DE102011016918A1 - Solvent free epoxy resin mixture containing components made of renewable resources, useful for preparing curable molding compositions, comprises multifunctional glycidyl compound, multi-functional aromatic monomer and/or activator - Google Patents

Abstract

Solvent free epoxy resin mixture containing components made of renewable resources (at least 70 wt.%), comprises (in wt.%) at least one multifunctional glycidyl compound made of renewable resources (20-90) as a cross-linking component, at least one multi-functional aromatic monomer with phenolic hydroxyl groups and their multifunctional oligomers and/or polymers (10-80) as a crosslinking agent, and/or an activator for crosslinking. Independent claims are also included for: (1) preparing the epoxy resin mixture, comprising dissolving the multi-functional glycidyl compound, multi-functional aromatic monomer with phenolic hydroxide groups and its oligomers and/or polymers, and the activator, in an organic solvent or in the dissolved oligomers, and then removing the solvent by vacuum; and (2) use of the epoxy resin mixture, for preparing curable molding compositions, textile tiles or prepregs by curing the epoxy resin mixture.

Description

The invention relates to a solvent-free epoxy resin mixture with a content of components of renewable raw materials of at least 70 wt .-%. The epoxy resin mixture contains at least one multifunctional glycidyl compound from renewable resources as the component to be crosslinked, at least one multifunctional crosslinker and an activator. Likewise, the invention relates to a method for producing such epoxy resin mixtures. Use find the epoxy resin mixtures according to the invention for the production of curable molding compositions, textile tiles or prepregs by curing the epoxy resin mixture.

The current interest in the development of polymer materials from renewable raw materials, d. H. Polymer materials from renewable raw materials, is currently particularly pronounced in the field of thermoplastically processable polymers. As a notable example, reference may be made to PLA development in this context. In spite of this, however, there is also evidence of the development of "green" resins for thermoset materials from renewable raw materials. Here, in particular, products based on epoxidized vegetable oils have been developed from a commercial point of view, which have been able to establish themselves in the fields of epoxy resins and polyols for PU-based foams. A third type of resin is structurally derived from acrylate esters of such polyols.

In the context of resin systems made from renewable raw materials, lignin, which was investigated many years ago, is also gaining in importance. There are four main reasons for this. On the one hand, demand for pulp and the associated overproduction of lignocellulosic black liquor are growing. However, their thermal utilization is limited by the capacities of the installed incinerators. Retrofitting is not always considered for economic reasons, so that arises from this situation, an interest in material recovery concepts for lignin. Secondly, there are technical developments that can more effectively isolate lignins from black liquor. Point three focuses on the extraction of sulfur-free lignins. These would very much complement the lignin market, which, in addition to some applications for kraft lignin (1-3% sulfur), has specialized mainly in lignosulfonates from the sulfite processes. A fourth reason can also be seen in the fact that lignin is a biobased raw material without nutritional value.

The use of lignin as a component of renewable raw materials for the development of various resin types, such as PF, UF, MF, EP, PU, or UP resins has been investigated. Emphasis was placed on epoxy resins and the resulting thermosets and composites. In addition to the use of lignin itself are also mixtures with other materials from renewable resources, such as vegetable oils, wood resins, polysaccharides, tannins and their combinations in the US 5,833,883 been described. The development of lignocellulosic epoxy resins is characterized by various emphases, and in principle it is necessary to differentiate between the use of lignin on the one hand and lignin derivatives on the other hand. Lignin can now be used again in an activated form, wherein an activation by adjustment of the pH during lignin isolation takes place ( US 3,149,085 A ). Lignin derivatization focuses on reactions of lignin itself or reactions with mixtures of lignin and co-components. The insertion of reactive epoxy groups in lignin is usually carried out by reactions with epichlorohydrin. A second alternative is the esterification with α, β-unsaturated carbonyl groups and subsequent oxidation of the double bond to the oxirane ring. Unmodified lignins are preferably used for the crosslinking of multifunctional glycidyl ethers. The crosslinking of lignin glycidyl ethers by lignin has also been described.

Sulfur-free lignins play an important role in lignins. Frequently preferred molecular weights are in the range between about 300 to 2000 g / mol. In order to ensure a sufficient degree of crosslinking by lignin, comparatively high lignin contents are necessary, they are sometimes given up to 60%.

The use of lignins, even low molecular weight lignin fractions, or similarly structured polymers of renewable raw materials in the order of up to 60% for the preparation of solvent-free epoxy resins is characterized by a relatively high resin viscosity. This leads to impairments during processing to duromers and composites. This concerns both occlusion of air bubbles and insufficient wettability. or impregnation of fibers, fabrics, etc.

Based on this, it was an object of the present invention to provide solvent-free epoxy resins from renewable raw materials, which lead to thermosets and composites with very good mechanical properties.

This object is achieved by the solvent-free epoxy resin mixture with the features of claim 1 and by the method for producing such epoxy resin mixtures having the features of claim 9. In claim 14 uses of the invention are given. The other dependent claims show advantageous developments.

• • 20 bis 90 Gew.-% mindestens einer multifunktionalen Glycidylverbindung aus nachwachsenden Rohstoffen als zu vernetzende Komponente,
• • 10 bis 80 Gew.-% mindestens eines multifunktionalen aromatischen Monomers mit phenolischen Hydroxid-Gruppen sowie Oligomere und/oder Polymere hiervon als Vernetzer und/oder
• • einen Aktivator für die Vernetzung.

According to the invention, a solvent-free epoxy resin mixture with a content of renewable raw materials of at least 70% by weight is provided which contains the following components:

• 20 to 90% by weight of at least one multifunctional glycidyl compound from renewable raw materials as the component to be crosslinked,
• From 10 to 80% by weight of at least one multifunctional aromatic monomer having phenolic hydroxide groups, and oligomers and / or polymers thereof as crosslinkers and / or
• • an activator for networking.

In the context of the present invention, multifunctional glycidyl compounds or multifunctional monomers are to be understood as meaning compounds which have at least two glycidyl compounds.

• • Glycidylethern, bevorzugt hergestellt aus einem multifunktionalen C₁-C₂₀-Alkohol, einem multifunktionalen C₁-C₂₀-Amin oder einem C₁-C₂₀-Aminoalkohol, besonders bevorzugt hergestellt aus einem multifunktionalen C₁-C₁₀-Alkohol, einem multifunktionalen C₁-C₁₀-Amin oder einem C₁-C₁₀-Aminoalkohol,
• • Glycidylestern, bevorzugt hergestellt aus einer multifunktionalen C₁-C₂₀-Carbonsäure, besonders bevorzugt hergestellt aus einer multifunktionalen C₁-C₁₀-Carbonsäure oder
• • Mischungen hiervon, insbesondere mit 5 bis 95 Gew.-% Glycidylether und 95 bis 5 Gew.-% Glycidylester.

Preferably, the at least one multifunctional glycidyl compound is selected from the group consisting of:

• Glycidyl ethers, preferably prepared from a multifunctional C ₁ -C ₂₀ -alcohol, a multifunctional C ₁ -C ₂₀ amine or a C ₁ -C ₂₀ -aminoalcohol, more preferably prepared from a multifunctional C ₁ -C ₁₀ -alcohol, a multifunctional C ₁ -C ₁₀ amine or a C ₁ -C ₁₀ aminoalcohol,
• Glycidyl esters, preferably prepared from a multifunctional C ₁ -C ₂₀ carboxylic acid, more preferably prepared from a multifunctional C ₁ -C ₁₀ carboxylic acid or
• Mixtures thereof, in particular with 5 to 95% by weight of glycidyl ether and 95 to 5% by weight of glycidyl ester.

• • den Polymeren Lignin und dessen Derivaten, insbesondere Lignin aus Kraft-Prozessen, schwefelfreien Ligninen und Tanninen,
• • aus den Polymeren, insbesondere durch Extraktion mit wässrigen und/oder organischen Lösungsmitteln, gewonnenen Oligomeren,
• • aus den Polymeren durch chemischen Abbau der Polymere gewonnenen multifunktionalen Monomeren mit mindestens zwei Hydroxylgruppen, insbesondere Pyrogallol sowie
• • Mischungen hiervon.

The crosslinker is preferably selected from the group consisting of

• The polymers lignin and its derivatives, in particular lignin from kraft processes, sulfur-free lignins and tannins,
• • Oligomers obtained from the polymers, in particular by extraction with aqueous and / or organic solvents,
• • from the polymers by chemical degradation of the polymers obtained multifunctional monomers having at least two hydroxyl groups, in particular pyrogallol and
• • mixtures thereof.

As crosslinkers of the multifunctional glycidyl ether, preference is given to using bio-based aromatic polymers, oligomers (preferred) and monomers (preferred) having high OH numbers of phenolic OH groups. The polymers are lignins from Kraft processes, sulfur-free lignins and tannins. Oligomers can be isolated from these polymers by extraction with aqueous liquids or organic solvents under defined conditions. Preference is given to molecular weights in the range. between 200 to 3000 g / mol. The monomers of renewable raw materials belong to the structurally identical and structurally related monomers of lignins and tannins, of which structurally dissipative substances and other naturally occurring aromatic compounds. They are characterized by at least two phenolic OH groups. In addition, other functional groups can be included which ideally support network formation, such as aliphatic OH groups, aliphatic and aromatic carboxyl groups, or combinations thereof. Examples include catechol (1,2-dihydroxybenzene), protocatechalcohol (3,4-dihydroxybenzyl alcohol) and protocatechuic acid (3,4-dihydroxybenzoic acid). But also monomeric compounds of tannins have a relatively high number of phenolic OH groups, which are suitable for the formation of three-dimensional polymer networks. Gallic acid (3,4,5-trihydroxybenzoic acid) is an essential component of hydrolyzable tannins (trigalloyl glucose, chebulinic acid), which can be converted by decarboxylation to pyrogallol (1,2,3-trihydroxybenzene). Monomeric compounds from the condensed tannins would be, for example, catechol (flavan-3-ol) and its derivatives. The low molecular weight degradation products of lignins and tannins by hydrolytic, solvolytic, oxidative and reductive reaction steps and mixtures thereof are also considered as monomers in the Meaning of this invention. The described components, oligomers and monomers are preferably used in combination.

The oligomers used as crosslinkers are preferably selected from low molecular weight fractions of the extraction having an average molecular weight in the range of 200 to 3000 g / mol, preferably 200 to 2000 g / mol and more preferably 200 to 1500 g / mol.

The molar ratio of the hydroxyl groups of the oligomers to the hydroxyl groups of the monomers (n _{OH oligomer} / n _{OH monomer} ) is preferably from 1 to 99, preferably from 20 to 80 and particularly preferably from 30 to 70%.

It is furthermore preferred that the molar ratio of the hydroxyl groups of the at least one crosslinker to the glycidyl ether or glycidyl ester groups of the at least one component to be crosslinked (n _OH / n _glycidyl ) is from 50 to 150%, preferably from 90 to 140% and particularly preferably from 95 to 135%.

• • Amine, insbesondere der tertiären Amine,
• • Stickstoffheterocyclen, insbesondere Imidazole, Epoxy-Imidazol-Addukte, Metallsalz-Imidazol-Komplexe, Umsetzungsprodukten von Imidazol mit Protonendonatoren
• • Carboxylate sowie
• • Mischungen hiervon.

The activator is preferably selected from the group of:

• Amines, in particular the tertiary amines,
• Nitrogen heterocycles, in particular imidazoles, epoxy-imidazole adducts, metal salt-imidazole complexes, reaction products of imidazole with proton donors
• • Carboxylates as well
• • mixtures thereof.

Surprisingly, it has been shown that the properties of the duromers obtainable therefrom are better than the properties of the thermosets produced by the combined use of oligomers or oligomer mixtures and monomers or monomer mixtures for the crosslinking of multifunctional glycidyl ethers from renewable raw materials in certain mixing ratios in each case one crosslinker component (oligomer or oligomer mixture or monomer or monomer mixture) and in each case the same number of OH groups.

Preferably, the epoxy resin mixture is free of bisphenol A.

The invention likewise provides a process for preparing the epoxy resin mixtures described above, in which the at least one multifunctional glycidyl compound from renewable raw materials, the at least one multifunctional aromatic monomer having phenolic hydroxide groups and its multifunctional oligomers and / or polymers, and the at least one activator in one dissolved organic solvent or in the dissolved oligomers and then the solvent is removed by vacuum.

The solvents used are preferably acetone, methyl ethyl ketone (MEK), dioxane, tetrahydrofuran, chloroform, dichloromethane, ethyl acetate, ethanol, methanol, propanol and mixtures thereof. In this case, the solvent is then preferably removed at temperatures of 30 to 90 ° C in vacuo.

Use find the epoxy resin mixtures according to the invention for the production of curable molding compositions, textile tiles or prepregs by curing the epoxy resin mixture.

The curing is preferably carried out at temperatures of 30 to 250 ° C, preferably from 60 to 200 ° C and particularly preferably from 90 to 180 ° C.

The subject according to the invention is intended to be explained in more detail with reference to the following examples, without wishing to restrict it to the specific embodiments shown here.

example 1

thermosets

19.35 g of a dried acetone fraction of softwood kraft lignin Indulin AT (MW = 2000 g / mol) is dissolved in 100 ml of dried acetone. Thereafter, 45 g of glycerol-1,3-diglycidyl ether, X g of pyrogallol and 0.95 g of imidazole are added. The homogeneous solution is completely freed from the solvent, you get a homogeneous liquid, which is then filled into a mold and cured there for 2 hours at 80 ° C and 3 hours at Y ° C. X and Y and the results for characterization are given in Table 1. Table 1 Results of the mechanical characterization of thermosets X [g] Y [° C] σ [MPa] E [MPa] ε [%] Tg [° C] HDT-A [° C] 0 80 1.34 ± 0.12 10.24 ± 0.26 23 ± 2 21.2 - 0 120 5.77 ± 0.24 115 ± 14 20 ± 3 20.6 34.1 6.45 120 73.98 ± 1.72 3098 ± 76 4.04 ± 0.2 57.3 47.2 12.9 120 86.35 ± 6.7 3638 ± 231 3.27 ± 0.19 61.9 49.1 6.45 160 52.99 ± 10.56 3335 ± 230 2.04 ± 0.5 60.5 43.7 12.9 160 69.82 ± 8.81 3355 ± 54 2.97 ± 0.53 66.3 48.2

Example 2

Unidirectional composites

A cellulose regenerated fiber is drawn through a resin (see Example 1) which has been heated to 50 to 60 ° C; then the winding of a carrier takes place. The number of windings can be controlled by a counter.

After completion of the winding process, the wound carrier is immediately placed in a mold. The curing takes place under pressure and the temperatures given in Example 1; excess resin is passed out of the mold. The resulting unidirectional composites can be removed from the support, cut to size and subjected to characterization. X and Y and the results for characterization are given in Table 2. Table 2 Results of mechanical characterization on unidirectional composites X [g] Y [° C] σ [MPa] E [MPa] ε [%] Tg [° C] HDT-A [° C] 0 120 128 ± 5 6700 ± 230 3.50 ± 0.2 38 160 9.67 120 180 ± 18 10500 ± 980 3.30 ± 0.2 44 124 12.9 120 208 ± 11 12500 ± 520 3.20 ± 0.6 58 -

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5833883 [0004]
• US 3149085 A [0004]

Claims (15)

Solvent-free epoxy resin mixture containing at least 70% by weight of components of renewable raw materials comprising: 20 to 90% by weight of at least one multifunctional glycidyl compound from renewable raw materials as the component to be crosslinked, 10 to 80 wt .-% of at least one multifunctional aromatic monomer having phenolic hydroxyl groups and multifunctional oligomers and / or polymers thereof as crosslinking agents, and / or • an activator for networking. Epoxy resin mixture according to claim 1, characterized in that the at least one multifunctional glycidyl compound is selected from: • glycidyl ethers, in particular prepared from a multifunctional C ₁ -C ₂₀ -alcohol, a multifunctional C ₁ -C ₂₀ amine or a C ₁ -C ₂₀ -Amino alcohol, • glycidyl esters, in particular prepared from a multifunctional C ₁ -C ₂₀ -carboxylic acid, or • mixtures thereof, in particular with 5 to 95% by weight of glycidyl ether and 95 to 5% by weight of glycidyl ester. Epoxy resin mixture according to one of the preceding claims, characterized in that the crosslinker is selected from: The polymers lignin and its derivatives, in particular lignin from kraft processes, sulfur-free lignins and tannins, • Oligomers obtained from the polymers, in particular by extraction with aqueous and / or organic solvents, • From the polymers obtained by chemical degradation of the polymers monomers having at least two hydroxyl groups, in particular pyrogallol, and • mixtures thereof. Epoxy resin mixture according to claim 3, characterized in that the oligomers are selected from low molecular weight fractions of the extraction having an average molecular weight in the range of 200 to 3000 g / mol, preferably 200 to 2000 g / mol and more preferably 200 to 1500 g / mol. Epoxy resin mixture according to claim 3 or 4, characterized in that the molar ratio of the hydroxyl groups of the oligomers to the hydroxyl groups of the monomers (n _{OH oligomer} / n _{OH monomer} ) of 1 to 99%, preferably from 20 to 80% and particularly preferably from 30 up to 70%. Epoxy resin mixture according to one of the preceding claims, characterized in that the molar ratio of the hydroxyl groups of the at least one crosslinker to the glycidyl ether or glycidyl ester groups of at least one component to be crosslinked (n _OH / n _glycidyl ) of 50 to 150%, preferably from 90 to 140% and more preferably from 95 to 135%. Epoxy resin mixture according to one of the preceding claims, characterized in that the activator is selected from the group of Amines, in particular the tertiary amines, Nitrogen heterocycles, in particular imidazoles, epoxy-imidazole adducts, metal salt-imidazole complexes, reaction products of imidazole with proton donors • Carboxylates as well • mixtures thereof. Epoxy resin mixture according to one of the preceding claims, characterized in that the epoxy resin mixture is free of bisphenol A. A process for preparing an epoxy resin mixture according to any one of the preceding claims, wherein the at least one multifunctional glycidyl compound from renewable resources, the at least one multifunctional aromatic monomer having phenolic hydroxide groups and its oligomers and / or polymers and the at least one activator in an organic solvent or is dissolved in the dissolved oligomers and then the solvent is removed by means of vacuum. A method according to claim 9, characterized in that are used as the solvent acetone, methyl ethyl ketone (MEK), dioxane, tetrahydrofuran, chloroform, dichloromethane, ethyl acetate, ethanol, methanol, propanol and mixtures thereof. Method according to one of claims 9 or 10, characterized in that the solvent is removed at temperatures of 30 to 90 ° C in vacuo. Method according to one of claims 9 to 11, characterized in that the oligomers are obtained by extraction and low molecular weight fractions of the extraction with an average molecular weight in the range of 200 to 3000 g / mol, preferably 200 to 2000 g / mol and particularly preferably 200 to 1500 g / mol. Method according to one of claims 9 to 12, characterized in that the activator is selected from the group of tertiary amines, imidazoles, carboxylates, epoxy-imidazole adducts, metal salt-imidazole complexes, reaction products of imidazole with proton donors and mixtures thereof. Use of the epoxy resin mixture according to one of claims 1 to 8 for the preparation of curable molding compositions, textile tiles or prepregs by curing the epoxy resin mixture. Use according to claim 14, characterized in that the curing takes place at temperatures of 30 to 250 ° C, preferably from 60 to 200 ° C and particularly preferably from 90 to 180 ° C.