A low-temperature baking type PVC plastisol and its preparation method

Abstract

The present invention relates to a low-temperature baking type PVC plastisol and a preparation method thereof, belonging to the technical field of polymer materials. The components of the PVC plastisol include PVC paste resin, copaiba resin, biphenyl epoxy resin, shea butter, dioctyl maleate, isopropyl myristate, PEG-10 distearate, calcium stearate, zinc stearate, nano calcium carbonate, M50 isocyanate curing agent, aziridine crosslinking agent, antioxidant 1010, antioxidant 168, silicone defoaming agent, pigment, diluent, etc.; each component is used in a specific proportion and the plastisol is prepared by a special preparation method, which has good high-temperature and low-temperature stability, high bonding strength, and rapid low-temperature curing. It is not only applicable to the bonding of PVC materials, but also applicable to the bonding of various metal materials, and can provide a relatively high bonding strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a low-temperature baking type PVC plastisol and a preparation method thereof. Background Art

[0002] In the early stage of material application, the materials used in various industries were relatively single and the structures were relatively simple. With the development of society and the progress of technology, higher requirements have been put forward for material properties in various fields, prompting people to continuously explore new materials and new processes to meet diversified needs.

[0003] Aluminum alloys are widely used in many fields due to their advantages such as light weight, high strength, and good corrosion resistance. In the fields of aerospace and automotive, aluminum alloys are used to manufacture structural components such as fuselages and interiors, effectively reducing weight, improving fuel efficiency and performance; in the construction field, aluminum alloys are used for window and door frames, curtain walls, etc., which are not only beautiful and durable, but also can reduce the overall weight of buildings and improve energy-saving effects; in the field of electronic device manufacturing, aluminum alloys are often used to manufacture the casings of mobile phones, computers and other devices, which can not only ensure the lightness and portability of products, but also provide good heat dissipation performance and mechanical strength.

[0004] PVC molded parts play an important role in many fields due to their low cost, strong plasticity, good insulation and excellent appearance effects. In the field of home decoration, PVC is widely used to make floors, wallpapers, door and window seals, etc., and its rich color and texture options can meet the needs of different decoration styles; in the electrical field, PVC is widely used as an insulating material for the outer skins of wires and cables to ensure the safety of power transmission; in the toy manufacturing field, PVC has become a commonly used material for making various toys due to its good plasticity and cost advantages. PVC molded parts are widely used in automotive interior trim strips, exterior protection parts and some functional parts due to their low cost, strong plasticity, good insulation and excellent appearance effects.

[0005] In practical applications, the combined use of different materials can give play to their respective advantages and achieve better performance. However, the surface of aluminum alloy is smooth and prone to form a dense oxide film. As a polymer, it is difficult to directly bond PVC with aluminum alloy. Traditional mechanical connection methods, such as riveting and bolt connection, not only increase weight, damage the integrity of materials, but also may reduce the strength of components due to stress concentration, affecting the aesthetics and sealing performance of products, and cannot meet the requirements of various industries for product lightweight and overall performance improvement. Therefore, developing a reliable and efficient connection method to achieve the firm adhesion of PVC molded parts to aluminum alloy has become an urgent problem to be solved in many industries.

[0006] The usage environment of the product is complex and diverse. The pasting process needs to ensure that the adhesion between PVC and aluminum alloy remains durable and stable under various conditions. For example, in high-temperature and humid industrial environments, the pasted area should not come apart to avoid equipment failures; in cold outdoor environments, the adhesive should not become brittle and lose its stickiness.

[0007] Early glue products faced many challenges when bonding PVC materials. Ordinary glues were difficult to form strong enough chemical bonds with the PVC surface, resulting in low bonding strength and easy debonding. At the same time, the PVC material had a low surface energy, making the wettability of the glue on its surface poor, which affected the penetration and adhesion effect of the glue. In addition, PVC might be affected by environmental factors such as temperature, humidity, and ultraviolet rays during use, which required the supporting glue to have good weather resistance and durability.

[0008] To solve these problems, researchers began to explore adding PVC components to the glue, and PVC plastic solution glue came into being. The principle of PVC plastic solution glue lies in the principle of "like dissolves like". The PVC components in the glue can better blend with the PVC materials to be bonded. When the glue is coated on the PVC surface, the solvent first causes the PVC material surface to swell, and at the same time, the PVC components in the glue are also in a dissolved or dispersed state. As the solvent volatilizes, the glue gradually cures, and the PVC components and the PVC materials to be bonded are intertwined at the molecular level, forming a tight connection, thus significantly improving the bonding strength and stability.

[0009] During the formulation research and development process, in addition to PVC resin, various auxiliary components also need to be added. For example, the addition of plasticizers can adjust the flexibility and plasticity of the glue, prevent the glue from cracking due to brittleness after curing, and also help improve the wettability of the glue to PVC materials; stabilizers can prevent PVC from degrading due to factors such as heat and light during processing and use, ensuring the performance stability of the glue; the selection of solvents should consider both the solubility in PVC resin and other components, as well as factors such as volatility, toxicity, and environmental protection to ensure the operability of the glue during construction and the safety after use; the use of fillers can adjust the physical properties of the glue, such as viscosity and hardness, and at the same time can also reduce costs.

[0010] With the continuous progress of technology and the continuous improvement of product quality requirements in various industries, it forces the PVC plastic solution glue to continuously develop and improve. The current PVC plastic solution glue still has the following technical problems:

[0011] (1) Slow curing speed: In some occasions that require rapid assembly or construction, the curing speed of PVC glue cannot meet the requirements, resulting in reduced production efficiency or extended construction periods. High-temperature baking at around 150°C is needed to accelerate curing, but high-temperature baking can cause degradation and denaturation of the base material, as well as affect the surrounding heat-sensitive devices due to the temperature.

[0012] (2) Low bonding strength: The bonding strength is relatively good when the glue is coated on the PVC material surface, but when pasting on metal materials such as aluminum and aluminum alloy surfaces, the bonding strength is uneven and generally needs to be improved.

[0013] Therefore, it is necessary to continuously develop the composition and production technology of the glue to meet the requirements of more efficient and stable use. Summary of the Invention

[0014] Aiming at the problems of slow curing speed, high baking temperature, and the need to improve the bonding strength existing in the existing PVC plastisol. The present invention provides a low-temperature baking type PVC plastisol and its preparation method. The components of the PVC plastisol include PVC paste resin, copaiba resin, biphenyl epoxy resin, shea butter, dioctyl maleate, isopropyl myristate, PEG-10 distearate, calcium stearate, zinc stearate, nano calcium carbonate, M50 isocyanate curing agent, aziridine crosslinking agent, antioxidant, etc. The plastisol is prepared by a special preparation method for each component, with good high-temperature and low-temperature stability, high bonding strength, and rapid low-temperature curing. It is applicable not only to the bonding of PVC materials but also to the bonding of various metal materials. The specific technical solution is as follows:

[0015] A low-temperature baking type PVC plastisol, the PVC plastisol comprises the following raw materials in parts by mass: 80 parts to 100 parts of PVC paste resin, 10 parts to 15 parts of copaiba resin, 5 parts to 10 parts of biphenyl epoxy resin, 5 parts to 8 parts of shea butter, 25 parts to 35 parts of dioctyl maleate, 10 parts to 15 parts of isopropyl myristate, 3 parts to 5 parts of PEG-10 distearate, 2 parts to 4 parts of calcium stearate, 1 part to 3 parts of zinc stearate, 10 parts to 20 parts of nano calcium carbonate, 2 parts to 3 parts of M50 isocyanate curing agent, 1 part to 3 parts of aziridine crosslinking agent, 0.5 part to 1 part of antioxidant 1010, 0.5 part to 1 part of antioxidant 168, 0.1 part to 0.3 part of organosilicon defoaming agent, 3 parts to 5 parts of pigment, and 15 parts to 25 parts of diluent.

[0016] In the above PVC plastisol, the PVC paste resin is a homopolymer resin with a polymerization degree of 1000 to 1300.

[0017] In the above PVC plastisol, the particle size of the calcium stearate is passed through a sieve of 800 to 900 meshes.

[0018] In the above PVC plastisol, the particle size of the zinc stearate is below the sieve of 650 mesh to 800 mesh.

[0019] In the above PVC plastisol, the particle size of the nano calcium carbonate is below 100 nm.

[0020] In the above PVC plastisol, the pigment is at least one of titanium dioxide and graphite powder.

[0021] In the above PVC plastisol, the titanium dioxide is rutile titanium dioxide, and the particle size of the titanium dioxide is below the sieve of 325 mesh to 500 mesh.

[0022] In the above PVC plastisol, the particle size of the graphite powder is below the sieve of 200 mesh to 325 mesh.

[0023] In the above PVC plastisol, the diluent includes ethyl acetate.

[0024] The preparation method of the above low-temperature baking type PVC plastisol includes the following steps:

[0025] S1: By mass fraction, add PVC paste resin to the reaction kettle, start stirring at a speed of 300 r / min to 500 r / min, add dioctyl maleate, stir at 25°C to 32°C for 15 min to 20 min, then add isopropyl myristate and PEG-10 distearate, and stir for 30 min to 45 min to fully swell and mix the PVC paste resin evenly to form a uniform basic glue solution;

[0026] S2: By mass fraction, add 80% to 90% mass fraction of diluent, shea butter, copaiba resin and biphenyl epoxy resin to the basic glue solution, and stir at a speed of 300 r / min to 500 r / min to mix evenly;

[0027] S3: By mass fraction, add calcium stearate, zinc stearate, nano calcium carbonate and pigment, and stir at a speed of 500 r / min to 600 r / min to mix evenly;

[0028] S4: By mass fraction, add antioxidant 1010, antioxidant 168 and silicone defoamer, stir at a speed of 150 r / min to 200 r / min for 10 min to 15 min, let it stand for 3 min to 5 min to fully overflow the bubbles, and then add M50 isocyanate curing agent and aziridine crosslinking agent, and stir at a speed of 200 r / min to 250 r / min to mix evenly and without bubble defects;

[0029] S5: Finally, add the remaining diluent, stir at a speed of 150 r / min to 250 r / min to adjust the viscosity until it is uniform, obtain the PVC plastisol, and store it sealed.

[0030] In the above preparation method, during the entire mixing process, the temperature does not exceed 32°C.

[0031] In step S3 of the above preparation method, calcium stearate, zinc stearate, nano calcium carbonate and pigment are uniformly mixed by double-cone mixing or pneumatic mixing before being added.

[0032] In step S2 of the above preparation method, the stirring time at a speed of 300 r / min to 500 r / min is 10 min to 20 min; shea butter, copaiba resin and biphenyl epoxy resin are pre-mixed uniformly with a diluent before being added.

[0033] In step S3 of the above preparation method, the stirring time at a speed of 500 r / min to 600 r / min is 20 min to 30 min.

[0034] In step S4 of the above preparation method, the stirring time at a speed of 200 r / min to 250 r / min is 30 min to 45 min.

[0035] In step S5 of the above preparation method, the stirring time at a speed of 150 r / min to 250 r / min is 25 min to 30 min.

[0036] In the using method of the above low-temperature baking type PVC plastisol, the coating amount of the PVC plastisol is controlled at 120 g / m² to 250 g / m², and the baking temperature is controlled at 65°C to 80°C.

[0037] A low-temperature baking type PVC plastisol and its preparation method provided by the present invention have the beneficial effects as follows:

[0038] I. PVC paste resin is the main component, providing the basic polymer skeleton and determining the basic properties of the material. Copaiba resin improves the viscosity and flexibility of PVC plastisol, enhances its adhesion to different materials, and meanwhile helps to improve the chemical resistance of the material. Biphenyl epoxy resin strengthens the cross-linked structure of PVC plastisol, enhances the hardness, abrasion resistance and chemical corrosion resistance of the material, making the material more stable after curing. Shea butter plays a plasticizing role, increasing the flexibility and ductility of the material, and at the same time can improve the processing performance of the material, making it easier to apply and mold. Dioctyl maleate is mainly used as a plasticizer, reducing the hardness of PVC paste resin, increasing flexibility, making the material softer, and reducing brittleness. Isopropyl myristate is an excellent solubilizer and lubricant, which can improve the compatibility between components, make the mixing more uniform, and at the same time also helps to improve the touch and gloss of the material. PEG-10 distearate has emulsifying and dispersing effects, which can prevent agglomeration between components and improve the stability of the system; it is also a plasticizer, enhancing the flexibility of the material. Calcium stearate and zinc stearate are used as heat stabilizers to prevent the performance degradation of PVC due to thermal decomposition during processing and use; at the same time, calcium stearate can also act as a lubricant to improve the processing performance. Nano calcium carbonate is a filler, which can improve the hardness, strength and abrasion resistance of the material, and at the same time reduce the cost; the nano-scale particle size can make the surface of the material smoother and improve the filling property of the material. M50 isocyanate curing agent and aziridine cross-linking agent are used for curing reaction, converting PVC plastisol from liquid state to solid state, forming a three-dimensional network structure, and improving the strength, hardness and chemical resistance of the material. Antioxidant 1010 and antioxidant 168 prevent the degradation of PVC resin and other components due to oxidation during processing and use, and extend the service life of the material. Organosilicon defoamer is used to eliminate the bubbles generated during stirring and mixing, making the internal structure of the material more dense, and improving the quality and appearance of the material. Rutile titanium dioxide is a white pigment, providing good hiding power and whiteness, making the material have a better appearance; at the same time, it can also improve the weather resistance and ultraviolet resistance of the material.

[0039] II. Copaiba resin and biphenyl epoxy resin cooperate with each other to build a more complex and tight cross-linked network. Copaiba resin provides flexibility and viscosity, making the material not too brittle and hard after curing; biphenyl epoxy resin enhances the degree of cross-linking, improving the hardness and abrasion resistance of the material. The combination of the two can make PVC plastisol have good bonding strength and flexibility, sufficient hardness after curing, improve the chemical corrosion resistance and water resistance of the material, and enhance the comprehensive performance of the material.

[0040] III. Shea butter and dioctyl maleate mainly provide flexibility, and PEG-10 distearate also has a plasticizing effect. Their combined action weakens the force between PVC molecular chains, making the molecular chains slide more easily, thus significantly improving the flexibility and ductility of the material. Isopropyl myristate, as a solubilizer and lubricant, can improve the compatibility between components, enabling shea butter and PEG-10 distearate to be better dispersed in the PVC paste resin system. Their mutual cooperation makes the whole system more uniform and stable, avoiding the phase separation phenomenon between components. Shea butter and PEG-10 distearate can improve the compatibility among PVC paste resin, copal resin and biphenyl epoxy resin, making the cross-linking reaction more uniform.

[0041] Shea butter contains some lipophilic groups and can interact with non-polar components such as PVC paste resin; PEG-10 distearate has emulsifying and dispersing functions, and its hydrophilic and lipophilic parts in the molecular structure can help dissolve some components with poor solubility in the system; isopropyl myristate itself is an excellent solubilizer. When they act together, by reducing the interfacial tension, the components that are originally difficult to dissolve can be better dispersed in the system. For some additives or pigments, they can wrap or disperse them, increasing their solubility in the PVC plastisol, thus making the whole system more uniform and improving the quality and performance of the material.

[0042] IV. The M50 isocyanate curing agent and aziridine cross-linking agent can cure the PVC plastisol through different reaction mechanisms. The isocyanate group (-NCO) and aziridine group (-C3H5N) can react with PVC paste resin or other components containing active hydrogen respectively to form a cross-linked structure. This double-curing system can make the curing reaction more complete, forming a more dense three-dimensional network structure, thus greatly improving the strength, hardness and chemical resistance of the material. At the same time, the reaction rates of the two curing agents can be adjusted with each other, making the curing process more controllable and avoiding material property defects caused by too fast or too slow curing. According to the specific properties of other components, the present invention designs to add a specific proportion of M50 isocyanate curing agent and aziridine cross-linking agent for combined use, which can ensure the short-time low-temperature curing of the PVC plastisol and ensure the curing quality.

[0043] V. In S1 of the preparation method, adding dioctyl maleate, isopropyl myristate and PEG-10 distearate can enable these plasticizers and solubilizers to better interact with PVC paste resin, forming a uniform basic glue solution. This process lays a good foundation for subsequent reactions and mixing, ensuring that each component can be evenly dispersed in the PVC paste resin.

[0044] In S2 of the preparation method, adding shea butter first can achieve good fusion of copal resin and biphenyl epoxy resin, and it can fuse with the base glue solution faster. Shea butter further plays a plasticizing role. In the initial process of the copal resin and biphenyl epoxy resin starting to participate in building the crosslinking network, through long-term stirring, they are uniformly mixed at the molecular level, preparing for the subsequent formation of a more perfect crosslinking structure.

[0045] In S4 of the preparation method, antioxidant 1010, antioxidant 168 and silicone defoamer are added. Cooling is to adapt to the addition of the antioxidant to avoid affecting its performance due to too high temperature. The antioxidant can effectively capture free radicals in the system at this stage to prevent the occurrence of oxidation reactions. The silicone defoamer can eliminate the bubbles generated in the previous stirring process under low-speed stirring, making the system more dense. Subsequently, M50 isocyanate curing agent and aziridine crosslinking agent are added and stirred. At a suitable temperature and stirring speed, the curing agent can fully react with the active components in the system to form a crosslinking structure. Specific embodiments

[0046] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these embodiments.

[0047] Example 1

[0048] A low-temperature baking type PVC plastisol, the PVC plastisol comprises the following raw materials in parts by mass: 90 parts of PVC paste resin, 12 parts of copal resin, 8 parts of biphenyl epoxy resin, 6 parts of shea butter, 30 parts of dioctyl maleate, 12 parts of isopropyl myristate, 4 parts of PEG-10 distearate, 3 parts of calcium stearate, 2 parts of zinc stearate, 15 parts of nano calcium carbonate, 2.5 parts of M50 isocyanate curing agent, 2 parts of aziridine crosslinking agent, 0.8 part of antioxidant 1010, 0.8 part of antioxidant 168, 0.2 part of silicone defoamer, 4 parts of rutile titanium dioxide and 20 parts of ethyl acetate.

[0049] Among them, the PVC paste resin is a homopolymer resin with a polymerization degree of 1000; the particle size of calcium stearate is below 800 mesh sieve; the particle size of zinc stearate is below 650 mesh sieve; the particle size of nano calcium carbonate is below 100 nm; the particle size of rutile titanium dioxide is below 425 mesh sieve.

[0050] The preparation method of the above-mentioned low-temperature baking type PVC plastisol comprises the following steps:

[0051] S1: By mass parts, add PVC paste resin into the reaction kettle, start stirring at a speed of 400 r / min, add dioctyl maleate, stir at 28 °C for 18 min, then add isopropyl myristate and PEG-10 distearate, and stir for 40 min to fully swell and mix the PVC paste resin evenly to form a uniform basic glue solution;

[0052] S2: By mass parts, add shea butter, copaiba resin and biphenyl epoxy resin premixed evenly with 85% mass parts of ethyl acetate into the basic glue solution, stir at a speed of 400 r / min for 15 min to mix evenly;

[0053] S3: By mass parts, add calcium stearate, zinc stearate, nano calcium carbonate and rutile titanium dioxide, stir at a speed of 550 r / min for 25 min to mix evenly;

[0054] Calcium stearate, zinc stearate, nano calcium carbonate and rutile titanium dioxide are mixed evenly by air flow before adding;

[0055] S4: By mass parts, add antioxidant 1010, antioxidant 168 and silicone defoamer, stir at a speed of 180 r / min for 12 min, let it stand for 4 min to allow the bubbles to overflow fully, then add M50 isocyanate curing agent and aziridine crosslinking agent, and stir at a speed of 220 r / min for 40 min to mix evenly and have no bubble defects;

[0056] S5: Finally, make up the remaining ethyl acetate, stir at a speed of 200 r / min for 28 min to adjust the viscosity, obtain PVC plastisol, and store it sealed.

[0057] In the above preparation method, during the whole mixing process, the temperature does not exceed 32 °C.

[0058] Example 2

[0059] A low-temperature baking type PVC plastisol, and the PVC plastisol comprises the following raw materials in mass parts: 80 parts of PVC paste resin, 10 parts of copaiba resin, 5 parts of biphenyl epoxy resin, 5 parts of shea butter, 25 parts of dioctyl maleate, 10 parts of isopropyl myristate, 3 parts of PEG-10 distearate, 2 parts of calcium stearate, 1 part of zinc stearate, 10 parts of nano calcium carbonate, 2 parts of M50 isocyanate curing agent, 1 part of aziridine crosslinking agent, 0.5 part of antioxidant 1010, 0.5 part of antioxidant 168, 0.1 part of silicone defoamer, 3 parts of graphite powder and 15 parts of ethyl acetate.

[0060] Among them, the PVC paste resin is a homopolymer resin with a polymerization degree of 1000; the particle size of calcium stearate is below 900 mesh sieve; the particle size of zinc stearate is below 800 mesh sieve; the particle size of nano calcium carbonate is below 100 nm; the particle size of graphite powder is below 250 mesh sieve.

[0061] The preparation method of the above-mentioned low-temperature baking type PVC plastisol includes the following steps:

[0062] S1: By mass fraction, add PVC paste resin to the reaction kettle, start stirring at a speed of 300 r / min, add dioctyl maleate, stir at 25 °C for 15 min, then add isopropyl myristate and PEG-10 distearate, and stir for 30 min to fully swell and mix the PVC paste resin evenly to form a uniform basic glue solution;

[0063] S2: By mass fraction, add shea butter, copaiba resin and biphenyl epoxy resin premixed evenly with 90% mass fraction of ethyl acetate to the basic glue solution, and stir at a speed of 300 r / min for 10 min to blend evenly;

[0064] S3: By mass fraction, add calcium stearate, zinc stearate, nano calcium carbonate and graphite powder, and stir at a speed of 500 r / min for 20 min to mix evenly;

[0065] Calcium stearate, zinc stearate, nano calcium carbonate and graphite powder are evenly mixed by air flow before adding;

[0066] S4: By mass fraction, add antioxidant 1010, antioxidant 168 and silicone defoamer, stir at a speed of 150 r / min for 10 min, stand for 3 min to allow the bubbles to overflow fully, then add M50 isocyanate curing agent and aziridine crosslinking agent, and stir at a speed of 200 r / min for 30 min to mix evenly and have no bubble defects;

[0067] S5: Finally, add the remaining ethyl acetate, stir at a speed of 150 r / min for 25 min to adjust the viscosity, obtain PVC plastisol, and store it sealed.

[0068] In the above preparation method, the temperature does not exceed 32 °C during the whole mixing process.

[0069] Example 3

[0070] A low-temperature baking type PVC plastisol, and the PVC plastisol comprises raw materials in the following parts by mass: 80 parts of PVC paste resin, 15 parts of copaiba resin, 5 parts of biphenyl epoxy resin, 8 parts of shea butter, 25 parts of dioctyl maleate, 15 parts of isopropyl myristate, 3 parts of PEG-10 distearate, 4 parts of calcium stearate, 1 part of zinc stearate, 20 parts of nano calcium carbonate, 2 parts of M50 isocyanate curing agent, 3 parts of aziridine crosslinking agent, 0.5 part of antioxidant 1010, 1 part of antioxidant 168, 0.1 part of silicone defoaming agent, 5 parts of pigment and 20 parts of ethyl acetate.

[0071] Among them, the PVC paste resin is a homopolymer resin with a polymerization degree of 1000; the particle size of calcium stearate is below 800 mesh sieve; the particle size of zinc stearate is below 800 mesh sieve; the particle size of nano calcium carbonate is below 100 nm.

[0072] Among them, the pigment is an equimolar mixture of titanium dioxide and graphite powder; the titanium dioxide is rutile type titanium dioxide, and the particle size is below 325 mesh sieve; the particle size of graphite powder is below 325 mesh sieve.

[0073] The preparation method of the above low-temperature baking type PVC plastisol comprises the following steps:

[0074] S1: According to the parts by mass, add PVC paste resin into a reaction kettle, start stirring at a speed of 300 r / min, add dioctyl maleate, stir at 26 °C for 15 min, then add isopropyl myristate and PEG-10 distearate, and stir for 30 min to fully swell and mix the PVC paste resin evenly to form a uniform basic glue solution;

[0075] S2: According to the parts by mass, add shea butter, copaiba resin and biphenyl epoxy resin which are pre-mixed evenly with 85% parts by mass of ethyl acetate into the basic glue solution, and stir at a speed of 500 r / min for 15 min to blend evenly;

[0076] S3: According to the parts by mass, add calcium stearate, zinc stearate, nano calcium carbonate and pigment, and stir at a speed of 500 r / min for 25 min to mix evenly;

[0077] Calcium stearate, zinc stearate, nano calcium carbonate and pigment are pre-mixed evenly by a double cone before adding;

[0078] S4: According to the parts by mass, add antioxidant 1010, antioxidant 168 and silicone defoaming agent, stir at a speed of 200 r / min for 10 min, stand for 5 min to allow the bubbles to overflow fully, then add M50 isocyanate curing agent and aziridine crosslinking agent, and stir at a speed of 200 r / min for 45 min to mix evenly and without bubble defects;

[0079] S5: Finally, add the remaining ethyl acetate, stir at a speed of 250 r / min for 25 min, adjust the viscosity to obtain PVC plastisol, and store it sealed.

[0080] In the above preparation method, during the entire mixing process, the temperature does not exceed 32 °C.

[0081] Example 4

[0082] A low-temperature baking PVC plastisol, the PVC plastisol comprises the following raw materials in parts by mass: 100 parts of PVC paste resin, 15 parts of Copaiba resin, 10 parts of biphenyl epoxy resin, 8 parts of shea butter, 35 parts of dioctyl maleate, 15 parts of isopropyl myristate, 5 parts of PEG-10 distearate, 4 parts of calcium stearate, 3 parts of zinc stearate, 20 parts of nano calcium carbonate, 3 parts of M50 isocyanate curing agent, 3 parts of aziridine crosslinking agent, 1 part of antioxidant 1010, 1 part of antioxidant 168, 0.3 part of silicone defoamer, 5 parts of rutile titanium dioxide and 25 parts of ethyl acetate.

[0083] Among them, the PVC paste resin is a homopolymer resin with a polymerization degree of 1000; the particle size of calcium stearate is below 900 mesh sieve; the particle size of zinc stearate is below 650 mesh sieve; the particle size of nano calcium carbonate is below 100 nm; the particle size of rutile titanium dioxide is below 500 mesh sieve.

[0084] The preparation method of the above low-temperature baking PVC plastisol comprises the following steps:

[0085] S1: According to the parts by mass, add PVC paste resin to the reaction kettle, start stirring at a speed of 500 r / min, add dioctyl maleate, stir at 30 °C for 20 min, then add isopropyl myristate and PEG-10 distearate, and stir for 45 min to fully swell and mix the PVC paste resin evenly to form a uniform basic glue solution;

[0086] S2: According to the parts by mass, add shea butter, Copaiba resin and biphenyl epoxy resin which are pre-mixed evenly with 80% of the parts by mass of ethyl acetate to the basic glue solution, and stir at a speed of 500 r / min for 20 min to mix evenly;

[0087] S3: According to the parts by mass, add calcium stearate, zinc stearate, nano calcium carbonate and rutile titanium dioxide, and stir at a speed of 600 r / min for 30 min to mix evenly;

[0088] Calcium stearate, zinc stearate, nano calcium carbonate and rutile titanium dioxide are pre-mixed evenly by double cone before adding;

[0089] S4: Add antioxidant 1010, antioxidant 168 and silicone defoamer according to the parts by mass, stir at a speed of 200 r / min for 15 min, let stand for 5 min to allow the bubbles to overflow fully, then add M50 isocyanate curing agent and aziridine crosslinking agent, and stir at a speed of 250 r / min for 45 min to mix evenly without bubble defects;

[0090] S5: Finally, add the remaining ethyl acetate, stir at a speed of 250 r / min for 30 min to adjust the viscosity, and obtain the PVC plastisol, which is sealed and stored.

[0091] In the above preparation method, during the whole mixing process, the temperature does not exceed 32 °C.

[0092] Example 5

[0093] A low-temperature baking PVC plastisol, the PVC plastisol comprises the following raw materials in parts by mass: 100 parts of PVC paste resin, 10 parts of copaiba resin, 10 parts of biphenyl epoxy resin, 5 parts of shea butter, 35 parts of dioctyl maleate, 10 parts of isopropyl myristate, 5 parts of PEG-10 distearate, 2 parts of calcium stearate, 3 parts of zinc stearate, 10 parts of nano calcium carbonate, 3 parts of M50 isocyanate curing agent, 1 part of aziridine crosslinking agent, 1 part of antioxidant 1010, 0.5 part of antioxidant 168, 0.3 part of silicone defoamer, 3 parts of graphite powder and 20 parts of ethyl acetate.

[0094] Among them, the PVC paste resin is a homopolymer resin with a polymerization degree of 1200; the particle size of calcium stearate is below 800 mesh sieve; the particle size of zinc stearate is below 800 mesh sieve; the particle size of nano calcium carbonate is below 100 nm; the particle size of graphite powder is below 325 mesh sieve.

[0095] The preparation method of the above low-temperature baking PVC plastisol comprises the following steps:

[0096] S1: Add PVC paste resin to the reaction kettle according to the parts by mass, start stirring at a speed of 500 r / min, add dioctyl maleate, stir at 32 °C for 20 min, then add isopropyl myristate and PEG-10 distearate, and stir for 45 min to fully swell and mix the PVC paste resin evenly to form a uniform base glue solution;

[0097] S2: Add shea butter, copaiba resin and biphenyl epoxy resin premixed evenly with 85% of the parts by mass of ethyl acetate to the base glue solution according to the parts by mass, and stir at a speed of 300 r / min for 20 min to fuse evenly;

[0098] S3: Add calcium stearate, zinc stearate, nano calcium carbonate and graphite powder according to the mass parts, stir at a speed of 600 r / min for 20 min until evenly mixed;

[0099] Calcium stearate, zinc stearate, nano calcium carbonate and graphite powder are evenly mixed by air flow before adding;

[0100] S4: Add antioxidant 1010, antioxidant 168 and silicone defoamer according to the mass parts, stir at a speed of 150 r / min for 15 min, let stand for 3 min to allow the bubbles to overflow fully, then add M50 isocyanate curing agent and aziridine crosslinking agent, stir at a speed of 250 r / min for 30 min until evenly mixed and free of bubble defects;

[0101] S5: Finally, add the remaining ethyl acetate, stir at a speed of 150 r / min for 30 min to adjust the viscosity, obtain the PVC plastisol, and store it sealed.

[0102] In the above preparation method, during the whole mixing process, the temperature does not exceed 32 °C.

[0103] Example 6

[0104] A low-temperature baking PVC plastisol, the PVC plastisol comprises the following raw materials in mass parts: 95 parts of PVC paste resin, 11 parts of copal resin, 9 parts of biphenyl epoxy resin, 6 parts of shea butter, 32 parts of dioctyl maleate, 12 parts of isopropyl myristate, 4 parts of PEG-10 distearate, 2 parts of calcium stearate, 2.5 parts of zinc stearate, 12 parts of nano calcium carbonate, 3 parts of M50 isocyanate curing agent, 1.5 parts of aziridine crosslinking agent, 0.8 part of antioxidant 1010, 0.6 part of antioxidant 168, 0.3 part of silicone defoamer, 3 parts of pigment and 18 parts of ethyl acetate.

[0105] Among them, the PVC paste resin is a homopolymer resin with a polymerization degree of 1300; the particle size of calcium stearate is below 800 mesh sieve; the particle size of zinc stearate is below 800 mesh sieve; the particle size of nano calcium carbonate is below 100 nm.

[0106] Among them, the pigment is a mixture of rutile titanium dioxide and graphite powder in a mass ratio of 3:2; the rutile titanium dioxide is rutile type titanium dioxide, and the particle size is below 500 mesh sieve; the particle size of graphite powder is below 200 mesh sieve.

[0107] The preparation method of the above low-temperature baking PVC plastisol comprises the following steps:

[0108] S1: By mass fraction, add PVC paste resin into a reaction kettle, start stirring at a speed of 350 r / min, add dioctyl maleate, stir at 30 °C for 20 min, then add isopropyl myristate and PEG-10 distearate, and stir for 30 min to fully swell and mix the PVC paste resin evenly to form a uniform basic glue solution;

[0109] S2: By mass fraction, add shea butter, copaiba resin and biphenyl epoxy resin that are pre-mixed evenly with 90% mass fraction of ethyl acetate into the basic glue solution, stir at a speed of 400 r / min for 10 min, and mix evenly;

[0110] S3: By mass fraction, add calcium stearate, zinc stearate, nano calcium carbonate and pigment, stir at a speed of 600 r / min for 30 min, and mix evenly;

[0111] Calcium stearate, zinc stearate, nano calcium carbonate and pigment are pre-mixed evenly by a double cone before adding;

[0112] S4: By mass fraction, add antioxidant 1010, antioxidant 168 and silicone defoamer, stir at a speed of 200 r / min for 15 min, let it stand for 3 min to fully overflow the bubbles, then add M50 isocyanate curing agent and aziridine crosslinking agent, and stir at a speed of 200 r / min for 40 min to mix evenly and have no bubble defects;

[0113] S5: Finally, add the remaining ethyl acetate, stir at a speed of 250 r / min for 30 min to adjust the viscosity, obtain PVC plastisol, and store it sealed.

[0114] In the above preparation method, during the whole mixing process, the temperature does not exceed 32 °C.

[0115] For the usage method of the low-temperature baking type PVC plastisol prepared in the above embodiments, the coating amount of the PVC plastisol is controlled at 120 g / m² - 250 g / m², and the baking temperature is controlled at 65 °C - 80 °C.

[0116] In the above embodiments: The model of the PVC paste resin is PR-450, sourced from Yuyao Mingzhi Plasticizing Co., Ltd.; the Copaiba resin is sourced from Shenzhen Regent Biotechnology Co., Ltd.; the model of the biphenyl epoxy resin is PA37346, sourced from Guangdong Wengjiang Chemical Reagent Co., Ltd.; the shea butter is sourced from Guangzhou Jiaqi Biotechnology Co., Ltd.; the model of dioctyl maleate is DOM, sourced from Shandong Jingtai Chemical Co., Ltd.; the model of isopropyl myristate is IPM, sourced from Guangzhou Zhengli Chemical Co., Ltd.; PEG-10 distearate is sourced from Shanghai Huijun Chemical Co., Ltd.; calcium stearate is sourced from Dongguan Kangjin New Materials Technology Co., Ltd.; zinc stearate is sourced from Dongguan Kangjin New Materials Technology Co., Ltd.; nano calcium carbonate is sourced from Shanghai Naiou Nano Technology Co., Ltd.; the model of the M50 isocyanate curing agent is YN1828, sourced from Shanghai Kaizhi New Materials Technology Co., Ltd.; the model of the aziridine crosslinking agent is HG-100, sourced from Guangzhou Hangeng New Materials Co., Ltd.; antioxidant 1010 is sourced from Dongguan Shanyi Plasticizing Co., Ltd.; antioxidant 168 is sourced from Dongguan Shanyi Plasticizing Co., Ltd.; the model of the silicone defoamer is DP-217, sourced from Guangdong Tianfeng Defoamer Co., Ltd.; ethyl acetate is sourced from Shandong Hengshuo Chemical Co., Ltd.

[0117] Comparative Example 1

[0118] In the PVC plastisol, Copaiba resin is not added, and the mass fraction of Copaiba resin is replaced by PVC paste resin; other parameters and methods are the same as in Example 1.

[0119] Comparative Example 2

[0120] In the PVC plastisol, biphenyl epoxy resin is not added, and the mass fraction of biphenyl epoxy resin is replaced by PVC paste resin; other parameters and methods are the same as in Example 1.

[0121] Comparative Example 3

[0122] In the PVC plastisol, both Copaiba resin and biphenyl epoxy resin are not added, and the mass fractions of both Copaiba resin and biphenyl epoxy resin are replaced by PVC paste resin; other parameters and methods are the same as in Example 1.

[0123] Comparative Example 4

[0124] In the PVC plastisol, shea butter is not added, and the shea butter is replaced by 2 parts of ethyl acetate (to adjust the appropriate viscosity); other parameters and methods are the same as in Example 1.

[0125] Comparative Example 5

[0126] In the PVC plastisol, isopropyl myristate is not added, and the isopropyl myristate is replaced by 4 parts of ethyl acetate (to adjust the appropriate viscosity); other parameters and methods are the same as in Example 1.

[0127] Comparative Example 6

[0128] PEG - 10 distearate is not added to the PVC plastisol, and 3 parts of ethyl acetate are used to replace PEG - 10 distearate (adjust the viscosity to be appropriate); other parameters and methods are the same as those in Example 1.

[0129] Comparative Example 7

[0130] Both shea butter and PEG - 10 distearate are not added to the PVC plastisol, and 5 parts of ethyl acetate are used to replace shea butter and PEG - 10 distearate (adjust the viscosity to be appropriate); other parameters and methods are the same as those in Example 1.

[0131] Comparative Example 8

[0132] Both shea butter, PEG - 10 distearate and isopropyl myristate are not added to the PVC plastisol, and 8 parts of ethyl acetate are used to replace shea butter, PEG - 10 distearate and isopropyl myristate (adjust the viscosity to be appropriate); other parameters and methods are the same as those in Example 1.

[0133] Perform performance tests on the PVC plastisols prepared in the above - mentioned examples and comparative examples.

[0134] I. Test sample:

[0135] 1. Material: Use a surface - treated aluminum alloy sheet with a thickness of 1 mm and a size of 150 mm × 50 mm. The aluminum alloy sheet has a strong material and a flat surface, and is not easily deformed during subsequent test operations.

[0136] 2. Surface treatment: Use sandpaper to polish the aluminum alloy sheet until the surface roughness Ra is 0.8 μm, and then clean and degrease it with acetone to ensure that the surface of the steel sheet is clean and free of oil and impurities, enhance the adhesion between the PVC plastisol and the aluminum alloy sheet, and make the test results more reliable.

[0137] II. Test items:

[0138] 1. Initial viscosity: Detect according to the method of GB / T 2794 "Determination of Viscosity of Adhesives - Single - Cylinder Rotating Viscometer Method". In a constant - temperature environment of 25 °C, take an appropriate amount of plastisol and place it in the measuring cylinder of the rotating viscometer. Select a suitable rotor to make the reading within 30% - 70% of the range, rotate at a speed of 60 r / min for 2 min and then read the value, with the unit of mPa·s. The test results are shown in Table 1 below.

[0139] 2. Adhesion (bonding strength with the substrate): Coat the plastisol on the sample plate at 160 g / m², bake it at 75 °C for 40 min until it is cured. Use a cross - cutter to make horizontal and vertical cuts on the cured coating to form 100 squares of 1 mm × 1 mm. After pasting and pressing with tape, quickly pull it up vertically, observe the coating peeling rate in the squares, and evaluate it according to the 0 - 5 level, with 0 level being the best. The test results are shown in Table 1 below.

[0140] 3. Water resistance (moisture-proof ability): Coat the plastisol on the sample plate at 160 g / m², bake at 75 °C for 40 min until cured, take out the sample plate after immersing it in distilled water at 40 °C for 24 h, 36 h, 48 h, 60 h, and 72 h, observe whether there are bubbles, peeling, and color change on the coating, record the time when obvious changes first occur, and the unit is h. The test results are shown in Table 1 below.

[0141] 4. Shear strength: Prepare an aluminum alloy plate with dimensions of 100 mm × 25 mm × 2 mm as the substrate, polish its surface with sandpaper until the surface roughness Ra is 1.6 μm, then clean and degrease it with acetone, and dry it for standby. Uniformly coat the low-temperature baking type PVC plastisol on the central area of an aluminum alloy plate, the coating area is 20 mm × 25 mm, control the coating amount to be 160 g / m², butt and fit another aluminum alloy plate treated in the same way, ensure there are no bubbles and gaps, fix it with a fixture, the fixture pressure is 0.5 MPa, place it at room temperature for 24 h, then put the sample into an oven at 75 °C and bake until cured, take it out and cool it to room temperature. Install the sample on the shear fixture of a universal material testing machine, make the force application direction parallel to the adhesive layer, load it at a constant speed of 5 mm / min until the adhesive layer is damaged, and record the maximum damage load F (unit: N). Calculate the shear strength = F / (20 × 25), unit: MPa. The test results are shown in Table 1 below.

[0142] 5. High-temperature resistance: Prepare multiple identical samples according to the sample preparation method for the shear strength test. Put the samples into a constant-temperature oven at the set temperature, start from 80 °C, increase the temperature in gradients of 5 °C, and keep the temperature at each point for 2 h. After the insulation ends, take out the samples, cool them to room temperature, observe whether there are phenomena such as cracking, bubbling, and peeling on the adhesive layer, and record the lowest temperature at which obvious damage occurs to the sample as the high-temperature resistance limit. The test results are shown in Table 1 below.

[0143] 6. Low-temperature resistance: Prepare samples in the same way as the sample preparation process for the shear strength test. Put the samples into a low-temperature test chamber, start from -20 °C, decrease the temperature in gradients of -5 °C, and keep the temperature at each point for 2 h. After the insulation ends, take out the samples and observe their appearance to check whether there are phenomena such as cracking and embrittlement, and record the lowest temperature at which obvious damage occurs to the sample as the low-temperature resistance limit. The test results are shown in Table 1 below.

[0144] Table 1 Viscosity and performance test results

[0145]

[0146] From the above test results, it can be seen that the PVC plastisols of each example have good bonding strength, water resistance, high and low temperature resistance, low baking temperature, and fast curing speed.

[0147] From the test results of Comparative Example 1 (without adding copal resin), it can be seen that copal resin helps to increase the cohesion and viscosity of the system in the PVC plastisol system. Without copal resin, the interaction of the system weakens, resulting in a decrease in the initial viscosity. Copal resin helps to enhance the bonding between the PVC plastisol and the substrate. Without copal resin, the adhesion decreases, and the bonding between the coating and the substrate becomes weaker. The tightness of the system becomes worse, and water molecules are more likely to penetrate. Copal resin may help to enhance the intermolecular interaction and cross-linked structure in the system. Without copal resin, the network structure after the glue cures is not tight enough. When subjected to shear force, the molecular chains are prone to relative sliding, resulting in a decrease in shear strength. Copal resin helps to maintain the structural stability of the glue at high temperatures. Without copal resin, the molecular chain movement of the glue intensifies at high temperatures. Due to insufficient cross-linking, phenomena such as cracking and blistering are more likely to occur, and the high-temperature resistance limit decreases. The absence of copal resin reduces the flexibility and anti-brittle properties of the molecular chains of the glue at low temperatures. At low temperatures, the activity of the molecular chains is limited. Without sufficient cross-linked structure to buffer the stress, the glue is more likely to become brittle and crack, and the low-temperature resistance limit decreases.

[0148] From the test results of Comparative Example 2 (without adding biphenyl epoxy resin), it can be seen that biphenyl epoxy resin helps to promote the reaction of the system, increase the cross-linking viscosity, and has a positive effect on adhesion; without biphenyl epoxy resin, the interaction of the components in the system changes, the overall fluidity increases, and the adhesion decreases. Without biphenyl epoxy resin, the loose structure of the system makes it easier for water molecules to enter the interior of the coating, and the water resistance decreases. Biphenyl epoxy resin participates in the cross-linking reaction during the curing process and enhances the cohesion of the glue. Without biphenyl epoxy resin, the degree of cross-linking is insufficient. When subjected to shear force, the bonding force inside the glue weakens, and the shear strength decreases. Biphenyl epoxy resin plays a key role in maintaining the structural integrity of the glue at high temperatures. Without biphenyl epoxy resin, the stability of the glue at high temperatures becomes worse, the force between the molecular chains weakens, and the temperature at which damage occurs decreases, and the high-temperature resistance limit decreases. Without biphenyl epoxy resin, the rigidity of the molecular chains of the glue increases and the flexibility becomes worse at low temperatures. In a low-temperature environment, the glue cannot effectively resist the internal stress generated by the temperature decrease, and the low-temperature resistance limit decreases.

[0149] From the test results of Comparative Example 3 (without adding copal resin and biphenyl epoxy resin), it can be seen that the two important resins are missing, the interaction of the system is severely damaged, and the viscosity drops significantly. The absence of the two resins severely reduces the adhesion between the coating and the substrate. The absence of the two resins severely damages the crosslinking network of the glue, and the intermolecular interaction is greatly weakened. Under the action of shear force, the glue hardly has enough cohesion to resist, and the shear strength drops significantly. The structural stability of the glue at high temperature is extremely poor. At high temperature, the molecular chains of the glue are loose and cannot maintain their original shape, and the high-temperature resistance limit drops significantly. Without these two resins to adjust the flexibility and cohesion of the glue, the molecular chains become very fragile at low temperature. In a low-temperature environment, the glue is easily damaged due to shrinkage and internal stress, and the low-temperature resistance limit drops.

[0150] From the test results of Comparative Example 4 (without adding shea butter), it can be seen that shea butter has little effect on the initial viscosity, and the other main components still maintain their original interactions. Shea butter has a certain auxiliary effect on adhesion, plasticization, and solubilization. Without shea butter, the fusion of other components is poor, the crosslinking effect is weakened, and the adhesion drops to level 1, and the combination between the coating and the substrate becomes weaker. Shea butter helps to form a waterproof barrier. Without shea butter, the water resistance drops. Shea butter has a certain plasticizing and solubilizing effect on the glue, enhances the lubricity between molecular chains, and enhances the fusion of resin components. Without shea butter, the friction between molecular chains increases, and under the action of shear force, the relative movement of molecular chains is hindered, and the shear strength drops. Shea butter helps to maintain the flexibility of the glue at high temperature. Without shea butter, the flexibility of the molecular chains of the glue at high temperature decreases, and it is more likely to be damaged, and the high-temperature resistance limit drops. The absence of shea butter weakens the activity of the molecular chains of the glue at low temperature. In a low-temperature environment, the glue lacks flexibility, and the molecular chains are easily broken, and the low-temperature resistance limit drops.

[0151] From the test results of Comparative Example 5 (without adding isopropyl myristate), it can be seen that isopropyl myristate has a solubilizing effect, improves the fusion of other components, improves the uniformity of the product, and thus makes a certain contribution to adhesion and water resistance. Without isopropyl myristate, the adhesion and water resistance drop. Isopropyl myristate helps the infiltration and adsorption of glue molecules on the surface of the adherend, thereby enhancing the bonding force. Without isopropyl myristate, the shear strength drops. Isopropyl myristate improves the fusion of other components and the uniformity of the product, and has better stability for the glue at high temperature. Without isopropyl myristate, the stability of the glue at high temperature is affected. Without isopropyl myristate, the bonding force between the glue and the substrate becomes weaker at low temperature, and at the same time the flexibility of the glue itself also decreases, and the low-temperature resistance limit drops.

[0152] From the test results of Comparative Example 6 (without adding PEG-10 distearate), it can be seen that PEG-10 distearate has a regulating effect on the viscosity of the system. PEG-10 distearate has a solubilizing effect, which can improve the fusion of other components, improve the uniformity of the cross-linking reaction of the product, improve the adhesion and water resistance. Without PEG-10 distearate, the adhesion and water resistance become poor. PEG-10 distearate plays a role in regulating the cohesion and flexibility of the glue, as well as a solubilizing effect. Without PEG-10 distearate, the internal structure of the glue is uneven. Under the action of shear force, the force distribution of the molecular chain is unreasonable and the shear strength decreases. PEG-10 distearate helps to maintain the uniformity and stability of the glue at high temperatures. Without PEG-10 distearate, the glue is prone to local structural damage at high temperatures and the high-temperature resistance limit decreases. Without PEG-10 distearate, the flexibility and uniformity of the glue become poor at low temperatures. In a low-temperature environment, the glue is prone to stress concentration due to uneven structure and the low-temperature resistance limit decreases.

[0153] In Comparative Example 7 (without adding shea butter and PEG-10 distearate at the same time), the lack of these two components makes the fusion and uniformity of the system seriously deteriorate, affecting the cross-linking quality of the system, and then greatly affecting the adhesion, shear strength, high-temperature resistance and low-temperature resistance.

[0154] In Comparative Example 8 (without adding shea butter, PEG-10 distearate and isopropyl myristate at the same time), the simultaneous absence of these three solubilizing components seriously affects the fusion of other components, the uniformity deteriorates severely, affects the uniformity of the cross-linking quality of the system, the internal stress is uneven, and the performance such as adhesion, shear strength, high-temperature resistance and low-temperature resistance decreases significantly.

Claims

1. A low-temperature baking type PVC plastisol, characterized in that: The PVC plastisol includes the following raw materials in parts by mass: 80 to 100 parts of PVC paste resin, 10 to 15 parts of Copal resin, 5 to 10 parts of biphenyl epoxy resin, 5 to 8 parts of shea butter, 25 to 35 parts of dioctyl maleate, 10 to 15 parts of isopropyl myristate, 3 to 5 parts of PEG-10 distearate, 2 to 4 parts of calcium stearate, 1 to 3 parts of zinc stearate, 10 to 20 parts of nano calcium carbonate, 2 to 3 parts of M50 isocyanate curing agent, 1 to 3 parts of aziridine crosslinking agent, 0.5 to 1 part of antioxidant 1010, 0.5 to 1 part of antioxidant 168, 0.1 to 0.3 parts of silicone defoaming agent, 3 to 5 parts of pigment and 15 to 25 parts of diluent.

2. A low-temperature baking type PVC plastisol according to claim 1, characterized in that: The PVC paste resin is a homopolymer resin with a polymerization degree of 1000-1300.

3. A low-temperature baking type PVC plastisol according to claim 1, characterized in that: The particle size of the calcium stearate is sieved through 800-900 mesh; the particle size of the zinc stearate is sieved through 650-800 mesh.

4. The low-temperature baking type PVC plastisol according to claim 1, characterized in that: The particle size of the nano calcium carbonate is less than 100 nm.

5. The low-temperature baking type PVC plastisol according to claim 1, characterized in that: The pigment is at least one of titanium dioxide and graphite powder; the titanium dioxide is rutile titanium dioxide, and the particle size of the titanium dioxide is 325-500 mesh sieve; the particle size of the graphite powder is 200-325 mesh sieve.

6. The low-temperature baking type PVC plastisol according to claim 1, characterized in that: The diluent is ethyl acetate.

7. A method for preparing a low-temperature baking type PVC plastisol, for preparing a low-temperature baking type PVC plastisol according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: S1: Add PVC paste resin to the reactor according to the mass fraction, stir at 300r / min~500r / min, add dioctyl maleate, stir at 25℃~32℃ for 15min~20min, then add isopropyl myristic acid and PEG-10 distearate, stir for 30min~45min, so that the PVC paste resin is fully swollen and mixed evenly to form a uniform basic glue solution; S2: Add 80% to 90% by mass of diluent, shea butter, Copal resin and biphenyl epoxy resin to the base glue solution, and stir at a speed of 300 r / min to 500 r / min to blend evenly; S3: Add calcium stearate, zinc stearate, nano calcium carbonate and pigment according to their mass fractions, stir at a speed of 500 r / min to 600 r / min, and mix evenly; S4: Add antioxidant 1010, antioxidant 168 and silicone defoamer according to their mass fractions, stir at a speed of 150r / min to 200r / min for 10min to 15min, let stand for 3min to 5min to allow bubbles to fully overflow, then add M50 isocyanate curing agent and aziridine crosslinking agent, stir at a speed of 200r / min to 250r / min, mix evenly and without bubble defects; S5: Finally, add the remaining diluent, stir at a speed of 150 r / min to 250 r / min, adjust the viscosity until it is uniform, and obtain PVC plastisol, which is sealed for storage.

8. The method for preparing a low-temperature baking type PVC plastisol according to claim 7, characterized in that: In S3, the calcium stearate, zinc stearate, nano calcium carbonate and pigment are uniformly mixed by double cone mixing or air flow mixing before being added.

9. The method for preparing a low-temperature baking type PVC plastisol according to claim 7, characterized in that: In S2, the stirring time at a speed of 300r / min to 500r / min is 10min to 20min; the shea butter, copal resin and biphenyl epoxy resin are pre-mixed with the diluent before being added; in S3, the stirring time at a speed of 500r / min to 600r / min is 20min to 30min; in S4, the stirring time at a speed of 200r / min to 250r / min is 30min to 45min; in S5, the stirring time at a speed of 150r / min to 250r / min is 25min to 30min.

10. A method for using a low-temperature baking type PVC plastisol, using the low-temperature baking type PVC plastisol according to any one of claims 1 to 6, characterized in that: The coating amount of PVC plastisol is controlled at 120g / m²~250g / m², and the baking temperature is controlled at 65℃~80℃.

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