TWI844481B - CROSS-LINKING AGENT WITH INDUCTIVE GROUP AT α-POSITION, SYNTHESIS METHOD THEREOF, VITRIMER AND PREPARATION METHOD THEREOF - Google Patents

Abstract

The present disclosure provides a method for synthesizing cross-linking agent with inductive group at α-position, which includes performing an esterification reaction, performing an atom free radical addition reaction and performing a removing protective group step. The esterification reaction is for an alcohol reacting with α-bromoisobutyryl bromide to form a precursor. The atom free radical addition reaction is for the precursor reacting with tertiary butyl acrylate to form an intermediate. The removing protecting group step is for removing a protective group in the intermediate to obtain a cross-linking agent with inductive group at α-position. Thus, the present disclosure connects a bromine inducing group at the α-position by the atom free radical addition reaction to synthesize the cross-linking agent with reduced activation energy required for the reaction, which can be used to prepare the vitrimer without adding a catalyst.

Description

Crosslinking agent with α-position inducing group, synthesis method thereof, plastic thermosetting resin and preparation method thereof

The present invention relates to a crosslinking agent and a synthesis method thereof, in particular to a crosslinking agent with an α-position inducing group, a synthesis method thereof, a plastic thermosetting resin and a preparation method thereof.

The advantages of general thermoplastic resins include plasticity and dimensional stability, but they still have disadvantages such as low chemical resistance, low heat resistance and low mechanical properties. In addition, in some special applications, the thermal properties of thermoplastic resins limit their development.

In order to solve the above shortcomings, a crosslinking agent is usually added to the thermoplastic resin to solidify it to form a thermosetting resin, and a catalyst is added to make it plastic and repairable to synthesize a plastic thermosetting resin (Vitrimer). While improving the chemical resistance, heat resistance and mechanical properties of the thermoplastic resin, it can also maintain the plasticity of the thermoplastic resin itself.

However, most catalysts are organic salts, strong bases or strong acids, which may cause environmental hazards. Therefore, it is necessary to find a cross-linking agent that can reduce the activation energy required for the reaction, so as to facilitate the synthesis of plastic thermosetting resins without adding catalysts.

In view of this, how to synthesize a cross-linking agent that can reduce the activation energy required for the reaction so that plastic thermosetting resins can be prepared without adding catalysts has become the goal of relevant industries.

One object of the present invention is to provide a crosslinking agent with an α-position inducing group and a synthesis method thereof, wherein the crosslinking agent with an α-position inducing group is synthesized by an atomic free radical addition reaction.

Another object of the present invention is to provide a plastic thermosetting resin and a preparation method thereof, wherein a crosslinking agent having an α-position inducing group is introduced into the thermoplastic resin, and a plastic thermosetting resin having a repairing effect can be synthesized without adding a catalyst.

One embodiment of the present invention provides a method for synthesizing a crosslinking agent having an α-inducing group, which comprises an esterification reaction, an atomic free radical addition reaction, and a protective group removal step. The esterification reaction is to react an alcohol with an α-bromoisobutyl bromide to form a precursor. The atomic free radical addition reaction is to react the precursor with tert-butyl acrylate to form an intermediate. The protective group removal step is to remove a protective group in the intermediate to obtain a crosslinking agent having an α-inducing group.

According to the synthesis method of the crosslinking agent with an α-inducing group described in the previous paragraph, the alcohol can be a diol, a tetraol or a hexaol.

According to the synthesis method of the cross-linking agent with an α-inducing group described in the previous paragraph, the alcohol can be ethylene glycol, pentaerythritol or dipentaerythritol.

According to the synthesis method of the crosslinking agent with an α-inducing group described in the previous paragraph, the protecting group can be a tert-butyl group.

Another embodiment of the present invention provides a crosslinking agent having an α-inducing group, which is prepared by the aforementioned synthesis method of the crosslinking agent having an α-inducing group.

According to the cross-linking agent with an α-inducing group described in the previous paragraph, it may have a structure as shown in formula (I), formula (II) or formula (III): Formula (I), Formula (II), Formula (III).

Another embodiment of the present invention provides a method for preparing a plastic thermosetting resin, which comprises providing a crosslinking agent having an α-position inducing group as described above and performing a crosslinking curing step. The crosslinking curing step is to mix a copolymer with the crosslinking agent having an α-position inducing group and perform an ester exchange reaction to obtain a plastic thermosetting resin in the absence of a catalyst.

According to the preparation method of the plastic thermosetting resin described in the previous paragraph, the copolymer can be polymerized from a methacrylate monomer and glycidyl methacrylate. In addition, the methacrylate monomer can be methyl methacrylate, ethyl methacrylate or butyl methacrylate.

Another embodiment of the present invention provides a plastic thermosetting resin, which is prepared by the preparation method of the plastic thermosetting resin as described above.

Thus, the present invention utilizes atomic free radical addition reaction to synthesize a crosslinking agent having an inducing group at the α position, and introduces it into a thermoplastic resin to synthesize a plastic thermosetting resin without adding a catalyst, which can improve the thermal and mechanical properties without affecting the optical properties, and can also achieve the plasticity and repairability of the resin at high temperatures.

The following will discuss various embodiments of the present invention in more detail. However, this embodiment can be an application of various inventive concepts and can be specifically implemented in various different specific scopes. The specific implementation is for illustrative purposes only and is not limited to the scope of the disclosure.

＜Method for synthesizing a crosslinking agent having an α-inducing group＞

Please refer to FIG. 1, which is a flow chart showing a method 100 for synthesizing a crosslinking agent having an α-inducing group according to an embodiment of the present invention. In FIG. 1, the method 100 for synthesizing a crosslinking agent having an α-inducing group comprises step 110, step 120 and step 130.

Step 110 is to perform an esterification reaction, which is to react an alcohol with α-bromoisobutyryl bromide (2-Bromoisobutyryl bromide, BiB) to form a precursor, wherein the alcohol can be but not limited to a diol, a tetraol or a hexaol, so as to synthesize a crosslinking agent with different arm numbers. Specifically, the diol of the present invention can be ethylene glycol, the tetraol can be pentaerythritol, and the hexaol can be dipentaerythritol.

Step 120 is to perform an atomic free radical addition reaction, which is to react the precursor with tert-butyl acrylate (TBA) to form an intermediate. Specifically, the purpose of the atomic free radical addition reaction is to attach a bromine inducing group to the α position of the intermediate.

Step 130 is a step of removing a protecting group, which is to remove a protecting group in the intermediate to obtain a crosslinking agent having an α-inducing group, wherein the protecting group is a tert-butyl group.

Accordingly, the present invention further provides a crosslinking agent having an α-inducing group prepared by the aforementioned synthesis method 100 of a crosslinking agent having an α-inducing group, which may have a structure as shown in formula (I), formula (II) or formula (III): Formula (I), Formula (II), Formula (III).

Specifically, the crosslinking agent with an α-inducing group represented by formula (I) is prepared from ethylene glycol, the crosslinking agent with an α-inducing group represented by formula (II) is prepared from pentaerythritol, and the crosslinking agent with an α-inducing group represented by formula (III) is prepared from dipentaerythritol.

＜Method for preparing plastic thermosetting resin＞

Please refer to FIG. 2, which is a flow chart showing a method 200 for preparing a plastic thermosetting resin according to another embodiment of the present invention. In FIG. 2, the method 200 for preparing a plastic thermosetting resin includes steps 210 and 220.

Step 210 is to provide the aforementioned crosslinking agent with an α-position inducing group, and then step 220 is to perform a crosslinking curing step, which is to mix a copolymer with the aforementioned crosslinking agent with an α-position inducing group and perform an ester exchange reaction to obtain a plastic thermosetting resin in the absence of a catalyst. The copolymer is polymerized from a methacrylate monomer and a glycidyl methacrylate, wherein the methacrylate monomer can be but is not limited to methyl methacrylate, ethyl methacrylate or butyl methacrylate.

In detail, the crosslinking agent synthesized by the present invention has an inducing group at its α-position, and the inducing group will pull the electron cloud of the ester group, so that the carbon on the ester group will lack electrons, thereby making the alcohol group more reactive. Therefore, the crosslinking agent with an inducing group at the α-position of the present invention has the effect of reducing the activation energy required for the reaction, which is conducive to the progress of the ester exchange reaction. The strength of the inducing group effect will also affect the repair speed of the resin.

Accordingly, the present invention further provides a plastic thermosetting resin prepared by the aforementioned plastic thermosetting resin preparation method 200, which has superior thermal and mechanical properties compared to pure thermoplastic resins and can also have a repairing effect.

The present invention is further illustrated by the following specific embodiments, which are used to facilitate those skilled in the art to which the present invention belongs, so that the present invention can be fully utilized and practiced without excessive interpretation. These embodiments should not be regarded as limiting the scope of the present invention, but are used to illustrate the materials and methods for implementing the present invention.

<Synthesis Example/Example>

＜Synthesis of precursor＞

Synthesis Example 1: 48.39 mmol of ethylene glycol, 111 mmol of triethanolamine (TEA) and 74 ml of dichloromethane (DCM) were added to a round-bottom flask and placed in an ice bath at 0 ^° C. Then, 111 mmol of α-bromoisobutyl bromide (BiB) was slowly added dropwise to the round-bottom flask and reacted at room temperature for 24 hours. Furthermore, dichloromethane and deionized water were used for extraction, and the organic layer was taken and concentrated under reduced pressure to remove the solvent to obtain a white crystalline solid, which is the precursor of Synthesis Example 1. The reaction equation of Synthesis Example 1 is shown in Table 1 below. Table I

Synthesis Example 2: Add 20 mmol of pentaerythritol and 186 ml of pyridine to a round-bottom flask and heat at 55 ^° C in a nitrogen environment until all are dissolved. Then, slowly add 84 mmol of BiB to the round-bottom flask and stir for 1 hour. After the reaction is completed, remove the pyridine by distillation. Furthermore, extract with dichloromethane and deionized water, take the organic layer, reduce pressure and concentrate to remove the solvent, and then place it in a freezer for recrystallization to obtain white transparent crystals, which are the precursor of Synthesis Example 2. The reaction equation of Synthesis Example 2 is shown in Table 2 below. Table II

Synthesis Example 3: 10 mmol of dipentaerythritol and 20 ml of pyridine were added to a round-bottom flask and placed in an ice bath at 0 ^° C. Then, 90 mmol of BiB was slowly added dropwise to the round-bottom flask and stirred for 12 hours. After the reaction was completed, pyridine was removed by distillation. Furthermore, dichloromethane and deionized water were used for extraction, and the organic layer was taken and concentrated under reduced pressure to remove the solvent, and then placed in a freezer for recrystallization to obtain white transparent crystals, which were the precursor of Synthesis Example 3. The reaction equation of Synthesis Example 3 is shown in Table 3 below. Table 3

＜Synthesis of intermediates＞

Synthesis Examples 4 to 6 of the present invention are prepared by adding the precursors of Synthesis Examples 1 to 3, tert-butyl acrylate (TBA), pentamethyldiethylenetriamine (PMDETA), cuprous bromide (CuBr ₂ ) and tetrahydrofuran (THF) into a Schlenk bottle, and reacting in an oil bath at 35 ^° C for 4 hours. Then, extraction is performed with dichloromethane and deionized water, and the organic layer is taken and concentrated under reduced pressure to remove the solvent to obtain a milky white colloid. The reaction equations of Synthesis Examples 4 to 6 are shown in Table 4 below. Table 4

＜Synthesis of crosslinking agent＞

In Examples 1 to 3 of the present invention, the intermediates of Synthesis Examples 4 to 6 are placed in a round-bottom flask, trifluoroacetic acid (TFA) and DCM are added in sequence, stirred at room temperature for 4 hours, and then the solvent is removed by concentration under reduced pressure to obtain a crosslinking agent. The reaction equations of Examples 1 to 3 are shown in Table 5 below. Table 5

Please refer to Figure 3A and Figure 3B, wherein Figure 3A shows the FTIR spectra of Synthesis Example 1, Synthesis Example 4 and Example 1, and Figure 3B shows the NMR spectra of Synthesis Example 1, Synthesis Example 4 and Example 1. From the results of Figure 3A, it can be seen that the signal of C=O in Example 1 shifts from the original 1731 cm ^-1 to 1783 cm ^-1 , and the signal of OH appears at the position of 3500 cm ^-1 , indicating that the protective group is successfully removed. In addition, from the results of Figure 3B, it can be seen that Synthesis Example 4 has a double peak at the position of 4.05 ppm to 4.20 ppm, indicating that bromine is successfully connected to the α position, so the present invention successfully connects the bromine inducing group to the α position of the intermediate by atomic free radical addition reaction.

＜Synthesis of plastic thermosetting resin＞

Examples 4 to 6 of the present invention are plastic thermosetting resins prepared using Examples 1 to 3. The preparation method is to add the crosslinking agent with α-inducing group and copolymer P (MMA- r -GMA) of Examples 1 to 3 into a sample bottle and dissolve them in THF to prepare a solution with a solid content of 25%. After that, evenly apply it on Teflon paper and place it at room temperature for 24 hours, preheat it at 100 ^o C and 120 ^o C respectively, and then heat it in an oven at 150 ^o C and 180 ^o C to complete crosslinking and curing. The crosslinking agent used in Examples 4 to 6 and the molar ratio of each component are shown in Table 6 below, where Comparative Example 1 is polymethyl methacrylate (PMMA). Table 6 Crosslinking agent Molar ratio (MMA:GMA:crosslinking agent) Embodiment 4 Embodiment 1 9:1:0.5 Embodiment 5 Embodiment 2 9:1:0.25 Embodiment 6 Embodiment 3 9:1:0.167 Comparison Example 1 - 100:0:0

Please refer to Figure 4, which shows the FTIR graphs before and after crosslinking of Example 4. From the results of Figure 4, it can be seen that the characteristic peak of the epoxy group is located at 908 cm ^-1 , and after crosslinking, the peak of the characteristic peak of the epoxy group gradually disappears, indicating that the plastic thermosetting resin of Example 4 has been crosslinked.

＜Optical property analysis＞

UV transmittance experiments were conducted on Examples 4 to 6 and Comparative Example 1, and the test wavelength ranged from 200 nm to 1000 nm. Please refer to FIG. 5 , which shows the UV analysis graph of Examples 4 to 6 and Comparative Example 1, wherein the light transmittance (T _λ ) of Examples 4 to 6 and Comparative Example 1 is shown in Table 7 below. Table 7 T _400nm T _{500nm Tmax} Embodiment 4 77.3% 82.5% 86.2% Embodiment 5 62.16% 76.5% 87.7% Embodiment 6 70.5% 80.4% 85.2% Comparison Example 1 80.1% 83.6% 86.7%

From the above results, it can be seen that when the wavelength is above 500 nm, the introduction of the covalent cross-linked network in Examples 4 to 6 has little effect on the overall optical properties.

＜Thermal property analysis＞

Thermal property analysis was performed on Examples 4 to 6 and Comparative Example 1. The thermal property analysis method included dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA).

Please refer to Figure 6, which shows the DMA analysis diagram of Examples 4 to 6 and Comparative Example 1. From the DMA analysis, the storage modulus (E'), glass transition temperature ( _Tg ), storage modulus above the glass transition temperature (+40 ^o C) (E'') and crosslinking density of Examples 4 to 6 and Comparative Example 1 can be obtained. The measurement results are shown in Table 8 below. Table 8 E' (Pa) _Tg ( ^o C) E'' (MPa) Crosslinking density (mmole/cm ³ ) Embodiment 4 4.17×10 ⁹ 154 2.6 0.22 Embodiment 5 6.50×10 ⁹ 155 5.7 0.49 Embodiment 6 6.80×10 ⁹ 154 2.8 0.23 Comparison Example 1 9.60×10 ⁹ 118 - -

Please refer to Figure 7, which shows the TGA analysis diagram of Examples 4 to 6 and Comparative Example 1. From the TGA analysis, the 5% thermal weight loss temperature (Td5 _% ), 10% thermal weight loss temperature ( _Td10% ) and 800 ^° C coke residue rate of Examples 4 to 6 and Comparative Example 1 can be obtained. The measurement results are shown in Table 9 below. Table 9 T _d5% ( ^o C) T _d10% ( ^o C) Coke residual rate (%) Embodiment 4 236 255 0.34 Embodiment 5 278 302 0.55 Embodiment 6 290 311 1.80 Comparison Example 1 176 223 1.80

From the above results, it can be seen that Examples 4 to 6 still maintain a certain storage modulus after exceeding the glass transition temperature, and the T _d5% of Example 6 is increased to 290 ^° C, which can be explained that when the number of arms of the crosslinking agent increases, the T _d5% will increase accordingly. Therefore, Examples 4 to 6 prepared by the crosslinking agent with an α-position inducing group of the present invention have improved thermal stability compared to Comparative Example 1.

＜Mechanical property analysis＞

The mechanical properties of Examples 4 to 6 and Comparative Example 1 were analyzed by tensile testing. Please refer to FIG. 8, which shows the stress-strain diagram of Examples 4 to 6 and Comparative Example 1. The stress, strain, Young's modulus and toughness of Examples 4 to 6 and Comparative Example 1 can be obtained from the tensile test. The measurement results are shown in Table 10 below. Table 10 Stress(MPa) Strain(%) Young's modulus (MPa) Toughness (kJ/m ³ ) Embodiment 4 33 2 16.5 370 Embodiment 5 45 3.99 11.2 1110 Embodiment 6 37 15 2.5 4800 Comparison Example 1 7 0.92 7.6 34

From the above results, it can be seen that in Examples 4 to 6, when the number of arms of the crosslinking agent increases, the stress increases accordingly, but the stress of Example 6 decreases instead, which is related to the small number of crosslinking agents per unit area. However, the toughness of Example 6 can still be increased to 4800 kJ/m ³ , so Examples 4 to 6 prepared by the crosslinking agent with α-position inducing groups of the present invention have greatly improved mechanical properties compared to Comparative Example 1.

＜Restorability Analysis＞

The surfaces of Examples 4 to 6 were scratched with a blade to create a scratch greater than 50 μm, and the repair conditions were observed at 10, 30, and 60 minutes using a hot press at 160 ^° C and 30 psi. Please refer to FIG. 9A and FIG. 9B, wherein FIG. 9A is a schematic diagram showing the repair of Examples 4 to 6 at 0, 10, 30, and 60 minutes, and FIG. 9B is a histogram showing the repair degree of Examples 4 to 6, and the measurement results of the repair degree of Examples 4 to 6 at different times are shown in Table 11 below. Table 11 0 minutes 10 minutes 30 minutes 60 minutes Embodiment 4 0% 75.5% 75.9% 80.1% Embodiment 5 0% 78.2% 78.1% 81.14% Embodiment 6 0% 62.8% 76.3% 93.2%

From the above results, it can be seen that Example 6 has the best repairing effect, which can explain that the alcohol group and the ester group in the ester exchange reaction are closer than those in other examples, so the required activation energy is lower.

In summary, the present invention successfully utilizes atomic free radical addition reaction to synthesize a crosslinking agent with an inducing group at the α position, and introduces it into a copolymer to synthesize a plastic thermosetting resin without adding a catalyst, and its thermal and mechanical properties are significantly improved and have a repairing effect.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined in the attached patent application.

100: Synthesis method of crosslinking agent with α-position inducing group 200: Preparation method of plastic thermosetting resin 110,120,130,210,220: Steps

In order to make the above and other purposes, features, advantages and embodiments of the present invention more clearly understandable, the attached drawings are described as follows: Figure 1 is a step flow chart of a method for synthesizing a crosslinking agent with an α-inducing group according to one embodiment of the present invention; Figure 2 is a step flow chart of a method for preparing a plastic thermosetting resin according to another embodiment of the present invention; Figure 3A is a FTIR spectrum of Synthesis Example 1, Synthesis Example 4 and Embodiment 1; Figure 3B is a NMR spectrum of Synthesis Example 1, Synthesis Example 4 and Embodiment 1; Figure 4 is a FTIR spectrum of Embodiment 4 before and after crosslinking; Figure 5 is a UV analysis of Embodiments 4 to 6 and Comparative Example 1; Figure 6 is a DMA analysis diagram of Examples 4 to 6 and Comparative Example 1; Figure 7 is a TGA analysis diagram of Examples 4 to 6 and Comparative Example 1; Figure 8 is a stress-strain diagram of Examples 4 to 6 and Comparative Example 1; Figure 9A is a schematic diagram of the repair of Examples 4 to 6 at 0, 10, 30, and 60 minutes; and Figure 9B is a histogram of the degree of repair of Examples 4 to 6.

100: Synthesis method of crosslinking agent with α-inducing group

110,120,130: Steps

Claims (10)

A method for synthesizing a crosslinker with an α-inducing group comprises: performing an esterification reaction, which is to react an alcohol with an α-bromoisobutyl bromide to form a precursor; performing an atomic free radical addition reaction, which is to react the precursor with tert-butyl acrylate to form an intermediate; and performing a protective group removal step, which is to remove a protective group in the intermediate to obtain a crosslinker with an α-inducing group. The method for synthesizing a crosslinking agent having an α-inducing group as described in claim 1, wherein the alcohol is a diol, a tetraol or a hexaol. A method for synthesizing a crosslinking agent having an α-inducing group as described in claim 2, wherein the alcohol is ethylene glycol, pentaerythritol or dipentaerythritol. A method for synthesizing a crosslinking agent having an α-inducing group as described in claim 1, wherein the protecting group is a tert-butyl group. A crosslinking agent having an α-inducing group is prepared by the synthesis method of a crosslinking agent having an α-inducing group as described in any one of claims 1 to 4. The crosslinking agent with an α-inducing group as described in claim 5, wherein the crosslinking agent with an α-inducing group has a structure as shown in formula (I), formula (II) or formula (III): Formula (I), Formula (II), Formula (III). A method for preparing a plastic thermosetting resin comprises: Providing a crosslinking agent having an α-position inducing group as described in claim 5; and Performing a crosslinking curing step, which is to mix a copolymer with the crosslinking agent having an α-position inducing group and perform an ester exchange reaction to obtain a plastic thermosetting resin in the absence of a catalyst. A method for preparing a plastic thermosetting resin as described in claim 7, wherein the copolymer is polymerized from a methacrylate monomer and glyceryl methacrylate. A method for preparing a plastic thermosetting resin as described in claim 8, wherein the methacrylate monomer is methyl methacrylate, ethyl methacrylate or butyl methacrylate. A plastic thermosetting resin is prepared by the method for preparing a plastic thermosetting resin as described in claim 7.