They make polypropylene run clearer and faster: New packaging opportunities are opening up for PP, thanks to a new crop of additives that boost clarify, stiffness, HDT, and processing rates. (New Clarifiers, & Nucleators).Prospects for polypropylene to penetrate further into injection molded, blow molded, and thermoformed packaging rely to a large extent on advanced nucleators and clariflers. These additives maximize the resin's aesthetic appeal (clarity) and its processing productivity. They also enhance certain performance properties, namely stiffness and heat resistance. These advantages are attracting a growing roster of suppliers who are bringing out new generations of additives that set new benchmarks for cost-performance. Clarifiers have been used since the mid-1980s in the medical arena to produce clear, radiation-resistant syringe barrels and lab devices. In recent years, as these additives improved in organoleptic or·gan·o·lep·tic adj. 1. Relating to perception by a sensory organ. 2. Involving the use of sense organs. organoleptic (taste/odor) characteristics and clarifying power, they have strongly influenced growth in PP applications for household containers for food and non-food storage. Today, deli cups, airline drink cups, and stadium cups of clarified PP are replacing PET and polystyrene. Robert Portnoy, senior staff application scientist at ExxonMobil Chemical, notes that improving clarity is not the only story: By speeding cycles and increasing stiffness (which permits thinner walls), nucleation nu·cle·a·tion n. 1. The beginning of chemical or physical changes at discrete points in a system, such as the formation of crystals in a liquid. 2. The formation of cell nuclei. has helped thermoformed PP cups gain ground from PET and PS even where clarity is not critical. What's more, Portnoy says that although most of these cup applications are currently thermoformed, nucleation has helped make injection molding injection molding n. A manufacturing process for forming objects, as of plastic or metal, by heating the molding material to a fluid state and injecting it into a mold. more competitive by improving its cycle times. "You are now starting to see nucleation almost as a baseline property of PP," Portnoy observes. Whereas only a few nucleated nucleated /nu·cle·at·ed/ (noo´kle-at?id) having a nucleus or nuclei. nu·cle·at·ed adj. Having a nucleus or nuclei. nucleated having a nucleus or nuclei. grades were offered in the past, they are much more widespread today. The benefits of nucleation are also being felt far from the packaging realm: In auto parts Auto parts are components of automobiles. They mainly are, in alphabetic order (only car specific articles or articles with car section):
tr. & intr.v. stiff·ened, stiff·en·ing, stiff·ens To make or become stiff or stiffer. stiff PP impact copolymers and TPOs, overcoming the softening imparted by rubber modification. Although most use so far of nucleators and clarifiers has been for injection molded consumer goods consumer goods Any tangible commodity purchased by households to satisfy their wants and needs. Consumer goods may be durable or nondurable. Durable goods (e.g., autos, furniture, and appliances) have a significant life span, often defined as three years or more, and and medical devices, these additives have opened doors for thermoformed and blow molded applications (see box). With the exception of stretch-blow molded bottles and some very thin-walled thermoformed parts, even clarified PP generally cannot match the crystal clarity of PET. However, these additives can give sufficient transmission and contact clarity--combined with PP's higher hot-fill temperatures, lower density and lower price--to make it a serious competitor for PET. Several examples are cited by Paul Wright Paul Wright may refer to:
n. 1. A film or layer one molecule thick formed at the interface between water and either oil or air by a substance such as a partially esterified fatty acid that contains both hydrophobic and hydrophilic groups in the same clarified-PP bottle for Aurora Foods' Log Cabin log cabin or log house, style of home typical of the American pioneer on the Western frontier of the United States in the great westward expansion after 1765. It was constructed with few tools, usually an axe or an adz and an auger. table syrup, which was previously produced in APET APET Amorphous Polyethylene Terephthalate APET Accident Progression Event Tree APET Algorithms Program Evaluation Tool APET Adaptable Performance Evaluation Testbed APET Australasian Perpetual Equity Trust APET Avionics Post-mission Evaluation Team . "Although not quite as clear as PET, clarified PP has excellent clarity and can better withstand hot-fill temperatures," Wright explains. Barry Dean Barry Dean (born February 26, 1955 in Maple Creek, Saskatchewan) is a retired former professional ice hockey player who was drafted number two overall in the 1975 NHL Amateur Draft by the Kansas City Scouts. , product-development manager at BP, believes clarified PP can expand in packaging markets even without matching PET's clarity. He says BP's 8249 clarified random copolymer copolymer: see polymer. is gaining ground in extrusion and stretch-blow molded sports-drink cups, jelly jars, and multi-layer bottles where clarity does not have to be as good as PET. How they work Nucleators and clarifiers (a subclass In programming, to add custom processing to an existing function or subroutine by hooking into the routine at a predefined point and adding additional lines of code. subclass - derived class of nucleators) essentially jumpstart the crystallization Crystallization The formation of a solid from a solution, melt, vapor, or a different solid phase. Crystallization from solution is an important industrial operation because of the large number of materials marketed as crystalline particles. process as the resin cools. PP normally forms crystals larger than the wavelength of light. Nucleators and clarifiers induce formation of smaller spherulites that scatter less light. What's more, says Robin Lee, senior research specialist at Dow Plastics, "Since the crystals form faster, the polymer solidifies faster and cooling time (Law) such a lapse of time as ought, taking all the circumstances of the case in view, to produce a subsiding of passion previously provoked. - Wharton. See also: Cooling is reduced." All clarifiers will nucleate nu·cle·ate adj. Nucleated. v. 1. To form into a nucleus. 2. To serve or act as a nucleus for. 3. To provide a nucleus for. n. A salt of a nucleic acid. , but all nucleators do not clarify, although many do provide a significant reduction in haze. Traditional nucleating agents are mostly aromatic carboxylic-acid salts, of which sodium benzoate sodium benzoate or benzoate of soda, chemical compound, C6H5CO2Na, colorless or white crystalline, aromatic compound; the sodium salt of benzoic acid. is the most common. They have been used in PP homopolymers since the 1960s to improve stiffness and increase processing rates. Talc talc, mineral ranging in color from white through various shades of gray and green to the red and brown of impure specimens, translucent to opaque, and having a greasy, soapy feel. and other inorganic fillers have also been found to have a nucleating effect. All these choices are limited in their ability to reduce haze, and they also suffer from poor organoleptics and inadequate heat stability. While traditional nucleators sell for $1.20-1.60/lb, more advanced nucleators and clarifiers sell in the range of $12 18/lb. The latter offer considerable performance enhancements at very low use levels, typically 0.15-0.25%. At such low levels, newer nucleators and clarifiers add 1.5cents to 4.5cents/lb to the resin cost, vs. 4-5cents/lb a decade ago. Of the advanced nucleators that are classified as clarifiers, most are organic derivatives of dibenzylidene sorbitol sorbitol /sor·bi·tol/ (sor´bi-tol) a six-carbon sugar alcohol from a variety of fruits, found in lens deposits in diabetes mellitus. (DBS (Direct Broadcast Satellite) A one-way TV broadcast service from a communications satellite to a small round or oval dish antenna no larger than 20" in diameter. ). The pioneer in this field is Milliken Chemical, now offering its third-generation DBS-based clarifier, Millad 3988. Other suppliers offer what may be termed first- and second-generation sorbitol acetals. These now include Irgaclear clarifiers produced by Roquette in France and sold here by Ciba Specialty Chemicals “Ciba” redirects here. For the pre-1971 company, see Novartis. Ciba Specialty Chemicals is a chemical company based in and near Basel, Switzerland. It was formed as the non-pharmaceuticals elements of Novartis were spun out in 1997, following the merger in the , as well as NC-4 clarifier from Mitsui Toatsu Chemicals in Japan, sold here by Mitsui Chemicals. Sorbitol-based clarifiers melt or dissolve in the polymer at temperatures from 390 to 430 F. When the resin cools, the clarifier crystals form a fine fibrous network that contributes to clarity by providing a very high crystal density with very small spherulites. "Crystallites are reduced to the point that they are less than the wavelength of visible light," explains Reed Walker, Milliken's polymer additives product-line manager. Because visible wavelengths are not significantly affected by the small crystallites, resulting parts are much more transparent. Better stiffness and higher HDT HDT Heat Deflection Temperature (plastics) HDT High Dose Therapy HDT Heatpipe Direct Touch (Xigmatek) HDT Heat Distortion Temperature (plastics) HDT Henry David Thoreau also result. Advanced nucleators (some of which also clarify) include organophosphate organophosphate /or·ga·no·phos·phate/ (or?gah-no-fos´fat) an organic ester of phosphoric or thiophosphoric acid; such compounds are powerful acetylcholinesterase inhibitors and are used as insecticides and nerve gases. salts and other inorganic materials. Until recently, the primary supplier was Asahi-Denka Kogyo of Japan (U.S. subsidiary is Amfine Chemical) with its ADKstab NA-11 and NA-21 phosphate esters. In the past year, Milliken Chemical entered the field with its Hyperform HPN-68 a norbornane carboxylic-acid salt. This new class of high-speed nucleator was recently registered by the FDA FDA abbr. Food and Drug Administration FDA, n.pr See Food and Drug Administration. FDA, n.pr the abbreviation for the Food and Drug Administration. for food contact. Nucleators do not disperse as easily as clarifiers, since they are typically inorganic materials with no solubility in the resin. They rely on dispersion by mechanical methods to nucleate the PP to form the small spherulites, explains Amfine's director of marketing, Peter Goman. When they are compounded into the polymer, they provide additional sites for nucleation, so spherulites become smaller. This leads to higher physical properties and some added clarity, depending on the nucleator's particle size Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. and ease of dispersion. Clarity is said to be enhanced with Amfine's NA-21 and to a lesser degree with NA-11, Milliken's HPN Home parenteral nutrition (HPN) Long-term parenteral nutrition, given through a central venous catheter and administered in the patient's home. Mentioned in: Nutrition through an Intravenous Line 68, and sodium benzoate, in descending order. "In general, the particles of nucleators are larger than the wavelength of light, and that is one reason why you don't get the clarity imparted by sorbitol-based clarifiers," explains Milliken's Walker. Evolution of clarifiers Clarifiers such as sorbitol acetals typically provide nucleation (crystallization speed enhancement) as good as that provided by phosphate ester nucleators in PP homopolymers and random copolymers. (Heterophasic impact copolymers, with their two different refractive indexes, cannot be clarified.) However, clarifiers are too costly to be used for nucleation alone if high clarity is not needed. Sorbitol-based clarifiers typically sell for $1418/lb vs. $13-$17/lb for organophosphate nucleators. However, clarifiers are used at higher levels--0.2% to 0.25% for Milliken's Millad 3988 and Ciba's Irgaclear clarifiers and 0.3% for Mitsui's NC-4. Organophosphate salts and other nucleators can be used at 0.1% to 0.15% or less. Clarity depends in part on the path length the light has to travel. Clarity decreases with increasing part thickness and is also dependent on the degree of orientation imparted during processing. According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. Milliken's Walker, achieving 7% haze is state of the art for injection molded random copolymer, while 9-10% haze can be obtained with injection molded homopolymer. However, stretch-blow molding and thin-wall thermoforming can achieve haze of only 1-2%, approaching the clarity of PET. (All these figures are based on results with Milliken's Millad 3988.) Millad 3988 is a third-generation clarifier that made its predecessors--Millad 3905 and 3940--obsolete. First-generation Millad 3905 could not be used at temperatures above 435 F, limiting its suitability for injection molding. Second-generation Millad 3940 could be processed at temperatures up to 480 F and also provided improved clarity, but it had poor organoleptics, which limited its use to medical devices. Millad 3988 reportedly overcame these deficiencies with heat stability up to 535 F plus excellent organoleptics. This allows it to be used in different types of resins with varying melt flows for everything from injection and blow molding to extrusion and thermoforming. Ciba Specialty Chemicals made its entry into sorbitol-based clarifiers in 1998 with first-generation Irgaclear D and second-generation Irgaclear DM. Ciba recently launched Irgaclear DM-LO, which is said to feature good organoleptic properties, approaching those of Millad 3988. (Milliken sources strongly disagree with Verb 1. disagree with - not be very easily digestible; "Spicy food disagrees with some people" hurt - give trouble or pain to; "This exercise will hurt your back" that claim.). Panel tests reportedly show that taste and odor have been reduced by half compared with Irgaclear DM. The company is initially testing DM-LO primarily in injection molded household containers but expects eventually to aim for food-packaging uses. Irgaclear DM-LO is not yet replacing its predecessors. Irgaclear DM is currently used in food packaging, medical syringes, and high-clarity housewares house·wares pl.n. Cooking utensils, dishes, and other small articles used in a household, especially in the kitchen. and cosmetics containers. Irgaclear D is still satisfactory for applications like CD boxes where less clarity can be tolerated. Haze value in a 1-mm PP homopolymer plaque is 40% with Irgaclear D and 10-15% with DM and DM-LO. Irgaclear D costs about half as much as Irgaclear DM, while Irgaclear DM-LO sells at a slight premium. Amfine Chemical recently completed tests at compounder A. Schulman Inc. in Akron, Ohio Akron is a city in the U.S. state of Ohio and the county seat of Summit County.GR6 The municipality is located in northeastern Ohio on the Cuyahoga River between Cleveland to the north and Canton to the south, approximately 60 miles (96 km) west of , where different clarifiers were used in BP's standard 1.8-MFR random copolymer for blow molding. According to Amfine's Goman, his firm's ADK ADK Adirondack Mountain Club ADK Archive Development Kit (SAP archiving) ADK Additional Decryption Key ADK Aggressors of Dark Kombat (video game) NA21 at 0.15% use level provided clarity equal to or better than that obtained with Millad 3988 at 0.2% (see graph below). Goman says organophosphate clarifiers such as ADK NA-21 are well suited to medical syringes, where clarity and high extraction resistance are critical. He says the all-organic sorbitol-based clarifiers are very soluble and therefore more extractable. They are also prone to cause die-lip buildup, requiring frequent mold cleaning or the addition of costly GMS GMS Greater Mekong Subregion GMS Global Mobile (Communications) System GMS Guild Management System GMS General Medical Services GMS Global Management System (Sonicwall) GMS GroupWise Mobile Server (glycerol glycerol, glycerin, glycerine, or 1,2,3-propanetriol (prō`pāntrī'ŏl), CH2OHCHOHCH2OH, colorless, odorless, sweet-tasting, syrupy liquid. monostearate) to the resin to prevent plate-out. (PP suppliers agree with this assessment.) But because NA-21 is difficult to disperse in high-flow PP grades, its use has been limited to thermoforming and blow molding--primarily as a clarifier, Goman notes. He says a new organophosphate salt clarifier now in development is expected to challenge Millad 3988 in injection molding. Changing benchmarks PP resin developments are changing the market's expectations with regard to clarity. Up to now, random copolymers have showed lower haze than homopolymers at a given wall thickness and clarifier concentration. Yet the new metallocene-catalyzed PP (mPP) homopolymers are said to be another story. "We can get a [clarified] homopolymer mPP with the same clarity and stiffness as a Ziegler-Natta [clarified] random copolymer," says Portnoy at ExxonMobil. A haze value of 8% was obtained in injection molded mPP homopolymer (Achieve 1635E1) vs. 12-14% haze in a Z-N random copolymer when Millad 3988 was used in both at the same concentration. Mike Musgrave, technical segment manager at AtoFina, says his firm has an mPP homopolymer with only half the haze of a Z-N homopolymer when both are clarified with Millad 3988. Both Finacene EOD-00-35 mPP and AtoFina PP 3289 Z-N PP are 2-MFR extrusion/thermoforming grades with the same flexural flexural pertaining to the flexure of a joint. flexural deformity fixation of joints in flexion. In the newborn called contracted calves or foals. modulus (225,000 psi) and HDT (192 F), despite the 19[degrees] lower melting point melting point, temperature at which a substance changes its state from solid to liquid. Under standard atmospheric pressure different pure crystalline solids will each melt at a different specific temperature; thus melting point is a characteristic of a substance and of the mPP. Disposable food containers produced with the clarified mPP have sidewall side·wall n. 1. A wall that forms the side of something. 2. A side surface of an automobile tire, between the edge of the tread and the wheel rim. Noun 1. haze of 15% vs. 31% for the Z-N grade, and bottom haze of 32% vs. 44%. AtoFina has obtained similar results with random copolymers of mPP vs. Z-N PP. The need for speed Resin suppliers report good results with advanced nucleators in injection molding and thermoforming. Improvements in cycle times can range from 5% to 40%. Dow's Lee cites the example of a non-nucleated resin that can be thermoformed at 1000 cycles/hr. Nucleating the same resin results in about 1500 cycles/hr, he claims. Comments Jennifer Hicks, technical-service representative for Phillips Sumika Polypropylene, "Compared with sodium benzoate, the new nucleators raise the freezing point so material sets up faster, and they can be used at lower concentrations--300 ppm vs. 1000 ppm." ExxonMobil is relying on nucleators to re-enter re·en·ter also re-en·ter v. re·en·tered, re·en·ter·ing, re·en·ters v.tr. 1. To enter or come in to again. 2. To record again on a list or ledger. v.intr. the extrusion/thermoforming market with the launch of PP5082KN. According to Portnoy, this new workhorse Z-N homopolymer is heavily nucleated, which provides significant cycle-time improvements. Milliken's new Hyperform HPN68, claimed to be the most powerful nucleator yet, is under evaluation at several PP suppliers. Results of one test are shown in the table on p. 46. One disadvantage of very quick crystallization induced by nucleators is the tendency to freeze stresses into the part, which can lead to warpage. This could be an issue particularly with large parts like automotive bumpers and interior trim. However, Amfine's Goman points out that both ADK NA-11 and NA-21 are used in impact PP for low-temperature automotive applications. NA-21 tends to promote a little slower crystallization than NA-11 and HPN-68, he says, so in certain applications NA-21 can provide slightly better impact at the expense of some stiffness. The company is preparing to bring out a new class of nucleators expected to prove even more effective for injection molding of high-flow (25-50 MFR MFR, n See myofascial release. ) PP. Ciba Specialty Chemicals is now marketing NA-11 through an agreement with Asahi Denka. Ciba will market the product, which will be made at Amfine Chemical's plant in Kentucky, under the name Irgastab NA 11. Ciba's market focus will be on customer-specific additive blends. [GRAPH OMITTED]
HIGH-PERFORMANCE PP CRYSTALLIZATION ENHANCEMENT
Heat Flow, mW Endothermic
HPN-68 [t.sub.1/2] = 0.78 min
Phosphate Ester 1 [t.sub.1/2] = 2.52 min
Millad 3988 [t.sub.1/2] = 2.83 min
NaBz [t.sub.1/2] = 8.05 min
Phosphate Ester 2 [t.sub.1/2] = 10.44 min
High crystalization speed with Milliken's HPN-68 nucleator can shorten
cycle times by as much as 40%.
Note: The times shown are to reach 50% crystallization.
(Source: Milliken Chemical)
Note: Table made from line graph
COOLING-TIME SAVINGS WITH NUCLEATORS IN 35-MFR PP (a)
(Medium-impact Copolymer, Injection Molded Rectangle 57 x 43 cm, 0.55
kg)
Resin Tc (b) Cooling Time Modulus, Gardner Imp.,
C Reduction, % Mpa J @ -30 C
Control 109 -- 1060 1.8
Millad 3988 (c) 124 32.4 1340 1.7
ADK NA-11 (d) 125 27.8 1260 1.3
HPN-68 (e) 127 39.8 1270 1.8
HDT,
C
Control 79
Millad 3988 (c) 95
ADK NA-11 (d) 102
HPN-68 (e) 102
(a)Source: Milliken Chemical.
(b)Peak crystallization temp.
(c)Dibenzylidene sorbitol-based clarifer, Milliken Chemical
(d)Organophosphate nucleator, Amfine Chemicals.
(e)Norbornane carboxylic acid salt nucleator. Milliken Chemical.
NEED TO KNOW MORE? Amfine Chemical Co., sub, of Asahi-Denka Kogyo, Allendale, N.J. (201) 818-0035, www.amfine.com AtoFina Petrochemicals, Inc., Houston (800) 344-3462, www.atofina.com BP, Chicago (877) 701-2726, www.bp.com Ciba Specialty Chemicals, Tarrytown, N.Y. (914) 785-2000, www.cibasc.com Dow Plastics, Midland, Mich. (800) 441-4369 www.dow.com ExxonMobil Chemical Co., Houston (281) 870-6171, www.exxonmobil.com Milliken Chemical, Spartanburg, S.C. (864) 503-2200, www.milliken.com Mitsui Chemicals America, Inc., Purchase, N.Y. (914) 251-1500, www.mitsuichem.com Phillips Sumika Polypropylene Co. (800) 392-2079, www.cpchem.com/phillipssumika RELATED ARTICLE: Where They're Used Today INJECTION MOLDING & THERMOFORMING (clarified and nucleated) Thin-walled food and deli containers microwayable containers drink cups storage containers, pill bottles, syringes automotive parts. STRETCH-BLOW MOLDING (clarified) Baby bottles wide-mouth house-ware jars, pill containers, bottles for hot-fill beverages such as teas and sports drinks. Outside the U.S.: non carbonated water bottles up to 1-liter size. EXTRUSION BLOW MOLDING (clarified) Fruit jars drink and medicine bottles for personal-care products and detergents. |
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