EP4168459A1

EP4168459A1 - Flameproof acrylate

Info

Publication number: EP4168459A1
Application number: EP21733425.9A
Authority: EP
Inventors: Dirk Heukelbach; Martin RÖSSLE; Manfred DÖRING; Michael Ciesielski
Original assignee: Renolit SE
Current assignee: Renolit SE
Priority date: 2020-06-17
Filing date: 2021-06-15
Publication date: 2023-04-26
Also published as: JP2023532201A; CA3178772A1; US20230219987A1; WO2021254993A1

Abstract

The invention relates to: a process for producing oxa phosphaphenanthrene oxide acrylate monomers by phospha-Michael addition to acrylates, in which process oxa phosphaphenanthrene oxide is reacted with an α,ω-alkyldiol diacrylate in a molar ratio of 1:1.5 to 1:10 in the presence of a base and a polymerisation inhibitor at temperatures of 70 to 120°C and unreacted α,ω-alkyldiol diacrylate is removed; monomers obtainable by means of the process and the use thereof for producing flameproof thermoplastic (meth)acrylate polymers and a process for producing flameproof thermoplastic (meth)acrylate polymers using the monomers; polymers obtainable thereby and the use thereof for producing transparent films and panels.

Description

Flame retardant acrylate

The present invention relates to a process for the production of oxaphosphaphenantrenoxide acrylate monomers, the monomers obtainable therewith and their use for the production of flame-retardant thermoplastic (meth) acrylate polymers and a process for the production of flame-retardant thermoplastic (meth) acrylate polymers with the monomers thus obtainable Polymers and their use for the production of films and sheets.

Thermoplastic acrylate and methacrylate polymers ((meth) acrylate polymers for short) are versatile plastics because of their transparency and UV resistance. For example, they can be used as a protective layer in decorative films for coating windows, doors and other components.

The disadvantage of (meth) acrylate polymers is that they are comparatively easily inflammable and combustible. To improve this, flame retardants are added. Inorganic flame retardants, such as metal hydroxides, are poorly suited, since the high loads required for adequate effectiveness suffer from transparency. Halogen-containing flame retardants are widespread, but have come under fire because of toxicological and ecological concerns. A wide variety of phosphorus-containing flame retardants have been proposed as halogen-free alternatives. If these are mixed in as low molecular weight compounds, the desired flame retardant effect is obtained, but the transparency can suffer and, in addition, migration of the flame retardants is frequent. This reduces their effect and the surface is changed or, in the case of multilayer films, the adhesion to adjacent layers is impaired.

To avoid this, copolymerizable flame retardants are considered optimal. However, by far not every flame retardant succeeds as a comonomer provide. A particularly effective group of phosphorus flame retardants are phosphinic acid derivatives such as 9,10-dihydro-9-oxa-10-phosphaphenantren-10-oxide (DOPO for short).

Examples of DOPO and other phosphorus-containing flame retardants are known per se. For example, US 2014/0346418 A1, WO 2015/096127 A1 and US 2017/0029704 A1 describe flame retardancy by copolymerization with phosphorus-containing monomers. However, none of the documents mention DOPO, other organic phosphates are described.

From WO 2008/132111 A1, additives based on DOPO are known which carry a carboxylic acid group or its ester on phosphorus. In the case of the preferred polyhydric alcohols for ester formation, additives with several DOPO groups result. A copolymerization is not provided, however, the additives should be mixed with the polymer and only polyamide and polyester are mentioned as polymers.

WO 2014/124933 A2 describes duromers made from DOPO and polyvalent acrylates with at least 3 acrylic groups, which are further reacted with (meth) acrylate. These thermosets should be suitable as flame retardant additives.

In the article by S. Jiang et al. "In situ synthesis of a novel transparent poly (methyl methacrylate) resin ...", DOPO is converted into a monomer via a reaction with formaldehyde and then with acrylic acid chloride and then copolymerized with methyl methacrylate. The procedure is analogous in EP 1 544227 A1, first of all the DOPO is coupled to an alcohol group, which is then reacted with acrylic acid chloride to form the DOPO acrylate monomer. Acrylic acid chlorides are very reactive substances whose use on an industrial scale is problematic. The article Wang et al. , "Flexible, transparent flame retardant membrane Fire and Materials 2018, Vol. 42, pp. 99-108, describes a reaction of methyl-ethylcarboxy-phosphinic acid with acrylic acid-hydroxyethyl ester.

DE 102013223915 A1, DE 102013 101 487 A1 and WO 2019/141572 A1 disclose phosphorus-containing (meth) acrylate monomers for producing flame-retardant, thermoplastic resin compositions. DOPO-oxymethylene methacrylate monomer is described as a phosphorus-containing (meth) acrylate monomer. The monomer is reacted with one or more at least trivalent (meth) acrylate monomers to form a copolymer, which then forms part of the resin composition as a flame retardant. The polymers of the first two documents mentioned are supposed to be thermosets and are. According to the last document, slightly crosslinked or uncrosslinked copolymers are to be obtained by direct copolymerization with (meth) acrylate monomers by preparing phosphorus-containing triacrylate monomers from approximately equimolar amounts of phosphorus compound and acrylate groups in the triacrylate.

According to JP 2016-060865 A, DOPO acrylate monomers are to be obtained by Michael addition with a DOPO deficit. The document contains long lists of possible (meth) acrylates, including 1,4-butanediol di (meth) acrylate and 1,6-hexanediol di (meth) acrylate. The aim is to achieve crosslinkable coatings in which the refractive index is set with DOPO. Copoly merization with acrylates is described. However, the person skilled in the art can neither infer from this document that non-crosslinking monomers can be prepared, nor how this could be achieved.

None of these proposals allows the economical production of transparent, thermoplastic (meth) acrylate polymers with sufficiently effective phosphorus-containing flame retardants as comonomers. There was thus the further object of providing useful flame retardants for thermoplastic, transparent (meth) acrylate polymers. Surprisingly, it has now been found that starting from DOPO and analogous oxaphosphaphenantrene oxides by phospha-Michael addition to α, w-alkyl diol diacrylates, useful comonomers can be obtained if the α, w-alkyl diol diacrylate is used in excess and unconverted a , w-alkyl diol diacrylate is removed, for example, by vacuum distillation and / or extraction.

The above object is therefore achieved by a process for the preparation of oxaphosphaphenantrene oxide acrylate monomers by phospha-Michael addition to α, w-alkyldiol diacrylates having 2 to 6 carbon atoms in the alkyl chain in the presence of a sterically hindered, non-nucleophilic base and a polymerization inhibitor , the oxaphosphaphenanthrene oxide being reacted with the α, w-alkyl diol diacrylate in a molar ratio of 1: 1.5 to 1:10 at temperatures of 70 to 120 ° C. in the absence of water and unreacted α, w-alkyl diol diacrylate - is separated off - preferably by vacuum distillation. The object is also achieved by the oxaphosphaphenantrene oxide acrylate monomers obtainable in this way, their use for the production of (meth) acrylate polymers and a process for the production of transparent, thermoplastic (meth) acrylate polymers by copolymerization of the oxaphosphaphenantrene oxide acrylate monomers with (meth) acrylate monomers.

As mentioned above, the term (meth) acrylate polymer includes methacrylate polymers and acrylate polymers, as well as copolymers of one or more acrylic acid ester monomer (s) and / or one or more methacrylic acid ester monomer (s). Both homopolymers and copolymers, terpolymers, etc. are thus included, the monomers being acrylic acid ester monomers, methacrylic acid ester monomers, or both acrylic acid ester and methacrylic acid ester monomers. In a preferred embodiment, the (meth) acrylate polymers contain, in addition to the oxaphosphaphenantrene oxide acrylate monomer (s) according to the invention, only (meth) acrylate monomer (s). 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. Methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate and 2-ethylhexyl acrylate, in particular ethyl acrylate, n-butyl acrylate, isobutyl acrylate and tert-butyl acrylate, are preferred. Usual methacrylic acid ester monomers are methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutymethacrylate, tert-butyl methacrylate, neopentyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, cyclohexyl methacrylate and benzyl methacrylate. Monomers that are less prone to chain transfer, such as ethyl acrylate, are particularly beneficial. Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutymethacrylate and tert-butymethacrylate, in particular methyl methacrylate, are preferred. The monomers are also collectively referred to herein as (meth) acrylate monomers.

In principle, acrylic acid and methacrylic acid can also be used as monomers, but these are not readily miscible with oxaphosphaphenantrene oxides such as DOPO and are therefore preferably not used.

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).

In addition, additional comonomers, such as acrylonitrile, can be polymerized in order to further improve the desired properties, including the fire behavior.

Oxaphosphaphenantrene oxides are known per se, including the preferred 9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide (DOPO), and are commercially available. According to the invention, these are reacted with a, w-alkyldiol diacrylate to give oxaphosphaphenantrene oxide acrylate monomers, which are then used as Comonomers can be polymerized into (meth) acrylate polymers. Suitable a, w-alkyldiol diacrylates are those with 2 to 6 carbon atoms in the alkyl chain. An important criterion with regard to the preferred removal of excess a, w-alkyldiol diacrylate by vacuum distillation is the boiling point; the lower it is, the lower the vacuum or temperature required to remove the unreacted a, w- Alkyl diol diacrylate. In this respect, α, w-alkyldiol diacrylates with 2 to 4 carbon atoms in the alkyl chain, including branched ones, are preferred, in particular ethylene glycol diacrylate and n-butylene glycol diacrylate.

The reaction takes place at a molar ratio of oxaphosphaphenantrene oxide to α, w-alkyldiol diacrylate of 1: 1.5 to 1:10, preferably 1: 3 to 1: 7 and in particular of about 1: 5. The choice of the ratio represents a compromise between the effort involved in removing the excess α, w-alkyl diol diacrylate and the selectivity of the reaction. The more α, w-alkyl diol diacrylate is used, the more difficult it is to remove the excess (lower Space-time yield), but the less doubly oxaphosphaphenantrene oxide-functionalized acrylate is formed.

The temperature is generally from 70 to 120.degree. C., preferably from 80 to 100.degree.

Either an aprotic solvent with good dissolving power for the phosphaphenantrene oxide or an excess of α, w-alkyl diol diacrylate is used as the reaction medium. In a preferred embodiment, the reaction is carried out without a solvent. This makes it easier to isolate the oxaphosphaphenanthene oxide acrylate monomer, which lowers costs. A solvent has the advantage that the risk of premature polymerization is reduced, and solvents can also be more easily distilled off. Preferred solvents are toluene, xylenes, ethyl acetate, acetonitrile and tetrahydrofuran, in particular toluene and xylenes (o-xylene, p-xylene, m-xylene and Mixtures thereof), most preferably toluene. Suitable amounts are, for example, volumes of solvent to the sum of the volumes of starting materials and base from 1: 5 to 5: 1, preferably from 1: 2 to 2: 1.

The base used is sterically hindered and non-nucleophilic compounds, for example tertiary alkylamines, typically in amounts of 0.15 to 2.0 mol per mole of oxaphosphaphenantrenoxide, preferably from 0.5 to 1.2 mol per mol, particularly preferably from 0, 9 to 1.1 moles per mole. The molar ratio of amine to DOPO can be reduced to about 0.15: 1; if the amount of amine is reduced still further, the addition becomes much slower and less selective. An excess of base is economically disadvantageous, but has little influence on the reaction. Tertiary alkylamines are particularly suitable as bases, triethylamine being the most suitable in terms of price, boiling point and low toxicity. For example, N-ethyldiisopropylamine and tripropylamine as well as tributylamine can also be used, while trimethylamine is less suitable because of its very low boiling point. Tertiary aromatic amines such as pyridine are also possible, but less preferred. It can be advantageous to add further base after the reaction has taken place for some time.

A polymerization inhibitor is added to prevent premature polymerization of the oxaphosphaphenantrene oxide acrylate and the α, w-alkyl diol diacrylate. For example, hydroquinone, phenothiazine, 1-dodecanethiol, hydroquinone monobenzyl ether, methoxyhydroquinone and other known substances are suitable. Hydroquinone and methoxyhydroquinone are preferred. The necessary quantities are known per se. For example, the amount of stabilizer contained in commercial α, w-alkyl diol diacrylate can be sufficient.

Since oxaphosphaphenantrene oxides can react with water and base with ring opening, the reaction takes place with exclusion of water. Water leads to ring opening and thus to side reactions, i.e. to the formation of the triethylammonium salt of the ring-opened oxaphosphaphenantrene oxide. With The absence of water here means a maximum content of less than 1% by weight of water, preferably less than 0.1% by weight of water and particularly preferably less than 0.05% by weight of water in the liquid phase.

The reaction is preferably carried out under a dry protective gas such as nitrogen. A reaction in air is not recommended for reasons of explosion protection. In addition, triethylamine, for example, is somewhat sensitive to oxidation and the reaction mixture could turn dark in the presence of air. However, small amounts of oxygen are not a problem and can even be advantageous if the most frequently used inhibitor methoxyhydroquinone is used, since this is only active in the presence of traces of oxygen. In this respect, removal of oxygen from the starting materials and other components of the reaction solution is not necessary and is preferably not carried out.

The reaction is carried out until the oxa-phosphaphenantrene oxide has essentially completely reacted, which typically takes from 1 to 10 hours, often from 2 to 5 hours. Here, the oxaphosphaphenanthrene oxide is added either in portions or continuously, e.g. with a solids feeder, for example in the course of 2.5-3 hours. To complete the reaction, the reaction temperature is maintained for a further 45-60 minutes after the addition has ended. The addition in portions or continuously is advisable, since the addition reaction is moderately exothermic. If, in larger batches, all of the oxaphosphaphenanthrene oxide is added at the beginning, too much heat of reaction is released in a short time, so that the temperature could rise too high. In addition, the continuous addition of oxaphosphaphenanthrene oxide, which takes place in portions or over a long period of time, improves the selectivity, and only very little double-oxaphosphaphenanthrene-functionalized diacrylate is formed.

The reaction product used is primarily oxaphosphaphenantrene oxide acrylate, in addition to small amounts of di-oxaphosphaphenantrene oxide acrylate and the excess a, w-alkyldiol diacrylate obtained. Substantially complete conversion means that a maximum of 5 mol%, preferably a maximum of 2 mol% of the oxaphosphaphenantrene oxide have not been converted. The time to essentially complete conversion can be determined, for example, by means of ³¹ P-NMR. After the time for specific conditions has been determined, no further controls are necessary. The reaction should be essentially complete, since residues of unconverted oxaphosphaphenantrene oxide are undesirable, but too long a reaction time does not bring any advantages.

When the reaction has taken place, the excess α, w-alkyldiol diacrylate and, if appropriate, the solvent are removed, preferably by means of vacuum distillation. Alternatively, the excess α, w-alkyl diol diacrylate and, if necessary, the solvent can also be removed by liquid-liquid extraction. When removing by vacuum distillation, the necessary temperature depends on the available vacuum and the necessary residence time at the high temperature. A thin-film evaporator is best suited because it only warms up for a very short time, which minimizes the risk of spontaneous polymerization. Here 75 - 140 ° C are useful. If the vacuum distillation is to be used for a longer period of time, 120 ° C should not be exceeded. To remove the excess α, w-alkyldiol diacrylate, a pressure of 0.01 to 0.2 mbar, preferably 0.02 to 0.2 mbar, is used. In one embodiment, a liquid-liquid extraction with a hydrocarbon solvent such as cyclohexane is carried out to separate the reaction product from the excess α, w-alkyldiol diacrylate. Other alkanes such as n-hexane, heptane, etc. can also be used, as can mixtures of alkanes, but cyclohexane was the most efficient of all the solvents tested. For this purpose, the solution of the reaction product is mixed intensively with the hydrocarbon solvent, if appropriate before or after the distillation, if appropriate after the addition of solvent, and the hydrocarbon solvent phase which is separated off is drawn off. This can be repeated a few times, e.g. 2, 3, 4 or 5 times. The vacuum distillation can be done before and / or take place after the separation of the α, w-alkyldiol diacrylate by extraction.

According to the invention, oxaphosphaphenantrene oxide acrylate monomer is obtained with a maximum of 3 mol% of diacrylate, in particular with a maximum of 0.5 mol% of diacrylate.

For the production of (meth) acrylate polymers according to the invention, the resulting oxaphosphaphenantrene oxide acrylate monomer can be polymerized in a manner known per se, e.g. by means of free-radical emulsion, suspension or bulk polymerization, with (meth) acrylate monomers and, if necessary, further comonomers. Usually, the monomers are mixed and a radical starter such as azobis (isobutyronitrile) (AIBN for short) or benzoyl peroxide is added. Usable proportions of oxaphosphaphenantrene oxide acrylate monomer depend on the desired or necessary flame retardancy and are normally in the range from 10 to 30 mol%, preferably from 20 to 25 mol%, of oxaphosphaphenantrene oxide acrylate monomer, based on the mixture of all monomers.

To limit the molar mass, additives known per se, such as thiols, can be added during the polymerization. The quantities that can be used are usually very small and are known in the prior art.

The (meth) acrylate polymers according to the invention can contain further additives in a manner known per se, for example, but not exclusively, one or more flame retardants, surface-active agents, nucleating agents, coupling agents, fillers, plasticizers, impact enhancers, lubricants, antibacterial agents, release agents, heat stabilizers, antioxidants , Light stabilizers, compatibilizers, inorganic additives, antistatic agents, pigments, dyes, etc. and combinations thereof. The additives can be added independently during the polymerization and / or during a pellet forming process (extrusion) to be included in the copolymer. The method for this and the amount added are known per se and are not particularly restricted. Typical contents of additive are in each case 0.001 to 10% by weight of additive based on the total mixture, but in the case of fillers up to 50% by weight and more. In a particularly preferred embodiment, in order to further improve the flame retardancy properties of the (meth) acrylate polymer prepared according to the invention, the solid phase also contains copolymerized phosphorus compounds with flame retardancy. These support the effect of the oxaphosphaphenantrenoxide acrylate comonomer, which is active in the gas phase. Particularly suitable are phosphorus-containing monomers based on alkyl (meth) acrylate and flydroxyalkyl (meth) acrylate, preferably based on flydroxyethyl (meth) acrylate, in particular the following:

These comonomers are commercially available or can be prepared in a manner known per se. For example, the first connection can be by means of

Reaction of diethyl chlorophosphate with hydroxyethyl acrylate can be synthesized in the presence of an auxiliary base, see, for example, Nair, CP Reghunadhan; Clouet, G .; European Polymer Journal (1989), 25 (3), 251. The second connection is possible by reacting diethyl chlorophosphate with hydroxyethyl methacrylate in the presence of the auxiliary base such as triethylamine and copper (I) chloride as a catalyst, see CPR Nair, G Clouet, J Brossas; Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 26, 1791-1807 (1988). The fourth compound is made by reacting diphenyl chlorophosphate (CAS No. 2524-64-3) with hydroxyethyl methacrylate prepared in the presence of an auxiliary base, see e.g. US 2019/0112457 A1. The fifth and sixth compounds are, for example, by reacting phosphorus oxychloride with neopentyl glycol to give 2-oxo-2-chloro-5,5-di-Me-1, 3,2-dioxa-phosphorinane and reacting the latter with hydroxyethyl acrylate or hydroxyethyl methacrylate available, see Xing, Weiyi; Song, lei; Lv, pin; Jie, Ganxin; Wang, Xin; Lv, Xiaoqi; Hu, Yuan; Materials Chemistry and Physics 123 (2010) 481-486 and CN 104497051 A. The seventh compound is accessible analogously to the process according to the invention.

The amounts of solid-phase active phosphorus-containing (meth) acrylate monomer depend on the flame retardant effect required and are, for example, in the range from 5 to 30 mol%, preferably from 10 to 25 mol%, of phosphorus-containing (meth) acrylate monomer, based on the mixture of all Monomers.

The combination of oxaphosphaphenatrene oxide acrylate monomer and a monomer with a flame retardant active phosphorus compound in the solid phase allows the amount of the two comonomers to be reduced so that a total of 10 to 20 mol% is contained. For example, 3, 4, or 5 to 10 mol% of the oxaphosphaphenate renoxide acrylate monomer according to the invention are sufficient. The amount of solid-phase active phosphorus-containing (meth) acrylate monomer can be reduced to from 3 to 20 mol%, preferably from 5 to 15 mol%.

The fire behavior is tested according to UL94 "Tests for Flammability of Plastic Materials for Parts in Devices and Appliances" according to IEC / DIN EN 60695-11-10 and -20 of the Underwriters Laboratories . The tests are carried out with an open flame (Bunsen burner). The ignition source has a power of 50 watts (20 mm high flame) and acts twice for 10 s on the test specimen during the V test and is then removed again. The burning time and the falling off of burning parts are evaluated with the aid of a cotton swab, which is located under the test specimen. There are 5 trial body (127 mm (5 in) long and 12.7 mm (0.5 in) wide, thickness application related). A classification occurs when the following requirements are met:

V2: Total burning time of the 10 flame applications max. 250 s, self-extinguishing up to 30 seconds at the latest, burning droplets are permitted V1: Total burning time of the 10 flame exposures max. 250 s, self-extinguishing up to 30 seconds at the latest, burning drops are not permitted, afterglow maximum 60 seconds

V0: Total burning time of the 10 flame applications max. 50 s, self-extinguishing up to 10 seconds at the latest, burning droplets are not permitted, afterglow max. 30 seconds.

The flame-retardant, transparent, thermoplastic (meth) acrylate polymers according to the invention generally achieve ratings of V1, frequently V0.

This makes them particularly 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, facade panels, etc. Such decorative films include, for example, a colored and / or printed base film, e.g. made of PVC or ( Meth) acrylate polymer. The base film can be provided with a primer and / or adhesive on the underside, depending on the material of the base film and the material to be laminated with. A protective film made of one or more layers of copolymer according to the invention is attached on the upper side to protect the base film and, if necessary, the print from UV radiation. Alternatively, the decorative film can also be made from a copolymer according to the invention, if necessary from several layers thereof. Polyvinylidene fluoride (PVDF) can be admixed as a non-flammable component in one or more layers of the copolymer according to the invention. Often a cover film or coating is provided as the outer layer made of particularly scratch-resistant and durable plastic such as polytetrafluoroethylene (PTFE), PVDF, etc., which usually also provides protection Pollution provides. Such decorative films can be partially or fully coextruded; non-coextruded layers are thermally laminated. The surface can be embossed, for example if a wood look is desired. Suitable thicknesses of the decorative film are, for example, from 100 to 300 μm, preferably from 130 or 150 to 200 μm. The protective layer made of copolymer according to the invention makes up 30 to 40% of the thickness and the cover layer, if present, makes up 3 to 4% of the thickness. The term "made of a polymer" means that the said polymer is the main polymer component of the layer. The presence of one or more other polymers is not excluded, but their amount is generally (in each case) less than 50% by weight, mostly less than 30% by weight and often less than 10% by weight, based on all Polymer components.

The flame-retardant, transparent, thermoplastic (meth) acrylate polymers according to the invention are also suitable for producing transparent and colored sheets. These panels can be used in many ways, e.g. in interior construction.

The invention is to be explained with the aid of the following examples, without, however, being restricted to the specifically described embodiments. Unless otherwise stated or the context necessarily indicates otherwise, percentages relate to the weight, in case of doubt to the total weight of the mixture.

The invention also relates to all combinations of preferred configurations, insofar as these are not mutually exclusive. The information "about" or "approx." in connection with a figure means that at least 10% higher or lower values or 5% higher or lower values and in any case 1% higher or lower values are included.

Examples

The oxaphosphaphenantrene oxide acrylate monomers were prepared in Three-necked flasks of various contents, which were equipped with a stirrer, a Claisen attachment with reflux condenser and a nitrogen supply. The temperature was controlled via an oil bath. Before each reaction, the apparatus was dried in vacuo with heating and filled with nitrogen. For the reaction, the α, w-alkyl diol diacrylate with the solvent (toluene) and the base (triethylamine) were introduced into the flask in a countercurrent of nitrogen. Then 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was added in portions over several hours. The α, w-alkyldiol diacrylates used contained methoxyhydroquinone (4-methoxyphenol) as a polymerization inhibitor. In order to keep this active during the reaction, around 20 ml of air were injected at intervals of around 20 minutes. The course of the reaction was followed by taking samples and determining ³¹ P-NMR spectra.

example 1

1,4-Butanediol diacrylate was reacted with DOPO in a molar ratio of 3.5: 1. For this purpose, 0.6 mol (118.93 g) were added to the 500 ml three-necked flask filled with nitrogen.

1,4-butanediol diacrylate and 14.05 g of DOPO were added. 80 ml of toluene and 0.17 mol (approx. 23.56 ml) of triethylamine were then added. The mixture was then heated to just below its boiling point with stirring and under a nitrogen atmosphere (approx. 96 ° C., oil bath temperature approx. 107 ° C.). Two further DOPO portions were added at 60 minute intervals (11.89 g, 10.81 g, a total of 36.75 g, 0.17 mol). The mixture was stirred for a further 60 minutes at the same internal temperature (approx. 96 ° C.). An NMR sample was then taken; the NMR indicated complete conversion.

Toluene and triethylamine were distilled off on a rotary evaporator in vacuo. Vacuum distillation was carried out on the residue. At an oil bath temperature of 90 ° C and a vacuum of 0.063 mbar, distillation was carried out until no more diacrylate condensed in the receiver. The temperature was then increased to 125 ° C. over several steps (vacuum 0.042 mbar). for Another vacuum distillation, the oil bath temperature was slowly increased to 150 ° C (vacuum 0.044 mbar). The distillation was stopped because the reaction product began to polymerize.

The reaction product obtained (49.91 g) of the formula: was then copolymerized with methyl methacrylate in an approximate molar ratio of 1: 2.7. For this purpose, the reaction product was dissolved in 200 ml of toluene and transferred to a three-necked flask. About 33.3 g of destabilized methyl methacrylate were then added and the solution was heated to 97 ° C. under nitrogen. Since the solution must not contain oxygen during the copolymerization because of the 4-methoxyphenol inhibitor, the mixture was stirred for 1.5 hours at the same temperature under nitrogen. Then, with vigorous stirring, 1 ml of a 0.2 M AIBN solution in toluene was added dropwise over the course of 2 minutes, and the temperature of the oil bath was increased to 117.degree. After 10 minutes, another 1 ml of AIBN solution was added. The reaction solution began to boil strongly. After 25 minutes the solution became more viscous and after 30 minutes a voluminous, gel-like substance separated from the solution. The copolymerization was then continued for 1 hour.

The polymer product obtained was dried in a vacuum drying cabinet at 100 ° C. for 24 hours. After drying, the product was slightly rubbery and could not be ground into small pieces. It became a thermogravimetric one Analysis (TGA) carried out. The sample was heated from 35 ° C to 800 ° C in a nitrogen stream at a heating rate of 10 K / min. The analysis showed a decomposition temperature of 318 ° C. with a weight loss of 5%. A test specimen was produced with the polymer product in a laboratory press at a pressure of 25 bar within 4 minutes. At a temperature of 190 ° C it remained very elastic and rubbery. At a temperature of 225 ° C. or more, the test specimen became solid and brittle, which indicates post-crosslinking, ie not yet complete polymerization.

The test specimen obtained at 225 ° C. was examined in a UL94 chamber. In the flame test, the pressed test specimen showed a significantly slower burning behavior compared to pure PMMA, but did not achieve a V1 classification because it was not self-extinguishing.

Example 2

The procedure was as in Example 1, with the difference that the reaction product was extracted several times with n-hexane after the vacuum distillation (oil bath temperature 140 ° C., vacuum 0.031 mbar). First 3 times with 50 ml of n-hexane each time, then after adding 20 ml of toluene 4 times with 40 ml of n-hexane each time and after adding a further 20 ml of toluene again 4 times with 40 ml of n-hexane each time. The solvents were then removed on a rotary evaporator.

For the copolymerization, the reaction product (52.82 g) was dissolved in 200 ml of toluene and transferred to a three-necked flask. Then about 35 g of destabilized methyl methacrylate were added, the solution was heated to 97 ° C. under a nitrogen atmosphere and stirred for 2 hours at the same temperature. Then, with vigorous stirring, 1 ml of the 0.2 M AIBN solution was added dropwise over the course of 2 minutes and the temperature of the oil bath was increased to 117.degree. After 14 minutes, another 1 ml of AIBN was added. The solution began to boil heavily. After 27 minutes the solution became more and more viscous A voluminous gel-like substance separated from the solution for 34 minutes. The reaction was continued for an additional hour.

The polymer product obtained was dried in a vacuum drying cabinet at 100 ° C. for 24 hours. After drying, the product remained slightly rubbery and could not be ground into small pieces with a mortar. The TGA analysis showed a similar decomposition temperature as in Example 1, 312 ° C. with a mass loss of 5%. Test specimens were produced with the product in a laboratory press at a pressure of 25 bar within 4 minutes. At 190 ° C the test specimen remained very elastic and rubbery. At a temperature of 225 ° C. or more, the test specimen became solid and brittle. The test specimen showed good transparency. During the investigation in the UL94 chamber, the test specimen, pressed briefly at 225 ° C, went out immediately after the first flame exposure of 10 seconds and after the second it burned only about 4 seconds, i.e. it achieved a classification V0.

Comparative example CE1

The procedure was analogous to Example 1, but with the difference that butylene glycol dimethacrylate and DOPO were converted in a molar ratio of 1: 1. 0.2 mol (45.25 g) of butylene glycol dimethacrylate and 9.24 g of DOPO were placed in the 500 ml three-necked flask filled with nitrogen. Then 100 ml of toluene and 0.12 mol (approx. 16.6 ml) of triethylamine were added. The mixture was then heated to just below its boiling point (approx. 96 ° C., oil bath temperature approx. 107 ° C.) with stirring and under a nitrogen atmosphere. 6 more DOPO portions were added every 30 minutes (8.54 g, 6.99 g, 6.50 g, 4.9 g, 4.00 g, 3.00 g, a total of 43.24 g, 0.2 mol). The mixture was stirred for a further 30 minutes at the same internal temperature (approx. 96 ° C.). An NMR sample was then taken. The reaction was not yet complete and under the same conditions (approx. 96 ° C internal temperature)

The mixture was stirred for a further 3 hours and then an NMR sample was taken. Since the The reaction was still not complete, a further 5 ml of triethylamine were added and the mixture was stirred for a further hour under unchanged conditions. Another NMR sample was taken. DOPO was now completely implemented.

For the copolymerization, the oxaphosphaphenantrene oxide acrylate monomer was initially stirred at an internal temperature of about 97 ° C. for 30 minutes. Then 0.4 mol (40.07 g) of destabilized methyl methacrylate were added in a countercurrent of nitrogen. Since the solution must not contain oxygen during the copolymerization because of the 4-methoxyphenol, the mixture was stirred for a further 1.5 hours at the same temperature. Then, with vigorous stirring, 2 ml of the 0.2 molar AIBN solution in toluene were added dropwise over the course of 2 minutes. The solution began to boil strongly and a voluminous gel-like substance separated from the solution after a reaction time of a few minutes. The temperature of the oil bath was raised to 117 ° C and the reaction was continued for 1 hour.

The polymer product obtained was dried in a vacuum drying cabinet at 100 ° C. for 24 hours and then finely ground. A white powder resulted. Thereafter, a thermogravimetric analysis (TGA) was carried out. The analysis showed a decomposition temperature of 255 ° C with a weight loss of 5%.

An attempt was made to produce test specimens with the powder in a laboratory press at temperatures of up to 260 ° C. and pressures of up to 25 bar. However, the powder could not be melted and no test specimen could be created.

A solubility test showed that the polymer obtained could not be dissolved in organic solvents. This shows that no thermoplastic was obtained.

Comparative example CE2

Compared to comparative example CE1, the amount of DOPO was increased slightly (45.40 g, 0.21 mol) to reduce the number of unreacted dimethacrylates. In addition, the amount of base and the time between the DOPO additions were increased to 60 minutes in order to ensure a faster conversion of the DOPO. 0.2 mol (45.25 g) of buthylene glycol dimethacrylate and 9.5 g of DOPO were placed in the 500 ml three-necked flask filled with nitrogen. 100 ml of toluene and 0.21 mol (approx. 29.11 ml) of triethylamine were then added. The mixture was then heated to just below its boiling point (approx. 96 ° C, oil bath temperature approx. 107 ° C) with stirring and a nitrogen atmosphere. 6 more DOPO portions were added at intervals of 60 minutes (8.5 g, 7.5 g, 6.5 g, 5.5 g, 4.5 g, 3.4 g, a total of 45.40 g, 0.21 mol). The mixture was stirred for a further 60 minutes at the same internal temperature (approx. 96 ° C.). An NMR sample was then taken. The reaction was not yet complete. For this reason, the mixture was stirred again for 2.5 hours under unchanged conditions (approx. 96 ° C. internal temperature) and a further NMR spectrum was recorded. After 3 hours, DOPO was ^{completely consumed according to 31} P-NMR.

After removing 4-methoxyphenol, the reaction product was copolymerized as in Comparative Example 1 with methyl methacrylate in a molar ratio of 1: 2. The polymer product obtained was dried in a vacuum drying cabinet at 100 ° C. for 24 hours and then finely ground with a ceramic mortar and pestle. The TGA analysis showed a decomposition temperature of 275 ° C with a weight loss of 5%. However, as in Comparative Example VB1, no test specimen could be produced with the product.

Comparative example CE3

Analogously to Example 1, ethylene glycol dimethacrylate was reacted with DOPO in a molar ratio of 1.76: 1. 0.25 mol (49.60 g) of ethylene glycol dimethacrylate and 8.65 g of DOPO were placed in the 500 ml three-necked flask filled with nitrogen. Then 70 ml of toluene and 0.10 mol (about 13.7 ml) of triethylamine were added added. The mixture was then heated to just below its boiling point (approx. 96 ° C., oil bath temperature approx. 107 ° C.) while stirring and under a nitrogen atmosphere. 4 more DOPO portions were added at 45 minute intervals (7.57 g, 6.49 g, 5.41 g, 4.32 g, a total of 32.44 g, 0.15 mol). The mixture was stirred for a further 60 minutes at the same internal temperature (approx. 96 ° C.). A ³¹ P-NMR sample showed traces of unconverted DOPO 1 hour after the last addition of DOPO. The reaction mixture was stored overnight and a further NMR sample showed an essentially complete conversion of the DOPO.

To separate off the excess ethylene glycol dimethacrylate, 31 ml of n-hexane were added. In order to achieve better phase separation, the flask was stored in the freezer for 12 hours. The two phases were separated in a separating funnel. Then another 100 ml of n-hexane were added and the phases were again separated in a separating funnel.

The reaction product was then copolymerized with 36 g of methyl methacrylate (molar ratio 1: 2). For this purpose, the reaction product and 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 the solution must not contain oxygen, the mixture was stirred for 1.5 hours at the same temperature. Then, with vigorous stirring, 3 ml of the 0.2 M AIBN solution were added dropwise over the course of 5 minutes. The solution began to boil heavily. After 10 minutes the temperature of the oil bath was increased to 117 ° C. After 10 minutes, a bulky gel-like substance precipitated out of the solution and the reaction was continued for an additional hour.

The polymer product obtained was dried in a vacuum drying cabinet at 150 ° C. for 24 hours and then finely ground. A yellowish white powder resulted. The drying temperature was possibly too high and the product had partially decomposed. The TGA analysis showed a decomposition temperature of 258 ° C with a mass loss of 5%. A test specimen was created with the powder in the laboratory press. This was yellowish, slightly transparent and very brittle, it could not be removed from the mold without breaking. The degree of networking was still too great.

The pieces obtained were examined in a UL94 chamber. In the flame test, the pressed test specimen showed a greatly slowed down burning behavior compared to pure PMMA, but not the desired self-extinguishing after exposure to the flame.

Comparative example CE4

Compared to Comparative Example 3, the excess ethylene glycol dimethacrylate was increased to 2.5: 1. 0.75 mol (148.6 g) of ethylene glycol dimethacrylate and 26 g of DOPO were placed in the 1 l three-necked flask filled with nitrogen. 140 ml of toluene and 0.5 mol (approx. 68 ml) of triethylamine were then added. The mixture was then heated to just below its boiling point (approx. 96 ° C., oil bath temperature approx. 107 ° C.) with stirring and under a nitrogen atmosphere. Two further DOPO portions were added at intervals of 60 minutes each (21.6 g, 17.3 g, a total of 64.88 g, 0.3 mol). The mixture was stirred for a further 60 minutes at the same internal temperature (approx. 96 ° C.). An NMR sample was then taken, which indicated complete conversion of DOPO.

Triethylamine and toluene were distilled off in vacuo on a rotary evaporator. Next, it was extracted 3 times with 100 ml of n-hexane. A vacuum distillation was then carried out until no more dimethacrylate condensed in the receiver at an oil bath temperature of 85 ° C., a head temperature of 50 ° C. and a vacuum of 0.05 mbar. The vacuum distillation was repeated twice at an elevated temperature, 95 ° and 105 ° C. oil bath temperature, respectively. However, some of the product solution polymerized spontaneously. The ¹ H-NMR showed that dimethacrylates were still contained in the reaction product.

The reaction product (119 g) was dissolved in 450 ml of toluene and transferred to the three-necked flask. About 36 g of destabilized methyl methacrylate were then added and the solution was heated to 97 ° C. under a nitrogen atmosphere. It was stirred for 1.5 hours at the same temperature. Then, with vigorous stirring, 2 ml of the 0.2 M AIBN solution were added dropwise over the course of 4 minutes, and the temperature of the oil bath was increased to 117.degree. After 10 minutes, another 1 ml of AIBN was added. The solution began to boil heavily. After 15 minutes the solution became more viscous. White flakes could be seen. After 17 minutes, a bulky gel-like substance precipitated from the solution and the reaction was continued for an additional hour.

The polymer product obtained was dried in a vacuum drying cabinet at 100 ° C. for 24 hours and then finely ground with a ceramic mortar and pestle. The TGA analysis showed a decomposition temperature of 241 ° C. with a weight loss of 5%. A test specimen was created with the powder in the laboratory press. This was more transparent than in the comparative examples CE1, CE2 and CE3, but still very brittle. It could not be removed from the mold without breaking.

The pieces obtained were examined in a UL94 chamber; the pressed test specimen did not show any improved fire behavior compared to VB3.

Comparative example CE5

The excess ethylene glycol dimethacrylate was increased even further to a molar ratio of 3.5: 1. 0.7 mol (138.8 g) of ethylene glycol dimethacrylate and 17.3 g of DOPO were placed in the 1 l three-necked flask filled with nitrogen. 100 ml of toluene and 0.4 mol (approx. 55.5 ml) of triethylamine were then added. The mixture was then stirred under a nitrogen atmosphere until heated to just below their boiling point (approx. 96 ° C, oil bath temperature approx. 107 ° C). Two further DOPO portions were added at intervals of 60 minutes each (15.3 g, 10.8 g, a total of 43.24 g, 0.2 mol). The mixture was stirred for a further 60 minutes at the same internal temperature (approx. 96 ° C.). An NMR sample was then taken which showed complete conversion of DOPO.

Triethylamine and toluene were distilled off in vacuo on a rotary evaporator and vacuum distillation (oil bath temperature 80 ° C., vacuum 0.04 mbar) was carried out with the residue. During the vacuum distillation, when the oil bath temperature was increased to 110 ° C., spontaneous polymerization of the product took place and it was no longer possible to stir.

The examples and comparative examples show that a usable acrylate comonomer is obtained neither with approximately equimolar amounts of starting material nor with an excess of oxaphosphaphenantrene oxide. Only if a sufficient excess of diacrylate is used, as provided according to the invention, can a diacrylate which has only simply reacted with oxaphospaphenantrene oxide be obtained.

The excess of α, w-alkyl diol diacrylate could be separated off with sufficient ease. In the case of the a, w-alkyldiol dimethacrylate, however, this does not succeed. In particular, comparative examples 1 and 2 show that with a direct copolymerization of oxaphosphaphenantrene oxide acrylate monomers with further (meth) acrylate monomers, as proposed in WO 2019/141572 A1 and JP 2016-060865 A, no thermoplastic (meth) acrylate polymers can be obtained. In addition to the selection of α, w-alkyl diol diacrylate and an excess thereof, the separation of the unreacted α, w-alkyl diol diacrylate provided according to the invention is also necessary in order to obtain thermoplastic (meth) acrylate polymers. The following table 1 gives an overview of the examples and comparative examples. Table 1

Example 6_

Analogously to Example 2, a DOPO acrylate monomer was produced from DOPO and 1,4-butanediol diacrylate, but with a molar ratio of butanediol diacrylate to DOPO of 7: 1. For this purpose, 1.25 mol (297.3 g) of distilled butanediol diacrylate, 13.6 g of DOPO and 30 mg of 4-methoxyphenol were placed in a 250 ml three-necked flask filled with nitrogen. 35 ml of triethylamine were then added via a syringe through the septum, and the mixture was heated to 85-87 ° C. over the course of 20 minutes (oil bath temperature) with stirring and under a nitrogen atmosphere. Then a further 9.0 g of DOPO was added. After a further 20 minutes a third portion of DOPO was added (9.0 g). Three further portions (7.5 g each) were added at intervals of 20 minutes each. The reaction mixture was stirred for a further 30 minutes at the same temperature. Then the heating was turned off. During the Phospha-Michael addition, 20 ml of air were injected at intervals of about 15 minutes each in order to keep the inhibitor active.

To isolate the DOPO monomer, the product solution obtained was divided into two parts. The product was isolated for both parts by first distilling off the triethylamine, a partial vacuum being applied at the beginning and the oil bath being heated to a maximum of 50 ° C. The main part of the excess butanediol diacrylate was then distilled (approx. 0.02 mbar), heating up to 105 ° C. in order to avoid spontaneous polymerization. 250 ml of cyclohexane were added to the distillation residue and the mixture was then rapidly heated to the boil. After about 5 minutes of intensive stirring under reflux, the oil bath was removed. The contents of the flask were then cooled to approx. 40 ° C. in a water bath, then cooled in the refrigerator, whereupon the slightly milky, cloudy phase above was decanted. A further nine extractions were carried out in an analogous manner (cyclohexane was recovered in each case). The extraction residue was then heated to 105 ° C. over a period of 45 minutes, the pressure being reduced to about 0.02 mbar. These conditions were maintained for about 20 minutes. After cooling, the DOPO mono- mer as a slightly cloudy, viscous and colorless oil. ^{The 1} H-NMR spectrum, recorded in deutero-chloroform, of the DOPO monomer obtained in this way showed good purity. In particular, it showed the successful removal of the excess 1,4-butanediol diacrylate (<1% by weight of diacrylate; the proportion of doubly DOPO-functionalized product was about 6% by weight).

52.82 g of the DOPO monomer were dissolved in 200 ml of toluene for the copolymerization with methyl methacrylate and transferred to a three-necked flask. About 35 g of destabilized methyl methacrylate were then added, the solution was heated to 97 ° C. under a nitrogen atmosphere and stirred for 2 hours at the same temperature. Then, with vigorous stirring, 1 ml of a 0.2 M AIBN solution was added dropwise over the course of 2 minutes, and the temperature of the oil bath was increased to 117.degree. After 14 minutes, another 1 ml of AIBN was added. The solution began to boil heavily. After 27 minutes the solution became more viscous and after 34 minutes a voluminous gel-like substance separated from the solution. The reaction was continued for an additional hour.

The polymer product obtained was dried in a vacuum drying cabinet at 100 ° C. for 24 hours. After drying, the product remained slightly rubbery and could not be ground into small pieces with a mortar. The TGA analysis showed a similar decomposition temperature as in Examples 1 and 2, 312 ° C. with a mass loss of 5%. Test specimens were produced with the product in a laboratory press at a pressure of 25 bar within 4 minutes. At 190 ° C the test specimen remained very elastic and rubbery. At a temperature of 225 ° C. or more, the test specimen became solid and brittle. The test specimen showed good transparency. During the investigation in the UL94 chamber, the test specimen pressed briefly at 225 ° C. went out immediately after the first exposure of 10 seconds and after the second it only burned for about 4 seconds, ie it achieved a classification V0. The results of the fire behavior test are listed in Table 2. Example 7

The DOPO monomer of Example 6 was used in various amounts

Methyl methacrylate and DDPO-HEMA, A = converted to a methyl acrylate polymer both with and without the addition of a further monomer, such as methyl acrylate or n-butyl methacrylate. A suspension polymerization took place in water with 1-decylthiol as regulator and dibenzoyl peroxide (BPO) as initiator. The liquid monomers were destabilized before the polymerization; DDPO-HEMA (A) was recrystallized from fe / f-butyl methyl ether (melting point 50.5 ° C.). The syntheses of the methacrylate polymers were carried out in a reaction apparatus which consisted of a 250 ml three-necked flask, magnetic stirrer, heating bath, a dropping funnel and a reflux condenser to which a three-way stopcock with a bubble counter was attached. Both the dropping funnel and the three-way stopcock on the reflux condenser were connected with a Schlenk line.

From the methacrylate polymers obtained, compact, transparent test bars and transparent films of different thicknesses were produced using an oil hydraulic laboratory press of the type HB 20300 (Schmidt Maschinentechnik; Bretten-Bauerbach, Germany). The test bars had the following dimensions: 70 mm x 10 mm x 0.8 mm. When pressing, temperatures of 210-245 ° C were used (depending on the melting behavior of the methacrylate polymers). The quantities and results of the fire behavior test are listed in Table 2.

Example 7a

For the copolymerization, a mixture of 1.35 g of DDPO-HEMA (A), 1.35 g of DOPO monomer, 7.3 g of methyl methacrylate, 34 mg was placed in the dropping funnel Given 1-decyl mercaptan and 67 mg of hydrous BPO. Vacuum was then applied twice briefly and nitrogen was allowed to flow in again in each case. To remove the oxygen, the mixture of water and 1.3 ml of a 2% solution of the suspension stabilizer Kuraray Poval 25-88 (partially hydrolyzed polyvinyl alcohol) was stirred for 30 minutes at 85-90 ° C., with a moderate stream of nitrogen flowing through it the three-way stopcock was fed into the apparatus and to the bubble counter. After the aqueous solution had been cooled to approx. 62 ° C., the solution was added from the dropping funnel. The contents of the flask were then heated to 73 ° C. over the course of 20 minutes while stirring. A milky emulsion resulted. The connection to the bubble counter was shut off 10 minutes after the addition of the monomer. Now, at intervals of approx.

The temperature was increased by 1 ° C. for 15 minutes until a temperature of 82 ° C. was reached. It was stirred vigorously for four hours. A solution of 65 mg of BPO and 500 mg of methyl methacrylate was then added and the temperature was increased to 87.degree. At this temperature, the reaction mixture was stirred for 12 hours under a nitrogen atmosphere. The result was globules and also somewhat compact material. The supernatant aqueous solution was decanted, then water was added and suction filtered through a paper filter. The methacrylate polymer was dried for 5 hours at 80 ° C. and for one hour at 100 ° C. in a vacuum (approx. 0.02 mbar). ^{The 31} P-NMR spectrum of this polymer recorded in deutero-chloroform only contained the signals of the DOPO unit (approx. 36 ppm) and the DDPO unit (-8.2 ppm). The ratio of the signal integrals almost corresponded to the expected value of 1.00: 1.50. Approx. 9 g of the methacrylate polymer were obtained.

Example 7b

For the copolymerization, 65 ml of deionized water and 1.3 ml of a 2% by weight aqueous solution of Kuraray Poval 25-88 KL (suspension stabilizer, partially hydrolyzed polyvinyl alcohol) were placed in the three-necked flask. One of 1.7 g of DDPO-HEMA (A), 1.5 g of des 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) were added. The dropping funnel was partially evacuated twice and refilled with nitrogen in order to remove the atmospheric oxygen from the reagent mixture. The reaction flask containing the aqueous solution was also partially evacuated twice and each time refilled with nitrogen. The contents of the flask were then heated to 95 ° C. with stirring, a moderate stream of nitrogen being passed through the three-way stopcock into the apparatus and to the bubble counter. After stirring for 30 minutes, the temperature was lowered to about 65 ° C. The contents of the dropping funnel were added to the aqueous solution thus deoxygenated. The contents of the flask were then heated to 73 ° C. in a gentle stream of nitrogen with stirring over a period of about 20 minutes. The temperature was increased to 83 ° C over the course of two hours. A moderate stream of nitrogen continued to be passed to the bubble counter. After a further hour, a solution of approx. 35 mg of hydrous BPO in 0.37 g of methyl methacrylate was added through the dropping funnel. The temperature of the heating bath was then increased to 87 ° C. After a further 30 minutes, the connection to the bubble counter was interrupted. Stirring at 87 ° C. was continued for 12 hours. Then the aqueous phase was decanted. A methacrylate polymer was obtained as compact pieces and sheet-like material. This polymer was soluble in chloroform and dimethyl sulfoxide. In order to remove monomer residues and water, the polymer was heated in vacuo (approx. 0.02 mbar) first to 90 ° C. for 3 hours and then to 105 ° C. for 45 minutes. In the ³¹ P-NMR spectrum of the methacrylate polymer thus obtained, the signals of the DOPO unit and the DDPO unit were present at approx. 36 ppm and approx. -8 ppm, the integral ratio approximately corresponding to the expected value.

Example 7c

For the copolymerization, 55 ml of deionized water and 1.5 ml of a 2% by weight aqueous solution from Kuraray Poval were placed in the three-necked flask 25-88 KL (suspension stabilizer, partially hydrolyzed polyvinyl alcohol). A solution of 1.9 g of DDPO-HEMA, 1.7 g of the 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 (corresponding to 67 mg of pure BPO ) added to the dropping funnel. The dropping funnel was partially evacuated twice and refilled with nitrogen in order to remove the atmospheric oxygen from the reagent mixture. The reaction flask containing the aqueous solution was also partially evacuated twice and each time refilled with nitrogen. The contents of the flask were then heated to 95 ° C. with stirring, a moderate stream of nitrogen being passed through the three-way stopcock into the apparatus and to the bubble counter. After stirring for 30 minutes, the temperature was lowered to about 65.degree. The contents of the dropping funnel were added to the aqueous solution thus freed from oxygen. The temperature of the oil bath was then increased to 75 ° C. with vigorous stirring of the reaction mixture, a milky-white suspension being formed. Stirring was continued for 3.5 hours, gradually increasing the temperature of the heating bath up 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 in a countercurrent of nitrogen through the dropping funnel. The temperature of the heating bath was then increased to 87 ° C. After a further hour, the connection to the bubble counter was interrupted and the cooling water was switched off. The reaction mixture was stirred under these conditions for a further 12 hours. Then the aqueous solution of the methacrylate polymer, which had formed partly as a bead and partly as a compact or sheet-like material, was decanted. The methacrylate polymer was washed three times with water and dried on filter paper. ^{The 1} H-NMR spectrum of the polymer recorded in deutero-chloroform showed that it contained unreacted monomers. The polymer was therefore heated in a fine vacuum (approx. 0.02 mbar) first to approx. 87 ° C. (4 h) and then to 93 ° C. (1 h). Thereafter, the ¹ H-NMR spectrum of the methacrylate polymer showed the almost complete disappearance of the acrylate / methacrylate groups. In the ³¹ P-NMR spectrum, the signals of the DOPO unit and the DDPO unit present at approx. 36 ppm or approx. -8 ppm, with the integral ratio roughly corresponding to the expected value of 1.00: 1.66

Example 7d

For the copolymerization, 60 ml of deionized water and 2.0 ml of a 2% by weight aqueous solution of Kuraray Poval 25-88 KL (suspension stabilizer, partially hydrolyzed polyvinyl alcohol) were placed in the three-necked flask. A solution of 2.22 g of DDPO-HEMA, 1.8 g of the 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 (corresponding to 81 mg of pure BPO ) added to the dropping funnel. The dropping funnel was partially evacuated twice and refilled with nitrogen in order to remove the atmospheric oxygen from the reagent mixture. The reaction flask containing the aqueous solution was also partially evacuated twice and each time refilled with nitrogen. The contents of the flask were then heated to 95 ° C. with stirring, a moderate stream of nitrogen being passed through the three-way stopcock into the apparatus and to the bubble counter. After stirring for 60 minutes, the temperature was lowered to about 63 ° C. The contents of the dropping funnel were added to the aqueous solution thus freed from oxygen. 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 30 minutes later increased to 80 ° C. This temperature was maintained for 50 minutes. Then the target temperature was increased to 85 ° C. A milky emulsion had formed. The mixture was stirred very vigorously for three hours and a stream of nitrogen was continued to be passed into the apparatus and to the bubble counter. The formation of polymer could be seen. The connection to the bubble counter was then interrupted, the cooling water was switched off and the mixture was stirred for a further 12 hours at 85 ° C. under a slight counterpressure of nitrogen. Then the aqueous solution of the methacrylate polymer, which had formed partly as small spheres and partly as a compact material, was decanted. The methacrylate polymer was washed three times with water and dried on filter paper. The NMR Spectra of the polymer obtained in this way showed an approx. 95% conversion of the acrylate and methacrylate groups. The polymer was dried in vacuo (0.02 mbar) for three hours at 87-95 ° C. in order to remove residual water. The ¹ H-NMR spectrum of the methacrylate polymer showed the almost complete disappearance of the acrylate / methacrylate groups. In the ³¹ P-NMR spectrum, the signals of the DOPO unit and the DDPO unit were present at approx. 36 ppm and approx. -8 ppm, the integral ratio approximately corresponding to the expected value of 1.00: 2.33 .: The methacrylate polymer thus obtained was well soluble in organic solvents such as chloroform. It softened at around 160 ° C and melted at around 200 ° C.

Example 8

The DOPO monomer of Example 6 was used in various amounts

Methyl methacrylate and converted to a methyl acrylate polymer both with and without the addition of a further monomer, such as methyl acrylate or n-butyl methacrylate. A suspension polymerization took place in water with 1-decylthiol as regulator and dibenzoyl peroxide (BPO) as initiator. The monomers were destabilized before the polymerization. The syntheses of the methacrylate polymers were carried out in a reaction apparatus which consisted of a 250 ml three-necked flask, magnetic stirrer, heating bath, a dropping funnel and a reflux condenser to which a three-way stopcock with a bubble counter was attached. Both the dropping funnel and the three-way stopcock on the reflux condenser were connected with a Schlenk line.

The methacrylate polymers obtained were converted into compact test rods and films of various thicknesses using an oil hydraulic laboratory press of the type HB 20300 (Schmidt Maschinentechnik; Bretten-Bauerbach, Germany). The test bars had the following dimensions: 70 mm x 10 mm x 0.8 mm. When pressing, temperatures of 220 - 245 ° C were used (depending on the melting behavior of the methacrylate polymers). The quantities and results of the fire behavior test are listed in Table 2.

Example 8a

The polymerization was carried out analogously to Example 7c. Most of the methacrylate polymer was obtained in compact pieces that were detached from the glass wall and washed with water. ^{The 1} H-NMR spectrum of this polymer recorded in deutero-chloroform showed that it contained unreacted monomers. Therefore, the polymer was placed in a fine vacuum (approx.

0.02 mbar) first to approx. 87 ° C (4 h) and then to 93 ° C (1 h). Thereafter, the ¹ H-NMR spectrum of the methacrylate polymer showed the almost complete disappearance of the acrylate / methacrylate groups. In the ³¹ P-NMR spectrum, the signals of the DOPO unit and the diethyl phosphate unit were present at about 36 ppm and -1.3 ppm, respectively, the integral ratio approximately corresponding to the expected value of 1.00: 1.74 .

Example 8b

The polymerization was carried out analogously to Example 7c. The methacrylate polymer was obtained as relatively large polymer spheres (granules) which were washed twice with water. The polymer was dried in vacuo (0.02 mbar) at 87-105 ° C. for 5 hours and then examined by means of NMR spectroscopy. The ¹ H-NMR spectrum of the methacrylate polymer showed the complete disappearance of the acrylate / methacrylate groups. The ³¹ P-NMR spectrum was also as expected: the signals of the DOPO unit and the diethyl phosphate unit were present at about 36 ppm and -1.3 ppm, respectively, with the integral ratio approaching the expected value of 1.00 : 1.74 corresponded. Comparative example VB8a

The polymerization was carried out analogously to Example 7c. The methacrylate polymer was obtained in compact pieces which were detached from the glass wall and washed with water. ^{The 1} H-NMR spectrum of this polymer recorded in deutero-chloroform showed a relatively high proportion of unreacted monomers. The polymer was heated in a fine vacuum (approx. 0.02 mbar) first to approx. 87 ° C. (3 h) and then to 97 ° C. (1 h). Thereafter, the ¹ H-NMR spectrum of the methacrylate polymer showed the almost complete disappearance of the acrylate / methacrylate groups. The methacrylate polymer thus obtained had a phosphorus content of about 4% by weight.

Table 2

These examples show that the combination of the oxaphosphaphenantrene oxide acrylate monomer according to the invention with a copolymerized, solid-phase-active phosphorus compound offers an optimal flame retardant effect. The solid-phase active phosphorus compound alone does not work sufficiently. This is shown by the methacrylate polymer from Comparative Example 8a, the flame retardant effect of which, despite the higher phosphorus content, was worse than that of Examples 7c, 8a and 8b.

Claims

1. Process for the preparation of oxaphosphaphenantrene oxide acrylate monomers by phospha-Michael addition to a, w-alkyldiol diacrylates with 2 to 5 carbon atoms in the alkyl chain, the oxaphosphaphenantrene oxide with the a, w-alkyldiol diacrylate in a molar ratio of 1: 1.5 to 1:10 is reacted in the presence of a base and a polymerization inhibitor, at temperatures of 70 to 120 ° C. and in the absence of water, and unreacted α, w-alkyldiol diacrylate is separated off.

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

3. The method according to claim 1 or 2, characterized in that the separation of unreacted α, w-alkyldiol diacrylate is carried out by vacuum distillation and / or 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, characterized in that the hydrocarbon solvent used is n-pentane, n-hexane and n-heptane, in particular n-hexane.

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

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

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

8. The method according to any one of claims 1 to 7, characterized in that a, w-alkyldiol diacrylate with 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 a, w-alkyldiol diacrylate.

9. Oxaphosphaphenantrenoxid-acrylate monomer obtainable by a process according to any one of claims 1 to 8.

10. Oxaphosphaphenantrenoxid-acrylate monomer according to claim 9, characterized in that it contains a maximum of 3 mol% of a, w-alkyldiol diacrylate, preferably a maximum of 0.5% by weight.

11. A process for the production of flame-retardant, thermoplastic (meth) acrylate polymers by copolymerization of at least one (meth) acrylate monomer with a phosphorus-containing acrylate monomer, characterized in that the phosphorus-containing acrylate monomer used is oxaphosphaphenantrene oxide acrylate monomer obtainable according to one of claims 1 to 8 will.

12. The method according to claim 11, characterized in that the (meth) acrylate monomers are selected from ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutymethacrylate, tert-butymethacrylate and mixtures thereof, especially methyl methacrylate and mixtures of methyl methacrylate with one or more of ethyl acrylate, butyl acrylate, methyl acrylate.

13. The method according to claim 11 or 12, characterized in that additionally active, copolymerized phosphorus compounds are polymerized in the solid phase, preferably phosphorus-containing monomers based on alkyl acrylate, hydroxyalkyl (meth) acrylate, particularly preferably based on hydroxyethyl (meth) acrylate , especially selected from and mixtures of two or more thereof.

14. Use of oxaphosphaphenantrenoxide acrylate monomers obtainable according to one of claims 1 to 8 for the production of flame-retardant, thermoplastic (meth) acrylate polymers.

15. Flame-retardant, thermoplastic (meth) acrylate polymer obtainable according to one of claims 11 to 13.

16. Use of a flame-retardant, thermoplastic (meth) acrylate polymer according to claim 15 for the production of films and sheets.

17. Use according to claim 16, characterized in that the films or plates are transparent.

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