Siloxane bridged protocatechuic acid-based epoxy resin as well as synthesis method and application thereof

Abstract

The invention discloses siloxane bridged protocatechuic acid-based epoxy resin as well as a synthesis method and application thereof. Carboxyl of protocatechuic acid is bridged with epoxy groups of polydimethylsiloxane with different chain segment lengths, and then phenolic hydroxyl of protocatechuic acid is subjected to epoxidation reaction through a two-step method, so that the siloxane bridged protocatechuic acid-based epoxy resin is obtained. A novel siloxane bridged protocatechuic acid-based epoxy resin monomer is synthesized, and the structural formula of the monomer is shown as a formula (III). The siloxane-bridged protocatechuic acid-based epoxy resin has the characteristics of low viscosity, high toughening property, low dielectric constant and strong hydrophobicity, the processability of the siloxane-bridged protocatechuic acid-based epoxy resin is improved, and the siloxane-bridged protocatechuic acid-based epoxy resin shows excellent fracture resistance. Through the synergistic improvement, the siloxane bridged protocatechuic acid-based epoxy resin obtained by the invention becomes novel high-performance thermosetting plastic, and has wide application prospects in the fields of electronic packaging and semiconductor industries and architectural coatings.

Description

Technical Field

[0001] The invention belongs to the technical field of high-performance polymer manufacturing, and specifically relates to a siloxane-bridged protocatechuic acid-based epoxy resin, a synthesis method for preparing the siloxane-bridged protocatechuic acid-based epoxy resin from protocatechuic acid, and application of the epoxy resin. Background Art

[0002] Epoxy resin is one of the most important thermosetting resins. Due to its excellent comprehensive properties, it is widely used as a matrix material for advanced composite materials, coatings, adhesives and electronic packaging. At present, about 90% of epoxy resins are bisphenol A epoxy resins (DGEBA) synthesized by bisphenol A (BPA) and epichlorohydrin through a shrinkage reaction. E51 epoxy resin is a representative one of DGEBA.

[0003] Due to the high degree of crosslinking, DGEBA epoxy resin exhibits rigid and brittle behavior and has poor crack growth resistance. Brittleness or lack of crack resistance will reduce the widespread use of DGEBA epoxy resin. Therefore, in order to expand the application range of DGEBA epoxy resin, it is necessary to toughen DGEBA epoxy resin.

[0004] So far, there are many ways to toughen epoxy resin, such as rubber particles, thermoplastics, liquid crystal polymers, etc. However, the incompatibility between the matrix and the modifier leads to high viscosity, opacity, and low fluidity, which limits its application in high-end fields such as electronic packaging and wind power insulation coatings. How to effectively toughen epoxy resin still needs to be developed.

[0005] Low surface energy epoxy resins are widely used in various fields such as environmental protection, medical treatment, industrial manufacturing, electronic equipment, etc. due to their excellent water resistance, pollution resistance, chemical corrosion resistance and easy cleaning properties. They improve material performance, extend service life, and play an important role in modern technology and life. With the increasing demand for high-performance materials, the application of low surface energy epoxy resins will continue to expand, especially in the fields of high technology and environmental protection.

[0006] As petroleum energy is becoming increasingly scarce, all countries are striving to develop sustainable energy, such as solar energy, wind energy, etc. The field of materials is focusing more on renewable resources that can be obtained in large quantities, such as anethole, eugenol, lignin, and cellulose, which are renewable energy sources that can be extracted from plants and crops in large quantities. How to simply and efficiently convert them into high-performance materials to gradually replace existing fossil energy is the top priority of current research.

[0007] Protocatechuic acid, also known as 3,4-dihydroxybenzoic acid, exists in many edible plants and is a new bio-based polyphenol compound. However, due to the electron-withdrawing effect and conjugation effect of its three functional groups, the activities of the hydroxyl group and carboxyl group are relatively low. Therefore, there are few reports on the synthesis of high-performance polymers from protocatechuic acid at present. Summary of the Invention

[0008] The first object of the present invention is to provide a novel silicone-bridged protocatechuic acid-based epoxy resin monomer (III), and the silicone-bridged protocatechuic acid-based epoxy resin monomer (III) has the characteristics of low viscosity, high toughness, high hydrophobicity and low dielectric constant.

[0009]

[0010] The second object of the present invention is to provide a preparation method of the above-mentioned silicone-bridged protocatechuic acid-based epoxy resin monomer, which is prepared from protocatechuic acid as a raw material.

[0011] Step (1) Preparation of silicone-bridged protocatechuic acid (I)

[0012] Mix protocatechuic acid and polydimethylsiloxane capped with glycidoxypropyl at different chain lengths in a solvent system of an alkaline catalyst, heat up and react for several hours. After dissolving the reaction system with dichloromethane, extract with water three times to remove the excess solvent and excess protocatechuic acid, and rotary evaporate the solvent in the dichloromethane layer to obtain silicone-bridged protocatechuic acid (I);

[0013]

[0014] Preferably, the alkaline catalyst is selected from one of sodium hydroxide, potassium carbonate, piperidine, pyridine, and triethylamine, and more preferably triethylamine.

[0015] Preferably, the solvent is selected from one of acetone, dioxane, tetrahydrofuran, and dimethylformamide, and more preferably dioxane.

[0016] Preferably, the reaction temperature is 100-140 °C; the reaction time is 2-10 h, and more preferably 4 h.

[0017] Preferably, the molar ratio of protocatechuic acid to polydimethylsiloxane capped with glycidoxypropyl is 2-3:1.

[0018] Preferably, the kinematic viscosity of the polydimethylsiloxane capped with glycidoxypropyl is 8-35 cSt (centistokes).

[0019] Step (2) Preparation of silicone-bridged vinyl-capped protocatechuic acid (II)

[0020] Under the action of a phase transfer catalyst and an acid-binding agent, siloxane-bridged protocatechuic acid (I) reacts with allyl bromide in N,N-dimethylformamide (DMF) as a solvent at room temperature for several hours. After dissolving the reaction system with ethyl acetate, it is extracted with water three times, and the ethyl acetate layer is dried by rotary evaporation to obtain siloxane-bridged vinyl-terminated protocatechuic acid (II);

[0021]

[0022] Preferably, the phase transfer catalyst is selected from one of tetrabutylammonium bromide, benzyltriethylammonium chloride, cetyltrimethylammonium chloride, and tetrabutylammonium chloride, and more preferably tetrabutylammonium bromide.

[0023] Preferably, the acid-binding agent is one of potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium bicarbonate, and more preferably potassium carbonate.

[0024] Preferably, the molar ratio of allyl bromide to protocatechuic acid ester (I) is 4-16:1, and more preferably 8:1.

[0025] Preferably, the reaction temperature is 10-40 °C, and more preferably 30 °C.

[0026] Preferably, the reaction time is 12-48 h, and more preferably 24 h.

[0027] Step (3), Preparation of protocatechuic acid epoxy resin monomer (III)

[0028] Dissolve siloxane-bridged vinyl-terminated protocatechuic acid (II) and m-chloroperbenzoic acid in a non-polar solvent and react at room temperature for several hours. After dissolving the reaction system with ethyl acetate, it is extracted with water three times, and the ethyl acetate layer is dried by rotary evaporation to obtain siloxane-bridged protocatechuic acid-based epoxy resin monomer (III), denoted as SIPAEP;

[0029]

[0030] Preferably, the molar ratio of m-chloroperbenzoic acid to siloxane-bridged vinyl-terminated protocatechuic acid ester (II) is 6-18:1, and more preferably 12:1.

[0031] Preferably, the reaction temperature is 10-40 °C, and more preferably 30 °C.

[0032] Preferably, the reaction time is 24-60 h, and more preferably 48 h.

[0033] Preferably, the solvent is selected from dichloromethane (DCM), chloroform or other non-polar solvents, and more preferably dichloromethane.

[0034] The third object of the present invention is to provide a siloxane-bridged protocatechuic acid-based epoxy resin, which is obtained by thermally curing the above-mentioned epoxy resin monomer (III).

[0035] The fourth object of the present invention is to provide the use of the above-mentioned epoxy resin monomer (III) or the above-mentioned epoxy resin in the preparation of a low-viscosity coating.

[0036] The fifth object of the present invention is to provide the use of the above-mentioned epoxy resin monomer (III) or the above-mentioned epoxy resin in the preparation of an electronic packaging material.

[0037] The introduction of the siloxane chain segment of the epoxy resin monomer in the present invention significantly reduces the molecular chain rigidity. The increased rotational freedom results in a substantial reduction in the resin viscosity. The regular and symmetric molecular structure reduces the entanglement between chains, further reducing the viscosity and exhibiting characteristics close to those of a Newtonian fluid.

[0038] Preferably, in the preparation method of the above-mentioned protocatechuic acid epoxy resin, the kinematic viscosity of the poly(dimethylsiloxane) capped with 3-glycidoxypropyl is 8-11 cSt. Dynamic rheology tests show that the dynamic viscosity of SIPAEP at 25 °C is only 3.3 Pa·s, while that of bisphenol A epoxy resin E51 is 15.4 Pa·s, indicating that the fluidity and processability of the modified epoxy resin have been significantly improved.

[0039] The electronegativity difference of the Si-O bond in the epoxy resin monomer of the present invention is significantly lower than that of the C-O bond and the C-C bond, resulting in a dipole moment. At the same time, the Si-O bond length is longer than the C-C bond, and the bond angle is larger, with a low rotational barrier for the molecular chain. The combined effect of this low polarization property and high flexibility reduces the dielectric constant of the material.

[0040] Preferably, in the preparation method of the above-mentioned protocatechuic acid epoxy resin, the kinematic viscosity of the poly(dimethylsiloxane) capped with 3-glycidoxypropyl is 20-35 cSt. Dielectric analyzer tests show that the dielectric constant of SIPAEP / DDM (4,4'-diaminodiphenylmethane) at 1 Hz - 1 MHz is 3.3 - 3.7, significantly lower than that of E51 / DDM, which is 5.6 - 5.8, indicating that the modified epoxy resin reduces energy absorption under an alternating electric field and has the potential to be an electronic packaging material.

[0041] The siloxane backbone (Si-O-Si) of the epoxy resin monomer in the present invention has a low bond energy density and high flexibility. The methyl (-CH3) group has the lowest polarity and preferentially orientates towards the outermost molecular layer, forming a dense hydrophobic barrier. At the same time, the long and slender Si-O bond length and wide bond angle endow excellent chain fluidity, enabling spontaneous surface reorganization to achieve thermodynamic stability.

[0042] Preferably, in the preparation method of the above protocatechuic acid epoxy resin, the kinematic viscosity of the epoxypropoxyl propyl-terminated polydimethylsiloxane is 20 - 35 cSt. The water contact angle of SIPAEP / DDM measured by a contact angle meter is 125°, which is significantly higher than 78° of E51 / DDM, indicating that the hydrophobicity of the modified epoxy resin has been significantly improved.

[0043] In the present invention, the siloxane segment of the epoxy resin monomer provides flexibility for the molecular chain. The Si-O bond is longer than the C-C bond, reducing the resistance to intramolecular rotation and increasing the flexibility of the molecular chain; the multifunctionality provides a crosslinked structure, and the epoxy resin monomer itself is relatively regular and symmetric. Therefore, while toughening and modifying E51, the storage modulus and T of the blend resin system can be ensured. g Basically remain unchanged.

[0044] Preferably, in the preparation method of the above protocatechuic acid epoxy resin, the kinematic viscosity of the epoxypropoxyl propyl-terminated polydimethylsiloxane is 20 - 35 cSt. The impact strength of the epoxy resin monomer is 50.7 kJ / m 2 , which is significantly higher than 19.9 kJ / m of E51 / DDM 2 . A hierarchical structure was observed by scanning electron microscopy, similar to a flaky hierarchical microarchitecture. This hierarchical structure effectively dissipates the impact energy through a continuous layer-by-layer deformation mechanism, while delaying the development of cracks, thus greatly improving the fracture resistance. The impact strength data and the SEM results indicate that the toughness of the modified epoxy resin has been significantly improved.

[0045] Compared with the prior art, the main advantages of the present invention include:

[0046] (1) The method provided by the present invention belongs to the deep processing and utilization of biomass, develops new applications of biomass resources, realizes sustainable development, and reduces the demand pressure on chemical energy.

[0047] (2) The synthesis steps of the present invention are simple, the process conditions are mild, and it can be used for large-scale industrial production.

[0048] (3) The protocatechuic acid-based epoxy resin monomer synthesized by the present invention can effectively improve the hydrophobicity and toughness of the epoxy resin, reduce the dielectric constant and viscosity of the epoxy resin, and has broad application prospects in the fields of electronic packaging and semiconductor industries, and architectural coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is the NMR spectrum of the siloxane-bridged protocatechuic acid-based epoxy resin, where A is the hydrogen spectrum and B is the carbon spectrum.

[0050] Figure 2Viscosity variation diagrams of DDM-cured siloxane-bridged protocatechuic acid-based epoxy resin and DDM-cured E51 epoxy resin with shear rate and temperature, where A is the shear rate and B is the temperature.

[0051] Figure 3 Dielectric constant and dielectric loss diagrams of DDM-cured siloxane-bridged protocatechuic acid-based epoxy resin and DDM-cured E51 epoxy resin, where A is the dielectric constant and B is the dielectric loss.

[0052] Figure 4 Bar charts of water contact angle, diiodomethane contact angle and surface energy of DDM-cured siloxane-bridged protocatechuic acid-based epoxy resin and DDM-cured E51 epoxy resin.

[0053] Figure 5 Bar chart of impact strength of DDM-cured siloxane-bridged protocatechuic acid-based epoxy resin and DDM-cured E51 epoxy resin.

[0054] Figure 6 SEM fracture morphology diagrams of DDM-cured siloxane-bridged protocatechuic acid-based epoxy resin and DDM-cured E51 epoxy resin, where A is E51 / DDM, B is SIPAEP-S / DDM, C is SIPAEP-M / DDM, and D is SIPAEP-L / DDM. Detailed implementation manners

[0055] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The raw materials used in the following embodiments can all be purchased commercially or prepared by conventional methods. The experimental methods without specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, percentages and parts are calculated by weight.

[0056] Synthesis of siloxane-bridged protocatechuic acid SIPA-S in Example 1-1

[0057] Under the protection of nitrogen gas, a magnetic stirrer was added to a dry three-necked flask. 30.7 g of protocatechuic acid (120 mmol), 18.4 g of epoxypropoxypropyl-terminated polydimethylsiloxane (8-11 cSt) (50 mmol) and 101 mg of triethylamine (1 mmol) were dissolved in 62 mL of dioxane. The reaction was carried out at 120 °C for 6 hours with a water-carrying device. After cooling to room temperature, the reaction system was dissolved with dichloromethane, and then extracted with water three times to remove the excess solvent and excess protocatechuic acid. The dichloromethane layer was rotary evaporated to obtain 43.8 g of pale yellow liquid siloxane-bridged protocatechuic acid.

[0058] Synthesis of siloxane-bridged protocatechuic acid SIPA-M in Example 1-2

[0059] The experimental method was the same as that in Example 1-1. 30.7 g of epoxypropyl-terminated polydimethylsiloxane (8-11 cSt) was changed to 56.7 g of epoxypropyl-terminated polydimethylsiloxane (12-18 cSt), and other reaction conditions remained unchanged. 61.7 g of the target monomer was obtained.

[0060] Synthesis of siloxane-bridged protocatechuic acid SIPA-L in Example 1-3

[0061] The experimental method was the same as that in Example 1-1. 30.7 g of epoxypropyl-terminated polydimethylsiloxane (8-11 cSt) was changed to 75.9 g of epoxypropyl-terminated polydimethylsiloxane (20-35 cSt), and other reaction conditions remained unchanged. 42.2 g of the target monomer was obtained.

[0062] Synthesis of siloxane-bridged protocatechuic acid SIPA-S in Example 1-4

[0063] The experimental method was the same as that in Example 1-1. The catalyst triethylamine was changed to pyridine, and other reaction conditions remained unchanged. 42.7 g of the target monomer was obtained.

[0064] Synthesis of siloxane-bridged protocatechuic acid SIPA-S in Example 1-5

[0065] The experimental method was the same as that in Example 1-1. The catalyst triethylamine was changed to pyridine, and other reaction conditions remained unchanged. 40.1 g of the target monomer was obtained.

[0066] Synthesis of siloxane-bridged protocatechuic acid SIPA-S in Example 1-6

[0067] The experimental method was the same as that in Example 1-1. The solvent dioxane was changed to tetrahydrofuran, and other reaction conditions remained unchanged. 39.6 g of the target monomer was obtained.

[0068] Synthesis of siloxane-bridged vinyl protocatechuic acid SIVPA-S in Example 2-1

[0069] Take 100 mmol of siloxane-bridged protocatechuic acid SIPA-S obtained in Example 1-1, 1200 mmol of potassium carbonate, 20 mmol of benzyltrimethylammonium chloride and 1200 mmol of allyl bromide, add 100 mL of DMF to dissolve and stir well, react at 30 °C for 24 h, add ethyl acetate to dissolve, extract with water 3 times, dry with anhydrous sodium sulfate, and concentrate to obtain 107.4 g of a dark yellow viscous liquid of siloxane-bridged vinyl protocatechuic acid.

[0070] Synthesis of siloxane-bridged vinyl protocatechuic acid SIVPA-M in Example 2-2

[0071] The experimental method was the same as that in Example 2-1. Siloxane-bridged protocatechuic acid SIPA-S was changed to siloxane-bridged protocatechuic acid SIPA-M, and other reaction conditions remained unchanged. 148.0 g of the target monomer was obtained.

[0072] Example 2-3 Synthesis of Siloxane-Bridged Vinyl Protocatechuic Acid SIVPA-L

[0073] The experimental method was the same as that in Example 2-1. Siloxane-bridged protocatechuic acid SIPA-S was changed to siloxane-bridged protocatechuic acid SIPA-L, and other reaction conditions remained unchanged. 167.5 g of the target monomer was obtained.

[0074] Example 2-4 Synthesis of Siloxane-Bridged Vinyl Protocatechuic Acid SIVPA-S

[0075] The experimental method was the same as that in Example 2-1. The catalyst benzyltrimethylammonium chloride was changed to tetrabutylammonium bromide, and other reaction conditions remained unchanged. 104.2 g of the target monomer was obtained.

[0076] Example 2-5 Synthesis of Siloxane-Bridged Vinyl Protocatechuic Acid SIVPA-S

[0077] The experimental method was the same as that in Example 2-1. The acid-binding agent potassium carbonate was changed to sodium carbonate, and other reaction conditions remained unchanged. 105.8 g of the target monomer was obtained.

[0078] Example 3-1 Synthesis of Siloxane-Bridged Protocatechuic Acid-Based Epoxy Resin Monomer SIPAEP-S

[0079] Take 100 mmol of siloxane-bridged vinyl protocatechuic acid SIVPA-S obtained in Example 2-1 and 1200 mmol of m-chloroperoxybenzoic acid, add them to 100 mL of dichloromethane and stir to mix evenly. React at 30 °C for 48 h. After dissolving the reaction system with dichloromethane, extract with water multiple times, dry with anhydrous sodium sulfate, and concentrate to obtain 115.9 g of a brown liquid siloxane-bridged protocatechuic acid-based epoxy resin monomer. The nuclear magnetic resonance spectrum of the obtained epoxy resin monomer is as Figure 1 shown, where A is the hydrogen spectrum and B is the carbon spectrum.

[0080] Example 3-2 Synthesis of Siloxane-Bridged Protocatechuic Acid-Based Epoxy Resin Monomer SIPAEP-M

[0081] The experimental method was the same as that in Example 3-1. Siloxane-bridged vinyl protocatechuic acid SIVPA-S was changed to siloxane-bridged vinyl protocatechuic acid SIVPA-M, and other reaction conditions remained unchanged. 156.5 g of the target monomer was obtained.

[0082] Example 3-3 Synthesis of Siloxane-Bridged Protocatechuic Acid-Based Epoxy Resin Monomer SIPAEP-L

[0083] The experimental method was the same as that in Example 3-1. Siloxane-bridged vinyl protocatechuic acid SIVPA-S was changed to siloxane-bridged vinyl protocatechuic acid SIVPA-L, and other reaction conditions remained unchanged. 173.1 g of the target monomer was obtained.

[0084] Example 3-4 Synthesis of Siloxane-Bridged Protocatechuic Acid-Based Epoxy Resin Monomer SIPAEP-S

[0085] The experimental method was the same as that in Example 3-1. The solvent dichloromethane was changed to chloroform, and other reaction conditions remained unchanged. 106.4 g of the target monomer was obtained.

[0086] Assignment of the NMR spectrum of SIPAEP: 1 H NMR(400MHz,DMSO-d 6 )δ7.60(s,2H),δ7.51(d,2H),δ7.12(d,2H),δ4.44(d,4H),δ4.29(tt,2H),δ3.67(t,4H),δ3.23(s,4H),δ2.87(d,12H),δ2.73(tt,6H),δ2.54(d,12H),δ1.54(tt,4H),δ0.50(t,4H),δ0.06(d,36H);

[0087] 13 C NMR(400MHz,DMSO-d 6 )δ166.20,151.12,145.61,122.37,121.04,121.04,116.91,115.74,73.94,72.70,72.15,71.05,67.93,66.28,63.70,39.98,23.60,14.36,0.80.

[0088] Measure the viscosity changes of SIPAEP-S, SIPAEP-M, SIPAEP-L and epoxy resin E51 at 1 - 100 s -1 and at 25 - 100 °C. The results are as Figure 2 shown. It can be seen from Figure 2 the data that the dynamic viscosity of SIPAEP-S at 25 °C is only 3.3 Pa·s, while that of bisphenol A epoxy resin E51 is 15.4 Pa·s. This shows that by introducing the siloxane segment in the present invention, the molecular chain rigidity is significantly reduced, thereby reducing the viscosity, and it exhibits the characteristics close to Newtonian fluid.

[0089] Example 4-1 Curing of Epoxy Resin

[0090] E51 is a representative commercially available bisphenol A epoxy resin, and its structure is shown in the following formula (a). Its epoxy value is 0.48 - 0.54.

[0091]

[0092] Take the siloxane-bridged protocatechuic acid-based epoxy resin monomers SIPAEP-S, SIPAEP-M, SIPAEP-L, and E51 from Example 3, and mix them with DDM in different proportions and heat to 100 °C. After ultrasonic melting into a uniform transparent solution, pour it into a polytetrafluoroethylene mold, where the molar ratio of N-H of DDM to the epoxy group is 1:1. The samples are cured at 120 °C for 2 h, heated to 160 °C and cured for 4 h, and then further heated to 200 °C and cured for 1 h. After cooling, the epoxy resins SIPAEP-S / DDM, SIPAEP-M / DDM, SIPAEP-L / DDM, and E51 / DDM are obtained.

[0093] Measure the dielectric constants of the obtained epoxy resins SIPAEP-S / DDM, SIPAEP-M / DDM, SIPAEP-L / DDM, and E51 / DDM. The results are as Figure 3 shown. It can be seen from the Figure 3 data that the dielectric constant of SIPAEP-L / DDM is 3.3 - 3.7 at 1 Hz - 1 MHz, which is significantly lower than that of E51 / DDM, which is 5.6 - 5.8.

[0094] Measure the contact angles of the obtained epoxy resins SIPAEP-S / DDM, SIPAEP-M / DDM, SIPAEP-L / DDM, E51 / DDM with water and diiodomethane, and calculate the surface energy by the Owens-Wendt method ( Figure 4 ). It can be seen from the Figure 4 data that the water contact angle of SIPAEP-L / DDM is 125°, which is significantly higher than that of E51 / DDM, which is 78°.

[0095] Conduct an impact strength test on the resin spline prepared in Example 4-1 ( Figure 5 , referring to the standard GB / T 1043-2008), and perform SEM scanning on its cross-section ( Figure 6 ). It can be seen from the Figure 5 data that the impact strength of SIPAEP-L / DDM is 50.7 kJ / m 2 , which is significantly higher than that of E51 / DDM, which is 19.9 kJ / m 2 . The cross-section structure of SIPAEP-L / DDM was observed by scanning electron microscope to be layered, similar to a scaly layered microarchitecture. This layered structure effectively dissipates the impact energy through a continuous layer-by-layer deformation mechanism, while delaying the development of cracks, thus greatly improving the fracture resistance. The impact strength data and the SEM results indicate that the toughness of the modified epoxy resin has been significantly improved.

[0096] In summary, a siloxane-bridged protocatechuic acid-based epoxy resin synthesized by the present invention can effectively improve the toughness and hydrophobicity of the epoxy resin, and reduce the dielectric constant and viscosity of the epoxy resin, having great application prospects.

[0097] All documents mentioned in the present invention are cited herein by reference as if each individual document was specifically and individually cited. Further, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present invention.

Claims

1. A siloxane-bridged protocatechuic acid-based epoxy resin monomer, characterized in that: Its chemical structure is shown in formula (III):

2. A method for preparing the siloxane-bridged protocatechuic acid-based epoxy resin monomer as claimed in claim 1, characterized in that: The preparation method comprises the following steps: Step (1), preparation of siloxane-bridged protocatechuic acid Protocatechuic acid and glycidoxypropyl-terminated polydimethylsiloxane are mixed in a solvent system of an alkaline catalyst, heated and reacted; after the reaction is completed, the solvent is purified and removed to obtain siloxane-bridged protocatechuic acid, the chemical structure of which is shown in formula (I); Step (2), preparation of siloxane-bridged vinyl-terminated protocatechuic acid The siloxane-bridged protocatechuic acid reacts with allyl bromide at room temperature in the presence of a phase transfer catalyst and an acid-binding agent using N,N-dimethylformamide as a solvent; after the reaction is completed, the solvent is purified and removed to obtain the siloxane-bridged vinyl-terminated protocatechuic acid, the chemical structure of which is shown in formula (II); Step (3), preparation of protocatechuic acid epoxy resin monomer The siloxane-bridged vinyl-terminated protocatechuic acid and meta-chloroperbenzoic acid are dissolved in a non-polar solvent and reacted at room temperature. After the reaction is completed, the solvent is purified and removed to obtain a siloxane-bridged protocatechuic acid-based epoxy resin monomer having a chemical structure shown in formula (III).

3. The preparation method according to claim 2, characterized in that: The kinematic viscosity of the glycidoxypropyl-terminated polydimethylsiloxane in step (1) is 8-35 cSt; the molar ratio of protocatechuic acid to the glycidoxypropyl-terminated polydimethylsiloxane is 2-3:

1.

4. The preparation method according to claim 2, characterized in that: In step (1), the alkaline catalyst is selected from one of sodium hydroxide, potassium carbonate, piperidine, pyridine and triethylamine; and the solvent is selected from one of acetone, dioxane, tetrahydrofuran and dimethylformamide.

5. The preparation method according to claim 2, characterized in that: In step (2), the phase transfer catalyst is selected from one of tetrabutylammonium bromide, benzyltriethylammonium chloride, hexadecyltrimethylammonium chloride and tetrabutylammonium chloride; and the acid binding agent is selected from one of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium bicarbonate.

6. The preparation method according to claim 2, characterized in that: In step (2), the molar ratio of propylene bromide to siloxane-bridged protocatechuic acid is 4-16:

1.

7. The preparation method according to claim 2, characterized in that: The molar ratio of chloroperoxybenzoic acid to siloxane-bridged vinyl-terminated protocatechuate in step (3) is 6-18:

1.

8. A siloxane-bridged protocatechuic acid-based epoxy resin, characterized in that: The invention is obtained by thermally curing the siloxane-bridged protocatechuic acid-based epoxy resin monomer according to claim 1.

9. Use of the siloxane-bridged protocatechuic acid-based epoxy resin monomer according to claim 1 or the siloxane-bridged protocatechuic acid-based epoxy resin according to claim 8 in the preparation of low-viscosity coatings.

10. Use of the siloxane-bridged protocatechuic acid-based epoxy resin monomer according to claim 1 or the siloxane-bridged protocatechuic acid-based epoxy resin according to claim 8 in the preparation of electronic packaging materials.

Images