The traditional dry process for silicone leather involves dissolving silicone polymers into a slurry using a solvent, coating it onto release paper, drying, laminating, and then peeling it off to produce the leather material. Its core lies in utilizing the inherent properties of silicone materials and relying on mature synthetic leather production lines.
Process Details and Key Control Points
1. Raw Materials and Formulation: Silicone polymers: High-temperature vulcanized silicone rubber (HTV) or addition-type liquid silicone rubber (LSR) are typically used, providing excellent mechanical properties and temperature resistance. Additives: These include crosslinking agents (to complete curing), catalysts (such as platinum catalysts to accelerate the reaction), reinforcing fillers (such as fumed silica to improve strength), colorants (to impart color), and feel agents (to adjust surface texture). Solvents: Toluene, xylene, etc., are commonly used to adjust the slurry viscosity, facilitate coating, and completely evaporate during the drying stage.
2. Detailed Explanation of Core Processes
Coating: This is crucial in determining the surface finish of the leather (glossy, matte, textured). The texture of the release paper is directly transferred to the leather surface. The coating thickness needs precise control, typically between 0.1-0.3 mm.
Drying/Curing: This is usually completed in a three-stage oven:
* Stage 1: Lower temperature (e.g., 80-120℃) allows most of the solvent to evaporate slowly, preventing pinholes on the surface.
* Stage 2: Medium temperature (e.g., 130-160℃) further removes the solvent and initiates pre-crosslinking.
* Stage 3: High temperature (e.g., 170-200℃) allows the silicone to undergo a full crosslinking reaction (vulcanization), forming a stable three-dimensional network structure and achieving the final physical properties.
Laminating: A layer of silicone adhesive is applied to the cured silicone surface layer, and then bonded to the base fabric (knitted, woven, or non-woven fabric) under heated rollers. This step determines the overall peel strength and softness of the leather.
Curing and peeling: The composite material needs to be placed in a constant temperature room (such as 40-60℃) for 24-72 hours to allow the adhesive layer to fully cure and achieve the best adhesion before it can be smoothly peeled from the release paper.
3. Process Characteristics and Evaluation
Advantages: The process is mature and stable, and can be directly upgraded on existing PVC/PU dry-process production lines; the product has a soft and smooth feel, and the inherent high and low temperature resistance (-60℃ to above 200℃), aging resistance, and non-toxic and environmentally friendly properties of silicone are outstanding.
Core Challenges: The wear resistance, scratch resistance, and mechanical strength of traditional pure silicone coatings are generally inferior to those of top-grade PU leather, which is determined by its molecular structure. This is also the reason for the development of hybrid structure technologies such as LuxSense™ for improvement.
Traditional dry processing is the fundamental and mainstream method for producing silicone leather. It perfectly inherits the environmentally friendly and durable characteristics of silicone materials, but it also faces the challenge of balancing performance. Among them, the performance parameters of the main raw materials LSR/HTV are the foundation for the final performance improvement of silicone leather. In order to standardize the quality of silicone leather products, guide enterprise production, and guide the industry to focus on positive development, the group standard "Liquid Silicone Rubber for Silicone Synthetic Leather" was successfully established, organized by Beijing Guohua New Materials Technology Research Institute and led by Guangdong Dinglisen New Materials Co., Ltd.
