Patent Application
20070117894
The present invention is described in the German priority application No. 102005055018.5, filed 18 Nov. 2005, which is hereby incorporated by reference as is fully disclosed herein.
The invention relates to hot melt compositions based on isotactic, low molecular mass, low viscosity homopolymer or copolymer waxes and atactic polyalpha-olefins (=APAOs), up to 40% by weight of isotactic homopolymer or copolymer wax and at least 60% by weight of atactic polyalpha-olefin being present in the hot melt compositions.
Hot melt compositions or hot melts are thermoplastic materials which are solid at ambient temperature and in the liquid melt state are applied layerwise to suitable substrate surfaces where, following solidification, they exert different functions. Their composition preferably comprises resins, waxes, thermoplastics, and elastomers, and they may optionally include further additions of fillers, pigments, and additives such as stabilizers, etc.
By way of example, hot melt compositions can be used as solvent-free adhesives for bonding. On account of their multifarious advantages, hot melt adhesives of this kind are increasingly being used in the production of products including hygiene articles and care articles and also in the paper, packaging, furniture, textiles, footwear, and construction industries as an economic and eco-friendly alternative to conventional, solvent-based adhesives.
Hot melt compositions are also used in road construction as thermoplastic binders for producing visual traffic guidance marks, such as “zebra stripes” at pedestrian crossings, center lines or boundary lines, or other signal indications for controlling traffic flow. Besides waxes, the binders employed for this purpose may additionally also comprise thermoplastics, resins, and plasticizers. For roadmarking application these binders are generally blended with fillers such as sand or lime, pigments such as titanium dioxide, and light-reflecting additions, e.g., glass beads.
Constituents of typical hot melt adhesive formulas are polar and apolar polymers, resins, and waxes.
The bond strength, which derives from the remanent, post-solidification adhesiveness of a pressure sensitive hot melt adhesive, depends on the one hand on the interaction of the adhesive with the substrate to which bonding is to take place, i.e., on the adhesion between pressure sensitive hot melt adhesive and substrate; in addition, however, the bond strength is also based on the cohesion (i.e., internal strength) of the pressure sensitive hot melt adhesive itself.
The polar and apolar polymers of the pressure sensitive hot melt adhesive serve as scaffold material. They ensure the cohesion of the adhesive and at the same time contribute to adhesion to the substrate. The resin addition enhances the adhesion and may promote compatibility between the various components of the adhesive. Waxes are used for modification in fractions, based on the hot melt adhesive compositions, of generally less than 10% by weight. They regulate important physical properties of the adhesives, such as hardness, melt viscosity, and softening point, and, in their effect on open time, adhesion, cohesion, etc., they decisively influence the performance characteristics. Use of wax in amounts of more than 10% by weight has generally been found to date to be accompanied by a deterioration in the properties, particularly a reduction in the bond strength of the hot melt adhesive.
EP 890 584 describes the preparation of propylene homopolymer waxes and propylene copolymer waxes by polymerization in the presence of metallocene as catalyst, and their use in hot melt compositions, among other systems, which essentially contain three components, a polymer, an adhesive component (tackifier), and a wax.
WO 2004/104128 discloses hot melt compositions containing as polyolefin wax copolymer waxes of propylene having 0.1% to 30% by weight of ethylene, and a fraction of 0.1% to 50% by weight of a branched or unbranched 1-alkene having 4 to 20 carbon atoms.
U.S. Pat. No. 5,397,843 describes hot melt compositions comprising high molecular mass ethylene-alpha-olefin copolymers and low molecular mass atactic polyalpha-olefins (APAOs).
US 2004/0115456 and US 2004/0081795 describe hot melt compositions containing 4% to 50% by weight of isotactic propylene copolymers and 20% to 65% by weight of an adhesive component (tackifier), examples being hydrocarbon resins, natural and modified resins, resin esters, and synthetic polyterpenes, and also, optionally, atactic polyalpha-olefins (APAOs), plasticizers, wax, stabilizers, filler material, and, optionally, a secondary polymer, examples being poly(meth)acrylates, etc. The hot melt composition examples set out in the two specifications comprise isotactic propylene copolymers with 1.5% to 20% by weight of ethylene or higher alpha-olefins, the copolymers having average molar masses Mw of between about 170 000 and 240 000 g/mol and number-average molar masses Mn of between about 60 000 and 80 000 g/mol. Such high molecular mass olefin polymers are plastic-like, of high viscosity to solid, and show very little, if any, adhesion. The hot melt compositions described in US 2004/0115456 and US 2004/0081795 contain, as well as isotactic propylene copolymers, 20% to 65% by weight of a tackifier. The use of such large amounts of tackifiers can, however, lead easily to corrosion, odor, and an adverse effect on operations of recycling products provided with hot melt compositions.
Suitable processing viscosities, sufficiently good initial adhesion, cohesion, adhesion to different surface materials, low-temperature and high-temperature stability, but also a sufficient measure of flexibility, tensile load and stretching load to which composite material and adhesive bond are subjected in their specified end use, are decisive features for the quality of hot melt compositions.
It was an object of the present invention to provide novel hot melt compositions which satisfy the very different performance requirements imposed on hot melt compositions in respect of adhesion, cohesion, melt viscosity, temperature stability, etc., which at the same time can be formulated and handled well, and which can be provided economically, i.e., inexpensively and on an industrial scale.
Completely surprisingly it has been found that this object is achieved through a specific combination of isotactic, low molecular mass, low-viscosity homopolymer or copolymer waxes with atactic polyalpha-olefins (APAOs).
Mixtures of atactic polyalpha-olefins (APAOs), which have a fraction of APAOs of 60% by weight or more, with isotactic, low molecular mass, low-viscosity homopolymer or copolymer waxes have a viscosity in the range of 500 to 10 000 mPa·s, preferably between 1000 and 5000 mPa·s, measured at a temperature of 170° C., can be applied easily to surfaces and exhibit very good cohesion.
The present invention provides hot melt compositions comprising
The invention preferably provides hot melt compositions comprising
Hot melt compositions further preferred in accordance with the invention comprise
In a further preferred embodiment of the invention the copolymer waxes present in the hot melt compositions originate from ethylene and at least one branched or unbranched 1-alkene having 3 to 20 carbon atoms, the amount of structural units from the one or more 1-alkenes having 3 to 20 carbon atoms in the copolymer waxes being from 0.1% to 30% by weight.
Hot melt compositions further preferred in accordance with the invention comprise
In a further preferred embodiment of the invention the polyolefin waxes present in the hot melt compositions are copolymer waxes of propylene and one or more further monomers selected from ethylene and branched or unbranched 1-alkenes having 4 to 20 carbon atoms, the content of structural units originating from ethylene in the copolymer waxes being from 0.1% to 30% by weight and the content of structural units originating from the one or more 1-alkenes having 4 to 20 carbon atoms in the copolymer waxes being from 0.1% to 50% by weight.
Hot melt compositions of the invention which are further preferred comprise homopolymer and/or copolymer waxes which have a number-average molar mass Mn of between 500 and 20 000 g/mol, more preferably between 800 and 10 000 g/mol, very preferably between 1000 and 5000 g/mol, and a weight-average molar mass Mw of between 1000 and 40 000 g/mol, more preferably between 1600 and 30 000 g/mol, and very preferably between 2000 and 25 000 g/mol.
In one preferred embodiment the hot melt compositions of the invention comprise
The atactic polyalpha-olefins (APAOs) used in accordance with the invention in hot melt compositions are predominantly amorphous and have a crystallinity of less than 30%, determined by DSC (differential scanning calorimetry). The APAOs employed may be homopolymers of propylene or copolymers of propylene with one or more alpha-olefins, examples being ethylene, 1-butene, 1-propene, 1-hexene, 1-heptene, and 1-octene. The weight-average molar mass Mw of the APAOs employed is in the range from 4000 to 150 000 g/mol, preferably between 10 000 and 100 000 g/mol. Their softening points are between 80 and 170° C., their glass transition temperatures Tg between −5 and −40° C.
Among the APAOs it is preferred to use propylene homopolymers, propylene-ethylene copolymers, propylene-1-butene copolymers, and propylene-ethylene-1-butene terpolymers. APAO polymers are obtainable under the trade names ®Eastoflex from Eastman Chemical Company, under the trade names ®Rextac from Huntsman Corporation or under the trade name ®Vestoplast from Degussa Corporation.
Resins available are aliphatic and cycloaliphatic hydrocarbons having softening points of 10 to 160° C., determined by ASTM method E28-58T. They may be prepared by polymerizing aliphatic and/or cycloaliphatic-olefins and diolefins. Likewise suitable are hydrogenated aliphatic and cycloaliphatic hydrocarbons from mineral oil, examples being the products obtainable from Eastman Chemical Company under the trade names Eastoflex, RegalREZ, Kristalex, Eastotac or Piccotac or from ExxonMobil Chemical Company under the name ®Escoreze.
Likewise suitable are aromatic hydrocarbons from petroleum and their hydrogenated derivatives, and also aliphatic/aromatic hydrocarbons from petroleum and their hydrogenated or acid-functionalized derivatives, aromatically modified cycloaliphatic resins and their hydrogenated derivatives, polyterpene resins having softening points between 110 and 140° C., which are prepared by polymerizing terpenes, pinene, for example, in the presence of a Friedel-Crafts catalyst, hydrogenated polyterpenes, copolymers and terpolymers of natural terpenes, examples being styrene/terpene, α-methylstyrene/terpene, and vinyltoluene/terpene. Additionally suitable are natural and modified rosins, especially resin esters, glycerol esters of tree resins, pentaerythritol esters of tree resins and tall oil resins, and their hydrogenated derivatives, and also phenol-modified pentaerythritol esters of resins, and phenol-modified terpene resins.
The hot melt compositions of the invention may further comprise polyolefin polymers, waxes, plasticizers, polar or apolar polymers, pigments, fillers, stabilizers and/or antioxidants.
The polyolefin waxes used in accordance with the invention are prepared using metallocene compounds of the formula I.
This formula also embraces compounds of the formula Ia
In formulae I, Ia and Ib, M1 is a metal from group IVb, Vb or VIb of the periodic system, examples being titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten, preferably titanium, zirconium or hafnium.
R1 and R2 are identical or different and are a hydrogen atom, a C1-C10, preferably C1-C3 alkyl group, especially methyl, a C1-C10, preferably C1-C3 alkoxy group, a C6-C10, preferably C6-C8 aryl group, a C6-C10, preferably C6-C8 aryloxy group, a C2-C10, preferably C2-C4 alkenyl group, a C7-C40, preferably C7-C10 arylalkyl group, a C7-C40, preferably C7-C12 alkylaryl group, a C8-C40, preferably C8-C12 arylalkenyl group, or a halogen atom, preferably chlorine atom.
R3 and R4 are identical or different and are a mononuclear or polynuclear hydrocarbon radical which together with the central atom M1 may form a sandwich structure. Preferably R3 and R4 are cyclopentadienyl, indenyl, tetrahydroindenyl, benzoindenyl or fluorenyl, it being possible for the parent structures to carry additional substituents or to be bridged with one another. It is also possible for one of the radicals R3 and R4 to be a substituted nitrogen atom, with R24 having the definition of R17 and being preferably methyl, tert-butyl or cyclohexyl.
R5, R6, R7, R8, R9, and R10 are identical or different and are a hydrogen atom, a halogen atom, preferably a fluorine, chlorine or bromine atom, a C1-C10, preferably C1-C4 alkyl group, a C6-C10, preferably C6-C8 aryl group, a C1-C10, preferably C1-C3 alkoxy group, a radical —NR162—, —SR16—, —OSiR163—, —SiR163— or —PR162—, in which R16 is a C1-C10, preferably C1-C3 alkyl group or C6-C10, preferably C6-C8 aryl group or else, in the case of radicals containing Si or P, is a halogen atom, preferably chlorine atom, or pairs of adjacent radicals R5, R6, R7, R8, R9, or R10 form a ring with the carbon atoms connecting them. Particularly preferred ligands are the substituted compounds of the parent structures cyclopentadienyl, indenyl, tetrahydroindenyl, benzoindenyl or fluorenyl.
R13 is
═BR17, ═AIR17, —Ge—, —Sn—, —O—, —S—, ═SO, ═SO2, ═NR17, ═CO, ═PR17 or ═P(O)R17, R17, R18, and R19 being identical or different and being a hydrogen atom, a halogen atom, preferably a fluorine, chlorine or bromine atom, a C1-C30, preferably C1-C4 alkyl, especially methyl, group, a C1-C10 fluoroalkyl, preferably CF3 group, a C6-C10 fluoroaryl, preferably pentafluorophenyl group, a C6-C10, preferably C6-C8 aryl group, a C1-C10, preferably C1-C4 alkoxy, especially methoxy group, a C2-C10, preferably C2-C4 alkenyl group, a C7-C40, preferably C7-C10 aralkyl group, a C8-C40, preferably C8-C12 arylalkenyl group or a C7-C40, preferably C7-C12 alkylaryl group, or R17 and R18, or R17 and R19, each form a ring together with the atoms connecting them.
M2 is silicon, germanium or tin, preferably silicon and germanium. R13 is preferably ═CR17R8, ═SiR17R18, ═GeR17R18—O—, —S—, ═SO, ═PR17 or ═P(O)R17.
R11 and R12 are identical or different and have the definition stated for R17. m and n are identical or different and denote zero, 1 or 2, preferably zero or 1, with m plus n being zero, 1 or 2, preferably zero or 1.
R14 and R15 have the definition of R17 and R18.
Examples of suitable metallocenes are:
bis(1,2,3-trimethylcyclopentadienyl)zirconium dichloride,
bis(1,2,4-trimethylcyclopentadienyl)zirconium dichloride,
bis(1,2-dimethylcyclopentadienyl)zirconium dichloride,
bis(1,3-dimethylcyclopentadienyl)zirconium dichloride,
bis(1-methylindenyl)zirconium dichloride,
bis(1-n-butyl-3-methylcyclopentadienyl)zirconium dichloride,
bis(2-methyl-4,6-diisopropylindenyl)zirconium dichloride,
bis(2-methylindenyl)zirconium dichloride,
bis(4-methylindenyl)zirconium dichloride,
bis(5-methylindenyl)zirconium dichloride,
bis(alkylcyclopentadienyl)zirconium dichloride,
bis(alkylindenyl)zirconium dichloride,
bis(cyclopentadienyl)zirconium dichloride,
bis(indenyl)zirconium dichloride,
bis(methylcyclopentadienyl)zirconium dichloride,
bis(n-butylcyclopentadienyl)zirconium dichloride,
bis(octadecylcyclopentadienyl)zirconium dichloride,
bis(pentamethylcyclopentadienyl)zirconium dichloride,
bis(trimethylsilylcyclopentadienyl)zirconium dichloride,
biscyclopentadienylzirconium dibenzyl,
biscyclopentadienylzirconium dimethyl,
bistetrahydroindenylzirconium dichloride,
dimethylsilyl-9-fluorenylcyclopentadienylzirconium dichloride,
dimethylsilylbis-1-(2,3,5-trimethylcyclopentadienyl)zirconium dichloride,
dimethylsilylbis-1-(2,4-dimethylcyclopentadienyl)zirconium dichloride,
dimethylsilylbis-1-(2-methyl-4,5-benzoindenyl)zirconium dichloride,
dimethylsilylbis-1-(2-methyl-4-ethylindenyl)zirconium dichloride,
dimethylsilylbis-1-(2-methyl-4-isopropylindenyl)zirconium dichloride,
dimethylsilylbis-1-(2-methyl-4-phenylindenyl)zirconium dichloride,
dimethylsilylbis-1-(2-methylindenyl)zirconium dichloride,
dimethylsilylbis-1-(2-methyltetrahydroindenyl)zirconium dichloride,
dimethylsilylbis-1-indenylzirconium dichloride,
dimethylsilylbis-1-indenylzirconium dimethyl,
dimethylsilylbis-1-tetrahydroindenylzirconium dichloride,
diphenylmethylene-9-fluorenylcyclopentadienylzirconium dichloride,
diphenylsilylbis-1-indenylzirconium dichloride,
ethylenebis-1-(2-methyl-4,5-benzoindenyl)zirconium dichloride,
ethylenebis-1-(2-methyl-4-phenylindenyl)zirconium dichloride,
ethylenbis-1-(2-methyltetrahydroindenyl)zirconium dichloride,
ethylenebis-1-(4,7-dimethylindenyl)zirconium dichloride,
ethylenebis-1-indenylzirconium dichloride,
ethylenebis-1-tetrahydroindenylzirconium dichloride,
indenylcyclopentadienylzirconium dichloride
isopropylidene(1-indenyl)(cyclopentadienyl)zirconium dichloride,
isopropylidene(9-fluorenyl)(cyclopentadienyl)zirconium dichloride,
phenylmethylsilylbis-1-(2-methylindenyl)zirconium dichloride, and the alkyl or aryl derivatives of each of these metallocene dichlorides.
The single-center catalyst systems are activated using suitable cocatalysts. Suitable cocatalysts for metallocenes of the formula I are organoaluminum compounds, especially aluminoxanes, or else aluminum-free systems such as R20xNH4-xBR214, R20xPH4-xBR214, R203CBR214 or BR213. In these formulae x is a number from 1 to 4, the radicals R20 are identical or different, preferably identical, and are C1-C10 alkyl or C6-C18 aryl, or two radicals R20 form a ring together with the atom connecting them, and the radicals R21 are identical or different, preferably identical, and are C6-C18 aryl which may be substituted by alkyl, haloalkyl or fluorine. In particular R20 is ethyl, propyl, butyl or phenyl and R21 is phenyl, pentafluorophenyl, 3,5-bistrifluoro-methylphenyl, mesityl, xylyl or tolyl.
Additionally a third component is often necessary in order to maintain protection against polar catalyst poisons. Suitable for this purpose are organoaluminum compounds such as triethylaluminum, tributylaluminum, etc., and also mixtures.
Depending on process it is also possible for supported single-center catalysts to be used. Preference is given to catalyst systems in which the residual amounts of support material and cocatalyst do not exceed a concentration of 100 ppm in the product.
The invention further provides for the use of the hot melt compositions of the invention as hot melt adhesives.
Further possible constituents are resins, waxes, and apolar or polar polymers such as, for example, ethylene-vinyl acetate copolymers, polyacrylates, polyesters, polyethers, polycarbonates, polyacetals, polyurethanes, polyolefins, and rubber polymers, such as nitrile or styrene/butadiene rubbers.
Polyisobutylene, styrene-butadiene-styrene block polymers or styrene-isoprene-styrene block polymers, and, for particularly heavy-duty bonds, polyamides or polyesters. Examples of resin components which may be present include rosins and their derivatives or hydrocarbon resins, while possible waxes are hydrocarbon waxes such as Fischer-Tropsch paraffins, and polyolefin waxes not prepared using metallocene catalysts, it being possible for said waxes to have undergone apolar or polar modification, by means, for example, of oxidation or of grafting with polar monomers such as maleic anhydride. The hot melt adhesive compositions may further comprise fillers or auxiliaries such as plasticizers, pigments, and stabilizers, such as antioxidants or light stabilizers.
The working examples which follow are intended to illustrate the invention to the person skilled in the art but are not to be understood as a restriction to specific working embodiments.
In the working examples the melt viscosities in accordance with DIN 53019 were determined using a rotational viscometer, the dropping points in accordance with DIN 51801/2, the ring & ball softening points in accordance with DIN EN 1427, and the glass transition temperatures by means of differential thermoanalysis in accordance with DIN 51700. The weight-average molar mass Mw, the number-average molar mass Mn, and the resulting quotient Mw/Mn were determined by gel permeation chromatography at 135° C. in 1,2-dichlorobenzene.
The metallocene-polyolefin waxes 1, 2 and 3 listed in Table 1 and employed in accordance with the invention have been prepared by copolymerization of propylene with ethylene in the presence of the metallocene dimethylsilylbisindenylzirkonium-dichloride as catalyst pursuant to the general procedure described in EP 384 264 (see examples 1 to 16). The weight fraction of the monomers appears in Table 1. The differences in softening points and viscosities resulted from variations in the ethylene supply and different polymerization temperatures.
* Dropping point
**Softening point
Performance results:
*Comparison experiment
The hot melt adhesive compositions listed in Table 3 were prepared from the copolymer waxes 1, 2 and 3 indicated in Table 1, and the atactic alpha-olefins (APAOs) available under the trade name Vestoplast 703 (Degussa), with the mixing proportion being 80% or 95% by weight APAO, and 20% or 5% by weight homo- or copolymer waxes. The components were jointly melted and stirred at 180° C. for a period of 1 h.
The melt viscosities of the hot melt compositions at 170° C. were determined in accordance with DIN 53019 using a rotational viscometer; the cohesions were determined in accordance with DIN 53455 by casting moldings and testing their mechanical stability in a tensile test.
The examples show that, by adding homopolymer or copolymer waxes of 5% by weight, and particularly 20% by weight, a considerable improvement to the cohesion is achieved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 055 018.5 | Nov 2005 | DE | national |
