An end group isocyanate polyurethane prepolymer toughened epoxy resin and its preparation method and application

Abstract

This invention provides an epoxy resin toughened with an isocyanate-terminated polyurethane prepolymer, its preparation method, and its application, belonging to the field of epoxy resin toughening technology. The epoxy resin toughened with an isocyanate-terminated polyurethane prepolymer provided by this invention is prepared from the following raw materials: an isocyanate-terminated polyurethane prepolymer, epoxy resin, and a curing agent; the mass ratio of the isocyanate-terminated polyurethane prepolymer, curing agent, and epoxy resin is (5~20):(25~35):100. This invention introduces an isocyanate (NCO) polyurethane prepolymer into the epoxy resin system. The NCO end groups react with the -OH groups of the epoxy resin to form an epoxy resin with a cross-linked network. Simultaneously, by controlling the amount of each raw material, the toughness of the epoxy resin is improved, and the impact strength is significantly enhanced.

Description

Technical Field

[0001] This invention belongs to the field of epoxy resin toughening technology, specifically relating to an epoxy resin toughened with an end-group isocyanate polyurethane prepolymer, its preparation method, and its application. Background Technology

[0002] Epoxy resins are widely used in electronic packaging due to their excellent mechanical strength, electrical insulation, temperature resistance, corrosion resistance, and transparency. However, they are prone to stress concentration and cracking under impact or vibration loads, thus jeopardizing packaging reliability. To overcome this bottleneck, numerous studies have focused on improving the toughness of epoxy resins, with polyurethane becoming a commonly used toughening material due to its excellent elasticity, high impact strength, and wide operating temperature range. However, the impact toughness of polyurethane-toughened epoxy resins in existing technologies still needs further improvement. Summary of the Invention

[0003] The purpose of this invention is to provide an epoxy resin toughened with an isocyanate-terminated polyurethane prepolymer, its preparation method, and its application. The epoxy resin provided by this invention exhibits better toughness (impact strength).

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an epoxy resin toughened by an end-isocyanate polyurethane prepolymer, which is prepared from the following raw materials: an end-isocyanate polyurethane prepolymer, an epoxy resin, and a curing agent. The mass ratio of the end-group isocyanate polyurethane prepolymer, curing agent and epoxy resin is (5~20):(25~35):100.

[0005] Preferably, the isocyanate group content in the terminal isocyanate polyurethane prepolymer is 0.1-8%.

[0006] Preferably, the method for preparing the terminal isocyanate polyurethane prepolymer includes: mixing polyether polyol and toluene diisocyanate, and carrying out a prepolymerization reaction to obtain the terminal isocyanate polyurethane prepolymer.

[0007] Preferably, the number average molecular weight of the polyether polyol is 1000~4000 g / mol.

[0008] Preferably, the temperature of the prepolymerization reaction is 75~85℃.

[0009] Preferably, the epoxy resin is a bisphenol A type epoxy resin.

[0010] Preferably, the curing agent is an aromatic amine curing agent.

[0011] Preferably, the aromatic amine curing agent includes one or more of m-phenylenediamine, 4,4-diaminodiphenyl sulfone, and diaminodiphenylmethane.

[0012] The present invention also provides a method for preparing epoxy resin toughened with the end-isocyanate polyurethane prepolymer described in the above technical solution, comprising: The isocyanate-terminated polyurethane prepolymer is mixed with epoxy resin and subjected to an addition reaction. Then, a curing agent is added for curing to obtain epoxy resin toughened with isocyanate-terminated polyurethane prepolymer.

[0013] The present invention also provides the application of epoxy resin toughened with terminal isocyanate polyurethane prepolymer as described in the above technical solution or epoxy resin toughened with terminal isocyanate polyurethane prepolymer prepared by the preparation method described in the above technical solution in the field of electronic packaging.

[0014] This invention provides an epoxy resin toughened with an end-group isocyanate polyurethane prepolymer, prepared from the following raw materials: an end-group isocyanate polyurethane prepolymer, an epoxy resin, and a curing agent; the mass ratio of the end-group isocyanate polyurethane prepolymer, curing agent, and epoxy resin is (5~20):(25~35):100. This invention introduces an end-group isocyanate (NCO) polyurethane prepolymer into the epoxy resin system. The end-group NCO in the end-group isocyanate polyurethane prepolymer reacts with the -OH groups of the epoxy resin to form an epoxy resin with a cross-linked network. Simultaneously, by controlling the amount of each raw material, the toughness of the epoxy resin is improved, and the impact strength is significantly enhanced. The results of the embodiments show that the impact strength of the epoxy resin toughened with the end-group isocyanate polyurethane prepolymer provided by this invention can reach up to 35 kJ·m. 2 . Attached Figure Description

[0015] Figure 1 This is a diagram illustrating the reaction process of the terminal isocyanate polyurethane prepolymer in Example 1; Figure 2 This is a schematic diagram of the reaction process between the terminal isocyanate polyurethane prepolymer and epoxy resin in Example 1. Detailed Implementation

[0016] This invention provides an epoxy resin toughened by an end-group isocyanate polyurethane prepolymer, which is prepared from the following raw materials: end-group isocyanate polyurethane prepolymer, epoxy resin and curing agent.

[0017] In this invention, the raw materials for preparing the epoxy resin toughened by the terminal isocyanate polyurethane prepolymer include the terminal isocyanate polyurethane prepolymer.

[0018] In this invention, the content of isocyanate groups (NCO) in the terminal isocyanate polyurethane prepolymer is preferably 0.1% to 8%. As one embodiment, the NCO content can specifically be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%. By controlling the NCO content within the above range, this invention enables the formation of a suitable cross-linking network structure with the -OH groups in the epoxy resin, further improving the toughness of the epoxy resin.

[0019] In this invention, the preferred method for preparing the terminal isocyanate polyurethane prepolymer includes: mixing a polyether polyol and toluene diisocyanate (TDI) and carrying out a prepolymerization reaction to obtain the terminal isocyanate polyurethane prepolymer. This invention uses TDI, which has better toughening effects compared to other isocyanates, while also exhibiting high reactivity, requiring no catalyst, low cost, and ease of processing.

[0020] In this invention, the polyether polyol is preferably polypropylene glycol (PPG); the number-average molecular weight of the polyether polyol is preferably 1000~4000 g / mol. As one embodiment, the number-average molecular weight of the polyether polyol can specifically be 1000 g / mol, 2000 g / mol, 3000 g / mol, or 4000 g / mol. This invention uses polypropylene glycol, which, during the curing process, forms a microphase separation structure of suitable size, achieving a synergistic effect of multiple toughening mechanisms. Simultaneously, the small and uniformly distributed phase regions in the system help maintain high modulus and strength. The molecular weight of PPG significantly affects the microphase separation structure and toughening mechanism of epoxy resin by controlling the soft segment length and system compatibility. Low molecular weight PPG, due to its good compatibility, only produces limited phase separation, resulting in minimal toughness improvement; while high molecular weight PPG can form a distinct rubber phase and promote cavitation toughening, it easily leads to phase region coarsening and interface weakening, thereby causing a decrease in mechanical properties. In contrast, medium molecular weight PPG (e.g., 1000-2000) can construct fine and uniform microphase separation structures. Through the synergistic effect of multiple mechanisms such as crack deflection, bifurcation, and matrix shear yielding, it can achieve an optimized balance between strength and toughness. By controlling the molecular weight of PPG within the above range, this invention can further improve the toughness of epoxy resin while maintaining good strength.

[0021] The present invention preferably determines the mass of polyether polyol and toluene diisocyanate according to Formula I to ensure the content of isocyanate groups in the end-group isocyanate polyurethane prepolymer.

[0022] Formula I; In Formula I, NCO% represents the isocyanate group content in the isocyanate-terminated polyurethane prepolymer, and m RNCO f RNCO M RNCOThe values ​​of m represent the mass, functionality, and molar mass of toluene diisocyanate, respectively. ROH f ROH M ROH These are the mass, functionality, and molecular weight of the polyether polyol.

[0023] The present invention does not have a specific limitation on the amount of polyether polyol and toluene diisocyanate used; the amount can be adjusted according to the content of isocyanate groups in the desired end-group isocyanate polyurethane prepolymer.

[0024] In this invention, the polyether polyol is preferably subjected to dehydration treatment and cooling sequentially before use; the temperature of the dehydration treatment is preferably 110~130℃, more preferably 120℃; the time of the dehydration treatment is preferably 2~3h; and the final temperature of the cooling is preferably the temperature of the prepolymerization reaction.

[0025] In this invention, the temperature of the prepolymerization reaction is preferably 75-85°C, more preferably 80°C; the prepolymerization reaction is preferably carried out under stirring conditions. This invention does not impose any special limitations on the stirring method and rate; stirring schemes well known to those skilled in the art can be used. This invention does not impose any special limitations on the time of the prepolymerization reaction, as long as the isocyanate group content in the post-reaction isocyanate polyurethane prepolymer is within the required range.

[0026] The present invention preferably uses the di-n-butylamine titration method to detect the isocyanate group content in the prepolymerization reaction product.

[0027] As one implementation method, the method for detecting isocyanate group content by di-n-butylamine titration is as follows: Take 1.0 g of the prepolymerization product into a dry iodine flask, add 10 mL of acetone to dissolve it, then add 20.00 mL of di-n-butylamine-acetone solution (the concentration of di-n-butylamine is 0.1 mol / L), stopper and seal, shake, and let stand for 30 min. Add 3 drops of bromocresol green indicator, and titrate with 0.1 mol / L hydrochloric acid standard solution to the endpoint (from blue to yellow). At the same time, perform a blank test, and calculate the isocyanate group content according to Formula II.

[0028] Formula II; In Formula II, V0 is the volume of HCl consumed by the blank sample (mL), V is the volume of HCl consumed by the sample (mL), c is the concentration of the HCl standard solution (mol / L), and m is the sample amount (g).

[0029] In one embodiment, the prepolymerization reaction takes 3 hours.

[0030] In this invention, the raw materials for preparing the epoxy resin toughened by the terminal isocyanate polyurethane prepolymer also include epoxy resin.

[0031] In this invention, the epoxy resin is preferably a bisphenol A type epoxy resin, more preferably an E-51 bisphenol A type epoxy resin or an E-44 bisphenol A type epoxy resin. Bisphenol A type epoxy resin has high tensile strength and flexural strength, and good processability, but poor toughness. Toughening it improves its overall performance.

[0032] In this invention, the raw materials for preparing the epoxy resin toughened by the end-isocyanate polyurethane prepolymer also include a curing agent.

[0033] In this invention, the curing agent is preferably an aromatic amine curing agent; the aromatic amine curing agent preferably includes one or more of m-phenylenediamine (m-PDA), 4,4-diaminodiphenyl sulfone (DDS) and diaminodiphenylmethane (DDM).

[0034] In this invention, the mass ratio of the end-group isocyanate polyurethane prepolymer, curing agent, and epoxy resin is (5~20):(25~35):100. As one embodiment, the mass ratio of the end-group isocyanate polyurethane prepolymer, curing agent, and epoxy resin can specifically be 5:30:100, 10:30:100, 15:30:100, or 20:30:100. This invention controls the mass ratio of the three components to further improve the toughness of the epoxy resin.

[0035] This invention introduces end-group isocyanate (NCO) polyurethane prepolymer into an epoxy resin system. The end-group NCO reacts with the -OH group of the epoxy resin to form an epoxy resin with a cross-linked network. At the same time, by controlling the type and amount of each raw material, the toughness of the epoxy resin is improved, and the impact strength is significantly enhanced while maintaining good strength.

[0036] The present invention also provides a method for preparing epoxy resin toughened with the end-isocyanate polyurethane prepolymer described in the above technical solution, comprising: The isocyanate-terminated polyurethane prepolymer is mixed with epoxy resin and subjected to an addition reaction. Then, a curing agent is added for curing to obtain epoxy resin toughened with isocyanate-terminated polyurethane prepolymer.

[0037] In this invention, the preferred method for mixing the end-group isocyanate polyurethane prepolymer with the epoxy resin is to preheat the epoxy resin at 75-85°C for 25-30 minutes, and then add the end-group isocyanate polyurethane prepolymer at 135-145°C. This invention first preheats the epoxy resin, reducing its viscosity and facilitating subsequent mixing with the end-group isocyanate polyurethane prepolymer.

[0038] In this invention, the temperature of the addition reaction is preferably 135-145°C, more preferably 140°C; the time of the addition reaction is preferably 110-130 min, more preferably 120 min; and the addition reaction is preferably carried out under stirring conditions. This invention does not impose any particular limitation on the stirring method and rate; stirring techniques well-known to those skilled in the art can be used. By controlling the temperature and time of the addition reaction within the above-mentioned ranges, this invention achieves a suitable reaction rate and further improves the toughness of the epoxy resin.

[0039] After the addition reaction is completed, the present invention preferably adds a curing agent to the product after the addition reaction, then vacuums the product for 25 to 35 minutes under stirring conditions, and then pours it into a mold for curing.

[0040] This invention does not impose any special limitations on the stirring and vacuuming operations; any technical solution well-known to those skilled in the art can be used. The vacuuming process in this invention removes air bubbles from the system, preventing the formation of voids after solidification.

[0041] The present invention does not impose any special limitations on the shape and size of the mold; it can be selected according to actual needs.

[0042] In this invention, the curing temperature is preferably 170~190℃, more preferably 180℃; the curing time is preferably 4~4.5h. By limiting the curing temperature and time to the above ranges, this invention can further improve the toughness and other properties of epoxy resin.

[0043] After curing, the present invention preferably cools the cured product to obtain epoxy resin toughened with end-group isocyanate polyurethane prepolymer.

[0044] The present invention does not impose any special limitations on the cooling operation; any technical solution known to those skilled in the art can be used to cool to room temperature.

[0045] The present invention also provides the application of epoxy resin toughened with terminal isocyanate polyurethane prepolymer as described in the above technical solution or epoxy resin toughened with terminal isocyanate polyurethane prepolymer prepared by the preparation method described in the above technical solution in the field of electronic packaging.

[0046] The present invention does not impose any special limitations on the operation of the application, and any technical solution known to those skilled in the art can be used.

[0047] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0048] Example 1 An epoxy resin toughened by an end-isocyanate polyurethane prepolymer is prepared from an end-isocyanate polyurethane prepolymer (isocyanate group content of 4%), an epoxy resin (E-44 type bisphenol A type epoxy resin) and a curing agent (4,4-diaminodiphenyl sulfone), wherein the mass ratio of the end-isocyanate polyurethane prepolymer, the curing agent and the epoxy resin is 5:30:100. The preparation method of the terminal isocyanate polyurethane prepolymer is as follows: 78.1g of polypropylene glycol (number average molecular weight of 1000g / mol) is dehydrated at 120℃ for 2.5h, and then cooled to 80℃. According to Formula I, 21.9g of toluene diisocyanate (isocyanate group content of 4%) is added, and the reaction is carried out at 80℃. The isocyanate group content is detected by di-n-butylamine titration. When the reaction time is 3h, the isocyanate group content in the prepolymer reaches the preset value, and the terminal isocyanate polyurethane prepolymer is obtained. The preparation method of epoxy resin toughened by end-group isocyanate polyurethane prepolymer is as follows: preheat epoxy resin at 80℃ for 30 min, then heat and stir it in an oil bath at 140℃, add end-group isocyanate polyurethane prepolymer, react at 140℃ for 2 h, add curing agent, and use a vacuum pump to evacuate for 30 min while stirring, pour into a mold, cure at 180℃ for 4 h, and cool to obtain epoxy resin toughened by end-group isocyanate polyurethane prepolymer.

[0049] The reaction process of the terminal isocyanate polyurethane prepolymer in Example 1 is as follows: Figure 1 As shown; a schematic diagram of the reaction process between the terminal isocyanate polyurethane prepolymer and epoxy resin in Example 1 is shown. Figure 2 As shown.

[0050] Example 2 The only difference from Example 1 is that the mass ratio of the end-group isocyanate polyurethane prepolymer, curing agent and epoxy resin is 10:30:100.

[0051] Example 3 The only difference from Example 1 is that the mass ratio of the end-group isocyanate polyurethane prepolymer, curing agent and epoxy resin is 15:30:100.

[0052] Example 4 The only difference from Example 1 is that the mass ratio of the end-group isocyanate polyurethane prepolymer, curing agent and epoxy resin is 20:30:100.

[0053] Example 5 The difference from Example 1 is that the number average molecular weight of polypropylene glycol is 2000 g / mol when preparing the end-isocyanate polyurethane prepolymer, and the mass ratio of end-isocyanate polyurethane prepolymer, curing agent and epoxy resin is 15:30:100.

[0054] Example 6 The difference from Example 1 is that the isocyanate group content in the terminal isocyanate polyurethane prepolymer is 2%, and the mass ratio of the terminal isocyanate polyurethane prepolymer, curing agent and epoxy resin is 15:30:100.

[0055] Example 7 The difference from Example 1 is that the isocyanate group content in the end-isocyanate polyurethane prepolymer is 6%, and the mass ratio of end-isocyanate polyurethane prepolymer, curing agent and epoxy resin is 15:30:100.

[0056] Comparative Example 1 The only difference from Example 1 is that the mass ratio of the end-group isocyanate polyurethane prepolymer, curing agent and epoxy resin is 0:30:100, that is, no end-group isocyanate polyurethane prepolymer is added.

[0057] The epoxy resins prepared in Examples 1-7 and Comparative Example 1 were subjected to performance tests according to the following test methods or standards, and the results are shown in Table 1.

[0058] Impact strength test: The standard GB / T 1843-2008, plastic-cantilever beam impact strength mode, was adopted. The JYM17XJJ-50 impact testing machine (size 80mm×10mm×4mm) was used to conduct unnotched impact tests. Ten tests were performed on each group of samples and the average value was taken.

[0059] Tensile strength test: According to GB / T 1040.2-2006 standard, the standard dumbbell-shaped spline is used, with a gauge length of 200mm×10mm×4mm, and the tensile rate is 2mm / min.

[0060] Thermogravimetric analysis (TG): A HITACHI STA200 thermogravimetric analyzer was used. The heating rate was 10℃ / min, the temperature range was 40~800℃, the mass of the test sample was 5~10mg, the flow rate of the protective gas (high purity nitrogen) was 20mL / min, and the flow rate of the purge gas was 50mL / min. Nitrogen was selected as the purge gas.

[0061] Dynamic thermomechanical analysis (DMA): A TA Q800 dynamic thermomechanical analyzer was used. The sample size was 35mm×12mm×4mm (length×width×thickness). The dynamic mechanical behavior of the material was tested in three-point bending mode at a frequency of 1Hz and a heating rate of 3℃ / min. The temperature range was -80~220℃.

[0062] Table 1. Performance test results of epoxy resins in Examples 1-7 and Comparative Example 1.

[0063] As shown in Table 1, the impact strength of toughened (modified) epoxy resins with different contents of end-group isocyanate polyurethane prepolymers was improved to varying degrees. Among them, the modified epoxy resin with an addition of 15% showed the best impact strength of 35.00 kJ·m. 2 This indicates that isocyanate-terminated polyurethane prepolymers (isocyanate-terminated polyurethane prepolymers) can increase the toughness of epoxy resins. Furthermore, the maximum thermal decomposition rate temperature of polyurethane-toughened epoxy resins generally exhibits better characteristics than that of pure epoxy resins, maintaining relative stability at high temperatures, improving the overall thermal stability of the material, and delaying decomposition. The glass transition temperature (Tg) of polyurethane-toughened epoxy resins is also lower. This is because the polyether soft segments in the polyurethane generate a free volume increase effect, increasing the spacing between epoxy segments, reducing molecular motion resistance, and making it easier for epoxy segments to undergo cooperative motion, thereby improving toughness.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An epoxy resin toughened by an end-isocyanate polyurethane prepolymer, comprising the following raw materials: an end-isocyanate polyurethane prepolymer, an epoxy resin, and a curing agent; The mass ratio of the end-group isocyanate polyurethane prepolymer, curing agent and epoxy resin is (5~20):(25~35):

100.

2. The epoxy resin according to claim 1, characterized in that, The isocyanate group content in the terminal isocyanate polyurethane prepolymer is 0.1-8%.

3. The epoxy resin according to claim 1 or 2, characterized in that, The method for preparing the terminal isocyanate polyurethane prepolymer includes: mixing polyether polyol and toluene diisocyanate, and carrying out a prepolymerization reaction to obtain the terminal isocyanate polyurethane prepolymer.

4. The epoxy resin according to claim 3, characterized in that, The number average molecular weight of the polyether polyol is 1000~4000 g / mol.

5. The epoxy resin according to claim 3, characterized in that, The temperature of the prepolymerization reaction is 75~85℃.

6. The epoxy resin according to claim 1, characterized in that, The epoxy resin is a bisphenol A type epoxy resin.

7. The epoxy resin according to claim 1, characterized in that, The curing agent is an aromatic amine curing agent.

8. The epoxy resin according to claim 7, characterized in that, The aromatic amine curing agent includes one or more of m-phenylenediamine, 4,4-diaminodiphenyl sulfone, and diaminodiphenylmethane.

9. A method for preparing the epoxy resin toughened with the end-group isocyanate polyurethane prepolymer according to any one of claims 1 to 8, comprising: The isocyanate-terminated polyurethane prepolymer is mixed with epoxy resin and subjected to an addition reaction. Then, a curing agent is added for curing to obtain epoxy resin toughened with isocyanate-terminated polyurethane prepolymer.

10. The application of the epoxy resin toughened with the end-isocyanate polyurethane prepolymer according to any one of claims 1 to 8, or the epoxy resin toughened with the end-isocyanate polyurethane prepolymer prepared by the preparation method according to claim 9, in the field of electronic packaging.

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