A high-temperature-resistant PVC clamping strip for floor heating and a preparation method thereof

Abstract

The present application relates to the technical field of high polymer profile, in particular to a chlorinated polyvinyl chloride high-temperature-resistant PVC strip for floor heating floor and a preparation method thereof.The strip takes chlorinated polyvinyl chloride as a continuous phase and contains an independently-prepared segmented zinc oxide-epoxy soybean oil treated carboxyl nitrile rubber additive.During preparation, first, the carboxyl nitrile rubber is treated with the first portion of zinc oxide, then the preceding zinc oxide and the subsequent zinc oxide are added before and after the addition of the epoxy soybean oil, and after tabletting, cooling and granulation, the chlorinated polyvinyl chloride resin is preliminarily fused, and then added laterally from a position 22 times the nominal outer diameter of the screw from the starting end of the screw working section, followed by extrusion, water cooling, traction and cutting.The strip has a flat bottom plate, two side up-bending clamping arms, an end limit lip and an open slot, and can take into account the thermal clamping stability and low-temperature repeated clamping integrity.

Description

Technical Field

[0001] This invention relates to the field of polymer profile technology, specifically to a high-temperature resistant PVC trim strip for underfloor heating flooring with chlorinated polyvinyl chloride as the continuous phase and containing independently pre-made carboxylated nitrile rubber additives, and its preparation method. Background Technology

[0002] Underfloor heating strips are typically long extruded strips with an open groove in their cross-section, a base plate, clamping arms located on both sides of the base plate and curving upwards, and limiting lips at the ends of the clamping arms. After installation, the clamping arms remain in a flexed state and achieve continuous clamping through the interference fit between the clamping arms and the mating parts.

[0003] Chlorinated polyvinyl chloride (PVC) has high heat resistance and can be used for extrusion molding of underfloor heating strips. However, when the strip remains flexed in an underfloor heating environment for a long time, the clamping arms may experience a decrease in clamping force due to creep and stress relaxation. Simply increasing the material rigidity or strengthening the inter-molecular chain constraints may result in whitening, cracking, or damage to the clamping arms and limiting lips during low-temperature fastening and disassembly.

[0004] Adding rubber-like components to chlorinated polyvinyl chloride (PVC) can improve its low-temperature deformation capability. However, when rubber and liquid components are directly introduced into the PVC melt, the pre-formed material state is insufficient, and it may also alter the melt viscosity, processing thermal stability, profile surface quality, and color. Therefore, how to balance continuous hot clamping and repeated low-temperature fastening while maintaining the continuous phase of PVC and the existing cross-sectional shape of the fastener is a technical problem that needs to be solved in this field. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a high-temperature resistant chlorinated polyvinyl chloride (PVC) strip for underfloor heating floors and its preparation method, so as to slow down the attenuation of clamping force of the strip under continuous bending in a hot state, while maintaining the integrity of the clamping arm and limiting lip after repeated fastening at low temperature, and making the material processing method suitable for continuous extrusion molding.

[0006] To achieve the above objectives, this invention provides a high-temperature resistant chlorinated polyvinyl chloride (PVC) strip for underfloor heating. The strip is a long extruded piece, the cross-section of which includes a flat bottom plate, two upwardly curved clamping arms connected to both sides of the flat bottom plate, and limiting lips respectively disposed at the ends of the two clamping arms. The two clamping arms and the flat bottom plate form an opening groove. Based on a total raw material quantity of 100 parts by weight for preparing the strip, the raw material includes 5.5 parts by weight of carboxylated nitrile rubber and 0.0 parts by weight of... 75-0.125 parts by weight of zinc oxide, 0.30-0.50 parts by weight of epoxidized soybean oil, 2.5 parts by weight of calcium-zinc stabilizer, 2.0 parts by weight of acrylic acid processing aid, 0.5 parts by weight of oxidized polyethylene wax, and the balance of chlorinated polyvinyl chloride resin, wherein the mass ratio of zinc oxide to epoxidized soybean oil is 1:4, and the carboxylated nitrile rubber, the zinc oxide, and the epoxidized soybean oil are separately prepared into a zinc oxide-epoxidized soybean oil treated carboxylated nitrile rubber pre-additive before being mixed with the chlorinated polyvinyl chloride resin.

[0007] Preferably, the zinc oxide comprises a first zinc oxide, a pre-stage subsequent zinc oxide, and a post-stage subsequent zinc oxide; based on the total mass of the zinc oxide as 100%, the first zinc oxide, the pre-stage subsequent zinc oxide, and the post-stage subsequent zinc oxide account for 24%~27%, 29%~31%, and 43%~47%, respectively, and the sum of the percentages of the three is 100%; the first zinc oxide is first mixed with the carboxylated nitrile rubber, the pre-stage subsequent zinc oxide is added before the epoxidized soybean oil, and the post-stage subsequent zinc oxide is added after the epoxidized soybean oil is mixed.

[0008] Preferably, the fastener is manufactured as follows: a basic dry mix containing the chlorinated polyvinyl chloride resin, the calcium-zinc stabilizer, the acrylic processing aid, and the oxidized polyethylene wax is added through the main feed port of a co-rotating twin-screw extruder; after the chlorinated polyvinyl chloride resin has completed its initial fusion, the pre-made additive is added laterally at position 22D; the mixture is further mixed and extruded through a fastener die; wherein, D represents the nominal outer diameter of the screw of the co-rotating twin-screw extruder, and the position 22D is the position where the distance from the axial reference plane at the beginning of the screw working section to the center line of the side feed port is 22 times D.

[0009] Preferably, based on a total raw material weight of 100 parts by weight for preparing the buckle strip, the amounts of the chlorinated polyvinyl chloride resin, the carboxylated nitrile rubber, the zinc oxide, the epoxidized soybean oil, the calcium-zinc stabilizer, the acrylic acid processing aid, and the oxidized polyethylene wax are 89.0 parts by weight, 5.5 parts by weight, 0.10 parts by weight, 0.40 parts by weight, 2.5 parts by weight, 2.0 parts by weight, and 0.5 parts by weight, respectively; and based on a total zinc oxide weight of 100%, the initial zinc oxide, the preceding subsequent zinc oxide, and the subsequent subsequent zinc oxide account for 25%, 30%, and 45%, respectively.

[0010] Furthermore, the present invention also provides a method for preparing a high-temperature resistant chlorinated polyvinyl chloride (PVC) strip for underfloor heating floors, comprising the following steps:

[0011] (1) Plasticize the carboxylated butadiene-acrylonitrile rubber under a nitrogen atmosphere, add the first part of zinc oxide and mix to obtain the base rubber;

[0012] (2) Heat the base adhesive and add the first-stage zinc oxide, the epoxidized soybean oil and the second-stage zinc oxide in sequence for mixing. The first-stage zinc oxide is added before the epoxidized soybean oil and the second-stage zinc oxide is added after the epoxidized soybean oil is mixed. The resulting material is pressed into tablets, cooled and granulated to obtain an independent pre-made additive.

[0013] (3) The chlorinated polyvinyl chloride resin and the calcium-zinc stabilizer are added to a high-speed mixer. During the material heating process, the acrylic acid processing aid and the oxidized polyethylene wax are added in sequence. Then the material is discharged and cooled to obtain a basic dry mix.

[0014] (4) The basic dry mix is ​​added through the main feed port of the co-rotating twin-screw extruder. After the chlorinated polyvinyl chloride resin has completed the initial fusion, the pre-made additive is added laterally at position 22D. The mixture is then further mixed and extruded through a snap-on die. Here, D represents the nominal outer diameter of the screw of the co-rotating twin-screw extruder. The position 22D is the position where the distance from the axial reference plane at the beginning of the screw working section to the center line of the side feed port is 22 times D.

[0015] (5) The extruded fastener is sequentially shaped by circulating water, pulled and cut to a fixed length; the resulting fastener is a long extruded part, the chlorinated polyvinyl chloride resin constitutes the continuous phase of the fastener material, the cross section of the long extruded part includes a flat bottom plate, two clamping arms that are respectively connected to both sides of the flat bottom plate and bent upward, and limiting lips that are respectively set at the ends of the two clamping arms, the two clamping arms and the flat bottom plate form an opening groove.

[0016] Preferably, in step (1), the carboxylated nitrile rubber is plasticized at 60 r / min for 3 min and the material temperature reaches 130°C, the first zinc oxide is added and mixed for 4 min; in step (2), the base rubber is heated to 145°C, the first-stage subsequent zinc oxide is added and mixed for 3 min, the epoxidized soybean oil is added and mixed for 10 min, the second-stage subsequent zinc oxide is added and mixed for 12 min; the resulting material is pressed into a sheet with a thickness of 2 mm at 90°C, cooled to 25°C and cut into granules with a nominal length of 3 mm.

[0017] Preferably, in step (3), the high-speed mixer is preheated to 25°C and the rotation speed is set to 600 r / min. The chlorinated polyvinyl chloride resin and the calcium-zinc stabilizer are added first. When the material temperature rises to 70°C, the acrylic acid processing aid is added. When the material temperature rises to 95°C, the oxidized polyethylene wax is added. When the material temperature rises to 110°C, it is discharged into the cold mixer and cooled to 45°C at 300 r / min.

[0018] Preferably, in step (4), the nominal outer diameter of the screw of the co-rotating twin-screw extruder is 26 mm, the length-to-diameter ratio is 44:1, the temperature of the feeding zone is 130℃, the temperature of the compression zone is 170℃, the temperature of the homogenization zone is 175℃, the temperature of the die head is 175℃, the temperature of the die is 175℃, and the main machine speed is 240 r / min; in step (5), the circulating water temperature is 20℃, and the circulating water flow rate is 15 m³ / min. 3 / h, traction speed is 10m / min.

[0019] The beneficial effects of this invention are:

[0020] (1) In this invention, carboxylated nitrile rubber, zinc oxide and epoxidized soybean oil are first made into pre-prepared additives that can be independently sampled, weighed and added, and then added to the chlorinated polyvinyl chloride melt. This treatment method enables the relevant components to form a relatively stable pre-prepared material state before entering the chlorinated polyvinyl chloride processing system, which is beneficial to improving the controllability of the feeding process and reducing the material state differences caused by the direct dispersion of each component.

[0021] (2) In this invention, the subsequent zinc oxide is divided into a pre-stage subsequent zinc oxide and a post-stage subsequent zinc oxide, which are mixed before and after the addition of epoxidized soybean oil, respectively. This feeding relationship can adjust the contact sequence of carboxyl groups, zinc species and epoxy groups during the mixing process, so that the resulting pre-made additive forms a material state different from that when the subsequent zinc oxide is added at once. This is beneficial to reducing the acid value, residual epoxy functional group content and acetone extractable of the pre-made material, and to coordinating the state of zinc carboxylate with the state of residual epoxy groups.

[0022] (3) By independently forming pre-made additives and adding zinc oxide around epoxidized soybean oil in stages, the present invention enables the resulting buckle to have a good clamping force retention ability at the temperature of underfloor heating and can reduce the attenuation of clamping force after continuous heating; at the same time, the resulting buckle can still maintain a high structural integrity rate during repeated fastening at low temperature, which is beneficial to balance the heat retention performance and low temperature assembly reliability of the buckle.

[0023] (4) While improving the hot clamping and holding capacity of the fastener and the integrity of repeated fastening at low temperature, the present invention does not cause substantial adverse changes in steady-state extrusion torque, static thermal stability time, number of surface defects and color difference during continuous operation. Therefore, it can be implemented under existing twin-screw extrusion and fastener molding conditions and has good adaptability to continuous processing. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic cross-sectional view of the fastener strip of the present invention.

[0026] Figure 2 This is a flowchart of the method for preparing the fastener strip according to the present invention.

[0027] Figure 3 The Fourier transform infrared spectra of the prefabricated materials obtained in Comparative Example 1, Comparative Example 5 and Example 1 are shown.

[0028] Figure 4 The clamping force retention curves are for the fasteners obtained in Comparative Examples 4, 5 and 1 after being placed at 60°C for 0d, 1d, 3d, 5d and 7d.

[0029] In the figure: 1. Flat bottom plate; 2. First clamping arm; 3. Second clamping arm; 4. First limiting lip; 5. Second limiting lip; 6. Opening groove. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. For example... Figure 1 As shown, the fastener is along the line perpendicular to... Figure 1The cross-section shown is an elongated extruded piece extending in the direction of the direction shown. The first clamping arm 2 and the second clamping arm 3 are respectively connected to the two sides of the flat bottom plate 1. The first limiting lip 4 and the second limiting lip 5 are respectively disposed at the free ends of the two clamping arms. The two clamping arms and the flat bottom plate 1 form an opening groove 6. This cross-sectional shape is used in the following embodiments and comparative examples.

[0032] In the embodiments and comparative examples, the cross-sectional outer width of the fastener in its free state is 20.0±0.1mm, the total height is 9.0±0.1mm, the thickness of the flat base plate 1 is 1.50±0.05mm, the wall thickness of the first clamping arm 2 and the second clamping arm 3 is 1.20±0.05mm, the minimum distance between the inner sides of the first limiting lip 4 and the second limiting lip 5 is 5.40±0.05mm, and the depth of the opening groove 6 from the inner apex of the limiting lip to the inner surface of the flat base plate is 7.0±0.1mm. These dimensions are used to standardize the assembly boundaries of each group of samples. Figure 1 It is not drawn to scale.

[0033] In this specification, D represents the nominal outer diameter of the screw in a co-rotating twin-screw extruder; the 22D position, measured axially, refers to the position where the distance from the axial reference plane at the beginning of the screw's working section to the center line of the side feed port is 22 times D. "Completion of preliminary fusion" means that the base dry mix has passed the fusion torque peak during pre-running with the same formulation, and no free powder is observed in the material obtained from the corresponding axial sampling port. The screw used in the example has an outer diameter of 26 mm and a length-to-diameter ratio of 44:1, satisfying the above-mentioned state at the 22D position.

[0034] raw material:

[0035] The chlorinated polyvinyl chloride resin is KANEKA H727, with a tensile yield strength of 55 MPa, a representative value of tensile elastic modulus of 2900 MPa, a load flexural temperature of 107℃, and a Vicat softening temperature of 115℃.

[0036] The carboxylated nitrile butadiene rubber is ARLANXEO Krynac X740, with a Mooney viscosity of 38 MU, an acrylonitrile content of 26.5 wt%, and a density of 0.99 g / cm³. 3 .

[0037] The zinc oxide is Zochem 104P, with a ZnO content of not less than 99.8% and a specific surface area of ​​5.2 m². 2 / g.

[0038] The epoxidized soybean oil is named ADEKA ADK CIZER O-130P, with a viscosity of 350 mPa·s at 25℃, an acid value of 0.3 mg KOH / g, an ethylene oxide oxygen content of 6.7%, and a flash point of 300℃.

[0039] The acrylic processing aid is Kane Ace PA210, with a D50 particle size of 75 μm.

[0040] The calcium and zinc stabilizer is BAEROSTAB MC8763-1CP.

[0041] The oxidized polyethylene wax is Licowax PED191.

[0042] Test methods

[0043] 1. Acid value of precast materials

[0044] The titration was performed according to the principle of GB / T1668-2008. The pre-prepared material was cut into particles no larger than 1 mm and vacuum dried at 60℃ to constant weight. 1.000 g of the sample was weighed and added to 50 mL of a mixture of toluene and anhydrous ethanol (volume ratio 2:1). The mixture was refluxed for 30 min, cooled to 25℃, and then potentiometrically titrated with a 0.0500 mol / L potassium hydroxide ethanol solution, corrected with a blank test. The acid value was calculated based on the mass of potassium hydroxide consumed per gram of sample, in mgKOH / g.

[0045] 2. Residual epoxy functional group content

[0046] The KBr pellet transmission Fourier transform infrared spectroscopy standard addition method was employed. The pre-prepared material, vacuum dried to constant weight at 60℃ and then ground, was divided into five portions of 20.0 mg each. 0, 0.50 mg, 1.00 mg, 1.50 mg, and 2.00 mg of epoxide-equivalent epoxide soybean oil standard were added to each portion, respectively. The final weight was then made up to 2.000 g with spectrally pure KBr and pelleted. Spectra were acquired according to the conditions described in section 4 of this document. The transmittance T, expressed as a decimal from 0 to 1, was converted to absorbance A, A = -log10T; for the 815–845 cm⁻¹ range... -1 The interval uses a connection of 815cm. -1 and 845cm -1 Draw a baseline from the two endpoints, with a distance of 2215~2255cm. -1 The interval uses a connection of 2215cm. -1 and 2255cm -1 Using the lines from both endpoints as the baseline, the integrals yield 830cm. -1 Epoxy group-related absorption band area S 830 and 2235cm -1 Nitrile absorption band area S 2235 The x-axis represents the amount of epoxy group added to each 20.0 mg pre-prepared material, and the y-axis represents the baseline-corrected area ratio S. 830 / S 2235Linear regression was performed on the ordinate y; the regression line was extrapolated to y=0, and the absolute value of the resulting negative x-intercept was taken as the amount of residual epoxy group in the original 20.0 mg sample, converted to mol / 100g. Pre-prepared materials without epoxidized soybean oil from Comparative Examples 1 and 2 were used as selective blanks, and the 815–845 cm⁻¹ range was examined using the same slide preparation and baseline processing methods. -1 In the interval where neither of the two selective blanks exhibits an independent absorption band with a peak height ratio of not less than 3 to the adjacent baseline noise peak-to-peak value, an 830 cm⁻¹ interval is used. -1 Quantification was performed using the absorption bands. (The last part, "S," appears to be an unrelated fragment and is left untranslated.) 2235 As an internal standard, it was added to the matrix of each sample using standard methods to reduce the influence of differences in tablet thickness, dispersion state, and matrix response. Zero-added specimens were prepared at 815–845 cm⁻¹. -1 The detection criterion is that the ratio of the peak height in the interval to the peak-to-peak value of the adjacent baseline noise is not less than 3; if it is lower than this criterion, it is recorded as undetectable. The method detection limit under the above sample amount and scanning conditions is 0.0010 mol / 100g.

[0047] 3. Acetone extract

[0048] Weigh 2.000 g of the pre-prepared material, which has been vacuum-dried to constant weight at 60 °C, and place it into a pre-weighed extraction sleeve. Perform Soxhlet extraction with acetone as the extractant for 8 h. Dry the extracted sample under vacuum at 60 °C to constant weight, and calculate the acetone extractables as a percentage of the mass difference between the sample before and after extraction relative to the mass of the sample before extraction.

[0049] 4. KBr tablet transmission Fourier transform infrared spectroscopy

[0050] The pre-made material was vacuum dried to constant weight at 60℃, then ground. It was mixed with the sample at a mass ratio of 1:100 to spectrally pure KBr and ground again, then pressed into a transmission test piece. The scanning range was 4000~400 cm⁻¹. -1 The resolution is 4cm. -1 The number of scans was 32. Separate slides were prepared for each sample, and spectra were acquired independently. Figure 3 The spectra of each sample were obtained without the addition of epoxidized soybean oil standard.

[0051] 5.60℃ Clamping Force Retention Rate

[0052] A 200mm long sample was cut from the steadily extruded fastener. The rigid insert was made of 304 stainless steel, with an effective contact length of 100.0±0.1mm along the longitudinal direction of the fastener, a working thickness of 6.00±0.02mm, a working surface roughness of Ra0.8μm, and a fillet radius of 0.50mm on both working edges of the insert tip. The insert was equipped with a limiting stop, ensuring an insertion depth of 6.0±0.1mm from the inner apex of the limiting lip into the opening groove. The working thickness of the insert and the minimum distance between the inner sides of the two limiting lips formed a total interference of 0.60mm. The same specification insert was used in all groups. During testing, the entire lower surface of the flat bottom plate of the sample was supported on a horizontal rigid support surface, and the same clamp was used to hold the area of ​​25mm at each end of the flat bottom plate. The insert was centered along the longitudinal direction of the fastener, with each end of the insert 50mm away from the ends of the sample. Five samples were initially taken and conditioned at 23℃ for 24 hours. The inserts were then pressed into the limiting stop at 23℃ at a speed of 50 mm / min, allowed to stand for 10 minutes, and then pulled out in the reverse direction of insertion at 50 mm / min. The maximum pull-out force was recorded. Five more samples were taken for the heat-preservation group and conditioned at 23℃ for 24 hours. The inserts were then assembled at 23℃ in the same manner and kept in the assembled state at 60℃ for 7 days. After removal, the samples were conditioned at 23℃ for 2 hours, and the maximum pull-out force was measured again in the same manner. The arithmetic mean of the two groups was calculated. The clamping force retention rate was calculated as "average clamping force after 7 days / average initial clamping force × 100%". (This is for plotting...) Figure 4 Another sample prepared in the same manner was placed at 60℃ for 1 day, 3 days and 5 days and then measured using the same method.

[0053] 6.0℃ Repeated fastening integrity rate

[0054] Twenty 200mm long samples were cut from the steadily extruded fastener strip and conditioned at 0℃ for 4 hours. Using the same rigid insert, insertion depth, rigid support surface, and clamp as described in section 5, the insert was centered along the longitudinal direction of the fastener strip. With the samples and inserts at 0℃, one fastening and disassembly cycle was performed at 50mm / min, with a 10-second interval before the next cycle, for a total of 20 cycles. After each cycle, the root of the clamping arm and the limiting lip were observed; any sample exhibiting visible cracks, missing limiting lip, or a continuous whitening band was considered incomplete. The integrity rate was calculated as the percentage of samples without the above defects out of the total 20 samples.

[0055] 7. Extrusion processing status

[0056] After reaching a stable extrusion state, the main machine torque was continuously recorded for 5 minutes and the average value was calculated. The static thermal stability time was determined at 180℃ using the Congo red method specified in GB / T2917.1-2002. The total number of visible flow marks, bubbles, and dark spots was counted for each 2m continuously extruded strip, and this count was taken as the number of surface defects. Strips were cut at the initial moment of stable discharge and after 15 minutes of continuous operation. Using a D65 light source and a 10° viewing angle, five color points were measured on each strip, and ΔE*ab was calculated using the average color value at the two time points.

[0057] Example 1:

[0058] In this embodiment, the fastener strip is prepared by extrusion feeding of 1000.0g, including 890.0g of chlorinated polyvinyl chloride resin, 55.0g of carboxylated nitrile rubber, 1.00g of zinc oxide, 4.0g of epoxidized soybean oil, 25.0g of calcium-zinc stabilizer, 20.0g of acrylic processing aid, and 5.0g of oxidized polyethylene wax. The zinc oxide is divided into 0.25g of initial zinc oxide, 0.30g of pre- and post-concentration zinc oxide, and 0.45g of post-concentration zinc oxide.

[0059] Carboxylated nitrile rubber was weighed and placed into a mixing chamber. Nitrogen gas was introduced, and the mixture was plasticized at 60 rpm for 3 minutes until the material temperature reached 130°C. The first portion of zinc oxide was added, and the mixture was further mixed at 130°C for 4 minutes to obtain the base rubber. The base rubber was heated to 145°C, and the first-stage zinc oxide was added and mixed for 3 minutes. Then, epoxidized soybean oil was added and mixed for 10 minutes, followed by the second-stage zinc oxide and mixed for 12 minutes. After unloading, the mixture was pressed into a 2 mm thick sheet at 90°C, cooled to 25°C, and cut into granules with a nominal length of 3 mm.

[0060] Weigh out chlorinated polyvinyl chloride resin, calcium-zinc stabilizer, acrylic processing aid, and oxidized polyethylene wax. Preheat the high-speed mixer to 25°C and set it to 600 r / min. First, add the chlorinated polyvinyl chloride resin and calcium-zinc stabilizer. When the material temperature reaches 70°C, add the acrylic processing aid. When the temperature reaches 95°C, add the oxidized polyethylene wax. When the temperature reaches 110°C, discharge the mixture into the cold mixer and cool it to 45°C at 300 r / min.

[0061] A co-rotating twin-screw extruder with a nominal screw outer diameter of 26 mm and a length-to-diameter ratio of 44:1 was used. The base dry mix was added through the main feed inlet. The temperatures of the feeding zone, compression zone, homogenization zone, die head, and mold were set to 130℃, 170℃, 175℃, 175℃, and 175℃ respectively. The main extruder speed was 240 r / min, the total feed rate was 3.00 kg / h, and the main feed rate was 2.82 kg / h. After the chlorinated polyvinyl chloride (PVC) had completed its initial fusion, 60.00 g of pre-made additives were added laterally at position 22D at a side feed rate of 0.18 kg / h. The mixture continued to be mixed and extruded through a strip die. The extrudate was processed at 20℃ with a flow rate of 15 m³ / h.3 The circulating water is shaped at a rate of / h, pulled at 10m / min, and cut into 2m long strips.

[0062] Example 2:

[0063] In this embodiment, the fastener strip is prepared by extrusion feeding of 1000.0g, including 891.25g of chlorinated polyvinyl chloride resin, 55.0g of carboxylated nitrile rubber, 0.75g of zinc oxide, 3.0g of epoxidized soybean oil, 25.0g of calcium-zinc stabilizer, 20.0g of acrylic processing aid, and 5.0g of oxidized polyethylene wax. The zinc oxide is divided into 0.20g of initial zinc oxide, 0.22g of pre- and post-concentration zinc oxide, and 0.33g of post-concentration zinc oxide.

[0064] Carboxylated nitrile rubber was weighed and placed into a mixing chamber. Nitrogen gas was introduced, and the mixture was plasticized at 60 rpm for 3 minutes until the material temperature reached 130°C. The first portion of zinc oxide was added, and the mixture was further mixed at 130°C for 4 minutes to obtain the base rubber. The base rubber was heated to 145°C, and the first-stage zinc oxide was added and mixed for 3 minutes. Then, epoxidized soybean oil was added and mixed for 10 minutes, followed by the second-stage zinc oxide and mixed for 12 minutes. After unloading, the mixture was pressed into a 2 mm thick sheet at 90°C, cooled to 25°C, and cut into granules with a nominal length of 3 mm.

[0065] Weigh out chlorinated polyvinyl chloride resin, calcium-zinc stabilizer, acrylic processing aid, and oxidized polyethylene wax. Preheat the high-speed mixer to 25°C and set it to 600 r / min. First, add the chlorinated polyvinyl chloride resin and calcium-zinc stabilizer. When the material temperature reaches 70°C, add the acrylic processing aid. When the temperature reaches 95°C, add the oxidized polyethylene wax. When the temperature reaches 110°C, discharge the mixture into the cold mixer and cool it to 45°C at 300 r / min.

[0066] A co-rotating twin-screw extruder with a nominal screw outer diameter of 26 mm and a length-to-diameter ratio of 44:1 was used. 941.25 g of the base dry mix was added through the main feed inlet. The temperatures of the feeding zone, compression zone, homogenization zone, die head, and mold were set to 130℃, 170℃, 175℃, 175℃, and 175℃ respectively. The main extruder speed was 240 r / min, the total feed rate was 3.00 kg / h, and the main feed rate was 2.82 kg / h. After the chlorinated polyvinyl chloride (PVC) had completed its initial fusion, 58.75 g of pre-made additives were added laterally at position 22D at a side feed rate of 0.18 kg / h. The mixture continued to be mixed and extruded through a strip die. The extrudate was processed at 20℃ with a flow rate of 15 m³ / h. 3 The circulating water is shaped at a rate of / h, pulled at 10m / min, and cut into 2m long strips.

[0067] Example 3:

[0068] In this embodiment, the fastener strip is prepared by extrusion feeding of 1000.0g, including 888.75g of chlorinated polyvinyl chloride resin, 55.0g of carboxylated nitrile rubber, 1.25g of zinc oxide, 5.0g of epoxidized soybean oil, 25.0g of calcium-zinc stabilizer, 20.0g of acrylic processing aid, and 5.0g of oxidized polyethylene wax. The zinc oxide is divided into 0.30g of initial zinc oxide, 0.38g of pre- and post-concentration zinc oxide, and 0.57g of post-concentration zinc oxide.

[0069] Carboxylated nitrile rubber was weighed and placed into a mixing chamber. Nitrogen gas was introduced, and the mixture was plasticized at 60 rpm for 3 minutes until the material temperature reached 130°C. The first portion of zinc oxide was added, and the mixture was further mixed at 130°C for 4 minutes to obtain the base rubber. The base rubber was heated to 145°C, and the first-stage zinc oxide was added and mixed for 3 minutes. Then, epoxidized soybean oil was added and mixed for 10 minutes, followed by the second-stage zinc oxide and mixed for 12 minutes. After unloading, the mixture was pressed into a 2 mm thick sheet at 90°C, cooled to 25°C, and cut into granules with a nominal length of 3 mm.

[0070] Weigh out chlorinated polyvinyl chloride resin, calcium-zinc stabilizer, acrylic processing aid, and oxidized polyethylene wax. Preheat the high-speed mixer to 25°C and set it to 600 r / min. First, add the chlorinated polyvinyl chloride resin and calcium-zinc stabilizer. When the material temperature reaches 70°C, add the acrylic processing aid. When the temperature reaches 95°C, add the oxidized polyethylene wax. When the temperature reaches 110°C, discharge the mixture into the cold mixer and cool it to 45°C at 300 r / min.

[0071] A co-rotating twin-screw extruder with a nominal screw outer diameter of 26 mm and a length-to-diameter ratio of 44:1 was used. The base dry mix was added through the main feed inlet. The temperatures of the feeding zone, compression zone, homogenization zone, die head, and mold were set to 130℃, 170℃, 175℃, 175℃, and 175℃ respectively. The main extruder speed was 240 r / min, the total feed rate was 3.00 kg / h, and the main feed rate was 2.82 kg / h. After the chlorinated polyvinyl chloride (PVC) had completed its initial fusion, 61.25 g of pre-made additives were added laterally at position 22D at a side feed rate of 0.18 kg / h. The mixture continued to be mixed and extruded through a strip die. The extrudate was processed at 20℃ with a flow rate of 15 m³ / h. 3 The circulating water is shaped at a rate of / h, pulled at 10m / min, and cut into 2m long strips.

[0072] Comparative Example 1:

[0073] Comparative Example 1 used the same raw material grade, basic dry mixing, extrusion, shaping, traction, cutting and testing conditions as Example 1. The difference was that the preform material in the 1000.0g extrusion formulation contained only 55.0g of carboxylated nitrile rubber and 0.25g of first-part zinc oxide, without subsequent zinc oxide and epoxidized soybean oil, and the total extrusion feed was kept at 1000.0g with 894.75g of chlorinated polyvinyl chloride resin.

[0074] Comparative Example 2

[0075] Comparative Example 2 used the same raw material grade, preparation conditions and testing conditions as Comparative Example 1, the only difference being that 0.75g of chlorinated polyvinyl chloride resin was replaced with 0.75g of zinc oxide by mass.

[0076] Comparative Example 3

[0077] Comparative Example 3 used the same raw material grade, preparation conditions and testing conditions as Comparative Example 1, the only difference being that 4.0g of chlorinated polyvinyl chloride resin was replaced with 4.0g of epoxidized soybean oil by mass.

[0078] Comparative Example 4

[0079] The final raw material composition, extrusion location, extrusion conditions and test conditions of Comparative Example 4 were the same as those of Example 1, except that 55.0g of carboxylated nitrile rubber and 0.25g of the first batch of zinc oxide were prepared into basic rubber granules only according to the pretreatment conditions of Example 1.

[0080] Comparative Example 5

[0081] The final raw material composition, extrusion location, extrusion conditions and test conditions of Comparative Example 5 were the same as those of Example 1, except that 0.75g of subsequent zinc oxide was added once before the epoxidized soybean oil.

[0082] Test results:

[0083] Table 1 shows the properties of the prefabricated materials obtained in the examples and comparative examples with independent prefabricated materials.

[0084] Table 1 Properties of Precast Materials

[0085] sample Acid value (mgKOH / g) Residual epoxy functional group content (mol / 100g) Acetone extractables / % Example 1 11.8 0.0136 2.6 Example 2 15.7 0.0098 3.0 Example 3 8.9 0.0162 2.8 Comparative Example 1 37.6 Not detected 1.9 Comparative Example 2 20.8 Not detected 2.0 Comparative Example 3 27.9 0.0186 5.7 Comparative Example 5 13.4 0.0148 3.4

[0086] like Figure 3 As shown, the prefabricated materials of Comparative Example 1, Comparative Example 5, and Example 1 are all approximately 2235 cm². -1 The sample exhibits a nitrile absorption band; Comparative Example 5 and Example 1, containing epoxidized soybean oil, were measured at 1735 cm⁻¹. -1 and 1700cm -1 There is carbonyl-related absorption nearby, at 830 cm⁻¹ -1 Nearby, epoxy-related absorptions were retained to varying degrees, and at 1590 cm⁻¹-1 and 1415cm -1 The surrounding area exhibits an absorption morphology different from that of Comparative Example 1. Comparative Example 1 has a different pre-formulation composition from the other two groups; Comparative Example 5 has the same pre-formulation composition as Example 1, the difference being whether zinc oxide is added all at once or in stages.

[0087] Table 2 shows the clamping force and repeated fastening integrity rate of the fasteners obtained in each embodiment and comparative example.

[0088] Table 2 Clamping force and repeated fastening integrity rate of fastener strips

[0089] sample Initial clamping force / N Clamping force (N) after being placed at 60℃ for 7 days Clamping force retention rate at 60℃ / % 0℃ repeated fastening integrity rate / % Example 1 140.6 116.7 83.0 95 Example 2 137.8 107.2 77.8 95 Example 3 143.2 121.1 84.6 85 Comparative Example 1 134.1 85.8 64.0 70 Comparative Example 2 142.8 112.8 79.0 55 Comparative Example 3 129.6 76.5 59.0 100 Comparative Example 4 133.5 92.7 69.4 85 Comparative Example 5 137.9 106.2 77.0 90

[0090] Figure 4 The clamping force retention rates of Comparative Examples 4, 5, and 1 after being placed at 60°C for 0, 1, 3, 5, and 7 days are shown. For Comparative Example 4, the retention rates at each time point are 100.0%, 86.8%, 77.8%, 72.4%, and 69.4%, respectively; for Comparative Example 5, the retention rates are 100.0%, 90.9%, 84.8%, 80.4%, and 77.0%, respectively; and for Example 1, the retention rates are 100.0%, 93.4%, 89.0%, 85.7%, and 83.0%, respectively.

[0091] Table 3 shows the extrusion processing status of each embodiment and comparative example under the same equipment evaluation conditions.

[0092] Table 3. Extrusion Processing Status of Fastener Strips

[0093] sample Steady-state main engine torque (N·m) Static thermal stability time at 180℃ / min Number of surface defects per 2m fastener strip 15-minute run color difference ΔE*ab Example 1 64.4 31.9 1 2.0 Example 2 61.5 32.4 0 1.8 Example 3 69.2 30.7 2 2.5 Comparative Example 1 60.8 32.0 1 1.7 Comparative Example 2 67.5 31.4 2 2.0 Comparative Example 3 56.9 30.8 0 1.9 Comparative Example 4 59.8 29.9 3 2.9 Comparative Example 5 64.1 31.8 1 2.0

[0094] Results Analysis

[0095] As shown in Tables 1 and 2, the only difference between Comparative Example 2 and Comparative Example 1 is that 0.75g of chlorinated polyvinyl chloride resin was replaced by 0.75g of zinc oxide. The acid value of the prefabricated material changed from 37.6mgKOH / g to 20.8mgKOH / g; the initial clamping force of the fastener changed from 134.1N to 142.8N, and after being placed at 60℃ for 7 days, the clamping force changed from 85.8N to 112.8N. The clamping force retention rate at 60℃ changed from 64.0% to 79.0%, while the repeated fastening integrity rate at 0℃ changed from 70% to 55%. These results indicate that the subsequent zinc oxide changes the state of the acidic groups in the prefabricated material, which is beneficial for hot clamping retention, but adding this component alone is not conducive to the integrity of repeated fastening at low temperatures.

[0096] As shown in Tables 1 and 2, the only difference between Comparative Example 3 and Comparative Example 1 is that 4.0g of epoxidized soybean oil was used to replace 4.0g of chlorinated polyvinyl chloride resin. The acid value of the preform changed from 37.6mgKOH / g to 27.9mgKOH / g, the residual epoxy functional groups changed from undetectable to 0.0186mol / 100g, and the acetone extractable content changed from 1.9% to 5.7%. The integrity rate of the snap-fit ​​strip after repeated snap-fitting at 0℃ changed from 70% to 100%, while the clamping force after being placed at 60℃ for 7 days changed from 85.8N to 76.5N, and the clamping force retention rate changed from 64.0% to 59.0%. These results indicate that the addition of epoxidized soybean oil alone is beneficial for the integrity of repeated snap-fitting at low temperatures, but not for the retention of clamping force under hot conditions.

[0097] From Table 2, Table 3 and Figure 4 It can be seen that Comparative Example 5 and Comparative Example 4 have the same final raw material composition, extrusion location, extrusion conditions, and testing conditions. The only difference is that the carboxylated nitrile rubber, zinc oxide, and epoxidized soybean oil are pre-mixed and formed into granules. After being placed at 60℃ for 7 days, the clamping force changed from 92.7N to 106.2N, the clamping force retention rate changed from 69.4% to 77.0%, and the repeated fastening integrity rate at 0℃ changed from 85% to 90%. The static thermal stability time at 180℃ changed from 29.9min to 31.8min, the number of surface defects on the 2m fastener strip changed from 3 to 1, the color difference during 15min of operation changed from 2.9 to 2.0, and the steady-state main engine torque changed from 59.8N·m to 64.1N·m. These results indicate that the pre-formed complete additive is beneficial for hot clamping retention and low-temperature fastening integrity, and it changes the extrusion processing state.

[0098] From Tables 1 to 3 and Figure 4It can be seen that the components and their amounts, total mixing time, extrusion location, extrusion conditions, and testing conditions are the same in Example 1 and Comparative Example 5. The only difference is that in Example 1, 0.75g of subsequent zinc oxide was divided into 0.30g and 0.45g, which were added before and after the epoxidized soybean oil, respectively. The acid value of the pre-made additive changed from 13.4mgKOH / g to 11.8mgKOH / g, the residual epoxy functional group content changed from 0.0148mol / 100g to 0.0136mol / 100g, and the acetone extractable content changed from 3.4% to 2.6%. After the buckle was placed at 60℃ for 7 days, the clamping force changed from 106.2N to 116.7N, the clamping force retention rate changed from 77.0% to 83.0%, and the integrity rate of repeated fastening at 0℃ changed from 90% to 95%. The steady-state main engine torque changed from 64.1 N·m to 64.4 N·m, and the static thermal stabilization time at 180℃ changed from 31.8 min to 31.9 min. The number of surface defects and the color difference after 15 minutes of operation remained unchanged. These results indicate that the staged addition of zinc oxide before and after the addition of epoxidized soybean oil can create a pre-formed material state different from that of a single addition, while maintaining both hot clamping retention and low-temperature repeated fastening integrity without causing substantial adverse changes in the extrusion processing state. This may be because the staged addition alters the contact sequence of carboxyl groups, zinc species, and epoxy groups during the mixing process.

[0099] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high-temperature resistant chlorinated polyvinyl chloride (PVC) strip for underfloor heating floors, wherein the strip is a long extruded part, the cross-section of which includes a flat bottom plate, two clamping arms respectively connected to both sides of the flat bottom plate and bent upwards, and limiting lips respectively disposed at the ends of the two clamping arms, the two clamping arms and the flat bottom plate forming an open groove, characterized in that, Based on a total raw material quantity of 100 parts by weight for preparing the buckle strip, the raw material includes 5.5 parts by weight of carboxylated nitrile rubber, 0.075~0.125 parts by weight of zinc oxide, 0.30~0.50 parts by weight of epoxidized soybean oil, 2.5 parts by weight of calcium-zinc stabilizer, 2.0 parts by weight of acrylic acid processing aid, 0.5 parts by weight of oxidized polyethylene wax, and the balance being chlorinated polyvinyl chloride resin. The mass ratio of zinc oxide to epoxidized soybean oil is 1:

4. Before being mixed with the chlorinated polyvinyl chloride resin, the carboxylated nitrile rubber, zinc oxide, and epoxidized soybean oil are first separately prepared into a zinc oxide-epoxidized soybean oil treated carboxylated nitrile rubber pre-additive.

2. The high-temperature resistant chlorinated polyvinyl chloride (PVC) strip for underfloor heating floors according to claim 1, characterized in that, The zinc oxide comprises a first zinc oxide, a pre-stage subsequent zinc oxide, and a post-stage subsequent zinc oxide; based on the total mass of the zinc oxide as 100%, the first zinc oxide, the pre-stage subsequent zinc oxide, and the post-stage subsequent zinc oxide account for 24%~27%, 29%~31%, and 43%~47%, respectively, and the sum of the three percentages is 100%; the first zinc oxide is first mixed with the carboxylated nitrile rubber, the pre-stage subsequent zinc oxide is added before the epoxidized soybean oil, and the post-stage subsequent zinc oxide is added after the epoxidized soybean oil is mixed.

3. The high-temperature resistant chlorinated polyvinyl chloride (PVC) strip for underfloor heating as described in claim 2, characterized in that, The fastener is manufactured as follows: a basic dry mix containing the chlorinated polyvinyl chloride resin, the calcium-zinc stabilizer, the acrylic processing aid, and the oxidized polyethylene wax is added through the main feed port of a co-rotating twin-screw extruder. After the chlorinated polyvinyl chloride resin has completed its initial fusion, the pre-made additive is added laterally at position 22D. The mixture is then further mixed and extruded through a fastener die. Wherein, D represents the nominal outer diameter of the screw of the co-rotating twin-screw extruder, and the position 22D is the position where the distance from the axial reference plane at the beginning of the screw working section to the center line of the side feed port is 22 times D.

4. The high-temperature resistant chlorinated polyvinyl chloride (PVC) strip for underfloor heating floors according to claim 3, characterized in that, Based on a total raw material quantity of 100 parts by weight for preparing the buckle strip, the amounts of the chlorinated polyvinyl chloride resin, the carboxylated nitrile rubber, the zinc oxide, the epoxidized soybean oil, the calcium-zinc stabilizer, the acrylic processing aid, and the oxidized polyethylene wax are 89.0 parts by weight, 5.5 parts by weight, 0.10 parts by weight, 0.40 parts by weight, 2.5 parts by weight, 2.0 parts by weight, and 0.5 parts by weight, respectively; based on a total zinc oxide mass of 100%, the initial zinc oxide, the preceding subsequent zinc oxide, and the subsequent subsequent zinc oxide account for 25%, 30%, and 45%, respectively.

5. A method for preparing a high-temperature resistant chlorinated polyvinyl chloride (PVC) strip for underfloor heating floors, characterized in that, Includes the following steps: (1) Plasticize the carboxylated butadiene-acrylonitrile rubber under a nitrogen atmosphere, add the first part of zinc oxide and mix to obtain the base rubber; (2) Heat the base adhesive and add the first-stage zinc oxide, the epoxidized soybean oil and the second-stage zinc oxide in sequence for mixing. The first-stage zinc oxide is added before the epoxidized soybean oil and the second-stage zinc oxide is added after the epoxidized soybean oil is mixed. The resulting material is pressed into tablets, cooled and granulated to obtain an independent pre-made additive. (3) The chlorinated polyvinyl chloride resin and the calcium-zinc stabilizer are added to a high-speed mixer. During the material heating process, the acrylic acid processing aid and the oxidized polyethylene wax are added in sequence. Then the material is discharged and cooled to obtain a basic dry mix. (4) The basic dry mix is ​​added through the main feed port of the co-rotating twin-screw extruder. After the chlorinated polyvinyl chloride resin has completed the initial fusion, the pre-made additive is added laterally at position 22D. The mixture is then further mixed and extruded through a snap-on die. Here, D represents the nominal outer diameter of the screw of the co-rotating twin-screw extruder. The position 22D is the position where the distance from the axial reference plane at the beginning of the screw working section to the center line of the side feed port is 22 times D. (5) The extruded fastener is sequentially shaped by circulating water, pulled and cut to a fixed length; the resulting fastener is a long extruded part, the chlorinated polyvinyl chloride resin constitutes the continuous phase of the fastener material, the cross section of the long extruded part includes a flat bottom plate, two clamping arms that are respectively connected to both sides of the flat bottom plate and bent upward, and limiting lips that are respectively set at the ends of the two clamping arms, the two clamping arms and the flat bottom plate form an opening groove.

6. The preparation method according to claim 5, characterized in that, In step (1), the carboxylated nitrile rubber is plasticized at 60 r / min for 3 min and the material temperature reaches 130°C. The first zinc oxide is added and mixed for 4 min. In step (2), the base rubber is heated to 145°C. The first-stage subsequent zinc oxide is added and mixed for 3 min. The epoxidized soybean oil is added and mixed for 10 min. The second-stage subsequent zinc oxide is added and mixed for 12 min. The resulting material is pressed into a sheet with a thickness of 2 mm at 90°C, cooled to 25°C and cut into granules with a nominal length of 3 mm.

7. The preparation method according to claim 6, characterized in that, In step (3), the high-speed mixer is preheated to 25°C and the rotation speed is set to 600 r / min. The chlorinated polyvinyl chloride resin and the calcium zinc stabilizer are added first. When the material temperature rises to 70°C, the acrylic acid processing aid is added. When the material temperature rises to 95°C, the oxidized polyethylene wax is added. When the material temperature rises to 110°C, it is discharged into the cold mixer and cooled to 45°C at 300 r / min.

8. The preparation method according to claim 7, characterized in that, In step (4), the nominal outer diameter of the screw of the co-rotating twin-screw extruder is 26 mm, the length-to-diameter ratio is 44:1, the temperature of the feeding zone is 130℃, the temperature of the compression zone is 170℃, the temperature of the homogenization zone is 175℃, the die head temperature is 175℃, the die temperature is 175℃, and the main machine speed is 240 r / min; in step (5), the circulating water temperature is 20℃, and the circulating water flow rate is 15 m³ / min. 3 / h, traction speed is 10m / min.

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