KR20030070874A - Process for obtaining low molecular weight thermoplastic resin by cracking cross-linkage/foaming polyolefin resin wastes - Google Patents

Abstract

PURPOSE: Provided is a preparation method of low molecular weight resin wax from crosslinked and foamed polyolefin which are known to be not recyclable. The polyolefins are crosslinked polyethylene, crosslinked polypropylene, crosslinked polyethylene-propylene elastomer, foamed polyethylene and foamed polypropylene. The recycled low molecular resin is used as a paper coating material, paraffin substitute, raw material for candle, plastic softener, lubricator, low price water repellent, etc. CONSTITUTION: The preparation method comprises the steps of: introducing crosslinked, foamed or crosslinked/foamed polyolefin resin waste into a combustion reactor; oxidizing it at high temperature of 600-1,200deg.C by using heat of self-combustion and oxygen in the air; and obtaining the low molecular weight resin mixture of 3,000-70,000 molecular weight by cracking high molecular polyolefin resin through high temperature oxidation reaction.

Description

Process for obtaining low molecular weight thermoplastic resin by cracking cross-linkage / foaming polyolefin resin wastes

The present invention relates to a method for producing a low molecular weight thermoplastic resin through cracking of crosslinked / foamed polyolefin resin waste.

More specifically, the present invention is to crack the cross-linked polymer and foamed / cross-linked polymer which is difficult to recycle in the reactor by preventing the loss of resources according to the difficulty and reducing the environmental pollution due to the waste cross-linking resin and solve economic difficulties and technical difficulties The present invention relates to a method for producing a polymer material that is recyclable and economical by converting it into a low molecular weight thermoplastic resin.

In general, many polymers such as polyolefin resin such as polyethylene resin, polypropylene resin, or ABS, acid (SAN), general polystyrene and impact polystyrene resin Styrene-based polymers are widely used in various fields such as various containers, wire coating materials, pipes, packaging materials, etc., due to their excellent physical properties, moldability, and economic advantages. Most of these plastics have been disposed of by incineration or landfill when they are finished. However, the disposal of these plastics is a huge waste of petroleum resources, and economic and environmental losses are large. This has led to much recycling in recent decades.

For example, PET bottles, yogurt bottles (HIPS), and many agricultural films (LDPE, HDPE, EVA) are recycled and manufactured into various plastic products. In addition, many polystyrene foams, such as styrofoam, have been developed and practiced in the industry and technology for recycling them into subgrade polystyrene.

In the recycling of polymers, most of the processes have been recycled by melting and extruding plastic resin by using a separator / washer, a crusher, an extruder, and a cutter as a set, and since the waste synthetic resin is thermoplastic, it can be used as a thermoplastic polymer. However, in the case of crosslinked polymers and foamed polymers, melting does not occur or extremely partial melting occurs, and current production of melt and extrusion is impossible, and in the case of foamed polymers, melting is difficult to transfer heat due to foaming voids. It is difficult to melt and extrude, such as slow melting, unbalanced due to its unique elasticity and volume, and many foams are crosslinked or semi-crosslinked, so that little melting occurs and recycling through existing melting and extrusion methods was impossible. Recently incinerators using plastic incinerators, It was used as a real-up spent fuel.

In addition, there was a plan to partially crack the crosslinked polymer and use it as a resin, but this requires a large-scale device industry and is not used practically because of the economical efficiency of recycled materials, and is used for the manufacture of special polymer wax using an extremely expensive wax manufacturing equipment. Even in general, a method of thermally decomposing general polymers using a pressurized kiln or the like is mainly used.

However, in the case of crosslinked polymers or expanded polyolefins (crosslinked foams), it is known that recycling is impossible, and still all parts are incinerated or landfilled. The reason for this is that the crosslinked polymer has not been melted because the polymer chain has a three-dimensional network in chemical structure, and it has been recognized that recycling is impossible.

The present invention relates to waste crosslinked and expanded polyolefin resins such as crosslinked polyethylene, crosslinked polypropylene, crosslinked vinyl acetate resin and expanded polyethylene (synthetic sponge, etc.), expanded vinyl acetate resin, expanded polypropylene, crosslinked / foamed polyethylene and crosslinked foamed vinyl acetate resin. The present invention relates to a device for manufacturing a low molecular weight thermoplastic resin through recycling, and more specifically, to a crosslinked polymer, a foamed polymer, and a waste polyolefin-based polymer, which is known to be economically unreasonable in recycling costs. The present invention relates to a method for producing a thermoplastic low molecular weight resin (polymer), wherein the molecular chain of a polyolefin polymer is destroyed at high pressure in the presence of oxygen and a catalyst at atmospheric pressure, and oxidized to lower molecular weight and impart high thermoplasticity. . In the case of crosslinked polymers or the three-dimensional network structure of the foamed / crosslinked polymer, the molecular structure is destroyed, and in the case of foams, the pores inside are expanded at high temperatures, the foamed cells are destroyed, and the molten phase is destroyed to destroy the molecular chains. It is a method of breaking the structure and converting it into a low molecular weight body which can be plasticized easily by heat.

Normally, 84 Kcal / mol of energy is needed to destroy the molecular chain of organic compounds-[to break the primary bonds between carbon and carbon], which is used industrially to adjust the molecular weight of polymers or organic compounds or to produce organic materials. In the conventional manner, this purpose has been achieved by supplying this energy through high temperature cracking, high pressure cracking, high temperature / high pressure methods, or supplying necessary energy through oxidation cracking under a catalyst. Therefore, this cracking method requires a large unit in order to use an expensive catalyst or to supply energy of high temperature and high pressure, and thus, the petrochemical industry for manufacturing organic materials has largely been a large-scale device industrialization, and thus productivity and economic efficiency have been adjusted. .

Recently, in order to manufacture low molecular weight resins, waxes, lubricants, and soft materials required for the polymer industry and chemical industry, low-molecular-weight resins are produced by using a general polyethylene resin on a small scale. It is common to manufacture by cracking, which has the advantage of easy control of purity and molecular weight distribution, but the high supply cost of energy to provide the pressure and temperature necessary for cracking, and difficult to process the crosslinked polymer of the present invention There is a difference from that.

In the present invention, by specially modifying and devising an incinerator or a combustion furnace for incineration of waste paper and waste plastics used in the existing incineration treatment method, the energy required for cracking is separately supplied using heat generated during its own partial combustion. By eliminating energy sources (heat sources), the economy and efficiency are increased.They can be used in semi-permanent ways by adding them in the form of a catalyzed net or punched porous plate that triggers polymer oxidation during the process. By supplying oxygen required for partial combustion as well as oxygen required for oxidation of polyolefin-based polymers, it causes cracking by causing oxidation reaction under high temperature and catalyst, thereby making it possible to utilize waste plastic materials that cannot be recycled. Switch. As for the cracking reactor through the oxidation of the polyolefin-based polymer, the present inventor has already filed in Korean Utility Model Application No. 2003-19685.

As described above, most commonly used general-purpose polymers are thermoplastic, and they can be easily recycled into products having excellent physical properties. However, in the case of expanded styrene, a forced melting step for reducing the volume before extrusion and melting is possible, but it can be recycled by the existing method, and in the case of using the present invention, a variety of unburned or combusted compounds containing benzene rings may be used. Compounds may appear and the cost of separating and removing them is high and therefore not dealt with in the present invention.

The device designed according to the present invention has the form of a specially designed incineration / combustion furnace. The present invention relates to a recycled resin manufacturing method using a polyolefin-based plastic raw material composed of a heating / melting unit coupled to a lower end of a heating unit and a portion for distributing and injecting a constant flow rate of air into a lower portion for increasing heating efficiency and increasing production yield.

The technical problem of the present invention is that plastics have the highest molecular weight among these polymers, so that the crosslinked polymers are forcibly oxidized by partial incineration in the presence of a catalyst and oxygen to break down the molecular chains of these crosslinked polymers, thereby lowering the molecular weight. By using the recycled resin by using the resin, its use can be used as a raw material for various paints (paints, inks, organic colorants), coating materials, paraffin substitutes, lubricants, waxes, plastics and the like.

Therefore, an object of the present invention is the step of injecting crosslinked, foamed, crosslinked-foamed polyolefin resin waste into the combustion reactor; A high temperature oxidation reaction of 600 to 1,200 ° C. using self-heat of combustion and oxygen in the atmosphere in a combustion reactor; A low molecular weight thermoplastic resin having a molecular weight of 3,000 to 70,000 through cracking of crosslinked / foamed polyolefin resin waste, comprising the step of cracking a high molecular weight polyolefin resin through a high temperature oxidation reaction to obtain a low molecular weight resin mixture. It is to provide a manufacturing method.

In addition, the flow rate is adjusted by the movement of the air ring in the combustion reactor, the temperature and melt through it is adjusted, characterized in that the cooling through the coil-type circulation system using the cooling water in the upper portion of the combustion reactor.

On the other hand, the present invention is a wax, a paper coating material, a paraffin substitute, a raw material of the candle, a plastic softener, a lubricant, a processing aid or a low-cost waterproofing material, a coal tar or asphalt substitute prepared by using a low molecular weight thermoplastic resin prepared by the above method , Emulsifiers, curing agents or secondary fuels.

Hereinafter, the present invention will be described in more detail.

The oxidation mechanism in the presence of oxygen of polyolefin is as follows.

Crosslinked / foamed polyolefin-based polymers having alkoxy, hydroxy, carboxyl groups and the like as functional groups in the polymer are thermally oxidized in the presence of catalysts such as iron, copper and chlorine, and in the case of carboxyl groups, they are decomposed into alkoxy groups and hydroxy radicals. Oxidation produces alcohols, carboxy, water, alkyl radicals, etc., and oxidization continues to crack into low molecular weight compounds such as esters, aliphatic hydrocarbon polymers, ketones, and the like.

In the reaction, the polyolefin is a catalyst such as iron and copper in the presence of oxygen and ultraviolet rays in the B region or when sufficient heat is applied to the energy, the molecular chain is cleaved and converted into a polyolefin radical, and the radical again attacks the polymer to react between radicals. This occurs and the oxidation reaction proceeds continuously until the reaction is completed. It is also known that by Arrhenius' law, every chemical reaction is accelerated by a factor of two per 10 ° K (Kelvin temperature) rise.

In the case of the crosslinked polyolefin polymer, as described many times, due to crosslinking, the geometrical shape of the molecular structure and the increased molecular weight make it difficult to melt or move the molecules even at high temperatures, and thus, it is very difficult to convert the thermoplastic molecules by a general oxidation reaction.

Therefore, in the present invention, in order to induce the oxidation reaction of the polymer by the above reaction mechanism, the waste crosslinked polymer is first combusted, and the heat generated thereby initiates the oxidation reaction of the polymer as well as accelerates the continuous generation and reaction of the oxidation reaction. It is used as an energy source for the destruction of molecular chains by forced pyrolysis and combustion.

In addition, by introducing a certain amount of air from the bottom, the combustion efficiency is increased to increase the rate and efficiency of molecular destruction, and oxygen is supplied for the oxidation reaction to induce a continuous radical reaction, and at the same time, a certain amount of air is released from the catalyst network. Oxygen may be supplied to sustain the reaction of the reaction material.

Some of the excess air circulates to the bottom of the reactor to convert and contribute to the cooling of the prepared low molecular weight resins, which may contribute to speeding up the reaction and solidifying the material.

The device used in the present invention is open and closed at the opening of the tank for collecting the thermoplastic low molecular weight resin is designed to be ignited by using the raw cross-linked polyolefin as a fuel and heated by the heat to be forcibly melted and the raw material is loaded and accumulated The part is composed of iron, platinum, copper, vanadium, etc., as a catalyst, so that the broken / melted resin can easily induce oxidation reaction. An air intake hole is installed in the bucket to increase the thermal efficiency of melting and incineration, thereby increasing the oxidation rate.

In the upper part, a punched iron plate, such as a net, which can be heated first by inputting a raw material, is installed on the inner wall to serve as a primary filtering plate, and at the same time, the entire wall surface is meshed or punched in the bottom opening of the combustion bucket. Perforated plate is tubular and installed at a certain distance from the filter plate (mesh).

The outer surface prevents the loss of molten and decomposed low molecular weight resin using general heat resistant stainless steel sheet, and installs an air ring at the bottom between the outer and inner mesh tubes to supply some of the air for combustion. Some have been designed to operate in a constant temperature range to prevent high temperature degradation and decomposition of the combustion reactor temperature and low molecular weight resins produced.

In the present invention, by modifying and modifying the shape of the existing incinerator, the flow rate of the inlet / outlet air is adjusted to maintain a constant amount of heat and an ignition state such that melting and pyrolysis can occur without the entire incineration, and the ignition crosslinking primer is short-lived. Pyrolysis and oxidation destroy the molecular structure so that it can be melted and dropped.

The present invention is installed in the lower end of the collection tank for collecting the resin melt dropping, heat melting to heat and melt the raw plastic waste material by partial combustion at a certain distance on the upper end of the product collection tank and thermal oxidation / decomposition The combustion bucket was inadvertently designed to collect most of the ash and carbonized ash in this area.

Combustion bucket of heating / melting part is composed of net or meshed steel plate or punched perforated plate, and is open to all directions (up, down, left and right) to facilitate inflow of intake air for combustion and oxidation. It is designed so that the melt can escape only as a liquid phase with a certain viscosity.

The upper part of the heating / melting part is ignited by the raw material-waste plastic- which is put in a large amount by striking the diaphragm with a very coarse net or a large diameter perforated steel plate so that the waste resin raw material cut to a certain size does not fall into the heating / melting part. A fire / heat section was designed to prevent fires from extinguishing and reducing the temperature of the heated melt.

In addition, one or two air rings are mounted on the outside of the heating / melting tube according to the height and length of the heating / melting part to adjust the flow rate of air flowing from the outside, resulting in loss of resources through complete combustion or incomplete ignition. In addition to preventing the light off, it is designed to uniformly distribute the inlet air, and to adjust the flow rate at the same time to adjust the desired productivity.

On the other hand, the air flowing from the air ring also moves to the lower end of the heating / melting part to reduce the amount of molten resin volatilized by high heat, and at the same time, it is sufficiently preheated in the heating melting part to help preheat the raw material located in the input / heating part. . The amount of input air can be adjusted through the blower and the valve device on the outside of the air ring, and if necessary, the shaft of the air ring is connected to the drive motor by using a gear to gradually rotate the air and distribute the inflow air more evenly. It is also possible to change the air flow to vortex flow.

Recycling apparatus according to an embodiment of the present invention has a housing on the outside of the device, the air inlet pipe is piped through the lower portion of the housing, the molten wax-like resin flows down by gravity under the housing It is loaded in the tank and has an open structure so that the separated and collected products can be discharged to different outlets according to specific gravity, and discharge ports are provided in the middle and the bottom, respectively.

As the raw materials of the recycling apparatus, polyethylene polymers are mainly divided into general, low-crosslinked and high-crosslinked polyethylene. First, general polyethylene or low-crosslinked polyethylene is only locally dissolved when ignited. The melt covers the non-ignition of polyethylene and blocks the oxygen supply in some cases, preventing continuous combustion. Therefore, in order to thermally decompose this kind of polyethylene, it is necessary to supply extra energy.

However, the high crosslinked polyethylene having a crosslinking rate of 70-80% or more is difficult to melt even during combustion, so the flow is low and thus continuously burns when ignited, so there is little or no supply of additional energy. Therefore, the higher the degree of crosslinking may have an advantage as a recycled raw material.

The cross-linked polyethylene raw material is combusted by appropriately combining with oxygen in the air supplied through the air ring installed in the housing, and the surface area is widened by deformation due to a decrease in viscosity during combustion, and with oxygen in a high temperature state due to heat generated by combustion. The reaction is facilitated and is subsequently cracked by chain reaction and reduced to low molecular weight. At this time, in order to increase the degree of oxidation and more easily destroy the network structure of the crosslinked polymer, a catalyst is used. The catalyst is composed of a network or porous phase having a good contact surface due to combustion or flow during heating / melting.

As is well known, catalysts for oxidative decomposition are advantageously metals such as iron and copper, and platinum, vanadium, or silver-based nets are advantageous for the completion of chain reactions. It can also serve as a constant catalyst.

The cross-linked polyolefin-based resin that has undergone this process is converted into a low molecular weight oxidized resin and flows or drips through the wall to be collected separately according to the specific gravity difference, and the gas and smoke generated by combustion are discharged out through the exhaust port. do. At this time, install a wire mesh of proper size in the lower part of the housing to filter out carbides and debris contained in the wax-like polymer recycled material, and collect the filtered wax from the collection tank, and centrifuge in a high-temperature liquid phase to purify or collect as it is. Cooling for a certain time can be obtained as a resin in a solid state.

In this process, the crosslinked polyethylene resin whose molecular weight cannot be measured was converted to a thermoplastic low molecular weight resin.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to these embodiments.

(Example 1)

500 Kg of HDPE or L / LDPE crosslinked polymer (XLPE ondol pipe) was introduced into a combustion reactor, and then thermally oxidized to crack the crosslinked polymer. In this case, 435 Kg of an oxidized low molecular weight resin having similar thermal properties as LDPE, L / LDPE, and HDPE was obtained. The molecular weight of the obtained material was 3,500 to 50,000, melting point was 82 ° C (paraffin), 102 ° C (LDPE), 114 ° C (L / LDPE), 124 ° C (HDPE), 132 (L-PP) and the flow index was 500 It was above. The reaction yield was about 87%.

(Example 2)

300 Kg of HDPE or L / LDPE crosslinked polymer (XLPE ondol pipe) was introduced into a combustion reactor, and thermally oxidized to crack the crosslinked polymer. In this case, 192 Kg of oxidized low molecular weight resin having similar thermal properties to that of Paraffin wax and LDPE and L / LDPE was obtained. The molecular weight of the obtained material was 5,000-35,000 and the melting point was 78 ° C. (paraffin), 104 ° C. (LDPE), 114 ° C. (L / LDPE) and the flowability index was 500 or more. The reaction yield was about 64%.

(Example 3)

500 Kg of LDPE high voltage crosslinked wire insulation coating material was introduced into a combustion reactor, and then heated and oxidized to crack the crosslinked polymer. In this case, 460 Kg of an oxidized low molecular weight resin having similar thermal properties as LDPE, L / LDPE, and HDPE was obtained. The molecular weight of the obtained material was 3,500-50,000, the melting point was 82 ° C. (paraffin), 102 ° C. (LDPE), 112 ° C. (L / LDPE) and the flowability index was 500 or more. The reaction yield was about 92%.

(Example 4)

500 Kg of HDPE or L / LDPE crosslinked polymer (XLPE ondol pipe) was introduced into a combustion reactor, and then thermally oxidized to crack the crosslinked polymer. In this case, 470 Kg of an oxidized low molecular weight resin having similar thermal properties as LDPE, L / LDPE, and HDPE was obtained. The molecular weight of the obtained material was 3,500-70,000, and the melting points were 82 ° C. (paraffin), 102 ° C. (LDPE), 114 ° C. (L / LDPE), 124 ° C. (HDPE), and 132 (L-PP). It was above. The reaction yield was about 84%. Meanwhile, the air volume of the combustion reactor was 5L / min and the average temperature in the combustion reactor was 600 ° C.

(Example 5)

500 Kg of HDPE or L / LDPE crosslinked polymer (XLPE ondol pipe) was introduced into a combustion reactor, and then thermally oxidized to crack the crosslinked polymer. In this case, 380 Kg of an oxidized low molecular weight resin having similar thermal properties as LDPE, L / LDPE, and HDPE was obtained. The molecular weight of the obtained material was 3,500 to 250,000, and the melting points were 82 ° C. (paraffin), 102 ° C. (LDPE), 114 ° C. (L / LDPE), 124 ° C. (HDPE), and 132 (L-PP). It was above. The reaction yield was about 76%. Meanwhile, the air volume of the combustion reactor was 5L / min and the average temperature in the combustion reactor was 1,000 ° C.

The effect of the present invention is to reduce the thermoplastic resin of low molecular weight by using the crosslinked and expanded polyolefin polymers which are previously embedded or incinerated and discarded, and are used as olefin waxes, paper coating materials, paraffin substitutes, raw materials of candles, plastic soft materials, It can be recycled as lubricant, processing aid or low cost waterproofing material, coal tar or asphalt substitute and emulsifier, hardener or secondary fuel. Therefore, conservation of petroleum resources and waste of resources can be reduced, economical alternatives can be produced, and environmental waste that cannot be disposed of can be reduced, thereby contributing to the improvement of the social environment.

Claims (3)

Injecting a crosslinked, foamed, crosslinked-foamed polyolefin resin waste into a combustion reactor; A high temperature oxidation reaction of 600 to 1,200 ° C. using self-heat of combustion and oxygen in the atmosphere in a combustion reactor; A low molecular weight thermoplastic resin having a molecular weight of 3,000 to 70,000 through cracking of crosslinked / foamed polyolefin resin waste, comprising the step of cracking a high molecular weight polyolefin resin through a high temperature oxidation reaction to obtain a low molecular weight resin mixture. Manufacturing Method According to claim 1, characterized in that the flow rate is adjusted by the movement of the air ring in the combustion reactor, the temperature and melt through it, and cooled through a coil-type circulation system using a cooling water in the upper portion of the combustion reactor Method for producing low molecular weight thermoplastics by cracking crosslinked / foamed polyolefin resin waste A wax, a paper coating material, a paraffin substitute, a raw material of a candle, a softener of a plastic, a lubricant, a processing aid or a low-cost waterproofing material, a coal tar or an asphalt substitute, an emulsifier, prepared using a low molecular weight thermoplastic resin prepared by the method of claim 1 Hardener or secondary fuel