A cardanol-based polyether polyol and preparation method thereof

Abstract

The present invention discloses a cardanol-based polyether polyol and a preparation method thereof. In the present invention, the phenolic hydroxyl groups of cardanol are replaced by epoxidation to prepare cardanol glycidyl ether, which is then further ring-opening polymerized with an alkylene oxide in the presence of a high-efficiency catalyst to prepare a cardanol-based polyether polyol. The cardanol-based polyether polyol prepared by the present invention retains the long alkyl side chains and double bonds in cardanol and has multiple active hydroxyl groups. It can be widely used in technical fields such as surfactants, modifiers, and polyurethane synthesis. The reaction conditions are mild and the product conversion rate is high.

Description

Technical Field

[0001] The invention belongs to the technical field of polyether polyol preparation, and particularly relates to a cardanol-based polyether polyol and a preparation method thereof. Background Art

[0002] Cardanol is extracted from natural cashew nut shell oil using advanced technology. It contains a large amount of active single-component phenol and a small amount of diphenol. It can replace or partially replace phenol in the manufacture of epoxy curing agents, liquid phenolic resins, liquid or powdered thermosetting phenolic resins. It has a wide range of uses and outstanding environmental performance. Cardanol has the activity of petroleum phenol. It is a monohydroxyphenol with a long hydrogen-containing carbon chain at its meta position. It has the characteristics of wide sources, renewability, low toxicity and biodegradability. Alkylphenol polyoxyethylene ether synthesized from petroleum phenol is not easy to decompose in the natural environment and will cause environmental pollution. It is a banned product in many developed countries. Cardanol replaces petroleum phenol to synthesize cardanol polyether surfactants, which have acid and alkali resistance. Due to its good biodegradability, it is called a "green" surfactant or biomass surfactant. Its special chemical structure and the resulting physical and chemical properties also provide many other advantages for improvement and modification.

[0003] Currently, cardanol polyethers are primarily prepared by the addition reaction of cardanol hydroxyl groups with ethylene oxide or propylene oxide, resulting in cardanol polyoxyethylene ethers or cardanol polyoxypropylene ethers. As a new generation of safe, mild, and environmentally friendly surfactants, these have found success in the synthesis of polymers such as thermosetting epoxy resins and phenolic resins. However, the resulting cardanol polyethers typically possess only one active hydroxyl group and are primarily used as end-capping agents in polymer synthesis, rather than being embedded within polymer chains. Furthermore, the phenolic hydroxyl groups of cardanol are less active than epoxy groups, leading to the synthesis temperature of cardanol polyethers generally being between 120 and 180°C. The phenolic hydroxyl groups in cardanol are susceptible to oxidation and discoloration, which is further exacerbated by catalysts and high-temperature reactions, affecting the product's color and performance. Therefore, developing a multifunctional, low-temperature, and mild synthesis method for cardanol polyether polyols is of great significance. Summary of the Invention

[0004] In order to effectively solve the above problems, the present invention aims to provide a cardanol-based polyether polyol and a preparation method thereof.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a cardanol-based polyether polyol comprises the following steps:

[0007] (1) reacting cardanol, epichlorohydrin, and benzyltriethylammonium chloride at 70-100°C for 4-4.5 hours, cooling and maintaining the temperature at 60-70°C, adding solid sodium hydroxide in batches within 1 hour, and then continuing the reaction for 4-4.5 hours, washing with water, standing to separate layers, removing the water layer, and distilling under reduced pressure to recover excess epichlorohydrin to obtain cardanol glycidyl ether;

[0008] The molar ratio of cardanol to epichlorohydrin is 1:2-10, the amount of benzyltriethylammonium chloride is 2% of the mass of cardanol, and the molar ratio of cardanol to solid sodium hydroxide is 1:1-2.

[0009] (2) Add the cardanol glycidyl ether into a high-pressure reactor, add a catalyst in an amount of 0.1 to 2% by weight, and perform nitrogen replacement. After the nitrogen replacement is completed, heat the reactor to 70 to 85°C, add alkylene oxide in an amount of 10 to 50% by weight of the cardanol glycidyl ether to initiate polymerization, and after the pressure drops and the temperature rises, continue to add alkylene oxide into the reactor, control the reaction temperature at 70 to 90°C, and the pressure below 0.4 MPa. After the reaction is completed, cool the reactor to 30 to 40°C, take out the reaction product, and obtain the cardanol-based polyether polyol.

[0010] The total mass ratio of the cardanol glycidyl ether to the alkylene oxide is 1:1-20.

[0011] The alkylene oxide is one of ethylene oxide and propylene oxide or a combination thereof in any proportion.

[0012] The catalyst is one of an alkali metal catalyst, a double metal cyanide catalyst, and an alkyl aluminum phosphate catalyst.

[0013] The cardanol-based polyether polyol prepared according to the above method has a hydroxyl functionality of ≥2 and contains one or more long-chain -C=C- double bonds.

[0014] The present invention first replaces the phenolic hydroxyl group of cardanol by epoxidation to prepare cardanol glycidyl ether, and then further ring-opening polymerizes the cardanol glycidyl ether with an alkylene oxide under the action of a high-efficiency catalyst to prepare a cardanol-based polyether polyol, which has the following beneficial effects:

[0015] 1. After the phenolic hydroxyl group of cardanol is replaced by epoxidation, its ring-opening addition reaction activity with alkylene oxide is greatly improved, so the reaction temperature is reduced and the efficiency is improved.

[0016] 2. The cardanol-based polyether polyol prepared by the present invention has two or more active hydroxyl functional groups and retains the long alkyl side chain and double bond in cardanol. It can be widely used in technical fields such as surfactants, modifiers, and polyurethane synthesis. In addition, the reaction conditions are mild and the product conversion rate is high. DETAILED DESCRIPTION

[0017] The following examples may enable those skilled in the art to better understand the present invention, but are not intended to limit the present invention in any form.

[0018] Example 1

[0019] A method for preparing a cardanol-based polyether polyol comprises the following steps:

[0020] (1) reacting cardanol in a molar ratio of 1:6 with epichlorohydrin and benzyltriethylammonium chloride (2% by mass of cardanol) at 80°C for 4 h; cooling and maintaining the temperature at 60°C, adding solid sodium hydroxide in batches over 1 h (the molar ratio of solid sodium hydroxide to cardanol is 2:1), and then continuing the reaction for 4 h, washing with water, standing to separate, removing the water layer, and distilling under reduced pressure to recover the excess epichlorohydrin to obtain cardanol glycidyl ether;

[0021] (2) Add the cardanol glycidyl ether into a high-pressure reactor, add 0.2% of its mass of sodium hydroxide, and replace the gas with nitrogen. After the nitrogen replacement is completed, heat it to 75°C, add 20% of its mass of ethylene oxide to initiate the polymerization reaction, and after the pressure drops and the temperature rises, continue to add 500% of the mass of cardanol glycidyl ether of ethylene oxide into the reactor, control the reaction temperature at 80°C and the pressure below 0.4MPa. After the reaction is completed, cool it to 30°C, take out the reaction product, and obtain cardanol-based polyether polyol.

[0022] After testing, the conversion rate of cardanol was 94.5%, and the hydroxyl value of the product was 82.16 mgKOH / g (GB / T7383-2007).

[0023] Example 2

[0024] A method for preparing a cardanol-based polyether polyol comprises the following steps:

[0025] (1) reacting cardanol in a molar ratio of 1:6 with epichlorohydrin and benzyltriethylammonium chloride (2% by mass of cardanol) at 80°C for 4 h, cooling and maintaining the temperature at 60°C, adding solid sodium hydroxide in batches within 1 h (the molar ratio of solid sodium hydroxide to cardanol is 2:1), and then continuing the reaction for 4 h, washing with water, standing to separate, removing the water layer, and distilling under reduced pressure to recover the excess epichlorohydrin to obtain cardanol glycidyl ether;

[0026] (2) Add cardanol glycidyl ether into a high-pressure reactor, add 0.2% of its mass of double metal cyanide, and perform nitrogen replacement. After the nitrogen replacement is completed, heat it to 85°C, add 30% of its mass of propylene oxide to initiate polymerization, wait for the pressure to drop and the temperature to rise, and continue to add 600% of the mass of cardanol glycidyl ether of propylene oxide into the reactor, control the reaction temperature at 80°C and the pressure below 0.4MPa, cool it to 30°C after the reaction is completed, take out the reaction product, and obtain cardanol-based polyether polyol.

[0027] After testing, the conversion rate of cardanol was 89.1%, and the hydroxyl value of the product was 75.33 mgKOH / g (GB / T7383-2007).

[0028] Example 3

[0029] A method for preparing a cardanol-based polyether polyol comprises the following steps:

[0030] (1) reacting cardanol in a molar ratio of 1:6 with epichlorohydrin and benzyltriethylammonium chloride (2% by mass of cardanol) at 80°C for 4 h, cooling and maintaining the temperature at 60°C, adding solid sodium hydroxide in batches within 1 h (the molar ratio of solid sodium hydroxide to cardanol is 2:1), and then continuing the reaction for 4 h, washing with water, standing to separate, removing the water layer, and distilling under reduced pressure to recover the excess epichlorohydrin to obtain cardanol glycidyl ether;

[0031] (2) Add the cardanol glycidyl ether into a high-pressure reactor, add 0.2% of its mass of alkyl aluminum phosphate catalyst, and perform nitrogen replacement. After the nitrogen replacement is completed, heat it to 85°C, add 30% of its mass of ethylene oxide to initiate polymerization, and after the pressure drops and the temperature rises, continue to add mixed alkyl oxides with a mass of 600% of the cardanol glycidyl ether into the reactor. In the mixed alkyl oxides, the mass ratio of ethylene oxide to propylene oxide is 1:1. Control the reaction temperature at 80°C and the pressure below 0.4 MPa. After the reaction is completed, cool it to 30°C, take out the reaction product, and obtain cardanol-based polyether polyol.

[0032] After testing, the conversion rate of cardanol was 91.1%, and the hydroxyl value of the product was 77.23 mgKOH / g (GB / T7383-2007).

[0033] Comparative Example 1

[0034] Preparation of Cardanol Polyether

[0035] Cardanol was added into a high-pressure reactor, and 0.2% by weight of sodium hydroxide was added to perform nitrogen replacement. After the nitrogen replacement was completed, the temperature was raised to 105° C., and 20% by weight of ethylene oxide was added to initiate the polymerization reaction. After the pressure dropped and the temperature rose, the remaining ethylene oxide (500% by weight of cardanol) was continuously added into the reactor. The reaction temperature was controlled at 120-150° C. and the pressure was lower than 0.4 MPa. After the reaction was completed, the temperature was lowered to 30° C., and the reaction product was taken out to obtain cardanol polyether.

[0036] After testing, the conversion rate of cardanol was 76.6%, and the hydroxyl value of the product was 38.16 mgKOH / g (GB / T7383-2007).

[0037] The above examples and comparative examples show that epoxidation of cardanol significantly reduces the reaction temperature for ring-opening addition reactions with alkylene oxides, significantly improving conversion and hydroxyl value. This is because the introduction of epoxy groups enhances its reactivity and, after ring opening, provides two active sites. The resulting product is a polyol molecule containing two or more hydroxyl groups, which increases cardanol conversion and hydroxyl content.

[0038] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art should understand that the above specific descriptions are illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

Claims

1. A method for preparing a cardanol-based polyether polyol, characterized in that: The following steps are involved: (1) reacting cardanol, epichlorohydrin, and benzyltriethylammonium chloride at 70-100°C for 4-4.5 hours, cooling and maintaining the temperature at 60-70°C, adding solid sodium hydroxide in batches within 1 hour, and then continuing the reaction for 4-4.5 hours, washing with water, standing to separate layers, removing the water layer, and distilling under reduced pressure to recover excess epichlorohydrin to obtain cardanol glycidyl ether; The molar ratio of cardanol to epichlorohydrin is 1:2-10, the amount of benzyltriethylammonium chloride is 2% of the mass of cardanol, and the molar ratio of cardanol to solid sodium hydroxide is 1:1-2. (2) Add the cardanol glycidyl ether into a high-pressure reactor, add a catalyst in an amount of 0.1 to 2% by weight, and perform nitrogen replacement. After the nitrogen replacement is completed, heat the reactor to 70 to 85°C, add alkylene oxide in an amount of 10 to 50% by weight of the cardanol glycidyl ether to initiate polymerization, and after the pressure drops and the temperature rises, continue to add alkylene oxide into the reactor, control the reaction temperature at 70 to 90°C, and the pressure is lower than 0.4 MPa. After the reaction is completed, cool the reactor to 30 to 40°C, take out the reaction product, and obtain a cardanol-based polyether polyol having a hydroxyl functionality ≥ 2 and containing one or more long-chain -C=C- double bonds.

2. The method for preparing a cardanol-based polyether polyol according to claim 1, wherein The total mass ratio of the cardanol glycidyl ether to the alkylene oxide is 1:1-20.

3. The preparation method of a cardanol-based polyether polyol according to claim 1, wherein The alkylene oxide is one of ethylene oxide and propylene oxide or a combination thereof in any proportion.

4. The method for preparing a cardanol-based polyether polyol according to claim 1, wherein The catalyst is one of an alkali metal catalyst, a double metal cyanide catalyst, and an alkyl aluminum phosphate catalyst.

5. A cardanol-based polyether polyol, characterized in that The invention discloses a novel cellulose acetate resin composition comprising the steps of any one of claims 1 to 4.