Caustic removable hot melt adhesive composition

Abstract

The present invention refers to a hot melt adhesive composition and relates, in particular, a hot melt adhesive composition for the beverage industry, more specifically, but not exclusively, for the application of labels on polyethylene terephthalate (PET) containers. The hot melt adhesive composition of the present invention has a high acid content, which allows the washing of substrates with an alkaline solution during their recycling process, facilitating the easy removal of labels. Additionally, the hot melt adhesive composition of the present invention exhibits stable adhesion over time, without losing its performance and a high bio-based content on its formulation.

Description

[0001] DESCRIPTION

[0002] CAUSTIC REMOVABLE HOT MELT ADHESIVE COMPOSITION

[0003] Field of the invention

[0004] The present invention refers to a hot melt adhesive composition and relates, in particular, a hot melt adhesive composition for the beverage industry, more specifically, but not exclusively, for the application of labels on polyethylene terephthalate (PET) containers . The hot melt adhesive composition of the present invention has a high acid content, which allows the washing of substrates with an alkaline solution during their recycling process, facilitating the easy removal of labels . Additionally, the hot melt adhesive composition of the present invention exhibits stable adhesion over time, without losing its performance and a high bio-based content on its formulation.

[0005] Summary of the invention

[0006] The present invention refers to a hot melt adhesive composition. Hot melt adhesives are products that are applied to the surface of a material in a molten state, at high temperatures, and harden when cooled to form a bond between at least two materials . Hot melt adhesives are usually supplied to their users in a solid state and then heated and applied in a liquid state . In general, the application temperature for this type of product varies between 100 and 200 ° C .

[0007] The hot melt adhesives are used in a wide variety of industrial applications, worldwide, and can respond to numerous complex requests from the adhesive' s industry. In this context, there is the containers market, among other industries . The hot melt adhesives market has grown exponentially in the last decades due to the production, on a large scale, of synthetic polymers . Beyond its economic advantages, these types of adhesives do not include organic solvents in its composition, which enhances its sustainability and makes it an interesting product for the industry .

[0008] Hot melt adhesives are used in a wide variety of industrial applications worldwide and can meet a vast array of complex requirements of the adhesive industry. In this context, among others, is the labelling of containers .

[0009] In containers labelling application, the type of adhesive to use essentially depends on the type of container and the type of label used. For glass containers, casein-based adhesives are predominantly used. This type of product offers numerous advantages, particularly, moisture resistance, as containers are exposed to humid environments during the production process, and it allows labels to be easily removed with hot water for recycling the packaging.

[0010] For plastic containers, styrene block copolymer (SBC) adhesives are predominantly used, specifically styrene-isoprene-styrene (SIS) based polymers . This type of product offers good adhesion to plastic materials, shows good processability on high-speed machine lines, and provides good humidity resistance .

[0011] Identification and solution to the technical problem

[0012] The production of bottles, both glass and plastic, is a globally important industry. Bottles are used to store a wide range of products, from beverages and food to cosmetics and pharmaceuticals . However, the production and improper disposal of these bottles have a significant impact on the environment . Plastic bottles, especially polyethylene terephthalate (PET) bottles, have become increasingly popular due to their lightness, strength, and low production cost . PET is widely used in water bottles, soft drinks, and other liquids and can be fully recycled, transformed into new bottles, fabrics, and other products .

[0013] For recycling to be efficient, it is necessary to remove the labels as well as the adhesive residues from the substrates . For this purpose, an alkaline solution at high temperatures is used to wash the plastic fragments .

[0014] Typically, pressure sensitive adhesives used in labelling applications are not easily removed from substrates using an alkaline solution. The purpose of the present invention is to provide a hot melt adhesive composition comprising at least one styrene block copolymer (SBC) , more specifically, styrene-isoprene-styrene copolymers (SIS) ; which allows an efficient removal of labels and adhesive residues . This phenomenon is achieved because the adhesive, with high acid content, completely and unexpectedly loses its adhesion when in contact with the alkaline solution.

[0015] Additionally, hot melt adhesive composition of the present invention exhibits stable adhesion over time and a high content of bio-based materials, above 50% .

[0016] Background of the invention

[0017] Typically, the formulation of a hot melt adhesive comprises the following types of raw materials :

[0018] • A polymeric component comprising at least one thermoplastic polymer capable of ensuring suitable rheological properties for its application. This component can be selected from among polyolefins, ethylene vinyl acetate (EVA) copolymers, styrenic block copolymers and others;

[0019] • A resin component used to increase adhesion strength to substrates, which can be selected from natural or synthetic resins . Some examples of natural resins include rosin resins, tall oil, phenolic polyterpenoid or terpene resins . The synthetic hydrocarbon resin can be selected from aliphatic (C5) , aromatic (C9) , aliphatic-aromatic (C5 / C9) and dicyclopentadiene (DCPD) resins;

[0020] • Additive components such as plasticizers and waxes that allow the viscosity, softening point and open time of the adhesive to be adjusted. A plasticizer can be selected from liquid polybutenes, saturated hydrocarbons, mineral oils, naphthenic or hydrotreated paraffinic oils, and isobutylene-butene copolymer, among others . On the other hand, some examples of waxes include modified acrylic or carboxylic, polyolefin copolymer, Fischer-Tropsch and paraffinic based products; • In addition, other components can be added to the composition of the hot melt adhesive, including, but not limited to, pigments and other additives .

[0021] There are numerous patent documents that describe hot melt adhesives compositions that are easily removed when in contact with a caustic soda solution. Some of these patent documents describe hot melt adhesive compositions that are not formulated with styrene block copolymers, in particular patent document WO2014127362A1, which refers to a polyester based hot melt adhesive formulation. This formulation exhibits at least 50% dissolution when in contact with caustic soda solution at a high temperature for 5 minutes .

[0022] Patent document US005385965A refers to a pressure sensitive formulation based on an acrylic emulsion with a rosin-based surfactant, that allows easy removal of labels from various types of materials in the recycling process .

[0023] Patent document EP4421144A1 refers to a pressure sensitive adhesive formulated with styrene block copolymer and additionally contains an acid modified glyceride, which imparts acidity to the final formulation, allowing the recycling of the substrate .

[0024] Patent documents WO2016186023A1, US20140120280A1, US20100255228A1, and W02010115564A1 describe formulations of a hot melt adhesive based on styrene block copolymers with a styrene and maleic anhydride copolymer (SMA) additive, which makes a conventional adhesive easily removable in the recycling process .

[0025] Patent document US20040220308A1 describe a formulation of a styrene block copolymer-based adhesive comprising a dimer acid.

[0026] Advantages of the invention

[0027] The present invention aims to provide a hot melt adhesive composition for application, specifically, but not exclusively, in the beverage industry, more specifically, but not exclusively, for the application of labels on polyethylene terephthalate (PET) containers . The hot melt adhesive composition of the present invention is suitable to the recycling of the containers, as it enables the removal of the labels and loses its stickiness when the containers are washed with a hot caustic soda solution at high temperature . This property is achieved by using hydrogenated rosin resin with high acid content .

[0028] Additionally, the hot melt adhesive composition of the present invention has good processability in labelling different materials, with a suitable viscosity and softening point, adhesion to the materials .

[0029] Typically, in a styrene block copolymer-based adhesive, comprising hydrogenated rosin as the entire resin component, the adhesive loses its adhesion over time due to resin oxidation. Unexpectedly, in the hot melt adhesive composition of the present invention, by introducing tall oil resin with a softening point between 102 and 108 ° C into the formulation, the adhesive maintains stable adhesion after 1 month.

[0030] Detailed description of the invention

[0031] The obj ect of the present invention is a hot melt adhesive composition for application, particularly but not exclusively, in the beverage industry, more specifically, in the applications for bonding labels to containers .

[0032] The hot melt adhesive composition of the present invention comprises a resin component with high acid content, which causes the adhesive to completely lose adhesion when in contact with an aqueous solution of caustic soda at a temperature between 60 and 80 °C, making the labels easily detachable from the container, enabling the recycling of substrates .

[0033] "Substrate" refers to the material or surface of the material in which the hot melt adhesive is applied and / or directly contact with. In the present invention, the most used substrates are PET and glass containers, as well as plastic and paper labels .

[0034] "Container" refers to a recipient, j ar, jug, vase, box, shape, casing, receptacle, reservoir, vessel, continent, package, pot, vessel, conceptacle, among others . "Suitable adhesion" means the ability of the hot melt adhesive to penetrate the substrate on which it is applied and allow a second substrate to adhere to the first efficiently and permanently .

[0035] "Stickiness" means the force applied by the adhesive after pressure is applied to its surface .

[0036] "Good processability" means that hot melt adhesives are easy to use and apply on industrial lines, which means, they do not accumulate contamination and consequently stop for cleaning and maintenance .

[0037] "Suitable rheological properties" means that the material ' s properties change with temperature, resulting in suitable technical properties such as open time and setting time .

[0038] "Polymer base" means the polymeric materials that contribute to the fundamental properties of the composition and form the foundation of the composition. Thus, the other components of the formulation have the function of modifying and / or improving the properties of the polymeric base .

[0039] "Open time" means the maximum time interval, after the hot melt adhesive has been applied to the first substrate, in which a second substrate can be effectively bonded.

[0040] "Setting time" is the minimum time interval in which pressure must be applied for two substrates to bond effectively. Thus, setting time is associated with the speed with which the adhesive recovers its cohesive forces .

[0041] "Suitable viscosity" means a viscosity value at 140 ° C between 500 and 3 000 mPa - s, more preferably between 700 and 1 500 mPa - s, more preferably between 800 and 1 000 mPa - s .

[0042] "Suitable softening point" means a softening point value between 50 and 120 ° C, more preferably between 55 and 90 ° C .

[0043] "Stable adhesion over time" means that after 1 month the adhesive presents a drop in Peel Adhesion 180° value lower than 20% .

[0044] "High content of bio-based materials" means that more than 50 per cent of the content of the formulation comprises raw materials derived from renewable sources - such as plants, algae or agricultural waste - and not from fossil fuels .

[0045] "High acid content" means that the adhesive contains a high proportion of acidic functional groups, such as carboxylic acids . This increases the polarity oh the formulation and enhances its solubility or dispersibility in an alkaline solution .

[0046] "Substantially" means that the description of the shape, position or value of an element / property of the present invention is not mathematically or geometrically exact, but that the shape, position or value of an element / property of the present invention is recognised by an expert in the field as having generically or approximately the shape or position described .

[0047] "Copolymer" means a polymer obtained by the polymerisation of at least two different monomers .

[0048] "ASTM" refers to the tests done according to the American Society for Testing and Materials . By "room conditions is meant a temperature 23 ± 1 C and a relative humidity 50 ± 5 %RH.

[0049] By "room temperature" is meant a temperature 23 ± 1

[0050]

[0051] According to the invention, the hot melt adhesive composition comprises :

[0052] - A polymeric component comprising at least one styrene block copolymer (SBC) , more specifically, styrene-isoprene-styrene copolymers (SIS) ;

[0053] - a resin component with high acidity;

[0054] - a plasticizer component comprising at least one plasticizer capable of forming a homogeneous mixture with the polymer base and controlling rheological properties such as viscosity; - an antioxidant component comprising at least one phenolic antioxidant capable of preventing degradation of the adhesive .

[0055] Polymeric component

[0056] The polymeric component of the hot melt adhesive composition of the present invention comprises a thermoplastic polymeric component .

[0057] The polymeric component suitable for the adhesive of the present invention is selected in particular, but not exclusively, from: styrene block copolymers (SBC) , more specifically, styrene-isoprene-styrene (SIS) .

[0058] The polymeric component that corresponds to the chemical base of the product and which is selected, in particular but not exclusively, from styrene block copolymers (SBC) , preferably, styrene-isoprene-styrene (SIS) , corresponds to up to 50% by weight of the hot melt adhesive, preferably up to 40%, more preferably between 10% and 30%, even more preferably between 12% and 18% .

[0059] Preferably, the polymeric component comprising styrene block copolymers (SBC) , more specifically, styrene-isoprene-styrene (SIS) , with a styrene content between 5% and 40%, preferably between 10% and 30%, more specifically between 17, 5% and 19%, measured according to TSRC method and a melt flow index measured at 200 "C / 5 kg, up to 40 g / 10 min, preferably up to 30 g / 10 min, more preferably between 9, 7 and 13, 8 g / 10 min, measured according to ASTM D1238.

[0060] Resin component

[0061] The resin component aims to ensure adequate adhesion to the materials used, namely, but not exclusively, plastic and glass in the case of containers, and paper and plastic in the case of labels . The resin component is selected from natural resins and comprises a mixture comprising two types of natural resins .

[0062] The resin present in the highest percentage in the formulation of the present invention has an acid value of between 100 and 200 mg KOH / h. Thus, the suitable resin present in the highest percentage in the formulation of the present invention is selected specifically, but not exclusively, from hydrogenated rosin resins, preferably fully hydrogenated rosin resins .

[0063] The resin suitable for the hot melt adhesive formulation of the present invention has an acid value of between 100 and 200 mg KOH / h measured according to ASTM D465 and a softening point between 60 and 100 ° C, preferably between 75 and 90 ° C measured according to ASTM E28, and represents up to 65% by weight of the hot melt adhesive composition, preferably between 35% and 65%, more preferably between 45% and 60% . Additionally, to prevent peel drop over time due to the oxidation of hydrogenated rosin resin, other natural based resins are added to this formulation. This resin is selected, including but not limited to : glycerol ester of rosin, pentaerythritol ester of rosin, triethylene glycol ester of rosin, methyl ester of rosin, polyterpene resin, terpene-phenolic resin, preferably tall oil resin, glycerol ester of tall oil resin, even more preferably pentaerythritol ester of tall oil rosin.

[0064] The resin capable of preventing adhesion drop suitable for the hot melt adhesive to prevent the loss of adhesion over time, presents a softening point between 80 and 120 ° C, preferably between 102 and 108 ° C measured according to ASTM E28.

[0065] The content of the resin in the lowest percentage to prevent peel drop accounts for up to 20% by weight of the hot melt adhesive composition, preferably up to 15%, more preferably between 5% and 10% .

[0066] The resin component comprising a mixture of two types of natural resins corresponds for up to 75% by weight of the hot melt adhesive composition, preferably between 40% and 70%, more preferably between 50% and 65% .

[0067] Plasticizer component

[0068] The use of the plasticizer component allows the adjustment of the viscosity and softening point of the hot melt adhesive to values considered appropriate, so that it can be easily applied in industrial lines . By ensuring that, the composition has the appropriate values for these properties, it is also ensured that the temperature required for the use of the adhesive in industrial lines is appropriate, between 100 and 200 ° C, preferably 100 and 160 ° C, and even more preferably between 120 and 140 ° C .

[0069] The plasticizer component comprises at least one liquid plasticizer at room temperature, namely, but not limited to, from liquid polymers, saturated hydrocarbons, mineral oils, naphthenic oils, isobutylene-butene copolymer, saturated or unsaturated fatty acids, more preferably paraffinic oils or their derivatives with flash point of 240 ° C measured according to ASTM D92 .

[0070] The plasticizer component corresponds to up to 50% of the total mass of the hot melt adhesive composition, preferably between 5% and 40%, more preferably between 15% and 35%, even more preferably between 20% and 25% .

[0071] Antioxidant component

[0072] The antioxidant component in the formulation aims to prevent the degradation of the hot melt adhesive due to heat exposure during production, application or storage of the final product . For the present invention, the use of an antioxidant component comprising of at least one primary, secondary, multifunctional antioxidant or mixtures thereof is particularly useful .

[0073] Thus, the antioxidant component is selected from phenolic antioxidants, phosphite antioxidants, thioester antioxidants or mixtures thereof .

[0074] The content of the antioxidant component suitable for the present invention corresponds to up to 4% by weight of the hot melt adhesive, preferably between 0, 2% and 2%, more preferably between 0, 3% and 1, 0% .

[0075] Optionally, other components / additives may be added to the hot melt adhesive composition. Including but not limited to pigments, fillers or waxes, to modify specific properties or enhance the performance of the hot melt adhesive used to bond labels to containers .

[0076] Production method

[0077] The method for production hot melt adhesive composition of the present invention comprises the following steps :

[0078] a) Mix the between 40% and 50% of the resin component with the plasticizer component and the antioxidant component at a temperature of 150 ° C until a paste is formed with a homogeneous appearance;

[0079] b) Adding the polymeric component to the paste formed in the previous step;

[0080] c) When the mixture obtained in step b) appears translucent, add the rest of the resin component;

[0081] d) Maintain constant stirring and temperature until the mixture obtained in step c) appears homogeneous .

[0082] Embodiments of the invention

[0083] To evaluate the results obtained with the composition / formulation of the hot melt adhesive composition of the present invention and compare it with a standard hot melt adhesive used to bond labels to containers, various tests and technical trials were conducted, as presented in Table 1 .

[0084] As will be clear to a skilled person, the application of the principles described herein is not limited to the embodiments presented .

[0085] This invention is further illustrated by the following nonlimiting examples . Example 1

[0086] In Example 1 is presented information regarding composition of a standard hot melt adhesive for labelling applications . This formulation presents suitable viscosity and softening point for the application, no drop in the peel after 4 weeks, however, this formulation does not present removability in caustic soda solution .

[0087] Example 2

[0088] Example 2 shows a hot melt adhesive composition, which the resin component is 100% hydrogenated rosin resin. This composition presents suitable viscosity and softening point for the application, good removability in caustic solution. However, it loses its adhesion over time, with a peel drop of 89% after 4 weeks .

[0089] Example 3

[0090] In Example 3, information is provided regarding the composition of a hot melt adhesive with a viscosity and softening point suitable for the application. This formulation demonstrates good performance in caustic soda test, however, it shows a high peel drop after 4 weeks .

[0091] Example 4

[0092] As in Example 3, this composition comprises the same components with the same percentage . However, in this formulation it was achieved a drop peel adhesion after 4 weeks less than 20% . The pentaerythritol ester of tall oil rosin used in this composition has a softening point 5 ° C higher than the one used in Example 3. Example 4 corresponds to the hot melt adhesive composition of the present invention with viscosity and softening point suitable for the labelling application . Additionally, this composition shows good removability in caustic soda solution at a temperature of 65 ° C and a drop peel adhesion after 4 weeks lower than 20% .

[0093] Table 1

[0094] Example Example Example Example 1 2 3 4 Resin component 1A34 , 0 g - - 8 , 5 g

[0095] Resin component 2B27 , 8 g - - -

[0096] Resin component 3C- 61 , 2 g 52 , 7 g 52 , 7 g

[0097] Resin component 4D- - 8 , 5 g - Antioxidant

[0098] 0 , 5 g 0 , 5 g 0 , 5 g 0 , 5 g component 5E

[0099] Plastici zer

[0100] 6 , 0 g - - - component 1F

[0101] Plastici zer

[0102] 16 , 8 g 23 , 3 g 23 , 3 g 23 , 3 g component 1G

[0103] Polymeric component

[0104] 1H 4 , 5 g 15 , 0 g 15 , 0 g 15 , 0 g Polymeric component

[0105] 10 , 4 g - - - 21

[0106] Viscosity at 1 000 900 1 200 900

[0107] 140 ° C#1mPa • s mPa • s mPa • s mPa • s Softening point#266 ° C 61 ° C 63 ° C 62 ° C Removability in

[0108] NOK OK OK OK

[0109] caustic solution#3

[0110] Peel drop#410 , 4 % 89 , 2 % 85 , 6% 11 , 8 %

[0111]

[0112] Captions :

[0113] A - Resin component based on a pentaerythritol ester of tall oil rosin with a softening point between 102 and 108 ° C, measured according to ASTM E28 and an acid number of 5 mg KOH / g, measured according to ASTM D465.

[0114] B - Resin component based on cycloaliphatic hydrocarbons with a softening point substantially of 86 ° C, measured according to ASTM E28 .

[0115] C - Hydrogenated rosin resin component with a softening point substantially of 80 ° C, measured according to ASTM E28 and an acid number of 161 mg KOH / g, measured according to ASTM D465.

[0116] D - Resin component based on a pentaerythritol ester of tall oil rosin with a softening point between 97 and 107 ° C, measured according to ASTM E28 and an acid number of 5 mg KOH / g, measured according to ASTM D465.

[0117] E - Primary phenolic antioxidant .

[0118] F - Non-phthalate plasticizer with a flash point of 212 ° C, measured according to ASTM D92 .

[0119] G - Paraffinic oil with a flash point of 240 ° C, measured according to ASTM D92 .

[0120] H - Block copolymer of styrene-isoprene with a styrene content between 17, 5% and 19, 0%, according to TSRC / Dexco method and a melt flow index measured at 200 ° C / 5 kg between 9, 7 and 13, 8 g / 10 min, measured according to ASTM D1238.

[0121] I - Block copolymer of styrene-isoprene with a styrene content between 28% and 31%, according to TSRC Corporation / Dexco method, and a melt flow index measured at 200 ° C / 5 kg between 10 and 16 g / 10 min, measured according to ASTM D1238.

[0122] #1 - Test method: Brookfield, Termosel System, ASTM D3236.

[0123] #2 - Test method: Ring and Ball, ASTM E28.

[0124] #3 - The purpose of this method is to assess the washability of the formulation when in contact in a caustic solution at a temperature of 65 ° C . This method comprises the following steps :

[0125] 1 ) Coat the adhesive in a biaxially oriented polypropylene (BOPP) label with a grammage of 25 g / m2;

[0126] 2 ) After 24 hours, bond the labels coated with adhesive to PET;

[0127] 3) After stabilization at (23, 0 ± 1, 0) °C and (50 ± 5) % RH for 24 hours, cut 50 specimens with 10X10 mm;

[0128] 4 ) Prepare a glass beaker with an aqueous solution with 2% of caustic soda and heat it up to 65 ° C with constant stirring;

[0129] 5) Add the specimens to the solution for 13 minutes;

[0130] 6) Rinse the samples with water at room temperature;

[0131] 7 ) The result is "OK" , if >50% of the samples bonded are detached (BOPP labels from PET) and the rest if the samples are separated easily without any force . The adhesive should lose its stickiness . If this does not happen, the result is considered "NOK" .

[0132] #4 - The peel adhesion was evaluated for 4 weeks to ensure that the adhesive does not lose its adhesion capacity. This value is considered "OK" if the drop of the peel adhesion at 180 ° C, measured according to ISO 29 862, is less than 20% .

[0133] Modifications and variations of this invention can be made without departing from its spirit and scope, as will be apparent to those skilled in the art . The specific embodiments described herein are offered by way of example only, and the invention is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled .

Claims

CLAIMS1. Caustic removable hot melt adhesive composition comprising between 10% and 30% by weight of a polymeric component wherein the polymeric component comprises styrene-isoprene- styrene (SIS) with a styrene content between 17, 5% and 19% and a melt flow index measured at 200 °C / 5 kg between 9, 7 and 13, 8 g / 10 min measured according to ASTM D1238 ; between 50% and 65% by weight of a resin component comprises a hydrogenated rosin resins with an acid value of between 100 and 200 mg KOH / h measured according to ASTM D465 and a softening point between 75 and 90 °C measured according to ASTM E28 and a pentaerythritol ester of tall oil rosin with a softening point between 102 and 108 °C measured according to ASTM E28 ; between 20% and 25% by weight of a plasticizer component and between 0, 3% to 1, 0% by weight of an antioxidant component .

2. Caustic removable hot melt adhesive composition according to the previous claim, wherein the resin component comprises between 45% and 60% of hydrogenated rosin resins with acid value of between 100 and 200 mg KOH / h measured according to ASTM D465 and softening point between 75 and 90 °C measured according to ASTM E28 and between 5% and 10% of pentaerythritol ester of tall oil rosin with softening point between 102 and 108 °C measured according to ASTM E28.

3. Caustic removable hot melt adhesive composition according to any one previous claim, wherein the hydrogenated rosin resins is a fully hydrogenated rosin resins .

4. Caustic removable hot melt adhesive composition according to any one of the previous claims, wherein the plasticizer component is selected from liquid polymers, saturatedhydrocarbons, mineral oils, naphthenic oils, isobutylenebutene copolymer, saturated or unsaturated fatty acids, paraffinic oils or their derivatives with flash point of 240 °C measured according to ASTM D92 .

5. Caustic removable hot melt adhesive composition according to any one of the previous claims, wherein antioxidant component is selected from phenolic antioxidants, phosphite antioxidants, thioester antioxidants or mixtures thereof .

6. Process for producing the caustic removable hot melt adhesive claimed in any of the previous claims, characterized by comprising the following steps :a) Mix the between 40% and 50% of the resin component with the plasticizer component and the antioxidant component at a temperature of 150 ° C until a paste is formed with a homogeneous appearance;b) Adding the polymeric component to the paste formed in the step a) ;c) When the mixture obtained in step b) appears translucent, add the rest of the resin component; d) Maintain constant stirring and temperature until the mixture obtained in step c) appears homogeneous .

7. Use of the caustic removable hot melt adhesive composition claimed in any claims 1 to 5 for labelling polyethylene terephthalate (PET) containers .

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