RU2421496C1 - Method of producing poly-beta-pinene - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: disclosed is a method of producing poly-β-pinene via cationic polymerisation of β-pinene in a medium of 1,1,1,3,3,3-hexafluoroisopropanol. The process is carried out in molar ratio β-pinene: 1,1,1,3,3,3-hexafluoroisopropanol equal to 1:2-20 at temperature between 0°C and +60°C. Isomerisation of β-pinene may be carried out in a mixture of 1,1,1,3,3,3-hexafluoroisopropanol and an additional organic solvents, as well as in the presence of a catalyst.

EFFECT: method of producing poly-β-pinene increases efficiency and environmental safety, significantly simplifies the process, increases output of the desired product, improves characteristics on molecular weight, composition and optical activity owing to avoiding the need to use Lewis acids.

4 cl, 1 tbl, 1 ex

Description

The present invention relates to a method for producing poly-β-pinene by acid-free polymerization of β-pinene, one of the representatives of natural terpenes.

Poly-β-pinene (PBP) is one of the most important commercially important polymers of the terpene resin group, which is determined primarily by the availability of the corresponding monomer, β-pinene, which is contained in large quantities in renewable raw materials - turpentine conifers. In the United States, FSN is produced annually at several thousand tons. So, Hercules Inc. (Wilmington, Delawar, USA, www.herc.com) produces various modifications of FBP under the general name Piccolyte S, which are widely used in industry for the production of thermoplastic and pressure-sensitive adhesive additives in the production of adhesives or hot melt adhesives, sealing and insulating materials films for coating biological samples

The characteristics of the resulting PBP, such as the average molecular weight, dispersion, rotation angle of the plane of polarization of light, glass transition temperature and thermal stability can vary widely depending on the nature of the initiator and the polymerization conditions.

The main disadvantages of the methods described in the literature for the preparation of poly-β-pinene by acid polymerization of β-pinene include, first of all, the use of significant amounts of Lewis acids (sometimes in combination with additional activators) as initiators, which necessitates a reaction in an inert atmosphere and elimination of traces of water, as well as the use of water treatment of reaction mixtures, extraction procedures with organic solvents, neutralization and removal of hydrolysis products Lewis acids being operated. All this leads to a noticeable decrease in the yield of PBP and the need for additional purification of the resulting product. These shortcomings not only increase the complexity of the production of FSN, but also create environmental problems due to environmental pollution by the production of FSN. Additional technical difficulties in carrying out the reaction under conditions of cationic initiation are caused by the need to carry out the reaction with strict control of the temperature regime, since the molecular weight of the polymer can significantly decrease with an increase in temperature by 10–20 ° C. In addition, PBP obtained using organic additives as activators necessarily contains a fragment of the activator molecule, which can adversely affect the properties of the product.

A typical example is the preparation of poly-β-pinene by cationic polymerization of β-pinene in an organic inert solvent - a mixture of aromatic hydrocarbons under the action of a Lewis acid, namely AlEt ₃ / H ₂ O, which serves as an initiator in the presence of various cocatalysts, for example, tert -butyl chloride (GDMalpass, Jr., U.S. Patent, 4487901, 1984). The process is carried out as follows: to a solution of 36 mmol AlEt ₃ in 300 ml of a mixture of aromatic hydrocarbons in an inert atmosphere at 0 ° C, 36 mmoles of water are added with stirring over 30 minutes, after which stirring is continued for another 50 minutes. Then the temperature was raised to 23 ° C and 102 g of β-pinene was added and, while stirring, 55 mmol of tert-butyl chloride was added over 60 minutes at such a rate that the temperature did not rise above 50-70 ° C. Next, the reaction mixture is treated with water with vigorous stirring for 5 minutes. The organic layer was separated and washed again with water. The organic phase is further distilled with superheated steam at 240 ° C. The yield of solid polymer is 81%.

The prototype adopted a method of producing poly-β-pinene by cationic polymerization of β-pinene in an inert organic solvent, for example, toluene, under the action of a Lewis acid, namely ethyl aluminum dichloride, which is used as an initiator (C ₂ H ₅ AlCl ₂ ) ( RPFQuine, J.A.A.M. Castro, "Polymerization of β-Pinene with Ethylalumnium Dichloride (C ₂ H ₅ AlCl ₂ )", Journal of Applied Science, 2001, 82, 2558).

The process is carried out as follows: to a solution of 20 g of C ₂ H ₅ AlCl ₂ in 700 ml of toluene, placed in a 3 L reactor, equipped with a stirrer and a cooled jacket, 611.1 g of β-pinene are added in a stream of nitrogen for two hours, maintaining the temperature + 10 ° C. After the addition is complete, stirring is continued for another 90 minutes, after which the mixture is treated with water and the organic layer is separated. The latter is further washed successively with dilute hydrochloric acid, 1% NaOH, 2% citric acid and again with water. After drying over molecular sieves, the solution is carefully filtered through diatomite to remove suspended particles. The solvent was removed by distillation at atmospheric pressure while heating to about 140 ° C, after which the residue was distilled with superheated steam at 200 ° C. Received 315.6 g (yield 52%) of poly-β-pinene in the form of a white powder with an average molecular weight of M _n = 2432.

The main disadvantages of the prototype, as well as the other methods of cationic polymerization described in the literature, include, first of all: a) the use of significant amounts of Lewis acids as initiators, which necessitates the reaction in an inert atmosphere and in the absence of traces of water; b) the need to use a multi-stage procedure for the isolation of the target product, which includes the stages of water treatment of the reaction mixtures, their neutralization and removal of the hydrolysis products of the used Lewis acids, and c) the need for additional purification of the resulting product by distillation with superheated steam. These shortcomings not only increase the complexity of the production of FSN and reduce the yield of the target product, but also create environmental problems due to environmental pollution by production of FSN. In addition, additional difficulties in carrying out the reaction under conditions of cationic initiation are caused by the need to carry out the reaction under strict control of the temperature regime, since, for example, when the temperature is increased by 10-20 ° C, the polymer’s molecular weight can significantly decrease by more than half as shown in the cited paper).

The objective of the present invention is to provide an effective and environmentally friendly method for producing poly-β-pinene, which can significantly simplify the process and increase the yield of the target product due to the elimination of the need to use Lewis acids.

The problem is achieved by the proposed method for producing poly-β-pinene by cationic polymerization of β-pinene in an organic solvent in the presence of an initiator, the distinguishing feature of which is that 1,1,1,3,3 are used as an organic solvent and at the same time a reaction initiator , 3-hexafluoroisopropanol (HFIP).

The process is carried out at a molar ratio of β-pinene: HFIP equal to 1: 2-20 at a temperature from 0 ° C to + 60 ° C. The yield of poly-β-pinene is close to quantitative (95-99%). Isolation of the polymer does not require any processing of the reaction mixture and additional purification steps, but is achieved by simple distillation of the HIPP, which can be regenerated in up to 85% yield.

The polymerization of β-pinene can be carried out in a mixture of HFIP and an additional organic solvent (co-solvent) selected from the group comprising a halogen-substituted hydrocarbon, for example, methylene chloride, or an aromatic hydrocarbon, for example, toluene, which in some cases reduces the amount of applied HFIP to molar ratios of β-pinene: HFIP: organic solvent 1: 2-10: 0.2-2.

It is also possible to polymerize β-pinene in HFIP medium in the presence of a catalyst selected from the group of silicon-containing derivatives, including trimethylsilyl chloride (TMSCl), trimethylsilyl triflate (TMSOTf), which also reduces the amount of HFIP and significantly increases the reaction rate.

The method of polymerization of β-pinene, according to the present invention, is carried out by mixing the monomer with a solvent, in the role of which can be used 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), or a mixture of the latter with cosolvents such as for example, methylene chloride or toluene. The molar ratios of monomer: HFIP can vary from 1: 2 to 1:20; in the case of using cosolvents, the usual ratio of monomer: GFIP: cosolvent = 1: 2-10: 0.2-2. The reaction is carried out with vigorous stirring using a magnetic or mechanical stirrer or, alternatively, using a rotating round-bottom flask of a rotary evaporator. No inert atmosphere or special drying of reagents and solvent is required. The reaction temperature is set using a thermostated bath, and it can vary from 0 ° C to + 20 ° C. It is also possible to carry out the reaction at an elevated temperature (preferably at + 60 ° C), which is achieved by heating the reaction mass at the boiling point of the solvent under reflux. It is also possible to use catalysts, for example, such as trimethylsilyl chloride or trimethylsilyl triflate, which can dramatically reduce the reaction time at temperatures of 0 ° C-5 ° C.

In all cases, the reaction begins almost immediately after the monomer is mixed with the solvent, which manifests itself in the formation of a white emulsion, the density of which increases with time. The completeness of polymerization was monitored according to the data of ¹ H NMR spectra (the disappearance of characteristic β-pinene signals) performed for periodically taken samples. At the end of the reaction, the solvent was removed by evaporation in vacuo (400 mbar). PBP is usually formed as a white powder, which, if necessary, is further dried in vacuo from traces of solvent. The polymer yield usually exceeds 95%.

The essence of the invention lies in the fact that for the first time the ability of fluorinated alcohols to act as both the initiator and the medium for the polymerization of β-pinene in the absence of any additional acid initiators (acid-free initiation, BKI) was discovered. The optimal solvent for the reaction is 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). The reaction proceeds by simple mixing of the monomer with HFIP as such or in the presence of a co-solvent. The reaction temperature can vary from 0 ° to 60 ° C. Isolation of the target polymer does not require any processing of the reaction mixture, but is achieved by simple removal of the solvent, which greatly simplifies the procedure for the isolation of PBP and makes it possible to almost completely regenerate the solvent used. Thus, the whole process of obtaining PBP includes only two separate operations, namely, mixing the reagents and removing the solvent. The polymer yield is usually close to quantitative, and its additional purification is not required; the process is not accompanied by the generation of any waste and therefore can be considered environmentally friendly.

The resulting PBP in its characteristics is not inferior to or even superior to the PBP obtained under standard conditions of cationic polymerization under the action of various Lewis acids. Thus, the weight average molecular weight (M _w ) for a PBP obtained using various Lewis acids can be 2842 (AlCl ₃ , MT Barros, KTPetrova, AMRamos, Potentially Biodegradable Polymers Based on α- or β-Pinene and Sugar Derivatives or Styrene Obtained under Normal Coditions and Microwave Irradiation ", Eur. J. Org. Chem. 2007, 1357), 2400 (EtAlCl ₂ , RPFGuine, JAAMCastro," Polymerization of β-Pinene with EtAlCl ₂ (C ₂ H ₅ AlCl ₂ ) ", J. Appl. Polym. Sci. 2001, 82, 2558) or 1670 (ZrCl ₄ , F. Cataldo, D. Capitani, M. Gobbino, O.Ursini, F. Forlini, "Determination of Chemical Structure of Poly β-Pinene by NMR Spectroscopy ", Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, 2008, 45, 839). For PBP obtained in terms of the BKI, i.e. under the conditions of the proposed method, Mw can range from 2501 to 3847. According to elemental analysis, the composition of such a polymer exactly corresponds to the gross formula C ₂ H ₈ , which indicates the absence of any impurities.

It is also important that the specific rotation of the plane of polarization of light for the samples obtained by us under the conditions of BKI is usually [a] _D = -21-35 °, while for polymerization under the action of Lewis acids it is typical to obtain PBP with [a] _D = -9.3 ° (F. Citaldo, M. Gobbino, O. Ursini, G. Angelini, "A Study on the Optically Active Polymer Polyβ-pinene", J. Macromol. Set, Part A: Pure and Applied Chemistry, 2007, 44 , 1225). These data indicate that, under the conditions of BKI, the possibility of racemization of PBP, which usually occurs when Lewis acids are present in the medium, is sharply suppressed.

The ability of HFIP to act as the initiator of the cationic polymerization of alkenes, equivalent to the traditionally used Lewis acids, is unprecedented and has never been observed before. The unexpectedness of the observed effect is also exacerbated by the fact that, according to Bronsted acidity, the GPI is much weaker than acetic acid and is comparable to phenol, which are absolutely not capable of causing any alkenes to polymerize.

The technical result obtained by the implementation of the proposed method for the production of PBP by polymerization of β-pinene using HFIP as an initiator and a medium consists in simplifying the process technology, since the reaction does not require the use of Lewis acids as additional initiators; polymerization under the conditions of the proposed method does not require careful elimination of traces of moisture and the use of cooling and can be carried out in standard equipment at room temperature; the process involves only two separate operations, namely, mixing the monomer and the solvent and removing the solvent; the isolation of the resulting PBP only requires removal of the solvent, due to which an almost quantitative yield of polymer is obtained, which does not require additional purification, since under the proposed conditions, no side products are formed, and the solvent used can be almost completely regenerated, which makes this process waste-free and environmentally friendly. The advantage of the proposed method is that the PBP samples obtained under the conditions of a BKI, usually have a higher molecular weight and specific rotation of the plane of polarization compared to those obtained under the conditions of reaction initiation by Lewis acids.

Example 1 (experiment 5, table)

To 12.0 g (0.088 mol) of β-pinene, placed in a 500 ml round-bottom flask, rotating on a rotary evaporator (maximum speed) while cooling in an ice bath, 54.0 g (0.33 mol) of cooled HFIP are added over 15 minutes. Turbidity and sedimentation were observed almost immediately with the addition of HFIP. The reaction mixture was kept for 1 hour in an ice bath, the solvent was evaporated on a rotor (400 m bar, 50 ° C), 45.0 g (84%) of HFIP were collected. The residue was dried in vacuo. Received 11.9 g (99%) of the polymer PBP in the form of a white powder. M _w 3182, D 1.27; [α _D ] -35.0 ° (toluene). Elemental analysis: calculated (%) C, 88.16, H, 11.84; Found C, 88.04, H, 11.63. The characteristics of the ¹ H and ¹³ C NMR spectra of the obtained sample correspond to the literature data for PBP, the product of cationic polymerization of β-pinene under standard conditions (F. Cataldo, G. Angelini, D. Capitani, M. Gobbino, O. Ursini, F. Forlini, "Determination of the Chemical Structure of Polyβ-pinene by NMR Spectroscopy", Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, 2008, 45, 839).

Typical examples of the conditions for the acid-free polymerization of β-pinene are given in the table below.

Experience Number The molar ratio: Reaction conditions: Output poly
measure,% M _w (M _w / M _n ) β-pinene GFIP Co-solvent, equiv. Time h Tempera-
round, ° C one one twenty 0.5 twenty > 95 3569 (1.48) 2 one 2 CH ₂ Cl ₂ , 2 6 twenty > 95 2501 (1.63) 3 one 2 Toluene 2 24 twenty 95 2783 (1.51) four one 2 CH ₂ Cl ₂ , 2 four 0-5 0 - 5 one four - one 0-5 99 3182 (1.27) 6 ^a one 2 CH ₂ Cl ₂ , 2 0.5 0-5 > 95 3221 (1.23) 7 ^b one 2 CH ₂ Cl ₂ , 2 0.5 0-5 > 95 2883 (1.65) 8 one 2 - 0.5 60 > 95 3847 (2.08) 9 one 3 CH ₂ Cl ₂ , 0.2 one 0-5 95 3553 (1.46) 10 one 10 - one 0-5 95 3608 (1.24) eleven one 10 CH ₂ Cl ₂ , 0.2 one 0-5 95 4256 (2.18) ^a - in the presence of catalytic amounts (0.01 equivalent) TMSOTf ^b - in the presence of catalytic amounts (0.01 equivalent) of TMSCl

From the above examples it follows that:

a) in pure HFIP, polymerization can be successfully carried out both at room temperature (experiment 1) and at 0 ° C (experiment 5), so; the ratio of β-pinene: HFIP can vary from 1:20 to 1: 4;

b) when methylene chloride is used as a co-solvent, the amount of HFIP used may decrease, but the reaction rate drops sharply at a temperature of 0 ° C and must be carried out at a temperature not lower than room temperature (cf. experiments 4 and 2);

c) the use of catalytic amounts of additives, such as trimethylsilyl chloride or trimethylsilyl triflate, allows the reaction to be carried out efficiently at 0 ° C in the presence of a co-solvent and a decrease in the amount of required HFIP (cf. experiments 6, 7 and 4);

g) the polymerization reaction in HFIP can also be carried out at the boiling point of the solvent; in this case, the reaction proceeds almost instantly (see experiment 8).

Thus, the proposed method for the production of PBP by cationic polymerization of β-pinene is based on the use of HFIP as a medium and initiator, which allows the process to be carried out according to a technically simple scheme and to obtain the target polymer with practically quantitative yield, with improved characteristics in molecular weight, composition and optical activity. The method does not require the use of any additional polymerization initiators; it is effective, methodologically simple, waste-free and environmentally friendly.

Claims (4)

1. The method of producing poly-β-pinene by polymerization of β-pinene in an organic solvent in the presence of an initiator, characterized in that 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) is used as an organic solvent and simultaneously an initiator . 2. The method according to claim 1, characterized in that the polymerization of β-pinene is carried out at a molar ratio of β-pinene: HFIP 1: 2-20 at a temperature of from 0 to + 60 ° C. 3. The method according to claim 1 or 2, characterized in that the polymerization of β-pinene is carried out in a mixture of HFIP and an additional organic solvent selected from the group comprising a halogenated hydrocarbon, aromatic hydrocarbon, with a molar ratio of β-pinene: HFIP: organic solvent 1: 2-10: 0.2-2. 4. The method according to claim 3, characterized in that the polymerization of β-pinene is carried out by additionally introducing a catalyst selected from the group of silicon-containing derivatives, including trimethylsilyl chloride, trimethylsilyl triflate.