PROCESS FOR PREPARING PREPOLYMERS THAT COMPRISE A POLYOXYMETHLYENE BLOCK

Abstract

The invention relates to a process for preparing prepolymers that comprise a polyoxymethylene block. The invention also relates to prepolymers that can be obtained by said process and to mixtures of the prepolymers with OH-reactive compounds, preferably polyisocyanates. The invention further relates to a chemical-technical process for preparing a chemical product of defined composition.

Claims

1. A process for preparing a prepolymer comprising a polyoxymethylene block, comprising: i) preparing a formaldehyde solution (a) by adding a solvent to polymeric formaldehyde in a first container; ii) withdrawing the formaldehyde solution prepared in step i) from the first container and transferring it to a second container containing OH-reactive compound to form a solution (b) containing the prepolymer; iii) distillatively recycling the solvent from the second container to the first container; wherein the polymeric formaldehyde has m terminal hydroxyl groups; wherein m is a natural number of two or more, wherein the OH-reactive compound has m terminal OH-reactive groups; wherein the solvent contains no OH-reactive functional groups and does not itself react with OH-reactive compounds; wherein the solution (b) in step ii) has a temperature in the second container of not more than 80° C.; and wherein the temperature of the formaldehyde solution (a) in the first container in step i) is not more than the temperature of the solution (b) in the second container.

2. The process as claimed in claim 1, wherein in step i) the solvent is added to the first container discontinuously or continuously.

3. The process as claimed in claim 1, wherein the formaldehyde solution prepared in step ii) is withdrawn from the first container discontinuously or continuously.

4. The process as claimed in claim 1, wherein in step iii) the solvent is recycled from the second container to the first container discontinuously or continuously.

5. The process as claimed in claim 1, wherein the solvent used in step i) comprises an aprotic solvent.

6. The process as claimed in claim 5, wherein the aprotic solvent has a boiling temperature of not more than 80° C. at 1 bara.

7. The process as claimed in claim 5, wherein the aprotic solvent comprises n-pentane, n-hexane, n-heptane, petroleum ether, carbon disulfide, carbon dioxide, trichlorethylene, methylene chloride, carbon tetrachloride, chloroform, trichlorofluoromethane, tetrabromomethane, bromodichloromethane, fluorobenzene, 1,4-difluorobenzene, dichlorofluoromethane, difluorodichloromethane, chlorodifluoromethane, ethyl acetate, isopropyl acetate, methyl formate, ethyl formate, isopropyl formate, propyl formate, acetaldehyde dimethyl acetal, acetonitrile, methyl tert-butyl ether, tert-butyl ethyl ether, tert-amyl methyl ether, methyl propyl ether, sec-butyl methyl ether, butyl methyl ether, methyl n-propyl ether, 1-ethoxypropane, 1,3-dioxolane, 1,1-dimethoxyethane, diisopropyl ether, 2-methyl-tetrahydrofuran, 2,2-dimethoxypropane, dimethyl ether, dimethoxymethane, ethyl methyl ether, diethyl ether, diethoxymethane, dimethoxyethane, tetrahydrofuran, 1,4,7,10-tetraoxacyclododecane ([12]crown-4), acetone, methyl ethyl ketone, or a combination of any two or more thereof.

8. The process as claimed in claim 1, wherein the OH-reactive compound comprises a dicarboxylic acid, a tricarboxylic acid, a dicarboxylic acid chloride, a tricarboxylic acid chloride, a dicarboxylic acid azide, a tricarboxylic acid azide, a dicarboxylic acid anhydride, a tricarboxylic acid anhydride, an organic diazide, an organic triazide, a diepoxide, a triepoxide, a halomethyloxirane, a diaziridine, a triaziridine, a disilyl chloride, a trisilyl chloride, a disilane, a trisilane, an n-alkyldi(magnesium halide), an n-alkyltri(magnesium halide), a disulfonyl chloride, a trisulfonyl chloride, an organic di(chlorosulfite), an organic tri(chlorosulfite), an organic di(phosphorus dibromide), an organic tri(phosphorus dibromide), a polythiocyanate, a polyisocyanate, or a combination of any two or more thereof.

9. The process as claimed in claim 8, wherein the OH-reactive compound comprises a polyisocyanate and the reaction is performed at an NCO index of ≥100 to ≤5000 to afford an NCO-terminated prepolymer.

10. The process as claimed in claim 9, wherein the polyisocyanate comprises 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 2-methyl-1,5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4-trimethyl-1,6-diisocyanatohexane, 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, 4,4′-diisocyanatodicyclohexylmethane, 4-isocyanatomethyl-1,8-octane diisocyanate, ω,ω′-diisocyanato-1,3-dimethylcyclohexane, 1-isocyanato-1-methyl-3-isocyanatomethylcyclohexane, 1-isocyanato-1-methyl-4-isocyanatomethylcyclohexane, bis(isocyanatomethyl)norbornane, 1,5-naphthalene diisocyanate, 1,3-bis(2-isocyanato-prop-2-yl)benzene, 1,4-bis(2-isocyanato-prop-2-yl)benzene, 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 2,4′-diisocyanatodiphenylmethane, 4,4′-diisocyanatodiphenylmethane, 1,5-diisocyanatonaphthalene, 1,3-bis(isocyanatomethyl) benzene, any desired mixtures of any two or more of the foregoing compounds, polyfunctional isocyanates obtained by dimerization or trimerization or higher oligomerization of any of the foregoing isocyanates containing isocyanurate rings, iminooxadiazinedione rings, uretdione rings, urethonimine rings, or a combination of any two or more thereof, polyfunctional isocyanates obtained through adduct formation of any of the foregoing isocyanates onto mixtures of different more than difunctional alcohols, or a combination of any two or more thereof.

11. A prepolymer comprising polyoxymethylene block prepared as claimed in claim 1, having a number-average number of polyoxymethylene repeating units of 2 to 50, wherein the number of polyoxymethylene repeating units is determined by proton resonance spectroscopy.

12. The prepolymer comprising polyoxymethylene block as claimed in claim 11, wherein the prepolymer comprising polyoxymethylene block is an NCO-terminated prepolymer having a content of reactive isocyanate groups of ≥4% by weight to ≤25% by weight based on the mass of the prepolymer comprising polyoxymethylene block of the isocyanate groups in the prepolymer comprising polyoxymethylene block, wherein the content of reactive isocyanate groups is determined by NMR spectroscopy by derivatization with methanol.

13. A mixture comprising the prepolymer comprising polyoxymethylene block as claimed in claim 11 and an OH-reactive compound.

14. The mixture as claimed in claim 13, wherein the mixture has a content of reactive isocyanate groups of ≥4% by weight to ≤50% by weight based on the total proportion of the isocyanate groups, wherein the content of reactive isocyanate groups is determined by NMR spectroscopy by derivatization with methanol.

15. An industrial chemical process for preparing a product of defined composition comprising: i) preparing, in a first container, a reactant solution by adding a solvent to a reactant having a solubility of <1 g/L and a melting point not less than its decomposition point, ii) withdrawing the reactant solution prepared in step i) from the first container and transferring it to a second container containing a compound reactive with the reactant to form a solution containing the product, and iii) distillatively recycling the solvent from the second container into the first container, wherein the solution containing the product in step ii) has a temperature in the second container of not more than 150° C.; wherein the temperature in the first container in step i) is not more than the temperature in the second container; and wherein the solvent does not react with the reactant, the compound reactive with the reactant and the product.

Description

EXAMPLES

Employed Compounds:

[0099] pFA-1: Paraformaldehyde (trade name: Granuform® 91 (formaldehyde content according to manufacturer 89.5-92.5%), INEOS Paraform GmbH & Co. KG). [0100] pFA-2: Paraformaldehyde (Granuform® M, (formaldehyde content according to manufacturer in each case 94.5-96.5%), INEOS Paraform GmbH & Co. KG).

[0101] Dimethoxymethane, DMM (99.9%, Sigma-Aldrich Chemie GmbH, dried over CaH.sub.2, distilled and stored over 4 A molecular sieve)

[0102] HDI (Desmodur H, >99%, Covestro Deutschland AG, no pretreatment)

[0103] TDI (Desmodur T 100, toluene 2,4-diisocyanate, >99%, Covestro Deutschland AG, no pretreatment)

[0104] IPDI (Isophorone Diisocyanate, 98%, Sigma-Aldrich Chemie GmbH, no pretreatment)

[0105] n-pentane (>99%, Sigma-Aldrich Chemie GmbH, distilled and stored over 3 A molecular sieve)

[0106] Methanol (99.8%, Sigma-Aldrich Chemie GmbH, dried over 3 A molecular sieve)

[0107] CDCL.sub.3 (99.80% D, Euriso-Top GmbH, dried over 4 A molecular sieve)

[0108] DMSO-d6 (99.80% D, Euriso-Top GmbH, dried over 4 A molecular sieve)

[0109] CH.sub.2Cl.sub.2 (>99.8%, Sigma-Aldrich Chemie GmbH, dried over 4 A molecular sieve)

Method Description:

[0110] Reactive soxhlet extraction: Continuous preparation of the NCO-terminated prepolymer comprising a polyoxymethylene block may employ a laboratory apparatus according to FIG. 2 consisting of a flask (second container (cf. FIG. 2 (c))) containing the solvent and the OH-reactive compound, an extraction attachment (Soxhlet extractor, first container, cf. FIG. 2 (a)) and a reflux condenser. Arranged in the Soxhlet extractor is a solid extraction thimble made of cellulose which contains the polymeric formaldehyde compound as the solid to be extracted. The solvent in the flask is partially evaporated; the condensate continuously fills the extractor and extraction thimble and soluble constituents accumulate in the solvent. As soon as the solution in the Soxhlet extractor reaches a level specified by a laterally arranged siphon, the extractor empties all at once into the round bottom flask (second container) therebelow. There the solvent is distilled off from the soluble constituents, ascends through the Soxhlet extractor, condenses in the reflux condenser (cf. FIG. 2 (c)) and runs into the extractor/the extraction thimble (cf. FIG. 2 (b)). In this way the solvent is recycled over a longer period of time, a small amount of soluble constituents of the solid always being transferred to the lower flask (cf. E. Fanghanel: Organikum, 22nd Ed., WILEY-VHC Verlag GmbH, Weinheim, 2004, page 540. In the lower flask the extracted solid will be reacted with a reaction partner (for example OH-reactive compound), i.e. a special form of combination of extraction and reaction will be carried out. The reaction of the extracted substance with the OH-reactive compounds is carried out with and without a catalyst. A possible industrial embodiment of this special form of reactive Soxhlet extraction is shown in FIG. 2.

[0111] .sup.1H NMR spectroscopy: The measurements were performed using a Bruker AV400 (400 MHz) instrument; the chemical shifts were calibrated relative to the residual proton signal (CDCl.sub.3: δ .sup.1H=7.26 ppm, DMSO-d6: δ .sup.1H=2.50 ppm); the multiplicity of the signals was indicated as follows: s=singlet, m=multiplet, b=broadened signal, cr=complex region (superimposed multiplets).

[0112] .sup.13C NMR spectroscopy: The measurements were performed using a Bruker AV400 (100 MHz) instrument; the chemical shifts were calibrated relative to the solvent signal (CDCl.sub.3: δ .sup.13C=77.16 ppm, DMSO-d6: δ .sup.13C=39.52 ppm);

[0113] Polyoxymethylene group content: The content of polyoxymethylene groups n in the NCO prepolymer was determined using .sup.1H-NMR spectroscopy. The relative contents of the individual groups were determined by integration of the characteristic proton signals. The characteristic signals of the polyoxymethylene groups directly adjacent to the carbamate unit (δ .sup.1H 5.34, 4H, OCH.sub.2*) are shifted downfield compared to those of the internal polyoxymethylene groups (δ .sup.1H 4.83, n H, OCH.sub.2). Once the integral of the OCH.sub.2* signal has been normalized to four the content of polyoxymethylene groups n in the NCO prepolymer may be calculated via the following formula:

[00001]$n-=\frac{\mathrm{Integral}\left({\mathrm{OCH}}_2\right)+4}{2}$

[0114] Characteristic proton signals of the polyoxymethylene groups directly adjacent to the carbamate unit correlate with the .sup.13C-NMR signals of the carbamate C═O units:

[0115] .sup.1H/.sup.13C HMBC-NMR (400/100 MHz, DMSO-d6, 298 K; selected cross-resonance) δ .sup.1H/δ .sup.1H/.sup.13C [ppm]: 5.34/153.07 (4H, OCH.sub.2*/C═O).

[0116] NCO content determination by isocyanate derivatization with MeOH: To determine the NCO contents the reactive NCO groups of the prepolymers were initially derivatized with excess methanol to afford the corresponding carbamate species. The product mixture was largely freed of solvent, admixed with an excess of dry methanol and stirred at 60° C. for 2 h. After thorough removal of the excess methanol under high vacuum the NCO content was determined by NMR spectroscopy by integration of the characteristic proton signals of the terminal methoxy groups (—OMe). To this end 40 mg of the prepolymer were dissolved in 0.5 mL of DMSO-d6 and admixed with a defined amount of a dry dichloromethane standard (integral=1). A .sup.1H-NMR spectrum of this mixture was recorded with 64 scans, the ratios of the corresponding fragments (—OMe [δ .sup.1H 3.80-3.45 ppm], CH.sub.2Cl.sub.2 [δ.sup.1H 5.76 ppm]) determined by integration and the NCO content calculated via the following formula:

[00002]$\mathrm{NCO}\mathrm{content}\left[\%\right]=\frac{\left(\frac{\mathrm{Integral}\left(\mathrm{OMe}\right)}{1.5\times \mathrm{Integral}\left(\mathrm{DCM}\right)}\right)\times m\mathrm{mol}\mathrm{DCM}}{\mathrm{mg}\mathrm{sample}}\times {\mathrm{MW}}_{\mathrm{NCO}\mathrm{group}}\times 100$

Example 1: Reaction of pFA-2 (INEOS, Granuform® M) with DMM and Toluene 2,4-Diisocyanate (TDI) by Reactive Soxhlet Extraction

[0117] Paraformaldehyde pFA-2 (Granuform® M, 10.5 g) was initially charged in the extraction thimble of a Soxhlet extractor. By Soxhlet extraction with dimethoxymethane (DMM for short) as solvent (200 ml) polymeric formaldehyde was extracted under reflux (60° C. oil bath temperature) and reacted with an excess of TDI (12.1 g) in the flask therebelow. After an extraction time of 66 hours the solvent was removed under reduced pressure, the residue was washed with dried n-pentane and the reaction product was obtained as a colorless solid.

[0118] According to the .sup.1H NMR spectrum the obtained NCO-terminated prepolymer has on average 12 oxymethylene units and the molecular weight calculated therefrom (MW.sub.calc) is thus 726.7 g/mol. The presence of urethane groups was determined via characteristic cross-resonances in the .sup.1H/.sup.13C HMBC NMR spectrum. Characteristic bands in the IR spectrum show the presence of NCO and carbamate functionalities. The NCO content was determined by derivatization of the free isocyanate groups with MeOH and subsequent integration of characteristic signals in the 41 NMR spectrum.

Characterization:

[0119] .sup.1H NMR (600 MHz, DMSO-d6, 298 K) δ [ppm]: 7.24 (m br, 6H, H.sub.Ar), 5.34 (m, 4H, OCH.sub.2), 4.83 (m, 20H, OCH.sub.2′), 2.34-1.86 (s, 6H, Me).

[0120] .sup.1H/.sup.13C HMBC NMR (600/150 MHz, DMSO-d6, 298 K; selected cross-resonance) δ.sup.1H/δ .sup.13C [ppm]: 5.34/153.07 (OCH.sub.2/CO).

[0121] IR: v (cm.sup.−1)=2251 (s, NCO), 1702 (s, .sup.NHCO).

[0122] NCO content: 18% by weight.

Example 2: Reaction of pFA-1 (INEOS, Granuform® 91) with DMM and Toluene 2,4-Diisocyanate (TDI) by Reactive Soxhlet Extraction to Afford the NCO-Terminated Prepolymer

[0123] The reaction, workup and analysis were performed analogously to example 1 with the exception that pFA-1, Granuform 91® (10.5 g) was employed as the starting material.

[0124] According to the .sup.1H NMR spectrum the obtained NCO prepolymer has on average 8 oxymethylene units and the molecular weight calculated therefrom (MW.sub.calc.) is thus 606.6 g/mol. The presence of urethane groups was determined via characteristic cross-resonances in the .sup.1H/.sup.13C HMBC NMR spectrum. Characteristic bands in the IR spectrum show the presence of NCO and carbamate functionalities. The NCO content was determined by derivatization of the free isocyanate groups with MeOH and subsequent integration of characteristic signals in the .sup.1H NMR spectrum.

Characterization:

[0125] .sup.1H NMR (400 MHz, DMSO-d6, 296 K) δ [ppm]: 7.78-6.79 (m br, 6H, H.sub.Ar), 5.35 (m, 4H, OCH.sub.2), 5.01-4.72 (m, 20H, OCH.sub.2′), 2.34-1.86 (s, 6H, Me).

[0126] .sup.1H/.sup.13C HMBC NMR (400/100 MHz, DMSO-d6, 298 K; selected cross-resonance) δ .sup.1H/δ .sup.13C [ppm]: 5.35/152.4 (OCH.sub.2/CO).

[0127] IR: v (cm.sup.−1)=2251 (s, NCO), 1702 (s, .sup.NHCO).

[0128] NCO content: 21% by weight.

Example 3 (Comparative): Reaction of pFA-2 (INEOS, Granuform® M) with Toluene 2,4-Diisocyanate (TDI) without Solvent Addition Under Reflux Conditions

[0129] pFA-2 (Granuform® M, 10.5 g) and TDI (12.1 g) were transferred to a Schlenk flask under argon and the resulting white suspension was stirred at 60° C. for 66 hours. This afforded a hard white solid which could no longer be stirred. The undefinable polymeric solid was mechanically comminuted, washed with hexane and dried under vacuum. The resulting residue was admixed with dry dichloromethane and filtered. The filtrate was then freed of solvent under reduced pressure. NMR spectroscopic analyses of the resulting white solid indicate a highly complex mixture which cannot be further characterized.

Example 4 (comparative): Reaction of pFA-1 (INEOS, Granuform® 91) with DMM and Toluene 2,4-Diisocyanate (TDI) Under Reflux Conditions

[0130] pFA-1 (10.5 g), dimethoxymethane (200 mL) and TDI (12.5 g) were transferred to a Schlenk flask under argon. The resulting white suspension was stirred under reflux (60° C. oil bath temperature) for 66 hours. The solvent was then removed under reduced pressure and the residue was washed multiple times with dry n-pentane. The obtained residue is a complex mixture of various components which cannot be further characterized. NMR spectroscopic analyses suggest that the chosen experimental conditions result in formation of monomeric formaldehyde which reacts with TDI to afford undefined adducts.

Example 5: Reaction of pFA-2 (INEOS, Granuform® M) with DMM and Toluene 2,4-Diisocyanate (TDI) by Reactive Soxhlet Extraction to Afford the Mixture of NCO-Terminated Prepolymer and TDI

[0131] The reaction was carried out analogously to Example 1 with the exception that a little less TDI (10.0 g) was used and the reaction product was not freed of excess TDI by washing after removing the solvent.

[0132] According to the .sup.1H NMR spectrum the obtained mixture of NCO-terminated prepolymer and unreacted TDI (NCO semi-prepolymer) has on average 9 oxymethylene units and the molecular weight calculated therefrom (MW.sub.calc) is thus 636.6 g/mol. The presence of urethane groups was determined via characteristic cross-resonances in the .sup.1H/.sup.13C HMBC NMR spectrum. Characteristic bands in the IR spectrum show the presence of NCO and carbamate functionalities. The NCO content was determined by derivatization of the free isocyanate groups with MeOH and subsequent integration of characteristic signals in the .sup.1H NMR spectrum.

Characterization:

[0133] .sup.1H NMR (400 MHz, DMSO-d6, 296 K) δ [ppm]: 7.78-6.79 (m br, 6H, H.sub.Ar), 5.35 (m, 4H, OCH.sub.2), 5.01-4.72 (m, 16H, OCH.sub.2′), 2.34-1.86 (s, 6H, Me) [NCO prepolymer].

[0134] 7.50 (s, 1H, H.sub.Ar), 7.17 (dm, .sup.3J.sub.HH=8.3 Hz, 1H, H.sub.Ar), 7.06 (d .sup.3J.sub.HH=8.3 Hz, 1H, H.sub.Ar), 2.12 (s, 3H, CH.sub.3) [TDI].

[0135] [GHG-260-FOR]

[0136] .sup.1H/.sup.13C HMBC NMR (400/100 MHz, DMSO-d6, 298 K; selected cross-resonance) δ .sup.1H/δ .sup.13C [ppm]: 5.35/152.3 (OCH.sub.2/CO).

[0137] IR: v (cm.sup.−1)=2251 (s, NCO), 1702 (s, .sup.NHCO).

[0138] NCO content: 32% by weight.

Example 6: Reaction of pFA-2 (INEOS, Granuform® M) with DMM and Hexamethylene Diisocyanate (HDI) by Reactive Soxhlet Extraction to Afford the NCO-Terminated Prepolymer

[0139] The reaction, workup and analysis were performed analogously to example 1 with the exception that HDI (9.64 g) was employed instead of TDI.

[0140] According to the 1H NMR spectrum the NCO prepolymer has on average 8 oxymethylene units and the molecular weight calculated therefrom (MWcalc.) is thus 606.6 g/mol. The presence of urethane groups on oxymethylene units was determined via characteristic cross-resonances in the 1H/13C HMBC NMR spectrum. Characteristic bands in the IR spectrum show the presence of NCO and carbamate functionalities. The NCO content was determined by derivatization of the free isocyanate groups with MeOH and subsequent integration of characteristic signals in the 1H NMR spectrum.

[0141] Characterization:

[0142] .sup.1H NMR (400 MHz, DMSO-d6, 296 K) δ [ppm]: 7.34 (m, 2H, NH), 5.19 (m, 4H, OCH.sub.2), 4.78 (m, 12H, OCH.sub.2′), 3.33 (m, 4H, .sup.NCOCH.sub.2), 3.13 (m, 4H, .sup.NHCH.sub.2), 1.54 (m, 4H, CH.sub.2), 1.35 (m, 12H, CH.sub.2′).

[0143] .sup.1H/.sup.13C HMBC NMR (600/150 MHz, DMSO-d6, 298 K; selected cross-resonance) δ .sup.1H/δ .sup.13C [ppm]: 5.35/155.1 (OCH.sub.2/CO).

[0144] IR: v (cm.sup.−1)=2251 (s, NCO), 1702 (s, .sup.NHCO).

[0145] NCO content: 16% by weight.

Example 7: Reaction of pFA-1 (INEOS, Granuform® M) with DMM and Isophorone Diisocyanate (IPDI) by Reactive Soxhlet Extraction to Afford the NCO-Terminated Prepolymer

[0146] Paraformaldehyde pFA-1 (Granuform® M, 15 g) was initially charged in the extraction thimble of a Soxhlet extractor. By Soxhlet extraction with dimethoxymethane as solvent (200 ml) soluble pFA oligomers were extracted under reflux (52° C. oil bath temperature) and reacted with an excess of IPDI (4.72 g) in the flask therebelow. After an extraction time of 138 hours the solvent was removed under reduced pressure, the residue was washed with dried n-pentane and the reaction product was obtained as a colorless solid.

[0147] According to the .sup.1H NMR spectrum the NCO prepolymer has on average 10 oxymethylene units and the molecular weight calculated therefrom (MW.sub.calc.) is thus 762.6 g/mol. The presence of urethane groups on oxymethylene units was determined via characteristic cross-resonances in the .sup.1H/.sup.13C HMBC NMR spectrum. Characteristic bands in the IR spectrum show the presence of NCO and carbamate functionalities. The NCO content was determined by derivatization of the free isocyanate groups with MeOH and subsequent integration of characteristic signals in the .sup.1H NMR spectrum.

[0148] Characterization:

[0149] .sup.1H NMR (400 MHz, DMSO-d6, 298 K) δ [ppm]: 7.34 (m, 2H, NH), 5.24 (m, 4H, OCH.sub.2), 4.80 (m, 17H, OCH.sub.2′), 3.89-3.03 (cr, 6H, .sup.NCH & .sup.NCH.sub.2), 1.88-1.10 (cr, 12H, CH.sub.2), 1.07-0.75 (m, 18H, CH.sub.3). .sup.1H/.sup.13C HMBC NMR (400/100 MHz, DMSO-d6, 299 K; selected cross-resonance) δ .sup.1H/δ .sup.13C [ppm]: 5.24/153.4 (OCH.sub.2/CO).

[0150] IR: v (cm.sup.−1)=2251 (s, NCO), 1702 (s, .sup.NHCO).

[0151] NCO content: 17% by weight.

Example 8 (Comparative): Reaction of pFA-1 (INEOS, Granuform® M) with Toluene Diisocyanate (TDI) According to Example 2 from U.S. Pat. No. 3,575,930 A1

[0152] Paraformaldehyde pFA-2 (Granuform® M, 10 g) was boiled in a flask with 90 g of dioxane for 2 minutes and filtered. The resulting solution was admixed with 20 mL of benzene and dried by azeotropic distillation. 16.7 g of TDI were then added and the reaction mixture was heated to 91° C. over 6 h. In contrast to example 2 from U.S. Pat. No. 3,575,930 A1 it was not possible to directly filter off any polymeric product from the reaction solution. Even after removal of the volatile constituents at 35° C. and 10 mbar no polymeric product or NCO prepolymer was obtained. The 41 NMR spectrum of this yellow residue showed only signals attributable to TDI. No build-up of polymers having NCO groups or NCO prepolymers was able to be observed.

Characterization:

[0153] .sup.1H NMR (400 MHz, DMSO-d6, 298 K) δ [ppm]: 7.27-7.20 (m, 2H, H.sub.Ar), 7.06-7.04 (m, 1H, H.sub.Ar), 2.26 (s, 3H, CH.sub.3).

TABLE-US-00001 OH-reactive Step Step M.sub.W(calc.) NCO Example pFA LM compound ii).sup.a) iii).sup.b) n.sup.c) [g/mol] [% by wt.] 1 2 DMM TDI yes yes 12  726.7 18 2 1 DMM TDI yes yes 8 606.6 21 3 (comp.) 2 — TDI no no —.sup.d) —.sup.d) —.sup.d) 4 (comp.) 1 DMM TDI no no —.sup.e) —.sup.e) —.sup.e) 5 2 DMM TDI yes yes 9 636.6 32 6 2 DMM HDI yes yes 8 606.6 16 7 2 DMM IPDI yes yes 10  762.6 17 8 (comp.) 1 Dioxane, TDI — — — .sup.  — .sup.  —.sup.f  Benzene .sup.a)step ii) withdrawing the formaldehyde solution prepared in step i) from the first container and transferring it to a second container containing OH-reactive compound, .sup.b)step iii) distillatively recycling the solvent from the second container to the first container, .sup.c)number-average number of polyoxymethylene repeating units, .sup.d)white solid comprising complex mixture which cannot be further characterized in the first container, .sup.e)complex mixture which cannot be further characterized in the first container, .sup.fno polymers having NCO groups or NCO prepolymers present.