Polyvinyl alcohol composition, water-soluble film and packaging material

Abstract

The invention discloses a polyvinyl alcohol composition, a water-soluble film and a packaging material, and belongs to the technical field of packaging materials, the polyvinyl alcohol composition comprises the following raw materials by weight: 100 parts of polyvinyl alcohol, 0.5-5 parts of a component A or a component B, and 20-35 parts of a component C; the component A is a salt solution which can be complexed with PVA (Polyvinyl Alcohol) resin; the component B is a cross-linking agent solution capable of being cross-linked with PVA (Polyvinyl Alcohol) resin; the component C is at least two of an alcohol plasticizer, caprolactam, formamide, acetamide, propanamide, polyacrylamide, diethanol amine and triethanolamine, and the mass percent of the alcohol plasticizer in the component C is 0-40%. When the polyethylene composition is used for preparing a water-soluble film, the problems of migration and precipitation of the water-soluble film and a packaging material plasticizer can be solved; and the prepared water-soluble film and packaging material have the characteristics that the water-soluble film and packaging material are insoluble at 60 DEG C and are soluble at 65 DEG C or above.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging materials, and in particular relates to a polyvinyl alcohol composition, a water-soluble film and a packaging material. Background Art

[0002] Polyvinyl alcohol (PVA) is a special high molecular polymer that can dissolve in water, known as "water-soluble plastic". At the same time, polyvinyl alcohol has many advantages such as being non-toxic, harmless, oil-resistant, solvent-resistant and biodegradable. At present, a variety of high value-added water-soluble film products based on polyvinyl alcohol have been widely used in the market. According to different specific applications, they can be divided into cold water soluble, warm water soluble and hot water soluble PVA film products.

[0003] Among the different methods of plastic processing and molding, the thermoplastic processing method has the advantages of continuous production, simple operation, low cost, energy saving, and fast production rate, and is widely used in the processing of plastic products such as ethylene, propylene, and polyvinylidene fluoride. However, since the alcoholysis degree of PVA raw materials used for high-temperature water-soluble is high (generally above 99%), and the molecules contain a large number of hydroxyl groups, the structure of the relatively low-temperature water-soluble PVA raw materials is more regular, there are strong hydrogen bonds within and between molecules, the crystallinity is high, the fluidity is poor, the melting temperature is close to the decomposition temperature, and a large amount of decomposition is likely to occur when heated and melted, and the melt processing is difficult, and it is difficult to directly perform thermoplastic processing.

[0004] At present, thermoplastic processing is mainly carried out by adding plasticizers to destroy the hydrogen bonds between molecules to lower the melting point of PVA and increase its fluidity. Commonly used plasticizers include water, glycerol, polyethylene glycol, diethylene glycol, triethylene glycol, sorbitol, etc., but due to the influence of the film thermoforming process on its physical structure such as crystallinity and grain size, the added plasticizer is easy to migrate and precipitate with the increase of air humidity, resulting in poor weather resistance, and the film is easily affected by air humidity and becomes sticky.

[0005] In this regard, the Chinese patent application number 202011189213.5 discloses a polyvinyl alcohol composition, a polyvinyl alcohol film and a method for preparing the same. In the process mentioned, a single alcohol plasticizer is compounded with a salt compound to reduce the amount of plasticizer used and inhibit the precipitation of the plasticizer. This method has limited effect and cannot solve the problem of plasticizer precipitation well. In actual production, too low a dosage of plasticizer leads to a decrease in melt flow rate and reduced production efficiency. Summary of the invention

[0006] The object of the present invention is to provide a polyvinyl alcohol composition, a water-soluble film and a packaging material, aiming to solve the problem of easy migration of plasticizers in existing polyvinyl alcohol film products.

[0007] In order to achieve the above object, the first aspect of the present invention provides a polyvinyl alcohol composition, which comprises the following raw materials in parts by weight: 100 parts of polyvinyl alcohol, 0.5-5 parts of component A or component B, and 20-35 parts of component C.

[0008] The PVA resin raw material has a polymerization degree of 1700 to 3000 and an alcoholysis degree of 90 to 99.99%.

[0009] The component A is a salt solution that can be complexed with the PVA resin, and is composed of a metal salt and deionized water in a mass ratio of 2 to 8:10. The metal salt is one or more of calcium chloride, magnesium chloride, lithium chloride, silver nitrate and copper sulfate.

[0010] The component B is a crosslinking agent solution that can be crosslinked with the PVA resin, and is composed of a crosslinking agent and deionized water in a mass ratio of 1 to 8:100. The crosslinking agent is one or more of boric acid, urea and citric acid.

[0011] The component C is at least two of alcohol plasticizers, caprolactam, formamide, acetamide, propionamide, polyacrylamide, diethanolamine and triethanolamine, and the mass percentage content of the alcohol plasticizer in component C is 0-40%.

[0012] The alcohol plasticizer is one or more of glycerol, polyethylene glycol, ethylene glycol, and diethylene glycol.

[0013] A second aspect of the present invention provides a method for preparing a polyvinyl alcohol composition, comprising the following steps:

[0014] Component A and component C are stirred and mixed, or component B and component C are stirred and mixed to obtain a compound plasticizer, and the compound plasticizer is stirred and mixed with polyvinyl alcohol to obtain a polyvinyl alcohol composition.

[0015] Preferably, the mixing time during the preparation of the compound plasticizer is 15 to 30 minutes.

[0016] Preferably, the mixing time of the compound plasticizer and polyvinyl alcohol is 15 minutes to 3 hours, the stirring rate is 200 to 500 r / min, and the stirring temperature is 25 to 80°C.

[0017] The present invention achieves the purpose of reducing the crystallinity and grain size of the prepared polyvinyl alcohol thermoplastic processing sample by adding a salt solution or a crosslinking agent solution that can complex with PVA to a conventional organic plasticizer and adjusting the ratio, thereby solving the problem of plasticizer precipitation in water-soluble films and packaging materials. 2+ , Ca 2+ , Li + 、Ag + , Cu 2+When complexed with the oxygen atom on the -OH in PVA, it can destroy the hydrogen bonds within and between the PVA molecular chains; the cheap and readily available boric acid solution, urea solution, and citric acid solution can form a lightly cross-linked network with PVA, and work together with hydroxyl- and / or amine-containing plasticizers (the amide groups and hydroxyl groups in the hydroxyl- and / or amine-containing plasticizers can form hydrogen bonds with the hydroxyl groups of the PVA molecules, and at the same time form complexes with the PVA molecules to reduce the regularity of the molecular chains), thereby aggravating the destruction of the internal structure of the PVA molecules and reducing the crystallinity of the polyvinyl alcohol composition.

[0018] During the hot melt processing of the polyvinyl alcohol composition, water can be tightly combined with PVA and hydroxyl groups in the plasticizer through hydrogen bonds, which has a certain plasticizing effect and has a great influence on the melt extrusion fluidity of PVA. However, due to the low boiling point of water, it evaporates violently during the hot melt processing, resulting in foaming in the PVA granulation process. In the method of the present invention, no additional water is added to the formula except for the water used to dissolve the cross-linking agent and the metal salt. At the same time, the water content of the final polyvinyl alcohol composition is controlled by the mixing temperature and time during the mixing process to avoid foaming during the granulation process.

[0019] The third aspect of the present invention provides a water-soluble film, comprising the polyvinyl alcohol composition.

[0020] A fourth aspect of the present invention provides a method for preparing a water-soluble film, comprising the following steps:

[0021] The polyvinyl alcohol composition is conveyed to a twin-screw extruder, melt-extruded under normal pressure or pressurized state, cooled to 20-40° C. by air cooling, and then granulated to obtain melt-processable polyvinyl alcohol resin particles, and then the melt-processable polyvinyl alcohol resin particles are blown into shape or melt-cast into a film, and wound up to obtain a water-soluble film.

[0022] Preferably, the feeding speed of the twin-screw extruder during the melt extrusion process is 15-40 r / min and the temperature is 150-210°C.

[0023] Preferably, the melt-processable polyvinyl alcohol resin particles have a melt flow rate of 10 to 25 g / 10 min at a load of 2.16 kg and 210° C., and a moisture content of 0.5 to 5%.

[0024] Preferably, the melt casting temperature is 170-210°C.

[0025] Preferably, the film blowing setting temperature is 150-220°C.

[0026] Preferably, the water-soluble film has a thickness of 30 to 120 μm.

[0027] A fifth aspect of the present invention provides a packaging material comprising the above-mentioned water-soluble film.

[0028] Beneficial effects of the present invention:

[0029] 1. The present invention provides a polyvinyl alcohol composition and a water-soluble film prepared therefrom. The preparation method of the water-soluble film is simple, and the crystallinity and grain size of polyvinyl alcohol can be effectively reduced, the problem of plasticizer migration and precipitation in water-soluble films and packaging materials can be solved, and the efficiency of thermoplastic processing of polyvinyl alcohol can be improved. The prepared water-soluble film and packaging material have the characteristics of being insoluble at 60°C and soluble above 65°C.

[0030] 2. The present invention uses wide-angle X-ray diffraction and DSC detection tools to explore the reasons for the precipitation of plasticizers during PVA thermoplastic processing from the perspective of PVA microstructure, and controls the degree of crystallinity during the melting process of PVA to adjust the plasticizer formula to achieve regulation of the free volume inside the film, thereby solving the problem of the plasticizer added during the film preparation process being affected by the environment and precipitating on the surface of the PVA film. At the same time, the PVA thermoplastic temperature is further reduced to achieve the purpose of efficient and low-energy thermoplastic processing of PVA films.

[0031] 3. Compared with the use of step-by-step plasticization mentioned in other current public materials related to high-temperature water-soluble PVA films to promote sufficient swelling of PVA and thus improve the problem of small molecule precipitation of plasticizers in high-temperature water-soluble PVA films, the processing technology provided by the present invention is time-saving and simple, and the improvement effect is better.

[0032] 4. The plasticizer formula used in the preparation process of the water-soluble film of the present invention avoids compounds such as starch and talcum powder that can compete with PVA for plasticizers, and the most critical mixing step in the film processing technology is to first prepare a compound plasticizer through a mixing process, and then mix the compound plasticizer with PVA powder for plasticization, thereby avoiding insufficient swelling of PVA due to uneven mixing and failure to fully plasticize during granulation, and at the same time reducing the PVA pre-plasticization step in the mixing process. PVA can directly and evenly absorb the plasticizer, effectively shortening the production time of water-soluble films and packaging materials.

[0033] 5. The water-soluble film and packaging material prepared by the method provided by the present invention have a wide range of application scenarios. Since the water-soluble film and packaging material prepared by the present invention have high-temperature water solubility and biodegradability, they can be used as agricultural seed bags, ground film base materials and other agricultural-related film materials, and can also be used as packaging for other products used in water, such as detergents, water treatment agents, cleaning agents, cement additives, etc. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The first aspect of the present invention provides a polyvinyl alcohol composition, which comprises the following raw materials in parts by weight: 100 parts of polyvinyl alcohol, 0.5 to 5 parts of component A or component B, and 20 to 35 parts of component C.

[0036] The PVA resin raw material has a polymerization degree of 1700 to 3000 and an alcoholysis degree of 90 to 99.99%.

[0037] Among them, the component A is a salt solution that can be complexed with the PVA resin, which is composed of a metal salt and deionized water in a mass ratio of 2 to 8:10, and the metal salt is one or more of calcium chloride, magnesium chloride, lithium chloride, silver nitrate and copper sulfate.

[0038] Wherein, the component B is a crosslinking agent solution that can be crosslinked with the PVA resin, which is composed of a crosslinking agent and deionized water in a mass ratio of 1 to 8:100, and the crosslinking agent is one or more of boric acid, urea and citric acid.

[0039] The component C is at least two of alcohol plasticizers, caprolactam, formamide, acetamide, propionamide, polyacrylamide, diethanolamine and triethanolamine, and the mass percentage content of the alcohol plasticizer in component C is 0-40%.

[0040] The alcohol plasticizer is one or more of glycerol, polyethylene glycol, ethylene glycol, and diethylene glycol.

[0041] A second aspect of the present invention provides a method for preparing a polyvinyl alcohol composition, comprising the following steps:

[0042] Component A and component C are stirred and mixed, or component B and component C are stirred and mixed to obtain a compound plasticizer, and the compound plasticizer is stirred and mixed with polyvinyl alcohol to obtain a polyvinyl alcohol composition.

[0043] The mixing time during the preparation of the compound plasticizer is 15 to 30 minutes.

[0044] The mixing time of the compound plasticizer and polyvinyl alcohol is 15 minutes to 3 hours, the stirring speed is 200 to 500 r / min, and the stirring temperature is 25 to 80°C.

[0045] The third aspect of the present invention provides a water-soluble film, comprising the polyvinyl alcohol composition.

[0046] A fourth aspect of the present invention provides a method for preparing a water-soluble film, comprising the following steps:

[0047] The polyvinyl alcohol composition is conveyed to a twin-screw extruder, melt-extruded under normal pressure or pressurized state, cooled to 20-40° C. by air cooling, and then granulated to obtain melt-processable polyvinyl alcohol resin particles, and then the melt-processable polyvinyl alcohol resin particles are blown into shape or melt-cast into a film, and wound up to obtain a water-soluble film.

[0048] The feeding speed of the twin-screw extruder during the melt extrusion process is 15-40 r / min and the temperature is 150-210°C.

[0049] The melt-processable polyvinyl alcohol resin particles have a melt flow rate of 10 to 25 g / 10 min at a load of 2.16 kg and 210° C., and a water content of 0.5 to 5%.

[0050] The melt casting temperature is 170-210°C.

[0051] Among them, the film blowing setting temperature is 150-220℃.

[0052] The water-soluble film has a thickness of 30 to 120 μm.

[0053] A fifth aspect of the present invention provides a packaging material comprising the above-mentioned water-soluble film.

[0054] Example 1

[0055] A method for preparing a water-soluble film comprises the following steps:

[0056] By weight, 10 parts of triethanolamine, 10 parts of caprolactam, and 0.5 parts of a 20% by mass magnesium chloride solution were mixed and stirred at 50° C. for 30 minutes to obtain a compound plasticizer; the compound plasticizer was mixed with 100 parts of polyvinyl alcohol (degree of polymerization 1700, degree of alcoholysis 99%) at 70° C. for 3 hours at a stirring rate of 200 r / min to obtain a polyvinyl alcohol composition;

[0057] The polyvinyl alcohol composition is added into a twin-screw extruder, the temperature is controlled at 200°C, the feeding speed is 40r / min, and after extrusion, it is air-cooled to 20°C and then granulated to obtain melt-processable polyvinyl alcohol resin particles. The melt-processable polyvinyl alcohol resin particles are added into a film blowing machine, blow-molded at 200°C, and rolled to obtain a water-soluble film with a thickness of 60±1um.

[0058] Example 2

[0059] A method for preparing a water-soluble film comprises the following steps:

[0060] By weight, 15 parts of acetamide, 15 parts of caprolactam, and 2 parts of 50% copper sulfate solution were mixed and stirred at 50° C. for 15 minutes to obtain a compound plasticizer, and the compound plasticizer was mixed with 100 parts of polyvinyl alcohol (polymerization degree 2400, alcoholysis degree 99%) at 80° C. for 3 hours at a stirring rate of 300 r / min to obtain a polyvinyl alcohol composition;

[0061] The polyvinyl alcohol composition is added into a twin-screw extruder, the temperature is controlled at 200°C, the feeding speed is 40r / min, and after extrusion, it is air-cooled to 20°C and then granulated to obtain melt-processable polyvinyl alcohol resin particles. The melt-processable polyvinyl alcohol resin particles are added into a film blowing machine, blow-molded at 200°C, and rolled to obtain a water-soluble film with a thickness of 60±1um.

[0062] Example 3

[0063] A method for preparing a water-soluble film comprises the following steps:

[0064] In parts by weight, 12 parts of formamide, 8 parts of glycerol, 15 parts of diethanolamine, and 5 parts of 80% by mass calcium chloride solution are mixed and stirred at 50° C. for 15 minutes to obtain a compound plasticizer. The compound plasticizer is mixed with 100 parts of polyvinyl alcohol (degree of polymerization: 1700, degree of alcoholysis: 99%) at 60° C. for 3 hours at a stirring rate of 300 r / min to obtain a polyvinyl alcohol composition.

[0065] The polyvinyl alcohol composition is added into a twin-screw extruder, the temperature is controlled at 210°C, the feeding speed is 15r / min, and after extrusion, it is air-cooled to 30°C and then granulated to obtain melt-processable polyvinyl alcohol resin particles. The melt-processable polyvinyl alcohol resin particles are added into a film blowing machine, blow-molded at 200°C, and rolled to obtain a water-soluble film with a thickness of 60±1um.

[0066] Example 4

[0067] A method for preparing a water-soluble film. Compared with Example 1, the "magnesium chloride solution with a mass fraction of 20%" in Example 1 is replaced by "citric acid solution with a mass fraction of 20%", and the remaining raw materials, parameters and preparation process are the same as Example 1.

[0068] Example 5

[0069] A method for preparing a water-soluble film. Compared with Example 2, the "copper sulfate solution with a mass fraction of 50%" in Example 2 is replaced by "boric acid solution with a mass fraction of 50%", and the remaining raw materials, parameters and preparation process are the same as Example 2.

[0070] Example 6

[0071] A method for preparing a water-soluble film, compared with Example 3, the "calcium chloride solution with a mass fraction of 80%" in Example 3 is replaced by "urea solution with a mass fraction of 80%", and the remaining raw materials, parameters and preparation process are the same as Example 3.

[0072] Comparative Example 1

[0073] A method for preparing a water-soluble film comprises the following steps:

[0074] By weight, 20 parts of glycerol and 100 parts of polyvinyl alcohol (degree of polymerization: 1700, degree of alcoholysis: 99%) were mixed and stirred at 60° C. for 3 h at a stirring rate of 200 r / min to obtain a polyvinyl alcohol composition;

[0075] The polyvinyl alcohol composition is added into a twin-screw extruder, the temperature is controlled at 210°C, the feeding speed is 35r / min, and after extrusion, it is air-cooled to 20°C and then granulated to obtain melt-processable polyvinyl alcohol resin particles. The melt-processable polyvinyl alcohol resin particles are added into a film blowing machine, blow-molded at 200°C, and rolled to obtain a water-soluble film with a thickness of 60±1um.

[0076] Comparative Example 2

[0077] A method for preparing a water-soluble film comprises the following steps:

[0078] By weight, 10.25 parts of triethanolamine and 10.25 parts of caprolactam were mixed and stirred at 50° C. for 30 minutes to obtain a compound plasticizer, and the compound plasticizer was mixed with 100 parts of polyvinyl alcohol (degree of polymerization 1700, degree of alcoholysis 99%) at 70° C. for 3 hours at a stirring rate of 200 r / min to obtain a polyvinyl alcohol composition;

[0079] The polyvinyl alcohol composition is added into a twin-screw extruder, the temperature is controlled at 200°C, the feeding speed is 40r / min, and after extrusion, it is air-cooled to 20°C and then granulated to obtain melt-processable polyvinyl alcohol resin particles. The melt-processable polyvinyl alcohol resin particles are added into a film blowing machine, blow-molded at 200°C, and rolled to obtain a water-soluble film with a thickness of 60±1um.

[0080] Comparative Example 3

[0081] A method for preparing a water-soluble film comprises the following steps:

[0082] By weight, 16 parts of acetamide and 16 parts of caprolactam were mixed and stirred at 50° C. for 15 minutes to obtain a compound plasticizer, and the compound plasticizer was mixed with 100 parts of polyvinyl alcohol (degree of polymerization 2400, degree of alcoholysis 99%) at 80° C. for 3 hours at a stirring rate of 300 r / min to obtain a polyvinyl alcohol composition;

[0083] The polyvinyl alcohol composition is added into a twin-screw extruder, the temperature is controlled at 200°C, the feeding speed is 40r / min, and after extrusion, it is air-cooled to 20°C and then granulated to obtain melt-processable polyvinyl alcohol resin particles. The melt-processable polyvinyl alcohol resin particles are added into a film blowing machine, blow-molded at 200°C, and rolled to obtain a water-soluble film with a thickness of 60±1um.

[0084] Comparative Example 4

[0085] A method for preparing a water-soluble film comprises the following steps:

[0086] By weight, 20 parts of glycerol and 0.5 parts of 20% magnesium chloride solution were stirred and mixed at 50° C. for 30 minutes to obtain a compound plasticizer. The compound plasticizer and 100 parts of polyvinyl alcohol (degree of polymerization 1700, degree of alcoholysis 99%) were continuously stirred at 70° C. for 3 hours to obtain a polyvinyl alcohol composition.

[0087] The polyvinyl alcohol composition is added into a twin-screw extruder, the temperature is controlled at 200°C, the feeding speed is 40r / min, and after extrusion, it is air-cooled to 20°C and then granulated to obtain melt-processable polyvinyl alcohol resin particles. The melt-processable polyvinyl alcohol resin particles are added into a film blowing machine, blow-molded at 200°C, and rolled to obtain a water-soluble film with a thickness of 60±1um.

[0088] Comparative Example 5

[0089] A method for preparing a water-soluble film comprises the following steps:

[0090] By weight, 20 parts of glycerol and 0.5 parts of 50% boric acid solution were stirred and mixed at 50° C. for 30 minutes to obtain a compound plasticizer. The compound plasticizer and 100 parts of polyvinyl alcohol (degree of polymerization 1700, degree of alcoholysis 99%) were continuously stirred at 80° C. for 3 hours to obtain a polyvinyl alcohol composition.

[0091] The polyvinyl alcohol composition is added into a twin-screw extruder, the temperature is controlled at 200°C, the feeding speed is 40r / min, and after extrusion, it is air-cooled to 20°C and then granulated to obtain melt-processable polyvinyl alcohol resin particles. The melt-processable polyvinyl alcohol resin particles are added into a film blowing machine, blow-molded at 200°C, and rolled to obtain a water-soluble film with a thickness of 60±1um.

[0092] (I) The crystallization of the water-soluble films obtained in Examples 1 to 6 and Comparative Examples 1 to 5 was observed by wide-angle X-ray diffraction and DSC detection tools; and the mobility of the water-soluble film plasticizers obtained in Examples 1 to 6 and Comparative Examples 1 to 5 was detected. The detection method includes the following steps:

[0093] a. Select a PVA film with uniform thickness, cut the film into small samples with a side length of 10 cm and weigh its initial mass m1;

[0094] b. Place the film in a constant temperature and humidity chamber with a set temperature of 25°C and a humidity of 90%, leave it for 24 hours, take it out, wipe the surface of the film with an alcohol cotton ball, wait for the alcohol to evaporate completely, rebalance the moisture content to the same as the initial state, and weigh its mass again, record it as m2;

[0095] c. Calculate the sustained release rate of the film. Test 5 samples in each group of experiments and take the average value of the final result. The sustained release rate ΔM calculation formula is:

[0096]

[0097] The test results are shown in Table 1:

[0098] Table 1

[0099]

[0100] It can be seen from the data recorded in Table 1 that, compared with Comparative Examples 1-5, the water-soluble film preparation method of Examples 1-6 can reduce the PVA crystallinity and grain size, and the film precipitation mobility is low.

[0101] (II) The polyvinyl alcohol compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 5 were tested for melting points. The test results are shown in Table 2:

[0102] Table 2

[0103]

[0104]

[0105] It can be seen from the data recorded in Table 2 that the polyvinyl alcohol compositions prepared in Examples 1-6 have lower melting points, indicating that the preparation method of the polyvinyl alcohol composition of the present invention can effectively reduce the processing melting temperature of PVA.

[0106] (III) The water solubility of the water-soluble films obtained in Examples 1 to 6 and Comparative Examples 1 to 5 was tested (the water solubility evaluation standard refers to QB / T 5658-2021), and the testing method included the following steps:

[0107] a. Add 1L pure water of corresponding temperature (40 / 60 / 65℃) into a 1L beaker and adjust the speed to 200r / min;

[0108] b. Cut a film sample with a length and width of 5cm*5cm and a thickness of 40-80um and fix it in a fixture. Immerse the sample in water and time it synchronously, recording the disintegration time (the water-soluble film does not disintegrate if one corner falls off or the middle is damaged) and the complete dissolution time;

[0109] c. Test the samples three times in parallel and record the solubility of the water-soluble film and packaging materials.

[0110] The test results are shown in Table 3:

[0111] Table 3

[0112]

[0113]

[0114] It can be seen from the data recorded in Table 3 that, compared with Comparative Examples 1-5, the water-soluble films obtained in Examples 1-6 have a shorter dissolution time at 65° C., indicating better water solubility.

[0115] (IV) The melt index of the polyvinyl alcohol composition obtained in Examples 1 to 6 and Comparative Examples 1 to 5 was tested, and the testing method included the following steps:

[0116] Prepare polyvinyl alcohol sample powder according to plasticizer formula and process;

[0117] Add 3-8g sample powder into the barrel, compact the sample to expel air, insert the piston into the barrel, preheat at a certain temperature (180-220℃) for 3min, and add load;

[0118] Collect the pellets cut within a certain period of time, calculate their average mass, and calculate the melt index of the polyvinyl alcohol composition;

[0119] The test results are shown in Table 4:

[0120] Table 4

[0121]

[0122]

[0123] It can be seen from the data recorded in Table 4 that the flow effects of Examples 1-6 are better than those of Comparative Examples 1-5, indicating that this method is beneficial to improving the processing fluidity of PVA.

[0124] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0125] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polyvinyl alcohol composition, characterized in that The method comprises the following raw materials in parts by weight: 100 parts of polyvinyl alcohol, 0.5 to 5 parts of component A or component B, and 20 to 35 parts of component C; The component A is a salt solution that can be complexed with the PVA resin; The component B is a cross-linking agent solution that can be cross-linked with the PVA resin; The component C is at least two of alcohol plasticizers, caprolactam, formamide, acetamide, propionamide, polyacrylamide, diethanolamine and triethanolamine, and the mass percentage content of the alcohol plasticizer in component C is 0-40%.

2. A polyvinyl alcohol composition according to claim 1, characterized in that: The component A is composed of metal salt and deionized water in a mass ratio of 2 to 8:

10.

3. A polyvinyl alcohol composition according to claim 2, characterized in that: The metal salt is one or more of calcium chloride, magnesium chloride, lithium chloride, silver nitrate and copper sulfate.

4. A polyvinyl alcohol composition according to claim 1 or 3, characterized in that: The component B is composed of a cross-linking agent and deionized water in a mass ratio of 1 to 8:

100.

5. A polyvinyl alcohol composition according to claim 4, characterized in that: The cross-linking agent is one or more of boric acid, urea and citric acid.

6. A polyvinyl alcohol composition according to claim 1, characterized in that: The alcohol plasticizer is one or more of glycerol, polyethylene glycol, ethylene glycol, and diethylene glycol.

7. A method for preparing the polyvinyl alcohol composition according to any one of claims 1 to 6, characterized in that: The following steps are involved: Component A and component C are stirred and mixed, or component B and component C are stirred and mixed to obtain a compound plasticizer, and the compound plasticizer is stirred and mixed with polyvinyl alcohol to obtain a polyvinyl alcohol composition.

8. The method for preparing the polyvinyl alcohol composition according to claim 7, characterized in that: The mixing time during the preparation of the compound plasticizer is 15 to 30 minutes.

9. The method for preparing the polyvinyl alcohol composition according to claim 7, characterized in that: The mixing time of the compound plasticizer and polyvinyl alcohol is 15 minutes to 3 hours, the stirring speed is 200 to 500 r / min, and the stirring temperature is 25 to 80°C.

10. A water-soluble film, characterized in that: The invention relates to a polyvinyl alcohol composition comprising the polyvinyl alcohol composition according to any one of claims 1 to 6.

11. The method for preparing a water-soluble film according to claim 10, characterized in that: The following steps are involved: The polyvinyl alcohol composition is conveyed to a twin-screw extruder, melt-extruded under normal pressure or pressurized state, cooled to 20-40° C. by air cooling, and then granulated to obtain melt-processable polyvinyl alcohol resin particles, and then the melt-processable polyvinyl alcohol resin particles are blown into shape or melt-cast into a film, and wound up to obtain a water-soluble film.

12. A packaging material, characterized in that: Comprising the water-soluble film according to claim 10.

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