Flame-retardant PBT (polybutylene terephthalate) and preparation method thereof

Abstract

The invention provides flame-retardant PBT (polybutylene terephthalate) and a preparation method thereof. The preparation method comprises the following steps: firstly, forming silicon dioxide-aluminum hydroxide core-shell particles through a hydrolysis-precipitation reaction, and then carrying out graft modification through a silane coupling agent to prepare a modified flame retardant 1; and carrying out copolymerization reaction on double-bond-containing polyester and double-bond-containing flame-retardant particles to obtain a modified flame retardant 2. The modified flame retardant 1, the modified flame retardant 2, a PBT base material, a halogen-free composite flame retardant and an auxiliary agent are subjected to blending and melting processing, by means of chemical bonding of an epoxy group and a hydroxyl group or a carboxyl group, tight interface bonding is achieved, and the problems that a traditional flame retardant is poor in compatibility and prone to agglomeration are solved. The comprehensive performance of the flame-retardant PBT is comprehensively optimized; the core-shell structure and the halogen-free composite flame retardant are in synergistic interaction, so that the flame-retardant grade is improved while the consumption of the flame retardant is reduced; defects are eliminated through interface chemical bonding, rigidity is enhanced through core-shell particles, and the mechanical property is remarkably improved; and tight interface combination and a compact matrix structure block permeation of organic solvents, delay cracking and prolong the service life.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a flame-retardant PBT and its preparation method. Background Technology

[0002] With the rapid development of industries such as electronics, electrical engineering, and automobile manufacturing, the application range of engineering plastics is constantly expanding. Polybutylene terephthalate (PBT), with its excellent mechanical properties, heat resistance, and molding processability, has become an indispensable material in this field. However, PBT itself is flammable and easily burns and releases toxic fumes in high-temperature or open-flame environments, which greatly limits its application in scenarios with strict safety requirements. Therefore, developing high-performance flame-retardant PBT materials has become an important research direction in the industry.

[0003] Currently, the preparation of flame-retardant PBT in existing technologies mostly involves adding flame retardants to the PBT substrate. Among these, halogen-free flame retardants are widely used due to their environmentally friendly and pollution-free advantages. Common halogen-free flame retardant systems include ammonium polyphosphate-based composite flame retardants. Simultaneously, to improve the overall performance of the material, antioxidants, lubricants, toughening agents, and other additives are often added, and the preparation is completed through processes such as melt blending and extrusion granulation to achieve a certain flame-retardant effect.

[0004] However, existing flame-retardant PBT technology still has significant shortcomings. In some products, the mechanical properties of the material are affected by the poor compatibility between the flame retardant and the PBT substrate after the addition of flame retardants. The tensile strength and notched impact strength are difficult to meet the requirements of high-end applications. In addition, the existing materials have poor solvent resistance and are prone to cracking after contact with organic solvents, which shortens their service life. Although some flame-retardant PBTs can achieve basic flame retardant ratings, they cannot achieve a good balance between flame retardant performance, mechanical properties and solvent resistance, which limits their application in complex working conditions.

[0005] In conclusion, a new technical solution is urgently needed to address the problems existing in the current technology. Summary of the Invention

[0006] Based on this, the present invention provides a flame-retardant PBT and its preparation method. The present invention first forms silica-alumina hydroxide core-shell particles through a hydrolysis-precipitation reaction, and then obtains modified flame retardant 1 through graft modification with a silane coupling agent; modified flame retardant 2 is obtained by copolymerizing double-bonded polyester with double-bonded flame-retardant particles. Modified flame retardant 1 and modified flame retardant 2 are then blended and melt-processed with PBT substrate, halogen-free composite flame retardant, and additives. Through the chemical bonding of epoxy groups and hydroxyl or carboxyl groups, a tight interfacial bond is achieved, solving the problems of poor compatibility and easy agglomeration of traditional flame retardants. The flame-retardant PBT of the present invention has comprehensively optimized overall performance: the core-shell structure and halogen-free composite flame retardant synergistically enhance each other, reducing the amount of flame retardant used while improving the flame retardant rating; interfacial chemical bonding eliminates defects, and core-shell particles enhance rigidity, significantly improving mechanical properties; tight interfacial bonding and dense matrix structure block the penetration of organic solvents, delaying cracking and extending service life, achieving a good balance between flame retardancy, mechanical properties, and solvent resistance.

[0007] One object of the present invention is to provide a flame-retardant PBT, wherein the flame-retardant PBT comprises the following raw materials in parts by weight: 60-80 parts of polybutylene terephthalate Modified flame retardant 1 3-8 parts Modified flame retardant 2 1-5 parts 5-15 parts of halogen-free composite flame retardant Additives: 0.1-10 parts; in, The modified flame retardant 1 is obtained by treating silica-alumina hydroxide core-shell particles with an epoxy silane coupling agent; The modified flame retardant 2 is obtained by copolymerization of double-bonded polyester and double-bonded flame retardant particles; The flame-retardant particles containing double bonds are obtained by treating silica-alumina hydroxide core-shell particles with a silane coupling agent containing double bonds. The halogen-free composite flame retardant is composed of diethyl aluminum hypophosphite and melamine polyphosphate; The flame-retardant PBT is prepared by melt processing.

[0008] Furthermore, the mass ratio of the aluminum diethylphosphite to the melamine polyphosphate is 7:(1-5).

[0009] Furthermore, the additive is selected from one or more of antioxidants, lubricants, and toughening agents.

[0010] Furthermore, the antioxidant is selected from one or more of antioxidant 1010 or antioxidant 168.

[0011] Furthermore, the lubricant is pentaerythritol stearate.

[0012] Furthermore, the preparation method of the flame-retardant PBT includes the following steps: S1. Add silica to sodium bicarbonate solution and disperse by ultrasonication to obtain silica dispersion; add aluminum nitrate solution to silica dispersion and stir to obtain silica-alumina hydroxide core-shell particles; S2. The silica-alumina hydroxide core-shell particles and epoxy silane coupling agent are mixed and heated and stirred to obtain modified flame retardant 1. S3. The silica-alumina hydroxide core-shell particles and the double-bonded silane coupling agent are mixed and heated and stirred to obtain flame-retardant particles containing double bonds. S4. Blend double-bonded polyester and double-bonded flame-retardant particles, add an initiator, and heat to react to obtain modified flame retardant 2. S5. Blend all components evenly, then add them to a twin-screw extruder for melt processing to obtain flame-retardant PBT.

[0013] Further, in step S1, the mass ratio of silicon dioxide to aluminum nitrate is 20:(0.5-5).

[0014] Further, in step S2, the mass ratio of the silica-alumina hydroxide core-shell particles to the epoxy silane coupling agent is 10:(0.1-0.9).

[0015] Furthermore, in step S2, the heating temperature is 60-80℃.

[0016] Further, in step S3, the mass ratio of the silica-alumina hydroxide core-shell particles to the double-bonded silane coupling agent is 10:(0.1-0.9); the heating temperature is 60-80℃.

[0017] Further, in step S4, the mass ratio of double-bonded polyester to double-bonded flame-retardant particles is 1:(2-4), and the heating temperature is 160-180℃.

[0018] Furthermore, in step S5, the temperature of the melt processing is 230-250°C.

[0019] The present invention has the following beneficial effects: This invention provides a flame-retardant PBT and its preparation method. First, using silica as the core particle, aluminum nitrate solution is added to a mixed dispersion of silica and sodium bicarbonate. Through a hydrolysis-precipitation reaction, silica-alumina hydroxide core-shell particles are formed, achieving a synergistic composite of the two inorganic flame-retardant components. Subsequently, the silanol groups generated by the hydrolysis of an epoxy-based silane coupling agent undergo a dehydration condensation reaction with the hydroxyl groups on the surface of the core-shell particles, achieving graft modification of the epoxy-based silane coupling agent on the surface of the core-shell particles, thus obtaining a modified flame retardant 1 with epoxy groups on the surface and excellent flame-retardant properties. Simultaneously, a double-bond-containing polyester is copolymerized with double-bond-containing flame-retardant particles to form a modified flame retardant 2 with good compatibility with the PBT substrate. When modified flame retardant 1 and modified flame retardant 2 are blended with PBT substrate, halogen-free composite flame retardant and additives, during melt processing, the epoxy groups on the surface of modified flame retardant 1 can react with the hydroxyl or carboxyl groups at the ends of the molecular chains of modified flame retardant 2 and PBT. Through chemical bonding, modified flame retardant 1 and modified flame retardant 2 achieve intermolecular bonding with PBT substrate and produce interpenetration, cross-linking and entanglement to form a network structure. This solves the problem of poor compatibility between traditional flame retardants and polymer substrates, ensures that the flame retardant is uniformly dispersed in PBT melt, and avoids agglomeration.

[0020] Based on the aforementioned interfacial chemical reactions and special component design, the flame-retardant PBT of this invention achieves comprehensive optimization of its overall performance. On one hand, the core-shell structure of modified flame retardant 1 (silica as the core, aluminum hydroxide as the shell) forms a synergistic flame-retardant system with the halogen-free composite flame retardant. While reducing the amount of halogen-free flame retardant used, the synergistic effect through multiple actions significantly improves the flame-retardant performance of the material, overcoming the shortcomings of insufficient flame-retardant ratings in existing products. On the other hand, the interfacial chemical bonding effectively eliminates interfacial defects between the flame retardant and the PBT substrate, reducing stress concentration and making stress transmission more uniform under stress, significantly improving the material's mechanical properties. Simultaneously, the silica-alumina hydroxide core-shell particles in modified flame retardant 1 and modified flame retardant 2 possess excellent rigidity and mechanical strength. Their dispersion in the system further enhances the material's mechanical properties, meeting the stringent requirements of high-end applications for material mechanical properties. Furthermore, because the core-shell particles are uniformly dispersed in the PBT substrate and bonded to the substrate through chemical bonds, they can block the combustion of the PBT material, thereby further improving the flame-retardant effect. Furthermore, the tight interfacial bond formed by the chemical bonding between modified flame retardant 1, modified flame retardant 2 and PBT substrate, as well as the dense matrix structure constructed after the flame retardants are uniformly dispersed, can effectively block the penetration and diffusion of organic solvents, preventing solvents from eroding the PBT molecular chains or damaging the interfacial bond between the substrate and the flame retardant. This delays the occurrence of material cracking and significantly extends the stable service time of the material after contact with organic solvents, solving the problems of poor solvent resistance, easy cracking, and short service life of existing flame-retardant PBT. Detailed Implementation

[0021] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0022] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0023] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0024] The present invention uses the following raw materials: Polybutylene terephthalate: grade P909269, purchased from Maclean's Reagents.

[0025] Halogen-free composite flame retardant: a mixture of diethylaluminum hypophosphite and melamine polyphosphate in a mass ratio of 7:3.

[0026] Antioxidant: Antioxidant 1010.

[0027] Lubricant: Pentaerythritol stearate.

[0028] Toughening agent: brand name S-2001, purchased from Mitsubishi, Japan.

[0029] Epoxy silane coupling agent: silane coupling agent KH560.

[0030] Silane coupling agents containing double bonds: Silane coupling agent KH570.

[0031] Silica: Monodisperse silica, grade M964359, purchased from Maclean's Reagents.

[0032] The preparation method of polyesters containing double bonds includes the following steps: A mixture of terephthalic acid, maleic anhydride, phthalic anhydride, and propylene glycol in a molar ratio of 1:4.5:4.5:10 was added to a reaction vessel and heated to 160°C under nitrogen protection. 5% (by mass) of p-toluenesulfonic acid catalyst was added, and the mixture was heated to 190°C and stirred for 4 h. Then, a vacuum of -0.095 MPa was applied, and the reaction continued for 2 h. The byproduct water was removed, and after cooling, a polyester containing double bonds was obtained.

[0033] Unless otherwise specified: All water used in this invention is deionized water.

[0034] In this invention, "parts" refers to parts by mass.

[0035] Example 1 A flame-retardant PBT, wherein the flame-retardant PBT is composed of the following raw materials in parts by weight: 70 parts of polybutylene terephthalate Modified flame retardant 1 6 parts Modified flame retardant 2-4 parts 10 parts of halogen-free composite flame retardant 0.5 parts antioxidant 1 part lubricant 5 parts toughening agent.

[0036] The preparation method of the flame-retardant PBT includes the following steps: S1. Add 20 g of silica to 1 L of sodium bicarbonate aqueous solution (0.5 mol / L) and disperse evenly by ultrasonication to obtain silica dispersion; add 0.025 L of aluminum nitrate aqueous solution (0.15 mol / L) to the silica dispersion, stir at 500 rpm for 5 h, filter, wash and dry to obtain silica-alumina hydroxide core-shell particles; S2. Disperse 10 g of the silica-alumina hydroxide core-shell particles in 50 mL of ethanol-water mixed solution (ethanol:water = 1:9, V / V), add 0.5 g of silane coupling agent KH560, stir and react at 80℃ for 5 h, filter, wash and dry to obtain modified flame retardant 1; S3. Disperse 10 g of the silica-alumina hydroxide core-shell particles in 50 mL of ethanol-water mixed solution (ethanol:water = 1:9, V / V), add 0.5 g of silane coupling agent KH570, stir and react at 80℃ for 5 h, filter, wash and dry to obtain flame-retardant particles containing double bonds. S4. Mix double-bonded polyester, double-bonded flame-retardant particles and dicumyl peroxide at a mass ratio of 20:50:0.03, add to the torque rheometer mixer for kneading, wherein the kneading temperature is 170℃, the kneading time is 8 min, and the kneading speed is 60 r / min to obtain modified flame retardant 2. S5. According to the above mass proportions, all components are mixed and then mixed evenly with a high-speed mixer. Then, the mixture is added to a twin-screw extruder and melt-extruded under the conditions of die temperature 230℃ and screw speed 60 r / min. After cooling, granulation and drying, flame-retardant PBT is obtained.

[0037] Example 2 A flame-retardant PBT, wherein the flame-retardant PBT is composed of the following raw materials in parts by weight: 60 parts of polybutylene terephthalate Modified flame retardant 1 4 parts 2-3 parts of modified flame retardant 7 parts of halogen-free composite flame retardant 0.5 parts antioxidant 1 part lubricant 5 parts toughening agent.

[0038] The preparation method of the flame-retardant PBT includes the following steps: S1. Add 20 g of silica to 1 L of sodium bicarbonate aqueous solution (0.5 mol / L) and disperse evenly by ultrasonication to obtain silica dispersion; add 0.025 L of aluminum nitrate aqueous solution (0.15 mol / L) to the silica dispersion, stir at 500 rpm for 5 h, filter, wash and dry to obtain silica-alumina hydroxide core-shell particles; S2. Disperse 10 g of the silica-alumina hydroxide core-shell particles in 50 mL of ethanol-water mixed solution (ethanol:water = 1:9, V / V), add 0.5 g of silane coupling agent KH560, stir and react at 80℃ for 5 h, filter, wash and dry to obtain modified flame retardant 1; S3. Disperse 10 g of the silica-alumina hydroxide core-shell particles in 50 mL of ethanol-water mixed solution (ethanol:water = 1:9, V / V), add 0.5 g of silane coupling agent KH570, stir and react at 80℃ for 5 h, filter, wash and dry to obtain flame-retardant particles containing double bonds. S4. Mix double-bonded polyester, double-bonded flame-retardant particles and dicumyl peroxide at a mass ratio of 20:50:0.03, add to the torque rheometer mixer for kneading, wherein the kneading temperature is 170℃, the kneading time is 8 min, and the kneading speed is 60 r / min to obtain modified flame retardant 2. S5. According to the above mass proportions, all components are mixed and then mixed evenly with a high-speed mixer. Then, the mixture is added to a twin-screw extruder and melt-extruded under the conditions of die temperature 230℃ and screw speed 60 r / min. After cooling, granulation and drying, flame-retardant PBT is obtained.

[0039] Example 3 A flame-retardant PBT, wherein the flame-retardant PBT is composed of the following raw materials in parts by weight: 80 parts of polybutylene terephthalate Modified flame retardant 1 8 parts Modified flame retardant 2-5 parts 13 parts of halogen-free composite flame retardant 0.5 parts antioxidant 1 part lubricant 5 parts toughening agent.

[0040] The preparation method of the flame-retardant PBT includes the following steps: S1. Add 20 g of silica to 1 L of sodium bicarbonate aqueous solution (0.5 mol / L) and disperse evenly by ultrasonication to obtain silica dispersion; add 0.025 L of aluminum nitrate aqueous solution (0.15 mol / L) to the silica dispersion, stir at 500 rpm for 5 h, filter, wash and dry to obtain silica-alumina hydroxide core-shell particles; S2. Disperse 10 g of the silica-alumina hydroxide core-shell particles in 50 mL of ethanol-water mixed solution (ethanol:water = 1:9, V / V), add 0.5 g of silane coupling agent KH560, stir and react at 80℃ for 5 h, filter, wash and dry to obtain modified flame retardant 1; S3. Disperse 10 g of the silica-alumina hydroxide core-shell particles in 50 mL of ethanol-water mixed solution (ethanol:water = 1:9, V / V), add 0.5 g of silane coupling agent KH570, stir and react at 80℃ for 5 h, filter, wash and dry to obtain flame-retardant particles containing double bonds. S4. Mix double-bonded polyester, double-bonded flame-retardant particles and dicumyl peroxide at a mass ratio of 20:50:0.03, add to the torque rheometer mixer for kneading, wherein the kneading temperature is 170℃, the kneading time is 8 min, and the kneading speed is 60 r / min to obtain modified flame retardant 2. S5. According to the above mass proportions, all components are mixed and then mixed evenly with a high-speed mixer. Then, the mixture is added to a twin-screw extruder and melt-extruded under the conditions of die temperature 230℃ and screw speed 60 r / min. After cooling, granulation and drying, flame-retardant PBT is obtained.

[0041] Comparative Example 1 A flame-retardant PBT, the difference between this comparative example and Example 1 is that step S2 is omitted. In step S5, the modified flame retardant 1 is replaced by silica-alumina hydroxide core-shell particles by an equal mass. Other steps and dosages are the same as in Example 1.

[0042] Comparative Example 2 A flame-retardant PBT, the difference between this comparative example and Example 1 is that step S1 is omitted, and in steps S2 and S3, the silica-alumina hydroxide core-shell particles are replaced with silica by the same mass. The other steps and amounts are the same as in Example 1.

[0043] Comparative Example 3 A flame-retardant PBT is described. The difference between this comparative example and Example 1 is that step S4 is omitted, and the modified flame retardant 2 is replaced with the same mass of the flame-retardant particles containing double bonds obtained in S3. The other steps and dosages are the same as in Example 1.

[0044] Test case The performance of Examples 1-3 and Comparative Examples 1-3 was tested.

[0045] Test method: Flame retardant rating: UL-94.

[0046] Tensile strength: ASTM D638.

[0047] Notched impact strength: ASTM D256.

[0048] Solvent resistance: A tensile specimen conforming to ISO 527-1-2012 standard was placed on a circular arc fixture with a diameter of 470 mm, and 3g of BP Carecut ES3 was evenly applied to the surface of the specimen. The time it took for the material to crack was then observed.

[0049] The test results are shown in Table 1.

[0050] Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-3 As can be seen from the above test results, the present invention has good flame retardant properties and mechanical properties, as well as good solvent resistance.

[0051] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0052] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A flame-retardant PBT, characterized in that, The flame-retardant PBT comprises the following raw materials in parts by weight: 60-80 parts of polybutylene terephthalate Modified flame retardant 1 3-8 parts Modified flame retardant 2 1-5 parts 5-15 parts of halogen-free composite flame retardant Additives: 0.1-10 parts; in, The modified flame retardant 1 is obtained by treating silica-alumina hydroxide core-shell particles with an epoxy silane coupling agent; The modified flame retardant 2 is obtained by copolymerization of double-bonded polyester and double-bonded flame retardant particles; The flame-retardant particles containing double bonds are obtained by treating silica-alumina hydroxide core-shell particles with a silane coupling agent containing double bonds. The halogen-free composite flame retardant is composed of diethyl aluminum hypophosphite and melamine polyphosphate; The flame-retardant PBT is prepared by melt processing.

2. The flame-retardant PBT according to claim 1, characterized in that, The mass ratio of diethylaluminum hypophosphite to melamine polyphosphate is 7:(1-5).

3. The flame-retardant PBT according to claim 1, characterized in that, The additives are selected from one or more of antioxidants, lubricants, and toughening agents.

4. The flame-retardant PBT according to claim 3, characterized in that, The antioxidant is selected from one or more of antioxidant 1010 or antioxidant 168.

5. The flame-retardant PBT according to claim 3, characterized in that, The lubricant is pentaerythritol stearate.

6. The method for preparing flame-retardant PBT according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Add silica to sodium bicarbonate solution and disperse by ultrasonication to obtain silica dispersion; add aluminum nitrate solution to silica dispersion and stir to obtain silica-alumina hydroxide core-shell particles; S2. The silica-alumina hydroxide core-shell particles and epoxy silane coupling agent are mixed and heated and stirred to obtain modified flame retardant 1. S3. The silica-alumina hydroxide core-shell particles and the double-bonded silane coupling agent are mixed and heated and stirred to obtain flame-retardant particles containing double bonds. S4. Blend double-bonded polyester and double-bonded flame-retardant particles, add an initiator, and heat to react to obtain modified flame retardant 2. S5. Blend all components evenly, then add them to a twin-screw extruder for melt processing to obtain flame-retardant PBT.

7. The method for preparing flame-retardant PBT according to claim 6, characterized in that, In step S1, the mass ratio of silicon dioxide to aluminum nitrate is 20:(0.5-5).

8. The method for preparing flame-retardant PBT according to claim 6, characterized in that, In step S2, the mass ratio of the silica-alumina hydroxide core-shell particles to the epoxy silane coupling agent is 10:(0.1-0.9).

9. The method for preparing flame-retardant PBT according to claim 6, characterized in that, In step S2, the heating temperature is 60-80℃.

10. The method for preparing flame-retardant PBT according to claim 6, characterized in that, In step S5, the temperature of the melt processing is 230-250℃.

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