Humidity indicating composition and application thereof

Abstract

The invention provides a humidity indicating composition and application thereof. The humidity indicating composition comprises the following components in percentage by mass: 15-35% of a buffering agent, 1-15% of an acid-base indicator, 0.1-10% of an antioxidant and 40-65% of a humectant, the buffering agent comprises phosphoric acid and lactic acid; the mass ratio of the phosphoric acid to the lactic acid is (2-5): 1. In the humidity indicating composition provided by the invention, the buffer agent comprises phosphoric acid and lactic acid in a mass ratio of (2-5): 1, the humidity indicating composition does not comprise metal elements and / or halogen elements, and the sensitivity and color discrimination of the humidity indicating card can be improved when the humidity indicating composition is applied to the humidity indicating card.

Description

Technical Field

[0001] The invention belongs to the technical field of indicators, and in particular relates to a humidity indicating composition and application thereof. Background Art

[0002] Humidity indicator cards with cobalt chloride as the indicator can show different color changes with different hydration levels within different humidity ranges. They are widely used in humidity management of electronic equipment, packaging materials and precision instruments.

[0003] In the prior art, some humidity indicator cards with cobalt-free metal compounds as important components are used to replace humidity indicator cards containing cobalt. For example, patent application CN105445269A discloses an environmentally friendly dry and wet indicator composition including a trivalent iron or divalent copper compound, sulfosalicylate ions, a moisturizer and an antioxidant, which can indicate the air humidity in a sealed package according to the color change under different air humidity. Patent application CN107315006A discloses two types of humidity indicator cards, namely: a humidity indicator card including copper chloride, lithium chloride, magnesium chloride, and water, and a humidity indicator card including copper sulfate, lithium bromide, copper bromide, and water, which have the advantages of high sensitivity, high color discrimination, and easy carrying.

[0004] Although the above humidity indicator card does not contain cobalt, it contains other heavy metal elements or halogen elements to a greater or lesser extent, which is not conducive to environmental protection. Therefore, it is urgent to develop an environmentally friendly humidity indicator card that does not contain metal elements and / or halogen elements, and the environmentally friendly humidity indicator card has high sensitivity and high color discrimination. Summary of the invention

[0005] The main purpose of the present invention is to provide a humidity indicating composition, which does not contain metal elements and / or halogen elements and is applied to a humidity indicating card to improve the sensitivity and color discrimination of the humidity indicating card.

[0006] The present invention also provides a humidity indicator card, comprising the humidity indicator composition, so the humidity indicator card does not contain metal elements and halogen elements, and has high sensitivity and high color discrimination.

[0007] The invention also provides a method for preparing a humidity indicator card, which can be used to prepare the humidity indicator card, and has simple process and low cost.

[0008] In a first aspect, the present invention provides a humidity indicating composition, comprising, by mass percentage: 15% to 35% buffer, 1% to 15% acid-base indicator, 0.1% to 10% antioxidant, and 40% to 65% humectant;

[0009] The buffer comprises phosphoric acid and lactic acid; the mass ratio of the phosphoric acid to the lactic acid is (2-5):1.

[0010] In the humidity indicating composition as described above, the buffer, acid-base indicator, antioxidant and moisturizer do not include metal elements and / or halogen elements.

[0011] In the humidity indicating composition as described above, the acid-base indicator comprises at least one of neutral red, bromocresol green, methyl orange, methyl red, xylenol blue, thymol blue, phenolphthalein, basic blue and thymolphthalein.

[0012] In the humidity indicating composition as described above, the antioxidant comprises at least one of sodium formate, ascorbic acid and citric acid.

[0013] In the humidity indicating composition as described above, the humectant comprises at least one of glycerin, propylene glycol and ethylene glycol.

[0014] In a second aspect, the present invention provides a humidity indicator card, comprising the humidity indicating composition as described above.

[0015] The humidity indicator card as described above further comprises a protective layer;

[0016] The protective layer includes a transparent polymer layer, and the transparent polymer layer includes at least one of polyethylene, polypropylene, and polyethylene terephthalate.

[0017] In a third aspect, the present invention provides a method for preparing the humidity indicator card as described above, comprising the following steps:

[0018] 1) drying a substrate including a humidity indicating composition and a solvent to obtain a first intermediate;

[0019] 2) Through heat-pressing laminating treatment, a transparent polymer layer is laminated on at least one surface of the first intermediate to obtain the humidity indicator card.

[0020] In the above-mentioned method for preparing the humidity indicator card, the solvent includes at least one of water, methanol, ethanol, propanol and acetone; preferably includes water and ethanol.

[0021] The method for preparing the humidity indicator card as described above, wherein the drying process comprises a heat drying process and / or a vacuum freeze drying process;

[0022] The heat drying treatment is performed at a temperature of 50°C to 60°C and a time of 1h to 5h;

[0023] The vacuum freeze drying process is performed at a temperature of -50°C to -40°C, a pressure of 25Pa to 40Pa, and a time of 3min to 5min;

[0024] And / or, the temperature of the hot pressing bonding treatment is 120° C. to 160° C., the pressure is 0.1 MPa to 0.5 MPa, and the time is 1 s to 5 s.

[0025] The humidity indicating composition provided by the present invention does not include metal elements and / or halogen elements, and includes phosphoric acid and lactic acid in a mass ratio of (2-5):1, which can provide a stable pH environment and can effectively adjust the pH value when the humidity changes. Since phosphoric acid and lactic acid have different acid strengths and buffering capacities, the combination of the two can maintain appropriate changes in the pH value within a wider humidity range, thereby making the color change of the acid-base indicator more obvious and more sensitive. The humidity indicating composition is applied to a humidity indicator card to improve the sensitivity and color discrimination of the humidity indicator card. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the related art, in order to avoid the use of cobalt chloride, humidity indicator cards usually use metal elements or halogen elements to achieve color changes in different humidity ranges. However, for environmental protection reasons, it is urgent to develop an environmentally friendly humidity indicator card that does not contain metal elements and halogen elements. The environmentally friendly humidity indicator card must not only meet the requirements of high sensitivity, but also require high color discrimination so that it can be effectively used in a variety of application scenarios. The solution to this technical problem has become the current research focus.

[0028] Based on this, in the first aspect, the present invention provides a humidity indicating composition, which comprises, by mass percentage: 15% to 35% buffer, 1% to 15% acid-base indicator, 0.1% to 10% antioxidant, and 40% to 65% humectant.

[0029] The buffer includes phosphoric acid and lactic acid; the mass ratio of phosphoric acid to lactic acid is (2-5):1, for example, it can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1 or a range consisting of any two of them.

[0030] Exemplarily, the mass percentage of the buffer can be 15%, 20%, 25%, 30%, 35% or a range consisting of any two of them. The mass percentage of the acid-base indicator can be 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15% or a range consisting of any two of them. The mass percentage of the antioxidant can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two of them. The mass percentage of the wetting agent can be 40%, 45%, 50%, 55%, 60%, 65% or a range consisting of any two of them.

[0031] The humidity indicating composition provided by the invention does not contain metal elements and halogen elements, and is applied to a humidity indicating card to improve the sensitivity and color discrimination of the humidity indicating card.

[0032] The humidity indicating composition provided by the present invention includes phosphoric acid and lactic acid in a mass ratio of (2-5):1. After phosphoric acid (polyinorganic acid) and lactic acid (single organic acid) are combined, a wider pH range (acidic to weakly acidic) can be covered, and it is suitable for a variety of environments. This system provides a stable buffering effect in a weakly acidic environment (pH value is 2-6), which can meet the needs of most humidity indications, industries and food storage. The composite system of phosphoric acid and lactic acid can optimize the color change sensitivity of the humidity indicating dye, ensuring that the humidity indication is clearer and more accurate. Lactic acid is a natural organic acid, which is biodegradable, and will not cause heavy metal pollution or other harmful emissions to the environment after combining with phosphoric acid.

[0033] The mass percentage of the acid-base indicator in the humidity indicating composition of the present invention is 1% to 15%, and the acid-base indicator can show color changes according to pH changes caused by humidity. By selecting a suitable acid-base indicator, it can be ensured that the color changes quickly and significantly when the humidity changes. This significant color change improves the color discrimination of the humidity indicator card, making it easier to identify the humidity level.

[0034] The mass percentage of the antioxidant in the humidity indicating composition of the present invention is 0.1% to 10%, which helps to prevent the performance degradation of the humidity indicating composition due to oxidation during storage and use. The presence of the antioxidant ensures the stability and reliability of the humidity indicator card in long-term use, thereby maintaining its sensitivity and color discrimination.

[0035] The mass percentage of the humectant in the humidity indicating composition of the present invention is 40% to 60%, which is used to maintain the moisture content of the humidity indicating composition, not only ensuring the stability of the humidity indicating composition under different environments, but also enabling it to quickly respond to humidity changes. The appropriate proportion of the humectant ensures that the humidity indicator card can respond in time when the humidity changes and presents obvious color changes.

[0036] The humidity indicating composition provided by the present invention does not include metal elements and / or halogen elements, and each component in the composition is cheap and easily available. The composition includes phosphoric acid and lactic acid in a mass ratio of (2-5):1. After phosphoric acid (polyinorganic acid) and lactic acid (single organic acid) are combined, a wider pH range (acidic to weakly acidic) can be covered, and it is suitable for a variety of environments. This system provides a stable buffering effect in a weakly acidic environment (pH value is 2-6), which can meet the needs of most humidity indications, industries and food storage. The composite system of phosphoric acid and lactic acid can optimize the color change sensitivity of the humidity indicating dye, ensuring that the humidity indication is clearer and more accurate. Lactic acid is a natural organic acid, biodegradable, and will not cause heavy metal pollution or other harmful emissions to the environment after combining with phosphoric acid.

[0037] In some embodiments of the present invention, the buffer, acid-base indicator, antioxidant, and moisturizer do not include metal elements and / or halogen elements, which can reduce potential pollution to the environment, comply with increasingly stringent environmental regulations and standards, reduce the impact on the ecosystem, and reduce the complexity of waste disposal. Under the premise of environmental protection, the sensitivity and color discrimination of the humidity indicator card can be improved.

[0038] In some embodiments of the present invention, the acid-base indicator includes at least one of neutral red, bromocresol green, methyl orange, methyl red, xylenol blue, thymol blue, phenolphthalein, basic blue, and thymolphthalein.

[0039] By choosing the right acid-base indicator, precise color indication can be achieved for specific temperature changes. These acid-base indicators usually show obvious color changes when the pH changes, making the humidity indicator card highly color-distinguished and helping to quickly and accurately determine humidity levels. In addition, these acid-base indicators are very sensitive to pH changes and can react quickly to small changes in humidity. This high sensitivity ensures the reliable performance of the humidity indicator card under various environmental conditions.

[0040] In some embodiments of the present invention, the antioxidant includes at least one of sodium formate, ascorbic acid, and citric acid.

[0041] The antioxidant in the present invention can effectively prevent other components in the composition from being oxidized during storage and use, which helps to maintain the chemical stability and functionality of the humidity indicator card and prolong its service life. In addition, the antioxidant has low toxicity and high safety, which meets the requirements of environmental protection and sustainable development.

[0042] In some embodiments of the present invention, the humectant includes at least one of glycerin, propylene glycol, and ethylene glycol.

[0043] The above-mentioned humectant in the present invention includes polyols, which are generally used to increase the hygroscopicity of the humidity indicating composition, so that it can quickly absorb and retain moisture. This type of compound has multiple hydroxyl groups and can form hydrogen bonds with water molecules, thereby increasing the response speed of the humidity indication. It helps the humidity indicator card maintain a stable moisture content under different humidity conditions, thereby ensuring its sensitivity and accuracy. In addition, the polyol is also beneficial to maintain the physical stability of the humidity indicating composition, preventing it from excessive shrinkage or expansion during moisture absorption or drying.

[0044] In a second aspect, the present invention provides a humidity indicator card, comprising the humidity indicating composition as described above.

[0045] The humidity indicator card of the present invention comprises the humidity indicating composition, so the humidity indicator card does not contain metal elements and halogen elements, and has high sensitivity and high color discrimination.

[0046] In some embodiments of the present invention, the humidity indicator card further comprises a protective layer; the protective layer comprises a transparent polymer layer, and the transparent polymer layer comprises at least one of polyethylene, polypropylene, and polyethylene terephthalate.

[0047] The humidity indicator card of the present invention further includes a protective layer, which is made of a transparent polymer material, such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), so that the color change of the humidity indicator card can be clearly observed without affecting its function. The existence of the protective layer can ensure that the humidity indicator card has good waterproof and dustproof functions, while ensuring air permeability, so that water vapor can enter the humidity indicator card without affecting the detection of humidity changes.

[0048] In a third aspect, the present invention provides a method for preparing the humidity indicator card as described above, comprising the following steps:

[0049] 1) drying a substrate including a humidity indicating composition and a solvent to obtain a first intermediate;

[0050] 2) Through heat-pressing laminating treatment, the transparent polymer layer is laminated on at least one surface of the first intermediate to obtain a humidity indicator card.

[0051] In step 1), the substrate may be white blotting paper with a thickness of less than 1 mm. Specifically, the humidity indicator composition may be dissolved in a solvent and dispersed evenly to obtain a composition solution, and the composition solution may be dispersed on the substrate or part of the substrate in the form of smearing or dripping to obtain a first intermediate. The dripping amount may be 5 μL / time, 10 μL / time, or 15 μL / time, and the dripping amount is determined according to the thickness of the substrate, otherwise, it is not conducive to observing the color change of the humidity indicator card.

[0052] In step 2), a thin transparent polymer film, such as PE, PP or PET film, is prepared with a thickness within tens of μm, and the polymer film is cut to a size suitable for the indicator card. A heat press is used to heat-press the transparent polymer film and the first intermediate at appropriate temperature and pressure to obtain a humidity indicator card.

[0053] The preparation method of the humidity indicator card provided by the present invention can prepare the humidity indicator card with high sensitivity and high color discrimination, and the raw materials are cheap and easily available, and the process is simple.

[0054] In some embodiments of the present invention, the solvent includes at least one of water, methanol, ethanol, propanol, and acetone; preferably includes water and ethanol.

[0055] In the preparation method of the humidity indicator card of the present invention, the solvent is used to adjust the viscosity and dispersibility of the humidity indicator composition, thereby ensuring the uniformity and stability of its dispersion.

[0056] In the mixed solution of ethanol and water, ethanol and water can be mixed in a volume ratio of 7:3. The ethanol can be commercially available ethanol with a purity of more than 95%, and the water can be deionized water or distilled water.

[0057] In some embodiments of the present invention, the drying process comprises a thermal drying process and / or a vacuum freeze drying process.

[0058] The temperature of the heat drying treatment is 50°C~60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C or a range consisting of any two thereof; the time is 1h~5h, for example, it can be 1h, 2h, 3h, 4h, 5h or a range consisting of any two thereof.

[0059] The temperature of the vacuum freeze-drying treatment is -50°C to -40°C, for example, it can be -50°C, -49°C, -48°C, -47°C, -46°C, -45°C, -44°C, -43°C, -42°C, -41°C, -40°C or a range consisting of any two of them; the pressure is 25Pa to 40Pa, for example, it can be 25Pa, 27Pa, 30Pa, 32Pa, 35Pa, 38Pa, 40Pa or a range consisting of any two of them; the time is 3min to 5min, for example, it can be 3min, 3.5min, 4min, 4.5min, 5min or a range consisting of any two of them.

[0060] In some embodiments, the temperature of the hot pressing bonding treatment is 120°C~160°C, for example, it can be 120°C, 130°C, 140°C, 150°C, 160°C or a range consisting of any two thereof; the pressure is 0.1MPa~0.5MPa, for example, it can be 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa or a range consisting of any two thereof; the time is 1s~5s, for example, it can be 1s, 2s, 3s, 4s, 5s or a range consisting of any two thereof.

[0061] In the heat drying treatment of the present invention, the substrate including the humidity indicating composition and the solvent, i.e., the white blotting paper carrying the humidity indicating composition and the solvent, is placed in an environment with a relative humidity of less than 15% (e.g., a dryer, a constant temperature and humidity chamber, etc.), and dried at 50°C to 60°C for 1h to 5h to obtain the first intermediate. The temperature and time of the heat drying treatment can effectively remove the solvent without causing the decomposition of the substances in the humidity indicating composition, thereby ensuring the chemical stability of the humidity indicator card.

[0062] The vacuum freeze drying process of the present invention can be performed by placing the substrate including the humidity indicating composition and the solvent, that is, the white blotting paper carrying the humidity indicating composition and the solvent, into a vacuum freeze drying machine, maintaining the temperature at -50°C to -40°C, the pressure at 25Pa to 40Pa, and the time at 3min to 5min, to obtain the first intermediate. The temperature, pressure and time of the vacuum freeze drying process can minimize the damage to the heat-sensitive components and maintain the activity and structural integrity of the chemical components of each substance in the humidity indicating composition.

[0063] The temperature and time of the hot pressing laminating treatment in the present invention are within the above range, which can effectively laminate the protective layer and the first intermediate together, ensuring the structural integrity and durability of the humidity indicator card. Specifically, when the protective layer is a polyethylene (PE) film, the temperature of the hot pressing laminating treatment can be 120°C to 140°C, the pressure can be 0.1MPa to 0.3MPa, and the time can be 1s to 3s; when the protective layer is a polypropylene (PP) film, the temperature of the hot pressing laminating treatment can be 130°C to 150°C, the pressure can be 0.1MPa to 0.3MPa, and the time can be 1s to 3s; when the protective layer is a polyethylene terephthalate (PET) film, the temperature of the hot pressing laminating treatment can be 130°C to 160°C, the pressure can be 0.2MPa to 0.5MPa, and the time can be 2s to 5s.

[0064] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0065] Example 1

[0066] The preparation method of the humidity indicator card of this embodiment comprises the following steps:

[0067] 1) placing a humidity indicating composition and a mixed solution of 3.0 mL of ethanol and water in a glass container, and stirring them evenly to obtain a composition solution; wherein the humidity indicating composition comprises, by mass percentage, 30% buffer, 10% neutral red, 5% ascorbic acid, and 55% propylene glycol, the buffer comprises phosphoric acid and lactic acid, and the mass ratio of phosphoric acid to lactic acid is 3:1.

[0068] 2) The composition solution is evenly applied once on a 0.5 mm thick white blotting paper, placed in a constant temperature and humidity chamber with a relative humidity of less than 15%, and dried at 50° C. for 3 h to obtain a first intermediate.

[0069] 3) Using a hot press machine, the polyethylene (PE) film and the first intermediate are hot-pressed and laminated at 130° C. and 0.2 MPa for 1 second to obtain a humidity indicator card.

[0070] The color development of the humidity indicator card at different humidity levels is shown in Table 1.

[0071] Table 1

[0072]

[0073] Example 2

[0074] The preparation method of the humidity indicator card of this embodiment comprises the following steps:

[0075] 1) placing a humidity indicating composition and a mixed solution of 3.0 mL of ethanol and water in a glass container, and stirring them evenly to obtain a composition solution; wherein the humidity indicating composition comprises, by mass percentage, 25% buffer, 5% neutral red, 8% sodium formate, and 62% propylene glycol, the buffer comprises phosphoric acid and lactic acid, and the mass ratio of phosphoric acid to lactic acid is 2:1.

[0076] 2) The composition solution is evenly applied once on a 0.5 mm thick white blotting paper, and placed in a vacuum freeze dryer, maintained at -40°C and a vacuum degree of 25 Pa, and dried for 3.5 minutes to obtain a first intermediate.

[0077] 3) Using a hot press machine, the polypropylene (PP) film and the first intermediate are hot-pressed and laminated at 130° C. and 0.1 MPa for 5 seconds to obtain a humidity indicator card.

[0078] The color development of the humidity indicator card at different humidity levels is shown in Table 2.

[0079] Table 2

[0080]

[0081] Example 3

[0082] The preparation method of the humidity indicator card of this embodiment comprises the following steps:

[0083] 1) placing a humidity indicating composition and a mixed solution of 3.0 mL of ethanol and water in a glass container, and stirring them evenly to obtain a composition solution; wherein the humidity indicating composition comprises, by mass percentage, 23% buffer, 8% neutral red, 9% citric acid, and 60% ethylene glycol, the buffer comprises phosphoric acid and lactic acid, and the mass ratio of phosphoric acid to lactic acid is 5:1.

[0084] 2) 10 μL of the composition solution was dropped onto 0.5 mm thick white blotting paper, placed in a constant temperature and humidity chamber with a relative humidity of less than 15%, and dried at 60° C. for 1 h to obtain a first intermediate.

[0085] 3) Using a hot press machine, the polyethylene terephthalate (PET) film and the first intermediate are hot-pressed and laminated at 160° C. and 0.5 MPa for 3 seconds to obtain a humidity indicator card.

[0086] The color development of the humidity indicator card at different humidity levels is shown in Table 3.

[0087] Table 3

[0088]

[0089] Example 4

[0090] The preparation method of the humidity indicator card of this embodiment comprises the following steps:

[0091] 1) placing a humidity indicating composition and a mixed solution of 3.0 mL of ethanol and water in a glass container, and stirring them evenly to obtain a composition solution; wherein the humidity indicating composition comprises, by mass percentage, 35% of a buffer, 13% of bromocresol green, 7% of sodium formate, and 45% of propylene glycol, the buffer comprises phosphoric acid and lactic acid, and the mass ratio of phosphoric acid to lactic acid is 5:1.

[0092] 2) 10 μL of the composition solution was dropped onto a 0.5 mm thick white blotting paper, and the paper was placed in a vacuum freeze dryer, maintained at -50°C and a vacuum degree of 40 Pa, and dried for 5 minutes to obtain a first intermediate.

[0093] 3) Using a hot press machine, the polypropylene (PP) film and the first intermediate are hot-pressed and laminated at 120° C. and 0.1 MPa for 3 seconds to obtain a humidity indicator card.

[0094] The color development of the humidity indicator card at different humidity levels is shown in Table 4.

[0095] Table 4

[0096]

[0097] Example 5

[0098] The preparation method of the humidity indicator card of Example 5 is basically the same as that of Example 1, except that the mass ratio of phosphoric acid to lactic acid is changed to 2:1. The color development of the humidity indicator card at different humidity is shown in Table 5.

[0099] Table 5

[0100]

[0101] Example 6

[0102] The preparation method of the humidity indicator card in Example 6 is basically the same as that in Example 1, except that the mass ratio of phosphoric acid to lactic acid is changed to 5:1. The color development of the humidity indicator card at different humidity levels is shown in Table 6.

[0103] Table 6

[0104]

[0105] Comparative Example 1

[0106] The preparation method of the humidity indicator card of Comparative Example 1 is basically the same as that of Example 1, except that the mass ratio of phosphoric acid to lactic acid is changed to 0.5:1. The color development of the humidity indicator card at different humidity is shown in Table 7.

[0107] Table 7

[0108]

[0109] Comparative Example 2

[0110] The preparation method of the humidity indicator card of Comparative Example 2 is basically the same as that of Example 1, except that the mass ratio of phosphoric acid to lactic acid is changed to 8:1. The color development of the humidity indicator card at different humidity is shown in Table 8.

[0111] Table 8

[0112]

[0113] Comparative Example 3

[0114] The preparation method of the humidity indicator card of Comparative Example 3 is basically the same as that of Example 1, except that phosphoric acid is used as a buffer. The color development of the humidity indicator card at different humidity levels is shown in Table 9.

[0115] Table 9

[0116]

[0117] Comparative Example 4

[0118] The preparation method of the humidity indicator card of Comparative Example 4 is basically the same as that of Example 1, except that lactic acid is used as a buffer. The color development of the humidity indicator card at different humidity levels is shown in Table 10.

[0119] Table 10

[0120]

[0121] Comparative Example 5

[0122] The preparation method of the humidity indicator card of Comparative Example 5 is basically the same as that of Example 1, except that sulfuric acid is used as a buffer. The color development of the humidity indicator card at different humidity levels is shown in Table 11.

[0123] Table 11

[0124]

[0125] Comparative Example 6

[0126] The preparation method of the humidity indicator card of Comparative Example 6 is basically the same as that of Example 1, except that hydrochloric acid is used as a buffer. The color development of the humidity indicator card at different humidity levels is shown in Table 12.

[0127] Table 12

[0128]

[0129] As can be seen from Tables 1-12, compared with the comparative example, the humidity indicating composition provided by the present invention does not include metal elements and / or halogen elements, and includes phosphoric acid and lactic acid in a mass ratio of (2-5):1. After phosphoric acid (polyinorganic acid) and lactic acid (single organic acid) are combined, a wider pH range (acidic to weakly acidic) can be covered. The composite system of phosphoric acid and lactic acid can optimize the color change sensitivity of the humidity indicating dye, ensuring that the humidity indication is clearer and more accurate. The organic properties of lactic acid give it a certain hygroscopic capacity, which helps the system respond to changes in humidity faster. The humidity indicating composition is applied to the humidity indicator card to improve the sensitivity and color discrimination of the humidity indicator card.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A humidity indicating composition, characterized in that According to the mass percentage, it includes: 15%~35% buffer, 1%~15% acid-base indicator, 0.1%~10% antioxidant, 40%~65% moisturizer; The buffer comprises phosphoric acid and lactic acid; the mass ratio of the phosphoric acid to the lactic acid is (2-5):

1.

2. The humidity indicating composition according to claim 1, characterized in that The buffer, acid-base indicator, antioxidant and moisturizer do not include metal elements and / or halogen elements.

3. The humidity indicating composition according to claim 1 or 2, characterized in that: The acid-base indicator comprises at least one of neutral red, bromocresol green, methyl orange, methyl red, xylenol blue, thymol blue, phenolphthalein, basic blue and thymolphthalein.

4. The humidity indicating composition according to any one of claims 1 to 3, characterized in that The antioxidant includes at least one of sodium formate, ascorbic acid and citric acid.

5. The humidity indicating composition according to any one of claims 1 to 4, characterized in that: The moisturizing agent includes at least one of glycerin, propylene glycol and ethylene glycol.

6. A humidity indicator card, characterized in that: The invention comprises the humidity indicating composition according to any one of claims 1 to 5.

7. The humidity indicator card according to claim 6, characterized in that: It also includes a protective layer; The protective layer includes a transparent polymer layer, and the transparent polymer layer includes at least one of polyethylene, polypropylene, and polyethylene terephthalate.

8. A method for preparing a humidity indicator card according to claim 6 or 7, characterized in that: The following steps are involved: 1) drying a substrate including a humidity indicating composition and a solvent to obtain a first intermediate; 2) Through heat-pressing laminating treatment, a transparent polymer layer is laminated on at least one surface of the first intermediate to obtain the humidity indicator card.

9. The method for preparing a humidity indicator card according to claim 8, characterized in that: The solvent includes at least one of water, methanol, ethanol, propanol and acetone; preferably includes water and ethanol.

10. The method for preparing a humidity indicator card according to claim 8 or 9, characterized in that: The drying process includes heat drying process and / or vacuum freeze drying process; The heat drying treatment is performed at a temperature of 50°C to 60°C and a time of 1h to 5h; The vacuum freeze drying process is performed at a temperature of -50°C to -40°C, a pressure of 25Pa to 40Pa, and a time of 3min to 5min; And / or, the temperature of the hot pressing bonding treatment is 120° C. to 160° C., the pressure is 0.1 MPa to 0.5 MPa, and the time is 1 s to 5 s.

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