Preparation method of low-smoke halogen-free flame-retardant cable sheath material

Abstract

The invention relates to a preparation method of a low-smoke halogen-free flame-retardant cable sheath material, and belongs to the technical field of cable materials. The cable sheath material is obtained by self-making a flame retardant and blending the flame retardant with polyethylene, a phosphorus-silicon-boron cross-linked network exists in the flame retardant, a protective layer is formed during combustion, the smoke amount is reduced while flame retardance is achieved, and low-smoke halogen-free flame retardance is achieved through phosphorus-silicon-boron synergy; according to the flame retardant disclosed by the invention, a phosphorus-oxygen group is connected with a silicon-oxygen group through a benzene ring, polarity mutation is buffered, and the flame retardant integrally presents low polarity, so that the compatibility between the flame retardant and a polyethylene matrix is enhanced, the flame retardant is more uniformly distributed in the matrix, the interface bonding is more excellent, and the mechanical property of the material is remarkably improved; and a long-chain siloxane coating structure in the flame retardant can form a water repellent layer on the surface of the material to achieve a hydrophobic effect, so that the dielectric property of the material is not influenced in a humid environment, and the stability and safety of power transmission are ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cable materials, and particularly relates to a preparation method of a low-smoke halogen-free flame-retardant cable sheath material. BACKGROUND

[0002] The low-smoke halogen-free flame-retardant cable sheath material has less smoke and releases no toxic gases such as halogenated hydrogen during combustion, and thus becomes a key material in the fields of rail transit, building, and new energy.

[0003] Although the traditional inorganic flame retardant has a significant effect on inhibiting flame propagation, it depends on high-polarity metal hydroxides with high filling amounts, and the polarity of the metal hydroxides does not match that of the low-polarity base resin, so that the flame retardant is difficult to uniformly disperse in the polymer base, the interfacial bonding force between the flame retardant and the polymer base is weak, and thus the mechanical properties of the material are reduced, which seriously limits the actual application effect of the material in high-demand scenarios. The phosphorus-silicon-boron composite system becomes a key research object due to its comprehensive advantages of high efficiency, smoke suppression, and anti-dripping. However, the phosphorus-silicon-boron composite flame retardant is separated due to the mismatched polarity during compounding, so that the dense carbon layer formed has gaps and is ineffective. Meanwhile, the components of the phosphorus-silicon-boron composite flame retardant contain polar groups, and the non-polarity of the polyolefin base is significantly different, so that the flame retardant is not uniformly dispersed in the base, and the material is prone to phase separation. Therefore, modification of the phosphorus-silicon-boron composite flame retardant becomes an effective path for preparing high-performance cable sheath materials.

[0004] Based on this, the application provides a preparation method of a low-smoke halogen-free flame-retardant cable sheath material. SUMMARY

[0005] The purpose of the application is to provide a preparation method of a low-smoke halogen-free flame-retardant cable sheath material to solve the problems mentioned in the background.

[0006] The purpose of the application can be achieved by the following technical solutions. A preparation method of a low-smoke halogen-free flame-retardant cable sheath material, comprising the following steps: Firstly, 3,4-dihydroxystyrene, phosphorus oxychloride, an acid binding agent, magnesium chloride, and acetonitrile are added to a three-necked flask, a condenser tube and a thermometer are installed, magnetic stirring is started, and the mixture is reacted at 55-65 DEG C for 2-3 hours. After being cooled to room temperature, the solid is filtered out, the remaining filtrate is washed with water and then eluted by column chromatography to obtain a phosphorus-containing flame-retardant unit. Secondly, the phosphorus-containing flame-retardant unit, trimethoxysilane, a platinum catalyst, and toluene are added to a three-necked flask under nitrogen protection, a condenser tube and a thermometer are installed, magnetic stirring is started, and the mixture is reacted at 70-90 DEG C for 4-8 hours. After being cooled to room temperature, the mixture is filtered, and the filtrate is eluted by column chromatography after being rotary evaporated to obtain a flame retardant precursor. Step 3: Add the flame retardant precursor, boric acid, hydrochloric acid and tetrahydrofuran into a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at 60-80°C for 8-12 hours. After the reaction, rotary evaporation is performed, and the flame retardant is washed with ethanol and acetone and then dried. Step 4: Add high-density polyethylene, low-density polyethylene, flame retardant, lubricant and antioxidant into an internal mixer and mix at 150-170° C. for 5-15 minutes, then transfer to a screw extruder for melt extrusion and granulation to obtain a low-smoke halogen-free flame-retardant cable sheath material.

[0007] Furthermore, the acid binding agent in the first step is at least one of triethylamine, 4-dimethylaminopyridine and N,N-diisopropylethylamine.

[0008] Furthermore, in the first step, the mass fractions of 3,4-dihydroxystyrene, phosphorus oxychloride, acid binding agent, magnesium chloride and acetonitrile are 13-16:18.5-21.5:25-30:0.9-2.8:200-240.

[0009] Furthermore, the platinum catalyst in the second step is at least one of a Speier catalyst and a Karstedt catalyst.

[0010] Furthermore, in the second step, the mass ratio of the phosphorus-containing flame retardant unit, trimethoxysilane, platinum catalyst and toluene is 17-25:12-18:0.5-2.5:120-140.

[0011] Furthermore, the mass fraction of hydrochloric acid in the third step is 30-38%.

[0012] Furthermore, in the third step, the mass ratio of the flame retardant precursor, boric acid, hydrochloric acid and tetrahydrofuran is 22-35:12-13.6:2.24-2.38:160-200.

[0013] Furthermore, in the fourth step, the lubricant is at least one of polyethylene wax or oxidized polyethylene wax.

[0014] Furthermore, in the fourth step, the antioxidant is at least one of antioxidant 300, antioxidant 1010 and antioxidant 3114.

[0015] Furthermore, in the fourth step, the mass ratio of high-density polyethylene, low-density polyethylene, flame retardant, lubricant and antioxidant is 65-75:25-35:15-20:1-3:1-3.

[0016] Furthermore, the temperature of the melt extrusion in the fourth step is 150-180°C.

[0017] A low-smoke, halogen-free, flame-retardant cable sheath material is prepared by any of the above preparation steps.

[0018] The beneficial effects of the present application are: The present application uses 3,4-dihydroxystyrene and phosphorus oxychloride as raw materials to carry out phosphate esterification reaction to obtain a phosphorus-containing flame retardant unit, uses the phosphorus-containing flame retardant unit and trimethoxysilane as raw materials to carry out a hydrosilylation reaction to obtain a flame retardant precursor, then uses the flame retardant precursor and boric acid as raw materials to carry out a hydrolysis condensation reaction to obtain a flame retardant, and finally uses high-density polyethylene, low-density polyethylene, the flame retardant, a lubricant and an antioxidant to carry out blending granulation to obtain a low-smoke halogen-free flame-retardant cable sheath material.

[0019] The flame retardant of the present application forms a phosphorus-silicon-boron crosslinking network through hydrolysis condensation, utilizes the synergistic effect of phosphorus-silicon-boron, and enables the low-smoke halogen-free flame-retardant cable sheath material to achieve efficient flame retardation. During combustion, the phosphorus system promotes the formation of carbon, the silicon system stabilizes the carbon layer, and the boron system enhances the compactness of the carbon layer, so as to form a hard and continuous protective ceramic layer. The protective layer has extremely high thermal stability, can effectively isolate heat and oxygen, and protects the internal material. At the same time, the barrier carbon layer greatly inhibits the generation of flammable volatile substances, thereby significantly reducing the smoke emission, and the material does not contain halogen, avoiding the generation of a large amount of dense smoke and toxic and corrosive gases during the combustion of halogen-based flame retardants. The low-smoke, flame-retardant, heat-resistant and environmentally friendly effects can be achieved at the same time.

[0020] The structure of the siloxane-coated boric acid ester group and the phosphate group in the flame retardant of the present application makes the overall flame retardant have low polarity, which is similar to the polarity of the polyethylene matrix. Therefore, the flame retardant has better compatibility with the low-polarity polyethylene matrix, the dispersion of the flame retardant in the polyethylene polymer matrix is more uniform, and the interface bonding is more superior. At the same time, the benzene ring structure in the flame retardant connects the strongly polar phosphorus-oxygen group and the non-polar silicon-oxygen group, which acts as a polarity bridge, avoiding the problem of polarity mismatch caused by direct connection, buffering the polarity mutation, and further forming a stable molecular structure, ensuring that the two fully play their flame-retardant mechanisms while making the internal combination of the flame retardant molecules more compact, thereby significantly improving the mechanical properties of the low-smoke halogen-free flame-retardant cable sheath material.

[0021] The siloxane-coated structure of the flame retardant in the present application forms a water-repellent layer on the surface of the material, preventing water from penetrating into the sheath interior, achieving a hydrophobic effect, greatly improving the storage stability and stability during processing of the flame retardant, avoiding premature decomposition due to high temperature and high humidity environment, and ensuring that the dielectric properties of the material are not affected in a humid environment, thereby ensuring the stability and safety of power transmission. DETAILED DESCRIPTION

[0022] The following is a clear and complete description of the technical solutions of the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection requested by this application.

[0023] The sources of all raw materials in the present invention are not particularly limited and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0024] Example 1:

[0025] A method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material comprises the following steps: Step 1: Add 13g of 3,4-dihydroxystyrene, 18.5g of phosphorus oxychloride, 25g of triethylamine, 0.9g of magnesium chloride and 200g of acetonitrile into a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, react at 55°C for 3h, and filter out the solid after cooling to room temperature. The remaining filtrate is evaporated to remove the solvent, washed with water, and then eluted by column chromatography to obtain a phosphorus-containing flame retardant unit; Step 2: Under nitrogen protection, 17 g of phosphorus-containing flame retardant unit, 12 g of trimethoxysilane, 0.5 g of Speier catalyst and 120 g of toluene were added to a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the mixture was reacted at 70° C. for 4 h and then cooled to room temperature. The mixture was then filtered, and the filtrate was subjected to rotary evaporation and column chromatography to obtain a flame retardant precursor. Step 3: Add 22g of flame retardant precursor, 12g of boric acid, 2.24g of 38% hydrochloric acid and 160g of tetrahydrofuran into a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at 60°C for 12h. After the reaction, evaporate the mixture and wash with ethanol and acetone, then dry to obtain a flame retardant. Step 4: Add 65g high-density polyethylene, 35g low-density polyethylene, 15g flame retardant, 1g polyethylene wax and 1g antioxidant 300 into an internal mixer and mix at 150°C for 15 minutes, then transfer to a screw extruder for melt extrusion at 150°C and granulate to obtain a low-smoke halogen-free flame-retardant cable sheath material.

[0026] A low-smoke, halogen-free, flame-retardant cable sheath material is prepared by the above preparation steps.

[0027] Example 2:

[0028] A method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material comprises the following steps: The first step is to add 16g of 3,4-dihydroxystyrene, 20g of phosphorus oxychloride, 27.5g of 4-dimethylaminopyridine, 1.85g of magnesium chloride and 220g of acetonitrile into a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, react at 60°C for 2.5h, and filter out the solid after cooling to room temperature. The remaining filtrate is evaporated to remove the solvent, washed with water, and then eluted by column chromatography to obtain a phosphorus-containing flame retardant unit; Step 2: Under nitrogen protection, 21 g of phosphorus-containing flame retardant unit, 15 g of trimethoxysilane, 1.5 g of Karstedt catalyst and 130 g of toluene were added to a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the mixture was reacted at 120° C. for 10 h, then cooled to room temperature and filtered. The filtrate was subjected to rotary evaporation and column chromatography to obtain a flame retardant precursor; Step 3: Add 28.5 g of flame retardant precursor, 12.8 g of boric acid, 2.36 g of 34% hydrochloric acid and 180 g of tetrahydrofuran into a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, and react at 70°C for 10 h. After the reaction, evaporate the mixture and wash with ethanol and acetone, then dry to obtain a flame retardant. Step 4: Add 70g high-density polyethylene, 30g low-density polyethylene, 17.5g flame retardant, 2g oxidized polyethylene wax and 2g antioxidant 1010 into an internal mixer and mix at 160°C for 10 minutes, then transfer to a screw extruder for melt extrusion at 165°C and granulate to obtain a low-smoke halogen-free flame-retardant cable sheath material.

[0029] A low-smoke, halogen-free, flame-retardant cable sheath material is prepared by the above preparation steps.

[0030] Example 3:

[0031] A method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material comprises the following steps: Step 1: Add 16 g of 3,4-dihydroxystyrene, 21.5 g of phosphorus oxychloride, 30 g of N,N-diisopropylethylamine, 2.8 g of magnesium chloride and 240 g of acetonitrile into a three-necked flask, install a condenser and a thermometer, turn on magnetic stirring, react at 65 ° C for 2 hours, and filter out the solid after cooling to room temperature. The remaining filtrate is evaporated to remove the solvent, washed with water, and then eluted by column chromatography to obtain a phosphorus-containing flame retardant unit; Step 2: Under nitrogen protection, 25 g of phosphorus-containing flame retardant unit, 18 g of trimethoxysilane, 2.5 g of Speier catalyst and 140 g of toluene were added to a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the mixture was reacted at 130 ° C for 8 hours and then cooled to room temperature. The mixture was then filtered, and the filtrate was subjected to rotary evaporation and column chromatography to obtain a flame retardant precursor; Third step, 35g flame retardant precursor, 13.6g boric acid, 2.38g 30% mass fraction hydrochloric acid and 200g tetrahydrofuran were added into a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was started, and the reaction was carried out at 80℃ for 8h. After the reaction, rotary evaporation was carried out, and the product was washed with ethanol and acetone and dried to obtain the flame retardant; Fourth step, 75g high-density polyethylene, 25g low-density polyethylene, 20g flame retardant, 3g polyethylene wax and 3g antioxidant 3114 were added into a banbury mixer, and after mixing at 170℃ for 5min, they were transferred into a screw extruder and melt-extruded at 180℃ to obtain a low-smoke halogen-free flame-retardant cable sheath material.

[0032] A low-smoke halogen-free flame-retardant cable sheath material was prepared by the above preparation steps.

[0033] Comparative Example 1 The difference between this comparative example and Example 2 is that the flame retardant is replaced by a commercially available phosphate ester flame retardant, and the other raw materials and preparation steps remain unchanged.

[0034] Experimental Example 1 The materials in Examples 1-3 and Comparative Example 1 were tested for performance, and the flame-retardant grades of the cable sheath materials in each group were tested according to GB / T19666-2019 "General Requirements for Flame Retardant and Fire-Resistant Wire and Cable or Optical Cable"; the tensile strength of the cable sheath materials in each group was tested according to GB / T2951.11-2008 "General Test Methods for Cable and Optical Cable Insulation and Sheath Materials"; and the surface water contact angle of the cable sheath materials in each group was tested according to GB / T32129-2015 "Halogen-Free Low-Smoke Flame-Retardant Cable Material for Wire and Cable". The test results are shown in Table 1.

[0035] Table 1

[0036]

[0037] As can be seen from Table 1, Examples 1-3 have higher flame-retardant grades, tensile strengths and surface contact angles than Comparative Example 1, indicating that the flame-retardant performance, mechanical properties and hydrophobic properties of Examples 1-3 are superior to those of Comparative Example 1. In combination with Comparative Example 1, it can be seen that the self-prepared flame retardant can effectively improve the flame-retardant performance, mechanical properties and hydrophobic properties of the cable sheath material.

[0038] The above examples are only used to help understand the method of the present application and its core idea. Various modifications to these examples will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these examples shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material, characterized in that: The following steps are involved: Preparation of the flame retardant: 3,4-dihydroxystyrene and phosphorus oxychloride undergo a phosphate esterification reaction in the presence of an acid binder to obtain a phosphorus-containing flame retardant unit. The phosphorus-containing flame retardant unit and trimethoxysilane undergo a hydrosilylation reaction in the presence of a platinum catalyst to obtain a flame retardant precursor. Finally, the flame retardant precursor and boric acid undergo a hydrolysis condensation reaction to obtain the flame retardant. Preparation of low-smoke halogen-free flame-retardant cable sheath material: high-density polyethylene, low-density polyethylene, flame retardant, lubricant, and antioxidant are blended, and then melt-extruded and granulated to obtain low-smoke halogen-free flame-retardant cable sheath material.

2. The method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material according to claim 1, characterized in that: The acid binding agent is at least one of triethylamine, 4-dimethylaminopyridine and N,N-diisopropylethylamine.

3. The method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material according to claim 1, characterized in that: The mass proportions of 3,4-dihydroxystyrene, phosphorus oxychloride and acid binding agent are 13-16:18.5-21.5:25-30.

4. The method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material according to claim 1, characterized in that: The platinum catalyst is at least one of a Speier catalyst and a Karstedt catalyst.

5. The method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material according to claim 1, characterized in that: The mass ratio of the phosphorus-containing flame retardant unit, trimethoxysilane and platinum catalyst is 17-25:12-18:0.5-2.

5.

6. The method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material according to claim 1, characterized in that: The mass ratio of the flame retardant precursor to the boric acid is 22-35:12-13.

6.

7. The method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material according to claim 1, characterized in that: The lubricant is at least one of polyethylene wax and oxidized polyethylene wax.

8. The method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material according to claim 1, characterized in that: The antioxidant is at least one of antioxidant 300, antioxidant 1010, and antioxidant 3114.

9. The method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material according to claim 1, characterized in that: The mass ratio of high-density polyethylene, low-density polyethylene, flame retardant, lubricant and antioxidant is 65-75:25-35:15-20:1-3:1-3.

10. The method for preparing a low-smoke, halogen-free, flame-retardant cable sheath material according to claim 1, characterized in that: The temperature of melt extrusion is 150 to 180°C.

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