Preparation method and application of coolant for biological ice bag

Abstract

The invention discloses a preparation method and application of a low-cost, high-performance and sustainable novel green cold storage agent capable of being used for a biological ice bag, and belongs to the technical field of cold chain cold storage. The natural starch is used as a main raw material, and the high-cold-capacity cold storage agent is obtained by utilizing the characteristics that the natural starch can be dissolved in an alkaline aqueous solution at room temperature, forms abundant hydrogen bonds with water molecules and has relatively high water binding capacity. The starch and the alkaline substance in the cold storage agent can be mixed in a wet state and a dry state to prepare the cold storage agent. The solid-liquid phase change enthalpy (heat absorption) of the obtained cold storage agent can reach 310.5 J / g at most, and the cold storage agent is obviously superior to a mainstream SAP type cold storage agent on the market at present. The obtained cold storage agent can be independently used, and can also be mixed and added into the SAP type cold storage agent to improve the cold storage capacity of the SAP type cold storage agent. Therefore, the invention has the advantages of green and recyclable raw material source, low cost, simple preparation process, easy large-scale preparation, excellent cold storage performance and the like, and has good application prospect and social and economic benefit prospect.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a green, low-cost, high-cold-capacity refrigerant, and belongs to the technical field of cold chain refrigerant storage. Background Art

[0002] In recent years, biological ice packs have become one of the important cold chain transportation methods. They have many advantages such as being small, flexible, and reusable. They are becoming more and more popular and valued in many transportation fields such as blood products, medicines, food, chemicals, and flowers. High-efficiency refrigerants are the key core material of biological ice packs and are also the key to determining the cooling effect of biological ice packs.

[0003] At present, the widely used biological ice pack coolants on the market are synthetic polymer water-absorbent resin (SAP) materials, such as polyacrylamide (PAM), sodium carboxymethyl cellulose (CMC), etc. While these coolants meet people's basic needs for cold chain transportation, they also have the following major problems: 1) The market price of synthetic SAP materials is relatively high, which pushes up the production cost of coolants; 2) The phase change latent heat of the coolant obtained after SAP materials are compounded with water is relatively low, resulting in a shorter cold preservation time under the same conditions; 3) The raw materials for SAP preparation come from non-renewable petrochemical products, and the preparation process will greatly increase carbon emissions; 4) Large-scale use is not sustainable, and it is easy to pollute the environment as a synthetic polymer material after being discarded.

[0004] In view of this, the present invention proposes a preparation method and application of a new type of coolant based on starch, a green, recyclable and sustainable natural polymer as the main raw material. Starch is a natural high molecular carbohydrate (polysaccharide) formed by the polymerization of glucose molecules. It is widely present in nature and its molecular formula can be expressed as (C6H 10 O5)n. As can be seen from its structure, starch molecules contain a large number of oxygen-containing functional groups. If they can be dissolved in water, they can form a large number of hydrogen bonds with water molecules. In the solid-liquid transition process, they can absorb a large amount of latent heat (phase change enthalpy) to become a potential cold storage material. At the same time, they can also use their long-chain molecular structure to bind water molecules, so that their latent heat is slowly released and the cold storage time is extended. However, starch is insoluble in water at room temperature and cannot be used directly as a cold storage agent. Therefore, it is necessary to change its microstructure through mild physical and chemical methods to meet the requirements of biological ice pack cold storage agents and give full play to its potential economic and social value. Summary of the invention

[0005] The present invention proposes a method for simply and quickly preparing a high-performance refrigerant based on common starch. At room temperature, add 2 to 3 parts of common starch to 97 to 98 parts of an alkaline aqueous solution with a mass fraction of 0.5 to 1.0%, and stir directly for several minutes to obtain a colorless, transparent, viscous liquid refrigerant. The obtained colorless viscous liquid can be used after being packaged and frozen. The present invention can also use solid phase direct compounding to obtain a dry refrigerant, that is, the starch and solid alkali are mixed in a solid phase at a mass ratio of 5:2 to 3 for standby use. When in use, add 30 to 50 times the dry weight of water, and then seal and dissolve before freezing for use. The phase change temperature of the refrigerant obtained by the present invention is about -3.7°C, and the solid-liquid phase change enthalpy (absorption) can reach up to 310.5 J / g (attached Figure 1 ), while the phase transition temperature and solid-liquid phase change enthalpy of the polymer water-absorbing resin refrigerant under the same experimental conditions were -2.6℃ and 164.5J / g respectively (Appendix Figure 2 ), the above two indicators show that the cold storage capacity of the cold storage agent obtained by the present invention is better. At the same time, when part of the starch-based cold storage agent is mixed with other types of cold storage agents (such as water-absorbing polymer resin), the cold storage capacity of other types of cold storage agents can also be significantly increased, that is, the cold storage agent can be used alone or mixed with other cold storage agents to improve and enhance the cold storage capacity of other cold storage agents (see Figure 3 The refrigerant obtained by the present invention and the synthetic polymer water-absorbing resin on the market were used to make biological ice bags, and actual cold preservation experiments were carried out under the same experimental conditions (see Appendix). Figure 4 , 5), the experimental results show that under the condition of the same low amount of biological ice pack usage, the biological ice pack containing the cold storage agent of the present invention has a faster cooling rate and a longer refrigeration (temperature below 10°C) time, showing a more excellent cold storage effect.

[0006] As can be seen from the above, the present invention has many advantages such as green and recyclable raw material source, low cost, simple preparation process, easy large-scale preparation, excellent cold storage performance, etc. Therefore, the present invention has good application prospects and social and economic benefit prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is the test result of starch-based coolant using differential scanning calorimeter.

[0009] Figure 2 It is the test result of differential scanning calorimeter of synthetic polymer water-absorbing resin based coolant.

[0010] Figure 3 It is the test result of differential scanning calorimeter of starch and water-absorbing polymer mixed base coolant.

[0011] Figure 4 This is the test result of starch-based biological ice pack cold preservation experiment.

[0012] Figure 5 It is the test result of the cold preservation experiment of synthetic polymer absorbent resin-based biological ice pack. DETAILED DESCRIPTION

[0014] Example 1: Accurately weigh 4.0 g of starch, add it to 200 mL of 0.5% sodium hydroxide aqueous solution under stirring, and continue stirring for 15 minutes, the white suspension gradually turns into a colorless transparent viscous liquid. Package and freeze for later use.

[0015] Example 2: 6.0 g of starch was accurately weighed and added to 200 mL of 1% sodium carbonate aqueous solution under stirring, and the stirring was continued for 20 minutes, and the white suspension gradually turned into a colorless, transparent, viscous liquid. The mixture was packaged and frozen for later use.

[0016] Example 3: 4.0 g of starch was accurately weighed and added to 200 mL of 0.5% potassium hydroxide aqueous solution under stirring, and the stirring was continued for 15 minutes, and the white suspension gradually turned into a colorless transparent viscous liquid. The mixture was packaged and frozen for later use.

[0017] Example 4: 6.0 g of starch was accurately weighed and added to 200 mL of 1% potassium carbonate aqueous solution under stirring, and the stirring was continued for 20 minutes, and the white suspension gradually turned into a colorless transparent viscous liquid. The mixture was packaged and frozen for later use.

[0018] Example 5: Accurately weigh 5.0 g of starch and 2.0 g of sodium hydroxide in a mortar, grind and mix evenly, and transfer to a sealable container to obtain a dry cold storage agent. When using, add 250 ml of water and shake well, freeze and set aside.

[0019] Example 6: 5.0 g of starch and 3.0 g of potassium hydroxide were accurately weighed in a mortar, ground and mixed evenly, and then transferred to a sealable container to obtain a dry cold storage agent. When used, 250 ml of water was added and shaken, and then frozen for later use.

[0020] Example 7: Take 0.8 L of the coolant obtained in Example 1 of the present invention, freeze it in a -18 ℃ refrigerator for 12 h, and then quickly transfer it to a 3.2 L incubator with automatic temperature recording to conduct an actual cold storage test. The temperature collection interval is 5 min, and the cold storage curve is plotted with temperature and time as the vertical and horizontal coordinates, as shown in the attached figure. Figure 4 shown.

[0021] Example 8: Weigh 16.0 g of sodium carboxymethyl cellulose polymer water-absorbing resin, slowly add it to 0.8 L of 0.5% sodium hydroxide aqueous solution under stirring until it is completely dissolved to obtain a colorless, transparent, viscous liquid, seal it and transfer it to a -18 ° C refrigerator for freezing. After freezing for 12 h, quickly transfer it to a 3.2 L incubator with automatic temperature recording, and conduct an actual cold preservation control test. The temperature collection interval is 5 min, and the temperature and time are plotted as the vertical and horizontal coordinates to obtain a cold preservation curve, as shown in the attached figure. Figure 5 shown.

[0022] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have similar substitutions and changes. Any modification, equivalent replacement, improvement, imitation, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A cold storage agent that can be used in a biological ice pack, characterized in that: Using low-cost green and recyclable starch as the main raw material, and utilizing its characteristics of being soluble in inorganic alkaline aqueous solution at room temperature and forming abundant hydrogen bonds and strong water-binding ability with water molecules, a low-cost, high-performance, sustainable new type of cold chain refrigerant is obtained. The starch and alkaline substances in the refrigerant can be mixed in both wet and dry states to prepare the refrigerant. At the same time, in addition to being used alone, this refrigerant can also be mixed with other refrigerants for use, and has the function of improving and enhancing the refrigerant capacity of other refrigerants.

2. The starch as claimed in claim 1 includes all bio-based starches from different sources.

3. The inorganic alkaline aqueous solution as claimed in claim 1 comprises aqueous solutions such as common sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, etc.

4. As claimed in claim 1, per 100 parts of the cooling agent, preferably 2 to 3 parts of starch, 0.5 to 1.0 parts of inorganic alkali, and 96 to 98 parts of water.

5. The starch and alkaline substance as claimed in claim 1 can obtain a cold storage agent in both wet and dry states.

6. The coolant as claimed in claim 1 can be used alone or mixed with other coolants.

7. Use of a biological ice pack refrigerant as claimed in any one of claims 1 to 6 in cold chain transportation and cold preservation.

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