KR102021037B1 - Bearing Element with Hydrophile Layer and the Producing Method thereof - Google Patents

Abstract

The present invention relates to an artificial joint including a surface made of a polymer material, and more particularly, to a bearing element capable of reducing a coefficient of friction by having a hydrophilic layer similar to a joint structure of a human body on a polymer surface and a method of manufacturing the same.

Description

Bearing element with hydrophile layer and the producing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing element comprising a surface of polymer material, and more particularly, to a bearing element capable of reducing a coefficient of friction by having a hydrophilic layer similar to the joint structure of a human body on a polymer surface and a method of manufacturing the same.

The joints of the human body have ciliary tissue on its surface, which retains hydrophilicity to store body fluid. Therefore, the body fluid is stored in the ciliated tissue, and functions as a lubricant to enable natural movement of the human joint.

The joints of the human body are one of the important organs that perform the functions of determining the overall shape and balance of the body and supporting the weight among various parts of the human body. As such, joints are frequently used and further exposed to frequent shocks, the aging progresses over time, or the function of the joints is weakened or lost due to various diseases or accidents. Since such joint damage is difficult to treat in a natural state, development of artificial joints that can replace damaged joints is steadily progressing. The quality of life is remarkably improved through the treatment of artificial joints. Knee, shoulder, hip, and ankle joints are typical artificial joints.

1 is a view showing a knee joint of the artificial joint, which is disclosed in Korean Patent Laid-Open No. 10-2009-0076346 (2009.07.13.). The knee joint includes a femur element 5 largely replacing the articular surface of the distal end of the femur, a tibia element 7 replacing the articular surface of the proximal end of the tibia, and a femur located between the femur element and the tibial element. Bearing element 1 having an articulation surface in contact with the articulation surface of the element. Here, the femur element is in contact with the bearing element and the joint movement, the joint surface of the bearing element has a surface of the polymer material. The surface of the polymer material wears out during the joint movement with the femoral element and generates wear particles during the wear process. These wear particles are ingested by macrophage around the joint, and macrophages secrete specific cytokine and prostaglandin along with the ingestion of wear particles through a signaling system called RANKL. Osteoclast is greatly activated around the joint under the influence of secreted cytokine, and the balance between osteoblast and osteoclast is broken and osteolysis occurs, resulting in destruction of osteocytes around the artificial joint. The problem is that the joints lose their function.

Such a problem arises from the fact that the polymer material constituting the surface of the bearing element is hydrophobic, and thus has significantly lower lubricity than the joints of the human body having hydrophilicity. Therefore, studies to give hydrophilicity to the surface of the polymer is steadily progressing, but due to the high cost, it is not easy to popularize. This high cost may act as a factor that increases the burden on the patient in the reality that the demand for artificial joints is rapidly increased due to aging. Therefore, while providing artificial joints having a hydrophilic polymer surface for the popularization of artificial joints, development of inexpensive artificial joints with a significant reduction of the friction coefficient using hydrophilicity is required.

The present invention has been made to solve the problems of the prior art, it is an object of the present invention to provide a bearing element and a method of manufacturing the same to reduce the friction coefficient to minimize the generation of wear particles.

Another object of the present invention is to provide a bearing element and a method of manufacturing the same, which can lead to popularization of artificial joints by reducing the manufacturing cost while minimizing the reduction of friction coefficient and the occurrence of wear particles.

According to one embodiment of the present invention, the bearing element of the present invention has a hydrophilic layer on the surface of the artificial joint including the polymer surface.

According to another embodiment of the present invention, in the bearing element of the present invention, the hydrophilic layer is formed by grafting a polymer material on the polymer surface.

According to another embodiment of the present invention, in the bearing element of the present invention, the polymer material is a zwitterionic polymer material.

According to another embodiment of the present invention, the bearing element of the present invention is formed by attaching the polymer material to the polymer surface by grafting a polymerizable monomer.

According to another embodiment of the present invention, in the bearing element of the present invention, the monomer consists of a methacryloyloxy alkyl group and a sulfopropyl-ammonium hydroxide group.

According to another embodiment of the present invention, in the bearing element of the present invention, one end of the methacryloyloxy alkyl group is bonded to the polymer surface and the sulfopropyl-ammonium hydroxide group is the methacryloyloxy alkyl. Connected to the group.

According to another embodiment of the present invention, in the bearing element of the present invention, the monomer is 2- (methacryloyloxy) ethyl dimethyl- (3-sulfopropyl) ammonium hydroxide.

According to another embodiment of the invention, the bearing element of the invention, the hydrophilic layer has a brush structure consisting of a plurality of strands.

       According to another embodiment of the present invention, in the bearing element of the present invention, the polymer surface is formed of crosslinked polyethylene.

According to another embodiment of the present invention, in the bearing element of the present invention, each strand constituting the brush structure does not cause connection or entanglement between the strands.

      According to another embodiment of the invention, in the bearing element of the invention, the hydrophilic layer has a thickness of at least 35 nm.

According to another embodiment of the invention, in the bearing element of the invention, the hydrophilic layer has a thickness of 35nm to 300nm.

According to another embodiment of the present invention, in the bearing element of the present invention, the coefficient of friction of the hydrophilic layer is 0.02 or less.

According to yet another embodiment of the present invention, in the bearing element of the present invention, the coefficient of friction of the hydrophilic layer is from 0.0093 to 0.02.

According to another embodiment of the present invention, in the bearing element of the present invention, the wear amount of the hydrophilic layer is 0.5 mm ³ or less.

According to another embodiment of the present invention, the manufacturing method of the bearing element of the present invention, the photoinitiator coating step of coating the photoinitiator on the surface by immersing and drying the bearing element having a polymer surface in a solution containing a photoinitiator for a predetermined time; And immersing the bearing element in a hydrophilic solution and irradiating ultraviolet light for a predetermined time to grow a hydrophilic layer.

According to still another embodiment of the present invention, in the method of manufacturing a bearing element of the present invention, the hydrophilic solution is ultrapure water in which a monomer composed of a methacryloyloxy alkyl group and a sulfopropyl-ammonium hydroxide group is dissolved.

According to another embodiment of the present invention, in the method for manufacturing a bearing element of the present invention, the polymer surface of the bearing element is formed of crosslinked polyethylene.

According to another embodiment of the present invention, the manufacturing method of the bearing element of the present invention, the hydrophilic layer forming step is a brush structure forming one end of the methacryloyloxy alkyl group is bonded to the polymer surface to form a brush structure Steps.

According to another embodiment of the present invention, in the method for manufacturing a bearing element of the present invention, in the brush structure forming step, the sulfopropyl-ammonium hydroxide group is connected to the methacryloyloxy alkyl group.

According to another embodiment of the present invention, the manufacturing method of the bearing element of the present invention, the hydrophilic layer forming step, 30 minutes ~ 120 to 10 ~ 40mW / ㎠ UV intensity in a hydrophilic solution of 0.25 ~ 0.5mol / L concentration Irradiate for minutes to grow the hydrophilic layer.

The present invention has the following effects.

 The present invention, by reducing the friction coefficient to minimize the occurrence of wear particles to prevent the osteolysis phenomenon can be obtained to extend the service life of the artificial joint.

The present invention can reduce the friction coefficient and minimize the occurrence of wear particles while lowering the manufacturing cost can achieve the effect that can lead to the popularization of artificial joints.

1 is a schematic diagram of the knee joint of the artificial joint.
2 is a cross-sectional view of a bearing element with a hydrophilic layer in accordance with one embodiment of the present invention.
3 is an enlarged view of a portion A of FIG. 2.
4A-4D illustrate the process by which the hydrophilic layer of FIG. 3 is formed.
5 is an XPS surface elemental analysis graph of a specimen surface without a hydrophilic layer.
6 is an XPS surface elemental analysis graph of a specimen surface with a hydrophilic layer.
FIG. 7 is a TEM photograph showing the change in hydrophilic layer thickness of a specimen without hydrophilic layer and with hydrophilic layer with UV irradiation time. FIG.
8 is a graph showing the relationship between ultraviolet irradiation time and the thickness of a hydrophilic layer.
FIG. 9 is a TEM photograph showing the change in hydrophilic layer thickness of a specimen without hydrophilic layer and with hydrophilic layer depending on UV irradiation intensity. FIG.
10 is a graph showing the relationship between ultraviolet irradiation intensity and thickness of a hydrophilic layer.
FIG. 11 is a TEM (Transmission Electron Microscope) photograph showing the change in the hydrophilic layer thickness of a specimen with a hydrophilic layer-free and with a hydrophilic layer with a CLPE surface.
12 is a graph showing the relationship between the concentration of the hydrophilic solution and the thickness of the hydrophilic layer.
13 is a graph showing the relationship between UV irradiation time and friction coefficient.
14 is a graph showing the relationship between ultraviolet irradiation intensity and friction coefficient.
15 is a graph showing the relationship between the concentration of the hydrophilic solution and the friction coefficient.
16 is a graph showing the relationship between temperature and coefficient of friction.
FIG. 17A is a 3-D image of a confocal laser microscope after measuring a coefficient of friction in a state in which a specimen without a hydrophilic layer is immersed in water. FIG.
FIG. 17B is a 3-D image of a confocal laser microscope taken after measuring a coefficient of friction while submerging a specimen having a hydrophilic layer in water.
FIG. 18A is a 3-D image of a confocal laser microscope taken after measuring a friction coefficient in a state in which a specimen without a hydrophilic layer is immersed in a similar biological solution. FIG.
FIG. 18B is a 3-D image of a confocal laser microscope after measuring the coefficient of friction in a state in which a specimen having a hydrophilic layer is immersed in an analogous biological solution. FIG.
19 is a graph showing the relationship between UV irradiation time and wear amount.
20 is a graph showing the relationship between ultraviolet irradiation intensity and wear.
21 is a graph showing the relationship between the concentration of a hydrophilic solution and the amount of wear.
22 is a graph showing the relationship between the coefficient of friction and the thickness of the hydrophilic layer of a specimen immersed in water.
FIG. 23 is a graph showing the relationship between the thickness of the hydrophilic layer and the coefficient of friction of specimens immersed in analogous biological solution.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

The present invention is to form a hydrophilic layer on the surface of the bearing element which is a part of the joint movement of the components of the artificial joint to replace the joint of the human body. Joints of the human body largely include the hip joint, knee joint, shoulder joint, ankle joint. Other than that, all the parts of the human body in which the bones and bones make relative movement are called joints, and the implants that replace them are called artificial joints. The element in which the hydrophilic layer is formed among the artificial joints refers to a bearing element having a polymer material or at least a joint surface having a polymer coated surface. Bearing elements are joint motions with other elements. If the femur and tibia elements perform the function of bearing elements, they may be bearing elements. The polymer material is preferably polyethylene (PE), and crosslinked polyethylene (CLPE) is particularly suitable.

As shown in FIG. 2, the bearing element 1 of the present invention comprises a substrate comprising a polymer material (hereinafter referred to as a 'polymer surface' 2) and a hydrophilic layer 4 bonded to the surface thereof. It includes.

The substrate may be formed entirely of a polymer material so that the surface 2 may be a polymer material. However, only the surface of the joint motion may be partially coated with the polymer material to form the polymer surface 2.

As shown in FIG. 3, the hydrophilic layer 4 has a brush structure comprising one or more strands 41. The brush structure is such that one end of each strand is bonded to the polymer surface 2 and the other end remains free. And, the neighboring strands 41 are maintained so as not to entangle with each other in the body fluid. Maintaining non-tangling in body fluids means that ions are present in the body fluid that can offset the tendency for intramolecular or intermolecular binding between the strands, and these ions wrap up the molecules that make up the strand, resulting in intermolecular or intramolecular binding of the strands. Reduce the tendency to prevent tangles.

4A to 4D show the process of growing the hydrophilic layer 4 on the polymer surface 2. First, a method of manufacturing a bearing element having a hydrophilic layer will be described.

The bearing element manufacturing method comprises a photoinitiator coating step and a hydrophilic layer forming step.

, Benzoin methyl ether :

, 4-Benzoylbiphenyl :

, 4,4'-Dimethylbenzil :

, 4'-Ethoxyacetophenone :

, Benzophenone :

를 사용할 수 있다. 베어링요소를 광개시제 포함된 용액에 일정시간 동안 침지시킨 후 건조시키게 된다. 상기 광개시제가 용해시키는 용매는 아세톤이 사용될 수 있다. The photoinitiator coating step is a step of coating the photoinitiator on the polymer surface by immersing and drying the bearing element having a polymer surface in a solution containing the photoinitiator for a predetermined time. Photoinitiator Benzil:

, Benzoin methyl ether:

, 4-Benzoylbiphenyl:

, 4,4'-Dimethylbenzil:

, 4'-Ethoxyacetophenone:

, Benzophenone:

Can be used. The bearing element is dipped in a solution containing a photoinitiator for a certain time and then dried. Acetone may be used as the solvent in which the photoinitiator is dissolved.

In the hydrophilic layer forming step, the dried bearing element is again immersed in a hydrophilic solution in which the monomer is dissolved, and then irradiated with ultraviolet light for a predetermined time to form the hydrophilic layer 4 on the polymer surface 2. The monomer is a hydrophilic monomer having zwitter-ion in a solution, and is composed of a methacryloyloxy alkyl group and a sulfopropyl-ammonium hydroxide group. The monomer has the following structural formula.

Structural Formula of Zwitterionic Monomer

R ₁ , R ₂ includes all C _n H _2n-1 (n = 1,2,3 ,,,, 6) as carbon chain, x, y also includes all zero or more as carbon chain, A ₁ means C (carbon) or O (oxygen).

Preferably, the monomer having a simple and inexpensive zwitterion is suitable 2- (methacryloyloxy) ethyl dimethyl- (3-sulfopropyl) ammonium hydroxide having the following structural formula.

[Structure of 2- (methacryloyloxy) ethyl dimethyl- (3-sulfopropyl) ammonium hydroxide]

The hydrophilic layer forming step includes a brush structure forming step.

Hereinafter, the brush structure forming step will be described.

The hydrophilic solution may be an ultrapure water solution in which the monomer is dissolved in distilled water and impurities are removed. The distilled water is ultra-pure grade water as a third distilled water to adjust the pH, and firstly remove the organic and inorganic materials, and then make a second purified water through reverse osmosis membrane, sterilization and the like.

When the dried bearing element 1 is immersed in the hydrophilic solution in which the monomer is dissolved, ultraviolet rays are irradiated for a predetermined time. As shown in FIG. 4A, radicals are generated on the surface of the polymer coated with the photoinitiator and the polymer is dried. The surface is surrounded by a zwitterionic monomer 410 in solution, and as shown in FIG. 4B, the methacryloyloxy alkyl group 412 of the monomer has a bearing element at one end thereof. It is grafted to the site | part which generate | occur | produced the radical of the polymer surface 2 of, and the other end keeps a free state. In this case, the sulfopropyl-ammonium hydroxide group (dimethyl- (3-sulfopropyl) ammonium hydroxide group, 414) is bonded to the polymer surface (2) in the state bonded to the methacryloyloxy alkyl group (methacryloyloxy alkyl group, 412) Will remain unbound. Subsequently, as shown in FIG. 4C, the other monomer 410 is polymerized through the process of being polymerized at the free end of the methacryloyloxy alkyl group 412 already bonded to the polymer surface 1. The strand 41 is grown. Through this process repeatedly, as shown in FIG. 4D, a plurality of strands 41 grow on the polymer surface to form a hydrophilic layer 4 having a brush structure.

The hydrophilic layer 4 consists of a plurality of strands, the strands comprising a zwitterionic sulfopropyl-ammonium hydroxide group, which may be considered to cause entanglement between strands, but as previously seen, The 41 are kept intact in the body fluids. Maintaining non-tangling in body fluids means that ions are present in the body fluid that can offset the tendency for intramolecular or intermolecular binding between the strands, and these ions wrap up the molecules that make up the strand, resulting in intermolecular or intramolecular binding of the strands. Reduce the tendency to prevent tangles. The hydrophilic layer is different from the ciliated layer formed on the joint surface of the human body and its components, but the structure is similar, so that the friction coefficient and the amount of wear can be significantly reduced by providing a lubricating function by supporting the body fluid. By using a low cost monomer, the above effects can be obtained.

Hereinafter, the effect of the embodiment of the present invention through various experiments.

Preparation of Specimen Comparative Examples and Examples 1 to 8

A disc made of cross-linked polyethylene (CLPE, Orthoplastice, USA) (diameter 20 mm x thickness 5 mm) was used in acetone (Sigma-aldrich, USA) solution in which benzophenone (Sigma-aldrich, USA) was dissolved at a concentration of 10 mg / ml. It was dipped for a second and then dried. Through this process, acetone evaporates and the disk surface remains coated with benzophenone.

Then, the concentration of the hydrophilic solution using an ultraviolet irradiator (Lichtzen, Korea) while immersing a dry disk in ultrapure water solution in which monomer 2- (methacryloyloxy) ethyl dimethyl- (3-sulfopropyl) ammonium hydroxide was dissolved at the following concentration, Comparative Examples of disks without a hydrophilic layer and Examples 1 to 8 having a hydrophilic layer 4 were prepared while changing the ultraviolet irradiation time and the ultraviolet irradiation intensity.

Process conditions of Comparative Example and Example division density
(mol / L) UV irradiation intensity
(mW / ㎠) UV irradiation time
(min) Comparative example 0 0 0 Example 1 0.5 40 30 Example 2 0.5 40 60 Example 3 0.5 40 90 Example 4 0.5 40 120 Example 5 0.5 10 90 Example 6 0.5 20 90 Example 7 0.5 30 90 Example 8 0.25 40 90

[Experiment 1]: XPS surface elemental analysis

In order to confirm that the hydrophilic layer of the zwitterionic polymer was well coated on the surface of the polymer, elemental analysis of the surface was performed by using an X-ray photoelectron spectrometer (XPS: FEI, USA) for Comparative Example and Example 3.

In Comparative Example, only peaks corresponding to C _1s are identified as shown in FIG. 5, while in Example 3, peaks corresponding to C _1S , N _1S and S _2P were observed as shown in FIG. 6. . Thus, it can be seen that the 2- (methacryloyloxy) ethyl dimethyl- (3-sulfopropyl) ammonium hydroxide monomer was stably bound to the polymer surface.

[Experiment 2] thickness of hydrophilic layer

In order to confirm the change in the thickness of the hydrophilic layer according to the ultraviolet irradiation time, the irradiation intensity, and the concentration of the hydrophilic solution, a transmission electron microscope (TEM: FEI, USA) was used to compare the comparative examples, Examples 1, 2, 3 and 4 The thickness of the specimen was cut and measured according to the irradiation time (Figs. 7 and 8), and the specimens of Comparative Examples, Examples 5, 6, 7 and 8 were cut to measure the thickness change according to the irradiation intensity (Fig. 9 and 10), Comparative Examples, The specimens of Examples 3 and 8 were cut to measure the thickness change according to the concentration of the hydrophilic solution (Figs. 11 and 12).

Looking at the correlation between the irradiation time and the thickness with reference to Figures 7 and 8, the comparative example confirmed that no hydrophilic layer was formed. In Examples 1, 2, 3, and 4, as the irradiation time is increased from 30 minutes to 120 minutes in units of 30 minutes, the thickness is from 99.25 nm to 278.25 nm as shown in Table 2 below. It could be confirmed that the increase.

Correlation between irradiation time and thickness Item Thickness (nm) Comparative example 0 Example 1 (30 minutes) 99.25 Example 2 (60 minutes) 106.75 Example 3 (90 minutes) 204.00 Example 4 (120 minutes) 278.25

In addition, looking at the correlation between the irradiation intensity and the thickness with reference to Figures 9 and 10, the comparative example confirmed that no hydrophilic layer was formed. In Examples 5, 6, 7, and 8, as shown in Table 3 below, as the irradiation intensity of ultraviolet rays increases from 10 mW / cm 2 to 40 mW / cm 2 in units of 10 mW / cm 2, the thickness is 37.5. It was confirmed that the increase from 204nm to 204nm.

Correlation between irradiation intensity and thickness Item Thickness (nm) Comparative example 0 Example 5 (10 mW / cm 2) 37.50 Example 6 (20 mW / cm 2) 97.25 Example 7 (30 mW / cm 2) 171.50 Example 8 (40 mW / cm 2) 204.00

Finally, looking at the correlation between the concentration and the thickness of the hydrophilic solution with reference to Figures 11 and 12, the comparative example confirmed that no hydrophilic layer was formed. And, in the case of Examples 3 and 8, as shown in Table 4 below, when the concentration of the solution is 0.5 mol / L and 0.25 mol / L, respectively, the thickness increases with increasing concentration Confirmed.

Correlation between Concentration and Thickness Item Thickness (nm) Comparative example 0 Example 8 (0.25 mol / L) 110.75 Example 3 (0.5 mol / L) 204.00

As described above, it can be seen that the thickness of the hydrophilic layer increases as the irradiation time and irradiation intensity of ultraviolet rays increase, and as the concentration of the hydrophilic solution increases, the thickness also increases.

[Experiment 3] Friction Coefficient

In order to check the friction coefficient change of the hydrophilic layer according to the irradiation time, irradiation intensity and concentration of the hydrophilic solution, a friction tester (CETR, USA) was used to perform a 10 mm sliding test with a load of 0.98N and a speed of 2mm / s. 100 times. For the specimens of Comparative Examples, Examples 1, 2, 3 and 4, the friction coefficient change was measured according to the irradiation time (FIG. 13). For Comparative Examples, Examples 5, 6, 7 and 8, The friction coefficient change was measured (FIG. 14). For the specimens of Comparative Examples, Examples 3 and 8, the friction coefficient change was measured according to the concentration of the hydrophilic solution (FIG. 15). The change in the coefficient of friction was measured (Fig. 16). Each experiment was performed in the same manner as the specimen was immersed in water and in a simulated body fluid.

Looking at the correlation between the irradiation time and the friction coefficient with reference to Figure 13, Examples 1, 2, 3, 4 it was found that the friction coefficient is smaller than the comparative example. In addition, it was confirmed that the friction coefficient decreased as the irradiation time increased among Examples 1, 2, 3, and 4, respectively. However, it was confirmed that there was no significant change between Examples 3 and 4.

Correlation between irradiation time and coefficient of friction Item
Coefficient of friction water  Analogous biological solution Comparative example 0.0284 0.0222 Example 1 (30 minutes) 0.0124 0.0131 Example 2 (60 minutes) 0.0117 0.0101 Example 3 (90 minutes) 0.0093 0.0107 Example 4 (120 minutes) 0.0098 0.0106

In addition, looking at the correlation between the irradiation strength and the friction coefficient with reference to Figure 14, Examples 5, 6, 7, and 8 it was found that the friction coefficient is smaller than the comparative example. In addition, even in Examples 5, 6, 7, and 8, as the irradiation intensity of the ultraviolet ray increases in units of 10 mW / cm 2, from 10 mW / cm 2 to 40 mW / cm 2, it was confirmed that the friction coefficient decreased.

Correlation between Irradiation Intensity and Friction Coefficient Item
Coefficient of friction water  Analogous biological solution Comparative example 0.02840 0.02220 Example 5 (10 mW / cm 2) 0.01903 0.01310 Example 6 (20 mW / cm 2) 0.01560 0.01010 Example 7 (30 mW / cm 2) 0.01169 0.01070 Example 8 (40 mW / cm 2) 0.00930 0.01060

In addition, looking at the correlation between the hydrophilic solution concentration and the friction coefficient with reference to Figure 15, it can be seen that Examples 3 and 8 have a smaller friction coefficient than the comparative example. And in the case of Examples 3 and 8, it was confirmed that as the concentration of the solution increased, the friction coefficient also decreased.

Correlation between Concentration and Thickness Item
Coefficient of friction water Analogous biological solution Comparative example 0.02840 0.0222 Example 8 (0.25 mol / L) 0.01721 0.0122 Example 3 (0.5 mol / L) 0.00930 0.0107

Finally, referring to the correlation between the temperature and the friction coefficient with reference to Figure 16, when the friction coefficient is measured at room temperature 25 ℃ and body temperature 37 ℃, Example 3 is friction compared to the comparative example It was confirmed that the coefficient was small. In addition, it was confirmed that Example 3 has a significantly lower coefficient of friction than the comparative example even at a body temperature of 37 ° C.

Correlation between Temperature and Thickness Item Coefficient of friction Comparative Example (25 ° C) water Analogous biological solution 0.02840 0.02220 Example 3 (25 ° C) 0.00930 0.01070 Comparative Example 37 ° C.) 0.03273 0.03096 Example 3 (37 ° C) 0.00924 0.00923

As described above, it can be seen that the friction coefficient decreases as the irradiation time and irradiation intensity of ultraviolet rays increase, and the higher the hydrophilic solution concentration, the friction coefficient decreases. Furthermore, it can be seen that the friction coefficient is markedly different even at room temperature and body temperature, and that the friction coefficient is low even at actual body temperature.

[Experiment 4] Abrasion Measurement

The confocal laser microscope (Conforcal Microscopy: Lecia, Germany) was used to determine the amount of abrasion reduction of the specimens subjected to the friction test after the friction coefficient was measured in the water and in the SBF. , Surface damage and wear of the specimens of Comparative Example and Example 3 were measured.

Surface damage

17A and 18A are 3-D images of Comparative Examples in water and similar biological solutions, respectively, and FIGS. 17B and 18B are 3-D Images of Example 3 in water and analogous biological solutions, respectively. Looking at these figures, it can be seen that the surface damage of Example 3 was significantly reduced compared to the comparative example.

Wear

Looking at the correlation between the irradiation time and the wear degree with reference to Figure 19, Examples 1, 2, 3, 4 it was found that the wear amount is significantly less than the comparative example. In addition, it was confirmed that the amount of wear decreases as the irradiation time increases among Examples 1, 2, 3, and 4, respectively. However, it was confirmed that there was no significant change between Examples 3 and 4.

Correlation between irradiation time and wear Item
Wear water  Analogous biological solution Comparative example 1.34 1.03 Example 1 (30 minutes) 0.84 0.58 Example 2 (60 minutes) 0.76 0.48 Example 3 (90 minutes) 0.43 0.44 Example 4 (120 minutes) 0.49 0.44

In addition, looking at the correlation between the irradiation strength and the wear degree with reference to Figure 20, Examples 5, 6, 7, and 8 it was found that the amount of wear is significantly less than the comparative example. In addition, even in Examples 5, 6, 7, and 8, as the irradiation intensity of the ultraviolet ray increases from 10mW / cm 2 to 40mW / cm 2 in units of 10mW / cm 2, it was confirmed that the amount of wear decreased.

Correlation between irradiation strength and wear Item
Wear water  Analogous biological solution Comparative example 1.34 1.03 Example 5 (10 mW / cm 2) 0.87 0.75 Example 6 (20 mW / cm 2) 0.79 0.61 Example 7 (30 mW / cm 2) 0.50 0.52 Example 8 (40 mW / cm 2) 0.43 0.44

In addition, looking at the correlation between the hydrophilic solution concentration and the friction coefficient with reference to Figure 21, Examples 3 and 8 was found to be less wear than the comparative example. And in the case of Examples 3 and 8, it confirmed that the wear amount also decreased with the density | concentration of a solution.

Correlation between Concentration and Wear Item Wear Comparative example water Analogous biological solution 1.34 1.03 Example 8 (0.25 mol / L) 0.90 0.56 Example 3 (0.5 mol / L) 0.43 0.44

No significant difference was found between the experiments in water and in analogous biological solutions.

As described above, it can be seen that the wear rate decreases as the irradiation time and irradiation intensity of ultraviolet rays increase, and as the concentration of the hydrophilic solution increases, the wear degree also decreases.

In addition, through the experimental results measured above, in order to confirm the correlation between the results, the correlation between the thickness and the friction coefficient is shown in the graphs of FIGS. 22 and 23. 22 is a graph showing the relationship between the thickness and the friction coefficient of the hydrophilic layer of the specimen immersed in water, Figure 23 is a graph showing the relationship between the thickness and friction coefficient of the hydrophilic layer of the specimen immersed in a similar biological solution. Referring to Figure 22 and 23, it can be seen that the friction coefficient decreases as the thickness increases, this phenomenon showed the same tendency in water or similar biological solution. In addition, it was confirmed that the coefficient of friction in water became constant after the thickness of 200 nm, and the coefficient of friction in the similar biological solution became constant after 40 nm.

Correlation between Thickness and Friction Coefficient Item
thickness
Coefficient of friction water Analogous biological solution Comparative example 0 0.02840 0.02216 Example 5 37.50 0.01903 0.01220 Example 6 97.25 0.01560 0.01261 Example 1 99.25 0.01240 0.01310 Example 2 106.75 0.01170 0.01010 Example 8 110.75 0.01721 0.01220 Example 7 171.50 0.01169 0.01230 Example 3 204.00 0.00930 0.01070 Example 4 278.25 0.00980 0.01060

Claims (21)

A polymer surface and a hydrophilic layer formed on the polymer surface,
The hydrophilic layer is formed by grafting a polymer material on the polymer surface,
The polymer material is a zwitterionic polymer material, and is formed by attaching a polymerizable monomer to the polymer surface by graft polymerization,
The monomer comprises a methacryloyloxy alkyl group and a sulfopropyl-ammonium hydroxide group,
One end of the sulfopropyl-ammonium hydroxide group is bonded to the methacryloyloxy alkyl group, the other end of the sulfopropyl-ammonium hydroxide group forms a free end,
One end of the methacryloyloxy alkyl group of one monomer is bonded to the polymer surface, the other end of the methacryloyloxy alkyl group of one monomer forms a free end, and the methacryloyloxy alkyl group of the one monomer Characterized in that one end of the methacryloyloxy alkyl group of the other monomer is bonded to the free end of the growth to the strand. delete delete delete delete delete The bearing element of claim 1, wherein the monomer is 2- (methacryloyloxy) ethyl dimethyl- (3-sulfopropyl) ammonium hydroxide. The bearing element according to claim 1 or 7, wherein the hydrophilic layer has a brush structure composed of a plurality of strands. The bearing element of claim 8, wherein the polymer surface is crosslinked polyethylene. 10. The bearing element according to claim 9, wherein each strand constituting the brush structure is free of connection or entanglement between neighboring strands. The bearing element of claim 10, wherein the hydrophilic layer has a thickness of at least 35 nm. The bearing element of claim 11, wherein the hydrophilic layer has a thickness of 35 nm to 300 nm. The bearing element of claim 12, wherein the coefficient of friction of the hydrophilic layer is 0.02 or less. The bearing element of claim 13, wherein the coefficient of friction of the hydrophilic layer is between 0.0093 and 0.02. The bearing element of claim 10, wherein the amount of wear of the hydrophilic layer is 0.5 mm ³ or less. A photoinitiator coating step of coating the photoinitiator on the surface by immersing and drying the bearing element having a polymer surface in a solution containing the photoinitiator for a predetermined time;
After immersing the bearing element in a hydrophilic solution, a hydrophilic layer forming step of growing a hydrophilic layer by irradiating ultraviolet light for a predetermined time,
The hydrophilic solution is ultrapure water in which a monomer composed of a methacryloyloxy alkyl group and a sulfopropyl-ammonium hydroxide group is dissolved,
One end of the sulfopropyl-ammonium hydroxide group is bonded to the methacryloyloxy alkyl group, the other end of the sulfopropyl-ammonium hydroxide group forms a free end, and one end of the methacryloyloxy alkyl group of one monomer It is bonded to the polymer surface, the other end of the methacryloyloxy alkyl group of one monomer forms a free end, and the methacryloyloxy of the other monomer at the free end of the methacryloyloxy alkyl group of the one monomer. Characterized in that one end of the alkyl group is bonded to grow into strands, bearing element manufacturing method. delete 17. The method of claim 16 wherein the polymer surface is crosslinked polyethylene. 19. The method of claim 18, wherein the forming of the hydrophilic layer comprises a brush structure forming step in which one end of the methacryloyloxy alkyl group is bonded to the polymer surface to form a brush structure. delete 20. The method of claim 19, wherein the forming of the hydrophilic layer comprises irradiating a hydrophilic solution having a concentration of 0.25˜0.5 mol / L at an intensity of 10˜40 mW / cm 2 for 30 minutes to 120 minutes to grow a hydrophilic layer.

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