Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/0053—Details of the reactor
  • B01J19/0066—Stirrers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/18—Stationary reactors having moving elements inside
  • B01J19/1812—Tubular reactors
  • B01J19/1818—Tubular reactors in series
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/18—Stationary reactors having moving elements inside
  • B01J19/20—Stationary reactors having moving elements inside in the form of helices, e.g. screw reactors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J4/00—Feed or outlet devices; Feed or outlet control devices
  • B01J4/02—Feed or outlet devices; Feed or outlet control devices for feeding measured, i.e. prescribed quantities of reagents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
  • B29C48/08—Flat, e.g. panels flexible, e.g. films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
  • B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
  • B29C48/435—Sub-screws
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
  • B29C48/40—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using two or more parallel screws or at least two parallel non-intermeshing screws, e.g. twin screw extruders
  • B29C48/435—Sub-screws
  • B29C48/44—Planetary screws
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/02—Polymerisation in bulk
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/04—Polymerisation in solution
  • C08F2/06—Organic solvent
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
  • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
  • C08F20/10—Esters
  • C08F20/12—Esters of monohydric alcohols or phenols
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
  • C08F220/10—Esters
  • C08F220/12—Esters of monohydric alcohols or phenols
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
  • C09D133/04—Homopolymers or copolymers of esters
  • C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C09D133/062—Copolymers with monomers not covered by C09D133/06
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
  • C09D133/04—Homopolymers or copolymers of esters
  • C09D133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C09D133/062—Copolymers with monomers not covered by C09D133/06
  • C09D133/066—Copolymers with monomers not covered by C09D133/06 containing -OH groups
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
  • C09J7/38—Pressure-sensitive adhesives [PSA]
  • C09J7/381—Pressure-sensitive adhesives [PSA] based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
  • C09J7/385—Acrylic polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00051—Controlling the temperature
  • B01J2219/00074—Controlling the temperature by indirect heating or cooling employing heat exchange fluids
  • B01J2219/00087—Controlling the temperature by indirect heating or cooling employing heat exchange fluids with heat exchange elements outside the reactor
  • B01J2219/00094—Jackets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00051—Controlling the temperature
  • B01J2219/00132—Controlling the temperature using electric heating or cooling elements
  • B01J2219/00135—Electric resistance heaters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00186—Controlling or regulating processes controlling the composition of the reactive mixture
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/18—Details relating to the spatial orientation of the reactor
  • B01J2219/182—Details relating to the spatial orientation of the reactor horizontal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
  • B29C48/50—Details of extruders
  • B29C48/76—Venting, drying means; Degassing means
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
  • C08L33/04—Homopolymers or copolymers of esters
  • C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/582—Recycling of unreacted starting or intermediate materials
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S526/00—Synthetic resins or natural rubbers -- part of the class 520 series
  • Y10S526/918—Polymerization reactors for addition polymer preparation

Definitions

• the present invention relates to an improved process for the continuous preparation of acrylate pressure-sensitive adhesives by solvent-free polymerization.
• polyacrylate pressure-sensitive adhesives For industrial pressure-sensitive adhesive tape applications it is very common to use polyacrylate pressure-sensitive adhesives.
• Polyacrylates possess a variety of advantages over other elastomers. They are highly stable toward UV light, oxygen, and ozone. Synthetic and natural rubber adhesives generally contain double bonds, which makes these adhesives unstable to the aforementioned environmental influences.
• Another advantage of polyacrylates is their transparency and their usefulness across a relatively wide temperature range.
• Polyacrylate pressure-sensitive adhesives are generally prepared in solution by a free-radical polymerization.
• the polyacrylates are generally coated onto the corresponding backing material from solution, using a coating bar, and then dried. In order to increase the cohesion the polymer is crosslinked. Curing proceeds thermally or by UV crosslinking or by EB curing (EB: electron beams).
• EB electron beams
• PSA pressure-sensitive adhesive
• This new technology has its limitations. Prior to coating, the solvent is removed from the PSA, which is still prepared in solution, in a drying extruder. This concentration procedure, as it is known, in the drying extruder removes the solvent from the polymer solution down to a residual level of ⁇ 2%. Since polymerization therefore continues to take place in solution, the high consumption of organic solvents represents a problem both environmentally and economically. A further factor is that possible solvent residues in the adhesive can lead to odor nuisance in the course of subsequent use.
• a solvent-free polymerization of the acrylate PSA therefore, would result in a considerable improvement of the process as a whole. This, however, is very difficult, since polymerizations are associated with considerable heat production and an increase in viscosity. The high viscosities can lead to problems of mixing and hence also of heat removal and reaction regime.
• the free-radical polymerization of vinyl monomers is known and extensively described (Ullmann's Encyclopedia of Industrial Chemistry, 2nd Edt. Vol. A21, 1992, 305ff, VCH Weinheim).
• EP 016 03 94 describes the solvent-free preparation of polyacrylates in a twin-screw extruder.
• the acrylate hotmelt PSAs prepared by that process have a gel fraction which is in some cases considerably high, of up to 55%, thereby severely impairing the further processing of the PSAs.
• the high gel fraction means that the adhesive can no longer be coated.
• a variety of polymerization methods are suitable for preparing low-molecular-weight PSAs.
• State of the art is the use of regulators, such as of alcohols or thiols (MakromolekOle, Hans-Georg Elias, 5th edition, 1990, Hüthig & Wepf Verlag Basle). These regulators reduce the molecular weight but broaden the molecular weight distribution.
• a further controlled polymerization method employed is that of atom transfer radical polymerization, ATRP, where the initiators used are preferably, monofunctional or difunctional, secondary or tertiary halides and the halide(s) is(are) abstracted using complexes of Cu, of Ni, of Fe, of Pd, of Pt, of Ru, of Os, of Rh, of Co, of Ir, of Cu, of Ag or of Au [EP 0 824 111; EP 0 826 698; EP 0 824 110; EP 0 841 346; EP 0 850 957].
• ATRP atom transfer radical polymerization
• metal catalysts are used, a side effect of which is to affect adversely the aging of the PSAs (gelling, transesterification). Furthermore, the majority of metal catalysts are toxic, discolor the adhesive, and are removable from the polymer only by means of costly and inconvenient precipitation procedures.
• U.S. Pat. No. 4,581,429 discloses a controlled free-radical polymerization process.
• the process employs as its initiator a compound of the formula R′R′′N—O—X, in which X represents a free radical species able to polymerize unsaturated monomers.
• X represents a free radical species able to polymerize unsaturated monomers.
• the reactions exhibit low conversion rates.
• a particular problem is the polymerization of acrylates, which proceeds only to very low yields and molecular weights.
• WO 98/13392 describes open-chain alkoxyamine compounds which have a symmetrical substitution pattern.
• EP 0 735 052 A1 discloses a process for preparing thermoplastic polymers having narrow polydispersities.
• WO 96/24620 describes a polymerization process for which very special radical compounds are described, such as phosphorus-containing nitroxides, for example.
• WO 98/30601 discloses specific nitroxyls based on imidazolidine.
• WO 98/4408 discloses specific nitroxyls based on morpholines, piperazinones, and piperazinediones.
• solvent-free polymerization in a planetary roller extruder produces polymers having a narrow molecular weight distribution.
• the fraction of low-molecular-weight and of high-molecular-weight molecules in the polymer is sharply reduced.
• the flow viscosity is lower. This leads to improved mixing in the planetary roller extruder and hence also to an improvement in heat input and heat removal.
• the invention accordingly provides a process for continuous polymerization of acrylic monomers to polyacrylates in the presence of polymerization regulators, at least one polymerization step being carried out within at least one reaction extruder.
• the reaction extruder is a planetary roller extruder, in particular a hydraulically filled planetary roller extruder.
• the polymerization regulators are selected advantageously from the group of nitroxide regulators and/or RAFT regulators, particularly the alkoxyamines, triazolinyl compounds, thioesters and/or thiocarbonates.
• Regulators which have proven particularly suitable for solvent-free polymerization in a planetary roller extruder are asymmetric alkoxyamines of type (II) in conjunction with their free nitroxyl precursors and with an azo or peroxo initiator which exhibits slow thermal decomposition.
• a combination of the compounds (Ia) and (IIa) is used as initiator system.
• free-radical sources are peroxides, hydroperoxides, and azo compounds; as a number of nonexclusive examples of typical free-radical initiators, mention may be made here of potassium peroxodisulfate, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-tert-butyl peroxide, azodiisobutyronitrile, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, tert-butyl peroctoate, and benzpinacol.
• the free-radical initiator used is 1,1′-azobis-(cyclohexanecarbonitrile) (Vazo 88TM from DuPont).
• the compounds of the formula (II) are present preferably in an amount of 0.0001 mol % to 1 mol %, more preferably in an amount of 0.0008 to 0.0002 mol %, based on the monomers.
• the compounds of the formula (I) is present preferably in an amount of 1 mol % to 10 mol %, more preferably in an amount of 3 to 7 mol %, based on compound (II).
• the thermally decomposing initiator from c) is present with particular preference in an amount of 1 to 10 mol %, more preferably in an amount of 3 to 7 mol %, based on compound of the formula (II).
• the reaction is initiated by scission of the X—O bond of the initiator component of the formula (II).
• the scission of the bond is brought about preferably by ultrasound treatment, heating or exposure to electromagnetic radiation in the wavelength range of y radiation, or by microwaves. More preferably the scission of the C—O bond is brought about by heating and takes place at a temperature between 70 and 160° C.
• the initiator system used is at least one triazolinyl compound of the general formula where R # , R ⁇ , R ### , and R #### are chosen independently of one another or are identical and are
• Control reagents (triazolinyl compounds in the sense of the initiator system depicted above) of type (I) are composed, in a more-preferred version, of the following, further-restricted compounds:
• Halogens here are preferably F, Cl, Br or I, more preferably Cl and Br.
• alkyl, alkenyl, and alkynyl radicals in the various substituents both linear chains and branched chains are outstandingly suitable.
• alkyl radicals containing 1 to 18 carbon atoms are methyl, ethyl, propyl, isobutyl, butyl, isobutyl, tert-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, tert-octyl, nonyl, decyl, undecyl, tridecyl, tetradecyl, hexadecyl and octadecyl.
• alkenyl radicals having 3 to 18 carbon atoms are propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2,4-pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, isododecenyl and oleyl.
• alkynyl having 3 to 18 carbon atoms examples include propynyl, 2-butynyl, 3-butynyl, n-2-octynyl and n-2-octadecynyl.
• hydroxy-substituted alkyl radicals are hydroxypropyl, hydroxybutyl or hydroxyhexyl.
• halogen-substituted alkyl radicals are dichlorobutyl, monobromobutyl or trichlorohexyl.
• a suitable C 2 -C 18 heteroaryl radical having at least one oxygen atom in the carbon chain is, for example, —CH 2 —CH 2 —O—CH 2 —CH 3 .
• C 3 -C 12 cycloalkyl radicals include cyclopropyl, cyclopentyl, cyclohexyl or trimethylcyclohexyl.
• C 6 -C 10 aryl radicals include phenyl, naphthyl, benzyl, or further substituted phenyl radicals, such as, for example, ethylbenzene, propylbenzene, p-tert-butylbenzyl, etc., toluene, xylene, mesitylene, isopropylbenzene, dichlorobenzene or bromotoluene.
• the triazolinyl compounds are selected such that R ### and R #### are joined to one another in the form of a spiro compound.
• the compounds of the initiator system are present preferably in an amount of 0.001 mol % to 10 mol %, preferably in an amount of 0.01 to 1 mol %, based on the monomer mixture.
• the solvent-free polymerization was carried out by virtue of the presence of at least one free-radical initiator with at least one thioester as polymerization regulator.
• the thioesters used are compounds of the following general structural formula where R ⁇ and R ⁇ are selected independently of one another and Rs is a radical from one of groups i) to iv) and R ⁇ is a radical from one of groups i) to iii):
• Regulators used are preferably dithioesters and trithiocarbonates.
• the thioester is used with a weight fraction of 0.001% -5%, in particular of 0.025% to 0.25%.
• the molar ratio of free-radical initiator to thioester is in the range from 50:1 and 1:1, in particular between 10:1 and 2:1.
• Polymerization regulators which can be used with great advantage in this case for the inventive purpose are trithiocarbonates or dithioesters.
• control reagent of the general formula: in which
• Control reagents of type (I) are composed, in a more-preferred version, of the following compounds:
• Halogens here are preferably F, Cl, Br or I, more preferably Cl and Br.
• alkyl, alkenyl, and alkynyl radicals in the various substituents both linear chains and branched chains are outstandingly suitable.
• alkyl radicals containing 1 to 18 carbon atoms are methyl, ethyl, propyl, isobutyl, butyl, isobutyl, tert-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, tert-octyl, nonyl, decyl, undecyl, tridecyl, tetradecyl, hexadecyl and octadecyl.
• alkenyl radicals having 3 to 18 carbon atoms are propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2,4-pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, isododecenyl and oleyl.
• alkynyl having 3 to 18 carbon atoms examples include propynyl, 2-butynyl, 3-butynyl, n-2-octynyl and n-2-octadecynyl.
• hydroxy-substituted alkyl radicals are hydroxypropyl, hydroxybutyl or hydroxyhexyl.
• halogen-substituted alkyl radicals are dichlorobutyl, monobromobutyl or trichlorohexyl.
• a suitable C 2 -C 18 heteroaryl radical having at least one oxygen atom in the carbon chain is, for example, —CH 2 —CH 2 —O—CH 2 —CH 3 .
• C 3 -C 12 cycloalkyl radicals include cyclopropyl, cyclopentyl, cyclohexyl or trimethylcyclohexyl.
• C 6 -C 10 aryl radicals include phenyl, naphthyl, benzyl, 4-tert-butylbenzyl or further substituted phenyl, such as, for example, ethyl, toluene, xylene, mesitylene, isopropylbenzene, dichlorobenzene or bromotoluene.
• R $$$ can comprise the aforementioned radicals R $ or R $$ , independently of their selection.
• compounds (la) and (lha) are used as control reagents.
• initiator systems which additionally comprise further free-radical initiators for the polymerization, especially thermally decomposing, free-radical-forming azo or peroxo initiators.
• thermally decomposing, free-radical-forming azo or peroxo initiators for the polymerization, especially thermally decomposing, free-radical-forming azo or peroxo initiators.
• suitability is possessed in principle by all customary initiators that are known for acrylates.
• the production of C-centered radicals is described in Houben Weyl, Methoden der Organischen Chemie, Vol. E 19a, pp. 60-147. These methods are preferentially employed analogously.
• further free-radical initiators for the polymerization are present, especially thermally decomposing initiators, particularly free-radical-forming azo or peroxo initiators.
• thermally decomposing initiators particularly free-radical-forming azo or peroxo initiators.
• the invention further provides a process for preparing acrylate pressure-sensitive adhesives, in which a monomer mixture composed of ethylenically unsaturated compounds, particularly of (meth)acrylic acid and/or derivatives thereof, is subjected to free-radical polymerization using the inventive initiator system described.
• the monomer mixture it is preferred to use a mixture composed of acrylic monomers of the general formula
• monomers used include, additionally, vinyl compounds having a fraction of up to 30% by weight, in particular one or more vinyl compounds selected from the following group:
• vinyl esters vinyl halides, vinylidene halides, nitrites of ethylenically unsaturated hydrocarbons.
• vinyl compounds of this kind examples include vinyl acetate, N-vinylformamide, vinylpyridines, acrylamides, acrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, ethyl vinyl ether, vinyl chloride, vinylidene chloride, acrylonitrile, maleic anhydride, styrene, without wishing by dint of this enumeration to impose any unnecessary restriction. Furthermore it is possible to use all additional vinyl compounds which fall within the group set out above, and also all other vinyl compounds which do not fall within the classes of compound specified above.
• the monomers are selected such that the resulting polymers can be used as industrially useful PSAs, particularly such that the resulting polymers possess PSA properties in accordance with the “Handbook of Pressure Sensitive Adhesive Technology” by Donatas Satas (van Nostrand, New York 1989).
• the static glass transition temperature of the resulting polymer is advantageously below 25° C.
• the polymers prepared preferably have an average molecular weight of 50 000 to 600 000 g/mol, more preferably between 100 000 and 500 000 g/mol.
• the average molecular weight is determined by size exclusion chromatography (SEC) or by matrix-assisted laser desorption/ionization—mass spectrometry (MALDI-MS).
• SEC size exclusion chromatography
• MALDI-MS matrix-assisted laser desorption/ionization—mass spectrometry
• the acrylate PSAs prepared by this process possess a polydispersity M w /M n of ⁇ 4.5.
• the planetary roller extruder has proven suitable for a process of this kind.
• Polymerization in the planetary roller extruder has the advantage that the tendency to form gel is substantially lower than in the case, for example, of a twin-screw extruder, and particularly when regulators and copolymerizable photoinitiators are used the observed tendency to form gel is particularly low. This produces, as a result, narrow-distribution polyacrylate hotmelt PSAs with very good properties for further processing, which, furthermore, can be crosslinked very efficiently.
• the low polydispersity leads to advantages in the case of polymerization in the planetary roller extruder, thereby reinforcing the outstanding mixing properties which mark out a planetary roller extruder.
• polymers of low polydispersity are produced, which has advantageous consequences for solvent-free polymerization.
• the viscosity which plays a decisive part particularly in the case of solvent-free polymerization, is brought, as a result of the low polydispersity, into a range which is favorable for solvent-free polymerization. With greater polydispersity the viscosity is likewise increased, thereby reducing the heat removal options and also the mixing action in the reactor. These properties are of critical importance to the reliable implementation of solvent-free polymerizations.
• the positive influence of polydispersity on the viscosity enables a higher conversion and also, as a result, reduces the tendency to form gel, which is in turn important for the use of the adhesive as a hotmelt PSA.
• the planetary roller extruder is suitable for this solvent-free polymerization in particular by virtue of its outstanding thermal characteristics and also of the extremely diverse possibilities of temperature control.
• the extruder used is preferably operated continuously. Partial recycling of the product stream, referred to as loop operation, may also be advantageous. The most advantageous is to prepare a solvent-free polyacrylate PSA in a hydraulically filled planetary roller extruder. Hydraulic filling simplifies compliance with oxygen-free conditions and also the best-possible utilization of the screw length. Moreover, phase boundaries are avoided; such boundaries can have a disruptive effect on the polymerization process.
• the monomers can be metered to the polymerization reactor either individually or as a mixture. Preliminary mixing, especially of the copolymerizable photoinitiator, ensures a uniform distribution of the reaction mixture. In principle, however, mixing in the reactor or by combining different reactant streams in an upstream continuous mixer, which is dynamically operated or which may be a static mixer or a micromixer, is also possible.
• the polymer following polymerization in a planetary roller extruder, is removed from residual volatile constituents such as unreacted monomers in a devolatilizing extruder. After determination of their composition, these constituents can be recycled to the reactant stream.
• the polymer following polymerization and, where necessary, devolatilization and the optional addition of one or more of the additives, the addition being able to take place in the polymerization extruder and/or in a downstream compounding extruder, is advantageously coated from the melt without gel onto a backing (“without gel” denotes compliance with the requirements for coatability of the compositions using the coating apparatus which is commonly used and is familiar to the skilled worker for these purposes, particularly for a coatability distinguished by a uniform (homogeneous) coating pattern without inhomogeneities or streaks when coating takes place through the coating nozzles that are commonly used or through a roller applicator).
• the polyacrylates prepared by the inventive process are optimized by optional blending with at least one resin.
• Tackifying resins for addition include, without exception, all existing tackifier resins which are described in the literature. Representatives that may be mentioned include the pinene resins, indene resins, and rosins, their disproportionated, hydrogenated, polymerized, and esterified derivatives and salts, the aliphatic and aromatic hydrocarbon resins, terpene resins and terpene-phenolic resins, and also C5, C9, and other hydrocarbon resins. Any desired combinations of these and further resins may be used in order to adjust the properties of the resulting adhesive in accordance with requirements.
• any resins that are compatible (soluble) with the corresponding polyacrylate in particular, reference may be made to all aliphatic, aromatic, and alkylaromatic hydrocarbon resins, hydrocarbon resins based on single monomers, hydrogenated hydrocarbon resins, functional hydrocarbon resins, and natural resins. Express reference is made to the depiction of the state of knowledge in the “Handbook of Pressure Sensitive Adhesive Technology”, by Donatas Satas (van Nostrand, 1989).
• one or more plasticizers are metered into the PSA, such as low-molecular-weight polyacrylates, phthalates, whale oil plasticizers or plasticizing resins, for example.
• the acrylate hotmelts may further be blended with one or more additives such as aging inhibitors, light stabilizers, ozone protectants, fatty acids, resins, nucleators, expandants, compounding agents and/or accelerants.
• additives such as aging inhibitors, light stabilizers, ozone protectants, fatty acids, resins, nucleators, expandants, compounding agents and/or accelerants.
• fillers such as fibers, carbon black, zinc oxide, titanium dioxide, solid or hollow glass (micro)beads, microbeads of other materials, silica, silicates, and chalk, the addition of blocking-free isocyanates being a further possibility.
• the polyacrylate is applied as a layer preferably from the melt to a backing or to a backing material.
• the polyacrylate material is applied as a hotmelt composition in the form of a layer to a backing or to a backing material.
• Backing materials used for the PSA are the materials that are customary and familiar to the skilled worker, such as films (polyesters, PET, PE, PP, BOPP, PVC), nonwovens, foams, wovens, and woven sheets, and also release paper (glassine, HDPE, LDPE). This enumeration is not exhaustive.
• crosslinking may be induced, advantageously, by thermal means or by means of high-energy radiation, in the latter case in particular by electron beams (EB) or, following the addition of appropriate photoinitiators, by means of ultraviolet radiation.
• EB electron beams
• Examples of preferred substances which crosslink under irradiation in accordance with the inventive process are difunctional or polyfunctional acrylates or difunctional or polyfunctional urethane acrylates, difunctional or polyfunctional isocyanates or difunctional or polyfunctional epoxides. Use may also be made here, however, of all further difunctional or polyfunctional compounds which are familiar to the skilled worker and are capable of crosslinking polyacrylates.
• Suitable photoinitiators are preferably Norrish type I and type II cleaving compounds, some possible examples of both classes being benzophenone derivatives, acetophenone derivatives, benzil derivatives, benzoin derivatives, hydroxyalkyphenone derivatives, phenyl cyclohexyl ketone derivatives, anthraquinone derivatives, thioxanthone derivatives, triazine derivatives, or fluorenone derivatives, this enumeration making no claim to completeness.
• polyacrylate PSA prepared as described for an adhesive tape, in which case the polyacrylate PSA may have been applied to one or both sides of a backing.
• the polymerization was implemented using a planetary roller extruder consisting of three roller barrels in series, as the reactor.
• the temperature-control medium used was pressurized water.
• the reactor is operated continuously. Before commencement of metering the reactor is flushed with nitrogen for one hour. A mixture is produced from monomers and initiator. Nitrogen is passed through this initial charge in order to render it inert.
• the reaction mixture is conveyed through a static mixer, which is equipped with further feed devices, and then through a heat exchanger into the reactor. The reaction mixture is added to the reactor continuously via a bore on the periphery of the first roller barrel. At the exit from the reactor there is a valve which is used to ensure the hydraulic filling of the reactor.
• the heat exchanger for feed preheating, central spindle, and roller barrels are controlled to the particular desired temperatures.
• the central spindle a temperature of 80° C. was set; the medium for feed preheating to 90° C.
• Roller barrels 1 and 3 were controlled to 100° C., roller barrel 2 to 95° C.
• the rotary speed of the central spindle was 50 revolutions per minute.
• the hydrodynamic residence time was 15 minutes. Following emergence from the reactor, a sample is taken for determination of the conversion. Subsequently, remaining volatile constituents are removed in a devolatilizing extruder.
• the adhesive is coated at 50 g/m 2 onto a Saran-primed PET film 23 ⁇ m thick, using a hotmelt coater with two heatable rollers.
• the 2,2′-bisphenylethyl thiocarbonate is synthesized starting from 2-phenylethyl bromide with carbon disulfide and sodium hydroxide in accordance with a set of instructions in Synth. Communications 18(13), pp. 1531-6, 1988. Yield after distillation: 72%. Characterization: 1 H NMR (CDCl 3 ) ⁇ (ppm): 7.20-7.40 (m, 10 H), 1.53, 1.59 (2 ⁇ d, 6 H), 3.71, 381 (2 ⁇ m, 2 H).
• the conversion was determined gravimetrically and is expressed as a percentage in relation to the amount by weight of the monomers used.
• the polymer is isolated by being dried in a vacuum oven. The weight of the polymer is taken and divided by the initial weight of the monomers employed. The calculated figure corresponds to the percentage conversion.
• the average molecular weight M w and the polydispersity PD were determined via gel permeation chromatography.
• the eluent used was THF with 0.1% by volume trifluoroacetic acid. Measurement took place at 25° C.
• the precolumn used was PSS-SDV, 5 ⁇ , 10 3 A, ID 8.0 mm ⁇ 50 mm. Separation was carried out using the columns PSS-SDV, 5 ⁇ , 10 3 and also 10 5 and 10 6 each with ID 8.0 mm ⁇ 300 mm.
• the sample concentration was 4 g/l, the flow rate 1.0 ml per minute. Measurement was carried out against PMMA standards.
• a polymer was prepared by method A.
• Components used were 5% acrylic acid, 95% n-butyl acrylate and 0.015% azoisobutyronitrile (AIBN, Vazo 64TM, DuPont).
• AIBN azoisobutyronitrile
• the average molecular weight and the polydispersity were determined by means of test B, the conversion by test A, and the gel value by test C. Subsequently a swatch specimen was produced in accordance with method B.
• a polymer was prepared by method A.
• Components used were 5% acrylic acid, 95% n-butyl acrylate and also 0.124% 2,2,-bisphenylethyl thiocarbonate and 0.015% azoisobutyronitrile (AIBN, Vazo 64TM, DuPont).
• AIBN 1,2,-bisphenylethyl thiocarbonate
• 0.015% azoisobutyronitrile AIBN, Vazo 64TM, DuPont.
• the average molecular weight and the polydispersity were determined by means of test B, the conversion by test A, and the gel value by test C. Subsequently a swatch specimen was produced in accordance with method B.
• a polymer was prepared by method A.
• Components used were 1 % acrylic acid, 49.5% n-butyl acrylate, 49.5% 2-ethylhexyl acrylate and also 0.124% 2,2,-bisphenylethyl thiocarbonate and 0.015% azoisobutyronitrile (AIBN, Vazo 64TM, DuPont).
• AIBN 1,2,-bisphenylethyl thiocarbonate
• the average molecular weight and the polydispersity were determined by means of test B, the conversion by test A, and the gel value by test C. Subsequently a swatch specimen was produced in accordance with method B.
• Example 1 serves as the reference example.
• examples 2 to 3 are added.
• examples 2 to 3 acrylate PSAs with a low molar mass were prepared. Through the use of a regulator, polymers having a narrow molecular weight distribution were obtained.
• Example 1 has a very high molecular mass and cannot be coated.
• the molecular weight is lowered to such an extent that coating, which is necessary for use in an adhesive tape, is possible.
• example 2 with a M w of 557 000 g/mol
• example 3 with a lower M w of 431 000 g/mol are coatable at 120° C. and at just 110° C.
• the adhesive tapes can be produced entirely without solvent.

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