Glycidyl ethers of limonene derivatives and oligomers thereof as curable epoxy resins

Abstract

Cured epoxy resins are widespread because of their excellent mechanical and chemical properties. Typically, epoxy resins based on bisphenol A diglycidyl ethers or bisphenol F diglycidyl ethers are used, but these are problematic for many sectors because of their effect on the endocrine system. The present invention relates to glycidyl ethers of limonene-based diols and/or polyols, and to curable epoxy resin compositions based thereon as alternatives to the bisphenol A diglycidyl ethers or bisphenol F diglycidyl ethers, or the epoxy resin compositions based thereon.

Claims

1. A glycidyl ether selected from the group consisting of a glycidyl ether of formula I ##STR00005## and an oligomeric glycidyl ether thereof, where R1=H and R2=CH.sub.2OA and R3=H, or R1=H and R2=CH.sub.2OA and R3=CR7R8OA, or R1=CH.sub.2OA and R2=H and R3=H, and where R4=H and R5=CH.sub.2OA and R6=H, or R4=H and R5=CH.sub.2OA and R6=CR7R8OA, or R4=CH.sub.2OA and R5=H and R6=H, and where A is a glycidyl group or a hydrogen atom, and R7 and R8 are each independently a hydrogen atom or a C.sub.1-C.sub.4-alkyl group, and where at least 2 A radicals are each a glycidyl group, and where when the glycidyl ether is the oligomeric glycidyl ether, the oligomeric glycidyl ether forms through an intermolecular reaction of glycidylated radicals with non-glycidylated radicals comprising a hydroxyl group in the monomeric glycidyl ether of the formula I and a partially glycidylated or non-glycidylated derivative thereof with ring opening of the oxirane ring, where the hydroxyl group which forms through the ring-opening of the oxirane ring in the oligomeric glycidyl ether is optionally in a glycidylated form, and where the oligomeric glycidyl ether has an oligomerization level of 2 to 100 and comprises, by average, at least 1.3 glycidyl groups.

2. The glycidyl ether according to claim 1, where R1=H and R2=CH.sub.2OA and R3=H, or R1=CH.sub.2OA and R2=H and R3=H, and where R4=H and R5=CH.sub.2OA and R6=H, or R4=CH.sub.2OA and R5=H and R6=H, and where A is a glycidyl group.

3. The glycidyl ether according to claim 1, where R3 and R6 are not both simultaneously a hydrogen atom.

4. A process for preparing the glycidyl ether according to claim 2, the process comprising hydroformulating limonene with a mixture of carbon monoxide and hydrogen in the presence of a hydroformylation catalyst at elevated pressure to give a corresponding dialdehyde, and catalytically hydrogenating the dialdehyde to give a corresponding diol, and reacting the diol with epichlorohydrin to give the glycidyl ether.

5. A process for preparing the glycidyl ether according to claim 3, the process comprising hydroformylating limonene with a mixture of carbon monoxide and hydrogen in the presence of a hydroformylation catalyst at elevated pressure to give a corresponding dialdehyde, and reacting the dialdehyde with a carbonyl compound of formula R7R8CO forming a new CC bond in an aldol reaction to give a corresponding beta-hydroxy aldehyde, catalytically hydrogenating the beta-hydroxy aldehyde to give a corresponding tri- and tetrahydric alcohols, and reacting the tri- and tetrahydric alcohols with epichlorohydrin to give the glycidyl ether.

6. A limonene derivative of formula II ##STR00006## where R9=H and R10=CH.sub.2OH and R11=H, or R9=H and R10=CH.sub.2OH and R11=CR7R8OH, or R9=CH.sub.2OH and R10=H and R11=H, and where R12=H and R13=CH.sub.2OH and R14=H, or R12=H and R13=CH.sub.2OH and R14=CR7R8OH, or R12=CH.sub.2OH and R13=H and R14=H, and where R7 and R8 are each independently a hydrogen atom or a C.sub.1-C.sub.4-alkyl group, and R11 and R14 are not both simultaneously a hydrogen atom.

7. An oligomer, obtained by a process comprising reacting the glycidyl ether according to claim 1 with one or more diols, wherein the glycidyl ether is the glycidyl ether of the formula I.

8. A curable epoxy resin composition, comprising a curing agent component comprising a curing agent, and a resin component comprising at least one polyepoxide compound selected from the group consisting of the glycidyl ether according to claim 1 and an oligomer obtained by reacting the glycidyl ether of the formula I with one or more diols.

9. The curable epoxy resin composition according to claim 8, wherein the polyepoxide compound is the glycidyl ether according to claim 1.

10. The curable epoxy resin composition according to claim 8, wherein the curing agent is at least one selected from the group consisting of an amino curing agent and a phenol resin.

11. The curable epoxy resin composition according to claim 8, wherein a portion of the polyepoxide compound is at least 40% by weight, based on an overall weight of the resin component.

12. The curable epoxy resin composition according to claim 8, which comprises bisphenol A- or F-based compounds in a portion of less than 40% by weight, based on an overall weight of the resin component.

13. A process for producing a cured epoxy resin, the process comprising curing the curable epoxy resin composition according to claim 8.

14. A cured epoxy resin, obtained by curing the curable epoxy resin composition according to claim 8.

15. A process for producing an adhesive, a composite, a molding, or a coating, the process comprising: employing the curable epoxy resin composition according to claim 8 in the process.

Description

Example 1

Preparation of Limonene Derivatives IIA

(1) Limonene can, for example after being admixed with an alcoholic solvent and an Rh-containing hydroformylation catalyst, be converted to the corresponding dialdehydes in a stirred autoclave at an elevated temperature of, for example, 70 to 150 C. and with injection of synthesis gas (CO/H.sub.2 (1:1)) up to a reaction pressure of, for example, 150 to 300 bar. The reaction mixture thus obtained, comprising the corresponding dialdehydes, after decompression to standard pressure and addition of distilled water and a hydrogenation catalyst, for example Raney nickel, and after injection of hydrogen to a reaction pressure of, for example, 50 to 200 bar, can be hydrogenated at an elevated temperature of, for example, 70 to 150 C. in a stirred autoclave. The reaction mixture thus obtained, comprising the corresponding diols, after decompression to standard pressure, can subsequently be freed of the hydrogenation catalyst by means of filtration and of the solvent by means of distillative removal, and then fractionally distilled for purification, in order to obtain the limonene derivative IIA, which is a mixture of the various diols.

Example 2

Preparation of Divinylbenzene Derivative IIB

(2) Limonene derivative IIB can be prepared from limonene according to example 1, except that the reaction mixture from the reaction with synthesis gas (hydroformylation product), which comprises the corresponding aldehydes, is first subjected to an aldol reaction with formaldehyde, for example, prior to the performance of the hydrogenation step. For this purpose, the dialdehyde-containing reaction mixture from the hydroformylation reaction can be, optionally after preceding distillative purification, for example with a molar excess of aqueous formaldehyde (36.5%), and then a catalytic amount of triethanolamine is gradually metered into this reaction mixture, and it is subsequently neutralized with formic acid (98%) on completion of the aldol reaction. The reaction mixture thus prepared can, optionally after distillative purification, be subjected to a hydrogenation as described in example 1, such that divinylbenzene derivative IIB, which is a mixture of the various polyols, is obtainable.

Example 3

Preparation of Monomeric and/or Oligomeric Glycidyl Ethers IA

(3) Limonene derivative IIA (0.7 mol, 136 g, according to ex. 1), which is, for example, a mixture of the various diols that would arise from the hydroformylation and subsequent hydrogenation of limonene, can be heated to 90 C. and admixed with tin(IV) chloride (7.6 mmol, 2 g). Subsequently, epichlorohydrin (1.4 mol, 129.5 g) can be added dropwise in portions, in the course of which the temperature was not supposed to rise, for example, above 140 C. or fall below 85 C. After the addition has ended, stirring, for example, at 90 C. can be continued until no epoxide content was measurable any longer. After cooling to room temperature, the reaction mixture can be admixed, for example, with 25% sodium hydroxide solution (1.4 mol, 224 g) and brought once to boiling. For workup, the product can be washed with water.

(4) The monomeric glycidyl ether IA can be freed from the oligomers by distillation.

Example 4

Preparation of Monomeric and/or Oligomeric Glycidyl Ethers IB

(5) Proceeding from the limonene derivative IIB (according to ex. 2), the glycidyl ether IB can be prepared analogously to example 3 by reaction with epichlorohydrin. In this case, the molar amount of epichlorohydrin used, based on the number of hydroxyl groups in the limonene derivative IIB, is preferably adjusted in comparison to the limonene derivative IIA.

(6) The monomeric glycidyl ethers IB can be freed of the oligomers by distillative purification.

Example 5

Preparation of Cured Epoxy Resin from Monomeric and/or Oligomeric Glycidyl Ethers IA

(7) Glycidyl ether IA from example 3 can, immediately after the preparation and without further purification, be mixed with a stoichiometric amount of an aminic curing agent. The curing agent used can, for example, be IPDA, TETA or polyetheramine D230. For comparison, corresponding stoichiometric mixtures of bisphenol A based epoxy resin (BADGE; Epilox A19-03 from LEUNA Harze, EEW 182 g/eq) and the aminic curing agents can be prepared. For the rheological characterization, the mixtures can be incubated, for example, at 23 C., 40 C. or 75 C.

(8) The rheological measurements for analysis of the reactivity profile can be conducted on a shear stress-controlled plate-plate rheometer (MCR 301 from Anton Paar) having a plate diameter of, for example, 15 mm and a gap distance of, for example, 0.25 mm at the different temperatures.

(9) The measurement of the gelation time can be conducted in rotating/oscillating mode on the above-specified rheometer at, for example, 23 C. and 75 C. The point of intersection of loss modulus (G) and storage modulus (G) gives the gelation time. The mean viscosity between 2 to 5 min after production of the mixture can be regarded as the starting viscosity.

(10) The measurement of the glass transition temperature (Tg) can be determined by means of DSC analysis (Differential Scanning calorimetry) of the curing reaction to ASTM D 3418 in the 2nd run.

Example 6

Preparation of Cured Epoxy Resin from Monomeric and/or Oligomeric Glycidyl Ethers IB

(11) Glycidyl ethers IB for example 4 can be used and characterized in accordance with example 5.