A method for preparing a halogen-free epoxy resin

Abstract

This invention discloses a method for preparing halogen-free epoxy resin: the compounds shown in Formula I and Formula II undergo a nucleophilic substitution reaction under the action of a catalyst to obtain the epoxy resin shown in Formula III. The method of this invention is simple to operate, requires no complex dehalogenation and purification operations in post-processing, and the obtained halogen-free epoxy resin material has no halogen residue and extremely high purity. It also leaves no phosphate ester residue and will not corrode circuits or electronic devices, making it suitable for use in advanced electronic packaging fields.

Description

Technical Field

[0001] This invention belongs to the field of thermosetting resin technology, specifically relating to a halogen-free epoxy resin and its preparation method. Background Technology

[0002] Epoxy resin is an important thermosetting resin formed by crosslinking epoxy monomers and curing agents, accounting for more than 70% of the thermosetting resin market share. Epoxy monomers generally refer to glycidyl ethers, glycidyl esters, or glycidyl amines containing at least two epoxy groups, including high-purity compounds and low-polymerization-degree prepolymers.

[0003] Epoxy resins, due to their excellent chemical stability, dielectric properties, thermal properties, and mechanical properties, have become the most important resin-based materials for electronic packaging. Among them, bisphenol A diglycidyl ether (DGEBA) is the most important epoxy monomer used in electronic packaging. Currently, the industrial production of DGEBA mainly involves ring-opening epichlorohydrin under alkaline conditions, condensing it with bisphenol A to obtain a β-chloroethanol anion structure, followed by an intramolecular nucleophilic substitution reaction to remove chloride ions and obtain the target monomer. However, in actual production, due to incomplete ring-closing reactions, the monomer contains chloride ions, commonly referred to as hydrolyzable chloride. In the practical application of epoxy resin as a packaging material, hydrolyzable chloride undergoes hydrolysis under high temperature and high humidity conditions, releasing chloride ions that corrode electronic devices. Therefore, the need for preparing epoxy monomers with low hydrolyzable chloride (<50 ppm) or no chloride is very urgent.

[0004] Currently, there are two main methods to reduce the hydrolyzable chlorine content in epoxy monomers. The first method involves altering the synthetic route of the epoxy monomer, specifically preparing compounds with terminal double bonds and using strong oxidants such as m-chloroperoxybenzoic acid to epoxidize the double bonds to obtain halogen-free epoxy monomers. While the double bond epoxidation strategy fundamentally solves the problem of residual hydrolyzable chlorine, the use of large amounts of oxidants, complex post-processing steps, and the incompatibility of the product's chemical structure with DGEBA, leading to resin processing incompatibility, make it difficult to practically apply in industrial production. The second method involves post-treating the product with strong alkalis such as sodium hydroxide and sodium hydride to hydrolyze the residual chlorine. However, this method not only generates large amounts of wastewater, but the strong alkaline solution treatment also causes some epoxy groups to open, thereby reducing the epoxy value of the epoxy monomer. Summary of the Invention

[0005] This invention addresses the difficulty of removing hydrolyzable chlorine from epoxy resins by proposing a method for directly synthesizing halogen-free epoxy resins. This method uses phosphorus-containing glycidyl esters, which do not corrode electronic circuit components, chips, or other devices, as a raw material to replace epichlorohydrin. The phosphorus-containing glycidyl ester is synthesized from bio-based glycidyl esters and phosphoric acid via a one-step esterification reaction. Subsequently, it is reacted with a diol or bisphenol to obtain a halogen-free electronic-grade epoxy resin through a one-step nucleophilic substitution reaction. Because the reaction process does not involve ring-opening of the epoxy resin, it also ensures the high purity of the epoxy resin product.

[0006] The technical solution provided by this invention is as follows:

[0007] A method for preparing a halogen-free epoxy resin, wherein the method comprises: a compound represented by Formula I and a compound represented by Formula II undergoing a nucleophilic substitution reaction under the action of a catalyst to obtain an epoxy resin represented by Formula III.

[0008]

[0009] In Formula I, A is selected from one of the following structures:

[0010]

[0011] R1 and R2 are each independently an unsubstituted or C1-C14 alkyl group containing a substituent A; the substituent A can be one or more of the following: C1-C10 branched or straight-chain alkoxy, C3-C20 branched or straight-chain cycloalkyl, and C6-C10 aromatic group.

[0012] R3~R 14 Each of the following is independent and does not exist, or each is an unsubstituted or C1-14 aliphatic carbon chain containing a substituent B; the substituent B can be one or more of the following: C1-C10 branched or straight-chain alkoxy, C3-C20 branched or straight-chain cycloalkyl, and C6-C10 aromatic group.

[0013] In Equation I, B and C can be independently represented as any one or more of the following structures:

[0014]

[0015] It is preferable that B and C have the same structure.

[0016] The compound shown in Formula I is bisphenol A.

[0017] In Formula II, R is selected from one of the following structures:

[0018]

[0019] Where R 15 -R17 The substituent C is independently selected from the following groups: C1-14 aliphatic carbon chains, C6-14 alicyclic groups, C6-14 aromatic groups, and C3-14 heterocyclic groups; wherein the substituent C can be one or more of the following: C1-C10 branched or straight-chain alkyl groups, C1-C10 branched or straight-chain alkoxy groups, C3-C20 branched or straight-chain cycloalkyl groups, and C6-C10 aromatic groups.

[0020] In the above chemical formula structures, For connection keys.

[0021] In Equation III, n is the degree of polymerization, 0 <n<50。

[0022] In Formula II, m is the number of epoxy groups linked by phosphate ester groups, and m can be 1, 2 or 3.

[0023] Preferably, the reaction temperature is -60 to 120°C, more preferably 50 to 80°C; the reaction time is 0.1 to 48 hours, more preferably 0.5 to 5 hours.

[0024] Preferably, the reaction is carried out in a solvent-free environment or in a solvent; wherein the solvent is selected from one or more of tetrahydrofuran, benzene, toluene, hexane, diethyl ether, ethyl acetate, 1,4-dioxane, pyridine, acetonitrile, methanol, and water.

[0025] Preferably, the ratio of the number of molar hydroxyl groups in the compound of Formula I to the number of molar epoxy groups in the compound of Formula II is between 1:1 and 100.

[0026] Preferably, the catalyst is selected from one or more of ammonium salts, phosphate salts, imidazolium salts, carbonates, and hydroxides.

[0027] More preferably, the structure of the catalyst is selected from one or more of the following.

[0028] M2CO3 MOH

[0029] NCO3 N(OH)2

[0030] Y2(CO3)3 Y((OH)3

[0031] M is selected from one or more of lithium, sodium, potassium, rubidium, cesium, and francium;

[0032] N is selected from one or more of beryllium, magnesium, calcium, strontium, barium, and radium;

[0033] Y is selected from one or more of aluminum, gallium, indium, and thallium.

[0034] The preferred catalyst is sodium hydroxide or sodium carbonate.

[0035] The amount of the catalyst used is 1 to 2 times the molar amount of the hydroxyl group in the compound represented by Formula I, preferably 1.2 to 1.5 times.

[0036] After the nucleophilic substitution reaction is completed, the reaction solution is post-treated to obtain the epoxy resin shown in Formula III. The post-treatment method of the reaction solution is as follows: the reaction solution is washed with deionized water, the crude product is added with NaHCO3 solution, heated and stirred for washing, and then vacuum dried to obtain the epoxy resin shown in Formula III.

[0037] In this invention, the compound shown in Formula II can be prepared by esterification of glycidol with a phosphoric acid compound with the following structure:

[0038]

[0039] The present invention also provides a halogen-free epoxy resin prepared by the above method.

[0040] Preferably, the molecular weight of the halogen-free epoxy resin is between 1.0 and 1.5.

[0041] The present invention also provides the application of the halogen-free epoxy resin in electronic packaging materials.

[0042] This invention prepares halogen-free epoxy resin by reacting epoxy monomers with highly leaving active groups on the side chains with diols. The product can be used for high-end packaging.

[0043] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0044] (1) Due to the strong leaving ability of the substituents in the epoxy side chain, compared with the epoxy resin produced by epichlorohydrin in industry, the reaction of the present invention is carried out by a one-step nucleophilic substitution reaction, which does not involve the ring opening of the epoxy. The product has extremely low halogen content and extremely high purity. When used in high-end packaging, no impurities will be generated during the process to corrode the circuit and electronic devices.

[0045] (2) The reaction method is simple to operate and does not require complex physical and chemical dehalogenation processes in the later stage of the reaction.

[0046] (3) The properties of the product are easy to adjust. The degree of polymerization n of the product can be controlled by changing the reaction temperature, monomer feed ratio and catalyst, thereby achieving the control of epoxy resin properties.

[0047] (4) The reactant monomer shown in formula II is a phosphate ester, synthesized from bio-based glycidyl ether and phosphoric acid via a one-step esterification reaction. The reactant contains no halogens. Phosphate esters have excellent leaving ability; washing is sufficient to remove the reactant, leaving no residue in the resin product. No purification by distillation is required, simplifying the process. Even if some residue remains, phosphorus is not corrosive to metals and will not corrode circuits or electronic devices. If sulfonate esters are used, sulfur may remain, which is corrosive to metals. Post-processing would require complex processes such as distillation, increasing costs. Attached Figure Description

[0048] Figure 1 The image shows the halogen-free epoxy resin material obtained in Example 1.

[0049] Figure 2 The image shows the 1H NMR spectrum of the halogen-free epoxy resin product obtained in Example 1.

[0050] Figure 3 The image shows the phosphorus NMR spectrum of the halogen-free epoxy resin obtained in Example 5.

[0051] Figure 4 This is an image of the cured epoxy resin obtained in Example 5.

[0052] Figure 5 The image shows the dynamic thermomechanical analysis (DMA) curve of the cured epoxy resin obtained in Example 5. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention.

[0054] The general formula for the synthesis reaction of the halogen-free epoxy resin provided by this invention is shown below.

[0055]

[0056] Examples 1-4

[0057]

[0058] The reaction parameters are shown in Table 1.

[0059] Bisphenol A (22.8 g, 0.1 mol) and glycidyl dimethyl phosphate (the molar ratio of phenolic hydroxyl to epoxy groups were 1:1, 1:2, 1:4, and 1:8, respectively) were dissolved in ethyl acetate (100 mL). The mixture was stirred at 75 °C for 10 min, and then NaOH solution (1 M, 0.24 mol) was slowly added dropwise. After the addition was complete, heating and stirring continued. The reaction times are shown in Table 1. After the reaction was complete, the mixture was cooled to room temperature, and the organic phase was washed with deionized water. The crude product was stirred in NaHCO3 solution (0.1 M, 100 mL) at 60 °C for 5 h, and the layers separated. The organic phase was then dried under vacuum to obtain the product shown in Table 1. Figure 1 The colorless, viscous liquid shown is DGEBA.

[0060] Table 1. Epoxy resins obtained under different reaction conditions

[0061]

[0062] like Figure 2 The image shows the 1H NMR spectrum of DGEBA prepared in Example 4. Signals at 2.7-2.8 ppm and 3.3 ppm confirm the epoxy functional groups in DGEBA, indicating that DGEBA was successfully synthesized in this example. The phosphate ester content of DGEBA was quantitatively analyzed using precipitation titration according to GB / T 4618.2-2008, and the results show that the DGEBA synthesized in this example has no phosphate ester residue. In summary, this demonstrates that a halogen-free epoxy monomer has been successfully prepared.

[0063] Example 5

[0064] The reaction equation is shown below:

[0065]

[0066] Bisphenol A (22.8 g, 0.1 mol) and triglycidyl phosphate (53.2 g, 0.2 mol) were dissolved in ethyl acetate (100 mL). The solution was stirred at 75 °C for 10 min, and then Na₂CO₃ solution (0.1 M, 0.24 mol) was slowly added dropwise. After the addition was complete, the mixture was heated and stirred for 1 h. The solution was cooled to room temperature and washed with deionized water. The crude product was stirred in NaHCO₃ solution (0.1 M, 100 mL) at 60 °C for 5 h, and then dried under vacuum to obtain a colorless, viscous liquid, DGEBA. The n value of the obtained DGEBA was 0.05, and the molecular weight distribution was 1.06.

[0067] The purified product was subjected to NMR phosphorus spectroscopy, and the results are as follows: Figure 3 As shown, the product did not exhibit absorption in the phosphorus NMR spectrum, resulting in a halogen-free epoxy resin with a high epoxy value.

[0068] The obtained halogen-free epoxy resin was uniformly mixed with isophorone diamine (the ratio of epoxy to amino was controlled at 2:1), poured into a rectangular silicone mold, and placed in a forced-air drying oven for segmental curing to obtain cross-linked epoxy resin. The specific steps for segmental curing were: heating at 60℃ for 1 hour, at 80℃ for 1 hour, at 100℃ for 1 hour, and at 120℃ for 1 hour. The appearance of the cured epoxy resin is as follows. Figure 4 As shown, the resin exhibits extremely high transparency. Dynamic thermomechanical property (DMA) tests were performed on the cured resin, and the results are as follows: Figure 5 As shown in the figure, the glass transition temperature of the resin, measured by the loss tangent curve, is 153℃, which is comparable to that of commercially available bisphenol A type epoxy resin. In summary, halogen-free epoxy resin has been successfully prepared, and its properties are indistinguishable from those of bisphenol A type epoxy resin obtained by traditional preparation methods.

Claims

1. A method for preparing a halogen-free epoxy resin, characterized in that... The method is as follows: the compound shown in Formula I and the compound shown in Formula II undergo a nucleophilic substitution reaction under the action of a catalyst to obtain the epoxy resin shown in Formula III; ； In Formula I, A is selected from one of the following structures: ； R1 and R2 are each independently an unsubstituted or C1-C14 alkyl group or a group containing a substituent A1; the substituent A1 is one or more of the following: a C1-C10 branched or straight-chain alkoxy group, a C3-C20 branched or straight-chain cycloalkyl group, and a C6-C10 aromatic group. R3~R 14 Each of the following is independent of the others, or each of the following is an independent C1-14 aliphatic carbon chain that is either unsubstituted or contains a substituent B1; the substituent B1 is one or more of the following: a branched or straight-chain alkoxy group of C1 to C10, a branched or straight-chain cycloalkyl group of C3 to C20, and an aromatic group of C6 to C10. In Equation I, B and C can be independently represented as any one or more of the following structures: ； In Formula II, R is selected from one of the following structures: ； Where R 15 ~R 17 The substituent is independently selected from the following groups that are either unsubstituted or substituted at C1: C1-14 aliphatic carbon chains, C6-14 alicyclic groups, C6-14 aromatic groups, and C3-14 heterocyclic groups; wherein the substituent C1 is one or more of the following: C1-C10 branched or straight-chain alkyl groups, C1-C10 branched or straight-chain alkoxy groups, C3-C20 branched or straight-chain cycloalkyl groups, and C6-C10 aromatic groups; In Equation III, n is the degree of polymerization, 0 <n<50; In Equation II, m is 1, 2, or 3.

2. The method as described in claim 1, characterized in that... The ratio of the number of molar hydroxyl groups in the compound shown in Formula I to the number of molar epoxy groups in the compound shown in Formula II is between 1:1 and 100.

3. The method as described in claim 1, characterized in that... The catalyst is selected from one or more of ammonium salts, phosphate salts, imidazolium salts, carbonates, and hydroxides.

4. The method as described in claim 3, characterized in that... The structure of the catalyst is selected from one or more of the following: ； M is selected from one or more of lithium, sodium, potassium, rubidium, and cesium; N is selected from one or more of beryllium, magnesium, calcium, strontium, and barium; Y is selected from one or more of gallium, indium, and thallium.

5. The method as described in claim 3, characterized in that... The amount of the catalyst used is 1 to 2 times the molar amount of the hydroxyl group in the compound shown in Formula I.

6. The method as described in claim 1, characterized in that... The reaction temperature is -60 to 120°C, and the reaction time is 0.1 to 48 h.

7. The method as described in claim 1, characterized in that... The reaction is carried out in a solvent-free environment or in a solvent; the solvent is selected from one or more of tetrahydrofuran, benzene, toluene, hexane, diethyl ether, ethyl acetate, 1,4-dioxane, pyridine, acetonitrile, and methanol.

8. The method as described in claim 1, characterized in that... After the nucleophilic substitution reaction is completed, the reaction solution is post-treated to obtain the epoxy resin shown in Formula III. The post-treatment method of the reaction solution is as follows: the reaction solution is washed with deionized water, the crude product is added with NaHCO3 solution, heated and stirred for washing, and then vacuum dried to obtain the epoxy resin shown in Formula III.

9. The halogen-free epoxy resin prepared by the method according to any one of claims 1 to 8, wherein the molecular weight distribution of the halogen-free epoxy resin is between 1.0 and 1.

5.

10. The application of the halogen-free epoxy resin as described in claim 9 in electronic packaging materials.

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