Microporous plastic particle material and preparation method thereof

Abstract

The invention discloses a microporous plastic particle material which is prepared from a prepolymer, a foaming agent, a catalyst and an antioxidant, and the prepolymer is prepared from the following raw materials in parts by mass: 40-60 parts of polyether polyol; 20 to 30 parts of isocyanate; 12-20 parts of a plasticizer; 1-5 parts of a cross-linking agent; 15 to 25 parts of filler; 10 to 15 parts of pigment; the micropore diameter of the plastic particles is 8-20 microns, and the hole depth is 10-25 microns. Reasonable preparation process parameters are designed by selecting raw materials such as a prepolymer, a foaming agent, a catalyst, an antioxidant and the like and the mass, so that the obtained plastic particles have microporous structures with certain pore diameters and pore depths, internal defects and stress concentration points are reduced, the material can bear loads more uniformly when subjected to tensile force, and the tensile strength of the material is improved. The stress concentration of the material under the action of external force is effectively relieved, so that when the material is stretched, the stress can be more uniformly distributed, the rapid fracture caused by overlarge local stress is reduced, the strength and the elasticity of the material are improved, and a wider application scene can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane synthesis, and in particular to a microporous plastic particle material and a preparation method thereof. Background Art

[0002] As an important polymer material, polyurethane (PU) has been widely used in many industrial fields, such as furniture, construction, automobiles, footwear and adhesives, due to its excellent physical properties and chemical stability. However, due to the limitations of its own structure and preparation process, traditional polyurethane particles have some significant defects, which restrict their further application and development.

[0003] First, traditional polyurethane particles tend to have greater hardness and lower elasticity. This is mainly due to improper control of parameters such as the ratio of polyether polyol and isocyanate used in its preparation process and molecular weight. High hardness makes the material prone to brittle fracture when subjected to external forces, while low elasticity makes it difficult for the material to return to its original shape after impact or extrusion, reducing its service life and safety.

[0004] In addition, the application range of traditional polyurethane particles is relatively limited. Due to the lack of adjustability, these materials are difficult to meet the changing industrial needs, especially in occasions with special requirements for material properties. Summary of the invention

[0005] The present invention overcomes the shortcomings of the prior art and provides a microporous plastic granular material and a preparation method thereof.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a microporous plastic particle material is prepared from a prepolymer, a foaming agent, a catalyst and an antioxidant, and the prepolymer includes the following raw materials in parts by weight:

[0007]

[0008]

[0009] The micropores of the plastic particles have a pore diameter of 8-20 μm and a pore depth of 10-25 μm.

[0010] In a preferred embodiment of the present invention, the mass ratio of the prepolymer, the blowing agent, the catalyst and the antioxidant is 1:0.1-0.2:0.03-0.08:0.05-0.1.

[0011] In a preferred embodiment of the present invention, the average molecular weight of the polyether polyol is 3000-3500; and the isocyanate is a mixture of toluene diisocyanate and diphenylmethane diisocyanate.

[0012] In a preferred embodiment of the present invention, the foaming agent is one of azodicarbonamide or azobisisobutyronitrile; the catalyst is a mixture of BL-17 and dibutyltin dilaurate or one of triethylamine; and the antioxidant is one of bisphenol A or triphenyl phosphate.

[0013] In a preferred embodiment of the present invention, the plasticizer is one of dibutyl phthalate or dioctyl phthalate; the cross-linking agent is one of diethanolamine, melamine or diphenylmethane diisocyanate; the filler is one of calcium carbonate, barium sulfate or talc; and the pigment is one of ultramarine blue or red iron oxide.

[0014] The present invention provides a method for preparing a microporous plastic granular material, comprising the following steps:

[0015] S1. Add polyether polyol to a reaction kettle, add isocyanate, plasticizer, filler and pigment in sequence under stirring, heat treatment to complete the first reaction, add isocyanate and cross-linking agent again, heat treatment, vacuum dehydration until the water content of the system is less than 0.1%, complete the second reaction, and obtain a prepolymer;

[0016] S2, adding the prepolymer into the reaction kettle, and adding a certain proportion of the blowing agent, the catalyst and the antioxidant in sequence under stirring, heating and reacting to obtain a plastic mixture;

[0017] S3, granulating the plastic mixture in a granulator, and obtaining microporous plastic particles after drying.

[0018] In a preferred embodiment of the present invention, in step S1, the conditions of the first reaction are: heating temperature 90-120°C, reaction time 1-3h; the conditions of the second reaction are: heating temperature 90-120°C, reaction time 1-3h.

[0019] In a preferred embodiment of the present invention, in step S1, the isocyanate in the first reaction and the second reaction has the same mass.

[0020] In a preferred embodiment of the present invention, in the step S2, the conditions of the heating reaction are: heating temperature 80-180° C., reaction time 1-4 h.

[0021] In a preferred embodiment of the present invention, in step S3, the drying conditions are: drying temperature 50-60° C., and drying time 20-40 min.

[0022] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0023] (1) The present invention provides a microporous plastic particle material and a preparation method thereof. By selecting raw materials and qualities such as prepolymers, foaming agents, catalysts, antioxidants, etc., reasonable preparation process parameters are designed so that the obtained plastic particles have a microporous structure with a certain pore diameter and pore depth, optimize the internal structure of the material, reduce internal defects and stress concentration points, so that the material can bear the load more evenly when subjected to tensile force, effectively alleviate the stress concentration of the material when subjected to external force, so that when the material is stretched, the stress can be more evenly distributed, reduce rapid fracture caused by excessive local stress, and improve the strength and elasticity of the material, thereby achieving a wider range of application scenarios.

[0024] (2) In the present invention, by appropriately increasing the amount of polyether polyol and reducing the amount of isocyanate, the hardness of the plastic particles can be reduced and the elasticity can be improved. Since the molecular chain of the polyether polyol is relatively soft, reducing the amount of isocyanate can reduce the degree of crosslinking, thereby making it more elastic. At the same time, by uniformly adding isocyanate in steps for reaction, the side reaction between isocyanate and other components can be reduced, ensuring the purity of the reaction system so as to improve the effect of subsequent reactions. At the same time, it is ensured that the isocyanate and other components such as the polyether polyol are fully in contact and react at the molecular level to form a uniform prepolymer, thereby improving the elasticity, mechanical strength and durability of the plastic particles.

[0025] (3) The amount of foaming agent used in the present invention directly affects the size of the microporous structure. During the foaming process, gas molecules first nucleate in the mixture to form tiny bubbles. Increasing the amount of foaming agent can increase the number of nucleation points, thereby increasing the number of micropores. By adding the selected foaming agent at an appropriate concentration and providing a certain temperature reaction condition, the foaming agent reaches a suitable foaming temperature during decomposition, so that the pore wall softens and breaks, promoting the cross-linking reaction and the decomposition of the foaming agent, and then making the foaming agent decompose evenly in the material, forming a microporous structure with a relatively suitable size and uniform distribution, thereby improving the mechanical properties of the plastic particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 It is a flow chart of a method for preparing a microporous plastic granular material according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0030] It should be noted that the raw materials, equipment and reagents used in the present invention can be purchased from the market or obtained through the preparation methods of existing technologies.

[0031] A microporous plastic particle material: prepared from a prepolymer, a foaming agent, a catalyst and an antioxidant, wherein the prepolymer includes the following raw materials in parts by weight:

[0032]

[0033] The micropores of the plastic particles have a pore diameter of 8-20 μm and a pore depth of 10-25 μm.

[0034] In some embodiments, the mass ratio of the prepolymer, the blowing agent, the catalyst and the antioxidant is 1: 0.1-0.2: 0.03-0.08: 0.05-0.1.

[0035] In some embodiments, the average molecular weight of the polyether polyol is 3000-3500; and the isocyanate is a mixture of toluene diisocyanate and diphenylmethane diisocyanate.

[0036] In some embodiments, the foaming agent is one of azodicarbonamide or azobisisobutyronitrile; the catalyst is one of a mixture of BL-17 and dibutyltin dilaurate or triethylamine; and the antioxidant is one of bisphenol A or triphenyl phosphate.

[0037] In some embodiments, the plasticizer is one of dibutyl phthalate or dioctyl phthalate; the crosslinker is one of diethanolamine, melamine or diphenylmethane diisocyanate; the filler is one of calcium carbonate, barium sulfate or talc; and the pigment is one of ultramarine blue or red iron oxide.

[0038] A method for preparing a microporous plastic granular material comprises the following steps:

[0039] S1. Add polyether polyol to a reaction kettle, add isocyanate, plasticizer, filler and pigment in sequence under stirring, heat treatment to complete the first reaction, add isocyanate and cross-linking agent again, heat treatment, vacuum dehydration until the water content of the system is less than 0.1%, complete the second reaction, and obtain a prepolymer;

[0040] S2, adding the prepolymer into the reaction kettle, and adding a certain proportion of the blowing agent, the catalyst and the antioxidant in sequence under stirring, heating and reacting to obtain a plastic mixture;

[0041] S3, granulating the plastic mixture in a granulator, and obtaining microporous plastic particles after drying.

[0042] In step S1 of the present invention, the conditions for the first reaction are: heating temperature 90-120° C., reaction time 1-3 h; the conditions for the second reaction are: heating temperature 90-120° C., reaction time 1-3 h.

[0043] In step S1 of the present invention, the mass of isocyanate in the first reaction and the second reaction is the same.

[0044] In step S2 of the present invention, the conditions for the heating reaction are: heating temperature 80-180° C., and reaction time 1-4 h.

[0045] In step S3 of the present invention, the drying conditions are: drying temperature 50-60° C., and drying time 20-40 min.

[0046] The following is a detailed description of the overall implementation of the present invention in conjunction with specific examples.

[0047] The raw material ratios of the prepolymers in Examples 1-5 are different, as shown in Table 1, and the raw materials are measured by mass fraction.

[0048] Table 1:

[0049]

[0050]

[0051] Example 1

[0052] A method for preparing a microporous plastic granular material comprises the following steps:

[0053] S1. Add polyether polyol to a reactor, and under stirring, sequentially add a mixture of toluene diisocyanate and diphenylmethane diisocyanate, dibutyl phthalate, talcum powder and red iron oxide, react at a temperature of 100° C. for 2 h to complete the first reaction, add a mixture of toluene diisocyanate and diphenylmethane diisocyanate and diethanolamine again, react at a temperature of 100° C. for 2 h, vacuum dehydrate until the water content of the system is less than 0.1%, complete the second reaction, and obtain a prepolymer;

[0054] S2, preparing a prepolymer, azodicarbonamide, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate in a mass ratio of 1:0.15:0.05:0.1, adding the prepolymer to a reactor, and adding azodicarbonamide, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate in sequence under stirring, reacting at a temperature of 160° C. for 3 hours to obtain a plastic mixture;

[0055] S3. Granulate the plastic mixture in a granulator, and dry the product at 50° C. for 30 minutes to obtain microporous plastic particles.

[0056] The average molecular weight of the polyether polyol is 3500, and the mass of the mixture of toluene diisocyanate and diphenylmethane diisocyanate in the first reaction and the second reaction is the same.

[0057] Example 2

[0058] This embodiment is basically the same as Embodiment 1, except that: the raw materials and the proportions are different, as shown in Table 1; the step of S2 is to prepare a prepolymer, azobisisobutyronitrile, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate in a mass ratio of 1:0.1:0.08:0.05, add the prepolymer to a reactor, and under stirring, sequentially add azobisisobutyronitrile, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate, and react at a temperature of 80°C for 4 hours to obtain a plastic mixture; wherein the average molecular weight of the polyether polyol is 3000.

[0059] Example 3

[0060] This embodiment is basically the same as Embodiment 1, except that: the raw materials and the proportions are different, as shown in Table 1; the step of S2 is to prepare a prepolymer, azodicarbonamide, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate in a mass ratio of 1:0.2:0.08:0.1, add the prepolymer to a reactor, and under stirring, sequentially add azodicarbonamide, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate, and react at a temperature of 140°C for 3 hours to obtain a plastic mixture.

[0061] Example 4

[0062] This embodiment is basically the same as Embodiment 1, except that the raw materials and proportions are different, as shown in Table 1; the step of S2 is to prepare a prepolymer, azodicarbonamide, triethylamine and bisphenol A in a mass ratio of 1:0.15:0.05:0.1, add the prepolymer to a reactor, add azodicarbonamide, triethylamine and bisphenol A in sequence under stirring, react at a temperature of 180°C for 3 hours to obtain a plastic mixture.

[0063] Example 5

[0064] This embodiment is basically the same as Embodiment 1, except that the raw materials and the proportions are different, as shown in Table 1; the step of S2 is to prepare a prepolymer, azobisisobutyronitrile, triethylamine and triphenyl phosphate in a mass ratio of 1:0.1:0.03:0.1, add the prepolymer to a reactor, add azobisisobutyronitrile, triethylamine and triphenyl phosphate in sequence under stirring, react at a temperature of 100°C for 2h to obtain a plastic mixture.

[0065] Comparative Example 1

[0066] This comparative example is substantially the same as Example 1, except that the mass fraction of the isocyanate (a mixture of toluene diisocyanate and diphenylmethane diisocyanate) in the prepolymer is 15 parts.

[0067] Comparative Example 2

[0068] This comparative example is basically the same as Example 1, except that: the step of S1 is: adding polyether polyol to a reaction kettle, and adding a mixture of toluene diisocyanate and diphenylmethane diisocyanate, dibutyl phthalate, talcum powder, red iron oxide and diethanolamine in sequence under stirring, reacting at a temperature of 100°C for 2h, and vacuum dehydrating until the water content of the system is less than 0.1%, to obtain a prepolymer.

[0069] Comparative Example 3

[0070] This comparative example is basically the same as Example 1, except that the average molecular weight of the polyether polyol is 4500.

[0071] Comparative Example 4

[0072] This comparative example is basically the same as Example 1, except that the average molecular weight of the polyether polyol is 2000.

[0073] Comparative Example 5

[0074] This comparative example is substantially the same as Example 1, except that the mass ratio of the prepolymer to azodicarbonamide is 1:0.05.

[0075] Comparative Example 6

[0076] This comparative example is substantially the same as Example 1, except that the mass ratio of the prepolymer to azodicarbonamide is 1:0.3.

[0077] Comparative Example 7

[0078] This comparative example is basically the same as Example 1, except that: the step of S2 is: preparing a prepolymer, azodicarbonamide, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate in a mass ratio of 1:0.15:0.05:0.1, adding the prepolymer to a reactor, and adding azodicarbonamide, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate in sequence under stirring, reacting at a temperature of 200°C for 3 hours to obtain a plastic mixture.

[0079] Comparative Example 8

[0080] This comparative example is basically the same as Example 1, except that: the step of S2 is: preparing a prepolymer, azodicarbonamide, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate in a mass ratio of 1:0.15:0.05:0.1, adding the prepolymer to a reactor, and adding azodicarbonamide, a mixture of BL-17 and dibutyltin dilaurate, and triphenyl phosphate in sequence under stirring, reacting at a temperature of 130°C for 3 hours to obtain a plastic mixture.

[0081] The microporous plastic particles prepared in the above Examples 1-5 and Comparative Examples 1-8 were observed for microporous structure and subjected to tensile tests. The results are shown in Table 2.

[0082] Table 2:

[0083]

[0084]

[0085] It can be seen from Tables 1 and 2 that:

[0086] The microporous plastic particles have a microporous structure of appropriate size, which can optimize the internal structure of the material, reduce internal defects and stress concentration points, so that the material can bear the load more evenly when subjected to tensile force, improve the mechanical properties of the material, and effectively alleviate the stress concentration of the material when subjected to external force, so that the stress can be more evenly distributed when the material is stretched, reducing the rapid fracture caused by excessive local stress. The existence of the microporous structure increases the elasticity of the material to a certain extent, so that the material can undergo a certain degree of deformation without immediate destruction when subjected to external force, and can effectively absorb and disperse impact energy, thereby playing a role in shock absorption and buffering.

[0087] It can be seen from Examples 1-5 that by appropriately increasing the amount of polyether polyol and reducing the amount of isocyanate (a mixture of toluene diisocyanate and diphenylmethane diisocyanate), the hardness of the plastic particles can be reduced and the elasticity can be improved. Since the molecular chain of the polyether polyol is relatively soft, reducing the amount of isocyanate can reduce the degree of crosslinking, thereby making it more elastic. By comparing Example 1 with Comparative Example 1, it can be seen that when the amount of isocyanate is too low, the unreacted polyether polyol molecular chain will be relatively long, which will increase the entanglement and curling of the molecular chain, thereby affecting the microstructure of the plastic particles, and at the same time will cause the network structure to be unstable, reducing the durability and service life of the material, and the change in the length and distribution of the molecular chain will affect its physical properties, reduce the overall mechanical properties of the material, and cause the microporous structure to collapse, crack or uneven pore structure.

[0088] By comparing Example 1 with Comparative Example 2, it can be seen that by uniformly adding isocyanate in steps to react, the side reactions between isocyanate and other components (such as moisture) can be reduced, the purity of the reaction system can be ensured, so as to improve the effect of subsequent reactions, and at the same time, it can be ensured that isocyanate and other components such as polyether polyols are fully contacted and reacted at the molecular level to form a uniform prepolymer. When isocyanate is added for the first time, the reaction rate is slow, which helps to form a stable prepolymer. When it is added for the second time, it is added together with the cross-linking agent, which can accurately control the start and progress of the cross-linking reaction, thereby affecting the network structure of the final product, better controlling the distribution and effect of the cross-linking agent, and affecting the connection mode between the molecular chains, making them more uniform and orderly, thereby improving the elasticity, mechanical strength and durability of the plastic particles.

[0089] By comparing Example 1 with Comparative Examples 3 and 4, it can be seen that the average molecular weight of the polyether polyol determines the length of its molecular chain. When polyether polyols of different molecular weights react with isocyanate, microporous structures of different sizes and depths will be formed. Polyether polyols with larger molecular weights have longer molecular chains. When long-chain polyether polyols react with components such as isocyanate, the formed polyurethane chain segments are longer and the distance between crosslinking points is farther. In the subsequent foaming process, it is easier for gas to form larger bubbles between the chain segments, that is, the size and depth of the microporous structure increase. When the molecular weight of the polyether polyol is larger, the size and depth of the microporous structure formed in the plastic particles are too large, thereby affecting the mechanical properties of the plastic particles. The network structure formed by polyether polyols with smaller molecular weights has a higher crosslinking density, because the shorter chain length leads to more crosslinking points per unit volume, and the high crosslinking density limits the expansion space of the gas during the foaming process, so the size of the formed micropores is smaller and evenly distributed. When the molecular weight of the polyether polyol is smaller, the size of the microporous structure formed in the plastic particles is too small, resulting in poor mechanical properties of the plastic particles.

[0090] By comparing Example 1 with Comparative Examples 5 and 6, it can be seen that the amount of foaming agent directly affects the size of the microporous structure. During the foaming process, gas molecules first nucleate in the mixture to form tiny bubbles. The increase in the amount of foaming agent can increase the number of nucleation points, thereby increasing the number of micropores. When the amount of foaming agent is too low, the size of the microporous structure will gradually decrease. Since the distribution of the foaming agent in the material is relatively uniform, a large number of micropores are formed, making the size of each micropore small. When the amount of foaming agent is too high, the size of the microporous structure will increase rapidly. Since the high concentration of the foaming agent releases a large amount of decomposition heat during decomposition, the initial foaming temperature is increased, and the internal temperature of the material is sharply increased, causing the pore wall to soften excessively. The foam cells grow rapidly or even rupture, making the size of each micropore larger; different foaming agents have different decomposition temperatures and decomposition rates, thereby affecting the formation and size of the micropores. The decomposition temperature of azodicarbonamide is higher than that of azobisisobutyronitrile. By comparing Example 1 with Comparative Examples 7 and 8, it can be seen that the reaction temperature has an important influence on the synthesis of plastic particles and the formation of micropores. An appropriate reaction temperature can promote the cross-linking reaction and the decomposition of the foaming agent, thereby facilitating the formation of micropores. However, too high a reaction temperature may cause the foaming agent to decompose too quickly and produce too large micropores, while too low a reaction temperature may cause the foaming agent to decompose incompletely, affecting the size of the micropores, thereby further reducing the mechanical properties of the plastic particles.

[0091] The microporous plastic particle material of the present invention designs reasonable preparation process parameters by selecting raw materials and qualities such as prepolymers, foaming agents, catalysts, antioxidants, etc., so that the obtained plastic particles have a microporous structure with a certain pore diameter and pore depth, optimize the internal structure of the material, reduce internal defects and stress concentration points, so that the material can bear the load more evenly when subjected to a tensile force, effectively alleviate the stress concentration of the material when subjected to an external force, so that when the material is stretched, the stress can be more evenly distributed, reduce rapid fracture caused by excessive local stress, and improve the strength and elasticity of the material, thereby achieving a wider range of application scenarios.

[0092] The above is based on the ideal embodiment of the present invention. Through the above description, it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0093] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A microporous plastic granular material, characterized in that: The prepolymer is prepared from a prepolymer, a blowing agent, a catalyst and an antioxidant, wherein the prepolymer comprises the following raw materials in parts by weight: The micropores of the plastic particles have a pore diameter of 8-20 μm and a pore depth of 10-25 μm.

2. The method for preparing a microporous plastic granular material according to claim 1, characterized in that: The mass ratio of the prepolymer, the blowing agent, the catalyst and the antioxidant is 1:0.1-0.2:0.03-0.08:0.05-0.

1.

3. The method for preparing a microporous plastic granular material according to claim 1, characterized in that: The average molecular weight of the polyether polyol is 3000-3500; the isocyanate is a mixture of toluene diisocyanate and diphenylmethane diisocyanate.

4. The method for preparing a microporous plastic granular material according to claim 1, characterized in that: The foaming agent is one of azodicarbonamide and azobisisobutyronitrile; the catalyst is a mixture of BL-17 and dibutyltin dilaurate or one of triethylamine; and the antioxidant is one of bisphenol A and triphenyl phosphate.

5. The method for preparing a microporous plastic granular material according to claim 1, characterized in that: The plasticizer is one of dibutyl phthalate or dioctyl phthalate; the crosslinking agent is one of diethanolamine, melamine or diphenylmethane diisocyanate; the filler is one of calcium carbonate, barium sulfate or talc; the pigment is one of ultramarine blue or red iron oxide.

6. A method for preparing a microporous plastic granular material according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Add polyether polyol to a reaction kettle, add isocyanate, plasticizer, filler and pigment in sequence under stirring, heat treatment to complete the first reaction, add isocyanate and cross-linking agent again, heat treatment, vacuum dehydration until the water content of the system is less than 0.1%, complete the second reaction, and obtain a prepolymer; S2, adding the prepolymer into the reaction kettle, and adding a certain proportion of the blowing agent, the catalyst and the antioxidant in sequence under stirring, heating and reacting to obtain a plastic mixture; S3, granulating the plastic mixture in a granulator, and obtaining microporous plastic particles after drying.

7. The method for preparing a microporous plastic granular material according to claim 6, characterized in that: In the step S1, the conditions of the first reaction are: heating temperature 90-120° C., reaction time 1-3 h; the conditions of the second reaction are: heating temperature 90-120° C., reaction time 1-3 h.

8. The method for preparing a microporous plastic granular material according to claim 6, characterized in that: In the step S1, the isocyanate in the first reaction and the second reaction has the same mass.

9. The method for preparing a microporous plastic granular material according to claim 6, characterized in that: In the step S2, the conditions of the heating reaction are: heating temperature 80-180°C, reaction time 1-4h.

10. The method for preparing a microporous plastic granular material according to claim 6, characterized in that: In the step S3, the drying conditions are: drying temperature 50-60°C, and drying time 20-40 minutes.

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