CN115449117B

CN115449117B - Preparation method of gradient cross-linked rubber material and gradient cross-linked rubber material

Info

Publication number: CN115449117B
Application number: CN202211043443.XA
Authority: CN
Inventors: 张继华; 皂伟涛; 梁鼒; 王璇; 曹子城; 赵鸿敬; 吴福迪
Original assignee: Aerospace Research Institute of Materials and Processing Technology
Current assignee: Aerospace Research Institute of Materials and Processing Technology
Priority date: 2022-08-29
Filing date: 2022-08-29
Publication date: 2023-08-29
Anticipated expiration: 2042-08-29
Also published as: CN115449117A

Abstract

The invention discloses a preparation method of a gradient cross-linked rubber material, which comprises the steps of preparing a rubber film by taking olefin rubber with ligand functional groups, a vulcanizing agent and an accelerator as raw materials; preparing two coordination salt solutions with different concentrations, namely a first concentration coordination salt solution and a second concentration coordination salt solution; soaking the rubber film in the first concentration coordination salt solution; moving the rubber film upwards perpendicular to the liquid level of the first concentration coordination salt solution, and injecting the second concentration coordination salt solution into the first concentration coordination salt solution in the moving process; and (3) separating the rubber film from the liquid level of the coordination salt solution, and then carrying out vacuum drying to obtain the gradient cross-linked rubber material. The invention also discloses a gradient cross-linked rubber material obtained based on the method, which has good mechanical property and functionality and is suitable for being used as a high-performance functional rubber material.

Description

Preparation method of gradient cross-linked rubber material and gradient cross-linked rubber material

Technical Field

The invention belongs to the technical field of rubber material processing, and relates to a preparation method of a gradient cross-linked rubber material and the gradient cross-linked rubber material.

Background

As an important industrial material, rubber is widely used for seals, dampers, tires, and the like. However, rubber is soft and low in strength and requires reinforcement. Rubber reinforcement technology has been the focus of research on rubber-like materials. The nano reinforcing technology is the most commonly used rubber reinforcing method, and is a method for filling nano filler into rubber in a certain process to obtain a nano composite material. Common rubber reinforcing agents include carbon black, white carbon black, graphene, carbon nanotubes, montmorillonite and the like. When the rubber composite material is acted by external force, the well-dispersed nano filler can effectively restrict chain sliding of rubber molecules, so that mechanical strengthening and toughening of rubber are realized. Since the nanofiller has a high specific surface area, an excessive amount of the nanofiller is easily agglomerated in the rubber, and thus not only the reinforcing effect is reduced, but also the processing difficulty is caused. Meanwhile, the interface between the nano filler and the rubber has a key influence on the reinforcing capacity of the nano filler, and the strong interface between the nano filler and the rubber can effectively transfer stress, so that the reinforcing effect is improved, and meanwhile, the dispersibility of the filler is improved; and the weak interface can aggravate the aggregation of the filler, and reduce the reinforcing effect. These complex effects have limited the development of rubber reinforcement technology.

Inspired by biological materials, sacrificial bonds, such as hydrogen bonds, ionic bonds, coordination bonds, and the like have been used as secondary cross-links for rubber materials to build dual network structures: (1) a covalent bond primary cross-linked network; (2) a victim key network. The crosslinked network density of the rubber increases due to the presence of the sacrificial bonds. And before the main covalent cross-linking structure breaks, the sacrificial bond will break in advance, so that the rubber material obtains high strength, toughness and ductility, thus getting rid of the limitation brought by the nano reinforcing technology and becoming a promising rubber manufacturing method. Coordinate bond is a non-covalent bond with covalent bond strength comparable to that of rubber, and the bond is introduced into rubber as a sacrificial bond, so that double-network design can be realized, and good performance is obtained. Meanwhile, due to the dynamic characteristics of coordination bonds, the rubber material has the functions of shape memory, self-healing and the like, and the application field of the rubber material is enriched. However, at present, the introduction of the coordination network is mainly performed by a rubber blending mode, so that the distribution of coordination bonds cannot be well controlled, and the stability and the effectiveness of the sacrifice bond network are reduced. How to effectively control the distribution of the sacrificial bond and realize better reinforcement and functionality is a problem to be solved urgently.

Disclosure of Invention

The invention aims to overcome the defects, and provides a preparation method of a gradient cross-linked rubber material and the gradient cross-linked rubber material, which solve the problem that the distribution of coordination bonds is difficult to control in the prior art, so that the stability and effectiveness of a sacrifice bond network are affected.

In order to achieve the above purpose, the present invention provides the following technical solutions:

a preparation method of a gradient cross-linked rubber material comprises the following steps:

preparing a rubber film by taking olefin rubber with ligand functional groups, a vulcanizing agent and an accelerator as raw materials;

preparing two coordination salt solutions with different concentrations, namely a first concentration coordination salt solution and a second concentration coordination salt solution;

soaking the rubber film in the first concentration coordination salt solution;

moving the rubber film upwards perpendicular to the liquid level of the first concentration coordination salt solution, and injecting the second concentration coordination salt solution into the first concentration coordination salt solution in the moving process;

and (3) separating the rubber film from the liquid level of the coordination salt solution, and then carrying out vacuum drying to obtain the gradient cross-linked rubber material.

Further, the mass parts of the olefin rubber with ligand functional groups, the vulcanizing agent and the accelerator are as follows:

100 parts of olefin rubber with ligand functional groups;

0.2-3 parts of vulcanizing agent;

0.1 to 5 parts of accelerator.

Further, the olefin rubber with ligand functional groups is at least one of nitrile rubber, hydrogenated nitrile rubber, hydroxy nitrile rubber, epoxy natural rubber or butylbenzene pyridine rubber;

the coordination salt is at least one of Cu salt containing sulfate radical, fe salt containing sulfate radical, zn salt containing sulfate radical, sn salt containing sulfate radical, cu chloride salt, fe chloride salt, zn chloride salt, sn chloride salt, cu bromide salt, fe bromide salt, zn bromide salt or Sn bromide salt;

coordination bonds are formed between the olefin rubber with ligand functional groups and the coordination salt.

Further, the vulcanizing agent is sulfur;

the accelerator is at least one of thiazole, thiuram or sulfenamide accelerators;

further, the solvent selected for preparing the complex salt solution can simultaneously dissolve the complex salt and swell the rubber film.

Further, when preparing two coordination salt solutions with different concentrations, the organic solvent is at least one of acetone, ethanol or diethyl ether.

Further, the method for preparing the rubber film by taking the olefin rubber with ligand functional groups, the vulcanizing agent and the accelerator as raw materials comprises the following steps: mixing olefin rubber with ligand functional groups, a vulcanizing agent and an accelerator on an open mill, and carrying out thin pass to obtain a rubber sheet; vulcanizing the rubber sheet at 140-170 ℃ to obtain a rubber film;

after the rubber film is separated from the liquid level of the coordination salt solution, the temperature for vacuum drying is 50-60 ℃, and the vacuum degree is less than or equal to 100Kpa.

Further, the thickness of the rubber film is not more than 1mm, and the length of the rubber film is not less than 10mm.

Further, in the first concentration coordination salt solution and the second concentration coordination salt solution, the mass fraction of the coordination salt in the coordination salt solution with larger concentration is more than or equal to 50%, and the mass fraction of the coordination salt in the coordination salt solution with smaller concentration is less than or equal to 20%.

Further, the rubber film is moved upwards by a traction device perpendicular to the liquid level of the coordination salt solution with the first concentration; the traction device comprises a traction rope, a fixed pulley and traction equipment; one end of the traction rope is connected with traction equipment, and the other end of the traction rope is connected with the upper end of the rubber film after passing through a fixed pulley arranged above the coordination salt solution;

the moving speed of the rubber film when the rubber film moves upwards perpendicular to the liquid level of the coordination salt solution with the first concentration is less than or equal to 2mm/h;

and when the second concentration coordination salt solution is injected into the first concentration coordination salt solution by using injection equipment in the moving process, the injection speed of the second concentration coordination salt solution is more than or equal to 1ml/h.

Further, the traction equipment and the injection equipment are controlled in a linkage way or respectively;

and when the rubber film is completely soaked in the first concentration coordination salt solution, the liquid level of the first concentration coordination salt solution is H, so that the rubber film moves upwards perpendicular to the liquid level of the first concentration coordination salt solution, and when the second concentration coordination salt solution is injected into the first concentration coordination salt solution in the moving process, the liquid level of the coordination salt solution is maintained to be H by adding a solvent used for the coordination salt solution or removing the coordination salt solution.

A gradient cross-linked rubber material is obtained by adopting the preparation method of the gradient cross-linked rubber material.

Compared with the prior art, the invention has the following beneficial effects:

(1) According to the invention, the coordination salt solutions with different concentrations are innovatively matched with the rubber sheet in a moving mode, so that the spatial gradient configuration change of a coordination network structure is realized through a swelling effect, and the gradient crosslinked rubber material is obtained;

(2) The preparation method is simple and quick, has universality, and can be flexibly adjusted according to the target performance of the rubber material after the general relation between the target performance of the rubber material, the coordination salt solution and the moving speed is determined through a pre-test;

(3) Specific parameters such as the optimal film size, the moving speed and the like suitable for the method are provided, and the formation of a coordination network with gradient is ensured to the maximum extent;

(4) The gradient cross-linked rubber material obtained by the invention realizes a double-network structure of the rubber material by utilizing the action of coordination bonds and covalent cross-linking bonds, has good mechanical property and functionality, and is suitable for being used as a high-performance functional rubber material.

Drawings

FIG. 1 is a flow chart of a method for preparing a gradient cross-linked rubber material according to the present invention;

FIG. 2 is a schematic drawing of the traction of a rubber sheet during the preparation of the gradient cross-linked rubber material of the present invention;

in the figure, 1-traction equipment, 2-fixed pulleys, 3-traction ropes, 4-containers, 5-dilute solution, 6-concentrated solution and 7-rubber films.

Detailed Description

The features and advantages of the present invention will become more apparent and clear from the following detailed description of the invention.

The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are illustrated in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

In the design method of the rubber material with the double-crosslinked structure, two crosslinked networks can be independently constructed and are connected with each other through ligand functional groups of a main rubber chain, so that the ligand crosslinked network is different from a vulcanization reaction of relatively fixed main crosslinked network, and can be introduced into rubber through more complex processing means, thereby realizing the design of the crosslinked network. For olefin rubber such as nitrile rubber, epoxy natural rubber and the like, a coordination bond can be formed with transition metal ions conveniently through the functional ligand group, so that a coordination crosslinking network is obtained.

The gradient structure design is an excellent method in material design, and the specific distribution of the polymer in the gradient direction of components, filler distribution, morphology and the like can be realized by means of chemical synthesis, physical methods and the like, so that the complex mechanics and functionality of the material are realized. The invention combines the thought of gradient design, and constructs a gradient distributed coordination cross-linking network in a double cross-linking network. Because of the important role of metal ions in coordination bonds, the number and distribution of rubber ligand groups are relatively fixed, and therefore, the structural design of the gradient coordination cross-linked network can be realized by constructing the gradient distribution of the metal ions. According to the invention, by utilizing the principle that the polymer can be swelled in a good solvent, metal ions are dissolved in the good solvent and introduced into a vulcanized rubber system through the swelling effect, so that coordination with a rubber functional ligand is realized, and a double-crosslinked network is constructed. In order to realize gradient design, a special device is developed, on one hand, chemically crosslinked rubber is moved along the gradient direction, and on the other hand, the concentration of metal solution can be adjusted in the rubber moving process, so that different metal ion numbers are introduced into the rubber along the gradient direction, and the gradient coordination crosslinked rubber material is obtained. Due to the gradient structure of coordination bonds, the rubber can be broken at different stages of stretching, so that the toughening effect of the rubber is effectively improved; meanwhile, gradient coordination crosslinking causes gradient change of the glass transition temperature of the rubber, thereby having a gradient shape memory effect.

As shown in FIG. 1, the preparation method of the gradient cross-linked rubber material comprises the following steps:

(1) The following raw materials were prepared in parts by mass

(2) Mixing the raw materials except the coordination salt in the step (1) on an open mill, and discharging the sheet after thin passing for several times.

(3) Adopting a mould pressing method to prepare a rubber film, and vulcanizing the following conditions: the vulcanization temperature of the sizing material is 140-170 ℃, and the vulcanization time is determined by the positive vulcanization time tested by a vulcanizing instrument.

(4) Preparing the coordination salt in the step (1) into two solutions with different concentrations by using an organic solvent at normal temperature, namely a dilute solution and a concentrated solution, and dissolving the two solutions by using ultrasonic waves for later use.

(5) The rubber film in the step (3) is completely and vertically immersed in a container 4 containing a dilute solution 5 of a coordination salt. The top end of the rubber film 7 is vertically hung at the traction rope 3, the traction rope 3 is connected with the other end of the traction rope through the fixed pulley 2, the rubber film vertically moves at a certain speed, and meanwhile, the concentrated solution 6 is injected into the dilute solution 5, as shown in fig. 2.

(6) The concentrated solution prepared in step (4) is placed in an injectable pumping device and poured into a container of the dilute solution at a certain speed.

(7) And after the rubber film is separated from the liquid surface of the container, taking out and placing the rubber film into a vacuum oven, and slowly drying the rubber film to constant weight.

In a preferred embodiment, the olefin rubber bearing ligand functional groups is at least one of nitrile rubber, hydrogenated nitrile, hydroxybutyronitrile rubber, epoxynatural rubber or butylpyridine rubber.

In a preferred embodiment, the coordination salt is one or more of a sulfate-, chloride-or bromide-containing Cu, fe, zn and Sn salt.

In a preferred embodiment, the vulcanizing agent is sulfur.

In a preferred embodiment, the accelerator is one or more of thiazole, thiuram, sulfenamide accelerators.

In a preferred embodiment, the organic solvent is one or more of acetone, ethanol or diethyl ether.

In a preferred embodiment, the thickness of the rubber film is no more than 1mm, the film length is no less than 10mm, the dimensions are such that a significant gradient is formed and the complex salt ions are able to enter the rubber sufficiently to form a complex network during vertical movement of the rubber film.

In a preferred embodiment, the coordination salt dilute solution concentration is below 20wt.% and the concentrated solution concentration is above 50% wt.

In a preferred embodiment, the height of the dilute solution in the container should be greater than the length of the rubber membrane; the liquid surface diameter of the container is 1.1 times larger than the width of the film, so that the rubber film can be completely immersed in the coordination salt solution, and the moving process is free from interference.

In a preferred embodiment, the movable distance of the traction rope should be greater than the length of the rubber membrane.

In a preferred embodiment, the pulling speed should be no greater than 2mm/h to ensure that the complex salt ions are able to fully enter the rubber interior to form a complex network during the vertical movement of the rubber film.

In a preferred embodiment, the concentrated solution injection rate is not less than 1ml/h.

In a preferred embodiment, the traction device and the injection device can be controlled in a linked manner or can be controlled separately.

In a preferred embodiment, the temperature of the vacuum oven is 50-60℃and the vacuum is less than or equal to 100KPa.

In a preferred embodiment, to avoid solvent evaporation in the vessel or changes in the liquid level due to the addition of the concentrated solution, a small amount of solvent may be supplemented during operation or a small amount of a mixture of the dilute solution and the concentrated solution may be withdrawn.

It should be noted that in the above preparation process, the preparation of the gradient cross-linked rubber material can be achieved by adding the concentrated solution to the diluted solution or by adding the diluted solution to the concentrated solution, and the gradient directions of the cross-linked rubber material are opposite in both cases.

Example 1:

(1) The following raw materials in parts by mass are prepared: 100g of nitrile rubber (Zhenjiang emperor, 1052); 50g of zinc chloride; 2.5g of sulfur; 0.5g of accelerator tetramethylthiuram sulfide (TT).

(2) Mixing the raw materials except zinc chloride in the step (1) on an open mill, and discharging sheets after ten thin passes.

(3) The mould size was 200X 1mm, vulcanization conditions: the vulcanization time is 20 minutes at 160 ℃ and the pressure is 3MPa. A rubber film having a thickness of 1mm was prepared.

(4) Preparing two solutions with different concentrations of the zinc chloride in the step (1) by acetone at normal temperature: 5wt% and 60wt% and ultrasonically dissolving for later use.

(5) The rubber film of step 1) was cut into a length by width by thickness of 50X 20X 1mm and completely immersed vertically in a container containing 5wt% zinc chloride solution. The vessel was cylindrical, the height of the solution was 100mm, and the diameter of the liquid surface was 22mm. The top end of the rubber film is vertically hung at the traction rope, the traction rope passes through the fixed pulley, the other end of the traction rope is connected to traction equipment, and the rubber film vertically moves at the speed of 1 mm/h.

(6) The concentrated solution was placed in an injectable pumping apparatus and a 60wt% concentrated zinc chloride solution was poured into the container at 10 ml/h.

(7) After the rubber film is separated from the liquid surface of the container, the rubber film is taken out and placed into a vacuum oven with the vacuum degree of 100KPa and the temperature of 50 ℃ to be slowly dried to constant weight.

Example 2:

(1) The following raw materials in parts by mass are prepared: 100g of epoxidized natural rubber (epoxy degree: 50%); 5g of ferric chloride; 0.5g of sulfur; accelerator N-cyclohexyl-2-benzothiazole sulfenamide (CZ) 2.2g

(2) Mixing the raw materials except the ferric chloride in the step (1) on an open mill, and discharging the tablets after eight times of thin pass.

(3) The mould dimensions were 100X 200X 0.5mm, vulcanization conditions: vulcanizing at 150 ℃ for 30 minutes under 5MPa. A rubber film having a thickness of 0.5mm was prepared.

(4) Preparing the ferric chloride in the step (1) into two solutions with different concentrations by using diethyl ether at normal temperature: 10wt% and 50wt% and ultrasonically dissolving for later use.

(5) The rubber film was cut into a length by width by thickness of 10X 0.5mm and completely immersed vertically in a container containing 10wt% ferric chloride solution. The vessel was cylindrical, the height of the solution was 20mm, and the diameter of the liquid surface was 12mm. The top end of the rubber film is vertically hung at the traction rope, the traction rope passes through the fixed pulley, the other end of the traction rope is connected to traction equipment, and the rubber film vertically moves at the speed of 2 mm/h.

(6) The concentrated solution was placed in an injectable pumping apparatus and a 50wt% concentrated ferric chloride solution was poured into the container at 2 ml/h.

(7) After the rubber film is separated from the liquid surface of the container, the rubber film is taken out and placed into a vacuum oven with the vacuum degree of 70KPa and the temperature of 60 ℃ to be slowly dried to constant weight.

Example 3:

(1) The following raw materials in parts by mass are prepared: 100g of hydrogenated nitrile rubber (Japanese rayleigh, 1020); 10g of copper chloride; 1g of sulfur; accelerator 2,2' -thiodibenzothiazyl (DM) 2g, accelerator TT 0.5g.

(2) Mixing the raw materials except copper chloride in the step (1) on an open mill, and discharging sheets after eight times of thin pass.

(3) The mould dimensions were 100X 200X 0.3mm, vulcanization conditions: the vulcanization time is 30 minutes at 160 ℃ and the pressure is 5MPa. A rubber film having a thickness of 0.3mm was prepared.

(4) Preparing the copper chloride in the step (1) into two solutions with different concentrations by using acetone at normal temperature: 20wt% and 66wt% and ultrasonically dissolving for later use.

(5) The rubber film was cut into a length by width by thickness of 15X 20X 0.3mm and completely immersed vertically in a container containing 20wt% copper chloride solution. The vessel was cylindrical, the height of the solution was 25mm, and the diameter of the liquid surface was 25mm. The top end of the rubber film is vertically hung at the traction rope, the traction rope passes through the fixed pulley, the other end of the traction rope is connected to traction equipment, and the rubber film vertically moves at the speed of 1.5 mm/h.

(6) The concentrated solution was placed in an injectable pumping apparatus and a 66wt% concentrated zinc chloride solution was poured into the container at 5 ml/h.

(7) After the rubber film is separated from the liquid surface of the container, the rubber film is taken out and placed into a vacuum oven with the vacuum degree of 100KPa and the temperature of 60 ℃ to be slowly dried to constant weight.

Example 4:

(1) The following raw materials in parts by mass are prepared: 100g of butylbenzene pyridine rubber; 10g of stannic chloride; 2.5g of sulfur; accelerator 2,2' -thiodibenzothiazyl (DM) 1g.

(2) Mixing the raw materials except the tin chloride in the step (1) on an open mill, and discharging the sheet after eight times of thin pass.

(4) Preparing the tin chloride in the step (1) into two solutions with different concentrations by using ethanol at normal temperature: 15wt% and 50wt% and ultrasonically dissolving for later use.

(5) The rubber film was cut into a length by width by thickness of 100X 20X 0.3mm and completely immersed vertically in a container containing 15wt% copper chloride solution. The vessel was cylindrical, the height of the solution was 110mm, and the diameter of the liquid surface was 25mm. The top end of the rubber film is vertically hung at the traction rope, the traction rope passes through the fixed pulley, the other end of the traction rope is connected to traction equipment, and the rubber film vertically moves at the speed of 0.5 mm/h.

(6) The concentrated solution was placed in an injectable pumping apparatus and a 50wt% concentrated zinc chloride solution was poured into the container at 10 ml/h.

(7) After the rubber film is separated from the liquid surface of the container, the rubber film is taken out and placed into a vacuum oven with the vacuum degree of 90KPa and the temperature of 60 ℃ to be slowly dried to constant weight.

Comparative example 1:

the raw materials in this example are the same as those in example 1, except that the dilute solution+the concentrated solution+the traction mode are replaced by the dilute solution+the soaking mode, and the specific steps are as follows:

(1) The following raw materials in parts by mass are prepared: 100g of nitrile rubber (Zhenjiang emperor, 1052); 50g of zinc chloride; 2.5g of sulfur; 0.5g of accelerator TT.

(3) The mold dimensions were 200 x 1mm, vulcanization conditions: the vulcanization time is 20 minutes at 160 ℃ and the pressure is 3MPa. A rubber film having a thickness of 1mm was prepared.

(4) Preparing the zinc chloride in the step (1) into a solution with the concentration of 5 weight percent by using acetone at normal temperature, and dissolving the solution by using ultrasonic waves for standby.

(5) The rubber film was cut to a length by width by thickness of 50X 20X 1mm and immersed in a container containing 5wt% zinc chloride solution by hanging vertically with a pulling rope. The vessel was cylindrical, the height of the solution was 100mm, and the diameter of the liquid surface was 22mm. The soaking time is 5 hours in total.

(6) The rubber film was taken out and placed in a vacuum oven with a vacuum degree of 100KPa and a temperature of 50℃and dried slowly to constant weight.

Comparative example 2:

the raw materials in this example are the same as those in example 1, except that the mode of dilute solution + concentrated solution + traction is replaced by the mode of concentrated solution + soaking, and the specific steps are as follows:

(1) The following raw materials in parts by mass are prepared: 100g of nitrile rubber (Zhenjiang emperor, 1052); 50g of zinc chloride; 2.5g of sulfur; accelerator TT 0.5g

(4) Preparing the zinc chloride in the step (1) into a solution with the concentration of 60wt% by using acetone at normal temperature, and dissolving the solution by using ultrasonic waves for standby.

(5) The rubber film was cut to a length by width by thickness of 50X 20X 1mm and immersed in a vessel containing a 60wt% zinc chloride solution by hanging vertically with a pulling rope. The vessel was cylindrical, the height of the solution was 100mm, and the diameter of the liquid surface was 22mm. The soaking time is 5 hours in total.

The tensile strength and the elongation at break of the rubbers obtained in examples 1 to 4 and comparative examples 1 to 2 are shown in Table 1, and it can be seen that the gradient cross-linked rubber obtained by the method of the present invention shows a remarkable improvement in the tensile strength and the elongation at break, and the method of the present invention can effectively improve the tensile properties of the rubber.

TABLE 1 tensile Properties of the products obtained in examples 1 to 4 and comparative examples 1 to 2

Examples	Tensile Strength/MPa	Elongation at break/%
			Example 1	31.2	566
Example 2	33.5	632
			Example 3	35.5	553
Example 4	30.4	489
			Comparative example 1	10.7	422
Comparative example 2	24.3	184

In order to observe the shape memory performance of the gradient crosslinked rubber, the rubber film is cut into 5 parts along the length gradient direction, the serial numbers are written as 1-5, the serial number 1 is the topmost position of the traction rope, and the serial number 5 is the part which finally leaves the solution. The deformation fixing temperature is set to be-10 ℃ and the shape recovery temperature is set to be 70 ℃. The relationship between the positions and recovery times of example 1 and comparative examples 1 and 2 is summarized in table 2. As can be seen from Table 2, example 1 showed a shape recovery time with an increase in gradient with an increase in the number of the marked portions, indicating that different coordination crosslinking gradients were formed inside the rubber, whereas comparative examples 1 and 2 were irregular, and the rubbers obtained in comparative examples 1 and 2 did not have shape memory properties. The preparation method of the invention simultaneously endows the rubber with good mechanical property and shape memory property, and is suitable for being used as a high-performance functional rubber material.

TABLE 2 relationship between position and recovery time for example 1, comparative examples 1 and 2

The invention has been described in detail in connection with the specific embodiments and exemplary examples thereof, but such description is not to be construed as limiting the invention. It will be understood by those skilled in the art that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, and these fall within the scope of the present invention. The scope of the invention is defined by the appended claims.

What is not described in detail in the present specification is a well known technology to those skilled in the art.

Claims

1. A preparation method of a gradient cross-linked rubber material is characterized by comprising the following steps:

soaking the rubber film in the first concentration coordination salt solution;

after the rubber film is separated from the liquid level of the coordination salt solution, vacuum drying is carried out to obtain a gradient cross-linked rubber material;

in the first concentration coordination salt solution and the second concentration coordination salt solution, the mass fraction of the coordination salt in the coordination salt solution with larger concentration is more than or equal to 50%, and the mass fraction of the coordination salt in the coordination salt solution with smaller concentration is less than or equal to 20%.

2. The preparation method of the gradient cross-linked rubber material according to claim 1, wherein the mass parts of the olefin rubber with ligand functional groups, the vulcanizing agent and the accelerator are as follows:

100 parts of olefin rubber with ligand functional groups;

0.2-3 parts of vulcanizing agent;

0.1 to 5 parts of accelerator.

3. The method for preparing the gradient cross-linked rubber material according to claim 1, wherein the olefin rubber with ligand functional groups is at least one of nitrile rubber, hydrogenated nitrile rubber, hydroxy nitrile rubber, epoxy natural rubber or styrene-butadiene pyridine rubber;

4. The method for preparing a gradient cross-linked rubber material according to claim 1, wherein the vulcanizing agent is sulfur;

when preparing two coordination salt solutions with different concentrations, the organic solvent is at least one of acetone, ethanol or diethyl ether.

5. The method for preparing the gradient cross-linked rubber material according to claim 1, wherein the method for preparing the rubber film by taking the olefin rubber with ligand functional groups, the vulcanizing agent and the accelerator as raw materials is as follows: mixing olefin rubber with ligand functional groups, a vulcanizing agent and an accelerator on an open mill, and carrying out thin pass to obtain a rubber sheet; vulcanizing the rubber sheet at 140-170 ℃ to obtain a rubber film;

6. The method for producing a gradient cross-linked rubber material according to claim 1, wherein the thickness of the rubber film is not more than 1mm, and the length of the rubber film is not less than 10mm.

7. The method for producing a gradient cross-linked rubber material according to claim 1, wherein the rubber film is moved upward by a traction means perpendicularly to the liquid surface of the first concentration complex salt solution; the traction device comprises a traction rope, a fixed pulley and traction equipment; one end of the traction rope is connected with traction equipment, and the other end of the traction rope is connected with the upper end of the rubber film after passing through a fixed pulley arranged above the coordination salt solution;

8. The method for preparing the gradient cross-linked rubber material according to claim 7, wherein the traction equipment and the injection equipment are controlled in a linkage manner or respectively;

9. A gradient cross-linked rubber material, characterized in that it is obtained by a method for producing a gradient cross-linked rubber material according to any one of claims 1 to 8.