JP2003301182A - Volume reducing agent and thermal decomposition method for plastic foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a volume reducing agent and to provide a thermal decomposition method excellent in the balance of (1) low viscosity at an ordinary temperature, (2) solubility of polystyrene foams or the like, (3) safety (boiling point, flash point), (4) high thermal decomposition efficiency (efficiency in reducing the molecular weight), (5) boiling point suitable for recovering the volume reducing agent at a high energy efficiency, and (6) chemical stability in volume reducing and thermal decomposition steps, or in reuse, or the like, based on the comprehensive consideration of these factors in studying volume reducing agents for use in reducing the volume of plastic foams such as polystyrene resin foams and in pyrolytically reducing the molecular weight. <P>SOLUTION: The volume reducing agent comprises an 11-15C bicyclic aromatic hydrocarbon compound having at least one aliphatic hydrocarbon residue and two aromatic rings. A 200-330°C boiling-point distillate separated from heavy oil byproducts in the manufacture of ethyl benzene, or a dehydrated product thereof can also be used as a volume reducing agent. Plastic foams are thermally decomposed and reduced in molecular weights to form a product that is suitable for fuel oils or the like, by subjecting them to melting and/or dissolving followed by heat treatment in the presence of the volume reducing agent. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for recovering resources from foamed plastics such as polyethylene resins, polypropylene resins, polystyrene resins, etc., which are widely used as packaging containers, packing materials, etc. The present invention relates to an oil reduction method by liquefaction and thermal decomposition.

[0002]

2. Description of the Related Art Foamed plastics such as foamed polystyrene are widely used as packaging containers and heat insulating materials because of their light weight and high heat insulating properties, but they are not susceptible to biodegradation and their treatment methods have become a social problem. . Although landfill treatment and incineration treatment are performed in the same form, it is preferable if they can be collected and reused.

However, foamed plastic materials such as expanded polystyrene for food containers and packaging, which are contaminated with blood and fat of fish meat, are not suitable for recovery and reuse as they are. In recent years, mineral oil, vegetable oil, organic solvent, etc. have been used. Disposal, recovery and incineration treatment including dissolution and volume reduction used are being considered. Further, it is being studied to recover and reuse it as a low molecular weight compound such as a monomer or a dimer or a trimer by thermal decomposition, or use it as a fuel. It is preferable to treat these at the used site as much as possible. However, low molecular weight compounds may cause new environmental problems such as environmental hormones.

Volume reduction techniques include a method of reducing the volume by compressing or degassing the foamed plastic and a method of dissolving the foamed plastic by using a solvent for the plastic as a volume reducing agent. is there. As a conventional technique relating to volume reduction, Japanese Patent Laid-Open No. 3-214
Japanese Patent Laid-Open No. 4-219186, Japanese Patent Laid-Open No. 6-9
1647 and the like. Regarding collection, Japanese Patent Laid-Open No. 5-
263065, JP-A-5-59212, JP-A-6-143284, and JP-A-6-143285.
JP-A-6-23753, JP-A-6-31
6646, JP-A-8-253618, JP-A-8-85735, JP-A-9-157435 and JP-A-2001-164037.

In the above-mentioned prior art, it is important to select mineral oil, vegetable oil and organic solvent as the volume reducing agent, and there are many specific examples. However, except that it was shown that the deterioration of the physical properties of the plastic with respect to d-limonene was relatively small, the selection was made only by the ability to dissolve and reduce the volume of the foamed plastic.

The inventor of the present invention firstly found that α-methylstyrene (M
SM) and its dimer 2,4-diphenyl-4
It was found that -methyl-1-pentene (MSD) is excellent in the action as a solvent for reducing the volume of expanded polystyrene, the action of promoting thermal decomposition (reduction of molecular weight), and the stabilizing action of the obtained oil product (special feature). Kai 2001-55467, Japan Food Science and Engineering Society, Vol. 46, No. 9, 570). According to this, while the conventional thermal decomposition of polystyrene is treated at a relatively high temperature of about 400 ° C. mainly for the purpose of recovering a monomer, the present inventor has a treatment temperature of 200 ° C. or less, specifically 160 ° C. The temperature range was set to ˜200 ° C., and MSM or MSD containing a low molecular weight oligostyrene component suitable for a fuel oil, which is a thermal decomposition product of expanded polystyrene obtained as a result, can be used as it is as a fuel oil.

However, since MSM has a boiling point of 165 ° C. and a low flash point of 45 ° C., there is a limit to the simplification of the equipment and process for ensuring the safety of the oilification process by thermal decomposition. . On the other hand, with respect to MSD, the boiling point and the flash point are 350 ° C. and 160 ° C., respectively, which is excellent in simplifying the device and ensuring safety. However, on the other hand, it is difficult to obtain a large amount, it has a little viscosity at room temperature, and when considering the recovery and reuse of the solvent, the boiling point is 350 ° C, so a stable operation of the distillation heat medium can be secured. However, there is room for improvement in that it is not easy and that it consumes a lot of energy for separation and recovery by distillation. Also,
Dissolution / volume reduction capacity and thermal decomposition capacity were also unsatisfactory compared to MSM.

[0008]

DISCLOSURE OF THE INVENTION According to the present invention, a volume reducing agent used for volume reduction of foamed plastic such as foamed polystyrene resin and reduction of molecular weight by thermal decomposition is used as low viscosity at room temperature, foamed polystyrene, etc. Solubility, safety (boiling point / flash point), high thermal decomposition efficiency (molecular weight reduction efficiency),
Excellent balance between these factors, considering the appropriate boiling point with high energy efficiency when recovering the volume reducing agent, chemical stability during volume reduction and thermal decomposition processes, or reuse, etc. It is intended to propose a volume reducing agent and a thermal decomposition method.

[0009]

The present inventor has found a volume reducing agent having a specific chemical structure suitable for dissolution / volume reduction and thermal decomposition / oil reduction of foamed plastic such as foamed polystyrene. A method of melting and / or dissolving foamed plastic in the presence of the volume reducing agent to heat the plastic to lower its molecular weight to make it suitable for fuel oil has been completed.

That is, the first aspect of the present invention is characterized by containing a bicyclic aromatic hydrocarbon compound having 11 to 15 carbon atoms and having at least one aliphatic hydrocarbon residue and two aromatic rings. The present invention relates to a volume reducing agent for foamed plastics.

According to a second aspect of the present invention, in the first aspect of the present invention,
The present invention relates to a volume reducing agent for foamed plastics, wherein the bicyclic aromatic hydrocarbon compound is 1,1-diphenylmethane, 1,1-diphenylethane or 1,1-diphenylethylene.

The third aspect of the present invention is to include a fraction having a boiling point of 200 ° C. or higher and 330 ° C. or lower and / or a dehydrogenated product thereof, which is obtained from a heavy by-product oil when ethylbenzene is produced from ethylene and benzene. And a volume reducing agent for foamed plastics.

A fourth aspect of the present invention is the presence of a liquid containing a bicyclic aromatic hydrocarbon compound having 11 to 15 carbon atoms, at least one aliphatic hydrocarbon residue and two aromatic rings. The present invention relates to a method for thermally decomposing a foamed plastic, which comprises melting and / or melting the foamed plastic and heat-treating the foamed plastic at a temperature of 120 ° C to 400 ° C.

The fifth aspect of the present invention is to increase the number average molecular weight of the plastic to 1 by heat treatment in the fourth aspect of the present invention.
The present invention relates to a method for thermally decomposing a foamed plastic, which is characterized by lowering it to 5,000 or less.

A sixth aspect of the present invention is that the bicyclic aromatic hydrocarbon compound according to the fourth or fifth aspect of the present invention is 1,1-diphenylmethane, 1,1-diphenylethane or 1,1-diphenylethylene. The present invention relates to a method for thermally decomposing a characteristic foamed plastic.

The seventh aspect of the present invention is to provide a liquid having a boiling point of 200 ° C. or higher and 330 ° C. or lower and / or a liquid containing a dehydrogenated product thereof, which is obtained from a heavy byproduct oil when ethylbenzene is produced from ethylene and benzene. Pyrolysis of a foamed plastic, characterized in that the number average molecular weight of the foamed plastic is reduced to 15,000 or less by melting and / or melting the foamed plastic in the presence and heat-treating at a temperature of 120 ° C to 400 ° C. It is about the method.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the term "volume-reducing agent" means an action of dissolving foamed plastic by heating in the presence thereof to reduce the volume and / or melting and / or melting in the presence thereof. It means a liquid having an action of promoting the decomposition of the above-mentioned plastic at a high temperature to decompose it into a desired molecular weight. The volume reducing agent does not necessarily require the plastic to be completely dissolved.

In the present invention, the volume reducing agent used for volume reduction and thermal decomposition (reduction of molecular weight) has 11 to 1 carbon atoms.
5, which contains a bicyclic aromatic hydrocarbon compound having at least one aliphatic hydrocarbon residue and two aromatic rings. The carbon number of the bicyclic aromatic hydrocarbon compound is 16
In the above cases, it begins to exhibit viscosity at room temperature and is not preferable as a volume reducing agent.

Such bicyclic aromatic hydrocarbon compounds include naphthalene compounds, biphenyl compounds and diphenyl compounds. Examples of the aliphatic hydrocarbon residue include an alkyl group, an alkenyl group and an alkylidene group.

Examples of preferred bicyclic aromatic hydrocarbon compounds are diphenylmethane, 1,1-diphenylethane,
1,2-diphenylethane, 1,1-diphenylethylene, 1,2-diphenylethylene, 1,1-diphenylpropane, 1,2-diphenylpropane, 2,2-diphenylpropane, 1,1-diphenylpropene, 1 , 2
-Diphenylpropene, 1-methylphenyl-1-phenylethane and the like. In addition to exhibiting an excellent dissolving ability, the structure has an excellent ability to accelerate thermal decomposition (reduction of molecular weight). The reason for this is not completely clear, but in the case of the thermal decomposition of polystyrene, the chemical structure of the volume reducing agent causes radical transfer between the radicalized polystyrene thermal decomposition product generated in the thermal decomposition process and the volume reducing agent. It is presumed that such interaction is facilitated and that this interaction contributes to the progress of thermal decomposition. The ease with which this interaction occurs is thought to be largely related to the resonance stabilizing structure when the volume reducing agent is radicalized. Therefore, in particular, the structure in which two aromatic rings are bonded to one carbon The 1,1-structure or 2,2-structure of is more preferable.

The bicyclic aromatic hydrocarbon has an aromatic ring as a main constituent, an aliphatic hydrocarbon residue does not contain a tertiary carbon atom, and even when it has a double bond, the steric ring of the aromatic ring. Olefin compounds with poor addition reactivity due to obstacles are chemically stable and can be easily collected and recycled. Further, the aromatic ring is chemically stable as compared with the cyclohexene ring contained in d-limonene, and has excellent chemical stability during recycling.

Since most of the bicyclic aromatic hydrocarbon compounds of the present invention have boiling points in the range of 200 ° C. to 330 ° C., the heating for the thermal decomposition of the molten and / or molten plastics is required. Even if it is carried out at a temperature not higher than the boiling point of the ring aromatic hydrocarbon compound, the desired molecular weight reduction effect can be easily obtained. This reduces the heating load in thermal decomposition, simplifies the equipment by omitting the reflux equipment and reducing the pressure load, prevents undesired deterioration of plastic due to overheating, and prevents runaway thermal decomposition and the generation of low-molecular volatile components. There is an advantage that avoidance can be avoided.

The bicyclic aromatic hydrocarbon compound of the present invention can be obtained by a known reaction. Further, they may be used alone or in combination of two or more.
Moreover, you may use it, mixing with a well-known polystyrene solvent in the range which does not impair the effect of these volume reducing agents.

In the residual oil after separation of ethylbenzene, which is a heavy by-product oil in the production of ethylbenzene from ethylene and benzene, diphenylmethane, 1, 2, which is the preferred bicyclic aromatic hydrocarbon of the present invention, Since it contains 1-diphenylethane and the like, the residual oil can be preferably used as it is or as a volume reducing agent by obtaining a fraction containing these components in an appropriate boiling range. The boiling point is preferably 200 ° C. or higher and 330 ° C. or lower, and more preferably 220 ° C. to 310 ° C. Alternatively, a dehydrogenated product of any of these may be used. The method for producing ethylbenzene is not particularly limited, and an example of the production method is “industrial organic chemistry-main raw materials and intermediates-” (K. Weissermel, HJ. Arpe: Mitsuaki Mukaiyama, Translated by: Tokyo Kagaku Dojin, published in 1978). Page 322 to 32
It is described on page 4.

The device used for reducing the volume of the foamed plastic with the volume reducing agent of the present invention is not particularly limited and a known device can be used. The present inventor first disclosed in Japanese Patent Laid-Open No. 2001-55467.
Those disclosed in the publication can also be preferably used. When the volume is reduced, the foamed plastic can be appropriately cut and used for volume reduction. It is not particularly necessary to heat the volume reducing agent for volume reduction, but it may be appropriately heated. When heating, it is preferable to perform the heating within a temperature range from room temperature to the boiling point of the volume reducing agent or less. There is no particular limitation on the amount of the volume reducing agent used, but since it has a high dissolution performance, a foamed plastic having a low density dissolves a considerable amount in an apparent volume. In the case of expanded polystyrene, the molar ratio is preferably 0.01 to 2.0, more preferably 0.01 to 1.0, but it is not particularly limited to this range.

The volume-reduced material of the foamed plastic obtained as described above can be re-obtained by separating and recovering the volume-reducing agent. However, this method requires a lot of energy for distillation of the volume reducing agent. When the volume-reduced material has an appropriate fluidity, it can be used as a fuel. Other fuels may be added to the volume-reduced material, or the composition may be appropriately changed and used by distillation of the volume-reduced material. More preferably, the dissolved plastic is subjected to a thermal decomposition treatment of the volume-reduced product to reduce the molecular weight thereof to obtain a product suitable for various uses such as fuel.

To pyrolyze the foamed plastic to a useful low molecular weight product, the foamed plastic is reduced in volume in the presence of a suitable liquid and pyrolyzed. If desired, other components may be added during the thermal decomposition, or the components may be appropriately changed by distillation or the like. When considering the viscosity, which is an index of the ease of handling when using the thermal decomposition product as fuel oil, the number average molecular weight of the thermal decomposition product is 1
It is preferably 5,000 or less, more preferably 10,0
Since it is not more than 00, particularly preferably not more than 5,000, it is preferable to appropriately adjust the thermal decomposition conditions such as temperature, pressure, time and atmosphere.

The thermal decomposition temperature is preferably above the temperature at which the material to be treated becomes in the liquid phase and below the boiling point range of the volume reducing agent used. Preferred thermal decomposition temperature is 120 ° C to 4
It is in the range of 00 ° C. If it is lower than 120 ° C, the thermal decomposition efficiency is low and it takes a long time, which is not preferable. If the temperature exceeds 400 ° C, the plastic is decomposed into monomers and is unsuitable for use as fuel oil, and the heating medium burden on the heating device increases. For the purpose of recovering and reusing as fuel oil, thermal decomposition conditions can be appropriately selected depending on the type of plastic, but the temperature is 120 ° C to 400 ° C and the time is 30 minutes to 6 minutes.
Range of time, preferably temperature is 180 ° C to 330 ° C, time is 30 minutes to 3 hours, more preferably temperature is 180 ° C
The time is in the range of 30 minutes to 2 hours at ˜310 ° C. The boiling point range of the volume reducing agent of the present invention is appropriate, and by heating at a temperature not higher than the boiling point, generation of decomposition products can be suppressed and thermal decomposition products of desired molecular weight can be obtained in high yield.

In the thermal decomposition of plastics, the progress of the decomposition is affected by the presence or absence of the interaction between the radicals of the polymer generated by the thermal decomposition and the volume reducing agent and the degree thereof. When a substance having a function as a chain transfer agent is used as the volume reducing agent, the decomposition is accelerated, so that the temperature and the time are shorter than those in the case where there is no volume reducing agent or when other volume reducing agents are used. Can achieve a low molecular weight. 1,1-Diphenylalkane, 1,1-diphenylalkene or their homologues are particularly excellent in their effects due to their chain transfer action. The amount of the volume-reducing agent used is not particularly limited, but if the amount of the volume-reducing agent used is excessive, it may rather hinder the progress of decomposition of the plastic. For example, when the volume reducing agent is used in a molar ratio of 1 or more with respect to the foamed plastic, the plastic once reduced in molecular weight by heat treatment may react with the heat treatment for a long time to increase the molecular weight. In order to obtain the effects of the present invention, the molar ratio of the volume reducing agent to the plastic used is in the range of 0.01 to 2.0, preferably 0.01 to 1.0.
Range, more preferably 0.1 to 0.6, particularly preferably 0.2 to 0.4.

There is no particular limitation on the type and type of the thermal decomposition apparatus, but the present inventor first disclosed in Japanese Patent Laid-Open No. 2001-5546.
The device disclosed in Japanese Patent No. 7 can be preferably used in this case as well.

[0031]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described in more detail. Of course, the present invention is not limited to the following embodiments.

<Materials used> (1) Foamed plastic: expanded polystyrene (number average molecular weight (Mn) = 67,000, which is a waste material for food packaging)
Molecular weight distribution (Mw / Mn) = 1.75) (2) Volume reducing agent: 1,1-diphenylethane (DP) separated by distillation from heavy by-products during the production of ethylbenzene
ET: molecular weight = 182, boiling point 272 ° C.), its dehydrogenated derivative 1,1-diphenylethylene (DPEL: molecular weight = 180, boiling point 277 ° C.) and obtained by distillation from heavy by-product oil during ethylbenzene production Boiling range 26
Fraction (MIX) between 5 ° C and 275 ° C. The composition of MIX was 45 to 55 mass% of diphenylmethane, 20 to 35 mass% of 1,1-diphenylethane, and 20 to 35 mass% of 1,2-diphenylethane. (3) Comparative volume reducing agent: α-methylstyrene (MSM: molecular weight = 118, boiling point 165 ° C.) and 2,4-diphenyl-4-methyl-1-pentene (MSD: molecular weight = 23)
6, boiling point 350 ° C)

<Evaluation of Solubility> 30 with screw cap
Put 10 ml of volume reducing agent into a 30 ml test tube,
It was immersed in a water bath at 60 ° C and 60 ° C. Expanded polystyrene was cut into a size that was easy to put in a test tube and dissolved in a volume reducing agent. After confirming the disappearance of bubbles generated during the dissolution of the expanded polystyrene, new expanded polystyrene was added.
The solubility evaluation test was completed when the dissolution rate became very slow, that is, when the expanded polystyrene remained undissolved even after standing overnight. The results are shown in Table 1. DP
ET showed a dissolution capacity above MSD.

[0034]

[Table 1]

<Pyrolysis Evaluation (1)> 2.5 g of expanded polystyrene, which is a waste material for food packaging that has been shredded into small pieces (Mn =
67,000: Mw / Mn = 1.75), and each volume reducing agent was added at a predetermined molar ratio, and the mixture was placed in a 500 ml four-necked flask equipped with a cooling tube, a nitrogen introducing tube, a stirring blade and a temperature sensor. 30 minutes while heating in an oil bath at 190 ° C for 2 hours
The mixture was stirred with 0 glass beads having a diameter of 5 mm at a speed of 15 rpm. The results are shown in Table 2. The four solvents showed almost the same thermal decomposition ability. When treated with an excess solvent system, the effect of lowering the molecular weight decreases. It was revealed that this tendency is strong in the case of MSM.

[0036]

[Table 2]

<Evaluation of Thermal Decomposition (2)> The molecular weight distribution of each thermally decomposed product according to the above evaluation was measured. The results are shown in Table 3. This molecular weight distribution is an indicator of whether the molecular weight reduction (pyrolysis) progresses uniformly or partially,
The smaller the molecular weight distribution, the more uniform the progress.

[0038]

[Table 3]

[0039]

EFFECT OF THE INVENTION By using the specific volume reducing agent of the present invention, it becomes possible to efficiently and safely reduce the volume of foamed plastic such as expanded polystyrene and recover resources by thermal decomposition. It was Further, the obtained thermal decomposition product can be used as fuel oil.

Claims (7)

[Claims] 1. A foamed plastic material having a carbon number of 11 to 15 and containing a bicyclic aromatic hydrocarbon compound having at least one aliphatic hydrocarbon residue and two aromatic rings. Agent. 2. The volume reducing agent for a foamed plastic according to claim 1, wherein the bicyclic aromatic hydrocarbon compound is diphenylmethane, 1,1-diphenylethane or 1,1-diphenylethylene. 3. A boiling point of 200 ° C. obtained from a heavy by-product oil when ethylbenzene is produced from ethylene and benzene.
A volume-reducing agent for foamed plastics, which comprises a fraction of not less than 330 ° C. and / or a dehydrogenated product thereof. 4. A foamed plastic is melted in the presence of a liquid containing a bicyclic aromatic hydrocarbon compound having 11 to 15 carbon atoms, at least one aliphatic hydrocarbon residue and two aromatic rings. And / or melts, 120 ° C.-4
A thermal decomposition method for foamed plastics, which comprises heat-treating at a temperature of 00 ° C. 5. The thermal decomposition method for a foamed plastic according to claim 4, wherein the number average molecular weight of the foamed plastic after the heat treatment is reduced to 15,000 or less. 6. The bicyclic aromatic hydrocarbon compound is diphenylmethane, 1,1-diphenylethane or 1,1-
It is diphenyl ethylene, The thermal decomposition method of the foamed plastic of Claim 4 or 5 characterized by the above-mentioned. 7. A boiling point of 200 ° C. obtained from a heavy by-product oil when ethylbenzene is produced from ethylene and benzene.
Number average molecular weight of the plastic by melting and / or melting the foamed plastic in the presence of a liquid having a temperature of not less than 330 ° C. and / or a liquid containing a dehydrogenated product thereof, and heat-treating at a temperature of 120 ° C. to 400 ° C. 15
000 or less, the thermal decomposition method of the foamed plastic.