1. A hyperbranched polyester modified polylactic acid/polypropylene carbonate composite material is prepared from a degradable plastic compound, hyperbranched polyester, a catalyst and a chain extender through melt extrusion.

2. The degradable plastic composite of claim 1, comprising the following raw material components in parts by weight: polylactic acid (PLA): 60-80 Parts of Polypropylene Carbonate (PPC) and 5-25 parts of PPC.

3. The hyperbranched polyester modified polylactic acid/polypropylene carbonate composite material as claimed in claim 1, wherein: one of Boltorn H20 and Boltorn H30, having the structural formula I and II:

4. hyperbranched polyester according to claim 3, used in an amount of 1 to 4 parts, preferably 2 to 4 parts.

5. The hyperbranched polyester modified polylactic acid/polypropylene carbonate composite material as claimed in claim 1, wherein: the catalyst is stannous octoate (Sn (Oct)₂) Tetrabutyl titanate (TBT).

6. The catalyst according to claim 5, which is used in an amount of 0.1 to 0.5 parts, preferably 0.3 to 0.5 parts.

7. The hyperbranched polyester modified polylactic acid/polypropylene carbonate composite material as claimed in claim 1, wherein: maleic Anhydride (MA), Diglycidyl Terephthalate (DTG), 2- (1, 3-phenylene) -bisoxazoline (1,3-PBO), and diphenylmethane diisocyanate (MDI).

8. The chain extender of claim 7, used in an amount of 0.4 to 0.8 parts, preferably 0.5 to 0.8 parts.

9. The preparation method of the hyperbranched polyester modified polylactic acid/polypropylene carbonate composite material according to claim 1, which is characterized in that: the method comprises the following steps: uniformly mixing PLA, PPC, hyperbranched polyester, a catalyst and a chain extender in a mass ratio, adding the mixture into a double-screw extruder, and extruding to obtain the PLA/PPC composite material.

10. The preparation method of the hyperbranched polyester modified polylactic acid/polypropylene carbonate composite material according to claim 9, wherein the preparation method comprises the following steps: the processing temperature of the double-screw extruder is 180-200 ℃, and the screw rotating speed is 300-500 rpm.

Background

Polylactic acid (PLA) is a straight-chain polyester polymerized from lactic acid, is a completely degradable material, and has great application prospect in the fields of biological medicine, tissue engineering, packaging materials and the like. However, PLA has the problems of high rigidity, lack of flexibility and poor processability, and modification is often required in the molding process. PBS, PBAT are commonly used PLA processing modifying components. For example, PBS/PLA composites and PBAT/PLA composites have been studied in Chinese patent application having application number CN 202010850461.3.

The polypropylene carbonate (PPC) is a white or transparent aliphatic polyester and is polymerized by taking propylene oxide and carbon dioxide as raw materials. The PPC does not consume petroleum resources in the synthetic process, and can also react with CO₂Plays a role in fixation and conforms to the current concept of green development. PPC has excellent biocompatibility and biodegradability, and simultaneously has high transparency, high elongation at break and excellent gas barrier property, so that PPC has great application prospect in the fields of biological medicine, tissue engineering, packaging materials and the like. In recent years, polypropylene carbonate (PPC) has been used as a novel degradable plastic material as PLA because of its good toughnessAnd (3) a modifying component. PLA/PPC composites are studied, for example, in chinese patent application No. cn200910258725. x.

By adding PPC into PLA, the toughening of PLA can be realized, and the defects of hard and brittle PLA and poor processability can be improved. However, in the practical application process, the thermal stability of the PPC is poor, the processing temperature is usually higher than 150 ℃, an obvious degradation phenomenon can occur, and meanwhile, the compatibility of the PLA and the PPC is poor, so that the mechanical property of the composite material is poor. In order to solve the problems, the invention modifies the PLA/PPC composite material through the hyperbranched polyester, on one hand, the characteristic of high-temperature molecular chain breakage of the PPC is utilized to realize the ester exchange reaction between the PLA and the PPC molecular chain, on the other hand, the hyperbranched polyester has a plurality of ester groups, has higher activity and can play a role in micro-crosslinking, thereby preparing the PLA/PPC composite material with excellent performance.

Disclosure of Invention

The invention aims to prepare a modified PLA/PPC composite material with excellent heat-resisting temperature and good mechanical property, and the modified PLA/PPC composite material with excellent heat-resisting temperature and mechanical property is prepared by introducing hyperbranched polyester into PLA/PPC, and the aim of the invention is realized by the following technical scheme:

one purpose of the invention is to provide a modified PLA/PPC composite material, which comprises the following raw material components in parts by weight: 60-80 parts of PLA, 5-25 parts of PPC, and a hyperbranched polyester: 1-4 parts, 0.2-0.5 part of catalyst, chain extender: 0.4 to 0.8 portion.

Preferably, the PLA has a melt index of 5 to 10g/10min (2.16kg, 190 ℃) and a density of 1.24g/cm³

Preferably, the PPC has a melt index of 3-20g/10min (2.16kg, 190 ℃ C.), and a density of 1.27g/cm³。

Preferably, the hyperbranched polyester is one of Boltorn H20 and Boltorn H30. The structural formulas are respectively shown as the following formulas I and II:

preferably, saidThe catalyst is stannous octoate (Sn (Oct)₂) Tetrabutyl titanate (TBT).

The chain extender is one of Maleic Anhydride (MA), Diglycidyl Terephthalate (DTG), 2- (1, 3-phenylene) -bisoxazoline (1,3-PBO) and diphenylmethane diisocyanate (MDI).

The invention also aims to provide a preparation method of the modified PLA/PPC composite material, which comprises the following steps:

uniformly mixing PLA, PPC, hyperbranched polyester and a chain extender in a mass ratio, and performing melt blending granulation by a double-screw extruder to obtain modified PLA/PPC modified particles.

Preferably, the mass ratio of PLA/PPC is 60-80: 5-25.

The amount of the hyperbranched polyester is 1-4 parts, preferably 2-4 parts.

The catalyst is used in an amount of 0.1 to 0.5 part, preferably 0.3 to 0.5 part.

The amount of the chain extender is 0.4-0.8 part, preferably 0.5-0.8 part.

Preferably, the processing temperature of the double-screw extruder is 180-200 ℃.

Preferably, the screw speed of the twin-screw extruder is 300-500 rpm.

Adding the prepared PLA/PPC modified plastic particles into an injection molding machine, preparing a sample according to GB/T1040.1-2018, and testing the mechanical property.

Preferably, the injection molding machine temperature is 190 ℃ to 200 ℃.

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

the principle of the invention is as follows: ester bonds in PPC and PLA are broken in the thermal processing process to generate ester exchange reaction, and after the hyperbranched polyester is added, the hyperbranched polyester has a highly branched chain structure, so that the branched chain can generate ester exchange reaction with the PPC and the PLA. Forming a novel hyperbranched polyester with PLA and PPC chain structures on branched chains. Therefore, the problem of compatibility between PLA and PPC is solved, the heat stability of PPC is improved by introducing a PLA chain segment into PPC, and the flexibility of PLA is improved by introducing the PPC chain segment into PLA. The hyperbranched polyester and the chain extender are added, so that the problem of molecular weight reduction caused by ester exchange reaction of pure PLA and PPC is solved, and the effect of continuing chain extension on the original hyperbranched structure can be achieved.

Compared with the prior art, the invention has the following beneficial effects: the modified PLA/PPC composite material has good thermal stability and compatibility, and the mechanical property and the toughness are obviously improved.

Detailed Description

The examples of the present invention, in which the specific conditions are not specified, were conducted under the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available. The raw materials used in the examples are all commercially available.

Example 1

60 parts of PLA,5 parts of PPC, 1 part of hyperbranched polyester I, 0.1 part of stannous octoate and 0.4 part of maleic anhydride are uniformly mixed and then melted, blended and granulated by a double-screw extruder. The nine zones of the double screw extruder are respectively at 180 ℃, 185 ℃, 190 ℃, 200 ℃ and 200 ℃. The twin-screw extruder speed was 350 rpm. Adding the granules into an injection molding machine, preparing samples according to the national standard GB/T1040.1-2018, and testing the mechanical property. The temperature of the injection molding machine is 190 ℃, 200 ℃ and 190 ℃. Specific results are shown in table 1.

Example 2

70 parts of PLA,15 parts of PPC, 2 parts of hyperbranched polyester II, 0.2 part of tetrabutyl titanate and 0.5 part of terephthalic acid and glycidyl ester are uniformly mixed and then are melted, blended and granulated by a double-screw extruder. The nine zones of the double screw extruder are respectively at 180 ℃, 185 ℃, 190 ℃, 200 ℃ and 200 ℃. The twin-screw extruder speed was 350 rpm. Adding the granules into an injection molding machine, preparing samples according to the national standard GB/T1040.1-2018, and testing the mechanical property. The temperature of the injection molding machine is 190 ℃, 200 ℃ and 190 ℃. Specific results are shown in table 1.

Example 3

80 parts of PLA,25 parts of PPC, 3 parts of hyperbranched polyester I, 0.3 part of stannous octoate and 0.5 part of 2,2- (1, 3-phenylene) -bisoxazoline are uniformly mixed and then are melted, blended and granulated by a double-screw extruder. The nine zones of the double screw extruder are respectively at 180 ℃, 185 ℃, 190 ℃, 200 ℃ and 200 ℃. The twin-screw extruder speed was 350 rpm. Adding the granules into an injection molding machine, preparing samples according to the national standard GB/T1040.1-2018, and testing the mechanical property. The temperature of the injection molding machine is 190 ℃, 200 ℃ and 190 ℃. Specific results are shown in table 1.

Example 4

80 parts of PLA,25 parts of PPC, 4 parts of hyperbranched polyester II, 0.5 part of tetrabutyl titanate and 0.8 part of diphenylmethane diisocyanate are uniformly mixed and then are subjected to melt blending granulation by a double-screw extruder. The nine zones of the double screw extruder are respectively at 180 ℃, 185 ℃, 190 ℃, 200 ℃ and 200 ℃. The twin-screw extruder speed was 350 rpm. Adding the granules into an injection molding machine, preparing samples according to the national standard GB/T1040.1-2018, and testing the mechanical property. The temperature of the injection molding machine is 190 ℃, 200 ℃ and 190 ℃. Specific results are shown in table 1.

Comparative example 1

80 parts of PLA and 25 parts of PPC are uniformly mixed and then melted, blended and granulated by a double-screw extruder. The nine zones of the double screw extruder are respectively at 180 ℃, 185 ℃, 190 ℃, 200 ℃ and 200 ℃. The twin-screw extruder speed was 350 rpm. Adding the granules into an injection molding machine, preparing samples according to the national standard GB/T1040.1-2018, and testing the mechanical property. The temperature of the injection molding machine is 190 ℃, 200 ℃ and 190 ℃. Specific results are shown in table 1.

TABLE 1 mechanical and thermal Properties of PLA/PPC composites in different examples

As can be seen from the data in Table 1, the comparative examples 1-4 and the comparative example 1 show that the hyperbranched polyester modified PLA/PPC composite material has higher heat resistance temperature and more excellent mechanical properties.

It is to be understood that the above examples are illustrative only for the purpose of clarity of description and are not limiting of the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.