Anti-static PVC (polyvinyl chloride) rubber mat as well as preparation method and application thereof

Abstract

The invention discloses an anti-static PVC (polyvinyl chloride) rubber mat as well as a preparation method and application thereof, and relates to the field of PVC rubber mats. The rubber mat comprises an anti-static surface layer and a conductive bottom layer which are tightly attached, wherein the conductive bottom layer adopts acetylene carbon black and carbon nanotube composite conductive filler which is synergistically modified by a silane coupling agent and a dispersing agent. During preparation, the composite conductive filler is prepared through ultrasonic dispersion, nitric acid activation and high-temperature shearing modification, then the surface layer raw material and the bottom layer raw material are mixed, melted and plasticized respectively, and a finished product is prepared through hot-pressing compounding, cooling and cutting. Through the composite conductive network and the layered design, the problems of agglomeration, poor compatibility and fast performance attenuation of traditional conductive carbon black are solved, and the conductive carbon black has efficient and stable antistatic performance and excellent interface bonding force and mechanical flexibility, and is suitable for table rubber or floor rubber electrostatic protection scenes in the industries of electronic manufacturing, semiconductor packaging and the like.

Description

Technical Field

[0001] This invention relates to the field of PVC pads, and particularly to an antistatic PVC pad, its preparation method, and its application. Background Technology

[0002] In precision electronics industries such as electronics manufacturing and semiconductor packaging, electrostatic discharge (ESD) protection is a crucial step in the production process. Static electricity has a certain impact on electronic components, integrated circuits, and other products. Furthermore, static electricity can attract dust, causing dust to adhere to products. Anti-static PVC mats (including table mats and floor mats) have become the mainstream material for ESD protection of work surfaces and floors in electronics factories due to their cost-effectiveness and ease of installation. They are primarily achieved by adding conductive fillers to the PVC matrix, using these fillers to create electrostatic conduction pathways.

[0003] Conductive carbon black is a commonly used conductive filler. However, due to the polar groups on its surface and the strong intermolecular forces, it easily forms aggregates in the PVC resin matrix, making it difficult to disperse evenly. This prevents static electricity from being quickly and uniformly dissipated from the surface of the pad. Furthermore, conductive carbon black is an inorganic filler, while PVC resin is a non-polar organic polymer, resulting in weak interfacial affinity and a lack of effective interfacial bonding. During long-term use, conductive carbon black easily precipitates and detaches from the PVC resin matrix, causing the originally constructed conductive pathways to break. Simultaneously, the conductive network formed by a single conductive carbon black component lacks stability, and the surface resistance gradually increases with prolonged use, affecting the antistatic performance.

[0004] In existing technologies, the amount of conductive carbon black added can be increased to improve the conductive pathway. However, excessive conductive carbon black can lead to decreased flexibility and increased brittleness of the adhesive pad. At the same time, high addition amounts increase raw material costs and further exacerbate agglomeration problems.

[0005] It is evident that existing technologies still need improvement and enhancement. Summary of the Invention

[0006] In view of the technical problems such as severe agglomeration and poor compatibility of existing conductive carbon black in PVC pad applications, the purpose of this invention is to develop an antistatic PVC pad that can achieve uniform dispersion of conductive fillers, stable interfacial bonding, and long-lasting and efficient conductivity, as well as its preparation method and application, so as to meet the requirements of electrostatic protection in electronic manufacturing.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: An antistatic PVC pad includes an antistatic surface layer and a conductive bottom layer tightly adhered to the lower surface of the antistatic surface layer. The antistatic surface layer comprises the following raw materials in parts by weight: 100 parts PVC resin, 3-8 parts antistatic agent, 20-40 parts plasticizer, 1-3 parts calcium-zinc stabilizer, and 0.5-2 parts lubricant. The conductive bottom layer comprises the following raw materials in parts by weight: 100 parts PVC resin, 16-25 parts composite conductive filler, 15-30 parts plasticizer, and 1-3 parts calcium-zinc stabilizer. The composite conductive filler is acetylene black and carbon nanotubes modified with silane coupling agent and dispersant.

[0008] The antistatic PVC pad, wherein the modification process of the composite conductive filler is as follows: acetylene black and carbon nanotubes are added to anhydrous ethanol and ultrasonically dispersed to form a suspension; nitric acid solution is added to the suspension and heated; silane coupling agent and dispersant are added to the suspension, the temperature is raised, and the mixture is stirred and dispersed; the filter residue obtained after filtering the suspension is dried, pulverized, and sieved.

[0009] The antistatic PVC pad, wherein the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane, and the dispersant is polyethylene glycol with a molecular weight of 400.

[0010] In the aforementioned antistatic PVC pad, by weight, during the modification process of the composite conductive filler, the acetylene black comprises 15-25 parts; the carbon nanotubes comprise 1-3 parts; the silane coupling agent comprises 2-4 parts; the dispersant comprises 1-2 parts; the anhydrous ethanol comprises 100-150 parts; and the nitric acid solution comprises 0.5-1 part with a concentration of 5%.

[0011] The antistatic PVC pad, wherein the acetylene black has a particle size of 20-50 nm, and the carbon nanotubes have an outer diameter of 10-20 nm and a length of 1-5 μm.

[0012] In the antistatic PVC pad, during the modification process of the composite conductive filler, after adding nitric acid solution, the suspension is heated to 60-65℃ and kept at that temperature for 30-35 minutes; after adding silane coupling agent and dispersant, the suspension is heated to 80-85℃ and sheared and dispersed for 60-70 minutes; the filter residue is dried at 100-110℃ for 2-3 hours and then passed through a 200-mesh sieve.

[0013] The antistatic PVC pad, wherein the antistatic agent is hexadecyltrimethylammonium chloride, bis(octadecyl)dimethylammonium chloride, dodecyldimethylbenzylammonium chloride, or octadecyltrimethylammonium bromide; the plasticizer is epoxy castor oil, diisononyl cyclohexane 1,2-dicarboxylate, or dibutyl adipate; and the lubricant is stearic acid or butyl stearate.

[0014] The antistatic PVC pad has an antistatic surface layer with a thickness of 0.8–2.5 mm and a conductive bottom layer with a thickness of 0.7–2.5 mm.

[0015] A method for preparing an antistatic PVC mat includes the following steps: mixing the raw materials for the antistatic top layer and the conductive bottom layer at 80-100°C for 15-30 minutes; adding the two sets of raw materials into an extruder and melting and plasticizing them at 160-180°C, extruding them to form a top layer blank and a bottom layer blank; hot-pressing the top layer blank and the bottom layer blank together at 150-170°C and 5-10 MPa, and then cooling them to obtain the above-mentioned antistatic PVC mat.

[0016] An application of an antistatic PVC mat is described, in which the aforementioned antistatic PVC mat is applied to a tabletop or floor mat; when the antistatic PVC mat is applied to a floor mat, the surface of the antistatic layer is formed with anti-slip texture.

[0017] Beneficial effects: This invention provides an antistatic PVC pad, its preparation method, and its application, which have the following advantages: 1. This invention constructs a dense and continuous three-dimensional conductive network through the synergistic enhancement and modification process of composite conductive fillers, which is beneficial to improving electrostatic conduction efficiency. Compared with existing technologies, the adhesive pad can not only quickly adsorb and dissipate surface static electricity, but also maintain stable antistatic performance over a long period of time, effectively avoiding the problem of increased surface resistance due to prolonged use.

[0018] 2. After being modified by silane coupling agent and dispersant, the composite conductive filler has improved compatibility with PVC resin. The modified filler can be uniformly dispersed in the resin matrix and is not easy to precipitate or fall off, making the antistatic surface layer and the conductive bottom layer more firmly bonded. This avoids problems such as delamination and breakage of conductive paths during long-term use and extends the service life of the pad.

[0019] 3. This invention utilizes the conductive bridging effect of carbon nanotubes to achieve a reduced amount of composite conductive filler, achieving excellent conductivity without relying on high doses of conductive carbon black. Simultaneously, through the synergistic effect of plasticizers, calcium-zinc stabilizers, and the filler system, the pad possesses both good flexibility and structural strength, avoiding the increased brittleness and cracking problems caused by traditional high carbon black additions. This makes it more suitable for practical applications such as work surfaces with frequent contact and foot traffic. Attached Figure Description

[0020] Figure 1 This is a photograph of the antistatic surface layer in an antistatic PVC pad.

[0021] Figure 2This is a picture of an antistatic PVC pad after it has been folded. The green part is the antistatic surface layer, and the black part is the conductive bottom layer. Detailed Implementation

[0022] This invention provides an antistatic PVC pad, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0023] Please see Figure 1 and Figure 2 This invention provides an antistatic PVC pad, comprising an antistatic surface layer and a conductive underlayer tightly adhered to the lower surface of the antistatic surface layer; the antistatic surface layer comprises the following raw materials in parts by weight: 100 parts PVC resin, 3-8 parts antistatic agent, 20-40 parts plasticizer, 1-3 parts calcium-zinc stabilizer, and 0.5-2 parts lubricant; the conductive underlayer comprises the following raw materials in parts by weight: 100 parts PVC resin, 16-25 parts composite conductive filler, 15-30 parts plasticizer, and 1-3 parts calcium-zinc stabilizer; the composite conductive filler is acetylene black and carbon nanotubes modified with silane coupling agent and dispersant.

[0024] In the antistatic surface layer, quaternary ammonium salts are selected as the antistatic agent, which quickly adsorbs and transfers surface static electricity and has good compatibility with PVC, preventing migration. Plasticizers lower the glass transition temperature and melt viscosity of PVC resin, improving the surface layer's flexibility, impact resistance, and processing fluidity, making it easier to mold during processing. They also prevent cracking of the pads due to the brittleness of PVC resin and, when working synergistically with the antistatic agent, do not affect ionic conductivity, ensuring a balance between antistatic and mechanical properties. Calcium-zinc stabilizers, as stabilizing components, inhibit thermal degradation and oxidative aging of PVC resin during subsequent processing, preventing surface layer performance deterioration caused by resin molecular chain breakage. They also improve the compatibility of the antistatic agent, plasticizer, and PVC resin, reducing component migration and extending the surface layer's service life. Lubricants, as processing aids, reduce friction between the PVC resin melt and equipment during processing, as well as internal friction between resin molecular chains, improving the surface layer's molding efficiency. Specifically, 1-5 parts of colorant can be added according to actual needs.

[0025] In the conductive substrate, a composite conductive filler system composed of acetylene black and carbon nanotubes is employed. This system is modified using a combination of silane coupling agent and dispersant. The silane coupling agent bonds to the polar groups on the surfaces of the carbon black and carbon nanotubes at one end, reducing the surface energy of the filler, while the other end forms physical entanglement with the non-polar PVC resin molecular chains, improving the compatibility between the filler and the resin and preventing secondary agglomeration. The dispersant further optimizes the dispersion of the filler in the resin matrix, controlling the particle size of the composite conductive filler agglomerates to below the micrometer level, ensuring uniform distribution of conductive particles. Simultaneously, carbon nanotubes, as one-dimensional nanomaterials, act as conductive bridges in the system due to their high aspect ratio, connecting the dispersed acetylene black particles to construct a point-line combined three-dimensional conductive network, achieving high conductivity without relying on high amounts of carbon black. Plasticizers, as processing and interface optimization components, can reduce the viscosity of the underlying PVC resin, improve the dispersibility and processability of the composite conductive filler, and enhance the flexibility and adhesion of the underlying layer to the top layer, preventing the breakage of conductive pathways due to the brittleness of the underlying layer. Their addition amount is lower than that of the top layer, balancing the structural strength and conductive stability of the underlying layer. Calcium-zinc stabilizers prevent thermal aging and oxidative degradation of the underlying PVC resin during processing and long-term use, avoiding the detachment of conductive fillers caused by resin matrix embrittlement; they also improve the compatibility of the composite conductive filler with the resin, ensuring the long-term stability of the conductive network.

[0026] In some embodiments, the antistatic agent is hexadecyltrimethylammonium chloride, dioctadecyldimethylammonium chloride, dodecyldimethylbenzylammonium chloride, or octadecyltrimethylammonium bromide. The antistatic agent selected is a quaternary ammonium salt cationic antistatic agent, which can quickly adsorb static electricity on the surface of the pad through an ionic conductivity mechanism and efficiently transfer it to the underlying conductive layer; moreover, the long-chain alkyl groups in its molecular structure can form physical entanglement with the PVC resin molecular chains, exhibiting excellent compatibility and effectively preventing migration and loss, ensuring the long-lasting and stable antistatic performance of the surface layer.

[0027] In some embodiments, the plasticizer is epoxy castor oil, diisononyl cyclohexane 1,2-dicarboxylate, or dibutyl adipate. Epoxy castor oil, as an environmentally friendly polymer plasticizer, has strong epoxy group stability, excellent compatibility with PVC resin, no VOC release, meets environmental protection requirements, and its temperature resistance is suitable for the PVC processing temperature of 160-180℃. It can improve the flexibility and anti-aging properties of the pad, and has no component interference with quaternary ammonium salt antistatic agents and composite conductive fillers, and will not damage the conductive network or affect the electrostatic conduction efficiency. Diisononyl cyclohexane 1,2-dicarboxylate (DINCH) is a low-migration, environmentally friendly plasticizer with good mixing uniformity with PVC resin and outstanding low-temperature toughness, which can prevent the pad from becoming brittle and cracking under different environments. At the same time, its chemical properties are stable, and it is compatible with the composite conductive filler in the conductive underlayer, ensuring the continuity of the conductive path. Dibutyl adipate (DBA) has good conductivity compatibility, strong synergy with PVC resin and composite conductive fillers, does not hinder the construction of conductive networks, and can improve the impact resistance of the pad. It is relatively affordable and has excellent processing fluidity, which can optimize the molding effect of the pad.

[0028] In some embodiments, the lubricant is stearic acid or butyl stearate. Stearic acid, as a commonly used fatty acid lubricant, exhibits good compatibility with PVC resin, quaternary ammonium salt antistatic agents, composite conductive fillers, and selected plasticizers. Its lubrication mechanism combines internal and external lubrication, effectively reducing the internal friction between PVC resin molecular chains and the external friction between the resin melt and processing equipment, improving the flowability and molding efficiency during pad processing, and ensuring uniform performance between the antistatic surface layer and the conductive underlayer. Butyl stearate, as an ester derivative of stearic acid, provides a milder and more durable lubrication effect. Its compatibility with PVC resin is further optimized, and its low migration characteristics prevent precipitation or penetration into the underlying conductive layer, thus avoiding damage to the conductive pathways formed by the conductive filler. Furthermore, its temperature resistance is suitable for PVC processing temperatures, exhibiting strong thermal stability and preventing decomposition and volatilization during processing.

[0029] Specifically, the thickness of the antistatic surface layer is 0.8–2.5 mm, and the thickness of the conductive underlayer is 0.7–2.5 mm. This thickness of the antistatic surface layer provides ample dispersion space for the quaternary ammonium salt antistatic agent, ensuring efficient adsorption and transfer of surface static electricity, while also ensuring good flexibility and wear resistance, suitable for the daily use of work surfaces or floors. The aforementioned thickness of the conductive underlayer fully encapsulates the composite conductive filler, providing a stable carrier for the construction of the three-dimensional conductive network, ensuring rapid static electricity dissipation, while also considering the structural strength of the underlayer and the tightness of the adhesion between the antistatic surface layer. This combination of two layer thicknesses allows for flexible adaptation to different application scenarios for tabletops and floors, balancing antistatic performance with overall durability.

[0030] In some embodiments, the modification process of the composite conductive filler is as follows: 15-25 parts of acetylene black and 1-3 parts of carbon nanotubes are added to 100-150 parts of anhydrous ethanol, and the mixture is ultrasonicated for 20-25 minutes in an ultrasonic disperser with a power of 300W and a frequency of 40kHz to form a suspension. This step utilizes the ultrasonic cavitation effect to disintegrate the acetylene black aggregates and carbon nanotube entanglements, initially achieving uniform suspension of both. 0.5-1 parts of a 5% nitric acid solution are added to the suspension, and the mixture is kept at 60-65℃ for 30-35 minutes. This activates polar groups on the filler surface through weak oxidation, providing active sites for subsequent grafting of modifiers. Next, add 2-4 parts of silane coupling agent and 1-2 parts of dispersant to the suspension. Heat the suspension to 80-85℃ and use a high-speed shear dispersant for 60-70 minutes. The silane coupling agent modifies the filler surface to improve compatibility with PVC, the dispersant optimizes the dispersion effect, and the high-speed shear further breaks down fine agglomerates, simultaneously completing modification and in-situ composite. Finally, vacuum filter the suspension to remove impurities. Dry the filter residue at 100-110℃ for 2-3 hours, pulverize it, and pass it through a 200-mesh sieve to obtain a composite conductive filler with uniform particle size.

[0031] Specifically, the acetylene black has a particle size of 20–50 nm, and the carbon nanotubes have an outer diameter of 10–20 nm and a length of 1–5 μm. Acetylene black within this particle size range has a moderate specific surface area, excellent conductivity, and provides sufficient conductive nodes while avoiding the problem of agglomeration caused by excessively small particle size. The carbon nanotubes, limiting their outer diameter and length, fully utilize their high aspect ratio, efficiently acting as conductive bridges to connect dispersed acetylene black particles, constructing a dense and continuous three-dimensional conductive network. This avoids entanglement and agglomeration caused by excessively large outer diameters or lengths, or reduced efficiency in constructing conductive pathways due to excessively small sizes. This size combination achieves high conductivity with an addition amount of 16–25 parts, without the need for excessive filler addition. It balances conductivity and pad flexibility, and is compatible with subsequent modification processes, ensuring sufficient surface modification of the filler and stable interfacial bonding with PVC resin, ultimately guaranteeing the long-lasting and efficient antistatic performance of the pad.

[0032] In this embodiment, the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane (KH-570). One end of the KH-570 molecule contains a trimethoxysilane group, which can chemically bond with polar groups activated by nitric acid on the surface of acetylene black and carbon nanotubes. The other end contains a double bond structure, which can cross-link with the resin molecular chain during PVC processing, effectively reducing the surface energy of the filler, breaking up agglomeration, and improving the interfacial bonding force between inorganic fillers and organic PVC resin. This prevents filler precipitation during long-term use and ensures the stability of the conductive network.

[0033] In this embodiment, the dispersant is polyethylene glycol (PEG-400) with a molecular weight of 400. PEG-400, as a nonionic dispersant, has a moderate molecular weight and good solubility. It can further suppress secondary agglomeration of fillers during modification through steric hindrance. Simultaneously, its hydrophilic-hydrophobic balanced structure is compatible with PVC resin and the selected plasticizer, without interfering with the conductive network construction or the ion conduction efficiency of the antistatic agent. Its synergistic effect with KH-570 can achieve uniform and stable dispersion of the composite conductive filler.

[0034] This invention also provides a method for preparing antistatic PVC mats, comprising the following steps: mixing the raw materials for the antistatic surface layer and the conductive bottom layer at 80–100°C for 15–30 min respectively; adding the two sets of raw materials separately into an extruder and melting and plasticizing them at 160–180°C, extruding to form a surface layer preform and a bottom layer preform; hot-pressing the surface layer preform and the bottom layer preform together at 150–170°C and 5–10 MPa to form a two-layer composite substrate. When preparing the antistatic PVC floor mat, during the composite calendering process, the upper surface of the antistatic surface layer is embossed using a calender with embossing rollers to form anti-slip textures. The composite substrate is fed into a cooling roller group for cooling and cut according to usage requirements to obtain the finished product.

[0035] The present invention also provides an application of antistatic PVC mats, which are applied to tabletops or floor mats.

[0036] To further illustrate the antistatic PVC pad, its preparation method, and its application provided by the present invention, the following embodiments and comparative examples are provided.

[0037] Example 1 An antistatic PVC tabletop adhesive comprises an antistatic top layer (2.0 mm thick) and a conductive bottom layer (2.2 mm thick). The antistatic top layer comprises the following raw materials in parts by weight: 100 parts PVC resin, 6 parts antistatic agent (hexadecyltrimethylammonium chloride), 32 parts plasticizer (diisononyl cyclohexane 1,2-dicarboxylate), 2 parts calcium-zinc stabilizer, and 1.2 parts lubricant (stearic acid). The conductive bottom layer comprises the following raw materials in parts by weight: 100 parts PVC resin, 20 parts composite conductive filler, 22 parts plasticizer (diisononyl cyclohexane 1,2-dicarboxylate), and 1.5 parts calcium-zinc stabilizer.

[0038] The modification process of the composite conductive filler is as follows: 19 parts of acetylene black and 1 part of carbon nanotubes were added to 120 parts of anhydrous ethanol and ultrasonicated for 22 minutes in an ultrasonic disperser with a power of 300W and a frequency of 40kHz to form a suspension. 0.7 parts of 5% nitric acid solution were added to the suspension and kept at 62℃ for 32 minutes. Then, 3 parts of silane coupling agent (KH-570) and 1.5 parts of dispersant (PEG-400) were added to the suspension, and the suspension was heated to 82℃ and sheared with a high-speed shear dispersant for 65 minutes. Finally, the suspension was vacuum filtered, and the filter residue was dried at 105℃ for 2.5 hours, pulverized, and passed through a 200-mesh sieve.

[0039] Example 2 An antistatic PVC tabletop adhesive comprises an antistatic top layer (2.2 mm thick) and a conductive bottom layer (2.0 mm thick); the antistatic top layer comprises the following raw materials in parts by weight: 100 parts PVC resin, 4 parts antistatic agent (bis(octadecyldimethylammonium chloride)), 25 parts plasticizer (dibutyl adipate), 1 part calcium-zinc stabilizer, and 0.8 parts lubricant (butyl stearate); the conductive bottom layer comprises the following raw materials in parts by weight: 100 parts PVC resin, 23 parts composite conductive filler, 18 parts plasticizer (dibutyl adipate), and 2.5 parts calcium-zinc stabilizer.

[0040] The modification process of the composite conductive filler is as follows: 21 parts of acetylene black and 2 parts of carbon nanotubes were added to 140 parts of anhydrous ethanol and ultrasonicated for 25 minutes in an ultrasonic disperser with a power of 300W and a frequency of 40kHz to form a suspension. 1 part of a 5% nitric acid solution was added to the suspension, and the mixture was kept at 65℃ for 35 minutes. Then, 3.5 parts of silane coupling agent (KH-570) and 1.2 parts of dispersant (PEG-400) were added to the suspension, and the suspension was heated to 85℃ and sheared for 60 minutes using a high-speed shear dispersant. Finally, the suspension was vacuum filtered, and the filter residue was dried at 110℃ for 2 hours, pulverized, and passed through a 200-mesh sieve.

[0041] Example 3 An antistatic PVC floor mat includes an antistatic surface layer (2.1 mm thick) and a conductive underlayer (2.0 mm thick). The surface of the antistatic surface layer is embossed with anti-slip texture. The antistatic surface layer comprises the following raw materials in parts by weight: 100 parts PVC resin, 7 parts antistatic agent (dodecyl dimethyl benzyl ammonium chloride), 38 parts plasticizer (epoxy castor oil), 2.8 parts calcium-zinc stabilizer, and 1.8 parts lubricant (stearic acid). The conductive underlayer comprises the following raw materials in parts by weight: 100 parts PVC resin, 18 parts composite conductive filler, 28 parts plasticizer (epoxy castor oil), and 1.2 parts calcium-zinc stabilizer.

[0042] The modification process of the composite conductive filler is as follows: 17 parts of acetylene black and 1 part of carbon nanotubes were added to 110 parts of anhydrous ethanol, and the mixture was ultrasonically dispersed in an ultrasonic disperser with a power of 300W and a frequency of 40kHz for 20 minutes to form a suspension. 0.5 parts of 5% nitric acid solution were added to the suspension, and the mixture was kept at 60℃ for 35 minutes. Then, 2.5 parts of silane coupling agent (KH-570) and 1.8 parts of dispersant (PEG-400) were added to the suspension, and the suspension was heated to 80℃ and sheared with a high-speed shear dispersant for 70 minutes. Finally, the suspension was vacuum filtered, and the filter residue was dried at 100℃ for 3 hours, pulverized, and passed through a 200-mesh sieve.

[0043] Comparative Example 1 The conductive filler consisted of 19 parts acetylene black and 1 part carbon nanotubes. In Comparative Example 1, the conductive filler was not modified, and other aspects were the same as in Example 1.

[0044] Comparative Example 2 The conductive filler was 19 parts of acetylene carbon black modified with silane coupling agent and dispersant, and the rest was the same as in Example 1.

[0045] The samples prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to the following performance tests, and the test data are shown in Table 1.

[0046] 1. Surface resistance test: In an environment with a temperature of 23℃ and a relative humidity of 50%, a high resistance meter is used. According to the standard of "General Specification for Antistatic Flooring and Laying Materials", 5 test points are evenly selected on the surface of each sample (antistatic surface layer). A voltage of 100V is applied and the data is recorded after stabilizing for 1 minute. The average value is taken.

[0047] 2. Static dissipation time test: Under an environment of 23℃ and 50% relative humidity, a static dissipation time tester was used. The sample was grounded, and a 5kV static voltage was applied to the sample surface. The time required for the static voltage to decay from 5kV to 50V was recorded. Each sample was tested 3 times, and the average value was taken.

[0048] 3. Peel strength test: According to the standard "Test method for 180° peel strength of adhesives", the sample is cut into strips 15mm wide along the thickness direction. A universal tensile testing machine is used to perform a 180° peel test at a tensile speed of 50mm / min. The maximum force value during the peel process is recorded, and the peel strength (N / mm) is calculated. Three samples are tested for each sample, and the average value is taken.

[0049] 4. Mechanical property testing (Shore hardness, elongation at break): Shore hardness: According to GB / T 2411-2008 standard, a Shore A hardness tester was used. Five test points were evenly selected on the sample surface. Each point was pre-pressed for 3 seconds before testing. The data were recorded and the average value was taken. Elongation at break: According to GB / T 1040.3-2006 standard, the sample was cut into dumbbell-shaped specimens (narrow neck width 4mm), and tested with a universal tensile testing machine at a tensile speed of 50mm / min. The ratio of the elongation at break to the initial length was recorded. Three specimens were tested for each sample, and the average value was taken.

[0050] 5. Antistatic Performance Degradation Test (Accelerated Aging Test): Place the sample in an aging test chamber, set the temperature to 70℃ and the relative humidity to 85%, and conduct a 1000-hour accelerated aging test. After aging, remove the sample and place it in a standard environment (23℃, 50%RH) for 24 hours. Then, test it according to the "Surface Resistance Test" and "Static Dissipation Time Test" methods, and calculate the performance degradation rate (degradation rate = (value before aging - value after aging) / value before aging × 100%). Because the surface resistance increases and the static dissipation time prolongs after aging, the results are all negative. The negative sign indicates performance degradation, and the smaller the absolute value, the better the stability.

[0051] Table 1 Summary of Test Data

[0052] Regarding antistatic performance: the surface resistance of each embodiment is superior to that of the comparative example, and the static dissipation time is faster than that of the comparative example. Although single modified carbon black (Comparative Example 2) or unmodified composite filler (Comparative Example 1) can meet the antistatic requirements, the continuity of the conductive network is insufficient. However, this invention improves the electrostatic conduction efficiency by using synergistic modification of silane coupling agent and dispersant, as well as the point-line composite formed by acetylene carbon black and carbon nanotubes to make the conductive pathway denser.

[0053] Regarding interface and long-term stability: the peel strength of each embodiment was higher than that of the comparative example, indicating that the modified filler has better compatibility with PVC resin and a stronger bond between the top and bottom layers, thus preventing delamination during long-term use. After accelerated aging, the surface resistance decay rate of each embodiment was lower than that of the comparative example, demonstrating the durability of the conductive network of the present invention. Although the comparative example met the initial performance requirements, its performance was prone to degradation during subsequent use due to filler precipitation and pathway breakage. The present invention can extend the service life of the pad.

[0054] In terms of mechanical properties: the elongation at break and Shore hardness of this embodiment are moderate. The carbon nanotubes added in this application act as conductive bridges, which can reduce the total amount of filler added. Excellent conductivity can be achieved without adding a high amount of carbon black, avoiding the problems of embrittlement and cracking of the pads caused by traditional high carbon black addition (usually more than 30 parts). It is more suitable for the actual use needs of frequent contact on the work surface and personnel walking on the ground.

[0055] The main reasons for the differences in comparative performance: Comparative Example 1: The polar groups on the filler surface were not modified, resulting in strong intermolecular forces, easy aggregation to form conductive blind areas, poor compatibility with PVC resin, and weak interfacial bonding, leading to the worst antistatic performance, peel strength, and long-term stability.

[0056] Comparative Example 2: The carbon black dispersion was improved by modification, but the conductive bridging effect of carbon nanotubes was lacking. The conductive network was only point-to-point contact with insufficient continuity. Therefore, the antistatic response speed and long-term stability were still inferior to those of the Example.

[0057] It is understood that those skilled in the art can make equivalent substitutions or changes to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. An antistatic PVC pad, characterized in that, The device includes an antistatic surface layer and a conductive underlayer that is tightly adhered to the lower surface of the antistatic surface layer. The antistatic surface layer comprises the following raw materials in parts by weight: 100 parts PVC resin, 3-8 parts antistatic agent, 20-40 parts plasticizer, 1-3 parts calcium-zinc stabilizer, and 0.5-2 parts lubricant. The conductive underlayer comprises the following raw materials in parts by weight: 100 parts PVC resin, 16-25 parts composite conductive filler, 15-30 parts plasticizer, and 1-3 parts calcium-zinc stabilizer. The composite conductive filler is acetylene black and carbon nanotubes modified with silane coupling agent and dispersant.

2. The antistatic PVC pad according to claim 1, characterized in that, The modification process of the composite conductive filler is as follows: acetylene black and carbon nanotubes are added to anhydrous ethanol and ultrasonically dispersed to form a suspension; nitric acid solution is added to the suspension and heated; silane coupling agent and dispersant are added to the suspension, the temperature is raised, and the mixture is stirred and dispersed; the filter residue obtained after filtering the suspension is dried, crushed, and sieved.

3. The antistatic PVC pad according to claim 2, characterized in that, The silane coupling agent is γ-methacryloxypropyltrimethoxysilane, and the dispersant is polyethylene glycol with a molecular weight of 400.

4. The antistatic PVC pad according to claim 3, characterized in that, In the modification process of the composite conductive filler, the acetylene black is 15-25 parts by weight; the carbon nanotubes are 1-3 parts; the silane coupling agent is 2-4 parts; the dispersant is 1-2 parts; the anhydrous ethanol is 100-150 parts; and the nitric acid solution is 0.5-1 part with a concentration of 5%.

5. The antistatic PVC pad according to claim 2, characterized in that, The acetylene black has a particle size of 20–50 nm, and the carbon nanotubes have an outer diameter of 10–20 nm and a length of 1–5 μm.

6. The antistatic PVC pad according to claim 2, characterized in that, During the modification process of the composite conductive filler, after adding nitric acid solution, the suspension is heated to 60-65℃ and kept at that temperature for 30-35 minutes; after adding silane coupling agent and dispersant, the suspension is heated to 80-85℃ and sheared and dispersed for 60-70 minutes; the filter residue is dried at 100-110℃ for 2-3 hours and then passed through a 200-mesh sieve.

7. The antistatic PVC pad according to claim 1, characterized in that, The antistatic agent is hexadecyltrimethylammonium chloride, dioctadecyldimethylammonium chloride, dodecyldimethylbenzylammonium chloride, or octadecyltrimethylammonium bromide; the plasticizer is epoxy castor oil, diisononyl cyclohexane 1,2-dicarboxylate, or dibutyl adipate; and the lubricant is stearic acid or butyl stearate.

8. The antistatic PVC pad according to claim 1, characterized in that, The thickness of the antistatic surface layer is 0.8–2.5 mm, and the thickness of the conductive bottom layer is 0.7–2.5 mm.

9. A method for preparing an antistatic PVC pad, characterized in that, The process includes the following steps: mixing the raw materials for the antistatic top layer and the conductive bottom layer at 80–100°C for 15–30 min; adding the two sets of raw materials into an extruder and melting and plasticizing them at 160–180°C, then extruding them to form a top layer blank and a bottom layer blank; hot-pressing the top layer blank and the bottom layer blank together at 150–170°C and 5–10 MPa, and then cooling them to obtain the antistatic PVC pad as described in any one of claims 1–8.

10. An application of an antistatic PVC pad, characterized in that, The antistatic PVC mat according to any one of claims 1-8 is applied to tabletops or floor mats; when the antistatic PVC mat is applied to floor mats, the surface of the antistatic surface layer is formed with anti-slip texture.

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