Preparation of polymers: It can be polymerized with continuous bulk or continuous solution. However, in order to control the polymerization speed and the viscosity of the polymerization system, in most cases, solution polymerization is better; when methyl styrene is selected as the aromatic vinyl compound, bulk polymerization is better. Because the degree of polymerization and viscosity of this system can be stably maintained within the appropriate range without any solvent. Solvents used for solution polymerization are: aromatic hydrocarbons, such as benzene, toluene, or ketones such as acetone, methyl ethyl ketone, etc. The monomers are: the first monomer, styrene and methylstyrene or a mixture of both; the second monomer, methyl methacrylate; the third monomer, methacrylic acid or tert-butyl methacrylate or a mixture of both.
The polymerization process is divided into five stages:
The prepolymer is prepared in the first stage. The above three copolymer monomers, solvent toluene and benzoyl peroxide are added to the reactor according to the formula, and the prepolymer is obtained by the usual polymerization method. At this stage, the ternary copolymerization reaction is carried out, and the polymer segment structural unit formed is (shown in the figure).
The second stage generates a six-membered cyclic anhydride unit. The prepolymer obtained in one stage is treated at high temperature and reduced pressure to form a prepolymer of six-membered cyclic anhydride monomer. Note that the reaction conditions should be strictly controlled at this stage, such as opaque or discoloration of products obtained by improper control. At this stage, a polymer reaction is carried out, that is, a dehydration reaction occurs between the carboxyl methacrylate groups on the polymer chain of the prepolymer that has been formed. A demethanol reaction occurs between the carboxyl group and the ester group.
The third stage of imidization. The hexagonal imide unit is generated, and the hexagonal acid anhydride-containing monomer prepolymer obtained in the second stage reacts with ammonia or primary amine under certain conditions. Hexagonal anhydride monomer units are converted to hexagonal imide units, and the amount of conversion is controlled by the amount of ammonia or primary amine added. This stage is still a polymer reaction, that is, the acid anhydride monomer of the chain segment reacts with small molecule ammonia or primary amine.
The pressure and temperature of the fourth stage and the third stage only extend the reaction time and continue the amidation.
The fifth stage strengthens the reaction conditions, the temperature is increased to 220-280 ℃, the pressure is smaller, and the amidation is made.
After the above five process stages, the copolymer resin required by the composite disc substrate is obtained.