Terryl, a Next-Generation Fiber: Innovative, Cost-competitive, Biobased Polyamide for Textiles

Special to the Digest

Cathay Industrial Biotech. has recently introduced Terryl a new biobased polyamide. Many recent biobased chemicals projects have unfortunately encountered challenges competing with existing petrochemical routes from lower cost oil and gas. Commercialization of Terryl, a cost-competitive fiber with excellent textile performance and a significantly sizeable market, may bring back some investor confidence to the industry.

Since 2003, Cathay has commercially produced and distributed worldwide dodecanedioic acid (DC12) and currently supplies approximately one half of the world market for DC12 used in high performance polyamide 612 and chemical resistant polyester adhesives.   DC12 is produce by Cathay through the fermentation of paraffins or fatty acids. In addition to DC12, Cathay produces other long chain diacids from carbon 11 to carbon 18.  These diacids are used in many specialty applications.  These special diacids are not easily available from a chemical process.  In the past year DC12 and other diacids has been the target of other biotechnology companies hoping to duplicate Cathay’s success started over 10 years ago.   DC12 is a rare example of a bioprocess successfully replacing the chemical process for an industrial chemical.

Building of the DC12 success, Cathay Biotech has developed proprietary technology to commercially produce biobased pentamethylenediamine (DN5), a novel five carbon platform chemical. The DN5 has been polymerized with adipic acid to make Terryl, a biobased polyamide 56 alternative to PA6 and PA66 (collectively referred to as nylon for the rest of this article).

Wallace Carothers invented the world’s first commercial synthetic fiber, polyamide 66 (PA66), in the 1930s. The polyamide structure was a synthetic analogue for the natural amide bonds in silk protein, replacing amino acids in silk with hexamethylenediamine (HMDA) and adipic acid produced by butadiene from naptha cracking. During World War II, PA66 served as a substitute for silk in parachutes and ropes, and its material properties and comfortable feel made it a preferred choice for women’s stockings. Polyamide 6 (PA6) was commercialized shortly after PA66, with a current combined global market over 6 million tons per annum.

Industrial biotech companies have commercialize production of biobased polymers materials such as PLA, PHA, 1,3-PDO, BDO/PBS, and PTT. All of these examples are polyesters. The only commercial biobased polyamides have involved longer chain monomers for the specialty long chain polyamide markets.  PA11, PA610 and PA1010 are all successful biobased polyamides based on castor oil chemistry.  Terryl is the first example of a biobased polyamide produced from plant sugars to compete in the PA6 and PA66 market

Terryl Molecular Structure

PA66 is a high end textile fiber due to its many advantages such as strength, wear resistance, moisture absorbance, comfort, dyeability, and antistatic and flame retardant properties. Nevertheless, there is still room for improvement. For example, PA66 spinning costs are significant on top of the resin cost, mainly due to gel formation during spinning and qualification issues for dyed fiber.

Despite the fact that PA66 dyes more readily than polyester, variability in dyeing reduces qualification rate for the highest AA textile grade, which increases costs in the forms of product downgrade, additional processing, or wastage. This variability is due to the structure of PA66, where chains line up with all internal amide hydrogen and oxygen moieties involved in hydrogen bonding. Because the internal hydrogen bonding sites in PA66 are all occupied, dyeing relies on the terminal ends of the polymer chains. These ends represent a small portion of the polymer and can be either amines or acids, making it a significant challenge to control end ratios for consistent dyeability.

PA66 can theoretically be modified on a structural level to improve performance properties while maintaining the advantageous mechanical properties by partially offsetting a portion of the internal hydrogen bonding without completely disrupting the chain alignments. This can be done by changing the even carbon number diamine-even carbon number diacid nylon chemistry to an odd-even chemistry, e.g. replacing HMDA with DN5 (see figure 2). This would partially offset the internal hydrogen bonds, increasing the number of potential interaction sites for dye or water by over two orders of magnitude. This was predicted to improve dyeability, fluidity, moisture absorbance, wicking and by extension comfort while reducing gel formation and dyeing variability.

The mechanical advantages such as strength and wear resistance of PA66 were expected to be preserved. Based on the molecular structure, Terryl was expected to have superior performance properties and reduced fiber spinning costs compared to PA66.

Terryl Performance Properties

Test data and customer feedback based on Terryl produced from Cathay Biotech’s initial 1000 ton per annum continuous production line confirmed the theoretical predictions. Terryl and nylon have comparable physical properties such as strength, density, and wear resistance. Using existing PA6 equipment, Terryl was successfully spun at high speed into common specifications for tricot swimwear fabric (44dtex/12f FDY) and knitted pantyhose (33dtex/12f DTY). As expected, Terryl’s fluidity also made direct polymerization melt-spinning possible for significant fiber cost savings.

Compared with PA66, Terryl fabric had superior elastic recovery, moisture absorbance and wicking (∆MR), comfort, and dyeability.

Terryl carpet fibers dyed as deeply at room temperature as PA66 fiber at high temperature. Under the same dyeing conditions, Terryl carpet, hosiery and seamless underwear dyed deeper and more color fast than nylon. By saving energy, chemical dye, and off-grade wastage, using Terryl improves both environmental footprint and fiber cost.

Unexpectedly, Terryl also had significantly improved antistatic and flame retardant properties. In fact, Terryl was found to be self-extinguishing.

Nylon has been used in carpet for its superior dyeability and wear resistance. Polyester PTT from biobased 1,3-PDO has recently gained some traction amongst carpet manufacturers for its renewability. Terryl wear resistant and lightweight like nylon and contains higher renewable content than renewable PTT.  According to biobased carbon content as determined per ASTM D6866, Terryl is 45% biobased carbon, compared to 27% for PTT made from biobased 1,3-propanediol.

Terryl’s elasticity, moisture wicking, comfort, antistatic, dyeability and flame retardant properties give it a potential performance advantage in numerous textile applications including carpet, hosiery, seamless underwear, and performance sportswear.
Future Prospects

Based on these promising initial results, Cathay Biotech has begun expansion of Terryl production. Purely focused on Industrial Biotechnology with a successful commercialization track record and an international R&D team dedicated to the industry for over ten years, Cathay Biotech is the world’s first and to date only commercial scale producer of DN5. Terryl will be the first new broad-use polyamide since the invention of nylon 66 (PA66) and nylon 6 (PA6) in the 1930s.

To promote Terryl, the China Chemical Fiber Association formally announced the inauguration of the Biobased Polyamide Fiber Material Technology Innovation Industry Alliance in March 2014. Led by Cathay Biotech, the industry alliance includes academic and industry leaders and will focus on research and development of Terryl applications.

Competitively viable today, Cathay Biotech’s DN5 technology still has much room for future optimization and improvement, whereas the mature chemical process for HMDA is close to theoretical yield leaving little runway for future improvement. Biobased raw materials are also expected to be more sustainable both environmentally and economically than butadiene from petroleum in the long run. Large-scale commercialization of Terryl will hopefully highlight the importance of industrial biotechnology for the chemicals industry.