Polyolefin composite modified shielding material and preparation method thereof

Abstract

The invention discloses a polyolefin composite modified shielding material and a preparation method thereof, and belongs to the technical field of shielding materials, the polyolefin composite modified shielding material comprises the following raw materials by weight: 100 parts of polyolefin resin, 20-30 parts of a modified shielding agent, 3-4 parts of an antioxidant, and 0.4-0.5 part of an initiator; the raw materials are mixed according to the proportion and then put into a double-screw extruder to be extruded and granulated, and the shielding material is obtained. According to the invention, high-density polyethylene or polypropylene is selected as a shielding material matrix, and compared with common polyethylene, the shielding material has higher heat resistance; modified boron carbide is selected as a shielding agent, boron carbide has the characteristic of being environmentally friendly, after modification, compatibility with polyolefin collective can be greatly improved, uniform dispersion in the shielding material is promoted, benzene rings and N positive ions can be introduced, and heat resistance and antistatic performance of the shielding material are improved; the application field of the shielding material is expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of shielding materials, and specifically relates to a polyolefin composite modified shielding material and a preparation method thereof. Background Art

[0002] The applications of nuclear technology have penetrated into various fields such as military, medicine, and industry, and the probability of humans being exposed to various nuclear radiation rays has increased significantly. Therefore, in order to ensure the health of workers and the safe and effective utilization of nuclear energy, it is necessary to effectively shield and protect nuclear radiation rays.

[0003] In recent years, shielding materials based on polyethylene have been developed for shielding and protecting neutron rays, including boron-containing polyethylene and lead-boron polyethylene shielding materials. However, the shielding material based solely on polyethylene has a relatively low heat-resistant temperature range (80 - 100 °C); at the same time, due to the presence of lead in lead-boron polyethylene, the environmental friendliness of the material is poor, and it will have an adverse impact on the environment and personnel during use.

[0004] In response to the above problems, the invention patent with the publication number CN112143067A discloses a polyolefin composite modified shielding material for a neutron shielding device. By replacing the polyolefin material and the types of shielding substances, the heat resistance and environmental friendliness of the composite material are expected to be improved. However, the shielding substance belongs to inorganic fillers, and its compatibility with high molecular polymers (polyolefins) is poor and it is prone to agglomeration, thus greatly affecting the mechanical properties of the composite material and restricting the application of the composite material. Summary of the Invention

[0005] The purpose of the present invention is to provide a polyolefin composite modified shielding material and a preparation method thereof. By selecting high-density polyethylene or polypropylene as the matrix of the shielding material, it has higher heat resistance compared to ordinary polyethylene; modified boron carbide is selected as the shielding agent. Boron carbide itself has the characteristic of environmental friendliness. After modification, it can not only greatly improve the compatibility with the polyolefin matrix, promote uniform dispersion in the shielding material, but also introduce benzene rings and N positive ions, improve the heat resistance and antistatic performance of the shielding material, and expand the application fields of the shielding material.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A polyolefin composite modified shielding material, comprising the following raw materials in parts by weight: 100 parts of polyolefin resin, 20 - 30 parts of modified shielding agent, 3 - 4 parts of antioxidant, and 0.4 - 0.5 parts of initiator.

[0008] Further, the polyolefin resin is high-density polyethylene or polypropylene.

[0009] Further, the antioxidant is antioxidant 1010 or antioxidant 168.

[0010] Further, the initiator is tert-butyl hydroperoxide or dicumyl peroxide.

[0011] Further, the modified shielding agent is prepared by the following steps:

[0012] First step: Place boron carbide in a conical flask, then add strong acid according to the solid-liquid ratio of 1 g: 12 mL, perform ultrasonic treatment in a water bath at 50 °C for 6 h. After the mixture is cooled to room temperature, add deionized water for dilution, perform centrifugal separation, and wash 3-4 times with ethanol and deionized water in sequence. Finally, dry in a vacuum oven at 60 °C, grind to obtain pre-modified boron carbide;

[0013] Among them, the strong acid is a mixture obtained by compounding concentrated sulfuric acid with a mass fraction of 98% and concentrated hydrochloric acid with a mass fraction of 37.5% according to a volume ratio of 5:1;

[0014] Ultrasonic shearing and oxidation treatment of boron carbide with strong acid can introduce active carboxyl groups and hydroxyl groups on the surface of boron carbide, laying a reaction site for subsequent modification;

[0015] Second step: Add propylenediamine, triethylamine, acetone and hexane to a three-necked flask equipped with a stirring device and a condensing device, stir and dissolve evenly, place the flask in an ice-water bath, control the system temperature not to exceed 2 °C, then slowly drop 6-chloro-1-hexene. After the dropping is completed, remove the ice bath, react at room temperature for 2 h. After the reaction is completed, filter (to remove the generated salt), take the organic phase (liquid phase), wash 4-5 times with a 20% NaCl aqueous solution by mass, and dry with anhydrous Mg 2 SO 4 Dry, filter, and finally remove the solvent (hexane) by vacuum distillation to obtain intermediate product 1;

[0016] The dosage ratio of propylenediamine, triethylamine, and 6-chloro-1-hexene is 7.4-8.2 g: 10.1 g: 11.8 g;

[0017] Under the action of triethylamine, the -NH 2 on the propylenediamine molecule undergoes a nucleophilic substitution reaction with the chloro group on the 6-chloro-1-hexene molecule. By controlling the molar ratio of the two to be close to 1:1 and propylenediamine being slightly in excess, a mono-substitution reaction occurs to obtain intermediate product 1. The reaction process is as follows:

[0018]

[0019] Step 3: Mix the pre-modified boron carbide with DMF (N,N-dimethylformamide), ultrasonically disperse for 1 h, then add Intermediate Product 1 and DCC (dicyclohexylcarbodiimide) under stirring, magnetically stir and react at 90 °C in an oil bath for 24 h. After the reaction, centrifuge and separate, wash 3 - 4 times with an ethanol aqueous solution, and finally vacuum dry and grind the filter cake to obtain Intermediate Product 2;

[0020] The dosage ratio of the pre-modified boron carbide, Intermediate Product 1, and DCC is 5 g:10 - 15 g:3 - 4 g;

[0021] Under the action of DCC, -COOH on the surface of the pre-modified boron carbide reacts with -NH on Intermediate Product 1 2 to undergo an amidation reaction, grafting Intermediate Product 1 onto the surface of the pre-modified boron carbide to obtain Intermediate Product 2;

[0022] Step 4: Ultrasonically disperse Intermediate Product 2 in DMSO (dimethyl sulfoxide), then add 2-phenylchloroethane, heat up to 50 °C and stir and react for 4 - 5 h. After the reaction, centrifuge and separate, wash 3 - 4 times with an ethanol aqueous solution, and finally vacuum dry and grind the filter cake to obtain the modified shielding agent;

[0023] The dosage ratio of Intermediate Product 2 and 2-phenylchloroethane is 10 g:15 - 20 g;

[0024] -NH- on the molecular chain grafted on the surface of Intermediate Product 2 undergoes a quaternization reaction with 2-phenylchloroethane to obtain the modified shielding agent. The reaction process is as follows:

[0025]

[0026] The boron carbide is modified through a series of chemical reactions, and an organic molecular chain is grafted on the surface of the boron carbide, which is equivalent to forming an organic coating layer on its surface, effectively improving the compatibility between the boron carbide and the polyolefin matrix, thereby promoting the uniform dispersion of the boron carbide in the shielding material; in addition, the organic molecular chain contains a carbon molecular chain. According to the principle of similar compatibility, it can further enhance the compatibility between the boron carbide and the polyolefin matrix, and the end of the carbon molecular chain is an unsaturated carbon-carbon double bond. Under the action of a trace initiator, it can be grafted onto the polyolefin molecular chain during the mixing process, thus greatly improving the interaction between the boron carbide and the polyolefin matrix, making the boron carbide not prone to migration and exudation during use and playing a role stably and durably; in addition, the organic molecular chain grafted on the boron carbide also contains a benzene ring and N positive ions. The benzene ring belongs to a rigid heat-resistant group, which can improve the mechanical strength and heat resistance of the shielding material to a certain extent, and the N positive ions can endow the shielding material with certain antistatic properties, thereby expanding the application fields of the shielding material.

[0027] The preparation method of the above shielding material includes the following steps:

[0028] After mixing the raw materials in the above proportions, they are put into a twin-screw extruder for extrusion granulation to obtain the shielding material.

[0029] Advantages of the present invention:

[0030] The present invention selects high-density polyethylene or polypropylene as the matrix of the shielding material, which has higher heat resistance compared to ordinary polyethylene; modified boron carbide is selected as the shielding agent. Boron carbide itself has the characteristic of environmental friendliness. After modification, it can not only greatly improve the compatibility with the polyolefin matrix and promote uniform dispersion in the shielding material, but also introduce benzene rings and N positive ions, improve the heat resistance and antistatic performance of the shielding material, and expand the application fields of the shielding material. Specific embodiments

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0032] Example 1

[0033] Prepare the modified shielding agent:

[0034] First step: Place 10 g of boron carbide in a conical flask, add 120 mL of strong acid (100 mL of concentrated sulfuric acid with a mass fraction of 98% and 20 mL of concentrated hydrochloric acid with a mass fraction of 37.5%), perform ultrasonic treatment in a water bath at 50 °C for 6 h. After the mixture cools to room temperature, add deionized water for dilution, perform centrifugal separation, and wash 3 times with ethanol and deionized water in sequence. Finally, dry in a vacuum oven at 60 °C, grind to obtain pre-modified boron carbide;

[0035] Second step: Add 7.4 g of propylenediamine, 10.1 g of triethylamine, 50 mL of acetone and 50 mL of hexane to a three-necked flask equipped with a stirring device and a condensing device, stir and dissolve evenly, place the flask in an ice-water bath, control the system temperature not to exceed 2 °C, then slowly drop 11.8 g of 6-chloro-1-hexene. After the dropping is completed, remove the ice bath and react at room temperature for 2 h. After the reaction is completed, filter (remove the generated salt), take the organic phase (liquid phase), wash 4 times with a 20% NaCl aqueous solution by mass, and dry with anhydrous Mg 2 SO 4 Dry, filter, and finally remove the solvent (hexane) by vacuum distillation to obtain intermediate product 1;

[0036] Step 3: Mix 5 g of pre-modified boron carbide with 80 mL of DMF, ultrasonically disperse for 1 h, then add 10 g of intermediate product 1 and 3 g of DCC under stirring, and magnetically stir and react at 90 °C in an oil bath for 24 h. After the reaction is completed, centrifuge and wash 3 times with an ethanol aqueous solution. Finally, vacuum dry and grind the filter cake to obtain intermediate product 2;

[0037] Step 4: Ultrasonically disperse 10 g of intermediate product 2 in 100 mL of DMSO, then add 15 g of 2-phenylchloroethane, raise the temperature to 50 °C and stir and react for 4 h. After the reaction is completed, centrifuge and wash 3 times with an ethanol aqueous solution. Finally, vacuum dry and grind the filter cake to obtain the modified shielding agent.

[0038] Example 2

[0039] The modified shielding agent is prepared by the following steps:

[0040] Step 1: Place 10 g of boron carbide in a conical flask, add 120 mL of strong acid (100 mL of concentrated sulfuric acid with a mass fraction of 98% and 20 mL of concentrated hydrochloric acid with a mass fraction of 37.5%), ultrasonically treat in a 50 °C water bath for 6 h. After the mixture cools to room temperature, add deionized water for dilution, centrifuge and wash 4 times with ethanol and deionized water in sequence. Finally, dry in a 60 °C vacuum oven and grind to obtain pre-modified boron carbide;

[0041] Step 2: Add 8.2 g of propylenediamine, 10.1 g of triethylamine, 50 mL of acetone and 50 mL of hexane to a three-necked flask equipped with a stirring device and a condensing device, stir and dissolve evenly, place the flask in an ice-water bath, control the system temperature not to exceed 2 °C, then slowly drop 11.8 g of 6-chloro-1-hexene. After the dropping is completed, remove the ice bath and react at room temperature for 2 h. After the reaction is completed, filter (to remove the generated salt), take the organic phase (liquid phase), wash 5 times with a 20% NaCl aqueous solution by mass, and dry with anhydrous Mg 2 SO 4 Filter, and finally remove the solvent (hexane) by vacuum distillation to obtain intermediate product 1;

[0042] Step 3: Mix 5 g of pre-modified boron carbide with 80 mL of DMF, ultrasonically disperse for 1 h, then add 15 g of intermediate product 1 and 4 g of DCC under stirring, and magnetically stir and react at 90 °C in an oil bath for 24 h. After the reaction is completed, centrifuge and wash 4 times with an ethanol aqueous solution. Finally, vacuum dry and grind the filter cake to obtain intermediate product 2;

[0043] Step 4: Ultrasonically disperse 10 g of Intermediate Product 2 in 100 mL of DMSO, then add 20 g of 2-phenylchloroethane, heat up to 50 °C and stir for reaction for 5 h. After the reaction is completed, perform centrifugal separation, wash 4 times with an ethanol aqueous solution, and finally vacuum-dry and grind the filter cake to obtain the modified shielding agent.

[0044] Example 3

[0045] Mix 100 parts by weight of high-density polyethylene (YuShun Plastification, high-density polyethylene of model 7260K), 20 parts by weight of the modified shielding agent prepared in Example 1, 3 parts by weight of antioxidant 1010, and 0.4 part by weight of tert-butyl hydroperoxide, and then put them into a twin-screw extruder for extrusion granulation to obtain the shielding material.

[0046] Example 4

[0047] Mix 100 parts by weight of high-density polyethylene (YuShun Plastification, high-density polyethylene of model 7260K), 25 parts by weight of the modified shielding agent prepared in Example 2, 3.5 parts by weight of antioxidant 168, and 0.45 part by weight of diisopropylbenzene peroxide, and then put them into a twin-screw extruder for extrusion granulation to obtain the shielding material.

[0048] Example 5

[0049] Mix 100 parts by weight of high-density polyethylene (YuShun Plastification, high-density polyethylene of model 7260K), 30 parts by weight of the modified shielding agent prepared in Example 1, 4 parts by weight of antioxidant 1010, and 0.5 part by weight of tert-butyl hydroperoxide, and then put them into a twin-screw extruder for extrusion granulation to obtain the shielding material.

[0050] Comparative Example 1

[0051] The shielding material obtained by replacing the modified shielding agent in Example 3 with boron carbide of the same mass, and keeping the other raw materials and the preparation process unchanged.

[0052] For the shielding materials obtained in Examples 3 to 5 and Comparative Example 1, process them into corresponding test specimens according to the following test standards respectively for performance testing:

[0053] Test the tensile strength and elongation at break according to GB / T 1040.1-2018;

[0054] Test the surface resistivity according to GB / T 1410-2006;

[0055] Test the Vicat softening temperature according to ASTM D1525-2017;

[0056] The measured results are shown in the following table:

[0057] Example III Example IV Example V Comparative Example I Tensile strength / MPa 26.9 27.8 29.4 20.3 Elongation at break / % 440 425 400 320 Resistivity / Ω <![CDATA[4.2*10 11 > <![CDATA[2.9*10 11 > <![CDATA[1.5*10 11 > <![CDATA[3.9*10 15 > Vicat softening temperature / °C 135 137 138 133

[0058] From the above test results, it can be seen that the shielding material of the present invention has high mechanical properties, heat resistance and certain antistatic properties; combined with the data of Comparative Example 1, it can be known that after boron carbide is modified, it can be evenly dispersed in the material, so that it will not have a great negative impact on the mechanical properties of polyolefin, and it can also improve the tensile strength to a certain extent. In addition, the modified boron carbide can also improve the heat resistance of the material to a certain extent and endow the material with certain antistatic properties.

[0059] The above content is only an example and explanation of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them. As long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should fall within the protection scope of the present invention.

Claims

1. A polyolefin composite modified shielding material, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of polyolefin resin, 20-30 parts of modified shielding agent, 3-4 parts of antioxidant and 0.4-0.5 parts of initiator.

2. The polyolefin composite modified shielding material according to claim 1, characterized in that: The antioxidant is antioxidant 1010 or antioxidant 168.

3. The polyolefin composite modified shielding material according to claim 1, characterized in that: The initiator is tert-butyl hydroperoxide or dicumyl peroxide.

4. The polyolefin composite modified shielding material according to claim 1, characterized in that: The modified shielding agent is prepared by the following steps: The first step is to place boron carbide in a conical flask, then add strong acid according to the solid-liquid ratio of 1g:12mL, ultrasonically treat in a 50°C water bath for 6h, centrifuge, wash, dry and grind to obtain pre-modified boron carbide; Step 2: Add propylenediamine, triethylamine, acetone and hexane into a three-necked flask, stir and dissolve evenly, place the flask in an ice-water bath, control the system temperature not to exceed 2°C, then slowly drop 6-chloro-1-hexene, react at room temperature for 2h, and obtain intermediate 1; Step 3: After pre-modified boron carbide and DMF are mixed, ultrasonic dispersion is performed for 1 hour, and then intermediate product 1 and DCC are added under stirring, and the mixture is reacted under magnetic stirring in an oil bath at 90°C for 24 hours, and then centrifuged, washed, dried, and ground to obtain intermediate product 2; Step 4: Ultrasonic dispersion of the intermediate product 2 in DMSO, then adding 2-phenylethyl chloride, heating to 50° C. and stirring for reaction for 4-5 hours, centrifuging, washing, drying, and grinding to obtain a modified shielding agent.

5. The polyolefin composite modified shielding material according to claim 4, characterized in that: In the first step, the strong acid is a mixture of 98% by mass concentrated sulfuric acid and 37.5% by mass concentrated hydrochloric acid in a volume ratio of 5:

1.

6. The polyolefin composite modified shielding material according to claim 4, characterized in that: In the second step, the ratio of propylenediamine, triethylamine and 6-chloro-1-hexene used is 7.4-8.2 g:10.1 g:11.8 g.

7. The polyolefin composite modified shielding material according to claim 4, characterized in that: In the third step, the ratio of the amount of pre-modified boron carbide, the intermediate product 1, and DCC is 5g:10-15g:3-4g.

8. The polyolefin composite modified shielding material according to claim 4, characterized in that: In the fourth step, the ratio of the amount of the intermediate product 2:2-phenylethyl chloride is 10g:15-20g.

9. The method for preparing the polyolefin composite modified shielding material according to any one of claims 1 to 8, characterized in that: The following steps are involved: After the raw materials are mixed according to the above proportions, they are put into a twin-screw extruder for extrusion granulation to obtain the shielding material.

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