Background technology of a method for reducing the relative molecular weight distribution of synthetic polytetrahydrofuran
Polytetrahydrofuran, also known as polytetramethylene ether glycol (PTMEG), is formed by the ring-opening polymerization of tetrahydrofuran (THF). It is used to produce polyurethane elastic fiber (the product name in my country is spandex, and internationally it is called spandex) and an important raw material for polyurethane elastomer materials.
Because there are no side chains in the molecular structure, the polymer structure is tightly arranged, and the product density is higher than other polyethers and is eye-catching. It is the main raw material for the synthesis of thermoplastic and cast polyurethane, polyurethane elastic fiber, ester-ether copolymer elastomer, etc. , widely used in industrial sectors such as petrochemicals, machinery, military industry, shipbuilding, automobiles and synthetic leather.
Commonly used PTMEG has an average relative molecular weight of 1000 and 2000. PTMEG with a relative molecular mass of 1000 and toluene diisocyanate (TDI) are made into rubber that is wear-resistant, oil-resistant, has good low-temperature performance and high strength, and is used for tires, Synthetic leather, cables, etc.; block polyether polyester elastic materials made with dimethyl terephthalate and butylene glycol and used as serpentine tubes, conveyor belts, compression spring materials and hoses, etc. PTMEG with a relative molecular mass of 2000 and methylene bis (4-phenyl) diisocyanate (MDI) are made into polyurethane elastic fiber, called spandex (Spandex), which has high strength and resilience close to natural rubber. The elastomer made by mixing PTMEG into wool textiles can resist wrinkles. It is a new material widely used in the wool spinning industry and silk fabrics in recent years.
The existing synthesis methods mainly include perchloric acid-acetic anhydride process, fluorosulfonic acid process, clay process, and heteropoly acid process.
A method for reducing the relative molecular weight distribution of synthetic polytetrahydrofuran Contents of the invention
The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method to reduce the synthesis of polytetrahydrofuran by adding a double molybdenum metal monomer compound [Mo2(Cis-R)2(NCCH3)4] (BF4)2 Relative molecular weight distribution method of products.
The object of the present invention can be achieved through the following technical solutions:
A method for reducing the relative molecular weight distribution of synthesized polytetrahydrofuran. Polytetrahydrofuran is polymerized in the presence of a catalyst to prepare polytetrahydrofuran. The catalyst is a double molybdenum metal unit compound. The molecular formula of the double molybdenum metal unit compound is [Mo2(Cis- R)2(NCCH3)4] (BF4)2, where R represents diformamide compounds or carboxylic acid compounds.
The described polymerization to prepare polytetrahydrofuran means adding a double molybdenum metal unit compound to a tetrahydrofuran solution to perform a synthesis reaction on a Schlenk vacuum line operation line. After the reaction, dissolve it with diethyl ether and air-dry the solid obtained, which is polytetrahydrofuran.
The ratio relationship between the double molybdenum metal unit compound and tetrahydrofuran is that 5 to 10 mg of the double molybdenum metal unit compound is added per milliliter of tetrahydrofuran.
The synthesis reaction conditions described are reaction under stirring for 4 to 6 hours, and the reaction temperature is 23 to 30 degrees Celsius.
The tetrahydrofuran solution and diethyl ether are deoxygenated and dehydrated before use.
The described oxygen and water removal refers to adding 2 to 4 grams of sodium and 0.5 to 2 grams of potassium per liter of tetrahydrofuran solution or diethyl ether, and refluxing under nitrogen for 24 hours.
The mass average molecular mass of the polytetrahydrofuran is 5.033X 104, the number average molecular mass is 4.285X IO4, the Z average molecular mass is 5.786 X IO4, and the relative molecular mass distribution is 1.174.
In the present invention, the double molybdenum metal unit compound [Mo2(Cis-DAniF)2(NCCH3)4] (BF heavy magnesium carbonate 4)2 (where R is a diformamide compound or a carboxylic acid compound, cis Indicates that the ligand DAniF is arranged in cis form. References for the synthesis method are Malcolm H.Chisholm, F.Albert Cotton, J.Chem.Soc., Dalton Trans., 1999, 1387-1391,
The synthesis reaction equation is as follows.
Use triethyl oxygen gun tetrafluoroboric acid to catalyze the polymerization of tetrahydrofuran to obtain high molecular weight polytetrahydrofuran.
Add triethyl oxygen lance tetrafluoroboric acid to the tetrahydrofuran solution and perform a synthesis reaction on the Schlenk vacuum line operation line. After the reaction, dissolve it with diethyl ether and air-dry the resulting solid, which is polytetrahydrofuran.
The proportional relationship between the triethyl oxygen gun tetrafluoroborate and tetrahydrofuran is that 6 to 20 mg of the double molybdenum metal unit compound is added to each milliliter of tetrahydrofuran.
The synthesis reaction conditions described are reaction under stirring for 5 hours, and the reaction temperature is 23~30 degrees Celsius.
The tetrahydrofuran solution and diethyl ether are deoxygenated and dehydrated before use.
The described oxygen and water removal refers to adding 2 to 4 grams of sodium and 0.5 to 2 grams of potassium per liter of tetrahydrofuran solution or diethyl ether, and refluxing under nitrogen for 24 hours.
The molecular weight of the polytetrahydrofuran is directly proportional to the concentration of triethyl oxygen lance tetrafluoroboric acid added. The greater the concentration, the greater the mass average molecular weight of the product.
In the existing BASF patent on polytetrahydrofuran, the maximum molecular weight can only reach 10,000. The method of the present invention can make the molecular weight reach 50,000, which is five times the limit value of BASF’s patent. At the same time, the product has a small relative molecular mass distribution (D = 1.174), which is very beneficial to industrial production applications.
Compared with the existing technology, the present invention has the following advantages:
(1) In the present invention, the double molybdenum metal unit compound [Mo2(Cis-DAniF)2(NCCH3)4](BF4)2 (where R is a diformamide compound or a carboxylic acid compound) is added during the reaction process. Greatly reduces the relative molecular weight distribution of polytetrahydrofuran;
(2) The present invention�It has the advantages of easy operation and control, simple post-processing process, and easy implementation of industrial production.
A method to reduce the relative molecular weight distribution of synthesized polytetrahydrofuran. Synthesis of polytetrahydrofuran
In a 100ml single-necked flask, weigh 300mg of triethyl oxygen lance tetrafluoroborate, add 50ml of tetrahydrofuran, and stir vigorously for 5 hours. The reaction temperature is 25 degrees Celsius to obtain a viscous liquid. Dissolve it with ether and evaporate in the air. A white filmy solid was obtained. The gel chromatogram is shown in Figure 1. The gel chromatography measured the mass average molecular mass of the synthesized polytetrahydrofuran Mw = 0.8318×104, the average molecular mass of methoxypyridine Mn = 0.3532×104, and the Z average molecular mass Mz = 1.5137 ×104, relative molecular mass distribution D = 2.3552.
