阅读说明：本技术 一种螺杆组合、平行双螺杆挤出机、高导电pp/hips复合材料及其制备方法 (Screw combination, parallel double-screw extruder, high-conductivity PP/HIPS composite material and preparation method thereof ) 是由 范木良 杨杰 安峰 申应军 蒋士鹏 张淼 于 2021-09-23 设计创作，主要内容包括：本发明涉及高分子材料制备领域,特别涉及一种螺杆组合、平行双螺杆挤出机、高导电PP/HIPS复合材料及其制备方法。所述螺杆组合包括两根相互啮合的螺杆,所述螺杆组合一端至另一端依次分为主喂物料输送段、主喂物料熔融混炼段、侧喂物料输送段、全部物料熔融混合段、排气计量段。所述主喂物料熔融混炼段采用包括错列角为45°和/或60°的片状剪切块与输送螺纹的螺纹元件组合；所述全部物料熔融混合段采用包括带左旋插槽的右旋螺纹块与错列角为45°和/或90°的片状剪切块的螺纹元件组合。本发明通过使用包含所述螺杆组合的平行双螺杆挤出机,配合特定的配方,最终制得低成本、密度小、综合力学性能优异的高导电PP/HIPS复合材料。(The invention relates to the field of preparation of high polymer materials, in particular to a screw combination, a parallel double-screw extruder, a high-conductivity PP/HIPS composite material and a preparation method thereof. The screw rod combination comprises two mutually meshed screw rods, and one end of the screw rod combination is sequentially divided into a main feeding material conveying section, a main feeding material melting and mixing section, a side feeding material conveying section, a whole material melting and mixing section and an exhaust metering section from one end to the other end. The main feeding material melting and mixing section adopts a combination of sheet-shaped shear blocks with staggered angles of 45 degrees and/or 60 degrees and a screw element of a conveying screw thread; and the whole material melting and mixing section adopts a threaded element combination comprising a right-handed thread block with a left-handed slot and sheet-shaped shearing blocks with staggered angles of 45 degrees and/or 90 degrees. According to the invention, the parallel double-screw extruder containing the screw combination is matched with a specific formula, so that the high-conductivity PP/HIPS composite material with low cost, low density and excellent comprehensive mechanical properties is finally prepared.)

1. A screw combination is characterized in that: the screw assembly comprises two mutually meshed screws, and the screw assembly is divided into a main feeding material conveying section, a main feeding material melting and mixing section, a side feeding material conveying section, a total material melting and mixing section and an exhaust metering section from one end to the other end in sequence;

the main feeding material melting and mixing section adopts a combination of sheet-shaped shear blocks with staggered angles of 45 degrees and/or 60 degrees and a screw element of a conveying screw thread; and the whole material melting and mixing section adopts a threaded element combination comprising a right-handed thread block with a left-handed slot and sheet-shaped shearing blocks with staggered angles of 45 degrees and/or 90 degrees.

2. The screw combination of claim 1, wherein: the sheet-shaped cutout comprises one or a combination of K45/72, K45/56, K60/44, K45/44 and K90/7/75; the delivery threads comprise one or a combination of 96/96, 72/72, 56/56; the right-handed thread block with the left-handed slot comprises SME 44/44.

3. The screw combination of claim 1, wherein: the length-diameter ratio of the screw is 44: 1.

4. A parallel twin-screw extruder, characterized in that a screw combination according to any one of claims 1 to 3 is used.

5. A preparation method of a high-conductivity PP/HIPS composite material, which is characterized by adopting the parallel double-screw extruder of claim 4, and comprises the following steps:

step a, weighing PP, SBS, conductive filler, antioxidant and lubricant according to a proportion, adding all the materials into a high-speed stirrer, and stirring and mixing uniformly at a high speed to obtain premix;

step b, adding the obtained premix into a parallel twin-screw extruder according to claim 4 from a main feeding port; adding the HIPS weighed in proportion from a side feeding port to enable all component materials to be melted, blended and extruded;

and c, cooling, drying and dicing the extruded material strips to obtain the high-conductivity PP/HIPS composite material.

6. The method for preparing the high-conductivity PP/HIPS composite material according to claim 5, wherein: the processing temperature of each zone of the parallel double-screw extruder is 180 ℃ in the first zone, 190 ℃ in the second zone, 200 ℃ in the third zone, 220 ℃ in the fourth zone, 220 ℃ in the fifth zone, 215 ℃ in the sixth zone, 215 ℃ in the seventh zone, 215 ℃ in the eighth zone, 210 ℃ in the ninth zone, 210 ℃ in the tenth zone and 220 ℃ in the head.

7. The method for preparing the high-conductivity PP/HIPS composite material according to claim 5, wherein: the weight percentages of the raw materials are as follows: 37.4 to 48.4 percent of PP, 42 to 53 percent of HIPS, 5 to 10 percent of SBS, 4 to 8 percent of conductive filler, 0 to 0.3 percent of antioxidant and 0 to 0.3 percent of lubricant.

8. The method for preparing the high-conductivity PP/HIPS composite material according to claim 5, wherein: the PP is one or a mixture of homo-polypropylene and co-polypropylene, and the melt index is 40-80 g/min (2.16KG/230 ℃).

9. The method for preparing the high-conductivity PP/HIPS composite material according to claim 5, wherein: the HIPS is high impact polystyrene, and the melt index is 3-8 g/min (5KG/200 ℃).

10. A high-conductivity PP/HIPS composite material is characterized in that: the high-conductivity PP/HIPS composite material is prepared by the preparation method of any one of claims 5 to 9.

Technical Field

The invention relates to the field of preparation of high polymer materials, in particular to a screw combination, a parallel double-screw extruder, a high-conductivity PP/HIPS composite material and a preparation method thereof.

Background

The polypropylene is one of five kinds of general plastics with the largest yield, has excellent mechanical property and chemical property, is widely applied to the fields of automobiles, household appliances, packaging, buildings and the like, and becomes the fastest developed variety in general resins. However, polypropylene is an insulating material, which limits its application in products requiring electrical conductivity in the electronic and electrical industries. The method for preparing the composite conductive polymer with the lasting and stable conductive performance by adding the conductive filler into the polymer is widely applied to various industries such as electronics, energy, chemical engineering, aerospace and the like in recent years due to simple process, low cost and wide adjustable range of resistivity.

Preferably, PP resin and conductive carbon black treated by a titanate coupling agent are used as conductive fillers and other auxiliaries which are mixed and then fed from a main feeding machine, the mixture is sheared, melted, mixed and dispersed by a first half section of twin screws, and then HIPS with a proper proportion is fed from a side feeding port machine, the PP resin and the uniform melt of the conductive fillers are mixed together in parallel twin screws for extrusion and granulation. Therefore, the high-conductivity PP/HIPS composite material with low cost, low density and excellent comprehensive mechanical property is prepared. The composite material is made to obtain conductivity by using the conductive carbon black, but a small amount of conductive carbon black is used for realizing good conductivity, and the key for solving the problem is how to make the conductive carbon black play a role to the maximum extent in the preparation process under the condition of ensuring other properties.

Disclosure of Invention

In order to solve the problem that the conductive carbon black plays a role to the maximum extent under the condition that other properties need to be ensured in the prior art. The invention provides a screw combination, which comprises two mutually meshed screws, and particularly, the meshing angle is 90 degrees. The screw rod combination is sequentially divided into a main feeding material conveying section, a main feeding material melting and mixing section, a side feeding material conveying section, a total material melting and mixing section and an exhaust metering section from one end to the other end;

the main feeding material melting and mixing section adopts a combination of sheet-shaped shearing blocks with staggered angles of 45 degrees and/or 60 degrees and a threaded element of a conveying thread to carry out shearing and dispersion on the materials for a plurality of times; and the whole material melting and mixing section adopts a threaded element combination comprising a right-handed thread block with a left-handed slot and sheet-shaped shearing blocks with staggered angles of 45 degrees and/or 90 degrees to mix and distribute the materials.

Specifically, the thread combination of the sheet-shaped shear block and the conveying threads is used in the main feeding material melting and mixing section to perform shearing dispersion on the materials for multiple times to generate a strong shearing strong dispersion effect, so that the conductive filler and the PP components are fully melted, dispersed and mixed, and the combination of the right-handed thread block with the left-handed slot and the thread elements of the sheet-shaped shear blocks with staggered angles of 45 degrees and/or 90 degrees is used in all the material melting and mixing sections to generate a weak shearing strong distribution effect so as to prevent the conductive filler in the PP phase from migrating into the HIPS phase and further keep the PP phase in a high conductive state. Meanwhile, in the selection of conveying threads, the conveying thread elements with large lead are beneficial to feeding, so that the conveying thread elements with large lead can be used at the feed opening; the small lead of the conveying screw element is beneficial to compressing the material, compacting the material and discharging air entrained in the material. The increase of the material compactness is helpful for improving the melting of the material by the screw and the dispersion and mixing effect of the subsequent shearing unit on the material, and the adjustment can be carried out by the technical personnel in the field according to the actual situation.

In one embodiment, the sheet-like cutouts comprise one or a combination of K45/72, K45/56, K60/44, K45/44, K90/7/75; the delivery threads comprise one or a combination of 96/96, 72/72, 56/56; the right-handed thread block with the left-handed slot comprises SME 44/44. Wherein K45/72 represents a stagger angle of 45 °, and 5 discs constitute a shear cell of 72 mm in length; k45/56 represents a shearing unit with a staggered angle of 45 degrees and a length of 56 mm consisting of 5 discs; k60/44 represents a shearing unit with a staggering angle of 60 degrees and a length of 44 mm consisting of 4 discs; k45/44 represents a shearing unit with a staggering angle of 45 degrees and a length of 44 mm consisting of 5 discs; k90/7/75 represents a shearing unit with a staggering angle of 90 degrees and a length of 72 mm consisting of 7 discs; the conveying screw thread is 96/96 as an example, 96/96 represents a conveying element with a lead of 96 mm and a length of 96 mm, and the rest of the conveying screw threads are not described in detail; SME44/44 represents a right-handed thread block with a lead length of 44 mm and a left-handed slot length of 44 mm.

Specifically, the screw elements of the main feeding material melt mixing section can be K45/72, K45/56, K60/44, K60/44, 96/96, 72/72, 72/72, 56/56, K45/72, K45/56, K45/44, K45/44, 72/72, 72/72, 72/72, K45/56, K60/44 and 44/22L in sequence. Wherein 44/22L represents a reverse threaded element having a lead of 44 mm and a length of 22 mm, where the reverse threaded element acts to enhance the shearing effect. When the staggered angle of the shearing block is 45 degrees and the length of the disc is longer, the shearing and dispersing effect of the screw combination on the material is better. The main feeding material melting and mixing section is provided with three shearing combinations, each shearing combination is a disc with large thickness, so that the material can be subjected to larger stretching deformation, and then the shearing dispersion is carried out through the combination elements with larger staggered angles, so that the mutual dispersion and uniform mixing of the component materials are facilitated. The arrangement is to ensure that all components can be fully and uniformly dispersed in the processes of shearing dispersion, mixing, re-shearing dispersion, mixing and re-shearing dispersion of materials, and particularly to ensure that the conductive filler is dispersed in the PP component.

The elements of the whole material melt mixing section can be K45/44, K45/44, SME44/44, SME44/44, K90/7/75 and 44/22L in sequence. Wherein K45/44 and K90/7/75 shear and mix the materials to a certain extent, while SME44/44 provides strong distribution and mixing effect to the materials, so that the PP component and the HIPS component are uniformly distributed. The 44/22L element acts as a liquid seal prior to evacuation. In the melting and mixing section of all the materials, the combination of the thread elements with weak shearing and strong distribution effects is adopted to ensure that the PP component and the HIPS component are uniformly distributed, and the conductive filler in the PP phase is prevented from entering the HIPS component, thereby influencing the conductivity.

In one embodiment, the screw length to diameter ratio is 44: 1. Compared with a 40:1 model and a 44:1 model, the screw combination can be better designed to improve the mixing effect of the main feeding material melting and mixing section.

The invention also provides a parallel twin-screw extruder, which adopts the screw combination as described above.

The invention also provides a preparation method of the high-conductivity PP/HIPS composite material, which uses the parallel double-screw extruder and comprises the following steps:

step a, weighing PP, SBS, conductive filler, antioxidant and lubricant according to a proportion, adding all materials into a high-speed stirrer, and stirring and mixing uniformly at a high speed to obtain premix;

b, adding the obtained premix into the parallel double-screw extruder from the main feeding hopper; adding HIPS weighed in proportion into the parallel double-screw extruder from a side feeding port, and shearing, melting, blending and extruding all component materials in the parallel double-screw extruder, wherein the processing temperature of the parallel double-screw extruder is 180-220 ℃;

and c, cooling, drying and granulating the material strips from the neck mold of the parallel double-screw extruder to obtain the high-conductivity PP/HIPS composite material.

In one embodiment, the processing temperature of each zone of the twin screw extruder is 180 ℃ in one zone, 190 ℃ in two zones, 200 ℃ in three zones, 220 ℃ in four zones, 220 ℃ in five zones, 215 ℃ in six zones, 215 ℃ in seven zones, 215 ℃ in eight zones, 210 ℃ in nine zones, 210 ℃ in ten zones, and 220 ℃ in a head.

In one embodiment, the weight percentages of the raw materials are as follows: 37.4-48.4% of PP, 42-53% of HIPS, 5-10% of SBS, 4-8% of conductive filler, 0.3% of antioxidant and 0.3% of lubricant.

In one embodiment, the PP is one or a mixture of homo-polypropylene and co-polypropylene, the melt index is 40-80 g/min, and the test condition is 2.16KG/230 ℃. Preferably, PP can be selected from BX 3900.

In one embodiment, the HIPS is high impact polystyrene, the melt index is 3-8 g/min, and the test condition is 5KG/200 ℃. Preferably, HIPS can be HIPS-622P.

In one embodiment, the SBS is a styrene butadiene block copolymer. Preferably, SBS is selected from SBS YH-792E.

In one embodiment, the conductive filler is conductive carbon black treated with a titanate coupling agent. The specific preparation method comprises the following steps: putting 100 parts by mass of conductive carbon black into a high-speed mixer at the temperature of 80 ℃ for premixing for 10 minutes, and then adding 1 part by mass of a titanate coupling agent dissolved in absolute ethyl alcohol, wherein the ratio of the absolute ethyl alcohol to the titanate coupling agent is 1: 1; heating to 100 ℃, mixing for 20 minutes, discharging, and standing for 1 hour at room temperature to volatilize excessive solvent, thereby obtaining the conductive filler. Preferably, the conductive carbon black is CB 3100, and the titanate coupling agent is NDZ-101.

In one embodiment, the antioxidant is one or a combination of hindered phenol antioxidants, thioester antioxidants and phosphite antioxidants.

In one embodiment, the lubricant is one or a combination of N, N' -ethylene bis stearamide, polyethylene wax, polypropylene wax, calcium stearate, zinc stearate, and magnesium stearate.

The invention also provides a high-conductivity PP/HIPS composite material, which is prepared by the preparation method of the high-conductivity PP/HIPS composite material.

Based on the above, compared with the prior art, the invention has the following beneficial effects:

according to the screw combination provided by the invention, the strong-shearing strong-dispersion threaded element is used in the melting and mixing section of the main feeding material, so that the components can be fully and uniformly dispersed under the action of strong-shearing strong dispersion of the material, and particularly, the conductive filler is uniformly dispersed in the PP component. And the weak shearing strength distribution screw thread elements are used in the whole material melting and mixing section, so that the PP component and the HIPS component are uniformly distributed, and meanwhile, the conductive filler in the PP phase is prevented from entering the HIPS component, the conductivity is further influenced, and the conductive filler plays the greatest role.

The parallel double-screw extruder provided by the invention uses the screw combination designed by using the strong-shearing strong-dispersion thread element in the main feeding material melting and mixing section and using the weak-shearing strong-distribution thread element in the whole material melting and mixing section, optimizes the pertinence to the material on the basis of meeting the basic production requirement, enables the conductive filler to play the greatest role, improves the performance and further reduces the production cost.

The invention provides a preparation method of high conductive PP/HIPS composite material, which screens PP and HIPS in specific proportion for blending, uses specific mixed materials and a production process to ensure that the PP and HIPS components are continuous phases, further uses a parallel double-screw extruder which uses a screw combination of a strong shearing strong dispersion screw thread element in a main feeding material melting and mixing section and a weak shearing strong distribution screw thread element in a whole material melting and mixing section, fully melts, disperses and mixes conductive filler and PP components in the main feeding material melting and mixing section, prevents the conductive filler in the PP phase from migrating into the HIPS phase in the whole material melting and mixing section, controls the distribution of the conductive filler to enrich in the PP phase to reach a conductive percolation threshold value, so as to reduce the percolation threshold value of a conductive path of the conductive filler in the whole composite material, thereby under the condition of ensuring other performances, the function of the conductive filler is exerted to the maximum extent.

The high-conductivity PP/HIPS composite material provided by the invention uses a specific formula system, and is matched with a parallel double-screw extruder adopting a screw combination with a specific design through a specific mixing and production process, so that the production cost is further reduced while the material is low in density and excellent in comprehensive mechanical property, and the high-conductivity PP/HIPS composite material has a wide application prospect and an industrial value.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; the technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any inventive step, are within the scope of the present invention.

In the description of the present invention, it is to be noted that all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs, and are not to be construed as limiting the present invention; it will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The invention also provides the following formula and preparation method examples:

example 1

Weighing the following raw materials in parts by weight: see table one

And then uniformly mixing the polypropylene, the styrene-butadiene block copolymer, the conductive filler, the antioxidant and the lubricant which are weighed according to the proportion, adding the mixture into a parallel double-screw extruder from a main feeding port, adding the high impact polystyrene which is weighed according to the proportion into the parallel double-screw extruder from a side feeding port, and shearing, melting, blending and extruding all the component materials in the parallel double-screw extruder.

Wherein the processing temperature of the double-screw extruder is 180 ℃ in the first zone, 190 ℃ in the second zone, 200 ℃ in the third zone, 220 ℃ in the fourth zone, 220 ℃ in the fifth zone, 215 ℃ in the sixth zone, 215 ℃ in the seventh zone, 215 ℃ in the eighth zone, 210 ℃ in the ninth zone, 210 ℃ in the tenth zone and 220 ℃ in the head.

The screw combination of the parallel double-screw extruder adopts a screw combination A which is a screw combination with strong shearing and strong dispersion in the front half section (main feeding material melting and mixing section) and weak shearing and strong distribution in the rear half section (all material melting and mixing section), and the screw combination is specifically shown in the table II.

And finally, cooling, drying and granulating the material strips from the neck mold of the parallel double-screw extruder to obtain the high-conductivity PP/HIPS composite material.

The preparation method of the conductive filler comprises the following steps: placing 100 parts by mass of conductive carbon black CB 3100 into a high-speed mixer at the temperature of 80 ℃ for premixing for 10 minutes, and then adding 1 part by mass of a titanate coupling agent NDZ-101 dissolved in absolute ethyl alcohol, wherein the ratio of the absolute ethyl alcohol to the titanate coupling agent is 1: 1; heating to 100 ℃, mixing for 20 minutes, discharging, and standing for 1 hour at room temperature to volatilize redundant solvent to obtain the conductive filler;

example 2

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III.

Example 3

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III.

Example 4

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III.

Example 5

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III.

Example 6

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III. The screw combination B is similar to the screw combination A and is a screw combination with strong shearing and strong dispersion in a main material feeding melting and mixing section and weak shearing and strong distribution in a whole material melting and mixing section, and the screw combination is specifically shown in the table II.

Comparative example 1

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III.

Comparative example 2

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III.

Comparative example 3

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III.

Comparative example 4

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III.

This formulation differs from example 1 in that the conductive filler used in this formulation is untreated conductive carbon black.

Comparative example 5

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III. Wherein, the screw of the parallel double-screw extruder adopts a screw combination C which is a screw combination with weak shearing and weak dispersion in the main material feeding melting and mixing section and weak shearing and strong distribution in the whole material melting and mixing section, and the screw combination is shown in the table II.

Comparative example 6

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III. The screw combination D is used as a main feeding material melting and mixing section, the whole material melting and mixing section is also a screw combination with strong shearing and strong dispersion, and the screw combination is shown in the table II.

Comparative example 7

Weighing the following raw materials in parts by weight: see table one

The preparation method is the same as example 1, and the effects are shown in Table III. Wherein the screws of the parallel twin-screw extruder use a screw combination E, the screw combination E moves forward relative to a screw combination B, and the screw combination is specifically shown in Table II.

The above examples and comparative examples were prepared according to the preparation method described in example 1, and samples to be tested were prepared and tested as follows: the density, the yield strength, the cantilever beam notch impact strength and the volume resistivity, and the specific detection standards are shown in the third table.

The amounts of each example and comparative example are given in table one:

TABLE amount of each example and comparative example TABLE (wt%)

The specification and sequence of the thread elements in each screw combination are as shown in the second table:

specification and sequence of screw elements in screw combination of watch two

The results of testing the materials obtained in the examples and comparative examples are shown in table three below:

TABLE III Experimental results Table for examples and comparative examples

Item	Density of	Yield strength	Notched impact strength of cantilever beam	Volume resistivity
					Unit of	g/cm3	Mpa	KJ/m2	Ω·m
Test standard	GB/T1033-1986	GB/T1040-2006	GB/T1843-2008	ASTMD-257
					Example 1	0.976	23.5	3.9	9.52*103
Example 2	0.987	23.8	4.2	8.24*103
					Example 3	0.971	25.1	5.8	7.33*103
Example 4	0.993	23.2	3.8	1.34*103
					Example 5	0.991	23.1	4.3	3.78*103
Example 6	0.992	23.3	4.2	3.69*103
					Comparative example 1	0.972	19.2	3.1	5.24*103
Comparative example 2	1.01	27.8	5.4	8.34*109
					Comparative example 3	0.995	21.2	3.3	4.12*103
Comparative example 4	0.978	22.7	4.1	5.39*104
					Comparative example 5	0.992	23.1	4.0	4.81*103
Comparative example 6	0.993	23.2	4.1	5.73*103
					Comparative example 7	0.992	23.4	4.3	7.11*103

As can be seen from the comparison between example 1 and example 2, when the HIPS component is increased from 42% to 53%, the PP component and the HIPS component are still in a bicontinuous phase structure, and the overall properties of the material are not greatly changed.

As can be seen from the comparison between example 1 and example 3, as the SBS component is increased, the PP component and the HIPS component are better compatible, the bonding force is stronger, and the mechanical properties are improved in tensile strength and impact strength to different degrees.

From a comparison of example 1 and example 4, it can be seen that as the conductive filler component is increased, the carbon black concentration within the PP component increases, the material volume resistivity decreases, and the conductivity properties increase.

From the comparison between the example 5 and the example 6, the screw combined threaded element of the extruder is not changed as a whole, the assembly sequence is slightly changed by only the shearing blocks of the melting and mixing section of the main feeding material, the number and the installation angle of the shearing blocks are still the same as those of the original shearing blocks, the strong shearing and strong dispersion properties are also consistent with those of the original shearing blocks, the good dispersion of the material discharged from the main feeding port can be ensured, and the integral performance of the material is not greatly different.

As can be seen from the comparison between example 1 and comparative example 1, when the HIPS component is reduced from 42% to 37%, the HIPS component is in a dispersed phase in the material, the mechanical properties of the material are mainly borne by the PP component in a continuous phase, and the external force borne by the HIPS component is reduced, so that the overall mechanical properties of the material are reduced.

As can be seen from a comparison of example 2 and comparative example 2, when the HIPS component is increased from 53% to 57%, the HIPS component is in the continuous phase in the material and the PP component is in the dispersed phase; the PP component in the dispersed phase is isolated into an island by the HIPS component in the continuous phase, so that the conductive filler distributed in the PP component cannot form a continuous conductive path on the whole material, and as a result, the volume resistivity of the material is greatly improved, and the conductive performance is reduced.

As can be seen from the comparison of example 5 with comparative example 3, without the addition of the SBS component, the compatibility of the PP component with the HIPS component is insufficient, the binding force is poor, and the overall mechanical properties of the material are reduced.

As can be seen from the comparison between example 5 and comparative example 4, the use of untreated conductive carbon black causes uneven dispersion due to easy agglomeration of the conductive carbon black, which affects the formation of good conductive paths in the PP component, and the overall conductive performance of the final material is lowered.

As can be seen from the comparison between example 6 and comparative example 5, in the first half section of the screw combination of the extruder, namely the melting and mixing section of the main feeding material, the number of the shear blocks is reduced, and the thickness and the angle of the residual shear blocks are thin, so that the screw combination has weak shear dispersion capability to the material, the conductive filler which is discharged from the main feeding port cannot be fully dispersed and mixed into the PP component, the carbon black concentration in the PP component is reduced, the volume resistivity of the material is large, and the conductive performance is reduced.

As can be seen from the comparison between example 6 and comparative example 6, in the latter half of the screw combination of the extruder, namely the melt mixing section of the whole material, the SME screw elements with weak shear strength distribution are replaced by the shear blocks, and the angle of the shear blocks is increased, so that the screw combination has strong shear dispersion capability to the material, the conductive filler originally enriched in the PP component is dispersed and mixed into the HIPS component, the concentration of the conductive filler in the PP component is reduced, the volume resistivity of the material is increased, and the conductivity is reduced.

As can be seen from the comparison between example 6 and comparative example 7, when the side feed port is moved forward, that is, the distance from the main feed port to the side feed port is shortened, the number of shear blocks in the main feed material melt-kneading section is also reduced, the material dispersing ability of the extruder from the main feed port is lowered, the mixing time of the materials in the main feed material melt-kneading section is shortened, the mutual dispersion of the component materials is relatively poor, and the conductive filler cannot be sufficiently dispersed and mixed into the PP component. In the melting and mixing section of all the materials, the time for mixing and dispersing all the materials together is prolonged, and the integral mixing and dispersing performance of all the materials is enhanced, so that the concentration of carbon black in the PP component is reduced, the volume resistivity of the materials is increased, and the conductivity is reduced.

The invention provides a method for preparing high-conductivity PP/HIPS composite material, which comprises the steps of uniformly mixing PP resin with an optimal grade and conductive carbon black treated by a titanate coupling agent as conductive fillers and other auxiliaries, then feeding the conductive fillers from a main feeding machine, shearing, melting, mixing and dispersing the conductive fillers by a first half section of double screws, and then carrying out co-mixing extrusion granulation on the HIPS with the PP resin and uniform melt of the conductive fillers in parallel double screws from a side feeding machine in a proper proportion. The conductive carbon black treated by the titanate coupling agent is not easy to agglomerate and is easier to uniformly disperse in PP resin; the PP resin is preferably of a high-fluidity low-viscosity grade, and the conductive filler is easier to be mixed, distributed and dispersed uniformly in the low-viscosity PP resin; HIPS is preferably low in melt and high in viscosity, so that the conductive carbon black in the melt of the PP resin-conductive filler mixture fed from the main feed port is less likely to migrate and disperse into the high viscosity HIPS phase during subsequent melt blending, finally, the conductive filler is enriched in the PP phase in the dual continuous phase structure system material to reach the conductive percolation threshold, the conductive performance of the PP phase in the dual continuous phase is greatly improved, the percolation threshold of a conductive path of the conductive filler in the whole composite material is reduced, the effect of greatly improving the conductive performance of the composite material by adding a small amount of conductive filler is achieved, and simultaneously, the HIPS with low melt index and high viscosity is selected as a blend, so that the HIPS with low melt index and high viscosity has more excellent impact strength and toughness, and the defects of the impact strength and the toughness of the PP resin with high flow viscosity and low viscosity can be overcome.

Because the PP resin and the HIPS are incompatible materials, and the PP resin and the HIPS with specific properties are selected from the formula, the SBS is also used as a compatilizer in the formula, so that the bonding force of the interface of the PP phase and the HIPS phase is increased, and the comprehensive mechanical property of the composite material is improved.

On the basis of the specific formula system, PP resin and HIPS in a specific proportion are researched and screened to be blended, and a specific mixing and production process is used to ensure that the whole system is in a double-continuous-phase structure. Meanwhile, a parallel double-screw extruder comprising a screw combination which uses a strong shearing strong dispersion thread element at a main feeding material melting and mixing section and uses a weak shearing strong distribution thread element at a whole material melting and mixing section is used, the strong shearing strong dispersion thread element is used at the main feeding material melting and mixing section of the extruder to ensure that the conductive filler and the PP component are fully melted, dispersed and mixed, the weak shearing strong distribution thread element is used at the whole material melting and mixing section of the extruder to prevent the conductive filler in the PP phase from migrating into the HIPS phase, the PP phase is kept in a high conductive state, namely the distribution of the conductive filler is controlled to enrich the PP phase in the conductive filler to reach a conductive percolation threshold value, the percolation threshold value of the conductive filler in a conductive path in the whole composite material is reduced, and therefore, the conductive carbon black can play a role to the maximum under the condition of ensuring other performances, finally, the high-conductivity PP/HIPS composite material with low cost, small density and excellent comprehensive mechanical property is successfully prepared.

In addition, it will be appreciated by those skilled in the art that, although there may be many problems with the prior art, each embodiment or aspect of the present invention may be improved only in one or several respects, without necessarily simultaneously solving all the technical problems listed in the prior art or in the background. It will be understood by those skilled in the art that nothing in a claim should be taken as a limitation on that claim.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.