CN107987300B - Temperature-sensitive film and preparation method thereof - Google Patents

Temperature-sensitive film and preparation method thereof Download PDF

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CN107987300B
CN107987300B CN201711479358.7A CN201711479358A CN107987300B CN 107987300 B CN107987300 B CN 107987300B CN 201711479358 A CN201711479358 A CN 201711479358A CN 107987300 B CN107987300 B CN 107987300B
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temperature
sensitive
hydrotalcite
layer
sensitive film
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CN107987300A (en
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韩景宾
王嘉杰
许晓芝
董思源
卫敏
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Beijing University of Chemical Technology
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04—Coating
    • C08J7/042—Coating with two or more layers, where at least one layer of a composition contains a polymer binder
    • C08J7/0423—Coating with two or more layers, where at least one layer of a composition contains a polymer binder with at least one layer of inorganic material and at least one layer of a composition containing a polymer binder
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/10—Homopolymers or copolymers of propene
    • C08J2323/12—Polypropene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2429/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
    • C08J2429/10—Homopolymers or copolymers of unsaturated ethers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2433/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
    • C08J2433/24—Homopolymers or copolymers of amides or imides

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Abstract

The invention belongs to the technical field of film materials, and particularly relates to a temperature-sensitive film and a preparation method thereof. The temperature-sensitive film provided by the invention comprises a substrate and a gas barrier layer, wherein the gas barrier layer comprises hydrotalcite nanosheets and temperature-sensitive polymer layers which are alternately laminated; the hydrotalcite nanosheet layer is connected with the substrate; the outermost layer of the temperature-sensitive film is a temperature-sensitive polymer layer. When the temperature of the temperature-sensitive film is lower than the phase-change temperature, the temperature-sensitive film has gas barrier property, and when the temperature is higher than the phase-change temperature, the temperature-sensitive film has gas permeability, so that the gas barrier property and the gas permeability of the temperature-sensitive film can be accurately regulated and controlled through the change of the temperature.

Description

Temperature-sensitive film and preparation method thereof
Technical Field
The invention relates to the technical field of film materials, in particular to a temperature-sensitive film and a preparation method thereof.
Background
In the chemical industry reaction field, compared with liquid raw materials and solid raw materials, the addition amount, the addition speed and the addition time of the gas raw materials are difficult to be effectively controlled, so that the control difficulty of the gas raw materials is increased. For a continuous or semi-continuous reaction system with gas, the addition amount, the addition speed and the addition time of the raw material gas have great influence on the reaction, and the reaction needs to be accurately controlled. At present, the adding time of the gas raw material is usually controlled by an artificial machine, and although the adding time of the gas raw material is controlled to a certain degree, certain defects still exist in the aspect of control accuracy.
Disclosure of Invention
The invention aims to provide a temperature-sensitive film and a preparation method thereof. The gas resistance and the air permeability of the temperature-sensitive film provided by the invention can be accurately controlled by changing the temperature, so that when the temperature-sensitive film is used as a raw material gas controller, the gas-sensitive film can accurately control the addition parameters of the gas raw materials.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention provides a temperature-sensitive film, which comprises a substrate and a gas barrier layer, wherein the gas barrier layer comprises hydrotalcite nanosheets and temperature-sensitive polymer layers which are alternately laminated; the hydrotalcite nanosheet layer is connected with the substrate; the outermost layer of the temperature-sensitive film is a temperature-sensitive polymer layer.
Preferably, the thickness of the temperature-sensitive film in a contraction state is 6.5-10 μm, and the thickness of the temperature-sensitive film in an expansion state is 18-23 μm.
Preferably, the thickness of the temperature-sensitive polymer layer in a contracted state is 200-500 nm, and the thickness of the temperature-sensitive polymer layer in an expanded state is 800-1300 nm.
Preferably, the temperature-sensitive polymer layer is composed of a polymer including poly-N-vinyl lactone, poly-hydroxypropyl methacrylamide, polyvinyl methyl ether or N-isopropyl acrylamide.
Preferably, the hydrotalcite nanosheet layer is formed by stacking hydrotalcite nanosheets in a manner of being parallel to the substrate, the thickness of the hydrotalcite nanosheet layer is 50-200 nm, and the length-diameter ratio of the hydrotalcite nanosheets is 20-200.
Preferably, the material of the substrate comprises polyethylene, polypropylene or polyethylene terephthalate.
The invention also provides a preparation method of the temperature-sensitive film in the technical scheme, which comprises the following steps:
providing a hydrotalcite nanosheet aqueous dispersion and a temperature-sensitive polymer aqueous dispersion;
alternately spin-coating the hydrotalcite nanosheet aqueous dispersion and the temperature-sensitive polymer aqueous dispersion on a substrate to obtain a composite film;
and drying the composite film to obtain the temperature-sensitive film.
Preferably, the mass concentration of the hydrotalcite nanosheet aqueous dispersion is 0.3-0.6%; the mass concentration of the temperature-sensitive polymer aqueous dispersion is 3-5%.
Preferably, the preparation method of the hydrotalcite nanosheet comprises:
will M2+、M3+Mixing with urea according to the ratio of 2.5-3: 1: 1 to obtain a raw material mixed solution, wherein M is2+Comprising Mg2 +、Zn2+Or Ni2+Said M is3+Including Fe3+、Al3+Or Co3+；
Carrying out crystallization reaction on the raw material mixed liquor to obtain a solid-liquid mixture;
and sequentially cooling, separating, washing and drying the solid-liquid mixture, and cooling to obtain the hydrotalcite nanosheet.
Preferably, the temperature of the crystallization reaction is 100-120 ℃, and the time of the crystallization reaction is 20-30 h.
The temperature-sensitive film provided by the invention comprises a substrate and a gas barrier layer, wherein the gas barrier layer comprises hydrotalcite nanosheets and temperature-sensitive polymer layers which are alternately laminated; the hydrotalcite nanosheet layer is connected with the substrate; the outermost layer of the temperature-sensitive film is a temperature-sensitive polymer layer. According to the invention, the hydrotalcite nanosheet layer is connected with the substrate, so that the stability and the mechanical strength of the temperature-sensitive film can be improved; the temperature-sensitive film is arranged on the outermost layer, and can timely complete the conversion between the expansion state and the contraction state when the temperature changes, thereby providing favorable conditions for the conversion of the air permeability and the air barrier performance. In the invention, when the temperature is lower than the phase transition temperature of the temperature-sensitive polymer, the temperature-sensitive polymer layer is in an expanded state, under the action of the lowest energy principle and gravity, hydrotalcite nanosheets are stacked in a manner of being parallel to a substrate to form hydrotalcite nanosheets, and the hydrotalcite nanosheets are connected with the temperature-sensitive polymer in the expanded state in a manner of being parallel to the substrate by hydrogen bonds to form a stable structure; when the temperature is lower than the phase transition temperature, the temperature-sensitive polymer is in a shrinkage state, a large amount of free volume appears on the temperature-sensitive polymer layer, the adjacent hydrotalcite nanosheets can fill up the volume vacancy under the action of hydrogen bonds, the ordered oriented structure of the hydrotalcite nanosheets disappears, and the hydrotalcite nanosheets cannot prolong the path of gas permeation, so that the effect of blocking the gas is lost. The example results show that the temperature-sensitive film provided by the invention has gas barrier property when the temperature is lower than the phase transition temperature, and the temperature-sensitive film has gas permeability when the temperature is higher than the phase transition temperature, which shows that the gas barrier property and the gas permeability of the temperature-sensitive film provided by the invention can be accurately regulated and controlled by changing the temperature.
Drawings
Fig. 1 is an SEM image of hydrotalcite nanosheets prepared in example 1;
FIG. 2 is an SEM photograph of a temperature-sensitive gas barrier film of example 1;
FIG. 3 is an AFM test chart of the temperature sensitive gas barrier film of example 1;
FIG. 4 is SEM images of the temperature-sensitive gas barrier film of example 1 in different states, wherein A is an expanded SEM image and B is a contracted SEM image;
FIG. 5 is a TEM image of a temperature-sensitive gas barrier film of example 1;
fig. 6 is a statistical chart of the gas transmission capacity of the temperature-sensitive gas barrier film of example 1 at different temperatures.
Detailed Description
The invention provides a temperature-sensitive film, which comprises a substrate and a gas barrier layer, wherein the gas barrier layer comprises hydrotalcite nanosheets and temperature-sensitive polymer layers which are alternately laminated; the hydrotalcite nanosheet layer is connected with the substrate; the outermost layer of the temperature-sensitive film is a temperature-sensitive polymer layer.
In the invention, the thickness of the temperature-sensitive film in a shrinkage state is preferably 6.5-10 μm, and more preferably 6.9-9.2 μm; the thickness of the temperature-sensitive film in the expanded state is preferably 18-23 μm, and more preferably 18.3-22.6 μm.
The temperature-sensitive film of the invention comprises a substrate. In the present invention, the material of the substrate is preferably polyethylene, polypropylene, or polyethylene terephthalate, and more preferably polyethylene terephthalate. In the invention, the thickness of the substrate is preferably 0.20-0.30 mm, and more preferably 0.24-0.28 mm. The invention provides a stable substrate for the gas barrier layer through the limitation of the composition and the thickness of the substrate, and further provides favorable conditions for the conversion of gas barrier and air permeability of the gas barrier layer.
The temperature-sensitive film of the present invention includes a gas barrier layer. In the invention, when the temperature of the temperature-sensitive film is lower than the phase-change temperature of the temperature-sensitive polymer, the temperature-sensitive film is in an expanded state; when the temperature of the temperature-sensitive film is higher than the phase-change temperature of the temperature-sensitive polymer, the temperature-sensitive film is in a shrinkage state. In the present invention, the phase transition temperature of the temperature sensitive polymer depends on the nature of the temperature sensitive polymer selected for use.
The gas barrier layer comprises hydrotalcite nanosheets and temperature-sensitive polymer layers which are alternately laminated. In the invention, the thickness of the hydrotalcite nanosheet layer is preferably 50-200 nm, more preferably 80-150 nm, and even more preferably 100-120 nm. According to the invention, the thickness of the hydrotalcite nanosheet layer is limited, so that the crack resistance and the gas barrier property of the temperature-sensitive film are further improved.
The hydrotalcite nano-sheet layer is formed by laminating hydrotalcite nano-sheets in a mode of being parallel to the substrate. In the invention, the diameter of the hydrotalcite nano-sheet is preferably 70-800 nm, and more preferably 100-600 nm; the thickness of the hydrotalcite nanosheet is preferably 4-30 nm, and more preferably 10-20 nm. In the invention, the length-diameter ratio of the hydrotalcite nanosheet is preferably 20 to 200, more preferably 40 to 100, and even more preferably 50 to 70. The length-diameter ratio is the ratio of the diameter of the hydrotalcite nano-sheet to the thickness of the hydrotalcite nano-sheet. The length-diameter ratio of the hydrotalcite nanosheets is limited to the range, so that the path of gas penetrating through the film can be further prolonged, and the effect of blocking the gas is achieved.
The gas barrier layer of the present invention further comprises a temperature sensitive polymer layer. In the present invention, the temperature-sensitive polymer layer is preferably composed of a polymer, and the polymer is preferably poly-N-vinyl lactone, poly-hydroxypropyl methacrylamide, polyvinyl methyl ether or N-isopropyl acrylamide. In the invention, the temperature-sensitive polymer layer is preferably one or more of a poly N-vinyl lactone layer, a poly-hydroxypropyl methacrylamide layer, a polyvinyl methyl ether layer and an N-isopropyl acrylamide layer, and is further preferably a poly N-vinyl lactone layer, a poly (DL) -hydroxypropyl methacrylamide layer, a polyvinyl methyl ether layer or an N-isopropyl acrylamide layer. In the invention, when different temperature-sensitive polymer layers are different components, the invention has no special requirement on the layer number proportion of the different components. The polymer provided by the invention has a large number of hydrophilic groups, so that the temperature-sensitive polymer layer can be connected with the hydrotalcite nano-layer through a hydrogen bond.
When the temperature-sensitive polymer layer is higher than the phase transition temperature, the temperature-sensitive polymer layer is in a shrinkage state, and the thickness of a single layer of the shrinkage-state temperature-sensitive polymer layer is preferably 200-500 nm, and is further preferably 280-450 nm. In the invention, when the temperature-sensitive polymer layer is lower than the phase transition temperature, the temperature-sensitive polymer layer is in an expanded state, and the thickness of a single layer of the expanded temperature-sensitive polymer layer is preferably 800-1300 nm, and more preferably 900-1200 nm. In the invention, the temperature-sensitive polymer layer is connected with the hydrotalcite nanosheet layer through a hydrogen bond. In an expanded state, the hydrotalcite nanosheets are stacked in parallel to the substrate to form hydrotalcite nanosheet layers under the influence of the lowest energy principle and gravity, the hydrotalcite nanosheet layers are connected with the temperature-sensitive polymer layer in a manner of being parallel to the substrate, the hydrotalcite nanosheets parallel to the substrate are in ordered orientation, the gas passing path is prolonged, and the purpose of blocking gas is achieved; in a shrinkage state, the hydrotalcite nanosheet layer expands along with the shrinkage of the temperature-sensitive polymer layer, and the ordered orientation of the hydrotalcite nanosheets disappears, so that the purpose of ventilation is achieved.
According to the invention, the hydrotalcite nanosheet layer and the temperature-sensitive polymer layer are alternately laminated to form the gas barrier layer, so that the stability of the temperature-sensitive film can be improved. The hydrotalcite nanosheet layer is connected with the substrate; the outermost layer of the temperature-sensitive film is a temperature-sensitive polymer layer. The outermost layer of the film is a temperature-sensitive polymer layer, when the temperature is lower than the phase transition temperature, the temperature-sensitive polymer is in an expanded state, and the hydrotalcite nanosheets are in an ordered structure parallel to the substrate, so that the path of gas penetrating through the film can be prolonged, and the purpose of blocking the gas is achieved; when the temperature is higher than the phase transition temperature, the temperature-sensitive polymer is in a shrinkage state, the hydrotalcite nanosheets cannot extend the path of the gas, and the film has a gas permeation function, so that the gas permeation and gas barrier performance of the temperature control film material can be regulated and controlled.
The invention also provides a preparation method of the temperature-sensitive film in the technical scheme, which comprises the following steps:
providing a hydrotalcite nanosheet aqueous dispersion and a temperature-sensitive polymer aqueous dispersion;
alternately spin-coating the hydrotalcite nanosheet aqueous dispersion and the temperature-sensitive polymer aqueous dispersion on a substrate to obtain a composite film;
and drying the composite film to obtain the temperature-sensitive film.
The invention provides a hydrotalcite nano-sheet water dispersion liquid. In the present invention, the mass concentration of the hydrotalcite nanosheet aqueous dispersion is preferably 0.3 to 0.6%, and more preferably 0.4 to 0.5%. The specific source of the hydrotalcite nanosheets is not particularly required, and those skilled in the art are familiar with the method. The preparation method of the hydrotalcite nanosheet aqueous dispersion liquid has no special requirement, and the method is well known by the technical personnel in the field.
In the invention, the hydrotalcite nanosheet is preferably prepared by a urea method, and the specific method comprises the following steps:
will M2+、M3+Mixing with urea according to the ratio of 2.5-3: 1: 1 to obtain a raw material mixed solution, wherein M is2+Comprising Mg2 +、Zn2+Or Ni2+Said M is3+Including Fe3+、Al3+Or Co3+；
Carrying out crystallization reaction on the raw material mixed liquor to obtain a solid-liquid mixture;
carrying out crystallization reaction on the raw material mixed liquor to obtain a solid-liquid mixture;
and sequentially cooling, separating, washing and drying the solid-liquid mixture to obtain the hydrotalcite nanosheet.
The invention will M2+、M3+Mixing with urea to obtain raw material mixtureAnd (4) mixing the liquid. In the present invention, said M2+、M3+The molar ratio of the urea to the urea is 2.5-3: 1: 1, more preferably 3: 1: 1. in the present invention, the solvent of the raw material mixture is water, and more preferably deionized water. In the present invention, said M2+Is Mg2+、Zn2+Or Ni2+More preferably Mg2+Said M is3+Is Fe3+、Al3+Or Co3+More preferably, Al3+. The invention is directed to said M2+、M3+The mixing with urea is not particularly critical and can be carried out in a manner known to those skilled in the art. The present invention does not require a particular source of the divalent metal ion and the trivalent metal ion, and those skilled in the art will be familiar with it. In an embodiment of the invention, the divalent metal ion and the trivalent metal ion are preferably provided by nitrates.
In the present invention, M is preferably first added2+And M3+Preparing salt solution, and mixing with urea to obtain raw material mixed solution. In the present invention, the solvent of the salt solution is preferably water, and more preferably deionized water. In the present invention, M is present in the salt solution2+The concentration of (B) is preferably 0.2 to 0.6M, more preferably 0.3 to 0.5M. The preparation method of the salt solution has no special requirement, and the preparation method is well known to those skilled in the art. In the present invention, the salt solution is preferably mixed with an aqueous urea solution when the salt solution is mixed with urea. The concentration of the urea aqueous solution is preferably 0.5-1.5M, and more preferably 0.8-1.2M. The invention has no special requirements on the preparation mode of the urea aqueous solution, and the preparation mode which is well known by the technicians in the field can be adopted. The invention has no special requirements on the mixing mode of the saline solution and the urea aqueous solution, and can achieve the aim of uniformly mixing all the components. According to the invention, the salt solution, the urea aqueous solution and the dosage are limited in the concentration range, and the hydrotalcite nanosheet with the large length-diameter ratio can be prepared.
After the raw material mixed liquid is obtained, the raw material mixed liquid is subjected to crystallization reaction to obtain a solid-liquid mixture. In the invention, the temperature of the crystallization reaction is preferably 100-120 ℃, and more preferably 105-110 ℃; the time of the crystallization reaction is preferably 20-30 hours, and more preferably 24-28 hours. The invention controls the condition of crystallization reaction in the range, and provides favorable conditions for obtaining the hydrotalcite nano-sheet with large length-diameter ratio. The present invention is not particularly limited to the specific embodiment of the crystallization reaction, and the temperature and the reaction time may be controlled. In the present invention, the crystallization reaction is preferably completed in an oven. In the invention, in the crystallization reaction process, the reaction system gradually becomes turbid, which represents that hydrotalcite nanosheets are generated through reaction.
After the solid-liquid mixture is obtained, the solid-liquid mixture is sequentially cooled, separated, washed and dried to obtain the hydrotalcite nanosheet. The cooling method of the solid-liquid mixture has no special requirement, and the solid-liquid mixture can be cooled to the room temperature. In the present invention, the cooling is preferably performed by natural cooling.
After cooling, the present invention preferably separates the solid-liquid mixture to obtain a separated solid. The present invention does not require special embodiments of the separation, which may be, for example, filtration or centrifugation. In the present invention, the separation is preferably performed by means of centrifugation. In the invention, the rotation speed of the centrifugal separation is preferably 1500-2000 r/min, and more preferably 1600-1800 r/min; the time for centrifugal separation is preferably 5-10 min, and more preferably 6-8 min.
After isolation, the isolated solids are preferably washed in accordance with the present invention. The invention has no special requirement on the washing mode, and the solid can be washed to be neutral. In the invention, the washing is preferably completed by deionized water, and the washing frequency is preferably 3-5 times, and more preferably 3-4 times. The invention washes the solid, can remove impurities and unreacted substances on the surface of the solid, and avoids the interference of the impurities or the unreacted substances on the temperature-sensitive film.
After washing, the washed solid is preferably dried to obtain the hydrotalcite nanosheet. The drying in the present invention is preferably vacuum drying or forced air drying, and more preferably forced air drying. In the invention, the temperature of the air-blast drying is preferably 50-70 ℃, and further preferably 55-65 ℃; the time for the air-blast drying is preferably 10-15 hours, and more preferably 12-14 hours. In the present invention, when the drying is vacuum drying, the present invention does not require a specific embodiment of the vacuum drying. The preparation method of the hydrotalcite nanosheet is limited to the above, so that the hydrotalcite nanosheet with a relatively large long diameter can be obtained.
The invention also provides aqueous dispersions of temperature sensitive polymers. The mass concentration of the temperature-sensitive polymer aqueous dispersion of the present invention is preferably 3 to 5%, and more preferably 4%. The invention has no special requirements on the preparation method of the temperature-sensitive polymer aqueous dispersion, and adopts a method which is well known by the technical personnel in the field.
After obtaining the hydrotalcite nano-sheet aqueous dispersion and the temperature-sensitive polymer aqueous dispersion, the invention alternately spin-coats the hydrotalcite nano-sheet aqueous dispersion and the temperature-sensitive polymer aqueous dispersion on a substrate to obtain the composite film. In the present invention, the spin coating preferably includes:
pretreating the substrate;
adsorbing the pretreated substrate on a film coating machine;
and (3) sequentially and alternately spin-coating the hydrotalcite nanosheet aqueous dispersion and the temperature-sensitive polymer aqueous dispersion on the surface of the substrate to obtain the composite film.
The present invention preferably pre-treats the substrate first. In the invention, the pretreatment comprises the ultrasonic cleaning of the substrate by sequentially using acetone, ethanol and deionized water. In the invention, the frequency of acetone ultrasonic cleaning, ethanol ultrasonic cleaning and deionized water ultrasonic cleaning is preferably 20000-30000 Hz independently, and is further preferably 24000-28000 Hz independently; the time for the acetone ultrasonic cleaning, the ethanol ultrasonic cleaning and the deionized water ultrasonic cleaning is preferably 20-40 min independently, and more preferably 25-35 min.
After pretreatment, the pretreated substrate is adsorbed on a rotary film coating machine. In the present invention, the adsorption is preferably performed by means of vacuum. The present invention does not require special embodiments of the adsorption, as will be familiar to those skilled in the art.
After the substrate is adsorbed on a rotary coating machine, the hydrotalcite nanosheet aqueous dispersion and the temperature-sensitive polymer aqueous dispersion are sequentially and alternately spin-coated on the substrate to obtain the composite film. In the invention, the hydrotalcite nanosheet aqueous dispersion is spin-coated, then the temperature-sensitive polymer aqueous dispersion is spin-coated, and the spin-coating is performed alternately in sequence, and the last layer is the temperature-sensitive polymer aqueous dispersion. In the invention, when the hydrotalcite nanosheet aqueous dispersion is spin-coated, the spin-coating speed is preferably 1800-2200 r/min, and more preferably 1900-2100 r/min; when the temperature-sensitive polymer aqueous dispersion is spin-coated, the spin-coating speed is preferably 4500-5500 r/min, and more preferably 4800-5200 r/min. In the process of alternately spin-coating the hydrotalcite nanosheet aqueous dispersion and the temperature-sensitive polymer aqueous dispersion on the substrate, the spin-coating liquid on the substrate is not additionally heated, and the water in the dispersion is removed by utilizing the spinning process. The invention limits the spin coating mode, and can obtain a composite film with uniform distribution and proper thickness.
After the composite film is obtained, the temperature-sensitive film is obtained by drying the composite film. The composite film is dried after being separated from the rotary film coating machine. The mode of separation is not particularly limited in the present invention, and those familiar to those skilled in the art can be used. The present invention is not particularly limited to the drying method of the composite film. In the present invention, the drying is preferably natural drying, which is drying at room temperature; the drying time is preferably 1 to 3 hours, and more preferably 1.5 to 2 hours.
In order to further illustrate the present invention, the following detailed description will be made of the temperature-sensitive film and the preparation method thereof, which are provided by the present invention, with reference to the examples and the accompanying drawings, but they should not be construed as limiting the scope of the present invention.
Example 1:
0.02mol of Mg (NO)3)2·6H2O、001mol of Al (NO)3)3·9H2Dissolving O in 50mL of deionized water to obtain a salt solution; dissolving 0.067mol of urea in 50mL of deionized water to obtain a urea aqueous solution; mixing the salt solution and the urea aqueous solution, uniformly stirring, placing in a drying oven at 110 ℃, crystallizing for 24 hours, naturally cooling a reaction system to room temperature, and performing centrifugal separation to obtain a solid; and washing the solid with deionized water until the washed deionized water is neutral to obtain the hydrotalcite nanosheet. The hydrotalcite nanosheets prepared in this example were characterized using a scanning electron microscope, as shown in fig. 1. As shown in FIG. 1, the hydrotalcite nanosheet obtained by the invention is of a two-dimensional layered structure, uniform in particle size distribution and large in length-diameter ratio. The diameter and thickness of the obtained hydrotalcite nanosheets were measured, and the measurement results are listed in table 1.
Preparing a hydrotalcite nanosheet water dispersion with the mass concentration of 0.5% and a polyvinyl methyl ether aqueous solution with the mass concentration of 4%;
ultrasonically cleaning a polypropylene film for 30min by using acetone, ethanol and deionized water in sequence, and then washing by using the deionized water to obtain a polypropylene film substrate;
adsorbing the polypropylene film substrate on a rotary film coating machine, spin-coating hydrotalcite nanosheet water dispersion, spin-coating polyvinyl methyl ether aqueous solution, and performing cyclic spin-coating for 30 times to obtain a composite film, wherein the cycle is regarded as one cycle;
and separating and airing the composite film from a film coating machine to obtain the temperature-sensitive film.
The temperature-sensitive film obtained in this example was characterized using a scanning electron microscope, as shown in FIG. 2. As shown in FIG. 2, the temperature-sensitive film obtained in this example has a flat surface, a uniform and complete temperature-sensitive film, and a good film formation.
The temperature-sensitive film obtained in the present example was tested by using an atomic microscope, and as shown in fig. 3, the surface of the temperature-sensitive film was flat, uniform and complete, and the film formed was good.
The cross section of the temperature-sensitive film obtained in this example was characterized by using a scanning electron microscope, as shown in fig. 4. In fig. 4, the darkest part is the film substrate, the middle part is the temperature sensitive gas barrier layer, and the lighter part is the background, which illustrates the structure of the temperature sensitive film obtained by the present invention, wherein the gas barrier layer is attached on the substrate, and in this embodiment, the thickness of the temperature sensitive film is 20.1 μm in the expanded state (fig. 4A); in the shrunk state, the thickness of the temperature-sensitive film was 9.2 μm (FIG. 4B).
The temperature-sensitive film obtained in this example was cryo-sectioned at-180 ℃ and its cross-section was characterized using a transmission electron microscope, as shown in FIG. 5. In fig. 5, the light layer is a temperature sensitive polymer layer, and the dark layer is a hydrotalcite nanosheet layer, and as a result of measurement, in the film obtained in this example, the average thickness of the temperature sensitive polymer layer is 182nm, and the average thickness of the hydrotalcite nanosheet layer is 53 nm.
The permeability of the temperature-sensitive film obtained in this example at different temperatures was tested by using GB/T1038-2000 standard, and the results are shown in FIG. 6. The oxygen transmission capacity of the polypropylene film substrate is 555.2cm3·m-2Day; when the temperature is higher than 36 ℃, the temperature-sensitive film is in a shrinkage state, and the oxygen transmission capacity is 485.5cm3·m-2Day; when the temperature is lower than 36 ℃, the temperature-sensitive film is in an expanded state, and the oxygen transmission capacity is 12.3cm3·m-2Day, which shows that the gas permeability and gas barrier properties of the temperature-sensitive film obtained in this example can be controlled by raising or lowering the temperature.
Example 2
A temperature-sensitive film was prepared as in example 1, except that: the crystallization reaction is crystallization at 100 ℃ for 26 hours; the temperature-sensitive polymer aqueous dispersion is a poly (N-vinyl lactone) aqueous dispersion with the mass concentration of 3.5%.
The product obtained in this example is tested according to the method of example 1, and the scanning electron microscope and atomic microscope results show that the temperature-sensitive film obtained in this example has a flat surface, a uniform and complete temperature-sensitive film, and a good film formation, and the temperature-sensitive film has a structure in which a gas barrier layer is attached to a substrate. The thickness of the temperature-sensitive film obtained in the embodiment is 18.3 μm in an expanded state; in a shrinkage state, the thickness of the temperature-sensitive film is 7.2 mu m; the average thickness of the temperature-sensitive polymer layer is 818nm, and the hydrotalcite sodium saltThe average thickness of the rice sheet layer was 74.1 nm. The oxygen transmission capacity of the polypropylene film substrate is 555.2cm3·m-2·day
Example 3
A temperature-sensitive film was prepared as in example 1, except that: the temperature-sensitive polymer aqueous dispersion is a poly-hydroxypropyl methacrylamide aqueous dispersion with the mass concentration of 4%.
The product obtained in this example is tested according to the method of example 1, and the scanning electron microscope and atomic microscope results show that the temperature-sensitive film obtained in this example has a flat surface, a uniform and complete temperature-sensitive film, and a good film formation, and the temperature-sensitive film has a structure in which a gas barrier layer is attached to a substrate.
The results of the other tests are shown in tables 1 and 2. The thickness of the temperature-sensitive film obtained in the embodiment is 19.7 μm in an expanded state; in a shrinkage state, the thickness of the temperature-sensitive film is 6.9 mu m; the average thickness of the temperature-sensitive polymer layer of the temperature-sensitive film is 1007nm, and the average thickness of the hydrotalcite nanosheet layer is 102 nm.
Example 4
A temperature-sensitive film was prepared according to the method of example 1, except that 4g of urea was dissolved in 100mL of deionized water; the temperature-sensitive polymer aqueous dispersion is N-isopropyl acrylamide aqueous dispersion with the mass concentration of 4%.
The product obtained in this example is tested according to the method of example 1, and the scanning electron microscope and atomic microscope results show that the temperature-sensitive film obtained in this example has a flat surface, a uniform and complete temperature-sensitive film, and a good film formation, and the temperature-sensitive film has a structure in which a gas barrier layer is attached to a substrate.
The results of the other tests are shown in tables 1 and 2. The thickness of the temperature-sensitive film obtained in the embodiment is 22.6 μm in an expanded state; under the shrinkage state, the thickness of the temperature-sensitive film is 7.0 μm; the average thickness of the temperature-sensitive polymer layer of the temperature-sensitive film is 1128nm, and the average thickness of the hydrotalcite nanosheet layer is 96 nm.
Table 1 examples 1-4 hydrotalcite nanoplatelets size test results
Numbering Average diameter/nm Average thickness/nm Aspect ratio
Example 1 658 32 20.5
Example 2 986 34 29
Example 3 1041 32 32.5
Example 4 1982 37 42.94
As shown in Table 1, the hydrotalcite nanosheet prepared by the method has a large aspect ratio.
Table 2 Performance test results of temperature-sensitive films of examples 1 to 4
Figure BDA0001533503320000111
As can be seen from the data in Table 2, when the temperature is higher than the phase transition temperature of the temperature-sensitive polymer, the gas permeability of the temperature-sensitive film is better; when the temperature is lower than the phase transition temperature of the temperature-sensitive polymer, the gas permeation amount is smaller, and the temperature-sensitive film has gas barrier property, which shows that the gas permeability and the gas barrier property of the temperature-sensitive polymer provided by the invention can be regulated and controlled by changing the temperature.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (8)

1. A temperature-sensitive film comprises a substrate and a gas barrier layer, wherein the gas barrier layer comprises hydrotalcite nano-sheet layers and temperature-sensitive polymer layers which are alternately laminated; the hydrotalcite nano-sheet layer in the gas barrier layer is connected with the substrate; the outermost layer of the temperature-sensitive film is a temperature-sensitive polymer layer;
the temperature-sensitive polymer layer is composed of a polymer, and the polymer comprises poly-N-vinyl lactone, poly-hydroxypropyl methacrylamide, polyvinyl methyl ether or N-isopropyl acrylamide;
the substrate is made of polyethylene, polypropylene or polyethylene terephthalate; the thickness of the substrate is 0.2-0.3 mm.
2. The temperature-sensitive film according to claim 1, wherein the thickness of the temperature-sensitive film in a contracted state is 6.5 to 10 μm, and the thickness of the temperature-sensitive film in an expanded state is 18 to 23 μm.
3. The temperature-sensitive film according to claim 1 or 2, wherein the thickness of the temperature-sensitive polymer layer in a contracted state is 200 to 500nm, and the thickness of the temperature-sensitive polymer layer in an expanded state is 800 to 1300 nm.
4. The temperature-sensitive film according to claim 1 or 2, wherein the hydrotalcite nanosheet layer is formed by layering hydrotalcite nanosheets in a manner parallel to the substrate; the thickness of the hydrotalcite nanosheet layer is 50-200 nm, and the length-diameter ratio of the hydrotalcite nanosheet is 20-200.
5. The method for preparing a temperature-sensitive film according to any one of claims 1 to 4, comprising:
providing a hydrotalcite nanosheet aqueous dispersion and a temperature-sensitive polymer aqueous dispersion;
alternately spin-coating the hydrotalcite nanosheet aqueous dispersion and the temperature-sensitive polymer aqueous dispersion on a substrate to obtain a composite film;
drying the composite film to obtain a temperature-sensitive film;
the drying is natural drying.
6. The preparation method of claim 5, wherein the mass concentration of the hydrotalcite nanosheet aqueous dispersion is 0.3-0.6%; the mass concentration of the temperature-sensitive polymer aqueous dispersion is 3-5%.
7. The production method according to claim 5 or 6, wherein the production method of the hydrotalcite nanosheet comprises:
will M2+、M3+Mixing with urea according to the ratio of 2.5-3: 1: 1 to obtain a raw material mixed solution, wherein M is2+Comprising Mg2+、Zn2+Or Ni2+Said M is3+Including Fe3+、Al3+Or Co3+；
Carrying out crystallization reaction on the raw material mixed liquor to obtain a solid-liquid mixture;
and sequentially cooling, separating, washing and drying the solid-liquid mixture to obtain the hydrotalcite nanosheet.
8. The method according to claim 7, wherein the temperature of the crystallization reaction is 100 to 120 ℃ and the time of the crystallization reaction is 20 to 30 hours.
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