Polyolefin-based hot melt adhesive composition

Abstract

The present disclosure provides a hot melt adhesive composition comprising: (A) 35-65 wt% of a blend comprising a first butene-1 polymer having MFR(1) ranging from 200 to less than 800 g / 10min and a second butene-1 polymer having MFR(2) ranging from 800 to 1,800 g / 10min, wherein MFR(1) and MFR(2) are measured according to ISO 1133-1:2011 (190°C, 2.16kg); (B) 10-30 wt% of a tackifier; (C) 10-30 wt% of a wax; and (D) 5-20 wt% of a plasticizer, wherein the amounts of components (A), (B), (C) and (D) are based on the total weight of the hot melt adhesive composition.

Description

TITLEPOLYOLEFIN-BASED HOT MELT ADHESIVE COMPOSITIONFIELD OF THE INVENTION

[0001] The present disclosure relates to a polyolefin-based hot melt adhesive (HMA) composition, in particular a polyolefin-based HMA composition including a combination of high melt flow butene polymers having different melt flow rates, tackifiers, waxes and plasticizers.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 their fast-setting properties, ease of use, and strong bonding capabilities, like in packaging industry, woodworking, product assembly, crafts, textiles, etc.

[0003] Hot Melt Adhesive (HMA) 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 compositions in some technical fields, such as food packaging.

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

[0005] 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 at ambient temperature, like ca. 25°C.

[0006] In the field of packaging it is felt the need of HMA compositions showing good adhesion properties not only at room temperature, but also at low temperatures, like below 0°C, e.g. for packaging of temperature-sensitive products which are stored, transported and handled at low temperatures.

[0007] The Applicant surprisingly found that an HMA composition based on butene polymers having different melt flow rates, in combination with tackifiers, waxes and plasticizers show excellent adhesion properties at low temperatures.

[0008] HMA compositions including poly-alpha-olefins with different melt flow rates are known from US2008190541A1, disclosing HMA compositions containing at least two metallocene-based poly-alpha-olefin copolymers, the copolymers differing from each other for the melt flow indices. HMA compositions including blends of ethylene-octene copolymers are exemplified and show good adhesion properties at 20°C. The patent document is silent about the adhesion properties of the compositions at low temperatures.

[0009] 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, said hot melt adhesive composition also showing good adhesion properties at low temperatures, like below 0°C.SUMMARY OF THE INVENTION

[0010] The present disclosure refers to a hot melt adhesive composition comprising:

[0011] (A) from 35% to 65% by weight of a blend comprising a first butene-1 polymer having MFR(l) ranging from 200 to less than 800 g / lOmin and a second butene-1 polymer having MFR(2) ranging from 800 to 1,800 g / lOmin, wherein MFR(l) and MFR(2) are measured according to ISO 1133-1 :2011 (190°C, 2.16kg);

[0012] (B) from 10% to 30% by weight of a tackifier;

[0013] (C) from 10% to 30% by weight of a wax; and

[0014] (D) from 5% to 20% by weight of a plasticizer,

[0015] wherein the amounts of components (A), (B), (C) and (D) are based on the total weight of the hot melt adhesive composition.

[0016] The polyolefin-based hot melt adhesive composition of the present disclosure is endowed with a good open / setting time balance, in combination with good mechanical properties, SAFT and softening properties, as evidenced by the values of the ring and ball test.

[0017] Additionally, the hot melt adhesive composition of the present disclosure shows excellent adhesion properties at low temperatures, like below 0°C. For this reason are particularly suitable for assembling articles, like packaging materials, intended for use at low temperatures.

[0018] Accordingly, in a second 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.

[0019] 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

[0020] In the context of the present disclosure:

[0021] - Hot Melt Adhesive compositions are sometimes referred to as HMA compositions;

[0022] - the percentages are expressed by weight, unless otherwise specified;

[0023] - the total weight of a polymer composition sums up to 100% by weight, unless otherwise specified;

[0024] - 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’;

[0025] - 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;

[0026] - 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;

[0027] - a cardboard is a thick and sturdy packaging material usually made by layering and compressing multiple sheets together. Cardboard can be made from various types of fibers, e.g. natural fibers, including paper and recycled paper, or synthetic fibers, like polyethylene fibers. Cardboard can be a composite or a laminated material, like plasticized cardboard.

[0028] In a first aspect, the present disclosure provides a hot melt adhesive (HMA) composition comprising:

[0029] (A) from 35% to 65% by weight, preferably from 45% to 55% by weight, of a blend comprising a first butene-1 polymer having MFR(l) ranging from 200 to less than 800 g / lOmin and a second butene-1 polymer having MFR(2) ranging from 800 to 1,800 g / lOmin, wherein MFR(l) and MFR(2) are measured according to ISO 1133-1 :2011 (190°C, 2.16kg);

[0030] (B) from 10% to 30%, preferably from 15% to 25% by weight, by weight of a tackifier;

[0031] (C) from 10% to 30% by weight, preferably from 15% to 25% by weight, of a wax; and

[0032] (D) from 5% to 20% by weight, preferably from 7% to 17% by weight, of a plasticizer,

[0033] wherein the amounts of components (A), (B), (C) and (D) are based on the total weight of the hot melt adhesive composition.

[0034] The individual components (A), (B), (C) and (D) of the HMA compositions are defined in greater detail below. The individual components may be comprised in the HMA composition in any combination.

[0035] In one embodiment, component (A) is a blend consisting of the first butene-1 polymer and the second butene-1 polymer as described below.

[0036] Preferably, the component (A) comprises or consists of:

[0037] - from 30% to 70% by weight, preferably from 40% to 60% by weigh, more preferably from 45% to 55% by weigh, of the first butene-1 polymer and

[0038] - from 70% to 30% by weight, preferably from 60% to 40% by weigh, more preferably from 55% to 45% by weigh, of the second butene-1 polymer,

[0039] wherein the amounts of the first and the second butene-1 polymer are based on the weight of the component (A).

[0040] Preferably, the MFR(l) of the first butene-1 polymer ranges from 300 to 700 g / lOmin, preferably from 400 to 650 g / lOmin (ISO 1133-l :2011;190°C, 2.16kg).

[0041] Preferably, the MFR(2) of the second butene-1 polymer ranges from 1,000 to 1,700 g / lOmin, preferably from 1,300 to 1,600 g / lOmin (ISO 1133-l :2011;190°C, 2.16kg).

[0042] In a particularly preferred embodiment both MFR(l) and MFR(2) are comprised in the ranges indicated above.

[0043] Preferably, each one of the first butene-1 polymer and the second butene-1 polymer is a copolymer of butene-1 with at least one comonomer independently selected from ethylene,propylene, C5-C10 alpha-olefins and combinations thereof, each one of the first and the second butene-1 polymer having a total comonomer content of from 0.5% to 8.0% by weight, preferably from 3.0% to 7.5% by weight, more preferably from 4.5% to 7.0% by weight, based on the weight of the respective butene-1 copolymer. The total comonomer content is determined via IR spectroscopy as described in the experimental section.

[0044] Preferably, each one of the first and the second butene-1 polymer contains a comonomer independently selected from ethylene, propylene, hexene- 1, octene- 1 and combinations thereof, ethylene being particularly preferred.

[0045] Preferably, each one of the first butene-1 polymer and the second butene-1 polymer is a butene-1 composition (I) comprising:

[0046] (Al) a butene-1 homopolymer or copolymer of butene-1 with a comonomer selected from ethylene, propylene, C5-C10 alpha-olefins and combinations thereof, having a copolymerized comonomer content (CAI) of less than 3.0% by weight, preferably from 0.1% to less than 3.0% by weight, based on the weight of (Al), a butene-1 homopolymer being particularly preferred; and

[0047] (A2) a copolymer of butene- 1 with a comonomer selected from ethylene, propylene,C5-C10 alpha-olefins and combinations thereof, having a copolymerized comonomer content (CA2) of from 3.0% to 10% by weight, based on the weight of (A2),

[0048] wherein the butene-1 copolymer composition (I) has:

[0049] - a total copolymerized comonomer content of from 0.5% to 8.0% by weight, based on the total weight of the butene-1 copolymer composition (I), and

[0050] - a fraction soluble in xylene, determined at 0°C with the method described in the experimental section, equal to or less than 80% by weight, based on the total weight of the butene-1 copolymer composition (I), the lower limit being 60% by weight.

[0051] The comonomer content of (Al) and (A2), and the total comonomer content is determined via IR spectroscopy as described in the experimental section.

[0052] Preferably, the copolymer of butene-1 (A2) contains a comonomer selected from ethylene, propylene, hexene- 1, octene- 1 and combinations thereof, ethylene being particularly preferred.

[0053] In a preferred embodiment, the butene-1 copolymer composition (I) comprises or consists of from 10% to 50% by weight, in particular from 15% to 40% by weight, of component (Al) and from 90% to 50% by weight, in particular from 85% to 60% by weight, of component (A2), wherein the amounts of components (Al) and (A2) are based on the total weight of the butene-1 copolymer composition (I).

[0054] Preferably, the first butene- 1 polymer and the second butene- 1 polymer are a butene- 1 copolymer composition (I) endowed with one or more features independently selected from:(a) a molecular weight distribution (Mw / Mn) measured by GPC with the method described in the experimental section lower than 4, preferably lower than 3; more preferably lower than 2.5, the lower limit being of 1.5 in all cases; and / or(b) a weight average molecular weight Mw measured by GPC with the method described in the experimental section equal to or greater than 30,000 g / mol, preferably ranging from 30,000 to 100,000 g / mol, more preferably from 40,000 to 70,000 g / mol; and / or(c) at least one melting peak Tm(II) measured by DSC with the method described in the experimental section at a temperature equal to or lower than 110°C, preferably equal to or lower than 100°C, more preferably ranging from 80° to 100°C; and / or(d) glass transition temperature (Tg) measured by DMTA with the method described in the experimental section in the range from - 40°C to - 10°C, preferably from -32°C to -10°C; and / or(e) Brookfield viscosity (BV) measured at 190°C with the method described in the experimental section lower than 15,000 mPa.s, preferably ranging from 3,000 to 15,000 mPa.s; and / or(f) X-ray crystallinity determined by XDPD with the method described in the experimental section comprised in the range 25-60%, preferably in the range 35-60%;(g) density (ISO 1183-1 / A) in the range from 0.89 to 0.91 g / cm3; and / or(h) yellowness index (ASTM D1925) of less than 0; in particular ranging from -1 to -5; and / or(i) flexural modulus (ISO 178) ranging from 50 to 120 MPa.

[0055] In a further preferred embodiment, the first butene- 1 polymer and the second butene- 1 polymer are a butene- 1 copolymer composition (I) endowed with all the features (a)- (i) above.

[0056] The first and the second butene- 1 polymers are preferably obtained by polymerizing butene- 1, and optionally the comonomer, in the presence of a catalyst system obtainable by contacting:

[0057] - a stereorigid metallocene compound;

[0058] - an alumoxane or a compound capable of forming an alkyl metallocene cation; and optionally but preferably

[0059] - an organo-aluminum compound.

[0060] The patent applications W02004 / 099269 and W02006 / 045687, which are herein incorporated by reference, describe a process and a catalysts system suitable for producing the first and the second butene- 1 polymer.

[0061] The first and the second butene- 1 polymer are preferably 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.

[0062] 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.

[0063] When butene- 1 copolymers are prepared, preferably 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.

[0064] The butene-1 copolymer composition (I) is preferably obtained by a polymerization process comprising at least two polymerization stages, carried out in at least two reactors connected in series. For the preparation of component (Al) the amount of the optional comonomer in the liquid phase preferably ranges from 0% to 1.2% by weight, and the amount of comonomer in the liquid phase of the second stage preferably ranges from 1% to 10% by weight for the preparation of component (A2).

[0065] In particular, the butene-1 copolymer composition (I) is obtainable as described in patent applications W02018 / 007280A1 and W02020 / 016143A1, which also are herein incorporated by reference.

[0066] The hot melt adhesive composition of the present disclosure comprises at least one tackifier (B). The tackifier (B) is preferably solid at ambient temperature, like at a temperature of 25°±l°C.

[0067] The tackifier (B) is preferably selected among hydrogenated hydrocarbon resins and derivatives thereof, like aliphatic hydrocarbon resins, aromatic hydrocarbon resins andaliphatic / aromatic hydrocarbon resins; terpene-derived resins, like polyterpenes and terpene / phenolic resins; natural resins and natural resin esters, like rosin, rosin ester and tall oil rosin ester; and combinations thereof. Preferably, the tackifier (B) is an hydrogenated hydrocarbon resin, more preferably a cycloaliphatic hydrocarbon resin.

[0068] In a preferred embodiment, the tackifier (B) has a softening point greater than 100°C.

[0069] 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.

[0070] The HMA composition of the present disclosure further comprises a wax (C) preferably selected is selected from the group consisting of polyolefin waxes; natural waxes, like mineral waxes, animal waxes and vegetal waxes; petroleum waxes, like paraffin waxes; synthetic waxes, like Fischer-Tropsch waxes; naphthalene waxes, and combinations thereof, Fischer-Tropsch waxes being particularly preferred.

[0071] The HMA composition of the present disclosure further comprises a plasticizer (D) preferably selected from the group consisting of plasticizing oils, like mineral oils; low molecular weight polyolefins, like low molecular weight polybutene; and combinations thereof, wherein low molecular weight polyolefins are preferred.

[0072] Among low molecular weight polyolefins low molecular weight polybutene is particularly preferred.

[0073] In the context of the present disclosure by “low molecular weight polyolefin” it is meant a polyolefin, particularly polybutene, having molecular weight Mn measured by GPC not greater than 6,000 g / mol, preferably not greater than 4,000 g / mol, more preferably not greater than 3,000 g / mol, still more preferably not greater than 2,500 g / mol. Preferably, the lower limit for the molecular weight Mn is 200 g / mol.

[0074] Preferably, the plasticizer (D) is a polybutene having molecular weight Mn measured by GPC not greater than 6,000 g / mol and / or a Brookfield viscosity (BV) measured at 190°C with the method described in the experimental section lower than 100 mPa.s.

[0075] In a further preferred embodiment, the plasticizer (D) is a polybutene having one or more of the following properties, preferably all:

[0076] - is selected from isobutylene / butene-1 copolymers, blends of polyisobutylene(PIB) with polybutene- 1 (PB) and combinations thereof, isobutylene / butene-1 copolymers being preferred; and / or

[0077] - molecular weight Mn measured by GPC with the method described in the experimental section not greater than 4,000 g / mol, preferably not greater than 3,000 g / mol, more preferably not greater than 2,500 g / mol; more preferably the molecular weight Mn is greater than 200 g / mol; and / or

[0078] - Mw / Mn not greater than 2.5, preferably not greater than 2.0, wherein Mw and Mn are determined by GPC with the method described in the experimental section; and / or

[0079] - Brookfield viscosity (BV) measured at 190°C with the method described in the experimental section lower than 100 mPa.s, preferably lower than 50 mPa.s, more preferably ranging from 1 to 100 mPa.s; and / or

[0080] - kinematic viscosity at 100°C not greater than 14,000 cSt, preferably not greater than 5,000 cSt, more preferably not greater than 1,000 cSt (ASTM D 445).

[0081] Optionally but preferably, the HMA composition of the present disclosure 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.

[0082] Preferably, the HMA composition of the present disclosure has one or more of the following properties, preferably all:

[0083] - a rotational Brookfield viscosity (BV) measured at 140°C with the method described in the experimental section equal to or lower than 7,000 mPa.s, preferably equal to or lower than 5,000 mPa.s; and / or

[0084] - a rotational Brookfield viscosity (BV) measured at 180°C with the method described in the experimental section equal to or lower than 5,000 mPa.s, preferably equal to or lower than 3,000 mPa.s, more preferably equal to or lower than 2,000 mPa.s; and / or

[0085] - a setting time measured with the method described in the experimental section equal to or lower than 0.6 s, preferably equal to or lower than 0.5 s; and / or

[0086] - an open time measured with the method described in the experimental section in the range of from 40 to 150 seconds; and / or

[0087] - tensile stress at yield measured with to the method described in the experimental section ranging from 1.20 to 0.60 MPa; and / or

[0088] - Ring & Ball softening point measured with to the method described in the experimental section ranging from 100 to 110°C, preferably from 102 to 107°C; and / or

[0089] - Shear Adhesion Failure Temperature (SAFT) measured with to the method described in the experimental section ranging from 70 to 90°C, preferably from 75 to 85°C.

[0090] The HMA composition of the present disclosure shows a good balance of adhesive and mechanical properties, in combination with good adhesion properties at low temperatures, like temperatures below 0°C.

[0091] In a second 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.

[0092] In a preferred embodiment, said the first and the second substrate are made of cardboard, preferably polyethylene cardboard or plasticized cardboard.

[0093] In a further preferred embodiment, the article of the second aspect is a packaging material.

[0094] The HMA composition of the present disclosure is prepared by known methods and equipment, like blending of the component in the molten state in a single- or twin screw extruder.

[0095] The features describing the subject matter of the present disclosure are not inextricably linked to each other. Hence, preferred ranges of a feature may be combined with more or less preferred ranges of a different feature, independently from their level of preference.

[0096] The following examples are illustrative only, and are not intended to limit the scope of the invention in any manner whatsoever.EXAMPLES

[0097] CHARACTERIZATION METHODS: the following methods are used to determine the properties indicated in the description, claims and examples.

[0098] Melt flow rate (MFR) was measured according to ISO 1133-1 :2011 (190°C, 2.16kg, except where different load and temperatures are specified).

[0099] Comonomer content (wt.%) measured via IR spectroscopy.

[0100] 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'1which is used for spectrometric normalization of film thickness;b) factor of subtraction (FCRc?) 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).

[0101] APPARATUSA 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.

[0102] METHOD

[0103] Calibration of (BEB + BEE) sequencesA 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.

[0104] Calibration of EEE sequencesA calibration straight line is obtained by plotting %(EEE)wt vs. Ac2, block / At. The slope GH and the intercept In are calculated from a linear regression.

[0105] Sample preparationUsing 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.

[0106] ProcedureThe 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.

[0107] CALCULATIONCalculate the concentration by weight of the BEE + BEB sequences of ethylene units:, . FCRC2%(BEE + BEB)wt = Gr + IrtCalculate 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 + %(EEE)wt]

[0108] Mn and 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 10'4dL / g and KPB = 1.78 x 10'4dL / 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.

[0109] 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:^EB= XE^PE ”f XBKpB

[0110] where KEB is the constant of the copolymer, KPE (4.06 x 10'4, dL / g) and KPB (1.78 x 10'4dL / g) are the constants of polyethylene (PE) and PB, xEand xBare the ethylene and the butene weight relative amount with xE+ xB= 1. The Mark-Houwink exponents a = 0.725 was used for all the butene / ethylene copolymers independently on their composition. Endprocessing 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.

[0111] 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:

[0112] - Tm(II) (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);

[0113] - 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).

[0114] 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 aviscoelastic 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 EZE" = tan (5) vs temperature.

[0115] 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).

[0116] 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).

[0117] Crystallinity was measured by X-Ray diffraction with an X-ray Diffraction Powder Diffractometer (XDPD) that uses the Cu-Kal 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; and5) Calculate the degree of crystallinity of the sample using the following formula:%Cr = lOO x Ca / Ta

[0118] 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 at 25°±1°C.

[0119] Fractions soluble and insoluble in xylene at 0°C: 2.5 g of polymer composition and 250 cm3of 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 cm3of 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 (%).

[0120] Sample preparation for determining tensile properties. Bring a 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. Allowto cool to 23±1°C. After 24 hours cut a standard dumbbell-shaped test specimens, with the following dimensions:

[0121] Condition the test specimens for at least 24h at 23 °C and reconfirm the thickness using a micrometer.

[0122] Tensile stress and elongation at yield. In a dynamometer, set the separation speed of 60 mm / min and elongation limit of 300 mm. Grip the compression molded 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 stress-strain 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.

[0123] Flexural modulus: determined according to ISO 178:2019 on compression molded plaques. 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.

[0124] Yellowness index. Determined according to ASTM D1925.

[0125] 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.

[0126] 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 / m2isused 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.

[0127] 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.

[0128] 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 / m2bonded 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.

[0129] Fiber tear: 70x50mm test specimens are used for testing. “PE carboard” is a cardboard with a polyethylene coating on one surface, and “Plasticized cardboard” is a carboard with a polyester coating on one surface. Test specimen are prepared by applying a uniform layer of 10x50 mm of adhesive molten at 180°C onto the plastic surface of a first cardboard by a spray gun with a pressure of Ibar. After a time span of 1 second (hold time), the carboard surface a second cardboard is bonded to the plastic surface by pressing for 1 second with a pressure of 0.8bar. The test specimens are conditioned for 24h at constant temperature andhumidity of 50%. After conditioning, the second cardboard is manually pulled perpendicular to the first cardboard. The seal fracture is visually inspected, and the degree of fiber tear is determined by comparing the surface of the fractured seal retaining fibers of the pulled cardboard, with respect to the entire surface of the fractured seal. The higher the fiber tear, the more effective is the adhesive. The joint is acceptable if there are more than 50% fibers on the fractured adhesive surface.

[0130] RAW MATERIALS

[0131] 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.

[0132] FT wax: KHWAX QP 115H by King Honor International Ltd.

[0133] Plasticizer: Indopol H300 marketed by Ineos, is a polybutene having molecular weight Mn of 1,300 g / mol, Mw / Mn of 1.65 a kinematic viscosity of 605-655 cSt at 100°C (ASTM D 445).

[0134] 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.

[0135] Preparation of the catalytic solution: Under nitrogen atmosphere, 6400 g of a 33 g / L solution of triisobutylaluminium (TIB A) 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:

[0136] 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.

[0137] PB(1) was prepared according to Example 1 of W02020 / 016143A1 and PB(2) prepared according to the polymerization process described in W02020 / 016143A1, in the following conditions:Table 1

[0138] The butene- 1 copolymers were recovered as melt from the solution and cut in pellets. The copolymers were further characterized and the data are reported in Table 2.Table 2

[0139] Preparation of the hot melt adhesive compositions: components were melt at 175°C in a aluminum can in a melter, and mix in the molten state at 175°C using small mixer IKA RW20 with stirring bar, operated at 200rpm for 2h.

[0140] Example El and comparative examples CE2-CE3

[0141] Hot melt adhesive compositions 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

[0142] The HMA compositions of example El and comparative examples CE2 and CE3 were tested for fiber tear after 24h conditioning at different temperatures. Test results are reported in Table 4.Table 4

Claims

CLAIMSWhat is claimed is:

1. A hot melt adhesive composition comprising:(A) from 35% to 65% by weight, preferably from 45% to 55% by weight, of a blend comprising a first butene-1 polymer having MFR(l) ranging from 200 to less than 800 g / lOmin and a second butene-1 polymer having MFR(2) ranging from 800 to 1,800 g / lOmin, wherein MFR(l) and MFR(2) are measured according to ISO 1133-1 :2011 (190°C, 2.16kg);(B) from 10% to 30%, preferably from 15% to 25% by weight, by weight of a tackifier;(C) from 10% to 30% by weight, preferably from 15% to 25% by weight, of a wax; and(D) from 5% to 20% by weight, preferably from 7% to 17% by weight, of a plasticizer, wherein the amounts of components (A), (B), (C) and (D) are based on the total weight of the hot melt adhesive composition.

2. The hot melt adhesive composition according to claim 1, wherein the MFR(l) of the first butene-1 polymer ranges from 300 to 700 g / lOmin, preferably from 400 to 650 g / lOmin (ISO 1133-l :2011;190°C, 2.16kg).

3. The hot melt adhesive composition according to any one of the preceding claims, wherein the MFR(2) of the second butene-1 polymer ranges from 1,000 to 1,700 g / lOmin, preferably from 1,300 to 1,600 g / lOmin (ISO 1133-l :2011;190°C, 2.16kg).

4. The hot melt adhesive composition according to any one of the preceding claims, wherein the component (A) comprises:- from 30% to 70% by weight, preferably from 40% to 60% by weigh, more preferably from 45% to 55% by weigh, of the first butene-1 polymer and- from 70% to 30% by weight, preferably from 60% to 40% by weigh, more preferably from 55% to 45% by weigh, of the second butene-1 polymer, wherein the amounts of the first and the second butene-1 polymer are based on the weight of the component (A).

5. The hot melt adhesive composition according to any one of the preceding claims, wherein each one of the first butene- 1 polymer and the second butene- 1 polymer is a copolymer of butene- 1 with at least one comonomer independently selected from ethylene, propylene, C5-C10 alpha-olefins and combinations thereof, having a total comonomer content of from 0.5% to 8.0% by weight, preferably from 3.0% to 7.5% by weight, more preferably from 4.5% to 7.0% by weight, based on the weight of the respective butene- 1 copolymer.

6. The hot melt adhesive composition according to any one of the preceding claims, wherein each one of the first butene- 1 polymer and the second butene- 1 polymer is a butene- 1 composition (I) comprising:(Al) a butene-1 homopolymer or copolymer of butene- 1 with a comonomer selected from ethylene, propylene, C5-C10 alpha-olefins and combinations thereof, having a copolymerized comonomer content (CAI) of less than 3.0% by weight, based on the weight of (Al), a butene-1 homopolymer being preferred; and(A2) a copolymer of butene-1 with a comonomer selected from ethylene, propylene, C5- C10 alpha-olefins and combinations thereof, having a copolymerized comonomer content (CA2) of from 3.0% to 10% by weight, based on the weight of (A2), wherein the butene-1 copolymer composition (I) has:- a total copolymerized comonomer content of from 0.5% to 8.0% by weight, based on the total weight of the butene-1 copolymer composition (I), and- a fraction soluble in xylene measured at 0°C with the method described in the experimental section equal to or less than 80% by weight, based on the total weight of the butene-1 copolymer composition (I).

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 claim 6 or 7, wherein the butene-1 copolymer composition (I) comprises from 10% to 50% by weight, in particular from 15% to 40% by weight, of component (Al) and from 90% to 50% by weight, in particular from 85% to 60% by weight, of component (A2), wherein the amounts of components (Al) and (A2) are based on the total weight of the butene-1 copolymer composition (I).

9. The hot melt adhesive composition according to any one of claims from 6 to 8, wherein the first butene- 1 polymer and the second butene- 1 polymer are a butene- 1 copolymer composition (I) endowed one or more features selected from:(a) a molecular weight distribution (Mw / Mn) measured by GPC with the method described in the experimental section lower than 4, preferably lower than 3; more preferably lower than 2.5, the lower limit being of 1.5 in all cases; and / or(b) a weight average molecular weight Mw measured by GPC with the method described in the experimental section equal to or greater than 30,000 g / mol, preferably ranging from 30,000 to 100,000 g / mol; and / or(c) at least one melting peak Tm(II) measured by DSC with the method described in the experimental section at a temperature equal to or lower than 110°C, preferably equal to or lower than 100°C, more preferably ranging from 80° to 100°C; and / or(d) glass transition temperature (Tg) measured by DMTA with the method described in the experimental section in the range from - 40°C to - 10°C, preferably from -32°C to - 10°C; and / or(e) Brookfield viscosity (BV) measured at 190°C with the method described in the experimental section lower than 15,000 mPa.s, preferably ranging from 3,000 to 15,000 mPa.s; and / or(f) X-ray crystallinity determined by XDPD with the method described in the experimental section comprised in the range 25-60%, preferably in the range 35-60%;(g) density (ISO 1183-1 / A) in the range from 0.89 to 0.91 g / cm3; and / or(h) yellowness index (ASTM D1925) of less than 0; in particular ranging from -1 to -5; and / or(i) flexural modulus (ISO 178) ranging from 50 to 120 MPa.

10. 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 is preferably selected among hydrogenated hydrocarbon resins and derivatives thereof, terpene-derived resins, natural resins and natural resin esters, and combinations thereof, hydrogenated hydrocarbon resin being preferred.

11. The hot melt adhesive composition according to any one of the preceding claims, wherein the wax (C) is selected among polyolefin waxes, natural waxes, petroleum waxes,Fischer-Tropsch waxes, naphthalene waxes, and combinations thereof, Fischer-Tropsch waxes being preferred.

12. The hot melt adhesive composition according to any one of the preceding claims, wherein the plasticizer (D) is selected from plasticizing oils, polyolefins having molecular weight Mn measured by GPC not greater than 6,000 g / mol, and combinations thereof, wherein polyolefins having molecular weight Mn measured by GPC not greater than 6,000 g / mol are preferred.

13. The hot melt adhesive composition according to any one of the preceding claims, wherein the plasticizer (D) is a polybutene having molecular weight Mn measured by GPC not greater than 6,000 g / mol and / or a Brookfield viscosity (BV) measured at 190°C with the method described in the experimental section lower than 100 mPa.s.

14. The hot melt adhesive composition according to any one of the preceding claims having one or more the following properties:- a rotational Brookfield viscosity measured at 140°C with the method described in the experimental section equal to or lower than 7,000 mPa.s, preferably equal to or lower than 5,000 mPa.s; and / or- a rotational Brookfield viscosity measured at 180°C with the method described in the experimental section equal to or lower than 5,000 mPa.s, preferably equal to or lower than 3,000 mPa.s, more preferably equal to or lower than 2,000 mPa.s; and / or- a setting time measured with the method described in the experimental section equal to or lower than 0.6 s, preferably equal to or lower than 0.5 s; and / or- an open time measured with the method described in the experimental section equal to or greater than 50 s, preferably equal to or greater than 70 s.

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 cardboard, preferably polyethylene cardboard or plasticized cardboard.

17. The article according to claim 15 or 16 being a packaging material.

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