Packaging
Ethylene copolymer-based hot-melt are widely used in packaging, for various applications including:
Cartons and Folding Boxes
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For this application, the key parameters to take into account for technical analysis are:
- Viscosity (depends on application technology): Typically between 500 mPa-s to 2000 mPa-s at application temperature (145-180°C)
- Open time: Between 0.5 to 5 seconds
- Setting time: 0.2 to 1 seconds
- Food Contact Regulations: In most case these products have to comply with "indirect food contact" standards
- Odor and color
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Current trends favor fast setting hot-melts to improve machine speed while keeping a "long" open time in order to reduce quality problems when the line is running at a low speed.
Deep Freeze Packages
For this application, very high performance at low temperatures are required is measured by:
- Peel test at -38°C
- Drop test at -5°C or -10°C
Because most of the cardboard used in deep freeze packages are difficult-to-bond, high "hot tack", enhanced adhesion properties are required. As low glass transition temperature is preferred, high copolymer content EVA or ethylene acrylic ester copolymers are widely used for this application.
Bottle Labeling
With very good adhesion on PET, OPP and paper, ethylene copolymer-based HMPSA are high performing products for bottle labeling. As they are not suitable for use under high shear, HMPSA products are recommended for the bottle labeling of non-carbonated drinks.
For this application, a water-white product or clear product is generally appreciated as users ask for low fumes and low odor. Typical formulations are based on high copolymer content EVA and hydrogenated resin.
Yogurt Labeling
Ethylene copolymers are successfully used for producing heat sealable layers. One application is labeling in molder with heat sealable hot-melts. The good compatibility of EVA copolymers with paraffins and waxes enables the formulation of blends that exhibit good properties, such as adhesion onto PS yogurt pots without any blocking of the adhesive layer.
Automotive Industry
Thermo-adhesive films based on ethylene copolymers are widely used for automotive interior-trim applications.
- In these applications, fabrics have to be supported by rigid structures as well on the doors or on the ceiling.
- These films are an easy and environmentally friendly way to associate fabrics with substrates like composites or rigid foams.
Ethylene acrylic esters/Maleic anhydride or
Ethylene vinyl acetate/Maleic anhydride products offer a large range of grades suitable for different structures and usage conditions.
Ethylene Copolymers in Automotive Industry
Depending on the substrates to be bonded a multi-layer film can be used. Original properties of bonded substrates will be preserved and additional performances like barrier effect can be added.
Building & Construction
The main application for ethylene copolymer-based hot-melts in building and construction is EVA-based glue sticks. These products are very useful when immediate bonding is required.
Depending of final application, water-white products can be formulated using hydrogenated resins.
Bookbinding
Ethylene copolymer-based hot-melts are widely used in bookbinding, depending on the application these formulas will be pigmented (white).
The key parameters to take into account for technical analysis of this application are:
- Viscosity (depends on application technology): Typically between 2000 to 5000 mPa-s at application temperature (145-180°C)
- Open time: Between 5 to 10 seconds
- Setting time: 1 to 2 seconds
- Good flexibility at low temperature
- Good creep resistance at high temperature
- No stringing
- Good cuttability
Ethylene Copolymers in Bookbinding Applications
Bookbinding hot-melts have to fulfill very demanding technical requirements, i.e. good performances at both low and high temperatures. This is generally obtained by the use of different grades of polymers (long & short chains), and a blend of grades of tackifiers & waxes to achieve adhesion and application requirements.
Woodworking
In woodworking, ethylene copolymer-based hot-melts are widely used in applications, such as edge banding and veneering.
In furniture manufacture, reconstituted and laminated wood can be given the appearance of noble wood using films (typically, PVC which can imitate the grain of the wood or colored for decorative purposes), or by rolling out a thin wood veneer onto boards.
Hot-melts for woodworking applications need a very high "hot-tack" to maintain the PVC edge under high stress immediately after application.
A good wettability of both wood and PVC is required to achieve immediate quality requirements and long-term aging performances. For some applications requiring very high heat and moisture resistance, reactive hot-melts are used, but the EVA and ethylene acrylic ester copolymers are suitable for a large number of applications in the furniture industry.
Hot-melts for woodworking applications can be highly filled and are applied at higher temperatures than packaging or bookbinding hot-melts in order to increase the "hot tack" by a "viscosity effect".
Sanitary/Disposables
Ethylene
copolymers can also be a good choice to formulate pressure sensitive hot-melts
for diapers applications or feminine care products.
In this type of adhesives, the flexibility provided by a high content of vinyl acetate or acrylate (more than 30%) is enhanced by adding a plasticizer, which ensures the "sticky" effect at an ambient temperature.
Ethylene copolymer-based HMPSA can provide very high adhesion on difficult substrates such as untreated polyolefins or various plastics, as well as high color stability in water-white or white formulations.
For "positioning hot-melt" in feminine-care products, adhesion of ethylene copolymer-based HMPSA can be adjusted to a precise value while keeping high internal cohesion to avoid any adhesive transfer onto the fabric.
High copolymer content and high MFI copolymers are preferred as they present a lower glass transition temperature as well as a lower crystallinity.
Textile Industry
Thermo-reactive Films
In textile applications, Ethylene acrylic esters/Maleic anhydride or Ethylene vinyl
acetate/Maleic anhydride-based thermo-reactive films are a very efficient way to bond various substrates using continuous or discontinuous processes including several reactivation technologies like calendering or infra-red.
This technology is widely used to bond fabrics to foams or fabrics to fabrics in many applications such as automotive or furniture.
Ethylene acrylic esters/Maleic
anhydride or Ethylene vinyl acetate/maleic anhydride products are the key choices for these applications.
Depending on the substrates to be bonded, a multi-layer film can be used. Original properties of bonded substrates will be preserved and additional performances like barrier effect can be added.
Thermo-reactive EVA-based Hot-melts
Kraft paper coated with EVA-based hot-melt is used as "patron" in textile applications. These sheets of paper are bonded to fabric by heat reactivation in order to make the cutting phase more accurate.
The key requirements include a good adhesion on various substrates (synthetic and natural) and no adhesive transfer onto the fabric after cutting.