1. The preparation method of the low-heat-conduction phase-change cold storage material is characterized by comprising the following process steps of:

putting gelatin and carboxylated-cellulose nano-fiber in a mass ratio of 1:10-1:40 (preferably 1:20) into a container, heating the container to 40-100 ℃ (preferably 60 ℃) for 2-8 hours (preferably 4 hours), continuously stirring, after the reaction is finished, stirring and blending hollow microspheres in a mass ratio of 2:1-1:1 (preferably 3:2) with the gelatin and the obtained reaction product, and then freezing the mixture in an environment of 0-minus 20 ℃ (preferably-15 ℃) for 2-8 hours (preferably 6 hours) to finally obtain a solid product, namely the low-thermal-conductivity cold-storage phase-change material.

2. The preparation method according to claim 1, wherein the mass ratio of the gelatin to the carboxylated-cellulose nanofibers is 1:20, the reaction temperature is 60 ℃, and the reaction time is 2 hours.

3. The method according to claim 1, wherein the carboxylated-cellulose nanofibers are an aqueous solution of medical absorbent cotton (medical absorbent cotton) as a raw material, wherein the raw material is 1 to 5 wt%.

4. The preparation method according to claim 1, wherein the hollow microspheres are hollow closed spherical and powdery ultra-light filling materials, the main component of which is soda lime borosilicate glass, the inner diameter of which is 15-35um, and the shell thickness of which is 1-5 um.

5. The method according to claim 1 or 4, wherein the mass ratio of the gelatin to the hollow microspheres is 2: 3.

6. The method of claim 1, wherein the product is frozen at-20 ℃ for 6 hours.

7. A phase change cold storage material with low thermal conductivity prepared by the preparation method of any one of claims 1 to 6.

Background

With the continuous development of human socioeconomic and large energy consumption, energy conservation and environmental protection become global topics of attention. The development and utilization of new energy and the improvement of energy efficiency have become key points of research and development in various countries. The phase-change material is utilized to balance the energy supply and demand, so that the energy efficiency can be effectively improved, and the aims of energy conservation and environmental protection are fulfilled. It has wide application prospect in the fields of energy, spaceflight, construction, agriculture, chemical industry and the like. Has become a worldwide research hotspot.

The phase-change material can absorb or release a large amount of latent heat in the phase-change process, and has the advantages of high heat storage density, small volume, constant temperature control, obvious energy-saving effect, wide phase-change temperature selection range, easiness in control and the like, so that the phase-change material is widely applied to the field of energy storage and temperature control. Meanwhile, the phase change cold storage material is one of phase change energy storage materials. However, the phase change cold storage material used in the market has large supercooling degree, small phase change enthalpy, low stability, complex preparation process, inconvenience for mass production and low production efficiency.

Disclosure of Invention

The invention aims to provide a low-thermal-conductivity phase-change cold storage material and a preparation method thereof, so as to solve the problems in the background technology.

The synthesis of the low-heat-conduction phase-change cold storage material comprises the following steps:

putting gelatin and carboxyl-cellulose nano-fiber in a mass ratio of 1:10-1:40 into a three-neck round-bottom flask, putting the round-bottom flask into an oil bath pot, heating to 40-100 ℃ for 2-8 hours, continuously stirring, after the reaction is finished, stirring and blending hollow microspheres in a mass ratio of 2:1-1:1 with the gelatin at a high speed and the obtained experimental product, and then freezing in an environment at 0-20 ℃ for 2-8 hours to finally obtain a white block sample, namely the low-thermal-conductivity phase-change cold storage material.

Further, the mass ratio of the gelatin to the carboxylated-cellulose nanofiber is 1:20, the reaction temperature is 60 ℃, and the reaction time is 2 hours.

Further, the carboxylated-cellulose nano-fiber in the step is an aqueous solution taking medical absorbent cotton as a raw material, wherein the raw material accounts for 1%.

Further, the mass ratio of the gelatin to the hollow microspheres in the step is 2: 3.

Further, the product in the step is frozen in an environment of-20 ℃ for 6 hours.

Further, the low-heat-conduction phase change cold storage material is a white massive solid.

According to the method, a composite low-thermal-conductivity phase change cold storage material is synthesized by blending a carboxylated-cellulose nanofiber serving as a phase change material, gelatin serving as a support carrier and hollow microspheres serving as a heat insulator. The low-heat-conductivity phase-change cold storage material synthesized by the method has the advantages of high phase-change latent heat, low preparation cost and low heat conductivity coefficient, is easy to apply to cold and heat transfer, and is suitable for industrial popularization.

The invention has the advantages of low requirements on process conditions, good cyclic charge and discharge cold performance, simple component proportion and easy operation of the preparation method, and the prepared low-heat-conduction phase-change cold storage material is a blocky substance and has the characteristics of high phase-change latent heat value and the like. In addition, because the heat conductivity coefficient is low, the heat transfer to the outside and the heat absorption to the inside are slow, the refrigeration time can be greatly prolonged, and the application range is enlarged.

Drawings

Fig. 1 is a differential scanning calorimetry curve of a low thermal conductivity phase change cold storage material.

Detailed Description

The hollow microspheres adopted in the following embodiments are hollow closed spherical and powdery ultra-light filling materials, the main component of which is soda lime borosilicate glass, the inner diameter of which is 15-35um, and the shell thickness of which is 1-5 um.

Example 1

(1) 10g of gelatin and 200g of carboxylated-cellulose nanofiber (Guilin Qiqi Daskywork, Inc.) (1 wt% of medical absorbent cotton) as an aqueous solution of the raw material were placed in a round-bottom flask, and the round-bottom flask was heated to 60 ℃ in a water bath, and stirred at a constant speed for 2 hours.

(2) And (3) after the reaction is finished, pouring the product obtained in the step (1) into a beaker, taking 15g of hollow microspheres into the beaker, and stirring the hollow microspheres and the beaker at a constant speed.

(3) And (3) freezing the product obtained in the step (2) in an environment of-20 ℃ for 6 hours to finally obtain the low-heat-conduction phase-change cold storage material with stable performance.

The low-thermal-conductivity phase-change cold storage material is white block-shaped, and the thermal conductivity coefficient of the low-thermal-conductivity phase-change cold storage material is 0.25W/mk measured by Hotdisk.

Example 2

(1) 10g of gelatin and 200g of carboxylated-cellulose nanofiber (Guilin Qiqi Daskywork, Inc.) (1 wt% of medical absorbent cotton) as an aqueous solution of the raw material were placed in a round-bottom flask, and the round-bottom flask was heated to 60 ℃ in a water bath, and stirred at a constant speed for 2 hours.

(2) And (2) freezing the product obtained in the step (1) in an environment at the temperature of-20 ℃ for 6 hours to obtain a transparent block-shaped phase change material, and measuring the thermal conductivity coefficient of the transparent block-shaped phase change material by Hotdisk to be 0.66W/mk.

Through phase change with the embodiment 1, the invention can greatly reduce the heat conductivity coefficient of the phase change material by doping the hollow microspheres, thereby slowing down the cold release speed of the material and prolonging the cold accumulation time.

Example 3

(1) 10g of gelatin and 250g of carboxylated-cellulose nanofiber (Guilin Qiqi Daskyu Co., Ltd.) (1 wt% of medical absorbent cotton) as an aqueous solution of the raw material were placed in a round-bottomed flask, and the round-bottomed flask was heated to 60 ℃ in a water bath, and stirred at a constant speed for 3 hours.

(2) And (3) after the reaction is finished, pouring the product obtained in the step (1) into a beaker, and then putting 20g of hollow microspheres into the beaker to stir the hollow microspheres with the beaker at a constant speed.

(3) And (3) freezing the product obtained in the step (2) in an environment of-20 ℃ for 5 hours to finally obtain the low-heat-conduction phase-change cold storage material with stable performance.

The low-heat-conduction phase-change cold storage material is white block-shaped. The differential scanning calorimetry curve is shown in FIG. 1. The fitted phase transition enthalpy value is 272J/g, the average phase transition enthalpy value of the products on the market is 180J/g, and the result shows that the invention has high phase transition latent heat value compared with most products on the market.