bus iness

ADHESIVES Technology remains major component for success for companies in a highly diverse, competitive industry

Paige Marie Morse C&EN Houston

Any industry that includes the basic glue used in most classrooms, the { high-performance structural ce­

ment used in aircraft, and the adhesive that holds the label on a shampoo bottle must be considered complex and varied. The obvious similarity of adhesive prod­ucts is that they hold two surfaces to­gether. After that, the differences seem to overwhelm most general statements about the industry.

"The adhesives industry is very di­verse," says Roger Lohman, senior part­ner at the consultant group ChemQuest, Cincinnati. "It affects nearly every indus­try using every type of substrate with ev­ery type of bonding material. Most peo­ple do not even realize that there are so many applications for adhesives."

The total annual growth of the adhe­sives market is slightly above that for gross domestic product (GDP), but this broad view hides pockets of high growth that offer significant opportunities for companies and chemical products that can deliver high performance. For exam­ple, the demand for pressure-sensitive adhesives in various end uses continues to grow at multiples of GDP, as they dis­place mechanical fasteners and various labeling methods.

"If you look at adhesives as an aggre­gate, you lose sight of higher growth sub-segments," says David Bloom, market manager for adhesives in the polymer

chemical division at Air Products & Chemicals. "There are definitely subseg-ments that can be accessed via a new technology or a special service."

The chemicals used for adhesives are not restricted to a single type. Most ma­jor chemical groups are required be­cause the variety of surfaces to be stuck together, often called substrates, requires that basic properties like polarity, viscos­ity, and molecular weight be modified to form strong bonds with the surfaces. Also, application methods vary from sol­vent-borne to waterborne to 100% solid systems, called hot-melt adhesives.

Natural products, such as starch and dextrin, continue to have a role in this industry, primarily in the packaging seg­ment. About one-third of the volume, or nearly 4 billion lb, of adhesives con­sumed in 1996 was based on natural products, according to the market re­search firm Freedonia Group, Cleveland. The remaining 8.5 billion lb of adhesives were based on synthetic polymers, a vol­ume that is growing as synthetic sub­strates become more prevalent.

The adhesives industry is highly com­petitive, with more than 500 companies vying for a piece of an $8 billion business in the U.S. These companies include a mix of chemical, formulating, and consumer products companies, each viewing the in­dustry from a different perspective. Specif­ic sales information for most companies is seldom provided because adhesives repre­sent only part of their businesses.

For a chemical company—like Air Products, Hercules, or Dow Chemical—the adhesives in­dustry is one of many out­lets for their monomers, polymer products, and addi­tives, which their customers formulate to serve a particu­lar end use.

Ato Findley, the Wauwatosa, Wis.-based adhesives unit of France's Elf Ato-chem, is a formulating company that pur­chases various chemical products to pre­pare formulations for specific applications. The rate of change and performance de­mands of its markets requires that Ato Findley work closely with its suppliers to develop new products and ensure a se­cure supply of raw materials.

Both Morton International and National Starch & Chemical make some of the base polymers for their own formulations, but they also purchase many others to make a wide range of products for various adhe­sives end uses.

Pasadena, Calif-based Avery Denni-son, a leader in the U.S. pressure-sensi­tive adhesive market, participates in ad­hesives at several levels. The company makes acrylic polymers for internal and merchant market consumption, formu­lates many adhesive products based on broad chemistries, and even supplies some consumer products.

The adhesives industry has also be­come increasingly global, like many oth­er segments in the chemical industry. Much of the consolidation that has oc­curred in recent years has been by large multinational companies buying smaller local companies to increase their geo­graphic base. Recent examples in the U.S. include the acquisition of Loctite by Germany's Henkel; the purchase of Na­tional Starch by the U.K.'s ICI from Uni­lever; and Elf Atochem's purchase of Findley Adhesives. Also, U.S.-based H. B. Fuller and National Starch, among others, have been purchasing adhesive compa­nies abroad.

This consolidation on a global basis has increased pressure on raw material suppliers to provide products through­out the world. "The multinational adhe­sive makers are moving to better orches­trate their technical and commercial ac­tivities on a global basis," says Rob Connors, market manager for adhesives, coatings, elastomers, and sealants in the polyurethane business of Dow Chemical. "If they have a technology or chemistry that works for a certain application in one part of the world, they do not want to reinvent it somewhere else. It calls for a supplier to supply globally."

Self-adhesive stamps are a big hit with postal patrons.

Nonwoven applications Page 24 Pressure-sensitive adhesives Page 26 Packaging adhesives Page 30

APRIL 20, 1998 C&EN 2 1

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The variety of companies and the — intense competition between them has created an industry that is fast moving and offers broad and highly differentiated product lines for a sig­nificant number of end uses.

To illustrate some of the com­plexity, consider the variety of adhe­sives in a typical office. The notice­able products include standard trans­parent tape and labels, made from a pressure-sensitive adhesive of natu­ral rubber or an acrylic emulsion; ba­sic glue, which is an aqueous solu­tion of polyvinyl alcohol; and fast-drying glue, made with a base of cyanoacrylates. There are also sever­al less obvious adhesives in use—in­cluding styrene-butadiene rubber (SBR) latex emulsions to bind car­pet, solvent-based SBR products to adhere floor and ceiling tiles, and water-based phenol- and urea-formalde­hyde resins to laminate wood and parti-cleboard for furniture.

This diversity of products and, there­fore, chemistries creates a significant challenge for the adhesive chemist. This is a formulating business, where several different chemical products are chemi­cally and/or physically combined to make the final adhesives formulation.

"We start with the base polymer," says Leonard J. Berlik, executive vice president for adhesives at National Starch, "then the additives, the rheology, and so on. We pull all the levers we have in our technology tool box to solve an adhesive problem."

One industry observer describes the formulation challenge saying: "The devel­opment of a good adhesive chemist is done much the same way as the develop-

Construction, packaging lead adhesives market

Durable goods

6%

Nondurable goods 11%

Packaging 39%

Industrial products

2%

Household adhesives

& other

Largest group of synthetic adhesives are based on phenolic polymers

Polyurethanes 3%

Synthetic elastomers

15%

Epoxies, polyesters

& other Phenolics

Urea & melamine 19%

1996 U.S.demand: Source: Freedonia Group

8.47 billion lb

Construction 40%

1996 U.S. demand3 = 12.31 billion lb a Includes synthetic and natural adhesives. Source: Freedonia Group

ment of a good musician, sculptor, or writer: Learn the basics and then prac­tice, practice, practice."

But even if a company practices well, it must be sure of its focus for product performance. In this highly fragmented market, most companies agree that suc­cess is tightly linked to maintaining strong relationships with customers and focusing on specific markets.

"We must stay close to the customer," agrees Berlik, "and respond to their ever-changing requirements. A successful ad­hesives company is one that can do this at all of the levels of the adhesives mar­ket—local, regional, and global."

Lynne Galligan, chief technology offi­cer at Avery Dennison, adds that technolo­gy is an important component. "We have 88 divisions in our company. Each is fast

on its feet and close to the market, so — we can get customer needs quickly

identified and adapt our technology systems to meet them."

"Adhesives is a core market for us," says James Fuerholzer, group vice president of Morton Adhesives & Specialty Chemicals, Chicago. "We do a lot of research to look at new com­pounds and new materials that can be turned into adhesives."

Technology is key to achieving the balance between customer re­quirements and the basic financial needs of an adhesive company, says National Starch's Berlik. "The main challenge in this market is to help customers lower costs and improve quality in a way that is profitable for our company and that has a strong technology component."^

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APRIL 20, 1998 C&EN 23

business-adhesives .

bus iness—adhes ives

Competition stiff in adhesives for nonwovens

The niche market of adhesives for nonwoven products is highly de­manding, both in terms of technolo­

gy and scope. It is dominated by three major adhesive companies—Ato Findley, H. B. Fuller, and National Starch & Chem­ical—that meet each other in market­places throughout the world. The com­petition among these companies is tight because their customers, many of which are also global, continually update and change their products and demand great­er performance from the adhesives that are required.

Adhesives for this market are used to hold together several layers of synthetic materials for such disposable consumer products as baby diapers, feminine nap­kins, and adult incontinence products. These adhesives—which are high-perfor­mance hot-melt adhesives—are flexible, solvent-free, and applied at elevated tem­perature, usually by spraying the adhe­sive onto the substrate. Styrene block co­polymers, with butadiene or isoprene polymers as the second block, and tacki-fier resins are the primary components of most of these adhesives. Some less de­manding applications, such as disposable surgical gowns, use ethylene vinyl ace­tate polymers.

The U.S. market is moderate in size, consuming 256 million lb of adhesives in 1996, or less than 20% of the larger nondu­rable goods market segment, and is grow­ing at 4% per year, according to market re­search firm Freedonia Group, Cleveland. H. B. Fuller values the current worldwide market at $300 million.

Although the volume may not be great, the high performance suggests that the margins can be. "Nonwoven producers want extremely consistent performance from their adhesives," says Roger Lohman, senior partner at the Cincinnati-based con­sultant group ChemQuest, "and they are willing to pay for it."

However, achieving that consistent performance from an adhesive is not an easy process, especially when customers are continually changing the features of their products.

"The maturing of the diaper and fem­inine napkin market requires that our customers innovate just to maintain their

market share," says Locke Scripps, direc­tor of nonwoven business development for Ato Findley, a Wauwatosa, Wis.-based unit of France's Elf Atochem. "The more rapidly they can bring a new product to market, the better chance they have to gain market share. That pressure comes back to us to be able to respond quickly to their requirements in adhesives."

Leonard J. Berlik, National Starch's ex­ecutive vice president for adhesives, adds that these product changes can lead to growth for the adhesives.

"There is good growth in nonwovens because it has a very strong innovation thrust involving a new feature for the dis­posable article. Often those new features require adhesives," he says.

A recent example of a new feature on a nonwoven product is the use of reseal-able hook-and-loop fasteners as the closure for baby diapers. This change has reduced the need for pressure-sensitive adhesives in this market—which are used to make the displaced sticky tape closures—but has increased the need for nonwoven ad­hesives that are required to attach the hook-and-loop closure parts.

The emerging economies of South America and Asia, with increasing demand for consumer products, represent a signifi­cant new and growing opportunity for nonwoven producers and their adhesives suppliers. Most participants estimate the

Most adhesives for nonwoven products are styrenic block copolymers

Other 15%

Ethylene vinyl

acetates 28%

1996 U.S. demand:

Source: Freedonia Group

Styrenic block copolymers

57%

256 million lb

growth potential for nonwoven adhesives at 10 to 15% per year. Compared with the more mature markets of the U.S., Western Europe, and Japan—where market pene­tration of disposable diapers is estimated at 90 to 95%—developing regions of the world have no greater than 40% penetra­tion. And many nations, including China, are at less than 10%.

When operating in these global mar­kets, adhesive suppliers must be sure that the products required by customers, the nonwoven producers, are available everywhere their customers manufac­ture. That means following their custom­ers around the globe. "The nonwoven market is truly global," says Berlik, "with global customers, global suppliers, and global competitors."

Shell Chemicals is the primary suppli­er of styrene block copolymers for non-woven adhesives, sold under the Kraton product name. High strength, low viscos­ity, and good heat stability are the major attributes of these polymers. Also, they are compatible with a variety of tackifi-ers, oils, and plasticizers, which are often used when formulating these adhesives.

Synthetic tackifier resins are low mo­lecular weight hydrocarbon oligomers used to modify the flow characteristics of an adhesive. In most adhesive formula­tions, these resins are used as low- to mod­erate-level additives compared with the base polymer. However, the performance demands of nonwoven adhesives requires that more tackifier than polymer be used.

"Nonwoven adhesives are fairly so­phisticated products," says Ruth T. Nor­man, director of resins marketing at Her­cules, the supplier of Regalyte tackifier resins. "The high-speed processing and

the spray application requires a cer-— tain flow profile of the adhesive, so

that it sprays well and then solidifies quickly," she explains.

Tackifier resins based on wood products, such as rosin esters and terpenes, can also be used for non-woven adhesives. They cost less than the synthetic materials, but their use in this market is limited because of the preference for low odor and min­imal color.

Another consideration in the selec­tion of raw materials for this applica­tion is that the adhesive must meet veiy demanding safety requirements. "The challenge is in the application it­self, and how it is related to human health," says National Starch's Berlik. "The products must be suitable for contact with skin."

24 APRIL 20, 1998 C&EN

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There was a time when a discussion of pressure-sensitive adhesives was synonymous with the tape and label

end-use markets. However, these relatively simple products, which are applied to sur­faces with light pressure, now have ex­panded to applications that include pack­aging, medical products, decorative lami­nates, and nonslip pads for stairways and flooring.

Movement into these new markets is possible because of recent advances in ad­hesives formulating and processing that have lowered their cost and increased the variety of substrates that can be used with them. Paper has been the dominant sub­strate, but now various polymer films, me­tallic foils, foams, and nonwoven products are used with pressure-sensitive adhesives. In most cases, the convenience of these new products has been readily accepted by manufacturers and consumers.

A recent example of a successful new consumer product is the self-adhesive post­age stamp. Avery Dennison, a major adhe­sive supplier based in Pasadena, Calif., has

sure-sensitive adhesive, meaning that it sticks to surfaces with only light pressure. As the nonwoven products are quickly as­sembled and moved through the equip­ment, the initial tack of the adhesives holds them together until the adhesives are able to fully cool and provide a strong bond.

With the many factors that must be in­cluded in the development of these prod­ucts and the high reliability required, only a few companies can fully address these requirements. And the reputation of the major adhesive suppliers in this market help these companies maintain their posi­tions. ChemQuest's Lohman estimates that these three companies—Ato Findley, H. B. Fuller, and National Starch—supply more than 95% of the global market.

"All three companies have demonstrat­ed the ability to meet the performance tar­gets of this market and to keep the pro­duction lines running," says Scripps. "That, combined with the safety factors and the very demanding product develop­ment requirements, tends to keep the smaller companies out."^

been working with the U.S. Postal Ser­vice since the early 1970s to develop this product. Full-scale production of the stamps began in 1992. By 1997, more than 80% of the 40 billion postage stamps sold in the U.S. were self-adhesive.

The Rauch Guide to the U.S. Adhesives & Sealants Industry, published in June 1996 by Impact Marketing Consultants, Manches­ter Center, Vt., provides a thorough, albeit dated, review of this prcxluct area. It esti­mates growth of pressure-sensitive adlie-

The label on a Duracell PowerCheck battery has 15 layers, each with a different function.

sives at 10 to 12% per year and includes the end uses of tapes, which are 30% of the product use; labels, at 26%; medical prod­ucts, 17%; with the remaining 27% in vari­ous end uses, including postage stamps. The Rauch Guide sets 1995 U.S. demand for pressure-sensitive adhesives at 850 million lb, with a value of $9(X) million.

Market research firm Freedonia Group, Cleveland, estimates a smaller annual growth rate of almost 5%, but considers only the tape and label segments in its 1997 adhesives study.

Avery Dennison expects annual growth at two to three times gross domestic pnxl-uct for these materials in the developed markets of the U.S., Western Europe, and Japan. In the emerging markets of South America and Asia, growth is expected to be twice that rate. Tliese estimates look be­yond the tape and label markets to include packaging, laminates for decorative appli­cations, and adhesive bandages. Avery's 1997 sales for its pressure-sensitive adhe­sives and materials division was $1.7 bil­lion worldwide.

Many products made with pressure-sensitive adhesives seem simple, often be­cause the products are so easy to use. This convenience hides complicated technical challenges for producers. A typical adhe­sive has three components: the face stock, which is the paper or film substrate that is held by the adhesive; the adhesive; and a release paper that is removed by the user.

As with most adhesive systems, the components of pressure-sensitive adhe­sives vary depending on the substrate and the application. Common polymers in the adhesives include natural and synthetic rubber—including styrene block copoly­mers and butyl rubber—and acrylic sys­tems that are formulated for a specific use.

Rubber-based polymers are typically blended with tackifier resins, oils, and an­tioxidants and are used for less demanding applications. Tliese products have limited high temperature stability and poor sol­vent and acid resistance, but they have good tack (stickiness).

Acrylic polymers offer much better chemical resistance but are more expensive than the rubber systems. When used with­out additives, tliese polymers are stiff and have pcx)r tack. The addition of tackifier resins increases their stickiness and adhe­sion but also reduces chemical resistance.

Air Products & Chemicals prepares for­mulated adhesives for the pressure-sen­sitive segment. The company makes for­mulated products for pressure-sensitive la­bels only, preferring to supply polymers and additives separately for other end-use

Pressure-sensitive adhesives on the move

2 6 APRIL 20, 1998 C&EN

business—adhes ives

Mechanical bonding offers a possible alternative to chemical adhesives for non-wovens. These types of bonds—which are made using ultrasonics, high pressure, and/or high temperature—are used in a few limited applications.

"Mechanical bonding requires that you have two materials that melt at or near the same temperature," says Ato Findley's Scripps. "And you have to be very careful in processing that you do not make holes when you melt the materials together."

Performance, in terms of quality and consistency, is fundamental for adhesives used in the nonwoven market. Although the adhesive is a relatively small part of the final product, representing only a few per­cent of the total cost, its failure leads to poor product performance and often caus­es costly downtime for the manufacturing equipment.

One recent product improvement in this market that aids the manufacturer is increased tack, or stickiness, in the adhe­sive to allow for increased speeds in the production line. In effect, the increase in tack makes an adhesive behave like a pres-

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business—adhesives

markets. Its product line includes neat acrylic emulsions and complete formula­tions—called coater-ready—for general-purpose, low-temperature, and removable pressure-sensitive labels.

At National Starch & Chemical, a vari­ety of polymers and additives are formulat­ed to develop new opportunities for these adhesives, according to executive vice president for adhesives, Leonard J. Berlik. "Through incremental improvements in shear strength, peel strength, and environ­mental resistance," he says, "we can use pressure-sensitive adhesives in ever more rigorous environments." Berlik cites exteri­or mounting topes for signs on buses as a new application area.

The increased variety of substrates that can be used with pressure-sensitive adhesives has had a significant impact on the product applications. The Rauch Guide reports that in 1995, 60% of the substrates were plastic or other films; 21%, paper; 11%, cloth; and 8%, rubber and metal foil backings.

The label market continues to be im­portant as well as being one that can take advantage of the variety of substrates.

"The fastest growing area for pressure-sen­sitive adhesives is labels," says Ruth T. Norman, director of marketing for the res­ins division of Hercules. "When you think about it, a lot of things have labels on them now that did not in the past."

Clear plastic labels have become more common in recent years. Instead of print­ing directly on a bottle or package, manu­facturers can now apply a label, allowing

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Avery-Dennison worker checks self-adhesive roll materials.

for more elaborate designs on packaging. Also, as regulations require that more information be provided to consumers, la­bels on many products are get­ting larger and, therefore, re­quire more adhesive.

Cost reduction has been a major factor in the increasing use of these adhesives for labels and other applications. "That is what has allowed pressure-sensi­tive adhesives growth to contin­ue," says Lynne Galligan, cliief technology officer at Avery Den-

nlson. "We are now at costs where we can compete with paper labels or glue-applied labels. The glue-applied market is so much larger than pressure-sensitive—there is still plenty of room for growth."

Improvements in the manufacturing process are the primary component in reducing the cost of using pressure-sensi­tive adhesives. These adhesives are usual­ly applied as hot melts, sprayed, or roller coated on the substrate. When the appli­cation of the adhesive can be done fast­er, producing more product on the same equipment, costs are reduced.

The adhesive formulation plays an im­portant function in increasing the produc­tion speed. "When the pressure-sensitive adhesive is applied in the process," com­ments Galligan, "the cure rate and the rhe-ology must be considered to get an even coating."

With continued improvement in the formulating technology and the manufac­turing process, the opportunities for pres­sure-sensitive adhesives will continue to grow. Removable pressure-sensitive prod­ucts are the latest area of development.

The Post-it Notes products from 3M are an example of this technology, which is based on a unique acrylic emulsion. This discover was recognized by the Ameri­can Chemical Society at its recent national meeting in Dallas, with presentation of the ACS Award for Creative Invention to 3M chief scientist Spencer F. Silver (C&EN, Feb. 9, page 42). The first Post-it Note product was introduced in 1980, and 3M now uses this technology for more than 200 products.

"Removable adhesive technology is a growth segment within the pressure-sen­sitive market," says Galligan. "More and more applications are being developed where the ability to stick and then re­move is a useful a t t r ibute/^

2 8 APRIL 20, 1998 C&EN

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Mote than you might expect CIRCLE 20 ON READER SERVICE CARD

but do you know the

whole story?

IS business—adhesives

Packaging adhesives become more flexible

I n the well-developed consumer mar­kets of the U.S. and Western Europe, changes in product packaging have

become a common marketing practice. Brighter colors, shinier surfaces, trans­parent materials, and other flashy tools are often used to encourage consumers to take note of products on crowded shelves. Such tactics in these highly competitive markets frequently translate into increases in the use of adhesives, particularly those based on synthetic materials.

However, advances in product pack­aging have also resulted in greater tech­nical challenges for adhesive makers. As more plastics and mixtures of man-made and natural materials are used for packag­ing, new chemical mixtures and new chemicals must be developed to adhere to these substrate surfaces. Also, increas­ing pressure to reduce solvent use and the inclusion of more recycled material in the substrate have made this task more difficult.

Packaging adhesives represent a large segment of the adhesives market, ac­counting for 39% of the total demand for adhesives in 1996, according to market research firm Freedonia Group, Cleve­land. This segment uses a variety of

chemistries and product forms, including waterborne, hot-melt (100% solid), and solvent-borne products.

More than half of the adhesives used in packaging are based on natural prod­ucts, which is greater than in an}' other segment in the adhesives market. These products are typically dispersed in water and rely on the porosity of the substrate to distribute the adhesive. The dominant substrate in this segment continues to be

Natural materials lead adhesives for packaging

Acrylics Elastomers 2° /o

10% \

Vinyls 19%

Other / 3%

Sodium silicates

3% Starch & dextrin 58%

1996 U.S. demand = 4.84 billion lb

Sources: Freedonia Group

paperboard, which includes paper and cardboard.

Natural product adhesives based on starch, dextrin, and sodium silicates will grow by only 2.5% per year from 1996 to 2001, according to Freedonia. Over the same time period, synthetic adhesives for packaging are predicted to grow 3.4% annually. The number of packages sealed with synthetic adhesives will grow faster, but the increasing efficiency of the adhe­sives means that less is required for an application, so the volume growth will not be as large.

Although natural products are general­ly lower in price than synthetics—close to 20 cents per lb versus acrylics at 66 cents, vinyls at 75 cents, and elastomers at $1.12—processing demands are forcing

the shift to synthetic adhesives for - — many packaging manufacturers.

"Synthetic adhesives are replac­ing natural polymers," says Roger Lohman, senior partner at the Cin­cinnati-based consultant group ChemQuest, "because of the speed and consistency that is required for the manufacturing operation. Some natural products will not set up [make a bond) fast enough for the process."

Variations in the quality and surface coating of paperboard are also facilitating the growth of syn­thetic adhesives. The availability of recycled paper from communi­ty recycling programs means that much more is being used in pack­aging material. This reduced qual-

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30 APRIL 20, 1998 C&EN

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ity substrate is less porous and hard to stick to.

"In the recycled paperboard, there are shorter fibers," according to Ruth T. Norman, director of resins marketing at Hercules. "You need better flow of your adhesive to encapsulate those short fi­bers. Also, building in more tack [sticki­ness] to the formulation can help to ac­count for substrate variability."

In an effort to make flashier paper packaging, the surface of paperboard is of­ten coated with various materials. "Innova­tions in product packaging have led to coated board, which provides enhanced printability and improved shelf stability," notes David Bloom, market manager for adhesives in the polymer chemical divi­sion at Air Products & Chemicals. "These packages are used for everything from cos­metic boxes to frozen food containers. This surface requires a more robust and higher performing adhesive."

Although starches may not be grow­ing as fast as man-made polymers, their use is not declining. National Starch & Chemical makes natural and synthetic polymers, and its executive vice presi­dent for adhesives, Leonard J. Berlik, re­ports that the realization that starches are "natural" has fueled some resurgence of their use. And product development con­tinues: "We have a number of products in the market today based on new starch technology and new natural product technology," Berlik adds.

"Paperboard is still the dominant sub­strate," says Hercules' Norman, "but plas­tics are becoming an issue. You need ad­hesives that are versatile enough to work on a variety of substrates, including the low-surface-tension plastics."

The move to plastic packaging has pushed much of the growth in synthetic adhesives but has also added to their complexity. Most plastic substrates are flexible and demand an adhesive that can bend with the package. Also, some poly­mer substrates can be particularly diffi­cult to adhere to, particularly nonpolar polyolefins.

And often the new substrates are not pure but instead are mixtures of materi­als. "We see many different substrates in packaging," says James Fuerholzer, group vice president at Morton Adhe­sives & Specialty Chemicals, Chicago. "Recent changes include the use of poly­propylene in flexible packaging, metal­lized surfaces—especially metallized polypropylene and polyester to replace aluminum foil—polyester film, and ny­lon film."

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business-—adhesives Hii; Substrate variation is facilitating the

growth of some polymers in this seg­ment. "Polyurethanes have very good ad­hesion to a wide variety of substrates," says Rob Connors, market manager for adhesives, coatings, elastomers, and seal­ants in the polyurethane business at Dow Chemical. "That performance, plus a general trend away from mechanical fas­teners, is contributing to the 6 to 8% an­nual growth that we are expecting for our polyurethane raw materials."

Some water-based polymeric adhe­sives are also being used in the packag­ing market, but they are particularly diffi­cult to use with polymeric substrates. In­creasing the tack of the adhesives is a common approach.

Air Products recently introduced a water-based vinyl acetate ethylene emul­sion that has a very high solid content of 72%, compared with emulsions typically at 50 to 60% solids. Vinyl acetate ethyl­ene polymers are polar materials with good tack and adhesion to many differ­ent substrates.

"Replacing a solvent-based system with a water-based one is not easy," says

Packaging for food products is being made from more flexible synthetic substrates.

Amir Famili, section manager for adhe­sives in the polymers division at Air Prod­ucts. "A solvent swells and dissolves the surface and creates adhesion. Water does not do that."

Cost is an important driver in this market, where the products are used briefly then thrown away by the consum­er. As in other adhesive segments, the adhesive is a small part of total package cost, but it has a major impact on the processing of the final product.

"When you talk about packaging," says National Starch's Berlik, "you think of fast-moving consumer goods, like food. You have a relentless drive from these types of industries to lower their cost, improve their efficiency, and in­crease their production line speeds."

The use of tackifier resins, which modify flow, in the adhesive formulation can increase performance at production speeds. "The higher speed equipment re­quires more reliable adhesives," says Nor­man, "and certain flow properties for the adhesive."

Variety is the standard for packaging adhesives. Substrates vary, processes and conditions vary, as do the perfor­mance demands for the package that the adhesive holds together. This com­bination means that an adhesive suppli­er must be prepared to work with sev­eral different chemistries to achieve the optimum performance, whether with synthetic polymers, natural products, or both.

For the variable packaging market, many of the formulating tools are used to create the most effective adhesive.^

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