Microencapsulation

As a long-term specialist in the field of microencapsulation for the production of carbonless papers, Koehler invests a great deal of effort into the advancement of this technology.

Since we started producing our own microcapsules in 1974, we have continuously optimized capsule production and the systems required for this purpose. Our own patents in the field of microencapsulation and more than 40 years of experience have made us Europe’s leading manufacturer of carbonless papers. With this knowledge of process development and large-scale production, we concentrate on what is feasible in order to systematically implement customized solutions.

microcapsule

In the microencapsulation process, microscopical small oil droplets or solid particles are evenly enveloped by a polymer shell. The encapsulated content is dispensed by mechanical destruction of the capsule wall or other release mechanisms, depending on the application.

 

Applications of Microencapsulation

Although it is not often visible to the naked eye, microcapsule technology can be found in a wide range of familiar, everyday products. This versatile technology offers solutions for many innovative products. The enormous spectrum of applications can be found in markets ranging from Paper industry to Household products. Microencapsulated actives can be dosed sparingly improving both profitability and sustainability of many products. Examples how microencapsulation adds functionality to active components are given below.

Microcapsules for Paper, packaging, print

Paper, packaging, print

In addition to the use of microcapsules in the paper industry, innovative marketing concepts rely on microencapsulated fragrances for targeted customer acquisition.

• Carbonless paper
• Scented coatings
• Scratch & Sniff advertisements in magazines
• Liquid crystals – colour changing labels

Microencapsulation for Household products

Household products

Although we may not be directly aware of it, microcapsules have long been a part of our everyday lives:

Encapsulated fragrance oils for fabric softeners
• Scented additives for laundry detergents
• Cleaning agents

Microcapsules for Phase Change Materials (PCM)

Phase Change Materials (PCM)

Phase Change Materials are substances that absorb and release thermal energy without any release of the core material into the environment. This effect is used to balance heat accumulation in different applications such as:

• Textiles
• Mattresses
• Building materials

Microcapsules for Chemical products

Chemical products

The list of products in this field is more or less endless, so here are just a few applications:

• Single part adhesives eg. for thread locking
• Slow release of biocides
• Lubricants for antifriction coating
• Self-healing coatings
• Fracking fluid

Microcapsules for Personal Care

Personal Care

There are a wide range of applications for encapsulated skin care active ingredients and fragrances in this field – here are just a few examples:

• Deodorants
• Bath and shower gel
• Shampoo
• Face cream

 

Technology

Microencapsulation is a generic term for various techniques which envelope substances in the micrometer range with a shell. The objective is to selectively isolate these chemical agents, often referred to as active ingredients, and to release them at a certain point in time. These core substances can be liquids, solids, or gases. Individual particles above 100 µm, can still be coated with different spray technologies whereas liquids are encapsulated using dripping processes. The formation of microcapsules with a diameter of less than 100 µm, is only possible by depositing so called “wall formers” at a phase interface. In the industrially used interfacial polymerization process, an emulsion or suspension of the hydrophobic core material is prepared in water. The monomers dissolved in the outer phase deposit in a layer around the emulsion droplets or the dispersed solid particles and polymerize forming a compact shell. Individual properties of the microcapsules are determined by the specific characteristic of the wall material and the degree of cross-linking.

The chemically and mechanically stable capsules are based on aminoplast resins. In addition to the high impermeability of the capsule shell, the wall is highly resistant to reactive chemicals. By applying pressure and shear force, the core liquid can be selectively released again. Other options are capsules made of acrylic and polyurethane monomers, biopolymer wall formers as gelatine or other proteins and inorganic sol gel systems.                                      

Structure of microcapsules

Structure of microcapsules
Performance of the capusule Shell and core material
Performance of the capusule Shell and core material
 
 
 

General scheme for microencapsulation via in-situ polymerization

General scheme for microencapsulation via in-situ polymerization

1. Emulsifying the core material in the aqueous Phase:

  • Water
  • Hydrophobic core material
  • Protective colloid
General scheme for microencapsulation via in-situ polymerization

2. Addition of the wall former

  • Condensation and Phase Separation through pH reduction
General scheme for microencapsulation via in-situ polymerization

3. Wall formation


  • Encapsulating the Emulsion droplets with wall material
General scheme for microencapsulation via in-situ polymerization

4. Cross-linking the wall material

  • Addition of melamine
  • Hardening through temperature increase


 

Functionality of Microencapsulation

Release profiles of diverse capsules

Functionality of microcapsules - Release profiles of capsules
Slow release

Slow release

The properties of a microcapsule’s polymer shell are defined by its thickness and degree of cross-linking. This is used to manipulate the diffusion-controlled release of the core material. In the agrochemical sector, long-term fertilizers benefit from the depot effect of the slow release of nutrients. The continuous release over time of microencapsulated biocides increase the efficiency of the agents in antifouling coatings.

 
Targeted release

Triggered release

Deliberately releasing a substance at a defined point in time in the application is a very complex task. Pre-applied thread-locking systems are an example of this principle in automotive industry. The adhesive is applied to the screw together with the microencapsulated initiator. Upon thightening the screw, the capsules are destroyed and the screw is glued and simultaneously sealed to the thread.
Depending on the capsule structure, various opening mechanisms (triggers) such as temperature, UV light, enzymatic activity, or a change in pH value are conceivable. The specific adaptation of wall material and opening mechanism requires a individual solution that can be realized within customized development project.


 
Release on demand

Release on demand

Pressure and friction are the most common opening mechanisms used in the industrial application of microcapsules.

Fabric softener with a long-lasting fresh scent is now considered state-of-the-art in the detergent and homecare industry. Microcapsules with a diameter of 20 µm to 30 µm, filled with perfume oil, are evenly distributed on the laundry and adhere to the fabric. When wearing the clothes, the capsules burst due to friction and immediately release the fragrance. With every further movement, this process repeats itself and produces a long-lasting fresh scent.

The use of microcapsules is an elegant solution for anti-friction coatings. The release of encapsulated oils on demand ensures efficient lubrication and thus a longer useful life of the dry-to-touch lubricant solutions.
Self-healing coatings based on microcapsule systems can be used for applications in paints. Every time a layer of coating is damaged, reactive monomers are released from the inside of the capsule and reseal the substrate autonomously. Together with corrosion inhibitors and indicators, it is possible to increase corrosion protection and significantly extend the life span of technical equipment.

Microencapsulation turns conventional paints into smart coatings.

 
Permanent capsules

Permanent core / Shell capsules

PCMs (phase change materials) store the latent heat that causes a change of phase from solid to liquid. When the environment cools down, the stored heat energy is released again. The microcapsules’ permanent shell, optimized specifically for this purpose, must be impermeable but still flexible to guarantee that the encapsulated wax can permanently change phase and that the capsule functions properly.

 

Contact

Papierfabrik August Koehler SE
Business Unit
Koehler Innovative Solutions
Hauptstrasse 2
77704 Oberkirch
Germany

+49 7802 81-0

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