Preparation method of halogen-free flame-retardant polyurethane (PU) sealant

Abstract

The invention relates to a preparation method of a halogen-free flame-retardant polyurethane (PU) sealant. The preparation method comprises the following steps: dewatering and drying the following materials, namely a filler, a thixotropic agent, a halogen-free flame retardant, a flame-retardant synergist, a plasticizer, a light stabilizer and an antioxidant in vacuum; stirring a PU prepolymer and the materials for dispersion in a double planet mixer with a high-speed dispersion disk or a tri-roller grinder at the temperature of 30-50 DEG C for 2-5 hours under the condition that the vacuum degree is not less than 0.092Mpa; under normal pressure and protection of high-purity nitrogen, adding a catalyst A, a silane adhesion promoter and a water scavenger, and stirring for 0.1-1 hour for dispersion; and removing small molecules and stirring for 0.3-1 hour under the condition that the vacuum degree is not less than 0.092Mpa to finally obtain the halogen-free flame-retardant PU sealant. The halogen-free flame-retardant PU sealant effectively overcomes the disadvantages of the PU sealant such as big flame, fast burning speed, severe drippage and the like in the prior art on the premise of ensuring the original physical properties of the PU sealant, thus the PU sealant has the advantages of flame retardance, no drippage during the burning process, good adhesive property and the like.

Description

technical field [0001] The invention relates to the technical field of polyurethane sealant, in particular to a preparation method of a halogen-free flame-retardant polyurethane sealant. Background technique [0002] Polyurethane sealants have excellent UV resistance, excellent bonding strength, chemical medium resistance, pull resistance, shrinkage, low temperature flexibility, wear resistance and other properties. Therefore, it is widely used in fields such as construction, automobiles and ships. [0003] When the polyurethane sealant is burned by an external heat source, it has the disadvantages of large flame, fast burning speed and severe dripping. With the improvement of people's safety awareness in the fields of home decoration and construction, more and more attention has been paid to the flame retardancy of polyurethane sealants. [0004] In the prior art, flame retardants such as inorganic hydroxides, red phosphorus, and ammonium polyphosphate are mostly used for...

AI Technical Summary

Problems solved by technology

[0004] In the prior art, flame retardants such as inorganic hydroxides, red phosphorus, and ammonium polyphosphate are mostly used for flame retardants of polyurethane sealants. However, inorganic hydroxide flame retardants have low flame retardant efficiency and large additions. , Poor compatibility with the resin matrix, large specificity resulting in high product density and other disadvantages; red phosphorus flame retardant, although the flame retardant efficiency is high, but the color is darker, it is mostly used in some black products, and absorbs moisture, and the abrasive will have a long time Phosphine and other highly toxic gases are released, and there is a danger of explosion; although the ammonium polyphosphate flame retardant has the advantages of high phosphorus content and large nitrogen content, in the actual application process, ammonium polyphosphate is easy to absorb moisture and Agglomeration, poor compatibility with resin, easy to precipitate from resin, seriously affecting its flame retardant effect

In order to improve the existing problems of ammonium polyphosphate flame retardants, people often use methods to modify the molecular structure to form other types of polyphosphates (such as melamine ammonium polyphosphate salts), modify the surface with coupling agents, etc. , but these methods cannot fundamentally change the problem of easy moisture absorption and precipitation