PCHC / PPC composite material and preparation method thereof

Abstract

The invention belongs to the field of modification of degradable fat polycarbonate materials, and particularly relates to a PCHC / PPC composite material and a preparation method thereof. A PCHC matrix material is added into PPC for blending modification, a PCHC / PPC blended matrix material is obtained, hydrophobic microcrystalline cellulose is further added, and the PCHC / PPC composite material is obtained. The invention aims to break through the limitation of an existing degradable material in specific application, the performance of a polypropylene carbonate PPC material is better improved through a layer-by-layer progressive optimization strategy, and a novel polycarbonate composite material is obtained, so that the thermal stability and the mechanical property of the material are improved, and wider application requirements are met.

Description

Technical Field

[0001] The present invention belongs to the field of modification of biodegradable aliphatic polycarbonate materials, and particularly relates to a PCHC / PPC composite material modified by hydrophobic microcrystalline cellulose and a preparation method thereof. Background Art

[0002] Aliphatic polycarbonates are a class of biodegradable polyester materials directly obtained by alternating copolymerization of carbon dioxide and alkylene oxides. They can be used as film materials, biomedical materials, and plastic modifiers, etc. They are an effective way to fix and utilize greenhouse gas carbon dioxide and have good development and application prospects. The currently mass-produced variety of aliphatic polycarbonate is poly(propylene carbonate) (PPC), which has good flexibility and biodegradability and has great application prospects in the medical device field. However, the currently produced varieties have defects such as low glass transition temperature, poor thermal stability, and poor dimensional stability, and it is difficult to meet the increasingly demanding user needs. Therefore, it is necessary to improve and modify it to broaden the application field.

[0003] In the current modification technical solutions, blending and modifying by introducing other matrix materials is a simple and effective technical means. Commonly used substances include polylactic acid, caprolactone, PBS, etc., and these substances are mostly carboxylic acid ester polymers. Due to the differences in molecular structures, the two components after blending usually retain their respective property attributes too much, such as having two glass transition temperatures and thermal decomposition temperatures, etc., resulting in the modification effect usually not being satisfactory. Therefore, exploring new blendable substances and scientific blending technical solutions is still an urgent problem to be solved currently. Summary of the Invention

[0004] The purpose of the present invention is to provide a PCHC / PPC composite material and a preparation method thereof, to overcome the defects of the current PPC material, improve its related properties such as mechanical strength, thermal stability, gas barrier property, etc., and broaden its application field.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A PCHC / PPC blend composite material, and its preparation method is to first add a poly(cyclohexylene carbonate) (PCHC) matrix material to PPC for blending and modification to obtain the PCHC / PPC matrix blend material.

[0007] Furthermore, the mass ratio of PCHC to PPC is 0 - 30:100 - 70.

[0008] Preferably, the mass ratio of PCHC to PPC is 5:95.

[0009] PCHC is a new type of polycarbonate developed in recent years. It, like PPC, is a fatty polycarbonate material, and has a relatively high glass transition temperature, thermal stability, and mechanical strength, showing good complementarity with the properties of PPC. Therefore, in this invention, the relevant properties of PPC are improved by blending PCHC with PPC.

[0010] Furthermore, microcrystalline cellulose is added to the blend matrix of PPC and PCHC.

[0011] Since the main chain structure of PPC is relatively flexible, while the main chain of PCHC is a rigid structure with low molecular freedom and a relatively compact aggregation state, phase separation occurs during blending, making it difficult to achieve "molecular-scale" mixing, thus affecting the performance of the blend.

[0012] When facing the phase separation phenomenon in material blending, the prior art usually uses adding a third component to enhance the binding strength between components in the blend material. Generally, organic or inorganic additives with strong interaction forces with both matrix components are added, such as nano-lignin, PEG, SiO2, TiO2, etc. This invention uses microcrystalline cellulose, the most abundant natural product, with a wide source and good application prospects.

[0013] Microcrystalline cellulose (MCC) is a partial hydrolyzate of cellulose, with a particle size in the micron range, having the advantages of high strength, high modulus, non-toxicity, good biocompatibility, etc., and having a large number of hydroxyl groups in the molecule. Theoretically, there is a large hydrogen bond interaction force with the two polyester matrices, and it is an ideal third additive component for the blend matrix of PPC and PCHC in this invention.

[0014] The inventors found that since the PCHC / PPC blend material is in an amorphous state and has a too large polarity difference from the highly crystalline MCC, the compatibility of the components is poor. Therefore, directly adding MCC cannot improve the relevant properties of the composite material, and technical means need to be taken to enhance its compatibility.

[0015] This invention adopts the strategy of hydrophobic modification of MCC to improve the affinity with the PCHC / PPC matrix.

[0016] Furthermore, two methods of physical adsorption hydrophobic modification and organic small molecule chemical hydrophobic modification are respectively adopted.

[0017] The microcrystalline cellulose described is preferably hydrophobic microcrystalline cellulose modified with cetyltrimethylammonium bromide or acetic anhydride.

[0018] For physical adsorption hydrophobic modification, hexadecyltrimethylammonium bromide (CTAB) was used as the modifier (the modified MCC is designated CMCC). CTAB is a cationic surfactant that readily adsorbs onto the negatively charged surface of MCC, forming a hydrophobic layer. It has high adsorption efficiency and, compared to some traditional organic solvents, requires less usage, resulting in less negative environmental impact, in line with the concept of "green chemistry." CTAB also has a bactericidal effect, imparting a degree of antifungal properties to the material.

[0019] Chemical hydrophobic modification uses acetic anhydride to esterify and cap the MCC surface (the modified MCC is referred to as AMCC). This reaction is highly efficient, simple, and generally does not require excessive amounts of organic solvents, thus meeting environmental requirements. Furthermore, the hydrophobic acetyl groups are firmly chemically bonded to the MCC surface and are not easily detached.

[0020] The added amount of the modified microcrystalline cellulose is 0.2-1% of the total mass of PPC and PCHC.

[0021] The present invention further provides a method for preparing a PCHC / PPC composite material, wherein PPC and PCHC are fully dissolved in a DMF solution according to a proportion to obtain a uniformly mixed casting solution, and then a PCHC / PPC blend matrix membrane is prepared.

[0022] The present invention optimizes the solvent. In the prior art, dichloromethane or chloroform is often used as a solvent. However, these two solvents can dissolve PCHC but can only swell PPC instead of dissolving it.

[0023] Furthermore, modified or unmodified microcrystalline cellulose is added to the blended matrix of PPC and PCHC, wherein the modified microcrystalline cellulose is microcrystalline cellulose modified with cetyltrimethylammonium bromide or acetic anhydride, and the amount of the modified microcrystalline cellulose added is 0.2-1% of the total mass of PPC and PCHC.

[0024] The process for modifying microcrystalline cellulose with cetyltrimethylammonium bromide is as follows: adding an aqueous solution of the modifier cetyltrimethylammonium bromide (CTAB) to a suspension of microcrystalline cellulose (MCC) at a pH of 7-13 and allowing the mixture to react fully; collecting the reaction product, purifying it, and drying it to obtain the modified microcrystalline cellulose; the mass ratio of CTAB:MCC is 0-0.08:1; the reaction temperature is 30-90°C, and the reaction time is 30-240 minutes. The pH of the MCC suspension needs to be maintained in the range of 7-13.

[0025] Specifically, NaOH with a mass concentration of 25-40% can be used to adjust the pH value of the solution.

[0026] The process of modifying microcrystalline cellulose with acetic anhydride is as follows: MCC is mixed with acetic anhydride and iodine and heated for reaction. After that, the excess iodine is removed at room temperature, and the reaction product is collected, purified and dried to obtain the modified microcrystalline cellulose. The molar ratio of glucose units in MCC to acetic anhydride and iodine is 1:10 - 60:0.01 - 0.06. The reaction temperature is 60 - 100 °C, and the reaction time is 30 - 180 min.

[0027] The present invention has the following innovative points:

[0028] 1. The present invention uses PCHC as a blend matrix component of PPC. Both PCHC and PPC are aliphatic polycarbonates, and their molecular structures are relatively similar, having a certain "affinity". At the same time, due to the rigid six-membered alicyclic structure in the PCHC molecule, it has high thermal stability and mechanical strength, and has a good compensating effect on the defects of PPC itself, such as low glass transition temperature and low mechanical strength.

[0029] 2. The present invention preferably uses hydrophobic MCC as the third component to improve the compatibility between the two matrices of PCHC and PPC. Untreated MCC has high crystallinity and strong polarity, and cannot be effectively dispersed in the PCHC / PPC system, and there are many agglomeration phenomena. Therefore, the composite film prepared is prone to structural defects and affects the performance to a certain extent. After hydrophobic treatment, the surface of MCC has both hydrophilic strong polar hydroxyl groups and hydrophobic weak polar long-chain alkyl or acetyl groups. The hydrophobic groups can make MCC evenly dispersed in the PCHC / PPC system, and the hydroxyl groups retained on the surface of MCC form relatively strong intermolecular hydrogen bonds with the carbonyl groups of the PCHC / PPC two components, thus firmly connecting the two components, resulting in a strong interaction between the two matrix components and improving the blending effect.

[0030] 3. The present invention proposes a differential hydrophobic modification strategy for MCC (physical adsorption and chemical bonding): CTAB physical adsorption hydrophobic modification: CTAB wraps the hydrophobic long-chain alkyl groups on the surface of MCC through electrostatic adsorption, enhancing the hydrophobicity of MCC. Acetic anhydride acetylation hydrophobic modification: Hydrophobic acetyl groups are introduced onto the surface of MCC through acetylation reaction, reducing the number of hydroxyl groups and forming a hydrophobic interfacial layer. The modified MCC forms physical entanglement with the PCHC / PPC system through long-chain alkyl or acetyl groups, enhancing the interfacial binding force. There are significant differences in polarity regulation, interfacial binding mechanism and stability between the two modification methods. Through systematic comparison, the applicable scenarios of different hydrophobic strategies can be clarified.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention aims to break through the limitations of existing degradable materials in specific applications, and better improve the performance of poly(propylene carbonate) (PPC) materials through a series of optimization strategies, so as to obtain a new type of polycarbonate composite material, improve the thermal stability and mechanical properties of the material, and meet more extensive application requirements. Description of the Drawings

[0033] Figure 1 It is the mechanism diagram of hydrophobic modification of MCC by physical adsorption of CTAB;

[0034] Figure 2 It is the schematic diagram of the experimental process of hydrophobic modification of MCC by physical adsorption of CTAB;

[0035] Figure 3 It is the mechanism diagram of hydrophobic modification of MCC by acetylation with acetic anhydride;

[0036] Figure 4 It is the process flow diagram of the preparation of hydrophobic MCC modified PCHC / PPC composite film;

[0037] Figure 5 、 Figure 6 It is the SEM images of two composite film materials (a: 5PCHC95PPC / 0.2CMCC sample, b: 5PCHC95PPC / 0.2AMCC sample). Detailed Embodiments

[0038] The following specific examples are used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto:

[0039] Example 1

[0040] Preparation of PPC film:

[0041] Put PPC into a blast drying oven at 40 °C and dry for 24 h for later use. At room temperature, weigh 1.00 g of PPC and add it to 10 mL of DMF solution, and stir magnetically for 4 h until completely dissolved to obtain a homogeneous casting solution. At room temperature, pour the casting solution onto a glass plate, evenly scrape the film with an I-shaped coater, and then put the glass plate into an oven at 80 °C to evaporate the solvent to constant weight to obtain a PPC film with a thickness of 0.08 mm.

[0042] Example 2

[0043] Preparation of 5PCHC95PPC blend film:

[0044] The PPC and PCHC were placed in a forced-air drying oven at 40 °C and dried for 24 h for later use. At room temperature, 0.05 g of PCHC and 0.95 g of PPC were weighed and added to 10 mL of DMF solution, and magnetically stirred for 4 h until completely dissolved to obtain a homogeneous casting solution. At room temperature, the casting solution was poured onto a glass plate and evenly scraped with an I-shaped coater, and then the glass plate was placed in an oven at 80 °C to evaporate the solvent to constant weight to obtain a 5PCHC95PPC blend film with a thickness of 0.08 mm.

[0045] Example 3

[0046] Preparation of MCC-modified PCHC / PPC composite film:

[0047] The PPC and PCHC were placed in a forced-air drying oven at 40 °C and dried for 24 h for later use. At room temperature, 0.05 g of PCHC and 0.95 g of PPC were weighed and added to 10 mL of DMF solvent and stirred until dissolved. Then 0.004 g of unmodified MCC was weighed and added to the above solution, and vigorously stirred for 6 h to obtain a uniform casting solution. At room temperature, the casting solution was poured onto a glass plate and evenly scraped with an I-shaped coater. After slightly solidifying, the glass plate was placed in an oven at 80 °C to dry, and the film was peeled off to obtain a (5PCHC95PPC) / 0.4MCC composite film with a thickness of 0.08 mm.

[0048] Example 4

[0049] Preparation of hydrophobically modified PCHC / PPC composite material with hydrophobic MCC:

[0050] (1) Physical adsorption hydrophobic modification of MCC with CTAB

[0051] 1.00 g of MCC was weighed and added to 40 mL of purified water. The pH of the MCC suspension was adjusted to 10 with 25% NaOH solution, and then stirred for 30 min. 0.02 g of CTAB was weighed and dissolved in 10 mL of purified water. Then the CTAB solution was slowly added to the MCC suspension, and the pH of the suspension was adjusted to 10 again with NaOH solution. Finally, the above suspension was stirred at 50 °C for 120 min and then filtered by suction, and the filter cake was washed with purified water and then dried in an oven at 60 °C for 48 h to obtain CMCC.

[0052] (2) Preparation of CMCC-modified PCHC / PPC composite film

[0053] At room temperature, 0.05 g of PCHC and 0.95 g of PPC were weighed and added to 10 mL of DMF solvent and stirred until dissolved. Then, 0.002 g of CMCC was weighed and added to the above solution, and after vigorous stirring for 6 h, a uniform casting solution was obtained. At room temperature, the casting solution was poured onto a glass plate and evenly coated with an I-shaped coater. After slightly solidifying, the glass plate was placed in an oven at 80 °C and dried, and then the film was peeled off to obtain a (5PCHC95PPC) / 0.2CMCC composite film with a thickness of 0.08 mm.

[0054] Examples 5 - 8

[0055] The addition amounts of CMCC were adjusted to 0.004 g, 0.006 g, 0.008 g, and 0.01 g respectively, and the others were the same as in Example 4.

[0056] Example 9

[0057] A preparation method of a hydrophobic MCC-modified PCHC / PPC composite material is as follows:

[0058] (1) Acetylation of hydrophobic modification of MCC

[0059] 1.00 g of MCC was weighed and placed in a reaction flask, and then 17 mL of acetic anhydride solution and 0.0627 g of iodine were added thereto. The suspension was heated to 80 °C and maintained for 90 min. After the reaction was completed, the flask was placed in an ice bath and cooled to room temperature, and then saturated sodium thiosulfate solution was slowly added to the flask under stirring until the color changed from dark red to colorless to remove the excess iodine. The suspension was filtered by suction, washed successively with ethanol and purified water, and finally dried in an oven at 60 °C for 48 h to obtain AMCC.

[0060] (2) Preparation of AMCC-modified PCHC / PPC composite film

[0061] At room temperature, 0.05 g of PCHC and 0.95 g of PPC were weighed and added to 10 mL of DMF solution. Then, 0.002 g of AMCC was weighed and added to the above solution, and after vigorous stirring for 6 h, a uniformly mixed casting solution was obtained. The casting solution was poured onto a glass plate and evenly coated with an I-shaped coater, and then the glass plate was placed in an oven at 80 °C and dried, and the film was peeled off to obtain a (5PCHC95PPC) / 0.2AMCC composite film with a thickness of 0.08 mm.

[0062] Examples 10 - 13

[0063] The addition amounts of AMCC were adjusted to 0.004 g, 0.006 g, 0.008 g, and 0.01 g respectively, and the others were the same as in Example 9.

[0064] The performance of the composite film materials obtained from the above embodiments was tested, and the specific test methods are as follows:

[0065] Transparency test: A baseline was established by scanning in the wavelength range of 200 - 800 nm with air as the background. A film with a thickness of 0.08 mm was cut into strips about 1.0 cm × 4.0 cm and placed in the groove of a UV-visible spectrophotometer to measure the transparency of the film sample in the wavelength range of 200 - 800 nm.

[0066] Microscopic morphology test: The film sample was brittle fractured in liquid nitrogen, and then the sample was glued to the sample stage with conductive adhesive, and the cross-section was sputter-coated with gold for 50 s. Then, a scanning electron microscope was used to observe the cross-sectional morphology.

[0067] Contact angle test: The film was cut into strips about 1.0 cm × 2.0 cm. The film sample was pasted on the sample stage with double-sided tape, the focal length and field of view were adjusted, the volume of purified water was set to 2 μL, and it was tested 3 times at different positions, and the average value was taken.

[0068] Mechanical property test: A film with a thickness of 0.08 mm was cut into strips about 10 mm × 70 mm, and the mechanical properties of the film were tested on a universal tensile testing machine. The spacing was set to 30 mm and the tensile speed was 50 mm / min to measure its tensile strength and elongation at break.

[0069] Water vapor transmission rate test: A film with a thickness of 0.08 mm was cut into a circle with a diameter of about 5.0 cm, and then the sample was placed in an oven and dried to a constant weight. After thoroughly grinding anhydrous calcium chloride powder, it was placed in an oven and dried to a constant weight. About 3.00 g of dried anhydrous calcium chloride powder was weighed and placed in a weighing bottle with an inner diameter of 22 mm. Immediately, the bottle mouth was sealed with the film, and the weight of the weighing bottle at this time was recorded as m0. The weighing bottle was placed in a desiccator with saturated sodium chloride solution at the bottom (relative humidity was maintained at 75%), and then the desiccator was placed in a constant temperature oven at 25 ± 0.1 °C for 48 h, and then the weight of the weighing bottle was weighed again and recorded as m1. The water vapor transmission rate (WVT) of the film was calculated by the following formula.

[0070] [[ID=1,8]]

[0071] In the formula, m1 is the weight of the weighing bottle at 48 h, g; m0 is the initial weight of the weighing bottle, g; S is the area of the weighing bottle mouth, m 2 ; t is the time, h.

[0072] Vitrification transition temperature measurement: Cut the membrane into fragments with a size of about 3 mm × 2 mm, weigh about 5 mg of the membrane sample and put it into an aluminum crucible. Under a N2 atmosphere of 10 mL / min, set the initial equilibrium temperature to 30 °C, then heat it at a rate of 10 °C / min to 150 °C, and keep it at 150 °C for 5 min to eliminate the previous thermal history of the sample. Then cool it to -20 °C at a rate of 10 °C / min, and then heat it to 150 °C at a rate of 10 °C / min. Record the data of the second heating.

[0073] Thermal decomposition temperature measurement: Dry the membrane sample in an oven until it reaches a constant weight. Weigh about 10 mg of the membrane sample, and heat the sample from 30 °C to 600 °C at a heating rate of 20 °C / min under an argon atmosphere of 20 mL / min.

[0074] Table 1 Performance test results of the membranes in Examples 1 - 3

[0075]

[0076] Note: The transparency of the composite membrane is the test result under the condition that the ultraviolet wavelength is 800 nm. The same applies hereinafter.

[0077] It can be seen from the test results that compared with PPC, the tensile strength of the 5PCHC95PPC blend membrane has increased by 13.98%; the initial thermal decomposition temperature, the maximum thermal decomposition rate temperature and the vitrification transition temperature have all increased.

[0078] Table 2 Performance test results of the (5PCHC95PPC) / CMCC composite membranes in Examples 4 - 8

[0079]

[0080] Table 3 Performance test results of the (5PCHC95PPC) / AMCC composite membranes in Examples 9 - 13

[0081]

[0082] By comparing the effects of different hydrophobic modification methods on the performance of the 5PCHC95PPC blend membrane, it can be concluded that the modification effect of AMCC is better than that of CMCC. And when the addition amount of AMCC is 0.004 g, the comprehensive performance of the composite membrane is the best. At this time, compared with the 5PCHC95PPC blend membrane, the tensile strength of the (5PCHC95PPC) / 0.4AMCC composite membrane has increased by 114.77%; the initial decomposition temperature has increased by 12.29 °C; the water vapor transmission rate has decreased by 40.54%; the vitrification transition temperature and the maximum thermal decomposition rate temperature are both single temperature values and have increased, indicating that the phase separation phenomenon between the matrices has been effectively inhibited, the membrane structure is more compact, and the surface is smoother; the transparency has increased.

[0083] The above examples are only used to illustrate the technical concept and features of the present invention, and should not be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the essence of the present invention, such as changing the experimental conditions of MCC hydrophobic modification, the preparation conditions of the blend film and the composite film, etc., should be covered within the protection scope of the present invention.

Claims

1. A PCHC / PPC composite material, characterized in that, The PCHC matrix material is added to PPC for blending and modification to obtain the PCHC / PPC composite material.

2. The PCHC / PPC composite material according to claim 1, wherein The mass ratio of PCHC to PPC is 0-30:100-70.

3. The PCHC / PPC composite material according to claim 2, wherein The mass ratio of PCHC to PPC is 5:

95.

4. The PCHC / PPC composite material according to any one of claims 1-3, characterized in that, Microcrystalline cellulose was added to the blend matrix of PCHC and PPC.

5. The PCHC / PPC composite material according to claim 4, characterized in that, The microcrystalline cellulose is hydrophobic microcrystalline cellulose obtained by modifying hexadecyltrimethylammonium bromide or acetic anhydride.

6. The PCHC / PPC composite material according to claim 5, wherein The added amount of the modified microcrystalline cellulose is 0.2-1% of the total mass of PCHC and PPC.

7. The preparation method of any one of the PCHC / PPC composites of claims 1-3, characterized in that, PCHC and PPC were fully dissolved in N,N-dimethylformamide solution according to a certain ratio to obtain a uniformly mixed casting solution, and then a PCHC / PPC blend membrane was prepared.

8. The preparation method of the PCHC / PPC composite material according to claim 7, wherein, Modified microcrystalline cellulose is added to the blended matrix of PCHC and PPC. The microcrystalline cellulose is microcrystalline cellulose modified with cetyltrimethylammonium bromide or acetic anhydride. The amount of the modified microcrystalline cellulose added is 0.2-1% of the total mass of PCHC and PPC.

9. The preparation method of the PCHC / PPC composite material according to claim 8, wherein The process of modifying microcrystalline cellulose with cetyltrimethylammonium bromide is as follows: adding an aqueous solution of the modifier cetyltrimethylammonium bromide (CTAB) to a suspension of microcrystalline cellulose (MCC) with a pH of 7-13 and allowing the mixture to react fully; collecting the reaction product, purifying it, and drying it to obtain the modified microcrystalline cellulose; the mass ratio of CTAB to MCC is 0-0.08:1, the reaction temperature is 30-90°C, and the reaction time is 30-240 minutes.

10. The preparation method of the PCHC / PPC composite material according to claim 8, characterized in that, The process of modifying microcrystalline cellulose with acetic anhydride is as follows: MCC is mixed with acetic anhydride and iodine and heated to react, then excess iodine is removed at room temperature, the reaction product is collected, purified and dried to obtain the modified microcrystalline cellulose; the molar ratio of glucose units in MCC to acetic anhydride and iodine is 1:10-60:0.01-0.06; the reaction temperature is 60-100°C, and the reaction time is 30-180 minutes.

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