Volume thermoplastics to challenge higher-cost 'engineering' resins.

Volume Thermoplastics To Challenge Higher-Cost 'Engineering' Resins

Much like engineering resins, developments in high-volume or "commodity" thermoplastics in the 1990s will hinge on new copolymer and alloy technologies. The results will be especially apparent in polyolefins.

With new ways of making higher-performance, "engineering-level" grades, commodity thermoplastic producers say their materials will be able to steal away many "over-engineered" applications from more pricey resins.

A second key trend in commodity thermoplastics will be to bolster the processability and cost competitiveness of standard, high-volume grades. Several suppliers say their new-material thrust for the 1990s includes boosting the processability and melt-flow rates. Once again, new copolymer, compatibilization and in-reactor catalyst technologies will hold the key to these developments.

PP & PE: EXCITING TIMES

The revolution in polyolefins that began with LLDPE is continuing. In polyethylene, there is additional potential to exploit in Union Carbide Corp.'s Unipol polymerization process, which started it all, as well as in newer technologies such as Exxon Chemical Co.'s Exxpol and proprietary technologies like that of Quantum Chemical's USI Div.

In polypropylene, the Unipol PP process (a Carbide/Shell Chemical Co. collaboration) and Himont's Spheripol process are starting to show real potential, and will be joined by newer developments like Himont's Catalloy process.

Robert J. Ockun, marketing v.p. for Himont Inc., Wilmington, Del., speaks of the "transmutation" of PP. He says the potential of the new polymerization processes has barely been appreciated so far, because initial efforts were largely directed at duplicating existing grades produced by older processes.

Ockun also believes the perception of PP will change. He says his firm believes PP already has become a family of materials in the same sense that PE is a family consisting of at least six separately identifiable product lines--conventional LDPE, LLDPE, HDPE, HMW-HDPE, UHMW-PE, and VLDPE. Just as many new PEs are actually ethylene copolymers with higher alpha-olefins, Ockun feels many new PPs will be copolymers with familiar and exotic comonomers--leading him to propose that "it might be more appropriate for the industry to adopt the term 'propylene-based' resins instead of PP."

One major trend for polyolefins during the next 10 years will be continued movement towards more reactive, functionalized material systems, according to Charles M. Neeley, senior research associate for the Texas Eastman Co. unit of Eastman Chemicals, Kings-port, Tenn. While ethylene copolymers have become familiar since the advent of LLDPE, a breakthrough will be successful commercial development of new catalyst technology to create polypropylene polar copolymers. This is a target area of material research for Eastman and other polyolefin producers, according to Neeley.

A polar-copolymer PP would have reactive or adhesive functionality, overcoming the usual inertness of PP and providing greater compatibility with other resins for alloying or better wettability of fillers and reinforcements. Research thrhoughout the industry is concentrating on developing new catalyst systems for functionalized polyolefins, Neeley says.

Research into new catalyst technology for polyolefins also is at the core of efforts under way at the USI Div. of Quantum Chemical Corp., Cincinnati. "New catalyst technology will be responsible for advances we'll see in polyolefins in the 1990s," William Bowles, director of process/catalyst research and technology acquisitions at Quantum, says. Bowles says catalysts will provide a greater control of properties in the resins, as well as higher outputs and more efficient production, which can be passed along to customers in the form of lower prices. An example of property control would be to make lower-molecular-weight polyolefins with melt-flow rates up to 100 g/10 min.

Besides better processing characteristics, new catalysts also will give rise to a broad range of in-reactor polyolefin alloys, elastomers and filled blends, eliminating post-reactor steps such as compounding, Bowles predicts. In fact, in-reactor TPOs and other copolymers, made without compounding, is a major thrust of Unipol PP work not only at Eastman but also at Shell Chemical Co., Houston, and at Himont and Quantum. Quantum also has technology for in-reactor incorporation of fillers into PP.

Attaining such a level of in-reactor modification could, to some extent, supersede technologies such as compatibilizers for new alloys and dynamic vulcanization for elastomers. Elimination of such additional processing and alloying steps would result in major economic benefits for both producers and processors. It's believed such an all-inclusive, in-reactor approach is the basis of the Catalloy technology now under development at Himont, although company officials decline to comment. However, Himont officials previously have said Catalloy technology will employ special catalysts to produce an assortment of "in-reactor alloys" by allowing PP to be copolymerized with different comonomers and termonomers, including ones never used before in polyolefins (PT, May '89 p. 15).

It's believed Catalloy is the focus of Himont's efforts to push PP into the ranks of an engineering resin for the 1990s. It announced plans to construct a 175-million-lb/yr Catalloy plant later this year in Bayport, Texas, coming on the heels of its first such facility in Ferrara, Italy (PT, May '89, P. 97).

A hint of what's to come from Himont's various processes is given by Bob Ockun:

* New high-crystallinity, heat-resistant grades (some of which are already available from Chisso of Japan), which are harder, glossier and more abrasion resistant.

* Melt-formable sheet extrusion grades, like those from Exxon Chemical Co., Houston (PT, Aug. '89, p. 53).

* Extrusion coating grades that process four to five times faster than previous PPs, equaling or exceeding coating line speeds possible with LDPE.

* Easy-to-mold 40-50% glass-filled compounds based on resins with unique rheological properties.

* In-reactor TPOs spanning a broad range from flexible to rigid, with better processability and performance than previous grades.

Himont also continues to focus on compatibilization technology as a means to deliver its next-generation materials. Kenneth R. Dargis, director of marketing, says Himont currently has two PP-based developmental alloys slated for commercial introduction in 1993. Dargis says they incorporate a Himont-developed compatibilizer to alloy PP with other unnamed polymers, and to provide better wetting of and adhesion to glass and mineral reinforcements.

The two developmental alloys are injection molding grades, offering heat-deflection temperatures up to 275 F and improvements in gloss, impact and physical properties compared with ABS, according to Dargis. He also foresees PP-based alloy grades for extrusion, thermoforming and blow molding.

A new post-treatment adjunct to Himont's Spheripol polymerization system (see PT, June '89, p. 29) will be a basis for launching many new PP-based products during the next 10 years, according to Craig Blizzard, industry director of the Natural Resins Group. The process involves the post-reactor coating of stabilizers and other additives onto the outside of polymer spheres, eliminating the need for conventional compounding (PT, June '89, p. 29). This "Valtec" technology reportedly retains a lower level of crystallinity for the material, requiring less energy for final molding or extrusion, plus faster melting and higher throughput rates. Slightly higher mechanical properties may also result. Himont has introduced at least seven Valtec PP grades (PT, Dec. '89, p. 64), including an 800-MFR grade for meltblown fibers and one of 0.2 MFR for heavy-gauge sheet, neither of which was possible with previous technology according to the company.

Improved grades of homopolymers and random copolymers for extrusion and thermoforming, as well as new clarified homopolymer and random copolymer grades for injection stretch-blow and injection blow molding are among the long-range polypropylene developments for Fina Oil & Chemical Co., Dallas. Joseph M. Schardl Jr., manager, customer technical services, says the company hopes to develop a random copolymer grade that will approach the clarity of PET.

Earlier this year the company introduced an injection molding grade, UL rated at 248 F for long-term heat aging. Fina is also working on a new high-uv-stability grade for tape extrusion.

Finally, two areas that virtually all PP suppliers are actively developing are improved thermoforming grades and high-clarity blow molding resins. (PT, Aug. '89, p. 51; Sept. '89, p. 15).

INTERPENETRATING NETWORKS

Another research thrust in polyolefins involves partially crosslinked systems, creating an "interpenetrating network" of previously incompatible resins, which is another development focus for Eastman. Neeley said this physical intertwining of two polymers would be an alternative to compatibilizing of two immiscible polymers with a third one.

Research at Eastman involves selection of special polyolefins, matching them with certain other resin groups, then chemically modifying the polymers to partially crosslink their respective molecular chains. Neeley says the resulting material can be processed as a thermoplastic, yet offers improved physical and mechanical properties, combining those of the two component resins. An example is Monsanto Chemical Co.'s Santoprene, which crosslinks diene rubber into a PP matrix.

A NEW TYPE OF POLYETHYLENE

In polyethylene, a new class of polymers that has just begun to be exploited is called "ultra-low" or "very low" density PE (VLDPE or ULDPE). Union Carbide Chemicals and Plastics Co. Inc., Danbury, Conn., was the first to commercialize it in 1984 (see PT, Oct. '84, p. 13), followed by Dow Chemical Co., Midland, Mich., and soon will be joined by Exxon Chemical Co., Houston. Quantum is researching this area. These materials can have densities as low as 0.88 g/cc and flex moduli down to 4000 psi, coupled with the toughness of LLDPE. They're beginning to find applications on their own and as replacements for ethylene-propylene rubber in TPO's.

Union Carbide's Michael Corwin, business manager for specialty polyolefins, says its VLDPE "Flexomers" will be a major thrust of Unipol-process research in the '90s. Flexomers are copolymers that can contain 20-25% propylene. They reportedly blend easily with polypropylene, showing good adhesion and resisting blushing.

A new catalyst system developed by the Polymers Group of Exxon Chemical is expected to yield advances in PE in the '90s. Known as the Exxpol family of single-site catalysts, the technology will be employed at the company's new 33-million-lb/yr facility in Baton Rouge, La., for producing specialty linear ethylene-based polymers (PT Feb. '90, p. 88; Nov. '89, p. 14). The plant is slated for completion later this year and will incorporate process technology licensed from Mitsubishi Petrochemical Co. Ltd. of Japan.

Conrad Jankowski, v.p. of Core Technology Polymers, says Exxpol technology will be the key to Exxon Chemical's polyolefin material development strategy during the next 10 years, in conjunction with several unspecified joint-development efforts.

While details of the Exxpol system remain confidential, the technology reportedly provides a high level of control of molecular-weight distribution of the resin and the insertion of comonomers. This more precise MWD control allows the polymer structure to be tailored for various properties, such as toughness, crystallinity, gloss, creep and processability.

The Exxpol system initially will be used for LLDPE, including Exxon's first "very low-density" PE (VLDPE), although Jankowski expects that Exxpol technology will also be applied to PP to extend its performance into the engineering plastics domain.

Other technical advances in PE during the next 10 years will continue work already begun in such areas as LLDPE, HDPE and HMW films (PT, Aug. '89, p. 23). One example is Quantum's prediction of a "renaissance" for its unique HMW-LDPE, which can make use of long-stalk, blown-film technology designed for HMW-HDPE (PT, Aug. '89, p. 23; Feb. '90, p. 72).

PVC: MORE STABLE

Increased thermal stability for hot-runner molding, more demanding high-heat end uses, and greater diversity in alloys and copolymers will be among the leading technical trends for PVC in the 1990s. PVC upgraded to an engineered material, offers inherent advantages of flame retardance, low cost and broad alloying properties, says William J. Windscheif, director, polymers business development for Vista Chemical Co., Houston.

Higher heat properties and mineral-filled resins for structural blow molding applications represent the leading edge of PVC development for the Geon Vinyl Div. of BFGoodrich, Cleveland. Don Knechtges, v.p. of marketing and business management, says laboratory technology now is in place to deliver a PVC alloy capable of attaining a heat-deflection temperature in the 220 F range (PT, March '90, p. 15). Existing PVC grades from Goodrich can achieve temperatures of up to 190 F.

In a separate development effort, Goodrich is looking to improve the thermal stability of PVC compounds for hot-runner injection molding and structural blow molding. Goodrich currently is involved in joint-development work with hot-runner tool makers and processors.

Goodrich officials said the new hot-runner material utilizes novel polymerization technology and monomer sources, as well as a "redesign" of the vinyl molecule. "PVC will need a higher order of heat stability for structural blow molding," asserts Clive J. Copsey, group leader for Geon Plastics technology. "High melt viscosity is needed for rigidity of melt in structural blow molding, but a high-viscosity material also tends to slow cycle times," he said. "We feel w've made major breakthroughs in understanding the heat stability of vinyl molecules. We now can play with those properties on a molecular level." He also said the firm's new Application Engineering and Design Laboratory (AEDL) will concentrate on mineral-filled grades of PVC for structural blow molding.

John Kirkpatrick, director of polymer technology for Vista, also indicates future R&D on improving the interface between PVC and inorganic fillers. "There's a variety of chemistry we can draw upon to help us improve the filler wettability and reduce the surface tension at interface."

Vista in a joint effort with Monsanto Co., St. Louis, is pursuing the alloy route to overcome long-standing skepticism about PVC among injection molders. Through PVC/styrenic blends, Vista hopes to market easy-molding, flame-retardant materials for a variety of markets (PT, April '90, p. 63).

The PVC Resins & Compounds Div. of Occidental Chemical Corp., Berwin Park, Pa., is focusing much effort on the development of new "hybrid" dispersion PVC resins for the 1990s (see PT, July '89, p. 41). The dispersion technology, which has been under development for several years, involves a new polymerization method that joins the emulsion and micro-suspension processes. This hybrid polymerization is adaptable to any dispersion resin, offering the ability to develop new polymers.

NON-PVC 'VINYLS'

Both Goodrich and Vista recently launched the first of what are expected to be larger families of proprietary materials that the suppliers say are "based on vinyl technology but are not PVC." Spokesmen for both firms decline to offer further explanations on the compositions at present. The first products of this type are Goodrich's Flexel copolymer alloys and Vista's Plenex TP elastomer, said to be neither a conventional alloy nor copolymer. (PT, Feb. '90, p. 19; March '90, p. 13).

Vista has since extended this technology with two unnamed, developmental injection molding grades. One boasts an HDT of 182 F, and future grades may achieve 219 F and higher. Windscheif describes the material as having superior moldability, flow and knit-line characteristics, while retaining inherent flame-retardant properties. The second new grade is a rigid injection material with HDT in the range of 150 to 180 F. Again, enhanced processability--without a sacrificing mechanical properties--is key.

Vista says these two materials will be the firm's "springboard" for future lines of more complex composite and alloy product lines during the next 10 years. Composite materials in particular, utilizing glass and mineral reinforcements, will be a focus for the company.

POLYSTYRENE: WIDER RANGE

Seeking to broaden the performance envelope of polystyrene through a major boost in thermal properties, the Plastics Group of Dow Chemical U.S.A., Midland, Mich., is developing a styrenic material with a heat deflection temperature in the range of 400F. Fred P. Corson, v.p. of R&D described the program as being in the initial stages of development, with hopes for a commercial product by the second half of the decade. He would not elaborate on the details of the project, but did say the technology behind the new styrenic involved modifying the chemical structure of the material, perhaps through copolymerization with another resin group.

A PS with elevated thermal properties also is a research thrust for the Polystyrene Business Group of Mobil Chemical Co., Edison, N.J. George Barile, manager of styrenics R&D, sees an opportunity to increase the thermal performance of PS through alloying and new comonomer technologies.

A new injection molding polystyrene grade, now under development at Fina Oil & Chemical, will seek to optimize such properties as faster cycle times, higher gloss and improved impact strength, according to Schardl. He would not elaborate further on the specific material development, saying only it's targeted for 1991-92 introduction.

And in the area of high-impact polystyrene food packaging applications, Schardl says the company is working on enhanced grades that resist stress cracking from animal and vegetable oils. Fina recently introduced a new PS grade for sheet thermoforming, fatty-food contact applications, known as CX9005.

Improved product consistency also will be a driving force behind styrenic material developments for Polysar Inc., Leominster, Mass. Polysar will look to improve toughness and impact resistance of its styrene/acrylic copolymers in the '90s through new polymerization methods and alloys.