Polyoxymethylene from CO2

Abstract

The present process for the production of polyoxymethylene comprises the following steps: - Presentation of CO2, - Conversion of CO2 to formaldehyde, - Polymerization of formaldehyde to an alcoholate derivative, and - Protonation of the alcoholate derivative with formation of polyoxymethylene provided. Furthermore, polyoxymethylene is produced according to a process according to the invention and the use of the polyoxymethylene is disclosed.

Description

[0001] The invention relates to a process for producing polyoxymethylene, polyoxymethylene produced by a process according to the invention and the use of polyoxymethylene.

[0002] Polyoxymethylene (POM) is a thermoplastic polymer primarily used for injection molding. POM, which is produced from formaldehyde, is characterized by oxymethylene groups (CH2-O-). n Formaldehyde typically comes from fossil fuels, for example as a byproduct of thermal / catalytic cracking of petroleum.

[0003] The use of sustainable materials is an effective lever for improving the overall carbon footprint of vehicles. Sustainable polymer solutions are therefore becoming increasingly important in the automotive industry. The three most relevant raw material sources for sustainable polymers include bio-based approaches based on renewable resources, recycled plastics, and CO2-based polymer approaches. A variety of bio-based polymers (PLA, PHB, etc.) are already known in the literature to reduce the carbon footprint over the entire product life cycle compared to petrochemical alternatives. Furthermore, polymers from recycled processes are increasingly being used to minimize the carbon footprint through a closed material cycle.However, these two polymer classes are often unsuitable for use in applications with demanding requirements, as both bio-based approaches and recycled plastics cannot achieve a defined molecular weight, due to natural synthesis processes and degradation effects during the recycling process. This can lead to variations in physical, mechanical, and chemical properties. CO2-based polymers have a defined molecular weight distribution and thus a property profile specific to the respective application. They are chemically indistinguishable from petrochemical plastic approaches. The greatest advantage over petrochemical polymer solutions is a reduced carbon footprint.

[0004] US 2008 / 0039538 A1 discloses a process for producing methanol and dimethyl ether from CO2 and H2O from the air.

[0005] Various processes for reducing CO2 are described, among others, in US 2010 / 0187123 A1.

[0006] A device for extracting CO2 from the air and producing hydrogen is disclosed, for example, in US 2008 / 0248350 A1.

[0007] The object of the present invention is to provide a process for the preparation of polyoxymethylene which at least partially overcomes the above-mentioned disadvantages.

[0008] This object is achieved by the process according to the invention according to claim 1, the polyoxymethylene according to claim 7 and the use according to claim 8.

[0009] Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred embodiments of the present invention.

[0010] A process according to the invention for producing polyoxymethylene comprises the steps: - Providing CO2, - Conversion of CO2 to formaldehyde, - polymerization of formaldehyde to an alkoxide derivative, and - Protonation of the alkoxide derivative to form polyoxymethylene.

[0011] In a process according to the invention, the CO2 is first introduced. The CO2 can be introduced in an appropriate form. The CO2 can be in solid, liquid, or gaseous form.

[0012] The CO2 can be from petrochemical deposits or from natural sources. The CO2 can be extracted from petrochemical processes, from exhaust gases, or from the atmosphere.

[0013] By using CO2 from the atmosphere, the carbon footprint can be reduced, thereby improving the carbon balance.

[0014] A process according to the invention comprises the step of converting CO2 to formaldehyde. In the process according to the invention, the conversion to formaldehyde occurs via various intermediate steps. The CO2 can be reduced to an intermediate carbon monoxide using hydrogen and then reduced to methanol by further addition of hydrogen. The reduction can be carried out by catalysis. The reduction can, for example, be transition metal-catalyzed or directly electrochemically using suitable electrocatalysts without forming an intermediate carbon monoxide.

[0015] The catalyst can be a transition metal catalyst. The catalyst can be selected from the group consisting of platinum, nickel, iron, silver, copper catalysts, and combinations thereof. For example, the catalyst can be selected from the group consisting of platinum, nickel, iron, silver, and copper-based phosphorus compounds.

[0016] The resulting methanol can then be oxidized to formaldehyde using oxygen. The oxidation can be carried out using known oxidation processes. One example is the so-called Formox process, in which methanol is reacted with atmospheric oxygen at temperatures of 350–450°C over iron(III) oxide and molybdenum(VI) oxide catalysts. Alternatively, formaldehyde can be formed from methanol by oxidative dehydrogenation. In this process, methanol is dehydrogenated over metallic silver catalysts at temperatures of 600–720°C, thus forming formaldehyde.

[0017] In a further process step of the process according to the invention, the formaldehyde is polymerized to form an alkoxide derivative. In a preferred embodiment, the polymerization takes place by means of chain polymerization, e.g., an anionic chain polymerization. The polymerization is preferably initiated using a base. The base is preferably a methanolate. Examples of methanolates are sodium methanolate, lithium methanolate, or potassium methanolate. The base is particularly preferably sodium methanolate. The base can bind to the partially positive carbon atom of the formaldehyde. Rearrangement of the double bond to the oxygen atom can thus form an intermediate alkoxide species. Chain growth can occur via anionic chain polymerization, in which further formaldehyde species can be added to the forming chain, thus forming the chain growth of the alkoxide derivative.

[0018] In a further reaction step, the alkoxide derivative is protonated to form polyoxymethylene. Protonation can be carried out using protic solvents. For example, the protic solvents can be water, methanol, or ethanol. Protonation can terminate the polymerization, thus forming polyoxymethylene. The protic solvents can be added or be present as traces in the reaction mixture. To control the protonation of the alkoxide derivative, and thus control the chain length of the polyoxymethylene, the protic solvent is preferably added.

[0019] In one embodiment, the protonation of the alkoxide derivative is carried out using water.

[0020] Depending on the manufacturing process, the polyoxymethylene may have a terminal OH group. Polyoxymethylenes with a terminal OH group can depolymerize under the influence of temperature, acids, etc., releasing formaldehyde. To prevent depolymerization, the terminal OH group of the resulting polyoxymethylene can be esterified. For example, the esterification can be carried out by adding acids, e.g., organic acids, or acid anhydrides, e.g., organic acid anhydrides. Preferably, the esterification can be carried out by adding acetic anhydride.

[0021] In a preferred embodiment, the CO2 is atmospheric CO2. The CO2 can originate from natural sources in the atmosphere, or from exhaust gases or byproducts of petrochemical processes.

[0022] A method according to the invention may comprise further steps.

[0023] A process according to the invention can comprise the step of introducing CO2 from the atmosphere. The CO2 can be in gaseous or bound form. If the CO2 is present in bound form, the bond is ideally reversible, so that the CO2 can be used for the further process according to the invention.

[0024] The present invention further provides polyoxymethylene produced by a process according to the present invention. A polyoxymethylene according to the invention preferably comprises CO2 from the atmosphere.

[0025] Furthermore, the present invention relates to the use of polyoxymethylene according to the present invention in the automotive industry.

[0026] Polyoxymethylenes according to the invention can also be used in other areas of application. For example, polyoxymethylenes according to the invention can be used in medical technology, household appliances, the construction industry, the packaging industry, the clothing industry, electrical engineering, mechanical engineering, etc.

[0027] A process according to the invention can also serve as a drop-in solution for POM manufacturing or POM processing industries as well as end users.

[0028] In one embodiment, the polyoxymethylene is used to manufacture gears, sliding and guide elements, housing parts, spring elements, chains, screws, nuts, fan wheels, pump parts, valve bodies, steering columns, window regulators, door lock systems, and joint shells. These components are particularly used in the automotive industry.

[0029] Furthermore, a polyoxymethylene according to the invention can also be used in other areas, such as everyday consumer goods. For example, a polyoxymethylene according to the invention can be used in insulators, coil formers, connectors, parts for electronic devices, fittings, locks, handles, hinges, curtain rods, sleeves for point fasteners in structural glass construction, aerosol cans, gas ampoules, zippers, etc.

[0030] Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 schematically shows a method according to the invention, and Fig. 2 schematically shows a reaction mechanism of a process according to the invention.

[0031] Fig. Figure 1 schematically shows a process 100 according to the invention for producing polyoxymethylene (POM). First, CO2 is introduced 101. In a subsequent step 102, the CO2 is converted to formaldehyde. The resulting formaldehyde is polymerized 103 to an alkoxide derivative. The alkoxide derivative is then protonated 104 to form polyoxymethylene.

[0032] Fig. Figure 2 shows schematically the synthesis of polyoxymethylene (POM) from CO2, e.g. atmospheric CO2, comprising the following synthesis steps:

[0033] The production of formaldehyde (3) from atmospheric CO2 (1) is initiated by the reduction of CO2, e.g., atmospheric CO2, with hydrogen to an intermediate carbon monoxide, which, through further reduction steps with hydrogen, forms methanol (2). This reaction can be catalyzed by transition metals or directly electrochemically with suitable electrocatalysts without forming an intermediate CO2. Suitable catalysts include Ni, Fe, Ag, and Cu-based phosphorus compounds. Subsequent oxidation of the compound results in formaldehyde (3).

[0034] The polymerization is initiated, for example, using a sodium methoxide (4), which, due to its basic structure, adds to the partially positive carbon atom of formaldehyde (3). Rearrangement of the double bond to the oxygen atom forms the alkoxide derivative (5). Subsequent growth occurs in an anionic chain polymerization, in which further formaldehyde species (3) are added to the forming chain (6).

[0035] The polymerization is terminated by the addition of water. The alkoxide derivative of the forming chain (6) is protonated, producing POM (7) and sodium hydroxide. Example 1. Synthesis of formaldehyde from CO2

[0036] During the synthesis of formaldehyde, carbon dioxide and hydrogen were passed over a PtCu / SiO2 catalyst at 600 kPa and 300 K. The ratio of the gases was 20 H2:1 CO2. The temperature was increased at a heating rate of 10 K*min. -1The temperature was increased to 650 K, and the product was collected via a cold trap. Subsequently, byproducts such as methanol were distilled off. 2. Polymerization

[0037] The reaction can be carried out, for example, in an autoclave equipped with an appropriate thermostat and a mechanical stirrer. The formaldehyde was added to the autoclave together with the ethanolate and stirred for 10 hours at a defined pressure and temperature (depending on the desired molecular weight). 3. Termination of polymerization

[0038] The polymerization was terminated by adding water. The alkoxide derivative of the forming chain was protonated, producing POM and sodium hydroxide. List of reference symbols 100 processes for the production of POM 101 Submission of CO2 102 Conversion of CO2 to formaldehyde 103 Polymerization of formaldehyde to an alkoxide derivative 104 Protonation of the alcoholate derivative to form polyoxymethylene QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2008 / 0039538 A1

[0004] US 2010 / 0187123 A1

[0005] US 2008 / 0248350 A1

[0006]

Claims

[1] Process for the preparation of polyoxymethylene comprising the steps: - Providing CO2, - Conversion of CO2 to formaldehyde, - polymerization of formaldehyde to an alkoxide derivative, and - Protonation of the alkoxide derivative to form polyoxymethylene. [2] A process for producing polyoxymethylene according to claim 1, wherein the conversion of CO2 to formaldehyde is carried out by catalysis. [3] A process for producing polyoxymethylene according to claim 2, wherein the catalyst is selected from the group consisting of platinum, nickel, iron, silver, copper catalysts and combinations thereof. [4] A process for producing polyoxymethylene according to any one of claims 1 to 3, wherein the polymerization of the formaldehyde to the alkoxide derivative is a chain polymerization. [5] A process for the preparation of polyoxymethylene according to any one of claims 1 to 4, wherein the protonation of the alcoholate derivative is carried out by means of water. [6] A process for producing polyoxymethylene according to any one of claims 1 to 5, wherein the CO2 is atmospheric CO2. [7] Polyoxymethylene prepared by a process of claims 1 to 6. [8] Use of polyoxymethylene according to claim 7 in the automotive industry. [9] Use of polyoxymethylene according to claim 8 for the production of gear wheels, sliding and guide elements, housing parts, spring elements, chains, screws, nuts, fan wheels, pump parts, valve bodies, steering columns, window lifters, door lock systems and joint shells.

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