Method for preparing photoactive polyester oligomer through ring opening of lactone

Abstract

The invention belongs to the technical field of synthesis of active intermediates, and particularly discloses a method for preparing a photoactive polyester oligomer through ring opening of lactone. The preparation method comprises the following steps: adding acrylic acid, a ring-opening catalyst, an esterification catalyst, a polymerization inhibitor and a solvent into a reaction container, heating to reflux, and then starting to continuously dropwise add lactone monomers to carry out heat preservation reaction; and after the reaction is finished, cooling the obtained reaction product, filtering, and evaporating to remove the solvent and unreacted acrylic acid under reduced pressure to obtain the target product photoactive polyester oligomer. The photoactive polyester oligomer prepared by the method is controllable in chain segment, small in molecular weight and flexible to adjust, raw materials do not need to be dehydrated, and reaction conditions are mild. The obtained product photoactive polyester oligomer can be used as a high-activity cross-linking agent and is suitable for the fields of free radical polymerization and photocuring.

Description

1. Technical field:

[0001] The invention relates to the technical field of active intermediate synthesis, and in particular to a method for preparing a photoactive polyester oligomer by lactone ring opening. 2. Background technology:

[0002] Photoactive polyesters are polyester compounds with one or more unsaturated double bonds at the end. They are generally used as oligomers or active crosslinkers in free radical polymerization or photocuring. The structure and properties of the polymer can be flexibly adjusted to meet different application requirements. The polyester segments in the photoactive polyester structure are generally generated by alcohol-initiated lactone ring-opening polymerization, and the double bonds are introduced by acrylic monomers. For example:

[0003] The invention patent of CN 111826012 A discloses a method for preparing modified acrylate using polyol, lactone, acrylic acid, catalyst, inhibitor and dehydrating agent, and the method synthesizes elastic acrylate with high functionality.

[0004] The invention patent application CN 110590984 A discloses a method for modifying acrylic acid using caprolactone and hydroxyethyl acrylate, and the method synthesizes acrylic resin for flexible plastics having different numbers of caprolactone groups.

[0005] The invention patent of CN 105924588 A discloses a methacrylic acid-terminated caprolactone ester synthesized by using a caprolactone monomer, an initiator, a polyol, and methacryloyl chloride.

[0006] In the methods disclosed in the above prior art solutions, the raw materials need to be strictly dehydrated during the lactone ring-opening polymerization process, and the reaction process requires the protection of a special atmosphere. The catalyst is often a composite of rare metals, and the production cost is relatively high. In addition, the polyester obtained by the above synthesis method has a large number of repeating units, a high molecular weight of the product, a low double bond content, and defects such as insufficient reactivity during photocuring. 3. Summary of the invention:

[0007] The technical problem to be solved by the present invention is: according to the defects of the existing preparation process of photoactive polyester, such as the large number of polyester repeating units, high molecular weight of the product, low double bond content, and insufficient reaction activity during photocuring, the present invention provides a method for preparing photoactive polyester oligomers by lactone ring opening. The photoactive polyester oligomer prepared by the technical solution of the present invention has controllable chain segments, small molecular weight and flexible adjustment, no dehydration treatment of the raw materials is required, and the reaction conditions are mild; one end of the prepared product is a carboxyl group, which can be further functionalized with alcohol or amine compounds, and the other end is a double bond, which can be used as a highly active crosslinking agent and is suitable for free radical polymerization and photocuring.

[0008] In order to solve the above problems, the technical solution adopted by the present invention is:

[0009] The present invention provides a method for preparing a photoactive polyester oligomer by lactone ring opening, the method comprising the following steps:

[0010] a. Add acrylic acid, a ring-opening catalyst, an esterification catalyst, a polymerization inhibitor and a solvent into a reaction vessel, heat to reflux, and then start to continuously dropwise add a lactone monomer to carry out a heat-insulating reaction;

[0011] b. After the reaction is completed, the obtained reaction product is cooled and filtered, and then the solvent and unreacted acrylic acid are evaporated under reduced pressure to obtain the target product, a photoactive polyester oligomer.

[0012] According to the above-mentioned method for preparing photoactive polyester oligomers by lactone ring opening, the molar ratio of the lactone monomer and acrylic acid added in step a is 1:1-6; the amount of the ring-opening catalyst added is 1-10% of the total mass of the lactone monomer and acrylic acid; the amount of the esterification catalyst added is 5-10% of the total mass of the lactone monomer and acrylic acid; the amount of the solvent added is an equal volume of the lactone monomer and acrylic acid; and the amount of the inhibitor added is 0.2-0.5% of the mass of acrylic acid.

[0013] According to the above method for preparing photoactive polyester oligomers by lactone ring-opening, the time for dripping the lactone monomer in step a is 1 to 2 hours, and the time for heat preservation reaction is 10 to 30 minutes.

[0014] According to the above method for preparing photoactive polyester oligomers by lactone ring opening, the ring opening catalyst in step a is any one or both of diphenyl phosphate and borate.

[0015] According to the above method for preparing photoactive polyester oligomers by lactone ring opening, the esterification catalyst in step a is at least one of p-toluenesulfonic acid, p-toluenesulfonic acid monohydrate, 732 strong acid cation exchange resin and phosphotungstic acid.

[0016] According to the above method for preparing photoactive polyester oligomers through lactone ring opening, the solvent is any one of petroleum ether, toluene and xylene.

[0017] According to the above method for preparing photoactive polyester oligomers by lactone ring opening, the lactone monomer in step a is any one of ε-caprolactone, γ-butyrolactone and δ-valerolactone.

[0018] According to the above method for preparing photoactive polyester oligomers by lactone ring opening, the polymerization inhibitor in step a is at least one of hydroquinone, p-hydroxyanisole and 2,2,6,6-tetramethylpiperidinyl oxide TEMPO.

[0019] The positive beneficial effects of the present invention are:

[0020] 1. The present invention utilizes a compound of a ring-opening catalyst and an esterification catalyst to achieve the synergistic effect of a lactone ring-opening reaction and an acrylic esterification reaction in the presence of a trace amount of water in the system, thereby synthesizing a photoactive polyester oligomer. Figure 1 As shown, trace amounts of water inhibit the chain growth after the lactone ring opening, generating hydroxy acids with fewer repeating segments; the hydroxy acids and acrylic acid are further esterified to generate photoactive polyester oligomers. The water generated by esterification circulates and participates in the lactone ring opening reaction, which is the key to controlling the product structure in the method of the present invention.

[0021] 2. The photoactive polyester oligomer generated by the present invention has a controllable number of chain segments and has two functional groups, namely, a carboxyl group and a double bond. The two-step reaction is coupled, and no pretreatment of the reactants or gas protection is required. The reaction conditions are mild, the operation is simple, and the method is suitable for industrial production. 4. Description of the drawings:

[0022] Figure 1 The schematic diagram of the reaction of preparing photoactive polyester oligomer by lactone ring opening of the present invention (taking ε-caprolactone as an example);

[0023] Figure 1 In this study, the number of repeating segments in the target product can be adjusted by changing the experimental conditions.

[0024] Figure 2 This is the infrared spectrum of the photoactive polyester oligomer synthesized in Example 6 of the present invention;

[0025] Depend on Figure 2 It can be seen that at 3520cm -1 The absorption peak of -OH appeared at 2950cm -1 The absorption peak of -CH2- appeared at 1740cm -1 The absorption peak of -C=O- appeared at 1635cm -1 The absorption peak of -H2C=CH- appeared at .

[0026] Figure 3 The photoactive polyester oligomer synthesized in Example 6 of the present invention 1 H NMR spectrum;

[0027] Depend on Figure 3 The analysis shows that 1H NMR (400MHz, CDCl3) δ6.29 (dd, J=17.3, 6.3Hz, 1H), 6.00 (dd, J=17.3, 10.4Hz, 1H), 5.73 (t, J=9.3Hz ,1H),4.05(t,J=6.6Hz,2H),2.77–2.44(m,1H),2.40–2.07(m,2H),1.57(s,4H),1.39–1.09(m,2H);

[0028] Depend on Figure 2 Infrared spectral data and Figure 3 Proton spectrum data showed that the target product was successfully synthesized. V. Specific implementation methods:

[0029] The technical content of the present invention is described in more detail below in conjunction with the embodiments. The implementation of the present invention is not limited to the following embodiments, and any form of modification or change made to the present invention should be within the protection scope of the present invention.

[0030] Comparative Example:

[0031] The method for preparing photoactive polyester oligomers by lactone ring opening of the present invention (in this method, no ring opening catalyst is added) comprises the following specific steps:

[0032] a. Add 200 mL of toluene, 0.25 g of p-hydroxyanisole, 9.3 g of p-toluenesulfonic acid monohydrate and 72 g of acrylic acid into a four-necked flask, heat to reflux, and after the temperature stabilizes, start to drop 114 g of ε-caprolactone continuously for 2 hours, and keep the reaction warm for 30 minutes;

[0033] b. After the reaction is completed, the obtained reaction solution is cooled and filtered to filter out p-toluenesulfonic acid, and then the solvent and unreacted acrylic acid are evaporated under reduced pressure to obtain a photoactive polyester with 14 to 15 repeating segments.

[0034] Embodiment 1:

[0035] The method for preparing a photoactive polyester oligomer by lactone ring opening of the present invention comprises the following specific steps:

[0036] a. Add 200 mL of toluene, 0.25 g of p-hydroxyanisole, 1.86 g of diphenyl phosphate, 9.3 g of p-toluenesulfonic acid monohydrate and 72 g of acrylic acid into a four-necked flask, heat to reflux, and after the temperature stabilizes, start to drop 114 g of ε-caprolactone continuously for 2 hours, and keep the reaction warm for 30 minutes;

[0037] b. After the reaction is completed, the obtained reaction solution is cooled and filtered to filter out p-toluenesulfonic acid, and then the solvent and unreacted acrylic acid are evaporated under reduced pressure to obtain a photoactive polyester oligomer with 5 to 6 repeating segments.

[0038] Embodiment 2:

[0039] The method for preparing photoactive polyester oligomers by lactone ring opening of the present invention comprises the following specific steps:

[0040] a. Add 200 mL of toluene, 0.25 g of p-hydroxyanisole, 5.58 g of diphenyl phosphate, 9.3 g of p-toluenesulfonic acid monohydrate and 72 g of acrylic acid into a four-necked flask, heat to reflux, and after the temperature stabilizes, start to continuously drop 114 g of ε-caprolactone, drip it over 2 h, and keep the reaction warm for 30 min;

[0041] b. After the reaction is completed, the obtained reaction solution is cooled and filtered to filter out p-toluenesulfonic acid, and then the solvent and unreacted acrylic acid are evaporated under reduced pressure to obtain a photoactive polyester oligomer with 2 to 3 repeating segments.

[0042] Embodiment 3:

[0043] The method for preparing photoactive polyester oligomers by lactone ring opening of the present invention comprises the following specific steps:

[0044] a. Add 160 mL of toluene, 0.35 g of hydroquinone, 7.90 g of boric acid ester, 9.3 g of p-toluenesulfonic acid and 72 g of acrylic acid into a four-necked flask, heat to reflux, and after the temperature stabilizes, start to drop 86 g of γ-butyrolactone continuously for 2 hours, and keep the temperature for reaction for 30 minutes;

[0045] b. After the reaction is completed, the obtained reaction solution is cooled and filtered to filter out p-toluenesulfonic acid, and then the solvent and unreacted acrylic acid are evaporated under reduced pressure to obtain a photoactive polyester oligomer with 3 to 4 repeating segments.

[0046] Embodiment 4:

[0047] The method for preparing photoactive polyester oligomers by lactone ring opening of the present invention comprises the following specific steps:

[0048] a. Add 180 mL of toluene, 0.35 g of TEMPO, 4.30 g of diphenyl phosphate, 4.30 g of boric acid ester, 9.3 g of p-toluenesulfonic acid and 72 g of acrylic acid into a four-necked flask, heat to reflux, and after the temperature stabilizes, start to drop 100 g of δ-valerolactone continuously, drip it over 2 h, and keep the temperature for reaction for 30 min;

[0049] b. After the reaction is completed, the obtained reaction solution is cooled and filtered to filter out p-toluenesulfonic acid, and then the solvent and unreacted acrylic acid are evaporated under reduced pressure to obtain a photoactive polyester oligomer with 2 to 3 repeating segments.

[0050] Embodiment 5:

[0051] The method for preparing photoactive polyester oligomers by lactone ring opening of the present invention comprises the following specific steps:

[0052] a, 330mL toluene, 0.215g TEMPO, 0.215g p-hydroxyanisole, 9.90g diphenyl phosphate, 33.0g storng-acid cation exchange resin 732 and 216g acrylic acid were added into a four-necked flask, heated to reflux, and after the temperature stabilized, 114g of ε-caprolactone was continuously added dropwise, and the mixture was dripped off for 1.5h, and the reaction was kept warm for 10min;

[0053] b. After the reaction is completed, the obtained reaction solution is cooled and filtered, and then the solvent and unreacted acrylic acid are evaporated under reduced pressure to obtain a photoactive polyester oligomer with 3 to 4 repeating segments.

[0054] Embodiment 6:

[0055] The method for preparing a photoactive polyester oligomer by lactone ring opening of the present invention comprises the following specific steps:

[0056] a. Add 550 mL of toluene, 0.5 g of TEMPO, 0.5 g of p-hydroxyanisole, 10.92 g of boric acid ester, 27.3 g of phosphotungstic acid and 432 g of acrylic acid into a four-necked flask, heat to reflux, and after the temperature stabilizes, start to drop 114 g of ε-caprolactone continuously, drip it over 2 h, and keep the reaction warm for 10 min;

[0057] b. After the reaction is completed, the obtained reaction solution is cooled and filtered, and then the solvent and unreacted acrylic acid are evaporated under reduced pressure to obtain a photoactive polyester oligomer with 1 to 2 repeating segments.

[0058] The test data of the photoactive polyester oligomers prepared in the comparative example and Examples 1-6 of the present invention are shown in Table 1, wherein the average molecular weight is determined by LC-MS or GPC, the number of repeating segments is calculated based on the average molecular weight and product structure, and the double bond content is determined by Weiss titration (C(Na2S2O3)=0.1079mol / L).

[0059] Table 1 Relevant performance test data of the products prepared in comparative examples and embodiments 1-6 of the present invention

[0060] Number of repeating segments, n Average molecular weight, g / mol Double bond content (mmol / g) Comparative Example 14～15 1686 0.58 Example 1 5～6 662 1.47 Example 2 2～3 334 2.85 Example 3 3～4 369 2.68 Example 4 2～3 292 3.41 Example 5 3～4 428 2.30 Example 6 1～2 213 4.64

Claims

1. A method for preparing a photoactive polyester oligomer by lactone ring opening, characterized in that: The method comprises the following steps: a. Add acrylic acid, a ring-opening catalyst, an esterification catalyst, a polymerization inhibitor and a solvent into a reaction vessel, heat to reflux, and then start to continuously dropwise add a lactone monomer to carry out a heat-insulating reaction; b. After the reaction is completed, the obtained reaction product is cooled and filtered, and then the solvent and unreacted acrylic acid are evaporated under reduced pressure to obtain the target product, a photoactive polyester oligomer.

2. The method for preparing photoactive polyester oligomers by lactone ring opening according to claim 1, characterized in that: In step a, the molar ratio of the lactone monomer to the acrylic acid is 1:1-6; the amount of the ring-opening catalyst added is 1-10% of the total mass of the lactone monomer and the acrylic acid; the amount of the esterification catalyst added is 5-10% of the total mass of the lactone monomer and the acrylic acid; the amount of the solvent added is an equal volume of the lactone monomer and the acrylic acid; and the amount of the inhibitor added is 0.2-0.5% of the mass of the acrylic acid.

3. The method for preparing photoactive polyester oligomers by lactone ring opening according to claim 1, characterized in that: In step a, the time for adding the lactone monomer dropwise is 1 to 2 hours, and the time for the heat preservation reaction is 10 to 30 minutes.

4. The method for preparing photoactive polyester oligomers by lactone ring opening according to claim 1, characterized in that: The ring-opening catalyst in step a is any one or both of diphenyl phosphate and borate.

5. The method for preparing photoactive polyester oligomers by lactone ring opening according to claim 1, characterized in that: The esterification catalyst in step a is at least one of p-toluenesulfonic acid, p-toluenesulfonic acid monohydrate, 732 strong acid cation exchange resin and phosphotungstic acid.

6. The method for preparing photoactive polyester oligomers by lactone ring opening according to claim 1, characterized in that: The solvent is any one of petroleum ether, toluene and xylene.

7. The method for preparing photoactive polyester oligomers by lactone ring opening according to claim 1, characterized in that: The lactone monomer in step a is any one of ε-caprolactone, γ-butyrolactone and δ-valerolactone.

8. The method for preparing photoactive polyester oligomers by lactone ring opening according to claim 1, characterized in that: The inhibitor in step a is at least one of hydroquinone, p-hydroxyanisole and 2,2,6,6-tetramethylpiperidinyl oxide TEMPO.

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