Classifications

• • 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
  • C08F4/00—Polymerisation catalysts

Definitions

• the invention relates to an initiator system for the thermal start of a radical polymerization of preparations, in particular paints, coating solutions, coating materials, molding compositions, fillers and adhesives, which contain monomers and / or oligomers with ethylenically unsaturated groups, which are formed in particular by acrylate and methacrylate derivatives , as well as a process for the radical polymerization of the preparations under protective gas or in air.
• compositions curable by means of polymerization have the broadest application, in particular as molding compositions, but also as lacquers, paints, coatings and adhesives.
• the radical polymerization of free-radically polymerizable components for example (meth) acrylate compounds, is very often chosen as the hardening mechanism.
• (meth) acrylate stands for methacrylate and acrylate.
• the polymerization is usually started thermally or photochemically, for example by UV light.
• the inhibition by atmospheric oxygen can be reduced in part by using large amounts of photoinitiators, coinitiators, high radiation power or wax-forming waxes.
• AI is also carried out to reduce the air access through a gas cushion made of protective gas.
• the protective gas preferably consists of C0 2 , which can be closed off into a gas cushion due to its high specific weight.
• photo-initiated (radiation-induced) polymerization has the disadvantage that uniform exposure to geometrically complex conditions is very difficult or even impossible due to shadowing. Particularly when spraying paints, there is often unintentional precipitation of spray mist in shadow areas that are not intended for painting.
• an initiator system which has a radical-forming group consisting of activated hyroxylamine, O-alkylhydroxylamine or 0-acylhydroxylamine derivative as starter.
• the activation of this grouping is effected according to the invention by two acyl groups bonded to the N.
• the central structural unit of the starter is summarized by the following general formulas:
• R-CO-N (0-CO-R ⁇ ⁇ ⁇ ) -CO-R ⁇ (3;
• R, R ⁇ , R , ⁇ and R ⁇ represent the same or different organic substituents.
• R, R ⁇ R , x , and / or R ⁇ , ⁇ are particularly selected from the group of aliphatic, linear, branched and / or cyclic, substituted and / or unsubstituted hydrocarbons.
• R, R ⁇ and / or R ⁇ can also be aromatic hydrocarbons, for example a phenyl radical.
• R, R ⁇ , R ⁇ ⁇ and / or R , ⁇ preferably comprise hydrocarbon chains with a chain length of 2 to 18 atoms.
• the hydrocarbon chains can optionally also be interrupted by heteroatoms from the group consisting of N, 0 and / or S.
• Organic substituents are particularly important for R ⁇ .
• R, R ⁇ , R ⁇ or R ⁇ can be derived from natural fatty acids.
• the radicals R and / or R ' are closed to form a chain, the length of which is 2 to 10 atoms.
• Cyclic N, N-diacyl-hydroxylamines or N, -diacyl derivatives with a ring size of 5 to 12 atoms are particularly preferably formed here.
• X represents according to the formulas (1), (2) or (3) -H, -R ⁇ , or -CO-R ⁇ .
• X is particularly preferably formed by -H.
• the two radicals R and R ⁇ form a closed ring system, the N, N-diacyl-hydroxylamine group being linked to the ring system via the acyl groups.
• the starter can be given in the following general schematic formula (5).
• X means according to the formulas (1), (2) or (3) -H, -R ⁇ , or -CO-R ⁇ .
• z represents a cyclic hydrocarbon with at least 4 and preferably 6 to 14 ring atoms.
• the chain links of z are preferably formed by methylene and / or alkylene groups which can carry side chains or substituents.
• one or more of the carbon atoms of the ring are substituted by heteroatoms.
• the ring z particularly preferably represents an aromatic ring system with 5 to 8 ring atoms, for example a system based on benzene, naphthalene or anthracene.
• the compounds according to the schematic formula (5) which are suitable according to the invention also include, in particular Derivatives based on benzene tricarboxylic acids, phthalic acid, homophthalic acid and pyromellitic acid. While two adjacent carboxylic acid groups form the N, N-diacyl grouping, the third carboxylic acid function is available as an active group for further derivatization.
• EP 0 424 115 B1 discloses electrophotographic photosensitive compounds which also have an N, N-diacyl-hydroxylamine group as the active group. These are ring systems in which this grouping is either part of the ring or is fused.
• the range of compounds suitable according to the invention as a thermal initiator for radical polymerization also extends in particular to formulas 1 to 104 shown in EP 0 424 115 B1, and their O-alkyl or O-acyl derivatives, according to the general formulas ( 2) or (3).
• the solubility can take place via a suitable selection of substituents on R and / or R ⁇ or z.
• substituents on non-polar media for example, aliphatic or aromatic substituents are preferred.
• polar media in particular aqueous media, substituents with hydroxyl, carboxyl, alkylene glycol and / or keto groups are particularly preferred.
• the particularly preferred O-acylated compounds include tributyroylhydroxylamine and those with acetyl or propionyl O-acylated N-hydroxyl pthalimides.
• the initiator system according to the invention can comprise, as a further component, a coinitiator which supports the activity of the starter. While in the case of the N, N-diacyl-hydroxylamines a coinitiator-free initiator system can also lead to polymerization and curing, one is for the 0-alkylated N, -diacyl-hydroxylamines and for the O-acylated N, N-diacyl-hydroxylamines Use of the coinitiator is usually required.
• Preferred coinitiators are formed by active metal ions and / or by tertiary amines. Although some of the starters are also capable of starting the polymerization without a coinitiator, the coinitiator brings about a considerable reduction in the curing temperature.
• the formation of the starter radical, which triggers the polymerization of the polymerizable components, is supported.
• the active metal ion of the coinitiator changes between a higher and a lower oxidation state.
• the oxidation in the higher oxidation state can be carried out by oxygen.
• the oxygen has an effect which supports the starting reaction.
• the initiator systems according to the invention are also suitable for thermally initiated polymerization in air.
• the metal ions suitable as active metal ions of the coinitiator generally have a number of oxidation states which are closely related in terms of their electrochemical potential.
• the oxidation stages should be easily convertible into one another by reaction with starter or oxygen.
• the corresponding metals are typically found among the transition metals.
• Metals which have at least two oxidation states in the range from I to VIII are preferred, for example the transition metals Ti, V, Cr, Mo, W, Mn, Fe, Co, Rh, Ir, Ni, Rh, Ir, Pd, Pt and / or Cu.
• Cobalt ions with oxidation states II or III, if appropriate with further metal ions, are particularly preferred.
• Ions of the alkali or alkaline earth metals for example of Li, K, Ca, Sr, Ba, as well as of Bi, Pb, Zn, Cu, Zr and / or Ce, which improve the effect of the coinitiator, can be present as further metal ions of the coinitiator.
• the metal ions are usually bound in complex form.
• the metal ions can be used, for example, as carboxylic acid salts of fatty acids or as acetylacetonates be used.
• Porphine complexes for example tetraphenylporphine complexes, or metal salt naphthenates are also suitable.
• the acetates or octanoates of Mn or Co in the oxidation states (II) and / or (III) are preferred.
• tertiary amines which are typically also known as amine accelerators. These include, for example, dimethylaniline, N, N-dimethyl-p-toluidine, N, N ⁇ - bis (2-hydroxypropyl) -p-toluidine.
• tertiary amines are N-methylpyrrolidine and / or diazabicyclooctane (DABCO).
• a preferred use of the initiator system according to the invention is in the curing of polymerizable preparations which contain monomers and / or oligomers (also referred to as prepolymers) with ethylenically unsaturated groups, such as in particular (meth) acrylates, vinyl esters, vinyl ethers, acrylamides, vinyl chloride, acrylonitrile, butadiene, unsaturated Fatty acids, styrene derivatives, maleic acid or fumaric acid groups.
• Typical oligomeric representatives that carry these reactive groups are polyesters, polyurethanes, alkyd resins, epoxies, polyethers or polyolefins.
• the preparation may also contain further reactive components or groups which are suitable for curing reactions.
• it can also contain polyol groups and isocyanate groups that cure to urethanes.
• initiator system is the curing of paints, Coating solutions, adhesives and resins, as are already known in a similar composition in a photochemically curing version.
• the amount of initiator required for radical initiation is generally the amount required for photochemical polymerization.
• initiator system according to the invention is used in combination with conventional radical initiators based on peroxides or azo compounds, even small amounts below 0.5% by weight are sufficient to start the polymerization at significantly reduced temperatures. This also applies to radical initiators with C-C bond cleavage, such as benzpinacol silyl ether.
• the initiator system according to the invention consisting of starter and coinitiator, is usually used in an amount of 0.1 to 8% by weight of the amount of the polymerizable preparation.
• Another aspect of the invention relates to a method for curing preparations with free-radically curable components by means of free-radical polymerization under the action of oxygen.
• this also includes the conditions which only bring about a reduction in the oxygen content without producing a completely oxygen-free atmosphere.
• inert purging gas such as C0 2 , argon or N 2 , generally does not completely prevent the Oxygen access from the gas space, so that the preparation is still exposed to oxygen.
• inert gas conditions generally permit a significantly better quality at lower temperatures.
• the polymerization is initiated by the thermally initiated formation of radicals from starters, which is optionally supported by coinitiators.
• radicals according to the invention are essentially oxyl radicals which consist of open-chain and / or cyclic N, N-diacyl-hydroxylamines and / or their O-alkyl or O-acyl derivatives with the general formulas
• R-CO-N (0-R , ) -CO-R ⁇ (2) or R-CO-N (0-CO-R ⁇ ⁇ ) -CO-R (3) (collectively referred to as starter) are formed.
• the oxyl radicals formally result from the breaking of the 0 — H, 0 — R , ⁇ , or the 0 — CO-R ⁇ ⁇ bonds of the general formulas (1), (2) or (3) listed.
• the formation of the oxyl radicals can be supported according to the invention by a coinitiator.
• the coinitiator contains a metal ion which is reduced during the radical formation step of the N, N-diacyl-hydroxylamines and / or their O-alkyl or 0-acyl derivatives from a higher to a lower oxidation state. With the O-alkyl or 0- Acyl derivatives generally cannot do without the use of a coinitiator.
• the coinitiator contains in particular active metal salts, the metal ions of which can be reduced by N, N-diacyl-hydroxylamines. Transition metal ions of oxidation states II to V which are complexly bound by organic compounds are particularly preferably used as coinitiators. Particularly preferred coinitiators are Co (II) carboxylic acid salts.
• the amount of starter and coinitiator required depends, among other things, on the type and amount of polymerizable compounds in the preparation and the reaction conditions, in particular the temperature and oxygen content.
• the preparation typically comprises the initiator system, the polymerizable compounds (components), solvents and the customary additives.
• the usual additives include, in particular, inorganic fillers and additives for optimizing rheology or surface quality, polymeric, metallic or ceramic fillers, pigments, stabilizers and UV absorbers.
• the radical-curable components are to be understood in particular as the monomers or oligomers with ethylenically unsaturated groups which have already been mentioned.
• the total amount of the initiator system comprising starter and coinitiator is usually 0.1 to 8% by weight of the total preparation.
• the amount of the coinitiator is preferably in the range from 0.5 to 80% by weight of the initiator system.
• Formulations with conventional radical initiators can tend to creep polymerisation even at room temperature. In contrast, the formulations with the initiator systems according to the invention show comparatively good storage stability.
• the coinitiator is added only immediately before the desired curing.
• a two-component technique is provided in which a first component, which comprises the entire coinitiator dissolved in solvents, and a second component, which comprises the entire ethylenically unsaturated compounds and the starters, are mixed together only immediately before the preparation is used.
• the preparation is divided into two monomer-containing (or oligomer-containing) components, one of which contains the starter according to the invention and the other the coinitiator.
• the polymerization and hardening process is supported by further thermal radical initiators contained in the initiator system, in particular on the basis of peroxides, azo compounds, or initiators cleaving CC bonds.
• the process for starting the polymerization involves heating the initiator-containing preparation to temperatures above 70 ° C.
• the preferred temperature range for the radical start is 90 to 150 ° C., the reactivity of the monomers or oligomers also being important here.
• the initiator system is also suitable for significantly higher temperatures, such as those that can occur during coil coating at approx. 200 ° C.
• the comparatively low starting temperature compared to the known systems represents a further advantage of the invention.
• starting temperatures below 70 ° C may also be possible. This is desirable for dental compositions, for example.
• Another advantage of the method according to the invention is the high tolerance towards the oxygen content of the ambient air.
• the oxygen content can usually be in the range from 25 to about 0.01% by volume.
• an improved paint quality at lower baking temperatures is achieved under inert gas conditions.
• dual-cure systems are used.
• the initiator system contains UV initiators as a further constituent, which start a polymerization by means of high-energy light, in particular UV light.
• a first process variant provides for a partial polymerization (prepolymerization) of the preparation to be carried out by means of high-energy light or UV light and then a thermally initiated post-polymerization to be carried out at elevated temperatures by the initiator system according to the invention.
• This procedure has the advantage that typical UV varnishes can be fully cured even in shadow areas.
• a second process variant provides for UV curing to be carried out during or after thermal curing. This has the effect that the (top) layer of the preparation facing the UV light is only hardened towards the end of the process.
• test series were carried out with a standard preparation.
• the standard preparation essentially corresponds to a common preparation for UV varnishes without UV initiators.
• composition of the standard preparation 60 parts Ebecryl 5129 (manufacturer: UCB) 20 parts Ebercyl 284 20 parts Ebercyl 40 40 parts xylene 20 parts butyl acetate 1 part Tinuvin 292 (manufacturer: Ciba Chemicals) 1.5 parts Tinuvin 400
• Example 1 In a first series of experiments, the influence of different amounts of coinitiator (co-octanoate) with the same starter content (1% by weight N-hydroxysuccinimide) and two different reaction temperatures (130 ° C, 100 ° C) was assessed using the microhardness of the polymer formed ( Lacquer layer) examined after a reaction time of 10 min.
• the results in Tables 1 and 2 show that the hardness of the standard preparation increases significantly with increasing Co content under otherwise identical conditions.
• the starting temperature which led to hard surfaces, was above 150 ° C.
• Example 2 In further series, the influence of different starter contents (N-hydroxylsuccinimide) with the same amount of coinitiator (0.02% by weight co-octanoate) at two reaction temperatures (130 ° C., 100 ° C.) was determined using the microhardness of the polymer formed after 10 min reaction time examined.
• the results in Tables 2 and 3 show that the hardness of the standard preparation increases significantly with increasing starter content under otherwise identical conditions.

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• 2003
  • 2003-06-25 DE DE10328473A patent/DE10328473A1/de not_active Withdrawn
• 2004
  • 2004-05-06 JP JP2006515765A patent/JP2007509190A/ja active Pending
  • 2004-05-06 US US10/562,234 patent/US20080249265A1/en not_active Abandoned
  • 2004-05-06 WO PCT/EP2004/004827 patent/WO2005000915A1/de not_active Ceased

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