Advances in adhesives promise better bonding
At CMM 2003, Rohm and Haas launched two laminating adhesives that it claimed are “distinctly different” from traditional solvent based products.
Adcote 812 is FDA compliant for high temperature applications, including retort, and can be used on existing equipment. It is also said to provide for attractive economics over traditional aliphatic isocyanate retort chemistries. “In retort packaging applications, the high running solids of the new adhesive make it very easy to apply, and the product also demonstrates excellent adhesion to a broad range of substrates,” North American marketing manager Bill Magee told Converting Today.
Adcote 577 is billed as one of a handful of adhesives that resists aggressive foods like flavoured coffees. It can also be used for the outer layer of retortable structures to laminate polyester to foil, or nylon to foil. Both adhesives are two-component systems.
Another innovation for water based dry bond laminating is the Robond L series. Designed to bond a wide variety of substrates – from metal to film, to foils, to typically difficult metallized films – these adhesives are said to provide performance characteristics comparable to those of certain solvent based systems, “with attractive economics”.
Also recently added to the Rohm and Haas portfolio is a series of extremely low monomer (ELM) adhesives. According to the company, their special formulation dramatically lowers the risk of primary aromatic amine formation to levels not possible with conventional adhesives. These products are tailored for a variety of medium performance packaging applications, such as coffee vacuum packs, and standup pouches for drinks and moist foods.
Another CMM introduction was a series of water based, self crosslinking adhesives designed to eliminate the need for catalysts. Developed by New York based Basic Adhesives, these products’ single component technology is said to enable them to replace two-part systems for many laminating applications, including film-to-film. Also claimed is excellent adhesion to various treated films, including PP, metallized polyester, clear vinyl and acetate. In addition to film-to-film laminating, the adhesives work well with film to printed board, says Basic.
“Everyone has permanent or removable labels that do one task well – no one adhesive does them all – until now,” is NAStar’s boast for its T1055 temporary adhesive. The company claims its product removes cleanly from glass – yet the same label will adhere to wood or frozen corrugated. A family of facestocks is offered for flexo, laser, thermal transfer, and direct thermal printing. The material can also be recycled/repulped. Not a microsphere technology, but a dispersion, the adhesive is offered in linered, linerless, and doubleface tape constructions.
Applications for which the temporary adhesive product is said to be particularly suited include single-ply instant redeemable coupons and replacement piggybacks for a truly repulpable response device, or paper mill labels.
Foaming is often preferred in paper laminating, as only a small amount of moisture enters the paper, using less adhesive, reducing costs and warping, and maximizing saleable product. National Adhesives has introduced a hybrid adhesive that meets this requirement. The Aerobond 32-192A product resists dripping off flute tips, a feature that helps ensure strong bonds and thrifty adhesive usage. According to National, it also stays stable “hour after hour”, enabling plant personnel to focus on other tasks rather than spending large amounts of time supervising adhesive application.
Formulated for Automatan and similar laminating equipment, the new adhesive is recommended for nip roller application because open pot systems dry out, resulting in poor foam dispersion and consistency. This off-white fluid adhesive contains 58 per cent solids. It can be used as is, with no need to adjust viscosity. Air injectors can be used to foam the adhesive.
Another innovation from National employs patent pending hotmelt technology claimed to eliminate the need for producing cartons with varnish blanks. The new Varni-Melt adhesive technology is said to have unrivalled adhesion to acrylic and UV varnishes – and excellent machine performance.
Producing varnish blanks creates extra work and cost. In the many stages taken to produce a finished carton, ensuring the gluing areas are left unvarnished is critical if the packed carton is to survive in the hands of the consumer. According to National, Varni-Melt has changed this. The cost of producing cartons with varnish blanks can now be removed, together with the cost of “putting right” incorrect varnishing.
Over 2000 bonding tests were used in the development of Varni-Melt with the close co-operation of varnish manufacturers. The product is said to have proven performance on over 40 varnishes, down to a surface energy level of 28 dynes/cm. Secure bonds are maintained in deep freeze and chilled conditions, and on cartons exported to hot climates, the company states.
HB Fuller’s Hydroflex waterborne film laminating adhesives now include a new dry bonding acrylic with crosslinker. This patented two-part technology is said to combine the performance of a polyurethane with the economics of an acrylic system. According to the company, when an application demands better resistance to heat, humidity, and chemicals than typical acrylics offer, Hydroflex dry bonding waterborne acrylics are the right choice on a wide range of flexible packaging and labelling applications.
Sovereign Specialty Chemicals (formerly Croda Adhesives) claims to be a ‘one-stop shop’ for all flexible packaging adhesive and coating requirements. New coldseal products include Primaseal C 22-475 for general purpose coldseal work, printed at speeds of up to 450m/min, said to provide excellent wipe and anti foaming properties. Also new is Primaseal C 22-865, claimed to give excellent release from plain PP and to be suitable for application onto untreated surfaces. This is particularly useful for converters producing laminates but without the facility to treat the inner substrate for coldseal application.
Specialized adhesives are needed for labelling recyclable PET containers. By developing the new Colfix HM 4433/1, KIC Krones is believed to be the first company to obtain an approval from Petcycle, one of Germany’s biggest operators of PET recycling systems.
Because the new hotmelt adhesive dissolves in caustic, the PET can be 100 per cent recycled. The adhesive is suitable for applying both paper and plastics labels, can be handled on all hotmelt stations and, says Krones, ensures that the machine concerned runs smoothly. A new generation of adhesives for cigarette packaging from Henkel Laesser, Tobacoll 6760-39 is claimed to be the only product that can be applied to a hinge lid blank by traditional wheel and roll drives and/or the more advanced and economical nozzle technology.
In the past, explains the company, adhesive was applied to the hinge lid blank cover by special wheels at a speed of 700 packs/min. Today, many producers simultaneously use the modern nozzle technique. The problem which arises from this production method is that both systems require different and contradicting adhesive flow properties – consequently two different adhesives. This meant a lot of trouble and costs as it required higher logistical efforts and bigger storage capacities. Additionally, expensive time-outs were caused by inadvertently choosing the wrong adhesive.
The product of two years’ research, Tobacoll 6760-39 is stated to meet all requirements. “As the product is suitable for both application systems, it significantly reduces not only the necessary production efforts but also the number of suppliers,” according to Henkel Laesser.
For the PSA market, Henkel has launched Technomelt Q 8746-21, touting it as “the right solution for almost every application” in the production of self adhesive labels and adhesive tapes for foils, paper or fabric. In particular, the adhesive is claimed to provide outstanding sticking power especially for gluing labels on difficult ‘apolar’ surfaces like those of plastics bottles for orange juice or milk. “Neither the surface structure nor the acidity of the fruit juice pose a limitation to its performance,” claims Henkel. “Once applied, Technomelt Q 8746-21 tolerates extreme temperatures ranging from –25 to +70degC without losing power. The adhesive provides a first class tack and excellent adhesion.”
Tel: +1 718 497 5200. www.BasicAdhesives.com
Tel: +1 651 236 3173. www.hbfuller.com
Tel: +49 211 797 6321. www.henkel.com
Tel: +44 (0)1942 845000. www.krones.com
Tel: +1 608 831 9600. www.nastar-inc.com
Tel: +44 (0)1753 501237. www.starch.com
Rohm and Haas
Tel: +33 (0)1 40 02 53 34. www.rohmhaas.com
Tel: +44 (0)1636 642320. www.sovereignsc.com