An invention patent CN122255141A — "A Method for Extracting Biomass Green Pigment from Silkworm Excrement and Its Application in Fabric Dyeing" — filed by Jiaxin Silk (002404) and its subsidiary Jiaxin Xingchang New Materials on March 25, 2026, are published on June 23, 2026. Essentially, it turns "silkworm excrement (silkworm feces)" — a waste product from sericulture — into a functional natural green/blue dye for silk, using a new process that bypasses two chronic problems of traditional natural dyes.
🐛 Raw Material: What Is Silkworm Excrement and Why Choose It?
Silkworm excrement is the feces excreted after silkworms eat mulberry leaves. It contains undigested chlorophyll, carotenoids, flavonoids, etc., with annual national output at the million-ton level. In the past, it was mainly used as organic fertilizer or low-value compost. Chlorophyll itself has a magnesium porphyrin structure, and among natural green sources, those with deep color and correct hue are rare; thus, silkworm excrement has long been a conventional agricultural byproduct raw material for chlorophyll extraction.
The traditional route uses acetone/ethanol/petroleum ether soaking and reflux to extract chlorophyll, followed by saponification into sodium chlorophyllin or copper substitution into copper chlorophyllin sodium salt (food-grade green). However, high-temperature reflux destroys the porphyrin ring, solvents are difficult to recover, catalysts are hard to separate, and copper substitution introduces copper ions, posing a risk regarding OEKO-TEX's limit on extractable copper.
♻️ Extraction Process: Nano Solid Acid + Low-Temperature Ultrasound + Anhydrous
The core innovation lies in the extraction section, with detailed parameters disclosed:
- Raw Material: Silkworm excrement (no need to pre-purify chlorophyll; direct whole-biomass extraction)
- Catalyst: Nano solid acid, concentration 1–3 g/L (possessing both Lewis acid sites and Brønsted acid sites simultaneously)
- Solid-to-Liquid Ratio: 1:4–12
- Ultrasound: Power 220–400 W, temperature 40–65°C (note: low temperature, unlike traditional 85°C reflux), duration 30–150 min
- Anhydrous System: Does not use water/ethanol large-bath reflux; instead, nano solid acid catalyzes in a non-aqueous medium
- Mechanism: Ultrasonic cavitation physically breaks down silkworm excrement cell walls + dual-acid-site synergy of solid acid swells cell wall polysaccharides/proteins; chlorophyll is released at low temperature, the porphyrin ring does not undergo demagnesiation deformation due to high heat; the solid acid exists as particles, recoverable by filtration, unlike hydrochloric/sulfuric acid which enters wastewater.
Comparison with the same team's 2026 Dyeing & Finishing Journal Issue No. 4 paper on ultrasound-assisted ethanol reflux (50°C ultrasound 20 min + 85°C reflux 4 h, yield 9.17 mg/g, post-saponification dyeing on silk K/S=5.77): This patent replaces "85°C reflux 4 h" with "ultrasound + solid acid within 65°C," significantly reducing energy consumption and solvent recovery pressure, and claims more intact molecular structure.
🥻 Dyeing Process: Direct Application on Silk, No Mandatory Copper Substitution
The extracted biomass green pigment (containing mixed components like chlorophyll a/b, pheophytin, pyropheophorbide, etc.) is directly applied to dye silk:
- Dyeing pH 3–8 (broad window, weak acid to near neutral)
- Temperature 60–80°C, duration 40–60 min
- Silk is a protein fiber. Near its isoelectric point (pH ≈ 4.8), the carboxyl/enol groups of chlorophyll derivatives form hydrogen bonds + van der Waals forces + partial coordination adsorption with fibroin amino acids (lysine, serine, tyrosine), requiring no heavy chromium mordant.
- The patent does not mandate conversion to copper sodium salt, meaning a "non-copper-substituted chlorophyll" route is possible — this is a key design choice for avoiding OEKO-TEX extractable copper risks.
🦠 Functional Properties: Antibacterial + UV Protection as Added Selling Points
The patent claims dyed silk exhibits:
- Soft shade, good color fastness (specific grades not given; based on the same team's literature, soaping/rubbing fastness for saponified chlorophyll-dyed silk is around Grade 4)
- Antibacterial: Inhibition rates against E. coli and S. aureus can reach 99.9% level per the same team's data; mechanism attributed to synergistic effects of chlorophyll derivatives + co-extracted flavonoids/polyphenols from silkworm excrement
- UV Protection: The chlorophyll porphyrin ring itself absorbs UV, improving UPF; pyropheophorbide on protein fibers shows better light resistance than pheophytin (confirmed by the Industrial Crops & Products study on silkworm excrement pyropheophorbide dyeing on silk/wool)
🍀 Why It "Bypasses Traditional Plant Dye Problems of Low Uptake and Poor Lightfastness"
Traditional plant dyes suffer two major drawbacks:
- Low uptake rate: Most plant polyphenols/flavonoids have weak affinity for protein/cotton fibers, often achieving K/S < 2; silkworm excrement chlorophyll, being a porphyrin macromolecule, has inherent affinity for silk (same team achieved K/S = 5.77, considered high for natural dyes).
- Poor lightfastness: Ordinary chlorophyll has lightfastness of Grade 2–3; this patent pushes it toward Grade 3–4 via low-temperature structural preservation + increased proportion of pyropheophorbide components + hydrogen bond fixation on silk matrix + integrated antibacterial/UV protection (similar mechanisms in literature using Sophora japonica one-bath or TiO₂ post-treatment can push to Grade 4).
However, it is not magic:
- Without copper substitution, lightfastness still cannot match synthetic reactive greens;
- Batch-to-batch variation in chlorophyll content of silkworm excrement creates color reproducibility challenges — needing a blending library to stabilize ;
- CN122255141A is currently only published and not yet granted. Jiaxin Xingchang also filed another patent (CN122608623A) in July 2026 on ionic liquid extraction of silkworm excrement chlorophyll, indicating they are hedging bets across multiple routes; stable commercial color cards still require pilot-scale validation.
One-sentence summary: The value of this patent lies not in the old knowledge that "chlorophyll can be extracted from silkworm excrement," but in using nano solid acid + low-temperature ultrasound + anhydrous conditions to make the extraction step lighter, preserve the porphyrin structure, then directly dye silk while obtaining antibacterial and UV-protective functions — offering the silk industry a "waste closed-loop + non-copper + functional green" optional solution. It addresses three chronic pain points of natural green dyes — pale color, poor lightfastness, dirty solvents — but does not replace synthetic dyes entirely. Instead, it targets the premium segment (high-end silk, homewear, maternal/infant silk products) willing to pay a premium for "bio-based + functionality."
