A process for the preparation of a phenol formaldehyde resin synthesized in part from pmi foam scrap
Phenolic resin is prepared by dissolving PMI foam waste powder in an alkaline solution and reacting it with phenol and formaldehyde. This solves the problems of uneconomical treatment of PMI foam waste and high cost of phenolic resin, achieves cost reduction and performance improvement, and is suitable for a variety of materials.
Patent Information
- Application Number
- CN202411468861.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-21
- Publication Date
- 2025-10-10
- Estimated Expiration
- 2044-10-21
AI Technical Summary
In the existing technology, the treatment of PMI foam scraps and dust is uneconomical and environmentally unfriendly. The synthesis cost of phenolic resin is high and the material is brittle, and there is a lack of effective improvement measures.
The PMI foam waste powder is dissolved in an alkaline solution to form a transparent liquid, which reacts with phenol and formaldehyde under alkaline conditions to prepare phenolic resin, thereby reducing the amount of phenol and formaldehyde used and improving the performance of the phenolic resin by utilizing the PMI structure.
The production cost of phenolic resin is reduced, its mechanical properties are improved, and the recycling of PMI foam waste is realized, which has environmental protection significance. The prepared phenolic resin can be used for a variety of materials.
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Figure CN119161550B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of resin synthesis and application, in particular to a method for preparing a phenolic resin partially synthesized from PMI foam waste. Background Art
[0002] Polymethacrylimide (PMI) foam, with its excellent mechanical properties and heat and pressure resistance, is widely used in high-performance composite sandwich materials. The preparation and application of PMI foam involves polymerizing unsaturated monomers into a sheet-like resin. This sheet is then heated and foamed in a baking machine to produce foam sheets. The foam sheets require peeling, cutting, and processing to achieve the desired product shape. Due to the unique foam preparation and processing methods, a large amount of scrap and dust is generated. Currently, there is no economical and environmentally friendly disposal method, and incineration and landfilling have adverse environmental impacts. As the market for PMI foam expands, the amount of PMI foam scrap and dust is also increasing. Finding an economical and environmentally friendly way to dispose of this large amount of PMI foam scrap and dust has high economic value and important social significance. However, PMI foam is acid-resistant but not alkali-resistant. The dust collected by vacuuming equipment is directly transferred into an alkaline solution and stirred thoroughly, completely dissolving it in the solution to form a transparent liquid.
[0003] The synthesis and application of phenolic resins have a long history. Due to their readily available raw materials, simple processing equipment, and excellent mechanical properties, along with heat and cold resistance, insulation, dimensional stability, easy molding, flame retardancy, and low smoke generation, phenolic resins are widely used in the preparation of foaming materials, molding materials, laminates, friction materials, insulation materials, grinding wheel resins, weathering fiberboard, metal casting molds, fiberglass molding adhesives, and coatings. In particular, phenolic foams prepared from thermosetting phenolic resins exhibit fine pores, extremely low thermal conductivity, excellent combustion resistance, low smoke toxicity during combustion, and stable dimensional and chemical properties. Known as the "king of thermal insulation materials," they are widely used for insulating pipes in various industries, including construction, chemical engineering, and shipbuilding. However, the synthesis of phenolic resins requires the relatively expensive raw material phenol, which poses a certain obstacle to product economics. Furthermore, phenolic resins exhibit significant steric hindrance and short molecular chains, making them brittle. This requires the use of various methods, such as toughening resins, to improve their mechanical properties, which also increases product costs.
[0004] PMI foam is a foam plastic with the best comprehensive performance. PMI dust is dissolved into liquid with sodium hydroxide solution and directly added to the raw materials of phenolic resin. The carboxyl structure in the PMI system undergoes condensation reaction with the hydroxymethyl of the phenolic resin, which can reduce the amount of phenol and formaldehyde added and save the production cost of phenolic resin. At the same time, the large number of hexagonal structures in the PMI structure can improve the mechanical properties of phenolic resin. Different addition amounts have different improvement effects.
[0005] Based on this, a method for preparing a phenolic resin partially synthesized using PMI foam waste is now provided, which can improve the performance of existing phenolic resins and save production costs. Summary of the Invention
[0006] The object of the present invention is to provide a method for preparing a phenolic resin synthesized partially using PMI foam waste, so as to solve the problems in the background technology.
[0007] To achieve the above object, the present invention provides the following technical solutions:
[0008] A method for preparing a phenolic resin partially synthesized using PMI foam waste comprises the following steps:
[0009] Step 1: Immerse the collected and processed PMI powder in sodium hydroxide solution and stir continuously until the powder turns into a transparent solution;
[0010] Step 2: Add phenol solid to a three-necked flask or reactor equipped with a jacket heating, a titration funnel, a temperature measurement, material stirring, and a reflux condenser, heat to 45°C to melt it, add the above-mentioned PMI powder alkaline solution, continue stirring, and reflux condense; then add formaldehyde, slowly raise the temperature to 75°C, and under the heating condition, condense the phenol, formaldehyde, and PMI liquid for 1 hour; slowly raise the temperature to 85°C and react for 1.5 hours; take samples every 10 minutes, and test the gel time at 150°C using the flat knife method; when the gel time reaches 100 seconds, add 85% phosphoric acid to neutralize the material to a pH of approximately 6.5 to 7.4, vacuum remove moisture, cool to 40°C, and discharge to obtain a transparent light brown liquid resin;
[0011] Step 3: Take a sample to test the viscosity and solid content of the resin. Use a rotational viscometer to test the viscosity of the resin at 25°C. Place the sample in a watch glass and heat it at 105°C for 3 hours to test the solid content of the resin. The resin with suitable viscosity and solid content is the resin for foaming.
[0012] On the basis of the above technical solutions, the present invention also provides the following optional technical solutions:
[0013] In an optional solution, the size of the PMI scrap powder is no larger than 3 mm to ensure that the powder is fully dissolved.
[0014] In an optional solution, the PMI scrap powder is soaked for no less than 4 hours, and the powder is not visible to the naked eye but is in a transparent liquid state.
[0015] In an optional solution, the phenol and formaldehyde only need to be used in an amount of 1 / 2 to 2 / 3 of the original amount.
[0016] Compared with the prior art, the present invention has the following beneficial effects:
[0017] 1. The present invention centrally processes PMI scraps and dust, converting them into liquid through alkalization. Under alkaline heating conditions, the imide ring will partially hydrolyze to form carboxylic acid, while phenol and formaldehyde will react under alkaline heating conditions to form hydroxymethyl. The carboxylic acid will undergo an esterification reaction with the hydroxymethyl, increasing the molecular weight of the resin and helping to improve the mechanical properties. PMI dust replaces a portion of phenol and formaldehyde and is added to the raw materials for preparing phenolic resin, thereby achieving the reuse of PMI scrap powder, reducing the preparation cost of phenolic resin, and having economic value. At the same time, the structure of PMI contains a large number of six-membered rings, which can improve the mechanical properties of phenolic resin. Different resin formulas and different powder dosages can be used to prepare different phenolic resins, which can be applied in different fields and have environmental protection significance.
[0018] 2. The phenolic resin of the present invention is a water-soluble thermosetting resol phenolic resin, which can be used as a raw material for phenolic foam; by reasonably controlling the performance parameters of the resin, it can also be used as a molding material, laminated sheet material, insulating material, weather-resistant fiberboard, metal casting mold and glass fiber reinforced plastic molding material glue, coating material, etc. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 This is the schematic diagram of the reaction between phenol and formaldehyde;
[0020] Figure 2 This is a schematic diagram showing the reaction principle between the carboxyl structure in the PMI system of the present invention and the hydroxymethyl group of the phenolic resin. DETAILED DESCRIPTION
[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.
[0022] Example 1 Preparation of phenolic resin and phenolic foam without PMI powder
[0023] Step 1: Prepare liquid phenolic resin for foaming
[0024] Use a 500ml three-necked glass flask equipped with a 100ml dropping funnel, an electric stirrer, a spherical condenser, an electric constant-temperature water bath, and a thermometer. Add 94g of solid phenol and heat to 45°C to melt. Add 10g of a 20% aqueous sodium hydroxide solution, continue stirring, and reflux to condense. Add 146g of a 37% aqueous formaldehyde solution, slowly raise the temperature to 75°C, and react for 1 hour; then slowly raise the temperature to 85°C and react for 1.5 hours. Samples are taken every 10 minutes and the gel time at 150°C is tested using the flat knife method. When the gel time reaches 100 seconds, add approximately 2.32g of 85% phosphoric acid to neutralize the material to a pH of approximately 6.5 to 7.4. Vacuum to remove approximately 58g of water, cool to 40°C, and discharge to obtain a transparent, light brownish-red liquid resin. The sample was placed in a watch glass and tested by heating at 105°C for 3 hours. The solid content of the resin was 82%. The viscosity of the resin at 25°C was 7000 mPa.s when tested by a rotational viscometer.
[0025] Step 2: Prepare flame-retardant thermal insulation phenolic foam
[0026] To 100g of the phenolic resin, add 16g of a blowing agent (5g of dichloromethane, 6g of petroleum ether, and 5g of cyclopentane), 8g of a surfactant (DC-193), and 8g of a curing agent (2g of water, 2g of ethylene glycol, 0.5g of 98% sulfuric acid, 0.5g of p-toluenesulfonic acid, and 3g of 85% phosphoric acid). Mix and stir, then pour into a mold at 65°C, seal, and foam and cure for 2 hours. After cooling, demold the mold to obtain a phenolic foam with fine and uniform pores.
[0027] After testing, the density of the phenolic foam is 60kg / m 3 , thermal conductivity of 0.032W / mK, compressive strength of 0.16MPa, tensile strength of 0.18MPa, oxygen index of 36%. The foam has uniform and dense cells, low density, moderate strength, low thermal conductivity, and can achieve thermal insulation and flame retardancy.
[0028] Example 2 Preparation of phenolic resin and phenolic foam using PMI powder
[0029] Step 1: Prepare a sodium hydroxide solution of PMI powder
[0030] In a glass flask equipped with an electric stirrer, 40 g of PMI leftover powder was placed, and 200 g of 15% sodium hydroxide solution was added. The mixture was stirred for about 5 hours to dissolve the powder and form a transparent solution.
[0031] Step 2: Prepare liquid phenolic resin for foaming
[0032] Use a 500ml three-necked glass flask equipped with a 100ml dropping funnel, an electric stirrer, a spherical condenser, an electric constant-temperature water bath, and a thermometer. Heat 62g of phenol solid to 45°C and melt. Add 17.2g of the alkaline aqueous solution of the aforementioned PMI powder, continue stirring, and reflux to condense. Add 96g of a 37% aqueous formaldehyde solution. Slowly raise the temperature to 75°C and react for 1.5 hours; then slowly raise the temperature to 85°C and react for 1.5 hours. Samples are taken every 10 minutes and the gel time at 150°C is tested using the flat knife method. When the gel time reaches 100 seconds, add approximately 2.32g of 85% phosphoric acid to neutralize the material to a pH of approximately 6.5 to 7.4. Vacuum to remove approximately 83g of water, cool to 40°C, and discharge to obtain a transparent, light brownish-red liquid resin, a PMI-modified phenolic resin. The sample was placed in a watch glass and tested by heating at 105°C for 3 hours. The solid content of the resin was 81%. The viscosity of the resin was 7050 mPa.s when tested with a rotational viscometer at 25°C.
[0033] The reaction principle diagram of phenol and formaldehyde is as follows Figure 1 shown.
[0034] Step 3: Prepare the Insulating Phenolic Foam
[0035] 100g of the phenolic resin was mixed with 16g of a blowing agent (5g of dichloromethane, 6g of petroleum ether, and 5g of cyclopentane), 8g of a surfactant (DC-193), and 8g of a curing agent (2g of water, 2g of ethylene glycol, 0.5g of 98% sulfuric acid, 0.5g of p-toluenesulfonic acid, and 3g of 85% phosphoric acid). The mixture was poured into a mold at 65°C, sealed, and foamed and cured for 2 hours. After cooling, the mold was removed to obtain a phenolic foam with fine and uniform pores.
[0036] After testing, the density of phenolic foam is 58kg / m 3 , thermal conductivity is 0.030W / mK, compressive strength is 0.19MPa, tensile strength is 0.2MPa, and oxygen index is 37%.
[0037] By adding an appropriate amount of PMI powder to an alkaline solution, the carboxyl groups in the PMI system react with the hydroxymethyl groups in the phenolic resin, reducing the amount of phenol and formaldehyde required to approximately two-thirds of the original amount. The abundant six-membered ring structure in the PMI structure allows the phenolic foam to have improved mechanical properties by approximately 10% compared to the phenolic foam in Example 1, while maintaining excellent thermal insulation and flame retardancy.
[0038] Example 3 Adjusting the Amount of PMI Powder Alkaline Solution to Prepare Phenolic Resin and Phenolic Foam
[0039] Step 1: Prepare a sodium hydroxide solution of PMI powder
[0040] In a glass flask equipped with an electric stirrer, 35 g of PMI leftover powder was placed, and 200 g of 12% sodium hydroxide solution was added. The mixture was stirred for about 5.5 hours to dissolve the powder and form a transparent solution.
[0041] Step 2: Prepare liquid phenolic resin for foaming
[0042] A 500ml three-necked glass flask was equipped with a 100ml dropping funnel, an electric stirrer, a spherical condenser, an electric constant-temperature water bath, and a thermometer. 62g of solid phenol was heated to 45°C, melted, and added to the three-necked flask. 21g of the alkaline aqueous solution of the aforementioned PMI powder was added, stirred continuously, and refluxed to condense. 48g of solid paraformaldehyde was added, and the temperature was slowly raised to 75°C and allowed to react for 1 hour; then to 85°C and allowed to react for 1.5 hours. Samples were taken every 10 minutes and the gel time at 150°C was measured using the flat knife method. When the gel time reached 90 seconds, approximately 2.32g of 85% phosphoric acid was added to neutralize the material to a pH of approximately 6.5 to 7.4. Approximately 42g of water was removed by vacuum evacuation, and the temperature was lowered to 40°C. The material was discharged to yield a transparent, light brownish-red liquid resin, a PMI-modified phenolic resin. The sample was placed in a watch glass and tested by heating at 105°C for 3 hours. The solid content of the resin was 82%. The viscosity of the resin was 7300 mPa.s when tested with a rotational viscometer at 25°C.
[0043] Step 3: Prepare the Insulating Phenolic Foam
[0044] Take 100g of the above-mentioned phenolic resin, 16g of a blowing agent (5g of dichloromethane, 6g of petroleum ether, 5g of cyclopentane), 8g of a surfactant (DC-193), and 8g of a curing agent (2g of water, 2g of ethylene glycol, 0.5g of 98% sulfuric acid, 0.5g of p-toluenesulfonic acid, and 3g of 85% phosphoric acid), mix and stir, pour into a mold at 65°C, seal, foam, and cure for 2 hours; and demold after cooling to obtain a phenolic foam with fine and uniform pores.
[0045] After testing, the density of phenolic foam is 62kg / m 3 , thermal conductivity is 0.030W / mK, compressive strength is 0.20MPa, tensile strength is 0.22MPa, and oxygen index is 36%.
[0046] The amount of phenol and formaldehyde remains unchanged, the amount of PMI powder alkali solution is appropriately increased, and the same alkaline environment is maintained. The prepared phenolic foam material has good thermal insulation and flame retardant properties, and its mechanical properties are improved by about 20% compared with the phenolic foam in Example 1.
[0047] Example 4: Preparation of Abrasives and Grinding Tools Using PMI Powder and Water-Soluble Liquid Phenolic Resin
[0048] Step 1: Prepare a sodium hydroxide solution of PMI powder
[0049] In a glass flask equipped with an electric stirrer, 55 g of PMI leftover powder was placed, and 200 g of 16% sodium hydroxide solution was added. The mixture was stirred for about 4.5 hours to dissolve the powder and form a transparent solution.
[0050] Step 2: Preparation of liquid phenolic resin for abrasives and grinding tools
[0051] Use a 500ml three-necked glass flask equipped with a 100ml dropping funnel, electric stirrer, spherical condenser, electric constant-temperature water bath, and thermometer. Heat 100g of solid phenol to 45°C, melt it, and add it to the three-necked flask. Add 20g of the alkaline aqueous solution of the aforementioned PMI powder (pH 11), continue stirring, and reflux the condenser. Raise the temperature to 70°C and dropwise add 120g of 37% aqueous formaldehyde solution over 1 hour. Keep the temperature constant for 1 hour. Then slowly raise the temperature to 90°C and react for 0.5 hours. Samples were taken every 10 minutes and the gel time at 150°C was tested using the flat knife method. When the gel time reached 90 seconds, approximately 7.23g of 85% phosphoric acid was added to neutralize the material to a pH of approximately 6.5 to 7.4. The material was cooled to below 40°C, and 1g of aminopropyltriethoxysilane and 1g of urea were added. The material was then distilled under reduced pressure to a moisture content of 14%. The material was then discharged to obtain a brown liquid phenolic resin, which was a PMI-modified phenolic resin. Tested at 25°C, the resin density was 1.18g / cm 3 , viscosity 118mPa.s.
[0052] The resin is added with an appropriate amount of PMI powder and alkali solution, and is fully integrated with the phenolic resin during the reaction process, which can effectively improve the comprehensive mechanical properties of the resin. It has low viscosity and is suitable for use in the abrasive tool industry. As a wet resin in the raw material, it can improve the strength and wear resistance of the prepared abrasive mold.
[0053] The principle diagram of the reaction between the carboxyl structure in the PMI system of the invention and the hydroxymethyl group of the phenolic resin is as follows: Figure 2 shown.
[0054] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.
Claims
1. A method for preparing a phenolic resin synthesized partially using PMI foam waste, characterized in that: The following steps are involved: Step 1: Immerse the collected and processed PMI powder in sodium hydroxide solution and stir continuously until the powder turns into a transparent liquid; Step 2: Add phenol solid to a three-necked flask or reactor equipped with a jacket heating, a titration funnel, a temperature measurement, material stirring, and a reflux condenser, heat to 45°C to melt it, add the above-mentioned PMI powder alkaline solution, continue stirring and reflux condensation; then add formaldehyde, slowly raise the temperature to 75°C, and under heating conditions, condense the phenol, formaldehyde, and PMI liquid for 1 hour; slowly raise the temperature to 85°C and react for 1.5 hours; take samples every 10 minutes, and test the gel time at 150°C using a flat knife method; when the gel time reaches 100 seconds, add 85% phosphoric acid to neutralize the material to a pH value of 6.5 to 7.4, vacuum remove moisture, cool to 40°C, and discharge to obtain a transparent light brown liquid resin; Step 3: Take a sample to test the viscosity and solid content of the resin. Use a rotational viscometer to test the viscosity of the resin at 25°C. Place the sample in a watch glass and heat it at 105°C for 3 hours to test the solid content of the resin. The resin with suitable viscosity and solid content is the resin for foaming.
2. The method for preparing a phenolic resin partially synthesized using PMI foam waste according to claim 1, characterized in that: The size of the PMI powder is no greater than 3 mm.
3. The method for preparing a phenolic resin partially synthesized using PMI foam waste according to claim 1, characterized in that: The PMI powder is stirred and dissolved for no less than 4 hours.