A compound multifunctional additive and its application in the preparation of polylactic acid sheets

Abstract

The present invention discloses a compounded multifunctional additive and its application in the preparation of polylactic acid sheets, relating to the technical field of polylactic acid modification. The compounded multifunctional additive exhibits good interfacial compatibility with polylactic acid and can simultaneously improve the thermal, mechanical, and flame retardant properties of polylactic acid. Furthermore, the addition of talc to the compounded additive offers a significant price advantage, making it widely applicable in the field of polylactic acid modification.

Description

Technical Field

[0001] The invention relates to a compound multifunctional auxiliary agent and application thereof in the preparation of polylactic acid sheets, belonging to the technical field of polymer materials. Background Art

[0002] With the increasing depletion of oil resources and growing environmental awareness, the research and development of environmentally friendly bio-based polymer materials has attracted widespread attention. Polylactic acid (PLA), a biodegradable polymer, has shown broad application prospects in the field of disposable lunch boxes due to its excellent biocompatibility and degradability.

[0003] However, polylactic acid (PLA) inherently suffers from poor crystallization, low toughness, and poor heat resistance, limiting its application in disposable lunch boxes. To overcome these drawbacks, melt blending PLA with nucleating agents or toughening agents is commonly used to improve its crystallization, toughness, and heat distortion temperature. For example, patent CN111333910A discloses a rare earth aryl phosphate polylactic acid nucleating agent that significantly enhances the heat resistance of PLA; patent CN119371789A discloses a method for preparing a talc-wollastonite masterbatch for improving the mechanical properties of PLA. However, a single additive often fails to simultaneously meet the comprehensive requirements of PLA in terms of crystallization, mechanical, thermal, and flame retardancy. Furthermore, compatibility issues between the additive and the PLA matrix can also affect its effectiveness, resulting in limited performance improvements. Furthermore, commercially available PLA functionalization additives are expensive, compounded by the relatively high price of PLA itself. Therefore, price is a significant limiting factor in the processing and modification of PLA.

[0004] Therefore, developing a compound multifunctional additive with price advantage can not only provide a strong guarantee for the high performance of polylactic acid, but also play a beneficial role in reducing costs and increasing efficiency in the polylactic acid processing industry. Summary of the Invention

[0005] The present invention provides a compound multifunctional additive and its application in the preparation of polylactic acid sheets. The compound multifunctional additive has a stable chemical structure during processing, and the organic sulfonate segment in its molecular chain can play an excellent nucleating role, promote the refinement of polylactic acid spherulites, thereby significantly improving the heat deformation temperature. At the same time, the compound multifunctional additive improves the toughness of polylactic acid by increasing its crystallinity. In addition, the long carbon chain component in the molecular chain can improve its interfacial compatibility with polylactic acid, and the nitrogen, sulfur and rich carbon elements contained in the compound multifunctional additive can play a synergistic flame retardant and accelerate combustion into carbon, thereby improving the flame retardant properties of polylactic acid. Most importantly, the effect of the additive is improved after compounding, but the production cost is greatly reduced.

[0006] The present invention provides a composite multifunctional additive characterized by being obtained by the following preparation method: dispersing 26.8 g of 5-sodium sulfoisophthalate in 150 mL of acetone, adding 56.2 g of oleamide and 5 mL of hydrochloric acid, and stirring the mixture at 50°C and 800 rpm for 12 hours. After the reaction, the mixture is filtered, washed with acetone until neutral, and then oven-dried at 60°C to constant weight. The dried white flaky solid and talc are mixed in a high-speed mixer at a weight ratio of 1:1 at 3000 rpm for 3 minutes to obtain the composite multifunctional additive.

[0007] The various reaction conditions and parameters in the preparation method of the composite multifunctional additive described in the present invention are all optimal conditions verified by experiments.

[0008] The present invention also provides an application of a compounded multifunctional auxiliary agent in the preparation of polylactic acid sheets, characterized in that the dosage of the compounded multifunctional auxiliary agent is 1%-5% of the polylactic acid.

[0009] Preferably, the amount of the processing aid is 3% of the polylactic acid.

[0010] The processing aid synthesized in the present invention must be added in an appropriate amount. Too little addition will not achieve the desired effect, while too much addition will reach the upper limit of performance improvement, resulting in waste of the compound multifunctional additive. The above addition amount is the optimal condition verified by experiments.

[0011] Compared with the prior art, the present invention has the following technical effects.

[0012] 1. The organic sulfonate segments in the compounded multifunctional additive act as excellent nucleators during the polylactic acid crystallization process, promoting the refinement of polylactic acid spherulites and a denser crystal structure. Furthermore, the rigid talc particles hinder the movement of polylactic acid molecular chains. Together, these two effects significantly increase its heat deformation temperature (HDT). This effect ensures the thermal performance of polylactic acid sheets for use in disposable lunch boxes.

[0013] 2. The combined effect of compound multifunctional additives and talc can significantly increase the crystallinity of polylactic acid, thereby significantly improving the toughness of polylactic acid, making it better suitable for the application of polylactic acid sheets in the field of disposable lunch boxes.

[0014] 3. The long carbon chain component of the compound multifunctional additive can greatly improve its interfacial compatibility with polylactic acid, thereby better promoting its effect.

[0015] 4. The compound multifunctional additive contains nitrogen, sulfur and rich carbon elements, which can play a synergistic flame retardant role and accelerate the combustion into carbon, thereby bringing good flame retardant properties to the polylactic acid sheet.

[0016] 5. The compound multifunctional additive contains 50% talc powder, which can significantly reduce its price without affecting its performance, making it suitable for industrial production. Specific implementation methods

[0017] To further clarify the technical problems, technical solutions, and beneficial effects of the present invention, the present invention is further described in detail below with reference to the following examples. It should be understood that the specific examples described herein are intended only to illustrate the present invention and are not intended to limit the present invention. The polylactic acid (brand: 2500HP), 5-sodium sulfoisophthalate (CAS: 6362-79-4), oleamide (CAS: 301-02-0), and talc (CAS: 14807-96-6) used in the present invention are all commercially available. Example 1

[0018] Disperse 26.8 g of 5-sulfoisophthalic acid sodium salt in 150 mL of acetone, add 56.2 g of oleamide and 5 mL of hydrochloric acid, and stir at 800 rpm for 12 hours at 50°C. After the reaction, filter and wash with acetone until neutral, then oven-dry at 60°C to constant weight. The resulting white flaky solid and talc are mixed in a high-speed mixer at a weight ratio of 1:1 at 3000 rpm for 3 minutes to obtain the resulting white solid, which is the composite multifunctional additive.

[0019] Polylactic acid and the compounded multifunctional additive were conventionally mixed in a high-speed mixer at a mass ratio of 100:3 (mixing speed 3000 rpm, mixing time 5 minutes), then extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and pelletized according to the method specified in GB / T 1843-2008. The notched impact strength, heat deformation temperature (HDT), and limiting oxygen index (LOI) of the samples were measured according to the method specified in GB / T 1634-2019. The specific data are shown in Table 1. Example 2

[0020] This embodiment is basically the same as Example 1, except that this embodiment uses the compound multifunctional additive synthesized in Example 1 and polylactic acid in a mass ratio of 100:1 to prepare samples. The test data are shown in Table 1. Example 3

[0021] This embodiment is basically the same as Example 1, except that this embodiment uses the compound multifunctional additive synthesized in Example 1 and polylactic acid in a mass ratio of 100:5 to prepare samples. The test data are shown in Table 1.

[0022] Comparative Example 1

[0023] Pure polylactic acid was extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and tested for notched impact strength according to GB / T 1843-2008, heat deformation temperature (HDT) according to GB / T 1634-2019, and limiting oxygen index (LOI) according to GB / T 2406.2-2009. Specific data are shown in Table 1.

[0024] Comparative Example 2

[0025] Polylactic acid and unblended white flaky solids were stirred in a high-speed mixer at a mass ratio of 100:3 (3000 rpm, 5 min). The mixture was then extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and their notched impact strength was measured according to GB / T 1843-2008, their heat deformation temperature (HDT) was measured according to GB / T 1634-2019, and their limiting oxygen index (LOI) was measured according to GB / T 2406.2-2009. Specific data are shown in Table 1.

[0026] Comparative Example 3

[0027] Polylactic acid and 5-sodium sulfoisophthalate were stirred in a high-speed mixer at a mass ratio of 100:3 (3000 rpm, 5 min), extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and pelletized according to the methods specified in GB / T 1843-2008. The notched impact strength, heat deformation temperature (HDT), and limiting oxygen index (LOI) of the samples were determined according to the methods specified in GB / T 1634-2019. The data are shown in Table 1.

[0028] Comparative Example 4

[0029] Polylactic acid and oleamide were stirred in a high-speed mixer at a mass ratio of 100:3 (3000 rpm, 5 min), extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and their notched impact strength was measured according to GB / T 1843-2008, their heat deformation temperature (HDT) was measured according to GB / T 1634-2019, and their limiting oxygen index (LOI) was measured according to GB / T 2406.2-2009. Specific data are shown in Table 1.

[0030] Comparative Example 5

[0031] Polylactic acid and talc were stirred in a high-speed mixer at a mass ratio of 100:3 (3000 rpm, 5 min), extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and tested for notched impact strength according to GB / T 1843-2008, heat deformation temperature (HDT) according to GB / T 1634-2019, and limiting oxygen index (LOI) according to GB / T 2406.2-2009. Specific data are shown in Table 1.

[0032] Comparative Example 6

[0033] 26.8 g of 5-sodium sulfoisophthalate and 56.2 g of oleamide were physically mixed. Polylactic acid, 5-sodium sulfoisophthalate, and oleamide were then mixed in a high-speed mixer at a mass ratio of 100:3 (mixing speed 3000 rpm, mixing time 5 min). The mixture was then extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and tested for notched impact strength according to GB / T 1843-2008, heat deformation temperature (HDT) according to GB / T 1634-2019, and limiting oxygen index (LOI) according to GB / T 2406.2-2009. Specific data are shown in Table 1.

[0034] Comparative Example 7

[0035] 26.8 g of 5-sodium sulfoisophthalate and 26.8 g of talc were physically mixed. Polylactic acid, 5-sodium sulfoisophthalate, and talc were mixed in a high-speed mixer at a mass ratio of 100:3 (mixing speed 3000 rpm, mixing time 5 min). The mixture was then extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and tested for notched impact strength according to GB / T 1843-2008, heat deformation temperature (HDT) according to GB / T 1634-2019, and limiting oxygen index (LOI) according to GB / T 2406.2-2009. Specific data are shown in Table 1.

[0036] Comparative Example 8

[0037] 56.2 g of oleamide and 56.2 g of talc were physically mixed. Polylactic acid (PLA) and the physically mixed oleamide and talc were conventionally mixed in a high-speed mixer at a mass ratio of 100:3 (mixing speed 3000 rpm, mixing time 5 min). The mixture was then extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and tested for notched impact strength according to GB / T 1843-2008, heat deformation temperature (HDT) according to GB / T 1634-2019, and limiting oxygen index (LOI) according to GB / T 2406.2-2009. Specific data are shown in Table 1.

[0038] Comparative Example 9

[0039] 26.8 g of 5-sodium sulfoisophthalate, 56.2 g of oleamide, and 83 g of talc were physically mixed. Polylactic acid (PLA) and the physically mixed 5-sodium sulfoisophthalate, oleamide, and talc were conventionally mixed in a high-speed mixer at a mass ratio of 100:3 (mixing speed 3000 rpm, mixing time 5 min). The mixture was then extruded and pelletized in a conventional twin-screw extruder. Samples were prepared and tested for notched impact strength according to GB / T 1843-2008, heat deformation temperature (HDT) according to GB / T 1634-2019, and limiting oxygen index (LOI) according to GB / T 2406.2-2009. Specific data are shown in Table 1.

[0040] Table 1 Test results of various embodiments and comparative examples

[0041] <![CDATA[Izod impact strength (KJ / m 2 )]]> HDT (℃) LOI (%) Example 1 7.47 113.4 28.9 Example 2 6.92 109.8 27.8 Example 3 7.46 112.9 28.7 Comparative Example 1 4.38 57.2 18.3 Comparative Example 2 5.41 98.6 22.6 Comparative Example 3 4.94 95.3 18.3 Comparative Example 4 4.37 57.3 18.3 Comparative Example 5 6.07 94.1 20.7 Comparative Example 6 4.59 93.5 21.4 Comparative Example 7 6.09 95.7 19.9 Comparative Example 8 5.88 93.6 19.9 Comparative Example 9 6.17 97.4 21.3

[0042] According to the experimental results in Table 1, the notched impact strength, heat deformation temperature, and limiting oxygen index of Examples 1-3 obtained by adding the compounded multifunctional additive prepared by the present invention are relatively high. Among them, Example 1 with an addition amount of 3% is the best. Compared with the pure polylactic acid in Comparative Example 1, it is shown that the processing aid synthesized by the present invention has the effect of significantly improving the notched impact strength, heat deformation temperature, and limiting oxygen index of polylactic acid. In addition, adding too much or too little compounded multifunctional additive will cause the notched impact strength, heat deformation temperature, and limiting oxygen index of polylactic acid to decrease.

[0043] The compounded multifunctional additive prepared by the present invention is synthesized by chemical reaction so that each segment plays a role at the same time and the chemical structure is stable. After compounding with talcum powder, the effect of each component is fully exerted, forming a complementary advantage system. Comparative Example 2 is a synthetic product without compounded talcum powder. Its molecular chain structure is stable, and the organic sulfonate segment can play a role in refining spherulites and improving crystallinity. In addition, its molecular chain contains nitrogen and sulfur elements, which can play a synergistic flame retardant role, thereby significantly improving HDT and LOI. However, due to the lack of toughening and inorganic flame retardant effect of talcum powder, its notched impact strength is not significantly improved, and all indicators are far worse than Examples 1-3.

[0044] Comparative Examples 3-9 are only single raw materials or simple mixtures of raw materials, without complete chemical reaction, and the above effects cannot be fully exerted.

[0045] Comparative Examples 3-5 consist of a single component or a simple mixture of raw materials, without a complete chemical reaction, and thus the aforementioned effects cannot be fully realized. The sodium 5-sulfoisophthalate added in Comparative Example 3 acts as a heterogeneous nucleation site, refining spherulites and increasing crystallinity, which can slightly improve the notched impact strength and heat distortion temperature of the polylactic acid. However, it has no effect on the flame retardancy of the polylactic acid and suffers from poor compatibility with the polylactic acid, resulting in limited performance improvements. The oleamide added in Comparative Example 4 only provides a lubricating effect, with little improvement in the various properties of the polylactic acid. The talc added in Comparative Example 5, as an inorganic particle, has a more pronounced toughening effect and also exerts an inorganic flame retardant effect. Its notched impact strength and LOI performance are the best in Comparative Examples 3-5, but its contribution to HDT improvement is limited. Furthermore, due to its poor compatibility with the polylactic acid, the improvement in notched impact strength, heat distortion temperature, and limiting oxygen index of the polylactic acid is still less than that of Examples 1-3.

[0046] Comparative Examples 6-8 are simple mixtures of two components. Among them, since oleamide only plays a lubricating effect, the role played in Comparative Examples 6 and 8 is limited, and due to its high content, the effect is slightly reduced compared to the corresponding Comparative Examples 3 and 5. At the same time, compared to adding sodium 5-sulfoisophthalic acid, the effect of talcum powder is more obvious, so the notched impact strength and heat deformation temperature improvement effect of Comparative Example 8 are better than those of Comparative Example 6. In Comparative Example 7, which adds sodium 5-sulfoisophthalic acid and talcum powder, both sodium 5-sulfoisophthalic acid and talcum powder can play a role in refining spherulites and improving crystallinity, so in Comparative Examples 6-8 of two-component mixing, the improvement effect of its notched impact strength and heat deformation temperature is the best. As for the flame retardant effect, the mixture of sodium 5-sulfonate and oleamide in Comparative Example 6 contains nitrogen and sulfur elements, which can exert a partial synergistic flame retardant effect, while the flame retardant effect of inorganic particles is weaker than the synergistic flame retardant effect, so the limiting oxygen index of Comparative Example 7 and Comparative Example 8 is lower than that of Comparative Example 6.

[0047] Comparative Example 9, which simultaneously added sodium 5-sulfoisophthalate, oleamide, and talc, exhibited multiple effects, achieving the best improvements in notched impact strength and heat deformation temperature compared to Comparative Examples 2-8. Furthermore, since this simple physical mixing provided a partial synergistic flame retardant effect without undergoing a chemical reaction and forming a stable chemical structure, the limiting oxygen index was lower than that of Comparative Example 2.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of the present invention.

Claims

1. A compound multifunctional additive, characterized in that: The preparation method comprises the following steps: dispersing 26.8 g of 5-sulfoisophthalic acid sodium salt in 150 mL of acetone, adding 56.2 g of oleamide and 5 mL of hydrochloric acid, controlling the system temperature at 50°C and stirring at 800 rpm for 12 hours, filtering after the reaction, washing with acetone until neutral, and drying in an oven at 60°C to constant weight, mixing the dried white flaky solid and talc powder in a high-speed mixer at a weight ratio of 1:1 at 3000 rpm for 3 minutes, and obtaining a white solid which is the composite multifunctional additive; The compound multifunctional auxiliary agent is used in the preparation of polylactic acid sheets.

2. A compound multifunctional additive according to claim 1, characterized in that: When the compounded multifunctional auxiliary agent is used in the preparation of polylactic acid sheets, the dosage of the compounded multifunctional auxiliary agent is 1%-5% of the polylactic acid.

3. A compound multifunctional additive according to claim 1, characterized in that: When the compounded multifunctional auxiliary agent is used in the preparation of polylactic acid sheets, the dosage of the compounded multifunctional auxiliary agent is 3% of the polylactic acid.