Method for preparing high-performance PVA / PBAT (polyvinyl acetate / poly (butylene adipate-co-terephthalate)) composite film by blow molding

Abstract

The invention provides a method for preparing a high-performance PVA / PBAT (polyvinyl alcohol / poly (butyleneadipate-co-terephthalate)) composite film by blow molding, which comprises the following steps: carrying out swelling plastification modification on polyvinyl alcohol by using an environment-friendly plasticizer to obtain modified polyvinyl alcohol; the preparation method comprises the following steps: modifying polyvinyl alcohol, blending the modified polyvinyl alcohol with a certain proportion of PBAT, carrying out screw extrusion granulation to prepare composite granules, and carrying out extrusion blow molding film formation to prepare the PVA / PBAT composite film. According to the method disclosed by the invention, the specific environment-friendly plasticizer is selected, so that the PBAT is well dispersed in a PVA matrix, the phase domain size of a dispersed phase is less than 1 mu m in a breakthrough manner, and the PVA / PBAT composite film with good mechanical properties is successfully prepared for the first time. The prepared PVA / PBAT composite film has good water resistance and blocking resistance, the application scene of the PVA film in the packaging field can be widened, and the PVA / PBAT composite film has good commercial application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing a PVA-based composite film by film blowing, and relates to a method suitable for preparing a high-performance PVA / PBAT composite film by film blowing. Background Art

[0002] Traditional plastic packaging films are made of polymer materials such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). They are non-biodegradable and difficult to recycle and reuse effectively, causing serious environmental pollution, harming the soil and water environment, and threatening the survival of animals and plants. In recent years, in order to develop environmentally friendly packaging materials, biodegradable plastic films such as polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) have been widely used. However, common biodegradable plastics usually face problems such as high cost, poor mechanical properties, and poor degradation controllability, making it difficult to replace non-degradable disposable packaging materials on a large scale.

[0003] Polyvinyl alcohol (PVA) is a polyhydroxy polymer material with excellent mechanical properties, transparency, barrier to oxygen and aroma substances, resistance to ultraviolet aging and other performance characteristics. It is water-soluble and the aqueous solution is non-toxic and harmless, biocompatible, can be used as a soil conditioner, and can be biodegraded and decomposed into carbon dioxide and water under certain conditions. It is regarded as an environmentally friendly packaging material. However, due to the strong hydrogen bonds between PVA molecules and within PVA molecules, its melting point is close to the decomposition temperature, making it difficult to process by thermoplastics. PVA films on the market are mainly produced based on the solution method, which has complex processes, low production efficiency, high energy consumption and cost, and is difficult to blend with other non-water-soluble polymer materials (such as PLA, PBAT, etc.). Pure PVA films have problems such as poor water resistance, easy adhesion, and slow biodegradation rate, which limit their application in the field of disposable packaging. In view of the above problems, it is urgent to develop an environmentally friendly and landfill-safe PVA-based blended composite film to replace traditional polyolefin packaging film materials (such as shopping bags, agricultural packaging, textile packaging, etc.) on a large scale. For example, Chinese invention patent CN202210588001.7 discloses a method for preparing a modified PVA / thermoplastic resin composite material, using dimethyl sulfoxide as a solvent and using a chemical method to sequentially achieve etherification and silanization of PVA, and then blending the silanized PVA resin with a thermoplastic resin. This method is cumbersome, involves the use of organic solvents, has poor environmental protection, and is costly.

[0004] The previous patents of the inventor's team, such as CN201210036388.1, CN200610022317.0, and CN201710107948.0, disclosed an efficient physical plasticization modification method for PVA, realized the thermoplastic processing of PVA, successfully produced PVA film based on melt extrusion, improved the production efficiency of PVA film, and reduced the production cost of film. However, the limitations of the performance of pure PVA film have not been overcome. Therefore, it is very important to develop PVA-based composite packaging film using a green and sustainable method, which can provide new materials for disposable packaging, broaden the application scenarios of PVA film, and help reduce the use of traditional plastic packaging film and reduce its damage to the environment. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention provides a method for preparing high-performance PVA / PBAT composite film by blow molding. The method of the present invention selects a specific environmentally friendly plasticizer to make PBAT well dispersed in the PVA matrix, and the dispersed phase domain size is breakthrough below 1μm, and a PVA / PBAT composite film with good mechanical properties is successfully prepared for the first time; in addition, the prepared composite film can be safely landfilled, digested in soil or water, and has biodegradability. The prepared PVA / PBAT composite film has good water resistance and anti-adhesion properties, which can broaden the application scenarios of PVA film in the packaging field and has good commercial application prospects.

[0006] To achieve the above objectives, the present invention is implemented by adopting a technical solution consisting of the following technical measures.

[0007] The present invention provides a method for preparing a high-performance PVA / PBAT composite film by blow molding, which mainly comprises the following steps:

[0008] (1) using an environmentally friendly plasticizer to perform swelling and plasticization modification on polyvinyl alcohol (PVA) to obtain modified polyvinyl alcohol;

[0009] Wherein, the environmentally friendly plasticizer is deionized water, or a mixed solution in which the mass percentage of deionized water is not less than 80wt%; other components in the mixed solution except deionized water include at least one of glycerol, polyglycerol, ethylene glycol, sorbitol, polyethylene glycol, and boric acid;

[0010] (2) The raw materials mainly including the following components are mixed and prepared as a mixed material by weight:

[0011] 100 parts of modified polyvinyl alcohol,

[0012] PBAT 5-54 parts;

[0013] (3) Extruding the mixture obtained in step (2) through a screw extruder to granulate to prepare PVA / PBAT composite granules;

[0014] (4) forming a PVA / PBAT composite film by extrusion blow molding the PVA / PBAT composite pellets obtained in step (3);

[0015] The process parameters of the extrusion blow molding film include: an extrusion temperature of 120 to 190° C. and a screw speed of 10 to 40 rpm.

[0016] In this article, the polyvinyl alcohol described in step (1) is a conventional commercially available polyvinyl alcohol raw material, and the raw material form can be powder or granules. It should be noted that polyvinyl alcohol (PVA) may agglomerate after being swollen and plasticized by an environmentally friendly plasticizer. In order to facilitate mixing with PBAT in step (2), it can be crushed to restore its powder or granule state.

[0017] In one of the technical solutions, the polyvinyl alcohol in step (1) can be selected from conventional polyvinyl alcohol raw materials on the market, such as polyvinyl alcohol with a degree of polymerization of 1000 to 2700 and a degree of alcoholysis of 88 to 99%. In order to further improve its biodegradability, through analysis and comparison, polyvinyl alcohol with a degree of polymerization of 1700 and a degree of alcoholysis of 88 to 99% is more preferred.

[0018] PBAT is a petroleum-based biodegradable polyester that has the characteristics of polybutylene terephthalate (PBA) and polybutylene terephthalate (PBT). It has excellent biodegradability, excellent film-forming properties, good tensile strength and toughness, and low processing temperature. Using PBAT to modify PVA is expected to improve the water resistance and opening of PVA film and enhance its environmental friendliness. At present, the main preparation method of PVA film is the solution method. Since PBAT is insoluble in water, it is difficult to achieve the preparation of PVA / PBAT composite film based on the solution method; the melt blending of PVA and PBAT faces the problem of mismatch in processing temperature and viscosity, which will lead to poor dispersion of the composite material, large domain size, and low strength of the composite film, which is difficult to meet the performance requirements of packaging materials.

[0019] In the present invention, the polyvinyl alcohol (PVA) described in step (1) is swelled and plasticized by an environmentally friendly plasticizer, and its technical principle is mainly based on the previous research results of the molecular composite and plasticization technology research project of the inventor's research group (Wang Ru, Wang Qi, Li Li, et al. Thermal properties of modified polyvinyl alcohol [J]. Plastic Industry, 2002, 30 (1): 3.). It should be added that, based on the above research results, the inventors of the present invention unexpectedly found that when a specific plasticizer is selected, the phase domain size of PBAT as a dispersed phase in the PVA matrix can be significantly reduced to less than 1 μm, while other conventionally used plasticizer systems (such as glycerol) usually have a PBAT dispersed phase phase domain size of about 30 μm, which significantly improves the extrusion blow molding film processing characteristics of the PVA / PBAT composite system and greatly improves the mechanical properties of the prepared composite film. In addition, when water or a mixed liquid with a water content of not less than 80wt% is selected as a plasticizer, the melting point of PVA can be greatly reduced, giving it good fluidity and suitable viscosity at the processing temperature, achieving efficient mixing of modified polyvinyl alcohol and PBAT, and water is easier to remove, which is more convenient and environmentally friendly for subsequent processing.

[0020] However, it is worth emphasizing that, due to the easy hydrolysis of PBAT, although the specific choice of water as a plasticizer is conducive to the good processability of PVA blended with PBAT after plasticization, the water precipitated during the processing of modified polyvinyl alcohol will still have a negative impact on PBAT. Based on this, it is necessary to specifically adapt the extrusion blow molding film forming process conditions to reduce the negative impact of PBAT hydrolysis. Studies have found that in the extrusion blow molding film forming process, the extrusion temperature is 120-190°C due to the good processability of the modified polyvinyl alcohol and PBAT blend, but the screw speed needs to be strictly controlled at 10-40rpm, corresponding to the shear rate in the screw section should not exceed 513s. -1 If the screw speed is too high, the internal water of the modified polyvinyl alcohol will be vaporized due to the shear force field during the processing, forming in-situ foaming and making it impossible to extrude smoothly; if the screw speed is too low, PBAT is prone to excessive hydrolysis during the processing, resulting in the deterioration of the mechanical properties of the composite film.

[0021] Generally speaking, the specific method of swelling and plasticizing the polyvinyl alcohol (PVA) using an environmentally friendly plasticizer in step (1) can refer to the plasticizing modification of conventional polyvinyl alcohol, especially the contents recorded in the inventor's previously disclosed papers and patent technologies.

[0022] In order to better illustrate the present invention and provide a method for reference, the step (1) of using an environmentally friendly plasticizer to swell and plasticize polyvinyl alcohol (PVA) is to immerse the polyvinyl alcohol in the environmentally friendly plasticizer and let it stand for 4 to 48 hours under closed conditions. Generally speaking, the environmentally friendly plasticizer needs to ensure that the polyvinyl alcohol can be completely immersed, but in order to better illustrate the present invention, in one of the technical solutions, the mass ratio of the environmentally friendly plasticizer to the polyvinyl alcohol is not less than 1:4.

[0023] In one of the more preferred technical solutions, in step (1), polyvinyl alcohol (PVA) is subjected to swelling and plasticization modification using an environmentally friendly plasticizer, and the temperature condition during the swelling and plasticization modification process is 40 to 80° C., which can accelerate the plasticization modification efficiency.

[0024] In one of the technical solutions, the adjuvants conventionally used in PVA processing and molding may be added to the mixture in step (2) to achieve further functional expansion / process assistance of the product. For the specific selection of adjuvants, those skilled in the art may refer to the prior art or existing literature, such as defoamers, antioxidants, heat stabilizers, antibacterial agents and other processing aids / functional adjuvants. It should be noted that the mixture in step (1) may or may not include adjuvants conventionally used in PVA processing and molding; in the preferred technical solution and specific implementation method described below, adjuvants were not added to the mixture in order to minimize the influencing factors in the comparative experiment, but this does not mean that appropriate adjuvants cannot be added to the mixture. Generally speaking, the total amount of adjuvants added is not higher than 10wt% of the mixture.

[0025] In this article, the mixed material in step (3) is extruded and granulated by a screw to prepare PVA / PBAT composite granules, which is a conventional screw extrusion granulation process. Those skilled in the art can directly refer to the extrusion granulation process of PVA.

[0026] In one of the technical solutions, since PVA has good processability after plasticization modification, the mixed material in step (3) is granulated by screw extrusion, wherein the extrusion temperature is 120-190°C.

[0027] In this article, the PVA / PBAT composite pellets in step (4) are extruded and blown into film to prepare a PVA / PBAT composite film, wherein the extrusion blown film is one of the plastic film forming methods. Except for the process parameters specified in the present invention, the remaining process parameters / process conditions / specific process steps can refer to the prior art in the art, preferably referring to the extrusion blown film process literature of PVA film.

[0028] In this article, since the environmentally friendly plasticizer used is water or a mixed solution with a water content of not less than 80wt%, the PVA / PBAT composite film prepared in step (4) can be dried at 40-80°C before storage to remove excess moisture.

[0029] The present invention has the following beneficial effects:

[0030] 1. The present invention provides a method for preparing a high-performance PVA / PBAT composite film by blow molding. By selecting a specific environmentally friendly plasticizer, the method allows PBAT to be well dispersed in a PVA matrix, and the domain size of the dispersed phase is breakthrough to be less than 1 μm. For the first time, a PVA / PBAT composite film with good mechanical properties is successfully prepared.

[0031] 2. The present invention selects a specific environmentally friendly plasticizer to perform swelling and plasticization modification on PVA, thereby broadening the processable temperature range and realizing melt blending of modified polyvinyl alcohol and PBAT. PBAT is well dispersed in the PVA matrix, and the dispersed phase domain size is less than 1 μm.

[0032] 3. The PVA / PBAT composite film prepared by the present invention has the characteristics of biodegradability, is environmentally friendly, can be safely landfilled, and will not cause environmental pollution.

[0033] 4. The PVA / PBAT composite film prepared by the present invention has good water resistance and anti-adhesion properties, and can broaden the application scenarios in the field of packaging materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a photo of the PVA / PBAT composite film prepared in Example 2 of the present invention being formed by extrusion blow molding.

[0035] Figure 2 This is a water-etched surface morphology of the intermediate product PVA / PBAT composite pellets of Example 4 of the present invention. It can be clearly seen that the dispersed phase domain size is less than 1 μm.

[0036] Figure 3 This is a cross-sectional morphology of the intermediate product PVA / PBAT composite granules of comparative example 4 of the present invention. After the phase inversion occurs, PVA is transformed into a dispersed phase, and the domain size is still far greater than 1 μm.

[0037] Figure 4 This is a cross-sectional morphology of the PVA / PBAT composite pellets prepared in Comparative Example 5 of the present invention. It can be found that the domain size of the PBAT dispersed phase in the conventionally used glycerol plasticizer system is about 30 μm.

[0038] Figure 5This is a photo of the PVA / PBAT composite film obtained in comparative example 4 of the present invention during the extrusion blow molding process. It is clearly seen that the film cannot be successfully blown.

[0039] Figure 6 It is a summary of the tensile performance results of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 of the present invention. Among them, Figure a is a stress-strain comparison curve of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 in the longitudinal direction; Figure b is a tensile strength comparison column chart of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 in the longitudinal direction; Figure c is a modulus comparison column chart of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 in the longitudinal direction; Figure d is a stress-strain comparison curve of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 in the transverse direction; Figure e is a tensile strength comparison column chart of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 in the transverse direction; Figure f is a modulus comparison column chart of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 in the transverse direction.

[0040] Figure 7 It is a summary diagram of the puncture performance of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 of the present invention. Among them, Figure a is a puncture stress-displacement comparison curve of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3; Figure b is a puncture strength comparison bar chart of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3.

[0041] Figure 8 This is a comparative bar chart of the adhesion strength of the PVA / PBAT composite films prepared in Examples 1 to 4 and Comparative Examples 1 to 3 of the present invention.

[0042] Fig. 9 The cross-sectional morphology of the PVA / PBAT composite film prepared in Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention is shown. Among them, the thickness of the PVA / PBAT composite film prepared in Examples 1 to 4 and Comparative Examples 1 to 3 is about 50 μm. Benefiting from the hydrogen bond interaction between macromolecules and the volume expansion effect of the stretching flow field, when the PBAT content is less than 25wt%, the PBAT dispersion is excellent and the two-phase interface is very fuzzy; when the PBAT content is 25-35wt%, PBAT dispersed particles can be observed, and their size is less than 1μm; and when the PBAT content increases to 45wt%, pore defects are generated, and when the PBAT content increases to 65wt%, the phase inversion occurs, and the PVA is transformed into a dispersed phase, and the phase domain size is close to 5μm. At the same time, the PVA / PBAT composite film prepared in Comparative Example 4 is significantly thickened due to the ineffective film formation. DETAILED DESCRIPTION

[0043] In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously change or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention. Although it is believed that those of ordinary skill in the art fully understand the following terms, the following definitions are still stated to help illustrate the subject matter disclosed by the present invention.

[0044] The present invention provides a method for preparing a high-performance PVA / PBAT composite film by blow molding, which mainly comprises the following steps:

[0045] (1) using an environmentally friendly plasticizer to perform swelling and plasticization modification on polyvinyl alcohol (PVA) to obtain modified polyvinyl alcohol;

[0046] Wherein, the environmentally friendly plasticizer is deionized water, or a mixed solution in which the mass percentage of deionized water is not less than 80wt%; other components in the mixed solution except deionized water include at least one of glycerol, polyglycerol, ethylene glycol, sorbitol, polyethylene glycol, and boric acid;

[0047] (2) The raw materials mainly including the following components are mixed and prepared as a mixed material by weight:

[0048] 100 parts of modified polyvinyl alcohol,

[0049] PBAT 5-54 parts;

[0050] (3) Extruding the mixture obtained in step (2) through a screw to granulate to prepare PVA / PBAT composite granules;

[0051] (4) forming a PVA / PBAT composite film by extrusion blow molding the PVA / PBAT composite pellets obtained in step (3);

[0052] The process parameters of the extrusion blow molding film include: an extrusion temperature of 120 to 190° C. and a screw speed of 10 to 40 rpm.

[0053] In this article, the polyvinyl alcohol described in step (1) is a conventional commercially available polyvinyl alcohol raw material, and the raw material form can be powder or granules. It should be noted that polyvinyl alcohol (PVA) may agglomerate after being swollen and plasticized by an environmentally friendly plasticizer. In order to facilitate mixing with PBAT in step (2), it can be crushed to restore its powder or granule state.

[0054] In one embodiment, the polyvinyl alcohol in step (1) can be selected from conventional polyvinyl alcohol raw materials on the market, such as polyvinyl alcohol with a degree of polymerization of 1000 to 2700 and a degree of alcoholysis of 88 to 99%. In order to further improve its biodegradability, through analysis and comparison, polyvinyl alcohol with a degree of polymerization of 1700 and a degree of alcoholysis of 88 to 99% is more preferred.

[0055] PBAT is a petroleum-based biodegradable polyester that has the characteristics of polybutylene terephthalate (PBA) and polybutylene terephthalate (PBT). It has excellent biodegradability, excellent film-forming properties, good tensile strength and toughness, and low processing temperature. Using PBAT to modify PVA is expected to improve the water resistance and opening of PVA film and enhance its environmental friendliness. At present, the main preparation method of PVA film is the solution method. Since PBAT is insoluble in water, it is difficult to achieve the preparation of PVA / PBAT composite film based on the solution method; the melt blending of PVA and PBAT faces the problem of mismatch in processing temperature and viscosity, which will lead to poor dispersion of the composite material, large domain size, and low strength of the composite film, which is difficult to meet the performance requirements of packaging materials.

[0056] In the present invention, the polyvinyl alcohol (PVA) described in step (1) is swelled and plasticized by an environmentally friendly plasticizer, and its technical principle is mainly based on the previous research results of the molecular composite and plasticization technology research project of the inventor's research group (Wang Ru, Wang Qi, Li Li, et al. Thermal properties of modified polyvinyl alcohol [J]. Plastic Industry, 2002, 30 (1): 3.). It should be added that, based on the above research results, the inventors of the present invention unexpectedly found that when a specific plasticizer is selected, the phase domain size of PBAT as a dispersed phase in the PVA matrix can be significantly reduced to less than 1 μm, while other conventionally used plasticizer systems (such as glycerol) usually have a PBAT dispersed phase phase domain size of about 30 μm, which significantly improves the extrusion blow molding film processing characteristics of the PVA / PBAT composite system and greatly improves the mechanical properties of the prepared composite film. In addition, when water or a mixed liquid with a water content of not less than 80wt% is selected as a plasticizer, the melting point of PVA can be greatly reduced, giving it good fluidity and suitable viscosity at the processing temperature, achieving efficient mixing of modified polyvinyl alcohol and PBAT, and water is easier to remove, which is more convenient and environmentally friendly for subsequent processing.

[0057] However, it is worth emphasizing that, due to the easy hydrolysis of PBAT, although the specific choice of water as a plasticizer is conducive to the good processability of PVA blended with PBAT after plasticization, the water precipitated during the processing of modified polyvinyl alcohol will still have a negative impact on PBAT. Based on this, it is necessary to specifically adapt the extrusion blow molding film forming process conditions to reduce the negative impact of PBAT hydrolysis. Studies have found that in the extrusion blow molding film forming process, the extrusion temperature is 120-190°C due to the good processability of the modified polyvinyl alcohol and PBAT blend, but the screw speed needs to be strictly controlled at 10-40rpm, corresponding to the shear rate in the screw section should not exceed 513s. -1 If the screw speed is too high, the internal water of the modified polyvinyl alcohol will be vaporized due to the shear force field during the processing, forming in-situ foaming and making it impossible to extrude smoothly; if the screw speed is too low, PBAT is prone to excessive hydrolysis during the processing, resulting in the deterioration of the mechanical properties of the composite film.

[0058] Generally speaking, the specific method of swelling and plasticizing the polyvinyl alcohol (PVA) using an environmentally friendly plasticizer in step (1) can refer to the plasticizing modification of conventional polyvinyl alcohol, especially the contents recorded in the inventor's previously disclosed papers and patent technologies.

[0059] In order to better illustrate the present invention and provide an embodiment for reference, the step (1) of using an environmentally friendly plasticizer to swell and plasticize the polyvinyl alcohol (PVA) is to immerse the polyvinyl alcohol in the environmentally friendly plasticizer and let it stand for 4 to 48 hours under closed conditions. Generally speaking, the environmentally friendly plasticizer needs to ensure that the polyvinyl alcohol can be completely immersed, but in order to better illustrate the present invention, in one embodiment, the mass ratio of the environmentally friendly plasticizer to the polyvinyl alcohol is not less than 1:4.

[0060] In one of the more preferred embodiments, in step (1), polyvinyl alcohol (PVA) is subjected to swelling and plasticization modification using an environmentally friendly plasticizer, and the temperature condition during the swelling and plasticization modification process is 40 to 80° C., which can accelerate the plasticization modification efficiency.

[0061] In one embodiment, the PBAT in step (2) is 5 to 54 parts, for example 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54 or any range or point value therebetween.

[0062] In one embodiment, the amount of PBAT added in step (2) is 25-35 wt % of the total mass of the mixture.

[0063] In one embodiment, the adjuvants conventionally used in PVA processing and molding may be added to the mixture in step (2) to achieve further functional expansion / process assistance of the product. For the specific selection of adjuvants, those skilled in the art may refer to the prior art or existing literature, such as defoamers, antioxidants, heat stabilizers, antibacterial agents and other processing aids / functional aids. It should be noted that the mixture in step (1) may or may not include adjuvants conventionally used in PVA processing and molding; in the preferred technical scheme and specific implementation method described below, adjuvants are not added to the mixture in order to minimize the influencing factors in the comparative experiment, but this does not mean that appropriate adjuvants cannot be added to the mixture. Generally speaking, the total amount of adjuvants added is not higher than 10wt% of the mixture.

[0064] Herein, the mixed material in step (3) is extruded and granulated by a screw to prepare PVA / PBAT composite granules, which is a conventional screw extrusion granulation process. Those skilled in the art can directly refer to the extrusion granulation process of PVA.

[0065] In one embodiment, since PVA has good processability after plasticization modification, the mixed material in step (3) is granulated by screw extrusion, wherein the extrusion temperature is 120-190°C.

[0066] In this article, the PVA / PBAT composite pellets in step (4) are extruded and blown into film to prepare a PVA / PBAT composite film, wherein the extrusion blown film is one of the plastic film forming methods. Except for the process parameters specified in the present invention, the remaining process parameters / process conditions / specific process steps can refer to the prior art in the art, preferably referring to the extrusion blown film process literature of PVA film.

[0067] In one embodiment, the extrusion temperature in step (4) is 120-190°C, for example, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C or any range or point value therebetween; the screw speed is 10-40rpm, for example, 10rpm, 15rpm, 20rpm, 25rpm, 30rpm, 35rpm, 40rpm or any range or point value therebetween.

[0068] In this article, since the environmentally friendly plasticizer used is water or a mixed solution with a water content of not less than 80wt%, the PVA / PBAT composite film prepared in step (4) can be dried at 40-80°C before storage to remove excess moisture.

[0069] The present invention will be further explained in detail with reference to the following examples. However, it should be understood by those skilled in the art that these examples are provided for illustrative purposes only and are not intended to limit the present invention.

[0070] Example

[0071] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. The specific conditions not specified in the examples are carried out according to the conditions recommended by normal conditions or manufacturers. The reagents used or the instruments not specified by the manufacturer are all conventional products that can be obtained commercially. The application should not be construed as being limited to the specific examples described.

[0072] 1. Raw materials

[0073] Polyvinyl alcohol (PVA) (degree of polymerization 1700, degree of alcoholysis 88%), supplied by Sichuan Vinylon Co., Ltd.;

[0074] Deionized water, provided by Chengdu Kelong Chemical Reagent Factory;

[0075] Glycerol, analytical grade, supplied by Xilong Scientific Co., Ltd.;

[0076] Polybutylene adipate terephthalate (PBAT), brand TH801T, was purchased from Xinjiang Lanshan Tunhe Energy Co., Ltd.

[0077] 2. Test Method

[0078] 1) Scanning electron microscope test (SEM)

[0079] An Inspect F scanning electron microscope (FEI, USA) was used to observe the microstructure of the samples with an accelerating voltage of 5 kV. The samples were gold-sprayed before testing. To obtain the sample cross section, the samples were immersed in liquid nitrogen for low-temperature brittle fracture. To obtain the sample etching surface, the sample surface was etched with room temperature water.

[0080] 2) Tensile performance test

[0081] The film samples were cut into dumbbell-shaped specimens and subjected to tensile property tests at a speed of 50 mm / min using an Instron 5567 electronic universal material testing machine (Instron, USA).

[0082] 3) Puncture performance test

[0083] The film samples were cut into circular specimens and the puncture resistance of the films was tested using an Instron 5567 electronic universal material testing machine (Instron, USA). The puncture needle dropped at a speed of 50 mm / min, the inner diameter of the sample fixing ring was 10.0 mm, the puncture needle had a diameter of 1.0 mm, and the puncture needle tip was hemispherical with a radius of 0.5 mm.

[0084] 4) Anti-adhesion performance test

[0085] Blown film is prone to adhesion between layers, which affects production, storage and actual use. The two-layer blown film sample was cut into rectangular strips with a width of 15 mm, one end was pre-peeled, and the adhesion strength of the blown film was tested using a DWD-10 universal material testing machine (Sichuan Dexiang Kechuang Instrument Co., Ltd.), with the fixture moving speed of 300 mm / min.

[0086] 3. Preparation method

[0087] (1) 75 parts of polyvinyl alcohol are immersed in an environmentally friendly plasticizer prepared by mixing 20 parts of deionized water and 5 parts of glycerol, and the mixture is sealed and allowed to stand for 8 hours at 80° C. to obtain modified polyvinyl alcohol;

[0088] (2) The following raw materials are mixed and prepared as a mixed material according to their mass fractions:

[0089] 100 parts of modified polyvinyl alcohol,

[0090] PBAT 5-54 parts;

[0091] (3) Extruding the mixture obtained in step (2) through a screw to obtain PVA / PBAT composite pellets at an extrusion temperature of 150° C.

[0092] (4) forming a PVA / PBAT composite film by extrusion blow molding the PVA / PBAT composite pellets obtained in step (3);

[0093] The process parameters of the extrusion blow molding film include: an extrusion temperature of 150° C. and a screw speed of 30 rpm.

[0094] Before testing, the prepared PVA / PBAT composite film was fully dried at a temperature of 60 to 80° C. to remove excess moisture.

[0095] Example 1

[0096] Example 1 is according to the steps of the above-mentioned "3. Preparation method", wherein the addition amount of PBAT is 5wt% of the total mass of the mixture, and finally a PVA / PBAT composite film is prepared.

[0097] Example 2

[0098] Example 2 is according to the steps of "3. Preparation method" above, wherein the amount of PBAT added is 15wt% of the total mass of the mixture, and finally a PVA / PBAT composite film is prepared.

[0099] Example 3

[0100] Example 3 follows the steps of “3. Preparation method” above, wherein the amount of PBAT added is 25wt% of the total mass of the mixture, and a PVA / PBAT composite film is finally prepared.

[0101] Example 4

[0102] Example 4 is according to the above-mentioned "3. Preparation method" steps, wherein the amount of PBAT added is 35wt% of the total mass of the mixture, and finally a PVA / PBAT composite film is prepared.

[0103] Comparative Example 1

[0104] Comparative Example 1 refers to the steps of the above “3. Preparation method”, but without adding PBAT, and finally a PVA film is prepared.

[0105] Comparative Example 2

[0106] Comparative Example 2 refers to the above-mentioned "3. Preparation method" step, wherein the amount of PBAT added is 45wt% of the total mass of the mixture, and a PVA / PBAT composite film is finally prepared.

[0107] Comparative Example 3

[0108] Comparative Example 3 refers to the above-mentioned "3. Preparation method" step, wherein the amount of PBAT added is 55wt% of the total mass of the mixture, and a PVA / PBAT composite film is finally prepared.

[0109] Comparative Example 4

[0110] Comparative Example 4 refers to the above-mentioned "3. Preparation method" step, wherein the amount of PBAT added is 65wt% of the total mass of the mixture, and a PVA / PBAT composite film is finally prepared.

[0111] Comparative Example 5

[0112] (1) 70 parts of polyvinyl alcohol, by weight, are immersed in an environmentally friendly plasticizer prepared by mixing 10 parts of deionized water and 20 parts of glycerol, and the mixture is sealed and allowed to stand for 8 hours at a temperature of 80° C. to obtain modified polyvinyl alcohol;

[0113] (2) The following raw materials are mixed and prepared as a mixed material according to their mass fractions:

[0114] 80 parts of modified polyvinyl alcohol,

[0115] PBAT 20 copies;

[0116] (3) The mixed material obtained in step (2) is extruded and granulated by a screw to prepare PVA / PBAT composite granules at an extrusion temperature of 170°C.

[0117] The prepared PVA / PBAT composite pellets were tested as comparative samples.

[0118] Example 5

[0119] (1) 75 parts of polyvinyl alcohol are immersed in 25 parts of deionized water as an environmentally friendly plasticizer, and the mixture is sealed and allowed to stand at 80° C. for 6 hours to obtain modified polyvinyl alcohol;

[0120] (2) The following raw materials are mixed and prepared as a mixed material according to their mass fractions:

[0121] 100 parts of modified polyvinyl alcohol,

[0122] PBAT 22 copies;

[0123] (3) Extruding the mixture obtained in step (2) through a screw to obtain PVA / PBAT composite pellets at an extrusion temperature of 150° C.

[0124] (4) forming a PVA / PBAT composite film by extrusion blow molding the PVA / PBAT composite pellets obtained in step (3);

[0125] The process parameters of the extrusion blow molding film include: an extrusion temperature of 150° C. and a screw speed of 30 rpm.

[0126] Before testing, the prepared PVA / PBAT composite film was fully dried at 60°C to remove excess moisture.

[0127] After testing, the PVA / PBAT composite film prepared in this embodiment has a tensile strength of 62 MPa, a puncture strength of 165 N / mm, and an adhesion strength of 0.12 N / 15 mm.

[0128] Example 6

[0129] (1) 75 parts of polyvinyl alcohol are immersed in an environmentally friendly plasticizer prepared by mixing 25 parts of deionized water and 0.1 parts of boric acid, and the mixture is sealed and allowed to stand at 40° C. for 48 hours to obtain modified polyvinyl alcohol;

[0130] (2) The following raw materials are mixed and prepared as a mixed material according to their mass fractions:

[0131] 100 parts of modified polyvinyl alcohol,

[0132] PBAT 40 parts;

[0133] (3) Extruding the mixture obtained in step (2) through a screw to obtain PVA / PBAT composite pellets at an extrusion temperature of 140° C.

[0134] (4) forming a PVA / PBAT composite film by extrusion blow molding the PVA / PBAT composite pellets obtained in step (3);

[0135] The process parameters of the extrusion blow molding film include: extrusion temperature of 140° C. and screw speed of 30 rpm.

[0136] Before testing, the prepared PVA / PBAT composite film was fully dried at 80°C to remove excess moisture.

[0137] After testing, the PVA / PBAT composite film prepared in this embodiment has a tensile strength of 48 MPa, a puncture strength of 127 N / mm, and an adhesion strength of 0.06 N / 15 mm.

[0138] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a high-performance PVA / PBAT composite film by blow molding, characterized in that The main steps include: (1) using an environmentally friendly plasticizer to perform swelling and plasticization modification on polyvinyl alcohol to obtain modified polyvinyl alcohol; Wherein, the environmentally friendly plasticizer is deionized water, or a mixed solution in which the mass percentage of deionized water is not less than 80wt%; other components in the mixed solution except deionized water include at least one of glycerol, polyglycerol, ethylene glycol, sorbitol, polyethylene glycol, and boric acid; (2) The raw materials mainly including the following components are mixed and prepared as a mixed material by weight: 100 parts of modified polyvinyl alcohol, PBAT 5-54 parts; (3) Extruding the mixture obtained in step (2) through a screw extruder to granulate to prepare PVA / PBAT composite granules; (4) forming a PVA / PBAT composite film by extrusion blow molding the PVA / PBAT composite pellets obtained in step (3); The process parameters of the extrusion blow molding film include: an extrusion temperature of 120 to 190° C. and a screw speed of 10 to 40 rpm.

2. The method according to claim 1, characterized in that: The degree of polymerization of the polyvinyl alcohol in step (1) is 1000-2700, and the degree of alcoholysis is 88-99%.

3. The method according to claim 1, characterized in that: In step (1), the polyvinyl alcohol is subjected to swelling and plasticization modification by using an environmentally friendly plasticizer, and the polyvinyl alcohol is immersed in the environmentally friendly plasticizer and allowed to stand in a sealed condition for 4 to 48 hours.

4. The method according to claim 1, characterized in that: In step (1), polyvinyl alcohol is subjected to swelling and plasticization modification using an environmentally friendly plasticizer, and the temperature condition during the swelling and plasticization modification process is 40 to 80°C.

5. The method according to claim 1, characterized in that: The mixture in step (2) also includes conventional additives.

6. The method according to claim 1, characterized in that: The mixed material in step (3) is extruded and granulated by a screw, wherein the extrusion temperature is 120-190°C.

7. The PVA / PBAT composite film prepared by the method for preparing a high-performance PVA / PBAT composite film by blow molding as claimed in claim 1.

8. Use of the PVA / PBAT composite film as claimed in claim 7 as a packaging material.

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