Two-component polyurethane pouring sealant for engineering plastics and preparation method thereof

Abstract

The application discloses a two-component polyurethane pouring sealant for engineering plastics and a preparation method thereof, and belongs to the field of chemical industry.The product is prepared by synthesizing special polyurethane prepolymer to form the two-component polyurethane pouring sealant, which can not only meet the required strength and hardness of product application, but also has good adhesion to various engineering plastics, and is mainly applied to pouring and pouring sealing of communication equipment, transformers, control power supplies, ignition controllers, electronic sensors and the like.

Description

Technical Field

[0001] This invention relates to the chemical industry, specifically to a two-component polyurethane potting compound for engineering plastics and its preparation method. Background Technology

[0002] In today's society, electronic products play a vital role in our daily lives. However, due to their precision, fragility, and limited lifespan, electronic products are easily affected by changes in temperature, humidity, dust, and vibration, which can even lead to malfunctions. To address these issues, we generally use electronic potting compounds as an effective protective measure. Polyurethane potting compounds can effectively encapsulate electronic devices, protecting them from environmental influences, improving mechanical strength, and providing excellent electrical insulation. They are widely used in various consumer electronics products, as well as in the automotive, aerospace, and other industries that frequently involve electronic assembly.

[0003] The bonding substrates of electronic potting compounds mainly include metal materials, inorganic materials, and various engineering plastics (such as PVC, PC, ABS). Currently, most mainstream potting compound products on the market test their bonding performance using metal or inorganic substrates, without conducting in-depth research on engineering plastic substrates. In practical applications, the bonding performance on plastic substrates is not as good as that on metal or inorganic substrates. Summary of the Invention

[0004] Based on the deficiencies of existing technologies, the purpose of this invention is to provide a two-component polyurethane potting compound for engineering plastics. This product is made by synthesizing a special polyurethane prepolymer to form a two-component polyurethane potting compound, which can not only meet the strength, hardness and other requirements of product applications, but also improve the adhesion of the potting compound to various engineering plastics, and meet the needs of casting and potting of communication equipment, transformers, control power supplies, ignition controllers, electronic sensors and the like.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-strength two-component polyurethane potting compound, comprising component A and component B;

[0007] Component A comprises the following components in parts by weight:

[0008] 20-40 parts of polyol, 60-80 parts of aluminum hydroxide, 0-5 parts of molecular sieve activation powder, 0-2 parts of coupling agent, and 0-0.01 parts of catalyst;

[0009] The polyol is a mixture of polyether polyol and castor oil polyol, with a mass ratio of 1:(0.5-1.5).

[0010] Component B comprises the following components in parts by weight:

[0011] 40-90 parts of polyurethane prepolymer, 0-50 parts of isocyanate and 10-40 parts of diluent;

[0012] The polyurethane prepolymer is obtained by reacting polyether polyol, urethane polyol and isocyanate.

[0013] The urethane polyol is a polyurethane polyol obtained by reacting cyclic carbonates and aliphatic primary amines.

[0014] The mass ratio of component A to component B is (4-6):1.

[0015] In the components of the polyurethane potting compound for engineering plastics described in this invention, the polyether polyol and castor oil polyol in component A, when compounded in the specified proportion, can effectively improve the intrinsic adhesive and mechanical properties of the product. In component B, the polyurethane prepolymer is obtained by reacting a urethane polyol with a specific structure, a polyether polyol, and an isocyanate. Since the urethane polyol contains a large number of polar urethane bonds after the reaction, it has high cohesive energy, thus enabling the final polyurethane to have sufficient adhesion and hardness. At the same time, since specific aliphatic primary amines and cyclic carbonates are selected as raw materials for the preparation of the urethane polyol, the reaction results in not only a high urethane bond content but also a high aliphatic segment density, improving the wettability and adhesion to the plastic substrate. This allows the final product to effectively bond and adhere to the surface of various engineering plastics.

[0016] It should be noted that the "castor oil polyol" in the technical solution of this invention refers to castor oil containing hydroxyl polyols, which is known to those skilled in the art. It is generally obtained by further refining crude castor oil, and is not a product synthesized by modifying castor oil with polyols. The latter mainly refers to "castor oil modified polyols", such as castor oil-based polyether polyols, which are different from the substances described in this invention.

[0017] Preferably, the polyether polyol in component A has a molecular weight of 300-3000, the castor oil polyol has a hydroxyl value of 160-168 mgKOH / g, and a functionality of 2.5-3.

[0018] At the specified molecular weight, the two can achieve a good synergistic effect. However, if only polyether polyols are used or the content of added castor oil polyols is too low, the product's molecular structure contains a large number of ether bonds, resulting in decreased cohesive energy and lower adhesive strength, hardness, and viscosity. Conversely, as the castor oil content increases, the product's molecular structure contains ester groups and carbon-carbon double bonds, forming a highly cross-linked flexible network, which improves adhesive strength and hardness, but reduces toughness and increases viscosity. However, if only castor oil polyols are used or the content of added polyether polyols is too low, the adhesive strength will actually decrease. Polyether polyols and castor oil polyols have good compatibility, and combining them in a certain proportion can yield a product with excellent overall performance.

[0019] More preferably, the mass ratio of the polyether polyol to the castor oil polyol is 1:(0.8 to 1.2).

[0020] More preferably, the polyether polyol is a mixture of polyether triol and polyether diol, wherein the mass ratio of the polyether triol, polyether diol and castor oil polyol is (6-7):(8-9):(13-16).

[0021] Preferably, the particle size D50 of the aluminum hydroxide is 10–20 μm;

[0022] More preferably, the aluminum hydroxide is treated with a silane coupling agent.

[0023] When aluminum hydroxide is pretreated with a silane coupling agent, the compatibility of this inorganic component with other components is significantly improved, achieving high dispersibility. This reduces the viscosity of the potting compound and improves its storage stability. It also coordinates the flame retardant to achieve a synergistic flame retardant effect, meeting the UL94 V0 standard. However, if the aluminum hydroxide particle size is small, the viscosity of the potting compound will be high, which is not conducive to potting operations. If the particle size is too large, the mechanical properties of the potting compound will be reduced, and sedimentation will easily occur during storage.

[0024] Preferably, the molecular sieve activation powder is at least one of 3A molecular sieve activation powder, 4A molecular sieve activation powder, and 5A molecular sieve activation powder.

[0025] More preferably, the 3A molecular sieve activated powder is present in 1 to 4 parts by weight in component A.

[0026] Preferably, the coupling agent is at least one selected from γ-aminopropyltriethoxysilane (A-1100), N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (A-1120), N-ethyl-3-trimethoxysilylmethylpropylamine (A-Link15), bis(γ-trimethoxysilylpropyl)amine (A-1170), 3-octanoylthio-1-propyltriethoxysilane (A-Link599), γ-isocyanopropyltriethoxysilane (A-Link 25), and γ-isocyanopropyltrimethoxysilane (A-Link 35).

[0027] Preferably, the catalyst is at least one of organobismuth, organozinc, and dibutyltin dilaurate.

[0028] More preferably, the catalyst is a mixture of organobismuth and organozinc.

[0029] Preferably, the isocyanate is at least one of diphenylmethane diisocyanate and polyphenylmethylene polyisocyanate.

[0030] Preferably, the diluent is at least one of phthalates and aliphatic diacids.

[0031] Preferably, the cyclic carbonate is propylene carbonate, and the aliphatic primary amine is at least one of aliphatic linear diamine, alicyclic diamine, and aliphatic polyamine.

[0032] More preferably, the aliphatic primary amine is at least one selected from ethylenediamine, cyclohexanediamine, tris(2-aminoethyl)amine, tris(3-aminopropyl)amine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0033] More preferably, the aliphatic primary amine is at least one of ethylenediamine, cyclohexanediamine, and tris(2-aminoethyl)amine.

[0034] More preferably, the molar ratio of the cyclic carbonate to the aliphatic primary amine is f:1, where f is the functionality of the aliphatic primary amine.

[0035] More preferably, the urethane polyol is obtained by reacting a cyclic carbonate and an aromatic primary amine at 60–90°C for 3–6 h.

[0036] More preferably, the preparation method of the urethane polyol is as follows: a specified amount of cyclic carbonate is placed in a reactor dish, then heated to the reaction temperature, and under nitrogen protection, a specified amount of aliphatic primary amine is added dropwise and the reaction is carried out to obtain urethane polyol.

[0037] Preferably, in the raw materials for preparing the polyurethane prepolymer, the mass ratio of polyether polyol to urethane polyol is 10:(3-7), more preferably 10:(4-6).

[0038] Optimization revealed that when the amount of urethane polyol added is small, the improvement in the strength of the polyurethane potting compound is minimal; when the amount added is too high, it will greatly increase the viscosity of the polyurethane prepolymer, making the potting compound difficult to apply.

[0039] More preferably, the polyurethane prepolymer is prepared by mixing polyether polyol and urethane polyol in the specified proportions and vacuum drying at 100-120°C for 2-3 hours, then cooling to below 40°C, adding isocyanate under nitrogen protection, and heating to 50-60°C for 2-3 hours to obtain the polyurethane prepolymer.

[0040] More preferably, the NCO content of the polyurethane prepolymer is 10-25%, more preferably 16-23%.

[0041] Another object of the present invention is to provide a method for preparing the two-component polyurethane potting compound for engineering plastics, comprising the following steps:

[0042] Polyol and aluminum hydroxide are mixed and heated to 110-130°C, then dehydrated under vacuum for 2-4 hours, cooled to 40-60°C, and then other components are added and mixed evenly under vacuum to obtain component A.

[0043] The diluent is pre-dried and dehydrated, and then mixed evenly with polyurethane prepolymer and isocyanate under vacuum to obtain component B.

[0044] The preparation method of the two-component polyurethane potting compound for engineering plastics described in this invention has simple operation steps, low requirements for production conditions and equipment, and can achieve industrial production.

[0045] The beneficial effects of this invention are that it provides a two-component polyurethane potting compound for engineering plastics. This product, through the combination of two specially formulated components, not only achieves controllable strength and hardness, but also exhibits excellent adhesion to various plastic substrates. The shear strength test results on different plastics are also excellent. Detailed Implementation

[0046] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0047] Examples 1-12

[0048] An embodiment of the polyurethane potting compound for engineering plastics and its preparation method according to the present invention includes the following steps:

[0049] Polyol and aluminum hydroxide were heated to 120°C, then dehydrated under vacuum for 2 hours, cooled to 60°C, and then other components were added and mixed evenly under vacuum to obtain component A.

[0050] The diluent is pre-dried and dehydrated, and then mixed evenly with polyurethane prepolymer and isocyanate under vacuum to obtain component B.

[0051] The composition ratio of components A and B is shown in Table 1.

[0052] In component A, polyether polyol 1 is a polyether triol with a molecular weight of 300; polyether polyol 2 is a polyether diol with a molecular weight of 2000; and the castor oil polyol is first-grade castor oil produced by Fucheng Huanyu Oil Co., Ltd., with an alcohol hydroxyl value of 165 mg KOH / g and a functionality of 2.7.

[0053] In component A, aluminum hydroxide 1 is aluminum hydroxide with a particle size D50 = 10 μm activated by a silane coupling agent; aluminum hydroxide 2 is aluminum hydroxide with a particle size D50 = 20 μm activated by a silane coupling agent; aluminum hydroxide 3 is aluminum hydroxide with a particle size D50 = 5 μm activated by a silane coupling agent; and aluminum hydroxide 4 is aluminum hydroxide with a particle size D50 = 50 μm activated by a silane coupling agent.

[0054] The molecular sieve activation powder in component A is 3A molecular sieve activation powder, which is produced by Jiangxi Xintao Technology Co., Ltd.

[0055] The catalyst in component A is a commercially available organic bismuth-zinc catalyst complex.

[0056] The coupling agent in component A is γ-glycidoxypropyltrimethoxysilane.

[0057] In component B, the polyurethane prepolymers 1-3 are obtained by reacting polyether polyol, urethane polyol and isocyanate. The preparation method is as follows: the polyether polyol and urethane polyol are mixed at a ratio of 10:5 (total 100g), and vacuum dried at 120°C for 3h. Then, the temperature is lowered to below 40°C, and under nitrogen protection, isocyanate is added for end-capping (440g isocyanate is added to polyurethane prepolymer 1, 410g isocyanate is added to polyurethane prepolymer 2, and 200g isocyanate is added to polyurethane prepolymer 3) and heated to 60°C for 3h to obtain the polyurethane prepolymer with an NCO content of 16-23%.

[0058] Among them, polyether polyol 3 is a polyether triol with a molecular weight of 3000 and a functionality of 3; isocyanate is a mixture of polymeric MDI and MDI-50;

[0059] The urethane polyols 1-3 are polyurethane polyols obtained by reacting cyclic carbonates and aliphatic primary amines. The preparation method is as follows: the specified amount of cyclic carbonate is placed in a reactor dish, then heated to 80°C, and under nitrogen protection, the specified amount of aliphatic primary amine is added dropwise and the reaction is carried out for 5 hours to obtain urethane polyols.

[0060] The molar ratio of cyclic carbonate to aliphatic primary amine is f:1, where f is the functionality of the aliphatic primary amine. Amino ester polyol 1 is obtained by reacting cyclic carbonate and aliphatic primary amine 1; amino ester polyol 2 is obtained by reacting cyclic carbonate and aliphatic primary amine 2; amino ester polyol 3 is obtained by reacting cyclic carbonate and aliphatic primary amine 3. The cyclic carbonate is propylene carbonate, the aliphatic primary amine 1 is ethylenediamine, the aliphatic primary amine 2 is cyclohexanediamine, and the aliphatic primary amine 3 is tris(2-aminoethyl)amine.

[0061] The details are shown in the table below.

[0062]

[0063] Comparative Examples 1-3

[0064] A polyurethane potting compound and its preparation method are disclosed, which differ from Example 1 only in the difference in the proportion of each component, as shown in Table 2.

[0065] Comparative Example 4

[0066] A polyurethane potting compound and its preparation method differ from Example 1 only in that the polyurethane prepolymer 4 is obtained by reacting polyether polyol, polyethylene glycol (molecular weight 400 g / mol) and isocyanate. The preparation method is as follows: the polyether polyol and polyethylene glycol are mixed at a ratio of 5:2 and vacuum dried at 120°C for 3 hours, then cooled to below 40°C. Under nitrogen protection, isocyanate polymerized MDI and MDI-50 are added and heated to 60°C for 3 hours to obtain the polyurethane prepolymer 4.

[0067] Comparative Example 5

[0068] A polyurethane potting compound and its preparation method differ from Example 1 only in that the polyurethane prepolymer 5 is obtained by reacting polyether polyol, poly(diethylene adipate diol) (formed by condensation polymerization of AA and DEG, with a molecular weight of 500 g / mol) and isocyanate. The preparation method is as follows: the polyether polyol and poly(diethylene adipate diol) are mixed at a ratio of 5:2 and vacuum dried at 120°C for 3 hours. Then, the temperature is lowered to below 40°C. Under nitrogen protection, isocyanate polymers MDI and MDI-50 are added and heated to 60°C for 3 hours to obtain the polyurethane prepolymer 5.

[0069] Comparative Example 6

[0070] A polyurethane potting compound and its preparation method differ from Example 1 only in that the polyurethane prepolymer 5 is obtained by reacting polyether polyol, polyester diol (formed by condensation polymerization of AA, MEG and DEG, with a molecular weight of 800 g / mol) and isocyanate. The preparation method is as follows: the polyether polyol and polyester diol are mixed at a ratio of 5:2 and vacuum dried at 120°C for 3 hours, then cooled to below 40°C. Under nitrogen protection, isocyanate polymerized MDI and MDI-50 are added and heated to 60°C for 3 hours to obtain the polyurethane prepolymer 6.

[0071] Table 1

[0072]

[0073]

[0074] Table 2

[0075]

[0076]

[0077] Example of effect 1

[0078] To verify the performance of the high-strength two-component polyurethane potting compound described in this invention, the following tests were conducted on the various embodiments, comparative examples, and commercially available Guangzhou Ruisheng Synthetic Materials Co., Ltd. RS-3016A / B polyurethane sealant / potting compound. When testing the shear strength of different substrates, the only difference from the conventional test for metal substrates was the type of substrate; all other parameters were the same.

[0079] Table 3

[0080]

[0081]

[0082] As shown in the table, the viscosity of the high-strength two-component polyurethane potting compound prepared by this invention can be maintained within the range of 5000 cps, and the construction will not be affected by excessively high or low viscosity. Simultaneously, its hardness is far higher than commercially available products. Most importantly, the shear strength of the product when applied to PVC, PC, and ABS bonding can reach 8.0 MPa or higher, demonstrating excellent overall performance and making it a complete replacement for existing commercially available products. In contrast, the product in Comparative Example 1 had an excessive amount of polyurethane prepolymer added during compounding, resulting in excessively high viscosity and making construction impossible. The improper compounding ratio of polyols in Comparative Examples 2 and 3 significantly reduced the bonding performance of the products. Comparative Examples 4-6 used inappropriate types of raw materials during the preparation of the polyurethane prepolymer, and the products prepared in these examples could not achieve the comprehensive performance of the products in Examples 1 and 6-8. In the product of this invention, the mass ratio of polyether polyol to castor oil polyol needs to be maintained within the range of 1:(0.5-1.5), preferably 1:(0.8-1.2).

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A two-component polyurethane potting compound for engineering plastics, characterized in that, Includes component A and component B; Component A comprises the following components in parts by weight: Polyol 20-40 parts, aluminum hydroxide 60-80 parts, molecular sieve activation powder 0-5 parts, coupling agent 0-2 parts, catalyst 0-0.01 parts; The polyol is a mixture of polyether polyol and castor oil polyol, with a mass ratio of 1:(0.5~1.5). Component B comprises the following components in parts by weight: 40-90 parts of polyurethane prepolymer, 0-50 parts of isocyanate and 10-40 parts of diluent; The polyurethane prepolymer is obtained by reacting polyether polyol, urethane polyol and isocyanate. The urethane polyol is an urethane polyol obtained by reacting a cyclic carbonate with an aliphatic primary amine; the aliphatic primary amine is at least one of an aliphatic linear diamine, an alicyclic diamine, and an aliphatic polyamine. The NCO content of the polyurethane prepolymer is 10-25%; The mass ratio of component A to component B is (4~6):

1.

2. The two-component polyurethane potting compound for engineering plastics as described in claim 1, characterized in that, The molecular weight of the polyether polyol in component A is 300~3000, the hydroxyl value of the castor oil polyol is 160~168mgKOH / g, and the functionality is 2.5~3.

3. The two-component polyurethane potting compound for engineering plastics as described in claim 1, characterized in that, The particle size D50 of the aluminum hydroxide is 10~20μm.

4. The two-component polyurethane potting compound for engineering plastics as described in claim 1, characterized in that, Includes at least one of the following (a) to (c): (a) The molecular sieve activation powder is at least one of 3A molecular sieve activation powder, 4A molecular sieve activation powder, and 5A molecular sieve activation powder; (b) The coupling agent is at least one of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-ethyl-3-trimethoxysilylmethylpropylamine, bis(γ-trimethoxysilylpropyl)amine, 3-octanoylthio-1-propyltriethoxysilane, γ-isocyanopropyltriethoxysilane, and γ-isocyanopropyltrimethoxysilane; (c) The catalyst is at least one of organobismuth, organozinc, and dibutyltin dilaurate.

5. The two-component polyurethane potting compound for engineering plastics as described in claim 1, characterized in that, The isocyanate is at least one of diphenylmethane diisocyanate and polyphenylmethylene polyisocyanate; the diluent is at least one of phthalates and aliphatic diacids.

6. The two-component polyurethane potting compound for engineering plastics as described in claim 1, characterized in that, Cyclic carbonates are propylene carbonates.

7. The two-component polyurethane potting compound for engineering plastics as described in claim 1, characterized in that, In the raw materials for preparing the polyurethane prepolymer, the mass ratio of polyether polyol to urethane polyol is 10:(3~7).

8. The two-component polyurethane potting compound for engineering plastics as described in claim 7, characterized in that, The polyurethane prepolymer is prepared by mixing polyether polyol and urethane polyol in the specified proportions and vacuum drying at 100-120°C for 2-3 hours. Then, the mixture is cooled to below 40°C, and under nitrogen protection, isocyanate is added and heated to 50-60°C for 2-3 hours to obtain the polyurethane prepolymer.

9. The two-component polyurethane potting compound for engineering plastics as described in claim 8, characterized in that, The NCO content of the polyurethane prepolymer is 10-25%.

10. A method for preparing a two-component polyurethane potting compound for engineering plastics as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Polyol and aluminum hydroxide are mixed and heated to 110~130℃, then dehydrated under vacuum for 2~4 hours, cooled to 40~60℃, and then other components are added and mixed evenly under vacuum to obtain component A. The diluent is pre-dried and dehydrated, and then mixed evenly with polyurethane prepolymer and isocyanate under vacuum to obtain component B.

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