Composite azo radical initiators and their use in polymer polyols

Abstract

This invention belongs to the field of polyurethane technology, specifically relating to a composite azo radical initiator and its application in polymeric polyols. The composite azo radical initiator is composed of an azo initiator and a macromolecular radical initiator, with a mass ratio of (2.5–10):1. The azo initiator is one of azobisisobutyronitrile (AIBN) and dimethyl azobisisobutyrate (DITB). The macromolecular radical initiator is formed by the condensation of an acylated azo compound with a polyether polyol. In this invention, in addition to the traditional azo initiator component, a macromolecular radical initiator is prepared using a polyether polyol, which then initiates the polymerization of vinyl monomers to form a polyether-vinyl polymer, increasing the compatibility between the polyether and the vinyl polymer and improving storage stability. This invention also provides its application in polymeric polyols.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane technology, specifically relating to composite azo radical initiators and their application in polymer polyols. Background Technology

[0002] Polymer polyols (POPs) are widely used in polyurethane flexible foams, polyurethane microporous elastomers, and other fields, playing a key role in improving the support and open-cell properties of polyurethane materials. The dispersibility of vinyl polymer particles in the polyether matrix of POPs directly determines their storage stability, thus affecting the performance and application effects of downstream products. To improve the dispersibility of polymer particles, existing technologies typically add dispersants to the POP system: for example, CN109721703A prepares a high-performance dispersant through the reaction of cyclic dicarboxylic anhydrides and end-capping with epoxy compounds, which can improve the strength and load-bearing capacity of polyurethane foams; CN109796575A prepares a prepolymer by reacting hydroxyalkyl acrylate (or hydroxyalkyl methacrylate) with a polyfunctional isocyanate, and then further reacts it with an oligomeric polyol, resulting in a POP with both excellent dispersion stability and low viscosity characteristics.

[0003] Currently, research on the dispersibility of POP particles mainly focuses on dispersant optimization, while exploration of POP initiator systems is relatively scarce. Besides traditional low-molecular-weight azo and peroxide initiators, a class of high-molecular-weight compounds containing decomposable free radical structures in their molecular chains—macromolecular free radical initiators—is gradually attracting attention. The free radicals generated by the decomposition of macromolecular initiators have advantages such as strong reaction controllability, mild reaction conditions, and a wide variety of compatible monomers, and have been widely used in the preparation of block copolymers, thus attracting considerable attention. Therefore, developing efficient free radical initiators suitable for POP preparation has become a key technical problem that urgently needs to be solved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a composite azo radical initiator. In addition to traditional azo initiator components, a macromolecular radical initiator is prepared using polyether polyols, which then initiates the polymerization of vinyl monomers to form a polyether-vinyl polymer, thereby increasing the compatibility between the polyether and the vinyl polymer and improving storage stability.

[0005] The present invention also provides its application in polymeric polyols.

[0006] The technical solution of the present invention is as follows:

[0007] The aforementioned composite azo radical initiator is composed of an azo initiator and a macromolecular radical initiator, with a mass ratio of azo initiator to macromolecular radical initiator of (2.5-10):1;

[0008] The azo initiator is one of azobisisobutyronitrile (AIBN) and dimethyl azobisisobutyrate (DIBO); the macromolecular free radical initiator is formed by the condensation of an acylated azo compound with a polyether polyol.

[0009] The mass ratio of azo initiator to macromolecular free radical initiator is controlled at (2.5~10):1 to better ensure the reactivity.

[0010] The azo compound is 4,4'-azobis(4-cyanopentaic acid). This substance contains a carboxyl group, enabling it to undergo the next acylation reaction.

[0011] The acylation reagent used is oxaloyl chloride.

[0012] The polyether polyol has a propylene oxide-ethylene oxide block structure, which facilitates reaction with acylated azo compounds. The polyether polyol has an average functionality of 2-3 functionalities and a number-average molecular weight of 1000-1500 g / mol, at which point its reactivity is appropriate.

[0013] The application of the composite azo radical initiator in polymer polyols according to the present invention involves adding vinyl monomers, a portion of the base polyether, a chain transfer agent, and the composite azo radical initiator to the remaining base polyether and dispersant for free radical polymerization to obtain polymer polyols.

[0014] in:

[0015] The vinyl monomers are styrene and acrylonitrile.

[0016] The amount of the composite azo radical initiator is 3-4‰ of the total mass of the vinyl monomer, base polyether, chain transfer agent, composite azo radical initiator, and dispersant.

[0017] The temperature for free radical polymerization is 120–130°C, preferably 120–125°C.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) In the composite azo radical initiator of the present invention, the decomposition rates of the azo initiator and the macromolecular radical initiator are complementary. The macromolecular radical initiator with a relatively slow decomposition rate can further improve the monomer conversion rate in the maturation stage, avoiding the traditional initiator from having a too fast decomposition rate and low conversion rate in the early stage of the reaction.

[0020] (2) Both the dispersant and the polyether-type macromolecular free radical initiator of the present invention can initiate the polymerization of vinyl monomers to form a dispersant structure of polyether-vinyl polymer, which increases the dispersibility of polymer particles in POP and reduces polymer particle agglomeration. Detailed Implementation

[0021] The present invention will be further described below with reference to the embodiments.

[0022] Dispersant, BDF-4, Jiangsu Bader Polyurethane Co., Ltd.

[0023] Unless otherwise specified, all raw materials used in the examples were commercially available.

[0024] The testing methods used are as follows:

[0025] Hydroxyl value determination: GB / T 12008.3-2009 "Plastics Polyether Polyols Part 3: Determination of Hydroxyl Value";

[0026] Viscosity determination: GB / T 12008.7-2010 "Plastics Polyether Polyols Part 7: Determination of Viscosity";

[0027] Solid content determination: GB / T 31062-2014 "Polymer Polyols";

[0028] Filtration performance evaluation: Mix 50g of polymer polyol with 100g of isopropanol at room temperature, filter through a 150-mesh filter, and observe whether there are residual particles on the filter surface.

[0029] Example 1

[0030] Preparation of polyether polyol 1: 106g of diethylene glycol and 3g of KOH were added to a pressure-resistant reactor. After nitrogen purging, the temperature was raised to 80℃ and 200g of propylene oxide was added dropwise. After the addition was completed, the reactor was pressurized for 2 hours and the monomer was removed for 30 minutes. The temperature was raised to 120℃ and 800g of ethylene oxide was added dropwise. After the addition was completed, the reactor was pressurized for 5 hours and the monomer was removed for 30 minutes. The temperature was lowered to 90℃ and 6.6g of phosphoric acid aqueous solution and 30g of water were added and stirred for 1 hour. Then, 5g of magnesium silicate was added for adsorption. The mixture was filtered to obtain polyether polyol 1.

[0031] Preparation of macromolecular free radical initiator 1:

[0032] 3 g of 4,4'-azobis(4-cyanopentanoic acid), 4.5 g of oxaloyl chloride, and 40 mL of benzene were added to a three-necked flask and stirred at room temperature for 24 h. After filtration and vacuum drying, the product was washed with a mixture of anhydrous diethyl ether and n-hexane, and recrystallized from dichloromethane and n-hexane to obtain an intermediate containing an acyl chloride structure. 15 g of polyether polyol 1, 1.5 g of triethylamine, and 30 mL of benzene were added to a three-necked flask, and a benzene solution containing the intermediate containing the acyl chloride structure was added dropwise. The mixture was reacted at room temperature for 6 h, filtered, and vacuum dried to obtain macromolecular free radical initiator 1.

[0033] Preparation of polymer polyol: 101g of base polyether polyol F5631 and 7g of dispersant BDF-4 were added to a four-necked flask. After nitrogen purging, the mixture was stirred and slowly heated to 110℃. Then, a mixture of 30g isopropanol, 37g base polyether polyol F5631, 37.2g acrylonitrile, 86.9g styrene, 0.9g azobisisobutyronitrile, and 0.1g macromolecular free radical initiator 1 was continuously added dropwise, controlling the temperature at 120-125℃. The addition was completed within 90 minutes. The mixture was aged for 1 hour, followed by vacuum monomer removal for 2 hours to obtain the product, and its indicators were measured.

[0034] Example 2

[0035] Preparation of polyether polyol 2: 92g of glycerol and 3g of KOH were added to a pressure-resistant reactor. After nitrogen purging, the temperature was raised to 80℃ and 250g of propylene oxide was added dropwise. After the addition was completed, the reactor was pressurized for 2 hours and the monomer was removed for 30 minutes. The temperature was raised to 120℃ and 1150g of ethylene oxide was added dropwise. After the addition was completed, the reactor was pressurized for 4 hours and the monomer was removed for 30 minutes. The temperature was lowered to 90℃ and 6.6g of phosphoric acid aqueous solution and 45g of water were added and stirred for 1 hour. Then, 4.5g of magnesium aluminum silicate was added for adsorption. The mixture was filtered to obtain polyether polyol 2.

[0036] Preparation of macromolecular free radical initiator 2:

[0037] 3 g of 4,4'-azobis(4-cyanopentanoic acid), 5.5 g of oxaloyl chloride, and 40 mL of benzene were added to a three-necked flask and stirred at room temperature for 24 h. After filtration and vacuum drying, the product was washed with a mixture of anhydrous diethyl ether and n-hexane, and recrystallized from dichloromethane and n-hexane to obtain an intermediate containing an acyl chloride structure. 22.5 g of polyether polyol 2, 1.6 g of triethylamine, and 30 mL of benzene were added to a three-necked flask, and a benzene solution containing the intermediate containing the acyl chloride structure was added dropwise. The mixture was reacted at room temperature for 6 h, filtered, and vacuum dried to obtain macromolecular free radical initiator 2.

[0038] Preparation of polymer polyol: 100g of base polyether polyol F5631 and 6.6g of dispersant BDF-4 were added to a four-necked flask. After nitrogen purging, the mixture was stirred and slowly heated to 110℃. Then, a mixture of 30g isopropanol, 35g base polyether polyol F5631, 35.5g acrylonitrile, 85g styrene, 0.85g dimethyl azobisisobutyrate, and 0.3g macromolecular free radical initiator 2 was continuously added dropwise, controlling the temperature at 120-125℃. The addition was completed within 90 minutes. The mixture was aged for 1 hour, followed by vacuum monomer removal for 2 hours to obtain the product, and its indicators were measured.

[0039] Example 3

[0040] The macromolecular free radical initiator used is macromolecular free radical initiator 2 from Example 2.

[0041] Preparation of polymer polyol: 100g of base polyether polyol F5631 and 6.6g of dispersant BDF-4 were added to a four-necked flask. After nitrogen purging, the mixture was stirred and slowly heated to 110℃. Then, a mixture of 30g isopropanol, 35g base polyether polyol F5631, 35.5g acrylonitrile, 85g styrene, 1g dimethyl azobisisobutyrate, and 0.15g macromolecular free radical initiator 2 was continuously added dropwise, controlling the temperature at 120-130℃. The addition was completed within 90 minutes. The mixture was aged for 1 hour, followed by vacuum monomer removal for 2 hours to obtain the product, and its indicators were measured.

[0042] Comparative Example 1

[0043] Preparation of polymer polyol: 101g of base polyether polyol F5631 and 7g of dispersant BDF-4 were added to a four-necked flask. After nitrogen purging, the mixture was stirred and slowly heated to 110℃. Then, a mixture (30g isopropanol, 37g base polyether polyol F5631, 37.2g acrylonitrile, 86.9g styrene, and 1g azobisisobutyronitrile) was continuously added dropwise, controlling the temperature at 120-125℃. The addition was completed within 90 minutes. The mixture was aged for 1 hour, followed by vacuum monomer removal for 2 hours to obtain the product, and its indicators were measured.

[0044] Comparative Example 2

[0045] Preparation of polymer polyol: 100g of base polyether polyol F5631 and 6.6g of dispersant BDF-4 were added to a four-necked flask. After nitrogen purging, the mixture was stirred and slowly heated to 110℃. Then, a mixture (30g isopropanol, 35g base polyether polyol F5631, 35.5g acrylonitrile, 85g styrene, and 1.15g dimethyl azobisisobutyrate) was continuously added dropwise, controlling the temperature at 120-125℃. The addition was completed within 90 minutes. The mixture was aged for 1 hour, followed by vacuum monomer removal for 2 hours to obtain the product, and its indicators were measured.

[0046] Comparative Example 3

[0047] Preparation of polymer polyol: 100g of base polyether polyol F5631 and 6.6g of dispersant BDF-4 were added to a four-necked flask. After nitrogen purging, the mixture was stirred and slowly heated to 110℃. Then, a mixture (30g isopropanol, 35g base polyether polyol F5631, 35.5g acrylonitrile, 85g styrene, 1g dimethyl azobisisobutyrate, and 0.15g 4,4'-azobis(4-cyanopentanoic acid)) was continuously added dropwise, controlling the temperature at 120-125℃. The addition was completed within 90 minutes. The mixture was aged for 1 hour, followed by vacuum monomer removal for 2 hours to obtain the product, and its indicators were measured.

[0048] The product performance results are shown in Table 1.

[0049] Table 1 Product Indicator Results

[0050]

[0051] As can be seen from Examples 1-3 and Comparative Examples 1-3, after adding the macromolecular free radical initiator, the macromolecular free radical initiator also acts as a dispersant, increasing the solid content and monomer conversion rate; and the filter residue is reduced, proving improved dispersibility. Comparing Examples 2 and 3, it was found that in Example 2, increasing the proportion of azo macromolecular free radical initiator resulted in a decrease in product viscosity, further demonstrating its good dispersibility in the POP system.

Claims

1. A composite azo radical initiator, characterized in that, It is composed of an azo initiator and a macromolecular free radical initiator, with a mass ratio of azo initiator to macromolecular free radical initiator of (2.5~10):1; The azo initiator is one of azobisisobutyronitrile (AIBN) and dimethyl azobisisobutyrate (DIBO). The macromolecular free radical initiator is formed by the condensation of an acylated azo compound and a polyether polyol. The azo compound is 4,4'-azobis(4-cyanopentanoic acid), the acylation reagent used is oxaloyl chloride, and the polyether polyol has a propylene oxide-ethylene oxide block structure. The polyether polyol has an average functionality of 2-3 and a number average molecular weight of 1000-1500 g / mol.

2. The application of the composite azo radical initiator according to claim 1 in polymer polyols, characterized in that, Vinyl monomers, a portion of the base polyether, chain transfer agent, and a complex azo radical initiator are added to the remaining base polyether and dispersant for free radical polymerization to obtain a polymer polyol.

3. The application of the composite azo radical initiator according to claim 2 in polymer polyols, characterized in that, The vinyl monomers are styrene and acrylonitrile.

4. The application of the composite azo radical initiator according to claim 2 in polymer polyols, characterized in that, The amount of the composite azo radical initiator is 3-4‰ of the total mass of the vinyl monomer, base polyether, chain transfer agent, composite azo radical initiator, and dispersant.

5. The application of the composite azo radical initiator according to claim 2 in polymer polyols, characterized in that, The temperature for free radical polymerization is 120–130℃.

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