Process for producing a multiphase polymer system

Abstract

The aim was to provide a process for the production of polymers based on monomers with functionalized vinyl groups, which would enable polymers with controlled architecture and narrow molecular weight distribution to be produced in such a way that their mechanical properties are largely retained upon subsequent thermal stress. This is achieved by processes for producing a polymer system in at least two phases, comprising the steps: a) RAFT polymerization of a monomer composition I comprising at least 80% by weight of one or more monomers selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group to form a polymer A; and b) RAFT polymerization of a monomer composition II comprising, to a total of at least 80% by weight, one or more monomers selected from the group consisting of methacrylic acid esters, methacrylamides, and monomers having at least one polymerizable vinyl group, wherein the monomer composition II differs from those of the monomer composition I in at least 50% by weight of its monomers, in the presence of the polymer A to form a polymer B to obtain a polymer system present in at least two phases comprising the polymers A and B; characterized in that the RAFT polymerizations of steps a) and b) take place independently of one another in the presence of a specifically constructed RAFT regulator substance.

Description

The present invention is in the technical field of polymerization processes as they are used in a great variety both with regard to the apparatus used and with regard to the process conditions for the targeted production of plastics having particular property profiles. More specifically, the invention proposes a process for preparing a multi-phase polymer system comprising an at least two-stage RAFT polymerization, the steps of which are each carried out in the presence of a specific RAFT regulator substance. The most important background of application for the multiphase polymer systems produced in this way is pressure-sensitive adhesive compositions for adhesive tapes, with which both temporary and permanent material bonds are generated in various fields of technology.For industrial adhesive tape applications, polymers are frequently used which are based on the polymerization of monomers having functionalized vinyl groups. A known example of such polymers are poly(meth)acrylates. Poly(meth)acrylates have various advantages over other plastics which serve as a basis for adhesive applications. For example, they are very stable to high-energy radiation and oxidizing substances. Synthetic rubbers and natural rubbers, in contrast to poly(meth)acrylates, frequently contain C-C double bonds, which make these polymers and thus also adhesive components based thereon susceptible to, for example, UV radiation, oxygen and ozone. Furthermore, poly(meth)acrylate-based plastic formulations can be transparent and can be used within a wide temperature range.An important aspect which acts on the properties of polymers based on monomers having functionalized vinyl groups is the polymer architecture. In the further past, random copolymers have mostly been used in which the monomers are randomly distributed over the polymer chain. In recent decades, polymers with controlled structures, such as block copolymers or copolymers, have become increasingly active with a distribution gradient of the monomers. It is therefore attempted to control the profile of properties of the polymers and plastics formulations based thereon in a targeted manner via the distribution or arrangement of the monomers. In this way, it can be possible to achieve properties which are in themselves in the opposite sense using one and the same polymer base. In this connection, so-called RAFT polymerization has proven to be a very suitable method."RAFT polymerization" means "reversible addition-fragmentation chain transfer polymerization". By this is meant a polymerization in which the control of the reaction is achieved by reversible chain transfer reactions. An active, growing radical chain adds to a specific regulator substance, the so-called RAFT agent, which is already linked to a further chain and is thus present as a higher molecular weight RAFT agent (macro-RAFT agent). The addition of the active radical chain produces an intermediate which, owing to its structure, has the possibility of fragmenting towards various sides. This process again gives rise to a macro-RAFT agent and an active radical chain available for propagation, the latter not having to correspond to the previous active radical chain. In this way, the probability of propagation is uniformly distributed over all chains, resulting in a narrow molecular weight distribution.Methods for the controlled polymerization of (meth)acrylates are described in the prior art.WO 2004 / 101627 A1 describes a process for the continuous polymerization of acrylic monomers to polyacrylates in the presence of polymerization-regulating substances, at least one polymerization step being carried out within at least one reaction extruder.WO 2013 / 072120 A1 relates to a process for preparing polymers based on acrylate, in which a controlled free-radical polymerization reaction of a reaction template comprising at least one monomer based on acrylate is first carried out in the presence of at least one regulator substance having at least one functional group S-C=X, where X=S, O or N, where the regulator substance is selected from the group comprising dithioesters, dithiocarbonates, dithiocarbamates, trithiocarbonates, imido dithiocarbonates and xanthates ("RAFT regulator"), where the plurality of regulator substance molecules is incorporated into the resulting polymer chains, after which the respective polymer chain has the functional group of the incorporated regulator, characterized in that at least one chemical compound, the at least two conjugated double bonds (hereinafter referred to as "conjugated diene") are brought into contact with the polymers thus obtained, so that hetero-Diels-Alder reactions are effected between the double bonds C=X of the functional groups S-C=X incorporated into the polymer chains and the conjugated double bonds of the conjugated diene.EP 2 607 394 A1 discloses a process for producing PSAs, in which a controlled free-radical polymerization reaction of a reaction template comprising one or more monomers is carried out in the presence of at least one free-radical initiator for producing at least one polymer, characterized in that the free-radical initiator used is at least one cyclic 1,4-diradical which is produced by means of a cyclization reaction from a compound which has at least two unsaturated C-C bonds ("diradical-forming compound"), the polymerization reaction being carried out in the presence of at least one regulator substance ("polymerization regulator").WO 2013 / 055978 A1 describes acrylic copolymers that include a controlled placement of particular functional groups within the polymer structure. The copolymers contain at least two reactive segments and are prepared by a controlled free radical polymerization process. The copolymers are useful in the preparation of adhesives and elastomers.WO 2018 / 118905 A1 describes a crosslinkable composition comprising a) a polymeric material of formula wherein R 1 is hydrogen, alkyl, fluorinated alkyl, aryl, aralkyl or substituted aralkyl; X is oxygen or -NR 2 wherein R 2 is hydrogen, alkyl, fluorinated alkyl, aryl, aralkyl or substituted aryl; each R 3 is an alkoxy, fluorinated alkoxy or -N(R 4)2 wherein each R 4 is alkyl or fluorinated alkyl or together with the nitrogen to which they are both attached form a heterocyclic ring; each P is a polymeric block comprising a polymerized product of a first monomer composition comprising at least one monomer having a single ethylenically unsaturated group; y is an integer from 1 to 5; and b) comprises a second monomer composition miscible with the polymeric material of the formula and comprising a crosslinking monomer having at least two ethylenically unsaturated groups.WO 2018 / 178829 A1 describes controlled radical initiators, reaction mixtures comprising these and various ethylenically unsaturated monomers; polymeric materials formed from these reaction mixtures; crosslinkable compositions comprising the polymeric materials and crosslinked compositions formed therefrom. The controlled radical initiators are bisdithiocarbamate and bisdithiocarbonate compounds having a single carbon atom between the two dithiocarbamate or dithiocarbonate groups.Polymers based on monomers having functionalized vinyl groups have in the past been prepared regularly from solution and obviously also processed further in this form, for example to (pressure-sensitive) adhesive compositions. The polymers, optionally mixed with further substances, are coated from solution with a doctor blade or a similar auxiliary agent onto a carrier material and then dried.To increase cohesion, the polymers are generally crosslinked, which is usually effected either thermally, by UV radiation or by electron radiation. The solvent process is economically quite inefficient and environmentally hazardous overall, since the solvents are either not recovered and then contaminate the environment or must be recovered at high energy costs.Moreover, qualitative disturbances are regularly also produced. For example, adhesive tapes with a higher mass application based on the described polymers can frequently be produced hardly free of bubbles.To reduce these disadvantages, attempts have been made to apply the polymers or the compositions produced with them to the backing material from the melt in a "hot melt" process in the production of adhesive tapes. However, limitations are also associated with this technique. It is the nature of a hot melt process that the polymers are exposed to high temperatures during processing from the melt. If certain RAFT regulators such as, for example, symmetrically substituted trithiocarbonates are now used in the RAFT polymerization for preparing the polymers, the resulting polymers have a central trithiocarbonate group. This group is thermally labile and can accordingly decompose in the hotmelt process. Such decomposition processes manifest themselves in polymer degradation and, as a consequence, in the case of, for example, adhesives, in a measurable loss of cohesion.WO 98 / 01478 A1 relates to a free radical polymerization process which comprises contacting:(i) a monomer selected from the group consisting of vinyl monomers, maleic anhydride, N-alkylmaleimide, N-arylmaleimide, dialkyl fumarate, and cyclopolymerizable monomers;(ii) a thiocarbonylthio compound having a chain transfer constant greater than 0.1; and(iii) Free radicals from a corresponding sourceand adjusting the polydispersity of the polymer by varying the number of molecules (ii) to the number of molecules (iii). In this context, thiocarbonylthio compounds are proposed which lead to polymers which are subject to degradation under thermal stress and thus are subject to a loss of cohesion.EP 1 312 658 A2 describes pressure-sensitive adhesive systems at least comprising a pressure-sensitive adhesive based on at least one block copolymer, where the weight fractions of the block copolymers make up in total at least 50% of the pressure-sensitive adhesive, where at least one block copolymer is composed at least partially on the basis of (meth)acrylic derivatives, where at least one block copolymer furthermore has at least the unit P(A)-P(B)-P(A) composed of at least one polymer block P(B) and at least two polymer blocks P(A), and whereP(A) independently of one another represent homo- or copolymer blocks of monomers A, where the polymer blocks P(A) each have a softening temperature in the range from + 20° C. to + 175° C.,P(B) represents a homo- or copolymer block of monomers B, the polymer block P(B) having a softening temperature in the range from -130° C. to + 10° C.,the polymer blocks P(A) and P(B) are not homogeneously miscible with one another,characterized in that the pressure-sensitive adhesive system is oriented in that it has a preferred direction, the refractive index nMD measured in the preferred direction being greater than the refractive index Ncd measured in a direction perpendicular to the preferred direction. The PSAs are coated from the melt. This document also describes regulator substances which appear critical with regard to polymer degradation as a result of thermal stress.It was an object of the invention to avoid the problems known from the prior art and to provide a process for preparing polymers based on monomers having functionalized vinyl groups, with which polymers having a controlled architecture and a narrow molecular weight distribution can be prepared in such a way that their mechanical properties are largely retained under subsequent thermal loading.It was a further object of the invention to provide such a process which offers high flexibility for changes in the polymer formulation and the desired polymer architecture.A supplementary object of the invention was to provide polymers which can be produced in this way and have good cohesion and good melt processability.In particular, it was an object of the invention to provide polymers based on monomers having functionalized vinyl groups with a controlled architecture and a narrow molecular weight distribution, which survive a coating on a carrier material from the melt without significant loss of cohesion.It was a further supplementary object of the invention to provide such polymers which are particularly suitable for adhesive tape applications.A first and general subject of the invention, with which these objects are achieved, is a process for preparing a polymer system present in at least two phases, comprising the steps: a) RAFT polymerization of a monomer composition I comprising a total of at least 80% by weight of one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group to give a polymer A; and b) RAFT polymerization of a monomer composition II comprising a total of at least 80% by weight of one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group, where the monomer composition II differs in at least 50% by weight of its monomers from those of the monomer composition I, in the presence of the polymer A to give a polymer B, giving a polymer system present in at least two phases comprising the polymers A and B; characterized in that the RAFT polymerizations of steps a) and b) are independent of one another in the presence of a RAFT regulator substance, which in its original state corresponds to the general structure (I) R'-C(=S)-S-R (I) or the general structure (II) R'-C(=S)-S-R"-S-C(=S)-R'(II), in which the substituents R' independently of one another represent an aryl, aralkyl, n-alkylthio, carboxy-n-alkylthio, carboxylic acid ester-n-alkylthio, hydroxy-n-alkylthio, arylthio, alkoxy, alcaryloxy or alkenoxy radical or a radical (NR 1)2, wherein the substituents R 1 independently of one another represent an alkyl or aryl radical or form with the N atom a heterocyclic ring having 1 to 3 heteroatoms independently of one another selected from the group consisting of N, O and S; R is a sec- or tert-alkyl radical, a cyano-sec-alkyl radical, a cyano-tert-alkyl radical, a carboxy-tert-alkyl radical, a carboxy-sec-alkyl radical, an aralkyl radical or a radical of the general structure (III)-CR 2 R 3 R 4( III) in which R 2 is an alkyl radical or H, R 3 is a cyano, carboxy or carboxylic ester group and R 4 is an aryl radical; and R" is a group of the general structure (IV)-CR 5 R 6- Y-CR 5 R 6- ( IV), in which R 5 and R 6 independently of one another are a hydrogen atom, an n-alkyl group, a cyano group, a carboxy group or a carboxylic acid ester group, and Y is an alkylene or arylene group or a group having a structure selected from -(CH 2)m- CO-O-(CH 2)n- O-CO-(CH 2)m- and -(CH 2)m- CO-NR 7-( CH 2)n- NR 7- CO-(CH 2)m-, wherein n is an integer from 1 to 12; m is 0 to 4; and R 7 is an organyl radical.As has been shown, in this way it is possible to produce polyphase polymer systems from solution which, even if the solvent is then required, which is usually associated with particularly high temperatures, can be removed without substantial loss of cohesion and can subsequently be further processed from the melt largely without problems.Details and embodiments of the invention are described below. Such embodiments, which are designated below as preferred in any form, are combined in particularly preferred embodiments with features of other embodiments designated in any form as preferred. Combinations of two or more of the embodiments referred to below as particularly preferred in any form are thus very particularly preferred. Also preferred are embodiments in which a feature of one embodiment designated as preferred to any extent is combined with one or more further features of other embodiments designated as preferred to any extent.Insofar as both specific amounts or proportions of this element and preferred embodiments of the element are disclosed below for an element, the specific amounts or proportions of the preferably configured elements are also disclosed in particular. In addition, it is disclosed that at least some of the elements can be preferably designed for the corresponding specific total amounts or total proportions of the elements and in particular also that preferably designed elements can again be present in the specific amounts or proportions within the specific total amounts or total proportions.According to the invention, the term "polymer system" denotes both a single polymer and a mixture of two or more polymers different from one another. A "polymer" or "a single polymer" is understood here, in accordance with the expert's understanding, to mean not only a single macromolecule but also a plurality of macromolecules which originate from one and the same polymerization process and have a specific molar mass distribution among one another.The polymer system resulting from the process of the invention is present in at least two phases. Those skilled in the art will understand that one phase is rich in or consists essentially of one component of the polymer system, for example polymer A, and the other phase is rich in or consists essentially of another component, for example polymer B. The presence of small amounts of one component in the other, which does not prevent the formation of the polyphase configuration, is considered to be unimportant. If the polymer system resulting from the process of the invention has more than two phases, the above applies correspondingly to all of these phases.The phase separation is particularly preferably realized in such a way that discrete regions ("domains") which are rich in polymer A or polymer B-i.e. are formed substantially from polymer A or polymer B-are present in a continuous matrix which is rich in the respective other polymer-i.e. is formed substantially from the respective other polymer.A polymer system resulting from the method according to the invention is considered to be present in at least two phases in particular if at least one of the criteria a) - c) listed below is fulfilled: a) In an evaluation of the height profile of an atomic force microscopy (AFM) image of the polymer system, phase boundaries can be seen. b) At least two mutually independent glass transition temperatures are obtained from a dynamic differential calorimetry (DSC) measurement carried out on the polymer system. c) At least two tan δ maxima are obtained from a dynamic mechanical analysis (DMA) carried out on the polymer system.According to the invention, the polymer system present in at least two phases also comprises a microphase-separated polymer system, i.e. a polymer system in which the discontinuous phase is present in a microscopically fine distribution.The process of the invention comprises a step a) in which the RAFT polymerization of a monomer composition I comprising a total of at least 80% by weight, based on the total weight of the monomer composition I, of one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group to give a polymer A takes place.The monomer composition I preferably comprises one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group to an extent of at least 85% by weight, more preferably to an extent of at least 90% by weight, particularly preferably to an extent of at least 95% by weight, in particular to an extent of at least 98% by weight. Very particularly preferably, the monomer composition I comprises exclusively one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group.The RAFT polymerization of step a) can in principle be carried out in any desired manner. It is preferably carried out in solvents, in particular in solvents, in a customary reactor designed for such polymerizations.The polymer A resulting from the polymerization of step a) is preferably a polymer block from which it is possible to polymerize on starting from or onto the at least one further polymer block which can be distinguished therefrom.The process of the invention comprises a step b) in which, in the presence of the polymer A, the RAFT polymerization of a monomer composition II which comprises a total of at least 80% by weight, based on the total weight of the monomer composition I, of one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group, where the monomer composition II in at least 50% by weight of its monomers differs from those of the monomer composition I, to give a polymer B to give a polymer system present in at least two phases comprising the polymers A and B.The monomer composition II preferably comprises one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group to an extent of at least 85% by weight, more preferably to an extent of at least 90% by weight, particularly preferably to an extent of at least 95% by weight, in particular to an extent of at least 98% by weight. Very particularly preferably, the monomer composition II comprises exclusively one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group.The RAFT polymerization of step b) can also be carried out in principle in any desired manner. It is preferably carried out in solvents, in particular in solvents, in a customary reactor designed for such polymerizations.The process according to the invention is intended to result in a polymer system present in at least two phases. It was also an object of the invention to provide the two- or multi-phase polymer system with as high a cohesion as possible. It therefore appeared important to use these and optionally further properties of the final polymer system in the selection of the monomers used in the two polymerization steps.Against this background, in one embodiment of the invention, one of the monomer compositions I and II comprises a total of at least 50% by weight, more preferably a total of at least 60% by weight, in particular a total of at least 75% by weight, of one or more monomers having a glass transition temperature of the relevant homopolymer of ≤0° C., more preferably of ≤-10° C., in particular of ≤-20° C.; and the respective other of the monomer compositions I and II comprises a total of at least 60% by weight, more preferably a total of at least 70% by weight, in particular a total of at least 80% by weight, of one or more monomers having a glass transition temperature of the relevant homopolymer of ≥50° C., more preferably of ≥75° C., in particular of ≥100 ° C.In a further development of this embodiment, a total of at least 50% by weight of one of the monomer compositions I and II, more preferably a total of at least 60% by weight, in particular a total of at least 75% by weight, of one or more monomers selected from the group consisting of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-heptyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl acrylate, isodecyl acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl acrylate, 2-cyanoethyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, phenoxyethyl acrylate, isostearyl acrylate, Docosyl acrylate, and 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate; and the other of the monomer compositions I and II in each case comprises a total of at least 60% by weight, more preferably a total of at least 70% by weight, in particular a total of at least 80% by weight, of one or more monomers selected from the group consisting of isobornyl acrylate, norbornyl acrylate, benzyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl acrylate, 4-[(6-acryloyloxy)hexyloxy]4'-cyanobiphenyl, N-succinimidyl acrylate, 1-ethylcyclopentyl acrylate, N-tert-octylacrylamide, N-tert-butylacrylamide, dimethylacrylamide, diethylacrylamide, N-isopropylacrylamide, acrylamide, N-[3-(dimethylamino)propyl]acrylamide, diacetoneacrylamide, N-(butoxymethyl)acrylamide, N-phenylacrylamide, N-[2-(dimethylamino)ethyl]acrylamide, N-[2-(diethylamino)ethyl]acrylamide, methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, isobornyl methacrylate, glycerol formal methacrylate, 2-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, 9-anthrylmethyl methacrylate, 2-ethyl-2-adamantyl methacrylate, 2-(acetoacetyloxy)ethyl methacrylate, 2-isopropyl-2-methacryloyloxyadamantane, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, furfuryl methacrylate, 2-methacryloyloxy-2-methyladamantane, 2-morpholinoethyl methacrylate, phenyl methacrylate, N-succinimidyl methacrylate, 2-(tert-butylamino)ethyl methacrylate, 2-cyclohexylpropan-2-yl methacrylate, 1-adamantyl methacrylate, 1-methylcyclopentyl methacrylate, 3-dimethylaminopropyl methacrylamide, N-tert-butyl methacrylamide, N-(methoxymethyl) methacrylamide, N,N-dimethyl methacrylamide, methacrylamide, N-phenyl methacrylamide, N,N-dimethyl methacrylamide, N-isopropyl methacrylamide, N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylcrbazole, N-vinylimidazole, vinylmethyloxazolidinone and N-vinyl-N-methylacetamide.More preferably, one of the monomer compositions I and II comprises a total of at least 50% by weight, more preferably a total of at least 60% by weight, in particular a total of at least 75% by weight, of one or more monomers selected from the group consisting of n-butyl acrylate, isoamyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, isooctyl acrylate, n-octyl acrylate, n-decyl acrylate and isodecyl acrylate; and the other of the monomer compositions I and II in each case comprises a total of at least 60% by weight, more preferably a total of at least 70% by weight, in particular a total of at least 80% by weight, of one or more monomers selected from the group consisting of isobornyl acrylate, norbornyl acrylate, tert-butyl methacrylate, benzyl acrylate, N-isopropylacrylamide, N-tert-octylacrylamide, N-tert-butylacrylamide and dimethylacrylamide.In a further development of this embodiment, preferably one of the monomer compositions I and II comprises a total of at least 50% by weight, more preferably a total of at least 60% by weight, in particular a total of at least 75% by weight, of one or more monomers selected from the group consisting of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isoamyl acrylate, n-hexyl acrylate, n-heptyl acrylate, 2-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl acrylate, isodecyl acrylate, 2-[[(butylamino)carbonyl]oxy]ethyl acrylate, 2-cyanoethyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, phenoxyethyl acrylate, isostearyl acrylate, docosyl acrylate, and 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate; a total of not more than 35% by weight, more preferably a total of not more than 25% by weight, in particular a total of not more than 20% by weight, of one or more monomers selected from the group consisting of isobornyl acrylate, norbornyl acrylate, methyl methacrylate, dimethylacrylamide, diethylacrylamide, 4-tert-butylcyclohexyl acrylate, tert-butyl acrylate, tert-butyl methacrylate, cyclohexyl methacrylate and cyclohexyl acrylate, and a total of not more than 10% by weight of one or more functionalized monomers; and the other of the monomer compositions I and II in each case comprises a total of at least 60% by weight, more preferably a total of at least 70% by weight, In particular, a total of at least 80% by weight of one or more monomers selected from the group consisting of isobornyl acrylate, norbornyl acrylate, benzyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl acrylate, 4-[(6-acryloyloxy)hexyloxy]4'-cyanobiphenyl, N-succinimidyl acrylate, 1-ethylcyclopentyl acrylate, N-tert-octylacrylamide, N-tert-butylacrylamide, dimethylacrylamide, diethylacrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, acrylamide, N-[3-(dimethylamino)propyl]acrylamide, diacetoneacrylamide, N-(butoxymethyl)acrylamide, N-phenylacrylamide, N-[2-(dimethylamino)ethyl]acrylamide, N-[2-(diethylamino)ethyl]acrylamide, methyl methacrylate, ethyl methacrylate, Cyclohexyl methacrylate, benzyl methacrylate, isobornyl methacrylate, glycerol formal methacrylate, 2-dimethylaminoethyl methacrylate, phenoxyethyl methacrylate, 9-anthrylmethyl methacrylate, 2-ethyl-2-adamantyl methacrylate, 2-(acetoacetyloxy)ethyl methacrylate, 2-isopropyl-2-methacryloyloxyadamantane, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, furfuryl methacrylate, 2-methacryloyloxy-2-methyladamantane, 2-morpholinoethyl methacrylate, phenyl methacrylate, N-succinimidyl methacrylate, 2-(tert-butylamino)ethyl methacrylate, 2-cyclohexylpropan-2-yl methacrylate, 1-adamantyl methacrylate, 1-methylcyclopentyl methacrylate, 3-dimethylaminopropyl methacrylamide, N-tert-butyl methacrylamide, N-(methoxymethyl) methacrylamide, N,N-dimethylmethacrylamide, N-phenylmethacrylamide, N,N-dimethylmethacrylamide, N-isopropylmethacrylamide, N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylcrbazole, N-vinylimidazole, vinylmethyloxazolidinone and N-vinyl-N-methylacetamide; and a total of not more than 10% by weight of one or more functionalized monomers, wherein the functionalized monomers are selected from the group consisting of hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxy-3-phenoxypropyl acrylates, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, 4-hydroxyethylacrylamide, acrylic acid, methacrylic acid, 2-acryloyloxyethylsuccinate, Methacryloyloxyethyl succinate, sulfoethyl methacrylate, acrylamide, methacrylamide, glycidyl acrylate, glycidyl methacrylate, 3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexylmethyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, 4-hydroxybutyl methacrylate glycidyl ether, isocyanatoethyl acrylate, isocyanatoethyl methacrylate, 2-[2-(methacryloyloxy)ethyloxy]ethyl isocyanate, 2-[2-(acryloyloxy)ethyloxy]ethyl isocyanate and α, α-dimethyl-m-isopropenylbenzyl isocyanate.In particular, one of the monomer compositions I and II comprises a total of at least 50% by weight, more preferably a total of at least 60% by weight, in particular a total of at least 75% by weight, of one or more monomers selected from the group consisting of n-butyl acrylate, isoamyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, isooctyl acrylate, n-octyl acrylate, n-decyl acrylate and isodecyl acrylate; a total of not more than 35% by weight, more preferably not more than 25% by weight, in particular not more than 20% by weight, of one or more monomers selected from the group consisting of isobornyl acrylate, norbornyl acrylate, methyl methacrylate, dimethylacrylamide and not more than 10% by weight, of one or more monomers selected from the group consisting of acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylates, hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 3,4-epoxycyclohexylmethyl acrylates, 3,4-epoxycyclohexylmethyl methacrylate, glycidyl acrylate and glycidyl methacrylate; The other of the monomer compositions I and II in each case comprises a total of at least 60% by weight, more preferably a total of at least 70% by weight, in particular a total of at least 80% by weight, of one or more monomers selected from the group consisting of isobornyl acrylate, norbornyl acrylate, tert-butyl methacrylate, benzyl acrylate, N-isopropylacrylamide, N-tert-octylacrylamide, N-tert-butylacrylamide and dimethylacrylamide; and a total of a maximum of 10% by weight of one or more monomers selected from the group consisting of acrylic acid, methacrylic acid, 2-hydroxyethylacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexylmethyl methacrylate, glycidyl acrylate and glycidyl methacrylate.In a specific embodiment of the process according to the invention, at least monomer composition II is free from methyl methacrylate; more preferably it is free from methacrylic esters and methacrylamides; in particular it is free from any methacrylic compounds.Preferably, the monomer composition I is also free of methyl methacrylate; more preferably it is free of methacrylic esters and methacrylamides; in particular it is free of any methacrylic compounds.As has been shown, the exclusion of the compounds mentioned has an advantageous effect on the polymerization rate.According to the invention, the polymerizations of steps a) and b) take place independently of one another in the presence of a special RAFT regulator substance which, in its original state, corresponds to the general structure (I) R'-C(=S)-S-R (I) or the general structure (II) R'-C(=S)-S-R"-S-C(=S)-R'(II). "In its original state" here means that the regulator substance in question, without any constituent resulting from the monomers used, is considered to be the polymer chain bonded to it from the beginning of the polymerization.The substituents R' in the general structures (I) and (II) independently of one another preferably represent an aryl, n-alkylthio, carboxy-n-alkylthio, carboxylic acid ester-n-alkylthio, hydroxy-n-alkylthio, arylthio or alkoxy radical or a radical (NR 1)2, in which the substituents R 1 independently of one another represent an aryl radical. More preferably, the n-alkyl groups contained in said substituents are C 3- C 20- n-alkyl groups, particularly C 10- C 15- n-alkyl groups; and the aryl groups are phenyl groups.Y in the general structure (IV) preferably represents an alkylene or arylene group, more preferably an arylene group, and particularly preferably a phenylene group.In one embodiment of the invention, the RAFT regulator substance in its original state corresponds to the general structure (I), R' represents an aryl, n-alkylthio, carboxy-n-alkylthio, carboxylic acid ester n-alkylthio, hydroxy-n-alkylthio, arylthio or alkoxy radical or a radical (NR 1)2, in which the substituents R 1 independently of one another represent an aryl radical; the n-alkyl groups are preferably C 3- C 20- n-alkyl groups, in particular C 10- C 15- n-alkyl groups, the aryl groups are preferably phenyl groups; and R represents a cyano-tert-alkyl group, a carboxy-tert-alkyl group or a benzylthio group.In a further embodiment, the RAFT regulator substance in its original state corresponds to the general structure (II) in which the substituents R' are identical. The substituents R' are preferably each an aryl, n-alkylthio, carboxy-n-alkylthio, carboxylic acid ester-n-alkylthio, hydroxy-n-alkylthio, arylthio or alkoxy radical or a radical (NR 1)2 in which the substituents R 1 are independently of one another an aryl radical. More preferably, the n-alkyl groups contained in said substituents are C 3- C 20- n-alkyl groups, particularly C 10- C 15- n-alkyl groups; and the aryl groups are phenyl groups. Independently of or in combination with the preferred substituents described so far, in this embodiment R" represents a group of the general structure (V)-CH 2- Y-CH 2- ( V). Y in this group preferably represents an arylene group and particularly preferably a phenylene group.In one embodiment of the process of the invention, at least the RAFT polymerization of step b) is carried out in a solvent and the process comprisesc) removing the solvent under the action of temperature.It is an important advantage of the process of the invention that the polymers prepared in steps a) and b) can pass through this step without substantial loss of cohesion, independently of the apparatus used to remove the solvent. The solvent is preferably removed in an extruder.The invention further provides a polymer system present in at least two phases which can be prepared by a process according to the invention. The polymer system obtainable by a process according to the invention is preferably a block copolymer. The polymer blocks of this block copolymer are preferably formed by the polymers A and B. More preferably, the polymer system obtainable by a process according to the invention is a triblock copolymer, in particular a triblock copolymer of the form ABA or BAB in which A and B are the polymers A and B.Polymer systems according to the invention are distinguished inter alia in that they resist the action of high temperatures, as are used in particular for the removal of solvents in concentration extruders and similar apparatuses, but also during further processing, for example by means of extrusion, without substantial loss of cohesion. Without wishing to be bound by this theory, the inventors assume that the selection of the RAFT regulators used in the process according to the invention ensures that the RAFT regulators are not localized within the polymer chains at the end of the polymerization, but are localized terminally. Since the RAFT regulators are the most thermally labile structures within the polymer systems, their degradation under thermal stress therefore does not lead to polymer degradation and the associated loss of cohesion, as would be expected in the case of chain-internal localization of the RAFT regulator structures.Because of their cohesive resistance, polymer systems according to the invention can preferably be used as a component of a pressure-sensitive adhesive which is produced by thermally-mechanically effected mixing of their underlying components, as is effected, for example, in an extruder. The invention therefore also provides for the use of a polymer system according to the invention as a component for producing a pressure-sensitive adhesive by means of a method comprising thermally-mechanically effected mixing of the components for producing the pressure-sensitive adhesive.In accordance with the expert's understanding, a pressure-sensitive adhesive is an adhesive which has pressure-sensitive adhesive properties, i.e. the property of forming a permanent bond to a primer even under relatively weak pressure. Corresponding adhesives or pressure-sensitive adhesive tapes are generally permanently self-tacky even at room temperature, which means that they have a certain viscosity and tack, so that they wet the surface of a substrate even at low pressure. Without wishing to be bound by this theory, it is frequently assumed that a pressure-sensitive adhesive composition can be considered an extremely highly viscous liquid having an elastic fraction, which consequently has characteristic viscoelastic properties which lead to the above-described permanent inherent tackiness and pressure-sensitive adhesion capacity. It is assumed that in the case of pressure-sensitive adhesive compositions, both viscous flow processes and the build-up of elastic restoring forces occur during mechanical deformation. The proportional viscous flow serves to achieve adhesion, while the proportional elastic restoring forces are necessary in particular to achieve cohesion. The relationships between rheology and pressure-sensitive adhesiveness are known in the prior art and are described, for example, in "Satas, Handbook of Pressure Sensitive Adhesives Technology", third edition, (1999), pages 153 to 203. To characterize the extent of elastic and viscous fraction, the storage modulus (G') and the loss modulus (G") are usually used, which can be determined by means of dynamic mechanical analysis (DMA), for example using a rheometer. In the context of the present invention, an adhesive is preferably understood to be pressure-sensitively adhesive and thus as pressure-sensitively adhesive if, at a temperature of 23° C., in the deformation frequency range from 10 0 to 10 1 rad / sec G' and G" are each at least partially in the range from 10 3 to 10 7 Pa.In the apparatus used for producing the pressure-sensitive adhesive composition, which may be an extruder, for example, further process steps such as mixing with additives, filtration or degassing may also be carried out. The PSA obtained in this way can be shaped to a desired layer form, for example by means of a calender, onto a carrier or a release liner.In the course of processing a polymer system according to the invention to give a pressure-sensitive adhesive, the polymer system can be mixed with further components. These further components can be selected from the group consisting of further polymers; adhesion-enhancing resins; fillers, for example electrically conductive filler materials, thermally conductive filler materials and the like; flame retardants, for example ammonium polyphosphate and derivatives thereof; foaming agents; antioxidants; light stabilizers; plasticizers and compounding particles.ExamplesMeasurement and test methods:Method 1 - Determination of the Glass Transition Temperature of PolymersThe static glass transition temperature of the polymers was determined by means of dynamic scanning calorimetry (DSC). For this purpose, 5 mg of an untreated sample of the relevant polymer were weighed into an aluminum crucible (volume 25 μl) and sealed with a perforated lid. For the measurement, a DSC 204 F1 from Netzsch was used. The reaction was carried out under nitrogen for inertization. The sample was first cooled to -150° C., then heated at a heating rate of 10 K / min to +150° C. and cooled again to -150° C. The subsequent second heating curve was again run at 10 K / min and the change in the heat capacity was recorded. Glass transitions are thereby recognized as steps in the thermogram (heat flux-temperature diagram, see FIG. 1 ).The glass transition temperature T g is obtained as follows (see FIG. 1 ):The respective linearly running region of the measurement curve before and after the step is extended in the direction of increasing (region before the step) or decreasing (region after the step) temperatures (extension straight lines 1 and 2). In the region of the step, a compensation line 5 is placed parallel to the ordinate in such a way that it intersects the two extension lines, namely in such a way that two surfaces 3 and 4 (between the respective one extension line, the compensation line and the measurement curve) of the same content are produced. The intersection of the compensation straight line positioned in this way with the measurement curve yields the glass transition temperature.Method 2 - Determination of Molar MassesThe data on the weight-average molar mass M w in this specification relate to the determination known per se by gel permeation chromatography (GPC). The determination is carried out on 100 μl of clear-filtered sample (sample concentration 3 g / l). Tetrahydrofuran is used as the eluent. The measurement is carried out at 25° C.The precolumn used is a column type PSS-SDV, 5 μm, 10 3 Å, 8.0 mm*50 mm (details here and below in the order: type, particle size, internal diameter*length; 1 Å=10 -10 m). For the separation, a combination of the columns of the type PSS SDV, 5 μm, 10 3 Å and 10 5 Å and 10 6 Å with in each case 8.0 mm*300 mm is used (columns from Agilent; detection by means of a differential refractometer PSS SECcurity 2). The flow rate is 1.0 ml per minute. The calibration is carried out by means of the commercially available ReadyCal kit Poly(styrene) high from Agilent. This is universally converted into polymethyl methacrylate (PMMA) on the basis of the Mark-Houwink parameters K and.alpha., so that the data are specified in PMMA mass equivalents.The polydispersity (PDI) is determined in a manner known to the skilled worker as the quotient of weight-average and number-average molar mass.Method 3 - Dynamic Mechanical Analysis (DMA)G' and G" are determined using a rheometer. The material to be examined is subjected to a sinusoidal oscillating shear stress in a plate-plate arrangement. In shear stress controlled devices, the deformation as a function of time and the time offset of this deformation with respect to the introduction of the shear stress are measured. This time offset is referred to as phase angle δ.The storage modulus G' is defined as follows: G' = (τ / γ)·cos(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress and deformation vector). The definition of the loss modulus G" is: G" = (τ / γ)·sin(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress and deformation vector). Apparatus: Deformation Controlled Rheometer (ARES), Plate-Plate, φ 25 mm Deformation: 1% Frequency: 10 rad / s.Method 4 - Determination of Static Shear Strength (Shear Life)The shear strength is a measure of the internal strength of the adhesive and was tested in the so-called static shear test as follows, the influence of a preceding thermal load additionally being investigated:The test was carried out under standard climate (23° C., 50% relative humidity) using a weight of 1 kg.A 1.3 cm wide strip of the pattern (50 μm polymer layer on 36 μm etched PET film) was bonded to a polished steel plate over a length of 2 cm by rolling over with a 2 kg roll (back and forth twice each). The samples thus prepared were stored in an oven at 200°C for 6 hours and then equilibrated under test conditions but without load for 30 minutes. Then, the test weight (1 kg) was suspended so as to generate a shear stress parallel to the bonding surface, and the time until the bonding failed was measured. The measurement result is given in minutes. The median is given from three individual measurements.Preparation of Polymer AA 3 I vessel conventional for radical polymerizations was charged with 900 g of isobornyl acrylate (IBOA) and 10.395 g of dibenzyltrithiocarbonate (DBTTC) and 900 g of ethyl acetate (EtAc). After passing nitrogen gas through the reactor for 45 minutes while stirring, the contents of the reactor were heated to 58° C. and 1.376 g of Vazo® 67 were added. The reactor contents were then heated further to 65° C. After a reaction time of 24 h, the contents of the reactor were cooled to 35° C. The conversion was >95% and the proportion by weight of the polymer A in the polymer solution was 50%.Preparation of Polymer BA 3 l vessel conventional for radical polymerizations was charged with 447.6 g of the solution of polymer A and 676.2 g of n-butyl acrylate (nBA) and 676.2 g of ethyl acetate (EtAc). After passing nitrogen gas through the reactor for 45 minutes while stirring, the contents of the reactor were heated to 58° C. and 0.258 g of Vazo® 67 were added. The reactor contents were then heated further to 65° C. After 5 hours, it was diluted with 300 g of ethyl acetate. After a reaction time of 24 h, the contents of the reactor were cooled to 35° C. The conversion was >98%.Preparation of Polymer CA 3 I vessel conventional for radical polymerizations was charged with 900 g of n-butyl acrylate (nBA) and 3.933 g of 1,4-phenylenebis(methylene)didodecyldicarboxylicothrithioates (BM1812®) and 900 g of ethyl acetate (EtAc). After passing nitrogen gas through the reactor for 45 minutes while stirring, the contents of the reactor were heated to 58° C. and 0.229 g of Vazo® 67 were added. The reactor contents were then heated further to 65° C. After a reaction time of 24 h, the contents of the reactor were cooled to 35° C. The conversion was >95% and the proportion by weight of the polymer A in the polymer solution was 50%.Preparation of Polymer DA 3 l vessel conventional for radical polymerizations was charged with 1350 g of the polymer solution of polymer C and 225 g of isobornyl acrylate (IBOA) and also 225 g of ethyl acetate (EtAc). After nitrogen gas had been passed through for 45 minutes while stirring, the contents of the reactor were heated to 58° C. and 0.172 g of Vazo® 67 were added. The reactor contents were then heated further to 65° C. After 5 hours, it was diluted with 300 g of ethyl acetate. After a reaction time of 24 h, the contents of the reactor were cooled to 35° C. The conversion was >98%. M w= 706.000 g / mol; PDI=10.22 Table 1: weight-average molar mass, polydispersity and shear life of the polymers Table 1: Weight average molecular weight, polydispersity and shear recovery time of the polymersA. A44.0001,70B. B176.0001,83< 1C. C238.0001,46D. D706.00010,22> 10.000References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2004 / 101627 A1

[0006] WO 2013 / 072120 A1

[0007] EP 2 607 394 A1

[0008] WO 2013 / 055978 A1

[0009] WO 2018 / 118905 A1

[0010] WO 2018 / 178829 A1

[0011] WO 98 / 01478 A1

[0016] EP 1 312 658 A2

[0017] Cited Non-Patent LiteratureSatas, Handbook of Pressure Sensitive Adhesives Technology", Third Edition, (1999), pages 153 to 203

[0058]

Claims

A process for preparing a polymer system present in at least two phases, comprising the steps: a) RAFT polymerization of a monomer composition I comprising a total of at least 80% by weight of one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group to give a polymer A; and b) RAFT polymerization of a monomer composition II comprising a total of at least 80% by weight of one or more monomers selected from the group consisting of methacrylic esters, methacrylamides and monomers having at least one polymerizable vinyl group, where the monomer composition II differs from that of the monomer composition I in at least 50% by weight of its monomers, in the presence of the polymer A to give a polymer B to give a polymer system present in at least two phases, comprising the polymers A and B; characterized in that the RAFT polymerizations of steps a) and b) correspond, independently of one another, in the presence of a RAFT regulator substance which, in its original state, corresponds to the general structure (I) R'-C(=S)-S-R (I) or the general structure (II) R'-C(=S)-S-R"-S-C(=S)-R'(II), in which the substituents R' independently of one another represent an aryl, aralkyl, n-alkylthio, carboxy-n-alkylthio, carboxylic ester n-alkylthio, hydroxy-n-alkylthio, arylthio, alkoxy, alkaryloxy or alkenoxy radical or a radical (NR 1)2 in which the substituents R 1 independently of one another represent an alkyl or aryl radical or form with the N atom a heterocyclic ring having 1 to 3 heteroatoms independently of one another selected from the group consisting of N, O and S; R is a sec- or tert-alkyl radical, a cyano-sec-alkyl radical, a cyano-tert-alkyl radical, a carboxy-tert-alkyl radical, a carboxy-sec-alkyl radical, an aralkyl radical or a radical of the general structure (III)-CR 2 R 3 R 4( III) in which R 2 is an alkyl radical or H, R 3 is a cyano, carboxy or carboxylic ester group and R 4 is an aryl radical; and R" represents a group of the general structure (IV)-CR 5 R 6- Y-CR 5 R 6- ( IV) wherein R 5 and R 6 independently represent a hydrogen atom, an n-alkyl group, a cyano group, a carboxy group or a carboxylic acid ester group; and Y represents an alkylene or arylene group or a group having a structure selected from -(CH 2)m- CO-O-(CH 2)n- O-CO-(CH 2)m- and -(CH 2)m- CO-NR 7-( CH 2)n- NR 7- CO-(CH 2)m-, wherein n represents an integer of from 1 to 12; m represents 0 to 4; and R 7 represents an organyl radical.Process according to Claim 1, characterized in that the substituents R' are, independently of one another, an aryl, n-alkylthio, carboxy-n-alkylthio, carboxylic acid ester n-alkylthio, hydroxy-n-alkylthio, arylthio or alkoxy radical or a radical (NR 1)2 in which the substituents R 1 are, independently of one another, an aryl radical.Process according to Claim 2, characterized in that the RAFT regulator substance, in its original state, corresponds to the general structure (I) in which R represents a cyano-tert-alkyl radical, a carboxy-tert-alkyl radical or a benzylthio radical.Process according to Claim 1, characterized in that the RAFT regulator substance, in its original state, corresponds to the general structure (II), in which the substituents R' are identical.Process according to Claim 4, characterized in that the substituents R' are each an aryl, n-alkylthio, carboxy-n-alkylthio, carboxylic acid ester n-alkylthio, hydroxy-n-alkylthio, arylthio or alkoxy radical or a radical (NR 1)2 in which the substituents R 1 are each independently an aryl radical.Process according to either of Claims 4 and 5, characterized in that R" represents a group of the general structure (V) -CH 2- Y-CH 2- ( V).Process according to any of Claims 4 to 6, characterized in that R" represents a group of the general structure (IV)-CR 5 R 6- Y-CR 5 R 6- ( IV), in which Y represents an arylene group.Process according to any of the preceding claims, characterized in that at least the RAFT polymerization of step b) is carried out in a solvent and process c) comprises removing the solvent under the action of temperature.Polymer system present in at least two phases, obtainable by a process according to any of Claims 1 to 8.Use of a polymer system according to Claim 9 as a component for producing a pressure-sensitive adhesive by means of a method comprising thermally-mechanically effected mixing of the components for producing the pressure-sensitive adhesive.

Images