News update: lubricants & processing aids.

The past year's new developments in lubricant additives include improved versions of conventional products, new uses for old products, and some unique specialty lubricant introductions. Most R&D has been aimed at increasing throughput rates, particularly in coextrusion of PVC pipe, siding and window profiles. Some lubricant developments are geared to weatherable PVC in siding and windows. Others are targeted for fast-growing vinyl-foam applications.

The move to lower-dusting forms of metallic stearates that reduce nuisance dust and the possibility of dust explosions has also accelerated. This is particularly the case with calcium stearates, now increasingly available in granular form, as well as zinc stearates, now available in prill form (small spheres). Multicomponent lubricant systems (e.g., paraffin wax with stearate and oxidized PE) now come in such forms as prills, pastilles, or pellets.

In processing aids, there are new products for vinyl foam and polyolefin extrusion and molding, new multifunctional blends, and products that improve dispersion of additives. One new anti-friction additive also appeared recently.

FOAM-CORE DRAWS R&D

Not much has changed in lubricant formulations for PVC pipe in at least five years, and suppliers say the reason is cost. "People are staying with formulations with proven cost/performance and are not about to look at products that may offer improved performance but at a higher cost," concedes one supplier. Traditional systems combining paraffin wax, oxidized PE wax, and calcium stearate still reign supreme.

The main exception is conduit for DWV (drain, waste, vent) applications, where suppliers are developing new lubricant formulations to support growing interest in PVC foam-core pipe. In fact, suppliers see emerging opportunities for foam in other rigid PVC applications--window lineals, picture frame profiles, and perhaps siding, as well as sheet for indoor signage.

Lou Brandewiede, technical services manager for Henkel Corp., Plastics Additives in Ambler, Pa., says the company is working on new ester wax-based co-stabilizing lubricant systems for rigid PVC foam. One product, Loxiol VGE-1875, is now available in the U.S. Henkel says the product's compatibility with PVC leads to more consistent foam density and its costabilizing action counter acts the negative effects of blowing agents.

Work on PVC foam-core extrusion is also under way at Morton International, Industrial Chemicals/Additives, Cincinnati, reports market manager Larry Kuykendall. "We are looking to produce a lubricant that incorporates an azo blowing agent and possibly other additives. This technology involves reacting, not just blending, together the single components. The advantage of putting the blowing agent into a package with lubricant and possibly heat stabilizer is that you eliminate handling problems associated with azos. Our aim is also to come up with products that give a more consistent foam density."

In addition, processors are moving rapidly away from fine-powder calcium stearate to granular forms in rigid PVC extrusion. In fact, there are indications that the increasing demand for granular product, combined with a general upturn in PVC market demand--particularly for construction--has resulted in a tight market for granular calcium stearate. One major supplier, the Synpro Lubricants Group of Cookson Specialty Additives, Cleveland, will raise prices of such products by 6% on March 1.

Two other trends are spurring lubricant reformulation efforts in PVC siding. Steve Walter, technical services manager for Akcros Chemicals, New Brunswick, N.J. (the new 50/50 joint venture of Akzo Chemicals, Inc. and England's Harcros Chemicals), reports increased demand for matte rather than glossy finish and a move to further boost output rates. In general, he says, processors are looking away from conventional calcium stearate and paraffins to complex-ester systems as well as lubricant packages with three, four, and even more ingredients. "A lot of this is due to higher outputs," Walter says. "It used to be 1000 lb/hr, then it became 1200 lb/hr, and now some are running at 1400 lb/hr."

Dark-colored window profiles are another area where lubricant reformulation efforts are evident, according to Walter. He sees increased interest in ester lubricants and in more traditional types in new combinations. One example may be an old style ester (a simple glycerine type used in bottle compounds) combined with a paraffin and EBS (ethylene bistearamide). Says Walter, "Essentially, you wind up using more internal lubricant than external."

Henkel's Brandewiede maintains that esters such as the company's Loxiol 1884 and 1728 (which cost about 81/lb and are used at 2-2.5 phr) can offer improved lubrication at today's high throughput rates. About 25% higher thermal stability can be achieved, he claims, allowing as much as 25% reduction in organotin stabilizer.

Lonza Inc., Fair Lawn, N.J., is offering a new internal lubricant, Glycolube CW-1, which is said to offer improved thermal stability in rigid PVC. It's an ester wax based on hydrogenated castor oil and is designed to compete with Henkel's Loxiol G-15. In principle, the two lubricants are identical in rheology. However, in Lonza's tests of generic PVC formulations containing 1.5 phr lubricant, CW-1 showed significantly better thermal stability by TGA (e.g., less weight loss at elevated temperatures) than the G-15. Lonza Marketing manager Tom Gazal says the product also has potential uses in polyolefin films.

MULTICOMPONENT PACKAGES

As noted above, multi-lubricant packages for rigid PVC are a recurrent theme in suppliers' R&D activities. Akcros' Walter hints that both lubricant systems and preblended lubricant/stabilizer "one-packs" are being explored by his company. And Witco Corp.'s Polymer Additives Group in N.Y.C. is focusing its efforts toward new multi-component lubricant packages of oxidized PE waxes, hydrocarbon waxes, and stearates.

Similarly, Rheochem Manufacturing Co., Watchung, N.J., aims to improve the efficiency of its lubricant systems that include oxidized PE, paraffin, and calcium stearate. "Paraffin wax and oxidized PE do not always provide adequate release properties," says president Tom Pedersen. "That can have a negative effect on heat stability and may result in surface burns and other problems such as plate-out and poor surface finish. By improving the balance of paraffin wax and oxidized PE, we have been able to reduce surface burns and minimize other processing problems."

Rheochem has launched a new line of synthetic stearate lubricant systems for rigid PVC injection molding that are fully meltable--unlike conventional calcium stearates--and also act as compatibilizing agents. The MLP (molding lubricant package) product line is designed for use with reduced levels of conventional calcium stearate. MLP 1810, for example, is used at typical levels of 1.8-2.2 phr with conventional calcium stearate at 0.75-1.00 phr. Calcium stearate is typically used at 1.50 phr. MLP products sell for around 60-70|cents~/lb.

Two other suppliers see growing use of multi-lubricant one-packs--Morton in pipe and Henkel in window profiles. Henkel now offers ester-based custom one-packs in small pellets.

Astor Wax Corp., Doraville, Ga., is looking to expand on the concept of its new lubricant/impact-modifier, Comboloob 0827 (see PT, July '93, p. 78) for rigid PVC. This one-pack contains paraffin, oxidized PE, and some organic esters. Ability to use less impact modifier to maintain toughness of highly filled compounds is said to result in cost savings. The product is also said to promote early fusion, preventing the melt from overheating. It sells for 80|cents~/lb and is used at 1.5-1.7 phr.

MORE NEW LUBRICANTS

AlliedSignal Inc., Morristown, N.J., is pursuing new applications for its high-density A-C oxidized PE products, says Robert Lindner, industry manager for plastics and rubber. Although traditionally used in clear PVC bottles, rigid PVC extrusion of sheet, window profiles, and siding now look promising, as does injection molding. Lindner notes that high-density A-C products melt at 280 F, higher than most other external lubricants.

The A-C 300 series of high-density oxidized PE includes an old product, A-C 316, and newer A-C 307 with lower acid value and higher viscosity. Recent experiments show that both products speed fusion in rigid PVC extrusion and in injection molding. The products can be used with either paraffins or esters; when combined with the latter, they reportedly eliminate the need for processing aids. In one experiment, PVC sheet produced with A-C 316 at only 0.3 phr, an ester internal lubricant at 1.7 phr, and calcium stearate at 1.0 phr exhibited 20% higher impact strength than PVC sheet produced with paraffin wax at 1.0 phr, processing aid at 1.5 phr, and calcium stearate at 1.0 phr.

John Stiverson of the A-C Performance Additives Div. sees potential in improving the processing of PVC regrind. And because A-C 307 has unusually low tendency to plate out, Stiverson also sees potential for it in PVC calendering. "Most oxidized PE tends to plate out in calendering, but this product is far less likely to," says Stiverson. High-density oxidized PE grades sell for $1.29-1.45/lb and are used at low levels--0.2-0.3 phr.

Although AlliedSignal until now has focused on PVC, Stiverson says new developmental A-C additives for ABS and other styrenics look promising. Details should be released soon.

Elf Atochem North America, Philadelphia, recently began importing from its French parent limited quantities of Stavinor CA-PSE, a high-purity grade of calcium stearate for rigid PVC. Also new from Elf Atochem is a specialty lubricant designed for use with calcium stearate in place of oxidized PE, ester wax, or montan wax in calendered and extruded, rigid or flexible PVC sheet and film. The product is described as a high-molecular-weight acrylic polymer that is very durable and gives superior metal release. List price is $3/lb, but use levels are less than 1 phr.

Hoechst Celanese Corp., Waxes Business Div., Somerville, N.J., has recently added to its line of Hoechst montan waxes. These include sodium, lithium, and calcium soaps that can act as nucleating agents, flow improvers, and mold releases in clear rigid PVC (film, bottles) and engineering plastics, including polyesters, nylon, styrenics, PPO, and PPS.

Witco has introduced an extra dense, heat-stable zinc stearate in prill form to enhance bulk handling as a lubricant for PS, polyolefins, and other thermoplastics.

NEWS IN PROCESSING AIDS

Elf Atochem is finding new applications for its two-year-old Metablen P530 acrylic processing aid, previously used in PVC sheet and profiles. According to market manager Art Van Norstrand, it shows promise in rigid foam and flexible PVC, such as automotive interior parts, as well as extruded exterior body parts. "P530 has very high molecular weight--probably the highest on the market--a key requirement for process aids used in foam," says Van Norstrand. P530 lists at $1.76/lb but reportedly can be used at half the levels of competitive products. Typical levels are 2-4 phr in foam-core pipe and a bit more in profile or sheet.

Rohm & Haas Co., Philadelphia, is offering new Paraloid K-400 acrylic processing aid for rigid PVC foam, which is said to allow for extremely low densities in combination with excellent surface qualities--a difficult balance to achieve, according to marketing manager Jim Souder. K-400 is aimed mainly at foam sheet for interior signs (replacing painted plywood), as well as foam core window profiles and DWV pipe. Use levels range 2-8 phr.

The company also has a new multifunctional blend, Paraloid KM 390, which combines an acrylic impact modifier with a processing aid and is gaining ground in siding at use levels of 5-6 phr.

Struktol Co., Stow, Ohio, has added to its relatively new Polydis TR line of fatty acid derivatives. Among the newest grades are TR 060 and 065 (PT, July '93, p. 79), designed to improve flow, dispersion, and retention of mechanical properties in highly filled ABS, polycarbonate, PPE, and PPS. They also are said to improve mixing of polymer alloys. TR 071, a fatty acid/zinc complex with amide functionality, is finding uses in PS at 0.1-0.5 phr and reportedly offers better lubrication than stearates in highly filled systems or PS compounds.

Still newer is a proprietary fatty-acid derivative, SA 9307, designed to replace EBS wax as a process aid in PP, PE, ABS, and filled systems--primarily for injection molding. Use levels are 0.1-0.5 phr, and it is priced competitively with EBS. Technical sales manager Joe Wasko says the product has a 36 |degrees~ F lower melt point than EBS, which makes it advantageous in processing lower-melting resins. Products come in mini pellets or prills.

OSi Specialties, Inc., Danbury, Conn., which acquired the organosilicon chemicals business of Union Carbide last year, reports that its PA-1 organosilicon processing aid for polyolefin films has found new uses in wire and cable and injection molding. In these processes, PA-1 serves as a dispersion aid or vehicle for pigments and stabilizers.

Hoechst Celanese Corp.'s Polymer Additives Group, Charlotte, N.C., introduced Hostalub G 1973 fluoroelastomer-based processing aid for LLDPE and HMW-HDPE film about a year and a half ago. It comes in pellet form, and a 1% addition is said to reduce back pressure by up to 40% and minimize melt fracture, enabling higher film outputs.

Hoechst Celanese also reports having found some processing benefits from its Hostastat HS-1 antistat system (sodium alkyl sulfonate), available in fine granular or masterbatch form and used in PS, ABS, PVC, styrenic alloys, copolymers, and acrylics. At use levels of 1-3 phr, the product reportedly also improves pigment dispersion and processability, reducing backpressure and melt temperature. It can also be used in PP and PE when masterbatched with the right carrier resin.

ANTI-FRICTION LUBRICANT

A lubricant of a different kind--for reducing friction and wear of a product in its end use, rather than processing--is the new Teflon MP 1600 micropowder PTFE from DuPont Co.'s Fluoroproducts Div., Wilmington, Del. (PT, Feb. '93, p. 72). This latest addition to its Teflon fluoro-additives line is said to have a very narrow molecular-weight distribution and contains no acid end groups so that there are no incompatibility problems with other blend components. The 4-12 micron particles are easily broken down into tiny 0.2-micron primary particles. It is also FDA-approved for food-contact applications.