A low-hardness rubber-plastic alloy and a preparation method thereof

Abstract

The application provides a low-hardness rubber-plastic alloy mixing rubber and a preparation method thereof, which comprises the following components in parts by weight: raw rubber 50-90 parts; PVC plasticizing premix rubber 65-85 parts; active agent 6-14 parts; anti-aging agent 3-11 parts; reinforcing agent 30-65 parts; first plasticizing agent 50-80 parts; vulcanizing agent 0.3-1 part; and accelerator 2-4.5 parts. The PVC plasticizing premix rubber comprises the following components in parts by weight: dispersed PVC resin 100 parts; second plasticizing agent 120-170 parts; composite stabilizer 4-10 parts; lubricant 1-3 parts; and activator 0.5-2 parts. The low-hardness rubber-plastic alloy mixing rubber is prepared by blending the dispersed PVC resin with the raw NBR rubber to obtain the PVC plasticizing premix rubber, which has good wettability, swelling property and compatibility, is not easy to decompose and has higher stability. The PVC plasticizing premix rubber is used in the preparation of the low-hardness rubber-plastic alloy mixing rubber, which simplifies the existing technology and greatly improves the stability of the quality of the low-hardness rubber-plastic alloy mixing rubber.

Description

Technical Field

[0001] This invention belongs to the field of rubber products and relates to a low-hardness rubber-plastic alloy compound and its preparation method. Background Technology

[0002] Nitrile rubber (NBR) blended with polyvinyl chloride (PVC) is currently one of the most successful and widely used rubber-plastic blends, also known as a rubber-plastic alloy. It combines the excellent ozone resistance and flame retardancy of PVC with the oil resistance, resilience, and crosslinkable vulcanizability of NBR. It improves and enhances the oil resistance, ozone resistance, heat resistance, and abrasion resistance of NBR, as well as its flowability, extrusion, and calendering properties. Furthermore, it improves the storage stability and colorability of NBR, making it suitable for producing colored products. Therefore, NBR+PVC blends are widely used.

[0003] Currently, NBR+PVC blending mainly employs emulsion co-precipitation, mechanical blending, and solution blending methods. In China, mechanical blending is the dominant method, with an NBR:PVC ratio of 70:30 being the most common. NBR can be selected based on actual needs, using nitrile butadiene rubber with varying acrylonitrile content, with medium-to-high acrylonitrile content being the most prevalent, and 32-36% acrylonitrile content being the mainstream in the market. This is because this acrylonitrile content offers the best compatibility with PVC, allowing for miscibility in any ratio. PVC is further divided into two types: suspension PVC (SPVC) and paste PVC (PPVC), with suspension PVC being the more prevalent.

[0004] There are many types of commercially available rubber-plastic alloys. These alloys are suitable for producing products with a standard hardness of 50-85 Shore A, but not for producing products with low hardness, such as those below 35 Shore A. Because the raw rubber base of these alloys has a high hardness, typically around 60-75 degrees or even higher, it's necessary to add more plasticizers to reduce the hardness, for example, to produce low-hardness printing ink rollers or ozone-resistant low-hardness products. However, adding excessive plasticizers can lead to problems such as difficulty in mixing the compound, excessively low shear strength, excessively long mixing time, or poor dispersion of the compound. This can prevent reinforcing particles like carbon black from mixing properly, resulting in poor compound properties, low strength, excessively low Mooney viscosity, and inconvenient storage and transportation. Furthermore, the finished product may exhibit issues such as oil spraying.

[0005] To meet market demand for products such as low-hardness printing rollers, some oil-extended rubber-plastic alloy compounds are available, but their high price significantly increases production costs. Therefore, there is an urgent need for a low-hardness rubber-plastic alloy compound to address and improve these issues, in order to reduce costs and produce low-hardness (Shore hardness less than 35A) rubber-plastic alloy compounds. Summary of the Invention

[0006] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a low-hardness rubber-plastic alloy compound.

[0007] The first objective of this invention is to provide a low-hardness rubber-plastic alloy compound comprising the following components in parts by weight:

[0008] 50-90 parts raw rubber;

[0009] 65-85 parts of PVC plasticized premix;

[0010] Surfactant 6-14 parts;

[0011] Anti-aging agent: 3-11 parts;

[0012] 30-65 parts of reinforcing agent;

[0013] 50-80 parts of the first plasticizer;

[0014] Vulcanizing agent 0.3 to 1 part;

[0015] Accelerator 2 to 4.5 parts.

[0016] Specifically, the raw rubber is a combination of 40-60 parts by weight of NBR3370 and 10-30 parts by weight of NBR3350;

[0017] The first plasticizer is a grafted ester plasticizer, selected from environmentally friendly plasticizer SP756 or environmentally friendly plasticizer DX-360.

[0018] Specifically, the activator is a mixture of zinc oxide, active magnesium oxide-150, and stearic acid;

[0019] Preferably, the activator comprises 4 to 7 parts by weight of zinc oxide, 1 to 4 parts by weight of active magnesium oxide-150 and 1 to 3 parts by weight of stearic acid.

[0020] Specifically, the antioxidant includes at least one or more of antioxidant MB, microcrystalline wax, antioxidant RD powder, and antioxidant 4010NA powder;

[0021] Preferably, the antioxidant is a combination of 0.5 to 2.5 parts by weight of antioxidant MB, 0.5 to 2.5 parts by weight of microcrystalline wax, 1 to 3 parts by weight of antioxidant RD powder and 1 to 3 parts by weight of antioxidant 4010NA powder.

[0022] Specifically, the reinforcing agent is at least one or a combination of two selected from N774 carbon black and N85 silica powder;

[0023] Preferably, the reinforcing agent is a combination of 15 to 30 parts by weight of N774 carbon black and 15 to 35 parts by weight of N85 silica powder.

[0024] Specifically, the reinforcing agent is a combination of 15-30 parts by weight of N774 carbon black and 15-35 parts by weight of N85 silica powder.

[0025] Specifically, the PVC plasticized premix comprises the following components in parts by weight:

[0026]

[0027] Specifically, the dispersed PVC resin is PSM-31 dispersed PVC resin selected from Shenyang Chemical; the second plasticizer is grafted ester plasticizer SP756 selected from Shanghai Shanzhen Industrial Co., Ltd. Specifically, the composite stabilizer is a combination of barium-zinc composite stabilizer and organotin stabilizer, including 3-7 parts by weight of barium-zinc composite stabilizer and 1-3 parts by weight of organotin stabilizer; the lubricant is polyethylene wax with a molecular weight of 3000-4000 g / mol; the activator is stearic acid with a mass of 0.5-2 parts by weight.

[0028] The second objective of this invention is to provide a method for preparing the low-hardness rubber-plastic alloy compound as described above, comprising the following steps:

[0029] (a) Plasticization: The formula amount of dispersed PVC resin, second plasticizer and composite stabilizer are added to the reaction vessel and stirred. After impregnation and swelling treatment for 6 to 10 hours, the mixture is heated to 100-120°C. Lubricant and activator are added and stirred for 40 to 60 minutes. Stirring is stopped and the mixture is heated to 150-160°C for high-temperature plasticization for 1 to 2 hours. After cooling and molding, the PVC plasticized premixed adhesive is obtained.

[0030] (b) Mixing: The internal mixer is heated to above 100°C. The weighed raw rubber, PVC plasticized premixed rubber, activator and antioxidant are added to the internal mixer for mixing. The speed of the internal mixer is 40-50 r / min, the mixing pressure is 5-7 KGf, and the mixing temperature is 135-145°C. After mixing for 3-5 minutes, the reinforcing agent and part of the first plasticizer are added. After mixing for 3-5 minutes, the remaining first plasticizer is added and the mixture is mixed for 4-6 minutes. The mixture is then cleaned by lifting the plug multiple times and discharged when the mixing temperature reaches 140±5°C to obtain the premixed rubber.

[0031] (c) Open milling: The premixed rubber is fed onto an open mill, cooled and filtered, then pressed into sheets, sheeted, cooled and sliced ​​by the open mill, and then tested for quality to obtain qualified rubber.

[0032] (d) Vulcanization: Weigh out qualified rubber compound, vulcanizing agent and accelerator for later use. Set the speed of the internal mixer to 20-25 r / min and the mixing pressure to 3-5 KGf. Add qualified rubber compound and stir for 50-70s. Then add vulcanizing agent and accelerator and mix for 50-60s. Discharge the material when the mixing temperature reaches 90-95℃. After passing through an open mill, the low hardness rubber-plastic alloy compound is obtained.

[0033] This invention relates to a low-hardness rubber-plastic alloy compound, which is prepared by blending dispersed PVC resin with NBR raw rubber and then plasticizing it to obtain a PVC plasticized premix. This premix exhibits good wettability, swelling properties, and compatibility; it is less prone to decomposition and has higher stability; it is easy to mix, disperses well, has good physical properties, short mixing time, and high efficiency. It is also easy to store and transport, and the hardness range of the rubber-plastic alloy compound can be easily adjusted. Using the PVC plasticized premix in the preparation of the low-hardness rubber-plastic alloy compound simplifies the refining process in existing technologies and significantly improves the stability of the low-hardness rubber-plastic alloy compound. It exhibits good elasticity, good resilience, good low-temperature resistance, no oil spraying or leakage, good product dimensional stability, no exudation or paper contamination, and is free of phthalic plasticizers, complying with EU environmental requirements such as RoHS 2.0, REACH, and PAHS. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the preparation of the PVC plasticized premixed adhesive of the present invention;

[0035] Figure 2 This is a flowchart of the method for preparing low-hardness rubber-plastic alloy compound according to the present invention. Detailed Implementation

[0036] The present invention relates to a low-hardness rubber-plastic alloy compound, which comprises the following components in parts by weight: 50-90 parts of raw rubber; 65-85 parts of PVC plasticized premix; 6-14 parts of activator; 3-11 parts of antioxidant; 30-65 parts of reinforcing agent; 50-80 parts of first plasticizer; 0.3-1 part of vulcanizing agent; and 2-4.5 parts of accelerator.

[0037] To prepare a low-hardness rubber-plastic alloy compound, we selected nitrile butadiene rubber (NBR) with a high Mooney viscosity and medium-high acrylonitrile content, such as NBR3365, NBR3370, and NBR3380. For example, this invention uses a combination of 40-60 parts by weight of NBR3370 and 10-30 parts by weight of NBR3350 as the raw rubber.

[0038] Because phthalate plasticizers such as DOP and DBP, which are highly compatible with NBR and PVC, contain benzene rings and are not environmentally friendly, posing potential carcinogenic risks, their use is now prohibited. Therefore, environmentally friendly plasticizers are required. After comparison, we selected Sanepar756 environmentally friendly grafted ester plasticizer from Shanghai Shanzhen Industry. Utilizing chemical grafting technology, it improves polarity, compatibility, and heat resistance, replacing traditional phthalate and paraben plasticizers. It also exhibits good compatibility, heat resistance, cold resistance, and high filler capacity, allowing for addition amounts of up to 80 parts or more without spraying. The first plasticizer is a grafted ester plasticizer, selected from environmentally friendly plasticizer SP756 or environmentally friendly plasticizer DX-360; DX-360 was purchased from Nantong Baocheng Plasticizer Technology Co., Ltd. The activator of this invention is a mixture of zinc oxide, activated magnesium oxide-150, and stearic acid; the activator comprises 4-7 parts by weight of zinc oxide, 1-4 parts by weight of activated magnesium oxide-150, and 1-3 parts by weight of stearic acid. The antioxidant comprises at least one or more of antioxidant MB, microcrystalline wax, antioxidant RD powder, and antioxidant 4010NA powder; the antioxidant is a combination of 0.5-2.5 parts by weight of antioxidant MB, 0.5-2.5 parts by weight of microcrystalline wax, 1-3 parts by weight of antioxidant RD powder, and 1-3 parts by weight of antioxidant 4010NA powder. The reinforcing agent is at least one or a combination of two selected from N774 carbon black and N85 silica powder; the reinforcing agent is a combination of 15-30 parts by weight of N774 carbon black and 15-35 parts by weight of N85 silica powder. The reinforcing agent is a combination of 15-30 parts by weight of N774 carbon black and 15-35 parts by weight of N85 silica powder.

[0039] The PVC plasticized premixed adhesive includes the following components in parts by weight: 100 parts of dispersed PVC resin; 120-170 parts of secondary plasticizer; 4-10 parts of composite stabilizer; 1-3 parts of lubricant; and 0.5-2 parts of activator.

[0040] Since most rubber-plastic blends on the market use suspension PVC (SPVC), which has the advantage of low price and low cost, its plasticizing temperature is high, requiring above 160℃ to fully plasticize. However, SPVC decomposes at around 180℃, releasing HCl gas, making the plasticizing temperature difficult to control, and the dispersion effect and physical properties of the blended rubber are also unstable. Dispersed PVC resin (PPVC), on the other hand, has advantages such as easy plasticization and absorption of plasticizers, easy wetting and dispersion, and excellent physical properties. While its price is relatively higher than SPVC, its plasticizing cost is lower. Therefore, after comprehensive evaluation and comparison, we selected PSM-31 dispersed PVC resin from Shenyang Chemical.

[0041] The principle is the same as above. The second plasticizer in the PVC plasticized premix is ​​SP756, a grafted ester plasticizer selected from Shanghai Shanzhen Industrial Co., Ltd.

[0042] Because PVC has poor thermal stability, it decomposes at temperatures above 180℃, releasing gases such as HCl. Therefore, stabilizers are added during the PVC plasticizing stage to repair defects in the PVC molecular chain and absorb the HCl produced during PVC dechlorination, thus inhibiting PVC decomposition at high temperatures. Traditionally, stearates such as lead stearate, barium stearate, and zinc stearate are used as PVC stabilizers. Lead stearate, in particular, was widely used in the past, but because it contains lead, it can pollute human health and the environment, and its use is now prohibited. Therefore, we use a barium-zinc composite stabilizer (barium stearate and zinc stearate) plus an organotin stabilizer to meet environmental protection requirements and improve the stability of PVC at high temperatures. The composite stabilizer is a combination of barium-zinc composite stabilizer and organotin stabilizer, including 3-7 parts by weight of barium-zinc composite stabilizer and 1-3 parts by weight of organotin stabilizer.

[0043] Due to the high viscosity and shear characteristics of PVC during processing, a corresponding lubricant, such as polyethylene wax, must be added along with the stabilizer. Polyethylene wax products can effectively improve the dynamic thermal stability and flowability of PVC during processing, increase the extrusion efficiency of PVC products, improve the surface gloss of the products, and effectively reduce the precipitation phenomenon during the processing of PVC products. The lubricant selected in this invention is polyethylene wax with a molecular weight of 3000-4000 g / mol; the activator is stearic acid in a mass fraction of 0.5-2 parts.

[0044] The second objective of this invention is to provide a method for preparing the low-hardness rubber-plastic alloy compound as described above, comprising the following steps:

[0045] (a) Plasticization: The formula amount of dispersed PVC resin, second plasticizer and composite stabilizer are added to the reaction vessel and stirred. After impregnation and swelling treatment for 6 to 10 hours, the mixture is heated to 100-120°C. Lubricant and activator are added and stirred for 40 to 60 minutes. Stirring is stopped and the mixture is heated to 150-160°C for high-temperature plasticization for 1 to 2 hours. After cooling and molding, the PVC plasticized premixed adhesive is obtained.

[0046] (b) Mixing: The internal mixer is heated to above 100°C. The weighed raw rubber, PVC plasticized premixed rubber, activator and antioxidant are added to the internal mixer for mixing. The speed of the internal mixer is 40-50 r / min, the mixing pressure is 5-7 KGf, and the mixing temperature is 135-145°C. After mixing for 3-5 minutes, the reinforcing agent and part of the first plasticizer are added. After mixing for 3-5 minutes, the remaining first plasticizer is added and the mixture is mixed for 4-6 minutes. The mixture is then cleaned by lifting the plug multiple times and discharged when the mixing temperature reaches 140±5°C to obtain the premixed rubber.

[0047] (c) Open milling: The premixed rubber is fed onto an open mill, cooled and filtered, then pressed into sheets, sheeted, cooled and sliced ​​by the open mill, and then tested for quality to obtain qualified rubber.

[0048] (d) Vulcanization: Weigh out qualified rubber compound, vulcanizing agent and accelerator for later use. Set the speed of the internal mixer to 20-25 r / min and the mixing pressure to 3-5 KGf. Add qualified rubber compound and stir for 50-70s. Then add vulcanizing agent and accelerator and mix for 50-60s. Discharge the material when the mixing temperature reaches 90-95℃. After passing through an open mill, the low hardness rubber-plastic alloy compound is obtained.

[0049] If PVC powder is directly mixed with NBR without undergoing plasticizing and swelling, the PVC powder will not disperse and will not be able to mix with NBR, severely affecting the physical and mechanical properties of the NBR-PVC rubber-plastic alloy. To achieve NBR-PVC blending, the first step in the process is to complete the plasticizing of the PVC. Traditional PVC plasticizing processes involve soaking for 2-3 hours, followed by heating and stirring, high-temperature plasticizing and cooling, and require steps such as soaking in containers, stirring in kneading machines, and plasticizing in high-temperature ovens. This method is complex, involves numerous handling steps, and uses a lot of equipment. Therefore, after extensive experimentation and demonstration, this invention integrates several plasticizing steps and simplifies them into a heatable and stirable reaction vessel, as described in step (a) above. The final result after plasticizing is a yellow, semi-transparent, flexible, and elastic block, namely, PVC plasticized premix.

[0050] The internal mixer used in this invention is a drop mixer. Since the formula of this invention is to produce a low-hardness NBR+PVC rubber-plastic alloy compound, in order to ensure the dispersion and uniformity of the compound and increase the friction and shear force between the rubber compound and the rotor chamber wall of the internal mixer, the mixing weight of this formula should be increased by 15-25% compared with the mixing weight of conventional formulas.

[0051] Furthermore, since the rubber compound of this invention is a low-hardness rubber-plastic alloy compound, it heats up more slowly than other ordinary rubber compounds. Therefore, the internal mixer needs to be preheated before mixing. Two methods can be used: the first is to raise the temperature of the mixing chamber of the internal mixer to above 100°C; the second is to first mix the same type of compound to raise the temperature of the mixing chamber wall and rotor of the internal mixer. The second method is more effective than the first because it relies on the mixing process of the internal mixer for heating, resulting in more uniform and stable temperature conduction. In step (b), to prevent decomposition of the NBR+PVC compound at high temperatures, the mixing temperature is set at 135–145°C. To prevent high-melting-point and high-softening-point additives such as antioxidant RD4010NA from failing to melt and causing potential problems such as bubbles during subsequent vulcanization, this invention uses powdered materials instead of granular materials.

[0052] Furthermore, in step (b), after three rounds of mixing and the addition of reinforcing agent and part of the first plasticizer, the mixing temperature and current increased, indicating that the raw rubber, carbon black, and the first plasticizer had already mixed together. However, the temperature and current should not rise too quickly or too high, because this state indicates that the mixed rubber has been completely mixed together. Adding more plasticizer later will result in no increase in current or temperature, causing the mixing time to be too long. At this point, the top plug is raised, and the remaining first plasticizer is added back into the internal mixer. Mixing for another 4-6 minutes, following the same process, the current and temperature rise slowly, indicating that the mixed rubber is slowly absorbing the first plasticizer.

[0053] Subsequently, the top bolt is raised every 3-5 minutes for cleaning, allowing the compound to be fully turned over for more uniform mixing. At this time, the current and temperature of the internal mixer are slowly rising. At around 135℃, the temperature and current change little. The temperature remains basically unchanged with a slight increase, but the current of the internal mixer shows a slow downward trend, indicating that the entire compound has been uniformly mixed and the rubber compound, carbon black plasticizer, etc. have been fully dissolved together. At this time, the material can be discharged. The discharge temperature is around 140℃, yielding the premixed rubber.

[0054] In step (c), the premixed rubber is fed onto a two-roll mill, and after simple refining and cooling, the extruded rubber is conveyed to a filter for filtration. The filter screen has a mesh size of 100 mesh. After filtration, the premixed rubber is passed through the two-roll mill again for several processes, including sheeting, sheeting, cooling, and slicing. After standing for 12 hours, the quality inspection department conducts relevant performance index tests on the batch of rubber (mainly Mooney strength, hardness, and tensile strength tests). If the tests are qualified, the rubber is qualified and can proceed to the final vulcanization process. Finally, the finished low-hardness rubber-plastic alloy compound is obtained.

[0055] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings.

[0056] Preparation Examples 1-5 provide a PVC plasticized premix, the content of each component of which is shown in Table 1.

[0057] Table 1. Components of the PVC plasticized premixed adhesives prepared in Examples 1-5 (unit: kg)

[0058]

[0059] Note: The PVC powder used in Preparation Example 4 was 100 parts of suspension PVC SG-5 type, and the plasticizer used in Preparation Example 5 was trioctyl trimellitate (TOTM); the PVC plasticized premixed rubbers from Preparation Examples 1-3 were used to prepare the low-hardness rubber-plastic alloy compound of Examples 1-3, the PVC plasticized premixed rubbers from Preparation Example 1 were used in Examples 4-7, and the PVC plasticized premixed rubbers from Preparation Examples 4-5 were used in Comparative Examples 1-2.

[0060] Examples 1-6 and Comparative Examples 1-2 each provide a low-hardness rubber-plastic alloy compound, the contents of each component of which are shown in Table 1.

[0061] Table 2. Composition of low-hardness rubber-plastic alloy compounds in Examples 1-6 and Comparative Examples 1-2 (unit: kg)

[0062]

[0063]

[0064] The performance of the low-hardness rubber-plastic alloy compounds in Examples 1-6 and Comparative Examples 1-2 was tested, and the results are shown in Table 3.

[0065] Table 3 Performance Test Table of Low Hardness Rubber-Plastic Alloy Compounds in Examples 1-6 and Comparative Examples 1-2

[0066]

[0067]

[0068] The composition includes: 50-90 parts raw rubber; 65-85 parts PVC plasticized premix; 6-14 parts activator; 3-11 parts antioxidant; 30-65 parts reinforcing agent; 50-80 parts primary plasticizer; 0.3-1 part vulcanizing agent; and 2-4.5 parts accelerator. In this invention, the raw rubber used is a combination of 40-60 parts by weight of NBR3370 and 10-30 parts by weight of NBR3350.

[0069] The activator comprises 4-7 parts by weight of zinc oxide, 1-4 parts by weight of activated magnesium oxide-150, and 1-3 parts by weight of stearic acid. The antioxidant is a combination of 0.5-2.5 parts by weight of antioxidant MB, 0.5-2.5 parts by weight of microcrystalline wax, 1-3 parts by weight of antioxidant RD powder, and 1-3 parts by weight of antioxidant 4010NA powder. The reinforcing agent is at least one or a combination of two selected from N774 carbon black and N85 silica powder; the reinforcing agent is a combination of 15-30 parts by weight of N774 carbon black and 15-35 parts by weight of N85 silica powder. Alternatively, the reinforcing agent may be a combination of 15-30 parts by weight of N774 carbon black and 15-35 parts by weight of N85 silica powder.

[0070] The PVC plasticized premixed adhesive includes the following components in parts by weight: 100 parts of dispersed PVC resin; 120-170 parts of secondary plasticizer; 4-10 parts of composite stabilizer; 1-3 parts of lubricant; and 0.5-2 parts of activator.

[0071] The composite stabilizer consists of 3 to 7 parts by weight of barium-zinc composite stabilizer and 1 to 3 parts by weight of organotin stabilizer (see Table 2 for details).

[0072] The test data in Table 3 for Examples 1-6 and Comparative Examples 1-2 show that: if a dispersion-type PVC resin is not selected, the PVC oil-extended premix made with conventional suspension PVC (SPVC) is inferior to that made with dispersion-type PVC (PPVC) in terms of tensile properties, compression set, aging resistance, and resilience. When using trioctyl trimellitate TOTM oil in excessive amounts (more than 80 parts), there is an oil seepage and spraying phenomenon. At the same time, the comprehensive properties of tensile and tear properties, compression set, and aging resistance are also inferior to those of the environmentally friendly plasticizer SP756. In addition, the mixing time is longer and the oil absorption rate is slower. Therefore, the proportions of this low-hardness rubber-plastic alloy compound are reasonable, all materials are indispensable, and the process cannot be simplified. The temperature of the internal mixer must be increased in advance. The entire impregnation, stirring, heating, and plasticizing process of the improved PPVC is carried out in a single reactor, saving a lot of handling, improving work efficiency, and reducing safety hazards. At the same time, the reactor is a jacketed heating and cooling type, and the stirring speed is frequency-adjustable, resulting in more uniform heating and better plasticizing effect. After the PPVC is plasticized, it is discharged into a rectangular mold tank of uniform size for cooling treatment. After cooling and standing for 8 hours, the solidified PPVC can be stacked together like rubber blocks, but each layer needs to be separated by a pad, since the plasticized PPVC is relatively soft and has a high oil content. This also facilitates transportation and handling, saving a lot of labor time, and the quality of plasticizing can be clearly distinguished.

[0073] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A low-hardness rubber-plastic alloy compound, characterized in that, It comprises the following components in parts by weight: 50-90 parts raw rubber; 65-85 parts of PVC plasticized premix; Surfactant 6-14 parts; Anti-aging agent: 3-11 parts; 30-65 parts of reinforcing agent; 50-80 parts of the first plasticizer; Vulcanizing agent 0.3~1 part; Accelerator 2-4.5 parts; The raw rubber is a combination of 40-60 parts by weight of NBR3370 and 10-30 parts by weight of NBR3350; The first plasticizer is a grafted ester plasticizer; The activator comprises 4-7 parts by weight of zinc oxide, 1-4 parts by weight of active magnesium oxide-150 and 1-3 parts by weight of stearic acid; The antioxidant is a combination of 0.5-2.5 parts by weight of antioxidant MB, 0.5-2.5 parts by weight of microcrystalline wax, 1-3 parts by weight of antioxidant RD powder and 1-3 parts by weight of antioxidant 4010NA powder; The reinforcing agent is a combination of 15-30 parts by weight of N774 carbon black and 15-35 parts by weight of N85 silica powder; The PVC plasticized premix comprises the following components in parts by weight: 100 parts of dispersion PVC resin; 120-170 parts of the second plasticizer; 4-10 parts of composite stabilizer; 1-3 parts lubricant; Activator 0.5-2 parts; The second plasticizer is selected from grafted ester plasticizer SP756.

2. The low-hardness rubber-plastic alloy compound according to claim 1, characterized in that, The first plasticizer is selected from environmentally friendly plasticizer SP756 or environmentally friendly plasticizer DX-360.

3. The low-hardness rubber-plastic alloy compound according to claim 1, characterized in that, The dispersed PVC resin is selected from PSM-31 dispersed PVC resin.

4. The low-hardness rubber-plastic alloy compound according to claim 1, characterized in that, The composite stabilizer is a combination of barium-zinc composite stabilizer and organotin stabilizer, including 3-7 parts by weight of barium-zinc composite stabilizer and 1-3 parts by weight of organotin stabilizer; the lubricant is polyethylene wax with a molecular weight of 3000-4000 g / mol; and the activator is stearic acid with a mass of 0.5-2 parts by weight.

5. A method for preparing a low-hardness rubber-plastic alloy compound as described in any one of claims 1-4, characterized in that, Includes the following steps: (a) Plasticization: The formula amount of dispersible PVC resin, second plasticizer and composite stabilizer are added to the reaction vessel and stirred. After impregnation and swelling treatment for 6 to 10 hours, the mixture is heated to 100-120°C. Then, lubricant and activator are added and stirred for 40 to 60 minutes. Stirring is stopped and the mixture is heated to 150-160°C for high-temperature plasticization for 1 to 2 hours. After cooling and molding, the PVC plasticized premixed adhesive is obtained. (b) Mixing: The internal mixer is heated to above 100°C. The weighed raw rubber, PVC plasticized premixed rubber, activator and antioxidant are added to the internal mixer for mixing. The speed of the internal mixer is 40~50 r / min, the mixing pressure is 5-7KGf, and the mixing temperature is 135~145°C. After mixing for 3~5 minutes, the reinforcing agent and part of the first plasticizer are added. After mixing for 3~5 minutes, the remaining first plasticizer is added and mixed for 4~6 minutes. The mixture is then cleaned by lifting the plug multiple times and discharged when the mixing temperature reaches 140±5°C to obtain the premixed rubber. (c) Open milling: The premixed rubber is fed onto an open mill, cooled and filtered, then pressed, sheeted, cooled and sliced ​​by the open mill, and then tested for quality to obtain qualified rubber. (d) Vulcanization: Weigh out qualified rubber compound, vulcanizing agent and accelerator for later use. Set the speed of the internal mixer to 20-25 r / min and the mixing pressure to 3-5 KGf. Add qualified rubber compound and stir for 50-70s. Then add vulcanizing agent and accelerator and mix for 50-60s. Discharge the material when the mixing temperature reaches 90-95℃. After passing through an open mill, the low hardness rubber-plastic alloy compound is obtained.

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