Several new developments in additives and polymers were unveiled at SPE's Polyolefins 2000 RETEC conference, held in Houston last month.

Several new developments in additives and polymers were unveiled at SPE's Polyolefins 2000 RETEC conference, held in Houston last month. New additives included a solid phosphite antioxidant that offers superior thermal stability; a HALS uv stabilizer with flame-retardant properties; another novel HALS that gives excellent uv stability to colored TPO, and a lubricant that improves the processability of mLLDPE blown film. Also new is a peroxide that improves the smell of "controlled-rheology" PP.

Among the highlights in new polymer technologies is the first of a new generation of PP impact copolymers with enhanced impact/stiffness balance. Also new is a heat-shrinkable LLDPE film resin that can be processed on older LDPE equipment, as well as elastomeric "branch-block" copolymers of PP with PE side chains, made with mixed metallocene catalysts.

 

HALS fights flame

Ciba Specialty Chemicals, Tarrytown, N.Y., unveiled new data on CGL-116, an N-alkoxy hindered amine light stabilizer (NOR-HALS) that was first launched two years ago. It is reportedly a potent, long-term thermal and uv light stabilizer for polyolefins that also acts synergistically with flame retardants to retard combustion in polyolefin fibers and molded parts.

Ciba researchers showed the synergy of CGL-116 NOR with brominated flame retardants such as decabromodiphenyl oxide (DBDPO) in polypropylene moldings. CGL-116 significantly reduced the burning time of the PP and allowed a UL 94V-2 rating to be achieved with a much lower level of DBDPO. Ciba also showed that the NOR-HALS can replace antimony oxide in V-2 formulations. Research is now aimed at obtaining a V-0 rating in filled PP.

At the conference, Ciba also presented a developmental non-interactive, low-basicity HALS for automotive TPOs and demanding PP applications. According to Ciba's data, new CGL-074 provides far better uv stability in pigmented and unpigmented TPOs and PP copolymers than a standard HALS such as Ciba's Tinuvin 770. Under simulated acid-rain testing, the new HALS also provided better protection against surface degradation. Because of its reduced interaction with acid-cured 1K paint systems, it also allowed much better paint adhesion to the TPO surface.

In the antioxidant field, Dover Chemical Corp., Dover, Ohio, discussed new versions of its D-Blends that contain its free-flowing solid phosphite, Doverphos S-9228. This high-activity, high-molecular-weight, low-volatility, and hydrolytically stable phosphite has only recently been made in commercial quantities. As shown in the accompanying graph, D-Blends with S-9228 can provide better stabilization in multi-pass extrusion of PP homopolymer than blends of workhorse phosphites such as Irgafos 168 from Ciba Specialty Chemicals or Dover's equivalent, Doverphos S-480. Although the new phosphite is more costly, its blends can be used at levels only one-third to half those incorporating the other phosphites. In addition, Doverphos S-9228 has received broader approval from the FDA permitting its use in all polymers with any type of food at any temperature.

 

New aids to processability

Improved taste and odor can now be combined with high melt flow in controlled-rheology (CR) PP by replacing the industry standard peroxide (2,5-dimethyl-2, 5-di-t-butylperoxyhexane, or DTBPH) with a t-amyl dialkyl peroxide from CK Witco Corp., Greenwich, Conn. This makes CR resin more suitable for food and medical packaging such as candy wrappers, bottles, and syringes. Witco says this alternative peroxide has been used in rubber and as a food additive, but not in polyolefins. A loading of 0.02% can convert an 8-MFR PP into an 18-MFR CR-PP.

New Glycolube ML-1, a fatty ester lubricant eases extrusion of mLLDPE blown films, according to Algroup Lonza, Fairlawn, N.J. The additive reduces the extruder drive energy required to process a 1-MI mLLDPE, as indicated by reduced amps/rpm and by an increase in film output/amp. Printability of film containing ML-1 is reportedly outstanding.

 

New polymers emerging

Newly commercial high-flow, medium-impact PP copolymers offering enhanced impact/stiffness balance are the first in a series of next-generation impact copolymers being developed by Union Carbide Corp., Danbury, Conn. Based on a new catalyst system, Imppax copolymers are produced in the Unipol gas-phase PP process. Grade SRD7646, a nucleated 35-MFR in-reactor copolymer is 20% stiffer than Carbide's 7C12N, a 22-MFR conventional CR impact copolymer that has nearly the same impact strength. Table 2 compares injection molded properties with those of three 35-MFR copolymers made with Montell's Spheripol process and Mitsubishi Petrochemical's Hypol process.

Progress in developing so-called "branch-block" copolymers with elastomeric properties was reported by Houston-based ExxonMobil Chemical Co. The process uses mixed metallocene catalysts. One catalyst generates vinyl-terminated,crystallizable PE "macromonomers" (or macromers) while the other incorporates the macromers into low-crystallinity backbones, such as PP. Mechanical properties of resulting resins can be controlled by varying the branch and backbone composition and length, as well as branching concentration. ExxonMobil has made block copolymers with modulus, tensile strength, and elastic recovery that surpass those of metallocene-catalyzed ethylene/butene plastomers with similar densities. ExxonMobil says this technology can produce a wide range of materials, including hard, elastic resins and impact-resistant copolymers, as well as materials suitable for use as compatibilizers of immiscible resin blends.

Union Carbide also unveiled a new Unipol gas-phase LLDPE of 0.7 MI and 0.9258 density that reportedly extrudes easily on equipment designed for LDPE and LDPE-rich blends. The resin was shown to extrude into heat-shrinkable film with good TD shrinkage at common blow-up ratios. It exhibits the toughness of conventional LLDPE, allowing for downgauging relative to LDPE.

Several new developments in additives and polymers were unveiled at SPE's Polyolefins 2000 RETEC conference, held in Houston last month. New additives included a solid phosphite antioxidant that offers superior thermal stability; a HALS uv stabilizer with flame-retardant properties; another novel HALS that gives excellent uv stability to colored TPO, and a lubricant that improves the processability of mLLDPE blown film. Also new is a peroxide that improves the smell of "controlled-rheology" PP.

Among the highlights in new polymer technologies is the first of a new generation of PP impact copolymers with enhanced impact/stiffness balance. Also new is a heat-shrinkable LLDPE film resin that can be processed on older LDPE equipment, as well as elastomeric "branch-block" copolymers of PP with PE side chains, made with mixed metallocene catalysts.

 

HALS fights flame

Ciba Specialty Chemicals, Tarrytown, N.Y., unveiled new data on CGL-116, an N-alkoxy hindered amine light stabilizer (NOR-HALS) that was first launched two years ago. It is reportedly a potent, long-term thermal and uv light stabilizer for polyolefins that also acts synergistically with flame retardants to retard combustion in polyolefin fibers and molded parts.

Ciba researchers showed the synergy of CGL-116 NOR with brominated flame retardants such as decabromodiphenyl oxide (DBDPO) in polypropylene moldings. CGL-116 significantly reduced the burning time of the PP and allowed a UL 94V-2 rating to be achieved with a much lower level of DBDPO. Ciba also showed that the NOR-HALS can replace antimony oxide in V-2 formulations. Research is now aimed at obtaining a V-0 rating in filled PP.

At the conference, Ciba also presented a developmental non-interactive, low-basicity HALS for automotive TPOs and demanding PP applications. According to Ciba's data, new CGL-074 provides far better uv stability in pigmented and unpigmented TPOs and PP copolymers than a standard HALS such as Ciba's Tinuvin 770. Under simulated acid-rain testing, the new HALS also provided better protection against surface degradation. Because of its reduced interaction with acid-cured 1K paint systems, it also allowed much better paint adhesion to the TPO surface.

In the antioxidant field, Dover Chemical Corp., Dover, Ohio, discussed new versions of its D-Blends that contain its free-flowing solid phosphite, Doverphos S-9228. This high-activity, high-molecular-weight, low-volatility, and hydrolytically stable phosphite has only recently been made in commercial quantities. As shown in the accompanying graph, D-Blends with S-9228 can provide better stabilization in multi-pass extrusion of PP homopolymer than blends of workhorse phosphites such as Irgafos 168 from Ciba Specialty Chemicals or Dover's equivalent, Doverphos S-480. Although the new phosphite is more costly, its blends can be used at levels only one-third to half those incorporating the other phosphites. In addition, Doverphos S-9228 has received broader approval from the FDA permitting its use in all polymers with any type of food at any temperature.

 

New aids to processability

Improved taste and odor can now be combined with high melt flow in controlled-rheology (CR) PP by replacing the industry standard peroxide (2,5-dimethyl-2, 5-di-t-butylperoxyhexane, or DTBPH) with a t-amyl dialkyl peroxide from CK Witco Corp., Greenwich, Conn. This makes CR resin more suitable for food and medical packaging such as candy wrappers, bottles, and syringes. Witco says this alternative peroxide has been used in rubber and as a food additive, but not in polyolefins. A loading of 0.02% can convert an 8-MFR PP into an 18-MFR CR-PP.

New Glycolube ML-1, a fatty ester lubricant eases extrusion of mLLDPE blown films, according to Algroup Lonza, Fairlawn, N.J. The additive reduces the extruder drive energy required to process a 1-MI mLLDPE, as indicated by reduced amps/rpm and by an increase in film output/amp. Printability of film containing ML-1 is reportedly outstanding.

 

New polymers emerging

Newly commercial high-flow, medium-impact PP copolymers offering enhanced impact/stiffness balance are the first in a series of next-generation impact copolymers being developed by Union Carbide Corp., Danbury, Conn. Based on a new catalyst system, Imppax copolymers are produced in the Unipol gas-phase PP process. Grade SRD7646, a nucleated 35-MFR in-reactor copolymer is 20% stiffer than Carbide's 7C12N, a 22-MFR conventional CR impact copolymer that has nearly the same impact strength. Table 2 compares injection molded properties with those of three 35-MFR copolymers made with Montell's Spheripol process and Mitsubishi Petrochemical's Hypol process.

Progress in developing so-called "branch-block" copolymers with elastomeric properties was reported by Houston-based ExxonMobil Chemical Co. The process uses mixed metallocene catalysts. One catalyst generates vinyl-terminated,crystallizable PE "macromonomers" (or macromers) while the other incorporates the macromers into low-crystallinity backbones, such as PP. Mechanical properties of resulting resins can be controlled by varying the branch and backbone composition and length, as well as branching concentration. ExxonMobil has made block copolymers with modulus, tensile strength, and elastic recovery that surpass those of metallocene-catalyzed ethylene/butene plastomers with similar densities. ExxonMobil says this technology can produce a wide range of materials, including hard, elastic resins and impact-resistant copolymers, as well as materials suitable for use as compatibilizers of immiscible resin blends.

Union Carbide also unveiled a new Unipol gas-phase LLDPE of 0.7 MI and 0.9258 density that reportedly extrudes easily on equipment designed for LDPE and LDPE-rich blends. The resin was shown to extrude into heat-shrinkable film with good TD shrinkage at common blow-up ratios. It exhibits the toughness of conventional LLDPE, allowing for downgauging relative to LDPE.