Molecular sieve desiccant tablet

Abstract

The invention relates to a molecular sieve desiccant tablet and a preparation method thereof. The molecular sieve desiccant tablet comprises 65%-70% of molecular sieve powder, 25%-30% of attapulgite clay and 2.5%-3% of magnesium stearate. The diameter of the tablet is 9mm, 11mm, 12mm and 16mm, and the height of the tablet is 5mm. The molecular sieve desiccant tablet can adsorb moisture under a low relative humidity (RH) condition (lt; 20% RH). According to the preparation method disclosed by the invention, the tablet with the best mechanical strength can be obtained, and the raw materials are prepared into slurry and mixed in water, so that uniform dispersion of all the components is ensured.

Description

Technical Field

[0001] This invention relates to molecular sieve desiccant compositions, and more specifically, to molecular sieve desiccant tablets with good mechanical stability. Background Technology

[0002] Desiccants play a vital role in daily life, removing moisture from products and items in the food, health supplement, and pharmaceutical industries. Therefore, by preventing the growth of microorganisms and fungi, desiccants help extend product shelf life and maintain product quality. Various desiccants are known on the market, suitable for different market sectors, including silica gel, activated alumina, activated carbon, zeolite, calcium chloride, clay, and molecular sieves.

[0003] Most desiccants on the market are currently in granular, bead-like, or pellet form, packaged in small bags and cans. Ni Shengwen's Chinese utility model patent CN207894150U discloses a molecular sieve type dehumidifier dryer, whose dehumidification chamber contains granular molecular sieve desiccant. Martinez Jim et al.'s US patent application US2008207434A1 discloses an adsorbent tablet comprising an adsorbent and a binder, wherein the adsorbent is selected from silica gel, molecular sieves, activated carbon, or clay, and the tablet surface is coated with a polymer.

[0004] Therefore, the preparation of molded desiccants typically requires coating with polymer reagents. Granular desiccants have the disadvantage of dust dispersion, which may contaminate pharmaceuticals and health products, and require specialized dehumidification equipment. Currently, there is an urgent need for a desiccant with uniformly mixed components that does not require physical blending, which should possess good mechanical stability after molding without affecting its moisture absorption properties. Furthermore, a tablet with strong adhesion and excellent mechanical stability is also needed. Summary of the Invention

[0005] This invention discloses a molecular sieve desiccant tablet that can adsorb moisture under low relative humidity (RH) conditions (<20%RH). The tablet contains 65% to 70% molecular sieve powder, 25% to 30% attapulgite clay, and 2.5% to 3% magnesium stearate.

[0006] The molecular sieve powder in the molecular sieve desiccant tablets is selected from 4A molecular sieve powder, 5A molecular sieve powder, or 13x molecular sieve powder.

[0007] The present invention also describes a method 100 for preparing molecular sieve desiccant tablets, comprising the following steps:

[0008] Step 110: In a laboratory mixer, the molecular sieve powder of a specific particle size is uniformly mixed with attapulgite clay and magnesium stearate.

[0009] Step 2, 120: Add water to the mixture from step 110 and continue stirring to obtain a uniform slurry;

[0010] Step 3, 130: Dry the slurry to obtain a semi-dry mixture;

[0011] Step 4, 140: Press the dried mixture under constant pressure in a tablet press to obtain tablets of a specific size;

[0012] Step 5, 150: Heat-treat the tablets to remove residual moisture and obtain tablets with optimal mechanical strength.

[0013] According to the present invention, in step 140, the tablet is compressed at a constant pressure of 20 to 25 kN. In step 150 of the method described in the present invention, the tablet is first heated to 550°C at a heating rate of 40 to 200°C / h and held at that temperature for 1 hour, then cooled to 200°C and held at that temperature for 30 minutes; then the tablet is heated again at a heating rate of 200 to 550°C / h for 1 hour, and finally held at 550°C for 30 minutes.

[0014] The molecular sieve desiccant tablets of the present invention can adsorb moisture under low relative humidity (RH) conditions (<20%RH). Detailed Implementation

[0015] The use of "an embodiment" or "a particular embodiment" in the specification means that a specific feature, structure, characteristic, or function associated with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing in different places in the specification does not necessarily refer to the same embodiment.

[0016] The “preferred embodiments” mentioned in the specification refer to a detailed description of specific features, structures, characteristics or functions, while omitting known structures and functions, in order to provide a clear description of the present invention.

[0017] The foregoing description of specific embodiments of the present invention is presented for illustrative and explanatory purposes. It is not intended to exhaustively describe all aspects of the invention, nor to limit the invention to the precise forms disclosed; obviously, based on the above teachings, the present invention can be modified and varied in many ways.

[0018] This invention discloses molecular sieve desiccant tablets prepared from a molecular sieve desiccant composition and a method for preparing molecular sieve desiccant tablets. This invention allows for the preparation of molecular sieve desiccant tablets without the use of polymers.

[0019] According to the present invention, the molecular sieve desiccant tablets of the present invention comprise the following molecular sieve desiccant composition:

[0020] 1) 65% to 70% molecular sieve powder;

[0021] 2) 25% to 30% attapulgite clay;

[0022] 3) 2.5% to 3% magnesium stearate.

[0023] In a preferred embodiment, the molecular sieve desiccant tablet comprises:

[0024] 1) 70 grams of molecular sieve powder;

[0025] 2) 30 grams of attapulgite clay;

[0026] 3) 3 grams of magnesium stearate.

[0027] In this preferred embodiment, the molecular sieve powder is 4A molecular sieve powder with a particle size of 100 to 200 mesh.

[0028] According to the present invention, molecular sieve powder is mixed with attapulgite clay and then pressed into tablets to obtain tablets with high mechanical strength. These tablets do not contain any polymers; the binding properties are achieved by adding attapulgite clay.

[0029] The following discloses a preferred method 100 for preparing molecular sieve desiccant tablets according to the present invention, comprising the following steps:

[0030] Step 110: In a laboratory mixer, the molecular sieve powder of a specific particle size is uniformly mixed with attapulgite clay and magnesium stearate.

[0031] Step 2 120: Add water to the mixture from step 110 above and stir continuously to obtain a uniform slurry;

[0032] Step 3, 130: Dry the slurry to obtain a semi-dry mixture;

[0033] Step 4, 140: Press the dried mixture in a tablet press at a preset constant pressure to obtain tablets of a preset size;

[0034] The final step, namely step 5, 150, involves heat-treating the tablets to remove residual moisture and obtain tablets with optimal mechanical strength.

[0035] In step 110, the molecular sieve powder is 4A molecular sieve powder with a particle size of 100 to 200 mesh. In step 2, approximately 300 ml of water is added to the mixture from step 1. In step 140, the tablets are compressed at a constant pressure of 20 to 25 kN. In the final step 150, the tablets are first heated to 550°C at a heating rate of 40–200°C / h and held at that temperature for 1 hour, then cooled to 200°C and held at that temperature for 30 minutes; then heated again at a heating rate of 200–550°C / h for 1 hour, and finally held at 550°C for 30 minutes.

[0036] According to the present invention, the prepared molecular sieve desiccant tablets can adsorb moisture under low relative humidity (RH) conditions (<20%RH). The tablets need to be dried at 450°C before packaging to remove internal moisture. During the preparation process, the final moisture content of the tablets is 15%, which contributes to efficient tableting; after heating to remove moisture, adsorption pores are formed in the tablet structure, thereby significantly improving the adsorption rate.

[0037] According to the present invention, tablets of various sizes, including 9×5 mm, 11×5 mm, 12×5 mm, and 16×5 mm, can be prepared by the preferred preparation method 100. Experimental observations show that increasing the tablet diameter has no significant effect on its hygroscopic properties; the percentage increase in tablet weight is directly related to the content of the tested tablets.

[0038] Example

[0039] This document discloses only some embodiments and implementation schemes. Based on the disclosed content, the embodiments and implementation schemes can be modified and improved, and other implementation schemes can be designed.

[0040] The following examples exemplify different amounts, types, and reaction conditions of reactants that can be used to implement the present invention. However, those skilled in the art should understand that the present invention can also employ reactant amounts, types, and reaction conditions other than those in the examples, and the resulting products will have different properties and uses based on the above disclosure and the following description.

[0041] Example 1: Molecular sieve desiccant tablets with unit dosage

[0042] This molecular sieve desiccant tablet contains:

[0043] 1) 70 grams of 4A molecular sieve powder with a particle size of 100 to 200 mesh;

[0044] 2) 30 grams of attapulgite clay;

[0045] 3) 3 grams of magnesium stearate.

[0046] The tablet specifications are as follows:

[0047] Table 1: Tablet Specifications

[0048]

[0049] Example 2: Preparation method of 4A molecular sieve desiccant tablets

[0050] The preparation method of 4A molecular sieve desiccant tablets is as follows:

[0051] 1) In a laboratory mixer, 70 grams of 4A molecular sieve powder with a particle size of 100 to 200 mesh is mixed with 30 grams of attapulgite clay and 3 grams of magnesium stearate to obtain a molecular sieve mixture.

[0052] 2) Add 300 ml of distilled water to the above mixture and stir continuously to obtain a uniform slurry;

[0053] 3) Dry the slurry at 200℃ for 90 minutes to obtain a semi-dry mixture with a moisture content of 15%;

[0054] 4) Pass the semi-dried mixture through an 18-mesh sieve;

[0055] 5) The semi-dry mixture is compressed in a tablet press at a pressure of 20 kN to obtain tablets;

[0056] 6) Heat the prepared tablets to 550°C at a heating rate of 40-200°C / h and hold for 1 hour; then cool to 200°C and hold for 30 minutes; then heat at a heating rate of 200-550°C / h for 1 hour, and finally hold at 550°C for 30 minutes.

[0057] Example 3: Preparation method of 5A molecular sieve desiccant tablets

[0058] The preparation method of 5A molecular sieve desiccant tablets is as follows:

[0059] 1) In a laboratory mixer, 72 g of 5A molecular sieve powder with a particle size of 100 to 200 mesh was mixed with 27 g of attapulgite clay and 2.6 g of magnesium stearate to obtain a molecular sieve mixture;

[0060] 2) Add 300 ml of distilled water to the above mixture and stir continuously to obtain a uniform slurry;

[0061] 3) Dry the slurry at 200℃ for 90 minutes to obtain a semi-dry mixture with a moisture content of 15%;

[0062] 4) Pass the semi-dried mixture through an 18-mesh sieve;

[0063] 5) The semi-dry mixture is compressed in a tablet press at a pressure of 22 kN to obtain tablets;

[0064] 6) Heat the prepared tablets to 550°C at a heating rate of 40-200°C / h and keep them at that temperature for 1 hour; then cool them down to 200°C and keep them at that temperature for 30 minutes; then heat them at a heating rate of 200-550°C / h for 1 hour, and finally keep them at 550°C for 30 minutes.

[0065] Example 4: Preparation method of 13x molecular sieve desiccant tablets

[0066] The preparation method of 13x molecular sieve desiccant tablets is as follows:

[0067] 1) In a laboratory mixer, 74 g of 13X molecular sieve powder with a particle size of 100 to 200 mesh was mixed with 29 g of attapulgite clay and 2.9 g of magnesium stearate to obtain a molecular sieve mixture;

[0068] 2) Add 300 ml of distilled water to the above mixture and stir continuously to obtain a uniform slurry;

[0069] 3) Dry the slurry at 200℃ for 90 minutes to obtain a semi-dry mixture with a moisture content of 15%;

[0070] 4) Pass the semi-dried mixture through an 18-mesh sieve;

[0071] 5) The semi-dry mixture is compressed in a tablet press at a pressure of 25 kN to obtain tablets;

[0072] 6) Heat treatment of the prepared tablets: first heat to 200℃ at a heating rate of 40-200℃ / hour and hold for 30 minutes; then heat to 550℃ at a heating rate of 200-550℃ / hour and hold for 30 minutes.

[0073] Example 5: Hygroscopic properties of molecular sieve desiccant tablets

[0074]

[0075] Tablets of different sizes (9×5 mm, 11×5 mm, 12×5 mm, and 16×5 mm) were prepared to observe the effect of increased diameter on the hygroscopic properties of the tablets. The results showed that tablet size had no significant effect on its hygroscopic properties; the percentage increase in tablet weight was directly related to the content of the tested tablets and the relative humidity.

[0076] Other embodiments of the present invention will be clearly understood by those skilled in the art and others through the following detailed description of some embodiments. However, it should be understood that the content and detailed description of the present invention are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the claimed invention.

[0077] Advantageously, the molecular sieve desiccant tablet preparation method of the present invention extends the service life of the desiccant. This method achieves uniform mixing of tablet components before tableting—by preparing the raw materials into a slurry and mixing them in water, uniform dispersion of each component is ensured. The molecular sieve desiccant tablets of the present invention can adsorb moisture under low relative humidity (RH) conditions (<20%RH). Furthermore, the partially moistened mixture forms a firmly bonded tablet, and after complete removal of moisture by drying, the mechanical stability of the tablet is further improved. Therefore, the present invention provides a tablet that requires no coating material, has high mechanical strength, and does not affect hygroscopic properties. The tablets prepared by the method of the present invention do not use any polymer binders (such as polyvinyl alcohol (PVA), povidone (PVP), or ethylene-vinyl acetate copolymer (EVA)), and therefore the tablets can be heated to 550°C.

[0078] The above embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, thereby enabling those skilled in the art to fully utilize the present invention and various embodiments with modifications according to specific application requirements.

[0079] It should be understood that, where appropriate, equivalent technical features may be omitted or replaced, and such modifications and replacements are all covered within the scope of protection of this invention and do not depart from the spirit and scope of this invention.

Claims

1. A molecular sieve desiccant tablet characterized by, capable of adsorbing moisture at low relative humidity (RH) conditions (<20% RH), the tablet comprising: a) 65% to 70% of molecular sieve powder having a particle size of 100 to 200 mesh; b) 25% to 30% of attapulgite clay; and c) 2.5% to 3% of magnesium stearate.

2. The molecular sieve desiccant tablet of claim 1, wherein, The molecular sieve powder is selected from 4A molecular sieve powder, 5A molecular sieve powder or 13x molecular sieve powder.

3. A method 100 for preparing the molecular sieve desiccant tablet of claim 1, comprising: a) first step 110: uniformly mixing the molecular sieve powder having a specific particle size with attapulgite clay and magnesium stearate in a laboratory mixer; b) second step 120: adding water to the mixture of step 110 and continuously stirring to obtain a uniform slurry; c) third step 130: drying the slurry to obtain a semi-dry mixture; d) fourth step 140: compressing the dry mixture in a tablet press at a constant pressure to obtain tablets of a specific size; e) fifth step 150: heat treating the tablets to remove residual moisture to obtain tablets of optimal mechanical strength.

4. The production method 100 according to claim 3, characterized by In the fourth step 140, the constant pressure for compressing the tablets is 20 to 25 kilo Newton (Kn).

5. The production method 100 according to claim 3, characterized by, In the fifth step 150, the tablets are first heated to 550°C at a heating rate of 40-200°C / h and held for 1 hour, then cooled to 200°C and held for 30 minutes; and then heated at a heating rate of 200-550°C / h for 1 hour, and finally held at 550°C for 30 minutes.

6. The molecular sieve desiccant tablet of claim 1, wherein, The tablets exhibit moisture adsorption properties at low relative humidity (RH) conditions (<20% RH).

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