Hot melt adhesive composition comprising a naturally sourced wax

Abstract

The present invention relates to a hot melt adhesive composition comprising: i) a copolymer polymerized by metallocene catalysis; ii) 2% to 50% by weight, relative to the total weight of said composition, of a naturally sourced wax having a dropping point of 65°C to 105°C; iii) a tackifying resin; said hot melt adhesive composition having a viscosity of less than 3000 mPa.s at 130°C.

Description

[0001] Hot melt adhesive composition comprising a wax of natural origin

[0002] Field of invention

[0003] The present invention relates to a hot melt adhesive composition comprising a wax of natural origin.

[0004] The present invention also relates to the uses of said composition.

[0005] Technical background

[0006] Hot melt adhesive products are widely used in various commercial applications such as assembly or packaging, including for example the closing of boxes or cases, especially cardboard.

[0007] Hot melt adhesives are typically applied to a substrate in a molten state. Most hot melt adhesives on the market require temperatures of 170°C or higher to fully melt the adhesive components and achieve a satisfactory viscosity for application. However, these high temperatures increase the risk of burns and the inhalation of residual volatile compounds for operators on production lines. In addition, the use of high temperatures requires significant energy consumption.

[0008] Hot melt adhesives allowing application at lower temperatures (for example, less than or equal to 150°C) have been developed recently. However, these hot melt adhesives do not allow good adhesion to be combined at both low and high temperatures. However, hot melt adhesives used for packaging, such as for example the closure of boxes or cases, particularly cardboard, are subjected during their transport and storage to various temperature ranges depending on climatic conditions, geographical areas, etc. Similarly, hot melt adhesives, to be useful in the packaging field, must be capable of ensuring good bonding of substrates such as paper, solid cardboard, corrugated, coated, varnished, laminated, metallized, treated, coated, etc. This good level of bonding results in defibration over a wide temperature range.

[0009] Finally, there are currently few hot melt adhesives made from renewable raw materials. There is a growing desire to reduce carbon footprints and produce more environmentally friendly products.

[0010] There is therefore a need for new hot melt adhesives that can at least partially overcome at least one of the above-mentioned drawbacks.

[0011] More particularly, there is a need for new hot melt adhesives applicable at low temperatures (e.g., less than or equal to 150°C) while exhibiting good adhesive properties over a wide temperature range, e.g., from -20°C to 60°C.

[0012] There is a need for new hot melt adhesives applicable at low temperatures (e.g., 150°C or less) having good adhesive properties over a wide temperature range, e.g., -20°C to 60°C, and good heat resistance (e.g., 50°C or more).

[0013] Description of the invention

[0014] The present invention relates to a hot-melt adhesive composition comprising: i) a copolymer polymerized by metallocene catalysis; ii) from 2% to 50% by weight of a wax of natural origin having a dropping point ranging from 65°C to 105°C, relative to the total weight of said composition; iii) a tackifying resin having a softening temperature of less than or equal to 115°C chosen from: a) terpene resins, b) partially or totally hydrogenated resins chosen from: b-1) rosins of natural origin or partially or totally hydrogenated modified rosins, such as for example rosin extracted from pine gum, wood rosin extracted from the roots of the tree and their dimerized, polymerized derivatives;b-2) partially or fully hydrogenated rosin esters such as, for example, partially or fully hydrogenated rosin glycerol esters, partially or fully hydrogenated rosin pentaerythritol esters; b-3) partially or fully hydrogenated aliphatic resins, b-4) partially or fully hydrogenated cycloaliphatic resins; b-5) partially or fully hydrogenated aromatic modified aliphatic or cycloaliphatic resins, c) and mixtures thereof; said hot melt adhesive composition having a viscosity of less than 3,000 mPa.s at 130°C. Copolymer i);

[0015] For the purposes of the present invention, the term "copolymer" refers to a polymer formed by polymerization of at least two different monomers. The term "copolymer" also covers terpolymers that contain at least three different types of monomers.

[0016] The copolymer i) polymerized by metallocene catalysis may be a copolymer comprising ethylene, a copolymer comprising propylene, or mixtures thereof.

[0017] The copolymer i) polymerized by metallocene catalysis can be chosen from:

[0018] - copolymers comprising ethylene and at least one C3-C20-a-olefin;

[0019] - copolymers comprising propylene and at least one monomer chosen from ethylene and C4-C20-a-olefins;

[0020] - their mixtures.

[0021] The blends may be a blend of at least two different copolymers comprising ethylene and at least one C3-C20-a-olefin; a blend of at least two different copolymers comprising propylene and at least one monomer selected from ethylene and C4-C20-a-olefins; a blend of one or more copolymers comprising ethylene and at least one C3-C20-a-olefin with one or more copolymers comprising propylene and at least one monomer selected from ethylene and C4-C20-a-olefins.

[0022] The copolymers comprising ethylene and at least one C3-C20-a-olefin are preferably those comprising ethylene in a majority mass proportion. The term "in a majority mass proportion of ethylene" means that the copolymer comprises a mass content of ethylene greater than the mass content of the other C3-C20-a-olefins.

[0023] The copolymers comprising propylene and at least one monomer chosen from ethylene and C4-C20-a-olefins are preferably those comprising propylene in a majority mass proportion. The term "in a majority mass proportion of propylene" means that the copolymer comprises a mass content of propylene greater than the mass content of the other monomers chosen from ethylene and C4-C20-a-olefins.

[0024] The copolymers comprising propylene and at least one monomer selected from ethylene and C4-C20-a-olefins are preferably propylene-ethylene copolymers. The C3-C20-a-olefins are preferably selected from C4-C10-a-olefins, and even more preferably selected from C4-C8-a-olefins.

[0025] The C4-C20-a-olefins are preferably chosen from C4-C10-a-olefins, and even more preferably chosen from C4-C8-a-olefins.

[0026] Preferably, the copolymer i) is chosen from copolymers comprising ethylene and at least one C3-C20-a-olefin.

[0027] The mass content of ethylene in said copolymer i) may range from 50% to 99%, preferably from 50% to 80%, and even more preferably from 50% to 70% by weight relative to the total weight of said copolymer i).

[0028] Although a polymer is often characterized as "made of" such monomers, or "based on" such monomers, or "comprising" such monomers, or the like, it is understood that one is referring to the remainder of said monomers and not to the unpolymerized monomers.

[0029] The aforementioned copolymer i) is obtained by polymerization of monomers in the presence of a metallocene catalytic system. Metallocene catalysis is well known to those skilled in the art. Metallocene catalytic systems may in particular comprise a central transition metal and one or more ligands coordinated to the metal center. Examples of such systems are for example described in US 9,998,469.

[0030] Copolymers can be obtained from monomers that are at least partially bio-sourced or from the circular economy.

[0031] The C3-C20-a-olefins may be linear or branched. They may be selected from the group consisting of propene, butene, pentene, 3-methylbutene, hexene, 3-methylpentene, octene, norbonene, norbonadiene, 1-dodecene, 1-hexadodecene, 1-decene, 1-nonene, 1-methylnonene, trimethylheptene, 4-methylpentene, ethylpentene, 3-methylhexene, and mixtures thereof.

[0032] The C4-C20 -a-olefins may be linear or branched. They may be selected from the group consisting of butene, pentene, 3-methylbutene, hexene, 3-methylpentene, octene, norbonene, norbonadiene, 1-dodecene, 1-hexadodecene, 1-decene, 1-nonene, 1-methylnonene, trimethylheptene, 4-methylpentene, ethylpentene, 3-methylhexene, and mixtures thereof.

[0033] Preferably, the C3-C20-a-olefins are chosen from propene, hexene, octene and mixtures thereof. The mass content of C3-C20-a-olefins in said copolymer i) may be at least 20%, preferably may range from 20% to 49%, even more preferably from 30% to 49%, relative to the total weight of said copolymer i).

[0034] Preferably, the copolymer i) is a copolymer comprising ethylene and octene, even more preferably the copolymer i) is a copolymer comprising only ethylene and octene, and in particular a copolymer comprising only ethylene and from 20% to 49% by weight of octene relative to the total weight of said copolymer.

[0035] The copolymer i) polymerized by metallocene catalysis may or may not be functionalized.

[0036] For the purposes of the present invention, the term “functionalized polymer” means a polymer chemically modified so as to obtain pendant functional groups in the backbone of said polymer. The functional groups may be chosen from epoxies, silanes, amides, carboxylic acids, esters, anhydrides, and mixtures thereof.

[0037] Preferably, the copolymer i) polymerized by metallocene catalysis is not functionalized.

[0038] The copolymer i) polymerized by metallocene catalysis may have a flow index (or MFI, also called in English “melt flow index”) greater than 15 g / 10 min, preferably greater than 400 g / 10 min, and even more preferably between 800 and 1500 g / 10 min.

[0039] The copolymer i) polymerized by metallocene catalysis preferably has a flow index greater than 400 g / 10 min, more preferably between 800 and 1500 g / 10 min.

[0040] The flow index of copolymer i) is measured at 190°C and for a total weight of 2.16 kg, and is measured in accordance with ASTM D1238.

[0041] The copolymer may have a glass transition temperature (Tg) less than or equal to -35°C. The glass transition temperature can be measured by DSC (Differential Scanning Calorimetry).

[0042] Copolymer i) may be a block or random copolymer.

[0043] The copolymer i) polymerized by metallocene catalysis can have a density ranging from 0.80 g / cm 3 at 0.90 g / cm 3 , preferably from 0.85 to 0.90 g / cm 3 . The density of the copolymer i) can be measured according to ASTM D792.

[0044] Copolymers i) polymerized by metallocene catalysis may be commercially available. Examples include Affinity™ marketed by Dow, such as Affinity® GA 1900 (C2 / C8 copolymer) or Affinity® GA 1950 (C2 / C8 copolymer), EXACT™ marketed by ExxonMobil Chemical (C2 copolymers), or Versify™ marketed by Dow Chemicals (C3 copolymers), or Vistamaxx™ marketed by ExxonMobil Chemical (C3 copolymers).

[0045] The hot-melt adhesive composition may comprise from 20% to 60% by weight, preferably from 25% to 50% by weight, and even more preferably from 25% to 45% by total weight of copolymer(s) i), relative to the total weight of said composition.

[0046] Wax of natural origin ii)

[0047] The hot melt adhesive composition comprises from 2% to 50% by weight, relative to the total weight of said composition, of a wax of natural origin having a dropping point ranging from 65°C to 105°C.

[0048] The dropping point is known as the “drop melting point” in English.

[0049] The wax preferably has a dropping point ranging from 70°C to 105°C, more preferably from 80°C to 105°C.

[0050] The dropping point of wax can be measured by the dropping point method according to ASTM D127.

[0051] The wax of natural origin ii) may be chosen from animal waxes and vegetable waxes, preferably from vegetable waxes.

[0052] Vegetable waxes can be chosen from the group consisting of Carnauba wax, rice bran wax, sugarcane wax, natural hydrogenated soybean, jojoba, castor or palm oil, and their mixtures.

[0053] Preferably, the wax of natural origin ii) is a vegetable wax chosen from Carnauba wax, rice bran wax, and mixtures thereof.

[0054] Carnauba is an extremely common palm tree in northeastern Brazil, and the wax on the surface of its leaves has been exploited on a large scale for many years.

[0055] Carnauba wax is typically composed of 80-90% esters combining:

[0056] - aliphatic acids (C24-C28) and alcohols (C30-C34);

[0057] - to the preceding acids and alcohols, p-hydroxy-acids (C22-C28) and diols (C24-C34);

[0058] - diols (C24-C34) and p-methoxycinnamic acid.

[0059] Carnauba wax can be present in several grades (T1, T3 and T4): T1 being the purest form. Naturally occurring wax ii) can have an acid value ranging from 0 to 30 mg KOH / g, preferably from 2 to 15 mg KOH / g. The acid value of the wax can be measured according to ASTM-1386.

[0060] The naturally occurring wax ii) may have a needle penetration value at 25°C ranging from 0 to 20 dmm, preferably from 0 to 15 dmm. The needle penetration value can be measured on the ASTM D1321 standard.

[0061] The adhesive composition preferably comprises from 2% to 50%, preferably from 4% to 45%, and even more preferably from 4% to 30% by weight of wax(es) ii) relative to the total weight of said composition.

[0062] Natural waxes are, for example, Carnauba T1 wax (dropping point 82-86°C) marketed by Norevo, Carnauba wax marketed by Munzig (dropping point: 81-89°C), Licocare RBW 300 wax (rice bran wax, dropping point = 91-105°C) marketed by Clariant, Deurex X52G wax (sugar cane wax, dropping point = 78-82°C) marketed by Deurex.

[0063] Tackifying resin iii)

[0064] The hot melt adhesive composition comprises a tackifying resin iii) having a softening temperature of less than or equal to 115°C, said tackifying resin being selected from the group consisting of: a) terpene resins, b) partially or fully hydrogenated resins selected from: b-1) rosins of natural origin or modified partially or fully hydrogenated, such as for example rosin extracted from pine gum, wood rosin extracted from the roots of the tree and their dimerized, polymerized derivatives; b-2) partially or fully hydrogenated rosin esters such as for example partially or fully hydrogenated rosin glycerol esters, partially or fully hydrogenated rosin pentaerythritol esters; b-3) partially or fully hydrogenated aliphatic resins, b-4) partially or fully hydrogenated cycloaliphatic resins;b-5) aromatic modified aliphatic or cycloaliphatic resins, partially or totally hydrogenated, c) and their mixtures.;

[0065] The softening temperature (or point) is determined in accordance with the standardized ASTM E28 test, the principle of which is as follows: a brass ring with a diameter of approximately 2 cm is filled with the resin to be tested in the molten state. After cooling to room temperature, the ring and the solid resin are placed horizontally in a glycerin or other thermostatically controlled bath whose temperature can vary by 5°C per minute. A steel ball with a diameter of approximately 9.5 mm is centered on the solid resin disc. The softening temperature is - during the phase of heating the bath at a rate of 5°C per minute - the temperature at which the resin disc creeps by a height of 25.4 mm under the weight of the ball.

[0066] The tackifying resin iii) preferably has a softening temperature ranging from 60°C to 115°C, more preferably from 80°C to 110°C, and even more preferably from 90°C to 110°C.

[0067] The tackifying resin iii) may have a weight-average molar mass Mw generally between 500 Daltons and 1000 Daltons, preferably between 600 Daltons and 900 Daltons.

[0068] The weight-average molecular masses of the tackifying resins can be measured according to methods well known to those skilled in the art, for example by size exclusion chromatography using a polystyrene standard.

[0069] Terpene resins a) include in particular resins synthesized by (co)-polymerization of one or more terpene monomers such as, for example, a-pinene, o-pinene, D-Limonene; resins synthesized by copolymerization of one or more terpene monomers with one or more non-terpene monomers, for example chosen from styrene, methylstyrene, isoprene, etc.; terpene-phenolic resins; and their partially or fully hydrogenated derivatives.

[0070] Resins synthesized by (co)polymerization of one or more terpene monomers are known as polyterpenes.

[0071] Terpene-phenolic resins, (also called terpene-phenols) are typically obtained by polymerization of terpene hydrocarbons and phenols, in the presence of a Friedel-Crafts catalyst.

[0072] Among the terpene resins, terpene-phenolic resins are preferred. Among the terpene resins, we can notably cite Dercolyte® M105 available from the company “Dérivés Résiniques et Terpéniques or DRT” (which is a polyterpene resin having a softening temperature of 105°C), Dertophene ® T105 marketed by DRT (which is a terpene-phenolic resin having a softening temperature of 105°C), Sylvalite 1105 marketed by Kraton (which is a terpene-phenolic resin having a softening temperature of 105°C), PICCO® AR-85 available from the company EASTMAN (having a softening point of 85°C), “PICCO® AR-100” also available from the company EASTMAN (having a softening point of 100°C).

[0073] Note that these resins b) mentioned above cover all resins possibly modified by an acid or anhydride (such as for example maleic acid or maleic anhydride).

[0074] Partially or fully hydrogenated aliphatic hydrocarbon resins b3) are well known to those skilled in the art. These are resins resulting from the polymerization of mixtures of unsaturated aliphatic hydrocarbons having, for example, 5 carbon atoms (which may, for example, be derived from petroleum or other fractions), followed by a hydrogenation step (total or partial).

[0075] Partially or fully hydrogenated cycloaliphatic hydrocarbon resins b4) are well known to those skilled in the art. These are resins resulting from the polymerization of mixtures of unsaturated cycloaliphatic hydrocarbons having, for example, 10 carbon atoms (which may, for example, be derived from petroleum or other fractions), followed by a hydrogenation step (total or partial). They can in particular be obtained from dicyclopentadiene and their derivatives (methyldicyclopentadiene, dimethyldicyclopentadiene, etc.). Among the cycloaliphatic hydrocarbon resins, DCPD (dicyclopentadiene) resins are particularly preferred.

[0076] Aromatic modified aliphatic or cycloaliphatic hydrocarbon resins can be derived from the copolymerization of aliphatic (e.g. C5) or cycloaliphatic olefins and aromatic (e.g. C9) olefins, followed by a hydrogenation step (total or partial), the content of aliphatic or cycloaliphatic olefins being predominant compared to aromatic olefins.

[0077] The aforementioned partially or fully hydrogenated resins b) are preferably selected from the group consisting of cycloaliphatic resins, aromatic modified aliphatic or cycloaliphatic resins, and mixtures thereof. Among the resins b-1), mention may be made, for example, of the Forai® DX resin (fully hydrogenated rosin resin) from DRT having a softening point above 70°C, the Forai® AX-E (fully hydrogenated rosin resin) from the company Eastman having a softening point of 80°C.

[0078] Among the resins b-2), we can for example cite Forai® 3085 (hydrogenated rosin glycerol ester resin) from DRT having a softening point of 80°C, Forai® 85E (hydrogenated rosin glycerol ester resin) from the Eastman company having a softening point of 85°C.

[0079] Among the b-3 resins), Eastotac® H100W (hydrogenated C5 resin) from Eastman has a softening point of 100°C.

[0080] Among the b-4) resins, we can cite for example the Escorez® 5400 resin from the Exxon Chemicals company (hydrogenated DCPD resin) having a softening point of 100°C, the Sukorez® SU 100 (hydrogenated DCPD resin) from Kolon having a softening point of 105°C.

[0081] Among the b-5 resins, we can for example cite Sukorez® SU400 (hydrogenated DCPD / C9 resin) marketed by Kolon having a softening point of 100°C.

[0082] Preferably, the tackifying resin iii) is chosen from terpene-phenolic resins and their partially or fully hydrogenated derivatives, partially or fully hydrogenated cycloaliphatic resins, partially or fully hydrogenated aromatic modified aliphatic or cycloaliphatic resins, and mixtures thereof, and even more preferably from terpene-phenolic resins and their partially or fully hydrogenated derivatives, and DCPD resins optionally partially or fully hydrogenated aromatic modified.

[0083] Preferably, the tackifying resin iii) is a bio-sourced tackifying resin.

[0084] In the context of the present invention, the term “bio-sourced tackifying resin” means a tackifying resin which is derived at least in part from a biomaterial.

[0085] In the context of the invention, the term “bio-carbon” or “bio-sourced carbon” means carbon of renewable origin or of natural origin derived from a biomaterial, as indicated below. The terms “bio-carbon content” and “biomaterial content” are used identically.

[0086] The carbon in biomaterials is derived from plant photosynthesis and therefore from atmospheric CO2. The degradation (by degradation is also understood as combustion / incineration at the end of their life) of these materials into CO2 therefore does not contribute to global warming since there is no increase in carbon emitted into the atmosphere. The CO2 balance of biomaterials is therefore improved and contributes to reducing the carbon footprint of the products obtained (only the manufacturing energy is to be taken into consideration). On the contrary, a material of fossil origin that degrades into CO2 contributes to increasing the level of CO2 and therefore to global warming.

[0087] In the context of the invention, the terms “biomaterials” and “bio-sourced materials” are used identically.

[0088] A renewable material, called a "biomaterial," is an organic material in which the carbon is derived from CO2 recently fixed (on a human scale) by photosynthesis in the atmosphere. On land, this CO2 is captured or fixed by plants. In the ocean, CO2 is captured or fixed by bacteria or plankton carrying out photosynthesis. A biomaterial (100% naturally occurring carbon) has an isotope ratio 14 C / 12 C greater than 10 -12 'typically approximately 1.2 x 10' 12 , while a fossil material has a ratio equal to 0. In fact, the isotope 14 C is formed in the atmosphere and then absorbed by photosynthesis, over a period of at most a few decades. The half-life of 14It is 5730 years. Thus, materials resulting from photosynthesis, for example plants in general, necessarily have a maximum content in the isotope 14 C.

[0089] Biomaterial content or biocarbon content is determined by ASTM D 6866 (ASTM D 6866-06) and ASTM D 7026 (ASTM D 7026-04). ASTM D 6866 is "Determining the biobased content of natural range materials using carbon and isotope ratio mass spectrometry analysis" while ASTM D 7026 is "Sampling and reporting of results for determination of biobased content of materials via carbon isotope analysis". The second standard refers in its first paragraphs to the first standard.

[0090] The first standard describes a test to measure the ratio 14 C / 12 C of a sample and compare it with the ratio 14 C / 12C of a reference sample of 100% renewable origin, to give a relative percentage of carbon of renewable origin in the sample.

[0091] Preferably, the tackifying resin iii) has a bio-carbon content greater than or equal to 70%, even more preferably greater than or equal to 80%.

[0092] The hot-melt adhesive composition may comprise from 30% to 60% by weight of tackifying resin(s) iii), preferably from 35% to 55% by weight, and even more preferably from 40% to 55% by weight relative to the total weight of said composition.

[0093] According to a preferred embodiment, the hot-melt adhesive composition does not comprise a tackifying resin chosen from partially or fully hydrogenated aromatic resins.

[0094] Other waxes iv)

[0095] The hot melt adhesive composition may further comprise one or more additional wax(es) iv) different from the above-mentioned waxes of natural origin ii). The waxes iv) may be chosen from the group consisting of synthetic waxes such as, for example, Fischer-Tropsch waxes, petroleum waxes such as microcrystalline waxes and paraffins, and mixtures thereof.

[0096] The hot melt adhesive composition may comprise a total content of additional wax(es) iv) ranging from 0% to 25%, preferably from 0% to 15%, relative to the total weight of said composition.

[0097] Preferably, the hot melt adhesive composition comprises less than 5% by weight of polyethylene wax (PE wax), preferably less than 3% by weight, even more preferably less than 1% by weight, and even more advantageously less than 0.1% by weight relative to the total weight of said composition. According to an even more preferred embodiment, the composition comprises less than 0.05% by weight of polyethylene wax, and even more preferably said adhesive composition does not comprise polyethylene wax.

[0098] Additional compounds

[0099] The hot melt adhesive composition may also include one or more additives appropriately chosen so as not to impair the properties of the adhesive. Examples include plasticizers, oils, antioxidants, anti-caking agents, pigments, fluorescent agents (IR or UV), IR or UV absorbers, flame retardants, colorants, fillers, and mixtures thereof. These additives may be chosen from those commonly used in adhesive compositions.

[0100] The total content of additional compound(s) may range from 0% to 10%, preferably from 0% to 5% by weight relative to the total weight of said composition.

[0101] Preferably, the hot melt adhesive composition does not comprise ethyl vinyl acetate (EVA) copolymer.

[0102] Preferably, the hot melt adhesive composition does not comprise styrenic block copolymers.

[0103] Preferably, the hot-melt adhesive composition comprises less than 5% by weight of plasticizer(s), preferably less than 2% by weight relative to the total weight of said composition, and even more preferably does not comprise any plasticizer.

[0104] Adhesive composition

[0105] The hot melt adhesive composition has a viscosity of less than 3000 mPa.s at 130°C, preferably between 500 mPa.s and 2500 mPa.s, and even more preferably between 1000 mPa.s and 2500 mPa.s. The viscosity is measured by Brookfield viscosity according to ASTM method D3236. This viscosity can be measured by using a Brookfield Thermosel apparatus or any other suitable viscometer, and by using the test techniques as described in this ASTM method.

[0106] The hot-melt adhesive composition may comprise a total biomaterial content greater than or equal to 2%, preferably greater than or equal to 9%, and even more preferably greater than or equal to 45% relative to the total weight of said composition. The biomaterial content is calculated as explained above for the tackifying resin.

[0107] The hot-melt adhesive composition according to the invention can be prepared by simply mixing its components at a temperature between 100°C and 250°C, preferably between 140°C and 200°C, until a homogeneous mixture is obtained. The required mixing techniques are well known to those skilled in the art.

[0108] The hot melt adhesive composition may have a softening point ranging from 70°C to 115°C, preferably from 75°C to 105°C. The softening point is measured according to the method described for the tackifying resin previously.

[0109] The hot-melt adhesive composition advantageously has a viscosity suitable for application at low temperatures (less than or equal to 150°C, for example 130°C or 150°C).

[0110] The hot melt adhesive composition advantageously further exhibits good adhesive properties over a wide temperature range, for example from -20°C to 60°C. The adhesive properties are advantageously good at low temperatures (for example -20°C) and at high temperatures (for example at 60°C), compared to hot melt adhesive compositions on the market.

[0111] The hot melt adhesive composition also advantageously has good heat resistance (for example at 50°C or more), namely good cohesion at these temperatures.

[0112] The hot-melt adhesive composition according to the invention is advantageously partly bio-sourced, through the use of wax of natural origin, which responds to the growing interest of the industry for this type of composition intended to reduce dependence on petroleum-based raw materials, while limiting the carbon footprint of manufacturing operations.

[0113] Uses

[0114] The hot melt adhesive composition of the invention can be used for a wide variety of applications, for example: packaging, paper and board converting, bookbinding, bag making and closing, nonwoven markets, and others. This type of adhesive is particularly used for the formation of boxes, crates, cartons and trays, and as a sealing adhesive, including heat sealing applications.

[0115] The present invention relates to the use of the hot-melt adhesive composition as defined above for bonding two substrates.

[0116] The present invention relates to a method for assembling two substrates by gluing, comprising: a first step of heating the hot-melt adhesive composition as defined above, for example at a temperature ranging from 90°C to 160°C, a step of coating at least one of the two substrates to be assembled with the composition obtained in the previous step; then effectively bringing the two substrates into contact so as to prepare an adhesive joint between the two substrates.

[0117] The substrates can be of the same or different nature.

[0118] The substrates may in particular be chosen from virgin or recycled paper, virgin or recycled kraft, high or low density kraft, all types of cardboard and cellulosic supports, composite materials, fiberboard or particleboard, non-wovens. All these substrates may be treated, coated or coated. The aforementioned composite materials may include papers, krafts or cardboards laminated to metallized or non-metallized films, such as polyethylene, polypropylene, polyethylene terephthalate, Mylar, polyvinylidene chloride, ethylene vinyl acetate and various other types of films, for example cellulosic-based, or others.

[0119] The above-mentioned substrates are by no means an exhaustive list, as a very wide variety of substrates, including composite materials, find use in the packaging industry.

[0120] The first heating step is carried out for a sufficiently long time to make the hot melt adhesive composition sufficiently liquid to be applied to a substrate.

[0121] In "on-demand" application systems, called tankless systems, hot melt adhesive compositions are fed in a solid state (e.g., as granules), into a heated tank in which the composition is melted, and rapidly applied to a substrate.

[0122] The coating step can be carried out by any methods known to those skilled in the art, such as injection, roller, fiberization or spraying. The hot-melt adhesive composition can be applied to a substrate in any shape such as, for example, continuous or discontinuous beads, dots, spirals, etc.

[0123] The hot-melt adhesive composition according to the invention can be used for bonding two different or different substrates, for example for making or closing packaging, boxes, cartons, cases, bags, mounting trays or trays, articles which include accessories (for example straws attached to drinks), ream packaging, cigarettes, filters, book binding.

[0124] All the embodiments described above may be combined with each other. In particular, the various aforementioned constituents of the composition, and in particular the preferred embodiments of the composition, may be combined with each other.

[0125] In the context of the invention, by "between x and y", or "ranging from x to y", is meant an interval in which the limits x and y are included. For example, the range "between 0% and 25%" includes in particular the values ​​0% and 25%.

[0126] The invention is now described in the following exemplary embodiments which are given purely for illustrative purposes and should not be interpreted to limit its scope.

[0127] Examples:

[0128] The following ingredients were used: Example 1: preparation of compositions

[0129] Hot melt adhesive compositions are obtained by hot mixing the ingredients using a Heidolph rod stirrer and a laboratory heating pot. The melting and mixing temperature is generally between 90 and 150°C.

[0130] The prepared compositions are collected in the following Table 1.

[0131] Example 2: Performance

[0132] The evaluation of the hot melt adhesive is carried out on a 200 g / m Kraft liner 2made from virgin paper fibers (Fipago), which is not treated with any type of primer or varnish.

[0133] The reference cardboard substrates are cut into 5 cm x 10 cm for the PAFT (temperature resistance) test, 5 cm x 6 cm for adhesion performance. For each product, 5 assemblies are prepared and tested.

[0134] For performance evaluation, the adhesive is applied with automatic equipment:

[0135] The adhesive is melted in a melting tank, then applied at 130°C in a bead equivalent to 2g / linear meter to the substrate with an automatic dispensing gun. The adhesive is applied across the width of the substrate in a 4 mm bead equivalent to 2g / linear meter. The second substrate is applied, opposite side, after 1 second of open time, and then pressed for 2 seconds by the machine.

[0136] The physical properties of the adhesives and their performance were measured by the following methods:

[0137] Viscosity measurement method:

[0138] Viscosity is determined using a Brookfield viscometer, a Brookfield Thermosel heated sample chamber, and a needle appropriate for the expected viscosity. Results are reported in mPa-s.

[0139] Method of measuring softening point:

[0140] The softening point is determined using an RB65G analyzer using the Ring-Ball method in accordance with ASTM E28. The Ring-Ball method involves determining the temperature at which a disc of the material held in a ring and loaded with a ball flows a defined distance when heated at a prescribed rate in a beaker of glycerin or the like. The results are expressed in °C. Evaluation of Heat Resistance - “PAFT” Test Method:

[0141] The peel adhesion failure temperature (or heat resistance test) is determined as follows:

[0142] The adhesive is applied at 130°C with automatic equipment at 2g / mL on a reference substrate (cut 5 cm x 10 cm) as explained previously.

[0143] After 24 hours, all assemblies are placed in an oven at the initial temperature of 30°C, the upper substrates of the assemblies are held by a metal structure in the oven and a hole is made on the lower substrates in order to place a weight of 100g.

[0144] The oven temperature is then increased by 5°C / 30 min until the adhesive seal breaks and the weight falls onto the detection cell. The temperature resistance value corresponds to the average value of the temperatures at which the weights fall, for all assemblies (5 assemblies tested per product).

[0145] Adhesion performance - Support defibration evaluation method:

[0146] The percentage of fiber defibration of the substrate is the percentage of fiber that covers the adhesive area after two substrates, which have been previously bonded together by the adhesive, are forcibly separated. The percentage of fiber defibration exhibited by an adhesive composition is determined as follows:

[0147] All the bonding assemblies are prepared (with an automatic device - 5cmx6cm), placed for 24 hours at room temperature, then stored for 3 days inside climatic chambers at -20°C, 5°C, 23°C, and 60°C (5 samples / temperature / adhesive).

[0148] After 3 days, the assemblies are separated from each other at conditioning temperature by manually pulling on the 2 substrates.

[0149] The surface of the adhesive composition is observed and the percentage of the surface of the adhesive composition that is covered with fibers is determined and recorded in units of % fiber tear according to the following scale: Compositions with a % defibration value of 5 are sought.

[0150] The results obtained using the methods described above are presented in the table below:

[0151] Table 1: Performance of the compositions

[0152]

[0153]

[0154] Comparative example 1 is a commercial adhesive. The combination of different raw materials allows for low-temperature application but does not allow for good performance at very low temperatures (-20°C), and high-temperature bonding performance is limited by low temperature resistance (PAFT).

[0155] The compositions of examples 1 to 4 advantageously have a good level of heat resistance (PAFT) > 50°C while maintaining very good adhesive performance over a wide temperature range: from -20°C to 60°C (fiber removal between 4 and 5 according to the indicative table). The viscosity level also allows them to be applied from 130°C and above, while maintaining good wettability of the support.

[0156] Comparative Example 2, which includes a non-hydrogenated rosin ester resin, does not achieve an acceptable viscosity level for application at 130°C. It was not possible to make the bonds with this comparative composition, which is not compatible.

[0157] Comparative Example 3 uses an EVA copolymer, not a metallocene copolymer. This composition has poor bonding performance at low temperatures (fiber removal 1 and 2 in value according to the reference table).

[0158] Comparative Example 4 does not use a tackifying resin as defined in the invention. This example uses a hydrogenated C9 aromatic tackifying resin. This composition leads to poor performance at low temperatures (fiberization 2 in value according to the reference table at -20°C). At 5°C, the fiberization values ​​are lower than those obtained with the compositions of Examples 1 to 4 using a composition according to the invention.

[0159] Comparative example s does not use a tackifying resin as defined in the invention. This example uses a non-hydrogenated aromatic modified aliphatic tackifying resin. This composition leads to poor performance at low temperature (fiber removal 1 in value according to the table at -20°C). At 5°C, the values ​​are lower than those obtained with examples 1 to 4 using the composition according to the invention.

Claims

CLAIMS Hot melt adhesive composition comprising: i) a copolymer polymerized by metallocene catalysis; ii) 2% to 50% by weight of a wax of natural origin having a dropping point of 65°C to 105°C, relative to the total weight of said composition; iii) a tackifying resin having a softening temperature less than or equal to 115°C selected from: a) terpene resins, b) partially or totally hydrogenated resins selected from: b-1) rosins of natural origin or modified partially or totally hydrogenated, such as, for example, rosin extracted from pine gum, wood rosin extracted from tree roots and their dimerized, polymerized derivatives; b-2) partially or totally hydrogenated rosin esters such as, for example, partially or totally hydrogenated glycerol esters of rosin, partially or totally hydrogenated pentaerythritol esters of rosin;b-3) partially or fully hydrogenated aliphatic resins, b-4) partially or fully hydrogenated cycloaliphatic resins; b-5) partially or fully hydrogenated aromatic modified aliphatic or cycloaliphatic resins, c) and mixtures thereof; said hot melt adhesive composition having a viscosity of less than 3,000 mPa.s at 130°C. Composition according to claim 1, characterized in that the copolymer i) polymerized by metallocene catalysis is selected from:; - copolymers comprising ethylene and at least one C3-C20-a-olefin; - copolymers comprising propylene and at least one monomer selected from ethylene and C4-C20-a-olefins; - their mixtures. Composition according to claim 1 or claim 2, characterized in that the copolymer i) is selected from copolymers comprising ethylene and at least one C3-C20-a-olefin, preferably selected from the group consisting of propene, butene, pentene, 3-methylbutene, hexene, 3-methylpentene, octene, norbonene, norbonadiene, 1-dodecene, 1-hexadodecene, 1-decene, 1-nonene, 1-methylnonene, trimethylheptene, 4-methylpentene, ethylpentene, 3-methylhexene, and mixtures thereof. Composition according to any one of claims 1 to 3, characterized in that copolymer i) is a copolymer comprising ethylene and octene, more preferably copolymer i) is a copolymer comprising only ethylene and octene, and in particular a copolymer comprising only ethylene and 20% to 49% by weight of octene relative to the total weight of said copolymer.A composition according to any one of claims 1 to 4, characterized in that the natural wax ii) has a dropping point from 70°C to 105°C, preferably from 80°C to 105°C. A composition according to any one of claims 1 to 5, characterized in that the natural wax ii) is selected from vegetable waxes, and preferably from the group consisting of carnauba wax, rice bran wax, sugar cane wax, hydrogenated natural soybean, jojoba, castor, or palm oil, and mixtures thereof. A composition according to any one of claims 1 to 6, characterized in that it comprises from 4% to 45%, preferably from 4% to 30% by weight of wax(s) ii) relative to the total weight of said composition.Composition according to any one of claims 1 to 7, characterized in that the tackifying resin iii) is selected from terpene-phenolic resins and their partially or totally hydrogenated derivatives, partially or totally hydrogenated cycloaliphatic resins, partially or totally hydrogenated aromatically modified aliphatic or cycloaliphatic resins, and mixtures thereof, and even more preferably from terpene-phenolic resins and their partially or totally hydrogenated derivatives, optionally partially or totally hydrogenated aromatically modified DCPD resins. A composition according to any one of claims 1 to 8, characterized in that it comprises from 30% to 60% by weight of tackifying resin(s) iii), preferably from 35% to 55% by weight, and even more preferably from 40% to 55% by weight relative to the total weight of said composition. A composition according to any one of claims 1 to 9, characterized in that it has a viscosity of less than 3000 mPa·s at 130°C, preferably between 500 mPa·s and 2500 mPa·s, and even more preferably between 1000 mPa·s and 2500 mPa·s. Composition according to any one of claims 1 to 10, characterized in that it comprises a total biomaterial content greater than or equal to 2%, preferably greater than or equal to 9%, and even more preferably greater than or equal to 45% relative to the total weight of said composition.A composition according to any one of claims 1 to 11, characterized in that it comprises less than 5% by weight of polyethylene wax, preferably less than 3% by weight, more preferably less than 1% by weight, and even more advantageously less than 0.1% by weight relative to the total weight of said composition. A composition according to any one of claims 1 to 12, characterized in that it does not comprise a partially or fully hydrogenated aromatic C9 tackifying resin. A composition according to any one of claims 1 to 13, characterized in that the metallocene-catalyzed copolymer (i) has a pour index greater than 400 g / 10 min, more preferably between 800 and 1500 g / 10 min. A composition according to any one of claims 1 to 14, characterized in that it does not comprise styrenic block copolymers.Composition according to any one of claims 1 to 15, characterized in that it comprises less than 5% by weight of plasticizer(s), preferably less than 2% by weight relative to the total weight of said composition, and even more preferably it does not comprise any plasticizer. Use of a composition according to any one of claims 1 to 16, for bonding two different or similar substrates, for example for making or closing packaging, boxes, cartons, cases, bags, assembling trays or platters, articles which include accessories (for example straws attached to drinks), ream packaging, cigarettes, filters, bookbinding.

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