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Microencapsulation

Competence in Microencapsulation. Since 1962.

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. 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.

Microencapsulation

Microencapsulation

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.

Contract Manufacturing

Contract Manufacturing

If external customers are interested, Koehler is available as a contact for contract manufacturing or technology licensing.

 After clarification of the fundamental applicability of the technologies available at Koehler to the customer's application and an economic evaluation of the application potential, the following steps typically follow:

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.
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.
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.
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.
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Technology OF MICROENCAPSULATION

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

Emulsifying the core material in the aqueous Phase

1. Emulsifying the core material in the aqueous Phase

  • Water
  • Hydrophobic core material
  • Protective colloid
Addition of the wall former

2. Addition of the wall former

  • Condensation and Phase Separation through pH reduction
Wall formation

3. Wall formation

  • Encapsulating the Emulsion droplets with wall material
Cross-linking the wall material

4. Cross-linking the wall material

  • Addition of cross-linker for curing

Functionality of Microencapsulation

Release profiles of diverse capsules

Release profiles of diverse 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.
Triggered 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 core / Shell 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.

Product development

The first step in the development of a suitable microcapsule is the exact description of the applications and the resulting requirements with regard to the capsule properties. The release, size of the capsule, and specific properties of the core substance are only a few parameters that affect both the formulation and process development.

Laboratory scale

Laboratory scale

The suitability of the chemical agent for microencapsulation is assessed in initial feasibility tests. Subsequently the active substance is encapsulated in laboratory scale providing samples for application testing. If an existing capsule system can be used, the compatibility of the core and wall materials is scrutinized, which is generally a productive project. More development work is necessary if the goal is a customized capsule with new functionalities and wall materials. This requires however, a partnership agreement with defined development stages and milestones.

Samples for application tests are produced at a laboratory scale of 0.5 kg to 1 kg.

Pilot scale and scale-up

Pilot scale and scale-up

Writing the formulas and process scale-up are followed by pilot production batches in our pilot plant. The long experience of our employees in performing laboratory and pilot tests ensures fast process adjustments enabling an easier transfer to the next larger installations. In this test phase many options for possible process optimization are automatically incorporated. The sample quantities produced in the pilot plant range from 100 kg to 300 kg per batch in order to be used for larger applications or market trials.

Production

Koehler operates production facilities of various sizes for manufacturing microcapsules. We produce mid-sized production quantities in batch sizes of 1.8 to 3.6 tons and an annual output of approximately 2,000 tons. Up to 13,500 tons of capsule dispersion can be produced for large-volume products. This makes Koehler one of the world’s largest suppliers in the encapsulation business. These capacities allow us to react with flexibility to our customers’ requests.

Quality control

Qualitätssicherung

Delivering products on time and the consistent quality of the microcapsules are our top priority. At our quality assurance laboratory, we conduct a wide array of customized analyses.

The standard physical specification parameters defined include total solids content, viscosity and capsule size distribution. The latter is determined via laser diffraction. The capsules can also be evaluated visually on scanning-electron-microscope images. For chemical analyses, wet-chemical as well as various spectroscopic and chromatographic methods are available.

CONTACT

If you have any questions related to our products, the Koehler sales team will be happy to help. Just send us your inquiries using our contact form.

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