Novel bio-based halogen-free flame-retardant acrylic emulsion

Abstract

The invention discloses a novel bio-based halogen-free flame-retardant acrylic emulsion which is prepared by taking phytic acid and chitosan as basic raw materials and reacting the basic raw materials with an acrylate pre-emulsion. The preparation method comprises the following steps: (1) emulsifying and dispersing: respectively adding the deionized water, the emulsifier, the acrylic monomer, the initiator and the reactive flame-retardant monomer into an emulsifying kettle, and stirring for 30-60 minutes for emulsifying and dispersing after the materials are added, so as to prepare an acrylate pre-emulsion; (2) condensation reaction: adding phytic acid into a reaction kettle, adding distilled water, adjusting the pH value to obtain a phytic acid aqueous solution, adjusting the temperature to 30-60 DEG C, then adding chitosan, and keeping the temperature of a reaction system unchanged in the process until the reaction is finished; and (3) polymerization reaction: adding the acrylate pre-emulsion prepared in the step (1) into the mixture in the step (2), and reacting at 30-60 DEG C for 3-6 hours to prepare the emulsion. And (4) adding a defoaming agent and a thickening agent into the emulsion prepared in the step (3), and adjusting the quality of the product to obtain the bio-based halogen-free flame-retardant acrylic emulsion product.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, and particularly to a novel bio-based halogen-free flame retardant acrylic emulsion and a preparation method thereof. Background Art

[0002] Although halogen-based flame retardants have the advantage of high cost performance, these flame retardants generate a large amount of toxic and corrosive gases during combustion, which has raised concerns about their environmental protection issues. In existing research, the development of flame retardants is moving towards a more environmentally friendly direction, and bio-based flame retardants have gradually become the mainstream research direction. However, how to simultaneously ensure the flame retardancy efficiency and durability of flame retardants still remains a challenge. Therefore, bio-based hydrophobic flame retardants with excellent performance are urgently needed functional products in the current market.

[0003] Bio-based materials have received increasing attention in the materials field due to their green, abundant sources, and biodegradable characteristics. Recent studies have shown that some bio-based materials in nature, such as cellulose, lignin, amino acids, phytic acid, etc., have rich functional groups and flame retardant characteristic elements in their structures, showing certain flame retardant properties. Phytic acid, also known as inositol hexaphosphate and cyclohexanehexol hexaphosphate, with the molecular formula C6H 18 O 24 P6, is an organic phosphorus compound extracted from plant seeds.

[0004] Patent CN113754900B discloses a chitosan microsphere flame retardant, whose structure includes chitosan microspheres and polyelectrolytes coated on the surface of the chitosan microspheres. Patent CN115594714A discloses a preparation method and application of a bio-based flame retardant with phytic acid as the substrate; Patent CN111440357A discloses a fully bio-based flame retardant, a flame retardant PLA composite material and a preparation method thereof; Patent CN 118667184 A discloses a bio-based flame retardant, a preparation method and an application; Patent CN 114539623A relates to the application of a chitosan-based flame retardant in polyurethane. Patent CN118165580A discloses a functional coating with flame retardancy formed by reacting gluconate, phytic acid and chitosan salt at room temperature through a sol-gel method. However, the above bio-based flame retardant technologies are not yet perfect, mainly reflected in the relatively cumbersome reaction system, and the overall flame retardant effect and application need to be further improved.

[0005] Therefore, the main technical problems existing in the existing flame retardant systems are as follows: (1) Halogen-based flame retardants generate a large amount of toxic and corrosive gases during combustion, which cause great harm to the environment and human body.

[0006] (2) The bio-based flame retardant technology is not yet perfect, and the flame retardant effect needs to be improved. Summary of the Invention

[0007] The object of the present invention is to provide a novel bio-based halogen-free flame retardant acrylic emulsion and a preparation method thereof to solve the above problems.

[0008] The object of the present invention is achieved by the following technical solutions: A novel bio-based halogen-free flame retardant acrylic emulsion is prepared by reacting phytic acid and chitosan as basic raw materials with an acrylate pre-emulsion.

[0009] It can be understood that phytic acid and chitosan undergo a condensation reaction to form a macromolecular structure, and then react with the acrylate pre-emulsion to prepare a flame retardant with a macromolecular structure, improving the flame retardant effect.

[0010] The acrylate pre-emulsion is prepared from the following raw materials in parts by weight: 50 - 60 parts of acrylic acid monomers, 5 - 8 parts of emulsifier, 0.5 - 1.0 part of initiator, 2 - 10 parts of reactive flame retardant monomer, and 30 - 40 parts of deionized water.

[0011] Among the raw materials for preparing the acrylate pre-emulsion, the acrylic acid monomer is a mixture of acrylic acid, ethyl acrylate, butyl acrylate, and methyl methacrylate; the mass ratio of acrylic acid, butyl acrylate, ethyl acrylate, and methyl methacrylate is 2:1:1:1.

[0012] The reactive flame retardant monomer is at least one of ammonium polyphosphate, phosphate ester, tricresyl phosphate, and urea.

[0013] The emulsifier is at least one of sodium dodecyl sulfate and sodium dodecylbenzenesulfonate; The initiator is at least one of sodium persulfate, potassium persulfate, and ammonium persulfate.

[0014] A preparation method of a novel bio-based halogen-free flame retardant acrylic emulsion includes the following steps: ① Emulsification and dispersion: Add deionized water, emulsifier, acrylic acid monomer, initiator, and reactive flame retardant monomer to an emulsification kettle respectively. After feeding, stir for 30 - 60 minutes for emulsification and dispersion to obtain an acrylate pre-emulsion; ② Condensation reaction: Add phytic acid to a reaction kettle, add distilled water, adjust the pH to obtain an aqueous phytic acid solution, adjust the temperature to 30 - 60 °C, and then add chitosan, keeping the temperature of the reaction system unchanged during the process until the reaction ends; ③ Polymerization reaction: Add the acrylate pre-emulsion prepared in ① to ② and react at 30 - 60 °C for 3 - 6 hours to obtain an emulsion; ④ Add defoamer and thickener to the emulsion prepared in ③ to adjust the product quality and obtain a bio-based halogen-free flame retardant acrylic emulsion product.

[0015] In the above reaction, the mass ratio of phytic acid, chitosan, and acrylic emulsion is 1:(0.5 - 12):(0.5 - 10).

[0016] The thickener is an alkali-swellable acrylate thickener; The defoamer is a mineral oil defoamer or a silicone defoamer; The mass ratio of the emulsion prepared in step ③, thickener, and defoamer is: (50 - 60):(2 - 2.5):0.5.

[0017] Preferably, in the condensation reaction, the pH value is 3 - 5.

[0018] Preferably, during the reaction processes of steps ② and ③, the temperature of the reaction system is controlled at 40 - 50 °C.

[0019] In step ④, when adding defoamer and thickener to the reaction solution, a bactericide can be added simultaneously.

[0020] A novel bio-based halogen-free flame retardant acrylic emulsion of the present invention has the following mechanism: 1. The acrylic emulsion endows the emulsion with certain flame retardancy by adjusting the functional monomers with double bonds and undergoing polymerization reactions with substances containing phosphorus, nitrogen, etc.

[0021] 2. Both phytic acid and chitosan in the bio-based halogen-free flame retardant acrylic emulsion are derived from bio-based sources. In the flame retardant system, phytic acid serves as the acid source, chitosan serves as the carbon source, and the acrylate pre-emulsion serves as the gas source. The three work together to play a good flame retardant role in the flame retardant material.

[0022] Meanwhile, the acrylic monomers are a mixture of acrylic acid, ethyl acrylate, butyl acrylate, and methyl methacrylate, which can improve the adhesion performance of the polymer and the adhesion of the coating, provide a basis for the crosslinking and curing of the emulsion in the later stage, facilitate the transfer of monomers from droplets to micelles during the reaction, play a "bridge transportation" role, and thus can increase the reaction rate; the emulsifier can reduce the interfacial tension between the oil phase and the water phase in the emulsion polymerization and obtain a stable emulsion system through its emulsification effect. Therefore, the novel bio-based halogen-free flame retardant acrylic emulsion prepared in this application has good mechanical properties, excellent flame retardant function, and durability. Through experimental comparison, it has good application and effects in insulating cloth for wire and cable, non-woven fabric for transportation, etc. Specific embodiments

[0023] The specific embodiments of the present invention will be described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. It should be noted that the experimental methods used in the following examples are all conventional methods unless otherwise specified; the materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0024] For those not specified in the examples, they are carried out under conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase. To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below.

[0025] Preparation Example 1 Take raw materials with the following mass fractions: 50 parts of acrylic monomer, 5 parts of emulsifier (sodium dodecylbenzenesulfonate), 0.5 part of initiator (sodium persulfate), 40 parts of deionized water, and 2 parts of reactive flame retardant monomer (ammonium polyphosphate), where the acrylic monomer is acrylic acid, butyl acrylate, ethyl acrylate, and methyl methacrylate, with a mass ratio of 2:1:1:1. The preparation method is as follows: Add the above-mentioned mass fractions of deionized water, emulsifier, acrylic monomer, and reactive flame retardant monomer into the emulsifying kettle respectively. After the feeding is completed, stir for 30 minutes for emulsifying and dispersing to obtain an acrylate pre-emulsion.

[0026] Preparation Example 2 Take raw materials with the following mass fractions: 60 parts of acrylic monomer, 8 parts of emulsifier (sodium dodecyl sulfate), 1 part of initiator (potassium persulfate), 35 parts of deionized water, and 10 parts of reactive flame retardant monomer (tricresyl phosphate), where the acrylic monomer is acrylic acid, butyl acrylate, ethyl acrylate, and methyl methacrylate, with a mass ratio of 2:1:1:1. The preparation method is as follows: Add the above-mentioned mass fractions of deionized water, emulsifier, acrylic monomer, and reactive flame retardant monomer into the emulsifying kettle respectively. After the feeding is completed, stir for 60 minutes for emulsifying and dispersing to obtain an acrylate pre-emulsion.

[0027] Preparation Example 3 Take raw materials with the following mass fractions: 55 parts of acrylic monomer, 6 parts of emulsifier (sodium dodecyl sulfate), 0.8 part of initiator (ammonium persulfate), 30 parts of deionized water, and 6 parts of reactive flame retardant monomer (urea), where the acrylic monomer is acrylic acid, butyl acrylate, ethyl acrylate, and methyl methacrylate, with a mass ratio of 2:1:1:1. The preparation method is as follows: Add the deionized water, emulsifier, acrylic monomer, and reactive flame retardant monomer in the above-mentioned parts by mass to the emulsifying kettle. After the feeding is completed, stir for 50 minutes for emulsification and dispersion to obtain an acrylate pre-emulsion.

[0028] In the above preparation example, the reactive flame retardant monomer is replaced with phosphate ester, urea, or a mixture thereof to obtain an acrylate pre-emulsion.

[0029] Example 1 Take raw materials with the following parts by mass: 10 parts of phytic acid, 5 parts of chitosan, 5 parts of the acrylate pre-emulsion obtained in Preparation Example 2, 1 part of a thickener (alkali-swellable acrylate thickener), and 0.5 part of an antifoaming agent (mineral oil antifoaming agent).

[0030] The preparation method of the novel bio-based halogen-free flame retardant acrylic emulsion is as follows: ① Take the acrylate pre-emulsion prepared in Preparation Example 2 for standby; ② Condensation reaction: Add phytic acid to the reaction kettle, add distilled water, adjust the pH to 3-5 to obtain an aqueous phytic acid solution, adjust the temperature to 30 °C, and then add chitosan, keeping the temperature of the reaction system unchanged during the process until the reaction ends; ③ Polymerization reaction: Add the acrylate pre-emulsion of ① to ② and react at 30 °C for 3-6 hours to obtain an emulsion.

[0031] ④ Add an antifoaming agent and a thickener to the emulsion obtained in ③, and adjust the product quality to obtain a bio-based halogen-free flame retardant acrylic emulsion product.

[0032] Examples 2-5 Take the components with the parts by mass shown in Table 1.

[0033] Table 1 Raw material component ratios of bio-based halogen-free flame retardant acrylic emulsion in Examples 2-5

[0034] Use the preparation method in Example 1 to prepare a bio-based halogen-free flame retardant acrylic emulsion. Each reaction parameter is different, and other steps are the same. The specific reaction parameters in Examples 2-5 are as follows: ① Emulsification and dispersion: The stirring times are: 40 minutes, 40 minutes, 50 minutes, and 60 minutes respectively; ② Condensation reaction: Adjust the pH to 3, 4, 4, and 5 respectively; adjust the temperature to 40 °C, 40 °C, 50 °C, and 60 °C respectively; ③ Polymerization reaction: The reaction temperature and time are: react at 40 °C for 3 hours, react at 40 °C for 4 hours, react at 50 °C for 5 hours, and react at 60 °C for 6 hours respectively.

[0035] Comparative Example 1 The method of Example 1 of the patent document CN111440357A in the references was used to prepare a flame retardant material. The specific steps are as follows: In a 55 °C constant temperature water bath, 37.7 g of 70% phytic acid solution was dissolved in 158.4 mL of distilled water. Subsequently, ammonia water was slowly added to adjust the pH to pH = 4.5. At the same time, 5.0 g of taurine was dissolved in the aqueous solution and then the taurine solution was slowly added to the phytic acid solution, and the reaction was carried out for 5 h; after the reaction ended, after the reaction product was cooled to room temperature, 600 ml of ethanol was added for recrystallization to precipitate the reaction product, and after suction filtration and drying, a fully bio-based flame retardant was obtained.

[0036] Comparative Example 2 5 parts of the acrylate pre-emulsion in Preparation Example 2 of this application were added with 0.5 part of an antifoaming agent (mineral oil antifoaming agent) and 1 part of a thickening agent (alkali-swellable acrylate thickening agent) after aging, degassing, and filtration to adjust the product quality, and a flame retardant material was prepared.

[0037] Test Example 1 The afterflame time and limiting oxygen index of the flame retardant materials prepared in Examples 1-5 and Comparative Examples 1-2 were compared, and the specific results are as follows: The products prepared in Examples 1-5 and Comparative Examples 1-2 were used as the soaking solution for insulating cloth for wire and cable. The insulating cloth for wire and cable was soaked in the above solution at 70 °C for 1 h, and the mass ratio of the insulating cloth for wire and cable to the volume of the flame retardant material (emulsion) was 1:20. After the soaked insulating cloth for wire and cable passed through a calender, the liquid carrying rate was maintained at 100%. The insulating cloth for wire and cable was passed through a continuous setting and drying oven at 190 °C for 5 min. Finally, after the flame retardant material (emulsion) attached to the surface of the insulating cloth for wire and cable was washed clean, it was dried in an oven at 60 °C. The above procedure was repeated once, and the limiting oxygen index determination (ASTM D2863-2000), vertical burning test (ASTM D6413-99), and flame retardant and wash fastness test of insulating cloth (AATCC 61-2006) were carried out on the insulating cloth for wire and cable respectively. The test results are shown in Table 2.

[0038] Table 2 Detection results of afterflame time and limiting oxygen index of the flame retardant materials obtained in Examples 1-5 and Comparative Examples 1-2

[0039] It can be seen from the data analysis in Table 2 that the products prepared in the examples of the present invention have excellent flame retardancy and durability. The examples all have a relatively high oxygen index, and the highest limiting oxygen index can reach 48.6%. Even after 50 washes, the highest limiting oxygen index can still remain at 34.8%, which can meet the requirements of the flame retardant standard. Compared with Comparative Examples 1 and 2, it has a better synergistic flame retardant effect.

[0040] In addition, the novel bio-based halogen-free flame-retardant acrylic emulsion of the present application also has good applications in transportation non-woven fabrics. Through experimental verification, compared with the products of Comparative Examples 1-2, it has a better synergistic flame-retardant effect and good application effects.

[0041] The above-described embodiments have detailed the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements, equivalent replacements, etc. made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel bio-based halogen-free flame-retardant acrylic emulsion, characterized in that, The bio-based halogen-free flame-retardant acrylic emulsion is prepared by reacting phytic acid and chitosan as basic raw materials with an acrylate pre-emulsion.

2. The bio-based halogen-free flame-retardant acrylic emulsion according to claim 1, wherein The mass ratio of the phytic acid, chitosan, and acrylate pre-emulsion is 1:(0.5 - 12):(0.5 - 10).

3. The bio-based halogen-free flame-retardant acrylic emulsion according to claim 2, wherein The preparation method of the bio-based halogen-free flame-retardant acrylic emulsion comprises the following steps: ① Emulsification and dispersion: Add deionized water, emulsifier, acrylic monomers, initiator, and reactive flame-retardant monomers into an emulsification kettle respectively. After feeding, stir for 30 - 60 minutes for emulsification and dispersion to obtain an acrylate pre-emulsion. ② Condensation reaction: Add phytic acid into a reaction kettle, add distilled water, adjust the pH to obtain an aqueous phytic acid solution, adjust the temperature to 30 - 60 °C, and then add chitosan, keeping the temperature of the reaction system unchanged during the process until the reaction ends. ③ Polymerization reaction: Add the acrylate pre-emulsion prepared in ① into ② and react at 30 - 60 °C for 3 - 6 hours to obtain an emulsion. ④ Add an antifoaming agent and a thickener to the emulsion obtained in ③, and adjust the product quality to obtain a bio-based halogen-free flame-retardant acrylic emulsion product.

4. The bio-based halogen-free flame-retardant acrylic emulsion according to claim 3, wherein, The acrylate pre-emulsion is prepared from the following raw materials in parts by weight: 50 - 60 parts of acrylic monomers, 5 - 8 parts of emulsifier, 0.5 - 1.0 part of initiator, 2 - 10 parts of reactive flame-retardant monomer, and 30 - 40 parts of deionized water.

5. The bio-based halogen-free flame-retardant acrylic emulsion according to claim 4, wherein Among the raw materials for preparing the acrylate pre-emulsion, the acrylic monomers are a mixture of acrylic acid, ethyl acrylate, butyl acrylate, and methyl methacrylate; the mass ratio of acrylic acid, butyl acrylate, ethyl acrylate, and methyl methacrylate is 2:1:1:

1.

6. The bio-based halogen-free flame-retardant acrylic emulsion according to claim 4, wherein The reactive flame-retardant monomer is at least one of ammonium polyphosphate, phosphate ester, tricresyl phosphate, and urea.

7. The bio-based halogen-free flame-retardant acrylic emulsion according to claim 3, wherein The emulsifier is at least one of sodium dodecyl sulfate and sodium dodecylbenzenesulfonate; The initiator is at least one of sodium persulfate, potassium persulfate, or ammonium persulfate; The thickener is an alkali-swellable acrylate thickener; The antifoaming agent is a mineral oil antifoaming agent or a silicone antifoaming agent; The mass ratio of the emulsion, thickener, and antifoaming agent obtained in step ③ is: (50 - 60):(2 - 2.5):0.

5.

8. The bio-based halogen-free flame-retardant acrylic emulsion according to claim 3, wherein During the reaction processes of steps ② and ③, the temperature of the reaction system is controlled at 40 - 50 °C; in the condensation reaction, the pH value is 3 - 5.

9. The bio-based halogen-free flame-retardant acrylic emulsion according to claim 3, wherein, In step ④, when adding the antifoaming agent and the thickener to the reaction solution, a bactericide is added simultaneously.

10. Application of the novel bio-based halogen-free flame-retardant acrylic emulsion according to any one of claims 1 - 3 in insulating cloth for wire and cable and non-woven fabric for transportation.

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