PROCESSING-OPTIMIZED, REACTIVE POLYMER COMPOSITION

Description

Technical field of the invention

[0001] The invention relates to a silane-modified polypropylene copolymer with a silicon content between 1 and 5 wt. %, a melting enthalpy between 20 J / g and 35 J / g, and a melt viscosity at 170°C between 500 mPas and 4500 mPas. Furthermore, the invention relates to processing-optimized, reactive hot-melt adhesive formulations comprising this silane-modified polypropylene copolymer and the use of these hot-melt adhesive formulations for bonding various substrates. Furthermore, the invention relates to a process for producing these silane-modified polypropylene copolymers. Background of the invention

[0002] Semi-crystalline poly-alpha-olefins are widely used as adhesive raw materials for a wide range of applications. Their use ranges from the hygiene sector, through lamination and packaging adhesives, to structural bonding and applications in wood processing.

[0003] By grafting with a cross-linking agent such as an alkoxysilane, the cohesion, adhesion, mechanical stability and heat resistance of unmodified poly-alpha-olefins can be modified, since the cross-linking of the polymer chains with each other changes the macromolecular properties and the grafted alkoxysilane further enables the covalent incorporation of reactive surface groups (such as -OH) into an adhesive bond.

[0004] A radically induced grafting of semi-crystalline poly-alpha-olefins with silane groups leads to a chain degradation of the ungrafted polymer, whereby often only very low functionalization rates are achieved and graft products with a strongly waxy character are formed (e.g. WO 89 / 11513), which do not appear suitable for stable bonding.

[0005] This also applies to the radically induced grafting reaction of polypropylene or a propylene-rich copolymer, which is known to also involve chain scission reactions, reducing the molecular weight (and thus the melt viscosity) of the polymer. Corresponding polymers with high functionalization rates therefore inevitably have very low molecular weights / melt viscosities and are unsuitable for many applications.

[0006] Furthermore, the subsequent cross-linking of the degraded chains by the silane groups causes a change in the mechanical properties, which in extreme cases can lead to stiff, high-strength materials with a low embrittlement temperature.

[0007] WO 2007 / 008765 (Dow) describes the use of low-viscosity, silane-grafted poly(ethylene-co-1-olefin) polymers as adhesive raw materials. The polymers used for modification have an ethylene content of at least 50 mol% ethylene and preferably a polydispersity of 1 to 3.5, with the entire range being specified as 1 to 5. They exhibit a low melt viscosity of a minimum of 2,000 and a maximum of 50,000 cP at 177 °C. Numerous higher 1-olefins such as 1-hexene and 1-octene are mentioned as 1-olefin comonomers. The silane-grafted polymers exhibit low failure temperatures in PAFT and SAFT analysis. The use of polyolefins with a high ethylene content inevitably results in the presence of long ethylene blocks in the polymer. This, in turn, leads to poor wetting and adhesion properties on many plastic surfaces, making it impossible to optimally solve many bonding problems.In addition, long polyethylene sequences tend to undergo peroxide crosslinking, which inevitably leads to gel formation. The ungrafted base polymers have a relatively low molecular weight and a melt viscosity of a maximum of 50,000 cP at 177°C.

[0008] The use of crystalline and semi-crystalline poly(propylene-co-1-olefin) polymers, which are also said to be suitable for grafting, is also described. These have a propylene content of at least 50 mol% and preferably a melt viscosity of a maximum of 50,000 cP at 170°C (before and after grafting), as well as a polydispersity of 1 to 3.5. The crystallinity is stated to be 2-60% (i.e., 3-100 J / g). However, there are no examples of these polypropylene-based copolymers, which are stated to be preferred. No further investigations have been conducted on polymers with a melting enthalpy between 20 and 35 J / g and a viscosity between 500 and 4500 mPas. Thus, WO 2007 / 008765 addresses neither specific feature combinations nor the advantageous processing and adhesion properties resulting from them.

[0009] EP0827994 (Huels) describes the use of silane-grafted, amorphous poly(alpha-olefins) as moisture-curing adhesive raw materials or adhesives. The base polymers used are atactic polypropylene (aPP), atactic poly(1-butene), or preferably copolymers or terpolymers of C4-C10 alpha-olefins (0-95 wt%), propene (5-100 wt%), and ethylene (0-20 wt%). The silane-modified APAO terpolymer presented in the examples has a softening point of 98 °C, a weight-average molecular weight of 38,000 g / mol, and a melt viscosity of 6000 mPas. The grafting resulted in a decrease in PDI of more than 35% and a decrease in viscosity of 88%. The processing properties in connection with the mechanical properties are not discussed in detail.

[0010] DE10338344A1 (Clariant) relates to semi-crystalline polyolefin homopolymers or copolymers radically modified with a silane compound, having a viscosity, measured at 170°C, between 10 and 50,000 MPas and a heat of fusion greater than 10 J / g. The examples disclose polyolefins with melt viscosities at 170°C of less than 1000 mPas, dropping points above 110°C, and heats of fusion of at least 60 J / g. They are suitable as components of hot-melt adhesive formulations. The combination of low melt viscosities with heats of fusion between 20 and 35 J / g is not disclosed.

[0011] The silane-modified crystalline polyolefin waxes are produced by metallocene catalysis and have a high propylene content.

[0012] For hot melt adhesive formulations containing silane-modified polyolefins, the bonding process is two-step. To avoid processing problems and ensure easy application, the expert seeks hot melt adhesive formulations with a low viscosity to allow the hot melt adhesive to be applied under pressure at relatively low temperatures. Once the adhesive is applied, crosslinking is initiated, increasing the viscosity and building the cohesion of the bond, which should ensure the mechanical stability for the final bond.

[0013] However, it should be noted that very low-viscosity products with viscosities below 8,000 mPas typically exhibit deficits in mechanical properties such as Young's modulus, strength, and elongation at break. This is because the very short chain lengths result in fewer polymer entanglements, resulting in products with more waxy properties. Furthermore, the very short chain lengths lead to rapid embrittlement of the material during crosslinking, as the short, interconnected polymer chains exhibit only limited flexibility. Thus, the state of the art discourages the use of very low-viscosity base polymers and recommends the use of larger quantities of tackifiers in conjunction with higher-viscosity silanized polyolefins.

[0014] The adhesive tackifier influences the viscosity of the bond as well as the initial adhesion and is often a resin. These resins are, for example, low-molecular-weight products from the C5 or C9 stream of petroleum processing, often contain aromatics, and usually have a glass transition temperature above room temperature.

[0015] Thus, the addition of resins in hot melt adhesive formulations increases the glass transition temperatures of the formulations, so that corresponding hot melt adhesives suffer from reduced cold flexibility and the temperature range in which the hot melt adhesive can be used is limited.

[0016] WO2010018027A1 (Evonik) describes silane-modified polypropylene co- and terpolymers with a high degree of functionalization, with a maximum poly(ethylene) triad content of 2.5 wt. %, fusion enthalpies of 9–20 J / g, and a xylene solubility of greater than 96 wt. %, whereby the best results were achieved with terpolymers comprising ethylene and 1-butene. Numerous example formulations for various bonds containing these modified polyolefins are mentioned. While these formulations offer relatively good mechanical stability after bonding, relatively high amounts of tackifier are required to ensure good processing properties and sufficient initial tack. The lowest proportion of modified polyolefins in a formulation is stated at 24.7 wt. % in an example formulation for edge banding. All other examples contain 30 wt. % or more.

[0017] Furthermore, WO2010018027A1 teaches that a peroxide-induced grafting reaction further reduces the polydispersity of the polymers used, concluding that the modified polymers have a polydispersity significantly less than 3.5, which allegedly leads to various disadvantages, especially in processing properties. Furthermore, the document teaches that the use of relatively low-molecular-weight base polymers generally leads to rather low functionalization rates.

[0018] EP3287276A1 (Sika) describes hot melt adhesive compositions comprising a silane-modified poly-alpha-olefin that is solid at 25°C, an unmodified amorphous C3 / C2 copolymer wax with a softening point < 120°C, and a paraffin wax with a softening point of 80-130°C. The adhesive compositions contain various silane-modified poly-alpha-olefins, the sum of which in the formulation is > 55 wt.%.

[0019] EP3711947A1 (Sika) also describes hot melt adhesive compositions comprising a silane-modified propylene-based polyolefin.

[0020] WO2009133093 (Sika) describes hot-melt adhesive compositions with an extended open time, comprising a silane-modified poly-alpha-olefin that is solid at 25°C and a soft resin with a melting or softening point of 10°C - 40°C. The example formulations contain 65 wt.% silane-modified poly-alpha-olefin. The proportion of all silane-grafted poly-alpha-olefins is over 50 wt.%, preferably between 60 and 90 wt.%.

[0021] This shows that tackifiers and low-viscosity components typically need to be added in relatively large quantities to silane-modified adhesive formulations to achieve a viscosity appropriate for processing and initial bond adhesion. Without these additions, silanized polyolefins exhibit high viscosity, which limits the application spectrum and presents the adhesive formulator with additional process-related and material-specific problems. Therefore, adhesive formulators are always looking for solutions that are suitable for a balanced, broad application spectrum, require as few individual components as possible, and keep the proportion of functional additives as low as possible.

[0022] There was therefore a need for functionalized polyolefins as and for hot melt adhesives which, due to their improved material properties, can be easily processed and applied even at low temperatures (below 170 °C) without the need for large amounts of resin or tackifier, and which nevertheless enable sufficient initial adhesion as well as flexible and stable bonding and high heat resistance of the hot melt adhesive. Subject of the invention

[0023] Surprisingly, it has been found that a silane-modified polypropylene copolymer with a silicon content of between 1 and 5 wt. %, based on the total amount of the modified polymer, a melt viscosity at 170°C of greater than 500 mPas and less than 4500 mPas, and a melting enthalpy of greater than 20 J / g and less than 35 J / g, preferably greater than 20 J / g and less than 30 J / g, as a hot-melt adhesive or as a component of a hot-melt adhesive formulation, imparts extremely advantageous properties to the formulation itself, which are reflected, among other things, in its improved processability. Copolymers in the sense of the invention refer to polymers composed of two or more different monomer units.The silane-modified polypropylene copolymer comprises as a further monomer one or more monomers selected from the group consisting of ethylene and 1-butene, wherein a binary copolymer is preferred and ethylene is particularly preferred as a comonomer alongside propylene.

[0024] The silane-modified polypropylene copolymer results in both excellent processability and excellent mechanical properties of the bond, which are reflected qualitatively and quantitatively in the hot melt adhesive's good cohesion, adhesion, heat resistance, and elongation at break. A lower proportion of the reactive silanized component in the formulation is required to achieve the same requirement profile of the hot melt adhesive regarding heat resistance, cohesion, elongation at break, etc., than would be the case with conventional formulations. The advantageous properties of the hot melt adhesive are particularly evident on polar substrates. Detailed description of the invention

[0025] The modification of the unmodified polypropylene copolymer is carried out by grafting. Grafting can result in side reactions that, among other things, lead to chain scission of the grafted polymer. Therefore, in the present application, grafting and modification are considered synonymous.

[0026] In addition to the described silicon content of between 1 and 5 wt.%, the melt viscosity at 170°C of greater than 500 mPas and less than 4500 mPas, and the enthalpy of fusion of greater than 20 J / g and less than 35 J / g, preferably greater than 20 J / g and less than 30 J / g, the silane-modified polypropylene copolymer preferably has a melt viscosity between 10% and 50% of the initial viscosity of the unmodified polypropylene. A corresponding percentage change in the melt viscosity enables particularly easy processing in combination with good mechanical stability through the correct degree of crosslinking.

[0027] The silane to be grafted preferably has olefinic double bonds and one to three alkoxy groups directly bonded to the silicon atom. In particular, the one or more silanes are selected from the group comprising vinyltrimethoxysilane (VTMO), vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, 3-methacryloxypropyltrimethoxysilane (MEMO; H2C=C(CH3)COO(CH2)3-Si(OCH3)3), 3-methacryloxypropyltriethoxysilane, vinyldimethylmethoxysilane, and / or vinylmethyldibutoxysilane. The silane is most preferably vinyltrimethoxysilane.

[0028] To achieve the desired mechanical properties, it is advantageous if the polypropylene copolymer backbone of the silane-modified polypropylene copolymer has a weight-average molecular weight, measured according to ISO 16014-1, of greater than 10,000 and less than 30,000 g / mol, preferably greater than 10,000 and less than 20,000 g / mol, since in this molecular weight range the polymer chains have been sufficiently functionalized and can be crosslinked accordingly, but they still have sufficient flexibility.

[0029] The silane-modified polypropylene copolymer preferably has a polydispersity index (PDI) of less than 2.5. This has preferably increased due to the grafting, and the increase compared to the ungrafted polymer is at least 20%. This change in PDI due to grafting apparently only occurs in silane-modified polypropylene-based copolymers, where the radical-induced chain degradation occurs to an extent that leads to a sufficient reduction in viscosity, but is nevertheless low enough to allow subsequent crosslinking to an extent that ensures both high flexibility and sufficient bond strength. This increase in PDI was completely surprising, since radical-induced chain degradation usually leads to a reduction in PDI.

[0030] Preferably, the silane-modified polypropylene copolymer has a softening point between 85 and 95°C. Silane-modified polypropylene copolymers with a softening point within this range exhibit sufficiently good properties for both heat resistance and processability.

[0031] Furthermore, the silane-modified polypropylene copolymer preferably has a density greater than 0.900 g / cm3.

[0032] Preferably, the silane-modified polypropylene copolymer has a mm triad of propylene content that is less than or equal to 90 mol% and an rr triad that is at least 5 mol%. A silane-modified polypropylene copolymer having this microstructure exhibits the desired processing and mechanical properties.

[0033] In a preferred embodiment, the silane-modified polypropylene copolymer was prepared using a metallocene catalyst.

[0034] In a preferred embodiment, the unmodified starting material of the silane-modified polypropylene copolymer has a propylene content of at least 60 mol% propylene, particularly preferably between 70 and 90 mol% propylene. In this range, the comonomer content is large enough to prevent embrittlement of the material, but not so large that the adhesion properties would be impaired due to an excessively high ethylene content.

[0035] Particularly preferably, the unmodified starting material of the silane-modified polypropylene copolymer has a propylene content, which was determined by means of a 13< C-NMR, of at least 60 mol% propylene.

[0036] Furthermore, a further subject of the invention is a process for producing a silane-modified polypropylene copolymer according to claim 1, comprising the steps a) Providing a polypropylene copolymer b) Adding the grafting component and the radical initiator c) Evaporating the excess monomer characterized in that the grafting reaction results in a decrease in the melt viscosity of 50 - 90% and an increase in the PDI of at least 20% of the graft product compared to the starting product.

[0037] Preferably, an unmodified polypropylene copolymer is used in the process according to the invention which has a melt viscosity, measured according to DIN 53019 at 170°C, between 500 and 7,000 mPas, preferably between 700 and 5,000 mPas, particularly preferably between 800 and 4,000 mPas, and a melting enthalpy, measured according to ISO 11357-3, between 30 J / g and 55 J / g, preferably between 30 and 50 J / g, particularly preferably between 30 and 45 J / g.

[0038] The invention further relates to a hot melt adhesive formulation comprising a silane-modified polypropylene copolymer according to the invention and one or more base polymers selected from the group consisting of unmodified polyolefins and unmodified, thermoplastic styrene block copolymers (TPE-S), wherein the silane-modified polypropylene copolymer and the base polymer form at least 50 wt.% of the hot melt adhesive formulation and the silane-modified polypropylene copolymer is used to a maximum of 30 wt.%, based on the total weight of the hot melt adhesive formulation.

[0039] The unmodified polyolefins are preferably crystalline or semi-crystalline polyolefins or amorphous polyolefins (APAO), ethylene-vinyl acetate copolymers (EVA) and polyisobutylene (PIB), whereby the polyolefins are particularly preferably formed from C3 / C2 copolymers and the unmodified styrene block copolymers are preferably SBS, SEBS, SEPS, SEEPS and MBS.

[0040] Preferably, the hot melt adhesive formulation has a melt viscosity at 170°C, measured according to DIN 53019, of less than 5000 mPas and a tensile strength of at least 4 MPa, since a hot melt adhesive with these properties represents an optimum between processability and mechanical stability.

[0041] The hot melt adhesive formulation according to the invention may contain synthetic and / or natural resins, in particular adhesive resins, synthetic and / or natural oils, inorganic and / or organic, synthetic and / or natural polymers, which may optionally be electrically conductive or insulating.

[0042] In particular, the hot-melt adhesive formulation according to the invention comprises tackifying resins (tackifiers), wherein the resins are used to adapt certain properties of the adhesive layer, in particular the tack and / or adhesion, the flow and creep behavior of the adhesive layer, and / or the adhesive viscosity, to specific requirements. These resins can be natural resins and / or synthetic resins. In the case of natural resins, these natural resins contain abietic acid (e.g., rosin) as their main component. Furthermore, the resins can be terpene or polyterpene resins, petroleum resins, and / or coumarone-indene resins, in particular so-called C5 resins and / or C9 resins and / or copolymers of C5 / C9 resins.

[0043] The proportion of tackifiers in the hotmelt adhesive according to the invention is a maximum of 35% by weight of tackifier, particularly preferably between 1 and 30% by weight and especially preferably between 3 and 20% by weight, based on the total formulation, since the viscosity of the hotmelt adhesive preferred for processing can also be achieved with low amounts of resin and these amounts in the hotmelt adhesive according to the invention are sufficient to ensure adequate initial adhesion.

[0044] The hot melt adhesive composition according to the invention may contain further components necessary to achieve specific properties, such as deformability, adhesion, processability, crosslinking rate, crosslinking density, (melt or solution) viscosity, strength, crystallization rate, tackiness, storage stability, etc.

[0045] The hot melt adhesive formulation particularly preferably contains, based on its total mass, 40-80 wt.% of the base polymer, 10-30 wt.% of the polypropylene copolymer, and 10-30 wt.% tackifier. A formulation with these weight ratios optimally utilizes the preferred properties, providing a hot melt adhesive with a particularly balanced property profile.

[0046] In a particular embodiment of the present invention, the proportion of the additional components is particularly preferably a maximum of 10 wt.%. This has the advantage that the material properties of the adhesive formulation are essentially those of the polymer according to the invention used. Such an adhesive formulation can be produced with very little effort.

[0047] The further components may be crosslinking accelerators, in particular silanol condensation catalysts, inorganic and / or organic fillers which may optionally be electrically conductive or insulating, inorganic and / or organic pigments which may optionally be electrically conductive or insulating, inorganic and / or organic, synthetic and / or natural fibers which may optionally be electrically conductive or insulating, inorganic and / or organic stabilizers and / or inorganic and / or organic flame retardants.

[0048] In an alternative embodiment, the silane-modified polypropylene copolymer or the hot melt adhesive formulation comprises a crosslinking accelerator present in an amount of 0.1 - 1 wt.%, based on the total amount of the mixture of silane-modified polypropylene copolymer and crosslinking accelerator or the hot melt adhesive formulation.

[0049] This is particularly preferred when the polymers according to the invention are used in an adhesive bond which is to reach its maximum load-bearing capacity within a short time after joining.

[0050] A variety of chemical compounds are suitable as crosslinking accelerators, in particular Brönsted and / or Lewis acids such as acetic acid, itaconic acid, zinc(II) acetate, cadmium acetate, zinc oxide, zinc stearate, zinc(II) chloride, tin(IV) chloride, dibutyltin oxide, dibutyltin dilaurate, bismuth citrate, bismuth(III) oxide, bismuth titanate, tetrabutylgermanium, tetrabutyltin, titanium boride, titanium(IV) oxide, titanium acetylacetonate, tributyl titanate, sodium chloride, magnesium(II) chloride, zinc acetylacetonate, zinc methacrylate, zinc niobate, tin(II) oxide, tin(IV) oxide, zirconium(IV) acetylacetonate, zirconium(IV) oxide and / or zirconium(IV) silicate. Measurement methods:

[0051] The listed polyolefins were characterized according to the standards listed. Characterizations deviating from the standard were performed according to the description.

[0052] The weight-average and number-average molecular weights M w and M n of the copolymers were determined in 1,3-ortho-dichlorobenzene using a PP calibration. The measurements were performed by gel permeation chromatography at a temperature of 135°C. The determination was carried out according to ISO 16014-1.

[0053] The softening points were determined according to ASTM D 3104.

[0054] The density was determined according to ISO 1183-3:1999.

[0055] The melt viscosity according to DIN 53019 is determined as follows: The fluid to be tested is located in an annular gap between two coaxial cylinders, one of which rotates at a constant speed (rotor), the other of which is stationary (stator). The speed and torque required to overcome the frictional resistance of the fluid in the annular gap are determined. The shear stress and velocity gradient prevailing in the fluid can be calculated from the geometric dimensions of the system as well as the determined torque and speed values. By specifying certain geometric relationships, the standard describes a standard flow diagram for measuring the flow behavior of Newtonian and non-Newtonian fluids in rotational viscometers with coaxial cylinders.Since the reactants and the silane-modified products are shear-thinning liquids, the dynamic viscosity was averaged from three measurements at 170°C at different shear rates (shear rate 1: 192 1 / s, shear rate 2: 318 1 / s, shear rate 3: 532 1 / s).

[0056] The enthalpy of fusion and the glass transition temperature were determined by differential scanning calorimetry (DSC) according to ISO 11357-3 and ISO 11357-2. The enthalpy of fusion, the glass transition temperature, and the melting range of the crystalline fraction were determined using DSC from the second heating curve at a heating rate of 10 K / min. The inflection point of the heat flow curve is evaluated as the glass transition temperature. In this case, the modified polymers were always measured in the uncrosslinked state without any further additives. It is advisable to blanket the polymers with a dry protective or inert gas (e.g., nitrogen, argon, etc.) during the measurement.

[0057] The polydispersity index PDI is calculated from the quotient of the weight-average molecular weight M w and the number-average molecular weight M n and was determined according to ISO 16014-1.

[0058] The silicon content was determined by adsorption photometry on a Lambda 35 photometer from Perkin Elmer.

[0059] For this purpose, the sample to be measured is digested as follows: Depending on the Si content, 0.1–0.15 g of the polymer is weighed into a platinum crucible and mixed with 0.5 ml of concentrated sulfuric acid. The liquid is evaporated on a hotplate and then ashed in a muffle furnace at 600°C for 1.5 to 2 hours, forming sulfate ash. The sulfate ash is then digested in a flame with as little sodium carbonate as possible, extracted from the platinum crucible with Millipore water, and poured into a 100 ml plastic volumetric flask.

[0060] To photometrically determine the silicon content of the digested sample, 10 ml of the digested solution is pipetted into a 50 ml plastic volumetric flask and mixed with 5 ml of 2M sulfuric acid to adjust the pH. Then, 10 ml of molybdate reagent is added, and the solution is made up to 50 ml with Millipore water.

[0061] Before measurement, the photometer is calibrated according to the following procedure: A calibration series with concentrations of 0, 1, 2, 4, and 5 mg Si / I is pipetted from the stock solution into a 50 ml flask. To adjust the pH, 5 ml of 2 m sulfuric acid is added. Then, 10 ml of molybdate reagent is added, and the calibration solutions are transferred to appropriate cuvettes. After 2 to 10 minutes of exposure to the photometer, the samples from the calibration series are calibrated at a wavelength of 400 nm. To verify the calibration, an external control standard with a concentration of 5 mg Si / I is prepared analogously and measured on the photometer.

[0062] The solution of the sample whose silicon content is to be determined is transferred into a cuvette and measured after 2 to 10 minutes on the photometer at a wavelength of 400 nm.

[0063] The adhesion was determined as adhesive shear strength in the tensile shear test according to DIN EN 1465.

[0064] All test specimens used are cleaned and dusted prior to sample preparation. All plastic and glass test specimens are also degreased with a suitable cleaning agent prior to sample preparation. The test specimens are then bonded in accordance with DIN EN 1465. All test specimens prepared in this way are stored in a climate-controlled cabinet at 20 °C and 50% relative humidity for 14 days prior to use. This ensures a consistent water content, for example, in wooden test specimens. This eliminates or minimizes singular effects caused by increased humidity, for example, in hydrophilic or hydrolysis-sensitive polymers.

[0065] The cohesion was determined as tensile strength in the tensile test according to DIN EN ISO 527-3.

[0066] The propylene content and the PP triads were determined by 13< C-NMR, with quantification being performed by integration of the characteristic signal: The 13< C NMR spectra were recorded on a Varian Mercury-VX 400 (9.4 Tesla) NMR spectrometer using a 5 mm probe head (nuc4, 13C-sensitive). The 13< C NMR measurements (Lamor frequency: 100.62 MHz) were performed under quantitative conditions, i.e., using the inverse-gated pulse sequence. Further parameters were as follows: spectral width: 25 kHz; acquisition time: 1.3 s; relaxation delay: 20 s; number of scans: approximately 4000; excitation angle: 90°; measurement temperature: 80°C. For this purpose, approximately 50 mg of the EP copolymer was dissolved in 0.7 ml of solvent (20% C6D6 / 80% 1,2,4-trichlorobenzene) and homogenized. The proportions of the triads were calculated according to a Markov probability statistic fitted to a PP / PE copolymer.

[0067] The elongation at break of the hot melt adhesives according to ISO 527 was determined according to ISO 527, with the exception that a non-standard test specimen was used in each case. This specimen was produced by melt pressing and differed from the standard test specimen in its dimensions. The test specimens used to measure strength and elongation at break had the following dimensions: total length: 50 mm, narrow section width: 3.3 mm, end width: 7 mm, narrow parallel section length: 25 mm, and thickness: 1 mm.

[0068] The elongation at break corresponds to the tensile strength at break and is determined according to ISO 527 using a tensile elongation test. This determines the force per unit area (specified in MPa) required for the test specimen to fracture. With the exception of the test specimen, the tensile test was performed according to ISO 527.

[0069] The invention is explained in more detail by the following examples and claims. Execution of the examples:

[0070] For the grafting of the polypropylene copolymers produced with metallocene catalysts listed in columns 2 and 3 of Table 1, 500 g of each polypropylene copolymer were melted under nitrogen in a glass apparatus equipped with a stirrer, internal thermometer, and distillation bridge. Columns 4 to 6 contain the available data on the ungrafted comparative polyolefins from the state of the art. Table 1 Base polyolefin Licocene PP 2602 Licocene PP 1302 Vestoplast 708 WO2010 / 018027 Ex. 6 EP0827994 Example 1 Softening point [°C] approx. 90 approx. 82 approx. 106 ± 4 (from TDS) 102 approx. 107 Glass transition temperature (Tg) [°C] -29 -32 -33 -39 Enthalpy of fusion (DSC) [J / g] 38 35 18,7 Weight-average molecular weight [g / mol] 30.000 8.800 75.000 92.000 Polydispersity Index (PDI) [ ] 1,7 1,7 4,1 Density [g / cm3] 0,900 0,900 0,87 Melt viscosity at 170°C [mPas] 6.300 200 8.000 ± 2.000 (@190°C) 68 000 (@190°C) 50.000 (@190°C) Propylene content [wt.%] >75 > 75 84 Ethylene triads content [wt.%] > 2,5 > 2,5 2,4

[0071] At a temperature of 160°C, 50 g of trimethoxyvinylsilane (10% based on the amount of polymer used) were continuously added from a dosing funnel over the course of 3 hours. Simultaneously, 10 g of di-tert-butyl peroxide was continuously added from a second dropping funnel. After the addition was complete, a further 1.1 g of di-tert-butyl peroxide was added to the reaction mixture, and the mixture was allowed to react for 1 h at 160°C.

[0072] Subsequently, a vacuum (approx. 30 mbar) was applied, and the volatile components were distilled off. After approximately 30 minutes, the pressure was reduced to atmospheric pressure by introducing nitrogen.

[0073] The properties of the resulting modification products are given in Table 2, columns 2 and 3. Columns 4 to 6 contain the available data on the grafted polyolefins from the state of the art. Table 2 Silane-modified polypropylene copolymer PP SI 1462 (Req.) PP SI 1362 (cf. DE10338344) Vestoplast 206 WO2010 / 018027 Ex. 14 EP0827994 Example 1 Softening point [°C] approx. 90 approx. 82 approx. 98 ± 4 (from TDS) 98 Glass transition temperature Tg [°C] -29 -32 -28 (from TDS) Melting enthalpy [J / g] 29 21 20 Weight average molecular weight [g / mol] 12.300 8.800 38,000 (from TDS) 38.000 Polydispersity Index (PDI) [ ] 2,3 2,0 2,6 2,6 Si content [wt.%] 1,4 - 1,8 1,4 - 1,8 0,5 0.43 (XRF spectroscopy) 6% VTMO used Density: [g / cm3] 0.900 0.900 0.87 Melt viscosity (at 170°C) [mPas] 1.000 110 5,000 ±1,000 (from TDS) 2,000 (at 190°C) 6,000 (at 190 °C) Propylene content [wt.%] >75 > 75 84 Ethylene triads content [wt.%] > 2,5 > 2,5 2,4 Production of hot melt adhesive formulations and bonding of various substrates.

[0074] To produce the hot melt adhesive formulations according to the invention, melt mixtures of the silane-modified polypropylene copolymer and the other components listed in Table 3 in the weight proportions indicated therein were prepared by hot melt mixing (approx. 180°C) using a propeller stirrer. Table 3 Hot melt adhesive formulation Example 1 (cf.) Example 2 (Exp.) Example 3 (cf.) Example 4 (cf.) Example 5 (Exp.) Example 6 (cf.) Example 7 (cf.) Example 8 (Exp.) Example 9 (cf.) PP 2602 [wt.%] 74,5 74,5 74,5 54,5 54,5 54,5 SI 1362 [wt.%] 99,5 25,0 25,0 SI 1462 [wt.%] 99,5 25,0 25,0 Vestoplast 206 [wt.%] 99,5 25,0 25,0 SU 400 [wt.%] 20,0 20,0 20,0 Hordaphos MDAH [wt%] 0,5 0,5 0,5 0,5 0,5 0,5 0,5 0,5 0,5 Total [wt%] 100 100 100 100 100 100 100 100 100 Visc, @170 °C [mPas] 200 1.000 12.000 2.400 4.300 8.000 1.590 2.800 5.300 Tensile strength [MPa] 2,4 5,8 3,6 6,0 7,0 4,5 4,0 5,1 3,6 Elongation at break [%] 13 34 442 128 206 143 149 206 530 Heat resistance [°C] 200 200 200 90 160 80 80 200 90 Adhesive shear strength [MPa] PP 1,0 1,3 2,9 1,7 1,7 2,9 3,8 3,4 3,4 ABS 0,7 0,8 1,6 0,4 0,7 0,5 2,9 3,0 2,7 Wood 4,1 7,1 4,0 3,6 5,1 1,1 5,0 5,9 3,3 Glass 3,6 0,7 nb 3,8 0,3

[0075] In the above hot-melt adhesive formulations, it can be seen in inventive examples 2, 5, and 8 that, at a low viscosity, increased cohesion (tensile strength), elongation at break, heat resistance, and adhesion (adhesive shear strength) can be achieved on various substrates, particularly on wood. When using the silane-modified polypropylene copolymer as the sole component of a hot-melt adhesive, the silane-modified component of the invention is significantly superior to the comparative examples on wood. The inventive component in its pure form also exhibits good adhesion on polypropylene (PP) and ABS and is significantly improved in terms of cohesion compared to comparative examples 1 and 3.

[0076] These favorable properties, even in their pure form, unfold their full potential in the formulation. Examples 5 and 8 according to the invention exhibit a much lower viscosity at the same concentration of the reactive component in the formulation, which significantly improves and expands the user's processing spectrum. Furthermore, they exhibit much higher heat resistance and significantly improved cohesion, adhesion, and elongation at break than Comparative Examples 4, 6, 7, and 9.

Claims

1. A silane-modified polypropylene copolymer containing ethylene and / or 1-butene, preferably ethylene or 1-butene, more preferably ethylene, as comonomer and having a silicon content ascertained photometrically of between 1% and 5% by weight, based on the total mass of the polymer, a melt viscosity, measured to DIN 53019 at 170°C, of greater than 500 mPas and less than 4500 mPas, and an enthalpy of fusion, measured to ISO 11357-3, of greater than 20 J / g and less than 35 J / g, preferably greater than 20 J / g and less than 30 J / g.

2. The silane-modified polypropylene copolymer as claimed in claim 1, characterized in that the melt viscosity, measured to DIN 53019, of the silane-modified polypropylene copolymer is between 10% and 50% of the original viscosity of the unmodified polypropylene copolymer.

3. The silane-modified polypropylene copolymer as claimed in claim 1 or 2, characterized in that the polypropylene copolymer backbone has a weight-average molecular weight, measured to ISO 16014-1, of greater than 10 000 and less than 30 000 g / mol, preferably greater than 10 000 and less than 20 000 g / mol.

4. The silane-modified polypropylene copolymer as claimed in any of the preceding claims, characterized in that it has a polydispersity index (PDI), determined according to standard ISO 16014-1, of less than 2.5, and the PDI increases as a result of the grafting with respect to the unmodified polypropylene copolymer, where the increase is preferably at least 20% of the original value.

5. The silane-modified polypropylene copolymer as claimed in any of the preceding claims, characterized in that it has a softening point, measured to ASTM D 3104, of between 85 and 95°C.

6. The silane-modified polypropylene copolymer as claimed in any of the preceding claims, characterized in that it has a density greater than 0.900 g / cm3, measured to ISO 1183-3:1999.

7. The silane-modified polypropylene copolymer as claimed in any of the preceding claims, characterized in that the mm triad of the propylene fraction that has been ascertained with the aid of 13C NMR is not more than 90 mol%, and the rr triad is at least 5 mol%.

8. The silane-modified polypropylene copolymer as claimed in any of the preceding claims, characterized in that the unmodified reactant has a propylene content that has been ascertained with the aid of 13C NMR of at least 60 mol% of propylene.

9. A process for preparing a silane-modified polypropylene copolymer as claimed in any of the preceding claims, comprising the steps of a) providing an unmodified polypropylene copolymer, b) adding the silane graft component and the free-radical initiator, c) evaporating the excess monomer, characterized in that the grafting reaction results in a decrease in melt viscosity, measured to DIN 53019 at 170°C, by 50-90% of the original viscosity of the unmodified polypropylene copolymer, and in an increase in the PDI, determined according to standard ISO 16014-1, by at least 20%.

10. The process as claimed in claim 9, characterized in that the unmodified polypropylene copolymer has a melt viscosity, measured to DIN 53019 at 170°C, of between 500 and 7000 mPas, preferably between 700 and 5000 mPas, more preferably between 800 and 4000 mPas, and an enthalpy of fusion, measured to ISO 11357-3, of between 30 J / g and 55 J / g.

11. A hotmelt adhesive formulation comprising a silane-modified polypropylene copolymer as claimed in any of claims 1-8 and one or more base polymers selected from the group consisting of unmodified polyolefins and unmodified thermoplastic styrene block copolymers (TPE-S), where these components together form at least 50% by weight of the hotmelt adhesive formulation and the silane-modified polyolefin is used to an extent of not more than 30% by weight, based on the total weight of the hotmelt adhesive formulation.

12. The hotmelt adhesive formulation as claimed in claim 11, characterized in that it has a melt viscosity at 170°C, measured to DIN 53019, of less than 5000 mPas and a tensile strength, measured to DIN EN ISO 527-3, of at least 4 MPa.

13. The hotmelt adhesive formulation as claimed in either of claims 11 and 12, characterized in that it contains less than 35% tackifier, based on the total mass of the hotmelt adhesive formulation.

14. The hotmelt adhesive formulation as claimed in any of claims 11 to 13, characterized in that it contains, based on the total mass of the hotmelt adhesive formulation, 40-80% by weight of base polymer, 10-30% by weight of silane-modified polypropylene copolymer and 10-30% by weight of tackifier.

15. The silane-modified polypropylene copolymer as claimed in any of claims 1-8 or hotmelt adhesive formulation as claimed in any of claims 11 to 14, characterized in that the silane-modified polypropylene copolymer or the hotmelt adhesive formulation comprises a crosslinking accelerator in an amount of 0.1-1% by weight, based on the total amount of the mixture of silane-modified polypropylene copolymer and crosslinking accelerator or of the hotmelt adhesive formulation.

16. The use of a silane-modified polypropylene copolymer as claimed in any of claims 1 to 8 or of a hotmelt adhesive formulation as claimed in any of claims 11 to 15 for adhesive bonding of substrates.