Polymers providing adhesion

Abstract

A material having the following structure: # imgabs0 # wherein R and R1 may be the same or different and each independently represents an alkyl group or an aryl group, X may be hydrogen or may be a branched or linear C1-C20 alkyl group, and wherein the aromatic ring substituent attached to polymer B is located meta-or para-position to the aromatic ring substituent attached to polymer A, and wherein polymer A is a non-polar polymer and polymer B is a polymer formed from at least two polar monomers for improving the adhesion of coatings such as paints, inks and adhesives to polyolefin substrates.

Description

[0001] The present invention relates to novel polymers having improved adhesion properties, in particular to olefin polymer and copolymer substrates such as polyethylene and polypropylene and copolymers of ethylene and propylene optionally with other olefin monomers. The polymers of the present invention are particularly useful for improving the adhesion of coatings such as paints, inks, adhesives, sealants, varnishes and primers to olefin polymers and copolymers.

[0002] Polyolefin-based resins such as polypropylene and polyethylene are inexpensive and have various good properties, such as good moldability, chemical resistance, water resistance and electrical properties. Such polyolefin-based resins are widely used in substrates such as sheets, films, molded products, etc. However, polyolefin-based resins are non-polar (hereinafter, these base materials containing polyolefin-based resins may be referred to as "polyolefin-based materials") and have a disadvantage in that they have low adhesion to polar materials such as those used in coatings such as paints, inks and adhesives.

[0003] It has been proposed to modify the surface of the polyolefin substrate by activation by plasma or gas flame treatment or corona treatment to improve the adhesion properties of the surface to overcome this problem. However, these methods are complex and require large equipment costs and involve time losses. Another disadvantage is that the effect of the surface treatment may be uneven, especially when the shape of the base material is complex and / or due to the influence of pigments or other additives in the polyolefin substrate, which only becomes apparent after a coating such as ink, paint or adhesive has been applied, which means that the part cannot be reprocessed and must be discarded with waste.

[0004] Another method to improve the adhesion of olefin polymers or copolymers to polar coatings is to use chlorinated polyolefin resins as primer coating compositions to improve the affinity of the polyolefin base material to polar paints or other polar materials, thereby improving adhesion properties. However, this method has stability issues due to dehydrochlorination. In addition, due to the recent increasing environmental awareness, there is a trend to avoid the use of chlorine.

[0005] European Patent EP2380917 relates to improving the adhesion of coatings to polyolefin substrates and provides an energy ray-curable resin composition comprising a block copolymer (C) comprising a polymer block (A) mainly composed of olefin-based monomer units and a polymer block (B) composed of units derived from (meth)acrylic acid and / or units derived from methacrylate, the weight average molecular weight of the block copolymer (C) being 5,000 or more and 100,000 or less; and an active energy ray-curable compound (D) selected from mono(meth)acrylates and poly(meth)acrylates. This technology is also disclosed in a paper entitled "Study on Propylene-Acrylic Block Copolymers as Additives in UV Curable Coatings" by Hideo Hosaka, Yu Takatu, Shuaiji Sekiguchi and Kon-ich-Fuji Iio.

[0006] The disadvantages of this technology are that both the block copolymer and a separate active energy ray curable resin compound must be used in order to obtain the desired adhesion of the coating to the olefin polymer or copolymer, and further, once applied to the polyolefin substrate, the material must be irradiated to activate the adhesive properties of the system. Furthermore, the molecular weight of the polymer is controlled by thermal degradation, which is not the best method for molecular weight control.

[0007] It has now been discovered that satisfactory adhesion between a coating and an olefin polymer or copolymer substrate can be achieved with certain diblock copolymers which can be applied as an intermediate primer layer to the surface of the olefin polymer or copolymer substrate or can be incorporated into the coating material as an additive. This provides good adhesion while requiring less surface preparation than earlier technologies. In many cases, the substrate can simply be coated and dried in preparation for application of the coating material.

[0008] European Patent EP2684940 and European Patent EP3144330 disclose certain block copolymers of the formula

[0009]

[0010] As a fuel and oil additive and a method for preparing such a block copolymer, European Patent EP3253810 discloses the use of such a polymer as a polymer additive.

[0011] It has now been discovered that certain block copolymers having the following structure are useful for promoting adhesion between olefin polymer substrates and polar coating materials such as inks and paints:

[0012]

[0013] Where R and R 1 X may be the same or different and each independently represent an alkyl or aryl group, X may be hydrogen or a branched or linear C1-C 20 The present invention relates to a polymer having an alkyl radical and wherein the aromatic ring substituent attached to polymer B is located at the meta or para position to the aromatic ring substituent attached to polymer A, and wherein polymer A is a non-polar polymer (or copolymer) and polymer B is a polar copolymer formed from two or more polar monomers. The selection of polymer A and polymer B will depend on the nature of the olefin polymers and coatings to be bonded together.

[0014] In a preferred embodiment,

[0015] i) polymer A comprises chains of ethylene or propylene structural units, optionally copolymerized with higher 1-olefin comonomers, preferably chains of polyethylene or polypropylene or propylene / ethylene copolymers, and

[0016] ii) polymer B is derived from two or more α,β-unsaturated polar monomers selected from styrene, substituted styrenes, unsaturated esters such as acrylates, methacrylates such as butyl acrylate, methyl (meth)acrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, poly(ethylene glycol) methacrylate, butyl methacrylate and hydroxyethyl acrylate, and vinyl esters, fumarates, itaconates, maleic anhydride, unsaturated acids such as acrylic acid and methacrylic acid ionomers and diene compounds and their derivatives, polymer B may comprise copolymers of such unsaturated monomers with olefins such as C2 to C8, preferably C2 to C6 olefins.

[0017] These polymers can be prepared by the following steps:

[0018] a) in a first step, an olefin, such as ethylene or propylene, and optionally one or more 1-higher olefin comonomers are polymerized to form a polymer A, which is a chain consisting of ethylene or propylene structural units optionally bearing side chain alkyl groups derived from the 1-olefin comonomers, the polymerization being carried out in the presence of a compound of formula (I):

[0019]

[0020] Wherein, during the reaction, the terminal of compound (I) is bonded to polymer A, resulting in the formation of a terminal unsaturated intermediate of formula (II):

[0021]

[0022] b) in an optional second step, recovering the intermediate (II) from the reaction mixture of the first step; and

[0023] c) in a third step, reacting the intermediate (II) at its terminal double bond with a mixture of two or more polar monomers (optionally copolymerized with non-polar monomers) in a subsequent polymerization reaction to form a polymer B attached to the intermediate (II), wherein R, R 1 and X are as defined previously.

[0024] Optionally, step a) can be carried out under hydrogen pressure to control the properties of polymer A. Step a) uses a catalyst for the polymerization of monomers and the reaction of the polymer with the compound of formula (I). Any suitable olefin polymerization catalyst can be used, such as a conventional Ziegler catalyst, with metallocene catalysts being preferred, although catalysts mentioned in Angie-Chem. Int. Ed 20142-25 entitled POST METALLOPENES IN THE INDUSTRIAL PRODUCTION OF POLYOLEFINS can be used.

[0025] In this specification, the word "terminal" when used in relation to a polymer chain (or block) refers only to the end of the polymer chain (or block), and does not express any additional mechanistic requirement that the chain (or block) end in question is the end at which the polymerization reaction is terminated. "Terminally" should be interpreted similarly.

[0026] It is important that polymer A is terminally linked to polymer B so that polymer A is exposed to interact with the polymer substrate, which is used together with the polymer substrate to provide improved adhesion of the coating to the substrate. Therefore, it is important that the link between polymer A and polymer B is at the end of the polymer chain of polymer A.

[0027] In order to achieve such terminal orientation of the linkage between polymer A and polymer B, it is necessary that the process for preparing the copolymer is specific with respect to the terminal functionalization of polymer A. Likewise, it is important that the terminal functionalization formed on polymer A is sufficiently reactive to enable subsequent formation of polymer B under free radical polymerization conditions typically used in industry, while not being so reactive that substantial undesirable side reactions occur.

[0028] Preferred materials of and for use in the present invention are those in which polymer A comprises chains of ethylene or propylene structures or ethylene / propylene copolymer chains optionally interrupted by one or more structural units derived from higher 1-olefin comonomers such as hexene or octene, and polymer B comprises chains of structural units derived from two or more α,β-unsaturated polar monomers selected from styrene, substituted styrenes, unsaturated esters such as acrylates and methacrylates, vinyl esters, fumarates, itaconates, maleic anhydride, unsaturated acids such as acrylic acid and methacrylic acid and diene compounds and derivatives thereof, polymer B being a copolymer of such monomers with an olefin such as a C2 to C8 olefin. In a preferred embodiment, polymer B is a copolymer of at least three monomers, at least some of which provide pendant polar groups on polymer B for interaction with polar groups in the coating material to be bonded to the polyolefin substrate.

[0029] The material used in the present invention can be prepared by a method comprising the following steps:

[0030] a) In a first step, an olefin, typically ethylene or propylene, and optionally one or more higher 1-olefin comonomers, are polymerized to form polymer A in the presence of a compound of formula (I):

[0031]

[0032] Wherein, during the reaction, the terminal of compound (I) is bonded to polymer A, resulting in the formation of a terminal unsaturated intermediate of formula (II):

[0033]

[0034] b) optionally, in a second step, recovering the intermediate (II) from the reaction mixture of the first step; and

[0035] c) In a third step, the intermediate (II) is reacted at its terminal double bond with two or more polar monomers to form polymer B in a subsequent polymerization reaction.

[0036] Where R, R 1 and X are as defined above.

[0037] The method aspect of step c) is preferably carried out in the presence of a free radical source, which initiates the polymerization of the two or more α,β-unsaturated monomers with each other and with the intermediate (II). Examples of such monomers include styrene, substituted styrene, unsaturated esters such as acrylates and methacrylates, vinyl esters, fumarates, itaconates (including esters containing polar groups such as hydroxyl groups), unsaturated acids such as acrylic acid and methacrylic acid, unsaturated anhydrides such as maleic anhydride and diene compounds and derivatives thereof. As known in the art, such a free radical source can be a chemical initiator substance, or it can be an external physical input into the reaction, such as light or other radiation sources. Preferably, the free radical source is a chemical initiator substance, such as a peroxide initiator, an azo initiator or other such substances. Preferred monomers for preparing polymer B include butyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, glycidyl methacrylate, poly(ethylene glycol) methacrylate, poly(propylene glycol) methacrylate, hydroxyethyl acrylate, acrylic acid and methacrylic acid, maleic anhydride and various ionomers. Preferred materials include block copolymers where polymer A is derived from propylene or ethylene, optionally together with other olefins, and polymer B is a terpolymer of butyl acrylate, acrylic acid and hydroxyethyl methacrylate.

[0038] Therefore, in a preferred embodiment, the material used in the present invention comprises two polymer segments A and B, wherein:

[0039] i) polymer A comprises chains of ethylenic and / or propylene structural units, optionally interrupted by one or more structural units derived from higher 1-olefin comonomers, and

[0040] ii) polymer B comprises a chain of structural units derived from two or more α,β-unsaturated monomers selected from styrene, substituted styrenes, unsaturated esters such as acrylates, methacrylates and vinyl esters, fumarates, itaconates, unsaturated acids such as acrylic acid and methacrylic acid, maleic anhydride and diene compounds and their derivatives, polymer B may comprise a copolymer of such unsaturated monomers with an olefin such as a C2 to C8, preferably a C2 to C6 olefin;

[0041] And wherein polymer A and polymer B are connected at the ends so that the copolymer has the following structure:

[0042]

[0043] Among them, R 1 and X are as defined above and wherein the aromatic ring substituent attached to polymer B is located at the meta or para position to the aromatic ring substituent attached to polymer A.

[0044] Preferably, each of R and R 1R and R are independently an alkyl group having 1 to 4 carbon atoms. 1 The same, most preferably both are methyl.

[0045] Preferably, the aromatic ring substituent attached to polymer B is located at a meta position to the aromatic ring substituent attached to polymer A.

[0046] Polymer A is selected to be compatible with the olefin polymer or copolymer that provides the substrate to which the coating is to be adhered. Preferably, when the polymer of the present invention is used with a substrate that is primarily based on polypropylene, polymer A consists primarily of propylene, although other comonomers may also be present. Similarly, when the polymer is used with a substrate that is primarily based on polyethylene, polymer A preferably consists primarily of polyethylene, although other comonomers may also be present. We generally find that this results in improved adhesion between the surface coating and the substrate.

[0047] In another preferred embodiment, polymer A used in the material of the invention consists of polypropylene chains.

[0048] In another preferred embodiment, polymer A used in the material of the present invention consists of an ethylene-propylene copolymer.

[0049] In another preferred embodiment, polymer A used in the material of the present invention consists of ethylene 1-hexene copolymer.

[0050] In another preferred embodiment, polymer A used in the material of the present invention consists of ethylene 1-octene copolymer.

[0051] If desired, polymer A can be provided with some polarity after formation by grafting unsaturated monomers such as maleic anhydride onto polymer A.

[0052] When one or more higher 1-olefin monomers are used in combination with ethylene or propylene to form polymer A, preferably the total proportion of higher 1-olefin monomers is 1 to 50 mol%, preferably 2 to 40 mol%, with the remainder of polymer A being derived from ethylene or propylene. When used, the amount of 1-olefin monomer in polymer A is preferably 2-15 mol%. The preferred 1-olefin monomer is octene.

[0053] Polymer A is preferably prepared using a metallocene catalyst, and suitable metallocene catalysts for preparing polymer A include transition metals, particularly metals of Group IV of the Periodic Table of Elements, such as Ti, Zr or Hf, with one or more ligands, such as cyclopentadienyl ("Cp"), substituted cyclopentadienyl (including indenyl, fluorenyl and derivatives thereof) and bridged variants of the above. Additional ligands may be coordinated or bonded to the metal via heteroatoms such as N, O, S or P, and may include bridges connected to the above Cp-type ligands.

[0054] The above catalysts are usually synthesized and stored as metal dichloride / dialkyl (e.g. dibenzyl) or monoalkyl-monochloride materials ("precatalysts"). This is activated in solution by the addition of a cocatalyst (usually methylaluminoxane (MAO) or polymethylaluminoxane (PMAO)), but alternatively non / weakly coordinating anions may be used, for example, a combination of a boron-containing material such as Ph3C+B(C6F5)4- and a trialkylaluminum material such as i-(C4H9)3Al.

[0055] Examples of the above catalysts include Cp2MCl2, Cp*2MCl2, EBIMCl2, Flu(Ph2Me)CpMCl2, and Cp(Me)4(Me2Si)NtBuMCl2, where M represents a transition metal. A preferred catalyst is one in which M represents zirconium. An exemplary catalyst is Cp2ZrCl2 and a co-catalyst.

[0056] The polymer B of the present invention is a copolymer of at least two polar monomers, wherein at least one of the monomers ensures the dispersion or dissolution of the block copolymer of the present invention in the medium in which it is used, which medium can be a solvent or liquid carrier when it is used as a primer coating, or a solvent or carrier for the coating material when the polymer of the present invention is included in the coating material. The polymer B also contains at least one other polar monomer, which provides adhesion between the olefin polymer or copolymer substrate and the coating to be applied thereto, and which tends to contain polar materials in the case of paints, inks or adhesives.

[0057] It is preferred that polymer B is derived from acrylate monomers because of their good reactivity with diisopropylbenzene, which is a preferred material for block copolymer manufacture. In particular, it has been found to be particularly useful to use butyl acrylate with acrylic acid because butyl acrylate provides solubility in solvents such as xylene and acrylic acid provides the polarity required to react with functional groups within coatings such as inks and paints.

[0058] The preferred composition of polymer A and polymer B will depend on the substrate with which it will be used and on the nature of the topcoat to be bonded to the substrate. However, when polymer A is primarily based on propylene, it is preferred that its number average molecular weight is 3000-5000. When polymer A is primarily based on ethylene, it is preferred that its number average molecular weight is 1000-10,000, preferably 1000-2000. The preferred range of the number average molecular weight of polymer B is 500-5000. All molecular weights are measured by NMR.

[0059] The polymers of the present invention can be used as an intermediate primer coating on a substrate for adhering a topcoat to the substrate. Alternatively, the polymer can be incorporated into the topcoat. As another or less preferred alternative, the polymers of the present invention can be contained in the substrate. In the case where the polymer is applied as a primer coating to a polyolefin substrate, it is preferably applied as a solution or suspension of the polymer and dried after application before applying the topcoat. The liquid used to prepare the solution or suspension depends on the conditions used, however, when the polymer is applied as a suspension, organic solvents such as xylene and butanol can also be used, water can also be used; surfactants can be included if necessary. Mixtures of solvents can also be used, for example a mixture of an organic solvent such as butyl acrylate and water.

[0060] Similarly, when the polymer is included in a topcoat and the topcoat is to be applied as a liquid, the polymer should be soluble or dispersible in the liquid medium used in the topcoat. If the topcoat is applied in the form of a melt, the polymer of the present invention should be miscible or soluble in the molten topcoat when applied.

[0061] Examples of topcoats that can be used in the present invention include paints, such as automotive paints that can be water-based or solvent-based. Typical paints include 2K paints, such as 2K polyurethane paints, acrylic paints, spray paints. Other coatings are inks, such as typical commercial inks, including solvent-based inks. The present invention can also be used to fix adhesives (including most typical commercial adhesives and other coatings such as varnishes) to polyolefin substrates.

[0062] It has been found that the polymers of the present invention can be used to promote the adhesion of coatings to various substrates. For example, the substrates can include molded and extruded articles, including films and heavy-duty sheets; various types of components such as automobiles and household appliances. The substrates can be filled with, for example, reinforcing fibers, such as glass or carbon fibers. The substrates can also contain other conventional additives.

[0063] The following Example 1 illustrates the preparation of a material useful in the present invention wherein polymer A is polypropylene.

[0064] Preparation of polypropylene, 1,3-diisopropylbenzene intermediate,

[0065] The catalyst used was a mixture of a 30 wt% solution of polymethylaluminoxane in toluene and racemic ethylenebis(1-indenyl)zirconium dichloride.

[0066] 0.013 kg of polymethylaluminoxane solution, 0.014 g of zirconium dichloride, 0.216 g of hydrogen, 0.316 liters of meta-diisopropylidene benzene, 1.391 kg of propylene and 0.685 liters of toluene were charged into a stirred high-pressure reactor.

[0067] The vessel was pressurized with nitrogen and heated to 60°C. Toluene, diisopropylidene benzene and catalyst were first charged into the reactor stirred at 850 rpm. Propylene was then fed into the reactor along with hydrogen. The reaction temperature was monitored and when the exothermic peak was reached, the temperature was maintained between 70°C and 75°C until the catalyst was consumed.

[0068] The reactor was then vented, the contents drained and allowed to cool; 7 liters of methanol were added to dissolve the polymer. Finally, the sample was filtered, washed with methanol and dried in vacuo at 85°C for 3 days.

[0069] When analyzed, the polymer had an Mn of 4400 g / mol and an Mw of 9400 g / mol.

[0070] The desired terminal functionalized structure was confirmed by NMR spectroscopy.

[0071] For example, NMR spectra can be recorded on Bruker DPX400 and DPX500 spectrometers, where 1 H and 13 C NMR spectra were internally referenced using the solvent resonance relative to tetramethylsilane. Routine NMR assignments (including polymer samples) can be made by 1 H- 1 H(COSY), 13 C- 1 H(HMQC) and 13 C- 1 Confirmed by H(HMBC) association experiment.

[0072] In particular, to confirm the terminal insertion of compound (I), 1 H NMR spectroscopy. The amount of terminal insertion is determined by comparing the spectral peaks of the methyl group at one end of the polyethylene chain (which has three protons) and the single proton on the benzylic carbon of the 1,3-DIB molecule remaining after step a) of the reaction. Any chain-incorporated 1,3-DIB does not have a proton on this carbon, so this proton resonance is used to distinguish terminal insertions of 1,3-DIB.

[0073] Related to these protons 1 The H NMR peaks have chemical shifts of 0.91 ppm and 2.71 ppm, respectively (chemical shift measured relative to the residual solvent signal in d2-TCE at 5.94 ppm). Comparison of the integrations of these two peaks gives the amount of terminal insertion by 1,3-DIB and indicates that essentially every polypropylene chain is end-functionalized with a residue from 1,3-DIB.

[0074] The third step c) of the process involves the formation of polymer B by free-radical polymerization. The following examples show how this can be done.

[0075] The polypropylene diisopropylbenzene feedstock thus prepared is then used as the starting material for preparing the polypropylene-diisopropylbenzene-block (butyl acrylate / acrylic acid / hydroxyethyl methacrylate) copolymer of the present invention, as described below.

[0076] 2.42 grams of benzoyl peroxide initiator are dissolved in 20 ml of xylene in a container, which is then purged with nitrogen. 15 grams of polypropylene diisopropylbenzene and 150 ml of xylene are charged into a separate container; acrylic acid and 12.31 ml of hydroxyethyl methacrylate are charged into a third container equipped with an air purge. Polypropylene diisopropylbenzene is placed in a reactor and heated to 125° C. under mechanical stirring while purging with nitrogen. The acrylic monomer mixture and initiator are then fed into the reactor while the reactor is maintained at 125-130° C. for a period of about 1 hour, and the reaction product is obtained in the form of a polymer dispersion in xylene.

[0077] The final polymer was found to have an Mw of approximately 1200 g / mol, and initial analysis of the polar block indicated a ratio of monomer units of 13 butyl acrylate: 5 acrylic acid: 5 hydroxyethyl methacrylate, and a molecular weight (Mw) of 2,700 g / mol.

[0078] In one run, the homopolymer formed together with any unreacted monomer is removed. In the second run, the homopolymer and unreacted monomer remain in the product.

[0079] Example 2

[0080] A product comprising polyethylene / diisopropylbenzene / poly(butyl acrylate / acrylic acid / hydroxyethyl methacrylate copolymer) was prepared in a manner similar to the product of Example 1, except that ethylene was used instead of propylene as the feed for the first preparation stage to produce a polyethylene / diisopropylbenzene polymer having an Mn of 1300 g / mol and an Mw of 4,200 g / mol.

[0081] Initial analysis of the polar block of the product indicated a ratio of 3 butyl acrylate: 2 acrylic acid: 2 hydroxyethyl methacrylate monomer units and an Mw of 800 g / mol, giving a final product Mw of approximately 5000 g / mol.

[0082] In both examples, molecular weight was determined by high temperature GPC in TCB at 160°C.

[0083] An important use of the polymers of the present invention is to provide interfacial activity, such as the interfacial activity required to provide a printable or paintable surface on a polyolefin substrate, such as for packaging films, bags, garbage disposal bags, automotive parts such as bumpers, etc., a material can be used wherein polymer A is a polyolefin such as polyethylene or polypropylene, and polymer B is a polymer of a polar monomer that reacts with a polar compound in a coating material such as a paint or ink to obtain the desired adhesion such as vinyl acetate, acrylates such as methyl acrylate and butyl acrylate or itaconate. Examples of preferred monomers for preparing polymer B are acrylates, substituted acrylates and unsaturated carboxylic acids.

[0084] Example 3

[0085] Example 1 was repeated except that 0.85 mol% of octene-1 was included in propylene to prepare a polymer wherein polymer A was a propylene / octene-1 copolymer.

[0086] The products of Examples 1, 2 and 3 were tested as coatings on polypropylene and polyethylene to determine their adhesive properties and were found to have good adhesion to polyethylene and polypropylene sheets and on biaxially oriented polypropylene film. Adhesion was found to be good.

[0087] Dispersions of the material of Example 1 in xylene were tested as primer coatings on polypropylene and propylene copolymer substrates to determine their ability to bond inks, automotive paints and adhesives (including epoxy and urethane based adhesives) and 2KPU clearcoats to the substrates. Adhesion was found to be good.

[0088] The dispersions of Example 2 in xylene were tested as primer coatings on polyethylene and ethylene copolymer substrates to determine their ability to bond inks, automotive paints and 2KPU clearcoats to the substrates and were found to have good adhesion.

[0089] Adhesion was tested according to ASTM-D3359 Test Method B (Cross Cut Tape Test) using Tesa 25mn 4651 tape and BYK Cross Cut Knife II Blade 1 - Edge 1.5mn (5127).

[0090] The products of both runs of Example 1 were also used as additives in inks and automotive paints at various concentrations and the adhesion of the inks and paints to propylene copolymer substrates was measured and good adhesion was achieved with these blends.

Claims

1. A block copolymer having the following structure: Where R and R 1 X may be the same or different and each independently represents an alkyl or aryl group, X may be hydrogen or a branched or linear C1-C 20 alkyl, and wherein the aromatic ring substituent attached to polymer B is located at the meta or para position of the aromatic ring substituent attached to polymer A, and wherein polymer A is a non-polar polymer (or copolymer), and polymer B is a polar copolymer formed from two or more polar monomers.

2. The block copolymer according to claim 1, wherein i) polymer A comprises chains of ethylenic or propylene structural units, optionally copolymerized with higher 1-olefin comonomers, ii) Polymer B is derived from two or more α,β-unsaturated polar monomers selected from styrene, substituted styrenes, unsaturated esters such as acrylates, methacrylates and vinyl esters, fumarates, itaconates, maleic anhydride, unsaturated acids such as acrylic acid and methacrylic acid, ionomers and diene compounds and their derivatives.

3. The block copolymer according to claim 2, wherein polymer B comprises a copolymer of an unsaturated monomer and a C2-C8 olefin.

4. The block copolymer according to any one of the preceding claims, wherein polymer B is a copolymer of at least three monomers, at least some of which provide pendant polar groups on polymer B.

5. The block copolymer according to any one of the preceding claims, wherein polymer B is a terpolymer.

6. The block copolymer according to any one of the preceding claims, wherein one of the monomers in polymer B is butyl acrylate.

7. The block copolymer according to claim 6, wherein polymer B is a terpolymer of butyl acrylate, acrylic acid and hydroxyethyl methacrylate.

8. The block copolymer according to any one of the preceding claims, wherein polymer A is polypropylene or a propylene-containing polymer and has a number average molecular weight in the range of 3000 to 5000.

9. The block copolymer according to any one of the preceding claims, wherein polymer A is polyethylene or an ethylene-containing polymer and has a number average molecular weight in the range of 1000 to 10,000.

10. The block copolymer according to any one of the preceding claims, wherein the number average molecular weight of polymer B is in the range of 500 to 5000.

11. A solution of a block copolymer according to any one of the preceding claims.

12. A dispersion of a block copolymer according to any one of the preceding claims.

13. The dispersion of claim 12 comprising an aqueous dispersion.

14. Use of a block copolymer according to any one of the preceding claims as an adhesive for fixing polar coating materials to polyolefin substrates.

15. Use according to claim 14, wherein the block copolymer comprises a primer coating on the polyolefin substrate and the polar coating material is a top coating.

16. The use according to claim 14, wherein the block copolymer is a component in the polar coating material.

17. The use according to any one of claims 14 to 16, wherein the polyolefin substrate is polypropylene or a propylene copolymer, and polymer A is also polypropylene or a propylene copolymer.

18. The use according to any one of claims 14 to 16, wherein the polyolefin substrate is polyethylene or an ethylene copolymer, and polymer A is also polyethylene or an ethylene copolymer.

19. Use according to any one of claims 14 to 18, wherein the polar coating material is a paint.

20. The use according to any one of claims 14 to 18, wherein the polar coating material is an ink.

21. The use according to any one of claims 14 to 18, wherein the polar coating is an adhesive.

22. An ink comprising the block copolymer according to any one of claims 1 to 10.

23. A paint comprising the block copolymer according to any one of claims 1 to 10.

24. An adhesive comprising the block copolymer according to any one of claims 1 to 10.

25. A method for preparing a block copolymer according to any one of claims 1 to 10, the method comprising the following steps: a) In a first step, an olefin, typically ethylene or propylene, and optionally one or more higher 1-olefin comonomers, are polymerized to form polymer A, said reaction being carried out in the presence of a compound of formula (I): In the reaction process, the terminal of compound (I) is bonded to polymer A, resulting in the formation of a terminal unsaturated intermediate of formula (II): (b) optionally, in a second step, recovering the intermediate (II) from the reaction mixture of the first step; and c) in a third step, reacting the intermediate (II) at its terminal double bond in a subsequent polymerization reaction with two or more polar monomers to form polymer B; wherein R, R1 and X are as defined above.

26. The method of claim 25, wherein step c) is performed in the presence of a free radical source which initiates polymerization of the two or more α,β-unsaturated monomers with each other and with the intermediate (II).

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