Composition, molding material, multilayer structure, molded body, food package, and method for producing composition and multilayer structure

Abstract

The present invention provides a composition excellent in thermal stability.　This composition contains an ethylene-vinyl alcohol copolymer, a titanium compound, and an alkali metal compound. At least a part of the ethylene-vinyl alcohol copolymer is derived from biomass, and mass ratio of the alkali metal element content of the alkali metal compound to the titanium element content of the titanium compound is 500-280,000.

Description

Composition, molding material, multilayer structure, molded article, food packaging, composition and method for producing multilayer structure

[0001] The present invention relates to a composition, a molding material, a multilayer structure, a molded article, a food packaging material, a composition, and a method for producing a multilayer structure.

[0002] Ethylene-vinyl alcohol copolymers (hereinafter, sometimes referred to as "EVOH resins") are excellent in transparency, gas barrier properties such as oxygen and other gases, aroma retention, solvent resistance, oil resistance, mechanical strength, and the like, and are formed into films, sheets, bottles, and the like, and are widely used as various packaging materials such as food packaging materials, pharmaceutical packaging materials, industrial chemical packaging materials, and agricultural chemical packaging materials.

[0003] Meanwhile, in recent years, with the aim of realizing a recycling-oriented society, there has been an increasing demand for bioplastics made from carbon-neutral biomass-derived raw materials. However, it is known that biomass-derived synthetic resins often have inferior performance compared to fossil fuel-derived synthetic resins. Therefore, efforts are being made to develop biomass-derived resins that are comparable in performance to fossil fuel-derived resins by combining biomass-derived raw materials with fossil fuel-derived raw materials.

[0004] For example, Patent Documents 1 and 2 disclose gas barrier resin compositions in which ethylene and vinyl ester, which are raw materials for EVOH resin, are partly derived from biomass, and disclose that the compositions have gas barrier properties and long-run properties comparable to those of compositions made using only raw materials derived from fossil fuels.

[0005] JP 2022-13857 A JP 2022-27726 A

[0006] According to the inventors' investigations, the techniques disclosed in the above Patent Documents 1 and 2 have insufficient thermal stability, and there is room for further improvement in thermal stability.

[0007] In view of this, the present invention provides a resin composition having excellent thermal stability, even if it is an EVOH resin made from a raw material derived from biomass.

[0008] However, in view of the above circumstances, the present inventors have conducted extensive research and have found that excellent thermal stability can be achieved by incorporating a titanium compound and an alkali metal compound in a specific mass ratio into an EVOH resin, part of which is made from raw materials derived from biomass.

[0009] That is, the present invention has the following aspects. [1] A composition containing an EVOH resin, a titanium compound, and an alkali metal compound, wherein at least a portion of the EVOH resin is derived from biomass, and the mass ratio of the metal-equivalent content of the alkali metal compound to the metal-equivalent content of the titanium compound is 500 to 280,000. [2] The composition according to [1], wherein the metal-equivalent content of the titanium compound is 0.0001 ppm or more and less than 5,000 ppm based on the mass of the composition. [3] The composition according to [1] or [2], wherein the metal-equivalent content of the titanium compound is 0.0001 ppm or more and less than 2 ppm based on the mass of the composition. [4] The composition according to any one of [1] to [3], wherein the metal-equivalent content of the titanium compound is 0.0001 ppm or more and less than 1 ppm based on the mass of the composition. [5] The composition according to any one of [1] to [4], wherein the biobased content of the EVOH resin is 0.01 to 100%. [6] The composition according to any one of [1] to [5], wherein the EVOH resin has a bio-based content of 1 to 99%. [7] A molding material comprising the composition according to any one of [1] to [6]. [8] A multilayer structure having a layer comprising the composition according to any one of [1] to [6]. [9] The multilayer structure according to [8], further comprising an adhesive resin layer.

[10] A molded article comprising the multilayer structure according to [8] or [9].

[11] A food packaging product comprising the multilayer structure according to [8] or [9].

[12] A method for producing the composition according to any one of [1] to [6], comprising a step of mixing the EVOH resin and the titanium compound.

[13] A method for producing the multilayer structure according to [8] or [9], comprising a step of melt-molding a layer comprising the composition.

[0010] The composition of the present invention has excellent thermal stability. In addition, molding materials formed from the composition of the present invention, as well as multilayer structures, molded articles, and food packages having a layer containing the composition of the present invention, also have excellent thermal stability.

[0011] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0012] In this specification, "x and / or y (x and y are optional)" refers to at least one of x and y, and can mean either x alone, y alone, or both x and y. When "X to Y" (X and Y are optional numbers) is used, unless otherwise specified, it also encompasses "X or more and Y or less," as well as "preferably more than X" or "preferably less than Y." When "X or more" (X is optional number) or "Y or less" (Y is optional number) is used, it also encompasses "preferably more than X" or "preferably less than Y." Regarding the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range can be replaced with the value shown in the examples. In this specification, the term "layer" refers to a thick layer as well as a relatively thin layer such as a "film," "tape," or "sheet."

[0013] <Composition> A composition according to one embodiment of the present invention (hereinafter sometimes referred to as "the composition") contains an EVOH resin as an essential component, a titanium compound, and an alkali metal compound in a specific mass ratio. That is, the content of the EVOH resin in the composition is typically 1 mass% or more, preferably 10 mass% or more, more preferably 50 mass% or more, even more preferably 60 mass% or more, particularly preferably 70 mass% or more, especially preferably 80 mass% or more, especially more preferably 90 mass% or more, and still more preferably 95 mass% or more. The upper limit is 100 mass%, but may also be 99 mass%, for example, 1 to 100 mass%, or 10 to 99 mass%. Each component will be described below.

[0014] [EVOH Resin] The EVOH resin used in this embodiment is at least partially derived from biomass. More specifically, this refers to an EVOH resin in which at least a portion of the ethylene structural units, vinyl alcohol structural units, and vinyl ester structural units of the EVOH resin are derived from biomass.

[0015] The EVOH resin is a water-insoluble thermoplastic resin obtained by saponifying an ethylene-vinyl ester copolymer, which is a copolymer of ethylene and vinyl ester, at least a portion of which is derived from biomass.

[0016] The biomass-derived origin of ethylene and / or vinyl esters used as raw materials can be confirmed by measuring the biobased content. The biobased content is an index that indicates the proportion of biomass-derived raw materials, and in this specification, it is determined by measuring the radiocarbon [ １４ The biobased carbon content is determined by measuring the concentration of carbon-14 (hereinafter referred to as "carbon-14"). Specifically, the biobased content can be measured according to the method described in ASTM D6866-18. That is, when the biobased content of an EVOH resin is more than 0% and 100% or less, it can generally be said that the ethylene and / or vinyl ester used as the raw material contains biomass-derived components.

[0017] "Biomass" refers to organic resources derived from plants and animals, excluding those derived from fossil fuels (fossil resources). From the standpoint of cost and the environment, it is preferable that biomass is an organic resource derived from plants, i.e., derived from biological raw materials.

[0018] Biomass-derived ethylene can be produced, for example, by purifying bioethanol from a biomass raw material and then subjecting it to a dehydration reaction, etc. Biomass-derived vinyl esters can be produced, for example, by a common industrial method of reacting ethylene, acetic acid, and molecular oxygen using a palladium catalyst.

[0019] Biomass raw materials include waste materials, unused materials, resource crop materials, etc., such as cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residues, etc.), wood, charcoal, compost, natural rubber, cotton, sugarcane, soybean refuse, oils and fats (rapeseed oil, cottonseed oil, soybean oil, coconut oil, castor oil, etc.), carbohydrate crops (corn, potatoes, wheat, rice, rice husks, rice bran, used rice, cassava, sago palm, etc.), bagasse, buckwheat, soybeans, essential oils (pine oil, orange oil, eucalyptus oil, etc.), pulp black liquor, vegetable oil cakes, etc. These can be used alone or in combination of two or more.

[0020] Examples of methods for producing bioethanol include pre-treating biomass raw materials as needed (compressed hot water treatment, acid treatment, alkali treatment, saccharification treatment using saccharifying enzymes), followed by yeast fermentation to produce bioethanol, and then purifying the bioethanol through a distillation process and a dehydration process. When saccharification treatment is performed during bioethanol production, sequential saccharification and fermentation, in which saccharification and fermentation are carried out in stages, may be used, or parallel saccharification and fermentation, in which saccharification and fermentation are carried out simultaneously, but from the perspective of production efficiency, parallel saccharification and fermentation is preferred for producing bioethanol.

[0021] The proportion of biomass-derived ethylene structural units in all ethylene structural units constituting the EVOH resin may be biomass-derived, but is typically 0.001 to 100 mol%, preferably 5 to 98 mol%, more preferably 15 to 97 mol%, even more preferably 25 to 96 mol%, and particularly preferably 35 to 95 mol%. The proportion of fossil fuel-derived ethylene structural units in all ethylene structural units constituting the EVOH resin is typically 99.999 mol% or less, preferably 95 mol% or less, more preferably 85 mol% or less, even more preferably 75 mol% or less, and particularly preferably 65 mol% or less. The lower limit is 0 mol%, for example, 0 to 99.999 mol%. Fossil fuel-derived ethylene structural units may not be present in all ethylene structural units. As the proportion of biomass-derived ethylene structural units in all ethylene structural units constituting the EVOH resin increases, the biobased content of the composition increases, tending to reduce the environmental impact. When the EVOH resin contains biomass-derived vinyl ester structural units and / or vinyl alcohol structural units, the proportion of biomass-derived ethylene structural units in all ethylene structural units may be 0.

[0022] As a vinyl ester other than biomass-derived vinyl esters, vinyl acetate is typically used because of its availability on the market and the efficiency of impurity treatment during production. Examples of vinyl esters other than vinyl acetate include aliphatic vinyl esters such as vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, and vinyl versatate, and aromatic vinyl esters such as vinyl benzoate. Typically, an aliphatic vinyl ester having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and more preferably 4 to 7 carbon atoms is used. These are typically used alone, but multiple types may be used simultaneously as necessary.

[0023] Examples of biomass-derived vinyl esters include vinyl esters produced using biomass-derived ethylene, such as vinyl acetate, in which the carbon in the vinyl group is derived from biomass.

[0024] Examples of methods for producing biomass-derived vinyl esters include a common industrial method of reacting ethylene, acetic acid, and molecular oxygen using a palladium catalyst. The biomass-derived vinyl ester may also be a vinyl ester produced using a biomass-derived carboxylic acid. When the saponification degree of the EVOH resin is not 100 mol%, acyl groups derived from the biomass remain.

[0025] The proportion of biomass-derived vinyl alcohol structural units in all vinyl alcohol structural units (vinyl ester structural units) constituting the EVOH resin is typically 0.001 to 100 mol%, preferably 5 to 98 mol%, more preferably 15 to 97 mol%, even more preferably 25 to 96 mol%, and particularly preferably 35 to 95 mol%. The proportion of fossil fuel-derived vinyl alcohol structural units in all vinyl alcohol structural units constituting the EVOH resin is typically 99.999 mol% or less, preferably 95 mol% or less, more preferably 85 mol% or less, even more preferably 75 mol% or less, and particularly preferably 65 mol% or less. The lower limit is 0 mol%, for example, 0 to 99.999 mol%. Fossil fuel-derived vinyl alcohol structural units may not be present in all vinyl alcohol structural units. As the proportion of biomass-derived vinyl alcohol structural units in all vinyl alcohol structural units constituting the EVOH resin increases, the biobased content of the composition increases, tending to reduce environmental impact.

[0026] In addition, when the EVOH resin contains biomass-derived ethylene structural units, the ratio of the total of the biomass-derived vinyl ester structural units and the biomass-derived vinyl alcohol structural units to the total of the vinyl ester structural units and the vinyl alcohol structural units may be 0.

[0027] The biomass-derived EVOH resin can be confirmed by checking for the presence of "sulfur compounds" and / or "carbon-14" in the composition. "Sulfur compounds" and / or "carbon-14" are impurities derived from biomass, and their presence cannot be confirmed in petroleum-derived EVOH resin, but can be confirmed in biomass-derived EVOH resin.

[0028] EVOH resin is said to have issues with thermal stability, and it is speculated that the main cause of thermal decomposition in particular is the polyene structure formed in the main chain of EVOH resin due to a dehydration reaction initiated by the hydroxyl group. It is speculated that the use of biomass-derived EVOH resin in this composition reduces the thermal decomposition rate of the EVOH resin itself due to the primary isotope effect of carbon-14 (increased bond energy), thereby improving thermal stability.

[0029] The ethylene structural unit content of the EVOH resin is usually 20 to 60 mol%, preferably 25 to 50 mol%, and particularly preferably 25 to 35 mol%. When the content is equal to or greater than the lower limit, the EVOH resin tends to have excellent gas barrier properties and melt moldability under high humidity conditions, while when the content is equal to or less than the upper limit, the EVOH resin tends to have excellent gas barrier properties. In this embodiment, the ethylene structural unit content of the EVOH resin means a value measured in accordance with ISO 14663.

[0030] The saponification degree of the EVOH resin is usually 90 to 100 mol%, preferably 95 to 100 mol%, and more preferably 99 to 100 mol%. When the saponification degree is equal to or greater than the lower limit, the EVOH resin tends to have excellent gas barrier properties, thermal stability, moisture resistance, etc. The saponification degree of the EVOH resin can be measured in accordance with JIS K6726 (wherein the EVOH resin is used as a solution uniformly dissolved in a water / methanol solvent).

[0031] The melt flow rate (MFR) (210°C, 2160 g load) of the EVOH resin is usually 0.5 to 100 g / 10 min, preferably 1 to 50 g / 10 min, and more preferably 3 to 35 g / 10 min. When the MFR is equal to or less than the upper limit, the resin tends to have excellent stability during film formation, while when the MFR is equal to or greater than the lower limit, the resin tends to have an appropriate viscosity and be excellent in melt extrusion. The MFR is an index of the degree of polymerization of the EVOH resin, and can be adjusted by the amount of polymerization initiator and the amount of solvent used when copolymerizing ethylene and vinyl ester.

[0032] The bio-based content of the EVOH resin is usually 0.001 to 100%, preferably 1 to 99%, more preferably 20 to 86%, still more preferably 38 to 76%, and particularly preferably 58 to 66%, with the upper limit being 100%.

[0033] The EVOH resin may further contain structural units derived from the comonomers shown below (for example, 10 mol % or less of the EVOH resin) within the range that does not impair the effects of the present invention.Examples of the comonomer include olefins such as propylene, 1-butene, and isobutene; hydroxy group-containing α-olefins such as 3-butene-1-ol, 3-butene-1,2-diol, 4-pentene-1-ol, and 5-hexene-1,2-diol, and derivatives thereof such as esters and acylation products; hydroxyalkylvinylidenes such as 2-methylenepropane-1,3-diol and 3-methylenepentane-1,5-diol; 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, and 1,3-dibutyl hydroxyalkylvinylidene diacetates such as methyloxy-2-methylenepropane; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, or their salts or mono- or di-alkyl esters in which the alkyl group has 1 to 18 carbon atoms; acrylamide, N-alkylacrylamide in which the alkyl group has 1 to 18 carbon atoms, N,N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or its salts, acrylamidopropyldimethylamine or its acid salts or quaternary salts thereof acrylamides such as methacrylamide, N-alkylmethacrylamides in which the alkyl group has 1 to 18 carbon atoms, N,N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or its salts, methacrylamidepropyldimethylamine or its acid salts or its quaternary salts; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide; vinyl cyanides such as acrylonitrile and methacrylonitrile; alkyl vinyl ethers in which the alkyl group has 1 to 18 carbon atoms, hydrochloric acid vinyl ethers such as alkoxyalkyl vinyl ether and alkoxyalkyl vinyl ether; halogenated vinyl compounds such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and vinyl bromide; vinyl silanes such as trimethoxyvinylsilane; halogenated allyl compounds such as allyl acetate and allyl chloride; allyl alcohols such as allyl alcohol and dimethoxyallyl alcohol; and comonomers such as trimethyl-(3-acrylamido-3-dimethylpropyl)-ammonium chloride and acrylamido-2-methylpropanesulfonic acid.These may be used alone or in combination of two or more.

[0034] Among these, hydroxy group-containing α-olefins are preferred, and 3-butene-1,2-diol and 5-hexene-1,2-diol are particularly preferred. When the hydroxy group-containing α-olefins are copolymerized, the resulting EVOH resin has primary hydroxyl groups in the side chains. Such EVOH resins having primary hydroxyl groups in the side chains, particularly EVOH resins having a 1,2-diol structure in the side chains, are preferred in that they exhibit good secondary moldability while maintaining gas barrier properties.

[0035] When the EVOH resin has a primary hydroxyl group in a side chain, the content of the structural unit derived from the monomer having the primary hydroxyl group is usually 0.1 to 20 mol %, preferably 0.5 to 15 mol %, particularly preferably 1 to 10 mol %, of the EVOH resin.

[0036] Furthermore, as the EVOH resin, EVOH resins that have been "post-modified" by esterification, urethanization, acetalization, cyanoethylation, oxyalkylenation, or the like can also be used.

[0037] When the post-modified EVOH resin is used, the modification rate is usually 10 mol% or less, preferably 4 mol% or less. The lower limit is usually 0.01 mol% or more, preferably 0.1 mol% or more, for example, 0.01 to 10 mol%, preferably 0.1 to 4 mol%. When the modification rate of the EVOH resin is within the above range, the resin tends to have excellent heat degradation resistance and long-run properties.

[0038] Furthermore, the EVOH resin may be a mixture of EVOH resins having different ethylene structural unit contents, saponification degrees, polymerization degrees, copolymerization components, and the like.

[0039] As described above, the EVOH resin used in this embodiment is obtained by saponifying a copolymer of ethylene and vinyl ester, at least a part of which is derived from biomass. The copolymerization can be carried out by any known polymerization method, such as solution polymerization, suspension polymerization, or emulsion polymerization.

[0040] Examples of the polymerization solvent include lower alcohols such as methanol, ethanol, propanol, and butanol, and ketones such as acetone and methyl ethyl ketone, and these may be used alone or in combination of two or more. Methanol is preferably used as the polymerization solvent in industrial applications.

[0041] The amount of the polymerization solvent used may be appropriately selected in accordance with the degree of polymerization of the target copolymer, taking into consideration the chain transfer constant of the polymerization solvent. For example, when the polymerization solvent is methanol, the amount is selected from the range of S (polymerization solvent) / M (monomer)=0.01 to 10 (mass ratio), preferably about 0.05 to 7 (mass ratio).

[0042] Examples of the polymerization catalyst include known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, and lauryl peroxide, as well as low-temperature active radical polymerization catalysts. Examples of the low-temperature active radical polymerization catalyst include peroxyesters such as t-butylperoxyneodecanoate, t-butylperoxypivalate, α,α'-bis(neodecanoylperoxy)diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, and t-hexylperoxypivalate; di-n-propylperoxydicarbonate, di-iso-propylperoxydicarbonate, di-sec-butylperoxydicarbonate, bis(4- Examples of the low-temperature active radical polymerization catalyst include peroxydicarbonates such as di(t-butylcyclohexyl)peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, dimethoxybutyl peroxydicarbonate, and di(3-methyl-3-methoxybutylperoxy)dicarbonate; organic peroxides such as diacyl peroxides such as 3,3,5-trimethylhexanoyl peroxide, diisobutyryl peroxide, and lauroyl peroxide; and azo compounds such as 2,2'-azobis-(2,4-dimethylvaleronitrile) and 2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile). The low-temperature active radical polymerization catalyst refers to an organic compound having a half-life at 60°C of 10 to 300 minutes. These polymerization catalysts may be used alone or in combination of two or more.

[0043] The amount of the polymerization catalyst used varies depending on the type of catalyst and cannot be generally determined, but is selected arbitrarily depending on the polymerization rate. For example, when azobisisobutyronitrile or acetyl peroxide is used, the amount is preferably 0.001 to 0.2 parts by mass, more preferably 0.005 to 0.1 parts by mass, per 100 parts by mass of the vinyl ester monomer.

[0044] The method for introducing ethylene into the copolymer may be a conventional pressurized polymerization of ethylene, and the amount of ethylene introduced can be controlled by the pressure of ethylene, which is usually selected from the range of 2.0 to 8.0 MPa, although it depends on the target content of ethylene structural units.

[0045] Although the reaction temperature of the copolymerization reaction varies depending on the polymerization solvent and pressure used and cannot be generally determined, it is usually carried out at a temperature equal to or lower than the boiling point of the polymerization solvent, and is usually preferably 40 to 80° C., particularly preferably 55 to 80° C. If the temperature is equal to or higher than the lower limit, the polymerization proceeds appropriately, and there is no need to set a large amount of catalyst to shorten the polymerization time. Conversely, if the temperature is equal to or lower than the upper limit, there is a tendency for polymerization control to be excellent.

[0046] In addition, in the case of a batch process, the polymerization time is usually 4 to 10 hours, and more preferably 6 to 9 hours. If the polymerization time is equal to or greater than the lower limit, there is a tendency that it is not necessary to increase the polymerization temperature or set a large amount of catalyst, and conversely, if the polymerization time is equal to or less than the upper limit, there is a tendency that productivity is excellent. In the case of a continuous process, the average residence time in the polymerization vessel is usually 2 to 8 hours, and more preferably 2 to 6 hours. If the residence time is equal to or greater than the lower limit, there is a tendency that it is not necessary to increase the polymerization temperature or set a large amount of catalyst, and conversely, if the polymerization time is equal to or less than the upper limit, there is a tendency that productivity is excellent.

[0047] The polymerization rate is set as high as possible within the range where polymerization control is possible from the viewpoint of productivity, and is preferably 30 to 60%. When the polymerization rate is equal to or higher than the lower limit, productivity is excellent and a large amount of unpolymerized vinyl ester monomer tends to be prevented from remaining. Conversely, when the polymerization rate is equal to or lower than the upper limit, polymerization control tends to be excellent.

[0048] The ethylene-vinyl ester copolymer thus obtained is saponified to obtain the EVOH resin of the present embodiment. The saponification is carried out using a saponification catalyst in a state where the ethylene-vinyl ester copolymer obtained above is dissolved in alcohol or aqueous alcohol.

[0049] Examples of the alcohol include lower alcohols having 1 to 5 carbon atoms, such as methanol, ethanol, and propanol. These may be used alone or in combination of two or more. Of these, methanol is preferred.

[0050] The concentration of the ethylene-vinyl ester copolymer in the alcohol is appropriately selected depending on the viscosity, and is usually 5 to 60% by mass.

[0051] Examples of the saponification catalyst include alkali catalysts such as hydroxides and alcoholates of alkali metals, such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate, and potassium ethylate; and acid catalysts such as sulfuric acid, hydrochloric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resins. These may be used alone or in combination of two or more. Among these, alkali catalysts such as hydroxides and alcoholates of alkali metals are preferred.

[0052] The temperature at which the saponification is carried out is not limited, but is preferably 20 to 140° C., and the saponification time is preferably 1 to 5 hours.

[0053] The EVOH resin produced in this manner may be at least partially derived from biomass, and preferably the ethylene structural units and / or vinyl alcohol structural units are derived from biomass. More preferably, from the viewpoint of availability, the vinyl alcohol structural units are derived from biomass. Such an EVOH resin is mainly composed of ethylene structural units and vinyl alcohol structural units, and optionally contains a small amount of vinyl ester structural units remaining without being saponified. When another comonomer is copolymerized, the EVOH resin further contains structural units derived from the comonomer.

[0054] In this specification, the term "mainly" refers to the component that accounts for the largest proportion in the target substance, and typically, it is preferably 50% by mass or more of the target substance, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and especially preferably 90% by mass or more, and may even be 100% by mass.

[0055] The EVOH resin produced by the above-described production method is contained in an alcohol-based solvent, and the content of the EVOH resin in the EVOH resin solution is preferably about 10 to 50 mass % from the viewpoint of producing the EVOH resin pellets described below.

[0056] The EVOH resin used in the present composition may be the alcohol solvent of the EVOH resin produced by the above-mentioned production method, but is preferably in the form of pellets, the shape and size of which are preferably the same as those of the composition described below.

[0057] The produced pellets are preferably washed by immersing them in an aqueous solution of an acid and / or its salt, and examples of such an acid include formic acid, acetic acid, adipic acid, phosphoric acid, boric acid, or salts thereof, with acetic acid being preferred. After that, the pellets are preferably washed with water.

[0058] The chemically treated and washed pellets may then be dried appropriately, preferably using a fluidized hot air dryer or a stationary hot air dryer, to produce EVOH resin pellets.

[0059] [Titanium Compound] Examples of the titanium compound include inorganic titanium compounds and organic titanium compounds. The titanium compounds may be used alone or in combination of two or more. Among these, inorganic titanium compounds are preferred.

[0060] Examples of the inorganic titanium compound include titanium oxide, titanium hydroxide, titanium chloride, and inorganic salts of titanium.

[0061] Examples of the titanium oxides include titanium(II) oxide, titanium(III) oxide, titanium(IV) oxide, and titanium zincate. Examples of the titanium hydroxides include titanium(II) hydroxide and titanium(II) hydroxide. Examples of the titanium chlorides include titanium(II) chloride and titanium(II) chloride. Examples of the titanium inorganic salts include titanium phosphate and titanium sulfate. Among these, titanium oxides are preferred, titanium(IV) oxide is more preferred, and rutile titanium(IV) oxide is particularly preferred.

[0062] Examples of the organic titanium compounds include titanium carboxylates such as titanium acetate, titanium butyrate, and titanium stearate.

[0063] The titanium compound may exist in the composition as a titanium compound, or may exist in an ionized state or in the form of a complex interacting with the EVOH resin or other ligands.

[0064] The average particle size of the titanium compound is usually 0.001 to 100 μm, preferably 0.01 to 50 μm, and more preferably 0.015 to 20 μm. When the average particle size of the titanium compound is within the above range, the discoloration suppression effect tends to be more excellent. The average particle size can be measured by a predetermined method, such as dynamic light scattering (DLS) or sedimentation velocity method.

[0065] The content of the titanium compound in terms of metal, relative to the mass of the composition, is usually 0.0001 ppm or more and 5000 ppm or less, preferably 0.0001 to 2 ppm, more preferably 0.0005 to 1.5 ppm, even more preferably 0.001 to 1 ppm, particularly preferably 0.005 ppm or more and less than 1 ppm, especially preferably 0.01 to 0.8 ppm, and even more preferably 0.01 to 0.5 ppm. When the content of the titanium compound is equal to or less than the upper limit, thermal decomposition of the EVOH resin tends to be prevented and coloration prevention properties are excellent, while when the content is equal to or more than the lower limit, thermal degradation tends to be suppressed. The content of the titanium compound in terms of metal is, in other words, the content of elemental titanium.

[0066] The content of the titanium compound in terms of metal can be quantified by weighing out the composition into a platinum crucible, ashing it successively using a burner and an electric furnace, thermally decomposing the ashed material with nitric acid and hydrofluoric acid, treating it with a mixed acid of dilute nitric acid and dilute hydrofluoric acid, and measuring the titanium in the resulting constant-volume solution by ICP mass spectrometry using an ICP mass spectrometer (Agilent 8800, manufactured by Agilent Technologies).

[0067] [Alkali Metal Compound] Examples of the alkali metal compound include salts and hydroxides of alkali metals. These may be used alone or in combination of two or more. Among these, the alkali metal compound is preferably water-soluble, and from the viewpoint of dispersibility, alkali metal salts are preferred.

[0068] Examples of the alkali metal salt include inorganic salts of alkali metals and carboxylates of alkali metals, among which carboxylates of alkali metals are preferred.

[0069] Examples of the inorganic salts of alkali metals include alkali metal carbonates, hydrogencarbonates, phosphates, borates, sulfates, chlorides, etc. Examples of the carboxylates of alkali metals include monocarboxylates having 2 to 11 carbon atoms, such as acetate, butyrate, propionate, enanthate, and caprate; dicarboxylates having 2 to 11 carbon atoms, such as oxalate, malonate, succinate, adipate, suberate, and sebacate; monocarboxylates having 12 or more carbon atoms, such as laurate, palmitate, stearate, 12-hydroxystearate, behenate, and montanate; and carboxylates with the polymerization terminal carboxy group of EVOH resin. Among these, monocarboxylates having 2 to 11 carbon atoms are preferred, and acetate is particularly preferred.

[0070] Examples of the alkali metal species of the alkali metal compound include lithium, sodium, potassium, rubidium, and cesium. Of these, sodium and potassium are preferred, and sodium is particularly preferred.

[0071] The molecular weight of the alkali metal compound is usually 20 to 10,000, preferably 20 to 1,000, and particularly preferably 20 to 500.

[0072] Of these, sodium acetate is preferred as the alkali metal compound. From the standpoints of economy and dispersibility, it is preferred that the alkali metal compound does not include inorganic layered compounds and double salts.

[0073] The content of the alkali metal compound in terms of metal is preferably 5 to 50,000 ppm, more preferably 10 to 45,000 ppm, even more preferably 20 to 30,000 ppm, particularly preferably 40 to 20,000 ppm, and especially preferably 80 to 10,000 ppm, based on the mass of the composition. When the content of the alkali metal compound is below the upper limit, the composition tends to have excellent thermal stability, while when the content is above the lower limit, the composition tends to have excellent moldability. The content of the alkali metal compound in terms of metal can be measured using an atomic absorption spectrophotometer, for example, by heating and incinerating the composition, treating the resulting solution with an acid such as hydrochloric acid, adding pure water to the resulting solution, and adjusting the volume. The content of the alkali metal compound in terms of metal is, in other words, the content of the alkali metal element.

[0074] The mass ratio of the alkali metal compound content in terms of metal to the titanium compound content in terms of metal is usually 500 to 280,000, preferably 800 to 250,000, more preferably 1,000 to 230,000, and particularly preferably 1,000 to 200,000. When the mass ratio value is equal to or less than the upper limit, coloration tends to be easily suppressed, and when the mass ratio value is equal to or greater than the lower limit, the effect of suppressing thermal degradation tends to be obtained.

[0075] It is generally known that blending an alkali metal compound with an EVOH resin tends to cause a decrease in viscosity over time when heated. Although the mechanism is unclear, it is speculated that blending an alkali metal compound makes the composition basic, and some anion acts as a nucleophile, abstracting hydrogen atoms bonded to carbon atoms in the main chain of the EVOH resin, thereby causing a decomposition reaction of the main chain and severing the main chain of the EVOH resin. It is speculated that the deterioration of EVOH resin after heating occurs because double bond structures are formed in the main chain of the EVOH resin during the reaction, and these structures again act as reaction starting points, causing dehydration reactions and the like, resulting in the formation of polyene structures in the main chain of the EVOH resin.

[0076] In contrast, the present composition contains an alkali metal compound and a titanium compound in a specific mass ratio, thereby suppressing the deterioration of the thermal stability of the EVOH resin. Normally, when a titanium compound is contained in a composition, it is thought that the composition will be colored by titanium ions, and therefore it is common technical knowledge for those skilled in the art to avoid using a titanium compound.

[0077] However, in this embodiment, contrary to such common technical knowledge, it has been discovered that a composition having excellent thermal stability can be obtained by containing a titanium compound and an alkali metal compound and using them in a specific mass ratio.

[0078] That is, titanium is stable as a tetravalent ion, and it is presumed that titanium is coordinated to the double bond in the main chain of the EVOH resin, stabilizing it by forming a chelate, etc., thereby suppressing the formation of a polyene structure in the main chain of the EVOH resin. On the other hand, it is thought that when the amount of the titanium compound is within a specific range, deterioration of the EVOH resin due to thermal decomposition caused by titanium tends to be suppressed.

[0079] [Other Thermoplastic Resins] The composition may contain thermoplastic resins other than EVOH resin within a range that does not impair the effects of the present invention (for example, typically 50% by mass or less of the composition, preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less; the lower limit is 0% by mass, e.g., 0 to 50% by mass). Examples of other thermoplastic resins that may be used include known thermoplastic resins, such as polyester resins, polystyrene resins, polyvinyl chloride resins, polycarbonate resins, ionomers, polyvinylidene chloride, polyester elastomers, polyurethane elastomers, chlorinated polyethylene, and chlorinated polypropylene. These may be used alone or in combination of two or more.

[0080] [Other Compounding Agents] The composition may also contain compounding agents generally compounded with EVOH resins (however, the term "compounding agent" as used herein excludes titanium compounds and alkali metal compounds) within a range that does not impair the effects of the present invention (for example, 5% by mass or less, preferably 3% by mass or less, with a lower limit of 0% by mass, e.g., 0 to 5% by mass). Examples of such compounding agents include inorganic double salts (e.g., hydrotalcite, etc.), plasticizers (e.g., aliphatic polyhydric alcohols such as ethylene glycol, glycerin, and hexanediol), oxygen absorbers [e.g., inorganic oxygen absorbers such as aluminum powder and potassium sulfite; ascorbic acid, its fatty acid esters and metal salts, etc.; gallic acid; polyhydric phenols such as hydroxyl group-containing phenolaldehyde resins; terpene compounds; blends of tertiary hydrogen-containing resins and transition metals (e.g., a combination of polypropylene and cobalt); blends of carbon-carbon unsaturated bond-containing resins and transition metals; Polymeric oxygen absorbers such as polymeric oxygen absorbers, such as polymeric compounds (e.g., a combination of polybutadiene and cobalt), photooxidatively degradable resins (e.g., polyketones), anthraquinone polymers (e.g., polyvinyl anthraquinone), and combinations thereof to which photoinitiators (e.g., benzophenone), antioxidants other than those mentioned above, and deodorants (e.g., activated carbon), heat stabilizers (boric acid, phosphoric acid), light stabilizers, ultraviolet absorbers, colorants, antistatic agents, surfactants (excluding those used as lubricants), antibacterial agents, antiblocking agents, and fillers (e.g., aluminum, inorganic fillers). These compounds may be used alone or in combination of two or more.

[0081] [Method for Producing the Composition] The composition can be produced, for example, by mixing the EVOH resin, titanium compound, and alkali metal compound by a known method such as a dry blending method, a melt mixing method, a solution mixing method, an impregnation method, etc. Among these, a method including a step of mixing the EVOH resin and the titanium compound is preferred. These production methods can also be used in any combination.

[0082] The dry blending method may be, for example, (i) a method in which a pelletized EVOH resin is dry blended with a titanium compound and / or an alkali metal compound using a tumbler or the like.

[0083] Examples of the melt-mixing method include (ii) a method in which a pelletized EVOH resin is dry-blended with a titanium compound and / or an alkali metal compound, and the resulting dry blend is melt-kneaded; and (iii) a method in which a titanium compound and / or an alkali metal compound is added to a molten EVOH resin, and the resulting mixture is melt-kneaded.

[0084] Examples of the solution mixing method include (iv) a method in which a solution is prepared using a commercially available EVOH resin, a titanium compound and / or an alkali metal compound is blended therein, the solution is coagulated and molded, and then the mixture is subjected to solid-liquid separation by known means and dried; and (v) a method in which a titanium compound and / or an alkali metal compound is added to an ethylene-vinyl ester copolymer solution before saponification or a homogeneous solution of EVOH resin (such as a water / alcohol solution) during the production of EVOH resin, the mixture is coagulated and molded, and then the mixture is subjected to solid-liquid separation by known means and dried.

[0085] The impregnation method includes, for example, (vi) a method in which pellets of EVOH resin are brought into contact with an aqueous solution containing a titanium compound and / or an alkali metal compound to incorporate the titanium compound and / or the alkali metal compound into the EVOH resin, followed by drying. The aqueous solution containing a titanium compound may be an aqueous solution of a titanium compound or a titanium compound immersed in water containing various chemicals to elute titanium ions.

[0086] In the impregnation method, the content of the titanium compound (in terms of metal) can be controlled by the concentration of the titanium compound in the aqueous solution in which the EVOH resin is immersed, the immersion temperature, the immersion time, etc. The immersion temperature and the immersion time are usually 0.5 to 48 hours, preferably 1 to 36 hours, and the immersion temperature is usually 10 to 40°C, preferably 20 to 35°C.

[0087] As the drying method in each of the above-mentioned production methods, various drying methods can be used, and either static drying or fluidized drying may be used, or these may be used in combination.

[0088] As described above, in this embodiment, the above-mentioned different methods can be combined. Among them, the melt mixing method is preferred, and method (ii) is particularly preferred, in terms of productivity and the fact that a resin composition with more pronounced effects of the present invention can be obtained. Furthermore, when using the other thermoplastic resins and other compounding agents, they may be compounded by a conventional method according to the above-mentioned manufacturing method.

[0089] The composition obtained by each of the above-described production methods may have any shape, but is preferably in the form of pellets. The pellets may be, for example, spherical, oval, cylindrical, die-shaped, or rectangular, but are typically oval or cylindrical. From the viewpoint of convenience when subsequently used as a molding material, the size of the pellets is such that, in the case of an oval shape, the minor axis is typically 1 to 10 mm, preferably 2 to 6 mm, and more preferably 2.5 to 5.5 mm, and the major axis is typically 1.5 to 30 mm, preferably 3 to 20 mm, and more preferably 3.5 to 10 mm. In the case of a cylindrical shape, the diameter of the base is typically 1 to 6 mm, preferably 2 to 5 mm, and the length is typically 1 to 6 mm, preferably 2 to 5 mm. In the case of a die-shaped shape, the length of one side is typically 1 to 6 mm, preferably 2 to 5 mm. The shape and size of the pelletized EVOH resin used in each of the above-described production methods are also preferably similar.

[0090] The water content of the present composition is not particularly limited, but is usually 0.01 to 0.5% by mass, preferably 0.05 to 0.35% by mass, and particularly preferably 0.1 to 0.3% by mass.

[0091] The water content of the composition is measured and calculated by the following method. １ ) was weighed on an electronic balance, dried in a hot air dryer at 150°C for 5 hours, and allowed to cool in a desiccator for 30 minutes, after which the mass (W ２ ) is weighed and calculated using the following formula: [Formula] Water content (mass%) = [(W １ -W２ ) / W １ ]×100

[0092] When the composition is in the form of pellets, it is also preferable to apply a known lubricant to the surface of the pellets in order to stabilize the feedability during melt molding. Examples of lubricants include higher fatty acids having 12 or more carbon atoms (e.g., lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, etc.), higher fatty acid esters (methyl esters, isopropyl esters, butyl esters, octyl esters of higher fatty acids, etc.), higher fatty acid amides (e.g., saturated higher fatty acid amides such as lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, etc.; unsaturated higher fatty acid amides such as oleic acid amide, erucic acid amide, etc.; bis-higher fatty acid amides such as ethylene bisstearic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, ethylene bislauric acid amide, etc.), low-molecular-weight polyolefins (e.g., low-molecular-weight polyethylene or low-molecular-weight polypropylene having a molecular weight of about 500 to 10,000, or acid-modified products thereof), higher alcohols having 6 or more carbon atoms, ester oligomers, and fluorinated ethylene resins. These compounds can be used alone or in combination of two or more. The content of such lubricants in the composition is usually 5% by mass or less, preferably 1% by mass or less. The lower limit is usually 0% by mass, for example, 0 to 5% by mass.

[0093] The composition thus obtained has excellent thermal stability. When measured using a visual analyzer, IRIS VA400 (manufactured by Alphamos), the ratio of the sum of color numbers "1058" (R: 72, G: 40, B: 40), "1059" (R: 72, G: 40, B: 56), and "1060" (R: 72, G: 40, B: 72) to the sum of color numbers "1314" (R: 88, G: 40, B: 40) and "1315" (R: 88, G: 40, B: 56) ("1058" + "1059" + "1060") / ("1314" + "1315") is typically 1.8 or less, preferably 1.4 or less, and more preferably 1 or less. The lower limit is typically 0, for example, typically 0 to 1.8. The smaller the ratio, the more suppressed is the coloration due to thermal degradation, and the higher the thermal stability tends to be. Note that a difference of 0.1 in the ratio is very significant, as it appears as a large difference in yield in actual production.

[0094] <Molding material> The present composition thus obtained is prepared into various forms, such as pellets, powder, or liquid, and provided as a molding material for various molded products. In particular, in the present embodiment, when the composition is provided as a material for melt molding, the effects of the present invention tend to be more efficiently obtained, which is preferable.

[0095] Examples of the molded article include a monolayer film molded from the present composition, as well as a multilayer structure having a layer made of the present composition.

[0096] <Multilayer Structure> A multilayer structure according to one embodiment of the present invention (hereinafter referred to as "the multilayer structure") contains the present composition and has at least one layer made of the present composition. The layer made of the present composition in the multilayer structure (hereinafter simply referred to as "the composition layer") may be a single layer or multiple layers. Furthermore, the present composition layer can be laminated with another substrate containing a thermoplastic resin other than EVOH resin as a main component (hereinafter, the resin used for the substrate may be abbreviated as "substrate resin") to further impart strength, protect the present composition layer from the effects of moisture, etc., or impart other functions.

[0097] Examples of the base resin include polyethylene-based resins such as linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-propylene (block and random) copolymers, and ethylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers; polypropylene-based resins such as polypropylene and propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers; (unmodified) polyolefin-based resins such as polybutene, polypentene, and polycyclic olefin-based resins (polymers having a cyclic olefin structure in at least one of the main chain and side chain); and polyolefins obtained by dissolving these polyolefins in an unsaturated carboxylic acid or Examples include polyolefin resins in the broad sense, including modified olefin resins such as unsaturated carboxylic acid-modified polyolefin resins graft-modified with an ester thereof, ionomers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, polyester resins, polyamide resins (including copolymerized polyamides), polyvinyl chloride, polyvinylidene chloride, acrylic resins, polystyrene resins, vinyl ester resins, polyester elastomers, polyurethane elastomers, polystyrene elastomers, halogenated polyolefins such as chlorinated polyethylene and chlorinated polypropylene, aromatic or aliphatic polyketones, etc. These may be used alone or in combination of two or more.

[0098] Of these, hydrophobic resins such as polyamide-based resins, polyolefin-based resins, polyester-based resins, and polystyrene-based resins are preferred, and more preferred are polyolefin-based resins such as polyethylene-based resins, polypropylene-based resins, polycyclic olefin-based resins, and unsaturated carboxylic acid-modified polyolefin-based resins thereof.

[0099] The layer structure of the present multilayer structure can be any combination, such as a / b, b / a / b, a / b / a, a1 / a2 / b, a / b1 / b2, b2 / b1 / a / b1 / b2, or b2 / b1 / a / b1 / a / b1 / b2, where a represents the composition layer and b represents the base resin layer. Furthermore, when R represents a recycled layer containing a mixture of the present composition and a thermoplastic resin other than EVOH resin, obtained by remelting and molding edges or defective products generated during the production of the present multilayer structure, the layer structure can also be b / R / a, b / R / a / b, b / R / a / R / b, b / a / R / a / b, b / R / a / R / a / R / b, or b / R / a / R / a / R / b. The total number of layers in the present multilayer structure is usually 2 to 15, and preferably 3 to 10. In the above layer structure, an adhesive resin layer containing an adhesive resin may be interposed between the respective layers, if necessary.

[0100] Known adhesive resins can be used, and may be selected appropriately depending on the type of thermoplastic resin used in the base resin layer "b." Representative examples include modified polyolefin polymers containing carboxy groups, which are obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to a polyolefin resin via addition reaction, graft reaction, or the like. Examples of modified polyolefin polymers containing carboxy groups include maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, maleic anhydride-grafted ethylene-propylene (block and random) copolymers, maleic anhydride-grafted ethylene-ethyl acrylate copolymers, maleic anhydride-grafted ethylene-vinyl acetate copolymers, maleic anhydride-grafted polycyclic olefin resins, and maleic anhydride-grafted polyolefin resins. These may be used alone or in combination of two or more.

[0101] In the present multilayer structure, when an adhesive resin layer is used between the present composition layer and the base resin layer, since the adhesive resin layers are located on both sides of the present composition layer, it is preferable to use an adhesive resin with excellent hydrophobicity.

[0102] The base resin and adhesive resin may contain conventionally known plasticizers, fillers, clay (montmorillonite, etc.), colorants, antioxidants, antistatic agents, lubricants, nucleating agents, antiblocking agents, waxes, etc., within a range that does not impair the spirit of the present invention (for example, usually 30% by mass or less, preferably 10% by mass or less, with the lower limit being 0% by mass, e.g., 0 to 30% by mass, based on the total resin). These may be used alone or in combination of two or more.

[0103] The lamination of the present composition layer and the above-mentioned substrate resin layer (including the case where an adhesive resin layer is interposed) can be carried out by a known method.For example, a method of melt-extrusion laminating the substrate resin onto a film, sheet, etc. of the present composition, a method of melt-extrusion laminating the present composition onto a substrate resin layer, a method of co-extruding the present composition and the substrate resin, a method of dry-laminating the present composition (layer) and the substrate resin (layer) using a known adhesive such as an organic titanium compound, an isocyanate compound, a polyester compound, a polyurethane compound, etc., a method of applying a solution of the present composition onto the substrate resin and then removing the solvent, etc.Among these, in consideration of cost and environmental aspects, it is preferable to produce the layer including the present composition layer by providing a step of melt-molding the layer, and specifically, a co-extrusion method is preferable.

[0104] The multilayer structure may be subjected to a (heat) stretching treatment, if necessary. The stretching treatment may be either uniaxial stretching or biaxial stretching, and in the case of biaxial stretching, it may be simultaneous stretching or sequential stretching. Furthermore, the stretching method may be a roll stretching method, tenter stretching method, tubular stretching method, stretch-blow method, vacuum pressure forming, or the like, whichever provides a higher stretch ratio. The stretching temperature is a temperature near the melting point of the multilayer structure, and is usually selected from the range of 40 to 170°C, preferably about 60 to 160°C. When the stretching temperature is equal to or higher than the lower limit, the stretchability tends to be excellent, and when it is equal to or lower than the upper limit, a stable stretched state tends to be easily maintained.

[0105] The stretched multilayer structure may be heat-set to provide dimensional stability. Heat-setting can be performed by known means, for example, by subjecting the stretched multilayer structure to heat treatment while maintaining tension, typically at 80 to 180°C, preferably 100 to 165°C, for typically 2 to 600 seconds.

[0106] When the stretched multilayer structure is to be used as a shrink film, the heat-shrinkability can be imparted by, for example, applying cold air to the stretched multilayer structure to cool and fix it, without carrying out the heat-setting process described above.

[0107] The thickness of the present multilayer structure (including a stretched structure), as well as the thickness of the present composition layer, base resin layer, and adhesive resin layer constituting the multilayer structure, cannot be generally determined depending on the layer configuration, type of base resin, type of adhesive resin, intended use, packaging form, required physical properties, etc., but the thickness of the present multilayer structure (including a stretched structure) is usually 10 to 5,000 μm, preferably 30 to 3,000 μm, and particularly preferably 50 to 2,000 μm. The present composition layer is usually 1 to 500 μm, preferably 3 to 300 μm, and particularly preferably 5 to 200 μm; the base resin layer is usually 5 to 3,000 μm, preferably 10 to 2,000 μm, and particularly preferably 20 to 1,000 μm; and the adhesive resin layer is usually 0.5 to 250 μm, preferably 1 to 150 μm, and particularly preferably 3 to 100 μm.

[0108] Furthermore, the thickness ratio of the present composition layer to the base resin layer in the present multilayer structure (present composition layer / base resin layer), expressed as the ratio between the thickest layers when there are multiple layers of each type, is usually 1 / 99 to 50 / 50, preferably 5 / 95 to 45 / 55, and particularly preferably 10 / 90 to 40 / 60. Furthermore, the thickness ratio of the present composition layer to the adhesive resin layer in the present multilayer structure (present composition layer / adhesive resin layer), expressed as the ratio between the thickest layers when there are multiple layers of each type, is usually 10 / 90 to 99 / 1, preferably 20 / 80 to 95 / 5, and particularly preferably 50 / 50 to 90 / 10.

[0109] <Molded Article> The multilayer structure can also be used to obtain cup- or tray-shaped molded articles. In this case, a drawing method is usually used, specifically vacuum forming, pressure forming, vacuum-pressure forming, plug-assisted vacuum-pressure forming, etc. Furthermore, when a tube- or bottle-shaped multilayer container (laminate structure) is obtained from a multilayer parison (a hollow tubular preform before blowing), a blow molding method is used. Specific examples include extrusion blow molding (two-head type, mold-moving type, parison-shift type, rotary type, accumulator type, horizontal parison type, etc.), cold parison blow molding, injection blow molding, and biaxial stretch blow molding (extrusion-type cold parison biaxial stretch blow molding, injection-type cold parison biaxial stretch blow molding, injection-molding in-line biaxial stretch blow molding, etc.). The resulting laminate may be subjected to heat treatment, cooling treatment, rolling treatment, printing treatment, dry lamination treatment, solution or melt coating treatment, bag making, deep drawing, box processing, tube processing, splitting processing, etc. as required.

[0110] <Packaging> Packaging such as a single layer film formed from the present composition, or a container or lid formed from a bag, cup, tray, tube, bottle, etc. made from the present multilayer structure is useful as a variety of packaging material containers (e.g., food packaging, drug packaging, cosmetic packaging) for general foods as well as seasonings such as mayonnaise and dressing, fermented foods such as miso, oily foods such as salad oil, beverages, cosmetics, pharmaceuticals, etc.

[0111] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are based on mass.

[0112] Prior to the examples, the following EVOH resin was prepared and manufactured. (Production of Ethylene-Vinyl Acetate Copolymer) A polymerization vessel was charged with 100 parts of vinyl acetate, the carbon in the vinyl group moiety of which was derived from biomass, and 16 parts of methanol. The system was first purged with nitriding gas, and then with ethylene, which was then introduced under pressure until the ethylene pressure reached 4.12 MPa. Under ethylene pressure, the temperature was raised to 67°C with stirring, and a peroxyester was added at a rate of 0.05 part / hr for 4 hours while the reaction was carried out for a total of 6 hours, yielding an ethylene-vinyl acetate copolymer. The polymerization rate of the resulting ethylene-vinyl acetate copolymer was 56%.

[0113] (Production of EVOH Resin) 70 parts of a methanol solution containing 0.02 equivalents of sodium hydroxide relative to the residual vinyl acetate groups in the copolymer was added to 100 parts of a methanol solution containing 50% of the above-mentioned ethylene-vinyl acetate copolymer, and a saponification reaction was carried out at 80°C for 80 minutes. Next, 100 parts of a methanol solution with a water content of 50% was added to the methanol solution of the EVOH resin under azeotropic conditions, and the methanol was distilled off until the resin concentration in the methanol / water solution of the EVOH resin reached 40%, yielding a completely transparent methanol / water homogeneous solution of the EVOH resin. The resulting methanol / water solution of the EVOH resin was then solidified into a thin plate and cut with a knife to obtain diced pellets with a side length of 3 mm. The resulting diced pellets were washed for 30 minutes with 250 parts of treated water containing 5 parts of acetic acid per 100 parts of pellets. The treated water was replaced and the washing was repeated three times. The resulting diced pellets were then washed for 30 minutes with 250 parts of water per 100 parts of pellets. The resulting pellets were washed twice with new water. The resulting die-shaped pellets were then dried at 118°C for 8 hours in a nitrogen gas stream with an oxygen concentration of 0.5% by volume or less to obtain pellets of EVOH resin (ethylene structural unit content: 32 mol%, saponification degree: 99.7 mol%, bio-based degree: 64% (content of biovinyl alcohol structural units in all vinyl alcohol structural units: 94%)).

[0114] Example 1 (Production of Titanium Compound and Alkali Metal Compound-Containing Composition Pellets) The obtained EVOH resin pellets were used along with rutile-type titanium(IV) oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) having an average particle size of 5 μm or less as the titanium compound, and sodium acetate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as the alkali metal compound. The EVOH resin pellets were melt-kneaded in a benchtop kneader "Xplore-HTMC15HT (15 mL capacity)" (manufactured by LeoLabo) under the following kneading conditions so that the titanium oxide content in terms of metal was 0.04 ppm relative to the mass of the composition, and the sodium acetate content in terms of metal was 8,000 ppm relative to the mass of the composition. The extruded and discharged strand was cooled and solidified by air cooling to obtain pellets of the composition. [Kneading Conditions] - Small kneader temperature: 200°C - Screw shape: Twin-screw conical type - Screw rotation: Same direction - Kneading time: 10 minutes

[0115] Example 2 A composition was obtained in the same manner as in Example 1, except that the content of sodium acetate in terms of metal was changed to 40 ppm relative to the mass of the composition.

[0116] Example 3 A composition was obtained in the same manner as in Example 1, except that the content of titanium oxide in terms of metal relative to the mass of the composition was changed to 0.1 ppm and the content of sodium acetate in terms of metal relative to the mass of the composition was changed to 200 ppm.

[0117] Comparative Example 1 A composition was obtained in the same manner as in Example 1, except that the content of sodium acetate in terms of metal was changed to 4 ppm relative to the mass of the composition.

[0118] Comparative Example 2 A composition was obtained in the same manner as in Example 1, except that the content of sodium acetate in terms of metal was changed to 12,000 ppm relative to the mass of the composition.

[0119] Comparative Example 3 A composition was obtained in the same manner as in Example 3, except that the content of sodium acetate in terms of metal was changed to 40 ppm relative to the mass of the composition.

[0120] The following thermal stability evaluation was carried out using the obtained compositions of Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Table 1 below.

[0121] [Evaluation of Thermal Stability] The obtained composition was cut with nippers and pulverized to prepare a sample. The sample was heated at 150°C for 5 hours in a vacuum dryer Vacuum Drying Over DP22 (manufactured by Ohira Rika Kogyo Co., Ltd.), and then analyzed using a visual analyzer IRIS VA400 (Alpha Using a chromatograph manufactured by MOS, the ratio of the sum of color numbers "1058" (R: 72, G: 40, B: 40), color number "1059" (R: 72, G: 40, B: 56), and color number "1060" (R: 72, G: 40, B: 72) to the sum of color number "1314" (R: 88, G: 40, B: 40) and color number "1315" (R: 88, G: 40, B: 56) was evaluated as ("1058" + "1059" + "1060") / ("1314" + "1315") The color numbers "1314" and "1315" are colors with a light yellow tint, and the color numbers "1058", "1059", and "1060" are colors with a deep yellow tint. The smaller this ratio, the more the yellow coloring due to thermal degradation is suppressed, which means that the thermal stability is high.

[0122]

[0123] The results in Table 1 above show that the compositions of Examples 1 to 3, which contain a titanium compound and an alkali metal compound at a specific mass ratio, have a lower proportion of deep yellowness (specifically, 50% lower) and are excellent in thermal stability compared to the compositions of Comparative Examples 1 to 3, which have a titanium compound and an alkali metal compound at a mass ratio outside the specified range. Furthermore, multilayer structures having layers made from the compositions of Examples 1 to 3 also have excellent thermal stability, and molded articles and food packages containing such multilayer structures also have excellent thermal stability.

[0124] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0125] Because the present composition has excellent thermal stability, it is useful as a packaging material for various foods, as well as seasonings such as mayonnaise and dressings, fermented foods such as miso, oily foods such as salad oil, beverages, cosmetics, pharmaceuticals, etc.

Claims

1. A composition containing an ethylene-vinyl alcohol copolymer, a titanium compound, and an alkali metal compound, wherein at least a portion of the ethylene-vinyl alcohol copolymer is derived from biomass, and the mass ratio of the content of the alkali metal compound in terms of the metal to the content of the titanium compound in terms of the metal is 500 to 280,000.

2. The composition according to claim 1, wherein the content of said titanium compound in terms of metal is 0.0001 ppm or more and 5000 ppm or less based on the mass of said composition.

3. The composition according to claim 1 or 2, wherein the content of the titanium compound in terms of metal is 0.0001 ppm or more and 2 ppm or less based on the mass of the composition.

4. The composition according to any one of claims 1 to 3, wherein the content of the titanium compound in terms of metal is 0.0001 ppm or more and less than 1 ppm based on the mass of the composition.

5. The composition according to any one of claims 1 to 4, wherein the ethylene-vinyl alcohol copolymer has a bio-based content of 0.01 to 100%.

6. The composition according to any one of claims 1 to 5, wherein the ethylene-vinyl alcohol copolymer has a bio-based content of 1 to 99%.

7. A molding material comprising the composition according to any one of claims 1 to 6.

8. A multilayer structure having a layer comprising the composition according to any one of claims 1 to 6.

9. The multilayer structure of claim 8, further comprising an adhesive resin layer.

10. A molded article comprising the multilayer structure according to claim 8 or 9.

11. A food package comprising the multi-layer structure of claim 8 or 9.

12. A method for producing the composition according to any one of claims 1 to 6, comprising the step of mixing said ethylene-vinyl alcohol copolymer and said titanium compound.

13. A method for producing a multi-layer structure according to claim 8 or 9, comprising the step of melt-molding a layer containing said composition.

Images