A method for preparing a uhmwpe profile and a uhmwpe profile and its use

Abstract

This invention discloses a method for preparing UHMWPE profiles, as well as the UHMWPE profiles and their applications, belonging to the field of biomedical polymer materials technology. The preparation method of the UHMWPE profiles enables the UHMWPE profiles to achieve a balance between "high wear resistance" and "high impact resistance." Furthermore, using the UHMWPE profiles to prepare implantable artificial joint materials can ensure the wear resistance required for clinical use while significantly improving the safety margin and long-term reliability of artificial joints under complex stresses.

Description

Technical Field

[0001] This invention relates to the field of biomedical polymer materials technology, and in particular to a method for preparing UHMWPE profiles and UHMWPE profiles and their applications. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) is widely used in the manufacture of load-bearing surfaces for artificial joints, such as acetabular liners and tibial pads, due to its excellent biocompatibility, low coefficient of friction, and high abrasion resistance. To further enhance its abrasion resistance and reduce osteolysis and prosthesis loosening caused by abrasion debris, the industry standard practice is to irradiate and crosslink it with high-energy rays (such as gamma rays or electron beams).

[0003] However, irradiation is a double-edged sword. While the wear resistance of UHMWPE increases during irradiation, its mechanical properties also decrease significantly. For example, when preparing GUR 1050 profiles, the increased irradiation dose leads to a significant reduction in the impact strength and yield strength of the GUR 1050 profiles. This negative impact poses a potential risk of edge breakage and premature fatigue failure for artificial joint components under the complex stress environments of the human body.

[0004] Therefore, the technical challenge in this field lies in how to break the "inverse relationship" between the wear resistance and mechanical strength of UHMWPE materials, and develop a new type of UHMWPE material that can simultaneously meet the requirements of high wear resistance and high mechanical strength, so as to adapt to the complex service conditions of artificial joints. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing UHMWPE profiles and UHMWPE profiles and their applications. The UHMWPE profiles prepared by the method simultaneously possess good mechanical properties and excellent wear resistance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a method for preparing UHMWPE profiles, characterized by comprising the following steps:

[0008] The UHMWPE profile was prepared by sequentially subjecting ultra-high molecular weight polyethylene resin powder to compression molding, irradiation crosslinking, heat treatment, and crystallization treatment.

[0009] The irradiation dose for crosslinking is 80~100 kGy;

[0010] The heat treatment temperature is 150℃~180℃;

[0011] The crystallization treatment temperature is 110℃~120℃.

[0012] The preparation method of the present invention combines irradiation crosslinking, heat treatment and crystallization treatment, which significantly reduces the lamellar size of the UHMWPE profile, so that the UHMWPE profile has both good mechanical properties and excellent wear resistance.

[0013] Regarding irradiation crosslinking, when the irradiation dose is between 80 and 100 kGy, the free radicals generated in the UHMWPE profile system tend to recombine, forming a moderately homogeneous crosslinked network. This network can further improve the material's strength, modulus, and wear resistance.

[0014] Furthermore, after irradiation at the irradiation dose (80~100 kGy) described in this invention, the cross-linking network in the UHMWPE profile system will hinder the growth of UHMWPE lamellar crystals, resulting in a smaller lamellar crystal thickness and a denser stacking, which to some extent improves toughness and impact resistance.

[0015] When the irradiation dose is too high (>100kGy), the crosslinking density is too large and the chain breaking reaction is intensified. The change in lamellar thickness is small, and the resulting crosslinking network is rigid and defective, which hinders the effective transfer of energy and leads to a sharp deterioration in the material's impact performance, exhibiting brittle fracture characteristics.

[0016] When the irradiation dose is too low (less than 80 kGy), the wear resistance is not sufficiently improved, and the notched impact strength does not reach its maximum value. When the irradiation dose is too low, the crosslinking density is low, and the binding between molecular chains is weak, making them prone to slippage or breakage during friction, thus making the material surface more susceptible to wear.

[0017] When the irradiation dose is 0 and no irradiation crosslinking is performed, UHMPWE is not crosslinked, has low wear resistance, and insufficient notched impact strength.

[0018] The present invention does not have any particular limitation on the irradiation source for the irradiation crosslinking, and any artificial ionizing radiation source well known to those skilled in the art is acceptable.

[0019] In some specific embodiments of the present invention, an electron accelerator is preferably used.

[0020] The beam energy of the electron accelerator is preferably 6 to 15 MeV; more preferably 10 MeV.

[0021] Preferably, the heat treatment temperature is 150°C to 180°C; more preferably, it is 150°C.

[0022] The heat treatment time is preferably 60 to 180 min; more preferably 180 min.

[0023] The heat treatment pressure is preferably 0.1~5 MPa.

[0024] The preferred temperature for the crystallization process is 110℃~120℃.

[0025] The crystallization treatment time is preferably 60~180 min.

[0026] The pressure for the crystallization process is 0.1~5 MPa.

[0027] Preferably, the temperature conditions for the compression molding are as follows:

[0028] First, heat the temperature to 180-220℃ at a rate of 1-5℃ / min and hold for 30-600 min.

[0029] Then, cool down to 110℃~120℃ at a cooling rate of 1~5℃ / min, and hold at that temperature for 60~180 min;

[0030] Finally, the temperature is lowered to below 50°C at a rate of 1~5°C / min to obtain the shaped powder material.

[0031] Preferably, the compression molding pressure is 7~12 MPa; more preferably 9~10 MPa.

[0032] The preparation method described in this invention uses UHMWPE powder with high crystallinity and suitable viscosity as the starting material, which successfully solves the contradiction between the material's wear resistance and high mechanical strength.

[0033] Preferably, the viscosity of the ultra-high molecular weight polyethylene resin powder is not less than 2000 mL / g.

[0034] Preferably, the ultra-high molecular weight polyethylene resin powder has a crystallinity ≥55%, a lamellar size ≥30nm, and a melt storage modulus ≥1.7 MPa (10 rad).

[0035] Preferably, the irradiation beam used for cross-linking in this invention is selected from gamma rays, electron beams, or X-rays.

[0036] The present invention also provides a UHMWPE profile, which is prepared by the above-described preparation method;

[0037] Preferably, the crosslinking density of the UHMWPE profile is 0.3~0.6 mol / dm³; more preferably, it is 0.4~0.5 mol / dm³.

[0038] Preferably, the wear rate of the UHMWPE profile is ≤4 mg / 5 million cycles; more preferably, the wear rate of the UHMWPE profile is ≤2 mg / 5 million cycles.

[0039] Preferably, the impact strength of the UHMWPE profile is ≥65 kJ / m².

[0040] Preferably, the tensile strength of the UHMWPE profile is >50MPa.

[0041] Preferably, the yield strength of the UHMWPE profile is ≥21 MPa.

[0042] The present invention also provides an implantable artificial joint material, including the UHMWPE profile prepared by the above preparation method or the UHMWPE profile described above.

[0043] The implantable artificial joint material simultaneously meets the requirements of high wear resistance and good mechanical properties (especially high impact resistance), which can further meet the complex service conditions of artificial joints.

[0044] Compared with existing technologies, the preparation method of UHMWPE profiles provided by this invention includes the following steps: ultra-high molecular weight polyethylene resin powder is sequentially subjected to compression molding, irradiation crosslinking, heat treatment, and crystallization treatment to prepare the UHMWPE profile; wherein, the irradiation dose for irradiation crosslinking is 80~100 kGy; the temperature for heat treatment is 150℃~180℃; and the temperature for crystallization treatment is 110℃~120℃. This preparation method enables the prepared UHMWPE profiles to achieve a balance between "high wear resistance" and "high impact resistance." Furthermore, using the UHMWPE profiles to prepare implantable artificial joint materials can ensure the wear resistance required for clinical use while significantly improving the safety margin and long-term reliability of artificial joints under complex stress conditions. Detailed Implementation

[0045] To further illustrate the present invention, the following describes in detail the preparation method of the UHMWPE profile provided by the present invention, as well as the UHMWPE profile and its applications, with reference to embodiments.

[0046] Experimental materials

[0047] Raw materials: linear UHMWPE, with viscosity numbers of 2300 mL / g and 3300 mL / g; GUR 1020 and GUR 1050 are both Celanese medical-grade ultra-high molecular weight polyethylene (UHMWPE) resin.

[0048] Test methods and standards

[0049] 1. Impact strength: Cantilever beam double-notch impact test

[0050] UHMWPE molded sheets were cut by machining to obtain standard-sized notched impact specimens. Cantilever beam double-notched impact tests were conducted according to the "ASTM F468-2014 Standard Specification for Ultra-High Molecular Weight Polyethylene Powder and Products for Surgical Implants". Each sample was tested in parallel three times, and the average value of the results was taken.

[0051] 2. Tensile strength and elongation at break: UHMWPE molded sheets were cut into standard-sized tensile test specimens by machining, and tensile tests were conducted according to GB / T 1040.1-2018 Determination of tensile properties of plastics. Each sample was tested in parallel three times, and the average value of the results was taken.

[0052] 3. Crosslinking density: UHMWPE irradiated sheets were cut into 10×10×6 mm pieces. 3 The crosslinking density of the left and right blocks was tested according to the standard ASTM F2214-02 (2008) Standard Test Method for In Situ Determination of Network Parameters of Crosslinked Ultra High Molecular Weight Polyethylene (UHMWPE). Each sample was tested in triplicate, and the average value was taken.

[0053] The swelling ratio q of UHMWPE after irradiation is calculated according to formula (2). s :

[0054] (2)

[0055] Where V f V0 represents the final volume of the UHMWPE block, and V0 represents the initial volume. According to Flory crosslinking network theory, the swelling ratio of the polymer-solvent system can be interpreted as a competition between elastic force and the force generated by the mixing free energy; therefore, the crosslinking density (v0) is... d It can be calculated based on the swelling ratio:

[0056] (3)

[0057] In the formula, χ1 is the Flory interaction parameter. For the o-xylene-UHMWPE system, at 130 °C, the value of χ1 is 0.33 + 0.55q. s φ1 is the molar volume of o-xylene, with a value of 136 cm³. 3 / mol.

[0058] Example 1

[0059] (1) Sample preparation: UHMWPE powder (viscosity of 2300 mL / g, crystallinity of 56%, lamellar size of 37nm, and melt storage modulus of 1.84 MPa) was molded into 6 mm thick plates and 1 mm thick samples at a certain temperature and 10 MPa.

[0060] The temperature is specifically:

[0061] First, the temperature is increased to 210℃ at a rate of 5℃ / min and held for 300 min.

[0062] Then, the temperature is lowered to 120°C at a rate of 5°C / min and held for 180 min.

[0063] Finally, the temperature is lowered to below 50°C at a rate of 5°C / min to obtain the shaped powder material.

[0064] The above parameters result in a more uniform dispersion of the internal structure of the molded powder material and fewer defects.

[0065] (2) Irradiation treatment: The sample was placed in an aluminum foil self-sealing bag and irradiated with an electron accelerator with a beam energy of 10 MeV and an irradiation dose of 80 kGy.

[0066] (3) Heat treatment: The irradiated sample was annealed at 150°C for 3 hours in a vacuum environment to eliminate residual free radicals. Then it was isothermally crystallized at 120°C for 3 hours.

[0067] (4) Performance test: Various performance tests were performed on the treated samples, and the results are recorded in Table 1.

[0068] Example 2

[0069] The steps are exactly the same as in Example 1, except that the irradiation dose is adjusted to 90 kGy.

[0070] Example 3

[0071] The steps are exactly the same as in Example 1, except that the irradiation dose is adjusted to 100 kGy.

[0072] Example 4

[0073] (1) Sample preparation: UHMWPE powder (viscosity of 3300 mL / g, crystallinity of 55%, lamellar size of 44nm, and melt storage modulus of 1.76 MPa) was molded into 6 mm thick plates and 1 mm thick samples at a certain temperature and 10 MPa.

[0074] The temperature is specifically:

[0075] First, the temperature is increased to 210℃ at a rate of 5℃ / min and held for 300 min.

[0076] Then, the temperature is lowered to 120°C at a rate of 5°C / min and held for 180 min.

[0077] Finally, the temperature is lowered to below 50°C at a rate of 5°C / min to obtain the shaped powder material.

[0078] The above parameters result in a more uniform dispersion of the internal structure of the molded powder material and fewer defects.

[0079] (2) Irradiation treatment: The sample was placed in an aluminum foil self-sealing bag and irradiated with an electron accelerator with a beam energy of 10 MeV and an irradiation dose of 80 kGy.

[0080] (3) Heat treatment: The irradiated sample was annealed at 150°C for 3 hours in a vacuum environment to eliminate residual free radicals. Then it was isothermally crystallized at 120°C for 3 hours. (4) Performance test: Various performance tests were performed on the treated sample, and the results are recorded in Table 1.

[0081] Example 5

[0082] The steps are exactly the same as in Example 4, except that the irradiation dose is adjusted to 90 kGy.

[0083] Example 6

[0084] The steps are exactly the same as in Example 4, except that the irradiation dose is adjusted to 100 kGy.

[0085] Comparative Example 1

[0086] The steps are exactly the same as in Example 1, but without irradiation (irradiation dose is 0 kGy).

[0087] Comparative Example 2

[0088] The steps are exactly the same as in Example 4, but without irradiation (irradiation dose is 0 kGy).

[0089] Comparative Example 3

[0090] The substrate was prepared using GUR 1020 without irradiation treatment (irradiation dose: 0 kGy).

[0091] Comparative Example 4

[0092] The material was irradiated using GUR 1020 plates at a dose of 100 kGy.

[0093] Comparative Example 5

[0094] The plates were prepared using GUR 1050 and were not subjected to irradiation treatment.

[0095] Comparative Example 6

[0096] The material was irradiated using GUR 1050 plates at a dose of 100 kGy.

[0097] Table 1 Summary of Performance Tests

[0098]

[0099] Table 1 shows that the tensile strength and yield strength of Comparative Examples 1 and 2 are higher than those of the UHMWPE used in Comparative Examples 3 and 5 currently in medical applications, but their disadvantages are lower impact strength and abrasion resistance. The results of Examples 1-6 show that, after the improvement of the method described in this invention, the abrasion resistance of the UHMWPE profiles after irradiation is significantly improved, and the yield strength is significantly increased. The yield strength of the UHMWPE profiles prepared in Examples 1-6 is higher than that of Comparative Examples 4 and 6, and the impact strength of the UHMWPE profiles prepared in Examples 1-6 is comparable to that of Comparative Examples 4 and 6. The core advantage lies in the larger lamellar size of the UHMWPE used in this invention, resulting in higher yield strength. Although the lamellar size decreases after irradiation crosslinking, it still retains a high yield strength. Simultaneously, the impact strength is significantly improved after the lamellar size decreases. Therefore, Examples 1-6 simultaneously achieve high abrasion resistance, high impact resistance, and high yield strength.

[0100] This invention successfully prepared a UHMWPE profile with good impact resistance, high wear resistance and high yield by using 80~100 kGy irradiation technology. This material is particularly suitable for manufacturing long-term implantable artificial joints with extremely high reliability requirements.

[0101] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing UHMWPE profiles, characterized in that, Includes the following steps: The UHMWPE profile was prepared by sequentially subjecting ultra-high molecular weight polyethylene resin powder to compression molding, irradiation crosslinking, heat treatment, and crystallization treatment. The irradiation dose for crosslinking is 80~100 kGy; The heat treatment temperature is 150℃~180℃; The crystallization temperature is 110℃~120℃; The ultra-high molecular weight polyethylene resin powder has a crystallinity of ≥55%, a lamellar size of ≥30nm, and a melt storage modulus of ≥1.7 MPa under 10 rad conditions. The viscosity of the ultra-high molecular weight polyethylene resin powder is not less than 2000 mL / g.

2. The preparation method according to claim 1, characterized in that, The temperature conditions for the compression molding are as follows: First, heat the temperature to 180℃~220℃ at a rate of 1~5℃ / min and hold for 30~600 min; Then, cool down to 110℃~120℃ at a cooling rate of 1~5℃ / min, and hold at that temperature for 60~180 min; Finally, the temperature is lowered to below 50°C at a rate of 1~5°C / min to obtain the shaped powder material.

3. The preparation method according to claim 1 or 2, characterized in that, The compression molding pressure is 7~12MPa.

4. The preparation method according to claim 1, characterized in that, The irradiation rays used for cross-linking are selected from gamma rays, electron beams, or X-rays.

5. A UHMWPE profile, characterized in that, Prepared by the preparation method according to any one of claims 1 to 4; The crosslinking density of the UHMWPE profile is 0.3~0.6 mol / dm³.

6. The UHMWPE profile according to claim 5, characterized in that, The wear rate of the UHMWPE profile is ≤4mg / 5 million cycles, and the impact strength is ≥65 kJ / m².

7. The UHMWPE profile according to claim 5, characterized in that, The UHMWPE profile has a tensile strength > 50 MPa and a yield strength ≥ 21 MPa.

8. An implantable artificial joint material, characterized in that, Includes the UHMWPE profile prepared by the preparation method according to any one of claims 1 to 4 or the UHMWPE profile according to any one of claims 5 to 7.

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