A humidity-adjusting coating, its preparation method and application in cigarette cases

Abstract

The present invention discloses a humidity-adjusting coating, a preparation method thereof, and an application in a cigarette case. After mixing diatomite evenly with a polyacrylic acid solution and a polyvinyl alcohol solution, shear emulsification is carried out to obtain an emulsion. After adding an inorganic acid catalyst to the emulsion to catalyze the esterification reaction, it is mixed evenly with a calcium chloride solution to obtain the humidity-adjusting coating. The humidity-adjusting coating has the function of adjusting the environmental humidity. It can absorb moisture in the air in a humid environment, and release its own moisture in a dry environment, thereby playing a buffering role to make the environment in a more suitable and stable humidity. Applying it to the cigarette case enables the environment inside the cigarette case to maintain a relatively stable and suitable humidity within a long time range.

Description

Technical Field

[0001] The present invention relates to a humidity - regulating coating, in particular to a humidity - regulating coating that can absorb moisture in the air in a humid environment and release its own moisture in a dry environment. The present invention also relates to a preparation method of the humidity - regulating coating and the application of the humidity - regulating coating in cigarette cartons, belonging to the technical field of cigarettes. Background Art

[0002] After the cigarette carton is opened, its barrier system is damaged, and the cigarettes inside the carton will be affected by the external environment. When the external environment is too humid, the tobacco leaves will get damp, the smoke will be dull and not fragrant, and the aroma will decline; when the external environment is too dry, the tobacco leaves will lose water, the smoke will be dry, with strong irritation and poor comfort. In order to enable consumers to maintain a good taste from the first cigarette to the last one, the cigarette carton needs to still have a certain moisture - proof and moisture - retaining ability after being opened. This requires adding materials with humidity - regulating effects inside the cigarette carton. Compared with putting humidity - regulating materials inside the cigarette carton, coating the humidity - regulating coating on the inner surface of the cigarette carton in advance is more conducive to simplifying the cigarette packing process. Summary of the Invention

[0003] Aiming at the above - mentioned technical problems existing in the prior art, the first object of the present invention is to provide a humidity - regulating coating, which has the function of regulating the environmental humidity, can absorb moisture in the air in a humid environment and release its own moisture in a dry environment, so as to play a buffering role and make the environment in a relatively suitable and stable humidity.

[0004] The second object of the present invention is to provide a preparation method of the humidity - regulating coating, which has simple operation, mild reaction conditions, low raw material cost and is conducive to large - scale production.

[0005] The third object of the present invention is to provide an application of the humidity - regulating coating. When the humidity - regulating coating is coated on the inner part of the cigarette carton, after the cigarette carton is opened, it can absorb moisture in the air in a humid environment and release its own moisture in a dry environment, so as to play a buffering role and make the environment inside the cigarette carton maintain a relatively stable and suitable humidity within a long time range, and well solve the defects that when the external environment is too humid, the tobacco leaves will get damp, the smoke will be dull and not fragrant, and the aroma will decline, and when the external environment is too dry, the tobacco leaves will lose water, the smoke will be dry, with strong irritation and poor comfort, etc., and greatly reduce the influence of the environment after the cigarette carton is opened on the quality of cigarettes.

[0006] In order to achieve the above - mentioned technical objects, the present invention provides a preparation method of a humidity - regulating coating, which comprises the following steps:

[0007] 1) Mix diatomite with polyacrylic acid solution and polyvinyl alcohol solution evenly, and then add an emulsifier for shear emulsification to obtain an emulsion;

[0008] 2) Add an inorganic acid catalyst to the emulsion to catalyze the esterification reaction to obtain an emulsion containing a reticular PVA / PAA / diatomite composite.

[0009] 3) Mix the calcium chloride solution evenly with the emulsion containing the reticular PVA / PAA / diatomite composite to obtain the product.

[0010] In the technical solution of the present invention, first, diatomite is shear-emulsified with polyacrylic acid and polyvinyl alcohol. Polyacrylic acid and polyvinyl alcohol have good hydrophilicity and can fully stretch their polymer chains in an aqueous solution. At the same time, they can play a dispersing role to promote the uniform dispersion of diatomite in the solution system. Thus, a uniform emulsion can be obtained through shear emulsification. Then, an acid catalyst is added to catalyze the esterification reaction, enabling the esterification reaction between the uniformly dispersed polyacrylic acid and polyvinyl alcohol to form an interpenetrating polymer network, while diatomite is uniformly dispersed in the polymer grid to form a reticular PVA / PAA / diatomite composite. Finally, through liquid-phase mixing, calcium chloride is loaded onto the reticular PVA / PAA / diatomite composite through the synergistic physical and chemical adsorption effect to form a humidity-adjusting coating composed of a cross-linked polymer network of polyacrylic acid and polyvinyl alcohol, calcium chloride inorganic salt, and diatomite mineral. In the humidity-adjusting coating of the technical solution of the present invention, diatomite is dispersed in the polymer grid to play a supporting role, and its rich pore structure is fully utilized to endow the coating layer with a developed pore structure inside. At the same time, some fine pores can also be formed at the junction between the inorganic mineral and the polymer network. These pore structures form good water vapor channels, increasing the effective contact area between the polymer inside the coating layer and the environment, enabling better introduction of water vapor into the material and also facilitating the diffusion of internal water vapor. The cross-linked polymer network of acrylic acid and polyvinyl alcohol contains a large number of two hydrophilic groups, carboxyl and hydroxyl, making the coating layer exhibit a high moisture absorption capacity and moisture retention performance. Calcium chloride is hygroscopic and has good water absorption performance, but its moisture absorption is prone to loss. Diatomite and the polymer network can store calcium chloride, making it not easy to lose after moisture absorption and deliquescence.

[0011] As a preferred solution, the mass ratio of the diatomite, polyacrylic acid solution, and polyvinyl alcohol solution is 5 - 8:5 - 8:105 - 115; the mass percentage concentration of the polyacrylic acid solution is 25 - 35%; the mass percentage concentration of the polyvinyl alcohol solution is 20 - 40%.

[0012] As a preferred embodiment, the polyvinyl alcohol in the polyvinyl alcohol solution is composed of 1788-type polyvinyl alcohol and 0588-type polyvinyl alcohol in a mass ratio of 10-15:15-20. In the humidity-adjusting coating of the present invention, a combination of polyvinyl alcohols with different molecular weights and degrees of alcoholysis is used. If only 0588-type polyvinyl alcohol is used, although its humidity-adjusting effect is good, when calcium chloride absorbs moisture, the free water in the composite material increases. Due to the relatively low molecular weight of 0588-type polyvinyl alcohol itself, the polymer molecular chains are prone to move, resulting in the stickiness of the material. By introducing an appropriate proportion of 1788-type polyvinyl alcohol to participate in the reaction, on the one hand, the molecular weight of the polymer can be increased, and on the other hand, molecular chains of different lengths can be prepared, enabling them to entangle better and not easily move.

[0013] As a preferred embodiment, the mass ratio of the emulsifier to the diatomaceous earth is 1-2:5-8.

[0014] As a preferred embodiment, the emulsifier is Tween 80.

[0015] As a preferred embodiment, the temperature of the esterification reaction is 85-100 °C, and the time is 3-4 h.

[0016] As a preferred embodiment, the mass percentage concentration of the calcium chloride solution is 40%-50%. An appropriate proportion of calcium chloride is introduced into the humidity-adjusting coating of the present invention. Calcium chloride mainly plays a role in quickly absorbing water. Since the humidity-adjusting rate needs to be fast after the cigarette case is opened. Calcium chloride can greatly improve the moisture absorption rate of the material. In a humid environment, it can absorb the moisture in the air and reduce the relative humidity of the environment. Part of the absorbed moisture forms a crystal hydrate with itself, and part exists in a free state in the pores of the coating. In a dry environment, the free moisture in the coating can be released into the air to increase the relative humidity of the environment.

[0017] As a preferred embodiment, the mass ratio of calcium chloride to diatomaceous earth in the calcium chloride solution is 10-15:5-8.

[0018] The inorganic acid catalyst involved in the present invention is a common inorganic acid such as hydrochloric acid.

[0019] The present invention provides a humidity-adjusting coating obtained by the preparation method.

[0020] The main components of the humidity-adjusting coating of the present invention are PVA / PAA / diatomite / calcium chloride composite. Among them, the interpenetrating cross-linked polymer network formed by the chain-like PVA and PAA through esterification reaction reduces the regularity inside the coating layer. At the same time, due to the presence of a large number of two hydrophilic groups, carboxyl and hydroxyl groups, on the cross-linked polymer network, its moisture absorption capacity is improved and it has good moisture retention performance. Diatomite itself has a porous structure and has good physical adsorption and loading functions. It fully utilizes its own developed pore structure to endow the inside of the coating layer with developed pores. At the same time, some fine pores can also be formed at the junction between the inorganic mineral and the polymer network. These pores increase the effective contact area between the polymer and the environment, can better introduce water vapor into the material interior, and are also conducive to the release of the adsorbed water vapor inside, achieving a better humidity-adjusting effect. Calcium chloride has good moisture absorption performance and can be stored in the polymer network and the pore structure of the inorganic mineral. It is not easy to lose after absorbing moisture and deliquescing.

[0021] The present invention also provides an application of the humidity-adjusting coating, which is applied to cigarette cartons.

[0022] As a preferred solution, it is coated on the inner side of the cigarette carton.

[0023] The humidity-adjusting coating provided by the present invention adopts the following specific steps:

[0024] 1) Take 10 - 15 parts of 1788-type polyvinyl alcohol (PVA) by mass fraction, 15 - 20 parts of 0588-type polyvinyl alcohol, and add them to 80 parts of deionized water. Heat to 95 °C and mechanically stir until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution.

[0025] 2) Take 5 - 8 parts of 200-mesh diatomite and 5 - 8 parts of 30% polyacrylic acid (PAA) solution, and add them to the dissolved polyvinyl alcohol solution. Mechanically stir evenly to obtain a PVA / PAA / diatomite mixture.

[0026] 3) Take 1 - 2 parts of Tween 80, dissolve it in 5 parts of deionized water as an emulsifier, and add the emulsifier to the mixture in the previous step. Increase the mechanical stirring speed and emulsify it for 10 - 20 min under the action of high shear force. After emulsification, obtain a PVA / PAA / diatomite emulsion.

[0027] 4) Add a small amount of hydrochloric acid and heat to 85 - 100 °C to carry out an esterification reaction between the hydroxyl groups on PVA and the carboxyl groups on PAA. Continue mechanical stirring for 3 - 4 h to obtain a network-structured PVA / PAA / diatomite emulsion.

[0028] 5) Take 10 - 15 parts of calcium chloride and dissolve it in 15 parts of deionized water to obtain a calcium chloride solution. Add the calcium chloride solution to the reticular PVA / PAA / diatomite emulsion and continue mechanical stirring for 1 h to fully mix them, finally obtaining the PVA / PAA / diatomite / calcium chloride coating with humidity control effect.

[0029] Compared with the current technology, the beneficial technical effects brought by the technical solution of the present invention are as follows:

[0030] 1) The humidity control coating of the present invention has a good effect of adjusting the environmental humidity. It can absorb moisture in the air in a humid environment and release its own moisture in a dry environment, thus playing a buffering role and making the environment in a more suitable humidity. The humidity control coating is formed by the crosslinking of PVA and PAA to form an interpenetrating polymer network as the matrix polymer. The interpenetrating polymer network reduces the regularity inside the humidity control coating. At the same time, due to the presence of a large number of two hydrophilic groups, carboxyl and hydroxyl groups, on the interpenetrating polymer network, the moisture absorption capacity of the humidity control coating is improved and it has a high moisture retention performance. Diatomite is in-situ compounded in the grids of the interpenetrating polymer network. It can bring its own developed pore structure into the interior of the composite material. At the same time, some fine pores can also be formed at the junction between diatomite and the polymer, increasing the contact area between the polymer and the environment. Therefore, these pores can better introduce water vapor into the interior of the humidity control coating and are also conducive to the volatilization of internal moisture, achieving a better humidity control effect. Calcium chloride is an inorganic salt with good moisture absorption performance and can be stored in the grids of the interpenetrating polymer network and the pore structure of diatomite. After absorbing moisture and deliquescing, it is not easy to lose.

[0031] 2) The humidity control coating of the present invention has a high solid content. After one-time coating and drying, more humidity control coating can be maintained on the cigarette box packaging cardboard per unit area, making the subsequent use process more convenient.

[0032] 3) The humidity control coating of the present invention has good stability and ensures no sedimentation for a long time.

[0033] 4) The preparation method of the humidity control coating of the present invention is simple in operation, mild in reaction conditions, low in raw material cost, and is conducive to large-scale production.

[0034] 5) When the humidity control coating of the present invention is coated inside the cigarette box, after the cigarette box is opened, it can absorb moisture in the air in a humid environment and release its own moisture in a dry environment, thus playing a buffering role and making the environment inside the cigarette box in a more suitable humidity, which well solves the problems that when the external environment is too humid, the tobacco leaves will get damp, the smoke will be dull and not pungent, the aroma will decline, and when the external environment is too dry, the tobacco leaves will lose water, the smoke will be dry and have a strong irritation, and the comfort is poor, greatly reducing the influence of the environment after the cigarette box is opened on the quality of cigarettes. Description of the Drawings

[0035] Figure 1 Moisture content change of cut tobacco over time under different humidity environments for the humidity-adjusting coating of Example 1.

[0036] Figure 2 Comparison of moisture absorption and moisture release properties of different humidity-adjusting coatings in contrast to Example 1. Detailed implementation manners

[0037] The following examples are intended to further illustrate the content of the present invention rather than limit the scope of protection of the claims.

[0038] Example 1

[0039] A) Take 10 parts of polyvinyl alcohol (PVA) of type 1788, 20 parts of polyvinyl alcohol of type 0588, and 80 parts of deionized water by mass fraction, heat to 95 °C, and mechanically stir until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution;

[0040] B) Take 6 parts of diatomaceous earth with 200 meshes and 6 parts of 30% polyacrylic acid (PAA) solution, add them to the dissolved polyvinyl alcohol solution, and mechanically stir evenly to obtain a PVA / PAA / diatomaceous earth mixture;

[0041] C) Take 1 part of Tween 80, dissolve it in 5 parts of deionized water as an emulsifier, add the emulsifier to the mixture in the previous step, increase the mechanical stirring speed, and emulsify it for 15 min under the action of high shear force. After emulsification, a PVA / PAA / diatomaceous earth emulsion is obtained;

[0042] D) Add a small amount of hydrochloric acid, heat to 95 °C, and carry out an esterification reaction between the hydroxyl groups on PVA and the carboxyl groups on PAA, and continue mechanical stirring for 3 h to obtain a PVA / PAA / diatomaceous earth emulsion with a network structure;

[0043] E) Take 15 parts of calcium chloride, dissolve it in 15 parts of deionized water to obtain a calcium chloride solution, add the calcium chloride solution to the PVA / PAA / diatomaceous earth emulsion with a network structure, and continue mechanical stirring for 1 h to make them fully mixed, and finally obtain a PVA / PAA / diatomaceous earth / calcium chloride coating with a humidity-adjusting effect.

[0044] Example 2

[0045] A) Take 15 parts of polyvinyl alcohol (PVA) of type 1788, 15 parts of polyvinyl alcohol of type 0588, and 80 parts of deionized water by mass fraction, heat to 95 °C, and mechanically stir until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution;

[0046] B) Take 5 parts of diatomaceous earth with a mesh size of 200 and 8 parts of 30% polyacrylic acid (PAA) solution, add them to the dissolved polyvinyl alcohol solution, and mechanically stir evenly to obtain a PVA / PAA / diatomaceous earth mixture;

[0047] C) Take 1 part of Tween 80, dissolve it in 5 parts of deionized water as an emulsifier, add the emulsifier to the mixture from the previous step, increase the mechanical stirring speed, and emulsify it under the action of high shear force for 10 min. After emulsification, a PVA / PAA / diatomaceous earth emulsion is obtained;

[0048] D) Add a small amount of hydrochloric acid and heat to 95 °C to carry out an esterification reaction between the hydroxyl groups on PVA and the carboxyl groups on PAA, and continue mechanical stirring for 3.5 h to obtain a PVA / PAA / diatomaceous earth emulsion with a network structure;

[0049] E) Take 10 parts of calcium chloride, dissolve it in 15 parts of deionized water to obtain a calcium chloride solution, add the calcium chloride solution to the PVA / PAA / diatomaceous earth emulsion with a network structure, and continue mechanical stirring for 1 h to make them fully mixed, and finally obtain a PVA / PAA / diatomaceous earth / calcium chloride coating with a humidity adjustment effect.

[0050] Example 3

[0051] A) Take 20 parts of 1788-type polyvinyl alcohol (PVA) and 10 parts of 0588-type polyvinyl alcohol by mass fraction, add them to 80 parts of deionized water, heat to 95 °C, and mechanically stir until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution;

[0052] B) Take 8 parts of diatomaceous earth with a mesh size of 200 and 5 parts of 30% polyacrylic acid (PAA) solution, add them to the dissolved polyvinyl alcohol solution, and mechanically stir evenly to obtain a PVA / PAA / diatomaceous earth mixture;

[0053] C) Take 2 parts of Tween 80, dissolve it in 5 parts of deionized water as an emulsifier, add the emulsifier to the mixture from the previous step, increase the mechanical stirring speed, and emulsify it under the action of high shear force for 20 min. After emulsification, a PVA / PAA / diatomaceous earth emulsion is obtained;

[0054] D) Add a small amount of hydrochloric acid and heat to 95 °C to carry out an esterification reaction between the hydroxyl groups on PVA and the carboxyl groups on PAA, and continue mechanical stirring for 4 h to obtain a PVA / PAA / diatomaceous earth emulsion with a network structure;

[0055] E) Take 12 parts of calcium chloride, dissolve it in 15 parts of deionized water to obtain a calcium chloride solution, add the calcium chloride solution to the PVA / PAA / diatomaceous earth emulsion with a network structure, and continue mechanical stirring for 1 h to make them fully mixed, and finally obtain a PVA / PAA / diatomaceous earth / calcium chloride coating with a humidity adjustment effect.

[0056] The humidity-adjusting coatings prepared in Examples 1 to 3 were applied to the interior of the cigarette box label paper, so that the cigarette box packaging had a humidity-adjusting effect. After the cigarette box was opened, it was placed in a constant temperature and humidity chamber at 22°C, 30% and 22°C, 80%. A certain number of cigarettes were taken at regular time intervals, and 20 cigarettes were taken within 24 hours. The moisture content of the cut tobacco was measured, and a blank control was also made at the same time. The humidity-adjusting effects of the humidity-adjusting coatings in Examples 1 to 3 were similar. Taking the humidity-adjusting effect of Example 1 as an example, the specific test results are as follows Figure 1 shown. Whether in a dry or humid environment, the change in the moisture content of the cut tobacco in the cigarette box with the humidity-adjusting material was less than that of the blank control sample. This shows that the humidity-adjusting material played a certain humidity-adjusting effect after the cigarette box was opened.

[0057] Comparative Example 1

[0058] The following three humidity-adjusting coatings were prepared as controls by the same method as in Example 1: 1) PVA / PAA / calcium chloride coating without diatomaceous earth, 2) PVA / PAA / diatomaceous earth coating without calcium chloride, 3) PVA / diatomaceous earth / calcium chloride coating prepared by physical blending. These three coatings and the PVA / PAA / diatomaceous earth / calcium chloride coating were placed in a constant temperature and humidity chamber for moisture absorption and desorption performance testing. The testing method was as follows: (a) Moisture absorption performance: The sample was placed in a constant temperature and humidity chamber at 22°C, 60% RH and equilibrated to a constant weight. Then the constant temperature and humidity chamber was adjusted to 22°C, 80% RH, and the change data of its mass over time within 48 hours was measured in the way of "dense at the front and sparse at the back", and the moisture absorption curve was plotted. (b) Desorption performance: The sample was placed in a constant temperature and humidity chamber at 22°C, 60% RH and equilibrated to a constant weight. Then the constant temperature and humidity chamber was adjusted to 22°C, 30% RH, and the change data of its mass over time within 48 hours was measured in the way of "dense at the front and sparse at the back", and the desorption curve was plotted. The test results are as follows Figure 2 shown. The addition of PVA increased the moisture absorption capacity of the material, the addition of diatomaceous earth increased the moisture desorption ability of the material, and the addition of calcium chloride greatly improved the moisture absorption and desorption performance of the humidity-adjusting material.

Claims

1. A preparation method of a humidity-regulating coating, characterized in that: It is prepared by the following steps: 1) After uniformly mixing diatomite with a polyacrylic acid solution and a polyvinyl alcohol solution, an emulsifier is added for shear emulsification to obtain an emulsion; 2) An inorganic acid catalyst is added to the emulsion to catalyze the esterification reaction to obtain an emulsion containing a network PVA / PAA / diatomite composite; 3) A calcium chloride solution is uniformly mixed with the emulsion containing the network PVA / PAA / diatomite composite to obtain the product; The mass ratio of the diatomite to the polyacrylic acid solution and the polyvinyl alcohol solution is 5-8:5-8:105-115; The mass percentage concentration of the polyacrylic acid solution is 25-35%; The mass percentage concentration of the polyvinyl alcohol solution is 20-40%; The polyvinyl alcohol in the polyvinyl alcohol solution is composed of polyvinyl alcohol of type 1788 and polyvinyl alcohol of type 0588 in a mass ratio of 10-15:15-20.

2. The preparation method of a humidity-regulating coating according to claim 1, characterized in that: The mass ratio of the emulsifier to the diatomite is 1-2:5-8.

3. The preparation method of a humidity-regulating coating according to claim 1 or 2, characterized in that: The emulsifier is Tween 80.

4. The preparation method of a humidity-regulating coating according to claim 1 or 2, characterized in that: The temperature of the esterification reaction is 85-100 °C and the time is 3-4 h.

5. The preparation method of a humidity-regulating coating according to claim 1, characterized in that: The mass percentage concentration of the calcium chloride solution is 40%-50%.

6. The preparation method of a humidity-regulating coating according to claim 1, characterized in that: The mass ratio of calcium chloride to diatomite in the calcium chloride solution is 10-15:5-8.

7. A humidity-regulating coating, characterized in that: It is obtained by the preparation method according to any one of claims 1-6.

8. The application of the humidity-regulating coating according to claim 7, characterized in that: It is applied to cigarette cartons.

9. The application of the humidity-regulating coating according to claim 8, characterized in that: It is coated on the inner side of cigarette cartons.

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