Toughening type composite modified magnesium hydroxide as well as preparation method and application thereof

Abstract

The invention provides toughened composite modified magnesium hydroxide as well as a preparation method and application thereof, and belongs to the technical field of chemical materials. The bonding effect of magnesium hydroxide particles and polyolefin resin is improved in a surface modification mode, meanwhile, nanoscale silicon dioxide particles with the high specific surface area are added in magnesium hydroxide powder particles, the nanoscale particles do not affect the flame retardant property of a product and do not affect the dispersity of the powder, the bonding force between the nanoscale particles and the polyolefin resin is good, and the flame retardant property of the product is improved. Therefore, the magnesium hydroxide has a good flame-retardant effect and elongation at break in a polyolefin flame-retardant product.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical materials, and in particular to a toughened composite modified magnesium hydroxide and a preparation method and application thereof. Background Art

[0002] With the continuous advancement of replacing steel with plastic, most products in our lives are now made of various plastics. The flammability of plastics poses a serious challenge to their safety, so most plastic products now require flame retardant properties.

[0003] Flame retardants are generally divided into organic flame retardants and inorganic flame retardants. Usually, in order to achieve the ideal flame retardant effect, it is necessary to use organic flame retardants and inorganic flame retardants together to achieve it. The most commonly used inorganic flame retardants are aluminum hydroxide and magnesium hydroxide. Among them, magnesium hydroxide is widely used in polyolefin low-smoke halogen-free flame retardant products due to its high processing decomposition temperature, good flame retardant effect and smoke suppression effect. However, due to the relatively high addition amount of magnesium hydroxide in the polyolefin flame retardant system, generally reaching more than 60%, and the hexagonal scaly morphology of magnesium hydroxide crystals, the high polarity of the particle surface, and poor compatibility with polyolefin resins, when magnesium hydroxide is added to polyolefin halogen-free flame retardant products, the elongation at break of the products is greatly affected, seriously affecting the performance of the products. Summary of the Invention

[0004] The object of the present invention is to provide a toughened composite modified magnesium hydroxide and a preparation method and application thereof. The composite modified magnesium hydroxide can improve the elongation at break of polyolefin low-smoke halogen-free products and has good application effect.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing toughened composite modified magnesium hydroxide, comprising the following steps:

[0007] Mixing nano-silica with water, mixing the obtained silica slurry with a first modifier, and performing surface treatment to obtain modified silica slurry;

[0008] The modified silicon dioxide slurry is mixed with magnesium hydroxide, and the mixture is ground and classified in sequence to obtain modified magnesium hydroxide;

[0009] The modified magnesium hydroxide is mixed with a second modifier and subjected to modification treatment to obtain a toughened composite modified magnesium hydroxide;

[0010] The first modifier includes a vinyl silane coupling agent;

[0011] The second modifier includes stearate, stearic acid or polymethyl methacrylate.

[0012] Preferably, the average particle size of the nano-silicon dioxide is 30 to 100 nm.

[0013] Preferably, the solid content of the silica slurry is 5 to 20 wt %; the mass of the first modifier is 5 to 10% of the dry weight of the nano-silica.

[0014] Preferably, the surface treatment temperature is 25° C. and the time is 10 to 30 minutes.

[0015] Preferably, the modified silicon dioxide slurry is mixed with magnesium hydroxide at a flow rate of 5 to 30 kg / h.

[0016] Preferably, the average particle size D of the modified magnesium hydroxide 50 1.0~3.0μm, D 98 3.5~6.5μm.

[0017] Preferably, the mass of the second modifier is 0.8-1.5% of the dry weight of the modified magnesium hydroxide.

[0018] Preferably, the temperature of the modification treatment is 80-120° C., the time is 10-20 min, and the stirring speed is 600-800 r / min.

[0019] The present invention provides toughened composite modified magnesium hydroxide prepared by the preparation method described in the above technical solution.

[0020] The present invention provides the use of the toughened composite modified magnesium hydroxide described in the above technical solution in polyolefin flame retardant products.

[0021] The present invention provides a method for preparing toughened composite modified magnesium hydroxide. The method improves the bonding between magnesium hydroxide particles and polyolefin resin by surface modification. Nano-scale silicon dioxide particles with a high specific surface area are added to magnesium hydroxide powder particles. These nano-scale particles do not affect the flame retardant properties of the product or the dispersibility of the powder. The prepared composite modified magnesium hydroxide particles have good bonding strength with the polyolefin resin, thereby enabling the magnesium hydroxide to obtain good flame retardant effect and elongation at break in the polyolefin flame retardant product.

[0022] The present invention uses nano-scale hydrophilic silica particles to form a suspension slurry, and performs surface modification on the nano-silica particles in the slurry to ensure the dispersibility of the silica particles. The good dispersibility of silica in the liquid phase allows the silica to be more evenly compounded with the magnesium hydroxide particles.

[0023] The present invention uses mechanical force and chemical bonding to jointly prepare modified magnesium hydroxide: when surface - modifying silicon dioxide particles in a slurry, a first modifier (organosilane) is added. When the silicon dioxide suspension is added to magnesium hydroxide particles for co - grinding, under the combined action of mechanical shear force and the chemical bonding force of the modifier, the first modifier acts as a linker between the silicon dioxide particles and the magnesium hydroxide particles, effectively binding the silicon dioxide particles and the magnesium hydroxide particles together. At the same time, the first modifier also modifies the magnesium hydroxide particles, ensuring that the surface of the magnesium hydroxide particles is jointly coated with nanoscale silicon dioxide particles and an organic modifier. The nanoscale silicon dioxide particles have a large specific surface area and act as a reinforcing material in polymers, thereby obtaining modified magnesium hydroxide with high dispersion and high reinforcement performance.

[0024] The present invention adopts a secondary modification technology. After the ground modified magnesium hydroxide is effectively coated with a silane coupling agent and nanoscale silicon dioxide particles, its dispersibility and reinforcement performance are significantly enhanced. However, due to the introduction of nanoscale silicon dioxide particles, the hydrophobicity and processing fluidity of the modified magnesium hydroxide are still insufficient. The present invention conducts secondary modification on the ground and modified ultrafine magnesium hydroxide by using a second modifier. The second modifier has good compatibility with polyolefin resins and good hydrophobicity itself. Therefore, it can greatly improve the compatibility and lubricity between magnesium hydroxide and polyolefin resins, while improving hydrophobicity and fluidity, enabling its reinforcement performance to be fully exerted and facilitating addition during application, thus improving production efficiency. Detailed implementation mode

[0025] In the present invention, unless otherwise specified, the raw materials or reagents used are well - known commercially available products in the art.

[0026] The present invention provides a preparation method of a toughened composite - modified magnesium hydroxide, comprising the following steps:

[0027] Mix nanoscale silicon dioxide with water, mix the obtained silicon dioxide slurry with a first modifier for surface treatment to obtain a modified silicon dioxide slurry;

[0028] Mix the modified silicon dioxide slurry with magnesium hydroxide, and conduct grinding and classification in sequence to obtain modified magnesium hydroxide;

[0029] Mix the modified magnesium hydroxide with a second modifier for modification treatment to obtain a toughened composite - modified magnesium hydroxide;

[0030] The first modifier includes a vinyl silane coupling agent;

[0031] The second modifier includes a stearate, stearic acid or polymethyl methacrylate.

[0032] In the present invention, nano-silica is mixed with water, and the obtained silica slurry is mixed with a first modifier for surface treatment to obtain a modified silica slurry.

[0033] In the present invention, the nano-silica is preferably precipitated silica or fumed silica; the average particle size of the nano-silica is preferably 30 - 100 nm, more preferably fumed silica with a particle size of 50 - 100 nm.

[0034] In the present invention, the solid content of the silica slurry is preferably 5 - 20 wt%, more preferably 6 - 15 wt%, and further preferably 7 - 8 wt%.

[0035] In the present invention, the first modifier includes a vinyl silane coupling agent; the vinyl silane coupling agent is preferably vinyltris(2 - methoxyethoxy)silane.

[0036] In the present invention, the mass of the first modifier is preferably 5 - 10% of the dry weight of the nano-silica, more preferably 7 - 8%.

[0037] In the present invention, the temperature of the surface treatment is preferably 25 °C, and the time is preferably 10 - 30 min, more preferably 30 min.

[0038] In the present invention, the surface treatment improves the dispersibility of the silica nanoparticles and the binding force between the particles and the polyolefin, obtaining highly dispersed nanoparticles.

[0039] After obtaining the modified silica slurry, in the present invention, the modified silica slurry is mixed with magnesium hydroxide, followed by grinding and classification in sequence to obtain modified magnesium hydroxide.

[0040] In the present invention, magnesium hydroxide ore (preferably brucite ore) is preferably crushed by a hammer crusher into magnesium hydroxide particles with a particle size ≤ 10 mm, lifted by a hoist to a silo for storage, the magnesium hydroxide particles in the silo are transported by a belt to a screw feeder, and the prepared modified silica slurry is fed into the screw feeder by a gear metering pump to be mixed with the magnesium hydroxide particles. The mixed material is fed into a drum ball mill by the screw feeder for grinding. The magnesium hydroxide particles ground by the ball mill are transported by air to a horizontal air classifier for classification treatment. After classification treatment by the classifier, modified magnesium hydroxide is obtained.

[0041] In the present invention, the diameter of the drum ball mill is preferably 2.0m to 4.0m, more preferably 2 to 3m, and further preferably 2.6 to 2.8m, and the length is preferably 8 to 12m, more preferably 8 to 9m, and further preferably 8.5 to 9.0m; the diameter of the classifying wheel in the classifier used for the classification is preferably 200mm, 300mm or 400mm, the number of classifying heads is preferably 3 to 6, more preferably 4 to 5, and the rotation speed of the classifier is preferably 2500 to 3400r / min, more preferably 3000 to 3400r / min, and further preferably 3200 to 3250r / min.

[0042] In the present invention, the modified silica slurry is preferably mixed with magnesium hydroxide at a flow rate of 5 to 30 kg / h, more preferably 8 to 20 kg / h, further preferably 10 to 15 kg / h, and most preferably 12 to 13 kg / h.

[0043] In the present invention, the average particle size D of the modified magnesium hydroxide is 50 Preferably, it is 1.0 to 3.0 μm, more preferably 2.0 to 3.0 μm, and even more preferably 2.3 to 2.5 μm; D 98 It is preferably 3.5 to 6.5 μm, more preferably 4.5 to 6.5 μm, and even more preferably 5.8 to 6.0 μm.

[0044] After obtaining the modified magnesium hydroxide, the present invention mixes the modified magnesium hydroxide with a second modifier and performs a modification treatment to obtain a toughened composite modified magnesium hydroxide.

[0045] In the present invention, the second modifier includes stearate, stearic acid or polymethyl methacrylate, more preferably hydroxyl-terminated polymethyl methacrylate.

[0046] In the present invention, the mass of the second modifier is preferably 0.8-1.5% of the dry weight of the modified magnesium hydroxide, more preferably 1.0-1.5%, and even more preferably 1.2-1.3%.

[0047] In the present invention, the modified magnesium hydroxide and the second modifier are preferably subjected to modification treatment in a high-speed mixer to obtain toughened composite modified magnesium hydroxide.

[0048] In the present invention, the temperature of the modification treatment is preferably 80-120°C, more preferably 112±2°C; the time is preferably 10-20 min, more preferably 15±1 min; the stirring speed is preferably 600-800 r / min, more preferably 780-790 r / min.

[0049] The present invention provides toughened composite modified magnesium hydroxide prepared by the preparation method described in the above technical solution.

[0050] The present invention provides the use of the toughened composite modified magnesium hydroxide described in the above technical solution in polyolefin flame retardant products. The present invention has no particular limitation on the method of application, and the application can be carried out according to methods well known in the art.

[0051] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0052] In the following examples, the raw magnesium hydroxide ore is brucite ore, which is sourced from Kuandian, Dandong, Liaoning;

[0053] Hydroxyl-terminated polymethyl methacrylate: Wuhan Chengtian Fine Chemical Co., Ltd.

[0054] Example 1

[0055] 1) Fumed nano-silica particles with an average particle size of 50 to 100 nm were prepared with water to form a slurry with a solid content of 6 wt %. A vinyl silane coupling agent (vinyl tris(2-methoxyethoxy)silane) accounting for 7 wt % of the dry weight of the nano-silica particles was added to the resulting silica slurry, and the mixture was stirred at room temperature for 30 minutes to obtain a modified silica slurry.

[0056] 2) The magnesium hydroxide ore is crushed into magnesium hydroxide particles with a particle size of less than 10 mm by a hammer crusher, and is lifted to a silo for storage by an elevator. The magnesium hydroxide particles in the silo are transported to a screw feeder via a belt, and the prepared modified silicon dioxide slurry is fed into the screw feeder at a flow rate of 12 kg / h by a gear metering pump to mix with the magnesium hydroxide particles. The mixed material is fed into a drum ball mill with a diameter of 2.6 m and a length of 8.5 m by a screw feeder for ultrafine grinding. The magnesium hydroxide particles ground by the ball mill are transported by airflow to a horizontal airflow classifier with a diameter of 200 mm×4 for classification treatment. The classifier speed is 3200 r / min to obtain modified magnesium hydroxide with an average particle size of D 50 2.3μm; D 98 5.8μm;

[0057] 3) The modified magnesium hydroxide was mixed with a modifier, terminal hydroxyl polymethyl methacrylate, in a high-speed mixer for secondary modification. The mass of the modifier was 1.2% of the dry weight of the modified magnesium hydroxide. The stirring speed of the high-speed mixer was 800 r / min, the modification temperature was 110° C., and the modification time was 15 min to obtain a composite modified magnesium hydroxide.

[0058] Example 2

[0059] 1) Prepare a slurry with a solid content of 7 wt% by using fumed silica particles with an average particle size of 50 - 100 nm and water. Add a vinyl silane coupling agent (vinyl tris(2 - methoxyethoxy)silane) accounting for 7% of the dry weight of the nano - silica particles to the silica slurry, and stir at room temperature for 30 min to obtain a modified silica slurry;

[0060] 2) Crush the original magnesium hydroxide ore into magnesium hydroxide particles with a particle size of less than 10 mm by a hammer crusher, lift them to a storage bin by a hoist, transport the magnesium hydroxide particle material in the bin to a screw feeder by a belt. Feed the prepared modified silica slurry into the screw feeder at a flow rate of 13 kg / h by a gear metering pump to mix with the magnesium hydroxide particles. The mixed material is fed into a drum ball mill with a diameter of 2.8 m and a length of 9.0 m for ultrafine grinding. After grinding by the ball mill, the magnesium hydroxide particles are pneumatically transported to a horizontal air classifier with a diameter of 200 mm × 4 for classification. The classifier rotates at 3200 r / min to obtain modified magnesium hydroxide; the average particle size D 50 is 2.4 μm; D 98 is 6.0 μm;

[0061] 3) Mix the modified magnesium hydroxide with a modifier, hydroxy - terminated polymethyl methacrylate, in a high - speed mixer for secondary modification. The mass of the modifier is 1.3% of the dry weight of the modified magnesium hydroxide. The stirring speed of the high - speed mixer is 800 r / min, the modification temperature is 110 °C, and the modification time is 15 min to obtain a composite - modified magnesium hydroxide.

[0062] Example 3

[0063] 1) Prepare a slurry with a solid content of 8 wt% by using fumed silica particles with an average particle size of 50 - 100 nm and water. Add a vinyl silane coupling agent (vinyl tris(2 - methoxyethoxy)silane) accounting for 8% of the dry weight of the nano - silica particles to the silica slurry, and stir at room temperature for 30 min to obtain a modified silica slurry;

[0064] 2) Crush the original magnesium hydroxide ore into magnesium hydroxide particles with a particle size of less than 10 mm by a hammer crusher, lift them to a storage bin by a hoist, transport the magnesium hydroxide particle material in the bin to a screw feeder by a belt. Feed the prepared modified silica slurry into the screw feeder at a flow rate of 13 kg / h by a gear metering pump to mix with the magnesium hydroxide particles. The mixed material is fed into a drum ball mill with a diameter of 2.4 m and a length of 8.5 m for ultrafine grinding. After grinding by the ball mill, the magnesium hydroxide particles are pneumatically transported to a horizontal air classifier with a diameter of 200 mm × 4 for classification. The classifier rotates at 3250 r / min to obtain modified magnesium hydroxide; the average particle size D50 is 2.3 μm; D 98 is 5.9 μm;

[0065] 3) Mix the modified magnesium hydroxide with the modifier, hydroxyl-terminated polymethyl methacrylate, in a high-speed mixer for secondary modification. The mass of the modifier is 1.3% of the dry weight of the modified magnesium hydroxide. The stirring speed of the high-speed mixer is 790 r / min, the modification temperature is 112 °C, and the modification time is 16 min to obtain the composite modified magnesium hydroxide.

[0066] Test Example 1

[0067] Test the particle size and oil absorption value of the composite modified magnesium hydroxide prepared in Test Examples 1 to 3. The results are shown in Table 2.

[0068] Apply the different composite modified magnesium hydroxides prepared in Examples 1 to 3 to the polyolefin low-smoke and halogen-free flame retardant system to prepare low-smoke and halogen-free cable specimens, and test the oxygen index, elongation at break, and tensile strength of the specimens: The test procedure is as follows:

[0069] Table 1 Test formula of different modified magnesium hydroxides in low-smoke and halogen-free cables

[0070] materials EVA PE Zinc stearate Modified magnesium hydroxide Addition amount (wt%) 15 18 2 65

[0071] According to the formula in Table 1, add EVA, PE resin, zinc stearate, and modified magnesium hydroxide to a 1 L internal mixer. Set the temperature of the internal mixer to 120 °C and the time to 30 min. Weigh 110 g of the kneaded material and press it into a sheet on a small press at a temperature of 180 °C and a pressure holding time of 20 min; Cut the pressed sheet into standard specimens by an automatic sampler (the specimen is type 5 and 1 mm thick). Test the oxygen index, elongation at break, and tensile strength of the specimens.

[0072] Comparative Examples 1 - 5

[0073] The samples of the comparative examples are Aitemag-55ZA2 of Jiangsu Aiteke Magnesium Hydroxide, JLH-QD2 of Jinhaohui, V-10 of Liaoning Weikete Rui, 2803T of Hefei Zhongke, and Brucite Ecopiren3.5CA of Russia, which are used as Comparative Examples 1 - 5 in turn.

[0074] According to the formula in Table 1, compare the samples of Comparative Examples 1 - 5 with the composite modified magnesium hydroxide of Examples 1 - 3. The results are shown in Table 2.

[0075] Table 2 Performance indicators of the modified magnesium hydroxide in Examples 1 - 3 and Comparative Examples 1 - 5 and its performance used in polyolefin

[0076]

[0077] As can be seen from Table 2, the modification technology and particle size control technology adopted in the present invention (in step 2, an air flow classifier is used to obtain modified ultrafine magnesium hydroxide, and the finer the particle size, the better the toughening effect) obtain high-performance composite modified magnesium hydroxide. Compared with conventional modified magnesium hydroxide, when applied to polyolefin low-smoke halogen-free flame retardant cables, its oxygen index is improved to a certain extent, and the elongation at break is greatly improved, thereby obtaining a cable material with excellent mechanical properties. Specifically, the elongation at break of the cable is increased from 400% to more than 500%, an increase of 25%, and the oxygen index is also improved on the original basis.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A preparation method of toughened composite modified magnesium hydroxide, characterized in that, It includes the following steps: Mix nano-silica with water, mix the obtained silica slurry with a first modifier, and conduct surface treatment to obtain a modified silica slurry; Mix the modified silica slurry with magnesium hydroxide, and conduct grinding and classification in sequence to obtain modified magnesium hydroxide; Mix the modified magnesium hydroxide with a second modifier, and conduct modification treatment to obtain a toughened composite modified magnesium hydroxide; The first modifier includes a vinyl silane coupling agent; The second modifier includes a stearate, stearic acid or polymethyl methacrylate.

2. The preparation method according to claim 1, characterized in that, The average particle size of the nano-silica is 30 - 100 nm.

3. The preparation method according to claim 2, wherein, The solid content of the silica slurry is 5 - 20 wt%; the mass of the first modifier is 5 - 10% of the dry weight of the nano-silica.

4. The preparation method according to claim 3, characterized in that, The temperature of the surface treatment is 25 °C, and the time is 10 - 30 min.

5. The preparation method according to claim 1, wherein The modified silica slurry is mixed with magnesium hydroxide at a flow rate of 5 - 30 kg / h.

6. The preparation method according to claim 1 or 5, characterized in that, The average particle size D of the modified magnesium hydroxide 50 is 1.0 to 3.0 μm, and D 98 is 3.5 to 6.5 μm.

7. The preparation method according to claim 1 or 6, characterized in that, The mass of the second modifier is 0.8 - 1.5% of the dry weight of the modified magnesium hydroxide.

8. The preparation method according to claim 7, characterized in that, The temperature of the modification treatment is 80 - 120 °C, the time is 10 - 20 min, and the stirring speed is 600 - 800 r / min.

9. The toughened composite modified magnesium hydroxide prepared by the preparation method according to any one of claims 1 - 8.

10. The application of the toughened composite modified magnesium hydroxide according to claim 9 in polyolefin flame-retardant products.

Images