METHOD FOR PRODUCING POLYOXYMETHYLENE POLYOXYALKYLENE BLOCK COPOLYMERS

Abstract

The invention relates to a method for producing a polyoxymethylene polyoxyalkylene block copolymer, said method including the process of reacting a polymer formaldehyde compound with alkylene oxide in the presence of a double metal cyanide (DMC) catalyst and an H-functional starter substance, wherein the theoretical molar mass of the polymer formaldehyde compound is lower than the theoretical molar mass of the H-functional starter substance, and the polymer formaldehyde compound has at least one terminal hydroxyl group, the theoretical molar mass of the H-functional starter substance being at least 500 g/mol. In the method according to the invention, a mixture i) is provided comprising the DMC catalyst and the H-functional starter substance in step (i); the polymer formaldehyde compound is then added to the mixture (i) in step (ii), thereby forming a mixture (ii); and the alkylene oxide is added in step (iii), step (ii) being carried out at the same time as or prior to step (iii).

Claims

1. A process for preparing a polyoxymethylene-polyoxyalkylene block copolymer comprising reacting of a polymeric formaldehyde compound with an alkylene oxide in the presence of a double metal cyanide (DMC) catalyst and an H-functional starter substance; wherein the theoretical molar mass of the polymeric formaldehyde compound is less than the theoretical molar mass of the H-functional starter substance; wherein the polymeric formaldehyde compound has at least one terminal hydroxyl group; and wherein the theoretical molar mass of the H-functional starter substance is at least 500 g/mol; the process comprising: (i) initially charging a mixture i) comprising the DMC catalyst and the H-functional starter substance; (ii) adding the polymeric formaldehyde compound to mixture i) to form a mixture ii); (iii) adding the alkylene oxide; wherein step (ii) is carried out simultaneously with or prior to step (iii).

2. The process as claimed in claim 1, wherein the polyoxymethylene-polyoxyalkylene blockcopolymer has a number-average molecular weight of 1000 g/mol to 10000 g/mol.

3. The process as claimed in claim 1, wherein the H-functional starter substance comprises a polyoxyalkylene polyol, a polyether polyol, a polyester polyol, a polycarbonate polyol, a polyether polyester polyol, a polyether carbonate polyol, a polyether polyester carbonate polyol, or a mixture of any two or more thereof.

4. The process as claimed in claim 3, wherein the H-functional starter substance comprises a polyether polyol comprising polyoxymethylene-polyoxyalkylene block copolymer, wherein the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter may be the same as or different from the polyoxymethylene-polyoxyalkylene block copolymer produced by the process.

5. The process as claimed in claim 4, wherein the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter comprises a reaction product of a polymeric formaldehyde compound with an alkylene oxide in the presence of a double metal cyanide (DMC) catalyst (A).

6. The process as claimed in claim 4, wherein the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter has an identical functionality to the polyoxymethylene-polyoxyalkylene block copolymer produced by the process and the number-average molecular weight of the polyoxymethylene-polyoxyalkylene block copolymer H-functional starter diverges from that of the polyoxymethylene-polyoxyalkylene block copolymer produced by the process by up to 20%.

7. The process as claimed in claim 1, wherein the double metal cyanide (DMC) catalyst is used in a theoretical amount of 100 to 800 ppm, based on the sum of the masses of the polymeric formaldehyde compound, of the alkylene oxide and of the H-functional starter substance.

8. The process as claimed in claim 5, wherein the double metal cyanide (DMC) catalyst comprises the double metal cyanide (DMC) catalyst (A) and optionally a double metal cyanide (DMC) catalyst (B).

9. The process as claimed in claim 8, wherein the mass ratio of the double metal cyanide (DMC) catalyst (A) based on the sum of the masses of double metal cyanide (DMC) catalyst (A) and double metal cyanide (DMC) catalyst (B) is 40% by weight to 100% by weight.

10. The process as claimed in claim 8, wherein the double metal cyanide (DMC) catalyst comprises the double metal cyanide (DMC) catalyst (A) and the double metal cyanide (DMC) catalyst (B) and the double metal cyanide (DMC) catalyst (B) is added to the polyoxymethylene-polyoxyalkylene block copolymer.

11. The process as claimed in claim 1, wherein the polymeric formaldehyde compound has 2 hydroxyl groups and 8 to 100 repeating oxymethylene units (n) or 3 hydroxyl groups and 8 to 100 repeating oxymethylene units (n).

12. The process as claimed in claim 1, wherein step (iii) is carried out at a temperature of 50° C. to 150° C.

Description

EXAMPLES

Compounds Used:

[0142] Paraformaldehyde (Granuform M®) from Ineos was used. Propylene oxide was sourced from Sigma-Aldrich and used without purification. The DMC catalyst used in all examples was DMC catalyst prepared according to example 6 in WO 01/80994 A1, containing zinc hexacyanocobaltate, tert-butanol and polypropylene glycol having a number-average molecular weight of 1000 g/mol.

Description of the Method

.SUP.1.H NMR

[0143] The composition of the polymer was determined by .sup.1H NMR (Bruker DPX 400, 400 MHz; pulse program zg30, relaxation time D1: 10s, 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: [0144] cyclic propylene carbonate (cPC), by-product, with resonance at 4.5 ppm, area integral corresponds to one hydrogen atom; [0145] monomeric propylene oxide (PO), which is not been fully depleted, with resonance at 2.4 and 2.75 ppm, each area integral corresponds to one H atom; [0146] polypropylene oxide (PPO), PO homopolymer, with resonances at 1.0 to 1.2 ppm, area integral corresponds to 3 H atoms; [0147] poly- or paraformaldehyde (pFA) with resonances at 4.6 to 5.2 ppm, area integral minus one H atom of cyclic propylene carbonate (cPC) thus corresponds to 2 hydrogen atoms;

[0148] The mole fractions (x) of the reaction mixture are determined as follows: [0149] x(cPC)=A(4.5 ppm) [0150] x(PO)=A(2.75 ppm) or A(2.4 ppm) [0151] x(PPO)=A(1.0-1.2 ppm)/3 [0152] x(pFA)=(A(4.6-5.2 ppm)-x(cPc)-x(1PC))/2

[0153] The percentage mole fraction is calculated by dividing the mole fraction (x) of the respective component by the sum of the mole fractions present in the sample. The weight fraction is also calculated by multiplying the mole fractions (x) by the accompanying molar masses and dividing by the sum of the weight fractions present. Conversion of the weight fractions uses the following molar masses (g/mol): cPC=102, PO and PPO=58, pFA=30. 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).

GPC

[0154] The weight-average and number-average molecular weights Mw and Mn of the resulting polymers were determined by gel permeation chromatography (GPC). The procedure was based on DIN 55672-1: “Gel permeation chromatography—Part 1: Tetrahydrofuran as elution solvent”. Polystyrene samples of known molar mass were used for calibration. The polydispersity index is calculated from that of the quotient of the weight-average and number-average molecular weights.

Example 1 (comparative)

Preparation of Polyoxymethylene-polyalkene Oxide Block Copolymer (A-1) As H-functional Starter Substance, DMC Total Catalyst Loading of 2000 ppm

[0155] 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 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). Once vacuum stripping was complete the vacuum pump was deactivated and the reactor was cooled to room temperature and brought to ambient pressure using nitrogen. 157.2 g of paraformaldehyde were added to the suspension and the reactor was resealed. The reactor internal temperature was set to 70° C. 160 g of propylene oxide were quickly added to the suspension at an addition rate of 10 g/min. 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 t1) was observable. The time interval between addition (t0) and onset of reaction (t1) is hereinbelow referred to as the activation time (t.sub.act). After the exothermic reaction had abated, the remaining amount of propylene oxide (362.8 g) was added at an addition rate of 3 g/min. 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 average molecular weight (determined by gel permeation chromatography) and the activation time are reported in table 1. The product was subsequently freed of the cPC in a thin-film evaporator (150° C., 0.05 mbar) and the reaction product is hereinbelow referred to as polyoxymethylene-polyalkylene oxide block copolymer (A-1).

Example 2

Preparation of a Polyoxymethylene-polyoxyalkylene Block Copolymer (A-2) Using the Polyoxymethylene-polyalkylene Oxide Block Copolymer (A-1) Having a DMC Total Catalyst Loading of 667 ppm

[0156] 21.6 g of paraformaldehyde (21.6 g) were suspended in 45 g of the above-prepared polyoxymethylene-polyalkylene oxide block copolymer (A-1) in a 300 ml pressure reactor having gas and liquid addition means. A total of three times the suspension was subjected to 25 bar of N.sub.2 at room temperature with stirring before the pressure was subsequently reduced to 5 bar of nitrogen (pressure stripping). Once pressure stripping was complete a pressure of 10 bar was established with nitrogen. The total amount of the propylene oxide (68.4 g) was subsequently added to the reactor. The reactor internal temperature was set to 70° C. and the suspension stirred at 500 rpm. After achievement of a constant temperature and pressure (time t.sub.0) the mixture was left until an exothermic reaction in the reactor coupled with a simultaneous pressure drop (time t.sub.1) was observable. The time interval between achieving the target temperature (t.sub.0) and onset of reaction (t.sub.1) is hereinbelow referred to as the activation time (t.sub.act). Once the exothermic reaction had abated the mixture was stirred at 70° C. until abatement of the exothermic reaction and until a constant pressure was achieved. The average molecular weight (determined by gel permeation chromatography) and the activation time are reported in table 1.

Example 3

Preparation of a Polyoxymethylene-polyoxyalkylene Block Copolymer (A-3) Using the Polyoxymethylene-polyalkylene Oxide Block Copolymer (A-2) having a DMC Total Catalyst Loading of 222 ppm

[0157] A polyoxymethylene-polyoxyalkylene block copolymer (A-3) was prepared according to example 2 but using the product from example 2 (A-2) as solvent instead of the polyoxymethylene-polyoxyalkylene oxide block copolymer (A-1).

Example 4

Preparation of a Polyoxymethylene-polyoxyalkylene Block Copolymer (A-4) Using the Polyoxymethylene-polyalkylene Oxide Block Copolymer (A-3) Having a DMC Total Catalyst Loading of 500 ppm

[0158] A polyoxymethylene-polyoxyalkylene block copolymer was prepared according to example 3 but using the product from example 3 (A-3) as solvent instead of the product from example 2 (A-2). In addition, 0.058 g of DMC catalyst was added to the initial suspension.

Example 5 (comparative)

Preparation of a Polyoxymethylene-polyoxyalkylene Block Copolymer Using 1000 ppm of DMC Catalyst and Toluene as Solvent

[0159] 500 mg of dried, unactivated DMC catalyst were suspended in 250.0 g of toluene in a 1.0 L pressure reactor using a gas introduction means. The suspension was heated to 130° C. with stirring (500 rpm). An N.sub.2 pressure of 40 bar was applied before the N.sub.2 pressure was reduced to 15 bar again. The application and release of N.sub.2 pressure was performed twice further in the same way (pressure stripping). Once pressure stripping was complete the reactor was cooled to room temperature and brought to ambient pressure using nitrogen. 112.3 g of paraformaldehyde were added to the suspension and the reactor was resealed. This was followed by renewed pressure stripping at room temperature. The reactor internal temperature was set to 70° C. After achieving the temperature 120 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 t.sub.0) the mixture was left until an exothermic reaction in the reactor coupled with a simultaneous pressure drop (time t.sub.1) was observable. The time interval between addition (t.sub.0) and onset of reaction (t.sub.1) is hereinbelow referred to as the activation time (t.sub.act). After the exothermic reaction had abated the reactor temperature was increased to 100° C. and the remaining amount of propylene oxide (376.7 g) was added at an addition rate of 3 g/min. 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 average molecular weight (determined by gel permeation chromatography) and the activation time are reported in table 1.

Example 6 (comparative)

Preparation of a Polyoxymethylene-polyoxyalkylene Block Copolymer Using 500 ppm of DMC Catalyst and Toluene as Solvent

[0160] A polyoxymethylene-polyoxyalkylene block copolymer was to be prepared according to example 4 but with only 250 mg of catalyst being added to the reactor at commencement of the reaction (500 ppm catalyst loading). After addition of the 120 g of propylene oxide during activation, neither an exothermic reaction nor a pressure drop were observable over a period of 8 hours.

Example 7

Preparation of a Polyoxymethylene-polyoxyalkylene Block Copolymer Using 513 ppm of DMC Catalyst and Polypropylene Glycol (2000 g/mol, PPG2000) as Solvent

[0161] 308 mg of dried, unactivated DMC catalyst were suspended in 200 g of a bifunctional polyether polyol (polypropylene glycol, PPG 2000 g/mol, Covestro AG, containing 131 mg of activated DMC catalyst) and 157.1 g of paraformaldehyde in a 1.0 L pressure reactor having a gas introduction means. The suspension was pretreated by vacuum stripping at 60° C. with stirring (500 rpm). Once vacuum stripping was complete (40 mbar) the reactor internal temperature was set to 70° C. and 45 g of propylene oxide were quickly added to the suspension at an addition rate of 10 g/min. Once addition was complete and after achievement of a constant pressure (time t0) the mixture was left until an exothermic reaction in the reactor coupled with a simultaneous pressure drop (time t1) was observable. The time interval between addition (t0) and onset of reaction (t1) is hereinbelow referred to as the activation time (t.sub.act). After the exothermic reaction had abated, the remaining amount of propylene oxide (452.7 g) was added at an addition rate of 3 g/min. 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 average molecular weight (determined by gel permeation chromatography) and the activation time are reported in table 1.

TABLE-US-00001 TABLE 1 Suspension medium.sup.a)/H- functional Catalyst Mn starter t.sub.act loading .sup.c) (GPC, Example substance.sup.b) [min] [ppm] g/mol).sup.d) PDI 1 (A-1) cPC .sup.a) 142 2000  2784 1.06 (comp.) 2 (A-2) (A-1) .sup.b) 15 667 2828 1.26 3 (A-3) (A-2) .sup.b) 130 222 2889 1.52 4 (A-4) (A-3) .sup.b) 40 500 2825 1.41 5 Toluene.sup.a) 128 810 3441 1.21 (comp.) 6 Toluene.sup.a) >480 404 No — (comp.) polymer .sup.e) 7 PPG2000 35 513 3036 1.04 .sup.a)suspension medium, .sup.b) H-functional starter substance .sup.c) DMC catalyst loading based on the sum of the masses of the polymeric formaldehyde compound, the alkylene oxide and the H-functional starter substance .sup.d)number-average molecular weight of the polyoxymethylene-polyoxyalkylene block copolymer .sup.e) no chain-extended product

[0162] Table 1 summarizes the results for the preparation of the polyoxymethylene-polyoxyalkylene block copolymers produced by the process according to the invention in examples 2 to 4 compared to the noninventive block copolymers in examples 1, 5 and 6. Comparative example 5 reflects the teaching of example 7 of W02015/155094 A1. The polyoxymethylene-polyoxyalkylene block copolymers prepared according to the inventive process exhibit markedly shorter activation times with comparable catalyst loading (e.g. example 2) than comparative systems (e.g. comparative example 5). Furthermore, reactions to afford the block copolymers are also possible at markedly lower catalyst loadings (e.g example 3) whereas the noninventive process, even at higher catalyst loadings (for example comparative example 6), no longer achieves reaction of the polymeric formaldehyde compound with the alkylene oxide and thus no longer affords chain-extended polyoxymethylene-polyoxyalkylene block copolymer products.