Siloxane-based azo amine chain extender, preparation method and application thereof

Abstract

The present application relates to a kind of siloxane-based azo amine chain extender and its preparation method and application, the siloxane-based azo amine chain extender of the present application can be used with isocyanate and biodegradable polyester polyol, produce polyurethane related products.Due to the special structure design of chain extender, it can be used as a latent curing agent, while ensuring sufficient stability and operability, it can realize the rapid curing of later stage, improve the overall production efficiency and mechanical properties of single-component polyurethane product.At the same time, in the process of degradation reaction of its product, the components promoting degradation reaction are continuously decomposed in the system, effectively improving the degradable ability of its product, promoting the degradation speed of product.This kind of product can be applied to polyurethane coating, adhesive and other fields.

Description

Technical Field

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

[0002] Chain extenders, as functional additives in polyurethane systems, extend the polymer's hard segment molecular chains, generating larger linear molecules and increasing the hard segment content, thereby improving the overall mechanical properties of the product. Amine chain extenders are an important type. Because they react with isocyanates to form urea bonds, exhibiting excellent mechanical properties, and also possess high reactivity with isocyanates, they can be applied in polyurethane coatings, polyurethane elastomers, and polyurethane adhesives.

[0003] Polyurethane is a cross-linked polymer material obtained by thermosetting isocyanates, polyesters, or polyether polyols. Due to its excellent properties, polyurethane materials are widely used in many application fields. However, polyurethane materials also have some problems that need to be solved. Polyurethane itself is non-degradable and cannot be recycled after disposal, causing "white pollution." The main methods for disposing of 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.

[0004] In recent years, research on biodegradable polyurethane has become a hot topic. Patent CN114989770A discloses a biodegradable bio-based polyurethane adhesive composition. By adding tannin-modified polyols, the hydrolysis of phenolic ester groups in the tannin-modified polyols improves the soil environment and promotes the hydrolysis of ester and amide groups in the system, thus achieving the degradation of the polyurethane material. However, the biodegradable portion of this system is only the polyol component, i.e., the soft segment of the polyurethane. A large number of undegradable hard segments remain, thus limiting the overall degradation effect. Patent CN113603852A provides a method for preparing biodegradable polyurethane, which involves introducing suspended chains into a chain extender to reduce intermolecular forces and decrease the crystallinity of the polyurethane system, making it easier for microorganisms to enter and promoting the degradation of the polyurethane system. However, it does not contribute to the degradation of the polyurethane structure itself. Summary of the Invention

[0005] The purpose of this invention is to provide a siloxane-alkyl azoamine chain extender, which, as a latent curing agent, can be stably present in a single-component polyurethane system while improving curing efficiency and the mechanical properties of the product. In addition, the polyurethane product with this chain extender can also be guaranteed to decompose under certain external conditions, and the degradation of polyurethane hard segments can be solved through its own degradation.

[0006] Another object of the present invention is to provide a method for preparing such siloxane azoamine chain extenders.

[0007] Another object of the present invention is to provide the application of such siloxane azoamine chain extenders.

[0008] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0009] A siloxane-alkyl azoamine chain extender, with the following structural formula:

[0010]

[0011] R1 is a C2-C20 alkyl group, preferably a C2-C10 alkyl group, and further preferably a C2-C4 alkyl group, more preferably any one of ethyl, propyl or butyl; R2 is an aromatic ring or an alicyclic ring, preferably an alicyclic ring, for example any one of cyclohexyl or dicyclohexylmethane.

[0012] In some specific embodiments, the structure of the siloxane-alkyl azoamine chain extender is as follows:

[0013]

[0014] Wherein, R1 is a C2-C20 alkyl group, and more preferably a C2-C4 alkyl group, and more preferably any one of ethyl, propyl or butyl.

[0015] In another aspect of the present invention, a method for preparing the aforementioned siloxane-alkyl azoamine chain extender includes the step of adding an aliphatic diamine monomer, an aromatic or alicyclic diamine monomer, a terminal amino siloxane monomer and a metal catalyst into a reactor to react and generate the siloxane-alkyl azoamine chain extender.

[0016] In some specific embodiments, the aliphatic diamine monomer is selected from C2-C20 alkyl diamines, preferably any one of ethylenediamine, propylenediamine, and hexamethylenediamine; and / or

[0017] The aromatic diamine monomer is selected from p-phenylenediamine; and / or

[0018] The alicyclic diamine monomer is selected from 4,4-diaminodicyclohexylmethane (HMDA). Or 1,4-cyclohexanediamine any of the following; and / or

[0019] The terminal aminosiloxane monomer is either 2-trimethoxysilylethylamine or 2-triethoxysilylethylamine.

[0020] In some specific embodiments, the molar ratio of the aliphatic diamine monomer, aromatic or alicyclic diamine monomer to the terminal aminosiloxane monomer is 1:1 to 5:1 to 5, for example 1:1:1, 1:3:5, 1:5:3, 1:5:5, 1:4:3, etc.

[0021] In some specific embodiments, the metal catalyst is selected from any one of zinc, bismuth, and tin, preferably zinc, and more preferably zinc powder. 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.

[0022] In some specific embodiments, the amount of the metal catalyst is 0.1-1% of the sum of the weights of the aliphatic diamine monomer, the aromatic or alicyclic diamine monomer, and the terminal aminosiloxane monomer, for example, 0.1%, 0.3%, 0.5%, 0.7%, 1%, etc.

[0023] 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.

[0024] In one specific embodiment, the preparation method includes adding an aliphatic diamine monomer, an aromatic or alicyclic diamine monomer, a terminal aminosiloxane monomer, and a zinc powder catalyst into a reactor, and reacting at 50–150°C for 1–5 hours to generate a siloxane azoamine.

[0025] The reaction equation for the aforementioned reaction is:

[0026]

[0027] The definitions of R1 and R2 are as described above.

[0028] In another aspect of the present invention, the siloxane azoamine chain extender is used in the preparation of polyurethane.

[0029] The siloxane azoamine 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 the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention develops a siloxane-based azoamine chain extender, which has an amino group at one end and a siloxane group at the other. Due to this unique structure, this substance can be used as a latent curing agent in single-component polyurethane systems. Specifically, the reaction process is divided into two parts. First, after mixing with isocyanate, the amino group at one end reacts rapidly with the isocyanate to form urea bonds, completing the initial chain extension reaction. Simultaneously, the siloxane group at the other end acts as a capping agent, pausing the crosslinking reaction and preventing the rapid crosslinking of the system caused by the high activity of diamine / diol chain extenders, which would lead to rapid viscosity increase and gelation, affecting overall operability and stability. In the first stage of the chain extension reaction, the formation of urea bonds, as a rigid structure, effectively improves 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 group in the system, quickly achieving complete crosslinking between the macromolecular chains and reaching a high level of curing performance. Therefore, using this type of novel chain extender as an enhanced latent curing agent can ensure system stability and significantly improve system performance, while achieving rapid curing during use, and avoiding the release of harmful substances such as formaldehyde when traditional ketimine latent curing agents are unsealed.

[0032] The azoamine structure of this invention can decompose under certain external conditions (e.g., under alkaline conditions and at an ambient temperature of 50°C–70°C, the azo bonds break, generating two primary amine groups). That is, while the hard segments decompose via chain extender decomposition, the presence of amine monomers makes the system alkaline. Under alkaline conditions, the decomposition of polyester segments such as polylactic acid and polycaprolactone can be effectively promoted. This achieves both hard segment decomposition and effectively promotes the degradation of soft segments containing polyester chains, thereby enhancing the overall degradation capability of polyurethane products. 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] HMDA, from Wanhua Chemical Group Co., Ltd.;

[0036] 1,4-Cyclohexanediamine, purchased from Tosoh Chemical.

[0037] p-Phenylenediamine was purchased from Tosoh Chemical.

[0038] Butanediamine, purchased from Tosoh Chemical;

[0039] Ethylenediamine, purchased from Tosoh Chemical.

[0040] Sebacdiamine, purchased from Tosoh Chemical;

[0041] Zinc Zn1910 catalyst, purchased from Umicore;

[0042] Bismuth Bi1610 catalyst, purchased from Umicore;

[0043] Tin T12 catalyst, purchased from Umicore;

[0044] 2-Trimethoxysilylethylamine (CAS: 65644-31-7), purchased from Shenzhen Aituo Chemical;

[0045] 2-Triethoxysilylethylamine (CAS: 45074-31-5), purchased from Shenzhen Aituo Chemical;

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

[0047] One-component MDI system coating: 270g C2020 polyether, 550g F3135 polyether, and 500g 400-mesh calcium carbonate were stirred for 30 minutes, then dehydrated at 105℃ for 2 hours. The mixture was then cooled to 83℃ and 188g MDI50 was added to initiate a polymerization reaction, producing the one-component MDI system coating. Both the polyether and MDI50 were sourced from Wanhua Chemical Group Co., Ltd.

[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 ethylenediamine, 1 mol of HMDA, and 1 mol of 2-trimethoxysilylethylamine were added to a dry reactor, along with 0.03 mol of zinc 1910 catalyst. The reaction was carried out at 50°C for 1 hour. After distillation, siloxane azoamine was obtained.

[0051] (2) Add 8g of the latent curing agent obtained in step (1) to 100g of MDI system single-component coating and mix for 30min to ensure uniform dispersion.

[0052] According to the national standard GB / T19250-2013, two coats were applied at room temperature to obtain a 2.5 mm thick standard mechanical property test sample. Surface drying was achieved after 1 hour. After curing at room temperature for 7 days, mechanical property tests were conducted. Using a universal tensile testing machine within the tensile speed range required by the national standard, the tensile shear strength of the sample reached 6.3 MPa, and the elongation at break reached 558%.

[0053] Degradation test: Small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of phosphate buffer solution (pH = 7.2). 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 15.9%.

[0054] Example 2

[0055] (1) 1 mol of ethylenediamine, 5 mol of HMDA, and 5 mol of 2-trimethoxysilylethylamine were added to a dry reactor, along with 0.011 mol of zinc 1910 catalyst. The reaction was carried out at 150°C for 5 hours. After distillation, siloxane azoamine was obtained.

[0056] (2) Add 8g of the latent curing agent obtained in step (1) to 100g of MDI system single-component coating and mix for 30min to ensure uniform dispersion.

[0057] According to the national standard GB / T19250-2013, two coats were applied at room temperature to obtain a 2.5 mm thick standard mechanical property test sample. Surface drying was achieved after 1 hour. After curing at room temperature for 7 days, mechanical property tests were conducted. Using a universal tensile testing machine, within the tensile speed range required by the national standard, the tensile shear strength of the sample reached 7.3 MPa, and the elongation at break reached 600%.

[0058] Degradation test: Small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of phosphate buffer solution (pH = 7.2). 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 16.8%.

[0059] Example 3

[0060] (1) 2 mol of propylenediamine, 5 mol of 1,4-cyclohexanediamine, and 5 mol of 2-trimethoxysilylethylamine were added to a dry reactor, along with 0.06 mol of tin T12 catalyst. The reaction was carried out at 100°C for 3 hours. After distillation, siloxane azoamine was obtained.

[0061] (2) Add 8g of the latent curing agent obtained in step (1) to 100g of MDI system single-component coating and mix for 30min to ensure uniform dispersion.

[0062] According to the national standard GB / T19250-2013, two coats were applied at room temperature to obtain a 2.5 mm thick standard mechanical property test sample. Surface drying was achieved after 1 hour. After curing at room temperature for 7 days, mechanical property tests were conducted. Using a universal tensile testing machine within the tensile speed range required by the national standard, the tensile shear strength of the sample reached 6.5 MPa, and the elongation at break reached 572%.

[0063] Degradation test: Small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of phosphate buffer solution (pH = 7.2). 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 16.0%.

[0064] Example 4

[0065] (1) 2 mol butanediamine, 4 mol 1,4-cyclohexanediamine, and 6 mol 2-trimethoxysilylethylamine were added to a dry reactor, along with 0.1 mol bismuth 1610 catalyst. The reaction was carried out at 80°C for 4 hours. After distillation, siloxane azoamine was obtained.

[0066] (2) Add 8g of the latent curing agent obtained in step (1) to 100g of MDI system single-component coating and mix for 30min to ensure uniform dispersion.

[0067] According to the national standard GB / T19250-2013, two coats were applied at room temperature to obtain a 2.5 mm thick standard mechanical property test sample. Surface drying was achieved after 1 hour. After curing at room temperature for 7 days, mechanical property tests were conducted. Using a universal tensile testing machine, within the tensile speed range required by the national standard, the tensile shear strength of the sample reached 6.1 MPa, and the elongation at break reached 610%.

[0068] Degradation test: Small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of phosphate buffer solution (pH = 7.2). 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 15.3%.

[0069] Example 5

[0070] (1) 2 mol of decanediamine, 6 mol of p-phenylenediamine, and 8 mol of 2-triethoxysilylethylamine were added to a dry reactor, along with 0.08 mol of tin T12 catalyst. The reaction was carried out at 70°C for 3.5 hours. After distillation, siloxane azoamine was obtained.

[0071] (2) Add 8g of the latent curing agent obtained in step (1) to 100g of MDI system single-component coating and mix for 30min to ensure uniform dispersion.

[0072] According to the national standard GB / T19250-2013, two coats were applied at room temperature to obtain a 2.5 mm thick standard mechanical property test sample. Surface drying was achieved after 1 hour. After curing at room temperature for 7 days, mechanical property tests were conducted. Using a universal tensile testing machine within the tensile speed range required by the national standard, the tensile shear strength of the sample reached 5.9 MPa, and the elongation at break reached 670%.

[0073] Degradation test: Small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of phosphate buffer solution (pH = 7.2). 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 15.6%.

[0074] Comparative Example

[0075] 8g 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. The sample was still not surface dry after 3 hours. After curing at room temperature for 7 days, mechanical property tests were conducted. Using a universal tensile testing machine within the tensile speed range required by the national standard, the tensile shear strength of the sample reached 5.5 MPa, and the elongation at break reached 520%.

[0076] For degradation testing, small sample pieces (10mm × 10mm × 5mm) were cut from the sample plate and immersed in 25ml of phosphate buffer solution (pH = 7.2). 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 1.26%.

[0077] Therefore, the siloxane-alkyl azoamine chain extender of the present invention contains a terminal primary amine group, which can react with isocyanate to form a rigid urea bond, significantly improving the tensile strength, hardness, and other mechanical properties of polyurethane products. The siloxane group at the other end can exist stably in the system, preventing complete cross-linking of the macromolecular chains and allowing the chain extender to exist as a latent curing agent within the system, while ensuring good stability over a long period 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 greatly improves construction efficiency. This latent curing agent achieves stable existence in a single-component polyurethane system while improving curing efficiency and the mechanical properties of the product. The polyurethane products containing this chain extender can also be decomposed 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. The alkaline nature of the amine monomers decomposed during the degradation process can effectively promote the decomposition of polyester polyols in the system, thereby achieving effective degradation in both the soft and hard segments and improving the overall degradation capability of polyurethane products.

Claims

1. A siloxane-based azo amine chain extender, characterized by, The structural formula is: wherein R1 is C2-C20 alkyl, and R2 is any one of cyclohexyl, dicyclohexyl methane, and phenyl.

2. The siloxane-based azoamine chain extender of claim 1, wherein, R1 is C2-C10 alkyl.

3. The siloxane-based azoamine chain extender of claim 2, wherein, R1 is C2-C4 alkyl.

4. The siloxane-based azoamine chain extender of claim 2, wherein, The R1 is any one of ethyl, propyl, or butyl.

5. A process for the preparation of the siloxane-based azoamine chain extender according to any one of claims 1 to 4, characterized in that, The method comprises the steps of adding aliphatic diamine monomer, aromatic or alicyclic diamine monomer, and terminal amino siloxane monomer into a reactor, and reacting to generate siloxane-based azo amine chain extender.

6. The production method according to claim 5, wherein The aliphatic diamine monomer is selected from C2-C20 alkyl diamine; and / or The aromatic diamine monomer is selected from p-phenylenediamine; and / or said cycloaliphatic diamine monomer is selected from any one of 4,4-diaminodicyclohexylmethane or 1,4-cyclohexanediamine and / or The terminal amino siloxane monomer is 2-trimethoxysilyl ethyl amine.

7. The preparation method according to claim 6, characterized in that, The aliphatic diamine monomer is any one of ethylenediamine, propylenediamine, and hexamethylenediamine.

8. The preparation method according to claim 6, characterized in that, The molar ratio of the aliphatic diamine monomer, aromatic or alicyclic diamine monomer, and terminal amino siloxane monomer is 1:1-5:1-5.

9. The method of any one of claims 5 to 8, wherein the method further comprises, The metal catalyst is selected from any one of zinc, bismuth, and tin.

10. The preparation method according to claim 9, characterized in that, The metal catalyst is zinc.

11. The method of claim 10, wherein, The metal catalyst is zinc powder.

12. The method of claim 9, wherein, The amount of the metal catalyst is 0.1-1% of the sum of the weights of the aliphatic diamine monomer, aromatic or alicyclic diamine monomer, and terminal amino siloxane monomer.

13. The method of claim 12, wherein, The reaction temperature is 50-150°C, and the reaction time is 1-5 hours.

14. Use of the siloxane-based azo amine chain extender of any one of claims 1-4 or prepared by the preparation method of any one of claims 5-13 in the preparation of polyurethane.

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