GB2451883A

GB2451883A - Fully biodegradable adhesives

Info

Publication number: GB2451883A
Application number: GB0715981A
Authority: GB
Inventors: Paul Howard James Roscoe
Original assignee: SUSTAINABLE ADHESIVE PRODUCTS
Current assignee: SUSTAINABLE ADHESIVE PRODUCTS
Priority date: 2007-08-16
Filing date: 2007-08-16
Publication date: 2009-02-18
Also published as: GB0715981D0; GB2451883A8

Abstract

The invention relates to a range of biodegradable and compostable adhesives useful in the packaging of supermarket goods. These adhesives comprise of polyester or acrylic polymers, which have been modified by co-polymerisation with a range of aldo-pentoses and polyhydric alcohols to increase their biodegradability. Examples of such polymers are acrylic sugar-based macromers. The biodegrability is enhanced by the incorporation of a range of additives. These adhesives have been designed to meet all three criteria for biodegradable materials testing according to European standard EN 13432 certification regarding biodegradability, disintegration and eco-toxicities. By controlling the degree of polymerisation, the adhesives can either be in the form of a water based emulsion or solids dispersed in a suitable carrier medium such as a wax or resin.

Description

There are grave concerns in the UK about large amounts of land being used as waste fill sites and it is predicted that in the next few years such land fill sites will be exhausted and that government legislation will be introduced to combat the problem by the introduction of financial penalties for the disposal of non-biodegradable materials.

By the use of these adhesives (which typically represent between 0.001 and 0.05 percent by weight of a typical item which requires such adhesives during manufacture), huge savings can be made both in financial and environmental terms. In essence, these adhesives are natural products and will be returned to the ecosystem with the minimum effect on waste filled sites and in general, the eco-system.

Adhesives are all around us. They are used to fabricate a large number of everyday products which may be soft or hard, washable, degradable, transparent or colorful. Up to 100,000 chemicals are in use in the EU, but for 99% (by volume) there exists only sketchy data about their effects on the environment.

A new regulatory system called REACH (Registration, Evaluation and Authorisation of Chemicals) will change this, providing us with the information we need to use chemicals safely. Currently, the European Parliament and the Council are in the process of adopting this ground-breaking piece of legislation. They are pushing hard for this new chemicals policy in order to offer a higher level of protection to consumers, workers and the environment in the decades to come.

Accelerating worldwide economic growth is increasing pressure on the global environment. Developing clean technologies -or eco-innovation' -is essential if we are to reduce these pressures and conserve increasingly scarce natural resources.

There has been innovation in industries such as the packaging sector for the development and use of eco-friendly and sustainable materials for the manufacture of a wide range of items, components and finished articles. Many of these have been fabricated using adhesives However, historically there have been many adhesives which have been manufactured using non-biodegradable, non-compostable, non-disintegrable and toxic chemicals.

There are many modem adhesives which use natural products as their major component.

Examples include:

I. Polysaccharides Examples of such natural polysaccharides include: * Inulin * Starch * Dextrin * Glycogen * Pectin * Cellulose * 7.Hemi-cellulose 2. Carbohydrates such as * Glucose * Surcrose * Maltose * Fructose * Dextrose 3. Natural polyesters such as * Polylactide * Poly-beta-hydroxybutyrate * Polyhydroxybutyrate-valerate * Polylactide aliphatic copolymer * Polycaprolactone 4. Natural proteins such as * Starch * Dextrin * Casein * Gelatine 5. Protein derived from Soya beans Adhesives made from the above materials may possess some of the favourable eco-friendly properties for biodegradability, disintegration and eco-toxicity but these adhesives do not have a range of the desirable properties required by the product manufacturer. Such properties include: * Adhesion to wide range of substrates * Adhesion in hostile environments such as freeze thaw conditions * High shear adhesion failure temperatures.

The above physical properties of any adhesive are often intrinsic to the structure of the organic molecule and in particular the side chains and functional groups attached to the main carbon chain. These structures are also of paramount importance in the mechanism of biodegradation in which active bacteria can cause bond cleavage and depolyrnersation of the carbon chain.

In Europe, about 60% of the adhesive industry is dominated by the applications of pressure sensitive adhesives and about 80% of these applications concern the product labeling industry.

in 2000, adhesives accounted for about 20 billion dollars worth of sales throughout European and American markets.

Environmental concerns are driving the advancement in adhesive technology and standards such as the ISO 14500 series are seeking companies to develop more environmentally responsible attitudes are to produce "eco-fliendly products".

Some of the desirable features of such adhesives are as follows: * Ultimate disposability * Very low VOC content * The use of renewal resource materials used in their manufacture * Biodegrability * Compostability * Repulpability * Recycleability 9.

This invention relates to a range of biodegradable and compostable adhesives, which will find major use in a wide range of industries but is primarily aimed at the packaging and labeling industries.

These adhesives are comprised of polyester polymers, which have been modified by co-polymerisation with a range of carbohydrates and polyhydric alcohols to increase their biodegradability.

The reactive sugar The preparation of the biodegradable adhesive is a two stage process.

The first stage involves the preparation of a partially polymerised sugar based macromer.

This is accomplished by the free radical suspension polymerisation of the sugar in aqueous conditions. By controlling the degree of polymerisation, a wide range of sugar based macromers can be produced ranging from low viscosity liquids to high viscosity solid resins.

The second stage in the preparation of these novel adhesives involves the emulsion polymerisation of the sugar macromer with a vinyl monomer using free radical initiation.

A wide range of co-polymers can be produced depending upon the stoiciometric composition of the mix, the order in which the monomers are added and the type of cross-linking agent employed in the polymerization process.

The resultant co-polymer mixes vary in both physical and chemical properties such as their degree of tackiness and their glass transition temperatures.

A method of preparing a resin-fortified polymer emulsion has previously been described in a number of intellectual property disclosures. In one embodiment, the method comprises polymerising at least one monomer in the presence of a surfactant, an initiator, a resin and sugar-based vinyl monomer under effective emulsion polymerisation reaction conditions. However such preparations are not fully biodegradable.

This invention concerns the introduction of a range of other ingredients which render the adhesive fully biodegradable.

The range of additives included in this invention rendering the biodegradability include: * Dicarboxylic acids * Tricarboxylic acids * Sugar acids * Additional disaccarides * Salts of transition metal elements including both saturated and unsaturated carboxylic acids Specifically, transition metal salts of cobalt, zinc and iron and specifically octadecanoic (stearic) acid, hexadecanoic (palmitic) acid and tetradecanoic (myristic) acid. These have proven to be effective catalysts in the biodegradation process when incorporated in small concentrations.

* Buffer solution These solutions based upon combinations of the above acids together with their sodium or potassium salts produce an adhesive which is resistant to slight changes in the pH of the mix which may lead to premature degradation.

* Hydrocarbon resins based upon synthetic hydrocarbons such as 2-ethyihexyl acrylate, a vinyl acryalte, carboxlated styrene and natural hydrocarbon resins such as rubber.

* Polyols These polyhydric alcohols derived from sugars enhance the degree of hydrogen bonding between adjacent hydroxyl groups and greatly increase the ease of biodegradability of such adhesives.

Examples include glycerol, lactilol, mannitol, sorbitol and xylitol.

* Natural polyesters, such as -Polylactide -Poly-beta-hydroxybutyrate -Polyhydroxybutyrate-valerate -Polylactide aliphatic copolymer -Polycaprolactone * Natural proteins These structures are also of paramount importance in the mechanism of biodegradation in which active bacteria can cause bond cleavage and depolymersation of the carbon chain. The presence of the amide groups affords sites for nitrogen fixation and thus biodegradation * Synthetic proteins These are more readily available than their natural counterparts and offer some advantages over natural proteins.

The incorporation of a synthetic protein has been found to enhance the wetting properties, increase the ability of the adhesive to readily form films and to increase film elasticity. More importantly however is the distinct advantage over conventional adhesives in that the inclusion of a synthetic protein facilities a catalytic effect in the biodegradation process. Once again this is due to the inclusion of a nitrogen containing group within the heterocyclic ring. Examples of such proteins used in this invention include: -N-vinyl pyrrolidone -Giutamine derived from wheat -Casein derived from milk * Wetting agent A wetting agent when added to the mix lowers its surface tension and thus increases the adhesives spreadability. The adhesives in this invention use a fully biodegradable wetting agent such as dioctyl sulphosuccinate.

* Preservative Adhesives composed largely of natural materials are prone to bacterial attack with the resultant loss of desirable adhesive properties. Examples of such effective biocides are alkyl isoazolinones such as methyl,butyl and methylcioro isoazolinones or a combination thereof.

This invention therefore concerns a combination of ingredients which when mixed with a reactive sugar-based macromer which has been co-polymerised with a conventional vinyl monomer in a certain order and when mixed in certain proportions, produce a fully biodegradable adhesive. It is the unique combination of these ingredients which combine together to have a dramatic synergistic effect which results in complete biodegradation.

In addition to the components listed above, the preparations may also contain additional ingredients which enhance the biodegradeability.

Examples

Example I

Propriety acrylic sugar-based macromer 1000 parts Propriety hydrocarbon resin 200 parts Cobalt stearate 20 parts Methyicloro isoazolinone 1 part Dioctyl sulphosuccinate I part

* Example 2

Propriety acrylic sugar-based macromer 100 parts Propriety hydrocarbon resin 22 parts PoIy-N-vinyl pyrrolidone 17 parts Cobalt stearate 2 parts Methylcioro isoazolinone I part Dioctyl sulphosuccinate I part * Examp'e 3 Propriety acrylic sugar-based macromer 1000 parts Propriety hydrocarbon resin 220 parts Sucrose syrup I 70 parts PoIy-N-vinyl pyrrolidone 170 parts Propriety surfactant 10 parts Propriety defoaming agent 5 parts

* Example 4

Propriety acrylic sugar-based macromer 100 parts Propriety hydrocarbon resin 100 parts Poly-N-vinyl pyrrolidone 8 parts Glucose liquid 6 parts Tartaric acid I part Ethylene diammine tetra acetic acid nickel (11) salt I part

ID

Claims

Claim set 1. A fully biodegradable adhesive comprising of a resin-fortified emulsion polymer.
2. An adhesive as in Claim I in which the resin-fortified emulsion polymer comprises a vinyl-based monomer, a resin and at least one emulsion-polymerisable monomer, wherein the sugar-based vinyl monomer is selected from a group consisting of alkyl polyglycoside maleic acid ester monomers.
3. An adhesive as in Claim 1 which is rendered fully biodegradable by the inclusion of a range of additives.
4. An adhesive as in Claim 3 which consists of some or all of i) Dicarboxylic acids ii) Tricarboxylic acids iii) Sugar acids iv) Disaccarides v) Salts of transition metal elements vi) Buffer solutions vii) Hydrocarbon resins viii) Polyols ix) Natural polyesters x) Natural proteins xi) Synthetic proteins xii) Wetting agents or surfactants xiii) Preservatives

4. An adhesive as in Claim 3 which consists of some or all of I) Dicarboxylic acids ii) Tricarboxylic acids iii) Sugar acids iv) Disaccarides v) Salts of transition metal elements vi) Buffer solutions vii) Hydrocarbon resins viii) Polyols ix) Natural polyesters x) Natural proteins xi) Synthetic proteins xii) Wetting agents or surfactants xiii) Preservatives

SI

AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:-

IZ

Claim set I. An adhesive comprising of a sugar based monomer co-polymerised with a vinyl monomer that has been modified to contain a reactive acrylic end group.

Furthermore, a synergistic effect occurs on the inclusion of a range of additives resulting in an adhesive, which for the first time passes all criteria tests (EN 13432) for biodegradability, compostabilty and eco-toxity.

2. An adhesive as in Claim I in which the resin-fortified emulsion polymer comprises a vinyl-based monomer, a resin and at least one emulsion-polymerisable monomer, wherein the sugar-based vinyl monomer is selected from a group consisting of alkyl polyglycoside maleic acid ester monomers.

3. An adhesive as in Claim I which is rendered fully biodegradable by the inclusion of a range of additives.