WO 2011/154893 discloses a process for the preparation of capsules, which includes mixing at least one aliphatic polyisocyanate and of at least one aromatic polyisocyanate, wherein the molar ratio between the two polyisocyanates is between 75:25 and 20:80. For the polycondensation reaction, suitable diisocyanate and symmetrical triisocyanate starting materials are disclosed in the prior art. For such applications, the capsules also require a relatively high mechanical strength. 6,133,197, polyurea and polyurethane capsules are often used for rugged applications, such as for encapsulation of agrochemicals, e.g., herbicides and pesticides, where slow time-release is desired to set the agents free. As is exemplified therein, and also in U.S. 4,640,709 and the publications described therein. Raw materials and processes for preparing capsules by polycondensation are described in U.S. Such wall materials are produced by having a first phase which is water-immiscible and includes a polyfunctional isocyanate, i.e., a polyisocyanate having two or more isocyanate groups, and a second aqueous phase which includes (i) a polyfunctional alcohol (i.e., a polyol) having two or more -OH groups, or (ii) a polyfunctional amine (i.e., a polyamine) having two or more -NH 2 and/or -NH groups. Interfacial polycondensation is a known technique for preparing capsules and versatile capsule wall materials are used including polyureas and polyurethanes (WO 2011/154893, WO 2012/107323, US 2011/0077188, U.S. ![]() Various techniques for preparing capsules are known in the art and are used, depending on the contents to be encapsulated, the environment in which the capsules should retain their integrity and the desired release mechanism. Microcapsules are used in a variety of different applications where there is a need to deliver, apply, or release an active material including a fragrance, flavor, and malodor counteraction agent to a target area in a time-delayed or controlled manner.
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