CN111675878A

CN111675878A - Halogen-free flame-retardant ABS material and preparation method thereof

Info

Publication number: CN111675878A
Application number: CN202010599279.5A
Authority: CN
Inventors: 喻慧文; 徐百平; 曹明轩; 肖书平; 张志旋
Original assignee: Wuyi University
Current assignee: Wuyi University
Priority date: 2020-06-28
Filing date: 2020-06-28
Publication date: 2020-09-18

Abstract

The invention discloses a halogen-free flame-retardant ABS material and a preparation method thereof, wherein the halogen-free flame-retardant ABS material comprises the following components in percentage by weight: 50-70% of ABS, 10-20% of POE, 25-30% of intumescent flame retardant, 1-5% of halloysite nanotube, 0.05-0.5% of antioxidant and 0-2% of liquid paraffin; the preparation method comprises the following steps: the raw materials are mixed in proportion, and the halogen-free flame retardant ABS material is prepared by adopting a differential double-screw rod processing mode. The halogen-free flame-retardant ABS material provided by the invention has the advantages of good flame retardance, high thermal stability, good mechanical properties and the like, and can be applied to products such as consumer robots, unmanned aerial vehicles, electric products and the like.

Description

Halogen-free flame-retardant ABS material and preparation method thereof

Technical Field

The invention relates to the field of flame-retardant materials, in particular to halogen-free flame-retardant ABS and a preparation method thereof.

Background

Acrylonitrile-butadiene-Styrene (ABS) is a terpolymer of Acrylonitrile, 1, 3-butadiene and Styrene, and is a thermoplastic polymer material with high strength, good toughness and easy processing and molding. In recent years, ABS has become widely used in the fields of automobiles, electronic and electrical appliances, intelligent robots, buildings, and the like, by virtue of its excellent chemical resistance, mechanical properties, and processing advantages. However, ABS has limited its further application in the areas associated with high-end electrical products due to its relatively high flammability and its concomitant emission of fumes and droplets during combustion. Therefore, how to improve the fire resistance and thermal stability is the key to the development of ABS applications.

With the rising green environmental protection requirement in the flame retardant field, the Intumescent Flame Retardant (IFR) has the advantages of environmental protection and the like compared with the traditional halogen-containing flame retardant, and becomes the first choice of the ABS flame retardant. By incorporating high concentrations of IFR additives into the ABS matrix during processing, the desired flame retardant properties can be achieved, but the mechanical properties of the composite are greatly reduced. It has hitherto been difficult to improve the flame retardancy and thermal stability of composite materials while maintaining the mechanical properties of the composite material as excellent as those of pure ABS matrices.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a halogen-free flame-retardant ABS material which can simultaneously meet higher flame retardance, thermal stability and mechanical property.

The invention also provides a preparation method of the halogen-free flame-retardant ABS material.

According to the embodiment of the first aspect of the invention, the raw materials of the halogen-free flame retardant ABS material comprise the following components in percentage by weight: 50-60% of ABS, 10-20% of thermoplastic Polyolefin Elastomer (POE), 25-30% of intumescent flame retardant, 1-5% of Halloysite Nanotubes (HNTs), 0.05-0.5% of antioxidant and 0-2% of liquid paraffin.

The halogen-free flame retardant ABS material provided by the embodiment of the invention has at least the following beneficial effects: the ABS material of the invention is added with POE as a toughening agent and a charring agent, HNTs as a synergist, and a certain proportion of an intumescent flame retardant, and is an ABS halogen-free flame retardant material with strong toughness and good flame retardant effect; wherein, the addition of POE toughens ABS, a certain amount of HNTs has refining effect on POE, and a synergistic effect is achieved in the process of toughening ABS by POE, so that the effect of enhancing and toughening is achieved; and the APP in the expansion type flame retardant is pyrolyzed to remove NH₃Dehydroxylating the generated acid with-OH between HNTs layers at high temperature to form a compact carbon layer, and reacting to generate H₂O takes away part of heat, and simultaneously HNTs contain crystal water, so that part of heat is taken away by dehydration during combustion, a certain promotion effect on the flame retardant effect is achieved, the ignition time is delayed, and the heat release rate is inhibited.

In the prior art, a synergist can be used together with IFR, and has certain effect on improving flame retardance and mechanical properties, such as montmorillonite, carbon nano tube, nano magnesium hydroxide and the like. However, the commonly used synergist is incompatible with the matrix, and the dosage is low, and the uniformity is difficult to break through; the proportion of the components of the synergist and the matrix can solve the problem of uniformity in the prior art.

According to some embodiments of the present invention, the halogen-free flame retardant ABS material comprises raw materials with the following component ratio (by weight percentage): 26-28% of intumescent flame retardant and 1-3% of halloysite nanotube.

Further preferably, the halogen-free flame retardant ABS material comprises the following raw materials in percentage by weight: 26-27% of intumescent flame retardant and 2-3% of halloysite nanotube.

According to some embodiments of the invention, the intumescent flame retardant comprises ammonium polyphosphate and pentaerythritol.

Further, the ratio of the ammonium polyphosphate to the pentaerythritol is (2-4): 1.

preferably, the ratio of the ammonium polyphosphate to the pentaerythritol is 3: 1.

according to some embodiments of the invention, the halloysite nanotubes have an outer diameter dimension of 20-70nm, an inner diameter dimension of 10-30nm, and a length of 0.5-2 μm.

According to some embodiments of the invention, the halloysite nanotubes are silane coupling agent modified halloysite nanotubes. After the HNTs are modified by a silane coupling agent through a surface modifier, the interface compatibility with ABS is improved, more energy is needed during external force separation, a synergistic effect is achieved in the process of toughening ABS through POE, and a better effect of enhancing and toughening is achieved.

Further, the silane coupling agent is gamma-aminopropyltriethoxysilane.

Further, the gamma-aminopropyltriethoxysilane accounts for 2.5% -3% of the halloysite nanotube by mass.

According to some embodiments of the invention, the method of making the silane coupling agent modified halloysite nanotubes comprises the steps of:

1) grinding and purifying the halloysite nanotube;

2) adding sodium carbonate and water into the purified HNTs to adjust the pH value to 7-8, adding a surface modifier with the amount accounting for 2.5-3% of the mass of the HNTs, stirring and reacting for 3-5 hours at the temperature of 60-80 ℃, washing, drying and grinding to obtain the modified halloysite nanotubes.

The molecular structural formula of the silane coupling agent is generally Y-R-Si (OR)₃(wherein Y is an organofunctional group, SiOR is a siloxy group, and Y is typically a vinyl, amino, epoxy, methacryloxy, mercapto or ureido group). The silicon alkoxy group is reactive to inorganic substances, and the organic functional group is pairedOrganic materials are reactive or compatible and therefore, when a silane coupling agent is interposed between the inorganic and organic interfaces, a bonding layer of organic matrix-silane coupling agent-inorganic matrix can be formed. The surface of the halloysite nanotube is modified by surface treatment by using a silane coupling agent as a surface modifier.

According to some embodiments of the invention, the antioxidant is pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ].

According to some embodiments of the invention, the halogen-free flame retardant ABS material further comprises 0-2% by weight of liquid paraffin.

The preparation method according to the embodiment of the second aspect of the invention comprises the following steps: the raw materials are mixed in proportion, and the halogen-free flame retardant ABS material is prepared by adopting a differential double-screw rod processing mode.

The preparation method provided by the embodiment of the invention has at least the following beneficial effects:

1. the material used in the preparation method of the invention adopts Halloysite Nanotubes (HNTs) as a synergist and POE flexibilizer as a synergist, thus solving the problems of incompatibility of the synergist and a matrix, low dosage and poor uniformity;

2. the preparation method is a differential double-screw processing method, adopts a differential double screw to uniformly disperse HNTs and IFR in ABS/POE, breaks through the problem of difficult dispersion caused by periodic symmetrical flow in the traditional double-screw processing process, solves the problem that the high flame retardance and high strength of ABS materials are difficult to meet simultaneously, and improves the thermal stability and mechanical property.

Compared with the traditional double-screw processing method, the differential double-screw processing method can further improve the performance of the material. The two traditional double-screw screws have the same structure, and are different in certain phase angle during installation, so that the geometric space of fluid passing along the two screws in the advancing process is consistent, the transformation of the geometric shape of the fluid processing space is lacked, the reorientation effect of an interface in the shearing process is weakened, the mixing effect is limited, especially, most of the fluid in the middle of a screw groove still belongs to laminar flow mixing, and the interface is linearly increased along with time. For halogen-free flame-retardant materials, one of the key points for improving the material performance is that the dispersibility does not generate an agglomeration phenomenon in the processing process and is uniformly dispersed in a continuous phase, the dispersion of the flame retardant is restricted by the traditional processing method, and in order to achieve higher flame-retardant performance and mechanical performance, a multi-step processing method is often adopted, for example, a master batch is prepared firstly or is granulated for multiple times, the energy consumption loss is large, the energy conservation, environmental protection and cost increase are not facilitated, the processing method can realize one-step forming, and the flame-retardant performance is greatly improved compared with the traditional processing method.

According to some embodiments of the invention, the method specifically comprises the following steps:

1) mixing ABS and POE, adding intumescent flame retardant, halloysite nanotube and antioxidant, and mixing for 2-5 min;

2) setting the temperature of the differential double-screw extruder to be 165-200 ℃, and adding the mixed raw materials into the differential double-screw extruder for dispersion; the differential double-screw extruder comprises a single-head threaded rod and a double-head threaded rod, and the rotating speed of the single-head threaded rod is twice that of the double-head threaded rod.

In the present invention, the end face configuration of the differential twin-screw extruder is shown in (b) of fig. 1, the combined structure is shown in (b) of fig. 2, and the end face structure is described in detail in patent CN 103434113A. The rotation speed of the single-end threads on the left side is twice that of the double-end threads on the right side, the two screws rotate in a differential mode, the screws alternate between full and non-full along the way, the filling degree of the screw grooves of the left screw and the right screw is asymmetric, the flowing space of fluid in the screw grooves is constantly changed, meanwhile, the fluid is alternately stretched and sheared continuously, the reorientation effect of an interface is increased, and the inorganic flame retardant and the synergist are uniformly dispersed into the ABS.

According to some embodiments of the invention, the method further comprises the step of pre-treating the feedstock: drying and sieving the halloysite nanotube; the intumescent flame retardant is dried for 4 hours at 70 ℃; the ABS is dried for 6 hours at 90 ℃; the POE was dried at 70 ℃ for 2 h.

The halogen-free flame-retardant ABS material prepared by the invention can be applied to products such as consumer robots, unmanned aerial vehicles, electric appliances and the like.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

FIG. 1 is a schematic view of the configuration of the end face of a twin-screw extruder apparatus according to the present invention, wherein (a) is a schematic view of the configuration of the end face of a conventional twin-screw extruder apparatus and (b) is a schematic view of the configuration of the end face of a differential twin-screw extruder apparatus;

FIG. 2 is a schematic view of the assembly structure of a twin-screw extruder apparatus according to the present invention, wherein (a) is a schematic view of the assembly structure of a conventional twin-screw extruder apparatus, and (b) is a schematic view of the assembly structure of a differential twin-screw extruder apparatus.

Detailed Description

In order to explain technical contents, achieved objects, and effects of the present invention in detail, the following description is made with reference to the accompanying drawings in combination with the embodiments.

The following embodiments of the invention all adopt the same technical conception, the step method actually comprises the following raw material preparation and treatment processes and an accelerated double-screw processing process, and the overall step scheme is as follows:

first, raw material preparation and treatment

1. Modifying the halloysite nanotube:

(1) the Halloysite Nanotubes (HNTs) with outer diameter of 20-70nm, inner diameter of 10-30nm and length of 0.5-2 μm are ground and purified;

(2) adding anhydrous sodium carbonate and deionized water into purified HNTs to adjust the pH value to be 7-8, adding gamma-aminopropyl triethoxysilane (KH550 or KH 570) with the amount accounting for 2.5-3% of the mass of the HNTs, stirring and reacting for 4 hours at 70 ℃, washing for multiple times by using deionized water and absolute ethyl alcohol respectively, drying for 4-6 hours at 70 ℃, and grinding to obtain modified HNTs powder.

2. Pretreatment of materials:

sieving the dried HNTs powder, and drying an intumescent flame retardant IFR (ammonium polyphosphate (APP)) and Pentaerythritol (PER) at an optimal mass ratio of 3: 1 at 70 ℃ for 4 hours; ABS is dried for 6h at 90 ℃; POE was dried at 70 ℃ for 2 h.

Two, differential double screw processing

1. Adding ABS and POE into a high-speed mixer, adding 0.8% of liquid paraffin by mass ratio, adding intumescent flame retardant, halloysite nanotube and antioxidant, and mixing for 2-5 min;

2. the temperature of the differential double-screw extruder is set to be 165-200 ℃, the mixed materials are added into the differential double-screw extruder, the end face configuration and the combination of the equipment are shown in (b) in figure 1, wherein the rotating speed of a single-end thread on the left side is twice of the rotating speed of a double-end thread on the right side, the two screws rotate in a differential speed mode, the screws alternate between full filling and non-full filling along the process, the filling degree of screw grooves of the left screw and the right screw is asymmetric, the flowing space of fluid in the screw grooves is continuously changed, and meanwhile, the fluid is continuously stretched and sheared alternately, the reorientation effect of an interface is increased, so that the inorganic flame retardant and the synergist.

Example 1

The halogen-free flame-retardant ABS material comprises the following raw materials in percentage by mass: ABS 52%; POE 18%; 27.8 percent of intumescent flame retardant; halloysite nanotubes 1.2%; 1% of other auxiliary agents; wherein, other auxiliary agents (the same as the following embodiments) comprise 0.2 percent of antioxidant and 0.8 percent of liquid paraffin, and the antioxidant is tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester. The specific preparation method of the halogen-free flame-retardant ABS material comprises the following steps:

1. the Halloysite Nanotubes (HNTs) with outer diameter of 20-70nm, inner diameter of 10-30nm and length of 0.5-2 μm are ground and purified;

2. adding anhydrous sodium carbonate and deionized water into the purified HNTs to adjust the pH value to be 7-8, adding gamma-aminopropyltriethoxysilane (KH550 or KH 570) with the amount accounting for 2.5-3% of the mass of the HNTs, stirring and reacting for 4 hours at 70 ℃, washing for multiple times by using the deionized water and absolute ethyl alcohol respectively, drying for 5 hours at 70 ℃, and grinding to obtain modified HNTs powder.

3. Sieving the dried HNTs powder, drying an intumescent flame retardant IFR (consisting of ammonium polyphosphate (APP) and Pentaerythritol (PER) in a mass ratio of 3: 1) at 70 ℃ for 4 hours, drying ABS at 90 ℃ for 6 hours, and drying POE at 70 ℃ for 2 hours;

4. adding ABS and POE into a high-speed mixer, adding 0.8% of liquid paraffin by mass ratio, adding intumescent flame retardant, halloysite nanotube and antioxidant, and mixing for 2-5 min;

5. the temperature of the differential double-screw extruder is set to be 180 ℃, the mixed materials are added into the differential double-screw extruder, the end surface configuration and combination of the device are shown in the following figure, wherein the rotating speed of a single-end thread on the left side is twice of that of a double-end thread on the right side, the rotating speed of an asymmetric double-screw single-end screw is 84rmp, and the rotating speed of a common double-screw is 63 rmp. The two screws rotate at different speeds, the screws alternate between full filling and non-full filling along the process, the filling degree of the screw grooves of the left screw and the right screw is asymmetric, the flowing space of fluid in the screw grooves is constantly changed, and meanwhile, the continuous stretching and shearing alternation is carried out, so that the reorientation effect of the interface is increased, and the inorganic flame retardant and the synergist are uniformly dispersed into the ABS.

Example 2

The halogen-free flame-retardant ABS material comprises the following raw materials in percentage by mass: ABS 52%; POE 18%; 26.6 percent of intumescent flame retardant; halloysite nanotubes 2.4%; 1% of other auxiliary agents; the specific preparation method is the same as that of example 1.

Example 3

The halogen-free flame-retardant ABS material comprises the following raw materials in percentage by mass: ABS 52%; POE 18%; 25.4 percent of intumescent flame retardant; halloysite nanotubes 3.6%; 1% of other auxiliary agents; the specific preparation method is the same as that of example 1.

Example 4

The halogen-free flame-retardant ABS material comprises the following raw materials in percentage by mass: ABS 52%; POE 18%; 24.2 percent of intumescent flame retardant; 4.8% of halloysite nanotubes; 1% of other auxiliary agents; the specific preparation method is the same as that of example 1.

Comparative example 1

The halogen-free flame-retardant ABS material comprises the following raw materials in percentage by mass: 70% of ABS; 29 percent of intumescent flame retardant; 1% of other auxiliary agents; the specific preparation method is the same as that of the embodiment 1, and POE and part related to the treatment and addition of the halloysite nanotubes are deleted in the step.

Comparative example 2

The halogen-free flame-retardant ABS material comprises the following raw materials in percentage by mass: ABS 52%; POE 18%; 29 percent of intumescent flame retardant; 1 percent of other auxiliary agents. The specific preparation method is the same as that of the embodiment 1, and the relevant processing and adding parts of the halloysite nanotubes are deleted in the steps.

Comparative example 3

The halogen-free flame-retardant ABS material comprises the following raw materials in percentage by mass: ABS 52%; POE 18%; 26.6 percent of intumescent flame retardant; halloysite nanotubes 2.4%; 1 percent of other auxiliary agents. The preparation method differs from the example 2 only in that a differential twin-screw processing method is not used, and a traditional twin-screw processing method is adopted.

Test example

The test method comprises the following steps: the tensile property is tested according to the GB/T1040.2-2006 standard, and the tensile rate is 5 mm/min; the bending performance is tested according to the GB/T9341-2008 standard, and the test speed is 20 mm/min; the impact strength is tested according to the GB/T1843-2008 standard, and an A-type notch sample is adopted; the limiting oxygen index is tested according to GB-T2406.2-2009 standard, and the sample size is 80mm multiplied by 10mm multiplied by 4 mm; the vertical burning was measured in accordance with GB/T2408-2008, and the sample size was 125 mm. times.13 mm. times.3 mm.

Wherein UL-94 is the flame retardant rating, TTI is the ignition time, pHRR is the peak value of the heat release rate, TpHRR is the time to reach the peak value of the heat release rate, MHRR is the average heat release rate, FPI is the fire performance index, which is the ratio of TTI to pHRR.

TABLE 1 Performance test results of halogen-free flame retardant ABS materials

From the results in table 1, it can be seen that the halogen-free flame retardant ABS prepared in example 2 has the best performance effect, and the best material raw material components are: ABS 52%; POE 18%; 26.6 percent of intumescent flame retardant; halloysite nanotubes 2.4%; 1% of other auxiliary agents; in examples 1 to 4, only the proportions of the intumescent flame retardant and the halloysite nanotubes are different, and the flame retardant performance and mechanical performance of example 2 are the best, which shows that the flame retardant performance and mechanical performance are the best when the intumescent flame retardant is 26% -27% and the halloysite nanotubes are 2% -3%. Compared with the prior art, the material prepared by using the comparative example 1 without adding the POE and the halloysite nanotube has greatly reduced flame retardant property and mechanical property; comparative example 3a conventional twin-screw processing method was applied instead of a differential twin-screw processing method, as shown in fig. 2, and in the case of uniform outer diameters of the screws, the conventional twin-screw had a longer length-diameter ratio and a longer residence time, but the material properties obtained by the conventional twin-screw preparation were also inferior to those of example 2; therefore, POE and halloysite nanotubes and a differential double-screw processing method all have important influence on the performance of the halogen-free flame-retardant ABS material.

In summary, the halogen-free flame retardant ABS material and the preparation method thereof provided by the invention have the following advantages:

1. according to the invention, thermoplastic polyolefin elastomer (POE) is added into ABS as a toughening agent and a charring agent, HNTs are used as a synergist, and a certain proportion of intumescent flame retardant is added to prepare the ABS halogen-free flame retardant material with strong toughness and good flame retardant effect; wherein, the addition of POE toughens ABS, a certain amount of HNTs has refining effect on POE, and a synergistic effect is achieved in the process of toughening ABS by POE, so that the effect of enhancing and toughening is achieved; and the APP in the expansion type flame retardant is pyrolyzed to remove NH₃Dehydroxylating the generated acid with-OH between HNTs layers at high temperature to form a compact carbon layer, and reacting to generate H₂O takes away part of heat, and simultaneously HNTs contain crystal water, so that part of heat is taken away by dehydration during combustion, a certain promotion effect on the flame retardant effect is achieved, the ignition time is delayed, and the heat release rate is inhibited.

2. The processing method used by the invention is a differential double-screw processing method, and compared with the traditional double-screw processing method, the processing method can further improve the performance of the material. The two traditional double-screw screws have the same structure, and are different in certain phase angle during installation, so that the geometric space of fluid passing along the two screws in the advancing process is consistent, the transformation of the geometric shape of the fluid processing space is lacked, the reorientation effect of an interface in the shearing process is weakened, the mixing effect is limited, especially, most of the fluid in the middle of a screw groove still belongs to laminar flow mixing, and the interface is linearly increased along with time. For halogen-free flame-retardant materials, one of the key points for improving the material performance is that the dispersibility does not generate an agglomeration phenomenon in the processing process and is uniformly dispersed in a continuous phase, the dispersion of the flame retardant is restricted by the traditional processing method, and in order to achieve higher flame-retardant performance and mechanical performance, a multi-step processing method is often adopted, for example, a master batch is prepared firstly or is granulated for multiple times, the energy consumption loss is large, the energy conservation, environmental protection and cost increase are not facilitated, the processing method can realize one-step forming, and the flame-retardant performance is greatly improved compared with the traditional processing method.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to the related technical fields, are included in the scope of the present invention.

Claims

1. A halogen-free flame-retardant ABS material is characterized in that: the raw materials comprise the following components in percentage by weight: 55-60% of ABS, 10-20% of POE, 25-30% of intumescent flame retardant, 1-5% of halloysite nanotube, 0.05-0.5% of antioxidant and 0-2% of liquid paraffin.

2. The halogen-free flame retardant ABS material according to claim 1 wherein: 26-28% of intumescent flame retardant and 1-3% of halloysite nanotube.

3. The halogen-free flame retardant ABS material according to claim 1 wherein: the intumescent flame retardant comprises ammonium polyphosphate and pentaerythritol.

4. The halogen-free flame retardant ABS material according to claim 3 wherein: the ratio of the ammonium polyphosphate to the pentaerythritol is (2-4): 1.

5. the halogen-free flame retardant ABS material according to claim 1 wherein: the halloysite nanotube has an outer diameter of 20-70nm, an inner diameter of 10-30nm and a length of 0.5-2 μm.

6. The halogen-free flame retardant ABS material according to claim 1 wherein: the halloysite nanotube is a silane coupling agent modified halloysite nanotube.

7. The halogen-free flame retardant ABS material of claim 6 wherein: the silane coupling agent is gamma-aminopropyl triethoxysilane.

8. The halogen-free flame retardant ABS material of claim 6 wherein: the antioxidant is tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester.

9. The method for preparing halogen-free flame retardant ABS material according to any of claims 1 to 8, characterized in that: the method comprises the following steps: the raw materials are mixed in proportion, and the halogen-free flame retardant ABS material is prepared by adopting a differential double-screw rod processing mode.

10. The method of claim 9, wherein: the method specifically comprises the following steps: