Intelligent humidity control barrier composite film and preparation method and application thereof
阅读说明：本技术 一种智能控湿阻隔复合薄膜及其制备方法和应用 (Intelligent humidity control barrier composite film and preparation method and application thereof ) 是由 张杨 郑萃 唐毓婧 宋建会 姚雪容 潘国元 刘轶群 于 2019-09-20 设计创作，主要内容包括：本发明一种智能控湿阻隔复合薄膜及其制备方法和应用。所述智能控湿阻隔复合薄膜包括基层和附加层,其中,所述基层为一层或两层结构,所述附加层存在于基层的一侧或者同时存在于基层的两侧；所述基层为多孔薄膜,基层的材料为聚乙烯、聚丙烯、聚苯乙烯、聚对苯二甲酸二醇酯、聚己内酰胺中的至少一种；所述附加层包含聚乙二醇、含有羧酸盐和磺酸盐基团的聚醚酮和/或聚醚砜、以及抗菌剂。本发明的智能控湿阻隔复合薄膜具有智能控湿能力,在相对湿度较低时保持果蔬湿度,在相对湿度较高时增大透湿从而防止水果蔬菜结露溃烂,并且具有氧气阻隔性能,可用于具有保鲜功能的果蔬盒及具有保鲜果蔬盒的冰箱。(The invention relates to an intelligent humidity control barrier composite film and a preparation method and application thereof. The intelligent humidity control barrier composite film comprises a base layer and additional layers, wherein the base layer is of a one-layer or two-layer structure, and the additional layers exist on one side of the base layer or on two sides of the base layer; the base layer is a porous film and is made of at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate and polycaprolactam; the additional layer comprises polyethylene glycol, polyetherketone and/or polyethersulfone containing carboxylate and sulfonate groups, and an antimicrobial agent. The intelligent humidity control barrier composite film has intelligent humidity control capability, can keep the humidity of fruits and vegetables when the relative humidity is low, can increase the moisture permeability when the relative humidity is high so as to prevent the fruits and vegetables from dewing and festering, has oxygen barrier performance, and can be used for fruit and vegetable boxes with fresh-keeping functions and refrigerators with fresh-keeping fruit and vegetable boxes.)
1. The intelligent humidity control and barrier composite film is characterized by comprising a base layer and additional layers, wherein the base layer is of a one-layer or two-layer structure, and the additional layers exist on one side of the base layer or on both sides of the base layer;
the base layer is a porous film and is made of at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate and polycaprolactam;
the additional layer comprises polyethylene glycol, polyetherketone and/or polyethersulfone containing carboxylate and sulfonate groups, and an antimicrobial agent.
2. The intelligent moisture control barrier composite film of claim 1, wherein:
the polyether ketone or polyether sulfone containing carboxylate and sulfonate groups is a copolymer, wherein only one structural unit contains sulfonate groups.
3. The intelligent moisture control barrier composite film of claim 2, wherein:
the polyether ketone or polyether sulfone containing carboxylate and sulfonate groups has at least one structure in the following formula:
wherein X is Na, K or Li; y is C ═ O or O ═ S ═ O; m and n are independently integers of 1-100.
4. The intelligent moisture control barrier composite film of claim 1, wherein:
the number average molecular weight of the polyether ketone or polyether sulfone containing carboxylate and sulfonate groups is 10000-300000, preferably 30000-200000.
5. The intelligent moisture control barrier composite film of claim 1, wherein:
the ion exchange capacity of the polyether ketone or polyether sulfone containing carboxylate and sulfonate groups is 0.2-2.5 mmol/g, and preferably 0.5-2.0 mmol/g.
6. The intelligent moisture control barrier composite film of claim 1, wherein:
the molecular weight of the polyethylene glycol is 1000-200000, and preferably 5000-100000.
7. The intelligent moisture control barrier composite film of claim 1, wherein:
based on the total weight of the single layer of the additional layer, the content of the polyether ketone and/or polyether sulfone containing carboxylate and sulfonate groups is 50-99 wt%, and preferably 80-98 wt%; the content of the polyethylene glycol is 0.5-40 wt%, preferably 1-15 wt%; the content of the antibacterial agent is 0.5-10 wt%, preferably 1-5 wt%.
8. The intelligent moisture control barrier composite film of claim 1, wherein:
the antibacterial agent is selected from at least one of nano zinc oxide, nano titanium oxide, nano silver, nano copper, sericin, quaternary ammonium salt, methyl hydroxybenzoate, potassium sorbate and chitosan.
9. The intelligent moisture control barrier composite film of claim 1, wherein:
the aperture of the base porous film is 0.02-10 microns, preferably 0.05-5 microns; the porosity is 30-80%, preferably 40-70%.
10. The intelligent moisture control barrier composite film of claim 1, wherein:
the thickness of the base layer is 5-1000 microns, preferably 10-100 microns; the thickness of the additional layer is 0.5-100 microns, and preferably 2-20 microns.
11. The preparation method of the intelligent moisture control barrier composite film according to claims 1-10, characterized by comprising the following steps:
(1) dissolving or dispersing the components of the additional layer into a solvent to prepare a solution or a dispersion liquid;
(2) attaching the solution or dispersion liquid obtained in the step (1) to one surface or two surfaces of the base layer, and drying to obtain the composite film;
alternatively, in the case where the solution or dispersion of the additional layer is attached to both sides of the base layer in the above-described method, the solution or dispersion of the additional layer in step (1) is prepared as two additional layer solutions or dispersions having different component contents, which are attached to both sides of the base layer, respectively.
12. The method for producing a composite film according to claim 11, characterized in that:
in the solution or dispersion liquid in the step (1), the mass concentration of polyether ketone and/or polyether sulfone containing carboxylate and sulfonate groups is 0.5-10%, preferably 1-8%; the mass concentration of the polyethylene glycol is 0.05-5%, preferably 0.1-2%; the mass concentration of the antibacterial agent is 0.01-2%, and preferably 0.05-1%.
13. The method for producing a composite film according to claim 11, characterized in that:
the solvent in the step (1) is one or more of formic acid, ethylene glycol monomethyl ether, N-dimethylformamide, N-dimethylacetamide or N-methylpyrrolidone.
14. The method for producing a composite film according to claim 11, characterized in that:
the drying temperature in the step (2) is 50-100 ℃, and preferably 60-90 ℃; the drying time is 1-60 min, preferably 5-20 min.
15. Use of the intelligent moisture control barrier composite film of any one of claims 1 to 10 in fresh-keeping packaging of vegetables and fruits.
Technical Field
The invention relates to the field of functional films, in particular to an intelligent humidity control barrier composite film and a preparation method and application thereof.
Background
Fruits and vegetables are important food products for humans and are the main source from which people obtain basic nutrients (vitamins, minerals, complex carbohydrates, etc.). With the increasing living standard of people, the requirement on the freshness of fresh fruits and vegetables is higher and higher. The fruits and vegetables can continue to breathe and transpire after being harvested, and water dispersion and nutrient substance consumption can occur in the storage process. The respiration intensity of the fruits and vegetables is doubled when the temperature is increased by 10 ℃. The household fruit and vegetable fresh-keeping method is to put the fruits and vegetables in a refrigerator for refrigeration to slow down the respiration of the fruits and vegetables. In fruits and vegetables, moisture is an important ingredient, affecting the tenderness, freshness and taste of fruits and vegetables. Too low ambient humidity can result in water loss and weight loss in fruits and vegetables, but too high humidity can cause condensation of water on the surfaces of fruits and vegetables, growth of fungi, and acceleration of rotting and deterioration of fruits and vegetables. Therefore, the control of the storage humidity of the fresh fruits and vegetables is very important, and the preservation time of the fruits and vegetables can be prolonged. The barrier film can prevent the permeation of oxygen and other gases, inhibit the respiration of fresh fruits and vegetables and prolong the fresh-keeping time of fruits and vegetables.
The effects of several functional films, namely a temperature-sensitive moisture-permeable film, a silicon filter film and a moisture-sensitive moisture-permeable film, on the fruit and vegetable box for reducing the water loss in the market are not satisfactory. The temperature-sensitive moisture-permeable film is easy to dewet on the surface of the film under high humidity and low temperature; the silicon filter membrane has the function of moisture retention, but the moisture permeability cannot be changed along with the humidity; the moisture-sensitive and moisture-permeable membrane is formed by coating an adhesive solution on a paper-based substrate, the performance meets the requirement, but the preparation process is not environment-friendly, the process is complex, and the problem that the chlorine content exceeds the standard possibly exists in the processing process.
CN105986511A discloses a technique of applying natural high molecular polymer with good hydrophilic water retention and film forming property on base paper with high dry and wet strength, but the cost is high. CN104029449B discloses a coating film with large moisture permeability, wherein the base layer is an expanded polytetrafluoroethylene film layer, the coating is a polyurethane emulsion copolymerization coating containing hemp stem core superfine micropowder, and the film is used for an automobile lamp shell but does not have intelligent moisture control performance. CN103507339A discloses a moisture-sensitive and moisture-permeable film which retains regenerated cellulose in a substrate of nonwoven fabric, but does not have gas barrier properties. CN103107301A discloses an inorganic coating lithium ion battery diaphragm, contains multilayer structure, is porous flexible basement membrane and the coating of coating in basement membrane both sides respectively, and the coating contains polyvinyl alcohol and zeolite particle, and the auxiliary component of this coating does not have the metal salt composition, and the complex film does not have the function of intelligent accuse humidity. CN1864829A discloses a hydrophilic-hydrophobic bipolar composite membrane and a preparation method thereof, the membrane has a double-layer structure, the bottom layer is a porous support layer, the upper layer is a hydrophilic membrane containing lithium chloride, the membrane has high moisture permeability and strong barrier effect on other gas molecules, but does not have intelligent moisture control property. WO2013066012a1 discloses a porous membrane containing inorganic particles and a polymer binder layer containing hydrophilic and hydrophobic substances, which membrane is used to improve the thermal stability of a lithium battery separator and does not have intelligent humidity control properties. WO2012133805a1 discloses a moisture-permeable film whose porous substrate is preferably polytetrafluoroethylene, which is expensive, and whose high moisture-permeability is not good. US20030054155a1 discloses a waterproof moisture-permeable composite film, the hydrophobic layer being polytetrafluoroethylene and the hydrophilic layer being polyurethane, which has high moisture permeability but does not have intelligent moisture control properties.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide an intelligent humidity control barrier composite film which can keep moisture under the condition of low humidity, has strong humidity elimination capability under the condition of high humidity and has oxygen barrier property. The invention further provides a preparation method of the film, and the method is simple in process and low in cost. Therefore, the film provided by the invention is particularly suitable for being applied to fresh-keeping packaging of vegetables and fruits.
One of the purposes of the invention is to provide an intelligent humidity control barrier composite film, which is characterized in that the composite film comprises a base layer and an additional layer, wherein the base layer is of a one-layer or two-layer structure, and the additional layer is present on one side of the base layer or both sides of the base layer; the base layer is a porous film and is made of at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate and polycaprolactam; the additional layer comprises polyethylene glycol, polyetherketone and/or polyethersulfone containing carboxylate and sulfonate groups, and an antimicrobial agent.
In the invention, in order to realize intelligent humidity control, the base layer needs to be a porous film, and the additional layer needs to be a compact (thin) film. The concepts and terminology categories of porous and dense (thin) membranes are well known to those skilled in the art. The dense film as the additional layer is opposite to the concept of a porous film, i.e. a non-porous (thin) film, and can be prepared by applying a solution containing the additional layer components to the surface of the base layer and drying.
According to the invention, in the base material, the polyethylene is preferably at least one of High Density Polyethylene (HDPE), Linear Low Density Polyethylene (LLDPE) and Low Density Polyethylene (LDPE); the polypropylene is preferably at least one of homo-polypropylene, random co-polypropylene, block co-polypropylene and impact co-polypropylene.
According to the invention, the polyether ketone or polyether sulfone containing carboxylate and sulfonate groups is preferably a copolymer, the degree of sulfonation of which cannot be too high in order to ensure the strength of the membrane, wherein only one structural unit contains sulfonate groups and the other structural units do not.
According to the invention, the polyether ketone or polyether sulfone containing carboxylate and sulfonate groups preferably has at least one of the following structures:
wherein X is Na, K or Li; y is C ═ O or O ═ S ═ O; m and n are independently integers of 1-100.
According to the invention, the number average molecular weight of the polyether ketone or polyether sulfone containing carboxylate and sulfonate groups is preferably 10000-300000, and more preferably 30000-200000.
The ion exchange capacity of the polyether ketone or polyether sulfone containing carboxylate and sulfonate groups is preferably 0.2-2.5 mmol/g, more preferably 0.5-2.0 mmol/g, and even more preferably 1.0-2.0 mmol/g.
The polyether ketone or polyether sulfone containing carboxylate and sulfonate groups can be obtained commercially or prepared by adopting a method in the prior art.
According to the invention, the molecular weight of the polyethylene glycol is preferably 1000-200000, and more preferably 5000-100000.
The antibacterial agent can be selected from antibacterial agents commonly used in the art, preferably at least one of nano zinc oxide, nano titanium oxide, nano silver, nano copper, sericin, quaternary ammonium salt, methylparaben, potassium sorbate or chitosan, and more preferably at least one of nano zinc oxide, nano silver or quaternary ammonium salt, such as cetylpyridinium chloride.
According to the invention, the relative contents of the polyether ketone and/or polyether sulfone containing carboxylate and sulfonate groups, the polyethylene glycol and the antibacterial agent are limited to the extent that a compact film can be formed, preferably, in a single layer of the additional layer, the content of the polyether ketone and/or polyether sulfone containing carboxylate and sulfonate groups is 50-99 wt%, preferably 80-98 wt%, the content of the polyethylene glycol is 0.5-40 wt%, preferably 1-15 wt%, and the content of the antibacterial agent is 0.5-10 wt%, preferably 1-5 wt%, based on the total weight of the additional layer.
In the invention, the aperture of the porous film of the base layer is preferably 0.02-10 microns, more preferably 0.05-5 microns, and even more preferably 0.1-2 microns; the porosity is 30-80%, preferably 40-70%; pores with a pore diameter within plus or minus one order of magnitude of the average pore diameter account for more than 50% of the total pores, preferably more than 80% of the total pores.
According to the invention, the thicknesses of the base layer and the additional layer can be determined according to needs, generally, the thickness of the base layer can be 5-1000 micrometers, preferably 10-100 micrometers, and further preferably 60-90 micrometers; the thickness of the additional layer can be 0.5-100 micrometers, and preferably 2-20 micrometers.
The invention also aims to provide a preparation method of the intelligent humidity control barrier composite film, which comprises the following steps:
(1) dissolving or dispersing the components of the additional layer into a solvent to prepare a solution or a dispersion liquid;
(2) attaching the solution or dispersion liquid obtained in the step (1) to one surface or two surfaces of the base layer, and drying to obtain the composite film;
alternatively, in the case where the solution or dispersion of the additional layer is attached to both sides of the base layer in the above-described method, the solution or dispersion of the additional layer in step (1) is prepared as two additional layer solutions or dispersions having different component contents, which are attached to both sides of the base layer, respectively.
The base porous film may be commercially available as a single layer, or may be prepared by a conventional film-forming method in the prior art. For example, the film of the support layer is obtained by stretching polyethylene, polypropylene, polystyrene, polyethylene terephthalate and polycaprolactam or a combination thereof using a film stretching machine of the prior art by a general film stretching process. The film stretcher may be a unidirectional or bidirectional stretcher.
When the base layer is two layers, the two layers may be made of different materials. The base layer can be obtained commercially or can be prepared by a conventional film-making method of a composite film in the prior art.
According to the invention, in the solution or dispersion liquid in the step (1), the mass concentration of polyether ketone and/or polyether sulfone containing carboxylate and sulfonate groups is 0.5-10%, preferably 1-8%; the mass concentration of the polyethylene glycol is 0.05-5%, preferably 0.1-2%; the mass concentration of the antibacterial agent is 0.01-2%, and preferably 0.05-1%.
According to the invention, the solvent used in the step (1) is one or a mixture of several of formic acid, ethylene glycol monomethyl ether, N-dimethylformamide, N-dimethylacetamide and N-methylpyrrolidone.
The solution or dispersion obtained in step (1) may be applied to a substrate using any conventional coating method, including but not limited to: brushing, curtain coating and spraying.
According to the invention, the drying temperature in the step (2) is 50-100 ℃, and preferably 60-90 ℃; the drying time is 1-60 min, preferably 5-20 min. The drying step may be accomplished in a variety of conventional heating devices, such as an oven.
The invention also aims to provide the application of the intelligent humidity control barrier composite film and/or the intelligent humidity control barrier composite film prepared by the preparation method in the fresh-keeping packaging of vegetables and fruits.
The intensive research of the inventor finds that the polyethylene glycol and carboxylate and sulfonate on the molecular chain of polyether ketone or polyether sulfone have ion chelation, so that the free volume between the molecular chains can be reduced, the compactness of a functional layer is increased, and the gas barrier property of the film is improved; on the other hand, the hydrophilicity of the polyethylene glycol is beneficial to improving the moisture permeability of the film.
The ion chelation mechanism between the sulfonate and the carboxylate in the molecular chain of the polyethylene glycol and the sulfonated polyether sulfone is as follows:
when the environment humidity is low, molecular chains of the functional layer of the composite film are arranged tightly, so that moisture is prevented from permeating; when the environmental humidity is high, the free volume among molecular chains is increased, and the moisture permeability is increased; therefore, the intelligent humidity control barrier composite film has intelligent humidity control capacity, can keep the humidity of fruits and vegetables when the relative humidity is low, can increase the moisture permeability when the relative humidity is high so as to prevent the fruits and vegetables from dewing and festering, has oxygen barrier performance, and can be used for fruit and vegetable boxes with fresh-keeping functions and refrigerators with fresh-keeping fruit and vegetable boxes.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below.
The thicknesses of the base layer and the additional layer of the intelligent humidity control film are measured by a Shanghai Heishizi thickness meter; the pore structure including pore size and porosity was measured by mercury intrusion using an instrument, model autopore iii-9420 mercury intrusion gauge.
Polypropylene, F1002B, medium petrochemical Yangtze river petrochemical.
Polyethylene, L501(5000S), medium petrochemical actinolite.
Polystyrene, GH-660, China petrochemical Guangzhou petrochemical.
Biaxially oriented polypropylene film, medium petrochemical and marine refining, F280Z.
99.5 percent of nano zinc oxide and carbofuran, and the grain diameter is 10-30 nm.
99.5 percent of nano silver and carbofuran, and the grain diameter is 10-30 nm.
Film uniaxial stretcher, common in Guangzhou, MESI-LL.
The ion exchange capacity is determined by acid-base titration, a detailed step reference (Journal of Power resources, 2009,191:253-258.Synthesis and characterization of novel sulfonated poly (aryl ether ketone) polymers with pendant carboxylic acid groups for proto-nexexchange membranes).
Polyether sulfones with structures of the formula I containing carboxylate and sulfonate sodium groups are known from the literature (Journal of Power Sources,2009,191:253-258.Synthesis and characterization of novel sulfonated polymers with pendant carboxylic acid groups for the preparation of polyether sulfones with a number average molecular weight of 58000.
Polyether sulfones with the structure of formula II containing carboxylate and sulfonate sodium groups are described in the literature (Journal of Power Sources,2009,193:507-514.Novel sulfonated poly (arylene ether ketone) copolymer bearing carboxylic or benzimidazole groups) and have a number average molecular weight of 73000.
Polyether sulfones with the structure of the formula III containing carboxylate and sulfonate sodium groups are described in the Journal of molecular Science 2009,343: 164. 170. Synthesis and property of a novel sulfonated poly (ether ketone) with high selectivity for direct methanol fuel cell applications and have a number average molecular weight of 85000.
Example 1
2kg of polypropylene was stretched on a film uniaxial stretcher to form a polypropylene porous film.
5g of polyethersulfone having the structure of formula I and containing carboxylate and sulfonate sodium salt groups (having an ion exchange capacity of 2.0mmol/g) and 0.5g of polyethylene glycol (molecular weight of 10000) were added to 94.3g N, N-dimethylformamide and dissolved thoroughly. 0.2g of nano zinc oxide is added into the obtained solution, and the solution is fully stirred until the nano zinc oxide and the nano zinc oxide are uniformly mixed to obtain the coating solution. Uniformly brushing the coating solution on one surface of a polypropylene porous film, then placing the polypropylene porous film in a drying oven, and drying for 5min at 90 ℃ to obtain an intelligent humidity control barrier composite film A1, wherein the thickness of a base layer is 70 microns, the pore diameter is 0.25 micron, the porosity is 50%, and the pores with the pore diameter within the range of plus or minus one order of magnitude of average pore diameter account for more than 85% of all pores; the additional layer has a thickness of 12 microns.
Example 2
2kg of polypropylene was stretched on a film uniaxial stretcher to form a polypropylene porous film.
7.5g of polyethersulfone having the structure of formula II containing carboxylate and sulfonate sodium salt groups (having an ion exchange capacity of 1.7mmol/g) and 0.2g of polyethylene glycol (molecular weight of 100000) were added to 91.8g N, N-dimethylacetamide and dissolved thoroughly. 0.5g of nano zinc oxide is added into the obtained solution, and the solution is fully stirred until the nano zinc oxide and the nano zinc oxide are uniformly mixed to obtain the coating solution. Uniformly brushing the coating solution on one surface of a polypropylene porous film, then placing the polypropylene porous film in a drying oven, and drying for 20min at 50 ℃ to obtain an intelligent humidity control barrier composite film A2, wherein the thickness of a base layer is 70 microns, the pore diameter is 0.25 micron, the porosity is 50%, and the pores with the pore diameter within the range of plus or minus one order of magnitude of average pore diameter account for more than 85% of all pores; the additional layer has a thickness of 15 microns.
Example 3
2kg of polyethylene was stretched on a film uniaxial stretcher to form a polyethylene porous film.
2.5g of polyethersulfone having the formula III containing carboxylate and sulfonic acid sodium salt groups (having an ion exchange capacity of 1.8mmol/g) and 0.1g of polyethylene glycol (molecular weight of 50000) were added to 97.3g N, N-dimethylacetamide and dissolved thoroughly. 0.1g of nano zinc oxide is added into the obtained solution, and the solution is fully stirred until the nano zinc oxide and the nano zinc oxide are uniformly mixed to obtain the coating solution. Uniformly brushing the coating solution on one surface of a polypropylene porous film, then placing the polypropylene porous film in a drying oven, and drying for 10min at 70 ℃ to obtain an intelligent humidity control barrier composite film A2, wherein the thickness of a base layer is 70 microns, the pore diameter is 0.25 micron, the porosity is 50%, and the pores with the pore diameter within the range of plus or minus one order of magnitude of average pore diameter account for more than 85% of all pores; the additional layer has a thickness of 8 microns.
Example 4
Preparing a film according to the same method as the example 1, except that the ion exchange capacity of the polyether sulfone containing carboxylate and sodium sulfonate salt groups in the coating solution is 1.0mmol/g), so as to obtain an intelligent humidity control barrier composite film A4, wherein the thickness of a base layer is 70 micrometers, the pore diameter is 0.25 micrometers, the porosity is 50%, and the pores with the pore diameter within the range of plus or minus one order of magnitude of the average pore diameter account for more than 85% of all pores; the additional layer has a thickness of 15 microns.
Example 5
Preparing a film according to the same method as the example 1, except that the ion exchange capacity of the polyether sulfone containing carboxylate and sodium sulfonate salt groups in the coating solution is 0.5mmol/g), so as to obtain an intelligent humidity control barrier composite film A5, wherein the thickness of a base layer is 70 micrometers, the pore diameter is 0.25 micrometers, the porosity is 50%, and the pores with the pore diameter within the range of plus or minus one order of magnitude of the average pore diameter account for more than 85% of all pores; the additional layer has a thickness of 17 microns.
Example 6
Preparing a film according to the same method as the embodiment 1, except that the molecular weight of polyethylene glycol in the coating solution is 5000, so as to obtain an intelligent humidity control barrier composite film A6, wherein the thickness of a base layer is 70 micrometers, the pore diameter is 0.25 micrometers, the porosity is 50%, and pores with the pore diameter within the range of plus or minus one order of magnitude of average pore diameter account for more than 85% of all pores; the additional layer has a thickness of 10 microns.
Example 7
2kg of polystyrene was stretched on a film uniaxial stretcher to obtain a polystyrene porous film.
5g of polyethersulfone having the structure of formula I and containing carboxylate and sulfonate sodium salt groups (having an ion exchange capacity of 2.0mmol/g) and 0.5g of polyethylene glycol (molecular weight of 10000) were added to 94.3g N, N-dimethylformamide and dissolved thoroughly. 0.2g of nano zinc oxide is added into the obtained solution, and the solution is fully stirred until the nano zinc oxide and the nano zinc oxide are uniformly mixed to obtain the coating solution. Uniformly brushing the coating solution on one surface of a polystyrene porous film, then placing the polystyrene porous film in a drying oven, and drying the polystyrene porous film for 10min at 70 ℃ to obtain an intelligent humidity control film A7, wherein the thickness of a base layer is 82 microns, the pore diameter is 0.15 micron, the porosity is 35%, and the pores with the pore diameter within the range of plus or minus one order of magnitude of average pore diameter account for more than 80% of all pores; the additional layer has a thickness of 12 microns.
Example 8
5g of polyethersulfone having the structure of formula I and containing carboxylate and sulfonate sodium groups (having an ion exchange capacity of 2.0mmol/g) and 4g of polyethylene glycol (molecular weight of 10000) were added to 90g N, N-dimethylformamide and dissolved thoroughly. Adding 1g of nano zinc oxide into the obtained solution, and fully stirring until the nano zinc oxide and the solution are uniformly mixed to obtain the coating solution. Uniformly brushing the coating solution on one surface of a polypropylene porous film, then placing the polypropylene porous film in a drying oven, and drying for 5min at 90 ℃ to obtain an intelligent humidity control barrier composite film A8, wherein the thickness of a base layer is 70 microns, the pore diameter is 0.25 micron, the porosity is 50%, and the pores with the pore diameter within the range of plus or minus one order of magnitude of average pore diameter account for more than 85% of all pores; the additional layer has a thickness of 20 microns.
Comparative example 1
A film was prepared according to the same method as in example 1, except that polyethylene glycol was not contained in the coating solution, to obtain an intelligent moisture-controlling barrier composite film D1.
Test example
The above films were subjected to a water vapor transmission rate test according to GB/T1037-1988, and the water vapor transmission rate per square meter of film per day (g/m) was obtained under test conditions of a test temperature of 25 ℃ and a transmission surface humidity of 50% and 90%, respectively2Day), data results are shown in table 1.
The gas barrier performance of the film is detected according to GB/T19789-3·cm/(cm2·s·Pa)]The data results are shown in table 1.
Table 1: test results of moisture permeability and gas barrier property of film
Serial number
Moisture permeability (50% RH)
Moisture permeability (90% RH)
Gas barrier property (O)2)
A1
420
1485
2.3×10-5
A2
352
1342
1.5×10-5
A3
395
1438
5.6×10-5
A4
223
1120
8.9×10-5
A5
156
875
3.4×10-4
A6
390
1365
4.9×10-5
A7
215
1050
4.0×10-5
A8
112
598
0.9×10-5
D1
403
1399
2.1×10-3
As can be seen from table 1, the polyethylene glycol and the carboxylate and sulfonate on the molecular chain of the polyether sulfone generate ion chelation, so that the free volume between the molecular chains can be reduced, the compactness of the functional layer can be increased, and the gas barrier property of the film can be improved; on the other hand, the hydrophilicity of the polyethylene glycol is beneficial to improving the moisture permeability of the film. The intelligent moisture control barrier composite film has good oxygen barrier property and intelligent moisture control capability, namely when the humidity is lower, the moisture permeability of the intelligent moisture control barrier composite film is reduced, the intelligent moisture control barrier composite film has the moisture retention capability, and the humidity of fruits and vegetables can be kept; on the contrary, when the humidity is higher, the moisture permeability of the intelligent moisture-control barrier composite film is improved, and the intelligent moisture-control barrier composite film has strong moisture-removing capacity, so that the fruit and vegetable can be prevented from dewing and festering.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.