Study On Preparation Of Vegetables Oil Based Polyols And Modified Isocyanate Adhesive

With the development of the society, chemical products whose main raw materials come from the fossil materials have been increasing used. Due to limited reserves of fossil resources and environmental pollution that may bring about in the process, it is a trend for the development of the chemical industry that green and renewable resources will be made good use of without fully relying on the fossil resources.Vegetable oil is a kind of green and renewable resource. When vegetable oil is in the state of hydroxylation, vegetable oil-based polyols which can replace the polyester or polyether polyols and other petrochemical products will be obtained. Polyurethane is a widely used chemical product and one of the main raw materials is polyol. The application and research of vegetable oil has already been conducted in the polyurethane industry, but only in castor oil and polyurethane foams. The main content of this article is based on soybean oil (SOB) as an example, through hydroxylation was soybean oil polyols (SOP), and applied this topreparate one-component isocyanate adhesive with moisture curing.The preparation of epoxy soybean oil (ESO) was studied in this paper. Through a series of comparative experiments, optimum experiment conditions were obtained by discussing the effects of dosage of hydrogen peroxide, formic acid and stirring speed on the double bond conversion rate. When the epoxy value of the product was up to6.4at most, double bond conversion rates high as88.89%. Through FT1R analysis, the new epoxy group was indeed obtained with C=C groups participating in the reaction conversion while the other peak did not change, which showed that the new epoxy groups were introduced when the soybean oil structure kept remaining in the reaction products.During the process of preparation of SOP, optimum experiment conditions were obtained by discussing the effects of the dosage of methanol, isopropanol and reaction time on epoxide group reaction conversion rate. When the hydroxyl value of the product reached198.8mgKOH/g, the epoxide bond conversion rate as high as94.8%.By FTIR analysis, new hydroxyl was transformed by the epoxy groups and the other peak did not change, which indicated that the new hydroxyl groups were introduced when the epoxy soybean oil structure kept remaining in the reaction products.Isocyanate adhesive was synthetized with SOP and PAPI. As the conventional isocyanate adhesives, the storage life, strength and thermal stability of the adhesive were affected somehow by the hydroxyl value and R value of soybean oil polyols (the molar ratio of-NCO and-OH, isocyanate index).But compared with PEG-400/PAPI system, storage life and strength were not ideal. The isocyanate adhesive in SOP/PEG-400/PAPI system was studied to investigate the effects of different SOP dosage on adhesive storage period and strength. It shows that SOP dosage increase, adhesive strength will be negatively influenced; and when the dosage is within20%(hydroxyl mole ratio), the storage period won’t be strongly impacted; in terms of thermal stability, the temperature of5%weightlessness rate has greatly improved. Thermal stability will be obviously improved when a pyro lysis stage is reduced.Next the effects of different hydroxyl value on isocyanate adhesive performance in the SOP/PEG400/PAPI system were studied. When the rate of soybean oil polyols and hydroxyl PEG-400is constant at20%, with the increasing hydroxyl value, the mass of introduced SOP relatively reduced, the dry and wet strength declined, but had no significant effect on storage period, the temperature of5%weightlessness rate has declined, thermal decomposition stage has no change. Under the condition thatthe69mgKOH/g hydroxyl value of soybean oil-based polyols, the20%SOP/PEG molar ratio, the7R value and the80%solid content, the final CPS of isocyanate adhesive was21.06MPa, pot life was more than three month, wet circulation strength was12.04MPa which was higher26.01%than that of PEG/PAPI system, and the adhesive had a higher thermal stability.From the above experiments, we found that:In the case of low hydroxyl value(commonly between70and90mg KOH/g), the more dosage of SOP, dry state strength was slight declines, but wet state strength and thermal stability were also greatly improved, storage period of adhesive without influence. On this condition, because of the reaction of hydroxyl and isocyanate, the triglyceride molecules lines were grafted on the polyurethane chains that was better than block。 without excessive block and cross-linking, which led to bigger viscosity, separate micro-phase, smaller adhesive storage period and strength. This also shows that due to the constant hydroxyl value, castor oil can’t be widely used in polyurethane; Consequently, the significance of this thesis research was highlighted.