Polyvinyl alcohol aqueous film and method of making same

Abstract

The application provides a polyvinyl alcohol water-soluble film and a preparation method thereof, and belongs to the technical field of polyvinyl alcohol modification, wherein the polyvinyl alcohol water-soluble film comprises first polyvinyl alcohol, second polyvinyl alcohol, a crosslinking agent, a plasticizer, a lubricant and an antioxidant; according to parts by weight, the first polyvinyl alcohol is 100 parts, the second polyvinyl alcohol is 20-50 parts, the crosslinking agent is 0.01-0.1 part, the plasticizer is 10-30 parts, the lubricant is 0.1-1 part, and the antioxidant is 0.1-2 parts.

Description

Technical Field

[0001] This invention belongs to the field of polyvinyl alcohol modification technology, specifically relating to a polyvinyl alcohol water-soluble film and its preparation method. Background Technology

[0002] With the development of the market economy, society is paying increasing attention to environmental protection, and plastic films used in production and daily life are gradually being replaced by biodegradable films. Polyvinyl alcohol (PVA) is a new type of environmentally friendly material with good water solubility, film-forming properties, and barrier properties. Water-soluble films made from PVA are often used in medical, agricultural, aquaculture, laundry, and water transfer printing industries. However, the dissolution rate of PVA water-soluble films still needs to be improved, and existing products are difficult to meet the needs of special application environments such as quick washing of clothes and rapid dissolution of water transfer printing films. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a polyvinyl alcohol water-soluble film and its preparation method, aiming to at least partially solve the above-mentioned technical problems. The specific technical solution provided by this invention is as follows.

[0004] As a first aspect of the present invention, the present invention provides a polyvinyl alcohol water-soluble film, comprising: polyvinyl alcohol of a first degree of polymerization, polyvinyl alcohol of a second degree of polymerization, a crosslinking agent, a plasticizer, a lubricant, and an antioxidant; wherein, by weight, the polyvinyl alcohol of the first degree of polymerization is 100 parts, the polyvinyl alcohol of the second degree of polymerization is 20-50 parts, the crosslinking agent is 0.01-0.1 parts, the plasticizer is 10-30 parts, the lubricant is 0.1-1 parts, and the antioxidant is 0.1-2 parts.

[0005] As a second aspect of the present invention, the present invention provides a method for preparing a polyvinyl alcohol water-soluble film, comprising: mixing polyvinyl alcohol of a first degree of polymerization, polyvinyl alcohol of a second degree of polymerization, a crosslinking agent, a plasticizer, a lubricant, and an antioxidant evenly to obtain a mixture; and forming the mixture into a film by a film-forming method to obtain a polyvinyl alcohol water-soluble film; wherein, by weight, the polyvinyl alcohol of the first degree of polymerization is 100 parts, the polyvinyl alcohol of the second degree of polymerization is 20-50 parts, the crosslinking agent is 0.01-0.1 parts, the plasticizer is 10-30 parts, the lubricant is 0.1-1 parts, and the antioxidant is 0.1-2 parts.

[0006] Based on the above technical solution, the polyvinyl alcohol aqueous film and its preparation method provided by the present invention have at least one of the following beneficial effects:

[0007] (1) In the embodiments of the present invention, a crosslinking agent is added to modify polyvinyl alcohol by crosslinking. The amount of crosslinking agent added is controlled to generate a small number of crosslinking points between polyvinyl alcohol molecular chains, thereby destroying the original condensed state structure of polyvinyl alcohol, reducing the crystallinity and melting point of polyvinyl alcohol, and increasing the dissolution rate of polyvinyl alcohol water-soluble film.

[0008] (2) In the embodiments of the present invention, the raw materials used to prepare the polyvinyl alcohol water-soluble film are directly mixed and the polyvinyl alcohol water-soluble film is formed by film formation. The preparation method is simple, the film formation time is short, the cost is low, and it can be applied to industrial production. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0010] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0011] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by those skilled in the art. Where the terms "first," "second," etc., are used throughout the text, they are only used to distinguish similar objects and should not be construed as indicating or implying their relative importance, order, or implicitly specifying the number of technical features indicated. It should be understood that the data in the descriptions of "first," "second," etc., can be interchanged where appropriate.

[0012] To address the problem that the current polyvinyl alcohol (PVA) water-soluble film has a slow dissolution rate and cannot meet the requirements of special application environments, this invention adds a small amount of crosslinking agent to crosslink and modify PVA, thereby destroying the original condensed state structure of PVA, reducing the crystallinity and melting point of PVA, and ultimately achieving the goal of improving the dissolution rate of PVA water-soluble film.

[0013] Specifically, as a first aspect of the present invention, the present invention provides a polyvinyl alcohol water-soluble film, comprising: polyvinyl alcohol of a first degree of polymerization, polyvinyl alcohol of a second degree of polymerization, a crosslinking agent, a plasticizer, a lubricant, and an antioxidant; wherein, by weight, the polyvinyl alcohol of the first degree of polymerization is 100 parts, the polyvinyl alcohol of the second degree of polymerization is 20-50 parts, the crosslinking agent is 0.01-0.1 parts, the plasticizer is 10-30 parts, the lubricant is 0.1-1 parts, and the antioxidant is 0.1-2 parts.

[0014] In embodiments of the present invention, a crosslinking agent is added to modify polyvinyl alcohol through crosslinking. By controlling the amount of crosslinking agent added, a small number of crosslinking points are generated between the polyvinyl alcohol molecular chains, thereby destroying the original condensed state structure of polyvinyl alcohol, reducing the crystallinity and melting point of polyvinyl alcohol, and increasing the dissolution rate of the polyvinyl alcohol water-soluble film.

[0015] According to an embodiment of the present invention, the above-described polyvinyl alcohol aqueous film is suitable for use at 0-25°C.

[0016] According to an embodiment of the present invention, the degree of hydrolysis of the first degree of polymerization polyvinyl alcohol is 86-90%, and the degree of polymerization is 300-800; the degree of hydrolysis of the second degree of polymerization polyvinyl alcohol is 86-90%, and the degree of polymerization is 1500-2000.

[0017] In embodiments of the present invention, the first degree of polymerization polyvinyl alcohol (PVA) can be any commercially available PVA, preferably PVA with a degree of hydrolysis of 88%. This is because PVA with a degree of hydrolysis less than 95% can dissolve in water at room temperature, while PVA with a degree of hydrolysis greater than 99.5% can only dissolve in hot water above 95°C. With the same degree of hydrolysis, PVA with the first degree of polymerization has better water solubility but lower mechanical strength; PVA with the second degree of polymerization has poorer water solubility but higher mechanical strength. Mixing a small amount of PVA with the second degree of polymerization can improve the mechanical properties of the first degree of polymerization PVA, thereby improving the mechanical properties of the PVA water-soluble film. If the amount of PVA with the second degree of polymerization added is less than 20 parts, it cannot effectively improve the mechanical strength of the PVA water-soluble film; however, if the amount of PVA with the second degree of polymerization added exceeds 50 parts, it will reduce the water solubility of the PVA water-soluble film.

[0018] According to embodiments of the present invention, the crosslinking agent is one or more of boric acid, dicarboxylic acid, and dialdehyde; wherein the dicarboxylic acid is selected from at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, and adipic acid, and the dialdehyde is selected from at least one of oxalic acid, malondialdehyde, succinic acid, glutaric acid, and adialdehyde.

[0019] In embodiments of the present invention, the crosslinking agent can generate a small number of crosslinking points between polyvinyl alcohol molecular chains, thereby disrupting the orderliness of polyvinyl alcohol crystals, reducing the crystallinity and melting point of polyvinyl alcohol, and improving the water solubility of the polyvinyl alcohol water-soluble film. If the amount of crosslinking agent added is less than 0.01 parts, it cannot effectively improve the water solubility of the polyvinyl alcohol water-soluble film; however, if the amount of crosslinking agent added is greater than 0.1 parts, too many crosslinking points will be generated, affecting the water solubility of the polyvinyl alcohol water-soluble film.

[0020] According to embodiments of the present invention, the plasticizer is one or more of polyol plasticizers and organic amine plasticizers; wherein, the polyol plasticizer is selected from at least one of ethylene glycol, glycerol, sorbitol, diethanolamine, polyethylene glycol 200, and polyethylene glycol 400, and the organic amine plasticizer is selected from at least one of diethanolamine and triethanolamine.

[0021] In embodiments of the present invention, the plasticizer can be any plasticizer commonly used in the art, without particular limitation. The plasticizer can lower the melting point and crystallinity of the polyvinyl alcohol (PVA) water-soluble film, providing a good thermal processing window and making PVA easier to mold and process. If the amount of plasticizer added is less than 10 parts, it cannot effectively lower the melting point of the PVA water-soluble film; however, if the amount of plasticizer added is greater than 30 parts, it will reduce the mechanical properties of the PVA water-soluble film.

[0022] According to an embodiment of the present invention, the lubricant is one or more of fatty acid and its metal soap lubricants, hydrocarbon lubricants, and organosilicon compound lubricants; wherein, the fatty acid and its metal soap lubricant is selected from at least one of stearic acid, calcium stearate, zinc stearate, and magnesium stearate, the hydrocarbon lubricant is selected from at least one of paraffin wax and microcrystalline wax, and the organosilicon compound lubricant is selected from at least one of silicone powder and silicone masterbatch.

[0023] In the embodiments of the present invention, the lubricant can be any lubricant commonly used in the art, without particular limitation. Adding a lubricant can effectively improve the processing performance of the polyvinyl alcohol water-soluble film. If the amount of lubricant added is less than 0.1 parts, it cannot exert a lubricating effect; however, if the amount of lubricant added is greater than 1 part, it will affect the water solubility of the polyvinyl alcohol water-soluble film.

[0024] According to embodiments of the present invention, the antioxidant is one or more of antioxidant 1024, antioxidant 1076, antioxidant 1098, antioxidant 1010, antioxidant 626, antioxidant 168, antioxidant DLTP, and antioxidant DSTP.

[0025] In the embodiments of the present invention, the antioxidant can be any antioxidant commonly used in the art, without particular limitation. The addition of antioxidant can prevent the degradation and aging of polyvinyl alcohol. If the amount of antioxidant added is less than 0.01 parts, it cannot effectively prevent the degradation and aging of the polyvinyl alcohol water-soluble film; however, if the amount of antioxidant added is greater than 2 parts, it will affect the water solubility of the polyvinyl alcohol water-soluble film.

[0026] As a second aspect of the present invention, the present invention provides a method for preparing a polyvinyl alcohol water-soluble film, comprising: mixing polyvinyl alcohol of a first degree of polymerization, polyvinyl alcohol of a second degree of polymerization, a crosslinking agent, a plasticizer, a lubricant, and an antioxidant evenly to obtain a mixture; and forming the mixture into a film by a film-forming method to obtain a polyvinyl alcohol water-soluble film; wherein, by weight, the polyvinyl alcohol of the first degree of polymerization is 100 parts, the polyvinyl alcohol of the second degree of polymerization is 20-50 parts, the crosslinking agent is 0.01-0.1 parts, the plasticizer is 10-30 parts, the lubricant is 0.1-1 parts, and the antioxidant is 0.1-2 parts.

[0027] In the embodiments of the present invention, the raw materials used to prepare the polyvinyl alcohol water-soluble film are directly mixed and the polyvinyl alcohol water-soluble film is formed by film formation. The preparation method is simple, the film formation time is short, the cost is low, and it can be applied to industrial production.

[0028] In embodiments of the present invention, the film-forming method is any one of blow molding, casting, or biaxial stretching. Blow molding includes: extruding the above mixture through an extruder to obtain an extruded sample; cooling the extruded sample to room temperature and then granulating it through a pelletizer to obtain polyvinyl alcohol granules; and blowing the polyvinyl alcohol granules through a blown film machine to obtain a polyvinyl alcohol water-soluble film; wherein the extrusion temperature of the extruder is 100-200℃, the screw speed of the extruder is 40-60 r / min, the blowing temperature of the blown film machine is 120-220℃, the extrusion rate of the blown film machine is 30-50 r / min, the traction rate of the blown film machine is 5-8 r / min, and the blown film diameter is 5-15 cm. The casting process includes: adding a mixture to water, heating and stirring to obtain a mixture solution; coating the mixture solution onto a casting medium, controlling the coating thickness with a doctor blade, and drying at a set temperature to obtain a polyvinyl alcohol water-soluble film; wherein the heating temperature is 80-200℃, the stirring time is 2-4h, the coating thickness is 70-80μm, the set temperature is 80-100℃, and the drying time is 30-90s.

[0029] The present invention will be further illustrated below through embodiments and related test experiments. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict. All instruments, consumables, and reagents used in the following embodiments are commercially available unless otherwise specified.

[0030] Example 1

[0031] The polyvinyl alcohol water-soluble film prepared in Example 1 mainly comprises: 100 parts of polyvinyl alcohol with a degree of hydrolysis of 88% and a degree of polymerization of 500; 30 parts of polyvinyl alcohol with a degree of hydrolysis of 88% and a degree of polymerization of 1800; 0.1 parts of boric acid; 20 parts of glycerol; 0.1 parts of zinc stearate; and 0.1 parts of antioxidant 1010.

[0032] The polyvinyl alcohol aqueous film of Example 1 was prepared by the following method:

[0033] The above raw materials were mixed evenly to obtain a mixture. The mixture was then fed into a twin-screw extruder for extrusion. The temperatures of the twin-screw extruder were set as follows: Zone 1: 110℃; Zone 2: 150℃; Zone 3: 160℃; Zone 4: 170℃; Zone 5: 175℃; Zone 6: 180℃; Zone 7: 180℃; Zone 8: 180℃; Zone 9: 180℃; Zone 10: 180℃; Die head temperature: 180℃; Screw speed: 50 r / min. Extruded samples were obtained. After cooling the extruded samples to room temperature, they were granulated using a pelletizer to obtain polyvinyl alcohol granules. Polyvinyl alcohol granules were blown into films using an extrusion blown film machine. The temperatures of the extrusion blown film machine were set as follows: Zone 1: 150℃, Zone 2: 185℃, Zone 3: 200℃, Zone 4: 195℃, Die head temperature: 195℃, Extrusion rate: 40r / min, Traction rate: 6r / min, Blown film diameter: 10cm, to obtain a polyvinyl alcohol water-soluble film.

[0034] Example 2

[0035] The polyvinyl alcohol aqueous film prepared in Example 2 has the same main components and preparation method as that in Example 1. The main difference is that the crosslinking agent is succinic acid.

[0036] Example 3

[0037] The polyvinyl alcohol aqueous film prepared in Example 3 has the same main components as that in Example 1, and it is prepared by the following method:

[0038] The raw materials were mixed evenly to obtain a mixture. The mixture was added to 320 parts of water and heated and stirred at 150°C for 3 hours to obtain a mixture solution. The mixture solution was coated and cast, and the coating thickness was controlled to be 75 μm using a doctor blade. It was then dried at 90°C for 60 seconds to obtain a polyvinyl alcohol water-soluble film.

[0039] Comparative Example 1

[0040] The main components and preparation method of the polyvinyl alcohol aqueous film prepared in Comparative Example 1 are the same as those in Example 1. The main difference is that the main components of the polyvinyl alcohol aqueous film prepared in Comparative Example 1 do not include crosslinking agents.

[0041] Comparative Example 2

[0042] The polyvinyl alcohol aqueous film prepared in Comparative Example 2 has the same main components and preparation method as that in Example 1, the main difference being that the content of boric acid is 0.2 parts.

[0043] Characterization and testing:

[0044] 1. Water solubility test: Tested according to Q / GDLJ 01-2019, with test temperatures of 5℃ and 18℃.

[0045] 2. Melting point and crystallinity test: Differential scanning calorimetry (DSC) was used to heat from 40℃ to 238℃ in a nitrogen atmosphere at a heating rate of 10℃ / min. Crystallinity = (melting peak area / theoretical enthalpy of 100% crystallization) * 100.

[0046] 3. Degree of polymerization test: The degree of polymerization is determined using the viscosity method to determine whether cross-linking has occurred and the degree of cross-linking.

[0047] 4. Mechanical property testing: Tested according to GB / T 1040.3-2006. Type 2 specimens were used, with a length of 150 mm and a width of 15 mm. The test speed was 500 mm / min. Three data points were tested for each polyvinyl alcohol water-soluble film, and the average value was calculated.

[0048] The results of water solubility test, melting point and crystallinity test, degree of polymerization test, and mechanical property test of different polyvinyl alcohol water-soluble films are shown in Table 1.

[0049] Table 1. Test results of the performance of different polyvinyl alcohol water-soluble films

[0050]

[0051] Table 1 shows that the degree of crosslinking between polyvinyl alcohol (PVA) molecular chains increases with the increase of crosslinking agent addition. The melting point and crystallinity of the PVA water-soluble film decrease with increasing crosslinking agent addition. The dissolution time of the PVA water-soluble film at 5℃ and 18℃ first shortens and then lengthens with increasing crosslinking agent addition. Therefore, the water solubility of the PVA water-soluble film can be improved by controlling the amount of crosslinking agent added. Experiments showed that replacing other crosslinking agents can also effectively improve the water solubility of the PVA water-soluble film; and that different film-forming methods, due to different processing temperatures, also affect the water solubility of the PVA water-soluble film. Simultaneously, mechanical property tests on the PVA water-soluble film showed that the tensile strength and elongation at break of the PVA water-soluble film also increase with increasing crosslinking agent addition. This indicates that adding a small amount of crosslinking agent can not only improve the water solubility of the PVA water-soluble film but also improve its mechanical properties.

[0052] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A polyvinyl alcohol water-soluble film, characterized in that, The polyvinyl alcohol aqueous film comprises: polyvinyl alcohol of a first degree of polymerization, polyvinyl alcohol of a second degree of polymerization, a crosslinking agent, a plasticizer, a lubricant, and an antioxidant; Of which, by weight, the first degree of polymerization polyvinyl alcohol is 100 parts, the second degree of polymerization polyvinyl alcohol is 20-50 parts, the crosslinking agent is 0.1 parts, the plasticizer is 10-30 parts, the lubricant is 0.1-1 parts, and the antioxidant is 0.1-2 parts; The polyvinyl alcohol water-soluble film is suitable for use at 0-25℃; The degree of alcoholysis of the first degree of polymerization polyvinyl alcohol is 86-90%, and the degree of polymerization is 300-800; The degree of alcoholysis of the second degree of polymerization polyvinyl alcohol is 86-90%, and the degree of polymerization is 1500-2000; The crosslinking agent is one or more of boric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, glyoxal, malondialdehyde, succinic acid, glutaraldehyde, and adipic acid.

2. The polyvinyl alcohol water-soluble film according to claim 1, characterized in that, The plasticizer is one or more of polyol plasticizers and organic amine plasticizers; The lubricant is one or more of the following: fatty acid and its metal soap lubricants, hydrocarbon lubricants, and organosilicon compound lubricants.

3. The polyvinyl alcohol water-soluble film according to claim 2, characterized in that, The polyol plasticizer is selected from at least one of ethylene glycol, glycerin, sorbitol, diethanol, polyethylene glycol 200, and polyethylene glycol 400; The organic amine plasticizer is selected from at least one of diethanolamine and triethanolamine; The fatty acids and their metal soap lubricants are selected from at least one of stearic acid, calcium stearate, zinc stearate, and magnesium stearate; The hydrocarbon lubricant is selected from at least one of paraffin wax and microcrystalline wax; The organosilicon compound lubricant is selected from at least one of silicone powder and silicone masterbatch.

4. The polyvinyl alcohol water-soluble film according to claim 1, characterized in that, The antioxidant is one or more of antioxidant 1024, antioxidant 1076, antioxidant 1098, antioxidant 1010, antioxidant 626, antioxidant 168, antioxidant DLTP, and antioxidant DSTP.

5. A method for preparing a polyvinyl alcohol aqueous film as described in any one of claims 1-4, characterized in that, The preparation method includes: The polyvinyl alcohol of the first degree of polymerization, the polyvinyl alcohol of the second degree of polymerization, the crosslinking agent, the plasticizer, the lubricant and the antioxidant are mixed evenly to obtain a mixture. The mixture is formed into a film by a film-forming method to obtain a polyvinyl alcohol water-soluble film.

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