A kind of casting furan resin and preparation method thereof

Abstract

The invention discloses a furan resin for casting and a preparation method thereof. The furan resin for casting has the formula proportion in parts by weight: 27 to 35 parts of formaldehyde, 40 to 50 parts of furfuryl alcohol, 8 to 12 parts of urea, 0.1 to 0.5 part of urotropin, 1 to 3 parts of ammonia solution, 5 to 10 parts of methanol, 0.1 to 0.8 part of coupling auxiliary agents, 5 to 15 parts of furfuryl alcohol substitutes and 0.1 to 0.5 part of formic acid, wherein the furfuryl alcohol substitutes are sorbitol, polyester polyol, or the mixture of the sorbitol and the polyester polyol. The preparation method comprises the steps of feeding, warming, three-time vacuum dewatering, dropping in temperature to mix, filtering and discharging and the like. Under the action of factors, such as the compounding ratio of charged raw materials, pH value, temperature, feeding mode, dehydration mode and the like, parts of furfuryl alcohol in the prior art are substituted, and under the circumstance that other performance parameters of the furan resin for casting are not sacrificed, the cost is effectively reduced.

Description

technical field [0001] The invention relates to a synthetic resin binder for casting, in particular to a furan resin for casting and a preparation method thereof. Background technique [0002] Furan resin is currently the most widely used synthetic resin binder for casting in the world, accounting for more than 50% of the total binder, and it is also the most advanced and mature molding material. The domestic demand for furan resin for casting was 200,000 tons in 2003, and its consumption has been increasing at an average annual rate of 10% since this century. Superior to other products. At present, there are mainly furan resins for casting such as phenolic furan resin synthesized by PF / FA process and urea-formaldehyde furan resin synthesized by UF / FA process in China. [0003] The synthesis of traditional furan-modified urea-formaldehyde resin is mainly through the addition reaction of formaldehyde and urea under alkaline conditions, and then the polycondensation reaction...

AI Technical Summary

Problems solved by technology

Since the reaction between formaldehyde and urea under this condition quickly reaches a dynamic equilibrium, there are many free formaldehydes that do not participate in the reaction. In order to break the dynamic equilibrium under this condition and reduce the content of free formaldehyde in the system, generally increase the urea to prolong the reaction time. To reduce and eliminate free formaldehyde that did not participate in the reaction in the system, thereby increasing the viscosity of the product, reducing the compatibility between the product and other components, increasing the nitrogen content in the product and increasing the amount of furfuryl alcohol added, greatly Raw material consumption cost is increased; in the existing synthesis process, mixtures such as monomethylol urea and dimethylol urea are mainly generated by 37% formaldehyde aqueous solution and urea under alkaline conditions, and then condensed with furfuryl alcohol under acidic conditions Synthesize modified furan resin, and after dehydration and aldehyde removal, furfuryl alcohol is used to prepare the product; the synthesis process and casting defects brought about by it are:

[0006] (3) Resin sand has poor solidity, and it is necessary to increase the amount of curing agent or increase the total acidity of curing agent to meet the demoulding requirements of the process, which will cause sulfur penetration on the surface of the casting and increase the probability of crack casting defects;

[0007] (4) The amount of curing agent added is too large and the acidity is too high, which reduces the tensile strength of the molding sand. It is necessary to increase the amount of resin added to improve the strength of the molding sand, which relatively increases the consumption cost of casting raw materials;

[0009] (6) The synthesis process takes a long time to dehydrate. In order to reduce the free formaldehyde and excessive moisture in the resin (most of the moisture comes from the introduction of formaldehyde solution), so that the product reaches the technical standard of control, it needs a relatively long process. Long-term dehydration, the general dehydration amount is as high as 110-140kg / ton, resulting in long production cycle, high loss of furfuryl alcohol (the azeotrope formed with water during vacuum dehydration is taken out), high energy consumption, and pollution caused by the released wastewater and waste gas;

[0010] (7) The furfuryl alcohol content is extremely high, and there are no other furfuryl alcohol substitutes, so the cost of materials is high, and the price of furfuryl alcohol is expensive. In the past year, the price has been 15,000-21,000 yuan / ton. There are no other low-cost furfuryl alcohol substitutes in the traditional technology high cost of materials

Images