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The forecast is cloudy for plastic bottles.

Until recently, tomorrow's packaging technology developments could be predicted from tomorrow's market potential. Blowmolded packaging grew during the past thirty years through an ongoing interaction between technology and market developments. Step by step, blowmolding technology became more sophisticated, and plastic bottles captured new ground. One needed only to look forward for answers to the perennial question, "What's left to be accomplished?"

Now this step-by-step progression has been halted by the solid waste issue, and plastics engineers are being asked to do things that would have been unthinkable at the start of the 1980s. This article seeks answers to the new questions by reassessing some old ideas and applications and developing scenarios for the 1990s.

Three Decades of Change

Progressive steps reflecting the market/technology interplay in blowmolded packaging are outlined in Table 1. In the 1950s, the household chemicals market wanted plastic bottles, and extrusion-blow technology's response ensured growth in the 1960s. In the 1960s, technology for in-plant milk bottle production was developed, and the dairy industry's response led to a mammoth market for HDPE--500 million lbs for blowmolding in the U.S. in 1969.

The technology focus of the 1970s was biaxial orientation. In Europe, market demand for bottles for water and edible oil drove developments for O-PVC. In the U.S., soft-drink-bottle potential first spotlighted polyacrylonitrile (AN) copolymers. AN soft drink bottles arrived in the early 1970s, but went out in 1977 with the U.S. Food and Drug Administration's ban on nitriles for soft drinks. The decade's key year was 1977, when O-PET became the only candidate for soft drink bottles.

There were also high hopes for O-PP bottles made by the Phillips Orbet and Hercules processes. Their heat resistance opened up the medical-irrigation-bottle market. Other applications came and eventually went. At mid-decade, indications that propylene monomer would drop in price relative to ethylene monomer led to speculation that O-PP could compete with HDPE in household chemicals. Because of PVC's problems at the time, O-PP also emerged as a candidate for PVC replacement.

Experimental PVC liquor bottles appeared in 1969 but went out in 1973 when evidence of vinyl chloride monomer (VCM) migration led the U.S. Bureau of Alcohol, Tobacco, and Firearms (BATF) to revoke its authorization. PVC compound suppliers quickly rectified the problem, but the cloud over PVC persisted. The height of the VCM scare saw all kinds of replacement activity. Some edible oil went from PVC to AN--a case of going from the frying pan into the fire! Some baby oil went to polycarbonate, and some mouthwash went to O-PP. It was at this time that Eastman introduced PETG as a PVC replacement.

Some interesting developments in injection-blow also occurred in the 1970s. Because the AN-styrene copolymer (AN/S) grades used offered heat resistance along with a fairly good oxygen barrier, American Can's Tuf-seal[R] containers held promise for food products and noncarbonated beverages. They also went out with the 1977 beverage-bottle ban, and metal and glass replacement became dormant for several years. In 1979 the first custom PET bottles appeared--injection-blown bottles for Scope mouthwash.

The year 1983, the key year of the 1980s, was extraordinary for all the major resins. Some of the events needed no new technology, just market acceptance. HDPE motor oil spouts, which had been available for several years, were adopted by Quaker State, and the whole motor oil industry converted overnight. PVC had long been ready for edible oil, but in 1983 Procter & Gamble (P&G) shifted from glass to PVC, and the whole edible oil industry also converted overnight. This triggered improvements in PVC productivity; not just for oil, but, pending BATF approval, also for liquor.

New technology led to the 1983 introduction of the first barrier coextrusions in the U.S., the PP/EVOH squeezable ketchup bottles with which Heinz scored a marketing coup.

The most important aspect of the 1980s for the plastic bottle business was a climate change. In my view, the edible oil conversion had more significance than the PP/EVOH bottle. Until 1983, all conversions to plastic bottles had been made for specific advantages: economy in very large or small sizes; safety in the bathroom; or squeezability. The edible oil conversion occurred in all sizes, without safety or squeezability as driving forces, and was made by market leader P&G while PVC was still under a regulatory cloud.

Once market leaders such as P&G and Heinz gave plastic bottles such resounding votes of confidence, every food/beverage packer had to at least consider them for all applications. The climate change was furthered by the U.S. Surface Transportation Assistance Act of 1982, which permitted very large trailers but allowed states to set weight limitations. Packers could take advantage of trailer size without exceeding weight limitations by replacing heavy glass with lightweight plastic bottles.

The long-awaited BATF go-ahead for liquor came in 1983, but it was for PET, not PVC. It was becoming apparent that PET would be the premier resin for glass replacement, but in the early 1980s, PET blowmolding technology lagged behind market potential. Needed were more versatile machines, heat resistance, and oxygen-barrier enhancement.

The 1980s brought heat stabilized bottles and a plethora of new machines and applications. By the end of the decade, PET was being used for hot filled, family size fruit drinks and had replaced PVC in most of the edible-oil bottles; the conversion from glass to plastic jars for peanut butter was well under way; and there were many other custom applications. But for more oxygen-sensitive products and for moderately sensitive products in small sizes, better oxygen barrier was still needed.

All in all, the 1980s appear to have been the decade of multilayer structures, though more in theory than in practice. The advent of the wheel-produced coextruded barrier bottle led all shuttle machine manufacturers to offer coex technology, and all sorts of multilayer combinations were proposed; for example, coinjection-stretch-blown PET/PA cans appeared at trade shows. A more subtle aspect of multilayer combinations was that the concept transferred market development power from the resin suppliers to the converters (bottle producers), who could mix and match. The converters also had the power to add heat resistance to PET.

Other important developments in the 1980s included O-PP's reappearance as an option on one-stage injection-stretch-blow machines for food and nonfood applications; clarifiers elevated PP clarity to new heights. For nonfood applications there was HDPE's acquisition of solvent resistance via fluorination, and/or coextrusion, or laminar/nylon technology, and the introduction of standard-size PET aerosols in the UK.

1990s--Old Scenario

At the start of the 1990s, what was left to be accomplished? Replacement of 13 billion glass containers for food and beverages held the greatest potential for new business. Anything seemed possible in the new favorable climate: Packers would be more willing to reformulate and modify filling procedures; resins could be mixed and matched; plastic bottles were freed from the need to be always cheaper than glass; and the drive for inventory reduction lowered shelf-life requirements.

The climate has now changed again, and today's major technology thrusts are responses to the solid waste issue. However, let us consider what might have been accomplished in the 1990s if developments had followed a natural progression (Table 2).

Starting point: For additional food/beverage glass replacement, the market needs glass-clear containers with very good oxygen barrier, often with heat resistance too.

The most significant new bottle in the market today is the coinjection-stretch-blown PET/EVOH squeeze bottle for Heinz ketchup. Is this a natural progression, or a response to the solid waste issue? My guess is that it would have come anyway for marketing reasons.

Heinz was forced to unveil this bottle in early 1990 as a direct response to environmentalists who were telling consumers not to buy Heinz ketchup in what they called nonrecyclable PP/EVOH bottles. At the 1990 Supermarket Show, Heinz revealed that a PET version had been in development for years. All ketchup producers were less than satisfied with the clarity and gloss of the PP/EVOH bottles and were looking for possible replacements. By working with Husky Injection Molding Systems Ltd. and Continental PET Technologies, and lowering the fill temperature, Heinz found a solution. Thus, the new bottle has inherent marketing advantages, but recyclability in the PET stream is an added advantage.

Under normal circumstances, the 1990s would have brought new clear and/or heat-resistant and/or oxygen-barrier containers. This combination is very difficult to achieve in blowmolded bottles at a competitive cost, but some applications don't require all three properties.

Most of the development work would have involved variations of PET, which starts out with clarity and pretty good oxygen barrier. Injection-stretch-blown PET, moreover, offers precise injection molded necks and eliminates possibly unclear multilayer regrind. Heat resistance can be imparted by the blowmolding process, although some methods impart greater heat stability than others.

Oxygen-barrier demands were lowered in the 1980s. At first, the unattainable shelf life of glass was the only standard. Then, the shelf life provided by PP/EVOH became the standard. Ketchup is one of the more oxygen-sensitive foods, and PET cannot handle it alone; but packers found that they didn't always need the high barrier of PP/EVOH bottles.

The new Heinz bottles prove that PET/EVOH is a viable combination, but they raise several interesting questions. Will other producers be able to make such bottles? Coinjection depends on matching melt viscosities, and PET and EVOH do not match well--one reason for the use of nylon MXD6, despite its lower barrier, in other countries.

Heinz does not need heat resistance, so their bottles are not heat stabilized. If these bottles are available to other ketchup producers, will they also lower their fill temperatures? Or will the PET/EVOH bottles be offered in a heat stabilized variety?

Given the problems of multilayer PET in any form and patent protection on heat stabilization processes, bottlemakers and product packers in the 1980s were asking for a monolayer material that would provide better clarity, heat resistance, and oxygen barrier than PET. One answer could be polyethylene 2,6 naphthalene dicarboxylate (PEN). It can offer five times (5X) the oxygen barrier of PET and heat resistance to boiling, but its price would be more than $2/lb. Very few applications warrant such a price. Ketchup packers said they would prefer a 2X barrier at much lower cost.

Some work has been done with organic coatings on PET--first with PVDC, then with EVOH. That activity has been replaced by still-experimental work with inorganic coatings. This raises another interesting question: To what extent can coatings make up for the poor barrier properties of the base material--not just for PET, but also PP and polycarbonate?

When heat resistance is called for, polycarbonate generally comes to mind despite its high cost and poor barrier. Coextruded PC/amorphous nylon has been considered, and PC/EVOH ketchup bottles are on the market in Denmark. The two major PC suppliers have taken different experimental approaches. GE Plastics has been testing PC coextrusions for some time. Mobay is experimenting with injection stretch blowmolding, and in 1990, the company presented results with coinjected PC/polyaliphatic imide copolymers.

Transition--Coexistence of Extremes

The PC/polyaliphatic imide copolymer work is an extreme example of how technology might have evolved in the 1990s--sophisticated blowmolding techniques applied to an ever-widening variety of materials. Today, at the other extreme, resins and bottles are being made from trash; not just off-spec material or floor sweepings, but trash from the municipal dump.

Extremes are clashing now because our basic assumptions are being challenged, and it will take some time to adjust:

* Continuous quality improvement in materials could always be assumed. Now, however, materials worse than traditional junk resins are being used. Another example: HDPE producers have for a long time been fine tuning copolymers for optimal environmental stress crack resistance. Now, at the other extreme, homopolymers are being seriously considered for copolymer applications--an unthinkable situation not very long ago.

* Growth has always been a legitimate goal, and blowmolding success has been reflected in steadily rising resin consumption. Now, however, there is public pressure against packaging growth and for little or no increase in resin consumption.

* Materials proliferation has been a traditional source of new market opportunities. But now, standardization is the byword. The solid-waste community would like to have all plastic bottles made of either HDPE or PET. This raises two issues: Whether any new applications will go to materials other than HDPE and PET, and whether HDPE or PET should or could replace all other blowmolding resins in existing applications.

Low quality resins have always cost less than high quality resins; now they cost more.

Capital investment in multilayer blowmolding is justified by added value in the product; now it's required just to maintain current position.

Now the answers to the new question--"what needs to be done?"--are unprecedented:

* Use less material;

* Incorporate lower quality resins; and

* Make HDPE and PET do everything in blowmolded packaging.

1990s--New Scenario

Use less material Because plastic bottles may be assumed to be already as light as possible, this is relevant to blowmolding only to the extent that packagers replace bottles with lighter weight alternatives such as flexible pouches. Multilayer barrier bottles aid in weight reduction, but this may be lost in the drive for standardization.

Recycled content in bottles. Although the logic of putting recycled resins back into bottles continues to be argued, there is plenty of state and federal legislation brewing that will require it. The required percentage appears to be coming down, but unless resin suppliers make blends widely available, such legislation could cause processors extreme hardship. It could even trigger conversions back to glass, if glass solves its own recycling problems.

Coextrusion is a viable, if costly, solution for continuous-extrusion blowmolders. The resins need further development, but the processing technology is readily available. In years past, one would not have predicted the development of coex capability beyond view striping on reciprocating screw machines, but that capability is available now. It is hard to believe that dairies will ever have to apply coex technology to milk bottles, but that idea must be considered in the new scenario (Table 3).

Without blends, injection blowmolding and injection stretch blowmolding processors will have a hard time complying, at any cost, with legislation regarding recycled content. Here again, the use of coinjection-injection blowmolding for recycled content is hard to imagine, but it must be considered. The demand for recycled content in bottles could hurt the competitive position of injection blowmolding versus extrusion blowmolding at a time when big multicavity machines often tilt the balance in the former's favor.

Make HDPE and PET do everything. U.S. consumption of blowmolding resins in 1990 was about 2.3 and 1.1 billion lbs for HDPE and PET, respectively, versus about 500 million lbs for all other resins. Legislation does not demand the exclusive use of HDPE and PET, but the effect is the same if it favors resins that are collected in recycling programs. Resins that are not collected may also incur advance-disposal fees, and consumers will presumably tend to favor recyclable plastic bottles rather than those sent to the landfill.

U.S. annual PVC bottle-compound consumption is more than 200 million lbs. As noted previously, efforts were made to replace PVC in the 1970s. At that time, many resins were candidates, including O-PP, EBM/PP copolymer, PC, AN, and PETG. Injection-stretch-blown PET was just introduced, and then only for soft drinks. Extrusion-blown PET was discussed, and some patents were issued, but the concept was never taken seriously.

Now, if nonproliferation is the rule, HDPE and PET are the only candidates, although many would argue that PP copolymers are in a far better position to replace PVC than they were in the 1970s. A few PVC applications could be taken by HDPE; for example, high gloss HDPE where opaque PVC is used for high gloss, and fluorinated HDPE where PVC is used for solvent resistance.

However, PET is the prime candidate for PVC replacement, even though it cannot do everything that PVC can. Injection-stretch-blown and injection-blown PET can take some applications, but their drawbacks are tooling costs, somewhat limited capability for odd shapes, and unsuitability for conventional handleware. And PVC bottle producers, with a huge base of installed machinery, have no use for injection-grade resin. For these reasons, extrusion-blown PET is in the spotlight now. Making it suitable to replace PVC for all products, sizes, and shapes will be a major challenge.

Other aspects of extrusion-blown PET are worth considering. Does it have market potential beyond PVC's achievements, e.g., liquor bottles? Will it provide an easier route to barrier enhancement than coinjection? Will satisfying the growing requirements for recycled content in bottles be easier or harder to accomplish with extrusion blowmolding than with injection technologies? Or is a return to extruded-pipe preforms necessary to incorporate recycled material? Today, all questions and answers must be explored.

TABLE 2. Technologies and Markets, 1990s--Old Scenario.
Process Resin, add-on Markets
SB/2/ML PET/EVOH, heat set FB/HF
SB/1,2 PET, inorg. ctg. FB,FB/HF
SB/1,2 PET, handles FB
IE/RS PP Water

* PEN = polyethylene 2,6 naphthalene dicarboxylate. PI = polyaliphatic imide copolymers; HR = heat resistant. See Table 1 for other abbreviations.

TABLE 3. Technologies and Markets, 1990s--New Scenario
Decade Process Resin, add-on Markets Action?
1950s IBM PS MH, TC Replace?
1960s CE PVC All Replace?
 ESB/2 PVC (Europe) -- For PET?
1970s CE PET -- Revive?
 CE PC RR, misc More RR?
 SB AN -- For RR?
 IBM AN/MA IC, AM Replace?
 IBM PVC TC Replace?
 E+SB/2 PP MH Replace?
 E+SB/2 PET (Europe) -- Revive?
1980s CE/ML PP/EVOH FB Replace?
 CE HDPE/PA IC Replace?
 IE/RS SBC Water Replace?
 SB/1 PP FB/HF MH Replace?
1990s SB/2/ML PET/EVOH, heat set FB/HF?
 SB/1, 2 PET, inorg. ctg. FB, FB/HF?
 IE/RS PET Water
 CE/ML PET/RPET* All but SD?
 SB/1/ML PET/RPET Viable?

* RHDPF = recycled HDPF; RPET = recycled PET. See Table 1 for other abbreviations.

TABLE 1. U.S. Technologies and Markets, History. Tabular Data Omitted

Key to abbreviations:

Markets: SD = soft drinks; FB/HF = food/beverage, hot-fill; DY = dairy, TC = toiletries, cosmetics. RR = refill/reuse; MH = medical/health; HC = household chem.; IC = industrial chem.; AM = automotive/marine.

Processes: IBM = injection blowmolding; CE = continuous extrusion; R = rotary; S = Shuttle; IE/RS = intermittent extrusion, reciprocating screw. SB = Stretch blow,/1 = 1-stage, 12 = 2-stage; ML = multilayer; ESB = extrusion-stretch-blow; E+SB/2 = extruded pipe preforms.

Uncommon resins: AN = polyacrylonitrile; AN/S = AN-styrene copolymer; AN/MA = AN-methacrylate copolymer; HD, fluorine = fluorine-treated HDPE; SBC = styrene butadiene copolymer
COPYRIGHT 1992 Society of Plastics Engineers, Inc.
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Author:Bakker, Marilyn
Publication:Plastics Engineering
Date:Jan 1, 1992
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