Preparation method of high-strength open-cell material, product and application thereof

Abstract

The application discloses a preparation method of high-strength open-cell material, a product and application thereof. The preparation method comprises the following steps: 85-99.99 mass parts of polymer resin and 0.01-15 mass parts of powder phase are mixed, melted and extruded to obtain a composite material; the polymer resin and the powder phase are dehydrated to less than 0.01 wt% of water content before use; the powder phase is low-activity magnesium oxide and phosphate with a mass ratio of 1:3-5; the phosphate is at least one of dihydrogen phosphate and monohydrogen phosphate; the low-activity magnesium oxide is obtained by heating the magnesium oxide to 1400-1600 DEG C at a heating rate of not more than 10 DEG C / min and keeping the temperature for 3-6 h; the composite material is saturated in a physical foaming agent to obtain a saturated system, and is foamed by pressure relief to obtain an open-cell material; the pressure of the physical foaming agent is 5-25 MPa; the pressure relief rate of the pressure relief foaming is 10-100 MPa / s; the open-cell material is immersed in water, the low-activity magnesium oxide and the phosphate react to generate bone cement, the strength of the open-cell material is improved, and the high-strength open-cell material is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polymer open-cell materials, in particular to a preparation method of high-strength open-cell material, product and application thereof. BACKGROUND

[0002] The physical foaming method is a commonly used method for preparing polymer open-cell materials.

[0003] For example, the patent specification with publication number CN114752097A discloses a method for preparing a polylactic acid foam material with an open-cell structure by using a supercritical carbon dioxide intermittent foaming method, and the steps are as follows: (1) melt and plasticize polylactic acid granules above the melting point, and hot-press into sheet materials with appropriate thickness; (2) cut the polylactic acid sheet material to an appropriate size, and place it in a clamp to limit the growth direction of the foam; (3) place the polylactic acid sheet material fixed by the clamp into a foaming kettle, and use a high-pressure injection pump to introduce supercritical fluid; (4) heat the foaming kettle, and when the temperature reaches the specified foaming temperature and the gas pressure reaches the set value, saturate for a period of time, so that the gas diffuses into the polylactic acid matrix and reaches an equilibrium state; (5) after the saturation is completed, instantaneously open the pressure relief valve of the foaming kettle to break the equilibrium state of the system, so that the polylactic acid foams, and a bio-based polylactic acid open-cell foam material is obtained. The open-cell polylactic acid foam prepared by the patent technology has an open-cell rate higher than 85% and an expansion ratio of 15-30 times.

[0004] For example, the patent specification with publication number CN113736128A discloses a polylactic acid-based foaming material and a preparation method thereof, the preparation method comprising: saturating treatment of polylactic acid-based material in foaming gas to obtain a saturated system, wherein the polylactic acid-based material includes stereocomplex crystals and homogeneous crystals, and the crystallinity of the stereocomplex crystals is greater than or equal to 15%, the saturating treatment includes a first saturating stage and a second saturating stage, the temperature of the first saturating stage is greater than or equal to the melting temperature of the homogeneous crystals and less than the melting temperature of the stereocomplex crystals, and the temperature of the second saturating stage is less than the temperature of the first saturating stage; then, pressure relief foaming of the saturated system is performed to obtain the polylactic acid-based foaming material, and the sum of the crystallinity of the stereocomplex crystals and the crystallinity of the homogeneous crystals in the polylactic acid-based foaming material is greater than or equal to 40%. The patent technology divides the saturating treatment of the polylactic acid-based material into two stages, and controls the temperature of the first saturating stage and the second saturating stage respectively, so that the saturated system obtained has more saturated gas absorbed and has appropriate melt strength. Therefore, when pressure relief foaming is performed, the cells can grow well, and a polylactic acid-based foaming material with high expansion ratio is obtained. In the specific implementation of the patent technology: the absolute value of the difference between the temperature of the first saturating stage and the melting temperature of the homogeneous crystals is 5-30℃; the pressure of the foaming gas is 10.0-25.0MPa; the cooling rate from the first saturating stage to the second saturating stage is 1-30℃ / min; in the step of pressure relief foaming of the saturated system, the pressure relief rate is 20.0-100.0MPa / s.

[0005] However, in actual situations, after introducing the cell structure, although the toughness of the polymer material is increased, the strength is obviously reduced. SUMMARY

[0006] In view of the above technical problems and the deficiencies existing in the field, the present application provides a preparation method of high-strength open-cell material, which introduces unreacted low-activity magnesium oxide and phosphate into the unfoamed polymer composite material. After the composite material is prepared into an open-cell material, it is immersed in water. The connected pore structure allows the magnesium oxide and the phosphate to fully contact water, promoting the reaction of the magnesium oxide and the phosphate into bone cement, thereby improving the strength of the open-cell material.

[0007] The specific technical solutions are as follows:

[0008] A preparation method of high-strength open-cell material, comprising the steps of:

[0009] S1, 85-99.99 parts by mass of a polymer resin and 0.01-15 parts by mass of a powder phase are mixed and melt-extruded to obtain a composite material; the polymer resin and the powder phase are first dehydrated to a water content of less than 0.01wt% before use;

[0010] The powder phase is low-activity magnesium oxide and phosphate with a mass ratio of 1:3-5; the phosphate is at least one of dihydrogen phosphate and monohydrogen phosphate; the preparation method of the low-activity magnesium oxide comprises: heating the magnesium oxide to 1400-1600 DEG C at a heating rate of not more than 10 DEG C / min and calcining at the temperature for 3-6 h to obtain the low-activity magnesium oxide;

[0011] S2, the composite material is saturated in a physical foaming agent to obtain a saturated system, and then the saturated system is pressure-released to obtain an open-cell material; the pressure of the physical foaming agent is 5-25 MPa; the pressure-released foaming has a pressure-released rate of 10-100 MPa / s;

[0012] S3, the open-cell material is immersed in water to make the low-activity magnesium oxide and the phosphate react to generate bone cement, thereby improving the strength of the open-cell material and obtaining the high-strength open-cell material.

[0013] The phosphate used in the application is at least one of dihydrogen phosphate and monohydrogen phosphate, and the magnesium phosphate cement reaction used in the application is that the magnesium oxide generates magnesium hydroxide in an acidic environment, and then reacts with hydrogen in the phosphate, which is an acid-base neutralization reaction.

[0014] In an embodiment, in step S1, the total mass of the polymer resin and the powder phase is 100 parts.

[0015] In the preparation method of the low-activity magnesium oxide, the heating rate cannot be higher than 10 DEG C / min, otherwise the activity of the magnesium oxide will be relatively high, and the magnesium oxide is easy to react with the phosphate to generate bone cement before the open-cell material is formed, thereby making it difficult to prepare the required open-cell material.

[0016] In the preparation method of the high-strength open-cell material, the polymer resin can be at least one of polylactic acid, polybutylene succinate, polycaprolactone, polypropylene carbonate and polybutylene terephthalate-hexanedioate.

[0017] Preferably, in the preparation method of the high-strength open-cell material, the storage modulus of the composite material is less than 100 Pa, which is beneficial to the preparation of the open-cell foaming material. The storage modulus of the composite material is tested by a rotary rheometer. First, the melting point of the composite material is measured by a differential scanning calorimeter (DSC), and the temperature for the storage modulus test is the melting point of the composite material+(4-30) DEG C. The frequency for the storage modulus test is 0.01 rad / s to 0.1 rad / s. The storage modulus of the composite material needs to be less than 1.0*10 2 Pa, which is beneficial to the preparation of the open-cell material.

[0018] In an embodiment, in the preparation method of the high-strength open-cell material, the particle size of the low-activity magnesium oxide is less than 200 mesh.

[0019] In the preparation method of the high-strength open-pore material, the phosphate may be at least one of potassium dihydrogen phosphate, sodium dihydrogen phosphate, calcium dihydrogen phosphate, ammonium dihydrogen phosphate, dipotassium hydrogen phosphate, and disodium hydrogen phosphate.

[0020] This invention requires that the open-pore material be reacted with water to form bone cement after preparation, thereby improving the strength of the open-pore material. By minimizing the moisture content in the raw materials, it is possible to avoid the reaction and formation of bone cement before the formation of the open-pore material, which would make it difficult to obtain the desired open-pore material. In the preparation method of the high-strength open-pore material, in step S1, the polymer resin and the powder phase are dehydrated to a moisture content of less than 0.01 wt% before use.

[0021] In one embodiment, in the method for preparing the high-strength open-cell material, step S2, the saturation treatment includes a first saturation stage and a second saturation stage. The temperature of the first saturation stage is greater than or equal to the melting temperature of the composite material, which can melt all the crystalline regions of the composite material, facilitating the entry of more physical foaming agent. The temperature of the second saturation stage is lower than the temperature of the first saturation stage. In one embodiment, the absolute value of the difference between the temperature of the first saturation stage and the melting temperature of the composite material is 4–100°C. In one embodiment, the cooling rate from the first saturation stage to the second saturation stage is 1–30°C / min.

[0022] In one embodiment, in the method for preparing the high-strength open-cell material, in step S2, the physical foaming agent is carbon dioxide and / or nitrogen.

[0023] In one embodiment, the method for preparing the high-strength open-pore material involves an open-pore ratio greater than 80% in the open-pore material, which facilitates the full reaction of magnesium oxide and phosphate with water, thereby achieving the purpose of preparing the high-strength open-pore material.

[0024] In the preparation method of the high-strength open-pore material, in step S3, the reaction time of the open-pore material immersed in water can be selected as needed, for example, the reaction time is not less than 10 minutes, and further, the reaction time can be 10 minutes to 1 hour.

[0025] The present application introduces low-activity magnesium oxide and phosphate as fillers into a polymer matrix, and controls the water content of the polymer resin and the powder mixture, to avoid the reaction of magnesium oxide and phosphate to form bone cement before the preparation of the open-cell material, which increases the strength of the polymer matrix and further causes difficulty in foaming to form the open-cell material. The present application further combines the regulation of the foaming process, immerses the prepared open-cell material in water, promotes the reaction of magnesium oxide and phosphate to form bone cement, and increases the strength of the open-cell material. When the open-cell rate of the open-cell material is low, it is not conducive to the immersion of water into the sample, and it is difficult to make the complete reaction of magnesium oxide and phosphate, which weakens the effect of increasing the strength of the open-cell material.

[0026] The present application also provides the high-strength open-cell material prepared by the preparation method, which has a wide application prospect in the field of tissue engineering.

[0027] The present application also provides the application of the high-strength open-cell material in the preparation of biomedical stents.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] The present application processes magnesium oxide into low-activity magnesium oxide in a specific way, and then mixes and melts it with phosphate and polymer resin to form a composite material, which is further physically foamed to form an open-cell material. Finally, the open-cell material is immersed in water to slowly and fully react magnesium oxide and phosphate to form bone cement, thereby increasing the strength of the open-cell material and obtaining a high-strength open-cell material. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The scanning electron microscope (SEM) photo of the high-strength open-cell material prepared in Example 1 after compression.

[0031] Figure 2 The SEM photo of the high-strength open-cell material prepared in Example 4 after stretching.

[0032] Figure 3 The SEM photo of the high-strength open-cell material prepared in Example 4 after stretching. DETAILED DESCRIPTION

[0033] The present application will be further described below in conjunction with the drawings and specific examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application.

[0034] Example 1

[0035] Preparation: Magnesium oxide was heated from room temperature to 1600°C at a rate of 5°C / min and calcined in air at 1600°C for 4h, then cooled to room temperature, the product was ground and sieved to 200 mesh to obtain low-activity magnesium oxide. PLA resin, low-activity magnesium oxide and potassium dihydrogen phosphate were dried in a vacuum oven at 80°C for 8h, and PCL resin was dried in a vacuum oven at 40°C for 8h.

[0036] A mixture containing 66 parts by mass of PLA resin, 20 parts by mass of PCL resin, 3 parts by mass of low-activity magnesium oxide and 11 parts by mass of potassium dihydrogen phosphate (all raw materials were dried as described above, and the water content of the mixture was 0.008wt%) was melt-extruded, air-cooled and pelletized to obtain composite particles. Then, the composite particles were hot-pressed into a PLA-based composite with a sheet structure having a thickness of 1mm at a temperature of 190°C using a pressure of 12MPa, and the melting point of the PLA-based composite was tested by DSC to be 161°C. The storage modulus of the composite was measured to be 9.8-13.4Pa at a temperature of 170°C and a test frequency of 0.01-0.1rad / s.

[0037] The PLA-based composite obtained above was placed in an autoclave and saturated with carbon dioxide in two stages, wherein the pressure of carbon dioxide was 20.0MPa, the temperature of the first saturation stage was 165°C, and the saturation time was 30min, then the temperature was decreased to the second saturation stage at a rate of 10°C / min, the temperature of the second saturation stage was 85°C, and the saturation time was 50min, to obtain a saturated system.

[0038] The saturated system obtained above was depressurized at a rate of 10.0MPa / s to obtain a PLA-based foamed open-cell material, having an expansion ratio of 3.1 and an open-cell rate of 82.2%.

[0039] The PLA-based foamed open-cell material obtained above was placed in water at a temperature of 25°C for 50min, then taken out and placed in room temperature air for 24h, then the sample was dried in a vacuum oven, and the compressive strength of the sample was tested to be 26.6MPa and the tensile strength was 67.8MPa. The SEM test results of the sample after compression are shown in Figure 1

[0040] Example 2

[0041] The difference from Example 1 is that the temperature of the second saturation stage is 95°C, and the depressurization rate is 100.0MPa / s, and the rest are the same.

[0042] The PLA-based foamed open-cell material obtained in Example 2 has an expansion ratio of 7.3 and an open-cell rate of 87.9%. ​

[0043] The prepared polylactic acid-based foamed open-cell material was placed in water at 25°C for 50 min, then taken out and left in air at room temperature for 24 hours. After drying the sample in a vacuum oven, the compressive strength of the sample was 21.2 MPa, and the tensile strength was 60.1 MPa.

[0044] Example 3

[0045] The difference from Example 2 is that the pressure of carbon dioxide is 8 MPa, and the rest is the same.

[0046] The polylactic acid-based foamed open-cell material prepared in Example 3 has an expansion ratio of 4.4 and an open-cell rate of 83.7%.

[0047] The prepared polylactic acid-based foamed open-cell material was placed in water at 25°C for 50 min, then taken out and left in air at room temperature for 24 hours. After drying the sample in a vacuum oven, the compressive strength of the sample was 21.2 MPa, and the tensile strength was 60.1 MPa.

[0048] Example 4

[0049] The preparation process is the same as Example 1.

[0050] A mixture containing 70 parts by mass of polylactic acid (PLA) resin, 20 parts by mass of polycaprolactone resin, and 2 parts by mass of low-activity magnesium oxide and 8 parts by mass of potassium dihydrogen phosphate was melt-extruded, air-cooled, and pelletized to obtain composite particles. Then, the composite particles were hot-pressed into a polylactic acid-based composite material with a thickness of 1 mm at a temperature of 190°C using a pressure of 12 MPa, and the melting point of the polylactic acid-based composite material was tested by DSC to be 160°C. The storage modulus of the sample measured at a temperature of 170°C and a test frequency of 0.01 rad / s to 0.1 rad / s was 8.1-12.1 Pa.

[0051] The above-obtained polylactic acid-based composite material was placed in an autoclave and saturated with carbon dioxide in two stages, wherein the pressure of carbon dioxide was 15.0 MPa, the temperature of the first saturation stage was 165°C, and the saturation treatment time was 30 min. Then, the temperature was lowered to the second saturation stage at a rate of 10°C / min, and the saturation treatment time was 50 min at a temperature of 105°C, to obtain a saturated system.

[0052] The above-obtained saturated system was depressurized at a rate of 30.0 MPa / s to prepare a polylactic acid-based foamed open-cell material with an expansion ratio of 12.1 and an open-cell rate of 95.1%.

[0053] The prepared PBS-based foamed open-cell material was put into water at 25°C for 40 min, then taken out and placed in air at room temperature for 24 hours. After drying the sample in a vacuum oven, the compressive strength of the sample was 10.6 MPa, and the tensile strength was 17.4 MPa. The SEM test results of the sample after stretching are shown in Figure 2

[0054] Example 5

[0055] Preparation: Magnesium oxide was heated from room temperature to 1600°C at a heating rate of 5°C / min and calcined in air at 1600°C for 4 h, then cooled to room temperature. The obtained product was ground and sieved through a 200 mesh sieve to obtain low-activity magnesium oxide. PLA resin, low-activity magnesium oxide, and calcium dihydrogen phosphate were dried in a vacuum oven at 80°C for 8 h, and PBS resin was dried in a vacuum oven at 60°C for 8 h.

[0056] A mixture containing 80 parts by mass of PBS resin, 6 parts by mass of PLA resin, 3 parts by mass of low-activity magnesium oxide, and 11 parts by mass of calcium dihydrogen phosphate (all raw materials were subjected to the above drying process, and the water content of the mixture was 0.008 wt%) was melt-extruded, air-cooled, and pelletized to obtain composite particles. Then, the composite particles were hot-pressed into a PBS-based composite material with a thickness of 1 mm at a pressure of 10 MPa at 140°C, and the melting point of the PBS-based composite material was tested by DSC to be 114°C. The storage modulus of the composite material was measured to be 10.1-13.9 Pa at a temperature of 120°C and a test frequency of 0.01-0.1 rad / s.

[0057] The above-obtained PBS-based composite material was placed in an autoclave and saturated with carbon dioxide in two stages, wherein the pressure of carbon dioxide was 20.0 MPa, the temperature of the first saturation stage was 120°C, and the saturation time was 30 min. Then, the temperature was decreased to the second saturation stage at a rate of 10°C / min, the temperature of the second saturation stage was 95°C, and the saturation time was 50 min, to obtain a saturated system.

[0058] The above-obtained saturated system was depressurized at a rate of 30.0 MPa / s to prepare a PBS-based foamed open-cell material, with an expansion ratio of 15.7 and an open-cell rate of 97.6%.

[0059] The prepared PBS-based foamed open-cell material was put into water at 25°C for 40 min, then taken out and placed in air at room temperature for 24 hours. After drying the sample in a vacuum oven, the compressive strength of the sample was 10.6 MPa, and the tensile strength was 17.4 MPa. The SEM test results of the sample after stretching are shown in Figure 3 ​as shown.

[0060] Comparative Example 1

[0061] The difference between Example 1 and Comparative Example 1 is that the heating rate of magnesium oxide is 20℃ / min in the preparation process, and the rest is the same.

[0062] The polylactic acid-based foamed porous material prepared by decompression in Comparative Example 1 has an expansion ratio of 1.1 and an open porosity of less than 5%.

[0063] Comparative Example 2

[0064] The difference between Example 1 and Comparative Example 2 is that the pressure of carbon dioxide is 3MPa, and the saturated system is decompressed at a rate of 5MPa / s, and the rest is the same.

[0065] The polylactic acid-based foamed porous material prepared by decompression in Comparative Example 2 has an expansion ratio of 2.7 and an open porosity of less than 10%.

[0066] Comparative Example 3

[0067] The difference between Example 1 and Comparative Example 3 is that the heating rate of magnesium oxide is 5℃ / min from room temperature to 1300℃ in the preparation process, and the rest is the same.

[0068] The polylactic acid-based foamed porous material prepared by decompression in Comparative Example 3 has an expansion ratio of 1.9 and an open porosity of less than 5%.

[0069] Comparative Example 4

[0070] The difference between Example 1 and Comparative Example 4 is that all raw materials are not subjected to a drying process, and the moisture content of the mixture is 3.6wt%, and the rest is the same.

[0071] It is difficult to prepare a material with a porous structure in Comparative Example 4.

[0072] Comparative Example 5

[0073] The difference between Example 1 and Comparative Example 5 is that low-activity magnesium oxide and potassium dihydrogen phosphate are not added, and the rest is the same.

[0074] The polylactic acid-based foamed open-cell material prepared in Comparative Example 5 has an expansion ratio of 14.7 and an open porosity of 92.3%.

[0075] The polylactic acid-based foamed open-cell material prepared is placed in water at a temperature of 25℃ for 50min, then taken out, and placed in room temperature air for 24 hours. After drying the sample in a vacuum oven, the compressive strength of the sample is 1.7MPa, and the tensile strength is 12.8MPa.

[0076] It is to be understood that even though numerous characteristics and embodiments of the application have been set forth in the foregoing disclosure, the details can be varied without departing from the application, which is defined by the claims.

Claims

1. A method for preparing a high-strength open-pore material, characterized in that, Including the following steps: S1, 85-99.99 parts by weight of polymer resin and 0.01-15 parts by weight of powder phase are mixed and melt-extruded to obtain a composite material; the polymer resin and the powder phase are dehydrated to a moisture content of less than 0.01 wt% before use; the polymer resin is at least one selected from polylactic acid, polybutylene succinate, polycaprolactone, polypropylene carbonate, and polybutylene terephthalate. The powder phase is low-activity magnesium oxide and phosphate in a mass ratio of 1:3~5; the phosphate is at least one of dihydrogen phosphate and monohydrogen phosphate; the preparation method of the low-activity magnesium oxide includes: heating magnesium oxide to 1400~1600℃ at a heating rate of no more than 10℃ / min and calcining it at this temperature for 3~6 h to obtain the low-activity magnesium oxide; S2, the composite material is saturated in a physical foaming agent to obtain a saturated system, and then depressurized and foamed to obtain an open-cell material; the pressure of the physical foaming agent is 5~25 MPa; the saturation treatment includes a first saturation stage and a second saturation stage, the temperature of the first saturation stage is greater than or equal to the melting temperature of the composite material, and the temperature of the second saturation stage is less than the temperature of the first saturation stage; the physical foaming agent is carbon dioxide and / or nitrogen; the cooling rate from the first saturation stage to the second saturation stage is 1~30℃ / min; the depressurization rate of the depressurization foaming is 10~100 MPa / s; S3, Immerse the open-pore material in water to allow the low-activity magnesium oxide and the phosphate to react and generate bone cement, thereby increasing the strength of the open-pore material and obtaining the high-strength open-pore material.

2. The preparation method according to claim 1, characterized in that, The energy storage modulus of the composite material is less than 100 Pa; the temperature for energy storage modulus testing is the melting point of the composite material + (4~30) °C, and the frequency for energy storage modulus testing is 0.01 rad / s to 0.1 rad / s.

3. The preparation method according to claim 1, characterized in that, The low-activity magnesium oxide has a particle size of less than 200 mesh.

4. The preparation method according to claim 1, characterized in that, The phosphate is at least one of potassium dihydrogen phosphate, sodium dihydrogen phosphate, calcium dihydrogen phosphate, ammonium dihydrogen phosphate, dipotassium hydrogen phosphate, and disodium hydrogen phosphate.

5. The preparation method according to claim 1, characterized in that, The absolute value of the difference between the temperature of the first saturation stage and the melting temperature of the composite material is 4~100℃.

6. The preparation method according to claim 1, characterized in that, The porosity of the perforated material is greater than 80%.

7. The high-strength open-pore material prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the high-strength perforated material according to claim 7 in the fabrication of biomedical scaffolds.

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