[0022] The invention provides a sealant with low modulus, high elongation, high thixotropy and aging resistance and a preparation method thereof, including silicone rubber, filler, reinforcing agent, crosslinking agent, catalyst, plasticizer, chain extender, Vulcanization accelerators, pigments, thixotropic agents, tackifiers, stabilizers, heat-resistant agents and anti-mold agents, the mass fraction of silicone rubber is 15-20, the mass fraction of fillers is 10-13, and the mass fraction of reinforcing agent The mass fraction is 7-8, the mass fraction of crosslinking agent is 5-7, the mass fraction of catalyst is 6-8, the mass fraction of plasticizer is 5-7, the mass fraction of chain extender is 2-3, The mass fraction of accelerator is 1-3, the mass fraction of pigment is 1-2, the mass fraction of thixotropic agent is 3-6, the mass fraction of tackifier is 4-5, and the mass fraction of stabilizer is 3-4 , The mass fraction of heat-resistant agent is 5-7 and the mass fraction of anti-fungal agent is 4-6;
[0023] The preparation method is as follows:
[0024] Step 1: Put the silicone rubber, filler, reinforcing agent and crosslinking agent into the double planetary stirring tank according to the measurement, stir for 1 hour and evacuate;
[0025] Step 2: After stirring and vacuuming for 1 hour, add metered catalysts, plasticizers, chain extenders, vulcanization accelerators, pigments, thixotropic agents, tackifiers, stabilizers, heat-resisting agents and anti-mold agents in sequence, and stir for 30 minute;
[0026] Step 3: Vacuum stirring for 30 minutes, then transfer to a plastic drum and seal the package.
[0027] Silicone rubber uses alkoxy-terminated polydimethylsiloxane; the filler is composed of 40% activated calcium carbonate and 60% octamethylcyclotetrasiloxane modified fumed silica, which is active Calcium carbonate is obtained by treating light calcium carbonate with stearic acid or rosin acid. It has a reinforcing effect on liquid silicone rubber, which can increase the viscosity of the rubber compound and impart thixotropy; after modification of octamethylcyclotetrasiloxane The fumed silica can achieve the purpose of improving the strength without reducing the elongation. The amount of fumed silica modified by octamethylcyclotetrasiloxane is controlled below 4% to obtain a low modulus The catalyst is two mixtures of organotin compounds and organotitanium compounds, the ratio is 4 to 6. The organotin compounds are stannous octoate, dibutyltin dilaurate, dibutyltin dioctoate, dibutyltin diacetate, and dimethoxy Any one or more of dibutyltin and dibutyltin oxide, the organic titanium compound is tetraisopropyl titanate, tetra-n-butyl titanate, tetratitanium, diisopropoxy-bis-titanium and Any one or more of propyl dioxydi-titanium; plasticizers are composed of two types of plasticizers, namely the first plasticizer and the second plasticizer, the first plasticizer is trifunctional silicone Alkyl oligomer, in addition to lowering modulus, also has the function of a tackifier, the viscosity is controlled at 15-300cps; the second plasticizer is linear organopolysiloxane, in order to ensure the minimum degree of crosslinking of the final product, The hydroxyl content is required to be less than 0.6wt%, because its trifunctional group can participate in the cross-linking reaction, and its excessive addition will cause the cross-linking of the sealing material to be too high, but it will reduce the elasticity; the appropriate addition amount is 5-15phr, which is to reduce the mold The second plasticizer linear organopolysiloxane must be added 10-50phr to control the viscosity at 10-1000cp; the crosslinking agent is aminooxysilane, and the chain extender is methyl vinyl bis N-methyl Acetamidosilane, in order to obtain a low modulus, high elongation silicone sealing material, when the viscosity of the base polymer at 25 degrees Celsius is 8000cp or less than 8000cp, aminooxy silane and methyl vinyl two N-methyl The ratio of the added amount of acetamidosilane should be 1:19-1:23; and when the viscosity of the base polymer at 25 degrees Celsius is greater than 8000cp, the ratio of the added amount is 1:4-1:1.2; aminooxysilane The addition amount of 2.5-10phr, and can not exceed the amount of methyl vinyl bis N-methyl acetamido silane; the glue uses a complex vulcanization crosslinking agent to prepare a high elongation amide hydroxylamine type glue, in bisamide Monoalcohol is introduced into the vulcanization cross-linking system of siloxane and polyaminooxysiloxane, so that the cross-linking system becomes a composite vulcanization cross-linking system with moderate vulcanization activity; choose the amide silane with a mass ratio of 3:1 The mixture with ketoxime silane is a compound vulcanization crosslinking agent to prepare amide ketoxime type high elongation sealant; the anti-mold agent is diiodomethyl p-methyl phenyl sulfone, and diiodomethyl p-methyl phenyl sulfone is Light gray or brown-yellow fine particles, with strong inhibition of mold and low toxicity; combined with mercury-type anti-mold fungicide to make a mixed agent, which can completely protect the material and become a kind of anti-mildew, anti-algae and bacteria-resistant Ideal defense Molding agent; tackifier is divided into any one of water-based tackifying emulsion, water-based tackifying resin and water-based tackifying powder; the main component of heat-resistant agent is rare earth nano material, which has high surface activity and is easy to uniformly disperse in silicone polymer ; It has the characteristics of macroscopic quantum effect, which can penetrate into the polymer chain to enhance the stability of the molecule; because the rare earth element has a large atomic radius and strong complexing ability, it has a special complexing effect on Si, which can increase the organic silicon material The cross-linking density and the stability between molecular chains greatly improve the heat resistance, oil resistance, strength, tear resistance, and abrasion resistance of the material; promote vulcanization, absorb and shield ultraviolet radiation, and make the product more resistant Ageing.
[0028] Performance Testing:
[0029] Tensile strength and elongation at break: The test film is prepared according to the method in the standard GB/rr 528-2009 "Determination of the tensile stress and strain properties of vulcanized rubber or thermoplastic rubber", the thickness of the film is (2±0.2) mm; in the standard After curing for 7 days under the conditions, a dumbbell-shaped specimen was made. The tensile strength and elongation at break of the specimen were tested by a tensile testing machine, and the tensile speed was set to 500m per minute. Extrudability, surface drying time and elastic recovery rate: test according to the method in the standard GB/111 3477 "Test Methods for Building Sealing Materials". Shore hardness: Test in accordance with the standard GB/r11 531.1-2008 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber Part 1: Shore hardness tester (Shore hardness)". Tensile adhesion and fixed elongation adhesion: Test according to the method in JC/T 88 1-2001 "Sealant for joints of concrete buildings".
