Preparation method of hot-melt phenolic resin with wide process window

Abstract

The invention discloses a preparation method of hot-melt phenolic resin with a wide process window. The preparation method of the hot-melt phenolic resin comprises the following steps: mixing phenol and formaldehyde, adding a compound A, and stirring; uniformly stirring and mixing, adding a basic catalyst, heating to 70-80 DEG C within 90 minutes, and keeping the temperature for 20-40 minutes; then continuously raising the temperature to 90 to 100 DEG C, and keeping the temperature for 80 to 140 minutes; and finally, cooling to 70 DEG C, dehydrating under reduced pressure, simultaneously keeping the temperature of the reaction kettle to be increased to 90 DEG C, detecting the viscosity of the cone plate, and obtaining the hot-melt phenolic resin after the index is reached. The compound A is a nitrogen-containing substance, a symmetric phenolic compound or a fused ring phenolic compound. By introducing nitrogen-containing or high-symmetry condensed ring units, the reaction crosslinking sites are reduced, the reaction activity of the resin system is reduced, and the heat resistance is not reduced on the basis of reducing the viscosity change rate of the resin.

Description

Technical Field

[0001] This invention relates to the field of phenolic resin modification technology, and in particular to a method for preparing a hot-melt phenolic resin with a wide process window. Background Technology

[0002] Prepreg is an intermediate product in resin-based composite materials, mainly composed of matrix resins (such as epoxy, phenolic, bismaleimide, etc.) and reinforcing fibers (such as carbon fiber, glass fiber, aramid fiber, etc.). Prepreg is made by impregnating the matrix with reinforcing fibers and is commonly used in the manufacture of advanced composite materials. Prepregs are widely used in the manufacture of aircraft structural components, engine parts, body structural components, automotive chassis components, wind turbine blades, and ship hull structural components. They possess excellent characteristics such as good mechanical properties, fewer product defects, good consistency in processing characteristics, and optimal performance-to-weight ratio. Dry-process prepregs, in particular, offer advantages such as high precision in resin content control, low environmental pollution, high production efficiency, and wide applicability, making them an important molding process for aerospace composite materials. To better utilize the comprehensive performance of prepregs, the requirements for matching resins are gradually increasing to ensure better compatibility with prepregs.

[0003] There are many types of resins used in dry prepregs. Currently, phenolic resin is the most widely used and has the lowest cost in my country. With the development of technology, the problems that restrict the production process of dry prepregs have been solved. With the increasing market demand for dry prepregs at home and abroad, the aerospace field now has higher requirements for phenolic resins used in dry prepregs to solve existing problems: (1) improve the wettability between resin and fiber; (2) have good film-forming properties to meet the requirements of prepreg molding; (3) have slow resin viscosity change to meet the requirements of prepreg molding; (4) have high carbon residue to improve the mechanical strength of the resin itself, etc. Summary of the Invention

[0004] Based on the above background technology, in order to solve the problem of the constraints of dry prepreg production process, the present invention provides a method for preparing hot-melt phenolic resin with a wide process window for dry prepreg production, so as to solve the problem that the viscosity of phenolic resin used in dry prepreg production changes rapidly, and the viscosity of the resin state changes too quickly during the composite molding process, making it difficult to meet the molding requirements of prepreg.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A method for preparing a wide-process-window hot-melt phenolic resin includes: mixing phenol and formaldehyde, adding compound A and stirring; after stirring until uniformly mixed, adding an alkaline catalyst, heating to 70-80°C within 90 min, and holding at that temperature for 20-40 min; then continuing to heat to 90-100°C and holding at that temperature for 80-140 min; finally cooling to 70°C, dehydrating under reduced pressure, while maintaining the reactor temperature at 90°C, detecting the cone-plate viscosity, and obtaining the hot-melt phenolic resin after reaching the specified index. The cone-plate viscosity index is set according to actual requirements.

[0007] Compound A is a nitrogen-containing substance, a symmetrical phenolic compound, or a fused-ring phenolic compound.

[0008] Furthermore, the molar ratio of phenol to formaldehyde in this invention is 1:1.3 to 1.75; the amount of compound A added is 5 to 30% of the molar amount of phenol.

[0009] Furthermore, the stirring temperature of the present invention is 30-40°C; and the vacuum degree during the dehydration process is not lower than -0.085 MPa.

[0010] Furthermore, if the viscosity of the cone plate described in this invention does not reach the target, dehydration under reduced pressure continues until the target is reached.

[0011] Furthermore, the alkaline catalyst of the present invention has a pH of 8-9 and is selected from any one or a mixture of more than one of sodium hydroxide, barium hydroxide, ammonia, triethylamine, methylamine, magnesium oxide, or zinc oxide. The amount of alkaline catalyst added is 2-10 wt% of the weight of phenol.

[0012] Furthermore, the nitrogen-containing substance described in this invention is selected from any one of melamine, caprolactam, p-hydroxybenzamide, p-acetaminophen, o-acetaminophen, aniline, o-aminophenol, or m-aminophenol.

[0013] Furthermore, the symmetrical phenolic or fused-ring phenolic compounds described in this invention are selected from any one of bisphenol A, bisphenol S, 2,2'-diallylbisphenol A, o-phenylphenol, biphenyl, p-tert-butylphenol, and p-phenylphenol.

[0014] Furthermore, the present invention also provides a hot-melt phenolic resin with a wide process window prepared based on the above method.

[0015] Furthermore, the present invention also provides an application of the above-mentioned wide process window hot-melt phenolic resin in the production of dry prepreg.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) This invention reduces the reactivity of phenolic resin by introducing nitrogen-containing compounds or compounds with high symmetry and fused rings during the synthesis stage of phenolic resin. From the perspective of molecular structure, introducing units containing nitrogen or with high symmetry and fused rings reduces the reaction crosslinking sites, reduces the reactivity of the resin system, and does not reduce the heat resistance while reducing the rate of change of resin viscosity.

[0018] (2) The present invention optimizes the synthesis process and produces a resin with good film-forming properties, so it will not have any other impact on the molding process of composite materials. Attached Figure Description

[0019] Figure 1 The viscosity-time curves are those of the hot-melt phenolic resins described in Examples 1 to 5 of this invention.

[0020] Figure 2 This is a thermogravimetric analysis diagram of the wide process window hot-melt phenolic resin described in Embodiment 1 of the present invention.

[0021] Figure 3 This is a thermogravimetric analysis (TGA) diagram of a common hot-melt phenolic resin.

[0022] Figure 4 This is a thermogravimetric analysis diagram of the wide process window hot-melt phenolic resin described in Embodiment 2 of the present invention.

[0023] Figure 5 Thermogravimetric analysis diagram of the wide process window hot-melt phenolic resin described in Embodiment 3 of the present invention;

[0024] Figure 6 This is a thermogravimetric analysis diagram of the wide process window hot-melt phenolic resin described in Embodiment 4 of the present invention;

[0025] Figure 7 This is a thermogravimetric analysis diagram of the wide process window hot-melt phenolic resin described in Embodiment 5 of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention discloses a method for preparing a wide-process-window hot-melt phenolic resin, comprising: mixing phenol and formaldehyde, adding compound A and stirring; after stirring and mixing evenly, adding an alkaline catalyst, heating to 70-80°C within 90 min, holding at that temperature for 20-40 min; then continuing to heat to 90-100°C, holding at that temperature for 80-140 min; finally cooling to 70°C, dehydrating under reduced pressure, while maintaining the reactor temperature at 90°C, detecting the cone-plate viscosity, and obtaining the hot-melt phenolic resin after reaching the specified index. The cone-plate viscosity index is set according to actual requirements.

[0028] Compound A is a nitrogen-containing substance, a symmetrical phenolic compound, or a fused-ring phenolic compound.

[0029] Furthermore, the molar ratio of phenol to formaldehyde in this invention is 1:1.3 to 1.75; the amount of compound A added is 5 to 30% of the molar amount of phenol.

[0030] Furthermore, the stirring temperature of the present invention is 30-40°C; and the vacuum degree during the dehydration process is not lower than -0.085 MPa.

[0031] Furthermore, if the viscosity of the cone plate described in this invention does not reach the target, dehydration under reduced pressure continues until the target is reached.

[0032] Furthermore, the alkaline catalyst of the present invention has a pH of 8-9 and is selected from any one or a mixture of more than one of sodium hydroxide, barium hydroxide, ammonia, triethylamine, methylamine, magnesium oxide, or zinc oxide. The amount of alkaline catalyst added is 2-10 wt% of the weight of phenol.

[0033] Furthermore, the nitrogen-containing substance described in this invention is selected from any one of melamine, caprolactam, p-hydroxybenzamide, p-acetaminophen, o-acetaminophen, aniline, o-aminophenol, or m-aminophenol.

[0034] Furthermore, the symmetrical phenolic or fused-ring phenolic compounds described in this invention are selected from any one of bisphenol A, bisphenol S, 2,2'-diallylbisphenol A, o-phenylphenol, biphenyl, p-tert-butylphenol, and p-phenylphenol.

[0035] Example 1

[0036] A method for preparing a wide-process-window hot-melt phenolic resin includes: adding 3.25 mol of phenol to a four-necked flask, adding 5.50 mol of formaldehyde while stirring at room temperature, mixing thoroughly, adding 0.9 mol of o-phenylphenol, stirring at 30°C, adding 12.5 g of ammonia, raising the temperature to 75°C within 90 min, holding at 75°C for 30 min, continuing to raise the temperature to 95°C, holding the reaction at 75°C for 100 min, cooling to 70°C, and dehydrating under reduced pressure. During the dehydration process, the vacuum degree is not lower than -0.085 MPa. After dehydration under reduced pressure, the temperature is raised to 90°C, and the cone-plate viscosity is tested intermittently. Once the target is met, a wide-process-window hot-melt phenolic resin is obtained.

[0037] The physical preparation of the hot-melt phenolic resin with a wide process window is as follows: free phenol 10.87%, solid content 95.59%, gel time at 150℃ 431s, and viscosity at 100℃ 7.95P.

[0038] Example 2

[0039] A method for preparing a wide-process-window hot-melt phenolic resin includes: adding 3.20 mol of phenol to a four-necked flask, adding 5.50 mol of formaldehyde while stirring at room temperature, mixing thoroughly, adding 0.45 mol of o-phenylphenol and 0.45 mol of p-tert-butylphenol, stirring at 35°C, adding 12.5 g of ammonia water, raising the temperature to 70°C within 90 min, holding at 75°C for 40 min, continuing to raise the temperature to 90°C, holding the reaction at 75°C for 140 min, cooling to 70°C, and dehydrating under reduced pressure. During the dehydration process, the vacuum degree is not lower than -0.085 MPa. After dehydration under reduced pressure, raising the temperature to 90°C, intermittently sampling and testing the cone-plate viscosity, and obtaining a wide-process-window hot-melt phenolic resin after the target is met.

[0040] The physical preparation of the hot-melt phenolic resin with a wide process window is as follows: free phenol 11.17%, solid content 94.26%, gel time at 150℃ 392s, and viscosity at 100℃ 8.36P.

[0041] Example 3

[0042] A method for preparing a wide-process-window hot-melt phenolic resin includes: adding 3.15 mol of phenol to a four-necked flask, stirring at room temperature and adding 5.50 mol of formaldehyde, mixing thoroughly, adding 0.45 mol of caprolactam, stirring at 40°C, adding 14.2 g of triethylamine, raising the temperature to 80°C within 90 min, holding at 75°C for 20 min, continuing to raise the temperature to 100°C, holding the reaction at 75°C for 80 min, cooling to 70°C, dehydrating under reduced pressure, with the vacuum degree not lower than -0.085 MPa during the dehydration process, raising the temperature to 90°C after dehydration, intermittently sampling and testing the cone-plate viscosity, and obtaining a wide-process-window hot-melt phenolic resin after the target is met.

[0043] The physical preparation of the hot-melt phenolic resin with a wide process window is as follows: free phenol 10.67%, solid content 96.82%, gel time 211s at 150℃, and viscosity 10.35P at 100℃.

[0044] Example 4

[0045] A method for preparing a wide-process-window hot-melt phenolic resin includes: adding 3.25 mol of phenol to a four-necked flask, adding 5.50 mol of formaldehyde while stirring at room temperature, mixing thoroughly, adding 0.9 mol of p-tert-butylphenol, stirring at 30°C, adding 12.5 g of ammonia, raising the temperature to 75°C within 90 min, holding at 75°C for 30 min, continuing to raise the temperature to 95°C, holding the reaction at 75°C for 100 min, cooling to 70°C, and dehydrating under reduced pressure. During the dehydration process, the vacuum degree is not lower than -0.085 MPa. After dehydration under reduced pressure, the temperature is raised to 90°C, and the cone-plate viscosity is tested intermittently. Once the target is met, a wide-process-window hot-melt phenolic resin is obtained.

[0046] The physical preparation of the hot-melt phenolic resin with a wide process window is as follows: free phenol 7.51%, solid content 95.73%, gel time at 150℃ 420s, and viscosity at 100℃ 8.10P.

[0047] Example 5

[0048] A method for preparing a wide-process-window hot-melt phenolic resin includes: adding 3.25 mol of phenol to a four-necked flask, adding 5.50 mol of formaldehyde while stirring at room temperature, mixing thoroughly, adding 0.22 mol of aniline, stirring at 30°C, adding 12.5 g of ammonia, raising the temperature to 75°C within 90 min, holding at 75°C for 30 min, continuing to raise the temperature to 95°C, holding the reaction at 75°C for 120 min, cooling to 70°C, and dehydrating under reduced pressure. During the dehydration process, the vacuum degree is not lower than -0.085 MPa. After dehydration under reduced pressure, the temperature is raised to 90°C, and the cone-plate viscosity is tested intermittently. Once the target is met, a wide-process-window hot-melt phenolic resin is obtained.

[0049] The physical preparation of the hot-melt phenolic resin with a wide process window is as follows: free phenol 14.67%, solid content 96.51%, gel time at 150℃ 364s, and viscosity at 100℃ 7.43P.

[0050] Performance testing

[0051] Viscosity-time curves of the wide-process-window hot-melt phenolic resins obtained in Examples 1-5 and ordinary hot-melt phenolic resins (from the North Glass Institute (Tengzhou) Composite Materials Co., Ltd. branch) were analyzed using a rheometer. (See attached figures.) Figure 1 As shown, by Figure 1The data shows that the viscosity of existing ordinary hot-melt phenolic resins changes rapidly over time, while the viscosity of the hot-melt phenolic resin with a wide process window obtained in the embodiments of the present invention changes more gradually over time, indicating that the hot-melt phenolic resin with a wide process window of the present invention has a longer process applicable time.

[0052] Thermogravimetric analysis (TGA) was performed on the wide process window hot-melt phenolic resins obtained in Examples 1-5 and ordinary hot-melt phenolic resins (from the branch of North Glass Institute (Tengzhou) Composite Materials Co., Ltd.). See [link to TGA analysis]. Figures 2-7 The residual carbon rates of existing ordinary hot-melt phenolic resin and the wide process window hot-melt phenolic resin of Example 1 of the present invention are 60.59% and 60.51%, respectively. The data in the figure show that the wide process window hot-melt phenolic resin of the present invention still has excellent thermal stability and ablation resistance.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a wide-process-window hot-melt phenolic resin, characterized in that, include: Phenol and formaldehyde were mixed, and compound A was added and stirred. After the mixture was homogeneous, an alkaline catalyst was added, and the temperature was raised to 70-80°C within 90 minutes and held for 20-40 minutes. Then the temperature was raised to 90-100°C and held for 80-140 minutes. Finally, the temperature was lowered to 70°C and dehydrated under reduced pressure, while the temperature of the reactor was raised to 90°C. The viscosity of the cone plate was measured. Once the target was met, hot-melt phenolic resin was obtained. Compound A is a nitrogen-containing substance, a symmetrical phenolic compound, or a fused-ring phenolic compound.

2. The method for preparing a wide process window hot-melt phenolic resin according to claim 1, characterized in that, The molar ratio of phenol to formaldehyde is 1:1.3 to 1.75; The amount of compound A added is 5-30% of the molar amount of phenol.

3. The method for preparing a wide process window hot-melt phenolic resin according to claim 1, characterized in that, The stirring temperature is 30–40°C; During the dehydration process, the vacuum level is not lower than -0.085 MPa.

4. The method for preparing a wide process window hot-melt phenolic resin according to claim 1, characterized in that, If the viscosity of the cone plate does not reach the target, dehydration under reduced pressure continues until the target is reached.

5. The method for preparing a wide process window hot-melt phenolic resin according to claim 1, characterized in that, The alkaline catalyst has a pH of 8-9 and is selected from any one or a mixture of more than one of sodium hydroxide, barium hydroxide, ammonia, triethylamine, methylamine, magnesium oxide, or zinc oxide. The amount of alkaline catalyst added is 2-10 wt% of the weight of phenol.

6. The method for preparing a wide process window hot-melt phenolic resin according to claim 1, characterized in that, The nitrogen-containing substance is selected from any one of melamine, caprolactam, p-hydroxybenzamide, p-acetaminophen, o-acetaminophen, aniline, o-aminophenol, or m-aminophenol.

7. The method for preparing a wide process window hot-melt phenolic resin according to claim 1, characterized in that, The symmetrical phenolic or fused-ring phenolic compound is selected from any one of bisphenol A, bisphenol S, 2,2'-diallylbisphenol A, o-phenylphenol, biphenyl, p-tert-butylphenol, and p-phenylphenol.

8. A hot-melt phenolic resin with a wide process window prepared by the method of any one of claims 1 to 7.

9. The application of the wide process window hot-melt phenolic resin of claim 8 in the production of dry prepreg.

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