1. Why is the pre-dispersion of rubber additives a development trend?
Rubber additives are chemicals that bring high added value to rubber products and can reduce costs. However, traditional rubber additives not only produce a large amount of dust and toxic and harmful gases during use, which bring great harm to the environment and the health of operators, but also have poor compatibility with rubber and are difficult to disperse uniformly, which affects its use effect.
Second, rubber additives pre-dispersed definition
Rubber additives pre-dispersed, also called rubber additives master batch. Pre-dispersed rubber additives are based on polymers (usually EPDM, SBR, NBR, EVA) as a carrier, rubber additives and softeners are added, and traditional rubber additives are pre-dispersed into the polymer through a special process to obtain a certain concentration Uniform pre-dispersion (extrusion granulation). Pre-dispersed rubber additives are upgraded products of traditional rubber additives. They have the advantages of no dust, easy to disperse, suitable for automatic weighing and automatic continuous low-temperature mixing, improved mixing efficiency, and good storage stability. They have received increasing attention in the industry. It is widely used in rubber products.
3. What are the advantages of pre-dispersing rubber additives?
1. Environmental protection. Avoid workshop dust pollution and protect workers' health.
2. Good dispersion and uniformity.
3. Good compatibility with rubber compounds, which can save mixing time.
4. It is convenient for weighing, suitable for automatic continuous operation, and convenient for transportation and storage.
5. There is no loss during processing, so that the quality between batches is stable.
6. Good development prospects. Pre-dispersed rubber additives masterbatches are mainly used in high-quality precision products in my country, such as high- and mid-range rubber shoes, automobile rubber products, and high-quality rubber pipe fittings. In the field of automotive applications, Chinese tire companies have successively introduced a number of radial tire production lines, and these production lines have begun to use pre-dispersed masterbatch products in order to increase the degree of automation. With the increase in the radialization rate of tires in my country, there is still a lot of room for growth in the pre-dispersed rubber masterbatch in the future. The advanced granulation processing of existing powder and liquid additives is an inevitable trend in the development of rubber additives.
Four. The main components of pre-dispersed rubber additives
1. Rubber additives: It is the main material of pre-dispersed rubber additives, its quality directly affects the quality of pre-dispersed rubber additives, generally 40%-80% content.
2. Carrier: The choice of carrier is very important for the production of pre-dispersed rubber additive masterbatch/master film. Pay attention to the solubility of the rubber additive in the carrier and the Compatibility of rubber.
3. Additives: Pre-dispersed rubber additives masterbatch/master film additives include plasticizers, lubricants, and anti-blocking agents. These additives can improve the rubber additives Dispersibility in rubber (carrier), storage stability, extrusion appearance quality and prevention of adhesion between pre-dispersed rubber additives.
5. Pre-dispersed production of rubber additives
1, production process< /p>
Add rubber material to the internal mixer for banburying at room temperature. The internal temperature of the internal mixer is 65-75℃. After a period of mixing, the base rubber is obtained. The accelerator and auxiliary materials are mixed for 5-10 minutes. After unloading, adjust the roller pitch of the mill to 2-2.5cm to open the material. After turning the rubber twice, it will be transferred to the filter for filtering. The internal temperature is 50-55℃, the pressure is 2600-2800Pa, and the 80-100 mesh filter screen; after filtering, the material is transferred to the pelletizer, the die temperature is maintained at 55-65℃, the knife speed is 120 rpm; the pelletizing The obtained product is cooled, and a batch is mixed, weighed, subpackaged, and packaged to obtain the finished product.
2, production status of various products< /span>
Sulfur is the most widely used rubber vulcanizing agent. In most cases, sulfur is added in the final process of mixing. Ordinary sulfur powder belongs to flammable and explosive hazardous chemicals. Its transportation and application have many inconveniences, and it is difficult to meet the dispersion speed and dispersion uniformity requirements in the rubber mixing process; insoluble sulfur powder is not flammable and explosive. Chemicals, and because of its increased solubility in rubber, the blooming phenomenon is reduced, but the insoluble sulfur powder is an inorganic powder material after all, and it has poor compatibility with the lipophilic rubber matrix, resulting in powder mixing during the mixing process Speed, dispersion speed and dispersion uniformity are not ideal, so sulfur masterbatch is currently the most promising variety of rubber additives masterbatch.
Zinc oxide is widely used as a vulcanization activator in the rubber industry, and nano-zinc oxide has attracted attention due to its small dosage. As an ultrafine inorganic polar powder, zinc oxide is more difficult to quickly and uniformly disperse in the lipophilic rubber matrix than sulfur, and its amount is usually 3 to 5 parts. Therefore, pre-dispersed zinc oxide masterbatch is also used in the rubber industry. One of the potential raw materials.
Rubber accelerators are mostly small-molecule organics. Compared with sulfur and zinc oxide, they have better compatibility with matrix rubber, but due to their small amount and The uniformity of dispersion in the rubber has a great influence on the performance of the product, and in most cases the accelerator is added together with sulfur on the open mill in the late mixing stage, so the preparation of pre-dispersed accelerator masterbatch is also very meaningful, especially in the tire industry The application prospects of masterbatch products such as commonly used accelerators TBBS, CBS and DM are very broad.
Compared with sulfur, zinc oxide, rubber accelerator, etc. in the vulcanization system, the application of antioxidant masterbatch is not so urgent. This is because the current mainstream varieties of anti-aging Products such as IPPD, 6PPD, RD, etc. are easier to mix and disperse in the matrix rubber, and the anti-aging agent can be added in the early stage of mixing to ensure sufficient dispersion time. Of course, for high-quality rubber products, pre-dispersed antioxidant masterbatch is still necessary. At present, in order to reduce dust pollution and improve measurement efficiency and accuracy, various additives manufacturers have adopted the technology of granulating powder into small rod-shaped particles. This type of product is bound to be welcomed by rubber products companies.
The compounding agent suitable for the production of rubber auxiliary masterbatch is mainly the compounding agent of the vulcanization system that has a small amount and has a greater impact on the performance of rubber products. Of course, for antioxidants and some special Functional additives, if the uniformity of the dispersion of these additives in the matrix rubber is critical to the product performance, it is necessary to prepare the additives masterbatch. At present, domestic manufacturers of pre-dispersed rubber additives are springing up like bamboo shoots after a rain. Among them, companies such as Ningbo Lihua and Zhuhai Kemao have gradually gained scale, complete varieties, and better production time experience and quality control.
Six. Main testing indicators
1. Appearance. The appearance requirements of the finished product are not significantly different from the standard samples. The particle length is between 4 and 8 mm. There are no triple particles, basically no fragments, no foreign matter and impurities, and no undispersed aggregates and colloids.
2. Sulfur content. The sulfur content of pre-dispersed rubber additives mainly characterizes the content of active components in the product. This index only needs to be determined for some products.
3. Density. The density of pre-dispersed rubber additives has a certain relationship with the properties of raw materials, the dispersion during processing and the content of anti-blocking agent.
4. Mooney viscosity. The Mooney viscosity of pre-dispersed rubber additives characterizes its storage, transportation and processing properties.
5. Dispersibility. The dispersibility of rubber additives in the pre-dispersed rubber additives directly affects the stability of rubber products, and its agglomeration has a greater impact on the energy production, so it is necessary to investigate the dispersibility of the pre-dispersed rubber additives.