Preparation method of high-grade borate type automobile brake fluid

Abstract

The invention relates to a preparation method of a high-grade borate type automobile brake fluid, which comprises a synthesis of polyxinolum and borate as well as blending of the brake fluid. The method is characterized in that n-propanol and epoxypropane are taken as raw materials, a polymerization is generated under the effect of a basic catalyst, and the high polyxinolum with 4-6polymerization degree can be obtained after decolouring, adsorbing, filtering and performing reduced pressure distillation. The method takes high polyxinolum, boric acid and 1,3-propylene glycol as raw materials to synthesize six-membered ring borate with low-viscosity by a two stages esterification method, and the dry equilibrium reflux boiling point and the hydrolytic stability of the brake fluid. The semi-polar boric acid diglyceride is synthesized, and can be used as a basic additive solution to increase the wet equilibrium reflux boiling point of the brake fluid, and can be used with glycerol to prevent the swelling of the rubber. According to the invention, the six-membered ring borate and the boric acid diglyceride are taken as basic liquids, low polyxinolum is taken as a diluent, a proper amount of additive is added, and the high-grade borate type automobile brake fluid can be blended.

Description

technical field [0001] The invention relates to a preparation method of high-grade borate type automobile brake fluid. Background technique [0002] Automobile brake fluid is a functional liquid used to transmit braking energy in the automobile hydraulic braking system, and its performance and quality are directly related to the driving safety of the vehicle. Since automobiles began to use brake fluid in the early 1930s, automobile brake fluid can be divided into three types according to its production raw materials: alcohol type, mineral oil type and synthetic brake fluid. Alcohol-type and mineral oil-type brake fluids have long been eliminated because of their low boiling point and high freezing point, and synthetic brake fluids are widely used. [0003] Synthetic brake fluid is divided into silicone oil type, alcohol ether type and alcohol ether borate type. In 1972, the U.S. Federal Department of Transportation promulgated and implemented brake fluid standards, which a...

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Problems solved by technology

However, boron trifluoride-diethyl ether is easy to hydrolyze to generate hydrogen fluoride fumes, which is not conducive to production control, and the complex needs an induction period as a catalyst, the reaction process cycle is long, and it is also easy to scale during the separation and refining process

In addition, the high molecular weight of butanol can easily lead to difficulty in controlling the degree of polymerization of the product, and the resulting product has precipitation and unstable color

[0006] In 2009, the Chinese patent CN101619258A used sodium hydroxide as a catalyst, and the reaction was fast, but the molecular weight distribution of the polyol ether generated was wide, and mono- and dipropanol monoethers accounted for 35% to 45% of the total amount, and the boric acid ester synthesized had a relatively high boiling point. Only use tri-propanol monoether, only by adding hydrolysis stabilizer to improve the hydrolysis stability of brake fluid, the effect is not good

However refined grading requires 7.0×10 -4 -2.0×10 -3 The high vacuum condition of MPa has too high requirements for rectification equipment

In addition, since boric acid, the middle distillate product, and the rear distillate product all have hydroxyl groups, the structure and composition of the product after esterification together are very complicated, and the performance indicators fluctuate too much.

[0009] In 2011, Chinese patent CN101955840A synthesized a high-boiling point borate-type brake fluid, using 5-15% triethylene glycol methyl ether as the diluent, 85-90% triethylene glycol methyl ether boron Ester is used as the base fluid, and the general borate content higher than 30% can make the brake fluid meet the requirements of high boiling point and low water sensitivity, and more than 70% will cause the product viscosity to be too high to meet the DOT5.1 standard. And compared to the super DOT4 brake fluid standard of the same level, its cost is too high to be put into the market

However, the polyalcohol ether synthesized by alkaline earth metal catalyst barium hydroxide has a degree of polymerization n≤4, which limits the boiling point range of the brake fluid, and it is impossible to obtain a polyalcohol ether base fluid with a higher degree of polymerization and a higher boiling point.

In addition, the use of alkaline earth metal catalysts requires the use of co-catalysts, an induction period, and low activity. Metal salts are physiologically toxic and their applications are limited.

The recovery cost of toluene-based water-carrying agent is high, and it is easy to cause environmental pollution

In addition, the esterification yield of cyclic boronic esters synthesized by the "one-pot method" is not high, and there are many other chain boronic ester by-products

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