Two-component bio-based flame-retardant polyurethane potting compound and its preparation method

Abstract

This invention belongs to the field of polyurethane adhesive technology, specifically relating to a two-component bio-based flame-retardant polyurethane potting compound and its preparation method. It consists of component A and component B, with the molar ratio of hydroxyl groups in component A to isocyanate groups in component B being 1:(1-1.05). Component A comprises the following raw materials in parts by weight: bio-based polyol I: 44-55 parts; bio-based polyol II: 44-55 parts; crosslinking agent: 1-2 parts; catalyst: 0.1-0.5 parts; defoamer: 1.0-3.0 parts; silane coupling agent: 0.1-0.5 parts; dehydrating agent: 0.5-1.0 parts; and component B is a modified isocyanate. The potting compound's component A uses bio-based raw materials such as castor oil to synthesize a comb-shaped polyol, improving hydrophobicity and adhesion; component B introduces nitrogen and phosphorus flame-retardant elements into the modified isocyanate, achieving intrinsic flame retardancy.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane adhesive technology, specifically relating to a two-component bio-based flame-retardant polyurethane potting compound and its preparation method. Background Technology

[0002] Potting compounds are critical protective materials for electronic components and precision equipment. Currently, the mainstream products on the market mainly include three categories: epoxy resin potting compounds, polyurethane potting compounds, and silicone potting compounds. From a raw material supply perspective, the core components of these traditional potting compounds largely originate from the petrochemical industry chain, relying on non-renewable fossil resources. This makes them not only susceptible to significant fluctuations in crude oil prices but also difficult to degrade naturally after disposal. In the area of ​​performance optimization, flame retardancy is one of the core performance indicators of potting compounds. Existing technologies still primarily rely on additive flame retardants, specifically by mixing inorganic flame retardants (such as magnesium hydroxide and aluminum hydroxide) or organic flame retardants (such as bromine-based and phosphorus-based compounds) into the matrix to enhance the flame retardant effect. However, this technical approach has inherent drawbacks: on the one hand, flame retardants are prone to long-term flame retardant performance degradation due to molecular migration, and may even precipitate and contaminate surrounding components; on the other hand, the addition of large amounts of flame retardants often destroys the molecular chain structure of the matrix, thereby causing problems such as reduced mechanical strength, deterioration of dielectric properties, and poor processing fluidity, which seriously restricts its promotion in high-end application scenarios such as new energy vehicle electronics and aerospace precision devices.

[0003] Chinese patent CN120118266A discloses a bio-based ultra-low permeability two-component polyurethane and its preparation method. The bio-based raw material used is mainly modified castor oil, with a low proportion of bio-based components, and the biodegradability of the material is not specified. Chinese patent CN120795858A discloses a bio-based two-component transparent flame-retardant potting compound, its preparation method, and its application. This compound improves the flame-retardant performance of the material by adding phosphate ester flame retardants. The bio-based raw materials used are mainly unmodified polyols such as castor oil and soybean oil. These raw materials have high acid values ​​and free fatty acid content, which can adversely affect the catalytic activity of the catalyst.

[0004] To overcome the bottlenecks of dependence on fossil resources and insufficient environmental protection, the industry has gradually begun to explore the research and development of bio-based potting compounds. However, the relevant technologies that take into account flame retardant properties are still in their infancy and have not yet formed a mature industrialization solution. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a two-component bio-based flame-retardant polyurethane potting compound. Component A of the potting compound uses bio-based raw materials such as castor oil, xylitol, and amino acids as initiators to synthesize a polyol containing bio-based segments. This polyol undergoes hexane polymerization to form a comb-like structure, which improves the material's hydrophobicity and adhesion. Component B incorporates nitrogen and phosphorus flame-retardant elements into the modified isocyanate molecular structure through a polymerization process, achieving intrinsic flame retardancy. This avoids the problems of flame retardant migration and phosphorus-containing polyol hydrolysis, and also enhances the material's biodegradability by introducing bio-based isocyanate. The resulting potting compound possesses excellent flame retardancy, hydrophobicity, adhesion, and environmental friendliness.

[0006] Another objective of this invention is to provide a method for preparing a two-component bio-based flame-retardant polyurethane potting compound.

[0007] The technical solution adopted in this invention is as follows:

[0008] The two-component bio-based flame-retardant polyurethane potting compound comprises component A and component B, wherein the molar ratio of hydroxyl groups in component A to isocyanate groups in component B is 1:(1-1.05); wherein component A comprises the following raw materials in parts by weight:

[0009] Bio-based polyol I: 44-55 parts;

[0010] Bio-based polyol II: 44-55 parts;

[0011] Crosslinking agent: 1-2 parts;

[0012] Catalyst: 0.1-0.5 parts;

[0013] Defoamer: 1.0-3.0 parts;

[0014] Silane coupling agent: 0.1-0.5 parts;

[0015] Dehydrating agent: 0.5-1.0 parts;

[0016] Component B is a modified isocyanate;

[0017] The initiator of the bio-based polyol I is an amino acid with a hydroxyl value of 278-282 mgKOH / g;

[0018] The initiators of the bio-based polyol II are castor oil and xylitol, with a hydroxyl value of 135-145 mgKOH / g;

[0019] The modified isocyanate is prepared from phosphorus-containing polyols, flame retardants, and bio-based isocyanates.

[0020] The preparation method of the bio-based polyol I includes the following steps: using amino acids as initiators, catalyzing the polymerization reaction of cyclohexane under the action of phosphazene salt catalyst to obtain bio-based polyol I;

[0021] The amount of phosphazene salt catalyst used in the bio-based polyol I is 0.15-0.20 wt. of the total amount of initiator and cyclohexane.

[0022] The amino acid in question is alanine, which can be prepared through natural protein hydrolysis, microbial fermentation, and other methods, and is widely available.

[0023] The preparation method of the bio-based polyol II includes the following steps: using castor oil and xylitol in a molar ratio of 4.0:(0.9-1.1) as initiators, and catalyzing the polymerization reaction of ethylene oxide under the action of a phosphazene salt catalyst, to obtain bio-based polyol II;

[0024] The amount of phosphazene salt catalyst used in the bio-based polyol II is 0.19-0.25 wt. of the total amount of initiator and cyclohexane.

[0025] Castor oil and xylitol are both widely available bio-based raw materials. Castor oil contains hydroxyl groups and unsaturated double bonds, while xylitol has a pentyl alcohol structure and a high hydroxyl density. Using these two as composite initiators in the synthesis of polyols can significantly improve the functionality and reactivity of the products. Applying these bio-based polyols to potting compound systems can effectively improve the crosslinking density and structural integrity of polyurethane networks, thereby enhancing the mechanical strength, thermal stability, and dimensional stability of the materials.

[0026] The crosslinking agent is trihydroxymethylphosphoric acid oxide.

[0027] The catalyst is Dabco ® T-120, purchased from Evonik Industries.

[0028] The defoamer mentioned is BYK-066N, purchased from BYK Chemicals in Germany.

[0029] The silane coupling agent is KH-540.

[0030] The dehydrating agent is a 3A molecular sieve.

[0031] The method for preparing the modified isocyanate includes the following steps: mixing a phosphorus-containing polyol with a flame retardant, vacuum dehydrating it to <500ppm at 100-110℃ and -0.09MPa, then cooling it to below 60℃, adding bio-based isocyanate, and continuing the reaction at 70-80℃ until the -NCO content is 9.8-10.2wt.%, cooling, loading, and sealing with nitrogen to obtain the modified isocyanate;

[0032] The molar ratio of the phosphorus-containing polyol, flame retardant and bio-based isocyanate is 4:1:(10.0-10.4).

[0033] The phosphorus-containing polyol is Exolit OP560, purchased from Clariant; the flame retardant is pentaerythritol phosphate melamine salt, purchased from Sichuan Zhuoan New Material Technology Co., Ltd., which contains active hydrogen reactive groups and can react with isocyanates; the bio-based isocyanate is L-lysine diisocyanate.

[0034] The preparation method of the two-component bio-based flame-retardant polyurethane potting compound includes the following steps:

[0035] (1) Mix bio-based polyol I, bio-based polyol II, crosslinking agent, defoamer and dehydrating agent, vacuum dehydrate to moisture <500ppm under 100-110℃ and -0.09MPa conditions, then cool to below 50℃, add silane coupling agent and catalyst, stir evenly, cool, load, and seal with nitrogen to obtain component A;

[0036] (2) Mix component A and component B and stir at 25-35℃ for 10-15 minutes until the mixture is uniform to obtain a two-component bio-based flame retardant polyurethane potting compound.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) The bio-based polyol of component A of the present invention is synthesized using bio-based raw materials such as castor oil, xylitol, and amino acids as initiators. By optimizing the molecular weight design, bio-based segments are introduced into the potting compound system, which effectively improves the biodegradability of the material. Using hexane oxide as the polymerization monomer, a comb-shaped molecular structure product can be obtained, which significantly improves the hydrophobicity of the material. At the same time, the carboxyl group in the amino acid molecular structure and the ester group in the castor oil molecular structure can synergistically improve the adhesion performance between the potting compound and the substrate.

[0039] (2) Component B of the present invention is prepared by conventional polymerization reaction. By using the reaction of isocyanate and active hydrogen, nitrogen and phosphorus, two flame retardant elements, are introduced into the molecular structure of modified isocyanate. On the one hand, the intrinsic flame retardant properties of the material are realized, and on the other hand, the defect of easy migration of additive flame retardants is effectively avoided. At the same time, the problem of easy hydrolysis of phosphorus-containing polyols is solved (hydrolysis of phosphorus-containing polyols will affect their storage stability and flame retardant properties). In addition, the use of bio-based isocyanate further improves the biodegradability of the material. Detailed Implementation

[0040] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.

[0041] Unless otherwise specified, the raw materials used in the examples are all commercially available and conventional, and the process methods used in the examples are all conventional methods in the art.

[0042] The following is a description of some of the raw materials used in the examples and comparative examples:

[0043] The preparation method of bio-based polyol I is as follows: 89g alanine is used as the starting agent, and 510g epoxide is catalyzed to undergo polymerization reaction at 120℃ and with 0.9g phosphazene catalyst. After the reaction is complete, the bio-based polyol I is prepared by acid water neutralization, drying and adsorption purification treatment, with a hydroxyl value of 280mgKOH / g.

[0044] The preparation method of bio-based polyol II is as follows: 31g xylitol and 752g castor oil are used as starting agents. Under the catalysis of 2.6g phosphazene catalyst at 120℃, 546g epoxide is catalyzed to carry out a polymerization reaction. After the reaction is complete, the product is prepared by acid water neutralization, drying, and adsorption purification treatment, with a hydroxyl value of 145mgKOH / g.

[0045] The preparation method of modified isocyanate is as follows: 520g of pentaerythritol phosphate melamine salt (PPMS, number average molecular weight of 520g / mol) and 1000g of Exolit OP560 (number average molecular weight of 250g / mol) are added to a reaction vessel and dehydrated under vacuum at 105℃ and -0.09MPa for 2h until the water content is <500ppm. Then, the temperature is lowered to 60℃, and 2050g of L-lysine diisocyanate (number average molecular weight of 198g / mol) is added. The reaction is continued at 80℃ for 2h until the -NCO content is 10wt.%. The mixture is then cooled, loaded, and sealed with nitrogen to obtain modified isocyanate.

[0046] Phosphazene catalyst was purchased from Shanghai Qike Fluorosilicon Materials Co., Ltd.

[0047] INOVOL C204 (hydroxyl value 280mgKOH / g) was purchased from Shandong Yinuowei New Materials Co., Ltd.

[0048] Glyceryl polyoxypropylene ether polyol: Glyceryl polyoxypropylene ether polyol is prepared by catalyzing the polymerization of propylene oxide with potassium hydroxide catalyst, using glycerol as the starting agent. After the reaction is complete, the polyol is neutralized with acid water, dried and purified by adsorption. The hydroxyl value is 145 mgKOH / g.

[0049] Example 1

[0050] The two-component bio-based flame-retardant polyurethane potting compound comprises component A and component B, wherein the molar ratio of hydroxyl groups in component A to isocyanate groups in component B is 1:1.05; wherein component A comprises the following raw materials in parts by weight:

[0051] Bio-based polyol I: 55 parts;

[0052] Bio-based polyol II: 44 parts;

[0053] Trimethylolphosphine oxide: 1 part;

[0054] Dabco ® T-120: 0.1 parts;

[0055] BYK-066N: 3.0 copies;

[0056] KH-540: 0.5 parts;

[0057] 3A molecular sieve: 0.5 parts;

[0058] Component B consists of 180.66 parts of modified isocyanate.

[0059] The preparation method of the two-component bio-based flame-retardant polyurethane potting compound includes the following steps:

[0060] (1) Bio-based polyol I, bio-based polyol II, trimethylolphosphine oxide, BYK-066N and 3A molecular sieve were mixed and vacuum dehydrated to <500ppm at 105℃ and -0.09MPa. Then the temperature was lowered to 50℃ and KH-540 and Dabco were added. ® T-120, stir evenly, cool, load, and seal with nitrogen to obtain component A;

[0061] (2) Mix component A and component B and stir at 25°C for 15 minutes until the mixture is uniform to obtain a two-component bio-based flame-retardant polyurethane potting compound.

[0062] Example 2

[0063] The two-component bio-based flame-retardant polyurethane potting compound comprises component A and component B, wherein the molar ratio of hydroxyl groups in component A to isocyanate groups in component B is 1:1.04; wherein component A comprises the following raw materials in parts by weight:

[0064] Bio-based polyol I: 44 parts;

[0065] Bio-based polyol II: 55 parts;

[0066] Trimethylolphosphine oxide: 1 part;

[0067] Dabco ®T-120: 0.5 portions;

[0068] BYK-066N: 2.0 copies;

[0069] KH-540: 0.1 part;

[0070] 3A molecular sieve: 0.5 parts;

[0071] Component B consists of 167.37 parts of modified isocyanate.

[0072] The preparation method of the two-component bio-based flame-retardant polyurethane potting compound is the same as that in Example 1.

[0073] Example 3

[0074] The two-component bio-based flame-retardant polyurethane potting compound comprises component A and component B, wherein the molar ratio of hydroxyl groups in component A to isocyanate groups in component B is 1:1.01; wherein component A comprises the following raw materials in parts by weight:

[0075] Bio-based polyol I: 49 parts;

[0076] Bio-based polyol II: 49 parts;

[0077] Tris(hydroxymethyl)phosphine oxide: 2 parts;

[0078] Dabco ® T-120: 0.3 parts;

[0079] BYK-066N: 1.0 copy;

[0080] KH-540: 0.1 part;

[0081] 3A molecular sieve: 1.0 part;

[0082] Component B consists of 175.64 parts of modified isocyanate.

[0083] The preparation method of the two-component bio-based flame-retardant polyurethane potting compound is the same as that in Example 1.

[0084] Comparative Example 1

[0085] The difference from Example 3 is that in component A, 49 parts by weight of INOVOL C204 is used to replace bio-based polyol I, and 49 parts by weight of glycerol-based polyoxypropylene ether polyol is used to replace bio-based polyol II. The molar ratio of hydroxyl groups in component A to isocyanate groups in component B is controlled to be 1:1.01. Other aspects are the same as in Example 3.

[0086] Comparative Example 2

[0087] The difference from Example 3 is that in component B, 47.3 parts by weight of L-lysine diisocyanate is used to replace the modified isocyanate, and the molar ratio of hydroxyl groups in component A to isocyanate groups in component B is controlled to be 1:1.01. Other aspects are the same as in Example 3.

[0088] The potting compounds prepared in the examples and comparative examples were subjected to performance tests, and the test methods are as follows:

[0089] The cumulative biodegradation percentage was tested in accordance with GB / T 19276.1-2003.

[0090] The 30-day water absorption rate was tested in accordance with GB / T 19250-2013.

[0091] Flame retardant (UL-94), tested according to UL 94-2023 Test for flammability of plastic materials for equipment and appliance parts.

[0092] The adhesion to the substrate shall be tested in accordance with GB / T 2791-1995.

[0093] The test results are shown in Table 1.

[0094] Table 1 Performance Test Results

[0095]

[0096] As shown in Table 1, introducing bio-based polyols into the crosslinking network structure of potting compounds can effectively improve the biodegradability of the materials; introducing ester, carboxyl, and urethane groups can enhance the adhesion of the potting compound to the substrate; and introducing reactive flame retardants can significantly improve the flame retardant properties of the materials. These performance optimizations can broaden the application scenarios of potting compounds.

Claims

1. A two-component bio-based flame-retardant polyurethane pour-in-place sealant, characterized in that, It consists of component A and component B, with a molar ratio of hydroxyl groups in component A to isocyanate groups in component B of 1:(1-1.05); wherein component A comprises the following raw materials in parts by weight: Bio-based polyol I: 44-55 parts; Bio-based polyol II: 44-55 parts; Crosslinking agent: 1-2 parts; Catalyst: 0.1-0.5 parts; Defoamer: 1.0-3.0 parts; Silane coupling agent: 0.1-0.5 parts; Dehydrating agent: 0.5-1.0 parts; Component B is a modified isocyanate; The preparation method of the bio-based polyol I includes the following steps: using an amino acid as a starting agent, catalyzing the polymerization reaction of cyclohexane under the action of a phosphazene salt catalyst to obtain bio-based polyol I with a hydroxyl value of 278-282 mgKOH / g; the amino acid is alanine. The preparation method of the bio-based polyol II includes the following steps: using castor oil and xylitol in a molar ratio of 4.0:(0.9-1.1) as initiators, and catalyzing the polymerization reaction of cyclohexane under the action of phosphazene salt catalyst, to obtain bio-based polyol II with a hydroxyl value of 135-145 mgKOH / g. The method for preparing the modified isocyanate includes the following steps: mixing a phosphorus-containing polyol with a flame retardant, vacuum dehydrating it to a moisture content of <500 ppm, then cooling it to below 60°C, adding a bio-based isocyanate, and continuing the reaction at 70-80°C until the -NCO content is 9.8-10.2 wt.%, thus obtaining the modified isocyanate; the flame retardant is pentaerythritol phosphate melamine salt.

2. The two-component bio-based flame-retardant polyurethane potting compound according to claim 1, characterized in that, In the preparation method of the bio-based polyol I, the amount of phosphazene salt catalyst used is 0.15-0.20 wt. of the total amount of initiator and cyclohexane.

3. The two-component bio-based flame-retardant polyurethane potting compound according to claim 1, characterized in that, In the preparation method of the bio-based polyol II, the amount of phosphazene salt catalyst used is 0.19-0.25 wt. of the total amount of initiator and cyclohexane.

4. The two-component bio-based flame-retardant polyurethane potting compound according to claim 1, characterized in that, The crosslinking agent is trihydroxymethylphosphoric acid oxide.

5. The two-component bio-based flame-retardant polyurethane potting compound according to claim 1, characterized in that, The catalyst is Dabco ® T-120.

6. The two-component bio-based flame-retardant polyurethane potting compound according to claim 1, characterized in that, The defoamer mentioned is BYK-066N.

7. The two-component bio-based flame-retardant polyurethane potting compound according to claim 1, characterized in that, The silane coupling agent is KH-540.

8. The two-component bio-based flame-retardant polyurethane potting compound according to claim 1, characterized in that, The dehydrating agent is a 3A molecular sieve.

9. The two-component bio-based flame-retardant polyurethane potting compound according to claim 1, characterized in that, In the preparation method of the modified isocyanate, the molar ratio of phosphorus-containing polyol, flame retardant and bio-based isocyanate is 4:1:(10.0-10.4); the phosphorus-containing polyol is Exolit OP560; and the bio-based isocyanate is L-lysine diisocyanate.

10. A method for preparing a two-component bio-based flame-retardant polyurethane potting compound according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Mix bio-based polyol I, bio-based polyol II, crosslinking agent, defoamer and dehydrating agent, vacuum dehydrate to water content <500ppm, then cool to below 50℃, add silane coupling agent and catalyst, stir evenly to obtain component A; (2) Mix component A and component B and stir at 25-35℃ for 10-15 minutes until the mixture is uniform to obtain a two-component bio-based flame retardant polyurethane potting compound.

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