EE201600010A - A polymer composite material contains oil shale ash and method for manufacture its - Google Patents

Abstract

The present invention relates to a polymer composite material containing 70 to 90% by weight of oil shale ash and 10 to 30% by weight of a polymer containing oil shale fly ash. The proposed composite is intended to be added to the polymeric material to alter its properties, to reinforce the product and / or to reduce the price of the finished product as a filler.

Description

TECHNOLOGY FIELD

The present invention belongs to the field of materials industry and relates to a composite of a polymeric material with a mineral filler and a method for its preparation.

STATE OF THE ART

The use of fly ash obtained from the combustion of coal is known from the prior art. However, this ash differs significantly from oil shale fly ash in terms of its composition, particle shape and color, which ranges from gray to black. Therefore, coal fly ash is not suitable for the production of light-colored finished products.

CN1110773 (A) discloses a plasticized fly ash pipe containing fly ash with a granule size greater than 200-300 mesh mixed together with used polyethylene or polyvinyl chloride at 160-180°C.

Coal fly ash is a solid, powdery material that is released during the combustion of coal and is captured by various filters. Coal fly ash particles range in size from 0.5 to 100 μm. The disadvantage of coal fly ash is that it contains toxic substances such as arsenic, barium, beryllium, boron, cadmium, selenium, strontium, etc. Another disadvantage of coal fly ash is its dark color, which does not allow the production of light-colored products from a composite containing this content.

The author of this patent application's earlier document EE05625B1 relates to a PVC composite material containing oil shale ash and products made from this material. The document demonstrates that the use of oil shale ash in a polymer composite is beneficial. The said document protects a PVC composite material containing oil shale ash, where 0.5 to 60% of the composition of the composite material is oil shale ash.

EE05628B1 relates to a composite of polymeric materials with mineral fillers, which can be used to manufacture films, pipes and other products. The composite contains a homogeneous mixture of mineral additives and thermoplastic polymers, where industrial waste is mainly used as a mineral filler, including oil shale fly ash. The composite contains thermoplastic polymeric materials in the range of 30 to 98% by weight and oil shale fly ash or cement clinker dust or limestone mud or a mixture thereof in the range of 2 to 70% by weight.

Previous documents EE05625B1 and EE05628B1 describe the mixing of mineral filler with polymeric material before dosing into the extruder. In the material mixed in this way, the concentration of mineral filler remains below 70%, since it is not possible to achieve a higher concentration in the extruder with a single mixing. At such a high concentration, with a single mixing, the mineral material (fly ash) forms separate units that prevent mixing and the material from moving forward in the extruder. The extruder jams or large counter forces can lead to the extruder breaking.

In addition, the process does not involve degassing, multiple dosing, and a short screw is used.

ESSENCE OF THE INVENTION

The present invention aims to expand the possibilities and convenience of using oil shale fly ash. The aim is to provide a composite containing 70 to 90% by weight of oil shale fly ash. The proposed composite is intended to be added to a polymer material to change its properties, to create reinforcement in the product and/or as a filler to reduce the cost of the finished product.

Ash cannot be used in industry in its pure form due to various requirements. Also, to obtain a composite with sufficient homogeneity, special mixing extruders are required, which are usually not available in the processing industry.

Filter ash, fractions with particle sizes from 1 to 100 microns, are used as oil shale fly ash. Oil shale fly ash is added to 10 to 30% by weight of polymer (PO) (polyethylene (PE), polypropylene (PP), etc.) granules. The materials are dosed into an extruder, where the mixing and melting process begins. Gases are separated for better mixing. After that, additional dosing takes place via side loaders. The mixing process with heating is repeated.

During heating, the matrix material, or PO, melts. Degassing occurs again and the process is repeated for the third time. The extruder screw is designed in such a way that, while the material is otherwise under pressure in the cylinder due to the shape of the screw, the pressure is significantly reduced in the degassing zone. This is necessary so that material does not escape from the degassing openings, but only gases are released. Such multiple dosing requires a long screw so that all processes can take place.

During the mixing process, repeated degassing occurs. Degassing is either natural or vacuum degassing. Degassing can increase concentration and also increase productivity. If gas molecules, which are present in the granules as bubbles, are separated, then ash particles take the place of these gas bubbles, which increases the ash concentration in the product.

The difference between atmospheric (natural) and vacuum degassing is that in the atmospheric (natural) degassing process, gases are allowed to escape, while in the vacuum degassing process, gases are sucked out using a vacuum.

Next, granulation takes place - the material mass exits through the mouth, which is then either immediately cut into 2-3 mm long granules into water, where cooling occurs, or cooled first and then cut into granules.

LIST OF ILLUSTRATIONS

The above and other features and advantages of the invention are described in more detail below with reference to the accompanying drawings illustrating preferred embodiments, in which Figure 1 shows a three-stage mixing scheme of polymers and oil shale fly ash according to the invention.

EXAMPLE

Figure 1 schematically shows the mixing of oil shale fly ash and polymers, where polymer(s) and oil shale fly ash (zone 1) are dosed into a previously prepared extruder (temperature range 120 to 400 degrees Celsius, preferably 230 degrees Celsius). Thanks to two mixing screws rotating in the same direction (diameter 40 mm, L/D 48), the polymer melts and mixes with the fly ash (zones 2 and 3).

In zone 4, additional dosing of fly ash takes place via a side feeder.

In the mixing process, it is important that the entire mixture mass is mixed as evenly as possible, so that the contact surface between the ash and polymer particles in the composite mass is as large as possible. Degassing removes excess gas molecules from the mass, which would otherwise remain in the resulting composite mass. The released gas molecules provide space for additional ash particles, which can increase the ash concentration in the composite.

Degassing occurs either naturally through the free release of gases or under vacuum.

In zone 5, the fly ash is dispersed with the previously mixed mass. Since air also enters the mixing cylinder with the side loader, its free release occurs in zone 6 through an opening in the cylinder.

In zone 7, fly ash is dosed again through another side loader, mixing occurs (zones 8 and 9), and air and other gases that have entered the working cylinder through the side loader are allowed to escape during degassing (zone 10).

To remove as much gas as possible, vacuum degassing (zone 11) is used, which draws even more gas from the melt through rarefaction, allowing the resulting composite material to be better homogenized (zone 12).

To increase productivity, there is an additional melt pump before the oral screen, which helps the melt to pass through the screen openings better, thereby increasing productivity (zone 13).

After exiting the mouth, the product is immediately granulated (underwater pelletizer, zone 14), after which the hot, pelletized, finished composite material is sent to cooling (zone 15).

Finally, the finished oil shale fly ash polymer composite material is packaged.

The finished granules are used as an additive in the polymer industry, where they are added to PO granules to provide strength, as a reinforcement agent and/or as a filler to reduce the price of the finished product.

For the entire process to be possible and also economically efficient, the length of the mixing screws and cylinder must be at least 40-60 L/D, where L/D is the ratio of the screw diameter to its length.

In the process, it is important that the operating pressure in the extruder cylinder does not rise above 200 bar, because then the extruder will automatically shut itself off to prevent possible breakage.

The pressure can be adjusted by changing the fly ash concentration and/or changing the screw speeds (the screw speed at maximum productivity is 350 rpm).

Claims (8)

1. A polymer composite material containing oil shale fly ash, characterized in that the composite contains 10 to 30% by weight of polymer and 70 to 90% by weight of oil shale fly ash. 2. A polymer composite material containing oil shale fly ash according to claim 1, characterized in that the oil shale fly ash is of a fraction with a particle size of 1 to 100 μm. 3. The polymer composite material containing oil shale fly ash according to claim 1, characterized in that the polymer is either polyethylene, polypropylene or polycarbonate. 4. A method for producing a polymer composite material containing oil shale ash according to claim 1, wherein a polymer and oil shale fly ash are dosed into a previously ready-to-use extruder with two mixing screws rotating in the same direction, the polymer is melted and mixed with the fly ash in the extruder; characterized in that an additional amount of fly ash is subsequently dosed through a side loader, the additionally dosed fly ash is mixed with the previous mixture; excess gas molecules are degassed from the mass of the mixture; an additional amount of fly ash is subsequently dosed through the next side loader, the additionally dosed fly ash is mixed with the previous mixture; excess gas molecules are degassed from the mass of the mixture; at the end of the extruder, before the mouth screen, there is an additional mixing pump, with which the molten mass is pumped through the mouth screen; upon exiting the mouth, the polymer composite material is granulated and cooled. 5. The method according to claim 4, characterized in that the operating temperature of the extruder is in the range of 120° to 400°C, preferably 230°C. 6. The method according to claim 4, characterized in that the degassing is carried out either naturally by free gas evolution or by vacuum. 7. The method according to claim 4, characterized in that the length of the mixing screws and the cylinder is at least 40-60 L/D, where L/D is the ratio of the screw diameter to the length. 8. The method according to claim 4, characterized in that the operating pressure of the extruder barrel is 200 bar or less.