A method for the synthesis of cyclohexyl lactone

Abstract

The application belongs to the technical field of polymer materials, and particularly relates to a synthesis method of cyclohexyl lactone. The application realizes the preparation of cyclohexyl lactone monomers which can be used for ring-opening polymerization by a 'polycondensation-directing depolymerization' method, and the conversion of cheap and readily available diols and 1,2-cyclohexane dicarboxylic acid into a series of diversified lactone monomers, thereby breaking the limitation of only commercially available cyclic monomers such as lactide and caprolactone, expanding the cyclic monomer system and polyester material categories, and having important significance for promoting the upgrading of green degradable polyester industry and widening the application scenarios of high-end functional materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a method for synthesizing and preparing cyclohexyl lactone. Technical Background

[0002] Among many biodegradable polymers, aliphatic polyesters are widely used in packaging, agriculture, textiles and biomedicine due to their good biocompatibility, degradability and mature synthesis process. There are three main technical routes for their industrial synthesis: (1) polycondensation of diols and diacids; (2) ring-opening polymerization of cyclic esters (ROP); and (3) ring-opening copolymerization of cyclic anhydrides and cyclic ethers (ROCOP).

[0003] In the field of ROP (Reactive Oxygen Extraction) monomers, the most industrialized and researched ROP monomers currently include ε-caprolactone, lactide, and glycolide. These monomers all have some shortcomings. ε-caprolactone has a flexible methylene backbone; while the polymer obtained by ring-opening polymerization has high crystallinity, its glass transition temperature (Tg) is extremely low, resulting in insufficient mechanical strength and a slow degradation rate. Although the polymers corresponding to lactide and glycolide have higher Tg, the presence of methyl groups in the side chains reduces the regularity of the backbone, and polylactic acid (PLA) suffers from high brittleness and poor heat resistance. Other cyclic esters, such as δ-valerolactone and β-butyrolactone, also suffer from insufficient rigidity or low polymerization activity. In summary, the existing lactone monomers have relatively simple structures and lack ROP monomers with a rigid backbone, making it difficult to prepare high-performance polyesters with high glass transition temperatures, good mechanical properties, and controllable degradation rates via the ROP route.

[0004] The introduction of alicyclic structures (such as the cyclohexane backbone) is an effective strategy for improving polyester properties. Compared with aromatic structures, alicyclic structures have many advantages. For example, the chair conformation of the cyclohexane ring provides significant rigidity, effectively improving the polymer's Tg and mechanical strength, while avoiding the potential toxicity problems of aromatic compounds; alicyclic structures do not contain conjugated double bonds, making them less susceptible to photo-oxidative degradation and exhibiting better weather resistance than aromatic polyesters; the dense arrangement of the cyclohexane backbone improves the polymer's barrier properties against water vapor and oxygen; and alicyclic structures and their degradation products generally have lower biotoxicity, making them more suitable for food packaging and biomedical applications.

[0005] Currently, alicyclic structures are mainly introduced into the polyester backbone through polycondensation, for example, using 1,4-cyclohexanediethanol or 1,2- / 1,3- / 1,4-cyclohexanedicarboxylic acid and its derivatives as raw materials, and polycondensing them with diacids / diols. However, polycondensation has inherent drawbacks such as harsh process conditions, high energy consumption, and limited molecular weight. In recent years, ring-opening alternating copolymerization (ROAC) using cyclic anhydrides (such as phthalic anhydride and cyclohexane-1,2-dicarboxylic anhydride) and epoxides as raw materials has become a new route for preparing polyesters with alicyclic structures. This method can be achieved under mild conditions, and the resulting polyester has a completely alternating structure. In 2007, Darensbourg et al. reported ROAC of cyclohexane-1,2-dicarboxylic anhydride (CHA) and epoxides, but this requires a two-component system and uses toxic epoxides. It is impossible to obtain structurally regular homopolymers through single-component homopolymerization, and precise control of the ratio and alternation selectivity is required.

[0006] Therefore, developing a universal, efficient, and scalable synthesis process to prepare novel lactone monomers with alicyclic rigid skeletons that can be used for ring-opening polymerization, and expanding the cyclic monomer system and polyester material categories, is of great significance for promoting the upgrading of the green and biodegradable polyester industry and broadening the application scenarios of high-end functional materials. Summary of the Invention

[0007] The problem this invention aims to solve is a large-scale method for directly synthesizing lactones using diols and 1,2-cyclohexanedicarboxylic acid. It provides a lactone synthesis method that uses diols and 1,2-cyclohexanedicarboxylic acid as raw materials, and through different combinations, can synthesize a series of lactones, filling a gap in the variety of cyclic monomer systems.

[0008] To solve the above-mentioned technical problems, the technical solution adopted in this invention is to prepare lactones through a process design of "condensation-directional depolymerization".

[0009] This invention provides a class of lactones, as shown in formula (I):

[0010]

[0011] Where n is 1-14.

[0012] The specific preparation method of the lactone of formula (I) prepared by the present invention is as follows: a diol and 1,2-cyclohexanedicarboxylic acid undergo a polycondensation reaction under the action of a catalyst to obtain a polyester, a diluent is added to depolymerize, and then recrystallization is carried out to obtain the product.

[0013] The reaction equation is as follows:

[0014]

[0015] Where n is 1-14 and m is the degree of polymerization.

[0016] The polycondensation reaction is preferably carried out under bulk conditions:

[0017] The molar ratio of the diol to 1,2-cyclohexanedicarboxylic acid is 1.0-2.0:1, preferably 1.4:1.

[0018] The catalyst may be stannous chloride, stannous octoate, stannous oxide, stannous oxide, dibutyltin oxide, dibutyltin dilaurate, stannous chloride, stannous oxalate, stannous bromide, stannous acetate, butyltin oxide hydroxide, tetraalkyltin, sodium stannate, tetraethyl stannate, tetrabutyl stannate, titanium dioxide, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate, tetratert-butyl titanate, tetraphenyl titanate, tetracyclohexyl titanate, or tetrabenzyl titanate. Tetrahexyloxy titanium, tetra(2-ethylhexyloxy) titanium, tetraoctyloxy titanium, titanium glycolate, titanium glycolate, titanium oxalate, potassium titanium oxalate, lithium oxalate titanium oxide, titanium oxyacetylacetone, titanium tetraacetylacetone, titanium diisopropanol acetylacetone, ammonium dilactic acid dihydroxylamine, ethyl diacetoacetate diisopropanol titanium, titanium triethanolamine isopropanol, titanium polyhydroxystearate, titanium lactate, titanium triethanolamine, titanium tetrabutyl titanate dimer, titanium-magnesium composite catalyst, titanium dioxide. Complex, antimony trioxide, antimony glycolate, antimony acetate, antimony pentoxide, sodium antimonate, potassium antimonate, germanium dioxide, germanium tetroxide, germanium hydroxide, germanium oxalate, tetraethoxy germanium, tetran-n-butoxy germanium, zirconium oxide, sodium zirconate, tetrabutyl zirconate, tetraethyl zirconate, tetrapropyl zirconate, tetraisopropyl zirconate, aluminum oxide, aluminum alkoxide, aluminum isopropoxide, aluminum trichloride, sodium aluminate, silicon dioxide, tetraethyl silicate, tetrabutyl silicate, silicotungstic acid, silicotungstate, trioxide Any one of tungsten carbide, paratungstic acid, metatungstic acid, tungstic acid, phosphotungstic acid, phosphotungstate, cobalt formate, cobalt acetate, cobalt stearate, cobalt oxalate, cobalt carbonate, cobalt bromide, cobalt oxide, cobalt hydroxide, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium dimethyl ether, magnesium acetate, magnesium chloride, calcium oxide, calcium hydroxide, calcium carbonate, calcium acetate, calcium dimethyl ether, zinc oxide, zinc acetate, zinc acetylacetonate, alkyl zinc, dialkyl zinc, zinc dimethyl ether, diethyl zinc, and zinc chloride.

[0019] The total amount of catalyst added is 1-20% of the total mass of the raw materials, preferably 2%.

[0020] The polycondensation reaction temperature is 60-340 °C, preferably 180-230 °C.

[0021] The polycondensation reaction is characterized in that the reaction is carried out under a vacuum of 0.001 MPa to 0.1 MPa, preferably 0.098 MPa.

[0022] The polycondensation reaction time is 3-12 h, preferably 4-6 h.

[0023] The depolymerization reaction temperature is 200-300 °C, preferably 270 °C.

[0024] The depolymerization reaction is characterized in that the reaction occurs at a temperature of 1 × 10⁻⁶. -3 MPa to 1×10 -7 The test is performed under a vacuum of MPa, preferably 1×10 MPa. -6 MPa.

[0025] The depolymerization reaction time is 8-24 h, preferably 12 h.

[0026] The diluent may be polyethylene glycol, silicone oil, polyethylene, polystyrene, polyvinyl chloride, polymethyl methacrylate, polypropylene glycol, polybutane glycol, polyethylene glycol-propylene glycol copolymer, polydimethylsiloxane, perfluoropolyether, polycaprolactone, polylactic acid-ethylene glycol copolymer, polyethylene adipate, polypropylene adipate, polybutylene adipate, polyethylene sebate, polypropylene sebate, polyetherimide oligomers, polysulfone oligomers, polyethersulfone oligomers, polyimide oligomers, etc. The following are all of the following: soluble polyimide, fluorinated polyimide, fluorinated polyamide, polyether ether ketone oligomer, polyimide oligomer, polyoxadiazole oligomer, polythiophene oligomer, polypyrrole oligomer, polysiloxane-polyether copolymer, polysiloxane-polyester copolymer, fluorinated polyether-polyether copolymer, fluorinated polyether-polyester copolymer, polyethylene glycol monomethyl ether, polypropylene glycol monobutyl ether, polybutylene glycol monomethyl ether, polycaprolactone monoacrylate, polydimethylsiloxane monohydroxy, perfluoropolyether monocarboxylic acid, and polyetheramine, preferably polyethylene glycol.

[0027] Beneficial effects

[0028] (1) Cyclohexyl lactones with the structure of formula (I) have not been reported before. They are bio-based, green, and environmentally friendly products with the dual benefits of saving petroleum resources and protecting the environment. They are of great significance to promoting the sustainable development of the polyester industry.

[0029] (2) The raw material used in this invention is a biologically derived diol, which has the advantages of being inexpensive, readily available, green and non-toxic. A cyclic lactone with the structure of formula (I) can be obtained through a simple condensation reaction and depolymerization reaction, and can be produced on a large scale using existing chemical equipment.

[0030] (3) The depolymerization reaction has a high yield, fast reaction rate, few by-products, and the catalyst has no highly toxic raw materials or highly corrosive waste. Attached Figure Description

[0031] The embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein...

[0032] Figure 1 Example 1 (I) of implementation: lactone E3H 1 H NMR image

[0033] Figure 2 Example 2 (I) Implementation of lactone E3R 1 H NMR image Detailed Implementation

[0034] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are as follows:

[0035] Unless otherwise specified, all items are available through commercial channels.

[0036] The 1H NMR spectra involved in the examples were measured using a Bruker Ascend TM-400 NMR spectrometer, and the deuterated reagent used was deuterated chloroform (CDCl3).

[0037] Example 1

[0038] (I) Preparation of lactone E3H: 80 g of 1,3-propanediol (30.62 g, 0.402 mol, 1.4 eq) and cis-1,2-cyclohexanedicarboxylic acid (49.49 mol, 0.287 mol, 1 eq) were added to a 250 mL round-bottom flask. The mixture was heated and stirred, and the vacuum was adjusted to 0.098 MPa. The mixture was dehydrated at 120 °C for 2 h. Stannous chloride (1.6 g, 2 wt%) was added, and the temperature was gradually increased from 180 °C to 220 °C. The reaction was carried out for 4 h to obtain a condensation product. Polyethylene glycol (30 g) was added, and the mixture was distilled under reduced pressure at 270 °C for 12 h to obtain a crude product. The crude product was then recrystallized from ethanol to obtain lactone E3H.

[0039] Example 2

[0040] (I) Preparation of lactone E3R: 80 g of 1,3-propanediol (30.62 g, 0.402 mol, 1.4 eq) and (1R,2R)-1,2-cyclohexanedicarboxylic acid (49.49 mol, 0.287 mol, 1 eq) were added to a 250 mL round-bottom flask. The mixture was heated and stirred, and the vacuum was adjusted to 0.098 MPa. The mixture was dehydrated at 120 °C for 2 h. Stannous octoate (1.6 g, 2 wt%) was added, and the temperature was gradually increased from 180 °C to 220 °C. The reaction was carried out for 4 h to obtain the condensation product. Polyethylene glycol (30 g) was added, and the mixture was distilled under reduced pressure at 270 °C for 12 h to obtain the crude product. The crude product was then recrystallized from ethanol to obtain lactone E3R.

Claims

1. A method for synthesizing cyclohexyl lactone: cyclohexyl lactone is prepared by a process design of "condensation-directional depolymerization".

2. A cyclohexyl lactone, characterized in that... It has a structure as shown in equation (I): Where n is 1-14.

3. The specific preparation method of the cyclohexyl lactone according to formula (I) in claim 2 is as follows: a diol and 1,2-cyclohexanedicarboxylic acid undergo a polycondensation reaction under the action of a catalyst to obtain a polyester, a diluent is added for depolymerization, and then recrystallization is carried out to obtain the product. The reaction equation is as follows: in, n is 1-14, and m is the degree of polymerization.

4. The molar ratio of the diol to 1,2-cyclohexanedicarboxylic acid as described in claim 3 is 1.2-1.6:1, preferably 1.4:

1.

5. The catalyst as described in claim 3 may be stannous chloride, stannous octoate, stannous oxide, stannous oxide, dibutyltin oxide, dibutyltin dilaurate, stannous chloride, stannous oxalate, stannous bromide, stannous acetate, butyltin oxide hydroxide, tetraalkyltin, sodium stannate, tetraethyl stannate, tetrabutyl stannate, titanium dioxide, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate, tetratert-butyl titanate, tetraphenyl titanate, or tetracyclohexyl titanate. Tetrabenzyl titanate, tetrahexyloxy titanium, tetra(2-ethylhexyloxy) titanium, tetraoctyloxy titanium, titanium glycolate, titanium glycolate, titanium oxalate, titanium potassium oxalate, lithium oxalate titanium oxide, titanium oxyacetylacetone, titanium tetraacetylacetone, titanium diisopropanol acetylacetone, ammonium dilactic acid dihydrogen phosphate, ethyl diacetoacetate diisopropanol titanium, titanium triethanolamine isopropanol, titanium polyhydroxystearate, titanium lactate, titanium triethanolamine, titanium tetrabutyl titanate dimer, titanium magnesium composite catalyst, silicon dioxide. Titanium dioxide complex, antimony trioxide, antimony glycolate, antimony acetate, antimony pentoxide, sodium antimonate, potassium antimonate, germanium dioxide, germanium tetroxide, germanium hydroxide, germanium oxalate, tetraethoxy germanium, tetran-n-butoxy germanium, zirconium oxide, sodium zirconate, tetrabutyl zirconate, tetraethyl zirconate, tetrapropyl zirconate, tetraisopropyl zirconate, aluminum oxide, aluminum alkoxide, aluminum isopropoxide, aluminum trichloride, sodium aluminate, silicon dioxide, tetraethyl silicate, tetrabutyl silicate, silicotungstic acid, silicotungstate. Any one of tungsten trioxide, paratungstic acid, metatungstic acid, tungstic acid, phosphotungstic acid, phosphotungstate, cobalt formate, cobalt acetate, cobalt stearate, cobalt oxalate, cobalt carbonate, cobalt bromide, cobalt oxide, cobalt hydroxide, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium dimethyl ether, magnesium acetate, magnesium chloride, calcium oxide, calcium hydroxide, calcium carbonate, calcium acetate, calcium dimethyl ether, zinc oxide, zinc acetate, zinc acetylacetonate, alkyl zinc, dialkyl zinc, zinc dimethyl ether, diethyl zinc, and zinc chloride.

6. The total amount of catalyst added as described in claim 3 is 1-20% of the total mass of the raw materials, preferably 2%.

7. The polycondensation reaction temperature as described in claim 3 is 60-340 °C, preferably 180-230 °C. The reaction is carried out under a vacuum of 0.001 MPa to 0.1 MPa, preferably 0.098 MPa. The reaction time is 3-12 h, preferably 4-6 h.

8. The depolymerization reaction temperature as described in claim 3 is 200-300 °C, preferably 270 °C. The reaction is carried out at 1 × 10⁻⁶ °C. -3 MPa to 1×10 -7 The test is performed under a vacuum of MPa, preferably 1×10 MPa. -6 MPa. The reaction time is 8-24 h, preferably 12 h.

9. The diluent as described in claim 3 may be polyethylene glycol, silicone oil, polyethylene, polystyrene, polyvinyl chloride, polymethyl methacrylate, polypropylene glycol, polybutane glycol, polyethylene glycol-propylene glycol copolymer, polydimethylsiloxane, perfluoropolyether, polycaprolactone, polylactic acid-ethylene glycol copolymer, polyethylene adipate, polypropylene adipate, polybutylene adipate, polyethylene sebate, polypropylene sebate, polyetherimide oligomer, polysulfone oligomer, polyethersulfone oligomer, polyimide oligomer, etc. The following are all of the following: polymers, soluble polyimides, fluorinated polyimides, fluorinated polyamides, polyether ether ketone oligomers, polyimide oligomers, polyoxadiazole oligomers, polythiophene oligomers, polypyrrole oligomers, polysiloxane-polyether copolymers, polysiloxane-polyester copolymers, fluorinated polyether-polyether copolymers, fluorinated polyether-polyester copolymers, polyethylene glycol monomethyl ether, polypropylene glycol monobutyl ether, polybutylene glycol monomethyl ether, polycaprolactone monoacrylate, polydimethylsiloxane monohydroxy, perfluoropolyether monocarboxylic acid, and polyetheramine, with polyethylene glycol being preferred.

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