JP2018109110A - Saponified ethylene-vinyl ester copolymer pellet, and method for producing saponified ethylene-vinyl ester copolymer pellet containing conjugated polyene and cinnamate - Google Patents

Abstract

The present invention provides an EVOH resin pellet capable of suppressing the generation of fine fish eyes having a diameter of 200 μm or less at an extremely high level and a method for producing the same. A saponified ethylene-vinyl ester copolymer pellet containing a conjugated polyene and cinnamic acid, wherein the content of the conjugated polyene in the surface layer of the pellet is 30 ppb or more per pellet weight, and cinnamon. The ethylene-vinyl ester copolymer saponified product pellets, wherein the acid content is 1 to 500 ppm per weight of the pellets. [Selection figure] None

Description

  The present invention relates to pellets of an ethylene-vinyl ester copolymer saponified product (hereinafter sometimes referred to as “EVOH resin”) that can provide a film with less fisheye and less odor when film-formed. Specifically, the present invention relates to an EVOH resin pellet containing cinnamic acids and adjusting the content of conjugated polyene present on the pellet surface and a method for producing the same.

  In EVOH resin, hydroxyl groups contained in the molecular chain are strongly hydrogen-bonded to form crystal parts, and these crystal parts prevent oxygen from entering from the outside. It is shown. Taking advantage of such characteristics, EVOH resin is used after being formed into a film or sheet of food packaging material, pharmaceutical packaging material, industrial chemical packaging material, agricultural chemical packaging material or the like, or a packaging container such as a bottle.

  In forming the EVOH resin, melt molding is usually performed, and the film is formed and processed into a film shape, a sheet shape, a bottle shape, a cup shape, a tube shape, a pipe shape, etc., and is put to practical use. Therefore, the moldability and processability of the EVOH resin are important.

  However, since the EVOH resin has a relatively active hydroxyl group in the molecule, there is a possibility that an oxidation / crosslinking reaction occurs in a high-temperature melted state even in an extruder with almost no oxygen, resulting in a thermally deteriorated product. And it is known that this thermally deteriorated product has a disadvantage of generating a gel-like lump causing fish eyes.

  In order to improve such an inconvenience, Patent Document 1 proposes an EVOH resin composition in which generation of fish eyes such as gel-like lumps due to melt molding is suppressed by adding a conjugated polyene to the EVOH resin.

  In Patent Document 1, in the method for producing a vinyl acetate copolymer, after copolymerizing a monomer such as vinyl acetate, a conjugated polyene having a boiling point of 20 ° C. or more is added, and the obtained vinyl acetate copolymer is further obtained. A method for saponification is disclosed. As an EVOH resin composition produced by the above method, a conjugated polyene having a boiling point of 20 ° C. or higher is added to the EVOH resin in an amount of 0.00002 to 1% by weight (0.2 ppm to 10000 ppm), preferably 0.0001 to 0.2% by weight ( 1 ppm to 2000 ppm) is disclosed (paragraph 0034).

In Patent Document 1, if the polyene compound remains in the final saponified product, it causes odor generation, oozing, etc., so that it is not desirable that the residual amount is excessive from the viewpoint of use in packaging containers and the like. Has been. It is described that it is preferable to use a polyene compound that is easily washed and removed by washing with water after saponification (paragraph 0011).
Specifically, after polymerizing vinyl acetate under ethylene pressure, conjugated polyene is added, and after removal of ethylene, EVOH resin is produced by saponification, and EVOH resin particles are washed with a large amount of water. The target EVOH resin particles are obtained (Example 1).
The film produced using the EVOH resin particles thus obtained is less colored, and the number of gel-like lumps of 100 μm or more is 3 to 10 per 100 cm ² (see Table 1).

  Moreover, in patent document 2, as a manufacturing method of the vinyl alcohol polymer which has few fish eyes at the time of shaping | molding, the coloring was also suppressed, and also the odor was suppressed, after superposition | polymerization of a vinyl acetate type compound, it is unreacted in a distillation tower. After removing the vinyl acetate, it has been proposed to supply at least one of N, N-dialkylhydroxylamine, styrene derivative, hydroquinone derivative, quinone derivative, piperidine derivative and conjugated polyene as a polymerization inhibitor.

  Further, in Patent Document 3, a resin composition that is excellent in melt-run long run properties, can suppress formation of defects such as streak and fish eye, and coloring, and can form a molded product having excellent appearance while suppressing generation of odor. For example, a resin composition containing a saturated ketone in an EVOH resin has been proposed, and a resin composition containing a conjugated polyene has been proposed.

JP-A-9-71620 JP 2003-89706 A Japanese Patent Laying-Open No. 2015-71691

  In recent years, the requirements for the appearance and odor of packaging materials have become more severe, and further improvement of fish eyes is desired while ensuring melt moldability. In particular, there is a demand for EVOH resin pellets that can sufficiently suppress the generation of fine fish eyes having a diameter of 200 μm or less, and that can sufficiently suppress the odor generated from the molded product.

  The present invention has been made in view of the circumstances as described above. The object of the present invention is to suppress generation of minute fish eyes having a diameter of 200 μm or less at an extremely high level and to suppress generation of odor. An object of the present invention is to provide an EVOH resin pellet and a manufacturing method thereof.

  The present inventors investigated the relationship between the generation of fish eyes and EVOH resin pellets containing a conjugated polyene. As a result of various studies, it has been found that the presence of conjugated polyene in the pellet surface layer in a predetermined amount or more can suppress the generation of fish eyes. Although it is not clear about the mechanism, when EVOH resin pellets are melted by an extruder, conjugated polyene is present in a predetermined amount or more on the pellet surface, which is a contact portion between a high-temperature metal such as a barrel or screw and the pellet. Thus, it is considered that radicals generated locally in the vicinity of the pellet surface can be trapped to suppress the generation of fish eyes.

  Furthermore, the present inventors have found that the generation of odor in a molded product can be suppressed by containing a predetermined amount of cinnamic acid in EVOH resin pellets. Although the mechanism of odor suppression is not clear, cinnamic acid itself has a relatively high boiling point and is not likely to cause odor itself, and also due to some interaction between odorous components generated by thermal decomposition of EVOH resin and cinnamic acid. This is thought to be because the volatilization of odor components was suppressed.

  That is, the present invention is an EVOH resin pellet containing a conjugated polyene and cinnamic acids (hereinafter sometimes simply referred to as “conjugated polyene and cinnamic acid-containing EVOH resin pellets”), EVOH resin pellets having a content of 30 ppb or more per pellet weight and a cinnamic acid content of 1 to 500 ppm per pellet weight are defined as a first gist.

  The present invention also relates to a method for producing conjugated polyene and cinnamic acid-containing EVOH resin pellets, the step of bringing EVOH resin pellets into contact with a treatment liquid containing conjugated polyene, and EVOH resin pellets and cinnamic acids. A second gist is a method for producing a conjugated polyene and cinnamic acid-containing EVOH resin pellets comprising a step of contacting.

  The conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention have a conjugated polyene content of the pellet surface layer of 30 ppb or more per pellet weight, and a cinnamic acid content of 1 to 500 ppm per pellet weight. Therefore, generation of odor and fish eye can be suppressed.

  Moreover, generation | occurrence | production of a fish eye can be suppressed more as the conjugated polyene total content of the whole conjugated polyene and cinnamic acid content EVOH resin pellet of this invention is 0.01-10000 ppm per the said pellet weight.

Furthermore, the weight ratio of the conjugated polyene content of the pellet surface layer part to the total conjugated polyene content of the whole conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention is: surface layer conjugated polyene content / total conjugated polyene content = 1. If it is 5 × 10 ⁻⁵ or more, the generation of fish eyes can be further suppressed.

  And when the conjugated polyene of this invention is at least 1 sort (s) chosen from the group which consists of sorbic acid, sorbic acid ester, and sorbate, the adjustment of the adhesion amount to the EVOH resin pellet surface will become easy.

  In addition, the method of producing EVOH resin pellets containing conjugated polyene and cinnamic acids, comprising the steps of bringing the EVOH resin pellets into contact with the treatment liquid containing the conjugated polyene and the step of bringing the EVOH resin pellets into contact with the cinnamic acids. According to the above, EVOH resin pellets containing conjugated polyene and cinnamic acids can be produced using conventional production equipment.

  In the production method of the present invention, if the EVOH resin pellets are obtained by coagulating an EVOH resin alcohol solution or a water / alcohol mixed solution into pellets, the pellets may be made into porous EVOH resin pellets. it can.

  Furthermore, in the production method of the present invention, when the EVOH resin pellet is a porous pellet, the conjugated polyene can be efficiently incorporated into the surface layer of the EVOH resin pellet.

  In addition, in the production method of the present invention, when a process of blending a conjugated polyene as a polymerization inhibitor is included in the production process of the ethylene-vinyl ester copolymer before saponification of the EVOH resin, generation of fish eyes and the like is caused. Can be suppressed.

  The present invention will be described in detail below, but these show examples of desirable embodiments and are not limited to these contents.

  The conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention have a conjugated polyene content of the pellet surface layer of 30 ppb or more per pellet weight and a cinnamic acid content of 1 to 500 ppm per pellet weight. .

  Here, “the conjugated polyene content in the pellet surface layer portion” means the amount of the conjugated polyene existing near the surface layer of the conjugated polyene and cinnamic acid-containing EVOH resin pellet. Specifically, the conjugated polyene-containing EVOH resin pellet For a solution obtained by stirring 20 g in 30 mL of a mixed solution of distilled water: methanol = 1: 1 (volume ratio) for 10 minutes, the amount of conjugated polyene measured using a liquid chromatograph is calculated based on the EVOH resin pellet weight ( 20 g).

  In addition, the “content of cinnamic acids” in the present invention refers to the amount of cinnamic acids contained on the surface, inside, or both of the conjugated polyene and the cinnamic acids-containing EVOH resin pellets. Specifically, when cinnamic acid is contained on the surface of the EVOH resin pellet, the amount of cinnamic acid added to the surface of the EVOH resin pellet may be the content, and when cinnamic acid is contained inside the EVOH resin pellet. Is obtained by LC / MS / MS analysis of the extract obtained by immersing 1 g of the EVOH resin pellets in 9 mL of an extract at 25 ° C. (methanol in the case of cinnamic acid) and sonicating for 2 hours. From the obtained value, it can be determined by converting the content of cinnamic acid per pellet weight.

  Hereinafter, prior to the description of the conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention, each component and a method for producing EVOH resin pellets before containing the conjugated polyene will be described.

<EVOH resin>
The EVOH resin constituting the conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention is usually a resin obtained by saponifying a copolymer of ethylene and a vinyl ester monomer (ethylene-vinyl ester copolymer). It is a water-insoluble thermoplastic resin.

  As the vinyl ester monomer, vinyl acetate is typically used because it is easily available from the market and has good treatment efficiency of impurities during production. Other vinyl ester monomers include, for example, vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, etc. Aromatic vinyl esters such as aromatic vinyl esters and vinyl benzoates, and the like. Usually, aliphatic vinyl esters having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, particularly preferably 4 to 7 carbon atoms are used. it can. These are usually used alone, but a plurality of them may be used simultaneously as necessary.

  The ethylene and vinyl ester monomers are usually derived from petroleum-derived raw materials such as naphtha, but are derived from natural gas such as shale gas, sugar, starch, etc. contained in sugar cane, sugar beet, corn, potato, etc. Or a monomer derived from a plant-derived raw material purified from a component such as cellulose contained in rice, wheat, millet, grass plant or the like.

The EVOH resin used in the present invention may be copolymerized with the following comonomer (referred to as “other comonomer”) within a range not inhibiting the effects of the present invention (for example, 10 mol% or less).
Examples of other comonomers include olefins such as propylene, 1-butene and isobutene; 3-buten-1-ol, 3-butene-1,2-diol, 4-penten-1-ol and 5-hexene- Hydroxy group-containing α-olefins such as 1,2-diol and derivatives thereof such as esterified products and acylated products; acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itacone Unsaturated acids such as acids or salts thereof, or mono- or dialkyl esters having 1 to 18 carbon atoms; acrylamide, N-alkyl acrylamide, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid having 1 to 18 carbon atoms, or the like Salt, acrylamidopropyldimethylamine or its acid salt or its quaternary Acrylamides such as: methacrylamide, N-alkylmethacrylamide having 1 to 18 carbon atoms, N, N-dimethylmethacrylamide, 2-methacrylamidepropanesulfonic acid or its salt, methacrylamidepropyldimethylamine or its acid salt or its Methacrylamides such as quaternary salts; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide and N-vinylacetamide; Vinyl cyanides such as acrylonitrile and methacrylonitrile; Alkyl vinyl ethers having 1 to 18 carbon atoms Vinyl ethers such as hydroxyalkyl vinyl ether and alkoxyalkyl vinyl ether; vinyl halide compounds such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and vinyl bromide; Vinyl silanes such as silane; halogenated allyl compounds such as allyl acetate and allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; trimethyl- (3-acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamide-2 -Comonomers such as methylpropanesulfonic acid. These may be used alone or in combination of two or more.

  Copolymerization of ethylene and vinyl ester monomer and other comonomer used as necessary can be performed by a known polymerization method, that is, solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization, etc., from the viewpoint of uniform diffusion, Solution polymerization is preferably used. The polymerization method may be either a continuous type or a batch type.

The solution polymerization is usually carried out by putting a solution containing a vinyl ester monomer, a solvent and a polymerization catalyst into a polymerization can, and injecting ethylene while heating the solution to polymerize it. The ethylene pressure is usually about ²⁰ to 80 kg / cm ² .

  As the solvent, alcohols are preferable, but other organic solvents (such as dimethyl sulfoxide) that can dissolve ethylene, vinyl acetate, and ethylene-vinyl acetate copolymer can be used. Examples of alcohols that can be used include aliphatic alcohols having 1 to 10 carbon atoms such as methanol, ethanol, propanol, n-butanol, and t-butanol. These may be used alone or in combination of two or more. Of these, methanol is particularly preferred.

  The catalyst used for the solution polymerization is not particularly limited as long as it is a radical initiator, but preferably 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobis- (2 , 4,4-trimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis- (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis- Azo compounds such as (2-methylisobutyrate); alkyl peresters such as t-butylperoxyneodecanoate, t-butylperpivalate, t-butylperoxy-2-ethylhexanoate; -(4-t-butylcyclohexyl) peroxy-dicarbonate, dicyclohexylperoxy-dicarbonate, bis (2-ethylhexyl) di-sec-butyl Peroxydicarbonates such as ruperoxy-dicarbonate and diisopropylperoxy-dicarbonate; acetyl peroxide, benzoyl peroxide, lauroyl peroxide, dilauroyl peroxide, didecanoyl peroxide, dioctanoyl peroxide, dipropyl Azonitrile-based initiators such as peroxides such as peroxides and initiators such as organic peroxide-based initiators can be used. These may be used alone or in combination of two or more. However, when a catalyst with a short half-life is used, batch preparation of the catalyst in a batch type is not possible, and it is necessary to continuously charge the catalyst.

  The polymerization temperature is usually 20 to 90 ° C, preferably 40 to 70 ° C. The polymerization time is usually 2 to 15 hours, preferably 3 to 11 hours. In the case of continuous polymerization, it is preferable that the average residence time in the polymerization tank is comparable.

  In the case of solution polymerization, the polymerization is stopped when a predetermined polymerization rate is reached. A polymerization rate is 10-90 mol% normally with respect to the preparation vinyl ester monomer, Preferably it is 30-80 mol%. Further, the resin content in the solution after polymerization is usually 5 to 85% by weight, preferably 20 to 70% by weight.

  The polymerization is usually stopped by adding a polymerization inhibitor. As the polymerization inhibitor, N, N-dialkylhydroxylamine, styrene derivatives, hydroquinone derivatives, quinone derivatives, piperidine derivatives, conjugated polyenes, and the like can be used. These may be used alone or in combination of two or more. Of these, conjugated polyenes are preferably used. This is because the conjugated polyene can contribute to the suppression of the occurrence of fish eyes and the like even if it remains in the relationship with the content of the surface layer portion of the pellet to be finally obtained.

  As the conjugated polyene used as the polymerization inhibitor, compounds listed as conjugated polyenes to be contained in the pellet surface layer described later can be used.

The conjugated polyene is preferably dissolved in the solvent used for the polymerization and added as a conjugated polyene solution from the viewpoint of uniform diffusion.
When conjugated polyene is used as a polymerization inhibitor, the amount added is usually 0.0001 to 3 parts by weight, preferably 0.0005 to 1 part by weight, more preferably 100 parts by weight of the charged amount of vinyl ester monomer. 0.001 to 0.5 parts by weight.

After completion of the polymerization, unreacted ethylene gas and unreacted vinyl ester monomer are removed and then saponified.
The unreacted ethylene gas can be removed by evaporative removal or the like, for example. Further, as a method for removing unreacted vinyl ester monomer from the ethylene-vinyl acetate copolymer solution, for example, the copolymer solution is continuously supplied at a constant rate from the upper part of the tower filled with Raschig rings, Ethylene-vinyl ester co-polymer from which vapor of organic solvent such as methanol is blown from the bottom, mixed vapor of organic solvent such as methanol and unreacted vinyl ester monomer is discharged from the top of the tower, and unreacted vinyl ester monomer is removed from the bottom of the tower A method of taking out the combined solution can be employed.

Saponification can be performed by a known method. Usually, a saponification reaction is started by adding an alkali catalyst to the ethylene-vinyl ester copolymer solution from which the unreacted vinyl ester monomer has been removed. As a saponification method, either a continuous method or a batch method is possible.
Examples of the alkali catalyst that is a saponification catalyst include sodium hydroxide, potassium hydroxide, and alkali metal alcoholate.

Saponification conditions vary depending on the catalyst used, the ethylene content of the ethylene-vinyl ester copolymer, the desired degree of saponification, and the like. For example, suitable saponification conditions in the case of a batch type are as follows. .
The saponification reaction temperature is preferably 30 to 60 ° C., and the use amount of the saponification catalyst is usually preferably 0.001 to 0.6 equivalent (per vinyl ester group). The saponification time depends on the saponification conditions and the desired degree of saponification, but is usually selected from 1 to 6 hours.

  In this way, an EVOH resin solution is obtained. The EVOH resin content in the EVOH resin solution is preferably about 10 to 50% by weight. As a solvent for this EVOH resin solution, alcohol such as methanol and a water / alcohol mixed solution are usually preferably used.

  The EVOH resin used in the present invention may be further subjected to “post-modification” such as urethanization, acetalization, cyanoethylation, oxyalkyleneation and the like.

  The EVOH resin as described above mainly contains ethylene-derived structural units and vinyl alcohol structural units, and usually contains a small amount of vinyl ester structural units that remain without being saponified as necessary. When another comonomer is copolymerized, a structural unit derived from the comonomer is further included.

  The EVOH resin used in the present invention preferably has the following composition.

  Content of the ethylene structural unit in EVOH resin is a value measured based on ISO14663, and is 20-60 mol% normally, Preferably it is 25-50 mol%. When the content is too low, the gas barrier property and melt moldability under high humidity tend to be lowered, and when it is too high, the gas barrier property tends to be lowered.

  The saponification degree of the vinyl ester component in the EVOH resin is a value measured based on JIS K6726 (however, the EVOH resin is a solution uniformly dissolved in water / methanol solvent) and is usually 90 to 100 mol%, preferably 95 to 100 mol%. When the degree of saponification is too low, gas barrier properties, thermal stability, moisture resistance and the like tend to decrease.

<Conjugated polyene>
The conjugated polyene used in the present invention has a structure in which carbon-carbon double bonds and carbon-carbon single bonds are alternately connected, and the number of carbon-carbon double bonds is two or more. It is a compound having a double bond. The conjugated polyene is a conjugated diene having a structure in which two carbon-carbon double bonds and one carbon-carbon single bond are alternately connected, three carbon-carbon double bonds, and two carbon-carbons. It may be a conjugated triene having a structure in which single bonds are alternately connected, or a conjugated polyene having a structure in which a larger number of carbon-carbon double bonds and carbon-carbon single bonds are alternately connected. However, if the number of conjugated carbon-carbon double bonds is 8 or more, the molded product may be colored by the color of the conjugated polyene itself, so the number of conjugated carbon-carbon double bonds is 7 or less. A polyene is preferred. Further, a plurality of conjugated double bonds composed of two or more carbon-carbon double bonds may be present in one molecule without being conjugated with each other. For example, a compound having three conjugated trienes in the same molecule such as tung oil is also included in the conjugated polyene.

  Examples of such conjugated polyenes include isoprene, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-t-butyl-1,3-butadiene, 1, 3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 2,4-dimethyl-1,3-pentadiene, 3,4-dimethyl-1,3-pentadiene, 3-ethyl-1,3-pentadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene, 2,5-dimethyl-2, 4-hexadiene, 1,3-octadiene, 1,3-cyclopentadiene, 1,3-cyclohexadiene, 1-phenyl-1,3-butadiene, 1,4-diphenyl-1,3- Tadiene, 1-methoxy-1,3-butadiene, 2-methoxy-1,3-butadiene, 1-ethoxy-1,3-butadiene, 2-ethoxy-1,3-butadiene, 2-nitro-1,3-butadiene Butadiene, chloroprene, 1-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 2-bromo-1,3-butadiene, fulvene, tropone, oximene, ferrandrene, myrcene, farnesene, semblene, sorbine Conjugated dienes composed of two carbon-carbon double bonds such as acid, sorbic acid ester, sorbate, and abietic acid; 1,3,5-hexatriene, 2,4,6-octatriene-1- Conjugated trienes having a conjugated structure with three carbon-carbon double bonds such as carboxylic acid, eleostearic acid, tung oil, cholecalciferol, etc. Cyclooctatetraene, 2,4,6,8 Dekatetoraen-1-carboxylic acid, retinol, carbon atoms such as retinoic acid - conjugated polyene such as consisting of carbon double bonds 4 or more conjugated structure and the like. Any of those having a plurality of stereoisomers such as 1,3-pentadiene, myrcene, and farnesene may be used. Two or more kinds of such polyene compounds can be used in combination.

  Among these, sorbic acid, sorbic acid ester, and sorbate have a carboxyl group and have high affinity with water, so that the amount of adhesion to the EVOH resin pellet surface can be easily adjusted. preferable.

<Cinnamon acids>
The cinnamic acid to be contained in the EVOH resin pellet of the present invention is not limited to cinnamic acid, and examples thereof include cinnamic acid esters, cinnamic acid having an alkoxy group, cinnamic acid amide, and cinnamic acid derivatives. These may be used alone or in combination of two or more. Among these, cinnamic acid is preferable. The content of cinnamic acids when using multiple types of cinnamic acids is the total content of all cinnamic acids.

<Manufacture of EVOH resin pellets>
As a method for producing pellets from EVOH resin, a conventionally known method can be adopted, for example,
a) A hot-cut method in which a fluid EVOH resin is extruded from a discharge port of an extruder, cut in a molten state, and then cooled and solidified to produce pellets.
b) A strand-cut method in which a fluid EVOH resin solution is extruded into a coagulation bath, and EVOH resin strands obtained by cooling and solidification are cut.
Among them, b) the strand cut method is preferable in that a porous pellet described later can be obtained.

  The EVOH resin used as a pellet raw material in any of the above a) hot cut method and b) strand cut method is (α) a solution of EVOH resin obtained by saponification in the above EVOH resin synthesis method. Alternatively, the EVOH resin water-containing composition after adjusting the water content of the solution or slurry as it is; or (β) EVOH resin pellets (dried EVOH resin composition pellets) are melted and EVOH in such a molten state Resin can be used.

  When the EVOH resin water-containing composition is used as the pellet raw material to be charged into the extruder, the EVOH resin water-containing composition contains 0 to 10 parts by weight of alcohol and 10 to 500 parts by weight of water with respect to 100 parts by weight of the EVOH resin. EVOH resin hydrous compositions are preferred. When the EVOH resin solution or slurry is used, alcohol, water / alcohol mixed solvent, or the like is used as the solvent. Of these, a water / alcohol mixed solvent is preferred. As said alcohol, C1-C10 aliphatic alcohols, such as methanol, ethanol, a propanol, n-butanol, t-butanol, can be used, for example, Methanol is especially preferable. The water / alcohol mixing weight ratio is preferably 80/20 to 5/95, and the EVOH resin concentration is preferably 20 to 60% by weight.

  Although it does not specifically limit as a method of adjusting the water content of the EVOH resin water-containing composition in pellet production, in order to increase the water content, a method of spraying water on the resin, a method of immersing the resin in water, It is possible to employ a method of contacting them. In order to lower the water content, it may be dried as appropriate, and for example, it can be dried using a fluid hot air dryer or a stationary hot air dryer.

a) Hot cut method When the EVOH resin hydrous composition is charged into an extruder as a pellet raw material produced by the hot cut method, the temperature of the EVOH resin hydrous composition in the extruder is preferably 70 to 170 ° C, more preferably. 80-170 degreeC, More preferably, it is 90-170 degreeC. When the temperature of the EVOH resin water-containing composition is too low, the EVOH resin tends not to melt completely, and when it is too high, the EVOH resin tends to be susceptible to thermal degradation. When the dry EVOH resin composition is used as a raw material for pellets, the temperature of the EVOH resin composition in the extruder is preferably 150 to 300 ° C, more preferably 160 to 280 ° C, and still more preferably 170 to 250 ° C. The temperature of the resin composition refers to the temperature detected in the vicinity of the discharge port at the tip of the extruder by a temperature sensor installed in the extruder cylinder.

  The EVOH resin (water-containing) composition extruded from the die, that is, the EVOH resin in a molten state is cut before being cooled and solidified. The hot cut method may be either cut in the atmosphere (air hot cut method) or extruded into a cutter installation container filled with cooling water and cut in cooling water (under water cut method).

The temperature of the cooling water in the underwater cutting method is a temperature at which the EVOH resin water-containing composition extruded in a molten state does not solidify (solidify) instantaneously. The temperature is preferably -20 to 50 ° C, more preferably -5 to 30 ° C.
However, when the dry EVOH resin composition is used as a raw material, it is easier to solidify than when the EVOH resin water-containing composition is used as a raw material. Therefore, the temperature of the cooling water in the underwater cutting method is based on the EVOH resin water-containing composition as a raw material. It is higher than the case, and is usually 0 to 90 ° C, preferably 20 to 70 ° C.

  The cooling water is not limited to water. Water / alcohol mixed solution; aromatic hydrocarbons such as benzene; ketones such as acetone and methyl ethyl ketone; ethers such as dipropyl ether; organic esters such as methyl acetate, ethyl acetate, and methyl propionate it can. Of these, water or a water / alcohol mixed solution is used because it is easy to handle. In the water / alcohol mixed solution, the water / alcohol (weight ratio) is usually 90/10 to 99/1. In addition, as said alcohol, lower alcohols, such as methanol, ethanol, propanol, can be used, and methanol is used preferably industrially.

b) Strand cut method In the case of the strand cut method, an EVOH resin solution, an EVOH water-containing composition, or a dry EVOH resin composition can be used as a pellet raw material.
However, when the EVOH resin solution is extruded into a coagulation bath, the temperature of the EVOH resin solution is usually 10 to 100 ° C., and the temperature of the coagulation bath is a temperature at which the extruded EVOH resin can be cooled and solidified, usually −10 to 10 It is 40 degreeC and residence time is about 10 to 400 second normally. Even when the EVOH resin hydrous composition is fed into the extruder as a pellet raw material, the temperature of the EVOH resin hydrous composition extruded to the coagulation bath is usually 10 to 100 ° C, and the temperature of the coagulation bath is usually -10 to 40 ° C. The residence time is usually about 10 to 400 seconds. When the dry EVOH resin composition is charged into the extruder as a pellet raw material, the temperature at which the dry EVOH resin composition is extruded into the coagulation bath is usually 150 to 300 ° C, and the temperature of the coagulation bath is usually 0 to 90 ° C. The residence time is about 2 to 400 seconds.

  As the coagulation liquid used in the coagulation bath, a solution similar to the above-mentioned a) hot cut type cooling water can be employed.

  In this way, EVOH resin pellets are obtained.

  Of the EVOH resin pellets described above, porous pellets are preferably used from the viewpoint of the conjugated polyene content treatment described below. Porous pellets can be obtained by cutting strands obtained by coagulating an alcohol or water / alcohol solution of EVOH resin in a coagulation bath in the b) strand cutting method. When the EVOH resin pellet is porous, the conjugated polyene permeates into the pores, whereby the conjugated polyene can be easily held in the pellet, and the conjugated polyene can be efficiently taken into the pellet surface layer. That is, the pore size of the porous structure here is not particularly limited as long as the conjugated polyene can penetrate into the pore.

  In the present invention, the shape of the pellet is not particularly limited. Any shape such as a spherical shape, a cylindrical shape, a cubic shape, and a rectangular parallelepiped shape may be used. The pellet shape depends on the pellet manufacturing method. From the viewpoint of convenience when used as a molding material, the pellet size is usually 1 to 6 mm, preferably 2 to 5 mm in diameter, and 1 to 6 mm, preferably 2 to 5 mm in height.

  In any of the pellet raw materials, that is, the EVOH resin solution and the EVOH resin water-containing composition appropriately adjusted in water content and the like, the alkali catalyst, by-product salts, other impurities and the like usually used at the time of saponification are contained. For this reason, the above-mentioned impurities and the like are usually contained in pellets of EVOH resin produced using such EVOH resin solution as a pellet raw material. Therefore, the porous pellets thus obtained may be subjected to a water washing treatment.

  When washing with water, the conjugated polyene added as a polymerization inhibitor is also removed. However, the ease of removal varies depending on the polarity of the conjugated polyene, and a certain amount remains in the EVOH resin.

<Manufacture of EVOH resin pellet containing conjugated polyene and cinnamic acid>
The conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention can be obtained through the following steps of manufacturing a conjugated polyene-containing EVOH resin pellet and manufacturing steps of a cinnamic acid-containing EVOH resin pellet. Any of these steps may be performed first or at the same time. When performing the said process simultaneously, it can carry out by using the process liquid which the conjugated polyene and cinnamic acid dissolved, for example.
Especially, it is preferable to carry out in order of the process of manufacture of the conjugated polyene containing EVOH resin pellet and the manufacture of a cinnamic acid containing EVOH resin pellet from the point of work efficiency.

<Manufacture of conjugated polyene-containing EVOH resin pellets>
The conjugated polyene-containing EVOH resin pellets can be produced by including conjugated polyene on the surface of the EVOH resin pellets.

  Examples of the method of containing the conjugated polyene on the surface of the EVOH resin pellet include a method of bringing the EVOH resin pellet and the conjugated polyene into contact with each other in advance, and a method of containing the conjugated polyene in the EVOH resin pellet manufacturing stage. Can be used.

  In the method of incorporating the conjugated polyene in the EVOH resin pellet manufacturing stage, as already described, since the conjugated polyene can be used as a polymerization inhibitor, by adding the conjugated polyene as a polymerization inhibitor at the end of the polymerization, EVOH resin pellets containing conjugated polyene can be produced. However, in the case of EVOH resin pellets produced by such a method, the conjugated polyene is contained almost uniformly in the entire pellet, and therefore the content of the conjugated polyene in the surface layer portion tends to be low. Further, when the amount of conjugated polyene added as a polymerization inhibitor is increased, it may cause pellet coloring, and thus washing with water may be necessary after pellet production. For this reason, it is generally difficult to adjust the amount of conjugated polyene in the pellet surface layer to an amount effective for suppressing the generation of fish eyes at the EVOH resin pellet manufacturing stage.

  Therefore, in order to contain the conjugated polyene in the surface layer portion of the EVOH resin pellet, a method of bringing the EVOH resin pellet prepared in advance into contact with the conjugated polyene is preferable.

  As a method of bringing the EVOH resin pellets and the conjugated polyene into contact with each other in advance, the EVOH resin pellets and a treatment liquid containing the conjugated polyene (hereinafter sometimes referred to as “conjugated polyene-containing treatment liquid”) may be contacted. However, as another contact method, the conjugated polyene may be directly contacted with the EVOH resin pellets and mixed for contact.

  Examples of the method of bringing the EVOH resin pellets into contact with the conjugated polyene-containing treatment liquid include, for example, a method of spraying the conjugated polyene-containing treatment liquid onto the EVOH resin pellets; and a method of immersing the EVOH resin pellets in the conjugated polyene-containing treatment liquid A method of washing EVOH resin pellets with a conjugated polyene-containing treatment solution; a method of spraying conjugated polyene dissolved in a solvent on a EVOH resin pellet whose surface has been adjusted to a specific high temperature, etc. Can do. Among these, a method of immersing in a conjugated polyene-containing treatment liquid or a method of washing with a conjugated polyene-containing treatment liquid is preferably used.

  By bringing the above-described production method, that is, the EVOH resin pellets into contact with the conjugated polyene-containing treatment liquid, it is possible to effectively increase the amount of conjugated polyene in the surface layer of the pellet.

  The conjugated polyene-containing treatment by bringing the EVOH resin pellets into contact with the conjugated polyene-containing treatment liquid has the following advantages in addition to the fact that the conjugated polyene content in the surface layer can be increased efficiently. is there. That is, by adjusting the conjugated polyene concentration of the treatment liquid, it is possible to adjust the conjugated polyene content in the pellet surface layer portion with high accuracy.

  Furthermore, the conjugated polyene-containing treatment by bringing the EVOH resin pellets into contact with the conjugated polyene-containing treatment solution also serves as a concentration adjusting treatment for other preferable additives, particularly boron-containing compounds such as acetic acid, acetate, and boric acid. You can also. Specifically, a treatment liquid containing an additive such as a boron-containing compound such as acetic acid, acetate, or boric acid may be used together with the conjugated polyene. By this method, the content ratio between the other additive components and the conjugated polyene can be easily adjusted.

  The density | concentration of the conjugated polyene in a conjugated polyene containing processing liquid is 0.01-500 ppm normally per weight of a conjugated polyene containing processing liquid, Preferably it is 0.1-50 ppm. If the concentration is too low, it tends to be difficult to contain a predetermined amount of the conjugated polyene. If the concentration is too high, precipitates of the conjugated polyene adhere to the pellet surface, so that agglomerated aggregates are formed in the molded film. May occur.

  In contact treatment with an aqueous solution of conjugated polyene, the content of conjugated polyene in the surface layer portion depends on the concentration of conjugated polyene, contact treatment time, contact treatment temperature, stirring speed at the time of contact treatment, moisture content of pellets of EVOH resin to be treated, etc. Can be controlled.

  After the contact treatment with the conjugated polyene, it may be used as it is in the next step, but it is usually preferable to dry the pellet. For such drying, a known method can be employed. For example, a cylindrical / groove type stirring dryer, a cylindrical dryer, a rotary dryer, a fluidized bed dryer, a vibrating fluidized bed dryer, a conical rotary dryer, etc. What is necessary is just to dry by the stationary drying etc. which used the fluidized drying used, the batch-type box dryer, the band dryer, the tunnel dryer, the vertical silo dryer, etc. By passing a gas such as nitrogen gas at 80 to 150 ° C. through the dryer, the gas can be efficiently dried.

  As described above, conjugated polyene-containing EVOH resin pellets are obtained.

<Manufacture of cinnamic acid-containing EVOH resin pellets>
The cinnamic acid-containing EVOH resin pellets can be produced by adding cinnamic acids to the EVOH resin pellets.

  As a method for adding cinnamic acids to EVOH resin pellets, a method in which EVOH resin pellets prepared in advance and cinnamic acids are brought into contact with each other is preferred. However, as another method, cinnamic acids are brought into contact with EVOH resin pellets in the production stage. Cinnamic acids may be contained by the method.

  Examples of the method of bringing the previously prepared EVOH resin pellets into contact with cinnamic acids include, for example, a method of spraying cinnamic acid solutions onto EVOH resin pellets; a method of immersing EVOH resin pellets in cinnamic acid solutions; Examples include a method of adding EVOH resin pellets while stirring an acid solution; a method of adding cinnamic acid powder directly to EVOH resin pellets and mixing them. Among these, a method in which cinnamic acid powders are directly added to EVOH resin pellets and mixed is preferably used because cinnamic acids can be efficiently contained.

  The amount of cinnamic acid contained in the EVOH resin pellets is usually 1 to 500 ppm, preferably 10 to 400 ppm, particularly preferably 50 to 350 ppm, per EVOH resin pellet weight. If the cinnamic acid content is too small, the film tends to generate a burnt odor. If the cinnamic acid content is too high, an acidic odor tends to be generated from the thermal decomposition product of cinnamic acid.

  By the said process, a cinnamic acid containing EVOH resin pellet is obtained.

  The conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention can be obtained through the step of containing the conjugated polyene and the step of containing cinnamic acid.

<Conjugated polyene and cinnamic acid-containing EVO resin pellets>
The conjugated polyene content of the surface layer part of the conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention is 30 ppb or more, preferably 34 ppb or more, more preferably 38 ppb or more per pellet weight. When the content of the conjugated polyene is small, a lot of fish eyes are generated. In addition, the upper limit of the content of the conjugated polyene in the surface layer portion is usually 10,000 ppb (10 ppm), preferably 8000 ppb (8 ppm), and particularly preferably 5000 ppb (5 ppm).

  The content of the conjugated polyene in the surface layer is determined by liquid chromatography using a solution obtained by stirring 20 g of conjugated polyene-containing EVOH resin pellets in 30 mL of a mixed solution of water / methanol = 1/1 (volume ratio) for 10 minutes. It is measured by quantifying the content of conjugated polyene and dividing by the weight of EVOH resin pellets (20 g).

  The amount of conjugated polyene measured by the above measurement method is the amount of conjugated polyene contained in the surface layer portion of the conjugated polyene and cinnamic acid-containing EVOH resin pellets as described above. The present inventors have found that the content of the conjugated polyene in the EVOH resin pellet surface layer is effective in suppressing the generation of fish eyes. By controlling the conjugated polyene content in the pellet surface layer part to 30 ppb or more, preferably 34 ppb or more, more preferably 38 ppb or more per pellet weight, it is possible to effectively suppress the generation of minute fish eyes having a diameter of 200 μm or less. it can.

  In the conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention, it is sufficient that at least the amount of the conjugated polyene in the pellet surface layer measured by the measurement method is 30 ppb or more per pellet weight. Such conjugated polyene and cinnamic acid-containing EVOH resin pellets may contain almost no conjugated polyene or may contain a larger amount of conjugated polyene.

  For example, when conjugated polyene is contained in the pellet production raw material (EVOH resin solution or EVOH resin water-containing composition) as in the case of adding conjugated polyene as a polymerization inhibitor, the content of conjugated polyene in the pellet is high. Tend to be.

  When the conjugated polyene is contained inside the conjugated polyene and cinnamic acid-containing EVOH resin pellets, the total content of the conjugated polyene is usually 0.01 to 10000 ppm, more preferably 0.1 to 8000 ppm, More preferably, it is 1-5000 ppm, Most preferably, it is 1-2000 ppm. When the total content of the conjugated polyene is too small, the content of the conjugated polyene in the pellet surface layer portion is relatively reduced, and the fish eyes tend to increase. Moreover, when there is too much content of conjugated polyene, there exists a possibility that a molded article may be colored with the color of conjugated polyene itself.

  The above-mentioned “total content of conjugated polyene” means the content of conjugated polyene contained in the conjugated polyene and cinnamic acid-containing EVOH resin pellets. Specifically, after the EVOH resin pellets are pulverized, solvent extraction is performed. The amount of the conjugated polyene in the extract is an amount converted from a value measured using a liquid chromatograph.

Weight ratio of conjugated polyene content in the surface layer of conjugated polyene and cinnamic acid-containing EVOH resin pellets to total content of conjugated polyene in EVOH resin pellets containing conjugated polyene and cinnamic acids (surface layer conjugated polyene content / total content of conjugated polyene) The amount is usually 1.5 × 10 ⁻⁵ or more, preferably 3 × 10 ⁻⁵ or more, more preferably 5 × 10 ⁻⁵ or more. If the weight ratio of the conjugated polyene content in the surface layer of the pellet to the total conjugated polyene content of the whole pellet is too small, there is a tendency that the effect of suppressing the generation of fish eyes cannot be sufficiently obtained. The upper limit is usually 1 × 10 ⁻² .

  The content of cinnamic acid in the conjugated polyene and cinnamic acid-containing EVOH resin pellets is 1 to 500 ppm, preferably 10 to 400 ppm, particularly preferably 50 to 350 ppm, per weight of the pellet. If the cinnamic acid content is too small, a burnt odor is likely to be generated on the film. If the cinnamic acid content is too high, an acidic odor is likely to be generated from the thermal decomposition product of cinnamic acid.

  The above-mentioned “content of cinnamic acids” refers to the amount of cinnamic acids contained on the surface, inside, or both of the conjugated polyene and cinnamic acids-containing EVOH resin pellets. Specifically, when cinnamic acid is contained on the surface of the EVOH resin pellet, the amount of cinnamic acid added to the surface of the EVOH resin pellet may be the content, and when cinnamic acid is contained inside the EVOH resin pellet. Is obtained by immersing 1 g of EVOH resin pellets in 9 mL of an extract at 25 ° C. (methanol in the case of cinnamic acid) and ultrasonically treating the extract for 2 hours from the value obtained by LC / MS / MS analysis. It can obtain | require by converting into cinnamic acid content per resin pellet weight.

  The water content of the conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention is usually 0.01 to 1% by weight, preferably 0.05 to 0.5% by weight. If the water content is too low, the EVOH resin will not be plasticized by water molecules, and the EVOH resin pellets will not be easily melted at the time of extrusion molding. A foaming phenomenon occurs, and the appearance of the molded product tends to deteriorate.

  The melt flow rate (MFR) (210 ° C., load 2160 g) of the conjugated polyene and cinnamic acid-containing EVOH resin pellets is usually 0.5 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, particularly preferably. Is 2 to 35 g / 10 min. When the MFR is too large, the film forming property tends to be unstable, and when it is too small, the viscosity becomes too high and melt extrusion tends to be difficult.

<Other ingredients>
In the conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention, if necessary, a compounding agent generally blended into the EVOH resin, for example, a heat stabilizer, an antioxidant, an antistatic agent, a colorant, an ultraviolet absorber, Lubricant, plasticizer, light stabilizer, surfactant, antibacterial agent, drying agent, antiblocking agent, flame retardant, crosslinking agent, curing agent, foaming agent, crystal nucleating agent, antifogging agent, biodegradation additive, silane Coupling agents, oxygen absorbers, fillers, reinforcing materials such as various fibers, and the like may be contained. In particular, partial salts of acids or polybasic acids such as phosphoric acid, pyrophosphoric acid, phosphorous acid, oxalic acid, succinic acid, adipic acid, tartaric acid, citric acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, acetic acid, etc. You may contain. These may be used alone or in combination of two or more.

<Application>
The conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention can be formed into, for example, a film, a sheet, a cup or a bottle by a melt molding method. Examples of such melt molding methods include extrusion molding methods (T-die extrusion, inflation extrusion, blow molding, melt spinning, profile extrusion, etc.), injection molding methods, and the like. In many cases, the melt molding temperature is usually selected from the range of 150 to 300 ° C. It is also possible to uniaxially or biaxially stretch films, sheets, fibers, and the like.

  The conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention may be used alone as they are for melt molding, or other thermoplastic resin pellets may be appropriately blended and used for melt molding. Further, as the conjugated polyene and cinnamic acid-containing EVOH resin pellet, a mixture of two or more kinds of conjugated polyene and cinnamic acid-containing EVOH resin pellet may be used. The mixture of two or more kinds of conjugated polyene and cinnamic acid-containing EVOH resin pellets refers to a mixture of EVOH resins having different ethylene content, saponification degree, MFR, and constitution.

  Examples of other thermoplastic resins include various polyolefins (for example, polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene, ethylene-propylene copolymer, ethylene and α-olefin having 4 or more carbon atoms). Copolymer, polyolefin-maleic anhydride copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, or modified polyolefin obtained by graft-modifying these with unsaturated carboxylic acid or a derivative thereof Etc.), various nylons (for example, nylon 6, nylon 66, nylon 6/66 copolymer, etc.), polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, modified polyvinyl alcohol resin, etc. It is possible .

  The EVOH resin film obtained by the present invention or an EVOH resin composition film obtained by mixing EVOH resin and another thermoplastic resin may be laminated with another thermoplastic resin film, or may be used together with another thermoplastic resin. A multilayer film may be extruded. Further, the saponified ethylene-vinyl acetate copolymer composition can be coextruded or solution coated on a substrate film such as paper, plastic film and metal foil.

  Bags and cups made of films, sheets, stretched films, cups, trays, tubes, bottles, etc. and lids thus obtained are excellent in appearance with little coloration and almost no fish eyes. For this reason, it can be suitably used as a packaging material that requires gas barrier properties and has strict requirements on appearance. Specifically, it is useful as a container for various packaging materials such as seasonings such as mayonnaise and dressing, fermented foods such as miso, fats and oils such as salad oil, beverages, cosmetics and pharmaceuticals in addition to general foods.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
In the examples, “part” means a weight basis.

  First, a method for measuring and evaluating pellets used in Examples and Comparative Examples will be described.

<Measurement evaluation method>
(1) Total content of conjugated polyene (sorbic acid) in pellets Concerning the content of conjugated polyene in conjugated polyene and cinnamic acid-containing EVOH resin pellets, if conjugated polyene is added directly to the EVOH resin pellet surface, it contains the added amount The amount of conjugated polyene was quantified by the following measuring method when conjugated polyene was present inside the EVOH resin pellet.
8 mL of extraction solvent (distilled water: methanol = 1: 1, volume ratio) was added to 1 g of powder obtained by freeze-pulverizing the EVOH resin pellets. This solution was sonicated for 1 hour at a temperature of 20 ° C. to extract sorbic acid in the resin, and after cooling, the volume was adjusted to 10 mL with an extraction solvent. After this solution was filtered with a filter having a pore size of 0.45 μm, sorbic acid in the extraction solution was quantified with a liquid chromatograph-ultraviolet spectroscopic detector.
[HPLC measurement conditions]
LC system: Agilent 1260/1290 [manufactured by Agilent Technologies]
Detector: Agilent 1260 infinity diode array detector [manufactured by Agilent Technologies]
Column: Cadenza CD-C18 (100 × 3.0 mm, 3 μm) [manufactured by Imtakt]
Column temperature: 40 ° C
Mobile phase A: 0.05% formic acid-containing aqueous solution of 5% acetonitrile Mobile phase B: 0.05% formic acid-containing 95% acetonitrile aqueous solution Time program: 0.0 → 5.0 minutes B% = 30%
5.0 → 8.0 minutes B% = 30% → 50%
8.0 → 10.0 min B% = 50%
10.0 → 13.0 minutes B% = 50% → 30%
13.0 → 15.0 minutes B% = 30%
Flow rate: 0.2 mL / min UV detection wavelength: 190 to 400 nm
Quantitative wavelength: 262 nm
“%” In the above HPLC measurement conditions means volume%.

(2) Conjugated polyene (sorbic acid) content in pellet surface layer part 20 g of conjugated polyene and cinnamic acid-containing EVOH resin pellets were stirred for 10 minutes in 30 mL of extraction solvent (distilled water: methanol = 1: 1, volume ratio). Extraction was performed. The obtained extract was concentrated to 2 mL, and then filtered through a filter having a pore size of 0.45 μm. The obtained filtrate was used as a test solution, and conjugated polyene was quantified by liquid chromatography. The amount of conjugated polyene in the filtrate was measured and divided by the EVOH resin pellet weight (20 g) to determine the conjugated polyene content in the pellet surface layer. The measurement conditions of the liquid chromatograph were the same as the measurement of the total conjugated polyene content of the above pellets.

(3) Content of cinnamic acid in pellet When cinnamic acid was contained only on the conjugated polyene and cinnamic acid-containing EVOH resin pellet surface, the amount of cinnamic acid added to the EVOH resin pellet surface was regarded as the content. Moreover, when cinnamic acid was contained inside the EVOH resin pellet, cinnamic acid content was calculated by the following method. In addition, although the following procedure describes the case where cinnamic acid is used as cinnamic acid as an example, cinnamic acid salts other than cinnamic acid are also performed in the same procedure.
[Preparation of standard solution]
Cinnamic acid (10.89 mg) is weighed into a 10 mL volumetric flask and dissolved in methanol to give a 10 mL solution (standard stock solution; 1089 μg / mL). Then, the prepared standard stock solution was diluted with methanol, and each mixed standard (multiple concentrations (0.109 μg / mL, 0.218 μg / mL, 0.545 μg / mL, 1.09 μg / mL, 2.18 μg / mL)) was mixed. Adjust the solution. LC / MS / MS analysis is performed using these mixed standard solutions, and a calibration curve is created.
[Preparation of sample solution]
(I) After weighing conjugated polyene and cinnamic acid-containing EVOH resin pellets (1 g) into a 10 mL volumetric flask, 9 mL of methanol is added.
(II) Sonication is performed for 120 minutes, and then allowed to cool at room temperature (25 ° C.).
(III) Add methanol to make 10 mL (sample solution (α)).
(IV) After collecting 1 mL of the sample solution (α) in a 10 mL volumetric flask, methanol is added and the volume is adjusted to 10 mL (sample solution (β)).
(V) A sample solution (α) or a liquid obtained by filtering the sample solution (β) with a PTFE filter (0.45 μm) is used as a measurement solution for LC / MS / MS analysis.
The detected concentration of cinnamic acid is calculated from the peak area value detected by LC / MS / MS analysis and the calibration curve of the standard solution. The cinnamic acid content in the EVOH resin pellet is calculated from the detected concentration.
[LC / MS / MS measurement conditions]
LC system: LC-20A [manufactured by Shimadzu Corporation]
Mass spectrometer: API4000 [AB / MDS Sciex]
Analytical column: Scherzo SM-C18 (3.0 × 75 mm, 3 μm)
Column temperature: 45 ° C
Mobile phase: A 10 mmol / L Ammonium acetate aqueous solution
B Methanol time program: 0.0 → 5.0 minutes B% = 30% → 95%
5.0 → 10.0 minutes B% = 95%
10.1 → 15.0 minutes B% = 30%
Flow rate: 0.4 mL / min switching valve: 2.0 to 6.0 min: to MS
Injection volume: 5 μL
Ionization: ESI detection: Negative ion detection (SRM method)
Monitor ion: Q1 = 147.0 → Q3 = 102.9 (CE: −15 eV)
“%” In the above LC / MS / MS measurement conditions means volume%.

(4) Moisture content of pellets (wt%)
Volatile matter was obtained from the weight of EVOH resin pellets before drying and the weight of EVOH resin pellets after drying at a temperature of 150 ° C. for 5 hours, and this was used as the moisture content of the EVOH resin pellets. Specifically, the moisture content is obtained by the following formula.
Water content (% by weight) = [(EVOH resin pellet weight before drying−EVOH resin pellet weight after drying) / EVOH resin pellet weight before drying] × 100

(5) Fisheye A monolayer film having a thickness of 30 μm was obtained by forming a film using the conjugated polyene (and cinnamic acid) -containing EVOH resin pellets under the following film forming conditions.
About the 30-micrometer-thick single layer film, the fish eye was measured using the digital defect inspection apparatus (The Mamiya Opie company make, GX-70LT).
The fish eye is measured by applying light from the lower surface of the single-layer film and not transmitting the light (0.1 to 0.2 mm in diameter) per fish eye per 100 cm ² (size: 10 cm × 10 cm). This was done by counting the number of fish eyes.
Note that the reading speed during measurement is 3 m / min.
[Film forming conditions]
Extruder: Diameter (D) 40 mm, L / D = 28
Screw: Full flight type compression ratio = 2.5
Screen pack: 60/90/60 mesh die: width 450 mm, coat hanger type Setting temperature: C1 / C2 / C3 / C4 / A / D = 180/200/220/220/210/210 ° C.
Screw rotation speed: 40rpm
Roll temperature: 80 ° C

<Manufacture of EVOH resin pellet containing conjugated polyene and cinnamic acid>
[Example 1]
A polymerization can equipped with a cooling coil was charged with 500 parts of vinyl acetate, 100 parts of methanol, 0.0585 part of acetyl peroxide (vs. vinyl acetate) and 0.015 part of citric acid (vs. vinyl acetate). After substituting once with nitrogen gas, it was then replaced with ethylene and injected until the ethylene pressure reached 40 kg / cm ² . Polymerization was started by raising the temperature to 67 ° C. while stirring under ethylene pressure. Six hours after the start of the polymerization, when the polymerization rate reached 60%, 0.0525 part of sorbic acid (vs. vinyl acetate [based on charged amount]) was added. As a result, an ethylene-vinyl acetate copolymer having an ethylene content of 32.5 mol% was obtained. Next, the reaction liquid containing the ethylene-vinyl acetate copolymer is supplied to the distillation column, and methanol vapor is introduced from the bottom of the column to remove unreacted vinyl acetate, thereby obtaining a methanol solution of ethylene-vinyl acetate copolymer. It was. Saponification was carried out by supplying a methanol solution containing 0.007 equivalents of sodium hydroxide to the remaining acetic acid groups in the copolymer to a methanol solution of the ethylene-vinyl acetate copolymer, and EVOH resin Of methanol (EVOH resin 30% by weight, methanol 70% by weight). The EVOH resin had a saponification degree of 99.7 mol%.
Steam was blown into the methanol solution of the obtained EVOH resin, and the generated methanol vapor was removed from the system to obtain a 40 wt% EVOH resin water / methanol = 40/60 (weight ratio) mixed solution. . The EVOH resin water / methanol mixed solution was extruded into cold water in the form of a strand, and the resulting strand (water-containing porous body) was cut with a cutter. The EVOH resin had a diameter of 3.8 mm and a length of 4 mm. A porous pellet of 35% by weight was obtained.

  300 parts of cleaning treatment liquid (treatment liquid) containing 0.1 part of sodium acetate / 0.1 part of acetic acid / 0.003 part of boric acid (in terms of boron) /0.0008 part of sorbic acid per 100 parts of this porous pellet The porous pellet was washed for 1 hour at a sorbic acid concentration of 2.7 ppm. The washing treatment was performed 5 times in total. Subsequently, the obtained porous pellet was dried at 110 ° C. for 8 hours under a nitrogen stream having an oxygen concentration of 0.5% by volume or less, and the water content per EVOH resin was 0.15 wt% / sodium 0.06 wt% / EVOH resin pellets containing 0.015% by weight of boric acid (in terms of boron) were obtained. The MFR of the pellet was 3.8 g / 10 min (210 ° C., load 2160 g). For the obtained EVOH resin pellets (conjugated polyene-containing EVOH resin pellets), the amount of conjugated polyene was measured based on the above evaluation method. The total conjugated polyene content was 150 ppm, and the conjugated polyene content in the surface layer portion was 39 ppb. It was.

The conjugated polyene-containing EVOH resin pellets were dry blended with cinnamic acid so as to be 300 ppm by weight to obtain EVOH resin pellets with adjusted conjugated polyene and cinnamic acid contents.
The obtained conjugated polyene and cinnamic acid-containing EVOH resin pellets were formed at a maximum temperature of 220 ° C. and a screw rotation speed of 40 rpm using a single-layer T-die extrusion apparatus to produce a single-layer film having a thickness of 30 μm. This single layer film was evaluated for the number of fish eyes generated and the odor by the above method. The results are shown in Table 1.

[Comparative Examples 1, 2, 3]
A conjugated polyene (and cinnamic acid) -containing EVOH resin pellet was prepared in the same manner as in Example 1, except that the content of cinnamic acid and the amount of sorbic acid in the surface layer were adjusted as shown in Table 1. .
Next, using this pellet, a single layer film was produced in the same manner as in Example 1, and the number of fish eyes generated and the odor were evaluated. The results are shown in Table 1.

As can be seen from Table 1, the conjugated polyene content in the EVOH resin pellet surface layer, that is, the sorbic acid content is 30 ppb or more per pellet weight, and the cinnamic acid content is 10 to 400 ppm per pellet weight. In Example 1, the generation of odor and fish eyes was suppressed.
On the other hand, in Comparative Examples 1 to 3 in which cinnamic acids were not in the predetermined content range, odor suppression was insufficient.

  Since the conjugated polyene and the cinnamic acid-containing EVOH resin pellets of the present invention can prevent the generation of odors and fish eyes, they can be suitably used as packaging materials that have strict requirements for the film appearance. Furthermore, according to the production method of the present invention, it is only necessary to change the composition of the pellet cleaning solution, and therefore the conjugated polyene and cinnamic acid-containing EVOH resin of the present invention can be produced using existing production equipment. .

The total conjugated polyene content of the conjugated polyene and cinnamic acid-containing EVOH resin pellets of the present invention is 0. 0 per pellet weight . The generation of fish eyes can be further suppressed when the content is 1 to 10000 ppm.

When the conjugated polyene and the cinnamic acid-containing EVOH resin pellet are also contained inside the conjugated polyene, the total content of the conjugated polyene is usually 0 . 1 to 10000 ppm, more preferably 0.1 to 8000 ppm, still more preferably 1 to 5000 ppm, and particularly preferably 1 to 2000 ppm. When the total content of the conjugated polyene is too small, the content of the conjugated polyene in the pellet surface layer portion is relatively reduced, and the fish eyes tend to increase. Moreover, when there is too much content of conjugated polyene, there exists a possibility that a molded article may be colored with the color of conjugated polyene itself.

Claims (8)

  A saponified ethylene-vinyl ester copolymer pellet containing a conjugated polyene and cinnamic acids, wherein the content of the conjugated polyene in the surface layer of the pellet is 30 ppb or more per pellet weight, and the content of cinnamic acids Is an ethylene-vinyl ester copolymer saponified pellet, characterized in that is 1 to 500 ppm per weight of the pellet.   2. The total conjugated polyene content of the saponified ethylene-vinyl ester copolymer saponified product containing the conjugated polyene and cinnamic acid is 0.01 to 10000 ppm per weight of the pellet according to claim 1. Ethylene-vinyl ester copolymer saponified product pellets. The weight ratio of the conjugated polyene content of the pellet surface layer part to the total conjugated polyene content of the saponified ethylene-vinyl ester copolymer saponified product containing the conjugated polyene and cinnamic acid is the conjugated polyene content / conjugate of the surface layer part. 3. The ethylene-vinyl ester copolymer saponified product pellet according to claim 1, wherein the total polyene content is 1.5 × 10 ⁻⁵ or more.   The ethylene-vinyl ester system according to any one of claims 1 to 3, wherein the conjugated polyene is at least one selected from the group consisting of sorbic acid, sorbic acid ester, and sorbate. Copolymer saponified pellets.   A method for producing an ethylene-vinyl ester copolymer saponified pellet containing the conjugated polyene according to any one of claims 1 to 4 and cinnamic acid, the saponified ethylene-vinyl ester copolymer Containing a conjugated polyene and a cinnamic acid, characterized by comprising a step of bringing a pellet of the polymer and a treatment liquid containing a conjugated polyene into contact with each other, and a step of bringing the pellet of a saponified ethylene-vinyl ester copolymer into a cinnamic acid A process for producing saponified pellets of ethylene-vinyl ester copolymer.   The saponified pellet of the ethylene-vinyl ester copolymer is obtained by coagulating an alcohol solution or a water / alcohol mixed solution of the saponified ethylene-vinyl ester copolymer. 5. A process for producing a saponified pellet of an ethylene-vinyl ester copolymer containing the conjugated polyene according to 5 and cinnamic acid.   7. The ethylene-vinyl ester copolymer saponified pellet containing the conjugated polyene and cinnamic acids according to claim 5, wherein the ethylene-vinyl ester copolymer saponified pellet is a porous pellet. Manufacturing method.   6. A process of blending conjugated polyene as a polymerization inhibitor in the process of producing an ethylene-vinyl ester copolymer before saponification of the saponified ethylene-vinyl ester copolymer. A process for producing saponified pellets of ethylene-vinyl ester copolymer containing the conjugated polyene according to any one of 7 to 7 and cinnamic acid.