Preparation method of multifunctional epoxy resin and its application in conductive adhesive

Abstract

The present invention relates to the field of epoxy resin materials, and in particular to a preparation method of a multifunctional epoxy resin and its application in conductive adhesives. The preparation method includes: introducing multiple propenyl groups on the dipentaerythritol molecule by reacting dipentaerythritol with allyl bromide, and then introducing multiple epoxy groups by reacting the introduced propenyl groups with the alkenyl groups on the 1-allyloxy-2,3-propylene oxide molecule under the action of an initiator, thereby preparing a multifunctional epoxy resin; the multifunctional structure can increase the crosslinking density of the epoxy resin-based adhesive after curing, thereby increasing the heat-resistant temperature and strength of the adhesive; the multifunctional epoxy resin with a branched structure formed on the basis of the multi-branched structure of dipentaerythritol can further increase the crosslinking density of the epoxy resin, thereby increasing the strength and heat resistance; the introduction of nano-silica can effectively improve the mechanical properties of the epoxy resin and enhance toughness.

Description

Technical Field

[0001] The present invention relates to the field of epoxy resin materials, and in particular to a preparation method of a multifunctional epoxy resin and its application in conductive adhesives. Background Art

[0002] Epoxy resin, a thermosetting polymer, contains two or more epoxy groups in its molecules. These groups undergo ring-opening and cross-linking under the action of a curing agent, and are used in a variety of applications, including architectural coatings and adhesives. Conductive adhesives, which exhibit a certain degree of conductivity after curing or drying, can connect various conductive materials, creating an electrical path between the connected materials. Epoxy resin-based conductive adhesives place high demands on the epoxy resin's heat resistance and mechanical properties.

[0003] Chinese patent CN115403741B discloses an epoxy resin and a method for synthesizing the same. One of the structural units of the epoxy resin is derived from a linear phenolic resin, and the second structural unit is derived from an epoxy ether. The resulting epoxy resin has a linear structure, few cross-linking sites, and its heat resistance needs to be improved. Chinese patent CN110204688B discloses a highly heat-resistant and high-toughness modified epoxy resin and a method for preparing the same. The modified epoxy resin has a high-functionality hyperbranched structure, which increases the overall cross-linking density of the epoxy resin and is combined with an aromatic curing agent containing a large number of rigid groups to improve the heat resistance of the epoxy resin. However, the toughness of the epoxy resin depends solely on the intramolecular stretching and slippage between the active functional groups of the modified epoxy resin with a hyperbranched structure under the action of external forces, and its mechanical properties need to be improved. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a multifunctional epoxy resin, a preparation method and an application in rubber to solve the problem in the prior art that the heat resistance and mechanical properties of epoxy resins need to be improved.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a multifunctional epoxy resin comprises the following steps:

[0007] Step 1: adding dipentaerythritol and potassium hydroxide to tetrahydrofuran, stirring and mixing to obtain a mixture;

[0008] Adding allyl bromide to tetrahydrofuran, stirring and mixing, to obtain an allyl bromide solution;

[0009] Adding the propylene bromide solution dropwise to the mixture for reaction, and performing rotary evaporation and purification after the reaction is completed to obtain propylene-modified dipentaerythritol;

[0010] Step 2: adding sodium dodecylsulfonate to deionized water, stirring, adding nano-silica, ultrasonically dispersing, and then dropping γ-methacryloxypropyltrimethoxysilane. After the dropwise addition is complete, reacting, filtering, washing, and drying to obtain alkenyl-modified nano-silica;

[0011] Mixing propenyl-modified dipentaerythritol, alkenyl-modified nano-silica, and 1-allyloxy-2,3-propylene oxide to obtain a mixed monomer;

[0012] The sodium bisulfite aqueous solution and deionized water are mixed, stirred and heated to a set temperature, and the mixed monomer and ammonium persulfate aqueous solution are added dropwise respectively to react. After the reaction is completed, the mixture is cooled, centrifuged, and washed to obtain a multifunctional epoxy resin.

[0013] Preferably, in step 1, the mass ratio of dipentaerythritol in the mixture to allyl bromide in the allyl bromide solution is 25.5:(75-80), and the reaction is carried out under reflux at 90-100° C. for 10-15 hours.

[0014] Preferably, in the step 1: when preparing the mixture, the mass ratio of dipentaerythritol, potassium hydroxide and tetrahydrofuran is 25.5:(3-6):(250-350), and the stirring and mixing conditions are stirring at a stirring speed of 300-500 r / min and a temperature of 60-80° C. for 1-2 h.

[0015] Preferably, in the step 1: when preparing the propylene bromide solution, the mass ratio of propylene bromide to tetrahydrofuran is 12:(50-75), and the stirring and mixing conditions are at a stirring speed of 300-500 r / min and at room temperature for 30-40 minutes.

[0016] Preferably, the purification comprises adding ethyl acetate for extraction, washing with a saturated aqueous sodium chloride solution, and finally drying with anhydrous sodium sulfate.

[0017] Preferably, in the step 2: when preparing alkenyl-modified nano-silica, the mass ratio of nano-silica, deionized water, sodium dodecylsulfonate, and γ-methacryloxypropyltrimethoxysilane is 60:(180-240):(1.2-2.4):(4.8-6), and the reaction conditions are 65-75°C for 6-8h.

[0018] Preferably, in the step 2: when preparing the multifunctional epoxy resin, the mass ratio of the mixed monomer, sodium bisulfite aqueous solution, deionized water, and ammonium persulfate aqueous solution is (115-120.5):(20-40):(100-150):(30-50).

[0019] Preferably, in the step 2: when preparing the multifunctional epoxy resin, the mass ratio of the propenyl-modified dipentaerythritol, the alkenyl-modified nano-silica, and the 1-allyloxy-2,3-epoxypropylene in the mixed monomer is 49.5:(3-6):(62.5-65);

[0020] The mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%;

[0021] The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 6-10%;

[0022] The mixed monomer and the aqueous ammonium persulfate solution are both added dropwise for 1-2 hours.

[0023] Preferably, in the step 2: when preparing the multifunctional epoxy resin, the reaction conditions are to react for 4-6 hours at a set temperature of 70-80°C.

[0024] The invention discloses an application of a multifunctional epoxy resin prepared by the above-mentioned method for preparing a multifunctional epoxy resin in a conductive adhesive.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] In the present invention, multiple propenyl groups are introduced by reacting dipentaerythritol with allyl bromide, and then multiple epoxy groups are introduced by reacting the propenyl groups with the alkenyl groups on the 1-allyloxy-2,3-propylene oxide molecule under the action of an initiator, thereby preparing a multifunctional epoxy resin. The introduction of multiple functional groups can increase the crosslinking density of the epoxy resin-based adhesive after curing, thereby improving the heat resistance temperature and strength of the adhesive.

[0027] In addition, the multi-functional epoxy resin with a branched structure formed on the basis of the multi-branched structure of dipentaerythritol has multiple epoxy groups that can participate in curing as cross-linking sites, which can further increase the cross-linking density of the epoxy resin, thereby improving its strength and heat resistance.

[0028] In the present invention, nano-silica is introduced to effectively improve the mechanical properties of epoxy resin and enhance toughness. At the same time, nano-silica is introduced into alkenyl groups by reacting with γ-methacryloxypropyltrimethoxysilane. Under the action of an initiator, the alkenyl groups participate in in-situ graft copolymerization, and the nano-silica is connected to the epoxy resin molecules with stable chemical bonds, thereby overcoming the problem of poor strengthening and toughening effects caused by poor compatibility and poor dispersion between the inorganic filler and the resin matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 1 is a flow chart of the preparation process of the multifunctional epoxy resin of the present invention;

[0030] Figure 2 This is a bar chart showing the heat resistance test results of the epoxy resins prepared in Examples 1-6 and Comparative Examples 1-2 of the present invention;

[0031] Figure 3 This is a bar chart showing the mechanical property test results of the epoxy resins prepared in Examples 1-6 and Comparative Examples 1-2 of the present invention. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment discloses a method for preparing a multifunctional epoxy resin, comprising the following steps:

[0035] Step 1: adding dipentaerythritol and potassium hydroxide to tetrahydrofuran, wherein the mass ratio of dipentaerythritol, potassium hydroxide and tetrahydrofuran is 25.5:3:250, stirring at a stirring speed of 300 r / min and a temperature of 60° C. for 2 h to obtain a mixture;

[0036] Adding allyl bromide to tetrahydrofuran in a mass ratio of 12:50, stirring at a stirring speed of 300 r / min at room temperature for 40 minutes to obtain an allyl bromide solution;

[0037] The propylene bromide solution was added dropwise to the mixture, and the mixture was refluxed at 90°C for 15 hours. After the reaction, the solvent tetrahydrofuran was removed by rotary evaporation at 50°C, and the mixture was extracted with ethyl acetate 3 times the weight of the propylene bromide solution and the mixture. The mixture was then washed with a saturated sodium chloride aqueous solution 5 times the weight of the propylene bromide solution and the mixture, and finally dried with anhydrous sodium sulfate to obtain propylene-modified dipentaerythritol.

[0038] The mass ratio of dipentaerythritol in the mixture to allyl bromide in the allyl bromide solution is 25.5:75;

[0039] Step 2: Sodium dodecyl sulfate is added to deionized water, and after stirring, nano-silica is added. After ultrasonic dispersion at a frequency of 40 kHz for 30 minutes, γ-methacryloxypropyltrimethoxysilane is added dropwise. The mass ratio of nano-silica, deionized water, sodium dodecyl sulfate, and γ-methacryloxypropyltrimethoxysilane is 60:180:1.2:4.8. The dropwise addition time of γ-methacryloxypropyltrimethoxysilane is 20 minutes. After the dropwise addition is completed, the mixture is reacted at a temperature of 65° C. for 8 hours. After the reaction is completed, the mixture is filtered, and the filtered residue is washed 3 times with deionized water and dried in a vacuum drying oven at 60° C. for 10 hours to obtain alkenyl-modified nano-silica.

[0040] Propylene-modified dipentaerythritol, alkenyl-modified nano-silica, and 1-allyloxy-2,3-propylene oxide are mixed, wherein the mass ratio of the propenyl-modified dipentaerythritol, the alkenyl-modified nano-silica, and the 1-allyloxy-2,3-propylene oxide is 49.5:3:62.5, to obtain a mixed monomer;

[0041] A sodium bisulfite aqueous solution and deionized water were mixed, stirred and heated to 70° C., and a mixed monomer and an ammonium persulfate aqueous solution were added dropwise, respectively. The mixed monomer and the ammonium persulfate aqueous solution were added dropwise for 1 hour each, and the mixture was reacted at 70° C. for 6 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The centrifugal sediment was washed with deionized water to obtain a multifunctional epoxy resin;

[0042] The mass ratio of the mixed monomer, sodium bisulfite aqueous solution, deionized water, and ammonium persulfate aqueous solution is 115:20:100:30;

[0043] The mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%;

[0044] The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 10%.

[0045] Example 2

[0046] This embodiment discloses a method for preparing a multifunctional epoxy resin, comprising the following steps:

[0047] Step 1, adding dipentaerythritol and potassium hydroxide to tetrahydrofuran, wherein the mass ratio of dipentaerythritol, potassium hydroxide and tetrahydrofuran is 25.5:6:350, stirring and mixing at a stirring speed of 500 r / min and a temperature of 80° C. for 1 hour to obtain a mixture;

[0048] Adding allyl bromide to tetrahydrofuran in a mass ratio of 12:75, stirring at a stirring speed of 500 r / min at room temperature for 30 minutes to obtain an allyl bromide solution;

[0049] The propylene bromide solution was added dropwise to the mixture, and the mixture was refluxed at 100°C for 10 hours. After the reaction, the solvent tetrahydrofuran was removed by rotary evaporation at 50°C, and the mixture was extracted with ethyl acetate 3 times the weight of the propylene bromide solution and the mixture. The mixture was then washed with a saturated sodium chloride aqueous solution 5 times the weight of the propylene bromide solution and the mixture, and finally dried with anhydrous sodium sulfate to obtain propylene-modified dipentaerythritol.

[0050] The mass ratio of dipentaerythritol in the mixture to allyl bromide in the allyl bromide solution is 25.5:80;

[0051] Step 2: Sodium dodecyl sulfate is added to deionized water, and after stirring, nano-silica is added. After ultrasonic dispersion at a frequency of 40 kHz for 30 minutes, γ-methacryloxypropyltrimethoxysilane is added dropwise. The mass ratio of nano-silica, deionized water, sodium dodecyl sulfate, and γ-methacryloxypropyltrimethoxysilane is 60:240:2.4:6. The dropwise addition time of γ-methacryloxypropyltrimethoxysilane is 30 minutes. After the dropwise addition is completed, the mixture is reacted at a temperature of 75° C. for 6 hours. After the reaction is completed, the mixture is filtered, and the filtered residue is washed 3 times with deionized water and dried in a vacuum drying oven at 60° C. for 10 hours to obtain alkenyl-modified nano-silica.

[0052] Mixing propenyl-modified dipentaerythritol, alkenyl-modified nano-silica, and 1-allyloxy-2,3-propylene oxide in a mass ratio of 49.5:6:65 to obtain a mixed monomer;

[0053] A sodium bisulfite aqueous solution and deionized water were mixed, stirred and heated to 80° C., and a mixed monomer and an ammonium persulfate aqueous solution were added dropwise, respectively. The mixed monomer and the ammonium persulfate aqueous solution were added dropwise for 2 hours each, and the mixture was reacted at 80° C. for 4 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The centrifugal sediment was washed with deionized water to obtain a multifunctional epoxy resin;

[0054] The mass ratio of the mixed monomer, sodium bisulfite aqueous solution, deionized water, and ammonium persulfate aqueous solution is 120.5:40:150:50;

[0055] The mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%;

[0056] The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 6%.

[0057] Example 3

[0058] This embodiment discloses a method for preparing a multifunctional epoxy resin, comprising the following steps:

[0059] Step 1, adding dipentaerythritol and potassium hydroxide to tetrahydrofuran, wherein the mass ratio of dipentaerythritol, potassium hydroxide and tetrahydrofuran is 25.5:3.5:270, stirring at a stirring speed of 400 r / min and a temperature of 70° C. for 1.5 hours to obtain a mixture;

[0060] Adding allyl bromide to tetrahydrofuran in a mass ratio of 12:55, stirring at a stirring speed of 400 r / min at room temperature for 35 minutes to obtain an allyl bromide solution;

[0061] The propylene bromide solution was added dropwise to the mixture, and the mixture was refluxed at 95°C for 12 hours. After the reaction, the solvent tetrahydrofuran was removed by rotary evaporation at 50°C, and the mixture was extracted with ethyl acetate 3 times the weight of the propylene bromide solution and the mixture. The mixture was then washed with a saturated sodium chloride aqueous solution 5 times the weight of the propylene bromide solution and the mixture, and finally dried with anhydrous sodium sulfate to obtain propylene-modified dipentaerythritol.

[0062] The mass ratio of dipentaerythritol in the mixture to allyl bromide in the allyl bromide solution is 25.5:76;

[0063] Step 2: Sodium dodecyl sulfate is added to deionized water, and after stirring, nano-silica is added. After ultrasonic dispersion at a frequency of 40 kHz for 30 minutes, γ-methacryloxypropyltrimethoxysilane is added dropwise. The mass ratio of nano-silica, deionized water, sodium dodecyl sulfate, and γ-methacryloxypropyltrimethoxysilane is 60:190:1.4:5. The dropwise addition time of γ-methacryloxypropyltrimethoxysilane is 30 minutes. After the dropwise addition is completed, the mixture is reacted at 70° C. for 7 hours. After the reaction is completed, the mixture is filtered, and the filtered residue is washed 3 times with deionized water and dried in a vacuum drying oven at 60° C. for 10 hours to obtain alkenyl-modified nano-silica.

[0064] Mixing propenyl-modified dipentaerythritol, alkenyl-modified nano-silica, and 1-allyloxy-2,3-propylene oxide in a mass ratio of 49.5:3.5:63 to obtain a mixed monomer;

[0065] A sodium bisulfite aqueous solution and deionized water were mixed, stirred and heated to 75° C., and a mixed monomer and an ammonium persulfate aqueous solution were added dropwise, respectively. The mixed monomer and the ammonium persulfate aqueous solution were added dropwise for 1.5 hours each. The mixture was reacted at 75° C. for 5 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The centrifugal sediment was washed with deionized water to obtain a multifunctional epoxy resin.

[0066] The mass ratio of the mixed monomer, sodium bisulfite aqueous solution, deionized water, and ammonium persulfate aqueous solution is 116:25:110:35;

[0067] The mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%;

[0068] The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 8%.

[0069] Example 4

[0070] This embodiment discloses a method for preparing a multifunctional epoxy resin, comprising the following steps:

[0071] Step 1, adding dipentaerythritol and potassium hydroxide to tetrahydrofuran, wherein the mass ratio of dipentaerythritol, potassium hydroxide and tetrahydrofuran is 25.5:4:290, stirring at a stirring speed of 400 r / min and a temperature of 70° C. for 1.5 hours to obtain a mixture;

[0072] Adding allyl bromide to tetrahydrofuran in a mass ratio of 12:60, stirring at a stirring speed of 400 r / min at room temperature for 35 minutes to obtain an allyl bromide solution;

[0073] The propylene bromide solution was added dropwise to the mixture, and the mixture was refluxed at 95°C for 12 hours. After the reaction, the solvent tetrahydrofuran was removed by rotary evaporation at 50°C, and the mixture was extracted with ethyl acetate 3 times the weight of the propylene bromide solution and the mixture. The mixture was then washed with a saturated sodium chloride aqueous solution 5 times the weight of the propylene bromide solution and the mixture, and finally dried with anhydrous sodium sulfate to obtain propylene-modified dipentaerythritol.

[0074] The mass ratio of dipentaerythritol in the mixture to allyl bromide in the allyl bromide solution is 25.5:77;

[0075] Step 2: Sodium dodecyl sulfate is added to deionized water, and after stirring, nano-silica is added. After ultrasonic dispersion at a frequency of 40 kHz for 30 minutes, γ-methacryloxypropyltrimethoxysilane is added dropwise. The mass ratio of nano-silica, deionized water, sodium dodecyl sulfate, and γ-methacryloxypropyltrimethoxysilane is 60:200:1.6:5.2. The dropwise addition time of γ-methacryloxypropyltrimethoxysilane is 30 minutes. After the dropwise addition is completed, the mixture is reacted at 70° C. for 7 hours. After the reaction is completed, the mixture is filtered, and the filtered residue is washed 3 times with deionized water and dried in a vacuum drying oven at 60° C. for 10 hours to obtain alkenyl-modified nano-silica.

[0076] Mixing propenyl-modified dipentaerythritol, alkenyl-modified nano-silica, and 1-allyloxy-2,3-propylene oxide in a mass ratio of 49.5:4:63.5 to obtain a mixed monomer;

[0077] A sodium bisulfite aqueous solution and deionized water were mixed, stirred and heated to 75° C., and a mixed monomer and an ammonium persulfate aqueous solution were added dropwise, respectively. The mixed monomer and the ammonium persulfate aqueous solution were added dropwise for 1.5 hours each. The mixture was reacted at 75° C. for 5 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The centrifugal sediment was washed with deionized water to obtain a multifunctional epoxy resin.

[0078] The mass ratio of the mixed monomer, sodium bisulfite aqueous solution, deionized water, and ammonium persulfate aqueous solution is 117.5:30:120:40;

[0079] The mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%;

[0080] The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 8%.

[0081] Example 5

[0082] This embodiment discloses a method for preparing a multifunctional epoxy resin, comprising the following steps:

[0083] Step 1, adding dipentaerythritol and potassium hydroxide to tetrahydrofuran, wherein the mass ratio of dipentaerythritol, potassium hydroxide and tetrahydrofuran is 25.5:5:310, stirring at a stirring speed of 400 r / min and a temperature of 70° C. for 1.5 hours to obtain a mixture;

[0084] Adding allyl bromide to tetrahydrofuran in a mass ratio of 12:65, stirring at a stirring speed of 400 r / min at room temperature for 35 minutes to obtain an allyl bromide solution;

[0085] The propylene bromide solution was added dropwise to the mixture, and the mixture was refluxed at 95°C for 12 hours. After the reaction, the solvent tetrahydrofuran was removed by rotary evaporation at 50°C, and the mixture was extracted with ethyl acetate 3 times the weight of the propylene bromide solution and the mixture. The mixture was then washed with a saturated sodium chloride aqueous solution 5 times the weight of the propylene bromide solution and the mixture, and finally dried with anhydrous sodium sulfate to obtain propylene-modified dipentaerythritol.

[0086] The mass ratio of dipentaerythritol in the mixture to allyl bromide in the allyl bromide solution is 25.5:78;

[0087] Step 2: Sodium dodecyl sulfate is added to deionized water, and after stirring, nano-silica is added. After ultrasonic dispersion at a frequency of 40 kHz for 30 minutes, γ-methacryloxypropyltrimethoxysilane is added dropwise. The mass ratio of nano-silica, deionized water, sodium dodecyl sulfate, and γ-methacryloxypropyltrimethoxysilane is 60:210:1.9:5.5. The dropwise addition time of γ-methacryloxypropyltrimethoxysilane is 30 minutes. After the dropwise addition is completed, the mixture is reacted at 70° C. for 7 hours. After the reaction is completed, the mixture is filtered, and the filtered residue is washed 3 times with deionized water and dried in a vacuum drying oven at 60° C. for 10 hours to obtain alkenyl-modified nano-silica.

[0088] Mixing propenyl-modified dipentaerythritol, alkenyl-modified nano-silica, and 1-allyloxy-2,3-propylene oxide in a mass ratio of 49.5:4:64 to obtain a mixed monomer;

[0089] A sodium bisulfite aqueous solution and deionized water were mixed, stirred and heated to 75° C., and a mixed monomer and an ammonium persulfate aqueous solution were added dropwise, respectively. The mixed monomer and the ammonium persulfate aqueous solution were added dropwise for 1.5 hours each. The mixture was reacted at 75° C. for 5 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The centrifugal sediment was washed with deionized water to obtain a multifunctional epoxy resin.

[0090] The mass ratio of the mixed monomer, sodium bisulfite aqueous solution, deionized water, and ammonium persulfate aqueous solution is 119:30:130:40;

[0091] The mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%;

[0092] The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 8%.

[0093] Example 6

[0094] This embodiment discloses a method for preparing a multifunctional epoxy resin, comprising the following steps:

[0095] Step 1, adding dipentaerythritol and potassium hydroxide to tetrahydrofuran, wherein the mass ratio of dipentaerythritol, potassium hydroxide and tetrahydrofuran is 25.5:5.5:330, stirring at a stirring speed of 400 r / min and a temperature of 70° C. for 1.5 hours to obtain a mixture;

[0096] Adding allyl bromide to tetrahydrofuran in a mass ratio of 12:70, stirring at a stirring speed of 400 r / min at room temperature for 35 minutes to obtain an allyl bromide solution;

[0097] The propylene bromide solution was added dropwise to the mixture, and the mixture was refluxed at 95°C for 12 hours. After the reaction, the solvent tetrahydrofuran was removed by rotary evaporation at 50°C, and the mixture was extracted with ethyl acetate 3 times the weight of the propylene bromide solution and the mixture. The mixture was then washed with a saturated sodium chloride aqueous solution 5 times the weight of the propylene bromide solution and the mixture, and finally dried with anhydrous sodium sulfate to obtain propylene-modified dipentaerythritol.

[0098] The mass ratio of dipentaerythritol in the mixture to allyl bromide in the allyl bromide solution is 25.5:79;

[0099] Step 2: Sodium dodecyl sulfate is added to deionized water, and after stirring, nano-silica is added. After ultrasonic dispersion at a frequency of 40 kHz for 30 minutes, γ-methacryloxypropyltrimethoxysilane is added dropwise. The mass ratio of nano-silica, deionized water, sodium dodecyl sulfate, and γ-methacryloxypropyltrimethoxysilane is 60:225:2.2:5.8. The dropwise addition time of γ-methacryloxypropyltrimethoxysilane is 30 minutes. After the dropwise addition is completed, the mixture is reacted at 70° C. for 7 hours. After the reaction is completed, the mixture is filtered, and the filtered residue is washed 3 times with deionized water and dried in a vacuum drying oven at 60° C. for 10 hours to obtain alkenyl-modified nano-silica.

[0100] Mixing propenyl-modified dipentaerythritol, alkenyl-modified nano-silica, and 1-allyloxy-2,3-propylene oxide in a mass ratio of 49.5:5:64.5 to obtain a mixed monomer;

[0101] A sodium bisulfite aqueous solution and deionized water were mixed, stirred and heated to 75° C., and a mixed monomer and an ammonium persulfate aqueous solution were added dropwise, respectively. The mixed monomer and the ammonium persulfate aqueous solution were added dropwise for 1.5 hours each. The mixture was reacted at 75° C. for 5 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The centrifugal sediment was washed with deionized water to obtain a multifunctional epoxy resin.

[0102] The mass ratio of the mixed monomer, sodium bisulfite aqueous solution, deionized water, and ammonium persulfate aqueous solution is 120:35:140:45;

[0103] The mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%;

[0104] The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 8%.

[0105] Comparative Example 1

[0106] This comparative example discloses a method for preparing a multifunctional epoxy resin, comprising the following steps:

[0107] Step 1: adding dipentaerythritol and potassium hydroxide to tetrahydrofuran, wherein the mass ratio of dipentaerythritol, potassium hydroxide and tetrahydrofuran is 25.5:3:250, stirring at a stirring speed of 300 r / min and a temperature of 60° C. for 2 h to obtain a mixture;

[0108] Adding allyl bromide to tetrahydrofuran in a mass ratio of 12:50, stirring at a stirring speed of 300 r / min at room temperature for 40 minutes to obtain an allyl bromide solution;

[0109] The propylene bromide solution was added dropwise to the mixture, and the mixture was refluxed at 90°C for 15 hours. After the reaction, the solvent tetrahydrofuran was removed by rotary evaporation at 50°C, and the mixture was extracted with ethyl acetate 3 times the weight of the propylene bromide solution and the mixture. The mixture was then washed with a saturated sodium chloride aqueous solution 5 times the weight of the propylene bromide solution and the mixture, and finally dried with anhydrous sodium sulfate to obtain propylene-modified dipentaerythritol.

[0110] The mass ratio of dipentaerythritol in the mixture to allyl bromide in the allyl bromide solution is 25.5:75;

[0111] Step 2: mixing propenyl-modified dipentaerythritol and 1-allyloxy-2,3-propylene oxide, wherein the mass ratio of propenyl-modified dipentaerythritol to 1-allyloxy-2,3-propylene oxide is 49.5:62.5, to obtain a mixed monomer;

[0112] A sodium bisulfite aqueous solution and deionized water were mixed, stirred and heated to 70° C., and a mixed monomer and an ammonium persulfate aqueous solution were added dropwise, respectively. The mixed monomer and the ammonium persulfate aqueous solution were added dropwise for 1 hour each, and the mixture was reacted at 70° C. for 6 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The centrifugal sediment was washed with deionized water to obtain a multifunctional epoxy resin;

[0113] The mass ratio of the mixed monomer, sodium bisulfite aqueous solution, deionized water, and ammonium persulfate aqueous solution is 115:20:100:30;

[0114] The mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%;

[0115] The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 10%.

[0116] Comparative Example 2

[0117] This comparative example discloses a method for preparing a multifunctional epoxy resin, comprising the following steps:

[0118] Step 1, sodium dodecyl sulfate is added to deionized water, and after stirring, nano-silica is added. After ultrasonic dispersion at a frequency of 40 kHz for 30 minutes, γ-methacryloxypropyltrimethoxysilane is added dropwise. The mass ratio of nano-silica, deionized water, sodium dodecyl sulfate, and γ-methacryloxypropyltrimethoxysilane is 60:180:1.2:4.8. The dropwise addition time of γ-methacryloxypropyltrimethoxysilane is 20 minutes. After the dropwise addition is completed, the mixture is reacted at a temperature of 65° C. for 8 hours. After the reaction is completed, the mixture is filtered, and the filtered residue is washed with deionized water 3 times and dried in a vacuum drying oven at 60° C. for 10 hours to obtain alkenyl-modified nano-silica;

[0119] Step 2: mixing alkenyl-modified nano-silica and 1-allyloxy-2,3-propylene oxide, wherein the mass ratio of alkenyl-modified nano-silica to 1-allyloxy-2,3-propylene oxide is 3:112, to obtain a mixed monomer;

[0120] A sodium bisulfite aqueous solution and deionized water were mixed, stirred and heated to 70° C., and a mixed monomer and an ammonium persulfate aqueous solution were added dropwise, respectively. The mixed monomer and the ammonium persulfate aqueous solution were added dropwise for 1 hour each, and the mixture was reacted at 70° C. for 6 hours. After the reaction was completed, the mixture was cooled to room temperature and centrifuged. The centrifugal sediment was washed with deionized water to obtain a multifunctional epoxy resin;

[0121] The mass ratio of the mixed monomer, sodium bisulfite aqueous solution, deionized water, and ammonium persulfate aqueous solution is 115:20:100:30;

[0122] The mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%;

[0123] The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 10%.

[0124] In the above embodiments and comparative examples: dipentaerythritol was purchased from Shanghai Jizhi Biochemical Technology Co., Ltd., CAS No.: 126-58-9; allyl bromide was purchased from Nanjing Chemical Reagent Co., Ltd., CAS No.: 106-95-6; nanosilica was purchased from Zhejiang Manli Nanotechnology Co., Ltd., model: ML-SiO2-N100, average particle size: 100 nm; γ-methacryloyloxypropyltrimethoxysilane was purchased from Shenzhen Yinyi Chemical Co., Ltd., CAS No.: 2530-85-0; 1-allyloxy-2,3-propylene oxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 106-92-3.

[0125] Test example

[0126] The epoxy resins prepared in the above examples and comparative examples were tested for performance:

[0127] (1) Heat resistance: The epoxy resins prepared in Examples 1-6 and Comparative Examples 1-2 were added to acetone to obtain an epoxy resin solution with a solid content of 50%. To the epoxy resin solution, 25% by mass of the epoxy resin solution of diethylenetriamine as a curing agent and 5% by mass of the epoxy resin solution of N-ethylimidazole as a curing accelerator were added. After mixing, the mixture was cured at room temperature for 2 days, at 90°C for 5 hours, and at 100°C for 8 hours to obtain a sample. The 5% weight loss temperature of the sample was measured by thermogravimetry (nitrogen range, heating rate of 10°C / min). The test results are shown in Table 1:

[0128] Table 1

[0129]

[0130] As can be seen from Table 1, the epoxy resin prepared by the present invention has good heat resistance. In the present invention, dipentaerythritol is reacted with propylene bromide and 1-allyloxy-2,3-propylene oxide in sequence to generate a multifunctional epoxy resin. By introducing multifunctional groups, the crosslinking density of the epoxy resin-based adhesive after curing can be increased, and the heat resistance temperature of the adhesive is increased. In addition, the multifunctional epoxy resin is a branched structure with multiple epoxy groups that can participate in curing as crosslinking sites, which can further increase the crosslinking density of the epoxy resin, thereby improving the heat resistance. Compared with Example 1, nano-silica was not introduced in Comparative Example 1, which mainly affected the mechanical properties of the epoxy resin and had no significant effect on the heat resistance of the epoxy resin. In the epoxy resin prepared in Comparative Example 2, dipentaerythritol was not added, that is, the epoxy resin was a non-branched structure, the crosslinking density of the epoxy resin was reduced, and the heat resistance decreased.

[0131] (2) Mechanical properties: The epoxy resins prepared in Examples 1-6 and Comparative Examples 1-3 were prepared into test specimens according to the method of Test Example (1). The impact strength of the test specimens was measured with reference to the standard GB / T1843-2008 "Determination of Izod Impact Strength of Plastics". The tensile strength of the test specimens was measured with reference to the standard GB / T2567-2008 "Test Method for Properties of Cast Resin Structures". The test results are shown in Table 2:

[0132] Table 2

[0133]

[0134] As shown in Table 2, the epoxy resin prepared by the present invention has good mechanical properties. The multi-branched structure of dipentaerythritol and the multifunctional epoxy resin with a branched structure formed on its structure have multiple epoxy groups that can participate in curing as cross-linking sites, which can further improve the cross-linking density of the epoxy resin, thereby improving the strength. In addition, the introduction of nano-silicon dioxide can effectively improve the mechanical properties of the epoxy resin and has the effect of strengthening and toughening. Compared with Example 1, nano-silicon dioxide was not introduced in Comparative Example 1, and the impact strength and tensile strength of the epoxy resin were significantly reduced; in the epoxy resin prepared in Comparative Example 2, dipentaerythritol was not added, that is, the epoxy resin was a non-branched structure, the cross-linking density of the epoxy resin was reduced, the tensile strength was weakened, and as the cross-linking density decreased, the brittleness of the cured product decreased, and the impact strength increased slightly.

[0135] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a multifunctional epoxy resin, characterized in that: The following steps are involved: Step 1: adding dipentaerythritol and potassium hydroxide to tetrahydrofuran, stirring and mixing to obtain a mixture; Wherein, the mass ratio of dipentaerythritol, potassium hydroxide and tetrahydrofuran is 25.5:(3-6):(250-350); Adding allyl bromide to tetrahydrofuran, stirring and mixing, to obtain an allyl bromide solution; Wherein, the mass ratio of allyl bromide to tetrahydrofuran is 12:(50-75); Adding the propylene bromide solution dropwise to the mixture for reaction, and performing rotary evaporation and purification after the reaction is completed to obtain propylene-modified dipentaerythritol; The mass ratio of dipentaerythritol in the mixture to allyl bromide in the allyl bromide solution is 25.5:(75-80); Step 2: Sodium dodecylsulfonate is added to deionized water, and after stirring, nano-silica is added. After ultrasonic dispersion, γ-methacryloxypropyltrimethoxysilane is added dropwise. After the addition is complete, the mixture is reacted. After the reaction is completed, the mixture is filtered, washed, and dried to obtain alkenyl-modified nano-silica. The mass ratio of nano-silica, deionized water, sodium dodecylsulfonate, and γ-methacryloxypropyltrimethoxysilane is 60:(180-240):(1.2-2.4):(4.8-6); Mixing propenyl-modified dipentaerythritol, alkenyl-modified nano-silica, and 1-allyloxy-2,3-propylene oxide to obtain a mixed monomer; Wherein, the mass ratio of propenyl-modified dipentaerythritol, alkenyl-modified nano-silica, and 1-allyloxy-2,3-propylene oxide is 49.5:(3-6):(62.5-65); The sodium bisulfite aqueous solution and deionized water are mixed, stirred and heated to a set temperature, and the mixed monomer and ammonium persulfate aqueous solution are added dropwise respectively, and reacted. After the reaction is completed, the mixture is cooled, centrifuged, and washed to obtain a multifunctional epoxy resin; The mass ratio of the mixed monomer, the sodium bisulfite aqueous solution, the deionized water, and the ammonium persulfate aqueous solution is (115-120.5):(20-40):(100-150):(30-50).

2. The method for preparing a multifunctional epoxy resin according to claim 1, wherein: In the step 1, the reaction conditions are reflux reaction at 90-100° C. for 10-15 hours.

3. The method for preparing a multifunctional epoxy resin according to claim 1, wherein: In the step 1, when preparing the mixture, the stirring and mixing conditions are: stirring at a speed of 300-500 r / min and a temperature of 60-80° C. for 1-2 hours.

4. The method for preparing a multifunctional epoxy resin according to claim 1, wherein: In the step 1, when preparing the propylene bromide solution, the stirring and mixing conditions are: stirring and mixing at a stirring speed of 300-500 r / min and at room temperature for 30-40 minutes.

5. The method for preparing a multifunctional epoxy resin according to claim 1, wherein: In the step 2, when preparing the alkenyl-modified nano-silica, the reaction conditions are 65-75° C. and 6-8 hours.

6. The method for preparing a multifunctional epoxy resin according to claim 1, wherein: In the step 2: when preparing the multifunctional epoxy resin, the mass percentage of sodium bisulfite in the sodium bisulfite aqueous solution is 5%; The mass percentage of ammonium persulfate in the ammonium persulfate aqueous solution is 6-10%; The mixed monomer and the aqueous ammonium persulfate solution are both added dropwise for 1-2 hours.

7. The method for preparing a multifunctional epoxy resin according to claim 1, wherein: In the step 2, when preparing the multifunctional epoxy resin, the reaction conditions are to react for 4-6 hours at a set temperature of 70-80°C.

8. A multifunctional epoxy resin prepared by the method for preparing a multifunctional epoxy resin according to any one of claims 1 to 7.

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