CN104045898A - Ultra-high molecular weight polyethylene (UHMWPE) material and preparation method thereof - Google Patents

Abstract

The invention aims to provide an ultra-high molecular weight polyethylene (UHMWPE) material with antistatic properties and certain processing fluidity and a preparation method thereof. By studying the effects of different types of carbon black and expanded graphite on the properties of UHMWPE/PP, through different types of compounding and dosage optimization, the impact of conductive filler types, compounding methods, and dosage on the volume resistivity and processing rheological properties of UHMWPE/PP was discussed. , The mechanical properties of composite materials, the impact of wear resistance (friction coefficient, wear scar width, etc.), and optimize the plan, carry out antistatic modification on UHMWPE, so that the antistatic performance of the product can be significantly improved. The antistatic modified UHMWPE can avoid static electricity generated by friction and extrusion during molding, transportation and use of pipe fittings, reduce the difficulty of material molding operations, and improve the appearance and quality of products. It can also avoid the phenomenon of static electricity arson caused by the accumulation of static electricity, which greatly increases the safety of production.

Description

A kind of ultra-high molecular weight polyethylene material and preparation method thereof

technical field

The invention relates to the technical field of polymer materials, in particular to an ultra-high molecular weight polyethylene (UHMWPE) material with antistatic properties and certain processing fluidity and a preparation method thereof.

Background technique

Ultra-high molecular weight polyethylene (UHMWPE) refers to linear high-density polyethylene with a viscosity average molecular weight of more than 1.5 million. UHMWPE has the same molecular structure as ordinary PE, and the main chain members are all (CH ₂ -CH ₂ ), but the extremely high molecular weight endows UHMWPE with many excellent properties that ordinary PE cannot match.

The extremely high molecular weight makes UHMWPE have excellent comprehensive properties in solid state, and also endows it with very unique melt characteristics, which brings great difficulties to molding processing. On the one hand, UHMWPE is a gel elastomer when it melts, with high viscosity, almost 0 melt flow index (MI), and extremely poor fluidity; on the other hand, the critical shear rate of UHMWPE melt is extremely low, and it is easy to melt. body rupture. Therefore, it is difficult to process UHMWPE products with conventional thermoplastic processing methods such as screw extrusion and injection molding.

At present, in view of the processing difficulties of UHMWPE, most of its flow processing modification is to use blending with other polyolefins or adding traditional lubricants or both methods. The polyolefins used to blend with UHMWPE to improve the processability of UHMWPE are mainly traditional PE and PP, and the lubricants include paraffin wax, polyethylene wax and calcium stearate. According to literature reports, the melt viscosity of LLDPE/UHMWPE, HDPE/UHMWPE and LDPE/UHMEPE blends is significantly lower than that of pure UHMWPE, but PE participates in the formation of UHMWPE chain entanglement network, which cannot effectively reduce UHMWPE chain entanglement Density, therefore, the processing modification effect of PE on UHMWPE is poor. Studies have shown that blending with polyolefin and lubricating modification can significantly improve the fluidity of UHMWPE and improve the processing performance of UHMWPE to a greater extent.

However, at present, many studies at home and abroad have shown that after the fluidity of UHMWPE is fully improved, the extrusion and injection processing can be realized by using conventional extrusion and injection molding equipment. It is obtained by blending common fluid polyolefins or lubricants, which will cause a sharp decline in the mechanical properties and friction and wear properties of the blend, and affect its performance. Therefore, improving the processing rheology of UHMWPE while optimizing or maintaining the excellent mechanical properties and friction and wear properties of UHMWPE has become an enduring hot topic in UHMWPE research for many years.

Due to the excellent comprehensive performance of UHMWPE, pipes made of this material are especially suitable for conveying various corrosive, abrasive, adhesive, and fouling media. Therefore, UHMWPE replaces metal pipes as wear-resistant conveying materials. Pipes have unique advantages. However, the volume resistivity of UHMWPE is relatively high, and ρ _v is about 10 ¹⁷ -10 ¹⁸ Ω·cm. During the molding, transportation and use of UHMWPE pipe fittings, it is easy to generate and accumulate static electricity when subjected to friction and extrusion, and sometimes the voltage can be up to tens of thousands of volts. The generation and accumulation of this kind of static electricity may bring difficulties to molding operations and affect product quality. It may also affect the appearance of plastic products and the application in ultra-clean environments due to severe dust collection and difficulty in purification. What's more serious is that when the static electricity accumulates to a certain value, electrostatic discharge will occur and sparks will be generated. At the same time, with the increasingly urgent demand for wear-resistant plastic pipes in water conservancy, thermal power, transportation, mining and other industries, the previous materials are difficult to meet the needs of social development, which promotes the formulation optimization and processing technology of UHMWPE materials. With the continuous development and progress, new UHMWPE materials will continue to emerge.

In order to better realize the continuous, high-efficiency and large-scale molding of UHMWPE products, the present invention, on the one hand, processes rheological modification of UHMWPE by adding compound processing aids, aiming at maintaining the excellent mechanical properties and friction and wear properties of UHMWPE as much as possible. , so that the processing rheology of the UHMWPE/PP blend system is further greatly improved; at the same time, in order to improve the antistatic effect of UHMWFE, different conductive fillers are used to conduct antistatic modification research on UHMWPE, and we are committed to producing a kind of antistatic. An ultra-high molecular weight polyethylene (UHMWPE) material with certain processing fluidity and a preparation method thereof.

Contents of the invention

In view of the shortcomings of the above-mentioned prior art, the inventor has accumulated many years of experience in this field, and after repeated research and demonstration, finally came into being the present invention. In order to better realize the continuous, high-efficiency and large-scale molding of UHMWPE products, the present invention, On the one hand, UHMWPE is modified by adding polypropylene (PP) resin and compound processing aids, aiming at maintaining the excellent mechanical properties and friction and wear properties of UHMWPE as much as possible, so that the processing of UHMWPE/PP blend system The rheology has been greatly improved; at the same time, in order to improve the antistatic effect of UHMWFE, different conductive fillers are used to conduct antistatic modification research on UHMWPE, and we are committed to producing an ultra-high molecular weight polyethylene with antistatic properties and certain processing fluidity. (UHMWPE) material and its preparation method.

The technical scheme adopted in the present invention: a kind of ultra-high molecular weight polyethylene (UHMWPE) material formula (according to weight percentage) disclosed by the present invention has antistatic property and certain processing fluidity is: (1) UHMWPE resin: 55-84% , (2) PP resin: 5-15% (3) self-made composite processing aid: 2-5%; (4) conductive carbon black: 5-15%; (5) expanded graphite: 3-8%; (6 ) Antioxidant: 0.2-0.6%; (7) Other additives: 0.8-1.4%. The components are mixed in a high-speed mixer for 1 to 2 minutes, and then put into a twin-screw extruder to extrude and granulate.

An ultra-high molecular weight polyethylene (UHMWPE) material with antistatic properties and certain processing fluidity described therein is characterized in that the UHMWPE resin is a polyethylene resin with a molecular weight of more than 1.5 million, and is baked at 90°C for 4 hours , control moisture below 0.1%;

PP resin is polypropylene resin, MI is 10g/10min, and it is baked at 90°C for 4 hours, and the moisture content is controlled below 0.1%. The self-made compound processing aid is grafted by maleic anhydride to PP/diatomaceous earth/glass beads According to the weight ratio of 15/50/35, it is mixed at 100°C in a high mixer, preferably, the maleic anhydride graft rate is greater than 1%; conductive carbon black is carbon black with low resistance properties, which can give materials conductivity or Antistatic effect; expanded graphite is a new type of carbon material with extremely strong electrical conductivity; the antioxidant is a phenolic antioxidant tetrakis[β-(3',5'-di-tert-butyl-4'-hydroxyphenyl ) propionic acid] pentaerythritol ester and phosphite antioxidant (2,4-di-tert-butylphenyl) phosphite triester; other additives are toner and brightener.

The method for preparing the above-mentioned ultra-high molecular weight polyethylene material with antistatic properties and certain processing fluidity of the present invention comprises the following steps:

(1) Handling and mixing of raw materials

UHMWPE resin is baked at 90°C for 4 hours to control the moisture below 0.1%; PP resin is baked at 90°C for 4 hours to control the moisture below 0.1%;

Mix the main ingredients with self-made composite processing aids, conductive carbon black, expanded graphite, antioxidants, and other additives in a high-speed mixer for 2 minutes to fully stir and disperse each component;

(2) Melt extrusion

Put the mixed material into the twin-screw extruder, the melt extrusion temperature is between 180-240°C, and the screw speed is 400 rpm;

(3) Granulation and post-processing

The extruded material is cooled, air-dried, pelletized, subjected to strong magnetism, and packaged to obtain the finished product.

An ultra-high molecular weight polyethylene (UHMWPE) material with antistatic properties and certain processing fluidity of the present invention can prevent the pipe fittings produced from this material from being molded while maintaining the processing rheology of the UHMWPE/PP blend system. 1. Static electricity is generated due to friction and extrusion during transportation and use, which reduces the difficulty of material forming operations and improves the appearance and quality of products; it can also avoid the phenomenon of static fire caused by static electricity accumulation, which greatly increases the production cost. safety.

Detailed ways

The present invention will be described in detail below in conjunction with the examples.

Example 1

First bake 55% by weight of UHMWPE resin at 90°C for 4 hours to control the moisture content below 0.1%, and bake 15% by weight of PP resin at 90°C for 4 hours to control the moisture content below 0.1%. agent, 15% by weight of conductive carbon black, 8% by weight of expanded graphite, 0.3% by weight of the main antioxidant tetrakis (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) pentaerythritol ester (1010) and 0.3% auxiliary antioxidant three (2,4-di-tert-butylphenyl) phosphite (168), other additives of 1.4% by weight are mixed from metering feeding after 2 minutes by high-speed mixer The device enters the twin-screw extruder to be plasticized and melted, and then the product is obtained through extrusion, cooling, magnetization and packaging.

Example 2

First bake 84% by weight of UHMWPE resin at 90°C for 4 hours to control the moisture content below 0.1%, and bake 5% by weight of PP resin at 90°C for 4 hours to control the moisture content below 0.1%. agent, 5% by weight of conductive carbon black, 3% by weight of expanded graphite, 0.1% by weight of the main antioxidant tetrakis (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) pentaerythritol ester (1010) and 0.1% auxiliary antioxidant three (2,4-di-tert-butylphenyl) phosphite (168), other additives of 0.8% by weight are mixed from metering feeding after 2 minutes by high-speed mixer The device enters the twin-screw extruder to be plasticized and melted, and then the product is obtained through extrusion, cooling, magnetization and packaging.

Example 3

First bake 70% by weight of UHMWPE resin at 90°C for 4 hours to control the moisture content below 0.1%, and bake 10% by weight of PP resin at 90°C for 4 hours to control the moisture content below 0.1%. agent, 10% by weight of conductive carbon black, 5.3% by weight of expanded graphite, 0.3% by weight of the main antioxidant tetrakis (β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) pentaerythritol ester (1010) and 0.4% auxiliary antioxidant three (2,4-di-tert-butylphenyl) phosphite (168), other additives of 1% by weight are mixed from metering feeding after 2 minutes by high-speed mixer The device enters the twin-screw extruder to be plasticized and melted, and then the product is obtained through extrusion, cooling, magnetization and packaging.

Example 4

The preparation method of the ultra-high molecular weight polyethylene in embodiment 1-3 is as follows:

(1) Handling and mixing of raw materials

Bake the UHMWPE resin at 90°C for 4 hours to control the moisture below 0.1%; bake the PP resin at 90°C for 4 hours to control the moisture below 0.1%;

Mix the main ingredients with self-made composite processing aids, conductive carbon black, expanded graphite, antioxidants, and other additives in a high-speed mixer for 2 minutes to fully stir and disperse each component;

(2) Melt extrusion

Put the mixed material into the twin-screw extruder, the melt extrusion temperature is between 180-240°C, and the screw speed is 400 rpm;

(3) Granulation and post-processing

The extruded material is cooled, air-dried, pelletized, subjected to strong magnetism, and packaged to obtain the finished product.

Example 5

The performance of a kind of ultra-high molecular weight polyethylene (UHMWPE) material with antistatic properties and certain processing fluidity to embodiment 1 and embodiment 2 gained is as follows:

Test items standard test Test Conditions Example 1 Example 2 Specific gravity (g/cm3) D792 23°C 0.98 0.97 Tensile strength (Mpa) D638 10mm/min 41 40 Elongation at break (%) D638 10mm/min 85 84 Bending strength (Mpa) D790 2mm/min 60 58 Flexural modulus (Mpa) D790 2mm/min 2000 1980 Notched impact strength (J/m) D256 3.2mm, 23℃ 700 680

Vicat softening temperature (℃) D1525 1.8Mpa,6.4mm 83 82 Relative wear rate (%) D3884 23°C 0.92 0.93 Surface resistivity (Ω·cm) D257 23°C 10 ² 10 ²

To sum up, it is a preferred embodiment of the present invention, and any changes made according to the technical solution of the present invention, if the resulting functional effects do not exceed the scope of the technical solution of the present invention, all belong to the protection scope of the present invention.

Claims (9)

1. a superhigh molecular weight polyethylene material with static resistance and certain processing fluidity, is characterized in that composed of the following components by weight percentage:

。

2. a kind of superhigh molecular weight polyethylene material with static resistance and certain processing fluidity as claimed in claim 1, is characterized in that UHMWPE resin is that molecular weight is more than 1,500,000 polyvinyl resin, and its moisture content is below 0.1%.

3. a kind of superhigh molecular weight polyethylene material with static resistance and certain processing fluidity as claimed in claim 1, is characterized in that PP resin is acrylic resin, and MI is 10g/10min, and its moisture content is below 0.1%.

4. a kind of superhigh molecular weight polyethylene material with static resistance and certain processing fluidity as claimed in claim 1, is characterized in that making by oneself composite auxiliary for processing and is by maleic anhydride graft PP/ diatomite/glass microballon and mix at 100 ℃ of high mixers by 15/50/35 part by weight.

5. a kind of superhigh molecular weight polyethylene material with static resistance and certain processing fluidity as claimed in claim 1, is characterized in that graphitized carbon black is the carbon black with low resistance performance, can give material conduction or anti-static electrification.

6. a kind of superhigh molecular weight polyethylene material with static resistance and certain processing fluidity as claimed in claim 1, is characterized in that expanded graphite is Novel carbon material, has extremely strong specific conductivity.

7. a kind of superhigh molecular weight polyethylene material with static resistance and certain processing fluidity as claimed in claim 1, it is characterized in that oxidation inhibitor is phenolic antioxidant four [β-(3', 5'-di-t-butyl-4'-hydroxy phenyl) propionic acid] pentaerythritol ester and phosphite ester kind antioxidant (2,4-di-tert-butyl-phenyl) tris phosphite.

8. a kind of superhigh molecular weight polyethylene material with static resistance and certain processing fluidity as claimed in claim 1, is characterized in that other auxiliary agents are toner and brightener.

9. a kind of preparation method with the superhigh molecular weight polyethylene material of static resistance and certain processing fluidity as claimed in claim 1, is characterized in that comprising the following steps:

(1) raw-material processing and mixing

UHMWPE resin dries at 90 ℃ controls moisture for 4 hours below 0.1%; PP resin dries 4 hours at 90 ℃, controls moisture below 0.1%;

Major ingredient and self-control composite auxiliary for processing, graphitized carbon black, expanded graphite, oxidation inhibitor, other auxiliary agents are mixed 2 minutes in high speed mixer, make the abundant dispersed with stirring of each component even;

(2) melt extrude

The material mixing is added in twin screw extruder, melt extrude temperature between 180-240 ℃, screw speed is 400 revs/min;

(3) granulation and aftertreatment

The material of extruding is carried out cooling, air-dry, pelletizing, crosses strong magnetic, is packaged to be finished product.