DESC:TECHNICAL FIELD

The present disclosure relates to a process for manufacturing a biodegradable printed material.

BACKGROUND

Synthetic polymers for indoor/outdoor advertisement make extensive use of polyvinylchloride (PVC), which employs plasticizers such as dioctyl phthalate (DOP) for flexibility of the film. Since a pressure-sensitive adhesive film containing the plasticizer emits harmful substances such as hydrogen chloride, dioxin, etc. when incinerated, use of polyvinylchloride (PVC) has recently been restricted in developed nations. Accordingly, various challenges have been made by manufacturers to develop alternative materials. Further, since it takes a long period of time for these materials to decompose when buried, there are problems of environmental pollution.

To solve these problems, there has been an attempt to use olefin resins, such as polyethylene and polypropylene, as replacement for the existing materials. However, the olefin resin has poor adhesion to a surface treatment agent for imparting printability, and has difficulty in attaining biodegradability which allows the material composed of the olefin resin to be completely decomposed into water and carbon dioxide as quickly as possible and to be harmless to humans without pollution.

In response to the demand for more environmentally friendly materials, a number of new biopolymers have been developed that have been shown to biodegrade when discarded into the environment. Examples of such polymers include polyesteramide (PEA), modified polyethylene terephthalate (PET). biopolymers based on polylactic acid (PLA), polyhydroxyalkanoates (PHA), which include polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV) and polyhydroxybutyrate-hydroxyval crate copolymer (PH B V), and poly (epsilon-caprolactone) (PCL).

Each of the foregoing biopolymers has unique properties, benefits and weaknesses. For example, PUB and PLA tend to be strong but are also quite rigid or even brittle. This makes them poor candidates when flexible sheets are desired. On the other hand, biopolymers such as PHBV and polybutylene adipate terphtalate (PBAT) are many times more flexible than the biopolymers discussed above, but have relatively low melting points so that they tend to be self-adhering and unstable when newly processed and/or exposed to heat.

Further, due to the limited number of biodegradable polymers, it is often difficult, or even impossible, to identify a single polymer or copolymer that meets all, or even most, of the desired performance criteria for a given application. For these and other reasons, biodegradable polymers are not as widely used for printing purposes, particularly for indoor and outdoor advertisements, as desired for ecological reasons.

In addition to the aforementioned drawbacks in the material itself, using these materials in the process for manufacturing the print, such as an indoor and outdoor advertisement, results in an increase in the overall cost of the printed material. The existing materials also require treatment with additional chemicals, such as solvents, plasticizers, etc. for rendering them useful and durable in the advertisement industry, thereby further increasing the overall cost.

Moreover, the printed material obtained using the existing materials need to be replaced frequently due to unfavorable weather conditions, thereby negatively impacting the overall aesthetics and print quality of the printing.

Therefore, there is required an improved process for manufacturing a biodegradable printed material for use in indoor and outdoor advertisement, which addresses at least the aforementioned problems.

DESCRIPTION OF THE INVENTION

An aspect of the present disclosure relates to a process for manufacturing a biodegradable printed material.

In one embodiment, the process of the present disclosure comprises at least the steps of:
(A) coating a biodegradable substrate with a first coating formulation,
(B) obtaining a print by subjecting the biodegradable substrate of step (A) to a printing device, and
(C) coating the biodegradable substrate with a second coating formulation to obtain the biodegradable printed material.

In the present context, “biodegradable printed material” is interchangeably referred as “printed material” and “biodegradable substrate” is interchangeably referred as “substrate”.

In an embodiment, the biodegradable substrate is a non-polymeric biodegradable substrate. In the present context, “non-polymeric” refers to the complete absence of any polymeric fiber in the biodegradable substrate. In another embodiment, the biodegradable substrate is a pregummed biodegradable substrate.

Pre-gumming or gumming is well known in the context of fibers which include cellulose, i.e., paper manufacturing. Suitable gums and/or adhesives for this purpose include pressure sensitive adhesives (PSAs), hot melt adhesives, and emulsion adhesives. PSAs are low modulus elastomers, i.e., do not require much pressure to deform and can be used on flat surfaces.

Hot melt adhesives are brought to liquid form with heat and can be used to coat entire surfaces before the adhesive cools onto the substrate. Many industrial sectors appreciate them for their eco-friendliness, safety and shelf life. Different types of hot melt adhesives include EVA-based, APAO-based and those that are pressure- sensitive.

Emulsion adhesives consist of a mixture of an acrylic polymer, surfactant(s) and other additives, which are used to manage adhesive performance, suspended in water. This dispersion is coated onto a webstock and the water is then dried off. During the drying process, polymers and other components semi-coalesce to form a functional pressure- sensitive adhesive layer. With water used to control the viscosity and allow for

coating, there are no solvents involved in coating process of these adhesives. Since solvent is generally more expensive than water, this typically results in an overall lower cost of coating than traditional solvent adhesives.

In an embodiment, the pregummed biodegrable substrate is in the form of rolls.

In another emebodiment, the biodegradable substrate includes fibers. The fibers can be made of natural fiber including natural cellulose fiber from either hardwood species or hardwood species and softwood species. In some examples, a ratio of hardwood fiber to softwood fiber can be within a range of about 100:0 to about 50:50. In some other examples, the biodegradable substrate contains fibers that are originating from wooded resource and that have more than 5% of fiber fines which have an average length that is less than 0.1 mm. In yet some other examples, the biodegradable substrate contains fibers, from wooded resource, that have at least 10% of fiber fines with an average length of less than 0.1 mm. Such fiber fines can be selected from any species of hardwood and softwood and/or mixture, or any recycling pulp source. As used herein, the wording “fines” refers to “fiber fines ” or “fiber debris” or to a type of fibers that have an average length that is less than 0.1 mm. Fines are very small fibers and fiber fragments such as fibrils which are thread-like elements unraveled from the wall of native cellulose fiber. Fiber fines types, or fines, can refer to small cellulosic materials that are small enough to pass through a forming fabric.

The fibers can be sourced from natural wood species and can include fibers from recycling pulps (i.e. wood fiber base) (no polymer fiber). The biodegradable substrate can also be made of any suitable wood or non-wood pulp. Non-limitative examples of suitable pulps include any kind of chemical pulp, mechanical wood pulp, chemically treated ground pulp, CTMP (chemical thermo mechanical pulp), and/or mixtures thereof. In some examples, ground-wood pulp, sulfite pulp, chemically ground pulp, refiner ground pulp, and thermo-mechanical pulp or their mixture can thus be used. In some examples, the raw base contains non-wood pulp such as pulp originating from bamboo, bagasse, kenaf, papyrus, etc. Bleached hardwood chemical pulps may make up the main pulp composition. In some examples, the fibril from wooded source are selected from both natural hardwood and softwood wood or combination of the both
species. Pulping process includes wood-free pulping (e.g., kraft chemical pulp and sulfite chemical pulp), or wood pulping (e.g., ground-wood pulp, thermo-mechanical pulp, and/or chemo-thermomechanical pulp), recycled fabric pulp, or combinations thereof.

In an embodiment, the first coating formulation has a viscosity ranging between 40 s to 60 s determined according to BS3900 using a Ford B4 cup at a temperature of 30°C.

In another embodiment, the first coating formulation is an aqueous coating formulation. The first coating formulation makes the biodegradable substrate ink receptive and at the same time not allowing the ink to penetrate in the fiber, thereby preventing the biodegradable substrate from becoming wavy and unprintable. Suitable first coating formulation includes, such as but not limited to, a polyurethane and an acrylic emulsion. In an embodiment, the first coating formulation comprises upto 70 wt.% of the polyurethane and the acrylic emulsion in the aqueous form.

The biodegradable substrate can be coated with the first coating formulation using suitable techniques known to a person skilled in the art. For instance, the coating in step (A) can be carried out using a liquid lamination technique.

Liquid lamination is compatible with most of mainstream inks and print media, thereby making it a popular choice and a highly effective way to make the printed material durable and scratch resistant. Alternative to film lamination, liquid lamination is a practical choice for roll to roll printed material. In digital printing, ink held in the printed material must be protected from a number of hazards, such as but not limited to, abrasion, marring, climatic conditions, wind-borne particles, handling, and UV exposure. Liquid laminates enhance the visual appearance of the ink and deepen the colour and increase the colour density.

Upon coating the biodegradable substrate with the first coating formulation, the coated substrate is passed through a heated air system for quick-drying. Once the biodegradable substrate is coated with the first coating formulation, the biodegradable

substrate is subjected to a printing device to obtain the print in step (B). In an embodiment, the printing device is a digital printing device.

In another embodiment, the printing device can be specifically designed to comprise any inkjet printable ink, such as, for example, organic solvent-based inkjet inks or aqueous-based inkjet inks. Examples of inkjet inks that may be deposited, established, or otherwise printed on the biodegradable substrate, include pigment-based inkjet inks, dye-based inkjet inks, pigmented latex-based inkjet inks, and UV curable inkjet inks. In some examples, the printing device is an inkjet printing device that is very well adapted to latex-based inkjet inks. While ink technology in inkjet printing has evolved significantly in recent years, even latex or solvent inks can use added protection from a liquid coating, especially for long-lasting or high-traffic prints, for instance wall coverings.

The print on the biodegradble substrate, described herein, includes printed images and articles that demonstrate excellent image quality (such as vivid image color reproduction, rich color gamut, low ink bleed and low image coalescence performance).The images printed on the biodegradble substrate have excellent durability under mechanical actions such as rubbing and scratching.

Subsequent to the printing step (B), the biodegradable substrate is further coated with the second coating formulation to obtain the biodegradable printed material. In an embodiment, the second coating formulation has a viscosity ranging between 50 s to 70 s determined according to BS3900 using a Ford B4 cup at a temperature of 30°C. In another embodiment, the second coating formulation meets the requirements of IS 15495:2004. The second coating formulation enhances the quality of print, imparts surface protection and enhances the quality of the printed material.

In another embodiment, the second coating formulation is an aqueous formulation or radiation curable formulation. Radiation curable formulation refers to material that polymerises or crosslinks when exposed to radiation, commonly ultraviolet light, in the presence of a photoinitiator. The radiation curable material can comprise a monomer with a molecular weight of 450 or less, an oligomer, or mixtures thereof. The monomers and/or oligomers may possess different degrees of functionality, and a
mixture including combinations of mono, di, tri and higher functionality monomers and/or oligomers may be used.

Radiation curable oligomers include, for example a polyester, urethane, epoxy or polyether backbone, and one or more radiation polymerisable groups. The polymerisable group can be any group that is capable of polymerising upon exposure to radiation. Preferred oligomers have a molecular weight of 500 to 4000, more preferably 600 to 4000. Molecular weights can be calculated if the structure of the oligomer is known or molecular weights can be measured using gel permeation chromatography using polystyrene standards. Thus, for polymeric materials, number average molecular weights can be obtained using gel permeation chromatography and polystyrene standards.

Suitable second coating formulation includes, such as but not limited to, polyurethane, epoxy, acrylic oligomers, acrylic emulsion, silicon, and mixtures thereof. The second coating formulation can be carried out using the liquid lamination technique, followed by drying the biodegradable printed material via infrared and/or ultraviolet radiation for improving water repellant and scratch resistance properties.

In an embodiment, the second coating formulation comprises upto 70 wt.% of acrylic emulsion in the aqueous form. In another embodiment, the second coating formulation comprises 25 wt.% to 50 wt.% of epoxy oligomers and 25 wt.% to 50 wt.% of acrylic oligomers which is UV curable.

In another embodiment, the first and/or the second coating formulation, independent of each other, may include additives known to the person skilled in the art. Suitable additives include, such as but not limited to, optical brightener agents and dyes for color adjustments, retention/drainage aids and biocides for operational efficiency. Other additives such as levelling agents, promoters, defoamers, antiaging agents, slitting agent, anti-bacterial agents can also be used.

Subsequent to coating with the second coating formulation, rolls of the printed material are fed to drying units over a conveyor belt to maintain the print quality.

In an embodiment, the first and/or the second coating formulation are dried aqueous formulations which are recyclable, biodegradable and re-pulpable.

In another aspect, the invention relates to the biodegradable printed material obtained using the process as hereinabove.

The biodegradable printed material obtained by the process described hereinabove is durable, cost effective and can be a suitable replacement for self-adhesive vinyl for indoor advertisements. For instance, the biodegradable printed material can be used for making, such as but not limited to, end cap and aisle branding, header, floor standing unit (FSU), standy, parasites, counter top units, poster, dangler, trays, wall branding, indoor shelf branding, shelf window, luxury displays, corrugated FSUs, bay branding, and any large format customized printing for indoor usage.

The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since the modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to the person skilled in the art, the invention should be construed to include everything within the scope of the disclosure
,CLAIMS:We Claim:

1. A process for manufacturing a biodegradable printed material comprising the step of
a) coating a biodegradable substrate with a first coating formulation,
b) obtaining a print by subjecting the biodegradable substrate of step (a) to a printing device, and
c) coating the biodegradable substrate with a second coating formulation to obtain the biodegradable printed material.

2. The process for manufacturing the biodegradable printed material as claimed in claim 1, wherein the biodegradable substrate comprises fibers selected from cellulose fiber, wood or non-wood.

3. The process for manufacturing the biodegradable printed material as claimed in claim 1, wherein the first coating formulation is a combination of a polyurethane and an acrylic emulsion.

4. The process for manufacturing the biodegradable printed material as claimed in claim 1, wherein the first coating formulation has a viscosity ranging between 40 s to 60 s determined according to BS3900 using a Ford B4 cup at a temperature of 30°C.

5. The process for manufacturing the biodegradable printed material as claimed in claim 1, wherein the second coating formulation is selected from polyurethane, epoxy, acrylic oligomers, acrylic emulsion, silicon, and mixtures thereof.

6. The process for manufacturing the biodegradable printed material as claimed in claim 1, wherein the second coating formulation has a viscosity ranging between 50 s to 70 s determined according to BS3900 using a Ford B4 cup at a temperature of 30°C.

7. The process for manufacturing the biodegradable printed material as claimed in claim 1, wherein the second coating formulation comprises upto 70 wt.% of acrylic emulsion in the aqueous form, 25 wt.% to 50 wt.% of epoxy oligomers and 25 wt.% to 50 wt.% of acrylic oligomers which is UV curable.

8. A biodegradable printed material obtained using the process as claimed in claim 1.

Dated this 11th day of June 2022

Spectrum Scan Pvt Ltd
By their Agent & Attorney

(Adheesh Nargolkar)
of Khaitan & Co
Reg No IN-PA-1086