Method for producing foamed rubber, foamed rubber and foamed article

Abstract

The application discloses a foamed rubber preparation method, foamed rubber and foamed product. The foamed rubber preparation method comprises the following steps: mixing a foaming agent, a rubber matrix, an additive and a carbon material to form a mixed product; and using a microwave process to prepare the mixed product into a foamed product. The application can make the foaming and vulcanization steps asynchronous in the preparation process of the foamed rubber, so that the foamed product prepared can be co-vulcanized with other materials.

Description

Technical Field

[0001] This application relates to the field of rubber technology, and more specifically, to a method for preparing foamed rubber, foamed rubber, and foamed products. Background Technology

[0002] In existing technologies, the foaming agent contained in rubber needs to foam at a temperature relatively higher than the vulcanization temperature of the rubber. Therefore, the preparation method of foamed rubber is usually as follows: first, the rubber and the foaming agent are mixed evenly, and then the mixture is placed in a mold for heating or hot pressing. This not only causes the foaming agent in the rubber to foam, but also causes the vulcanizing agent in the rubber to vulcanize, achieving simultaneous completion of foaming and vulcanization, which facilitates the formation of vulcanized foamed rubber.

[0003] However, although the above preparation method can complete foaming and vulcanization simultaneously, saving process steps, the foamed rubber formed has already been vulcanized and is difficult to further process into the desired shape, or difficult to co-vulcanize with other materials to form composite products, forming foamed products with high storage performance and whose cells will not collapse during storage, such as foamed tubes or foamed boards.

[0004] Current foamed products such as foamed pipes or foamed boards typically use thermosetting resins as the base material. Foaming is achieved by foaming uncured or incompletely cured monomeric or oligomeric resins to form foamed products. These foamed products can then be bonded to other desired materials to form the desired pipes or boards, which are then cured during subsequent processing or application. However, because thermosetting resins are used, the foamed products prepared using this method require adhesives to bond with other material layers during subsequent use, leading to the formation of interlayer interfaces. Consequently, when the prepared foamed products need to be bent, interlayer delamination may occur, resulting in poor bending performance. Furthermore, when producing pipe foamed products, the foamed material layers formed with thermosetting resin as the base material are prone to breakage and even pulverization due to frequent bending, further degrading mechanical properties and severely affecting the overall pipe structure.

[0005] Therefore, a new technical solution is needed to enable the foaming and vulcanization steps to be carried out asynchronously during the preparation of foamed rubber, so as to prepare foamed products that can be co-vulcanized with other materials. Summary of the Invention

[0006] One objective of this application is to provide a new technical solution for a method of preparing foamed rubber, foamed rubber, and foamed products.

[0007] According to a first aspect of this application, a method for preparing foamed rubber is provided, comprising: The foaming agent, rubber matrix, additives and carbon materials are mixed to form a compound; The mixture was prepared into a foamed product using a microwave process. The preparation of the foamed product from the compound using microwave technology includes: A. The compound is microwave irradiated with constant, gradual or intermittent power, and during the microwave irradiation, the ratio of the power of the microwave irradiation received by the compound to the mass of the rubber matrix and the carbon material is greater than or equal to 40 W / g. B. Before and after the microwave process, the surface temperature of at least one surface of the foamed product is controlled to be lower than the vulcanization temperature of the foamed product, so that at least a portion of the surface of the foamed product is not vulcanized or not completely vulcanized. Furthermore, the carbon material includes at least one of the following carbon materials: C. Graphene, wherein the graphene includes single-layer graphene, multi-layer graphene, or stacked graphene. D. Graphene oxide, wherein the graphene oxide includes single-layer graphene oxide, multi-layer graphene oxide, or stacked graphene oxide. E. Graphite; F. Expandable carbon material, wherein the expandable carbon material includes unexpanded expandable graphite; Furthermore, when the carbon material includes the expandable carbon material, the expandable carbon material is also considered as a type of foaming agent.

[0008] Preferably, when the foaming agent is not a carbon material, the vaporization or decomposition temperature of the foaming agent is less than or equal to 300°C; And / or, when the carbon material contains expandable carbon material, the foaming agent vaporizes or decomposes to produce gas at a temperature not exceeding a first temperature; wherein, the first temperature is the temperature at which the expandable carbon material loses 30% of its mass under an inert gas atmosphere.

[0009] Preferably, the mass ratio of the foaming agent to the rubber matrix is ​​1~80:100; Furthermore, the mass ratio of the carbon material to the rubber matrix is ​​less than or equal to 80:100.

[0010] Preferably, after mixing the foaming agent, rubber matrix, additives, and carbon material to form a compound, and before preparing the compound into a foamed product using a microwave process, the method further includes: The mixture is preheated.

[0011] Preferably, the preparation of the foamed product from the compound using a microwave process includes: The heating rate of the carbon material is greater than or equal to 10℃ / s; The heating rate of the rubber matrix in the region adjacent to the carbon material is greater than or equal to 10°C / s.

[0012] Preferably, the preparation of the foamed product from the compound using a microwave process includes: The mixture is placed in a mold and microwaved, or the mixture is fixed with a fastener and then microwaved, or the mixture is placed in a medium or on the surface of a medium and microwaved.

[0013] Preferably, the process before and after microwave treatment includes: The temperature of the mold surface in contact with the compound is lower than the vulcanization temperature of the foamed product. Alternatively, the temperature of the surface of the medium or the interface between the compound and the medium is lower than the vulcanization temperature of the foamed product.

[0014] Preferably, the material of the mold includes at least one of microwave-transparent material and metal material; Wherein, the mold or medium made of metal material cannot completely shield the microwave source used in the microwave process from microwave irradiation of the mixture.

[0015] Preferably, the carbon material comprises an expandable carbon material, and the foamed product contains pores having all or part of pore walls formed of a non-rubber material.

[0016] Preferably, the process of preparing the foamed product from the compound using a microwave process includes: In the unvulcanized or incompletely vulcanized state of the foamed product, it is bonded to plastic, fiber, metal, ceramic or unvulcanized or incompletely vulcanized rubber; Then, the foamed product is prepared into foamed rubber using a vulcanization process.

[0017] Preferably, the preparation of foamed rubber from the foamed product using a vulcanization process includes: The foamed product is placed in a mold for shaping and vulcanization.

[0018] According to a second aspect of this application, a foamed rubber is provided, wherein the foamed rubber is prepared by a foamed rubber preparation method as described in any one of the first aspects.

[0019] According to a third aspect of this application, a foamed article is provided, wherein the foamed article is made of foamed rubber as described in the second aspect, and the foamed article includes a rubber tube.

[0020] The foamed rubber preparation method of this application first mixes a foaming agent, a rubber matrix, additives, and carbon materials to form a compound. This facilitates the subsequent preparation of the foamed product using a microwave process. The carbon materials in the compound absorb microwaves and form localized hot spots. The temperature of these hot spots allows the carbon materials themselves and the foaming agent in the adjacent areas to foam. Simultaneously, because the rubber matrix has weak microwave absorption capacity, it does not rapidly heat up upon absorbing microwaves. Therefore, the overall temperature of the rubber matrix remains below the vulcanization temperature of rubber, making it easier to subsequently prepare the foamed product into foamed rubber using a vulcanization process. Thus, the foamed rubber preparation method of this application effectively separates the foaming and vulcanization steps, facilitating the preparation of foamed products that can be co-vulcanized with other materials.

[0021] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments of this application with reference to the accompanying drawings. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the present application and, together with their description, serve to explain the principles of the present application.

[0023] Figure 1 This is a flowchart of a foamed rubber preparation method in one embodiment of this application.

[0024] Figure 2 This is a thermogravimetric analysis diagram of expandable graphite in one embodiment of this application.

[0025] Figure 3 This is a schematic diagram of the structure of the foaming agent without foaming in one embodiment of this application.

[0026] Figure 4 This is a schematic diagram of the foaming agent in one embodiment of this application.

[0027] Figure 5 This is an exploded view of a mixture being prepared into a foamed product using a microwave process in one embodiment of this application.

[0028] Figure 6 This is a schematic diagram of the structure of the compound prepared into a foamed product using microwave technology in one embodiment of this application. Figure 1 .

[0029] Figure 7 This is a schematic diagram of the structure of the compound prepared into a foamed product using microwave technology in one embodiment of this application. Figure 2 .

[0030] Figure 8 This is a schematic diagram of the structure of the compound prepared into a foamed product using microwave technology in one embodiment of this application. Figure 3 .

[0031] Figure 9 This is a schematic diagram of the structure of foamed product A in Embodiment 1 of this application.

[0032] Figure 10 This is a cross-sectional view of foamed product A in Embodiment 1 of this application.

[0033] Figure 11 This is a schematic diagram of the structure of foamed product B in Embodiment 2 of this application.

[0034] Figure 12 This is a cross-sectional view of foamed product B in Embodiment 2 of this application.

[0035] Figure 13 This is a schematic diagram of the structure of foamed product C in Embodiment 3 of this application.

[0036] Figure 14 This is a cross-sectional view of the foamed product C in Example 3 of this application.

[0037] Figure 15 This is a schematic diagram of the structure of foamed product L in Embodiment 12 of this application.

[0038] Figure 16 This is a cross-sectional view of the foamed product L in Embodiment 12 of this application.

[0039] Figure 17 This is a scanning electron microscope image of the foamed rubber G in Embodiment 7 of this application. Figure 1 .

[0040] Figure 18 This is a scanning electron microscope image of the foamed rubber G in Embodiment 7 of this application. Figure 2 .

[0041] Figure 19 This is a scanning electron microscope image of foamed rubber I in Example 9 of this application.

[0042] Figure 20 This is a scanning electron microscope image of the foamed rubber L in Embodiment 13 of this application.

[0043] Explanation of reference numerals in the attached figures: 1. Foaming agent; 2. Rubber matrix; 3. Carbon material; 4. Hot spot; 5. Cell; 6. Microwave; 7. Foaming product; 8. Mold; 9. Medium. Detailed Implementation

[0044] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0045] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0046] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0047] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0048] like Figure 1 As shown, the method for preparing foamed rubber in this application includes the following steps S101~S102: S101, foaming agent 1, rubber matrix 2, additives and carbon material 3 are mixed to form a compound; It should be noted that, in this embodiment of the application, by mixing the foaming agent 1, the rubber matrix 2, the additives and the carbon material 3, it is convenient that when the mixture is prepared into a foamed product 7 using a microwave process, the carbon material 3 in the mixture can absorb microwaves 6 and form local hot spots 4. The temperature of these hot spots 4 can cause the carbon material 3 itself and the foaming agent 1 in the adjacent area to foam. At the same time, since the rubber matrix 2 has a weak microwave absorption capacity of 6, the rubber matrix 2 will not heat up rapidly due to the absorption of microwaves 6, so that the rubber matrix 2 as a whole is still below the vulcanization temperature of rubber.

[0049] In one embodiment, the foaming agent 1 includes at least one selected from AC foaming agent, paraffin wax, cyclohexane, butyl acetate, and paraffin oil.

[0050] Specifically, embodiments of this application may select a single foaming agent or multiple foaming agents according to the actual needs of the foamed rubber. For example, any single foaming agent 1 selected from AC foaming agent, paraffin wax, cyclohexane, butyl acetate, and paraffin oil may be used to improve the foaming stability of the compound; or a combination of any two or more foaming agents selected from AC foaming agent, paraffin wax, cyclohexane, butyl acetate, and paraffin oil may be used to adjust the foaming speed of the compound and improve the quality of the foamed product 7. Those skilled in the art may select according to actual needs, and this application does not impose specific limitations here.

[0051] In one embodiment, the rubber matrix 2 includes at least one of natural rubber, styrene-butadiene rubber, cis-butadiene rubber, ethylene propylene diene monomer (EPDM) rubber, and silicone rubber.

[0052] Specifically, in this embodiment, a single rubber matrix 2 can be selected according to the actual needs of the foamed rubber. For example, a single natural rubber can be selected, so that the excellent elasticity, mechanical strength, and processing performance of natural rubber can provide good basic mechanical properties for the foamed rubber, making it suitable for foamed products with high strength and toughness requirements; or, a single styrene-butadiene rubber can be selected, so that the good wear resistance, aging resistance, and processing stability of styrene-butadiene rubber can make it compatible with various foaming agents 1, additives, and carbon materials 3, facilitating the formation of uniform foamed products 7; or, a single butadiene rubber can be selected, so that the high elasticity, low hysteresis loss, and low temperature resistance of butadiene rubber can improve the resilience of the foamed rubber. Its elastic properties and shock absorption make it suitable for applications such as shock-absorbing products and floating materials. Alternatively, EPDM rubber can be selected alone to extend the service life of the foamed rubber in outdoor or harsh environments due to its excellent weather resistance, ozone resistance, and chemical resistance, making it suitable for products used for long-term purposes such as heat insulation, sealing, and sound insulation. Alternatively, silicone rubber can be selected alone to maintain a stable foam structure and elasticity under extreme temperature conditions due to its wide range of high and low temperature resistance, strong chemical stability, and low surface energy, making it suitable for special foamed products with high temperature resistance requirements.

[0053] In other embodiments, the rubber matrix 2 in this application embodiment may also be any two or more of natural rubber, styrene-butadiene rubber, cis-butadiene rubber, ethylene propylene diene monomer (EPDM) rubber and silicone rubber mixed in any proportion to form a blended rubber. Those skilled in the art can choose according to actual needs, and this application does not impose specific restrictions here.

[0054] In one embodiment, the additives include a vulcanizing agent and a vulcanization accelerator.

[0055] For example, when the foaming agent 1 is AC foaming agent, the rubber matrix 2 is natural rubber, the additives are vulcanizing agent and vulcanization accelerator, and the carbon material 3 is graphene, the graphene, which heats up due to the absorption of microwaves 6, can heat up the natural rubber in the adjacent area, thereby causing the AC foaming agent contained in this adjacent area to decompose and foam. The decomposed gas will generate bubbles in the natural rubber in this area, and the heated natural rubber will have a lower viscosity, which is conducive to the formation of bubbles and the initiation of the vulcanization process in this area; then, after the microwave heating process stops or after a short period of continuous microwave heating... When the process stops, the already formed heating area will remain at a high temperature for a certain period of time, so the vulcanization process in that area will continue, and the bubbles will at least maintain their volume. As the vulcanization process continues, the natural rubber around the bubbles is gradually vulcanized and formed, and then a vulcanized wall with a certain strength is formed inside the foamed product 7 from the interface between the bubbles and the natural rubber. During the subsequent cooling or heating of the foamed rubber, the vulcanized wall can further prevent the expansion or closure of the bubbles, thereby ensuring the strength and integrity of the cell 5, that is, ensuring that the foamed product 7 has a low density.

[0056] In some embodiments, since the vulcanized wall should be formed at least after the foaming agent 1 foams to form the cells 5, or the vulcanized wall is still in the scorching or hot vulcanization stage when the cells 5 are formed, it is generally difficult to form the desired cells 5 if the vulcanization of the foamed product 7 is faster than the formation of the cells 5.

[0057] Therefore, in order for the vulcanization accelerator to have a relatively slow vulcanization speed, the vulcanization accelerator preferably includes at least one of thiazole vulcanization accelerators, sulfenamide vulcanization accelerators, guanidine vulcanization accelerators, aldehyde-amine vulcanization accelerators, and thiourea vulcanization accelerators. For example, the vulcanization accelerator may include at least one of accelerator TT, accelerator CZ, accelerator H, accelerator DPG, accelerator DM, and accelerator DOTG.

[0058] In one embodiment, the carbon material 3 includes at least one of graphene, graphene oxide, graphite, and expandable carbon material; wherein the graphene is single-layer graphene, multi-layer graphene, or stacked graphene; the graphene oxide is single-layer graphene oxide, multi-layer graphene oxide, or stacked graphene oxide; the expandable carbon material includes unexpanded expandable graphite; and when the carbon material includes expandable carbon material, the expandable carbon material is also considered as a foaming agent.

[0059] Specifically, in this application embodiment, by adding at least one of graphene, graphene oxide, graphite, and expandable carbon material to the compound, the excellent microwave absorption and heating characteristics of the aforementioned carbon material 3 enable it to be adapted to various foamed products with different performance requirements, thereby further improving the applicability of foamed rubber.

[0060] In some embodiments, since expandable carbon materials include materials such as unexpandable expandable graphite, and materials such as unexpandable expandable graphite can expand and foam, some components of foaming agent 1 can also be expandable carbon materials, i.e., expandable carbon materials are also considered as a type of foaming agent. Thus, by using such carbon material 3 that has both microwave absorption and heating properties and foaming function, the complexity of materials required for production is reduced, while the synergy between microwave absorption and heating of carbon material 3 and foaming of foaming agent 1 is improved, the foaming effect of foamed product 7 is optimized, and the preparation quality of foamed product 7 is improved.

[0061] In one embodiment, when the foaming agent 1 is not a carbon material, the vaporization or decomposition temperature of the foaming agent 1 is less than or equal to 300°C.

[0062] Specifically, in this embodiment, by controlling the vaporization or decomposition temperature of the foaming agent 1 to 300°C or below, it ensures that the foaming agent 1 generates bubbles in a timely manner under the rapid heating condition of microwave 6, thereby improving the foaming efficiency of the compound. Furthermore, it avoids the problem of premature vulcanization of the rubber matrix 2 due to excessively high temperatures, which is beneficial for forming a foamed product 7 with uniform structure and stable performance. If the vaporization or decomposition temperature of the foaming agent is higher, it will inevitably require that the hot spot temperature generated by the carbon material 3 absorbing microwave 6 also be higher than 300°C. This will lead to a significantly high-temperature region near the carbon material 3, which may cause the rubber to vulcanize rapidly, which is not conducive to the formation of the desired cells. Additionally, it may cause the rubber matrix 2 to carbonize due to excessively high temperatures. Carbonized rubber will be difficult to form the desired cells and will no longer have the desired bending properties, or even be unable to form the desired foamed product.

[0063] Among them, foaming agent 1 needs to generate bubbles during the decomposition process in order to improve the foaming efficiency of the mixture.

[0064] In one embodiment, when the carbon material 3 contains expandable carbon material, the foaming agent 1 vaporizes or decomposes to generate gas at a temperature not exceeding a first temperature; wherein, the first temperature is the temperature at which the expandable carbon material loses 30% of its mass under an inert gas atmosphere.

[0065] Specifically, in this embodiment of the application, foamed product 7 is prepared by using expandable carbon material, that is, carbon material 3 includes expandable carbon material, so that expandable carbon material 3 is also a type of foaming agent 1. At this time, the first temperature in foaming agent 1 is the temperature at which the expandable carbon material loses 30% of its mass under inert gas atmosphere.

[0066] Therefore, setting the vaporization or decomposition temperature of the foaming agent 1 to the temperature corresponding to a 30% mass loss of expandable carbon material under an inert gas atmosphere allows for a more precise match to the actual heating behavior of the carbon material 3 in the microwave field, reducing energy consumption. In other words, by limiting the vaporization or decomposition temperature of the foaming agent 1, this embodiment ensures that the foaming agent 1 is effectively triggered by the local hot spots 4 formed by the carbon material 3 during microwave heating, thereby completing foaming quickly and uniformly. Simultaneously, it avoids premature complete vulcanization of the rubber matrix 2 due to excessively high foaming temperatures, ensuring that the foamed product 7 is at least partially incompletely vulcanized, facilitating the subsequent vulcanization process to prepare foamed rubber from the foamed product 7.

[0067] In addition, when the expandable carbon material is expandable graphite, thermogravimetric analysis and other methods can be used to measure and characterize the expansion process of expandable graphite.

[0068] For example, see Figure 2 In thermogravimetric analysis, by heating expandable graphite in a nitrogen atmosphere at a heating rate of 10 K / min, the expansion temperature of expandable graphite can be measured to start at about 180 °C (this temperature is the temperature at which mass loss begins and expansion and foaming begin), and mass loss of about 10%, 28%, 30%, 37%, and 40% of its initial mass occurs at about 200 °C, about 270 °C, about 300 °C, about 360 °C, and about 700 °C, respectively.

[0069] Therefore, by controlling the temperature of expandable graphite at about 30% of its mass loss, i.e., about 300°C, effective expansion of expandable graphite can be achieved without causing the temperature around it to rise too high (i.e., with the expansion endpoint of about 40% mass loss at about 700°C, it has already expanded by about 75% at 300°C), which is beneficial for saving energy and improving processing efficiency.

[0070] In one embodiment, the mass ratio of foaming agent 1 to rubber matrix 2 is 1 to 80:100; and the mass ratio of carbon material 3 to rubber matrix 2 is less than or equal to 80:100.

[0071] Specifically, when more than 80:100 of the foaming agent 1 is added, the foamed product 7 and the final vulcanized foamed rubber become hard and brittle, losing their elasticity and making it difficult to use as a foamed rubber material in the corresponding applications. When the amount of foaming agent 1 added is too small, for example, when the mass ratio with the rubber matrix 2 is less than 1:100, the final foamed rubber product is unlikely to produce a significant decrease in density and cannot produce the lightweight properties required for foamed rubber materials. Therefore, the mass ratio of foaming agent 1 to rubber matrix 2 can be set to 1~80:100, or preferably 1~30:100, more preferably 1~20:100, and even more preferably 1~15:100.

[0072] Furthermore, when too much carbon material 3 is added, it not only causes the mixture to form too many and densely distributed hot spots 4 during microwave heating 6, but also prevents the foamed product from forming unvulcanized or incompletely vulcanized parts or surfaces, severely affecting the separation of the foaming and vulcanization steps. When too little carbon material 3 is added, it not only prevents the mixture from forming local hot spots 4, but also causes the foaming agent 1 to not foam. Therefore, in this embodiment, by setting the mass ratio of carbon material 3 to rubber matrix 2 to be less than or equal to 80:100, or preferably less than or equal to 30:100, or more preferably less than or equal to 15:100, it can ensure that at least part of the foamed product is not completely vulcanized, which facilitates the subsequent vulcanization process to prepare the foamed product 7 into foamed rubber. This not only effectively promotes the foaming effect of the foaming agent 1, but also significantly improves the quality of the foamed rubber preparation, without significantly adversely affecting the performance of the final foamed rubber.

[0073] In some embodiments, since carbon materials such as graphene and graphene oxide are used as local hot spots, for example, adding 1 part of graphene or graphene oxide carbon is sufficient to generate enough hot spots to absorb microwaves and raise the temperature of the foaming agent 1 in the adjacent area to the temperature required for its expansion. Moreover, carbon materials such as graphene and graphene oxide generally have good dispersibility in rubber. Therefore, adding more carbon material not only easily leads to an overly uniform heating of the rubber matrix 2, but also makes it difficult to form uncured or incompletely cured areas in the resulting foamed product 7. Furthermore, excessive carbon material can also easily reduce the bending properties of the rubber. Therefore, in order to reduce the influence of carbon material 3 on the mechanical properties of the foamed rubber, such as bending properties, when carbon material 3 does not contain a component as a foaming agent, the mass ratio of carbon material 3 to rubber matrix 2 is preferably less than or equal to 30:100, more preferably less than or equal to 15:100, and even more preferably less than or equal to 5:100.

[0074] Since the carbon material 3 does not contain any components that act as a foaming agent, it can form significant hot spots in the rubber matrix 2 and achieve significant temperature rise in itself and its adjacent areas. Therefore, considering cost and the benefits of improved bending performance, the mass ratio of carbon material 3 to rubber matrix 2 can be further less than or equal to 1:100.

[0075] In one embodiment, the carbon material 3 includes an expandable carbon material, and the foam product 7 contains pores having all or part of pore walls formed of a non-rubber material.

[0076] Specifically, based on the carbon material 3 including expandable carbon materials, unexpectedly, when expandable carbon materials, such as unexpanded expandable graphite, are used as foaming agent 1, they can expand and foam under microwave action to form cells, simultaneously generating cell walls with a carbon material structure (graphene structure), i.e., producing solid bubbles. Therefore, since the cell walls with the carbon material structure (graphene structure) not only support the cells but also act as a heat source, they can also heat the adjacent rubber matrix 2, promoting the vulcanization of the rubber matrix 2 and forming a barrier to prevent gas from passing through its surface, thus helping to maintain the cells. Furthermore, when expandable carbon materials such as unexpanded expandable graphite are not used as foaming agent 1, for example, cyclohexane or AC... Foaming agents, such as those that vaporize upon heating (e.g., cyclohexane) or decompose (AC foaming agents) to produce gas and form hollow bubbles, have no walls. That is, the pores are enclosed by the rubber matrix 2, which means that the pores rely entirely on the curing and shaping of the rubber matrix 2 to maintain their shape. Therefore, if curing and shaping are not carried out in time, such as when the temperature drops and cyclohexane condenses, the pores will shrink. At the same time, the gas is more likely to dissolve significantly in the rubber, causing gas escape, which can create negative pressure inside the pores and lead to pore collapse. Therefore, in order to ensure the storage stability of the foamed product 7 and facilitate the formation of a relatively long-term storage stability of the foamed product 7, preferably, the mass ratio of such expandable carbon material 3 to rubber matrix 2 is 1~30:100, more preferably 5~15:100.

[0077] In one embodiment, before preparing the foamed product 7 by microwave process after mixing the foaming agent 1, rubber matrix 2, additives and carbon material 3 to form a compound, the process further includes: preheating the compound.

[0078] Specifically, since the heated compound will have a lower viscosity than before heating, it is beneficial for the foaming agent 1 contained therein to foam and form cells 5 with larger pore size, resulting in the foamed product 7 having a lower density. Therefore, the compound can be preheated before using microwave technology to prepare the foamed product 7, for example, by heating with a lower microwave power, to effectively promote the formation of cells 5.

[0079] For example, in some embodiments, the heating of these materials during the mixing or compounding of the foaming agent 1, rubber matrix 2, additives and carbon material 3 (e.g., heating these materials to a temperature below the foaming temperature of the foaming agent, such as about 60°C, during compounding) can also achieve the purpose of preheating.

[0080] S102, the mixture is prepared into foamed product 7 using microwave technology; It should be noted that the embodiments of this application use microwave technology to prepare the compound into foamed product 7. By controlling the specific parameters of the microwave technology, the foamed product 7 can be precisely maintained in an unvulcanized or incompletely vulcanized state, which facilitates the subsequent use of vulcanization process to prepare the foamed product 7 into the required higher quality foamed rubber, that is, to achieve the separation of foaming and vulcanization steps.

[0081] See Figure 3 and Figure 4 When the compound is prepared into foamed product 7 using microwave technology, the carbon material 3 in the compound can absorb microwaves 6 and form local hot spots 4. The temperature of these hot spots 4 can cause the carbon material 3 itself and the foaming agent 1 in the adjacent area to foam. At the same time, since the rubber matrix 2 has a weak microwave absorption capacity of 6, the rubber matrix 2 will not absorb microwaves 6 and heat up rapidly. Even so, the rubber matrix 2 as a whole is still below the vulcanization temperature of rubber, thus ultimately forming an unvulcanized or incompletely vulcanized foamed product 7.

[0082] Because the rubber matrix 2 has a relatively lower microwave absorption and heat generation capacity compared to the carbon material 3, when heated with a lower microwave power 6, for a given mass of the compound, especially for a given mass of the compound formed by the rubber matrix 2 and the carbon material 3, the microwave absorption capacity of the rubber matrix 2 will have a shielding effect on the carbon material 3, resulting in a reduction in the microwave power 6 that the carbon material 3 can absorb. This will make it difficult for the carbon material 3 to heat up to the temperature required for it and the foaming agent 1 in the adjacent area to foam and expand in a short time, thus requiring... On the other hand, a longer microwave heating time can also cause the rubber matrix 2 to gradually heat up to a higher temperature under the combined effect of microwave absorption and heat conduction. This allows the rubber matrix 2, which is far from the carbon material 3, to also heat up sufficiently, resulting in a lack of significant temperature difference between the rubber matrix region far from the carbon material 3 and the carbon material 3. Consequently, when the temperature of the carbon material 3 and its adjacent region rises to a level sufficient to cause the foaming agent 1 to foam, the temperature of other regions is also likely to rise to a level far exceeding the vulcanization temperature of the rubber matrix 2, leading to complete vulcanization of the rubber matrix 2.

[0083] Therefore, in order to solve the above problems, it is preferable that the ratio of the power of microwave radiation received by the compound to the mass of the rubber matrix 2 and the carbon material 3 is greater than or equal to 40 W / g, so that the carbon material 3 and the rubber matrix in the adjacent area can achieve a heating rate of more than 10 °C / s, thereby forming a significant temperature difference in the compound, so that the foamed product 7 has unvulcanized or incompletely vulcanized parts or surfaces, that is, at least part of the surface of the foamed product is unvulcanized or incompletely vulcanized.

[0084] Of course, in order to ensure the efficiency and quality of the preparation of foamed product 7, the ratio of the power of microwave radiation received by the compound to the mass of rubber matrix 2 and carbon material 3 can be greater than or equal to 80W / g, or the ratio of the power of microwave radiation received by the compound to the mass of rubber matrix 2 and carbon material 3 can be greater than or equal to 100W / g.

[0085] In some embodiments, a constant power is used to microwave irradiate the compound, and during microwave irradiation, the ratio of the power of the microwave irradiation received by the compound to the sum of the masses of the rubber matrix 2 and the carbon material 3 is greater than or equal to 40 W / g.

[0086] Specifically, in this embodiment, the power output of the microwave equipment is kept stable throughout the entire microwave process, and the power output of the microwave equipment is not adjusted with changes in heating time, mixture temperature or foaming state, thereby ensuring the stability of the microwave absorption heating rate of carbon material 3 and improving the uniformity of foaming agent 1.

[0087] In some embodiments, the compound is microwave-irradiated with a gradually varying power, and during microwave irradiation, the ratio of the power of the microwave irradiation received by the compound to the sum of the masses of the rubber matrix 2 and the carbon material 3 is greater than or equal to 40 W / g.

[0088] Specifically, in this embodiment, the power output of the microwave equipment is gradually adjusted according to a preset rule throughout the entire microwave process, which is convenient to adapt to the heat requirements of different stages of microwave foaming 6, ensures the compatibility between the microwave absorption heating rate of carbon material 3 and the gas production rule of foaming agent 1, and improves the uniformity, density and structural stability of the foamed product 7.

[0089] In some embodiments, the compound is microwave-irradiated with intermittent power, and during microwave irradiation, the ratio of the power of the microwave irradiation received by the compound to the mass of the rubber matrix 2 and the carbon material 3 is greater than or equal to 40 W / g.

[0090] Specifically, this embodiment of the application adopts a preset mode of "microwave application → pause heating → microwave application" throughout the entire microwave process, and processes the compound in at least two stages. This effectively achieves precise control over the heat accumulation inside the compound, avoids local overheating that could lead to degradation of the rubber matrix 2 or rupture of the cells 5, and ensures that the surface temperature of at least one surface of the foamed product 7 is lower than the vulcanization temperature of the foamed product 7 or that at least part of the surface of the foamed product 7 is not fully vulcanized.

[0091] Since the interval between two adjacent microwave heating segments 6 exceeds 60s, the temperature of the hot spot 4 region in the mixture will drop significantly, and the temperature difference between different regions in the entire mixture will be significantly reduced. Therefore, when the mixture is treated with microwave power applied at least twice, the interval between two adjacent microwave heating segments 6 is preferably no more than 60s.

[0092] In addition, when using intermittently applied microwaves to treat the compound, the intermittently applied microwaves can also be gradually applied microwaves to meet the different production requirements of the foamed product 7.

[0093] In some embodiments, before and after the microwave process, the surface temperature of at least one surface of the foamed product 7 is controlled to be lower than the vulcanization temperature of the foamed product 7, so that at least a portion of the surface of the foamed product 7 is not vulcanized or not fully vulcanized.

[0094] Specifically, in this embodiment, by controlling the surface temperature of at least one surface of the foamed product 7 to be lower than the vulcanization temperature of the foamed product 7, the separation of the foaming and vulcanization steps is ensured, which facilitates the subsequent vulcanization process to prepare the foamed product 7 into the required foamed rubber. This effectively solves the technical pain point that it is difficult to process the foamed product 7 after the foaming and vulcanization are completed simultaneously in the traditional method. On the other hand, it also ensures that the surface layer of the foamed product 7 is not completely vulcanized, so that the subsequent bonding and co-vulcanization steps can be carried out smoothly, avoiding the problem of interlayer delamination of the composite material and improving the preparation quality of the foamed rubber.

[0095] Furthermore, by ensuring that at least a portion of the surface of the foamed product 7 is not vulcanized or not fully vulcanized, this embodiment of the application ensures the separation of the foaming and vulcanization steps. This facilitates the preparation of the foamed product 7 into the required foamed rubber using a subsequent vulcanization process, effectively solving the technical pain point that it is difficult to process the foamed product 7 after the simultaneous completion of foaming and vulcanization in traditional methods. On the other hand, it also ensures that the surface of the foamed product 7 has the activity of incomplete vulcanization, improving the effect of subsequent bonding and co-vulcanization, avoiding the problem of interlayer delamination of composite materials, and improving the quality of the final foamed product.

[0096] In some embodiments, a vulcanizer can be used to perform vulcanization analysis on the foamed product 7 to confirm that the surface of the foamed product 7 is in an unvulcanized state.

[0097] Specifically, the surface of the foamed product 7 prepared by microwave process must show at least one of the scorching stage and the thermal vulcanization stage. For example, for the unvulcanized surface of the selected foamed product 7, a region 1 mm, 3 mm, or 5 mm below the unvulcanized surface must show at least one of the scorching stage and the thermal vulcanization stage.

[0098] In some embodiments, to create a significant temperature gradient between the rubber matrix 2 and the carbon material 3 regions, facilitating the separation of the foaming and vulcanization steps and improving the preparation efficiency of the foamed product 7, the microwave power of the microwave process is preferably greater than or equal to 200W, and more preferably greater than or equal to 400W. For example, the microwave power of the microwave process can be 560W, 800W, 1000W, or 1800W to significantly increase the temperature difference between the rubber matrix 2 and the carbon material 3 regions.

[0099] It should be noted that microwave irradiation power below 200W may result in the carbon material 3 not generating enough heat due to microwave heating, that is, the heat generated by microwave heating is insufficient to expand the expandable carbon material and to prevent the formation of a significant temperature gradient within the rubber matrix 2.

[0100] In one embodiment, preparing the compound into foamed product 7 using a microwave process includes: a heating rate of carbon material 3 greater than or equal to 10°C / s; and a heating rate of the rubber matrix in the region adjacent to the carbon material greater than or equal to 10°C / s.

[0101] Specifically, in this embodiment, by setting the heating rate of the carbon material 3 to be greater than or equal to 10°C / s, it can ensure that the carbon material 3 itself and its adjacent area can quickly form local hot spots 4 (for example, the heating rate of the rubber matrix 2 in its adjacent area can be greater than or equal to 10°C / s by the carbon material 3), so that the foaming agent 1 can generate bubbles in time, improve the foaming efficiency, and shorten the microwave heating time 6; on the other hand, it can also precisely control the foaming timing and avoid problems such as the foaming agent not being able to foam in time due to excessive heating lag between the foaming agent 1 and the carbon material 3 in the adjacent area of ​​the carbon material.

[0102] In one embodiment, preparing a foamed product 7 from a compound using a microwave process includes placing the compound in a mold 8 and subjecting it to microwave treatment.

[0103] Specifically, such as Figures 5 to 7As shown, in this embodiment of the application, by using a mold 8 to place the compound, the shape of the compound can be constrained, making it easier to use a vulcanization process to prepare the foamed product 7 into the desired shape of foamed rubber, thereby improving the preparation efficiency of foamed rubber. On the other hand, it can also help ensure that the surface temperature of at least one surface of the foamed product 7 is lower than the vulcanization temperature of the foamed product 7, ensuring that it is in an unvulcanized or incompletely vulcanized state. Furthermore, it also avoids irregular deformation or expansion of the compound due to the gas expansion of the foaming agent 1 during the microwave heating process, thereby improving the preparation quality of foamed rubber.

[0104] In one embodiment, preparing a foamed product 7 from a compound using a microwave process includes: fixing the compound with a fastener and then subjecting it to microwave treatment.

[0105] Specifically, in this embodiment, by using a fixing component to fix the compound, the shape of the compound can be constrained, facilitating the subsequent vulcanization process to prepare the foamed product 7 into the desired shape of foamed rubber, thus improving the preparation efficiency of the foamed rubber. Furthermore, it can help ensure that at least part of the surface of the foamed product 7 is not completely vulcanized or not fully vulcanized. Additionally, the shape of the compound can be flexibly adjusted to improve the processing effect. For example, for block-shaped compounds, a ceramic support can be used to clamp and fix them from all sides to ensure the position of the compound is fixed during microwave heating; for sheet-shaped compounds, a quartz sheet can be used in conjunction with a ceramic base. To prevent the sheet-like mixture from curling or wrinkling during foaming, multiple spaced ceramic clamps can be used to fix the long strip-shaped mixture, ensuring the regularity of the foamed product 7. For tubular mixtures, a rod-like fastener can be used to secure the tubular mixture to the rod. It should be understood that since the mixture usually has good elasticity or plasticity, the rod diameter can be basically the same as or larger than the inner diameter of the tubular mixture. In this case, the tubular mixture will be able to be fixed to the rod due to its own elasticity or plasticity. Since the tubular mixture usually expands after microwave treatment, the rod diameter can also be smaller than the inner diameter of the tubular mixture.

[0106] In one embodiment, preparing a foamed product 7 from a compound using a microwave process includes placing the compound in or on the surface of a medium 9 and subjecting it to microwave treatment.

[0107] Specifically, such as Figure 8 As shown, in the embodiments of this application, the compound can also be completely or partially coated or impregnated with medium 9, and then microwave-treated with medium 9 to form foamed product 7. This molding method is particularly suitable for foaming tubular compounds and helps to achieve at least a portion of the surface of the foamed product 7 not being completely vulcanized or not fully vulcanized, thereby effectively improving the preparation efficiency of foamed rubber.

[0108] In one embodiment, the conditions before and after microwave treatment include: the temperature of the surface of the mold 8 in contact with the compound is lower than the vulcanization temperature of the foamed product 7.

[0109] Specifically, in this embodiment, by setting the temperature of the contact surface between the mold 8 and the mixture before and after microwave treatment to be lower than the vulcanization temperature of the foamed product 7, the carbon material 3 in the mixture can quickly absorb microwaves and form local hot spots 4. The surface heat of the mixture can be quickly conducted away through the heat conduction between the contact surface of the mold 8 and the mixture, avoiding the accumulation of heat at the contact interface. This ensures that the surface temperature of at least one surface of the foamed product 7 is lower than the vulcanization temperature of the foamed product 7 or that at least part of the surface of the foamed product 7 is not vulcanized or not completely vulcanized.

[0110] In one embodiment, before and after microwave treatment include: the temperature of the surface of the medium 9 or the interface between the compound and the medium 9 is lower than the vulcanization temperature of the foamed product 7.

[0111] Specifically, in this embodiment, the compound is completely or partially coated or impregnated with medium 9, and then microwave-treated to form foamed product 7. The temperature of the interface between the compound and the medium before and after microwave treatment is lower than the vulcanization temperature of the foamed product 7. Based on the rapid absorption of microwaves by carbon material 3 in the compound and the formation of local hot spots 4, the heat on the surface of the compound can be quickly conducted away through the heat conduction between the surfaces of the medium 9 and the compound, avoiding the accumulation of heat at the contact interface. This ensures that the surface temperature of at least one surface of the foamed product 7 is lower than the vulcanization temperature of the foamed product 7 or that at least part of the surface of the foamed product 7 is not vulcanized or not completely vulcanized.

[0112] In some embodiments, such as Figure 6 As shown, the compound can be placed directly on mold 8 for processing in order to form a larger area of ​​incompletely vulcanized surface.

[0113] In some embodiments, such as Figure 7 As shown, the compound can be placed between two molds 8 for processing in order to form a larger area of ​​incompletely vulcanized surface.

[0114] In some embodiments, such as Figure 8 As shown, the compound can be placed in medium 9 for processing in order to form a larger area of ​​incompletely vulcanized surface.

[0115] In one embodiment, the material of the mold 8 includes at least one of microwave-transparent material and metal material; wherein the metal material mold 8 cannot completely shield the microwave irradiation of the mixture by the microwave source used in the microwave process.

[0116] Specifically, in this embodiment, the mold 8 is made of a microwave-transparent material to allow microwave energy 6 to penetrate smoothly, ensuring that the microwave energy 6 can accurately act on the carbon material 3 in the mixture, thereby improving the preparation efficiency of the foamed product 7. Examples of microwave-transparent materials include ceramics or quartz, and those skilled in the art can choose according to actual needs; this application does not impose specific limitations here.

[0117] Furthermore, the mold 8 in this embodiment can also be made of metal, thereby utilizing the excellent thermal conductivity of metal to quickly dissipate heat from the surface of the mixture, precisely controlling the surface temperature of at least one surface of the foamed product 7 to be lower than the vulcanization temperature of the foamed product 7 or to ensure that at least part of the surface of the foamed product 7 is not completely vulcanized, thus ensuring the separation of the foaming and vulcanization steps; on the other hand, utilizing the high mechanical strength of metal to withstand the expansion pressure generated during the foaming of the mixture, thus ensuring the regularity of the molding of the foamed product 7.

[0118] Since metal materials are not transparent to microwaves, in order to avoid the inability to use microwaves to process the mixture, the mold 8 made of metal materials cannot completely shield the microwave source used in the microwave process from microwave irradiation of the mixture.

[0119] In one embodiment, the material of the medium 9 includes at least one of microwave-transparent material and metal material; wherein the metal material medium 9 cannot completely shield the microwave irradiation of the mixture by the microwave source used in the microwave process.

[0120] Specifically, in this embodiment, the medium 9 is made of a microwave-transparent material. This allows the microwave energy 6 to penetrate smoothly, ensuring that the microwave energy 6 can accurately act on the carbon material 3 in the mixture, thereby improving the preparation efficiency of the foamed product 7. Examples of microwave-transparent materials include solid paraffin or liquid paraffin. Those skilled in the art can choose according to actual needs, and this application does not impose specific limitations.

[0121] Furthermore, the medium 9 in this embodiment can also be made of metal, thereby utilizing the excellent thermal conductivity of metal to quickly dissipate heat from the surface of the mixture, precisely controlling the surface temperature of at least one surface of the foamed product 7 to be lower than the vulcanization temperature of the foamed product 7 or to ensure that at least part of the surface of the foamed product 7 is not completely vulcanized, thus ensuring the separation of the foaming and vulcanization steps; on the other hand, utilizing the high mechanical strength of metal to withstand the expansion pressure generated during the foaming of the mixture, thus ensuring the regularity of the molding of the foamed product 7.

[0122] Since metallic materials are not transparent to microwaves, in order to avoid the inability to use microwaves to process the mixture, the dielectric 9 of the metallic material cannot completely shield the microwave source used in the microwave process from microwave irradiation of the mixture.

[0123] In one embodiment, preparing the compound into foamed product 7 using a microwave process includes: the microwave heating time is 10~1800s.

[0124] Specifically, the heating time for the microwave process should be just enough to cause the foaming agent 1 to foam. For example, it can be determined whether the foaming agent 1 has foamed by observing the cross-sectional morphology of the foamed product 7.

[0125] Although the heating time required varies depending on the type of foaming agent 1, the amount of carbon material 3 added, or the microwave heating power, when using unexpanded expandable graphite and / or AC foaming agent as the foaming agent, excessive heating time may cause the mixture to heat up to excessively high temperatures, resulting in excessive sulfidation or even carbonization. Insufficient heating time is not enough for the foaming agent 1 to foam. Therefore, the heating time of the microwave process should be in the range of 10 to 1800 s, preferably in the range of 10 to 900 s, more preferably in the range of 15 to 600 s, or even further in the range of 30 to 420 s.

[0126] In one embodiment, after preparing the compound into foamed product 7 using a microwave process, the process includes: bonding the foamed product 7 to plastic, fiber, metal, ceramic, or unvulcanized or incompletely vulcanized rubber in an unvulcanized or incompletely vulcanized state; and then preparing the foamed product 7 into foamed rubber using a vulcanization process.

[0127] Specifically, since the foamed product 7 obtained by microwave foaming 6 has an unvulcanized surface, the surface of the foamed product 7 can be bonded to other plastics, fibers, metals, ceramics, or unvulcanized or incompletely vulcanized rubber surfaces to achieve vulcanization or co-vulcanization.

[0128] In particular, when foamed product 7 is laminated with uncured or incompletely vulcanized rubber and then co-cured to prepare foamed rubber, the vulcanizing agent migrates at the interface between foamed product 7 and uncured or incompletely vulcanized rubber, thereby bridging the chain segments at the interface between foamed product 7 and uncured or incompletely vulcanized rubber, thus eliminating the phase interface between foamed product 7 and uncured or incompletely vulcanized rubber and enhancing the mechanical strength of foamed rubber.

[0129] In some embodiments, the foamed product 7 can be bonded to other plastics, fibers, metals, ceramics, or unvulcanized or incompletely vulcanized rubber surfaces in a single manner to achieve vulcanization or co-vulcanization; or, multiple methods can be used in combination to achieve vulcanization or co-vulcanization. For example, when the foamed product 7 has multiple unvulcanized surfaces, one unvulcanized surface can be bonded to an unvulcanized or incompletely vulcanized rubber material, while another unvulcanized surface can be bonded to a metal, thereby achieving vulcanization or co-vulcanization.

[0130] In one embodiment, preparing foamed product 7 into foamed rubber using a vulcanization process includes: using the residual heat of foamed product 7 to prepare foamed product 7 into foamed rubber; or, heating foamed product 7 to prepare foamed product 7 into foamed rubber.

[0131] Specifically, the heat source for further vulcanizing the foamed product 7 into foamed rubber can be either the residual heat of the foamed product 7 or the reheating of the foamed product 7.

[0132] In one embodiment, preparing foamed rubber from foamed product 7 using a vulcanization process includes: placing foamed product 7 in a mold 8 for shaping and vulcanization.

[0133] Specifically, since the foamed product 7 includes unvulcanized or incompletely vulcanized portions, which are plastic and can be further shaped into the desired form through shaping and vulcanization, foamed rubber of the desired shape can be prepared by placing the foamed product 7 in the mold 8 for shaping and vulcanization, thus further improving the applicability of the foamed rubber.

[0134] According to another embodiment of this application, a foamed rubber is provided, which is prepared by the foamed rubber preparation method as described in the embodiments of this application.

[0135] According to another embodiment of this application, a foamed article is provided, which is made of foamed rubber as described in the embodiments of this application, and the foamed article includes a rubber tube.

[0136] The present application will be further described below with reference to specific embodiments.

[0137] Example 1 S111: 10 parts expandable graphite, 100 parts butadiene rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator TT are placed in an open mill and mixed to obtain compound A. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0138] S112, 8g of compound A was obtained, and compound A was prepared into foamed product A using a microwave process (see...). Figure 9 and Figure 10The mold is made of ceramic, and the mixture A is sandwiched between two ceramic plates. The microwave power of the microwave process is 800W, and the total heating time of the microwave process is 300s. The mixture A is processed by intermittently applied microwaves, with each microwave segment lasting 60s and the interval between two adjacent microwave heating segments being 60s.

[0139] S113, hot-pressing and vulcanizing foamed product A into foamed rubber A in a mold.

[0140] Example 2 S211, 15 parts expandable graphite, 100 parts butadiene rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator TT are placed in an open mill and mixed to obtain compound B. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0141] S212, obtain 7g of compound B, and use microwave technology to prepare foamed product B from compound B (see...). Figure 11 and Figure 12 The mold is made of ceramic, and the mixture B is sandwiched between two ceramic plates. The microwave power of the microwave process is 560W, the total heating time of the microwave process is 420s, and the mixture B is processed by intermittently applied microwaves. Each microwave segment lasts for 60s, and the interval between two adjacent microwave heating segments is 30s.

[0142] S213, hot-pressing and vulcanizing the foamed product B into foamed rubber B in a mold.

[0143] Example 3 S311: 20 parts expandable graphite, 100 parts butadiene rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator TT are placed in an open mill and mixed to obtain compound C. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0144] S312, 7g of compound C was obtained, and compound C was prepared into foamed product C using a microwave process (see...). Figure 13 and Figure 14 The mold is made of ceramic, and the mixture C is sandwiched between two ceramic plates. The microwave power of the microwave process is 560W, the total heating time of the microwave process is 480s, and the mixture C is processed by intermittently applied microwaves. Each microwave segment lasts for 120s, and the interval between two adjacent microwave heating segments is 45s.

[0145] S313, hot-pressing and vulcanizing the foamed product C into foamed rubber C in a mold.

[0146] Example 4 S411, 20 parts AC foaming agent, 10 parts expandable graphite, 100 parts butadiene rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator CZ are placed in an open mill and mixed to obtain compound D. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0147] S412, 9g of compound D was obtained, and compound D was prepared into foamed product D using a microwave process. The mold was made of metal, compound D was placed on the metal, and no other covering was applied to compound D. The microwave power was 1800W, the total heating time was 30s, and the compound D was treated with intermittently applied microwaves, each microwave segment lasting 15s, with a 15s interval between adjacent microwave heating segments.

[0148] S413, hot-pressing and vulcanizing the foamed product D into foamed rubber D in a mold.

[0149] Example 5 S511, 10 parts AC foaming agent, 5 parts graphene, 100 parts natural rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator CZ are placed in an open mill and mixed to obtain compound E. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0150] S512, 9g of compound E was obtained, and compound E was prepared into foamed product E using a microwave process. The mold was made of ceramic, and compound E was placed on the ceramic without any other covering. The microwave power was 560W, the total heating time was 420s, and the compound E was treated with intermittently applied microwaves, each segment lasting 60s, with a 30s interval between adjacent microwave heating segments.

[0151] S513, foamed product E is bonded to the surface of brass and then hot-pressed and vulcanized to form foamed rubber E.

[0152] Example 6 S611, 1 part AC foaming agent, 1 part expandable graphite, 100 parts styrene-butadiene rubber, 1 part sulfur, 1 part vulcanization accelerator DPG, and 1 part vulcanization accelerator DM are placed in an open mill and mixed to obtain compound F. The mixing temperature is 60℃ and the mixing time does not exceed 15 minutes.

[0153] S612, 10g of compound F is obtained, and compound F is prepared into foamed product F using microwave process. The mold is made of metal, compound F is placed on the metal, and no other covering is applied to compound F. The microwave power of the microwave process is 1800W, and the total heating time of the microwave process is 10s.

[0154] S613, two foamed products F are bonded together and then hot-pressed and vulcanized to form foamed rubber F.

[0155] Example 7 S711, 6 parts AC foaming agent, 10 parts expandable graphite, 100 parts butadiene rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator TT are placed in an open mill and mixed to obtain compound G. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0156] S712, 8g of compound G was obtained, and the compound G was prepared into a foamed product G using a microwave process. The mold was made of ceramic, and the compound G was sandwiched between two ceramic plates. The microwave power was 400W, the total heating time was 600s, and the compound G was treated with intermittently applied microwaves, each segment lasting 150s, with a 30s interval between adjacent microwave heating segments.

[0157] S713, allow foamed product G to stand, so that the residual heat of foamed product G can be used to vulcanize foamed product 7 into foamed rubber G (see...). Figure 17 and Figure 18 ).

[0158] Example 8 S811, 5 parts AC foaming agent, 1 part paraffin wax, 10 parts expandable graphite, 1 part graphene oxide, 50 parts butadiene rubber, 50 parts natural rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator H are placed in an open mill and mixed to obtain compound H. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0159] S812, 9g of compound H was obtained, and the compound H was prepared into foamed product H using a microwave process. The mold was made of ceramic, and the compound H was placed on the ceramic without any other covering. The microwave power was 560W, the total heating time was 420s, and the compound H was treated with intermittently applied microwaves, each segment lasting 60s, with a 30s interval between adjacent microwave heating segments.

[0160] S813, the foamed product H is hot-pressed and vulcanized into foamed rubber H in a mold.

[0161] Example 9 S911, 6 parts AC foaming agent, 10 parts expandable graphite, 100 parts butadiene rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator H are placed in an open mill and mixed to obtain compound I. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0162] S912, 9g of compound I was obtained, and compound I was prepared into foamed product I using microwave technology. The mold was made of ceramic, compound I was placed on the ceramic, and no other covering was applied to compound I. The microwave power was 400W, the total heating time was 540s, and the compound I was treated with intermittently applied microwaves, each segment lasting 90s, with a 30s interval between adjacent microwave heating segments.

[0163] S913, hot-pressing and vulcanizing foamed product I into foamed rubber I in a mold (see S913). Figure 19 ).

[0164] Example 10 S1011, 5 parts paraffin wax, 5 parts graphene, 50 parts butadiene rubber, 50 parts natural rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator TT are placed in an open mill and mixed to obtain compound J. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0165] S1012, 6g of compound J was obtained, and the compound J was prepared into foamed product J using microwave technology. The mold was made of ceramic, and the compound J was sandwiched between two ceramic plates. The microwave power of the microwave process was 1000W, and the total heating time of the microwave process was 60s.

[0166] S1013, the foamed product J is hot-pressed and vulcanized into foamed rubber J in a mold.

[0167] Example 11 S1111: 5 parts AC foaming agent, 3 parts paraffin wax, 2 parts paraffin oil, 2 parts graphene, 1 part graphene oxide, 100 parts butadiene rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator TT are placed in an open mill and mixed to obtain compound K. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0168] S1112, 5g of compound K was obtained, and the compound K was prepared into a foamed product K using a microwave process. The mold was made of ceramic, and the compound K was placed on the ceramic without any other covering. The total heating time of the microwave process was 300s. Five intermittent microwave segments were applied to treat the compound K, with power values ​​of 400W, 400W, 560W, 800W, and 800W respectively. Each microwave segment lasted 60s, and the interval between adjacent microwave segments was 30s.

[0169] S1113, the foamed product K is hot-pressed and vulcanized into foamed rubber K in a mold.

[0170] Example 12 S1211, 5 parts expandable graphite, 1 part graphene oxide, 100 parts butadiene rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator TT are placed in an open mill and mixed to obtain compound L. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0171] S1212, 10g of compound L was obtained, and compound L was prepared into foamed product L using a microwave process (see...). Figure 15 and Figure 16 The mold is made of metal, and the mixture L is placed on the metal without any other covering. The total heating time of the microwave process is 360s. The mixture L is treated with three intermittently applied microwaves with powers of 400W, 400W and 560W respectively. Each microwave segment lasts for 120s, and the interval between two adjacent microwave heating segments is 30s.

[0172] S1213, two foamed products L are bonded together and then hot-pressed and vulcanized to form foamed rubber L.

[0173] Example 13 S1311, 6 parts AC foaming agent, 10 parts expandable graphite, 100 parts butadiene rubber, 1 part sulfur, and 1.5 parts vulcanization accelerator H are placed in an open mill and mixed to obtain compound M. The mixing temperature is 60℃, and the mixing time does not exceed 15 minutes.

[0174] S1312, 10g of compound M was obtained, and the compound M was prepared into a foamed product M using a microwave process. The mold was made of ceramic, and the compound M was sandwiched between two ceramic plates. The microwave power was 200W, and the total heating time was 1800s. Intermittent microwave application was used to treat the compound M, with each microwave segment lasting 600s and an interval of 30s between adjacent microwave heating segments.

[0175] S1313, hot-pressing and vulcanizing the foamed product M into foamed rubber M in a mold (see...) Figure 20 ).

[0176] The foamed rubbers prepared in Examples 1 to 13 were transported to a testing device for testing. The tests showed that the foamed rubbers prepared in Examples 1 to 13 had low density and good shock absorption performance.

[0177] In addition, such as Figures 17 to 20 As shown, the foamed rubber prepared by the foamed rubber preparation method in this application embodiment also has solid bubbles, which can prevent the cells from collapsing during storage, that is, a layered structure is formed on the cell wall of the foamed rubber. Figures 17 to 20(As shown in the dashed box or dashed arrow), which also gives the foamed rubber high storage performance.

[0178] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0179] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A method for preparing foamed rubber, characterized in that, include: The foaming agent, rubber matrix, additives and carbon materials are mixed to form a compound; The mixture was prepared into a foamed product using a microwave process. The preparation of the foamed product from the compound using microwave technology includes: A. The compound is microwave irradiated with constant, gradual or intermittent power, and during the microwave irradiation, the ratio of the power of the microwave irradiation received by the compound to the mass of the rubber matrix and the carbon material is greater than or equal to 40 W / g. B. Before and after the microwave process, the surface temperature of at least one surface of the foamed product is controlled to be lower than the vulcanization temperature of the foamed product, so that at least a portion of the surface of the foamed product is not vulcanized or not completely vulcanized. Furthermore, the carbon material includes at least one of the following carbon materials: C. Graphene, wherein the graphene includes single-layer graphene, multi-layer graphene, or stacked graphene. D. Graphene oxide, wherein the graphene oxide includes single-layer graphene oxide, multi-layer graphene oxide, or stacked graphene oxide. E. Graphite; F. Expandable carbon material, wherein the expandable carbon material includes unexpanded expandable graphite; Furthermore, when the carbon material includes the expandable carbon material, the expandable carbon material is also considered as a type of foaming agent.

2. The method for preparing foamed rubber according to claim 1, characterized in that, When the foaming agent is not a carbon material, the vaporization or decomposition temperature of the foaming agent is less than or equal to 300°C; And / or, when the carbon material contains expandable carbon material, the foaming agent vaporizes or decomposes to produce gas at a temperature not exceeding a first temperature; wherein, the first temperature is the temperature at which the expandable carbon material loses 30% of its mass under an inert gas atmosphere.

3. The method for preparing foamed rubber according to claim 1, characterized in that, The mass ratio of the foaming agent to the rubber matrix is ​​1~80:100; Furthermore, the mass ratio of the carbon material to the rubber matrix is ​​less than or equal to 80:

100.

4. The method for preparing foamed rubber according to claim 1, characterized in that, Preferably, after mixing the foaming agent, rubber matrix, additives, and carbon material to form a compound, and before preparing the compound into a foamed product using a microwave process, the method further includes: The mixture is preheated.

5. The method for preparing foamed rubber according to claim 1, characterized in that, Preferably, the preparation of the foamed product from the compound using a microwave process includes: The heating rate of the carbon material is greater than or equal to 10℃ / s; The heating rate of the rubber matrix in the region adjacent to the carbon material is greater than or equal to 10°C / s.

6. The method for preparing foamed rubber according to claim 1, characterized in that, Preferably, the preparation of the foamed product from the compound using a microwave process includes: The mixture is placed in a mold and microwaved, or the mixture is fixed with a fastener and then microwaved, or the mixture is placed in a medium or on the surface of a medium and microwaved.

7. The method for preparing foamed rubber according to claim 6, characterized in that, Preferably, the process before and after microwave treatment includes: The temperature of the mold surface in contact with the compound is lower than the vulcanization temperature of the foamed product. Alternatively, the temperature of the surface of the medium or the interface between the compound and the medium is lower than the vulcanization temperature of the foamed product.

8. The method for preparing foamed rubber according to claim 6, characterized in that, Preferably, the mold and the medium are made of at least one of microwave-transparent materials and metallic materials; Wherein, the mold or medium made of metal material cannot completely shield the microwave source used in the microwave process from microwave irradiation of the mixture.

9. The method for preparing foamed rubber according to claim 1, characterized in that, Preferably, the carbon material includes an expandable carbon material, and the foamed product contains pores having all or part of pore walls formed of a non-rubber material.

10. The method for preparing foamed rubber according to claim 1, characterized in that, After preparing the compound into a foamed product using microwave technology, the process includes: In the unvulcanized or incompletely vulcanized state of the foamed product, it is bonded to plastic, fiber, metal, ceramic or unvulcanized or incompletely vulcanized rubber; Then, the foamed product is prepared into foamed rubber using a vulcanization process.

11. The method for preparing foamed rubber according to claim 10, characterized in that, Preferably, the preparation of foamed rubber from the foamed product using a vulcanization process includes: The foamed product is placed in a mold for shaping and vulcanization.

12. A type of foamed rubber, characterized in that, The foamed rubber is prepared by the foamed rubber preparation method as described in any one of claims 1 to 11.

13. A foamed product, characterized in that, The foamed product is made of the foamed rubber as described in claim 12, and the foamed product includes a rubber tube.

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