A high-strength masterbatch for plastic pipes and preparation method thereof

Abstract

The invention discloses a high-strength masterbatch of plastic pipe and a preparation method thereof, belonging to the technical field of polymer materials, including 15-20 parts of polyolefin elastomer, 65-70 parts of flame retardant, 15-20 parts of dispersant, and 1-3 parts of compatibilizer; the flame retardant is prepared by the following steps: 3-hydroxybutyric acid is added dropwise to 2-methyl-2,5-dioxy-1,2-oxaphospholane, and the reaction is stirred to obtain carboxyl phosphate; carboxyl phosphate is added to a magnesium chloride solution while stirring, heat-activated diatomaceous earth is added, and the dispersion is stirred and dispersed to obtain a dispersion liquid; the dispersion liquid is adjusted to be alkaline to obtain a flame retardant. The flame retardant has good toughening and flame retardant effects. In plastic masterbatch and in application, the internal structure of plastic polymer material is too regular, which is not conducive to the dispersion of flame retardant, and the short chain in the carboxyl phosphate structure in the flame retardant can play the role of connecting molecules, so that the toughness of the material is enhanced, so that the performance of the material blending system is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of functional polymer materials, and in particular relates to a high-strength masterbatch for plastic pipes and a preparation method thereof. Background Art

[0002] Polyethylene pipes have excellent mechanical strength and corrosion resistance. In addition, they are light, smooth, low-priced and easy to install. Therefore, they have been widely used in water pipes for construction, agricultural irrigation and drainage pipes, gas pipes and sewage pipes. Taking high-density polyethylene (HDPE) as an example, HDPE has a crystallinity of 80% to 90%, a softening point of 125 to 135°C, and an operating temperature of up to 100°C. HDPE has good chemical stability. At room temperature, HDPE is insoluble in any organic solvent and is resistant to corrosion by acids, alkalis and various salts. Plastic products are formed by injection, extrusion, blow molding and rotational molding.

[0003] However, polyethylene is a flammable polymer with an oxygen index of 17%-18%. The thermal degradation reaction of polyethylene is random chain breaking and intramolecular and intermolecular transfer reactions. It is degraded into low molecular weight substances under high temperature, which can easily spread flames and cause fires. There are two commonly used flame retardants: one is reactive flame retardant; the other is additive flame retardant. Reactive flame retardants are limited by technology and application conditions, which is not conducive to promotion. Additive flame retardants are easy to use and low in price, so they are currently a common method to achieve polyethylene flame retardancy, but additive flame retardants are poor in compatibility and the effect of maintaining the original properties of the polyethylene resin matrix. Summary of the invention

[0004] The object of the present invention is to provide a high-strength masterbatch for plastic pipes and a preparation method thereof, so as to solve the problem that the effect of adding flame retardants in a polyethylene resin matrix is ​​poor in maintaining the original performance of the polyethylene resin matrix.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A high-strength masterbatch for plastic pipes, comprising, by weight, 15-20 parts of a polyolefin elastomer, 65-70 parts of a flame retardant, 15-20 parts of a dispersant, and 1-3 parts of a compatibilizer; the flame retardant is prepared by the following steps:

[0007] Step S1, adding 3-hydroxybutyric acid dropwise to 2-methyl-2,5-dioxo-1,2-oxaphospholane, stirring for reaction, the reaction temperature is 105° C., to obtain carboxyl phosphate; the molar ratio of 2-methyl-2,5-dioxo-1,2-oxaphospholane to 3-hydroxybutyric acid is 1:1;

[0008] Step S2, adding carboxyl phosphate to the magnesium chloride solution while stirring, adding heat-activated diatomaceous earth, stirring and dispersing, and obtaining a dispersion; adding sodium hydroxide aqueous solution to the dispersion to adjust the pH value to alkaline, and obtaining a flame retardant. The carboxyl phosphate undergoes a grafting reaction with the silanol group on the surface of the heat-activated diatomaceous earth or the hydroxyl group on the surface of the magnesium hydroxide to improve the dispersibility and prevent agglomeration.

[0009] Furthermore, magnesium chloride and an ethanol aqueous solution are mixed to obtain a magnesium chloride solution, wherein the concentration of the magnesium chloride solution is 0.8-1.2 mol / L, and the volume fraction of ethanol in the ethanol aqueous solution is 70%.

[0010] Furthermore, the reaction time in step S1 is 1.5-2h.

[0011] Furthermore, the alkaline pH value in step S2 is in the range of 12-13.

[0012] Furthermore, the heat-activated diatomaceous earth is prepared by the following steps:

[0013] The diatomaceous earth is thermally activated at 400-450° C. for 1.5-2 hours to obtain thermally activated diatomaceous earth.

[0014] Furthermore, the particle size of the diatomaceous earth is 1-10 μm.

[0015] Furthermore, the dispersant is a mixture of linear low-density polyethylene and vinyl acetate copolymer in a mass ratio of 3:2.

[0016] Furthermore, the compatibilizer is any one of maleic anhydride grafted ethylene-vinyl acetate copolymer, acrylic acid grafted ethylene-vinyl acetate copolymer and maleic anhydride grafted polyethylene.

[0017] A method for preparing high-strength masterbatch for plastic pipes comprises the following steps:

[0018] Step 1: Mixing: Weigh the polyolefin elastomer, flame retardant, dispersant and compatibilizer according to the weight ratio, put them into a high-speed mixer and stir for 5-15 minutes at a temperature of 80℃-90℃;

[0019] Step 2: Twin-screw extrusion: Add the mixed materials into a twin-screw extruder for granulation, with the screw speed of the extruder being 400-600r / min;

[0020] Step 3: Pelletizing and drying: The extruded material strips are water-cooled and then sent to a pelletizer for drying at a drying temperature of 70-80°C.

[0021] Furthermore, the temperatures of the six heating sections and the die head are 140-145°C, 170-175°C, 190-200°C, 205-210°C, 205-210°C, 210-215°C, and 210-215°C, respectively.

[0022] Beneficial effects of the present invention:

[0023] The present invention provides a high-strength masterbatch for plastic pipes and a preparation method thereof. A self-made flame retardant is added to the masterbatch, which has good toughening and flame retardant effects. In the plastic masterbatch and in its application, the internal structure of the plastic polymer material is too regular, which is not conducive to the dispersion of the flame retardant. The short chain in the carboxyl phosphate structure in the flame retardant in the present invention can play a role in connecting molecules, thereby enhancing the toughness of the material and improving the performance of the material blending system.

[0024] The flame retardant prepared by the present invention uses diatomite as the core and the unique microporous structure of diatomite itself to fix magnesium hydroxide by a precipitation method. In the fixing process, carboxyl phosphate is added to inhibit the agglomeration of magnesium hydroxide. Carboxyl phosphate is a phosphorus-containing material. As a carbon promoter, it promotes the material to form a complex phosphorus-rich carbon slag covering layer during combustion, which can prevent the transfer of oxygen and heat. In the present invention, a synergistic flame retardant system is formed with the inorganic flame retardant magnesium hydroxide to improve the flame retardant performance of plastic products.

[0025] The residual substances formed by the oxidation of metals such as silicon dioxide and ferric oxide in the diatomite used as the core of the present invention increase the strength and thickness of the carbon layer, so that it can better block the polymer matrix from the high temperature and combustible gas outside: the large number of micropores of the diatomite itself can absorb part of the heat and combustible gas, thereby slowing down the combustion of the polymer matrix. In the present invention, through the interaction of organic and inorganic flame retardants, the flame retardant plays a certain good role in the flame retardancy of the plastic matrix. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Polyolefin elastomer (produced by DuPont, USA), high-density polyethylene (HDPE5306J (Yangzi Petrochemical)).

[0028] Example 1

[0029] This embodiment provides a flame retardant, which is prepared by the following steps:

[0030] Step S1, adding 3-hydroxybutyric acid dropwise to 2-methyl-2,5-dioxo-1,2-oxaphospholane, stirring and reacting for 1.5 hours at a reaction temperature of 105° C. to obtain carboxyl phosphate; the molar ratio of 2-methyl-2,5-dioxo-1,2-oxaphospholane to 3-hydroxybutyric acid is 1:1;

[0031] Step S2, thermally activating diatomite with a particle size of 1-10 μm at 400° C. for 1.5 h to obtain thermally activated diatomite; the volume fraction of ethanol in the ethanol aqueous solution is 70%, and magnesium chloride and the ethanol aqueous solution are mixed to obtain a magnesium chloride solution, wherein the concentration of the magnesium chloride solution is 0.8 mol / L;

[0032] 3 g of carboxyl phosphate was added to 100 mL of magnesium chloride solution while stirring, and 0.1 g of heat-activated diatomaceous earth was added, and the mixture was stirred and dispersed to obtain a dispersion; sodium hydroxide aqueous solution was added dropwise to the dispersion to adjust the pH value to be alkaline, and the alkaline pH value range was 12-13 to generate precipitation. After the stirring was completed, the temperature was kept constant, and the stirring reaction was continued for 50 minutes to obtain a suspension, which was centrifuged and freeze-dried to obtain a flame retardant.

[0033] Example 2

[0034] This embodiment provides a flame retardant, which is prepared by the following steps:

[0035] Step S1, adding 3-hydroxybutyric acid dropwise to 2-methyl-2,5-dioxo-1,2-oxaphospholane, stirring and reacting for 1.5 hours at a reaction temperature of 105° C. to obtain carboxyl phosphate; the molar ratio of 2-methyl-2,5-dioxo-1,2-oxaphospholane to 3-hydroxybutyric acid is 1:1;

[0036] Step S2, thermally activating diatomite with a particle size of 1-10 μm at 450° C. for 1.5 h to obtain thermally activated diatomite; the volume fraction of ethanol in the ethanol aqueous solution is 70%, and magnesium chloride and the ethanol aqueous solution are mixed to obtain a magnesium chloride solution, wherein the concentration of the magnesium chloride solution is 1 mol / L;

[0037] 3 g of carboxyl phosphate and 0.1 g of heat-activated diatomaceous earth were added to 100 mL of magnesium chloride solution while stirring, and the mixture was dispersed by stirring to obtain a dispersion; sodium hydroxide aqueous solution was added dropwise to the dispersion to adjust the pH value to be alkaline, and the alkaline pH value range was 12-13 to generate precipitation. After the stirring was completed, the temperature was kept constant, and the stirring reaction was continued for 60 minutes to obtain a suspension, which was then centrifuged and freeze-dried to obtain a flame retardant.

[0038] Example 3

[0039] This embodiment provides a flame retardant, which is prepared by the following steps:

[0040] Step S1, adding 3-hydroxybutyric acid dropwise to 2-methyl-2,5-dioxo-1,2-oxaphospholane, stirring and reacting for 2 hours at a reaction temperature of 105° C. to obtain carboxyl phosphate; the molar ratio of 2-methyl-2,5-dioxo-1,2-oxaphospholane to 3-hydroxybutyric acid is 1:1;

[0041] Step S2, thermally activating diatomite with a particle size of 1-10 μm at 400° C. for 2 h to obtain thermally activated diatomite; the volume fraction of ethanol in the ethanol aqueous solution is 70%, and magnesium chloride and the ethanol aqueous solution are mixed to obtain a magnesium chloride solution, wherein the concentration of the magnesium chloride solution is 1.2 mol / L;

[0042] 3 g of carboxyl phosphate and 0.1 g of heat-activated diatomaceous earth were added to 100 mL of magnesium chloride solution while stirring, and the mixture was dispersed by stirring to obtain a dispersion; sodium hydroxide aqueous solution was added dropwise to the dispersion to adjust the pH value to be alkaline, and the alkaline pH value range was 12-13 to generate precipitation. After the stirring was completed, the temperature was kept constant, and the stirring reaction was continued for 60 minutes to obtain a suspension, which was then centrifuged and freeze-dried to obtain a flame retardant.

[0043] Comparative Example 1

[0044] Compared with Example 2, this comparative example does not add carboxyl phosphate, and the remaining raw materials and preparation process remain the same as Example 2.

[0045] Example 4

[0046] A high-strength masterbatch for plastic pipes, comprising, by weight, a polyolefin elastomer (octene mass fraction 24%, density 0.87 g·cm -3 ), 15 parts of a flame retardant prepared according to the method of Example 1, 65 parts of a dispersant, and 3 parts of maleic anhydride grafted ethylene-vinyl acetate copolymer; the dispersant is a mixture of a linear low-density polyethylene (DFDA-7042 Yangzi Petrochemical) and a vinyl acetate copolymer (EVA4355) in a mass ratio of 3:2.

[0047] Furthermore, the compatibilizer is any one of acrylic acid grafted ethylene-vinyl acetate copolymer and maleic anhydride grafted polyethylene.

[0048] Step 1: Mixing: Weigh the following materials according to the weight ratio: polyolefin elastomer, flame retardant, dispersant, compatibilizer, put them into a high-speed mixer and stir for 5 minutes at a temperature of 90°C.

[0049] Step 2, twin-screw extrusion: add the mixed materials into a twin-screw extruder for granulation, the extruder screw speed is 400r / min; the temperatures of the six heating sections and the die head are: 140℃, 170℃, 190℃, 205℃, 205℃, 210℃, 210℃;

[0050] Step 3: Pelletizing and drying: The extruded material strips are cooled by water and then sent to a pelletizer for drying at a drying temperature of 70°C.

[0051] Example 5

[0052] Compared with Example 4, the flame retardant in this example is replaced with the flame retardant prepared by the method in Example 2, and the other raw materials and preparation process remain the same as those in Example 4.

[0053] Example 6

[0054] Compared with Example 4, the flame retardant in this example is replaced with the flame retardant prepared by the method in Example 3, and the other raw materials and preparation process remain the same as those in Example 4.

[0055] Example 7

[0056] A high-strength masterbatch for plastic pipes, comprising, by weight, a polyolefin elastomer (octene mass fraction 24%, density 0.87 g·cm -3 ) 20 parts, 68 parts of a flame retardant prepared according to the method in Example 2, 15 parts of a dispersant, and 2 parts of maleic anhydride grafted ethylene-vinyl acetate copolymer; the dispersant is a mixture of linear low-density polyethylene (DFDA-7042 Yangzi Petrochemical) and vinyl acetate copolymer (EVA4355) in a mass ratio of 3:2.

[0057] Step 1: Mixing: Weigh the following materials according to the weight ratio: polyolefin elastomer, flame retardant, dispersant, compatibilizer, put them into a high-speed mixer and stir for 15 minutes at a temperature of 80°C.

[0058] Step 2, twin-screw extrusion: add the mixed materials into a twin-screw extruder for granulation, and the extruder screw speed is 500r / min; the temperatures of the six heating sections and the die head are: 145℃, 175℃, 200℃, 210℃, 210℃, 215℃, 215℃;

[0059] Step 3: Pelletizing and drying: The extruded material strips are water-cooled and then sent to a pelletizer for drying at a drying temperature of 80°C.

[0060] Comparative Example 2

[0061] Compared with Example 4, the flame retardant in this comparative example is replaced with the sample prepared in Comparative Example 1, and the other raw materials and preparation process remain the same as those in Example 4.

[0062] Comparative Example 3

[0063] Compared with Example 4, the flame retardant in this comparative example is replaced with magnesium hydroxide, and the other raw materials and preparation process remain the same as those in Example 4.

[0064] Performance tests were performed on Examples 4 to 7 and Comparative Examples 2 to 3:

[0065] According to weight parts, 100 parts of high-density polyethylene, 30 parts of high-strength masterbatch of plastic pipes prepared in Examples 4-7 and Comparative Examples 2-3 of the present invention, 10 parts of EPDM rubber, and titanate coupling agent 201 are mixed evenly and melt-blended and extruded through a twin-screw extruder. The temperature of the twin-screw extruder is 190°C. The tensile properties are tested as follows: GB / T1040-2006; impact properties: GB / T1043-1993; UL94 vertical combustion flame retardant grade. The results are shown in Table 1:

[0066] Table 1

[0067] project Flame retardant grade Tensile properties / MPa <![CDATA[Impact strength / J·m -1 > Example 4 V-0 30.5 164.5 Example 5 V-0 31.2 168.5 Example 6 V-0 30.8 165.2 Example 7 V-0 30.9 164.7 Comparative Example 2 V-1 28.5 145.6 Comparative Example 3 V-1 20.7 112.2

[0068] It can be seen from Table 1 that the masterbatches prepared in Examples 4 to 7 of the present invention have good toughening and flame retardant effects, and as the amount of carboxyl phosphate in the masterbatch increases, the mechanical properties of the prepared material are enhanced. The short chains in the carboxyl phosphate structure in the masterbatch can play the role of connecting molecules, thereby enhancing the toughness of the material and improving the performance of the material blending system.

[0069] Carboxyl phosphate is also a phosphorus-containing material. As a carbon promoter, it promotes the material to form a complex phosphorus-rich carbon slag covering layer during combustion, which can prevent the transfer of oxygen and heat. In the present invention, it forms a synergistic flame retardant system with the inorganic flame retardant magnesium hydroxide to improve the flame retardant properties of plastic products.

[0070] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0071] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-strength masterbatch for plastic pipes, characterized in that: The invention comprises, by weight, 15-20 parts of polyolefin elastomer, 65-70 parts of flame retardant, 15-20 parts of dispersant and 1-3 parts of compatibilizer; the flame retardant is prepared by the following steps: Step S1, adding 3-hydroxybutyric acid dropwise to 2-methyl-2,5-dioxo-1,2-oxaphospholane, stirring for reaction, the reaction temperature is 105° C., to obtain carboxyl phosphate; the molar ratio of 2-methyl-2,5-dioxo-1,2-oxaphospholane to 3-hydroxybutyric acid is 1:1; Step S2, mixing magnesium chloride and an ethanol aqueous solution to obtain a magnesium chloride solution, wherein the concentration of the magnesium chloride solution is 0.8-1.2 mol / L, and the volume fraction of ethanol in the ethanol aqueous solution is 70%; adding 3 g of carboxyl phosphate to 100 mL of the magnesium chloride solution while stirring, adding 0.1 g of heat-activated diatomaceous earth, stirring and dispersing, and obtaining a dispersion; adding a sodium hydroxide aqueous solution dropwise to the dispersion to adjust the pH value to be alkaline, the alkaline pH value range is 12-13, and a precipitate is generated. After the stirring is completed, the temperature is kept unchanged, and the stirring reaction is continued for 50 minutes to obtain a suspension, and the suspension is subjected to centrifugal separation and freeze-drying to obtain a flame retardant.

2. A high-strength masterbatch for plastic pipes according to claim 1, characterized in that: The reaction time in step S1 is 1.5-2 h.

3. A high-strength masterbatch for plastic pipes according to claim 1, characterized in that: The thermally activated diatomaceous earth is prepared by the following steps: The diatomaceous earth is thermally activated at 400-450° C. for 1.5-2 hours to obtain thermally activated diatomaceous earth.

4. A high-strength masterbatch for plastic pipes according to claim 3, characterized in that: The particle size of the diatomaceous earth is 1-10 μm.

5. The high-strength masterbatch for plastic pipes according to claim 1, characterized in that: The dispersant is a mixture of linear low-density polyethylene and vinyl acetate copolymer in a mass ratio of 3:

2.

6. The high-strength masterbatch for plastic pipes according to claim 1, characterized in that: The compatibilizer is any one of maleic anhydride grafted ethylene-vinyl acetate copolymer, acrylic acid grafted ethylene-vinyl acetate copolymer and maleic anhydride grafted polyethylene.

7. The method for preparing a high-strength masterbatch for plastic pipes according to claim 1, characterized in that: The steps include: Step 1: Mixing: Weigh the polyolefin elastomer, flame retardant, dispersant and compatibilizer according to the weight ratio, put them into a high-speed mixer and stir for 5-15 minutes at a temperature of 80℃-90℃; Step 2: Twin-screw extrusion: Add the mixed materials into a twin-screw extruder for granulation, with the screw speed of the extruder being 400-600r / min; Step 3: Pelletizing and drying: The extruded material strips are water-cooled and then sent to a pelletizer for drying at a drying temperature of 70-80°C.

8. The method for preparing a high-strength masterbatch for plastic pipes according to claim 7, characterized in that: The temperatures of the six heating sections and the die head are 140-145°C, 170-175°C, 190-200°C, 205-210°C, 205-210°C, 210-215°C, and 210-215°C respectively.