Water-soluble film and package

Abstract

Provided is a water-soluble film that maintains excellent solubility in water and has excellent heat sealability at high speed, and a package using the same. The water-soluble film of the present invention contains a polyvinyl alcohol-based resin. A first melting temperature Tm1, which is determined from a melting curve when temperature is raised at 500°C / sec to 200°C after conditioning at a temperature of 20°C and a relative humidity of 60% for 24 hours, and a second melting temperature Tm2, which is determined from a melting curve when temperature is cooled at 100°C / sec to 0°C after the temperature raising and then raised at 100°C / sec to 200°C, satisfy the following relationships (1) and (2). 105°C ≤ Tm1 ≤ 165°C …… (1) Tm3 - Tm1 ≥ 20°C …… (2).

Description

Technical Field

[0001] This invention relates to a water-soluble film containing polyvinyl alcohol resin and a packaging body using the same. Background Technology

[0002] In the past, water-soluble films have been used in a wide range of fields, such as packaging of various agents, pesticides and fungicides, as well as seed strips containing seeds, due to their excellent solubility in water.

[0003] In water-soluble films used for this purpose, polyvinyl alcohol resin (hereinafter sometimes referred to as PVA) is mainly used. Furthermore, films whose water solubility is improved by incorporating various additives such as plasticizers or by using modified polyvinyl alcohol have been proposed (e.g., Patent Document 1).

[0004] Previous technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-078166 Summary of the Invention

[0007] The technical problem to be solved by the invention

[0008] In the manufacture of pharmaceutical packaging using water-soluble films, sealing via heat pressing (hereinafter sometimes referred to as heat sealing) is sometimes used. Heat sealing typically takes several seconds, but in recent years, to further improve production efficiency, water-soluble film pharmaceutical packaging has been manufactured by high-speed heat pressing of the film at high temperatures for a very short time of one second or less. However, in the case of high-speed heat sealing of water-soluble films, if the sealing part does not melt rapidly, the seal deteriorates, sometimes leading to problems such as leakage of the contents of the pharmaceutical packaging. On the other hand, if plasticizers or the like are added to the film-forming solution of the water-soluble film to improve its heat-sealing performance at high speeds, making the water-soluble film easier to melt, the molten film sometimes adheres to the heat-pressing mold, resulting in film defects in the pharmaceutical packaging. Furthermore, considering various applications such as pharmaceutical packaging, excellent water solubility is a fundamental physical property required for water-soluble films. Therefore, a water-soluble film with excellent water solubility and excellent heat-sealing performance at high speeds is needed.

[0009] means for solving technical problems

[0010] As mentioned above, sealing via hot pressing of water-soluble films involves pressing the films at high speeds in a very short time. Therefore, the PVA in the water-soluble film undergoes repeated crystallization and melting processes instantaneously. Thus, to obtain good heat-sealing properties at high speeds, it is crucial to understand the melting behavior of the PVA crystals in the film.

[0011] Among the methods for measuring the melting temperature of polymer crystals in thin films, there is a method using a differential scanning calorimeter (hereinafter, sometimes referred to as DSC). When measuring a water-soluble thin film containing PVA using this method, the temperature at which the PVA crystals begin to melt (melting temperature, hereinafter sometimes referred to as Tm) and the heat generated during melting (heat of fusion, hereinafter sometimes referred to as ΔH) can be evaluated by observing the endothermic / exothermic peaks.

[0012] However, in typical DSC measurements, a heating rate of several °C / s is the limit. At such low heating rates, when measuring water-soluble films containing PVA with moisture content, water evaporation occurs during the heating process before the PVA melts, leading to PVA recrystallization. Therefore, it is impossible to determine the original amount of PVA crystals in the film, its melting temperature, or the film's behavior at heating rates such as instantaneous melting.

[0013] In recent years, it has become possible to perform analysis at heating rates of hundreds of °C / second using a device called ultra-high-speed differential scanning calorimetry (hereinafter, sometimes referred to as flash DSC). Using this device, for the first time, it has been possible to understand the melting behavior of water-soluble films containing PVA, such as heat sealing, under high-speed conditions, caused by the instantaneous heat received. The inventors conducted an in-depth study using flash DSC on the relationship between the analytical results of water-soluble films under various measurement conditions and their heat-sealing properties at high speeds. They discovered that by setting the melting temperature at the first heating stage and the difference between that melting temperature and the melting temperature at the second heating stage within a specific range when repeatedly heating / cooling and measuring, good heat-sealing properties at high speeds were achieved. Based on this insight, further research was conducted, leading to the completion of this invention.

[0014] That is, the present invention relates to the following [1] to [7]. [1]

[0016] A water-soluble film containing polyvinyl alcohol resin.

[0017] The first melting temperature Tm1 and the second melting temperature Tm2 satisfy the following relationship (1) and (2). The first melting temperature Tm1 is determined by the melting curve when the temperature is increased to 200°C at 500°C / second after 24 hours of conditioning at 20°C and 60% relative humidity. The second melting temperature Tm2 is determined by the melting curve when the temperature is increased, cooled to 0°C at 100°C / second, and then increased to 200°C at 100°C / second.

[0018] 105℃≤Tm1≤165℃……(1)

[0019] Tm2-Tm1≥20℃……(2) [2]

[0021] According to the water-soluble film described above [1], wherein,

[0022] The second melting temperature Tm2 is above 150°C and below 180°C. [3]

[0024] According to the water-soluble film described in [1] or [2] above, wherein,

[0025] The first melting heat ΔH1, calculated from the melting curve measured at Tm1, is above 2 J / g and below 15 J / g. [4]

[0027] The water-soluble film according to any one of [1] to [3] above, wherein,

[0028] The resin contains 10 to 50 parts by weight of plasticizer relative to 100 parts by weight of the polyvinyl alcohol resin. [5]

[0030] A type of packaging, wherein,

[0031] The water-soluble film described in any one of [1] to [4] above contains a pharmaceutical agent. [6]

[0033] According to the packaging body described above [5], wherein,

[0034] The agent is a pesticide, detergent, or fungicide. [7]

[0036] The packaging body described in [5] or [6] above is made by heat sealing.

[0037] Invention Effects

[0038] According to the present invention, a water-soluble film with excellent solubility in water and excellent heat-sealing properties at high speeds is provided, as well as a packaging body using the same. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the melting curve of the water-soluble film of the present invention obtained by an ultra-high-speed differential scanning calorimetry device. Detailed Implementation

[0040] The present invention will now be described in detail.

[0041] The water-soluble film of the present invention contains PVA. The first melting temperature Tm1 and the second melting temperature Tm2 satisfy the following relationship (1) and (2). The first melting temperature Tm1 is determined by the melting curve when the temperature is increased to 200°C at 500°C / second after 24 hours of conditioning at 20°C and 60% relative humidity. The second melting temperature Tm2 is determined by the melting curve when the temperature is increased to 0°C at 100°C / second and then increased to 200°C at 100°C / second.

[0042] 105℃≤Tm1≤165℃……(1)

[0043] Tm2-Tm1≥20℃……(2)

[0044] The aforementioned heating and cooling rates can be achieved, for example, using an ultra-high-speed differential scanning calorimetry (flash DSC) device. A schematic diagram of the melting curve obtained by flash DSC is shown below. Figure 1 In this context, the vertex of the curve representing the protrusion is defined as the melting temperature (Tm) of the thin film. Furthermore, the area enclosed by the melting curve and the baseline is defined as the heat of melting of the measured sample.

[0045] The baseline above is a straight line connecting the heat flux values ​​in the range of 100°C to 200°C.

[0046] The aforementioned apparatus employs a mechanism that allows the sample to directly contact the sensor, enabling measurements with sample quantities in the hundreds of ng range. Therefore, the thermal conductivity between the sample and the sensor is excellent, allowing for ultra-high-speed heating. For the sample piece used in the measurement, the film thickness and slice size are measured, and the weight of the sample is calculated per unit weight. For the sample piece size, a film thickness of approximately 30 to 100 μm and a slice size of approximately 50 to 100 μm are preferred as they facilitate measurement. The heat of fusion, ΔH (J / g), can be obtained by dividing the weight of the measured sample by its heat of fusion. The melting temperature (Tm) and heat of fusion (ΔH) can be determined from the obtained melting curve using conventionally known methods, but are typically calculated using analysis software attached to the apparatus.

[0047] Typically, melting temperature and heat of fusion are affected by the temperature and moisture content of the sample being measured. Therefore, when measuring melting temperature, by placing the sample under constant temperature and humidity conditions for a constant time and conditioning the sample, the deviation of the measurement results is reduced. Based on the above viewpoint, in this invention, the sample is conditioned for 24 hours at 20°C and 60% relative humidity before measuring melting temperature, and then the melting temperature and heat of fusion are measured under the aforementioned heating and cooling conditions.

[0048] In this invention, the melting temperature Tm determined based on the melting curve (hereinafter sometimes referred to as the first heating curve) obtained by heating from 500°C / second to 200°C is used as the first melting temperature Tm1. Tm1 is 105°C or higher and 165°C or lower, preferably 110°C or higher, and more preferably 150°C or lower. If Tm1 is lower than the above range, the water-soluble film easily melts at low temperatures, and therefore, during heat sealing, the molten film adheres to the heat-sealing mold portion, easily causing film defects. On the other hand, if Tm1 exceeds the above range, the PVA crystals in the water-soluble film do not melt during high-speed heat sealing, and the sealing strength of the water-soluble film may not be sufficiently obtained.

[0049] After heating to 200°C, it is preferable to maintain the temperature at 200°C for about a few seconds. There is no particular limitation on the holding time, but it is usually preferable to maintain it for 0.05 seconds to 1 second, and more preferably for 0.05 seconds to 0.5 seconds.

[0050] After the initial heating described above, the temperature is cooled to 0°C at a rate of 100°C / second. After cooling to 0°C, it is preferable to maintain the temperature at 0°C for approximately several seconds. There is no particular limitation on the holding time, but it is generally preferable to maintain it for 0.05 seconds to 1 second, and more preferably for 0.05 seconds to 0.5 seconds.

[0051] In this invention, the melting temperature Tm, determined based on the melting curve (hereinafter sometimes referred to as the second heating curve) obtained by heating to 200°C again at 100°C / second after the aforementioned cooling, is taken as the second melting temperature Tm2. In this invention, the difference between Tm2 and Tm1 (Tm2-Tm1) is 20°C or more. It is believed that if Tm2-Tm1 is large, the structural changes of PVA crystals in the water-soluble film during melting are significant, thus ensuring sufficient sealing strength even when the water-soluble film is heat-sealed at high speed. Tm2-Tm1 is preferably 30°C or more, more preferably 40°C or more. There is no particular limitation on the upper limit of Tm2-Tm1; it is typically 75°C, preferably 60°C.

[0052] The Tm2 mentioned above is preferably 150°C or higher and 180°C or lower. If Tm2 is lower than 150°C, the sealing strength may be insufficient due to the insufficient mechanical strength of the water-soluble film. On the other hand, if Tm2 exceeds 180°C, the water-soluble film may be insufficiently soluble in water.

[0053] In this invention, the melting heat ΔH obtained from the first heating curve obtained during the above-mentioned Tm1 measurement is used as the first melting heat ΔH1. ΔH1 is preferably 2 J / g or more and 15 J / g or less. If ΔH1 is lower than the above range, sometimes the molten film adheres to the hot-pressing mold portion during heat sealing of the water-soluble film, resulting in film defects. On the other hand, if ΔH1 exceeds the above range, insufficient heat is required during high-speed heat sealing of the water-soluble film, causing the PVA crystals in the water-soluble film to not melt, sometimes resulting in poor sealing.

[0054] In this invention, the heat of fusion ΔH obtained from the second heating curve obtained during the above-mentioned Tm2 measurement is used as the second heat of fusion ΔH2. ΔH2 is preferably 2 J / g or more and 20 J / g or less. If ΔH2 is below this range, the seal deteriorates, and the contents may sometimes leak from the water-soluble film packaging. On the other hand, if ΔH2 exceeds this range, the water solubility of the sealing portion of the water-soluble film packaging is insufficient, and sometimes residual solvent may be generated.

[0055] In this invention, it is important to control the parameters such as Tm1 and Tm2 as described above within the aforementioned ranges. Methods for controlling these parameters include, for example, adjusting the type of PVA (degree of saponification, degree of modification, mixing ratio of unmodified PVA / modified PVA, etc.); adjusting the type or amount of plasticizer; adjusting film manufacturing conditions (surface temperature of the support, heat treatment conditions, etc.); or a combination of the above methods.

[0056] Polyvinyl alcohol resins

[0057] The PVA contained in the water-soluble film of the present invention can be a polymer manufactured by saponifying a vinyl ester polymer obtained by polymerizing vinyl ester monomers.

[0058] Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl 2,2-dimethylpropionate, and vinyl tert-carbonate. Of these, vinyl acetate is preferred as the vinyl ester monomer.

[0059] Vinyl ester polymers are not particularly limited, but polymers obtained by using only one or more vinyl ester monomers as monomers are preferred, and polymers obtained by using only one vinyl ester monomer as monomers are more preferred. Furthermore, vinyl ester polymers can be copolymers of one or more vinyl ester monomers and other monomers capable of copolymerizing with one or more vinyl ester monomers.

[0060] Other monomers include, for example, ethylene; olefins with 3 to 30 carbon atoms such as propylene, 1-butene, and isobutene; acrylic acid or its salts; acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid or its salts; methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid or its salts, dimethylaminopropylacrylamide or its salts, and N-hydroxymethylacrylamide or its derivatives. Bio-based acrylamide derivatives; methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid or its salts, dimethylaminopropylmethacrylamide or its salts, N-hydroxymethylmethacrylamide or its derivatives; N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone or other N-vinylamides; vinyl ethers such as methyl vinyl ether, vinyl ethyl ether, n-propyl vinyl ether, isopropyl vinyl ether, vinyl n-butyl ether, vinyl isobutyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether; vinyl cyanide such as acrylonitrile and methacrylonitrile; halogenated vinylides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; propylene compounds such as allyl acetate and allyl chloride; maleic acid or its salts, esters or anhydrides; itaconic acid or its salts, esters or anhydrides; vinyl silyl compounds such as vinyltrimethoxysilane; isopropyl acetate, etc.

[0061] In addition, vinyl ester polymers can have one or more structural units derived from the other monomers mentioned above.

[0062] From the viewpoint of improving the heat-sealing properties and mechanical strength of water-soluble films by controlling parameters such as Tm1 and Tm2 within the aforementioned range, the proportion of structural units derived from other monomers in the vinyl ester polymer (hereinafter sometimes referred to as "degree of modification") is preferably 15 mol% or less, more preferably 5 mol% or less, depending on the molar number of all structural units constituting the vinyl ester polymer.

[0063] The degree of polymerization of PVA is not particularly limited, but is preferably within the following range. That is, from the viewpoint of maintaining sufficient mechanical strength of the water-soluble film, the degree of polymerization is preferably 200 or more, more preferably 300 or more, and even more preferably 500 or more. On the other hand, the degree of polymerization is not particularly limited, but from the viewpoint of improving the productivity of PVA or the productivity of water-soluble films, it is preferably 8,000 or less, more preferably 5,000 or less, and even more preferably 3,000 or less.

[0064] Here, the degree of polymerization is expressed as the average degree of polymerization measured in accordance with JIS K 6726-1994. That is, in this specification, the degree of polymerization is calculated from the limiting viscosity [η] (unit: deciliters / g) measured in water at 30°C after resaponification and purification of the residual acetate of PVA, by the following formula.

[0065] Degree of polymerization Po = ([η] × 10) 4 / 8.29) (1 / 0.62)

[0066] In this invention, the value of subtracting the degree of modification from the degree of saponification of PVA is preferably 64 to 97 mol%. By adjusting this value within this range, parameters such as Tm1 and Tm2 are controlled within the aforementioned range, thereby achieving a balance between the heat-sealing properties and mechanical strength of the water-soluble film. This value is more preferably 70 mol% or more, and even more preferably 75 mol% or more. On the other hand, this value is more preferably 93 mol% or less, even more preferably 91 mol% or less, and particularly preferably 90 mol% or less.

[0067] Here, the degree of saponification of PVA refers to the proportion (mol%) of the number of moles of vinyl alcohol units relative to the total number of moles of structural units (typically vinyl ester monomer units) and vinyl alcohol units that can be converted into vinyl alcohol units through saponification.

[0068] The degree of saponification of PVA can be measured in accordance with the specifications in JIS K 6726-1994.

[0069] Water-soluble films can contain only one type of PVA, or they can contain two or more types of PVA with different degrees of polymerization, saponification, and modification.

[0070] The PVA content in the water-soluble film is preferably 100% by mass or less. On the other hand, the PVA content is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more.

[0071] <Plasticizer>

[0072] Water-soluble films preferably contain plasticizers. By including plasticizers, water-soluble films can be given the same flexibility as other plastic films. Therefore, the mechanical strength, such as impact strength, and the processability during secondary processing of water-soluble films are improved.

[0073] Examples of plasticizers include ethylene glycol, glycerol, diglycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, sorbitol, and other polyols. These plasticizers can be used alone or in combination of two or more. From the viewpoint of inhibiting exudation to the surface of water-soluble films, ethylene glycol or glycerol is preferred as a plasticizer, and glycerol is more preferred.

[0074] The content of plasticizer in the water-soluble film is preferably 10 parts by weight or more, more preferably 15 parts by weight or more, relative to 100 parts by weight of PVA. On the other hand, the content of plasticizer is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, relative to 100 parts by weight of PVA. If the content of plasticizer is within the above range, it is easy to control parameters such as Tm1 and Tm2 within the above range. Furthermore, it is possible to appropriately prevent or suppress problems such as reduced operability due to excessive softening of the water-soluble film or seepage to the surface.

[0075] Starch / Water-soluble polymers

[0076] Water-soluble films may contain water-soluble polymers other than starch and / or PVA. By containing water-soluble polymers other than starch and / or PVA, it is possible to impart mechanical strength to the water-soluble film, maintain its moisture resistance during operation, or regulate the rate at which the water-soluble film softens due to water absorption during dissolution.

[0077] Examples of starches include natural starches such as corn starch, potato starch, sweet potato starch, wheat starch, rice starch, cassava starch, and sago starch; processed starches that have undergone etherification, esterification, oxidation, or other processing methods; and processed starches are particularly preferred.

[0078] The starch content in the water-soluble film is preferably 15 parts by weight or less, more preferably 10 parts by weight or less, relative to 100 parts by weight of PVA. If the starch content is within the above range, it is possible to prevent or suppress the deterioration of the process permeability of the water-soluble film.

[0079] Other water-soluble polymers besides PVA include dextrin, gelatin, animal glue, casein, shellac, gum arabic, polyacrylamide, sodium polyacrylate, polyvinyl methyl ether, copolymers of methyl vinyl ether and maleic anhydride, copolymers of vinyl acetate and itaconic acid, polyvinylpyrrolidone, cellulose, acetylcellulose, acetylbutylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, sodium alginate, etc.

[0080] The content of water-soluble polymers other than PVA in the water-soluble film is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, relative to 100 parts by mass of PVA. If the content of water-soluble polymers other than PVA is within the above range, the water solubility of the water-soluble film can be sufficiently improved.

[0081] <surfactants>

[0082] Water-soluble films preferably contain surfactants. By containing surfactants, the operability of the water-soluble film or its peelability from the film-forming apparatus during manufacturing can be improved.

[0083] There are no particular restrictions on its use as a surfactant; for example, anionic surfactants and nonionic surfactants can be used.

[0084] Examples of anionic surfactants include carboxylic acid surfactants such as potassium laurate; sulfate ester surfactants such as octyl sulfate; and sulfonic acid surfactants such as dodecylbenzene sulfonate.

[0085] Examples of nonionic surfactants include alkyl ether surfactants such as polyoxyethylene lauryl ether and polyoxyethylene oleyl ether; alkyl phenyl ether surfactants such as polyoxyethylene octylphenyl ether; alkyl ester surfactants such as polyoxyethylene laurate; alkylamine surfactants such as polyethylene glycol dodecylamide; alkylamide surfactants such as polyoxyethylene laurylamide; polypropylene glycol ether surfactants such as polyoxyethylene polyoxypropylene ether; alkanolamide surfactants such as lauric acid diethanolamide and oleic acid diethanolamide; and propylene phenyl ether surfactants such as polyoxypropylene phenyl ether.

[0086] This surfactant can be used alone or in combination with two or more. Among these, considering its excellent effect in reducing surface abnormalities such as streaks when manufacturing water-soluble films, nonionic surfactants are preferred, alkanolamide type surfactants are more preferred, and dialkylolamides (e.g., diethanolamine) of aliphatic carboxylic acids (e.g., saturated or unsaturated aliphatic carboxylic acids with 8 to 30 carbon atoms) are even more preferred.

[0087] The surfactant content in the water-soluble film, relative to 100 parts by weight of PVA, is preferably 0.01 parts by weight or more, more preferably 0.02 parts by weight or more, and even more preferably 0.05 parts by weight or more. On the other hand, the surfactant content, relative to 100 parts by weight of PVA, is preferably 10 parts by weight or less, more preferably 1 part by weight or less, even more preferably 0.5 parts by weight or less, and particularly preferably 0.3 parts by weight or less. If the surfactant content is within the above range, the peelability of the water-soluble film from the film-forming apparatus during manufacturing is improved, and problems such as the formation of agglomerates between water-soluble films are less likely to occur. Furthermore, problems such as surfactant seepage onto the surface of the water-soluble film or deterioration of the appearance of the water-soluble film due to surfactant aggregation are also less likely to occur.

[0088] <Other Ingredients>

[0089] In addition to plasticizers, starch, water-soluble polymers other than PVA, and surfactants, the water-soluble film of the present invention may also contain water, antioxidants, ultraviolet absorbers, lubricants, crosslinking agents, colorants, fillers, preservatives, mildew inhibitors, and other polymer compounds, within a range that does not impair the effects of the present invention.

[0090] The total mass of PVA, plasticizer, starch, water-soluble polymers other than PVA, and surfactants constitutes 60 to 100% of the total mass of the water-soluble film, more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass.

[0091] Water-soluble film

[0092] The complete dissolution time of the water-soluble film of the present invention when immersed in deionized water at 10°C is not particularly limited, but is preferably within the following range. The complete dissolution time is preferably within 150 seconds, more preferably within 60 seconds, further preferably within 45 seconds, and especially preferably within 35 seconds. Water-soluble films with complete dissolution times within the above range dissolve relatively early, thus making them suitable for use as packaging films (packaging materials) for pharmaceuticals, etc. On the other hand, the complete dissolution time is preferably 5 seconds or more, more preferably 10 seconds or more, further preferably 15 seconds or more, and especially preferably 20 seconds or more. Thus, if the complete dissolution time of the water-soluble film is not too short, it is difficult to produce problems such as clumping of the water-soluble film due to the absorption of moisture in the atmosphere or a decrease in mechanical strength.

[0093] The complete dissolution time of a water-soluble film when immersed in deionized water at 10°C can be measured as follows.

[0094] <1> The water-soluble film was placed in a constant temperature and humidity chamber set at 20°C and 65% relative humidity for more than 16 hours to adjust the humidity.

[0095] <2> After cutting a rectangular sample with a length of 40mm and a width of 35mm from the conditioned water-soluble film, the sample is sandwiched between two 50mm × 50mm plastic plates with a rectangular window of 35mm in length and 23mm in width, with the length of the sample parallel to the length of the window (hole) and the window located approximately in the center of the width of the sample.

[0096] <3> Add 300 mL of deionized water to a 500 mL beaker, stir with a magnetic stirrer with a 3 cm long rod at 280 rpm, and adjust the water temperature to 10 °C.

[0097] <4> While being careful not to let it come into contact with the rod of the magnetic stirrer, at the same time, in the above <2> The sample fixed to the plastic plate was completely immersed in deionized water in the beaker.

[0098] <5> The time from when the sample was immersed in deionized water until it was observed to have completely disappeared from the deionized water was measured.

[0099] The total dissolution time measured by the above method depends on the thickness of the sample, but in this specification, the total dissolution time is defined as the time until a sample of the above size is completely dissolved, regardless of its thickness.

[0100] The thickness of the water-soluble film is not particularly limited, but is preferably within the following range: preferably 200 μm or less, more preferably 150 μm or less, further preferably 100 μm or less, and especially preferably 50 μm or less. On the other hand, the thickness is preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm or more, and especially preferably 20 μm or more. Since the thickness within the above range is not too large, it is possible to appropriately prevent a deterioration in the secondary processability of the water-soluble film; on the other hand, since it is not too small, sufficient mechanical strength can be ensured in the water-soluble film.

[0101] In addition, it is possible to measure the thickness at any 10 points (e.g., any 10 points on a straight line drawn along the length of the water-soluble film) and calculate their average value as the thickness of the water-soluble film.

[0102] <Method for manufacturing water-soluble thin films>

[0103] The method for manufacturing the water-soluble film of the present invention is not particularly limited, and for example, the following method can be used.

[0104] Examples of methods for manufacturing water-soluble films include casting, wet casting (expelling into a poor solvent), dry-wet casting, gel casting (temporarily cooling and gelling the film-forming solution before extracting and removing the solvent), or combinations thereof, where a homogenized film-forming solution obtained by adding solvents, additives, etc. to PVA is used to form a film; melt extrusion casting or blow molding is used to form a film by extruding the film-forming solution obtained using an extruder or the like through a T-die. Among these, casting and melt extrusion casting are preferred. Using casting and melt extrusion casting methods allows for the production of homogeneous water-soluble films with high productivity.

[0105] The following describes the methods for manufacturing water-soluble films using casting or melt extrusion.

[0106] First, prepare PVA, solvent, and a film-forming solution containing additives such as plasticizers and surfactants as needed. Furthermore, if the film-forming solution contains additives, the ratio of additives to PVA in the film-forming solution is substantially equal to the ratio of additives to PVA in the aforementioned water-soluble film. Next, the film-forming solution is supplied in a film-like manner to a rotating support such as a metal roller or metal belt.

[0107] Thus, a liquid coating of the film-forming solution is formed on the support. The liquid coating is heated on the support to remove the solvent, thereby solidifying and forming a thin film.

[0108] The cured long film is peeled off from the support, dried as needed by drying rollers, drying ovens, etc., further heat-treated as needed, and then wound into rolls.

[0109] In the drying process (solvent removal process) of the liquid coating deposited onto the support, and the subsequent drying process of the water-soluble film, PVA crystallizes during heating. Heating is particularly effective in areas with high moisture content, which increases the mobility of the PVA molecular chains, thus facilitating crystallization. Therefore, the degree of PVA crystallization can be controlled by the drying rate in the drying process. For example, increasing the drying rate hinders crystal growth, leading to smaller crystal sizes and higher melting temperatures. Conversely, slowing down the drying rate promotes crystal growth, resulting in larger crystal sizes and lower melting temperatures. Furthermore, increasing the applied heat tends to increase crystallinity and melting heat.

[0110] In addition, the drying speed can be adjusted according to the temperature of the support, the contact time with the support, the temperature and amount of hot air, and the temperature of the drying roller and the drying oven.

[0111] The volatile content (concentration of volatile components such as solvents that are removed by evaporation or volatilization during film formation) of the above-mentioned film-forming stock solution is not particularly limited, but is preferably 50 to 90% by mass, more preferably 55 to 80% by mass. If the volatile content is within the above range, the viscosity of the film-forming stock solution can be adjusted to an appropriate range, thereby improving the film-forming properties of water-soluble films (liquid coatings) and making it easier to obtain water-soluble films with uniform thickness.

[0112] Here, the “volatile fraction of film-forming solution” in this specification refers to the value obtained by the following formula.

[0113] The volatile fraction (mass%) of the film-forming solution = {(Wa-Wb) / Wa} × 100

[0114] In the formula, Wa represents the mass (g) of the film-forming stock solution, and Wb represents the mass (g) of the film-forming stock solution after Wa(g) has been dried in an electric dryer at 105℃ for 16 hours.

[0115] There are no particular limitations on the method of adjusting the film-forming solution. For example, one can dissolve PVA and additives such as plasticizers and surfactants in a dissolving tank; or use a single-screw or twin-screw extruder to melt-blend PVA in an aqueous state with additives such as plasticizers and surfactants.

[0116] The surface temperature of the support for casting the film-forming solution is not particularly limited, but is preferably 50 to 110°C, more preferably 60 to 100°C, and even more preferably 65 to 95°C. If the surface temperature is within the above range, the drying time required for the liquid coating will not become excessively long by drying it at an appropriate rate, thus the productivity of the water-soluble film will not decrease. Furthermore, by drying the liquid coating at an appropriate rate, abnormalities such as foaming are less likely to occur on the surface of the water-soluble film.

[0117] While heating the liquid coating on the support, hot air at a velocity of 1 to 10 m / s can be uniformly sprayed onto the entire non-contact side of the liquid coating. This allows for adjustment of the drying speed of the liquid coating. The temperature of the hot air sprayed onto the non-contact side is not particularly limited, but is preferably 50 to 150°C, more preferably 70 to 120°C. If the hot air temperature is within the above range, the drying efficiency or uniformity of the liquid coating can be further improved.

[0118] When the supply speed (discharge speed) of the film-forming solution on the support is set to S0 [m / min], and the rotational speed (circumferential speed) of the support is set to S1 [m / min], the ratio (S1 / S0) of the rotational speed (circumferential speed) S1 of the support to the supply speed (discharge speed) S0 of the film-forming solution on the support is preferably within the following range. That is, (S1 / S0) is not particularly limited, but is preferably 7 or less, more preferably 6.8 or less, and even more preferably 6.5 or less. On the other hand, (S1 / S0) is not particularly limited, but is preferably greater than 3, more preferably greater than 5, even more preferably greater than 5.2, and particularly preferably greater than 5.5. If (S1 / S0) is within the above range, crystallization caused by the orientation of the PVA molecular chains in the liquid coating will proceed appropriately, and Tm2-Tm1 can be easily adjusted within an appropriate range. Furthermore, deformation caused by the gravity of the liquid coating can be suppressed between the die lip and the support, thus reducing the likelihood of uneven thickness in the PVA film.

[0119] Furthermore, the supply rate (S0) of the film-forming solution refers to the linear velocity of the film-forming solution in the flow direction. Specifically, the supply rate (S0) of the film-forming solution can be calculated by dividing the opening area of ​​the slit portion of the film-forming dispensing device (the product of the slit width and the average slit opening of the film-forming dispensing device) by the volume of film-forming solution supplied (dispensed) from the film-forming dispensing device per unit time. From the viewpoint of drying uniformity, drying speed, and PVA film productivity, the rotational speed (S1) of the support is preferably 5 to 30 m / min.

[0120] The water-soluble film is preferably dried (solvent removed) on the support to a volatile content of 5 to 50% by mass, then peeled off from the support and further dried as needed.

[0121] There are no particular limitations on the drying method; methods such as drying in a drying oven or contact with drying rollers can be cited.

[0122] When using multiple drying rollers to dry a water-soluble film, it is preferable to alternately contact one side and the other side of the water-soluble film with the drying rollers. This allows for the homogenization of the crystallinity of PVA on both sides of the water-soluble film. In this case, the number of drying rollers is preferably three or more, more preferably four or more, and even more preferably five to thirty.

[0123] The temperature of the drying oven or drying roller is preferably 40 to 110°C. More preferably, the temperature of the drying oven or drying roller is below 100°C, further preferably below 90°C, and especially preferably below 85°C. On the other hand, the temperature of the drying oven or drying roller is more preferably above 45°C, and further preferably above 50°C.

[0124] As needed, the dried water-soluble film can be further heat-treated. By performing heat treatment, parameters such as Tm1 and Tm2 can be controlled within the aforementioned range, thereby adjusting the mechanical strength, water solubility, birefringence, and other properties of the water-soluble film. The heat treatment temperature is preferably between 60 and 135°C. More preferably, the heat treatment temperature is below 130°C.

[0125] To achieve a desired surface roughness on a water-soluble film, methods can be employed to obtain a water-soluble film with an uneven shape during film formation by creating an uneven surface on a support surface, or by creating an uneven shape on the water-soluble film through embossing. For example, by forming recesses with an average depth of 1.8 μm or less and a maximum depth of 20 μm or more but less than 50 μm on the support surface in contact with the glossy surface, a water-soluble film with the target surface roughness can be obtained.

[0126] When forming a film by shaping the surface of a support to obtain a water-soluble film with an uneven shape, the drying temperature of the film is preferably 50 to 170°C, more preferably 60 to 140°C. The drying time on the support is preferably 0.5 to 20 minutes, more preferably 1 to 15 minutes.

[0127] When embossing a water-soluble film to create a textured surface, the processing temperature is preferably 60 to 150°C, more preferably 80 to 140°C. The processing pressure is preferably 0.1 to 15 MPa, more preferably 0.3 to 8 MPa. The film conveying speed during embossing is preferably 5 m / min or more, more preferably 10 to 30 m / min.

[0128] If necessary, the water-soluble film thus manufactured is further subjected to moisture conditioning treatment, and the ends (ears) of the film are cut. Then, it is wound into a cylindrical core and packaged in a moisture-proof manner to become a product.

[0129] <Applications>

[0130] The water-soluble film of the present invention can be more appropriately used in various film applications where conventional water-soluble films are applicable.

[0131] Examples of applications for this film include pharmaceutical packaging films, base films for hydraulic transfer printing, substrate films for embroidery, release films for artificial marble molding, seed packaging films, and films for waste collection bags. Among these, the water-soluble film of the present invention is preferably suitable for pharmaceutical packaging films.

[0132] When the water-soluble film of the present invention is applied to a pharmaceutical packaging film, examples of pharmaceuticals include pesticides, detergents (including bleach), and bactericides.

[0133] There are no particular restrictions on the physical properties of the reagent; it can be acidic, neutral, or alkaline.

[0134] Furthermore, the agent may contain boron-containing compounds or halogen-containing compounds.

[0135] As a pharmaceutical preparation, it can be in any of the following forms: powder, block, gel, or liquid.

[0136] There are no particular restrictions on the packaging method. From an operational point of view, unit packaging of the medicine in units (preferably sealed packaging) is preferred.

[0137] By applying the water-soluble film of the present invention to a pharmaceutical packaging film to package pharmaceuticals, the packaging body of the present invention can be obtained. In other words, the packaging body of the present invention includes a packaging material (capsule) made of the water-soluble film of the present invention and a pharmaceutical preparation contained within the packaging material.

[0138] By manufacturing the packaging body by bonding the matte surfaces of the water-soluble film of the present invention together with the glossy surfaces as the surface side, it is possible to obtain a packaging body with excellent surface gloss and excellent resistance to clumping.

[0139] There are no particular limitations on the method of laminating the film, and known methods can be used, such as heat sealing, water sealing, and adhesive sealing, with heat sealing or water sealing being preferred. Among these, the water-soluble film of the present invention is suitable for heat sealing.

[0140] Example

[0141] The present invention will now be specifically described through examples, etc., but the present invention is not limited to any of the following examples. Furthermore, the evaluation items and methods used in the following examples and comparative examples are as follows.

[0142] (1) Flash DSC measurement

[0143] The water-soluble thin film was conditioned for 24 hours at 20°C and 60% relative humidity. Then, the film was cut into 50μm × 50μm pieces to obtain measurement samples. These samples were then placed on the measurement unit with the film thickness direction horizontal to the unit surface, and DSC measurements were performed. During measurement, the weight per unit volume of the film was measured beforehand, and the weight of the measurement sample was determined based on its film thickness and dimensions.

[0144] Measuring device: Flash DSC 1 STAR system (manufactured by Metler Toled)

[0145] Analysis software: STAR software (manufactured by Metler Toled)

[0146] First heating: 0℃ to 200℃, heating rate: 500℃ / s (after reaching 200℃, hold at an isothermal temperature for 0.1s).

[0147] First cooling: 200℃ to 0℃, cooling rate: 100℃ / s (after reaching 0℃, hold at an isothermal temperature for 0.1s).

[0148] Second heating: 0℃ to 200℃, heating rate: 100℃ / s

[0149] Measurement Unit: This device uses a dedicated chip sensor (manufactured by Metler Toled).

[0150] The obtained melting curves were analyzed, and Tm1, Tm2, ​​ΔH1, and ΔH2 were calculated.

[0151] (2) Sealing strength

[0152] The water-soluble film was conditioned at 20°C and 65% relative humidity for 24 hours. Then, the film was cut into 15mm wide x 200mm pieces. Measurement samples were prepared by folding the resulting film sheet lengthwise and heat-sealing the portion 10mm from the fold using a pulse-type benchtop manual sealing machine "P-300" manufactured by FUJI IMPULSE CO.,LTD. The sealing time was set to 0.5 seconds or 0.8 seconds.

[0153] Using a stereographic measuring instrument, the obtained sample is stretched at a scanning speed of 300 mm / min and a chuck spacing of 50 mm to determine the maximum test force (N / 15 mm) at break / peel. This process is repeated at least five times, and the average of at least three points (excluding the maximum and minimum values) is taken as the sealing strength.

[0154] (3) Total dissolution time of the film

[0155] The complete dissolution time of the water-soluble film in deionized water at 10°C was determined using the method described above.

[0156] <Example 1>

[0157] First, a film-forming stock solution was prepared by combining 100 parts by mass of PVA (88 mol% saponification, 1700 average degree of polymerization) obtained by saponification of polyvinyl acetate, 10 parts by mass of glycerol as a plasticizer, 0.1 parts by mass of diethanolamide laurate as a surfactant, and water. The volatile content of the film-forming stock solution was 68% by mass.

[0158] Next, the film-forming solution is discharged in film form from the T-die onto the support, namely the metal roller (surface temperature 80°C), forming a liquid coating on the metal roller. On the metal roller, the non-contact surface of the liquid coating is dried by blowing hot air at 85°C at a speed of 5 m / s. Thus, a PVA film is obtained. Furthermore, the circumferential speed (S1) of the metal roller is set to 5.6 m / min, and the ratio (S1 / S0) of the circumferential speed (S1) of the metal roller to the discharge speed (S0) of the film-forming solution on the metal roller is set to 4.8.

[0159] Next, the PVA film is peeled off from the metal rollers, and after alternating contact and drying with one side and the other side of the PVA film with each drying roller, it is wound into a cylindrical core. The surface temperature of each drying roller is set to 75°C. The resulting water-soluble film has a thickness of 35 μm and a length of 1200 m.

[0160] The results of flash DSC measurements on the obtained thin film are as follows: Tm1 is 144℃, Tm2 is 189℃, ΔH1 is 10.2J / g, ΔH2 is 15.6J / g, and Tm2-Tm1 is 45℃.

[0161] Furthermore, the sealing strength measured using the obtained film was 5.3 N / m at a sealing time of 0.5 seconds. 2 The sealing time is 5.4 N / m. 2 Even with a short sealing time, sufficient sealing strength was achieved.

[0162] Furthermore, the measured total dissolution time of the obtained film was 45 seconds.

[0163] <Comparative Example 1>

[0164] The amount of glycerol used to prepare the film-forming solution was changed to 3 parts by mass. Otherwise, a water-soluble film was obtained in the same manner as in Example 1.

[0165] <Example 2 and Example 3>

[0166] As a plasticizer used to prepare the film-forming solution, glycerol was replaced with equal parts of glycerol and polyethylene glycol, and the amounts of plasticizer were changed to 20 parts by weight and 40 parts by weight, respectively. Otherwise, a water-soluble film was obtained in the same manner as in Example 1.

[0167] <Examples 4 and 5>

[0168] The surface temperature of the metal roller that dispenses the film-forming solution was changed to 75°C and 90°C, respectively. Otherwise, a water-soluble film was obtained in the same manner as in Example 2.

[0169] <Example 6>

[0170] The temperature of the hot air blown during the drying of the liquid coating on the metal roller was changed to 90°C. Otherwise, a water-soluble film was obtained in the same manner as in Example 2.

[0171] <Comparative Example 2>

[0172] As a plasticizer used to prepare the film-forming solution, glycerol was replaced with equal parts of glycerol and polyethylene glycol, and the amount of plasticizer was changed to 60 parts by mass. Otherwise, a water-soluble film was obtained in the same manner as in Example 1.

[0173] <Comparative Example 3>

[0174] The flow rate of the film-forming solution was changed to 28 m / min, and (S1 / S0) was changed to 48. Otherwise, a water-soluble film was obtained in the same manner as in Example 2.

[0175] <Comparative Example 4>

[0176] The dried water-soluble film was further heat-treated at 140°C. Otherwise, the water-soluble film was obtained in the same manner as in Example 2.

[0177] <Example 7>

[0178] The PVA used in the preparation of the film-forming solution was changed to monomethyl maleate (MMM) modified PVA (saponification degree of 90 mol%, polymerization degree of 1700, and MMM modification degree of 5 mol%). Otherwise, a water-soluble film was obtained in the same manner as in Example 3.

[0179] In addition, in Table 1, monomethyl maleate modified PVA is abbreviated as "MMMΔ5".

[0180] <Example 8>

[0181] The PVA used to prepare the film-forming solution was changed to sodium acrylamide-2-methylpropanesulfonate (AMPS) modified PVA (88 mol% saponification, 1700% polymerization, and 2 mol% AMPS modification), and the amount of plasticizer was set to 25 parts by mass. Otherwise, a water-soluble film was obtained in the same manner as in Example 2.

[0182] Additionally, in Table 1, sodium acrylamide-2-methylpropanesulfonate modified PVA is abbreviated as "AMPSΔ2".

[0183] <Comparative Example 5>

[0184] The PVA used to prepare the film-forming solution was changed to fully saponified PVA (99 mol% saponification and 1700% polymerization). Otherwise, a water-soluble film was obtained in the same manner as in Example 1.

[0185] The evaluation results of the obtained water-soluble films are shown in Table 1.

[0186]

[0187] As shown in Table 1, it can be confirmed that the thermophysical properties of the water-soluble film, including Tm1 and Tm2, ​​can be adjusted by changing at least one of the following: the type of PVA, the type of plasticizer, the amount of plasticizer added, the surface temperature of the support (metal roller), the value of (S1 / S0), and whether or not there is additional heat treatment.

[0188] Furthermore, in the examples where Tm1 is 105°C or higher and 165°C or lower, and Tm2-Tm1 is 20°C or higher, the water-soluble films exhibit excellent heat-sealing properties at high speeds and superior water solubility. In contrast, the water-soluble films of the comparative examples that do not meet the above conditions exhibit poor heat-sealing properties at high speeds.

[0189] Symbol Explanation

[0190] 1-Baseline, 2-Region surrounded by the melting curve and the baseline, 3-Melting temperature (Tm).

Claims

1. A water-soluble film containing polyvinyl alcohol resin, The first melting temperature Tm1 and the second melting temperature Tm2 satisfy the following equations (1) and (2). The first melting temperature Tm1 is determined by the melting curve when the temperature is increased from 500°C / second to 200°C after 24 hours of conditioning at 20°C and 60% relative humidity. The second melting temperature Tm2 is determined by the melting curve when the temperature is increased, cooled to 0°C at 100°C / second, and then increased to 200°C at 100°C / second. The value of the degree of saponification minus the degree of modification of the polyvinyl alcohol resin is 64% to 93 mol%, indicating that the resin contains 10 to 50 parts by weight of plasticizer relative to 100 parts by weight of the polyvinyl alcohol resin. The plasticizer is ethylene glycol or glycerin. The polyvinyl alcohol resin is manufactured by saponifying a vinyl ester polymer obtained by polymerizing vinyl ester monomers. The proportion of structural units derived from other monomers in the vinyl ester polymer is less than 15 mol%, based on the total molar number of all structural units constituting the vinyl ester polymer. The water-soluble film is manufactured using a casting method. A film-forming solution is supplied in a film-like form to a rotating support, forming a liquid coating of the solution on the support. This liquid coating is heated on the support to remove the solvent, thereby solidifying and forming a thin film. The solidified, elongated film is peeled off from the support, dried by drying rollers or a drying oven, and then wound into a roll. The ratio of the rotational speed S1 of the support to the supply speed S0 of the film-forming solution on the support, S1 / S0, is greater than 3 but less than 7. The rotational speed S1 of the support body is 5 to 30 m / min. Hot air with a velocity of 1 to 10 m / s is blown onto the entire area of ​​the non-contact side of the liquid coating. The temperature of the hot air is 50 to 150°C. 105℃≤Tm1≤165℃……(1) Tm2-Tm1≥20℃……(2).

2. The water-soluble film according to claim 1, wherein, The second melting temperature Tm2 is above 150°C and below 180°C.

3. The water-soluble film according to claim 1 or 2, wherein, The first melting heat ΔH1, calculated from the melting curve measured at Tm1, is above 2 J / g and below 15 J / g.

4. The water-soluble film according to claim 1 or 2, wherein, The product contains 15 to 40 parts by weight of plasticizer relative to 100 parts by weight of the polyvinyl alcohol resin.

5. A packaging body, wherein, The water-soluble film according to any one of claims 1 to 4 contains a pharmaceutical agent.

6. The packaging body according to claim 5, wherein, The agent is a pesticide, detergent, or fungicide.

7. The packaging body according to claim 5 or 6, which is manufactured by heat sealing.

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