A rosin-based epoxy resin with fluorescence properties, its preparation method and its application

Abstract

The present invention discloses a rosin-based epoxy resin with fluorescence properties, its preparation method and its applications. The rosin-based epoxy resin with fluorescence properties, abbreviated as HAR-EP, has the following structural formula: wherein, n = 0, 0.2, 0.4, 0.5, 2.3, 4.7. The present invention uses hydrogenated acrylic rosin (HAR) and bisphenol A epoxy resin (EP) as raw materials, uses triphenylphosphine as a catalyst, monitors the reaction process through acid value, and prepares a rosin-based epoxy resin with fluorescence properties through epoxy acid ring-opening reaction at high temperature. Its preparation is simple, solvent-free, the reaction is easy to control, it has excellent mechanical properties and thermal stability, has a relatively high bonding strength without curing, can be recycled, and at the same time has strong fluorescence properties, and can emit blue light of 492 nm under the excitation of ultraviolet light.

Description

Technical Field

[0001] The present invention relates to a rosin-based epoxy resin with fluorescent properties, a preparation method thereof and an application thereof, and belongs to the technical field of chemical engineering materials. Background Art

[0002] The earliest patent for epoxy resin adhesives appeared in 1940. It is a synthetic adhesive that started early and is widely used. Currently, it is widely applied in the fields of aviation, shipbuilding, automobiles, trains, machinery manufacturing, light industry, electronics, military, and people's daily lives. Epoxy adhesives are highly regarded in the industry because of their excellent performance, wide application range, simple process, low investment, and the fact that the vast majority of varieties can be prepared and used immediately. More and more scholars have started basic theoretical research and technological innovation on epoxy resin adhesives from different aspects. Although there are many types of epoxy resins, their development is uneven. Among them, bisphenol A-type epoxy resin was the first to be commercialized, with good comprehensive performance and the largest output, accounting for 90% of the total amount of epoxy resins. It is also the most commonly used and technically mature epoxy resin in epoxy adhesives. Understanding the composition, structure, and properties of bisphenol A-type epoxy resin is the basis for engaging in the practice of epoxy adhesives and also the starting point for understanding the entire field of epoxy adhesives, so it is very important.

[0003] Bisphenol A-type epoxy resin is a polycondensation product of bisphenol A and epichlorohydrin under alkaline catalysis. Depending on the reaction conditions, resins with low molecular weight or medium molecular weight are formed. Usually, its composition can be expressed by the following ideal structural formula:

[0004]

[0005] In the formula, n is the degree of polycondensation and also represents the number of hydroxyl groups in the molecular chain. When the molecular chain of the resin is short (n < 2), the resin is a yellow to amber viscous syrup-like liquid at room temperature; when the molecular chain is longer (2 < n < 10), the resin is an amber solid at room temperature; when n = 0, the molecular weight of the epoxy resin is 340, which is actually a low molecular weight epoxide.

[0006] As can be seen from the formula, the two epoxy groups in the molecule are located at both ends of the molecule, and there are ether bonds, methylene bonds, benzene rings, isopropylidene groups, and a small amount of hydroxyl side chains in the middle. Generally, the groups in the middle part are relatively stable and mainly endow the molecular chain with mechanical properties. For example, the benzene ring endows rigidity, and the methylene group and ether bond endow flexibility. The combination of rigidity and flexibility makes it have good load-bearing performance and appropriate thermal properties after curing. The epoxy groups at both ends are active and can further form hydroxyl groups and ether bonds during the curing process, endowing the cured resin with high cohesion and strong adhesion to the surface of the adherend. The hydroxyl groups in the side chain play a beneficial role in the curing of epoxy resin. The structure of bisphenol A epoxy resin also endows it with good solubility and compatibility with polar solvents, plasticizers, diluents, curing agents, and polar polymers, which also promotes its application in adhesive technology.

[0007] The epoxy groups contained in bisphenol A epoxy resin are three-membered ring ethers. Due to the ring strain of the three-membered ring and the combination of the oxygen atom and the vinyl π bond, the three-membered ring is very unstable and the carbon-oxygen bond is prone to breakage, so the epoxy group shows activity. At the same time, the epoxy group in bisphenol A epoxy resin has an asymmetric structure, and the ring group is adjacent to the ether bond through the methylene group. The oxygen atom in the ether bond has electronegativity and can produce a static electrophilic inductive effect on the epoxy group; the other end of the ether bond is a benzene ring, and the oxygen atom also has a static electrophilic inductive effect on the benzene ring. At the same time, the unshared electron pair on the oxygen atom forms a p-π conjugate system with the π electron cloud on the benzene ring, having a hyperconjugation effect. The combination of the oxygen atom and the benzene ring reduces the electron cloud density of the benzene ring due to the static electrophilic inductive effect; the hyperconjugation effect increases the electron cloud density of the benzene ring. During the reaction, the dynamic conjugation effect dominates. In other words, the benzene ring makes the unshared electron pair on the oxygen atom of the ether bond conjugate with itself, which strengthens the static electrophilic inductive effect of the oxygen atom on the epoxy group, making the carbon atom on the epoxy group more positively charged and more susceptible to nucleophilic attack and ring opening. The above effects can be expressed as follows.

[0008]

[0009] It can be seen that the structure of bisphenol A epoxy resin determines its suitable ring-opening activity, which is the internal reason for its good storage stability and processability.

[0010] Bisphenol A epoxy resin has been used in adhesives for decades, and no obvious poisoning symptoms have been found. Animal experiments show that this type of resin is non-toxic. Some people placed experimental animals in the vapor of bisphenol A epoxy resin for 50 days, and no significant toxicity was visible.

[0011] However, epoxy resin cannot be used alone and can only crosslink into a thermosetting resin after being cured with a curing agent. In existing reports, most of the curing agents for epoxy resin adhesives are derived from petroleum-based resources. Although petrochemical raw materials are cheap and easily available, they will cause environmental pollution when burned! And fossil raw materials, as non-renewable energy sources, are limited in resources! Uncontrolled use will cause resource and environmental crises such as oil depletion, greenhouse effect, and white waste. Due to the increasing consumption of fossil resources and the increasingly severe environmental pollution, the development of biodegradable bio-based materials has become the key to maintaining social sustainable development. To build a more sustainable society, it is necessary to gradually use bio-based materials to replace traditional petroleum-based materials. More and more biomass resources, including vegetable oil, lignin, cellulose, and rosin, have been reported. Rosin is a biomass with rich resources, low price, and renewable, containing carboxyl active groups and being easy to chemically modify. China is rich in rosin resources, with an average annual output of more than 400,000 tons, accounting for about 60% of the total global rosin output. Rosin is used in the production of adhesives due to its rich properties and low price. Liu et al. developed two rosin acid-based epoxy resins and epoxy resin curing agents with better thermal and mechanical properties than petroleum-based systems. However, most epoxy resin adhesives use irreversible chemical reactions between curing agents and epoxy resins to generate a three-dimensional network substance, thereby improving the stability and mechanical strength of the entire system, but it will lead to inherent defects such as poor toughness, difficulty in recycling, and insufficient shape plasticity, greatly limiting the application of epoxy resin. And the existing reported epoxy resin adhesives almost have no fluorescence properties. Summary of the Invention

[0012] The present invention provides a rosin-based epoxy resin with fluorescence properties, its preparation method, and its application. Using hydrogenated acrylic rosin (HAR) and bisphenol A epoxy resin (EP) as raw materials, and triphenylphosphine as a catalyst, the progress of the reaction is monitored by acid value. At high temperature, through the epoxy acid ring-opening reaction, a rosin-based epoxy resin with fluorescence properties is prepared. Its preparation is simple, solvent-free, and the reaction is easy to control. Without the premise of curing, it still has a high bonding strength and strong fluorescence properties. Under the excitation of ultraviolet light, it can emit blue light of 492 nm.

[0013] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0014] A rosin-based epoxy resin with fluorescence properties, abbreviated as HAR-EP, has the following structural formula:

[0015]

[0016] Among them, n = 0, 0.2, 0.4, 0.5, 2.3, 4.7.

[0017] In this study, hydrogenated acrylic rosin was used as the raw material, enabling the prepared epoxy resin to maintain its linear structure and thermoplastic properties without the need for further curing. It can be directly applied to adhesives and can achieve 8 cycles while still maintaining more than 80% of its original bonding performance. Under the excitation of ultraviolet light, it can emit blue light at 492 nm, making it applicable to anti-counterfeiting and information transmission, thus broadening the application value of rosin.

[0018] The above-mentioned rosin-based epoxy resin with fluorescence properties is prepared by acid-ring opening of hydrogenated acrylic rosin and bisphenol A type epoxy resin without the need for solvents during the reaction process.

[0019] The above-mentioned introduction of the rosin skeleton into the epoxy resin prepared a rosin-based epoxy resin with fluorescence properties, which can emit blue light at 492 nm under the excitation of ultraviolet light.

[0020] The above-mentioned bisphenol A type epoxy resin is at least one of bisphenol A diglycidyl ether (BADGE), E-51 epoxy resin, E-44 epoxy resin, E-42 epoxy resin, E-20 epoxy resin or E-12 epoxy resin.

[0021] To ensure the performance of the obtained rosin-based epoxy resin fluorescence anti-counterfeiting adhesive, as one of the preferred implementation schemes, the above-mentioned bisphenol A type epoxy resin uses E-51 epoxy resin;

[0022] The preparation method of the above-mentioned rosin-based epoxy resin with fluorescence properties is to stir and react hydrogenated acrylic rosin, bisphenol A type epoxy resin and triphenylphosphine at a temperature of 160 - 180 °C until the acid value is less than 1 mgKOH / g, and then pour it into a polytetrafluoroethylene mold while it is hot and cool it. The obtained solid is HAR-EP.

[0023] This application accurately measures the acid value of hydrogenated abietic acid using a 0.1 mol / L KOH standard solution and accurately measures the epoxy value of bisphenol A type epoxy resin according to the method described in GB / T1677 - 2008. During the reaction, the reaction process is accurately monitored every half hour using a 0.1 mol / L KOH standard solution, and the reaction is stopped when the acid value of the mixed system is less than 1 mgKOH / g.

[0024] To ensure product quality, the molar ratio of -COOH in hydrogenated acrylic rosin to the epoxy group in bisphenol A type epoxy resin is 1:(2 - 2.1); triphenylphosphine is used as a catalyst, and the mass dosage of triphenylphosphine is 1 - 3 g / 500 g of the total mass; among them, the total mass is the sum of the masses of hydrogenated acrylic rosin and bisphenol A type epoxy resin.

[0025] Further preferably, the mass ratio of hydrogenated abietic acid rosin to bisphenol A epoxy resin is preferably 1:(1.5 - 8), more preferably 1:(1.6 - 1.9); the mass dosage of triphenylphosphine is preferably 1 - 2 g / 500 g of the total mass; the stirring speed is 100 - 300 rpm; the reaction time is 1 - 2 h.

[0026] The above-mentioned rosin-based epoxy resin with fluorescence properties can be directly applied to adhesives without a curing agent.

[0027] One implementation scheme as an adhesive is: preparing HAR-EP into a hot melt adhesive film; placing the hot melt adhesive film between two substrates, and treating it in a hot press at 65 - 95 °C (pressure 15 - 25 N / m 2 ) for 1 - 3 minutes, and the two substrates are bonded together; the hot melt adhesive film can be recycled, that is, the hot melt adhesive film can be used repeatedly as an adhesive.

[0028] The above-mentioned bonded substrates are preferably wood boards, stainless steel, glass, etc.

[0029] The forming conditions of the above-mentioned hot melt adhesive film are: hot pressing into a film at 70 - 80 °C and 2.5 MPa; the thickness of the hot melt adhesive film is 0.05 - 0.25 mm. These conditions are also the recycling conditions, and the recycled rosin-based epoxy resin with fluorescence properties is hot pressed into a film at 70 - 80 °C and 2.5 MPa and recycled for use in adhesives.

[0030] The above-mentioned rosin-based epoxy resin with fluorescence properties emits blue light of 492 nm under the excitation of ultraviolet light and can be applied to fluorescence anti-counterfeiting and / or information transmission.

[0031] Technologies not mentioned in the present invention refer to the prior art.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) By combining the structural characteristics of rosin and bisphenol A epoxy resin, the present invention synthesizes a class of rosin-based epoxy resins with strong fluorescence properties through an epoxy acid ring-opening reaction. The product retains the original molecular linear structure and thermoplastic properties, can be applied to adhesives without adding a curing agent, and can be recycled.

[0034] (2) Based on the unique structures of bisphenol A epoxy resin and rosin, the preparation method of the present invention is simple, without solvents, the raw materials are widely sourced and the cost is extremely low. The prepared rosin-based epoxy resin has excellent mechanical properties and thermal stability;

[0035] (3) The rosin-based epoxy resin prepared by the present invention has strong fluorescence properties. Under the excitation of ultraviolet light, it can emit blue light with a wavelength of 492 nm, and the quantum yield can reach 10.78%. It can be applied to fluorescence anti-counterfeiting, broadening the application value of rosin and realizing the high-value sustainable utilization of rosin. Description of the Drawings

[0036] Figure 1 is the NMR spectrum of HAR-EP;

[0037] Figure 2 is the bonding schematic diagram of HAR-EP;

[0038] Figure 3 is the tensile shear strength curve of HAR-EP on a wooden board (upper figure) and a stainless steel plate (lower figure);

[0039] Figure 4 is the thermogravimetric diagram of HAR-EP;

[0040] Figure 5 is the lap shear strength of HAR-EP when bonding the wooden board after each reuse 0.2 ;

[0041] Figure 6 is HAR-EP 0.2 , the fluorescence spectra of E-51 epoxy resin and HAR;

[0042] Figure 7 is HAR-EP 0.2 in the physical diagram under white light and ultraviolet light irradiation;

[0043] Figure 8 is HAR-EP 0.2 image of bonding stainless steel, used to lift an adult with a total weight of 75 kg and a bonding area of 3.125 cm2 Detailed Embodiments

[0044] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments. However, the content of the present invention is not limited to the following embodiments.

[0045] In each example, operations were carried out at room temperature (15 - 25 °C) unless otherwise specified. Hydrogenated acrylic rosin (HAR) was purchased from Shenzhen Giteng Industry Co., Ltd. Bisphenol A diglycidyl ether (BADGE) was purchased from Aladdin Reagent Co., Ltd. in China. E-51, E-44, and E-42 epoxy resins were purchased from Macklin Reagent Co., Ltd. E-20 and E-42 resins were purchased from Baling Petrochemical Branch of Sinopec Group Asset Management Company. Triphenylphosphine was purchased from Aladdin Reagent Co., Ltd. in China. Potassium hydroxide was purchased from Sinopharm Chemical Reagent Co., Ltd. All reagents were used as received without any further purification.

[0046] Example 1

[0047] The synthesis of a rosin-based epoxy resin includes the following steps:

[0048] (1) Weigh 10 g of hydrogenated acrylic rosin, 18.378 g of E-51 epoxy resin, and 0.1135 g of triphenylphosphine, add them to a three-necked flask, stir mechanically, and carry out condensation reflux. Slowly heat up to 180 °C, accurately monitor the reaction process every half hour using a 0.1 mol / L KOH standard solution, stop the reaction when the acid value of the mixed system is less than 1 mgKOH / g, which takes 1.2 h. Pour it into a polytetrafluoroethylene mold while it is hot and let it cool naturally. The obtained solid is HAR-EP 0.2 , and no solvent is required during the preparation process. Use the same method to prepare rosin-based epoxy resins with different degrees of polycondensation. The formulations of rosin-based epoxy resins with different degrees of polycondensation are shown in Table 1.

[0049] Table 1. Contents of HAR, EP, and catalyst corresponding to rosin-based epoxy resins with different degrees of polycondensation

[0050]

[0051] Note that HAR is hydrogenated acrylic rosin, EP is bisphenol A epoxy resin; aR is the ratio of carboxyl group content to epoxy group content; BADGE is bisphenol A diglycidyl ether.

[0052] The NMR spectrum of HAR-EP0 is as Figure 1 shown. Hydrogenated acrylic rosin has a large steric hindrance and a low crosslinking density. Introducing hydrogenated acrylic rosin into bisphenol A epoxy resin, keeping the ratio aR of carboxyl group to epoxy group at 1:2, it is not easy to crosslink to form an irreversible three-dimensional network structure, so that the product maintains its original thermoplastic properties. The obtained rosin-based epoxy resins with fluorescence properties can all be thermoplastically deformed at 65 - 95 °C and a pressure of 15 - 25 N.

[0053] Example 2

[0054] According to the determination method of tensile shear strength in GB / T 7124-2008, mechanical property tests were carried out on six specimens of HAR-EP0, HAR-EP 0.2 , HAR-EP 0.4 , HAR-EP 0.5 , HAR-EP 2.3 , HAR-EP 4.7 , and the method is as follows:

[0055] The HAR-EP prepared in Example 1 was pressed into a film with a thickness of 0.10 mm within 1 minute under the conditions of 70-80 °C and 2.5 MPa, and cut into a rectangle (25 mm × 12.5 mm) and placed in the center of a wooden board and a stainless steel substrate with the specifications of 100 mm × 25 mm × 1.6 mm. The bonding area was 25 mm × 12.5 mm, and the substrates were fixed together with two paper clips; hot-pressed at 85 °C for 1.5 min and cooled to room temperature. No curing agent was required during the bonding of the substrates; the tensile shear strength was tested using a universal testing machine, and the test was conducted in parallel three times, and the average value was taken to obtain the shear strength-displacement curve and the shear strength histogram of HAR-EP on the wooden board and stainless steel, as Figure 3 shown. The upper figure shows the bonding of wooden boards together, and the lower figure shows the bonding of stainless steel plates together. It can be seen from Figure 3 that HAR-EP 0.2 has the best mechanical properties. In the figure, a is HAR-EP0, b is HAR-EP 0.2 , c is HAR-EP 0.4 , d is HAR-EP 0.5 , e is HAR-EP 2.3 , f is HAR-EP 4.7 .

[0056] Example 3

[0057] Thermal stability tests were carried out on six specimens of HAR-EP0, HAR-EP 0.2 , HAR-EP 0.4 , HAR-EP 0.5 , HAR-EP 2.3 , HAR-EP 4.7 . Under the condition that the nitrogen gas flow rate was 100 mL / min, 3-10 g of the sample was heated from 0 °C to 800 °C at a heating rate of 10 °C / min. The test results are as Figure 4 shown. Let the temperature at which the mass loss of the sample is 10 wt.% be T d . Among them, the Td of HAR-EP0 is 354.43 °C, the Td of HAR-EP 0.2 is 354.53 °C, the Td of HAR-EP 0.4 is 362.05 °C, the Td of HAR-EP 0.5 is = 362.06 °C, the Td of HAR-EP 2.3 is 395.44 °C, and the Td of HAR-EP 4.7 is 406.73 °C. With the increase of the polycondensation degree content, Td increases slightly, and the Td values of all specimens are higher than 350 °C, indicating that they have good thermal stability.

[0058] Example 4

[0059] For HAR-EP 0.2 A cyclic adhesion test was carried out. After the wood board substrate was tested once (Example 2), the substrate was fixed together with two paper clips, and the overlapping area remained the same as before. It was hot-pressed at 85 °C and 20 N / m 2 for 1.5 min. A universal testing machine was used to test its tensile shear strength, and the test was repeated 6 times. Its adhesion strength is as Figure 5 shown. After 6 cycles (essentially 7 adhesions), its adhesion strength can still maintain more than 80% of the initial adhesion strength. After 8 cycles, the adhesion strength can still maintain more than 80% of the initial adhesion strength.

[0060] Example 5

[0061] The fluorescence properties of HAR-EP 0.2 , E-51 epoxy resin, and HAR were measured using a fluorescence spectrometer. The test results are as Figure 6 shown. Under ultraviolet light excitation, HAR-EP 0.2 has strong fluorescence properties (Curve 3), can emit blue light at 492 nm, and the quantum yield can reach 10.78%. While HAR has relatively weak fluorescence properties (Curve 1), and E-51 has no fluorescence properties (Curve 2). Figure 7 The physical pictures of HAR-EP 0.2 under white light and ultraviolet light irradiation are shown. It can be seen that it is yellow under white light and cyan under ultraviolet light irradiation, and it can be effectively used for fluorescence anti-counterfeiting.

[0062] Example 6

[0063] Two stainless steel plates with holes at one end were bonded using HAR-EP 0.2 (the method is the same as Example 2). The bonding area is only 12.5×25 mm. The bonded stainless steel plates were placed vertically, with an electronic tensile machine hung above and an adult (weight 65 kg) hung below. As Figure 8 shown, this stainless steel plate can be used to hang an adult. The reading of the electronic tensile machine shows a load-bearing of 753 N, that is, it can bear a weight of 76 kg. After the bonding, the resin on the surface of the substrate was recovered and remelted into a film within 1 minute under the conditions of 70 - 80 °C and 2.5 MPa, and continued to be applied to the adhesive. Compared with the previous use, the loss of mechanical properties is less than 0.2%.

Claims

1. Use of a rosin-based epoxy resin with fluorescence properties, characterized in that: The rosin-based epoxy resin with fluorescence properties is simply called HAR-EP, and its structural formula is as follows: Among them, n = 0, 0.2, 0.4, 0.5, 2.3, 4.7; The rosin-based epoxy resin with fluorescence properties is used as an adhesive and does not require a curing agent.

2. Use of the rosin-based epoxy resin with fluorescence property as claimed in claim 1, characterized in that: The rosin-based epoxy resin with fluorescence properties is prepared by the acid ring-opening of hydrogenated acrylic rosin and bisphenol A epoxy resin, and no solvent is required during the reaction process.

3. Use of the rosin-based epoxy resin having fluorescence properties according to claim 2, characterized in that: The bisphenol A epoxy resin is at least one of E-51 epoxy resin, E-44 epoxy resin, E-42 epoxy resin, E-20 epoxy resin or E-12 epoxy resin.

4. Use of the rosin-based epoxy resin with fluorescent properties according to claim 3, characterized in that: The bisphenol A epoxy resin adopts E-51 epoxy resin.

5. Use of the rosin-based epoxy resin with fluorescence property according to any one of claims 2-4, characterized in that: The preparation method of the rosin-based epoxy resin with fluorescence properties is as follows: hydrogenated acrylic rosin, bisphenol A epoxy resin and triphenylphosphine are stirred and reacted at a temperature of 160-180 °C until the acid value is less than 1 mgKOH / g, and then poured into a polytetrafluoroethylene mold while it is hot, and cooled. The obtained solid is HAR-EP; among them, the molar ratio of -COOH in hydrogenated acrylic rosin to epoxy groups in bisphenol A epoxy resin is 1:(2-2.1); triphenylphosphine is used as a catalyst, and the mass dosage of triphenylphosphine is 1-3 g / 500 g of the total mass; among them, the total mass is the sum of the masses of hydrogenated acrylic rosin and bisphenol A epoxy resin.

6. Use of the rosin-based epoxy resin having fluorescence properties as claimed in claim 5, characterized in that: The mass ratio of hydrogenated acrylic rosin to bisphenol A epoxy resin is 1:(1.5-8); the mass dosage of triphenylphosphine is 1-2 g / 500 g of the total mass; the stirring speed is 100-300 rpm; the reaction time is 1-2 h.

7. Use of the rosin-based epoxy resin with fluorescent properties according to any one of claims 1-4, characterized in that: Prepare HAR-EP into a hot melt adhesive film; place the hot melt adhesive film between two substrates, and process it for 1 to 3 minutes under the hot pressing conditions of a temperature of 65 - 95 °C and a pressure of 15 - 25 N / m 2 , so that the two substrates are bonded together; the hot melt adhesive film can be recycled.

8. The use according to claim 7, characterized in that: The forming conditions of the hot-melt adhesive film are: hot pressing into a film at 70-80 °C and 2.5 MPa; the thickness of the hot-melt adhesive film is 0.05-0.25 mm; the substrate is a wooden board, stainless steel or glass.

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