Vinyl Chloride Copolymers for food safe tin can coatings

Vinyl chloride resins, specifically polyvinyl chloride (PVC) resins, are used in tin can coatings due to their dense, impermeable film and excellent resistance to moisture, salt spray, acids, and alkalis. These coatings help protect the integrity of the can and prevent interactions between the metal and the food or beverage inside.

PVC-based coatings are commonly applied as organic solvent coatings, where PVC dispersion resin is mixed with plasticizers and diluted with organic solvents to create a high-solid-content coating. This type of coating is particularly useful for easy-open lids and two-piece food cans, as it maintains its protective properties even after multiple stretching and pressing operations during manufacturing.

Additionally, PVC coatings are sometimes used as adhesives in specialized applications, such as internal adhesives for crown caps and twist-off caps, as well as touch-up coatings for three-piece can weld seams. Their ability to withstand high-temperature sterilization, acid exposure, and sulfur resistance makes them a reliable choice for food packaging.

Functional groups to improve adhesion to metals

Some companies have developed modified vinyl chloride (VC) polymers with functional groups to enhance adhesion to metals. These modifications typically involve grafting functional groups onto polyvinyl chloride (PVC) chains to improve bonding with metal surfaces.

Some approaches include:

• Amino-functionalized PVC: By introducing benzylamine or diethylenetriamine groups, PVC can achieve better adhesion and even be used for metal ion adsorption.
• Metal-based additives: Certain metal stabilizers and synergists incorporated into PVC formulations can improve adhesion and durability.
• Silane-modified PVC plastisols: Adding aminofunctional organotrialkoxysilanes to PVC plastisols enhances adhesion to glass, metal, and fabrics.

VC copolymers available with hydroxyl (-OH) groups?

Yes! Vinyl chloride (VC) copolymers with groups are available and used in various applications, including coatings and adhesives. These copolymers are typically modified with vinyl acetate, hydroxy acrylate, or vinyl alcohol to introduce hydroxyl functionality, improving adhesion and compatibility with other materials.

Some examples include:

• Vinyl chloride-vinyl acetate copolymers with hydroxyl content for enhanced bonding.
• Vinyl chloride-vinyl alcohol copolymers, synthesized for specialized applications.
• Vinyl chloride-hydroxy acrylate copolymers, offering improved solubility and adhesion.

These modifications make VC copolymers more versatile, particularly in coatings for metals, where hydroxyl groups enhance adhesion and durability.

Common industrial applications of these copolymers

Vinyl chloride copolymers have a wide range of industrial applications, thanks to their versatility, adhesion properties, and chemical resistance. Some common uses include:

• Surface coatings: These copolymers are widely used in protective coatings for metals, plastics, and wood, offering chemical resistance, flexibility, and durability.
• Packaging films: They are used in high-performance films and foils for labels, graphic applications, and food packaging, providing moisture and oxygen barrier properties.
• Textile coatings: Certain formulations are applied to technical textiles and home furnishings to enhance flame resistance, abrasion resistance, and durability.
• Industrial adhesives: Their excellent adhesion to metals and plastics makes them ideal for heat-sealable coatings, printing inks, and industrial adhesives.
• Corrosion protection: Some copolymers, such as polyvinylidene chloride (PVDC) emulsions, are used in anti-corrosion coatings for metal, offering superior moisture barrier properties.

Commercially available VC copolymers

Companies offer a range of vinyl chloride (VC) copolymers, which includes co- and terpolymers designed for industrial coatings, printing inks, and heat-sealable coatings. Some key products include:

• VC Emulsion polymerized grades : Produced via emulsion polymerization, these resins offer excellent pigment wetting and are ideal for pigmented coatings.
• VC suspension polymerized grades : Manufactured through suspension polymerization, these resins are best suited for transparent coatings.
• VC carboxyl group grades: Contain carboxyl functional groups, improving adhesion and crosslinking properties.
• Other VC grades: Like those that feature hydroxyl functional groups, enhancing adhesion and compatibility with other resins.

These copolymers are widely used in heat-sealable coatings, printing inks, and industrial coatings, offering strong adhesion to metals and plastics, chemical resistance, and mechanical durability.

VC Emulsion polymerized grades

VC Emulsion polymerized grades are vinyl chloride copolymers produced via emulsion polymerization, making them particularly well-suited for pigmented coatings due to their excellent pigment wetting properties. These resins are widely used in printing inks, industrial coatings, and heat-sealable lacquers.

Key Features:

• Superior adhesion to metals, plastics, and porous substrates.
• High toughness and flexibility, ensuring durability.
• Excellent chemical and water resistance, making them ideal for protective coatings.
• Outstanding pigment wetting, improving color dispersion in inks and coatings.
• Flame retardant properties, adding safety benefits.

Common Applications:

• Heat-sealable coatings for aluminum foil.
• Printing inks for various substrates.
• Industrial coatings for corrosion protection.
• Adhesives for specialized bonding applications.