The sponge midsole produced with rubber as the main material has good elasticity and flexibility and is not easy to be deformed. On the sole (especially for sports shoes), there are more elastic shock-absorbing layers to protect the foot from injury. Under normal circumstances, the sponge in the bottom of the physical and mechanical properties of rubber raw material requirements are not high, and more use of low-cost tire reclaimed rubber or rubber shoes reclaimed rubber, including tire reclaimed rubber can be regarded as the production of rubber sponge in the bottom of the main force, different grades Sponge midsoles have different requirements for tire reclaimed rubber, and tire reclaimers need to pay attention to many issues when designing a sponge midsole.
1. Pay attention to the relationship between the cost and the rubber content in the sponge bottom
When using tire reclaimed rubber to produce sponge midsole, the required tensile strength and softness of the tire reclaimed rubber is high, and the amount of rubber contained in the formula needs to be controlled between 5% and 30%. Some low-grade rubber sponges can be used in midsoles. A large number of tire reclaimed rubbers can also be used in combination with lower-priced rubber reclaimed rubber. The amount of rubber contained in the sponge's midsole formula is controlled between 5% and 10%, which greatly reduces the cost of raw materials. Some sponges used in high-end sports shoes are used. The midsole is more demanding on the amount of rubber contained in the formula. Rubber product manufacturers can choose tire tread reclaimed rubber with high gel content and good elasticity as the main raw material, and use a small amount of natural rubber, styrene-butadiene rubber or butadiene rubber in the formula. , The glue content of the entire formula is increased to about 30%, and the quality of sponge rubber midsole is maximized under the condition that the cost permits.
2. Pay attention to the effect of curing agents, accelerants, reinforcing agents, softeners and other compounding agents on the foaming conditions in the reclaimed rubber sponge midsole formula
In the sponge midsole formula, when the tire reclaimed rubber is used as the main raw material to design the formula, it is necessary to consider the cooperation between various compounding agents, mainly in the following points:
1 The vulcanization velocity of the sponge's midsole needs to be consistent with the foaming speed of the rubber. If the vulcanization rate is too fast, it will cause the rubber to be shaped early and the foaming agent can not fully exert its effect. The sponge's midsole has a small hole diameter and the vulcanization speed is too slow and will lead to the sponge. Bottom cells are too large. Therefore, it is necessary to choose accelerators with long vulcanization induction time and even if they reach positive vulcanization, such as accelerators M, DM, D or M, DM, and TMTD. When the clay is used in a large amount in the midsole of reclaimed rubber sponges It is also necessary to increase the amount of accelerator, so it is necessary to reasonably control the amount of the accelerator and the amount of accelerator used in the formula.
2 The softener can improve the elasticity of the sponge midsole and promote the foaming of the tire reclaimed rubber compound. The liquid gumarone, industrial grease, engine oil, petrolatum and black grease are commonly used softeners. Take black ointment as an example. Although the increase can improve the processing and elasticity of the sponge's midsole, too much of it will cause the strength and anti-aging performance of the sponge's midsole to decrease, and the sponge's midsole will become sticky. Therefore, it is necessary to reasonably control the dosage; Aging of the sponge in the bottom, you must add anti-aging agents in the formula such as antioxidant A, antioxidant RD and so on.
3 foaming system in the production of foam in the end is particularly important, foaming agent can be divided in organic foaming agent and inorganic foaming agent, organic foaming agent in the foaming out of nitrogen, resulting in high elasticity, compression deformation, Anti-aging closed-cell structure. Commonly used foaming agents are foaming agent H, baking soda, and alum. Among them, alum is easy to agglomerate during use and is not easily crushed, which may affect the foaming quality of sponge midsole to a certain extent. Therefore, more manufacturers are currently using it. Ammonium bicarbonate and urea are used as blowing agents.
4 The most important thing in the sponge's midsole is foaming. The choice of vulcanizing agent and accelerator will affect the foaming condition of the midsole of the reclaimed rubber sponge. The type of filler also affects the “foaming” of the tire; in the sponge foaming midsole In production, most rubber manufacturers will choose calcium carbonate as a filler, but from the perspective of performance, clay is more friendly to the foaming of sponges and the improvement of softness of plastics. What should be the choice?
There are many issues to be aware of when using tire reclaimed rubber to produce sponge midsole. Do you have any good ideas for this? Welcome to discuss.