How to recycle used printing plates

Abstract

A method for producing granules from photopolymer printing plate material. This method includes (a) a step of sorting photopolymer printing plate material based on identifiable properties, wherein the photopolymer printing plate material contains one or more photopolymer layers; (b) an exposure step of exposing the photopolymer printing plate material to UV-C light from a UV-C light source for a certain period of time to reduce the tackiness and increase the brittleness of the photopolymer printing plate material; (c) a grinding step of grinding the photopolymer printing plate material into particles; and (d) a screening step of screening the particles to remove particles exceeding a certain size and produce granules.

Description

Technical Field

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[0001] Technical Field of the Invention The present invention generally relates to a method for recycling flexographic printing elements.

[0002] Background of the Invention A flexographic printing element is typically a relief plate in which the image elements protrude from the blank area. Such plates offer many advantages to printers, mainly based on their durability and ease of manufacture. Flexographic printing elements can be used at high printing speeds for high-volume printing operations on various substrates, including films, foils, papers, cardboard, paperboard, and the like.

[0003] A typical flexographic printing blank supplied by its manufacturer is usually a multi-layer article that includes, in order, a backing layer or support layer, one or more unexposed photocurable layers, a protective layer or slip film, and a cover sheet. The processed flexographic relief image printing element has a relief image on the surface of the printing element.

[0004] This relief image can be created in various ways. For example, a flexographic printing element can be manufactured by imaging a photocurable printing blank to generate a relief image on the surface of the printing element. This is generally achieved by selectively exposing a photocurable material to actinic radiation through a mask or negative, and this exposure acts to cure or crosslink the photocurable material in the irradiated areas. Alternatively, the relief image can also be formed by selectively laser engraving a photocured, photopolymerized, or vulcanized layer to generate the desired relief image. Other methods of creating a relief image are also known to those skilled in the art. The photocurable printing blank may be in the form of a continuous (seamless) sleeve or in the form of a flat planar plate attached to a carrier.

[0005] Printing elements can be selectively exposed to chemical beams in various ways. For example, the transmission of chemical beams to the printing plate elements is selectively blocked by using a photographic negative having transparent and substantially opaque regions. Alternatively, an in-situ negative can be created by selectively laser ablating a chemical beam (substantially) opaque layer over one or more laser ablation-sensitive photopolymer layers. Yet another alternative method involves selectively exposing the photopolymer using a focused beam of chemical beam. Any of these alternative methods are acceptable, and the criterion is their ability to selectively expose the photopolymer to chemical beams and thereby selectively cure portions of the photopolymer.

[0006] Liquid photopolymers can also be used to construct flexographic elements, where they are selectively crosslinked and cured to form desired relief images. The use of liquid photopolymers in liquid platemaking processes involves casting and exposure steps, in which a photographic negative is placed on a bottom glass platen and a cover film is placed on top of the negative in an exposure unit. An exposure unit generally includes a bottom glass platen with a UV light source (bottom light source) below it and a lid with a flat top glass platen with a UV light source (top light source) above it. Liquid photopolymers not exposed to the bottom light source (i.e., uncured photopolymers) remain in a liquid state and can be recovered and reused. For example, various processes for manufacturing printing plates from liquid photopolymer resins have been developed, as described in U.S. Patent No. 5,213,949 by Kojima et al., U.S. Patent No. 5,813,342 by Strong et al., U.S. Patent Publication No. 2008 / 0107908 by Long et al., U.S. Patent Publication No. 2020 / 0207142 by Vest et al., and U.S. Patent No. 3,597,080 by Gush, and each of these subjects is incorporated herein by reference in whole.

[0007] Subsequently, the photopolymer layer of the printed element is developed to remove the uncured (i.e., non-crosslinked) portions of the photopolymer without disturbing the cured portions of the photopolymer layer, thereby generating a relief image. The development process can be carried out by various methods, such as water washing, solvent washing, and thermal development (blotting).

[0008] Photopolymers used in flexographic printing elements generally contain one or more binders, monomers, plasticizers, and photoinitiators, along with other performance additives. Particularly preferred binders for sheet polymers include polystyrene-isoprene-styrene and polystyrene-butadiene-styrene, especially the aforementioned block copolymers. An example of a photopolymer composition for sheet polymers is described in Roberts et al., U.S. Patent Application Publication 2004 / 0146806, the teachings of which are incorporated herein by reference in their entirety. Printing plates made from the processed photopolymer and laser-engravable printing elements may contain various combinations of binders, monomers, plasticizers, photoinitiators, and other additives to obtain the desired results. For example, printing plates manufactured from liquid photopolymers or photoresins can be based on ethylenically unsaturated prepolymers, such as unsaturated polyester resins, unsaturated polyurethane resins, unsaturated polyamide resins, and unsaturated poly(meth)acrylate resins, or polyether polyester urethane copolymers such as polyether polyester urethane methacrylate photopolymers.

[0009] Once the relief image printing element is prepared by any of the above methods and / or as known in the art, the flexographic printing element can be mounted on a printing cylinder and printing can be started.

[0010] Once the printing process is complete (or when the printing plate is worn out from use), the printing plate must be discarded. Printing plate waste is a significant problem in industry, and companies are increasingly seeking more sustainable materials, along with improved processes for recycling used materials without relying on incineration or landfill. Furthermore, unused photopolymer materials (unexposed materials remaining from the manufacturing process of photopolymerizable printing plate blanks, such as edge strips, losses due to the start and stop of production, and outdated, unprocessed printing plates that are no longer usable) also constitute waste, and it is desirable that these materials be recycled as well.

[0011] Therefore, an object of the present invention is to develop an improved process for recycling and / or reusing and / or using for another purpose photopolymer relief image printing plates and unused photopolymer materials that would otherwise be discarded.

[0012] A recognized problem is that crosslinked, cured, or vulcanized materials cannot be easily reprocessed, reformatted, reused, or recycled to their original composition and application. Crosslinking elastomeric photopolymer compositions requires complex material formulations, which can lead to manufacturing complexities and difficulties, including premature setup, incomplete curing, and short compositional pot life (i.e., premature crosslinking), especially when forming relatively thick flexographic printing plate precursors. Furthermore, even if elastomeric photopolymer compositions are recyclable, it is generally necessary to remove at least the backing layer from the photopolymer composition before further processing, as recycling the entire printing plate without separation is usually impossible. In addition, it may be necessary to ensure that the photocurable materials being processed are at least relatively similar to each other, because dissimilar materials may require different recycling needs and further separation and sorting to provide reusable recycled products in a reproducible manner.

[0013] As described above, flexographic printing plates generally consist of a backing layer and one or more layers of photocurable material, which may be the same or different from one another. Other layers include, for example, a compression layer, an oxygen barrier layer, an adhesive layer, a capping layer, and an anti-halation layer. Therefore, it is widely believed that flexographic printing plates usually contain both thermosetting and thermoplastic materials, and that these materials must be separated from each other (and thus processed separately). This is because these materials are incompatible with each other, and the resulting product does not possess the desirable properties for further processing.

[0014] Compared to the styrene / diene copolymer-based starting chemicals before processing, the thermosetting crosslinked materials differ significantly in the following ways: a. Crosslinking makes the material insoluble, resulting in significant differences in its physical properties such as solvent resistance and swelling resistance, as well as in the use of mechanical or dispersive mechanisms for mixing (i.e., dissolution is not an option). b. Thermal stability - The cross-linked material is thermosetting and does not flow with heat. c. The presence of additional materials (i.e., oils, stabilizers, etc.) affects properties such as lightfastness in a different way than the unreacted starting product. In some cases, the materials are already bound to the matrix. d. Because the chains are bonded together, the orientation / phrasing is fixed, which is one of the most important differences between crosslinked SBC-based materials and uncrosslinked SBC-based materials.

[0015] As a result of cross-linking caused by exposure to chemical rays, used printing plates undergo significant chemical changes from their original styrene / butadiene or styrene / isoprene chemical composition. This is the main reason why developing new applications for used printing plate materials is difficult.

[0016] Furthermore, for many years, one of the main difficulties in recycling elastomer-based photopolymer printing elements has been the "sandwich" effect that occurs when elastomer plates are present in addition to polyester backing, and when printing by-products such as dried ink are also present. Moreover, because photopolymer flexographic printing plates are synthetic resin composites, recycling unexposed and exposed photopolymers tends to be difficult. Traditionally, before recycling such photopolymers, the bonds between the individual synthetic resins must first be dissolved. Based on this, there remains a significant market need to develop a method that overcomes the shortcomings of conventional technology, enabling the easy and cost-effective reuse of used printing plates, including photocurable and uncured photocurable materials, backing layers, cover layers, oxygen barrier layers, adhesive layers, capping layers, anti-halation layers, and printing by-products.

[0017] Kraska et al.'s U.S. Patent No. 5,552,261 (whose entire subject matter is incorporated herein by reference) describes a process for recycling exposed and / or unexposed photopolymer flexographic printing plates, including a photopolymerizable recording layer and a support. However, this method requires first separating the recording layer from the support layer and other such layers.

[0018] Landry-Coltrain et al.'s U.S. Patent No. 8,920,692 (the entire subject matter of which is incorporated herein by reference) describes a method for recycling used and unused laser-engravable flexographic printing plate precursors and laser-engraved flexographic printing elements. However, this method also requires the physical separation of the laser-engravable or laser-engraved layer from the support layer and other layers. Furthermore, as part of the described recycling process, this method also requires a step of melting the laser-engravable or laser-engraved layer.

[0019] Document DE4026786A2 describes a method for recycling shredded old parts and waste from fiber-reinforced cross-linked duroplastics. However, these materials are thermosetting materials.

[0020] Vest's U.S. Patent Application Publication No. 2022 / 0235551 (the entire subject matter of which is incorporated herein by reference) describes a method for recycling used printing plates to produce granules that do not require layer separation before processing. However, certain materials, including plates made from liquid photopolymers and / or liquid-treated printing plates, have been found to be difficult to process due to the high level of tackiness of these materials. Thus, there is still a need in the art for a recycling process that can yield good results for a wider range of materials, including printing plates made from liquid photopolymers and other more tacky materials. [Overview of the project]

[0021] The object of the present invention is to provide a method for recycling precursor materials for flexographic printing plates.

[0022] Another object of the present invention is to provide a method for recycling used flexo-relief image printing elements, including used printing plates and used printing sleeves containing both thermosetting and thermoplastic components.

[0023] Another object of the present invention is to provide a method for recycling flexographic elements and materials without requiring the removal of backing layers, substrate layers, compressible layers, and / or other dissimilar intermediate layers during processing.

[0024] Another objective of the present invention is to provide a recycling method that enables the recycling of the entire flexographic printing plate structure in a simple and cost-effective manner.

[0025] Therefore, in one embodiment, the present invention generally relates to a method for producing granules from a photopolymer printing plate material, comprising: a) a sorting step of sorting the photopolymer printing plate material based on distinguishable characteristics; b) optionally, a shredding or chipping step of shredding or chipping the photopolymer printing plate material to reduce the size of the photopolymer printing plate material to smaller chips or shreds having a relatively uniform size; c) an exposure step of exposing the photopolymer printing plate material to UV-C light from a UV-C light source for a certain period of time to reduce the adhesiveness of the photopolymer printing plate material and increase its brittleness; d) a grinding step of grinding the photopolymer printing plate material into particles; and e) a screening step of screening the particles to remove particles exceeding a specific size and producing granules relates to a method.

[0026] Detailed Description of Preferred Embodiments As described herein, in one embodiment, the present invention generally relates to a method for recycling a photopolymer printing plate material in a simple and cost-effective manner for producing granules without the need to separate layers before processing. The resulting granules can be incorporated into various products either alone or in combination with other used recycled materials.

[0027] It should be understood that the disclosed embodiments are merely illustrative of the present disclosure, which can be embodied in various forms. Therefore, the details disclosed herein with reference to exemplary assembly / manufacturing methods and related processes / techniques of assembly and use should not be construed in a limiting sense, but should be construed merely as a basis for teaching those skilled in the art how to make and use the advantageous assemblies / systems of the present disclosure.

[0028] As used herein, "a", "an", and "the" refer to both singular and plural referents unless the context clearly dictates otherwise.

[0029] As used herein, the term “about” refers to a measurable value such as a parameter, quantity, duration, etc., and is intended to include variations of no more than + / -15%, preferably no more than + / -10%, more preferably no more than + / -5%, even more preferably no more than + / -1%, and even more preferably no more than + / -0.1%, of the value particularly described herein, insofar as such variations are appropriate for carrying out the invention described herein. Furthermore, it should be understood that the value itself referred to by the modifier “about” is also specifically disclosed herein.

[0030] As used herein, spatially relative terms such as “beneath,” “below,” “lower,” “above,” “upper,” “front,” and “back” are used to facilitate the description of the relationship between one element or feature and another. Furthermore, it is understood that the terms “front” and “back” are not intended to be limiting, but rather to be interchangeable where appropriate.

[0031] As used herein, the terms “comprise(s)” and / or “comprising” specify the presence of the described features, integers, processes, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, processes, operations, elements, components, and / or groups thereof.

[0032] The inventors of the present invention have found that various elastomeric photopolymers used in printing plates, including flexorelief image printing plates containing ink residue, can be processed together with one or more layers of photopolymer, a backing layer, and other such layers to produce granules that can be used as a substitute or addition to other consumer recycled materials in various products. One of the main advantages of the method of the present invention is that it is not necessary to separate any of the layers of the printing plate, and the entire photocurable printing element, including the ink residue, cured photopolymer layer, backing layer, and any intermediate layer, can be subjected to the process described herein to produce granules.

[0033] Therefore, in one embodiment, the present invention is generally a method for producing granules from photopolymer printing plate material, a) A sorting step for sorting photopolymer printing plate materials based on identifiable characteristics, wherein the photopolymer printing plate material comprises one or more photopolymer layers; b) Optionally, a shredding or chipping process to reduce the size of the photopolymer printing plate material to smaller chips or fragments of relatively uniform size; c) An exposure process in which the photopolymer printing plate material is exposed to UV-C light from a UV-C light source for a certain period of time, thereby reducing the tackiness and increasing the brittleness of the photopolymer printing plate material; d) A grinding step to produce particles or granules by grinding photopolymer printing plate material; and e) A screening process to screen for particles or granules and remove particles or granules that exceed a certain size. This includes methods.

[0034] In one embodiment, the photopolymer printing plate material includes one or more types of unused photocurable and / or photosensitive printing blanks and / or used photocurable and / or photopolymerized printing elements.

[0035] In one preferred embodiment, the photopolymer printing plate material includes used photocured and / or photopolymerized printing elements, as the inventors have found that these materials are more easily pulverized to produce granules. Furthermore, the inventors have found that uncured printing plate material is more hazardous and can cause irritation to workers handling the product.

[0036] As described herein, one step of the present invention involves identifying specific properties of printing plate materials, so that the materials can be sorted or screened based on such identifiable properties. This ensures that the granules are consistent and reproducible. In one embodiment, materials can be sorted based on the type of binder, the melting point of the photopolymer material, the Shore A hardness of the photopolymer material, or other identifiable properties. Importantly, sorting the materials results in products with identifiable and consistent properties suitable for use in specific end-user products. This also makes it possible to identify materials that do not contain any undesirable, non-recyclable layers.

[0037] In one embodiment, the inventors of the present invention have found that photopolymer printing plate materials based on styrene-based block copolymers yield good results. In a preferred embodiment, the photopolymer printing plate material is based on a styrene-butadiene-styrene (SBS) type photopolymer. In another embodiment, the photopolymer printing plate material is based on a styrene-isoprene-styrene (SIS) type photopolymer. Other types of photopolymers are also known and can be used in the implementation of the present invention, but the inventors of the present invention have found that SBS type photopolymer materials have higher stability and therefore produce consistent granules. Therefore, in one embodiment, the printing plate material is selected to contain only materials containing an SBS binder.

[0038] In another embodiment, the photopolymer printing plate material includes printing plates processed from liquid photoresins based on ethylenically unsaturated prepolymers, such as unsaturated polyester resins, unsaturated polyurethane resins, unsaturated polyamide resins, and unsaturated poly(meth)acrylate resins, such as polyether urethane polymers or polyether polyester urethane copolymers, such as polyether polyester urethane methacrylate photopolymers. Thus, the printing plate material can also be separated to include only materials containing specific ethylenically unsaturated prepolymers.

[0039] Alternatively, the sorting process may be based on the type of printing plate (i.e., liquid polymer or sheet polymer), the Shore A hardness of thick plates versus thin plates, etc. In one embodiment, the photopolymer printing plate material may be sorted into plates with a Shore A hardness of less than about 40 and plates with a Shore A hardness greater than about 40. Generally, plates with a lower Shore A hardness (i.e., less than about 40, or less than about 35, or less than about 30) exhibit higher tackiness.

[0040] Alternatively, the photopolymer printing plates may be sorted into plates with a gauge of less than approximately 0.107 inches and plates with a gauge greater than approximately 0.107 inches. Other sorting methods will also be known to those skilled in the art. However, sorting the photopolymer printing plate materials based on the type of binder is a preferred sorting method.

[0041] Typical backing and / or support layers include thermoplastic materials containing polyester such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), and these materials are suitable for recycling together with the photocurable or photocured layer of the photopolymer printing plate material. Therefore, these backing and / or support layers do not need to be removed before recycling the photopolymer printing plate material. Furthermore, the carbon black layer and its residues do not need to be removed from the photopolymer printing plate material, nor do they need to be removed before recycling the photopolymer printing plate material. Similarly, ink residues remaining on the surface of used printing plates do not need to be removed before recycling used flexographic printing plates. However, certain layers that may be contained in the photopolymer printing plate material may be considered unsuitable for recycling and / or may produce granules that do not have the desired properties suitable for use in a particular product, and these particular layers can and should be removed before the grinding process.

[0042] Once the materials are identified and / or sorted, these sorted materials are subjected to a grinding process. This grinding process may be a single-step or multi-step process, and one or more grinding steps may be carried out at cryogenic or non-cryogenic temperatures.

[0043] The grinding step is a crucial step in the method of the present invention because it provides reproducible and consistent granules. However, it has been found that the grinding step can be affected by the tackiness of the printing plate material being processed. For example, as mentioned above, printing plates made from sheet polymers can generally be processed / recycled efficiently because they are not tackiness, but printing plates made from liquid photopolymers and / or certain liquid-treated sheet polymers may be more difficult to process due to their high tackiness. Furthermore, water-washed sheet polymers can also be highly tackiness and similarly difficult to process. Other examples of plates with high levels of tackiness include flexible photopolymer plates (e.g., those used in corrugated printing applications) and compressible printing plates (which may include one or more compressible backing layers or compressible printing layers). This high level of tackiness makes it more difficult to produce granules, and the resulting granules are non-uniform in size and have a strong tendency to aggregate. Therefore, it is desirable to reduce the level of tackiness before the grinding step.

[0044] In one embodiment, the photopolymer printing plate material is subjected to an initial shredding process in which it is shredded, cut, or chipped to reduce it to smaller chips or fragments of generally uniform size (e.g., about 0.1 to about 10 cm, or about 0.5 to about 8 cm, or about 1 to about 5 cm). These chips or fragments can then be subjected to a granulation process to produce particles or granules having a desired particle size.

[0045] In one embodiment, prior to the granulation process and after the initial shredding process, the chips or fragments are subjected to an exposure process to reduce tackiness and increase material brittleness. In one embodiment, this exposure process is achieved by exposing the chips or fragments to UV-C light with wavelengths in the range of 200–280 nm for about 1–45 minutes, or about 2–40 minutes, or about 5–30 minutes. Various UV-C light sources are available, but in one embodiment, the UV-C light source includes one or more quartz lamps.

[0046] This exposure process can be achieved either in batch or continuous processing, but in one embodiment, the chips or fragments are spread substantially in a single layer on a conveyor belt, and the conveyor belt is moved toward a UV-C light source at a speed that gives sufficient time to reduce the stickiness of the chips or fragments and increase their brittleness. In one embodiment, the UV-C light source is positioned at a height of 2 to 20 cm above the surface of the conveyor belt. The UV-C light source is positioned across the entire width of the conveyor belt, processing the width of the material on the conveyor belt simultaneously. The speed of the conveyor belt is generally in the range of about 0.1 to about 5 feet / minute. However, other speeds are possible as long as sufficient exposure time to the UV-C light source is obtained.

[0047] The UV-C light source may include a light bar containing one or more quartz lamps arranged across the entire width of the conveyor belt. Alternatively, the UV-C light source may include an array of UV-C light sources arranged in a staggered pattern across the entire width of the conveyor belt. Other arrangements of UV-C light sources will also be known to those skilled in the art. The important thing is that one or more UV-C light sources are arranged so as to expose the chip or fragment to UV light for a sufficient time to reduce tackiness and increase brittleness.

[0048] In one embodiment, the brittleness of a chip, fragment, or other printing plate material can be determined by observing the surface of the material. That is, if surface cracks are observed on the surface, the chip, fragment, or other printing plate material is sufficiently brittle. In one embodiment, the chip, fragment, or other printing plate material is exposed to a UV-C light source until cracks are observed on more than 40%, 50%, 60%, 70%, or 80% of the surface. In another embodiment, sufficiently high brittleness can be confirmed by the occurrence of haze when the plate material is bent. In yet another embodiment, sufficient brittleness is achieved when the fragment, chip, or other printing plate material easily breaks or shatters when pressure is applied.

[0049] As described above, the grinding process may include one or more of cryogenic grinding and non-cryogenic grinding, and these processes may be used individually or in combination.

[0050] In non-cryogenic grinding, after the initial shredding process is carried out, a finishing mill grinds the material to the desired particle size. This process may be carried out one or more times until the desired particle size is achieved. After each processing step, the material is separated by a sieving screen or other similar means, and any excess material may be returned to a granulator or mill for further processing. Magnets may be used to remove metallic contaminants if necessary.

[0051] In cryogenic processing, used fragments or chips are frozen using liquid nitrogen or other materials / methods before sizing. Most photocurable materials or photocurable materials described herein become brittle or “glassy” at temperatures below approximately -80°C. The use of cryogenics can be applied at any stage of sizing. The material can be cooled in a tunnel-type chamber and immersed in a “bath” of liquid nitrogen, or liquid nitrogen can be sprayed to lower the temperature of the granules. The cooled particles can be reduced in size using an impact shrinker, centrifuge, or hammer mill. This process transforms the photopolymer printing plate material into granules. Cryogenic pulverization avoids thermal degradation of the photopolymer printing plate material and produces high-yield granules.

[0052] Granules can also be produced using a wet grinding method. In this method, chips or fine fragments of photopolymer printing plate material are mixed with water to produce a slurry. This slurry is then transported through a size reduction and classification device. Once the desired size is reached, the slurry is transported to a device for removing most of the water and then drying. Except for the use of water, the wet grinding method utilizes the same basic principles as those used in ambient environmental processes.

[0053] Any of these processes can be used to grind photopolymer printing plate materials and produce granules. However, the inventors of the present invention have found that while cryogenic grinding is preferable in the grinding process, other grinding processes may be included in addition to the cryogenic grinding process to further refine the end-use product.

[0054] As described herein, the granules are subjected to a sizing or screening process to remove particles exceeding a certain size. This sizing or screening process may be part of the grinding process or a separate process performed after the grinding process. In one embodiment, the polyethylene terephthalate (PET) backing layer is part of the larger screened material and generally consists of larger PET flakes, which are typically larger than 2 mm or about 3 mm, or between 3 mm and about 10 mm, and tend to be biased towards larger particle sizes. This material can be used in many applications where recycled PET flakes are used, such as food packaging, non-food packaging, automotive parts, industrial fibers and textile fibers, such as clothing, carpets and bedding.

[0055] The sized granules generally have a desired particle size within the range of less than about 10 mm, more preferably less than about 10 mm, even more preferably less than about 5 mm, or even further less than about 3 mm. In one embodiment, the particles are screened to remove particles having a diameter greater than about 5 mm, more preferably greater than about 3 mm. In one embodiment, more than 80%, or more than 90%, or more than 95% of the particles have a diameter within the range of about 6 to about 9.5 mm.

[0056] In one embodiment, the sizing and / or screening step may include a first step of screening the granules to remove large flakes or particles that mainly constitute polyethylene terephthalate (PET) from the cover film and backing layer, and a second step of screening for even larger particles (i.e., particles larger than 10 mm, preferably larger than 5 mm), which may be returned to the process to reduce their size or sized and removed for further use.

[0057] Alternatively, a first screening step may be performed to screen for larger particles (i.e., particles larger than 10 mm, or larger than 15 mm, or larger than 20 mm), and these particles may be returned to the process to reduce their size or removed for further use. The particles can then be screened to remove PET flakes having a diameter of approximately larger than 3 mm, or larger than 6 mm, or between 3 mm and 10 mm.

[0058] Once the granules are screened, aggregation can be prevented by adding an anti-tack agent to the screened and granulated particles. For example, the anti-tack agent may be selected from the group consisting of fumed silica, fillers such as talc, mica, clay, and carbonates, metal stearates such as zinc stearate, magnesium stearate, calcium stearate, potassium stearate, stearic acid, liquid lubricants, emulsifying waxes, and calcium silicate. In one embodiment, the anti-tack agent includes fumed silica.

[0059] Granules can be used to replace used recycled materials (PCRM) entirely or partially in various building materials and other sustainable products. Therefore, in one embodiment, used flexographic printing elements and / or unused photocurable printing blank materials can be used to produce granules that replace PCRM in sustainable building materials such as asphalt shingles.

[0060] In one embodiment, the sustainable building material is a roof tile or roofing board, and the crushed material is used in combination with other materials to produce a roof tile or roofing board incorporating a high concentration of granular recycled material. Other materials include, but are not limited to, asphalt, paving materials, and synthetic building materials, including synthetic wood. For example, the sustainable building material may also be a fibrous cement product (a commercially available product under the trade name Hardie®) composed of cement, sand, and cellulose fibers, and may include boards, sizing, or trim. The granules may replace at least some of the cement, sand, and / or cellulose fibers. The same applies to other industrial products, such as industrial wood products, in which the granules can be used to reduce some or all of the fillers or other materials contained in the industrial product. Other products include, but are not limited to, flotation in docking systems, aftermarket repair products, and concrete formwork.

[0061] Vehicle structural materials also include a variety of filler materials that can be replaced whole or partially by the granules described herein, including, among other things, vehicle structural materials such as door frame casings, interior trim, and floor partitions for trains and trucks.

[0062] Other industrial products that can be constructed using the granules described herein include, among others, pallets, cabinets, cargo crates, temporary structures, sheds, trusses, laminated beam substitutes, subflooring, wall cladding, roof cladding, laminated flooring, drywall substitutes, interior doors, exterior doors, air conditioners, industrial shelving, underlayment, exterior cladding, prefabricated furniture, pre-molded steps, bathtubs, sink countertops, swimming pools, sound-absorbing ceiling tiles, Formica countertops (wood substitutes), outdoor furniture, indoor furniture, templates, prefabricated housing, structural structures, frameworks, soundproofing panels, and window frames.

[0063] The granules described herein may also be used in marine applications, such as marine piles (round and square), marine decks, marine deck frame systems, mezzanine decks, ship decks, ship stringers and interior furnishings, deck boards, and piers, as well as in other similar materials that can be constructed as fillers, in whole or in part, of which at least a portion may be replaced by the granules described herein.

[0064] Another area in which the granules described herein may be used is printing applications, for example, cutting dies (flat) for the foldable carton and corrugated cardboard market, cutting dies (circular) for the corrugated cardboard market, printing forms for the corrugated cardboard market, and printing tapes for the flexographic printing (non-corrugated cardboard) market.

[0065] Further applications include, but are not limited to, military bulletproofing, lightweight structures, temporary structures, signs, returnable containers, slate substitutes for swimming pools and billiard tables, storefront containers for fruits and vegetables that can be returned for reuse, aircraft interior materials, circuit boards and other non-conductive electronic substrates, electronic equipment housings, and insulated concrete formwork (ICF).

[0066] Example 1: Photopolymer printing plate materials were evaluated and sorted to remove those without a styrene-butadiene-styrene binder, leaving only those photopolymer printing plate materials based on a styrene-butadiene-styrene photopolymer with a polyethylene terephthalate (PET) backing layer. These photopolymer printing plate materials were pulverized by cryogenic grinding to produce granules. The granules were then screened to remove particles larger than 10 mm. The remaining product, including larger polyethylene terephthalate flakes (including flake sizes ranging from approximately 1400 microns to approximately 0.125 inches), was further processed for further use.

[0067] Example 2: Photopolymer printing plate materials were evaluated and sorted to remove those that did not use a styrene-butadiene-styrene binder, leaving only photopolymer printing plate materials that were based on a styrene-butadiene-styrene photopolymer and included a polyethylene terephthalate (PET) backing layer.

[0068] Prior to the pulverization process, the photopolymer printing plate material was first subjected to an initial shredding process to break it into smaller fragments. Next, these fragments of the photopolymer printing plate were exposed to a UV-C light source for a sufficient amount of time to reduce their tackiness and make them more brittle.

[0069] Subsequently, the shredded and UV-C treated photopolymer printing plate material was pulverized by cryogenic grinding to produce granules. The granules were then screened to remove particles larger than 10 mm. The remaining product, including larger polyethylene terephthalate flakes (including flake sizes ranging from approximately 1400 microns to approximately 0.125 inches), was further processed for further use.

[0070] Example 3: The granules from Example 1 were evaluated, and the product's compatibility with other used recycled materials (PCRM) and polymers was tested.

[0071] Typically, a complex formulation consisting of 5% PCRM + 3% polymer + 3% polymer ~ 3% PCRM was selected. 2.5% of the 5% PCRM was replaced with 2.5% of the granules from Example 1. The blending results showed that the granules were compatible with other PCRMs and other types of polymers. Furthermore, the test results were slightly better than the control results.

[0072] Example 4: In the next blend, 5% PCRM was completely replaced with 5% of the granules from Example 1. This material was then blended with both filled and unfilled portions. These test results were also better than the control results.

[0073] The examples demonstrate that the granules described herein are viable products for replacing at least a portion of PCRM in asphalt compositions. Furthermore, the granules described herein may also be used to replace at least a portion of PCRM in building materials and other products that contain a portion of PCRM.

[0074] Finally, it should be understood that the following claims are intended to encompass all the general and specific features of the invention described herein, as well as, as a matter of language, all descriptions of the scope of the invention that may fall between them.

[0075] Additional embodiments:

[0076] Item 1: A method for producing granules from photopolymer printing plate material, A sorting process for selecting photopolymer printing plate materials based on identifiable characteristics; Optionally, a shredding or chipping process to reduce the size of the photopolymer printing plate material to smaller chips or fragments of relatively uniform size; An exposure process in which a photopolymer printing plate material is exposed to UV-C light from a UV-C light source for a certain period of time, thereby reducing the tackiness and increasing the brittleness of the photopolymer printing plate material; A grinding process for grinding photopolymer printing plate material into particles; and A screening process that screens particles to remove particles exceeding a certain size and produces granules. Methods that include...

[0077] Item 2: The method according to Item 1, wherein the photopolymer printing plate material comprises a used photocured or photopolymerized flexographic printing element having one or more cured photopolymer layers on a support layer.

[0078] Item 3: The method described in Item 1 or 2, wherein a shredding or chipping process is performed.

[0079] Item 4: A method according to any one of items 1 through 3, wherein the steps are performed in order.

[0080] Item 5: The method according to any one of items 1 to 4, wherein the grinding step and the screening step are repeated at least once.

[0081] Item 6: The method according to any one of Items 1 through 5, wherein the screened particles exceeding a certain size contain polyethylene terephthalate, and the polyethylene terephthalate is in the form of flakes or particles having a size of approximately 1400 microns to approximately 0.125 inches.

[0082] Item 7: The method according to Item 2, wherein one or more cured photopolymer layers comprise a binder selected from styrene-isoprene-styrene and styrene-butadiene-styrene.

[0083] Item 8: The method according to Item 3, wherein the binder comprises styrene-butadiene-styrene.

[0084] Item 9: The method according to Item 2, wherein one or more cured photopolymer layers are processed from a liquid photoresin based on an ethylenically unsaturated prepolymer selected from the group consisting of unsaturated polyester resins, unsaturated polyurethane resins, unsaturated polyamide resins, and unsaturated poly(meth)acrylate resins.

[0085] Item 10: The method according to Item 9, wherein the photoresin comprises an unsaturated polyurethane resin.

[0086] Item 11: The method according to Item 2, wherein the support layer is not removed from one or more photopolymer layers before the grinding step.

[0087] Item 12: The method according to any one of items 1 to 11, wherein the identifiable characteristics are selected from the group consisting of binder type, Shore A hardness of photopolymer, gauge of printing plate, and one or more combinations thereof.

[0088] Item 13: The method according to any one of items 1 to 12, wherein the granules have a particle size of less than 20 mm.

[0089] Item 14: The method according to Item 13, wherein the granules have a particle size of less than 10 mm, preferably less than 5 mm.

[0090] Item 15: The method according to any one of items 1 to 14, wherein an anti-tack agent is added to the granules after step c).

[0091] Item 16: The method according to Item 15, wherein the anti-tack agent is selected from the group consisting of fumed silica, talc, mica, clay, carbonate, zinc stearate, magnesium stearate, calcium stearate, potassium stearate, stearic acid, liquid lubricants, emulsifying waxes, and calcium silicate.

Claims

1. A method for producing granules from photopolymer printing plate material, a) A sorting step for sorting the photopolymer printing plate material based on identifiable characteristics; b) Optionally, a shredding or chipping step, which reduces the size of the photopolymer printing plate material to smaller chips or fragments having a relatively uniform size; c) An exposure step in which the photopolymer printing plate material is exposed to UV-C light from a UV-C light source for a certain period of time, thereby reducing the tackiness and increasing the brittleness of the photopolymer printing plate material; d) A grinding step of grinding the photopolymer printing plate material into particles; and e) A screening process for screening the particles to remove particles exceeding a specific size and to produce the granulated product. Methods that include...

2. The method according to claim 1, wherein the photopolymer printing plate material includes a used photocured or photopolymerized flexographic printing element having one or more cured photopolymer layers on a support layer.

3. The method according to claim 1 or 2, wherein a shredding or chipping step is performed.

4. The method according to claim 1 or 2, wherein the above steps are performed in order.

5. The method according to claim 1 or 2, wherein the grinding step and the screening step are repeated at least once.

6. The method according to claim 1 or 2, wherein the screened particles exceeding the specified size include polyethylene terephthalate, and the polyethylene terephthalate is in the form of flakes or particles having a size of about 3 mm to about 10 mm.

7. The method according to claim 2, wherein the one or more cured photopolymer layers include a binder selected from styrene-isoprene-styrene and styrene-butadiene-styrene.

8. The method according to claim 3, wherein the binder comprises styrene-butadiene-styrene.

9. The method according to claim 2, wherein the one or more cured photopolymer layers are processed from a liquid photoresin based on an ethylenically unsaturated prepolymer selected from the group consisting of unsaturated polyester resin, unsaturated polyurethane resin, unsaturated polyamide resin, and unsaturated poly(meth)acrylate resin.

10. The method according to claim 9, wherein the photoresin includes an unsaturated polyurethane resin.

11. The method according to claim 2, wherein the support layer is not removed from one or more photopolymer layers before the grinding step.

12. The method according to claim 1 or 2, wherein the identifiable characteristic is selected from the group consisting of the type of binder, the Shore A hardness of the photopolymer, the gauge of the printing plate, and one or more combinations thereof.

13. The method according to claim 1 or 2, wherein the granulated material has a particle size of less than 20 mm.

14. The method according to claim 13, wherein the granulated material has a particle size of less than 10 mm.

15. The method according to claim 14, wherein the granulated material has a particle size of less than 5 mm.

16. The method according to claim 1 or 2, wherein an anti-sticking agent is added to the granules after step c).

17. The method according to claim 16, wherein the anti-tack agent is selected from the group consisting of fumed silica, talc, mica, clay, carbonate, zinc stearate, magnesium stearate, calcium stearate, potassium stearate, stearic acid, liquid lubricant, emulsifying wax, and calcium silicate.

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