Application of flame retardant in modified casting nylon material

Abstract

The invention discloses application of a flame retardant in a modified casting nylon material. The modified casting nylon material comprises the flame retardant and casting nylon, the structural general formula of the flame retardant is shown in the specification, and OR is methoxy or ethyoxyl. The flame retardant property and the mechanical property of the modified casting nylon material are improved, and meanwhile, the water absorption of the modified casting nylon material is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flame retardants, and particularly relates to application of a flame retardant in modified cast nylon materials. BACKGROUND

[0002] Cast nylon (MC nylon), also known as monomer cast nylon, is a kind of engineering plastic, which is prepared by directly casting monomers into a mold to be polymerized under the action of a catalyst and a cocatalyst. Due to its simple production process, fast polymerization speed and good comprehensive performance of products, the cast nylon is widely used in the fields of machinery, textiles, transportation, petrochemical industry and metallurgy, and can directly replace some metal products such as copper, stainless steel and aluminum alloy. In recent years, the cast nylon products such as pulleys, sliding blocks, gears, worm wheels, supporting wheels, running wheels, water pump impellers, shaft sleeves, bearing shells, valve bodies, rubber blocking plates, belt pulleys, rotating wheels, rods, pipes and plates not only replace the corresponding metal products, reduce the cost and prolong the service life of the whole machine and parts, but also significantly improve the economic benefits.

[0003] However, the limiting oxygen index (LOI) of the cast nylon is only 21% to 23%, and the cast nylon is extremely flammable; in the reaction system of the traditional flame retardant melamine cyanurate (MCA) in the anionic in-situ polymerization cast nylon, the high temperature and the environment containing water cause the melamine cyanurate to easily decompose into melamine and cyanuric acid. On the one hand, the decomposed melamine and cyanuric acid can seriously interfere with the anionic in-situ polymerization reaction, cause the side reaction to intensify and seriously affect the polymerization degree of the cast nylon; on the other hand, compared with the melamine cyanurate, the decomposed melamine and cyanuric acid are more likely to crystallize and agglomerate, and it is difficult to achieve good compatibility with the final cast nylon polymer and uniform dispersion in the cast nylon polymer matrix, resulting in poor flame retardant effect and mechanical properties. SUMMARY

[0004] In order to solve the above technical problems, the purpose of the present application is to provide application of a flame retardant in modified cast nylon materials, so as to improve the flame retardant properties and mechanical properties of the modified cast nylon materials, and reduce the water absorption of the modified cast nylon materials.

[0005] The application provides application of a flame retardant in modified cast nylon materials, characterized in that the modified cast nylon material comprises the flame retardant and cast nylon. The structural general formula of the flame retardant is as follows: , In the formula, OR is methoxy or ethoxy.

[0006] The application provides application of a flame retardant in modified cast nylon material, on the one hand, the flame retardant has excellent compatibility with the cast nylon (anionic in-situ polymerization nylon), and the flame retardant can be uniformly dispersed in the cast nylon matrix, so that the flame retardation and mechanical properties of the modified cast nylon material can be effectively improved, the principle lies in that: the modified cast nylon material is prepared by anionic in-situ polymerization, before polymerization, the flame retardant is added into molten caprolactam monomers, the amide group in the caprolactam monomers endows it with specific polarity, the amide bond (-CO-NH-) in the structural formula of the flame retardant of the application also has polarity, the polarity characteristics of the two are highly matched, which provides a basis for the interaction of the two; and the carbonyl oxygen and amino hydrogen in the amide bond can be respectively used as a hydrogen bond acceptor and a hydrogen bond donor, so as to promote the flame retardant and the caprolactam monomers to form hydrogen bonds; the polarity matching and hydrogen bond interaction synergize, the interaction force between the flame retardant and the molten caprolactam monomers is enhanced, the compatibility and dispersibility of the flame retardant in the final cast nylon polymer are effectively improved, so that the flame retardation and mechanical properties of the modified cast nylon material are improved; meanwhile, when the flame retardant of the application is added into the molten caprolactam monomers before polymerization, the influence on the viscosity and fluidity of the reaction system is small, which is conducive to improving the dispersibility of the flame retardant in the cast nylon, and facilitating the mixing of the two molten caprolactam monomer systems during the preparation of the modified cast nylon material; furthermore, the flame retardant of the application has little interference with the initiation and growth process of the anionic polymerization of the modified cast nylon material, the side reaction is less, and the molecular chain of the generated modified cast nylon material is long and regular, and the polymerization degree is high. On the other hand, the -Si-O- structure in the flame retardant can construct a physical barrier in the cast nylon matrix, effectively prolonging the diffusion path of water molecules, at the same time, since the flame retardant can be uniformly dispersed in the cast nylon polymer, the physical barrier constructed by the -Si-O- structure in the flame retardant in the cast nylon matrix is continuous and dense, which can further reduce the water absorption of the modified cast nylon material; in addition, the hydrophobicity of the -Si-O- structure in the flame retardant further reduces the adsorption of water molecules; the flame retardant can effectively reduce the water absorption of the modified cast nylon material by constructing a continuous and dense physical barrier in the cast nylon matrix and utilizing the hydrophobicity thereof. Compared with the prior art, the application provides application of a flame retardant in modified cast nylon material, the synergistic effect of the above two aspects can improve the flame retardation and mechanical properties of the modified cast nylon material, and reduce the water absorption of the modified cast nylon material at the same time, by improving the compatibility and dispersibility of the flame retardant in the cast nylon polymer, and constructing a continuous and dense physical barrier in the cast nylon matrix by the flame retardant and utilizing the hydrophobicity thereof.

[0007] Preferably, the mass ratio of the flame retardant to the cast nylon is (5-10):100, for example, it can be 5:100, 6:100, 7:100, 8:100, 9:100, 10:100, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0008] The mass ratio of the flame retardant to the cast nylon in the present solution is (5-10):100, and the amount of the flame retardant in this range can ensure that there is enough flame retardant in the modified cast nylon material, so that the modified cast nylon material has excellent flame retardant performance and effectively reduces water absorption, and can also avoid excessive flame retardant exceeding the compatibility limit of the cast nylon, causing intermolecular agglomeration of the flame retardant, and the agglomerates act as stress concentration sources, preferentially causing crack propagation when the material is subjected to external force, resulting in a decrease in bending strength and tensile strength, and also avoiding excessive flame retardant causing excessive increase in viscosity of the reaction system and excessive interference with the initiation and growth process of anionic polymerization.

[0009] Further preferably, the mass ratio of the flame retardant to the cast nylon is (8-10):100.

[0010] The mass ratio of the flame retardant to the cast nylon in the present solution is (8-10):100, and the amount of the flame retardant in this range is sufficient in the modified cast nylon material, which can further improve the flame retardant performance of the modified cast nylon material and further effectively reduce water absorption.

[0011] Preferably, the preparation method of the modified cast nylon material comprises the following steps: S1. Dividing caprolactam into component A and component B and heating and melting, mixing the component A with a catalyst to obtain component A1, and mixing the component B with a co-catalyst to obtain component B1; S2. Mixing the flame retardant with the component B1 to obtain component B2; S3. Mixing the component B2 with the component A1, warming and polymerizing to solidify, to obtain the modified cast nylon material.

[0012] The preparation method of the modified cast nylon material provided in the scheme, the flame retardant is first mixed with component B1 (containing a catalyst) to obtain component B2, and then component B2 is mixed with component A1 (containing a catalyst). The principle of this feeding sequence is as follows: if the flame retardant is first mixed with component A1, on the one hand, the Si(OR)3 at the end of the flame retardant molecule will rapidly hydrolyze to form silanol (-Si-(OH)3) under strong alkaline conditions, and the silanol is easy to condense to form Si-O-Si bonds under alkaline conditions, resulting in intermolecular crosslinking and increased viscosity of the system, which is not conducive to subsequent uniform mixing with component B1. On the other hand, the flame retardant molecules are crosslinked into macromolecules, losing their dispersibility and mobility as small molecule flame retardants, resulting in a significant decrease in the flame retardant effect and mechanical properties of the modified cast nylon material, and an increase in its water absorption. Therefore, the flame retardant is first mixed with component B1 to obtain component B2, and then component B2 is mixed with component A1. This feeding method can fully utilize the function of the flame retardant in the preparation of the modified cast nylon material, thereby enabling the prepared modified cast nylon material to have good flame retardant performance and mechanical properties, as well as low water absorption.

[0013] Further preferably, in the S1, the mass ratio of the component A to the component B is (4-6):(4-6), which can be 4:6, 4.5:5.5, 5:5, 5.5:4.5, 6:4, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0014] Further preferably, in the S1, the catalyst comprises at least one of sodium metal, sodium hydroxide, potassium hydroxide, and sodium methoxide.

[0015] Further preferably, in the S1, the catalyst comprises at least one of toluene diisocyanate, diphenylmethane diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0016] Further preferably, in the S1, the component A1 and the component B1 are further subjected to dehydration.

[0017] In the S1, the component A1 and the component B1 are further subjected to dehydration, which can reduce the occurrence of side reactions and improve the polymerization degree of the cast nylon, thereby improving the mechanical properties of the modified cast nylon.

[0018] Further preferably, in the S3, the temperature for mixing the component B2 with the component A1 is 70-90 ℃, which can be 70 ℃, 75 ℃, 80 ℃, 85 ℃, or 90 ℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0019] In the S3, the temperature for mixing the component B2 with the component A1 is 70-90 ℃. The mixing temperature in this range can ensure sufficient temperature to enable the caprolactam melt to have a suitable viscosity, which is conducive to the rapid, sufficient and uniform mixing of the component B2 with the component A1. In addition, the mixing of the component B2 with the component A1 under the condition close to the casting temperature can avoid the rapid initiation of the polymerization reaction and the violent heat release, thus effectively delaying the premature initiation of the polymerization reaction, providing a sufficient safety time window for the mixing operation, and ensuring that the uniformly mixed melt can be successfully cast into the mold before the reaction starts violently.

[0020] Preferably, the preparation method of the flame retardant comprises the following steps: S1. Synthesis of DOPO-COOH: under the protection of inert gas, the DOPO and the alkaline reagent are dissolved in a solvent, then chloroacetic acid is added for heating reaction, after the reaction is completed, hydrochloric acid is added for acidification, and the DOPO-COOH is prepared; S2. Acyl chloride reaction: the DOPO-COOH is mixed with SOCl2, and heated for reaction to prepare DOPO-COCl; S3. Condensation reaction: the DOPO-COCl is dissolved in a solvent, then the amino silane coupling agent and triethylamine are added under ice bath condition, the amino silane coupling agent is KH-540 or KH-550, and the reaction is carried out at room temperature to prepare the flame retardant.

[0021] Further preferably, in the S1 of the preparation method of the flame retardant, the alkaline reagent is at least one of potassium carbonate and sodium carbonate.

[0022] Further preferably, in the S1 of the preparation method of the flame retardant, the temperature of the heating reaction is 90-95 ℃, for example, it can be 90 ℃, 91 ℃, 92 ℃, 93 ℃, 94 ℃, 95 ℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0023] Further preferably, in the S1 of the preparation method of the flame retardant, after the addition of hydrochloric acid for acidification, recrystallization purification of DOPO-COOH is further included, and the solvent used for the recrystallization is ethyl acetate and n-hexane.

[0024] Further preferably, the volume ratio of the ethyl acetate and n-hexane is 1: (2.5-3.5), for example, it can be 1:2.5, 1:3, 1:3.5, but is not limited to the listed values, and other values not listed in the value range are also applicable. DETAILED DESCRIPTION

[0025] In order to make the technical scheme in the present application better understood by the person skilled in the art, the technical scheme of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the protection scope of the present application.

[0026] A method for preparing a flame retardant, comprising: S1. Synthesis of DOPO-COOH: Under nitrogen protection, 0.1 mol of DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) was weighed into a container, 150 mL of N,N-dimethylformamide (DMF) was added, and the mixture was stirred and mixed uniformly. Then, 0.12 mol of potassium carbonate was added into the container, and stirred uniformly under a stirrer. A chloroacetic acid solution (0.12 mol of chloroacetic acid was dissolved in 50 mL of DMF) was added dropwise into the container under stirring, and the temperature was raised to 95 ℃. The reaction was continuously stirred for 10 hours, and then cooled to room temperature. Hydrochloric acid was added dropwise until the pH value was 2. White solid was precipitated, and was filtered by a Buchner funnel. The filter cake was washed with ice water (0 ℃) for 3 times, and then was dried by suction. The solid was transferred to a beaker, and a mixed solution of ethyl acetate and n-hexane (volume ratio of 1:3) was added. The solution was heated to 60 ℃ for dissolution, and then was filtered while hot. The filtrate was cooled to -20 ℃ and was left to stand for 4 hours. White crystals were precipitated, and were dried by suction to obtain DOPO-COOH.

[0027] S2. Acyl chloride reaction: 0.1 mol of DOPO-COOH was placed in a container, 50 mL of SOCl2 was added, and the mixture was stirred and mixed uniformly. The temperature was raised to 75 ℃ for reaction for 3 hours, and then was distilled under reduced pressure to obtain DOPO-COCl.

[0028] S3. Condensation reaction: 200 mL of anhydrous tetrahydrofuran (THF) was added into DOPO-COCl, and the mixture was stirred uniformly. 0.11 mol of γ-aminopropyl triethoxysilane (silane coupling agent KH-550) was added dropwise under ice bath (0-5 ℃), followed by dropwise addition of 0.12 mol of triethylamine. The ice bath was removed, and the reaction was stirred at room temperature for 24 hours. Then, the flame retardant (white solid, yield of 82%) was purified by column chromatography.

[0029] Example 1 The flame retardant used in the present embodiment is:

[0030] Preparation of modified cast nylon material S1. 100 parts by mass of caprolactam was evenly divided into two portions (50 parts by mass each), and placed into two reaction kettles A and B. The caprolactam monomers in the two reaction kettles A and B were heated and melted, 0.2 parts by mass of catalyst NaOH was added to kettle A, and 0.3 parts by mass of co-catalyst toluene diisocyanate (TDI) was added to kettle B. The two reaction kettles A and B were warmed to 130°C, and vacuum dehydration was performed for 20 minutes.

[0031] S2. 8 parts by mass of flame retardant was added to kettle B, and the temperature of kettle B was maintained at 130°C, and stirring was performed for 30 minutes at a stirring speed of 300 r / min.

[0032] S3. The materials in the two reaction kettles A and B were cooled to 80°C (the temperature was reduced here only to delay the time available for the operator to operate, and the performance was basically not affected), the materials in the two kettles A and B were mixed uniformly in a mixing container, and then cast in a mold, warmed to 160°C, and maintained for 2 hours. After solidification, the temperature was cooled to room temperature, and the modified cast nylon material was obtained after demolding.

[0033] Example 2 The flame retardant used in this example is the same as in Example 1.

[0034] Preparation of modified cast nylon material In the preparation of the modified cast nylon material of this example, except that the flame retardant in step S2 was 5 parts by mass, the rest was the same as in Example 1.

[0035] Example 3 The flame retardant used in this example is the same as in Example 1.

[0036] Preparation of modified cast nylon material In the preparation of the modified cast nylon material of this example, except that the flame retardant in step S2 was 6 parts by mass, the rest was the same as in Example 1.

[0037] Example 4 The flame retardant used in this example is the same as in Example 1.

[0038] Preparation of modified cast nylon material In the preparation of the modified cast nylon material of this example, except that the flame retardant in step S2 was 7 parts by mass, the rest was the same as in Example 1.

[0039] Example 5 The flame retardant used in this example is the same as in Example 1.

[0040] Preparation of modified cast nylon material In the preparation of the modified cast nylon material of this example, except that the flame retardant in step S2 was 9 parts by mass, the rest was the same as in Example 1.

[0041] Example 6 The flame retardant used in this example is the same as that in Example 1.

[0042] Preparation of modified cast nylon material The preparation of modified cast nylon material in this example is the same as that in Example 1 except that the flame retardant in step S2 is 10 parts by mass.

[0043] Example 7 The flame retardant used in this example is the same as that in Example 1.

[0044] Preparation of modified cast nylon material The preparation of modified cast nylon material in this example is the same as that in Example 1 except that the flame retardant in step S2 is 11 parts by mass.

[0045] Example 8 The flame retardant used in this example is the same as that in Example 1.

[0046] Preparation of modified cast nylon material The preparation of modified cast nylon material in this example is the same as that in Example 1 except that the flame retardant in step S2 is 15 parts by mass.

[0047] Example 9 The flame retardant used in this example is the same as that in Example 1.

[0048] Preparation of modified cast nylon material The preparation of modified cast nylon material in this example is the same as that in Example 1 except that 8 parts by mass of flame retardant is added to the A kettle in step S2.

[0049] Performance test (1) Limiting oxygen index test (LOI): tested according to ASTM D2863.

[0050] (2) Vertical burning test UL-94: tested according to ASTM D3801.

[0051] (3) Tensile strength test: tested according to ASTM D638.

[0052] (4) Flexural strength test: ISO 178.

[0053] (5) Water absorption: tested according to ISO 62.

[0054] The modified cast nylon material prepared in the above examples is subjected to the above performance test, and the test results are shown in Table 1.

[0055] Table 1

[0056] From Table 1, it can be seen that: The ordinary cast nylon does not have the flame-retardant property, and the existing flame retardant on the market has poor compatibility, and the mechanical properties are sacrificed to achieve the purpose of flame retardation; after adding the flame retardant prepared in the application, the flame retardance of the modified cast nylon is greatly improved, and due to the existence of amide bond (-CO-NH-) and the like, the compatibility problem is solved, so that the prepared modified cast nylon achieves better flame retardance grade with smaller sacrifice of mechanical properties; in the 1-8 embodiments of the experiment, embodiments 1 and 4 perform best. They successfully maintain the flame retardance grade at V-0, while the decline of the mechanical properties (tensile, bending) is within an acceptable range, and the water absorption is low. And the water absorption is lower than that of the conventional cast nylon in the prior art (0.9%). Embodiments 7 and 8 are typical “excessive addition” counterexamples. Although the highest LOI and the lowest water absorption are obtained, the flame retardance grade drops sharply (V-2) and the mechanical properties deteriorate severely, which makes the material almost lose its value in practical application. And the flame retardant is first mixed with component A1 in embodiment 9, which causes the Si(OR)3 at the end of the flame retardant molecule to hydrolyze rapidly to generate silanol (-Si-(OH)3) under strong alkaline conditions. Silanol is easy to condense to form Si-O-Si bond under alkaline conditions, causing intermolecular crosslinking and increasing the viscosity of the system, which is not conducive to subsequent uniform mixing with component B1; at the same time, the flame retardant molecules are crosslinked into macromolecules, losing their dispersibility and mobility as small molecule flame retardants, resulting in a significant decline in the flame retardant effect and mechanical properties of the modified cast nylon material, and the water absorption is also increased.

[0057] From the data of 1-8, it can be clearly seen that blindly increasing the proportion of flame retardant is a dead end. The core of a successful flame retardant formula design is to find the lowest effective amount that can meet the target flame retardance grade (such as V-0) and mechanical properties. For the experimental system, this best point falls within the addition amount range represented by embodiments 1 to 6.

[0058] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. Use of a flame retardant in a modified cast nylon material, characterized in that, The modified cast nylon material comprises a flame retardant and a cast nylon; The structural general formula of the flame retardant is: ， Wherein, OR is methoxy or ethoxy.

2. Use of the flame retardant according to claim 1 in modified cast nylon materials, characterized in that, The mass ratio of the flame retardant to the cast nylon is (5-10):

100.

3. Use of a flame retardant according to claim 1 or 2 in a modified cast nylon material, characterized in that, The mass ratio of the flame retardant to the cast nylon is (8-10):

100.

4. Use of the flame retardant according to claim 1 in modified cast nylon materials, characterized in that, The preparation method of the modified cast nylon material comprises the following steps: S1. The caprolactam is divided into component A and component B and heated to melt, the component A is mixed with a catalyst to obtain component A1, and the component B is mixed with a cocatalyst to obtain component B1; S2. The flame retardant is mixed with the component B1 to obtain component B2; S3. The component B2 is mixed with the component A1, and the temperature is raised for polymerization and curing to obtain the modified cast nylon material.

5. Use of the flame retardant according to claim 4 in modified cast nylon materials, characterized in that, In the S1, the mass ratio of the component A to the component B is (4-6):(4-6).

6. Use of the flame retardant according to claim 4 in modified cast nylon materials, characterized in that, In the S1, the catalyst comprises at least one of metallic sodium, sodium hydroxide, potassium hydroxide and sodium methoxide.

7. Use of the flame retardant according to claim 4 in modified cast nylon materials, characterized in that, In the S1, the cocatalyst comprises at least one of toluene diisocyanate, diphenyl methane diisocyanate and polymethylene polyphenyl polyisocyanate.

8. Use of the flame retardant according to claim 4 in modified cast nylon materials, characterized in that, In the S1, component A1 and component B1 are also dehydrated.

9. Use of the flame retardant according to claim 4 in modified cast nylon materials, characterized in that, In the S3, the temperature for mixing the component B2 with the component A1 is 70-90 ℃.

10. Use of the flame retardant according to claim 1 in modified cast nylon materials, characterized in that, The preparation method of the flame retardant comprises the following steps: S1. Synthesis of DOPO-COOH: under the protection of inert gas, DOPO and alkaline reagent are dissolved in a solvent, chloroacetic acid is added for heating reaction, after the reaction is completed, hydrochloric acid is added for acidification to prepare the DOPO-COOH; S2. Acyl chloride reaction: the DOPO-COOH is mixed with SOCl2 for heating reaction to prepare DOPO-COCl; S3. Condensation reaction: the DOPO-COCl is dissolved in a solvent, and under ice bath condition, amino silane coupling agent and triethylamine are added, the amino silane coupling agent is KH-540 or KH-550, and the reaction is carried out at room temperature to prepare the flame retardant.

Images