Title of Invention

LOW COST MACHINABLE WOOD SUBSTITUTE FROM INDIGENOUS MATERIALS AND PROCESS FOR PREPARING THE SAME

Abstract

Conventional artificial wood substitutes normally use expensive adhesives and curing of the laminates formed therefrom necessitate prolonged thermal treatment. The resultant materials are often costly, and less expensive materials are prone to attack from rot and/or termite. The present invention provides a low cost, machinable wood substitute made from cashew nut shell liquid (CNSL), phenol, formaldehyde, caustic soda and pazatoluene sulfonic acid (PTSA), and using industrial or vegetative waste materials or cellulosic materials of low economic value. The composition thus formed are immune to action of chemicals, water or steam, does not easily burn and termite or rot does not affect them. The invention also describes a process for preparing composites and laminates.

Full Text

The present invention relates to a low cost machinable wood-substitute and process for preparing the same. More particularly, this invention pertains to low cost wood-like materials made from indigenously available cellulosic materials including agro-waste and agro bye-products and a process for making such materials which are not only eco-friendly, but are also considerably cheaper than other medium density fibre (M.D.F.) boards and natural wood. Wood has occupied an important place in human civilization forming a near-indispensable part of human society. With the rise in population and impact of industrialization, deforestation and destruction of forest cover have been rampant with disastrous aftermaths. Demand for wood has been on the rise and in consequence thereof indiscriminate tree-felling without subsequent plantation has caused eradication of virgin rain forests, both in equatorial African, South American and some of the Asian countries has not only led to loss of various life forms including animals, birds and insects, but has also resulted in wide-scale draughts, mudslides and erosion of top soil, rendering the land fallow and unsuitable for growth of vegetation, not to speak of loss of human lives. To bring an end to such senseless deforestation and also to restore ecological balance, scientists world over are endeavouring to evolve technologies to produce low cost wood substitutes which would effectively replace use of natural wood. Way back in the year 1909, Leo Hendrik Bakeland introduced a polymeric substance made by the interaction between phenol and formaldehyde and the resin (P.F.) entered the market under the trade name "Bakelite". Some wood substitutes were made by using the "Bakelite", but such resin-based polymer were found to be fragile and unmachinable, Attempts have been made in many developing countries, particularly in India, and to some extent success has been achieved in preparing new kind of boards, laminates or composites to replace wood or plywood for panelling, cladding, surfacing and partitioning for interior applications and making of furniture. Such types of boards are being prepared these days by using wood or wood fibers / particles / shavings or other natural or artificial fibrous materials. A number of products are now available in the market which are capable of being used for the aforesaid applications, but almost all of them are based on either wood particles / fibers, or bagasse fibers or other natural fibers like sisal, banana, coir, jute, etc., while using synthetic resin like phenol-formaldehyde, epoxy, urea-formaldehyde, polyester, etc., or inorganic binder like cement, gypsum etc. as binder or matrix. Preparation of boards and sheets by using prepag technique has been reported which has used coir / banana / sisal fibers and polyester and epoxy as binder matrix. Work is in progress in Roorkee and RRL, Trivandrum, for development of laminates, boards or composites using natural fibrous materials from vegetative source. Coconut leaf laminated composites have been made using a synthetic product based on polyvinyl acetate proprietary product along with lignin and Cashew Nut Shell Liquid (hereinafter abbreviated as 'CNSL' in this specification) as the binder. Other composites like glass fiber reinforced CNSL resin, particle board from jute stick using PF and UF (urea-formaldehyde), lantana camara composite boards using PF (phenol-formaldehyde resin, a synthetic product) have been reported. Indian Patent Application No. 4664/KOL/93 dated 8.9.1993 deals with coir fiber reinforced CNSL resin board. Although the product was machinable, but visually it did not resemble natural wood and hence it was not favoured with customer-acceptance. The principal object of this invention is to provide a low-cost, machinable product closely resembling natural wood and made entirely from indigenously available raw materials. A further object of this invention is to provide a low cost machinable composite product which uses agro-wastes or agro by-products in the course of its production / fabrication. A still further object is to produce a low-cost product which can be machined, sawed, nailed, screwed and painted. Another object of this invention is to provide a process for preparing a low-cost, machinable product resembling natural wood, but resistant to termite or rot, water-proof and eco-friendly. Yet another object of this invention is to provide a process which uses all kinds of cellulosic materials from vegetative kingdom in arriving at the wood-like product. The foregoing objects are achieved by this invention which provides a low-cost, machineable wood substitute obtained from CNSL, phenol, formaldehyde, caustic soda and para toluene sulphonic acid (hereinafter abbreviated and designated as 'PTSA'), and the semi-solid mass applied to suitable substrate, moulded, pressed and cured. This invention also relates to a process for preparing a low-cost, machinable wood-substitute as defined herein, which comprises - (i) interacting CSNL, phenol and formaldehyde in proportion of around 2:1, 1.87- 1.90 by weight; (ii) adding NaOH solution under stirring (around 33% w/v) till attaining a PH of 8-9; (iii) maintaining the mixture of (i) and (ii) at around 45°C for 12 hours to allow polymerisation to set in; (iv) adding PTSA (25% - 65% w/v) solution to the mass from step (iii) to adjust the PH between 5 and 6 to produce an intermediate compound "RESOL". (v) adding 25% - 65% aqueous PTSA solution (5 : 2 volume ratio) to the intermediate 'RESOL' obtained from step (iv); (vi) applying the viscous mass from step (v) to desired cellulosic substrate and thereafter spreading the same in a mould; (vii) applying pressure to the mould, keeping the mould and its contents at room temperature for around 8 hours for curing and then releasing the mould and, if desired. (viii) effecting post curing of the moulded articles in an own maintained at around 40°C for around 4 to 8 hours to attain desirable physico - chemical properties resembling wood. In the coastal areas of India, particularly in Andhra Pradesh, Goa, Kerala and West Bengal considerable amounts of cashew nuts are produced. The agro-waste namely cashew nut shell was generally used as fuel, and to some extent as cattle feed and/or fertilizer. But in recent times, an oily liquid known as "cashew nut shell liquid (CNSL)" is being extracted from the agro by-product which is rich in phenolic derivatives, which can be used as a substitute for phenol, Cashew nut shell containing a dark reddish brown liquid, the pericarp fluid of the nuts, is an excellent source of such natural resin. CNSL consists mainly of two naturally occurring unsaturated phenolic compounds, (a) anacardic acid (-90%) and cardol (-10%), apart from minor amounts of 2-methyl cardol. This has emerged as a versatile industrial raw material and finds a wide array of applications such as, for instance, in anti-friction linings and lubricants, paints and varnishes, laminating resins, rubber compounding resins, surfactants, foundry chemicals, copolymers with polyurethane and intermediates for chemical industry-to name just a few. It is much cheaper than phenol and finds use in preparing surface coating and adhesive, apart from those mentioned hereinbefore. This eco-friendly low cost and easily available raw material (i.e, CNSL) has been used as a major ingredient in the present invention. This invention will now be described in detail by means of the following working example, which is given by way of illustration and not by way of limitation. Example - 1 (i) Preparation of an intermediate compound termed "RESQL" 150 gm CNSL (Mol. wt. around 300), 75 gms. phenol and 130 gm formalin which contains (36-37%) w/w formaldehyde are taken in a suitable receptacle, e.g. 500 ml. beaker. NaOH solution (33% wt./vol) is slowly added to this mixture under constant stirring till attaining a pH of 8-9. Then the mixture is kept at 45°C for 12 hours to allow polymerisation to set in. Thereafter PTSA (25% - 65% wt./vol) aqueous solution is added to the above mixture to adjust pH between 5 and 6, and such addition decelerates rate of polymerisation quite appreciably. This results in an intermediate compound called "RESOL". (ii) Preparation of composite 180 ml. of Resol and 90 ml. of PTSA aqueous solution of (25% - 65% w/v) are mixed together and stirred well. 130 gm. of jute fiber is impregnated with 'Resol' and thoroughly mixed together in a metallic tray. The mixing was done carefully such that each individual fiber was wet with 'Resol'. Then the wet mass fibers were uniformly spread into a 18.5cm x 13.5 cm. x 1.5 cm sized 3-part steel mould, to which there is applied a pressure of 25 kg/cm2 and kept at ambient temperature for 8 hours to effect curing. At the end of such curing time, the contents are removed from the mould. (iii) Post curing of the composite The composite may be of any desired shape, size and configuration depending on the type of the mould used, the most common being boards, sheets or blocks. After releasing from mould, the articles may be kept in an oven maintained between 70°C and 80°C for around 4 hr. to achieve post-curing, particularly to impart desirable characteristics to the composites. Formation of laminate :- The composite as obtained in step (iii) may be formed into a laminate by subjecting the same to pressure by means of a hydraulic press at an elevated temperature. A suitable laminate was found to be formed at a temperature of between 90°C and 100°C and at a pressure of 10 tonnes/sq. in. Prior to formation of composite, filler materials selected from industrial or vegetative waste materials, or cellulosic materials of low economic value may be added to the mix in predetermined amounts to impart desirable characteristics like hardness, abrasion resistance and heat insulating properties. Such filler materials may include, inter alia, fly ash, China clay (plastic grade), talc, steatite, hemp, jute, coir, bagasse, banana tree skin, pineapple leaves, jute waste, grass (particularly the variety commonly known as "babu" grass ), and the like. Incorporation of compounds like borax and / or phthalic anhydride has been found to impart fire resistant characteristics. Example 2 The post-cured composite samples were subjected to a number of tests as per IS : 2380-1977 to determine their physico-mechanical properties, and the results are summarised hereinbelow. a) Density - 0.8 - 1.2 gm/cc. b) Initial moisture content - 6.83% (wt.) c) Water absorption (i) after 2 hours soaking - 1.85 - 1.92% (wt.) (ii) after 24 hours soaking- 5.54 - 7.24% (wt.) d) Swelling after 24 hours soaking - 1.90 - 2.4% e) Tensile strength - 375.2 kg/cm2 [speed of test, 50mm/min.) f) Flexural strength - 39.95 M.Pa. g) Cross breaking strength - 258.73 kg/cm2 h) Softening point - Softens at 110°-130°; no ignition i) Action of water - Negligible j) Action of termite rot, etc. - None k) Dielectric strength - 0.053 Kv/mm. The process outline may be illustrated by the undernoted flow-sheet diagram : The principal advantages of the articles produced in accordance with the present invention may be summarised as follows : i) The process uses industrial wastes, cellulosic agro-waste and agro by-products, which are renewable materials indigenously available from vegetative sources; ii) the products are water proof and are not attacked by termite or rot; iii) the products can be machined, worked upon and painted; iv) both the process and product are eco-friendly and v) the composites produced by this invention are cheaper than other M.D.F. (medium density fiber) boards and solid wood now in use. While the invention has been described in detail and with reference to the specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without deviating or departing from the spirit and scope of the invention. Thus the disclosure contained herein includes with its ambit the obvious equivalents and substitutes as well. Having described the invention in detail with particular reference to the illustrative Examples given above, it will be more specifically defined by means of claims appended hereafter. We claim, 1. A low cost, machinable wood substitute from indigenous materials, having cashew nut shell liquid (CNSL), phenol, formaldehyde, caustic soda and para toluene sulphonic acid (PTSA), forming a semi-solid mass, which is applied to suitable substrate, moulded, pressed and cured. 2. A low cost machinable wood-substitute as claimed in Claim 1, wherein the substrate is selected from, inter alia, a fibrous material like jute, coir, bagasse, hemp, banana the skin, pineapple waste, jute waste, grass and the like. 3. A low-cost machinable wood-substitute as claimed in Claims 1 and 2, wherein the cured material is subjected to post-curing at a temperature of around 40°C for a period of around 4 hours. 4. A low-cost machinable wood-substitute as claimed in Claims 1 to 3 having the following physical characteristics :- a) Density - 0.8-1.2 gm/cc. b) Initial moisture content - 6.83% (wt.) c) Water absorption (i) after 2 hours soaking - 1.85-1.92% (wt.) (ii) after 24 hours soaking- 5.54 - 7.24% (wt.) d) Swelling after 24 hours soaking - 1.90 - 2.4% f) Tensile strength - 375.2 kg/cm2 [speed of test, 50mm/min.) 0 Flexural strength - 39.95 M.Pa. g) Cross breaking strength - 258.73 kg/cm2 h) Softening point - Softens at 110°-130°; no ignition i) Action of water - Negligible j) Action of termite rot, etc. - None k) Dielectric strength - 0.053 Kv/mm. 5. A low-cost machinable wood-substitute from indigenous materials substantially as herebefore described. 6. A process for preparing a low-cost, machinable wood substitute from indigenous materials as claimed in the proceeding claims, which comprises : (i) interacting CSNL, phenol and formaldehyde in proportion of around 2 :1, 1.87- 1.90 by weight; (ii) adding NaOH solution under stirring (around 33% w/v) till attaining a pH of 8-9; (iii) maintaining the mixture of (i) and (ii) at around 45°C for 12 hours to allow polymerisation to set in; (iv) adding PTSA (25% - 65% w/v) solution to the mass from step (iii) to adjust the PH between 5 and 6 to produce an intermediate compound "RESOL". (v) adding 25% - 65% aqueous PTSA solution (5 : 2 volume ratio) to the intermediate 'RESOL' obtained from step (iv); (vi) applying the viscous mass from step (v) to desired cellulosic substrate and thereafter spreading the same in a mould; (vii) applying pressure to the mould, keeping the mould and its contents at room temperature for around 8 hours for curing and then releasing the mould and, if desired. (viii) effecting post curing of the moulded articles in an own maintained at around 40°C for around 4 to 8 hours to attain desirable physico - chemical properties resembling wood. 7. A process as claimed in Claim 6, wherein filler materials selected from industrial or vegative waste materials, or cellulosic materials of low economic value such as herein described is added to the mix in step (v) in predetermined amounts to impart desirable characteristics like abrasion resistance, hardness, heat insulation and the like. 8. A process as claimed in Claim 6, wherein phthalic anhydride or borax is incorporated for imparting fire-retardant properties; 9. A process for preparing a low-cost machinable wood-substitute from indigenous materials substantially as hereinbefore described with particular reference to the illustrative Examples. Conventional artificial wood substitutes normally use expensive adhesives and curing of the laminates formed therefrom necessitate prolonged thermal treatment. The resultant materials are often costly, and less expensive materials are prone to attack from rot and/or termite. The present invention provides a low cost, machinable wood substitute made from cashew nut shell liquid (CNSL), phenol, formaldehyde, caustic soda and pazatoluene sulfonic acid (PTSA), and using industrial or vegetative waste materials or cellulosic materials of low economic value. The composition thus formed are immune to action of chemicals, water or steam, does not easily burn and termite or rot does not affect them. The invention also describes a process for preparing composites and laminates.

Documents:

465-KOL-2005-(12-12-2011)-FORM-13-(12-12-2011).pdf

465-KOL-2005-CORRESPONDENCE-(12-12-2011).pdf

465-KOL-2005-CORRESPONDENCE-1.1.pdf

465-KOL-2005-CORRESPONDENCE.pdf

465-KOL-2005-FORM 27-1.1.pdf

465-KOL-2005-FORM 27.pdf

465-KOL-2005-FORM-1-(12-12-2011).pdf

465-KOL-2005-FORM-13-(12-12-2011).pdf

465-KOL-2005-FORM-27.pdf

465-kol-2005-granted-abstract.pdf

465-kol-2005-granted-claims.pdf

465-kol-2005-granted-correspondence.pdf

465-kol-2005-granted-description (complete).pdf

465-kol-2005-granted-examination report.pdf

465-kol-2005-granted-form 1.pdf

465-kol-2005-granted-form 18.pdf

465-kol-2005-granted-form 2.pdf

465-kol-2005-granted-form 3.pdf

465-kol-2005-granted-form 5.pdf

465-kol-2005-granted-pa.pdf

465-kol-2005-granted-reply to examination report.pdf

465-kol-2005-granted-specification.pdf