Method for producing silicone elastomer molds

A method of preparing a negative mold MN produced from silicone elastomer for use in the manufacture of molded articles produced from different reproduction materials, the method comprising the following steps a) to d):

• a) preparing a polyorganosiloxane composition X that can be cured to produce an elastomer by polycondensation reactions, which does not contain a metallic catalyst, and comprising:
• a silicone base B comprising at least one polyorganosiloxane oil A that can be cured by a polycondensation reaction, and
• catalytic quantity of at least one polycondensation catalyst C, which is an organic compound having a general formula (I):
• (R″)2NH
• in which the symbols R″, which are identical or different, represent aliphatic hydrocarbon radicals containing 1 to 30 carbon atoms,
• b) applying said polyorganosiloxane X to a master to be duplicated, optionally already covered with a release agent,
• c) curing said polyorganosiloxane composition X in the presence of moisture supplied by ambient air or by a prior addition of water, in order to form the negative mold MN produced from silicone elastomer, which is an impression corresponding to the exterior contour of the master to be duplicated, and
• d) separating the negative mold MN produced from silicone elastomer from the master to be duplicated,
• wherein:
• a) the polyorganosiloxane composition X has a pot life of between 20 and 200 minutes,
• b) the curing of said polyorganosiloxane composition X, as measured by the Shore A hardness (SAH) of the negative mold MN,
• i) when measured at 4 days and 14 days after mixing, the the difference in the SAH polyorganosiloxane composition X, is less than 2, and
• ii) when measured 24 hours and 14 days after mixing, the, the Shore A hardness is at least 68% of the SAH measured at 14 days, and
• c) the negative mold MN produced can be used in greater than 37 successive molding/demolding cycles when used in demolding polyurethane replicas.