CN112870448B - Ultrahigh molecular weight polyethylene plate and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of polymer materials, and in particular relates to an ultra-high molecular weight polyethylene sheet and a preparation method and application thereof. The invention provides a method for preparing an ultra-high molecular weight polyethylene sheet, which comprises the following steps: mixing an antioxidant and ultra-high molecular weight polyethylene to obtain various mixed powders with different antioxidant contents; The powders are stacked according to the antioxidant content and then subjected to compression molding, radiation cross-linking and annealing treatment in sequence to obtain the ultra-high molecular weight polyethylene sheet; the layered materials are arranged symmetrically with the center layer as the center; after the stacking The content of antioxidants in the materials of each layer increases outward based on the center layer. In the invention, the mixed powders with different antioxidant concentrations are stacked in a manner that the antioxidant concentration increases from the inside to the outside, so as to ensure that the ratio of the antioxidant content and the irradiation dose of different sample depths in the irradiation process is kept constant, and cross-linking is obtained. UHMWPE sheet with uniform density.

Description

A kind of ultra-high molecular weight polyethylene sheet and its preparation method and application

technical field

The invention belongs to the technical field of polymer materials, and in particular relates to an ultra-high molecular weight polyethylene sheet and a preparation method and application thereof.

Background technique

Ultra-high molecular weight polyethylene (polyethylene with a molecular weight of more than 1 million) has unparalleled wear resistance, corrosion resistance, impact resistance and self-lubrication properties of other engineering plastics due to its excellent comprehensive properties. It is a new type of thermoplastic. Engineering plastics are widely used in artificial joint replacement. However, during the long-term service of the UHMWPE artificial joint in the body, friction with its matching material produces wear debris that is phagocytosed by macrophages and cannot be absorbed and degraded, resulting in the death of macrophages. At the same time, wear and active osteolysis will occur. Bacterial loosening, inflammation, etc., often require a second operation or multiple revision and replacement operations. In order to solve the above problems, ultra-high molecular weight polyethylene chemically cross-linked with silane has been developed, but its yield is extremely low and the clinical wear rate is extremely high (Kurtz S.UHMWPE Biomaterials Handbook[J].2009,33-43), Subsequent methods of crosslinking with high-energy electron beams and γ-ray irradiation improved the abrasion resistance of crosslinked UHMWPE.

However, there is a problem of ray penetration during irradiation cross-linking, and the distribution of the irradiation dose in the thick plate is not uniform. The general trend is that the outer layer dose is large and the inner layer dose is small. The experiment found that the penetration depth of 10MeV linear electron accelerator to ultra-high molecular weight polyethylene is less than 50mm, and the radiation dose of the inner and outer layers of the plate is very different. The difference in irradiation dose directly leads to the uneven distribution of crosslinking density. The crosslinking density and its distribution are closely related to the distribution of the crystal and amorphous regions of the UHMWPE sheet and the strength, toughness and wear resistance of the crosslinked UHMWPE sheet product. Although radiation crosslinking greatly improves wear resistance by increasing its crosslinking degree, the residual free radicals in the process of crosslinking formation can undergo chain oxidation reaction with dissolved oxygen to form unstable peroxides. The degradation of the polymer embrittles the polymer through chain scission and recrystallization, which leads to the decline of the polymer performance, and finally manifests as oxidative fragmentation and delamination of the cross-linked ultra-high molecular weight polyethylene material. In order to solve the above problems, biocompatible antioxidants (such as vitamin E) are added to the ultra-high molecular weight polyethylene sheet to eliminate residual free radicals and improve the oxidative stability of ultra-high molecular weight polyethylene artificial joints.

The traditional methods of adding antioxidants are mainly divided into two categories. One is to mix antioxidants into ultra-high molecular weight polyethylene powder before irradiation to form pre-products, such as the solutions disclosed in patents with publication numbers EP2291417B1 and CN102089333A. However, studies have shown that adding antioxidants before irradiation crosslinking will inhibit crosslinking. When the content of antioxidants in ultra-high molecular weight polyethylene is high (for example, the concentration of vitamin E is higher than 0.1 wt%), antioxidants will interact with polyolefins. The free radical reaction generated by irradiation hinders the cross-linking reaction between free radicals in the polymer; the antioxidant not only inhibits the cross-linking reaction, but also accelerates the breakage of the ultra-high molecular weight polyethylene molecular chain, reduces the molecular weight, and prevents the It is beneficial to improve the degree of cross-linking and affect the wear resistance and comprehensive mechanical properties; when the content of vitamin E is too low (for example, when the content of vitamin E is less than 0.01wt%), vitamin E will lose its antioxidant activity when irradiated by high-energy rays , loses its antioxidant effect. Another way to add antioxidant is to immerse the cross-linked ultra-high molecular weight polyethylene in the antioxidant, and make the antioxidant diffuse to the surface of the ultra-high molecular weight polyethylene sheet at about 120°C. After the plate was taken out, it was kept at 120°C for a period of time to diffuse the antioxidant into the interior. The ultra-high molecular weight polyethylene prosthesis blank can also be irradiated and cross-linked and then immersed in an antioxidant solution, taken out, and further heat-treated to diffuse the antioxidant to the inside. However, with the method of irradiation-immersion-diffusion, the diffusion of antioxidants is difficult, mainly distributed in the surface layer, the content of internal antioxidants is very small, and the concentration inside and outside is not uniform. Moreover, the heat treatment process takes a long time, and the long time heat treatment also leads to the deterioration of material properties. However, the internal antioxidant content that is too low cannot eliminate free radicals, and cannot effectively eliminate free radicals generated during the irradiation process and play an antioxidant role in the subsequent use process.

SUMMARY OF THE INVENTION

In view of this, the present invention provides an ultra-high molecular weight polyethylene sheet and a preparation method and application thereof. The present invention increases the concentration of antioxidants from the inside to the outside, so as to ensure that during the irradiation process, the antioxidants at different sample depths are The ratio of the content and the irradiation dose was kept constant, so that UHMWPE sheets with uniform crosslink density were obtained.

In order to solve the above-mentioned technical problems, the present invention provides a method for preparing an ultra-high molecular weight polyethylene sheet, comprising the following steps:

Mixing antioxidant and ultra-high molecular weight polyethylene to obtain various mixed powders with different antioxidant contents;

The multiple mixed powders are layered according to the antioxidant content and then subjected to compression molding, irradiation crosslinking and annealing treatment in sequence to obtain the ultra-high molecular weight polyethylene sheet;

The layered materials are arranged symmetrically with the center layer as the center;

After the lamination, the content of the antioxidant in the materials of each layer increases outward on the basis of the center layer.

Preferably, the mass percentage content of antioxidants in the mixed powder is 0.01-1%.

Preferably, the number of the stacked layers is 3 to 9 layers.

Preferably, the mass percentage content of the antioxidant in the central layer is 0.01-0.3%; the mass percentage content of the antioxidant in the surface layer of the ultra-high molecular weight polyethylene sheet is 0.1-1%.

Preferably, the thickness of the ultra-high molecular weight polyethylene sheet is 30mm˜100mm.

Preferably, the compression molding comprises: sequentially performing high temperature compression molding and low temperature compression molding;

The temperature of the high-temperature compression molding is 170-240° C., the pressure is 1-50MPa, and the time is 0.5-10h;

The temperature of the low-temperature molding is 110-130° C., the pressure is 1-50 MPa, and the time is 0.5-72 h.

Preferably, the irradiation dose of the irradiation crosslinking is 25-150 kGy, and the dose rate is 5-50 kGy/pass;

The temperature of the annealing treatment is 110-130° C., and the holding time is 0.5-72 h.

Preferably, the antioxidants include phosphite compounds, gallic acid, catechins, lauryl gallic acid, propyl gallate, lauryl gallate, caffeic acid, hindered amine stabilizer TH-944, vitamins E. One or more of antioxidant 1076 and antioxidant 1010.

The present invention also provides an ultra-high molecular weight polyethylene sheet prepared by the preparation method described in the above technical solution, wherein the difference between the highest cross-linking density and the lowest cross-linking density in the ultra-high molecular weight polyethylene sheet is 0-100 mol/m ³ . .

The present invention also provides the application of the ultra-high molecular weight polyethylene sheet in the above technical solution in the preparation of artificial joints.

The invention provides a method for preparing an ultra-high molecular weight polyethylene sheet, which comprises the following steps: mixing an antioxidant and ultra-high molecular weight polyethylene to obtain various mixed powders with different antioxidant contents; The powders are layered according to the antioxidant content and then subjected to compression molding, irradiation cross-linking and annealing treatment in sequence to obtain the ultra-high molecular weight polyethylene sheet; the layered materials are arranged symmetrically with the center layer as the center; after the layering The content of antioxidants in the materials of each layer increases outward based on the center layer. In the present invention, antioxidants are mixed with ultra-high molecular weight polyethylene according to a certain concentration sequence, and mixed powders with different antioxidant concentrations are stacked in a manner in which the antioxidant concentrations increase from the inside to the outside, so as to ensure different sample depths during the irradiation process. The ratio of the antioxidant content and the irradiation dose is kept constant, and the ultra-high molecular weight polyethylene sheet with uniform crosslinking density is obtained. At the same time, the present invention regulates the effect of the antioxidant on the inhibition of radiation crosslinking by setting the concentration of the antioxidant in layers, so as to ensure that the effective concentration of the antioxidant in the inner and outer layers is sufficient to eliminate residual free radicals, and the tensile strength of the ultra-high molecular weight polyethylene sheet is improved. Tensile strength, elongation at break and impact strength.

The present invention also provides an ultra-high molecular weight polyethylene sheet prepared by the preparation method described in the above technical solution, wherein the difference between the highest cross-linking density and the lowest cross-linking density in the ultra-high molecular weight polyethylene sheet is 0-100 mol/m ³ . . The ultra-high molecular weight polyethylene sheet provided by the invention has uniform cross-linking density, thereby improving the tensile strength, elongation at break and impact strength of the ultra-high molecular weight polyethylene sheet.

Description of drawings

1 is a schematic structural diagram of the ultra-high molecular weight polyethylene sheet prepared in Example 2.

Detailed ways

The invention provides a method for preparing an ultra-high molecular weight polyethylene sheet, comprising the following steps:

Mixing antioxidant and ultra-high molecular weight polyethylene to obtain various mixed powders with different antioxidant contents;

The multiple mixed powders are layered according to the antioxidant content and then subjected to compression molding, irradiation crosslinking and annealing treatment in sequence to obtain the ultra-high molecular weight polyethylene sheet;

The layered materials are arranged symmetrically with the center layer as the center;

After the lamination, the content of the antioxidant in the materials of each layer increases outward on the basis of the center layer.

In the invention, the antioxidant and the ultra-high molecular weight polyethylene are mixed to obtain various mixed powders with different contents of the antioxidant. In the present invention, the antioxidant preferably includes phosphite compounds, gallic acid, catechins, lauryl gallic acid, propyl gallate, lauryl gallate, caffeic acid, hindered amine stabilizer TH- 944. One or more of vitamin E, antioxidant 1076 and antioxidant 1010, more preferably vitamin E; when the antioxidant includes two or more of the above-mentioned specific substances, the The proportion of specific substances is not particularly limited, and any proportion may be used. In the present invention, the mass percentage content of antioxidants in the various mixed powders is preferably a variety of 0.01-1%, more preferably 0.1-0.9%, still more preferably 0.175-0.35%, the present The invention obtains mixed powders with various oxidant contents. In the present invention, the average particle size of the mixed powder is preferably 50-200 μm, more preferably 80-130 μm. In the present invention, the mixing preferably includes any one of two mixing modes:

The first mixing method preferably includes the following steps: mixing the antioxidant and ultra-high molecular weight polyethylene and then performing ball milling; the rotation speed of the ball milling is preferably 30-800 r/min, more preferably 100-400 r/min; the time is preferably 5 to 60 minutes, more preferably 10 to 30 minutes.

The second mixing method preferably includes the following steps: dissolving the antioxidant in an organic solvent to obtain an antioxidant solution;

The antioxidant solution and the ultra-high molecular weight polyethylene are mixed and then dried to obtain a mixed powder.

In the present invention, the antioxidant is dissolved in an organic solvent to obtain an antioxidant solution. In the present invention, the organic solvent preferably includes acetone, n-butanol, ethanol, petroleum ether or cyclohexane, more preferably n-butanol or ethanol; the concentration of the antioxidant solution is preferably 20-300 g/L , more preferably 80 to 200 g/L.

After the antioxidant solution is obtained, in the present invention, the antioxidant solution is mixed with ultra-high molecular weight polyethylene and then dried to obtain a mixed powder. The present invention does not specifically limit the manner of mixing, as long as the mixing can be uniform. In the present invention, the drying temperature is preferably 30-90°C, more preferably 40-70°C; the time is preferably 3-15 days, more preferably 6-10 days. In the present invention, the drying method is not particularly limited, as long as the above-mentioned temperature can be reached.

After obtaining multiple mixed powders with different antioxidant contents, the present invention stacks the multiple mixed powders according to the antioxidant content and sequentially performs compression molding, irradiation crosslinking and annealing treatment to obtain the ultra-high molecular weight. Polyethylene sheet; the layer materials after lamination are arranged symmetrically with the center layer as the center; the content of antioxidants in each layer material after the lamination increases outwards based on the center layer. In the present invention, the number of layers to be stacked is preferably 3 to 9 layers, and more preferably 5 to 7 layers. In the present invention, if the antioxidant concentration in the two adjacent layers is the same, the two adjacent layers are regarded as one layer. In the present invention, the blanks obtained after the lamination are symmetrically arranged with the center layer as the center, the content of the antioxidant in the two symmetrical layers is the same, and the thicknesses of the two symmetrical layers are also the same. In the present invention, the thickness of each symmetrical layer is not particularly limited, as long as the ratio of the antioxidant content and the irradiation dose can be kept constant as the depth of the laminated material changes.

In the present invention, the mass percentage content of the antioxidant in the center layer material of the UHMWPE sheet is preferably 0.01-0.3%, more preferably 0.05-0.1%; The mass percentage content of the antioxidant in the surface layer material is preferably 0.1-1%, more preferably 0.3-0.9%. In the present invention, after the lamination, the content of antioxidants in the materials of each layer increases outward based on the center layer; the present invention does not limit the range of the increase, as long as the antioxidant content and the radiation dose can be adjusted. It is sufficient that the ratio remains constant as the depth of the laminate changes.

In the present invention, the number of laminated layers of the ultra-high molecular weight polyethylene sheet is specifically 3 layers, 5 layers, 7 layers or 9 layers. When the number of layers is 3, the mass percentage content of antioxidant in the central layer is 0.1%; the mass percentage content of antioxidant in the surface layer is 0.3%. When the number of layers is 5, the mass percentage of antioxidant in the central layer is 0.1%; the mass percentage of antioxidant in the layer adjacent to the central layer is 0.2%; the mass percentage of antioxidant in the surface layer is 100% The sub-content is 0.3%. When the number of layers is 5, the mass percentage of antioxidant in the central layer is 0.3%; the mass percentage of antioxidant in the layer adjacent to the central layer is 0.6%; the antioxidant in the surface layer is 0.6% by mass. The mass percentage of 0.9%. When the number of layers is 7, the mass percentage of antioxidant in the central layer is 0.1%; the mass percentage of antioxidant in the layer adjacent to the central layer is 0.15%; the antioxidant in the layer adjacent to the surface layer is 0.15% by mass The mass percentage of the agent is 0.25%; the mass percentage of the antioxidant in the surface layer is 0.3%. When the number of layers is 7, the mass percentage content of antioxidant in the central layer is 0.05%; the mass percentage content of antioxidant in the layer adjacent to the central layer is 0.15%; the mass percentage content of the layer adjacent to the surface layer The mass percentage content of the antioxidant in the middle layer is 0.2%; the mass percentage content of the antioxidant in the surface layer is 0.3%. When the number of layers is 9, the mass percentage of antioxidant in the central layer is 0.05%; the mass percentage of antioxidant in the layer adjacent to the central layer is 0.075%; starting from the surface layer, the antioxidant in the third layer The mass percentage content of the oxygen agent is 0.175%; the mass percentage content of the antioxidant in the layer adjacent to the surface layer is 0.27%; the mass percentage content of the antioxidant in the surface layer is 0.35%.

In the present invention, the lamination is preferably performed in a mold, and the shape of the mold is not particularly limited in the present invention, and can be set according to the desired shape of the ultra-high molecular weight polyethylene sheet.

The present invention does not have a special limitation on the press forming device. In the embodiment of the present invention, the press forming is performed in a flat plate vulcanizer. The present invention preferably also includes performing preliminary molding on the laminated product before molding, and the pressure of the preliminary molding is preferably 5-15 MPa, more preferably 8-10 MPa; the time is preferably 0.8-1.2 h, more preferably is 1h. In the present invention, the preliminary compression molding can compact the mixed powder, which is beneficial to the subsequent compression molding. In the present invention, the compression molding preferably includes: performing high temperature compression molding and low temperature compression molding in sequence; the temperature of the high temperature compression molding is preferably 170-240°C, more preferably 200-220°C; the pressure is preferably 1-50MPa , more preferably 3-20MPa; time is preferably 0.5-10h, more preferably 3-6h. The temperature of the low temperature compression molding is preferably 110-130°C, more preferably 120-125°C; the pressure is preferably 1-50 MPa, more preferably 10-20 MPa; the time is preferably 0.5-72 h, more preferably 2.5-10 h. In the present invention, the temperature of the low temperature compression molding is preferably obtained by lowering the temperature on the basis of the high temperature compression molding temperature. The present invention has no special requirements on the cooling rate, as long as the temperature can be lowered to the desired temperature. In the present invention, the preliminary compression molding and compression molding are preferably performed under vacuum conditions, and the vacuum degree of the vacuum conditions is not particularly limited in the present invention, as long as the air in the compression molding environment can be removed.

In the present invention, after the compression molding, the compression molding product is preferably cooled and then demolded. In the present invention, the temperature after cooling is preferably room temperature. The present invention has no particular limitation on the cooling method, and a method well known to those skilled in the art may be adopted.

In the present invention, the molded product is preferably vacuum-packed before irradiation cross-linking, and the vacuum-packaging material is preferably an aluminum-plastic bag. In the present invention, the irradiation cross-linking preferably includes high-energy electron beam irradiation cross-linking, γ-ray irradiation cross-linking formed by cobalt source decay, or X-ray irradiation cross-linking, more preferably high-energy electron beam irradiation cross-linking . In the present invention, the electron beam energy used for the high-energy electron beam irradiation crosslinking is preferably 1-20 MeV, more preferably 10-15 MeV. In the present invention, the irradiation dose of the irradiation crosslinking is preferably 25-150kGy, more preferably 75-100kGy; the dose rate is 5-50kGy/pass, more preferably 20-40kGy/pass, still more preferably 25～35kGy/pass.

In the present invention, the annealing treatment is preferably performed under a protective atmosphere, and the protective atmosphere preferably includes an argon atmosphere or a nitrogen atmosphere, more preferably an argon atmosphere. In the present invention, the temperature of the annealing treatment is preferably 110-130°C, more preferably 115-120°C; the holding time is preferably 0.5-72h, more preferably 6-15h. In the present invention, the annealing treatment can fully react the antioxidant with the free radicals and eliminate the redundant free radicals.

The present invention can relate to the thickness of the ultra-high molecular weight polyethylene sheet according to actual needs. In the present invention, the thickness of the ultra-high molecular weight polyethylene sheet is preferably 30-100 mm, more preferably 70-90 mm.

The present invention also provides an ultra-high molecular weight polyethylene sheet prepared by the preparation method described in the above technical solution, wherein the difference between the highest cross-linking density and the lowest cross-linking density in the ultra-high molecular weight polyethylene sheet is 0-100 mol/m ³ . . In the present invention, the ultra-high molecular weight polyethylene sheet has a uniform crosslinking density, thereby improving the tensile strength, elongation at break and impact strength of the ultra-high molecular weight polyethylene sheet.

The present invention also provides the application of the ultra-high molecular weight polyethylene sheet in the above technical solution in the preparation of artificial joints. In the present invention, the artificial joint preferably includes an artificial hip joint or an artificial knee joint.

In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below with reference to the examples, but they should not be construed as limiting the protection scope of the present invention.

Example 1

Ball milling 1.8g vitamin E and 1800g ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm for 50min at a rotational speed of 100r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.1%;

5.4g of vitamin E and 1800g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 50 minutes at a speed of 100r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.3%;

Spread 900g of mixed powder with a mass percentage of vitamin E of 0.3% in the film cavity of the mold (size is 250mm*250mm*125mm) as the first layer; lay 1800g of vitamin E on the surface of the first layer. The mixed powder with a mass percentage of 0.1% is used as the second layer; 900g of mixed powder with a mass percentage of vitamin E of 0.3% is laid on the surface of the second layer as the third layer;

The product obtained after lamination was placed in a flat vulcanizer, vacuumed and then subjected to preliminary compression molding at 80 °C and 10 MPa for 1 hour; after preliminary compression molding, the temperature was raised to 200 °C, and high temperature compression molding was performed at a pressure of 6 MPa for 6 hours; The temperature is lowered to 125°C, and the low-temperature compression molding is carried out under the pressure of 10 MPa for 2.5 hours, and the low-temperature compression molding product is cooled to room temperature for release;

The product after stripping is vacuum-packed in an aluminum-plastic bag, and cross-linked by irradiation with a high-energy electron beam (energy of 10MeV), the irradiation dose rate is 25kGy/pass, and the total dose is 75kGy;

The irradiated cross-linked product was annealed at 110° C. for 10 h in an argon atmosphere to obtain an ultra-high molecular weight polyethylene sheet.

Example 2

1.2g of vitamin E and 1200g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 40 minutes at a rotational speed of 200r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.1%;

2.4g of vitamin E and 1200g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 40 minutes at a speed of 200r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.2%;

3.6g of vitamin E and 1200g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 40 minutes at a speed of 200r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.3%;

Spread 600g of mixed powder with a mass percentage of vitamin E of 0.3% in the film cavity of the mold (size is 250mm*250mm*125mm) as the first layer; lay 600g of vitamin E on the surface of the first layer. The mixed powder with a mass percentage of 0.2% is used as the second layer; 1200g of mixed powder with a mass percentage of vitamin E of 0.1% is spread on the surface of the second layer as the third layer; on the surface of the third layer Spread 600g of mixed powder with a mass percentage of vitamin E of 0.2% as the fourth layer; spread 600g of mixed powder with a mass percentage of vitamin E of 0.3% on the surface of the fourth layer as the fifth layer ;

The product obtained after lamination was placed in a flat vulcanizer, vacuumed and then subjected to preliminary compression molding at 80 °C and 10 MPa for 1 hour; after preliminary compression molding, the temperature was raised to 210 °C, and high temperature compression molding was carried out under the pressure of 6 MPa for 4 hours; The temperature is lowered to 125°C, and the low-temperature compression molding is carried out under the pressure of 10 MPa for 2.5 hours, and the low-temperature compression molding product is cooled to room temperature for release;

The product after stripping is vacuum-packed in an aluminum-plastic bag, and cross-linked by irradiation with a high-energy electron beam (energy of 10MeV), the irradiation dose rate is 25kGy/pass, and the total dose is 75kGy;

The irradiated cross-linked product was annealed at 110° C. for 10 h in an argon atmosphere to obtain an ultra-high molecular weight polyethylene sheet.

The schematic structural diagram of the ultra-high molecular weight polyethylene sheet prepared in Example 2 is shown in FIG. 1 .

Example 3

Ball milling 2.7g of vitamin E and 900g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm for 30min at a rotational speed of 300r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.3%;

Ball milling 2.25g vitamin E and 900g ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm for 30min at a rotational speed of 300r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.25%;

Ball milling 1.35g vitamin E and 900g ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm for 30min at a rotational speed of 300r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.15%;

0.9g of vitamin E and 900g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 30 minutes at a rotational speed of 300r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.1%;

Spread 450g of mixed powder with a mass percentage of vitamin E of 0.15% in the film cavity of the mold (size is 250mm*250mm*125mm) as the first layer; lay 450g of vitamin E on the surface of the first layer. Mixed powder with a mass percentage of 0.25% is used as the second layer; 450g of mixed powder with a mass percentage of vitamin E of 0.15% is spread on the surface of the second layer as the third layer; on the surface of the third layer Spread 900g of mixed powder with a mass percentage of vitamin E of 0.1% as the fourth layer; spread 450g of mixed powder with a mass percentage of vitamin E of 0.15% on the surface of the fourth layer as the fifth layer ; Spread 450g of mixed powder with 0.25% vitamin E mass percentage on the surface of the 5th layer as the 6th layer; Spread 450g of mixed powder with 0.3% vitamin E mass percentage on the surface of the 6th layer material, as layer 7;

The product obtained after lamination was placed in a flat vulcanizer, vacuumed and then subjected to preliminary molding at 80 °C and 10 MPa for 1 h; after preliminary molding, the temperature was raised to 230 °C, and high-temperature molding was carried out under a pressure of 6 MPa for 2 h; The temperature was lowered to 120°C, and the low-temperature compression molding was carried out under the pressure of 15MPa for 2.5 hours, and the low-temperature compression molding product was cooled to room temperature for release;

The product after stripping is vacuum-packed in an aluminum-plastic bag, and cross-linked by irradiation with a high-energy electron beam (energy of 10MeV), the irradiation dose rate is 20kGy/pass, and the total dose is 80kGy;

The irradiated cross-linked product was annealed at 110° C. for 10 h in an argon atmosphere to obtain an ultra-high molecular weight polyethylene sheet.

Example 4

Ball milling 2.8g vitamin E and 800g ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm at a speed of 400r/min for 20min to obtain a mixed powder with a mass percentage of vitamin E of 0.35%;

2.2g of vitamin E and 800g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 20 minutes at a speed of 400r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.275%;

1.4g of vitamin E and 800g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 20 minutes at a speed of 400r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.175%;

0.6g of vitamin E and 800g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 20 minutes at a rotational speed of 400r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.075%;

0.2g of vitamin E and 400g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm were ball-milled for 20min at a speed of 400r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.05%

Spread 400g of mixed powder with a mass percentage of vitamin E of 0.35% in the film cavity of the mold (size is 250mm*250mm*125mm) as the first layer; lay 400g of vitamin E on the surface of the first layer. The mixed powder with a mass percentage of 0.275% is used as the second layer; 400g of mixed powder with a mass percentage of vitamin E of 0.175% is spread on the surface of the second layer as the third layer; on the surface of the third layer Spread 400g of mixed powder with a mass percentage of vitamin E of 0.075% as the fourth layer; spread 400g of mixed powder with a mass percentage of vitamin E of 0.05% on the surface of the fourth layer as the fifth layer ; Spread 400g of mixed powder with 0.075% vitamin E mass percentage on the surface of the 5th layer as the 6th layer; Spread 400g of mixed powder with 0.175% vitamin E mass percentage on the surface of the 6th layer material, as the seventh layer; 400g of mixed powder with 0.275% vitamin E mass percentage on the surface of the seventh layer, as the eighth layer; 400g, vitamin E mass percentage on the surface of the eighth layer. It is 0.35% mixed powder as the 9th layer;

The product obtained after lamination was placed in a flat vulcanizer, vacuumed and then subjected to preliminary molding at 80 °C and 10 MPa for 1 hour; after preliminary molding, the temperature was raised to 190 °C, and high-temperature molding was carried out at a pressure of 10 MPa for 8 hours; The temperature is lowered to 125°C, and the low-temperature compression molding is carried out under the pressure of 10 MPa for 2.5 hours, and the low-temperature compression molding product is cooled to room temperature for release;

The product after stripping is vacuum-packed in an aluminum-plastic bag, and cross-linked by irradiation with a high-energy electron beam (energy of 10MeV), the irradiation dose rate is 30kGy/pass, and the total dose is 90kGy;

The irradiated cross-linked product was annealed at 110° C. for 72 hours in an argon atmosphere to obtain an ultra-high molecular weight polyethylene sheet.

Example 5

Ball milling 3.6g vitamin E and 1200g ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm for 10min at a rotational speed of 500r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.3%;

7.2g of vitamin E and 1200g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 10 minutes at a rotational speed of 500r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.6%;

Ball milling 10.8g vitamin E and 1200g ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm for 10min at a rotational speed of 500r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.9%;

Spread 600g of mixed powder with a mass percentage of vitamin E of 0.9% in the film cavity of the mold (size is 250mm*250mm*125mm) as the first layer; lay 600g of vitamin E on the surface of the first layer. The mixed powder with a mass percentage of 0.6% is used as the second layer; 600g of mixed powder with a mass percentage of vitamin E of 0.3% is spread on the surface of the second layer as the third layer; on the surface of the third layer Spread 600g of mixed powder with 0.6% vitamin E mass percentage as the fourth layer; spread 600g of mixed powder with 0.9% vitamin E mass percentage on the surface of the fourth layer as the fifth layer ;

The product obtained after lamination was placed in a flat vulcanizer, vacuumed and then subjected to preliminary compression molding at 80 °C and 10 MPa for 1 hour; after preliminary compression molding, the temperature was raised to 200 °C, and high temperature compression molding was performed at a pressure of 6 MPa for 6 hours; The temperature was lowered to 115 °C, and the low-temperature compression molding was carried out under the pressure of 30 MPa for 4 hours, and the low-temperature compression molding product was cooled to room temperature for release;

The product after stripping is vacuum-packed in an aluminum-plastic bag, and cross-linked by irradiation with a high-energy electron beam (energy of 10MeV), the irradiation dose rate is 40kGy/pass, and the total dose is 80kGy;

The irradiated cross-linked product was annealed at 130° C. for 0.5 h in an argon atmosphere to obtain an ultra-high molecular weight polyethylene sheet.

Example 6

Ball milling 3.6g vitamin E and 1200g ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm for 50min at a rotational speed of 50r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.3%;

Ball-milling 2.0g vitamin E and 1000g ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120μm for 50min at a rotational speed of 50r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.2%;

1.2g of vitamin E and 800g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 50 minutes at a speed of 50r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.15%;

0.4g of vitamin E and 800g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm are ball-milled for 50 minutes at a rotational speed of 50r/min to obtain a mixed powder with a mass percentage of vitamin E of 0.05%;

Spread 600g of mixed powder with a mass percentage of vitamin E of 0.3% in the film cavity of the mold (size is 250mm*250mm*125mm) as the first layer; lay 500g of vitamin E on the surface of the first layer. The mixed powder with a mass percentage of 0.2% is used as the second layer; 400g of mixed powder with a mass percentage of vitamin E of 0.15% is spread on the surface of the second layer as the third layer; on the surface of the third layer Lay 800g of mixed powder with 0.05% vitamin E mass percentage as the 4th layer; spread 400g of mixed powder with 0.15% vitamin E mass percentage on the surface of the 4th layer as the 5th layer ; Spread 500g of mixed powder with 0.2% vitamin E mass percentage on the surface of the 5th layer as the 6th layer; Spread 600g of mixed powder with 0.3% vitamin E mass percentage on the surface of the 6th layer material, as layer 7;

The product obtained after lamination was placed in a flat vulcanizer, vacuumed and then subjected to preliminary compression molding at 80 °C and 10 MPa for 1 hour; after preliminary compression molding, the temperature was raised to 200 °C, and high temperature compression molding was performed at a pressure of 6 MPa for 6 hours; The temperature is lowered to 125°C, and the low-temperature compression molding is carried out under the pressure of 10 MPa for 2.5 hours, and the low-temperature compression molding product is cooled to room temperature for release;

The product after stripping is vacuum-packed in an aluminum-plastic bag, and cross-linked by irradiation with a high-energy electron beam (energy of 10MeV), the irradiation dose rate is 25kGy/pass, and the total dose is 75kGy;

The irradiated cross-linked product was annealed at 110° C. for 10 h in an argon atmosphere to obtain an ultra-high molecular weight polyethylene sheet.

Comparative Example 1

Ball-milling 7.2 g of vitamin E and 3600 g of ultra-high molecular weight polyethylene with a molecular weight of 3 million and an average particle size of 90-120 μm to obtain a mixed powder with a mass percentage of vitamin E of 0.2%;

The mixed powder is flattened in the film cavity, and the flattened product is sequentially subjected to preliminary molding, molding, irradiation crosslinking and annealing according to the method of Example 1 to obtain an ultra-high molecular weight polyethylene sheet.

test case

The ultra-high molecular weight polyethylene sheets prepared in Examples 1 to 6 and Comparative Example 1 were sampled by using high-precision engraving and milling equipment, and the sampling positions were the surface layer, central layer (1/2 depth) and Three positions at 1/4 of the depth; the obtained samples were tested for tensile properties according to ASTM D638, impact properties according to ASTM F648, and crosslinking density according to ASTM F2214. The results are listed in Table 1 .

Table 1 Properties of Examples 1 to 6 and Comparative Example 1 UHMWPE sheets.

From the data in Table 1, it can be seen that the uniformity of the crosslinking density distribution at different positions of the crosslinked sheet is improved after the antioxidant is added in layers. The layer thickness is different, but the trend of decreasing the antioxidant concentration from both sides to the center is maintained, which also achieves the effect of uniform crosslink density distribution. The ultra-high molecular weight polyethylene sheet prepared in Comparative Example 1 has a uniform distribution of antioxidant concentration, and the high radiation intensity of the antioxidant in the center inhibits the cross-linking reaction weakly. , the overall crosslink density is not uniform.

Although the above embodiment has made a detailed description of the present invention, it is only a part of the embodiments of the present invention, rather than all the embodiments. People can also obtain other embodiments according to the present embodiment without creativity. These embodiments All belong to the protection scope of the present invention.

Claims (6)

1. A method for preparing an ultra-high molecular weight polyethylene sheet, comprising the following steps: Mixing the antioxidant and the ultra-high molecular weight polyethylene to obtain various mixed powders with different antioxidant contents; the mass percentage content of the antioxidants in the mixed powder is a variety of 0.01-1%; The multiple mixed powders are layered according to the antioxidant content and then subjected to compression molding, irradiation crosslinking and annealing treatment in sequence to obtain the ultra-high molecular weight polyethylene sheet; the irradiation dose of the irradiation crosslinking is 25 ～150kGy, the dose rate is 5～50kGy/pass; the temperature of the annealing treatment is 110～130℃, and the holding time is 0.5～72h; the thickness of the ultra-high molecular weight polyethylene sheet is 30mm～100mm; After the compression molding, it also includes releasing the molded product after cooling down; The layered materials are arranged symmetrically with the center layer as the center; After the lamination, the content of antioxidants in each layer of materials increases outwards based on the center layer; the mass percentage content of the antioxidants in the center layer is 0.01-0.3%; the content of the ultra-high molecular weight polyethylene sheet is The mass percentage content of the antioxidant in the surface layer is 0.1-1%. 2 . The preparation method according to claim 1 , wherein the number of the stacked layers is 3 to 9 layers. 3 . 3. The preparation method according to claim 1, wherein the compression molding comprises: sequentially performing high temperature compression molding and low temperature compression molding; The temperature of the high-temperature compression molding is 170-240° C., the pressure is 1-50MPa, and the time is 0.5-10h; The temperature of the low-temperature molding is 110-130° C., the pressure is 1-50 MPa, and the time is 0.5-72 h. 4. preparation method according to claim 1 is characterized in that, described antioxidant comprises phosphite compound, gallic acid, catechin, lauryl gallic acid, propyl gallate, lauryl gallate, One or more of caffeic acid, hindered amine stabilizer TH-944, vitamin E, antioxidant 1076 and antioxidant 1010. 5. The ultra-high molecular weight polyethylene sheet prepared by the preparation method according to any one of claims 1 to 4, wherein the difference between the highest cross-linking density and the lowest cross-linking density in the ultra-high molecular weight polyethylene sheet is 0-100 mol/ m ³ . 6. The application of the ultra-high molecular weight polyethylene sheet of claim 5 in the preparation of artificial joints.

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