A micro-positive pressure reaction process for unsaturated polyester resin

Abstract

The invention discloses a micro-positive pressure reaction process of an unsaturated polyester resin, and belongs to the technical field of polymer materials. The micro-positive pressure reaction process of the unsaturated polyester resin comprises the following steps: step (1): adding a diol into a sealed system, starting a stirrer for stirring, adding anhydride, an initiator and a composite cross-linking agent during the stirring process, and first dehydrating under stirring, heating and inert gas protection conditions; step (2): after the dehydration is completed, closing the drain valve to keep the entire sealed system in a micro-positive pressure state, then continuing to heat and stir the prepolymer, and after the reaction is completed, draining the wastewater in the wastewater collection tank to obtain a polyester resin compound; step (3): adding a modified inhibitor to the polyester resin compound, stirring and reacting, filtering, and obtaining an unsaturated polyester resin. The unsaturated polyester resin prepared by the process has excellent corrosion resistance and mechanical properties, and saves reaction time and energy consumption.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a micro-positive pressure reaction process of an unsaturated polyester resin. Background Art

[0002] The polymerization reaction of unsaturated polyester resin is a complex chemical process involving the mixing of multiple raw materials, the control of reaction temperature and pressure, and the selection of catalysts and initiators. Traditional production processes often find it difficult to accurately control these reaction conditions, resulting in unstable resin performance and low production efficiency. The micro-positive pressure reaction process provides a more stable and optimized environment for the polymerization reaction by accurately controlling the pressure and temperature in the reactor, which helps to improve the performance and yield of the resin. At the same time, the micro-positive pressure reaction process helps to reduce the interference of oxygen and moisture in the reaction process. Unsaturated polyester resin easily reacts with oxygen and water during the polymerization process, causing the resin to darken in color and deteriorate in performance. The micro-positive pressure reaction process introduces a small amount of inert gas (such as nitrogen) into the reactor to remove oxygen and moisture from the reaction system, thereby effectively avoiding the influence of these adverse factors and improving the purity and stability of the resin. In addition, the micro-positive pressure reaction process can realize continuous production, reduce the number of operations and material losses, and improve production efficiency and resource utilization.

[0003] Patent CN 108948338 B discloses a blocked unsaturated polyester resin and a synthesis process thereof, the process comprising: step (1) adding diol, saturated dibasic acid / anhydride A, and unsaturated dibasic acid / anhydride to a reaction, heating to 160-170°C and keeping the temperature for reaction for 25-35 minutes, then heating to 200-210°C and reacting for 1 hour, until the acid value of the system is 55-62KOH / g; step (2) cooling to 165-175°C, adding saturated monobasic acid / anhydride and saturated dibasic acid / anhydride B, and heating to 200-210°C for blocking reaction , react until the acid value drops to 54-60KOH / g; (3) maintain the temperature at 200-203°C, react under reduced pressure until the acid value drops to 32-36KOH / g; cool to 150°C and dilute, react until the acid value is 17-24KOH / g, and obtain a blocked unsaturated polyester resin. The obtained unsaturated polyester resin has excellent heat resistance, corrosion resistance, rigidity and hardness. However, the method for preparing the unsaturated polyester resin is relatively cumbersome and requires frequent temperature adjustment. In addition, the comprehensive performance of the obtained unsaturated polyester resin still has room for improvement. Summary of the invention

[0004] The purpose of the present invention is to provide a micro-positive pressure reaction process for unsaturated polyester resin, which is used to solve the technical problems that the reaction process for synthesizing unsaturated polyester resin in the prior art is complicated and the comprehensive performance of unsaturated polyester resin is poor.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a micro-positive pressure reaction process of an unsaturated polyester resin, comprising the following steps:

[0007] Step (1): adding diol into a sealed system, starting a stirrer for stirring, adding anhydride, initiator and composite cross-linking agent during stirring, and first dehydrating under stirring, heating and inert gas protection conditions;

[0008] Step (2): After the dehydration is completed, the drain valve is closed to maintain a slightly positive pressure in the entire sealed system, and then the prepolymer is continued to be heated and stirred. After the reaction is completed, the wastewater in the wastewater collection tank is drained to obtain a polyester resin compound;

[0009] Step (3): adding a modified polymerization inhibitor to the polyester resin compound, stirring for reaction, and filtering to obtain an unsaturated polyester resin.

[0010] Preferably, in step (1), the diol is composed of one or more combinations of ethylene glycol, propylene glycol, tetramethylethylene glycol and 2-methyl-2-propyl-1,3-propanediol; the acid anhydride is composed of one or more combinations of phthalic anhydride, maleic anhydride and 2-methylmaleic anhydride; and the initiator is composed of one or more combinations of cyclohexanone peroxide, methyl ethyl ketone peroxide and benzoyl peroxide.

[0011] Preferably, in step (1), the sealing system comprises: a reactor, a packed tower, a vertical condenser, a horizontal condenser, and a wastewater collection tank, wherein the diol is added to the reactor in the sealing system.

[0012] Preferably, the method for preparing the composite cross-linking agent comprises the following steps:

[0013] Q1: 5-methylfurfural, acetic anhydride, potassium carbonate and polyethylene glycol are added to a container, heated, stirred and refluxed for reaction, and after the reaction is completed, a reaction mixture is obtained, the reaction mixture is added to a container filled with distilled water, stirred to precipitate crystals, heated to dissolve the crystals, decolorized, filtered, acidified the filtrate, allowed to stand, and filtered to obtain compound 1;

[0014] Q2: Add compound 1 and diethylene glycol into a container, add distilled water and p-toluenesulfonic acid, pass nitrogen to deoxygenate, heat to reflux for reaction, and after the reaction is completed, cool, add distilled water, let stand, wash the organic layer, dry, rotary evaporate, dissolve, recrystallize, and dry to obtain a composite cross-linking agent.

[0015] In the above process, 5-methylfurfural and acetic anhydride are used as raw materials to obtain compound 1, and then compound 1 and diethylene glycol are reacted with p-toluenesulfonic acid as a catalyst to introduce an alkoxy flexible segment to obtain a composite crosslinking agent, wherein the synthetic reaction formula of the composite crosslinking agent is as follows:

[0016]

[0017] The results of mass spectrometry analysis were: m / z: 374.14 (100.0%), 375.14 (22.2%), 376.14 (3.7%).

[0018] Preferably, in Q1, the molar ratio of 5-methylfurfural to acetic anhydride is (1-2): (1.1-2.1), the temperature of the heated stirring reflux reaction is 140-160°C, the reflux reaction time is 5-7h, the heating temperature is 70-80°C, activated carbon is added for decolorization, acidified with hydrochloric acid to pH=2-3, and allowed to stand for 8-12h.

[0019] Preferably, in Q2, the molar ratio of compound 1 to diethylene glycol is (2-3): (1-1.2), the heating reflux temperature is 90-110°C, the reaction time is 4-6h, the standing time is 4-6h, and the product is washed with sodium carbonate and saturated brine respectively, and dried by adding anhydrous calcium chloride.

[0020] Preferably, in step (2), the sealing system and the valve are connected via a pressure sensor, and the nitrogen filling is stopped after the pressure is filled to 0.1-0.2 MPa. The heating rate during the heating process is 12-15°C / h and the temperature is 180-200°C.

[0021] Preferably, the method for preparing the modified polymerization inhibitor comprises the following steps:

[0022] S1: adding butyrophenone to a reaction vessel, adding thionyl bromide dropwise, controlling the adding time, reacting, neutralizing, extracting, combining the organic phases, drying, and rotary evaporating to obtain an intermediate product 1;

[0023] S2: adding the intermediate product 1 to a reaction container, and sequentially adding hydroxylamine hydrochloride, potassium hydroxide, n-butane bromide, ethanol and distilled water to react. After the reaction is completed, performing chromatography to obtain a modified inhibitor.

[0024] In the above process, firstly, phenylbutyl ketone is used as a raw material and thionyl bromide is used as a brominating agent to undergo an electrophilic substitution reaction to obtain an intermediate product 1, and then the intermediate product 1 reacts with hydroxylamine hydrochloride to generate an oxime intermediate. Subsequently, under alkaline conditions, n-butane bromide is used as an alkylating agent to attack the nitrogen atom of the oxime intermediate, and an N-alkylation reaction occurs to prepare a modified inhibitor.

[0025] Preferably, in S1, the molar ratio of butyrophenone to thionyl bromide is (1-2): (1.4-3.6), the dropping time is 30-60 min, the reaction time is 2-4 h, neutralization is performed with saturated sodium carbonate aqueous solution, extraction is performed with ethyl acetate, and drying is performed with anhydrous magnesium sulfate.

[0026] Preferably, in S2, the molar ratio of the intermediate product 1, hydroxylamine hydrochloride, potassium hydroxide, n-butane bromide, ethanol and distilled water is (1-2): (1-2): (0.8-1.2): (1-2): (2-5): (1-2), and the reaction time is 10-12 h.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] The present invention first uses 5-methylfurfural, acetic anhydride and diethylene glycol as raw materials to prepare a composite crosslinking agent, then uses phenylbutyric acid ketone, thionyl bromide, hydroxylamine hydrochloride and n-butyl bromide as raw materials to prepare a modified polymerization inhibitor, adds the composite crosslinking agent and the modified polymerization inhibitor in the preparation process of unsaturated polyester resin, and adopts a micro-positive pressure reaction process in the preparation process. The addition of the composite crosslinking agent can effectively improve the mechanical properties, heat resistance and chemical corrosion resistance of the resin, the active functional groups in the composite crosslinking agent and the unsaturated double bonds in the unsaturated polyester resin undergo crosslinking reactions to form a three-dimensional network structure, improve the mechanical properties and heat resistance of the resin, the crosslinking network restricts the movement of the molecular chain, and improves the thermal stability and chemical corrosion resistance of the resin; the addition of the modified polymerization inhibitor can effectively improve the thermal stability of the resin, and the groups contained in the modified polymerization inhibitor can react with free radicals in the resin, consume or capture free radicals, and prevent the further occurrence of polymerization reaction; the micro-positive pressure reaction process adopted can reduce the loss of low-boiling reactants, improve reaction efficiency, reduce reaction temperature, and save reaction time and energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 Schematic diagram of the sealing system of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0032] This embodiment discloses a method for preparing a composite cross-linking agent, comprising the following steps:

[0033] Q1: 1.5 g 5-methylfurfural, 1.49 g acetic anhydride, 0.23 g potassium carbonate and 0.21 g polyethylene glycol were added to a container, heated to 140°C, stirred and refluxed for 7 h, and a reaction mixture was obtained after the reaction was completed. The reaction mixture was added to a container filled with distilled water, stirred to precipitate crystals, heated to 80°C to dissolve the crystals, activated carbon was added for decolorization, filtered, and the filtrate was acidified with hydrochloric acid to pH = 2, allowed to stand for 12 h, and filtered to obtain compound 1;

[0034] Q2: Add 1.25g of compound 1 and 0.42g of diethylene glycol into a container, add 20mL of distilled water and 0.03g of p-toluenesulfonic acid, pass nitrogen to deoxygenate, heat at 110°C for reflux reaction for 6h. After the reaction is completed, cool, add distilled water, let stand for 4h, wash the organic layer with sodium carbonate and saturated brine respectively, add anhydrous calcium chloride to dry, rotary evaporate, dissolve, recrystallize, and dry to obtain a composite cross-linking agent.

[0035] This embodiment discloses a method for preparing a modified polymerization inhibitor, comprising the following steps:

[0036] S1: 0.75 g of butyrophenone was added to a reaction container, and 0.66 mL of thionyl bromide was added dropwise. The addition time was controlled to be 30 min and the reaction was carried out for 4 h. After the reaction was completed, the mixture was neutralized with a saturated aqueous sodium carbonate solution, extracted with ethyl acetate, the organic phases were combined, dried with anhydrous magnesium sulfate, and subjected to rotary evaporation under reduced pressure to obtain an intermediate product 1;

[0037] S2: Add 1.5 g of the intermediate product 1 to a reaction container, and then add 0.41 g of hydroxylamine hydrochloride, 0.223 g of potassium hydroxide, 0.65 mL of n-butane bromide, 0.81 mL of ethanol and 0.11 mL of distilled water. The reaction was carried out for 12 h. After the reaction was completed, chromatography was performed to obtain a modified inhibitor.

[0038] See also Figure 1 As shown, this embodiment discloses a micro-positive pressure reaction process of an unsaturated polyester resin, comprising the following steps:

[0039] Step (1): adding ethylene glycol to a reactor in a sealed system (composed of a reactor, a packing tower, a vertical condenser, a horizontal condenser and a wastewater collection tank), starting a stirrer for stirring, adding phthalic anhydride, cyclohexanone peroxide and a composite cross-linking agent during the stirring process, and first dehydrating under stirring and heating and inert gas protection conditions;

[0040] Step (2): After the dehydration is completed, the drain valve is closed, and the sealing system and the valve are connected via a pressure sensor. After the nitrogen is pressurized to 0.2 MPa, the nitrogen is stopped, so that the entire sealing system is maintained in a slightly positive pressure state, and then the prepolymer is continued to be heated and stirred at a heating rate of 12°C / h and a heating temperature of 200°C. After the reaction is completed, the wastewater in the wastewater collection tank is drained to obtain a polyester resin compound;

[0041] Step (3): adding a modified polymerization inhibitor to the polyester resin compound, stirring the reaction, filtering, centrifuging, separating, and distilling to obtain an unsaturated polyester resin. Example 2

[0042] This embodiment discloses a method for preparing a composite cross-linking agent, comprising the following steps:

[0043] Q1: 1 g 5-methylfurfural, 1.02 g acetic anhydride, 0.23 g potassium carbonate and 0.21 g polyethylene glycol were added to a container, heated to 140°C, stirred and refluxed for reaction for 7 h. After the reaction was completed, a reaction mixture was obtained. The reaction mixture was added to a container filled with distilled water, stirred to precipitate crystals, heated to 80°C to dissolve the crystals, activated carbon was added for decolorization, filtered, and the filtrate was acidified with hydrochloric acid to pH = 2, allowed to stand for 12 h, and filtered to obtain compound 1;

[0044] Q2: Add 1g of compound 1 and 0.38g of diethylene glycol into a container, add 20mL of distilled water and 0.03g of p-toluenesulfonic acid, pass nitrogen to deoxygenate, heat at 110°C for reflux reaction for 6h. After the reaction is completed, cool, add distilled water, let stand for 4h, wash the organic layer with sodium carbonate and saturated brine respectively, add anhydrous calcium chloride to dry, rotary evaporate, dissolve, recrystallize, and dry to obtain a composite cross-linking agent.

[0045] This embodiment discloses a method for preparing a modified polymerization inhibitor, comprising the following steps:

[0046] S1: 0.5 g of butyrophenone was added to a reaction container, and 0.37 mL of thionyl bromide was added dropwise. The addition time was controlled to be 30 min and the reaction was carried out for 4 h. After the reaction was completed, the mixture was neutralized with a saturated aqueous sodium carbonate solution, extracted with ethyl acetate, and the organic phases were combined and dried with anhydrous magnesium sulfate. The mixture was subjected to rotary evaporation under reduced pressure to obtain an intermediate product 1.

[0047] S2: Add 1 g of intermediate product 1 to a reaction container, and then add 0.27 g of hydroxylamine hydrochloride, 0.178 g of potassium hydroxide, 0.43 mL of n-butane bromide, 0.46 mL of ethanol and 0.07 mL of distilled water. The reaction was carried out for 12 h. After the reaction was completed, chromatography was performed to obtain a modified inhibitor.

[0048] See also Figure 1 As shown, this embodiment discloses a micro-positive pressure reaction process of an unsaturated polyester resin, comprising the following steps:

[0049] Step (1): adding ethylene glycol to a reactor in a sealed system (composed of a reactor, a packing tower, a vertical condenser, a horizontal condenser and a wastewater collection tank), starting a stirrer for stirring, adding phthalic anhydride, cyclohexanone peroxide and a composite cross-linking agent during the stirring process, and first dehydrating under stirring and heating and inert gas protection conditions;

[0050] Step (2): After the dehydration is completed, the drain valve is closed, and the sealing system and the valve are connected via a pressure sensor. After the nitrogen is pressurized to 0.2 MPa, the nitrogen is stopped, so that the entire sealing system is maintained in a slightly positive pressure state, and then the prepolymer is continued to be heated and stirred at a heating rate of 12°C / h and a heating temperature of 200°C. After the reaction is completed, the wastewater in the wastewater collection tank is drained to obtain a polyester resin compound;

[0051] Step (3): adding a modified polymerization inhibitor to the polyester resin compound, stirring the reaction, filtering, centrifuging, separating, and distilling to obtain an unsaturated polyester resin. Example 3

[0052] This embodiment discloses a method for preparing a composite cross-linking agent, comprising the following steps:

[0053] Q1: 2 g 5-methylfurfural, 1.95 g acetic anhydride, 0.23 g potassium carbonate and 0.21 g polyethylene glycol were added to a container, heated to 140°C, stirred and refluxed for 7 h, and after the reaction was completed, a reaction mixture was obtained. The reaction mixture was added to a container filled with distilled water, stirred to precipitate crystals, heated to 80°C to dissolve the crystals, activated carbon was added for decolorization, filtered, and the filtrate was acidified with hydrochloric acid to pH = 2, allowed to stand for 12 h, and filtered to obtain compound 1;

[0054] Q2: Add 1.5g of compound 1 and 0.46g of diethylene glycol into a container, add 20mL of distilled water and 0.03g of p-toluenesulfonic acid, pass nitrogen to deoxygenate, heat at 110°C for reflux reaction for 6h. After the reaction is completed, cool, add distilled water, let stand for 4h, wash the organic layer with sodium carbonate and saturated brine respectively, add anhydrous calcium chloride to dry, rotary evaporate, dissolve, recrystallize, and dry to obtain a composite cross-linking agent.

[0055] This embodiment discloses a method for preparing a modified polymerization inhibitor, comprising the following steps:

[0056] S1: 1 g of butyrophenone was added to a reaction vessel, and 0.94 mL of thionyl bromide was added dropwise. The addition time was controlled to be 30 min and the reaction was carried out for 4 h. After the reaction was completed, the mixture was neutralized with a saturated sodium carbonate aqueous solution, extracted with ethyl acetate, the organic phases were combined, dried with anhydrous magnesium sulfate, and subjected to rotary evaporation under reduced pressure to obtain an intermediate product 1;

[0057] S2: Add 2 g of intermediate product 1 to a reaction container, and add 0.54 g of hydroxylamine hydrochloride, 0.268 g of potassium hydroxide, 0.86 mL of n-butane bromide, 1.16 mL of ethanol and 0.14 mL of distilled water in sequence, and react for 12 h. After the reaction is completed, perform chromatography to obtain a modified inhibitor.

[0058] See also Figure 1 As shown, this embodiment discloses a micro-positive pressure reaction process of an unsaturated polyester resin, comprising the following steps:

[0059] Step (1): adding ethylene glycol to a reactor in a sealed system (composed of a reactor, a packing tower, a vertical condenser, a horizontal condenser and a wastewater collection tank), starting a stirrer for stirring, adding phthalic anhydride, cyclohexanone peroxide and a composite cross-linking agent during the stirring process, and first dehydrating under stirring and heating and inert gas protection conditions;

[0060] Step (2): After the dehydration is completed, the drain valve is closed, and the sealing system and the valve are connected via a pressure sensor. After the nitrogen is pressurized to 0.2 MPa, the nitrogen is stopped, so that the entire sealing system is maintained in a slightly positive pressure state, and then the prepolymer is continued to be heated and stirred at a heating rate of 12°C / h and a heating temperature of 200°C. After the reaction is completed, the wastewater in the wastewater collection tank is drained to obtain a polyester resin compound;

[0061] Step (3): adding a modified polymerization inhibitor to the polyester resin compound, stirring the reaction, filtering, centrifuging, separating, and distilling to obtain an unsaturated polyester resin. Example 4

[0062] This embodiment discloses a method for preparing a composite cross-linking agent, comprising the following steps:

[0063] Q1: 1.2 g 5-methylfurfural, 1.26 g acetic anhydride, 0.23 g potassium carbonate and 0.21 g polyethylene glycol were added to a container, heated to 140°C, stirred and refluxed for reaction for 7 h. After the reaction was completed, a reaction mixture was obtained. The reaction mixture was added to a container filled with distilled water, stirred to precipitate crystals, heated to 80°C to dissolve the crystals, activated carbon was added for decolorization, filtered, and the filtrate was acidified with hydrochloric acid to pH = 2, allowed to stand for 12 h, and filtered to obtain compound 1;

[0064] Q2: Add 1.2g of compound 1 and 0.4g of diethylene glycol into a container, add 20mL of distilled water and 0.03g of p-toluenesulfonic acid, pass nitrogen to deoxygenate, heat at 110°C for reflux reaction for 6h. After the reaction is completed, cool, add distilled water, let stand for 4h, wash the organic layer with sodium carbonate and saturated brine respectively, add anhydrous calcium chloride to dry, rotary evaporate, dissolve, recrystallize, and dry to obtain a composite cross-linking agent.

[0065] This embodiment discloses a method for preparing a modified polymerization inhibitor, comprising the following steps:

[0066] S1: 0.6 g of butyrophenone was added to a reaction container, and 0.51 mL of thionyl bromide was added dropwise. The addition time was controlled to be 30 min and the reaction was carried out for 4 h. After the reaction was completed, the mixture was neutralized with a saturated aqueous sodium carbonate solution, extracted with ethyl acetate, and the organic phases were combined and dried with anhydrous magnesium sulfate. The mixture was subjected to rotary evaporation under reduced pressure to obtain an intermediate product 1.

[0067] S2: Add 1.2 g of the intermediate product 1 to a reaction container, and then add 0.34 g of hydroxylamine hydrochloride, 0.201 g of potassium hydroxide, 0.54 mL of n-butane bromide, 0.64 mL of ethanol and 0.08 mL of distilled water. The reaction was carried out for 12 h. After the reaction was completed, chromatography was performed to obtain a modified inhibitor.

[0068] See also Figure 1 As shown, this embodiment discloses a micro-positive pressure reaction process of an unsaturated polyester resin, comprising the following steps:

[0069] Step (1): adding ethylene glycol to a reactor in a sealed system (composed of a reactor, a packing tower, a vertical condenser, a horizontal condenser and a wastewater collection tank), starting a stirrer for stirring, adding phthalic anhydride, cyclohexanone peroxide and a composite cross-linking agent during the stirring process, and first dehydrating under stirring and heating and inert gas protection conditions;

[0070] Step (2): After the dehydration is completed, the drain valve is closed, and the sealing system and the valve are connected via a pressure sensor. After the nitrogen is pressurized to 0.2 MPa, the nitrogen is stopped, so that the entire sealing system is maintained in a slightly positive pressure state, and then the prepolymer is continued to be heated and stirred at a heating rate of 12°C / h and a heating temperature of 200°C. After the reaction is completed, the wastewater in the wastewater collection tank is drained to obtain a polyester resin compound;

[0071] Step (3): adding a modified polymerization inhibitor to the polyester resin compound, stirring the reaction, filtering, centrifuging, separating, and distilling to obtain an unsaturated polyester resin.

[0072] Comparative Example 1

[0073] Comparative Example 1 Compared with Example 1, in the process of preparing the composite cross-linking agent in Comparative Example 1, no diethylene glycol was added, and other conditions remained unchanged.

[0074] Comparative Example 2

[0075] Comparative Example 2 Compared with Example 1, in the process of preparing the modified polymerization inhibitor in Comparative Example 2, thionyl bromide was not added, and other conditions remained unchanged.

[0076] Comparative Example 3

[0077] Comparative Example 3 Compared with Example 1, in the preparation process of the unsaturated polyester resin in Comparative Example 3, the micro-positive pressure reaction process is not used, and the normal pressure process is used instead, and other conditions remain unchanged.

[0078] The samples prepared by Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests. The Barcol hardness, bending strength, heat deformation temperature and alkali resistance of the samples were tested according to GB / T 8237-2005. The test results are shown in Table 1:

[0079] Table 1

[0080] project Barcol Hardness Bending strength / MPa Heat deformation temperature / ℃ Mass reduction rate / % Example 1 43 94 168 0.25 Example 2 41 93 165 0.28 Example 3 42 91 166 0.27 Example 4 42 92 167 0.29 Comparative Example 1 36 83 151 0.41 Comparative Example 2 40 89 152 0.30 Comparative Example 3 41 90 150 0.31

[0081] It can be seen from the test results in Table 1 that the methods of Examples 1-4 of the present invention can effectively improve the corrosion resistance, thermal stability and mechanical properties of unsaturated polyester resin. Comparison between Comparative Example 1 and Examples 1-4 shows that the addition of diethylene glycol can effectively improve the corrosion resistance, thermal stability and mechanical properties of unsaturated polyester resin; comparison between Comparative Example 2 and Examples 1-4 shows that the addition of thionyl bromide can effectively improve the thermal stability of unsaturated polyester resin; comparison between Comparative Example 3 and Examples 1-4 shows that the use of a micro-positive pressure reaction process can effectively improve the thermal stability of unsaturated polyester resin.

[0082] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0083] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A micro-positive pressure reaction process for unsaturated polyester resin, characterized in that: The following steps are involved: Step (1): adding diol into a sealed system, starting a stirrer for stirring, adding anhydride, initiator and composite cross-linking agent during stirring, and first dehydrating under stirring, heating and inert gas protection conditions; Step (2): After the dehydration is completed, the drain valve is closed to maintain a slightly positive pressure in the entire sealed system, and then the prepolymer is continued to be heated and stirred. After the reaction is completed, the wastewater in the wastewater collection tank is drained to obtain a polyester resin compound; Step (3): adding a modified polymerization inhibitor to the polyester resin compound, stirring for reaction, and filtering to obtain an unsaturated polyester resin; The preparation method of the composite cross-linking agent comprises the following steps: Q1: 5-methylfurfural, acetic anhydride, potassium carbonate and polyethylene glycol are added to a container, heated, stirred and refluxed for reaction, and after the reaction is completed, a reaction mixture is obtained, the reaction mixture is added to a container filled with distilled water, stirred to precipitate crystals, heated to dissolve the crystals, decolorized, filtered, acidified the filtrate, allowed to stand, and filtered to obtain compound 1; Q2: Compound 1 and diethylene glycol are added to a container, distilled water and p-toluenesulfonic acid are added, nitrogen is passed to deoxygenate, and the mixture is heated to reflux for reaction. After the reaction is completed, the mixture is cooled, distilled water is added, the mixture is allowed to stand, the organic layer is washed, dried, rotary evaporated, dissolved, recrystallized, and dried to obtain a composite cross-linking agent; The preparation method of the modified polymerization inhibitor comprises the following steps: S1: adding butyrophenone to a reaction vessel, adding thionyl bromide dropwise, controlling the adding time, reacting, neutralizing, extracting, combining the organic phases, drying, and rotary evaporating to obtain an intermediate product 1; S2: adding the intermediate product 1 to a reaction container, and sequentially adding hydroxylamine hydrochloride, potassium hydroxide, n-butane bromide, ethanol and distilled water to react. After the reaction is completed, performing chromatography to obtain a modified polymerization inhibitor.

2. The micro-positive pressure reaction process of unsaturated polyester resin according to claim 1, characterized in that: In the step (1), the diol is composed of one or more combinations of ethylene glycol, propylene glycol, tetramethylethylene glycol and 2-methyl-2-propyl-1,3-propanediol; the acid anhydride is composed of one or more combinations of phthalic anhydride, maleic anhydride and 2-methylmaleic anhydride; and the initiator is composed of one or more combinations of cyclohexanone peroxide, methyl ethyl ketone peroxide and benzoyl peroxide.

3. The micro-positive pressure reaction process of unsaturated polyester resin according to claim 1, characterized in that: In the step (1), the sealing system includes: a reactor, a packed tower, a vertical condenser, a horizontal condenser and a wastewater collection tank, wherein the diol is added into the reactor in the sealing system.

4. The micro-positive pressure reaction process of unsaturated polyester resin according to claim 1, characterized in that: In the Q1, the molar ratio of 5-methylfurfural to acetic anhydride is (1-2): (1.1-2.1), the temperature of the heated stirring reflux reaction is 140-160°C, the reflux reaction time is 5-7h, the heating temperature is 70-80°C, activated carbon is added for decolorization, hydrochloric acid is used to acidify to pH=2-3, and the reaction is allowed to stand for 8-12h.

5. The micro-positive pressure reaction process of unsaturated polyester resin according to claim 1, characterized in that: In Q2, the molar ratio of compound 1 to diethylene glycol is (2-3): (1-1.2), the heating reflux temperature is 90-110°C, the reaction time is 4-6h, the standing time is 4-6h, and it is washed with sodium carbonate and saturated brine respectively, and dried by adding anhydrous calcium chloride.

6. The micro-positive pressure reaction process of unsaturated polyester resin according to claim 1, characterized in that: In the step (2), the sealing system and the valve are connected via a pressure sensor, and the nitrogen filling is stopped after the pressure is filled to 0.1-0.2 MPa. The heating rate during the heating process is 12-15°C / h, and the temperature is 180-200°C.

7. The micro-positive pressure reaction process of unsaturated polyester resin according to claim 1, characterized in that: In S1, the molar ratio of butyrophenone to thionyl bromide is (1-2): (1.4-3.6), the dropping time is 30-60 min, the reaction time is 2-4 h, neutralization is performed with a saturated sodium carbonate aqueous solution, extraction is performed with ethyl acetate, and drying is performed with anhydrous magnesium sulfate.

8. The micro-positive pressure reaction process of unsaturated polyester resin according to claim 1, characterized in that: In S2, the molar ratio of the intermediate product 1, hydroxylamine hydrochloride, potassium hydroxide, n-butane bromide, ethanol and distilled water is (1-2): (1-2): (0.8-1.2): (1-2): (2-5): (1-2), and the reaction time is 10-12 hours.

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