Lignin-based polyols and a process for the preparation thereof

Abstract

A polyether polyol comprising lignin and having an acid number lower than 0.1 mg KOH / g.

Description

[0001] Lignin-based polyols and a process for the preparation thereof

[0002] Field of the invention

[0003] The present invention relates to a polyether polyol comprising lignin and a process for the preparation of a polyol comprising lignin. The invention further relates to the use of such a polyol for the production of polyurethanes, a process for the preparation of a polyurethane, and a polyurethane based on the polyol according to the invention and polyisocyanate.

[0004] Background of the invention

[0005] To address the growing interest in polyurethane (Pll) systems with a reduced product carbon footprint, polyols based on bio-based materials are needed. Lignin is the second most abundant biomaterial on earth and is highly attractive as a starting material for polyols. For the use as a polyol in the preparation of polyurethanes, lignin must be alkoxylated due to the low reactivity of phenolic groups of lignin towards the isocyanate. Lignin must therefore be chemically modified to carry aliphatic OH groups.

[0006] For the reduction of the product carbon footprint of the polyol, a high lignin content in the lignin polyol is desirable. At the same time, it must be ensured that the lignin polyol can be used to replace traditional polyols in the preparation of polyurethanes without sacrificing the quality of the polyurethane or negatively affecting the polyurethane synthesis.

[0007] For the use in the preparation of polyurethanes, it is important that the reaction of the polyols with polyisocyanates runs efficiently. To avoid negatively affecting the reactivity of the polyurethane synthesis, it is very important that the acidity of the lignin-based polyol is as low as possible. The lignin-based polyol must thus have a low acid number. Further, the phenolic hydroxyl groups coming from the lignin should be reacted with the alkylene oxide. This is important because the reactivity of phenolic groups towards NCO groups is slow. In addition, the reverse reaction is favored at elevated temperatures, causing the urethane to split into free isocyanate and alcohol.

[0008] The polyether polyol should further have an OH number which is suitable for the application in polyurethanes.

[0009] Moreover, for industrial-scale production, the safety of the polyol production process is essential. For example, any uncontrolled accumulation of alkylene oxide must be avoided. EP 3 077447 B1 relates to the manufacturing of lignin-based polyols and their use in rigid polyurethane foams. The lignin polyols are not free from phenolic OH groups, which limits the reactivity of the final polyol. Moreover, the reaction temperature of the alkoxylation is very low, leading to a very slow reaction which is not suited for industrial processes.

[0010] US 2015 / 0038665 A1 relates to the production of polyols from sources such as dried distillers grains plus solubles (DDGS). The lignin fraction of DDGS is alkoxylated; alternatively, also lignin from other sources can be used. The resulting polyols have an extremely high acid number of 1.34 mg KOH / g and are thus not suitable for use in PU applications. Moreover, the process is not suitable for industrial use because of the amount of alkylene oxide present at the beginning of the reaction is causing an uncontrolled exothermic runaway reaction in the first step of the process.

[0011] It was therefore the object of the invention to provide lignin-based polyether polyols and a process for the production of lignin-based polyether polyols that overcome the above-mentioned drawbacks. Specifically, the lignin-based polyols should have a sufficiently high lignin content and be suitable for use in polyurethane production without negatively affecting the polyurethane synthesis or the properties of the polyurethane.

[0012] Detailed description

[0013] The object was surprisingly achieved by a polyether polyol comprising lignin and having an acid number lower than 0.1 mg KOH / g. The object was further achieved by a process for the preparation the polyether polyol, the process comprising the steps a) providing a mixture M1) comprising lignin, alkoxylation catalyst and one or more compounds selected from monoalcohols, polyhydric alcohols, fatty acid esters and polyetherols b) dosing alkylene oxide to the mixture M1) c) reacting the mixture M1) with the alkylene oxide d) obtaining an intermediate polyether polyol H) e) mixing further lignin in the obtained intermediate polyether polyol H) to obtain a mixture M2), wherein the amount of further lignin is 10-150 wt.-% based on the amount of the intermediate polyether polyol H) f) dosing alkylene oxide to the mixture M2) g) reacting the mixture M2) with an alkylene oxide h) obtaining a polyether polyol. The object was further achieved by the use of the polyether polyol for the production of polyurethanes, a process for the preparation of a polyurethane, wherein a polyol composition comprising the polyether polyol is reacted with a polyisocyanate, a polyurethane obtained by the process and a polyurethane based on the polyether polyol and a polyisocyanate.

[0014] The polyether polyol according to the invention is well suited for use in the production of polyurethanes without negatively affecting the polyurethane synthesis or the properties of the polyurethane. The process according to the invention results in polyether polyols with a high lignin content, a low acid number and very few or no phenolic OH groups.

[0015] Polyether polyol

[0016] A polyol in the context of the present invention is an organic compound that contains at least two OH groups that are reactive towards isocyanate. Polyols are prepared by alkoxylation of one or several starter compounds; the reaction of the starter compounds and alkylene oxides as well as the preparation of polyols per se is known to those skilled in the art. The starter compounds are compounds having active hydrogen atoms. In the reaction with the alkylene oxides, the alkylene oxides are added to the starter compound(s), this possibly taking place with use of a catalyst. One or several starter compounds can take part in the reaction. This reaction is known per se to those skilled in the art. Starter compounds are often also called starter molecules, starting compounds, or starters.

[0017] A polyether polyol in the context of the present invention is an organic compound that contains at least ether bonds in the chain and OH groups as functional groups. Polyether polyols are reaction products of starter compounds with at least two alkylene oxide reactive hydrogen atoms with alkylene oxides. Starter compounds for polyether polyols include compounds with at least two OH groups as well as polyamines with at least one NH2 group. Further starter compounds are fatty acid esters like biodiesel. The preparation of polyether polyols is known per se to those skilled in the art.

[0018] Preference is given to using one or more C2 to C4 alkylene oxides. Suitable C2 to C4 alkylene oxides are ethylene oxide, 1,2-propylene oxide, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide, in each case either alone or in the form of mixtures. Ethylene oxide and / or 1,2-propylene oxide are particularly preferred. Hereinafter, the term “propylene oxide” is used to mean 1,2-propylene oxide.

[0019] Propylene oxide may be used as the sole alkylene oxide. Ethylene oxide may be used as the sole alkylene oxide.

[0020] Propylene oxide and ethylene oxide may both be used as the alkylene oxide.

[0021] The amount of alkylene oxide is preferably at least 0.01 mol alkylene oxide I mol OH groups in the starter compounds of the polyether polyol, more preferred at least 0.1 mol alkylene oxide I mol OH groups in the starter compounds of the polyether polyol, even more preferred at least 0.25mol alkylene oxide I mol OH groups in the starter compounds of the polyether polyol.

[0022] The amount of alkylene oxide is preferably at most 25 mol alkylene oxide I mol OH groups in the starter compounds of the polyether polyol, more preferred at most 20 mol alkylene oxide I mol OH groups in the starter compounds of the polyether polyol, even more preferred at most 15 mol alkylene oxide I mol OH groups in the starter compounds of the polyether polyol.

[0023] The amount of alkylene oxide is preferably in 0.01-25 mol alkylene oxide I mol OH groups in the starter compounds of the polyether polyol, more preferred 0.1-20 mol alkylene oxide I mol OH groups in the starter compounds of the polyether polyol, even more preferred 0.25-15 mol alkylene oxide I mol OH groups in the starter compounds of the polyether polyol.

[0024] In the context of the present invention, the expression “lignin” comprises any lignin which may be used as a starter compound for a polyether polyol.

[0025] The lignin according to the present invention may be obtained e.g. by the sulfate process, soda process and / or organosolv-process (Organosolv lignin). Processes to obtain lignin are e.g. described in US4507172, CA2256923, EP3156409, WO2013 / 070130, DE3901662, WO2012 / 027767 and / or W02006 / 038863.

[0026] Lignin may be precipitated as lignin solid out of a Kraft pulp mill “black liquor” stream by acidification and filtration (e.g. by the Lignoboost process described in US20170355723 or equivalent approaches). This type of lignin is referred to as Kraft lignin.

[0027] Black liquor is the aqueous basic solution of the Kraft pulping process after separation of the cellulosic pulp. It comprises besides dissolved lignin inorganic cooking salts and degraded sugar components from the original biomass like acetic acid, diverse sugar acids etc. More information can be found e.g. in Bajpai, Pratim: Biermann's Handbook of Pulp and Paper - Raw Material and Pulp Making, Volume 1 and 2 (3rd Edition) 2018, Elsevier - pp. 332, 12.8.5 Green Liquor, Chemical Recovery.

[0028] Preferably, the lignin is kraft lignin. The OH number of the lignin is preferably at least 25 mg KOH / g, more preferred at least 50 mg KOH / g, even more preferred at least 100 mg KOH / g. The OH number of the lignin is preferably at most 800mg KOH / g, more preferred at most 600mg KOH / g, even more preferred at most 400 mg KOH / g.

[0029] The lignin preferably has an OH number in the range of 25-800 mg KOH / g, more preferred in the range of 50-600 mg KOH / g, even more preferred in the range of 100-400mg KOH / g.

[0030] The amount of acidic phenolic OH groups in the lignin is preferably 0.1 - 0.8 mmol COOH I g, more preferred 0.2 - 0.6 more preferred 0.3-0.5 mmol COOH I g, determined by31P-NMR as described in Stucker et. Al. Anal. Methods, 2018, 10, 3481-348.

[0031] The number average molecular weight of the lignin is preferably in the range of 100-10000 g / mol, more preferred in the range of 150-6000 g / mol, even more preferred in the range of 200- 4000 g / mol.

[0032] The polyether polyol preferably comprises at least 15 wt.-%, more preferred at least 20 wt.-%, even more preferred at least 25 wt.-%, even more preferred at least 30 wt.-%, particularly preferred at least 35 wt.-% lignin, based on the total weight of the polyether polyol.

[0033] The polyether polyol preferably comprises at most 80 wt.-%, more preferred at most 70 wt.-%, even more preferred at most 65 wt.-%, even more preferred at most 60 wt.-%, particularly preferred at most 55 wt.-% lignin, based on the total weight of the polyether polyol.

[0034] The amount of lignin in the polyether polyol is preferably 15-80 wt.-%, more preferred 20-70 wt.- %, even more preferred 25-65 wt.-%, even more preferred 30-60 wt-%, particularly preferred 35-55 wt.-%, based on the total weight of the polyether polyol.

[0035] The polyether polyol may comprise one or more compounds selected from mono alcohols, polyhydric alcohols, fatty acid esters and / or polyetherols as starters. Preferably, the polyether polyol may comprise one or more compounds selected from mono alcohols, polyhydric alcohols, fatty acid esters and / or polyetherols selected from 1 -hexanol, 1 -heptanol, 1 -octanol, 1- decanol, 1-dodecanol, 1 -tetradecanol, 1-tridecanol, diethylene glycol, dipropylene glycol, polyethylene glycol, tetraethylene glycol, polypropylene glycol, glycerol, trimethylolpropane, sorbitol, biodiesel, propoxylated glycerol, ethoxylated pentaerythrite, alkoxylated saccharose polyols, alkoxylated sorbitol polyols and / or their mixtures. Mono alcohols, polyhydric alcohols, fatty acid esters and polyetherols are preferred that form a dispersion or a solution with lignin.

[0036] Preferably, the polyether polyol comprises one or more compounds selected from mono alcohols, polyhydric alcohols, fatty acid esters and / or polyetherols in which lignin is soluble.

[0037] Preferably, the polyether polyol comprises a polyhydric alcohol, a fatty acid ester and / or a polyether polyol selected from diethylene glycol, dipropylene glycol, polyethylene glycol, tetraethylene glycol, polypropylene glycol, glycerol, trimethylolpropane, sorbitol, biodiesel, propoxylated glycerol, ethoxylated pentaerythrite, alkoxylated saccharose polyols, alkoxylated sorbitol polyols and their mixtures.

[0038] Particularly preferably, the polyether polyol comprises one or more compounds selected from mono alcohols, polyhydric alcohols, fatty acid esters and / or polyetherols selected from diethylene glycol, dipropylene glycol, biodiesel and polyethylene glycol and their mixtures.

[0039] The polyethylene glycol (PEG) is preferably selected from PEG100, PEG200, PEG400 and PEG600.

[0040] The amount of lignin is preferably in the range of 15-90 wt.-%, more preferred 20-80 wt.-%, even more preferred 25 - 70 wt.-%, particularly preferred 30-65 wt.-%, based on the total weight of lignin and to the one or more compounds selected from monoalcohols, polyhydric alcohols, the fatty acid esters and / or polyether polyols.

[0041] The acid number of the polyether polyol is lower than 0.1 mg KOH / g. Preferably, the acid number is lower than 0.075 mg KOH / g. More preferred, the acid number is lower than 0.05 mg KOH / g.

[0042] The acid number of the polyether polyol is preferably in the range of 0.001 - lower than 0.1 mg KOH / g, more preferred in the range of 0.005-0.075 mg KOH / g, even more preferred in the range of 0.01-0.05 mg KOH / g.

[0043] The acid number of the polyether polyol is preferably in the range of 0.001- lower than 0.1 mg KOH / g, more preferred in the range of 0.005 - lower than 0.075 mg KOH / g, even more preferred in the range of 0.01- lower than 0.05 mg KOH / g.

[0044] The acid number can be determined by means of well-established methods. For example, the acid number can be determined according to DIN EN 1241 (May 1998). The polyether polyol preferably comprises less than 0.1 mmol / g phenolic OH groups. More preferred, the polyether polyol comprises less than 0.05 mmol / g phenolic OH groups. Even more preferred, the polyether polyol comprises less than 0.01 mmol / g phenolic OH groups.

[0045] The polyether polyol preferably comprises 0-0.1 mmol / g phenolic OH groups, more preferred 0- 0.05 mmol / g phenolic OH groups, even more preferred 0-0.01 mmol / g phenolic OH groups.

[0046] Particularly preferably, the polyether polyol does not comprise phenolic OH groups.

[0047] The amount of phenolic OH groups can be determined by31P-NMR according to the method described in Stucker et. Al. Anal. Methods, 2018, 10, 3481-348.

[0048] The OH number of the polyether polyol is preferably at least 15 mg KOH / g, more preferred at least 100 mg KOH / g, even more preferred at least 180 mg KOH / g, particularly preferred at least 200 mg KOH / g.

[0049] The OH number of the polyether polyol is preferably at most 850 mg KOH / g, more preferred at most 700 mg KOH / g, even more preferred at most 500 mg KOH / g.

[0050] The OH number of the polyether polyol is preferably in the range of 15-850 mg KOH / g, more preferred in the range of 100-700 mg KOH / g, even more preferred in the range of 180-500 mg KOH / g, particularly preferred in the range of 200-500 mg KOH / g.

[0051] The OH number (hydroxyl number) can be determined by means of well-established methods. By way of example, the OH number can be determined according to DIN 53240 (1971 -12).

[0052] The functionality of a polyol, especially of the polyether polyol according to the invention, within the context of the present invention means the number of alkylene oxide-reactive hydrogen atoms per mole of starter compound or per mole of mixture of the starter compounds prior to the time of alkylene oxide metering. The time of the alkylene oxide metering is in this case the start of the addition of the alkylene oxide component to the starter compound(s). The calculation takes into account all alkylene oxide-reactive hydrogen atoms of the starter compound(s) that are present in the mixture of starter compounds.

[0053] The functionality F in the context of the present invention is calculated according to the following formula (I): nt = moles of starter i ft = functionality of starter i m = number of starters in the starter mixture

[0054] F = functionality

[0055] The functionality F of a polyol produced from a mixture of two starter compounds (m=2) is calculated as follows:

[0056] F = (moles of starter compound A * functionality of starter compound A + moles of starter compound B * functionality of starter compound B) / (moles of starter A + moles of starter B).

[0057] The formula can be amended accordingly for other starter molecules. Thus, for example, a polyether polyol has a functionality of 5.12 when 626.48 mol of glycerol (functionality 3), 559.74 mol of sucrose (functionality 8) and 67.31 mol of dimethylethanolamine (functionality 1) are used.

[0058] The functionality F determined by the formula presented above is also called equivalent functionality and is known to those skilled in the art as a readily accessible method for determining the functionality of polyols, see M. lonescu “Chemistry and Technology of Polyols for Polyurethanes”, 2005, Rapra Technology Limited, pages 34 to 39.

[0059] The functionality of the polyols, as defined above according to the invention, can differ from the functionality after commencement of the addition of at least one alkylene oxide, that is, during the reaction of the at least one alkylene oxide with a starter compound, or of the reaction product, since during the reaction there is formation of by-products such as glycols and unsaturated monofunctional constituents. The side-reactions are known in the literature. The functionality of the polyols can thus also be referred to as the functionality of the starter compound or starter compound mixture used for the preparation of the respective polyol.

[0060] The polyether polyol preferably has a functionality of at least 2, more preferred at least 2.25, even more preferred at least 2.5.

[0061] The polyether polyol preferably has a functionality of at most 8, more preferred at most 7, even more preferred at most 6. The functionality of the polyether polyol is preferably in the range of 2-8, more preferred in the range of 2.25-7, even more preferred in the range of 2.5-6.

[0062] Process for the production of the polyether polyol

[0063] All information about the polyether polyol described in the above section is also applicable to the polyether polyol and its components in this aspect of the invention.

[0064] The invention further relates to a process for the production of a polyether polyol having an acid number lower than 0.1 mg KOH / g and comprising the steps a) providing a mixture M1) comprising lignin, an alkoxylation catalyst and one or more compounds selected from monoalcohols, polyhydric alcohols, fatty acid esters and polyetherols b) dosing alkylene oxide to the mixture M1) c) reacting the mixture M1) with the alkylene oxide d) obtaining an intermediate polyether polyol H) e) mixing further lignin in the obtained intermediate polyether polyol H) to obtain a mixture M2), wherein the amount of further lignin is 10-150 wt.-% based on the amount of the intermediate polyether polyol H) f) dosing alkylene oxide to the mixture M2) g) reacting the mixture M2) with an alkylene oxide h) obtaining a polyether polyol.

[0065] The mixture M1) preferably comprises at most 10 wt.-% alkylene oxide, more preferred at most 5 wt.-% alkylene oxide. Particularly preferred, the mixture M1) does not comprise alkylene oxide.

[0066] The mixture M1) is preferably a dispersion or a solution. Particularly preferably, the mixture M1) is a solution.

[0067] The information related to the monoalcohols, polyhydric alcohols, fatty acid esters and polyetherols in the above section related to the polyether polyol is applicable to the polyhydric alcohols and polyetherols in step a). Monoalcohols, polyhydric alcohols, fatty acid esters and polyetherols that form a dispersion or a solution with lignin are preferred. Preferably, lignin is soluble in the polyhydric alcohols and polyetherols. The mixture M1) preferably consists of lignin and one or more compounds selected from monoalcohols, polyhydric alcohols, fatty acid esters and polyetherols as described above and in the section related to the polyether polyol and optionally at most 20 wt.-% alkylene oxide.

[0068] The mixture M1) more preferred consists of lignin and one or more compounds selected from monoalcohols, polyhydric alcohols, fatty acid esters and polyetherols as described above and in the section related to the polyether polyol and optionally at most 10 wt.-% alkylene oxide.

[0069] The mixture M1) particularly consists of lignin and one or more compounds selected from monoalcohols, polyhydric alcohols, fatty acid esters and polyetherols as described above and in the section related to the polyether polyol.

[0070] The alkoxylation catalyst is preferably selected from alkali metal hydroxides, alkali metal alkoxides and amines, in particular from alkali metal hydroxides and amines.

[0071] The alkali metal hydroxides are preferably selected from sodium, cesium and potassium hydroxide; potassium hydroxide is particularly preferred.

[0072] The alkali metal alkoxides are preferably selected from sodium methoxide, potassium methoxide and potassium isopropoxide.

[0073] The amine catalysts are preferably selected from the group comprising trialkylamines, such as for example trimethylamine, triethylamine, tripropylamine and tributylamine; dimethylalkylamines such as dimethylethanolamine, dimethylcyclohexylamine, dimethylethylamine and dimethylbutylamine; aromatic amines such as dimethylaniline, dimethylaminopyridine, dimethylbenzylamine, pyridine, imidazoles such as imidazole, 4(5)-methylimidazole, 3- methylimidazole and 1 -hydroxypropylimidazole; guanidines and amidines such as for example 1 ,5-diazabicyclo[4.3.0]non-5-ene and 1 ,5-diazabicyclo[5.4.0]undec-7-ene.

[0074] The alkoxylation catalyst is preferably selected from potassium hydroxide, imidazole, caesium hydroxide Even more preferred, the alkoxylation catalyst is selected from potassium hydroxide and imidazole. Particularly preferred, the alkoxylation catalyst is imidazole.

[0075] The information related to the alkylene oxide in the above section related to the polyether polyol is applicable to the alkylene oxide used in the process in this aspect of the invention.

[0076] Preferably, at least 80 wt.-% of the alkylene oxide used in the preparation of the intermediate polyether polyol H) is dosed in step b) and at least 80 wt.-% of the alkylene oxide used in the preparation of the polyether polyol is dosed in step f). More preferred, at least 95 wt.-% of the alkylene oxide used in the preparation of the intermediate polyether polyol H) is dosed in step b) and at least 95 wt.-% alkylene oxide used in the preparation of the polyether polyol is dosed in step f). Even more preferred, at least 99 wt.-% of the alkylene oxide used in the preparation of the intermediate polyether polyol H) is dosed in step b) and at least 99 wt.-% alkylene oxide used in the preparation of the polyether polyol is dosed in step f). Particularly preferred, all alkylene oxide used in the preparation of the intermediate polyether polyol H) is dosed in step b) and all alkylene oxide used in the preparation of the polyether polyol is dosed in step f). The expressions “dosed in step b)” and “dosed in step f)” mean that the given amount of the alkylene oxide is dosed at once in the respective process step. In particular, the given amount of alkylene oxide is dosed at once in one portion in the respective process step and is not, for example, added to the reaction mixture M1 and / or M2.

[0077] The steps b), c) and d) may overlap. Also, the steps f), g) and h) may overlap.

[0078] A different alkylene oxide may be used in steps b) and f).

[0079] Propylene oxide and / or ethylene oxide are preferably used as the alkylene oxide in steps b) and f).

[0080] If both propylene oxide and ethylene oxide are used as the alkylene oxide in step b), step f) or in both of the steps b) and f), they may be dosed simultaneously, propylene oxide before ethylene oxide, and / or ethylene oxide before propylene oxide.

[0081] Preferably, the same alkylene oxide or the same mixture of alkylene oxides is used in steps b) and f).

[0082] Preferably, ethylene oxide is used in steps b) and / or f). More preferred, ethylene oxide is used in steps b) and f). Even more preferred, ethylene oxide is the only alkylene oxide used in steps b) and f).

[0083] Preferably, propylene oxide is used in steps b) and / or f). More preferred, propylene oxide is used in steps b) and f). Even more preferred, propylene oxide is the only alkylene oxide used in steps b) and f).

[0084] The reactor is preferably heated to the reaction temperature before the dosing of the alkylene oxide in steps b) and / or f). More preferred, the reactor is heated to the reaction temperature before the dosing of the alkylene oxide in steps b) and f). The reaction temperature in steps c) and g) is preferably at least 105°C, more preferred at least 110 °C, even more preferred at least 115 °C. The reaction temperature in steps d) and h) is preferably at most 160 °C, more preferred at most 150 °C, even more preferred at most 135 °C.

[0085] The reaction temperature in steps c) and g) is preferably 105-160 °C, more preferred 110- 150°C, even more preferred 115-135 °C.

[0086] These reaction temperatures ensure a fast consumption of the dosed alkylene oxide and prevent an accumulation of the alkylene oxide in the reactor at industrial relevant batch times.

[0087] The acid number of the intermediate polyether polyol H) obtained in step e) is preferably lower than 0.15 mg KOH / g. More preferred, the acid number of the intermediate polyether polyol H) is lower than 0.1 mg KOH / g. Even more preferred, the acid number of the intermediate polyether polyol H) is lower than 0.075 mg KOH / g. Particularly preferred, the acid number of the intermediate polyether polyol H) is lower than 0.05 mg KOH / g.

[0088] The acid number of the intermediate polyether polyol H) is preferably in the range of 0.001-0.15 mg KOH / g, more preferred in the range of 0.005-0.1 mg KOH / g, even more preferred in the range of 0.01-0.075 mg KOH / g, particularly preferred in the range of 0.01-0.05 mg KOH / g.

[0089] In step e), further lignin is mixed with the intermediate polyether polyol H) to obtain a mixture M2). Preferably, further lignin is dispersed or dissolved in the intermediate polyether polyol H) to obtain a mixture M2). Preferably, the further lignin is the same type of lignin as used in step a). The further lignin is preferably kraft lignin.

[0090] The amount of further lignin is 10-150 wt.-% based on the amount of the intermediate polyether polyol H). Preferably, the amount of further lignin is 15-100 wt.-%, more preferred 18-80 wt.-%, based on the amount of the intermediate polyether polyol H).

[0091] The total amount of lignin in steps a) and e) is preferably chosen so that the lignin content of the polyether polyol is in the range of 15-80 wt.-%, more preferred 20-70 wt.-%, even more preferred 25-65 wt.-%, even more preferred 30-60 wt-%, particularly preferred 35-55 wt.-%, based on the total weight of the polyether polyol.

[0092] The mixture M2) is preferably a dispersion or a solution. Particularly preferred, the mixture M2) is a solution. The mixture M2) preferably does not comprise unreacted alkylene oxide.

[0093] An alkoxylation catalyst is preferably added to mixture M2). If an alkoxylation catalyst is added to mixture M2), it is preferably selected from the hydroxides of alkali metals, alkali metal alkoxides and amines listed above. The alkoxylation catalyst added to mixture M2) is preferably selected from potassium hydroxide and imidazole. Particularly preferred, the alkoxylation catalyst added to mixture M2) is imidazole. If an alkoxylation catalyst is added to mixture M2), it is preferably the same alkoxylation catalyst as the alkoxylation catalyst added to mixture M1) in step b).

[0094] The polyether polyol described above and the prepared according to the process described above is well suitable for the use in polyurethanes. Further aspects of the invention are thus a process for the preparation of a polyurethane, wherein a polyol composition comprising the polyether polyol described above or the polyether polyol prepared by the process described above is reacted with a polyisocyanate; and a polyurethane obtained by the process.

[0095] A further aspect of the invention is a polyurethane based on the polyether polyol described above and polyisocyanate.

[0096] In case the resulting polyurethane is used for insulation purposes, it is desirable that it has a low thermal conductivity. Further, if the resulting polyurethane is used in applications in which the burning behavior is of importance, a low total heat release, low heat release rate, low smoke generation, low flame spread as well as low flame height upon ignition are desirable. For some applications, in particular construction applications like sandwich panels or laminate boards, an EN 13501 class E rating of the polyurethane is required.

[0097] The term “polyurethane” is known by the person skilled in the art as including not only polymers containing urethane groups but as also including polymers containing no or very low amounts of urethane groups, as long as these polymers are derived from difunctional or polyfunctional isocyanates, see Polyurethane Handbook, 2nd edition 1993, editor Guether Oertel, Carl Hanser Verlag Munich, Chapter 2.1.1. Examples are polyetherureas, polyisocyanurates, polyureas and polycarbodiimides. Preferably, the polyurethanes according to the invention comprise functional units selected from urethane, isocyanurate and mixtures of both. Isocyanurate formation leads to flame-resistant PIR foams which are preferably used in industrial rigid foam, for example in the building industry as insulating panels or sandwich elements.

[0098] The polyurethane is preferably a polyurethane foam. More preferred, the polyurethane is a rigid polyurethane foam or a flexible polyurethane foam. Particularly preferred, the polyurethane is a rigid polyurethane foam.

[0099] A polyurethane is obtained from the reaction of a di- or polyisocyanate component and a polyol component in a reaction mixture. It has proven to be particularly advantageous to employ a two- component system and to combine the mixture of polyols, catalysts, chain extenders, crosslinking agents, blowing agents, auxiliaries and additives as a polyol component and to use organic polyisocyanates as the isocyanate component. An advantage of this method is that the isocyanate and the polyol components can be stored separately and can be transported in a space saving manner.

[0100] The di- or polyisocyanate used may include any aliphatic, cycloaliphatic, and aromatic di- or polyfunctional isocyanates known from the prior art and any desired mixture of these. The di- or polyisocyanates can optionally be modified.

[0101] Specific examples include alkylene diisocyanates having 4 to 12 carbon atoms in the alkylene radical, such as dodecane 1 ,12-diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate, 2- methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate and preferably hexamethylene 1,6-diisocyanate; cycloaliphatic diisocyanates such as cyclohexane 1,3- and 1,4- diisocyanate and also any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane (IPDI), hexahydrotolylene 2,4- and 2,6-diisocyanate and also the corresponding isomer mixtures, dicyclohexylmethane 4,4'-, 2,2'- and 2,4'-diisocyanate and also the corresponding isomer mixtures, and preferably aromatic di- and polyisocyanates such as, for example, tolylene 2,4- and 2,6-diisocyanate (TDI) and the corresponding isomer mixtures, methylene diphenyl 4,4'-, 2,4'- and 2,2'-diisocyanate (MDI) and the corresponding isomer mixtures, mixtures of methylene diphenyl 4,4'- and 2,4'-diisocyanates, polyphenylpolymethylene polyisocyanates, mixtures of methylene diphenyl 4,4'-, 2,4'- and 2,2'-diisocyanates and polyphenylpolymethylene polyisocyanates (polymeric MDI, also called PMDI) and mixtures of polymeric MDI and tolylene diisocyanates. The di- or polyisocyanates can be used individually or in the form of their mixtures.

[0102] Use is frequently also made of modified polyfunctional isocyanates, i.e. products which are obtained by chemical reaction of organic polyisocyanates. Examples which may be mentioned are polyisocyanates comprising ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdi- one, carbamate and / or urethane groups.

[0103] The di- or polyisocyanates can also be applied in form of prepolymers. These polyisocyanate prepolymers are obtained by reacting the above-described di- or polyisocyanates with compounds having at least two groups reactive towards isocyanate to form a prepolymer.

[0104] Furthermore, prepolymers and mixtures of the above-described isocyanates and prepolymers can be used as the isocyanate. These polyisocyanate prepolymers are obtainable by reacting polyisocyanates described above in excess with compounds having at least two groups reactive toward isocyanates to give the prepolymer. The reaction may take place at temperatures of 30 to 100 °C, for example, preferably at about 45 to 60 °C. The prepolymers usually have an NCO content in the range of 14 to 32 wt.-%, preferably in the range of 25 to 30 wt.-%.

[0105] Preferred di- or polyisocyanates (a) are TDI, MDI, polymeric MDI and / or related isocyanate prepolymers. Particularly preferably, the di- or polyisocyanate is selected from the group consisting of MDI and / or polymeric MDI and / or related isocyanate prepolymers.

[0106] Very particular preference is given to employing polymeric MDI.

[0107] The polyol component comprises the polyether polyol described above or the polyether polyol produced according to the process described above. Preferably, it also comprises additional polyols. The additional polyols may for example be further polyether polyols; polyester polyols; polyetherester polyols; graft polyether polyols or polyester polyols; hydroxyl-containing polyesteramides, polyacetals, polycarbonates and / or polyetherpolyamines; and / or further compounds having at least two isocyanate-reactive groups.

[0108] Suitable further polyether polyols are typically prepared by known processes from at least one starter molecule with 2 to 8, preferably 2 to 6, reactive hydrogen atoms and one or more alkylene oxides. Preference is given to using C2 to C4 alkylene oxides, e.g. ethylene oxide, 1 ,2- propylene oxide, tetrahydrofuran, 1 ,3-propylene oxide, 1 ,2- or 2,3-butylene oxide, in each case either alone or in the form of mixtures, particularly preferably ethylene oxide and / or 1 ,2- propylene oxide, as alkylene oxides.

[0109] Examples of suitable starter molecules are water; organic dicarboxylic acids, such as succinic acid, adipic acid, phthalic acid and terephthalic acid; aliphatic and aromatic, unsubstituted or kimono-, N, N-and N, N '-dialkyl-substituted diamines having 1 to 4 carbon atoms in the alkyl radical, such as optionally mono-and dialkyl-substituted ethylenediamine, diethylenetriamine, triethylenetetramine, 1 ,3-propylenediamine, 1 ,3- and 1 ,4-butylenediamine, 1 ,2-, 1 ,3-, 1 ,4-, 1 ,5- and 1 ,6-hexamethylenediamine, phenylenediamines, 2,3-, 2,4- and 2,6-toluylenediamine and 4,4 '-, 2,4'-and 2,2 '-diaminodiphenylmethane.

[0110] Other suitable starter molecules are alkanolamines, for example ethanolamine, N-methyl- and N-ethylethanolamine, dialkanolamines, for example diethanolamine, N-methyl- and N- ethyldiethanolamine, and trialkanolamines, for example triethanolamine, and ammonia. Further suitable starter molecules are dihydric or polyhydric alcohols, such as ethanediol, 1 ,2-and 1 ,3- propanediol, diethylene glycol, dipropylene glycol, 1 ,4-butanediol, 1 ,6-hexanediol, glycerol, trimethylolpropane, pentaerythritol, sorbitol and sucrose. Preference is given to using dihydric or polyhydric alcohols.

[0111] The polyether polyols, preferably polyoxypropylene polyols and / or polyoxyethylene polyols, have functionalities of preferably 2-8. The polyether polyols preferably have hydroxyl numbers of 10-850. The polyether polyols preferably have number average molecular weights of from 150 to 3000 g / mol, preferably from 200 to 2000 g / mol and in particular from 250 to 1000 g / mol.

[0112] Other suitable polyether polyols are polymer-modified polyether polyols, preferably graft polyether polyols, in particular those based on styrene and / or acrylonitrile, which are obtained by in situ polymerisation of acrylonitrile, styrene or preferably mixtures of styrene and acrylonitrile, for ex-ample in a weight ratio of 90:10 to 10:90, preferably 70:30 to 30:70, are prepared in an expedient manner analogously to the instructions of German patent specifications 1 1 1 1 394, 12 22 669 (U.S. PAT. NOs. 3,304,273, 3,383,351 , 3,523,093), 1 1 52 536 (GB 10 40 452) and 1 1 52 537 (GB 987,618), and polyether polyol dispersions which are prepared as disperse phase, the following are usually present in an amount of from 1 to 50% by weight, preferably from 2 to 25% by weight: for example polyureas, polyhydrazides, polyurethanes containing bonded tert-amino groups and / or melamine and are described, for example, in EP-B 01 1 752 (U.S. Pat. no. 4,304,708), U.S. Pat. no. 4,374,209 and DE-A, 32 31 497.

[0113] Suitable polyester polyols can be prepared, for example, from organic dicarboxylic acids having 2 to 12 carbon atoms, preferably aromatic or a mixture of aromatic and aliphatic dicarboxylic acids, and polyhydric alcohols, preferably diols, having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms. Examples of suitable dicarboxylic acids are succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, and terephthalic acid. The dicarboxylic acids can be used either individually or as a mixture with one another. Instead of the free dicarboxylic acids, it is also possible to use the corresponding dicarboxylic acid derivatives, such as, for example, dicarboxylic esters of alcohols having 1 to 4 carbon atoms or dicarboxylic anhydrides. The aromatic dicarboxylic acids used are preferably phthalic acid, phthalic anhydride, and / or isophthalic acid in a mixture or alone. The aliphatic dicarboxylic acids used are preferably mixtures of succinic, glutaric and adipic acid in proportions of, for example, from 20 to 35:35 to 50:20 to 32 parts by weight, and in particular adipic acid. Examples of dihydric and polyhydric alcohols, in particular diols, are ethanediol, diethylene glycol, 1 ,2-and 1 ,3-propanediol, dipropylene glycol, 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 1 ,10-decanediol, glycerol, trimethylolpropane, and pentaerythritol. Ethanediol, diethylene glycol, 1 ,4-butanediol, 1 ,5- pentanediol, 1 ,6- hexanediol or mixtures of at least two of the diols mentioned, in particular mixtures of 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol, are preferably used. It is also possible to use polyesterpolyols from lactones, for ex-ample E-caprolactone, or hydroxycarboxylic acids, for example co-hydroxycaproic acid.

[0114] For the preparation of the polyester polyols, biobased starting materials and / or derivatives thereof are also suitable, such as castor oil, polyhydroxy fatty acids, ricinoleic acid, hydroxylmodified oils, grape seed oil, black caraway oil, pumpkin seed oil, borage seed oil, soybean oil, wheat seed oil, rapeseed oil, sunflower seed oil, peanut oil, apriac seed oil, pistachio oil, almond oil, olive oil, avocado oil, sand mandrel oil, sesame oil, hemp oil, hazelnut oil, primrose oil, wild rose oil, safflower oil, walnut oil, hydroxyl-modified fatty acids and fatty acid esters based on myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, a-and y-linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, oleic acid, clupanodonic acid, and cerionic acid.

[0115] Both the polyether polyols and the polyester polyols may be used individually or in the form of mixtures. They may also be mixed with graft polyether polyols, polyetherester polyols, hydroxylcontaining polyesteramides, polyacetals, polycarbonates, polyetherpolyamines and / or further compounds having at least two isocyanate-reactive groups.

[0116] Suitable further compounds having at least two isocyanate-reactive groups, i.e. having at least two hydrogen atoms reactive toward isocyanate groups, are, in particular, those which contain two or more reactive groups selected from OH groups, SH groups, NH groups, NH2-groups and CH-acidic groups, such as, for example, [3-diketo groups.

[0117] If the intention is that the polyurethane of the invention takes the form of a foam, the polyurethanes are prepared by addition of at least one blowing agent. Preferably, the at least one blowing agent is added to the reaction mixture prior to the reaction. Blowing agents which are used for producing the polyurethane foams include chemical blowing agents and / or physical blowing agents.

[0118] Suitable chemical blowing agents are water and acids, in particular water, formic acid and mixtures of water and acids. Water and formic acid are preferred chemical blowing agents.

[0119] Based on the total weight of all components that are mixed with the polyisocyanate or mixtures thereof, the amount of water is preferably at least 0.5 wt.-%, preferably at least 0.6 wt.-%, more preferred at least 0.7 wt.-%. The amount of water is preferably at most 5 wt.-%, more preferred at most 4 wt.-%, even more preferred at most 3 wt.-%. Preferably, the amount of water is in the range of 0.5 wt.-% to 5 wt.-%, more preferred in the range of 0.6 wt.-% to 4 wt.-%, even more preferred in the range of 0.7 wt.-% to 3 wt.-%.

[0120] Based on the total weight of all components that are mixed with the polyisocyanate or mixtures thereof, the amount of formic acid is preferably at least 0.5 wt.-%, preferably at least 0.6 wt.-%, more preferred at least 0.7 wt.-%. The amount of water is preferably at most 8 wt.-%, more preferred at most 7 wt.-%, even more preferred at most 6 wt.-%. Preferably, the amount of water is in the range of 0.5 wt.-% to 8 wt.-%, more preferred in the range of 0.6 wt.-% to 7 wt.-%, even more preferred in the range of 0.7 wt.-% to 6 wt.-%.

[0121] Preferably, water is the sole chemical blowing agent. One advantage of using water instead of other chemical blowing agents such as formic acid or other acids is the easy pro-cessing without a need for safety measures.

[0122] Preferably, formic acid is the sole chemical blowing agent. The use of formic acid offers advantages such as improved product properties like surface texture.

[0123] Preferably, the blowing agent comprises water and / or formic acid and a physical blowing agent. In one embodiment, the blowing agent comprises water and a physical blowing agent. In one embodiment, the blowing agent comprises formic acid and a physical blowing agent.

[0124] Suitable physical blowing agents that can be used are in general all hydrocarbons known to those skilled in the art as blowing agents, for example non-halogenated hydrocarbons and halogenated, preferably fluorinated, alkenes.

[0125] Examples of fluorinated alkenes are propenes, butenes, pentenes and hexenes having 3 to 6 fluorine substituents, where other substituents such as chlorine may be present, for example tetrafluoropropenes, fluorochloropropenes such as trifluoromonochloropropenes, pentafluoropropenes, fluorochlorobutenes, hexafluorobutenes or mixtures thereof. Preference is given to 1 ,1,1,3-tetrafluoropropene, 1,1,1-trifluoro-2-chloropropene, 1-chloro-3,3,3- trifluoropropene, 1 ,1 ,1,2,3-pentafluoropropene, Z-1 ,1 ,1,4,4,4-hexafluoro-2-butene, E- 1 ,1 ,1,4,4,4-hexafluoro-2-butene, 1 -brompentafluoropropene, 2-brompentafluoropropene, 3- brompentafluoropropene, 1,1 ,2,3,3,4,4-heptafluoro-1-butene, 1 -chloro-2, 3,3,3- tetrafluoropropene, 1-brom-2,3,3,3-tetrafluoropropene, 2-brom-1,3,3,3-tetrafluoropropene, 3- brom-1 ,1 ,3,3-tetrafluoropropene, 2-brom-3,3,3-trifluoropropene, E-1-brom-3,3,3- trifluoropropene, 3,3,3-trifluoro-2-(trifluoromethyl)propene, 1,1,1-trifluoro-2-butene and / or mixtures thereof. Examples of non-halogenated hydrocarbon blowing agents are acyclic pentane isomers and / or cyclopentane, especially cyclopentane. Preference is given to using acyclic pentane isomers and / or cyclopentane. Preference is given to cyclopentane and mixtures of isopentane with cyclopentane having a content of at least 70 wt.-% of cyclopentane, and particular preference is given to using cyclopentane having a purity of at least 90 wt.-%, especially of at least 95 wt.-%.

[0126] Preferably, the physical blowing agent is selected from acyclic pentane isomers, cyclopentane, and fluorinated alkenes. Particularly preferred, the physical blowing agent is selected from pentane, mixtures of pentane with isopentane having a content of at least 80 % pentane, cyclopentane, mixtures of isopentane with cyclopentane having a content of at least 70 wt.-% of cyclopentane, cyclopentane having a purity of at least 90 wt.-%, cyclopentane having a purity of at least 95 wt.-%, Z-1,1 ,1 ,4,4,4-hexafluoro-2-butene, E-1,1,1,4,4,4-hexafluoro-2-butene, 1- chloro-3,3,3-trifluoropropene and 1-chloro-2,3,3,3-tetrafluoropropene.

[0127] Preferably, the total amount of the at blowing agents is >0-35 wt.-%, more preferred >0-20 wt.- %, more preferred 0.5-17 wt.-%, even more preferred 0.7-15 wt.-%, based on the amount of the components that are mixed with the at least one di- or polyisocyanate or mixtures thereof.

[0128] The blowing agents are either wholly or partly present in the polyol component or are metered into the polyol component via a static mixture directly before foaming. Water or formic acid are usually completely or partly dissolved in the polyol component and the physical blowing agent (for example cyclopentane) and, if applicable, the remainder of the chemical blowing agent are metered "online", i.e. , during the foam preparation process.

[0129] The physical blowing agent, possibly parts of the chemical blowing agent, and / or some or all of the catalysts are preferably metered into the polyol component in situ, but the polyol component usually already contains at least portions of the chemical blowing agent and / or some or all of the catalysts. The auxiliaries and additives, as well as the flame retardants, are already present in the polyol component, if present.

[0130] As catalysts, it is possible to use all compounds which accelerate the isocyanate-water reaction or the isocyanate-polyol reaction. Such compounds are known and are described, for example, in " Polyurethane Handbook”, Carl Hanser Publishers, 2nd edition 1993, chapter 3.4.1.

[0131] Further auxiliaries and / or additives can optionally be added to the polyurethane foam reaction mixture. Mention may be made of, for example, surface-active substances, antioxidants, chain extenders, cross linkers, cell regulators, fillers, dyes, pigments, flame retardants, hydrolysis inhibitors, fungistatic and bacteriostatic substances. Chain extenders and cross linkers have usually a molecular weight between 60 g / mol to 300 g / mol. Bifunctional chain extenders and the trifunctional and higher-functional cross linkers or, if appropriate, mixtures thereof might be added. Chain extenders and / or cross linkers used are preferably alkanol amines and in particular diols and / or triols having molecular weights preferably between 60 g / mol to 300 g / mol.

[0132] Optionally flame retardants might be used as additives for the polyurethane foam. As flame retardants, it is generally possible to use the flame retardants known from the prior art.

[0133] More detailed information regarding the starting materials, blowing agents, catalysts and auxiliaries and / or additives used to carry out the process according to the invention can be found, for example, in the “Polyurethane Handbook”, Carl Hanser Publishers, 2nd edition 1993.

[0134] When producing polyurethane foams by the process according to the invention, the polyisocyanate and the isocyanate reactive compounds are preferably reacted at an isocyanate index of 70-800, more preferred 85-600, even more preferred 100-500.

[0135] Experimental part

[0136] The present invention is intended to be illustrated by the following examples, the examples being intended only to illustrate certain aspects of the invention and in no way to be regarded as limiting the scope of the invention.

[0137] Preparation of lignin polyols

[0138] Analytical methods:

[0139] 31P NMR analysis in N,N-dimethylformamid (DMF) was performed according to the method described in Stucker et. Al. Anal. Methods, 2018, 10, 3481-348: Approx. 15 mg lignin polyol was phosphitylated with 100 ul 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane in 350 pl DMF- d7. In addition, endo-N-hydroxy-5-norbornene-2,3-dicarboxylic acid imide (eHNDI) (as internal standard) with approx. 18mg / ml in 75 pl DMF-d7 and Cr(lll)-acetylacetonate (as relaxation reagent) with approx. 6 mg / ml in 75 pl pyridine were added. Viscosity determination:

[0140] Unless stated otherwise, the viscosity of the polyester polyols was determined at 25°C to DIN EN ISO 3219 (October 1994) with a Anton Parr viscosimeter using the CO 25 DIN spindle (spindle diameter: 12.5 mm; internal measuring cylinder diameter: 13.56 mm) at a shear rate of 50 1 / s.

[0141] Hydroxyl number: Hydroxyl numbers were determined by the acetic acid anhydride method DIN 53240 (December 1971) and are reported in mg KOH / g.

[0142] Acid number:

[0143] Acid numbers were determined to DIN EN 1241 (May 1998) and are reported in mg KOH / g.

[0144] Materials:

[0145] Lignin: Hardwood lignin from Eucalyptus, Mw 1700 g / mol KOH: aqueous solution of 0.48 wt.-% KOH in water Imidazole: aqueous solution of 0.50 wt.-% imidazole in water Diethlene glycol (DEG): 98% purity Propylene oxide: 99.8 % pure Ethylene oxide: 99.8 % pure Phosphoric acid: 98% purity Layer silicate: Ambosol MP20

[0146] Inventive example 1

[0147] 64.53 g of lignin powder was dissolved in 98.8 g PEG 600 at 80 °C for 2 h. Afterwards, 1.48 g of the aqueous KOH solution (0.48 % in water) was added, and the reactor was inertised with nitrogen three times at 25 °C. The reaction mixture was heated up to 100 °C, after which the stirrer was started. The reaction mixture was dried at 120 °C for 60 min. The reaction mixture was heated up to 130 °C and the dosing of 88.08 g propylene oxide (0.73 mol PO / mol OH) was started with a dosing speed of 0.5 ml / min. The temperature was kept at 130 °C until the reduction in pressure was below 0.02 bar / h. After this, the reaction mixture was vacuum stripped to remove the remaining amount of unreacted alkylene oxide. The resulting polyol was neutralized with phosphoric acid and by the addition of a layer silicate the remaining potassium was removed. Finally, the polyol was filtered to remove the formed salts and the silicate. In the next step, the polyol produced in the first step was used as solvent for additional lignin powder to increase the lignin amount. 40 g of lignin powder were dissolved in 150 g of the sample. 64.10 g of this mixture were used in the following alkoxylation.

[0148] Afterwards, 0.64 g of the aqueous KOH solution (0.48 % in water) was added, and the reactor was inertised with nitrogen three times at 25 °C. The reaction mixture was heated up to 100 °C, after which the stirrer was started. The reaction mixture was dried at 120 °C for 60 min. The reaction mixture was heated up to 130 °C and the dosing of 35.23 g propylene oxide (2.24 mol PO / mol OH) was started with a dosing speed of 0.5 ml / min. The temperature was kept at 130 °C until the reduction in pressure was below 0.02 bar / h. After this, the reaction mixture was vacuum stripped to remove the remaining amount of unreacted alkylene oxide. The resulting polyol was neutralized with phosphoric acid and by the addition of a layer silicate the remaining potassium was removed. Finally, the polyol was filtered to remove the formed salts and the silicate.

[0149] Inventive example 2

[0150] 77.45 g lignin powder was dissolved in 116.22 g DEG at 80 °C for 2 h. Afterwards, 0.6 g of the aqueous imidazole solution (50 wt%) was added, and the reactor was inertised with nitrogen three times at 25 °C. The reaction mixture was heated up to 100 °C, after which the stirrer was started. The reaction mixture was dried at 120 °C for 60 min. The reaction mixture was heated up to 130 °C and the dosing of 107 g propylene oxide (0.73 mol PO / mol OH) is started with a dosing speed of 0.5 ml / min. The temperature was kept at 130 °C until the reduction in pressure was below 0.02 bar / h. After this, the reaction mixture was vacuum stripped to remove the remaining amount of unreacted alkylene oxide.

[0151] In the next step, the polyol produced in the first step was used as solvent for additional Lignin powder to increase the amount. 45 g of lignin powder were dissolved in 150 g of the polyol produced in step 1. Afterwards, 0.65 g of the aqueous imidazole solution (50 wt%) was added, and the reactor was inertised with nitrogen three times at 25 °C. The reaction mixture was heated up to 100 °C, after which the stirrer was started. The reaction mixture was dried at 120 °C for 60 min. The reaction mixture was heated up to 130 °C and the dosing of propylene oxide (0.56mol PO / mol OH) is started with a dosing speed of 0.5 ml / min. The temperature was kept at 130 °C until the reduction in pressure was below 0.02 bar / h. After this, the reaction mixture was vacuum stripped to remove the remaining amount of unreacted alkylene oxide.

[0152] Comparative example 1 : One-step process to produce a lignin polyol to reach equivalent amount of lignin in the final polyol 85,67 g lignin powder was dissolved in 128.5g DEG at 80 °C for 2 h. Afterwards, 1.76 g aqueous KOH solution (0.48 % in water) was added, and the reactor was inertised with nitrogen three times at 25 °C. The reaction mixture was heated up to 100 °C, after which the stirrer was started. The reaction mixture was dried at 120 °C for 60 min. The reaction mixture was heated up to 130 °C and the dosing of 35.23 g propylene oxide (0.22mol PO / mol OH) is started with a dosing speed of 0.5 ml / min. The temperature was kept at 130 °C until the reduction in pressure was below 0.02 bar / h. After this, the reaction mixture was vacuum stripped to remove the remaining amount of unreacted alkylene oxide. The resulting polyol was neutralized with phosphoric acid and by the addition of a layer silicate the remaining potassium is removed. Finally, the polyol was filtered to remove the formed salts and the silicate. Unreacted lignin powder was located within the filter cake.

[0153] Table 1.31P NMR analysis of the lignin powder and the lignin polyols Table 2. Analysis of the used lignin powder and the polyols

[0154] *’ lignin content in the final polyol

[0155] Preparation of polyurethane foams

[0156] Methods

[0157] Core density:

[0158] The core density was determined by measuring the foam density in the core in accordance with DIN EN ISO 845.

[0159] Gel time:

[0160] Time from the commencement of mixing of the reaction mixture up to the time until it is possible to draw threads in contact with the foam (for example with a wooden rod). This point thus represents the transition from a liquid to a solid state.

[0161] Needle height:

[0162] The post-expansion of a respective foam was evaluated by the needle height test. Therefore, 80 g of a reaction mixture for the preparation of the respective foam were mixed in a cardboard cup having a volume of 0.735 I. At the time of the gel time, a pin was pressed into the foam at the upper edge of the cup. After the rising process of the polyurethane foam mold had ended, the difference in length between cup edge and needle was read off with a ruler.

[0163] Thermal conductivity:

[0164] The thermal conductivity was measured according to DIN EN 12667 on a TAURUS TCA 300 DTX at an average temperature of 10 °C. Three samples with a size of 300 x 300 x 30 mm3were tested.

[0165] Class E flame height test: The DIN EN 13501 class E test was performed according to the EN ISO 11925-2 standard. For each material, three specimens with a size of 190 x 91 x 20 mm3were tested.

[0166] Materials

[0167] Polyol 1: Polyester polyol based on phthalic anhydride, diethylene glycol, oleic acid and ethylene glycol; functionality 1.7 and OH number 215 mg KOH / g

[0168] Polyol 2: Polyether polyol based on diethylene glycol and ethylene oxide; functionality 2.0 and OH number 180 mg KOH / g

[0169] Polyol 3: Polyether polyol based on lignin, diethylene glycol and ethylene oxide; functionality 2.6, OH number 389 mg KOH / g, acid number <0,01 mgKOH / g, lignin content 36 wt.- %;

[0170] Polyol 4: Polyether polyol based on lignin, diethylene glycol and ethylene oxide; functionality 2.6, OH number 389 mg KOH / g, acid number 0.58 mg KOH / g, lignin content 36 wt.- %;

[0171] Polyol 5: Polyether polyol based on sucrose, glycerine and propylene oxide; functionality 6.0 and OH number 425 mg KOH / g

[0172] Polyol 6: Polyesterpolyol, OH number 350 mg KOH / g

[0173] Polyol 7: Polyether polyol based on lignin, diethylene glycol, propylene oxide and ethylene oxide; functionality 2.6, OH number 422 mg KOH / g, acid number <0,01 mg KOH / g, lignin content 32 wt.-%;

[0174] Polyol 8: Polyether polyol based on lignin, diethylene glycol, propylene oxide and ethylene oxide; functionality 2.6, OH number 422 mg KOH / g, acid number 0.11 mg KOH / g, lignin content 32 wt.-%;

[0175] Polyol 9: Polyether polyol based on lignin, diethylene glycol, propylene oxide and ethylene oxide; functionality 2.6 and OH number 422 mg KOH / g, acid number 0.81 mg KOH / g, lignin content 32 wt%;

[0176] Blowing agent 1: Formic acid 85%

[0177] Blowing agent 2: Pentane S 80 / 20

[0178] Blowing agent 3: Solstice LBA

[0179] Catalyst 1 : Potassium formate (40 wt%)

[0180] Catalyst 2: Bis(dimethylaminoethyl)ether solution (23 wt%)

[0181] Catalyst 3: Tertiary aliphatic amine

[0182] Catalyst 4: T ertiary aliphatic amine

[0183] Catalyst 5: Lupragen N 600 from BASF SE

[0184] Flame retardant 1: Tris(chloropropyl) phosphate

[0185] Flame retardant 2: Triethyl phosphate Flame retardant 3: Brominated polyetherpolyol, OH number 217 mg KOH / g

[0186] Isocyanate 1 : Lupranat M 50 from BASF SE

[0187] Isocyanate 2: Lupranat M 20 S from BASF SE Table 3. Comparison of lignin-based polyols with varying acid number in PIR foams

[0188] Table 4. Comparison of lignin-based polyols with varying acid number in Pll foams

[0189]

[0190] In both PIR and Pll foams, the inventive lignin-based polyether polyols with an acid number below 0.1 mg KOH / g led to a faster reactivity as well as better thermal conductivity and burning behavior than comparative lignin-based polyols with a higher acid number.

Claims

Claims1. A polyether polyol comprising lignin and having an acid number lower than 0.1 mg KOH / g.

2. The polyether polyol of claim 1 , wherein the acid number of the polyether polyol is lower than 0.05 mg KOH / g.

3. The polyether polyol of any of claims 1 or 2, wherein the polyether polyol comprises less than 0.1 mmol / g phenolic OH groups.

4. The polyether polyol of any of claims 1 to 3, wherein the amount of lignin is 15-80 wt.-%, based on the total weight of the polyether polyol.

5. The polyether polyol of any of claims 1 to 4, wherein the lignin is kraft lignin.

6. A process for the production of a polyether polyol according to any of claims 1 to 5, the process comprising the steps a) providing a mixture M1) comprising lignin, alkoxylation catalyst and one or more compounds selected from monoalcohols, polyhydric alcohols, fatty acid esters and polyetherols b) dosing alkylene oxide to the mixture M1) c) reacting the mixture M1) with the alkylene oxide d) obtaining an intermediate polyether polyol H) e) mixing further lignin in the obtained polyether polyol H) to obtain a mixture M2), wherein the amount of further lignin is 10-150 wt.-% based on the amount of the polyether polyol H) f) dosing alkylene oxide to the mixture M2) g) reacting the mixture M2) with an alkylene oxide h) obtaining a polyether polyol.

7. The process according to claim 6, wherein at least 80 wt.-% of the alkylene oxide used in the preparation of the polyether polyol H) is dosed in step b) and at least 80 wt.-% of the alkylene oxide used in the preparation of the polyether polyol is dosed in step f).

8. The process according to claim 7, wherein at least 95 wt.-% of the alkylene oxide used in the preparation of the intermediate polyether polyol H) is dosed in step b) and at least 95 wt.-% alkylene oxide used in the preparation of the polyether polyol is dosed in step f).

9. The process according to any of claims 6 to 8, wherein the reaction temperature in steps d) and h) is 110-150 °C.

10. The process according to any of claims 6 to 9, wherein the catalyst is an alkaline metal hydroxide or an amine.

11. The process according to claim 10, wherein the catalyst is imidazole.

12. Use of the polyether polyol according to claims 1 to 5 or the polyether polyol prepared by the process of any of claims 6 to 11 for the production of polyurethanes.

13. Process for the preparation of a polyurethane, wherein a polyol composition comprising the polyether polyol according to claims 1 to 5 or the polyether polyol prepared by to the process of any of claims 6 to 11 is reacted with a polyisocyanate.

14. A polyurethane obtained by the process of claim 13.

15. A polyurethane based on the polyether polyol of any of claims 1 to 5 and polyisocyanate.

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