Last year, approximately 1. 073.1 billion lb of PE resins were consumed in the production of sheet and tubing film, also referred to as converter film. With an average annual growth rate (AAGR) of 3.6%, PE resin consumption for the production of sheet and tubing film should reach 1.194 billion lb by 2017.
Several processing companies are periodically involved in the sheet and tubing market,manufacturing sheet and tubing on an “as needed basis” to fill capacity during slower periods of demand for other traditional PE film products. Other PE film extrusion companies reported manufacturing sheet and tubing intermittently according to specifications by film converters or end-use customers. Some participants in this market extrude film only, while others extrude film and also convert film into various packaging products.
According to Mastio research, during 2014, the six largest sheet and tubing processors that participated in the company’s study were market were: Sigma Plastics Group; Apollo Management, L.P. (Berry Plastics Corp. Div.); Next Generation Films, Inc.; Emballages Polystar (Polystar Packaging Canada, Inc. Div.); Inteplast Group Ltd. (IBS Div.; Lone Star Plastics, Inc. Div.; Niaflex Corp. Div. & Trinity Plastics, Inc. Div.) and Inteplast Group Ltd. (P&O Packaging, L.L.C. Div.). Collectively, those processors gobbled up close to 50% of the material consumed in this market.
Overall consumption of LLDPE-butene, LLDPE-hexene, LLDPE-super hexene, LLDPE-octene, and mLLDPE resins have outpaced overall consumption of LDPE resin for the sheet and tubing market, according to Mastio research. LLDPE resins yield greater impact strength and puncture resistance in lower gauges than LDPE resin. High-clarity grades of LLDPE resin allows manufacturers to produce films with high optical properties in thinner gauges than was previously possible with LDPE/LLDPE resin blends. This has further eroded LDPE resin’s dominance in this market.
LDPE resins were the second most utilized material of choice for the production of sheet and tubing, either utilized alone, in blends, or in multi-layer film coextrusion. LDPE resin’s characteristics of high clarity, ease of processing, low relative costs, and adaptability of blending with other PE resins are some of the reasons for its greater use. LDPE-copolymers, such as LDPE-ethylene vinyl acetate copolymer (LDPE-EVA copolymer), LDPE-ethylene methyl acrylate copolymer (LDPE-EMA copolymer), and LDPE-ethylene acrylic acid copolymer (LDPE-EAA copolymer) resins will continue to be utilized in blends or in multi-layer film coextrusion with other PE resins.
Medium molecular weight-HDPE (MMW-HDPE) and high molecular weight-HDPE (HMW-HDPE) resins are extruded solely, in blends, or in film coextrusion with LDPE and LLDPE resins. HDPE resins allow even further downgauging, while providing even greater film strength than LLDPE resins. HDPE resin is also utilized as an additive in blends with LDPE or LLDPE resins, or as a processing aid to add stiffness and increase bubble stability in blown film extrusion. This is especially helpful in bubble diameters greater than 80 in. Additional benefits of utilizing HDPE resin are added barrier properties, excellent environmental stress crack resistance (ESCR), and greater ease for converting the film into finished bags or sacks. However, when implementing HDPE resin, some film clarity is sacrificed.
Other resins reported in the market during 2014 included the following: medium density PE (MDPE), polypropylene (PP), nylon, and ethylene-vinyl alcohol copolymer.
During 2014, the 99.7% of film for the sheet and tubing market was produced utilizing the blown film process, accounting for 1,069.6 MM lbs. (99.7%) of resin consumption, states Mastio. Cast film accounted for the rest. Monolayer sheet accounted for about 60.3% of PE resin consumption, with coextruded sheet representing the rest.
Improvements in both film coextrusion and PE resin technologies have greatly increased the sophistication of PE films. A greater variety of film characteristics are now possible, such as a three-layer form, fill and seal sheeting with different levels of coefficient of friction (COF). The film can have outside high cling, inside high slip, and a sandwiched layer of linear low density PE (LLDPE) resin manufactured using the metallocene single-site catalyst process (mLLDPE). The high cling side helps prevent the packaged product from shifting or slipping after being stacked. The one side high slip allows greater ease of inserting the product into the package. The inner layer of mLLDPE resin allows faster production rates by affording greater hot tack strength than conventionally produced PE resins.
Film downgauging is another advantage of film coextrusion technology, by allowing film processors to combine low density PE (LDPE) resin with stronger LLDPE or high density PE (HDPE) resins. Coextruded sheet and tubing film ranged from two-layer to seven-layer constructions, with the three-layer structure being the most typical.
MY TWO CENTS
Converter film is one market where complex film structures will continue to be developed as processors seek a means to distinguish their products from competitive offerings. Today’s three-layer structures will be tomorrow’s five-layer configurations, as suppliers of both materials and extrusion technology continue to push the envelope in product development. Another trend to watch is development of new equipment technologies that help processors switch from one product to another to minimize waste and allow them to more ready deal with lower-volume runs.