Multi-core channel hollow fiber membrane spinning spinneret

10. Collaboration details and technical outcomes:

In 2017, LSJ Filter Technology, a domestic specialist in membrane R&D, launched a project to develop high-performance multi-channel composite membranes to overcome the flux bottleneck and mass-transfer limitations of conventional single channel hollow fibers.  The customer planned to adopt Multi-core Spinning to build multiple uniformly distributed flow guiding channels within a single fiber, forming a "one shell, multiple cores" structure.  This architecture significantly increases specific surface area, lowers filtration resistance, and enhances hydraulic transport, making it suitable for high load, fouling prone environmental remediation and water purification scenarios.

Trustech's multi-core spinneret enables polymer dope to flow along the outer layer of the spinneret, while the bore fluid (pore-forming agent) is delivered through multiple precisely arranged micro-orifices inside, producing a special hollow fiber with several parallel internal channels within a single strand.  Trustech muti-core spineret key challenge was to ensure structural uniformity and performance consistency in the final fibers, which requires every bore fluid orifice inside the spinneret to be highly consistent in size, geometry, and internal flow path characteristics.  Even slight deviations can cause uneven bore fluid velocities, leading to irregular multi channel structures and adversely affecting separation accuracy and mechanical strength.

I. Multi-core spinneret breakthroughs: uniform bore fluid distribution and structural optimization

● Multi-core distribution design: Trustech multiple-core spinneret adopts an outer layer dope flow with multi-orifice bore fluid distribution, supporting 3-core, 4-core, 5-core, and 7-core configurations.  Using a conical guide plus cross flow splitter, it ensures identical bore orifice sizes and controls bore fluid distribution fluctuation to <3%, fundamentally guaranteeing fiber structural uniformity.

● Precision control of bore orifices: With ±0.002 mm aperture tolerance and 0.005 mm assembly concentricity, bore orifice diameter variation is held within 0.004 mm;  fiber wall thickness fluctuation is <5%, markedly improving flux consistency and separation efficiency.

● NIPS compatibility: Tailored stepped flow guiding structures tune the diffusion rates of bore fluid and polymer dope in the coagulation bath, avoiding locally dense or loose regions in the fiber and improving pore-distribution uniformity.

II. NIPS process optimization: phase-separation control and fiber performance enhancement

● Rapid phase-separation tuning: An anti-swelling structure in the multi-core spinneret regulates the exchange rate between the bore fluid and the coagulation bath (e.g., water/DMAC mixtures), forming a uniform composite of finger like and sponge like pores, increasing compressive strength and stabilizing flux (fluctuation <5%).

● Hydrophilicity optimization: Uniform bore fluid distribution yields consistent surface hydrophilicity;  water contact angle drops and pure water flux is high, and antifouling performance is significantly enhanced.

● Material reliability: The stainless steel spinneret features surface hardening for improved corrosion resistance, suitable for long-term use with NIPS solvents such as DMAC.

III. Flexible multi-core configurations and improved production efficiency

● Flexible core-count options: Trustech can customizable 3- to 7-core designs let customers choose core counts suited to specific water-treatment scenarios (e.g., municipal sewage, industrial wastewater), enabling rapid transition from lab scale to mass production.

● Production efficiency gains: The multi-core design increases the effective filtration area per unit spinning time by 3–5× versus traditional single-core spinnerets, boosting throughput and reducing production cost.

● Easy maintenance: Available in conventional constructions or with detachable bore fluid core modules;  a failed core can be replaced independently, simplifying maintenance and adapting to material formulation changes.