Foamed rubber as well as preparation method and application thereof

Abstract

The invention provides foamed rubber as well as a preparation method and application thereof, and particularly relates to white high-damping foamed rubber as well as a preparation method and application thereof. The foaming rubber is prepared from the following components in parts by weight: 80 to 100 parts of ethylene propylene diene monomer, 10 to 40 parts of damping agent, 20 to 80 parts of white carbon black, 3 to 5 parts of vulcanization system, 0.5 to 2 parts of zinc stearate, 2 to 5 parts of zinc oxide, 11 to 25 parts of protection system, 3 to 6 parts of foaming system and 5 to 20 parts of naphthenic oil. The foamed rubber disclosed by the invention has relatively low density and good damping performance, can improve the sensitivity and sound pressure level of products such as loudspeakers and the like, improves the damping performance of the products, can be used for white appearance parts, and basically has no yellowing phenomenon under relatively severe UV illumination.

Description

Technical Field

[0001] This invention belongs to the field of rubber technology, specifically relating to a foamed rubber, its preparation method and application, and more particularly to a white high-damping foamed rubber, its preparation method and application. Background Technology

[0002] Butyl rubber, nitrile rubber, and EPDM rubber are commonly used materials for rubber ring folds. Butyl rubber has an extremely slow vulcanization rate and low production efficiency; therefore, brominated butyl rubber is generally used to accelerate the vulcanization rate. Brominated butyl rubber has good damping properties but slightly poor resistance to photo-oxidative aging. Nitrile rubber has moderate damping properties but extremely poor resistance to photo-oxidative aging. EPDM rubber has relatively poor damping but good resistance to photo-oxidative aging. Meanwhile, solid rubber has a high density, generally greater than 1.2 g / cm³. 3 This leads to a decrease in speaker sensitivity and sound pressure level. To reduce the vibrational mass of the system, PU foam is a common choice; however, PU foam has poor hydrolysis resistance, moderate resistance to photo-oxidative aging, and moderate damping performance, resulting in significant limitations in its use. Therefore, there is no mature rubber formulation on the market that simultaneously satisfies the requirements of white color, UV resistance to yellowing, low density, and high damping. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a foamed rubber, its preparation method, and its applications. The foamed rubber of the present invention has low density and good damping properties, which can improve the sensitivity and sound pressure level of products such as loudspeakers, enhance their damping performance, and can be used in white-looking parts, exhibiting virtually no yellowing even under severe UV irradiation.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] On one hand, the present invention provides a foamed rubber, wherein the raw materials for preparing the foamed rubber, by weight, include the following components: 80-100 parts of EPDM rubber (e.g., 80, 83, 85, 88, 90, 93, 95, 98, or 100 parts), 10-40 parts of damping agent (e.g., 10, 15, 18, 20, 25, 28, 30, 35, 38, or 40 parts), 20-80 parts of silica (e.g., 20, 25, 30, 40, 50, 60, 70, or 80 parts), and vulcanizate. The composition includes 3-5 parts (e.g., 3, 3.5, 4, 4.5, or 5 parts), 0.5-2 parts (e.g., 0.5, 0.8, 1, 1.5, 1.8, or 2 parts) of zinc stearate, 2-5 parts (e.g., 2, 3, 4, or 5 parts) of zinc oxide, 11-25 parts (e.g., 11, 13, 15, 18, 20, 22, or 25 parts) of protective system, 3-6 parts (e.g., 3, 4, 5, or 6 parts) of foaming system, and 5-20 parts (e.g., 5, 8, 10, 12, 15, 18, or 20 parts) of naphthenic oil.

[0006] Preferably, the damping agent is polyisobutylene resin.

[0007] Preferably, the polyisobutylene resin has a weight-average molecular weight of 60-500W, such as 60W, 80W, 100W, 130W, 150W, 180W, 210W, 250W, 280W, 310W, 350W, 380W, 400W, 430W, 450W, 480W, or 500W.

[0008] In this invention, polyisobutylene resin, due to the densely packed side methyl groups on its molecular chains, increases internal friction during molecular chain movement, thereby increasing the system's damping. Simultaneously, its molecular chains are saturated and do not participate in the vulcanization process, while also exhibiting excellent aging resistance.

[0009] Preferably, the vulcanization system comprises a combination of sulfur, thiuram-based accelerators, dithiocarbamate-based accelerators, and thiazole-based accelerators.

[0010] Preferably, the weight ratio of sulfur, thiuram accelerator, dithiocarbamate accelerator and thiazole accelerator in the vulcanization system is 1-1.5:0.5-1:1-2:1-2. Examples include 1:0.5:1:1, 1:0.8:1:1, 1:1:1:1, 1:0.5:2:1, 1:0.5:2:2, 1.2:0.5:1:1, 1.2:0.5:1.5:1, 1.2:0.5:1.5:1, 1.2:0.5:2:1, 1.2:0.5:2:2, 1.2:0.8:1:1, 1.2:1:1:1, 1.2:1:2:1, 1.2:1:2:2, 1.5:0.5:1:1, 1.5:0.8:1:1, 1.5:1:1:1, 1.5:1:2:1, 1.5:1:1:2, 1.5:0.8:1.5:1.5, 1.5:1:1.8:1, etc.

[0011] Preferably, the thiuram-based accelerator is accelerator TRA.

[0012] Preferably, the dithiocarbamate accelerator is accelerator PZ.

[0013] Preferably, the thiazole accelerator is accelerator DM.

[0014] In this invention, zinc stearate and zinc oxide serve as sulfidation activators and also play a role in promoting foaming.

[0015] Preferably, the protective system is a combination of titanium dioxide, pentaerythritol ester hindered phenolic antioxidants, phosphite antioxidants, and benzophenone antioxidants.

[0016] Preferably, the weight ratio of titanium dioxide, pentaerythritol ester hindered phenolic antioxidants, phosphite antioxidants, and benzophenone antioxidants in the protective system is 5-15:1-2:1-2:4-6, for example 5:1:1:4, 6:1:1:4, 8:1:1:4, 10:1:1:4, 12:1:1:4, 15:1:1:4, 5:1.5:1:4, 5:1.5:2:5, 5:2:1:5, 5:2:2:2, 5:2:2:6, 7:1:2:4, 7:2:2 :5, 7:1:2:6, 9:1:2:4, 9:1:2:5, 9:2:1:4, 9:2:2:5, 9:2:2:6, 10:1:2:4, 10:2:2:4, 10:2:1:6, 10:2:1:5, 10:1:2:5, 12:1:1:5, 12:2:1:5, 12:2:2:6, 14:1:1:4, 14:2:2:5, 14:2:1:6, 15:2:1:4, 15:1:2:5, 15:1:2:6, etc.

[0017] Preferably, the titanium dioxide is rutile titanium dioxide. More preferably, the average particle size of the rutile titanium dioxide is in the range of 0.1-1 μm, for example, 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm or 1 μm.

[0018] Preferably, the pentaerythritol ester hindered phenolic antioxidant is antioxidant 1076.

[0019] Preferably, the phosphite antioxidant is antioxidant 168.

[0020] Preferably, the benzophenone antioxidant is ultraviolet absorber 531.

[0021] In this invention, titanium dioxide, as a light shielding agent, mainly achieves its protective effect by reflecting ultraviolet rays. Antioxidant 1076 and antioxidant 168 work synergistically to directly capture free radicals and prevent the occurrence of chain reactions in the aging process. Ultraviolet absorber 531 can efficiently absorb 240-340nm ultraviolet light.

[0022] Preferably, the foaming system includes a primary foaming agent and a secondary foaming agent.

[0023] Preferably, the weight ratio of the main foaming agent to the auxiliary foaming agent is 4-6:1-3, for example 4:1, 4:2, 4:3, 5:1, 5:2, 5:3, 6:1 or 6:2.

[0024] Preferably, the primary foaming agent includes foaming agent AC and / or foaming agent OBHS.

[0025] Preferably, the foaming agent comprises any one or a combination of at least two of urea, ethanolamine, phthalic acid, stearic acid, or calcium stearate.

[0026] On the other hand, the present invention provides a method for preparing the foamed rubber as described above, the method comprising the following steps:

[0027] Step (1): Mix and preheat the damping agent and naphthenic oil;

[0028] Step (2): Then add EPDM rubber, zinc stearate, silica, zinc oxide and protective system to the mixture obtained in step (1) and mix.

[0029] Step (3): Cool the mixture obtained in step (2), add it to the vulcanization system and the foaming system, and mix.

[0030] Step (4): The material obtained in step (3) is refining, thinned and sheeted, the rubber is taken out and cooled, placed, and then vulcanized to obtain the foamed rubber.

[0031] Preferably, the preheating in step (1) is carried out at 90-110°C (e.g., 90°C, 95°C, 98°C, 100°C, 105°C, 108°C or 110°C).

[0032] Preferably, the preheating in step (1) is carried out under stirring, and the stirring speed is 10-40 r / min, for example 10 r / min, 13 r / min, 15 r / min, 18 r / min, 20 r / min, 25 r / min, 28 r / min, 30 r / min, 35 r / min, 38 r / min or 40 r / min.

[0033] Preferably, the preheating time in step (1) is 5-10 min, for example 5 min, 6 min, 7 min, 8 min, 9 min or 10 min.

[0034] Preferably, in step (2), EPDM rubber, zinc stearate, silica, zinc oxide, and the protective system are added sequentially to the mixture obtained in step (1) while maintaining a temperature of 90-110°C (e.g., 90°C, 95°C, 98°C, 100°C, 105°C, 108°C, or 110°C).

[0035] Preferably, the mixing in step (2) is carried out under stirring, and the stirring speed is 15-40 r / min, for example 15 r / min, 18 r / min, 20 r / min, 25 r / min, 28 r / min, 30 r / min, 35 r / min, 38 r / min or 40 r / min.

[0036] Preferably, the mixing time in step (2) is 7-10 min, for example 7 min, 8 min, 9 min or 10 min.

[0037] Preferably, the cooling in step (3) is to reduce the temperature to 40-60°C, for example, 40°C, 45°C, 50°C, 55°C or 60°C.

[0038] Preferably, the mixing in step (3) is carried out under stirring, and the stirring speed is 15-40 r / min, for example 15 r / min, 18 r / min, 20 r / min, 25 r / min, 28 r / min, 30 r / min, 35 r / min, 38 r / min or 40 r / min.

[0039] Preferably, the mixing time in step (3) is 3-5 minutes, for example, 3 minutes, 4 minutes or 5 minutes.

[0040] Preferably, the thin pass in step (4) is 3-4 thin passes.

[0041] Preferably, the placement in step (4) is for more than 8 hours, such as 8h, 9h, 10h, 12h, 15h, 18h, 20h, 22h, 24h, etc.

[0042] Preferably, the vulcanization molding in step (4) is carried out at a temperature of 150°C-190°C (e.g., 150°C, 160°C, 170°C, 180°C or 190°C).

[0043] On the other hand, the present invention provides a speaker rubber surround, the speaker rubber surround comprising the foamed rubber as described above.

[0044] On the other hand, the present invention provides the application of foamed rubber as described above in speaker enclosures, loudspeakers or damping materials.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The foamed rubber provided by this invention has the characteristics of UV resistance to yellowing and high damping. By using the synergistic compounding of various component raw materials, its density can be stabilized at 0.703-0.741 g / cm3. In the ultraviolet aging test chamber, the color change ΔE after 96 hours is ≤0.8. It can stably produce ultra-thin low-density folded rings and has excellent damping performance. At 100Hz / 25℃, the loss factor tanδ increases to 0.562-0.639, which can improve the sensitivity and sound pressure level of products such as loudspeakers and improve damping performance. It can be used for white appearance parts. Detailed Implementation

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0048] The main experimental materials used in the following embodiments and comparative examples of this invention include:

[0049] (1) EPDM rubber, purchased from Arlanxyn. 2650C; Halogenated butyl rubber and brominated butyl rubber are supplied by ExxonMobil, USA. TM Bromobutyl 2255.

[0050] (2) Polyisobutylene, HB-50 (weight average molecular weight 60W), HB-200 (weight average molecular weight 310W) and HB-400 (weight average molecular weight 410W) were purchased from Zhejiang Xinhui New Material Co., Ltd.; damping agent A0-60 was purchased from Jiangsu Diyang New Material Co., Ltd.

[0051] (3) Protection system: Titanium dioxide was purchased from Chemours R960 in the United States, and other antioxidants were purchased from BASF in Germany.

[0052] (4) Foaming system: foaming agents AC and OBHS were purchased from Kemaowei New Materials Co., Ltd.

[0053] Example 1

[0054] A UV-resistant, high-damping foamed rubber, the main components by weight are: 100 parts EPDM rubber, 10 parts polyisobutylene PB-50, 20 parts silica, 3 parts vulcanization system, 0.5 parts zinc stearate, 2 parts zinc oxide, 25 parts protective system, 3 parts foaming system, and 5 parts naphthenic oil.

[0055] The vulcanization system is a mixture of sulfur, accelerator TRA, accelerator PZ and accelerator DM in a weight ratio of 1:0.5:1:1.

[0056] The protective system is composed of titanium dioxide, antioxidant 1076, antioxidant 168 and ultraviolet absorber 531 mixed in a weight ratio of 15:2:2:6.

[0057] The foaming system is a mixture of foaming agent AC and stearic acid in a weight ratio of 6:3.

[0058] The preparation method of the high-damping rubber is as follows:

[0059] Step 1: Raise the temperature of the internal mixer to 90°C, pour in polyisobutylene and naphthenic oil, and preheat at 10 r / min for 5 min.

[0060] Step 2: Keep the internal mixer temperature at 90℃, and add EPDM rubber, zinc stearate, silica, zinc oxide and protective system to the internal mixer in sequence, and mix at 15r / min for 7min.

[0061] Step 3: Reduce the temperature of the internal mixer to 40°C, add the vulcanization system and foaming system, and continue mixing at 30 r / min for 3 min.

[0062] Step 4: Tumble the mixed rubber compound in a two-roll mill, pass it through the mill three times, then sheet it out, remove it and dry it with strong air, and let the rubber compound stand for more than 8 hours.

[0063] Step 5: Cut the rubber material and put it into a flat vulcanizing machine, then vulcanize it at 150°C.

[0064] Example 2

[0065] A UV-resistant, high-damping foamed rubber, the main components by weight are: 90 parts EPDM rubber, 30 parts polyisobutylene HB-200, 60 parts silica, 4 parts vulcanization system, 1 part zinc stearate, 3 parts zinc oxide, 18 parts protective system, 4 parts foaming system, and 10 parts naphthenic oil.

[0066] The vulcanization system is a mixture of sulfur, accelerator TRA, accelerator PZ and accelerator DM in a weight ratio of 1.2:0.75:1.5:1.5.

[0067] The aforementioned protective system is composed of titanium dioxide, antioxidant 1076, antioxidant 168 and ultraviolet absorber 531 mixed in a weight ratio of 10:1.5:1.5:5.

[0068] The foaming system is a mixture of foaming agent AC and urea in a weight ratio of 5:2.

[0069] The preparation method of the high-damping rubber is as follows:

[0070] Step 1: Raise the temperature of the internal mixer to 100°C, pour in the damping agent and naphthenic oil, and preheat at 30 r / min for 7 min.

[0071] Step 2: Keep the internal mixer temperature at 100℃, and add EPDM rubber, zinc stearate, silica, zinc oxide and protective system to the internal mixer in sequence, and mix at 30r / min for 8min.

[0072] Step 3: Reduce the temperature of the internal mixer to 50°C, add the vulcanization system and foaming system, and continue mixing at 30 r / min for 4 min.

[0073] Step 4: Tumble the mixed rubber compound in a two-roll mill, pass it through a thin mill 4 times, then sheet it out, take it out and dry it with a strong air blower, and let the rubber compound stand for more than 8 hours.

[0074] Step 5: Cut the rubber material and put it into a flat vulcanizing machine, then vulcanize it at 170℃.

[0075] Example 3

[0076] A UV-resistant, high-damping foamed rubber, the main components by weight are: 80 parts EPDM rubber, 40 parts polyisobutylene HB-400, 80 parts silica, 5 parts vulcanization system, 2 parts zinc stearate, 5 parts zinc oxide, 11 parts protective system, 6 parts foaming system, and 20 parts naphthenic oil.

[0077] The vulcanization system is a mixture of sulfur, accelerator TRA, accelerator PZ and accelerator DM in a weight ratio of 1.5:1:2:2.

[0078] The aforementioned protective system is a mixture of titanium dioxide, antioxidant 1076, antioxidant 168, and ultraviolet absorber 531 in a weight ratio of 5:1:1:4.

[0079] The foaming system described herein is a mixture of foaming agent OBHS and calcium stearate in a weight ratio of 4:1.

[0080] The preparation method of the high-damping rubber is as follows:

[0081] Step 1: Raise the temperature of the internal mixer to 110°C, pour in the damping agent and naphthenic oil, and preheat at 40 r / min for 10 min.

[0082] Step 2: Keep the internal mixer temperature at 110℃, and add EPDM rubber, zinc stearate, silica, zinc oxide and protective system to the internal mixer in sequence, and mix at 40r / min for 10min.

[0083] Step 3: Reduce the temperature of the internal mixer to 60℃, add the vulcanization system and foaming system, and continue mixing at 30r / min for 5min.

[0084] Step 4: Tumble the mixed rubber compound in a two-roll mill, pass it through the mill three times, then sheet it out, remove it and dry it with strong air, and let the rubber compound stand for more than 8 hours.

[0085] Step 5: Cut the rubber material and put it into a flat vulcanizing machine, where it is vulcanized at 190°C.

[0086] Example 4

[0087] A UV-resistant, high-damping foamed rubber, the main components by weight are: 100 parts brominated butyl rubber, 10 parts polyisobutylene PB-50, 20 parts silica, 3 parts vulcanization system, 0.5 parts zinc stearate, 2 parts zinc oxide, 25 parts protective system, 3 parts foaming system, and 5 parts naphthenic oil.

[0088] The vulcanization system is a mixture of sulfur, accelerator TRA, accelerator PZ and accelerator DM in a weight ratio of 1:0.5:1:1.

[0089] The aforementioned protective system is composed of titanium dioxide, antioxidant 1076, antioxidant 168 and ultraviolet absorber 531 mixed in a weight ratio of 15:2:2:6.

[0090] The foaming system is a mixture of foaming agent AC and stearic acid in a weight ratio of 6:3.

[0091] The preparation method of the high-damping rubber is as follows:

[0092] Step 1: Raise the temperature of the internal mixer to 90°C, pour in polyisobutylene and naphthenic oil, and preheat at 10 r / min for 5 min.

[0093] Step 2: Keep the internal mixer temperature at 90℃, and add EPDM rubber, zinc stearate, silica, zinc oxide and protective system to the internal mixer in sequence, and mix at 30r / min for 7min.

[0094] Step 3: Reduce the temperature of the internal mixer to 40°C, add the vulcanization system and foaming system, and continue mixing at 30 r / min for 3 min.

[0095] Step 4: Tumble the mixed rubber compound in a two-roll mill, pass it through a thin mill 4 times, then sheet it out, take it out and dry it with a strong air blower, and let the rubber compound stand for more than 8 hours.

[0096] Step 5: Cut the rubber material and put it into a flat vulcanizing machine, then vulcanize it at 150°C.

[0097] The foamed rubber products prepared in Examples 1-4 have a smooth surface appearance.

[0098] Comparative Example 1

[0099] The only difference from Example 1 is that the damping agent polyisobutylene is not added.

[0100] Comparative Example 2

[0101] The only difference from Example 1 is that the amount of protective system added is 25 parts, and the protective system is a mixture of antioxidant 1076, antioxidant 168 and ultraviolet absorber 531 in a weight ratio of 2:2:6.

[0102] Comparative Example 3

[0103] The only difference from Example 1 is that the amount of protective system added is 25 parts, and the protective system is a mixture of titanium dioxide and ultraviolet absorber 531 in a weight ratio of 15:6.

[0104] Comparative Example 4

[0105] The only difference from Example 1 is that the amount of protective system added is 25 parts, and the protective system is a mixture of titanium dioxide, antioxidant 1076 and antioxidant 168 in a weight ratio of 15:2:2.

[0106] Comparative Example 5

[0107] The only difference from Example 1 is that no foaming system is added.

[0108] Comparative Example 6

[0109] The only difference from Example 1 is that the foaming system includes only the foaming agent AC.

[0110] Comparative Example 7

[0111] The only difference from Example 1 is that the foaming system contains only stearic acid.

[0112] Comparative Example 8

[0113] The only difference from Example 1 is that the vulcanization system is composed of sulfur, accelerator TRA and accelerator PZ mixed in a weight ratio of 1:0.5:1, and the amount of the vulcanization system added is 3 parts.

[0114] Comparative Example 9

[0115] The only difference from Example 1 is that the vulcanization system is composed of sulfur, accelerator TRA and accelerator DM mixed in a weight ratio of 1:0.5:1, and the amount of the vulcanization system added is 3 parts.

[0116] Comparative Example 10

[0117] The only difference from Example 1 is that the vulcanization system is composed of sulfur, accelerator PZ and accelerator DM mixed in a weight ratio of 1:1:1, and the amount of the vulcanization system added is 3 parts.

[0118] The foamed rubber prepared in this comparative example has open pores on its surface and a poor appearance.

[0119] Comparative Example 11

[0120] The only difference from Example 1 is that the sulfur in the vulcanization system is replaced with dicumyl peroxide.

[0121] In this comparative example, the vulcanization system reacts with antioxidants 1076 and 168, resulting in insufficient vulcanization and product deformation.

[0122] Performance testing:

[0123] (1) Loss factor tanδ: Measured using a dynamic thermomechanical analyzer (DMA) to characterize the damping performance of rubber. The frequency was set to 0.1 Hz, 1 Hz and 10 Hz, the temperature range was -80℃ to 100℃, the heating rate was 10℃ / min, and the main curve was obtained by frequency extrapolation.

[0124] (2) Tensile strength and elongation at break: Tested according to the methods specified in national standard GB / T 528-2009;

[0125] (3) Anti-photo-oxidative aging test: A UVA-340 fluorescent ultraviolet lamp was used, with the temperature set at 60℃ and the light intensity at 0.89W / m². 2 The irradiation time was 96 hours, and the color difference ΔE of the material before and after irradiation was tested.

[0126] (4) Density: Tested in accordance with GB / T 6343-2009.

[0127] Table 1

[0128]

[0129] The applicant declares that the present invention is illustrated by the above embodiments to demonstrate the foamed rubber, its preparation method, and its application. However, the present invention is not limited to the above embodiments, meaning that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials for the products of the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of the present invention.

[0130] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A type of foamed rubber, characterized in that, The raw materials for preparing the foamed rubber, by weight, include the following components: 80-100 parts of EPDM rubber, 10-40 parts of damping agent, 20-80 parts of silica, 3-5 parts of vulcanization system, 0.5-2 parts of zinc stearate, 2-5 parts of zinc oxide, 11-25 parts of protective system, 3-6 parts of foaming system, and 5-20 parts of naphthenic oil.

2. The foamed rubber according to claim 1, characterized in that, The damping agent is polyisobutylene resin; Preferably, the polyisobutylene resin has a weight-average molecular weight of 60-500W.

3. The foamed rubber according to claim 1 or 2, characterized in that, The vulcanization system comprises a combination of sulfur, thiuram-based accelerators, dithiocarbamate-based accelerators, and thiazole-based accelerators. Preferably, the weight ratio of sulfur, thiuram accelerator, dithiocarbamate accelerator and thiazole accelerator in the vulcanization system is 1-1.5:0.5-1:1-2:1-2; Preferably, the thiuram-based accelerator is accelerator TRA. Preferably, the dithiocarbamate accelerator is accelerator PZ. Preferably, the thiazole accelerator is accelerator DM.

4. The foamed rubber according to any one of claims 1-3, characterized in that, The protective system is a combination of titanium dioxide, pentaerythritol ester hindered phenolic antioxidants, phosphite antioxidants, and benzophenone antioxidants. Preferably, the weight ratio of titanium dioxide, pentaerythritol ester hindered phenolic antioxidant, phosphite antioxidant and benzophenone antioxidant in the protective system is 5-15:1-2:1-2:4-6; Preferably, the titanium dioxide is rutile titanium dioxide; Preferably, the pentaerythritol ester hindered phenolic antioxidant is antioxidant 1076; Preferably, the phosphite antioxidant is antioxidant 168; Preferably, the benzophenone antioxidant is ultraviolet absorber 531.

5. The foamed rubber according to any one of claims 1-4, characterized in that, The foaming system includes a primary foaming agent and a secondary foaming agent; Preferably, the weight ratio of the primary foaming agent to the secondary foaming agent is 4-6:1-3; Preferably, the main foaming agent includes foaming agent AC and / or foaming agent OBHS; Preferably, the foaming agent includes any one or a combination of at least two of urea, ethanolamine, phthalic acid, stearic acid, or calcium stearate.

6. The method for preparing foamed rubber according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: Step (1): Mix and preheat the damping agent and naphthenic oil; Step (2): Then add EPDM rubber, zinc stearate, silica, zinc oxide and protective system to the mixture obtained in step (1) and mix. Step (3): Cool the mixture obtained in step (2), add it to the vulcanization system and the foaming system, and mix. Step (4): The material obtained in step (3) is refining, thinned and sheeted, the rubber is taken out and cooled, placed, and then vulcanized to obtain the foamed rubber.

7. The preparation method according to claim 6, characterized in that, The preheating in step (1) is carried out at 90-110℃; Preferably, the preheating in step (1) is carried out under stirring, and the stirring speed is 10-40 r / min; Preferably, the preheating time in step (1) is 5-10 minutes; Preferably, in step (2), EPDM rubber, zinc stearate, silica, zinc oxide, and the protective system are added sequentially to the mixture obtained in step (1) while maintaining a temperature of 90-110°C. Preferably, the mixing in step (2) is carried out under stirring, and the stirring speed is 15-40 r / min; Preferably, the mixing time in step (2) is 7-10 minutes.

8. The preparation method according to claim 6, characterized in that, The cooling process described in step (3) involves reducing the temperature to 40-60℃. Preferably, the mixing in step (3) is carried out under stirring, and the stirring speed is 15-40 r / min; Preferably, the mixing time in step (3) is 3-5 minutes; Preferably, the thin-passing in step (4) involves 3-4 thin-passing passes; Preferably, the placement in step (4) is for more than 8 hours; Preferably, the vulcanization molding in step (4) is carried out at a temperature of 150℃-190℃.

9. A speaker rubber surround, characterized in that, The speaker rubber surround comprises the foamed rubber according to any one of claims 1-5.

10. The use of foamed rubber according to any one of claims 1-5 in speaker enclosures, loudspeakers or damping materials.

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