Flame-retardant acrylate

Abstract

A process for producing oxaphosphaphenanthrene oxide-acrylate monomers by phospha-Michael addition to acrylates, comprising reacting oxaphosphaphenanthrene oxide with α,ω-alkyldiol-diacrylate in a molar ratio of 1:1.5 to 1:10 in the presence of a base and a polymerization inhibitor at a temperature of 70 to 120°C and separating the unconverted α,ω-alkyldiol-diacrylate; the monomers obtained by this process and their use for producing flame-retardant thermoplastic (meth)acrylate polymers; a process for producing flame-retardant thermoplastic (meth)acrylate polymers using the monomers; the polymers thus obtained and their use for producing transparent films and panels.

Description

[Technical Field]

[0001] The present invention relates to a method for producing oxaphosphaphenanthrene oxide-acrylate monomers, to the monomers obtained therewith and their use for the production of flame-retardant thermoplastic (meth)acrylate polymers, and to a method for producing flame-retardant thermoplastic (meth)acrylate polymers using said monomers, to the polymers so obtained and their use for the production of films and panels. [Background technology]

[0002] Thermoplastic acrylate and methacrylate polymers ((meth)acrylate polymers for short) are versatile plastics due to their transparency and UV resistance. For example, they can be used as protective layers in decorative films for coating windows, doors, and other components.

[0003] A disadvantage of (meth)acrylate polymers is that they are relatively easily flammable and combustible. To remedy this, flame retardants are added. Inorganic flame retardants, such as metal hydroxides, are not very suitable because they require high loadings for full effectiveness, which impairs transparency. Halogen-containing flame retardants are widely used but have been criticized from toxicological and environmental standpoints. Various phosphorus-containing flame retardants have been proposed as halogen-free alternatives. While incorporating these as low-molecular-weight compounds does indeed achieve the desired flame retardant effect, it can impair transparency and frequently leads to migration of the flame retardant. This reduces their effectiveness and can alter the surface or, in the case of multilayer films, impair adhesion to adjacent layers.

[0004] To avoid this, copolymerizable flame retardants are considered optimal. However, it is simply not possible to provide every flame retardant as a comonomer. The most effective group of phosphorus-based flame retardants are phosphinic acid derivatives, such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (abbreviated as DOPO).

[0005] Examples of DOPO and other phosphorus-containing flame retardants are known per se. For example, US2014 / 0346418A1 (Patent Document 1), WO2015 / 096127A1 (Patent Document 2), and US2017 / 0029704A1 (Patent Document 3) disclose flame retardancy through copolymerization with phosphorus-containing monomers. However, none of these documents mention DOPO, and instead describe other organic phosphates.

[0006] WO 2008 / 132111 A1 (Patent Document 4) discloses additives based on DOPO, which have a carboxylic acid group or its ester on the phosphorus. In the case of the preferred polyhydric alcohols for ester formation, additives with multiple DOPO groups are obtained. However, copolymerization is not contemplated; the additives are described as being mixed into polymers, and only polyamides and polyesters are mentioned as polymers.

[0007] WO2014 / 124933A2 (Patent Document 5) describes thermosetting resins consisting of DOPO and a polyacrylate having at least three acrylic groups, which are further reacted with a (meth)acrylate. These thermosetting resins are described as being suitable as flame retardant additives.

[0008] In the paper "In situ synthesis of a novel transparent poly(methyl methacrylate) resin..." by S. Jiang et al. (Non-Patent Document 1), DOPO is converted to a monomer via reaction with formaldehyde, followed by reaction with acrylic acid chloride, and finally copolymerized with methyl methacrylate. Similarly, in EP1544227A1 (Patent Document 6), DOPO is first coupled to an alcohol group, which is then reacted with acrylic acid chloride to form the DOPO acrylate monomer. Acrylic acid chloride is a highly reactive substance, making its large-scale use problematic.

[0009] Wang et al., "Flexible, transparent flame retardant membrane...", Fire and Materials 2018, Vol. 42, pp. 99-108, describes the reaction of methyl-ethylcarboxy-phosphinic acid with acrylic acid-hydroxyethyl ester.

[0010] DE 10 2013 223 915 A1 (Patent Document 7), DE 10 2013 101 487 A1 (Patent Document 8), and WO 2019 / 141572 A1 (Patent Document 9) disclose phosphorus-containing (meth)acrylate monomers for producing flame-retardant thermoplastic resin compositions. Among the phosphorus-containing (meth)acrylate monomers described are DOPO-oxymethylene methacrylate monomers. This monomer is reacted with one or more at least trivalent (meth)acrylate monomers to form copolymers, which then serve as flame retardants and form part of the resin composition. The polymers in the first two documents are intended to be thermosetting resins and are thermosetting resins. According to the latter document, slightly crosslinked or uncrosslinked copolymers can be obtained by direct copolymerization of a phosphorus-containing triacrylate monomer with a (meth)acrylate monomer by preparing the copolymer from approximately equimolar amounts of a phosphorus compound and the acrylate groups in the triacrylate.

[0011] According to JP2016-060865A (Patent Document 10), DOPO-acrylate monomers can be obtained by Michael addition reaction with a deficient amount of DOPO. The document includes a long list of possible (meth)acrylates, among which 1,4-butanediol di(meth)acrylate and 1,6-hexanediol di(meth)acrylate are specifically listed. The objective is a crosslinkable coating with a refractive index adjusted using DOPO. Copolymerization with acrylates is indeed described. However, those skilled in the art cannot know from the document that non-crosslinkable monomers can be produced, nor how this can be achieved. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] US2014 / 0346418A1 [Patent Document 2] WO2015 / 096127A1 [Patent Document 3] US2017 / 0029704A1 [License 4] WO2008 / 132111A1 [Patent Document 5] WO2014 / 124933A2( [License 6] EP1544227A1 [License 7] DE102013223915A1 [License 8] DE102013101487A1 [License 9] WO2019 / 141572A1 [License 10] JP2016-060865A [License 11] US2019 / 0112457A1 [License 12] CN104497051A [Non-licensed literature]

[0013] [Non-licensed Document 1] S.Jiang et al, "In situ synthesis of a novel transparent poly (methyl methacrylate) resin···" [Non-licensed Document 2] Wang et al, "Flexible, transparent flame retardant membrane···", Fire and Materials 2018, Vol.42, pp.99-108 [Non-licensed Document 3] CPReghunadhan;Cluet,G.;European Polymer Journal(1989),25(3),251 [Non-licensed Document 4] CPR Nair,G Clouet,J Brossas;Journal of Polymer Science:Part A:Polymer Chemistry,Vol.26,1791-1807(1988) [Non-patent document 5] Xing,Weiyi;Song,Lei;Lv,Pin;Jie,Ganxin;Wang,Xin;Lv,Xiaoqi;Hu,Yuan;Materials Chemistry and Physics 123(2010)481-486 Summary of the Invention [Problem to be solved by the invention]

[0014] None of these proposals allow for the economical production of transparent thermoplastic (meth)acrylate polymers having a sufficiently effective phosphorus-containing flame retardant as a comonomer. Therefore, a further problem exists of providing useful flame retardants for thermoplastic transparent (meth)acrylate polymers. [Means for solving the problem]

[0015] Surprisingly, it has been found that starting from DOPO and similar oxaphosphaphenanthrene oxides, useful copolymers can be obtained by phospha-Michael addition onto α,ω-alkyldiol-diacrylates if the latter are used in excess and the unconverted α,ω-alkyldiol-diacrylate is removed, for example, by vacuum distillation and / or extraction.

[0016] Therefore, the above-mentioned problems are solved by a method for producing an oxaphosphaphenanthrene oxide-acrylate monomer by a phospha-Michael addition reaction on an α,ω-alkyldiol-diacrylate having 2 to 6 carbon atoms in the alkyl chain in the presence of a sterically hindered non-nucleophilic base and a polymerization inhibitor, which comprises reacting the oxaphosphaphenanthrene oxide with the α,ω-alkyldiol-diacrylate in a molar ratio of 1:1.5 to 1:10 at a temperature of 70 to 120°C in the absence of water, and separating the unconverted α,ω-alkyldiol-diacrylate, preferably by vacuum distillation. The above-mentioned problems are also solved by the oxaphosphaphenanthrene oxide-acrylate monomer thus obtained, its use for producing a (meth)acrylate polymer, and a method for producing a transparent thermoplastic (meth)acrylate polymer by copolymerizing the oxaphosphaphenanthrene oxide-acrylate monomer with a (meth)acrylate monomer.

[0017] The term (meth)acrylate polymer, as described above, includes methacrylate polymers and acrylate polymers, as well as copolymers of one or more acrylic acid ester monomers and / or one or more methacrylic acid ester monomers. That is, it includes not only homopolymers but also copolymers, terpolymers, etc., in which the monomers are acrylic acid ester monomers or methacrylic acid ester monomers, or both acrylic acid ester monomers and methacrylic acid ester monomers. In one preferred embodiment, the (meth)acrylate polymer contains only (meth)acrylate monomer(s) in addition to the oxaphosphaphenanthrene oxide-acrylate monomer(s) according to the present invention.

[0018] Typical acrylic acid ester monomers are methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, and benzyl acrylate. Preferred are methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and 2-ethylhexyl acrylate, particularly ethyl acrylate, n-butyl acrylate, isobutyl acrylate, and tert-butyl acrylate. Common methacrylic acid ester monomers are methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, neopentyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate. Monomers that are difficult to chain transfer, such as ethyl acrylate, are particularly advantageous. Preferred are methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, and tert-butyl methacrylate, especially methyl methacrylate. These monomers are also collectively referred to herein as (meth)acrylate monomers.

[0019] In principle, acrylic acid and methacrylic acid also come into consideration as monomers, but these are not well miscible with oxaphosphaphenanthrene oxides such as DOPO and are therefore preferably not used.

[0020] Preferred (meth)acrylate polymers are polymethyl methacrylate (PMMA) and copolymers of methyl methacrylate (MMA) with methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA) and n-butyl methacrylate (BMA).

[0021] Furthermore, additional comonomers such as acrylonitrile can be polymerized in to further improve desired properties, including burn behavior.

[0022] Oxaphosphaphenanthrene oxides, including the preferred 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), are known and commercially available. In the present invention, they are reacted with α,ω-alkyldiol-diacrylate to form oxaphosphaphenanthrene oxide-acrylate monomers, which can then be polymerized into (meth)acrylate polymers as comonomers. Suitable α,ω-alkyldiol-diacrylates have 2 to 6 carbon atoms in the alkyl chain. One important criterion for the preferred removal of excess α,ω-alkyldiol-diacrylate by vacuum distillation is the boiling point; the lower the boiling point, the lower the vacuum or temperature required for removing unconverted α,ω-alkyldiol-diacrylate. Therefore, α,ω-alkyldiol-diacrylates having 2 to 4 carbon atoms in the alkyl chain, including branched chains, are preferred, in particular ethylene glycol-diacrylate and n-butylene glycol-diacrylate.

[0023] The conversion is carried out in a molar ratio of oxaphosphaphenanthrene to α,ω-alkyldiol-diacrylate of 1:1.5 to 1:10, preferably 1:3 to 1:7, and in particular about 1:5. The choice of ratio is a compromise between the cost and effort of removing the excess α,ω-alkyldiol-diacrylate and the selectivity of the conversion. The more α,ω-alkyldiol-diacrylate used, the greater the cost and effort of removing the excess (lower space-time yield), but the less doubly oxaphosphaphenanthrene oxide-functionalized acrylate is formed.

[0024] The temperature is generally 70 to 120°C, preferably 80 to 100°C. The reaction medium is an aprotic solvent with good dissolving power for either the phosphaphenanthrene oxide or the excess α,ω-alkyldiol-diacrylate. In one preferred embodiment, the conversion is carried out without using a solvent. This facilitates isolation of the oxaphosphaphenanthrene oxide-acrylate monomer, which reduces costs. The use of a solvent has the advantage of reducing the risk of premature polymerization and, in addition, making it easier to distill off the solvent. Preferred solvents are toluene, xylenes, acetic acid esters, acetonitrile, and tetrahydrofuran, particularly toluene and xylenes (o-xylene, p-xylene, m-xylene, and mixtures thereof), most preferably toluene. A suitable amount is, for example, a ratio of the volume of the solvent to the total volume of the raw materials and base of 1:5 to 5:1, preferably 1:2 to 2:1.

[0025] The base is a sterically hindered and non-nucleophilic compound, such as a tertiary alkylamine, typically in an amount of 0.15 to 2.0 moles per mole of oxaphosphaphenanthrene oxide, preferably 0.5 to 1.2 moles per mole, and particularly preferably 0.9 to 1.1 moles per mole. The molar ratio of amine to DOPO can be reduced to about 0.15:1; further reductions in the amount of amine significantly slow the addition reaction and reduce selectivity. An excess of base is detrimental over time, but has little effect on the reaction. Tertiary amines are particularly suitable as bases, with triethylamine being the most suitable in terms of price, boiling point, and low toxicity. N-ethyldiisopropylamine, tripropylamine, and tributylamine are also useful, while trimethylamine is less suitable due to its very low boiling point. Tertiary aromatic amines such as pyridine are also possible but less preferred. It may be advantageous to add additional base some time after the start of the conversion.

[0026] The polymerization inhibitor is added to prevent premature polymerization of the oxaphosphaphenanthrene oxide-acrylate and the α,ω-alkyldiol-diacrylate. For example, hydroquinone, phenothiazine, 1-dodecanethiol, hydroquinone monobenzyl ether, methoxyhydroquinone, and other known substances are suitable. Hydroquinone and methoxyhydroquinone are preferred. The required amount is known per se. For example, the amount of stabilizer contained in commercially available α,ω-alkyldiol-diacrylate may be sufficient.

[0027] Since oxaphosphaphenanthrene oxide can react with water and bases, resulting in ring-opening, the conversion is carried out without water. Water leads to ring-opening and thus to a side reaction, i.e., the formation of the triethylammonium salt of the ring-opened oxaphosphaphenanthrene oxide. Here, the absence of water means a maximum water content of less than 1% by weight, preferably less than 0.1% by weight, particularly preferably less than 0.05% by weight, of water in the liquid phase.

[0028] Preferably, the conversion is carried out under dry protective gas, such as nitrogen.Reaction under air is not recommended for reasons of explosion protection.In addition, for example, triethylamine is somewhat sensitive to oxidation, and the reaction mixture may darken in the presence of air.On the other hand, a small amount of oxygen is not a problem, and may even be advantageous when using methoxyhydroquinone, the most frequently used inhibitor, because it is only active in the presence of trace amounts of oxygen.In this respect, removing oxygen from raw materials and other components of the reaction solution is unnecessary and is preferably not carried out.

[0029] The conversion is carried out until the oxaphosphaphenanthrene oxide is essentially completely converted, typically for 1 to 10 hours, and often for 2 to 5 hours. In this case, the oxaphosphaphenanthrene oxide is added in portions or continuously, for example, over a period of 2.5 to 3 hours, using, for example, a solids feed unit. To ensure complete conversion, the reaction temperature is maintained for an additional 45 to 60 minutes after the addition is complete. The addition in portions or continuously is sensible because the addition reaction is mildly exothermic. For relatively large batches, adding all the oxaphosphaphenanthrene oxide at the beginning can release too much heat of reaction in a short time, resulting in excessively high temperatures. Furthermore, the addition of oxaphosphaphenanthrene oxide in portions or continuously over a longer period improves selectivity, resulting in very little doubly oxaphosphaphenanthrene oxide-functionalized diacrylate.

[0030] The conversion product is, inter alia, oxaphosphaphenanthrene oxide-acrylate in addition to small amounts of di-oxaphosphaphenanthrene oxide-acrylate and excess α,ω-alkyldiol-diacrylate. Essentially complete conversion means that at most 5 mol %, preferably at most 2 mol %, of the oxaphosphaphenanthrene oxide has not been converted. The time to essentially complete conversion can be, for example, 31 The conversion time can be determined using P-NMR. After the time for a particular condition has been determined, further control of the conversion is no longer necessary. The conversion should be essentially complete, since residual unconverted oxaphosphaphenanthrene oxide is undesirable, but too long a reaction time does not provide any advantage.

[0031] During the conversion, the excess α,ω-alkyldiol-diacrylate, optionally with the solvent, is preferably removed by vacuum distillation. Alternatively, the excess α,ω-alkyldiol-diacrylate, optionally with the solvent, can be removed by liquid-liquid extraction. In the case of removal by vacuum distillation, the required temperature depends on the available vacuum and the required residence time at high temperature. Thin-film evaporators are optimal because only very short heating times are required, which minimizes the risk of spontaneous polymerization. In this case, temperatures of 75 to 140°C are useful. For longer vacuum distillation times, temperatures should not exceed 120°C. Preferably, the removal of the excess α,ω-alkyldiol-diacrylate is performed at a pressure of 0.01 to 0.2 mbar, preferably 0.02 to 0.2 mbar. In one embodiment, to separate the excess α,ω-alkyldiol-diacrylate from the reaction product, liquid-liquid extraction is (additionally) performed with a hydrocarbon solvent such as cyclohexane. Of all the solvents tested, cyclohexane was the most effective, although other alkanes, such as n-hexane, heptane, etc., or even alkane mixtures, can be used. To do this, the reaction product solvent is vigorously mixed with a hydrocarbon solvent, optionally before or after distillation, and optionally after the addition of a solvent, and the hydrocarbon solvent phase that separates is removed. This can be repeated multiple times, for example, two, three, four, or five times. Vacuum distillation can be performed before and / or after the isolation of the α,ω-alkyldiol-diacrylate by extraction.

[0032] According to the invention, oxaphosphaphenanthrene oxide-acrylate monomers are obtained which contain at most 3 mol % diacrylate, in particular at most 0.5 mol % diacrylate.

[0033] The resulting oxaphosphaphenanthrene oxide-acrylate monomers can be polymerized with (meth)acrylate monomers, and optionally further comonomers, in a manner known per se, for example by radical emulsion, suspension, or bulk polymerization, to produce (meth)acrylate polymers according to the invention. Typically, this is accomplished by mixing the monomers and then adding a radical initiator, such as azobis(isobutyronitrile) (abbreviated AIBN) or benzoyl peroxide. The useful proportion of oxaphosphaphenanthrene oxide-acrylate monomer depends on the desired or required flame retardancy and is usually in the range of 10 to 30 mol %, preferably 20 to 25 mol %, of oxaphosphaphenanthrene oxide-acrylate monomer, based on the mixture of all monomers.

[0034] To limit the molar mass, additives known per se, such as thiols, can be added during the polymerization, the useful amounts of which are generally very small and are known in the prior art.

[0035] The (meth)acrylate polymers according to the present invention can contain further additives, as is known per se, such as, but not exclusively, one or more flame retardants, surfactants, nucleating agents, coupling agents, fillers, plasticizers, impact modifiers, lubricants, antibacterial agents, mold release agents, heat stabilizers, antioxidants, light protectants, compatibilizers, inorganic additives, antistatic agents, pigments, dyes, and combinations thereof. The additives can be added independently of one another during polymerization and / or during the pelletization process (extrusion) so that they can be incorporated into the copolymer. The process and the amount added are known per se and are not particularly limited. Typical additive contents are 0.001 to 10% by weight of each additive, based on the total mixture, but fillers can be up to 50% by weight or more.

[0036] In one particularly preferred embodiment, in order to further improve the flame retardant properties of the (meth)acrylate polymers produced according to the present invention, additional copolymerized phosphorus compounds active in the solid phase as flame retardants are included. These support the effect of the oxaphosphaphenanthrene oxide-acrylate comonomers active in the gas phase. Suitable are, inter alia, phosphorus-containing monomers based on alkyl (meth)acrylates and hydroxyalkyl (meth)acrylates, preferably hydroxyethyl (meth)acrylate, in particular:

[0037] [ka] These comonomers are commercially available or can be prepared by methods known per se. For example, the first compound can be synthesized by reacting diethyl chlorophosphate with hydroxyethyl acrylate in the presence of an auxiliary base. See, for example, Nair, C.P. Reghunadhan; Clouet, G.; European Polymer Journal (1989), 25(3), 251 (Non-Patent Document 3). The second compound can be synthesized by reacting diethyl chlorophosphate with hydroxyethyl methacrylate in the presence of an auxiliary base such as triethylamine and copper(I) chloride as a catalyst. See, for example, C.P. Nair, G. Clouet, J. Brossas; Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 26, 1791-1807 (1988) (Non-Patent Document 4). The fourth compound can be prepared by reacting diphenyl chlorophosphate (CAS No. 2524-64-3) with hydroxyethyl methacrylate in the presence of an auxiliary base. See US2019 / 0112457A1 (Patent Document 11). The fifth and sixth compounds can be obtained, for example, by reacting phosphorus oxychloride with neopentyl glycol to form 2-oxo-2-chloro-5,5-di-Me-1,3,2-dioxaphosphorinane, and then reacting the latter with hydroxyethyl acrylate or hydroxyethyl methacrylate. See Xing, Weiyi; Song, Lei; Lv, Pin; Jie, Ganxin; Wang, Xin; Lv, Xiaoqi; Hu, Yuan; Materials Chemistry and Physics 123 (2010) 481-486 (Non-Patent Document 5) and CN104497051A (Patent Document 12). The sixth compound can be obtained similarly to the method according to the present invention.

[0038] The amount of solid-phase active phosphorus-containing (meth)acrylate monomer depends on the required flame retardancy and ranges, for example, from 5 to 30 mol %, preferably from 10 to 25 mol %, based on the mixture of all monomers. By combining an oxaphosphaphenanthrene oxide-acrylate monomer with a monomer containing a flame-retardant active phosphorus compound in the solid phase, the amounts of both comonomers can be reduced so that they total 10 to 20 mol %. For example, an amount of 3, 4, or 5 to 10 mol % of the oxaphosphaphenanthrene oxide-acrylate monomer according to the present invention is already sufficient. The amount of solid-phase active phosphorus-containing (meth)acrylate monomer can be reduced from 3 to 20 mol %, preferably from 5 to 15 mol %.

[0039] The flammability behavior is tested according to the UL94 standard "Tests for Flammability of Plastic Materials for Parts in Devices and Appliances" in accordance with IEC / DIN EN 60695-11-10 and -20 by Underwriters Laboratories. These tests are carried out using an open flame (Bunsen burner). The ignition source has a power of 50 watts (flame height 20 mm) and acts on the specimen twice for 10 seconds in a V test, then is removed again. The burning time and the drop of the burning part are evaluated using a cotton pad placed under the specimen. Five specimens (127 mm (5 in) long, 12.7 mm (0.5 in) wide, thickness depending on the application) should be tested for each test. A classification is made when the following requirements are met: V2: The total burning time of 10 flame exposures is a maximum of 250 seconds, with the fire self-extinguishing within 30 seconds at the latest, and fireball dripping is permitted. V1: The total burn time of 10 flames is a maximum of 250 seconds, with self-extinguishing within 30 seconds at the latest, no fireball drips are permitted, and the afterglow is a maximum of 60 seconds. V0: The total burning time of 10 flame exposures is a maximum of 50 seconds, with self-extinguishing within 10 seconds at the latest, no fireball drips are permitted, and the afterglow is a maximum of 30 seconds.

[0040] Flame retardant, transparent thermoplastic (meth)acrylate polymers according to the present invention typically achieve a V1 rating, and often a V0 rating.

[0041] This makes the thermoplastic (meth)acrylate polymers according to the invention suitable for use in decorative film layers for lamination with metal, wood, and plastic components, such as window and door frames, fences, and facade panels. Such decorative films include, for example, colored and / or printed base films, such as those made of PVC or (meth)acrylate polymers. The underside of this base film can be provided with a primer and / or adhesive, depending on the base film's composition and the materials to be laminated thereto. On the upper side, a protective film made of one or more layers of the copolymer according to the invention is present to protect the base film, and optionally the printing, from UV radiation. Alternatively, the decorative film can also consist of the copolymer according to the invention, or optionally several layers thereof. One or more layers of the copolymer according to the invention can be blended with polyvinylidene fluoride (PVDF) as a non-flammable component. In many cases, a cover film or cover coat is applied as an outer layer, typically made of a particularly scratch-resistant and durable plastic, such as polytetrafluoroethylene (PTFE) or PVDF, which also typically provides protection against dirt. Such decorative films can be partially or completely coextruded, with the non-coextruded layer being thermally laminated. For example, if a wood appearance is desired, the surface can be embossed. Suitable thicknesses for decorative films range from 100 to 300 μm, preferably from 130 or 150 to 200 μm. In this case, the protective layer made of the copolymer of the present invention accounts for 30 to 40% of the thickness, and the cover layer, if present, accounts for 3 to 4% of the thickness. The terms "made of a polymer" or "consisting of a polymer" mean that the specified polymer is the main polymer component of the layer. The presence of one or more additional polymers is not excluded, but the amount thereof is typically less than 50 wt. %, usually less than 30 wt. %, and often less than 10 wt. % (respectively), based on the total polymer components.

[0042] Furthermore, the flame-retardant, transparent thermoplastic (meth)acrylate polymers according to the invention are suitable for the production of transparent and colored panels, which can be used in a wide range of applications, for example in interior decoration.

[0043] The present invention is illustrated by the following examples, but should not be limited to these specifically described embodiments. Unless otherwise stated or necessarily dictated otherwise by the context, percentage values ​​are by weight, and, if uncertain, by the total weight of the mixture.

[0044] The present invention also relates to all combinations of preferred embodiments except where mutually incompatible. The term "about" in reference to a numerical value means that the value is at least 10% larger or smaller, or 5% larger or smaller, and in individual cases 1% larger or smaller. [Example]

[0045] The preparation of oxaphosphaphenanthrene oxide-acrylate monomers was carried out in three-necked flasks of different internal volumes equipped with a stirrer, a Claisen-type side tube with a reflux condenser, and a nitrogen supply. The temperature was controlled with an oil bath. Before each reaction, the apparatus was heated under vacuum to dryness and filled with nitrogen. For the reaction, each α,ω-alkyldiol-diacrylate was charged into a flask under countercurrent nitrogen along with the solvent (toluene) and base (triethylamine). 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was then added in portions over several hours. The α,ω-alkyldiol-diacrylate used contained methoxyhydroquinone (4-methoxyphenol) as a polymerization inhibitor. To maintain the activity of the inhibitor during the reaction, approximately 20 ml of air was injected at intervals of approximately 20 minutes each time. Samples were taken and the reaction was monitored. 31 P-NMR spectra were measured and followed.

[0046] Example 1 1,4-Butanediol diacrylate was reacted with DOPO in a 3.5:1 molar ratio. To this end, 0.6 moles (118.93 g) of 1,4-butanediol diacrylate and 14.05 g of DOPO were added to a nitrogen-filled 500 mL three-neck flask. 80 mL of toluene and 0.17 moles (approximately 23.56 mL) of triethylamine were then added. The mixture was then stirred and heated under a nitrogen atmosphere to a temperature slightly below its boiling point (approximately 96 °C, oil bath temperature approximately 107 °C). At intervals of 60 minutes each, two additional portions of DOPO were added (11.89 g, 10.81 g, for a total of 36.75 g, 0.17 moles). Stirring was continued for an additional 60 minutes at the same internal temperature (approximately 96 °C). An NMR sample was then taken, which indicated complete conversion.

[0047] Toluene and triethylamine were distilled off under vacuum on a rotary evaporator. The residue was subjected to vacuum distillation. Distillation was carried out at an oil bath temperature of 90°C and a vacuum of 0.063 mbar until the diacrylate no longer condensed in the receiver. The temperature was then increased in several steps to 125°C (0.042 mbar vacuum). For further vacuum distillation, the oil bath temperature was slowly increased to 150°C (0.044 mbar vacuum). The distillation was stopped because the reaction product began to polymerize.

[0048] Then, the following formula:

[0049] [ka] The resulting reaction product (49.91 g) was copolymerized with methyl methacrylate in an approximate molar ratio of 1:2.7. To do this, the reaction product was dissolved in 200 mL of toluene and transferred to a three-necked flask. Approximately 33.3 g of destabilized methyl methacrylate was then added, and the solution was heated to 97°C under nitrogen. The solution was stirred at a constant temperature under nitrogen for 1.5 hours, since oxygen must be excluded during copolymerization due to the 4-methoxyphenol inhibitor. Next, under vigorous stirring, 1 mL of a 0.2 M AIBN solution in toluene was added dropwise within 2 minutes, and the oil bath temperature was increased to 117°C. After 10 minutes, an additional 1 mL of AIBN solution was added. The reaction solution began to boil vigorously. After 25 minutes, the solution became viscous, and after 30 minutes, a bulky gel-like material precipitated from the solution. The copolymerization was then continued for another hour.

[0050] The resulting polymer product was dried in a vacuum oven at 100°C for 24 hours. After drying, the product became slightly rubbery and could not be crushed into small pieces. Thermogravimetric analysis (TGA) was performed. In this case, the sample was heated from 35°C to 800°C at a heating rate of 10 K / min in a nitrogen stream. This analysis showed a decomposition temperature of 318°C with a mass loss of 5%. Test specimens were prepared from this polymer product in a laboratory press under a pressure of 25 bar within 4 minutes. They remained very elastic and rubbery at a temperature of 190°C. Above 225°C, the specimens became hard and brittle, indicating post-crosslinking, i.e., incomplete polymerization.

[0051] The specimens obtained at 225°C were tested in a UL94 chamber. The pressed specimens showed significantly delayed burning behavior in the flame test compared to pure PMMA, but did not self-extinguish and therefore did not achieve a V1 rating.

[0052] Example 2 The reaction mixture was vacuum distilled (oil bath temperature 140°C, 0.031 mbar vacuum) as in Example 1, except that it was shaken multiple times with n-hexane: first three times with 50 ml of n-hexane, then four more times with 40 ml of n-hexane after adding 20 ml of toluene, and four more times with 40 ml of n-hexane after adding another 20 ml of toluene. The solvents were then removed on a rotary evaporator.

[0053] For copolymerization, the reaction product (52.82 g) was dissolved in 200 mL of toluene and transferred to a three-necked flask. Approximately 35 g of destabilized methyl methacrylate was then added, and the solution was heated to 97°C under a nitrogen atmosphere and stirred at constant temperature for 2 hours. Next, 1 mL of 0.2 M AIBN solution was added dropwise over 2 minutes under vigorous stirring, and the oil bath temperature was increased to 117°C. After 14 minutes, another 1 mL of AIBN was added. The solution began to boil vigorously. After 27 minutes, the solution became viscous, and after 34 minutes, a bulky gel-like material precipitated from the solution. The reaction was continued for another hour.

[0054] The resulting polymer product was dried in a vacuum oven at 100°C for 24 hours. After drying, the product became slightly rubbery and could not be finely ground using a mortar. TGA analysis showed a decomposition temperature of 312°C, similar to Example 1, with a 5% mass loss. Test specimens were prepared from this product in a laboratory press under 25 bar pressure within 4 minutes. At 190°C, the specimens remained very elastic and rubbery. Above a temperature of 225°C, the specimens became hard and brittle. The specimens exhibited good transparency. When tested in a UL94 chamber, the specimens briefly pressed at 225°C immediately extinguished after a 10-second first flame exposure, and after a second flame exposure, they burned for only about 4 seconds, achieving a V0 rating.

[0055] Comparative example VB1 A similar procedure to Example 1 was followed, except that butylene glycol dimethacrylate and DOPO were reacted in a 1:1 molar ratio. In a nitrogen-filled 500 mL three-necked flask, 0.2 mole (45.25 g) of butylene glycol dimethacrylate and 9.24 g of DOPO were added. Next, 100 mL of toluene and 0.12 mole (approximately 16.6 mL) of triethylamine were added. The mixture was then stirred and heated under a nitrogen atmosphere to a temperature slightly below its boiling point (approximately 96°C, oil bath temperature approximately 107°C). Six additional portions of DOPO were added at 30-minute intervals (8.54 g, 6.99 g, 6.50 g, 4.9 g, 4.00 g, and 3.00 g, totaling 43.24 g, 0.2 mole). Stirring was continued for an additional 30 minutes at a constant internal temperature (approximately 96°C). NMR samples were then taken. The reaction was still not complete, and was stirred for an additional 3 hours under the same conditions (internal temperature of about 96°C), after which an NMR sample was taken. The reaction was still not complete, so another 5 ml of triethylamine was added and stirred for an additional hour under the same conditions. An additional NMR sample was taken. The DOPO was now completely converted.

[0056] For the copolymerization, the oxaphosphaphenanthrene oxide-acrylate monomer was first stirred for 30 minutes at an internal temperature of approximately 97°C. Then, 0.4 mole (40.07 g) of destabilized methyl methacrylate was added in a nitrogen counterflow. The solution was stirred at constant temperature for an additional 1.5 hours, since oxygen must be avoided during copolymerization due to the 4-methoxyphenol. Then, 2 ml of a 0.2 molar solution of AIBN in toluene was added dropwise over a 2-minute period with vigorous stirring. The solution began to boil vigorously, and after a few minutes of reaction time, a bulky gel-like material precipitated from the solution. The oil bath temperature was increased to 117°C, and the reaction was allowed to proceed for 1 hour.

[0057] The resulting polymer product was dried in a vacuum oven at 100°C for 24 hours and then crushed into small pieces. A white powder was obtained. Thermogravimetric analysis (TGA) was then performed. This analysis showed a decomposition temperature of 255°C with a mass loss of 5%.

[0058] Attempts were made to produce test specimens using this powder in a laboratory press at temperatures up to 260°C and pressures up to 25 bar. However, the powder could not be melted, and no test specimens could be produced. Solubility tests showed that the resulting polymer was insoluble in organic solvents, indicating that a thermoplastic was not obtained.

[0059] Comparative example VB2 Unlike Comparative Example VB1, the amount of DOPO was slightly increased (45.40 g, 0.21 mol) to reduce the amount of unconverted dimethacrylate. Furthermore, the amount of base was increased and the time between DOPO additions was increased to 60 minutes to ensure faster conversion of DOPO. In a 500 ml three-necked flask filled with nitrogen, 0.2 mol (45.25 g) of butylene glycol dimethacrylate and 9.5 g of DOPO were added. Then, 100 ml of toluene and 0.21 mol (approximately 29.11 ml) of triethylamine were added. The mixture was then stirred and heated under a nitrogen atmosphere to a temperature slightly below its boiling point (approximately 96 °C, oil bath temperature approximately 107 °C). Six more portions of DOPO were added (8.5 g, 7.5 g, 6.5 g, 5.5 g, 4.5 g, and 3.4 g, totaling 45.40 g, 0.21 mol), each at 60-minute intervals. Stirring continued for 60 minutes at the same internal temperature (approximately 96°C). An NMR sample was then taken. The reaction was not yet complete. Therefore, stirring continued for another 2.5 hours under the same conditions (approximately 96°C internal temperature), and additional NMR spectra were recorded. After 3 hours, 31 P-NMR showed that DOPO was completely consumed.

[0060] The reaction product was copolymerized with methyl methacrylate in a 1:2 molar ratio after removal of 4-methoxyphenol, as in Comparative Example 1. The resulting polymer product was dried in a vacuum oven at 100°C for 24 hours and then crushed into small pieces using a ceramic mortar and pestle. TGA analysis showed a decomposition temperature of 275°C with a mass loss of 5%. However, test specimens could not be prepared using this product, as in Comparative Example VB1.

[0061] Comparative example VB3 Similar to Example 1, ethylene glycol dimethacrylate was reacted with DOPO in a 1.76:1 molar ratio. In a nitrogen-filled 500 mL three-necked flask, 0.25 moles (49.60 g) of ethylene glycol dimethacrylate and 8.65 g of DOPO were added. Then, 70 mL of toluene and 0.10 moles (approximately 13.7 mL) of triethylamine were added. The mixture was then stirred and warmed to just below its boiling point (approximately 96°C, oil bath temperature approximately 107°C) under a nitrogen atmosphere. Four additional portions of DOPO were added (7.57 g, 6.49 g, 5.41 g, and 4.32 g, totaling 32.44 g, 0.15 moles) at 45-minute intervals. The mixture was stirred for an additional 60 minutes at the same internal temperature (approximately 96°C). 31 P-NMR samples still showed traces of unconverted DOPO 1 h after the final DOPO addition. The reaction mixture was stored overnight, and further NMR samples now showed essentially complete conversion of DOPO.

[0062] After separating the excess ethylene glycol-dimethacrylate, 31 ml of n-hexane was added. To achieve better phase separation, the flask was stored in a freezer for 12 hours. The two phases were separated using a separatory funnel. Then, 100 ml of n-hexane was added again, and the phases were again separated using a separatory funnel.

[0063] The reaction product was then copolymerized with 36 g of methyl methacrylate (molar ratio 1:2). To do this, the reaction product, 200 ml of toluene, and 36 g of destabilized methyl methacrylate were placed in a three-necked flask, and the solution was heated to 97°C under a nitrogen atmosphere. The solution, which must be oxygen-free, was stirred at a constant temperature for 1.5 hours. Then, 3 ml of 0.2 M AIBN solution was added dropwise over a 5-minute period with vigorous stirring. The solution began to boil vigorously. After 10 minutes, the temperature of the oil bath was increased to 117°C. After 10 minutes, a bulky gel-like material precipitated from the solution, and the reaction was continued for another hour.

[0064] The resulting polymer product was dried in a vacuum oven at 150°C for 24 hours and then crushed into small pieces. A yellowish-white powder was obtained. The drying temperature was probably too high, causing partial decomposition of the product. TGA analysis showed a decomposition temperature of 258°C with a mass loss of 5%. Test specimens were made from the powder in a laboratory press. They were yellowish, slightly transparent, and very brittle; they could not be removed from the mold without breaking. The degree of crosslinking was still too high.

[0065] The resulting specimens were tested in a UL94 chamber. The pressed specimens exhibited significantly delayed burning behavior in flame tests compared to pure PMMA, but did not exhibit the desired self-extinguishing behavior after exposure to flame.

[0066] Comparative example VB4 Unlike Comparative Example 3, the excess ethylene glycol-dimethacrylate was increased to 2.5:1. In a nitrogen-filled 1 L three-necked flask, 0.75 moles (148.6 g) of ethylene glycol-dimethacrylate and 26 g of DOPO were added. Then, 140 ml of toluene and 0.5 moles (approximately 68 ml) of triethylamine were added. The mixture was then stirred and heated under a nitrogen atmosphere to a temperature slightly below its boiling point (approximately 96 °C, oil bath temperature approximately 107 °C). At intervals of 60 minutes each, two additional portions of DOPO were added (21.6 g, 17.3 g, totaling 64.88 g, 0.3 moles). Stirring was continued for 60 minutes at the same internal temperature (approximately 96 °C). An NMR sample was then taken, which indicated complete conversion of DOPO.

[0067] The triethylamine and toluene were distilled off under vacuum on a rotary evaporator. The mixture was then shaken three times with 100 ml of n-hexane. Vacuum distillation was then carried out at an oil bath temperature of 85°C, an overhead temperature of 50°C, and a vacuum of 0.05 mbar until dimethacrylate no longer condensed in the receiver. The vacuum distillation was repeated two more times, each at an elevated oil bath temperature of 95°C or 105°C. However, in this case, the product solution spontaneously partially polymerized. 1H-NMR showed that the dimethacrylate was still present in the reaction product.

[0068] The reaction product (119 g) was dissolved in 450 ml of toluene and transferred to a three-necked flask. Approximately 36 g of destabilized methyl methacrylate was then added, and the solution was heated to 97°C under a nitrogen atmosphere. Stirring was continued at constant temperature for 1.5 hours. Then, under vigorous stirring, 2 ml of 0.2 M AIBN solution was added dropwise within 4 minutes, and the oil bath temperature was increased to 117°C. After 10 minutes, 1 ml of AIBN was added again. The solution began to boil vigorously. After 15 minutes, the solution became more viscous. White flakes were observed. After 17 minutes, a bulky gel-like material precipitated from the solution, and the reaction was continued for another hour.

[0069] The resulting polymer product was dried in a vacuum oven at 100°C for 24 hours and then crushed into small pieces using a ceramic mortar and pestle. TGA analysis showed a decomposition temperature of 241°C with a mass loss of 5%. The powder was used to make test specimens in a laboratory press. These were more transparent than those in Comparative Examples VB1, VB2, and VB3, but were still very brittle. They could not be removed from the mold without breaking.

[0070] The resulting specimens were tested in a UL94 chamber and the pressed specimens did not have improved flammability behavior compared to VB3.

[0071] Comparative example VB5 The excess ethylene glycol-dimethacrylate was further increased to a molar ratio of 3.5:1. In a nitrogen-filled 1 L three-necked flask, 0.7 moles (138.8 g) of ethylene glycol-dimethacrylate and 17.3 g of DOPO were added. Then, 100 ml of toluene and 0.4 moles (approximately 55.5 ml) of triethylamine were added. The mixture was then stirred and warmed to a temperature slightly below its boiling point (approximately 96 °C, oil bath temperature approximately 107 °C) under a nitrogen atmosphere. Two additional portions of DOPO were added (15.3 g, 10.8 g, totaling 43.24 g, 0.2 moles) at intervals of 60 minutes each. Stirring was continued for 60 minutes at the same internal temperature (approximately 96 °C). An NMR sample was then taken, which indicated complete conversion of DOPO.

[0072] Triethylamine and toluene were distilled off under vacuum on a rotary evaporator, and the residue was subjected to vacuum distillation (oil bath temperature 80°C, vacuum 0.04 mbar). During the vacuum distillation, when the oil bath temperature rose to 110°C, spontaneous polymerization of the product occurred, and it was no longer stirrable.

[0073] The examples and comparative examples show that even when equimolar amounts of raw materials are used, or when excess oxaphosphaphenanthrene oxide is used, no usable acrylate comonomer is obtained. Only when a sufficient excess of diacrylate is used, as contemplated by the present invention, can a diacrylate reacted with oxaphosphaphenanthrene oxide only once be obtained. The excess α,ω-alkyldiol-diacrylate could be separated satisfactorily. In contrast, this is not the case with α,ω-alkyldiol-dimethacrylate. In particular, comparative examples 1 and 2 demonstrate that direct copolymerization of oxaphosphaphenanthrene oxide-acrylate monomer with another (meth)acrylate monomer, as proposed in WO 2019 / 141572 A1 and JP 2016-060865 A, does not result in a thermoplastic (meth)acrylate polymer. In addition to the selection of the α,ω-alkyldiol-diacrylate and its excess amount, the separation of unreacted α,ω-alkyldiol-diacrylate, as contemplated in accordance with the present invention, is also necessary to obtain a thermoplastic (meth)acrylate polymer. Table 1 below provides an overview of examples and comparative examples.

[0074] [Table 1]

[0075] Example 6 DOPO-acrylate monomer was prepared from DOPO and 1,4-butanediol diacrylate in a similar manner to Example 2, except that the molar ratio of butanediol diacrylate to DOPO was 7:1. To this end, 1.25 moles (297.3 g) of distilled butanediol diacrylate, 13.6 g of DOPO, and 30 mg of 4-methoxyphenol were added to a nitrogen-filled 250 mL three-neck flask. Then, 35 mL of triethylamine was added via syringe through the septum, and the mixture was heated to 85-87°C (oil bath temperature) over 20 minutes under stirring and nitrogen atmosphere. An additional 9.0 g of DOPO was then added. After another 20 minutes, a third portion of DOPO was added (9.0 g). Three additional portions (7.5 g each) were added in the same manner, each at 20-minute intervals. The reaction mixture was stirred at the same temperature for an additional 30 minutes. Heating was then discontinued. During the phospha-Michael addition, 20 mL of air was injected at intervals of approximately 15 minutes each to keep the inhibitor active.

[0076] For the isolation of the DOPO monomer, the resulting product solution was divided into two portions. Product isolation was carried out by first distilling off triethylamine, initially applying a partial vacuum and warming the oil bath to a maximum of 50°C for both portions. The main part of the excess butanediol diacrylate was then distilled (approximately 0.02 mbar), warming to 105°C to avoid spontaneous polymerization. 250 mL of cyclohexane was added to the distillation residue, which was then rapidly heated to the boiling point. After approximately 5 minutes of vigorous stirring under reflux, the oil bath was removed. The contents of the flask were then cooled to approximately 40°C in a water bath and then in a refrigerator, after which the slightly cloudy supernatant phase was decanted. Nine more extractions were carried out in the same manner (in each case, cyclohexane was recovered). The extraction residue was then heated to 105°C within 45 minutes, during which the pressure dropped to approximately 0.02 mbar. These conditions were maintained for about 20 minutes. After cooling, the DOPO monomer was obtained as a slightly cloudy, viscous, colorless oil. The DOPO monomer thus obtained was recorded in deuterated chloroform. 1The H-NMR spectrum showed good purity, especially the successful separation of excess 1,4-butanediol diacrylate (<1 wt. % diacrylate; the proportion of double DOPO-functionalized product was approximately 6 wt. %).

[0077] 52.82 g of DOPO monomer was dissolved in 200 mL of toluene and transferred to a three-necked flask for copolymerization with methyl methacrylate. Approximately 35 g of destabilized methyl methacrylate was then added, and the solution was heated to 97°C under a nitrogen atmosphere and stirred at constant temperature for 2 hours. Next, 1 mL of 0.2 M AIBN solution was added dropwise within 2 minutes under vigorous stirring, and the oil bath temperature was increased to 117°C. After 14 minutes, another 1 mL of AIBN was added. The solution began to boil vigorously. After 27 minutes, the solution became viscous, and after 34 minutes, a bulky gel-like material precipitated from the solution. The reaction was continued for another hour.

[0078] The resulting polymer product was dried in a vacuum oven at 100°C for 24 hours. After drying, the product remained slightly rubbery and could not be finely ground using a mortar. TGA analysis showed a decomposition temperature of 312°C, similar to Examples 1 and 2, with a 5% mass loss. Test specimens were prepared from this product in a laboratory press under 25 bar pressure within 4 minutes. At 190°C, the specimens remained elastic and rubbery. Above a temperature of 225°C, the specimens became hard and brittle. The specimens exhibited good transparency. When tested in a UL94 chamber, the specimens pressed briefly at 225°C immediately extinguished after a 10-second first flame exposure, and after a second flame exposure, they burned for only 4 seconds, achieving a V0 rating. The results of the flame behavior test are listed in Table 2.

[0079] Example 7 The DOPO monomer of Example 6 was mixed with various amounts of methyl methacrylate and DDPO-HEMA, A=

[0080] [ka] The methyl acrylate polymer was prepared by reaction with 1-decylthiol as a modifier and dibenzoyl peroxide (BPO) as an initiator. Suspension polymerization was carried out in water using 1-decylthiol as a modifier and dibenzoyl peroxide (BPO) as an initiator. The liquid monomer was destabilized before polymerization; DDPO-HEMA (A) was recrystallized from tert-butyl methyl ether (melting point: 50.5°C). The synthesis of the methacrylate polymer was carried out in a reaction apparatus consisting of a 250 mL three-necked flask, a magnetic stirrer, a heating bath, a dropping funnel, and a reflux condenser equipped with a three-way stopcock and a bubble counter. The dropping funnel and the three-way stopcock on the reflux condenser were connected via a Schlenk line.

[0081] Dense transparent test rods as well as transparent films of different thicknesses were prepared from the resulting methacrylate polymers using a hydraulic laboratory press, type HB20 300 (Schmidt Maschinentechnik GmbH; Bretten-Bauerbach, Germany). The test rods had the following dimensions: 70 mm x 10 mm x 0.8 mm. Temperatures ranging from 210 to 245 °C were used during pressing (depending on the melting behavior of the methacrylate polymer). The results of the weight and burning behavior tests are listed in Table 2.

[0082] Example 7a For the copolymerization, a mixture consisting of 1.35 g of DDPO-HEMA (A), 1.35 g of DOPO monomer, 7.3 g of methyl methacrylate, 34 mg of 1-decyl mercaptan, and 67 mg of aqueous BPO was added to the dropping funnel. A short vacuum was then applied twice, and nitrogen was re-injected each time. To remove oxygen, a mixture consisting of water and 1.3 ml of a 2% solution of Kuraray's Poval 25-88 (partially hydrolyzed polyvinyl alcohol) suspension stabilizer was stirred for 30 minutes at 85-90 °C. A gentle stream of nitrogen was passed through the three-way stopcock into the apparatus and into the bubble counter. After cooling the aqueous solution to approximately 62 °C, the solution was added through the dropping funnel. The contents of the flask were then heated to 73 °C with stirring within 20 minutes. A milky emulsion was formed. The connection to the bubble counter was disconnected 10 minutes after the monomer addition. The temperature was then increased by 1°C at intervals of approximately 15 minutes each, until a temperature of 82°C was reached. Stirring was continued vigorously for four hours. A solution consisting of 65 mg of BPO and 500 mg of methyl methacrylate was then added, and the temperature was increased to 87°C. At this temperature, the reaction mixture was stirred for 12 hours under a nitrogen atmosphere. Small spheres and some dense material formed. The supernatant aqueous solution was decanted, and then water was added and suctioned through a filter paper. The methacrylate polymer was dried at 80°C for 5 hours and at 100°C under vacuum (approximately 0.02 mbar) for 1 hour. The solubility of this polymer recorded in deuterated chloroform was 31 The P-NMR spectrum contained only the signals of the DOPO unit (approximately 36 ppm) and the DDPO unit (-8.2 ppm). The ratio of the integrals of the signals was approximately 1.00:1.50, which was in close agreement with the expected value. Approximately 9 g of the methacrylate polymer was obtained.

[0083] Example 7b For the copolymerization, 65 ml of deionized water and 1.3 ml of a 2 wt. % aqueous solution of Kuraray's Poval 25-88KL (suspension stabilizer, partially hydrolyzed polyvinyl alcohol) were added to a three-necked flask. A solution consisting of 1.7 g of DDPO-HEMA (A), 1.5 g of DOPO monomer, 6.0 g of methyl methacrylate, 0.8 g of methyl acrylate, 45 mg of 1-decylthiol, and 80 mg of hydrous BPO (60 mg of pure BPO) was added to the dropping funnel. The dropping funnel was partially evacuated twice and refilled with nitrogen to remove atmospheric oxygen from the reagent mixture. The reaction flask containing the aqueous solution was also partially evacuated twice and refilled with nitrogen each time. The contents of the flask were then heated to 95°C with stirring. A gentle stream of nitrogen was passed through the apparatus and bubble counter via the three-way stopcock. After 30 minutes of stirring, the temperature was lowered to approximately 65°C. The contents of the dropping funnel were added to the aqueous solution, from which oxygen had been removed. The contents of the flask were then heated to 73°C in approximately 20 minutes under stirring and a gentle nitrogen flow. Over the course of 2 hours, the temperature was raised to 83°C. A gentle nitrogen flow was then applied to the bubble counter. After another hour, a solution of approximately 35 mg of aqueous BPO in 0.37 g of methyl methacrylate was added via the dropping funnel. The temperature of the heating bath was then increased to 87°C. After another 30 minutes, the connection to the bubble counter was cut off. Stirring at 87°C was continued for 12 hours. The aqueous phase was then decanted. A methacrylate polymer was obtained as compact fragments and a film-like material. This polymer was soluble in chloroform and dimethyl sulfoxide. To remove residual monomer and water, the polymer was heated under vacuum (approximately 0.02 mbar) first at 90°C for 3 hours, then at 105°C for 45 minutes. The methacrylate polymer thus obtained was 31 In the P-NMR spectrum, the signals of the DOPO and DDPO units were present at approximately 36 ppm and approximately −8 ppm, respectively, and the integral ratio was almost consistent with the expected value.

[0084] Example 7c For the copolymerization, 55 ml of deionized water and 1.5 ml of a 2 wt. % aqueous solution of Kuraray's Poval 25-88KL (suspension stabilizer, partially hydrolyzed polyvinyl alcohol) were added to a three-necked flask. A solution consisting of 1.9 g of DDPO-HEMA, 1.7 g of DOPO monomer, 5.4 g of methyl methacrylate, 1.0 g of methyl acrylate, 25 mg of 1-decylthiol, and 90 mg of hydrous BPO (equivalent to 67 mg of pure BPO) was added to the dropping funnel. The dropping funnel was partially evacuated twice and refilled with nitrogen to remove atmospheric oxygen from the reagent mixture. The reaction flask containing the aqueous solution was also partially evacuated twice and refilled with nitrogen each time. The contents of the flask were then heated to 95°C with stirring. A gentle stream of nitrogen was passed through the apparatus and bubble counter via the three-way stopcock. After 30 minutes of stirring, the temperature was lowered to approximately 65°C. The contents of the dropping funnel were added to the oxygen-free aqueous solution. The temperature of the oil bath was then raised to 75°C while vigorously stirring the reaction mixture. A milky white suspension formed. Stirring was continued for 3.5 hours. During this time, the temperature of the heating bath was gradually raised to 84°C. A solution of 35 mg of BPO, 0.33 g of methyl methacrylate, and 0.07 g of methyl acrylate was then added via the dropping funnel in a countercurrent of nitrogen. The temperature of the heating bath was then raised to 87°C. After another hour, the connection to the bubble counter was cut off, and the cooling water was stopped. The reaction mixture was stirred under these conditions for another 12 hours. The aqueous solution of the methacrylate polymer, which had formed partly as spheres and partly as a dense or film-like material, was then decanted. The methacrylate polymer was washed three times with water and dried on a filter paper. The composition of the polymer recorded in deuterated chloroform was as follows: 1 The H-NMR spectrum showed that it contained unconverted monomer. Therefore, the polymer was heated under high vacuum (about 0.02 mbar) first to about 87°C (4 hours) and then to 93°C (1 hour). After that, the methacrylate polymer 1 The 1 H-NMR spectrum showed almost complete disappearance of the acrylate / methacrylate groups. 31In the P-NMR spectrum, the signals of the DOPO unit and the DDPO unit were present at approximately 36 ppm and approximately −8 ppm, respectively, with an integral ratio of 1.00:1.66, which was almost consistent with the expected value.

[0085] Example 7d For the copolymerization, 60 ml of deionized water and 2.0 ml of a 2 wt. % aqueous solution of Kuraray's Poval 25-88KL (suspension stabilizer, partially hydrolyzed polyvinyl alcohol) were added to a three-necked flask. A solution consisting of 2.22 g of DDPO-HEMA, 1.8 g of DOPO monomer, 7.08 g of methyl methacrylate, 0.9 g of butyl methacrylate, 35 mg of 1-decylthiol, and 108 mg of hydrous BPO (equivalent to 81 mg of pure BPO) was then added to the dropping funnel. The dropping funnel was partially evacuated twice and refilled with nitrogen to remove atmospheric oxygen from the reagent mixture. The reaction flask containing the aqueous solution was also partially evacuated twice and refilled with nitrogen each time. The contents of the flask were then heated to 95°C with stirring. A gentle stream of nitrogen was passed through the apparatus and bubble counter via the three-way stopcock. After 60 minutes of stirring, the temperature was lowered to approximately 63°C. The contents of the dropping funnel were added to the oxygen-free aqueous solution. The temperature of the heating bath was then increased to 75°C. This temperature was maintained for 20 minutes, then the set temperature was increased to 77°C, and after 30 minutes, to 80°C. This temperature was maintained for 50 minutes. The set temperature was then increased to 85°C. A milky emulsion was formed. The mixture was stirred very vigorously for three hours, and a stream of nitrogen was passed through the apparatus and into the bubble counter. Polymer evolution was evident. The connection to the bubble counter was then cut off, the cooling water was stopped, and the mixture was stirred for an additional 12 hours at 85°C under a slight nitrogen backpressure. The aqueous solution of methacrylate polymer, which had formed partly as small globules and partly as a dense material, was then decanted. The methacrylate polymer was washed three times with water and dried on a filter paper. NMR spectra of the polymer thus obtained indicated approximately 95% conversion of the acrylate and methacrylate groups. The polymer was dried under vacuum (0.02 mbar) for 3 hours at 87-95°C to remove residual water. 1 The 1 H-NMR spectrum showed almost complete disappearance of the acrylate / methacrylate groups. 31In the P-NMR spectrum, the signals of the DOPO and DDPO units were present at approximately 36 ppm and approximately -8 ppm, respectively, with an integral ratio of 1.00:2.33, which was approximately consistent with the expected value. The methacrylate polymer thus obtained was readily soluble in organic solvents such as chloroform. It softened at approximately 160°C and melted at approximately 200°C.

[0086] Example 8 The DOPO monomer of Example 6 was mixed in various amounts with methyl methacrylate and DEPO-HEMA, B=

[0087] [ka] The methyl acrylate polymer was prepared by reacting 1-decylthiol with or without additional monomers, such as methyl methacrylate or n-butyl methacrylate. Suspension polymerization was carried out in water using 1-decylthiol as a modifier and dibenzoyl peroxide (BPO) as an initiator. These monomers were destabilized prior to polymerization. The synthesis of the methacrylate polymer was carried out in a reaction apparatus consisting of a 250 mL three-neck flask, a magnetic stirrer, a heating bath, a dropping funnel, and a reflux condenser equipped with a three-way stopcock and a bubble counter. The dropping funnel and the three-way stopcock on the reflux condenser were connected via a Schlenk line.

[0088] Dense test rods as well as films of different thicknesses were prepared from the resulting methacrylate polymers using a hydraulic laboratory press, type HB20 300 (Schmidt Maschinentechnik GmbH; Bretten-Bauerbach, Germany). The test rods had the following dimensions: 70 mm x 10 mm x 0.8 mm. Temperatures of 220–245 °C were used during pressing (depending on the melting point of the methacrylate polymer). The amounts and results of the burning behavior tests are listed in Table 2.

[0089] Example 8a The polymerization was carried out similarly to Example 7c. The methacrylate polymer was obtained mostly as compact pieces, which were peeled off from the glass wall and washed with water. The polymer was recorded in deuterated chloroform. 1 The H-NMR spectrum showed that it contained unconverted monomer. Therefore, the polymer was heated under high vacuum (about 0.02 mbar) first to about 87°C (4 hours) and then to 93°C (1 hour). After that, the methacrylate polymer 1 The 1 H-NMR spectrum showed almost complete disappearance of the acrylate / methacrylate groups. 31 In the P-NMR spectrum, the signals of the DOPO unit and the diethyl phosphate unit were located at approximately 36 ppm and approximately −1.3 ppm, respectively, with an integral ratio of 1.00:1.74, which was approximately consistent with the expected value.

[0090] Example 8b The polymerization was carried out similarly to Example 7c. The methacrylate polymer was obtained as relatively large polymer granules, which were washed twice with water. The polymer was dried at 87-105°C under vacuum (0.02 mbar) for 5 hours and then examined using NMR spectroscopy. 1 H-NMR spectra showed the complete disappearance of the acrylate / methacrylate groups. 31 The P-NMR spectrum was also as expected: the signals of the DOPO and diethylphosphate units were present at approximately 36 ppm and approximately −1.3 ppm, respectively, with an integral ratio of 1.00:1.74, which was in close agreement with the expected value.

[0091] Comparative example VB8a The polymerization was carried out similarly to Example 7c. The methacrylate polymer was obtained as compact pieces, which were peeled off from the glass wall and washed with water. The polymer was recorded in deuterated chloroform. 1 The H-NMR spectrum showed a relatively high proportion of unconverted monomer. The polymer was heated under high vacuum (about 0.02 mbar) first to about 87°C (3 hours) and then to 97°C (1 hour). The methacrylate polymer was then 1The H-NMR spectrum showed almost complete disappearance of the acrylate / methacrylate groups. The methacrylate polymer thus obtained had a phosphorus content of about 4% by weight.

[0092] [Table 2]

[0093] These examples demonstrate that the combination of an oxaphosphaphenanthrene oxide-acrylate monomer according to the present invention with a copolymerized solid-phase active phosphorus compound provides optimal flame retardancy. The solid-phase active phosphorus compound alone does not work well. This is illustrated by the methacrylate polymer of Comparative Example 8a, which, despite its relatively high phosphorus content, exhibits poorer flame retardancy than Examples 7c, 8a, and 8b. While this application is directed to the invention set forth in the claims, the disclosure of this application also includes: 1. A method for producing oxaphosphaphenanthrene oxide-acrylate monomers by phospha-Michael addition to α,ω-alkyldiol-diacrylates having 2 to 6 carbon atoms in the alkyl chain, comprising reacting oxaphosphaphenanthrene oxide with α,ω-alkyldiol-diacrylate in a molar ratio of 1:1.5 to 1:10 in the presence of a base and a polymerization inhibitor at a temperature of 70 to 120°C in the absence of water, and separating the unconverted α,ω-alkyldiol-diacrylate. 2. The method according to claim 1, wherein 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is used as the oxaphosphaphenanthrene oxide. 3. The method according to 1. or 2., characterized in that the separation of unconverted α,ω-alkyldiol-diacrylate is carried out by vacuum distillation and / or by liquid-liquid extraction with a hydrocarbon solvent, preferably by vacuum distillation or by vacuum distillation and liquid-liquid extraction before and / or after vacuum distillation. 4. The method according to claim 3, wherein n-pentane, n-hexane and n-heptane, particularly n-hexane, are used as the hydrocarbon solvent. 5. The method according to any one of the above 1. to 4., characterized in that the phospha-Michael addition is carried out in a solvent such as toluene, o-xylene, m-xylene, p-xylene or a mixture of two or more thereof, in particular in toluene. 6. The method according to any one of the above 1. to 5., wherein a sterically hindered tertiary amine, particularly triethylamine, is used as the base. 7. The method according to any one of the above items 1. to 6., wherein the base is used in an amount of 0.15 to 2.0 mol per 1 mol of oxaphosphaphenanthrene oxide, preferably 0.5 to 1.2 mol per 1 mol, and particularly preferably 0.9 to 1.1 mol per 1 mol. 8. The method according to any one of the above items 1 to 7, characterized in that an α,ω-alkyldiol-diacrylate having 2 to 5 carbon atoms in the alkyl chain, preferably 2 to 4 carbon atoms in the alkyl chain, particularly preferably ethylene glycol-diacrylate or n-butylene glycol-diacrylate, most preferably ethylene glycol-diacrylate, is used as the α,ω-alkyldiol-diacrylate. 9. An oxaphosphaphenanthrene oxide-acrylate monomer obtained by the method described in any one of 1. to 8. above. 10. The oxaphosphaphenanthrene oxide-acrylate monomer according to 9 above, characterized in that it contains up to 3 mol %, preferably up to 0.5 wt % of an α,ω-alkyldiol-diacrylate. 11. A method for producing a flame-retardant thermoplastic (meth)acrylate polymer by copolymerizing at least one (meth)acrylate monomer with a phosphorus-containing acrylate monomer, characterized in that the phosphorus-containing acrylate monomer is an oxaphosphaphenanthrene oxide-acrylate monomer obtained according to any one of 1. to 8. above. 12. The method according to claim 11, characterized in that the (meth)acrylate monomer is selected from ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, and mixtures thereof, in particular methyl methacrylate, and mixtures of methyl methacrylate with one or more of ethyl acrylate, butyl acrylate, and methyl acrylate. 13. The method according to claim 11 or 12, characterized in that the solid-phase active copolymerized phosphorus compound is additionally polymerized with a phosphorus-containing monomer, preferably based on alkyl acrylate, hydroxyalkyl (meth)acrylate, particularly preferably based on hydroxyethyl (meth)acrylate, and in particular selected from the group consisting of the following formulae and mixtures of two or more thereof: [ka] 14. Use of an oxaphosphaphenanthrene oxide-acrylate monomer obtained according to any one of the above 1. to 8. for producing a flame-retardant thermoplastic (meth)acrylate polymer. 15. A flame-retardant thermoplastic (meth)acrylate polymer obtained according to any one of the above 11 to 13. 16. Use of the flame-retardant thermoplastic (meth)acrylate polymer according to claim 15 for the production of films and panels. 17. The use according to claim 16, wherein the film or panel is transparent. 18. The use according to 16. or 17. above, wherein the film is a decorative film and the decorative film comprises a layer containing the (meth)acrylate polymer according to 15. above.

Claims

1. A process for producing oxaphosphaphenanthrene oxide-acrylate monomers by phospha-Michael addition to α,ω-alkyldiol-diacrylates having 2 to 6 carbon atoms in the alkyl chain, comprising reacting oxaphosphaphenanthrene oxide with α,ω-alkyldiol-diacrylate in a molar ratio of 1:1.5 to 1:10 in the presence of a sterically hindered non-nucleophilic base and a polymerization inhibitor at a temperature of 70 to 120°C and in the absence of water, and separating unconverted α,ω-alkyldiol-diacrylate by vacuum distillation and / or liquid-liquid extraction with a hydrocarbon solvent.

2. 2. The method according to claim 1, wherein 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is used as the oxaphosphaphenanthrene oxide.

3. 3. The process according to claim 1, wherein the separation of the unconverted α,ω-alkyldiol-diacrylate is carried out by vacuum distillation and liquid-liquid extraction before and / or after the vacuum distillation.

4. 4. The process according to claim 1, 2 or 3, characterized in that as hydrocarbon solvent one of cyclohexane, n-pentane, n-hexane and n-heptane or a mixture thereof is used.

5. 5. The process according to claim 1, wherein the phospha-Michael addition is carried out in toluene, o-xylene, m-xylene, p-xylene or a mixture of two or more thereof as solvent.

6. 6. The process according to claim 1, wherein a sterically hindered tertiary amine is used as the base.

7. 7. The process according to claim 1, wherein the base is used in an amount of 0.15 to 2.0 moles per mole of oxaphosphaphenanthrene oxide.

8. 8. The process according to claim 7, characterized in that the base is used in an amount of 0.5 to 1.2 moles per mole of oxaphosphaphenanthrene oxide.

9. 9. The process according to claim 1, wherein an α,ω-alkyldiol-diacrylate having 2 to 4 carbon atoms in the alkyl chain is used as the α,ω-alkyldiol-diacrylate.

10. 10. The method according to claim 1, wherein ethylene glycol diacrylate or n-butylene glycol diacrylate is used as the α,ω-alkyldiol diacrylate.

11. 11. A method for producing a flame-retardant thermoplastic (meth)acrylate polymer by copolymerizing at least one (meth)acrylate monomer with a phosphorus-containing acrylate monomer, characterized in that as the phosphorus-containing acrylate monomer an oxaphosphaphenanthrene oxide-acrylate monomer obtained according to any one of claims 1 to 10 is used.

12. 12. The method of claim 11, wherein the (meth)acrylate monomer is selected from ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, and mixtures thereof.

13. 13. The method of claim 12, wherein the (meth)acrylate monomer is selected from methyl methacrylate and mixtures of methyl methacrylate with one or more of ethyl acrylate, butyl acrylate, methyl acrylate.

14. 14. The method according to claim 11, 12 or 13, characterized in that a copolymerized phosphorus compound active in the solid phase is additionally polymerized.

15. 15. The method of claim 14, wherein a phosphorus-containing monomer selected from the group consisting of the following formulae and mixtures of two or more thereof is polymerized: 【Chemistry 1】

16. Use of an oxaphosphaphenanthrene oxide-acrylate monomer obtained according to any one of claims 1 to 10 for the preparation of a flame-retardant thermoplastic (meth)acrylate polymer.

17. Use of the flame-retardant thermoplastic (meth)acrylate polymers obtainable according to any one of claims 11 to 15 for the production of films and panels.

18. 18. Use according to claim 17, characterized in that the film or panel is transparent.

19. Use according to claim 17 or 18, characterized in that the film is a decorative film, which comprises a layer comprising a (meth)acrylate polymer obtainable according to any one of claims 11 to 15.

Images