Polymer Recycling Technology for Food-Use ... - ACS Publications

Chapter 39

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 16, 2018 | https://pubs.acs.org Publication Date: May 5, 1995 | doi: 10.1021/bk-1995-0609.ch039

Polymer Recycling Technology for Food-Use Technical Requirements To Meet Safety and Quality Assurance L. D. Tacito Plastics Forming Systems, Inc., 850 East Industrial Park Drive, Manchester, NH 03109

The ability to produce recycle polymers for Food-Use is very confusing to the average package designer/manufacturer. The primary issue after price is quality. This has been addressed primarilyfromthe food safety perspective and not from the quality as it relates toflavorand taste. It is generally accepted, that if quality requirements are satisfied, then the material safety data will also meet the requirements. This paper is directed toward the technology required to produce recycled polymers that met the safety and quality assurance needed to satisfy the consumer product companies. We will be discussing the specific areas of: 1) 2) 3)

Supply feedstock continuity and handling Process Instrumentation and Control Strategy Migration testing for Indirect Food Additives

The basic premise of the technology is to provide Good Manufacturing Practices (GMP) with the ability to have systems in place controlling the critical parameters. These will be addressed in the following area: 1) 2) 3) 4)

Statistical Automatic Sampling Detection, Measurement and Control of Process and Quality Recycling Process Control (SPC/ISO 9000) Food Container Manufacturing

Various known contaminates required by both Government and Industry testing, need to be correlated to "Real World Data" for both safety and quality of the food products.

0097-6156/95/0609-0488$12.00/0 © 1995 American Chemical Society Rader et al.; Plastics, Rubber, and Paper Recycling ACS Symposium Series; American Chemical Society: Washington, DC, 1995.

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Polymer Recycling Technology for Food-Use Requirements

We will present the technology currently produced by the recycling industry in Automatic Sortation, Cleaning Processes, Quality AssurancefromLot to Lot.


Environmental Roots The environmental issues were the initial starting point of interest in recovering the polymers used in producing food and beverage packaging. The litter issue created the first in a series of legislative actions that gave birth to deposit bills or bottle bills. This was the controlled means of guaranteeing the consumer a path to recover the waste that ended up by the side of the road. Along with the plastic bottles were aluminum cans, glass bottles and the cardboard boxes and plastic bags to collect these returned containers. As time progressed, the interest expanded into the landfill issues of running out of space and creating leach fields of toxic chemical wastes. The outgrowth was more legislation that focused on the domestic and industrial waste. The target of 25% reduction by 1995 was established by the EPA and shortly thereafter industry and government were in the Trash Business. Commercial Interests The industry with the greatest interest was the consumer driven entities such as beverage and food manufacturers and the retail distribution outlets. Also, the collection and trash haulers became interested in the commercial aspects of landfill costs rising to higher and higher levels. As with all secondary materials recovered from the scrap piles, entrepreneurs and large companies alike looked long and hard at the profitability of such an investment. Commodity material values are established in the marketplace and will fluctuate with supply and demand. Plastic waste is in its infancy and will grow as the supply, technology and markets develop. PET and HDPE However, the primary polymer materials being recovered are PET (#7) and HDPE (#2). Soda bottles and milk bottles were thefirstto be identified by the consumer, collectors and recyclers. Many programs are underway to increase the types of materials being collected but this is an oscillating process of environmental and commercial reality. PET bottle recycling is a maturing business opportunity because the primary resin producers and packaging converters arefindingboth the consumer demand and the recovery system are very profitable. HDPE is growing also for the same reason, but is not as rapid in its secondary applications for food use due to source control and migration issues. The other polymer materials are finding it difficult to compete with PET and HDPE and are needing a strategy to maintain and grow their applications in the largest markets such as packaging and durable goods. Plastics recycling other than PET and HDPE are competing with other materials perceived to be more recyclable as well. The key to the future markets will be to reduce the cost while creating less waste.

Rader et al.; Plastics, Rubber, and Paper Recycling ACS Symposium Series; American Chemical Society: Washington, DC, 1995.

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PLASTICS, RUBBER, AND PAPER RECYCLING

RECYCLE PET PACKAGING


History of Commercial Processing Having been involved in the R & D of the polymer and processes, we were very involved in the strategy dating back to the mid-seventies where all of the technology and market development began. The first major effort to establish a process to produce a combined food and beverage package was Monsanto's CycleSafe Bottle. In 1975 this package was commercialized in New England, Midwest and Mid-Atlantic States until the FDA ruling on the migration of acrylonitrile stopped the production of the package. Research was being conducted to produce new bottles from the recovered polymer but was never implemented because of the shut down of the production operations. Soon after, the birth of the PET bottle was launched. By 1980, this new rigid packaging material was being produced nationally and the soft drink industry has never been the same. Simultaneously, the deposit legislation caused the industry to collect the used beverage containers (UBC) and the existing PET polyester material market had a new raw material source.

Continental Can Company (CCC) and Owens-Illinois (OI) were the two primary producers but found the maturity of the business and the subsequent profit margin were not acceptable and sold their operations. Hoover and Sewell Packaging who are Johnson Controls and Constar respectively became the two non-



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captive suppliers in the US. Coke (CCE) and Pepsi (PPB) formed their selfmanufacturing companies who today are Southeastern/ Western Container and Brunswick Container respectively. Continental Can sold their PET business to ACI Australia and are now Continental PET Technologies (CPT). The foundation of this industry was developed by these companies and the future growth of many new players worldwide is creating an industry comparable to metal and glass packaging. In the early nineties, the demand for Recycle Content gave birth to technologies to produce secondary polymers for packaging. The PET fiber business was the only large market for the material.

Wellman, DuPont and St. Jude Polymers were the only three (3) producers who were buying the materials from the deposit state collection systems. Soon after the market started to grow. By the mid to late 1980's a number of PET recyclers started to emerge. But it was not until early 1990 the market needed FDA approved packages madefromrecycled material. The resin producers were the first (See Table III) to produce a polymer from repolymerized feed stocks. The market for non-food packaging applications was developing through producers such as Day Products (currently owned by Wellman). The next year technical breakthrough was produced by ACI Australia when they produced an FDA approved beverage bottle using the CPT technology of multilayer bottles. This functional barrier approach was considered the option to the higher priced repolymerized resin but could only be produced under license to CPT. CPT also produced multilayer packages without recycle content in the US for products such as juice, ketchup, etc. With the recent approval of direct food contact of source controlled materials, JCI has introduced another possibility to produce Food Grade Recycled PET. It is somewhat uncertain as to the effect of source control and process efficacy on the acceptance by all consumer product companies. Technology will continue to advance as mentioned later in this paper.


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Future Recycled PET Packaging


Most of the existing recyclers in the US are preparing for global expansion. The ability to recycle other polymers with PET will become increasingly important especially if curbside collection systems expect to grow the fastest. Polymer recycling will need continued R & D for the higher quality applications such as food use. The tremendous growth in PET packaging will be exciting to all of the world markets (See Table IV). By the year 2000, the market will have doubled in size from 1995 estimates. This means the growth of resin and recycled resin will be approximately 4,000,000 tons or 8 billion pounds per year. If 25% of this packaging is recovered, a potential of 2 billion pounds per year of Recycled Polymer could be used in secondary markets. FOOD PACKAGING AND QUALITY REQUIREMENTS The federal regulations define the food product type and the conditions of use the polymer must be able to certify compliance. The typical migration data generated was produced by contaminating the recycled material and subsequently by processing into an article. The article is tested with the specific solvents simulating types of foods and beverages. From the quality assurance systems, the raw material certification and cleaning process control parameters can be set-up to certify the finished product is safe for food use. The consumer product company sets the package specifications and direct the supplier to meet performance and taste requirements. The alternative choices for recycled PET are developing from: 1) 2) 3)

Repolymerized Materials Functional Barrier Layers Direct Contact/Superclean Materials

The depolymerization and multilayer functional barriers are well proven and accepted methods by both the government and industry. The direct food contact is still not completely accepted due to the inability to guarantee the source control and process control to be completely "air tight". Source Control The typical plastic recycling facility has multiple sources of supplyfromloose bottles to baled bottles to ground flake. The materials have incoming inspection to test for various quality standards. Supply systems are monitored and analyzed. Failure to meet specifications will cause the supplier to be rated accordingly and possibly disqualified.


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The materials are manually and automatically sorted to separate the specific polymersfromthe non-polymer contaminates. The material is constantly monitored for levels of contaminants and non-compliance to specifications. The granulated material is stored in lots for feeding and cleaning process. The dirty flake data base allows the raw material to be certified prior to processing. The process and quality information is necessary to define the individual unit operations for the recycle process (See Figure 1). Another element of the PET source control is the deposit collection system versus the curbside collection system. The specific handling techniques of bottle deposit system inherently produces a less contaminated material with overall better quality. The curbside bottles produce a wider range of Non-PET contaminants which must be sorted in the process. Technology continues to progress in both the sensing/detection and separation technologies for removing these various polymer and non-polymer contaminates. A number of technologies are available for detection of compounds which the FDA consider part of the source control strategy. In order to produce a feedstock from recycled containers the non-compliant polymers and additives need to be quantified and controlled using Good Manufacturing Practices (GMP). Studies confirming the incidences of contamination will help to support the acceptance of recycled containers "actually received" in the system. The statisticsfromthese real world surveys will reinforce the requirements for purity to produce containers for Food-Use. Process Efficacy This is the capability of the process to prepare these materials for the condition under which the packaging is intended for use. The FDA breaks down some of these conditions to the types of food and beverage, the time and temperature of service and the packaging structures. The Points to Consider and Guidelines for the Safe Use of Recycled Plastics are two good sources to better understand these basic principles other than the Federal Regulations themselves. Process and Quality management technology helps insure food grade requirements and it achieves and maintains quality specifications. Quality assurance systems for food and beverage applications of post consumer polymers are essential. The chain of manufacturers needs to be coupled to the source. In other words, the 1) Food and Beverage Manufacturers need to certify the quality of the package manufacturer, the 2) Package Manufacturer needs to certify the raw material manufacturer and the 3) Raw Material Manufacturer needs to certify the source of the feedstocks. With the strong implementation of a Quality Assurance Database, corrective action and employee training reduces the risk to an acceptable level for the Consumer Product Companies and Government Regulations. The Polymer Recycling industry continues to mature with some of the processing technologies used to achieve and maintain the purity levels being: 1) 2)

Automatic Sortation and Granulation with sophisticated detection systems Cleaning Processes with SPC/ISO 9000 at critical points in the process.



Figure 1. Process and quality information flowsheet: recycle process.

CCP„ - Critical Control Parameters


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3) 4)


Automatic sampling techniques to improve the SQC of the unit operations. Additional Process Controls on the package manufacturing to insure safety and quality.

These advanced instrumentation's and control strategies for both standard processing as well as proprietary processing are key to the overall acceptance of recycled polymers. Much like the HACCPP concepts for food safety on the product, these same basic techniques will also apply to the packaging manufacturers. Whether it is virgin or recycled materials, the process capability will depend on well engineered, well controlled processing facilities. The ability to apply these techniques to the recycle facility will be discussed in more detail. In summary, the processing efficacy will depend on: 1) 2) 3)

On-Line Process Monitoring Closed Loop Process Controls Material Quality Certification

Migration Testing The detailed analytical science of migration testing will be covered by other authors in this publication. The objective in this section will be to explain how an engineer interprets this theory and data, then, applies it to commercialization of the recycling technology. The most well known article published is Begley and Hollifield which states, "when recycled polymers are used in packaging, the possibility that toxic contaminates may migrate into the food must be determined". This led to the

Figure 2. Predicted migration from a single layer package.



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Polymer Recycling Technology for Food-Use Requirements 497

prediction model which compares monolayer to multilayer theory. Continental PET Technologies designed a packaging system to meet these predictions then tested it. It was also coupled to the "Points to Consider" when the Dietary Exposure Concentrations of specific volatile and solid surrogate contaminates was estimated in the recycled materials. These levels were purposely placed in both the monolayer and the multilayer to determine migration. The functional barrier proved to work very well and is commercially acceptable to both the FDA and consumer product companies. There appears to be data and psychological barriers to direct contact with the product. Recycled material is sandwiched between two virgin layers to ensure and maintain the function barrier layer. The predicted migration values for the single layer and two layer structures are proving to be a good estimate of the acceptable levels of contaminates in the recycled layer.

Figure 3. Predicted migration from a two layer package. As you can seefromthese figures, there is an order of magnitude for the contaminate level in the food verses the concentration in the recycled polymer. More recently, the approach to reduce the amount of specific surrogate through thermal processing has resulted in the JCI Non-Objection letter. Again, this will be a new approach to reducing the level of contaminates verses assuming the contamination making it through either the repolymerized or functional barrier layer processes. In the direct food contact by JCI, the responsibility is on the material producer and the package producer, as well as the consumer product company to ensure and maintain the maximum dietary concentration level. The current incidences of contamination reported will also help to define the statistical risk involved with direct food contact. As previously mention, the process


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efficiency to detect and control these incidences will be even more important to the polymer recycling technology. POLYMER RECYCLING TECHNOLOGY


Separation Technology This specific area has been growing the fastest. Both whole bottle sortation and granulated flake separation techniques have advanced to a significant level where curbside sources of material are now acceptable for recycling into food use. Continuing evaluation and R & D will improve the equipment technology as well as the process capability to produce more purified streams of material. These unit operations are not restricted to either the dry process or to the wet process, therefore, a wide range of options can be engineered into the process. The least cost and highest quality material options are open to the collection system, cleaning system or packaging manufacturing system as long as the process efficacy can be ensured and maintained. The ability to have Processing and Quality Systems in place and controlling is the next generation of technology to produce high quality material for food-use applications. Cleaning Process Technology Once the material has been tested and prepared for the washing operation, the process allows for the material to separate specific contaminates in the solid form and also penetrate, remove andrinseclean of dissolved solids and suspended solids. Depending on the specific end use, the unit operations can have multiple prewash, wash, separation,rinseand drying steps. The feedstock will determine the necessary process design required to meet the end-use. Food use is the most stringent! The cleaning process requires preparation of the cleaning solutions and the continuous monitoring and adjustment of the chemistry. This has to be accomplished while removing the contamination from the cleaning solutions and recovering the water and chemicals. This balance of wash chemistry needs to consider contents of the post consumer containers as well as the components of the container (such as labels, adhesives, inks, other polymer materials) The basic principles of separation employ known and modified technologiesfromthe refining processes associated with paper, glass, metal, and polymer industries. The systems integration of these technologies has been an evolution and the ultimate challenge has been the various raw materials and developing markets. The process development has proven to be exciting and rewarding. This aspect has turned the trash business into a high-tech business. The emerging technologies fall into a couple of areas. The first is the dry purification of bottles and clean flake. The ability to detect and separate these contaminates we are now capable of operating at 95% efficiency. The second area is the cleaning processes based on statistical process controls (SPC) and ISO-9000



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criteria to monitor on-line/off-line data and implementation of closed-loop controls. Computer Integrated Manufacturing (CIM) allows for a tremendous capability for all aspects of the recycling and container manufacturing facilities. This method of process and quality management technology is designed not only to feedback information and control but also to achieve and maintain Process and Quality specifications and certification of Lot to Lot through GMP. Process and quality management technology is the application of these principles to the specific data. The (WAN) Wide Area Network and (LAN) Local Area Network now allow plant wide and enterprise wide networking to ensure the information is secured and maintained for specific users. Specific applications of the technology to the Packaging Industry are: 1) 2) 3) 4) 5)

Incoming Raw Material Inspection and Certification Process and Quality Monitoring of both on-line data and off-line data into a single sophisticated data base. Integrated Database serves countless reporting functions Computer System provides product quality and Lot to Lot certification. Provides Plant Wide applications for: a) b) c) d)

Supervisory Control QC Lab Engineering/Development Management

The key to Good Manufacturing Practice (GMP) is good people and good data. The ability to measure and control the process will grow into a multitude of Packaging, Food and Beverage Applications. CONCLUSIONS The basic conclusion we have reached is recycled polymers will be driven by cost reduction in the raw material. This is a well developed business in the paper, metal and glass industries. The margin between primary and secondary materials may grow or shrink but it will always maintain a minimum value for collection and a maximum value below virgin. The supply is currently limiting the market growth but as with the commodities, it will cycle as the material value changes. Research and Development will continue to change the technology but economies of scale and vertical integration will determine the few players for each market. Packaging dominates the recycled material business because necessity caused the recovery process to be integrated into the metal, paper and glass packaging business. We see the market developing in a similar manner with regional growth coming when economics drive the value and subsequently the investment. Environmental issues will remain cyclical and important to the manufacturers, distributors, consumers and the raw material suppliers.


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LITERATURE CITED 1) 2)


3)

4) 5) 6) 7)

USFDA, "Points to Consider for the Use of Recycled Plastics in Food Packaging: Chemistry Considerations". Begley, T. H., Hollifield, HC, "Recycled Polymers in Food Packaging: Migration Considerations". Plastics Recycling Task Force, National Food Processors Association, The Society of the Plastics Industry, Inc. "Guidelines for the Safe Use of Recycled Plastics for Food Packaging Applications". Thorsheim, H. R., Ph.D., "Recycled Plastic in Food Contact Applications: The View from the Food and Drug Administration". Sadler, G.D., IIT/NCFST, "Recycled PET for Food Contact: Current Status of Research Required for Regulatory Review". KomolPrasert, V., Lawson, A., USFDA/NCFST, "Residual Contaminants in Recycled PET-Effects of Washing and Drying". Code of Federal Regulations, Indirect Food Additives: 21CFR175.300

RECEIVED September 22, 1995


Polymer Recycling Technology for Food-Use ... - ACS Publications

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