Package made of oxyalkylene group-containing PVA based resin, and manufacturing method therefor

Abstract

To disclose a package that prevents a thickening problem from being generated when being melted and kneaded, even when being stored for a long time in a state of the package, in regard to an oxyalkylene group-containing PVA based resin; and to disclose a manufacturing method of the package therefor.SOLUTION: According to a package, an oxyalkylene group-containing PVA based resin is stored inside a bag body exhibiting an oxygen permeability of 1000 cc / m2 day atm or less as an oxygen amount permeated in 24 hours per m2 of a film under an environment of 25°C and 65% RH. According to the package, oxyalkylene group-containing PVA is prevented from being oxidized; and a carboxyl group-containing compound, that causes thickening when being melted and kneaded is prevented from being generated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a package capable of stably storing an oxyalkylene group-containing PVA resin, and a method for producing the same. [Background technology]

[0002] Polyvinyl alcohol resin (PVA resin) is usually shipped from the production site in the form of powder or pellets sealed in bags, i.e., as a package, and then distributed and traded on the market. Therefore, when the package reaches the user, the user removes the PVA resin from the package and uses it according to their intended purpose, and the package is stored in a container or warehouse, or if it is exported overseas, it is distributed in the packaged state for a long period of time.

[0003] After these distribution and storage processes, when users remove the PVA resin from the packaging and attempt to melt-mold it or prepare an aqueous solution depending on the intended use, defects that were not particularly recognized at the production site may occur. The causes and symptoms of defects vary depending on the type of PVA resin, storage period, distribution method, etc., but it is possible to prevent or suppress the occurrence of defects by devising packaging bags.

[0004] For example, in the case of acetoacetyl group-modified PVA resin powder, a crosslinking reaction occurs between the modified groups containing the active hydrogen atoms of the acetoacetyl groups during long-term storage, resulting in the formation of crosslinked products, which in turn produce insoluble components when the powder is dissolved in water. 2 It has been proposed to solve this problem by packaging the product in a packaging bag made of a film that has been in use for 10 days or less (Patent Document 1: WO2016 / 052446). Because the formation of such crosslinked products is particularly likely to occur when moisture is absorbed, the formation of crosslinked products during storage is avoided by using a packaging bag with low water vapor permeability.

[0005] On the other hand, when a user melt-processes a PVA resin, such as a PVA resin containing 1,2-glycol bonds in the side chain, the PVA resin (mainly powder or granules) fed into the melt-processing machine flows back together with the volatile components, causing the operation of the melt extruder to become unstable. This problem is believed to be caused by the residual volatile components, particularly methanol, used in the synthesis of the PVA resin, and therefore, the PVA resin should have a methanol vapor permeability of 0.5 to 1,000 g / m. 2 It has been proposed to solve this problem by using packaging bags made from recycled film (Patent Document 2: WO2017 / 104501).

[0006] Furthermore, PVA resins have the property of easily absorbing moisture, and if the volatile components (water) increase during melt molding as a result of moisture absorption, the PVA resin will flow back together with the water, just as with residual methanol, causing the problem of unstable operation of the melt extruder. For this reason, Patent Document 2 proposes the use of low-density polyethylene film bags as packaging bags that can reduce weight by suppressing water vapor permeation (moisture absorption) while allowing methanol vapor contained in the PVA resin to permeate.

[0007] However, when oxyalkylene group-containing PVA resins are stored or distributed for long periods of time in a package sealed in a low-density polyethylene bag, new problems have been discovered, such as thickening or discoloration, which can occur during the melt-kneading process required for melt molding by the user. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] WO2016 / 052446 publication [Patent Document 2] WO2017 / 104501 publication Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a package of an oxyalkylene group-containing PVA resin that is less likely to develop a problem of thickening during melt-kneading even when stored in the packaged state for a long period of time, and a method for producing the package. [Means for solving the problem]

[0010] The present inventors have conducted various studies on the problem of viscosity increase during melt-kneading of oxyalkylene group-containing PVA resins stored for long periods of time, and have concluded that the viscosity increase occurs because the oxyalkylene group portion reacts with oxygen as shown in the following formula to produce a compound having a carboxyl group, and the compound having a carboxyl group reacts with the hydroxyl group in the PVA resin molecule to form a crosslink, resulting in viscosity increase.

[0011] [ka]

[0012] Therefore, the present inventors have conducted research from the viewpoint of preventing oxidation of oxyalkylene group-containing PVA resins during storage, and as a result have arrived at the present invention.

[0013] That is, the packaging of the present invention is such that the film 1 m thick under an environment of 25°C and 65% RH 2 Oxygen permeability is the amount of oxygen that passes through per 24 hours. 2 A packaging body comprising a bag made of a film having a temperature of 100°C / day or less atm, and an oxyalkylene group-containing polyvinyl alcohol resin contained in the bag. The film may be a single-layer film or a multilayer structure.

[0014] The film was further subjected to a test under a temperature of 40°C and a relative humidity of 90% for 1 m of the film. 2 The water vapor permeability, as the amount of water vapor that passes through per 24 hours, is 300 g / m 2 ·day or less is preferable.

[0015] Another aspect of the present invention is a method for producing a packaging body, the method comprising:2 Oxygen permeability is the amount of oxygen that passes through per 24 hours. 2 The method includes a step of placing an oxyalkylene group-containing polyvinyl alcohol resin in a bag made of a film having a capacity of 1000 ppm or less.

[0016] In the present invention, the oxyalkylene group-containing polyvinyl alcohol resin generally refers to one having a structural unit represented by the following general formula (3):

[0017] [ka]

[0018] In formula (3), X is a single bond or a bonding chain, Y is a hydrogen atom or a methyl group, n is an integer of 1 to 50, and R 1 , R 2 are each independently a hydrogen atom or an alkyl group. [Effects of the Invention]

[0019] The package of the present invention and the package obtained by the manufacturing method of the present invention suppress oxidation of the oxyalkylene group-containing PVA resin contained therein, thereby suppressing thickening due to storage. Therefore, the package of the present invention can provide an oxyalkylene group-containing PVA resin in a state similar to that immediately after production, even if it is stored for a long period of time during distribution. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a graph showing the dynamic viscosity behavior of an oxyalkylene group-containing PVA resin taken out of package No. 1. [Figure 2] 1 is a graph showing the dynamic viscosity behavior of an oxyalkylene group-containing PVA resin taken out from package No. 4. DETAILED DESCRIPTION OF THE INVENTION

[0021] [Package of oxyalkylene group-containing PVA resin] The packaging of the present invention is a film of 1 m under an environment of 25°C and 65% RH. 2 Oxygen permeability is the amount of oxygen that passes through per 24 hours. 2 The present invention includes a bag body made of a film having a saturation of 1000 times the saturation temperature of 1000°C or less; and an oxyalkylene group-containing polyvinyl alcohol resin contained in the bag body.

[0022] <Oxyalkylene group-containing PVA resin> The oxyalkylene group-containing PVA resin contained in the package refers to a PVA resin that contains, in addition to the vinyl alcohol unit represented by the following general formula (1), which is the basic structural unit of the PVA resin, and the vinyl ester unit represented by the following general formula (2), which corresponds to the unsaponified portion when the saponification degree is less than 100%, and further contains an oxyalkylene group-containing unit represented by the following general formula (3). [ka] [ka] [ka]

[0023] The vinyl alcohol unit represented by formula (1) and the vinyl ester unit represented by formula (2) are derived from vinyl ester compounds used as raw material monomers for PVA resins. Examples of the vinyl ester compounds include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, and vinyl versatate, with vinyl acetate being preferred from the standpoint of economy.

[0024] Therefore, in equation (2), R a is an alkyl group having 1 to 18 carbon atoms, and depends on the vinyl ester compound used as a synthetic raw material for the PVA resin. ais preferably a methyl group, and a preferred vinyl ester unit is a vinyl acetate unit represented by the following formula (2'):

[0025] [ka]

[0026] The oxyalkylene group-containing unit represented by formula (3) is derived from an oxyalkylene group-donating vinyl monomer used in copolymerization with a vinyl ester monomer. The oxyalkylene group-donating vinyl monomer may be a compound in which an oxyalkylene group is bonded to a vinyl-containing group. Specifically, (meth)acrylic acid esters, (meth)acrylic acid amides, (meth)allyl ethers, vinyl ethers, etc., bonded to an oxyalkylene group may be used.

[0027] Therefore, in formula (3), Y is hydrogen or a methyl group, and X between the vinyl group and the oxyalkylene group is usually a single bond or a linking chain. Examples of linking chains include methylene groups, ethylene groups, ether bonds (-O-), amide bonds (-CONH-), ester bonds (-COO-), and -CHO-. Among these, methylene groups, ether bonds, and amide bonds are preferred because they have little effect on the properties of the PVA resin and the oxyalkylene group. Also, R 1 , R 2 Although the values ​​depend on the type of oxyalkylene group, they are usually each independently hydrogen or an alkyl group having 1 to 10 carbon atoms, and n is an integer of 1 to 50. Here, n is the average value of the oxyalkylene group-containing units in the polymer, and the individual oxyalkylene groups generally have a distribution of 1 to 100 repeating units as an integer. The average value of n can generally be measured by nuclear magnetic resonance spectroscopy (NMR).

[0028] The oxyalkylene group-containing PVA resin of the present invention is not particularly limited, but the oxyalkylene group content is usually 0.1 to 10 mol %, preferably 0.5 to 5 mol %. If the oxyalkylene group content is too high, it generally becomes difficult to obtain a PVA resin with a high degree of polymerization, and the desired physical properties of the product tend to be difficult to obtain. At the same time, the physical properties of the PVA resin (mechanical strength, gas barrier properties) tend to be impaired. On the other hand, if the oxyalkylene group content is too low, flexibility tends to decrease, the melting point tends to increase, and moldability tends to be impaired. Note that the oxyalkylene group content referred to in this specification is based on the charge ratio (mol %) in the vinyl monomer.

[0029] The saponification degree of the oxyalkylene group-containing PVA resin is usually 60 to 100 mol%, preferably 70 to 99 mol%, more preferably 80 to 95 mol%, and even more preferably 88 to 94 mol%. The saponification degree is appropriately selected depending on the desired water solubility. The saponification degree is determined from the amount of alkali consumption required for hydrolysis of residual acetate ester groups in the resin, and is measured in accordance with JIS K6726.

[0030] The average degree of polymerization of the oxyalkylene group-containing PVA resin (according to JIS K6726) is usually 100 to 3000, and preferably 200 to 1000. If the average degree of polymerization is too high, melt molding tends to become difficult, and if it is too low, strength tends to be insufficient.

[0031] In addition to the vinyl ester monomers and oxyalkylene group-donating vinyl monomers described above, the oxyalkylene group-containing PVA resins of the present invention may contain the following monomers (other monomers) copolymerized in an amount of, for example, 10 mol % or less, preferably 5 mol %, and particularly preferably 1 mol % or less: olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, and 3,4-dihydroxy-1-butene, as well as their acylated derivatives; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid, as well as their salts, monoesters, and dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; and acrylamide. olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, or their salts; alkyl vinyl ethers; vinyl compounds such as dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, and glycerin monoallyl ether; substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate, vinylidene chloride, 1,4-diacetoxy-2-butene, 1,4-dihydroxy-2-butene, and vinylene carbonate.

[0032] As the method for polymerizing and saponifying the vinyl monomers as described above, any method known in the art for producing polyvinyl alcohol can be used.

[0033] The oxyalkylene group-containing PVA resin having the above-mentioned structure has the property that the oxyalkylene group is easily oxidized and easily generates a compound having a carboxyl group. Here, compounds having a carboxyl group generated by oxidation of an oxyalkylene group include compounds in which the terminal primary hydroxyl group of the oxyalkylene group in a PVA resin is oxidized, as well as oxidative decomposition products of polyethylene glycol in which the oxyalkylene group in a PVA resin is hydrolyzed and detached from the main chain. Examples of oxidative decomposition products of polyethylene glycol include low-boiling point compounds such as acetic acid and long-chain high-boiling point compounds. Carboxylic acids, which are long-chain high-boiling point compounds, cause significant thickening during melt-kneading. The structure of the long-chain high-boiling compound having a carboxyl group depends on the type of oxyalkylene group in the oxyalkylene group-containing PVA resin used, but is usually a monocarboxylic acid or dicarboxylic acid having a repeating unit of an oxyalkylene group where n is an integer of 1 to 50. Examples of long-chain high-boiling compounds having a carboxyl group include monocarboxylic acids such as diethylene glycol monocarboxymethyl ether and triethylene glycol monocarboxymethyl ether, and dicarboxylic acids such as ethylene bisglycolic acid and diethylene glycol biscarboxymethyl ether.

[0034] The above-mentioned carboxyl group-containing compounds may cause coloration of the oxyalkylene group-containing PVA resin. Furthermore, when the above-mentioned carboxyl group-containing compounds are contained in the oxyalkylene group-containing PVA resin, the viscosity tends to increase during melt-kneading. In particular, carboxylic acids, which are long-chain high-boiling point compounds, cause significant viscosity increase during melt-kneading.

[0035] The acid value of the above-mentioned carboxyl group-containing compounds can usually be measured by the methods for determining the acid value in chemical products described in JIS K0070 (neutralization titration, potentiometric titration, or a gas chromatograph equipped with a mass spectrometer (GC-MS) in the case of low-boiling point compounds, or a high-performance liquid chromatograph equipped with a mass spectrometer (HPLC-MS) in the case of high-boiling point compounds).

[0036] The oxyalkylene group-containing PVA resin as described above is contained in the bag in the form of powder, granules, pellets, or the like.

[0037] <Bag body> The bag used in the packaging of the present invention is made of 1 m of film. 2 The oxygen permeability, which is the amount of oxygen that permeates per 24 hours (1 day) (25°C, 65% RH), is 1000cc / m 2 ·day·atm or less, preferably 500cc / m 2 ·day·atm or less, preferably 300cc / m 2 ·day·atm or less, more preferably 100cc / m 2 ·day·atm or less, particularly preferably 10cc / m 2 ·day·atm or less.

[0038] The film constituting the bag may be either a single-layer film or a multilayer structure. In the case of a multilayer structure, examples include a plastic film laminate having 2 to 10 layers, preferably 2 to 6 layers, of plastic film laminated together; a metal foil-attached film having a metal foil attached to a plastic film; a metal-deposited film having metal deposited on one or both sides of a plastic film; and a laminate having a plastic film laminated on a metal-deposited film or a metal foil-attached film. Furthermore, a protective sheet made of paper, nonwoven fabric, woven fabric or knitted fabric may be attached to the outer surface of the single layer film or multilayer structure.

[0039] In the case of a multilayer structure, the lamination method is not particularly limited, and may be a lamination method in which films are laminated together via an adhesive layer, a method in which a laminated film is produced by extruding a molten thermoplastic resin onto a base film, or a multilayer structure produced by co-extruding multiple types of thermoplastic resins.

[0040] In the case of a multilayer structure, one layer included in the structure may be a multilayer structure that includes an oxygen barrier layer that satisfies the above gas barrier properties, or the multilayer structure as a whole may satisfy the above oxygen barrier properties.

[0041] Examples of the oxygen barrier layer include metal foils such as aluminum foils, metal vapor-deposited layers of aluminum or the like, (biaxially) oriented polypropylene films, polyethylene terephthalate films, polyamide films, ethylene-vinyl alcohol (EVOH) films, vinylidene chloride films, etc. The oxygen barrier layer may be contained in a single layer or in a multilayer structure in combination of multiple layers.

[0042] Among the oxygen barrier layers, aluminum foil, aluminum vapor deposition layer, and biaxially oriented polypropylene film are particularly preferred. These have a thickness of 25 μm and are equivalent to 1 m of film. 2 The oxygen permeability, which is the amount of oxygen that permeates per 24 hours (1 day) (25°C, 65% RH), is 100cc / m 2 ·day·atm or less, preferably 10cc / m 2 Therefore, by using such a multilayer structure having gas barrier properties, it is possible to select a layer structure according to desired properties other than oxygen gas barrier properties, such as flexibility, strength, weight as a bag, and ease of handling.

[0043] As described above, the oxyalkylene groups in oxyalkylene-containing PVA resins are easily oxidized, generating carboxyl-containing compounds. The generated carboxyl groups then undergo crosslinking reactions with OH groups in the PVA molecular chain or with OH groups in PVA resins with different molecular chains. Since the generated crosslinked products are thought to be the cause of thickening during melt-kneading, preventing an increase in the oxygen concentration in the package is thought to suppress the oxidation of oxyalkylene groups, and thus the thickening during melt-kneading. Furthermore, since carboxyl group-containing compounds cause discoloration of PVA-based resins, suppressing the generation of carboxyl group-containing compounds suppresses discoloration, and as a result, prevents deterioration in the quality of PVA-based resin molded products such as films.

[0044] The film constituting the bag of the present invention is further 2The water vapor permeability is 300g / m², which is the amount of water vapor that permeates per 24 hours (1 day) (40°C, 90% RH). 2 1 day or less, and more preferably 200 g / m 2 ·day or less, more preferably 100g / m 2 ·day or less, particularly preferably 10 g / m 2 ·day or less. Like other PVA resins, oxyalkylene group-containing PVA resins have the property of easily absorbing moisture. Moisture absorption plasticizes the PVA resin, increasing the reactivity of the oxyalkylene groups, which tends to cause oxidation reactions with oxygen and generate decomposition products. Furthermore, moisture absorption can cause PVA resin powders or pellets to stick together, forming agglomerates. From this perspective, the lower the water vapor permeability of the film constituting the bag used, the better.

[0045] The thickness of the film constituting the bag is related to oxygen permeability, strength, flexibility, and ease of handling, and is therefore selected appropriately depending on the type of film. In the case of a multilayer structure having a gas barrier layer, the total thickness is usually 20 to 500 μm, preferably 30 to 200 μm. If the thickness is too large, the bag becomes heavy and flexibility tends to be impaired. On the other hand, in the case of a multilayer structure having a gas barrier layer, a predetermined gas barrier property can be achieved even when the structure is thin, and the necessary strength can be ensured by laminating a protective sheet such as paper or fabric. When a protective sheet is laminated, the total thickness may exceed 500 μm as long as the handling properties, such as flexibility, of the bag and the handling properties of the package are not impaired.

[0046] The bag used in the packaging of the present invention is formed by molding the above-mentioned film into a bag shape. The form and shape of the bag may be any as long as it can seal the contents. Specific examples include three-sided sealed bags in which both sides and the bottom of the bag are heat-sealed; side-sealed bags in which the bag is folded in half and both sides are heat-sealed; bags made by sealing and cutting two overlapping films into an L-shape so that two adjacent sides form openings; bottom-gusseted bags with a gusset on the bottom as packaging bags; side-gusseted bags with gussets on both sides; and bags with a zipper or fastener at the opening.

[0047] Such a bag may be formed by heat-sealing the film that constitutes the bag, or in the case of a single-layer film, by extruding the thermoplastic resin that is the raw material for the film into a tubular shape through a ring die by inflation molding.

[0048] There are no particular limitations on the method for closing the opening of the bag, and various methods such as heat sealing, adhesive, or sealing with a zipper or zip lock can be applied, and an appropriate method can be selected depending on the configuration of the bag.

[0049] The shape of the bag is generally rectangular, with long sides of 50 to 150 cm and short sides of 30 to 80 cm, so that the contents can be 10 to 30 kg in a typical distribution format.

[0050] <Other storage items> In the package of the present invention, the following may be enclosed together with the desired oxyalkylene group-containing PVA resin.

[0051] (1) PVA resins other than oxyalkylene group-containing PVA resins As PVA resins other than the oxyalkylene group-containing PVA resin, unmodified PVA resins and other modified PVA resins (collectively referred to as "other PVA resins") may be stored together. These other PVA resins are stored in the form of powder, granules, pellets, etc.

[0052] When the oxyalkylene group-containing PVA resin is stored as a mixture with other PVA resins, the content of the oxyalkylene group-containing PVA resin in the PVA resin content of the package should 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.

[0053] (2) Antioxidants Examples of antioxidants include dibutylhydroxytoluene, butylhydroxyanisole, and tocopherol. Such antioxidants may be stored as a mixture by mixing a powder, pellet, or granular antioxidant with a powder or pellet-like oxyalkylene group-containing PVA-based resin, or individually packaged pellet or granular antioxidants may be stored in a container together with the oxyalkylene group-containing PVA-based resin. The amount of the antioxidant enclosed in the package is 1 to 10,000 ppm, preferably 1 to 1,000 ppm, and more preferably 5 to 500 ppm, relative to the oxyalkylene group-containing PVA resin.

[0054] (3) Other storage items In addition to the above, a desiccant for preventing moisture absorption by the PVA resin, a lubricant for improving processing characteristics during melt molding, etc. may be contained within the range that does not impair the effects of the present invention. These may be mixed in the form of powder, pellets, or granules with the powder or pellet-like oxyalkylene group-containing PVA resin and contained as a mixture, or individually packaged items of other contents may be contained in the housing together with the oxyalkylene group-containing PVA resin.

[0055] <Package> The oxyalkylene-containing PVA resin as described above, and the stored items stored together as necessary, are stored in a container having an oxygen permeability of 1000cc / m 2 The package of the present invention can be produced by placing the product in a bag with a temperature of 100°C or less and sealing the opening.

[0056] The contents (packaged items) are placed through the opening of the bag, and then the opening is closed. The opening can be closed using adhesive, heat sealing, a zipper, or a zipper, depending on the type of bag.

[0057] In the package having the above-described configuration, even if the package is stored for one to several months from the time of shipment from the manufacturing site until the user removes the PVA resin (oxyalkylene group-containing PVA resin) contained therein for melt molding, oxidation of the oxyalkylene group-containing PVA resin is prevented, and therefore unexpected thickening does not occur during melt mixing.

[0058] [Method for manufacturing packaging body] The present invention is a method for measuring the temperature of a film of 1 m under an environment of 25°C and 65% RH. 2 Oxygen permeability is the amount of oxygen that passes through per 24 hours. 2 The present invention also encompasses a method for producing a package, which includes a step of placing an oxyalkylene group-containing polyvinyl alcohol resin in a bag made of a film having a viscosity of 1000 psi or less.

[0059] As the bag used in the manufacturing method of the present invention, the bag described in the packaging body of the present invention can be used. The oxyalkylene group-containing polyvinyl alcohol resin contained in the bag is the oxyalkylene group-containing polyvinyl alcohol resin described in the package of the present invention. When other stored items such as those listed in the package of the present invention are also stored, they may be filled as a mixture with the oxyalkylene group-containing polyvinyl alcohol resin, or before or after storing the oxyalkylene group-containing polyvinyl alcohol resin.

[0060] After the contents are stored, the opening of the bag is closed. The method of storing the contents and sealing the opening is selected appropriately depending on the type and shape of the bag used. Depending on the type of bag, sealing may be done with a heat seal, a zipper, a zipper, or an adhesive. [Example]

[0061] [Measurement and evaluation method] 1. Oxygen permeability (cc / m 2 ·day·atm) The film that makes up the bag is subjected to 1m of storage at 25°C and 65% RH for 24 hours. 2 The oxygen permeation rate per unit area was measured using the MOCON method (OXTRAN coulometric method) in accordance with JIS7126-2.

[0062] 2. Water vapor permeability (g / m 2 ·day) The film that makes up the bag is measured at 40°C and 90% RH for 1 m of the target film. 2 The water vapor permeation rate per 1000 ml of fabric for 24 hours was measured using the cup method in accordance with JIS Z0208.

[0063] 3. Acid value (mgKOH / mg) A package containing PVA resin (powder particles passed through a mesh with 2800 μm openings) immediately after production was stored in a 60°C air dryer for a certain period (1 month, 2 months, or 3 months), and then the PVA resin was removed from the package and its acid value was measured by potentiometric titration in accordance with JIS K0070. A high acid value means a high content of carboxyl group-containing compounds, indicating that the oxidation of oxyalkylene groups has progressed.

[0064] 4. Melt viscosity stability Freshly manufactured PVA-based resin (powdered particles passed through a 2800 μm mesh) was packed in a sealed package and stored for a set period (1, 2, or 3 months). The PVA-based resin was then removed from the packaging and compared for changes in dynamic viscosity behavior over time in the molten state. The test was performed using a Brabender Lab Plastomill (PLASTOGRAPH EC PLUS). The viscosity behavior was measured after mixing for 2 hours at 210°C and 50 rpm, and a graph was created showing the relationship between mixing time and the torque of the mill. The time (in minutes) to reach the viscosity peak (maximum torque) was also calculated and used as an index of melt viscosity stability. Increased torque indicates increased viscosity of the molten resin. The peak time was compared with the peak time of the PVA-based resin immediately after production.

[0065] 5. Yellowness index (YI value) Packages containing PVA resin (powdered after passing through a mesh with 2800 μm openings) immediately after production were stored for a certain period (1 month, 2 months, or 3 months), and then the PVA resin was removed from the packaging bag, and the yellowness index (YI value) of each was measured using a spectrophotometer SE6000 manufactured by Nippon Denshoku Industries Co., Ltd. The YI value data used was the ΔYI ASTM (D1925) value.

[0066] [Storage items] The contents of the package, that is, the stored material, were powders of oxyethylene group-containing PVA resins or unmodified polyvinyl alcohol as follows.

[0067] (1) Oxyethylene group-containing PVA resin A polymerization vessel was charged with 8.6 parts (1 mol % relative to the charged vinyl acetate) of an oxyethylene group-containing monomer (polyoxyethylene allyl ether with an average chain length n = 15), 35 parts of vinyl acetate, and 15 parts of methanol. The temperature was raised to reflux, and then 0.3 mol % (relative to the total vinyl acetate) of azobisisobutyronitrile was added. The polymerization reaction was then allowed to proceed, and 65 parts of vinyl acetate (65% of the total charge) was added dropwise to the polymerization vessel at a constant rate to obtain a methanol solution of oxyethylene group-containing polyvinyl acetate. The oxyethylene group-containing polyvinyl acetate was then alkali-saponified with sodium hydroxide to obtain the desired oxyethylene group-containing PVA resin.

[0068] The stored material was the oxyethylene group-containing PVA resin (powdered after passing through a mesh with an opening of 2800 μm) obtained above, which had an oxyethylene group content of 1 mol%. The saponification degree of this oxyethylene group-containing PVA resin was 93.5 mol%, and the average polymerization degree was 550. The saponification degree was determined in accordance with JIS K6726 from the amount of alkali consumed for the hydrolysis of the remaining vinyl acetate. The average polymerization degree was determined in accordance with JIS K6726. The volatile content (water, methanol) of this oxyethylene group-containing PVA resin was 4% by weight.

[0069] The acid value of the oxyethylene group-containing PVA resin immediately after production, measured using the above-mentioned measurement method, was less than 0.05 mg KOH / mg (below the detection sensitivity). The time to peak determined from the melt viscosity stability test was 94 minutes. The ΔYI ASTM (D1925) value was 5.8.

[0070] (2) Unmodified polyvinyl alcohol resin It is an unmodified polyvinyl alcohol resin with a degree of saponification of 88 mol% measured in accordance with JIS K6726, an average degree of polymerization of 500 determined in accordance with JIS K6726, and a volatile content (water, methanol) of 4% by weight.

[0071] The acid value of the unmodified PVA resin immediately after production, measured using the above method, was 0.37 mg KOH / mg. This was higher than the acid value of the oxyethylene group-containing PVA resin immediately after production, presumably because the acetyl groups in the unsaponified portion were hydrolyzed to produce acetic acid. The time to peak determined from the melt viscosity stability test was 76 minutes. The ΔYI ASTM (D1925) value was 6.2.

[0072] [Bag body] The following four types of bags (f1-f4) were used. The oxygen permeability and water vapor permeability of the film constituting each bag were as shown in Table 1.

[0073] f1: ALH-8 aluminum standard vacuum packaging bag (Tokyo Glass Equipment Co., Ltd., a three-sided sealed bag made of a multi-layered film (total thickness 116 μm) with a multi-layer structure of polyethylene terephthalate (12 μm) / aluminum (9 μm) / polyamide (15 μm) / unstretched polypropylene (80 μm) from the inside of the bag). The oxygen permeation rate of the aluminum foil that makes up the gas barrier layer (equivalent to a thickness of 25 μm) is below the detection limit (0.01 cc / m 2 The oxygen permeability of the film (thickness 116 μm) constituting the bag was also below the detection limit.

[0074] f2: A three-sided sealed bag made of five-layer film (total thickness 71μm) with the following layer structure (the left side is the inside of the bag) obtained by co-extrusion of polyamide (PA), adhesive resin, and polyethylene (PE) using a three-type five-layer extruder. PA / PA / adhesive / PE / PE (total thickness of PA layer: 53 μm, total thickness of PE layer: 15 μm) The oxygen permeability of the bag's constituent film (total thickness 71 μm) is 61 cc / m 2 ·day·atm, and the oxygen permeability of the polyamide film that constitutes the gas barrier layer (converted to a thickness of 25 μm) is 129 cc / m 2 ·day·atm.

[0075] f3: This is a three-sided sealed bag made of a laminated film (60 μm thick) dry-laminated from biaxially oriented polypropylene (OPP) film (20 μm thick) and unoriented polypropylene (unoriented PP) film (40 μm thick), with the OPP film on the inside of the bag. The oxygen permeability of the film that makes up the bag (thickness 60 μm) is 3.9 cc / m 2 ·day·atm, and the oxygen permeability of the OPP film that forms the gas barrier layer (converted to a thickness of 25 μm) is 3.1 cc / m 2 ·day·atm.

[0076] f4: The bag is a Unipack (registered trademark) with a zipper manufactured by Japan Co., Ltd. The film that makes up the bag is a single layer of low-density polyethylene (thickness 40 μm). Oxygen permeability of 2000cc / m converted to a 25μm thickness of low-density polyethylene film 2 ·day·atm.

[0077] [Table 1]

[0078] [Packaging Creation and Evaluation] As shown in Table 2, packages No. 1 to No. 6 were produced by using any of the bags f1 to f4, placing the oxyethylene group-containing PVA resin powder or unmodified PVA resin powder synthesized above as the packaged item, and sealing the opening by heat sealing or zipper. The resulting packages were left in a thermostatic oven at 60°C for one, two, or three months, after which the PVA resins were removed from the packages and examined for acid value, melt viscosity stability, and yellowness index using the methods described above. Table 1 shows the structure of each package and the results of the measurements. Figures 1 and 2 show graphs showing the viscosity behavior of the oxyethylene group-containing PVA resins removed from packages No. 1 and No. 4, respectively. In the figures, the vertical axis represents the torque (Nm) of the device, and the horizontal axis represents time (minutes).

[0079] [Table 2]

[0080] As can be seen from Table 2, the oxygen permeability is 1000cc / m 2 Packaging (No. 1-No. 3) using bags (f1, f2, f3) made of films with an oxygen permeability of 2000cc / m 2 Compared to the packaging (No. 4) using a bag (f4) made of a film exceeding 10 ...

[0081] In particular, the oxygen permeability when converted to a thickness of 25 μm is 100 cc / m 2 The change over time in acid value of the packaging (No. 1, 3) of the bag (f1, f3) made of a multilayer structure including an oxygen barrier layer of 1000 kJ / day atm or less was small.

[0082] The effect of changes in acid value over time was confirmed by the viscosity behavior in Figures 1 and 2. In other words, while the viscosity behavior in Figure 1 showed almost no change between 1 month and 3 months, the peak value shifted to the left after 1 month, 2 months, and 3 months in the viscosity behavior in Figure 2. In package No. 4, carboxylation progressed due to the oxidation of oxyethylene groups, which likely led to crosslinking with hydroxyl groups in the PVA-based resin during melt-kneading, resulting in increased viscosity. Therefore, it can be seen that packaging in a packaging bag with low oxygen permeability can suppress the generation of carboxyl-containing compounds during storage of the oxyethylene-containing PVA-based resin, thereby stabilizing the viscosity behavior during melt-kneading.

[0083] On the other hand, if the contents are made of unmodified PVA resin, the oxygen permeability is 2000cc / m 2 Even in the case of the package (No. 6) using a bag (f4) made of a film exceeding 1000 kJ / day atm, there was almost no change in the acid value, which shows that the effect of the bag's oxygen permeability is unique to cases where the contents are PVA-based resins containing oxyalkylene groups.

[0084] In addition, the acid value of the package (No. 5), in which the unmodified PVA resin was packaged in the bag f1, increased. This is presumably due to the hydrolysis of residual acetate groups due to residual moisture in the unmodified PVA resin, resulting in the generation of acetic acid. The acid generated here is a volatile, low-molecular-weight compound, such as acetic acid, and is therefore distinct from the carboxyl-containing polymeric compounds that cause thickening, i.e., polymeric compounds that are generated as a result of the reaction of oxyalkylene-containing PVA with oxygen. Therefore, although the acid value increased in No. 5, the viscosity behavior during melt-kneading was stable because no crosslinking reaction occurred.

[0085] The YI value increased over time, but after storage for two and three months, the increase in the YI value for packages (No. 1 and No. 3) using bags with low oxygen permeability (f1 and f3) was less than half, and in favorable cases less than one-third, of the increase in the YI value for packages (No. 2 and No. 4) using bags with high acid permeability (f2 and f4), indicating that discoloration was suppressed. The level of discoloration suppression was comparable to that of unmodified PVA resin. [Industrial Applicability]

[0086] The package of the present invention can suppress oxidation of the oxyalkylene group-containing PVA resin as the enclosed substance even when stored in the package for a long period of time, thereby avoiding problems with workability during melt-kneading and melt-molding when the PVA resin is delivered to the user after passing through a distribution process under harsh conditions. Furthermore, coloration due to storage can be suppressed, so that users can provide PVA resin products of the quality originally expected by using the PVA resin stored in the package of the present invention.

Claims

1. 1m of film under 25℃, 65%RH environment ２ Oxygen permeability is 1000cc / m as the amount of oxygen permeating per 24 hours ２ A bag made of a film of 10 ... The oxyalkylene group-containing polyvinyl alcohol resin contained in the bag A package comprising:

2. 2. The packaging material according to claim 1, wherein the oxyalkylene group-containing polyvinyl alcohol resin has a structural unit represented by the following general formula (3): 【Chemistry 3】 (In formula (3), X is a single bond or a bonded chain, Y is a hydrogen atom or a methyl group, n is an integer of 1 to 50, and R １ , R ２ are each independently a hydrogen atom or an alkyl group.

3. The film constituting the bag body was measured under an environment of 40°C and 90% RH for 1 m of the film. ２ The water vapor permeability, as the amount of water vapor that permeates per 24 hours, is 300 g / m ２ 3. The package according to claim 1 or 2, wherein the shelf life is 10 days or less.

4. The film constituting the bag body is resistant to aging for 1 m under an environment of 25°C and 65% RH. ２ Oxygen permeability is 1000cc / m as the amount of oxygen permeating per 24 hours ２ The packaging body according to any one of claims 1 to 3, which is a multilayer film having a capacity of 10 ...

5. The multilayer film has a thickness of 25 μm and a film thickness of 1 m under an environment of 25° C. and 65% RH. ２ Oxygen permeability is the amount of oxygen that permeates per 24 hours. ２ 5. The package of claim 4, which is a multi-layer structure including a barrier layer having a temperature of not more than 100°C.

6. 6. The package according to claim 5, wherein the barrier layer is an aluminum foil, an aluminum vapor deposition layer, or a biaxially oriented polypropylene film.

7. 1m of film under 25℃, 65%RH environment ２ Oxygen permeability is 1000cc / m as the amount of oxygen permeating per 24 hours ２ A method for producing a package, comprising a step of placing an oxyalkylene group-containing polyvinyl alcohol resin in a bag made of a film having a capacity of 1000 ppm or less.

8. The method for producing a packaging body according to claim 7, wherein the oxyalkylene group-containing polyvinyl alcohol resin has a structural unit represented by the following general formula (3): 【Chemistry 3】 (In formula (3), X is a single bond or a bonded chain, Y is a hydrogen atom or a methyl group, n is an integer of 1 to 50, and R １ , R ２ are each independently a hydrogen atom or an alkyl group.

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