WO2014123432A1

WO2014123432A1 - Small-scale thermoplastic recycling apparatus and method for producing fiber strands for insulation

Info

Publication number: WO2014123432A1
Application number: PCT/PH2014/000002
Authority: WO
Inventors: Rene P. DAVID
Original assignee: David Rene P
Priority date: 2013-02-08
Filing date: 2014-01-22
Publication date: 2014-08-14
Also published as: IN2014DN09864A; PH12013000051A1

Abstract

The invention describes a small-scale thermoplastic recycling apparatus and method in producing fiber strands used as an alternative for -insulation. The claimed invention is a small-scale recycling thermoplastic apparatus with two components, mainly, the extruder and the spinner. The extruder accepts and melts the shredded thermoplastic to produce a continuous flow of molten plastic called extrudate. The extrudate is fed to the spinner through a nozzle. Using centrifugal force, molten plastic passes through perforated holes of the spinner producing the individual fiber strands. The said thermoplastic recycling apparatus is capable of recycling polypropylene (PP) plastic, PET plastic, HDPE plastics and LDPE plastics. The produced thermoplastic fiber strands may be used as an alternative material for insulation such as low thermal insulation, sound proofing and packaging.

Description

Title: SMALL SCALE THERMOPLASTIC RECYCLING APPARATUS AND

METHOD FOR PRODUCING FIBER STRANDS FOR INSULATION

Background of the Invention

Field of the Invention

The invention relates to recycling apparatus for thermoplastics, more particularly, the claimed invention is directed to an apparatus and method for producing recycled thermoplastic fiber strands used as an alternative material for insulation such as low thermal insulation, sound proofing and packaging.

Background of the Invention

Plastic has become the most widely used material for both domestic and commercial purposes. They are basic materials for food containers and food packaging. There was a significant increase in plastic production through the years and this has contributed to the increasing solid waste burden. The characteristics of plastics make them an especially troublesome part of rash because they do not decay quickly. One study showed that polyvinyl chlorides (PVC) do break down in landfills but will be only half gone after 85years in the soil.

One way to reduce the amount of plastic waste in the environment is by recycling. In the Philippines, discarded thermoplastics are recycled into products with less demanding performance requirements than the original material. They are commonly recycled into household utensils and some are formed for construction support materials. Since they are recycled and used in less demanding performance requirement, they easily end up to the solid waste stream or recycled again. Repetitive recycling reduces the strength and capability of the plastic and finally they end up at landfills.

Growing environmental awareness and reduction in available dump site have prompted the development of a small-scale apparatus for mechanical recycling of discarded thermoplastic into fiber as an alternative material for insulation.

At present, small scale recycling apparatus that convert discarded thermoplastic into fiber for insulation has not been introduced in the Philippines. In advanced countries, discarded polyethylene terehthalate (PET) thermoplastic are commonly recycled into fiber from various applications on a large scale due to the establishment of material recovery facility, recycling centers and market for plastic fiber. The possibility of acquiring a recycling apparatus for discarded thermoplastic may be remote for the Philippines as such apparatus are deemed costly. In addition, the establishment of material collecting facilities/ centers needed for input capacity is wanting.

US5834033, issued November 10, 1998 speeds of an apparatus for melt spinning feedstock material having a flow restring ring. Said apparatus has a spinner head for the production of high fat content floss. The chamber is spun and the feedstock material is heated and expelled through the spaces between the heating elements. The apparatus provides an improved apparatus for processing feedstock materials in a spinner head that produce materials with repeatable consistency. The apparatus provides spinner head which restricts the flow of processed material exiting there from. The said apparatus advantageously provides melt spun material having high fat to sugar content which employs the flash flow process to form material having primarily floss morphology.

US4323524, issued April 6, 1982 refers to a process where fibers are produced by centrifugally spinning virgin thermosetting formaldehyde resin plus a catalyst and contacting the spun fibers with a stream of hot dry air to dry the fibers. Cold, humid air is supplied to the interior of the cup to prevent premature airing of the resin and evaporation of the solvent. Fibers are spun from part of the perimeter of per formations in the wall of the spinning cup with the outwardly directed stream of cold, humid air that entrains the fibers flowing through the remainder of the perforation. The product is used for paper making.

Summary of the Invention

It is therefore an object of this invention to provide a small scale apparatus that will recycle thermoplastic into fiber strands as an alternative material for insulation such as cooling systems, low thermal, packaging insulations and soundproofing. The recycling of discarded thermoplastic into fiber strands will reduce the amount of plastics in the solid waste stream. Further, the claimed invention can help prolong the useful life of thermoplastic therefore decreasing the need for virgin plastic materials.

Most of the inventions based on prior art (US6756412B2) note relates to a mechanical machine used for recycling waste materials other than plastics. The claimed invention has discarded the formation of plastic into pellets. The shredded plastic is now used direction to form the fiber strands. The problem of plastic as waste material may now be reduced. The claimed invention is generally embodied in a method of making continuous long strands of fibers from thermoplastics and an apparatus for converting discarded shredded thermoplastic feedstock into fiber plastic strands. The apparatus includes a plastic extruder assembly and a spinner assembly. The plastic extruder produces the continuous flow of molten plastic which is received by the spinner assembly where molten plastic is forced through small holes resulting in individual fiber strands.

The plastic extruder assembly essentially includes a tubular barrel electrically heated, a rotating feed screw within the barrel, a driver mechanism to turn the screw, a hopper at one end from which the material to be extruded is fed through and a nozzle at the opposite end for consolidating extruded mass.

The claimed invention has an advantage over US 5834033 and US 4323524 as it converts clean discarded thermoplastic into fibers and may be used as an alternative material for insulation. Further, the spinner is combined with extruder to liquefy the feedstock.

The features and advantages of the claimed invention will be more readily apparent from the following detailed description in conjunction with the accompanying drawings. Brief Description of the Different Views of the Drawings

Figure 1 is the sectional view of the entire small-scale thermoplastic recycling apparatus used in producing fiber strands for insulation which has the plastic extruder section and the fiber spinning section.

Figure 2 is the sectional view of the plastic extruder section.

Figure 3 is the sectional view of the fiber spinning section.

Figure 4 is a detail showing of the components of the spinner head assembly.

Figure 5 is the perspective view of the spinner section frame.

Figure 6 is the perspective view of the spinner drive assembly.

Detailed Description of the Invention

Reference would be made in detail to the description of the claimed invention as illustrated in the drawings, wherein like reference numbers indicate like parts throughout the different views. Referring now to Figure 1 , the small scale recycling apparatus has two components - the plastic extruder section and the fiber spinner section. The plastic extruder section is the machine for producing continuous flow of molten plastic called extrudate. At the end of the extruder is the fiber spinner section where molten plastic is forced through small holes resulting in individual fiber strands.

Figure 2, the plastic extruder section essential components are a hopper 1 , a feed screw 2, a tubular barrel 3, an electrical barrel band heaters 4, a nozzle 5 with an electrical nozzle band heaters 6, and these electrical nozzle band heaters 6 temperatures are set through the extruder control panel 7. The hopper 1 is a funnel shape component where the shredded plastics are fed. The feed screw 2 is a raised helix that traps materials and moves it forward through an enclosed tubular barrel 3 and heated to molten state by a combination of heating from electrical barrel band heaters 4 and shear heating from the feed screw 2.

The tubular barrel 3 is a thick-walled steel chamber that is expected to withstand high pressures. It is tightly fitted with the feedscrew 2 and is made of special steel alloy to resist surface wear.

For the clearance between the tubular barrel 3 and the feedscrew 2, a class RC 9 was fitted. The computed tubular barrel 3 bore diameter is 50.15mm for the 50mm diameter feedscrew.

The tubular barrel 3 is heated to facilitate melting of the plastic. Electrical resistance heating is the most common method employed. Its advantages are that several temperature zones can be set up with multiple temperature profiles. A jacketed chamber uses cooling water to prevent the overheating of the feed screw 2 and the tubular barrel 3 at the feed zone.

Electrical barrel band heaters 4 are the electrical resistance heating elements which are designed to supply heat by conduction to the outer cylindrical surface of the tubular barrel 3. These electrical barrel band heaters 4 were wrapped around and secured to the tubular barrel 3 being heated by a heavy duty clamping band.

Electrical band heaters are commonly used in the plastic molding industry to heat barrels and nozzles carrying molten plastic for injection molding or extrusion.

The feedscrew 2 is composed of three sections or zones, each designed for a specific purpose. The feed section contains deep channels between the flights to begin the process of melting and mixing, and to make sure the material constantly moves forward into the next section. The transition section gradually decreases the flight depth to further compact, melt, and mix the material. Finally, the metering section further reduces the flight depth to create compression and finalize the melting process. The melted plastic is then pumped through the nozzle 5.

The feed screw 2 transports, melts and mixes the granules at the same time. At the end, the melted mass will be pushed into the nozzle 5 while the electrical nozzle band heaters 6 maintain the melt temperature.

During the extrusion process, low shear and controlled melt temperature are important factors in preventing degradation of plastic mixes. Preserving melt quality by preventing excessive heating is essential. Poor melt qualit can lead to insufficient materials properties and poor surface quality of the final product.

Plastic degradation also occurs when maximum shear rates are exceeded within the screw and barrel. Shear rate is defined as "the surface velocity at the barrel wall divided by flight depth." Many Post Consumer Plastic (PCP) materials are heat sensitive and have lower permissible shear rates than do virgin materials. Since flight depth is inversely proportional to shear rate, PCP materials may require deeper screw channels also have the added benefit of allowing a larger volume of material to be processed and a greater output.

The design of the feed screw 2 considered two feed screw lengths which is an approach to obtain low temperature. One length uses extruders in the 30: 1 length/ diameter (L/D) range. Average L/D for extruders is 25: 1. The longer-than- average extruders blend plastic materials better than shorter extruders, and have the flexibility to process more types of material. The other approach emphasizes the use of shorter extruders, e.g., 20: 1 L/D, in order to decrease the residence time (and potential degradation) of the material. Since the raw material is in the form of shredded plastic, (shredded plastics occupy space at lesser volume) the short feedscrew was used. Compared with a pelletized plastic raw material, the compression is less. This result in higher compression from the feed section to the metering section of the screw.

The feed section of the screw is the first part of the screw where the shredded plastic is introduced. This is also the deepest portion of the screw.

As a rule, the feed section of a screw should not be deeper than Fdmax = 0.2 of the screw diameter. This applies for screws that are 4.5 inch in diameter or smaller. In this project, the feed section depth is computed as Fd = 0.24 of 50mm screw diameter which is equal to 12mm. consideration for this measurement is that the raw material is shredded plastic and not the pelletized plastic, where the shredded plastic side dimensions range from 10mm to 16mm.

The melting of the plastics takes place mostly in the transition or compression section of the feedscrew 2. This is the portion of the screw that transcends from the feed depth to the metering depth and where work is done on the plastic causing melting to occur. In this section of the screw, the root of the screw gradually becomes shallower forcing the material towards the tubular barrel 3 wall where the melting takes place.

The metering or pumping section of the screw is where the melting of the plastic is completed and pumping to overcome the head pressure. The compression ratio is measured as the channel depth at the end of this zone divided by the channel depth in the feed zone. Different compounds or operating pressures require different compression ratios. A natural compression ratio is 12:1. Slightly higher compression than this helps to assure proper pressure generation and melting rates. Additionally some extruders use high compression ratios because the scrap is low density and does not feed well. The length of the compression zone affects the rate of compression.

In figure 3, the fiber spinner section are composed of the following components - a spinner head assembly 8, a spinner drive 9, a spinner frame 10 and a spinner control panel 11.

In figure 4, is an exploded view of the spinner head assembly 8 which show the following components: a spinner head base 12, a spindle 13, a spinner bowl 14, a spinner electric heater coil 15, a clamp plate 16, a lock nut 17, a slip ring 18 and a spindle pulley 19.

In figure 5, the spinner frame 10 assembly which show the following components: a structural frame 20, a metal cylindrical bowl 21 and a spinner control panel 11.

In figure 6, the spinner drive 9 with the following components: a spinner motor 22, a spinner motor base 23 and a drive pulley 24.

The molten plastic from the nozzle 5 will fall into a rotating spinner bowl 14 with perforations about its periphery, centrifugally forcing the molten plastic through the small holes to form the fibers. Spinner electric heater coil 15 near the rim of the spinner bowl 14 maintains the molten temperature of the plastic melt. As the molten plastic spins out through small holes, it solidifies in the air and the formed fiber is caught in a large open metal cylindrical bowl 21. The fibers are collected at the bottom of the metal cylindrical bowl 21.

A pair of slip rings 18 alternatively contacts respective studs extending to electrical terminals of the spinner electric heater coil 15 to commutate the necessary electric power from the spinner control panel 11.

The spindle 13 holds the entire spinner head assembly 8. The spinner head base 12 fastens the spindle 13 to the spinner frame 10. The spinner motor base 23 holds the spinner motor 22 to the structural frame 20.

The drive pulley 24 which is coupled to the spinner motor 22 drives the spindle pulley 19 via v-belt.

The clamp plate 16 supports the spinner electric heater coil 15 under the spinner bowl 14.

The lock nut 17 is fasten to the spindle 13 to hold the spinner bowl 14, spinner electric heater coil 15 and clamp plate 16 together.

The structural frame 20 holds the metal cylindrical bowl 21 in place.

The machine used to make cotton candy consists of a small bowl into which sugar is poured and food coloring is added. Heaters near the rim melt the sugar and it is spun out through tiny holes where it solidifies in the air and is caught in a large metal bowl.

A method for recycling discarded thermoplastic into fibers to be used as insulators comprising the following steps:

Plastics were first sorted prior to recycling. Plastics are made from different types of resins with different melting temperature and characteristics. Plastics were sorted into polymer type and/ or color. Once sorted, the plastics were thoroughly cleaned and dried to prevent contamination of non - plastic material. The plastic materials were then shredded and grinded into plastic flakes. The plastics, in all shapes and sizes, were broken into uniform pieces for some degree of consistency.

Four types of plastic were identifies and classified into classes. Polypropylene (PP) plastics used as caps for soda and other beverage bottles are categorized as type A. Plastics used for soda and beverages known as PET plastics are categorized as type B. Plastics used for shampoo and detergent bottles known as HDPE plastics were categorized as type C. Clear plastics used as disposable drinking cups known as LDPE plastics are categorized as type D. The clean shredded discarded thermoplastic, in particular, LDPE plastics are fed in the hopper 1; by gravity the clean shredded discarded thermoplastic falls into the rotating feed screw 2; the feed screw 2 traps clean shredded discarded thermoplastic and moves it forward through an enclosed tubular barrel 3 and heated to molten state by a combination of heating from electrical barrel band heaters 4 and shear heating from the feed screw 2. The molten plastic passes through the nozzle 5 wherein the temperature of the molten plastic is maintained by the electric nozzle band heater 6 to allow the continuous flow of molten plastic; the molten plastic drops at the rotating spinner bowl 14, a spinner electric heater coil 15 at the bottom of spinner bowl 14 maintain the temperature of the plastics in the spinner bowl 14; by a combination of hydrostatic pressure and centrifugal force, the molten plastic spun out of the plurality of the spinner bowl 14 perforations, the plastic stretches outside the spinner bowl 14, fiber strands are form once in contact with air and it partly solidifies; as this fiber strands hit the metal cylindrical bowl 21 wall, the fiber strands binds when they come in contact with each other.

An example of the product of the machine, plastic fiber from LDPE found in a clear disposable plastic cup showed the following characteristics and average flow rate of 4.31 g/min with an average energy consumption of 0.9 kW/hr and compression ratio of 2.4. The said method produced an average of 65 grams of collected fibers. The table below presents the results

Claims

1. An apparatus for converting discarded shredded thermoplastic feedstock into fiber plastic comprising an extruder assembly for melting shredded thermoplastic including a hopper, a feed screw, a tubular barrel, an electrical barrel band heaters, a nozzle with electric band heater, and extruder control panel; a spinner assembly comprises of:

a. a spinner drive which houses the spinner motor,

b. a rotatable spindle attached to the spinner drive,

c. a nozzle attached to both the plastic extruder assembly and the spinner assembly,

d. a spinner bowl with perforation on its peripheral wall for fiber receptacles, e. an spinner electric heater coil placed below the spinner to maintain temperature of the recycled plastic in the spinner bowl,

f. a clamp plate that holds the spinner electric heater coil under the spinner bowl,

g. a lock nut that fasten the spinner bowl to the spindle, a spinner electric heater coil and a clamp plate,

h. A slip ring which commutates electricity to the spinner electric heater coil via two elongated electric wires, and

i. A carbon brush that transmit the electrical power from the spinner control panel to the slip ring.

2. A method for recycling discarded thermoplastic into fiber to be used as insulators comprising the following steps:

a. the clean shredded discarded thermoplastic are fed in the hopper;

b. the extruder melts the plastic and discharge the molten plastic at its nozzle wherein the temperature of the molten plastic is maintained by the electric band heater to allow the continuous flow of molten plastic;

c. the molten plastic drops at the rotating spinner bowl, an electric heating element at the bottom of spinner bowl maintain the temperature of the plastics in the spinner bowl;

d. by a combination of hydrostatic pressure and centrifugal force, the molten plastic spun out of the plurality of the spinner bowl perforations, the plastic stretches outside the spinner bowl, strands are form once in contact with air and it partly solidifies; e. as this fiber hits the spinner assembly cylindrical wall, the fiber strands binds when they come in contact with each other.

A recycled thermoplastic fiber used as an alternative materials for insulation produced by the apparatus of claim 1 , wherein it could be:

a. a low thermal insulation;

b. a sound proofing insulation; and

c. a packaging insulation.