Environment-friendly unsaturated resin and preparation method thereof

Abstract

The invention discloses environment-friendly unsaturated resin and a preparation method thereof, and belongs to the technical field of resin materials. The unsaturated resin is prepared from the following raw materials in parts by weight: 22 to 26 parts of polyethylene glycol terephthalate, 28 to 32 parts of dipropylene glycol, 14 to 18 parts of maleic anhydride, 2 to 4 parts of furan ring-containing dihydric alcohol, 2 to 4 parts of adipic acid, 2 to 3 parts of benzoic acid, 1 to 2 parts of glycerol, 18 to 22 parts of dimethyl itaconate, 1 to 3 parts of trimethylolpropane triacrylate, 2 to 4 parts of polyethylene glycol diacrylate, 0.5 to 2 parts of bismaleimide and the like. The preparation method comprises the following steps: introducing a furan group into polyester synthesis, cooling, and sequentially adding a mixed crosslinking agent and bismaleimide for pre-crosslinking. The resin not only has excellent mechanical properties, is green and environment-friendly, but also has heat-initiated self-repairing capability and recoverability and reprocessability, and widens the application of the resin in the field of high-end composite materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of resin materials, and particularly relates to an environmentally friendly unsaturated resin and a preparation method thereof. BACKGROUND

[0002] Unsaturated polyester resin is a common thermosetting resin, which is widely used due to its easy processing and low price. Unsaturated resin is mainly prepared by polycondensation of dihydric alcohol and diacid, and then dissolved in a crosslinking monomer. The diacid is generally selected from phthalic anhydride and derivatives of benzene, or dicyclopentadiene is used to modify the resin. The dihydric alcohol is ethylene glycol, diethylene glycol, etc. The most common crosslinking monomer is styrene, which has a large dependence on petroleum resources. At the same time, the normal temperature vapor pressure of styrene is 853 Pa, which is easy to volatilize and has high toxicity. In the production and use process of unsaturated resin, it causes great harm to the human body and the environment. With the continuous improvement of people's environmental protection concept, developing safer and more environmentally friendly products has gradually become a research hotspot.

[0003] At present, the methods for reducing the volatility of unsaturated polyester resin mainly include external film-forming agent method, low styrene content method, use of styrene inhibition additive method, and low volatility monomer substitution method, etc.

[0004] For example, patent CN114478931B discloses an unsaturated polyester resin composition with low styrene volatility. The patent significantly reduces the volatility of styrene and the shrinkage rate of the resin by introducing methylstyrene, hydroxy acrylate monomer and benzene diallyl ester as comonomers. However, the core raw material of this technical solution still mainly comes from petroleum-based chemicals, and the efficient use of bio-based or renewable resources has not been achieved.

[0005] In addition, once the traditional unsaturated polyester resin is cured, it forms a three-dimensional network structure and becomes a thermosetting material that is insoluble and infusible. It is difficult to repair damage and cannot be recycled, which causes resource waste and environmental pressure. Therefore, developing unsaturated polyester resin with low toxicity, low volatility, self-repairing ability and recyclability has become a key problem to be solved in this field. SUMMARY

[0006] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide an environmentally friendly unsaturated resin with reduced environmental pollution and effectively reduced curing volatile fraction, and a preparation method thereof.

[0007] The technical scheme adopted by the present application to solve its technical problems is: the raw material weight parts composition of the environment-friendly unsaturated resin comprises: polyethylene terephthalate 22-26 parts, dipropylene glycol 28-32 parts, maleic anhydride 14-18 parts, furan ring containing diol 2-4 parts, adipic acid 2-4 parts, benzoic acid 2-3 parts, glycerol 1-2 parts, dimethyl itaconate 18-22 parts, trimethylolpropane triacrylate 1-3 parts, polyethylene glycol diacrylate 2-4 parts, bismaleimide 0.5-2 parts, antioxidant 0.05-0.07 parts, polymerization inhibitor 0.015-0.03 parts, catalyst 0.03-0.05 parts, paraffin 0.005-0.007 parts.

[0008] The source of polyethylene terephthalate in the present formula is preferably waste PET material, which can reduce the accumulation of plastic garbage and reduce the demand for new raw materials, saving petroleum resources. The benzene structure and ethylene glycol structure provided by polyethylene terephthalate greatly improve the strength, heat distortion temperature and chemical resistance of the resin to meet the application of artificial stone and the like.

[0009] More importantly, the diol in the present application is dipropylene glycol, which on the one hand increases the toughness of the resin, and on the other hand reduces the crystallinity, and at the same time the methyl groups in the dipropylene glycol have a space shielding protection effect on the oxygen bridge and the ester bond, improving the water resistance of the resin.

[0010] The molecular structure of dipropylene glycol further enhances the synergistic effect of the resin system: the steric hindrance effect of the propyl side chain in its molecule can significantly reduce the aromatic ring stacking density of polyethylene terephthalate depolymerization products, inhibit the regeneration of the crystalline region, and fundamentally improve the compatibility with dimethyl itaconate; at the same time, the ether bond oxygen atom forms a hydrogen bond network with the carboxyl group of benzoic acid, effectively delaying the reaction exothermic peak during the curing stage, avoiding local overheating caused by curing stress; and the hydrophobic propyl segment of dipropylene glycol and the hydrophilic ether bond form an amphiphilic structure, which can bridge inorganic fillers and resin matrix when the filler interface is oriented and arranged, so that the bending strength of the high filler content system is improved. This multiple action mechanism synergistically optimizes the processing stability and mechanical properties of the bio-based resin.

[0011] Glycerol has three hydroxyl groups, providing a branched structure for the resin, improving the stiffness of the resin, and improving the wettability of the resin to the filler, meeting the process requirement of 70%-80% filler content in artificial stone.

[0012] An appropriate amount of dimethyl itaconate is added in the present application, which has a normal temperature vapor pressure of 4 Pa and a boiling point of 208℃, has the advantages of low toxicity and low volatility, contains a double bond in the molecule which can participate in crosslinking polymerization reaction, and has less volatilization during the curing process, can improve the curing rate and obtain excellent curing effect, and can fundamentally solve the environmental pollution problem of styrene.

[0013] The molecular structure of dimethyl itaconate itself brings triple synergistic gains to the system: the beta-positioned double carboxylic acid methyl ester structure increases the rigidity of the molecular chain through intramolecular hydrogen bonding, so that the bending modulus of the cured product is improved; the electron-withdrawing effect of the two methyl ester groups significantly activates the double bond on the central methylene group, so that the copolymerization rate with maleic anhydride is improved; meanwhile, the ester group oxygen atom and the Ca 2+ Form a coordination bond, and still maintain high tensile strength in a 80% high filler system. This unique multifunctional monomer structure simultaneously strengthens the reactivity, mechanical properties and interfacial bonding force at the molecular level.

[0014] The present application introduces Diels-Alder (D-A) dynamic covalent bonds and mixed crosslinking systems by the high-efficiency Diels-Alder reaction between the maleimide group of bismaleimide (BMI) and the furan group on the polyester chain, so that the resin has self-repairing ability and recyclability. When the material is damaged, heating at 120℃~130℃ can trigger the reverse reaction of D-A bond, so that the crosslinking network is temporarily dissociated, the chain segment movement ability is enhanced, so that the crack interface contacts and flows; then, at 60℃~90℃, the D-A bond reacts to realize the self-repairing of the crack, and significantly prolong the service life of the product. Further, at a higher temperature of >130℃, the D-A bond reversible reaction can make the resin network after curing de-crosslinking, restore the processing properties of solubility and fusibility, so as to realize closed-loop recycling and reprocessing, and solve the solid waste problem of thermosetting resin.

[0015] At the same time, trimethylolpropane triacrylate (TMPTA) as a multifunctional crosslinking agent, cooperates with dimethyl itaconate to effectively improve the crosslinking density, hardness and heat resistance of the final cured product. The long flexible chain of polyethylene glycol diacrylate (PEGDA) plays a toughening role between crosslinking points, and produces a synergistic effect with TMPTA, so that the resin has high strength, impact toughness and elongation at break are significantly improved, and the rigid and tough balance is realized.

[0016] Preferably, in the above-mentioned environmentally friendly unsaturated resin, the furan ring-containing diol is a furan diol ester obtained by reacting 2,5-furan dicarboxylic acid with a diol. The regular furan ring structure in 2,5-furan dicarboxylic acid is derived from renewable biomass, which improves the green sustainability of the resin. This structure as a highly efficient diene has higher reactivity and more uniform sites with bismaleimide, thereby constructing a more regular and better reversible D-A dynamic crosslinking network. This not only enhances the controllability and repair efficiency of the self-repairing process, but also improves the performance consistency of the product after recycling and reprocessing. At the same time, the rigidity of the furan ring also synergistically enhances the initial rigidity and thermal stability of the resin matrix.

[0017] The preparation process of the furan ring-containing diol: under nitrogen protection, approximately 1:1~1.05 equimolar 2,5-furan dicarboxylic acid, diol (1,4-butanediol, ethylene glycol, 1,6-hexanediol) and 0.27%~0.32% titanium acid tetraisopropyl ester catalyst of total material mass are added to a reactor, and esterification is carried out by gradually heating to 180~200°C until the acid value is less than 5 mgKOH / g, and then excess diol is removed under reduced pressure to obtain a light yellow viscous liquid with a hydroxyl value of 280~320 mgKOH / g, which is the desired furan ring-containing diol (furan-based diol ester).

[0018] Preferably, in the above-mentioned environmentally friendly unsaturated resin, the number average molecular weight of the polyethylene glycol diacrylate is 400~600. The PEGDA with this molecular weight range has moderate flexible segment length, which can not only serve as an effective flexible spacer inserted into the crosslinked network to significantly absorb impact energy and greatly improve the toughness and crack resistance of the cured resin, but also ensure its appropriate reactivity and flowability, and excellent compatibility when blended with dimethyl itaconate, TMPTA and other monomers, avoiding phase separation, thereby ensuring the uniformity and storage stability of the resin system, and ultimately achieving the ideal balance of high strength and high toughness.

[0019] Preferably, in the above-mentioned environmentally friendly unsaturated resin, the antioxidant is a complex of one or more of 2,6-di-tert-butyl phenol (BHT), p-tert-butyl phenol (TBP) and triphenyl phosphite (TPP). Based on the characteristics of the carboxyl and hydroxyl groups generated by the degradation of waste PET that easily initiate oxidation side reactions, BHT directly protects the active groups by quenching free radicals, while TBP inhibits the generation of peroxides during the degradation process, reducing the risk of gelation; in the dimethyl itaconate crosslinking system, BHT avoids the pre-oxidation of double bonds to cause a decrease in curing rate by establishing an initial antioxidant barrier, and TBP ensures the integrity of the crosslinking reaction by decomposing residual peroxides; for the challenge of wet heat aging of high filler artificial stone, BHT effectively inhibits the oxidation degradation of the resin caused by water adsorbed on the surface of the filler, and TBP blocks the oxidation chain reaction catalyzed by metal impurities in the filler. Both of them act from the paths of free radical inhibition and peroxide decomposition, which significantly improves the environmental tolerance and application reliability of the resin.

[0020] Preferably, in the above-mentioned environmentally friendly unsaturated resin, the polymerization inhibitor is one or more than two arbitrary ratio mixture of hydroquinone, methyl hydroquinone, p-tert-butyl catechol and methyl hydroquinone. Preferably, the polymerization inhibitor has high free radical capture ability, and the polymerization inhibitor contains phenolic hydroxyl or quinone group, which can effectively capture the free radicals generated in the resin, especially the free radicals generated in the double bond polymerization process, thereby significantly prolonging the storage period of the resin, effectively preventing the resin from gelling due to self-polymerization reaction during storage and transportation, and ensuring that the resin maintains good flowability and stability before use.

[0021] Preferably, in the above-mentioned environmentally friendly unsaturated resin, the catalyst is one of monobutyl tin oxide, zinc acetate and tetrabutyl titanate. In the above-mentioned environmentally friendly unsaturated resin, one of monobutyl tin oxide, zinc acetate and tetrabutyl titanate is selected as the catalyst, which can significantly improve the synthesis efficiency and performance of the resin. Monobutyl tin oxide has high catalytic performance, can accelerate the esterification reaction rate, shorten the reaction time, and has good compatibility with the resin system, which helps to synthesize a resin with narrower molecular weight distribution and better performance. Zinc acetate is a mild catalyst that can promote the reaction at a lower temperature, reduce energy consumption, and improve the PET depolymerization efficiency and improve the color of the resin. Tetrabutyl titanate can synergistically act with other catalysts to improve the catalytic efficiency, adjust the molecular structure of the resin, improve the compatibility, and further improve the mechanical properties and heat resistance of the resin.

[0022] A preparation method of the above-mentioned environmentally friendly unsaturated resin, comprising the following steps: (1) Put the proportioned amount of polyethylene terephthalate, catalyst, diol containing furan ring, 22-26 parts of dipropylene glycol, 0.03-0.04 parts of antioxidant, and 0.005-0.007 parts of polymerization inhibitor into a reaction kettle, stir and heat, control the kettle temperature at 210-220°C for 1-2 hours until the material is clear and transparent, and then cool to below 100°C; (2) Add the proportioned amount of maleic anhydride, adipic acid, benzoic acid, glycerol, the remaining part of dipropylene glycol and antioxidant, and 0.005-0.007 parts of polymerization inhibitor to the product of step (1); then heat to 158-163°C, start the polycondensation and keep for 0.5-1 hour; continue to heat to 200-210°C and keep until the acid value reaches 15-25 mgKOH / g; (3) First cooling, reduce to below 180°C, add the remaining part of the polymerization inhibitor and the proportioned amount of paraffin wax, and stir uniformly; (4) Second cooling, reduce to 90-100°C, then add the proportioned amount of dimethyl itaconate, trimethylolpropane triacrylate and polyethylene glycol diacrylate in sequence, stir uniformly, and finally add the proportioned amount of bismaleimide, and stir and keep at this temperature for 0.5-1 hour; (5) Cool to room temperature, discharge.

[0023] The preparation method ensures the stability of the molecular structure and performance of the resin by precisely controlling the reaction conditions such as temperature, time and raw material addition sequence, avoids the occurrence of side reactions, and improves the quality and performance consistency of the resin. In addition, using low volatility and low toxicity dimethyl itaconate as a crosslinking monomer instead of traditional styrene fundamentally reduces the volatilization of styrene, reduces the harm to the human body and the environment during production, and makes the production and application of the resin more green and environmentally friendly. In addition, the method can improve the strength, heat distortion temperature, chemical resistance and toughness of the resin by reasonably matching various raw materials and additives, and can improve the rigidity and wettability of the resin to fillers, which can meet the application scenarios of high filler content such as artificial stone, and broaden the application range of the resin. The batch addition of polymerization inhibitors and antioxidants during the reaction process can effectively prevent oxidation and polymerization of the resin during production, storage and use, and prolong the storage period and service life of the resin.

[0024] During the polycondensation stage of preparing unsaturated polyester, the dihydric alcohol containing furan ring in the raw material participates in the reaction, and the furan ring structure is successfully embedded into the main chain or side chain of the polymer, providing the system with rich furan groups.

[0025] In step (4) of the synthesis process, after the polyester base resin is cooled to 90°C-100°C, the active diluent containing unsaturated double bonds (dimethyl itaconate, TMPTA, PEGDA) is first added, and then the bismaleimide (BMI) is added. Under this mild temperature condition, the maleimide group (diphenyl) of BMI will undergo a highly efficient Diels-Alder cycloaddition reaction with the furan group on the polyester chain to form a D-A adduct containing a six-membered ring. This process forms a part of reversible crosslinking points, namely D-A dynamic covalent bonds, before the resin is used. The combination of D-A dynamic covalent bonds and mixed crosslinking system enables the resin to have self-repairing ability and recyclability.

[0026] Preferably, the temperature rising speed during stirring and temperature rising in step (1) of the above preparation method is controlled at 150°C / h-250°C / h. The temperature rising rate of 150°C / h-250°C / h can rapidly raise the polyethylene terephthalate to a depolymerization temperature of 210°C-220°C in the reaction kettle, greatly shorten the reaction induction period and the overall time, and improve the production efficiency. At the same time, rapid heating reduces the residence time of the material in the low temperature zone, effectively inhibits the oxidation side reaction induced by the terminal carboxyl and terminal hydroxyl groups in the PET degradation process, reduces the risk of gelation, and ensures that the depolymerization product quickly forms a clear and transparent state.

[0027] Preferably, the cooling rate in step (1) of the above preparation method is controlled at 200-250°C / h. This cooling rate can quickly reduce the reaction system from the high-temperature depolymerization stage to a safe temperature, greatly shortening the residence time of the material in the high-temperature zone. The risk of oxidation side reactions or excessive chain scission of residual end carboxyl and end hydroxyl groups at high temperatures is effectively reduced, and the tendency of resin molecular weight distribution to widen and subsequent by-product generation during the induction period is reduced.

[0028] Preferably, the heating rate in step (2) of the above preparation method is controlled at 15-20°C / h. Maleic anhydride, adipic acid, benzoic acid, glycerol and other raw materials need to be fully mixed with the prepolymer after being added and participate in the reaction. Controlling the heating rate can avoid local overheating and ensure uniform distribution of these raw materials in the reaction system, thereby improving the conversion rate and efficiency of the reaction. At the same time, this heating rate helps to maintain the smooth progress of the reaction, reduces side reactions caused by rapid temperature changes, and ensures that the generated resin has a good molecular weight distribution and uniform structure. In addition, controlling the heating rate can also effectively protect the activity of the catalyst and avoid catalyst deactivation caused by sudden temperature rise.

[0029] Preferably, the cooling rate in step (3) of the above preparation method is controlled at 160-200°C / h for the first time, and the cooling rate in step (4) is controlled at 220-260°C / h for the second time. This two-stage cooling design ensures the performance of the resin by precisely controlling the rate: the first cooling rate quickly reduces the system from the high-temperature polycondensation endpoint of 200-210°C to below 180°C, significantly shortening the residence time of the material in the high-temperature oxidation-sensitive interval above 180°C, avoiding thermal initiation of prepolymers or molecular chain degradation of residual maleic anhydride double bonds, while maintaining melt flowability to facilitate uniform dispersion of paraffin into a film; the second ultra-high rate cooling to below 120°C can instantly cross the flash point risk zone of dimethyl itaconate 128°C, preventing loss of low-boiling-point monomers and thermal decomposition of the polymerization inhibitor. Both of them cooperate to complete the cooling process within 20 seconds, avoiding the risk of gelation caused by high-temperature side reactions, ensuring the activity of crosslinking monomers and the integrity of paraffin surface film formation, and providing a stable prepolymer base for high-filler impregnated resin.

[0030] Compared with the prior art, the environmentally friendly unsaturated resin and the preparation method thereof have the beneficial effects that: the raw materials used in the application have low volatility and toxicity, especially using waste polyethylene terephthalate (PET) as one of the main raw materials, which not only realizes waste recycling and reduces plastic garbage accumulation, but also saves petroleum resources, and meets the requirements of green environmental protection. Using low volatility and low toxicity dimethyl itaconate as a crosslinking monomer instead of traditional styrene, the emission of volatile organic compounds (VOCs) is fundamentally reduced, and the harm to the environment and human health is further reduced. By reasonably selecting and proportioning the raw materials and finely controlling the reaction conditions, a resin with uniform molecular weight distribution and stable performance can be synthesized. The resin has higher strength, heat distortion temperature, chemical resistance and toughness, and improves the wettability of fillers, which can meet the strict requirements of high filler ratio applications such as artificial stone. DETAILED DESCRIPTION

[0031] The application will be further described below in combination with examples. In order to facilitate the comparison of other process conditions, the same kind of furan ring dihydric alcohol is used in the examples and comparative examples, and example 7 is the best embodiment of the application.

[0032] When the environmentally friendly unsaturated polyester resin is prepared in examples 1-8, the raw material ratio is shown in table 1, and the preparation method comprises the following steps: (1) Put polyethylene terephthalate, catalyst, dihydric alcohol containing furan ring, and first part of dipropylene glycol, first part of antioxidant, and first part of polymerization inhibitor into the reaction kettle, heat to the specified temperature at the heating rate shown in table 1, and keep for a certain time until the material is clear and transparent, and then cool to below 100℃ at the cooling rate shown in table 1; (2) Add maleic anhydride, adipic acid, benzoic acid, glycerol, the remaining part of dipropylene glycol and antioxidant, and the second part of polymerization inhibitor to the product of step (1); then heat to 158-163℃ at the heating rate shown in table 1, and keep for a period of time after the beginning of polycondensation; continue to heat to 200-210℃ and keep until the acid value reaches the specified range; (3) First cooling, add the third part of polymerization inhibitor and paraffin to below 180℃ at the cooling rate shown in table 1, and stir uniformly; (4) Second cooling, after cooling to 90-100℃ at the cooling rate shown in table 1, add dimethyl itaconate, trimethylolpropane triacrylate (TMPTA) and polyethylene glycol diacrylate (PEGDA) in turn, stir uniformly, and finally add bismaleimide (BMI), and stir and keep at this temperature for 0.5-1h (all examples 1-8 are under this condition); (5) Cool to room temperature, discharge, and the self-repairable and recyclable environmentally friendly unsaturated polyester resin is obtained.

[0033] Table 1 Raw material ratio (by weight) and key process parameters used in each example .

[0034] The preparation method of Comparative Examples 1-6 was carried out according to Example 1, and the raw materials were different as shown in Table 2.

[0035] Table 2 Raw material ratio (by weight) and key process parameters used in each example .

[0036] Note: The "furan ring diol" listed in Table 1 and Table 2 is a furan-based diol ester prepared by esterification of bio-based 2,5-furan dicarboxylic acid and 1,4-butanediol, with a hydroxyl value range of 280-320 mgKOH / g, providing the furan ring structure required for D-A reaction in the system.

[0037] Performance test The unsaturated resins obtained in the examples and comparative examples were respectively tested for performance, and the test results were recorded in Table 3.

[0038] Sample preparation and performance testing were carried out according to standards GB / T24148, GB / T3854, GB / T2567, GB / T1634, GB / T39818.

[0039] The detection method of curing volatilization is to take a clean culture dish, weigh it as M1, and evenly spread the unsaturated resin with accelerant and curing agent on the culture dish, and the total mass is recorded as M2. After curing at 80℃ for 2h, the total mass of the culture dish and the cured resin is M3. The calculation method of curing volatilization is: curing volatilization%= (1- (M3-M1) / (M2-M1) ) / 100%.

[0040] The determination method of filler oil absorption value in standard GB / T 19281-2014 was referred to. 100g of dry 800 mesh calcium carbonate filler was placed on a glass plate or a paint mixing plate, and the resin to be tested was slowly added with a burette at a constant temperature of 25℃, and a spatula was used for constant stirring and rolling, so that the resin and the filler were fully infiltrated. When the filler and resin mixture agglomerates into a non-broken paste, it is the end point. Record the mass (g) of the resin consumed, which is the oil absorption value of the filler in this resin system, expressed as g / 100g.

[0041] The unsaturated resins obtained in the examples and comparative examples were respectively tested for performance, and the test results were recorded in Table 3.

[0042] Table 3 Performance test results of Examples 1-8 and Comparative Examples 1-6 .

[0043] Note: 1. "-" means that the performance is not applicable or cannot be tested. 2. The self-repairing efficiency refers to the ratio of the bending strength after repair to the original bending strength. 3. The reprocessing performance retention rate refers to the ratio of the bending strength of the product after hot-pressing reprocessing to the original strength.

[0044] As can be seen from Table 3, compared with Comparative Example 1, the use of polyethylene terephthalate greatly improves the mechanical performance of the resin, and the resin has high mechanical strength, meeting the application conditions of stone resin; compared with Comparative Example 2, the use of dipropylene glycol improves the toughness and other properties of the resin; compared with Comparative Example 3, the addition of glycerol reduces the oil absorption value of the resin, which is beneficial to the addition of fillers; compared with Comparative Example 4, both dimethyl itaconate and styrene have good curing performance as the crosslinking agent of the resin, but dimethyl itaconate has small volatility, and the unsaturated resin prepared by using dimethyl itaconate has good environmental performance. After Comparative Example 5 does not contain BMI and furan monomer, the material completely loses the self-repairing and recyclable ability, proving that the D-A dynamic covalent bond is a necessary condition for realizing new functions. The mechanical performance (especially the impact strength) of the material of Comparative Example 6 without TMPTA and PEGDA is significantly reduced, proving that the synergistic effect of the mixed crosslinking agent is the key to realizing the high rigidity and toughness balance.

[0045] The above merely describes preferred embodiments of the present application, but does not represent other forms of the present application, and any person skilled in the art can modify or reform the above disclosed technical content into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and reform of the above embodiments made according to the technical essence of the present application without departing from the technical solution content of the present application still falls within the protection scope of the present application.

Claims

1. An environmentally friendly unsaturated resin, characterized by, The raw material weight parts composition includes: polyethylene terephthalate 22~26 parts, dipropylene glycol 28~32 parts, maleic anhydride 14~18 parts, furan ring containing dihydric alcohol 2~4 parts, adipic acid 2~4 parts, benzoic acid 2~3 parts, glycerol 1~2 parts, itaconic acid dimethyl ester 18~22 parts, trimethylolpropane triacrylate 1~3 parts, polyethylene glycol diacrylate 2~4 parts, bismaleimide 0.5~2 parts, antioxidant 0.05~0.07 parts, polymerization inhibitor 0.015~0.03 parts, catalyst 0.03~0.05 parts, paraffin 0.005~0.007 parts.

2. The environmentally friendly unsaturated resin according to claim 1, characterized in that: The furan ring containing dihydric alcohol is furan dihydric alcohol ester obtained by reacting 2,5-furan dicarboxylic acid with dihydric alcohol.

3. The environmentally friendly unsaturated resin according to claim 1, characterized in that: The number average molecular weight of the polyethylene glycol diacrylate is 400~600.

4. The environmentally friendly unsaturated resin according to claim 1, characterized in that: The antioxidant is a complex of one or more of 2,6-di-tert-butyl phenol, p-tert-butyl phenol and triphenyl phosphite.

5. The environmentally friendly unsaturated resin according to claim 1, characterized in that: The polymerization inhibitor is a mixture of one or more of hydroquinone, methyl hydroquinone, p-tert-butyl catechol and methyl p-benzoquinone in any ratio.

6. The environmentally friendly unsaturated resin according to claim 1, characterized in that: The catalyst is one of monobutyl tin oxide, zinc acetate and tetrabutyl titanate.

7. A method for preparing the environmentally friendly unsaturated resin according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: (1) Put the proportioned polyethylene terephthalate, catalyst, furan ring containing dihydric alcohol and 22~26 parts of dipropylene glycol, 0.03~0.04 parts of antioxidant, 0.005~0.007 parts of polymerization inhibitor into a reaction kettle, stir and heat, control the kettle temperature at 210℃~220℃ for 1h~2h until the material is clear and transparent, and then cool to below 100℃; (2) Add the proportioned maleic anhydride, adipic acid, benzoic acid, glycerol, the remaining part of dipropylene glycol and antioxidant, and 0.005~0.007 parts of polymerization inhibitor to the product of step (1), then heat to 158℃~163℃, start the polycondensation and keep for 0.5h~1h, continue to heat to 200℃~210℃ until the acid value reaches 15mgKOH / g~25mgKOH / g; (3) First cooling, reduce to below 180℃, add the remaining part of polymerization inhibitor and the proportioned paraffin, and stir uniformly; (4) Second cooling, reduce to 90℃~100℃, then add the proportioned itaconic acid dimethyl ester, trimethylolpropane triacrylate and polyethylene glycol diacrylate in sequence, stir uniformly, and finally add the proportioned bismaleimide, stir and keep at this temperature for 0.5h~1h; (5) Cool to room temperature and discharge.

8. The method according to claim 7, wherein the method is characterized by: The heating rate during the stirring and heating in step (1) is controlled at 150℃ / h~250℃ / h, and the cooling rate is controlled at 200℃ / h~250℃ / h.

9. The method according to claim 7, wherein the method is characterized by: The heating rate during the heating in step (2) is controlled at 15℃ / h~20℃ / h.

10. The method for preparing an environmentally friendly unsaturated resin according to claim 7, characterized in that: The cooling rate during the first cooling in step (3) is controlled at 160℃ / h~200℃ / h, and the cooling rate during the second cooling in step (4) is controlled at 220℃ / h~260℃ / h.