Extrusion coating, paper adhesion

Today, it has almost totally been replaced by LLDPE. The main market for LDPE is in high-clarity products, which includes produce bags, bakery film, and textile and paper overwrap. Overall film use is declining by 0.4% per year. With the exception of extrusion coatings and adhesives and sealants, LDPE s other application segments are declining 2-3% annually, largely as a result of displacement by LLDPE. 

Ecovio FS Paper is also a compound of Ecoflex FS and PLA with a very high content of renewable resources. This grade was optimized for extrusion coating of paperboard. It can be processed on standard PE equipment and shows an excellent adhesion to card board and paper. The Ecovio coating forms a barrier for fat vegetable and mineral oil, liquid and aroma. Applications of choice are compostable paper cups for hot and cold drinks, freezer boxes or paper wraps for snacks. 

In contrast to most extmsion processes, extrusion coating involves a hot melt, ca 340°C. The thin web cools rapidly between the die and nip even at high linear rates. Both mechanical and chemical bonding to substrates are involved. Mechanical locking of resin around fibers contributes to the resin s adhesion to paper. Some oxidation of the melt takes place in the air gap, thereby providing sites for chemical bonding to aluminum foil. Excessive oxidation causes poor heat-sealing characteristics. 

Extrusion Coating. In extrusion coating, a thin film of molten polymer is pressed onto or into the substrate. Coating thickness may range from 6.5 ua or less to more than 100 xm. In polymer lamination, a related operation, two or more substrates, such as paper or aluminum foil, are combined by using the polymer film as adhesive and moisture barrier. In order to coat a substrate, the polymer must be extruded through a narrow slit in the extrusion coating die by an extruder screw. 

Extrusion coating is the process of applying a thin bonded film of a plastic to a continuous substrate (web) such as paper, board, foil, fabric, as well as a plastic. A high melt temperature is employed with a downwardly directed slit die to produce a low viscosity melt web that adheres to the substrate (Figure 5.15). The plastic must adhere well to the substrate and exhibit good sealing properties. If necessary, the substrate may be given a pretreatment to improve adhesion. 

Since the above has moved from a double-ply construction to a multi-ply lamination (the paper to foil may be an adhesive or extrusion coating), the latter is more costly to produce. As a result of this, any change to the new combination is only likely to be economical (how increase in cost of manufacture is counterbalanced by the reduction in material costs—i.e. savings on foil) if the thinnest gauge of foil acceptable is employed. What is acceptable depends on the product properties (is it extremely moisture or oxygen sensitive ) and the handling characteristics of the processing equipment. 

In the first operation, the paper and the foil are extrusion laminated using an acid copolymer as the adhesive. Next, the sealant layer is applied as an extrusion coating. The operation can be accomplished in two passes, or in a single pass in a tandem extrusion line as shown in Fig. 8.2. In such a line, both extrusion heads are usually capable of coextrusion, as well. To understand the process of extrusion coating and laminating, it is necessary to start with the process in its simplest form, which, by the way, is how it is still practiced today by some converters. 

To reduce the need for such high temperatures, primers are used to improve adhesion. These primers are organic compounds that are coated onto the paper in-line with the extrusion coating to provide nonpolar groups to which the PE can adhere, as well as polar groups which can adhere to the paper. Polyethylene imine (PEI) is one such compound. These primers allow the melt temperature to be reduced to 288°C (550°F), so less oxidation occurs and there is less potential for off-odors. 

PEA is well known for its use in conventional extrusion coating, co-extrusion coating, and extrusion lamination [105]. The beneficial properties of PEA, such as excellent adhesion to various substrates such as foils, paper, and films, can add value to other polymers that require these properties for specific apphcations. PEA/LDPE blends have many industrial uses because of their good mechanical strength, processability, and impact strength. 

Chem. Descrip. Low m.w. polyethylene wax CAS 9002-884 EINECS/ELINCS 200-815-3 Uses Extrusion lubricant for polyolefins mold release agent and lubricant in rubber processing extrusion and calendering aid for vinyl food pkg. adhesives, coatings, paper, cellophane, rubber defoamer in food-contact coatings, paper/paperboard chewing gum base Regulatory FDA 21 CFR 172.615,175.105,175.300,175.320,176.170,... 

Chem. Descrip. Stearic acid CAS 57-11-4 EINECS/ELINCS 200-313-4 Uses External lubricant for rigid and soft PVC, esp. for cable extrusions food pkg. adhesives, coatings, paper, polymers, cellophane, rubber articles, textiles, animal glue defoamer in food-contact paper/paperboard flavoring agent, adjuvant in foods... 

Uses Adhesive polymer for extrusion coating and laminating, textile, lumber, plastic, rubber, metal, formed prods., paper, packing film, etc. Features Exc. adhesion with most substrates easy peel seals for plastic containers... 

Uses Adhesive/sealant resin for extrusion coating appiics. inci. foii-con-taining shampoo, toothpaste, toweiette, condiment, and misc. non-food pouches and sachets, medicai/pharmaceuticai pkg., snack structures other foii, metaiized fiim, or paper coatings as heat seai or tie iayer food-contact poiymers... 

Uses Phenoxy resin for structural adhesives, film extrusion, inj. molding, plastics modifiers, and polymer alloys food-contact adhesives, coatings, paper, closures with sealing gaskets for food containers Regulatory FDA 21 CFR 175.105,175.300,176.170,176.180,177.1210 Properties Translucent pellets low odor m.w. 10-16,000 sp.gr. 1.17-1.19 vise. 535-895 cps melt index 2-3 g/10 min. 99% min. NV (2 hrs. 135C + 1 hr. 220C)... 

Storage Store in cool, dry place keep tightly closed Uses For extrusion coating, adhesives, food-pkg. adhesives for coatings and laminations with oriented PP, PET, papers, clay-coated board and nylon substrates for specialty pkg. 

Uses Extrusion coating resin fiber-to-metal and fiber-to-fiber lubricant for textiles and paper film-former for surf, coatings or adhesives food pkg. food-contact paper/paperboard, polymer Manuf./Distrib. Dow Equistar Trade Names Containing Sclaii 35BPM... 

Uses Plasticizer, extrusion and molding process aid in ABS, PVC, CPVC, and semirigid vinyl, thermoplastic urethanes, molded rubbers, and thermoplastic elastomers modifier and reinforcer in adhesives, thermoplastic powd. coatings, hot-melt coatings in food-contact coatings, paper/paperboard... 

Uses Extrusion coating resin fiber-to-metal and fiber-to-fiber lubricant for textiles and paper film-former for surf, coatings or adhesives food pkg. food-contact paper/paperboard, polymer Manuf./Distrib. Dow http //www.dow.com] Equistar http //www. equistarchem. com Trade Name Synonyms Chevron PE 5961 [ChevronPhi 11 i ps http //www. cpchem. com] Mariex HHM TR 305 [ChevronPhillips http //www.cpchem.com]] Mariex HHM TR-400 [ChevronPhiIlips http //www.cpchem.com] Mariex HHM TR-418 [ChevronPhillips http //www.cpchem.com]] Mariex mPact D350 [ChevronPhillips http //WWW. cpchem. com]... 

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