Food Grade Adhesives for Equipment and Filters
Food grade adhesives are required for both production line equipment where food and beverage is processed as well as for applications for kitchen goods and of course packaging applications.
Typical applications which could require FDA approved or FDA compliant adhesives could include:
- Potting filter media into endcap for water or beverage filters
- Bonding mesh gauze to frame for filters, sieves, strainers and separators
- Production line machinery and equipment – applications include bonding and sealing apparatus, conveyors
- Sealing parts for dispensing equipment e.g. drinks dispensers, ice cream / smoothie dispensers
- Kitchenware – e.g. bonding ceramics, handles onto knives, tea and coffee pots, cake stands
- Packaging and labelling
Food safe legislations
There are a number of country-specific legislations. Probably the most widely recognised would be the FDA (Food and Drug Adminstration) which is US based. Within Europe different countries have different legislations, for example.
- German Federal Institute for Risk Assessment (Bundesamt fur Risikobewertung BfR)
- Packaging and Food Utensils Regulation (Commodity Act) of the Netherlands of 20 November 1979 and its amendments up to and including VGB/PSL 2773095 of 6th June 2007
There are also other approvals such as potable water which differ from country to country – e.g WRAS (UK), KIWA (Netherlands), DVGW (Germany), NSF (USA).
As FDA is most recognised, adhesive manufacturers producing food-safe adhesives, would mainly follow formulation rules as stipulated by FDA 175.105 and 175.300. When formulating FDA compliant adhesives, it is necessary to select FDA approved raw materials only from an official list. Very often we are asked for FDA approved cyanoacrylates or FDA approved UV Curable adhesives; it is not possible to manufacture cyanoacrylates or UV curables that comply to these FDA guidelines as the raw materials needed are not listed.
EU 2002/72/EC and 1935/2004 Food contact regulations concern plastic materials and chemicals which can come into contact with food – even for items such as conveyor belts which food must pass along in a production plant. Therefore, food safe adhesives are required in factory production environments, not just for packaging.
One of the “biggies” which has had the industry all of a flutter for a while is BPA. Now everybody is rushing out to buy BPA-free drinks bottles, baby items, BPA-free food storage solutions. BPA is the abbreviated name, Bisphenol A, and is quite a popular raw material in many adhesive formulations. To make an adhesive food-safe the formulation must be completely revised to exclude this constituent. There are many food-safe raw materials which can be used instead but there may be trade-offs in terms of adhesive performance (final strength, environmental resistance, cure time, handling characteristics etc).
In fact, FDA compliant adhesives are quite limited in terms of adhesive technology and performance features, so no fancy structural acrylic adhesives unfortunately. Permabond offers a small range of two-part FDA epoxies and can custom formulate to meet specific cure or viscosity requirements – providing the formulation can remain in compliance with the FDA formulation guidelines.
One of the biggest users of food safe epoxy is the filter industry. The adhesive is used to pot filter media into end caps. The filters are used for filtering water, fruit juice etc. There are a number of factors to consider when formulating a filter potting epoxy:
- Nature of the filter media – what material is it made of, what is the porosity / how densely pleated is it – this could give some indication as to the preferred viscosity of the adhesive.
- What is the side and depth of the area to be potted – large volumes of mixed epoxy can exotherm if cured in bulk (particularly if they are fast setting grades or the working environment is quite hot). Cure speed can be adjusted to take this into account, also considering the preferred cure speed to keep the production line moving (it is a fine balance).
- What is going through the filter and at what temperature and pressure – what affects may this have on the long term durability of the adhesive. Will there be any exposure to cleaning chemicals or sterilisation processes.
- If filling an end cap, what material is this made out of and will the adhesive be able to bond to this.
- Mixing, mix ratio and handling the adhesive on the production line – it is important to formulate the adhesive to be as user friendly as possible – e.g. a 1:1 resin to hardener mix ratio is a lot easier to manage than 100:28 ratio! The 1:1 product can easily be packaged in a dual cartridge or easily go into an automated dispensing system. The 100:28 product is going to have to be carefully measured. Compatibility between resin and hardener is also useful to take into consideration, mixing a thick heavy paste with a thin liquid is not much fun so a nice equal match between A and B components is generally preferred.
- Colour – normally to look “hygienic”, white coloured products are favoured.
- Odour – must not taint foodstuffs / beverages.
As well as filter potting, there are similar applications such as casting epoxy for producing the filter end (so it is not encased in a plastic or steel end cap). Bonding mesh to frames for screens and sieves is another popular application – not just for food but also for mining and silk screen industries. This type of application is particularly sensitive to the rheology (flow behaviour) of the adhesive as the adhesive needs to be compatible with the gauge of the mesh so as to wick into the mesh but then not flow everywhere outside of the bonding area.
Are adhesives dishwasher safe?
Good question, some are, many aren’t. FDA epoxies have a reasonable resistance to hot soapy water, once epoxy adhesive has cured, it is inert and resistant to attack. However, you do need to be careful regarding the materials the adhesive is bonding. For example, dissimilar materials where there could be differential thermal expansion and contraction at high temperatures and some substrate materials could absorb water or corrode which could damage the bond. It is always a good idea to perform accelerated ageing tests on bonded parts to check long term durability is satisfactory for your application.
What other types of bonding application are there where potable water safe / food grade adhesives may be used?
Sealing pipework on equipment such as coffee machines, ice cream / smoothie dispensers or even automatic dispensers on food production lines. Generally, a drinking water approved anaerobic thread sealant is used for this type of application although FDA epoxy can be used, particularly on plastic threaded parts and for permanent bonding and sealing.
Things like handles on cutlery or knives may be bonded. Porcelain crockery such as plate stands and other assemblies made up of two or more piece. Kitchen utensils, weighing scales, handles on pots and pans. Decorative items such as tea caddies, ornate decorations on whiskey bottles, glasses and novelty items also have requirements for adhesives.
A big area for food-safe adhesive is for packaging, in fact many film packaging materials have a heat activated layer which works very effectively as a cheap, fast way of hermetically sealing food packaging without having to apply a separate adhesive. No requirement for a two-part epoxy glue here!
For further information about Permabond’s food safe adhesives, please contact Permabond, we would be happy to assist.