Method for detecting the polymerization ratio of two-component polyurethane coating

Abstract

The application relates to the technical field of paint production, and particularly discloses a method for detecting the polymerization reaction proportion of two-component polyurethane paint. The method comprises the following steps: S1, crushing and sieving a polyurethane coating to be detected to obtain coating powder; S2, taking the A component, the B component and the coating powder of the two-component polyurethane paint as samples to be detected, digesting each sample to be detected, then measuring the nitrogen content of the digestion product, and calculating the polymerization reaction proportion of the polyurethane coating to be detected according to a formula. The application creatively detects the nitrogen content of the coating and the two-component paint to infer the polymerization reaction proportion of the two components, and then assesses whether the control of the mixing proportion of the two-component polyurethane paint is accurate, so that spraying abnormalities can be found in time, and the stability of the polyurethane paint quality can be ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of paint production, and particularly relates to a detection method for polymerization reaction proportion of two-component polyurethane paint. BACKGROUND

[0002] Polyurethane paint is a new type of paint developed rapidly in recent years, which can be divided into single-component polyurethane paint and two-component polyurethane paint. The two-component polyurethane paint is widely used in many fields of national economy due to its excellent performance. The two-component polyurethane paint is generally composed of water-based polyol containing -OH group and low-viscosity polyisocyanate curing agent containing -NCO group. When used, the A component and the B component are mixed according to the specified proportion, and the two components are polymerized and cured into a film at a certain temperature to obtain a two-component polyurethane film. The mixing ratio of the A component and the B component is the key to affect the performance of the final film. When the reaction proportion of the two components exceeds the specified reaction ratio of the paint, the performance of the polyurethane coating prepared will be poor. For example, when the curing agent is too much, the toughness of the paint film will decrease and become brittle, and even cracks and color yellowing will occur.

[0003] In the prior art, the two-component polyurethane paint is mainly used in mechanical hand spraying, manual brushing and mechanical automatic spraying. The mechanical hand spraying and manual brushing are affected by the subjective judgment of the operator, and there is a certain error in the uniformity and accuracy of the spraying amount, so it is difficult to ensure that the polymerization reaction proportion of the two components is within the specified range. When the mechanical automatic spraying is used, the A and B components spraying systems need to be monitored at all times to see if there is any abnormal working state. Once the abnormality occurs, the mixing and reaction proportion of the two components in the mixer will be out of tolerance, which will affect the performance of the paint film. However, it is difficult to find the abnormal reaction proportion of the components caused by the small error of the machine. SUMMARY

[0004] In view of this, the present application provides a detection method for the polymerization reaction proportion of two-component polyurethane paint, which calculates the polymerization reaction proportion of the two components of the polyurethane paint by measuring the nitrogen content, so as to judge whether the control of the reaction proportion of the two components is accurate and ensure the stability of the quality of the polyurethane paint.

[0005] To achieve the above-mentioned application purposes, the embodiments of the present application adopt the following technical solutions:

[0006] The embodiments of the present application provide a detection method for the polymerization reaction proportion of two-component polyurethane paint, which comprises the following steps:

[0007] S1, crushing and sieving the polyurethane coating to be tested to obtain a coating powder;

[0008] S2, taking the A component, the B component and the coating powder of the two-component polyurethane coating as the samples to be tested, respectively, digesting each sample to be tested, then measuring the nitrogen content of the digestion product, and calculating the polymerization ratio of the polyurethane coating to be tested according to the following formula:

[0009]

[0010] wherein m is the polymerization ratio of the two-component polyurethane coating; N A N is the nitrogen content of the A component of the two-component polyurethane coating, in %; B N is the nitrogen content of the B component of the two-component polyurethane coating, in %; 涂层 N is the nitrogen content of the polyurethane coating, in %;

[0011] The digestion step comprises: respectively keeping each sample to be tested at a temperature of 220-230 DEG C for 15-20 min, then raising the temperature to 320-330 DEG C for 10-15 min, and then raising the temperature to 410-420 DEG C for 135-140 min.

[0012] At present, there is no related literature recording the technology of determining the accuracy of the spraying system by the polymerization ratio of the two-component polyurethane coating. The inventor accidentally found that the reaction ratio derived from the nitrogen content can accurately reflect the reaction degree of the A and B components in the two-component polyurethane coating. The inventor has also tried to derive the polymerization ratio by C element and other elements. When the mass ratio of the A and B components is within a certain range, the calculated polymerization ratio is close to the theoretical polymerization ratio. However, once the mass ratio of the A and B components exceeds a specific range, the derived ratio error will be larger.

[0013] The detection method of the polymerization ratio of the two-component polyurethane coating provided by the present application creatively infers the polymerization ratio of the A and B components in the two-component polyurethane coating by detecting the nitrogen content of the coating and the two-component coating, and then evaluates whether the control of the mixing ratio of the two-component polyurethane coating is accurate, so as to timely find production abnormalities, ensure the stability of the quality of the polyurethane coating, and ensure the quality of the polyurethane coating. The detection process is simple, short in cycle and low in cost, and is convenient for judging whether the reaction ratio of the coating meets the quality requirements, and can be used as one of the quality control means in the production process of the two-component polyurethane coating.

[0014] In the digestion process, digestion temperature and digestion time are the key parameters affecting the digestion effect, and the co-heating of sulfuric acid and polyurethane coating or coating will convert the nitrogen in it into ammonium sulfate, and if the digestion time is too long or the digestion temperature is too high, the reaction by-products will participate in the end-point titration, resulting in high nitrogen content; if the digestion time is too short or the digestion temperature is too low, the digestion is not complete, resulting in low nitrogen content. The three-stage digestion process can fully digest the polyurethane coating or coating, so that the nitrogen element is completely dissolved in the digestion solution, and the nitrogen content is not increased due to side reactions, ensuring the accuracy of the nitrogen element detection data.

[0015] Optionally, when the absolute value of the deviation of the calculated polymerization reaction ratio of the measured polyurethane coating from the theoretical polymerization reaction ratio is less than 5%, it is considered normal production, and the equipment is normal. The theoretical polymerization reaction ratio is the mass ratio of component A and component B in the two-component polyurethane coating. The formula for calculating the deviation is:

[0016]

[0017] In the formula, E is the absolute value of the deviation of the polymerization reaction ratio of the measured polyurethane coating from the theoretical polymerization reaction ratio; m0 is the theoretical polymerization reaction ratio.

[0018] When the absolute value of the deviation of the calculated polymerization reaction ratio of the measured polyurethane coating from the theoretical polymerization reaction ratio is less than 5%, it indicates that the raw material feeding control mechanism of the production equipment such as the spraying system and the mixing system is operating normally; once the absolute value of the deviation is greater than or equal to 5%, the production equipment may be in a poor working condition, affecting the quality and production stability of the product, and timely troubleshooting is required to ensure smooth production.

[0019] Optionally, in step S1, the measured coating is first incubated at 40-50℃ for 16-24h before being crushed.

[0020] The preferred temperature and time can ensure that the two-component coating is fully reacted, avoiding incomplete reaction and affecting the evaluation results.

[0021] Optionally, in step S1, the screen mesh diameter is 1mm.

[0022] Optionally, in step S2, the digestion solution used in the digestion includes potassium sulfate, copper sulfate and concentrated sulfuric acid.

[0023] Optionally, in step S2, the mass concentration of the concentrated sulfuric acid is 96%-98%.

[0024] Optionally, in step S2, the mass-volume ratio of each sample to be tested, potassium sulfate, copper sulfate and concentrated sulfuric acid is 0.8g-1g:1g:0.066g-0.1g:1.5ml-3ml.

[0025] The preferred concentration and ratio of concentrated sulfuric acid can convert the nitrogen-containing organic matter into ammonium bisulfate, completely digest the nitrogen-containing components in the paint, and have good digestion effect. Meanwhile, the appropriate amount of potassium sulfate and copper sulfate can increase the boiling point of the liquid phase system, accelerate the decomposition of organic matter, shorten the digestion time, and improve the detection efficiency and accuracy of nitrogen content detection.

[0026] Optionally, in step S2, the Kjeldahl method is used to determine the nitrogen content of the digestion product.

[0027] Optionally, in step S2, the Kjeldahl method is used to determine the nitrogen content of the digestion product, including the following steps:

[0028] Step a, start the Kjeldahl nitrogen analyzer, set the distillation program, put the digestion product into the Kjeldahl nitrogen analyzer, drop the mixed indicator into the conical flask, and place it under the collection pipeline, and start distillation;

[0029] Step b, titrate with a standard titration solution until the collected liquid changes from blue-green to purple-red;

[0030] Step c, calculate the nitrogen content in the sample according to the standard calculation equation.

[0031] Optionally, in step S2, the standard calculation equation is:

[0032]

[0033] In the formula, ω is the mass fraction of nitrogen content, the value is %; V is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed by the titration solution, the unit is mL; V0 is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed by the blank (i.e. the blank value), the unit is mL; c is the concentration of the standard acid solution for titration, the unit is mol / L; m is the sample mass, the unit is g.

[0034] Further optionally, when the Kjeldahl method is used to determine the nitrogen content of the digestion product, different concentrations of acid need to be selected according to the nitrogen content in the sample to be tested, and the relationship between the titration standard solution and the nitrogen content in the sample to be tested is shown in the following table:

[0035] DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0037] Example 1

[0038] The embodiment of the present application provides a detection method for the polymerization reaction ratio of a two-component polyurethane coating.

[0039] 1. Main instruments and equipment

[0040] Balance, crusher, graphite digestion instrument and K1100 full-automatic Kjeldahl nitrogen determination instrument.

[0041] 2. Chemical reagents

[0042] (1) According to the nitrogen content of the coating A component, the nitrogen content of the B component and the coating layer, the concentration of the sulfuric acid standard titration solution is preliminarily estimated, the concentration of the titration solution used for the A component is c (1 / 2H2SO4) = 0.1 mol / L, and the concentration of the titration solution used for the B component and the coating layer is c (1 / 2H2SO4) = 0.02 mol / L.

[0043] The preparation method of the c (1 / 2H2SO4) = 0.02 mol / L solution is as follows: 0.6 mL of concentrated sulfuric acid (density is 1.8419 g / mL) is taken out, distilled water is diluted and constant volume is added to a 1000 mL volumetric flask, and then it is shaken and calibrated with anhydrous sodium carbonate.

[0044] The preparation method of the c (1 / 2H2SO4) = 0.1 mol / L solution is as follows: 3 mL of concentrated sulfuric acid (density is 1.8419 g / mL) is taken out, distilled water is diluted and constant volume is added to a 1000 mL volumetric flask, and then it is shaken and calibrated with anhydrous sodium carbonate.

[0045] (2) 40% sodium hydroxide solution 1000ml (400g / L) (preparation method: 400g of sodium hydroxide is dissolved in 1000ml of ammonia-free distilled water).

[0046] (3) 2% concentration boric acid solution 2000ml (20g / L) (preparation method: 40g of analytical pure boric acid is dissolved in 2000ml of ammonia-free distilled water).

[0047] (4) Methyl red and bromocresol green mixed indicator (preparation method: 0.1g of methyl red is weighed, constant volume is added to 100ml with anhydrous ethanol; 0.1g of bromocresol green is weighed, constant volume is added to 100ml with anhydrous ethanol; when used, the volume ratio of methyl red ethanol solution to bromocresol green ethanol solution is 1:5).

[0048] (5) The mixed indicator is mixed with the boric acid solution at a ratio of 1:100, for example: 10ml of mixed indicator is added to 1000ml of boric acid solution.

[0049] 3. Detection of the polymerization reaction ratio of the two-component polyurethane coating

[0050] S1, randomly extract three different positions of the coating, after curing the coating at 50℃ for 24h, put into the crusher to break into fine powder, then screen through the 1mm diameter sieve, get the coating powder.

[0051] S2, respectively weighing paint A component, paint B component and the above coating powder, each sample weighing 6 parallel samples. Add 1g potassium sulfate, 0.066g copper sulfate, 0.8g sample and 1.5ml concentrated sulfuric acid in the digestion tube, then according to the program of 220℃, 15min; 320℃, 10min; 420℃, 135min to digest, get the digestion product.

[0052] S3, start the Kjeldahl nitrogen determination instrument, clean the boric acid pipeline, replace the acid cleaning and alkali pipeline cleaning, then detect the empty tube to get the blank test value.

[0053] S4, after setting the distillation program in the test interface of the Kjeldahl nitrogen determination instrument, put the above digestion product into the Kjeldahl nitrogen determination instrument, drop the mixed indicator in the conical flask, and place it under the collection pipeline, start distillation. Among them, the distillation program is: add 40% sodium hydroxide solution for 8s, add 2% concentration boric acid solution for 4s, and then distill for 6min.

[0054] S5, titrate with sulfuric acid standard titration solution until the collected liquid changes from blue-green to purple-red, and calculate the nitrogen content of each sample according to the following formula:

[0055]

[0056] Among them, ω is the mass fraction of nitrogen content, the value is %; V is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed by the titration test solution, unit is mL; V0 is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed by the titration blank (i.e. blank value), unit is mL; c is the concentration of standard acid solution for titration, unit is mol / L; m is the sample mass, unit is g.

[0057] S6, calculate the polymerization reaction ratio of the coating to be measured according to the following formula, and measure 3 groups of different two-component polyurethane coatings, the test results are shown in Table 1:

[0058]

[0059] Among them, m is the polymerization reaction ratio of two-component polyurethane coating; N A is the nitrogen content of paint A component, unit is %; N B is the nitrogen content of paint B component, unit is %; N 涂层 is the nitrogen content of polyurethane coating, unit is %.

[0060] Table 1 polymerization reaction ratio test results

[0061] No. Theoretical polymerization ratio Actual polymerization ratio calculation result 1 0.410 0.412 2 0.357 0.367 3 0.312 0.320

[0062] Example 2

[0063] The embodiment of the present application provides a detection method for the polymerization reaction ratio of a two-component polyurethane coating.

[0064] 1. Main instruments and equipment

[0065] Balance, crusher, graphite digestion instrument and K1100 full-automatic Kjeldahl nitrogen determination instrument.

[0066] 2. Chemical reagents

[0067] (1) The concentration of hydrochloric acid standard titration solution is preliminarily estimated according to the nitrogen content of coating A component, the nitrogen content of coating B component and the nitrogen content of the coating, and the concentration of the titration solution used is c(HCl) = 0.02 mol / L.

[0068] The preparation method of the c(HCl) = 0.02 mol / L solution is as follows: 1.8 mL of concentrated hydrochloric acid (hydrochloric acid concentration 36% to 38%) is taken out, diluted with distilled water and made up to 1000 mL in a volumetric flask, shaken well, and calibrated with anhydrous sodium carbonate.

[0069] (2) 40% sodium hydroxide solution 1000 ml (400 g / L) (preparation method: 400 g of sodium hydroxide is dissolved in 1000 mL of ammonia-free distilled water).

[0070] (3) 2% concentration boric acid solution 2000 ml (20 g / L) (preparation method: 40 g of analytical pure boric acid is dissolved in 2000 ml of ammonia-free distilled water).

[0071] (4) Methyl red and bromocresol green mixed indicator (preparation method: 0.1 g of methyl red is weighed, made up to 100 ml with anhydrous ethanol; 0.1 g of bromocresol green is weighed, made up to 100 ml with anhydrous ethanol; and just before use, the methyl red ethanol solution and the bromocresol green ethanol solution are mixed in a volume ratio of 1:5).

[0072] (5) The mixed indicator is mixed with the boric acid solution at a ratio of 1:100, for example: 10 ml of mixed indicator is added to 1000 ml of boric acid solution.

[0073] 3. Detection of the polymerization reaction ratio of the two-component polyurethane coating

[0074] S1, randomly select three coatings at different positions, after curing the coatings at 50°C for 24 h, put them into a crusher to crush into fine powder, and then screen through a 1 mm diameter sieve to obtain coating powder.

[0075] S2, respectively, take the paint A component, paint B component and the above coating powder, each sample weighing 6 parallel samples. Add 1g potassium sulfate, 0.1g copper sulfate, 1g sample and 3ml concentrated sulfuric acid in the digestive tube, then follow the procedure of 230 DEG C, 20min; 330 DEG C, 15min; 410 DEG C, 140min to digest, and obtain the digestion product.

[0076] S3, start the Kjeldahl nitrogen determination instrument, and perform boric acid pipeline cleaning, acid replacement cleaning and alkali pipeline cleaning, then detect the empty tube to perform blank test, and obtain the blank value.

[0077] S4, after setting the distillation procedure in the test interface of the Kjeldahl nitrogen determination instrument, place the above digestion product into the Kjeldahl nitrogen determination instrument, drop the mixed indicator into the conical flask, and place it under the collection pipeline, and start distillation. The distillation procedure is as follows: add 40% sodium hydroxide solution for 8s, add 2% boric acid solution for 4s, and then distill for 6min.

[0078] S5, titrate with hydrochloric acid standard titration solution until the collected solution changes from blue-green to purple-red, and calculate the nitrogen content of each sample according to the following formula:

[0079]

[0080] Wherein, ω is the mass fraction of nitrogen content, the value is %; V is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed by the titration test solution, the unit is mL; V0 is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed by the titration blank (i.e. the blank value), the unit is mL; c is the concentration of the standard acid solution for titration, the unit is mol / L; m is the sample mass, the unit is g.

[0081] S6, calculate the polymerization reaction ratio of the coating to be measured according to the following formula, and measure three different two-component polyurethane coatings, and the test results are shown in Table 2:

[0082]

[0083] Wherein, m is the polymerization reaction ratio of the two-component polyurethane coating; N A is the nitrogen content of the paint A component, the unit is %; N B is the nitrogen content of the paint B component, the unit is %; N 涂层 is the nitrogen content of the polyurethane coating, the unit is %.

[0084] Table 2 Polymerization reaction ratio test results

[0085] No. Theoretical polymerization ratio Polymerization ratio calculation result 1 1.041 1.029 2 1.041 1.052

[0086] Example 3

[0087] The embodiment of the application provides a detection method for the polymerization reaction ratio of a two-component polyurethane coating.

[0088] 1. Main instruments and equipment

[0089] Balance, crusher, graphite digestion instrument and K1100 automatic Kjeldahl nitrogen determination instrument.

[0090] 2. Chemical reagents

[0091] (1) According to the nitrogen content of paint component A, the nitrogen content of component B and the nitrogen content of coating, the concentration of sulfuric acid standard titration solution is preliminarily estimated, the concentration of titration solution used for component A is c (1 / 2H2SO4) = 0.1 mol / L, and the concentration of titration solution used for component B and coating is c (1 / 2H2SO4) = 0.02 mol / L.

[0092] The preparation method of c (1 / 2H2SO4) = 0.02 mol / L solution is as follows: 0.6 mL of concentrated sulfuric acid (density is 1.8419 g / mL) is taken out, distilled water is diluted and constant volume is added to a 1000 mL volumetric flask, and then it is shaken uniformly and calibrated with anhydrous sodium carbonate.

[0093] The preparation method of c (1 / 2H2SO4) = 0.1 mol / L solution is as follows: 3 mL of concentrated sulfuric acid (density is 1.8419 g / mL) is taken out, distilled water is diluted and constant volume is added to a 1000 mL volumetric flask, and then it is shaken uniformly and calibrated with anhydrous sodium carbonate.

[0094] (2) 40% sodium hydroxide solution 1000 ml (400 g / L) (preparation method: 400 g of sodium hydroxide is dissolved in 1000 mL of ammonia-free distilled water).

[0095] (3) 2% concentration boric acid solution 2000 ml (20 g / L) (preparation method: 40 g of analytical pure boric acid is dissolved in 2000 ml of ammonia-free distilled water).

[0096] (4) Methyl red and bromocresol green mixed indicator (preparation method: 0.1 g of methyl red is weighed, constant volume is added to 100 ml with anhydrous ethanol; 0.1 g of bromocresol green is weighed, constant volume is added to 100 ml with anhydrous ethanol; when used, the volume ratio of methyl red ethanol solution to bromocresol green ethanol solution is 1:5).

[0097] (5) The mixed indicator is mixed with the boric acid solution at a ratio of 1:100, for example: 10 ml of mixed indicator is added to 1000 ml of boric acid solution.

[0098] 3. Detection of polymerization reaction ratio of two-component polyurethane paint

[0099] S1, randomly select three coatings at different positions, after curing at 50°C for 24 h, put them into a crusher to crush into fine powder, then screen through a 1 mm diameter sieve to obtain coating powder.

[0100] S2, weigh paint A component, paint B component and the coating powder respectively, and weigh 6 parallel samples for each sample. Add 1 g of potassium sulfate, 0.08 g of copper sulfate, 0.9 g of sample and 2.2 ml of concentrated sulfuric acid in the digestion tube, and then perform digestion according to the program of 225℃, 18 min; 325℃, 13 min; 415℃, 138 min to obtain the digestion product.

[0101] S3, start the Kjeldahl apparatus, perform borate pipeline cleaning, acid replacement cleaning and alkali pipeline cleaning, and then detect the empty tube to perform blank test to obtain the blank value.

[0102] S4, after setting the distillation program on the test interface of the Kjeldahl apparatus, put the above digestion product into the Kjeldahl apparatus, drop the mixed indicator into the conical flask, and place it under the collection pipeline, and start distillation. The distillation program is: add 40% sodium hydroxide solution for 8 s, add 2% concentrated boric acid solution for 4 s, and then distill for 6 min.

[0103] S5, titrate with sulfuric acid standard titration solution until the collected solution changes from blue-green to purple-red, and calculate the nitrogen content of each sample according to the following formula:

[0104]

[0105] Wherein, ω is the mass fraction of nitrogen content, the value is %; V is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed by the titration test solution, in mL; V0 is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed by the titration blank (i.e. the blank value), in mL; c is the concentration of the standard acid solution for titration, in mol / L; m is the sample mass, in g.

[0106] S6, calculate the polymerization reaction ratio of the coating to be tested according to the following formula, and measure 3 different two-component polyurethane coatings, and the test results are shown in Table 3:

[0107]

[0108] Wherein, m is the polymerization reaction ratio of the two-component polyurethane coating; N A is the nitrogen content of paint A component, in %; N B is the nitrogen content of paint B component, in %; N 涂层 is the nitrogen content of the polyurethane coating, in %.

[0109] Table 3 Polymerization reaction ratio test results

[0110] No. Theoretical polymerization ratio Actual polymerization ratio calculation result 1 0.410 0.418 2 0.357 0.364 3 0.312 0.321

[0111] Comparative Example 1

[0112] The present application comparative example provides a kind of detection method of polymerization reaction proportion of two-component polyurethane coating, and the difference with example 1 is that in step S2, the digestion procedure is 220 DEG C, 25 min;320 DEG C, 10 min;420 DEG C, 135 min.The test results are as shown in table 4:

[0113] Table 4 polymerization reaction proportion detection results

[0114]

[0115]

[0116] Comparative example 2

[0117] The present application comparative example provides a kind of detection method of polymerization reaction proportion of two-component polyurethane coating, and the difference with example 1 is that in step S2, the digestion procedure is 220 DEG C, 15 min;320 DEG C, 10 min;420 DEG C, 180 min.The test results are as shown in table 5:

[0118] Table 5 polymerization reaction proportion detection results

[0119] No. Theoretical polymerization ratio Polymerization ratio calculation result 1 0.410 0.521 2 0.357 0.446 3 0.312 0.398

[0120] Comparative example 3

[0121] The present application comparative example provides a kind of detection method of polymerization reaction proportion of two-component polyurethane coating, and the difference with example 1 is that in step S2, the digestion procedure is 220 DEG C, 15 min;360 DEG C, 10 min;420 DEG C, 135 min.The test results are as shown in table 6:

[0122] Table 6 polymerization reaction proportion detection results

[0123] No. Theoretical polymerization ratio Polymerization ratio calculation result No. Theoretical polymerization ratio Polymerization ratio calculation result 1 0.410 0.457 2 0.357 0.402 3 0.312 0.369

[0124] The above only is the preferred embodiment of the present application, and does not limit the present application, any modification, equivalent replacement or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for detecting the polymerization reaction ratio of a two-component polyurethane coating, characterized by, It comprises the following steps: S1, crushing and sieving the polyurethane coating to be tested to obtain coating powder; S2, taking the A component, B component of the two-component polyurethane coating and the coating powder as the samples to be tested, digesting each sample to be tested, then measuring the nitrogen content of the digestion product, and calculating the polymerization ratio of the polyurethane coating to be tested according to the following formula: ； Wherein, m is the polymerization ratio of the two-component polyurethane coating; NA is the nitrogen content of the A component of the two-component polyurethane coating, unit %; NB is the nitrogen content of the B component of the two-component polyurethane coating, unit %; Ncoating is the nitrogen content of the polyurethane coating, unit %; The digestion step comprises: keeping each sample to be tested at a temperature of 220-230℃ for 15-20min, then raising the temperature to 320-330℃ for 10-15min, and then raising the temperature to 410-420℃ for 135-140min; When the absolute value of the deviation between the calculated polymerization ratio of the polyurethane coating to be tested and the theoretical polymerization ratio is less than 5%, it is considered to be normal production and the equipment is normal; Wherein, the theoretical polymerization ratio is the mass ratio of the A component to the B component in the two-component polyurethane coating; the deviation calculation formula is: In the formula, E is the absolute value of the deviation between the polymerization ratio of the polyurethane coating to be tested and the theoretical polymerization ratio; m0 is the theoretical polymerization ratio.

2. The method of claim 1, wherein the ratio of the polyaddition reaction of the two-component polyurethane coating is detected. In step S1, the polyurethane coating to be tested is first kept at 40-50℃ for 16-24h before crushing.

3. The method of claim 1, wherein the ratio of the polyaddition reaction of the two-component polyurethane coating is detected by measuring the amount of the isocyanate group of the polyurethane coating. In step S1, the diameter of the sieve for sieving is 1mm.

4. The method of claim 1, wherein the ratio of the polyaddition reaction of the two-component polyurethane coating is detected. In step S2, the digestion solution used in digestion comprises potassium sulfate, copper sulfate and concentrated sulfuric acid.

5. The method of claim 4, wherein the ratio of the polyaddition reaction of the two-component polyurethane coating is detected by measuring the amount of the polyaddition reaction product. In step S2, the mass concentration of the concentrated sulfuric acid is 96-98%.

6. The method for detecting the polymerization reaction ratio of a two-component polyurethane coating according to claim 4 or 5, characterized by, In step S2, the mass-volume ratio of each sample to be tested, potassium sulfate, copper sulfate and concentrated sulfuric acid is 0.8-1g: 1g: 0.066-0.1g: 1.5-3ml.

7. The method according to claim 1, wherein the ratio of the polymerization reaction of the two-component polyurethane coating is detected. In step S2, the Kjeldahl method is used to measure the nitrogen content of the digestion product.

8. The method for detecting the polymerization reaction ratio of the two-component polyurethane coating as described in claim 7, characterized in that, In step S2, the Kjeldahl method for measuring the nitrogen content of the digestion product comprises the following steps: Step a, start the Kjeldahl apparatus, set the distillation program, then put the digestion product into the Kjeldahl apparatus, drop the mixed indicator into the conical flask, and place it under the collection pipeline, and start distillation; Step b, titrate with standard titration solution until the collected liquid changes from blue-green to purple-red; Step c, calculate the nitrogen content in the sample according to the standard calculation equation.

9. The method according to claim 8, wherein the ratio of the polymerization reaction of the two-component polyurethane coating is detected by measuring the change in the intensity of the light emitted from the luminescent material. The standard calculation equation is: In the formula, ω is the mass fraction of nitrogen content, the value is %; V is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed, unit mL; V0 is the volume of hydrochloric acid or sulfuric acid standard titration solution consumed by the blank, i.e. the blank value, unit mL; c is the concentration of standard acid solution for titration, unit mol / L; m is the mass of the sample, unit g.

Images