Ethylene-tetrafluoroethylene copolymer modified heat shrinkable sleeve and preparation method thereof

Abstract

The invention relates to the technical field of heat shrinkable sleeve preparation, and in particular to an ethylene-tetrafluoroethylene copolymer modified heat shrinkable sleeve and a preparation method thereof. The invention comprises the following steps: mixing a first master batch with an ethylene-tetrafluoroethylene copolymer to obtain a second master batch, and then processing the heat shrinkable sleeve to be expanded; performing expansion molding on the heat shrinkable sleeve to be expanded with a plurality of point groups marked on the surface; calculating a material extension and expansion characterization coefficient according to data of adjacent point groups and adjacent marking points in a surface image of the heat shrinkable sleeve after expansion molding to adjust the expansion molding speed; calculating the line segment overlap of a plurality of material expansion marking lines through material expansion marking lines corresponding to each point group to determine whether the adjustment of the expansion molding speed is effective; and finally rolling up the heat shrinkable sleeve after expansion molding, thereby realizing the digitized and intuitive characterization of the expansion degree of the heat shrinkable sleeve, adaptively adjusting the preparation parameters and accurately verifying the adjustment effect, and improving the preparation stability of the heat shrinkable sleeve.

Description

Technical Field

[0001] The invention relates to the technical field of heat shrinkable tube preparation, in particular to an ethylene-tetrafluoroethylene copolymer modified heat shrinkable tube and a preparation method thereof. Background Art

[0002] Heat shrink tubing and molded products are a common way to protect cables. As the demand for heat shrink tubing and molded products in extreme working conditions in various fields continues to emerge, current heat shrink products cannot protect electronic components in instantaneous and long-term high temperature environments because the heat shrink resin skeleton is easily softened and thermally torn in instantaneous and long-term high temperature environments. Generally, high-temperature resistant heat shrink tubing uses perfluoroether rubber with a higher temperature resistance grade. Although it can meet the temperature resistance requirements, the raw material cost of perfluoroether rubber is extremely high, which is not suitable for conventional factory experiments and production in the heat shrink industry. The preparation process of low-cost and high-performance heat shrink tubing and heat shrink products is very critical.

[0003] For example, Chinese patent application: CN109337188A, the invention discloses a radiation cross-linked high temperature resistant heat shrink tubing, which comprises the following materials in weight: 100 parts of ethylene-tetrafluoroethylene copolymer, the molar ratio of CF group to CH group of the cross-linked ethylene-tetrafluoroethylene copolymer is 1: (2-9); 0.3 to 3 parts of a cross-linking agent; 0.3 to 8 parts of a heat resistant agent; 0.3 to 3 parts of an antioxidant; 1 to 10 parts of antimony trioxide; 0.1 to 3 parts of pentaerythritol stearate; 0.1 to 2 parts of N′N-ethylene bisstearamide; 0.1 to 3 parts of white oil. The radiation cross-linked high temperature resistant heat shrink tubing of the invention can be processed at a temperature of 200°C to 238°C.

[0004] The prior art also has the following problems:

[0005] The prior art does not take into account the uneven distribution of the added ethylene-tetrafluoroethylene copolymer in the heat shrinkable tube. Since the strong tensile strength of the heat shrinkable tube affects the expansion molding of the heat shrinkable tube, the prior art cannot digitize and intuitively characterize the expansion degree of the heat shrinkable tube in the expansion molding stage, and cannot adaptively adjust the preparation parameters and accurately verify the adjustment effect, which affects the preparation stability of the heat shrinkable tube. Summary of the invention

[0006] To this end, the present invention provides an ethylene-tetrafluoroethylene copolymer modified heat shrinkable tube and a preparation method thereof, so as to overcome the problems in the prior art that the expansion degree of the heat shrinkable tube in the expansion molding stage cannot be digitally and intuitively represented, and the preparation parameters cannot be adaptively adjusted and the adjustment effect cannot be accurately verified.

[0007] To achieve the above object, the present invention provides a method for preparing an ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing, comprising:

[0008] Step S1, mixing fluororubber and a modifier to obtain a first masterbatch, and mixing the first masterbatch with ethylene-tetrafluoroethylene copolymer to obtain a second masterbatch;

[0009] Step S2, heating the second masterbatch to a preset temperature, extruding and irradiating and cross-linking to obtain a heat shrinkable tube to be expanded, marking a plurality of point groups at predetermined length intervals along the length direction on the surface of the heat shrinkable tube to be expanded, wherein the point group includes a plurality of marking points arranged at predetermined width intervals along the width direction;

[0010] Step S3, expanding and molding the heat shrinkable sleeve to be expanded, collecting a surface image of the heat shrinkable sleeve after expansion and molding, and calculating a material extension and expansion characterization coefficient based on the fluctuation of the length interval between adjacent point groups and the fluctuation of the width interval between adjacent marking points in the surface image, so as to determine whether the expansion uniformity of the heat shrinkable sleeve meets the preset standard;

[0011] Step S4, adjusting the expansion forming speed of the heat shrinkable sleeve to be expanded based on the material ductility expansion characterization coefficient;

[0012] Step S5, drawing material expansion marking lines based on a number of marking points of each point group, and calculating line segment coincidence based on the material expansion marking lines corresponding to the several point groups to determine whether adjusting the expansion forming speed is effective;

[0013] Step S6, rolling up the heat shrinkable tube that has been expanded and formed.

[0014] Furthermore, in step S3, the fluctuation of the length interval between adjacent point groups in the surface image is determined based on formula (1):

[0015]

[0016] In formula (1), Ds is the standard deviation of the length interval between adjacent point groups in the surface image, Ds i is the length interval between the i-th adjacent point groups, Ds av is the average length interval between adjacent point groups in the surface image, i=1,2,3…n, n is the number of length intervals between adjacent point groups in the surface image.

[0017] Furthermore, in step S3, the fluctuation of the width interval between adjacent marking points is determined based on formula (2):

[0018]

[0019] In formula (2), Dc is the standard deviation of the width interval between adjacent marking points, Dc jis the width interval between the jth adjacent marking points, Dc av is the average value of the width intervals between adjacent marking points, j=1,2,3…m, and m is the number of width intervals between adjacent marking points.

[0020] Furthermore, in step S3, the material extension coefficient is determined based on formula (3):

[0021]

[0022] In formula (3), E is the material extension coefficient, Ds is the length interval standard deviation between adjacent point groups in the surface image, Ds0 is a preset length interval reference value, Dc is the width interval standard deviation between adjacent marking points, Dc0 is a preset width interval reference value, α is the length interval weight coefficient, and β is the width interval weight coefficient.

[0023] Furthermore, in step S3, the process of determining whether the expansion uniformity of the heat shrinkable tube meets the preset standard is as follows:

[0024] The material extension and expansion characterization coefficient is compared with a preset material extension and expansion characterization coefficient threshold value,

[0025] If the material extension and expansion characterization coefficient is greater than the material extension and expansion characterization coefficient threshold, it is determined that the expansion uniformity of the heat shrinkable tube does not meet the preset standard.

[0026] Furthermore, in the step S4, the expansion molding speed of the heat shrinkable tube to be expanded is negatively correlated with the material extension and expansion characterization coefficient.

[0027] Furthermore, in step S5, the process of drawing the material expansion marking line is as follows:

[0028] The marking points in the point group are sequentially connected into line segments along the width direction, and the line segments are determined as material expansion marking lines corresponding to the point group.

[0029] Furthermore, in step S5, the process of determining whether the adjustment of the expansion molding speed is effective is as follows:

[0030] The line segment overlap is compared with a preset line segment overlap threshold,

[0031] If the line segment overlap is greater than the line segment overlap threshold, it is determined that the adjustment of the expansion forming speed is effective;

[0032] If the line segment overlap is less than or equal to the line segment overlap threshold, it is determined that the adjustment of the expansion forming speed is invalid, and an alarm is issued.

[0033] Furthermore, the present invention also provides an ethylene-tetrafluoroethylene copolymer modified heat shrinkable sleeve, comprising:

[0034] Fluororubber;

[0035] Ethylene-tetrafluoroethylene copolymer;

[0036] Modifier.

[0037] Furthermore, the modifier includes barium sulfate, light magnesium oxide, palm wax lubricant, cross-linking aid TAIC and thermal cracking carbon black powder.

[0038] Compared with the prior art, the beneficial effect of the present invention lies in that the present invention obtains a first masterbatch by mixing fluororubber and a modifier and obtains a second masterbatch by mixing the first masterbatch with an ethylene-tetrafluoroethylene copolymer, obtains a heat shrinkable sleeve to be expanded by heating the second masterbatch to a preset temperature, extruding and irradiating and cross-linking, marks a plurality of point groups on the surface of the heat shrinkable sleeve to be expanded, expands and forms the heat shrinkable sleeve to be expanded, calculates a material extension and expansion characterization coefficient according to data of adjacent point groups and adjacent marking points in a surface image of the heat shrinkable sleeve that has been expanded and formed, so as to adjust the expansion and forming speed of the heat shrinkable sleeve to be expanded, calculates the line segment overlap of a plurality of material expansion marking lines through material expansion marking lines corresponding to each point group, so as to determine whether the adjustment of the expansion and forming speed is effective, and finally rolls up the heat shrinkable sleeve that has been expanded and formed, thereby realizing a digital and intuitive characterization of the expansion degree of the heat shrinkable sleeve in the expansion and forming stage, adaptively adjusting the preparation parameters and accurately verifying the adjustment effect, and improving the preparation stability of the heat shrinkable sleeve.

[0039] In particular, the present invention marks a plurality of point groups at predetermined length intervals along the length direction on the surface of the heat shrinkable tube to be expanded, and each point group includes a plurality of marking points arranged at predetermined width intervals along the width direction. In the actual expansion and molding process of the heat shrinkable tube, the heat shrinkable tube subjected to extrusion force or tensile force will undergo material extension and expansion along the length direction and the width direction. The present invention facilitates the digitization of the expansion degree of the heat shrinkable tube in the expansion and molding stage by setting point groups at predetermined length intervals and marking points at predetermined width intervals, thereby improving the scientificity and accuracy of the expansion degree detection.

[0040] In particular, the present invention determines whether the expansion uniformity of the heat shrinkable tube meets the preset standard by calculating the material extension and expansion characterization coefficient. In the actual expansion and molding process of the heat shrinkable tube, the length interval fluctuation of adjacent point groups on the surface of the heat shrinkable tube where the material undergoes uniform extension and expansion is very small. The larger the fluctuation, the more uneven the extension and expansion of the heat shrinkable tube in the length direction of the material occurs. Similarly, in the width direction of the heat shrinkable tube, the width interval fluctuation of adjacent marking points on the surface of the heat shrinkable tube where the material undergoes uniform extension and expansion is also very small. The larger the fluctuation, the more uneven the extension and expansion of the heat shrinkable tube in the width direction of the material occurs. The present invention combines the two to calculate the material extension and expansion characterization coefficient, thereby avoiding the bias of the calculation result. The larger the calculation result, the more uneven the extension and expansion of the heat shrinkable tube is, thereby realizing the digitized and intuitive characterization of the expansion degree of the heat shrinkable tube in the expansion and molding stage.

[0041] In particular, the present invention improves the uniformity of material expansion and ductility of the heat shrinkable sleeve by adjusting the expansion and forming speed of the heat shrinkable sleeve to be expanded. In the actual heating and expansion process of the heat shrinkable sleeve, the ethylene-tetrafluoroethylene copolymer added to the heat shrinkable sleeve causes the heat shrinkable sleeve to have strong tensile properties. Excessively fast expansion and forming speed leads to local expansion differences in the heat shrinkable sleeve, affecting the uniformity of material expansion and ductility. The present invention adaptively slows down the expansion and forming speed of the heat shrinkable sleeve to be expanded through the material expansion and ductility characterization coefficient, thereby achieving adaptive adjustment of preparation parameters, ensuring that the heat shrinkable sleeve expands uniformly during the heating process, and obtaining better expansion uniformity and consistency of the final product.

[0042] In particular, the present invention draws material expansion marking lines through several marking points of each point group, and by connecting several marking points in the point group into a line segment in sequence, it is possible to more intuitively judge the actual extension direction and degree of the material surface where the material expansion occurs, thereby realizing the quantification of the extension changes of materials that are difficult to characterize.

[0043] In particular, the present invention determines whether the adjustment of the expansion molding speed is effective by calculating the line segment overlap of several material expansion marking lines. In the actual heating and expansion process of the heat shrinkable tube, by comparing the line segment overlap of the material expansion marking lines corresponding to each point group, the difference in the material extension direction and extension degree of the heat shrinkable tube at the point group position can be intuitively obtained. The higher the line segment overlap of several material expansion marking lines, the higher the consistency of the material extension of the heat shrinkable tube at the point group position, and the expansion molding of the heat shrinkable tube is uniform, thereby realizing accurate verification of the adjustment effect and improving the preparation stability of the heat shrinkable tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a step diagram of a method for preparing an ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to an embodiment of the present invention;

[0045] Figure 2 A schematic diagram of the length interval between adjacent point groups and the width interval between adjacent marking points in a surface image according to an embodiment of the present invention;

[0046] Figure 3 A logic flow chart for determining whether the expansion uniformity of a heat shrinkable tube meets a preset standard according to an embodiment of the present invention;

[0047] Figure 4 A logic flow chart for determining whether the adjustment of the expansion molding speed is effective according to an embodiment of the present invention;

[0048] In the figure, 1: heat shrink tubing, 2: marking point, 3: point group. DETAILED DESCRIPTION

[0049] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0051] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0052] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] See also Figure 1 as well as Figure 2 As shown, Figure 1 This is a step diagram of a method for preparing an ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to an embodiment of the present invention. Figure 2The figure is a schematic diagram of the length interval between adjacent point groups and the width interval between adjacent marking points 2 in the surface image of an embodiment of the present invention. The method for preparing the ethylene-tetrafluoroethylene copolymer modified heat shrinkable sleeve of the present invention comprises:

[0054] Step S1, mixing fluororubber and a modifier to obtain a first masterbatch, and mixing the first masterbatch with ethylene-tetrafluoroethylene copolymer to obtain a second masterbatch;

[0055] Step S2, heating the second masterbatch to a preset temperature, extruding and irradiating and cross-linking to obtain a heat shrinkable tube 1 to be expanded, marking a plurality of point groups at predetermined length intervals along the length direction on the surface of the heat shrinkable tube 1 to be expanded, wherein the point group 3 includes a plurality of marking points 2 arranged at predetermined width intervals along the width direction;

[0056] Step S3, expanding and molding the heat shrinkable tube 1 to be expanded, collecting a surface image of the heat shrinkable tube 1 after the expansion and molding, and calculating a material extension and expansion characterization coefficient based on the length interval fluctuation between adjacent point groups and the width interval fluctuation between adjacent marking points 2 in the surface image, so as to determine whether the expansion uniformity of the heat shrinkable tube meets the preset standard;

[0057] Step S4, adjusting the expansion forming speed of the heat shrinkable sleeve to be expanded based on the material ductility expansion characterization coefficient;

[0058] Step S5, drawing material expansion marking lines based on a number of marking points 2 of each point group, and calculating line segment coincidence based on the material expansion marking lines corresponding to the several point groups to determine whether adjusting the expansion forming speed is effective;

[0059] Step S6, rolling up the heat shrinkable tube that has been expanded and formed.

[0060] Specifically, the present invention does not limit the process of mixing fluororubber and modifier to obtain the first masterbatch. In the real-time embodiment of the present invention, the first masterbatch can be prepared by stirring with a mixer and then by an internal mixer and a twin-screw granulator. This is the prior art and will not be described in detail here.

[0061] Specifically, the present invention does not limit the process of mixing the first masterbatch with the ethylene-tetrafluoroethylene copolymer to obtain the second masterbatch. In the real-time embodiment of the present invention, the second masterbatch can be obtained by stirring with a mixer and secondary granulating with a twin-screw granulator. This is a prior art and will not be described in detail here.

[0062] Specifically, in the embodiment of the present invention, the preset temperature for heating the second masterbatch for extrusion molding is 300°C.

[0063] Specifically, the present invention does not limit the radiation cross-linking process of the heat shrinkable tube. Preferably, the heat shrinkable tube can be placed under a radiation source for radiation cross-linking treatment. The radiation process includes radiation energy penetrating the heat shrinkable tube material, interacting with the molecules, causing chain breakage, free radical formation and cross-linking reaction, and performing necessary post-processing, such as cooling, cleaning, etc. This is the prior art and will not be repeated here.

[0064] Specifically, the present invention does not limit the method of marking several point groups and marking point 2. It can use an erasable fluorescent marker to mark the point group 3 and marking point 2 on the heat shrink tube. The fluorescent marker can make the marking point 2 still visible under dim or low light conditions. This is a prior art and will not be repeated here.

[0065] Specifically, in an embodiment of the present invention, the predetermined length interval L1 between adjacent point groups is determined based on actual production requirements by technicians in this field. Preferably, the value range of the predetermined length interval L1 is [1, 3], and the interval unit is m. The predetermined width interval L2 between adjacent marking points 2 is determined based on the width Ls of the heat shrinkable tube 1 actually produced by technicians in this field. L2 = λ × Ls, λ is the width interval determination factor, and the value range of λ is [0.2, 0.25].

[0066] Specifically, the present invention marks a plurality of point groups at predetermined length intervals along the length direction on the surface of the heat shrinkable tube 1 to be expanded, and each point group includes a plurality of marking points 2 arranged at predetermined width intervals along the width direction. During the actual expansion and molding process of the heat shrinkable tube 1, the heat shrinkable tube 1 subjected to extrusion force or tensile force will undergo material extension and expansion along the length direction and the width direction. The present invention facilitates the digitization of the expansion degree of the heat shrinkable tube 1 in the expansion and molding stage by setting point groups 3 at predetermined length intervals and marking points 2 at predetermined width intervals, thereby improving the scientificity and accuracy of the expansion degree detection.

[0067] Specifically, the present invention does not limit the specific method of collecting surface images. An industrial CCD camera or a high-definition camera can be used to obtain the required image, which will not be described in detail here.

[0068] Specifically, the present invention does not limit the method for adjusting the expansion molding speed. Preferably, the expansion molding speed can be adjusted by adjusting the running speed of the roller of the expansion molding equipment. This is a prior art and will not be described in detail here.

[0069] Specifically, the present invention does not limit the implementation method of drawing material expansion marking lines. Preferably, an image processor or a dedicated GPU can be selected to determine the position of the marking point through the custom pixel point coordinates in the surface image, and the marking points 2 at each position are connected in sequence through smooth curves. This technology is widely used in feature extraction, target tracking and image segmentation in image processing, and will not be repeated here.

[0070] Specifically, the present invention does not limit the calculation method of line segment overlap. Preferably, a minimum overlap calculation method can be selected. The minimum overlap calculation method characterizes the overlap between line segments by calculating the overlapping length of the line segments. This is a prior art and will not be described in detail here.

[0071] Specifically, in step S3, the fluctuation of the length interval between adjacent point groups in the surface image is determined based on formula (1):

[0072]

[0073] In formula (1), Ds is the standard deviation of the length interval between adjacent point groups in the surface image, Ds i is the length interval between the i-th adjacent point groups, Ds av is the average length interval between adjacent point groups in the surface image, i=1,2,3…n, n is the number of length intervals between adjacent point groups in the surface image.

[0074] Specifically, in step S3, the fluctuation of the width interval between adjacent marking points is determined based on formula (2):

[0075]

[0076] In formula (2), Dc is the standard deviation of the width interval between adjacent marking points, Dc j is the width interval between the jth adjacent marking points, Dc av is the average value of the width intervals between adjacent marking points, j=1,2,3…m, and m is the number of width intervals between adjacent marking points.

[0077] Specifically, see Figure 3 As shown, it is a logic flow chart of determining whether the expansion uniformity of the heat shrinkable tube meets the preset standard in an embodiment of the present invention. In step S3, the material extension and expansion characterization coefficient is determined based on formula (3):

[0078]

[0079] In formula (3), E is the material extension coefficient, Ds is the length interval standard deviation between adjacent point groups in the surface image, Ds0 is a preset length interval reference value, Dc is the width interval standard deviation between adjacent marking points, Dc0 is a preset width interval reference value, α is the length interval weight coefficient, β is the width interval weight coefficient, and α+β=1.

[0080] In an embodiment of the present invention, the length interval reference value Ds0 is obtained based on a preliminary test. The length intervals between adjacent point groups during the expansion and molding of the same specification heat shrink tubing under the same preset length interval conditions are pre-tested and recorded several times. The average value of the standard deviation of the length intervals between several adjacent point groups is calculated, and the average value is determined as the length interval reference value Ds0, in units of m.

[0081] In an embodiment of the present invention, the width interval reference value Dc0 is obtained based on a preliminary test. The width intervals between adjacent marking points during the expansion molding process of the same specification heat shrink tubing under the same preset width interval conditions are pre-tested and recorded several times, and the average value of the standard deviation of the width intervals between several adjacent marking points is calculated. The average value is determined as the width interval reference value Dc0, in mm.

[0082] Specifically, the present invention determines whether the expansion uniformity of the heat shrinkable tube 1 meets the preset standard by calculating the material extension and expansion characterization coefficient. In the actual expansion and molding process of the heat shrinkable tube 1, the length interval fluctuation of adjacent point groups on the surface of the heat shrinkable tube 1 where the material undergoes uniform extension and expansion is very small. The larger the fluctuation, the more it indicates that the extension and expansion of the heat shrinkable tube 1 in the length direction of the material is uneven. Similarly, in the width direction of the heat shrinkable tube 1, the width interval fluctuation of adjacent marking points on the surface of the heat shrinkable tube 1 where the material undergoes uniform extension and expansion is also very small. The larger the fluctuation, the more it indicates that the extension and expansion of the heat shrinkable tube 1 in the width direction of the material is uneven. The present invention combines the two to calculate the material extension and expansion characterization coefficient, thereby avoiding the bias of the calculation result. The larger the calculation result, the more it indicates that the extension and expansion of the heat shrinkable tube 1 is uneven, thereby realizing the digitized and intuitive characterization of the expansion degree of the heat shrinkable tube 1 in the expansion and molding stage.

[0083] Specifically, in step S3, the process of determining whether the expansion uniformity of the heat shrinkable tube 1 meets the preset standard is as follows:

[0084] The material extension and expansion characterization coefficient E is compared with a preset material extension and expansion characterization coefficient threshold value E0,

[0085] If the material extension and expansion characterization coefficient E is less than or equal to the material extension and expansion characterization coefficient threshold E0, it is determined that the expansion uniformity of the heat shrinkable tube meets the preset standard;

[0086] If the material extension and expansion characterization coefficient E is greater than the material extension and expansion characterization coefficient threshold E0, it is determined that the expansion uniformity of the heat shrinkable tube does not meet the preset standard.

[0087] Preferably, in an embodiment of the present invention, the value range of the material extension and expansion characterization coefficient threshold E0 is [2.9, 3].

[0088] Specifically, in step S4, the expansion molding speed of the heat shrinkable tube to be expanded is negatively correlated with the material extension and expansion characterization coefficient.

[0089] Preferably, in this embodiment, at least three speed adjustment methods are set to determine the expansion molding speed of the heat shrinkable sleeve to be expanded based on the material extension and expansion characterization coefficient E, wherein the material extension and expansion characterization coefficient E is compared with the preset first material extension and expansion characterization coefficient E1 and the second material extension and expansion characterization coefficient E2,

[0090] If E<E1, it is determined to adopt the first speed adjustment method, which is to adjust the expansion molding speed of the heat shrinkable sleeve to be expanded to the first expansion molding speed V1, and set V1=V0-Δv1;

[0091] If E1≤E≤E2, it is determined to adopt the second speed adjustment method, which is to adjust the expansion molding speed of the heat shrinkable sleeve to be expanded to the second expansion molding speed V2, and set V2=V0-Δv2;

[0092] If E>E2, it is determined to adopt the third speed adjustment method, wherein the third speed adjustment method is to adjust the expansion molding speed of the heat shrinkable sleeve to be expanded to the third expansion molding speed V3, and set V3=V0-Δv3;

[0093] Among them, V0 represents the initial value of the expansion molding speed of the heat shrinkable tube to be expanded, Δv1 represents the first speed adjustment amount, Δv2 represents the second speed adjustment amount, and Δv3 represents the third speed adjustment amount. In this embodiment, in order to make the first material extension and expansion characterization coefficient E1 and the second material extension and expansion characterization coefficient E2 able to distinguish the differences in material extension during the expansion molding process of the heat shrinkable tube, in this embodiment, E1=1.1E0 and E2=1.2E0 are set. In order to make the adjustment effective and avoid excessive adjustment, in this embodiment, 0.1V0≤Δv1<Δv2<Δv3≤0.25V0.

[0094] Specifically, the present invention improves the uniformity of material expansion and ductility of the heat shrinkable sleeve by adjusting the expansion and forming speed of the heat shrinkable sleeve to be expanded. In the actual heating and expansion process of the heat shrinkable sleeve, the ethylene-tetrafluoroethylene copolymer added to the heat shrinkable sleeve causes the heat shrinkable sleeve to have strong tensile properties. Excessively fast expansion and forming speed leads to local expansion differences in the heat shrinkable sleeve, affecting the uniformity of material expansion and ductility. The present invention adaptively slows down the expansion and forming speed of the heat shrinkable sleeve to be expanded through the material expansion and ductility characterization coefficient, thereby achieving adaptive adjustment of preparation parameters, ensuring that the heat shrinkable sleeve expands uniformly during the heating process, and obtaining better expansion uniformity and consistency of the final product.

[0095] Specifically, in step S5, the process of drawing the material expansion marking line is as follows:

[0096] The marking points in the point group are sequentially connected into line segments along the width direction, and the line segments are determined as material expansion marking lines corresponding to the point group.

[0097] Specifically, the present invention draws material expansion marking lines through several marking points of each point group, and by connecting several marking points in the point group into a line segment in sequence, it is possible to more intuitively judge the actual extension direction and degree of the material surface where the material expansion occurs, thereby realizing the quantification of the extension changes of materials that are difficult to characterize.

[0098] Specifically, see Figure 4 As shown, it is a logic flow chart for determining whether the adjustment of the expansion molding speed is effective according to an embodiment of the present invention. In step S5, the process of determining whether the adjustment of the expansion molding speed is effective is as follows:

[0099] The line segment overlap degree k is compared with a preset line segment overlap degree threshold k0,

[0100] If the line segment overlap k is greater than the line segment overlap threshold k0, it is determined that the adjustment of the expansion forming speed is effective;

[0101] If the line segment overlap k is less than or equal to the line segment overlap threshold k0, it is determined that the adjustment of the expansion forming speed is invalid, and an alarm is issued.

[0102] Preferably, in the embodiment of the present invention, the value range of the line segment coincidence threshold k0 is [85%, 95%].

[0103] Specifically, the present invention determines whether the adjustment of the expansion molding speed is effective by calculating the line segment overlap of several material expansion marking lines. In the actual heating and expansion process of the heat shrinkable tube, by comparing the line segment overlap of the material expansion marking lines corresponding to each point group, the difference in the material extension direction and extension degree of the heat shrinkable tube at the point group position can be intuitively obtained. The higher the line segment overlap of several material expansion marking lines, the higher the consistency of the material extension of the heat shrinkable tube at the point group position, and the expansion molding of the heat shrinkable tube is uniform, thereby realizing accurate verification of the adjustment effect and improving the preparation stability of the heat shrinkable tube.

[0104] Specifically, the present invention also provides an ethylene-tetrafluoroethylene copolymer modified heat shrinkable sleeve, comprising the following raw materials in parts by weight:

[0105] 100 parts of fluororubber;

[0106] 60-80 parts of ethylene-tetrafluoroethylene copolymer;

[0107] Modifier 24-34 parts.

[0108] Specifically, the modifier includes 10-20 parts of barium sulfate, 6 parts of light magnesium oxide, 1 part of palm wax lubricant, 2 parts of cross-linking aid TAIC, and 5 parts of thermal cracking carbon black powder.

[0109] Embodiment 1;

[0110] 100kg fluororubber, 10kg barium sulfate, 6kg light magnesium oxide, 1kg palm wax lubricant, 2kg cross-linking aid TAIC, 5kg thermal cracking carbon black powder, 60kg ethylene-tetrafluoroethylene copolymer.

[0111] Embodiment 2;

[0112] 100kg fluororubber, 10kg barium sulfate, 6kg light magnesium oxide, 1kg palm wax lubricant, 2kg cross-linking aid TAIC, 5kg thermal cracking carbon black powder, 70kg ethylene-tetrafluoroethylene copolymer.

[0113] Embodiment 3;

[0114] 100kg fluororubber, 10kg barium sulfate, 6kg light magnesium oxide, 1kg palm wax lubricant, 2kg cross-linking aid TAIC, 5kg thermal cracking carbon black powder, 80kg ethylene-tetrafluoroethylene copolymer.

[0115] Embodiment 4;

[0116] 100kg fluororubber, 20kg barium sulfate, 6kg light magnesium oxide, 1kg palm wax lubricant, 2kg cross-linking aid TAIC, 5kg thermal cracking carbon black powder, 80kg ethylene-tetrafluoroethylene copolymer.

[0117] The raw materials of Examples 1 to 4 were respectively used to prepare ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to the above-mentioned method for preparing ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing.

[0118] The test results of the samples produced by the above methods in Examples 1 to 4 are as follows:

[0119]

[0120]

[0121] Preferably, the ethylene-tetrafluoroethylene copolymer modified heat shrink tubing can be prepared by using a weight formula of 100 kg fluororubber, 10 kg barium sulfate, 6 kg light magnesium oxide, 1 kg palm wax lubricant, 2 kg crosslinking aid TAIC, 5 kg thermal cracking carbon black powder, and 80 kg ethylene-tetrafluoroethylene copolymer.

[0122] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle 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 fall within the protection scope of the present invention.

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing, characterized in that: include: Step S1, mixing fluororubber and a modifier to obtain a first masterbatch, and mixing the first masterbatch with ethylene-tetrafluoroethylene copolymer to obtain a second masterbatch; Step S2, heating the second masterbatch to a preset temperature, extruding and irradiating and cross-linking to obtain a heat shrinkable tube to be expanded, marking a plurality of point groups at predetermined length intervals along the length direction on the surface of the heat shrinkable tube to be expanded, wherein the point group includes a plurality of marking points arranged at predetermined width intervals along the width direction; Step S3, expanding and molding the heat shrinkable sleeve to be expanded, collecting a surface image of the heat shrinkable sleeve after expansion and molding, and calculating a material extension and expansion characterization coefficient based on the fluctuation of the length interval between adjacent point groups and the fluctuation of the width interval between adjacent marking points in the surface image, so as to determine whether the expansion uniformity of the heat shrinkable sleeve meets the preset standard; Step S4, adjusting the expansion forming speed of the heat shrinkable sleeve to be expanded based on the material ductility and expansion characterization coefficient; Step S5, drawing material expansion marking lines based on a number of marking points of each point group, and calculating line segment coincidence based on the material expansion marking lines corresponding to the several point groups to determine whether adjusting the expansion forming speed is effective; Step S6, rolling up the expanded heat shrink tubing.

2. The method for preparing the ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to claim 1, characterized in that: In step S3, the fluctuation of the length interval between adjacent point groups in the surface image is determined based on formula (1): In formula (1), Ds is the standard deviation of the length interval between adjacent point groups in the surface image, Ds i is the length interval between the i-th adjacent point groups, Ds av is the average length interval between adjacent point groups in the surface image, i=1,2,3…n, n is the number of length intervals between adjacent point groups in the surface image.

3. The method for preparing the ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to claim 2, characterized in that: In step S3, the fluctuation of the width interval between adjacent marking points is determined based on formula (2): In formula (2), Dc is the standard deviation of the width interval between adjacent marking points, Dc j is the width interval between the jth adjacent marking points, Dc av is the average width interval between adjacent marking points, j=1,2,3…m, and m is the number of width intervals between adjacent marking points.

4. The method for preparing the ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to claim 3, characterized in that: In step S3, the material extension coefficient is determined based on formula (3): In formula (3), E is the material extension coefficient, Ds is the length interval standard deviation between adjacent point groups in the surface image, Ds0 is a preset length interval reference value, Dc is the width interval standard deviation between adjacent marking points, Dc0 is a preset width interval reference value, α is the length interval weight coefficient, and β is the width interval weight coefficient.

5. The method for preparing the ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to claim 4, characterized in that: In step S3, the process of determining whether the expansion uniformity of the heat shrinkable tube meets the preset standard is as follows: The material extension and expansion characterization coefficient is compared with a preset material extension and expansion characterization coefficient threshold value, If the material extension and expansion characterization coefficient is greater than the material extension and expansion characterization coefficient threshold, it is determined that the expansion uniformity of the heat shrinkable tube does not meet the preset standard.

6. The method for preparing the ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to claim 5, characterized in that: In the step S4, the expansion molding speed of the heat shrinkable tube to be expanded is negatively correlated with the material extension and expansion characterization coefficient.

7. The method for preparing the ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to claim 1, characterized in that: In step S5, the process of drawing the material expansion marking line is as follows: The marking points in the point group are sequentially connected into line segments along the width direction, and the line segments are determined as material expansion marking lines corresponding to the point group.

8. The method for preparing the ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to claim 1, characterized in that: In step S5, the process of determining whether the adjustment of the expansion molding speed is effective is as follows: The line segment overlap is compared with a preset line segment overlap threshold, If the line segment overlap is greater than the line segment overlap threshold, it is determined that the adjustment of the expansion forming speed is effective; If the line segment overlap is less than or equal to the line segment overlap threshold, it is determined that the adjustment of the expansion forming speed is invalid, and an alarm is issued.

9. The ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing prepared according to the method for preparing the ethylene-tetrafluoroethylene copolymer modified heat shrinkable tubing according to any one of claims 1 to 8, characterized in that: include: Fluororubber; Ethylene-tetrafluoroethylene copolymer; Modifier.

10. The ethylene-tetrafluoroethylene copolymer modified heat shrink tubing according to claim 9, characterized in that: The modifier includes barium sulfate, light magnesium oxide, palm wax lubricant, cross-linking aid TAIC and thermal cracking carbon black powder.

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