Multi-layer co-extrusion forming method of composite membrane material for building

Abstract

The invention relates to the technical field of co-extrusion molding, in particular to a multi-layer co-extrusion molding method of a building composite membrane material, which comprises the following steps: melting and plasticizing a polymer mixture of each layer, and then synchronously co-extruding to obtain a composite tubular melt blank; injecting gas into the composite tubular melt blank and drawing to obtain a composite tubular bubble; judging whether the preparation of the composite tubular vesicle reaches the standard or not according to the vesicle form characterization value; cooling and curing the composite tubular film bubbles reaching the standard to obtain a composite tubular film; when it is judged that the preparation of the composite tubular membrane does not reach the standard according to the circumferential cooling uniformity characterization value, an adjustment strategy when the preparation of the composite tubular membrane does not reach the standard is determined according to the circumferential wind speed extreme value ratio of the cooling wind ring; and flattening and rolling the composite tubular membrane reaching the standard to obtain the composite membrane material for the building. The co-extrusion forming efficiency of the composite membrane material for the building is improved.

Description

Technical Field

[0001] This invention relates to the field of co-extrusion molding technology, and in particular to a multi-layer co-extrusion molding method for composite membrane materials for building applications. Background Technology

[0002] Co-extrusion lamination refers to the production of polymer films using a multi-layer co-extrusion process. It has excellent barrier properties, mechanical properties, molding properties, and heat-sealing properties. The process does not require a separate glue lamination process and does not involve residual solvents such as inks, adhesives, and additives. Therefore, the application range of co-extrusion lamination technology is becoming increasingly wide.

[0003] Composite membrane materials for architecture, as a new type of enclosure material, are widely used in inflatable membrane stadiums, temporary building enclosures, building waterproofing and seepage prevention layers, energy-saving and environmentally friendly greenhouses, and outdoor public facility sunshades due to their advantages such as light weight, convenient construction, large span, and strong weather resistance. These membrane materials must simultaneously meet core requirements such as long-term outdoor weather resistance, mechanical structural stability, sealing and seepage prevention, and splicability. The co-extrusion composite process can precisely match these requirements through its multi-layer functional integrated molding characteristics.

[0004] However, the operating environment for composite membrane materials used in construction is far more demanding than that of packaging films, placing significantly higher requirements on the dimensional stability, circumferential uniformity, and process controllability of the products compared to ordinary films.

[0005] Chinese Patent Application Publication No. CN109732892A discloses a method and equipment for manufacturing multilayer thermal insulation plastic inflatable films. The equipment of this invention mainly consists of a multilayer co-extrusion blow molding die head, which is composed of an outer die ring, an inner die ring, and several intermediate die rings located between the inner and outer die rings. The airflow from the blower is ejected from the outlet located in the center of the hollow part of each die ring through the duct and the air inlet on each intermediate die ring. Each blow molding machine heats and melts the plastic polymer granules of each component in its respective hopper into a liquid state, and then extrudes the molten liquid material into the feed inlet of the corresponding die ring, and then flows out from the film outlet of each die ring. The airflow ejected from the outlet in the center of the hollow part of each film ring divides the liquid material flowing out of each film outlet into cavity-like bodies and pushes them away from the heated multilayer co-extrusion blow molding die head surface.

[0006] However, the existing technology still has the following problems: it does not consider the influence of the membrane bubble morphology during the blown film process and the uniformity of the circumferential cooling process of the tubular membrane on the thickness and size of the building membrane material, which leads to poor co-extrusion molding efficiency of the building composite membrane material. Summary of the Invention

[0007] Therefore, the present invention provides a multi-layer co-extrusion molding method for architectural composite membrane materials to overcome the problem that the existing technology does not consider the influence of the membrane bubble morphology during the blown film process and the uniformity of the circumferential cooling process of the tubular membrane on the thickness and size of the architectural membrane material, thus resulting in poor co-extrusion molding efficiency of architectural composite membrane materials.

[0008] To achieve the above objectives, the present invention provides a multilayer co-extrusion molding method for architectural composite membrane materials, comprising: The polymer mixture of each layer is placed in an independent extruder and melted and plasticized at a preset maximum melting temperature difference. Then it is introduced into the co-extrusion die of a co-extrusion blown film machine and co-extruded synchronously at a preset processing temperature to obtain a composite tubular melt preform. Gas is injected into the interior of the composite tubular melt billet at a preset blowing pressure, and the composite tubular melt billet is pulled at a preset traction rate to obtain a composite tubular film bubble. Based on the outline pixel area of ​​the image of the composite tubular membrane bubble, the membrane bubble morphology stability characterization value is obtained, and the preparation of the composite tubular membrane bubble is determined according to the membrane bubble morphology characterization value to determine whether it meets the preset standard. The composite tubular membrane bubble that meets the preset standard is cooled and solidified through a cooling air ring to obtain a composite tubular membrane; based on the circumferential temperature of the composite tubular membrane before and after cooling and solidification, the circumferential cooling uniformity characterization value is obtained. When it is determined that the preparation of the composite tubular membrane is at risk of not meeting the preset standard based on the circumferential cooling uniformity characterization value, the preparation of the composite tubular membrane is further determined based on the diameter fluctuation variance of the composite tubular membrane to determine whether the preparation of the composite tubular membrane meets the preset standard. When the preparation of the composite tubular membrane does not meet the preset standard based on the circumferential cooling uniformity characterization value, the adjustment strategy for the preparation of the composite tubular membrane does not meet the preset standard is determined based on the circumferential wind speed extreme ratio of the cooling wind ring. The adjustment strategy is to reduce the preset processing temperature or reduce the air volume of the outlet corresponding to the maximum wind speed of the cooling wind ring. The composite tubular membrane that meets the preset standards is flattened and rolled up to obtain a composite membrane material for building.

[0009] Furthermore, the polymer mixtures of each layer are respectively a mixture of linear low-density polyethylene, antioxidant and ultraviolet absorber for the outer layer; a mixture of linear low-density polyethylene, polyolefin elastomer, ethylene-butyl acrylate copolymer and reinforcing filler for the middle layer; and a mixture of linear low-density polyethylene and ethylene-butyl acrylate copolymer for the inner layer.

[0010] Furthermore, the process of determining whether the preparation of the composite tubular membrane vesicle meets the preset standard based on the membrane vesicle morphology characterization value includes: The membrane vesicle morphology characterization values ​​are compared with the first preset membrane vesicle morphology characterization values ​​and the second preset membrane vesicle morphology characterization values, respectively. If the membrane morphology characterization value is less than the first preset membrane morphology characterization value, then the preparation of the composite tubular membrane vesicle is determined to meet the preset standard. If the membrane bubble morphology characterization value is greater than or equal to the first preset membrane bubble morphology characterization value and less than the second preset membrane bubble morphology characterization value, then it is determined that the preparation of the composite tubular membrane bubble does not meet the preset standard, and the preset inflation pressure is increased according to the difference between the membrane bubble morphology characterization value and the first preset membrane bubble morphology characterization value. If the membrane bubble morphology characterization value is greater than or equal to the second preset membrane bubble morphology characterization value, it is determined that the preparation of the composite tubular membrane bubble does not meet the preset standard, and the preset maximum melting temperature difference is reduced according to the difference between the membrane bubble morphology characterization value and the second preset membrane bubble morphology characterization value.

[0011] Furthermore, the process of obtaining the characterization values ​​for membrane vesicle morphology stability includes: Within a first preset time period, a number of orthographic images of the composite tubular membrane bubble are captured at a preset frequency. Extract the pixel area enclosed by the outline of the composite tubular membrane bubble in each image; Calculate the standard deviation of the area of ​​all pixels and denote it as the morphological stability characterization value of the bubble.

[0012] Furthermore, several temperature difference adjustment methods are provided for reducing the preset maximum melting temperature difference, and each temperature difference adjustment method reduces the preset maximum melting temperature difference by a different amount.

[0013] Furthermore, the process of determining whether the preparation of the composite tubular membrane meets the preset standard based on the circumferential cooling uniformity characterization value of the composite tubular membrane includes: The circumferential cooling uniformity characterization value is compared with the first preset circumferential cooling uniformity characterization value and the second preset circumferential cooling uniformity characterization value, respectively. If the circumferential cooling uniformity characterization value is less than the first preset circumferential cooling uniformity characterization value, then the preparation of the composite tubular membrane is determined to meet the preset standard. If the circumferential cooling uniformity characterization value is greater than or equal to the first preset circumferential cooling uniformity characterization value and less than the second preset circumferential cooling uniformity characterization value, it is determined that the preparation of the composite tubular membrane has a risk of not meeting the preset standard, and the preparation of the composite tubular membrane is determined a second time based on the diameter fluctuation variance of the composite tubular membrane to determine whether the preparation of the composite tubular membrane meets the preset standard. If the circumferential cooling uniformity characterization value is greater than or equal to the second preset circumferential cooling uniformity characterization value, it is determined that the preparation of the composite tubular membrane does not meet the preset standard, and the adjustment strategy when the preparation of the composite tubular membrane does not meet the preset standard is determined according to the extreme ratio of the circumferential wind speed of the cooling wind ring.

[0014] Furthermore, the process of obtaining the circumferential cooling uniformity characterization value includes: Before cooling and solidification, the temperature of several circumferentially set monitoring points of the composite tubular membrane to be cooled is collected; After cooling and solidification, the temperature at the monitoring points is collected; Calculate the difference between the temperature before cooling and the temperature after cooling at each monitoring point, and record it as the cooling temperature difference at each monitoring point; The standard deviation of all cooling temperature differences is denoted as the circumferential cooling uniformity characterization value.

[0015] Furthermore, if the preparation of the composite tubular membrane does not meet the preset standard, based on a comparison result showing that the diameter fluctuation variance of the composite tubular membrane is greater than or equal to the preset diameter fluctuation variance, the preset traction rate is reduced according to the ratio of the diameter fluctuation variance to the preset fluctuation variance.

[0016] Furthermore, the process of obtaining the diameter fluctuation variance of the composite tubular membrane includes: After the composite tubular membrane is cooled and solidified, the diameters of several composite tubular membranes are collected at a preset sampling frequency within a second preset time period. The variance of all diameters is calculated, which is the diameter fluctuation variance of the composite tubular membrane.

[0017] Furthermore, the adjustment strategy for determining when the preparation of the composite tubular membrane does not meet the preset standard based on the extreme wind speed ratio of the cooling air ring includes: If the extreme wind speed ratio is less than the preset extreme wind speed ratio, the preset processing temperature of the co-extrusion die is reduced according to the difference between the preset extreme wind speed ratio and the extreme wind speed ratio. If the extreme wind speed ratio is greater than or equal to the preset extreme wind speed ratio, the air volume of the outlet corresponding to the maximum wind speed of the cooling air ring is reduced according to the difference between the extreme wind speed ratio and the preset extreme wind speed ratio. The extreme wind speed ratio of the cooling air ring is the ratio of the maximum wind speed to the minimum wind speed at each air outlet of the cooling air ring.

[0018] Compared with the prior art, the beneficial effects of this invention are as follows: by setting an outer layer with added antioxidants and ultraviolet absorbers, the invention solves the problem of insufficient outdoor weather resistance of architectural membrane materials; the introduction of polyolefin elastomer and reinforcing fillers in the middle layer improves the mechanical load-bearing capacity of the membrane material; the inner layer of ethylene-butyl acrylate copolymer optimizes heat-sealing splicing performance; and the use of linear low-density polyethylene as the substrate for each layer ensures interlayer compatibility. By monitoring the morphology of the membrane bubble and the cooling uniformity of the tubular membrane, the thickness uniformity and dimensional stability of the film are ensured, making the mechanical properties of the obtained architectural membrane material reliable. By introducing membrane bubble morphology stability characterization values ​​and circumferential cooling uniformity characterization values, intelligent monitoring of the production process is realized, thereby improving the co-extrusion molding efficiency of architectural composite membrane materials.

[0019] Furthermore, this invention addresses the instability of membrane bubbles by comparing the membrane bubble morphology characterization values ​​with two preset thresholds. For slight fluctuations, the blowing pressure is adjusted; for severe fluctuations, the melting temperature difference is adjusted. This tiered strategy, combined with an adjustment amount proportional to the magnitude of the deviation, enables rapid and precise process correction, thereby improving the stability of the preparation.

[0020] Furthermore, this invention constructs a three-level monitoring mechanism for cooling quality based on the circumferential cooling uniformity characterization value. In the event of a risk warning of non-compliance, the system does not directly make a final adjustment, but instead makes a secondary judgment through the diameter fluctuation variance to avoid misjudgment. For non-compliance, the adjustment strategy is determined by combining the extreme ratio of the circumferential wind speed of the cooling air ring to ensure the circumferential dimensional uniformity of the membrane material, thereby improving the reliability of the judgment.

[0021] Furthermore, when the composite tubular membrane fails to meet the preparation standards due to early warning of cooling uniformity and secondary determination of diameter fluctuation variance, the present invention reduces the traction rate, thereby reducing the overall tensile strain during the membrane preparation process and reserving more time for cooling and shaping of the tubular membrane, thus ensuring the uniformity of the circumferential dimensions of the membrane material.

[0022] Furthermore, this invention directly judges the uniformity of circumferential airflow in the cooling air ring by the extreme value ratio of wind speed. The larger the extreme value ratio of wind speed, the greater the difference in circumferential wind speed and the more prominent the problem of uneven cooling, thereby achieving accurate positioning of the root cause of uneven cooling. Attached Figure Description

[0023] Figure 1 This is a flowchart of a multilayer co-extrusion molding method for architectural composite membrane materials according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating how to determine whether the preparation of the composite tubular membrane bubble meets a preset standard, according to an embodiment of the present invention. Figure 3 This is a flowchart illustrating how the preparation of the composite tubular membrane meets a preset standard based on the circumferential cooling uniformity characterization value of the composite tubular membrane, according to an embodiment of the present invention. Figure 4 This is a flowchart illustrating the adjustment strategy for determining when the preparation of the composite tubular membrane does not meet the preset standards in an embodiment of the present invention. Detailed Implementation

[0024] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0025] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0026] It should be noted that the data in this embodiment are all derived from a comprehensive analysis and evaluation of historical test data and corresponding historical test results from the three months prior to this test. Those skilled in the art will understand that the method described in this invention can determine the above-mentioned parameters in the following ways: selecting the value with the highest proportion based on the data distribution as the preset standard parameter; using weighted summation to obtain the value as the preset standard parameter; substituting each historical data point into a specific formula and using the value obtained by that formula as the preset standard parameter; or other selection methods, as long as the method described in this invention can clearly define different specific situations in the single-item judgment process through the obtained values.

[0027] Please see Figure 1 , Figure 2 , Figure 3 as well as Figure 4 The flowcharts shown are respectively: a flowchart of a multilayer co-extrusion molding method for composite membrane materials for buildings according to an embodiment of the present invention; a flowchart of determining whether the preparation of composite tubular membrane bubbles meets a preset standard according to an embodiment of the present invention; a flowchart of determining whether the preparation of composite tubular membranes meets a preset standard based on the circumferential cooling uniformity characterization value of the composite tubular membrane according to an embodiment of the present invention; and a flowchart of an adjustment strategy when the preparation of composite tubular membranes does not meet the preset standard according to an embodiment of the present invention.

[0028] The multilayer co-extrusion molding method for architectural composite membrane materials according to embodiments of the present invention includes: Step S1: The polymer mixture of each layer is placed in an independent extruder and melted and plasticized at a preset maximum melting temperature difference of 10°C. Then, it is introduced into the co-extrusion die of a co-extrusion blown film machine and co-extruded simultaneously at a preset processing temperature of 200°C to obtain a composite tubular melt preform. The composite tubular melt preform is a hollow, thin-walled cylindrical melt extruded by the co-extrusion die and is shaped as a vertically downward-facing melt. The melt layers are composited into one piece within the die.

[0029] Step S2: Inject air into the interior of the composite tubular melt billet at a preset blowing pressure of 0.02 MPa, and pull the composite tubular melt billet at a preset traction speed of 8 m / min using a traction roller to obtain a composite tubular film bubble; Step S3: Based on the outline pixel area of ​​the image of the composite tubular membrane bubble, the membrane bubble morphology stability characterization value is obtained, and the composite tubular membrane bubble preparation is determined according to the membrane bubble morphology characterization value to determine whether it meets the preset standard. Step S4: The composite tubular membrane bubble that meets the preset standard is cooled and solidified through a cooling air ring to obtain a composite tubular membrane; based on the circumferential temperature of the composite tubular membrane before and after cooling and solidification, the circumferential cooling uniformity characterization value is obtained. Step S5: If it is determined that the preparation of the composite tubular membrane is at risk of not meeting the preset standard based on the circumferential cooling uniformity characterization value, the preparation of the composite tubular membrane is further determined based on the diameter fluctuation variance of the composite tubular membrane to determine whether the preparation of the composite tubular membrane meets the preset standard. Step S6: When it is determined that the preparation of the composite tubular membrane does not meet the preset standard based on the circumferential cooling uniformity characterization value, an adjustment strategy is determined based on the circumferential wind speed extreme ratio of the cooling wind ring. The adjustment strategy is to reduce the preset processing temperature or reduce the air volume of the outlet corresponding to the maximum wind speed of the cooling wind ring. Step S7: The composite tubular membrane that meets the preset standard is flattened by a herringbone plate and then wound up by a winding machine to obtain a composite membrane material for building.

[0030] Specifically, the three polymer mixtures for each layer are as follows: for the outer layer, a mixture of 93 parts by weight of linear low-density polyethylene, 5 parts by weight of antioxidant, and 2 parts by weight of ultraviolet absorber; for the middle layer, a mixture of 80 parts by weight of linear low-density polyethylene, 10 parts by weight of polyolefin elastomer, 8 parts by weight of ethylene-butyl acrylate copolymer, and 2 parts by weight of reinforcing filler; and for the inner layer, a mixture of 70 parts by weight of linear low-density polyethylene and 30 parts by weight of ethylene-butyl acrylate copolymer. In this embodiment, the antioxidant is BASF Irganox 1010, the ultraviolet absorber is UV-531, the polyolefin elastomer is ethylene-octene copolymer, the ethylene-butyl acrylate copolymer contains 25-35 wt% butyl acrylate monomer, and the reinforcing filler is 2000 mesh talc.

[0031] In this embodiment, the outer layer is a weather-resistant layer with a thickness of 0.08 mm; the middle layer is a reinforcing layer with a thickness of 0.12 mm; and the inner layer is an adhesive layer with a thickness of 0.05 mm.

[0032] Specifically, the three polymer mixtures are fed into three independent single-screw extruders, with the outer extruder having a melt temperature of 195°C, the middle extruder having a melt temperature of 200°C, and the inner extruder having a melt temperature of 190°C.

[0033] Specifically, the process of determining whether the preparation of the composite tubular membrane vesicle meets the preset standard based on the membrane vesicle morphology characterization value includes: The membrane vesicle morphology characterization value is compared with the first preset membrane vesicle morphology characterization value of 0.020 and the second preset membrane vesicle morphology characterization value of 0.050, respectively. If the membrane morphology characterization value is less than the first preset membrane morphology characterization value, then the preparation of the composite tubular membrane vesicle is determined to meet the preset standard. If the membrane bubble morphology characterization value is greater than or equal to the first preset membrane bubble morphology characterization value and less than the second preset membrane bubble morphology characterization value, then it is determined that the preparation of the composite tubular membrane bubble does not meet the preset standard, and the preset inflation pressure is increased according to the difference between the membrane bubble morphology characterization value and the first preset membrane bubble morphology characterization value. If the membrane bubble morphology characterization value is greater than or equal to the second preset membrane bubble morphology characterization value, it is determined that the preparation of the composite tubular membrane bubble does not meet the preset standard, and the preset maximum melting temperature difference is reduced according to the difference between the membrane bubble morphology characterization value and the second preset membrane bubble morphology characterization value.

[0034] Specifically, the first preset membrane vesicle morphology characterization value ranges from [0.010, 0.025], and the second preset membrane vesicle morphology characterization value ranges from [0.045, 0.060]. Preferably, the first preset membrane vesicle morphology characterization value is 0.020 and the second preset membrane vesicle morphology characterization value is 0.050. However, the above values ​​are not limited to these values, and those skilled in the art can adjust the above values ​​according to actual needs.

[0035] Specifically, the smaller the bubble morphology characterization value, the closer the bubble size is to the baseline value at each instant, meaning the morphology is more stable; the larger the bubble morphology characterization value, the more violent the bubble shaking, oscillation, or periodic expansion or contraction, and the less stable the morphology. When the bubble morphology characterization value is between the two thresholds, since the blowing pressure directly determines the bubble expansion force and morphology maintenance, fine adjustments can quickly correct area fluctuations, so the strategy of increasing the blowing pressure is adopted. When the bubble morphology characterization value is greater than or equal to the second preset value, the root cause is that the excessive melting temperature difference between each layer of melt leads to viscosity mismatch, which in turn causes uneven force and morphology loss during bubble blowing. By reducing the preset maximum melting temperature difference, the melt flow adaptability is optimized from the plasticizing source.

[0036] Specifically, the process of obtaining the morphological stability characterization values ​​of membrane vesicles includes: Within a first preset duration of 30 seconds, several orthographic images of the composite tubular membrane bubble are captured using an industrial linear scan camera at a preset frequency of 5Hz. The acquisition range of the orthographic images is the vertical space area of ​​the composite tubular membrane bubble from the die lip plane at the lower edge of the co-extrusion die head to the inlet plane of the cooling air ring. This vertical space area covers the complete free blowing area of ​​the membrane bubble from extrusion, blowing, to entering forced cooling, and is the area where the membrane bubble morphology is most active and most susceptible to the influence of process parameters. Gaussian filtering is applied to each acquired orthographic projection image of a membrane bubble using the OpenCV library to suppress noise and output a smooth image. An adaptive threshold segmentation algorithm is then used to process the smooth image, dynamically separating the membrane bubble from the background and outputting a binarized image. A contour search algorithm (such as cv2.findContours) is used to retrieve the outer contour of the binarized image, and the sequence of main contour points with the largest area and located in the central region of the image is extracted as the output, resulting in the contour point sequence of the outermost contour of the membrane bubble. The contour point sequence is then input into a contour area calculation function (such as cv2.contourArea), and the pixel area enclosed by the outermost contour of the membrane bubble is calculated according to Green's formula. This image processing method based on the OpenCV library provides a conventional technical means for those skilled in the art to realize the conversion from images to quantitative data. Calculate the standard deviation of the area of ​​all pixels and denote it as the morphological stability characterization value of the bubble.

[0037] Specifically, several temperature difference adjustment methods are provided to reduce the preset maximum melting temperature difference, among which, If the difference in membrane bubble morphology is less than the first preset difference in membrane bubble morphology of 0.035, then the preset maximum melting temperature difference is reduced to the corresponding value using the first adjustment coefficient of 0.97. If the difference in membrane bubble morphology is greater than or equal to the first preset difference in membrane bubble morphology and less than the second preset difference in membrane bubble morphology of 0.061, then the preset maximum melting temperature difference is reduced to the corresponding value using the second adjustment coefficient of 0.95. If the difference in membrane bubble morphology is greater than or equal to the second preset difference in membrane bubble morphology, then the preset maximum melting temperature difference is reduced to the corresponding value using a third adjustment coefficient of 0.93. The membrane morphology difference is the difference between the membrane morphology characterization value and the second preset membrane morphology characterization value.

[0038] Specifically, the process of determining whether the preparation of the composite tubular membrane meets the preset standard based on the circumferential cooling uniformity characterization value of the composite tubular membrane includes: The circumferential cooling uniformity characterization value is compared with the first preset circumferential cooling uniformity characterization value of 2.1℃ and the second preset circumferential cooling uniformity characterization value of 7.1℃. If the circumferential cooling uniformity characterization value is less than the first preset circumferential cooling uniformity characterization value, then the preparation of the composite tubular membrane is determined to meet the preset standard. If the circumferential cooling uniformity characterization value is greater than or equal to the first preset circumferential cooling uniformity characterization value and less than the second preset circumferential cooling uniformity characterization value, it is determined that the preparation of the composite tubular membrane has a risk of not meeting the preset standard, and the preparation of the composite tubular membrane is determined a second time based on the diameter fluctuation variance of the composite tubular membrane to determine whether the preparation of the composite tubular membrane meets the preset standard. If the circumferential cooling uniformity characterization value is greater than or equal to the second preset circumferential cooling uniformity characterization value, it is determined that the preparation of the composite tubular membrane does not meet the preset standard, and the adjustment strategy when the preparation of the composite tubular membrane does not meet the preset standard is determined according to the extreme ratio of the circumferential wind speed of the cooling wind ring.

[0039] Specifically, the first preset circumferential cooling uniformity characterization value ranges from [1.7℃ to 3.5℃], and the second preset circumferential cooling uniformity characterization value ranges from [6.7℃ to 8.5℃]. Preferably, the first preset circumferential cooling uniformity characterization value is 2.1℃ and the second preset circumferential cooling uniformity characterization value is 7.1℃. However, the above values ​​are not limited to these values, and those skilled in the art can adjust the above values ​​according to actual needs.

[0040] Specifically, the circumferential cooling uniformity characterization value reflects the consistency of the cooling rate at various positions around the membrane bubble. The smaller the circumferential cooling uniformity characterization value, the more uniform the cooling and the more consistent the circumferential thermal shrinkage rate of the membrane material, avoiding splicing misalignment and stress cracking. Conversely, uneven cooling can easily lead to dimensional fluctuations in the finished composite membrane material for building applications.

[0041] Specifically, by setting a circumferential cooling uniformity characterization value and comparing it with the first and second preset thresholds, the cooling state corresponding to the circumferential cooling uniformity characterization value is divided into three categories: compliant, risky, and non-compliant. When the circumferential cooling uniformity characterization value is less than the first preset value, the circumferential cooling temperature difference of the tubular membrane is minimal, and the consistency of the thermal shrinkage rate meets the requirements for splicing and long-term use of architectural membrane materials, and is directly judged as qualified to ensure production efficiency. When the circumferential cooling uniformity characterization value is greater than or equal to the second preset value, it indicates uneven cooling, which leads to significant differences in the internal crystallization state and shrinkage of the tubular membrane material, causing dimensional fluctuations and stress concentration, and is directly judged as unqualified. Furthermore, for the risky state where the circumferential cooling uniformity characterization value is between the two thresholds, the diameter fluctuation variance is introduced for secondary verification to realize the correlation between the cooling process characterization and the finished product size results, effectively avoiding missed judgments.

[0042] Specifically, the process of obtaining the circumferential cooling uniformity characterization value includes: Eight infrared temperature probes are arranged circumferentially at equal intervals at 10cm above the inlet plane and 10cm below the outlet plane of the cooling air ring as monitoring points to form a temperature measurement array. The optical axis of each infrared temperature probe is vertically aligned with the surface of the composite tubular membrane and focused at the same measurement distance. Before cooling and solidification, the temperature of the composite tubular membrane to be cooled is collected at monitoring points set around its circumference; After cooling and solidification, the temperature at the monitoring points is collected; Calculate the difference between the temperature before cooling and the temperature after cooling at each monitoring point, and record it as the cooling temperature difference at each monitoring point; The standard deviation of all cooling temperature differences is recorded as the circumferential cooling uniformity characterization value; in this embodiment, the infrared temperature probe is preferably a colorimetric infrared thermometer.

[0043] Specifically, the preparation of the composite tubular membrane is determined twice based on the diameter fluctuation variance of the composite tubular membrane to determine whether it meets the preset standard. If the diameter fluctuation variance is less than the preset diameter fluctuation variance of 0.0004mm 2 If the preparation of the composite tubular membrane meets the preset standard, then it is determined that the preparation of the composite tubular membrane meets the preset standard. If the diameter fluctuation variance is greater than or equal to the preset diameter fluctuation variance, it is determined that the preparation of the composite tubular membrane does not meet the preset standard, and the preset traction rate is reduced according to the ratio of the diameter fluctuation variance to the preset fluctuation variance.

[0044] Specifically, through 50 data validations, it was found that when the diameter fluctuation variance is less than 0.00038 mm... 2 At that time, the dimensional qualification rate of the finished building composite membrane material was greater than 90%. In this embodiment, the preset diameter fluctuation variance was set to 0.0004 mm. 2 However, the above values ​​are not limited to these, and those skilled in the art can adjust the above values ​​according to actual needs.

[0045] Specifically, the diameter fluctuation variance characterizes the dimensional stability of the composite tubular membrane after cooling and solidification. When the diameter fluctuation variance is less than the preset value, it indicates that the dimensional consistency of the composite tubular membrane meets the requirements for building splicing and long-term stress, and it is directly judged as qualified to ensure production efficiency. When the diameter fluctuation variance is greater than or equal to the preset value, it indicates that problems such as uneven cooling and insufficient traction and cooling coordination have been transformed into actual dimensional defects, which will lead to risks such as subsequent splicing gaps and stress cracking, and therefore it is judged as unqualified. At the same time, adjusting the traction rate affects the membrane material cooling and setting time, avoiding process fluctuations caused by blind adjustments.

[0046] Specifically, the reduction in the preset traction rate is positively correlated with the ratio of the diameter fluctuation variance to the preset fluctuation variance. This positive correlation can be linear or nonlinear, and the linear slope of a linear positive correlation is not specifically limited. For example, the reduction in the preset traction rate can be set to... The ratio of diameter fluctuation variance to preset fluctuation variance is set to... ,but α is the rate adjustment coefficient. With α=0.96, it can be understood that the larger the ratio of the diameter fluctuation variance to the preset fluctuation variance, the greater the reduction in the preset traction rate.

[0047] Specifically, the process of obtaining the diameter fluctuation variance of the composite tubular membrane includes: After the composite tubular membrane is cooled and solidified, the diameter of several composite tubular membranes is collected using a diameter measuring instrument at a preset sampling frequency of 10Hz within a second preset time period of 60s. The variance of all diameters is calculated, which is the diameter fluctuation variance of the composite tubular membrane.

[0048] Specifically, the adjustment strategies for determining when the preparation of the composite tubular membrane does not meet the preset standard based on the extreme wind speed ratio of the cooling air ring include: If the extreme wind speed ratio is less than the preset extreme wind speed ratio of 1.15, the preset processing temperature of the co-extrusion die is reduced according to the difference between the preset extreme wind speed ratio and the extreme wind speed ratio. If the extreme wind speed ratio is greater than or equal to the preset extreme wind speed ratio, the air volume of the outlet corresponding to the maximum wind speed of the cooling air ring is reduced according to the difference between the extreme wind speed ratio and the preset extreme wind speed ratio. The extreme wind speed ratio of the cooling air ring is the ratio of the maximum wind speed to the minimum wind speed at each air outlet of the cooling air ring. Miniature wind speed sensors are installed at each independent air outlet of the cooling air ring to form a wind speed monitoring array that is uniformly distributed along the circumference.

[0049] Specifically, the reduction in the preset processing temperature of the co-extrusion die is positively correlated with the difference between the preset extreme wind speed ratio and the extreme wind speed ratio. This positive correlation can be linear or nonlinear, and the linear slope of a linear positive correlation is not specifically limited. For example, the reduction in the preset processing temperature of the co-extrusion die can be set to... The difference between the preset wind speed extreme value ratio and the wind speed extreme value ratio is set to... ,but k is the temperature adjustment coefficient, set to k=0.94. It can be understood that the greater the difference between the preset wind speed extreme value ratio and the wind speed extreme value ratio, the greater the reduction in the preset processing temperature of the co-extrusion die.

[0050] Specifically, the decrease in airflow at the outlet corresponding to the maximum wind speed of the cooling air ring is positively correlated with the difference between the extreme wind speed ratio and the preset extreme wind speed ratio. This positive correlation can be linear or non-linear. The slope of the linear positive correlation is not specifically limited; for example, the decrease in airflow at the outlet corresponding to the maximum wind speed of the cooling air ring can be set to... The difference between the extreme wind speed ratio and the preset extreme wind speed ratio is set to... ,but , Set the air volume adjustment coefficient. It is understandable that the greater the difference between the extreme wind speed ratio and the preset extreme wind speed ratio, the greater the reduction in air volume at the outlet corresponding to the maximum wind speed of the cooling air ring.

[0051] In this embodiment, the preset extreme wind speed ratio is 1.15, but the above value is not limited to this. Those skilled in the art can adjust the above value according to actual needs.

[0052] Specifically, when the extreme wind speed ratio is less than the preset value, it indicates that the wind speed difference between each air outlet is small and the circumferential air distribution is uniform. However, the circumferential cooling uniformity indicator value is still not up to standard. The root cause is not the wind speed distribution problem, but the excessively high preset processing temperature of the co-extrusion die, which leads to a high initial temperature of the film bubble. Even if the wind speed is uniform, the large temperature difference between the film bubble surface and the cooling air will still cause an imbalance in the local heat dissipation rate. Therefore, reducing the preset processing temperature of the co-extrusion die can lower the initial temperature of the film bubble, reduce the temperature difference fluctuation during the cooling process, and optimize the cooling uniformity from the source of heat conduction. When the extreme wind speed ratio is greater than or equal to the preset value, it indicates that the circumferential wind speed difference has exceeded the reasonable range. The area corresponding to the air outlet with the maximum wind speed cools too quickly, while the area with the minimum wind speed cools too slowly. This is the direct root cause of uneven cooling. At this time, by reducing the air volume of the air outlet corresponding to the maximum wind speed, the circumferential wind speed difference can be reduced, the cooling rate of each area can be balanced, and the co-extrusion molding efficiency can be improved.

[0053] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A multilayer co-extrusion molding method for a composite membrane material for building applications, characterized in that, include: The polymer mixture of each layer is placed in an independent extruder and melted and plasticized at a preset maximum melting temperature difference. Then it is introduced into the co-extrusion die of a co-extrusion blown film machine and co-extruded synchronously at a preset processing temperature to obtain a composite tubular melt preform. Gas is injected into the interior of the composite tubular melt billet at a preset blowing pressure, and the composite tubular melt billet is pulled at a preset traction rate to obtain a composite tubular film bubble. Based on the outline pixel area of ​​the image of the composite tubular membrane bubble, the membrane bubble morphology stability characterization value is obtained, and the preparation of the composite tubular membrane bubble is determined according to the membrane bubble morphology characterization value to determine whether it meets the preset standard. The composite tubular membrane bubble that meets the preset standard is cooled and solidified through a cooling air ring to obtain a composite tubular membrane; Based on the circumferential temperature of the composite tubular membrane before and after cooling and solidification, the circumferential cooling uniformity characterization value is obtained. When it is determined that the preparation of the composite tubular membrane is at risk of not meeting the preset standard based on the circumferential cooling uniformity characterization value, the preparation of the composite tubular membrane is further determined based on the diameter fluctuation variance of the composite tubular membrane to determine whether the preparation of the composite tubular membrane meets the preset standard. When the preparation of the composite tubular membrane does not meet the preset standard based on the circumferential cooling uniformity characterization value, the adjustment strategy for the preparation of the composite tubular membrane does not meet the preset standard is determined based on the circumferential wind speed extreme ratio of the cooling wind ring. The adjustment strategy is to reduce the preset processing temperature or reduce the air volume of the outlet corresponding to the maximum wind speed of the cooling wind ring. The composite tubular membrane that meets the preset standards is flattened and rolled up to obtain a composite membrane material for building.

2. The multilayer co-extrusion molding method for architectural composite membrane materials according to claim 1, characterized in that, The polymer mixtures of each layer are respectively a mixture of linear low-density polyethylene, antioxidant and ultraviolet absorber for the outer layer; a mixture of linear low-density polyethylene, polyolefin elastomer, ethylene-butyl acrylate copolymer and reinforcing filler for the middle layer; and a mixture of linear low-density polyethylene and ethylene-butyl acrylate copolymer for the inner layer.

3. The multilayer co-extrusion molding method for architectural composite membrane materials according to claim 1, characterized in that, The process of determining whether the preparation of the composite tubular membrane vesicle meets the preset standard based on the membrane vesicle morphology characterization values ​​includes: The membrane vesicle morphology characterization values ​​are compared with the first preset membrane vesicle morphology characterization values ​​and the second preset membrane vesicle morphology characterization values, respectively. If the membrane morphology characterization value is less than the first preset membrane morphology characterization value, then the preparation of the composite tubular membrane vesicle is determined to meet the preset standard. If the membrane bubble morphology characterization value is greater than or equal to the first preset membrane bubble morphology characterization value and less than the second preset membrane bubble morphology characterization value, then it is determined that the preparation of the composite tubular membrane bubble does not meet the preset standard, and the preset inflation pressure is increased according to the difference between the membrane bubble morphology characterization value and the first preset membrane bubble morphology characterization value. If the membrane bubble morphology characterization value is greater than or equal to the second preset membrane bubble morphology characterization value, it is determined that the preparation of the composite tubular membrane bubble does not meet the preset standard, and the preset maximum melting temperature difference is reduced according to the difference between the membrane bubble morphology characterization value and the second preset membrane bubble morphology characterization value.

4. The multilayer co-extrusion molding method for architectural composite membrane materials according to claim 3, characterized in that, The process of obtaining the characterization values ​​for membrane vesicle morphology stability includes: Within a first preset time period, a number of orthographic images of the composite tubular membrane bubble are captured at a preset frequency. Extract the pixel area enclosed by the outline of the composite tubular membrane bubble in each image; Calculate the standard deviation of the area of ​​all pixels and denote it as the morphological stability characterization value of the bubble.

5. The multilayer co-extrusion molding method for architectural composite membrane materials according to claim 4, characterized in that, Several temperature difference adjustment methods are provided to reduce the preset maximum melting temperature difference, and each temperature difference adjustment method reduces the preset maximum melting temperature difference by a different amount.

6. The multilayer co-extrusion molding method for architectural composite membrane materials according to claim 5, characterized in that, The process of determining whether the preparation of the composite tubular membrane meets the preset standard based on the circumferential cooling uniformity characterization value of the composite tubular membrane includes: The circumferential cooling uniformity characterization value is compared with the first preset circumferential cooling uniformity characterization value and the second preset circumferential cooling uniformity characterization value, respectively. If the circumferential cooling uniformity characterization value is less than the first preset circumferential cooling uniformity characterization value, then the preparation of the composite tubular membrane is determined to meet the preset standard. If the circumferential cooling uniformity characterization value is greater than or equal to the first preset circumferential cooling uniformity characterization value and less than the second preset circumferential cooling uniformity characterization value, it is determined that the preparation of the composite tubular membrane has a risk of not meeting the preset standard, and the preparation of the composite tubular membrane is determined a second time based on the diameter fluctuation variance of the composite tubular membrane to determine whether the preparation of the composite tubular membrane meets the preset standard. If the circumferential cooling uniformity characterization value is greater than or equal to the second preset circumferential cooling uniformity characterization value, it is determined that the preparation of the composite tubular membrane does not meet the preset standard, and the adjustment strategy when the preparation of the composite tubular membrane does not meet the preset standard is determined according to the extreme ratio of the circumferential wind speed of the cooling wind ring.

7. The multilayer co-extrusion molding method for architectural composite membrane materials according to claim 6, characterized in that, The process of obtaining the circumferential cooling uniformity characterization value includes: Before cooling and solidification, the temperature of several circumferentially set monitoring points of the composite tubular membrane to be cooled is collected; After cooling and solidification, the temperature at the monitoring points is collected; Calculate the difference between the temperature before cooling and the temperature after cooling at each monitoring point, and record it as the cooling temperature difference at each monitoring point; The standard deviation of all cooling temperature differences is denoted as the circumferential cooling uniformity characterization value.

8. The multilayer co-extrusion molding method for architectural composite membrane materials according to claim 7, characterized in that, If the preparation of the composite tubular membrane does not meet the preset standard, the preset traction rate is reduced based on the ratio of the diameter fluctuation variance to the preset fluctuation variance, according to the comparison result of the diameter fluctuation variance being greater than or equal to the preset diameter fluctuation variance.

9. The multilayer co-extrusion molding method for architectural composite membrane materials according to claim 8, characterized in that, The process of obtaining the diameter fluctuation variance of the composite tubular membrane includes: After the composite tubular membrane is cooled and solidified, the diameters of several composite tubular membranes are collected at a preset sampling frequency within a second preset time period. The variance of all diameters is calculated, which is the diameter fluctuation variance of the composite tubular membrane.

10. The multilayer co-extrusion molding method for architectural composite membrane materials according to claim 9, characterized in that, Adjustment strategies for when the preparation of the composite tubular membrane does not meet the preset standards, based on the extreme ratio of the cooling air ring's wind speed, include: If the extreme wind speed ratio is less than the preset extreme wind speed ratio, the preset processing temperature of the co-extrusion die is reduced according to the difference between the preset extreme wind speed ratio and the extreme wind speed ratio. If the extreme wind speed ratio is greater than or equal to the preset extreme wind speed ratio, the air volume of the outlet corresponding to the maximum wind speed of the cooling air ring is reduced according to the difference between the extreme wind speed ratio and the preset extreme wind speed ratio. The extreme wind speed ratio of the cooling air ring is the ratio of the maximum wind speed to the minimum wind speed at each air outlet of the cooling air ring.

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