WO2018087415A1

WO2018087415A1 - Method for obtaining polymers with isocyanate groups

Info

Publication number: WO2018087415A1
Application number: PCT/ES2017/070751
Authority: WO
Inventors: Helmut Reinecke; Alberto Gallardo Ruiz; Rodrigo Navarro Crespo; Carolina GARCÍA SÁNCHEZ; Tamara MÁRQUES MATESANZ; Carlos Elvira Pujalte
Original assignee: Consejo Superior De Investigaciones Científicas (Csic)
Priority date: 2016-11-11
Filing date: 2017-11-13
Publication date: 2018-05-17
Also published as: ES2671881A1; ES2671881B1

Abstract

The invention relates to a method for obtaining polymers bearing isocyanate groups from amino polymers, with both aromatic and aliphatic amines, in a simple manner and under mild conditions. The polymers bearing isocyanate groups can be used as intermediates that react with compounds comprising amine, alcohol, thiol and carboxylic acid groups, in order to obtain polymers with subsequent alterations.

Description

PROCEDURE FOR OBTAINING POLYMERS WITH ISOCIANATE GROUPS

DESCRIPTION The present invention relates to a process for obtaining polymers bearing isocyanate groups from amino polymers, both with aliphatic and aromatic amines, and simply and under mild conditions. These polymers bearing isocyanate groups can be used as intermediates by reacting with compounds comprising amine, alcohol, thioies or carboxylic acid groups, to obtain polymers with subsequent modifications. Therefore, the present invention belongs to the sector of new functionalized polymeric materials. STATE OF THE TECHNIQUE

The preparation of polymers carrying isocyanate groups (NCO) in the side chain are of great interest due to the high reactivity of this functional group against alcohols, amine, thioies and other groups with active hydrogens. Through the isocyanate groups these polymers can be easily modified, crosslinked or used to connect other chains as grafts.

There are some wine monomers carrying isocyanate groups such as vinyl isocyanate or isopropeniiisocyanate that have been used to form and study the corresponding homopoiimers and copoiimers (Werner Mormann and Kerstin Schmalz, Macromolecules, 27, 71 15-7120 (1994)). Other co-polymers carrying NCO groups have been described with co-monomer carrying the isocyanate group, such as, for example, β-allyloxyethyl isocyanate and 9-decenyl isocyanate (GB Butler and SB Monroe, J. Macromo !. Sci.-Chem., A5 (6), 1057 (1971)), O-isocyanatoethyl methacrylate (RK Graham, J. Polyrn. ScL, 24, 367 (1957)) and N- (6- isocyanate) -hexylacrylamide (B. Voilmert, Angew Makromol. Chem., 3-1, 1 (1968)).

The use of β-styrene isocyanate as a co-monomer in the co-polymerization of styrene and acryionitrile has also been described (A. Liebersohn, DH Kohn, Journal o Applied Polymer Science, 23, 3445-3448 (1979)). In most of the cases described, the polymers obtained have low molecular weights and low isocyanate group contents. For this reason, these materials have had little utility and low impact. On the other hand, in the case of mono- and diamines, the corresponding isocyanates are obtained in general with excellent yields (US6265739B1), well above 90% and the secondary products formed, mainly ureas that form between the isocyanates formed and groups amine still present in the mixture, are easily removed by distillation or recrystallization. In multi-amine compounds such as an aminated polymer, however, urea bonds are formed between different polymer chains, crosslinked and therefore unusable products are obtained.

Therefore, there is a need to find alternative processes of obtaining polymers bearing isocyanate groups simply and under mild conditions.

DESCRIPTION OF THE INVENTION

The present invention relates to a general method for synthesizing, from amine polymers in the side chains, both with primary alliic and aromatic amines, and simply and under mild reaction conditions, polymers with isocyanate groups.

The process of the invention provides for the transformation of the corresponding primary amine groups (-NH ₂ ) and contained in the polymer side chains into isocyanates, preferably using equal amounts of diphosgene or triphosgene, as phosgenating agents, and a soluble tertiary amine such as acid acceptor (scheme 1). The sludge transformation Sos amine groups is carried out simultaneously and instantaneously, as shown by the invariability of the molecular weight of the polymer and the absence of crosslinked products. Therefore, the degree of isocyanation of the polymers formed corresponds to the degree of amination of the starting polymers.

Scheme 1. Scheme of the process of the invention.

Therefore, a first aspect of the present invention relates to a process for obtaining a polymer, preferably linear, carrying isocyanate groups in its side chains, wherein said process comprises the following steps:

to. preparing a polymer solution comprising:

i. a polymer with amino groups in its side chains, which can be both aliphatic and aromatic primary amines, ii. a soluble base in the reaction medium, and

iii. an inert and dry solvent,

where the moles of the base (ii) with respect to one mole of the amino groups of the polymer (i) is greater than 2;

b. adding the polymer solution of step (a) to a phosgenation solution comprising a phosgenation agent selected from triphosgene or diphosgene and an inert and dry solvent; Y

C. wash with cold water (water at a temperature between 0 ° C and 14 ° C, more preferably between 0 ° C and 7 ° C) and dry the organic phase obtained in step (b) and add hexane to precipitate the polymer with isocyanate groups obtained.

The phosgenation agents, trichloromethylchloroformate (diphosgene), a liquid at room temperature and bis (trichloromethylcarbonate (triphosgene), a crystalline substance, are used in the presence of a base to capture the hydrochloric formed during the process. In a preferred embodiment of the process of the invention, the base (ii) of step (a) is a tertiary amine. Preferably the aminated base is selected from triethylamine, diisopropylethylamine or DABCO (1 _< 4-diazabcyclo [2.2.23octane). More preferably the moles of the base (ii) with respect to one mole of the amino groups of the polymer (i) is between 2.0 and 3.5, even more preferably it is between 2.0 and 2.1.

The solvent (iii) of step (a) or solvent of the phosgenation solution of step (a) is any dry and inert solvent that does not contain acidic protons known to any person skilled in the art and which, for example, can be Select from tetrahydrofuran (THF), CHCI ₃ , CH ₂ CI ₂ (DCM), toluene, dioxane, benzene or any combination thereof. In a preferred embodiment, the solvent (iii) of step (a) is THF / DCM, more preferably THF / DCM 1: 4.

In another preferred embodiment, the solvent of the phosgenation solution of step (a) is DCM.

In a preferred embodiment, the amount of phosgene formed by the phosgenating agent is in an equimolar amount with respect to the amino groups of the polymer, therefore, the moles of the phosgenating agent with respect to one mole of the amino groups of the polymer. (i) depend on the phosgenation agent used. If the phosgenation agent is triphosgene, the amount of phosgenation agents used will be 0.333 mol of triphosgene per mol of the polymer amino groups. In the event that the phosgenation agent is biphosgene, 0.5 mol of bisphosgene per mol of the amino groups of the polymer will be needed. In another preferred embodiment, step (b) is carried out at a temperature between -30 ° C and 80 ° C, more preferably 0 ^s C-20 ° C.

The aminated polymer (i) of step (a) may be selected from the list comprising, aminated polyepichlorohydrin, aminated polyethylene glycol, aminated polyvinyl pyrrolidone, aminated vinyl polychloride, aminated polyacrylate, aminated polyalkylacrylate, aminated, aminoalkylated or aminochlorinated polystyrene, and any combination thereof in the form of copolymers.

The polymers bearing side chain isocyanate groups obtained by the process described in the present invention can be used as intermediates to obtain polymers with subsequent modifications, due to the high reactivity of this functional group against compounds containing groups with active hydrogens, as for example but not limited to compounds with at least one amine group, primary or secondary (-NH ₂ or -NR'H, where R 'can be a C _r C ₆ alkyl group or an aryl group), alcohol (-OH ), thiol (-SH) or carboxylic acid (-COOH).

Therefore, a second aspect of the present invention relates to a process for obtaining functionalized linear polymers comprising the reaction between a polymer with isocyanate groups in its side chains obtained by the process described in the present invention and a reagent containing groups with active hydrogens selected from amine groups, alcohols, thiols or carboxylic acid.

A particular embodiment of the previous aspect of the present invention relates to a process for obtaining a linear polymer with urea groups in its side chains, wherein said process comprises:

to. obtaining a polymer with isocyanate groups in its side chains by the process of the first aspect of the present invention described above;

b. dissolve the polymer obtained in (a) in a neutral solvent and add an amine, preferably a mono-, dialkyl- or aryl amine, more preferably diethylamine at a temperature between 0 ° C and 120 ° C, preferably 60 ° C, during a time between 10 minutes and 2 hours; C. precipitate the polymer obtained in (b), and

d. purify the polymer obtained in (c) by three dissolution-precipitation cycles in the appropriate solvents.

Throughout the description and the claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be derived partly from the description and partly from the practice of the invention. The following examples and figures are provided by way of illustration, and are not intended to be limiting of the present invention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1.- FTIR-ATR spectra of PVC, aminated PVC and PVC carrying NCO groups.

FIG. 2.- H-NMR of PVC-NH ₂ -8% converted through PVC-NCO-8% into PVC- N (CH ₂ CH ₃ ) ₂

EXAMPLES

The invention will now be illustrated by tests carried out by the inventors, which demonstrates the effectiveness of the product of the invention.

Example 1.- Preparation of PVC-NH ₂ -10%: 1 gram (0.016 mol) of PVC (polyvinyl chloride) was dissolved in 20 ml of THF and add 80 ml of acetone. To this was added a solution of 200 mg (0.0016 mol) of amino thiophenol and 64 mg (0.0016 mol) of NaOH (powder) in 10 ml of ethanol and the mixture was heated, under a flow of nitrogen, for 15 hours at 80 ° C. The mixture was then precipitated in methanol and purified the precipitated polymer using three solution / precipitation cycles in THF / MeOH. After drying, 1.1 g of a PVC was obtained in which approximately 10 mol% of the chlorides were replaced by aliphatic primary amine groups.

Example 2.- Preparation of PVC-NCO-10%: 1 gram (14 mmol) of PVC-NH ₂ -10% obtained in example 1 was dissolved in 20 ml of dry THF and 80 ml of dichloromethane and 0, 4 ml (2.8 mmol) of triethylamine. This solution was added at room temperature under stirring to a solution of 140 mg (0.5 mmol) of triphosgene in 10 ml of dichloromethane. After one minute the reaction mixture was washed twice with water / ice to remove the quaternary salts formed, the organic phase was dried with MgSO ₄ and the solution precipitated in hexane. The modified polymer was isolated by centrifugation or filtration and about 800 mg of PVC-NCO-10% was obtained after drying (FIG. 1). Example 3.- Preparation of PVC-NHCON (C ₂ H ₅ ) 2-8%: 1 gram (14 mmol) of PVC-NH ₂ -8% was transformed into PVC-NCO-8% under the same conditions as in the Example 2 above and dissolved in 50 ml of absolute THF. 10 mg (1.4 mmol) of diethylamine was added and stirred at 60 ° C for 3 hours. It was then precipitated in methanol and purified the polymer obtained with three dissolution-precipitation cycles in THF-methanol (MeOH). 1 g of a PVC-NHCON (C ₂ H ₅ ) ₂ -8% polymer whose H-NMR is shown in FIG. 2.

The above examples are shown in the following reaction scheme:

Scheme 2: a) Preparation of aminated PVC and subsequent phosgenation to PVC with isocyanate group, b) transformation of the polymer carrying isocyanate groups to PVC carrying urea groups. In this reaction (a) using PVC carrying aromatic primary amine groups, it was obtained by a nucleophilic substitution reaction of 8 mol% of the chlorine atoms by aminothiophenol.

In order to achieve the objective of a quantitative transformation of all the amine groups and to obtain a linear and soluble polymer carrying isocyanate groups, a series of experiments have been carried out using different experimental conditions. In particular, a 15% by weight solution of phosgene in toluene, diphosgene and triphosgene was used as a phosgenating agent using different stoichiometries with respect to the number of amino groups in the aminated polymer. In addition, different types and amounts of base needed to capture the hydrochloric formed during the reaction were used. The experimental conditions tested they are summarized in table 1 and correspond to the same synthesis protocol described in example 2.

Table 1: Experimental conditions used to transform 8 mol% PVC carrying aromatic primary amine groups into a polymer carrying isocyanate groups.

diazabicyclo [2.2.2] octane.

The phosgenations were carried out in dry 1: 4 mixtures of THF / CH ₂ CI ₂ . It is essential to add the polymer / base solution to the solution containing the phosgenating agent and not vice versa. After the addition, it was diluted with CH ₂ CI ₂ and extracted twice with cold water to remove the quaternary salts formed during the reaction between the base and the hydrochloric acid. The organic phase was then dried and the modified hexane polymer precipitated. It is concluded that it is not possible to achieve soluble polymers using phosgene in solution, even using a large excess with respect to the number of amine groups. On the other hand, the use of 0.5 mol / mol diphosgene amine as a precursor of two phosgene equivalents or 0.35 mol / triphosgene amine as a precursor of three phosgene equivalents allows quantitative transformation of all polymer amine groups in isocyanate groups when there is a minimum of two equivalents of a soluble base in the reaction medium. Using a slight base defect or the use of a base that is not soluble in the medium, such as Na ₂ C0 ₃ , the desired products are not achieved.

Claims

CLAIMS 1. Process for obtaining a linear polymer with isocyanate groups in its side chains, where said process comprises the following steps: a. preparing a polymer solution comprising:

i. a polymer with amino groups in its side chains,

ii. a base, soluble in the reaction medium, and

iii. an inert and dry solvent,

C. wash with water at a temperature between 0 ° C and 14 ° C, dry the organic phase obtained in step (b) and add hexane for precipitation of the polymer with isocyanate groups obtained.

2. Method according to claim 1, wherein the base (ii) of step (a) is a tertiary amine.

3. The method according to claim 2, wherein the base is selected from triethylamine, diisopropylethylamine or DABCO (1,4-diazabicyclo {2.2.2] octane).

4. Process according to any one of claims 1 to 3, wherein the moles of the base (ii) with respect to one mole of the amino groups of the polymer (i) is between 2.0 and 3.5.

5. Process according to claim 4, wherein the moles of the base (ii) with respect to one mole of the amino groups of the polymer (i) is between 2.0 and 2.1.

Method according to any one of claims 1 to 5, wherein the solvent (iii) of step (a) or the solvent of the phosgenation solution of step (a) is selected from THF, CHCI ₃ , CH ₂ CI ₂ , toluene, dioxane, benzene or any combination thereof.

7. Process according to any one of claims 1 to 6, wherein the solvent (iii) of step (a) is THF / DCM and / or the solvent of the phosgenation solution of step (a) is DCM.

8. Process according to any one of claims 1 to 7, wherein the moles of phosgene from the phosgenation agent are in an equimolar amount with respect to the amino groups of the polymer (i).

9. Method according to any of claims 1 to 8, wherein step (b) is carried out at a temperature between -30 ° C and 80 ° C, more preferably between 0 ° C and 30 ° C.

10. The method according to any one of claims 1 to 9, wherein the aminated polymer of step (a) is selected from the list comprising aminated polyepichlorohydrin, aminated polyethylene glycol, aminated polyvinyl pyrrolidone, aminated polyvinyl chloride, aminated polyacrylate, aminated polyalkylacrylate, polystyrene aminated, aminoalkylated or aminochlorinated and any of its copolymers.

1 1. Process for obtaining functionalized linear polymers comprising the reaction between a polymer with isocyanate groups in its side chains obtained by the method described according to any of claims 1 to 10 and a reagent containing a group with active hydrogens selected from amine groups, alcohols, thiols or carboxylic acid.

12. Method of obtaining a linear polymer with urea groups in its side chains, wherein said process comprises:

to. obtaining a polymer with isocyanate groups in its side chains by the method described according to any one of claims 1 to 10;

b. dissolve the polymer obtained in (a) in a neutral solvent and add an amine at a temperature between 0 ° C and 120 ° C for a time between 10 mn and 2 h;

C. precipitate the polymer obtained in (b); Y

d. purify the polymer obtained in (c) by three dissolution-precipitation cycles.