A flame retardant and smoke suppressant for PVC and its preparation method

Abstract

The present invention discloses a flame retardant and smoke suppressant for PVC and its preparation method. In the present invention, magnesium oxide reacts with water to generate a magnesium hydroxide solution (active solution). In this solution system, zinc oxide and calcium oxide are further added to react with boric acid to form a calcium zinc borate and magnesium hydroxide composite, achieving the effect of high-efficiency flame retardancy and smoke suppression. Experiments have proved that the use of this flame retardant and smoke suppressant can significantly reduce the smoke density when PVC products burn, and the smoke suppression efficiency can be increased by more than 10%; at the same time, it can also endow PVC products with good flame retardant properties and excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to a flame retardant and smoke suppressant for PVC and a preparation method thereof, belonging to the technical field of inorganic material synthesis. Background Art

[0002] Polyvinyl chloride (PVC) is the second largest general-purpose plastic. Due to its excellent electrical properties, chemical corrosion resistance, high mechanical properties, low price, rich raw material sources, and mature manufacturing processes, it is widely used in light industry, machinery, electronics, construction, textiles, aerospace and other fields. However, when PVC is heated and burned, it will decompose a large amount of toxic gases such as hydrogen chloride and benzene compounds, and produce a large amount of smoke. Once a fire occurs, it will bring difficulties to fire fighting, evacuation, life-saving and other work. Therefore, the flame retardancy and smoke suppression of PVC materials are an important research hotspot in the application field of PVC.

[0003] In the prior art, the flame retardants applied to PVC mainly include halogen-antimony synergistic flame retardants, phosphorus-nitrogen flame retardants, inorganic aluminum-magnesium flame retardants, etc. The halogen-antimony synergistic flame retardants have good flame retardant properties, but will increase the smoke generation amount during combustion and have a relatively high price; although flame retardants such as phosphorus-nitrogen flame retardants and inorganic aluminum-magnesium flame retardants have good flame retardant effects, they have a greater impact on the mechanics of materials. Hydrotalcite series compounds, transition metal oxides in inorganic substances and some other metal oxides such as zinc oxide, copper oxide, cobalt oxide, molybdenum oxide, etc. all have flame retardant and smoke elimination effects on PVC, but have poor compatibility with polymers and have a greater impact on the mechanical properties of PVC.

[0004] CN1583869A discloses a PVC flame retardant and smoke suppressant, PVC prepared therefrom and a preparation method thereof. The main components of the PVC flame retardant and smoke suppressant are molybdenum oxide (MoO 3 ), antimony trioxide (Sb 2 O 3 ), zinc borate (ZB) and an interface enhancer. The flame retardant and smoke suppression properties of the PVC product obtained by adding this flame retardant and smoke suppressant to the PVC resin are greatly improved.

[0005] CN103113688A discloses a flame retardant and smoke suppressant for PVC materials, a preparation method thereof and an application. The flame retardant and smoke suppressant is composed of the following components in parts by weight: 2-15 parts of aluminum hydroxide, 0.5-5 parts of ammonium octamolybdate, 0.5-4 parts of zinc borate, 0.5-5 parts of zinc molybdate, 0.5-4 parts of zinc oxide, 0.01-0.10 parts of stearic acid, and it has good flame retardant properties and excellent smoke control performance.

[0006] CN108102145A discloses a preparation method of a supported hydrotalcite-based flame retardant and heat stabilizer and a PVC product, which is carried out as follows: Dissolve 4.5 - 7.5 parts of a surface modifier in absolute ethanol, and then put 100 - 120 parts of magnesium-aluminum hydrotalcite and 30 - 50 parts of brucite into a ball milling tank. After grinding, dry it in an oven to obtain the supported hydrotalcite-based flame retardant and heat stabilizer.

[0007] The above patents all use transition metal oxides such as molybdenum, antimony, zinc or hydrotalcite for flame retardancy and smoke suppression, which have the problem of poor compatibility with polymers and need to adopt certain measures to improve their compatibility. Therefore, it is of great significance to find a flame retardant for PVC that not only has flame retardancy and smoke suppression performance but also has little impact on the mechanical properties of materials. Summary of the Invention

[0008] In order to solve the problems of "poor flame retardancy and smoke suppression performance and / or seriously affecting the mechanical properties of materials" that occur in the application of existing flame retardants in PVC materials, the present invention provides a flame retardant and smoke suppressant for PVC and its preparation method. This method uses the reaction of magnesium oxide and water to generate magnesium hydroxide solution (active solution). In this solution system, zinc oxide and calcium oxide are further added to react with boric acid to generate a calcium zinc borate and magnesium hydroxide complex, achieving the effect of efficient flame retardancy and smoke suppression. Compared with traditional physically compounded products, the components of this product are more evenly distributed, have better compatibility with the substrate, and have less impact on the mechanical properties of the substrate.

[0009] The technical solution of the present invention is: A preparation method of a flame retardant and smoke suppressant for PVC, comprising the following steps:

[0010] 1) Hydrate magnesium oxide with water at 80 - 90 °C for 8 - 10 h to obtain a magnesium hydroxide reaction solution;

[0011] 2) At 40 - 50 °C, add boric acid to the magnesium hydroxide reaction solution. After it is completely dissolved and clarified, add zinc oxide, calcium oxide and a modifier in sequence. After stirring evenly, adjust the pH of the system to 5 - 6, heat up to 95 - 105 °C, and react at a constant temperature for 2 - 4 h; then add boric acid again and continue to react for 6 - 10 h. After filtration, washing, drying and sieving, obtain the flame retardant and smoke suppressant for PVC.

[0012] Further, the preparation method of the magnesium oxide is: Calcinate type I magnesium hydroxide in a muffle furnace at 700 - 900 °C to obtain well-crystallized magnesium oxide; wherein the particle size (D 50 ) of type I magnesium hydroxide is 1 - 2 μm and the content is above 98%.

[0013] The mass ratio of the above magnesium oxide, zinc oxide, calcium oxide and boric acid (in total) is 1:1 - 2.4:0.25 - 0.6:5 - 8.

[0014] In the above step 1), the mass ratio of magnesium oxide to water is 1:15 - 25, preferably 1:20.

[0015] In the above step 2), the mass ratio of the first addition amount of boric acid to the second addition amount of boric acid is 1.8 - 2.2:1, preferably 2:1.

[0016] In the above step 2), the modifier is one or more of sodium dodecylbenzenesulfonate, disodium ethylenediaminetetraacetate, vinyltris(β - methoxyethoxy)silane, and sodium citrate, and the dosage of the modifier is 1% - 3% of the mass of magnesium oxide.

[0017] No by - products are produced in the above reaction, and the mother liquor can be recycled.

[0018] The flame - retardant and smoke - suppressing agent for PVC prepared by the above preparation method has product performance indicators as shown in Table 1.

[0019] Table 1 Indicators of the product of the present invention

[0020] Project Index Appearance White powder Boron oxide w / % 39.9-45.7 Zinc oxide w / % 13.5-23.3 Calcium oxide w / % 4.81-5.5 Magnesium oxide w / % 9.4-16.8 Moisture w / % ≤0.3 Whiteness / % 96-99

[0021] The flame - retardant and smoke - suppressing mechanism of the present invention is as follows:

[0022] 1) Magnesium hydroxide solution is generated by the reaction of magnesium oxide and water. At this time, the solution is an active solution. In this solution system, zinc oxide and calcium oxide react with boric acid to form a calcium zinc borate and magnesium hydroxide complex.

[0023] 2) When PVC burns, this flame - retardant material can produce a large amount of substances that inhibit free - radical chain reactions and a high - boiling - point solid (Zn / CaCl 2 ) covering layer, reducing the combustion performance and smoke production of the material.

[0024] 3) The synergistic effect of calcium, zinc, and magnesium metal ions is utilized to make up for each other's deficiencies and improve the flame - retardant efficiency. The main manifestations are as follows: The water vapor formed by magnesium hydroxide dilutes the oxygen concentration on the surface of the combustible, significantly inhibiting the combustion of the combustible. However, the magnesium hydroxide covering layer formed after the dehydration of magnesium hydroxide is not continuous, while the glassy foam structure formed after the dehydration of borate flame - retardants can make it continuous. In this way, it can not only isolate air well but also play a role in heat insulation and smoke suppression. Moreover, due to the fast thermal decomposition rate of this flame - retardant and smoke - suppressing agent during combustion, the heat absorption capacity is enhanced, thereby reducing the surface temperature of the combustible and more quickly inhibiting the combustion reaction.

[0025] 4) The modifier added during the preparation of the product of the present invention utilizes the charge interaction or steric hindrance repulsion between particles. First, it can weaken the agglomeration of inorganic particles. Second, through the interaction of van der Waals forces, hydrogen bonds, or coordination bonds, the compatibility between the product and the resin substrate is improved, making the product more uniformly dispersed in the substrate.

[0026] The technical effects of the present invention are as follows: The halogen-free flame retardant and smoke suppressant of the present invention is environmentally friendly and pollution-free, and has both flame retardant performance and smoke suppression performance for PVC. Compared with traditional physically compounded products, the components of this product are more evenly distributed, and it has better compatibility with the substrate, with less impact on the mechanical properties of the substrate. It has been proven by experiments that when the halogen-free flame retardant and smoke suppressant of the present invention is applied to PVC, with a relatively small amount added, compared with flame retardant products or their composites such as hydrotalcite, magnesium hydroxide, zinc borate, and antimony trioxide, the smoke density during the combustion of PVC products can be significantly reduced, and the smoke suppression efficiency can be increased by more than 10%. At the same time, it can also endow PVC products with good flame retardant performance and excellent mechanical properties. Specific embodiments

[0027] Example 1:

[0028] 1) Calcinate type I magnesium hydroxide in a muffle furnace at 800 °C to obtain well-crystallized magnesium oxide. Add 10 Kg of water to a 20 L reaction kettle, heat to 85 °C, and then add 0.5 Kg of magnesium oxide for hydration reaction. After reacting at a constant temperature for 9 h, a magnesium hydroxide reaction solution is obtained.

[0029] 2) Add 2 Kg of boric acid to the magnesium hydroxide reaction solution at 40 °C. After it is completely dissolved and clarified, add 730 g of zinc oxide, 182.5 g of calcium oxide, and 7.5 g of sodium dodecylbenzenesulfonate in sequence, stir evenly. After stirring evenly, adjust the pH of the system to 5.5 with sodium hydroxide (concentration 0.1 mol / L), raise the temperature to 102 °C, react at a constant temperature for 2 h, then add 1 Kg of boric acid, continue to react for 8 h, then filter, wash, dry, and pass through a 325-mesh sieve to obtain the required flame retardant and smoke suppressant for PVC.

[0030] Example 2:

[0031] 1) Calcinate type I magnesium hydroxide in a muffle furnace at 850 °C to obtain well-crystallized magnesium oxide. Add 10 Kg of water to a 20 L reaction kettle, heat to 88 °C, and then add 0.5 Kg of magnesium oxide for hydration reaction. After reacting at a constant temperature for 10 h, a magnesium hydroxide reaction solution is obtained.

[0032] 2) Add 2.5 Kg of boric acid to the magnesium hydroxide reaction solution at 50 °C. After it is completely dissolved and clarified, add 950 g of zinc oxide, 237.5 g of calcium oxide, and 10 g of disodium ethylenediaminetetraacetate in sequence, stir evenly. After stirring evenly, adjust the pH of the system to 5.5 with sodium hydroxide (concentration 0.1 mol / L), raise the temperature to 102 °C, react at a constant temperature for 3 h, then add 1.25 Kg of boric acid, continue to react for 8 h, then filter, wash, dry, and perform sieving treatment to obtain the required flame retardant and smoke suppressant for PVC.

[0033] Example 3:

[0034] 1) Calcinate type I magnesium hydroxide in a muffle furnace at 750 °C to obtain well-crystallized magnesium oxide; add 10 Kg of water to a 20 L reaction kettle, heat to 83 °C, and then add 0.5 Kg of magnesium oxide for hydration reaction. After reacting at a constant temperature for 8 h, obtain a magnesium hydroxide reaction solution.

[0035] 2) Add 2.4 Kg of boric acid to the magnesium hydroxide reaction solution at 48 °C. After it is completely dissolved and clarified, add 900 g of zinc oxide, 225 g of calcium oxide, and 12.5 g of sodium citrate in sequence, stir evenly, and then adjust the pH of the system to 6 with sodium hydroxide (concentration 0.1 mol / L). Heat to 98 °C and react at a constant temperature for 2.5 h. Then add 1.2 Kg of boric acid and continue to react for 10 h. After filtration, washing, drying, and sieving, the required flame retardant and smoke suppressant for PVC can be obtained.

[0036] Example 4:

[0037] 1) Calcinate type I magnesium hydroxide in a muffle furnace at 800 °C to obtain well-crystallized magnesium oxide; add 10 Kg of water to a 20 L reaction kettle, heat to 85 °C, and then add 0.5 Kg of magnesium oxide for hydration reaction. After reacting at a constant temperature for 9 h, obtain a magnesium hydroxide reaction solution.

[0038] 2) Add 1.8 Kg of boric acid to the magnesium hydroxide reaction solution at 45 °C. After it is completely dissolved and clarified, add 640 g of zinc oxide, 160 g of calcium oxide, and 6 g of a 1:1 mass ratio mixture of sodium dodecylbenzenesulfonate and vinyltris(β-methoxyethoxy)silane in sequence, stir evenly, and then adjust the pH of the system to 5 with sodium hydroxide (concentration 0.1 mol / L). Heat to 100 °C and react at a constant temperature for 3.5 h. Then add 0.9 Kg of boric acid and continue to react for 7 h. After filtration, washing, drying, and sieving, the required flame retardant and smoke suppressant for PVC can be obtained.

[0039] Application Example

[0040] Apply the products of Examples 1 - 4 of the present invention and the products of Comparative Examples 1 - 5 to PVC at an addition amount of 5% respectively. Among them, Comparative Examples 1 - 5 are respectively adding hydrotalcite, magnesium hydroxide, zinc borate, antimony trioxide, and a magnesium-zinc 1:1 composite formula. The experimental formulas and the test results of flame retardancy, mechanical properties, and smoke density are shown in Table 2.

[0041] Table 2 shows the comparison of the application effects of different flame retardant products

[0042]

[0043]

[0044] As can be seen from Table 2, in PVC, with the same addition amount, the flame retardancy and smoke suppression performance of the product of the present invention are superior to those of products such as hydrotalcite, magnesium hydroxide, zinc borate and antimony trioxide. The smoke density of PVC products can be reduced by more than 10% year-on-year, and the mechanical properties of the PVC substrate are least affected under the same conditions.

Claims

1. Preparation method of flame retardant and smoke suppressant for PVC, characterized in that, it includes the following steps: 1) Add water to magnesium oxide and carry out a hydration reaction at 80 - 90 °C for 8 - 10 h to obtain a magnesium hydroxide reaction solution; 2) At 40 - 50 °C, add boric acid to the magnesium hydroxide reaction solution. After it is completely dissolved and clarified, add zinc oxide, calcium oxide and a modifier in sequence. After stirring evenly, adjust the pH of the system to 5 - 6, raise the temperature to 95 - 105 °C, and carry out a constant temperature reaction for 2 - 4 h; Then add boric acid again, continue the reaction for 6 - 10 h, carry out suction filtration, washing, drying and sieving treatment to obtain a flame retardant and smoke suppressant for PVC; The mass ratio of the magnesium oxide, zinc oxide, calcium oxide and boric acid is 1:1 - 2.4:0.25 - 0.6:5 - 8.

2. The preparation method of the flame retardant and smoke suppressant for PVC according to claim 1, characterized in that, the preparation method of the magnesium oxide is: calcine type I magnesium hydroxide in a muffle furnace at 700 - 900 °C to obtain well - crystallized magnesium oxide.

3. The preparation method of the flame retardant and smoke suppressant for PVC according to claim 2, characterized in that, The particle size D of the type I magnesium hydroxide 50 is 1 - 2 μm, and the content is above 98%.

4. The preparation method of the flame retardant and smoke suppressant for PVC according to claim 1, characterized in that, the mass ratio of magnesium oxide and water in step 1) is 1:15 - 25.

5. The preparation method of the flame retardant and smoke suppressant for PVC according to claim 1, characterized in that, the mass ratio of the first addition amount of boric acid and the second addition amount of boric acid in step 2) is 1.8 - 2.2:

1.

6. The preparation method of the flame retardant and smoke suppressant for PVC according to claim 1, characterized in that, the modifier in step 2) is one or more of sodium dodecylbenzenesulfonate, disodium ethylenediaminetetraacetate, vinyltris(β - methoxyethoxy)silane, sodium citrate.

7. The preparation method of the flame retardant and smoke suppressant for PVC according to claim 6, characterized in that, the dosage of the modifier is 1% - 3% of the mass of magnesium oxide.

8. The flame retardant and smoke suppressant for PVC prepared by the preparation method according to any one of claims 1 - 7.

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