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WO2025017406A1 - Adhésifs thermofusibles présentant des propriétés optimisées pour l'application par extrusion - Google Patents

Adhésifs thermofusibles présentant des propriétés optimisées pour l'application par extrusion Download PDF

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Publication number
WO2025017406A1
WO2025017406A1 PCT/IB2024/056475 IB2024056475W WO2025017406A1 WO 2025017406 A1 WO2025017406 A1 WO 2025017406A1 IB 2024056475 W IB2024056475 W IB 2024056475W WO 2025017406 A1 WO2025017406 A1 WO 2025017406A1
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WO
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Prior art keywords
melt adhesive
adhesive formulation
hot melt
hot
formulation according
Prior art date
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PCT/IB2024/056475
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English (en)
Inventor
Alberto BUGANA
Italo Corzani
Original Assignee
Savare' I.C. S.R.L.
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Application filed by Savare' I.C. S.R.L. filed Critical Savare' I.C. S.R.L.
Publication of WO2025017406A1 publication Critical patent/WO2025017406A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J123/00—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J123/00—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers
    • C09J123/02—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers not modified by chemical after-treatment
    • C09J123/10—Homopolymers or copolymers of propene
    • C09J123/14—Copolymers of propene
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J123/00—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers
    • C09J123/02—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers not modified by chemical after-treatment
    • C09J123/18—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms
    • C09J123/20—Homopolymers or copolymers of hydrocarbons having four or more carbon atoms having four to nine carbon atoms
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
    • C08L2205/035—Polymer mixtures characterised by other features containing three or more polymers in a blend containing four or more polymers in a blend
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2314/00—Polymer mixtures characterised by way of preparation
    • C08L2314/06—Metallocene or single site catalysts

Definitions

  • the present invention relates to hot-melt adhesive formulations that , besides having excellent adhesive and cohesive properties , exhibit also an unexpected and greatly improved processability, which allows to apply them by extrusion, without any problem, even on industrial lines running at high speed (e . g . at 200 m/minute and more ) , both by slot-die coating and by spraying .
  • hot-melt adhesives comprise , as their basic component ( s ) , a thermoplastic polymer or a mixture of thermoplastic polymers , blended with various additives , like tackifiers and plasticisers . And it is also well known that , even in those cases when the polymer or the mixture of polymers constitutes only a minor fraction of the whole adhesive formulation, even lower than e . g . 50% by weight , the characteristics and properties of the polymer or of the mixture of polymers always play the most important role in determining all the main properties of the final adhesive formulation .
  • hot-melt adhesives are processed and applied in the molten state , usually at a temperature ranging from about 130 ° C to about 170 ° C, by substantially utilising two types of processes of application which anyhow both require an extrusion in the molten state of the adhesive :
  • extrusion processes as more in general many other processes of extrusion at high temperature, are both not specific just for hot-melt adhesives , but they are commonly utilised for processing by extrusion many other thermoplastic pure polymers or polymeric mixtures also for other various final uses .
  • Patent Applications US 2021 /0115303 e US 2022 /0135845 are both, first of all , highlighting the fact that the "die build-up" or "blobbing" phenomenon on the extrusion die or in its vicinity, is a problem of very high severity, with many very negative consequences , mainly in processing hot- melt adhesives by slot-die coating; and that this harmful phenomenon may appear very quickly, just within a few minutes , or even less , from the starting of the extrusion, in particular on industrial lines running at high speed, such as 200 m/minute or more , as e . g . are the industrial lines used to manufacture hygienic absorbent articles .
  • US 2021 /0115303 claims to be able to solve this problem of "blobbing"/"die build-up" in slot-die coating/extrusion even on high speed lines , by formulating hot- melt adhesives in such a way that they comprise a mixture of at least three polymers , whose peak molecular weights Mp fall into three well defined ranges : a first polymer with Mp lower than 40 , 000 g/mole ; a second polymer with Mp greater than 40 , 000 g/mole; and a third polymer with Mp in the range from 70 , 000 g/mole to 700 , 000 g/mole .
  • US 2022 /0135845 claims to be able to avoid said greatly negative phenomenon in extrusion, by still formulating a hot-melt adhesive composition that comprises three polymers : in this case the first polymer is a metallocenic polymer having Mp lower than 130 , 000 g/mole; the second polymer is a polyolefin with Mp in the range from 130 , 000 g/mole to 700 , 000 g/mole; and the third polymer is an amorphous polyolefin having an Enthalpy of Crystallisation of less than 10 J/g .
  • the very peculiar above mentioned rheological experiment measures the speed at which the Elastic Modulus G' of the polymer or of the mixture of polymers is increasing, at a certain constant temperature and after the application of a fixed shear-stress , compared with the speed at which the Elastic Modulus G' of the same polymer or mixture of polymers is increasing at the same temperature , but without the application of any shear-stress .
  • this rather unusual rheological text for predicting the possible presence in extrusion of a build-up phenomenon, is carried out at a reference temperature equal to 80 ° C .
  • this reference temperature represents the average temperature at which an extruded hot-melt adhesive formulation is , in about the first five centimeters of distance from the extrusion die , immediately after its extrusion . While this assertion is certainly true in general terms for a ma jority of cases in hot- melt processing, however it is also necessary to notice that in an even larger ma j ority of cases a reference temperature equal to 80 ° C is typically also below the setting temperature of most hot-melts , as it occurs also e . g . for all the three Examples according to the invention shown by WO 2023007257 itself , which all have a Ring & Ball Softening Point well above 80 °C .
  • the inventors of the present invention have done by selecting the reference temperature of 150 ° C (a typical average extrusion temperature for the great ma jority of hot-melt adhesives ) for measuring the Relaxation Time t r of the various adhesives as a predictor of the presence or absence of die build-up phenomena at the moment of their extrusion, as it will be also explained below in more details .
  • Said fouling phenomenon caused by a film of semi-molten adhesive , which has been already extruded and coated on perforated substrates , even in a regular shape , is , as said, a totally dif ferent phenomenon than the "die build-up" described and solved in the present invention and which is completely unrelated to it .
  • the die build-up phenomenon described herein is a fully chaotic event which occurs exclusively on the extrusion die and during the extrusion itself , and that causes , as said, strong unevennesses and inhomogeneities in the thickness and coated area of the film of extruded adhesive when it is coated on any type of substrates , both perforated and not perforated ones .
  • the problem that the present invention aims at solving is to teach how to formulate hot-melt adhesives that do not exhibit during extrusion, and especially in slot-die coating, the highly negative phenomenon known as “die drool” or “die build-up” or also “blobbing” , and other similar phenomena that cause a very irregular and inhomogeneous flow in extrusion .
  • the hot-melt adhesives according to the present invention exhibit an optimum and improved processability, even on industrial lines running at high speed, like 200 m/minute and more , although utilising standard slotdies and without modifying too much the basic parameters of the process , like the temperature of the extrusion tool .
  • the temperature can be kept at its optimum value, typical of a certain hot-melt adhesive , without causing further problems ensuing from its variation; like e . g . damages of thermo-sensitive substrates , in the case that the temperature is increased too much, or possible issues in extrusion due to a too high viscosity, if on the contrary the temperature is decreased .
  • the inventors of the present invention have surprisingly found that this highly improved processability in extrusion, that in particular fully avoids all die build-up phenomena and other similar phenomena of irregular and inhomogeneous extrusion, is achieved by formulating the hot-melt adhesive composition in such a way that one of its rheological parameters , i . e . its rheological Relaxation Time at 150 ° C, a parameter which is widely known by any person who has an average expertise in the field of hot-melt adhesives and of their Rheology, and which is often indicated with the symbol t r , is not lower than 0 . 5 ms . Said rheological parameter can be easily measured for every hot-melt adhesive formulation by the simple method which is described in detail below .
  • thermoplastic polymeric systems including hot-melt adhesives
  • thermoplastic polymeric systems in general show in the molten state a viscoelastic behaviour
  • the rheological Relaxation Time t r is a parameter which is characteristic of any polymer and of any polymeric composition, like hot-melt formulations . More specifically, this rheological parameter is defined as the characteristic time with which a certain polymer or polymeric composition is able to dissipate ( e . g .
  • the rheological Relaxation Time of the hot-melt adhesive formulations disclosed herein is , as said, expressed in seconds ( s ) and is measured, according to the method described below, at the reference temperature of 150 °C .
  • the choice of this reference temperature for the rheological Relaxation Time of the present thermoplastic adhesives has been suggested by the following considerations : the operating range of temperatures for the extrusion die most frequently used on industrial lines that process hot-melt adhesives , usually ranges from about 130 ° C to about 170 ° C .
  • the hot-melt adhesive formulations disclosed herein exhibit also an optimum adhesive strength, expressed e . g . by a Peel Strength, measured according to the method described below, that is not lower than 1 . 0 N/50 mm at the very low basis weight of just 1 . 5 g/m 2 .
  • This excellent adhesive strength is not only an essential requirement for any good adhesive , but , in a certain sense, it is also an indirect evidence that the extrusion of the present adhesives on a substrate has occurred without any "die build-up" , in a way that is as much as possible smooth .
  • the first negative consequence of a "die build-up" phenomenon, in the processing by extrusion of a hot-melt adhesive is an unacceptable decrease of the overall observed adhesive strength .
  • the film of adhesive, extruded on the substrate is grossly uneven and inhomogeneous , with areas where the adhesive is present in very low amounts or is fully absent , and, on the contrary, areas where rare big lumps of adhesive are gathering, usually already heavily degraded for their prolonged residence at high temperature on the hot metal of the extrusion die .
  • the inventors of the present invention have furthermore discovered that , at least in the case of hot-melt adhesives "at high viscosity" (as this attribute is defined below, i . e . for adhesives showing a Brookfield viscosity at 150 °C, conventionally not lower than 3 , 500 mPa . s ) , it is preferable that the hot-melt formulations which have a rheological Relaxation Time t r , measured at 150 ° C, not lower than 0 .
  • the facility with which the polymeric chains may be aligned under the shear stress inside the extrusion-die and may produce a "premature crystallisation" even in the still molten state depends certainly on many other parameters of the polymeric material , besides the system' s melt viscosity . E . g . it depends certainly on the structure of these polymeric chains , in the sense that , at a certain viscosity of the molten system, structurally linear and regular polymeric chains can be certainly aligned ( and therefore produce this very negative premature crystallisation) much more easily than highly branched polymeric chains .
  • the additional and optional requirement of having a Zero Shear Viscosity Etao at the Reference Temperature of 150 °C which is not not too low and preferably not lower than 4 , 000 mPa . s , may only help in avoiding die build-up phenomena especially for highly viscous systems which comprise polymers with very linear and regular chain structures .
  • the problem that the present invention aims at solving can be considered certainly solved in an optimum and unexpectedly effective way by hot-melt adhesives which exhibits the characteristics of claim 1 ) and of the claims from 2 ) to 23 ) ; by a bonded structure which exhibits the characteristics of claim 24 ) ; and by an article which shows the characteristics of claims from 25 ) to 32 ) .
  • the other sub-claims disclose preferred embodiments .
  • polymer ( s ) is used herein according to the definition given in the document issued by ECHA - European Chemical Agency - edition of December 2017 - and titled "How to decide whether a substance is a polymer or not and how to proceed with the relevant registration” .
  • a polymer any chemical substance that contains more than 50% by weight of “polymeric molecules” ; where said “polymeric molecules” are in turn defined as those molecules that contain at least three base units (monomeric ones or more complex ) that are bound to a fourth unit , that can be equal or different from the first three units .
  • said polymeric molecules contain in total at least four base units , that can be monomeric units or more complex ones (when e . g . the base unit is , in its turn, composed by two or more monomers as it happens in condensation polymers ) .
  • oligomer ( s ) means herein a chemical substance that contains more than 50% by weight of “oligomeric molecules” ; where said “oligomeric molecules” contain less than three base units (monomeric ones or more complex) bound to another unit that can be equal or different from the first three units .
  • oligomer ( s ) comprises both oligomeric molecules formed by just one type of base units / monomer (homo-oligomer) as well as by multiple different types ( co-oligomer ) .
  • homopolymer ( s ) is used herein according to the definition given by IUPAC ( International Union of Pure and Applied Chemistry ) in the article “Glossary of Basic Terms in Polymer Science”, published in “Pure and Applied Chemistry", Vol . 68 , No . 12 , pp . 2287-231 1 , 1996 . Therefore , the expression “homopolymer ( s ) " means herein a polymer that is synthesised from just one type of monomer .
  • copolymer ( s ) means in the present invention (unless it is specifically indicated a different meaning) not only a polymer in the chemical composition of which two dif ferent monomers are used, but also polymers in the chemical composition of which three , four, five or more dif ferent monomers are used .
  • the expressions "bipolymer" when one wants to emphasize the number of different comonomers that constitute a certain copolymer, one can also use, as an alternative , the expressions "bipolymer”,
  • this definition comprises all the materials that not only may be defined as “liquid” (both at high and low viscosity ) according to the common meaning of this adj ective , but also all those materials that , in the common language, are for example defined as “creamy”, “pasty”, “ j elly-like” , “ fluid” , “greasy”, “semisolid” and the like .
  • the "Rheological Setting Point" Tx identifies , in particular, the temperature at which the hot-melt adhesive, when applied in the molten state on a substrate, starts to form the final adhesive bond in the solid state .
  • the Dynamic Viscosity of a molten or liquid material at a certain temperature is expressed in mPa . s and it is measured according to the Method ASTM D 3236 - 88 ( 2014 ) . In particular, this Method teaches to measure the parameter that , in the technology of hot-melt adhesives , is generally referred to as the "Brookfield viscosity" of the adhesive .
  • the Enthalpy of Fusion, Enthalpy of Crystallisation and the Glass Transition Temperature of a certain material are herein measured by Dif ferential Scanning Calorimetry (DSC ) . All these DSC measurements , both in crystallisation cycles , i . e . in decreasing temperature , and in fusion cycles , i . e . in increasing temperature , are herein performed according to the method ASTM D 3417 - 99 . Said cycles are performed between + 180 ° C and - 70 ° C ( or vice versa) , with a rate of change of temperature (both in increasing and decreasing temperature ) that is equal to 10 ° C / minute .
  • the Peak Temperature of the peak which has the largest area, and hence the greatest Enthalpy is defined herein as "Temperature of the Fusion Peak” for the material or "Temperature of the Crystallisation Peak” of the material .
  • the overall value of the Fusion Enthalpy or of the Crystallisation Enthalpy is calculated as the sum of all the peaks of fusion or of crystallisation which have been detected by DSC .
  • the Enthalpies of Crystallisation and of Fusion are expressed in J/g and are given by the area ( calculated by integration) of the peak or by the sum of the areas of the peaks detected during the DSC cycles .
  • Room temperature if not specifically defined in a dif ferent way, means a temperature equal to 23 °C; and "room conditions” means the conditions of an environment at a controlled temperature and relative humidity, equal to 23 ° C and 50% relative humidity .
  • all rheological parameters measured for the present invention e . g . the Elastic Modulus G' of a material , are measured at the frequency of 1 Hz, in a rheological test in decreasing temperature, between 170 ° C and - 20 °C, at a decreasing rate for the temperature equal to 3 °C / minute .
  • a certain property "at Time Zero” (for example , an Elastic Modulus G' at Time Zero ) , that may also be called as an "initial” property, or a property “in the initial conditions” , means that said property is measured at 23 °C (unless a dif ferent temperature is specifically indicated) and at 50% relative humidity, and at a time that is not longer than 120 minutes from the solidification of the material under test from the molten state .
  • a certain property that is e . g . "aged at five days” or “at five days” or “in aged conditions” means that said property is measured at 23 ° C (unless a different temperature is specifically indicated) and at 50% relative humidity, after five days from the solidification from the molten state of the material under test . During these five days of aging the material under test is kept in a climatic room, at 23 ° C and 50% relative humidity .
  • the Yield Stress is defined as the stress at the Yield Point .
  • the Toughness of a certain material is numerically expressed by the whole area under the Stress - Elongation curve , calculated by integration . It measures the specific energy that is required to mechanically break a certain material and it is expressed in MJ/m 3 .
  • the rheological and tensile properties as well as the curve Stress - Elongation are herein measured with a rotational Rheometer Ares G2 , supplied by TA Instruments .
  • a rotational Rheometer Ares G2 , supplied by TA Instruments .
  • said rheometer is equipped with an accessory tool called Extensional Viscosity Fixture (EVF ) .
  • EVF Extensional Viscosity Fixture
  • the rheometer is equipped also with a controlled temperature space (FCO ) that allows to perform tests at a controlled and fixed temperature between - 50 ° C and + 250 ° C .
  • FCO controlled temperature space
  • the tested material is extruded, by a lab-coater for hot melt adhesives, at the temperature of 160°C, on silicone paper as a continuous strip having a width of 50 mm and a thickness of 0.2 mm.
  • the extruded adhesive is aged for five days in a climatic room at 23°C and 50% relative humidity before performing the test. After five days of aging, the samples for the test, with a length of 100 mm each are cut from this continuous strip of aged adhesive. Said samples are tested by using the EVF tool at the temperature of 23°C (or at a different temperature, as specified) and at the rotation frequency of the extension-roll equal to 0.01 turn / s, i.e. at the frequency of 0.01 Hz.
  • Open Time of an adhesive refers , especially for a hot- melt adhesive , to the interval of time during which, after its application from the melt on a first substrate , the adhesive is able to form sufficiently strong adhesive bonds for the intended use, with a second substrate that is brought into contact under moderate pressure with the first one . It is evident that too short open times may make dif f icult-to-manage the application of an adhesive and the formation of suf ficiently strong bonds .
  • the open time of a holt-melt adhesive may be measured according to the test method ASTM D 4497 - 94 , under the following conditions for the hot-melt adhesives disclosed herein :
  • Ring & Ball Softening Point or “Ring & Ball Softening Temperature” refer to the softening temperature of a material , measured according to the Method ASTM D 36 - 95 .
  • the Softening Point (known in this case also as “Dropping Point” or as “Drop Melt Point” ) is measured according to the Method ASTM D 3954 - 94 .
  • the overall Adhesive Strength or "Peel Strength” is defined as the average strength per unit of width needed to separate two substrates , bonded by the adhesive under test . It is measured through a separation test made at a controlled and constant speed, and under a controlled and constant de-bonding angle . It is herein measured according to the Method ASTM D 1876 - 01 , separating the two substrates under a de-bonding angle of 180 degrees , by applying a separation speed of the two substrates equal to 150 mm/minute, that means that the testing dynamometer is actually moving at a speed of 300 mm/minute .
  • the two substrates used herein are a polyethylene film, with a basis weight of 15 g/m 2 , supplied by Poligof ( Italy ) , that is glued to a polypropylene non-woven with a basis weight of 12 g/m 2 , supplied by Union Industries ( Italy) .
  • the adhesive under test is melted at 150 ° C and it is then applied by slot-die coating on the non-woven substrate at a basis weight of 1 . 5 g/m 2 and immediately put into contact and adhered with the polyethylene film .
  • the bonded laminates are then aged for five days in a climatic room kept at 23 ° C and 50% relative humidity . At the end of such aging, the samples are tested for their Peel Strength . This measurement is made by recording the strength needed for separating the two glued substrates on a width of 50 mm, according to the recommendations of the above mentioned ASTM method, and working at 23 ° C and 50% relative humidity .
  • Hygienic absorbent articles refers to devices and/or methods concerning disposable absorbing and nonabsorbing articles , that comprise diapers and undergarments for incontinent adults , baby diapers and bibs , training pants , infant and toddler care wipes , feminine catamenial pads , interlabial pads , panty liners , pessaries , sanitary napkins , tampons and tampon applicators , wound dressing products , absorbent care mats , detergent wipes , and the like .
  • the Zero Shear Viscosity of a polymeric system is herein expressed in mPa . s and it is measured, according to the method described below, at the reference temperature of 150 ° C, for the reasons that have been already explained .
  • This rheological parameter is also indicated with the symbol Etao .
  • polymeric systems have, in their molten state or in solution, a behaviour which is strongly viscoelastic/non- newtonian .
  • the great ma jority of these systems exhibit a pseudo-plastic behaviour, i . e .
  • the Zero Shear Viscosity Etao of the hot-melt adhesives disclosed herein, or of their related polymers is measured according to the following method: the hot-melt adhesive formulation under test is placed between two parallel plates, with a diameter of 25 mm, of a Rheometer Ares - G2 supplied by TA Instruments, equipped with an ECT oven for heating the sample, and with a cooling system suitable for rapid cooling. The material is heated and melted at 180°C. Then it is conditioned at this temperature for 300 s, applying during all this conditioning period a shear rate equal to 1 s(-l) .
  • This initial heating up to the temperature of 180°C and the following conditioning at said temperature for 300 s, are aimed at deleting the possible memory of the "thermal history" of the sample, by bringing the material into its fully amorphous form, destroying all the crystals that may have formed during the previous thermal treatments . In this way every material undergoing the test has the same "thermal history" as all the other samples.
  • the conditioning step ends the material is analysed in a way that allows to measure its Zero Shear Viscosity at the reference temperature of 150°C.
  • EXP (-7) Hz to 159 Hz) EXP (-7) Hz to 159 Hz) .
  • the Zero Shear Viscosity is identified as the asymptotic value (plateau) to which the viscosity tends, in the field of the lowest frequencies, as the frequency of the applied Shear Stress tends to zero.
  • high viscosity or “at high viscosity” mean in particular hot- melt formulations or related polymers or blends of polymers that have a Brookfield viscosity, measured at 150°C according to the Method ASTM D 3236 - 88 (2014) , which is not lower than 3,500 mPa . s .
  • the hot-melt adhesive formulations according to the present invention have an optimum and strongly improved processability compared to the present status of the art .
  • they can be easily processed and applied by a slotdie extrusion coating process , even at high or very high line speed, e . g . 200 m/minute and more , without showing the very harmful phenomenon known with the names of "die drool” or “die build-up” or also "blobbing" .
  • the hot-melt adhesive formulations according to the present invention exhibit : a rheological Relaxation Time t r not lower than 0 . 5 ms , when measured at 150 °C according to the herein described method; a Brookfield viscosity at 150 ° C ranging from 500 mPa . s to 150 , 000 mPa . s .
  • the present hot-melt adhesive formulations comprise , as their fundamental component , from 5% by weight to 100% by weight , and preferably from 10% by weight to 95% by weight , of a polymer (which can be either a homopolymer or a copolymer) or of a mixture of two or more polymers (which individually can be both homopolymers or copolymers ) and which are mutually compatible .
  • Tackifiers are also components of the hot . melt adhesives according to the present invention.
  • the hot-melt adhesive formulations that are disclosed herein also comprise at least one tackifying resin, which has a Ring & Ball softening temperature ranging from 5 ° C to 160 °C .
  • the tackifiers comprised in the hot-melt formulations of the present invention can be selected from aliphatic hydrocarbon resins and their partially or totally hydrogenated derivatives ; aromatic hydrocarbon resins and their partially or totally hydrogenated derivatives ; aliphatic- aromatic hydrocarbon resins and their partially or totally hydrogenated derivatives ; polyterpene and modified terpene resins and their partially or totally hydrogenated derivatives ; rosins ( colophonies ) , their esters and their partially or totally hydrogenated derivatives ; and mixtures thereof . It has been moreover discovered that it is preferable that the tackifying resins used in the hot-melt adhesives of the present invention have a Ring & Ball softening temperature ranging from 50 ° C to 155 °C .
  • tackifying resins that are highly purified and which contain an extremely low quantity of impurities and of volatile monomeric compounds , such as xylene, toluene, hexene , vinyl-toluene , indene etc . , monomers that contribute to the generation of malodours in the finished product and to the decrease of the tackifier' s thermal stability .
  • volatile monomeric compounds such as xylene, toluene, hexene , vinyl-toluene , indene etc .
  • Said volatile compounds are analysed and quantified by ionic Gas-chromatography with head-space , by heating a sample of 2 g of the tested tackifier for 30 minutes at 190 °C and with a head-space of 20 ml .
  • tackifying resins which contain a quantity of volatile compounds not greater than 5 ppm (parts per million ) , preferably not greater than 2 ppm and even more preferably not greater than 1 ppm are particularly preferred .
  • Industrial examples of similar tackifying resins at a very low level of volatile impurities are the tackifiers sold by Synthomer (USA) under the trade mark UltraPure .
  • hot-melt adhesive formulations comprise at least one tackifying resin or a mixture of tackifying resins
  • they comprise from zero to 75% by weight of at least one tackifying resin or of a mixture of tackifying resins , preferably from 10% by weight to 70% by weight and more preferably from 20% by weight to 65% by weight, referred to the whole hot-melt adhesive formulation.
  • the present hot-melt adhesive formulations comprise also at least one plasticiser which is not solid at room temperature, i.e. at the temperature of 23°C, or of a mixture of plasticisers which are not solid at room temperature. Said plasticisers further lower the melt viscosity of the molten adhesive compositions and increase their tackiness.
  • the plasticisers which are not solid at room temperature and the mixtures of plasticisers which are not solid at room temperature, and that can be used in the hot-melt adhesives of the present invention, are selected, for example, from paraffinic mineral oils and naphthenic mineral oils and mixtures thereof; paraffinic and naphthenic hydrocarbons which are not solid at room temperature, and mixtures thereof; polyolefin oligomers which are not solid at room temperature, and copolymers thereof, such as oligomers derived from ethene, propene, butene, iso-butylene, copolymers thereof, and mixtures thereof; plasticizers which are not solid at room temperature formed by esters, such as phthalates, benzoates, sebacates, citrates; natural and synthetic fats; vegetable oils; and mixtures thereof.
  • Said PAO plasticisers are fully saturated and can have a substantially paraf finic structure , both linear and branched .
  • Synthetic poly- alpha-olefins not solid at room temperature , usable as plasticisers in the present invention are manufactured and sold e . g . by ExxonMobil with the trade marks SpectraSyn and Elevast ; by Ineos with the trade mark Durasyn, by Chevron Phillips with the trade mark Synfluid etc .
  • the herein disclosed hot-melt adhesive formulations comprise at least one plasticiser which is not solid at room temperature or a mixture of plasticisers which are not solid at room temperature
  • the adhesives disclosed herein comprise from zero to 50% by weight of said plasticiser or mixture of plasticisers , preferably from 5% by weight to 40% by weight and even more preferably from 10% by weight to 35% by weight , referred to the whole hot-melt adhesive formulation .
  • the present hot-melt adhesive formulations comprise also at least one wax or a mixture of waxes , natural or synthetic ones , which have a dropping point , measured according to the method ASTM D 3952- 94 , ranging from 40 °C and 170 °C .
  • Waxes that can be used in the present invention are for example , synthetic hydrocarbon waxes , such as paraffinic waxes , and especially waxes synthesised from olefins from C2 to CIO and their blends ; hydrocarbon waxes from C12 to C40 , even in their variants modified with carboxylic/acidic or with alcoholic groups ; copolymer waxes synthesised from ethene and maleic anhydride or from propene and maleic anhydride; Fischer-Tropsch waxes ; waxes formed by esters of fatty acids from C12 to C40 ; natural waxes like beeswax, carnauba wax, montan wax and the like ; and mixtures thereof .
  • synthetic hydrocarbon waxes such as paraffinic waxes , and especially waxes synthesised from olefins from C2 to CIO and their blends
  • hydrocarbon waxes from C12 to C40 even in their variants modified
  • hot-melt adhesive formulations comprise at least one wax or a mixture of waxes , they comprise from zero to 20% by weight , preferably from zero to 10% by weight of said wax or mixture of waxes , referred to the whole hot-melt adhesive formulation .
  • Other additional components
  • the hot-melt adhesive formulations according to the present invention can furthermore comprise from 0 . 01% by weight to 10% by weight of at least one stabiliser, such as antioxidants , anti-UV photo-stabilisers , and mixtures thereof .
  • at least one stabiliser such as antioxidants , anti-UV photo-stabilisers , and mixtures thereof .
  • they can also further comprise up to a maximum of about 15% by weight of other optional additional components , such as mineral fillers , pigments , dyes , perfumes , surfactants , antistatic agents , and mixtures thereof .
  • additional components such as mineral fillers , pigments , dyes , perfumes , surfactants , antistatic agents , and mixtures thereof .
  • the rheological Relaxation Time t r of a polymer or of a polymeric composition/f ormulation, such as a hot-melt adhesive formulation is herein defined, as already mentioned, as that characteristic time that is needed by said polymer or polymeric composition/f ormulation for dissipating (e . g . by internal molecular frictions and by heat ) the energy received from an external force , in this way returning to its primitive equilibrium state .
  • said rheological Relaxation Time t r expressed in seconds ( s ) , is herein measured at the reference temperature of 150 °C, for the already explained reasons , and according to the following method .
  • the hot-melt adhesive formulation under test is placed between two parallel plates , with a diameter of 25 mm, of a Rheometer Ares - G2 supplied by TA Instruments , equipped with an ECT oven for heating the sample, and with a cooling system suitable for rapid cooling .
  • the material is heated up to 180 ° C and melted . Then it is conditioned at this temperature for 300 s , applying during all this conditioning time a shear rate equal to 1 s (-l ) .
  • This initial heating up to the temperature of 180 °C and the following conditioning at said temperature for 300 s are aimed at deleting the possible memory of the "thermal history" of the sample , by bringing the material into its fully amorphous form, destroying all the crystals that may have formed during the previous thermal treatments. In this way every material undergoing the test has the same "thermal history” like all the other samples .
  • the material is analysed in a way that allows to measure its main and characteristic rheological Relaxation Time t r at the reference temperature of 150°C.
  • TTS Time-Temperature Superposition Principle
  • WLF Williams-Landel-Ferry
  • the measurement method for the rheological Relaxation Time is simpler than it can initially appear.
  • the method used herein is also clearly explained in details e.g. in the article "Basic principles and good practices of rheology for polymers for teachers and beginners", by H. Ramsi et alii, published in "Chemistry Teacher International" 2022; 4 (4) : pages 307-326.
  • the tested material undergoes a series of "Frequency Sweeps" in a range of frequencies from 0.01 rad/s and 200 rad/s (i.e.
  • this zone of the curve is the one that relates to the "terminal relaxation" of the material ; i . e . it is the zone of frequencies in which a viscoelastic material (like the adhesive polymeric formulations disclosed herein ) is ideally behaving like a "Maxwell fluid" .
  • the curve that represents the Viscous Modulus G' ' tends to an asymptotic value , with a slope equal to 1 ; while the curve that represents the Elastic Modulus G' tends to another asymptotic value , with a slope equal to 2 .
  • the frequency of that crossing point of the two rheological Moduli is the characteristic frequency at which the tested material is relaxing; and the inverse of that frequency gives directly the value of the main rheological Relaxation Time t r for the polymeric material under test .
  • the die build-up or die drool phenomenon i . e . a chaotic accretion of extruded material on the extrusion die, is to be absolutely avoided, because it leads to highly negative consequences during the application process of the adhesives , as well as on the adhesive strength that is achievable and on the quality of the final products (gross unevenness of the coated adhesive layer; absence of the adhesive in various areas of the substrate ; presence of big lumps of adhesive in other areas ; fouling of the line etc . ) .
  • the presence or absence of the die build-up phenomenon for the hot-melt adhesives of the present invention is herein qualitatively assessed, operating under conditions which reproduce the typical operating conditions of the production lines of hygienic absorbent articles .
  • the presence or absence of this phenomenon in the extrusion of the tested adhesives is assessed by coating a polypropylene nonwoven substrate , with a basis weight of 12 g/m 2 , supplied by Union Industries ( Italy ) .
  • the tested adhesive is extruded by slotdie at the temperature of 150 ° C and coated on the mentioned nonwoven at a basis weight of 1 . 5 g/m 2 .
  • the presence at a significant level ( or the absence ) of the die build-up phenomenon is checked visually, by observing the possible accretion of extruded material nearby the extrusion die .
  • the following hot-melt adhesive formulation according to the present invention has been prepared by mixing its components in the molten state at 170 ° C .
  • the hot-melt formulation of Example 1 comprises , as its only polymeric component , Vistamaxx 6902 , which is a metallocene copolymer of propene with 12% by weight of ethene . It is believed to have a Weight Average Molecular Weight Mw of about 95,000 g/mole.
  • the basic polymer has been plasticised with Primol 352, a paraffinic mineral oil with a Weight Average Molecular Weight Mw equal to 480 g/mole.
  • Vistamaxx 6902 has been also tackified with Regalite R 1100, a hydrogenated hydrocarbon tackifying with a Ring & Ball softening point of 100°C.
  • the above hot-melt adhesive exhibits, at the reference temperature of 150°C, a rheological Relaxation Time t r , measured according to the previously described method, equal to 2.29 ms, and a Brookfield viscosity at 150°C, equal to 4,410 mPa.s. It exhibits also a Brookfield viscosity at 170°C equal to 1,950 mPa.s.
  • the following hot-melt adhesive formulation according to the present invention has been prepared by mixing its components in the molten state at 170°C.
  • the hot-melt formulation of Example 2 comprises one polymer that, in this case, is plasticised with a liquid oligomer. More precisely, the polymer is the styrenic block copolymer Europrene SOL T 9113, which is a Styrene-Isoprene- Styrene block copolymer with a content of styrene of 18% b.w. and a Weight Average Molecular Weight Mw that is believed to be about 142,000 g/mole.
  • the plasticising oligomer is Indopol H-300, which is a liquid poly-iso-butene (PIB) oligomer with a Weight Average Molecular Weight Mw equal to 2,150 g/mole .
  • PIB liquid poly-iso-butene
  • Example 2 The adhesive formulation of Example 2 has been tackified with Escorez 5400, a hydrogenated cycloaliphatic hydrocarbon tackifying resin that has a Ring & Ball softening temperature of 104.3°C.
  • the hot-melt adhesive of Example 2 has a rheological Relaxation Time t r , measured at 150°C according to the previously described method, equal to 2.10 ms, and a Brookfield viscosity at 150°C, equal to 3, 970 mPa.s. Its Brookfield viscosity at 170°C is equal to 1,860 mPa.s.
  • the following hot-melt adhesive formulation according to the present invention has been prepared by mixing its components in the molten state at 170°C.
  • the adhesive formulation of Example 3 comprises a mixture of three polymers which are all metallocene semi-crystalline copolymers of propene with minor amounts of ethene .
  • the other two polymers are Vistamaxx 8380 which is also a C3-C2 copolymer with a C2 content of 12% by weight and that is believed to have a Weight Average Molecular Weight Mw equal to about 43 , 000 g/mole; and Vistamaxx 6502 that has a C2 content of 13% by weight and that is believed to have a Weight Average Molecular Weight Mw equal to about 115 , 000 g/mole .
  • the mixture of polymers is tackified with Regalite R 1100 , a hydrogenated hydrocarbon tackifier with a Ring & Ball softening temperature of 100 ° C) ; and it is also plasticised with the paraf finic mineral oil Primol 352 .
  • the adhesive formulation of this Example 3 When tested for its rheological Relaxation Time at 150 °C, the adhesive formulation of this Example 3 , according to the present invention, exhibits a t r equal to 0 . 91 ms . At the same temperature of 150 ° C, this hot-melt adhesive has a Brookfield viscosity of 6, 600 mPa.s. Its Brookfield viscosity at 170°C is equal to 3,240 mPa.s.
  • the hot-melt adhesive of the present Example 3 can be processed by extrusion in slot-die coating, even at the line speed of 250 m/minute without showing any trace of die build-up, even after 15 minutes of continuous running of the line.
  • This excellent processability is indirectly confirmed also by the strong value of the adhesive Peel Strength achieved by this formulation, peel strength that, when tested according to the above described method, reaches the value of 2.1 N / 50 mm at the very low basis weight of just 1.5 g/m 2 .
  • the following hot-melt adhesive formulation according to the present invention has been prepared by mixing its components in the molten state at 170°C.
  • the hot-melt adhesive formulation disclosed in Example 4 comprises a mixture of three polymers as the previous Example 3.
  • the comprised polymers are all metallocene semi-crystalline copolymers of butene-1, with minor amounts of ethene.
  • Koattro PB M 1500M is supposed to contain about 6.0% by weight ethene and to have a Weight Average Molecular Weight Mw of about 45, 000 g/mole
  • Koattro PB M 8911M is supposed to contain about 4.0% by weight ethene and to have a Weight Average Molecular Weight Mw of about 93,000 g/mole
  • Koattro PB M 8510M is supposed to have a C2 content of also about 4.0 by weight and a Weight Average Molecular Weight Mw of about 130,000 g/mole.
  • this mixture of polymers is tackified with Regalite R 1100 and is plasticised with the paraffinic mineral oil Primol 352.
  • Example 4 Tested for its rheological Relaxation Time at 150°C, the formulation of Example 4 shows a Relaxation Time equal to 0.69 ms. At the same temperature of 150 °C this formulation has a Brookfield viscosity of 6,380 mPa.s. Its Brookfield viscosity at 170°C is equal to 3,060 mPa.s.
  • This hot-melt formulation of Example 4 can be extruded by slot-die coating even at high line speed, like 250 m/minute, with no trace at all of any die build-up even after 15 minutes of line running.
  • this hot-melt formulation exhibits an excellent adhesive behaviour, with a Peel Strength of 1.7 N / 50 mm, even at the low basis weight of 1.5 g/m 2 .
  • the following hot-melt adhesive formulation according to the present invention has been prepared, by mixing its components in the molten state at 170°C.
  • the hot-melt adhesive formulation disclosed in Example 5 comprises a mixture of as many as four metallocene polymers , said mixture being also plasticized with a semi-fluid metallocene oligomer of propene and ethene .
  • This oligomer which is not solid at room temperature , is Licocene PPA 330 , that is supposed to contain about 20 . 5% ethene and to have a Weight Average Molecular Weight Mw of about 6, 400 g/mole .
  • Example 5 The four polymers in Example 5 are first of all Vistamaxx 6902 and Vistamaxx 6502 , that have been already described in the previous Examples .
  • the hot-melt adhesive formulation of the present Example 5 comprises also Licocene PP 1302 and Licocene PP 3602 that are both metallocenic copolymers of propene with minor amounts of ethene .
  • Licocene 1302 is a C3-C2 copolymer which is supposed to have a Weight
  • Licocene 3602 is believed to have a Weight Average Molecular Weight Mw of about 45, 100 g/mole and a C2 content of about 8% by weight.
  • the above hot-melt adhesive exhibits, at the reference temperature of 150°C, a rheological Relaxation Time t r , measured according to the previously described method, equal to 1.24 ms, and a Brookfield viscosity at 150°C, equal to 7,860 mPa.s.
  • Said hot-melt formulation has also a Brookfield viscosity at 170°C equal to 4,120 mPa.s.
  • This formulation can be processed without any problem of die build-up even after 15 minutes of continuous extrusion on a line running at 250 m/minute; and when tested for its adhesive properties, it shows an optimum Peel Strength as high as 2.6 N / 50 mm, at the very low adhesive basis weight of 1.5 g/m 2 .
  • the following comparative hot-melt adhesive formulation has been prepared by mixing its components in the molten state at 170 °C.
  • Comparative Example 1 The hot-melt formulation of Comparative Example 1 is analogous to the previous Example 1 according to the invention. The main difference is that this comparative example comprises, as its only polymeric component, Vistamaxx 8380, that has been already described in the previous Example 3 according to the invention, as a substitute for Vistamaxx 6902.
  • the above comparative hot-melt adhesive shows, at the reference temperature of 150°C, a too low rheological Relaxation Time t r , measured according to the previously described method, being equal just to 0.15 ms; and it has a Brookfield viscosity at 150°C, equal to 2, 900 mPa.s. Its Brookfield viscosity at 170°C is equal to 1,530 mPa.s.
  • the hot-melt adhesive formulation of the Comparative Example 1 is processed very badly in extrusion.
  • this hot-melt exhibits a massive die build-up that is very evident just after less than 20 seconds of line running.
  • the following comparative hot-melt adhesive formulation has been prepared by mixing its components in the molten state at 170°C.
  • the hot-melt adhesive formulation disclosed in Comparative Example 2 has been prepared by following the teachings of a prior patent.
  • the results of the behaviour in extrusion of this hot-melt formulation have been very negative because, in the above described test for the assessment of build-up phenomena, this adhesive shows the presence of a massive die build-up that appears very visibly even just a few seconds after the starting of the extrusion .
  • the presence of such massive build-up is related to the fact that the present formulation of Comparative Example 2 , has a too low rheological Relaxation Time t r , at the reference temperature of 150 ° C . Indeed, from the previously described test for such parameter, its rheological Relaxation Time at 150 °C is just 0 . 28 ms .
  • the following comparative hot-melt adhesive formulation has been prepared by mixing its components in the molten state at 170 ° C .
  • Licocene 1602 is a metallocene C3-C2 copolymer which is supposed to have a Weight Average Molecular Weight Mw of about 25, 900 g/mole and a C2 content of about 10% by weight.
  • the hot-melt formulation of Comparative Example 3 has a Brookfield viscosity equal to 4, 610 mPa.s; while at 170°C the Brookfield viscosity is 2,440 mPa . s .
  • the following comparative hot-melt adhesive formulation has been prepared by mixing its components in the molten state at 170°C.
  • the hot-melt formulation of Comparative Example 4 is similar to the adhesive formulation shown in the previous Example 3 according to the present invention.
  • the main difference is the fact that in this comparative example Vistamaxx 6902 has been substituted by Vistamaxx 8880 which is a C3-C2 copolymer with a C2 content of 12% by weight and which is believed to have a Weight Average Molecular Weight Mw equal to about 27, 600 g/mole.
  • the present comparative formulation has a Brookfield viscosity at 150°C and at 170°V, which are respectively 5, 600 mPa, s and 2,970 mPa,s.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Adhesives Or Adhesive Processes (AREA)

Abstract

La présente invention concerne de nouvelles formulations adhésives thermofusibles qui, en plus de présenter d'excellentes propriétés en utilisation, telles qu'une adhérence optimale et une cohésion optimale, présentent également une aptitude au traitement inattendue et fortement améliorée, qui permet de les appliquer sans problème même sur des lignes fonctionnant à une grande vitesse, telle que 200 m/minute ou plus. En particulier, les présentes formulations adhésives thermofusibles ne présentent pas lors de l'extrusion, et notamment lors de l'extrusion en filière à fente, le phénomène très négatif connu sous le nom de "coulure de filière" ou "accumulation dans la filière" ou "formation d'amas (blobbing)" et autres phénomènes similaires qui provoquent en extrusion un écoulement inégal et non homogène de l'adhésif. Les inventeurs ont découvert de manière surprenante que des formulations adhésives thermofusibles qui ont un Temps de Relaxation rhéologique tr, mesuré à 150°C selon le procédé décrit ici, qui n'est pas inférieur à 0,5 ms, montrent, même lors de l'extrusion en filière à fente, une aptitude au traitement optimale qui est complètement exempte de tout phénomène d'accumulation dans la filière, même dans les conditions de fonctionnement les plus sévères de lignes d'application, fonctionnant à grande vitesse.
PCT/IB2024/056475 2023-07-19 2024-07-03 Adhésifs thermofusibles présentant des propriétés optimisées pour l'application par extrusion WO2025017406A1 (fr)

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Citations (6)

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US20060135694A1 (en) * 2004-12-17 2006-06-22 Vaughan Steven R Hot melt adhesive composition
EP2999760A1 (fr) * 2013-05-23 2016-03-30 Bostik, Inc. Adhésif thermofusible basé sur des homopolymères de polypropylène à bas point de fusion
US20190202188A1 (en) 2016-08-05 2019-07-04 Bostik, Inc. Method of reducing adhesive build-up on roller surfaces
US20210115303A1 (en) 2019-10-21 2021-04-22 The Procter & Gamble Company Hotmelt composition comprising three polymers having different peak molecular weights
US20220135845A1 (en) 2020-10-30 2022-05-05 The Procter & Gamble Company Tackified hotmelt adhesive composition
WO2023007257A1 (fr) 2021-07-27 2023-02-02 Savare' I.C. S.R.L. Formulations adhésives thermofusibles à aptitude au traitement améliorée en revêtement par filière droite plate

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Publication number Priority date Publication date Assignee Title
US20060135694A1 (en) * 2004-12-17 2006-06-22 Vaughan Steven R Hot melt adhesive composition
EP2999760A1 (fr) * 2013-05-23 2016-03-30 Bostik, Inc. Adhésif thermofusible basé sur des homopolymères de polypropylène à bas point de fusion
US20190202188A1 (en) 2016-08-05 2019-07-04 Bostik, Inc. Method of reducing adhesive build-up on roller surfaces
US20210115303A1 (en) 2019-10-21 2021-04-22 The Procter & Gamble Company Hotmelt composition comprising three polymers having different peak molecular weights
US20220135845A1 (en) 2020-10-30 2022-05-05 The Procter & Gamble Company Tackified hotmelt adhesive composition
WO2023007257A1 (fr) 2021-07-27 2023-02-02 Savare' I.C. S.R.L. Formulations adhésives thermofusibles à aptitude au traitement améliorée en revêtement par filière droite plate

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