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United States Patent Office Patented June 16, 1942 2,286,643 UNITED STATES PATENT OFFICE 2,286,643 MOLDING COMPOSITONS FROM NATURA LY OCCURRNG CELLULOSC MATERALS AND METHOD FOR PREPARNG THE SAME Ralph Oliver Phillips, Ridgewood, N.J., and Ernst Hugo Werner Rottsieper, Epsom, England, as signors to The Forestal Land, Timber and Railways Company Limited, Epsom, England, a British company No Drawing. Application March 8, 1941, Serial No. 382,448. In Great Britain February 13, 1940 10 Claims. (C. 260-10) This invention relates to the manufacture of densation products with aldehydes. It is, of molded products of the phenol formaldehyde type course, common practice in the plastic industries and in particular to molding materials of the to use wood flour as a filling material but it is kind which include as a phenolic Component a Well known that woods ordinarily used in the natural tanning agent. manufacture of wood flour are the soft woods, Hitherto the tanning material employed has principally pine, spruce and fir which do not con been extracted from the fibrous material in which tain any tannin (Carleton Ellis, The Chemistry it naturally occurs prior to being mixed with the of Synthetic Resins, 1935 Edition, vol. II, page other molding materials and wood flour or simi 1273). It has been proposed hitherto to make lar filling materials have therefore been added O boards by treating wood fibre which may be ob to impart the necessary strength to the molded tained by grinding Wood to a fine powder, with a product. The two main tanning extracts, namely Substance capable of reacting with a phenol, such quebracho and mimosa, are generally obtained as an aldehyde, to form a condensation product, in solid form containing about 80% of dry mat and Submitting the material to heat and pres ter, and to improve the strength of the molded 5 sure. There is no suggestion, however, that the products, proposals have previously been made Woods to be employed should be tannin-contain to impregnate the Wood flour used as a filling ing Woods-still less is there any suggestion that with a liquid tanning extract or with a solution Woods containing catechol tannins should be em of tanning extract obtained by dissolving the ployed. solid extract and reevaporating the solvent prior 20 The wood or bark or like natural tannin-con to the addition of the condensation component, taining material is disintegrated as by grinding i. e. the aldehyde. The present invention is based or milling prior to its admixture with the alde upon the discovery that by using fibrous nate hyde, and the molded articles which are produced rials which are naturally specially rich in cer show great mechanical strength which is attrib tain tannins it is possible to produce a molded 25 uted to the relatively large amount of fibrous material simply by mixing the fibrous material material employed and to the thorough natural with the aldehyde component, e. g. a formalde distribution of tannin in the fibres. The term hyde yielding body. "powder' is to be read as including material in According to the present invention a moldable the form of granules or pellets in addition to the material, e. g. a powder or sheet for use in the 30 fine dust or powder referred to in the specific manufacture of molded products, comprises Wood, examples hereafter given. bark or like natural tannin-containing material It will thus be seen that according to the as hereinafter defined and an aldehyde, e. g. a present invention many of the steps previously formaldehyde yielding body. necessary in the manufacture of a molding As utilized in the claims hereunder, the ex powder or composition containing natural tan pression “formaldehyde yielding body' is in ning agents are omitted and that it is only tended to include hexamethylene tetramine and necessary to disintegrate the bark or other tan polyoxymethylenes, the latter being illustrated nin-containing material to the requisite degree by paraformaldehyde. of fineness and then to mix the powder so ob By the term “tannin-containing materials' 40 tained with the other molding ingredients. employed in this specification is meant such It will thus be seen that according to the pres materials as quebracho wood, mimosa bark, ent invention many of the steps previously neces spruce bark, mangrove bark, hemlock bark, urun Sary in the manufacture of a molding powder or day wood, tizera wood, and roots and other mate composition containing natural tanning agents trials which in their natural state contain tan 45 are omitted and that it is only necessary to dis nins of the catechol type which on reacting With integrate the bark or other tannin-containing an aldehyde form water-insoluble condensation material to the requisite degree of fineness and products. These materials are illustrative of a then to mix the powder so obtained with the preferred embodiment of the invention in view other molding ingredients. of their natural content of catechol tannins and 50 Preferably the aldehyde is added to the which substantially do not hydrolyze with acids powdered tannin-containing bark or the like in and which on reacting with an aldehyde form Solid form, e.g. paraformaldehyde, but aqueous water-insoluble condensation products as distinct Solutions or non-aqueous solutions may also be from the pyrogallol tannins which are hydrolyz employed. able with acids and do not yield insoluble con- 55 The percentage of aldehyde necessary depends 2 2,288,643 upon the quantity of tanning matter which the require the use of approximately equal quan original material contains and in the case of -tities of tanning extract and wood flour if the quebracho wood not less than 2% or 2%% of are to have the necessary strength. Thus th paraformaldehyde is found sufficient to give good employment of fibrous materials which naturally results, for mimosa bark a minimum of 3% to 4% contain tannin produces a better article at less is necessary and with spruce bark 2%. or less is expense and owing to the intimate and complete required. These percentages may be increased natural distribution of tannin in the fibrous ma to suit the desired finish or degree of hardness. terial used, practical difficulties in the molding A plasticiser may be added to the moldable operation and inconsistent results are obviated. material in particular glycerine or other plas ) The following specific examples are given by ticisers which are soluble-in water and able to way of illustration although it will be under dissolve the tannin in the powdered material stood that the invention is not limited to these may be added with good results. Water or a examples. solvent for the tannin is preferably employed to assist the flow of the powder in the mold espe s . v Eacample I cially if no plasticiser is employed. Colouring 100 parts of fresh mimosa bark having a water matter can of course be included. content of 15% after preliminary drying were In the preparation of the powder the raw ma ground in a rod mill to a powder capable of pass terial, that is to say the wood, bark, roots or other ing through an 80 I. M. M. mesh sieve. The tannin-containing material, may first be dried so powder was thoroughly mixed with 3.5 parts of as to reduce its moisture content to 5% or 10% paraformaldehyde and 6 parts of glycerine and and is then disintegrated by grinding or milling subjected to thorough homogenisation. The powder so obtained when molded to form an ash in a suitable mill to the requisite degree of fine tray at a temperature of 325' F. for 3 minutes at ness for example not less than that usual in the a pressure of 2 tons per Square inch showed manufacture of wood filler or flour employed 2 5 great hardness, did not crack when permitted to in the production of plastic articles. Prelimi fall from a height of 12 feet on to a concrete nary drying is not always essential, as good re floor, possessed good water resistance and when sults can be obtained even if this step is omitted. boiled for 1 hour in Water did not give up any By drying, however, the time occupied in grind colouring matter. ing is reduced and in some cases the raw ma 30 terial is dried until it contains no moisture. In Eacample II certain cases the tannin content of the powdered 150 parts of previously completely dried que materialso obtained can be increased by the addi bracho wood were ground in a mechanical mill tion of tanning extract. Where, as in excep and passed through a sieve of the kind de tional cases, the initial tannin content of the 35 scribed in Example I. This powder was inti tanning material is high, some of the tannin mately mixed with 3.75 parts of paraformalde may first be extracted and used for other pur hyde and With a solution containing 9 parts of poses or a suitable fibrous filler may be added glycerine, 3 parts of methyl lactate and 27 parts to compensate for any deficiency of fibre in the of Water. The resultant powder was molded natural material. Thus mangrove bark may con 40 under conditions similar to those given in the tain up to 50% of tannin and this renders ad first example; a good flow was obtained and the visable the addition of wood flour. The powder molded article showed exceptional mechanical so produced with or without the addition of tan strength. ning extract in powdered or liquid form, is thor Eacample III oughly mixed with a condensing agent such as 45 an aldehyde and preferably a solid material such 75 parts of dried larch bark and 75 parts of as paraformaldehyde or a polyoxymethylene is dried mimosa bark were ground to a powder used.
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