Silica gel desiccant tablet

Abstract

The invention discloses a silica gel desiccant tablet and a preparation method of the silica gel desiccant tablet. The silica gel desiccant tablet comprises: 60-65% of silica gel powder with a particle size of 200-400 meshes; 25 to 30% of a powdery bentonite; 1.5 to 2% of magnesium stearate; 5 to 10% of a water soluble polymer; and 200 ml of distilled water. The diameters of the tablets are 9 mm, 11 mm, 12 mm and 16 mm; and the height is 5mm. The tablet is obtained in a mechanically stable form without affecting the hygroscopic properties. The silica gel desiccant tablet shows the maximum moisture absorption capacity of 22.8% at the temperature of 25 DEG C and the relative humidity of 80% after being exposed in a closed space for 24 hours.

Description

Technical Field

[0001] The present invention relates to a silica gel desiccant composition, and more particularly to a silica gel desiccant tablet. Background Art

[0002] The shelf life of pharmaceuticals, nutraceuticals and foods in packaged form is affected by a variety of factors including microbial or fungal contamination. In the pharmaceutical, nutraceutical and food industries, desiccants and dehumidifiers are always needed to keep the packaging of the products free from moisture. The most common desiccants on the market include silica gel, activated carbon, calcium chloride, activated alumina, montmorillonite clay and different types of molecular sieves.

[0003] The desiccants available on the market are mainly in the form of granules, beads or pellets enclosed in bags and cans. Dai Xinhua's patent application WO2009026755A1 discloses a silica desiccant with silica powder and starch. Hekalihab M's patent application WO1997032663A1 describes a desiccant-entrained polymer, wherein the desiccant is located inside the polymer structure; and a method for preparing such a polymer. Peetaa Hentsureru et al.'s Japanese patent application JPH0347513A discloses a desiccant tablet coated with a coating material that does not reduce the drying rate and drying capacity.

[0004] Therefore, forming a desiccant in a shaped form requires coating with a polymeric agent and high temperature processing. Available desiccant is in granular form, which has the disadvantages of dust spillage and subsequent contamination of pharmaceuticals and nutraceuticals. There is a need for a shaped form of desiccant that is mechanically stable without compromising hygroscopic properties. Summary of the invention

[0005] The present invention describes a silica gel desiccant tablet, which includes: 60 to 65% of silica gel powder with a particle size of 200 to 400 meshes; 25 to 30% of powdered bentonite with a particle size of 200 to 400 meshes; 1.5 to 2% of magnesium stearate; 5 to 10% of a water-soluble polymer; and 200 ml of distilled water.

[0006] The silica gel desiccant tablets specifically include: 70 gm of powdered silica gel with a particle size of 200 to 400 meshes; 30 gm of bentonite with a particle size of 200 to 400 meshes; 2 gm of magnesium stearate; 10 gm of polyvinyl alcohol and 300 ml of distilled water.

[0007] The present invention also describes a method for preparing a silica gel desiccant tablet, which comprises: mixing 60 to 65% of silica gel powder with a particle size of 200 to 400 meshes with 25 to 30% of powdered bentonite with a particle size of 200 to 400 meshes and 1.5 to 2% of magnesium stearate to form a silica gel mixture; then dissolving 5 to 10% of a water-soluble polymer in 200 ml of distilled water and heating at a first preset temperature for a first preset time; cooling the polymer solution to a second preset temperature and maintaining it for a second preset time; mixing the polymer solution into the above-mentioned silica gel mixture under continuous stirring; adding 200 ml of distilled water to the mixture to form a uniform slurry; drying the slurry at a third preset temperature for a third preset time to obtain a dry mixture containing 20% ​​moisture; pressing the dry mixture at a preset pressure to form tablets; and further heating the tablets to remove residual moisture.

[0008] In this method of the present invention, a water-soluble polymer is dissolved in 200 ml of distilled water and heated at 60° C. for 1 hour; the polymer solution is cooled to room temperature for 1.5 hours; the slurry is dried at 110° C. for 2 hours to obtain a dry mixture containing 20% ​​moisture; and the dry mixture is pressed at a pressure between 12 and 17 KN to form tablets.

[0009] The preparation method of silica gel desiccant tablets having a unit amount of silica gel desiccant composition comprises: mixing 70 g of powdered silica gel with a particle size of 200 to 400 meshes, 30 g of bentonite with a particle size of 200 to 400 meshes, and 2 g of magnesium stearate in a laboratory mixer to form a silica gel mixture; dissolving 10 g of polyvinyl alcohol in 100 ml of distilled water and heating at 60° C. for 1 hour; cooling the polymer solution at room temperature for 1.5 hours; adding the PVA solution to the silica gel mixture under continuous stirring; ; adding 200 ml of distilled water to the mixture to form a uniform slurry; drying the slurry at 110° C. for 2 hours to obtain a semi-dried mixture containing 20% ​​moisture, and passing the mixture through an 18-mesh sieve; pressing the dry mixture in a tablet press at a pressure of 15 KN to form tablets; and further heating the tablets to 110° C. at a heating rate of 40-70° C. for 1 hour, and then keeping at 70° C. for 30 minutes; then heating at a heating rate of 70-110° C. for 1 hour, and keeping at 110° C. for 30 minutes.

[0010] Silica gel desiccant tablets showed a maximum moisture absorption capacity of 22.8% at 25°C and 80% relative humidity after exposure in a closed space for 24 hours. DETAILED DESCRIPTION

[0011] The present invention relates to a silica gel desiccant composition compressed in tablet form.

[0012] As described below in preferred embodiments, the present invention achieves the above-mentioned objects of the present invention and overcomes the problems and disadvantages associated with the prior art, techniques and methods.

[0013] All materials used herein were either purchased commercially as described herein or prepared from commercially purchased materials as described herein.

[0014] Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to specific structures of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.

[0015] The “preferred embodiment” mentioned in the specification refers to a specific feature, structure, characteristic or function described in detail, thereby omitting known constructions and functions in order to clearly describe the present invention.

[0016] According to the present invention, the silica gel desiccant tablet comprises:

[0017] a) Silica gel powder;

[0018] b) Powdered bentonite;

[0019] c) magnesium stearate;

[0020] d) adhesives; and

[0021] e) Distilled water.

[0022] According to a preferred embodiment, the silica gel desiccant tablet of the present invention comprises:

[0023] a) 60 to 65% silica gel powder;

[0024] b) 25 to 30% of powdered bentonite;

[0025] c) 1.5 to 2% magnesium stearate;

[0026] d) 5 to 10% of a water-soluble polymer; and

[0027] e) 200 ml of distilled water.

[0028] In this preferred embodiment, the particle size of the silica gel powder is between 200 and 400 meshes; more preferably between 250 and 320 meshes.

[0029] The particle size of the silica gel powder enables uniform compression of the tablets. Furthermore, a reduction in the particle size results in a reduction in the porosity and ultimately in a reduction in the hygroscopic properties of the final product. The particle size is selected in such a way that the porosity of the silica gel remains intact during the synthesis steps and in the final product.

[0030] In a preferred embodiment, the binder is selected from water-soluble polymers including polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), polyacrylic acid (PAA), polyacrylamide, polyoxazoline, polyphosphate and polyphosphazene.

[0031] Polyvinyl alcohol (PVA) was chosen as the binder because the polymer is easily soluble and can bind the silica gel particles firmly.

[0032] In a preferred embodiment, the particle size of the powdered bentonite is the same as that of the silica gel, that is, the particle size is between 200 and 400 meshes.

[0033] Now, a preferred method for preparing silica gel desiccant tablets according to the present invention is disclosed. The process comprises:

[0034] a) thoroughly mixing 60 to 65% of silica gel powder having a particle size of 200 to 400 meshes with about 25 to 30% of powdered bentonite having a particle size of 200 to 400 meshes and 1.5 to 2% of magnesium stearate to form a silica gel mixture;

[0035] b) dissolving 5 to 10% of a water-soluble polymer in 200 ml of distilled water and heating at a first preset temperature for a first preset time;

[0036] c) cooling the polymer solution to a second preset temperature and for a second preset time;

[0037] d) mixing the polymer solution into the silica gel mixture under continuous stirring;

[0038] e) adding 200 ml of distilled water to the mixture to form a uniform slurry;

[0039] f) drying the slurry at a third predetermined temperature for a third predetermined time to obtain a dry mixture containing about 20% moisture;

[0040] g) compressing the dry mixture at a predetermined pressure to form a tablet; and

[0041] h) The tablets are further heated to remove residual moisture.

[0042] The detailed steps of the preparation method of the above silica gel desiccant tablets are as follows:

[0043] In step b), the first preset temperature is 60° C., and the first preset time is 1 hour.

[0044] In step c), the second preset temperature is room temperature, and the second preset time is 1.5 hours.

[0045] In step f), the third preset temperature is 110° C., and the third preset time is 2 hours.

[0046] In step g), the preset pressure is between 12 and 17 KN.

[0047] According to the present invention, heating the tablet removes any residual moisture and provides the tablet with maximum mechanical strength. The ingredients such as silica gel, bentonite and polyvinyl alcohol are uniformly mixed to obtain optimal properties. The 20% moisture content within the tablet during tableting can remove the moisture within the tablet pores. In addition, during the dehumidification process, the development of the internal channels of the tablet ensures the hygroscopic sites of the dry tablet.

[0048] In addition, tablets with various sizes are prepared according to the required adsorption performance. The diameters of the tablets are 9 mm, 11 mm, 12 mm and 16 mm; the heights are between 3.5 mm and 6.5 mm.

[0049] Example:

[0050] Only a few embodiments and implementations are disclosed. Variations, modifications and enhancements may be made to the described embodiments and implementations and other implementations based on what is disclosed.

[0051] The following examples are set forth and illustrate different amounts and types of reactants and reaction conditions that can be used to implement the present disclosure. However, it is apparent that the present disclosure can be implemented with other amounts and types of reactants and reaction conditions that are different from those used in the examples, and that the resulting devices have a variety of different properties and uses, as disclosed above and indicated below.

[0052] Example 1: Silica gel desiccant tablets having a unit amount of silica gel desiccant composition:

[0053] The silica gel desiccant tablet comprises:

[0054] 1) 70 gm of powdered silica gel with a particle size of 200 to 400 mesh;

[0055] 2) 30 gm of bentonite with a particle size of 200 to 400 mesh;

[0056] 3) 2 g of magnesium stearate;

[0057] 4) 10 gm of polyvinyl alcohol; and

[0058] 5) 300ml of distilled water.

[0059] The tablet specifications are as follows:

[0060]

[0061] Table 1: Tablet specifications

[0062] Example 2: Preparation method of silica gel desiccant tablets having a unit amount of silica gel desiccant composition:

[0063] The preparation method of silica gel desiccant tablets is as follows:

[0064] 1) 70 g of powdered silica gel with a particle size of 200 to 400 mesh, 30 g of bentonite with a particle size of 200 to 400 mesh, and 2 g of magnesium stearate were mixed in a laboratory blender to form a silica gel mixture;

[0065] 2) Dissolve 10 g of polyvinyl alcohol in 100 ml of distilled water and heat at 60°C for 1 hour;

[0066] 3) cooling the polymer solution at room temperature for about 1.5 hours;

[0067] 4) Add the PVA solution to the silica gel mixture under continuous stirring;

[0068] 5) adding about 200 ml of distilled water to the mixture to form a uniform slurry;

[0069] 6) drying the slurry at 110° C. for about 2 hours to obtain a semi-dried mixture containing 20% ​​water, and passing the mixture through an 18-mesh sieve;

[0070] 7) compressing the dry mixture in a tablet press at a pressure of 15 KN to form tablets; and

[0071] 8) The tablets were further heated to 110°C at a heating rate of 40-70°C for 1 hour, and then at 70

[0072] ℃ for 30 minutes; then increase the temperature at a rate of 70-110℃ for 1 hour and continue at 110℃

[0073] Keep it on for 30 minutes.

[0074] Example 3: Moisture absorption capacity of silica gel desiccant tablets:

[0075] 3.1: Determination of the moisture absorption capacity of silica gel desiccant tablets

[0076] Record the weight of the silica gel sheet as M1. The silica gel sheet is then stored in a humidity chamber at 80% RH and 25°C. The silica gel sheet is removed from the humidity chamber after a specific time interval and the weight reading is recorded (M2). This process is continued until a constant mass is observed. The weight increase over time is recorded until equilibrium is reached, where the difference between two consecutive weighings does not exceed 3 mg / g of the substance used. The second weighing is performed after an additional 3±1 hour of storage under the desired temperature and humidity conditions.

[0077] 3.2: Determination formula of moisture absorption capacity of silica gel desiccant tablets

[0078] The moisture absorption capacity was calculated as the % weight increase relative to the initial sample weight using the following formula.

[0079] calculate:

[0080] Moisture absorption capacity (MAC) % = [(M2-M1) / M1]*100

[0081] in,

[0082] M2 = weight of silica gel sheet after adsorption

[0083] M1=weight of silica gel sheet before adsorption

[0084] 3.3: Determination results of moisture absorption capacity of silica gel desiccant tablets

[0085] Silica gel desiccant tablets showed a maximum moisture absorption capacity of 32% at 25°C and 80% relative humidity after exposure in a closed space for 24 hours.

[0086] Example 4: Moisture absorption capacity based on tablet size:

[0087] Tablets of different sizes (9x5 mm, 11x5 mm, 12x5 mm and 16x5 mm) were prepared to observe the effect of increasing diameter on the moisture absorption capacity of the tablets.

[0088] Tablet number diameter high MAC at 80% RH & 25° 1 9mm 5mm 22.0％ 2 11mm 5mm 21.8％ 3 12mm 5mm 22.2％ 4 16mm 5mm 22.8％

[0089] Table 2: Hygroscopicity of tablets

[0090] The final results showed that there was no significant difference in the hygroscopic properties of the tablet compositions. The specific weight gain percentage was proportional to the observed tablet content.

[0091] In view of the following detailed description of some embodiments, these and other embodiments will be obvious to those skilled in the art and others. However, it should be understood that the summary and specific embodiments only show some examples of various embodiments and are not intended to limit the claimed invention.

[0092] The silica gel desiccant tablets of the present invention do not need to be embedded in a polymer material to form a shaped tablet. In addition, the silica gel desiccant tablets do not require high temperature treatment during synthesis. The tablets are obtained in a mechanically stable form without affecting the hygroscopic properties. Tablets of various sizes can be prepared according to the required adsorption properties. The maximum hygroscopic capacity of the silica gel desiccant tablets at 25°C and 80% relative humidity is 22.8%. It is the hygroscopic capacity contributed by the 70% silica gel content in each tablet. Therefore, the silica gel content and ultimately the weight of the tablets can be increased to prepare tablets equivalent to the conventionally used 100% silica gel particles.

[0093] The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

[0094] It is to be understood that various omissions and substitutions of equivalents may be contemplated as circumstances may suggest or render convenient, but these are intended to encompass applications or implementations without departing from the spirit or scope of the invention.

Claims

1. A silica gel desiccant tablet comprising: a) 60 to 65% of silica gel powder having a particle size of 200 to 400 mesh; b) 25 to 30% of powdered bentonite having a particle size of 200 to 400 mesh; c) 1.5 to 2% magnesium stearate; d) 5 to 10% of a water-soluble polymer; and e) 200 ml of distilled water.

2. The silica gel desiccant tablet according to claim 1, comprising: a) 70 gm of powdered silica gel with a particle size of 200 to 400 mesh; b) 30 gm of bentonite with a particle size of 200 to 400 mesh; c) 2 gm of magnesium stearate; d) 10 gm of polyvinyl alcohol; and e) 300 ml of distilled water.

3. A method for preparing the silica gel desiccant tablet according to claim 1, comprising the following steps: a) mixing 60 to 65% of silica gel powder having a particle size of 200 to 400 meshes with 25 to 30% of powdered bentonite having a particle size of 200 to 400 meshes and 1.5 to 2% of magnesium stearate to form a silica gel mixture; b) dissolving 5 to 10% of a water-soluble polymer in 200 ml of distilled water and heating at a first preset temperature for a first preset time; c) cooling the polymer solution to a second preset temperature and for a second preset time; d) mixing the polymer solution into the silica gel mixture under continuous stirring; e) adding 200 ml of distilled water to the mixture to form a uniform slurry; f) drying the slurry at a third preset temperature for a third preset time to obtain a dry mixture containing 20% ​​moisture; g) compressing the dry mixture at a predetermined pressure to form a tablet; and h) The tablets are further heated to remove residual moisture.

4. The method for preparing the silica gel desiccant tablet according to claim 3, wherein: a) dissolving the water-soluble polymer in 200 ml of distilled water and heating at 60° C. for 1 hour; b) cooling the polymer solution to room temperature for 1.5 hours; c) drying the slurry at 110° C. for 2 hours to obtain a dry mixture containing 20% ​​moisture; and d) The dry mixture is compressed at a pressure between 12 and 17 kN to form tablets.

5. The method for preparing the silica gel desiccant tablet according to claim 3, wherein the silica gel desiccant tablet has a unit amount of silica gel desiccant composition, and the method for preparing the silica gel desiccant tablet comprises the following steps: a) mixing 70 g of powdered silica gel having a particle size of 200 to 400 mesh, 30 g of bentonite having a particle size of 200 to 400 mesh, and 2 g of magnesium stearate in a laboratory blender to form a silica gel mixture; b) dissolving 10 g of polyvinyl alcohol in 100 ml of distilled water and heating at 60° C. for 1 hour; c) cooling the polymer solution at room temperature for 1.5 hours; d) adding the PVA solution to the silica gel mixture under continuous stirring; e) adding 200 ml of distilled water to the mixture to form a uniform slurry; f) drying the slurry at 110° C. for 2 hours to obtain a semi-dried mixture containing 20% ​​water, and passing the mixture through an 18-mesh sieve; g) compressing the dry mixture in a tablet press at a pressure of 15 KN to form tablets; and h) The tablets were further heated to 110°C at a heating rate of 40-70°C for 1 hour, followed by holding at 70°C for 30 minutes; then heated at a heating rate of 70-110°C for 1 hour and held at 110°C for 30 minutes.

6. The silica gel desiccant tablet according to claim 1, which exhibits a maximum moisture absorption capacity of 22.8% at 25°C and 80% relative humidity after exposure in a closed space for 24 hours.

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