1. Technical Overview
Castor-Based Polyamide Resins are high-molecular-weight polymers synthesized through the polycondensation of dimer fatty acids (derived from castor oil) with diamines. Unlike petroleum-derived polyamides, these resins leverage the unique 18-carbon architecture of the ricinoleic chain. In industrial R&D, they are classified into Alcohol-Soluble and Co-Solvent grades. These resins are the industry standard for high-speed flexographic and gravure printing inks due to their exceptional adhesion to non-porous substrates (like PE, PP, and BOPP), high gloss, and superior resistance to water and chemicals.
2. Chemical Structure & Composition
The molecular structure of these polyamides is characterized by a repeating amide ($–CONH–$) linkage along a long-chain aliphatic backbone.
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Dimer Acid Base: Provides flexibility and excellent wetting properties.
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Amine Functionality: Determines the resin’s solubility and reactivity (reactive vs. non-reactive grades).
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Bio-Content: Depending on the formulation, these resins can achieve up to 100% renewable carbon content.
The long hydrocarbon segments between the amide groups provide these resins with a unique “soft-segment” character, offering far better flexibility than rigid Nylon 6 or Nylon 6,6.
3. Physical & Chemical Properties
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Appearance: Pale yellow to amber transparent pellets or granules.
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Softening Point: 105°C to 125°C (Customizable for heat-seal applications).
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Acid Value: <5.0 mg KOH/g.
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Amine Value: <5.0 mg KOH/g (for non-reactive ink grades).
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Solubility: Excellent in Ethanol/Isopropanol (Alcohol-soluble) or Hydrocarbon/Alcohol blends (Co-solvent).
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Viscosity: 2.0 to 6.0 Poise at 25°C (in 40% solution).
4. Reaction Chemistry
The performance of Castor-Based Polyamides is driven by their intermolecular interactions:
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Hydrogen Bonding: The amide groups form strong bonds with the surface of plastic films, providing unmatched adhesion.
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Thermoplasticity: These resins melt and solidify predictably, making them ideal for high-speed heat-sealing in packaging.
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Chemical Resistance: The fatty acid backbone provides a hydrophobic shield, making the cured resin resistant to fats, oils, and moisture.
5. When to Use vs. When NOT to Use
Use Castor-Based Polyamides when:
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Formulating flexographic and gravure inks for plastic film packaging (snacks, bread bags).
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Manufacturing high-performance hot-melt adhesives for the footwear or automotive industries.
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Producing “Overprint Varnishes” (OPV) that require high gloss and scuff resistance.
Do NOT use Castor-Based Polyamides when:
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The application requires high-clarity optical lenses (the resins are transparent but have a slight amber tint).
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The service temperature exceeds 150°C, as the resin may begin to soften or undergo oxidative darkening.
6. Compatibility Profile
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Nitrocellulose (NC): Excellent compatibility; often blended to improve the heat resistance and hardness of printing inks.
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Solvents: Highly compatible with Isopropyl Alcohol (IPA), n-Propanol, and Toluene.
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Plasticizers: Works synergistically with Dibutyl Sebacate (DBS) to increase film elongation.
7. Manufacturing Process (Product Focus)
Nova Industries utilizes a precision polymerization process:
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Dimerization: Castor fatty acids are dimerized to create a $C_{36}$ dicarboxylic acid.
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Polycondensation: The dimer acid is reacted with diamines (like EDA or HMDA) in a vacuum reactor.
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Molecular Weight Control: The reaction is timed to reach a specific viscosity and softening point.
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Pelletization: The molten resin is extruded through a die, water-cooled, and cut into uniform granules.
8. Technical Specifications Table
| Parameter | Alcohol Soluble Grade | Co-Solvent Grade |
| Appearance | Yellowish Granules | Yellowish Granules |
| Softening Point | 115°C – 125°C | 105°C – 115°C |
| Viscosity (40% in IPA) | 2.5 – 4.5 Poise | 3.5 – 5.5 Poise |
| Color (Gardner) | 7 Max | 8 Max |
| Acid Value | 5.0 Max | 5.0 Max |
| Amine Value | 5.0 Max | 5.0 Max |
9. Quality Grade Analysis
Nova Industries monitors Solubility Clarity and Gel Resistance. A high-quality polyamide must dissolve completely to form a crystal-clear solution. We ensure that our resins do not “gel” or thicken significantly during storage, which is a common failure point in lower-grade bio-polyamides.
10. Industry-Wise Application 1: Flexible Packaging
This is the primary application for castor-based polyamides. They act as the binder in inks for PE and PP films. Their ability to “bite” into the non-polar surface of plastic ensures that the printing does not peel or scratch off during the packaging process or in the consumer’s hands.
11. Industry-Wise Application 2: Hot-Melt Adhesives
Due to their low melt viscosity and high bond strength, these resins are used as adhesives in the assembly of filter elements, side-seam bonding in cans, and in the “lasting” process of shoe manufacturing.
12. Industry-Wise Application 3: Thixotropic Alkyds
Reactive grades of polyamide resin are used to modify alkyd resins, creating “Thixotropic Paints” that are creamy in the can but flow easily under a brush, significantly reducing drips and splatters for the DIY market.
13. Formulation Guide
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Ink Formulation: Typically 20–30% resin, 10–15% pigment, and 50–60% solvent.
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Dilution: Always add the solvent to the resin under high-speed agitation to prevent the formation of “clumps” that are difficult to dissolve later.
14. Sustainability Data
Castor-Based Polyamide Resins are a flagship “Green” product. By utilizing the waste or byproduct fatty acids of the castor industry, we provide a high-value engineering resin that reduces the packaging industry’s reliance on crude oil derivatives.
15. Packaging & Logistics (Technical)
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Standard: 25kg Multi-wall paper bags.
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Logistics: Non-hazardous. Protect from moisture and high-heat environments (to prevent granules from sticking together).
16. Storage Science
Must be stored in a cool, dry place. Polyamide resins are slightly hygroscopic and can absorb moisture, which may affect the drying time of the finished ink. Keep bags sealed until use.
17. Troubleshooting Guide
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Problem: Ink is not adhering to the film. Solution: Check the “Dyne level” of the film (Corona treatment) or increase the resin percentage in the ink formulation.
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Problem: Ink “scums” on the printing press. Solution: This may indicate poor resin solubility; ensure the alcohol-to-hydrocarbon solvent ratio is correct.
18. Regulatory Compliance
Our Polyamide Resins are REACH Compliant, TSCA listed, and meet the FDA requirements for indirect food contact in packaging materials (21 CFR 175.300).
19. Sample Validation Process
Verify the Softening Point and Viscosity. For ink manufacturers, a “Drawdown Test” on a target PE film followed by a “Tape Adhesion Test” is the most effective way to validate performance.
20. Contact CTA
For Technical Data Sheets (TDS), specific solubility profiles, or to request a sample for your next packaging ink project, please contact our technical export team: export@novaind.in
