CN116945569A - Preparation method of multilayer film capable of flexibly adjusting thickness gradient, multilayer film and film extrusion equipment - Google Patents
Preparation method of multilayer film capable of flexibly adjusting thickness gradient, multilayer film and film extrusion equipment Download PDFInfo
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- 238000001125 extrusion Methods 0.000 title claims abstract description 38
- 238000002360 preparation method Methods 0.000 title abstract description 9
- 238000001816 cooling Methods 0.000 claims abstract description 112
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 16
- 229920000642 polymer Polymers 0.000 claims description 97
- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims description 19
- 239000004926 polymethyl methacrylate Substances 0.000 claims description 19
- 229920000515 polycarbonate Polymers 0.000 claims description 15
- 239000004417 polycarbonate Substances 0.000 claims description 15
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- 238000002844 melting Methods 0.000 claims description 11
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- -1 polyethylene terephthalate Polymers 0.000 claims description 9
- 239000004698 Polyethylene Substances 0.000 claims description 6
- 239000004743 Polypropylene Substances 0.000 claims description 6
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 6
- 229920000573 polyethylene Polymers 0.000 claims description 6
- 239000005020 polyethylene terephthalate Substances 0.000 claims description 6
- 229920000139 polyethylene terephthalate Polymers 0.000 claims description 6
- 229920001155 polypropylene Polymers 0.000 claims description 6
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 6
- 229920001169 thermoplastic Polymers 0.000 claims description 6
- 239000004676 acrylonitrile butadiene styrene Substances 0.000 claims description 5
- XECAHXYUAAWDEL-UHFFFAOYSA-N acrylonitrile butadiene styrene Chemical compound C=CC=C.C=CC#N.C=CC1=CC=CC=C1 XECAHXYUAAWDEL-UHFFFAOYSA-N 0.000 claims description 4
- 229920000122 acrylonitrile butadiene styrene Polymers 0.000 claims description 4
- 238000011166 aliquoting Methods 0.000 claims description 3
- 229920000306 polymethylpentene Polymers 0.000 claims description 3
- 239000011116 polymethylpentene Substances 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
- B29C55/30—Drawing through a die
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
- B29C35/16—Cooling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/30—Extrusion nozzles or dies
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
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- Extrusion Moulding Of Plastics Or The Like (AREA)
Abstract
The application discloses a preparation method of a multilayer film capable of flexibly adjusting thickness gradient, the multilayer film and film extrusion equipment, and belongs to the field of optical films. The application controls the two surfaces of the multi-layer membranous melt to be cooled and stretched and molded under different flow rates, and the film layers in the multi-layer membranous melt generate different tensile strengths due to the different flow rates of the two surfaces, so as to obtain different film layer thicknesses, and finally, the multi-layer film with a gradient thickness structure is obtained. Wherein the thickness of the film layer decreases from the side with poor fluidity to the side with strong fluidity. The application also sets a cooling area and a heating area in the stage of cooling and forming of the film extrusion equipment, so that the two surfaces of the multi-layer film melt have different cooling temperatures, and the two surfaces obtain a flow rate difference. Compared with the thickness gradient formed by means of an unequal multiplier, the thickness gradient proportion of the multilayer film obtained by the method can be flexibly adjusted according to the cooling rate.
Description
Technical Field
The application relates to the technical field of optical films, in particular to a preparation method of a multilayer film capable of flexibly adjusting thickness gradient, the multilayer film and film extrusion equipment.
Background
The high-reflection film is an optical film with a reflection increasing function, can have extremely high reflectivity in a certain specific wave band range, is usually composed of two materials with different refractive indexes which are alternately overlapped with each other, and is often classified as a one-dimensional photonic crystal material. Such optical films typically have a highly reflective band with a center wavelength of bandwidth proportional to the thickness of each film layer. While the bandwidth of the high reflection band is related to the difference in refractive index of the two materials, the greater the difference in refractive index of the two materials, the wider the high reflection band of the optical film.
Therefore, in order to increase the reflection band width, there are generally two solutions. The first approach is to increase the refractive index difference between the two materials, since the refractive index difference between different polymer materials is very small, there are typically three options: a high refractive index inorganic material and a polymer material, a low refractive index inorganic material and a polymer material, a high refractive index inorganic material and a low refractive index inorganic material. However, in either option, there is a need to use an inorganic material, and the inorganic material layer is usually formed by magnetron sputtering, vacuum evaporation and other processes, so that the high-reflection film manufactured by the process has high precision, is commonly used for precise instruments and equipment, has high cost, and is not suitable for large-area production and manufacture. The second scheme is to stack film layers with different thicknesses, and the reflection bands can be subjected to superposition broadening. Therefore, the second scheme can be manufactured by processing two polymer materials, has simple process and lower cost, and can be prepared in a large area.
The multilayer polymer coextrusion processing technology is used as one of the processing modes of the polymer multilayer film, and the working principle is that two polymers are respectively melted by two extruders and then injected into a feeding block, a layered structure is preliminarily formed by the two polymer melts in the feeding block, the number of layers of the layered structure is required after the melt continuously flows through a plurality of multipliers, and the multilayer polymer melt is extruded by a die head, stretched by a roller, cooled and wound into a finished product material. To achieve a film layer of graded thickness, one or several multipliers are typically replaced with unequal multipliers. It is difficult to modify the thickness gradient by adjusting parameters after the machine is installed.
Disclosure of Invention
In order to solve the problems of the background technology, the application mainly provides a preparation method of a multilayer film capable of flexibly adjusting thickness gradient, the multilayer film and film extrusion equipment.
In order to achieve the above object, the present application provides a method for preparing a multilayer film capable of flexibly adjusting a thickness gradient, comprising the steps of:
extrusion: extruding a multilayer polymer melt to form a multilayer film-like melt, the multilayer polymer melt comprising two or more different polymers;
and (3) forming: and cooling and stretching the two surfaces of the multilayer membranous melt at different flow rates to obtain the multilayer film with the gradient thickness lamellar structure.
In some embodiments of the present application, in the molding step, a cooling device is provided, the cooling device including a cooling roller and a heater,
one surface of the multilayer membranous melt is attached to the surface of the cooling roller, and the heater heats one surface of the multilayer membranous melt, which is away from the cooling roller, so that the two surfaces of the multilayer membranous melt are cooled and stretched to form under different flow rates.
In some embodiments of the present application,
before the extruding step, the method further comprises the following steps:
melting: respectively melting the two or more different polymers to obtain two or more different polymer melts;
layering: the two or more different polymer melts initially form a layered polymer melt in a feed block;
multiplication: the layered polymer melt is multiplied to form a multi-layer polymer melt.
In some embodiments of the present application,
the layered polymer melt is multiplied in a multiplication system comprising a layered multiplier to form the multi-layered polymer melt, wherein,
types of the stacked multipliers include "one-in-two", "one-in-three", "one-in-four", and "one-in-five";
and/or the stack multiplier comprises an aliquoting stack multiplier or an unequal stack multiplier;
and/or a plurality of said stacked multipliers in series to form said multiplication system;
and/or the number of the laminated multipliers ranges from 1 to 10.
In some embodiments of the application, the polymer comprises a thermoplastic polymer;
and/or the refractive index ratio between any two of said polymers is greater than 1.0;
and/or the multilayer film comprises a thickest layer and a thinnest layer, wherein the thickness ratio of the thickest layer to the thinnest layer is 1.0-1.2.
In some embodiments of the application, the polymer comprises at least one of polymethyl methacrylate (PMMA), polymethylpentene (TPX), polycarbonate (PC), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene copolymer (ABS), polyethylene (PE).
In order to achieve the above object, the present application also provides a film extrusion apparatus, which includes a die and a cooling device, the cooling device includes a cooling area and a heating area, two surfaces of a multilayer film-shaped melt extruded by the die face the cooling area and the heating area respectively, and the multilayer film having a gradient thickness layered structure is obtained by cooling and stretch forming at different flow rates.
In some embodiments of the present application, the cooling region includes a cooling roller, the heating region includes a heater, a surface of the multilayer film melt is attached to the surface of the cooling roller, and the heater heats a surface of the multilayer film melt facing away from the cooling roller, so that both surfaces of the multilayer film melt are cooled and stretch-formed at different flow rates.
In some embodiments of the application, the heater is secured by a bracket, the bracket comprising a rotatable bracket with which the heater can rotate;
and/or the die width of the die is in the range of 20 μm to 3mm;
and/or the temperature of the die head ranges from 20 ℃ to 500 ℃;
and/or the heater comprises an infrared heater, a hot air blower and a heating roller;
and/or the heater is externally provided with a heat preservation cover.
In some embodiments of the application, the cooling roller is replaceable in size;
and/or the position of the cooling roller is adjustable;
and/or the cooling mode of the cooling roller comprises oil cooling and water cooling.
In order to achieve the above object, the present application also provides a multilayer film prepared by the method for preparing a multilayer film according to the present application.
The application has the beneficial effects that:
in the forming stage of the multilayer film, cooling and stretching forming are carried out on the two surfaces of the multilayer film melt at different flow rates, and the film layers of the multilayer film melt generate different tensile strengths due to the different flow rates of the two surfaces so as to obtain different film layer thicknesses, so that the multilayer film with gradient thickness is finally obtained. Specifically, the surface with a large flow rate, i.e., strong fluidity, has a strong tensile strength, and the surface with a small flow rate, i.e., weak fluidity, has a weak tensile strength, so that the film thickness of the multilayer film decreases from the side with poor fluidity of the multilayer film melt to the side with strong fluidity, and then the multilayer film with a gradient thickness layered structure is obtained.
The application can generate temperature difference on the two surfaces of the multi-layer film melt, and then the two surfaces obtain flow rate difference, namely the surface with higher cooling temperature of the multi-layer film melt has strong fluidity and the surface with lower cooling temperature has poor fluidity, and the thickness of the film layer of the multi-layer film is gradually decreased from the side with lower cooling temperature of the multi-layer film melt to the side with higher cooling temperature, so as to obtain the multi-layer film with a layered structure with gradient thickness.
Compared with the prior art that the thickness gradient is formed by means of a non-uniform multiplier, the thickness gradient proportion of the multilayer film obtained by the method can be adjusted by controlling the two surfaces of the multilayer film melt to be molded at different flow rates according to factors such as cooling temperature. Therefore, the size of the thickness gradient of the multilayer film can be adjusted according to production requirements so as to adjust the bandwidth of the reflection band of the multilayer film, an excellent reflection function can be realized, the multilayer film can be applied as a high-reflection film, and a set of equipment can be used for producing the multilayer films with different bandwidths.
Drawings
For a clearer description of embodiments of the application or of solutions in the prior art, the following brief description of the drawings is given for the purpose of illustrating the embodiments or the solutions in the prior art, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained from the structures shown in these drawings without the need for inventive effort for a person skilled in the art.
FIG. 1 is a schematic view showing a partial structure of a film extrusion apparatus according to the present application.
FIG. 2 is a graph showing the reflection bandwidth results of the multilayer films obtained in example 1 and comparative example 1 of the present application.
Wherein, 1: a die head; 2: a bracket; 3: a heater; 4: a multilayer film-like melt; 5: and (5) cooling the roller.
The achievement of the objects, functional features and advantages of the present application will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The description as it relates to "first", "second", etc. in the present application is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present application.
The application provides a preparation method of a multilayer film capable of flexibly adjusting thickness gradient, which comprises the following steps:
extrusion: extruding a multilayer polymer melt to form a multilayer film-like melt, the multilayer polymer melt comprising two or more different polymers;
and (3) forming: and cooling and stretching the two surfaces of the multi-layer membranous melt formed by extrusion at different flow rates to obtain the multi-layer film with the gradient thickness lamellar structure.
The multilayer film is formed by stacking film layers with different thicknesses, has a layered structure with gradient thickness, has a wide bandwidth due to superposition of the film layers with different thicknesses, has an excellent reflection function, and can be applied as a high-reflection film.
In addition, the flow rates of the two surfaces of the multi-layer membranous melt are adjusted in the cooling forming stage, so that the film layers of the multi-layer membranous melt can obtain different thicknesses, the film layer stacks with different thicknesses are beneficial to obtaining wide reflection bandwidths, and the reflection bandwidth of the multi-layer membranous melt can be flexibly adjusted according to the requirements by controlling the flow rates.
In the molding step, the present application is not limited to a manner of obtaining different flow rates on both surfaces of the multilayer film-like melt, and in some embodiments, the cooling temperature of both surfaces of the multilayer film-like melt may be controlled to produce a temperature difference to obtain a flow rate difference, and finally cooling and stretch molding are performed to obtain the multilayer film having a layered structure with a gradient thickness.
In some embodiments, a cooling device is provided in the forming step, the cooling device comprises a cooling roller and a heater, one surface of the multi-layer film melt is attached to the surface of the cooling roller, the heater heats one surface of the multi-layer film melt, which is away from the cooling roller, so that temperature difference exists between two surfaces of the multi-layer film melt, and cooling and stretching forming can be performed under different flow rates, and a layered structure with gradient thickness is obtained. In this embodiment, the two surfaces of the multilayer film melt obtain different cooling temperature differences due to different cooling temperatures, so that a flow rate difference is generated, that is, the surface with higher cooling temperature has strong fluidity, the surface with lower cooling temperature has poor fluidity, and the thickness of the film layer of the multilayer film decreases from the side with lower cooling temperature to the side with higher cooling temperature. Compared with the thickness gradient formed by means of the uneven multiplier in the prior art, the thickness gradient proportion of the multilayer film can be flexibly adjusted according to the cooling temperature, and the thickness gradient of the multilayer film can be adjusted according to the production requirement so as to adjust the bandwidth width of the reflection band of the multilayer film.
In some embodiments, the flow rate of the two surfaces of the multilayer film melt can also be controlled by adjusting the working temperature and the size of the die head of the film extrusion equipment, the position and the size of the roller through which the film is extruded, and the like, so that the two surfaces generate a flow rate difference, and a thickness gradient structure is formed. For example, by increasing the size of the roller, a slower stretching flow rate is obtained on the surface of the roller, which is close to the multilayer film melt, and a faster stretching flow rate is obtained on the surface of the roller, so that a flow rate difference is formed, and the obtained multilayer film is thicker on the side close to the roller and thinner on the side away from the roller, so that a gradient thickness structure is formed.
In some embodiments, prior to the extruding step, further comprising the steps of:
melting: respectively melting the two or more different polymers to obtain two or more different polymer melts;
layering: the two or more different polymer melts initially form a layered polymer melt in a feed block;
multiplication: the layered polymer melt is multiplied to form a multi-layer polymer melt.
In the melting step of this embodiment, the polymer may be dried in a drying apparatus including an atmospheric dryer and a vacuum dryer, preferably a vacuum dryer, wherein the drying temperature and time are determined according to the properties of the polymer and the drying temperature cannot be higher than the decomposition temperature of the polymer. The polymer with higher dryness can easily obtain uniform polymer melt with better fluidity in the melting stage.
In some embodiments, the polymer is PMMA, the drying temperature of the PMMA is 90 ℃ and the drying time is 12 hours.
In some embodiments, the polymer is PC, the drying temperature of the PC is 110 ℃, and the drying time is 12 hours.
In the layering step of this embodiment, the polymer melt flows through a flow channel into a feedblock, forming a layered polymer melt within the feedblock. It can be understood that different polymer melts are stacked in the step to form a layered polymer melt, and then the subsequent process steps are combined to enable each polymer film layer to obtain different thicknesses, and finally the obtained multilayer film has a wide widened reflection band, can meet the requirement of a high-reflection film, and is simple in process, low in cost and more beneficial to large-area generation and manufacture compared with a preparation process using an inorganic material as a high-reflection film substrate.
In some embodiments, the layered polymer melt is multiplied in a multiplication system that includes a stacked multiplier to form a multi-layered polymer melt.
The application is not limited to the types of stacked multipliers, and in some embodiments, the types of stacked multipliers include, but are not limited to, "one-in-two," one-in-three, "" one-in-four, "and" one-in-five.
In this embodiment, the stack multiplier includes an aliquoting stack multiplier or an unequal stack multiplier.
In some embodiments, a plurality of the stacked multipliers are connected in series to form the multiplication system. It will be appreciated that a plurality of stacked multipliers of the same type may be connected in series to form a multiplication system, or a plurality of stacked multipliers of different types may be connected in series to form a multiplication system.
The present application is not limited to the number of stacked multipliers in the multiplication system, and in some embodiments, the number of stacked multipliers may range from 1 to 10, and may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.
The application is not limited to the type of polymer, and the polymer has fluidity in a certain temperature range and does not decompose, and can be extruded and molded by extrusion equipment to meet the requirements of the application.
In some embodiments, the polymer includes, but is not limited to, a thermoplastic polymer that has fluidity and plasticity over a range of temperatures that can be extruded through an extrusion device and that can control the flow rate on different surfaces of the polymer as it has fluidity and plasticity such that the different surfaces achieve a flow rate differential, thereby achieving a gradient thickness structure.
In some embodiments, thermoplastic polymers include, but are not limited to, thermoplastic resins and thermoplastic polyesters. The thermoplastic resin and the thermoplastic polyester can be prepared into film products through an extrusion process, and are suitable for the film industry.
In some embodiments, the polymer has high transparency, and the polymer with high transparency can obtain better light transmittance after extrusion molding, and under the effect of the gradient thickness structure, the polymer is beneficial to increasing the reflectivity of the reflection belt and reducing the absorptivity.
In some embodiments, the polymer also includes modified polymers resulting from modification thereof, including but not limited to blend modification, fill modification, chemical modification, composite materials, and the like.
In some embodiments, the polymer includes, but is not limited to, polymethyl methacrylate (PMMA), polymethylpentene (TPX), polycarbonate (PC), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl alcohol (PVA), acrylonitrile Butadiene Styrene (ABS), polyethylene (PE).
The above polymer has fluidity and plasticity in a certain temperature range, can be extruded and molded by extrusion equipment, and has fluidity and plasticity so as to control the flow rate on different surfaces thereof, and the different surfaces obtain a flow rate difference, thereby obtaining a gradient thickness structure.
In addition, the interface between any two polymers is not easy to be stripped, and the refractive index between any two polymers is relatively large, so that the refractive index difference is large, and the requirement of the high-reflection film on the bandwidth is more easily met.
In some embodiments, during layering of the polymer melt flowing into the feed block, a metering pump may be used to regulate the flow of the polymer melt, and by controlling the flow of the polymer melt to control the layered structure of the layered polymer melt and the thickness of each layer of film, two or more polymers may form a layered structure before multiplication, and the thickness ratio between each other is ensured, which is beneficial to help regulate the formation of a gradient thickness structure of the multilayer film.
In some embodiments, the polymer melts are PMMA melt and PC melt, and the outflow ratio of PMMA melt and PC melt is adjusted by a metering pump to be 16:15, the layered polymer melt flowing into the feed block and stacked to form a bilayer structure.
The ratio of the thicknesses of the respective film layers in the layered polymer melt in the feed block may be adjusted, and in some embodiments, the thickness of the respective film layers may be determined based on the refractive index of the polymers, preferably the ratio of the thicknesses between the respective film layers of the different polymers in the layered polymer melt is inversely proportional to the refractive index between the polymers.
The application does not limit the refractive index ratio between any two polymers in the multilayer film, and the refractive index ratio between any two polymers is larger, so that the requirement of the high-reflection film on bandwidth is more easily met. In some embodiments, the refractive index ratio between any two of the polymers is greater than 1.0, which may be 1.01, 1.02, 1.05, 1.07, 1.1, etc., which is more likely to meet the bandwidth requirements of highly reflective films.
The application is not limited to the ratio of the thickness of the thickest layer to the thinnest layer in the multilayer film, and in some embodiments, the ratio of the thickness of the thickest layer to the thinnest layer is 1.0 to 1.2, and may be, for example, any one of the ratios in the range of 1.0 to 1.2, such as 1.01, 1.02, 1.05, 1.07, 1.1, 1.15, 1.2, etc. In the range of the ratio, the thickness gradient of the multilayer film is easy to control, so that excellent reflection function is obtained, and the use requirement of the high-reflection film is met.
The present application also provides a film extrusion apparatus which can produce not only a single-layer film but also a multi-layer film. The film extrusion equipment at least comprises a die head and a cooling device, wherein the cooling device comprises a cooling area and a heating area, two surfaces of the multilayer film melt extruded by the die head face the cooling area and the heating area respectively, and the multilayer film with the gradient thickness lamellar structure is obtained by cooling and stretch forming under different flow rates.
The film extrusion apparatus of the present application includes, in addition to the die and cooling means, other components common in film extrusion apparatus in the art including, but not limited to, feeding means, barrels, screws, multipliers, and the like.
It should be noted that, when the film extrusion apparatus is provided with a multiplier, the process of preparing the film also includes multiplying the film by the multiplier in the film extrusion apparatus, and the multilayer film is prepared.
It is understood that the two surfaces of the multi-layer film melt face the cooling area and the heating area respectively, and the two surfaces generate temperature difference and have different cooling rates, so that the multi-layer film with the gradient thickness lamellar structure can be obtained by cooling and stretching at different flow rates.
In some embodiments, the cooling region comprises a cooling roller, the heating region comprises a heater, one surface of the multi-layer film melt is attached to the surface of the cooling roller, the heater heats the surface of the multi-layer film melt, which is away from the cooling roller, so that the cooling temperature of the two surfaces of the multi-layer film melt generates a temperature difference, and the multi-layer film melt can be cooled and stretched to be formed under different flow rates. It will be appreciated that a lower surface temperature of the multilayer film-like melt attached to the cooling roll, a faster cooling rate and thus a slower flow rate, results in a poorer tensile strength, and a slower cooling rate and thus a faster flow rate of the multilayer film-like melt heated by the heater, results in a stronger tensile strength, and therefore, the difference in tensile strength exists between the two surfaces of the multilayer film-like melt due to the difference in flow rate, and the film thickness of the layer film-like melt decreases from the side with the lower cooling temperature to the side with the higher cooling temperature. Compared with the thickness gradient formed by means of the uneven multiplier in the prior art, the thickness gradient proportion of the multilayer film can be flexibly adjusted according to the cooling temperature, and the thickness gradient of the multilayer film can be adjusted according to the production requirement so as to adjust the bandwidth width of the reflection band of the multilayer film.
In some embodiments, the heater is secured by a support comprising a rotatable support, and the heater can be rotated with the rotatable support to a desired angle by means of the support to ensure that the multilayer film melt is heated more uniformly.
The application is not limited to the die width of the die and may be designed as desired, and in some embodiments the die width may range from 20 μm to 3mm.
The application does not limit the working temperature of the die head, the working temperature of the die head needs to be regulated according to the type of the polymer, the temperature needs to be regulated to ensure that the polymer is cooled and stretched in a molten state, and meanwhile, the polymer is not decomposed due to overhigh temperature.
Illustratively, the melting point of PMMA is around 150 ℃, but decomposition occurs easily at around 300 ℃, so when the polymer contains PMMA, the die temperature can be adjusted between 150 ℃ and 300 ℃, so that the PMMA can be kept in a molten state, and is easy to stretch-form, and meanwhile, the polymer is not decomposed at high temperature.
Illustratively, when the melting point of PC is about 240℃and the decomposition temperature is about 350℃then when the polymer contains PC, the die temperature can be adjusted between 240℃and 350℃to allow PC to remain in a molten state for ease of stretch forming while ensuring that it is not decomposed at high temperatures.
Illustratively, the die may have a temperature in the range of 20 ℃ to 500 ℃ which is sufficient to bring the polymer of the type described above into a molten state for ease of stretch forming and to ensure that the polymer does not decompose at high temperatures.
In some embodiments, the heater comprises an infrared heater, a hot air blower, a heated roller, preferably an infrared heater, which may cause the multilayer film melt to be heated more uniformly.
In some embodiments, a heat retaining shroud is provided external to the heater to help ensure that the multilayer film melt is heated more uniformly.
The size and position of the chill roll in the film extrusion apparatus of the present application may be adjustable, in some embodiments, the chill roll position may be adjustable in four directions, including up and down and back and forth. The upper part and the lower part are respectively close to and far away from the die head, the length from the die head to the cooling roller section is adjusted, and the angle and the position of the joint of the melt film and the cooling roller can be adjusted.
In some embodiments, the cooling means of the cooling roller includes oil cooling and water cooling, which are advantageous for uniformly cooling the multilayer film-like melt.
In some embodiments, referring to fig. 1, fig. 1 is a schematic partial structure of a film extrusion apparatus of the present application, which includes a die 1 and a cooling device including a heater 3 and a cooling roller 5, the heater 3 being fixed at an extrusion port of the die 1 by a bracket 2. The multilayer film-like melt 4 extruded through the die 1 has one surface facing the heater 3 and the other surface facing the cooling roller 5, and is cooled and stretch-formed by the cooling roller. Since the heater 3 heats one surface of the multilayer film-like melt 4 and the cooling roller 5 cools the other surface of the multilayer film-like melt 4, the temperature difference is generated between the two surfaces of the multilayer film-like melt 4, and the temperature difference has different cooling rates, the multilayer film having a layered structure with gradient thickness can be obtained by cooling and stretch forming at different flow rates.
In some embodiments, after the shaping step, the method further comprises the steps of:
biaxial stretching: heating and biaxially stretching the multilayer film;
and (3) rolling: and after the biaxially oriented multilayer film is cooled, cutting and winding the biaxially oriented multilayer film into a wound product.
The center wavelength of the multilayer film reflection band can meet application requirements through biaxial stretching.
The application also provides a multilayer film prepared by the preparation method of the multilayer film with flexibly adjustable thickness gradient and a multilayer film prepared by the film extrusion equipment, and the two multilayer films have multilayer structures with gradient thickness and can be applied as high-reflection films.
The technical scheme of the present application will be further described in detail with reference to the following specific examples, which are to be construed as merely illustrative, and not limitative of the remainder of the disclosure.
Example 1
Referring to fig. 1, the film extrusion apparatus of the present embodiment comprises a die head 1 and a cooling device including a heater 3 and a cooling roller 5, the heater 3 being fixed at the extrusion port of the die head 1 by a bracket 2, the heater 3 being an infrared heater.
The preparation method of the multilayer film of the embodiment is as follows:
and (3) drying: respectively placing polymethyl methacrylate (PMMA) and Polycarbonate (PC) into a low-pressure dryer for drying, wherein the PMMA is dried at 90 ℃ for 12 hours; the PC drying temperature is 110 ℃ and the drying time is 12h.
Feeding: the two polymers dried above were added separately to the feed ports of two extruders preheated for 4 hours.
Melting: PMMA is melted at 285 ℃ to obtain PMMA melt, and PC is melted at 270 ℃ to obtain PC melt.
Layering: the PMMA polymer melt and the PC polymer melt are regulated by a metering pump and flow into a feeding block according to the outflow amount of 16:15, and are stacked to form a lamellar polymer melt with a double-layer structure.
Multiplication: the layered polymer melt with the double-layer structure is multiplied by three 'one-to-four' type and one 'one-to-two' type equal division multipliers to form 256 layers of multi-layer polymer melt.
Extrusion: the extrusion die length of the extrusion apparatus was set to 40cm, the temperature was set to 210℃and 256 layers of the multilayer film-like melt 4 were obtained by extrusion at a rate of 17 kg/h.
And (3) forming: the heating temperature of the heater 3 was set to 200 ℃, the diameter of the cooling roller 5 was set to 30cm, the cooling temperature was set to 110 ℃, the rotational speed of the cooling roller 5 was 1rpm, the multilayer film-like melt 4 having 256 layers was cooled by the dual action of the heater 3 and the cooling roller 5, and a multilayer film having a layered structure of gradient thickness was formed after 2×2 biaxial stretching, and the thickness ratio of the thickest layer to the thinnest layer of the multilayer film was 1.1.
Biaxial stretching: and heating and biaxially stretching the multilayer film.
And (3) rolling: and after the biaxially oriented multilayer film is cooled, rolling by a rolling machine.
The total thickness of the finally formed multilayer film of example 1 was 48 μm.
Comparative example 1
Comparative example 1 a multilayer film was produced with reference to example 1, but except that in the molding stage, heating was not performed by a heater, and both surfaces of the multilayer film-like melt were kept at the same cooling temperature and subjected to cooling stretch molding to obtain a multilayer film having no gradient thickness.
Performance testing
The theoretical reflection bands of the multilayer films obtained in example 1 and comparative example 1 are compared as shown in fig. 2. As can be seen from fig. 2, the multilayer film having a gradient thickness obtains a wider reflection bandwidth than the multilayer film having no gradient thickness, and can meet the requirements of the highly reflective film.
The foregoing description is only of the preferred embodiments of the present application, and is not intended to limit the scope of the application, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.
Claims (10)
1. A method for preparing a multilayer film with flexibly adjustable thickness gradient, comprising the steps of:
extrusion: extruding a multilayer polymer melt to form a multilayer film-like melt, the multilayer polymer melt comprising two or more different polymers;
and (3) forming: and cooling and stretching the two surfaces of the multilayer membranous melt at different flow rates to obtain the multilayer film with the gradient thickness lamellar structure.
2. The method for producing a multilayer film with flexibly adjustable thickness gradient according to claim 1,
in the forming step, a cooling device is provided, the cooling device comprises a cooling roller and a heater, one surface of the multilayer film-shaped melt is attached to the surface of the cooling roller, and the heater heats one surface of the multilayer film-shaped melt, which is away from the cooling roller, so that the two surfaces of the multilayer film-shaped melt are cooled and stretched to form under different flow rates;
and/or, before the extruding step, further comprising the steps of:
melting: respectively melting the two or more different polymers to obtain two or more different polymer melts;
layering: the two or more different polymer melts initially form a layered polymer melt in a feed block;
multiplication: the layered polymer melt is multiplied to form a multi-layer polymer melt.
3. The method for producing a multilayer film with flexibly adjustable thickness gradient according to claim 2,
the layered polymer melt is multiplied in a multiplication system comprising a layered multiplier to form the multi-layered polymer melt, wherein,
types of the stacked multipliers include "one-in-two", "one-in-three", "one-in-four", and "one-in-five";
and/or the stack multiplier comprises an aliquoting stack multiplier or an unequal stack multiplier;
and/or a plurality of said stacked multipliers in series to form said multiplication system;
and/or the number of the laminated multipliers ranges from 1 to 10.
4. The method for producing a multilayer film with flexibly adjustable thickness gradient according to claim 1,
the polymer comprises a thermoplastic polymer;
and/or the refractive index ratio between any two of said polymers is greater than 1.0;
and/or the multilayer film comprises a thickest layer and a thinnest layer, wherein the thickness ratio of the thickest layer to the thinnest layer is 1.0-1.2.
5. The method for preparing a multilayer film with flexible thickness gradient adjustment according to claim 4, wherein the polymer comprises at least one of polymethyl methacrylate (PMMA), polymethylpentene (TPX), polycarbonate (PC), polyethylene terephthalate (PET), polypropylene (PP), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene copolymer (ABS), polyethylene (PE).
6. The film extrusion equipment is characterized by comprising a die head and a cooling device, wherein the cooling device comprises a cooling area and a heating area, two surfaces of the multilayer film-shaped melt extruded by the die head face the cooling area and the heating area respectively, and the multilayer film with the gradient thickness lamellar structure is obtained by cooling and stretch forming at different flow rates.
7. The film extrusion apparatus of claim 6, wherein the cooling zone comprises a cooling roller, the heating zone comprises a heater, a surface of the multilayer film melt is attached to the surface of the cooling roller, and the heater heats a surface of the multilayer film melt facing away from the cooling roller, so that both surfaces of the multilayer film melt are cooled and stretch-formed at different flow rates.
8. The film extrusion apparatus of claim 7, wherein said heater is secured by a bracket, said bracket comprising a rotatable bracket, said heater rotatable with said rotatable bracket;
and/or the die width of the die is in the range of 20 μm to 3mm;
and/or the temperature of the die head ranges from 20 ℃ to 500 ℃;
and/or the heater comprises an infrared heater, a hot air blower and a heating roller;
and/or the heater is externally provided with a heat preservation cover.
9. The film extrusion apparatus of claim 8, wherein the cooling roller is replaceable in size;
and/or the position of the cooling roller is adjustable;
and/or the cooling mode of the cooling roller comprises oil cooling and water cooling.
10. A multilayer film produced by the method for producing a multilayer film capable of flexibly adjusting a thickness gradient according to any one of claims 1 to 5.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117283834A (en) * | 2023-11-24 | 2023-12-26 | 中国科学技术大学先进技术研究院 | Polymer-based radiation refrigeration film and preparation method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117283834A (en) * | 2023-11-24 | 2023-12-26 | 中国科学技术大学先进技术研究院 | Polymer-based radiation refrigeration film and preparation method thereof |
| CN117283834B (en) * | 2023-11-24 | 2024-02-09 | 中国科学技术大学先进技术研究院 | Polymer-based radiation refrigeration film and preparation method thereof |
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