Microencapsulation

As a long-term specialist in the field of microencapsulation for the production of carbonless papers, Koehler is also familiar with adapting this technology for other industries, especially for the production of fragrance capsules.

Since we started producing our own microcapsules in 1974, the technology has been regularly developed and our own production facilities have been adapted accordingly. 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 also support external customers as a contract manufacturer.

microcapsule

In the microencapsulation process, microscopical small oil droplets or solid particles are evenly enveloped by a polymer shell. The encapsulated content is usually released again in a targeted manner by mechanical destruction of the capsule wall.

 

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 Home Care 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 in scented coatings for targeted customer acquisition.

Microcapsules for Phase Change Materials (PCM)

Other industrial applications

Include phase change materials (latent heat storage) e.g. for construction chemicals, 2K adhesives for threadlockers and encapsulation of healing agents for self-healing paints.

Microencapsulation for Household products

Home Care Products

Microcapsules have long been part of everyday life without us being immediately aware of it, among other things as fragrance capsules in fabric softeners and detergents.

 

Technology

Microencapsulation is a generic term for various techniques which envelope substances in the micrometer range with a shell. The aim is often to protect active ingredients and release them in a targeted manner at a specific point in the application.

The chemically and mechanically stable capsules are based on aminoplast resins, for example. In addition to the high impermeability of the capsule shell, the wall is highly resistant to reactive chemicals. The core liquid can be released again selectively by pressure and shear. Microcapsules can also be made from biopolymers, which ensure biodegradability after application.                                 

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 cross-linker for curing
 

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.

 
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

Koehler Paper SE
Business Unit
Koehler Innovative Solutions
Hauptstrasse 2
77704 Oberkirch
Germany

+49 7802 81-0

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