Flame-retardant acrylate

Abstract

We provide thermoplastic and transparent (meth)acrylate polymers. [Solution] A flame-retardant thermoplastic (meth)acrylate polymer comprising units derived from oxaphosphaphenanthrene oxide-acrylate monomers and units derived from (meth)acrylate monomers. Furthermore, the proportion of oxaphosphaphenanthrene oxide-acrylate monomers is in the range of 10 to 30 mol%, based on the mixture of all monomers.

Description

[Technical Field]

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

[0002] Thermoplastic acrylate and methacrylate polymers (simply known as (meth)acrylate polymers) 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] The drawback of (meth)acrylate polymers is that they are relatively easily ignitable and combustible. To improve this, flame retardants are added. Inorganic flame retardants, such as metal hydroxides, are not very suitable because a large amount of filler is required for sufficient effect, which impairs transparency. Halogen-containing flame retardants are widely used, but they have been criticized from toxicological and environmental perspectives. As halogen-free alternatives, various phosphorus-containing flame retardants have been proposed. When these are mixed as low molecular weight compounds, the desired flame retardant effect is certainly obtained, but there is a risk of impaired transparency, and furthermore, migration of the flame retardants occurs frequently. As a result, their effect is reduced, the surface is altered, or, in the case of multilayer films, adhesion to adjacent layers is impaired.

[0004] To avoid this, copolymerizable flame retardants are considered optimal. However, it is impossible 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 in themselves. For example, US2014 / 0346418A1 (Patent Document 1), WO2015 / 096127A1 (Patent Document 2), and US2017 / 0029704A1 (Patent Document 3) disclose flame retardation by copolymerization with phosphorus-containing monomers. However, none of these documents mention DOPO, and other organic phosphates are described.

[0006] WO2008 / 132111A1 (Patent Document 4) indicates that DOPO-based additives are known, and these have a carboxylic acid group or an ester thereof on phosphorus. In the case of a preferred polyhydric alcohol for ester formation, an additive having multiple DOPO groups can be obtained. However, copolymerization is not intended, and it is stated that the additive is mixed with a polymer, and only polyamides and polyesters are given as polymers.

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

[0008] In the paper "In situ synthesis of a novel transparent poly (methyl methacrylate) resin..." (Non-Patent Literature 1) by S. Jiang et al., DOPO is converted to a monomer by reacting with formaldehyde, then with acrylate chloride, and finally copolymerized with methyl methacrylate. Similarly, EP1544227A1 (Patent Literature 6) first couples DOPO to an alcohol group, and then reacts this with acrylate chloride to obtain a DOPO acrylate monomer. Acrylic acid chloride is a highly reactive substance, which poses problems for its large-scale use.

[0009] Wang et al.'s paper, "Flexible, transparent flame retardant membrane," Fire and Materials 2018, Vol. 42, pp. 99-108 (Non-patent document 2), describes the reaction between methyl-ethyl carboxyphosphinic acid and hydroxyethyl acrylate.

[0010] DE102013223915A1 (Patent Document 7), DE102013101487A1 (Patent Document 8), and WO2019 / 141572A1 (Patent Document 9) disclose phosphorus-containing (meth)acrylate monomers for producing flame-retardant thermoplastic resin compositions. Among the phosphorus-containing (meth)acrylate monomers, DOPO-oxymethylene methacrylate monomer is described. This monomer is reacted with one or more types of at least trivalent (meth)acrylate monomers to form copolymers, which then form part of the resin composition as flame retardants. The polymers in the first two documents should be and are thermosetting resins. According to the latter document, slightly crosslinked or uncrosslinked copolymers can be obtained by direct copolymerization with (meth)acrylate monomers by producing phosphorus-containing triacrylate monomers from approximately equimolar amounts of phosphorus compounds and acrylate groups in the triacrylate.

[0011] According to JP2016-060865A (Patent Document 10), DOPO-acrylate monomers are obtained by a Michael addition reaction with a deficiency in DOPO. The document contains 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. Indeed, copolymerization with acrylates is described. However, those skilled in the art cannot learn from the document whether non-crosslinkable monomers are possible or 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 [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] None of these proposals enable an economical method for producing transparent, thermoplastic (meth)acrylate polymers having a sufficiently effective phosphorus-containing flame retardant as a comonomer. Therefore, there remains the challenge of providing a useful flame retardant for thermoplastic, transparent (meth)acrylate polymers. [Means for solving the problem]

[0015] Surprisingly, it was found that useful copolymers can be obtained by phospha-Michael addition reactions to α,ω-alkyldiol-diaacrylate, starting from DOPO and similar oxaphosphaphenanthrene oxides, by using an excess of α,ω-alkyldiol-diaacrylate and removing the unconverted α,ω-alkyldiol-diaacrylate, for example, by vacuum distillation and / or extraction.

[0016] Therefore, the above problem is resolved by a method for producing an oxaphosphaphenanthrene oxide-acrylate monomer by a phospha-Michael addition reaction to an α,ω-alkyldiol-diaacrylate having 2 to 6 carbon atoms in the alkyl chain in the presence of a sterically hindered non-nucleophilic base and a polymerization inhibitor, wherein the oxaphosphaphenanthrene oxide and the α,ω-alkyldiol-diaacrylate are reacted 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 the unconverted α,ω-alkyldiol-diaacrylate is separated, preferably by vacuum distillation. Furthermore, the above problem is also resolved by the use of the oxaphosphaphenanthrene oxide-acrylate monomer thus obtained for the production of (meth)acrylate polymers, and by a method for producing a transparent thermoplastic (meth)acrylate polymer by copolymerization of the oxaphosphaphenanthrene oxide-acrylate monomer and the (meth)acrylate monomer.

[0017] The term (meth)acrylate polymer, as previously described, encompasses methacrylate polymers and acrylate polymers, as well as copolymers of one or more acrylic acid ester monomers and / or one or more methacrylate ester monomers. That is, it includes not only homopolymers but also copolymers, terpolymers, etc., in which case the monomer is either an acrylic acid ester monomer or a methacrylate ester monomer, or both an acrylic acid ester monomer and a methacrylate ester monomer. In one preferred embodiment, the (meth)acrylate polymer comprises only (meth)acrylate monomers, 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, iso-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, and benzyl acrylate. Preferred ones are methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, and 2-ethylhexyl acrylate, particularly ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, and tert-butyl acrylate. Common methacrylic acid ester monomers are methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, iso-butyl 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 ones are methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, and tert-butyl methacrylate, especially methyl methacrylate. Here, these monomers are collectively referred to as (meth)acrylate monomers.

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

[0020] Preferred (meth)acrylate polymers are copolymers of polymethyl methacrylate (PMMA) and 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 to further improve desired properties, including combustion behavior.

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

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

[0024] The temperature is generally 70-120°C, preferably 80-100°C. As the reaction medium, an aprotic solvent having good solubility for either the excess phosphaphenanthrene oxide or the α,ω-alkyldiol-diaacrylate is used. In one preferred embodiment, conversion is carried out without a solvent. This facilitates the isolation of the oxaphosphaphenanthrene oxide-acrylate monomer, which reduces costs. The solvent has the advantage of reducing the risk of premature polymerization, and in addition, it can be removed more easily by distillation. Preferred solvents are toluene, xylenes, acetates, acetonitrile, and tetrahydrofuran, particularly toluene and xylenes (o-xylene, p-xylene, m-xylene, and mixtures thereof), most preferably toluene. Suitable amounts are, for example, 1:5 to 5:1, preferably 1:2 to 2:1, as the ratio of the volume of solvent to the total volume of the starting materials and base.

[0025] As the base, sterically hindered and non-nucleophilic compounds, such as tertiary alkylamines, are used, typically in amounts 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 amine:DOPO molar ratio can be reduced to about 0.15:1; further reduction of the amine amount considerably slows down the addition reaction and lowers selectivity. An excess of base is unfavorable 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 more base some time after the start of conversion.

[0026] Polymerization inhibitors are added to prevent premature polymerization of oxaphosphaphenanthrene oxide acrylates and α,ω-alkyldiol diacrylates. Suitable examples include hydroquinone, phenothiazine, 1-dodecanethiol, hydroquinone monobenzyl ether, methoxyhydroquinone, and other known substances. Hydroquinone and methoxyhydroquinone are preferred. The required amount is known in itself. For example, the amount of stabilizer contained in commercially available α,ω-alkyldiol diacrylates may be sufficient.

[0027] Since oxaphosphaphenanthrene oxide can react with water and a base while undergoing ring-opening, the conversion is carried out in the absence of water. Water causes ring-opening and, therefore, a side reaction, namely, 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 in the liquid phase, preferably less than 0.1% by weight, and particularly preferably less than 0.05% by weight.

[0028] Preferably, the conversion is carried out under a drying protective gas, such as nitrogen. Reactions in air are not recommended for reasons of protection against explosion. Furthermore, triethylamine, for example, is somewhat susceptible to oxidation, and the reaction mixture may darken in the presence of air. In contrast, small amounts of oxygen are not a problem, and may even be advantageous when methoxyhydroquinone, the most frequently used inhibitor, is used, since these are only active in the presence of trace amounts of oxygen. In this respect, the removal of oxygen from the starting materials and other components of the reaction solution is unnecessary and preferably not done.

[0029] The conversion is carried out until the oxaphosphaphenanthrene oxide is essentially completely converted, which typically takes 1 to 10 hours, and often 2 to 5 hours. In this case, the oxaphosphaphenanthrene oxide is added in multiple stages or continuously, for example, over 2.5 to 3 hours, using a solids feed unit. To complete the conversion, the reaction temperature is maintained for a further 45 to 60 minutes after the completion of the addition. Adding in multiple stages or continuously is meaningful because the addition reaction is mildly exothermic. For relatively large batches, adding all of the oxaphosphaphenanthrene oxide at once can release too much reaction heat in a short time, potentially causing the temperature to rise too high. Furthermore, adding the oxaphosphaphenanthrene oxide in multiple stages or continuously over a relatively long period improves selectivity, resulting in very little bioxaphosphaphenanthrene oxide-functionalized diacrylate being formed.

[0030] The conversion products include, among others, a small amount of di-oxaphosphaphenanthrene oxide-acrylate and an excess of α,ω-alkyldiol-diaacrylate, as well as oxaphosphaphenanthrene oxide-acrylate. Essentially complete conversion means that up to 5 mol%, preferably up to 2 mol%, of the oxaphosphaphenanthrene oxide was not converted. The time until essentially complete conversion is, for example, 31 This can be determined using P-NMR. Once the time for specific conditions has been determined, further control is no longer necessary in subsequent conversions. It is desirable for the conversion to be essentially complete, as the residue of unconverted oxaphosphaphenanthrene oxide is undesirable, but excessively long reaction times do not offer any advantages.

[0031] During conversion, excess α,ω-alkyldiol-diacrylate, and optionally the solvent, are removed, preferably by vacuum distillation. Alternatively, excess α,ω-alkyldiol-diacrylate, and optionally the solvent, can also 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. A thin-film evaporator is optimal because only very short heating times are performed, which minimizes the risk of spontaneous polymerization. In this case, temperatures of 75 to 140°C are useful. If the vacuum distillation time is relatively long, it is preferable not to exceed 120°C. Preferably, for the removal of excess α,ω-alkyldiol-diacrylate, the work is carried out at a pressure of 0.01 to 0.2 mbar, preferably 0.02 to 0.2 mbar. In one embodiment, liquid-liquid extraction using a hydrocarbon solvent such as cyclohexane is (additionally) performed to separate the excess α,ω-alkyldiol-diacrylate from the reaction product. Other alkanes such as n-hexane and heptane, or even mixtures of alkanes, can be used, but cyclohexane was the most effective of all the solvents tested. To achieve this, the solvent of the reaction product is vigorously mixed with the hydrocarbon solvent, sometimes before or after distillation, and sometimes after the addition of the solvent, and the hydrocarbon solvent phase to be separated 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 separation of α,ω-alkyldiol-diacrylate by extraction.

[0032] According to the present invention, an oxaphosphaphenanthrene oxide-acrylate monomer containing at most 3 mol% of diacrylate, and particularly at most 0.5 mol% of diacrylate, can be obtained.

[0033] The obtained oxaphosphaphenanthrene oxide-acrylate monomer can be polymerized with (meth)acrylate monomers, and optionally and further with other comonomers, in ways known by themselves, for example, by radical emulsification, suspension, or bulk polymerization, for the production of (meth)acrylate polymers according to the present invention. Typically, this involves mixing the monomers and then mixing them with a radical initiator, such as azobis(isobutyronitrile) (abbreviated as AIBN) or benzoyl peroxide. The useful proportion of oxaphosphaphenanthrene oxide-acrylate monomer depends on the desired or required flame retardancy and is typically in the range of 10 to 30 mol%, preferably 20 to 25 mol%, of the oxaphosphaphenanthrene oxide-acrylate monomer, based on the mixture of all monomers.

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

[0035] The (meth)acrylate polymer according to the present invention may contain further additives, as is known in itself, and may include, but is not exclusive, one or more flame retardants, surfactants, nucleating agents, coupling agents, fillers, plasticizers, impact enhancers, lubricants, antibacterial agents, mold release agents, heat stabilizers, antioxidants, photoprotective agents, compatibilizers, inorganic additives, antistatic agents, pigments, dyes, and combinations thereof. The additives may be added independently of each other during polymerization and / or during the pellet formation process (extrusion) so that they can be incorporated into the copolymer. The processes and amounts for this are known in themselves and are not particularly limited. Typical additive content is 0.001 to 10% by weight of each additive based on the total mixture, while fillers may be up to 50% by weight or more.

[0036] In one particularly preferred embodiment, to further improve the flame retardant properties of the (meth)acrylate polymer produced according to the present invention, a copolymerized phosphorus compound with flame retardant activity in the solid phase is additionally included. These support the effect of the oxaphosphaphenanthrene oxide-acrylate comonomer active in the gas phase. Suitable are phosphorus-containing monomers based on alkyl (meth)acrylates and hydroxyalkyl (meth)acrylates, preferably hydroxyethyl (meth)acrylates, particularly the following:

[0037] [ka] These comonomers are commercially available or can be produced by methods known in themselves. 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 Literature 3). The second compound can be produced 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, C.P. Nair, G. Clouet, J. Brossas; Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 26, 1791-1807 (1988) (Non-Patent Literature 4). The fourth compound is produced 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 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 is available by a method similar to that according to the present invention.

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

[0039] The combustion behavior is tested according to UL94 standards "Tests for Flammability of Plastic Materials for Parts in Devices and Appliances" in accordance with Underwriter Laboratory's IEC / DIN EN 60695-11-10 and -20. These tests are performed using an open flame (Bunsen burner). The ignition source has a power of 50 watts (flame height 20 mm) and is applied to the test specimen twice for 10 seconds each time in the V test, and then removed again. During this process, the burning time and the fall of the burning portion are evaluated using a cotton pad placed beneath the test specimen. Five test specimens (127 mm (5 inch) long, 12.7 mm (0.5 inch) wide, with a thickness appropriate for the application) should be tested. Classification is performed when the following requirements are met: V2: The total burning time for 10 flame contacts is a maximum of 250 seconds, and it will self-extinguish within 30 seconds at the latest, with the dripping of flames being acceptable. V1: The total burning time for 10 flame contacts is a maximum of 250 seconds, self-extinguishing within 30 seconds at the latest, no dripping of flames is permitted, and the afterglow lasts a maximum of 60 seconds. V0: The total burning time for 10 flame contacts must be a maximum of 50 seconds, self-extinguishing within 10 seconds at the latest, no dripping of flames is permitted, and the afterglow must last a maximum of 30 seconds.

[0040] The flame-retardant, transparent thermoplastic (meth)acrylate polymer according to the present invention typically achieves a V1 grade, often a V0 grade.

[0041] This makes the thermoplastic (meth)acrylate polymer according to the present invention suitable for use in layers of decorative films for lamination with components made of metal, wood, and plastic, such as window and door frames, fences, and facade panels. Such decorative films include, for example, colored and / or printed base films, such as base films made of PVC or (meth)acrylate polymer. A primer and / or adhesive may be provided on the underside of this base film, depending on the material of the base film and the material to be laminated with it. On the top surface, there is a protective film made of one or more layers of the copolymer according to the present invention to protect the base film and optionally the printing from UV radiation. Alternatively, the decorative film may also consist of one or more layers of the copolymer according to the present invention. One or more layers made of the copolymer according to the present invention may be mixed with polyvinylidene fluoride (PVDF) as a non-flammable component. In many cases, a cover film or cover coat is provided as an outer layer, made of a plastic with particularly high scratch resistance and durability, such as polytetrafluoroethylene (PTFE) or PVDF, which usually also provides protection against dirt. Such decorative films can be partially or completely co-extruded, and the non-co-extruded layers are thermally laminated. For example, if a wood-like appearance is desired, the surface can be embossed. A suitable thickness for the decorative film is, for example, 100 to 300 μm, preferably 130 or 150 to 200 μm. In this case, the protective layer made of the copolymer according to 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 expressions "made of polymer" or "consisting of polymer" mean that the polymer described is the main polymer component of the layer. The presence of one or more further polymers is not ruled out, but their amounts are usually (each) less than 50% by weight, mostly less than 30% by weight, and often less than 10% by weight, based on the total polymer component.

[0042] Furthermore, the flame-retardant and transparent thermoplastic (meth)acrylate polymer according to the present invention is suitable for the manufacture of transparent and colored panels. These panels can be used in a wide range of applications, such as interior fittings.

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

[0044] The present invention also relates to all combinations of preferred embodiments, except where they are incompatible. The term "approximately" with respect to numerical values ​​means that the values ​​will be at least 10% greater or less, or 5% greater or less, and in individual cases, 1% greater or less. [Examples]

[0045] The preparation of oxaphosphaphenanthrene oxide-acrylate monomers was carried out in three-neck flasks of different volumes, equipped with a stirrer, a Claisen-type branched tube with a reflux condenser, and a nitrogen supply. The temperature was controlled in an oil bath. Before each reaction, the apparatus was heated and dried under vacuum and then filled with nitrogen. For the reaction, α,ω-alkyldiol-diacrylate was packed into the flasks together with a solvent (toluene) and a base (triethylamine) under countercurrent nitrogen. Then, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was added in several 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. The reaction process was followed by sampling, and 31 The P-NMR spectrum was measured and tracked.

[0046] Example 1 1,4-butanediol diacrylate was reacted with DOPO in a molar ratio of 3.5:1. To this end, 0.6 moles (118.93 g) of 1,4-butanediol diacrylate and 14.05 g of DOPO were added to a 500 ml three-necked flask filled with nitrogen. Then, 80 ml of toluene and 0.17 moles (approximately 23.56 ml) of triethylamine were added. The mixture was then heated under a nitrogen atmosphere with stirring to a temperature slightly below its boiling point (approximately 96°C, oil bath temperature approximately 107°C). Two further portions of DOPO were added at 60-minute intervals (11.89 g, 10.81 g, totaling 36.75 g, 0.17 moles). The mixture was stirred for another 60 minutes at the same internal temperature (approximately 96°C). An NMR sample was then taken, and the NMR spectrum showed complete conversion.

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

[0048] Next, the following equation:

[0049] [ka] The reaction product obtained (49.91 g) was copolymerized with methyl methacrylate in a molar ratio of approximately 1:2.7. For this purpose, the reaction product was dissolved in 200 mL of toluene and transferred to a three-necked flask. Then, approximately 33.3 g of destabilized methyl methacrylate was added, and the solution was heated to 97°C under nitrogen. Because this solution contains a 4-methoxyphenol inhibitor, it must not contain oxygen during copolymerization, so it was stirred under nitrogen at a constant temperature for 1.5 hours. Next, under vigorous stirring, 1 ml of 0.2 M AIBN solution in toluene was added dropwise within 2 minutes, and the oil bath temperature was raised to 117°C. After 10 minutes, another 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 substance precipitated from the solution. Copolymerization was then continued for another hour.

[0050] The obtained 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. Thermogravimetric analysis (TGA) was performed. In this case, the sample was heated from 35°C to 800°C in a nitrogen stream at a heating rate of 10 K / min. This analysis showed a decomposition temperature of 318°C with a 5% mass loss. Using this polymer product, test specimens were prepared in 4 minutes under a pressure of 25 bar in a laboratory press. These specimens maintained a very elastic and rubbery state at a temperature of 190°C. Above 225°C, the test specimens became hard and brittle, suggesting post-crosslinking, i.e., incomplete polymerization.

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

[0052] Example 2 The reaction was carried out as in Example 1, except that the reaction products were subjected to vacuum distillation (oil bath temperature 140°C, 0.031 mbar vacuum) followed by multiple shaking with n-hexane. Initially, each product was mixed with 50 ml of n-hexane three times, then 20 ml of toluene was added, followed by four more mixing cycles with 40 ml of n-hexane each, and then another 20 ml of toluene was added, followed by four more mixing cycles with 40 ml of n-hexane each. These solvents were then removed using 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. Then, approximately 35 g of destabilized methyl methacrylate was added, and the solution was heated to 97°C under a nitrogen atmosphere and stirred at a constant temperature for 2 hours. Next, under vigorous stirring, 1 ml of 0.2 M AIBN solution was added dropwise within 2 minutes, 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 substance precipitated from the solution. The reaction was continued for another hour.

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

[0055] Comparative example VB1 The procedure was similar to Example 1, except that butylene glycol-dimethacrylate and DOPO were reacted in a 1:1 molar ratio. In a 500 ml three-necked flask filled with nitrogen, 0.2 moles (45.25 g) of butylene glycol-dimethacrylate and 9.24 g of DOPO were added. Then, 100 ml of toluene and 0.12 moles (approximately 16.6 ml) of triethylamine were added. The mixture was then heated with stirring and 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 at 30-minute intervals (8.54 g, 6.99 g, 6.50 g, 4.9 g, 4.00 g, 3.00 g, totaling 43.24 g, 0.2 moles). The mixture was stirred for another 30 minutes at a constant internal temperature (approximately 96°C). Then, an NMR sample was taken. The reaction was not yet complete, so the mixture was stirred for another 3 hours under the same conditions (internal temperature of approximately 96°C), and then an NMR sample was taken. Since the reaction was still not complete, another 5 ml of triethylamine was added, and the mixture was stirred for another hour under the same conditions. Further NMR samples were taken. The DOPO was now completely converted.

[0056] For copolymerization, the oxaphosphaphenanthrene oxide-acrylate monomer was first stirred at an internal temperature of approximately 97°C for 30 minutes. Next, 0.4 moles (40.07 g) of destabilized methyl methacrylate were added under countercurrent nitrogen. Since this solution must not contain oxygen during copolymerization due to its 4-methoxyphenol content, it was stirred at a constant temperature for a further 1.5 hours. Then, 2 ml of 0.2 moles of AIBN solution in toluene was added dropwise over 2 minutes with vigorous stirring. The solution began to boil vigorously, and after a reaction time of several minutes, a bulky gel-like substance precipitated from the solution. The oil bath temperature was increased to 117°C, and the reaction was continued for 1 hour.

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

[0058] Using this powder, we attempted to produce test specimens using a laboratory press at temperatures up to 260°C and pressures up to 25 bar. However, the powder could not be melted, and test specimens could not be produced. Solubility tests showed that the obtained polymer could not be dissolved in organic solvents. This indicates that a thermoplastic plastic 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 number of unconverted dimethacrylates. Furthermore, to ensure faster conversion of DOPO, the amount of base was increased and the time between DOPO additions was extended to 60 minutes. 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 heated with stirring and 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 at 60-minute intervals (8.5g, 7.5g, 6.5g, 5.5g, 4.5g, 3.4g, totaling 45.40g, 0.21 mol). The mixture was stirred for another 60 minutes at the same internal temperature (approximately 96°C). An NMR sample was then taken. The reaction was not yet complete. Therefore, the mixture was stirred again for 2.5 hours under the same conditions (internal temperature approximately 96°C), and further NMR spectra were recorded. After 3 hours, 31 According to P-NMR, DOPO was completely consumed.

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

[0061] Comparative example VB3 Similar to Example 1, ethylene glycol-dimethacrylate was reacted with DOPO in a molar ratio of 1.76:1. In a 500 ml three-necked flask filled with nitrogen, 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 heated with stirring and under a nitrogen atmosphere to a temperature slightly below its boiling point (approximately 96°C, oil bath temperature approximately 107°C). Four more portions of DOPO were added at 45-minute intervals (7.57 g, 6.49 g, 5.41 g, 4.32 g, totaling 32.44 g, 0.15 moles). The mixture was then stirred for a further 60 minutes at the same internal temperature (approximately 96°C). 31 The P-NMR sample still showed traces of unconverted DOPO one hour after the final DOPO addition. This 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. Both phases were separated using a separatory funnel. Then, another 100 ml of n-hexane was added, and each phase was separated again using a separatory funnel.

[0063] Next, the reaction product was copolymerized with 36 g of methyl methacrylate (molar ratio 1:2). For this purpose, the reaction product, along with 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. Since this solution must not contain oxygen, it was stirred at a constant temperature for 1.5 hours. Then, 3 ml of 0.2 M AIBN solution was added dropwise over 5 minutes while stirring vigorously. The solution began to boil vigorously. After 10 minutes, the oil bath temperature was increased to 117°C. After 10 minutes, a bulky gel-like substance 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 finely ground. A yellowish-white powder was produced. The drying temperature may have been too high, causing partial decomposition of the product. TGA analysis showed a decomposition temperature of 258°C with a 5% mass loss. Using this powder, test specimens were prepared in a laboratory press. These specimens were yellowish, slightly transparent, extremely brittle, and could not be removed from the mold without breaking. The degree of crosslinking was still too high.

[0065] The obtained specimens were tested in an UL94 chamber. The pressed specimens exhibited significantly delayed combustion behavior compared to pure PMMA in flame tests, but did not show the desired self-extinguishing after flame contact.

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

[0067] Triethylamine and toluene were removed under vacuum in a rotary evaporator. The mixture was then shaken three times with 100 ml of n-hexane. Vacuum distillation was then carried out under an oil bath temperature of 85°C, a column top temperature of 50°C, and a vacuum of 0.05 mbar until the dimethacrylate no longer condensed in the receiver. Vacuum distillation was repeated two more times at increased temperatures, i.e., oil bath temperatures of 95°C or 105°C. However, in this case, the product solution spontaneously partially polymerized. 11H-NMR showed that 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. Then, approximately 36 g of destabilized methyl methacrylate was added, and the solution was heated to 97°C under a nitrogen atmosphere. The mixture was stirred at a constant temperature for 1.5 hours. Next, 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, another 1 ml of AIBN was added. 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 substance precipitated from the solution, and the reaction was continued for another hour.

[0069] The obtained polymer product was dried in a vacuum oven at 100°C for 24 hours and then finely ground using a ceramic mortar and pestle. TGA analysis showed a decomposition temperature of 241°C with a 5% mass loss. Test specimens were prepared using the powder in a laboratory press. These were more transparent than those of comparative examples VB1, VB2, and VB3, but were still very brittle. They could not be removed from the mold without breaking.

[0070] The obtained test specimens were tested in an UL94 chamber, and the pressed specimens did not exhibit improved combustion 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 1 L three-necked flask filled with nitrogen, 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 heated with stirring and under a nitrogen atmosphere to a temperature slightly below its boiling point (approximately 96°C, oil bath temperature approximately 107°C). Two more portions of DOPO were added at 60-minute intervals (15.3 g, 10.8 g, totaling 43.24 g, 0.2 moles). The mixture was further stirred for 60 minutes at the same internal temperature (approximately 96°C). An NMR sample was then taken, which showed complete conversion of DOPO.

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

[0073] The examples and comparative examples demonstrate that usable acrylate comonomers cannot be obtained using equimolar amounts of raw materials or using excess oxaphosphaphenanthrene oxide. Diacrylate reacted with oxaphosphaphenanthrene oxide only once, as intended in the present invention, can be obtained by using a sufficiently large excess amount of diacrylate. Excess α,ω-alkyldiol-diacrylate could be separated quite well. In contrast, this was not the case with α,ω-alkyldiol-dimethacrylate. In particular, Comparative Examples 1 and 2 demonstrate that thermoplastic (meth)acrylate polymers cannot be obtained by using direct copolymerization of oxaphosphaphenanthrene oxide-acrylate monomer with another (meth)acrylate monomer, as proposed in WO2019 / 141572A1 (Patent Document 9) and JP2016-060865A (Patent Document 10). In addition to the selection of α,ω-alkyldiol-diacrylate and its excess amount, the separation of unreacted α,ω-alkyldiol-diacrylate as intended by this invention is also necessary to obtain thermoplastic (meth)acrylate polymers. Table 1 below provides an overview of examples and comparative examples.

[0074] [Table 1]

[0075] Example 6 In the same manner as in Example 2, DOPO-acrylate monomers were prepared from DOPO and 1,4-butanediol diacrylate, with a molar ratio of butanediol diacrylate to DOPO of 7:1. To achieve this, 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 250 ml three-necked flask filled with nitrogen. Then, 35 ml of triethylamine was added using a syringe through the septum, and the mixture was heated to 85-87°C (oil bath temperature) over 20 minutes with stirring and under a nitrogen atmosphere. Next, 9.0 g of DOPO was added. After another 20 minutes, a third portion of DOPO (9.0 g) was added. Three more 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 a further 30 minutes. Then, heating was stopped. During the phosphatamine addition, 20 mL of air was injected at approximately 15-minute intervals to keep the inhibitor active.

[0076] To isolate the DOPO monomer, the resulting product solution was divided into two parts. The isolation of the product was carried out on both parts by first removing triethylamine by distillation, with partial vacuum applied at the start and the oil bath heated to a maximum of 50°C. Next, the excess butanediol diacrylate was distilled (approximately 0.02 mbar), heated to 105°C to avoid spontaneous polymerization. 250 mL of cyclohexane was added to the distillation residue and then rapidly heated to boiling point. After vigorous stirring under reflux for approximately 5 minutes, the oil bath was removed. The contents of the flask were then cooled to approximately 40°C in a water bath, then cooled in a refrigerator, and the slightly cloudy supernatant phase was decanted. Nine further extractions were performed in the same manner (cyclohexane was recovered in each case). The extraction residue was then heated to 105°C over 45 minutes, during which the pressure was reduced to approximately 0.02 mbar. These conditions were maintained for approximately 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 1H-NMR spectrum showed good purity. In particular, it demonstrated good separation of excess 1,4-butanediol diacrylate (<1 wt% diacrylate; the proportion of the double DOPO-functionalized product was approximately 6 wt%).

[0077] 52.82 g of DOPO monomer was dissolved in 200 mL of toluene for copolymerization with methyl methacrylate 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 a constant temperature for 2 hours. Next, under vigorous stirring, 1 ml of 0.2 M AIBN solution was added dropwise within 2 minutes, 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 substance precipitated from the solution. The reaction was continued for another hour.

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

[0079] Example 7 The DOPO monomer of Example 6 is mixed with and without other monomers such as methyl acrylate or n-butyl methacrylate in various amounts, resulting in methyl methacrylate and DDPO-HEMA,A=

[0080] [ka] The monomers were reacted with 1-decylthiol as a modifier and dibenzoyl peroxide (BPO) as an initiator to form a methyl acrylate polymer. Suspension polymerization was carried out in water. The liquid monomers were 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-neck flask, a magnetic stirrer, a heating bath, a dropping funnel, and a reflux condenser equipped with a three-way stopcock with a bubble counter. The dropping funnel and the three-way stopcock on the reflux condenser were connected via a Schlenklein.

[0081] From the obtained methacrylate polymer, dense transparent test rods and transparent films of different thicknesses were prepared using a Type HB20 300 hydraulic laboratory press (Schmidt Maschinentechnik GmbH; Bretten-Bauerbach, Germany). The test rods had the following dimensions: 70 mm × 10 mm × 0.8 mm. A temperature of 210–245°C was used during pressing (depending on the melting behavior of the methacrylate polymer). The results of the quantity and combustion behavior tests are shown in Table 2.

[0082] Example 7a For 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 hydrated BPO was added to a dropping funnel. A short vacuum was then applied twice, and nitrogen was introduced again in each case. To remove oxygen, a mixture of water and 1.3 ml of a 2% solution of Kuraray's Poval 25-88 (partially hydrolyzed polyvinyl alcohol) as a suspension stabilizer was stirred at 85-90°C for 30 minutes. During this time, a gentle stream of nitrogen was introduced into the apparatus via a three-way stopcock and flowed to the bubble counter. After cooling this aqueous solution to approximately 62°C, the solution was added from the dropping funnel. The contents of the flask were then heated to 73°C with stirring for 20 minutes. A milky emulsion was formed. The connection to the bubble counter was cut off 10 minutes after the addition of the monomer. The temperature was then increased by 1°C at intervals of approximately 15 minutes each until it reached 82°C. The mixture was vigorously stirred for four hours. After that, a solution consisting of 65 mg of BPO and 500 mg of methyl methacrylate was added, and the temperature was raised to 87°C. At this temperature, the reaction mixture was stirred under a nitrogen atmosphere for 12 hours. Small spherical particles and some dense material were produced. The supernatant aqueous solution was decanted, then water was added, and the mixture was drawn up through filter paper. This methacrylate polymer was dried at 80°C for 5 hours and at 100°C for 1 hour under vacuum (approximately 0.02 mbar). The polymer was recorded in deuterated chloroform. 31 The P-NMR spectrum contained only signals in DOPO units (approximately 36 ppm) and DDPO units (-8.2 ppm). The ratio of the integrated signal values ​​closely matched the expected value of 1.00:1.50. Approximately 9 g of methacrylate polymer was obtained.

[0083] Example 7b For 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-neck 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 aqueous BPO (60 mg of pure BPO) was added to a dropping funnel. The dropping funnel was partially evacuated twice and then refilled with nitrogen to remove air oxygen from the reagent mixture. The reaction flask containing the aqueous solution was also partially evacuated twice and refilled with nitrogen in each case. The contents of the flask were then heated to 95°C with stirring. During this time, a gentle stream of nitrogen was supplied to the apparatus and to the bubble counter via a three-way stopcock. After stirring for 30 minutes, the temperature was reduced to approximately 65°C. The contents of the dropping funnel were added to the aqueous solution from which oxygen had been removed in this manner. The contents of the flask were then heated to 73°C in an open atmosphere with a weak nitrogen stream for about 20 minutes under stirring. The temperature was increased to 83°C over 2 hours. A gentle nitrogen stream was then passed through a bubble counter. After another 1 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 disconnected. Stirring at 87°C was continued for 12 hours. The aqueous phase was then decanted. A methacrylate polymer as dense fragments and a film-like material were obtained. This polymer was soluble in chloroform and dimethyl sulfoxide. To remove monomer residue and water, the polymer was heated under vacuum (approximately 0.02 mbar) first to 90°C for 3 hours, and then to 105°C for 45 minutes. The methacrylate polymer thus obtained was... 31 In the P-NMR spectrum, signals in DOPO and DDPO units were present at approximately 36 ppm and -8 ppm, respectively, and the integral ratio closely matched the expected value.

[0084] Example 7c For copolymerization, 55 ml of deionized water and 1.5 ml of a 2 wt% aqueous solution of Kuraray's Poval 25-88KL (a suspension stabilizer, partially hydrolyzed polyvinyl alcohol) were added to a three-neck 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 a dropping funnel. The dropping funnel was evacuated partially twice and then refilled with nitrogen again to remove air oxygen from the reagent mixture. The reaction flask containing the aqueous solution was also evacuated partially twice and refilled with nitrogen in each case. Then, the contents of the flask were heated to 95 °C with stirring. At this time, a gentle nitrogen stream was passed through the apparatus and into the bubble counter via a three-way cock. After stirring for 30 minutes, the temperature was lowered to about 65 °C. The contents of the dropping funnel were added to the thus oxygen-removed aqueous solution. Then, the temperature of the oil bath was raised to 75 °C while stirring the reaction mixture vigorously. At this time, 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. Then, a solution of 35 mg of BPO, 0.33 g of methyl methacrylate, and 0.07 g of methyl acrylate was added via the dropping funnel in a nitrogen countercurrent. Then, the temperature of the heating bath was raised to 87 °C. After another 1 hour, the connection to the bubble counter was cut off and the cooling water was stopped. Under these conditions, the reaction mixture was stirred for a further 12 hours. Then, an aqueous solution of the methacrylate polymer, which formed partly as spherical objects and partly as a dense or film-like material, was decanted. The methacrylate polymer was washed three times with water and dried on filter paper. The 1 1H-NMR spectrum of the polymer recorded in deuterated chloroform showed that it contained unreacted monomers. Therefore, the polymer was heated under high vacuum (about 0.02 mbar), first to about 87 °C (for 4 hours), then to 93 °C (for 1 hour). After that, the 1 1H-NMR spectrum of the methacrylate polymer showed almost complete disappearance of the acrylate- / methacrylate groups. 31In the P-NMR spectrum, signals in DOPO and DDPO units were present at approximately 36 ppm and -8 ppm, respectively, and the integral ratio closely matched the expected value of 1.00:1.66.

[0085] Example 7d For 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-neck flask. Next, 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 aqueous BPO (equivalent to 81 mg of pure BPO) was added to a dropping funnel. The dropping funnel was partially evacuated twice and then refilled with nitrogen to remove air oxygen from the reagent mixture. The reaction flask containing the aqueous solution was also partially evacuated twice and refilled with nitrogen in each case. Next, the contents of the flask were heated to 95°C with stirring. During this time, a gentle stream of nitrogen was supplied to the apparatus and to the bubble counter via a three-way stopcock. After stirring for 60 minutes, the temperature was reduced to approximately 63°C. The contents of the dropping funnel were added to the aqueous solution from which oxygen had been removed in this manner. Next, the temperature of the heating bath was raised to 75°C. This temperature was maintained for 20 minutes, then the set temperature was raised to 77°C, and then to 80°C after 30 minutes. This temperature was maintained for 50 minutes. Next, the set temperature was raised to 85°C. A milky white emulsion was formed. The mixture was stirred very vigorously for three hours, and then a nitrogen stream was introduced into the apparatus and flowed to the bubble counter. Polymer formation could be observed. Subsequently, the connection to the bubble counter was disconnected, the cooling water was stopped, and the mixture was stirred for another 12 hours at 85°C under weak nitrogen back pressure. Next, the aqueous solution of the methacrylate polymer, which had formed partly as small spherical particles and partly as a dense material, was decanted. This methacrylate polymer was washed three times with water and dried on filter paper. The NMR spectrum of the polymer thus obtained showed a conversion rate of approximately 95% of the acrylate- and methacrylate groups. The polymer was dried under vacuum (0.02 mbar) at 87-95°C for 3 hours to remove residual water. 1 The 1H-NMR spectrum showed almost complete disappearance of the acrylate- / methacrylate groups. 31In the P-NMR spectrum, signals for DOPO and DDPO units were present at approximately 36 ppm and -8 ppm, respectively, with an integral ratio of approximately 1.00:2.33, which closely matched the expected value. The resulting methacrylate polymer dissolved well in organic solvents such as chloroform. It softened at approximately 160°C and melted at approximately 200°C.

[0086] Example 8 In Example 6, DOPO monomers were used in various amounts to form methyl methacrylate and DEPO-HEMA, B=

[0087] [ka] The monomers were then reacted with or without the addition of further monomers such as methyl methacrylate or n-butyl methacrylate to obtain a methyl acrylate polymer. Suspension polymerization was carried out in water using 1-decylthiol as a modifier and dibenzoyl peroxide (BPO) as an initiator. These monomers were destabilized before 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 with a bubble counter. The dropping funnel and the three-way stopcock on the reflux condenser were connected via a Schlenklein.

[0088] From the obtained methacrylate polymer, dense test rods and films of different thicknesses were prepared using a Type HB20 300 hydraulic laboratory press (Schmidt Maschinentechnik GmbH; Bretten-Bauerbach, Germany). The test rods had the following dimensions: 70 mm × 10 mm × 0.8 mm. A temperature of 220–245°C was used during pressing (depending on the melting point of the methacrylate polymer). The results of the quantity and combustion behavior tests are shown in Table 2.

[0089] Example 8a Polymerization was carried out in a manner similar to Example 7c. The methacrylate polymer was obtained mostly as dense fragments, which were peeled from the glass wall and washed with water. The polymer was recorded in deuterated chloroform. 1 The 1H-NMR spectrum showed that it contained unconverted monomers. Therefore, the polymer was heated under high vacuum (approximately 0.02 mbar) first to approximately 87°C (4 hours) and then to 93°C (1 hour). Subsequently, the methacrylate polymer was... 1 The 1H-NMR spectrum showed almost complete disappearance of the acrylate- / methacrylate groups. 31 In the P-NMR spectrum, the signals for DOPO units and diethyl phosphate units were present at approximately 36 ppm and -1.3 ppm, respectively, with the integral ratio closely matching the expected value of 1.00:1.74.

[0090] Example 8b 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 under vacuum (0.02 mbar) at 87-105°C for 5 hours and then examined using NMR spectroscopy. 1 The 1H-NMR spectrum showed complete disappearance of the acrylate- / methacrylate groups. 31 The P-NMR spectrum was also as expected. Specifically, the signals for DOPO units and diethyl phosphate units were present at approximately 36 ppm and -1.3 ppm, respectively, and the integral ratio closely matched the expected value of 1.00:1.74.

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

[0092] [Table 2]

[0093] These examples demonstrate that the combination of the oxaphosphaphenanthrene oxide-acrylate monomer according to the present invention and the copolymerized solid-phase activated phosphorus compound provides optimal flame retardancy. The solid-phase activated phosphorus compound alone does not function sufficiently. This is demonstrated by the methacrylate polymer of Comparative Example 8a, which exhibits worse flame retardancy than Examples 7c, 8a, and 8b despite a relatively high phosphorus content.

Claims

1. A method for producing an oxaphosphaphenanthrene oxide-acrylate monomer by phospha-Michael addition to an α,ω-alkyldiol-diaacrylate having 2 to 5 carbon atoms in an alkyl chain, comprising reacting oxaphosphaphenanthrene oxide and an α,ω-alkyldiol-diaacrylate 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 in the absence of water, and separating the unconverted α,ω-alkyldiol-diaacrylate.

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

3. The method according to claim 1 or 2, characterized in that the unconverted α,ω-alkyldiol-diaacrylate is separated by vacuum distillation and / or by liquid-liquid extraction using 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, characterized in that n-pentane, n-hexane, and n-heptane, particularly n-hexane, are used as the hydrocarbon solvent.

5. The method according to any one of claims 1 to 4, characterized in that the phosphine addition is carried out in toluene, o-xylene, m-xylene, p-xylene, or a mixture of two or more thereof as a solvent, particularly in toluene.

6. The method according to any one of claims 1 to 5, characterized in that a sterically hindered tertiary amine, particularly triethylamine, is used as the base.

7. The method according to any one of claims 1 to 6, characterized in that the base is used in an amount of 0.15 to 2.0 moles, preferably 0.5 to 1.2 moles, and particularly preferably 0.9 to 1.1 moles, per mole of oxaphosphaphenanthrene oxide.

8. The method according to any one of claims 1 to 7, characterized in that an α,ω-alkyldiol-diacrylate having 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 claims 1 to 8.

10. The oxaphosphaphenanthrene oxide-acrylate monomer according to claim 9, characterized in that it contains up to 3 mol%, preferably up to 0.5 wt%, of α,ω-alkyldiol-diaacrylate.

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 claims 1 to 8.

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, particularly 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 a phosphorus-containing monomer, preferably based on alkyl acrylates, hydroxyalkyl (meth)acrylates, and particularly preferably based on hydroxyethyl (meth)acrylates, is additionally polymerized and introduced, wherein the phosphorus-containing monomer is selected from those of the following formulas and mixtures of two or more thereof. 【Chemistry 1】

14. Use of an oxaphosphaphenanthrene oxide-acrylate monomer obtained according to any one of claims 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 claims 11 to 13.

16. Use of the flame-retardant thermoplastic (meth)acrylate polymer according to claim 15 for the manufacture of films and panels.

17. The use according to claim 16, characterized in that the film or panel is transparent.

18. The use according to claim 16 or 17, characterized in that the film is a decorative film, and the decorative film comprises a layer containing the (meth)acrylate polymer described in claim 15.

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