Branched polylactic acid as well as preparation method and application thereof

Abstract

The invention provides branched polylactic acid as well as a preparation method and application thereof. The branched polylactic acid is prepared from the following raw materials: lactide and an initiator, the initiator comprises a first initiator, and the molecular structure of the first initiator contains a hydroxyl group and an epoxy group. The branched polylactic acid adopts a compound containing hydroxyl and epoxy as an initiator, so that the branched polylactic acid has the advantages of high melt strength, good flowability, easiness in processing, low cost and simple preparation method.

Description

Technical Field

[0001] The invention belongs to the technical field of degradable materials, and specifically relates to a branched polylactic acid and a preparation method and application thereof. Background Art

[0002] Polylactic acid is a widely used biodegradable polymer. Since it is derived from renewable resources and has good biocompatibility and biodegradability, it has shown broad application prospects in packaging, textiles, biomedicine and other fields. Although polylactic acid has many advantages, traditional polylactic acid materials usually show low melt strength, which limits its application in some fields with high performance requirements.

[0003] Patent CN102675577A discloses a long-chain branched polylactic acid resin, which uses diisocyanate as a coupling agent to connect multi-arm polylactic acid through coupling segments. However, the addition of diisocyanate increases the processing cost of the material and reduces the degradation performance of the polylactic acid material.

[0004] Another example is CN113265029A, which discloses a long-chain branched polylactic acid, which uses an organic peroxide and a branching regulator having both a carbon-carbon double bond, an epoxy group, and an isocyanate group, wherein one functional group reacts with the middle position of the polylactic acid molecular chain, and one functional group reacts with the head of the polylactic acid molecular chain, but the addition of the branching regulator and the post-processing method of the peroxide increases the processing cost of the material. Patent CN106317338A discloses a method for preparing long-chain branched polylactic acid, wherein linear polylactic acid is blended with castor oil, and then subjected to radiation polymerization under radiation. This method has high operating costs and a high radiation risk.

[0005] Therefore, developing a branched polylactic acid with high melt strength, good fluidity, easy processing, low cost and simple preparation method is an urgent problem to be solved in the art. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a branched polylactic acid and a preparation method and application thereof. The branched polylactic acid has high melt strength, low cost and simple preparation process.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a branched polylactic acid, wherein the raw materials of the branched polylactic acid include lactide and an initiator; the initiator includes a first initiator, and the molecular structure of the first initiator contains a hydroxyl group and an epoxy group.

[0009] In the present invention, a compound containing a hydroxyl group and an epoxy group is used as an initiator to obtain highly branched polylactic acid, which is beneficial to improving the melt strength of the polylactic acid and can ensure that the polylactic acid has good fluidity, good processing performance and low material cost.

[0010] Preferably, based on 100 parts by mass of lactide, the added mass of the initiator is 0.01 to 1.3 parts, for example, it can be 0.01 part, 0.02 part, 0.03 part, 0.04 part, 0.05 part, 0.06 part, 0.07 part, 0.08 part, 0.09 part, 0.1 part, 0.15 part, 0.2 part, 0.25 part, 0.3 part, 0.35 part, 0.4 part, 0.45 part, 0.5 part, 0.55 part, 0.6 part, 0.65 part, 0.7 part, 0.75 part, 0.8 part, 0.85 part, 0.9 part, 0.95 part, 1 part, 1.1 parts, 1.3 parts or the range between any values ​​of the above numbers; preferably 0.1 to 1 part, more preferably 0.2 to 0.8 parts.

[0011] In the present invention, if the initiator content is too much, the fluidity of the polylactic acid is poor, which is not conducive to processing; if the initiator content is too little, the melt strength of the polylactic acid is low.

[0012] Preferably, the first initiator comprises 4-(oxirane-2-methoxy)-1-butanol and / or glycidol.

[0013] Preferably, the initiator further comprises a second initiator, and the molecular structure of the second initiator contains a hydroxyl group.

[0014] Preferably, the number of hydroxyl groups in the second initiator is ≥1, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, etc.; more preferably, the number of hydroxyl groups is >2.

[0015] Preferably, the second initiator comprises at least one of ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, trimethylolpropane, glycerol, 1,2,4-butanetriol, pentaerythritol, mannitol, erythritol, dipentaerythritol, arabinol, sorbitol, isosorbide, fructose alcohol, polytetrahydrofuran diol, polyoxypropylene glycol, polyvinyl alcohol, cellulose, cellulose acetate, cellulose butyrate or cellulose acetate butyrate.

[0016] Preferably, the initiator includes a first initiator and a second initiator, and the mass ratio of the first initiator to the second initiator is (0.01-10):1, wherein the specific value in (0.01-10) can be, for example, 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.2, 0.4, 0.6, 0.8, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or the range between any of the above values; preferably (1-8):1.

[0017] In the present invention, the second initiator is compounded with the first initiator in a specific content, so that the polylactic acid can have both high melt strength and good fluidity.

[0018] Preferably, the lactide includes at least one of levorotatory lactide, dextrorotatory lactide or meso-lactide.

[0019] Preferably, according to the test standard of GB / T 3682-2018, at 190°C and 2.16kg, the melt index of the branched polylactic acid is ≥0.1g / 10min, for example, it can be 0.1g / 10min, 0.2g / 10min, 0.4g / 10min, 0.6g / 10min, 0.8g / 10min, 1g / 10min, 1.2g / 10min, 1.4g / 10min, 1.6g / 10min, 1.8g / 10min, 2g / 10min, 2.1g / 10min, 2.2g / 10min, 2.4g / 10min, 2.6g / 10min, 2.8g / 10min, 3g / 10min or a range between any of the above values; more preferably, the melt index is ≥1g / 10min.

[0020] Preferably, the maximum pulling speed of the branched polylactic acid is ≥350 mm / s.

[0021] Preferably, the tensile strength at break of the branched polylactic acid is ≥40 mN.

[0022] In a second aspect, the present invention provides a method for preparing the branched polylactic acid according to the first aspect, the preparation method comprising the following steps:

[0023] Lactide and an initiator are mixed and reacted to obtain the branched polylactic acid.

[0024] In the present invention, the initiator includes a compound containing a hydroxyl group and an epoxy group, which initiates the ring-opening polymerization of lactide, can simplify the preparation process of branched polylactic acid, and can obtain highly branched polylactic acid in one step, avoiding the use of a chain extender for secondary processing, thereby reducing production costs.

[0025] Preferably, the reaction is carried out in the presence of a catalyst.

[0026] In the present invention, the catalyst includes at least one of ferric chloride, chromium chloride, chromium acetate, sodium alcoholate, potassium alcoholate, stannous octoate, stannous chloride, hydrogen chloride or hydrogen bromide.

[0027] Preferably, the molar ratio of the catalyst to lactide is 1:(100-1000000); wherein the specific value in (100-1000000) can be, for example, 100, 200, 400, 600, 800, 1000, 5000, 10000, 50000, 100000, 500000, 1000000 or a range between any of the above values.

[0028] Preferably, the reaction is carried out in the presence of an inert atmosphere.

[0029] In the present invention, the inert atmosphere includes but is not limited to nitrogen.

[0030] Preferably, the reaction temperature is 160-200°C, for example, 160°C, 170°C, 180°C, 190°C, 200°C or any range between the above values; the reaction time is 4-18h, for example, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h or any range between the above values.

[0031] In the present invention, the reaction further includes a post-treatment step; the post-treatment includes treating for 20 to 40 minutes (for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes or a range between the above values) under the conditions of a pressure of 0 to 260 Pa (for example, 0 Pa, 10 Pa, 20 Pa, 40 Pa, 60 Pa, 80 Pa, 100 Pa, 120 Pa, 150 Pa, 180 Pa, 200 Pa, 220 Pa, 250 Pa, 260 Pa or a range between the above values), and a temperature of 200 to 220° C. (for example, 201° C., 202° C., 205° C., 208° C., 210° C., 212° C., 214° C., 216° C., 218° C., 220° C. or a range between the above values).

[0032] In the present invention, the post-treatment step is convenient for removing unreacted monomers or other volatile components.

[0033] In a third aspect, the present invention provides a 3D printed product, wherein the material of the 3D printed product includes the branched polylactic acid according to the first aspect.

[0034] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The branched polylactic acid provided by the present invention adopts a compound containing a hydroxyl group and an epoxy group as an initiator, which can ensure that the branched polylactic acid has good processing fluidity and improve its melt strength, and has low material cost and simple preparation process. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] The materials used in the present invention can be purchased from the market or prepared by conventional methods.

[0039] In Tables 1 to 3 of the present invention, the materials used are all commercially available, wherein the lactide is L-lactide.

[0040] Examples 1 to 13, Comparative Examples 1 to 3

[0041] Examples 1 to 13 and Comparative Examples 1 to 3 respectively provide a branched polylactic acid, and the raw material types and contents of the branched polylactic acid are shown in Tables 1 to 3 in parts by weight, wherein “ / ” indicates that the component is not present in the raw material.

[0042] The preparation method of the branched polylactic acid comprises: uniformly mixing lactide with an initiator and a catalyst (stannous octoate, with a molar ratio of 1:500 to lactide) to obtain a mixed material; adding the mixed material to a vacuum reactor, repeatedly evacuating and filling with nitrogen for 5 times, raising the temperature of the reactor to 180°C, adjusting the stirring speed to 20rpm, reacting for 6h, and then treating at a pressure of 203Pa and a temperature of 213°C for 32min to obtain the branched polylactic acid.

[0043] Table 1

[0044]

[0045] Table 2

[0046]

[0047] Table 3

[0048]

[0049] Performance Testing

[0050] The branched polylactic acid provided in Examples 1 to 13 and Comparative Examples 1 to 3 was extruded, stretched, granulated and dried at 190° C. to obtain samples; and then the following performance tests were performed.

[0051] (1) Melt index: The samples were tested at 190°C and 2.16 kg using the GB / T 3682-2018 test standard. The larger the melt index, the better the fluidity.

[0052] (2) Melt strength: The maximum tensile speed and maximum tensile force at break of the sample were tested using the RHROTENS system of Goettfert Company of Germany. The screw extrusion temperature was set to 210°C, the extrusion rate was 10 mm / s, and the extrusion die diameter was 1.5 mm. The maximum tensile speed and maximum tensile force at break were used to characterize the melt strength. The greater the maximum tensile speed and the maximum tensile force at break, the higher the melt strength. The maximum tensile speed was the tensile test at the maximum tensile force at break. The tensile speed was adjusted and the maximum tensile speed at break was recorded.

[0053] The specific test results are shown in Table 4.

[0054] Table 4

[0055] Melt index / g / 10min Maximum stretching speed / mm / s Maximum tensile force at break / mN Example 1 1.72 355 45 Example 2 1.65 442 51 Example 3 1.5 621 60 Example 4 1.21 561 60 Example 5 1.15 375 42 Example 6 1.77 630 62 Example 7 1.71 579 58 Example 8 1.72 531 55 Example 9 1.66 490 51 Example 10 1.67 445 46 Embodiment 11 1.70 437 45 Example 12 1.69 432 48 Embodiment 13 1.81 401 47 Comparative Example 1 1.77 345 39 Comparative Example 2 2.11 286 37 Comparative Example 3 1.72 365 40

[0056] As can be seen from Table 4, the branched polylactic acid provided by the present invention adopts a compound containing hydroxyl and epoxy groups as an initiator, which can not only ensure that the branched polylactic acid has good processing fluidity, but also improve its melt strength, and has low material cost and simple preparation process; the melt index of the branched polylactic acid is ≥1.0g / 10min, the maximum tensile speed is ≥355mm / s, and the maximum tensile force at break is ≥42mN.

[0057] It can be seen from the comparison between Example 2 and Examples 12 and 13 that the first initiator and the second initiator are compounded to ensure that the branched polylactic acid has a higher melt strength while ensuring that the branched polylactic acid has a considerable fluidity.

[0058] By comparing Examples 12 and 13 with Comparative Examples 1 and 2, it can be seen that the present invention uses compounds containing hydroxyl and epoxy groups as initiators. Compared with using only polyols as initiators, it can ensure that polylactic acid has considerable fluidity while also improving the melt strength of polylactic acid, which is beneficial to the stability of the material under high-speed processing.

[0059] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A branched polylactic acid, characterized in that: The raw materials of the branched polylactic acid include lactide and an initiator; The initiator comprises a first initiator, and the molecular structure of the first initiator contains a hydroxyl group and an epoxy group.

2. The branched polylactic acid according to claim 1, characterized in that Based on 100 parts of lactide, the added amount of the initiator is 0.01 to 1.3 parts, preferably 0.1 to 1 part.

3. The branched polylactic acid according to claim 1 or 2, characterized in that The first initiator includes 4-(oxirane-2-methoxy)-1-butanol and / or glycidol.

4. The branched polylactic acid according to any one of claims 1 to 3, characterized in that: The initiator further comprises a second initiator, wherein the molecular structure of the second initiator contains a hydroxyl group; Preferably, the number of hydroxyl groups of the second initiator is ≥1, more preferably the number of hydroxyl groups is >2; Preferably, the second initiator comprises at least one of ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, trimethylolpropane, glycerol, 1,2,4-butanetriol, pentaerythritol, mannitol, erythritol, dipentaerythritol, arabinol, sorbitol, isosorbide, fructose alcohol, polytetrahydrofuran diol, polyoxypropylene glycol, polyvinyl alcohol, cellulose, cellulose acetate, cellulose butyrate or cellulose acetate butyrate.

5. The branched polylactic acid according to claim 4, characterized in that The initiator comprises a first initiator and a second initiator, wherein the mass ratio of the first initiator to the second initiator is (0.01-10):1, preferably (1-8):1; Preferably, the lactide includes at least one of levorotatory lactide, dextrorotatory lactide or meso-lactide.

6. The branched polylactic acid according to any one of claims 1 to 5, characterized in that: According to the GB / T3682-2018 test standard, at 190°C and 2.16kg, the melt index of the branched polylactic acid is ≥0.1g / 10min, preferably ≥1g / 10min.

7. The branched polylactic acid according to any one of claims 1 to 6, characterized in that: The maximum pulling speed of the branched polylactic acid is ≥350 mm / s; Preferably, the tensile strength at break of the branched polylactic acid is ≥40 mN.

8. A method for preparing branched polylactic acid according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: Lactide is mixed with an initiator and reacted to obtain the branched polylactic acid.

9. The preparation method according to claim 8, characterized in that: The reaction is carried out in the presence of a catalyst; Preferably, the molar ratio of the catalyst to lactide is 1:(100-1000000); Preferably, the reaction is carried out in the presence of an inert atmosphere; Preferably, the reaction temperature is 160-200° C., and the reaction time is 4-18 hours.

10. A 3D printed product, characterized in that: The material of the 3D printed product includes the branched polylactic acid according to any one of claims 1 to 7.

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