6

SURFACTANTS & DETERGENTS Home laundry detergents are complex products that blend diverse ingredients. some of which are not readily compatible, to meet consumers' demands for cleaning performance at on acceptable COSI. Here's a review of the challenges that formulators must meet.

Detergents'tumultuous omelaundry detergents have evolved into the complex products of today through a

H

series of changes. Sometimes these

changes have been slow and mcthodi-

Topic

Page number

Surfactants 10 Fabric softeners 10 Builders 15 Bleaches 17 Sodium perborate 30 Enzymes 19 Polymers 20 Fragrances 23 Fluorescent whitening agents 7,38 Other additives 21 Future directions 23 Washing machine design 25

cal, because of gradual advances in technology, and other times they have been abrupt, due to sudden external or internal pressures. Keeping detergent formulations in step with the times has kept many company executives up late at night. One compounding problem is the ever-increasing number of ingredients used in formulations. Today's detergents combine surfactants and builders with additives such as enzymes, polymers. bleaches, fabric softeners, optical brighteners. fragrances. colorants, antifoaming agents, anti redeposition agents, dyetransfer inhibitors, corrosion inhibitors. and processing aids. The mixture of these has changed as processing technology has leapt beyond the venerable spray tower. Concentration efforts affect components' use as well. Add in the funda-

mental differences between liquid and powder detergents, sprinkle with concern over future washing machine changes in the United States, and you have a recipe for hypertension. at least from a formulator's viewpoint. "The period since the Montreux conference in the fall of 1993 has been perhaps one of the most tumultuous that we have ever seen on a global scaJe," says Keith Grime. director of North American laundry product development for Procter & Gamble (P&G). "Detergent formulators have the ability to change formulations more rapidly than they have in the past," says Karin Knapp of Vista Chemicals. "Since the RWE-DEA Chemical Group---which includes Vista in the Americas and CONDEA, DAC, and Enichem Augusta in Europe and Southeast Asia-is now the largest

This section was written by INFORM editor/writer Tom Krawczyk. INFORM. Vol. 7. no. 1 (January 1996)

7

times supplier of detergent ingredients in the world, we must be prepared to offer detergent manufacturers the ingredients they need, when they need it." The industry may have entered a period of relative stability. at least temporarily. "I see more of a continuous evolution rather than any massive changes ahead," says Jesse Lynn, director of fabric products development for Lever Brothers.

"Manufacturers are always looking for ways to improve their product." Last year's line of laundry detergent products placed P&G and Lever Brothers as the leaders in market share. Dial had grown to third place, with Church & Dwight and ColgatePalmolive next in line. "In the United States, laundry detergent usage is approximately 56% powders and 44% liquids," says Janet

Donohue of The Soap and Detergent

Association. "Compacts now represent about 90% of laundry powders and 75% of liquid laundry products." All is subject 10 change, however, based on the current

and future

trends of each specific detergent additive. How the individual ingredients evolve and coexist will have as much Importance as total product design.

Fluorescent whitening agents Optical brighteners, also known as fluorescent whitening agents (FWAs), originated as the cyanuric chloride/diaminostilbene derivative DASC-l. William R. Findley reviews the progression of FWAs in his paper, "Fluorescent whitening agents and detergent industry trends," in this issue of INFORM (page 38). According to Findley, variations of DASC-l rapidly proliferated, as did their use in formulations until the drastic reductions of the 1970s led to an absence of polyester whiteners, few nylon whiteners, and 80% fewer cotton whiteners. FWAs recovered to become a standard additive in formulations, especially with the arrival of "ultra" detergents. Increasing the concentration of detergents, such as raising the level of actives in detergent, generally increases the yellowness of the product and highlights the use of FWAs.

INFORM. Vol. 7. no. 1 (January

1996)

10

SURFACTANTS & DETERGENTS

Surfactants Linear alkyl benzene sulfonate (LAS) has been the surfactant of choice for decades, but has faced a growing number of environmental

questions.

The issue of biodegradability keeps following LAS despite recent evidence of environmental acceptability. Also, scientific studies have suggested that there is lillie difference in terms of biodegradability and toxicity between olcochemicals and petrochemicals as bases for surfacrants. "The biodegradation of LAS has been studied and documented

in hun-

dreds. if not thousands, of publications," says Arne Cahn. president of Arne Cahn Consulting Services. "As long as LAS is environmentally acceptable. there is no reason anyone would move away from it:' adds Paul Sosis, president of Scientific Detergent Research Associates. "Even in Europe, where there is a strong focus on the environment, they know it is the most cost-effective surfactant." The environmental safety of LAS recently received a boost by a study undertaken jointly by the Council of LAB/LAS Environmental Research and P&O. The study examined the effluent from 10 U.S. sewage treatment plants and found only low concentrations of LAS and biodegradation intermedintcs in the rivers and streams that recei ve treated water from the plants. "LAS is still the world's most

I

widely used surfactant-after 30 years of usebecause of its costcompetitiveness, cleaning effectiveness, and proven environmental safety," Knapp says. Regardless, LAS usage in North America declined last year, mostly because of laundry detergent reformulation in 1994 that moved away from linear alkyl benzene (LAB) toward Unear alky1benzene lulfonele: lur1actant workhorA detergent alcohols. The gradual shift from LAS to alcohol-based surand holds the trademark on the factants, including alcohol elhoxylates acronym APG through its research on (AE) and alcohol ether sulfates (AF.S), and production of alkylpolyglucois accompanied by a growing usage of sides. the new sugar-based surfactants, such P&O removed LAS from its leadas alkylpolyglucosides and N-alkyling U.S. brand and added a patented glucosamides. sugar-based surfactant. N-methyl gfuAlkylpolyglucosides comprise an camide, an alkylpolyglucoside analog. entirely new nonionic surfactant famiP&O's new "Ariel Future" formulaly. They can be produced from renewtion in Europe uses this surfactant. able raw materials such as corn starch reportedly produced by Hoechst in and natural fatty alcohols. Germany. Henkel uses "sugar surfactants" in "Glucosamide processing and two of its European detergent brands, applications ure heavily patented by

Fabric softeners Detergent-with-fabric softener formulations have been in decline. displaced by detergents-with-bleach. Consumers have not abandoned fabric softeners, but have returned to using stand-alone rinse-cycle and dryer sheet softeners. "Clay. or bentonite, can be used as a fabric softening agent in powder laundry detergents:' Sosis says. "Cationic quaternary ammonium compounds (quats) are far more commonly used as fabric softeners. Anionic surfactants. however. are incompatible with cationic quats used in detergent formulations." Surfucrants generally interfere with anything deposited on fabric. The better the surfactant, the more it either strips the fabric softener additive ofT the fabric or complexes with the additive in the wash solution. preventing deposition.

INFORM. Vol. 7. no. 1 (January 1996)

11

P&G," Sosis says, "and they are not readily available for everyone else."

Lever uses the anionic primary alcohol sulfate (PAS) in its "New Generation" detergent in Europe. Although PAS receives high marks in biodegradation, it does not lend itself easily to spray drying, so nonlower mixing processes are often used. Another development is the intro-

duction of methyl ester sulfonates (MES), also derived from oleochemieals. MES has advantages of biodegradability, mildness, and tolerance of water hardness. The technology to manufacture MES has been around for decades, but recent advances in processing have led to more economical quality products. MES is used in some Japanese and Korean detergents, but rnosr experts feel that performance and economic limitations will restrict these surfactarns to roles as low-level co-surfactants in the United States.

"MES is a very good anionic surfactant. and can be formulated into any system," says Sosis. "It is based on raw materials readily available in Asia. which is why more MES has been used there. But manufacturing MES is not as straightforward as sulfonating LAB. The process is a little different, and uses some different equipment. Still. the technology is available and the equipment is available. Everything is available to implement production of MES on a wide scale." With the current acceptability of LAS, however, Sosis feels the allure of current equipment is too great: "I don't see why any company in the U.S. right now would make that sort of capital investment. Several other factors must first fall into place." "Cost-effective performance will be the key." Lynn says. "MES and alkylpolyglucosides will take an active role if costs can be brought down."

Still, surfacrants such as MES, glucamides. and alkylpolyglucosides contribute to the continuing trend toward "natural-based" surfactants. Naturalbased products include fatty alcohols and derivatives, as well as surfactants derived from renewable vegetable sources, such as corn, coconut, and palm kernel. Nonetheless, formulators of compact granules use three basic surfactant systems: LAS/AES/AE, LAS/AE, and AE alone. AEs are the most frequently used nonionics in Europe, having displaced alkylphenol ethoxylates for environmental reasons. "Some might even call alcohol ethoxylates the primary surfactant in laundry detergents," Sosis says, "but they are really the second-most used behind LAS, and it should remain that way until the end of the century. "You might, however, see more alcohol ether sulfates. Previously these have mostly been used in light-

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12

SURFACTANTS Be DETERGENTS duty liquid dishwashing detergent. Now you find them in powdered laundry detergents. They are now available at a high level of actives. up to 70%, without a solvent such as ethanol. The traditional spray-lower equipment can be used without worrying about burning the tower up. AES can be shipped economically. and are based on linear fatty alcohols. so they use natural, renewable resources. "If anything catches up to LAS, it will be alcohol ether sulfates. Unlike MES. they use the same equipment that producers already have, and arc already being processed on a relatively large scale here in the U.S. They are economical. less susceptible to hard water, highly soluble. and have a good foaming profile," In his paper. "Changes in Detergents and Personal-Care ProductsChances for Surfuctants,' presented during October 1995 at the 21st ISF

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World Congress, Paul Hovelmann estimated that the total North American market for detergents was 3.1 million metric tons, containing 600,000 metric tons of surfactarus. The market share of LAS was 30%, and AES, AS, and AE each had 20%. Hove+mann predicts worldwide growth rates of 5% for AS, 4.5% for AES, and 4% for AE. Other surfactants. such as alpha olefin sulfonate (AOS) and secondary alkane sulfonate (SAS) have been developed and used in various countries, but not to a large extent in North America. "Both surfactants are used (in the United States), but have a limited role in the detergent industry." Knapp says. Anionics such as LAS, AOS. and SAS are used in Japan. Also, some compact powders are formulated with a-sulfonated fatty acid ester or AE. The critical micelle concentrations of these are lower than that of LAS. and mixtures of these surfactants with LAS provide high detergency at low concentrations and favorable biodegradability. The mixing of surtacrams. especially with nonionics, will grow in importance. "As detergent formulations become more complex, they will continue to include multiple surfactarns," Knapp says. "P&G has introduced a new nonionic surfactant, cocoyl N-methyl gtucamide, which has replaced LAS in our liquid formulas," says David Kitko, an associate director of P&G. "This surfactant has a more compact head group than conventional nonienres. promoting stronger interactions with alcohol sulfate and alcohol ether sulfates in contrast to AEs, where the interaction is weak." According to The Freedonia Group, a market research firm, anionics' market share is expected to decrease gradually, mostly because of the increasing use of nonionics in heavy-duty laundry liquids. Nonionic surfactants also aid the solubility of highly concentrated powders in cold water. Solubility in colder water will become more important as wash temperatures continue to decline. a trend that favors both liquid detergents as well as powders that can dissolve

rapidly. Either way. nonionics will gain, especially when based on renewable resources. Freedonia also estimated in its 1995 study, "Detergent Additives," that surfactant consumption in household laundry detergents is projected to increase at close to 3% per year to reach 1.5 billion pounds in 1998. Surfactants have benefitted from the trend away from phosphates because higher surfactant loadings are required to maintain the same level of cleaning ability. Liquid detergents also can carry larger concentrations of surIacranrs due to recent advances in technology. Kitko also points to developments that include high-active surfactant particles. with the ultimate being Shell's dry powder form of secondary alkyl sulfate. New research may focus on imparting builder-like properties to surfacrants in response to the loss of sodium tripolyphosphate (STPP). "Surfactants or surfactant combinations must pick up some of the role of this multifunctional ingredient," Kitko says. "Pepuzauon and soil suspension or antiredeposition will become critical attributes for surfactant systems." Kitko even feels confident enough to hazard a prediction: "One or more new surfactant technologies will be deployed in North American laundry products in the last half of the decade." For any new surfactants to compete against the established favorites. they will have to meet at least one criterion. "Cost-effectiveness is the fundamental issue," Lynn says. In fact, one industry consultant commented on the environmental aspects of materials, rather than cost, being touted as the foremost future trend: "There's a 101of noise saying that it is, but nobody is stampeding toward it." Despite all the verbal emphasis on the environment. the higher price of new options will lead to a continuation of the status quo for a while. "LAS will continue as the workhorse surfactant. but suppliers and formulators will continue to work to overcome its processing and performance limitations with cost-effective ahcmarives," Kitko says.

15

SURFACTANTS & DETERGENTS When phosphates were under attack as detergent builders for perceived negative environmemal effects, formulators turned to other builders. At left is a molecular model of one complexing agent.

Builders The effects of phosphates' fall from grace still linger within the detergent industry. That whole complex environmental scenario has driven builder changes in detergent formulations for years, and promises to favor future changes as well. The irony is that it all may have been for naught. Research has secondguessed the previously perceived horrors of phosphates in the environment, acknowledging that perhaps the environmental card was overplayed in that particular game. "Some European countries found the cure was worse than the illness, and appear to be returning 10 limited phosphate use:' Paul Sosis says. "Whether this will make it across 10 the United States is anyone's guess." As one industry consultant put it, "Once the environmentally righteous genie is out of the boule. it is hard to put it back in." Canadian regulations allow the use of up to 8.7% STPP in household detergents. but some companies choose nOI 10 use it. Mexico does not restrict the use of phosphates: Aus-

shoes of phosphates. Today's multitralia and most of Africa use phoscomponent builder systems may phates. incorporate zeolite, sodium carbonate, According to Freedonia's study. P&G's move to pull STPP out of its sodium silicate, sodium sulfate, poly"Tide With Bleach" laundry powder in cerboxylares. and sometimes sodium early 1994 made it the last major U.S. citrate in premium brands. Zeolite removes hardness from brand to abandon phosphates. water through ion Some smaller regional brands arc the wash exchange, sodium carbonate removes the only household detergent products hardness ions by precipitation while now using STPP. Major U.S. producimparting alkalinity to the water, and ers readied nitrilomacetic acid (NTA) sodium silicate provides alkalinity as a one-for-one drop-in phosphate replacement in the latter part of the and corrosion resistance. Originally, I96Os. This came to a halt when the the formation of insoluble calcium and poor dispersion of U.S. Surgeon General identified NTA carbonate insoluble zeolite led to fabric incrusas a possible teratogen in December 1971. The accompanying ban of NTA tation, giving a rough, faded appearby the state of New York effectively prevented its introduction nationwide. With no standI alone builder replacement for I I I STPP, formulators turned to a hodgepodge mixture of other materials that ZeolitllSwere among earty candidates to reptece sodium tripolyphosphate in det~t fonnuiatlons. attempted to fill the

Al?

Si9

AIO

O-Si-O

-AI

-O-Si-O

AlO

SiO

AlO

INFORM. Vol. 7. no. 1 (January 1996)

16

SURFACTANTS Be DETERGENTS ance to clothes after repeated washings.

At first. zeolite was perceived as the standard material 10 design a multicomponent builder system around. Zeolite A is favored for concentrated powders because its high surface area permits adsorption of high concentrations of liquid nonionics. Zeolite has not been used in traditional laundry liquids because it is insoluble and settles out of solution, but new structured liquid technology has been developed to suspend zeolite.

Production soared when zeolite was introduced into detergent formulations. In 1994.66% of all zeolite produced was used in detergents. Zeolite A usage grew almost 40% from 1990 to 1993, but a trend to more soluble builders has curtailed much more growth. In Japan. some detergents use soluble sequestrarns , such as curates. Sodium citrate supports dispersion and solubility, but cost and limited sequestering ability have limited its role in powder formulas. Still. Freedo-

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I

nia states thai sodium citrate is the most widely used liquid detergent builder. Polycarboxylates are materials including homopolymers of acrylic acid and copolymers of acrylic and maleic acids. Polymers interfere with the growth of inorganic crystals and help dispersion of detergent materials. Polycarboxylates also sequester hardness. but are normally employed at such low levels that they do not approach the hardness removal duties of the primary builder agents. Polymers also serve roles as both soil dispersants in the wash and processing aids during manufacturing. The role of processing aid becomes more important as the filler material, sodium sulfate. gets squeezed out in the ongoing quest for increasing density. The function of modern builder systems. then, is to provide control of water hardness. alkalinity or buffering effect. dispersant activity. anuredeposition. corrosion inhibition, control of heavy metal ions, and liquids loading capacity. Binding water hardness ions also inhibits incrustation on fabrics and washing machines. and also leads to increased soil removal. Builders can do their work through precipitation (carbonate, amorphous silicate), sequestration (STPP. carboxylates), or ion-exchange (zeolite, layered silicate). "Despite the position of prominence given to zeolite:' Cahn says. "sequestration is the preferred route for builder activity." Advances in builder technology continue to strive toward regaining what was lost through STPP's demise. The focus. however. is mostly on improvements in individual components. Unilever recently introduced zeolite MAP into European detergent formulations. Their wholly-owned subsidiary Crosfield makes the material for Unilevers exclusive use. Zeolite MAP is said to have a different structure and crystal size, offering improved calcium ion exchange. especially at low temperatures. Silicates have served a variety of roles in detergent formulations. Soluble amorphous stticates. or waterglass. was first used with soda ash as a precipitating builder. As precipitating builders lost favor, waterg+ass

17

Bleaches Bleach additives in detergents fall into two categories: peroxide bleaches and activated peroxide bleaches. With peroxide bleaches, detergents have moved away from perborate tetrahydrate to the monohydrate form, which is more soluble in the cooler U.S. wash water. Up to 95% of U.S. detergent-withbleach is formulated with sodium perborate monohydrate, and the remaining 5% with sodium percarbonate. SOdium perborale monohydrate Sodium perborate acts as a source of borate in the wash, which is shown to have some important properties of builders besides its role as a bleach by Greenhill-Hooper and Quill in their paper, "Detergent builder functionalities of borate" in this issue of INFORM (page 30). As bleach systems move ahead, Rieck expects an increase in the use of percarbonate bleach at the expense of perborate. P&G's new "Ariel Future" formulation in Europe uses sodium percarbonate bleach. Bleach activators transform peroxide into more effective peracid bleach by a perhydrolysis reaction of the perhydroxyl anion with the activator. For peroxide activators, the all-important wash water temperature is 6O"C, the dividing line between the United States and Europe. Above this temperature, tetraacetylethylenediamine (TAED) is a commonly used bleach activator, especially in Europe. Below 6Q'c. however. is the realm of nonanoyloxylbenzene sulfonate (NaBS). P&G introduced the NOBSactivated bleach system in 1988, and it is still the only system in use in the United States. "NOBS bleach benefits are seen over a wider range of stains than TAED at lower temperatures due to a wider hydrophobic-hydrophilic balance," Grime says. Trying to provide the best bleaching action yet, Lever Brothers earlier introduced the use of a manganese "accelerator" in their European "Persil Power" and "Orne Power" detergents. In theory, the manganese serves as a catalyst for oxygen/electron transfer between the activator and the peracidlperoxide formed in the wash. P&G alleged fabrics could be damaged under certain laboratory conditions, and Lever was forced to backtrack. Lever's "New Generation" includes a more traditional TAED percarbonate bleach system instead. Freedonin's detergent additive study points out that sales of bleach additives used in home laundry detergents have increased rapidly over the past few years. P&G's "Tide With Bleach Alternative" is the second leading powdered detergent and third leading liquid detergent. Some consumers, however, are reluctant to use detergentwith-bleach products because they feel they cannot control the dose of bleach and may not want bleach in every washload, according to Preedonia. Although research continues on designing bleach activators to compete with NaBS, another focus is to avoid the use of an activator by designing stable peracids that can be included in detergent. Use of a peracid rather than sodium perborate or sodium percarbonate has been plagued with problems of thermal stability, product compatibility, and cost. Nonetheless, preformed peracids such as dipercarboxylic acids have been manufactured in some quantity. In 1,12-dodecanedipercarboxylic acid, the percarboxyl groups are connected by a methylene chain. In magnesium monoperoxyphthalate, a single percarboxyl group is carried on a benzene ring.

was used as a source of alkalinity, a buffering agent. and a corrosion inhibitor. Insoluble sodium aluminosilicates are familiarly known as zeolites. Insoluble clay-type silicates, such as bentonite, can be used alone or with cationic surfacrants or tertiary amines for fabric softening. Hoechst AG has focused beyond the traditional roles of silicates to search for new forms that can serve

detergent formulators better. Its research efforts may have hit upon a silicate that serves more as a standalone replacement to STPP. Layered silicates have a polymeric inorganic structure with a regular arrangement, as opposed to the amorphous silicate, with a molecular structure of various disordered small silicate rings or chains. Of the several forms of layered silicates, &-disilicate is of most interest to Hoechst.

According to Hoechst, &-disilicate softens water, provides alkalinity, adsorbs moisture, binds heavy metal ions to stabilize bleaching agents, suspends soil in the wash, carries surfacrants, and supports compaction and granulation. By providing these benefits, Sdisilicares reduce the other raw materials needed in builder systems, providing cost savings. Hoechst says that o-disilicate works by capturing water hardness INFORM. Vol. 7. no. 1 (January 1996)

18

SURFACTANTS ions through ion exchange while insoluble in the alkaline (pH 10) wash water. When the wash liquor is diluted through addition of rinse water and movement into the waste stream, the pH decreases until the hardness ions arc released. The disilicate dissolves completely in the waste stream, which is receiving increased focus today. According to Hoechst, some countries want soluble builder systems to curb sludge increases at sewage treatment plants and deposition in rivers and lakes. Hoecbst is manufacturing &'disilicares in Germany under the brand name SKS-6. Hoechst is said to be supplying SKS-6 to P&G for its brands in Europe, and the Hoechst Tokuyama Limited joint venture in Japan is producing SKS-6 for the Asian market. Are 5-disilicates the fabled STPP replacement? "We know it is possi-

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ble to use SKS-6 as a stand-alone builder in formulations," says Hoechst researcher Hans-Peter Rieck, "but the use of a small percentage of polycarboxylates further enhances the performance, and SKS6 can also be used in combination with zeolites." Hoechst is reluctant to assert that 5-disilicates can ascend to claim the vacant throne of phosphates. Rather, Rieck points to the roles SKS-6 can fill. "It is a multifunctional builder. Controlling water hardness, essential for any builder today, is just one function. Providing reserve alkalinity is another, as is maintaining loading capacity for non ionic surfuctenrs." The trend toward increasing concentration of laundry products favors the most advantageous aspect of 5dtsilicates. Hoechst claims the combination of benefits makes SKS-6 ideal for compactness, and the total

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dosage of detergent can be reduced for the same or better washing results. The price of layered silicates, however, is still at the high end of builder materials. "Decreasing the cost of processing and further optimizing the product quality are goals for making SKS-6 more viable:' Rieck says. "&-Disilicate is not easy to produce in pure form. You get alpha, beta. gamma, and delta forms, but delta is the most advantageous for laundry detergent use." The trend toward non tower processing, however, favors disilicates, which hydrolyze in a spray tower. SK5-6 would need either to be postadded or processed in a completely nonrower system. Regardless, Hoechst acknowledges that, cost and production hurdles aside, it takes years to establish a new builder on a large scale. "The switch from phosphates to zeolite as a major builder took ten years," Rieck says. "We expect the currently used materials to still be the main builders at the tum of the century." Plans for SK5-6 are moving ahead. though, and Hcechsr already has started market preparation in the United Slates. Hoechst might have competition in the form of RhonePoutenc. which is now offering a granular form of sodium carbonate/sodium disilicate. Builders and surfactants comprise the largest portion of detergent ingredients. Freedonia predicts the demand for all ingredients in all forms of household detergents to rise from 4.5 billion pounds in 1983 to 6.9 billion pounds in 1998. The actual share of these going into laundry detergent, however, will shrink from 55% in 1983 to 52% by 1998. According to Freedonia, consumption or additives other than surfactants and builders will expand 4.1 % per year to 305 million pounds in 1998. These other additives fall into two groups of special ingredients. The first is proactive ingredients. such as enzymes. polymers, bleaches. fabric softeners, optical brighteners, fragrances, and colorants.

19

CoHon fibers damaged by repeated washing

Cotton libers washed in detergent containing

cellulase

Enzymes Enzymes are biochemical catalysts that are not consumed in reactions. As catalysts, they are very efficient and only a small amount is needed in detergent formulations, typically less than I % by weight. Enzymes were introduced in detergent formulations in the 196Os. Problems arose when factory workers suffered from allergic reactions to dust formed

both during

enzyme produc-

tion and during detergent processing. Improved enzyme technology and industrial hygiene have substantially alleviated that risk. Proteases were the first enzymes to appear in detergents, and now are the most widely used. Proteases act on blood, eggs, grass, and other proteina-

ceous soils. Next came amylases, which act on starchy stains, and then lipases that act on oily and greasy soils. Starch and fat stains are easier to remove in hot water, and the demand for amylase and lipase increased because of decreasing wash water temperature. The newest and most innovative addition to the enzymatic cleaning line is cellulase. Cellulase reacts with both cellulosic and particulate soils,

such as clay. It also acts on microfibrils found on colton and cotton blend clothes. Removal of damaged microfibrils called "pills" leads to brighter colors and softer fabrics. "Cellulase is used for color restoration, depilling of cotton fabrics, and cleaning of particulate matter, but most usage is for color maintenance and fabric softening:' says Peter Plank, senior applications chemist at Genencor International. Damaged microfibrils make cotton garments look dull and fuzzy. These fibrils reflect light, making the fabric look duller or more faded than the rest of the fabric. Even new garments can rapidly look worn and drab. As damaged fibrils fray from the bulk fiber, their accessibility allows selective hydrolysis of glycosidic linkages by the cellulase enzyme. The damaged fibers are weakened and then removed by abrasion during the washing and drying processes. Currently, only P&G uses cellulase in their detergent formulations. "Lever has not used cellulase to date," Lynn says. "A significant percentage of products on the market include cellulase, and there is nothing proprietary about it."

The largest use of industrial enzymes is in detergent applications, according to Plank. Genencor acquired another enzyme producer, Gist-brocades, last June. That left three main enzyme producers: Novo Nordisk (45-50% of the market), Genencor (30-35%), and Solvay (10-15%).

"The market for detergent enzymes totals about $400 million," Plank says. Enzymatic laundry detergents comprise roughly 80% of the market in the United States, but, "Usage drops significantly once you get outside the U.S. and Europe." Part of the difference may have to do with wash temperatures. Although European wash water temperatures have come down, they are still higher than those in the United States, and many detergent components achieve maximum performance. at high temperatures. Enzymes, however, function best at low temperatures, between 30-70·C. Enzymes are thus consistent with the primary drivers in detergent industry, such as cost-effectiveness at low concentrations, acceptable environINFORM. Vol. 7. no. 1 (Januarv

1996)

20

SURFACTANTS mental profile, biodegradability, and low-temperature performance. They are also multifunctional, providing service in stain removal, antiredeposition. whitenesslbrightness retention, color maintenance, and fabric softening. Continuing efforts to increase the concentration of detergents also favor the space efficiency of a catalyst. Still, dctergent enzymes lose some efficiency in water at 10-20·C. The mechanism behind this is not completely understood, but protein engineering research is underway to boost cleaning performance at very low washing temperatures. Protein engineering is used to improve enzyme performance through modification of the enzyme molecule, according to Hans Hagan of Novo Nordisk, who spoke at the New Hori-

a. DETERGENTS

zons '95 Detergent Industry Conference. Modifications are usually made by replacing a few specific amino acids in the enzyme protein structure with other amino acids that have different properties. This can change the sensitivity of the enzyme to oxidating agents, alkali, ionic strength, and temperature. "Protein engineering offers many alternatives," Plank says. "Our Prop-

erase protease product is currently on the market as a low-temperature protease. We are now looking for lipases. amylases. and oxidases with higher activity at low temperatures plus oxidative stability." Oxidases are an intriguing avenue of enzyme research. Enzymes for bleaching would catalyze oxidation reactions with peroxygen bleaches to

ensure economic bleaching at low washing temperature, with a minimum of hann to fabrics and environment "Oxidases can replace the activator in the presence of perborate for bleaching in lower temperature wash water:' says Plank. "Bicbleacbing," a term coined by Novo Nordisk, is a growing area of research. "It is especially attractive if it means you can remove chlorine from the laundry environment," Plank says. Increasing the number of enzymes used in combination leads to problems of enzyme compatibility, especially in liquid detergents. An enzyme product that works well in one detergent may not work as well in another formulation. Also, researchers are still looking for oxidative stability of enzymes in the presence of bleaches.

Polymers Polymers' role in detergent formulation has increased from humble beginnings. "If you look over the past 20 years, polymers have been used to compensate for the removal of STPP," Lynn says. "Polymers have proven 10 be great sequestrams. soil removers, suspension agents. and even processing aids. With polymers in the mix. the complex builder systems that have replaced STPP are competitive with STPP, and maybe even benet" Most of the market is for polymers containing anionic groups. such as the carboxyl groups. Nonionk polymers are mostly polyalkylene glycol derivatives and polyvinylpyrrolidone (PVP). which is used as a dyetransfer inhibitor. "Poly acrylate homopolymers and copolymers of acrylic and maleic acids are used as powder-strucnnins aids." Lynn says. "They also help in soil removal aDd soil suspension." Cellulose derivatives such as carboxymethylcellulose (CMC) and hydroxymethylpropylcellulose serve as antiredeposition agents. "Polycarboxylates are used as processing aids 10 disperse slurries. such as those found in a crutcher," says Bill McCullen. research manager of fannulation chemicals for Room & Haas. "'Adding polymers decreases the slurry viscosity. so the processor can either use less power or make Ihe mix more concentrated. increasing the Ihroughput of the spray tower." Sarath Chandar. senior marketing manager of house-

NORM. Vol. 7. no. I

(Jonuay

1996)

hold products for BF Goodrich, promotes a different kind of polymer. ''Cross-linked Carbopol polymers have been shown to deliver structuring to liquid products that otherwise would separate," Chandar says. "Cross-linked polymers have high molecular weight. roughly I million as opposed to molecular weights of 70.000 for polyacrylate and 4,500 for the acrylic/maleic acid copolymers," McCullen says, "Lightly cross-linking them makes them appear even larger. Such large polymers add viscosity to liquid laundry detergents, stabilizing fannulations that would fall apart otherwise due 10 incompatible components," For use in concentrated powders. though, the common liquid polycarboxylate polymers are at a disadvantage. since they are delivered as a diluted water solution with roughly 40% active polymer. Dry polymers have been available for a while. but they are hygroscopic which leads 10 difficulty in handling. In the new round of waterless poIymers.1he waIer has been replaced by an inorganic carrier. and the polymer can rest on a builder. Using this method. densities over 750 gil can be acIUeved and used in concenbalCd pow-

den. "Dry granules are one direction polymers are beading," McCullen says. "If polymers are supplied in water, the water tint must be removed, and that traditionally has been done with spray towers. The industry is mavins away from spray lowers, toward agglomeration and dry

21

Other additives Besides proactive ingredients. detergents also include a second class of additives that satisfies further functional requirements.

Foam control agents. In the standard U.S. vertical-axis washing machine. a small amount of foam can be tolerated. "Standard suds control agent formulations contain silicone, silica, and fatty acids," Caho says. "Silicone anlifoams typically work more quickly. last longer. and can be used in smaller concentrations than organic defoemers," says

OSi Specialties' Brad Larson. global marketing manager for foam control agents.

Antiredeposttion ag~nts. Carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA). and other polycarboxylates arc the most common antiredeposition agents in detergent formulations. "These agents work by coating the soil or coating the fabric, depending on whom you talk to," Cahn says. "I believe more in their acting to coat the soil. Of course, the role of anti redeposition agents will increase in importance

........... So odded flexibility i.pined by suppIyinJ dry poI~ _ dull ... be uaed ill these processes," Problems exist ill die pn>ductioo ODd use of dry poly...... !bough. ProcIuceno want '" .void bygroscopic dry polymers, as any absorbed wale' could affect bleachi., systems ODd enzymes ODd promote caking and bleeding of the detergent. Yel detefJenl polymers have been deaiped to be water-soluble. WbiJe in a dry state. they tend to absorb WIler to reach a more stable staIC. _ poI~ problem is die i....of biodegradlbility. PoIyc:arlloxyl_ are oaIy .iipdy biodegradable. but Ibeir concentration in die environment is mIuced by .... __ by die 01..... ill SIilI, IlleR: is 1ft increued _ for biodegndable polymen Ibat eaa be UIed II higher levels than the cuncnt poIyeod1oxy_. Polyaspartale is seen as meeting that need. '1bese polymers resemble a protein," McCullen says. "That way, the bacteria and funSi can recognize them and

Iy leading

with new washing machines that use less water." (See "Changes in washing machines can affect formulations" on page 25.) While CMC is useful for cotton, hydroxymethylpropylcellulose will work better with synthetic fabrics. International Specialty Products (lSP) developed its Gaftex P product using polyvinylpyrrolidone (PVP), which also serves as a dye-transfer inhibitor.

Dye-transfu inhibitors. The term "color-safe" has appeared as a term applying to laundry detergents that

10 inefficienl

depo ilion and poor perfor-

mance. decreased particulate soil removal, and phase instability in liquid deteraenL Some success has come with control of molecular weight by introducing capping groups, which have increased solubility and minimized adverse effects on clay removal. Crystallinity can be controlled by limiting the lize and symmetry of the polyester blocks. Additional research involves making polymers more like swfactants. "In prioc:iple. it is possible to tailor the surface activity of polymers." McCullen says. "This can

_-plan...

dopado diem.

"We .... adJI -.. teriltiCI.

bul lioear

.. die _-paformaocc dwac-polyaapartate seems to be vel)'

biocIcpIabIe." In me arena of liquid detel'leDtI~ Dew polymer r~I ell is beiDa direeIed toward Cbe CIOIICCpt of tbrouJbtbe-wasb soil rt:lease. Applying • bydrophilic COIIiag dull remaiaa _ -.. ODd dryiD8 bas proYOd cbaI1enainI. Problems beea limited to aqueous soIubili-

"ve

be achieved by balancing the hydrophobic and hydrophilic compoents of a polymer." McCullen feels that the de ip of a polymer to function at a specific interface is a definite possibility, and the patcnt. literature reflects efforts by several companies. Polymers already serve several functions. and will become more important with decreasing wash temperatures. "Polymers will continue to have a major role in liquids and POWders. with producers claiming them as soil removers. soil dispenants. processing aids., antiredepooilion _ ODd dyo-cnasfor inhibitors." Lynn .. ys. "They _ reduce fabric: _ by k£cpi., calcium _ ill from dopooitiDa." With contiruing researdt on even more roles for polymer&., Cbey _y move mm mere additive 10 the buiIdin& _ of __ formulaliona. "Polymers cou1d be Ihc builden of the future. .. Cahn .. ys.

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22

SURFACTANTS Be DETERGENTS do not require sorting of clothes. These formulations usually avoid bleaching agents. have slight surfacrant modifications that reduce dye fading. and incorporate specific polymers to reduce dye transfer. The most common of these dye-transfer inhibitors is PVP, although polyvinylimidazoJe and poly 4vinylpyridine N-oxide can also fill the role. "PVP will be needed in greater quantities by more detergents as dyetransfer inhibitors grow in imporlance," Lynn says. "There is room for significant improvement of these agents. but I don't foresee much relief in the immediate future:'

Others. Stand-alone inhibitors

are decreasing

corrosion in impor-

lance as more multipurpose builders and other additives accomplish this task in a more space-efficient manner. "Corrosion used to be a problem back when most exposed parts of the washing machine were aluminum," Cahn says. With non-metal and coated-metal parts more predominant. corrosion inhibition is moving down the formulators' priority list. The formerly rock-solid role of processing aids has narrowed considerably. squeezing out single-purpose materials like sodium sulfate. The move to compact powders led to cutbacks in sulfate use that will continue as other materials fill this role in addition to providing other services. Hydrotropes ensure good physical properties of liquid detergents. These

detergents are often formulated with ingredients that are not physically compatible and tend to split into separate phases or layers. Hydrotropes prevent this separation, but so do other materials being developed, such as cross-linked polymers. Additional efforts to concentrate liquid detergents further may well push formulations away from isotropic liquids (that use hydrotropes) toward newer high-density designs. such as structured liquids and nonaqueous liquids. Some solvents, such as ethanol. playa role as additives in high-concentration liquid detergents. By replacing water in isotropic liquid formulations, solvents preserve enzyme activity and maintain detergent uniformity.

Flaxseed In Human Nutrition ,Stephen C. Cunnane and Lilian U. Thompson, Editors

Contents Chapter 9

ChaptCT 18

Processing Flaxseed for Human Consumption

Chapter 19

Incorporation of Flaxseed or Flaueed Components into Cereal FOOds

Effects of Flaxseed on Selenium Toxicity

Chapter 20

Flaxseed in Artic Charr and R.~inbow Trout Nutrition

Chapter 12

Fiber Effects on Hyperlipidemia

Chopter21

Designing Poultry Products Using Flaxseed

Chapter 13

The Effect of Dietafd: a-linolenic Acid on Blood Ltf:i a and Lipoproteins in umens

Chapter 22

Incorporation of Flaxseed Fatty Acids into Cow's Milk

Chapter 23

Flaxseed and the Composition and Quality of Pork

Chapter 24

~Jation of Flaxseed as a FoOd Ingredient in the United

Conclusion

Introduction

Flax-Some Historical Considerations

Chapter I

Structure of Fla: