EP4774333A1

EP4774333A1 - Polyolefin-based hot melt adhesive composition

Info

Publication number: EP4774333A1
Application number: EP24758256.2A
Authority: EP
Inventors: Stefano Pasquali; Jos TUNS; Roberta Marchini; Ilaria Federica TORRISI; Daniele ARIOLDI
Original assignee: Basell Poliolefine Italia SRL
Current assignee: Basell Poliolefine Italia SRL
Priority date: 2023-09-07
Filing date: 2024-08-19
Publication date: 2026-07-15
Also published as: KR20260058228A; CN121752686A; WO2025051517A1

Abstract

In the present disclosure provided is a hot melt adhesive composition comprising: (A) 25-50 wt% of a copolymer of butene-1 with at least one comonomer selected from ethylene, propylene, C5-C10 alpha-olefins and combinations thereof, having copolymerized comonomer content of 0.5-8.0 wt% and a melt flow rate MFR(A) (ISO 1133:2011, 190°C/2.16kg) equal to or greater than 200 g/10min; (B) 30-60 wt% of a tackifier; and (C) 5-30 wt% of a polypropylene wax, wherein the amounts of (A), (B) and (C) are referred to the total weight of (A)+(B)+(C). An article comprising the HMA composition is also provided.

Description

TITLE

POLYOLEFIN-BASED HOT MELT ADHESIVE COMPOSITION

FIELD OF THE INVENTION

[0001] The present disclosure relates to polyolefin-based hot melt adhesive (HMA) compositions, in particular HMA compositions including high melt flow polybutene- 1, tackifiers and a specific class of waxes, namely polypropylene-based waxes.

BACKGROUND OF THE INVENTION

[0002] Hot melt plastic adhesives are a type of thermoplastic adhesive that are applied in a molten state and solidify upon cooling. They are widely used in various industries and for numerous applications due to its fast-setting properties, ease of use, and strong bonding capabilities, like packaging industry, woodworking, product assembly, crafts, textiles, etc.

[0003] Hot melt adhesive compositions comprising highly flowable butene- 1 homo- or copolymers are known in the art, for example from the European patent applications EP671431 (Himont Inc.) or from EP314495 (Shell Oil Company). These references disclose butene-1 polymers that are visbroken with peroxides to achieve low viscosity values. It is however known that peroxidic degradation brings about some disadvantages, like unpleasant odor and high yellow index, which may prevent the use of peroxide-degraded composition in some technical fields, such as food packaging.

[0004] Ex-reactor highly flowable polubutene-1 is also known to be suitable for use in hot melt adhesive compositions.

[0005] US2008190541 Al discloses hot melt adhesive compositions containing at least two butene-1 copolymers from metallocene catalyst, the copolymers differing from each other for the melt flow indices. The low melt index component is essential to obtain the balance of properties for the hot melt adhesive.

[0006] Butene-1 copolymers having MFR ranging from 200 to 1500 g/10 min which are suitable for use in HMA compositions are known from the International patent application W02015/074830A1. The International patent application W02020/016143A1 discloses HMA compositions including polybutene-1 with MFR 200-1500 g/lOmin in combination with a tackifier and Fischer Tropsch waxes Said compositions are known to show a good compromise between rheological and thermal properties. [0007] In this context, it is still felt the need of polyolefin-based hot melt adhesive compositions with a good balance of adhesive and mechanical properties.

SUMMARY OF THE INVENTION

[0008] The present disclosure refers to a hot melt adhesive composition comprising:

(A) from 25% to 50% by weight of a copolymer of butene- 1 with at least one comonomer selected from ethylene, propylene, C5-C10 alpha-olefms and combinations thereof, having total copolymerized comonomer content of from 0.5% to 8.0% by weight, determined by IR Spectroscopy with the method described in the example section, and a melt flow rate MFR(A) measured according to ISO 1133-1 :2011 (190°C, 2.16kg) equal to or greater than 200 g/lOmin;

(B) from 30% to 60% by weight of a tackifier; and

(C) from 5 to 30% by weight of a polypropylene wax, wherein the amounts of (A), (B) and (C) are referred to the total weight of (A)+(B)+(C).

[0009] The polyolefin-based hot melt adhesive composition of the present disclosure is endowed with a good balance of properties, like good mechanical properties, SAFT, open and setting time, and softening properties, as evidenced by the values of the ring and ball test.

[0010] In a further aspect, the present disclosure refers to an article comprising a first substrate and a second substrate, wherein the first substrate is bonded to the second substrate by the hot melt adhesive composition of the present disclosure, interposed between the first and the second substrate.

[0011] While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, certain embodiments, as disclosed herein, are capable of modifications in various obvious aspects, all without departing from the spirit and scope of the claims as presented herein. Accordingly, the following detailed description is to be regarded as illustrative in nature and not restrictive.

DETAILED DESCRIPTION OF THE INVENTION

[0012] In the context of the present disclosure:

[0013] - the percentages are expressed by weight, unless otherwise specified;

[0014] - the total weight of a polymer composition sums up to 100% by weight, unless otherwise specified; [0015] - the term “comprising” referred to a polymer or to a polymer composition, mixture or blend should be construed to mean “comprising or consisting essentially of’;

[0016] - the term “consisting essentially of’ means that, in addition to those components which are mandatory, other components may also be present in the material, provided that the essential characteristics of the material are not materially affected by their presence. Examples of components that, when present in customary amounts, do not materially affect the characteristics of a polymer or of a polyolefin composition, mixture or blend are catalyst residues, antistatic agents and processing aids;

[0017] - the term “copolymer” is referred to a polymer deriving from the intentional polymerization of at least two different comonomers, i.e. the term “copolymer” includes terpolymers.

[0018] - the term “film” refers to a thin layer of material having thickness equal to or lower than 2,000 microns;

[0019] - the term “sheet” refers to a layer of material more than 2,000 microns thick.

[0020] An object of the present disclosure is therefore a hot melt adhesive (HMA) composition comprising:

(A) from 25% to 50% by weight of a copolymer of butene- 1 with at least one comonomer selected from ethylene, propylene, C5-C10 alpha-olefins and combinations thereof, having copolymerized comonomer content of from 0.5% to 8.0% by weight and a melt flow rate MFR(A) measured according to ISO 1133-1:2011 (190°C, 2.16kg) equal to or greater than 200 g/lOmin;

(B) from 30% to 60% by weight of a tackifier; and

(C) from 5 to 30% by weight, preferably from 15% to 30% by weight, of a polypropylene wax, wherein the amounts of (A), (B) and (C) are referred to the total weight of (A)+(B)+(C).

[0021] The individual components (A), (B) and (C) of the HMA compositions are defined in greater detail below. The individual components may be comprised in the HMA composition in any combination.

[0022] Preferably, the butene- 1 copolymer (A) has a melt flow rate MFR(A) measured according to ISO 1133-1 :2011 (190°C/2.16 kg) of from 200 to 3,000 g/10 min, more preferably from 400 to 1,700 g/10min., still preferably from 500 to 1,600 g/lOmin.

[0023] The butene- 1 copolymer (A) preferably has a (total) copolymerized comonomer content of from 0.7% to 7.0% by weight, based on the total weight of butene- 1 copolymer (A). [0024] The butene- 1 copolymer (A) preferably contains a comonomer selected from ethylene, propylene, hexene-1, octene-1 and combinations thereof, ethylene being particularly preferred.

[0025] In a preferred embodiment, the butene- 1 copolymer (A) comprises:

- a fraction (Al) comprising a butene-1 homopolymer or a copolymer of butene-1 with less than 3% by weight, based on the weight of fraction (Al) of a comonomer selected from ethylene, propylene, C5-C10 alpha-olefins, and combinations thereof;

- a fraction (A2) comprising a copolymer of butene-1 with from 3% to 10% by weight, based on the weight of fraction (A2), of a comonomer selected from ethylene, propylene, C5-C10 alpha-olefins and combinations thereof, wherein the butene-1 copolymer (A) has:

- a total copolymerized comonomer content of from 0.5% to 8.0% by weight, preferably from 0.7% to 7.0% by weight, based on the total weight of fractions (Al) and (A2);

- a melt flow rate MFR(I) measured according to ISO 1133-1 :2011 (190°C, 2.16kg) equal to or greater than 200 g/lOmin; and

- a content of fraction soluble in xylene at 0°C equal to or less than 80% by weight, preferably ranging from 20% to 80% by weight, based on the total weight of fractions (Al) and (A2) and determined with the method described in the example section, and wherein the comonomer content is determined by IR Spectroscopy with the method described in the example section.

[0026] Preferably, the butene-1 copolymer (A) comprises from 15% to 70% by weight, in particular from 20% to 65%, by weight of fraction (Al) and from 30% to 85% by weight, in particular from 35% to 80% by weight of fraction (A2), wherein the amounts of fractions (Al) and (A) are based on the total weight of fractions (Al) and (A2).

[0027] Preferably, the comonomer optionally contained in butene-1 copolymer fraction (Al) and in butene-1 copolymer fraction (A2) is ethylene.

[0028] Preferably, the butene-1 copolymer (A) has at least one, more preferably all, the following additional features:

(a) a molecular weight distribution (Mw/Mn) lower than 4, preferably lower than 3; more preferably lower than 2.5, the lower limit being of 1.5 in all cases, where the molecular weight distribution is determined by NMR with the method escribed in the example section; and/or

(b) has one or more melting peaks Tm(II) at temperatures equal to or lower than 110°C, preferably equal to or lower than 105°C, more preferably ranging from 80° to 103°C, where the Tm(II) is measured by DSC with the method described in the example section; and/or (c) glass transition temperature (Tg) in the range from - 40°C to - 10°C, preferably from -30°C to -10°C, where the Tg is measured by DSC with the method described in the example section; and/or

(d) Brookfield viscosity at 190°C lower than 15,000 mPa.s, preferably ranging from 3,000 to 15,000 mPa.s; and/or

(e) X-ray crystallinity comprised in the range from 20 to 60%, preferably in the range from 25 to 50%;

(f) density in the range from 0.89 to 0.91 g/cm³; and/or

(g) yellowness index of less than 0; in particular ranging from -1 to -5.

[0029] In one embodiment, the butene- 1 copolymer (A) may have all the features (a)-(g).

[0030] The butene- 1 copolymer (A) can be obtained by copolymerizing butene- 1 and a comonomer in the presence of a catalyst system obtainable by contacting:

- a stereorigid metallocene compound;

- an alumoxane or a compound capable of forming an alkyl metallocene cation; and, optionally,

- an organo-aluminum compound.

[0031] The patent applications W02004/099269, W02006/045687, W02015/074830, WO20 18/007279 and W02022/0084081, which are herein incorporated by reference, describe processes and catalysts systems suitable for producing the butene- 1 copolymer (A).

[0032] The butene- 1 copolymer (A) may be obtained by a polymerization process carried out in one or more reactors connected in series. In the latter case, the catalyst may be added in the first reactor only, or in more than one reactor. As explained in W02004/099269, the polymerization process may be carried out in the liquid phase, optionally in the presence of an inert hydrocarbon solvent, or in the gas phase, using fluidized bed or mechanically agitated gas phase reactors. Preferably, the polymerization process is carried out by using liquid butene-1 as polymerization medium. The polymerization temperature ranges typically from 20°C to 150°C, preferably from 50°C to 90°C, more preferably it is from 65°C to 82°C.

[0033] As explained in W02006/045687, hydrogen can be advantageously used to regulate the molecular weight of butene-1 copolymers. The concentration of hydrogen during the polymerization reaction carried out in the liquid phase is higher than 1,800 molar ppm and lower than 6,000 molar ppm, preferably it ranges from 2,000 molar ppm to 6,000 molar ppm. [0034] Butene-1 copolymers having low melting point can be obtained by properly selecting the copolymerized comonomer content, in particular ethylene content. Thus, the butene-1 copolymer (A) may be obtained with a polymerization process wherein the amount of the comonomer, in particular of ethylene, in the liquid phase ranges from 0.1% to 8% by weight, preferably from 0.2% to 6% by weight, with respect to the total weight of butene- 1 monomer present in the polymerization reactor.

[0035] When the butene-1 copolymer (A) is a butene-1 copolymer composition (I) comprising components (Al) and (A2), the butene-1 copolymer composition (I) is obtained by melt blending components (Al) and (A2) in appropriate amounts. Alternatively, and preferably, the butene-1 copolymer composition (I) is obtained by a polymerization process comprising at least two polymerization stages, carried out in at least two reactors connected in series. When component (Al) is a copolymer, for the preparation of component (Al) the amount of comonomer in the liquid phase may range from 0% to 1.2% by weight, while the amount of comonomer in the liquid phase of the second stage may range from 1% to 10% by weight for the preparation of component (A2).

[0036] The hot melt adhesive composition of the present disclosure comprises at least one tackifier (B). The tackifier (B) is preferably solid at a temperature of 25°±1°C.

[0037] The tackifier (B) is preferably selected among hydrogenated hydrocarbon resins and derivatives thereof, such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins and aliphatic/aromatic hydrocarbon resins; terpene-derived resins, such as polyterpenes, terpene/phenolic resins; natural resins and natural resin esters, such as rosin, rosin ester and tall oil rosin ester; and mixtures thereof. Preferably, the tackifier (B) is an hydrogenated hydrocarbon resins, more preferably a cycloaliphatic hydrocarbon resin.

[0038] In a preferred embodiment, the tackifier (B) has a softening point greater than 100°C.

[0039] Tackifiers suitable for use as component (B) in the HMA compositions of the present disclosure are known in the art and marketed eg. By ExxonMobil with the tradename Escorez™, like Escorez™ 5400.

[0040] The HMA composition of the present disclosure further comprises a polypropylene wax (C). In a preferred embodiment, the HMA composition of the present disclosure does not comprise any wax other than the polypropylene wax (C). More preferably, the HMA composition does not comprise a Fischer-Tropsch wax.

[0041] The polypropylene wax (C) may be a modified polypropylene wax, like a maleic anhydride grafted polypropylene wax.

[0042] The polypropylene wax (C) preferably has weight average molecular weight Mw, measured by GPC, equal to or lower than 10,000 g/mol, preferably equal to or lower than 8,000 g/mol, more preferably ranging from 3,000 to 7,000 g/mol and/or a molecular weight distribution Mw/Mn, measured by GPC, ranging from 3.0 to 6.0. [0043] The polypropylene wax (C) preferably also has a drop melting point (DGF M-III 3, analogous to DIN 51801) of from 140°C to 157°C, preferably from 145° to 155°C.

[0044] The polypropylene wax (C) preferably also has needle penetration ranging from 2 to 7 dmm (DIN 51579:2010).

[0045] Optionally, the HMA composition of the present disclosure comprises an additional component (D) selected from plasticizers, like plasticizing oils (such as mineral oils), olefin oligomers or low molecular weight polyolefins (such as liquid polybutylenes); amorphous poly-alpha-olefins different from polybutene- 1 component (A), thermoplastic polyurethanes, ethylene/(meth)acrylate copolymers, ethylene/vinyl acetate copolymers, and combinations thereof. The amount of the additional component (D) ranges from 0% to 15% by weight, based on the total weight of the HMA composition (including the additional component).

[0046] Optionally but preferably, the HMA composition comprises from 0.05% to 5.0% by weight, based on total weight of the HMA composition, of an additive (E) selected from additives commonly used in HMA compositions, like antioxidants, light stabilizers and combinations thereof.

[0047] The viscosity of the hot melt adhesive composition of the present disclosure can be tailored, thereby optimizing the composition for different applications. The hot melt adhesive composition of the present disclosure is therefore suitable for use in woodworking, for packaging, in the general assembly field; particularly to assemble components of electrical equipment, ceramics, furniture, textiles, upholstery, leather, plastic, paper and cardboard.

[0048] Accordingly, in a further aspect the present disclosure refers to the use of the hot melt adhesive composition for bonding articles in woodworking, for packaging, in the general assembly field; particularly to assemble components of electrical equipment, ceramics, furniture, textiles, upholstery, leather, plastic, paper and cardboard.

[0049] In a further aspect, the present disclosure refers to an article comprising a first substrate and a second substrate, wherein the first substrate is bonded to the second substrate by the hot melt adhesive composition of the present disclosure interposed between the first and the second substrate.

[0050] Preferably, the first and the second substrate are made of a material independently selected from wood, paper, cardboard, natural leather, plastic material, natural fibers, like cotton or hemp, and combinations thereof.

[0051] Preferably, the first and the second substrate are independently selected from films, sheets, panels, woven and non-woven fabrics. [0052] In one embodiment, the hot melt adhesive composition of the present disclosure preferably has rotational (Brookfield) viscosity at 180°C equal to or lower than 7,000 mPa.s, more preferably lower than 5,000 mPa.s, still more preferably lower than 2,000 mPa.s. In one embodiment, the lower limit is 500 mPa.s for each upper limit. HMA compositions with viscosity in these ranges are particularly suitable for use in in the packaging field to assemble paper, cardboard and the like.

[0053] The hot melt adhesive composition of the present disclosure show very good thermal stability.

[0054] The composition of the invention can be prepared by known methods and equipment, such as melt blending the component, like in a stirred tank or in a single- or twin screw extruder.

[0055] The features describing the subject matter of the present disclosure are not inextricably linked to each other. Hence, preferred ranges of one feature may be combined with more or less preferred ranges of a different feature, independently from their level of preference.

[0056] The following examples are illustrative only, and are not intended to limit the scope of the invention in any manner whatsoever.

EXAMPLES

[0057] CHARACTERIZATION METHODS: the following methods are used to determine the properties indicated in the description, claims and examples.

[0058] Melt flow rate (MFR) was measured according to ISO 1133-1 :2011 (190°C, 2.16kg, except where different load and temperatures are specified).

[0059] Comonomer content (wt.%) measured via IR spectroscopy.

[0060] The spectrum of a pressed film of the polymer was recorded in absorbance vs. wavenumbers (cm'¹). The following measurements were used to calculate the ethylene content: a) area (At) of the combination absorption bands between 4482 and 3950 cm'¹ which is used for spectrometric normalization of film thickness; b) factor of subtraction (FCRc2) of the digital subtraction between the spectrum of the polymer sample and the absorption band due to the sequences BEE and BEB (B: 1-butene units, E: ethylene units) of the methylenic groups (CH2 rocking vibration); c) Area (Ac2, block) of the residual band after subtraction of the C2PB spectrum. It comes from the sequences EEE of the methylenic groups (CH2 rocking vibration). [0061] APPARATUS

A Fourier Transform Infrared spectrometer (FTIR) was used, which is capable of providing the spectroscopic measurements above reported. A hydraulic press with platens heatable to 200°C (Carver or equivalent) was used.

[0062] METHOD

[0063] Calibration of (BEB + BEE) sequences

A calibration straight line is obtained by plotting %(BEB + BEE)wt vs. FCRc2/At. The slope Gr and the intercept Lr are calculated from a linear regression.

[0064] Calibration of EEE sequences

A calibration straight line is obtained by plotting %(EEE)wt vs. Ac2, block/ At. The slope Gn and the intercept IH are calculated from a linear regression.

[0065] Sample preparation

Using a hydraulic press, a thick sheet is obtained by pressing about g 1.5 of sample between two aluminum foils. If homogeneity is in question, a minimum of two pressing operations are recommended. A small portion is cut from this sheet to mold a film. Recommended film thickness ranges between 0.1-0.3 mm. The pressing temperature is 140 ± 10 °C. A crystalline phase modification takes place with time, therefore it is recommended to collect the IR spectrum of the sample film as soon as it is molded.

[0066] Procedure

The instrument data acquisition parameters are as follows:

Purge time: 30 seconds minimum.

Collect time: 3 minutes minimum.

Apodization: Happ-Genzel.

Resolution: 2 cm'¹.

Collect the IR spectrum of the sample vs. an air background.

[0067] CALCULATION

Calculate the concentration by weight of the BEE + BEB sequences of ethylene units:

Calculate the residual area (AC2, block) after the subtraction described above, using a baseline between the shoulders of the residual band.

Calculate the concentration by weight of the EEE sequences of ethylene units: Calculate the total amount of ethylene percent by weight:

% C2wt = [%(BEE + BEB wt + %(£££)wt]

[0068] Mw/Mn determination. Measured by way of Gel Permeation Chromatography (GPC) in 1, 2, 4-tri chlorobenzene (TCB). Molecular weight parameters (Mn, Mw, Mz) and molecular weight distributions Mw/Mn for all the samples were measured by using a GPC-IR apparatus by PolymerChar, which was equipped with a column set of four PLgel Olexis mixed- bed (Polymer Laboratories) and an IR5 infrared detector (PolymerChar). The dimensions of the columns were 300 x 7.5 mm and their particle size was 13 pm. The mobile phase flow rate was kept at 1.0 mL/min. All the measurements were carried out at 150 °C. Solution concentrations were 2.0 mg/mL (at 150 °C) and 0.3 g/L of 2,6-diterbuthyl-p-chresole were added to prevent degradation. For GPC calculation, a universal calibration curve was obtained using 12 polystyrene (PS) standard samples supplied by PolymerChar (peak molecular weights ranging from 266 to 1220000). A third-order polynomial fit was used for interpolate the experimental data and obtain the relevant calibration curve. Data acquisition and processing was done by using Empower 3 (Waters). The Mark-Houwink relationship was used to determine the molecular weight distribution and the relevant average molecular weights: the K values were KPS = 1.21 x 10'⁴ dL/g and KPB = 1.78 x 10'⁴ dL/g for PS and polybutene (PB) respectively, while the Mark-Houwink exponents a = 0.706 for PS and a = 0.725 for PB were used.

[0069] For butene/ethylene copolymers, as far as the data evaluation is concerned, it was assumed for each sample that the composition was constant in the whole range of molecular weight and the K value of the Mark-Houwink relationship was calculated using a linear combination as reported below: l^EB ^{= X}E^PE + ^XB ^PB

[0070] where KEB is the constant of the copolymer, KPE (4.06 ^x 10'⁴, dL/g) and KPB (1.78 x 10'⁴ dL/g) are the constants of polyethylene (PE) and PB, x_E and x_B are the ethylene and the butene weight relative amount with x_E + x_B = 1. The Mark-Houwink exponents a = 0.725 was used for all the butene/ethylene copolymers independently on their composition. End processing data treatment was fixed for all samples to include fractions up at 1000 in terms of molecular weight equivalent. Fractions below 1000 were investigated via GC.

[0071] The thermal properties were determined by Differential Scanning Calorimetry (D S C.) on a Perkin Elmer DSC-7 instrument. The melting temperatures of butene-1 copolymers and of the HMA compositions were determined according to the following method:

- Tmll (melting temperature/s measured in second heating run): a weighted sample (5-10 mg) obtained from the polymerization (or a weighted sample of the HMA composition) was sealed into aluminium pans and heated at 200°C with a scanning speed corresponding to 10°C/minute. The sample was kept at 200°C for 5 minutes to allow a complete melting of all the crystallites thus cancelling the thermal history of the sample. Successively, after cooling to -20°C with a scanning speed corresponding to 10°C/minute, the peak temperature was taken as crystallization temperature (Tc). After standing 5 minutes at - 20°C, the sample was heated for the second time at 200°C with a scanning speed corresponding to 10°C/min. In this second heating run, the peak temperature measured were marked as (Tmll). If more than one peak was present, the highest one (most intense) was taken as Tmll. The area under the peak (or peaks) as global melting enthalpy (DH Tmll).

- The melting enthalpy and the melting temperature were measured also after aging (without cancelling the thermal history) as follows by using the Differential Scanning Calorimetry (D S C.) on an Perkin Elmer DSC-7 instrument. A weighted sample (5-10 mg) obtained from the polymerization (or a weighted sample of the HMA composition) was sealed into aluminium pans and heated at 200°C with a scanning speed corresponding to 10°C/minute. The sample was kept at 200°C for 5 minutes to allow a complete melting of all the crystallites and cooled down to 20°C at a cooling rate of 10°C/min. The sample was then stored for 10 days at room temperature. After 10 days the sample was subjected to DSC, it was cooled to -20°C, and then it was heated at 200°C with a scanning speed corresponding to 10°C/min. In this heating run, the peak temperature was recorded as the melting temperatures (Tml). If more than one peak was present, the highest one (most intense) was taken as Tml. The area under the peak (or peaks) as global melting enthalpy after 10 days (DH Tml).

[0072] Glass transition temperature (Tg) via Dynamic Mechanical Thermal Analysis (DMTA). Molded specimens of 76 mm by 13 mm by 1 mm are fixed to the DMTA machine for tensile stress. The frequency of the tension and relies of the sample is fixed at 1 Hz. The DMTA translates the elastic response of the specimen starting from -100°C to 130°C. In this way it is possible to plot the elastic response versus temperature. The elastic modulus for a viscoelastic material is defined as E=E'+iE". The DMTA can split the two components E' and E" by their resonance and plot E' vs temperature and E/E" = tan (5) vs temperature. The glass transition temperature Tg is assumed to be the temperature at the maximum of the curve E/E" = tan (5) vs temperature. [0073] Brookfield viscosity of butene-1 copolymers: measured at 190°C with a Cylindrical Spindle Rotational Viscometer HA Ametek/Benelux Scientific, model DV2T, equipped with a drive motor capable of variable testing speed and a set of spindles capable of achieving and maintaining a torque at -80%. The selected spindle/chamber combination was SC4-27/SC4-13R/RP. The sample was subjected to a stepwise rotation increase until a torque value of -80% was reached and maintained. Rotation started at 10 rpm, then increased stepwise by 2 rpm every 5 seconds. The Brookfield viscosity [mPa*s] was calculated as Shear Stress (mPa)/Shear rate (sec-1) ratio and was determined by averaging the results obtained during the last 20 minutes of acquisition (1 datapoint/min).

[0074] Brookfield viscosity for the HMA: measured at 180°C with a Cylindrical Spindle Rotational Viscometer HA Ametek, model DV2T, equipped with a drive motor capable of variable testing speed and a set of spindles capable of achieving and maintaining a torque at -50%. The selected spindle/chamber combination was SC4/27. The sample (10.5g) was subjected to a stepwise rotation increase until a torque value of -50% was reached and maintained. Rotation started at 5 rpm up 20 rpm, when it’s stable rotation is kept for 20 min. The Brookfield viscosity [mPa*s] was calculated as Shear Stress (mPa)/Shear rate (sec-1) ratio and was determined by averaging the results obtained during the last 20 minutes of acquisition (1 datapoint/min).

[0075] Crystallinity was measured by X-Ray diffraction with an X-ray Diffraction Powder Diffractometer (XDPD) that uses the Cu-Kotl radiation with fixed slits and able to collect spectra between diffraction angle 20 = 5° and 20 = 35° with step of 0.1° every 6 seconds.

The samples are diskettes of about 1.5-2.5 mm of thickness and 2.5-4.0 cm of diameter made by compression molding. The diskettes are aged at 23°C for 96 hours.

After this preparation the specimen is inserted in the XDPD sample holder. Set the XRPD instrument in order to collect the XRPD spectrum of the sample from diffraction angle 20 = 5° to 20 = 35° with step of 0.1° by using counting time of 6 seconds, at the end the final spectrum is collected.

Defining Ta as the total area between the spectrum profile and the baseline expressed in counts/sec’20.; and Aa as the total amorphous area expressed in counts/sec»20. Ca is total crystalline area expressed in counts/sec*20.

The spectrum or diffraction pattern is analyzed in the following steps:

1) define a suitable linear baseline for the whole spectrum and calculate the total area (Ta) between the spectrum profile and the baseline; 2) define a suitable amorphous profile, along the whole spectrum, that separate , the amorphous regions from the crystalline ones according to the two phase model;

3) calculate the amorphous area (Aa) as the area between the amorphous profile and the baseline;

4) calculate the crystalline area (Ca) as the area between the spectrum profile and the amorphous profile as Ca = Ta- Aa; and

5) Calculate the degree of crystallinity of the sample using the following formula:

%Cr = lOO x Ca / Ta

[0076] Density: Determined according to norm ISO 1183-1, method A, Part 1 : immersion method. Test specimens were obtained by compression molded plaques. For polybutene-1 density is measured after 10 days conditioning.

[0077] Fractions soluble and insoluble in xylene at 0°C: 2.5 g of polymer composition and 250 cm³ of o-xylene are introduced in a glass flask equipped with a refrigerator and a magnetic stirrer. The temperature is raised in 30 minutes up to the boiling point of the solvent. The so obtained clear solution is then kept under reflux and stirring for further 30 minutes. The closed flask is then cooled to 100°C in air for 10 to 15 minutes under stirring and then kept for 30 minutes in thermostatic water bath at 0°C for 60 minutes as well. The so formed solid is filtered on quick filtering paper at 0°C. 100 cm³ of the filtered liquid is poured in a previously weighed aluminum container which is heated on a heating plate under nitrogen flow, to remove the solvent by evaporation. Thus, the fraction (percent by weight) of polymer soluble in xylene (XS) is calculated from the average weight of the residues. The polymer fraction insoluble in o-xylene at 0°C (XI) is calculated as: XI (%) = 100 - XS (%).

[0078] Yellowness index measured according to ASTM method D1925.

[0079] Tensile stress and elongation at yield. Sample preparation: bring the oven to 175°C. Fill an aluminum cup with the adhesive to be tested and put the cup in the oven to melt for about 1 hour. Pour melted adhesive over a silicone paper sheet and allow to cool to 23±1°C. Cut out squares of about 10 gr from each sample. Turn on the hot press and set the plate temperatures to 85°C. Place the pre-weighed square of adhesive in the center of two sheets of silicone paper, in which two 0.5mm metal shims are placed on each sides. Press for about 2 minutes, open the press and check that a flat and homogeneous surface with a thickness of about 0.5mm ± 0.05 is obtained; in case it is not, repeat the operation with a new sample. Allow to cool to 23±1°C. After 24 hours cut a standard dumbbell-shaped test specimens, with the following dimensions:

[0080] Condition the test specimens for at least 24h at 23 °C and reconfirm the thickness using a micrometer. Test method: in a dynamometer, set the separation speed of 60 mm/min and elongation limit of 300 mm. Grip the test specimen to the forceps of the dynamometer, start the traction and plot the stress-strain curve. The Yield Point is the first point on the stressstrain curve at which an increase in strain occurs without an increase in stress. The tensile stress at yield is the value of the stress at the yield point; the elongation at yield is the percentage deformation at the yield point.

[0081] Ring & Ball softening point. The softening point is defined as the temperature at which a disk of the sample held within a horizontal ring is forced downward at a distance of 25.4 mm under the weight of a steel ball (diameter: 9.5mm; weight: 3.5±0.05g) as the sample is heated at 5°C/min in a glycerin bath. This test method is intended for determining the softening point of hot melt adhesives and hot melt raw materials by means of the ring-and-ball apparatus HERZOG mod HRB 754. Melt the adhesive sample in the oven and fill the ring. Condition for at least 4 hours at 23±1°C. Insert the rings precisely into the holder, place the guide cages for the beads and check that the beads are free to move, then immerse in the bath containing glycerin. Place the beaker on the heating plate of the instrument, immerse the holder with the rings and the thermometer of the instrument. Set the sample identification data (name and batch no.) on the control panel, start the determination. At the end of the analysis, the instrument will indicate the detected temperature. Results are expressed in °C.

[0082] Cloud point. The cloud point is the temperature at which the HMA composition becomes cloudy on cooling. The HMA compositions are molten at a temperature of 170°C, a thermometer is dipped into the molten adhesive mass and the adhesive mass is allowed to cool. The temperature measured by the thermometer when the adhesive turns cloudy is recorded as the cloud point of the adhesive.

[0083] Open time. The open time is defined as the longest time that an adhesive material remains capable of adhesion. The open time is the time after an adhesive is applied during which a serviceable bond can be made. 70x50mm one-side coated cardboard of 400 g/m² is used for testing. A uniform layer of 10x50 mm of adhesive molten at 180°C is applied onto a first cardboard by a spray gun with a pressure of Ibar. After a time span of 1 second (hold time), a second cardboard is bonded to the first carboard by pressing it for 1 sec with a pressure of 0.8bar. Immediately after pressing, the second substrate is pulled perpendicular to the first cardboard, with a speed of 3000 mm/min. If a serviceable bond is formed, 100% of the fibers in the bonding area are torn off. The test is repeated increasing the hold time by 1 second. The open time is the hold time at which less than 100% of the cardboard fibers are tom off. An average of the open time was taken from 5 tests carried out on the same HMA composition.

[0084] Setting time: the setting time is the time it takes to form an acceptable bond when two substrates are combined with an adhesive. A uniform layer of 10x50 mm of adhesive molten at 180°C is applied onto a first cardboard by a spray gun with a pressure of Ibar. After 1 second, a second cardboard is bonded to the first carboard by pressing it for 0.05 sec with a pressure of 0.8bar. After pressing, the second substrate is pulled perpendicular to the first cardboard, with a speed of 3000 mm/min. The pressing time is increased by 0.02 sec until a total tear of the cardboard fibers is obtained (setting time). An average of the setting time was taken from 5 tests carried out on the same HMA composition.

[0085] Shear Adhesion Failure Temperature (SAFT). The test method determines the temperature at which specimens bonded with a hot-melt adhesive delaminate under static load in shear. Test specimens are prepared as follows: a 10x50mm line of hot melt adhesive is applied at a temperature of 180°C by a spray gun operating with a pressure of 1 bar on a first 70x50mm one-side coated cardboard of 400 g/m²; a second 70x50mm one-side coated cardboard of 400 g/m² bonded to the first cardboard with a pressure of 0.8bar. At least 5 test specimens are prepared for each adhesive, and conditioned for 24 hours at 23°C and 50% rh. Preheat the oven at 50°C, hung one end of the test specimen in the oven and hung a 500g weight at the opposite end of the test specimen. Ramp up the oven temperature at a rate of 5°C per hour. The temperature at which adhesive fails (delaminate) is recorded as the shear adhesion failure temperature.

[0086] Flexural modulus was measured according to ISO 178. Specimens for flexural test were cut from compression molded plaques pressed at 200°C and aged for 10 days at 25°±1°C. Specimens thickness was of 4mm.

[0087] RAW MATERIALS

[0088] Tackifier: Escorez™ 5400 a cycloaliphatic hydrocarbon resin marketed by ExxonMobil having softening point of 103.4°C and melt viscosity at 160°C of 800 mPa.s.

[0089] PPwax: Deurex® P 3815 M marketed by Deurex AG, a polypropylene wax with drop melting point of 150°C, penetration of 3 dmm, weight average molecular weight Mw of 5,781 and Mw/Mn of 4.2. [0090] FT wax (1): Sasolwax Hl, a high melting point Fischer-Tropsch wax marketed by Sasol having drop melting point of 112°C, a penetration of 1 dmm, weight average molecular weight Mw of 1,863 and Mw/Mn of 1.3.

[0091] FT wax (2): Sasolwax C80M, a low melting point Fischer-Tropsch wax marketed by Sasol having drop melting point of 97°C, a penetration of 7 dmm, a weight average molecular weight of 1, 145 and a Mw/Mn of 1.1.

[0092] Preparation of catalyst components: Dimethylsilyl{(2,4,7-trimethyl-l-indenyl)- 7-(2,5-dimethyl-cyclopenta[l,2-b:4,3-b']-dithiophene)} zirconium dichloride (metallocene A- 1) was prepared according to Example 32 of WOOl/47939.

[0093] Preparation of the catalytic solution: Under nitrogen atmosphere, 6400 g of a 33 g/L solution of triisobutylaluminium (TIBA) in isododecane and 567 g of 30% wt/wt solution of methylalum oxane (MAO) in toluene are loaded in a 20 L jacketed glass reactor, stirred by means of an anchor stirrer, and allowed to react at 25°C for about 1 hour under stirring. After this time, 1.27 g of metallocene A-l is added and dissolved under stirring for about 30 minutes. The final solution is discharged from the reactor into a cylinder through a filter to remove eventual solid residues. The composition of the solution resulted to be:

[0094] Preparation of butene-1 copolymers [component (A)]: The polymerization was carried out in two stirred reactors operated in series, in which liquid butene-1 constituted the liquid medium. The catalyst system described above was injected in both reactors and the polymerization was carried out in continuous.

[0095] PB(1) was prepared according to Example 1 of W02020/016143A1 and PB(2) was prepared according to the preparation of Butene-1 polymer B)-I described in W02022/084081, Table 1. PB(3) was prepared according to the polymerization process described in W02020/016143A1, in the following conditions: Table 1

[0096] The butene-1 copolymer was recovered as melt from the solution and cut in pellets.

The copolymer was further characterized and the data are reported in Table 2.

Table 2

*BV: Brookfield Viscosity

[0097] Preparation of the hot melt adhesive compositions: melt the components at 175°C in a aluminum can in a melter, and mix the molten composition at 175°C using small mixer IKA RW20 with stirring bar at 200rpm for 2h. [0098] Examples E1-E3

[0099] Hot melt adhesive compositions according to the disclosure were prepared as described above, with the formulation indicated in Table 3. Results of the tests carried out on the compositions are collected in the same Table 3.

Table 3

*BV: Brookfield Viscosity

[0100] Comparative examples CE4-CE9

[0101] Hot melt adhesive compositions containing Fischer-Tropsch waxes were prepared for comparative purposes according to the method described above. The formulations and the test results are collected in table 4.

Table 4

*BV: Brookfield Viscosity

[0102] The HMA composition of the present disclosure show the best balance of properties, like an improved combination of mechanical properties, SAFT, open and setting time, and ring and ball softening point.

Claims

CLAIMS What is claimed is:

1. A hot melt adhesive composition comprising:

(A) from 25% to 50% by weight of a copolymer of butene- 1 with at least one comonomer selected from ethylene, propylene, C5-C10 alpha-olefins and combinations thereof, having total copolymerized comonomer content of from 0.5% to 8 0% by weight, determined by IR Spectroscopy, and a melt flow rate MFR(A) measured according to ISO 1133-1 :2011 (190°C, 2.16kg) equal to or greater than 200 g/lOmin;

(B) from 30% to 60% by weight of a tackifier; and

2. The hot melt adhesive composition according to claim 1, wherein the butene-1 copolymer (A) has a melt flow rate MFR(A) (ISO 1133-1 :2011, 190°C/2.16 kg) of 200 to 3,000 g/ 10 min., preferably from 400 to 1,700 g/10min., more preferably from 500 to 1,600 g/lOmin.

3. The hot melt adhesive composition according to claim 1 or 2, wherein the butene-1 copolymer (A) has a total copolymerized comonomer content of from 0.7% to 7.0% by weight, based on the total weight of butene-1 copolymer (A), where the comonomer content is determined by IR Spectroscopy.

4. The hot melt adhesive composition according to any one of the preceding claims, wherein the butene-1 copolymer (A) contains a comonomer selected from ethylene, propylene, hexene- 1, octene- 1 and combinations thereof, ethylene being particularly preferred.

5. The hot melt adhesive composition according to any one of the preceding claims, wherein the butene-1 copolymer (A) comprises:

- a fraction (Al) comprising a butene-1 homopolymer or a copolymer of butene-1 with less than 3% by weight, based on the weight of fraction (Al) of a comonomer selected from ethylene, propylene, C5-C10 alpha-olefins, and combinations thereof; - a fraction (A2) comprising a copolymer of butene- 1 with from 3% to 10% by weight, based on the weight of fraction (A2), of a comonomer selected from ethylene, propylene, C5-C10 alpha-ol efins and combinations thereof, wherein the butene- 1 copolymer (A) has:

- a total copolymerized comonomer content of from 0.5% to 8.0% by weight, preferably from 0.7% to 7.0% by weight, based on the total weight of fractions (Al) and (A2)„

- a melt flow rate MFR(I) measured according to ISO 1133-1:2011 (190°C, 2.16kg) equal to or greater than 200 g/lOmin; and

- a content of fraction soluble in xylene at 0°C equal to or less than 80% by weight, preferably ranging from 20% to 80% by weight, based on the total weight of fractions (Al) and (A2) and determined with the method described in the example section, and wherein the comonomer content is determined by IR Spectroscopy.

6. The hot melt adhesive composition according to claim 5, wherein the butene-1 copolymer (A) comprises from 15% to 70% by weight, in particular from 20% to 65%, by weight of fraction (Al) and from 30% to 85% by weight, in particular from 35% to 80% by weight of fraction (A2), wherein the amounts of fractions (Al) and (A) are based on the total weight of fractions (Al) and (A2).

7. The hot melt adhesive composition according to claim 5 or 6, wherein the comonomer is ethylene.

8. The hot melt adhesive composition according to any one of the preceding claims, wherein the butene-1 copolymer (A) has at least one of the following features:

(a) a molecular weight distribution Mw/Mn lower than 4, preferably lower than 3; more preferably lower than 2.5, the lower limit being of 1.5 in all cases, where the molecular weight distribution is determined by NMR; and/or

(b) has one or more melting peaks Tm(II) at temperatures equal to or lower than 110°C, preferably equal to or lower than 105°C, more preferably ranging from 80° to 103°C, , where the Tm(II) is measured by DSC; and/or

(c) glass transition temperature (Tg) measured by DSC in the range from - 40°C to - 10°C, preferably from -30°C to -10°C; and/or

(d) Brookfield viscosity at 190°C lower than 15,000 mPa.s, preferably ranging from 3,000 to 15,000 mPa.s; and/or (e) X-ray crystallinity comprised in the range from 20 to 60%, preferably in the range from 25 to 50%;

(f) density in the range from 0.89 to 0.91 g/cm³; and/or

(g) yellowness index of less than 0; in particular ranging from -1 to -5.

9. The hot melt adhesive composition according to any one of the preceding claims, wherein the tackifier (B) is solid at a temperature of 25°±1°C and preferably has softening point greater than 100°C.

10. The hot melt adhesive composition according to any one of the preceding claims, wherein the polypropylene wax (C) has weight average molecular weight Mw, measured by GPC, equal to or lower than 10,000 g/mol, preferably equal to or lower than 8,000 g/mol, more preferably ranging from 3,000 to 7,000 g/mol and/or a molecular weight distribution Mw/Mn, measured by GPC, ranging from 3.0 to 6.0.

11. The hot melt adhesive composition according to any one of the preceding claims, wherein the polypropylene wax (C) has a drop melting point (DGF M-III 3, analogous to DIN 51801) of from 140°C to 157°C, preferably from 145° to 155°C.

12. The hot melt adhesive composition according to any one of the preceding claims further comprising a component (D) selected from plasticizers, olefin oligomers or low molecular weight polyolefins, amorphous poly-alpha-olefins different from polybutene- 1 component (A), thermoplastic polyurethanes, ethylene/(meth)acrylate copolymers, ethylene/vinyl acetate copolymers, and combinations thereof.

13. The hot melt adhesive composition according to claim 12, wherein the amount of component (D) ranges from 0% to 15% by weight, based on the total weight of the HMA composition.

14. The hot melt adhesive composition according to any one of the preceding claims further comprising from 0.05% to 5.0% by weight, based on total weight of the HMA composition, of an additive (E), preferably selected from antioxidants, light stabilizers and combinations thereof.

15. An article comprising a first substrate and a second substrate, wherein the first substrate is bonded to the second substrate by an hot melt adhesive composition according to any one of claims 1-14 interposed between the first and the second substrate.

16. The article according to claim 15, wherein the first and the second substrate are made of a material independently selected from wood, paper, cardboard, natural leather, plastic material, natural fibers, like cotton or hemp, and combinations thereof.

17. The article according to claim 15 or 16 wherein the first and the second substrate are independently selected from films, sheets, panels, woven fabrics and non-woven fabrics.

18. The article according to claim 15 wherein the first and the second substrate are made of paper or cardboard and the hot melt adhesive composition according to any one of claims 1-14 interposed between the first and the second substrate has rotational (Brookfield) viscosity at 180°C equal to or lower than 7,000 mPa.s, more preferably lower than 5,000 mPa.s, still more preferably lower than 2,000 mPa.s.