Method for detecting content of carbon black in black silk

Abstract

The invention discloses a method for detecting the content of carbon black in black yarn, belongs to the technical field of material detection, and is suitable for a black yarn product taking polyethylene glycol terephthalate (PET) as a matrix. The method comprises the following steps: taking a certain amount of a black filament sample, adding methanol, and carrying out alcoholysis reaction under the conditions of 240 DEG C and 2 hours so as to fully dissolve a PET (Polyethylene Terephthalate) matrix; filtering and separating out insoluble substances (containing carbon black and possible ash impurities); and drying the insoluble substances, firing at high temperature, weighing the mass of the contained ash, and calculating the accurate content of the carbon black in the black filament by combining the initial mass of the sample. The method is easy and convenient to operate, effective separation of the matrix and the carbon black is achieved by means of specific dissolution of methanol to PET, interference of inorganic impurities is eliminated through the ash removal step, operation is easy, the detection cost is low, the detection result is accurate, and key data support can be provided for quality control and performance optimization of black yarn production.

Description

Technical Field

[0001] This invention relates to the field of materials testing technology, specifically to a method for accurately determining the carbon black content in black filament products based on polyethylene terephthalate (PET) using an alcoholysis method. In particular, this application utilizes a specific alcoholysis reaction system, leveraging the solubility properties of methanol in the PET matrix of the black filament to achieve efficient separation of carbon black from the matrix. Subsequent filtration, drying, and weighing processes then allow for the accurate determination of the carbon black content in the black filament—an innovative technical solution. Background Technology

[0002] Black yarn is a functional fiber based on polyethylene terephthalate (PET). Due to its excellent physicochemical properties and stable black appearance, it is widely used in clothing, industry, and decoration. Carbon black is a key colorant and functional additive in the production of black yarn, and its content directly affects the color fastness, weather resistance, and mechanical properties of the product. Excessive content may cause the fiber to become brittle, while insufficient content may lead to fading. Therefore, accurate detection of carbon black content is crucial for quality control in the production process.

[0003] Currently, the main methods used in the industry to detect carbon black content in polymer materials are as follows: Thermogravimetric analysis (TGA) calculates carbon black content by analyzing the mass loss of a sample at high temperatures. However, this method is susceptible to interference from other heat-resistant components in the sample (such as inorganic fillers), and the thermal decomposition of small-molecule additives can also affect the accuracy of the results.

[0004] The ignition method involves directly igniting the sample at high temperatures to remove the organic matrix, and then weighing the residue to determine the carbon black content. However, carbon black is lost through oxidation under high-temperature and aerobic conditions, leading to lower measurement results. Furthermore, the fibrous structure may result in incomplete combustion of the matrix, introducing further errors.

[0005] Traditional chemical dissolution methods use highly polar solvents (such as tetrahydrofuran and phenol) to dissolve the PET matrix to separate carbon black. These solvents are usually highly toxic and require stringent dissolution conditions. For highly crystalline PET black fibers, the dissolution efficiency is low, easily leading to incomplete separation of the matrix from the carbon black, thus affecting the accuracy of the detection.

[0006] In summary, existing methods for detecting carbon black in PET-based filaments have limitations such as weak anti-interference ability, easy carbon black loss, high solvent toxicity, or poor separation effect. Therefore, there is an urgent need to develop a new method for detecting carbon black content that is highly targeted, uses low-toxicity and efficient solvents, achieves thorough separation, and provides accurate results. Summary of the Invention

[0007] The present invention aims to improve or further solve at least one of the following problems in the existing technology for detecting carbon black content in PET-based black filaments: low accuracy, complex operation, high solvent toxicity, and incomplete separation, and provides a new method for detecting carbon black content in black filaments.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for detecting carbon black content in black silk includes the following steps: S1. Weigh G of black filament into a reaction tube, add methanol, seal and tighten, and heat in an oven to carry out alcoholysis. S2. Remove the reaction tube and cool it to room temperature in running water. After opening the lid, pour the solution in the reaction tube into filter paper with a mass of W0. Rinse the reaction tube with methanol and pour it into the filter paper to completely transfer the solution. Rinse the filter residue with methanol 2-3 times until dimethyl terephthalate (DMT) is completely dissolved, leaving carbon black filter residue. Place the filter paper with the filter residue in a drying oven to dry it. The mass of the filter paper and filter residue after drying is W1. S3. Place the dried filter paper with filter residue into a crucible with a mass of W2, and place it on an electric furnace for ashing. Then transfer the crucible to a muffle furnace for calcination. After constant weight, weigh the crucible and ash to obtain a mass of W3. S4. Calculate the carbon black content in the black fiber using the following formula: The ash content of carbon black is ω1 = (W1 - W0) / G × 100%; The ash content in the sample is calculated as ASH = (W3 - W2) / G × 100%. The carbon black content in black silk is ω = ω1 - ASH. That is to say .

[0009] As a further optimization, the complete dissolution of dimethyl phthalate (DMT) was determined as follows: Rinsing conditions: Use 40 mL of methanol each time. Add methanol until there is no filter residue. Let stand until the methanol flows out completely. Rinse 2 to 3 times under these conditions.

[0010] Judgment criteria: During the rinsing process, continuously observe whether the color of the filter residue is uniform. If the filter residue remains uniformly black, without white spots, white powder, or uneven areas that appear "grayish," and without any obvious granular texture (the feel of DMT crystals), then it can be preliminarily determined that there is no DMT residue. After each rinse, the methanol solution should be completely clear and transparent, without turbidity, white flocculent matter, or sediment (if present, it indicates that DMT is still undissolved). Compare the last two rinse solutions; if they are completely identical in appearance (clarity and color) and show no abnormalities, it can help determine that the DMT has been rinsed clean.

[0011] Standard verification: Validation method: High performance liquid chromatography (HPLC) detection; Operating steps: 3.2.1. Take the last rinse solution, filter it through an organic phase filter membrane, and use it as the "sample injection solution"; 3.2.2. Prepare a DMT standard solution with methanol and establish a standard curve; 3.2.3. Inject and analyze the samples under the same chromatographic conditions.

[0012] 3.3. In the chromatogram of the sample injection solution, if there is no chromatographic peak at the position corresponding to the retention time of the DMT standard, it is determined that the DMT has been completely dissolved.

[0013] 4. Each sample test shall be conducted under the rinsing conditions determined above, and the judgment criteria shall be used to assist in the judgment.

[0014] As a further optimization, the ratio of the mass of the black filament to the methanol in step S1 is (1-2) g:(25-50) mL, preferably 1.6 g:40 mL.

[0015] As a further optimization, the alcoholysis temperature in step S1 is 220–260°C, preferably 240°C, and the alcoholysis time is 1–4 h, preferably 2 h.

[0016] As a further optimization, the reaction tube in step S1 is made of 50ml stainless steel.

[0017] As a further optimization, the solvent temperature in step S2 is 60°C.

[0018] As a further optimization, in step S2, the drying temperature is 100-105℃ and the drying time is 1-2 hours, preferably 105℃ and 2 hours.

[0019] As a further optimization, the calcination temperature in step S3 is 900-950℃, and the calcination time is 1-2h.

[0020] As a further optimization, the ashing process in step S3 needs to be completed until no smoke is produced, and the calcination process needs to be completed until no carbon black is produced.

[0021] As a further optimization, to ensure the accuracy of experimental results, all filter paper and crucibles used must be weighed before use.

[0022] As a further optimization, in step S4, the experimental results are taken as the arithmetic mean of two parallel samples, and the absolute error of parallelism does not exceed 0.2%.

[0023] As a further optimization, the absence of carbon black residue was determined according to the following method: Place the dried insoluble material into a pre-weighed crucible and record the total mass m1 before initial ignition. Heat at 900°C in a muffle furnace for 1–2 hours; Remove the crucible, place it in a desiccator to cool to room temperature, and accurately weigh the total mass m2; Place it back into the muffle furnace and heat at the same temperature for 30 minutes. After cooling, weigh m3. If the mass difference between two consecutive weighings (∣m3−m2∣) is ≤0.1mg-0.5mg, then it is determined that there is no carbon black residue.

[0024] Compared with the prior art, the beneficial effects of the present invention include: 1. High Detection Accuracy: This method converts the PET matrix into dimethyl terephthalate (DMT), which is soluble in methanol, through an alcoholysis reaction, achieving efficient separation of carbon black from the matrix. Subsequent high-temperature calcination steps accurately determine and subtract the mass of inorganic ash impurities in the sample, eliminating their interference with the results, thus obtaining a highly accurate net carbon black content with a deviation of ±0.10% of the actual content.

[0025] 2. Targeted and Effective Separation: This method is specifically designed for PET-based carbon black filament materials. It utilizes the alcoholysis properties of methanol on PET at a specific temperature (e.g., 240℃) to ensure complete matrix decomposition. Washing the filter residue with a hot solvent (e.g., 60℃ methanol) effectively removes residual soluble degradation products, ensuring the purity of the separated carbon black.

[0026] 3. Simple operation and low cost: The entire testing process only involves conventional chemical operations such as weighing, alcoholysis, filtration, drying and calcination. The equipment used (such as ovens and muffle furnaces) are commonly used equipment in laboratories or factory quality inspection departments. No complicated pretreatment is required, the skill requirements for operators are not high, and the testing cost is low.

[0027] 4. Material recycling potential: The main product of alcoholysis is DMT, which can be reused after collection and purification. For example, some patents use recycled DMT to prepare recycled polyester chips. Compared with detection methods that easily generate difficult-to-treat waste, this is more environmentally friendly and in line with the trend of green chemistry development.

[0028] 5. Environmentally friendly: Compared with similar patents on alcoholysis for carbon black content determination, such as patent CN103115835B, which uses methanol to alcoholyze PBT+PET when testing the carbon black content of masterbatch and then uses No. 190 solvent oil to remove impurities, the method of this invention always uses methanol for rinsing. Compared with the highly toxic solvents such as phenol used in traditional methods, it is more environmentally friendly and friendly to operators. It also avoids the problems of introducing other solvents that complicate the composition and require subsequent oil removal. In specific scenarios, it simplifies the process and avoids interference from solvent oil residue. Detailed Implementation

[0029] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0030] The present invention will be further described in detail below through examples. All reagents used are commercially available, and the testing instruments used are an electronic analytical balance, an oven, an electric furnace, a muffle furnace, and a water bath heater. The following examples use black silk samples from the same batch for testing, aiming to verify the applicability of the method of the present invention under different process parameters. Example

[0031] A method for detecting carbon black content in black silk includes the following steps: S1. Weigh 1.6018g of black filament and pour it into a stainless steel reaction tube. Add 40ml of methanol, seal and tighten the reaction tube, and place it in an oven at 220℃ for 2 hours for alcoholysis. S2. Remove the reaction tube and cool it to room temperature in running water. After opening the lid, transfer the contents of the reaction tube to filter paper that has been pre-weighed (mass W0 = 0.9725 g). Rinse the reaction tube and filter residue with methanol 2-3 times to ensure complete transfer of the contents. Dry the filter paper with the filter residue in an oven at 105°C for 2 hours, and weigh it to obtain a total mass W1 = 0.9946 g.

[0032] S3. Place the above filter paper and filter residue into a crucible that has been pre-weighed (mass W2 = 55.7579 g), and heat it on an electric furnace to ashing until no smoke is produced. Then, transfer the crucible to a muffle furnace at 900°C and calcine for 1-2 hours until the carbon black completely disappears. After cooling to room temperature and pre-weighing, the total mass W3 = 55.7587 g is obtained.

[0033] S4. Calculate the carbon black content in the black fiber using the following formula: The carbon black (including ash) content ω1=(0.9946-0.9725) / 1.6018×100%=1.38%.

[0034] The ash content ASH = (55.7587 - 55.7579) / 1.6018 × 100% = 0.05%.

[0035] The net carbon black content in the black filament is ω = ω1 - ASH = 1.33%. Example

[0036] A method for detecting carbon black content in black silk includes the following steps: S1. Weigh 1.5997g of black filament and pour it into a stainless steel reaction tube. Add methanol, seal and tighten the tube, and heat it in an oven at 240℃ for 2 hours for alcoholysis. The volume of methanol is 40ml. S2. Remove the reaction tube and cool it to room temperature in running water. After opening the lid, pour the solution in the reaction tube into filter paper (constant weight) with a mass of W0. Rinse the reaction tube and filter residue with methanol 2-3 times. Place the filter paper with filter residue in a drying oven and dry it at 105℃ for 2 hours. The mass of the filter paper and filter residue after drying is W1, where W0 is 0.9838g and W1 is 1.0057g. S3. Place the dried filter paper with filter residue into a crucible with a mass of W2, and place it on an electric furnace for ashing until it burns without smoke. Then transfer the crucible to a muffle furnace for calcination at 900℃ for 1-2 hours until the carbon black disappears. After cooling and constant weight, weigh the crucible and ash to obtain W3, where W2 is 55.7568g and W3 is 55.7578g. S4. Calculate the carbon black content in the black fiber using the following formula: ω=(W1-W0) / G×100%-(W3-W2) / G×100%=1.31%, Where: ω is the carbon black content in the black filament, (W1-W0) / G×100% is the carbon black (including ash) content in the sample, ω1=1.37%, (W3-W2) / G×100% is the ash content in the sample, ASH=0.06%. Example

[0037] A method for detecting carbon black content in black silk includes the following steps: S1. Weigh 1.6003g of black filament and pour it into a stainless steel reaction tube. Add methanol, seal and tighten the tube, and heat it in an oven at 260℃ for 2 hours for alcoholysis. The volume of methanol is 40ml. S2. Remove the reaction tube and cool it to room temperature in running water. After opening the lid, pour the solution in the reaction tube into filter paper with a mass of W0. Rinse the reaction tube and filter residue with methanol 2-3 times. Place the filter paper with filter residue in a drying oven and dry it at 105℃ for 2 hours. The mass of the filter paper and filter residue after drying is W1, where W0 is 0.9829g and W1 is 1.0049g. S3. Place the dried filter paper with filter residue into a crucible with a mass of W2, and place it on an electric furnace for ashing until it burns without smoke. Then transfer the crucible to a muffle furnace for calcination at 900℃ for 1-2 hours until the carbon black disappears. After cooling and constant weight, weigh the crucible and ash to obtain W3, where W2 is 56.7134g and W3 is 56.7142g. S4. Calculate the carbon black content in the black fiber using the following formula: ω=(W1-W0) / G×100%-(W3-W2) / G×100%=1.32%, Where: ω is the carbon black content in the black filament, (W1-W0) / G×100% is the carbon black (including ash) content in the sample, ω1=1.37%, (W3-W2) / G×100% is the ash content in the sample, ASH=0.05%. Example

[0038] A method for detecting carbon black content in black silk includes the following steps: S1. Weigh 1.5995g of black filament and pour it into a stainless steel reaction tube. Add methanol, seal and tighten the tube, and heat it in an oven at 240℃ for 1 hour for alcoholysis. The volume of methanol is 40mlg. S2. Remove the reaction tube and cool it to room temperature in running water. After opening the lid, pour the solution in the reaction tube into filter paper with a mass of W0. Rinse the reaction tube and filter residue with methanol 2-3 times. Place the filter paper with filter residue in a drying oven and dry it at 105℃ for 2 hours. The mass of the filter paper and filter residue after drying is W1, where W0 is 0.9754g and W1 is 0.9979g. S3. Place the dried filter paper with filter residue into a crucible with a mass of W2, and place it on an electric furnace for ashing until it burns without smoke. Then transfer the crucible to a muffle furnace for calcination at 900℃ for 1-2 hours until the carbon black disappears. After cooling and constant weight, weigh the crucible and ash to obtain W3, where W2 is 56.6830g and W3 is 56.6840g. S4. Calculate the carbon black content in the black fiber using the following formula: ω=(W1-W0) / G×100%-(W3-W2) / G×100%=1.34%, Where: ω is the carbon black content in the black filament, (W1-W0) / G×100% is the carbon black (including ash) content in the sample, ω1=1.41%, (W3-W2) / G×100% is the ash content in the sample, ASH=0.06%. Example

[0039] A method for detecting carbon black content in black silk includes the following steps: S1. Weigh 1.5998g of black filament and pour it into a stainless steel reaction tube. Add methanol, seal and tighten the tube, and heat it in an oven at 240℃ for 2 hours for alcoholysis. The volume of methanol is 40ml. S2. Remove the reaction tube and cool it to room temperature in running water. After opening the lid, pour the solution in the reaction tube into filter paper with a mass of W0. Rinse the reaction tube and filter residue 2-3 times with methanol heated to 60°C. Place the filter paper with filter residue in a drying oven and dry it at 105°C for 2 hours. The mass of the filter paper and filter residue after drying is W1, where W0 is 0.9795g and W1 is 0.9998g. S3. Place the dried filter paper with filter residue into a crucible with a mass of W2, and place it on an electric furnace for ashing until it burns without smoke. Then transfer the crucible to a muffle furnace for calcination at 900℃ for 1-2 hours until the carbon black disappears. After cooling and constant weight, weigh the crucible and ash to obtain W3, where W2 is 56.6847g and W3 is 56.6856g. S4. Calculate the carbon black content in the black fiber using the following formula: ω=(W1-W0) / G×100%-(W3-W2) / G×100%=1.21%, Where: ω is the carbon black content in the black filament, (W1-W0) / G×100% is the carbon black (including ash) content in the sample, ω1=1.27%, (W3-W2) / G×100% is the ash content in the sample, ASH=0.06%. Example

[0040] A method for detecting carbon black content in black silk includes the following steps: S1. Weigh 1.6002g of black filament and pour it into a stainless steel reaction tube. Add methanol, seal and tighten the tube, and heat it in an oven at 240℃ for 3 hours for alcoholysis. The volume of methanol is 40ml. S2. Remove the reaction tube and cool it to room temperature in running water. After opening the lid, pour the solution in the reaction tube into filter paper with a mass of W0. Rinse the reaction tube and filter residue 2-3 times with methanol heated to 60°C. Place the filter paper with filter residue in a drying oven and dry it at 105°C for 2 hours. The mass of the filter paper and filter residue after drying is W1, where W0 is 0.9749g and W1 is 0.9945g. S3. Place the dried filter paper with filter residue into a crucible with a mass of W2, and place it on an electric furnace for ashing until it burns without smoke. Then transfer the crucible to a muffle furnace for calcination at 900℃ for 1-2 hours until the carbon black disappears. After cooling and constant weight, weigh the crucible and ash to obtain W3, where W2 is 56.7135g and W3 is 56.7143g. S4. Calculate the carbon black content in the black fiber using the following formula: ω=(W1-W0) / G×100%-(W3-W2) / G×100%=1.17%, Where: ω is the carbon black content in the black filament, (W1-W0) / G×100% is the carbon black (including ash) content in the sample, ω1=1.22%, (W3-W2) / G×100% is the ash content in the sample, ASH=0.05%. Example

[0041] A method for detecting carbon black content in black silk includes the following steps: S1. Weigh 1.6031g of black filament and pour it into a stainless steel reaction tube. Add methanol, seal and tighten the tube, and heat it in an oven at 240℃ for 4 hours for alcoholysis. The volume of methanol is 40ml. S2. Remove the reaction tube and cool it to room temperature in running water. After opening the lid, pour the solution in the reaction tube into filter paper with a mass of W0. Rinse the reaction tube and filter residue 2-3 times with methanol heated to 60°C. Place the filter paper with filter residue in a drying oven and dry it at 105°C for 2 hours. The mass of the filter paper and filter residue after drying is W1, where W0 is 0.9913g and W1 is 1.0111g. S3. Place the dried filter paper with filter residue into a crucible with a mass of W2, and place it on an electric furnace for ashing until it burns without smoke. Then transfer the crucible to a muffle furnace for calcination at 900℃ for 1-2 hours until the carbon black disappears. After cooling and constant weight, weigh the crucible and ash to obtain W3, where W2 is 56.6835g and W3 is 56.6845g. S4. Calculate the carbon black content in the black fiber using the following formula: ω=(W1-W0) / G×100%-(W3-W2) / G×100%=1.17%, Where: ω is the carbon black content in the black filament, (W1-W0) / G×100% is the carbon black (including ash) content in the sample, ω1=1.24%, (W3-W2) / G×100% is the ash content in the sample, ASH=0.06%.

[0042] In Examples 1-7, the samples used were from the same batch, and the actual carbon black content was the same.

[0043] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for detecting the carbon black content in black silk, characterized in that, Includes the following steps: S1. Weigh G of black filament into a reaction tube, add methanol, and heat under sealed conditions to carry out alcoholysis. S2. Remove the reaction tube and cool it to room temperature. Filter the substance in the reaction tube through filter paper with a mass of W0. Rinse the reaction tube and filter residue with methanol. Dry the filter paper with filter residue and weigh the total mass of the dried filter paper and filter residue as W1. S3. Place the dried filter paper with filter residue into a crucible with a mass of W2 for ashing, then transfer the crucible to a muffle furnace for calcination to constant weight. After constant weight, weigh the crucible and the ash to get W3. S4. Calculate using the following formula: The ash content of carbon black is ω1 = (W1 - W0) / G × 100%; The ash content in the sample is calculated as ASH = (W3 - W2) / G × 100%. The carbon black content in black silk is ω=ω1-ASH.

2. The method for detecting carbon black content in black filament according to claim 1, characterized in that, In step S1, the ratio of the mass of the black filament to the volume of the methanol is (1-2) g:(25-50) mL.

3. The method for detecting carbon black content in black filament according to claim 1, characterized in that, The alcoholysis temperature in step S1 is 220–260°C, and the alcoholysis time is 1–4 h.

4. The method for detecting carbon black content in black filament according to claim 1, characterized in that, The reaction tube mentioned in step S1 is made of stainless steel, which is capable of high-temperature and high-pressure reactions.

5. The method for detecting carbon black content in black filament according to claim 1, characterized in that, The solvent temperature for rinsing the filter residue in step S2 is 60°C.

6. The method for detecting carbon black content in black filament according to claim 1, characterized in that, In step S2, the drying temperature is 100-105℃ and the drying time is 1-2 hours.

7. The method for detecting carbon black content in black filament according to claim 1, characterized in that, In step S3, the calcination temperature is 900–950℃ and the calcination time is 1–2 hours.

8. A method for detecting carbon black content in black filament according to claim 1 or 7, characterized in that, In step S3, the ashing process is heated until no smoke is produced, and the calcination process is heated until no carbon black residue remains.

9. The method for detecting carbon black content in black filament according to claim 8, characterized in that, Determine the absence of carbon black residue using the following method: Place the dried insoluble material into a pre-weighed crucible and record the total mass m1 before initial ignition. Heat at 900°C in a muffle furnace for 1–2 hours; Remove the crucible, place it in a desiccator to cool to room temperature, and accurately weigh the total mass m2; Place it back into the muffle furnace and heat at the same temperature for 30 minutes. After cooling, weigh m3. If the mass difference between two consecutive weighings (∣m3−m2∣) is ≤0.1mg-0.5mg, then it is determined that there is no carbon black residue.