Packaging of polyvinyl alcohol resin containing oxyalkylene group and method for manufacturing the same

Abstract

Disclosed are: a packaging body configured so that even if an oxyalkylene group-containing PVA-based resin is stored for a long period of time in a state of the packaging body, the oxyalkylene group-containing PVA-based resin is unlikely to cause a problem of thickening during melt kneading; and a manufacturing method of the packaging body. The packaging body is obtained by housing the oxyalkylene group-containing PVA-based resin in a bag body, the bag body being configured so that the permeation amount of oxygen is 1 m 2 The oxygen permeation degree of the film of the oxygen meter is 1000 cc / m 2 ·day·atm or less. In the packaging body, oxidation of the oxyalkylene group-containing PVA-based resin is inhibited, and generation of a carboxyl group-containing compound, which is a main cause of thickening during melt kneading, is inhibited.

Description

Technical Field

[0001] This invention relates to a packaging material capable of stably storing PVA-based resins containing oxidized alkenyl groups and a method for manufacturing the same. Background Technology

[0002] Polyvinyl alcohol (PVA) resins are typically shipped from their manufacturing sites in packages containing PVA resin powder or granules sealed in bags. These packages circulate and are traded in the market. The packages can be stored in containers or warehouses until the user receives the package and removes the PVA resin from it. In cases of export overseas, the PVA resin will circulate in a long-term state, remaining within the package.

[0003] After this distribution / storage process, the user removes the PVA-based resin from the packaging and uses it for melt molding or preparing aqueous solutions according to the intended application. The PVA-based resin removed from the packaging sometimes has defects that were not anticipated at the manufacturing site. Although the causes of these defects vary depending on the type of PVA-based resin, storage period, distribution method, etc., their occurrence can be reduced or avoided by selecting suitable packaging bags.

[0004] For example, during long-term storage, acetyl-modified PVA resin powder packaged in bags undergoes a cross-linking reaction between the acetyl groups, which are the modifying groups, because the acetyl groups contain active hydrogen. It is a known problem that the cross-linked products generated by the cross-linking reaction are insoluble in aqueous solutions when preparing aqueous solutions of the acetyl-modified PVA resin powder. To solve this problem, Patent Document 1 (WO 2016 / 052446) proposes using a water vapor permeability of 10 g / m... 2 • Bags made of membranes with a permeability of less than 1000 m are used to package acetyl-modified PVA resin powder. In particular, due to moisture absorption, cross-linking products of the acetyl-modified PVA resin can be formed. Therefore, bags with low water vapor permeability can prevent the formation of cross-linking products while storing the packaged product.

[0005] On the other hand, regarding melt-formable PVA resins, such as PVA resins containing 1,2-diol side chains, there are problems related to the melt forming of PVA resins. When PVA resins are formed using a melt extruder, controlled operation can sometimes become difficult due to the backflow of the PVA resin (usually in powder or granular form) and volatile components added to the extruder. Patent Document 2 (WO2017 / 104501) proposes using a methanol vapor permeability of 0.5 to 1000 g / m 2 The problem can be solved by using a bag made of a membrane. This proposal is based on the fact that the residual volatile components can be components such as methanol used in the synthesis of PVA-based resins.

[0006] Considering the hygroscopic nature of PVA resins, another problem exists. When PVA resins are melt-formed, the absorbed moisture evaporates. This absorbed moisture increases the amount of volatile components and, like residual methanol, can cause PVA resin to recirculate, leading to unstable operation of the melt extruder. Patent Document 2 proposes using a low-density polyethylene (LDPE) film bag for packaging. The LPE film can suppress the permeation of water vapor that can be absorbed by the PVA resin packaged in the bag, but allows methanol vapor contained in the PVA resin to escape from the inside of the bag, thereby reducing the amount of methanol and moisture evaporated when the PVA resin is melt-formed.

[0007] However, another issue concerns low-density polyethylene film bags containing oxidized alkenyl-based PVA resins. If the packaging is distributed to users after prolonged storage, users may notice discoloration of the oxidized alkenyl-based PVA resins when supplied for melt molding, and further notice a significant increase in viscosity of the oxidized alkenyl-based PVA resins when melt-blended.

[0008] Existing technical documents

[0009] Patent documents

[0010] [Patent Document 1] WO 2016 / 052446

[0011] [Patent Document 2] WO 2017 / 104501 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] One object of the present invention is to provide a packaging body for a PVA-based resin containing oxidized alkenyl groups, which does not exhibit viscosity increase during melt mixing even after long-term storage. Furthermore, a method for manufacturing this packaging body is provided.

[0014] Solution for solving the problem

[0015] The inventors analyzed a problem related to the increased viscosity of PVA-based resins containing oxidized alkenyl groups during melt mixing after long-term storage. The inventors believe that oxidized alkenyl groups, as shown in the following formula, can react with oxygen to generate compounds with carboxyl groups, and these carboxyl-containing compounds can undergo cross-linking reactions with the hydroxyl groups in the oxidized alkenyl group-containing PVA-based resins, resulting in increased viscosity.

[0016] [Chemical Formula 5]

[0017]

[0018] Based on this analysis, the inventors conducted research from the perspective of preventing the oxidation of PVA-based resins containing oxidized alkenyl groups during storage, and completed the present invention.

[0019] The packaging of the present invention comprises a bag made of film, the film being permeable to 1m³ within 24 hours at 25°C and 65% RH. 2 The oxygen permeability of the membrane oxygen meter is 1000 cc / m 2 • Days • atm and below; and polyvinyl alcohol resin containing oxidized alkenyl groups stored inside the bag. The film can be a single-layer film or a multi-layer film.

[0020] According to the present invention, the preferred membrane is capable of permeating 1m of water within 24 hours at 40°C and 90% RH. 2 The water vapor permeability of the membrane water vapor meter is 300 g / m. 2 Below the heavens.

[0021] Another aspect of the invention is a method for manufacturing a packaging body. The method includes encapsulating a polyvinyl alcohol-based resin containing oxidized alkenyl groups in a bag made of a film, the film being permeable to 1m³ within 24 hours at 25°C and 65% RH. 2 The oxygen permeability of the membrane oxygen meter is 1000 cc / m 2 ·day·atm and below.

[0022] In this invention, polyvinyl alcohol resin containing oxidized alkenyl groups generally refers to resin having structural units represented by the following general formula (3).

[0023]

[0024] In equation (3), X is a single bond or a bonded chain, Y is a hydrogen atom or a methyl group, n is an integer from 1 to 50, and R 1 and R 2 Each is independently a hydrogen atom or an alkyl group.

[0025] The effects of the invention

[0026] The packaging body according to the present invention, or the packaging body that can be obtained by the manufacturing method of the present invention, can suppress the oxidation of the oxidized alkenyl PVA resin contained in the packaging body, thereby suppressing the increase in viscosity caused by storage. Therefore, even if the packaging body of the oxidized alkenyl PVA resin is stored for a long time during circulation, the oxidized alkenyl PVA resin can be provided in a state close to that immediately after manufacturing. Attached Figure Description

[0027] Figure 1A graph illustrating the dynamic viscosity behavior of the oxidized alkenyl PVA resin removed from package No. 1.

[0028] Figure 2 A graph illustrating the dynamic viscosity behavior of the oxidized alkenyl PVA resin removed from package No. 4. Detailed Implementation

[0029] Packaging for PVA-based resins containing oxidized alkenyl groups

[0030] The packaging of the present invention comprises a bag made of film, the film being permeable to 1m³ within 24 hours at 25°C and 65% RH. 2 The oxygen permeability of the membrane oxygen meter is 1000 cc / m 2 • Days • atm and below; and polyvinyl alcohol resin containing oxidized alkenyl groups stored in the bag.

[0031] <PVA-based resins containing oxidized alkenyl groups>

[0032] The PVA-based resin containing oxidized alkenyl groups, which is the contents of the packaging, is a PVA-based resin comprising an ethylene alcohol unit represented by general formula (1), an ethylene ester unit represented by general formula (2), and an oxidized alkenyl group unit represented by general formula (3). The ethylene alcohol unit is the basic structural unit of the PVA-based resin. When the degree of saponification is less than 100%, the ethylene ester unit corresponds to the unsaponified portion.

[0033]

[0034] Both the vinyl alcohol unit (1) and the vinyl ester unit (2) are derived from vinyl ester compounds used as monomers to form PVA-based resins.

[0035] Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl neovalerate, vinyl decanoate, vinyl laurate, vinyl stearate, vinyl benzoate, and vinyl tert-carbonate. Among these, vinyl acetate is preferred due to its economic efficiency.

[0036] Therefore, in equation (2), R a It is an alkyl group having 1 to 18 carbon atoms and depends on the ethylene ester compound used as a raw material for the synthesis of PVA-based resins. R a The preferred unit is methyl, and the preferred vinyl ester unit is vinyl acetate unit represented by formula (2').

[0037]

[0038] The oxidized alkenyl unit represented by formula (3) originates from a vinyl monomer (i.e., a vinyl monomer having an oxidized alkenyl group) that provides the oxidized alkenyl group for copolymerization with vinyl ester monomers. Compounds in which the oxidized alkenyl group and the vinyl-containing group are linked can be used as vinyl monomers providing the oxidized alkenyl group. Specifically, (meth)acrylates, (meth)acrylamides, (meth)allyl ethers, and vinyl ethers can be used, as long as they contain an oxidized alkenyl group.

[0039] Therefore, in formula (3), Y is hydrogen or methyl, and X, which connects the vinyl group to the oxidized alkenyl group, is typically a single bond or a chain. Examples of chains include methylene, ethylene, ether (-O-), amide (-CONH-), ester (-COO-), and -CH2O-. Among these, methylene, ether, and amide bonds are preferred because they have little effect on the PVA-based resin and the oxidized alkenyl group.

[0040] R 1 and R 2 Typically, each alkyl group is independently composed of 1 to 10 hydrogen atoms or carbon atoms, and n is an integer from 1 to 50, depending on the type of oxidized alkenyl group. Hereinafter, n is the average number of oxidized alkenyl groups contained in the PVA-based resin. Generally, for a single oxidized alkenyl group, the repeating number (n) of the oxidized alkenyl group is an integer selected from the range of 1 to 100. The average repeating number n is provided using nuclear magnetic resonance spectroscopy (NMR) measurements.

[0041] The proportion of oxidized alkenyl groups in the oxidized alkenyl-containing PVA resins, which are elements of the present invention, is not particularly limited, but this proportion is typically from 0.1 to 10 mol%, preferably from 0.5 to 5 mol%. Generally, oxidized alkenyl-containing PVA resins with an excessively high proportion of oxidized alkenyl groups may have difficulty increasing the degree of polymerization during their synthesis, resulting in difficulty in meeting the physical properties desired as the final product. Furthermore, in the case of such oxidized alkenyl-containing PVA resins without the desired high degree of polymerization, physical properties such as mechanical strength and gas barrier properties may be compromised. On the other hand, oxidized alkenyl-containing PVA resins with an excessively low proportion of oxidized alkenyl groups tend to have low flexibility, relatively high melting points, and compromised formability. Hereinafter, the proportion of oxidized alkenyl groups is determined based on the ratio (mol%) of the monomer providing the oxidized alkenyl groups relative to all added vinyl monomers used in the synthesis.

[0042] The degree of saponification of PVA-based resins containing oxidized alkenyl groups is typically 60 to 100 mol%, preferably 70 to 99 mol%, more preferably 80 to 95 mol%, and even more preferably 88 to 94 mol%. The degree of saponification is appropriately selected based on the desired water solubility. The degree of saponification is determined based on the amount of alkali consumed in the hydrolysis of residual acetate in the resin and is measured according to JIS K6726.

[0043] The average degree of polymerization (based on JIS K6726) of oxidized alkenyl PVA resins is typically between 100 and 3000, and preferably between 200 and 1000. PVA resins containing oxidized alkenyl groups with excessively high average polymerization may become difficult to melt-form. PVA resins containing oxidized alkenyl groups with excessively low average polymerization may not achieve satisfactory strength.

[0044] In addition to the ethylene ester monomers and vinyl monomers providing oxidized alkenyl groups mentioned above, the oxidized alkenyl-containing PVA resin to be packaged may include other monomers copolymerized in the range of 10 mol% or less, preferably 5 mol% or less, and particularly preferably 1 mol% or less. Examples of other monomers include, for example, olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, and 3,4-dihydroxy-1-butene, and their derivatives such as acylates; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecenoic acid, or their salts, monoesters, or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; and acrylamide and methacrylamide. Amides; such as olefin sulfonic acids or their salts, such as vinyl sulfonic acid, allyl sulfonic acid, and methyl allyl sulfonic acid; alkyl vinyl ethers; such as vinyl compounds, such as dimethyl allyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinyl vinyl carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, and glycerol monoallyl ether; substituted vinyl acetates, such as isopropyl acetate and 1-methoxyvinyl acetate; vinylidene chloride, 1,4-diacetoxy-2-butene, 1,4-dihydroxy-2-butene, and vinylene carbonate.

[0045] The polymerization of vinyl monomers and the saponification of the resulting polymers can be carried out using various methods known in the manufacture of polyvinyl alcohol.

[0046] The oxidized alkenyl groups in PVA resins containing the above-mentioned units are easily oxidized to generate compounds with carboxyl groups.

[0047] Compounds containing carboxyl groups are not limited to those generated by oxidizing the primary hydroxyl groups at the ends of the oxidized alkenyl groups in PVA-based resins containing oxidized alkenyl groups. The oxidized alkenyl groups in oxidized alkenyl group-containing PVA-based resins undergo hydrolysis to generate polyethylene glycol (PEG), which separates from the main chain of the PVA-based resin. PEG generated as an oxidative decomposition product is also included in compounds containing carboxyl groups generated by the oxidation of the oxidized alkenyl groups. PEG as an oxidative decomposition product can be not only low-boiling-point compounds such as acetic acid, but also high-boiling-point long-chain compounds. Long-chain carboxylic acids, as long-chain compounds, can increase viscosity during melt mixing.

[0048] Long-chain carboxylic acids can be monocarboxylic acids or dicarboxylic acids with repeating oxidized alkenyl groups. The number of repeats (n) is typically an integer from 1 to 50, depending on the oxidized alkenyl unit derived from the oxidized alkenyl-containing PVA-based resin.

[0049] Long-chain, high-boiling-point compounds with carboxyl groups include monocarboxylic acids such as diethylene glycol monocarboxymethyl ether and triethylene glycol monocarboxymethyl ether; and dicarboxylic acids such as ethylene diglycolic acid and diethylene glycol dicarboxymethyl ether.

[0050] The aforementioned carboxyl-containing compounds can cause coloration in PVA resins containing oxidized alkenyl groups. Furthermore, the presence of carboxyl-containing compounds can increase the viscosity of PVA resins containing oxidized alkenyl groups during melt mixing. In particular, long-chain carboxylic acids, being high-boiling-point compounds, cause a significant increase in the viscosity of PVA resins containing oxidized alkenyl groups during melt mixing.

[0051] Compounds containing carboxyl groups can be detected by methods for determining the acid value of chemicals according to JIS K0070, such as neutralization titration, potentiometric titration, gas chromatography-mass spectrometry (GC-MS) for low-boiling compounds, and high-performance liquid chromatography-mass spectrometry (HPLC-MS) for high-boiling compounds.

[0052] The PVA-based resin containing oxidized alkenyl groups with the above structure is stored in the bag in the form of powder, granules, or pellets.

[0053] <Bag>

[0054] The bag used in the packaging of this invention is designed to allow for 1m of permeability within 24 hours (1 day) at 25°C and 65% RH. 2 The oxygen permeability of the membrane oxygen meter is 1000 cc / m 2 For temperatures below 1.5 liters per minute, 500 cc / m is preferred. 2 • For temperatures below 100 atm, 300cc / m is preferred. 2 For temperatures below 1.5 pm, 100 cc / m is even better. 2 For temperatures below 1 atm, 10cc / m is particularly preferred. 2 ·day·atm and below.

[0055] The membrane constituting the bag body can be a single-layer membrane or a multi-layer membrane. Examples of multi-layer membranes include laminated membranes in which 2 to 10 layers, preferably 2 to 6 layers, of plastic film are stacked; metal foil-attached membranes in which metal foil is attached to plastic film; metal vapor deposition membranes in which metal is deposited on one or both sides of plastic film; and laminates in which plastic film is further stacked on metal vapor deposition membranes or metal foil-attached membranes, etc.

[0056] A protective sheet made of paper, non-woven or woven fabric, or woven cloth can be further attached to the outer surface of a single-layer or multi-layer film.

[0057] In the case of multilayer films, there are no particular limitations on the lamination method. Films can be laminated via adhesive layers, and laminated films can be produced by extruding molten thermoplastic resin onto a substrate film, or by co-extruding multiple thermoplastic resins.

[0058] The multilayer membrane can be a multilayer membrane containing an oxygen barrier layer that satisfies the above-mentioned gas barrier properties, or a multilayer membrane with an overall multilayer structure that satisfies the above-mentioned oxygen barrier properties.

[0059] Examples of oxygen barrier layers include metal foils such as aluminum foil, metal (e.g., aluminum) vapor-deposited layers, (biaxial) stretched polypropylene films, polyethylene terephthalate films, polyamide films, ethylene-vinyl alcohol (EVOH) films, and vinylidene chloride films. One or more of these oxygen barrier layers may be included in a multilayer film.

[0060] Aluminum foil, aluminum vapor deposition layer, and biaxially stretched polypropylene film are particularly preferred as oxygen barrier layers. These can achieve a thickness equivalent to 25 μm, allowing for oxygen permeability of 1 m³ within 24 hours (1 day) at 25°C and 65% RH. 2 The oxygen permeability of the membrane oxygen meter is 100 cc / m 2 For temperatures below 1 atm, 10cc / m is preferred. 2 • Days • Atm and below. This type of oxygen barrier layer can be used as a layer in a multilayer film that includes various layers other than gas barrier properties as needed. Thus, the multilayer film has desired properties in addition to gas barrier properties, such as flexibility, strength, lightweight as a bag body, and operability.

[0061] As mentioned above, in PVA resins containing oxidized alkenyl groups, the oxidized alkenyl groups are easily oxidized to form compounds containing carboxyl groups. The carboxyl groups then undergo cross-linking reactions with the OH groups in the molecular chain of the same oxidized alkenyl-containing PVA resin or with the OH groups of other oxidized alkenyl-containing PVA resins. It is believed that the resulting cross-linked products cause an increase in viscosity during melt mixing. Therefore, avoiding an increase in oxygen concentration within the packaging is effective in suppressing the oxidation of the oxidized alkenyl groups. Consequently, this suppression is also effective in suppressing the increase in viscosity during melt mixing.

[0062] Furthermore, since carboxyl-containing compounds also cause coloring of PVA-based resins, suppressing the generation of carboxyl-containing compounds can suppress coloring, thereby preventing the deterioration of the quality of PVA-based resin molded products such as films.

[0063] According to the present invention, the membrane constituting the bag body is preferably permeable to 1m in 24 hours (1 day) at 40°C and 90% RH. 2The water vapor permeability of the membrane water vapor meter is further increased to 300 g / m. 2 · Less than 200g / m 2 · Less than 100g / m 2 · Less than 10 days, and even more specifically 10g / m 2 Below the heavens.

[0064] Like typical PVA resins, PVA resins containing oxidized alkenyl groups are prone to moisture absorption. Once these resins absorb moisture and plasticize, they undergo oxidation via oxygen, generating decomposition products. Furthermore, due to moisture absorption, powders or granules of PVA resins containing oxidized alkenyl groups tend to adhere to each other, forming agglomerates. From this perspective, lower water vapor permeability of the membrane constituting the bag is preferable.

[0065] The thickness of the membrane constituting the bag should be appropriately selected based on the type of membrane, as thickness affects oxygen permeability, strength, flexibility, and operability. In the case of multilayer membranes including an air barrier layer, the total thickness is typically 20 to 500 μm, preferably 30 to 200 μm. Excessively thick membranes provide a heavy bag and tend to impair the bag's flexibility.

[0066] If the multilayer film includes a gas barrier layer, the desired gas barrier properties can be achieved regardless of the thickness. In the case of multilayer films, the required strength can be ensured by stacking protective sheets such as paper or cloth. When protective sheets are stacked, the total thickness can exceed 500 μm, provided that the bag and packaging meet operational requirements such as flexibility.

[0067] The bag used in the packaging of the present invention can be obtained by forming the above-mentioned film into a bag. The bag can have any shape or form, as long as the contents can be contained within the bag. Specific examples include a three-sided sealed bag with heat-sealed sides and bottom; a side-sealed bag formed by folding the film in half and heat-sealing it on both sides; a bag with openings on adjacent sides formed by cutting two stacked films with an L-shaped seal; a bottom-fastening bag with a gusset at the bottom; a transverse-fastening bag with gussets on both sides; and a bag with fasteners or zippers at the openings, etc.

[0068] These bags can be constructed, for example, by heat-sealing the bag with a film. Alternatively, in the case of a single-layer film, the bag can be constructed directly from a thermoplastic resin as a raw material by a tubular film method, which involves extruding a tubular film via a ring die.

[0069] There are no particular limitations on the method for closing the opening of the bag. Various methods can be used, such as heat sealing, adhesives, fasteners, or zippers, and the method should be appropriately selected according to the structure of the bag.

[0070] The bag has a common shape typical of general circulation. Typically, when the contents range from 10 to 30 kg, square bags with a long side of 50 to 150 cm and a short side of 30 to 80 cm are common.

[0071] <Other possible storage items>

[0072] In addition to PVA-based resins containing oxidized alkenyl groups, the following can also be sealed in the packaging of this invention.

[0073] (1) PVA resins other than those containing oxidized alkenyl groups

[0074] For example, unmodified PVA resins and other modified PVA resins (collectively referred to as "other types of PVA resins"), excluding PVA resins containing oxidized alkenyl groups, can be stored together. These other types of PVA resins can be stored in powder, granule, or pellet form.

[0075] When packaged as a mixture with other types of PVA-based resins, the content of the oxidized alkenyl PVA-based resin can be 50% by weight or more, preferably 60% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more, based on the total weight of the PVA-based resin contained in the package.

[0076] (2) Antioxidants

[0077] Examples of antioxidants include butylated hydroxytoluene, butylated hydroxyanisole, and tocopherol.

[0078] These antioxidants can be packaged in powder, granule, or pellet form and can be mixed with powdered or granular PVA-based resins containing oxidized alkenyl groups. Optionally, individually packaged granules or pellets of antioxidant can be packaged within a package of oxidized alkenyl group-containing PVA-based resin.

[0079] The amount of antioxidant contained in the packaging is 1 to 10,000 ppm relative to the oxidized alkenyl PVA resin, preferably 1 to 1,000 ppm, and more preferably 5 to 500 ppm.

[0080] (3) Other possible storage items

[0081] In addition to the substances mentioned above, desiccants to prevent the PVA-based resin from absorbing moisture and lubricants to improve processing characteristics during melt molding can be included, as long as they do not impair the effects of the present invention. These can be mixed with the powdered or granular PVA-based resin containing oxidized alkenyl groups in powder, granule, or pellet form. Optionally, these individually packaged components can be housed together within the packaging of the oxidized alkenyl group-containing PVA-based resin.

[0082] <Packaging>

[0083] The packaging body of the present invention can be made by placing a PVA-based resin containing oxidized alkenyl groups and other necessary containers or items to be packaged into an oxygen permeability of 1000 cc / m³. 2 It is manufactured by filling a bag with a volume of 1.5 atm or less and then sealing the opening of the bag.

[0084] After placing the items to be stored or packaged through the opening of the bag, the opening can be closed. The method of closing the opening depends on the type of bag: adhesive, heat sealing, fasteners, or a zipper.

[0085] The packaging with the above structure can be stored at the manufacturing site for one to several months. Even after one to several months of storage, when the user takes out the PVA-based resin (PVA-based resin containing oxidized alkenyl groups) supplied as a melt-forming material, the PVA-based resin containing oxidized alkenyl groups will not exhibit an unexpected increase in viscosity during melt mixing because the PVA-based resin is prevented from oxidizing.

[0086] [Manufacturing method of packaging]

[0087] According to the present invention, a method for manufacturing a packaging body is also included. This method includes encapsulating a polyvinyl alcohol resin containing oxidized alkenyl groups in a bag made of a film, the film being permeable to 1m³ within 24 hours at 25°C and 65% RH. 2 The oxygen permeability of the membrane oxygen meter is 1000 cc / m 2 ·day·atm and below.

[0088] The bag body described in the packaging body of the present invention can be used in the manufacturing method of the present invention.

[0089] The oxidized alkenyl-containing polyvinyl alcohol resin contained in the bag is the oxidized alkenyl-containing polyvinyl alcohol resin described in the packaging of the present invention. In the case of further containing other possible contents or items to be packaged as listed above, they may be filled as a mixture with the oxidized alkenyl-containing polyvinyl alcohol resin before or after containing the oxidized alkenyl-containing polyvinyl alcohol resin.

[0090] After storage, close the opening of the bag. Choose the appropriate storage method and opening sealing method based on the type and shape of the bag. For sealing, depending on the type of bag, heat sealing, fasteners, zippers, or adhesives can be used.

[0091] Example

[0092] [Measurement and Evaluation Methods]

[0093] 1. Oxygen permeability (cc / m 2 ·day·atm)

[0094] For the membrane constituting the bag, at 25°C and 65% RH, 1m [unclear] within 24 hours 2 The oxygen permeability was measured according to JIS 7126-2 using the MOCON method (OXTRAN coulometric method).

[0095] 2. Water vapor transmission rate (g / m 2 ·sky)

[0096] For the membrane constituting the bag body, at 40°C and 90%RH, 1m 2 The water vapor permeation of the membrane was measured by the cup method according to JIS Z0208.

[0097] 3. Acid value (mgKOH / mg)

[0098] Powdered PVA-based resin, immediately after manufacturing and passed through a sieve with a mesh size of 2800 μm, is sealed into bags to prepare the packaging. After storing the packaging in an air-dried oven at 60°C for a period of time (1 month, 2 months, or 3 months), the PVA-based resin is removed from the bags, and the acid value is measured by potentiometric titration according to JIS K0070. A high acid value indicates a high content of carboxyl-containing compounds and suggests that oxidized alkenyl groups have occurred.

[0099] 4. Melt viscosity stability

[0100] Immediately after manufacturing, PVA-based resin was passed through a sieve with a mesh size of 2800 μm in powder form. The PVA-based resin was sealed in bags to prepare packaging. After storing the packaging for a period of time (1 month, 2 months, or 3 months), the PVA-based resin was removed from the bags, and its dynamic viscosity behavior in the molten state was measured at each storage time. The change in dynamic viscosity behavior over time was compared. In the experiment, the dynamic viscosity behavior of the mixing operation at 210°C and 50 rpm was monitored for 2 hours using a Lab-Plast mill (Plastograph ECPlus) from Brabender GmbH & Co. A graph showing the relationship between mixing time and instrument torque value was obtained from this monitoring. Furthermore, the time (in minutes) until the viscosity reached the peak point or maximum torque value was determined from the graph and used as an indicator of melt viscosity stability. An increase in instrument torque indicates an increase in the viscosity of the resin in the molten state. Additionally, the peak arrival time was compared with the peak arrival time of the PVA-based resin immediately after manufacturing.

[0101] 5. Yellowness (YI value)

[0102] Powdered PVA-based resin, passed through a 2800 μm mesh immediately after manufacturing, is sealed into bags to prepare the packaging. After storing the packaging for a period of time (1 month, 2 months, or 3 months), the PVA-based resin is removed from the bags and the yellowness (YI value) is measured using a SE6000 spectrophotometer manufactured by Nippon Denshoku Industries Co., Ltd. The ΔYI value according to ASTM (D1925) is used as the YI value data.

[0103] [Storage Items]

[0104] The following PVA-based resins or unmodified polyvinyl alcohol powders containing oxyethylene group are used to prepare the packaging.

[0105] (1) PVA resins containing vinyl oxide

[0106] Polyoxyethylene allyl ether with an average chain length of n = 15 was used as the vinyl oxide-containing monomer. 35 parts of vinyl acetate, 8.6 parts (corresponding to 1 mol% based on the amount of vinyl acetate added), and 15 parts of methanol were added to a polymerization reactor. The reactor was heated to a reflux state. Then, 0.3 mol% (based on the total amount of vinyl acetate) of azobisisobutyronitrile was added to the reactor, and polymerization was carried out. Simultaneously with the polymerization, 65 parts (based on 65% of the total amount added) of vinyl acetate were added dropwise to the reactor at a constant rate, and a methanol solution of vinyl oxide-containing polyvinyl acetate was obtained. The vinyl oxide-containing polyvinyl acetate was saponified with sodium hydroxide to obtain the desired vinyl oxide-containing PVA-based resin.

[0107] The resulting vinyl oxide-containing PVA resin has a vinyl oxide content of 1 mol%. The vinyl oxide-containing PVA resin was obtained as powder using a sieve with a mesh size of 2800 μm. The degree of saponification of this vinyl oxide-containing PVA resin is 93.5 mol%, and the average degree of polymerization is 550. The degree of saponification was determined according to JIS K6726 based on the amount of alkali consumed in the hydrolysis of residual vinyl acetate. The average degree of polymerization was measured according to JIS K6726.

[0108] The PVA-based resin containing vinyl oxide contains volatile components such as water and methanol at a concentration of 4% by weight.

[0109] Immediately after manufacturing, the acid value of the vinyl oxide-containing PVA resin, measured using the above-described measurement method, was less than 0.05 mg KOH / mg (below the detection limit). The peak arrival time, determined by melt viscosity stability testing, was 94 minutes. Furthermore, the ΔYI ASTM (D1925) value was 5.8.

[0110] (2) Unmodified polyvinyl alcohol resin

[0111] The resin used was an unmodified polyvinyl alcohol resin with a saponification degree of 88 mol% as measured according to JIS K6726, an average degree of polymerization of 500 as measured according to JIS K6726, and containing 4 wt% volatile components (water, methanol).

[0112] The acid value of the unmodified PVA-based resin immediately after manufacturing, measured according to the above method, was 0.37 mg KOH / mg. This acid value is higher than that of the vinyl oxide-containing PVA-based resin immediately after manufacturing, presumably due to the formation of acetic acid through the hydrolysis of unsaponified acetyl groups. The peak arrival time, determined by melt viscosity stability testing, was 76 minutes. Furthermore, the ΔYI ASTM (D1925) value was 6.2.

[0113] [Bag]

[0114] The following four types of bags (f1-f4) are used. The oxygen permeability and water vapor permeability of the membranes constituting each bag are shown in Table 1.

[0115] f1:

[0116] The ALH-8 standard aluminum bag for vacuum packaging (Tokyo Garasu Kikai Co., Ltd.) is a multi-layered (total thickness 116μm) three-sided sealed bag with a layered structure of polyethylene terephthalate (12μm) / aluminum (9μm) / polyamide (15μm) / unstretched polypropylene (80μm) positioned from the inside of the bag.

[0117] When aluminum foil is used as a gas barrier layer and its oxygen permeability is below the detection limit (less than 0.01 cc / m) at a thickness equivalent to 25 μm, the permeability is determined. 2 (·day·atm). The bag is also made of a membrane with a thickness of 116μm and an oxygen permeability below the detection limit.

[0118] f2:

[0119] The three-sided sealed bag body is composed of a five-layer film obtained by co-extruding polyamide (PA), adhesive resin, and polyethylene (PE) using three five-layer extruders. The total thickness of the five-layer film is 71 μm and has the following layer structure (the left end is positioned on the inside of the bag body).

[0120] PA / PA / Adhesive / PE / PE (Total thickness of PA layer: 53μm, and total thickness of PE layer: 15μm).

[0121] The bag has an oxygen permeability of 61 cc / m³. 2 The membrane (total thickness 71 μm) is composed of a ·atom 1m membrane. With the polyamide membrane acting as a gas barrier layer, the oxygen permeability at a thickness equivalent to 25 μm is 129 cc / m³. 2 ·day·atm.

[0122] f3:

[0123] The three-sided sealed bag is composed of a laminated film (60 μm thick) obtained by dry lamination of a biaxially stretched polypropylene (OPP) film (20 μm thick) and an unstretched polypropylene (unstretched PP) film (40 μm thick), wherein the OPP film is positioned on the inside of the bag.

[0124] The bag has an oxygen permeability of 3.9 cc / m³. 2 The membrane (60 μm thick) has a permeability of · t· a m. With the OPP membrane acting as a gas barrier layer and its equivalent thickness of 25 μm, the oxygen permeability is 3.1 cc / m³. 2·day·atm.

[0125] f4:

[0126] use (SEISANNIPPONSHA LTD.), which is a bag made of a single layer of low-density polyethylene film (40 μm thick) with a zipper.

[0127] The oxygen permeability of a low-density polyethylene film at a thickness of 25 μm is 2000 cc / m³. 2 ·day·atm.

[0128] [Table 1]

[0129]

[0130] [Packaging Manufacturing and Evaluation]

[0131] As shown in Table 2, packaging bodies No.1 to No.6 are prepared by placing either the vinyl oxide-containing PVA resin powder or the unmodified PVA resin powder produced above into a bag body selected from f1 to f4, and closing the opening of the bag body by heat sealing or zipper.

[0132] The prepared packages were stored in a constant temperature chamber at 60°C for 1, 2, or 3 months. Subsequently, the PVA-based resin was removed from the packages, and the acid value, melt viscosity stability, and yellowness were checked according to the above measurement methods. Table 1 shows the structure and measurement results of each package. Furthermore, graphs showing the viscosity behavior of the vinyl oxide-containing PVA-based resin removed from packages No. 1 and No. 4 are respectively shown in... Figure 1 and Figure 2 In the graph, the vertical axis represents the instrument's torque (Nm), and the horizontal axis represents time (minutes).

[0133] [Table 2]

[0134]

[0135] ※OE Modification: Polyvinyl alcohol containing vinyl oxide

[0136] Unmodified: Unmodified polyvinyl alcohol

[0137] As can be seen from Table 2, using an oxygen permeability of 1000 cc / m 2 Packaging bodies (No. 1-No. 3) made of bags (f1, f2, or f3) with an oxygen permeability greater than 2000 cc / m³ are subject to acid value and use. 2 The acid value of the bag (f4) made of a membrane with an acid value of · atm changes less over time compared to the packaging (No.4).

[0138] Specifically, an oxygen permeability of 100 cc / m was used at a thickness including a thickness of 25 μm. 2 Packaging materials (No. 1 and 3) made of multi-layered films with oxygen barrier layers below 1 atm have less acid value change over time.

[0139] The effect of acid value changes over time can be seen from Figure 1 and Figure 2 We can understand this by considering the viscosity behavior within the medium. Figure 1 The viscosity behavior shown is almost unchanged between 1 month and 3 months, while Figure 2 The viscosity behavior shown indicates that the peaks shift to the left sequentially after 1, 2, and 3 months of storage. It is believed that in the case of package No. 4, carboxylation occurs due to the oxidation of vinyl oxides, leading to crosslinking of carboxyl groups with hydroxyl groups in the PVA-based resin during melt mixing, resulting in increased viscosity. Therefore, by using bags with low oxygen permeability, the formation of carboxyl-containing compounds derived from vinyl oxide-containing PVA-based resins within the package during storage can be suppressed. This is understandable from the fact that the viscosity behavior remains stable during melt mixing.

[0140] On the other hand, when using unmodified PVA-based resins, even when employing resins with an oxygen permeability greater than 2000 cc / m 2 In packaging (No. 6) made of a bag (f4) with a membrane of ·atom·atm, the acid value does not fluctuate. This fact also demonstrates that, in the case of packaging made of PVA-based resins containing oxidized alkenyl groups, the oxygen permeability of the bag is particularly affected.

[0141] Furthermore, regarding the packaging (No. 5) containing unmodified PVA-based resin in bag f1, an increase in acid value was observed. This is presumably due to the hydrolysis of residual acetic acid groups initiated by water remaining in the unmodified PVA-based resin, resulting in acetic acid. The generated acetic acid is volatile because it is a low molecular weight compound. This acetic acid derived from unmodified PVA-based resin can be distinguished from polymers containing carboxyl groups, which are produced from the reaction of oxidized alkenyl groups in PVA with oxygen. Polymers containing carboxyl groups cause increased viscosity, which is the problem this invention aims to solve. In other words, the problem solved by this invention does not involve acetic acid derived from unmodified PVA. Therefore, in the case of No. 5, no crosslinking reaction occurs regardless of whether the acid value increases, and the viscosity behavior is stable during melt mixing.

[0142] The YI value increases over time, but after 2 or 3 months of storage, the increase in coloring is suppressed to less than 1 / 2, preferably less than 1 / 3, when using packaging with bags of low oxygen permeability (f1 or f3) (No.1 or No.3) compared to packaging with bags of high oxygen permeability (f2 or f4) (No.2 or No.4). The level of coloring suppression is as good as that of unmodified PVA resin.

[0143] Industrial availability

[0144] According to the packaging of the present invention, oxidation of the oxidized alkenyl-containing PVA resin sealed within the packaging can be suppressed even during long-term storage. Therefore, if the packaging of the oxidized alkenyl-containing PVA resin is delivered to the user through the distribution process under harsh conditions, the user does not need to worry about workability issues during melt mixing and melt forming. Furthermore, since discoloration of the oxidized alkenyl-containing PVA resin due to storage of the packaging can be suppressed, the user of the oxidized alkenyl-containing PVA resin can be provided with articles having the properties expected from the inherent properties of the contained oxidized alkenyl-containing PVA resin.

Claims

1. A packaging body comprising: A bag made of a membrane, the membrane being able to permeate 1m of water within 24 hours at 25°C and 65% RH. 2 The oxygen permeability of the membrane's oxygen meter is 1000 cc / m. 2 ·days ·atoms and below; and The polyvinyl alcohol resin containing oxidized alkenyl groups contained within the bag.

2. The packaging body according to claim 1, wherein the polyvinyl alcohol resin containing oxidized alkenyl groups has a structural unit represented by general formula (3), wherein X is a single bond or a bonded chain, Y is a hydrogen atom or a methyl group, n is an integer from 1 to 50, and R 1 and R 2 Each is independently a hydrogen atom or an alkyl group.

3. The packaging body according to claim 1 or 2, wherein the film constituting the bag body is permeable to 1m³ within 24 hours at 40°C and 90% RH. 2 The water vapor permeability of the membrane is 300 g / m³. 2 Below the heavens.

4. The packaging body according to claim 1 or 2, wherein the film constituting the bag body is capable of permeating 1m³ of water within 24 hours at 25°C and 65% RH. 2 The oxygen permeability of the membrane's oxygen meter is 1000 cc / m. 2 Multilayer films with a time of less than 1000 atm.

5. The packaging body according to claim 4, wherein the multilayer film comprises a thickness equivalent to 25 μm, and is capable of permeating 1 m of material within 24 hours at 25°C and 65% RH. 2 The oxygen permeability of the membrane's oxygen meter is 100 cc / m. 2 A barrier layer below 1.5 ATM.

6. The packaging body according to claim 5, wherein the barrier layer is aluminum foil, aluminum vapor deposition layer, or biaxially stretched polypropylene film.

7. A method for manufacturing a packaging body, comprising encapsulating an oxidized alkenyl polyvinyl alcohol resin in a bag made of a film, said film being permeable to 1m³ within 24 hours at 25°C and 65% RH. 2 The oxygen permeability of the membrane's oxygen meter is 1000 cc / m. 2 ·day·atm and below.

8. The method for manufacturing a packaging body according to claim 7, wherein the polyvinyl alcohol resin containing oxidized alkenyl groups has a structural unit represented by general formula (3), wherein X is a single bond or a bonded chain, Y is a hydrogen atom or a methyl group, n is an integer from 1 to 50, and R 1 and R 2 Each is independently a hydrogen atom or an alkyl group.

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