US 1790346 A
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Patented Jan. 27, 1931 UNITED STATES PATENT OFFICE ELLERY H. HARVEY, ,OF LANSDALE, iENNSYLVANIA, ASSIGNOR T PERKINS GLUE I COMPANY, A COIRZPORATION OF DELAWARE rnocnss or MAKING VEGETABLE GLUE My invention relates to improvements in rying out the factory control method, the
processes of making vegetable glue and more particularly vegetable glue having substantially the adhesive properties of animal veneering glue.
It has been common for many years to make vegetable glue for furniture veneering by dissolvingone part starch in about 3 parts or less by weight of water with caustic alkali such as caustic soda which acts as a solvent of the starch in water. Sometimes a partially hydrolyzedor degenerated starch is used and sometimes a starch just as it comes on the market is used, cassava starch, or
tapioca flour as it is sometimes called, being preferred. See U. S. Reissued Letters Pats ent 13,436 granted July 2, 1912. As therein described the starch may be dissolved at or-.
dinary temperature or a carefully regulated heat (preferably below 175 F.) may be used, the amount of caustic solvent used being less when heat is used in dissolving.
The starches more commonly used (whether partially hydrolyzed or not) have been such that the resulting glue has had a specific viscosity of] 80,000 or more; A glue havinga viscosity of about 80,000 I'believe to be the best for all around furniture veneering. 'lhe viscosity may be somewhatv greater without greatly aflecting the workability of the glue but I prefer that it be not over 175,000.
Such an increase in viscosity is not so disadvantageous as a viscosity materially below 80,000. These viscosity figures represent the specific viscosity of the glue as compared with that of water at 20 C. and are measured when the glue is at substantially 75 F. and
- may be measured by an apparatus andin a not represent the same viscosities as would be obtained upon glue made up in a large kettle as employed for factory conversion. In car- Application (filed September 19, 1923. Serial No; 663,713.
specific procedure is preferably employed as follows :814 cc, of water are placed in a kettle geared to run 84 'R. P. M., 400 rams of flour having a moisture content of is spun and agitation continued for about 5 i to 16% are added, the agitator in the kettle minutes. Add 36 cc. of 3 to l C. P. caustic soda solution,,taking 5 minutes to add it. Turn on the steam in the kettle carefully so that the glue is gradually and smoothly converted to 170 F. taking 20 minutes to bring of water would produce a glue having a viscosity of 80,000 or more. For-this purpose it has been necessary to select the so-called high grade starches (such as the high grade cassava starches) which starches are the more expensive. When it has been attempted to make the glue from the lower grade or less expensive starches, and particularly low grade cassava, in the manner above set forth it is found that the viscosity of the resulting glue, even if as little as 2 parts of water be used, is materiallybelow 80,000 and while the glue has considerable adhesiveness, it is sloppy and diflicult to apply with the spreading machines commonly used to apply the same in furniture veneering. It is diflicult if not impossible toapply it to the wood veneer layersevenly and in proper quantity, Itfrequently slops oil the spreading rolls and wood veneer sheets onto the floor causing a very considerable loss of glue as well asadding to the labor necessary to keep the factory clean and in proper order. The glue also slops ofi onto the hands of the workmen increasing the dificulties of handling the machines and wood veneers and making the work very disagreeable. Finally such a low viscosity glue is likely to penetrate, too readily into porous parts of the wood or any soft porous kinds of wood and make unreliable joints.
According to my invention I use such cheap, low grade, low viscosity starch, but avoid the disadvantages above pointed out by adding a coagulating agent to increase the viscosity of the resulting glue to 80,000 or more whereby the sloppy characteristic of the glue is removed and the glue is substantially the same in its adhesive qualities and workability as if made with the higher grade starches as above pointed out.
I am aware that it has been suggested that coagulating agents may be added to different vegetable glues for different purposes. It has been suggested that more economy might be obtained with the high grade, high priced starches by increasing the water in the glue made therefrom to, say, from 4 to 7 parts of water and then, in order to counteract the tendency of the increased water to make the glue too fluid, coagulating or thickening agents have been added. In this way a given amount of starch will produce a great deal more glue which may be spread over a great deal more surface thus considerably decreasing the glue cost for a given area glued. But such glue is disadvantageous particularly with some classes of work, in that the water has to be almost entirely dried out in producing the glued joint, and the increased water increases the drying time, and tends to warp the wood veneers and produce weak oints, all of very serious consequence.
It has also been suggested that great economy might be obtained by using these high grade, high priced starches (which Without any coagulating agent produce glues in the manner above described having a viscosity of 80,000 or over) and using a coagulating agent therewith to increase the viscosity of the l esulting glue very greatly above 80,000. For example the addition of the coagulating agent in such case might increase the viscosity of the glue from say 90,000 to 100,000 to 150,000 or 200,000. With such a heavy viscous glue, the glue penetrates the wood less and it was supposed therefore that it might be spread much thinner and therefore a greater area may be glued with a given amount of glue or starch and thus greater economy obtained. I have found, however, that for good reliable joints in furniture work this method of seeking economy is not satisfactory and I believe it to be because too little dry material is finally left in the joints. For certain classes of work, some consider such a glue to have a better consistency. Such a glue, however, has the disadvantage that it is more difficult to handle in the glue mixing and spreading apparatus.
So far as I am aware, in all cases where a coagulating agent has been used, it has been in a glue, the starch in which would produce without the coagulating agent and with 2 parts of water, a glue having a viscosity of 80,000 or more, and the high grade, higher priced cassava starches were used, and economy was attempted by increasing the spread per unit of starch used.
In contradistinction thereto, I use the low grade or low priced starches which when dissolved in 2 parts of water by mixing the starch with the Water and 8% of caustic soda and heating to 170 F. and continuing the heating with agitation until the starch has been dissolved to produce a fluent glue, without any coagulating agent would produce a glue having a. viscosity below 80,000 and I overcome any sloppy tendency and increase the viscosity thereof by the addition of a coagulating agent, and I obtain greater economy by using a less expensive starch as'a base instead of by increased spread per unit of high grade starch. Also I thus avoid the use of so much water as to retard the time of drying and risk of injury to the wood, but materially more than 3 parts of water may be used in some classes of work. -I also fully maintain the'desired quantity of dry material in the final joint. In this manner I am able to obtain a long sought improvement in economy without danger of injury to the quality of the joint.
By coagulating agent I mean any chemical or chemicals or medium which serves to cause the viscosity of the glue to be increased. Many different salts may be used for this purpose for example salts of the amphoteric polyvalent metals such as iron sulphate FesO tin chloride, nickel chloride, etc. or ,borax or certain of the natural oxids or phosphates which may be present in starch, but I prefer touse the iron sulphate because of its availability and cheapness.
The coagulating agent may be thoroughly mixed with the starch before it is mixed with the water and dissolved. In this way by adjusting the amount of coagulating agent to the particular starch being used, a starch base of uniform viscosity may be easily produced. Or the coagulating agent may be added to the mixture of starch and water and mixed therewith before the solvent is added to dissolve the starch; or it may be added while the glue is being dissolved, or, in some cases after it has been dissolved. By solvent I mean any agent which aids in dissolving the starch in water. In some cases solvents other than caustic soda or caustic alkali may be used, such as trisodium phosphate. sodium aluminate, tribasic acetate of lead, formaldehyde etc. (see U. S. Letters Patent 1,378,105), but the solvent should be non-acid in character to give the best results with most of the coagulating agents I prefer to use because of their cheapness. When the coagulating agent is mixed with the starch by hand it may be added thereto in dry form or may be sprayed on the dry starch in the form of a solution, the
Generally only a small amount of coagulating agent is required so that the expense thereof is inconsiderable. For example, with a certain cheap grade of cassava starch I found that the viscosity of glue at 75 F. made therewith by dissolving it in 2 parts of water with 3% of caustic soda and heating the batch to 170 F. and continuing the heat with agitation until the starch was dissolved to produce a fluent glue, was 44,000. By adding two-tenths of one per cent (2%) of iron sulphate (FeSO the viscosity of the resulting glue was increased to 80,000. By using one quarter of one per cent of iron sulphate the viscosity was increased to 138,000. The iron sulphate was added and stirred in when the be added before or after.
' mined by similar experimental testing. The
particular viscosity to which the glue should be increased will vary somewhat according to the conditions under which the glue is to be used or purposes for which it is to be used, but generally speaking I prefer to add such a quantity of coagulent as will increase the, viscosity of the resulting glue from under 60,000 to over 60,000.
The expression starch of a specific viscosity less than 60,000 employed in the claims refers to a starch which when dissolved and tested according to the procedure for determining viscosities above set forth, will indicate a viscosity of the figure mentioned. 7
What I claim as new and desire to secure by Letters Patent, is:
1. The process of making vegetable glue suitable without dilution for general furniture veneering which comprises dissolving one part of starch of a specific viscosity less than 60,000 in about three parts or less of water with an alkaline solvent inthe presence of a suflicient quantity of an iron compound for increasing the viscosity to form a uent glue with a specific viscosity of at least about 80,000.
2. The process of making vegetable glue suitable without dilution for general furniture veneering which comprises dissolving one part of cassava starch of a specific viscosity less than 60,000 in about three parts or less of water with about 3% of cautic soda and heating the batch to about 170 F. in the presence of an iron salt to form a fluent glue with a specific viscosity of at least about 80,000.
3,. The process of making vegetable glue suitable without dilution for general furniture veneering which comprises dissolving one part of cassava starch of a specific viscosity less than 60,000 in about three parts or less of water with about 3% of caustic soda and heating the batch to about 17 0 F. in the presence of ferrous sulphate to form a fluent glue with a specific viscosity of at least about 80,000.
4. A fluent vegetable glue suitable without dilution for general furniture veneering having a specific viscosity of about at least 80,000 prepared by dissolving about one part of cassava starch of a specific viscosity less than 60,000 in about three parts or less of water with about 3% of cautic soda and heating the batch to about 17 0 F. in the presence of an iron salt.
In testimony whereof I have signed my