High-strength digital printing conveying belt of multi-layer structure

Abstract

The invention relates to the technical field of conveying belts, discloses a high-strength digital printing conveying belt of a multi-layer structure, and aims to solve the problem of pitch deviation caused by interface stress concentration, thermally induced size instability and creep deformation. The conveying belt is characterized by being sequentially provided with a transmission friction layer, a bottom bonding transition layer, a composite reinforcing framework layer, a stress compensation layer and a surface printing bearing layer from bottom to top. Wherein the framework layer adopts a high-modulus para-aramid fiber three-dimensional weaving structure, and the stress compensation layer is formed by compounding a tungsten phosphate zirconium filler with a negative thermal expansion characteristic and an elastomer. All the layers are integrated through chemical bonding or dipping treatment. According to the scheme, the longitudinal modulus and the dynamic thermal stability of the conveying belt are remarkably improved, thermally induced deformation and edge wrinkling are effectively restrained, and the registration precision of high-resolution printing is ensured.

Description

Technical Field

[0001] This invention relates to the field of conveyor belt technology, specifically to a high-strength digital printing conveyor belt with a multi-layer structure. Background Technology

[0002] In existing technologies, industrial-grade digital printing conveyor belts generally employ a multi-layer composite structure. The design aims to balance structural strength and surface properties by utilizing the complementary functions of different materials. Typically, the middle layer of this type of conveyor belt is a reinforcing core layer, often composed of high-strength synthetic fiber fabrics (such as polyester or polyamide fibers) to provide the necessary longitudinal tensile stiffness and prevent irreversible plastic elongation under long-term high-load tension. The upper surface is usually laminated with an elastomer layer (such as polyurethane or polyvinyl chloride) with a specific coefficient of friction and chemical resistance, designed to ensure a tight bond with the fabric and resist chemical erosion from printing pastes and cleaning agents. For a considerable period, this multi-layer composite design effectively met the operational needs of low-speed or medium-speed digital printing equipment, making a significant contribution to the automation of the printing industry.

[0003] Furthermore, digital printing processes are often accompanied by drying or heat setting processes, requiring the conveyor belt to frequently shuttle between the ambient temperature printing zone and the high temperature drying zone. Due to the significant difference in the coefficients of thermal expansion between the synthetic fibers reinforcing the core layer and the surface elastomer material, persistent thermal stress is generated within the multi-layered structure under cyclical temperature changes. This thermal stress not only induces microscopic warping or edge curling of the conveyor belt, damaging the physical flatness of the printing platform and causing fluctuations in the distance between the printhead and the fabric, resulting in misalignment or ghosting; more seriously, this internal stress accelerates the fatigue aging of the interlayer adhesive layer, leading to catastrophic failures such as localized delamination and blistering after a period of use. Simultaneously, to ensure transmission accuracy, technicians typically increase the initial tension of the conveyor belt. However, this creates a contradiction between material creep deformation and stress relaxation: while excessive tension can improve instantaneous response speed, it accelerates the rearrangement of the molecular chains in the skeleton material, causing a slight shift in the conveyor belt pitch. This deviation accumulates over continuous production over several kilometers, severely affecting the longitudinal alignment accuracy of the pattern.

[0004] In summary, existing multi-layer conveyor belts, while pursuing high strength, often struggle to simultaneously achieve excellent interlayer bonding, thermomechanical stability, and creep resistance. How to fundamentally solve the problems of stress imbalance, thermal deformation, and fatigue delamination during dynamic service through structural optimization and material synergistic design, while ensuring the conveyor belt possesses extremely high load-bearing capacity, has become a key challenge and an urgent technical problem for those skilled in the art. Summary of the Invention

[0005] This invention provides a multi-layered high-strength digital printing conveyor belt, aiming to solve the technical defects of existing digital printing conveyor belts under high-speed operation and high-frequency temperature change conditions, such as interfacial stress concentration, thermally induced dimensional instability, and pitch deviation due to material creep. To achieve the above-mentioned objective, the multi-layered high-strength digital printing conveyor belt of this invention is characterized by comprising, from bottom to top, a transmission friction layer, a bottom adhesive transition layer, a composite reinforcing skeleton layer, a stress compensation layer, and a surface printing bearing layer; the layers are integrated through an interfacial cross-linking structure to form a composite entity with a preset dynamic modulus gradient.

[0006] The transmission friction layer uses a synthetic rubber substrate with a Shore A hardness of 75 to 85 degrees, and uniformly disperses 5% to 8% by mass of short-cut carbon fibers therein, with the length of the short-cut carbon fibers ranging from 0.5 mm to 1.2 mm. The synthetic rubber substrate is selected from hydrogenated acrylonitrile rubber with a saturation greater than 99%, and its compression set at 150 degrees Celsius is less than 15%. The lower surface of the transmission friction layer has a cross-grid anti-slip texture with a depth of 0.2 mm to 0.4 mm, which serves to increase the coefficient of friction between the conveyor belt and the drive roller, ensuring the non-slip characteristics of the power transmission under high acceleration and deceleration conditions.

[0007] Furthermore, a bottom adhesive transition layer is disposed above the transmission friction layer, the thickness of which is set to 0.15 mm to 0.25 mm. The bottom adhesive transition layer is composed of a two-component isocyanate-modified phenolic resin system, containing 10% by mass of nano-sized silica particles, the average particle size of which is 20 nm to 40 nm. This transition layer, through chemical bonding, constructs molecular-level anchoring points between the rubber matrix of the transmission friction layer and the fiber surface of the upper composite reinforcing skeleton layer, thereby improving the interlayer peel strength.

[0008] As the core load-bearing unit of the multi-layered high-strength digital printing conveyor belt described in this invention, the composite reinforcing skeleton layer adopts a three-dimensional multi-directional weaving structure. This structure consists of longitudinal warp threads, transverse weft threads, and connecting threads running through both layers. The longitudinal warp threads are made of high-modulus para-aramid filaments with a fineness of 1500D to 3000D, a breaking strength greater than 22cN / dtex, and an initial modulus greater than 450cN / dtex. The transverse weft threads are made of modified polyester monofilaments with a diameter of 0.3mm to 0.5mm, exhibiting low heat shrinkage and high lateral bending stiffness. The weaving density of the composite reinforcing skeleton layer is controlled as follows: 120 to 160 warp threads / 10cm and 80 to 100 weft threads / 10cm. To ensure the wettability of the fiber to the polymer matrix, the composite reinforcing skeleton layer is entirely impregnated with resorcinol-formaldehyde-latex (RFL), with the impregnation weight gain controlled between 4% and 6%. The latex component in the impregnation solution is selected from a mixture of carboxylated styrene-butadiene latex and chloroprene latex in a mass ratio of 7:3 to achieve a balance between high modulus and dynamic fatigue resistance.

[0009] Furthermore, a stress compensation layer is provided above the composite reinforcing skeleton layer, which is a key structure for solving thermally induced deformation. The stress compensation layer employs a composite system of filler with a negative coefficient of thermal expansion and a flexible elastomer matrix. The filler is selected as zirconium tungsten phosphate (ZrW2O8) micro powder, with a particle size distribution of 1 to 5 micrometers, accounting for 12% to 18% of the mass in the elastomer matrix. The elastomer matrix is ​​linear low-density polyethylene modified thermoplastic polyurethane (TPU). The physical function of the stress compensation layer is that when the conveyor belt enters the high-temperature drying zone of the digital printing machine, the matrix material undergoes thermal expansion, while the filler generates a contraction effect. Through the mutual cancellation of macroscopic and microscopic deformations, the overall linear expansion coefficient of the stress compensation layer is controlled within a certain range. to Within this range, the thermal properties of the surface printing carrier layer are matched, eliminating edge curling caused by thermal stress.

[0010] The surface printing carrier layer is located on the top layer of the conveyor belt and is in direct contact with the fabric to be printed. This layer uses a high molecular weight special polyurethane system with a weight-average molecular weight distribution between 200,000 and 300,000. To meet the requirements of high-precision inkjet printing, the flatness deviation of the surface printing carrier layer is controlled within ±0.01mm. 3% to 5% by mass of nano-alumina particles are specially added to the material composition to improve the surface's wear resistance and resistance to chemical corrosion from the printing paste. Simultaneously, the surface of this layer undergoes plasma activation treatment, maintaining its surface tension at 38mN / m to 45mN / m to ensure adhesion during fabric application and easy removal during cleaning.

[0011] Furthermore, the Young's modulus of the overall structure of the high-strength digital printing conveyor belt with a multi-layer structure described in this invention is precisely calibrated in the longitudinal tensile direction using the following formula: ,in Representing the The volume fraction of the layer material in the thickness direction. Representing the The elastic modulus of the layer material. By adjusting the fiber volume fraction of the composite reinforcing skeleton layer, the elastic modulus of the layer material is determined. The pressure reaches 5000MPa to 8000MPa, so that under the rated tension, the elastic elongation of the conveyor belt is less than 0.1%, and the creep rate is less than 0.02% after 1000 hours of continuous operation.

[0012] The manufacturing process of a multi-layered high-strength digital printing conveyor belt according to this invention first involves pre-impregnation and constant-tension heat setting of the composite reinforcing skeleton layer. The woven skeleton fabric is passed through an RFL impregnation tank and then into a drying zone, where a longitudinal tension of 150N to 200N per centimeter of width is applied at a temperature of 160°C to 180°C for 3 to 5 minutes. This process aims to eliminate residual internal stress in the fiber molecules and establish preliminary physical locking points to inhibit subsequent creep behavior.

[0013] Following this, a multi-layer continuous extrusion lamination process is performed. Using multi-head co-extrusion or sequential coating processes, the underlying adhesive transition layer, stress compensation layer, and surface printed carrier layer are sequentially laminated onto the composite reinforcing skeleton layer under controlled process conditions. The temperature of each section of the extruder is precisely set according to the material properties, and the melt pressure is maintained between 15MPa and 25MPa. During lamination, a linear pressure of 0.5MPa to 0.8MPa is applied through a precision pressure roller assembly to eliminate residual micro-bubbles between layers and ensure interface wetting.

[0014] After the multi-layer structure is composited, the conveyor belt enters the continuous vulcanizing press. The vulcanizing pressure is controlled between 2.0 MPa and 3.5 MPa, and the vulcanizing temperature gradient is set as follows: 120 degrees Celsius for 10 minutes (preheating and softening stage), 165 degrees Celsius for 20 minutes (core vulcanizing stage), and then slowly cooled to room temperature at a rate of 5 degrees Celsius per minute. This gradient temperature-controlled vulcanizing process can effectively prevent stress concentration caused by rapid cooling.

[0015] Furthermore, to achieve micron-level thickness consistency, the finished conveyor belt requires high-precision grinding. An online thickness monitoring system is used in conjunction with a belt grinder to finely grind the surface printing layer. The grinding allowance is controlled between 0.05mm and 0.10mm, and the surface roughness Ra after grinding reaches 0.4 to 0.8 microns, ensuring a constant printing height for the digital printhead across the entire width.

[0016] The multi-layered high-strength digital printing conveyor belt described in this invention has significant technical advantages in terms of dynamic stability. Due to the introduction of high-modulus para-aramid fibers and a pre-forming process in the composite reinforcing skeleton layer, the long-term stability of its longitudinal pitch is fundamentally improved. Specifically, during conveyor belt operation, its longitudinal displacement deviation... With running time ,tension The relations satisfy the following constitutive model: ,in Let be the creep function of the material. Because... The significant improvement and The pre-formation process effectively suppresses the longitudinal pattern alignment deviation, ensuring that the cumulative deviation does not exceed 0.05mm during a continuous printing operation of up to 5000 meters on the conveyor belt.

[0017] Furthermore, the synergistic design of the stress compensation layer and each transition layer enables this invention to possess excellent deformation self-compensation capabilities under complex temperature variations. When the ambient temperature fluctuates between 20 degrees Celsius and 85 degrees Celsius, due to the matching of the linear expansion coefficients between each layer and the internal stress dissipation effect of the nanofillers, the lateral shrinkage rate of the conveyor belt is less than 0.01%, effectively avoiding edge wrinkling and ensuring the imaging quality of ultra-high resolution printing above 1200 dpi.

[0018] In a preferred embodiment, the surface-printed carrier layer also integrates an antistatic network composed of conductive polyaniline. This network forms an interpenetrating polymer network structure within the polyurethane matrix, thereby maintaining the surface resistivity of the conveyor belt at a certain level. Up to 1 This design can export the static charge generated during high-speed friction in real time, preventing static electricity from interfering with the flight trajectory of tiny ink droplets generated by the digital printhead, thereby eliminating ghosting and ink splatter.

[0019] In terms of physical and mechanical properties, the multi-layer high-strength digital printing conveyor belt of this invention exhibits a breaking strength exceeding 4500N per centimeter of width, and a fatigue life exceeding 2 million cycles under a 200mm diameter roller and a 10Hz cyclic load without delamination. Its interlayer adhesive strength has been tested to be greater than 12N / mm, ensuring structural integrity under harsh chemical cleaning environments and mechanical shear stress.

[0020] In summary, this invention achieves integrated optimization from microscopic molecular chain segment control to macroscopic system architecture through meticulous design of the multi-layered structure and functional customization of materials. The composite reinforcing skeleton layer provides extremely high load-bearing capacity and dimensional stability, the stress compensation layer solves the problem of thermally induced deformation, and the gradient transition layer ensures a long bonding life through a stress dissipation mechanism. This invention not only meets the needs of current high-speed, high-precision digital printing equipment but also provides reliable technical support for future more advanced precision conveying applications. The proportions of the material components in each layer, their physical specifications, and the pressure and temperature control during the preparation process together constitute a rigorous and inseparable technical solution, ensuring that this invention exhibits excellent engineering reliability in practical applications.

[0021] The material composition and structural layers used in this invention have all undergone rigorous mechanical simulation analysis and experimental verification. For example, when analyzing the interlayer shear stress distribution, a multi-layer composite beam model was established to calculate the maximum shear stress at the interface between the bottom adhesive transition layer and the composite reinforcing skeleton layer. ,in The total shear force, For the cross-sectional area moment, For the moment of inertia, The width is specified. By adding nano-silica particles to the bottom adhesive transition layer, the effective contact area and physical cross-linking density at the interface are effectively increased, resulting in a shear strength increase of over 40% at that location.

[0022] In addressing thermodynamic challenges, the stress compensation layer of this invention is designed based on the principles of anisotropic heat conduction and strain coordination. When the conveyor belt is heated, heat is transferred downwards through the surface-printed bearing layer. Due to the negative expansion characteristics caused by the special phonon vibration modes of the ZrW2O8 particles in the stress compensation layer, the resulting microscopic contraction strain... Thermal expansion strain with TPU matrix The directions are opposite. Under a specific mass ratio, the resultant strain... The value tends to a minimum, thus physically cutting off the path of thermal stress transmission to the core skeleton layer and avoiding interlayer shear failure caused by differences in thermal expansion and contraction.

[0023] The structural design of this invention also fully considers the neutral layer offset problem during dynamic bending. By accurately calculating the thickness ratio of each layer, the stressed neutral layer is set at the center plane position of the composite reinforcing skeleton layer. When the conveyor belt bends around the roller, the upper surface layer is under tension and the lower transmission layer is under pressure. Due to the stability of the neutral layer, the fiber skeleton layer does not bear additional bending stress, thereby greatly extending the bending fatigue life of the high-modulus aramid fiber.

[0024] Furthermore, the bottom adhesive transition layer not only serves an adhesive function, but its isocyanate groups also undergo a strong chemical reaction with the active hydrogen atoms in the rubber matrix and the hydroxyl groups on the fiber surface during vulcanization, forming covalent bonds such as urea or urea bonds. The energy of this chemical bonding is much higher than that of physical adsorption, which allows the interlayer interface to maintain chemical inertness and structural stability even under long-term contact with printing auxiliaries (such as urea, glycerin, reactive dyes, etc.).

[0025] In the manufacturing process of this invention, the accuracy of the tension control system is a key factor determining product quality. Throughout the entire production line from unwinding to rewinding, a high-precision closed-loop tension sensor is used to control longitudinal tension fluctuations within ±1%. Particularly at multi-layer bonding points, servo-driven compensation rollers provide real-time compensation for speed differences caused by minute variations in material thickness, ensuring that each layer of material completes bonding without initial strain differences. This is a crucial engineering guarantee for preventing internal stress in the finished conveyor belt and ensuring its flatness.

[0026] For the practical conditions of large-scale continuous production, this invention also optimizes the hardness gradient of the surface printing support layer. From the top surface to the interface with the stress compensation layer, the hardness of this layer exhibits a slight, continuous decreasing trend (gradient difference approximately Shore A 2-3 degrees). This hardness gradient effectively buffers the instantaneous impact generated by fabric splices or foreign objects passing through the pressure roller, preventing permanent indentations on the surface and ensuring long-term consistency in printing accuracy.

[0027] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0028] This invention discloses a multi-layered high-strength digital printing conveyor belt. By synergistically coupling the physicochemical properties of each functional layer, it successfully resolves the inherent contradictions between high strength and high flexibility, and high rigidity and high thermal stability. Its complex multi-layered architecture is not merely a simple stacking of materials, but a deep integration based on the principles of engineering mechanics and materials science, laying a solid foundation for the digital printing industry to advance towards ultra-high speed and ultra-high precision. All the technical parameters, material ratios, and processes involved are essential technical means to achieve this high-performance composite conveyor belt. These elements are interconnected, jointly ensuring the integrity and advancement of the technical solution of this invention. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall process of the digital printing conveyor belt of the present invention;

[0030] Figure 2 This is a schematic diagram of the three-dimensional multi-directional weaving process of the composite reinforcing skeleton layer in this invention;

[0031] Figure 3This is a schematic diagram of the bottom anti-slip texture of the transmission friction layer in this invention;

[0032] Figure 4 This is a schematic diagram of the manufacturing process of the digital printing conveyor belt of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The high-strength digital printing conveyor belt with a multi-layered structure described in this invention presents itself as a highly integrated five-layer composite entity in its macroscopic structure. From the bottom driving contact surface to the top printing bearing surface, this entity sequentially comprises a transmission friction layer, a bottom adhesive transition layer, a composite reinforcing skeleton layer, a stress compensation layer, and a surface printing bearing layer. This layered architecture is not a simple physical stacking, but rather achieves a continuous gradient transition in elastic modulus and thermal expansion coefficient between layers through chemical cross-linking and physical anchoring at the interfaces.

[0035] At the bottom layer of the conveyor belt, the transmission friction layer plays a crucial role in power transmission and suppressing slippage. This layer uses a highly saturated hydrogenated acrylonitrile butadiene rubber (HNBR) as its base material, with its saturation strictly controlled above 99% to ensure excellent chemical stability and anti-aging properties under long-term contact with industrial oils and high-temperature environments. Within this base material, 5% to 8% by mass of chopped carbon fibers 101 are uniformly dispersed. The length distribution of these chopped carbon fibers 101 is controlled between 0.5 mm and 1.2 mm. By applying a specific shear flow field during the mixing process, the carbon fibers exhibit a quasi-directional arrangement within the rubber matrix, thereby increasing the hardness of the transmission friction layer (Shore A 75 to 85 degrees) while simultaneously imparting extremely high tensile modulus in the circumferential direction. To further enhance the non-slip characteristics of power transmission, a cross-grid anti-slip texture is formed on the lower surface of the transmission friction layer using precision die pressing, with a depth ranging from 0.2 mm to 0.4 mm. When this geometric texture comes into contact with the drive roller, it can generate a significant mechanical interlocking effect through micro-deformation, ensuring zero slippage between the conveyor belt and the roller even under pulse loads of high acceleration and deceleration (e.g., acceleration exceeding 2g) in the drive system.

[0036] Adjacent to the transmission friction layer is the bottom adhesive transition layer, with a designed thickness of 0.15mm to 0.25mm. This layer serves as a modulus conversion bridge between the rubber matrix and the fiber skeleton, employing a two-component isocyanate-modified phenolic resin system. Within this resin system, 10% by mass of nano-sized silica particles are highly dispersed, with an average particle size precisely controlled between 20nm and 40nm. From an interfacial chemistry perspective, the isocyanate groups in the bottom adhesive transition layer can form covalent bonds with the active sites on the HNBR molecular chains in the transmission friction layer during the vulcanization reaction, while simultaneously exhibiting strong physical adsorption and chemical bonding with the functional groups on the fiber surface in the upper composite reinforcing skeleton layer. The presence of nano-silica particles, through their high specific surface area, increases the effective contact sites at the interface, forming numerous stress dissipation centers at the microscopic level, thereby increasing the interlayer peel strength to over 12N / mm, effectively solving the bubbling and delamination phenomenon that easily occurs in traditional conveyor belts under long-term high-frequency bending.

[0037] As the core load-bearing component of the multi-layered high-strength digital printing conveyor belt described in this invention, the composite reinforcing skeleton layer employs an advanced three-dimensional multi-directional weaving structure. This structure consists of longitudinal warp threads, transverse weft threads, and bonding threads running throughout the entire thickness direction. The longitudinal warp threads are made of high-modulus para-aramid filaments with a fineness of 1500D to 3000D, possessing a breaking strength greater than 22cN / dtex and an initial modulus greater than 450cN / dtex. These high-performance fibers provide the extremely high longitudinal stiffness required for the conveyor belt. The transverse weft threads are made of modified polyester monofilaments with a diameter of 0.3mm to 0.5mm, designed to provide the necessary lateral bending stiffness, ensuring that the conveyor belt does not laterally serpentine or edge curling during operation. The introduction of bonding threads is the essence of this structure; it tightly locks the multi-layered fabric structure, fundamentally eliminating interlayer slippage. The weaving density of the composite reinforcing skeleton layer is precisely set to 120 to 160 fibers / 10cm in the warp direction and 80 to 100 fibers / 10cm in the weft direction. To optimize the interfacial bonding between the fibers and the polymer matrix, the entire skeleton layer is impregnated with resorcinol-formaldehyde-latex (RFL), with the impregnation weight gain strictly controlled between 4% and 6%. The latex component in the impregnation solution consists of carboxylated styrene-butadiene-pyridine latex and chloroprene latex in a mass ratio of 7:3. This specific mixture forms an elastic film with both high modulus and dynamic fatigue resistance after vulcanization, tightly coating the surface of each fiber.

[0038] Above the composite reinforcing skeleton layer, a specially designed stress compensation layer is installed. This layer is designed to address the dimensional instability caused by the high temperature in the drying zone of the digital printing machine. The stress compensation layer uses linear low-density polyethylene (LLDPE) modified thermoplastic polyurethane (TPU) as the elastomer matrix, and incorporates 12% to 18% by mass of tungsten zirconium phosphate (ZrW2O8) micropowder as a negative thermal expansion coefficient filler 401. The particle size distribution of the tungsten zirconium phosphate particles ranges from 1 micrometer to 5 micrometers. When the conveyor belt is heated, the positive thermal expansion of the TPU matrix and the negative contraction of the tungsten zirconium phosphate cancel each other out in the micro-strain field. By precisely adjusting the filler loading, the overall linear expansion coefficient of the stress compensation layer is compressed to a minimum. to This value is highly compatible with the thermal properties of the lower skeleton layer and the upper load-bearing layer, eliminating the accumulation of thermal stress from the physical source and ensuring that the lateral shrinkage rate of the conveyor belt is always less than 0.01% under temperature change cycles from 20 degrees Celsius to 85 degrees Celsius.

[0039] The topmost surface printing carrier layer directly affects printing accuracy and fabric adhesion. This layer is made of high-molecular-weight specialty polyurethane with a weight-average molecular weight between 200,000 and 300,000. To enhance abrasion resistance and chemical protection, 3% to 5% by mass of nano-alumina particles are uniformly dispersed in the matrix. Through the dispersion reinforcement of nano-sized inorganic particles, the surface of this layer has extremely high smoothness, with deviations controlled within ±0.01 mm. Furthermore, the surface printing carrier layer integrates an antistatic network composed of conductive polyaniline. This network forms microscopic continuous conductive pathways within the polyurethane matrix through in-situ polymerization, stabilizing the surface resistivity. to This antistatic design effectively dissipates static electricity generated during high-speed operation, preventing the electric field from deflecting and interfering with the micron-sized ink droplets ejected by the digital printhead, thus ensuring edge sharpness for ultra-high resolution printing above 1200 dpi. The surface is also plasma-activated, maintaining a surface tension of 38 mN / m to 45 mN / m, ensuring reliable fabric placement and facilitating the rapid removal of residual ink during subsequent cleaning.

[0040] From a systems engineering perspective, the longitudinal total elastic modulus of the multi-layered high-strength digital printing conveyor belt described in this invention is... Based on the elastic modulus of each layer of material and its volume fraction Weighted summation Precise calibration was performed. This was achieved by adjusting the volume fraction of para-aramid fibers in the composite reinforcing skeleton layer to ensure the overall... Reaching 5000MPa to 8000MPa. This high-rigidity design ensures that the instantaneous elastic elongation of the conveyor belt is less than 0.1% under the standard tension force of industrial production, and that the creep rate due to material molecular chain rearrangement is less than 0.02% after 1000 hours of continuous operation, which provides a solid foundation for high-precision matching operations.

[0041] In terms of the manufacturing process, this invention follows an extremely stringent engineering control procedure. First, the composite reinforcing skeleton layer undergoes pre-impregnation and constant-tension heat setting. After passing through the RFL impregnation tank, the skeleton fabric enters a drying and setting zone at 160°C to 180°C. During this process, a precise longitudinal tension of 150N to 200N per centimeter of width is applied and maintained for 3 to 5 minutes. The purpose of this step is to eliminate residual internal stress within the fibers through a thermodynamic process and to establish preliminary physical locking points at the molecular level.

[0042] The subsequent continuous extrusion lamination process is crucial for determining interlayer quality. Using multi-head co-extrusion or sequential coating equipment, under melt pressures of 15MPa to 25MPa, the underlying adhesive transition layer, stress compensation layer, and surface printing carrier layer are sequentially laminated onto the pretreated skeleton layer. During lamination, a precision pressure roller group applies a uniform linear pressure of 0.5MPa to 0.8MPa to thoroughly eliminate interlayer microbubbles. Immediately afterward, the composite strip enters a continuous vulcanization press. The vulcanization process employs a three-stage gradient temperature control strategy: the first stage maintains 120 degrees Celsius for 10 minutes to fully wet the interfaces of each polymer layer; the second stage maintains 165 degrees Celsius for 20 minutes to complete the core chemical cross-linking; the final stage slowly cools to room temperature at a constant rate of 5 degrees Celsius per minute to prevent stress concentration caused by slight differences in thermal shrinkage.

[0043] The final processing step for the finished product is high-precision grinding. With real-time feedback from an online thickness monitoring system, a belt grinder performs fine grinding on the surface printing carrier layer, with a grinding allowance set to 0.05mm to 0.10mm, ultimately achieving a surface roughness Ra of 0.4 micrometers to 0.8 micrometers, ensuring a high degree of consistency between the printhead and the belt surface during inkjet printing.

[0044] To further demonstrate the significant improvement of the technical solution of the present invention compared with the traditional structure, the following will provide a detailed data demonstration through specific embodiments and comparative examples.

[0045] Example 1

[0046] The specific specifications of the multi-layer high-strength digital printing conveyor belt described in this embodiment are as follows:

[0047] The transmission friction layer is made of HNBR with a saturation of 99.5% and contains 6% by mass of short-cut carbon fiber (0.8mm in length), with a surface anti-slip texture depth of 0.3mm.

[0048] The thickness of the bottom adhesive transition layer is 0.20 mm, the content of nano-silica is 10%, and the particle size is 30 nm.

[0049] The longitudinal warp of the composite reinforcing skeleton layer is 2000D para-aramid, and the transverse weft is 0.4mm polyester monofilament. The weaving density is 140 warp threads / 10cm and 90 weft threads / 10cm. The impregnation weight gain is 5%.

[0050] In the stress compensation layer, ZrW2O8 filler accounts for 15%, and the matrix is ​​a TPU / LLDPE mixture.

[0051] The surface printing carrier layer is made of polyurethane with a weight average molecular weight of 250,000, with a nano alumina content of 4%, and the antistatic network is composed of 3% polyaniline.

[0052] The overall E_total design value is 6500MPa.

[0053] Example 2

[0054] This embodiment describes a multi-layered high-strength digital printing conveyor belt, focusing on applications requiring even higher strength.

[0055] The proportion of short-cut carbon fibers in the transmission friction layer has been increased to 8%, with a length of 1.0 mm.

[0056] The longitudinal warp of the composite reinforcing skeleton layer is made of 3000D para-aramid, and the warp density is increased to 160 warp threads / 10cm.

[0057] In the stress compensation layer, ZrW2O8 filler accounts for 18%.

[0058] Other parameters remain the same as in Example 1, and the overall E_total design value is 7800MPa.

[0059] Comparative Example 1

[0060] The conveyor belt uses a conventional two-layer structure, consisting of a base of ordinary nitrile rubber and a single-layer polyester fabric reinforcement layer, with a surface coating of ordinary polyurethane. It lacks a dedicated stress compensation layer and a nanoscale transition layer.

[0061] Comparative Example 2

[0062] The structure is similar to that of Example 1, but the negative thermal expansion coefficient filler (ZrW2O8) in the stress compensation layer is removed, and the bottom adhesive transition layer does not contain nano-silica.

[0063] For the above embodiments and comparative examples, a performance comparison test was conducted for 1000 hours under the same experimental environment (ambient temperature 25-85 degrees Celsius cycle, operating tension 20 N / mm, operating speed 150 m / min). The test results are summarized in Table 1.

[0064] Table 1: Comparison of Performance Test Data between Embodiments and Comparative Examples of the Invention

[0065] Test Project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Longitudinal total elastic modulus (MPa) 6520 7850 2100 4800 Creep rate (%) after 1000 hours of operation 0.015 0.012 0.45 0.08 Lateral shrinkage rate (%) at 85℃ 0.008 0.006 0.22 0.12 Interlayer peel strength (N / mm) 14.5 15.2 4.8 7.5 Pattern matching deviation for 5000m continuous printing (mm) 0.03 0.02 1.85 0.42 Surface resistivity (Ω) 5×10^7 3×10^7 >10^12 8×10^11 Fatigue life (millions of cycles) >2.5 >2.8 0.6 1.2

[0066] As can be clearly observed from the experimental data in Table 1, the multi-layer high-strength digital printing conveyor belt of the present invention demonstrates generational advantages in all key engineering indicators.

[0067] In terms of dimensional stability, the creep rates of Examples 1 and 2 after 1000 hours were only 0.015% and 0.012%, respectively, far superior to the 0.45% of Comparative Example 1. This is directly attributed to the application of high-modulus para-aramid in the composite reinforcing skeleton layer and the effective elimination of residual stress in fiber molecules by the pre-forming process. The extremely low creep rate means that the conveyor belt pitch can remain constant during long-term industrial production, thereby controlling the pattern alignment deviation within 0.03mm for 5000-meter continuous operation, which is crucial for digital printing processes that pursue ultimate color reproduction and pattern accuracy.

[0068] In terms of thermodynamic performance, thanks to the introduction of negative thermal expansion coefficient filler 401 (ZrW2O8) in the stress compensation layer, the transverse shrinkage rate of the embodiment at a high temperature of 85 degrees Celsius was reduced to less than 0.08%. In contrast, the shrinkage rate of Comparative Example 2 without the compensation filler reached 0.12%, while that of the conventional Comparative Example 1 was as high as 0.22%. This difference in magnitude ensures that the tape surface of the present invention will not produce any visible wrinkles or edge curling when passing through the drying unit of the printing machine, thereby guaranteeing the physical safety of the printhead and the consistency of imaging during high-speed scanning.

[0069] Regarding interfacial bonding strength, through the chemical bonding of the underlying adhesive transition layer and the dispersion enhancement of nano-silica particles, the interlayer peel strength of this embodiment reached over 14 N / mm, more than three times that of Comparative Example 1. This extremely high interfacial strength ensures that the conveyor belt does not exhibit any microscopic delamination after undergoing more than 2 million bending cycles on small-diameter (200 mm) rollers, greatly extending the service life of the equipment and reducing maintenance costs.

[0070] Further analysis from a microscopic mechanical perspective reveals that the conveyor belt described in this invention exhibits dynamic performance consistent with a rigorous mechanical model. The maximum shear stress at the interface between the bottom adhesive transition layer and the composite reinforcing skeleton layer is [data missing]. Through formula An evaluation was conducted. In actual working conditions, due to the physical cross-linking network formed by the nano-silica particles, the effective shear modulus of this region was significantly improved, allowing stress to be transferred more evenly from the flexible rubber layer to the rigid fiber layer, thus avoiding interface failure caused by stress concentration.

[0071] When addressing the challenges of dynamic bending, the thickness of each layer in this invention is precisely proportioned, ensuring that the stress-bearing neutral layer is accurately positioned at the geometric center plane of the composite reinforcing skeleton layer. According to the principles of materials mechanics, when the conveyor belt bends around the rollers, the aramid fiber skeleton located in the neutral layer bears only minimal bending stress; its primary load remains longitudinal tension. This design maximizes the protection of the high-modulus but repeatedly flexurally sensitive aramid fibers, resulting in a significant increase in the overall structure's fatigue life.

[0072] Furthermore, the integration of an antistatic network in the surface-printed carrier layer solves the technical challenge of static charge accumulation under high-speed operation. The surface resistivity measured in the example is... The ink droplet placement accuracy was within the ideal range for electrostatic dissipation. In the 1200dpi printing test, the example demonstrated extremely high ink droplet placement accuracy, completely eliminating the "ink splatter" or image blurring phenomena commonly seen in the comparative example due to electrostatic deflection.

[0073] This invention discloses a multi-layered high-strength digital printing conveyor belt. Through microscopic modification of material components, macroscopic design of the three-dimensional weaving structure, and a precise gradient fabrication process, a complex system with highly synergistic mechanical, thermal, and electrical properties is constructed. The parameter settings for each layer, such as the length of chopped carbon fibers, the particle size of nanoparticles, the fineness of aramid fibers, and the temperature control gradient during vulcanization, are all optimal solutions derived from extensive engineering experiments. These technical elements are coupled together to solve long-standing problems in the digital printing field, such as conveyor belt deformation instability, interlayer delamination, and electrostatic interference, providing reliable hardware support for achieving industrialized, large-scale, and high-precision digital printing production.

[0074] In practical engineering applications, this invention is not limited to the parameter range described in the above embodiments. Depending on the specific printing machine model and processing width, the volume fraction Vi of each layer and the material composition ratio can be fine-tuned, but the core multi-layer stress balance architecture and interfacial cross-linking mechanism remain unchanged. This flexibility and rigor based on engineering principles ensures the universality and advancement of this invention in different industrial environments.

[0075] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-strength digital printing conveyor belt with a multi-layer structure, characterized in that, The conveyor belt is provided with a transmission friction layer, a bottom adhesive transition layer, a composite reinforcing skeleton layer, a stress compensation layer, and a surface printed bearing layer from bottom to top. The transmission friction layer, the bottom adhesive transition layer, the composite reinforcing skeleton layer, the stress compensation layer, and the surface printed bearing layer are integrated through an interface cross-linking structure to form a composite entity with a preset dynamic modulus gradient. The transmission friction layer is composed of a synthetic rubber substrate containing short-cut carbon fibers, and its lower surface has an anti-slip texture; the bottom adhesive transition layer is composed of an isocyanate-modified resin system containing nano-sized silica particles; the composite reinforcing skeleton layer is a three-dimensional multi-directional woven structure composed of longitudinal warp, transverse weft, and bonding threads, and the whole is treated with resorcinol-formaldehyde-latex impregnation; the stress compensation layer is composed of an elastomer matrix containing fillers with a negative thermal expansion coefficient; and the surface printed bearing layer is composed of a high molecular weight polyurethane system containing nano-alumina particles and an antistatic network.

2. The high-strength digital printing conveyor belt with a multi-layer structure according to claim 1, characterized in that, The synthetic rubber substrate of the transmission friction layer is selected from hydrogenated acrylonitrile rubber with a saturation greater than 99%, and its compression set at 150 degrees Celsius is less than 15%, and the hardness of the substrate is Shore A 75 to 85 degrees. Short carbon fibers with a mass fraction of 5% to 8% are uniformly dispersed in the transmission friction layer. The length of the short carbon fibers is distributed between 0.5 mm and 1.2 mm, and they are quasi-oriented in the rubber matrix to improve the circumferential tensile modulus. The anti-slip texture is a cross-grid structure pressed on the bottom of the transmission friction layer. The depth of the anti-slip texture is 0.2 mm to 0.4 mm, which is used to form a mechanical interlock with the drive roller through micro-deformation.

3. The high-strength digital printing conveyor belt with a multi-layer structure according to claim 1, characterized in that, The thickness of the bottom adhesive transition layer is set to 0.15 mm to 0.25 mm. This layer uses a two-component isocyanate-modified phenolic resin system as the continuous phase, and highly disperses 10% by mass of nano-sized silica particles therein. The average particle size of the nano-sized silica particles is 20 nm to 40 nm. The bottom adhesive transition layer is covalently connected to the rubber molecular chains in the transmission friction layer through isocyanate groups, and achieves physical anchoring and chemical bonding coupling with the fiber surface functional groups in the composite reinforcing skeleton layer, so that the interlayer peel strength is maintained above 12 N / mm.

4. The high-strength digital printing conveyor belt with a multi-layer structure according to claim 1, characterized in that, The longitudinal warp of the composite reinforcing skeleton layer is made of high-modulus para-aramid filament with a fineness of 1500D to 3000D, a breaking strength greater than 22cN / dtex, and an initial modulus greater than 450cN / dtex; the transverse weft is made of modified polyester monofilament with a diameter of 0.3mm to 0.5mm; the bonding thread runs through the longitudinal and transverse layers to suppress interlayer slippage; the weaving density of the composite reinforcing skeleton layer is limited to: 120 to 160 warp threads / 10cm and 80 to 100 weft threads / 10cm; the overall weight gain of the composite reinforcing skeleton layer is 4% to 6% due to the impregnation treatment of resorcinol-formaldehyde-latex, wherein the latex component in the impregnation solution is a mixture of carboxylated styrene-butadiene latex and chloroprene latex in a mass ratio of 7:

3.

5. A high-strength digital printing conveyor belt with a multi-layer structure according to claim 1, characterized in that, The elastomeric matrix of the stress compensation layer is made of linear low-density polyethylene modified thermoplastic polyurethane; the negative thermal expansion coefficient filler is made of tungsten zirconium phosphate micro powder with a particle size distribution of 1 micrometer to 5 micrometers, accounting for 12% to 18% of the mass in the elastomeric matrix; the overall linear expansion coefficient of the stress compensation layer is controlled within a certain range. to Within the range, the thermal shrinkage effect of tungsten zirconium phosphate micropowder is used to offset the thermal expansion strain of the matrix material, so as to match the thermal deformation characteristics of the surface printing support layer and eliminate edge curling caused by thermal stress.

6. The high-strength digital printing conveyor belt with a multi-layer structure according to claim 1, characterized in that, The weight-average molecular weight distribution of the surface printing carrier layer is between 200,000 and 300,000, and the flatness deviation of this layer is controlled within ±0.01 mm. Nano-alumina particles with a mass fraction of 3% to 5% are added to the surface printing carrier layer. The antistatic network is composed of conductive polyaniline, forming an interpenetrating polymer network structure in the polyurethane matrix, thereby maintaining the surface resistivity of the surface printing carrier layer at a certain level. to The surface of the printed substrate is subjected to plasma activation treatment, and its surface tension is set between 38mN / m and 45mN / m.

7. The high-strength digital printing conveyor belt with a multi-layer structure according to claim 1, characterized in that, The total elastic modulus of the conveyor belt in the longitudinal tensile direction The following calibration formula must be satisfied: ,in Representing the The volume fraction of the layer material in the thickness direction. Represents the elastic modulus of the i-th layer material; by adjusting the volume fraction of para-aramid in the composite reinforcing skeleton layer, ... The conveyor belt has a stress range of 5000MPa to 8000MPa, and under rated tension, the elastic elongation is less than 0.1%, and the creep rate after 1000 hours of continuous operation is less than 0.02%; the stress-bearing neutral layer of the conveyor belt is set at the center plane of the composite reinforcing skeleton layer.

8. A method for preparing a multi-layered high-strength digital printing conveyor belt according to any one of claims 1 to 7, characterized in that, Includes the following steps: 1) Pretreatment of the skeleton layer: The woven composite reinforcing skeleton layer is passed through a resorcinol-formaldehyde-latex impregnation tank, and then placed in a drying zone at 160°C to 180°C. A longitudinal shaping tension of 150N to 200N per centimeter of width is applied and maintained for 3 to 5 minutes to eliminate residual internal stress in the fibers. 2) Continuous lamination: Using multi-head co-extrusion or sequential coating process, under a melt pressure of 15MPa to 25MPa, the bottom adhesive transition layer, stress compensation layer and surface printing carrier layer are sequentially laminated onto the treated composite reinforcing skeleton layer. During the lamination process, a linear pressure of 0.5MPa to 0.8MPa is applied by pressure rollers to eliminate interlayer air bubbles. 3) Gradient vulcanization: The composite strip is fed into a continuous vulcanization press. The vulcanization pressure is controlled between 2.0 MPa and 3.5 MPa, and the vulcanization temperature gradient is set as follows: preheating and softening at 120 degrees Celsius for 10 minutes, followed by core vulcanization at 165 degrees Celsius for 20 minutes. After vulcanization, the temperature is reduced to room temperature at a rate of 5 degrees Celsius per minute.

9. The method for preparing a multi-layered high-strength digital printing conveyor belt according to claim 8, characterized in that, After step 3), a high-precision grinding process is also included: an online thickness monitoring system is used in conjunction with a belt grinder to perform fine grinding on the printed bearing layer on the surface. The grinding allowance is controlled between 0.05 mm and 0.10 mm, and the surface roughness Ra after grinding reaches 0.4 micrometers to 0.8 micrometers.

10. The method for preparing a multi-layered high-strength digital printing conveyor belt according to claim 8, characterized in that, In step 2), a closed-loop tension sensor is used to control the longitudinal tension fluctuation of each layer of material at the bonding point within ±1%, and a servo-driven compensation roller is used to compensate for the material speed difference in real time, so as to ensure that the interface composite of each layer of material is completed without initial strain difference.

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