CN112126117A

CN112126117A - Soft plastic renewable treatment method

Info

Publication number: CN112126117A
Application number: CN202010934996.9A
Authority: CN
Inventors: 王炳超; 张梦妍; 冯浩; 杨兆举
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-09-08
Filing date: 2020-09-08
Publication date: 2020-12-25

Abstract

The invention discloses a renewable treatment method of soft plastics, which comprises the following steps: (1) putting the soft plastic into glycerol with the temperature of 190-260 ℃ to soften the soft plastic until the soft plastic becomes viscous state; (2) the viscous state forms a plastic product through molding. The invention relates to a heat treatment method based on a glycerol organic solvent, which is characterized in that plastic is in a viscous state by high-temperature softening, a remolded plastic product can be regenerated by means of stamping and the like, and toxic and harmful substances such as pungent odor gas, smoke dust, dioxin and the like cannot be generated in the treatment process.

Description

Soft plastic renewable treatment method

Technical Field

The invention relates to the technical field of plastic treatment, in particular to a renewable treatment method for soft plastics.

Background

The plastic is a common polymer plastic, has extremely excellent performance and has a wide application range. But the disposal of the waste plastics after their use also becomes a problem that we must pay attention to at present. If not properly handled, the environment will be more damaged. There is data indicating that about 70% to 80% of the total plastic of all-purpose plastic will be converted to waste plastic in 10 years. Of which about 50% will be converted into waste plastics in two years.

The existing plastic treatment modes are landfill treatment, combustion treatment and regeneration granulation generally, the mode of landfill treatment of plastics damages land resources due to the fact that the plastics are difficult to degrade, the landfill treatment lasts for a long time, a large amount of land resources are occupied, and the recycling value of waste plastics is wasted.

The mode of combustion treatment causes harm to air resources, and the plastic incineration process can produce toxic substance dioxin, which is also a part difficult to treat in the incineration treatment, and the dioxin, as a substance with strong toxicity synthesized carelessly, directly threatens the reproductive function of organisms and causes various diseases, and is called by scientists as a pollution problem which can cause death of human beings. Dioxins are the generic names of polychlorinated dibenzodioxins (PCDD, Polycholoro dibenzozo-p-dioxins) and polychlorinated dibenzofurans (PCDF, Polycholoro dibenzozo-furans), abbreviated as PCDD/Fs.

Dioxin is easily accumulated in the fat of an organism through a food chain and is concentrated, and the dioxin easily damages the reproductive function of the organism. From the chemical structure, the benzene ring structure and chlorine can form dioxin through simple processes such as heating and the like. The generation of dioxin in the process of generating power by incinerating garbage is concentrated in the combustion process of plastics in an incinerator. There are three main mechanisms by which dioxins are produced: firstly, from the original garbage, the original garbage contains dioxin substances which are not destroyed in the incineration process and exist in the burnt smoke; generating PCDD in a gas phase at high temperature (500-800 ℃); secondly, in the initial drying stage of the garbage entering the incinerator, after volatilizing low boiling point organic matters containing water and hydrocarbon components, reacting the volatilized low boiling point organic matters with oxygen in the air to generate water and carbon dioxide to form a temporary anoxic condition, and reacting part of the organic matters with hydrogen chloride (HC1) to generate PCDD; thirdly, the fuel is synthesized again in the tail flue gas of the combustion, and the fuel is produced by incomplete combustion in the combustion processAnnular precursors (chlorinated aromatic hydrocarbons) with similar structures to dioxin are generated, the precursors are subjected to heterogeneous catalytic reaction on the surface of solid fly ash to synthesize dioxin at a lower temperature (250-400 ℃), namely, residual carbon, oxygen, hydrogen, chlorine and the like in the fly ash are subjected to catalytic synthesis on the surface of the fly ash to obtain intermediate products or dioxin, or the precursors in a gas phase are subjected to multiple reactions with nonvolatile metals and salts thereof on the surface of the fly ash to generate surface active chlorides, and then the dioxin adsorbed on the surface of fly ash particles is generated through multiple complex organic reactions, wherein the change relationship of the generation amount of the dioxin along with the temperature is shown in figure 1. Dioxin is more toxic than other toxic substances. Chronic exposure to dioxin produces chronic toxins in the human reproductive system, resulting in the production of infertility, miscarriage, premature labor, and malformations. If the toxic and harmful gases are further treated, blast furnace injection can be adopted, but the comprehensive economic cost is higher.

The regeneration granulation mainly comprises three stages of sorting, crushing and granulation, waste plastics are sorted and classified and then put into a crusher for crushing, and then the waste plastics are subjected to hot melting, wire drawing, cooling and granule cutting by a granulator to prepare plastic regeneration granules which are packaged and sold. The analysis of the market clean production process by combining the production process has three main problems of waste plastic regeneration granulation: firstly, the granulator energy consumption is higher, and in the granulation process is regenerated to waste plastic, the granulator need extensively be used to electrical heating, and this kind of heating method mainly leans on contact conduction to transmit heat energy, only just can transmit the feed cylinder near the heat at feed cylinder surface inboard on, and the heat in the outside most scatters and disappears to the air like this, has heat conduction loss to lead to ambient temperature to rise, the lower problem of heat utilization rate. Secondly, the filter screen is frequently replaced, and the solid waste yield is large. The solid wastes generated in the waste plastic regeneration granulation process are various, and mainly comprise impurities such as metal, wood dust and the like generated in the sorting process; filtering impurities, waste filter screens, waste rubber heads and the like generated in the wire drawing process; cutting defective grains; spent activated carbon from waste gas treatment; cleaning wastewater and treating sludge, etc. The material balance actual measurement result shows that the material loss link in the granulation process mainly comprises waste rubber heads and impurity filtering, and the generated waste which cannot be utilized is a waste filter screen. If the waste filter screen is improperly treated, the environment is greatly affected, and if the waste filter screen is burnt by partial enterprises, the waste filter screen is reused, so that waste gas and dioxin are generated to pollute the environment. Thirdly, the waste gas treatment is not standard, the waste plastics are gradually melted or decomposed when heated, and the waste gas containing hydrocarbons and benzenes is released in the process, and the odor of petroleum, irritant sour taste and the like is given off. At present, most waste plastic regeneration granulation enterprises mainly adopt an activated carbon adsorption method for organic waste gas: organic waste gas enters the activated carbon adsorption device through the gas collecting hood, and the treated gas is discharged to the upper air through the exhaust funnel by utilizing the induced draft fan. Although some enterprises install the waste gas collecting system and the treatment facility, the gas collecting hood is too high, the air extracting and collecting area is too small, and the waste gas collecting point is unreasonable; workers are convenient for production operation, and the waste gas collecting effect is poor due to the fact that the gas collecting hood is lifted; the poor organic waste gas adsorption effect can also be caused by untimely replacement of the activated carbon or purchase of the activated carbon with poor quality.

In conclusion, the energy consumption is high, the replacement of a filter screen and the treatment of waste gas are limitations of regeneration granulation, the plasticizer needs to be added for remodeling, the di (2-ethylhexyl) phthalate is the main component of the plasticizer, C24H38O4 is a colorless transparent liquid with special smell, the melting point is-55 ℃, the boiling point is 386.9 ℃, the solubility in water is less than 0.01% at 25 ℃, and the solubility of water in the product is 0.2%. Is soluble in most organic solvents and hydrocarbons, and slightly soluble in glycerol and ethylene glycol. Scientific research shows that the phthalate plasticizer is an environmental estrogen with reproductive toxicity and developmental toxicity, and can enter the body through the contact of a digestive system, a respiratory system, the skin and the like; some phthalate esters even have carcinogenic properties. It follows that plasticizers need to be used with caution. Therefore, a new technology for recycling and reprocessing plastics is urgently needed to solve the above problems.

Disclosure of Invention

The invention aims to provide a treatment method for recycling soft plastics, which is a heat treatment method based on a glycerol organic solvent, wherein the plastic is in a viscous state through high-temperature softening, and a remolded plastic product can be recycled through means such as stamping, and toxic and harmful substances such as pungent odor gas, smoke dust, dioxin and the like cannot be generated in the treatment process.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect of the present invention, there is provided a method for recycling soft plastics, comprising the steps of:

(1) putting the soft plastic into glycerol with the temperature of 190-260 ℃, and softening the soft plastic until the soft plastic becomes a viscous state, wherein;

(2) the viscous state forms a plastic product through molding.

Preferably, in the step (1), the flexible plastic is a waste plastic bag or a plastic foam.

Preferably, in step (1), the softening time is 1-5 s.

The glycerol is only used as a heat carrier and has no consumption, so the requirement on the using amount of the glycerol is not strict. The softening time is different according to the size of the put plastic, the softening speed of the plastic is high, and the plastic is softened after basically contacting the liquid level of the glycerol.

Preferably, in the step (2), the molding is specifically punch molding or blow molding.

Preferably, in the step (2), the molding temperature is 180-210 ℃.

In a second aspect of the invention, the application of the above treatment method in the renewable treatment of the waste mask is provided.

In a third aspect of the invention, there is provided the use of glycerol for softening flexible plastics.

The invention mainly aims at a method for treating soft plastics with good compressibility, the soft plastics are plastic bags and plastic foams which are common at present, the common treatment is to press the soft plastics into blocks and then burn or bury the soft plastics, and the soft plastics are granulated, need to be cleaned and are not easy to crush. The common plastic bag and the like mainly comprise polyethylene, the mask mainly comprises polypropylene, and the polyethylene and the polypropylene have similar thermoplasticity, so that the common plastic bag and the like can be treated by adopting the method.

The invention has the beneficial effects that:

1. the treatment method does not generate toxic and harmful substances such as pungent odor gas, smoke dust, dioxin and the like, and is a heat treatment method based on the glycerol organic solvent.

2. The glycerol treatment method adopted by the invention can effectively avoid the emission of toxic and harmful gases, can not generate black smoke, can not cause burden to the environment, effectively reduces the emission of waste gas in the treatment process, saves energy and improves the recovery efficiency of waste plastics; because the treatment temperature of the glycerol organic solvent is controlled to be 190-260 ℃, the generation of toxic gases such as dioxin and the like is avoided in the mechanism, plastic bags, foams or masks can be directly placed into the high-temperature glycerol solvent by the recovery treatment method of the product, the plastics are changed into viscous state, dust and other garbage can be filtered and removed, and the glycerol can be recycled after being filtered, so that the utilization efficiency of resources is greatly improved, and the requirements of energy conservation and emission reduction are met.

3. Compared with the regeneration granulation, the treatment method has the advantages of low energy consumption, low emission and simple operation, and does not need to add plasticizers such as diester phthalate and the like, thereby improving the utilization rate of resources and increasing the feasibility of a glycerol treatment mode; since the main component of the plasticizer is dissolved in most organic solvents and can cause volatilization due to burning hot melt and the like, but the plasticizer is only slightly soluble in glycerol, a large amount of toxic and harmful plasticizer does not need to be added in the recycling process.

4. The main component of the mask is polypropylene, the outer layer and the inner layer can be burnt, the middle layer is melt-blown cloth, the mask can not be ignited under the condition of an alcohol lamp, and the rest part can not be burnt sufficiently to generate carbon monoxide and carbon black tail gas.

Drawings

FIG. 1 is a graph of the concentration of PCDD and PCDF as a function of temperature;

FIG. 2 is a diagram of a molded object of the present invention;

FIG. 3 is a diagram of another shaped object of the present invention;

FIG. 4 is a representation of the weighing of a plastic bag;

FIG. 5 is an illustration of an initial stage of a hot melt process for plastic bags;

FIG. 6 is a representation of the later stage of the hot melt processing of plastic bags;

FIG. 7 is a graph showing the rate of change in mass of raw materials in different treatment modes, wherein a represents the rate of change in mass of raw materials from burning to extinguishing, b represents the rate of change in mass of raw materials that are sufficiently hot-melted or sufficiently burnt, c represents the rate of change in mass of raw materials after 30 seconds of hot melting, and d represents the rate of change in mass of raw materials treated with glycerol;

FIG. 8 is a view showing a short-time hot-melting process of a plastic bag;

FIG. 9 is a view showing a longer time hot-melting process of a plastic bag;

FIG. 10 is a schematic view of the weighing of a plastic bag after it has been completely burned, 1.36g being the weight of the asbestos gauge;

fig. 11 is a schematic diagram of weighing the plastic bag after it is completely hot-melted, and 1.36g is the weight of the asbestos gauge.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

As introduced in the background art, the current plastic treatment modes are landfill treatment, combustion treatment and regeneration granulation, the plastic landfill treatment mode damages land resources due to the difficulty in degradation, the landfill treatment lasts for a long time, and a large amount of land resources are occupied; the combustion treatment mode causes harm to air resources, and toxic substance dioxin can be generated in the plastic incineration process; the energy consumption is high, the replacement of a filter screen and the treatment of waste gas are all limitations of regeneration granulation, and a plasticizer is required to be added for remodeling.

Based on the above, the present invention proposes that glycerin is used as an organic solvent to heat the soft plastic at a high temperature to change the soft plastic into a viscous state. The glycerol is colorless, odorless, nontoxic and sweet in taste, is in a clear and viscous liquid state, has a boiling point of 290.0 ℃, can meet the temperature requirement of common soft plastics changed into a viscous state, and has a treatment temperature of 190-260 ℃ so as to avoid the generation of toxic gases such as dioxin and the like in mechanism; the plasticizer is mainly dissolved in most organic solvents, and can volatilize due to burning, hot melting and the like, but is only slightly soluble in glycerol, so that a large amount of toxic and harmful plasticizer does not need to be added in the recycling process; the glycerol can be recycled after being filtered, so that the utilization efficiency of resources is greatly improved; therefore, the invention has the advantages of low energy consumption, low emission and simple operation.

In order to make the technical solutions of the present application more clearly understood by those skilled in the art, the technical solutions of the present application will be described in detail below with reference to specific embodiments.

The test materials used in the examples of the present invention are all conventional in the art and commercially available.

Example 1: a processing method for recycling soft plastics comprises the following steps:

(1) putting the waste plastic bag into glycerol at the temperature of 190 ℃, and softening the plastic bag until the plastic bag becomes viscous state;

(2) the viscous state is formed into a hard plastic product by punch forming.

Example 2: a processing method for recycling soft plastics comprises the following steps:

(1) putting the waste plastic foam into glycerol at the temperature of 240 ℃, and softening the waste plastic foam until the plastic foam is changed into a viscous state;

(2) the viscous state is formed into a hard plastic product by punch forming.

Example 3: a processing method for recycling soft plastics comprises the following steps:

(1) putting the waste mask into glycerol at the temperature of 260 ℃ and softening the mask until the mask becomes viscous state;

(2) the viscous state is formed into a hard plastic product by punch forming.

Volatile matter determination and weighing experiment

Respectively carrying out combustion, hot melting and glycerol internal heat treatment molding on plastic bags with mass m, then measuring the mass of the plastic left after full reaction as m', and calculating the mass difference as delta m1, delta m2 and delta m3, wherein the delta m is the mass of combustible volatile components, and the larger the volatile mass is, the more easily the damage is caused. An analytical balance with an accuracy of 0.1g was used as a measuring tool to compare the mass before and after the treatment, and fig. 4 is a representation of the weighing of the plastic bag.

The shape of the plastic can affect the ignition difficulty and the combustion sufficiency, the plastic bag can be extinguished after being fully combusted for a period of time in the experimental process, and the quality of the raw materials and the quality of residues after being extinguished are shown in the following table 1. Since the combustion residue was collected, the weighing and combustion were performed on asbestos mesh, and the data in the following table are the net weight of the plastic bag and the residue.

TABLE 1 Mass Change from Combustion to flame-out

Raw material mass m/g	0.8	1.2	1.6	2.0	2.4	2.8
							Mass m of residue/g after flameout	0.4	0.7	0.9	1.0	1.5	1.8
Rate of change of mass	0.500	0.417	0.437	0.500	0.375	0.357

Plastic articles have the property of being flammable but not flammable, and their burnout capability depends on the shape of the plastic. The experimental plastic does not generate black smoke basically before combustion and flameout, but generates a large amount of pungent odor gas. The residues after flameout can be re-ignited by an alcohol burner after being cooled, a large amount of black smoke and pungent odor gas are generated during re-ignition, the asbestos gauze is weighed after being burnt out, and the residual mass after combustion is considered to be 0 under the measuring condition of 0.1g precision.

In summary, in addition to considering toxic volatile pollutants, the burning conditions of plastics are optimized when burning, and the burning on a plane generates adhesive residues, while the residues are difficult to burn on the plane and generate a large amount of smoke when burning.

The plastic state is different due to different heating time of the hot melting treatment, the plastic state is represented as a viscous state at the beginning and accompanied by a large amount of pungent smell, the plastic state is represented as a liquid state at the later stage and accompanied by a large amount of pungent smell, the mass of the residual substance after full reaction is measured as 0 under the precision of 0.1g, and the plastic state change in the treatment process is shown in figures 5 and 6.

The glycerol treatment method was performed by the method of example 1, and since the treatment was performed by immersing in glycerol and cooling with water, a certain amount of liquid remained after cooling, data of 1 hour after the treatment was also measured. The weighing in the hot melt process is that the plastic bag is weighed together with the asbestos web and heated, m represents the mass of the pure plastic bag and m' represents the mass of the remaining plastic. The experimental data are shown in tables 2 and 3 below, wherein the unit of mass is g, and the mass change rate is expressed by eta.

TABLE 2 weight of hot melt process (treatment time 30 seconds)

Raw material mass m/g	0.8	1.2	1.6	2.0	2.4	2.8
							Mass m 'after treatment'	0.6	0.9	1.1	1.6	1.7	1.9
Rate of change of mass eta	0.25	0.25	0.31	0.20	0.29	0.32

TABLE 3 Glycerol treatment weighing (one hour later weighing)

Raw material mass m/g	0.8	1.2	1.6	2.0	2.4	2.8
							Mass m 'after treatment'	0.8	1.2	1.6	2.0	2.4	2.8
Rate of change of mass eta	0	0	0	0	0	0

Figure 7 is a graph of the rate of change of mass for three treatment methods.

According to the weighing experiment result, a large amount of volatile matters are separated out from the plastic subjected to combustion and hot melting, strong pungent smell is accompanied in the experiment process, the smoke is black during combustion, and the smoke is grey black during hot melting. The glycerol recycling treatment process does not produce pungent odor gas, but is accompanied by a little sweet taste, and the glycerol has sweet taste.

To compare the three treatment methods, a weighing experiment and a gas composition assay were performed after 24 hours. During hot melting, the plastic first changes to viscous state, as shown in fig. 8, and then assumes a liquefied state similar to the liquid dripping during burning, as shown in fig. 9. And the mass change rate of the solid mass remaining after the hot-melting treatment fully reacted is approximately considered as 100% under the condition of weighing with the precision of 0.1g analytical balance. After 1 hour, the change rate of the weight of the glycerol treatment method in the weighing experiment is 0, so the treatment method is low-toxicity or non-toxicity treatment.

Glycerol was chosen because the qualified high boiling point organic solvents were glycerol and ethylene glycol phenyl ether, but only glycerol was non-toxic and harmless. The major component of the plasticizer, di (2-ethylhexyl) phthalate, has a boiling point of 386.9 ℃ which is well above the processing temperature, and is soluble in most organic solvents and hydrocarbons, but is slightly soluble in glycerol, so that the use of glycerol, both for the above-described effect, also reduces or avoids the need for further plasticizer addition during the remodeling process.

The plastic can be softened at about 100 ℃, but the molding requirement is not met, and the reason for selecting the temperature range of 190 ℃ and 260 ℃ is as follows: first, plastics can soften rapidly; secondly, the temperature interval can meet the molding temperature of common plastic products; thirdly, in terms of a generation mechanism of dioxin, the temperature interval does not meet the requirement of the lowest generation temperature of the dioxin; fourthly, the temperature interval is lower than the boiling point of the glycerol, so that the consumption of the glycerol is prevented, and impurity water can be removed; fifthly, the microorganisms can not survive basically under the temperature condition, and the sanitary requirement of the plastic after the reshaping is met.

The materials of the plastic bags on the market at present are polyethylene and polyvinyl chloride, but the national requirements require that the existing polyvinyl chloride plastics are basically rare, and polyethylene plastic products (including various shopping bags, food bags, express packaging bags and the like) and masks taking polypropylene as main materials can be treated by the method.

In the actual production process, the coloration of some recycled plastics is slightly different from the production coloration of new plastics. Because the variety and color of the recycled plastic are different, and the color of the finished product is difficult to control, black or gray color master batches are generally added to ensure that the final product has uniform color.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A processing method for recycling soft plastics is characterized by comprising the following steps:

(1) putting the soft plastic into glycerol with the temperature of 190-260 ℃ to soften the soft plastic until the soft plastic becomes viscous state;

(2) the viscous state forms a plastic product through molding.

2. The processing method according to claim 1, characterized in that: in the step (1), the flexible plastic is a waste plastic bag or plastic foam.

3. The processing method according to claim 1, characterized in that: in the step (1), the softening time is 1-5 s.

4. The processing method according to claim 1, characterized in that: in the step (2), the molding is specifically punch molding or blow molding.

5. The processing method according to claim 1, characterized in that: in the step (2), the molding temperature is 180-.

6. Use of the treatment method according to any one of claims 1 to 5 for the reproducible treatment of waste masks.

7. Use of glycerol for softening flexible plastics.