A test method for the resistance of carbodiimide anti-hydrolysis agent powder to phenolic yellowing and its application

Abstract

This invention relates to a method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder and its application. The testing method includes: (1) grinding the sample to be tested and spreading it evenly in a petri dish; (2) placing 2,6-di-tert-butyl-p-cresol in a petri dish of the same size as in step (1); (3) placing the test reagent in a container; (4) placing the petri dish from step (1), the petri dish from step (2), and the container from step (3) into a sealed container for aging; (5) immediately using a colorimeter to detect the yellowing index of the sample after aging in step (4). The method of this invention can accurately detect powdered or crystalline carbodiimide anti-hydrolysis agents, solving the problem that it is currently impossible to accurately detect the phenolic yellowing resistance of powdered samples.

Description

Technical Field

[0001] This invention relates to the field of material performance testing technology, and in particular to a method for testing the resistance of carbodiimide anti-hydrolysis agent powder to phenolic yellowing and its application. Background Technology

[0002] Carbodiimide anti-hydrolysis agents, as high-performance anti-hydrolysis agents, are widely used in polyester polymers containing ester bonds, such as PET, PBT, PBT-PET copolyesters, biodegradable polyester PBAT / PLA, and polyester-based TPU. Polyester polymers commonly face the problem of phenolic oxidative yellowing (phenolic yellowing) during processing, storage, and long-term use. This type of yellowing is not directly caused by light, high temperature, or hydrolysis, but rather by the reaction of added phenolic antioxidants (such as BHT and hindered phenolic stabilizers) with air and trace amounts of nitrogen oxides (NOx). x When phenolic yellowing occurs in packaging materials or coexists with amine auxiliaries, it can lead to oxidation and coupling reactions, generating quinone-like colored substances. This causes the product to gradually change from white / transparent to slightly yellow, yellowish-brown, or even pink, severely affecting its appearance and product grade. In fields with strict requirements for appearance and color, such as textiles, clothing, home textiles, films, packaging, automotive interiors, and white goods casings, resistance to phenolic yellowing has become a critical indicator that polyester materials must meet. White, light-colored, and highly transparent products are particularly sensitive to phenolic yellowing; even slight color differences can lead to product scrap. Furthermore, long-term storage, logistics transportation, and sealed packaging can exacerbate phenolic yellowing, resulting in noticeable color differences before the material is even used, significantly reducing the pass rate and service life.

[0003] The raw material for synthesizing carbodiimide anti-hydrolysis agents is isocyanate-based substances, which are condensed to obtain the finished product. Since isocyanates are easily oxidized during the condensation process, antioxidants are usually added to improve the product color. The antioxidants added during the condensation process are mostly hindered phenolic antioxidants. These substances usually remain in the carbodiimide anti-hydrolysis finished product. The residue of these substances will cause the product to have poor resistance to phenolic yellowing in downstream application environments. Introducing anti-hydrolysis agents into downstream materials for phenolic yellowing resistance testing involves a complex sample preparation process, a long evaluation cycle, and slow feedback on the performance against hydrolysate agents. How to achieve rapid testing of the phenolic yellowing resistance of anti-hydrolysate powder is an urgent problem to be solved.

[0004] Currently, commonly used phenol yellowing resistance testing methods are mainly based on textiles or plastic sheets, following ISO 105-X1 or GB / T 29778. These methods primarily involve sandwiching the sample and phenol-containing test paper between a glass plate, then placing it in an oven for the addition process. However, this method has significant drawbacks in powder testing. Due to the large interparticle gaps in powder materials, traditional paper contact methods cannot ensure uniform penetration of phenolic compounds into the powder, resulting in large fluctuations in test results. Therefore, it is essential to develop a phenol yellowing resistance testing method specifically suitable for powder or crystalline samples. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for testing the resistance of carbodiimide anti-hydrolysis agent powder to phenolic yellowing, thereby resolving the issues of inaccuracy and inapplicability of existing phenolic yellowing tests for powdered or crystalline samples.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for testing the resistance to phenolic yellowing of carbodiimide antihydrolysis agent powder. The testing method includes: (1) grinding the sample to be tested and spreading it evenly in a petri dish; (2) placing 2,6-di-tert-butyl-p-cresol in a petri dish of the same size; (3) placing the test reagent in a container of appropriate size; (4) placing the containers of steps (1), (2), and (3) into a sealed container for aging; (5) immediately using a colorimeter to detect the yellowing index of the sample to be tested after aging in step (4), and judging the resistance to phenolic yellowing of the sample to be tested by the yellowing index; the standard for judgment is: calculating ∆YI before and after aging of the antihydrolysis agent powder (the difference in yellowing value of ∆YI represents the magnitude of color change), the smaller the difference in yellowing value, the better the resistance to phenolic yellowing of the powder.

[0007] In this invention, BHT (2,6-di-tert-butyl-p-cresol) is used as a reference standard in NO. x Under gaseous atmosphere and oxidative heating conditions, phenolic substances are oxidized into quinones, which adsorb or interact with the powder surface, causing the sample to yellow. The yellowness index (YI) is measured using a colorimeter to determine the powder's resistance to phenolic yellowing; a value of ∆YI > 5 indicates the experiment is valid.

[0008] Preferably, in step (1), the amount of the sample to be tested added is 5-10 g. The 5-10 g can be, for example, 5 g, 6 g, 7 g, 8 g, 9 g, or 10 g.

[0009] Preferably, in step (1), the grinding includes grinding the sample to be tested and then passing it through a 100-300 mesh sieve. The 100-300 mesh can be, for example, 100 mesh, 150 mesh, 200 mesh, 250 mesh, or 300 mesh.

[0010] Preferably, in step (1), the thickness of the paving is 2-5 mm; more preferably, it is 2-3 mm. The 2-5 mm can be, for example, 2 mm, 3 mm, 4 mm or 5 mm. The 2-3 mm can be, for example, 2 mm, 2.2 mm, 2.4 mm, 2.6 mm, 2.8 mm or 3 mm.

[0011] Preferably, in step (2), the amount of 2,6-di-tert-butyl-p-cresol added is the same as the weight of the sample to be tested.

[0012] Preferably, in step (3), the detection reagent includes sodium nitrite and 5%-15% acetic acid. The 5%-15% can be, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, etc.

[0013] The detection reagents sodium nitrite and acetic acid in this invention can generate NOx gas, serving as a gas source to simulate an aging environment. First, nitrite is generated through metathesis: acetic acid is a stronger acid than nitrite, resulting in a strong acid displacing a weak acid, producing nitrite and sodium acetate. Equation: NaNO2 + CH3COOH → CH3COONa + HNO2. Second, nitrite undergoes disproportionation: nitrite is extremely unstable and decomposes at room temperature, producing NO, NO2, and water. Equation: 2HNO2 → NO↑ + NO2↑ + H2O. The overall reaction (after combining) is: 2NaNO2 + 2CH3COOH → 2CH3COONa + NO↑ + NO2↑ + H2O.

[0014] Preferably, the detection reagent comprises 0.2-0.8 g of sodium nitrite and 1-10 mL of 5%-15% acetic acid. The 0.2-0.8 g can be, for example, 0.2 g, 0.3 g, 0.4 g, 0.5 g, 0.6 g, 0.7 g, or 0.8 g. The 5%-15% can be, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. The 1-10 mL can be, for example, 1 mL, 2 mL, 3 mL, 4 mL, 5 mL, 6 mL, 7 mL, 8 mL, 9 mL, or 10 mL.

[0015] Preferably, in step (3), the aging temperature is 40℃-50℃ and the time is 8-12 h. The 40℃-50℃ can be, for example, 40℃, 42℃, 44℃, 46℃, 48℃ or 50℃. The 8-12 h can be, for example, 8 h, 9 h, 10 h, 11 h or 12 h.

[0016] Preferably, the determination of the validity of the test includes: if the difference in the yellowness index of 2,6-di-tert-butyl-p-cresol before and after aging is ≥5, then the test result is considered valid.

[0017] In a second aspect, the present invention provides a method for testing the phenolic yellowing resistance of carbodiimide antihydrolysis agent powder according to the first aspect, for detecting the phenolic yellowing resistance of powdered or crystalline carbodiimide antihydrolysis agents.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: This invention addresses the inaccuracy of existing testing techniques for powder resistance to phenolic yellowing by proposing a new testing method that solves the problem of inaccurate powder testing. A benchtop colorimeter is used to directly test the powder color, providing a direct visual representation of the degree of color change during the aging process of the powder in relation to phenolic yellowing. Detailed Implementation

[0019] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0020] The sources of reagents used in the following examples are: BHT (AR grade): from Tianjin Lianlong New Materials Co., Ltd.

[0021] Sodium nitrite (AR grade): from TCI.

[0022] Acetic acid (AR grade): derived from TCI.

[0023] Carbodiimide anti-hydrolysis agent: from Shanghai Langyi Functional Materials Co., Ltd.

[0024] Colorimeter: X-Rite Ci7800.

[0025] Example 1 This embodiment tests the resistance to phenolic yellowing of carbodiimide as an anti-hydrolysis agent. Take 5 g of carbodiimide anti-hydrolysis agent, grind it, pass it through a 100-mesh sieve, and spread it evenly in a petri dish to a thickness of 3 mm. Weigh 5 g of 2,6-di-tert-butyl-p-cresol powder and place it in a petri dish. Weigh 0.5 g of sodium nitrite and 5 mL of 10% dilute acetic acid and place them in a 10 mL beaker. Immediately transfer the beaker to a sealed container, seal it, and place it in an oven. Set the oven temperature to 45℃ and age for 10 h. Immediately after aging, remove the powder and use a colorimeter to measure the color difference.

[0026] Example 2 This embodiment tests the resistance to phenolic yellowing of carbodiimide as an anti-hydrolysis agent. Take 8 g of carbodiimide anti-hydrolysis agent, grind it, pass it through a 300-mesh sieve, and spread it evenly in a petri dish to a thickness of 2 mm. Weigh 8 g of 2,6-di-tert-butyl-p-cresol powder and place it in a petri dish. Weigh 0.2 g of sodium nitrite and 1 mL of 15% dilute acetic acid and place them in a 10 mL beaker. Immediately transfer the beaker to a sealed container, seal it, and place it in an oven. Set the oven temperature to 40℃ and age for 12 h. Immediately after aging, remove the powder and use a colorimeter to measure the color difference.

[0027] Example 3 This embodiment tests the resistance to phenolic yellowing of carbodiimide as an anti-hydrolysis agent. Take 10 g of carbodiimide anti-hydrolysis agent, grind it, pass it through a 200-mesh sieve, and spread it evenly in a petri dish to a thickness of 3 mm. Weigh 10 g of 2,6-di-tert-butyl-p-cresol powder and place it in a petri dish. Weigh 0.8 g of sodium nitrite and 10 mL of 5% dilute acetic acid and place them in a 10 mL beaker. Immediately transfer the beaker to a sealed container, seal it, and place it in an oven. Set the oven temperature to 50℃ and age for 8 hours. Immediately after aging, remove the powder and use a colorimeter to measure the color difference.

[0028] Example 4 This embodiment tests the resistance of carbodiimide antihydrolysis agent to phenolic yellowing. The only difference between this embodiment and Example 1 is that sodium nitrite is not added; otherwise, they are the same as in Example 1.

[0029] Example 5 This embodiment tests the resistance of carbodiimide anti-hydrolysis agent to phenolic yellowing. The only difference between this embodiment and Example 1 is that 10% dilute acetic acid is not added; otherwise, they are the same as in Example 1.

[0030] Example 6 This embodiment tests the carbodiimide anti-hydrolysis agent against phenolic yellowing. The only difference between this embodiment and Example 1 is that the thickness of the carbodiimide anti-hydrolysis agent is 1 mm. All other aspects are the same as in Example 1.

[0031] Example 7 This embodiment tests the resistance of carbodiimide anti-hydrolysis agent to phenolic yellowing. The only difference between this embodiment and Example 1 is that the thickness of the carbodiimide anti-hydrolysis agent is 8 mm. All other aspects are the same as in Example 1.

[0032] Example 8 This embodiment tests the resistance of carbodiimide antihydrolysis agent to phenolic yellowing. The only difference between this embodiment and Example 1 is that the aging temperature is 30°C and the time is 15 hours. All other aspects are the same as in Example 1.

[0033] Example 9 This embodiment tests the resistance of carbodiimide anti-hydrolysis agent to phenolic yellowing. The only difference between this embodiment and Example 1 is that the aging temperature is 60°C and the time is 1 to 5 hours. All other aspects are the same as in Example 1.

[0034] Comparative Example 1 This comparative example underwent a test for the resistance of carbodiimide anti-hydrolysis agent to phenolic yellowing. The only difference between this example and Example 1 is that the test was conducted using the method of GB / T29778; otherwise, they were identical to Example 1.

[0035] Test Example 1 This test case investigates the detection effect of carbodiimide antihydrolysis agent on phenolic yellowing resistance. The aged samples of the above embodiments and comparative examples were tested using a colorimeter, and the specific results are shown in Table 1.

[0036] Table 1 The results above show that: (1) By comparing Example 1 with Examples 2-3, it can be seen that the method of the present invention can accurately detect powdered or crystalline carbodiimide anti-hydrolysis agent, which solves the problem that the current powdered sample cannot be accurately detected for its resistance to phenolic yellowing.

[0037] (2) By comparing Example 1 with Examples 4-5, it can be seen that the Nox gas generator in this invention can effectively generate Nox mixed gas and can effectively accelerate the aging results, truly reflecting the anti-phenol yellowing effect of powder or crystalline carbodiimide anti-hydrolysis agent.

[0038] (3) By comparing Example 1 with Examples 6-7, it can be seen that the sample distribution thickness in this invention has a certain impact on the accuracy of the test results. If the sample thickness is too thin and the sample quantity is too small, it cannot meet the test requirements and the test will fail. If the sample is too thick, the material cannot fully interact with NOx, resulting in inaccurate test results.

[0039] (4) A comparison between Example 1 and Examples 8-9 shows that the temperature is too low, resulting in less NOx production, which cannot guarantee the full function of the system, and the test results are invalid. When the temperature is too high, it is not suitable for monomeric carbodiimide anti-hydrolysis agents. The melting point of monomeric carbodiimide is 51°C, and the sample melts, making it impossible to test.

[0040] (5) By comparing Example 1 with Comparative Example 1, it can be seen that the GB / T29778 general test method is not applicable to the detection of powder materials.

[0041] In summary, the method of the present invention can accurately detect powdered or crystalline carbodiimide anti-hydrolysis agents, solving the problem that it is currently impossible to accurately detect the phenol yellowing resistance of powdered samples.

[0042] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for testing the resistance of carbodiimide anti-hydrolysis agent powder to phenolic yellowing, characterized in that, The testing method includes: (1) Grind the sample to be tested and spread it evenly in a petri dish; (2) Place 2,6-di-tert-butyl-p-cresol into a petri dish of the same size as in step (1); (3) Place the test reagent into the container; (4) Place the petri dish from step (1), the petri dish from step (2), and the container from step (3) into a sealed container for aging; (5) After aging in step (4), the yellowness index of the test sample is immediately obtained by colorimeter. The yellowness index is used to determine the resistance of the test sample to phenol yellowing. The criterion for judgment is: calculate the difference in yellowness value before and after aging of the anti-hydrolysis agent powder. The smaller the difference in yellowness value, the better the powder's resistance to phenolic yellowing.

2. The method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder according to claim 1, characterized in that, In step (1), the amount of the sample to be tested added is 5-10 g.

3. The method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder according to claim 1 or 2, characterized in that, In step (1), the grinding includes grinding the sample to be tested and then passing it through a 100-300 mesh sieve.

4. The method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder according to any one of claims 1-3, characterized in that, In step (1), the thickness of the paving is 2-5 mm; more preferably 2-3 mm.

5. The method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder according to any one of claims 1-4, characterized in that, In step (2), the amount of 2,6-di-tert-butyl-p-cresol added is consistent with the amount of the sample to be tested.

6. The method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder according to any one of claims 1-5, characterized in that, In step (2), the detection reagent includes sodium nitrite and 5%-15% acetic acid.

7. The method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder according to claim 6, characterized in that, The detection reagent comprises 0.2-0.8 g sodium nitrite and 1-10 mL 5%-15% acetic acid.

8. The method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder according to any one of claims 1-7, characterized in that, In step (3), the aging temperature is 40℃-50℃ and the time is 8-12 h.

9. The method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder according to any one of claims 1-8, characterized in that, The validity of the test is determined by the following criteria: if the difference in the yellowness index of 2,6-di-tert-butyl-p-cresol before and after aging is ≥5, then the test result is considered valid.

10. The method for testing the resistance to phenolic yellowing of carbodiimide anti-hydrolysis agent powder according to any one of claims 1-9 is used to test the resistance to phenolic yellowing of powdered or crystalline carbodiimide anti-hydrolysis agent.

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