POLYMER, PREPARATION AND FORMULATIONS FOR PREPARATION THEREOF AND USE FOR PRODUCTION OF BONDED MATERIALS

Abstract: A polymer containing carboxylate groups which is formed by polymerization, in the absence of toxic or inflammable solvents, of a water-soluble salt of a compound of the formula: in which R represents C₁₅H 31-n , C₁₇H 35-n or C₁₁H₂₃ in which n is 0, 2, 4 or 6, and X represents H or OH, with an aldehyde, preferably formaldehyde in the form of paraformaldehyde. Preferred starting materials are derived from both natural and Technical cashew nut shell liquid (CNSL) including 4-pentadecyl-salicyclic acid and 5-pen­ tadecylresorcinol-2-carboxylic acid, both new compounds, obtained by subjecting Technical CNSL to carboxylation by the Kolbe reaction. The components may be polymerized in alkaline aqueous medium and used to bond particulate and/­ or fibrous materials, e.g. particle board of wood chips.

Description: Polymer, preparation and formulations for preparation thereof, use for production of bonded materials, inter mediates and preparation thereof. This invention relates to polymers, to their preparation and to their use as bonding agents in the production of bonded particulate or fibrous material. In particular the invention relates to polymers containing carboxylate groups which are formed by polymerizing certain carboxyl-containing phenols with aldehydes. Proposals have hitherto been made to produce particle board by using as a binder a polymer of cashew nut shell liquid (CNSL) with an aldehyde. Such processes have however required the use of organic and chlorinated solvents which may be undesirably toxic, inflammable or expensive. It has now been found that similar polymers may be obtained in which the use of such solvents is obviated. Therefore according to the invention there is provided a polymer containing carboxylate groups characterised in that it is formed by polymerization of a water-soluble salt of a compound of the formula: EMI2.1 in which R represents C15H31¯nss C17H35-n or C11 23 in which n is 0, 2, 4 or 6, and X represents H or OH, with an aldehyde. The polymer of the invention may be used in the preparation of bonded particulate or fibrous materials to effect the bond between the particles and/or fibres. The compounds of formula (I) are generally naturally occurring materials. For example, pelandjauic acid, the compound in which X is H, R is C17H35 and the COOH is ortho to R and OH, is present in latex extracted from certain trees. Anagigantic acid, the compound in which X is H, R is C11H23 and the COOH is ortho to R and OH is present in the nutshells obtained from the tree Anacardium giganteum. A particularly preferred compound of formula (I) is anacardic acid, in which X is H, R is C15H31-n and the COOH is ortho to R and OH, which is obtained from the outer shell of the cashew nut obtained from the cashew nut shell tree, Anacardium occidentale. Cashew nut shell liquid (CNSL) is extracted from the outer shell of the cashew nut obtained from the cashew nut tree, Anacardium occidentale, after the kernels have been removed by freezing and fracturing. In the shell CNSL comprises anacardic acid (2-carboxy-3-pentadecadienyl phenol) at a level exceeding 70% and related acids of different degrees of unsaturation, together with cardol (m-pentadecadienyl resorcinol). There are two main processes for extracting CNSL. According to one process a cold solvent extraction is conducted on the shells, for example as disclosed in United States Patent Specification No. 1 954 650 and in J.H.P. Tyman, J. Chem. Soc. Perkin I Trans. 1973, 1639. Cold solvent extracted CNSL consists essentially of anacardic acid and minor amounts of cardol. This liquid may be used directly for the production of a polymer of the invention providing an alkali metal hydroxide is present to form the salt in situ. Alternatively the liquid may be pre-treated to form the salt. Cardol and other constituents which are non-carboxylic, may be incorporated into the polymer as component units or may also contribute to the bonding properties of the product as separate polymers produced by polymerization with the aldehyde. For example, the cardol may be present in the polymer in amounts of 15% or more. According to the second process CNSL is extracted from the shells by a heating process which results in decarboxylation of the acids so that the material obtained contains cardanol EMI4.1 and cardol EMI4.2 and related compounds of varying degrees of unsaturation. This liquid is referred to herein as Technical CNSL. Whilst cardanol and cardol alone are not suitable for preparing the polymers of the invention it has been found that these compounds may be carboxylated using the Kolbe reaction. Conditions or conducting the Kolbe Schmitt reaction are disclosed in A.S. Lindsey and H. Jeskey, Chem. Rev., 1957, 57, 483. The compounds are treated with carbon dioxide at elevated temperature, generally above 1000C preferably above 150 0C usually under pressure and sometimes in the presence of a solvent. The compounds are preferably treated in the form of an alkali metal salt of the phenol or under suitably alkaline conditions. Suitable solvents include diglym and dimethyl formamide; water is not preferred although cardol is less affected than cardanol by its presence in the carboxylaation. It is desirable to keep the reaction temperature below 2000C since decarboxylation occurs in excess of this temperature. The products of the Kolbe reaction on cardanol and cardol are essentially 4-pentadecyl-salicyclic acid and 5-pentadecylresorcinol-2-carboxylic acid respectively, which are new compounds within the scope of the invention, i.e. the carboxylate group is introduced into the para-position relative the C15H3l n chain. These compounds are suitable for use in the preparation of polymers of the invention. If desired cold extracted CNSL may be subjected to the Kolbe reaction to yield a mixture containing a high proportion of anacardic acid and 5-pentadecylresorcinol-2-carboxylic acid. It is also possible to separate the components of CNSL by fractionation if it is desired to use specific compounds for the preparation of the polymers. The various compounds which may be derived from CNSL may be expressed schematically as follows: EMI6.1 cold extracted CNSL EMI6.2 decarboxylation on heating EMI6.3 cardol Technical CNSL EMI6.4 Kolbe Reaction EMI6.5 EMI6.6 In practice the salt.of the compound of formula (I) is usually mixed with the aldehyde to produce a single formulation, preferably in an aqueous diluent. Typical formulations contain for each mole of compound of formula (I), from 1 to 5 moles of aldehyde and optionally up to 2 moles of alkali metal hydroxide, e.g. sodium or potassium hydroxide. The solids content of the formulations is generally between 25 and 50%. Suitable aldehydes for use in the invention include formaldehyde, preferably in the form of paraformaldehyde, acetaldehyde and furfuraldehyde. Other low molecular weight aldehydes may also be used. The polymer is formed by the reaction of the salt of the compound of formula (I) and the aldehyde at a temperature insufficient to decarboxylate the product preferably at ambient temperature. The salt may be prepared in situ in the reaction medium by reaction of a compound of formula (I) with an alkali metal hydroxide. Alkaline conditions are preferred for the polymerization The polymer of the invention is suitable for use as a binder or adhesive in many applications. Particles or fibres which may be bonded by the polymer of the invention include cellulosic materials, for example cashew nut shell, flax, hemp, jute, sugar cane and cotton stalks, and siliceous materials. Wood chips are however of special interest for the production of particle board, such chips being normally no greater than 30 mm in length. Although the fibres or particles may be treated with the binder formulation at elevated temperatures, e.g. up to 65 0C, ambient temperatures are generally preferable. It is usually convenient for the particles or fibres to be treated with binder formulation in the form of a spray and the temperature thereof is dependent on the viscosity of the solution. It will be appreciated that whilst polymerization may take place wholly after treatment of the particles or fibres with the binder formulation, polymers may form to a limited extent on storage of the formulation and this may be tolerable provided that the treatment operation, for example the spraying of the particles or fibres, is not adversely affected. The relative amounts of binder formulation and particles or fibres are of course chosen in accordance with the properties required in the finished material. For guidance however the amounts of the wood chips and binder are generally chosen so as to yield a wood particle material with a resin content between 6 and 12% w/w. Particle board is of course produced by heat treating pressed wood chips treated with the binder and the applied pressure is usually chosen so as to give 3 a board density at least 400 kg/m . The temperature at which bonding is effected is normally no greater than 250 0C and preferably no greater than 150 0C, the pressing time desirably being no greater than 15 minutes. At high pressing temperatures significant decarboxylation of the polymer may take place as indicated above. Such decarboxylation may be desirable in reducing the water absorptive characteristics of the polymer binder. The invention will now be illustrated by the following Examples. Example 1 8 g of the sodium salt of saturated cardanol: EMI9.1 = = 0 were dissolved in 16 ml of diglym (2,2'-dimethoxydiethylether). The solution was maintained at 155 to 160 C for 21/2 hours during which carbon dioxide was passed through the solution. The product was isolated by recovery of the diglym, cooling of the reaction mixture, dilution with water and acidification. The pure carboxylic acid was isolated by recrystallisation and was characterised by elemental analysis and its spectroscopic and chromatographic properties. The isolated product was consistent with the structure 4-pentadecyl-salicyclic acid and exhibited a melting point of 89 to 900C. Elemental Analysis: EMI10.1 <tb> <SEP> C% <SEP> H% <SEP> <tb> Found <SEP> 76.25 <SEP> 10.54 <tb> Calculated <SEP> 75.86 <SEP> 10.34 <tb> The above procedure was repeated using the sodium salt of saturated cardol EMI10.2 n=0 with a heating period of 1 hour. The isolated product was consistent with the structure 5-pentadecylresorcinol2-carboxylic acid and exhibited a melting point of 140 to 141 0C. Elemental Analysis: EMI11.1 <SEP> C% <SEP> H% <tb> Found <SEP> 72.72 <SEP> 10.15 <tb> Calculate <SEP> 72.55 <SEP> 9.89 <tb> Additional experiments were conducted using mixed cardanol (n = 0, 2, 4, 6) and mixed cardol (n = 0, 2, 4, 6) and using pure saturated cardol mixed with K2CO3 in water. The results are reported in Table 1. Table 1 EMI12.1 Substance/Amount <SEP> (g) <SEP> Solvent/Amount <SEP> (cm ) <SEP> Reaction <SEP> Heating <SEP> Yield <tb> <SEP> temp <SEP> time <SEP> (%) <tb> <SEP> ( C) <SEP> (hours) <tb> Saturated <SEP> cardanol <SEP> 8 <SEP> Diglyme <SEP> 16 <SEP> 155-160 <SEP> 21/2 <SEP> 50 <tb> Saturated <SEP> cardanol <SEP> 8 <SEP> Diglyme <SEP> 16 <SEP> 155-160 <SEP> 1 <SEP> 100 <tb> Saturated <SEP> cardanol <SEP> 2 <SEP> Water <SEP> 20 <SEP> 100 <SEP> 3 <SEP> 50 <tb> Mixed <SEP> cardol <SEP> 16 <SEP> Diglyme <SEP> 32 <SEP> 155-160 <SEP> 1 <SEP> 100 <tb> Mixed <SEP> cardanol <SEP> 15 <SEP> Diglyme <SEP> 20 <SEP> 155-160 <SEP> 21/2 <SEP> 50 <tb> Example. 2 In this preparation Technical cashew nut shell liquid (CNSL) containing approximately 85% mixed cardanol and 15% mixed cardol with a little 2-methyl-cardol was carbonated. For the purpose of the experiment the molecular weight of the -reactants was taken to be 302. A three-necked reaction vessel equipped with mechanical stirrer, carbon dioxide gas inlet and condenser adjustable for reflux or distillation was charged with methanol (1000 cm3) containing sodium methoxide from sodium (23 g) and Technical CNSL (302 g) added. To the mixture diglyme (600 g) was introduced and the methanol removed by distillation. Towards the end of the recovery the admission of carbon dioxide was commenced. As removel of the remaining methanol occured the reactiopn temperature rose to 170 and was maintained at this point for four hours while carbon dioxide was continuously passed into the reaction mixture. The course of the reaction was monitored by withdrawal of samples and exa:mination of the acidified and recovered products by thin layer chromatography. When the amount of cardanol and cardol had significantly been reduced the reaction was judged to be complete. The condenser was then adjusted for distillation and the diglyme substantially removed over a period of 2 hours during which the temperature of the reaction rose to about 190 C and passage of carbon dioxide was continued. The mixture was cooled with continued carbon dioxide admission and, at ambient temperature, was diluted with water to dissolve the product, the solution acidified and solvent extracted to give carboxylated CNSL. Thin layer chromatographic examination indicated the presence of a polar product with little cardanol and cardol remaining. Infrared spectroscopic examination gave #(max) at 3550 cm-1 (Oh absorption) and 1750 cm-1 (carbonyl absorption) with other additional bands in other regions. The 'H NMR spectrum (carbon tetrachloride solution) showed hydrogen-bonded OH HO,C absorption (exchangeable D2O) at T 7.63 - 7.77 and olefinic absorption unchanged in the region 4.80 - 5.45 comparable with that of Technical CNSL, indicating the presence of -CH=CH- and -CH=CH2 unsaturation. Argentation thin layer chromatography shdwed the presence of (monoene), diene and triene constituents of cardanol and cardol. Example 3 The product of Example 2 was polymerized in the following way. The carboxylated CNSL (5.0 g) was heated at 80 C with the addition of sodium hydroxide (0.25 g) in water (12 cm3) and paraformaldehyde (1.0 g). An insoluble polymer was gradually formed and precipitated from solution. When this material was isolated and then heated at 2000C the evolution of carbon dioxide was observed. Similar polymerization reactions were performed as reported in- Table 2. Table 2 EMI15.1 <tb> Substance <SEP> Amount <SEP> Water <SEP> NaOH <SEP> PFA <SEP> Bath <SEP> Heating <tb> <SEP> g <SEP> ml <SEP> g <SEP> g <SEP> C <SEP> min. <tb> Anacardic <SEP> Acid <SEP> 1.0 <SEP> 3.5 <SEP> 0.1 <SEP> 0.4 <SEP> 200 <SEP> 15 <tb> Carboxy <SEP> Cardanol <SEP> 0.6 <SEP> 2.0 <SEP> 0.06 <SEP> 0.3 <SEP> 200 <SEP> 15 <tb> Carboxy <SEP> Cardol <SEP> 1.0 <SEP> 3.5 <SEP> 0.1 <SEP> 0.4 <SEP> 200 <SEP> 15 <tb> Example 4 Binder Formulation A formulation was prepared from CNSL solution containing natural CNSL (930 g), caustic soda (100 g) made up to 2,700 cm3, (the density is 1.002). Paraformaldehyde (166 g) was thoroughly mixed with the CNSL solution. Production of Particle Board 1600 g chips of Scots Pine 30 mm in length x 0.6 mm thickness, dried to 5% moisture content were sprayed with a reduced amount of the above formulation containing 287 g of the above solution mixed with 18 g paraformaldehyde at room temperature from a spray gun whilst the chips were contained in a rotating bin. The nominal resin solids content of the board was approximately 8%. The sprayed chips (1730 g) with a moisture content of 11% were hand spread onto a plate provided with a circumferential former approximately 6 inches high. The chips were consolidated by cold pressing and the former removed to leave a mat which was then provided with a top plate and the whole placed in a platen press, the top and bottom plates of which were maintained at 260 C. Pressing was maintained for 35 minutes and after 2 minutes the temperature rose from approximately 20 C to 100 C and then over the next 33 minutes to 260 C. The properties of the product are reported in Table 3. Example 5 The process of Example 4 was repeated except that in this case the particles were dried to 1% moisture content, 1600 g chips, 341 g solution and 21 g paraformaldehyde were employed (nominal resin content 9.5%). The moisture content of the sprayed chips was 9%. In this case the platen pressure was released for 15 seconds at 3 minutes and 5 minutes from the commencement of pressing to allow release of steam. The results are reported in Table 3. Table 3 EMI17.1 Example <SEP> No. <SEP> Moisture <SEP> Content <SEP> % <SEP> Resin <SEP> Resin <SEP> Board <SEP> Modulus <SEP> Tensile <SEP> Water <SEP> Thickness <SEP> Pressing <tb> <SEP> % <SEP> Temp. <SEP> Density <SEP> of <SEP> strength <SEP> Absorp- <SEP> swelling <SEP> time <tb> <SEP> C <SEP> Rupture <SEP> pepen- <SEP> tion <SEP> 1 <SEP> % <SEP> mins. <tb> <SEP> Dried <SEP> Sprayed <SEP> Kg/m <SEP> MN/mê <SEP> dicular <SEP> hour <SEP> % <tb> <SEP> Particle <SEP> 'Chips' <SEP> MN/mê <tb> <SEP> 4 <SEP> 5 <SEP> 11.0 <SEP> 8 <SEP> Room <SEP> 590 <SEP> 12.5 <SEP> 0.19 <SEP> 13.8 <SEP> 5.3 <SEP> 35 <tb> <SEP> 5 <SEP> 1 <SEP> 9 <SEP> 9.5 <SEP> Room <SEP> 614 <SEP> 17.8 <SEP> 0.41 <SEP> 11.7 <SEP> 4.9 <SEP> 31 <tb> BS <SEP> 2604 <tb> <SEP> 1970 <SEP> N/A <SEP> N/A <SEP> N/A <SEP> N/A <SEP> Min <SEP> 13.8 <SEP> 0.34 <SEP> - <SEP> 12.0 <SEP> N/A <tb> (comparison) <SEP> 480 <tb>

Claims: CLAIMS: 1. A polymer containing'arboxylate groups characterised in that it is formed by polymerization of a water-soluble salt of a compound of the formula: EMI18.1 in which R represents C15H31¯nX C17H35,n or C11 23 in which n is 0, 2, 4 or 6, and X represents H or OH, with an aldehyde. 2. A polymer as claimed in Claim 1 characterised in that the aldehyde is selected from formaldehyde, paraformaldehyde, acetaldehyde and furfuraldehyde, and the compound of formula (I) is selected from pelandjauic acid, anagigantic acid, anacardic acid, 4-pentadecylsalicyclic acid, 5-pentadecylresorcinol-2-carboxylic acid and mixtures thereof. 3. A method of preparing a polymer containing carboxyl groups characterised in that a water-soluble salt of a compound of the formula: EMI18.2 in which R represents C15H31,,' C17H35-n or C11H23 in which n is 0, 2, 4 or 6, and X represents H or OH, is reacted with an aldehyde in a molar ratio of from 1:1 to 1:5 respectively, at a temperature insufficient to decarboxylate the product. 4. A method as claimed in Claim 3 characterised in that the salt of the compound of formula (I) is prepared in situ by reaction of a compound of formula (I) with an alkali metal hydroxide in a molar ratio up to 1:2 respectively. 5. A method as claimed in Claim 3 or Claim 4 characterised in that the aldehyde is selected from formaldehyde, paraformaldehyde, acetaldehyde and furfuraldehyde and the compound of formula (I) is selected from pelandjauic acid, anagigantic acid, anacardic acid, 4-pentadecyl-salicyclic acid, 5-pentadecylresorcinol-2-carboxylic acid and mixtures thereof. 6. A method as claimed in any of claims 3 to 5 characterised in that the compound formula (I) is in the form of cashew nut shell liquid obtained by cold solvent extraction from the shells. 7. A method as claimed in any of claims 3 to 5 characterised in that the compound of formula (I) is in the form of carboxylated Technical cashew nut shell liquid. 8. A formulation comprising a water-soluble salt of a compound of the formula: EMI20.1 in which R represents C15H31¯na C17H35-n or C11H23 in which n is 0, 2, 4 or 6, and X represents H or OH, and an aldehyde in a molar ratio of from 1:1 to 1:5 respectively, in an aqueous diluent. 9. A formulation as claimed in Claim 8 characterised in that the aldehyde is selected from formaldehyde, paraformaldehyde, acetaldehyde and furfuraldehyde, and the compound of formula (I) is selected from-pelandjauic acid, anagigantic acid, anacardic acid, 4-pentadecylsalicyclic acid, 5-pentadecylresorcinol-2-carboxylic acid and mixtures thereof. 10. A material comprising particles and/or fibres which are bonded together characterised in that the bonding is effected by a polymer containing carboxylate groups which is formed by polymerization of a water-soluble salt of a compound of the formula: EMI21.1 in which R represents C15H31¯n, C17H35-n or C11 23 in which n is 0, 2, 4 or 6, and X represents H or OH, with an aldehyde. 11. A material as claimed in Claim 10 characterised in that the particles and/or fibres comprise cellulosic or siliceous materials. 12. A method of preparing bonded particulate and/or fibrous material comprising treating said particles and/or fibres with a formulation as claimed in Claim 8 or Claim 9, shaping the resulting mix and allowing the diluent to evaporate and the components to polymerize. 13. A A compound of the formula: EMI21.2 in which X is H or OH, and ni;s 0, 2, .4, or 6, or a salt thereof, 14. A method of preparing a salt of a compound of the formula: EMI22.1 in which X is H or OH and n is 0, 2, 4 or 6, in which an alkali metal salt of a compound of the formula: EMI22.2 in which X and n are as defined above, is treated with carbon dioxide at elevated temperature.

Inventors: HAWKES, ANTHONY JACK, DURRANI, AZIZ AHMED, TYMAN, JOHN HENRY PAUL
Applicants: DURRANI, AZIZ AHMED, HAWKES, ANTHONY JACK, TYMAN, JOHN HENRY PAUL
Application year: 1980
Main classification: C08G8
IPC codes: C08L97, C08G8, C07C51, C07C65, C07C67