Modifying agent and preparation method, modified inorganic flame retardant and preparation method and application

Abstract

The application discloses a modifier, and a molecular structural formula of the modifier is shown in the following formula: the modifier is prepared by adding 3,5-diiodosalicylic acid, gamma-aminopropyl triethoxysilane, an amine ligand, a catalyst, alkali and an organic solvent into a reaction container and reacting in a nitrogen atmosphere. The application further discloses a method for modifying inorganic flame retardants by using the modifier and application of the modified inorganic flame retardants in rubber materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and particularly relates to a modifier and its preparation method, a modified inorganic flame retardant and its preparation method, and its application in rubber materials. Background Technology

[0002] The key to fire prevention lies in the flame retardancy of polymer materials, and the flame retardant performance of polymer materials depends on flame retardants. Inorganic flame retardants containing nitrogen (N) and oxygen (O) are commonly used environmentally friendly flame retardants in polymer materials such as rubber and plastics, including aluminum hydroxide (ATH), magnesium hydroxide (MH), and antimony trioxide (Sb₂O₃). However, due to their strong polarity and hydrophilicity, these inorganic flame retardants are prone to aggregation and are difficult to disperse in polymer materials. Therefore, an addition amount of ≥60wt% is generally required to achieve a certain flame retardant effect, which inevitably leads to a loss of the mechanical properties of polymer materials. Therefore, in order to balance the flame retardancy and mechanical properties of polymer materials, it is urgent to explore methods to improve the flame retardant efficiency of inorganic flame retardants containing N and O.

[0003] Generally, methods to improve the flame retardant efficiency of inorganic flame retardants mainly include compounding, particle ultrafine processing, and chemical modification. Compounding primarily improves flame retardant efficiency through the synergistic effect between different types of flame retardants. Particle ultrafine processing mainly controls the preparation process of raw materials, typically using a hydrothermal method first, followed by processes such as ultrasonication, grinding, and calcination to make the particle size as uniform and ultrafine as possible, thereby obtaining better dispersion performance. Compounding and particle ultrafine processing are mainly physical processes, and their improvement on the flame retardant efficiency of inorganic flame retardants is relatively limited.

[0004] Chemical modification can fundamentally solve the problems of strong hydrophilicity, easy agglomeration, and poor thermal stability of inorganic flame retardants containing N and O elements. Chemical modification requires the use of chemical modifiers, and hydrophilic oxygen-containing small molecules are generally preferred. The main modification methods are dry and wet methods. Dry modification refers to the injection of chemical modifiers into inorganic flame retardant solid particles under high-speed stirring. For example, Lan et al. used methacryloyloxypropyltrimethoxysilane (VTMS) and vinyltriethoxysilane (VTES) to dry modify magnesium hydroxide (MH). After modification, the surface of MH particles changed from hydrophilic to hydrophobic, and the dispersibility and compatibility in the organic phase were significantly improved. In addition, the thermal stability of the modified MH particles was also significantly improved (Lan S, Zhu D, Li L, et al. Surface modification of magnesium hydroxide particles using silanecoupling agent by dry process[J]. Surface and interface analysis,2018,50(3):277-283). Zhu et al. prepared pure aluminum hydroxide (ATH) using Al(NO3)3 as a raw material via a hydrothermal method, and then modified it with ethyl acetoacetate (EAA). The modified ATH was dispersed in n-hexane solvent, ultrasonically treated, dried, ground, and calcined (Zhu L, Pu S, Lu F, et al. Preparation of dispersed aluminum hydroxide nanoparticles via non-aqueous route and surface modification[J]. Materials Chemistry and Physics, 2012, 135(2-3):979-984.). Wet modification involves pre-dispersing an inorganic flame retardant in a specific solvent, and then adding a small molecule modifier for a chemical reaction. For example, Zhang et al. used VTES wet modification of MH. MH was pre-dispersed in water and VTES was added under stirring to obtain VTES-MH. When applied to silicone rubber, it showed excellent flame retardant properties (Zhang W, Li X, Shan Z, et al. Surface modification of magnesiumhydroxide by wet process and effect on the thermal stability of silicone rubber[J]. Applied Surface Science, 2019, 465: 740-746.).

[0005] However, most current chemical modifications of inorganic flame retardants use commercially available small-molecule modifiers. These modifiers have limited functionality and are mainly used to improve the dispersion and thermal stability of inorganic flame retardants. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a modifier and its preparation method, a modified inorganic flame retardant and its preparation method, and its application in rubber materials.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0008] A modifier, the molecular structural formula of which is:

[0009]

[0010] As a general inventive concept, the present invention also provides a method for preparing the above-mentioned modifier, wherein 3,5-diiodosalicylic acid, γ-aminopropyltriethoxysilane, amine ligand, catalyst, base, and organic solvent are added to a reaction vessel and reacted in a nitrogen atmosphere to prepare the modifier.

[0011] In the above preparation method, preferably, the amine ligand is selected from one of dimethylethylenediamine, L-proline, and 1,2-cyclohexanediamine;

[0012] The catalyst is cuprous iodide;

[0013] The alkali is selected from one of potassium carbonate, sodium carbonate, and cesium carbonate;

[0014] The organic solvent is selected from one of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0015] In the above preparation method, preferably, the reaction temperature is 60-120℃ and the reaction time is 12-48h.

[0016] In the above preparation method, preferably, the molar ratio of 3,5-diiodosalicylic acid, γ-aminopropyltriethoxysilane, amine ligand, catalyst, base and organic solvent is 1:(2-3.5):(0.5-1.4):(0.5-1):(3.0-6.5):(50-300).

[0017] In the above preparation method, the synthetic route of the modifier is as follows:

[0018]

[0019] As a general inventive concept, the present invention also provides a modified inorganic flame retardant, which is aluminum hydroxide or magnesium hydroxide modified by the above-mentioned modifier or the modifier prepared by the above-mentioned preparation method.

[0020] As a general inventive concept, the present invention also provides a method for preparing the above-mentioned modified inorganic flame retardant, comprising the following steps:

[0021] (1) Disperse aluminum hydroxide or magnesium hydroxide in water to form an aluminum hydroxide suspension or a magnesium hydroxide suspension;

[0022] (2) Dissolve the above-mentioned modifier or the modifier prepared by any of the above preparation methods in water;

[0023] (3) Add the suspension obtained in step (1) dropwise to the modifier solution obtained in step (2), and heat to 60-80℃ to carry out the reaction;

[0024] (4) After the reaction is complete, filter, wash and dry to obtain the modified flame retardant.

[0025] In the above preparation method, the reaction model for modifying aluminum hydroxide with a modifier is as follows: Figure 1 As shown.

[0026] In the above preparation method, preferably, the mass ratio of the modifier to the aluminum hydroxide is (1-5):50, and the mass ratio of the modifier to the magnesium hydroxide is (1-5):50.

[0027] In the above preparation method, preferably, in step (1), the mass ratio of aluminum hydroxide or magnesium hydroxide to water is 1:(2-6). The specific process of dispersing aluminum hydroxide or magnesium hydroxide in water is as follows: aluminum hydroxide or magnesium hydroxide is added to water, and mechanical stirring and ultrasonic dispersion are carried out simultaneously for 1-2 hours. The mechanical stirring speed is 500-2000 r / min, and the ultrasonic power is 100-300 w.

[0028] In the above preparation method, preferably, in step (3), the reaction time is 5-12h, the reaction is carried out under mechanical stirring and ultrasound, the mechanical stirring speed is 500-2000r / min, and the ultrasound power is 100-300w.

[0029] In the above preparation method, preferably, in step (4), the drying is carried out by vacuum drying, the drying temperature is 20-35℃, and the drying time is 72-96h.

[0030] As a general inventive concept, the present invention also provides the application of the modified inorganic flame retardant described above or obtained by the above preparation method in rubber materials.

[0031] In the above-mentioned applications, preferably, the rubber material is mainly prepared from the following raw materials in parts by weight: 100 parts natural rubber, 40-60 parts modified inorganic flame retardant, 3-10 parts zinc oxide, 1-2 parts stearic acid, 3-10 parts antioxidant, 10-30 parts carbon black, 10-30 parts silica, and 3.0-5.0 parts vulcanization accelerator.

[0032] For the above applications, preferably, the preparation process of the rubber material includes the following steps:

[0033] S1: Add natural rubber to a general rubber mixing equipment at 70-90℃ and break it up for 5-10 minutes;

[0034] S2: Then add zinc oxide, stearic acid, antioxidant, modified inorganic flame retardant, carbon black, and silica, and mix at 90-100℃ for 3-5 minutes.

[0035] S3: Add vulcanization accelerator, mix for 3-5 minutes, mix at 70℃-90℃, then pass through the open mill 3-5 times or make triangular wraps 3-5 times to obtain the two-stage compound.

[0036] S4: After the two-stage compound rubber is left to stand for 16-24 hours, it is subjected to vulcanization treatment to obtain vulcanized rubber. The vulcanization temperature is 150℃ and the vulcanization time is 10min-30min.

[0037] Compared with the prior art, the advantages of the present invention are as follows:

[0038] (1) In the modifier of the present invention, 1 eq of the modifier contains 2 eq of silyl ethoxy, 1 eq of aldehyde, 2 eq of secondary amino, and 1 eq of phenolic hydroxyl, which can be completely dissolved in water. The modifier contains abundant N and O groups, which can achieve hydrogen bond enhancement with aluminum hydroxide and magnesium hydroxide in water, thus enabling wet modification. The aldehyde group can undergo addition reaction with the double bond in natural rubber to improve the dispersibility of aluminum hydroxide and magnesium hydroxide, thereby improving the flame retardant properties of rubber. The phenolic hydroxyl group can improve the antioxidant aging resistance of natural rubber.

[0039] (2) The modifier of the present invention is prepared by wet process technology, which can further enhance hydrogen bonding, facilitate the dispersion of aluminum hydroxide or magnesium hydroxide in rubber, reduce the heat release rate and maximum smoke density of rubber material significantly, greatly improve the flame retardant performance of vulcanized rubber, and solve the problem of poor fatigue performance of flame retardant rubber.

[0040] (3) The modifier of the present invention can enhance the interfacial bonding force between inorganic flame retardants and polymer materials, and can improve the mechanical properties of rubber materials such as hardness, tensile strength, and 300% constant elongation stress.

[0041] (4) The preparation methods of the modifier and the modified inorganic flame retardant of the present invention are simple and easy to operate, have high versatility, can be prepared using organic synthesis instruments and equipment, have high equipment versatility, and have good market application value in the rubber industry. Attached Figure Description

[0042] Figure 1 It is a reaction model of the modifier and aluminum hydroxide.

[0043] Figure 2 This is the NMR spectrum of the modifier prepared in Example 1 of this invention.

[0044] Figure 3 This is the infrared spectrum of the modifier prepared in Example 1 of this invention.

[0045] Figure 4 These are the vulcanization curves of the compound rubber in Example 3 and Comparative Example 1 of this invention. Detailed Implementation

[0046] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0047] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0048] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0049] Example 1:

[0050] A modifier of the present invention has the following molecular structural formula:

[0051]

[0052] The preparation method of the modifier in this embodiment is as follows:

[0053] 3,5-Diiodosalicylic acid (0.01 mol, 3.74 g) and γ-aminopropyltriethoxysilane (0.035 mol, 7.75 g) were placed in a reaction vessel, and cuprous iodide (0.006 mol, 1.14 g), L-proline (0.006 mol, 0.7 g), potassium carbonate (0.06 mol, 8.3 g), and 100 mL of dimethyl sulfoxide (DMSO) were added. After purging the reactor with nitrogen for 30 min, the reactor was heated to 100 °C under a nitrogen atmosphere and stirred for 24 h. After the reaction was completed, the mixture was filtered, the supernatant was collected, the solvent was concentrated, and the mixture was dried at 25 °C for 72 h to obtain the modifier. Its NMR spectrum is shown below. Figure 2 As shown, the infrared spectrum is as follows Figure 3 As shown.

[0054] Example 2:

[0055] A modified inorganic flame retardant of the present invention is prepared by the following method:

[0056] (1) Take 200g of aluminum hydroxide and add it to 500g of distilled water. At the same time, mechanical stirring and ultrasonic dispersion are carried out for 1h. The mechanical stirring speed is 2000r / min and the ultrasonic power is 200w.

[0057] (2) Take 4g of the modifier prepared in Example 1 and dissolve it in 20g of distilled water. After complete dissolution, slowly add it dropwise to the aluminum hydroxide suspension obtained in step (1) and heat it to 60°C. At the same time, mechanical stirring and ultrasonic dispersion are carried out for 12h. The mechanical stirring speed is 2000r / min and the ultrasonic power is 300w.

[0058] (3) After the reaction is complete, the solvent water is removed by filtration and the filter cake is thoroughly washed with distilled water. Then, it is vacuum dried at 30°C for 96 hours to obtain the modified inorganic flame retardant, namely, the wet-modified aluminum hydroxide.

[0059] Example 3:

[0060] The modified inorganic flame retardant (wet-process modified aluminum hydroxide) prepared in Example 2 was applied to rubber. The specific rubber formulation is shown in Table 1. The preparation steps of the rubber are as follows:

[0061] (1) At 70°C, natural rubber is added to a general rubber mixing equipment and broken for 5 minutes;

[0062] (2) Add zinc oxide, stearic acid, antioxidant 6PPD, antioxidant RD, microcrystalline wax, wet-modified aluminum hydroxide, carbon black, and silica, and mix at 90°C for 5 minutes.

[0063] (3) Add sulfur and accelerator CBS and mix. Set the internal mixer temperature to 90℃ and mix for 5 minutes. Then, pass the mixture through the open mill 5 times and sheet it to obtain compound rubber #2.

[0064] (4) After the compound obtained in step (3) is left to stand for 16 hours, vulcanized rubber 2# is prepared according to the vulcanization conditions of vulcanization temperature of 150℃ and vulcanization time of 15min.

[0065] Comparative Example 1:

[0066] The only difference between this comparative example and Example 3 is that the wet-modified aluminum hydroxide is replaced with ordinary aluminum hydroxide. The specific formula is shown in Table 1. The preparation process is the same as in Example 3. The resulting compound is denoted as Compound 1# and the vulcanized rubber is denoted as Vulcanized Rubber 1#.

[0067] Table 1. Rubber formulations (parts by mass) for Example 3 and Comparative Example 1

[0068] raw materials 1# 2# natural rubber 100 100 Zinc oxide 5 5 stearic acid 2 2 6PPD 2 2 RD 2 2 Microcrystalline wax 2 2 carbon black 10 10 precipitate 20 20 Ordinary aluminum hydroxide 50 \ Wet-process modified aluminum hydroxide \ 50 sulfur 2 2 Accelerator CBS 1.3 1.3

[0069] The vulcanization curves of compound 1# in Comparative Example 1 and compound 2# in Example 3 are as follows: Figure 4 As shown, from Figure 4 It can be seen that wet-modified aluminum hydroxide can increase the MH value of rubber and has a certain promoting effect on vulcanization, thus improving vulcanization efficiency.

[0070] The physical and mechanical properties of the vulcanized rubbers prepared in Example 3 and Comparative Example 1 are shown in Table 2. As can be seen from Table 2, compared to vulcanized rubber 1# in Comparative Example 1, vulcanized rubber 2# showed slight improvements in hardness, tensile strength, 300% elongation stress, and antioxidant aging resistance. This indicates that the wet-process modified aluminum hydroxide not only improved the dispersion of fillers in natural rubber but also enhanced the crosslinking density. The heat release rate and maximum smoke density of vulcanized rubber 2# were significantly reduced, indicating that the wet-process modified aluminum hydroxide can significantly improve the flame retardant properties of vulcanized rubber. Furthermore, the fatigue performance of the rubber compound filled with wet-process modified aluminum hydroxide was significantly improved, addressing the problem of poor fatigue performance in flame-retardant rubbers.

[0071] Table 2 Physical and flame retardant properties of vulcanized rubber

[0072]

Claims

1. A modifier, characterized in that, Its molecular structural formula is: 。 2. A method for preparing the modifier as described in claim 1, characterized in that, 3,5-Diiodosalicylic acid, γ-aminopropyltriethoxysilane, amine ligands, catalyst, base, and organic solvent are added to a reaction vessel and reacted under a nitrogen atmosphere to prepare a modifier. The amine ligand is selected from dimethylethylenediamine, L-proline, and 1,2-cyclohexanediamine; the catalyst is cuprous iodide.

3. The preparation method according to claim 2, characterized in that, The alkali is selected from one of potassium carbonate, sodium carbonate, and cesium carbonate; The organic solvent is selected from one of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

4. The preparation method according to claim 2, characterized in that, The reaction temperature is 60-120℃, and the reaction time is 12-48h.

5. The preparation method according to claim 2, characterized in that, The molar ratio of 3,5-diiodosalicylic acid, γ-aminopropyltriethoxysilane, amine ligand, catalyst, base and organic solvent is 1:(2-3.5):(0.5-1.4):(0.5-1):(3.0-6.5):(50-300).

6. A modified inorganic flame retardant, characterized in that, The modified inorganic flame retardant is aluminum hydroxide or magnesium hydroxide modified by the modifier described in claim 1 or prepared by any one of the preparation methods in claims 2 to 5.

7. A method for preparing the modified inorganic flame retardant as described in claim 6, characterized in that, Includes the following steps: (1) Disperse aluminum hydroxide or magnesium hydroxide in water to form an aluminum hydroxide suspension or a magnesium hydroxide suspension; (2) Dissolve the modifier according to claim 1 or the modifier prepared by any one of the preparation methods in claims 2 to 5 in water to form a modifier solution; (3) Add the suspension obtained in step (1) dropwise to the modifier solution obtained in step (2), and heat to 60-80℃ to carry out the reaction; (4) After the reaction is complete, filter, wash and dry to obtain the modified flame retardant.

8. The preparation method according to claim 7, characterized in that, The mass ratio of the modifier to the aluminum hydroxide is (1-5):50, and the mass ratio of the modifier to the magnesium hydroxide is (1-5):

50.

9. The preparation method according to claim 7, characterized in that, In step (1), the mass ratio of aluminum hydroxide or magnesium hydroxide to water is 1:(2-6). The specific process of dispersing aluminum hydroxide or magnesium hydroxide in water is as follows: aluminum hydroxide or magnesium hydroxide is added to water, and mechanical stirring and ultrasonic dispersion are carried out at the same time for 1-2 hours. The mechanical stirring speed is 500-2000 r / min, and the ultrasonic power is 100-300w.

10. The preparation method according to claim 7, characterized in that, In step (3), the reaction time is 5-12 hours. The reaction is carried out under mechanical stirring and ultrasound. The mechanical stirring speed is 500-2000 r / min, and the ultrasound power is 100-300 w.

11. The preparation method according to claim 7, characterized in that, In step (4), vacuum drying is used, the drying temperature is 20-35℃, and the drying time is 72-96h.

12. The application of a modified inorganic flame retardant as described in claim 6 or obtained by any one of the preparation methods of claims 7 to 11 in rubber materials.

13. The application as described in claim 12, characterized in that, The rubber material is mainly prepared from the following raw materials in parts by weight: 100 parts natural rubber, 40-60 parts modified inorganic flame retardant, 3-10 parts zinc oxide, 1-2 parts stearic acid, 3-10 parts rubber antioxidant, 10-30 parts carbon black, 10-30 parts silica, and 3.0-5.0 parts vulcanization accelerator.

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