A flame-retardant polyolefin composition and its preparation method

Abstract

The present invention relates to the preparation of a compound flame retardant and its surface treatment, and the preparation of a flame-retardant polyolefin composition. Specifically, it relates to a flame-retardant polyolefin resin composition having excellent melt strength, dispersibility, flame retardancy, smooth surface of the molded article, and excellent resistance to exudation. The flame-retardant polyolefin resin composition of the present invention has high melt strength and high product stability, and is more suitable for plates and profiles, thermoformed products and blow molded products with high requirements for the appearance surface such as extrusion grade, and is applied to fields such as automobiles, buildings, and household appliances with flame retardancy and appearance requirements.

Description

Technical Field

[0001] The present invention relates to the preparation of a compound flame retardant and its surface treatment, and the preparation of a flame-retardant polyolefin composition. Specifically, it relates to a flame-retardant polyolefin resin composition having excellent melt strength, as well as excellent dispersibility, flame retardancy, and a smooth surface of the molded article. The flame-retardant polyolefin resin composition of the present invention has a low melt index and high product stability, and is more suitable for plates and profiles, thermoformed products, and blow molded products with high requirements for the appearance surface, such as extrusion grades, and is applied to fields such as automobiles, buildings, and household appliances with flame retardancy and appearance requirements. Background Art

[0002] Flame retardant technologies are mainly divided into halogen-containing flame retardants and halogen-free flame retardants. In the prior art, due to environmental protection factors, the use of some halogen-containing flame retardants is restricted in various countries. The Stockholm Convention was adopted in Switzerland in 2001, mainly to protect humans and the natural environment from the harm of persistent organic pollutants. In 2009, pentabromodiphenyl ether and octabromodiphenyl ether were included in the convention list. In 2013, hexabromocyclododecane was added to the convention-controlled list. In 2017, the amendment to the convention added decabromodiphenyl ether to the list. China signed the convention in 2001 and began to partially implement the convention for polybrominated diphenyl ethers since 2014. It mainly prohibits the production and circulation of hexabromobiphenyl, tetrabromodiphenyl ether, pentabromodiphenyl ether, hexabromodiphenyl ether, and heptabromodiphenyl ether. For decabromodiphenyl ether, China has completed the basic work of implementing the convention, but the relevant amendment has not come into force in China. For hexabromocyclododecane, China applied for a 5-year exemption period and has completely phased out the production and use of hexabromocyclododecane since December 2021. As a new type of flame retardant, decabromodiphenylethane is currently used to replace decabromodiphenyl ether in halogen-containing flame retardants at home and abroad, which meets the requirements of the Stockholm Convention, the European RoHS Directive, the EU REACH Regulation, and the Measures for the Administration of the Restriction of the Use of Hazardous Substances in Electrical and Electronic Products in China. Halogen-free flame retardants traditionally use red phosphorus, ammonium polyphosphate, organophosphorus flame retardants such as phosphate esters, and metal hydroxides. This series of flame retardants have problems such as low flame retardancy efficiency, poor water resistance, easy precipitation, poor compatibility with polymers, poor processability, or high addition amounts. Although the water resistance and precipitation resistance of the new type of piperazine pyrophosphate and melamine pyrophosphate compound flame retardants have been greatly improved, the long-term aging precipitation and dispersibility are still poor, and there are still great difficulties in normal production.

[0003] At present, most of the halogen-containing flame-retardant resin materials in the domestic market are applied to injection-molded products, and very few are used for thermoformed and blow-molded products. The main reason is that the amount of halogen-containing flame retardant added in the material formula is large, and its compatibility with polyolefin resin is poor. Especially when the viscosity of the matrix resin is extremely high, during the extrusion process in a twin-screw extruder, the screw torque is large, the main machine current is high, and it is very difficult to disperse the halogen-containing flame retardant. As a result, when processing halogen-containing flame-retardant materials in thermoforming or blow molding, the undispersed flame retardant or filler during the high-temperature softening and stretching process will present a large number of white dots, pockmarks and pits on the surface of the product parts, resulting in defective products.

[0004] Thermoforming-grade or blow-molding-grade flame-retardant polyolefin materials require the flame-retardant polyolefin materials to have relatively high melt strength. Especially for products with large longitudinal deep-drawing dimensions or large thin-walled product parts, low melt strength will lead to problems such as difficult forming or uneven wall thickness during thermoforming or blow molding of product parts.

[0005] Patents such as Patent CN 110582553 A, Patent CN 111433326 B, Patent CN 105209576 A, Patent CN109563410 B, Patent CN 107075378 A, Patent CN 111278950 A and Patent CN 110869447 B disclose flame retardant compositions and flame-retardant resin compositions containing the same by ADEKA CORPORATION. These represent advanced synthesis and application of intumescent halogen-free flame retardants at home and abroad, with high flame retardancy and good product stability. However, when directly added and applied, they have poor compatibility with polyolefin resins, poor dispersibility during the processing process, are prone to decomposition during the production and processing of high-viscosity matrix materials, and have a relatively low cost performance compared with domestic similar flame retardants. Domestic Patent CN104672492A discloses that silicone oil can inhibit coking during the processing of piperazine phosphate compound flame retardants. Patent CN 110483898 A discloses that lubricants and silicone oil substances are used to coat flame retardants to improve their water resistance and moisture absorption migration in polypropylene materials. Patent CN107075378A discloses that silicone oil and silane coupling agents can prevent the agglomeration of flame retardants, improve dispersibility, and endow water resistance and heat resistance. Spraying or dropping silicone oil, coupling agents and lubricants directly on the halogen-free flame retardants cannot completely solve the problem of highly dispersing the flame retardants in the material, and secondary agglomeration phenomena will still occur during the processing process. Especially when extruding plates or profiles, problems such as many white dots and small pits on the surface will be exposed, and there will be partial precipitation phenomena under high temperature and high humidity conditions. The application of halogen-containing flame-retardant polyolefin materials to thermoformed and blow-molded products is very few. Summary of the Invention

[0006] In order to overcome the defects such as white spots, pockmarks and pits on the surface of the above-mentioned manufactured parts after molding, as well as problems in thermoforming and blow molding processes, the present invention provides a flame retardant composition and a preparation method of a polyolefin-based composition, including the compound preparation of the flame retardant composition, the surface treatment of the flame retardant composition, and the preparation of the polyolefin-based composition of the flame retardant composition. After surface treatment, the compatibility and dispersibility of the flame retardant composition with polyolefin resin are greatly improved. Especially in a high-viscosity matrix, its dispersibility performance is also very excellent. At the same time, the polyolefin-based composition is micro-crosslinked to improve the melt strength of the material at high temperatures and the thermoforming or blow molding properties.

[0007] The flame retardant composition of the present invention is composed of four flame retardant substances, among which the mass percentage of the flame retardant decabromodiphenylethane is 35-50%, the mass percentage of the flame retardant synergist antimony trioxide is 6-18%, the mass percentage of the anti-dripping agent polytetrafluoroethylene is 0.4-2%, and the mass percentage of the flame retardant synergistic filler magnesium silicate salt is 10-50%.

[0008] For the decabromodiphenylethane of the present invention, the 1% thermal weight loss temperature is not less than 330 °C, the particle size (D 50 ) is not greater than 3 μm, the whiteness is not less than 89, and the pH value is 7-9.

[0009] For the flame retardant synergistic filler magnesium silicate salt of the present invention, the pH value is 9-9.5, the mass percentage of silicon dioxide is greater than 61%, and the average particle size (D 50 ) is 3-8 μm, which increases the stiffness of the material and reduces the material cost. The present invention further preferably uses magnesium silicate salt with a particle size of 5 μm, a silicon dioxide mass percentage of 62%, and a pH value of 9.3.

[0010] The preparation of the flame retardant composition of the present invention is to place the four flame retardant substances in a high-speed mixer according to a certain mass ratio, and mix them evenly at a temperature of 100 °C to 120 °C for 5 minutes, and then cool to room temperature for standby.

[0011] The surface treatment of the flame retardant composition of the present invention is to achieve good compatibility and dispersibility between the flame retardant and the matrix resin material through chemical coupling and physical lubrication pre-dispersion. The surface-treated flame retardant composition is easy to store and can be directly added to the polyolefin resin. After thermoforming or blow molding, there are no pockmarks or pits on the surface of the manufactured parts.

[0012] The main steps of the preparation method adopted for the surface treatment of the flame retardant composition of the present invention are as follows:

[0013] Step 1: In a high-speed mixer with a high-temperature spray gun, add component A in proportion. At a high temperature of 100-120 °C in the high-speed mixer, first mix at a low speed of 200-300 r / min for 1-2 minutes.

[0014] Step 2: Set the temperature of the high-temperature spray gun at 50 - 60°C, continuously spray Component B into the high-speed mixer through the spray gun in a certain amount, keep the high-speed mixer at 100 - 120°C, and mix at a high speed of 600 - 1400 r / min for 3 - 5 min.

[0015] Step 3: Add Component C and Component D at the feeding port of the high-speed mixer, mix at a high speed of 600 - 1400 r / min for 3 - 5 min, and then discharge and cool for standby.

[0016] Component A of the surface pretreatment material of the flame retardant composition of the present invention is the standby flame retardant composition, and the addition amount is 91 - 96% by mass percentage.

[0017] Component B of the surface pretreatment material of the flame retardant composition of the present invention is a coupling agent, and the coupling agent is one or a mixture of silane coupling agents, maleic anhydride grafts, titanate coupling agents, and aluminate coupling agents. It bonds to the surface of the flame retardant at high temperature. The present invention further preferably uses a silane coupling agent, and the addition amount is 0.5 - 2% by mass percentage.

[0018] Component C of the surface pretreatment material of the flame retardant composition of the present invention is a hyperdispersant, and the hyperdispersant is one or a mixture of polyester hyperdispersants, polyether hyperdispersants, and polyolefin hyperdispersants. Part of the hyperdispersant is an anchoring group, which can be tightly bound to the particle surface through ion pairs, hydrogen bonds, van der Waals forces, etc. to prevent the desorption of the hyperdispersant; the other part is a solvating chain, which is a polymer chain that can be solvated by the medium and can play a role in dispersing and stabilizing the particles through steric hindrance effects. The present invention further preferably uses an acrylic polyester hyperdispersant, and the polyester hyperdispersant is a polymer obtained by free radical random polymerization of m-pentadecyl phenyl acrylate, phosphonic acid, and (meth)acrylic acid alkyl esters, and the addition amount is 3 - 5% by mass percentage.

[0019] Component D of the surface pretreatment material of the flame retardant composition of the present invention is a stearate, and the stearate is one or a mixture of magnesium stearate, calcium stearate, potassium stearate, and zinc stearate. It neutralizes a part of the acidity of the halogen-free flame retardant, promotes the dispersion of the flame retardant, and changes the crystallinity of the matrix resin, and the addition amount is 0.5 - 2% by mass percentage.

[0020] The polyolefin-based composition of the flame retardant composition of the present invention is the final molded product. Its combined formula is as follows:

[0021] The polyolefin resin is 53 - 58% by mass percentage;

[0022] The surface-treated flame retardant composition is 40 - 45% by mass percentage;

[0023] The crosslinking aid is 0.2 - 2% by mass percentage;

[0024] The mass percentage of the free radical initiator is 0.02 - 0.1%;

[0025] The percentage of the processing aid is 0.5 - 2%.

[0026] The polyolefin resin in the flame retardant composition polyolefin - based composition of the present invention is one or more resins selected from the following: polyethylene, low - density polyethylene, ultra - high molecular weight polyethylene, high - density polyethylene, polypropylene, homopolypropylene, random copolymer polypropylene, block copolymer polypropylene, impact copolymer polypropylene, high - impact copolymer polypropylene, isotactic polypropylene, syndiotactic polypropylene, semi - isotactic polypropylene, maleic anhydride - modified polypropylene, polybutene, cycloolefin polymer, stereoblock polypropylene, poly - 3 - methyl - 1 - butene, poly - 3 - methyl - 1 - pentene, poly - 4 - methyl - 1 - pentene and other α - olefin polymers, ethylene / propylene block or random copolymer, ethylene / octene block or random copolymer, ethylene - methyl methacrylate copolymer, ethylene - vinyl acetate copolymer and other α - olefin copolymers.

[0027] The cross - linking agent in the flame retardant composition polyolefin - based composition of the present invention is one of trimethylolpropane trimethacrylate (TMPTMA), divinylbenzene (DVB), triallyl cyanurate (TAIC), polyethylene glycol dimethacrylate (MPL). Under the action of shear heat, the molecular chains of the high - viscosity polyolefin resin break, and a part of the tertiary carbon atom macromolecular free radicals are generated. After adding the cross - linking agent, during the actual extrusion and melt blending process, the degradation and cross - linking of the macromolecular free radicals occur simultaneously. Under the action of high - temperature shear, the polyolefin and the toughening agent material are partially micro - cross - linked, which not only helps with later thermoforming, but also increases the adhesion state of the halogen - free flame retardant material at high temperatures, can remove the anti - dripping agent, reduce the influence of the anti - dripping agent on the surface pitting of the product parts, and can also improve the flame retardant effect of the halogen - free flame retardant material. The present invention further preferably uses TMPTMA as the cross - linking agent, and the double bonds in the TMPTMA molecule can participate in the cross - linking reaction.

[0028] The free radical initiator in the flame retardant composition polyolefin - based composition of the present invention is one or a mixture of several of dicumyl peroxide (DCP), benzoyl peroxide (BPO), di - tert - butyl peroxide (DBP), azobisisobutyronitrile (AIBN). The present invention further preferably uses DBP as the free radical initiator to initiate the reaction between polypropylene and the cross - linking agent at a certain temperature and shear rate in the extruder.

[0029] The processing aids in the flame retardant composition polyolefin - based composition of the present invention include one or a mixture of several of hindered phenol antioxidants, phosphite antioxidants, distearyl thiodipropionate, white oil, silicone oil, zinc stearate, calcium stearate, silicone masterbatch, erucamide and polyethylene wax.

[0030] The preparation method of the above-mentioned flame retardant composition polyolefin-based composition comprises the following steps:

[0031] Step 1: First, mix the polyolefin resin, crosslinking aid, and free radical initiator evenly in a high-speed mixer according to certain mass ratio requirements, add them to a single-screw extruder with a length-diameter ratio of 56:1 for melting and mixing extrusion, pelletize and dry to obtain a high melt strength matrix spare material.

[0032] Step 2: Then, mix the high melt strength matrix spare material, surface-treated flame retardant composition, and processing aid evenly in a high-speed mixer according to mass ratio requirements, and perform melting and mixing extrusion on a twin-screw extruder with a length-diameter ratio of more than 40:1. The present invention further preferably uses a twin-screw extruder with a length-diameter ratio of 44:1.

[0033] Step 3: The vacuum extraction pressure value in the metering section of the twin-screw extruder is about -0.9 MPa. Except for the feeding port, natural exhaust port, vacuum exhaust port, and conveying section, kneading blocks are added as much as possible in other sections, and the application of 90-degree and 45-degree screw elements in the screw combination is increased. The temperature of each section of the screw is set in the range of 150-210 °C, and a reasonable main machine speed is set. The flame retardant polyolefin composition is obtained by melt blending on the twin-screw extruder.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention performs surface treatment on the flame retardant composition. Through the combined action of a coupling agent, a superdispersant, and a stearate, the surface of the flame retardant composition is treated in a "solid-liquid-solid" coating modification method. Through chemical reaction and physical dispersion pretreatment, the dispersibility and compatibility of the halogen-free flame retardant composition are synergistically improved, and the problems of appearance pitting, protrusions, and pits of the product parts are further effectively solved.

[0036] During the preparation of the flame retardant composition polyolefin-based composition of the present invention, a crosslinking aid and a free radical initiator are added. During the extrusion process, micro-crosslinking occurs between polyolefin resins, improving the thermoforming or blow molding formability, enabling the formation of larger depth stretches and more complex product parts, and ensuring more uniform thickness of thin-walled product parts.

[0037] The processing process for preparing the flame retardant composition polyolefin-based composition of the present invention is different from that of conventional modified polyolefins. By micro-crosslinking polyolefins, the thermoforming or blow molding formability and the wall thickness problem of product parts are effectively solved. At the same time, the special screw arrangement method of the twin-screw extruder can further promote the dispersion of the flame retardant. Specific embodiments

[0038] The present invention will be further described below through examples and comparative examples. Without violating the purpose of the present invention, the present invention should not be limited to the specific content explicitly shown in the following examples.

[0039] In the following examples, the flame retardants used were all purchased in batches from the market. The preferred ratio of the flame retardant composition and the processing technology are as follows:

[0040] Dodecabromodiphenylethane, antimony trioxide, polytetrafluoroethylene and magnesium silicate salt were sequentially placed in a high-speed mixer as a flame retardant composition with mass percentages of 45%, 14%, 1% and 40%, respectively, and uniformly mixed at 105 °C for 5 min, and then cooled to room temperature for standby.

[0041] In the following examples, the surface pretreatment materials of the flame retardant composition used were self-made in batches according to the present invention. The preferred material ratios are as follows:

[0042] Flame retardant composition: 94% by mass;

[0043] Titanate coupling agent: 1.5% by mass;

[0044] Acrylic polyester type super dispersant: 4% by mass;

[0045] Magnesium stearate: 0.5% by mass.

[0046] In the following examples, the surface pretreatment materials of the flame retardant composition used were self-made in batches according to the present invention. The preferred processing technology is as follows:

[0047] In a high-speed mixer with a high-temperature spray gun, 94% of the halogen-free flame retardant composition was put into the high-speed mixer. At a high temperature of 105 °C in the high-speed mixer, it was mixed at a low speed of 300 r / min for 1 min. The temperature of the high-temperature spray gun was set at 55 °C, and the titanate coupling agent mixture was continuously sprayed in through the spray gun at 1.5%. The high-speed mixer was maintained at 105 °C and mixed at a high speed of 750 r / min for 4 min. The acrylic polyester type super dispersant and zinc stearate were added at the feed port of the high-speed mixer. After mixing at a high speed of 750 r / min for 3 min, the material was discharged and cooled for standby.

[0048] In the following comparative examples, the flame retardants used were commercially available flame retardants of the same manufacturer and the same brand.

[0049] Example 1

[0050] A flame retardant composition polypropylene-based masterbatch is composed of the following mass percentages:

[0051] Random copolymerized polypropylene: 58.2% by mass, surface pretreated flame retardant composition: 39.5% by mass, crosslinking aid TMPTMA: 0.77% by mass, free radical initiator DBP: 0.03% by mass, processing aids hindered phenolic antioxidant: 0.2% by mass, phosphite antioxidant: 0.2% by mass, dilauryl thiodipropionate: 0.1% by mass, silicone masterbatch: 1% by mass.

[0052] The preparation method includes the following steps:

[0053] The process parameters for melt extrusion by a single-screw extruder are as follows: the temperature in Zone 1 is 120 - 160 °C, the temperatures from Zone 2 to the die head are all 170 - 190 °C, the main motor current is 350 - 400 A, the main motor speed is 250 rpm, the vacuum extraction pressure value in the metering section is about -0.5 MPa, the material is premixed in a high-speed mixer at 350 r / min for 2 min, and the length-diameter ratio of the twin-screw extruder is 56∶1.

[0054] Random copolymer polypropylene, a crosslinking aid, and a free radical initiator are fed at the main feed port of the single-screw extruder according to the specified mass ratio, and the natural exhaust port is blocked. Pre-crosslinked polypropylene is obtained by melt blending using the single-screw extruder, and pellets are obtained after drawing, cooling, and pelletizing.

[0055] The process parameters for melt extrusion by a twin-screw extruder are as follows: the temperature in Zone 1 is 120 - 160 °C, the temperatures from Zone 2 to the die head are all 170 - 220 °C, the main motor current is 350 - 430 A, the main motor speed is 450 rpm, the vacuum extraction pressure value in the metering section is about -0.9 MPa, the material is premixed in a high-speed mixer at 750 r / min for 3 min, and the length-diameter ratio of the twin-screw extruder is 48∶1.

[0056] Pre-crosslinked random copolymer polypropylene, a processing aid, and a surface pretreated flame retardant composition are pre-mixed evenly in a high-speed mixer according to the specified mass ratio and fed at the main feed port of the twin-screw extruder. Except for the feed port, natural exhaust port, vacuum exhaust port, and conveying section, kneading blocks are added as much as possible in other sections, and 90-degree and 45-degree screw elements in the screw combination are increased. A polypropylene-based composition of the flame retardant composition is obtained by melt blending using the twin-screw extruder, and pellets are obtained after drawing, cooling, and pelletizing.

[0057] Example 2

[0058] A polyvinyl composition of a flame retardant composition consists of the following mass percentages:

[0059] High-density polyethylene: 58% by mass percentage, surface pretreated flame retardant composition: 40.8% by mass percentage, crosslinking aid TMPTMA: 0.19% by mass percentage, free radical initiator DBP: 0.01% by mass percentage, processing aids: hindered phenol antioxidant: 0.2% by mass percentage, phosphite antioxidant: 0.2% by mass percentage, distearyl thiodipropionate: 0.1% by mass percentage, silicone oil: 0.5% by mass percentage.

[0060] The preparation method includes the following steps:

[0061] The process parameters for melt extrusion by a single-screw extruder are as follows: the temperature in Zone 1 is 120 - 150 °C, the temperatures from Zone 2 to the die head are all 150 - 180 °C, the main machine current is 350 - 400 A, the main machine speed is 200 rpm, the vacuum extraction pressure value in the metering section is about -0.5 MPa, the material is premixed in a high-speed mixer at 350 r / min for 2 min, and the length-diameter ratio of the twin-screw extruder is 56∶1.

[0062] High-density polyethylene, crosslinking aid, and free radical initiator are fed at the main feeding port of the single-screw extruder according to the specified mass ratio, and the natural exhaust port is blocked. Pre-crosslinked polypropylene is prepared by melt blending using the single-screw extruder, and pellets are obtained after traction cooling and pelletizing.

[0063] The process parameters for melt extrusion by a twin-screw extruder are as follows: the temperature in Zone 1 is 120 - 150 °C, the temperatures from Zone 2 to the die head are all 160 - 170 °C, the main machine current is 390 - 460 A, the main machine speed is 450 rpm, the vacuum extraction pressure value in the metering section is about -0.9 MPa, the material is premixed in a high-speed mixer at 750 r / min for 3 min, and the length-diameter ratio of the twin-screw extruder is 48∶1.

[0064] Pre-crosslinked high-density polyethylene, processing aid, and surface pretreatment flame retardant composition are pre-mixed evenly in a high-speed mixer according to the specified mass ratio and fed at the main feeding port of the twin-screw extruder. Except for the feeding port, natural exhaust port, vacuum exhaust port, and conveying section, kneading blocks are added as much as possible in other sections, and 90-degree and 45-degree screw elements in the screw combination are increased. A polyethylene-based composition of the flame retardant composition is prepared by melt blending using the twin-screw extruder, and pellets are obtained after traction cooling and pelletizing.

[0065] Example 3

[0066] A halogen-free flame retardant composition toughened polypropylene-based composition of metallocene linear low-density polyethylene (mLLDPE) consists of the following mass percentages:

[0067] Random copolymerized polypropylene: mass percentage 40%, metallocene linear low-density polyethylene (mLLDPE): mass percentage 10.8%, surface pretreatment flame retardant composition: mass percentage 39.8%, crosslinking aid TMPTMA: mass percentage 0.38%, free radical initiator DBP: mass percentage 0.02%, processing aids: hindered phenolic antioxidant: mass percentage 0.2%, phosphite antioxidant: mass percentage 0.2%, distearyl thiodipropionate: mass percentage 0.1%, silicone oil: mass percentage 0.5%.

[0068] The preparation method includes the following steps:

[0069] The process parameters for melt extrusion of a single-screw extruder are as follows: the temperature in zone 1 is 120 - 150 °C, the temperatures from zone 2 to the die head are all 170 - 200 °C, the main machine current is 340 - 360 A, the main machine speed is 220 rpm, the vacuum extraction pressure value in the metering section is about -0.5 MPa, the material is premixed in a high-speed mixer at 350 r / min for 2 min, and the length-diameter ratio of the twin-screw extruder is 56∶1.

[0070] Random copolymerized polypropylene, metallocene linear low-density polyethylene (mLLDPE), crosslinking aid, and free radical initiator are fed at the main feed port of a single-screw extruder according to the specified mass ratio, and the natural exhaust port is blocked. Pre-crosslinked polypropylene is prepared by melt blending using the single-screw extruder, and pellets are obtained after traction cooling.

[0071] The process parameters for melt extrusion of a twin-screw extruder are as follows: the temperature in zone 1 is 120 - 150 °C, the temperatures from zone 2 to the die head are all 160 - 200 °C, the main machine current is 350 - 420 A, the main machine speed is 450 rpm, the vacuum extraction pressure value in the metering section is about -0.9 MPa, the material is premixed in a high-speed mixer at 750 r / min for 3 min, and the length-diameter ratio of the twin-screw extruder is 48∶1.

[0072] Pre-crosslinked random copolymerized polypropylene, metallocene linear low-density polyethylene, processing aid, and surface pretreatment flame retardant composition are pre-mixed evenly in a high-speed mixer according to the specified mass ratio and fed at the main feed port of the twin-screw extruder. Except for the feed port, natural exhaust port, vacuum exhaust port, and conveying section, kneading blocks are added as much as possible in other sections, and the application of 90-degree and 45-degree screw elements in the screw combination is increased. A polyethylene-based composition of the flame retardant composition is prepared by melt blending using the twin-screw extruder, and pellets are obtained after traction cooling.

[0073] Comparative Example 1

[0074] A polypropylene-based masterbatch of a flame retardant composition, where the flame retardant composition is not surface-treated, and the mass percentage composition is:

[0075] Random copolymerized polypropylene 58.2% by mass, flame retardant composition without surface pretreatment 39.5% by mass, crosslinking aid TMPTMA 0.77% by mass, free radical initiator DBP 0.03% by mass, processing aid phenolic antioxidant 0.2% by mass, phosphite antioxidant 0.2% by mass, distearyl thiodipropionate 0.1% by mass, silicone masterbatch 1% by mass.

[0076] The preparation method includes the following steps:

[0077] The process parameters for melt extrusion of a single-screw extruder are as follows: the temperature in zone 1 is 120 - 160 °C, the temperatures from zone 2 to the die head are all 170 - 190 °C, the main motor current is 350 - 400 A, the main motor speed is 250 rpm, the vacuum extraction pressure value in the metering section is about -0.5 MPa, the material is premixed in a high-speed mixer at 350 r / min for 2 min, and the length-diameter ratio of the twin-screw extruder is 56∶1.

[0078] Random copolymer polypropylene, crosslinking agent and free radical initiator are fed at the main feeding port of the single-screw extruder according to the specified mass ratio, and the natural exhaust port is blocked. Pre-crosslinked polypropylene is prepared by melt blending in the single-screw extruder, and pellets are obtained after drawing, cooling and pelletizing.

[0079] The process parameters for melt extrusion of the twin-screw extruder are as follows: the temperature in zone 1 is 120 - 160 °C, the temperatures from zone 2 to the die head are all 170 - 220 °C, the main motor current is 370 - 450 A, the main motor speed is 450 rpm, the vacuum extraction pressure value in the metering section is about -0.9 MPa, the material is premixed in a high-speed mixer at 750 r / min for 3 min, and the length-diameter ratio of the twin-screw extruder is 48∶1.

[0080] Pre-crosslinked random copolymer polypropylene, processing aids and surface-pretreated flame retardant composition are pre-mixed evenly in a high-speed mixer according to the specified mass ratio and fed at the main feeding port of the twin-screw extruder. Except for the feeding port, natural exhaust port, vacuum exhaust port and conveying section, kneading blocks are added as much as possible in other sections, and the application of 90-degree and 45-degree screw elements in the screw combination is increased. A polypropylene-based composition of the flame retardant composition is prepared by melt blending in the twin-screw extruder, and pellets are obtained after drawing, cooling and pelletizing.

[0081] Comparative Example 2

[0082] A halogen-free flame retardant polypropylene-based masterbatch produced by using a commercially available general-purpose screw element twin-screw extruder consists of the following mass percentages:

[0083] Random copolymer polypropylene 58.2% by mass, surface-pretreated flame retardant composition 39.5% by mass, crosslinking agent TMPTMA 0.77% by mass, free radical initiator DBP 0.03% by mass, processing aids hindered phenol antioxidant 0.2% by mass, phosphite antioxidant 0.2% by mass, distearyl thiodipropionate 0.1% by mass, silicone masterbatch 1% by mass.

[0084] The preparation method includes the following steps:

[0085] The process parameters for melt extrusion by a single-screw extruder are as follows: the temperature in zone 1 is 120 - 160 °C, the temperatures from zone 2 to the die head are all 170 - 190 °C, the main machine current is 350 - 400 A, the main machine speed is 250 rpm, the vacuum extraction pressure value in the metering section is about -0.5 MPa, the material is premixed in a high-speed mixer at 350 r / min for 2 min, and the length-diameter ratio of the twin-screw extruder is 56∶1.

[0086] Random copolymer polypropylene, crosslinking assistant, and free radical initiator are fed at the main feeding port of a single-screw extruder according to the specified mass ratio, and the natural exhaust port is blocked. Pre-crosslinked polypropylene is prepared by melt blending using the single-screw extruder, and pellets are obtained after traction cooling and pelletizing.

[0087] The process parameters for melt extrusion by a twin-screw extruder are as follows: the temperature in zone 1 is 120 - 160 °C, the temperatures from zone 2 to the die head are all 170 - 220 °C, the main machine current is 330 - 410 A, the main machine speed is 450 rpm, the vacuum extraction pressure value in the metering section is about -0.9 MPa, the material is premixed in a high-speed mixer at 750 r / min for 3 min, and the length-diameter ratio of the twin-screw extruder is 48∶1.

[0088] Pre-crosslinked random copolymer polypropylene, processing aids, and surface pretreatment flame retardant composition are pre-mixed evenly in a high-speed mixer according to the specified mass ratio and fed at the main feeding port of a twin-screw extruder. The kneading block combination is produced according to general-purpose modified polypropylene, reducing the application of 90-degree and 45-degree screw elements in the examples. A polypropylene-based composition of the flame retardant composition is prepared by melt blending using the twin-screw extruder, and pellets are obtained after traction cooling and pelletizing.

[0089] Comparative Example 3

[0090] An uncrosslinked halogen-free flame retardant polypropylene-based masterbatch consists of the following mass percentages:

[0091] The mass percentage of random copolymer polypropylene is 59%, the mass percentage of the flame retardant composition without surface pretreatment is 39.5%, the mass percentage of the processing aid hindered phenolic antioxidant is 0.2%, the mass percentage of the phosphite antioxidant is 0.2%, the mass percentage of distearyl thiodipropionate is 0.1%, and the mass percentage of the silicone masterbatch is 1%.

[0092] The preparation method includes the following steps:

[0093] The process parameters for melt extrusion by a single-screw extruder are as follows: the temperature in zone 1 is 120 - 160 °C, the temperatures from zone 2 to the die head are all 170 - 190 °C, the main machine current is 310 - 360 A, the main machine speed is 250 rpm, the vacuum extraction pressure value in the metering section is about -0.5 MPa, the material is premixed in a high-speed mixer at 350 r / min for 2 min, and the length-diameter ratio of the twin-screw extruder is 56∶1.

[0094] Random copolymer polypropylene is fed at the main feeding port of a single-screw extruder, and the natural exhaust port is blocked. Pre-crosslinked polypropylene is prepared by melt blending in the single-screw extruder, and pellets are obtained after traction cooling.

[0095] The process parameters for melt extrusion by a twin-screw extruder are as follows: the temperature in the first zone is 120 - 160 °C, the temperatures from the second zone to the die head are all 170 - 220 °C, the main machine current is 340 - 420 A, the main machine speed is 450 rpm, the vacuum extraction pressure value in the metering section is about -0.9 MPa, the material is premixed in a high-speed mixer at 750 r / min for 3 min, and the length-diameter ratio of the twin-screw extruder is 48:1.

[0096] Random copolymer polypropylene, processing aids, and a surface-pretreated flame retardant composition are pre-mixed evenly in a high-speed mixer according to the specified mass ratio and fed at the main feeding port of a twin-screw extruder. Except for the feeding port, natural exhaust port, vacuum exhaust port, and conveying section, kneading blocks are added as much as possible in other sections, and the application of 90-degree and 45-degree screw elements in the screw combination is increased. A polypropylene-based composition of the flame retardant composition is prepared by melt blending in the twin-screw extruder, and pellets are obtained after traction cooling.

[0097] Comparative Example 4

[0098] A general-purpose halogen-free flame retardant polypropylene-based masterbatch without any treatment consists of the following mass percentages:

[0099] The mass percentage of random copolymer polypropylene is 59%, the mass percentage of the flame retardant composition without surface pretreatment is 39.5%, the mass percentage of the processing aid phenolic antioxidant is 0.2%, the mass percentage of the phosphite antioxidant is 0.2%, the mass percentage of distearyl thiodipropionate is 0.1%, and the mass percentage of the silicone masterbatch is 1%.

[0100] The preparation method includes the following steps:

[0101] The process parameters for melt extrusion by a twin-screw extruder are as follows: the temperature in the first zone is 120 - 160 °C, the temperatures from the second zone to the die head are all 170 - 220 °C, the main machine current is 370 - 450 A, the main machine speed is 450 rpm, the vacuum extraction pressure value in the metering section is about -0.9 MPa, the material is premixed in a high-speed mixer at 750 r / min for 3 min, and the length-diameter ratio of the twin-screw extruder is 48:1.

[0102] Random copolymer polypropylene, processing aids and a flame retardant composition with an untreated surface are pre-mixed evenly in a high-speed mixer according to specified mass ratios and fed into the main feeding port of a twin-screw extruder. The kneading block combination is produced according to general-purpose modified polypropylene, reducing the application of 90-degree and 45-degree screw elements in the examples. A polypropylene-based composition of the flame retardant composition is prepared by melt blending through a twin-screw extruder, and pellets are obtained after traction cooling and pelletizing.

[0103] Performance testing

[0104] The materials prepared in the above examples and comparative examples are injection molded into test specimens, where:

[0105] (1) Tensile strength and elongation at break: Tested according to ISO 527 at a speed of 50 mm / min;

[0106] (2) Izod notched impact strength: Tested according to ISO 179 at 23 °C with a pendulum of 5.5 J;

[0107] (3) Density: Tested according to ISO1183;

[0108] (5) Vertical burning: Tested according to UL94 at 1.6 mm;

[0109] (6) Water-cut particle surface: After water-cooled strand pelletizing of the modification, observe the particle surface to judge the dispersion and decomposition;

[0110] (7) Plate appearance surface: Extrude the materials of the examples and comparative examples through a three-roll plate extruder and observe whether there are pits and depressions on the surface;

[0111] (8) Melt strength: Tested with a Rheotens 71.97 melt strength tester from GOTTFERT Company, Germany. The die diameter is 2 mm, the die temperature is 230 °C, the distance from the die to the upper edge of the drawing wheel is 40 mm, the distance from the die to the center of the drawing wheel is 58 mm, the gap of the drawing wheel is 0.4 mm, and the drawing acceleration is 20 mm / s 2 .

[0112] Table 1 Performance test results of the flame-retardant polyolefin materials of the examples and comparative examples

[0113]

[0114] From the test results of the products in the examples and comparative examples in Table 1, it can be seen that the polyolefin-based compositions of the flame retardant compositions prepared in Examples 1 to 3 of the present invention have excellent tensile strength and notched impact strength, and excellent melt strength. From the data of elongation at break, notched impact strength, water-cut particle surface and plate appearance surface, it can be shown that the flame retardant compositions have high flame retardancy efficiency and very good dispersion in polyolefin materials.

[0115] Comparing Example 1 with Comparative Example 1, after the flame retardant composition is surface-treated, the material mechanics, flame retardancy, and the surfaces of the material and the board are better than those of the flame retardant composition polyolefin-based composition without surface treatment.

[0116] Comparing Example 1 with Comparative Example 2 shows that the processing technology is relatively important and has a great influence on the dispersion of the flame retardant.

[0117] Comparing Example 1 with Comparative Example 3, after crosslinking, the melt strength of the flame retardant composition polyolefin-based composition is greatly improved.

[0118] Comparing Example 1 with Comparative Example 4 shows that the surface treatment, processing method, and crosslinking treatment of the flame retardant composition have obvious improvements on the final product.

[0119] The flame retardant composition and its polyolefin-based composition prepared by the present invention can have advantages in terms of dispersibility, high melt strength, mechanical properties, etc., mainly due to the application of polyolefin material crosslinking technology, the application of self-made flame retardant composition preparation technology, the application of flame retardant composition surface treatment technology, and the application of polyolefin masterbatch processing and preparation technology of the flame retardant composition.

[0120] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A flame-retardant polyolefin composition, characterized in that, Comprising: Polyolefin resin: 53 - 58% by mass percentage; Surface-treated flame retardant composition: 40 - 45% by mass percentage; Crosslinking aid: 0.2 - 2% by mass percentage; Free radical initiator: 0.02 - 0.1% by mass percentage; Processing aid: 0.5 - 2% by mass percentage; The material of the surface-treated flame retardant composition consists of component A, component B, component C, and component D; Component A is a flame retardant composition: 91 - 96% by mass percentage; Component B is a coupling agent: 0.5 - 2% by mass percentage; Component C is a hyperdispersant: 3 - 5% by mass percentage; Component D is a stearate: 0.5 - 2% by mass percentage; The said flame retardant composition is composed of the following components: decabromodiphenylethane as the flame retardant: 35 - 50% by mass percentage, antimony trioxide as the flame retardant synergist: 6 - 18% by mass percentage, polytetrafluoroethylene as the anti-dripping agent: 0.4 - 2% by mass percentage, magnesium silicate salt as the flame retardant synergistic filler: 10 - 50% by mass percentage; The decabromodiphenylethane described has a 1% thermal weight loss temperature of not less than 330 °C, a particle size D 50 of not greater than 3 μm, a whiteness of not less than 89, and a pH value of 7-9; The magnesium silicate salt has a pH value of 9.3, a silica mass percentage of 62%, and an average particle size D50 of 5 μm; The preparation method includes: (1) First, mix the polyolefin resin, crosslinking aid, and free radical initiator uniformly in a high-speed mixer according to certain mass ratio requirements, add them to a single-screw extruder with a length-diameter ratio of 56:1 for melt mixing and extrusion. The processing temperature is 120°C - 190°C, the natural exhaust port is blocked, the vacuum extraction pressure value in the metering section is about -0.5 MPa, pelletize and dry to obtain a high melt strength matrix standby material; (2) Then, mix the high melt strength matrix standby material, surface-treated flame retardant composition, and processing aid uniformly in a high-speed mixer according to mass ratio requirements, and melt mix and extrude in a twin-screw extruder with a length-diameter ratio of more than 40:1; (3) The vacuum extraction pressure value in the metering section of the twin-screw extruder is -0.9 MPa. Kneading blocks are added to other sections except the feeding port, natural exhaust port, vacuum exhaust port, and conveying section, and the application of 90-degree and 45-degree screw elements in the screw combination is increased. The temperature of each section of the screw is set in the range of 150 - 210°C, a reasonable main machine speed is set, and a flame-retardant polyolefin composition is obtained through melt blending in the twin-screw extruder.

2. The flame-retardant polyolefin composition according to claim 1, characterized in that, The coupling agent is one or a mixture of silane coupling agents, maleic anhydride grafts, titanate coupling agents, and aluminate coupling agents.

3. The flame-retardant polyolefin composition according to claim 1, characterized in that, The hyperdispersant is one or a mixture of polyester-based hyperdispersants, polyether hyperdispersants, and polyolefin hyperdispersants.

4. The flame-retardant polyolefin composition according to claim 1, characterized in that, The stearate is one or a mixture of magnesium stearate, calcium stearate, potassium stearate, and zinc stearate.

5. The flame-retardant polyolefin composition according to any one of claims 1-4, characterized in that, The preparation method of the surface-treated flame retardant composition includes: In a high-speed mixer with a high-temperature spray gun, add component A in proportion, mix at a low speed of 200 - 300 r / min, set the temperature of the high-speed mixer to 100 - 120°C during uniform mixing, and at the same time, continuously spray the component B mixture into it with the high-temperature spray gun. After a certain time, add component C and component D, increase the speed of the high-speed mixer to 600 - 1400 r / min, mix at high speed for a certain time, and then discharge for standby.

6. The flame-retardant polyolefin composition according to any one of claims 1-4, characterized in that, The polyolefin resin described above is selected from α-olefin polymers or α-olefin copolymers.

7. The flame-retardant polyolefin composition according to claim 6, characterized in that, The α-olefin polymer is selected from one or more of polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, high-density polyethylene, polypropylene, homopolypropylene, random copolymer polypropylene, block copolymer polypropylene, impact copolymer polypropylene, high impact copolymer polypropylene, isotactic polypropylene, syndiotactic polypropylene, semi-isotactic polypropylene, maleic anhydride modified polypropylene, polybutene, cycloolefin polymer, stereoblock polypropylene, poly-3-methyl-1-butene, poly-3-methyl-1-pentene, poly-4-methyl-1-pentene.

8. The flame-retardant polyolefin composition according to claim 6, characterized in that, The α-olefin copolymer is selected from one or more of ethylene / propylene block or random copolymers, ethylene / octene block or random copolymers, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate copolymer.

9. The flame-retardant polyolefin composition according to any one of claims 1-4, characterized in that, The crosslinking aid described above is one of trimethylolpropane trimethacrylate, divinylbenzene, triallyl cyanurate, polyethylene glycol dimethacrylate.

10. The flame-retardant polyolefin composition according to any one of claims 1-4, characterized in that, The radical initiator is one or a mixture of several of dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, azobisisobutyronitrile.

11. The flame-retardant polyolefin composition according to any one of claims 1-4, characterized in that, The processing aid is selected from one or a mixture of several of hindered phenol antioxidants, phosphite antioxidants, distearyl thiodipropionate, white oil, silicone oil, silicone masterbatch, erucamide, polypropylene wax, and polyethylene wax.

12. A method for preparing the flame-retardant polyolefin composition according to any one of claims 1-11, characterized in that: (1) First, the polyolefin resin, crosslinking aid, and radical initiator are pre-mixed evenly in a high-speed mixer according to certain mass ratio requirements, added to a single-screw extruder with a length-diameter ratio of 56:1 for melt mixing and extrusion. The processing temperature is 120°C - 190°C, the natural exhaust port is blocked, the vacuum extraction pressure value in the metering section is about -0.5 MPa, pelletized and dried to be used as a high melt strength matrix spare material; (2) Then, the high melt strength matrix spare material, surface-treated flame retardant composition, and processing aid are pre-mixed evenly in a high-speed mixer according to mass ratio requirements, and melt mixed and extruded in a twin-screw extruder with a length-diameter ratio of more than 40:1; (3) The vacuum extraction pressure value in the metering section of the twin-screw extruder is -0.9 MPa. Kneading blocks are added to other sections except the feeding port, natural exhaust port, vacuum exhaust port, and conveying section. The application of 90-degree and 45-degree screw elements in the screw combination is increased. The temperature of each section of the screw is set in the range of 150 - 210°C, and a reasonable main machine speed is set. The flame-retardant polyolefin composition is obtained by melt blending in the twin-screw extruder.

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