Heterophase Polymerizations

Heterophase polymerizations - polymerization processes resulting in polymer dispersions - allow the synthesis of high molecular weight polymers in systems with low viscosity and high polymer content. The use of water as dispersion- and reaction medium respectively is favourably both in terms of sustainability and of other aspects like toxicity, flammability and odour.

Emulsion Polymerization

More then 90% of all polymer dispersions are produced by free-radical emulsion polymerization. Due to the compartmentalized character of the process a broad diversity of product properties can be created. This applies to the molecular level – for example the choice of the monomers, the length of the polymer chains, the degree of branching or cross-linking – as well as to the level of the particles consisting of particle size and size distribution, morphology of the particles and surface functinality. An appropriate core-shell-structure of the particles leads, for instance, to rigid coatings with low film forming temperature, dispersions with extremely high solid content are accessible by means of the adjustment of defined bi- or multimodal particle size distributions and the integration of suitable functional comonomers gives reactive particles which can be subsequently cross-linked or linked to a matrix.

Applications areas of polymer dispersions range from coatings and adhesives to additives for paper, textiles and leather fabrication.

Heterophase Polymerization of Watersoluble Monomers

Polyelectrolytes und other water soluble polymers may be synthesized by means of inverse heterophase polymerization in organic media. Polymers with properties, especially molecular weights, not accessible using alternative polymerization techniques like solution polymerization become available by thorough optimization of the systems in respect of composition of the reaction mixture, stabilization and mechanism of initiation thus opening up additional market areas for the products. An heterophase polymerization of water soluble monomers in aqueous media becomes possible applying a combination of low molecular or polymeric salts causing a precipitation of the polymer and suitable stabilizers.
Polyelectrolytes are applied as flocculation and retention agents, for surface refinement, for hair cosmetics or as thickener.

Secondary and Hybrid Dispersions

For a considerable number of applications particularly in exterior areas coatings based on primary dispersions are inappropriate since they show a large water absorption due to the surfactants contained. Secondary dispersions, which are made in a two-step process - with the first step being a solution polymerization in small amounts of organic media and the second step being the dispersion of the resulting polymer in water without adding surfactants – provide an alternative to solution based coatings in this field. In order to obtain stable dispersions with high polymer content the composition of the first step polymer has to be carefully optimized.

Hybrid dispersions result from an emulsion polymerization of one or more additional monomers within a secondary dispersion. The benefit of hybrid dispersions is the frequently observed synergistic intensification of the positive properties of both of the compounds, which is not to be found in simple mixtures of two dispersions.

Applications and Services

We offer process developments with implementation of modern technologies for heterophase polymerizations from laboratory to pilot plant scale. For the process design a modern reaction calorimeter, an automated lab reactor as well as diverse facilities for particle and dispersion characterization (online and offline) are available. This enables a continous monitoring of the course of polymerization.

• Emulsion polymerization batch, semi-batch, seeded etc.
• Synthesis of defined particle architectures and morphologies and studies on the resulting dispersion properties
• Synthesis of reactive polymer dispersions for subsequent reactions like linking to a matrix, cross-linking etc.
• Miniemulsion polymerisations, synthesis of composite materials
• Suspension polymerizations
• Inverse emulsion, miniemulsion, microemulsion polymerization
• Dispersion polymerization of water soluble monomers in aqueous media
• Dispersion polymerization in organic media
• Secondary and hybrid dispersions

Selected Patents

J. Bohrisch, M. Hahn, A. Mädler, M. Stoll
„Core-shell type gel particles for controllable release of water-organic solvent mixtures comprise a hydrogel core from a lower critical solution temperature (LCST) polymer and a permeable shell from a precipitation copolymer“
DE 102004002206A1 (2005)

M. Hahn, B. R. Paulke, W. Jaeger:
„Stabilizers used for the polymerization of water-soluble viny monomers, and method for producing highly concentrated polymer dispersions“
DE 100 55 470 A1, WO 02/38 639 A1 (2002)

Struck, O.; Przybyla, C.; Sieger, A.; Hahn, M.; Ruppelt, D.; Jaeger, W.:
„ Process for preparing a polymer dispersion“
US2006229401(2006)

Jaeger, W.; Hahn, M.; Lieske, A.; Korth, H.; Staeck, R.; Scordialo, A.
„ Water-soluble branched block cationic copolymers“
WO 2003082938 (2003)

Gai, S.; Hampel, C.; Hahn, M.; Lieske, A.:
„Preparation of polymers comprises at least partially initiating the polymerization reaction through radicals, which are produced by a cavitation process“
DE102005027757 (2006)

Thünemann, A.F.; Lochhaas, H.; Paulke, B.-R.; Lieske, A.,:
„Polyelectrolyte and ionic surfactant complexes containing aqueous colloidal dispersions, methods for the produchtion und use of thereof “
WO0029489 (2000)