Preparation of terminally unsaturated (METH)acrylate crosslinkers

Abstract

The present invention relates to a method for producing a di(meth)acrylate diester mixture, which contains a first and a second di(meth)acrylate diester, by reacting a hydroxyalkyl(meth)acrylate mixture with (meth)acrylic acid and / or a C1-C4 alkyl(meth)acrylate. The invention further relates to a di(meth)acrylate diester mixture obtainable using the claimed method.

Description

[0001] Preparation of terminally unsaturated (meth)acrylate crosslinkers

[0002] Description

[0003] Field of the invention

[0004] 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 a C1-C4 alkyl (meth)acrylate. The invention further relates to a di(meth)acrylate diester mixture obtainable by the process according to the invention.

[0005] State of the art

[0006] Di(meth)acrylate diesters are known as crosslinkers for polyalkyl(meth)acrylates and are often prepared by transesterification of methyl(meth)acrylate with a diol or an epoxide or by esterification of (meth)acrylic anhydride with a diol or an epoxide. Various processes for this purpose are described in the prior art.

[0007] DE 1 147 938 describes the preparation of ethane-1,2-diol mono(meth)acrylate (hydroxyethyl(meth)acrylate) and hydroxypropyl(meth)acrylate starting from (meth)acrylic acid and an ethylene or propylene oxide in the presence of an iron(III) chloride catalyst. Di(meth)acrylate diesters are not formed.

[0008] DE 10 2011 005 003 A1 describes a reactor for the conversion of alkylene oxides, in particular for the production of glycol esters of (meth)acrylic acid, such as hydroxyalkyl (meth)acrylates. Di(meth)acrylate diesters are not formed, or are formed only to a very small extent.

[0009] US 5,001,102 describes an iron-containing catalyst for the production of unsaturated hydroxyalkyl esters. Di(meth)acrylate diesters are formed only to a very small extent, if at all.

[0010] WO 2020 / 035561 describes the preparation of a di(meth)acrylate diester by reacting a (meth)acrylic anhydride with an epoxide in the presence of a catalyst and a chromium-containing cocatalyst.

[0011] The processes described in the prior art are sometimes complex and costly. They require highly pure products as starting materials and often do not allow complete esterification, so that frequently only hydroxyalkyl (meth)acrylates are formed, but not di(meth)acrylate diesters.

[0012] There is therefore a need for a process for producing di(meth)acrylate diesters that does not have, or only to a reduced extent, the disadvantages of the processes described in the prior art. In particular, the process should be simple and cost-effective to carry out.

[0013] Solution

[0014] This object was 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): (A) at least one first di(meth)acrylate diester of the general formula (I) in the

[0015] R 1 H or CH3,

[0016] R 2 H or CH3, and

[0017] R 3 H or CH3;

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

[0019] R 4 H or CH3,

[0020] R 5 H or CH3,

[0021] R 6H or CH3, and n is 2 or 3; wherein the process comprises the following steps: a) reacting (meth)acrylic acid with at least one epoxide selected from the group consisting of 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 the first catalyst: (C) at least one first hydroxyalkyl (meth)acrylate of the general formula (III) in the

[0022] R 1 H or CH3, and

[0023] R 2 H or CH3;

[0024] (D) at least one second hydroxyalkyl (meth)acrylate of the general formula (IV) in the

[0025] R 4 H or CH3, R 5H or CH3, 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 residues of component (C) and also the first catalyst, c) reacting the first bottom stream obtained in step b) with (meth)acrylic acid and / or a Ci-C4-alkyl (meth)acrylate in the presence of a second catalyst to obtain a mixture comprising 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.

[0026] It has surprisingly been found that a first bottom stream formed in the process for preparing a hydroxyalkyl (meth)acrylate can be reacted with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylate to form a di(meth)acrylate diester mixture. This avoids purely thermal and thus inefficient utilization of the first bottom stream. The di(meth)acrylate diester mixture formed can instead be reused, for example as a crosslinker. This makes the process according to the invention particularly cost-effective and environmentally friendly. It has also surprisingly been found that complex purification of the reactants, in particular of hydroxyalkyl (meth)acrylate, prior to reaction with (meth)acrylic acid and / or C1-C4-alkyl (meth)acrylate, can be avoided, which likewise contributes to the cost-effectiveness and economic viability of the process according to the invention.

[0027] At the same time, the process according to the invention allows a simple adjustment of the composition of the hydroxyalkyl (meth)acrylate mixture and thus of the di(meth)acrylate diester mixture, so that the di(meth)acrylate diester mixture can be produced reproducibly in its composition.

[0028] The di(meth)acrylate diester mixture prepared according to the invention can be used as a crosslinker, for example, in reactive resins and / or in the polymerization of alkyl (meth)acrylates. The resulting polymers exhibit mechanical properties comparable to those achieved 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 production of the di(meth)acrylate diester mixtures according to the invention is more sustainable.

[0029] The method according to the invention is explained in more detail below.

[0030] In step a) of the process according to the invention, (meth)acrylic acid is reacted with at least one epoxide selected from the group consisting of ethylene oxide and propylene oxide in the presence of a first catalyst to obtain a hydroxyalkyl (meth)acrylate mixture.

[0031] In the context of the present invention, “(meth)acrylic acid” means both acrylic acid and methacrylic acid.

[0032] The term "at least one epoxy" refers to either exactly one epoxy or a mixture of two or more epoxides. Exactly one epoxy is preferred.

[0033] The at least one epoxide is selected from the group consisting of ethylene oxide and propylene oxide. Ethylene oxide is also called oxirane. Propylene oxide is also called 2-methyloxirane.

[0034] 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 to 1 to 1 to 2, preferably in the range from 1 to 0.95 to 1 to 1.5 and particularly preferably about 1 to 1.1.

[0035] It goes without saying that the molar ratio can change during the reaction in step a). The stated molar ratio of (meth)acrylic acid to the at least one epoxide in the reaction in step a) therefore refers to the molar ratio before the reaction, i.e., before the (meth)acrylic acid and the at least one epoxide have reacted with each other.

[0036] The reaction in step a) takes place in the presence of a first catalyst.

[0037] For the purposes of the present invention, "a first catalyst" means both precisely one first catalyst and a mixture of two or more first catalysts. Precisely one first catalyst is preferred.

[0038] It is clear to those skilled in the art that the composition of the first catalyst can change during the reaction in step a), for example, due to transesterification. Therefore, it is possible for the reaction in step a) to begin in the presence of exactly one first catalyst, but for the composition of the first catalyst to change during the reaction, so that a mixture of two or more first catalysts can be formed during the reaction in step a), and the reaction in step a) then takes place in the presence of a mixture of two or more catalysts.

[0039] For example, the reaction in step a) is carried out in the presence of 0.02 to 2.0 wt.% of the first catalyst, preferably in the range of 0.1 to 0.5 wt.% of the first catalyst, in each case based on the total weight of (meth)acrylic acid.

[0040] Suitable as the first catalyst 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.

[0041] Preferably, the first catalyst is a homogeneous catalyst.

[0042] A homogeneous catalyst is one that is completely miscible with and / or soluble in (meth)acrylic acid. For example, the first catalyst can be present as a solid under standard conditions and dissolve in (meth)acrylic acid. It is also possible for the first catalyst to be present as a liquid under standard conditions, and this liquid is completely miscible with (meth)acrylic acid.

[0043] According to the invention, therefore, a process in which the first catalyst is a homogeneous catalyst is also preferred.

[0044] The first catalyst is preferably selected from the group consisting of metal salts and organic compounds of metals selected from the group consisting of chromium and iron. Therefore, a process in which the first catalyst is selected from the group consisting of metal salts and organic compounds, each of metals selected from the group consisting of chromium and iron, is also preferred.

[0045] Suitable metal salts of metals selected from the group consisting of chromium and iron are, for example, chromium chlorides and / or iron chlorides.

[0046] 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) octanoate, 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.

[0047] The reaction in step a) usually takes place at a temperature in the range of 30 to 120 °C, preferably in the range of 50 to 100 °C.

[0048] The pressure during the reaction in step a) is usually in the range from 0 to 6 bar, preferably in the range from 1 bar to 5 bar and particularly preferably in the range from 2 bar to 3 bar.

[0049] The reaction in step a) can take place in esterification reactors known to those skilled in the art. Esterification processes and reactors for this are known per se and are described, for example, in DE 2011 10005003.

[0050] The reaction in step a) is also referred to as esterification. In the reaction in step a), the (meth)acrylic acid is esterified with the at least one epoxide. This reaction is known to those skilled in the art.

[0051] During the reaction, component (C), at least one first hydroxyalkyl (meth)acrylate of the general formula (III), is formed. in the

[0052] R 1 H or CH3, and

[0053] R 2 H or CH3. It will be clear to the person skilled in the art that R 1H is when ethylene oxide is used as the at least one epoxide. If propylene oxide is used as the at least one epoxide, then R 1 CH3.

[0054] R 2 is H, if acrylic acid is converted as (meth)acrylic acid. If methacrylic acid is converted as (meth)acrylic acid, then R is 2 usually CH3.

[0055] Component (C) is therefore usually selected from the group consisting of hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

[0056] Hydroxyethyl (meth)acrylate is also referred to as glycol (meth)acrylate or ethylene glycol (meth)acrylate. In the context of the present invention, the term "hydroxyethyl (meth)acrylate" refers to both hydroxyethyl acrylate and hydroxyethyl methacrylate.

[0057] 2-Hydroxypropyl (meth)acrylate is also known as propylene glycol (meth)acrylate or 2-hydroxy-1-propane (meth)acrylate. For the purposes of the present invention, the term "2-hydroxypropyl (meth)acrylate" refers to both 2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate.

[0058] If propylene oxide is reacted as the at least one epoxide in the reaction in step a), in addition to 2-hydroxy-1-propane(meth)acrylate, the corresponding isomer, 1-hydroxy-2-propane(meth)acrylate, can also be formed.

[0059] The hydroxyalkyl (meth)acrylate mixture may therefore additionally contain an isomer of the first hydroxyalkyl (meth)acrylate.

[0060] The OH group of the first hydroxyalkyl (meth)acrylate of the general formula (III) can react with the at least one epoxide to obtain component (D), at least one second hydroxyalkyl (meth)acrylate of the general formula (IV) in the

[0061] R 4 H or CH3, R 5 H or CH3, and n is 2 or 3. It goes without saying that R 4 H is when ethylene oxide is used as the at least one epoxide. If propylene oxide is used as the at least one epoxide, then R 4 CH3.

[0062] R 5 is H, if acrylic acid is converted as (meth)acrylic acid. If methacrylic acid is converted as (meth)acrylic acid, then R is 5 usually CH3.

[0063] It goes without saying that when n is 2 in formula (IV), component (D) typically comprises diethylene glycol mono(meth)acrylate and / or dipropylene glycol mono(meth)acrylate. When n is 3 in formula (IV), component (D) typically comprises triethylene glycol mono(meth)acrylate and / or tripropylene glycol mono(meth)acrylate.

[0064] Component (D) is therefore usually 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.

[0065] The term "dipropylene glycol mono(meth)acrylate" encompasses, within the scope of the present invention, all isomers of dipropylene glycol mono(meth)acrylate. Within the scope of the present invention, the term dipropylene glycol mono(meth)acrylate thus encompasses 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.

[0066] The hydroxyalkyl (meth)acrylate mixture obtained in step a) contains, for example, in the range from 90 to 99.99 wt.% of component (C) and in the range from 0.01 to 10 wt.% of component (D), in each case based on the total weight of the hydroxyalkyl (meth)acrylate mixture.

[0067] (Meth)acrylic acid is preferably reacted with exactly one epoxide in step a). Therefore, R 1 in the general formula (III) and R 4 in the general formula (IV) are preferably the same. R 2 in the general formula (III) and R 5 in the general formula (IV).

[0068] Therefore, the hydroxyalkyl (meth)acrylate mixture obtained in step a) preferably contains either hydroxyethyl (meth)acrylate as the first hydroxyalkyl (meth)acrylate and at least one second hydroxyalkyl (meth)acrylate selected from the group consisting of diethylene glycol mono(meth)acrylate and triethylene glycol mono(meth)acrylate or propylene glycol (meth)acrylate as the first hydroxyalkyl (meth)acrylate and at least one second hydroxyalkyl (meth)acrylate selected from the group consisting of dipropylene glycol mono(meth)acrylate and tripropylene glycol mono(meth)acrylate.

[0069] 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 the group consisting of diethylene glycol mono(meth)acrylate and triethylene glycol mono(meth)acrylate, the hydroxyalkyl (meth)acrylate mixture is also referred to as hydroxyethyl (meth)acrylate mixture in the context of the present invention.

[0070] 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 the group consisting of dipropylene glycol mono(meth)acrylate and tripropylene glycol mono(meth)acrylate, the hydroxyalkyl (meth)acrylate mixture is also referred to as propylene glycol (meth)acrylate mixture in the context of the present invention.

[0071] The reaction in step a) can take place in the presence of additional components. Such additional components are known per se and include, for example, stabilizers.

[0072] Particularly suitable stabilizers are compounds that inhibit the polymerization of (meth)acrylic acid, the first hydroxyalkyl (meth)acrylate, and / or the second hydroxyalkyl (meth)acrylate. These stabilizers are therefore also referred to as polymerization inhibitors.

[0073] Suitable stabilizers include, for example, hydroquinone monomethyl ether in combination with oxygen, phenol, hydroquinone, nitrophenol and / or butylhydroxytoluene.

[0074] The preferred stabilizers include, in particular, phenol compounds, such as hydroquinones, hydroquinone ethers, such as hydroquinone monomethyl ether, tert-butylhydroquinone, 2,6-di-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2,4-dimethyl-6-tert-butylphenol or di-tert-butylpyrocatechol; p-phenylenediamines, such as N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N'-di-p-tolyl-p-phenylenediamine, 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 dimethyldithiocarbamates, copper diethyldithiocarbamates and copper dibutyldithiocarbamates; nitroso compounds, such as nitrosodiphenylamine, isoamyl nitrite, N-nitrosocyclohexylhydroxylamine, N-nitroso-N-phenyl-N-hydroxylamine and their salts;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-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 6-aza-7,7-dimethylspiro[4,5]decane-6-oxyl, 2,2,6,6-tetramethyl-4-acetoxypiperidine-1-oxyl and 2,2,6,6-tetramethyl-4-benzoyloxypiperidine-1-oxyl; Methylene blue, Nigrosine Base BA, 1,4-benzoquinone, sterically hindered phenols, for example 2,4-dimethyl-6-tert-butylphenol and / or tocopherol compounds, preferably a-tocopherol.;

[0075] The stabilizers can be used individually or in mixtures and are generally commercially available. For further details, please refer to the current specialist literature, in particular to the Römpp Encyclopedia of Chemistry; editors: J. Falbe, M. Regitz; Stuttgart, New York; 10th edition (1996); keyword "antioxidants" and the references cited here.

[0076] For example, the reaction in step a) is carried out in the presence of 1 to 5000 ppm by weight of stabilizer, preferably 5 to 1000 ppm by weight, particularly preferably 10 to 100 ppm by weight, in each case based on the total weight of (meth)acrylic acid.

[0077] Therefore, the hydroxyalkyl (meth)acrylate mixture obtained in step a) preferably contains at least one stabilizer.

[0078] In step b), the hydroxyalkyl (meth)acrylate mixture obtained in step a) is distilled to obtain a first overhead stream and a first bottoms stream. The first overhead stream contains component (C), and the first bottoms stream contains component (D), residues of component (C), and the first catalyst.

[0079] The distillation in step b) can be carried out by methods known to those skilled in the art. For example, the hydroxyalkyl (meth)acrylate mixture obtained in step a) can be transferred to a distillation column and / or a rectification column and distilled there. This embodiment is preferred according to the invention.

[0080] In addition, it is possible that the distillation in step b) takes place in the same reactor as

[0081] Step a) is carried out. Then, the distillation in step b) is 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 then takes place simultaneously with the distillation of the resulting hydroxyalkyl (meth)acrylate mixture.

[0082] The distillation in step b) can, for example, take place at a temperature in the range of 70 to 140 °C.

[0083] The distillation in step b) can, for example, be carried out at a pressure in the range of 0 to 100 mbar.

[0084] During the distillation in step b), a first overhead stream is obtained. The first overhead stream contains component (C), the first hydroxyalkyl (meth)acrylate of general formula (III).

[0085] A first swamp stream will also be maintained.

[0086] In the context of the present invention, a “bottom stream” is understood to mean not only a bottom product which is continuously removed from the distillation in step b), but also a bottom product which, for example in the case of a batchwise operation, remains as a distillation residue in the distillation or the reactor and is only removed at a later time.

[0087] The first bottom stream contains component (D), residues of component (C), and the first catalyst. If the hydroxyalkyl (meth)acrylate mixture additionally contains at least one stabilizer, the first bottom stream typically also additionally contains at least one stabilizer.

[0088] The term “residues of component (C)” in the context of the present invention means, for example, 0.1% to 15% of component (C) based on the amount of component (C) contained in the hydroxyalkyl (meth)acrylate mixture.

[0089] For example, the first bottom stream contains in the range of 40 to 90 wt.% of component (C), preferably in the range of 55 to 75 wt.%, in each case based on the total weight of the first bottom stream.

[0090] For example, the first bottom stream contains in the range of 10 to 65 wt.% of component (D), preferably in the range of 15 to 35 wt.%, in each case based on the total weight of the first bottom stream.

[0091] For example, the first bottoms stream contains in the range of 0.1 to 15 wt.% of the first catalyst, preferably in the range of 1.0 to 6.0 wt.%, in each case based on the total weight of the first bottoms stream.

[0092] For example, the first bottoms stream contains in the range of 0.1 to 15 wt.% of the at least one stabilizer, preferably in the range of 0.5 to 6.0 wt.%, in each case based on the total weight of the first bottoms stream.

[0093] The wt.% of component (C), component (D), the first catalyst and optionally the at least one stabilizer preferably add up to 100 wt.%.

[0094] After step b) and before step c), at least one of the following components can be added to the first bottom stream:

[0095] (E) at least one hydroxyalkyl (meth)acrylate selected from the group consisting of ethylene glycol (meth)acrylate and propylene glycol (meth)acrylate and / or

[0096] (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. Component (E), which can be added to the first bottom stream, can be the same as or different from component (C) present in the first bottom stream.

[0097] The component (F) which can be added to the first bottoms stream can be the same as or different from the component (D) contained in the first bottoms stream.

[0098] The addition of 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. This allows the composition of the di(meth)acrylate diester mixture obtained in the process according to the invention to be adjusted.

[0099] In step c), the first bottom stream obtained in step b) is reacted with (meth)acrylic acid and / or a Ci-C4-alkyl (meth)acrylate in the presence of a second catalyst to obtain a mixture comprising the di(meth)acrylate diester mixture and the first catalyst and the second catalyst.

[0100] For the purposes of the present invention, the term "a C1-C4 alkyl (meth)acrylate" refers to both precisely one C1-C4 alkyl (meth)acrylate and a mixture of two or more C1-C4 alkyl (meth)acrylates. "C1-C4 alkyl (meth)acrylates" are understood to mean alkyl esters of (meth)acrylic acid that have 1 to 4 carbon atoms in the alkyl radical. The alkyl radical can be linear or branched.

[0101] For example, the C1-C4 alkyl (meth)acrylate is selected from the group consisting of 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. The C1-C4 alkyl (meth)acrylate is particularly preferably methyl (meth)acrylate.

[0102] The first bottom stream is reacted in step c) with (meth)acrylic acid and / or a C1-C4 alkyl (meth)acrylate. Preferably, the first bottom stream is reacted in step c) either with (meth)acrylic acid or with a C1-C4 alkyl (meth)acrylate.

[0103] In a preferred embodiment, the first bottom stream in step c) is reacted with acrylic acid and / or a C1-C4-alkyl acrylate if acrylic acid was reacted with the epoxide in step a). It is also preferred that the first bottom stream in step c) is reacted with methacrylic acid and / or a C1-C4-alkyl methacrylate if methacrylic acid was reacted with the epoxide in step a). In this embodiment, R 2 and R 3 in formula (I). Likewise, R 5 and R 6in formula (II) are the same. The components (A) and (B) present in the di(meth)acrylate diester mixture are then also referred to as symmetrical di(meth)acrylate diesters. In a further, likewise preferred embodiment, the first bottom stream in step c) is reacted with acrylic acid and / or a C1-C4-alkyl acrylate if methacrylic acid was reacted with the epoxide in step a). It is also preferred that the first bottom stream in step c) is reacted with methacrylic acid and / or a C1-C4-alkyl methacrylate if acrylic acid was reacted with the epoxide in step a). In this embodiment, R 2 and R 3 in formula (I) are different from each other. Likewise, R 5 and R 6 in formula (II) are different from each other. Components (A) and (B) contained in the di(meth)acrylate diester mixture are then also referred to as asymmetric di(meth)acrylate diesters.

[0104] For example, the molar ratio of the first bottom stream to the (meth)acrylic acid and / or the Ci-C4 alkyl (meth)acrylate in the reaction in step c) is in the range from 1 to 1 to 1 to 20.

[0105] If in step c) the first bottom stream is reacted with (meth)acrylic acid, for example the molar ratio of the first bottom stream to the (meth)acrylic acid in the reaction in step c) is in the range from 1 to 1 to 1 to 3, preferably in the range from 1 to 1 to 1 to 1.5.

[0106] If in step c) the first bottom stream is reacted with Ci-C4-alkyl (meth)acrylate, the molar ratio of the first bottom stream to the Ci-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.

[0107] It goes without saying that the molar ratio can change during the reaction in step c). The molar ratio of the first bottom stream to the (meth)acrylic acid and / or the C1-C4 alkyl (meth)acrylate thus refers to the molar ratio before the reaction, i.e., before the first bottom stream and the (meth)acrylic acid and / or the C1-C4 alkyl (meth)acrylate have reacted with each other.

[0108] The reaction in step c) takes place in the presence of a second catalyst.

[0109] “A second catalyst” in the context of the present invention means both precisely one second catalyst and a mixture of two or more second catalysts. Preference is given to precisely one second catalyst. It is clear to those skilled in the art that the composition of the second catalyst can change during the reaction in step c), for example as a result of transesterification. It is therefore possible for the reaction to begin in the presence of precisely one second catalyst, but for the composition of the second catalyst to change during the course of the reaction, so that a mixture of two or more second catalysts can be formed during the reaction in step c) and the reaction in step c) then takes place in the presence of a mixture of two or more catalysts. For example, the reaction in step c) takes place in the presence of 0.1 to 10% by weight of the second catalyst, preferably in the range from 0.1 to 5% by weight.-% of the second catalyst, each based on the total weight of the first bottom stream.

[0110] Suitable as the second catalyst are all catalysts known to the person skilled in the art which catalyze the reaction of the first bottom stream, in particular of components (C) and (D) present in the first bottom stream, with (meth)acrylic acid and / or the Ci-C4-alkyl (meth)acrylate.

[0111] The second catalyst is preferably selected from the group consisting of Bronsted acids and metal salts and organic compounds of metals selected from the group consisting of tin, titanium, zirconium, alkali metals and alkaline earth metals.

[0112] Therefore, a process is also preferred in which the second catalyst is selected from the group consisting of Brönsted acids and metal salts and organic compounds, each of metals selected from the group consisting of tin, titanium, zirconium, alkali metals and alkaline earth metals.

[0113] Suitable Brönsted acids are known to the person skilled in the art and are selected, for example, from the group consisting of sulfuric acid (H2SO4), hydrochloric acid (HCl), para-toluenesulfonic acid, methanesulfonic acid and acidic ion exchangers.

[0114] 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, preferred are alkali metal chlorides and / or alkali metal hydroxides, particularly preferred are mixtures of alkali metal chlorides and / or alkali metal hydroxides with alkaline earth metal oxides.

[0115] 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 acetonyl acetonate. Tetraisopropyl titanate and / or zirconium acetonyl acetonate is preferred.

[0116] The reaction in step c) is preferably carried out in the presence of a Brönsted acid as a second catalyst when the second bottom stream is reacted with (meth)acrylic acid.

[0117] The reaction in step c) is preferably carried out in the presence of a metal salt and / or an organic compound of metals selected from the group consisting of tin, titanium, zirconium, alkali metals, and alkaline earth metals when the second bottom stream is reacted with the C1-C4 alkyl (meth)acrylate. The reaction in step c) typically takes place at a temperature in the range of 60 to 140 °C.

[0118] If the first bottom stream is reacted with (meth)acrylic acid in step c), the reaction in step c) preferably takes place at a temperature in the range of 60 to 115 °C.

[0119] If the first bottom stream is reacted with Ci-C4-alkyl (meth)acrylate in step c), the reaction in step c) preferably takes place at a temperature in the range from 90 to 130 °C.

[0120] The pressure during the reaction in step c) is usually in the range from 0 to 1500 mbar, preferably in the range from 500 to 1013 mbar.

[0121] The reaction in step c) can take place in reactors for esterification and / or transesterification known to those skilled in the art. For example, reactors for esterification can be equipped with a water separator, while reactors for transesterification can be equipped with a suitable column to separate the alcohol formed from the reactor.

[0122] The reaction in step c) is also referred to as esterification or transesterification. In particular, the reaction in step c) is referred to as esterification when the first bottom stream is reacted with the (meth)acrylic acid. The reaction in step c) is referred to as transesterification when the first bottom stream is reacted with the C1-C4 alkyl (meth)acrylate.

[0123] It goes without saying that in the reaction in step c), component (D) present in the first bottom stream and the residues of component (C), as well as any components (E) and (F) present, are typically reacted with the (meth)acrylic acid and / or the C1-C4-alkyl (meth)acrylate. The first catalyst present in the first bottom stream and any stabilizer present are preferably not reacted with the (meth)acrylic acid and / or the C1-C4-alkyl (meth)acrylate. However, it is possible that any stabilizer present is partially (meth)acrylated.

[0124] During the reaction in step c), the di(meth)acrylate diester mixture is formed. The di(meth)acrylate diester mixture contains components (A) and (B) and is described in detail below.

[0125] Component (A) is typically formed when the residues of component (C) present in the bottom stream and optionally component (E) are reacted with the (meth)acrylic acid and / or the C1-C4-alkyl (meth)acrylate. Component (A) is described in detail below. Component (B) is typically formed when component (D) present in the bottom stream and optionally component (F) are reacted with the (meth)acrylic acid and / or the C1-C4-alkyl (meth)acrylate. Component (B) is described in detail below.

[0126] As stated above, the first catalyst is typically not converted in step c). The at least one stabilizer optionally present in the first bottom stream in step c) can be partially (meth)acrylated. Therefore, in step c), a mixture is obtained which comprises the di(meth)acrylate diester mixture, the first catalyst, and the second catalyst.

[0127] If the first bottom stream contains the at least one stabilizer, the mixture obtained in step c) usually also contains the at least one stabilizer; optionally, the at least one stabilizer is partially (meth)acrylated.

[0128] If the first bottom stream is reacted with (meth)acrylic acid, water is typically formed as a by-product during the reaction. If the first bottom stream is reacted with the C1-C4 alkyl (meth)acrylate, a C1-C4 alcohol is typically formed as a by-product during the reaction. The C1-C4 alcohol is selected, for example, from the group consisting of methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, and isobutanol. The formation of by-products during the reaction is known to the person skilled in the art.

[0129] During the reaction in step c), a by-product selected from the group consisting of water and a C1-C4 alcohol is usually formed. The mixture obtained in step c) therefore usually also contains a by-product. Preferably, after step c) and before step d) or simultaneously with step c), the mixture is distilled to obtain a third overhead stream containing the (meth)acrylic acid and / or the C1-C4 alkyl (meth)acrylate and the by-product, and a third bottoms stream containing the di(meth)acrylate diester mixture as well as the first catalyst and the second catalyst, the third bottoms stream then being used as the mixture in step d).

[0130] During the reaction of the first bottoms stream in step c) with C1-C4 alkyl (meth)acrylate, a C1-C4 alcohol is formed as a by-product. In one embodiment, a C1-C4 alcohol is thus formed in step c), and after step c) and procedure d) or during step c), the resulting mixture is distilled to obtain a third top stream which comprises the C1-C4 alkyl (meth)acrylate and the C1-C4 alcohol and a third bottoms stream which comprises the di(meth)acrylate diester mixture and also the first catalyst and the second catalyst and optionally the at least one stabilizer, the third bottoms stream being used as the mixture in step c). If appropriate, excess C1-C4 alkyl (meth)acrylate can be separated off from the third bottoms stream before it is used as a mixture in step c).Therefore, a process is also preferred in which Ci-C4 alcohol is formed in the reaction in step c) and after step c) and before step d) or simultaneously with step c) the resulting mixture is distilled to obtain a third top stream which contains the Ci-C4 alkyl (meth)acrylate and Ci-C4 alcohol, and a third bottom stream which contains the di(meth)acrylate diester mixture and the first catalyst and the second catalyst, the third bottom stream being used as the mixture in step d).

[0131] Methyl (meth)acrylate is preferably reacted as the C 1 -C 4 alkyl (meth)acrylate. Therefore, methanol is preferably formed as a by-product. It is therefore preferred that methanol is formed in step c) and that after step c) and before step d) or during step c) the resulting mixture is distilled to obtain a third top stream containing the C 1 -C 4 alkyl (meth)acrylate, in particular methyl (meth)acrylate, and methanol, and a third bottom stream containing the di(meth)acrylate diester mixture and the first catalyst and the second catalyst and optionally the at least one stabilizer, the third bottom stream being used as the mixture in step d).

[0132] Therefore, a process is also preferred in which methanol is formed in the reaction in step c) and after step c) and before step d) or simultaneously with step c) the resulting mixture is distilled to obtain a third top stream which contains the Ci-C4-alkyl (meth)acrylate and methanol, and a third bottom stream which contains the di(meth)acrylate diester mixture and the first catalyst and the second catalyst, the third bottom stream being used as the mixture in step d).

[0133] The third overhead stream obtained during distillation can, for example, be recycled to step c).

[0134] A process in which the third top stream is recycled in step c) is therefore also preferred.

[0135] The third overhead stream can be recycled directly to step c). It is also possible to purify the third overhead stream before recycling to step c) using methods known to those skilled in the art. In particular, it is preferred to remove the byproduct, especially methanol, from the third overhead stream as completely as possible before recycling the third overhead stream to step c).

[0136] If the first bottom stream is reacted with (meth)acrylic acid in step c), the reaction is preferably also carried out in the presence of an entraining agent. This allows the water formed as a by-product to be more effectively separated by distillation in the third top stream. Suitable entraining agents are known to those skilled in the art and are selected, for example, from the group consisting of n-hexane, n-heptane, cyclohexane, methylcyclohexane, toluene, and alkyl (meth)acrylates. Alkyl (meth)acrylates suitable as entraining agents include, for example, methyl acrylate, ethyl acrylate, and methyl methacrylate, preferably methyl methacrylate.

[0137] Following step c) and before step d), the first catalyst and / or the second catalyst can be partially separated from the mixture. This results in a low-catalyst mixture. In this embodiment, the low-catalyst mixture is then used as the mixture in step d).

[0138] Also preferred is a process in which, after step c) and before step d), the first catalyst and / or the second catalyst is partially separated from the mixture to obtain a catalyst-poor mixture, the catalyst-poor mixture then being used as a mixture in step d).

[0139] The separation of the first catalyst and / or the second catalyst can be carried out by methods known to the person skilled in the art, for example by filtration.

[0140] The low-catalyst mixture is obtained by partially separating the first catalyst and / or the second catalyst from the mixture. The low-catalyst mixture contains residues of the first catalyst and residues of the second catalyst. The low-catalyst mixture also contains the remaining components that were present in the mixture.

[0141] 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 the low-catalyst mixture, in which case the low-catalyst mixture is then used as the mixture in step d). For the partial separation of the first catalyst and / or the second catalyst from the third bottom stream obtained in the distillation, the previously described embodiments and preferences for the partial separation of the first catalyst and / or the second catalyst from the mixture apply accordingly. In this embodiment, the low-catalyst mixture typically comprises the di(meth)acrylate diester mixture, residues of the first catalyst, and residues of the second catalyst. The low-catalyst mixture can additionally comprise the at least one stabilizer.

[0142] The term “residues of the first catalyst” is understood to mean in the range from 0.001 to 100% of the first catalyst, preferably in the range from 0.001 to 10%, particularly preferably in the range from 0.001 to 2%, in each case based on the total amount of the first catalyst contained in the mixture.

[0143] The term “residues of the second catalyst” is understood to mean in the range from 0.001 to 100% of the second catalyst, preferably in the range from 0.001 to 10%, particularly preferably in the range from 0.001 to 2%, in each case based on the total amount of the second catalyst contained in the mixture.

[0144] The partially separated first catalyst can, for example, be recycled to step a) of the process according to the invention. It is also possible for the partially separated second catalyst to be recycled to step c) of the process according to the invention.

[0145] Therefore, a process in which the first catalyst and / or the second catalyst is recycled in step a) and / or in step c) is also preferred.

[0146] The first catalyst and / or the second catalyst can be purified by methods known to the person skilled in the art before being recycled to step a) and / or step c).

[0147] In step d) of the process according to the invention, the mixture obtained in step c) is distilled to obtain a second overhead stream and a second bottoms stream. The second overhead stream contains the di(meth)acrylate diester mixture. The second bottoms stream contains the first catalyst and the second catalyst.

[0148] 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 there. Furthermore, it is possible for the distillation in step d) to be carried out in the same reactor as step c).

[0149] The distillation in step d) can, for example, be carried out at a temperature in the range of 70 to 140 °C.

[0150] The distillation in step d) can, for example, be carried out at a pressure in the range of 0 to 100 mbar.

[0151] During the distillation in step d), a second bottom stream is obtained. 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) typically also contains the at least one stabilizer. The second bottom stream may also contain residues of the di(meth)acrylate diester mixture.

[0152] The term "residues of the di(meth)acrylate diester mixture" is understood to mean in the range of 0.1 to 20%, preferably in the range of 2 to 10%, of di(meth)acrylate diester mixture, based on the total amount of di(meth)acrylate diester mixture present in the mixture. It goes without saying that if the low-catalyst mixture was used in step d), the second bottom stream contains the residues of the first catalyst and the residues of the second catalyst.

[0153] The second bottom stream can be recycled, for example, to step a) and / or c). It is possible to purify the second bottom stream prior to recycling to step a) and / or step c) using methods known to those skilled in the art. 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 prior to recycling. Methods for this are known to those skilled in the art.

[0154] During the distillation in step d), a second overhead stream is obtained. This second overhead stream contains the di(meth)acrylate diester mixture.

[0155] The second overhead stream preferably contains in the range of 80 to 99.99 wt. %, preferably in the range of 90 to 98 wt. %, of the di(meth)acrylate diester mixture, based on the total weight of the second overhead stream.

[0156] Preferably, the second overhead stream consists essentially of the di(meth)acrylate diester mixture.

[0157] The second overhead stream may also contain residues of the components contained in the mixture.

[0158] Following step d), the second overhead stream can be purified by methods known to the person skilled in the art to obtain the di(meth)acrylate diester mixture.

[0159] The present invention therefore also relates to a di(meth)acrylate diester mixture obtainable by the process according to the invention.

[0160] The di(meth)acrylate diester mixture contains components (A) and (B).

[0161] The di(meth)acrylate diester mixture contains, for example, in the range of 50 to 90 wt.% of component (A), preferably in the range of 60 to 80 wt.%, in each case based on the total weight of the di(meth)acrylate diester mixture.

[0162] The di(meth)acrylate diester mixture contains, for example, in the range of 10 to 50 wt.% of component (B), preferably in the range of 20 to 40 wt.%, in each case based on the total weight of the di(meth)acrylate diester mixture.

[0163] Therefore, a process is also preferred in which 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 based on the total weight of the di(meth)acrylate diester mixture.

[0164] The wt. % of components (A) and (B) in the di(meth)acrylate diester mixture typically add up to 100 wt. %. It is therefore preferred that the di(meth)acrylate diester mixture consists essentially of components (A) and (B).

[0165] Component (A) is at least one first di(meth)acrylate diester of the general formula (I) in the

[0166] R 1 H or CH3,

[0167] R 2H or CH3, and

[0168] R 3 H or CH3.

[0169] If in formula (I) R 1 H, the first di(meth)acrylate of this type is ethylene glycol di(meth)acrylate. Ethylene glycol di(meth)acrylate is also called 1,2-ethanediol di(meth)acrylate.

[0170] Is R 1 in formula (I) CH3, the first di(meth)acrylate diester is propylene glycol di(meth)acrylate. Propylene glycol di(meth)acrylate is also called 1,2-propanediol di(meth)acrylate.

[0171] Component (A) preferably comprises ethylene glycol di(meth)acrylate and propylene glycol di(meth)acrylate.

[0172] Therefore, a process in which component (A) comprises ethylene glycol di(meth)acrylate and propylene glycol di(meth)acrylate is also preferred.

[0173] For example, component (A) comprises in the range of 30 to 80 wt.% ethylene glycol di(meth)acrylate, preferably in the range of 50 to 70 wt.%, in each case based on the total weight of component (A).

[0174] For example, component (A) comprises in the range of 20 to 70 wt.% propylene glycol di(meth)acrylate, preferably in the range of 30 to 50 wt.%, in each case based on the total weight of component (A).

[0175] Therefore, a process is also preferred in which component (A)

[0176] 30 to 80 wt.% ethylene glycol di(meth)acrylate and 20 to 70 wt.% propylene glycol di(meth)acrylate, each based on the total weight of component (A).

[0177] Component (B) is at least one second di(meth)acrylate diester of the general formula (II) in the

[0178] R 4 H or CH3,

[0179] R 5 H or CH3,

[0180] R6 H or CH3, and n is 2 or 3.

[0181] If in formula (II) R 4 H, the second di(meth)acrylate diester is usually diethylene glycol di(meth)acrylate and / or triethylene glycol di(meth)acrylate. When in formula (II) R 4 CH3, the second di(meth)acrylate diester is usually dipropylene glycol di(meth)acrylate and / or tripropylene glycol di(meth)acrylate. When in formula (II) R 4 CH3, then in the context of the present invention, formula (II) and the terms dipropylene glycol di(meth)acrylate and tripropylene glycol di(meth)acrylate also include the corresponding isomers.

[0182] It goes without saying that when n is 2 in formula (II), component (B) typically comprises diethylene glycol di(meth)acrylate and / or dipropylene glycol di(meth)acrylate. When n is 3 in formula (II), component (B) typically comprises triethylene glycol di(meth)acrylate and / or tripropylene glycol di(meth)acrylate.

[0183] Component (B) preferably comprises diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate.

[0184] Therefore, a process in which component (B) comprises diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate is also preferred.

[0185] Component (B) comprises, for example, 50 to 90 wt.% diethylene glycol di(meth)acrylate, preferably in the range of 60 to 80 wt.% diethylene glycol di(meth)acrylate, in each case based on the total weight of component (B).

[0186] Component (B) comprises, for example, 10 to 50 wt.% dipropylene glycol di(meth)acrylate, preferably in the range of 20 to 40 wt.% dipropylene glycol di(meth)acrylate, in each case based on the total weight of component (B). Therefore, a process is also preferred in which component (B)

[0187] 50 to 90 wt.% diethylene glycol di(meth)acrylate and

[0188] 10 to 50 wt.% dipropylene glycol di(meth)acrylate, in each case based on the total weight of component (B).

[0189] In one embodiment of the present invention, the weight percent 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 for component (B) to comprise further components.

[0190] 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.

[0191] The di(meth)acrylate diester mixture therefore preferably contains

[0192] 25 to 50 wt.% ethylene glycol di(meth)acrylate,

[0193] 10 to 35 wt.% diethylene glycol di(meth)acrylate,

[0194] 0 to 2 wt.% triethylene glycol di(meth)acrylate,

[0195] 20 to 35 wt.% propylene glycol di(meth)acrylate,

[0196] 2 to 15 wt.% dipropylene glycol di(meth)acrylate and

[0197] 0 to 2 wt.% tripropylene glycol di(meth)acrylate, each based on the total weight of the di(meth)acrylate diester mixture.

[0198] Steps a) to d) can be carried out discontinuously or continuously. In the context of the present invention, the term "discontinuously" means that the process according to the invention is interrupted between at least two of steps a) to d). For example, the process according to the invention can be interrupted between steps b) and c). If steps a) to d) are carried out discontinuously, the process according to the invention is also referred to as a batch process.

[0199] Preferably, steps a) to d) are carried out continuously.

[0200] The term "continuous" in the context of the present invention means that steps a) to d) are carried out without interruption. A semi-continuous procedure also falls within the scope of the present invention. For example, it is possible for steps a) and b) to be carried out in a batch reactor, but the first bottom stream from this is transferred directly to step c). This embodiment also falls within the scope of the present invention under the term "continuous."

[0201] In particular, when the process according to the invention is carried out continuously, all reactants are continuously fed to the various process steps, while at the same time all products or product mixtures are continuously removed from the process steps and, if appropriate, transferred to the next process step.

[0202] The invention is explained in more detail below using examples, without being limited thereto.

[0203] Examples

[0204] Example 1: Preparation of hydroxyester from methacrylic acid and ethylene oxide

[0205] According to the reaction known from the prior art (e.g. DE 2011 10 005 003) for the preparation of hydroxy esters from unsaturated acids and epoxides, methacrylic acid was initially charged in four different batches in a reactor, and 300 ppm by weight of stabilizer (hydroquinone monomethyl ether, MEHQ) and 0.25% by weight of first catalyst (chromium(III) acetate) were added. At a temperature in the range of 50 to 100 °C and a pressure in the range of 2 to 3 bar, ethylene oxide (molar ratio of methacrylic acid to ethylene oxide 1:1) was metered in while controlling the reaction temperature. Component (C) (hydroxyethyl methacrylate) formed during the reaction was essentially separated off as the first overhead stream in a rectification. The composition of the resulting first bottom stream is given in Table 1.

[0206] Table 1

[0207] Example 2: Preparation of hydroxyester from methacrylic acid and propylene oxide

[0208] Analogously to Example 1, using propylene oxide instead of ethylene oxide, the hydroxy ester was prepared from methacrylic acid and propylene oxide. The composition of the resulting first bottom stream is given in Table 2. Table 2

[0209] Example 3: Methacrylation of the first bottom stream obtained in Example 1 by transesterification of methyl methacrylate

[0210] 390.3 g of the first bottom stream from Example 1, Batch 2, and 900.9 g of methyl methacrylate were heated to reflux in a 2-liter flask equipped with a stirrer and distillation column. A second catalyst (a mixture of 5.47 g of lithium hydroxide and 14.05 g of calcium oxide) was added, and the mixture was again heated to boiling. A third top stream was distilled off at the same time. The resulting third bottom stream (the mixture) was cooled to room temperature and then filtered. The resulting filtrate was transferred to a second flask and distilled. This gave 466.9 g of the second top stream with the composition shown in Table 3.

[0211] Table 3

[0212] Example 4: Methacrylation of the first bottom stream obtained in Example 2 by transesterification of methyl methacrylate

[0213] 432.6 g of the first bottom stream from Example 2, Batch 2 and 900.9 g of methyl methacrylate were heated to reflux in a 2-liter flask equipped with a stirrer and distillation column. A second catalyst (a mixture of 6.06 g of lithium hydroxide and 15.57 g of calcium oxide) was added and the mixture was again heated to boiling. A third top stream was distilled off at the same time. The resulting third bottom stream (the mixture) was cooled to room temperature and then filtered. The resulting filtrate was transferred to a second flask and distilled.

[0214] 445.5 g of the second overhead stream with the composition given in Table 4 were obtained.

[0215] Table 4

[0216] Example 5: Methacrylation of the first bottom stream obtained in Example 2 by transesterification of methyl methacrylate

[0217] 432.6 g of the first bottom stream from Example 2, Batch 1 and 1201.2 g of methyl methacrylate were heated to reflux in a 2-liter flask equipped with a stirrer and distillation column. A second catalyst (a mixture of 1.62 g of lithium amide and 0.54 g of lithium chloride) was added and the mixture was heated to boiling again. A third top stream was distilled off at the same time. The resulting third bottom stream (the mixture) was cooled to room temperature and then filtered. The resulting filtrate was transferred to a second flask and distilled.

[0218] 496.2 g of the second overhead stream with the composition given in Table 5 were obtained.

[0219] Table 5

[0220] Example 6: Methacrylation of a mixture of the substance mixtures obtained in Example 1 and Example 2 by transesterification of methyl methacrylate

[0221] 1213.2 g of a mixture of the first bottom streams from Example 1, Batch 3, and Example 2, Batch 4, and 2252.3 g of methyl methacrylate were heated to reflux in a 4-liter flask equipped with a stirrer and distillation column. A second catalyst (a mixture of 13.59 g of lithium hydroxide and 34.95 g of calcium oxide) was added and the mixture was again heated to boiling. A third top stream was distilled off at the same time. The resulting third bottom stream (the mixture) was cooled to room temperature and then filtered. The resulting filtrate was transferred to a second flask and distilled. 1339 g of the second top stream with the composition given in Table 6 were obtained. Table 6

Claims

Claims: A process for producing a di(meth)acrylate diester mixture, wherein the di(meth)acrylate diester mixture comprises the following components (A) and (B): (A) at least one first di(meth)acrylate diester of general formula (I) in the R 1 H or CH3ist R 2 H or CH3 is, and R 3 H or CH3ist; (B) at least one second di(meth)acrylate diester of general formula (II) (II), in the R 4 H or CH3ist R 5 H or CH3ist R 6H or CH3, and n 2 or 3; wherein the process comprises the following steps: a) reacting (meth)acrylic acid with at least one epoxide selected from the group consisting of 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 the first catalyst: (C) at least one first hydroxyalkyl(meth)acrylate of general formula (III) in the R 1 H or CH3 is, and R 2 H or CH3 is; (D) at least one second hydroxyalkyl(meth)acrylate of general formula (IV) in the R 4 H or CH3ist R 5H or CH3, and n 2 or 3; b) Distillation of the hydroxyalkyl(meth)acrylate mixture obtained in step a) to obtain a first overhead stream containing component (C) and a first bottom stream containing component (D) and residues of component (C) as well as the first catalyst; c) Reaction of the first bottom stream obtained in step b) with (meth)acrylic acid and / or a Ci-C4 alkyl(meth)acrylate in the presence of a second catalyst to obtain a mixture containing the di(meth)acrylate diester mixture as well as the first catalyst and the second catalyst; d) Distillation of the mixture obtained in step c) to obtain a second overhead stream containing the di(meth)acrylate diester mixture and a second bottom stream containing the first catalyst and the second catalyst. Process according to claim 1, characterized in that the di(meth)acrylate diester mixture 50 to 90 wt.% of component (A) and Contains 10 to 50 wt% of component (B), in each case based on the total weight of the di(meth)acrylate diester mixture. A process according to claim 1 or 2, characterized in that component (A) comprises ethylene glycol di(meth)acrylate and propylene glycol di(meth)acrylate. A process according to claim 3, characterized in that component (A) 30 to 80 wt% ethylene glycol di(meth)acrylate and comprising 20 to 70 wt.% propylene glycol di(meth)acrylate, in each case based on the total weight of component (A). A method according to any one of claims 1 to 4, characterized in that component (B) comprises diethylene glycol di(meth)acrylate and dipropylene glycol di(meth)acrylate. A method according to claim 5, characterized in that component (B) 50 to 90 wt% diethylene glycol di(meth)acrylate and comprising 10 to 50 wt% dipropylene glycol di(meth)acrylate, in each case based on the total weight of component (B). A process according to any one of claims 1 to 6, characterized in that the first catalyst is a homogeneous catalyst. A process according to any one of claims 1 to 7, characterized in that the first catalyst is selected from the group consisting of metal salts and organic compounds, each metal being selected from the group consisting of chromium and iron. A process according to any one of claims 1 to 8, characterized in that the second catalyst is selected from the group consisting of Brønsted acids and metal salts and organic compounds, each metal being selected from the group consisting of tin, titanium, zirconium, alkali metals, and alkaline earth metals.A process according to any one of claims 1 to 9, characterized in that, after step c) and before step d), the first catalyst and / or the second catalyst is partially removed from the mixture, obtaining a catalyst-poor mixture, wherein the catalyst-poor mixture is then used as the mixture in step d). A process according to claim 10, characterized in that the first catalyst and / or the second catalyst is recycled in step a) and / or in step c).A process according to any one of claims 1 to 11, characterized in that, during the reaction in step c), Ci-C4 alcohol is formed and, after step c) and before step d) or simultaneously with step c), the mixture obtained is distilled to obtain a third overhead stream containing the Ci-C4 alkyl(meth)acrylate and Ci-C4 alcohol, and a third bottom stream containing the di(meth)acrylate diester mixture as well as the first catalyst and the second catalyst, wherein the third bottom stream is used as the mixture in step d). A process according to any one of claims 1 to 12, characterized in that, during the reaction in step c), methanol is formed and, after step c) and before step d) or simultaneously with step c), the mixture obtained is distilled to obtain a third overhead stream containing the Ci-C4 alkyl(meth)acrylate and methanol, and a third bottom stream containing the di(meth)acrylate diester mixture as well as the first catalyst and the second catalyst. Bottom stream containing the di(meth)acrylate diester mixture as well as the first catalyst and the second catalyst, wherein the third bottom stream is used as the mixture in step d).

14. Method according to claim 12 or 13, characterized in that the third top stream in Step c) is traced back.

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

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