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Feb 2, 2021
Epoxy resin is an excellent thermosetting polymer material. It has the advantages of excellent mechanical properties, thermal properties, chemical resistance, etc., high bonding strength, low curing shrinkage, etc. However, epoxy resin also has certain advantages Limitations, such as poor flexibility and low temperature resistance. Although the limitations of epoxy resin can be modified by physical or chemical methods, the comprehensive performance after modification still cannot meet the more demanding environment.
Silicone resin is a kind of polymer with -si-o-si- as the molecular backbone. Since the bond energy of silicon-oxygen bond is higher than that of carbon-carbon bond, silicone resin has good heat resistance, water resistance, Excellent electrical insulation and weather resistance. However, silicone resins also have significant shortcomings. Generally, their high curing temperature and longer curing time, poor resistance to organic solvents, and low adhesion to the coating have largely limited their wide-ranging applications. . Thus limiting its application.
Silicone-modified epoxy resin has been developed in recent years to not only reduce the internal stress of epoxy resin, but also increase the toughness and high temperature resistance of epoxy resin. At present, there are many researches on silicone modified epoxy resin at home and abroad, mainly including reactive end group reaction, use of silicon-oxygen coupling agent to generate block copolymer, substitution of siloxane partial side groups, and pre-preparation of polysiloxane particles Wait 4 kinds. The main parties are blending and copolymerization. Polymer blending modification is to blend different kinds of polymers. Although the cost of blending modification is low, the modification effect is not particularly ideal due to the poor compatibility of silicone polymer and epoxy resin.
Technical realization elements:
The purpose of the present invention is to provide a method for preparing silicone-modified epoxy resin. The method utilizes the active end groups on the silicone such as hydroxyl, amino, alkoxy and epoxy and hydroxyl in the epoxy resin. Reaction to generate graft or block copolymers, thereby solving the compatibility problem, and introducing stable and flexible silicon-oxygen chains into the cured structure to improve the fracture toughness of the epoxy resin.
In order to achieve the above objectives, the technical solutions adopted by the present invention are:
A preparation method of silicone modified epoxy resin, which comprises the following steps:
Step 1. Preparation of organosilicon oligomer: add 30-40 parts of alkoxysilane monomer and 5-10 parts of solvent A into a reactor equipped with heating, stirring and reflux device according to mass parts; Under the condition, the temperature is raised to 80℃, and the mixture composed of 2-5 parts of catalyst A and 20-30 parts of distilled water is added dropwise. The dropping time is controlled at 1-1.5h. After the addition is completed, keep the temperature at 80-90℃ React for 2h, and then distill under reduced pressure for 0.5-1h. Distill the ethanol and part of the solvent produced by the reaction, reduce to room temperature, and filter to obtain 5-10% by mass of ethoxy group and greater than 80% by mass of solid Silicone oligomer;
Step 2. Prepare silicone-modified epoxy resin: add 5-10 parts of solvent B, 1-3 parts of catalyst B, 10-15 parts of silicone oligomer prepared in step 1, 40 parts by mass. -50 parts of bisphenol-a epoxy resin are added to the reactor equipped with heating, stirring and refluxing devices in sequence, and protected by nitrogen. Under stirring, the temperature is raised to 80℃ for 1-1.5h, 120℃ for 3- 4h, and then under reduced pressure distillation for 0.5-1h to prepare organic silicon modified epoxy resin.
Preferably, the alkoxysilane monomer in step one is selected from compounds of the following general structural formula:
y(4-n)si(or)n;
Wherein, y represents a phenyl group or a primary or secondary alkyl group having 1-4 carbon atoms, r represents an alkyl group having 1-3 carbon atoms, and n is an integer of 1-4.
Preferably, the alkoxysilane monomer includes at least one of dimethyldiethoxysilane, monomethyltriethoxysilane or diphenyldiethoxysilane.
Preferably, the bisphenol A epoxy resin in step 2 is epoxy resin e-44 or epoxy resin e-51, and the epoxy value is 0.41-0.54 mol/100 g.
Preferably, the catalyst A in step 1 is hydrochloric acid or phosphoric acid
Preferably, the catalyst B in step 2 is at least one of dibutyl tin dilaurate or butyl titanate.
Preferably, the solvent methane in step one is at least one of xylene, butyl acetate or butanol.
Preferably, the solvent B in step 2 is at least one of xylene and butanol.
The silicone-modified epoxy resin prepared by the present invention utilizes a polysiloxane with an alkoxy group and the hydroxyl group (-oh) in the molecular chain of the bisphenol a epoxy resin to perform co-condensation reaction to generate roh and form a stable The si-or key.