A two-component polyurethane potting compound and its preparation method

Abstract

This invention relates to a two-component polyurethane potting compound and its preparation method, belonging to the field of adhesive technology. The invention provides a two-component polyurethane potting compound comprising component A and component B. Component A comprises the following raw materials by weight: 10-20 parts polyether polyol, 20-30 parts sorbitan-based polyol, 40-60 parts filler, 5-10 parts plasticizer a, 1-5 parts water-absorbing agent, and 0.01-0.1 parts catalyst. Component B comprises the following raw materials: 70-95 parts isocyanate and 5-30 parts plasticizer b. The mass ratio of component A to component B is 5:(1-3). This invention, by designing hard and soft segments in the polyurethane, reacts sorbitan-based polyol and isocyanate to form a hard segment structure, while the polyether polyol serves as the soft segment structure. Combined with filler, plasticizer, catalyst, and water-absorbing agent, this results in a polyurethane potting compound with faster curing speed and higher hardness.

Description

Technical Field

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

[0002] Polyurethane is prepared by reacting isocyanates, polyols, and chain extenders. Thermoplastic polyurethane has -(AB) n - A block copolymer with a structure where A is the hard segment and B is the soft segment. The hard segments formed by the reaction of isocyanate with chain extenders have low molecular weight, rigidity, and high polarity; while the soft segments correspond to the long hydrocarbon chains of polyols, exhibiting flexibility and non-polarity. The distribution of hard and soft segments in polyurethane determines its properties and hardness. Polyurethane adhesives can be classified into single-component and two-component adhesives according to different applications. Single-component adhesives cure by reacting with moisture in the air, making them easy to handle, but their curing speed is usually slow; while two-component polyurethane potting compounds can adjust their curing speed by using organic heavy metal and amine catalysts, allowing polyurethane to cure rapidly at room temperature, making them particularly suitable for assembly line production.

[0003] Traditional two-component polyurethane potting compounds mostly use polyether diols, polyether triols, polyester diols, and vegetable oil-modified alcohols with molecular weights of 500-3000 and hydroxyl values ​​of 50-400 mg KOH / g as the hydroxyl component. The resulting potting compounds are flexible but soft to the touch, making them easily cut by metal casings, far inferior to the high strength, high hardness, and cut resistance of epoxy potting compounds. Currently, high-hardness epoxy potting compounds are mostly used in igniters, transformers, and capacitors for waterproofing, bonding, insulation, and external cut resistance. However, due to the lack of flexibility in epoxy itself, epoxy adhesives are prone to cracking and delamination under high and low temperature impacts. While some high-hardness polyurethane potting compounds can achieve a hardness of 70D, the cumbersome modification methods and high-temperature baking processes greatly limit their application.

[0004] Therefore, providing a polyurethane potting compound that is simple to process and has high hardness is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a two-component polyurethane potting compound with high hardness that does not require a complicated modification process and can be obtained simply by designing the distribution of hard and soft segments, as well as its preparation method.

[0006] This invention is achieved through the following technical solution:

[0007] This invention provides a two-component polyurethane potting compound, comprising component A and component B. Component A comprises the following raw materials by weight: 10-20 parts polyether polyol, 20-30 parts sorbitan-based polyol, 40-60 parts filler, 5-10 parts plasticizer a, 1-5 parts water-absorbing agent, and 0.01-0.1 parts catalyst. Component B comprises the following raw materials: 70-95 parts isocyanate and 5-30 parts plasticizer b. The mass ratio of component A to component B is 5:(1-3).

[0008] This invention achieves high hardness in a polyurethane potting compound by designing the distribution of hard and soft segments. Component A of the potting compound is a polyether component with numerous hydroxyl groups and incorporates sorbitan-based polyols. Component B is a curing agent component with numerous isocyanate groups. The sorbitan-based polyol and isocyanate react to form a hard segment structure, while the polyether polyol serves as the soft segment structure. Combined with fillers, plasticizers, catalysts, and water-absorbing agents, a polyurethane potting compound that cures rapidly at room temperature and exhibits high hardness is obtained. This two-component polyurethane potting compound can address the issues of high and low temperature cracking and cumbersome processing of current epoxy potting compounds in igniters, transformers, and aluminum-shell capacitors. The inherent flexibility of the polyurethane soft segments effectively prevents cracking under high and low temperature shocks.

[0009] In a preferred embodiment of the two-component polyurethane potting compound of the present invention, the mass ratio of the polyether polyol to the sorbitol polyol is 1:(1.5-3).

[0010] In a preferred embodiment of the two-component polyurethane potting compound of the present invention, the number average molecular weight of the polyether polyol is 500 to 3000; the polyether polyol includes at least one of polyoxypropylene diol and polyoxypropylene triol.

[0011] Polyether polyols with a number average molecular weight below 500 tend to make the potting compound brittle, while polyether polyols with a number average molecular weight above 3000 tend to make the potting compound too soft.

[0012] In a preferred embodiment of the two-component polyurethane potting compound of the present invention, the sorbitol-based polyol is a sorbitol-based polyether polyol, and the number-average molecular weight of the sorbitol-based polyether polyol is 200 to 1000.

[0013] In a preferred embodiment of the two-component polyurethane potting compound of the present invention, the filler includes at least one of aluminum hydroxide, aluminum oxide, calcium carbonate, silica, mica, talc, and carbon black.

[0014] In a preferred embodiment of the two-component polyurethane potting compound of the present invention, plasticizer a and plasticizer b each independently include at least one of dimethyl phthalate, diisooctyl phthalate, dihexyl phthalate, diisodecyl phthalate, diisononyl phthalate, dibutyl sebacate, dioctyl sebacate, dioctyl adipate, triethyl phosphate, tributyl phosphate, and trioctyl phosphate.

[0015] In a preferred embodiment of the two-component polyurethane potting compound of the present invention, the water absorbent includes at least one of 3A molecular sieve, phosphorus pentoxide and calcium oxide.

[0016] In a preferred embodiment of the two-component polyurethane potting compound of the present invention, the catalyst includes at least one of organotin catalysts, organobismuth catalysts, organozinc catalysts, dimethylamine, trimethylamine, and triethylamine.

[0017] In a preferred embodiment of the two-component polyurethane potting compound of the present invention, the isocyanate includes at least one of 2,4'-toluene diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate.

[0018] Another object of the present invention is to provide a method for preparing the two-component polyurethane potting compound, comprising the following steps:

[0019] (1) The polyether polyol, sorbitol polyol, filler, plasticizer a, water absorbent and catalyst are mixed evenly according to the weight parts, and vacuum dehydrated at 110℃~130℃ to obtain component A; the plasticizer b is vacuum dehydrated at 110℃~130℃, cooled to 50℃~70℃, and the isocyanate is added and mixed evenly to obtain component B;

[0020] (2) Mix the obtained components A and B evenly according to the mass ratio, degas under vacuum, and cure to obtain the two-component polyurethane potting compound.

[0021] In this invention, the two-component polyurethane potting compound contains components A and B that crosslink through the reaction of isocyanate and hydroxyl groups to form a high-density network structure. This results in a polyurethane potting compound with high hardness, fast curing speed at room temperature, simple process, and elimination of baking process, making it suitable for assembly line production.

[0022] The present invention has the following beneficial effects: By designing the distribution of polyurethane hard and soft segments, the present invention reacts sorbitol-based polyether polyol and isocyanate to form a hard segment structure, and the polyether polyol serves as the soft segment structure. Combined with fillers, plasticizers, catalysts and water absorbents, the polyurethane potting compound has a faster curing speed and higher hardness, reaching 80D, comparable to conventional epoxy potting compounds on the market. It can be used as an alternative to epoxy adhesives and is suitable for potting protection in igniters, transformers, capacitors and power supplies and other related fields. Detailed Implementation

[0023] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0024] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0025] Example 1

[0026] A two-component polyurethane potting compound includes component A and component B. By weight, component A comprises the following raw materials: 15 parts of polypropylene glycol with a molecular weight of 1000, 25 parts of sorbitol polyether polyol with a molecular weight of 1000, 50 parts of aluminum hydroxide, 5 parts of dioctyl adipate, 5 parts of 3A molecular sieve, and 0.01 parts of dibutyltin dilaurate; component B comprises the following raw materials: 90 parts of 4,4'-diphenylmethane diisocyanate and 10 parts of dioctyl adipate; the mass ratio of component A to component B is 5:2.

[0027] The preparation method of the two-component polyurethane potting compound includes the following steps:

[0028] (1) Weigh the raw materials of component A according to the stated weight proportions and add them to a high-speed disperser. Disperse at 400 rpm for 1 hour and mix evenly. Pour the mixture into a flask, stir and heat to 120°C, and vacuum dehydrate for 2 hours to obtain component A. Weigh the plasticizer β-dioctyl adipate of component B according to the stated weight proportions and vacuum dehydrate at 120°C for 1 hour. Cool down to 60°C and add the 4,4'-diphenylmethane diisocyanate. Stir for 30 minutes and mix evenly to obtain component B.

[0029] (2) Mix the obtained components A and B at a mass ratio of 5:2, then degas under vacuum and cure at room temperature of 25°C to obtain the two-component polyurethane potting compound.

[0030] Example 2

[0031] A two-component polyurethane potting compound comprises component A and component B. Component A, by weight, comprises the following raw materials: 12 parts of polypropylene glycol with a molecular weight of 500, 28 parts of sorbitol polyether polyol with a molecular weight of 200, 50 parts of calcium carbonate, 5 parts of dimethyl phthalate, 5 parts of phosphorus pentoxide, and 0.01 parts of bismuth 2-ethylhexanoate, an organic bismuth catalyst. Component B comprises the following raw materials: 90 parts of 2,4'-toluene diisocyanate and 10 parts of dimethyl phthalate. The mass ratio of component A to component B is 5:2.

[0032] The preparation method of the two-component polyurethane potting compound is the same as that in Example 1.

[0033] Example 3

[0034] A two-component polyurethane potting compound includes component A and component B. By weight, component A comprises the following raw materials: 10 parts of polypropylene glycol with a molecular weight of 3000, 30 parts of sorbitol polyether polyol with a molecular weight of 1000, 50 parts of silica, 5 parts of triethyl phosphate, 5 parts of calcium oxide, and 0.01 parts of dibutyltin dilaurate; component B comprises the following raw materials: 90 parts of 4,4'-diphenylmethane diisocyanate and 5 parts of triethyl phosphate; the mass ratio of component A to component B is 5:2.

[0035] The preparation method of the two-component polyurethane potting compound is the same as that in Example 1.

[0036] Example 4

[0037] A two-component polyurethane potting compound includes component A and component B. By weight, component A comprises the following raw materials: 20 parts of polypropylene triol with a molecular weight of 2000, 30 parts of sorbitol polyether polyol with a molecular weight of 1000, 60 parts of talc, 5 parts of dioctyl sebacate, 1 part of 3A molecular sieve, and 0.01 parts of dibutyltin dilaurate; component B comprises the following raw materials: 70 parts of 4,4'-diphenylmethane diisocyanate and 5 parts of dioctyl sebacate; the mass ratio of component A to component B is 5:3.

[0038] The preparation method of the two-component polyurethane potting compound is the same as that in Example 1.

[0039] Example 5

[0040] A two-component polyurethane potting compound includes component A and component B. By weight, component A comprises the following raw materials: 20 parts of polypropylene triol with a molecular weight of 1000, 20 parts of sorbitol polyether polyol with a molecular weight of 1000, 40 parts of alumina, 10 parts of trioctyl phosphate, 5 parts of 3A molecular sieve, and 0.01 parts of dibutyltin dilaurate; component B comprises the following raw materials: 95 parts of isocyanate and 30 parts of trioctyl phosphate; the mass ratio of component A to component B is 5:1.

[0041] The preparation method of the two-component polyurethane potting compound is the same as that in Example 1.

[0042] Comparative Example 1

[0043] A two-component polyurethane potting compound differs from Example 1 in that 25 parts castor oil are used instead of 25 parts sorbitol-based polyether polyol, while the remaining components and contents are the same as in Example 1; thus, a two-component polyurethane potting compound is obtained.

[0044] Comparative Example 2

[0045] A two-component polyurethane potting compound differs from Example 1 in that 25 parts of sucrose-based polyether polyol are used instead of 25 parts of sorbitol-based polyether polyol, while the remaining components and contents are the same as in Example 1; thus, a two-component polyurethane potting compound is obtained.

[0046] Comparative Example 3

[0047] A two-component polyurethane potting compound differs from Example 1 in that the A component does not contain sorbitol-based polyether polyol, and the amount of polyoxypropylene diol is 40 parts. The remaining components and contents are the same as in Example 1; thus, a two-component polyurethane potting compound is obtained.

[0048] Comparative Example 4

[0049] A two-component polyurethane potting compound differs from Example 1 in that the raw material of component A does not contain polyoxypropylene diol, and the amount of sorbitol-based polyether polyol is 40 parts, while the remaining components and contents are the same as in Example 1; thus, a two-component polyurethane potting compound is obtained.

[0050] Comparative Example 5

[0051] A two-component polyurethane potting compound includes component A and component B. By weight, component A comprises the following raw materials: 15 parts of polypropylene glycol with a molecular weight of 1000, 50 parts of sorbitol polyether polyol with a molecular weight of 1000, 50 parts of aluminum hydroxide, 5 parts of dioctyl adipate, 5 parts of 3A molecular sieve, and 0.01 parts of dibutyltin dilaurate; component B comprises the following raw materials: 90 parts of 4,4'-diphenylmethane diisocyanate and 10 parts of dioctyl adipate; the mass ratio of component A to component B is 5:2.

[0052] The preparation method of the two-component polyurethane potting compound is the same as that in Example 1.

[0053] Comparative Example 6

[0054] A two-component polyurethane potting compound includes component A and component B. By weight, component A comprises the following raw materials: 15 parts of polypropylene glycol with a molecular weight of 1000, 10 parts of sorbitol polyether polyol with a molecular weight of 1000, 50 parts of aluminum hydroxide, 5 parts of dioctyl adipate, 5 parts of 3A molecular sieve, and 0.01 parts of dibutyltin dilaurate; component B comprises the following raw materials: 90 parts of 4,4'-diphenylmethane diisocyanate and 10 parts of dioctyl adipate; the mass ratio of component A to component B is 5:2.

[0055] The preparation method of the two-component polyurethane potting compound is the same as that in Example 1.

[0056] Comparative Example 7

[0057] A two-component polyurethane potting compound includes component A and component B. By weight, component A comprises the following raw materials: 8 parts of polypropylene glycol with a molecular weight of 1000, 25 parts of sorbitol polyether polyol with a molecular weight of 1000, 50 parts of aluminum hydroxide, 5 parts of dioctyl adipate, 5 parts of 3A molecular sieve, and 0.01 parts of dibutyltin dilaurate; component B comprises the following raw materials: 90 parts of 4,4'-diphenylmethane diisocyanate and 10 parts of dioctyl adipate; the mass ratio of component A to component B is 5:2.

[0058] The preparation method of the two-component polyurethane potting compound is the same as that in Example 1.

[0059] Comparative Example 8

[0060] A two-component polyurethane potting compound differs from Example 1 in that the mass ratio of component A to component B is 5:4, while the remaining components and their contents are the same as in Example 1; thus, a two-component polyurethane potting compound is obtained.

[0061] The two-component polyurethane potting compound used in the examples and comparative examples, as well as the commercially available two-component polyurethane potting compound 9102 from Dongguan Lido Electronic Materials Co., Ltd. (as product 1) and the commercially available two-component epoxy potting compound 5225 from Guangzhou Polymer New Material Technology Co., Ltd. (as product 2), were subjected to performance testing.

[0062] Test method:

[0063] ① Hardness: GB / T531~1999 Rubber Pocket Hardness Tester Indentation Hardness Test Method

[0064] ② Surface drying time at room temperature: The curing process of the cured block is continuously observed in a constant temperature chamber at 25℃ and RH 60%. The surface drying time is defined as when the surface of the cured block is dry and not sticky to the touch.

[0065] ③ Bonding strength: Apply the adhesive evenly to a 12.5mm*25mm stainless steel or galvanized sheet, use another sheet to clamp the adhesive area, and test the bonding strength with a universal testing machine after it has fully cured.

[0066] ④ Defoaming property: After mixing components A and B evenly according to the ratio, vacuum defoaming is performed and the mixture is then filled into the workpiece containing the circuit board. After complete curing, it is observed whether there are air bubbles on the surface.

[0067] ⑤ High-temperature aging: Place the glue-cured block containing the circuit board in a 120℃ oven and bake for seven days, then observe whether the cured block cracks.

[0068] The test results of the two-component polyurethane potting compound and commercially available products in the examples and comparative examples are shown in Table 1.

[0069] Table 1 Performance Test Results

[0070]

[0071]

[0072] In Examples 1-5 of this invention, by designing the distribution of polyurethane hard and soft segments, sorbitol-based polyether polyol and isocyanate are reacted to form a hard segment structure, and polyether diol serves as the soft segment structure. Combined with fillers, plasticizers, catalysts and water absorbents, the resulting two-component polyurethane potting compound can cure rapidly and has high hardness and strong bonding strength.

[0073] In Comparative Example 1, conventional castor oil was used to replace sorbitol-based polyether polyol. Due to the inability to form a high-density cross-linked structure, the hardness of the potting compound was only 21D, the bond strength was significantly reduced, and it cracked at high temperatures. In Comparative Example 2, while sucrose-based polyol could achieve high hardness, its activity and defoaming properties were unsatisfactory. In Comparative Example 3, using polyether polyol alone resulted in a decrease in the hardness of the potting compound, accompanied by high-temperature cracking. In Comparative Example 4, using sorbitol-based polyether polyol alone caused the potting compound to crack at high temperatures, generating a large number of bubbles, failing to obtain a polyurethane potting compound with excellent overall performance. In Comparative Example 5, a large amount of sorbitol-based polyether polyol only increased hardness without providing a toughening effect, increasing the product's brittleness and making it prone to cracking. In Comparative Example 6, the opposite was true; too little sorbitol-based polyether polyol had virtually no toughening or hardening effect. In Comparative Example 7, too little polyoxypropylene diol led to a decrease in the defoaming properties of the potting compound. In Comparative Example 8, the ratio of component A to component B was increased to 5:4. The large number of hard segments and excessive isocyanate groups led to severe brittleness and cracking of the colloid.

[0074] Compared with commercially available products 1 and 2, the potting compound of this invention has a faster curing speed and higher hardness, reaching 80D, comparable to conventional epoxy potting compounds on the market. It can be used as an alternative to epoxy compounds and is suitable for potting protection in igniters, transformers, capacitors, power supplies and other related fields.

[0075] 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 pouring sealant, characterized by, The A component and the B component, the A component comprises the following raw materials by weight parts: polyether polyol 10-20 parts, sorbitol-based polyol 20-30 parts, filler 40-60 parts, plasticizer a 5-10 parts, water absorbing agent 1-5 parts, catalyst 0.01-0.1 parts; the B component comprises the following raw materials: isocyanate 70-95 parts, plasticizer b 5-30 parts; the mass ratio of the A component and the B component is 5:(1-3); the mass ratio of the polyether polyol and the sorbitol-based polyol is 1:(1.5-3).

2. The two-component polyurethane pouring sealant according to claim 1, characterized in that, The molecular weight of the polyether polyol is 500-3000; the polyether polyol comprises at least one of polyoxypropylene diol and polyoxypropylene triol.

3. The two-component polyurethane pouring sealant according to claim 1, characterized in that, The sorbitol-based polyol is sorbitol-based polyether polyol, and the molecular weight of the sorbitol-based polyether polyol is 200-1000.

4. The two-component polyurethane pouring sealant according to claim 1, characterized in that, The filler comprises at least one of aluminum hydroxide, aluminum oxide, calcium carbonate, silicon dioxide, mica, talc powder, carbon black.

5. The two-component polyurethane pouring sealant according to claim 1, characterized in that, The plasticizer a and the plasticizer b each independently comprises at least one of dimethyl phthalate, diisooctyl phthalate, dihexyl phthalate, diisodecyl phthalate, diisononyl phthalate, dibutyl sebacate, dioctyl sebacate, dioctyl adipate, triethyl phosphate, tributyl phosphate and trioctyl phosphate.

6. The two-component polyurethane pouring sealant according to claim 1, characterized in that, The water absorbing agent comprises at least one of 3A molecular sieve, diphosphorus pentoxide and calcium oxide.

7. The two-component polyurethane pouring sealant according to claim 1, characterized in that, The catalyst comprises at least one of organic tin catalyst, organic bismuth catalyst, organic zinc catalyst, dimethylamine, trimethylamine and triethylamine.

8. The two-component polyurethane pouring sealant according to claim 1, characterized in that, The isocyanate comprises at least one of 2,4'-toluene diisocyanate, 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate.

9. The method of claim 1-8, wherein the two-component polyurethane pouring sealant is prepared by the steps of: (1) mixing the polyol component and the isocyanate component to form a mixture; (2) pouring the mixture into a mold; (3) curing the mixture in the mold to form the two-component polyurethane pouring sealant. The method comprises the following steps: (1) the polyether polyol, sorbitol-based polyol, filler, plasticizer a, water absorbing agent, catalyst are mixed uniformly according to the weight parts, vacuum dehydration at 110-130 DEG C, the plasticizer b is vacuum dehydrated at 110-130 DEG C, and then cooled to 50-70 DEG C, and the isocyanate is added and mixed uniformly, to obtain the B component; (2) the obtained A component and B component are mixed uniformly according to the mass ratio, vacuum defoaming, curing, to obtain the two-component polyurethane pouring sealant.

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