EP0554379A4

EP0554379A4 - Decontamination of polystyrene

Info

Publication number: EP0554379A4
Application number: EP19910920509
Authority: EP
Inventors: Charles Marion Krutchen
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1990-10-22
Filing date: 1991-10-22
Publication date: 1993-08-18
Also published as: EP0554379A1; KR930702432A; JPH06502446A; WO1992007025A1

Abstract

A method of decontaminating waste contaminated polystyrene involves dissolving the contaminated product in liquid styrene monomer and recovering the contaminant-free solution.

Description

Ω~~~~ ^{~ ~~~ ~}τC^" OF POLYSTYRENE The present invention relates to a process for deαxrtaminating post-σonsumer-use waste «>ntaminated polystyrene. The present process is directed to recovering polystyrene resin by processing the waste resin product.

Polystyrene, in foamed or unfoamed form, is an indispensable material in present-day low-cost packaging. Supermarkets and fast-food restaurants use thermofarmed polystyrene products in enormous quantities. They are low-cost, attractive packaging products which have short lifetimes but, along with a superb utility in relation to food products, they also present a formidable waste disposable problem. The industry is constantly on the lookout for better disposal means for these used products as alternatives to merely transporting them to a landfill for either incineration or burial. U.S. Patent No. 4,517,312, issued to Rumasaka et al. and assigned to oyo Rubber Chemical Industry Company, Ltd., describes a process for regenerating polystyrene resin from waste ccartaminated polystyrene. This technique, however, involves the use of organic solvents and water. The subsequent removal of these organic solvents and water to reclaim the regenerated polymer can be economically urattractive.

If a process for decontaminating polystyrene can be successfully proposed, such a process will contribute much to the solution of the commercial and post consumer waste problem and permit the ccaiservation of resources. SUM &RY OF THE INVENTION

The present invention relates to a method of purifying and recovering a polystyrene product from post consumer waste contaminated polystyrene product σαrprising:

(a) subjecting said waste contaminated product to the solvent action of styrene moncmer, in vSiich the -ccnta inaπts are at least substantially insoluble, to form a polystyrene produσt-styrene mαncmer solution; and

(b) recovering the contøπ nant-free solution. DETAILED DESCRIPTION OF THE ^~~~^~~~~ I^~"

The term "waste cxartaminated polystyrene product" is meant to include any foamed or unfoamed polystyrene material which has become contaminated during the product's useful life. Of course, the usual situation involves the contact of polystyrene with food products, usually in a fast-food or supermarket environment. In these instances, the waste is leftover and discarded food and drink products which are in surface contact with the polystyrene foam or sheet container or tray. There may, of course, be other polystyrene contaminants which are not of a food or drink nature. For example, polystyrene beads are molded into a variety of shapes and structures other than coffee cups, such as packing material, members used as spacers to keep fragile product separated, etc. During the -useful life of these materials, they can become contaminated with whatever dirt and debris of the environment with which they come into contact.

The term "polystyrene product" as employed herein is to be understood in its broadest sense so as to include not only polystyrene but para****methylstyrene, para-t-butylstyrene, morxxhlαrostyrene, dichlαrostyrene, impact polystyrene, blends of polystyrene and other polymers, for example, polystyrene and polyphenylene oxide, etc.

The technique of the present invention is elegant in its simplicity. The contaminated polystyrene product is merely fed into a volume of liquid styrene oncπer, which monomer is at a temperature suited to effectively dissolve the polystyrene. The common waste products such as hamburger particles, bread and rolls, the usual fast-food condiments, milk, soft drinks, fish particles, remain undissolved in the styrene monomer. Althσu . it is intended that the solution process (scrap polystyrene into styrene) occurs at a polymerization plant site, it is understood that, if convenient, the scrap polystyrene may be dissolved in the styrene monomer at earlier stages in the return process. At some convenient polystyrene concentration in the styrene monomer, the solution can be separated fcy airy convenient means from the excluded waste material.

The means for separating the polystyrene-styrene solution frcm the waste material includes filtration, or cσuntercurrent washing for. dissolved contaminants or for undissolved liquid contaminants, or continuous solution stream withdrawal, etc.

The recovered polystyrene-styrene monomer solution has utility as a feedstock or cσrrtributing feedstock in a commercial styrene polymerization process. Basically, styrene monomer is heated to its polymerization temperature and polystyrene is removed frcm the system. The recovered product of the present invention can be blended with styrene monomer feedstock and utilized as the sole or a ∞πtributing factor in the formation of polystyrene in a bulk suspension or (xntinuous process. In the following example, "thermally densified" means heating the contaminated foamed or unfoamed polystyrene to reduce its density. -Ierrperatures may reach carbonization teπperatures for the food contaminants.

The present invention is new described by way of Examples. EXAMPLE 1

440 lbs. of thermally densified waste contaminated polystyrene foam fast-food containers which had been adherently contacted with the usual output of a fast-food restaurant, e.g., meat and fish sandwiches, French fries, soft drink, milk, cxϊndiments, etc., were dissolved in 1,600 lbs. of liquid styrene monomer at room teπperature. With moderate stirring, the polystyrene dissolved in the styrene mαncmer over a period of 30 minutes. A sample of the overall mixture in its quiescent state revealed a noticeable surface scum and seme floating particles within the solution. The system was filtered through a 5 micron filter to yield a surprisingly clear solution product. EXAMPLE 2

Employing a laboratory scale, styrene polymerization process, the filtered solution of Example 1 which contained approximately 20% of polystyrene was employed as the styrene feedstock to the polymerization process. The polymerization process was carried out to 80% solids (25% post consumer recycle) yielding a polystyrene product which appeared indistinguishable from virgin polystyrene. During the polymerization process, teπperatures reached 140°C which effectively sterilizes airy remaining bacteria which may have carried over from the process of Example 1.

It is clear that fcy the technique described above, an effective process has been presented, not only to greatly contribute to the elimination of a waste disposal problem but done so in a manner which provides an effective economical use for the recovered polystyrene-styrene solution.

Claims

WHAT IS CLAIMED IS;

1. A method of purifying and recovering a polystyrene product frcm a waste contaminated polystyrene comprising:

(a) subjecting said waste contaminated product to the solvent action of styrene monomer, in viiich the contaminants are at least substantially insoluble, to form a polystyrene product-styrene mαncmer solution; and

(b) recovering the c^*ontaminant-free solution.

2. The method of claim 1 wherein the polystyrene product is polystyrene.

3. The method of claim 1 wherein the ^•contaminant-free solution is recovered by filtration.

4. The method of claim 1 wherein the recovered contaminant-free solution is employed as at least part of the feedstock in a bulk suspension or bulk continuous process for farming polystyrene frcm styrene.