Among the Amino resins, Melamine formaldehyde-Melamine Urea formaldehyde resins, possess better water resistance properties compared to Uf resins. Studies have been made to develop MF/MUF resin adhesives for the manufacture of flooring tiles from bamboo, Bamboo laminates and also for finger jointing of Saw mill waste timbers. The required percentage of hardener for cold setting at room temperature have been worked out. The process parameters for manufacture laminates/tiles like spread, Assembly time, hot press temperature, pressure, time have been optimized.
RESINS FOR PREPRESSING TECHNIQUES IN PANEL MAKING
(a) UF resin adhesives:
Method for the manufacture of UF resin suitable to adopt prepressing has been evolved and detailed process parameters for prepressing and hot pressing have been worked out. Few factories producing plywood have adopted the prepressing technique.
(b) PF resin Adhesives:
Process details for the manufacture of PF resin by adopting conventional as well as by modified methods suitable for pre-pressing plywood have been worked out. Factories have successfully adopted this technique as it gives improved bond, increased productivity at reduced costs, production of defect free panels, etc.
PARTIAL SUBSTITUTION OF PHENOL IN PF RESIN WITH NATURALLY OCCURRING RENEWABLE MATERIALS
Among the synthetic resin adhesives – PF resins finds wide acceptance in the manufacture of plywood and other wood based panel products. This is mainly due to their highly durable bonds under exterior application.
The main raw materials for PF resins are phenol and formaldehyde both based on petroleum products. Although it is believed that adequate supplies of formaldehyde would be available in future but long term supply of phenol is considered to be less assured.
Worldwide shortage increase in price and doubts about future supplies of phenol for the wood based panel industries have added new impetus to replace phenol partially or fully by renewable bio materials processing phenolic nature for the manufacture of PF resin. Institute has developed resin formulations by substituting lignin, cardanol, black liquor, Tannin and para phenol sulphonic acid partially for phenol in PF resin manufacture.
a. DEVELOPMENT OF HIGHLY WATER SOLUBLE PHENOL CARDANOL FORMALDEHYDE
Water soluble PCF resin by substituting phenol to the extent of 30-35 percent has been developed to bond BWR and BWP grade panels. A suitable deforming agent to reduce the foaming problems caused on high speed glue spreaders has also been worked out. This resins are also suitable for paper laminates.
Cost of PCF resin is cheaper by 25-30 percent compared to conventional PF resin.
b. Lignin – formaldehyde (LF) resin as a partial substitute for PF resin Process parameters to obtain lignin were worked out. Methodology for the preparation of lignin formaldehyde has been established. Encouraging results have been obtained by replacing 50 percent of PF resin with lignin formaldehyde resin developed. c. Lignosulphonate modified phenolic resins for bonding BWR and BWP grade plywood Initial studies have been taken up to partially replace phenol in PF resin with commercially available lignosulphonates produces in one of the rayon mills in the country. Laboratory scale experiments have given encouraging results with ammonium lignosulphonates. Pilot scale trials posed lot of problems during resin manufacture and its application. However, further studies were continued to partially replace phenol by lignin. In the present technology developed lignin with trade name proto bind 1075 supplied by M/s.Asian Lignin manufacturing Unit Ltd., Chandigarh was used. The requisite characteristics of proto bind 1075 with the proportion of phenol, proto bind 1075, formaldehyde and caustic have been worked out. The resin formulation for manufacturing PLF resin and process parameters for making BWR and BWP grade panels have been optimized. Phenol can be replaced to the extent of 20-30% by proto bind 1075 in PLF resin. Few industries have adopted this technology for panel making. d. Partial substitution of Phenol and formaldehyde in the phenolic resin by coconut shell flour (CSP) Technology has been developed wherein about 40 percent of phenol and 30-34 percent of formalin could be replaced with CSF in CSF-PF resin suitable to bon BWR and BWP grade plywood cost of resultant resin is reduced by around 40% in comparison with PF resin. The process for conversion of CSF into resin forming intermediates, copolymerization of phenol with CSF resin forming intermediates and formaldehyde to form resin have been worked out. Adhesive composition has been developed. Process parameters for plywood manufacture bonded with CSF-PF resin have been optimized. e. Development of Phenol paraphenol sulphonic Acid formaldehyde resin Laboratory scale investigations have been carried out to replace phenol by para phenol Sulphoric Acid partially in PF resin manufacture. The research finding indicate that about 30 percent of phenol can be replaced by paraphenol sulphoric acid in phenol formaldehyde resin which is suitable to bond BWR grade panels. The resin formulations have been worked out. The process parameters for making BWR grade panels have been optimized. Needs further study for upgradation in pilot scale.
f. Development of phenolic resin for bonding veneers from low durability wood
treated with preservative chemicals: Conventional PF resin cannot be used for bonding preservative treated veneers as this lead to bonding problems. Treatment of veneers is very important to ensure the product from insects and termite attack. Also the bonding is required to panels for enhanced durability of the products. Hence and improved PF resin compositions for bonding preservative treated veneers have been developed. The process parameters for manufacturing the panels are standardized. Veneer treatment ensures required retention of preservative chemical in the panels and also improved the durability.
The panels made using the treated veneers with improved PF resin finds wide applications for exterior grade plywood like marine and shuttering type. These products are termite and decay proof. g. Adhesives based on wattle bark tannin: Adhesive formulations have been developed for BWP grade plywood based on suitably formulated phenolic resin blended with mimosa wattle tannin extract. As much as 400- 600 percent of mimosa wattle tannin extract on phenolic resin has been used to produce a strong boil proof bond with veneers of a number of wood species. The process parameters for making the panels have been standardized. Press temperature required for the resin to cure is lower than that of the conventional PF resins. These adhesive formulations have been adopted in plywood manufacture. The direct savings in the cost of adhesive is 30 – 40 percent. h. Neyveli Catechol formaldehyde resin adhesives: A sample of catechol received from Neyveli Lignite Corporation Ltd., Neyveli (Tamil nadu), as a byproduct in their operations was received for investigation . The process for condensing catechol with formaldehyde was worked out. The process parameters for manufacturing the panels were optimized. The products confirmed to the requirement of IS 848 for BWR grade panels w. r.t species of vellapine, pali, white cedar, poon. Whereas the strength properties were not met w.r.t. gurjan species. However addition of ammonium maleate improved the glue adhesions strength properties with gurjan. Also the catechol was tried as an accelerator for cashewnut shell liquid phenol formaldehyde resin and CNSL formaldehyde resin. The results have been encouraging for the manufacture of BWR grade panels. i. Plywood Adhesives based on Neyveli Multivalent Phenol: Initially when multivalent phenol was used in the manufacture of phenol formaldehyde resin, it posed problems for the workers because of free formaldehyde vapour in the resin. Also the resin possessed lesser pot life. To overcome this problem, IPIRTI had taken up studies. Under this study, the resin formulation for the manufacture of phenol formaldehyde resin with reduced free formaldehyde and increased pot life using multivalent phenol received from Neyveli Lignite Corporation Ltd., Neyveli (TamilNadu) have been worked out. The process parameters for the manufacture of BWR grade panels has been optimized. This technology has been adopted by few industries for commercial production of panels. j. Development of phenolic coating compositions for plywood Phenolic adhesive composition suitable for concrete shuttering plywood have been developed. Composition were of self releasing type without the aid of releasing agents.
k. Development of room temperature setting sealants for panel edges Suitable room temperature setting pehnolic based sealant compositions were developed and introduced in the industry successfully. l. Putty for repair of plywood Putty compositions based on cellulose nitrate as well as UF-PVAc was developed which finds wide application for surface repair of plywood. m. Development of Adhesives for species refractory to bonding in plywood
manufacture Some species such as kapur, oily keruing and chilauni were found to pose problems bonding. To overcome this bonding problems a resin system based on phenol and formaldehyde has been developed and adhesive formulation has been optimised and the process parameters are worked out for achieving good bond strength . III Development of Resin adhesives for other wood based panels
(a) Suitable PF resin for bonding Bamboo Mat based composites have been developed. Process parameters for mats dipping, moisture content, Assembly time and hot pressing schedules have been optimized.
(b) Efficient resin system has been developed for bonding Rice husk particle boards. The process for making particles, resin application system, mat forming system have been worked out. The phenolic resin system developed is less expensive as they are based on naturally occurring phenolic materials.
(c) Cardanol substituted phenolic resin was developed to bond chir pine needles particles. The process parameters like moisture content of glued particles. Assembly time, Mat formation and hot press schedules have been worked out to manufacture grade II chir pine needle particle board.
LATEST ADHESIVES DEVELOPED
(1) Development of phenolic resin system for bonding high moisture content veneers (14% - 16%)
(2) Development of adhesives from Bio materials
(3) Development of Amino resin system for particle board manufacture with less formaldehyde emission (Upgradation of laboratory studies to pilot scale)
(4) Development of powder phenolic resin for the manufacture of bamboo mat based composites.
(5) Studies on the use of surface coating on bamboo flooring tiles to enhance the abrasion resistance properties.
(6) Development of low cost phenol formaldehyde resin (3 stage process)
(7) Studies to optimize resin formulation to bond fibres of sesal for Acoustic purpose.
(8) Detailed investigation on the treatment of battens and modified resin formulation to develop fire retardant flush door.
(9) Optimisation of resin formulation for the manufacture of compregs and highly densified shuttering grade materials using Bamboo mat and plantation timbers.
(10) Development of resin system for wood plastic bonding.
(11) Development of isocyanate resins .
(12) Activities are continued to effect improvements on existing resins, adhesives and process parameters for panel making.