Development Of Reusable And Heat-sealable Paper For Paper Bags

With the enhancement of people’s awareness of environmental protection,the plastic restriction order has been upgraded again,and the use of non-degradable plastic bags has been gradually banned in various places,and the use of reusable and biodegradable shopping bags are encouraged.In order to reduce the negative impact of plastic bags on the environment,this paper uses Manila hemp pulp（BMHP）,unbleached bamboo pulp（UBP）and unbleached softwood pulp（USKP）as the main raw materials,by adding polyamide polyamine epichlorohydrin（PAE）,alkyl ketene dimer（AKD）and water-soluble polyvinyl alcohol（PVA）fibers in pulp to develop reusable and heat-sealable paper for paper bags.Firstly,this paper explores the beating characteristics of the three fiber raw materials and the influence of different beating methods and beating degrees on the fiber morphology and paper strength properties of the raw materials,and determines the appropriate beating methods and beating degrees for each fiber raw material.BMHP or UBP and USKP were combined to develop different grades of paper for paper bags,and the appropriate preparation method and proportion were determined.The research results show that when using PFI beating,the beating degree of the three fiber raw materials has an approximate linear relationship with the beating revolutions.Among them,BMHP is the easiest to beat,UBP is the next,and USKP is the most difficult to beat.The suitable beating methods and beating degrees of the three raw materials are as follows:USKP uses PFI beating alone,and the beating degree is 32°SR;BMHP uses Valley beating,and the beating degree is 51°SR;UBP uses PFI beating,and the beating degree is 27°SR.The appropriate preparation method is to beat each raw material separately and then prepare,and the proportion of USKP is 70%.Secondly,using USKP and UBP as fiber raw materials,under the above conditions,handsheets with a weight of 60 g·m^-2 were made to explore the effects of PAE and AKD on paper strength,disintegration recovery and water resistance,and determined the optimum dosages of additives are 1.5%and 0.3%,respectively.Under these conditions,the dry tensile index of the handsheet is 72.9 N·m/g,the wet tensile index is 23.4 N·m/g,and the tear index is 14.7 m N·m²/g.Among them,the dry tensile index and tear index can meet the minimum requirements of high-quality paper for paper bags in GB/T 7968-2015.The dry tensile index,wet tensile index and contact angle of the handsheets are almost unchanged after being soaked and dried for many times,which confirms the feasibility of the paper being reusable.Finally,the water-soluble PVA fibers are added as an auxiliary agent to make paper in the pulp,and then the heat sealing of the paper for paper bags is realized under the combined action of water,temperature,time and pressure,which is innovative and practical.The optimum process conditions for heat sealing are found out by testing the bond strength of the bonding parts of the handsheets.The results show that when the addition amount of water-soluble PVA fiber is 9%,the heat-sealing temperature is 110°C,and the heat-sealing time is6 s,the heat-sealing effect is better.And the bonding strength is 2.61 k N/m,which is higher than the 2.50 k N/m required by the standard QB/T 4379-2019.