High-elasticity flame-retardant latex thread and preparation method thereof

Abstract

The invention relates to a high-elasticity flame-retardant latex thread and a preparation method thereof, and belongs to the technical field of latex threads. The flame-retardant latex thread comprises an inert material and an active material, the inert material comprises the following components in parts by weight: 100 parts of concentrated latex, 2-3 parts of a potassium hydroxide solution, 0.5-2 parts of an accelerant MZ, 2-5 parts of kaolin, 1-3 parts of sulfur, 1-3 parts of oleic acid, 1-5 parts of an antioxidant, 20-60 parts of a flame retardant and 1-3 parts of phytic acid; the active material comprises the following components: 2-3 parts of a potassium hydroxide solution, 0.5-2 parts of an accelerant BZ and 3-5 parts of zinc oxide. In the preparation of the flame-retardant latex thread, the natural liquid latex, the melamine-coated red phosphorus and other components are adopted, the melamine-coated red phosphorus has high flame-retardant efficiency, and can play a role and generate a synergistic flame-retardant effect when a gas phase and a coagulation phase are identical when being matched with phytic acid, and the total dosage of a flame retardant can be reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of latex thread, and particularly relates to a high-elasticity flame-retardant latex thread and a preparation method thereof. BACKGROUND

[0002] Natural rubber latex is a kind of macromolecular environment-friendly material collected from rubber trees, and is widely used in various fields of production and life.

[0003] Latex thread is a high-elasticity thread-like latex product prepared by mixing natural concentrated latex as a main raw material (main component is cis-polyisoprene), titanium dioxide, kaolin and various organic and inorganic raw materials, and then by acid coagulation, washing, drying and vulcanization. It is a linear elastic body with a circular cross section, has fiber morphology and elastic function, and has the characteristics of good tear resistance and ductility, high tensile strength, good heat preservation performance, high softness, wear resistance, durability and strong antibacterial performance, and is widely used in the fields of textiles, sports and medical treatment.

[0004] However, the traditional latex product has the problems of poor tensile strength, no fireproofing, insulation and the like, which limits its higher-level application. Whether the latex thread prepared from pure rubber or a blend is highly flammable, and when burning, it releases toxic gases and a large amount of smoke. Therefore, in order to meet the requirements of flame-retardant latex thread used in different scenarios, higher requirements and expectations are put forward for it.

[0005] In view of this, the patent with the application publication number CN203295722U discloses a latex thread with flame-retardant function, which mainly coats an elastic fiber layer on the base layer of the latex thread, and coats a flame-retardant fiber layer on the elastic fiber layer, so that the latex thread has the function of flame retardation. And the elastic fiber layer and the base layer of the latex thread, and the flame-retardant fiber layer and the elastic fiber layer are connected together by flame-retardant viscose fibers. However, it fails to consider the wear resistance of the flame-retardant layer of the latex thread in actual use. It also fails to consider the tensile of the latex thread and the negative influence of the flame-retardant performance of the latex thread.

[0006] In addition, the patent with the application publication number CN203382907U also discloses a water-blocking and air-permeable flame-retardant latex thread. The patent coats a layer of air-permeable but water-impermeable polyester film layer on the outer surface of the latex thread strip, and a layer of nano flame-retardant film layer is arranged on the outer surface of the polyester film layer. The nano flame-retardant film layer is a halogen-free electronic flame-retardant film synthesized by using nano inorganic silicate and phosphorus-nitrogen compound as a flame retardant and polyurethane material as a structure. However, the process of this nano flame-retardant film is relatively complex and has high processing cost, and the process conditions need to be accurately controlled. In addition, the problem of balance between flame retardation and mechanical properties is difficult to solve, and the problem of precipitation or decomposition in the process of long-term use may occur, resulting in a decrease in the flame-retardant performance. SUMMARY

[0007] The present application aims to provide a high-elasticity flame-retardant latex thread and a preparation method thereof, which has the characteristics of high elasticity and flame retardation.

[0008] The present application can be achieved by the following technical solutions. A high-elasticity flame-retardant latex thread comprises inert materials and active materials; the inert materials comprise the following components in parts by weight: 100 parts of concentrated latex; 2-3 parts of potassium hydroxide solution; 0.5-2 parts of accelerator MZ; 2-5 parts of kaolin; 1-3 parts of sulfur; 1-3 parts of oleic acid; 1-5 parts of antioxidant; 20-60 parts of flame retardant; and 1-3 parts of phytic acid; The active materials comprise the following components: 2-3 parts of potassium hydroxide solution; 0.5-2 parts of accelerator BZ; and 3-5 parts of zinc oxide.

[0009] Preferably, the concentrated latex is liquid natural latex.

[0010] Preferably, the concentration of the potassium hydroxide solution in the inert materials is 25-35%, and the concentration of the potassium hydroxide solution in the active materials is 15-25%.

[0011] The accelerator MZ is 2-mercaptobenzothiazole zinc salt, which has a high vulcanization critical temperature of 138℃, a wide vulcanization flatness, is not prone to early vulcanization, has a moderate vulcanization speed, meets the characteristics of quasi-ultra-speed accelerator, and has quasi-ultra-speed characteristics. The accelerator MZ contains an acidic group in its chemical structure, is a thiazole accelerator in nature, has the characteristics of acidic accelerator, and plays a role in promoting the crosslinking vulcanization reaction of natural rubber.

[0012] The accelerator BZ is zinc dibutyl dithiocarbamate, which is an ultra-ultra-speed accelerator and an acidic accelerator. It has the characteristics of high activity, fast vulcanization speed, and short induction period. In the present technical solution, the accelerator BZ is added mainly to work together with the accelerator MZ to promote the crosslinking vulcanization reaction of natural rubber.

[0013] As a preferred technical solution of the present application, the flame retardant is red phosphorus coated with melamine.

[0014] Red phosphorus itself is a high-efficiency phosphorus flame retardant without halogen, and melamine is a typical nitrogen flame retardant. After being coated, the two form a "phosphorus-nitrogen synergistic effect". The polyphosphoric acid generated by red phosphorus can catalyze the cross-linking of the melamine decomposition product to form a more compact and heat shock-resistant carbon layer, which can more effectively block the transfer of heat and oxygen to the inside of the substrate and reduce the molten dripping. The inert gas released by the high-temperature decomposition of melamine can form a "gas phase + condensed phase" dual flame retardant system with the condensed phase flame retardant of red phosphorus, further improve the limiting oxygen index of the substrate, reduce the heat release rate, and meet higher flame retardant grades. On the other hand, pure red phosphorus has low surface polarity and poor hydrophilicity, and when mixed with a polar substrate, it is prone to "agglomeration", resulting in uneven dispersion. The molecular structure of melamine contains multiple amino groups, which have high polarity. After being coated, the surface of the red phosphorus particles is modified by melamine, which can be uniformly dispersed in the substrate to avoid agglomeration and enhance the bonding force between the flame retardant and the substrate.

[0015] As a preferred technical solution of the present application, the phytic acid is myo-inositol hexakisphosphate. Myo-inositol hexakisphosphate is an organic phosphorus compound extracted from plant seeds, with a phosphorus content as high as 28%. It can act as an acid source and carbon source, and synergize with other substances to exhibit high-efficiency flame retardant performance. Therefore, it is a high-efficiency bio-based phosphorus-containing flame retardant.

[0016] As a preferred technical solution of the present application, the particle size of the kaolin, sulfur and zinc oxide is 1-10 microns.

[0017] Specifically, the kaolin, sulfur and zinc oxide are ground to a particle size of 1-10 microns by a ball mill. The grinding balls in the ball mill are cobalt dioxide with a diameter of 2 mm.

[0018] Among them, kaolin mainly acts as a synergistic flame-retardant filler in rubber, which is economical and efficient. At the same time, kaolin can also produce synergistic effect with melamine-coated red phosphorus, phytic acid and other flame retardants, further improving the flame retardant performance of the latex thread, reducing the smoke release amount, and making the latex thread safer during combustion. Sulfur, as a vulcanizing agent in the vulcanization system of natural rubber, plays a cross-linking role in rubber. Zinc oxide, as a vulcanization activator, can react with sulfur and accelerators to form a more active vulcanization system, and make the cross-linking degree of the latex thread more uniform, thereby improving its heat resistance, wear resistance and aging resistance.

[0019] Further, the oleic acid is a fatty acid containing an unsaturated double bond. In this way, it plays a role in lubricating the rubber molecular chain and improving the flexibility of the latex thread.

[0020] Further, the antioxidant is a p-cresol and dicyclopentadiene butylated reactant, which is used in combination with oleic acid to prevent the oxidation of oleic acid and accelerate the aging of rubber.

[0021] Among them, p-cresol and dicyclopentadiene butylated reactant is an important polymeric hindered phenolic antioxidant, also known as antioxidant 616, antioxidant TH-CPL or antioxidant-SD, etc., CAS number 68610-51-5.

[0022] The preparation method of the above-mentioned high-elasticity flame-retardant latex yarn includes the following steps: S1. Mix the inert materials and stir for the first time, then add the active materials except acetic acid and stir for the second time to obtain the flame-retardant mixed latex. S2. Using the acid coagulation molding method, gravity is used to make the flame-retardant mixed latex flow, forming a continuous thin liquid stream. Then, the latex is solidified from a liquid state into filaments by the action of acid, thus obtaining latex filaments.

[0023] Furthermore, in step S1, the initial stirring speed is 150-400 rpm, and the stirring time is 30-150 minutes; the second stirring speed is 200-500 rpm, and the stirring time is 90-200 minutes.

[0024] Further, in step S2, the acid is acetic acid with a mass percentage of 25-35%.

[0025] Furthermore, in step S2, after the latex is solidified from a liquid state into filaments by the action of acid, the following steps are also included: washing the latex filaments in warm water, and then placing them in an oven for vulcanization and drying to obtain flame-retardant latex filaments. The oven temperature is 110-125℃, and the time is 8-15 minutes.

[0026] The addition of potassium hydroxide helps maintain the alkaline pH of the natural rubber latex, thus keeping the flame-retardant blended latex in a stable liquid state. This improves flowability during processing and makes the preparation of latex fibers smoother. Potassium hydroxide may affect the form of phytic acid, causing it to react and form phytates. These phytates may more effectively promote the formation of a char layer during combustion, producing a stronger synergistic flame-retardant effect. Furthermore, the generated phytates may act as a filler, uniformly dispersed in the latex matrix, providing reinforcement and improving the tensile and tear strength of the latex fibers. Additionally, potassium hydroxide may alter the surface properties of the melamine-coated red phosphorus coating, making it easier to release active phosphorus free radicals, thereby enhancing the flame-retardant effect.

[0027] The beneficial effects of this invention are: (1) In the preparation of the flame-retardant latex thread, the concentrated latex adopts natural liquid latex, and the flame retardant adopts melamine-coated red phosphorus. The melamine-coated red phosphorus has high flame-retardant efficiency, high phosphorus content, and can release more active phosphorus free radicals during combustion to capture H、HO free radicals in the combustion flame, cut off the oxidation chain reaction of the flame, thereby effectively inhibiting combustion. Compared with other flame retardants, the same flame-retardant grade can be achieved with relatively less melamine-coated red phosphorus. Adding a small amount of the flame retardant to the latex thread can significantly improve the oxygen index of the latex thread and effectively prevent the spread of fire. On the other hand, the melamine resin has good film-forming property and flexibility, and can tightly wrap the red phosphorus particles, improving the compatibility of red phosphorus and natural liquid latex. This makes the melamine-coated red phosphorus more uniformly dispersed in the latex thread, reduces the segregation and sedimentation phenomenon, and makes the flame-retardant performance of the latex thread more uniform and stable, while also helping to maintain the mechanical properties of the latex thread.

[0028] (2) In the preparation of the flame-retardant latex thread, phytic acid and melamine-coated red phosphorus are used together. Phytic acid contains multiple phosphoric acid groups and has a high phosphorus content. During combustion, it can decompose to produce non-combustible substances such as phosphoric acid and polyphosphoric acid, which can cover the surface of the latex thread and insulate the transmission of oxygen and heat. In combination with melamine-coated red phosphorus, it can work in both the gas phase and the condensed phase, producing a synergistic flame-retardant effect. Due to the synergistic effect between phytic acid and melamine-coated red phosphorus, the total amount of flame retardant can be reduced under the premise of achieving the same flame-retardant effect. This not only reduces costs, but also reduces the impact of flame retardants on the performance of natural liquid latex, helping to maintain the original characteristics of the latex thread such as mechanical properties and elasticity. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The figure is the mechanical property test result of examples 1-3 and examples 5-7. DETAILED DESCRIPTION

[0030] To further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following embodiments are combined to explain the specific embodiments, structures, features and effects according to the present application in detail.

[0031] Example 1 A high-elasticity flame-retardant latex thread includes inert materials and active materials. The inert materials include the following components by weight: The present embodiment also provides a preparation method of the flame-retardant latex thread, which includes the following steps: S1, various raw materials are weighed according to the proportion, then the inert materials are sequentially added into the container for the first stirring, the rotating speed of the first stirring is 200 rpm, and the stirring time is 120 minutes; then the active materials except for the acetic acid are sequentially added for the second stirring, the rotating speed of the second stirring is 300 rpm, and the stirring time is 150 minutes, and the flame-retardant mixed latex is obtained; S2, the acetic acid is added into the acetic acid tank, then the flame-retardant mixed latex is placed in the machine, and the acid setting forming method is used to make the flame-retardant mixed latex flow by gravity to form a continuous and slender liquid flow, then the latex yarn sequentially passes through the acetic acid tank for acid setting, so that the latex is solidified from liquid into a filamentous shape, and the latex yarn is obtained; S3, the latex yarn is washed in warm water, and then is placed in an oven at 120 DEG C for vulcanization drying for 12 minutes, and the final flame-retardant latex yarn product is obtained.

[0032] Example 2 A high-elasticity flame-retardant latex yarn comprises inert materials and active materials; the inert materials comprise the following components in parts by weight: The preparation method is the same as that of Example 1.

[0033] Example 3 A high-elasticity flame-retardant latex yarn comprises inert materials and active materials; the inert materials comprise the following components in parts by weight: The preparation method is the same as that of Example 1.

[0034] Example 4 The difference between the present example and Example 1 is that the flame-retardant additive amount of the present example is 60 parts by weight, and the phytic acid additive amount is 0. The preparation method is the same as that of Example 1.

[0035] Example 5 The difference between the present example and Example 1 is that the flame-retardant additive amount of the present example is 40 parts by weight, and the phytic acid additive amount is 0. The preparation method comprises the following steps: S1, various raw materials are weighed according to the proportion, then the inert materials are sequentially added into the container for the first stirring, the rotating speed of the first stirring is 200 rpm, and the stirring time is 120 minutes; then the active materials except for the acetic acid are sequentially added for the second stirring, the rotating speed of the second stirring is 300 rpm, and the stirring time is 150 minutes, and the flame-retardant mixed latex is obtained; S2, the acetic acid is added into the acetic acid tank, then the flame-retardant mixed latex is placed in the machine, and the acid setting forming method is used to make the flame-retardant mixed latex flow by gravity to form a continuous and slender liquid flow, then the latex yarn sequentially passes through the acetic acid tank for acid setting, so that the latex is solidified from liquid into a filamentous shape, and the latex yarn is obtained; S3, the latex yarn is washed in warm water, and then is placed in an oven at 115°C for vulcanization drying for 15 minutes to obtain the final flame-retardant latex yarn product.

[0036] Example 6 The difference between this example and Example 1 is that the flame retardant additive amount of this example is 20 parts by weight, and the addition amount of phytic acid is 0. The preparation method comprises the following steps: S1, various raw materials are weighed according to the proportion, and then the inert materials are sequentially added into the container for primary stirring, the stirring speed is 150 rpm, and the stirring time is 90 minutes; then the active materials except for acetic acid are sequentially added for secondary stirring, the stirring speed is 250 rpm, and the stirring time is 120 minutes, to obtain the flame-retardant mixed latex; S2, the acetic acid is added into the acetic acid tank, and then the flame-retardant mixed latex is placed in the machine, and by using the acid coagulation forming method and gravity, the mixed latex is flowed to form a continuous and slender liquid flow, and then the latex yarn sequentially passes through the acid coagulation tank to solidify the latex from liquid into a filamentous shape, to obtain the latex yarn; S3, the latex yarn is washed in warm water, and then is placed in an oven at 112°C for vulcanization drying for 13 minutes to obtain the final flame-retardant latex yarn product.

[0037] Example 7 The difference between this example and Example 1 is that the flame retardant additive amount of this example is 0, and the addition amount of phytic acid is 0. The preparation method comprises the following steps: S1, various raw materials are weighed according to the proportion, and then the inert materials are sequentially added into the container for primary stirring, the stirring speed is 150 rpm, and the stirring time is 60 minutes; then the active materials except for acetic acid are sequentially added for secondary stirring, the stirring speed is 250 rpm, and the stirring time is 120 minutes, to obtain the mixed latex; S2, the acetic acid is added into the acetic acid tank, and then the mixed latex is placed in the machine, and by using the acid coagulation forming method and gravity, the mixed latex is flowed to form a continuous and slender liquid flow, and then the latex yarn sequentially passes through the acid coagulation tank to solidify the latex from liquid into a filamentous shape, to obtain the latex yarn; S3, the latex yarn is washed in warm water, and then is placed in an oven at 112°C for vulcanization drying for 13 minutes to obtain the final flame-retardant latex yarn product.

[0038] (1) According to GB / T2406.2-2009, the flame-retardant performance of Examples 1-7 is tested, and the test results are shown in Table 1.

[0039] Table 1 LOI is commonly used to evaluate the macroscopic combustion performance of composite materials. As shown in Table 1, among Examples 1-7, Example 7 is a blank control group without added flame retardants, consisting of pure latex fibers. It has the lowest LOI content, only 18.5%, and produces a large amount of thick black smoke during combustion, accompanied by numerous molten droplets. Therefore, pure latex fibers exhibit the worst flame retardant performance.

[0040] Compared to the pure latex filaments of Example 7, Examples 1-6 contain melamine-coated red phosphorus as a flame retardant. Furthermore, as the weight percentage of the flame retardant increases, the LOI index of the latex filaments rises, and the smoke and dripping during combustion are significantly reduced. This demonstrates that the melamine-coated red phosphorus in this technical solution provides a significant flame-retardant effect.

[0041] Compared with Examples 4-6, Examples 1-3 achieved an LOI index of over 29.0 with a lower amount of flame retardant added, indicating that phytic acid and melamine-coated red phosphorus have a synergistic flame retardant effect in natural rubber.

[0042] (2) Referring to GB / T528-2009, mechanical property tests were conducted on Examples 1-3 and 5-7 respectively, and the test results are as follows: Figure 1 As shown.

[0043] from Figure 1 It can be seen that the pure latex filament in Example 7 exhibits the best tensile strength and elongation at break; while in Example 1, the latex filament with 30 parts flame retardant and 3 parts phytic acid added shows relatively good tensile strength and elongation at break, demonstrating the best overall performance; the tensile strength of Examples 2-3 is lower than that of Example 1, but the elongation at break is better than that of Example 1, and the overall performance is also relatively good. This indicates that the flame retardant and phytic acid in this technical solution have a synergistic effect, ensuring excellent mechanical properties while maintaining flame retardant performance.

[0044] Example 5, with the addition of 40 parts of flame retardant, showed significantly lower tensile strength than Examples 1-3, but slightly better elongation at break than Examples 1 and 2. Example 6, with the addition of 20 parts of flame retardant, had lower tensile strength than Example 5, but slightly better elongation at break than Examples 5 and Examples 1-3. In other words, in Examples 5 and 6, the tensile strength of the latex filaments decreased with decreasing amounts of flame retardant, indicating that using melamine-coated red phosphorus as a flame retardant resulted in superior mechanical properties.

[0045] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, as long as the changes or modifications do not deviate from the technical solution of the present application. Any modification, change, equivalent change and modification of the above embodiments made according to the technical essence of the present application still belong to the scope of the technical solution of the present application.

Claims

1. A highly elastic flame-retardant latex filament, comprising an inert material and an active material; The inert material comprises the following components by weight: 100 parts concentrated latex; 2-3 parts potassium hydroxide solution; Accelerator MZ 0.5-2 parts; 2-5 parts of kaolin; 1-3 parts sulfur; 1-3 parts oleic acid; Antioxidant 1-5 parts; 20-60 parts flame retardant; and Phytic acid 1-3 parts; The active material comprises the following components: 2-3 parts potassium hydroxide solution; Accelerator BZ 0.5-2 parts; and 3-5 parts zinc oxide.

2. The high-elasticity flame-retardant latex filament according to claim 1, characterized in that, The concentrated latex is a liquid natural latex, the concentration of potassium hydroxide solution in the inert material is 25-35%, and the concentration of potassium hydroxide solution in the active material is 15-25%.

3. The high-elasticity flame-retardant latex filament according to claim 1, characterized in that, The flame retardant is melamine-coated red phosphorus.

4. The high-elasticity flame-retardant latex filament according to claim 1, characterized in that, The phytic acid is inositol hexaphosphate.

5. The high-elasticity flame-retardant latex filament according to claim 1, characterized in that, The kaolin, sulfur, and zinc oxide have a particle size of 1-10 micrometers.

6. The high-elasticity flame-retardant latex filament according to claim 1, characterized in that, The oleic acid is a fatty acid containing unsaturated double bonds.

7. The high-elasticity flame-retardant latex filament according to claim 1, characterized in that, The antioxidant is a product of the reaction of p-cresol and dicyclopentadiene butylation.

8. A method for preparing a highly elastic flame-retardant latex filament as described in any one of claims 1-7, characterized in that, The preparation method includes the following steps: S1. Mix the inert materials and stir for the first time, then add the active materials except acetic acid and stir for the second time to obtain the flame-retardant mixed latex. S2. Using the acid coagulation molding method, gravity is used to make the flame-retardant mixed latex flow, forming a continuous thin liquid flow. Then, the latex is solidified from a liquid state into filaments by the action of acid, thus obtaining latex filaments.

9. The method for preparing highly elastic flame-retardant latex yarn according to claim 8, characterized in that, In step S1, the initial stirring speed is 150-400 rpm and the stirring time is 30-150 minutes; the second stirring speed is 200-500 rpm and the stirring time is 90-200 minutes.

10. The method for preparing highly elastic flame-retardant latex yarn according to claim 8, characterized in that, In step S2, the acid is acetic acid with a mass percentage of 25-35%; After the latex is solidified from a liquid state into filaments by the action of acid, the following steps are also included: washing the latex filaments in warm water, and then placing them in an oven for vulcanization and drying to obtain flame-retardant latex filaments.

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