Production method of variable multicolor carbon dioxide concentration indicator

Abstract

The invention discloses a production method of a variable multicolor carbon dioxide concentration indicator, and belongs to the field of carbon dioxide detection.The production method comprises the steps that carbon dioxide with the purity of 95% is introduced and stirred, the initial reaction performance of the carbon dioxide indicator is improved, and a composite indicator is added to improve the color changing interval; the added sodium chloride is beneficial to improving the color changing effect under the low-temperature condition, the added glycerol is beneficial to improving the high-temperature use performance, reducing volatilization and improving the stability, and after being packaged in a high-breathability and high-strength packaging material, an effective color changing effect can be achieved, deliquescence and influence or pollution to surrounding products are not prone to occurring, the excellent color changing effect can be achieved under the low-temperature condition, and the service life of the product is prolonged. The carbon dioxide indicator is blue under the carbon dioxide concentration of 0-10%, purple under the carbon dioxide concentration of 10%-20%, green under the carbon dioxide concentration of 20%-50%, yellow under the carbon dioxide concentration of 50%-90% and red under the carbon dioxide concentration of 90%-100%, and has more excellent utilization value and economic value.

Description

Technical Field

[0001] The invention relates to the field of carbon dioxide detection, and in particular to a method for producing a variable multicolor carbon dioxide concentration indicator. Background Art

[0002] The mainstream carbon dioxide indicators in the prior art generally change color in a single manner, that is, one color in the presence of oxygen and another color in the absence of oxygen, and cannot change different colors according to the concentration of carbon dioxide. For example, the Chinese patent application number CN1222069A discloses a bicarbonate-containing drug solution package, including a gas-permeable plastic container for storing a bicarbonate-containing drug solution and a gas-impermeable plastic component for accommodating the gas-permeable plastic container. When accommodating, a carbon dioxide atmosphere has been established in the space defined by the container and the packaging component, and the space also contains a pH indicator device, which includes a gas-permeable plastic box for holding a bicarbonate-containing liquid (similar to a drug solution) and a pH indicator having a color-changing property as the pH of the liquid changes. The method proposed in the patent uses sodium bicarbonate to absorb carbon dioxide in the air to change color, which is purple under aerobic conditions and yellow under anaerobic conditions. A single indicator solution can only distinguish between aerobic and anaerobic conditions, and cannot accurately determine the specific concentration of carbon dioxide. Another example is the Chinese patent application number CN 112957254, which still fails to solve the color change effect of carbon dioxide at different concentrations. Another example is the Chinese patent application number CN94118585.0, which discloses a carbon dioxide indicator and preparation method for detecting carbon dioxide concentration in mixed gas, belonging to the field of clinical medicine and environmental health monitoring. The indicator is mainly composed of potassium hydroxide or sodium hydroxide or calcium hydroxide, ethanol, indicator Nile Blue A, phenolphthalein, and activated alumina. When the indicator contacts the mixed oxygen gas containing carbon dioxide, it changes from deep red → purple red → purple gray → gray blue → blue. The patent involves activated alumina whose color-changing floor material is solid. There is a problem that it will deliquesce after absorbing water vapor in the air and pollute the surrounding products. When used, other containers are needed to wrap and fix, which is troublesome to operate. In addition, the color-changing temperature range of the patent is narrow, and the carbon dioxide concentration is only different between 1% and 5%, and then 5% to 100% is the same color. When actually used, the distinction is not large and cannot be used as a basis for judging the carbon dioxide concentration.

[0003] Therefore, there are problems in the prior art that the carbon dioxide indicator cannot change color according to the carbon dioxide concentration, the color change range is narrow, and the color change effect is poor under low temperature conditions, and it cannot change color normally in an environment below 10°C, which needs to be solved urgently. Summary of the invention

[0004] Based on this, in order to solve the problems in the prior art that the carbon dioxide indicator cannot change color according to the carbon dioxide concentration, the color change range is narrow, and the color change effect is poor under low temperature conditions, and it cannot change color normally under an environment below 10°C, the present invention provides a method for producing a variable multicolor carbon dioxide concentration indicator, and the specific technical scheme is as follows:

[0005] A method for producing a variable multicolor carbon dioxide concentration indicator, the method comprising the following steps:

[0006] Calcium hydroxide is ball-milled, and then sodium chloride and a solvent are added, and a first stirring process is performed to obtain a mixture A;

[0007] Adding a color-changing agent to the mixture A, performing a second stirring treatment to obtain a mixture B, and introducing carbon dioxide gas with a concentration of 95% for 10 to 20 minutes while stirring, and then continuously stirring in air for 10 to 20 hours until the mixture stabilizes in blue, filtering the filtrate, and then adding glycerol, performing a third stirring treatment to obtain a carbon dioxide indicator;

[0008] The carbon dioxide indicator is blue at a carbon dioxide concentration of 0-10%, purple at a carbon dioxide concentration of 10-20%, green at a carbon dioxide concentration of 20-50%, yellow at a carbon dioxide concentration of 50-90%, and red at a carbon dioxide concentration of 90-100%.

[0009] Furthermore, the carbon dioxide indicator is packaged in a packaging material with high air permeability and high strength.

[0010] Furthermore, the solvent is water.

[0011] Furthermore, the rotation speed of the ball milling treatment is 100 r / min to 200 r / min, the time is 10 min to 15 min, and the average particle size of the calcium hydroxide powder after the ball milling treatment is 10 μm to 30 μm.

[0012] Furthermore, the addition ratio of the calcium hydroxide to the solvent is (10g-15g) / 1000mL.

[0013] Furthermore, the addition ratio of the sodium chloride to the solvent is (400 g to 450 g) / 1000 mL.

[0014] Furthermore, the addition ratio of the color-changing agent to the solvent is (2 g to 10 g) / 1000 mL.

[0015] Furthermore, the color changing agent is at least two of phenol red, cresol red, bromophenol blue and thymol blue.

[0016] Furthermore, the addition ratio of the glycerol to the solvent is (1 g to 5 g) / 1000 mL.

[0017] Furthermore, the rotation speed of the third stirring treatment is 200 r / min to 500 r / min, the temperature is raised to 30° C. to 50° C. at a heating rate of 3° C. to 5° C., and the time is 20 min to 30 min.

[0018] Compared with the prior art, this application has the following beneficial effects:

[0019] 1. The present invention can show excellent color-changing effect under low temperature conditions by optimizing the composition and ratio of the carbon dioxide indicator. The carbon dioxide indicator is blue at a carbon dioxide concentration of 0-10%, purple at a carbon dioxide concentration of 10-20%, green at a carbon dioxide concentration of 20-50%, yellow at a carbon dioxide concentration of 50-90%, and red at a carbon dioxide concentration of 90-100%, and has better utilization value and economic value.

[0020] 2. The present invention introduces 95% pure carbon dioxide for stirring to improve the initial reaction performance of the carbon dioxide indicator, adds a composite indicator to increase the color change range, adds sodium chloride to help improve the color change effect under low temperature conditions, and adds a proper amount of glycerol so that the carbon dioxide indicator can be used under high temperature conditions, thereby reducing volatilization, extending the service life, and improving stability. After being packaged in a highly breathable and high-strength packaging material, it can exert an effective color change effect, is not easy to deliquesce, affect or contaminate surrounding products, and has high safety in use.

[0021] 3. The present invention optimizes the packaging material of the carbon dioxide indicator, which has a positive impact on the stability and effect of color change, and will not contaminate surrounding products. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0024] A method for producing a variable multicolor carbon dioxide concentration indicator in one embodiment of the present invention comprises the following steps:

[0025] Calcium hydroxide is ball-milled, and then sodium chloride and a solvent are added, and a first stirring process is performed to obtain a mixture A;

[0026] Adding a color-changing agent to the mixture A, performing a second stirring treatment to obtain a mixture B, and introducing carbon dioxide gas with a concentration of 95% for 10 to 20 minutes while stirring, and then continuously stirring in air for 10 to 20 hours until the mixture stabilizes in blue, filtering the filtrate, and then adding glycerol, performing a third stirring treatment to obtain a carbon dioxide indicator;

[0027] The carbon dioxide indicator is blue at a carbon dioxide concentration of 0-10%, purple at a carbon dioxide concentration of 10-20%, green at a carbon dioxide concentration of 20-50%, yellow at a carbon dioxide concentration of 50-90%, and red at a carbon dioxide concentration of 90-100%.

[0028] In one embodiment, the carbon dioxide indicator is packaged in a packaging material with high air permeability and high strength.

[0029] In one embodiment, the solvent is water. In one embodiment, the ball milling process is performed at a rotation speed of 100 r / min to 200 r / min for 10 min to 15 min, and the average particle size of the calcium hydroxide powder after ball milling is 10 μm to 30 μm.

[0030] In one embodiment, the first stirring treatment has a rotation speed of 150 r / min to 250 r / min and a time of 20 min to 30 min.

[0031] In one embodiment, the addition ratio of calcium hydroxide to solvent is (10g-15g) / 1000mL.

[0032] In one embodiment, the addition ratio of sodium chloride to solvent is (400g-450g) / 1000mL.

[0033] In one embodiment, the ratio of the amount of the color-changing agent to the amount of the solvent added is (2 g to 10 g) / 1000 mL.

[0034] In one embodiment, the color changing agent is at least two of phenol red, cresol red, bromophenol blue, and thymol blue.

[0035] In one embodiment, the color changing agent is a mixture of cresol red and bromophenol blue, and the mass ratio of cresol red to bromophenol blue is (2-3):1.

[0036] In one embodiment, the second stirring treatment is performed at a rotation speed of 200 r / min to 500 r / min and for a time of 15 min to 30 min.

[0037] In one embodiment, the addition ratio of the glycerol to the solvent is (1 g to 5 g) / 1000 mL.

[0038] In one embodiment, the third stirring treatment is performed at a rotation speed of 200 r / min to 500 r / min, and the temperature is raised to 30° C. to 50° C. at a heating rate of 3° C. to 5° C. for 20 min to 30 min.

[0039] In one embodiment, the highly air-permeable and high-strength packaging material comprises the following ingredients in parts by weight: 25 to 30 parts of polymethyl methacrylate, 5 to 7 parts of tributyl phosphate, 12 to 17 parts of chitosan, and 5 to 9 parts of calcium carbonate.

[0040] In one embodiment, the degree of polymerization of the polymethyl methacrylate is 10,000 to 50,000.

[0041] In one embodiment, the preparation method of the high-permeability and high-strength guarantee material is: adding polymethyl methacrylate, tributyl phosphate, chitosan and calcium carbonate into an extruder for melting, and the process parameters are: the feeding section temperature is 120℃~135℃, the melting section temperature is 150℃~220℃, the homogenization section temperature is 150℃~180℃, and the die head temperature is 160℃~200℃; then the film is cast and stretched at a force of 0.5Mpa~0.8Mpa to obtain a film.

[0042] In one embodiment, the packaging is performed using a liquid packaging machine with a film as the packaging material.

[0043] The present invention can obtain a carbon dioxide indicator with a wide color change range, ideal color change effect and color change temperature through optimization of components, component ratio and process.

[0044] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0045] Embodiment 1:

[0046] A method for producing a variable multicolor carbon dioxide concentration indicator, the method comprising the following steps:

[0047] 10 g of calcium hydroxide was ball-milled at a speed of 100 r / min for 15 min to obtain calcium hydroxide powder with an average particle size of 25 μm, and then 400 g of sodium chloride and 1000 mL of water were added, and a first stirring treatment was performed at a speed of 250 r / min for 20 min to obtain a mixture A;

[0048] 2 g of cresol red and 1 g of bromophenol blue are added to the mixture A, and a second stirring treatment is performed at a speed of 250 r / min for 20 min to obtain a mixture B, and a carbon dioxide gas with a concentration of 95% is introduced for 15 min while stirring, and then the mixture is continuously stirred in air for 10 h until it stabilizes in a blue color, and the filtrate is filtered to obtain the filtrate, and 3 g of glycerol is added, and a third stirring treatment is performed at a speed of 200 r / min for 20 min, and during the third stirring treatment, the temperature is raised to 45° C. at a heating rate of 3° C. to obtain a carbon dioxide indicator;

[0049] According to weight, 30 parts of polymethyl methacrylate, 5 parts of tributyl phosphate, 15 parts of chitosan and 7 parts of calcium carbonate are added into an extruder for melting, and the process parameters are as follows: the temperature of the feeding section is 125°C, the temperature of the melting section is 180°C, the temperature of the homogenizing section is 150°C, and the temperature of the die head is 200°C; then, a casting process is performed, and the film is stretched under a force of 0.8Mpa to obtain a film; a liquid packaging machine is used, the film is used as a packaging material, and a carbon dioxide indicator is encapsulated in the packaging material to obtain a product.

[0050] The product obtained in Example 1 was tested for its effect, and the results are shown in Table 1.

[0051] Table 1: Color change effect verification of the product in Example 1

[0052]

[0053] From the test results analysis of Table 1, it can be seen that the carbon dioxide indicator prepared in the present application has a wide detection range, can effectively detect carbon dioxide contents of different concentrations under different temperature conditions, and has excellent color development effect.

[0054] Embodiment 2:

[0055] A method for producing a variable multicolor carbon dioxide concentration indicator, the method comprising the following steps:

[0056] 10 g of calcium hydroxide was ball-milled at a speed of 150 r / min for 10 min to obtain calcium hydroxide powder with an average particle size of 30 μm, and then 400 g of sodium chloride and 1000 mL of water were added, and a first stirring treatment was performed at a speed of 200 r / min for 25 min to obtain a mixture A;

[0057] 2 g of cresol red and 1 g of bromophenol blue were added to the mixture A, and a second stirring treatment was performed at a speed of 300 r / min for 25 min to obtain a mixture B, and a carbon dioxide gas with a concentration of 95% was introduced for 15 min while stirring, and then the mixture was continuously stirred in air for 10 h until it stabilized in blue, the filtrate was filtered, and 3 g of glycerol was added, and a third stirring treatment was performed at a speed of 250 r / min for 30 min, and during the third stirring treatment, the temperature was raised to 45° C. at a heating rate of 5° C. to obtain a carbon dioxide indicator;

[0058] According to weight, 27 parts of polymethyl methacrylate, 6 parts of tributyl phosphate, 16 parts of chitosan and 9 parts of calcium carbonate are added into an extruder for melting, and the process parameters are as follows: the temperature of the feeding section is 130°C, the temperature of the melting section is 200°C, the temperature of the homogenizing section is 180°C, and the temperature of the die head is 200°C; then, a casting process is performed, and the film is stretched under a force of 0.8Mpa to obtain a film; a liquid packaging machine is used, the film is used as a packaging material, and a carbon dioxide indicator is encapsulated in the packaging material to obtain a product.

[0059] The product obtained in Example 2 was tested for its effect, and the results are shown in Table 2.

[0060] Table 2: Color change effect verification of the product in Example 2

[0061]

[0062] From the test results analysis of Table 2, it can be seen that the carbon dioxide indicator prepared in the present application has a wide detection range, can effectively detect carbon dioxide contents of different concentrations under different temperature conditions, and has excellent color development effect.

[0063] Embodiment 3:

[0064] A method for producing a variable multicolor carbon dioxide concentration indicator, the method comprising the following steps:

[0065] 10 g of calcium hydroxide was ball-milled at a speed of 200 r / min for 15 min to obtain calcium hydroxide powder with an average particle size of 30 μm, and then 400 g of sodium chloride and 1000 mL of water were added, and a first stirring treatment was performed at a speed of 250 r / min for 30 min to obtain a mixture A;

[0066] 2 g of cresol red and 1 g of bromophenol blue are added to the mixture A, and a second stirring treatment is performed at a speed of 250 r / min for 30 min to obtain a mixture B, and a carbon dioxide gas with a concentration of 95% is introduced for 20 min while stirring, and then the mixture is continuously stirred in air for 10 h until it stabilizes in a blue color, and the filtrate is filtered to obtain the filtrate, and 3 g of glycerol is added, and a third stirring treatment is performed at a speed of 300 r / min for 30 min, and during the third stirring treatment, the temperature is raised to 50° C. at a heating rate of 5° C. to obtain a carbon dioxide indicator;

[0067] According to weight, 30 parts of polymethyl methacrylate, 7 parts of tributyl phosphate, 17 parts of chitosan and 9 parts of calcium carbonate are added into an extruder for melting, and the process parameters are as follows: the temperature of the feeding section is 130°C, the temperature of the melting section is 220°C, the temperature of the homogenizing section is 160°C, and the temperature of the die head is 200°C; then, a casting process is performed, and the film is stretched under a force of 0.8Mpa to obtain a film; a liquid packaging machine is used, the film is used as a packaging material, and a carbon dioxide indicator is encapsulated in the packaging material to obtain a product.

[0068] The product obtained in Example 3 was tested for its effect, and the results are shown in Table 3.

[0069] Table 3: Color change effect verification of the product in Example 3

[0070]

[0071] From the test results analysis of Table 3, it can be seen that the carbon dioxide indicator prepared in the present application has a wide detection range, can effectively detect carbon dioxide contents of different concentrations under different temperature conditions, and has excellent color development effect.

[0072] Comparative Example 1:

[0073] The difference between Comparative Example 1 and Example 3 is that no sodium chloride is added in Comparative Example 1, and the rest is the same as Example 3.

[0074] The comparative product in Example 1 was subjected to relevant performance tests, and the results are shown in Table 4.

[0075] Table 4: Verification of color change effect of comparative products in Example 1

[0076]

[0077] It can be seen from Table 4 that due to the lack of sodium chloride, the color development effect of the product is unstable under conditions below 25°C, indicating that adding sodium chloride helps improve the performance of the product under low temperature conditions.

[0078] Comparative Example 2:

[0079] The difference between Comparative Example 2 and Example 3 is that the amount of sodium chloride added in Comparative Example 2 is 200 g, and the rest is the same as Example 3.

[0080] The color development effect of the product prepared in Example 4 was verified, and the color development effect was ultimately similar to that of Example 3, but the color change rate was slow, indicating that the content of sodium chloride added in this application can help to increase the color development rate and increase the color development efficiency of carbon dioxide.

[0081] Comparative Example 3:

[0082] The difference between Comparative Example 3 and Example 3 is that in Comparative Example 3, the added amount of cresol red is 1 g, the added amount of bromophenol blue is 1 g, and the rest is the same as Example 3.

[0083] The comparative product prepared in comparative example 3 was tested for its effect, and the results are shown in Table 5 below.

[0084] Table 5: Verification of the color change effect of the comparative product of Comparative Example 3

[0085]

[0086] From the data analysis of Table 5, it can be seen that the different ratios of the color-changing agents in the present application will affect the color-changing range of the product, making the color-changing effect unable to meet the use requirements.

[0087] Comparative Example 4:

[0088] The difference between Comparative Example 5 and Example 3 is that only cresol red is added in Comparative Example 4, and the rest is the same as Example 3.

[0089] The comparative product in Example 4 was subjected to relevant performance tests, and the results are shown in Table 6 below.

[0090] Table 6: Verification of the color change effect of the comparative product of Comparative Example 4

[0091]

[0092] It can be seen from Table 6 that when a single cresol red color-changing agent is added, the color change range of the product becomes narrower and the content of carbon dioxide at different concentrations cannot be detected more accurately.

[0093] Comparative Example 5:

[0094] The difference between Comparative Example 5 and Example 3 is that no glycerol is added in Comparative Example 5, and the other parts are the same as Example 3.

[0095] The comparative samples in Comparative Example 5 were subjected to relevant performance tests, and the results are shown in Table 7 below.

[0096] Table 7: Verification of color change effect of comparative product in Example 6

[0097]

[0098] It can be seen from Table 7 that no glycerol was added in Comparative Example 6, but the color change was unstable above 75°C and the color change range was narrow, indicating that glycerol had a significant effect on the color change effect of the carbon dioxide indicator of the present application.

[0099] Comparative Example 6:

[0100] The difference between Comparative Example 6 and Example 3 is that 95% pure carbon dioxide gas is not introduced into Comparative Example 6, and the rest is the same as Example 3.

[0101] The comparative product obtained in Comparative Example 6 was verified for its effect, and the results showed that the color change effect was similar to that of Example 3, but the color change rate was slower and the stability was average, indicating that the introduction of 95% pure carbon dioxide gas helps to improve the color change stability of the product and increase the reaction performance of the product.

[0102] Comparative Example 7:

[0103] The difference between Comparative Example 7 and Example 3 is that chitosan is not added in Comparative Example 7, and the rest is the same as Example 3.

[0104] The comparative product of Example 7 was verified for its effect. The results showed that the color change effect in Example 7 was poor, the color change rate was slow, and the color change was unstable, which means that the composition of the packaging material also affects the color change effect. The present application can ensure the stability of the color change by optimizing the composition of the packaging material.

[0105] Comparative Example 8:

[0106] The difference between Comparative Example 8 and Example 3 is that polypropylene is used as the packaging material in Comparative Example 8, and the rest is the same as Example 3.

[0107] The comparative product of Example 8 was verified for its effect, and the results showed that the color change efficiency in Example 8 was slow.

[0108] By comparing Example 3 with Comparative Examples 1 to 8, it can be clearly seen that the ingredients, ingredient ratios and processes of the present application, as a complete technical solution, can increase the color change range, stabilize the color change effect, and can solve the problem in the prior art that the carbon dioxide indicator cannot change color according to the carbon dioxide concentration, and the color change range is narrow, and under low temperature conditions, the color change effect is poor and cannot change color normally in an environment below 10°C.

[0109] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for producing a variable multicolor carbon dioxide concentration indicator, characterized in that: The production method comprises the following steps: Calcium hydroxide is ball-milled, and then sodium chloride and a solvent are added, and a first stirring process is performed to obtain a mixture A; Adding a color-changing agent to the mixture A, performing a second stirring treatment to obtain a mixture B, and introducing carbon dioxide gas with a concentration of 95% for 10 to 20 minutes while stirring, and then continuously stirring in air for 10 to 20 hours until the mixture stabilizes in blue, filtering the filtrate, and then adding glycerol, performing a third stirring treatment to obtain a carbon dioxide indicator; The carbon dioxide indicator is blue at a carbon dioxide concentration of 0-10%, purple at a carbon dioxide concentration of 10-20%, green at a carbon dioxide concentration of 20-50%, yellow at a carbon dioxide concentration of 50-90%, and red at a carbon dioxide concentration of 90-100%.

2. The production method according to claim 1, characterized in that The carbon dioxide indicator is packaged in a packaging material with high air permeability and high strength.

3. The production method according to claim 1, characterized in that The solvent is water.

4. The production method according to claim 1, characterized in that The rotation speed of the ball milling treatment is 100 r / min to 200 r / min, the time is 10 min to 15 min, and the average particle size of the calcium hydroxide powder after the ball milling treatment is 10 μm to 30 μm.

5. The production method according to claim 1, characterized in that: The addition ratio of the calcium hydroxide to the solvent is (10 g to 15 g) / 1000 mL.

6. The production method according to claim 1, characterized in that: The addition ratio of the sodium chloride to the solvent is (400 g to 450 g) / 1000 mL.

7. The production method according to claim 1, characterized in that: The addition ratio of the color-changing agent to the solvent is (2 g to 10 g) / 1000 mL.

8. The production method according to claim 1, characterized in that: The color changing agent is at least two of phenol red, cresol red, bromophenol blue and thymol blue.

9. The production method according to claim 1, characterized in that: The addition ratio of the glycerol to the solvent is (1 g to 5 g) / 1000 mL.

10. The production method according to claim 1, characterized in that: The rotation speed of the third stirring treatment is 200 r / min to 500 r / min, the temperature is raised to 30° C. to 50° C. at a heating rate of 3° C. to 5° C., and the time is 20 min to 30 min.

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