The invention relates to printed foam structures and methods of printing onto foam. In

particular, the foams are polyolefin type foams which have widespread use for example

in children's toys, sports equipment and camping accessories.

In order to provide a printed design on top of a layer of polyolefin foam, it is known

first to coat the foam with a material such as polyester to which certain types of inks are

able to bond. The requirement of an intermediate bonding layer or coat leads to

additional cost and attempts to print directly onto foam has lead to an unsatisfactory

quality of the printed image. This is because of the difficulty in rendering the printed

image stable and the printed image being inflexible, subject to cracking, having a low

rub resistance. Additionally the result is not waterproof and unable to be moulded.

An object of the invention is to overcome the problems of the prior art and to provide

better quality printed images on polyolefin foams. Accordingly, one aspect of the

invention provides a printed foam structure comprising a layer of foamed polyolefin

plastic and a layer of textile ink in direct contact with the foamed polyolefin plastic. A

textile ink is one which is suitable for printing on to cotton and other textiles including

nylon. For example, the textile ink can be plastisol based and comprise a vinyl resin

such as polyvinyl chloride, polyvinyi acetate, or vinyl acetate/vinyl chioride co-

polymer, or a mixture of these. Preferably, the plastisol based ink comprises a

plasticizer such as phthalate.

The textile ink can be one which is suitable for printing onto polyamides such as nylon

and such inks are generally polyester based. The ink can be urethane based, or

comprise poly(ethyiene terephthalate) or indeed 2-PET.

Preferably the foamed plastic is a polyolefin foam such as physically or chemically

cross-linked polyolefin incorporating polyethelene and polyethelene containing ethyl

vinyl acetate.

Another aspect of the invention provides a method of creating a printed foam structure,

comprising the step of bringing a textile ink into direct contact with a layer of foamed

plastic.

Embodiments of the invention will now be described by way of example only.

In a first example, a heat curable plastisol ink is used to create a full colour design on

a 30kg m ^'3 density expanded cross link polyethelene foam. The plastisol ink is an

Easiprint trichromatic set available from Sericol Limited of Broadstairs. Kent. The

image is printed using a four colour screen-printing technique. A 120 T screen mesh

is used and each colour was printed wet on wet and then heat cured. An infrared dryer

was used at a temperature of 150°C for approximately 30 seconds. Example 1 provides

a well defined full colour image which is waterproof, non toxic, rub-resistant and

flexible.

By way of a second example, an air drying nylon ink known as "Sericol Nylobag"

available from Sericol of Broadstairs, Kent, is used to create a single colour image on

a 167kg m ^"3 density polyethelene ethyl vinyl acetate co-polymer foam such as made by

Copex or O.K. Company of Gava, Barcelona, Spain. Again the image was screen

printed on to the foam using a 43 T screen mesh and the ink was allowed to dry

overnight in the ambient atmosphere. Again, the result was a well defined single colour

image which was waterproof, non toxic, rub-resistant and flexible.

Beneficially the foam and printed image are mouldable together.

Nylobag ink is a polyester based ink system. A suitable ink can comprise polyurethane

and aiso a curing catalyst such as isocyanate.

In a third example a 60 kg m ^'3 density plastic foam made by Sentinel Products

Corporation of Hyannis, Massachusetts was printed on using a single colour image. A

suitable ink is a plastisol phosphorescent ink such as Sericol Texopaque OP. The ink

was printed through a 55 T mesh and then heat cured at 185 °C for forty seconds.

In a fourth example, a 60 kg m ^"3 density foam made by Alveo and a plastisol

trichomatic set plastic made by Gibbon Marler Limited of Wimbledon London is used.

Accordingly, a full colour image can be created on the foam using a four colour printing

process. In this example a 90 T mesh was used for screen printing wet on wet. The ink

was then cured using an infrared dryer at a temperature of 180° C for approximately

forty seconds.

In a fifth example, a 167 kg m ^'3 density foam made by Copex was printed in full colour

using Sericol Easiprint Trichomatic set as described above. Again the colours were

printed in a four colour screen printing process and the ink was then cured by placing

the printed foam structure in an oven at a temperature of 150° C for one minute. The

foam was then transferred to a press moulding machine and moulded for approximately

50 seconds. For example, a three dimensional hand puppet can be created by printing

a flat caricature image of a famous actor or cartoon character for example on a flat

foam surface and then pressing the foam in a mould to a desired three dimensional

shape.

Accordingly, the invention relates in particular to polyolefin foam such as physically

or chemically cross-linked polyolefin incorporating polyethelene and polyethelene

containing ethyl vinyl acetate, and to textile ink. Textile inks are capable of being

printed onto textiles such as cotton and nyion in a reasonably permanent manner, e.g.

usually colourfast over successive washes. Such textile inks include plastisol based

inks comprising vinyl resins and nylon inks being polyester based.

Printed foamed structure according to the invention can comprise a well defined and

full colour image on the foam which is waterproof, non-toxic, rub-resistant and flexible.

Moreover the foam and image can be moulded for example using known press

moulding machinery. In moulding, it is preferable to use plastisol inks. When using

low density foam, air drying plastisol inks are preferred. Low density foam is foam

generally less than 40 kg/m ³ and more particularly for densities less than 70 kg/m ³ .