Siloxane-based secondary amide chain extender, and preparation method and application thereof

Abstract

The present application relates to a kind of siloxane-based amide secondary amine chain extender and its preparation method and application, the siloxane-based amide secondary amine chain extender of the present application can be used with isocyanate and biodegradable polyester polyol, and related products of degradable polyurethane are prepared.Can be used as a slow-release type latent curing agent due to the special design of chain extender in structure, while ensuring that the system has sufficient operability, excellent after-ripening effect can be realized, the forming effect and mechanical properties of one-component polyurethane product are improved.At the same time, because it contains degradable groups inside, as the hard segment of the system, it can undergo degradation reaction during the degradation reaction of its product.The degradation degree of product is significantly improved.This kind of product can be applied to polyurethane composites, coatings, adhesives and other fields.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane, specifically relating to a siloxane alkyl amide secondary amine chain extender, its preparation method, and its application. Background Technology

[0002] In polyurethane systems, chain extenders are used as functional additives to extend the hard segment molecular chains of polymers, generating linear molecules with larger molecular weights, thereby increasing the hard segment content and improving the overall mechanical properties of the product. Amine chain extenders are an important type of high-performance chain extender. Due to the urea bonds formed by their reaction with isocyanates, they possess excellent mechanical properties and simultaneously form hydrogen bonds with chain segments, resulting in an overall improvement in product performance. They are widely used in polyurethane coatings, polyurethane elastomers, polyurethane adhesives, and other fields requiring high performance.

[0003] Polyurethane is a cross-linked polymer material obtained by thermosetting isocyanates and polyols. Due to its excellent properties, polyurethane materials are widely used in many application fields. However, some problems also remain to be solved.

[0004] Firstly, amines have high reactivity with isocyanates. Although adding amine chain extenders to polyurethane systems can effectively improve product performance, inappropriate types or amounts of amine chain extenders can affect the system's operability and even cause explosive polymerization. Especially in single-component polyurethane systems, amine chain extenders must be used as latent curing agents. Currently, ketimide or aldehyde imide latent curing agents are commonly used, but these latent curing agents release harmful monomers during decomposition and activation, affecting the environmental friendliness of the products.

[0005] Meanwhile, polyurethane materials are non-degradable and cannot be recycled after disposal, causing "white pollution." Currently, the main methods for treating polyurethane waste are landfill and incineration, which continuously cause various forms of environmental damage. Therefore, developing environmentally friendly, biodegradable polyurethane materials has become crucial for the industry's sustainable development in the future.

[0006] In recent years, research on biodegradable polyurethane has become a hot topic. Patent CN115417964A discloses a biodegradable polyurethane, its preparation method, and garden water pipes made from it. By adding lignin as a biodegradable component in the polyurethane system, it provides rigid aromatic groups, enhancing the polymer's mechanical properties, and also provides active hydrogen reaction sites, which can replace some petroleum-based polyols, thus constituting a biodegradable polyurethane material. CN114133507A discloses a one-pot preparation method for bio-based biodegradable polyurethane. By using biodegradable butyrolactone as the polyurethane soft segment, the resulting product possesses both biodegradability and good biocompatibility, making it suitable for applications in packaging and biomedical fields.

[0007] The above patents employ biodegradable materials in the soft segment structure and fillers of polyurethane systems, thereby enhancing the biodegradability of the products. However, polyurethane systems are composed of both hard and soft segments, and residues in the hard segments can lead to incomplete decomposition and recycling of the products, failing to completely solve the degradation problem of polyurethane products. Only when both hard and soft segments degrade simultaneously can the desired effect be achieved. Summary of the Invention

[0008] The purpose of this invention is to provide a siloxane alkylamide secondary amine chain extender. This chain extender can act as a slow-reaction latent curing agent, stably existing in a single-component polyurethane system. Through a secondary reaction with water in the air, it enhances the overall curing effect after use, thereby improving the mechanical properties of the product. Furthermore, polyurethane products using this chain extender can also decompose under certain external conditions, achieving degradation of the polyurethane hard segment structure. In synergy with other degradable soft segment structures, it further enhances the overall degradability of polyurethane products.

[0009] Another object of the present invention is to provide a method for preparing such a siloxane alkyl amide secondary amine chain extender.

[0010] Another object of the present invention is to provide the application of this siloxane alkylamide secondary amine chain extender.

[0011] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0012] A siloxane alkylamide secondary amine chain extender, with the following structural formula:

[0013]

[0014] Wherein, R1 is an aromatic ring or an aliphatic ring, preferably any one of benzene ring, diphenylmethane, cyclohexyl, and dicyclohexylmethane; R2 is a C2-C10 alkyl group, preferably a C2-C5 alkyl group, more preferably any one of ethyl, propyl, butyl, and pentyl.

[0015] In some specific embodiments, the structure of the siloxane alkyl amide secondary amine chain extender is as follows:

[0016]

[0017]

[0018] R2 is a C2-C10 alkyl group, preferably a C2-C5 alkyl group, and more preferably any one of ethyl, propyl, butyl, and pentyl.

[0019] In another aspect, the present invention provides a method for preparing the aforementioned siloxane alkyl amide secondary amine chain extender, comprising the following steps:

[0020] In the presence of a metal catalyst, one of the modified aromatic secondary amine monomers or the modified alicyclic secondary amine monomers reacts with a terminal carboxyl siloxane monomer.

[0021] In some specific embodiments, the modified aromatic secondary amine monomer is selected from acrylonitrile-modified 4,4'-diaminodiphenylmethane. Or acrylonitrile-modified 1,4-phenylenediamine Any one of them.

[0022] In some specific embodiments, the alicyclic diamine monomer is selected from acrylonitrile-modified 4,4'-diaminodicyclohexylmethane. Or acrylonitrile-modified 1,4-cyclohexanediamine Any one of them.

[0023] In some specific implementations, the terminal carboxyl siloxane monomer is trimethoxysilyl acetic acid.

[0024] In some specific embodiments, the molar ratio of one of the modified aromatic secondary amine monomers or modified alicyclic secondary amine monomers to the terminal carboxyl siloxane monomer is 1:1 to 5.

[0025] In some specific embodiments, the metal catalyst is selected from one or more of zinc, bismuth, and tin, preferably bismuth and / or zinc, and more preferably zinc. The metal catalyst is preferably added in the form of metal powder to increase the contact area of ​​the catalyst, and zinc powder is preferred.

[0026] In some specific embodiments, the amount of the metal catalyst is 0.1-1% of the weight of one of the modified aromatic secondary amine monomers or modified alicyclic secondary amine monomers and the terminal carboxyl siloxane monomer, for example 0.1%, 0.3%, 0.5%, 0.7%, 1%, etc.

[0027] In some specific implementations, the reaction temperature is 50-150°C, such as 50°C, 60°C, 65°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, etc., and the reaction time is 1-5 hours, such as 2 hours, 3 hours, 4 hours, etc.

[0028] In another aspect, the present invention provides the use of the aforementioned siloxane alkyl amide secondary amine chain extender in the preparation of polyurethane.

[0029] The siloxane alkyl amide secondary amine chain extender of the present invention can be used alone or in combination with other chain extenders. When mixed with polyethers and plasticizers, it can be used as a curing agent component in the production of polyurethane-related products. These products can be applied in the fields of polyurethane coatings and adhesives.

[0030] Compared with existing technologies, the beneficial effects of this invention are as follows: the chain extender of this invention has a secondary amine group at one end and a siloxane group at the other end. Due to this special structure, the substance can be used as a latent curing agent in polyurethane systems. Specifically, the reaction process is divided into two parts. First, after mixing with isocyanate, the secondary amine group at one end reacts with the isocyanate with appropriate activity to generate urea bonds, completing the initial chain extension reaction. Because the secondary amine structure has significantly lower reactivity in the system than the primary amine structure, the reaction intensity at this stage is milder, avoiding problems such as rapid exothermic reactions and significant increases in system viscosity. At the same time, its side chain structure modified with acrylonitrile can play an internal plasticizing role, reducing the inter-segment forces in the system and enhancing the flexibility of the product. The siloxane group at the other end plays a capping and protective role, preventing it from reacting with the active substances in the system, thus temporarily slowing down the overall crosslinking reaction. This avoids the rapid crosslinking of the system caused by the excessive activity of diamine / diol chain extenders, which leads to rapid viscosity increase and gelation, affecting the overall operability and stability. In the first stage of the chain extension reaction, the formation of urea bonds acts as a rigid structure, enhancing the mechanical properties of the system. In the second stage of chain extension, after being coated and exposed to air, the water in the air reacts with the siloxane groups in the system, rapidly completing the cross-linking of the macromolecular chains and achieving full curing. This allows the product's performance to quickly reach a high level. Therefore, using the chain extender of this invention as an enhanced latent curing agent ensures system stability and significantly improves system performance while achieving rapid curing during use. It also avoids the release of harmful substances such as formaldehyde during the unsealing process of traditional ketimine-based latent curing agents.

[0031] The amide structure of the chain extender of this invention can be decomposed under certain external conditions (e.g., under alkaline conditions and at an ambient temperature of 60℃~80℃, the amide bond undergoes a hydrolysis reaction to generate primary amine and carboxyl groups). That is, the hard segment is decomposed through chain extender decomposition, while simultaneously, under these alkaline conditions, the decomposition of polyester segments such as polylactic acid and polycaprolactone (i.e., the soft segment structure of polyurethane) is effectively promoted. Thus, while achieving hard segment decomposition, it also effectively promotes the degradation of soft segments containing polyester chains, enhancing the overall degradation capability of polyurethane products. Attached Figure Description

[0032] Figure 1-4 The NMR spectra of the products in Examples 1-4 are respectively. Detailed Implementation

[0033] The following embodiments will further illustrate the method provided by the present invention, but the present invention is not limited to the listed embodiments, and should also include any other known modifications within the scope of the claims of the present invention.

[0034] Sources of some raw materials:

[0035] Acrylonitrile-modified HMDA, Beijing Bailingwei;

[0036] Acrylonitrile-modified MDA, Beijing Bailingwei;

[0037] Acrylonitrile-modified 1,4-cyclohexanediamine, Beijing Bailingwei;

[0038] Acrylonitrile-modified p-phenylenediamine, Beijing Bailingwei;

[0039] Zinc powder, Umicore;

[0040] Bismuth isooctanoate catalyst, Umicore;

[0041] Dibutyltin dilaurate catalyst, Umicore;

[0042] MDI-50 is from Wanhua Chemical Group Co., Ltd.

[0043] C2020 polyether is from Wanhua Chemical Group Co., Ltd.

[0044] F3135 polyether is from Wanhua Chemical Group Co., Ltd.

[0045] 2-Trimethoxysilylacetic acid, Dow Corning;

[0046] Ketoimine latent curing agent ALT-403, Changzhou Elite.

[0047] MDI-based one-component coating: 200g C2020 polyether, 400g F3135 polyether, and 350g 400-mesh calcium carbonate were stirred for 30 minutes, then dehydrated at 100℃ for 2 hours. The mixture was then cooled to 80℃ and 165g MDI50 was added to initiate the polymerization reaction, producing an MDI-based one-component coating.

[0048] Other raw materials not specifically mentioned in the embodiments of the present invention can be purchased directly from the market.

[0049] Example 1

[0050] (1) 1 mol of acrylonitrile-modified HMDA secondary amine and 1 mol of terminal carboxyl siloxane were added to a dry reactor, along with 0.02 mol of zinc powder catalyst. The reaction was carried out at 50°C for 1 hour. After distillation, a siloxane alkyl amide secondary amine latent curing agent was obtained.

[0051] (2) Add 18g of the latent curing agent obtained in step (1) to 100g of MDI system single-component coating and mix for 20min to ensure uniform dispersion.

[0052] According to the national standard GBT19250-2013, the coating was applied twice at room temperature to obtain a 1.5 mm thick standard mechanical property test sample. After curing at room temperature for 7 days, the mechanical properties were tested. Using a universal tensile testing machine, the test was conducted within the tensile speed range required by the national standard. The tensile shear strength of the sample reached 4.5 MPa, and the elongation at break reached 506%.

[0053] Degradation test: Small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of NaOH solution (pH = 8.5). The samples were placed at 60±1℃ and removed every 6–7 days. After vacuum drying at 80℃ until constant weight, the samples were weighed and the percentage of mass loss was calculated. After 20 days of immersion, the weight loss rate reached 13.9%.

[0054]

[0055] The peak value of HMDA alicyclic amine is 1.6, the peak value of secondary amine is 3.3, and the peak value of siloxane is 3.55.

[0056] Example 2

[0057] (1) 2 mol of acrylonitrile-modified MDA and 10 mol of terminal carboxyl siloxane were added to a dry reactor, along with 0.012 mol of bismuth catalyst. The reaction was carried out at 150°C for 5 hours. After distillation, a siloxane alkyl amide secondary amine latent curing agent was obtained.

[0058] (2) Add 18g of the latent curing agent obtained in step (1) to 100g of MDI system single-component coating and mix for 20min to ensure uniform dispersion.

[0059] According to the national standard GBT19250-2013, the coating was applied twice at room temperature to obtain a 1.5mm thick standard mechanical property test sample. After curing at room temperature for 7 days, the mechanical properties were tested. Using a universal tensile testing machine, the test was conducted within the tensile speed range required by the national standard. The tensile shear strength of the sample reached 5.3 MPa, and the elongation at break reached 564%.

[0060] Degradation test: Small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of NaOH solution (pH = 8.5). The samples were placed at 37±1℃ and removed every 6–7 days. After vacuum drying at 80℃ until constant weight, the samples were weighed and the percentage of mass loss was calculated. After 20 days of immersion, the weight loss rate reached 16.1%.

[0061]

[0062] The benzene ring NMR peaks are at 6.5 and 7.0, the secondary amine peak is at 7.3, and the siloxane peak is at 3.5.

[0063] Example 3

[0064] (1) 3 mol of acrylonitrile-modified 1,4-cyclohexanediamine and 9 mol of terminal carboxylsiloxane were added to a dry reactor, along with 0.06 mol of tin catalyst. The reaction was carried out at 120°C for 3 hours. After distillation, a siloxane alkyl amide secondary amine latent curing agent was obtained.

[0065] (2) Add 18g of the latent curing agent obtained in step (1) to 100g of MDI system single-component coating and mix for 20min to ensure uniform dispersion.

[0066] According to the national standard GBT19250-2013, the coating was applied twice at room temperature to obtain a 1.5mm thick standard mechanical property test sample. After curing at room temperature for 7 days, the mechanical properties were tested. Using a universal tensile testing machine, the test was conducted within the tensile speed range required by the national standard. The tensile shear strength of the sample reached 3.9 MPa, and the elongation at break reached 499%.

[0067] Degradation test: Small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of NaOH solution (pH = 8.5). The samples were placed at 37±1℃ and removed every 6–7 days. After vacuum drying at 80℃ until constant weight, the samples were weighed and the percentage of mass loss was calculated. After 20 days of immersion, the weight loss rate reached 12.1%.

[0068]

[0069] The peaks for the cyclohexanediamine ester ring are 3.5, 2.7, and 1.4, the peak for the secondary amine is 3.3, and the peak for the siloxane is 3.5.

[0070] Example 4

[0071] (1) 4 mol of acrylonitrile-modified p-phenylenediamine and 16 mol of terminal carboxylsiloxane were added to a dry reactor, along with 0.16 mol of tin catalyst. The reaction was carried out at 108 °C for 2.5 hours. After distillation, a siloxane alkyl amide secondary amine latent curing agent was obtained.

[0072] (2) Add 18g of the latent curing agent obtained in step (1) to 100g of MDI system single-component coating and mix for 20min to ensure uniform dispersion.

[0073] According to the national standard GBT19250-2013, the coating was applied twice at room temperature to obtain a 1.5mm thick standard mechanical property test sample. After curing at room temperature for 7 days, the mechanical properties were tested. Using a universal tensile testing machine, the test was conducted within the tensile speed range required by the national standard. The tensile shear strength of the sample reached 4.1 MPa, and the elongation at break reached 504%.

[0074] Degradation test: Small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of NaOH solution (pH = 8.5). The samples were placed at 37±1℃ and removed every 6–7 days. After vacuum drying at 80℃ until constant weight, the samples were weighed and the percentage of mass loss was calculated. After 20 days of immersion, the weight loss rate reached 13.5%.

[0075]

[0076] The benzene ring peak is 6.67, the siloxane peak is 3.55, and the secondary amine peak is 6.76.

[0077] Comparative Example

[0078] 18g of ketimide latent curing agent was mixed with 100g of MDI-based single-component coating and stirred for 30 minutes. Following the national standard GB / T 19250-2013, the mixture was applied twice at room temperature to obtain a 2.5mm thick standard mechanical property test sample. After curing at room temperature for 7 days, mechanical property tests were conducted. The test was performed using a universal tensile testing machine within the tensile speed range required by the national standard. The tensile shear strength of the sample was 3.1 MPa, and the elongation at break was 510%.

[0079] For degradation testing, small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of NaOH solution (pH = 8.5). The samples were placed at 37±1℃ and removed every 6–7 days. After vacuum drying at 80℃ until constant weight, the samples were weighed and the percentage of mass loss was calculated. After 20 days of immersion, the weight loss rate was 2.3%.

[0080] Therefore, the siloxane amide secondary amine chain extender of the present invention contains a terminal secondary amine group. This amine group can react with isocyanate to form a rigid urea bond, which significantly improves the tensile strength, hardness, and other mechanical properties of polyurethane products. Because the secondary amine has more moderate reactivity, the reactivity of the system can be better controlled, keeping the heat of release and system viscosity within a suitable range. The siloxane group at the other end can exist stably in the system, preventing complete cross-linking of the macromolecular chains. This allows the chain extender to exist as a latent curing agent in the system, ensuring long-term good stability before use. When applied, the siloxane group rapidly undergoes a cross-linking reaction upon contact with water in the air, causing the system to quickly set and cure. This effectively improves construction efficiency. This latent curing agent achieves stable existence in a single-component polyurethane system while effectively improving curing efficiency and the mechanical properties of the product. The polyurethane products produced by this chain extender can also decompose under certain external conditions. Since the chain extender belongs to the hard segment of polyurethane, the degradation of the hard segment of polyurethane can be solved through its own degradation. This avoids the need for complex and costly modification of isocyanate monomers to achieve the degradation of the hard segment of polyurethane. When used in conjunction with biodegradable polyol components, it can effectively degrade both the soft and hard segments, thereby improving the overall degradation capability of polyurethane products.

Claims

1. A siloxane-based amide secondary amine chain extender, having a structure of: wherein R1 is any one of a benzene ring, diphenyl methane, cyclohexyl, dicyclohexyl methane; and R2 is a C2-C10 alkyl group. wherein R2 is a C2-C5 alkyl group.

2. The siloxane-based amido secondary amine chain extender of claim 1, wherein, R2 is any one of an ethyl group, a propyl group, a butyl group, and a pentyl group.

3. The siloxane-based amido secondary amine chain extender of claim 1, wherein, 4.The siloxane-based amide secondary amine chain extender of claim 1, wherein the siloxane-based amide secondary amine chain extender has a structure of: wherein R1 is any one of a benzene ring, diphenyl methane, cyclohexyl, dicyclohexyl methane; and R2 is a C2-C10 alkyl group. one of a modified aromatic secondary amine monomer and a modified alicyclic secondary amine monomer is reacted with a carboxyl-terminated siloxane monomer in the presence of a metal catalyst. The modified aromatic secondary amine monomer is selected from acrylonitrile-modified 4, 4'-diaminodiphenyl methane.

5. A process for the preparation of the siloxane-based secondary amide chain extender of claim 1 comprising the steps of: The carboxyl-terminated siloxane monomer is trimethoxysilyl acetic acid.

6. The method of claim 5, wherein, The molar ratio of one of the modified aromatic secondary amine monomer and the modified alicyclic secondary amine monomer to the carboxyl-terminated siloxane monomer is 1:1-5. or acrylonitrile-modified 1,4-cyclohexanediamine; and / or, the alicyclic diamine monomer is selected from any one of acrylonitrile-modified 4,4'-diaminodicyclohexylmethane or acrylonitrile-modified 1,4-cyclohexanediamine; and / or, the alicyclic diamine monomer is selected from any one of acrylonitrile-modified 4,4'-diaminodicyclohexylmethane or acrylonitrile-modified 1,4-cyclohexanediamine; and / or, the alicyclic diamine monomer is selected from any one of acrylonitrile-modified 4,4'-diaminodicyclohexylmethane or acrylonitrile-modified 1,4-cyclohex 7. The method of claim 5, wherein, The metal catalyst is selected from one or more of zinc, bismuth, and tin.

8. The method of claim 5, wherein, The metal catalyst is zinc powder.

9. The method of claim 5, wherein, The amount of the metal catalyst is 0.1-1% of the sum of the weight of one of the modified aromatic secondary amine monomer and the modified alicyclic secondary amine monomer and the carboxyl-terminated siloxane monomer.

10. The method of claim 9, wherein, The reaction temperature is 50-150 ℃, and the reaction time is 1-5 hours.

11. The method of claim 5, wherein, 13.Use of the siloxane-based amide secondary amine chain extender of any one of claims 1-4 or the siloxane-based amide secondary amine chain extender prepared by the method of any one of claims 5-12 in the preparation of a polyurethane.

12. The method of claim 5, wherein, ​ ​

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