A low-odor, latent-curing, one-component polyurethane sealant and its preparation method

Abstract

This invention provides a low-odor, latent-curing, one-component polyurethane sealant and its preparation method, belonging to the field of one-component polyurethane adhesives. Every 100 parts of this polyurethane sealant comprises the following components: 25-35 parts of isocyanate-terminated polyurethane prepolymer, 35-60 parts of filler, 5-10 parts of a first plasticizer or 20-30 parts of an organic thixotropic agent, 0.1-0.5 parts of p-toluenesulfonyl isocyanate, 0.1-0.5 parts of an oxazolidine latent-curing agent, 0.01-0.5 parts of a stabilizer, 0.5-1.5 parts of hydrophobic fumed silica, 0.1-0.5 parts of a silane coupling agent, and 0.1-1 parts of a first catalyst; the polyurethane prepolymer is composed of the following components: 50-75 parts of polyether polyol, 5-25 parts of a second plasticizer, 10-20 parts of 4,4'-diphenylmethane diisocyanate, and 0.01-1 parts of a second catalyst. This polyurethane sealant features low odor, no bubbling during high-temperature baking, and good storage stability.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, and particularly relates to the field of single-component polyurethane adhesive technology, specifically to a low-odor latent curing single-component polyurethane sealant and its preparation method. Background Technology

[0002] In recent years, one-component polyurethane sealants have been widely used in the rail transit industry due to their excellent handling properties and superior adhesion and mechanical properties after curing. However, the gas release characteristics of one-component polyurethane sealants during moisture curing also present some challenges. For example, in some processes, one-component polyurethane sealants need to undergo a high-temperature baking process in the early stages of curing. This process can cause a rapid foaming reaction in a short period of time, resulting in a large number of bulges on the surface of the sealant.

[0003] To address the aforementioned issues, the use of latent curing agents is a good solution. However, latent curing agents based on aldehydes or polyaldehydes release benzaldehyde with an irritating odor during the curing process, causing discomfort to operators and failing to meet the current environmental protection requirements of the rail transit industry. Furthermore, latent curing agents are extremely sensitive to moisture, requiring special formulation design and strict control during use; otherwise, poor storage stability can easily occur. Summary of the Invention

[0004] To simultaneously address the problems of excessive blistering during high-temperature baking of single-component polyurethane sealants, the strong odor of existing latent curing agents, and poor product stability, this invention provides a low-odor latent curing single-component polyurethane sealant and its preparation method. This single-component polyurethane sealant features low odor, no blistering during high-temperature baking, and good storage stability.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A low-odor, latent-curing, one-component polyurethane sealant, comprising, by weight, 100 parts of the polyurethane sealant: 25-35 parts of isocyanate-terminated polyurethane prepolymer, 35-60 parts of filler, 5-10 parts of a first plasticizer, 0.1-0.5 parts of p-toluenesulfonyl isocyanate, 0.1-0.5 parts of oxazolidine latent curing agent, 0.01-0.5 parts of stabilizer, 0.5-1.5 parts of hydrophobic fumed silica, 0.1-0.5 parts of silane coupling agent, and 0.1-1 parts of a first catalyst; Alternatively, every 100 parts of the polyurethane sealant may contain the following components: 25-35 parts of isocyanate-terminated polyurethane prepolymer, 35-60 parts of filler, 20-30 parts of organic thixotropic agent, 0.1-0.5 parts of p-toluenesulfonyl isocyanate, 0.1-0.5 parts of oxazolidine latent curing agent, 0.01-0.5 parts of stabilizer, 0.5-1.5 parts of hydrophobic fumed silica, 0.1-0.5 parts of silane coupling agent, and 0.1-1 parts of first catalyst; The isocyanate-terminated polyurethane prepolymer is composed of the following components: 50-75 parts of polyether polyol, 5-25 parts of second plasticizer, 10-20 parts of 4,4'-diphenylmethane diisocyanate, and 0.01-1 parts of second catalyst.

[0006] In a preferred embodiment, the isocyanate-terminated polyurethane prepolymer contains 1.5% to 3.0% isocyanate groups and has a rotational viscosity of 10,000 to 50,000 mPa·s.

[0007] In a preferred embodiment, the first plasticizer is one or more of dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and Mesamoll.

[0008] In a preferred embodiment, the filler is one or more of heavy calcium carbonate, nano calcium carbonate, PVC paste resin, and calcined kaolin.

[0009] In a preferred embodiment, the oxazolidine latent curing agent is selected from JH-326 and ALT-402.

[0010] In a preferred embodiment, the stabilizer is stabilizer 002 from Quzhou Deyu Technology Co., Ltd.

[0011] In a preferred embodiment, the silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0012] In a preferred embodiment, the first catalyst is an organic bismuth catalyst.

[0013] In a preferred embodiment, the polyether polyol is WANOL. ® F3135, WANOL ® One or more of the following: F3128, EP-3600, VORANOL 2000LM, and EP-330N.

[0014] In a preferred embodiment, the second plasticizer is one or more of dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and Mesamoll.

[0015] In a preferred embodiment, the second catalyst is stannous octoate.

[0016] The preparation method of the low-odor latent curing one-component polyurethane sealant includes the following steps: The isocyanate-terminated polyurethane prepolymer is mixed uniformly with the first plasticizer, the filler, the p-toluenesulfonyl isocyanate, the hydrophobic fumed silica, and the silane coupling agent under vacuum. The resulting mixture is cooled to below 45°C, and the oxazolidine latent curing agent, the stabilizer, and the first catalyst are added. The mixture is then mixed uniformly under vacuum, with the temperature controlled to be ≤50°C during the mixing process, to obtain the low-odor latent curing one-component polyurethane sealant. Alternatively, the preparation method of the low-odor latent curing one-component polyurethane sealant may include the following steps: mixing the isocyanate-terminated polyurethane prepolymer with the organic thixotropic agent, the filler, the p-toluenesulfonyl isocyanate, the hydrophobic fumed silica, and the silane coupling agent under vacuum; cooling the resulting mixture to below 45°C, adding the oxazolidine latent curing agent, the stabilizer, and the first catalyst, and mixing them uniformly under vacuum, controlling the temperature to ≤50°C during the mixing process, to obtain the low-odor latent curing one-component polyurethane sealant.

[0017] In a preferred embodiment, the preparation method of the isocyanate-terminated polyurethane prepolymer includes the following steps: adding the polyether polyol to a reaction vessel, heating to 120°C and dehydrating under vacuum for 1 hour, cooling to 60°C, adding the 4,4'-diphenylmethane diisocyanate, the second plasticizer and the second catalyst, heating to 78°C, reacting for 4 hours under dry inert gas protection, cooling to 50°C and discharging to obtain the isocyanate-terminated polyurethane prepolymer.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) The single-component polyurethane sealant provided by the present invention eliminates the problem of conventional polyurethane releasing carbon dioxide gas during the curing process by adopting a latent curing method, thereby achieving high-temperature curing without blistering.

[0019] (2) The single-component polyurethane sealant provided by the present invention uses a low-odor latent curing agent, which has little odor during the curing process, effectively improving the problem of existing latent curing agents releasing a large amount of irritating odor gas during use.

[0020] (3) In this invention, a stabilizer is used in combination with a low-odor latent curing agent, which effectively improves the storage stability of the product.

[0021] (4) The single-component polyurethane sealant provided by the present invention does not require the use of carbon black, and the color of the sealant can be changed according to actual needs, making it more adaptable to sheet metal and paint colors. Therefore, the single-component polyurethane sealant of the present invention has the advantages of not bulging during high-temperature baking, low odor during curing, and good storage stability, and can be used for sealing operations in the rail transit industry. Detailed Implementation

[0022] The following description, in conjunction with embodiments, clearly and completely describes the technical solutions of this application, so that those skilled in the art can fully understand this application. Obviously, the described embodiments are merely some preferred embodiments of this application, and not all embodiments. Any equivalent modifications or substitutions made by those skilled in the art to the following embodiments without creative effort are within the protection scope of this application.

[0023] The ordinal numbers used in this application, such as “first” and “second”, are used only for descriptive purposes to distinguish identical or similar objects, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0024] A specific embodiment of the present invention provides a low-odor latent curing one-component polyurethane sealant. By weight, every 100 parts of the polyurethane sealant comprises the following components: 25-35 parts of isocyanate-terminated polyurethane prepolymer, 5-10 parts of a first plasticizer, 35-60 parts of filler, 0.1-0.5 parts of p-toluenesulfonyl isocyanate, 0.1-0.5 parts of oxazolidine latent curing agent, 0.01-0.5 parts of stabilizer, 0.5-1.5 parts of hydrophobic fumed silica, 0.1-0.5 parts of silane coupling agent, and 0.1-1 parts of a first catalyst; the isocyanate-terminated polyurethane prepolymer is composed of the following components: 50-75 parts of polyether polyol, 5-25 parts of a second plasticizer, 10-20 parts of 4,4'-diphenylmethane diisocyanate, and 0.01-1 parts of a second catalyst.

[0025] In some other embodiments of the present invention, per 100 parts by weight of the polyurethane sealant, the following components are included: 25-35 parts of isocyanate-terminated polyurethane prepolymer, 20-30 parts of organic thixotropic agent, 35-60 parts of filler, 0.1-0.5 parts of p-toluenesulfonyl isocyanate, 0.1-0.5 parts of oxazolidine latent curing agent, 0.01-0.5 parts of stabilizer, 0.5-1.5 parts of hydrophobic fumed silica, 0.1-0.5 parts of silane coupling agent, and 0.1-1 parts of first catalyst; wherein the isocyanate-terminated polyurethane prepolymer is composed of the following components: 50-75 parts of polyether polyol, 5-25 parts of second plasticizer, 10-20 parts of 4,4'-diphenylmethane diisocyanate, and 0.01-1 parts of second catalyst.

[0026] As an example, the isocyanate-terminated polyurethane prepolymer may be in the form of 25 parts, 30 parts, 32 parts, or 35 parts, but is not limited thereto.

[0027] As an example, the number of parts of the first plasticizer may be 5, 6, 7, 8, 10, 12 or 15, and is not limited thereto.

[0028] As an example, the amount of the organic thixotropic agent is 20 parts, 25 parts, 28 parts or 30 parts, but is not limited thereto.

[0029] As an example, the number of parts of the filler is 35, 36, 38, 40, 45 or 50, and is not limited thereto.

[0030] As an example, the amount of p-toluenesulfonyl isocyanate is 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, or 0.5 parts, but is not limited thereto.

[0031] As an example, the amount of the oxazolidine latent curing agent is 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, or 0.5 parts, but is not limited thereto.

[0032] As an example, the amount of stabilizer may be 0.01 parts, 0.02 parts, 0.03 parts, 0.04 parts, 0.05 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, or 0.5 parts, and is not limited thereto.

[0033] As an example, the amount of hydrophobic fumed silica is 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, or 1.5 parts, and is not limited thereto.

[0034] As an example, the amount of the silane coupling agent is 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, or 0.5 parts, and is not limited thereto.

[0035] As an example, the amount of the first catalyst may be 0.01 parts, 0.02 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.5 parts, 0.8 parts, or 1 part, and is not limited thereto.

[0036] As an example, the polyether polyol is in parts of 50, 52, 53, 55, 58, 60, 63, 65, 68, 70 or 75, and is not limited thereto.

[0037] As an example, the number of parts of the second plasticizer is 5, 6, 8, 10, 12, 15, 18, 20, 23 or 25, and is not limited thereto.

[0038] As an example, the 4,4'-diphenylmethane diisocyanate is present in parts of 10, 11, 12, 13, 15, 16, 18, or 20, and is not limited thereto.

[0039] As an example, the amount of the second catalyst may be 0.01 parts, 0.02 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.2 parts, 0.5 parts, 0.8 parts, or 1 part, and is not limited thereto.

[0040] In some preferred embodiments, the isocyanate-terminated polyurethane prepolymer contains 1.5wt% to 3.0wt% isocyanate groups (NCO) and has a rotational viscosity of 10,000 to 50,000 mPa·s.

[0041] As an example, the isocyanate-terminated polyurethane prepolymer contains 1.5%~1.6%, 1.7%~1.85%, 1.8%~1.95%, 1.9%~2.0%, 2%~2.15%, 2.15%~2.25%, 2.2%~2.3%, 2.7%~2.8%, or 2.9%~3%, and is not limited thereto; the rotational viscosity is 10000mPa·s~20000mPa·s, 15000mPa·s~25000mPa·s, 10000mPa·s~30000mPa·s, 30000mPa·s~40000mPa·s, 28000mPa·s~50000mPa·s, and is not limited thereto.

[0042] In some preferred embodiments, the first plasticizer is one or more of diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), dioctyl phthalate (DOP), and Mesamoll from LANXESS.

[0043] In some preferred embodiments, the organic thixotropic agent is THIXATROL from Elementis PLC. ® MAX or / and THIXCIN ® R.

[0044] In some preferred embodiments, the filler is one or more of heavy calcium carbonate, nano calcium carbonate, PVC (polyvinyl chloride) paste resin, and calcined kaolin.

[0045] In some preferred embodiments, the oxazolidine latent curing agent is JH-326 from Quzhou Deyu Technology Co., Ltd. or ALT-402 from Changde Elite New Materials Co., Ltd.

[0046] In some preferred embodiments, the stabilizer is stabilizer 002 from Quzhou Deyu Technology Co., Ltd.

[0047] In some preferred embodiments, the silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0048] In some preferred embodiments, the first catalyst is an organobismuth catalyst. As examples, the organobismuth catalyst is Cascat 83 from Vertellus Specialty Chemicals, Inc., or BiCAT from The Shepherd Chemical Company, Inc. ® 8118 (CAS No.: 34364-26-6), BiCAT ® One or more of 8210 (CAS No.: 67874-71-9).

[0049] In some preferred embodiments, the polyether polyol is WANOL from Wanhua Chemical Group Co., Ltd. (hereinafter referred to as "Wanhua Chemical"). ® F3135, Wanhua Chemical's WANOL ® One or more of the following: F3128, EP-3600 and EP-330N from Bluestar Dongda Chemical Co., Ltd., and VORANOL 2000LM from Dow Chemical Company.

[0050] In some preferred embodiments, the second plasticizer is one or more of diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), dioctyl phthalate (DOP), and Mesamoll from LANXESS.

[0051] In some preferred embodiments, the second catalyst is stannous octoate.

[0052] Specific embodiments of the present invention also provide a method for preparing the low-odor latent curing one-component polyurethane sealant, comprising the following steps: S1. Add the polyether polyol to a reaction vessel, heat to above 120°C and dehydrate under vacuum (gauge pressure ≤ -0.095MPa) for 1 hour, cool to 60°C, add the 4,4'-diphenylmethane diisocyanate, the second plasticizer and the second catalyst, raise the temperature to (78±0.5)°C within 10 minutes, react for 4 hours under dry nitrogen protection, cool to 50°C and discharge to obtain an isocyanate-terminated polyurethane prepolymer with an isocyanate group content of 1.5wt%~3wt% and a rotational viscosity of 10000~50000mPa·s.

[0053] S2. The polyurethane prepolymer prepared in step S1 is mixed evenly with the first plasticizer, the filler, the p-toluenesulfonyl isocyanate, the hydrophobic fumed silica and the silane coupling agent under vacuum (gauge pressure ≤ -0.095MPa).

[0054] S3. Cool the mixture obtained in step S2 to below 45°C, add the latent curing agent, the stabilizer and the first catalyst in sequence, stir for 5 minutes under vacuum (gauge pressure ≤ -0.095MPa), and control the temperature ≤ 50°C during the stirring process to obtain the low-odor latent curing one-component polyurethane sealant.

[0055] In some other specific embodiments of the present invention, the preparation method of the low-odor latent curing one-component polyurethane sealant includes the following steps: S1. Add the polyether polyol to a reaction vessel, heat to above 120°C and dehydrate under vacuum (gauge pressure ≤ -0.095MPa) for 1 hour, cool to 60°C, add the 4,4'-diphenylmethane diisocyanate, the second plasticizer and the second catalyst, raise the temperature to (78±0.5)°C within 10 minutes, react for 4 hours under dry nitrogen protection, cool to 50°C and discharge to obtain an isocyanate-terminated polyurethane prepolymer with an isocyanate group content of 1.5wt%~3wt% and a rotational viscosity of 10000~50000mPa·s.

[0056] S2. The polyurethane prepolymer prepared in step S1 is mixed uniformly with the organic thixotropic agent, the filler, the p-toluenesulfonyl isocyanate, the hydrophobic fumed silica and the silane coupling agent under vacuum (gauge pressure ≤ -0.095 MPa).

[0057] S3. Cool the mixture obtained in step S2 to below 45°C, add the latent curing agent, the stabilizer and the first catalyst in sequence, stir for 5 minutes under vacuum (gauge pressure ≤ -0.095MPa), and control the temperature ≤ 50°C during the stirring process to obtain the low-odor latent curing one-component polyurethane sealant.

[0058] In the following examples and comparative examples, the hydrophobic fumed silica used was AEROSIL from Evonik Industries. ® R 972.

[0059] Example 1 A low-odor, latent-curing, one-component polyurethane sealant, by weight, comprises the following components per 100 parts of the polyurethane sealant: 28 parts isocyanate-terminated polyurethane prepolymer, 10 parts diisononyl phthalate (first plasticizer), 20 parts PVC paste resin (filler), 29.33 parts heavy calcium carbonate, 10 parts calcined kaolin, 0.2 parts p-toluenesulfonyl isocyanate, 0.5 parts ALT-402 (oxazolidine latent curing agent), 0.02 parts stabilizer 002 (stabilizer), 1.5 parts hydrophobic fumed silica, 0.3 parts γ-(2,3-epoxypropoxy)propyltrimethoxysilane (silane coupling agent), and BiCAT. ® 8210 (first catalyst) 0.15 parts; the isocyanate-terminated polyurethane prepolymer is composed of the following components: polyether polyol WANOL ® 70 parts of F3135, 11 parts of 4,4'-diphenylmethane diisocyanate, 18.99 parts of Mesamoll (second plasticizer), and 0.01 parts of stannous octoate (second catalyst).

[0060] The preparation method of this low-odor, latent-curing, one-component polyurethane sealant includes the following steps: S1. Add 700g of polyether polyol to a 2L three-necked flask, heat to 120℃ and dehydrate under vacuum for 1h, cool to 60℃, add 110g of 4,4'-diphenylmethane diisocyanate, 100g of second plasticizer and 0.1g of second catalyst, heat to 78℃ within 10min, react for 4 hours under dry nitrogen protection, cool to 50℃ and discharge to obtain isocyanate-terminated polyurethane prepolymer with isocyanate group content of 1.9~2.0% and rotational viscosity of 15000~25000mPa·s.

[0061] S2. Add 280g of the polyurethane prepolymer prepared in step S1, 100g of the first plasticizer, 200g of PVC paste resin, 293.3g of heavy calcium carbonate, 100g of calcined kaolin, 2g of p-toluenesulfonyl isocyanate, 15g of hydrophobic fumed silica and 3g of silane coupling agent to the planetary stirred tank. Stir for 20 minutes at a revolution speed of 30rpm and a rotation speed of 700rpm under vacuum (gauge pressure ≤ -0.09MPa) to ensure that the raw materials are mixed evenly.

[0062] S3. Cool the mixture obtained in step S2 to below 45°C, then add 5g of oxazolidine latent curing agent, 0.2g of stabilizer, and 1.5g of the first catalyst sequentially. Stir under vacuum at a revolution speed of 30rpm and a rotation speed of 700rpm for 5 minutes, controlling the temperature to ≤50°C during stirring, to obtain a low-odor latent curing one-component polyurethane sealant. After stirring, discharge the material and fill it into a sealed container for later use.

[0063] Example 2 A low-odor, latent-curing, one-component polyurethane sealant, comprising, by weight, 100 parts of the polyurethane sealant, the following components: 28 parts isocyanate-terminated polyurethane prepolymer, THIXATROL... ® MAX (organic thixotropic agent) 30 parts, heavy calcium carbonate 29.53 parts, calcined kaolin 10 parts, p-toluenesulfonyl isocyanate 0.2 parts, JH-326 (oxazolidine latent curing agent) 0.3 parts, stabilizer 002 (stabilizer) 0.02 parts, hydrophobic fumed silica 1.5 parts, γ-(2,3-epoxypropoxy)propyltrimethoxysilane (silane coupling agent) 0.3 parts, BiCAT ® 0.15 parts of 8118 (first catalyst); the isocyanate-terminated polyurethane prepolymer is composed of the following components: polyether polyol WANOL ® 70 parts of F3135, 18.99 parts of Mesamoll (second plasticizer), 11 parts of 4,4'-diphenylmethane diisocyanate, and 0.01 parts of stannous octoate (second catalyst).

[0064] The preparation method of this low-odor, latent-curing, one-component polyurethane sealant includes the following steps: S1. Add 700g of polyether polyol to a 2L three-necked flask, heat to 120℃ and dehydrate under vacuum for 1h, cool to 60℃, add 110g of 4,4'-diphenylmethane diisocyanate, 189.9g of second plasticizer and 0.1g of second catalyst, heat to 78℃ within 10min, react for 4 hours under dry nitrogen protection, cool to 50℃ and discharge to obtain isocyanate-terminated polyurethane prepolymer with isocyanate group content of 1.9%~2.0% and rotational viscosity of 15000~25000mPa·s.

[0065] S2. Add 280g of the polyurethane prepolymer prepared in step S1, 300g of organic thixotropic agent, 295.3g of heavy calcium carbonate, 100g of calcined kaolin, 2g of p-toluenesulfonyl isocyanate, 15g of hydrophobic fumed silica and 3g of silane coupling agent to the planetary stirred tank. Stir at a revolution speed of 30rpm and a rotation speed of 700rpm for 20 minutes under vacuum (gauge pressure ≤ -0.09MPa) to ensure that the raw materials are mixed evenly.

[0066] S3. Cool the mixture obtained in step S2 to below 45°C, then add 3g of oxazolidine latent curing agent, 0.2g of stabilizer, and 1.5g of the first catalyst sequentially. Stir under vacuum at a revolution speed of 30rpm and a rotation speed of 700rpm for 5 minutes, controlling the temperature to ≤50°C during stirring, to obtain a low-odor latent curing one-component polyurethane sealant. After stirring, discharge the material and fill it into a sealed container for later use.

[0067] Example 3 A low-odor, latent-curing, one-component polyurethane sealant, comprising, by weight, 28 parts isocyanate-terminated polyurethane prepolymer, THIXCIN... ® 30 parts of R (organic thixotropic agent), 29.53 parts of heavy calcium carbonate, 10 parts of calcined kaolin, 0.2 parts of p-toluenesulfonyl isocyanate, 0.3 parts of JH-326 (oxazolidine latent curing agent), 0.02 parts of stabilizer 002 (stabilizer), 1.5 parts of hydrophobic fumed silica, 0.3 parts of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (silane coupling agent), and BiCAT. ® 8210 (first catalyst) 0.15 parts; the isocyanate-terminated polyurethane prepolymer is composed of the following components: polyether polyol WANOL ® 75 parts of F3128, 14.99 parts of DINP (second plasticizer), 10 parts of 4,4'-diphenylmethane diisocyanate, and 0.01 parts of stannous octoate (second catalyst).

[0068] The preparation method of this low-odor, latent-curing, one-component polyurethane sealant includes the following steps: S1. Add 750g of polyether polyol to a 2L three-necked flask, heat to 120℃ and dehydrate under vacuum for 1h, cool to 60℃, add 100g of 4,4'-diphenylmethane diisocyanate, 149.9g of the second plasticizer and 0.1g of the second catalyst, heat to 78℃ within 10min, react for 4 hours under dry nitrogen protection, cool to 50℃ and discharge to obtain an isocyanate-terminated polyurethane prepolymer with an isocyanate group content of 1.70%~1.85% and a rotational viscosity of 28000~50000mPa·s.

[0069] Steps S2 and S3 are the same as in Example 2, except that the specific types of raw materials are different.

[0070] Example 4 A low-odor, latent-curing, one-component polyurethane sealant, comprising, by weight, 100 parts of the polyurethane sealant, the following components: 28 parts isocyanate-terminated polyurethane prepolymer, THIXATROL... ®The composition includes: 30 parts MAX (organic thixotropic agent), 29.53 parts heavy calcium carbonate, 10 parts calcined kaolin, 0.2 parts p-toluenesulfonyl isocyanate, 0.3 parts JH-326 (oxazolidine latent curing agent), 0.02 parts stabilizer 002 (stabilizer), 1.5 parts hydrophobic fumed silica, 0.3 parts γ-(2,3-epoxypropoxy)propyltrimethoxysilane (silane coupling agent), and 0.15 parts Cascat 83 (first catalyst); the isocyanate-terminated polyurethane prepolymer is composed of the following components: 15 parts polyether polyol VORANOL 2000LM, polyether polyol WANOL... ® 60 parts of F3135, 10.92 parts of DIDP (second plasticizer), 14 parts of 4,4'-diphenylmethane diisocyanate, and 0.08 parts of stannous octoate (second catalyst).

[0071] The preparation method of this low-odor, latent-curing, one-component polyurethane sealant includes the following steps: S1. Mix 150g VORANOL 2000LM and 600g WANOL ® F3135 was added to a 2L three-necked flask, heated to 120℃ and dehydrated under vacuum for 1 hour, then cooled to 60℃. 140g of 4,4'-diphenylmethane diisocyanate, 109.2g of the second plasticizer, and 0.8g of the second catalyst were added. The temperature was raised to 78℃ within 10 minutes, and the reaction was carried out for 4 hours under dry nitrogen protection. The mixture was then cooled to 50℃ and discharged to obtain an isocyanate-terminated polyurethane prepolymer with an isocyanate group content of 2.15-2.25% and a rotational viscosity of 10000-30000 mPa·s.

[0072] Steps S2 and S3 are the same as in Example 2, except that the specific types of raw materials are different.

[0073] Example 5 A low-odor, latent-curing, one-component polyurethane sealant, comprising, by weight, 28 parts isocyanate-terminated polyurethane prepolymer, THIXCIN... ® 30 parts of R (organic thixotropic agent), 29.33 parts of heavy calcium carbonate, 10 parts of calcined kaolin, 0.2 parts of p-toluenesulfonyl isocyanate, 0.5 parts of ALT-402 (latent curing agent), 0.02 parts of stabilizer 002 (stabilizer), 1.5 parts of hydrophobic fumed silica, 0.3 parts of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (silane coupling agent), and BiCAT. ® 0.15 parts of 8118 (first catalyst); the isocyanate-terminated polyurethane prepolymer is composed of the following components: polyether polyol WANOL ®The mixture contains 70 parts of F3135, 18.99 parts of Mesamoll (second plasticizer), 11 parts of 4,4'-diphenylmethane diisocyanate, and 0.01 parts of stannous octoate (second catalyst). The preparation method of this low-odor, latent-curing, one-component polyurethane sealant is the same as in Example 2, except for the specific types and amounts of raw materials. The isocyanate-terminated polyurethane prepolymer prepared in step S1 has an isocyanate group content of 1.9%~2.0% and a rotational viscosity of 15000 mPa·s~25000 mPa·s.

[0074] Comparative Example 1 This comparative example provides a polyurethane sealant, which differs from Example 1 in that the first catalyst in the components of Example 1 is replaced with dibutyltin dilaurate. The preparation method of this polyurethane sealant is basically the same as that in Example 2, except that the first catalyst in step S3 is replaced with dibutyltin dilaurate.

[0075] Comparative Example 2 This comparative example provides a polyurethane sealant, which differs from Example 1 in that it does not contain a stabilizer in its composition. The preparation method of this polyurethane sealant is basically the same as that in Example 2, except that there is no stabilizer in step S3.

[0076] Comparative Example 3 This comparative example provides a polyurethane sealant that differs from Example 1 in that it does not contain stabilizers or latent curing agents in its composition. The preparation method of this polyurethane sealant is basically the same as that in Example 2, except that step S3 does not include stabilizers or latent curing agents.

[0077] Comparative Example 4 This comparative example provides a polyurethane sealant, which differs from Example 1 in that the oxazolidine latent curing agent in the components of Example 1 is replaced with DY-402, an aldehyde-imide curing agent from Quzhou Deyu Technology Co., Ltd. The preparation method of this polyurethane sealant is basically the same as that in Example 2, except that the oxazolidine latent curing agent in step S3 is replaced with DY-402.

[0078] Product performance testing The properties of the one-component polyurethane sealants prepared in Examples 1-5 and Comparative Examples 1-4 were tested using the following methods, and the test results are shown in Table 1.

[0079] 1. Baking and curing performance test: The single-component polyurethane sealant was scraped into a 100mm×100mm×2mm film on the electrophoresis plate and placed in a 90℃ oven for 30 minutes. After taking it out, the surface of the film was pressed with a finger to test whether it was sticky and whether the film was completely cured.

[0080] 2. Baking Anti-bubbling Test: The single-component polyurethane sealant was scraped into a 100mm×100mm×2mm film on the electrophoresis plate, placed in a 90℃ oven and baked for 30 minutes. After taking it out, the surface bubbling was observed.

[0081] 3. Surface drying time test: The test shall be conducted in accordance with the viscous method in GB / T 13477.5-2002 "Test methods for building sealing materials - Part 5: Determination of surface drying time", with a test temperature of (23±2)℃ and a humidity of (50±5)%RH.

[0082] 4. Odor test: 4.1 Odor of the sealant: Take 20g of single-component polyurethane sealant, apply it to aluminum foil, put it into a 1L wide-mouth bottle, seal it and place it in an environment of (23±2)℃. After 2 hours, conduct an odor test according to VDA270 standard.

[0083] 4.2 Odor after curing: After the sample cured by the first test (baking and curing performance test) is placed for 7 days, take 20g and put it into a 1L wide-mouth bottle, seal it and place it in an environment of (23±2)℃. After 2 hours, conduct an odor test according to the VDA270 standard.

[0084] 5. Stability test: The packaged single-component polyurethane sealant was aged at 60°C for 7 days. The viscosity before and after aging was tested, and the viscosity change rate after aging was calculated.

[0085] 6. Room temperature curing adhesion test: The one-component polyurethane sealant was scraped into a 100mm×100mm×2mm sheet on the electrophoresis plate and cured for 7 days at (23±2)℃ and (50±5)%RH. The test was carried out according to the method in Appendix A of QC / T 1024-2015 "One-component polyurethane sealant for automobiles".

[0086] 7. Baking and curing adhesion test: After completing the first test (baking and curing performance test), the sample was air-dried at (23±2)℃ and (50±5)%RH for 2 hours, and then tested according to the method in Appendix A of QC / T 1024-2015 "One-component polyurethane sealant for automobiles".

[0087] 8. Sagging performance test: The test shall be conducted in accordance with the viscosity method in GB / T 13477.6-2002 "Test methods for building sealing materials - Part 6: Determination of flowability", with a test temperature of (23±2)℃ and a humidity of (50±5)%RH.

[0088] Table 1 Performance test results of one-component polyurethane sealant

[0089] In Table 1, "N / A" indicates no experimental results, and "C-1" indicates cohesive failure. Table 1 shows that the single-component polyurethane sealant prepared by this invention exhibits good adhesion while remaining blister-free after baking at 90°C for 30 minutes. It cures rapidly after baking to provide adhesion, has low odor, and good storage stability. Compared to Example 2, Comparative Example 1 showed blistering during high-temperature baking, demonstrating that the choice of catalyst in this invention has a crucial impact on its anti-blistering performance during high-temperature baking. This is related to the highly selective catalytic crosslinking reaction of the organobismuth catalyst and its almost non-selective catalytic reaction between isocyanate and water. Compared to Example 2, Comparative Example 2 showed complete curing after aging, indicating a significant decrease in product storage stability. This proves that the stabilizer used in this invention plays a vital role in improving product storage stability, mainly because the stabilizer can quickly react with residual moisture in the system. Compared to Example 2, Comparative Example 3 failed to fully cure at high temperatures, and the operating time at room temperature was also significantly prolonged. Combining the conclusions of Comparative Example 1 and Example 2, this invention demonstrates that the preferred organobismuth catalyst selection requires the application of a latent curing agent. This is related to the catalytic selectivity of the organobismuth catalyst and the formation of amino and hydroxyl compounds after the hydrolysis of the latent curing agent. Compared with Example 2, Comparative Example 4 has a stronger odor and poorer storage stability, indicating that the latent curing agent selected in this invention has a smaller odor and higher hydrolysis stability compared to aldehyde-imine type latent curing agents; this is related to the hydrolysis products of the latent curing agent selected in this invention on the one hand, and the activity of the latent curing agent in the reaction with water on the other hand.

[0090] In summary, this invention has prepared a low-odor, latent-curing, one-component polyurethane sealant that meets the construction process requirements of curing without blistering after baking at 90°C for 30 minutes; at the same time, the product has the characteristics of low odor and good storage stability.

[0091] The embodiments described above are merely preferred embodiments of this application and are not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by anyone skilled in the art. Any simple equivalent changes and modifications made based on the scope of protection claimed in this application and the content of the specification should be included within the scope of protection of this application.

Claims

1. A low-odor, latent-curing, one-component polyurethane sealant, characterized by, The polyurethane sealant contains the following components in parts by mass per 100 parts: isocyanate-terminated polyurethane prepolymer 25-35 parts, filler 35-60 parts, first plasticizer 5-10 parts or organic thixotropic agent 20-30 parts, p-toluenesulfonyl isocyanate 0.1-0.5 parts, oxazolidine latent curing agent 0.1-0.5 parts, stabilizer 0.01-0.5 parts, hydrophobic fumed silica 0.5-1.5 parts, silane coupling agent 0.1-0.5 parts, first catalyst 0.1-1 part; the isocyanate-terminated polyurethane prepolymer is composed of polyether polyol 50-75 parts, second plasticizer 5-25 parts, 4,4'-diphenyl methane diisocyanate 10-20 parts, and second catalyst 0.01-1 part.

2. The one-component polyurethane sealant according to claim 1, characterized in that, The content of isocyanate groups in the isocyanate-terminated polyurethane prepolymer is 1.5wt%-3.0wt%, and the rotational viscosity is 10000-50000mPa·s.

3. The one-component polyurethane sealant according to claim 1, wherein The organic thixotropic agent is THIXATROL ® MAX or / and THIXCIN ® R.

4. The one-component polyurethane sealant of claim 1, wherein, The first plasticizer is one or more of dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and Mesamoll; or / and, the filler is one or more of heavy calcium carbonate, nano calcium carbonate, PVC paste resin, and calcined kaolin.

5. The one-component polyurethane sealant of claim 1, wherein, The oxazolidine latent curing agent is selected from JH-326 and ALT-402; Or / and, the stabilizer is stabilizer 002 from Quzhou Duyu Technology Co., Ltd.

6. The one-component polyurethane sealant of claim 1, wherein, The silane coupling agent is γ-(2,3-epoxypropoxy) propyl trimethoxysilane. Or / and, the first catalyst is an organic bismuth catalyst.

7. The one-component polyurethane sealant of claim 1, wherein, The polyether polyol is WANOL ® F3135, WANOL ® F3128, EP-3600, VORANOL 2000LM, EP-330N.

8. The one-component polyurethane sealant of claim 1, wherein, The second plasticizer is one or more of dioctyl phthalate, diisononyl phthalate, diisodecyl phthalate, and Mesamoll; Or / and, the second catalyst is stannous octoate.

9. The process for the preparation of one-component polyurethane sealant according to any one of claims 1 to 8, characterized in that The method comprises the following steps: The isocyanate-terminated polyurethane prepolymer is mixed with the filler, the first plasticizer or the organic thixotropic agent, the p-toluenesulfonyl isocyanate, the hydrophobic fumed silica, and the silane coupling agent under vacuum; the obtained mixture is cooled to below 45℃, and the oxazolidine latent curing agent, the stabilizer, and the first catalyst are added and uniformly mixed under vacuum, with the temperature controlled to ≤50℃ during the mixing process, to obtain the low-odor latent curing type one-component polyurethane sealant.

10. The method of claim 9, wherein, The preparation method of the isocyanate-terminated polyurethane prepolymer comprises the following steps: the polyether polyol is added to a reaction container, heated to 120℃, vacuum dehydrated for 1h, cooled to 60℃, and then the 4,4'-diphenyl methane diisocyanate, the second plasticizer, and the second catalyst are added, heated to 78℃, reacted for 4 hours under the protection of dry inert gas, cooled to 50℃, and discharged to obtain the isocyanate-terminated polyurethane prepolymer.

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