PROCESS FOR PRODUCING POLYOXYMETHYLENE-POLYALKYLENE OXIDE BLOCK COPOLYMERS

Abstract

In a process for producing polyoxymethylene-polyalkylene oxide block copolymers comprising the step of polymerizing an alkylene oxide in the presence of an OH-terminated polyoxymethylene polymer and a catalyst, the polyoxymethylene polymer has a number-average molecular weight Mn determined after derivatization with propylene oxide and gel permeation chromatography against polystyrene standards with tetrahydrofuran as the eluent of ≥1100 g/mol to ≤2300 g/mol and the ratio of alkylene oxide to polyoxymethylene polymer is ≥0.05 mol/g. The invention further relates to copolymers obtainable by the process, to a process for producing polyurethane polymers using these copolymers and to polyurethanes obtainable therefrom.

Claims

1. A process for producing a polyoxymethylene-polyalkylene oxide block copolymer, comprising polymerizing an alkylene oxide in the presence of an OH-terminated polyoxymethylene polymer and a catalyst, wherein the polyoxymethylene polymer has a number-average molecular weight M.sub.n determined after derivatization with propylene oxide and gel permeation chromatography of ≥1100 g/mol to ≤2300 g/mol with tetrahydrofuran as eluent against polystyrene standards and the ratio of alkylene oxide to polyoxymethylene polymer is ≥0.05 mol/g.

2. The process as claimed in claim 1, wherein the catalyst comprises a double metal cyanide catalyst.

3. The process as claimed in claim 1, wherein alkylene oxide and polyoxymethylene polymer are present in a weight ratio of alkylene oxide to polyoxymethylene polymer of ≤4.5:1.

4. The process as claimed in claim 1, wherein the polyoxymethylene polymer has an average OH functionality of >1.9.

5. The process as claimed in claim 1, wherein a comonomer other than alkylene oxide is co-used in the reaction.

6. The process as claimed in claim 1, wherein the catalyst comprises a double metal cyanide catalyst (DMC catalyst) and wherein (i) in a first step the DMC catalyst is activated in the presence of the polyoxymethylene polymer, wherein the DMC catalyst is activated by addition of a sub-amount of an alkylene oxide, and (ii) in a second step an alkylene oxide is added to the mixture resulting from step (i), wherein the alkylene oxide employed in step (ii) may be identical or different to the alkylene oxide employed in step (i) and wherein the activation of the DMC catalyst in the first step (i) is carried out at an activation temperature of ≥20° C. to ≤120° C.

7. The process as claimed in claim 6, wherein in the first step (i) (α) a suspension medium or the polyoxymethylene polymer is initially charged and the suspension medium or polyoxymethylene polymer is dried by removing any water and/or other volatile compounds present, wherein the DMC catalyst is added to the polyoxymethylene polymer or to the suspension medium before or after the drying, (β) the DMC catalyst is activated in the presence of the polyoxymethylene polymer by addition of a sub-amount of alkylene oxide to the mixture resulting from step (α) and wherein the temperature peak occurring on account of the subsequent exothermic chemical reaction and/or a pressure drop in the reactor is then awaited, and wherein step (β) for activation may optionally be carried out two or more times, and in the second step (ii) (γ) an alkylene oxide are added to the mixture resulting from step (β), wherein alkylene oxide employed in step (γ) may be identical or different to alkylene oxide employed in step (β) and wherein at least in one of the steps (α) and (β) at least one polyoxymethylene polymer is added.

8. The process as claimed in claim 7, wherein step (γ) is performed at a temperature of ≥60° C. to ≤70° C.

9. The process as claimed in claim 7, wherein the suspension medium used in step (α) comprises 4 methyl-2-oxo-1,3-dioxolane, 1,3-dioxolan-2-one, acetone, methyl ethyl ketone, acetonitrile, nitromethane, dimethyl sulfoxide, sulfolane, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dioxane, diethyl ether, methyl tert-butyl ether, tetrahydrofuran, ethyl acetate, butyl acetate, pentane, n-hexane, benzene, toluene, xylene, ethylbenzene, chloroform, chlorobenzene, dichlorobenzene, propylene carbonate, carbon tetrachloride, or a mixture thereof.

10. The process as claimed in claim 7, wherein step (α) comprises: (α1) initially charging a suspension medium and the DMC catalyst and removing water and/or other volatile compounds by at least once pressurizing the mixture with >1 bar to ≤100 bar (absolute) of an inert gas at a temperature of ≥90° C. to ≤150° C. and in each case subsequently reducing the positive pressure to >1 bar to ≤20 bar (absolute) and in a subsequent step; and (α2) adding the polyoxymethylene polymer to the mixture from step (α1).

11. A polyoxymethylene-polyalkylene oxide block copolymer obtained by the process as claimed in claim 1.

12. The polyoxymethylene-polyalkylene oxide block copolymer as claimed in claim 11, wherein the polyoxymethylene-polyalkylene oxide block copolymer has a viscosity at 20° C. determined according to DIN 51562 of ≥22,000 mPas to ≤26,000 mPas.

13. The polyoxymethylene-polyalkylene oxide block copolymer as claimed in claim 11, wherein the polyoxymethylene-polyalkylene oxide block copolymer is a polyoxymethylene-polyoxyalkylene carbonate block copolymer comprising an inner polyoxymethylene block and at least one outer polyoxyalkylene carbonate block according to the formula: ##STR00002## wherein R independently at each occurrence represents an organic radical, a, b and c each represent an integer, each R may be the same or different, the structural unit “starter” represents a polyoxymethylene block derived from the polyoxymethylene polymer and a, b and c are chosen such that the proportion of the “starter” accounts for ≤35% by weight, the proportion of structural units deriving from CO.sub.2 accounts for ≤25% by weight and the proportion of structural units deriving from alkylene oxides accounts for the remainder to 100% by weight in each case based on the total weight of the polymer.

14. A process for producing a polyurethane polymer comprising the step of reacting a polyisocyanate component with a polyol component, wherein the polyol component comprises a polyoxymethylene-polyalkylene oxide block copolymer as claimed in claim 11.

15. A polyurethane polymer obtained by the process as claimed in claim 14.

Description

EXAMPLES

[0073] The present invention is elucidated in detail by the examples and figures that follow, but without being restricted thereto.

[0074] FIG. 1 shows a gel permeation chromatogram of a sample from example 1

[0075] FIG. 2 shows a gel permeation chromatogram of a sample from example 2

[0076] FIG. 3 shows a gel permeation chromatogram of a sample from example 3

[0077] FIG. 4 shows a gel permeation chromatogram of a sample from counterexample 2

GPC METHOD

[0078] The molecular weight determination of the block copolymers by gel permeation chromatography (GPC) was carried out using tetrahydrofuran (THF) as eluent against polystyrene standards. In addition the hydroxyl numbers (OHN) of the samples were determined according to DIN 53240 and the molecular weights of the block copolymers were calculated according to the formula MW=1000 mg/g.Math.(F.Math.56.106 g/mol)/OHN, wherein functionality F was assumed to be 2. Polydispersity indices PDI were calculated from M.sub.w/M.sub.n (GPC).

NMR Method for Determining Polymer Composition:

[0079] The composition of the polymer were determined by .sup.1H NMR (Bruker DPX 400, 400 MHz; pulse program zg30, relaxation time D1: 10 s, 64 scans). Each sample was dissolved in deuterated chloroform. The relevant resonances in the .sup.1H NMR (based on TMS=0 ppm) and the assignment of the area integrals (A) are as follows: [0080] cyclic propylene carbonate (cPC), solvent, resonance at 4.5 ppm, area integral corresponds to one hydrogen atom; [0081] unreacted monomeric propylene oxide (PO), resonance at 2.4 and 2.75 ppm, area integral corresponds to one hydrogen atom in each case; [0082] polypropylene oxide (PPO), PO homopolymer, resonances at 1.2 to 1.0 ppm, area integral corresponds to 3 hydrogen atoms; [0083] poly- or paraformaldehyde (pFA) with resonances at 4.6 to 5.2 ppm, area integral minus one H atom of cyclic propylene carbonate (cPC) in each case; [0084] formate (HCOO), by-product, resonance at 8.1 ppm, area integral corresponds to one hydrogen atom; [0085] methoxy (MeO), trace by-product, resonance at 3.4 ppm.

[0086] Determination of the mole fractions (x) of the reaction mixture is carried out as follows: [0087] x(cPC)=A(4.5 ppm) [0088] x(P0)=A(2.75 ppm) or A(2.4 ppm) [0089] x(PPO)=A(1.2-10 ppm)/3 [0090] x(pFA)=(A(4.6-5.2 ppm)-x(cPC) [0091] x(HCOO)=A(8.1 ppm)

[0092] The composition of the reaction mixture thus determined is subsequently converted to parts by weight and normalized to 100. Conversion of the weight fractions uses the following molar masses (g/mol): cPC=102, PO and PPO=58, pFA=30 and HCOO=45. The polymer composition is calculated and normalized using the proportions of PPO and pFA so that here too the reported amounts are in parts by weight out of 100 (% by weight).

Molar Mass of Paraformaldehyde Block:

[0093] The molar mass of the pFA block in the product polymer was calculated using gravimetric and NMR analytical methods performed according to the formulae below: [0094] 1) Determination by mass fraction: MW(pFA)=M.sub.n(OHN).Math.(m(PFA)/(m(pFA)+m(PO))) [0095] 2) Determination by NMR: MW(pFA)=M.sub.n(OHN).Math.(pFA proportion in polymer, NMR)/100
wherein M.sub.n(OHN) is the molecular weight MW determined by OH number titration (MW=56 100*2/OH number).

Synthesis of Polyoxymethylene Polymer

[0096] This polymer was synthesized as described in the European patent application filed on Nov. 22, 2018 having the application number EP18207740. The polyoxymethylene polymer used in examples 1 and 2 was produced according to example 1 of EP18207740 and the polyoxymethylene polymer used in example 3 was produced according to example 2 of EP18207740.

Example 1 (Inventive): Production of a Polyoxymethylene-Polyoxyalkylene Block Copolymer Using the Polyoxymethylene Polymer as Starter Material

[0097] In this example the mass ratio of propylene oxide to pFA starter excluding the propylene oxide used for catalyst activation was 200 g/50 g=4 g/g. Converted to the amount of substance of propylene oxide the ratio was 3.44 mol/50 g=0.069 mol/g. Including the propylene oxide (10 g) used for activation the ratios were 4.2 g/g and 0.072 mol/g.

[0098] 500 mg of dried unactivated DMC catalyst were suspended in 200.0 g of 4-methyl-2-oxo-1,3-dioxolane (also referred to hereinafter as cyclic propylene carbonate or cPC) in a 1.0 L pressure reactor fitted with a gas introduction means. The suspension was heated to 130° C. with stirring (500 rpm). Simultaneously a vacuum was applied for 30 min and the pressure was set to 100 mbar with a constant volume flow of nitrogen through the reactor (vacuum stripping).

[0099] Once vacuum stripping was complete the pressure was adjusted to 5 bar with nitrogen and a pulse of propylene oxide (10 g) was added to the reaction solution. Activation of the catalyst was apparent from a temperature increase with a simultaneous pressure drop. The catalyst activation was followed by cooling of the reactor to room temperature and depressurization. 50.0 g of polyoxymethylene polymer (pFA) were added to the reactor and the reactor was re-sealed and purged by pressurization and depressurization with nitrogen. A pressure of 10 bar was then established with nitrogen. The reactor internal temperature was set to 70° C.

[0100] 50 g of propylene oxide were quickly added to the suspension at an addition rate of 10 g/min (activation). Once addition was complete and after achievement of a constant pressure (time to) the mixture was left until an exothermic reaction in the reactor coupled with a simultaneous pressure drop (time ti) was observable. The time interval between addition (to) and onset of reaction (ti) is hereinbelow referred to as the activation time (t.sub.act).

[0101] After the exothermic reaction had abated the reactor temperature was increased to 100° C. and the remaining amount of propylene oxide (150 g) was added at an addition rate of 3 g/min (semi-batch phase). Once addition was complete the mixture was stirred at 100° C. until the exothermic reaction had abated and until a constant pressure was achieved. The reactor was then cooled and the product withdrawn. The analytical data are reported in table 1. The molar mass distribution is shown in the GPC diagram of FIG. 1.

Example 2 (Inventive): Production of a Polyoxymethylene-Polyoxyalkylene Block Copolymer Using the Polyoxymethylene Polymer as Starter Material

[0102] In this example the mass ratio of propylene oxide to pFA starter excluding the propylene oxide used for catalyst activation was 150 g/50 g=3 g/g. Converted to the amount of substance of propylene oxide the ratio was 2.57 mol/50 g=0.051 mol/g. Including the propylene oxide (10 g) used for activation the ratios were 3.2 g/g and 0.055 mol/g.

[0103] A polyoxymethylene-polyoxyalkylene block copolymer was produced according to example 1 but only 100 g of propylene oxide were supplied during the semi-batch phase. The molar mass distribution is shown in the GPC diagram of FIG. 2.

Example 3 (Inventive): Production of a Polyoxymethylene-Polyoxyalkylene Block Copolymer Using the Polyoxymethylene Polymer as Starter Material

[0104] In this example a smaller amount of catalyst and a larger amount of propylene oxide compared to example 2 were used for catalyst activation. The propylene oxide metered addition amount was also different. The mass ratio of propylene oxide to PFA starter excluding the propylene oxide used for catalyst activation was 150 g/50 g=3 g/g. Converted to the amount of substance of propylene oxide the ratio was 3.44 mol/50 g=0.069 mol/g. Including the propylene oxide (20 g) used for activation the ratios were 3.4 g/g and 0.059 mol/g.

[0105] 300 mg of dried unactivated DMC catalyst were suspended in 200.0 g of 4-methyl-2-oxo-1,3-dioxolane (also referred to hereinafter as cyclic propylene carbonate or cPC) in a 1.0 L pressure reactor fitted with a gas introduction means. The suspension was heated to 130° C. with stirring (500 rpm). Simultaneously a vacuum was applied for 30 min and the pressure was set to 100 mbar with a constant volume flow of nitrogen through the reactor (vacuum stripping).

[0106] Once vacuum stripping was complete the pressure was adjusted to 10 bar with nitrogen and a pulse of propylene oxide (10 g) was added to the reaction solution. The procedure was carried out twice in total. Activation of the catalyst was apparent from a temperature increase with a simultaneous pressure drop. The catalyst activation was followed by cooling of the reactor to room temperature and depressurization. 50.0 g of polyoxymethylene polymer were added to the reactor and the reactor was re-sealed and purged by pressurization and depressurization with nitrogen. A pressure of 10 bar was then established with nitrogen. The reactor internal temperature was set to 70° C.

[0107] 10 g of propylene oxide were quickly added to the suspension at an addition rate of 10 g/min (activation). Once addition was complete and after achievement of a constant pressure (time to) the mixture was left until an exothermic reaction in the reactor coupled with a simultaneous pressure drop (time ti) was observable. The time interval between addition (to) and onset of reaction (ti) is hereinbelow referred to as the activation time (t.sub.act).

[0108] After the exothermic reaction had abated, the remaining amount of propylene oxide (140 g) was added at an addition rate of 3 g/min (semi-batch phase). Once addition was complete the mixture was stirred at 70° C. until the exothermic reaction had abated and until a constant pressure was achieved. The reactor was then cooled and the product withdrawn. The analytical data are reported in table 1. The molar mass distribution is shown in the GPC diagram of FIG. 3.

Counterexample G1: Production of a Polyoxymethylene-Polyoxyalkylene Block Copolymer Using the Polyoxymethylene Polymer as Starter Material

[0109] This example is a comparative example since the ratio of the amount of substance of propylene oxide to the mass of the polyoxymethylene polymer (PO/pFA=1.67) is below the lower limit according to the invention.

[0110] A polyoxymethylene-polyoxyalkylene block copolymer was produced according to example 1 but only 50 g of propylene oxide were supplied during the semi-batch phase. After addition of propylene oxide there was a lot of solid in the reaction solution and on the reactor wall and the reaction mixture therefore could not be analyzed.

Counterexample G2: Production of a Polyoxymethylene-Polyoxyalkylene Block Copolymer Using Commercial Paraformaldehyde (Granuform M)

[0111] This example is a comparative example since the molar mass of the paraformaldehyde is not in the range provided for according to the invention.

[0112] 1400 mg of dried unactivated DMC catalyst were suspended in 200.0 g of 4-methyl-2-oxo-1,3-dioxolane (also referred to hereinafter as cyclic propylene carbonate or cPC) in a 1.0 L pressure reactor. The suspension was heated to 130° C. with stirring (500 rpm). Simultaneously a vacuum was applied for 30 min and the pressure was set to 100 mbar with a constant volume flow of nitrogen through the reactor (vacuum stripping).

[0113] Once vacuum stripping was complete the pressure was adjusted to 10 bar with nitrogen and a pulse of propylene oxide (10 g) was added to the reaction solution. Activation of the catalyst was apparent from a temperature increase with a simultaneous pressure drop. The catalyst activation was followed by cooling of the reactor to room temperature and depressurization. 50 g of paraformaldehyde (Granuform M) were added to the reactor and the reactor was re-sealed and purged by pressurization and depressurization with nitrogen. A pressure of 10 bar was then established with nitrogen. The reactor internal temperature was set to 70° C.

[0114] 50 g of propylene oxide were quickly added to the suspension at an addition rate of 10 g/min (activation). Once addition was complete and after achievement of a constant pressure (time to) the mixture was left until an exothermic reaction in the reactor coupled with a simultaneous pressure drop (time ti) was observable. The time interval between addition (to) and onset of reaction (ti) is hereinbelow referred to as the activation time (t.sub.act).

[0115] After the exothermic reaction had abated, the remaining amount of propylene oxide (150 g) was added at an addition rate of 3 g/min (semi-batch phase). Once addition was complete the mixture was stirred until the exothermic reaction had abated and until a constant pressure was achieved. The reactor was then cooled and the product withdrawn. The analytical data are reported in table 1. The molar mass distribution is shown in the GPC diagram of FIG. 4.

TABLE-US-00001 TABLE 1 pFA in MW MW MW polymer (pFA) (pFA) (g .Math. (%) by NMR gravim. t.sub.act, No. mol.sup.−1) PDI NMR (g .Math. mol.sup.−1) (g .Math. mol.sup.−1) [min] 1 7430.5 1.62 19.4 1442 1427 120 min 2 6759.0 1.49 23.2 1568 1298 120 min 3 8904*  1.60 22.8  2030**  1709**  70 min G1 n.d. n.d. n.d. n.d. n.d. no activation G2 2300*  1.31 18.7  430  442 210 min “Starter” refers to polyoxymethylene polymer or paraformaldehyde. “pFA” refers to polymeric formaldehyde (polyoxymethylene polymer). “n.d.”: not determined. *calculated with MW = M.sub.n(GPC) .Math. 0.7 (correction factor); **based on calculated MW of the block copolymer.