A tpu supercritical foaming material and a preparation process thereof

Abstract

The application relates to the technical field of high polymer material preparation, in particular to a TPU supercritical foaming material and a preparation process thereof, which comprises the following steps: preparing the TPU supercritical foaming material through the steps of dosing, blending granulation, extruding small embryos and supercritical physical foaming, controlling and adjusting the foaming temperature by analyzing the foaming temperature change in the supercritical physical foaming process; and cutting the TPU foaming plate material after the supercritical physical foaming through a cutting machine, and sticking cloth or adhesive film through a sticking machine to obtain a foaming finished product. The application aims to avoid the foaming temperature in the foaming kettle being too large or too small, and improve the TPU foaming effect in the supercritical physical foaming process.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of high polymer material preparation, and particularly relates to a TPU supercritical foaming material and a preparation process thereof. BACKGROUND

[0002] The TPU foaming material is a high polymer material, and is widely applied to shoe soles, pillows and boards due to good wear resistance, corrosion resistance and high resilience. In the existing preparation process of the TPU foaming material, a certain proportion of mixed gas of supercritical nitrogen and carbon dioxide is introduced, and a supercritical foaming technology is used for pure physical foaming, so that the foaming effect and the foaming efficiency in the foaming process are improved. In addition, the supercritical nitrogen and the carbon dioxide are friendly to the ecological environment, so that the supercritical foaming technology can avoid pollution to the ecological environment. Therefore, the supercritical foaming technology has important application value in the existing preparation process of the TPU foaming material.

[0003] In the supercritical physical foaming process, an inappropriate foaming temperature can have a serious adverse effect on foaming expansion, so that the foaming temperature in the foaming process needs to be controlled. In the prior art, a PID controller is usually used to control and adjust the foaming temperature, so that the foaming temperature is prevented from being too high or too low, and the foaming effect in the foaming process is ensured. However, due to the nonlinear random fluctuation of the temperature in the supercritical physical foaming process, the prior art does not fully consider the nonlinear random fluctuation to accurately control and adjust the foaming temperature, so that the phenomenon of thermal runaway in the supercritical physical foaming process is easily caused, the foaming effect in the foaming process cannot be ensured, and finally the use performance of the TPU foaming product is affected. SUMMARY

[0004] In order to solve the above technical problems, the application provides a TPU supercritical foaming material and a preparation process thereof to solve the existing problems.

[0005] The TPU supercritical foaming material and the preparation process thereof adopt the following technical scheme:

[0006] One embodiment of the application provides a preparation process of a TPU supercritical foaming material, and the process comprises the following steps:

[0007] (1) Dosing: 70-90 parts of TPU particles, 10-25 parts of ammonium polyphosphate, 1-5 parts of nano-hydroxide, 1-3 parts of a crosslinking aid, 0.1-3 parts of an anti-dripping aid and 0.5-3 parts of an anti-hydrolysis aid are weighed according to the weight fraction;

[0008] (2) Blending and granulation: all the dosages are granulated after being melt-blended by an extruder to obtain micro-modified particles;

[0009] (3) Extruding small embryo: after the micro-modified particles are molded by an extruder, a plate is obtained;

[0010] (4) Supercritical physical foaming: the plate is put into a supercritical foaming kettle, a mixed gas of carbon dioxide and nitrogen is introduced, and after heating and pressurizing, supercritical physical foaming is carried out for 2-3 hours, and after expansion, a TPU foamed plate is obtained;

[0011] Among them, the foaming temperature of several temperature measuring points in the kettle is collected during the supercritical physical foaming process;

[0012] The difference between the foaming temperature data of each temperature measuring point in any historical time period and the data after smoothing processing is used to construct a high-frequency subsequence;

[0013] In any historical time period, according to the difference distance of any temperature measuring point and the high-frequency subsequences of all temperature measuring points, and the chaotic degree of the high-frequency subsequence of any temperature measuring point, the high-frequency variation coefficient of any temperature measuring point is determined; and combined with the residual characteristics of the foaming temperature data of each temperature measuring point, the nonlinear evaluation parameter of the foaming temperature in any historical time period is determined;

[0014] The nonlinear evaluation parameters of all historical time periods before each collection time are respectively weighted and summed according to the collection time interval between the historical time period and the collection time, to obtain the random disturbance characteristic value of each collection time, and the difference between the random disturbance characteristic values of adjacent collection times is used to feedback adjust the actual foaming temperature; the PID controller is used to control and adjust the foaming temperature in the foaming kettle based on the feedback foaming temperature and the actual foaming temperature;

[0015] The TPU foamed plate after supercritical physical foaming is cut by a slicing machine, and cloth or adhesive film is attached by a laminating machine to obtain a foamed finished product.

[0016] Preferably, the crosslinking aid is one of dicumyl peroxide or di-(tert-butylperoxy isopropyl) benzene.

[0017] Preferably, the plasticizing section temperature of the extruder is set to 170-190°C, and the temperature of the metering section in the rear section is set to 150-170°C.

[0018] Preferably, the mixed gas is 10:90 ratio of carbon dioxide and nitrogen.

[0019] Preferably, the construction method of the high-frequency subsequence is:

[0020] The sequence after smoothing processing of the foaming temperature data of each temperature measuring point in any historical time period is recorded as a low-frequency subsequence;

[0021] A sequence obtained by subtracting corresponding elements between the sequence of foaming temperature data of each temperature measuring point in any historical time period and the low-frequency sub-sequence, is recorded as a high-frequency sub-sequence of each temperature measuring point in any historical time period.

[0022] Preferably, the method for determining the high-frequency variation coefficient of any temperature measuring point is:

[0023]

[0024] In the formula, is the high-frequency variation parameter of the i-th temperature measuring point, is the approximate entropy of the high-frequency sub-sequence of the i-th temperature measuring point, is the number of temperature measuring points in the supercritical foaming kettle, is the difference distance of the high-frequency sub-sequence between the i-th temperature measuring point and the j-th temperature measuring point.

[0025] Preferably, the method for determining the nonlinear evaluation parameter of the foaming temperature in any historical time period is:

[0026]

[0027] In the formula, is the nonlinear evaluation parameter of the foaming temperature in the k-th historical time period, is the residual feature of the i-th temperature measuring point in the k-th historical time period, is the high-frequency variation parameter of the i-th temperature measuring point in the k-th historical time period; wherein the method for obtaining the residual feature is: extracting a residual sequence of the foaming temperature data of the i-th temperature measuring point in the k-th historical time period; and normalizing the range difference of the product of the range difference and the standard deviation in the residual sequence, recorded as the residual feature of the i-th temperature measuring point in the k-th historical time period.

[0028] Preferably, the method for obtaining the random disturbance feature value of each collection time is:

[0029]

[0030] In the formula, is the random disturbance feature value of the t-th collection time, is the hyperbolic tangent function, is the number of elements in the nonlinear evaluation parameter sequence of the t-th collection time, is the bit sequence number of the element in the nonlinear evaluation parameter sequence of the t-th collection time, is the s-th element in the nonlinear evaluation parameter sequence of the t-th collection time; wherein the nonlinear evaluation parameter sequence of the t-th collection time is obtained by sorting all the nonlinear evaluation parameters of all the historical time periods before the t-th collection time in chronological order.

[0031] Preferably, the method for obtaining the feedback foaming temperature at the current acquisition time is:

[0032]

[0033] In the formula, is the feedback foaming temperature at the current acquisition time, is the actual foaming temperature at the current acquisition time, and the calculation method is the average of the foaming temperatures of all temperature measurement points at the current acquisition time, and are the preset minimum foaming temperature and the preset maximum foaming temperature in the TPU supercritical physical foaming process, respectively, and are the random disturbance characteristic values at the current acquisition time and the previous acquisition time, respectively, is the absolute difference value of the random disturbance characteristic values between the current acquisition time and the previous acquisition time.

[0034] The second embodiment of the present application provides a TPU supercritical foaming material prepared by the preparation process described above.

[0035] In the above scheme, the beneficial effects are:

[0036] (1) The present application combines the high-frequency characteristics and residual characteristics of the foaming temperature change to more accurately measure the nonlinear random fluctuations of the foaming temperature in the supercritical foaming kettle in the historical time period, which is beneficial to timely downward adjustment of the foaming temperature in the supercritical foaming kettle, thereby avoiding the phenomenon of foaming thermal runaway due to rapid temperature rise in the nonlinear random fluctuation process.

[0037] (2) The present application constructs a random characteristic sequence through the nonlinear random fluctuations of the foaming temperature, and sets different weights for the elements in the random characteristic sequence, thereby accurately and timely responding to the random disturbance characteristics of the foaming temperature at each acquisition time, which is beneficial to more accurate control and adjustment of the foaming temperature in the supercritical foaming kettle.

[0038] (3) The present application adjusts the foaming temperature in the TPU supercritical physical foaming process through the change of the random disturbance characteristic value, and effectively ensures that the feedback-adjusted foaming temperature is within a reasonable range, thereby avoiding excessive or insufficient foaming temperature, and improving the TPU foaming effect in the supercritical physical foaming process. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0040] Figure 1 A step flow chart of a preparation process of a TPU supercritical foaming material provided by an embodiment of the present application is shown in

[0041] Figure 2 A step flow chart of controlling and adjusting the foaming temperature in the supercritical physical foaming process provided by an embodiment of the present application is shown in DETAILED DESCRIPTION

[0042] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined purposes, the specific embodiments, structures, features and effects of the TPU supercritical foaming material and the preparation process thereof according to the present application are described in detail below in combination with the drawings and preferred embodiments. Different "one embodiment" or "another embodiment" in the following description do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0044] The specific scheme of the TPU supercritical foaming material and the preparation process thereof provided by the present application is described in detail below in combination with the drawings.

[0045] The preparation process of the TPU supercritical foaming material provided by an embodiment of the present application is shown in the preparation flow chart Figure 1 , and the specific preparation process is as follows:

[0046] (1) Dosing: 70-90 parts by weight of TPU particles, 10-25 parts by weight of ammonium polyphosphate, 1-5 parts by weight of nano-hydroxide, 1-3 parts by weight of crosslinking aid, 0.1-3 parts by weight of anti-dripping aid, and 0.5-3 parts by weight of anti-hydrolysis aid are weighed, wherein the crosslinking aid can be dicumyl peroxide (DCP) or bis-(tert-butyl peroxyisopropyl) benzene (BIBP), the anti-dripping aid is polytetrafluoroethylene, and the anti-hydrolysis aid is a carbodiimide compound.

[0047] In this embodiment, the TPU particles are 80 parts, 10 parts of ammonium polyphosphate, 4 parts of nano-hydroxide, 2 parts of crosslinking aid, 2 parts of anti-dripping aid, and 2 parts of anti-hydrolysis aid. The crosslinking aid is dicumyl peroxide (DCP).

[0048] (2) Blending and granulation: melt blend all ingredients through an extruder, and granulate the melt blended ingredients through the extruder to obtain micro modified particles, wherein the plasticizing section temperature of the extruder is set to 170-190°C, and the temperature of the metering section of the rear section is set to 150-170°C.

[0049] (3) Extruding small embryos: forming the micro modified particles through an extruder to obtain a plate, or injecting the micro modified particles through an injection molding machine to obtain a midsole small embryo.

[0050] (4) Supercritical physical foaming: placing the plate or midsole small embryo into a supercritical foaming kettle, and introducing a mixed gas of carbon dioxide and nitrogen in a ratio of 10:90, and then performing supercritical physical foaming for 2-3 hours after heating and pressurizing, and obtaining a TPU foamed plate after expansion. In this embodiment, the supercritical physical foaming time is 2.5h.

[0051] In order to improve the foaming effect and efficiency in the foaming process, the foaming temperature in the supercritical physical foaming process needs to be controlled and adjusted. In this embodiment, the step flow chart of controlling and adjusting the foaming temperature in the supercritical physical foaming process is shown in the attached Figure 2 , which is specifically as follows:

[0052] Step 1: collecting the foaming temperature of several temperature measuring points in the supercritical physical foaming process.

[0053] In order to more accurately control and adjust the foaming temperature in the supercritical physical foaming process, through the several evenly arranged temperature measuring points in the supercritical foaming kettle, this embodiment sets 9 temperature measuring points, and uses thermocouples as temperature measuring elements to collect real-time data of the foaming temperature of each temperature measuring point in the supercritical physical foaming process. In this embodiment, the collection frequency of the foaming temperature is 10Hz. In other embodiments, the collection frequency can be adaptively set according to the speed of the change of the foaming temperature, such as a faster change of the foaming temperature, which is suitable for a larger sampling frequency, so as to reflect the detailed information of the change of the foaming temperature; a slower change of the foaming temperature, which is suitable for a smaller sampling frequency, to reduce the repeated redundancy of the foaming temperature.

[0054] Further, in order to accurately analyze the nonlinear random fluctuations of the temperature, the foaming temperature of each temperature measuring point at each historical collection time before each collection time is arranged in time sequence respectively, and the arranged sequence is normalized by a range normalization function respectively, and the normalized sequence is recorded as the foaming temperature sequence of each temperature measuring point at each collection time.

[0055] Step 2: Obtain the nonlinear evaluation parameters of the foaming temperature by analyzing the high-frequency characteristics and residual characteristics of the foaming temperature change.

[0056] Due to the large difference between the internal and external temperatures of the supercritical foaming kettle, the foaming temperature of the supercritical physical foaming is easily affected by external temperature interference, which causes nonlinear random fluctuations in the foaming temperature change over time, and the nonlinear random fluctuations of the foaming temperature easily cause rapid temperature rise or excessively high temperature, thereby further exacerbating the risk of thermal runaway. Therefore, in order to avoid the phenomenon of thermal runaway in the supercritical physical foaming process, it is necessary to fully consider the nonlinear random fluctuations for accurately controlling and adjusting the foaming temperature.

[0057] In order to analyze the nonlinear random fluctuations of the foaming temperature at each temperature measuring point in different historical time periods, the foaming temperature sequence of each temperature measuring point at each collection time is divided into sequences every minute, obtaining the foaming temperature subsequence of each temperature measuring point in each historical time period, so that the time length of each foaming temperature subsequence after division is 1 min. If the time length of a certain foaming temperature subsequence is less than 1 min, the missing values in the foaming temperature subsequence are completed by mean filling. Mean filling is a known technology, and the specific process will not be repeated.

[0058] Further, the foaming temperature subsequence of each temperature measuring point in each historical time period is taken as the input of the moving average method, the foaming temperature subsequence is smoothed by the moving average method, the smoothed foaming temperature subsequence is recorded as the low-frequency subsequence, and the sequence obtained by subtracting the corresponding elements between the foaming temperature subsequence and the low-frequency subsequence is recorded as the high-frequency subsequence of each temperature measuring point in each historical time period, reflecting the high-frequency characteristics of the temperature change at different temperature measuring points. The moving average method is a known technology, and the specific process will not be repeated.

[0059] Normally, the similarity degree between the high-frequency characteristics of temperature changes at different temperature measuring points is high, which indicates that the foaming temperature at different positions in the supercritical physical foaming process is relatively uniform, so that the bubble structure foamed at different positions is relatively stable. However, the higher the difference between the high-frequency characteristics of temperature changes at different temperature measuring points, and the higher the chaotic degree of high-frequency changes in the temperature at the temperature measuring points, the more it can reflect the nonlinear random fluctuations of the foaming temperature under the influence of external temperature interference, which is not conducive to maintaining the stability of the foaming environment at this time.

[0060] Based on the above analysis, for each historical time period, the high-frequency change parameter of each temperature measuring point is calculated:

[0061]

[0062] In the formula, is the high-frequency change parameter of the ith temperature measuring point, is the approximate entropy of the high-frequency subsequence of the ith temperature measuring point, is the number of temperature measuring points in the supercritical foaming kettle, is the difference distance between the high-frequency subsequence of the ith temperature measuring point and the jth temperature measuring point. The difference distance can be measured by DTW dynamic programming distance, Euclidean distance or Mahalanobis distance. In this embodiment, the DTW dynamic programming distance is used to measure the difference distance.

[0063] The high-frequency change parameter reflects the possibility of nonlinear random fluctuations of the collected temperature data at each temperature measuring point in the historical time period under the influence of external temperature interference. The greater the high-frequency change parameter, the more it can reflect the nonlinear random fluctuations of the foaming temperature under the influence of external temperature interference, which can easily exacerbate the risk of foaming thermal runaway and affect the TPU foaming effect in the supercritical physical foaming process.

[0064] Further, in order to more accurately measure the nonlinear random fluctuations of the foaming temperature in each historical time period, the foaming temperature subsequence of each temperature measuring point in each historical time period is taken as an STL time series decomposition algorithm (Seasonal-Trend decomposition using LOESS), and the temperature residual sequence of each temperature measuring point in each historical time period is extracted by the STL time series decomposition algorithm. The STL time series decomposition algorithm is a known technology, and the specific process will not be described again.

[0065] The temperature residual sequence reflects the random fluctuation component of the temperature affected by external temperature interference. If the range of residual fluctuation in the temperature residual sequence is larger and the dispersion degree of residual fluctuation is higher, the nonlinear random fluctuation of the foaming temperature in the supercritical foaming process at this time can be better reflected. Therefore, the range normalization result of the product of the range and the standard deviation of the temperature residual sequence of each temperature measurement point in each historical time period is recorded as the residual feature of each temperature measurement point in each historical time period. The larger the residual feature is, the more prominent the nonlinear random fluctuation of the foaming temperature change is. The range normalization result is a known technology and will not be described again.

[0066] Therefore, based on the above analysis, the nonlinear evaluation parameter of the foaming temperature in each historical time period is calculated:

[0067]

[0068] In the formula, is the nonlinear evaluation parameter of the foaming temperature in the kth historical time period, is the residual feature of the ith temperature measurement point in the kth historical time period, is the high-frequency variation parameter of the ith temperature measurement point in the kth historical time period.

[0069] The nonlinear evaluation parameter reflects the nonlinear random fluctuation of the foaming temperature in the supercritical foaming kettle in the historical time period. By using the residual features and high-frequency variation parameters of all temperature measurement points in the supercritical foaming kettle, the nonlinear random fluctuation of the foaming temperature is more accurately measured by using the weighted summation method. The greater the nonlinear random fluctuation of the foaming temperature is, the worse the stability of the foaming temperature in the historical time period is, and the phenomenon of foaming thermal runaway caused by rapid temperature rise in the nonlinear random fluctuation process needs to be avoided in time.

[0070] Step 3: The random disturbance characteristic value is obtained by weighting the nonlinear evaluation parameter to feedback adjust the actual foaming temperature. The PID controller is used to control and adjust the foaming temperature based on the feedback foaming temperature and the actual foaming temperature, and the supercritical physical foaming of the TPU material is completed.

[0071] Further, the nonlinear evaluation parameters corresponding to all historical time periods before each collection time are arranged in time sequence to obtain the nonlinear evaluation parameter sequence of each collection time, which reflects the nonlinear random fluctuation change of the foaming temperature in different historical time periods before each collection time.

[0072] In order to accurately respond to the random disturbance characteristics of the foaming temperature at each collection time, the nonlinear evaluation parameters corresponding to the time periods with small time intervals between each collection time should be given greater weights, and the nonlinear evaluation parameters corresponding to the time periods with large time intervals should be given smaller weights, so that the recent data of each collection time is emphasized when the random disturbance characteristics of the foaming temperature are measured, and the random disturbance characteristics of the foaming temperature at each collection time are more accurately measured.

[0073] Based on the above analysis, the random disturbance characteristic value of each collection time is calculated:

[0074]

[0075] In the formula, is the random disturbance characteristic value of the tth collection time, is the hyperbolic tangent function, is the number of elements in the nonlinear evaluation parameter sequence of the tth collection time, is the bit sequence number of the element in the nonlinear evaluation parameter sequence of the tth collection time, is the s th element in the nonlinear evaluation parameter sequence of the tth collection time.

[0076] The random disturbance characteristic value reflects the random disturbance characteristics of the foaming temperature at each collection time. By setting different weights for the elements in the nonlinear evaluation parameter sequence, the random disturbance characteristics of the foaming temperature at each collection time are accurately measured. The greater the random disturbance characteristic value, the greater the random disturbance change of the foaming temperature in the supercritical foaming kettle, and the more appropriate it is to reduce the foaming temperature in the supercritical foaming kettle, thereby avoiding the phenomenon of foaming thermal runaway caused by rapid temperature rise in the nonlinear random fluctuation process.

[0077] In order to timely avoid the phenomenon of foaming thermal runaway caused by rapid temperature rise in the nonlinear random fluctuation process, if the random disturbance characteristics of the foaming temperature show an upward trend during the preparation of the TPU foaming material, it is more likely to cause the phenomenon of foaming thermal runaway caused by rapid temperature rise, so the foaming temperature needs to be appropriately reduced. Conversely, if the random disturbance characteristic value shows a downward trend, the possibility of foaming thermal runaway is smaller, and in order to avoid the problem of insufficient foaming caused by the reduction of the foaming temperature, the foaming temperature needs to be appropriately increased.

[0078] Based on the above analysis, the feedback foaming temperature of the current collection time is calculated:

[0079]

[0080] In the formula, is the feedback foaming temperature of the current collection time, The actual foaming temperature at the current collection time is the average of the foaming temperatures of all temperature measurement points at the current collection time, and respectively, the minimum foaming temperature and the maximum foaming temperature preset in the TPU supercritical physical foaming process, 100°C and 150°C respectively, and respectively, the random disturbance eigenvalues of the current collection time and the previous collection time, is the absolute difference between the random disturbance eigenvalues of the current collection time and the previous collection time.

[0081] The foaming temperature in the TPU supercritical physical foaming process is feedback adjusted through the change of the random disturbance eigenvalues, while ensuring that the feedback-adjusted foaming temperature is within a reasonable range, thereby avoiding excessively high or low foaming temperatures.

[0082] Therefore, the feedback foaming temperature and the actual foaming temperature at the current collection time are input into the PID controller, the PID controller generates a control signal for the foaming temperature through the temperature error between the feedback foaming temperature and the actual foaming temperature, and the PID controller transmits the control signal to the heater in the supercritical foaming kettle. The foaming temperature in the supercritical physical foaming process is controlled and adjusted through the heater in the supercritical foaming kettle, thereby achieving control and adjustment of the foaming temperature in the supercritical physical foaming process.

[0083] Step 4: The TPU foamed sheet after supercritical physical foaming is cut by a cutting machine, and is laminated with cloth or film by a laminating machine to obtain a foamed finished product.

[0084] The supercritical physical foaming is completed by the above method, and the TPU foamed sheet is obtained after expansion. The remaining preparation steps of the TPU supercritical foaming material preparation process are as follows:

[0085] (5) Material processing: the expanded TPU foamed sheet is surface finished by a sander to remove irregular parts on the surface of the TPU foamed sheet, and the surface finished TPU foamed sheet is placed in a cutting machine to cut the TPU foamed sheet by the cutting machine to obtain foamed sheets of various thicknesses.

[0086] (6) Finished product: the foamed sheets of various thicknesses are placed in a laminating machine, and the foamed sheets of various thicknesses are laminated with cloth or film by the laminating machine to obtain a TPU foamed finished product.

[0087] Thus, the invention of a TPU supercritical foaming material and its preparation process is completed.

[0088] Example 2

[0089] (1) Dosing: In this embodiment, the TPU particles are 70 parts, 15 parts of ammonium polyphosphate, 1 part of nano-hydroxide, 1 part of crosslinking aid, 0.1 part of anti-dripping aid, and 0.5 part of anti-hydrolysis aid. Among them, the crosslinking aid is bis-(tert-butyl peroxy isopropyl) benzene (BIBP).

[0090] (2) Blending and granulation.

[0091] (3) Extruding small embryos.

[0092] (4) Supercritical physical foaming: In this embodiment, the supercritical physical foaming time is 2h.

[0093] (5) Material processing: In this embodiment, the expanded TPU foaming plate is molded and shaped by a setting machine, and the surface of the TPU foaming plate after molding and shaping is finished by using a sander to remove the irregular parts on the surface of the TPU foaming plate, and a molded midsole is obtained.

[0094] (6) Finished product: In this embodiment, the molded midsole and the rubber outsole are attached by an attaching machine to obtain a sole, wherein the rubber outsole is the bottom material of the footwear product, mainly made of natural rubber or synthetic rubber.

[0095] In this embodiment, the steps or methods not specifically expanded are the same as the implementation method of Example 1.

[0096] Example 3

[0097] (1) Dosing: In this embodiment, the TPU particles are 90 parts, 25 parts of ammonium polyphosphate, 5 parts of nano-hydroxide, 3 parts of crosslinking aid, 3 parts of anti-dripping aid, and 3 parts of anti-hydrolysis aid. Among them, the crosslinking aid is dicumyl peroxide (DCP).

[0098] (2) Blending and granulation.

[0099] (3) Extruding small embryos.

[0100] (4) Supercritical physical foaming: In this embodiment, the supercritical physical foaming time is 3h.

[0101] (5) Material processing: In this embodiment, the expanded TPU foaming plate is molded and shaped by a setting machine, and the surface of the TPU foaming plate after molding and shaping is finished by using a sander to remove the irregular parts on the surface of the TPU foaming plate, and a molded midsole is obtained.

[0102] (6) Finished product: In this embodiment, the molded midsole and the rubber outsole are attached by an attaching machine to obtain a sole, wherein the rubber outsole is the bottom material of the footwear product, mainly made of natural rubber or synthetic rubber.

[0103] In the present embodiment, the steps or methods not specifically expanded are the same as the implementation method of embodiment 1.

[0104] The TPU foamed soles prepared from embodiments 1-3 and comparative examples 1-2 of the present application were subjected to performance detection, wherein embodiments 1-3 were subjected to supercritical physical foaming by using the control and adjustment method of foaming temperature in the present application, comparative example 1 was subjected to supercritical physical foaming by using the preset fixed foaming temperature 120℃ in the prior art, and comparative example 2 was subjected to supercritical physical foaming by using the preset fixed foaming temperature 135℃ in the prior art, and the detection results are shown in Table 1 below:

[0105] Table 1

[0106]

[0107] Each of the embodiments in the present application is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment mainly explains the difference from other embodiments.

[0108] It should be noted that unless otherwise specified and limited, terms such as "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that the circuit structure, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such article or device. Without more limitation, the element limited by the phrase "including a" does not exclude the presence of another identical element in the article or device including the element. In addition, the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0109] Other embodiments of the present application will be apparent to those skilled in the art upon consideration of the specification and practice of the application disclosed herein. The present application is intended to cover any variations, uses or adaptive changes of the present application following the general principles of the present application and including common knowledge or conventional techniques in the art which are not invented by the present application.

[0110] It should be understood that the present application is not limited to the precise construction that has been described and shown in the accompanying drawings, and that various modifications and changes can be made without departing from the scope thereof.

Claims

1. A process for the preparation of a TPU supercritical foamed material, characterized in that, The process comprises the following steps: (1) batching: according to the weight fraction, 70-90 parts of TPU particles, 10-25 parts of ammonium polyphosphate, 1-5 parts of nano-hydroxide, 1-3 parts of crosslinking auxiliary agent, 0.1-3 parts of anti-dripping auxiliary agent, 0.5-3 parts of anti-hydrolysis auxiliary agent are weighed; (2) blending and granulation: after melting blending of all ingredients through the extruder, granulation is carried out to obtain micro-modified particles; (3) extruding small embryos: after molding of the micro-modified particles through the extruder, a plate is obtained; (4) supercritical physical foaming: the plate is placed in a supercritical foaming kettle, a mixed gas of carbon dioxide and nitrogen is introduced, and after heating and pressurizing, supercritical physical foaming is carried out for 2-3 hours, and after expansion, a TPU foamed plate is obtained; During the supercritical physical foaming process, the foaming temperature of several temperature measuring points in the kettle is collected; Using the difference between the foaming temperature data of each temperature measuring point in any historical time period and the data after smoothing processing, the high-frequency sub-sequence is constructed; In any historical time period, according to the difference distance of any temperature measuring point and the high-frequency sub-sequence of all temperature measuring points and the chaotic degree of the high-frequency sub-sequence of any temperature measuring point, the high-frequency variation coefficient of any temperature measuring point is determined; and combined with the residual characteristics of the foaming temperature data of each temperature measuring point, the nonlinear evaluation parameter of the foaming temperature in any historical time period is determined; The nonlinear evaluation parameters of all historical time periods before each collection time are respectively weighted and summed according to the collection time interval between the historical time period where the nonlinear evaluation parameter is located and the collection time, to obtain the random disturbance characteristic value of each collection time, and the actual foaming temperature is feedback adjusted by using the difference of the random disturbance characteristic values of adjacent collection times; the foaming temperature in the foaming kettle is controlled and adjusted by using the PID controller based on the feedback foaming temperature and the actual foaming temperature; The TPU foamed plate after supercritical physical foaming is cut by a cutting machine, and cloth or adhesive film is attached by a laminating machine to obtain a foamed finished product.

2. The process for preparing a TPU supercritical foamed material according to claim 1, wherein The crosslinking auxiliary agent is one of dicumyl peroxide or di-(tert-butyl peroxy isopropyl) benzene.

3. The process for preparing a TPU supercritical foamed material according to claim 1, wherein The plasticizing section temperature of the extruder is set to 170-190℃, and the temperature of the rear section metering section is set to 150-170℃.

4. The process for preparing a TPU supercritical foamed material according to claim 1, wherein The mixed gas is 10:90 ratio of carbon dioxide and nitrogen.

5. The process for preparing a TPU supercritical foamed material according to claim 1, wherein The construction method of the high-frequency sub-sequence is: The sequence of the foaming temperature data of each temperature measuring point in any historical time period after smoothing processing is recorded as a low-frequency sub-sequence; The sequence obtained by subtracting the corresponding elements between the sequence composed of the foaming temperature data of each temperature measuring point in any historical time period and the low-frequency sub-sequence is recorded as the high-frequency sub-sequence of each temperature measuring point in any historical time period.

6. The process for preparing a TPU supercritical foamed material according to claim 5, wherein The determination method of the high-frequency variation coefficient of any temperature measuring point is: In the formula, is the high-frequency variation parameter of the i-th temperature measuring point, is the approximate entropy of the high-frequency sub-sequence of the i-th temperature measuring point, is the number of temperature measuring points in the supercritical foaming kettle, is the difference distance of the high-frequency sub-sequence between the i-th temperature measuring point and the j-th temperature measuring point.

7. The process for preparing a TPU supercritical foamed material according to claim 6, wherein The determination method of the nonlinear evaluation parameter of the foaming temperature in any historical time period is: In the formula, is a nonlinear evaluation parameter of the foaming temperature in the kth historical time period, is a residual feature of the ith temperature measurement point in the kth historical time period, is a high-frequency variation parameter of the ith temperature measurement point in the kth historical time period; wherein the method for obtaining the residual feature is: extracting a residual sequence of the foaming temperature data of the ith temperature measurement point in the kth historical time period; and normalizing the difference of the product of the range and the standard deviation in the residual sequence, denoted as the residual feature of the ith temperature measurement point in the kth historical time period.

8. The process for preparing a TPU supercritical foamed material according to claim 7, wherein The obtaining method of the random disturbance characteristic value of each collection time is: In the formula, is the random disturbance eigenvalue of the tth acquisition moment, is the hyperbolic tangent function, is the number of elements in the nonlinear evaluation parameter sequence of the tth acquisition moment, is the bit sequence number of the element in the nonlinear evaluation parameter sequence of the tth acquisition moment, is the s th element in the nonlinear evaluation parameter sequence of the tth acquisition moment; wherein the nonlinear evaluation parameter sequence of the tth acquisition moment is obtained by sorting the nonlinear evaluation parameters of all historical time periods before the tth acquisition moment in time order.

9. The process for preparing a TPU supercritical foamed material according to claim 1, wherein, The obtaining method of the feedback foaming temperature of the current collection time is: In the formula, is the feedback foaming temperature at the current collection time, is the actual foaming temperature at the current collection time, and the calculation method is the average of the foaming temperatures of all temperature measurement points at the current collection time, and are respectively the minimum foaming temperature and the maximum foaming temperature preset in the supercritical physical foaming process of the TPU, and are respectively the random disturbance eigenvalues at the current collection time and the previous collection time, is the absolute difference of the random disturbance eigenvalues between the current collection time and the previous collection time.

10. A TPU supercritical foamed material, characterized in that, Prepared by the preparation process of any one of claims 1-9.

Images