CN105061971A - Method for preparing completely-degradable composite material through acid anhydride and microcrystalline cellulose synergetic modification on poly(propylene carbonate) - Google Patents

Abstract

The invention discloses a method for synergistically modifying polymethylethylene carbonate with acid anhydride and microcrystalline cellulose to prepare a fully degradable composite material. The degradable polymethylethylene carbonate, acid anhydride and microcrystalline cellulose are melt-mixed Form the masterbatch of the fully degradable composite material, and then mold it into a sample; the mass ratio of polymethylethylene carbonate, acid anhydride and microcrystalline cellulose is: 50-95 parts of polymethylethylene carbonate, microcrystalline fiber 5-50 parts of plain, 0.1-10 parts of acid anhydride. The fully degradable composite material prepared by the above method has good mechanical properties and thermal stability, and can effectively improve the processing stability and mechanical properties of the obtained product.

Description

Synergistic modification of polymethylethylene carbonate with acid anhydride and microcrystalline cellulose to prepare fully degradable composite materials

technical field

The invention relates to the technical field of polymer composite material preparation, in particular to a method for preparing a fully degradable composite material by synergistically modifying polymethylethylene carbonate with acid anhydride and microcrystalline cellulose.

Background technique

Polymethylethylene carbonate (PPC) is a fully biodegradable plastic synthesized from carbon dioxide (CO ₂ ) and propylene oxide, which opens up a way for large-scale comprehensive utilization of CO ₂ . Using _CO2 as a raw material to synthesize PPC, on the one hand, can reduce the dependence of plastics on petroleum resources; pollute". Moreover, polymethylethylene carbonate has excellent gas barrier properties, biocompatibility and easy processing, and is an environmentally friendly material with great development prospects. However, in practical applications, due to the presence of ether bonds in PPC, the chain segments are prone to internal rotation around the ether bonds, which increases the flexibility of the chain and makes it have a lower glass transition temperature; while the terminal hydroxyl group (-OH) is the The active point of the molecular chain can induce "unzip" degradation and reduce the thermal stability of PPC. Therefore, the poor thermodynamic properties of PPC limit its application. In order to expand the application range of PPC, it must be modified.

At present, the reports on the blending modification of PPC are mainly divided into the following three categories: PPC/synthetic polymer blends, PPC/inorganic particle composite materials, and PPC/natural polymer composite materials. Natural polymer materials are diverse, inexpensive, renewable, and can be completely degraded under various natural conditions. Moreover, general natural polymer materials contain a large number of hydroxyl groups, which can interact with carbonyl groups in PPC through hydrogen bonds, improve the mechanical properties and heat resistance of PPC, and obtain fully biodegradable PPC-based composite materials. Plant fibers and their derivatives are the largest and most abundant types of natural polymer materials. There are also some reports in the preparation of PPC-based composites using plant fibers as reinforcements.

Jiao Jian of Sun Yat-Sen University mixed cotton fiber and PPC to prepare PPC/cotton fiber composite material through a mixer, which effectively improved the tensile strength of PPC. The thermal stability effect of composite materials is not obvious, and its application range is limited.

Li et al. used Indian Hildegardia populifolia fibers to melt blend with PPC to prepare fiber-reinforced composite materials. The research results showed that: with the addition of fibers, the tensile strength of composite materials increased, but the elongation at break of PPC decreased significantly.

In the invention application with the publication number CN103571166A, a cellulose, microcrystalline cellulose, polymethylethylene carbonate composition and its preparation method are disclosed, wherein end-capping agents, lubricants, antioxidants, The composite material prepared by various additives such as plasticizers in a certain ratio improves the mechanical strength of polymethylethylene carbonate.

Among the above-mentioned various treatment methods, the actual research results show that the method of modifying PPC with plant fibers still has insufficient heat resistance of PPC and a significant decrease in toughness.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, provide a kind of method that acid anhydride and microcrystalline cellulose synergistically modify polymethylethylene carbonate to prepare fully degradable composite material, the fully degradable composite material prepared by this method has Good mechanical properties and thermal stability can effectively improve the processing stability and mechanical properties of the prepared products.

The technical scheme of the present invention is: a method for preparing a fully degradable composite material by synergistically modifying polymethylethylene carbonate with acid anhydride and microcrystalline cellulose, which is characterized in that degradable polymethylethylene carbonate, acid anhydride Melt and knead with microcrystalline cellulose to form a masterbatch of a fully degradable composite material, and then mold it into a sample;

Wherein, the mass ratio of polymethylethylene carbonate, acid anhydride and microcrystalline cellulose is as follows:

Polymethylethylene carbonate: 50-95 parts,

Microcrystalline cellulose: 5-50 parts,

Anhydride: 0.1 to 10 parts.

The polymethylethylene carbonate is used as the matrix of the fully degradable composite material, the acid anhydride is used as the end-capping agent and compatibilizer, and the microcrystalline cellulose is used as the filling material.

The number average molecular weight of the polymethylethylene carbonate is 10,000-100,000.

The acid anhydride is acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, tetrahydrophthalic anhydride, itaconic anhydride , pyromellitic dianhydride or mellitic anhydride or a combination of several.

The microcrystalline cellulose is prepared from natural plant fibers through acid hydrolysis.

The particle size of the microcrystalline cellulose is 20-100 μm.

The concrete process that described polymethylethylene carbonate, acid anhydride and microcrystalline cellulose are carried out melt mixing is as follows:

(1) After weighing polymethylethylene carbonate, acid anhydride and microcrystalline cellulose by weight percentage, first dry at 40-80°C for 12-36 hours, and then perform mechanical mixing to form a premix;

(2) Put the premixed material into the mixing equipment for melting and mixing to obtain the masterbatch of the fully degradable composite material.

Wherein, the equipment used for the mechanical mixing is a high-speed mixer, and the time for mechanical mixing is 0.5-3 minutes.

The mixing equipment is a single-screw extruder, a twin-screw extruder, an internal mixer or an open mixer, the melting and mixing temperature in the mixing equipment is 110-150°C, and the die head temperature in the mixing equipment is 110-170°C, the rotational speed of the mixing equipment is 10-200r/min, and the blending time in the mixing equipment is 3-10min.

In the method for the above-mentioned acid anhydride and microcrystalline cellulose synergistically modifying polymethylethylene carbonate to prepare a fully degradable composite material, its mechanism is as shown in Figure 1, specifically: based on the activity of microcrystalline cellulose (MCC) surface hydroxyl and The active hydroxyl group at the end of PPC is added with various acid anhydrides as compatibilizers, and the synergistic effect of acid anhydrides and MCC is used to modify PPC. A fully degradable PPC-based composite material is prepared by a simple and easy method. Under heating conditions, the acid anhydride bond is broken to form a carboxyl group, which can undergo an esterification reaction with the hydroxyl group of PPC and MCC, making it not only a simple physical blend, but a chemical interaction, which strengthens the interaction between the filler and the matrix. In addition, the acid anhydride can also be used as a capping agent to cap the PPC and improve the tensile strength and mechanical properties of the PPC.

Compared with the prior art, the present invention has the following beneficial effects:

In the invention, degradable polymethylethylene carbonate resin is used as composite material matrix, acid anhydride is used as end-capping agent, microcrystalline cellulose with degradable performance is added as filling material, and the composite material is prepared through melt blending. Microcrystalline cellulose with small size, complete crystalline structure, excellent mechanical properties and high reactivity is used as a filler to solve the interface and dispersion problems of cellulose in the matrix polymethylethylene carbonate. After adding microcrystalline cellulose to the copolymerization system of acid anhydride-terminated polymethylethylene carbonate, the thermal stability and mechanical properties of the material can be improved, and both the microcrystalline cellulose and the matrix material can be degraded, thus making The composite material can eventually be degraded naturally, and it is a new type of sustainable composite material. The microcrystalline cellulose has the advantages of abundant sources, low price and complete degradation, which greatly reduces the production cost of the material of the present invention. The product prepared by the method also has the advantages of safety and environmental protection, low cost, good processing performance and the like.

Description of drawings

Figure 1 is a schematic diagram of the mechanism for the preparation of fully degradable composite materials by synergistically modifying polymethylethylene carbonate with anhydride and microcrystalline cellulose.

Detailed ways

The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

Example 1

The number-average molecular weight of the PPC used is 5.91×10 ⁴ , and the dried PPC and maleic anhydride (MA) are mixed according to the mass ratio of 100:0.5, 100:1, 100:3, and 100:5 to form 4 samples The premixed materials are then put into the twin-screw extruder to prepare maleic anhydride-terminated PPC, the screw speed is 80r/min, the die head temperature of the extruder is 120°C, and the products are respectively marked as PPC-MA0.5, PPC-MA1, PPC-MA3, PPC-MA5.

At the same time, a pure PPC sample without MA was prepared as a blank control, which was labeled as pure PPC.

The same amount of samples obtained by extrusion was selected and observed with an infrared scanner. There was an obvious absorption peak at 1640cm ^-1 in the spectrum of PPC-MA1, indicating that MA successfully blocked PPC.

Select the same amount of samples obtained by extrusion, and use a thermogravimetric analyzer for TG analysis in a nitrogen environment at a heating rate of 10°C/min during the entire process. The T _{- 5%} , T- _50% , T- _95% (that is, the temperatures corresponding to the total mass reduction of 5%, 50%, and 95%) are shown in Table 1.

Table 1 The thermal decomposition temperature values of pure PPC and MA with different contents of PPC-MA

It can be seen from Table 1 that the improvement of the thermal stability of PPC-MA is closely related to the content of MA. As the content of MA increases, the thermal stability of the product improves; among them, when the amount of MA added is 1phr, the grafting rate of PPC-MA The maximum, T _-5% , reaches the highest at 264.8°C. The reason is that the capping reaction between MA and the terminal hydroxyl group of PPC inhibits the "unzip" degradation of PPC.

Example 2

The number-average molecular weight of the PPC used is 9.17×10 ⁴ , and the dried PPC, maleic anhydride (MA), phthalic anhydride (PA), and pyromellitic dianhydride (PMDA) are respectively mixed in a mass ratio of 100:1 Mix separately to form a premix of 3 samples, and then put them into a twin-screw extruder to prepare three different types of anhydride-terminated PPC. The screw speed is 80r/min, and the die temperature of the extruder is 120 ° C. The product PPC-MA1, PPC-PA1, PPC-PMDA1 were labeled respectively.

At the same time, a pure PPC sample without acid anhydride was prepared as a blank control, which was labeled as pure PPC.

Choose 4 kinds of samples obtained by extrusion of the same amount, carry out thermal stability analysis according to the method identical with example 1, the T- _5% of pure PPC, PPC-MA1, PPC-PA1, PPC-PMDA1, T- _{50 %} , T- _95% are shown in Table 2.

The thermal decomposition temperature value of table 2 pure PPC, PPC-MA1, PPC-PA1, PPC-PMDA1

It can be seen from Table 2 that after adding the three anhydrides of MA, PA, and PMDA, the T- _5% of pure PPC is increased to varying degrees. Among them, the T _-5% of PPC-PMDA1 was the highest, increasing by 26.3°C. This is because PMDA is an aromatic dianhydride, which not only contains benzene rings in its molecular structure, but also has a large number of carbonyl groups, so it can more effectively improve the thermal stability of PPC.

Example 3

The number-average molecular weight of the PPC used is 9.17×10 ⁴ , and the dried PPC, maleic anhydride (MA), phthalic anhydride (PA), and pyromellitic dianhydride (PMDA) are respectively mixed in a mass ratio of 100:1 Mix separately to form a premix of 3 samples, and then put them into a twin-screw extruder to prepare three different types of anhydride-terminated PPC. The screw speed is 80r/min, and the die temperature of the extruder is 120 ° C. The product PPC-MA1, PPC-PA1, PPC-PMDA1 were labeled respectively.

At the same time, a pure PPC sample without acid anhydride was prepared as a blank control, which was labeled as pure PPC.

Take four samples of the same amount for extrusion experiments, first vacuum-dry them at 60°C for 24 hours, then put each sample into a flat vulcanizer and press it into tablets, and perform mechanical property tests according to the standard sample preparation of IOS527-2 and IOS179-1982. The results are shown in Table 3.

Table 3 Mechanical property values of pure PPC, PPC-MA1, PPC-PA1, PPC-PMDA1

It can be seen from Table 3 that compared with the tensile strength of pure PPC, the tensile strength of PPC-MA1, PPC-PA1, and PPC-PMDA1 has different degrees of improvement. Among them, PPC-PMDA1 is the largest, which is 4.15MPa higher than that of pure PPC. The reason is that PPC-PMDA1 has the largest intrinsic viscosity and therefore the largest tensile strength.

Example 4

The number-average molecular weight of the PPC used is 9.17×10 ⁴ . Add the dried PPC to the internal mixer and mix at a certain speed for 3 minutes at 160°C. After the PPC is fully melted, add microcrystalline cellulose (MCC) powder , mixed for 10min, the mass ratios of PPC and MCC were respectively: 95:5, 90:10, 85:15, 80:20, forming 4 parts of PPC/MCC composite materials (respectively marked as: PPC/MCC-5, PPC/ MCC-10, PPC/MCC-15, PPC/MCC-20). And the obtained 4 parts of composite materials are pressed into tablets by a flat vulcanizing machine. MCC was dried before the experiment, and the powder was filtered through a 200-mesh sieve.

At the same time, the pure PPC tablet sample without MCC was prepared as a blank control, and the mechanical properties were tested according to the standard sample preparation of IOS527-2 and IOS179-1982. The results are shown in Table 4.

Table 4 Mechanical properties of pure PPC and PPC/MCC composites

It can be seen from Table 4 that with the increase of MCC content, the tensile strength of the composite material first increases and then decreases, and they are all greater than pure PPC. Among them, the tensile strength of the composite material added with 15% MCC increased the most, from 5.11MPa to 7.12MPa, an increase of 39.33%. This is due to the fact that MCC can effectively bear loads and stresses in the PPC resin matrix.

Example 5

The number-average molecular weight of the PPC used is 9.17×10 ⁴ , and the dried PPC, maleic anhydride (MA), phthalic anhydride (PA), and pyromellitic dianhydride (PMDA) are respectively mixed in a mass ratio of 100:1 Mix separately to form a premix of 3 samples, and then put them into a twin-screw extruder to prepare three different types of anhydride-terminated PPC. The screw speed is 80r/min, and the die temperature of the extruder is 120 ° C. The product PPC-MA1, PPC-PA1, PPC-PMDA1 were labeled respectively.

At the same time, a pure PPC sample without acid anhydride was prepared as a blank control, which was labeled as pure PPC.

Take four parts of the same amount of extrusion test samples and dry them in vacuum at 60°C for 24 hours, put the dried extruded samples into the internal mixer, and mix them at a certain speed for 3 minutes at 160°C until the samples are fully melted, then Add MCC powder, mix 10min, the mass ratio of each sample and MCC is 85:15, form 4 parts of composite materials (respectively marked as PPC/MCC-15, PPC-MA1/MCC-15, PPC-PA1/MCC-15, PPC-PA1/MCC-15, PPC-PMDA1/MCC-15). MCC was dried before the experiment, and the powder was filtered through a 200-mesh sieve.

The resulting 4 composite materials were pressed into tablets by a flat vulcanizer, and the mechanical properties were tested according to the standard sample preparation of IOS527-2 and IOS179-1982. The results are shown in Table 5.

Table 5 Mechanical properties of PPC/MCC and three anhydride-terminated PPC/MCC composites

It can be seen from Table 5 that compared with the tensile strength of PPC/MCC, the tensile strength of PPC-MA1/MCC-15, PPC-PA1/MCC-15, and PPC-PMDA1/MCC-15 has different degrees of improvement. Among them, PPC-PMDA1/MCC-1 is the largest, and it is 34.5% higher than that of PPC-PMDA1.

Example 6

The number-average molecular weight of the PPC used is 9.17×10 ⁴ , and the dry PPC and maleic anhydride (MA), phthalic anhydride (PA), and pyromellitic dianhydride (PMDA) are respectively mixed in a mass ratio of 100:1. Mix to form a premix of 3 samples, and then put them into a twin-screw extruder to prepare three different types of anhydride-terminated PPC. The screw speed is 80r/min, and the die temperature of the extruder is 120°C. The products are respectively Label PPC-MA1, PPC-PA1, PPC-PMDA1.

At the same time, a pure PPC sample without acid anhydride was prepared as a blank control, which was labeled as pure PPC.

Take four parts of the same amount of extrusion test samples and dry them in vacuum at 60°C for 24 hours, put the dried extruded samples into the internal mixer, and mix them at a certain speed for 3 minutes at 160°C until the samples are fully melted, then Add MCC powder, mix 10min, the weight ratio of each sample and MCC is 85:15, form 4 parts of composite materials (respectively marked as PPC/MCC-15, PPC-MA1/MCC-15, PPC-PA1/MCC-15, PPC-PA1/MCC-15, PPC-PMDA1/MCC-15). MCC was dried before the experiment, and the powder was filtered through a 200-mesh sieve.

Take the same amount of samples for the 4 composite materials, and use a thermogravimetric analyzer for TG analysis in a nitrogen environment at a heating rate of 10°C/min during the whole process, and its T _-5% , T _-50% , and T _-95% (That is, the temperatures corresponding to the total mass reduction of 5%, 50%, and 95%) are shown in Table 6.

Table 6PPC/MCC and three kinds of anhydride-terminated PPC/MCC composite thermal decomposition temperature values

It can be seen from Table 6 that when pure PPC is added with 15wt% MCC, the T _-5% of the material increases from 210.5°C to 239.6°C, an increase of 29.1°C.

Comparing Table 2 and Table 6, it can be seen that after adding MCC to the anhydride-terminated PPC system, the thermal stability of the composite material has also been greatly improved. For example, after adding MCC to the PPC-PMDA1 system, the composite material T- _{5 %} increased from 236.8°C to 257.3°C, an increase of 20.5°C. This is because there are many hydroxyl groups on the surface of MCC, which can strengthen the interaction with PPC molecular chains and inhibit the thermal degradation of PPC. Compared with the thermal decomposition temperature of PPC/MCC composites, the T _-5% of the three anhydride-terminated PPC/MCC composites has different degrees of improvement. This is because the addition of acid anhydride strengthens the interaction between PPC and MCC in the composite material. After heating, the acid anhydride can undergo esterification reaction with the hydroxyl groups of PPC and MCC, which makes MCC chemically bond with the PPC matrix and improves the thermal stability of PPC. .

From above-mentioned example 2 to example 6 as can be known, when end-capping agent anhydride is PMDA, when the mass ratio of PPC, PMDA and microcrystalline cellulose is 85:15:1, promptly the mechanical property of PPC-PMDA1/MCC-15 composite material and The thermal stability is the best. It can be seen that the above-mentioned modification method of polymethylethylene carbonate has simple process, low cost, can be completely degraded, and has good mechanical properties and high thermal stability, which greatly broadens the application of carbon dioxide-based compounds.

As mentioned above, the present invention can be better realized. The above-mentioned embodiment is only a preferred embodiment of the present invention, and is not used to limit the scope of the present invention; Covered by the scope of protection required by the claims of the present invention.

Claims (9)

1. The method for preparing the fully-degradable composite material by using the acid anhydride and the microcrystalline cellulose to synergistically modify the polymethyl ethylene carbonate is characterized in that degradable polymethyl ethylene carbonate, acid anhydride and microcrystalline cellulose are melted and mixed to form master batch of the fully-degradable composite material, and then the master batch is molded into a sample by compression;

wherein the mass ratio of the polymethyl ethylene carbonate, the acid anhydride and the microcrystalline cellulose is as follows:

polymethyl ethylene carbonate: 50 to 95 parts of a water-soluble polymer,

microcrystalline cellulose: 5 to 50 parts of (A) a water-soluble polymer,

acid anhydride: 0.1-10 parts.

2. The method for preparing the fully-degradable composite material by using the anhydride and the microcrystalline cellulose for synergistically modifying the polymethyl ethylene carbonate as the claim 1, wherein the polymethyl ethylene carbonate is used as a matrix of the fully-degradable composite material, the anhydride is used as an end-capping agent and a compatibilizer, and the microcrystalline cellulose is used as a filling material.

3. The method for preparing the fully degradable composite material by using the anhydride and the microcrystalline cellulose for synergistic modification of the polymethyl ethylene carbonate according to claim 1, wherein the number average molecular weight of the polymethyl ethylene carbonate is 10000-100000.

4. The method for preparing fully degradable composite material by using the anhydride and microcrystalline cellulose to synergistically modify the polymethyl ethylene carbonate according to claim 1, wherein the anhydride is one or more of acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, tetrahydrophthalic anhydride, itaconic anhydride, pyromellitic dianhydride or mellitic anhydride.

5. The method for preparing the fully-degradable composite material by using the anhydride and the microcrystalline cellulose to synergistically modify the polymethyl ethylene carbonate, which is characterized in that the microcrystalline cellulose is prepared by acidolysis of natural plant fibers.

6. The method for preparing the fully degradable composite material by the anhydride and microcrystalline cellulose synergistic modification of the polymethyl ethylene carbonate according to claim 1, wherein the grain size of the microcrystalline cellulose is 20-100 μm.

7. The method for preparing the fully degradable composite material by the acid anhydride and microcrystalline cellulose synergistic modification of the polymethyl ethylene carbonate according to claim 1, wherein the specific process of melt mixing the polymethyl ethylene carbonate, the acid anhydride and the microcrystalline cellulose is as follows:

(1) weighing polymethyl ethylene carbonate, anhydride and microcrystalline cellulose according to weight percentage, drying for 12-36 h at 40-80 ℃, and then mechanically mixing to form premix;

(2) and putting the premix into mixing equipment for melt mixing to obtain the master batch of the fully-degradable composite material.

8. The method for preparing the fully-degradable composite material from the anhydride and the microcrystalline cellulose synergistically modified polymethyl ethylene carbonate according to claim 7, wherein the equipment for mechanical mixing is a high-speed mixer, and the time for mechanical mixing is 0.5-3 min.

9. The method for preparing the fully-degradable composite material from the anhydride and the microcrystalline cellulose synergistically modified polymethyl ethylene carbonate, according to claim 7, wherein the mixing equipment is a single screw extruder, a double screw extruder, an internal mixer or an open mill, the melt mixing temperature in the mixing equipment is 110-150 ℃, the die head temperature in the mixing equipment is 110-170 ℃, the rotation speed of the mixing equipment is 10-200 r/min, and the mixing time in the mixing equipment is 3-10 min.