Study On Modification Of Cottonseed Protein Adhesive

Formaldehyde-based thermosetting synthetic resin adhesives release formaldehyde from wood bonding materials,and its raw materials come from nonrenewable petrochemical resources.With the reduction of petrochemical resources and the enhancement of public awareness of environmental protection,the development and utilization of environmental adhesives based on renewable biomass resources is in line with the current industry and social development trend.Cottonseed meal is the residue of cottonseed oil.At present,China’s annual output of cottonseed is more than 11 million tons,and the annual output of cottonseed is more than 6 million tons.The protein content of cottonseed meal is very close to that of soybean meal,and its price is lower than that of soybean meal.Cottonseed meal has a wide range of sources and has a high utilization value as a plant protein resource.Using cottonseed meal as the main raw material to prepare protein adhesive can effectively use agricultural residues,reduce the cost of adhesive and reduce environmental pressure.China is the largest producer and exporter of cocoon and silk in the world.In the reeling process of cocoon processing,550-950 m~3 reeling wastewater will be produced per ton of raw silk.Sericin in silk reeling wastewater is a less utilized by-product in textile industry.It has good biological activity and film-forming property,and has potential application value in biotechnology.In the papermaking industry,paper agents are often used to improve the dry and wet strength of paper,and some of them are also used to modify protein based wood adhesives.In this study,washed cottonseed meal was used as raw material to prepare cottonseed protein adhesive with reeling wastewater,papermaking agent and reeling wastewater papermaking additives.The structure,thermal stability,surface micromorphology,and bonding performance of cottonseed protein adhesive with three different modification methods were studied,and the suitable type and dosage of modifier were explored to obtain the modified cottonseed protein adhesive meeting the use requirements.The conclusions are as follows(1)Using silk reeling wastewater as modifier,cottonseed protein adhesive was prepared at 55°C reaction temperature and 2mol/L urea concentration.The dry bonding strength was improved to a certain extent,but the wet bonding strength decreased significantly,which did not meet the requirements of national class II board standard.(2)Cottonseed protein adhesive was prepared by using papermaking agent as modifier.The dry and wet bonding strength of the adhesive was improved to a certain extent.The results show that the wet strength of plywood can meet the requirements of national class II board standard when the additive content is 15%or more.(3)The dry and wet bonding strength of cottonseed protein adhesive was further improved by using reeling wastewater and papermaking agent.When the mass ratio of silk reeling wastewater and papermaking agent is 1:2 and the amount of modifier is 20%,the wet strength of plywood reaches the maximum value(0.968 MPa).(4)The results of infrared test showed that the characteristic peak of epoxide in cotton seed protein adhesive modified by silk reeling wastewater and papermaking agent disappeared,which proved that epoxide in papermaking agent reacted with protein molecules.(5)The results of thermogravimetric analysis showed that the cottonseed protein adhesive modified by silk reeling wastewater and papermaking agent had better thermal stability at higher temperature(250~oC-360~oC),and the temperature at which the pyrolysis rate reached the peak was 17 ~oC higher than other adhesives.(6)The SEM results showed that the surface structure of the cottonseed protein adhesive modified by silk reeling wastewater and papermaking agent was smoother and tighter after curing.The water-resistant bonding strength was improved.