Compound multifunctional auxiliary agent and application thereof in sheet preparation in polylactic acid

Abstract

The invention discloses a compound multifunctional additive and application thereof in sheet preparation in polylactic acid, and relates to the technical field of polylactic acid modification. The compound multifunctional additive and polylactic acid have good interfacial compatibility, and the thermal performance, mechanical performance and flame retardant property of polylactic acid can be improved at the same time. Meanwhile, due to the addition of the compound talcum powder, the compound multifunctional additive has a relatively high price advantage and can be widely applied to 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 the increasing awareness of environmental protection, the research and development of environmentally friendly bio-based polymer materials has received widespread attention. Polylactic acid (PLA), as a biodegradable polymer material, has shown broad application prospects in the field of disposable lunch boxes due to its good biocompatibility and degradability.

[0003] However, the polylactic acid material itself has problems such as poor crystallization performance, low toughness and poor heat resistance, which limits its application in the field of disposable lunch boxes. In order to overcome these defects, a method of melt blending polylactic acid and a nucleating agent or a toughening agent is usually adopted to improve its crystallization performance, toughness and heat deformation temperature. For example, patent CN111333910A discloses a rare earth aryl phosphate polylactic acid nucleating agent, which can significantly improve the heat resistance of polylactic acid; patent CN119371789A discloses a preparation method of talc-wollastonite masterbatch for improving the mechanical properties of polylactic acid. However, a single additive is often difficult to simultaneously meet the comprehensive requirements of polylactic acid in terms of crystallization performance, mechanical properties, thermal properties and flame retardant properties. In addition, the compatibility problem between the additive and the polylactic acid matrix may also affect its effect, resulting in limited performance improvement. In addition, commercially available polylactic acid functional additives have problems such as high prices, and the price of polylactic acid itself is relatively high. Therefore, the price problem has also become an important limiting factor in the processing and modification of polylactic acid.

[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 nucleation role, promote the refinement of polylactic acid spherulites, and thus significantly improve 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 compound multifunctional additive contains nitrogen and sulfur elements and rich carbon elements, which 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 in that: it is obtained by the following preparation method, including: dispersing 26.8 g of sodium 5-sulfoisophthalic acid in 150 mL of acetone, adding 56.2 g of oleamide, 5 mL of hydrochloric acid, controlling the system temperature at 50 ° C and stirring at a speed of 800 rpm for 12 h. After the reaction is completed, suction filtration is performed, and then washed with acetone to neutrality, and then dried in an oven at 60 ° C to constant weight, and the dried white flaky solid and talcum powder are mixed in a high-speed mixer at a weight ratio of 1:1 at a speed of 3000 rpm for 3 min, and the obtained white solid is 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 compound multifunctional additive in the preparation of polylactic acid sheets, characterized in that the dosage of the compound multifunctional additive 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 expected effect, and 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 chain segments in the compound multifunctional additives can play an excellent nucleation role in the crystallization process of polylactic acid, promote the refinement of polylactic acid spherulites, and make the crystal structure more compact. In addition, the rigid particles of talcum powder can hinder the movement of polylactic acid molecular chains. The two work together to promote a significant increase in its heat deformation temperature (HDT). This effect provides thermal performance guarantee for the application of polylactic acid sheets in the field of disposable lunch boxes.

[0013] 2. The combined effect of compound multifunctional additives and talcum powder can promote a significant increase in the crystallinity of polylactic acid, thereby greatly improving the toughness of polylactic acid, so that polylactic acid sheets can be better adapted to the application 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, thus bringing good flame retardant properties to the polylactic acid sheet.

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

[0017] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The polylactic acid (brand name: 2500HP), sodium 5-sulfoisophthalate (CAS number: 6362-79-4), oleamide (CAS number: 301-02-0) and talc (CAS number: 14807-96-6) used in the present invention are all commercially available in the art. 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, control the system temperature at 50 °C, stir at 800 rpm and react for 12 h. After the reaction is completed, filter, wash with acetone to neutrality, and then dry in an oven at 60 °C to constant weight. Mix the dried white flaky solid and talcum powder in a high-speed mixer at a weight ratio of 1:1 at 3000 rpm for 3 min. The obtained white solid is the composite multifunctional additive.

[0019] Polylactic acid and the compound multifunctional additive were conventionally mixed in a high-speed mixer at a mass ratio of 100:3 (mixing speed 3000 rpm, mixing time 5 min), and then extruded and granulated in a conventional twin-screw extruder. Samples were prepared and notched impact strength was measured according to the method specified in GB / T1843-2008, and heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019. Samples were prepared and limiting oxygen index (LOI) of the samples were measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1. Example 2

[0020] This embodiment is basically the same as Embodiment 1, except that this embodiment uses the composite multifunctional additive synthesized in Embodiment 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 Embodiment 1, except that this embodiment uses the composite multifunctional additive synthesized in Embodiment 1 and polylactic acid in a mass ratio of 100:5 to prepare a sample. The test data are shown in Table 1.

[0022] Comparative Example 1 Pure polylactic acid was extruded and granulated in a conventional twin-screw extruder. Samples were prepared and notched impact strength was measured according to the method specified in GB / T 1843-2008, heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019, and limiting oxygen index (LOI) of the samples was measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1.

[0023] Comparative Example 2 Polylactic acid and white flaky solids without talcum powder were stirred in a high-speed mixer at a mass ratio of 100:3 (stirring speed 3000 rpm, stirring time 5 min), extruded and granulated in a conventional twin-screw extruder. Samples were prepared and their notched impact strength was measured according to the method specified in GB / T 1843-2008, samples were prepared and their heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019, and samples were prepared and their limiting oxygen index (LOI) was measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1.

[0024] Comparative Example 3 Polylactic acid and 5-sodium sulfoisophthalate were stirred in a high-speed mixer at a mass ratio of 100:3 (stirring speed 3000 rpm, stirring time 5 min), extruded and granulated in a conventional twin-screw extruder. Samples were prepared and their notched impact strength was measured according to the method specified in GB / T1843-2008, samples were prepared and their heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019, and samples were prepared and their limiting oxygen index (LOI) was measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1.

[0025] Comparative Example 4 Polylactic acid and oleamide were stirred in a high-speed mixer at a mass ratio of 100:3 (stirring speed 3000 rpm, stirring time 5 min), extruded and granulated in a conventional twin-screw extruder. Samples were prepared and their notched impact strength was measured according to the method specified in GB / T 1843-2008, samples were prepared and their heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019, and samples were prepared and their limiting oxygen index (LOI) was measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1.

[0026] Comparative Example 5 Polylactic acid and talc were stirred in a high-speed mixer at a mass ratio of 100:3 (stirring speed 3000rpm, stirring time 5 min), extruded and granulated in a conventional twin-screw extruder. Samples were prepared and their notched impact strength was measured according to the method specified in GB / T 1843-2008, samples were prepared and their heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019, and samples were prepared and their limiting oxygen index (LOI) was measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1.

[0027] Comparative Example 6 26.8 g of sodium 5-sulfoisophthalic acid and 56.2 g of oleamide were physically mixed. Polylactic acid and the physically mixed sodium 5-sulfoisophthalic acid and oleamide were conventionally mixed in a high-speed mixer at a mass ratio of 100:3 (mixing speed 3000 rpm, mixing time 5 min), and then extruded and granulated in a conventional twin-screw extruder. After extrusion and granulation in a conventional twin-screw extruder. Samples were prepared and notched impact strength was measured according to the method specified in GB / T 1843-2008, samples were prepared and heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019, and limiting oxygen index (LOI) of the samples was measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1.

[0028] Comparative Example 7 26.8 g of sodium 5-sulfonisophthalate and 26.8 g of talc were physically mixed. Polylactic acid and the physically mixed sodium 5-sulfonisophthalate 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), and then extruded and granulated in a conventional twin-screw extruder. After extrusion and granulation in a conventional twin-screw extruder. Samples were prepared and notched impact strength was measured according to the method specified in GB / T 1843-2008, samples were prepared and heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019, and limiting oxygen index (LOI) of the samples was measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1.

[0029] Comparative Example 8 56.2 g of oleic acid amide and 56.2 g of talc were physically mixed. Polylactic acid and the physically mixed oleic acid amide 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), and then extruded and granulated in a conventional twin-screw extruder. After extrusion and granulation in a conventional twin-screw extruder. Samples were prepared and notched impact strength was measured according to the method specified in GB / T 1843-2008, samples were prepared and heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019, and limiting oxygen index (LOI) of the samples was measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1.

[0030] Comparative Example 9 26.8 g of sodium 5-sulfonate of isophthalic acid, 56.2 g of oleamide and 83 g of talc were physically mixed. Polylactic acid and the physically mixed sodium 5-sulfonate of isophthalic acid, 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), and then extruded and granulated in a conventional twin-screw extruder. After extrusion and granulation in a conventional twin-screw extruder. Samples were prepared and notched impact strength was measured according to the method specified in GB / T 1843-2008, samples were prepared and heat deformation temperature (HDT) was measured according to the method specified in GB / T 1634-2019, and limiting oxygen index (LOI) of the samples was measured according to the method specified in GB / T 2406.2-2009. The specific data are shown in Table 1.

[0031] Table 1 Test results of various embodiments and comparative examples <![CDATA[Notched 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 According to the experimental results in Table 1, the notched impact strength, heat deformation temperature and limiting oxygen index of the compound multifunctional additive prepared by the present invention in Examples 1-3 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, too much or too little addition of the compound multifunctional additive will reduce the notched impact strength, heat deformation temperature and limiting oxygen index of polylactic acid.

[0032] The compound 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, and then the role of each component is fully exerted after compounding with talcum powder, forming a complementary advantage system. Comparative Example 2 is a synthetic product of uncompounded talcum powder, and 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 making HDT and LOI improve more significantly, but 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.

[0033] Comparative Examples 3-9 are only single raw materials or simple mixtures of raw materials, and no complete chemical reaction is carried out, so the above effects cannot be fully exerted.

[0034] Among them, comparative examples 3-5 are simple mixtures of a single component or raw materials, and no complete chemical reaction is performed, so the above effects cannot be fully exerted. The sodium 5-sulfonate of isophthalic acid added in comparative example 3 can play a role in refining spherulites and improving crystallinity as a heterogeneous nucleation point, and can slightly improve the notched impact strength and heat deformation temperature of polylactic acid, but has no effect on the flame retardant properties of polylactic acid, and has poor compatibility with polylactic acid, so the performance improvement is limited. The oleic acid amide added in comparative example 4 only has a lubricating effect, and has almost no effect on the various properties of polylactic acid. The talcum powder added in comparative example 5 has a more obvious toughening effect as an inorganic particle, and can play an inorganic flame retardant role. Its notched impact strength and LOI have the best performance in comparative examples 3-5, but its contribution to HDT improvement is limited. In addition, due to the problem of poor compatibility with polylactic acid, there is still a gap in the improvement effect of notched impact strength, heat deformation temperature and limiting oxygen index of polylactic acid compared with Examples 1-3.

[0035] 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 with the corresponding Comparative Examples 3 and 5. At the same time, compared with the addition of 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 in which sodium 5-sulfoisophthalic acid and talcum powder are added, sodium 5-sulfoisophthalic acid and talcum powder can both play the role of refining spherulites and improving crystallinity, so in Comparative Examples 6-8 of two-component mixing, the improvement effect of notched impact strength and heat deformation temperature is the best. As for the flame retardant effect, the mixture of sodium 5-sulfonate of isophthalic acid and oleamide in Comparative Example 6 contains nitrogen and sulfur elements, which can play 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.

[0036] Comparative Example 9, in which sodium 5-sulfoisophthalate, oleamide and talc are added simultaneously, has multiple effects at the same time, and the effect of improving notched impact strength and heat deformation temperature is the best compared with Comparative Examples 2 to 8. In addition, since it is only a simple physical mixture that can play a partial synergistic flame retardant role, it has not undergone a chemical reaction and has not formed a stable chemical structure, so the limiting oxygen index is lower than that of Comparative Example 2.

[0037] 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 principle of the present invention should be included in the scope of the present invention.

Claims

1. A composite multifunctional additive, characterized in that: The preparation method comprises the following steps: 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, controlling the system temperature at 50°C and stirring at a speed of 800 rpm for 12 h, filtering after the reaction, washing with acetone to neutrality, and drying in an oven at 60°C to constant weight, mixing the dried white flaky solid and talc in a high-speed mixer at a weight ratio of 1:1 at a speed of 3000 rpm for 3 min, and obtaining the obtained white solid, which is the composite multifunctional auxiliary agent.

2. Use of a composite multifunctional additive according to claim 1 in the preparation of polylactic acid sheets.

3. The use of a compound multifunctional additive in the preparation of polylactic acid sheets according to claim 2, characterized in that: The dosage of the compound multifunctional auxiliary agent is 1%-5% of the polylactic acid.

4. The use of a compound multifunctional additive in the preparation of polylactic acid sheets according to claim 3, characterized in that: The dosage of the compound multifunctional auxiliary agent is 3% of the polylactic acid.