2. By replacing, an EVOH-containing composition having a concentration of 50% was obtained from the bottom of the column. Subsequently, the obtained water-containing composition was introduced into an extruder having a slit for discharging water, extruded at a die temperature of 118° C., and cut and granulated with a center hot cutter to obtain pellet-shaped EVOH. The pellets thus obtained were introduced from the upper part of the tower type countercurrent washing device, pure water of 50°C was introduced from the lower part to wash the pellets countercurrently, and the pellets were taken out from the bottom part of the column and solid-liquid separated by a wet shifter to obtain ethylene An EVOH having a rate of 32 mol%, a saponification degree of 99.7 mol% and a water content of 35% by mass was obtained. The EVOH thus obtained was charged into a twin-screw extruder, the resin temperature at the discharge port was set to 100° C., and the acetic acid/orthoboric acid/sodium acetate/potassium dihydrogen phosphate aqueous solution was added from the trace component addition section at the discharge port side. The treatment liquid was added. The amount of EVOH charged per unit time was 10 kg/hr (including the mass of water contained), the amount of treatment liquid charged per unit time was 0.65 L/hr, and the composition of the treatment liquid was acetic acid 4. It was an aqueous solution containing 3 g/L, orthoboric acid 5.3 g/L, sodium acetate 4.6 g/L, and potassium dihydrogen phosphate 1.4 g/L.
Type Twin-screw extruder L/D 45.5
Caliber 30mmφ
Screw same direction complete meshing type rotation speed 300 rpm
Motor capacity DC22KW
Heater 13 division type Die hole number 5 holes (3mmφ)
Resin temperature in the die 105℃
The resin composition extruded from the outlet of the twin-screw extruder was cut into pellets by the hot cutter 10 having the form shown in FIG. Specifically, in the hot cutter 10 of FIG. 1, the resin composition discharged from the discharge port 11 of the twin-screw extruder is extruded from the die 12 and cut by the rotary blade 13. The rotary blade 13 rotates together with the rotary shaft 14 directly connected to the rotary blade 13. Cooling water 17 is supplied from the cooling water supply port 16 into the cutter box 15. The pellet immediately after being cut is cooled by the water film 18 formed by the cooling water 17, and the cooling water and the pellet 20 are discharged from the pellet discharge port 19. The discharged pellets were flat spheres, and the water content was 80% by mass. The pellets thus obtained were taken out and dehydrated by a centrifuge (mesh diameter 1 mm, rotation speed 4000 rpm, treatment time 2 minutes), and then preliminarily dried using a hot air dryer under air atmosphere at 80° C., 11 Time drying was performed to reduce the water content to 4.2% by mass. Subsequently, as main drying, drying was performed at 120° C. for 16 hours under vacuum conditions to obtain a resin composition 25 with a water content of 0.08 mass% or less. For the resin composition 25, the metal component and the acid component were quantified according to the method described in (4) above. The content of acetic acid and its salts is 300 ppm (5 μmol/g) in terms of acetate radicals, the content of phosphate compounds is 100 ppm in terms of phosphate radicals, and the content of alkali metal salts is 40 ppm in terms of metal equivalents for potassium and 40 ppm for sodium equivalents. Was 130 ppm.

Production Examples 26 to 30, Production Examples C21 and C22
Resin composition in the same manner as in Production Example 25 except that the concentration of orthoboric acid added to the extruder, centrifugal dehydration conditions (treatment time and water content after centrifugal dehydration), and the treatment temperature for main drying were changed as shown in Table 4. 26-30, resin composition C21 and C22 were manufactured. In each of the production examples, main drying was performed for the treatment time shown in Table 4 until the water content in the pellets became 0.08 mass% or less.

Production Examples 31 to 34
Resin was prepared in the same manner as in Production Example 1 except that the orthoboric acid concentration of the immersion liquid, centrifugal dehydration conditions (treatment time, and water content after centrifugal dehydration), and the atmosphere, temperature, and time of main drying were changed as shown in Table 5. Compositions 31-34 were produced.

Production Example C23
A resin composition C23 was produced in the same manner as in Production Example C2, except that the components of the immersion liquid were changed to 0.5L of the immersion liquid containing 1.66 g/L of orthoboric acid and 0.11 g/L of potassium hydroxide. .. The metal component and the acid component were quantified according to the method described in (4) above. The acetic acid and its salts were 0 ppm in terms of acetate radicals, the alkali metal salts were 160 ppm in terms of metals, and the phosphate compounds were 0 ppm in terms of phosphate radicals.

<Examples 1-34, Comparative Examples 1-23>
(A) Film-forming property Synthetic silica ("Sylysia 310P" manufactured by Fuji Silysia Chemical Ltd.; average particle size measured by laser method) was used for 100 parts by mass of pellets of the resin composition obtained in Production Example. 7 μm) 0.03 parts by mass were dry blended with a tumbler. The obtained mixture (resin composition containing synthetic silica) is melted at 260° C. and extruded from a die having a width of 1200 mm onto a casting roll, and at the same time, air is blown with an air knife at a wind speed of 30 m/sec to take up the mixture. An unstretched film was obtained by winding it at 100 m/min. Each unstretched film obtained was evaluated as follows.

(A-1) Neck-in The unstretched film obtained immediately after startup was sampled for 10 m, and the width of the unstretched film was measured at 1 m intervals. The value obtained by subtracting from the die width was defined as the neck-in width and evaluated according to the following criteria. In the cases of A to C, it was determined that neck-in was suppressed.
A: Less than 96 mm B: 96 mm or more and less than 192 mm C: 192 mm or more and less than 384 mm D: 384 mm or more

(A-2) Fish eye For each unstretched film obtained after continuous operation for 48 hours and after continuous operation for 96 hours, the number of fish eyes per 10 cm square was visually counted and evaluated according to the following criteria. In the case of A to C, it was determined that the generation of fish eyes was suppressed.
A: Less than 5 B: 5 or more and less than 20 C: 20 or more and less than 50 D: 50 or more

(B) Stretchability The unstretched film obtained in (a) above was brought into contact with warm water at 80°C for 10 seconds, and was ten times at 90°C in the longitudinal direction by a tenter simultaneous biaxial stretching equipment, and was stretched in the transverse direction at 3.2 times. The film was stretched 3.0 times and further heat-treated in a tenter set at 170° C. for 5 seconds to prepare a biaxially stretched film having a total width of 3.6 m. A biaxially stretched film was produced in the same manner except that the resin composition 11 was set to a stretching temperature of 83° C. and the heat treatment temperature was 152° C., and the resin composition 12 was set to a stretching temperature of 93° C. and a heat treatment temperature of 177° C. .. While rewinding the produced biaxially stretched film, a width of 80 cm was slit around the center position in the entire width of the film to obtain a roll having a length of 4000 m. Further, a film was continuously produced, and 432 rolls each having a length of 4000 m were taken for each resin composition. The average thickness of each stretched film was 12 μm. The biaxially stretched film produced from the unstretched film after being operated for 96 hours was visually observed for occurrence of stripe-shaped stretching unevenness, and evaluated according to the following criteria. In the case of A to C, the stretchability was judged to be good.
A: No stretching unevenness was confirmed B: Thin stretching unevenness was confirmed C: Clear stretching unevenness was confirmed D: Paper breakage or perforation occurred

(C) Impact resistance evaluation at low temperature The biaxially stretched film obtained in the above (b) is cut out to A4 size from the center portion in the width direction, and an adhesive for dry lamination (Takelac A manufactured by Mitsui Chemicals, Inc. -520 and Takenate A-50 were mixed at a mass ratio of 6:1 to obtain an ethyl acetate solution having a solid content concentration of 23 mass%), which was manufactured by Dai-Rika Co., Ltd. No. 12 was used for coating, followed by hot air drying at 50° C. for 5 minutes. An LLDPE film (Unilux LS-760C manufactured by Idemitsu Unitech Co., Ltd.: thickness 50 μm) was attached to the surface coated with the adhesive and laminated with a nip roll heated to 80° C. Further, a non-stretched polypropylene (CPP) film (RXC-21 manufactured by Mitsui Chemicals Tohcello Co., Ltd., thickness 50 μm) was laminated on the other surface in the same manner, and aged at 40° C. for 5 days (outer side) LLDPE layer/adhesive layer/ A multilayer structure having a layer structure of EVOH layer/adhesive layer/CPP layer (inside) was obtained.
The obtained two-layered structure is heat-sealed to form a pouch bag, and the ceramic spheres having the radii shown in Tables 6 to 11 below are packed in a layer so that the spheres come into contact with each other. After cooling in a thermostatic chamber at 20° C. for 6 hours, vacuum packaging was performed. A transportation test in which 50 vacuum packaging bags are packed in a cardboard box (15 cm × 35 cm × 45 cm) in a cardboard lined with cushioning material inside, and the cardboard boxes are loaded on a truck and transported back and forth between Tokyo and Okayama prefecture at -20°C for 10 times. Was carried out. After the transportation test, the pouch bag was opened, and the multilayer structure was cut into a 10 cm square. The larger the radius of the ceramic sphere, the stronger the bending during vacuum packaging. Those having the same content of the boron compound (B) were evaluated under the same conditions, that is, using ceramic spheres having the same radius. The cut multi-layer structure was connected to MOCON OX-TRAN 2/20 (detection limit 0.01 mL/(m ² ·day·atm)) manufactured by Modern Control Co., and oxygen permeability was measured, and evaluated according to the following criteria. did. The measurement conditions were 23° C. and 65% RH on both the carrier gas side and the oxygen gas side, the oxygen pressure was 1 atm, and the carrier gas pressure was 1 atm. In the case of A to C, the impact resistance at low temperature was judged to be good.
A: 0.6 mL/(m ² ·day·atm) or less B: 0.6 mL/(m ² ·day·atm) or more and 1.2 mL/(m ² ·day·atm) or less C: 1.2 mL/( m ² ·day ·atm) or more and less than 1.8 mL/(m ² ·day ·atm) D: 1.8 mL/(m ² ·day ·atm) or more

For each example and comparative example using the resin compositions 1 to 34 and the resin compositions C1 to C23, a boron compound (B) was prepared according to the method described in (1) to (3), (a) and (b) above. ) And free boric acid (C), MI was measured and evaluated. Further, resin compositions 1, 3, 5, 9 to 13, 16, 19 to 21, 24, 26 to 29, 31 to 34, C1 to C4, C13, C15, C17, C18, C20, C21 and C23 are used. The respective examples and comparative examples were evaluated according to the method described in (c) above. The results are shown in Tables 6-11.

For example, from the comparison of Production Examples 3, 9, 10, 19, C2 and C9 (Examples 3, 9, 10, 19 and Comparative Examples 2, 9) in which boron was added by immersion, the treatment time of centrifugal dehydration was lengthened, Further, by lowering the temperature during the main drying, even if the concentration of the boron compound (B) is the same, the ratio of free boric acid (C) is low. Even when boric acid is added by an extruder, the same tendency can be seen from the comparison of Production Examples 26 to 29, C21 and C22 (Examples 26 to 29, Comparative Examples 21 and 22).

In the neck-in, when MI was less than 2 g/10 minutes (190°C/2160 g), the neck-in was less than 50 mm (evaluation A). When MI is 2 g/10 minutes (190°C/2160 g) or more and 6 g/10 minutes (190°C/2160 g) or less, the neck-in is 50 to 100 mm (evaluation B) and exceeds 6 g/10 minutes (190°C/2160 g). At 6.6 g/10 minutes (190°C/2160 g) or less, the neck-in was 100 to 200 mm (evaluation C). Comparative Example 5 in which the content of the boron compound (B) was small was the neck-in evaluation D. Further, by comparing Example 1 and Comparative Example 7, even if the boron compound (B) was the same as 110 ppm, in Comparative Example 7 in which the ratio of free boric acid (C) was 12%, MI was 6. It was slightly higher at 7 g/10 minutes (190° C./2160 g), and the neck-in was further deteriorated to 200 mm or more (evaluation D). On the other hand, in Comparative Example 6 in which the content of the boron compound (B) was large, the MI was low and the drawability was poor.

Focusing on the content ratio of free boron (C), Comparative Examples 1 to 4 and 7 to 23 in which the content ratio of free boron (C) is less than 0.1% by mass or more than 10% by mass are film-forming properties (neck). In and fish eye), stretchability and impact resistance at low temperature were all poor.

On the other hand, in Examples 1 to 34 in which the content of the boron compound (B) and the content ratio of the free boric acid (C) were within the predetermined ranges, film forming properties, stretchability and impact resistance at low temperature were all found. All had good results.

Further, from the comparison of Examples 10, 33 and 34 (Production Examples 10, 33, 34), when the treatment temperature of the main drying is the same, by performing vacuum drying, the concentration of the boron compound (B) is the same. As a result, the ratio of free boric acid (C) becomes low. Further, it can be seen from the comparison between Comparative Example 2 and Comparative Example 23 (Production Examples C2 and C23) that the presence of acid components such as acetic acid and phosphoric acid can suppress the generation of fish eyes.

ADVANTAGE OF THE INVENTION According to this invention, the film excellent in film forming property, stretchability, and impact resistance in low temperature, its manufacturing method, and the packaging material and vacuum packaging bag using such a film can be provided.

10 Hot Cutter 11 Discharge Port 12 Die 13 Rotating Blade 14 Rotating Shaft 15 Cutter Box 16 Cooling Water Supply Port 17 Cooling Water 18 Water Film 19 Pellet Discharging Port 20 Cooling Water and Pellets

Claims (8)

A film formed from a resin composition containing an ethylene-vinyl alcohol copolymer (A) having an ethylene unit content of 20 to 60 mol% and a boron compound (B),
The boron compound (B) contains free boric acid (C),
The content of the boron compound (B) with respect to the ethylene-vinyl alcohol copolymer (A) in the resin composition is 100 ppm or more and 5000 ppm or less in terms of orthoboric acid, and the free boric acid (C) in the boron compound (B) is A film having a ratio of 0.1% by mass or more and 10% by mass or less in terms of orthoboric acid. The film according to claim 1, wherein the resin composition contains a phosphate compound in an amount of 1 ppm or more and 500 ppm or less in terms of phosphate radical. The film according to claim 1, wherein the resin composition contains a carboxylic acid and/or a carboxylate ion in an amount of 0.01 μmol/g or more and 20 μmol/g or less in terms of carboxylic acid radical. The film according to any one of claims 1 to 3, wherein a melt index of the resin composition measured at 190°C under a load of 2160 g according to ASTM D1238 is 0.1 to 15 g/10 minutes. The film according to any one of claims 1 to 4, which is a stretched film. A method for producing a film according to claim 5, wherein
A method for producing a film, comprising the step of stretching the film according to claim 1. A packaging material comprising the film according to claim 1. A vacuum packaging bag comprising the film according to claim 1.

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