Preparation of terminally unsaturated (meth) acrylate crosslinkers

Abstract

The invention relates to a method for producing a di (meth) acrylate diester mixture containing a first and a second di (meth) acrylate diester by reacting a hydroxyalkyl (meth) acrylate mixture with (meth) acrylic acid and / or C1-C4-alkyl (meth) acrylates. The invention further relates to di (meth) acrylate diester mixtures obtainable according to the method of the invention.

Description

Technical Field

[0001] The present invention relates to a process for preparing a di(meth)acrylate diester mixture containing a first and a second di(meth)acrylate diester by reacting a hydroxyalkyl(meth)acrylate mixture with (meth)acrylic acid and / or C1-C4-alkyl(meth)acrylates. The present invention further relates to a di(meth)acrylate diester mixture obtainable by the process according to the invention. Background Art

[0002] Di(meth)acrylate diesters are known as crosslinkers for polyalkyl(meth)acrylates and are usually prepared by transesterification of methyl(meth)acrylate with diols or epoxides or by esterification of (meth)acrylic anhydride with diols or epoxides. The prior art describes various processes for this purpose.

[0003] DE 1 147 938 describes the preparation of 1,2-ethylene glycol mono(meth)acrylate (hydroxyethyl(meth)acrylate) and hydroxypropyl(meth)acrylate from (meth)acrylic acid and ethylene oxide or propylene oxide in the presence of iron(III) chloride catalysts. No di(meth)acrylate diesters are formed.

[0004] DE 10 2011 005 003 A1 describes a reactor for the conversion of alkylene oxides, in particular for the preparation of diol (meth)acrylic acid esters, such as hydroxyalkyl (meth)acrylates, wherein no or only a very small amount of di(meth)acrylate diesters are formed.

[0005] No. 5,001,102 describes iron-containing catalysts for preparing unsaturated hydroxyalkyl esters. No di(meth)acrylate diesters are formed or are formed only to a very small extent.

[0006] WO 2020 / 035561 describes the preparation of di(meth)acrylate diesters by reaction of (meth)acrylic anhydride with epoxides in the presence of a catalyst and a chromium-containing cocatalyst.

[0007] The processes described in the prior art are somewhat laborious and expensive. They require high-purity products as starting materials and generally do not allow complete esterification, so that generally only hydroxyalkyl (meth)acrylates are formed, rather than di(meth)acrylate diesters. Summary of the invention

[0008] Purpose

[0009] There is therefore a need for a process for preparing di(meth)acrylate diesters which does not have the disadvantages of the processes described in the prior art or has them only to a reduced extent. In particular, the process should be simple and inexpensive to carry out.

[0010] Achievement of purpose

[0011] The object is achieved by a process for preparing a di(meth)acrylate diester mixture, wherein the di(meth)acrylate diester mixture contains the following components (A) and (B):

[0012] (A) at least one first di(meth)acrylate diester of the general formula (I)

[0013]

[0014] in

[0015] R 1 is H or CH3,

[0016] R 2 is H or CH3, and

[0017] R 3 is H or CH3;

[0018] (B) at least one second di(meth)acrylate diester of the general formula (II)

[0019]

[0020] in

[0021] R 4 is H or CH3,

[0022] R 5 is H or CH3,

[0023] R 6 is H or CH3, and

[0024] n is 2 or 3;

[0025] The method comprises the following steps:

[0026] a) reacting (meth)acrylic acid with at least one epoxide selected from ethylene oxide and propylene oxide in the presence of a first catalyst to obtain a hydroxyalkyl (meth)acrylate mixture, wherein the hydroxyalkyl (meth)acrylate mixture contains the following components (C) and (D) and a first catalyst:

[0027] (C) at least one first hydroxyalkyl (meth)acrylate of the general formula (III)

[0028]

[0029] in

[0030] R 1 is H or CH3, and

[0031] R 2 is H or CH3;

[0032] (D) at least one second hydroxyalkyl (meth)acrylate of the general formula (IV)

[0033]

[0034] in

[0035] R 4 is H or CH3,

[0036] R 5 is H or CH3, and

[0037] n is 2 or 3;

[0038] b) distilling the hydroxyalkyl (meth)acrylate mixture obtained in step a) to obtain a first top stream comprising component (C), and a first bottom stream comprising component (D) and the residue of component (C) and a first catalyst,

[0039] c) reacting the first bottom stream obtained in step b) with (meth)acrylic acid and / or C1-C4-alkyl(meth)acrylate in the presence of a second catalyst to obtain a mixture containing the di(meth)acrylate diester mixture and the first catalyst and the second catalyst,

[0040] d) distilling the mixture obtained in step c) to obtain a second top stream comprising the di(meth)acrylate diester mixture, and a second bottom stream comprising the first catalyst and the second catalyst.

[0041] Surprisingly, it has been found that the first bottoms stream formed in the process for preparing hydroxyalkyl (meth)acrylates can be reacted with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylates to form a di(meth)acrylate diester mixture. This can avoid purely thermal utilization of the first bottoms stream and thus relatively inefficient utilization. The di(meth)acrylate diester mixture formed can instead be used further, for example as a crosslinking agent. This makes the process of the invention particularly cost-effective and environmentally friendly.

[0042] It has also surprisingly been found that complex purification of the reactants, in particular hydroxyalkyl (meth)acrylates, before the reaction with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylates can be avoided, which likewise contributes to the cost-efficiency and economic feasibility of the process according to the invention.

[0043] At the same time, the process of the invention permits simple adjustment of the composition of the hydroxyalkyl(meth)acrylate mixture and thus of the di(meth)acrylate diester mixture, so that di(meth)acrylate diester mixtures can be prepared with reproducible composition.

[0044] The di(meth)acrylate diester mixtures prepared according to the invention can be used as crosslinkers, for example in reactive resins and / or in the polymerization of alkyl(meth)acrylates. The mechanical properties of the polymers obtained here are comparable to those achieved when using known crosslinkers such as pure ethylene glycol di(meth)acrylate or pure 1,3- or -1,4-butanediol di(meth)acrylate. At the same time, the preparation of the di(meth)acrylate diester mixtures according to the invention is more sustainable.

[0045] The method of the present invention is explained in detail below.

[0046] In step a) of the process of the present invention, (meth)acrylic acid is reacted with at least one epoxide selected from ethylene oxide and propylene oxide in the presence of a first catalyst to obtain a hydroxyalkyl (meth)acrylate mixture.

[0047] The "(meth)acrylic acid" in the present invention refers to acrylic acid and methacrylic acid.

[0048] The expression "at least one epoxide" refers to exactly one epoxide or a mixture of two or more epoxides. Preferred is exactly one epoxide.

[0049] The at least one epoxide is selected from ethylene oxide and propylene oxide. Ethylene oxide is also known as oxirane (Oxiran). Propylene oxide is also known as 2-methylethylene oxide.

[0050] For example, the molar ratio of (meth)acrylic acid to the at least one epoxide in the reaction in step a) is in the range from 2:1 to 1:2, preferably in the range from 1:0.95 to 1:1.5, particularly preferably about 1:1.1.

[0051] Obviously, this molar ratio may change during the reaction in step a). The molar ratio of (meth)acrylic acid to the at least one epoxide in the reaction in step a) given is therefore based on the molar ratio before the reaction, i.e. before (meth)acrylic acid and the at least one epoxide have reacted with one another.

[0052] The reaction in step a) is carried out in the presence of a first catalyst.

[0053] "First catalyst" in the present invention refers to exactly one first catalyst or a mixture of two or more first catalysts. Preferred is exactly one first catalyst.

[0054] It is clear to the person skilled in the art that during the reaction in step a), the composition of the first catalyst may change, for example due to transesterification. Thus, it is possible that the reaction in step a) is started in the presence of exactly one first catalyst, but the composition of the first catalyst may change during the reaction, so that during the reaction in step a) a mixture of two or more first catalysts may be formed, and the reaction in step a) is then carried out in the presence of a mixture of two or more catalysts.

[0055] For example, the reaction in step a) is carried out in the presence of 0.02% to 2.0% by weight of the first catalyst, preferably 0.1% to 0.5% by weight of the first catalyst, based in each case on the total weight of (meth)acrylic acid.

[0056] Suitable first catalysts are all catalysts known to the person skilled in the art which catalyze the reaction of (meth)acrylic acid with the at least one epoxide.

[0057] The first catalyst is preferably a homogeneous catalyst.

[0058] A homogeneous catalyst is a catalyst that is completely miscible with (meth)acrylic acid and / or soluble in (meth)acrylic acid. For example, the first catalyst may be present in solid form under standard conditions and may be soluble in (meth)acrylic acid. It is also possible that the first catalyst is present in liquid form under standard conditions and is completely miscible with (meth)acrylic acid.

[0059] Preference is therefore also given according to the invention to a process in which the first catalyst is a homogeneous catalyst.

[0060] The first catalyst is preferably selected from metal salts and organic compounds of metals selected from chromium and iron.

[0061] Preference is therefore also given to a process in which the first catalyst is selected from metal salts and organic compounds, the metals being each selected from chromium and iron.

[0062] Suitable metal salts of metals selected from chromium and iron are, for example, chromium chloride and / or iron chloride.

[0063] Suitable organic compounds of metals selected from the group consisting of chromium and iron are, for example, chromium(III) acetate, chromium(III) methacrylate, chromium(III) acetylacetonate, chromium(III) formate, chromium(III) acrylate, chromium(III) methacrylate, chromium(III) hexanoate, chromium(III) heptanoate, chromium(III) octoate, chromium(III) ethylhexanoate, chromium(III) dibutyldithiocarbamate, iron(III) formate, iron(III) acetate, iron(III) acrylate and / or iron(III) methacrylate, with chromium(III) acetate and iron(III) acetate being particularly preferred. Also particularly preferred as the first catalyst are chromium(III) salts of carboxylic acids.

[0064] The reaction in step a) is generally carried out at a temperature in the range of 30 to 120°C, preferably in the range of 50 to 100°C.

[0065] The pressure in the reaction in step a) is generally in the range of 0 to 6 bar, preferably in the range of 1 to 5 bar, more preferably in the range of 2 to 3 bar.

[0066] The reaction in step a) can be carried out in reactors known to the person skilled in the art for esterification. Esterification and reactors for this purpose are known per se and are described, for example, in DE 2011 10005003.

[0067] The reaction in step a) is also referred to as esterification. In the reaction in step a), (meth)acrylic acid is esterified with the at least one epoxide. Such a reaction is known per se to those skilled in the art.

[0068] In this reaction, component (C) is formed, at least one first hydroxyalkyl (meth)acrylate of the general formula (III),

[0069]

[0070] in

[0071] R 1 is H or CH3, and

[0072] R 2 It is H or CH3.

[0073] It is clear to the skilled person that when the at least one epoxide converted is ethylene oxide, R 1 is H. If the at least one epoxide converted is propylene oxide, R 1 It is CH3.

[0074] When the converted (meth)acrylic acid is acrylic acid, R 2 is H. If the converted (meth)acrylic acid is methacrylic acid, R2 Usually CH3.

[0075] Component (C) is therefore generally selected from hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

[0076] Hydroxyethyl (meth)acrylate is also known as glycol (meth)acrylate or ethylene glycol (meth)acrylate. The term "hydroxyethyl (meth)acrylate" in the present invention refers to both hydroxyethyl acrylate and hydroxyethyl methacrylate.

[0077] 2-Hydroxypropyl (meth)acrylate is also known as propylene glycol (meth)acrylate or 2-hydroxy-1-propane (meth)acrylate. The term "2-hydroxypropyl (meth)acrylate" in the present invention refers to both 2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate.

[0078] If the at least one epoxide converted in the reaction in step a) is propylene oxide, it is possible to form not only 2-hydroxy-1-propane (meth)acrylate but also the corresponding isomer, ie 1-hydroxy-2-propane (meth)acrylate.

[0079] The hydroxyalkyl (meth)acrylate mixture may therefore additionally contain isomers of the first hydroxyalkyl (meth)acrylate.

[0080] The OH groups of the first hydroxyalkyl (meth)acrylate of the general formula (III) can be reacted with the at least one epoxide to obtain component (D), at least one second hydroxyalkyl (meth)acrylate of the general formula (IV):

[0081]

[0082] in

[0083] R 4 is H or CH3,

[0084] R 5 is H or CH3, and

[0085] n is 2 or 3.

[0086] Obviously, when the at least one epoxide converted is ethylene oxide, R 4 is H. If the at least one epoxide converted is propylene oxide, R 4 It is CH3.

[0087] When the converted (meth)acrylic acid is acrylic acid, R 5 is H. If the converted (meth)acrylic acid is methacrylic acid, R 5 Usually CH3.

[0088] Obviously, when n in formula (IV) is 2, component (D) generally comprises diethylene glycol mono(meth)acrylate and / or dipropylene glycol mono(meth)acrylate. When n in formula (IV) is 3, component (D) generally comprises triethylene glycol mono(meth)acrylate and / or tripropylene glycol mono(meth)acrylate.

[0089] Component (D) is therefore generally selected from diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate and tripropylene glycol mono(meth)acrylate.

[0090] The expression "dipropylene glycol mono(meth)acrylate" in the context of the present invention includes all isomers of dipropylene glycol mono(meth)acrylate. The expression "dipropylene glycol mono(meth)acrylate" in the context of the present invention therefore includes the following compounds: 2-(2-hydroxypropan-1-yloxy)-1-propane methacrylate, 2-(1-hydroxypropan-2-yloxy)-1-propane methacrylate, 1-(1-hydroxypropan-2-yloxy)-2-propane methacrylate and 1-(2-hydroxypropan-1-yloxy)-2-propane methacrylate.

[0091] The hydroxyalkyl (meth)acrylate mixture obtained in step a) contains, for example, component (C) in the range from 90% to 99.99% by weight and component (D) in the range from 0.01% to 10% by weight, in each case based on the total weight of the hydroxyalkyl (meth)acrylate mixture.

[0092] (Meth)acrylic acid is preferably reacted in step a) with exactly one epoxide. 1 and R in the general formula (IV) 4 Preferably, R in the general formula (III) 2 and R in the general formula (IV) 5 same.

[0093] Therefore, the hydroxyalkyl (meth)acrylate mixture obtained in step a) preferably contains hydroxyethyl (meth)acrylate as the first hydroxyalkyl (meth)acrylate and at least one second hydroxyalkyl (meth)acrylate selected from diethylene glycol mono(meth)acrylate and triethylene glycol mono(meth)acrylate, or contains propylene glycol (meth)acrylate as the first hydroxyalkyl (meth)acrylate and at least one second hydroxyalkyl (meth)acrylate selected from dipropylene glycol mono(meth)acrylate and tripropylene glycol mono(meth)acrylate.

[0094] If the hydroxyalkyl (meth)acrylate mixture contains hydroxyethyl (meth)acrylate as the first hydroxyalkyl (meth)acrylate and at least one second hydroxyalkyl (meth)acrylate selected from diethylene glycol mono(meth)acrylate and triethylene glycol mono(meth)acrylate, the hydroxyalkyl (meth)acrylate mixture is also referred to as a hydroxyethyl (meth)acrylate mixture in the present invention.

[0095] If the hydroxyalkyl (meth)acrylate mixture contains propylene glycol (meth)acrylate as the first hydroxyalkyl (meth)acrylate and at least one second hydroxyalkyl (meth)acrylate selected from dipropylene glycol mono(meth)acrylate and tripropylene glycol mono(meth)acrylate, the hydroxyalkyl (meth)acrylate mixture is also referred to as a propylene glycol (meth)acrylate mixture in the present invention.

[0096] The reaction in step a) can be carried out in the presence of additional components. Such additional components are known per se and are, for example, stabilizers.

[0097] Suitable stabilizers are, in particular, compounds which inhibit the polymerization of (meth)acrylic acid, the first hydroxyalkyl (meth)acrylate and / or the second hydroxyalkyl (meth)acrylate. Such stabilizers are therefore also referred to as polymerization inhibitors.

[0098] Suitable stabilizers are, for example, hydroquinone monomethyl ether in combination with oxygen, phenol, hydroquinone, nitrophenol and / or butylhydroxytoluene.

[0099] The stabilizers preferably used include, in particular, phenolic compounds, for example hydroquinone, hydroquinone ethers, such as hydroquinone monomethyl ether, tert-butyl hydroquinone, 2,6-di-tert-butyl hydroquinone, 2,5-di-tert-butyl hydroquinone, 2,4-dimethyl-6-tert-butylphenol or di-tert-butylcatechol; p-phenylenediamines, for example N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N'-di-p-tolyl-p-phenylenediamine, amines, such as N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine and N-1,4-dimethylpentyl-N'-phenyl-p-phenylenediamine; amines, such as thiodiphenylamine and phenothiazine; copper dialkyldithiocarbamates, such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate and copper dibutyldithiocarbamate; nitroso compounds, such as nitrosodiphenylamine, isopentyl nitrite, N- ... nitrocyclohexylhydroxylamine, N-nitroso-N-phenyl-N-hydroxylamine and salts thereof; and N-oxyl compounds such as 2,2,4,4-tetramethylazetidine-1-oxyl, 2,2-dimethyl-4,4-dipropylazetidine-1-oxyl, 2,2,5,5-tetramethylpyrrolidine-1-oxyl, 2,2,5,5-tetramethyl-3-oxopyrrolidine-1-oxyl, 2,2,6,6-tetramethylpiperidin-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, 6-aza-7,7-dimethylspiro[4,5]decane-6-oxyl, 2,2,6,6-tetramethyl-4-acetoxypiperidin-1-oxyl and 2,2,6,6-tetramethyl-4-benzoyloxypiperidin-1-oxyl; methylene blue, oil-soluble aniline black BA (Nigrosin Base BA), 1,4-benzoquinone, a hindered phenol, such as 2,4-dimethyl-6-tert-butylphenol and / or a tocopherol compound, preferably α-tocopherol.

[0100] Stabilizers can be used individually or in mixtures and are generally commercially available. For further details, reference is made to the usual professional literature, in particular to Chemie Encyclopedia of Chemistry; Editors: J. Falbe, M. Regitz; Stuttgart, New York; 10th edition (1996); keyword "Antioxidantien" and references cited therein.

[0101] For example, the reaction in step a) is carried out in the presence of 1 to 5000 ppm by weight, preferably 5 to 1000 ppm by weight and more preferably 10 to 100 ppm by weight, of stabilizer, in each case based on the total weight of (meth)acrylic acid.

[0102] Preferably, therefore, the hydroxyalkyl (meth)acrylate mixture obtained in step a) contains at least one stabilizer.

[0103] In step b), the hydroxyalkyl (meth)acrylate mixture obtained in step a) is distilled to obtain a first top stream and a first bottom stream. The first top stream contains component (C); the first bottom stream contains component (D), the residue of component (C) and the first catalyst.

[0104] The distillation in step b) can be carried out by methods known to those skilled in the art. For example, the (meth) acrylate hydroxyalkyl ester mixture obtained in step a) can be transferred to a distillation column and / or a rectification column and distilled therein. This embodiment is preferred according to the present invention.

[0105] Furthermore, it is possible that the distillation in step b) is carried out in the same reactor as in step a). The distillation in step b) is then optionally carried out simultaneously with the reaction in step a). The reaction of (meth)acrylic acid with the at least one epoxide in the presence of the first catalyst is thus carried out simultaneously with the distillation of the resulting hydroxyalkyl (meth)acrylate mixture.

[0106] The distillation in step b) can be carried out, for example, at a temperature in the range of 70 to 140°C.

[0107] The distillation in step b) can be carried out, for example, at a pressure in the range from 0 to 100 mbar.

[0108] A first top stream is obtained in the distillation in step b). The first top stream contains component (C), a first hydroxyalkyl (meth)acrylate of the general formula (III).

[0109] Furthermore, a first bottom stream is obtained.

[0110] “Bottom stream” is understood in the present invention to mean not only the bottom product which is removed continuously from the distillation in step b), but also the bottom product which, for example in batch operation mode, remains in the distillation or in the reactor as distillation residue and is removed only at a later point in time.

[0111] The first bottom stream contains component (D), the residue of component (C) and the first catalyst. If the hydroxyalkyl (meth)acrylate mixture additionally contains at least one stabilizer, the first bottom stream generally likewise additionally contains the at least one stabilizer.

[0112] The expression “residues of component (C)” means in the present invention, for example, 0.1% to 15% of component (C), based on the amount of component (C) present in the hydroxyalkyl (meth)acrylate mixture.

[0113] For example, the first bottom stream contains component (C) in the range from 40% to 90% by weight, preferably in the range from 55% to 75% by weight, based in each case on the total weight of the first bottom stream.

[0114] For example, the first bottom stream contains component (D) in the range from 10% to 65% by weight, preferably in the range from 15% to 35% by weight, based in each case on the total weight of the first bottom stream.

[0115] For example, the first bottom stream contains the first catalyst in the range from 0.1% to 15% by weight, preferably in the range from 1.0% to 6.0% by weight, based in each case on the total weight of the first bottom stream.

[0116] For example, the first bottom stream contains the at least one stabilizer in the range from 0.1% to 15% by weight, preferably in the range from 0.5% to 6.0% by weight, based in each case on the total weight of the first bottom stream.

[0117] The weight percentages of component (C), component (D), the first catalyst and the optional at least one stabilizer preferably add up to 100 weight percent.

[0118] After step b) and before step c), at least one of the following components can be fed into the first bottom stream:

[0119] (E) at least one hydroxyalkyl (meth)acrylate selected from ethylene glycol (meth)acrylate and propylene glycol (meth)acrylate, and / or

[0120] (F) At least one hydroxyalkyl (meth)acrylate selected from the group consisting of diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, and tripropylene glycol mono(meth)acrylate.

[0121] The component (E) that may be added to the first bottoms stream may be the same as or different from the component (C) present in the first bottoms stream.

[0122] The component (F) that may be added to the first bottoms stream may be the same as or different from the component (D) present in the first bottoms stream.

[0123] Adding at least one of components (E) and / or (F) after step b) and before step c) is particularly advantageous for adjusting the composition of the first bottom stream. In this way, the composition of the di(meth)acrylate diester mixture obtained in the process of the invention can be adjusted.

[0124] In step c), the first bottom stream obtained in step b) is reacted with (meth)acrylic acid and / or C1-C4-alkyl(meth)acrylate in the presence of a second catalyst to obtain a mixture containing the di(meth)acrylate diester mixture and the first catalyst and the second catalyst.

[0125] The expression "C1-C4-alkyl (meth)acrylate" refers in the present invention to exactly one C1-C4-alkyl (meth)acrylate and also to mixtures of two or more C1-C4-alkyl (meth)acrylates. "C1-C4-alkyl (meth)acrylate" refers to an alkyl ester of (meth)acrylic acid having 1 to 4 carbons in the alkyl group. The alkyl group may be linear or branched.

[0126] For example, the C1-C4-alkyl (meth)acrylate is selected from methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate and isobutyl (meth)acrylate. More preferably, the C1-C4-alkyl (meth)acrylate is methyl (meth)acrylate.

[0127] The first bottom stream is reacted in step c) with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylate. Preferably, the first bottom stream is reacted in step c) with (meth)acrylic acid or with C1-C4-alkyl (meth)acrylate.

[0128] In a preferred embodiment, when acrylic acid is reacted with an epoxide in step a), the first bottom stream is reacted with acrylic acid and / or a C1-C4-alkyl acrylate in step c). It is also preferred that when methacrylic acid is reacted with an epoxide in step a), the first bottom stream is reacted with methacrylic acid and / or a C1-C4-alkyl methacrylate in step c). In this embodiment, R in formula (I) 2 and R 3 The same. Then, R in formula (II) 5 and R 6 The components (A) and (B) present in the di(meth)acrylate diester mixture are also referred to subsequently as symmetrical di(meth)acrylate diesters.

[0129] In another likewise preferred embodiment, when methacrylic acid is reacted with the epoxide in step a), the first bottom stream is reacted with acrylic acid and / or C1-C4-alkyl acrylate in step c). It is likewise preferred that when acrylic acid is reacted with the epoxide in step a), the first bottom stream is reacted with methacrylic acid and / or C1-C4-alkyl methacrylate in step c). In this embodiment, R in formula (I) 2 and R 3 Different from each other. Then, R in formula (II) 5 and R 6Different from each other. Components (A) and (B) present in the di(meth)acrylate diester mixture are subsequently also referred to as asymmetric di(meth)acrylate diesters.

[0130] For example, the molar ratio of the first bottom stream to (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylate in the reaction in step c) is in the range from 1:1 to 1:20.

[0131] If the first bottom stream is reacted with (meth)acrylic acid in step c), for example, the molar ratio of first bottom stream to (meth)acrylic acid in the reaction in step c) is in the range from 1:1 to 1:3, preferably in the range from 1:1 to 1:1.5.

[0132] If the first bottom stream is reacted in step c) with a C1-C4-alkyl(meth)acrylate, the molar ratio of first bottom stream to C1-C4-alkyl(meth)acrylate in the reaction in step c) is, for example, in the range from 1:1 to 1:20, preferably in the range from 1:2 to 1:10.

[0133] It is obvious that this molar ratio may change during the reaction in step c). The molar ratio of the first bottom stream to (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylate therefore relates to the molar ratio before the reaction, i.e. before the first bottom stream and (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylate have reacted with one another.

[0134] The reaction in step c) is carried out in the presence of a second catalyst.

[0135] "Second catalyst" refers in the present invention to exactly one second catalyst or a mixture of two or more second catalysts. Preference is given to exactly one second catalyst. It is clear to the person skilled in the art that during the reaction in step c), the composition of the second catalyst may change, for example due to transesterification. Thus, it is possible that the reaction is started in the presence of exactly one second catalyst, but the composition of the second catalyst may change during the reaction, so that during the reaction in step c), a mixture of two or more second catalysts may be formed, and the reaction in step c) is then carried out in the presence of a mixture of two or more catalysts.

[0136] For example, the reaction in step c) is carried out in the presence of 0.1 to 10% by weight of the second catalyst, preferably 0.1 to 5% by weight of the second catalyst, based in each case on the total weight of the first bottom stream.

[0137] Suitable second catalysts are all catalysts known to the person skilled in the art which catalyze the reaction of the first bottom stream, in particular components (C) and (D) present in the first bottom stream, with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylates.

[0138] The second catalyst is preferably selected from Bronsted acids and metal salts of metals selected from tin, titanium, zirconium, alkali metals and alkaline earth metals, and organic compounds.

[0139] Preference is therefore also given to a process in which the second catalyst is selected from Bronsted acids and metal salts and organic compounds, the metals being each selected from tin, titanium, zirconium, alkali metals and alkaline earth metals.

[0140] Suitable Bronsted acids are known per se to the person skilled in the art and are selected, for example, from sulfuric acid (H2SO4), hydrochloric acid (HCl), p-toluenesulfonic acid, methanesulfonic acid and acidic ion exchangers.

[0141] Suitable metal salts of metals selected from the group consisting of tin, titanium, zirconium, alkali metals and alkaline earth metals are known to the person skilled in the art and are, for example, lithium hydroxide, calcium hydroxide, calcium oxide, lithium amide, lithium chloride, sodium hydroxide and / or potassium hydroxide, preferably alkali metal chlorides and / or alkali metal hydroxides, more preferably mixtures of alkali metal chlorides and / or alkali metal hydroxides with alkaline earth metal oxides.

[0142] Suitable organic compounds of metals selected from the group consisting of tin, titanium, zirconium, alkali metals and alkaline earth metals are known to the person skilled in the art and are, for example, dibutyltin oxide, dioctyltin oxide, tetraisopropyl titanate and / or zirconium acetylacetonate, preferably tetraisopropyl titanate and / or zirconium acetylacetonate.

[0143] When the second bottom stream is reacted with (meth)acrylic acid, the reaction in step c) is preferably carried out in the presence of a Brønsted acid as second catalyst.

[0144] When the second bottom stream is reacted with C1 -C4 -alkyl (meth)acrylates, the reaction in step c) is preferably carried out in the presence of metal salts of metals selected from tin, titanium, zirconium, alkali metals and alkaline earth metals and / or organic compounds.

[0145] The reaction in step c) is generally carried out at a temperature in the range of 60 to 140°C.

[0146] If in step c) the first bottom stream is reacted with (meth)acrylic acid, the reaction in step c) is preferably carried out at a temperature in the range from 60 to 115°C.

[0147] If the first bottom stream is reacted in step c) with a C1 -C4 -alkyl (meth)acrylate, the reaction in step c) is preferably carried out at a temperature in the range from 90 to 130°C.

[0148] The pressure in the reaction in step c) is generally in the range from 0 to 1500 mbar, preferably in the range from 500 to 1013 mbar.

[0149] The reaction in step c) can be carried out in a reactor known to those skilled in the art for esterification and / or transesterification. For example, the reactor for esterification can be equipped with a water separator, and the reactor for transesterification can be equipped with a suitable tower to separate and remove the alcohol formed from the reactor.

[0150] The reaction in step c) is also referred to as esterification or transesterification. In particular, when the first bottom stream is reacted with (meth)acrylic acid, the reaction in step c) is referred to as esterification, and when the first bottom stream is reacted with (meth)acrylic acid C1-C4-alkyl ester, the reaction in step c) is referred to as transesterification.

[0151] It is obvious that in the reaction in step c), the component (D) and the residue of the component (C) present in the first bottom stream and the optional components (E) and (F) are usually reacted with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylate. The first catalyst and the optional at least one stabilizer present in the first bottom stream preferably do not react with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylate. However, it is possible to partially (meth)acrylate the optional at least one stabilizer.

[0152] The reaction in step c) forms a di(meth)acrylate diester mixture. The di(meth)acrylate diester mixture contains components (A) and (B) and is described in further detail below.

[0153] When the residues of component (C) present in the bottom stream and optionally component (E) are reacted with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylates, component (A) is generally formed. Component (A) is described in further detail below.

[0154] When component (D) and optionally component (F) present in the bottom stream react with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylates, component (B) is generally formed. Component (B) is described in further detail below.

[0155] As already mentioned above, the first catalyst is usually not converted in step c). At least one stabilizer optionally present in the first bottom stream may be partially (meth)acrylated in step c). Thus, in step c), a mixture containing a di(meth)acrylate diester mixture, a first catalyst and a second catalyst is obtained.

[0156] If the first bottom stream contains the at least one stabilizer, the mixture obtained in step c) generally likewise contains the at least one stabilizer, which is optionally partially (meth)acrylated.

[0157] If the first bottom stream is reacted with (meth)acrylic acid, water is usually formed as a by-product in the reaction. If the first bottom stream is reacted with a C1-C4-alkyl (meth)acrylate, a C1-C4 alcohol is usually formed as a by-product in the reaction. The C1-C4 alcohol is selected, for example, from methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol and isobutanol. The formation of by-products in the reaction is known per se to the person skilled in the art.

[0158] The reaction in step c) thus usually forms by-products selected from water and C1-C4 alcohols. The mixture obtained in step c) thus usually contains additional by-products. Preferably, after step c) and before step d) or simultaneously with step c), the mixture is distilled to obtain a third top stream containing (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylate and by-products and a third bottom stream containing a di(meth)acrylate diester mixture and the first catalyst and the second catalyst, in which case the third bottom stream is used as the mixture in step d).

[0159] The reaction of the first bottoms stream with the C1-C4-alkyl (meth)acrylate in step c) forms a C1-C4 alcohol as a by-product. In one embodiment, the C1-C4 alcohol is thus formed in step c), and after step c) and before step d) or during step c), the resulting mixture is distilled to obtain a third top stream containing C1-C4-alkyl (meth)acrylate and C1-C4 alcohol, and a third bottoms stream containing a mixture of di(meth)acrylate diesters and the first and second catalysts and possibly the at least one stabilizer, wherein the third bottoms stream is used as the mixture in step c). Optionally, it is possible to separate excess C1-C4-alkyl (meth)acrylate from the third bottoms stream before the third bottoms stream is used as the mixture in step c).

[0160] Preference is therefore also given to a process in which the reaction in step c) forms a C1-C4 alcohol and, after step c) and before step d) or simultaneously with step c), the resulting mixture is distilled to obtain a third top stream comprising C1-C4-alkyl (meth)acrylate and C1-C4 alcohol, and a third bottom stream comprising a di(meth)acrylate diester mixture and the first and second catalyst, wherein the third bottom stream is used as the mixture in step d).

[0161] The converted C1-C4-alkyl (meth)acrylate is preferably methyl (meth)acrylate. Therefore, the by-product formed is preferably methanol. It is therefore preferred that methanol is formed in step c), and after step c) and before step d) or during step c), the resulting mixture is distilled to obtain a third top stream containing C1-C4-alkyl (meth)acrylate, in particular methyl (meth)acrylate and methanol, and a third bottom stream containing a mixture of di(meth)acrylate diesters and the first and second catalysts and possibly the at least one stabilizer, wherein the third bottom stream is used as the mixture in step d).

[0162] Preference is therefore also given to a process in which the reaction in step c) forms methanol and, after step c) and before step d) or simultaneously with step c), the resulting mixture is distilled to obtain a third top stream comprising C1-C4-alkyl(meth)acrylate and methanol, and a third bottom stream comprising a di(meth)acrylate diester mixture and the first and second catalyst, wherein the third bottom stream is used as the mixture in step d).

[0163] The third top stream obtained in the distillation can, for example, be recirculated into step c).

[0164] Preference is therefore also given to a process in which the third top stream is recirculated into step c).

[0165] The third top stream can be recycled directly into step c). It is likewise possible to purify the third top stream by methods known to those skilled in the art before recycling the third top stream into step c). In particular, it is preferred to remove by-products, in particular methanol, from the third top stream as completely as possible before recycling the third top stream into step c).

[0166] If the first bottom stream is reacted with (meth)acrylic acid in step c), the reaction is preferably carried out in the presence of an entrainer. In this way, it is possible to better separate the water formed as a by-product in the third top stream by distillation. Suitable entrainers are known per se to the person skilled in the art and are selected, for example, from n-hexane, n-heptane, cyclohexane, methylcyclohexane, toluene and alkyl (meth)acrylates. Alkyl (meth)acrylates suitable as entrainers are, for example, methyl acrylate, ethyl acrylate and methyl methacrylate, preferably methyl methacrylate.

[0167] After step c) and before step d), the first catalyst and / or the second catalyst can be partially separated from the mixture. A mixture with a low catalyst content is thus obtained. In this embodiment, the mixture with a low catalyst content is subsequently used as the mixture in step d).

[0168] Also preferred is a process wherein after step c) and before step d), the first catalyst and / or the second catalyst is partially separated from the mixture to obtain a mixture with a low catalyst content, in which case the mixture with a low catalyst content is then used as the mixture in step d).

[0169] The first catalyst and / or the second catalyst can be separated off by methods known to those skilled in the art, for example by filtration.

[0170] A mixture with a low catalyst content is obtained by partially separating the first catalyst and / or the second catalyst from the mixture. The mixture with a low catalyst content contains residues of the first catalyst and residues of the second catalyst. The mixture with a low catalyst content also contains the remaining components present in the mixture.

[0171] If the mixture is distilled after step c) and before step d) or simultaneously with step c), the first catalyst and / or the second catalyst can be partially separated from the third bottom stream obtained in the distillation to obtain a mixture with a low catalyst content, in which case the mixture with a low catalyst content is then used as the mixture in step d). The partial separation of the first catalyst and / or the second catalyst from the third bottom stream obtained in the distillation is correspondingly applicable to the embodiments and preferred modes described above for partially separating the first catalyst and / or the second catalyst from the mixture. In this embodiment, the mixture with a low catalyst content generally contains a di(meth)acrylate diester mixture, residues of the first catalyst and residues of the second catalyst. The mixture with a low catalyst content may additionally contain the at least one stabilizer.

[0172] The expression "residues of the first catalyst" is understood to mean amounts in the range from 0.001 to 100% of the first catalyst, preferably in the range from 0.001 to 10%, more preferably in the range from 0.001 to 2%, in each case based on the total amount of first catalyst present in the mixture.

[0173] The expression "residues of the second catalyst" is understood to mean amounts in the range from 0.001 to 100% of the second catalyst, preferably in the range from 0.001 to 10%, more preferably in the range from 0.001 to 2%, based in each case on the total amount of second catalyst present in the mixture.

[0174] The already partially separated first catalyst can, for example, be recycled into step a) of the process according to the invention. It is likewise possible to recycle the already partially separated second catalyst into step c) of the process according to the invention.

[0175] Preference is therefore also given to processes in which the first catalyst and / or the second catalyst is recycled into step a) and / or step c).

[0176] The first catalyst and / or the second catalyst can be purified by methods known to those skilled in the art before being recycled into step a) and / or step c).

[0177] In step d) of the process of the present invention, the mixture obtained in step c) is distilled to obtain a second top stream and a second bottom stream. The second top stream contains the di(meth)acrylate diester mixture. The second bottom stream contains the first catalyst and the second catalyst.

[0178] The distillation in step d) can be carried out by methods known to those skilled in the art. For example, the mixture obtained in step c) can be transferred to a distillation column and / or a rectification column and distilled therein. In addition, it is possible that the distillation in step d) is carried out in the same reactor as in step c).

[0179] The distillation in step d) may, for example, be carried out at a temperature in the range of 70 to 140°C.

[0180] The distillation in step d) can be carried out, for example, at a pressure in the range from 0 to 100 mbar.

[0181] The distillation in step d) provides a second bottom stream. The second bottom stream contains the first catalyst and the second catalyst. If the mixture contains the at least one stabilizer, the second bottom stream obtained in step d) usually also contains the at least one stabilizer. The second bottom stream may additionally contain residues of the di(meth)acrylate diester mixture.

[0182] The expression "residues of di(meth)acrylate diester mixture" refers to di(meth)acrylate diester mixture in the range of 0.1% to 20%, preferably in the range of 2% to 10%, based on the total amount of di(meth)acrylate diester mixture present in the mixture.

[0183] It is obvious that when a mixture with a low catalyst content has been used in step d), the second bottom stream contains residues of the first catalyst and residues of the second catalyst.

[0184] The second bottom stream can, for example, be recycled into step a) and / or c). It is possible to purify the second bottom stream by methods known to the person skilled in the art before recycling the second bottom stream into step a) and / or step c). In particular, it is possible to separate the first catalyst present in the second bottom stream from the second catalyst present in the second bottom stream before recycling. Methods for this purpose are known to the person skilled in the art.

[0185] A second top stream is obtained in the distillation in step d). The second top stream contains the di(meth)acrylate diester mixture.

[0186] The second top stream preferably contains in the range of 80% to 99.99% by weight, preferably in the range of 90% to 98% by weight, of the di(meth)acrylate diester mixture, based on the total weight of the second top stream.

[0187] The second top stream preferably consists essentially of the di(meth)acrylate diester mixture.

[0188] The second overhead stream may additionally contain residues of components present in the mixture.

[0189] After step d), the second top stream can be purified by methods known to those skilled in the art to obtain a di(meth)acrylate diester mixture.

[0190] The present invention therefore also provides the di(meth)acrylate diester mixtures obtainable by the process according to the invention.

[0191] The di(meth)acrylate diester mixture contains components (A) and (B).

[0192] The di(meth)acrylate diester mixture contains, for example, component (A) in the range from 50 to 90% by weight, preferably in the range from 60 to 80% by weight, based in each case on the total weight of the di(meth)acrylate diester mixture.

[0193] The di(meth)acrylate diester mixture contains, for example, component (B) in the range from 10 to 50% by weight, preferably in the range from 20 to 40% by weight, based in each case on the total weight of the di(meth)acrylate diester mixture.

[0194] Preference is therefore also given to a process in which the di(meth)acrylate diester mixture contains 50 to 90% by weight of component (A) and

[0195] 10 to 50 wt. % of component (B),

[0196] In each case this is based on the total weight of the di(meth)acrylate diester mixture.

[0197] The weight percentages of components (A) and (B) in the di(meth)acrylate diester mixture generally add up to 100 weight percent. It is therefore preferred that the di(meth)acrylate diester mixture consists essentially of components (A) and (B).

[0198] Component (A) is at least one first di(meth)acrylate diester of the general formula (I)

[0199]

[0200] in

[0201] R 1 is H or CH3,

[0202] R 2 is H or CH3, and

[0203] R 3 It is H or CH3.

[0204] When R in formula (I) 1 When is H, the first di(meth)acrylate diester is ethylene glycol di(meth)acrylate. Ethylene glycol di(meth)acrylate is also known as 1,2-ethylene glycol di(meth)acrylate.

[0205] If R in formula (I) 1 The first di(meth)acrylate diester is propylene glycol di(meth)acrylate. Propylene glycol di(meth)acrylate is also known as 1,2-propylene glycol di(meth)acrylate.

[0206] Component (A) preferably comprises ethylene glycol di(meth)acrylate and propylene glycol di(meth)acrylate.

[0207] Preference is therefore also given to a process in which component (A) comprises ethylene glycol di(meth)acrylate and propylene glycol di(meth)acrylate.

[0208] For example, component (A) comprises ethylene glycol di(meth)acrylate in the range from 30% to 80% by weight, preferably in the range from 50% to 70% by weight, based in each case on the total weight of component (A).

[0209] For example, component (A) comprises propylene glycol di(meth)acrylate in the range from 20% to 70% by weight, preferably in the range from 30% to 50% by weight, based in each case on the total weight of component (A).

[0210] Preference is therefore also given to a process in which component (A) comprises

[0211] 30 to 80 wt% of ethylene glycol di(meth)acrylate and

[0212] 20 to 70% by weight of propylene glycol di(meth)acrylate,

[0213] In each case this is based on the total weight of component (A).

[0214] Component (B) is at least one second di(meth)acrylate diester of the general formula (II)

[0215]

[0216] in

[0217] R 4 is H or CH3,

[0218] R 5 is H or CH3,

[0219] R 6 is H or CH3, and

[0220] n is 2 or 3.

[0221] When R in formula (II) 4 When R in formula (II) is H, the second di(meth)acrylate diester is usually diethylene glycol di(meth)acrylate and / or triethylene glycol di(meth)acrylate. 4 When R in formula (II) is CH3, the second di(meth)acrylate diester is usually dipropylene glycol di(meth)acrylate and / or tripropylene glycol di(meth)acrylate. 4 When it is CH3, in the present invention, the formula (II) and the terms "dipropylene glycol di(meth)acrylate" and "tripropylene glycol di(meth)acrylate" also include the corresponding isomers.

[0222] Obviously, when n in formula (II) is 2, component (B) generally comprises diethylene glycol di(meth)acrylate and / or dipropylene glycol di(meth)acrylate. When n in formula (II) is 3, component (B) generally comprises triethylene glycol di(meth)acrylate and / or tripropylene glycol di(meth)acrylate.

[0223] Component (B) preferably comprises diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate.

[0224] Preference is therefore also given to a process in which component (B) comprises diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate.

[0225] Component (B) comprises, for example, 50 to 90% by weight of diethylene glycol di(meth)acrylate, preferably in the range from 60 to 80% by weight of diethylene glycol di(meth)acrylate, based in each case on the total weight of component (B).

[0226] Component (B) comprises, for example, 10 to 50% by weight of dipropylene glycol di(meth)acrylate, preferably in the range from 20 to 40% by weight, based in each case on the total weight of component (B).

[0227] Preference is therefore also given to a process in which component (B) comprises

[0228] 50 to 90 wt % of diethylene glycol di(meth)acrylate and

[0229] 10 to 50% by weight of dipropylene glycol di(meth)acrylate,

[0230] In each case this is based on the total weight of component (B).

[0231] In one embodiment of the present invention, the weight percentages of diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate in component (B) add up to 100 weight percent. It is also possible that component (B) contains additional components.

[0232] For example, component (B) includes diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate.

[0233] The di(meth)acrylate diester mixture therefore preferably contains

[0234] 25 to 50% by weight of ethylene glycol di(meth)acrylate,

[0235] 10 to 35% by weight of diethylene glycol di(meth)acrylate,

[0236] 0 to 2% by weight of triethylene glycol di(meth)acrylate,

[0237] 20 to 35% by weight of propylene glycol di(meth)acrylate,

[0238] 2 to 15 wt % of dipropylene glycol di(meth)acrylate and

[0239] 0 to 2% by weight of tripropylene glycol di(meth)acrylate,

[0240] In each case this is based on the total weight of the di(meth)acrylate diester mixture.

[0241] Steps a) to d) can be carried out discontinuously or continuously. The term "discontinuously" in the present invention means that the method of the present invention is interrupted between at least two steps of steps a) to d). For example, the method of the present invention can be interrupted between steps b) and c). If steps a) to d) are carried out discontinuously, the method of the present invention is also called a batch process or a charge process.

[0242] Steps a) to d) are preferably carried out continuously.

[0243] The term "continuous" in the context of the present invention means that steps a) to d) are carried out without interruption. The term "continuous" in the context of the present invention also encompasses semi-continuous embodiments. For example, it is possible that steps a) and b) are carried out in a batch reactor, but from which the first bottom stream is transferred directly to step c). The term "continuous" in the context of the present invention also encompasses this embodiment.

[0244] In particular, in the case of continuous performance of the process according to the invention, all reactants are fed continuously to the individual process steps, while all products or product mixtures are simultaneously continuously discharged from said process step and optionally transferred to the next process step.

[0245] The present invention is explained in detail below by way of examples, but the present invention is not limited thereto. DETAILED DESCRIPTION

[0246] Example

[0247] Example 1: Preparation of hydroxy esters from methacrylic acid and ethylene oxide

[0248] By means of a reaction known from the prior art (e.g. DE 2011 10 005 003) for preparing hydroxy esters from unsaturated acids and epoxides, the reactor was pre-loaded with methacrylic acid in four different batches and 300 ppm by weight of a stabilizer (hydroquinone monomethyl ether, MEHQ) and 0.25% by weight of a first catalyst (chromium (III) acetate) were added. At a temperature of 50 to 100° C. and a pressure of 2 to 3 bar, ethylene oxide was metered in (the molar ratio of methacrylic acid to ethylene oxide was 1:1.1) while monitoring the reaction temperature. Component (C) (hydroxyethyl methacrylate) formed in the reaction was essentially separated off as a first top stream in the rectification. The composition of the resulting first bottom stream is reported in Table 1.

[0249] Table 1

[0250]

[0251] Example 2: Preparation of Hydroxy Ester from Methacrylic Acid and Propylene Oxide

[0252] The hydroxy esters were prepared from methacrylic acid and propylene oxide in analogy to Example 1, except that propylene oxide was used here instead of ethylene oxide. The composition of the resulting first bottoms stream is reported in Table 2.

[0253] Table 2

[0254]

[0255] Example 3: Transesterification of the first bottom stream obtained in Example 1 with methyl methacrylate Acrylation

[0256] 390.3 grams of the first bottom stream from Example 1, batch 2 and 900.9 grams of methyl methacrylate were heated in a 2-liter flask with a stirrer and a distillation column until boiling under reflux. A second catalyst (a mixture of 5.47 grams of lithium hydroxide and 14.05 grams of calcium oxide) was added and the mixture was heated to boiling again. A third top stream was distilled simultaneously. The resulting third bottom stream (mixture) was cooled to room temperature and then filtered. The resulting filtrate was transferred to a second flask and distilled. 466.9 grams of a second top stream having the composition given in Table 3 were obtained.

[0257] Table 3

[0258] Second top stream [GC area %] Ethylene glycol dimethacrylate content 69.45 Diethylene glycol dimethacrylate content 27.26 Triethylene glycol dimethacrylate content 1.12 Other ingredients 2.17

[0259] Example 4: Transesterification of the first bottom stream obtained in Example 2 with methyl methacrylate Acrylation

[0260] 432.6 grams of the first bottom stream from Example 2, batch 2 and 900.9 grams of methyl methacrylate were heated in a 2-liter flask with a stirrer and a distillation column until boiling under reflux. A second catalyst (a mixture of 6.06 grams of lithium hydroxide and 15.57 grams of calcium oxide) was added and the mixture was heated to boiling again. A third top stream was distilled simultaneously. The resulting third bottom stream (mixture) was cooled to room temperature and then filtered. The resulting filtrate was transferred to a second flask and distilled. 445.5 grams of a second top stream having the composition given in Table 4 were obtained.

[0261] Table 4

[0262]

[0263] Example 5: Transesterification of the first bottom stream obtained in Example 2 with methyl methacrylate Acrylation

[0264] 432.6 grams of the first bottoms stream from Example 2, batch 1 and 1201.2 grams of methyl methacrylate were heated in a 2-liter flask with a stirrer and a distillation column until boiling under reflux. A second catalyst (a mixture of 1.62 grams of lithium amide and 0.54 grams of lithium chloride) was added and the mixture was heated to boiling again. A third top stream was distilled out simultaneously. The resulting third bottoms stream (mixture) was cooled to room temperature and then filtered. The resulting filtrate was transferred to a second flask and distilled. 496.2 grams of a second top stream having a composition given in Table 5 were obtained.

[0265] Table 5

[0266]

[0267] Example 6: Mixing the materials obtained in Example 1 and Example 2 by transesterification of methyl methacrylate Methacrylation of the mixture

[0268] A mixture of 1213.2 grams of the first bottom stream from Example 1, batch 3 and Example 2, batch 4 and 2252.3 grams of methyl methacrylate were heated in a 4-liter flask with an agitator and a distillation column until boiling under reflux. A second catalyst (a mixture of 13.59 grams of lithium hydroxide and 34.95 grams of calcium oxide) was added and the mixture was heated to boiling again. A third top stream was distilled out at the same time. The resulting third bottom stream (mixture) was cooled to room temperature and then filtered. The resulting filtrate was transferred to a second flask and distilled. 1339 grams of a second top stream having a composition given in Table 6 were obtained.

[0269] Table 6

[0270]

Claims

1. A method for preparing a di(meth)acrylate diester mixture, wherein the di(meth)acrylate diester mixture contains the following components (A) and (B): (A) at least one first di(meth)acrylate diester of the general formula (I) in R 1 is H or CH 3 , R 2 is H or CH 3 ,and R 3 is H or CH 3 ; (B) at least one second di(meth)acrylate diester of the general formula (II) in R 4 is H or CH 3 , R 5 is H or CH 3 , R 6 is H or CH 3 ,and n is 2 or 3; The method The following steps are involved: a) reacting (meth)acrylic acid with at least one epoxide selected from ethylene oxide and propylene oxide in the presence of a first catalyst to obtain a hydroxyalkyl (meth)acrylate mixture, wherein the hydroxyalkyl (meth)acrylate mixture contains the following components (C) and (D) and a first catalyst: (C) at least one first hydroxyalkyl (meth)acrylate of the general formula (III) in R 1 is H or CH 3 ,and R 2 is H or CH 3 ; (D) at least one second hydroxyalkyl (meth)acrylate of the general formula (IV) in R 4 is H or CH 3 , R 5 is H or CH 3 ,and n is 2 or 3; b) distilling the hydroxyalkyl (meth)acrylate mixture obtained in step a) to obtain a first top stream comprising component (C), and a first bottom stream comprising component (D) and the residue of component (C) and a first catalyst, c) reacting the first bottom stream obtained in step b) with (meth)acrylic acid and / or (meth)acrylic acid C 1 -C 4 - the alkyl ester is reacted in the presence of a second catalyst to obtain a mixture containing the di(meth)acrylate diester mixture and the first catalyst and the second catalyst, d) distilling the mixture obtained in step c) to obtain a second top stream comprising the di(meth)acrylate diester mixture, and a second bottom stream comprising the first catalyst and the second catalyst.

2. The method according to claim 1, Features The di(meth)acrylate diester mixture contains 50 to 90 wt% of component (A) and 10 to 50 wt. % of component (B), In each case this is based on the total weight of the di(meth)acrylate diester mixture.

3. The method according to claim 1 or 2, Features Component (A) comprises ethylene glycol di(meth)acrylate and propylene glycol di(meth)acrylate.

4. The method according to claim 3, Features Component (A) comprises 30 to 80 wt% of ethylene glycol di(meth)acrylate and 20 to 70% by weight of propylene glycol di(meth)acrylate, In each case this is based on the total weight of component (A).

5. The method according to any one of claims 1 to 4, Features Component (B) comprises diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate.

6. The method according to claim 5, Features Component (B) comprises 50 to 90 wt % of diethylene glycol di(meth)acrylate and 10 to 50% by weight of dipropylene glycol di(meth)acrylate, In each case this is based on the total weight of component (B).

7. The method according to any one of claims 1 to 6, Features The first catalyst is a homogeneous catalyst.

8. The method according to any one of claims 1 to 7, Features The first catalyst is selected from metal salts and organic compounds, and the metals are each selected from chromium and iron.

9. The method according to any one of claims 1 to 8, Features The second catalyst is selected from Bronsted acids and metal salts and organic compounds, the metals being each selected from tin, titanium, zirconium, alkali metals and alkaline earth metals.

10. The method according to any one of claims 1 to 9, It is characterized in that After step c) and before step d), the first catalyst and / or the second catalyst is partially separated from the mixture, thereby obtaining a mixture with a low catalyst content, in which case the mixture with a low catalyst content is used as the mixture in step d).

11. The method according to claim 10, Features The first catalyst and / or the second catalyst is recycled into step a) and / or step c).

12. The method according to any one of claims 1 to 11, Features The reaction in step c) forms C 1 -C 4 alcohol, and after step c) and before step d) or simultaneously with step c), distilling the resulting mixture to obtain a (meth)acrylic acid C 1 -C 4 -alkyl esters and C 1 -C 4 a third top stream of alcohols, and a third bottom stream containing the di(meth)acrylate diester mixture and the first catalyst and the second catalyst, wherein the third bottom stream is used as the mixture in step d).

13. The method according to any one of claims 1 to 12, Features The reaction in step c) forms methanol, and after step c) and before step d) or simultaneously with step c), the resulting mixture is distilled to obtain a (meth)acrylic acid C 1 -C 4 a third top stream of alkyl esters and methanol, and a third bottom stream comprising a di(meth)acrylate diester mixture and the first catalyst and the second catalyst, wherein the third bottom stream is used as mixture in step d).

14. The method according to claim 12 or 13, Features The third top stream is recycled into step c).

15. Di(meth)acrylate diester mixture obtainable by the process according to any one of claims 1 to 14.

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