Shoe coating dispersant: the invisible revolution from the microscopic world to the technology under your feet
In the precision process of shoe manufacturing, there is a substance that is not directly visible, but it has a profound
impact on the appearance, performance and environmental properties of shoes-it is the shoe coating dispersant.
This special additive becomes a bridge between material science and industrial application by regulating the
microscopic distribution state of pigments and fillers. This article will take you to explore how dispersants can reshape
the infinite possibilities of shoe coatings with precise molecular operations.
1. Dispersant: the "molecular commander" of the coating system
The essence of the dispersant is a surfactant with an amphiphilic structure, one end of the molecule is hydrophilic
(or lipophilic) and the other end is pigment-philic. This unique structure gives it three core functions:
Steric hindrance effect: polymer dispersants (molecular weight 3000-40000) form a thick adsorption layer on the surface of
the pigment, preventing particles from colliding and agglomerating through steric hindrance, ensuring that the pigment is
evenly distributed at the nanometer particle size.
Electrostatic repulsion mechanism:
Anionic dispersants make pigment particles negatively charged, forming a diffuse double layer. When the absolute value of the
Zeta potential exceeds ±30mV, the electrostatic repulsion between the pigment particles is sufficient to overcome the van der Waals
attraction and achieve long-term stable dispersion.
Wetting improvement:
Non-ionic dispersants can reduce the surface tension of the pigment. For example, in water-based leather coatings, specific
dispersants can shorten the wetting time by 40%, ensuring that the pigment quickly penetrates the fiber gap.
2. Multi-scenario application map in the field of footwear
(I) Sports shoes: a technological barrier against extreme deformation
Sports equipment such as basketball shoes and running shoes need to withstand tens of thousands of bends, and their coating
dispersants must meet strict requirements:
High shear stability: During the grinding stage, polyurethane dispersants (HLB value 12-18) can control the carbon black particle
size D50 to 1.2μm, reducing the grinding time by 40% compared to traditional products, significantly improving production
efficiency.
Dynamic anti-sedimentation:
Verified by a 50℃ centrifugal test, polymer dispersants can reduce the sedimentation rate of pigments to less than 5% within 30
days, ensuring that the shoe side LOGO still maintains a clear outline after long-term use.
Elastic compatibility:
Silicate dispersants form a flexible adsorption layer in the TPU substrate, so that the coating will not crack after bending 100,000
times, which is perfectly adapted to the high elasticity requirements of sports shoes.
(II) Leather shoes: Micro-control of luxurious texture
High-end leather shoe coatings have strict requirements on gloss, feel and environmental protection:
Precise color control: Anionic dispersants achieve color paste fineness ≤15μm through electrostatic repulsion, ensuring that the
gloss of black patent leather reaches more than 85%, presenting a mirror-like high-end texture.
Penetration enhancement technology:
Coupling agent dispersants can increase the penetration depth of pigments in leather fibers. Experimental data show that specific
dispersants can improve the color fastness of aniline dyes to level 4-5 (80℃ water washing test), effectively solving the problem of
easy fading in traditional processes.
Low VOC solution: The biodegradability rate of water-based dispersants exceeds 60%, meeting the requirements of the EU REACH
regulations on footwear chemicals and promoting the transformation of leather shoe manufacturing to green and environmental
protection.
(III) Outdoor shoes: Guardians of extreme environments
Outdoor equipment such as mountaineering shoes and snow boots need to cope with challenges such as ultraviolet rays and low
temperatures:
Anti-ultraviolet design: Fluorine-containing polymer dispersants form a dense protective film in the PU coating, which improves the
color fastness to level 7-8 (1000 hours of xenon lamp aging), and can maintain bright colors even in strong ultraviolet environments
on the plateau.
Adaptation for low-temperature construction: Solvent-based dispersants adjust the solvent ratio to keep the coating fluid at -5°C,
avoiding coating defects caused by excessive viscosity during construction in northern winter.
Anti-mildew and antibacterial function: Silver-loaded nano-dispersants can inhibit the growth of mold. Laboratory tests show that
the antibacterial rate of the inner coating of shoes with the dispersant added reaches 99.9% (JIS Z 2801 standard), providing health
protection for outdoor enthusiasts.
3. Technological innovation and industry trends
Water-based revolution: The 190A superdispersant developed by domestic enterprises has achieved a 30% reduction in the viscosity
of water-based color pastes, and its haze value in styrene-acrylic emulsion systems is better than that of imported competitors,
which has driven the VOC emissions of sports shoe coatings to below 50g/L and accelerated the green transformation of the industry.
Intelligent dispersion:
Dynamic dispersion test technology improves dispersion efficiency by 25% through real-time monitoring of the grinding power
curve, reducing energy consumption while ensuring uniformity of particle size distribution.
Composite functional integration: Amphoteric dispersants have both wetting and rheological control functions, allowing
single-component coatings to have both high gloss (≥90%) and anti-sagging performance (200μm wet film does not flow),
simplifying the construction process.
4. Core considerations for selecting dispersants
When selecting dispersants for shoe coatings, the following dimensions need to be comprehensively evaluated:
Dispersion efficiency: The grinding time reduction rate and particle size distribution (D90) are key indicators. For example, a certain
dispersant can reduce the grinding time of sports shoe white paint from 4 hours to 2.5 hours, significantly improving production capacity.
System compatibility:
It is necessary to ensure the compatibility of the dispersant with the resin (such as polyurethane, acrylic acid), as well as the stability
under different pH environments, to avoid defects such as wrinkling in the leather shoe coating.
Long-term stability:
Through the accelerated test of 30 days of storage at 50°C without stratification, the reliability of the dispersant in the winter transportation
of outdoor shoe coatings is verified.
Environmental compliance: Pay attention to the APEO/VOC content and biodegradability, and ensure that the children's shoe coating
passes international certifications such as Oeko-Tex® Standard 100 to meet consumers' high requirements for safety.
Economic efficiency:
Under the premise of ensuring performance, optimize the addition amount (usually 0.2%-0.8%) and reduce waste. A case shows that
10,000 liters of paint reduce pigment waste by 1.3 tons per year, significantly reducing production costs.
