| Epoxy acrylate resin is a kind of early development of resin which is the largest amount and the most widely used photo-curable resin. And it has a very wide range of uses because of its many advantages such as good chemical resistance, strong adhesion, low price, etc. According to factory requirement and the shortage in flexibility and heat resistance of epoxy acrylate resin using in flexible circuit boards with UV light-cured solder mask ink, this subject suggest that using polyimide to modify epoxy acrylate resin whose flexibility and heat resistance is good.The main work includes three parts: the optimization of synthesis condition of a soluble polyimide; the optimization of synthesis condition of epoxy acrylate resin; the optimization of synthesis condition of soluble polyimide-modified epoxy acrylate resin.First, the better synthesis condition of a soluble polyimide was obtained by researching the synthesis of soluble polyimide. The molar ratio of the three kind of Raw material combination which including 3,4’-diaminodiphenyl ether(3,4’-ODA), 3,3’,4,4’-biphenyltetracarboxylic dianhydride(BPDA), 3,3’,4,4’-diphenyl tetracarboxylic dianhydride(ODPA) was 1:0.505:0.505. The polyamide acid was synthesized in N-methylpyrrolidone at 0 ℃ about 2h. Then the polyimide was synthesized at 70-80℃ about 4-5h by adding triethylamine(1% of the total mass fraction of reactants) as catalyst and acetic anhydride(1% of the total mass fraction of reactants) as dehydrating agent. The polyimide could dissolve in DMF, DMAc, NMP, pyridine and the concentrated sulfuric acid and so on, and swell in tetrahydrofuran, cyclohexanone, dimethyl sulfoxide, but couldn’t dissolve in other solvents. The polyamide’s average molecular weight was 41064.2 ′, and its thermal decomposition temperature was 508℃, which indicated its high thermal stability.The better synthesis condition of epoxy acrylic resin had been obtained. The molar ratio of acrylic acid and epoxy resin was 2:1. The epoxy resin(type: NPEL128 E, epoxy value: 187-190g/eq) was dissolved in N-methyl pyrrolidone mixed with a polymerization inhibitor 4-Methoxyphenol(1% of the total mass fraction of reactant), and then the solution of acrylic acid and the catalyst triethylamine(1% of the total mass fraction of reactant) was added dropwise in 1-2h at 90℃. The mixture reacted another 4h. And considered that the system acid value reduced less than 5mg KOH/g, which meant that the conversion rate of acrylic acid was higher than 97.8%. Characterized by IR, the reaction had occurred determined by the appearance of the asymmetric stretching vibration absorption peak of C=C at 1725cm-1 and the disappearance of the epoxy absorption peak at 913cm-1.Finally, the synthesis condition of the soluble polyimide-modified epoxy acrylate resin was optimized. The reaction ratio of soluble polyimide and epoxy acrylate resin was 1:3, and the tetrabutyl titanate was used as catalyst whose mass fraction was 1%. The reaction was taken at 140℃ about 5-6h. The product’s average molecular weight was4.10225 ′. From the IR characterization we could see that the soluble polyimide had reacted with the epoxy acrylate resin. The modified resin’s decomposition temperature was 374℃ whose thermal performance was higher than epoxy acrylate resin. The modified resin had better alkaline water solution in Na2CO3 aqueous solution after reacted with pyromellitic anhydride. |
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