A method for preparing a polyurethane foam with methyl formate as a blowing agent

Abstract

The application discloses a preparation method of polyurethane foam with methyl formate as a foaming agent, comprising the following steps: preparing a multifunctional polyether ester polyol by using PET waste and an intercalation ester-based ethoxylation catalyst, and preparing the polyurethane foam by using the multifunctional polyether ester polyol, wherein the application only uses one catalyst to complete alcoholysis of PET and intercalation of ethylene oxide to prepare aromatic polyether ester polyol with low viscosity and high functionality, so as to improve the size stability of the polyurethane foam with methyl formate as a foaming agent and avoid shrinkage problems; the intercalation ester-based ethoxylation catalyst is a hydrotalcite-like substance, which not only plays a role of a catalyst to realize alcoholysis of PET and intercalation of ethylene oxide in the preparation process, but also can improve the size stability of the polyurethane foam with methyl formate as a foaming agent and avoid shrinkage problems as an inorganic powder material; and the preparation process is provided with a flame-retardant polyester polyol to enhance the flame-retardant performance of the polyurethane foam.

Description

Technical Field

[0001] This invention relates to the field of polyurethane materials, specifically a method for preparing polyurethane foam using methyl formate as a blowing agent. Background Technology

[0002] The blowing agent initially used in polyurethane foam, chlorofluorocarbons (CFCs) (F-11), are potent ozone-depleting substances (ODS) and have a high global greenhouse effect (GWP). The Montreal Protocol of 1987 banned F-11. Currently, hydrochlorofluorocarbons (HCFCs), such as 1,1-dichloro-1-fluoroethane (HCFC-141b), are primarily used. These compounds have a lower chlorine content than CFCs, thus reducing their ozone-depleting potential, but their ODP remains relatively high, classifying them as transitional blowing agents.

[0003] The Ministry of Ecology and Environment issued an announcement on prohibiting the production of refrigerators, freezers, refrigerated containers, and electric water heaters using HCFC-141b as a foaming agent. The announcement clearly stipulates that from January 1, 2019, no enterprise may use HCFC-141b as a foaming agent to produce refrigerators, freezers, refrigerated containers, or electric water heaters.

[0004] Methyl formate belongs to the fourth generation of blowing agents. Its boiling point is similar to HCFC-141B, and it features a small molecular weight, low dosage, and low cost. It is a zero-ODP and zero-GWP chemical. While it is a good solvent and compatible with most currently used blowing agents, solvents, surfactants, and catalysts, it suffers from shrinkage due to decreased foam dimensional stability caused by the swelling of the polyurethane cross-linked network structure. Finally, because methyl formate is a flammable and explosive chemical, it is necessary to enhance the flame-retardant properties of the polyurethane foam produced by its foaming process to ensure its safety during use. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for preparing polyurethane foam using methyl formate as a blowing agent. This method solves the problem of product shrinkage caused by decreased foam dimensional stability due to swelling of the polyurethane cross-linked network structure when using methyl formate as a blowing agent, as well as the flame retardancy issue of the polyurethane foam produced during foaming.

[0006] To achieve the above objectives, the present invention provides a method for preparing polyurethane foam using methyl formate as a blowing agent, comprising the following steps: Step 1: Add 100 parts of waste PET, 100-200 parts of phthalic anhydride polyester polyol, 25-40 parts of small molecule polyol and inserted ester ethoxylation catalyst to the reactor, heat to 230-240℃, and stir to allow the PET to gradually dissolve in the polyester polyol. Continue the reaction for 2-4 hours, then lower the temperature to 180℃, add 10-20 parts of ethylene glycol, and continue the reaction for 2-4 hours to obtain aromatic polyester polyol. Take 100 parts of aromatic polyester polyol, stir evenly, and remove water by vacuum at 100℃ for 2 hours. Raise the temperature to 180℃ to start the induced reaction, and then raise the temperature to 210℃ to continuously introduce ethylene oxide or propylene oxide, adding the calculated amount of ethylene oxide or propylene oxide to the aromatic polyester polyol. Stop the introduction of nitrogen and heating, lower the temperature to 140℃, and continue the reaction for 1-2 hours, allowing the ethylene oxide in the system to continue reacting until the pressure in the system drops to 0.11-0.2 MPa. Discharge the material to obtain the multifunctional aromatic polyether ester polyol. Step 2: Mix 100 parts of aromatic polyether ester polyol, 3-6 parts of catalyst, 10-18 parts of methyl formate foaming agent, 0.5-1 parts of water, 1.2-2 parts of foam stabilizer, and 20-30 parts of flame-retardant polyester polyol at room temperature for 30-50 minutes to obtain polyurethane component B. Mix polyurethane component A with polyurethane component A at a mass ratio of 1:1 and stir at high speed to obtain polyurethane foam.

[0007] Preferably, the PET waste is waste PET bottle flakes or waste PET fiber.

[0008] Preferably, the small molecule polyol is glycerol, trihydroxypropane, pentaerythritol, ethanolamine, diethanolamine, triethanolamine, etc.

[0009] Preferably, the phthalic anhydride polyester polyol is characterized by an acid value of 2-3 mgKOH / g, a hydroxyl value of 180-320 mgKOH / g, and a viscosity of 2000-4000 mPa*s at 25°C.

[0010] Preferably, the inserted ester ethoxylation catalyst is a hydrotalcite-like compound with an average particle size of 0.6-5 μm, a specific surface area of ​​30-200 m² / g, a magnesium oxide content of 26.0%-28.0%, and an aluminum oxide content of 20.0%-26.0%. The amount of the inserted ester ethoxylation catalyst used in step 1 is 0.6-1.2% of the total mass of the reactants.

[0011] Preferably, the catalyst is a solution of pentamethyldiethylenetriene, N,N-dimethylcyclohexene, potassium octanoate in diethylene glycol, or potassium acetate in diethylene glycol, and the foam stabilizer is a block or graft copolymer of polysiloxane-olefin oxide.

[0012] Preferably, the polyurethane A material is a polyphenylene polymethylene polyisocyanate with an average functionality of 2.7-2.9, a viscosity of 1500-4500 mPa·s at 20°C, and an isocyanate content of ≥30%.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses only one catalyst to complete the alcoholysis of PET and the insertion of ethylene oxide to prepare a low-viscosity, high-functionality aromatic polyether ester polyol, which is used to improve the dimensional stability of polyurethane foam with methyl formate as the blowing agent and avoid shrinkage problems. The inserted ester-based ethoxylation catalyst used is a hydrotalcite-like substance, which not only acts as a catalyst in the preparation process to realize the alcoholysis of PET and the insertion of ethylene oxide, but also, as an inorganic powder material, can synergistically improve the dimensional stability of polyurethane foam with methyl formate as the blowing agent and avoid shrinkage problems. At the same time, flame-retardant polyester polyol is added in the preparation process to enhance the flame-retardant properties of polyurethane foam.

[0014] 2. This invention replaces a portion of the small-molecule diols with phthalic anhydride polyester polyols, reducing the amount of small-molecule diols used in the alcoholysis process. It eliminates the need for vacuum extraction or the addition of new small-molecule diacids to prepare the polyester polyols, shortening the preparation steps and saving preparation time. The absence of small-molecule diacids helps reduce the impact of acidic substances on the insertion ester ethoxylation catalyst, preventing its deactivation during polyester polyol preparation. The resulting polyester polyol has a lower acid value, eliminating the need to consider the ethoxylation reaction of the terminal COOH during the insertion ester ethoxylation reaction (i.e., the addition reaction with ethylene oxide / propylene oxide at 140℃ is unnecessary). If propylene oxide is used, the terminal hydroxyl group can be guaranteed to be a primary hydroxyl group, ensuring that the polyol's reactivity is not reduced. Detailed Implementation

[0015] The technical solution of the present invention will be clearly and completely described below.

[0016] Implementation Case 1: Step 1): 100 parts of waste PET, 150 parts of phthalic anhydride polyester polyol (hydroxyl value 315 mgKOH / g), 40 parts of glycerol and 3.0 parts of inserted ester ethoxylation catalyst are added to the reactor and heated to 230-240℃. The PET is gradually dissolved in the polyester polyol under stirring. The reaction continues for 2 hours. Then the temperature is lowered to 180℃, 10 parts of ethylene glycol are added, and the reaction continues for 2 hours to obtain aromatic polyester polyol.

[0017] Take 100 parts of aromatic polyester polyol, stir evenly, and remove water by vacuum at 100℃ for 2 hours. Raise the temperature to 180℃ to start the induced reaction, and then raise the temperature to 210℃ and continuously introduce ethylene oxide to add 100 parts of ethylene oxide to the aromatic polyester polyol. Stop the introduction of nitrogen and heating, and lower the temperature to 100℃ to allow the ethylene oxide in the system to continue to react until the pressure in the system drops to 0.11-0.2 MPa. Discharge the material to obtain the multifunctional aromatic polyether ester polyol.

[0018] Its acid value was measured to be 0.2 mg KOH / g, its hydroxyl value to be 231 mg KOH / g, and it was a pale yellow, opaque liquid with a viscosity (25℃) of 4560 mPa*s.

[0019] Step 2) Mix 100 parts of aromatic polyether ester polyol, 2.5 parts of pentamethyldiethylenetriene, 1.3 parts of potassium acetate diethylene glycol solution (concentration of 33%), 14 parts of methyl formate foaming agent, 0.6 parts of water, 1 part of foam stabilizer, and 25 parts of flame retardant polyester polyol at room temperature for 30-50 minutes to obtain polyurethane B material. Mix it with polyurethane A material PM200 at a mass ratio of (1:1) and stir at high speed to obtain polyurethane foam.

[0020] Implementation Case 2: Step 1): 100 parts of waste PET, 100 parts of phthalic anhydride polyester polyol (hydroxyl value 315 mgKOH / g), 40 parts of glycerol and 3.5 parts of inserted ester ethoxylation catalyst are added to the reactor and heated to 230-240℃. The PET is gradually dissolved in the polyester polyol under stirring. The reaction continues for 2 hours. Then the temperature is lowered to 180℃, 10 parts of ethylene glycol are added, and the reaction continues for 2 hours to obtain aromatic polyester polyol.

[0021] Take 100 parts of aromatic polyester polyol, stir evenly, and remove water by vacuum at 100℃ for 2 hours. Raise the temperature to 180℃ to start the induced reaction, and then raise the temperature to 210℃ and continuously introduce ethylene oxide to add 50 parts of ethylene oxide to the aromatic polyester polyol. Stop the introduction of nitrogen and heating, and lower the temperature to 100℃ to allow the ethylene oxide in the system to continue to react until the pressure in the system drops to 0.11-0.2 MPa. Discharge the material to obtain the multifunctional aromatic polyether ester polyol.

[0022] Its acid value was measured to be 0.3 mgKOH / g, its hydroxyl value to be 320 mgKOH / g, and it was a pale yellow, opaque liquid with a viscosity (25℃) of 5340 mPa*s.

[0023] Step 2) Mix 100 parts of aromatic polyether ester polyol, 2.7 parts of pentamethyldiethylenetriene, 1.4 parts of potassium acetate diethylene glycol solution (concentration of 33%), 14 parts of methyl formate foaming agent, 0.6 parts of water, 1 part of foam stabilizer, and 25 parts of flame retardant polyester polyol at room temperature for 30-50 minutes to obtain polyurethane B material. Mix it with polyurethane A material PM200 at a mass ratio of (1:1) and stir at high speed to obtain polyurethane foam.

[0024] Implementation Case 3: Step 1): 100 parts waste PET, 200 parts phthalic anhydride polyester polyol (hydroxyl value 315 mgKOH / g), 40 parts glycerol and 4.5 parts inserted ester ethoxylation catalyst are added to the reactor and heated to 230-240℃. The PET is gradually dissolved in the polyester polyol under stirring. The reaction continues for 2 hours. Then the temperature is lowered to 180℃, 10 parts ethylene glycol are added, and the reaction continues for 2 hours to obtain aromatic polyester polyol.

[0025] Take 100 parts of aromatic polyester polyol, stir evenly, and remove water by vacuum at 100℃ for 2 hours. Raise the temperature to 180℃ to start the induced reaction, and then raise the temperature to 210℃ and continuously introduce ethylene oxide to add 50 parts of ethylene oxide to the aromatic polyester polyol. Stop the introduction of nitrogen and heating, and lower the temperature to 100℃ to allow the ethylene oxide in the system to continue to react until the pressure in the system drops to 0.11-0.2 MPa. Discharge the material to obtain the multifunctional aromatic polyether ester polyol.

[0026] Its acid value was measured to be 0.2 mgKOH / g, its hydroxyl value to be 280 mgKOH / g, and it was a pale yellow, opaque liquid with a viscosity (25℃) of 4340 mPa*s.

[0027] Step 2) Mix 100 parts of aromatic polyether ester polyol, 2.7 parts of pentamethyldiethylenetriene, 1.4 parts of potassium acetate diethylene glycol solution (concentration of 33%), 14 parts of methyl formate foaming agent, 0.6 parts of water, 1 part of foam stabilizer, and 30 parts of flame retardant polyester polyol at room temperature for 30-50 minutes to obtain polyurethane B material. Mix it with polyurethane A material PM200 at a mass ratio of (1:1) and stir at high speed to obtain polyurethane foam.

[0028] A comparison of the performance of the polyurethane foam obtained in the three embodiments of this application: The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for preparing polyurethane foam using methyl formate as a blowing agent, characterized in that: Includes the following steps: Step 1: Add 100 parts PET, 100-200 parts phthalic anhydride polyester polyol, 25-40 parts small molecule polyol and inserted ester ethoxylation catalyst to the reactor, heat to 230-240℃, and stir to allow PET to gradually dissolve in the polyester polyol. Continue the reaction for 2-4 hours, then lower the temperature to 180℃, add 10-20 parts ethylene glycol, and continue the reaction for 2-4 hours to obtain aromatic polyester polyol. Take 100 parts of aromatic polyester polyol, stir evenly, and remove water under vacuum at 100℃ for 2 hours. Raise the temperature to 180℃ to start the induced reaction, and then raise the temperature to 210℃ and continuously introduce ethylene oxide or propylene oxide to add the calculated amount of ethylene oxide or propylene oxide to the aromatic polyester polyol. Stop the introduction of nitrogen and heating, lower the temperature to 140℃, and continue the reaction for 1-2 hours, allowing the ethylene oxide in the system to continue reacting until the pressure in the system drops to 0.11-0.2 MPa. Discharge the material to obtain the multifunctional aromatic polyether ester polyol. Step 2: Mix 100 parts of aromatic polyether ester polyol, 3-6 parts of catalyst, 10-18 parts of methyl formate foaming agent, 0.5-1 parts of water, 1.2-2 parts of foam stabilizer, and 20-30 parts of flame-retardant polyester polyol at room temperature for 30-50 minutes to obtain polyurethane component B. Mix polyurethane component A with polyurethane component A at a mass ratio of 1:1 and stir at high speed to obtain polyurethane foam. The small molecule polyols are glycerol, trihydroxypropane, pentaerythritol, ethanolamine, diethanolamine, triethanolamine, etc. The phthalic anhydride polyester polyol has an acid value of 2-3 mgKOH / g, a hydroxyl value of 180-320 mgKOH / g, and a viscosity of 2000-4000 mPa·s at 25℃. The inserted ester-based ethoxylation catalyst is a hydrotalcite-like compound with an average particle size of 0.6-5 μm, a specific surface area of ​​30-200 m² / g, a magnesium oxide content of 26.0%-28.0%, and an aluminum oxide content of 20.0%-26.0%. The amount of the inserted ester ethoxylation catalyst used in step 1 is 0.6-1.2% of the total mass of the reactants.

2. The method for preparing polyurethane foam using methyl formate as a blowing agent according to claim 1, characterized in that: The PET refers to waste PET bottle flakes and waste PET fibers.

3. The method for preparing polyurethane foam using methyl formate as a blowing agent according to claim 1, characterized in that: The catalyst is a solution of pentamethyldiethylenetriene, N,N-dimethylcyclohexene, potassium octanoate in diethylene glycol, and potassium acetate in diethylene glycol. The foam stabilizer is a block or graft copolymer of polysiloxane-olefin oxide.

4. The method for preparing polyurethane foam using methyl formate as a blowing agent according to claim 1, characterized in that: The polyurethane component A is a polyphenyl polymethylene polyisocyanate with an average functionality of 2.7-2.9, a viscosity of 1500-4500 mPa·s at 20°C, and an isocyanate content of ≥30%.