Odour-free composition for flexographic printing

Abstract

The present invention relates to a low-odour liquid composition with low VOC emissions, suitable for producing flexographic relief printing plates.

Description

Description Title: Odorless composition for flexogravure Technical field

[0001] The present disclosure relates to the field of liquid compositions used in flexogravure as well as a method of manufacturing a relief flexographic printing plate using such compositions. Prior art

[0002] Flexographic printing, a popular method in the packaging industry, uses flexible photopolymer plates to transfer images onto various substrates such as flat or corrugated cardboard, polyethylene films, or paper. A flexible photopolymer plate is produced by a process involving: a flexographic plate comprising a photopolymer layer covered with a mask comprising carbon black and a polymer binder.Said method comprises the following steps: etching the mask (for example, carbon black) from the flexographic plate (for example, a laser technique) to obtain an etched plate comprising: a portion of the uncovered plate, and a portion of the plate covered with the mask, exposing the etched plate to UVA to crosslink the photopolymer of the uncovered portion of the mask to obtain a plate comprising a crosslinked photopolymer region, removing the portion of the uncrosslinked photopolymer layer covered with the mask by a liquid developing composition to obtain a washed plate comprising a crosslinked photopolymer region, and drying the washed plate to obtain the flexible photopolymer plate.

[0003] The manufacture of these plates requires the removal of the uncrosslinked photopolymer and mask layer. To achieve this, the plate is washed in a bath of the liquid composition, gently heated to 25-30°C, and mechanically brushed. The uncrosslinked photopolymer, along with the remaining mask layer, dissolves in the liquid composition, which may be followed by a drying step to remove residual solvent from the plate. The final steps include post-exposure to UV light (UVA and UVC, with UVC light acting as a germicide) to complete the crosslinking of the photopolymer, which improves the durability of the plate for subsequent printing applications and ensures germicidal treatment of the plate.

[0004] The liquid compositions used in development have a dual function: removing the mask layer and dissolving the uncrosslinked photopolymer. However, these liquid compositions often present challenges, including the possibility of dissolving or slightly swelling the cured photopolymer, which leads to prolonged drying times, quality defects in the plate engraving, and problems with the flexible photopolymer plate itself, such as warping or self-winding. These effects can have a negative impact on the final print quality.

[0005] In addition, many traditionally used liquid compositions are characterized by the release of highly unpleasant odors, significant emissions of volatile organic compounds (VOCs) and therefore potential risks to the health of workers.

[0006] Furthermore, the use of ecotoxic and / or flammable liquid compositions raises environmental concerns, hence the need to develop safer and more environmentally friendly alternatives. Indeed, the environmental footprint of these solvents has become an increasingly pressing concern.

[0007] There is therefore a need to provide less odorous liquid compositions that emit fewer VOCs into the environment to prevent worker exposure through inhalation but allow the efficient production of flexible photopolymer plates suitable for flexographic printing. In particular, flexible photopolymer plates must not exhibit defects, such as softening, stickiness, swelling, and warping.

[0008] In addition, there is a need for these liquid compositions to also have minimal toxicity, a high flash point (preferably above 60°C) to reduce the risk of ignition, and to be suitable for efficient regeneration by distillation. Summary

[0009] This disclosure improves the situation.

[0010] According to a first aspect, there is provided a liquid composition comprising: between 20 and 80% by mass relative to the total mass of the liquid composition of a solvent (A), and between 20 and 80% by mass relative to the total mass of the liquid composition of a mixture of solvents (B), (C) and (D) in which the boiling point of each of the solvents (A), (B), (C) and (D) is between 150°C and 250°C, in particular between 170°C and 230°C, the solvent (A) is chosen from the compounds of general formula R - O- CHR'-OR” where R and R” are independently of one another chosen from linear, branched or cyclic alkyl groups, substituted or not, in particular linear, branched alkyl groups, substituted or not, more particularly linear C2 to C5 alkyl groups, substituted or not, R' is H or a linear or branched C1 to C4 alkyl group, in particular H, methyl or ethyl, more particularly H; the solvent (B) is a C9 to C16 hydrocarbon, in particular C10-C13 or C11-C13, preferably C10-C13, the solvent (C) is chosen from aliphatic alcohols and the solvent (D) is chosen from aromatic alcohols, the concentration of solvent (B) in the solvent mixture is between 40 and 65% by mass relative to the total mass of the solvent mixture, in particular between 50 and 62%, particularly between 50 and 60% by mass; the solvent concentration (C) in the solvent mixture is between 0.1 and 20% by mass relative to the total mass of the solvent mixture, in particular between 1 and 10%, particularly between 3 and 10% by mass;and the solvent concentration (D) in the solvent mixture is between 20 and 60% by mass relative to the total mass of the solvent mixture, in particular between 30 and 50%, particularly between 35 and 45% by mass.;

[0011] The sum of the concentrations of solvents (B), (C) and (D) in the solvent mixture is equal to 100% relative to the total mass of the solvent mixture (B), (C) and (D).

[0012] The sum of the concentrations of solvents (A), (B), (C) and (D) in the liquid composition is equal to 100% relative to the total mass of the liquid composition comprising solvents (A), (B), (C) and (D).

[0013] Advantageously, the liquid composition of the invention meets the aforementioned needs.

[0014] In particular, the specific selection of the four solvents (A), (B), (C) and (D) of the liquid composition allows the liquid composition not to release an unpleasant odor.

[0015] This specific selection of solvents and their content in the liquid composition of the invention also allows the liquid composition to emit fewer Volatile Organic Compounds (VOCs) than the liquid compositions conventionally used in the production of flexible photopolymer plates. This is very advantageous because, compared to conventional liquid compositions, the liquid composition of the invention: - allows to minimize the health risks for users of liquid compositions during the production of photopolymer plates, and - has a lower environmental impact because, - it emits fewer toxic compounds into the environment, - it does not emit CMR compounds, - it makes it possible to reduce the size of air treatment units guaranteeing healthy air around the flexible photopolymer plate production process and therefore to reduce the energy consumption necessary to guarantee this healthy air, and - it allows to reduce the consumption of liquid composition by a process of production of photopolymer plates because it “loses” less of its compounds.

[0016] Furthermore, the liquid composition allows the efficient production of flexible photopolymer plates. In particular, it can be implemented in a conventional photopolymer plate production process without modification of the installations to implement this process. Furthermore, it allows the time (UVA, UVC exposure, etching and drying) and temperature (etching and drying) parameters for implementing the process to be preserved or even shortened. This guarantees continuity in the manufacturing process. In addition, the boiling point of each of the solvents (A), (B), (C) and (D) of the liquid composition of the invention ensures compatibility with existing liquid composition recovery and regeneration systems, in particular distillation. Indeed, by maintaining the stability of the conditions of the existing distillation system, the overall management of solvent recovery is ensured.

[0017] The concentration ranges specified for solvents (B), (C) and (D) ensure that the solvent blend is optimized for the development of flexographic printing plates, while ensuring a balance between efficient development, reduced toxicity and lower environmental impact.

[0018] According to a second aspect, there is provided a method of manufacturing a relief flexographic printing plate from a flexographic plate comprising a photopolymer layer covered with a mask, said mask possibly comprising carbon black and a polymeric binder, said method comprising the following steps: a) etching the mask of the flexographic plate to obtain an etched plate comprising: - a portion not covered with a photopolymer layer, and - a portion of photopolymer layer covered with the mask, b) exposure to UVA of the etched plate to crosslink the photopolymer of the portion not covered with photopolymer layer to obtain a plate comprising a crosslinked photopolymer area, c) removing the portion of photopolymer layer covered with the mask by a liquid development composition to obtain a washed plate comprising a crosslinked photopolymer area, and d) optionally, drying the washed plate to obtain the flexible photopolymer plate, wherein the liquid development composition is the liquid composition as defined above. Brief description of the drawings

[0019] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which: Fig. 1

[0020] [Fig. 1] illustrates the olfactory profile of composition I at 20°C. Fig. 2

[0021] [Fig. 2] illustrates the olfactory profile of composition C1 at 20°C. Fig. 3

[0022] [Fig. 3] illustrates the olfactory profile of composition C2 at 20°C. Detailed description

[0023] According to the first aspect, the invention relates to a liquid composition comprising: between 20 and 80% by mass relative to the total mass of the liquid composition of a solvent (A), and between 20 and 80% by mass relative to the total mass of the liquid composition of a mixture of solvents (B), (C) and (D) in which the boiling point of each of the solvents (A), (B), (C) and (D) is between 150°C and 250°C, in particular between 170°C and 230°C, the solvent (A) is chosen from the compounds of general formula R - O- CHR'-OR” where R and R” are independently of one another chosen from linear, branched or cyclic alkyl groups, substituted or not, in particular linear, branched alkyl groups, substituted or not, more particularly linear C2 to C5 alkyl groups, substituted or not, R' is H or a linear or branched C1 to C4 alkyl group, in particular H, methyl or ethyl, more particularly H; the solvent (B) is a C9 to C16 hydrocarbon, in particular C10-C13 or C11-C13, of preferably in C10-C13 the solvent (C) is chosen from aliphatic alcohols and the solvent (D) is chosen from aromatic alcohols, the concentration of solvent (B) in the mixture of solvents is between 40 and 65% by mass relative to the total mass of the mixture of solvents, in particular between 50 and 62%, particularly between 50 and 60% by mass; the concentration of solvent (C) in the mixture of solvents is between 0.1 and 20% by mass relative to the total mass of the mixture of solvents, in particular between 1 and 10%, particularly between 3 and 10% by mass; the concentration of solvent (D) in the mixture of solvents is between 20 and 60% by mass relative to the total mass of the mixture of solvents, in particular between 30 and 50%, particularly between 35 and 45% by mass.

[0024] A Cn hydrocarbon is an organic hydrocarbon compound consisting of only carbon and hydrogen atoms, with a carbon chain of n carbon atoms. For example, a C9 hydrocarbon is an organic hydrocarbon compound consisting of only carbon and hydrogen atoms, with a carbon chain of 9 carbon atoms.

[0025] By "aromatic compound" we mean a molecule which has at least one conjugated cyclic structure.

[0026] By "aliphatic compound" is meant an organic compound with open or cyclic carbon chains, linear or branched, without a conjugated cyclic structure.

[0027] By “liquid composition” we mean a composition in a liquid state at a temperature between 20 and 35°C.

[0028] By “substituted” is meant that the alkyl groups R and R” may be substituted by one or more groups comprising a heteroatom, such as oxygen or nitrogen, for example a C1 to C3 ether group.

[0029] The solvent (A) may be selected from Dipentoxyethane (Cas no. 13002-08-9), dibutoxymethane (or 1 -(butoxymethoxy)butane or butylal, Cas no. 2568-90-3), 1 - [(Pentyloxy)methoxy]butane, 1 -(1 -Butoxyethoxy)-3-methylbutane (Cas no. 238757-27-2), 1 -(1 -Ethoxypropoxy)-3-methylbutane (Cas no. 238757-30-7), 1 -(1 -Isobutoxyethoxy)-3-methylbutane (Cas no. 75048-15-6), 3-Methyl-1 -[1 -(3-methylbutoxy)propoxy]butane (Cas no. 13002-13-6), 1 -(1 -(lsopentyloxy)ethoxy)-3-methylbutane (Cas no. 13002-09-0), 2,5,7, 10-Tetraoxaundecane (Cas no. 4431-83-8) or mixtures thereof, in particular dibutoxymethane.

[0030] In particular, the use of dibutoxymethane, which is not classified for toxicity or ecotoxicity under the CLP Regulation, contributes to a safer working environment by reducing user exposure to harmful solvent vapors. This results in a liquid composition that is less hazardous to handle and has a lower environmental impact compared to compositions containing more toxic petroleum-based aromatic solvents.

[0031] European Regulation No. 1272 / 2008, known as CLP for classification, labelling and packaging of substances and mixtures, is a European regulation published in the OJEU on 31 December 2008 and entered into force on 20 January 2009.

[0032] Additionally, the specified solvents, particularly dibutoxymethane, contribute to a liquid composition with reduced odor intensity. This feature improves the user experience by reducing odor discomfort during the production of flexible photopolymer plates and potentially reducing residual odor on the final plate.

[0033] The solvent (B) may be a hydrocarbon having at least one of the following two characteristics, in particular the following two characteristics: - it comprises n-alkanes, isoalkanes, and cyclic compounds or a mixture thereof, preferably a mixture of n-alkanes, isoalkanes, and cyclic compounds whose carbon number is in the range C10-C13 or isoalkanes in the range C11-C13, preferably a mixture of n-alkanes, isoalkanes, and cyclic compounds whose carbon number is in the range C10-C13, and - it has a content of less than 2% by mass in aromatic compounds.

[0034] The solvent (B) may be a fraction of hydrocarbons hydrotreated into CI O- CI 3 chains, n-alkanes, isoalkanes, cyclics, with a low aromatic content (<2% aromatics relative to the mass of the solvent (B)) (Cas no. 1174522-09-8, EC number 918-481-9), having a flash point between 60 and 66 °C (according to ASTM D 93) and a boiling range: between 160 - 245 °C (according to ASTM D 86).

[0035] Solvent (B) may be a fraction, having low aromatic (<2% aromatics relative to the mass of solvent (B)) C11-C13 isoalkane hydrocarbon chains, having an initial boiling point between 180 and 195°C and a boiling range up to 210°C and a flash point between 65 and 71°C. The boiling temperatures (initial boiling and range) may be measured according to ASTM D 86 and the flash point may be measured according to ASTM D 93.

[0036] The solvent (B) can be a mixture of these two cuts.

[0037] The solvent (C) may be chosen from aliphatic alcohols whose carbon number is in the range C7 to C15, preferably branched C7 to C11 alcohols, preferably 2-ethylhexan-1-ol (Cas no. 104-76-7, EC no.: 203-234-3).

[0038] The solvent (D) may be selected from benzyl alcohol (Cas no. 100-51-6), 1-phenylethanol (Cas no. 98-85-1 (racemic), Cas no. 1517-69-7 (R) or Cas no. 1445-91-6 (S)), 2-phenylethanol (Cas no. 60-12-8).

[0039] The liquid composition may be free of dialkilene glycol-alkyl ether or diisoalkylbenzene, in particular free of dipropylene glycol-n-butylether (Cas no. 29911-28-2) or diisopropylbenzene (DIPB) (Cas no. 25321-09-9).

[0040] By excluding diisopropylbenzene from the liquid composition, the formulation reduces the potential health risks (headaches, drowsiness if inhaled) associated with the use of this chemical and can help reduce the impact on the environment, as this toxic chemical is persistent in the environment, particularly for aquatic organisms, and poses ecological risks. The liquid composition without diisopropylbenzene therefore complies with environmental safety regulations and sustainability objectives. Its exclusion ensures that the composition does not contain substances classified as carcinogenic, mutagenic and reprotoxic (CMR), such as cumene, which is an impurity resulting from the production of diisopropylbenzene and therefore may be contained in commercial diisopropylbenzene.

[0041] Additionally, the removal of diisopropylbenzene can result in a reduction in the intensity of the solvent's pungent odor, improving working conditions for operators by providing a more pleasant olfactory environment during the production of flexible photopolymer plates.

[0042] The liquid composition may be free of odor masking agent.

[0043] An odor masking agent is an additional chemical substance or compound added to a composition according to the invention to disguise or reduce the perception of an undesirable odor. This agent acts either by neutralizing the molecules responsible for the odor or by emitting a more pleasant or neutral odor, thus creating a masking effect.

[0044] The absence of an odor masking agent in the liquid composition reveals the true olfactory character of the liquid composition, allowing for a more accurate assessment of its odor intensity. This promotes a safer working environment by allowing users to more easily detect the presence of solvent vapors, thus enabling compliance with occupational health and safety standards.

[0045] Additionally, eliminating odor-masking agents can simplify formulation, potentially reducing manufacturing costs and avoiding the introduction of additional chemicals that could have their own environmental and health impacts. This approach is part of the goal of creating a solvent with reduced toxicity and a reduced environmental footprint.

[0046] The liquid composition does not emit any substance classified as carcinogenic, mutagenic and toxic to reproduction (CMR) according to Commission Regulation (EU) 2023 / 1132 of 8 June 2023 amending Regulation (EC) No 1907 / 2006 of the European Parliament and of the Council as regards restricted carcinogenic, mutagenic or toxic for reproduction substances, such as cumene.

[0047] The liquid composition of the invention minimizes the emission of hazardous substances, thus reducing potential health risks for workers involved in the development of polymer printing plates for flexography. The liquid composition of the invention thus contributes to a safer working environment by complying with regulatory standards relating to substances classified as carcinogenic, mutagenic or toxic for reproduction.

[0048] The absence of such harmful emissions from CMR compounds also reduces the need for specialized ventilation or personal protective equipment, which can reduce operating costs and simplify compliance with occupational health and safety standards.

[0049] The liquid composition may include: - between 20% and 80% by mass relative to the total mass of the liquid composition of a solvent (A), in particular between 20% and 50%, in particular between 20% and 30%, - between 25% and 60% by mass relative to the total mass of the liquid composition of a solvent (B), in particular between 35% and 50%, - between 1% and 15% by mass relative to the total mass of the liquid composition of a solvent (C), in particular between 1% and 7% and - between 22% and 50% by mass relative to the total mass of the liquid composition of a solvent (D), in particular between 25% and 35%.

[0050] The specified proportions of solvents in the liquid composition ensure a balanced formulation that allows for efficient dissolution of the uncrosslinked photopolymer while preserving the integrity of the crosslinked photopolymer. This selective dissolution capability enables a high-quality development process for flexographic printing plates, with minimal impact on final print quality due to reduced plate softening, swelling, or warping. By minimizing the occurrence of these defects, the possible loss of solvents in the etching machine is also reduced.

[0051] In addition, the specified proportions of solvents in the liquid composition are kept stable over time. This stability is maintained during etching and distillation and persists even after solvent regeneration (e.g. after distillation). Therefore, no formulation adjustment is required, ensuring consistent performance.

[0052] The liquid composition may have a flash point between 60°C and 93°C.

[0053] By choosing these solvent concentration ranges, the composition has a reduced toxicity and flammability profile, with a flash point above 60°C. This contributes to safer working conditions by minimizing worker exposure to harmful solvent vapors and reducing the risk of fire in industrial environments. Thus, the non-ADR composition benefits from the advantage of not being subject to ADR regulations for transport, simplifying classification and labeling. ADR stands for “Accord for Dangerous Goods by Road.”

[0054] Additionally, the composition helps reduce the development and drying time of photopolymer plates, streamlining the production process and increasing efficiency.

[0055] It also facilitates the maintenance of engraving machines by preventing the deposition of photopolymer and preventing the clogging of said machines by effectively solubilizing the photopolymer. In addition, it does not corrode brushes or machine components, thus reducing the frequency of interventions and maintenance costs.

[0056] The mixture of solvents (B), (C) and (D) can be a ternary mixture.

[0057] The liquid composition comprising the solvents (A), (B), (C) and (D) may be a quaternary mixture.

[0058] The liquid composition also facilitates the regeneration of used etching solvent by vacuum distillation, which promotes sustainable practices by allowing the recovery and reuse of the solvent. Indeed, the composition comprising liquid has a boiling point between 150°C and 250°C, in particular between 170°C and 230°C, which means that it can be used on distillation installations already existing at engravers, not requiring adaptation of their installations. The use of this liquid composition helps reduce solvent loss during distillation and thus results in better distillation and therefore less presence in the distillation sludge.

[0059] Distilling etching solvents involves several steps to recover them for reuse. First, the liquid composition is heated to its boiling point to evaporate the components and obtain a solvent vapor. Then, the solvent vapor is cooled to condense it into a solvent liquid. At this stage, the solvents in the solvent liquid are separated from the impurities and contaminants in the solvent liquid. The separated solvents are collected for reuse. Depending on the needs, other steps such as filtration or purification may be required to meet the specific requirements of the solvent recovery and reuse process.

[0060] Thus, distilling etching solvents allows them to be efficiently recovered for later reuse. Reusing recovered solvents reduces waste and the costs associated with purchasing new solvents, while contributing to more sustainable and environmentally friendly practices.

[0061] The inclusion of these solvents (A) to (D) in the liquid composition helps to reduce the odor intensity of the final composition, which improves working conditions by reducing the odor discomfort that can be caused by more odorous solvents traditionally used. This is particularly beneficial in closed industrial environments where solvent vapors can accumulate and affect worker well-being.

[0062] The composition of the developer solution effectively dissolves the carbon black and polymer binder mask without adversely affecting the crosslinked photopolymer. This contributes to a cleaner and more precise engraving of the image, which is essential for the fidelity of the printed image to the original drawing.

[0063] Additionally, the developer solution's composition is designed to minimize toxicity and reduce flammability, enhancing the safety of the manufacturing process. The solvent's lower volatility also reduces the emission of volatile organic compounds (VOCs), reducing environmental impact and improving operator working conditions by limiting their exposure to harmful solvent vapors. Its use therefore reduces solvent loss in etching machines thanks to reduced evaporation of its components.

[0064] The use of solvent (A) in the composition, as a replacement for more toxic aromatic petroleum solvents, not only reduces the health risks associated with inhalation of solvents, but also significantly reduces the intensity of the odor of the solution. This results in a more pleasant working environment and a relief flexographic printing plate with minimal residual odor, which can be advantageous in packaging applications where odor neutrality is desired.

[0065] According to another aspect, the invention relates to a method of manufacturing a relief flexographic printing plate from a flexographic plate comprising a photopolymer layer covered with a mask comprising carbon black and a polymeric binder, said method comprising the following steps: a) etching the mask of the flexographic plate to obtain an etched plate comprising: - a portion not covered with a photopolymer layer, and - a portion of photopolymer layer covered with the mask, b) exposure to UVA of the etched plate to crosslink the photopolymer of the portion not covered with photopolymer layer to obtain a plate comprising a zone of crosslinked photopolymer, c) removal of the portion of photopolymer layer covered with the mask by a liquid development composition to obtain a washed plate comprising a zone of crosslinked photopolymer, and d) optionally, drying the washed plate to obtain the flexible photopolymer plate in which the liquid development composition is the liquid composition as defined above.

[0066] Step d) consists of a drying operation at a temperature suitable for removing the residual solvent present on the plate. For example, this temperature may be between 40 and 100°C, in particular between 45 and 55°C.

[0067] Step c) or the possible step d) can be followed by a post-exposure step to UVA and UVC light.

[0068] Advantageously, this post-exposure step can complete the crosslinking of the photopolymer layer, improving the durability of the plate for subsequent printing applications and providing germicidal treatment of the plate using UVC light.

[0069] UVA means type A ultraviolet rays. UVA rays have wavelengths between 320 and 400 nm.

[0070] UVC refers to type C ultraviolet rays. UVC rays have wavelengths between 100 and 280 nm.

[0071] Flexographic printing products are used in a variety of markets. They are primarily used in food packaging, including bags, flexible packaging or wrapping films, cardboard packaging, cups, napkins, tablecloths, and various types of tissue paper. Cardboard is also an important market for flexographic printing products. They are particularly found in the production of cardboard packaging, such as boxes, cases, and packaging for various products. Flexography offers an efficient and versatile printing solution for these applications, allowing for a wide variety of designs and high-quality printing on cardboard substrates. Examples Example 1. Liquid compositions tested

[0072] Compositions I (according to the invention), C1 (comparative) and C2 (comparative) are obtained by mixing the different compounds at room temperature.

[0073] Composition I comprises 20% butylal, 50% of a CI 0-CI 3 hydrocarbon fraction (Cas no. 1 174522-09-8, EC number 918-481-9), 5% of 2-ethylhexan-1-ol and 25% of benzyl alcohol, the percentages being expressed as mass percentages relative to the total weight of composition I.

[0074] Composition C1 comprises 30% of an aromatic hydrocarbon cut (marketed under the name Solvesso 150 Fluid from ExxonMobil Chemical), 50% of a C10-C13 hydrocarbon cut (Cas no. 1 174522-09-8, EC number 918-481-9), 4% of 2-ethylhexan-1-ol and 16% of benzyl alcohol, the percentages being expressed as mass percentages relative to the total weight of composition C1.

[0075] Composition C2 comprises 60% of a C11-C13 hydrocarbon fraction, 26% of diisopropylbenzene, 2% of 2-ethylhexan-1-ol and 12% of benzyl alcohol, the percentages being expressed as mass percentages relative to the total weight of composition C2. Example 2. Olfactometric analyses

[0076] The odor of these three compositions was analyzed under normal conditions of use (20°C and 30°C).

[0077] A sample of each of the three compositions was conditioned in a temperature-controlled room (20°C or 30°C ±2°C). For each composition, 500 μL was first introduced into a circular cup. This was placed inside a Nalophan® bag subsequently filled with 40 L of nitrogen. The samples thus constituted were placed in a temperature-controlled room (20°C or 30°C ±2°C).

[0078] Example 2A. Odor Concentration

[0079] To measure the odor concentration, the odorant gas to be analyzed (present inside the Nalophan® bag) was presented at different concentrations to a panel of six people in the form of successive dilutions. This sensory analysis was carried out with an Odile® multi-station dynamic dilution olfactometer and complies with the NF EN 13725 standard. For each dilution, each person indicated whether they perceived the odor or not. Thus, the odor concentration (the perception threshold) of the odors could be determined by each person and then for the panel.

[0080] The results of the odor concentration thresholds (UOE / m 3 ) measured are shown in Table 1.

[0081] Table 1

[0082] Composition I exhibits the least persistent odor at both temperatures tested. In particular, composition I emits a significantly less persistent odor than composition C2, and ten times less persistent than composition C1.

[0083] Example 2B. Acceptability

[0084] The use of a ten-person panel allowed the characterization of odor acceptability. The ten people had to rank the samples from the least unpleasant to the most unpleasant odor.

[0085] The compilation of the results revealed the same ranking as that obtained with Example 2A. The most appreciated odor is that of composition I, followed by that of composition C2 and finally that of composition C1.

[0086] Example 2C. Quality

[0087] The odor quality was assessed at 20°C by a panel of 10 people. This olfactory analysis made it possible to directly characterize the odor qualities and obtain an olfactory "profile". The olfactory profiles obtained through the odor quality analysis include 6 descriptors: Petroleum distillates, Rubber / Plastic, Burnt, Cleaning product, Polish and Fruity.

[0088] Each member of the jury must describe the odor by assigning 5 points to the primary tone(s). The secondary tones are evaluated on a scale of 1 to 4. The results are weighted and an olfactory profile is obtained.

[0089] The results are presented in Figures 1 to 3.

[0090] Figure 1 illustrates the olfactory profile of composition I at 20°C. The dominant note of “Petroleum Distillates” is accompanied by secondary odor notes of “Cleaning Product” and “Fruity”.

[0091] Figure 2 illustrates the olfactory profile of composition C1 at 20°C. Its odor has a single, largely dominant note of “Petroleum Distillates”.

[0092] Figure 3 illustrates the olfactory profile of composition C2 at 20°C. Its odor appears more complex and presents the dominant note “Petroleum distillates” and four secondary notes: “Rubber / Plastic”, “Burned”, “Cleaning product” and “Fruity”.

[0093] The presence of the “Fruity” note in the olfactory profiles of composition C2 and composition I seems to be linked to their lower nuisance potential compared to composition C1. However, the comparison of the olfactory profiles of compositions C2 and I shows that the “Rubber / Plastic” and “Burnt” notes are more marked in the olfactory profiles of composition C2. This observation reveals a higher nuisance potential of composition C2 compared to that of composition I.

[0094] In terms of odor, that of composition I is considered the least bothersome of the three compositions tested.

[0095] Example 3. Analysis of Volatile Organic Compound (VOC) emissions

[0096] The objective of this test is to characterize and quantify the VOC emissions of compositions I, C1 and C2 in a micro-chamber according to ISO 16000-1 1:2006 and ISO 12219-3 (dated 2012).

[0097] Samples are conditioned as specified in ISO 16000-11:2006 and ISO 12219-3 at 30°C in a micro-chamber with a specific air flow rate per unit area. 10-second air samples are taken after 20 min of stabilization according to ISO 12219-3 and analyzed by Thermodesorption / Gas Chromatography / Mass Spectrometry / Flame Ionization Detection according to ISO 16000-6:2021.

[0098] VOC analysis is carried out using a Perkin Elmer 650 thermodesorber coupled with a Clarus 680 chromatograph, a Clarus 600C mass spectrometer, and a Perkin Elmer Flame Ionization detector according to the NF ISO 16000-6:2021 standard.

[0099] The tubes are heated by the thermodesorber for 30 min at 280°C. This heating causes desorption of volatile substances which then pass through the chromatographic column of the chromatograph and are then detected by the mass spectrometer and Flame Ionization detector. Screening and quantification are carried out by mass spectrometry.

[0100] Analytical parameters and conditions of each device: Thermodesorber: Valve temperature: 250°C, Tube temperature: 280°C, Tube desorption time: 15 min, Desorption flow rate: 30 ml / min, Cryogenic temperature: - 30°C, Trap heating temperature: 300°C, Trap heating ramp: 40°C / s. Gas chromatograph: GC temperature programming: 40°C for 2 min, 3°C / min up to 92°C, 5°C / min up to 160°C, 10°C / min up to 280°C, 280°C for 10 min, Apolar capillary column (stationary phase: 5% phenyl-methyl siloxane) 50 mx 0.32 mm x 0.52 pm. Flame Ionization Detector: O2: 450ml / min H2: 45ml / min Attenuation: -6. Mass spectrometer: Scan 29 to 520 amu, Inter scan time 0.1 s.

[0101] The results are illustrated in Table 2.

[0102] Table 2

[0103] Composition I has the lowest amount of total VOCs. In particular, composition I emits significantly fewer VOCs than composition C2, and half as many as composition C1 at 20°C.

[0104] Example 4. Pilot-scale testing

[0105] A test on a pilot process for manufacturing relief flexographic printing plates was carried out during 4 weeks of activity with composition I.

[0106] During the 4 weeks of activity, 2300 m 2 of plates (plates from 1.14 to 6.35 mm) were etched. The quality of the plates obtained is very good and no problems of clogging of the pilot process were observed.

[0107] The operators of the pilot process were much less bothered by the working environment (VOC emissions, odor) and they did not change their etching habits (etching time, number of etching cycles with the solvent, drying time).

[0108] The consumption of composition I was lower than the consumption of composition C2, if composition C2 had been implemented during this test on the pilot process.

Claims

Claims

1. Liquid composition comprising: between 20 and 80% by mass relative to the total mass of the liquid composition of a solvent (A), and between 20 and 80% by mass relative to the total mass of the liquid composition of a mixture of solvents (B), (C) and (D), in which the boiling point of each of the solvents (A), (B), (C) and (D) is between 150°C and 250°C, the solvent (A) is chosen from the compounds of general formula R - O- CHR'-OR” where R and R” are independently of one another chosen from linear, branched or cyclic alkyl groups, substituted or not, R' is H or a linear or branched C1 to C4 alkyl group; the solvent (B) is a C9 to C16 hydrocarbon, in particular C10-C13 or C11-C13, preferably C10-C13; the solvent (C) is chosen from aliphatic alcohols; the solvent (D) is chosen from aromatic alcohols; the concentration of solvent (B) in the solvent mixture is between 40 and 65% by mass relative to the total mass of the solvent mixture; the concentration of solvent (C) in the solvent mixture is between 0.1 and 20% by mass relative to the total mass of the solvent mixture; the concentration of solvent (D) in the solvent mixture is between 20 and 60% by mass relative to the total mass of the solvent mixture.

2. Liquid composition according to claim 1, wherein the solvent (A) is selected from Dipentoxyethane, dibutoxymethane, 1-[(Pentyloxy)methoxy]butane, 1-(1-Butoxyethoxy)-3-methylbutane, 1-(1-Ethoxypropoxy)-3-methylbutane, 1-(1-isobutoxyethoxy)-3-methylbutane, 3-Methyl-1-[1-(3-methylbutoxy)propoxy]butane, 1-(1-(lsopentyloxy)ethoxy)-3-methylbutane, 2,5,7,10-Tetraoxaundecane or mixtures thereof, in particular dibutoxymethane.

3. Liquid composition according to one of claims 1 or 2, where the solvent (B) is a hydrocarbon having at least one of the following two characteristics: - it includes n-alkanes, isoalkanes, and cyclic compounds or their mixture, and - it has a content of less than 2% by mass in aromatic compounds.

4. Liquid composition according to one of claims 1 to 3, wherein the solvent (C) is selected from aliphatic alcohols having a carbon number in the range C7 to C15.

5. Liquid composition according to one of claims 1 to 4, wherein the solvent (D) is selected from benzyl alcohol, 1-phenylethanol, 2-phenylethanol.

6. Liquid composition according to one of claims 1 to 5, free from odor masking agent.

7. Liquid composition according to one of claims 1 to 6, not emitting any substance classified as carcinogenic, mutagenic and toxic for reproduction according to Commission Regulation (EU) 2023 / 1132 of 8 June 2023 amending Regulation (EC) No 1907 / 2006 of the European Parliament and of the Council as regards restricted carcinogenic, mutagenic or toxic for reproduction substances.

8. Liquid composition according to one of claims 1 to 7, free of dialkilene glycol-alkylether or diisoalkylbenzene.

9. Liquid composition according to one of claims 1 to 8, in which the mixture of solvents (B), (C) and (D) is a ternary mixture.

10. A method of manufacturing a relief flexographic printing plate from a flexographic plate comprising a photopolymer layer covered with a mask, said method comprising the following steps: a) etching the mask of the flexographic plate to obtain an etched plate comprising: - a portion not covered with a photopolymer layer, and - a portion of photopolymer layer covered with the mask, b) exposing the etched plate to UVA to crosslink the photopolymer of the portion not covered with photopolymer layer to obtain a plate comprising a zone of crosslinked photopolymer, c) removing the portion of photopolymer layer covered with the mask with a liquid development composition to obtain a washed plate comprising a zone of crosslinked photopolymer, and d) optionally, drying the washed plate to obtain the flexible photopolymer plate in which the liquid development composition is the liquid composition as defined in any one of claims 1 to 9.

Images