US1976436A - Adhesive and process of making same - Google Patents

Description

Patented Oct. 9, 1934 PATENT orrlca 1,976,436 Anrmsrvn AND rnooess or MAKING SAME Charles N. Cone, Seattle, wash, asslgnor to I. F. Laucks, Inc., Seattle, Wash, a corporation of Washington No Drawing. Application November-6, 1931,

Serial No. 573,516

22 claims.

My invention relates to the process of making a laminated construction unit, the laminated product of said process, the process of making the adhesive for such unit and the adhesive product,

of said last process;

More particularly, my invention relates to a new laminated construction unit characterized by its exceedingly high water and weather resistingproperties, and byits being cold pressed for the w initial setting of the glue binder for the plies and then its being heated without pressure to increase the water resistance; and my invention relates to the process of treating blood to serve as the glue basefor the binder of the plies of such unit and to the blood glue composition as a whole.

While it has'been known for a long time that blood, the form of a wet glue, when hot pressed made a highly water resistant construction unit, nevertheless, the hot press with wet glues has so many serious disadvantages in practice that its use is exceedngly limited and rare in American plywood plants. In fact, its use with wet glues is so limited that for-practical purposes, it can be said to be scarcely used at all in the United States for the manufacturing of plywood. The

hot press, besides being of itself exceedingly expensive, does not lend itself to economical large scale production, for among other reasons, too much of the press opening is occupied with the press members. Hot pressing is expensive and cumbersome and is limited to stock sizes of panels, being uneconomical and inconvenient t6 use when making panels of varied sizes.- There have also been proposals'to first cold press blood glued plywood panels, and then follow this with a hot pressing. This, of course, has all the disadvantages of hot pressing, coupled with the extra expense of cold pressing.

A primary object of my invention is to eliminate 4c the hot press in making laminated products with a dispersed blood glue, and still obtain the high water resistance which is a concomitant of a heated blood glue line.

By far the greatest part of total amount of plywood laid up today in the United States is composed of coniferouswoods as, for example, fir, pine, etc. However, heretofore, hot pressing with wet blood glue has not been adaptable to the manufacture of plywoodfrom coniferous woods because these woods do not have sap vessels, nor do they have'any ducts or cells of sufllcient length to permit escape of moisture during hot pressing, there by resulting in severe checking and blistering of the faces. A primary object o! my invention, or discovery, is to make the'water resistant properthe shear test after soaking forty-eight hours-in water, as well as the ability of the panels to remain sound during soaking in water for months.

Also serious objection obtains to the process followed in the manufacture of blood glued plywood in that it is quite impossible to control the moisture content of the plywood panel when the hot press is used, and as a result the great difliculty of blistering is encountered, i. e., the bulging out of areas due to internal steam pressure of trapped moisture. Also, there is the necessity to dry out or season the panel after removal from the hot press as heretofore employed. A primary object of my invention is to overcome this objection and to provide a plywood blood glued panel of exceedingly high dry strength and high water resistance, in which the moisture content is controllable so that subsequent seasoning is obviated. It is to be understood that my invention is applicable not only to plywood, but other materials suitable for lamination, such as cellulose containing composition boards, etc.

Blood glue as heretofore commonly spread Q gether, so that the panel can be handled and subjected to a nibsequent heating operation in the absence of pressure without damage. In provid- 10o .ing such a blood base glue, my invention goes directly contrary to prior teachingin that instead or no alkalinity, or very low alkalinity, I find in my new blood base glueand processes, that a positive alkalinity is essential to obtain the necessary invenprotein, which'samejma'ybe thus used to constitute a considerable percentage, even seventyfive percent of the base of the glue used in my process, as well as by the fact that the water requirement is increased by using proper percentage of alkalinity. My discovery includes the fact,

that with such degree of alkalinity as will'give the necessary water requirement toprovide an economical spread, nevertheless the initial set in the cold press is of suflicient strength to hold the plies without pressure against the stresses developed during heating and that such alkalinity does not prevent the heating step imparting the necessary water resistance. Also my discovery includes the fact that such initial setting does not prevent the development of water resistance in the glue upon subsequent heating.

Finally, a primary purpose of my invention is to make a plywood product as characterized by the properties above set forth which can be rapidly produced in large scale production and at greatly reduced cost.

These objects are achieved by my invention or discoveries which will next be fully set forth. Before giving the details the invention will be set forth in a summary manner.

Briefly, therefore incompletely stated, my invention or discovery comprises that blood can be treated as the base of an adhesive or glue, or as the critical portion of the base, with chemicals which impart a positive and essential alkalinity so as to make a glue which, when spread by means of the usual mechanical rollers and laid up to form a panel and cold pressed as usual as one member of a rack of panels, will have the requisite dry' strength and sufficient adhesion to hold the plies, despite the severe strains developed when the moisture content of the panel changes during the next following step. Then, the panel is heated without pressure, (i. e., without using a hot press), the heat being sufficient, about 212 F., to so act on the blood as to give a very unexpected increase in wet strength, and usually some increase in dry strength. Instead of a mild or no alkalinity, my adhesive composition comprises the reaction products of blood and alkalinity producing chemicals of 3% to 20% of the glue base, besides lime and soluble silicate salts in some formulae, and as a foam eliminating agent terpineol. The panel thus produced by this process and by means of this adhesive, results in a panel practically waterproof and weather resistant so as to be useful for outdoor purposes in contrast to the indoor use of plywood generally at the present time.

While a high water resistance is obtained even in the unheated panels and While highly water resistant glues have been known before, I believe that this new discovery of mine enables the mak- 1 ing of a different character of plywood than has been heretofore known certainly at least with coniferous Woods, namely, that it has such properties that will enable plywood made by the use of my glue and process to withstand the action of moisture indefinitely. While the commonly used shear strength test on plywood after soaking for 48 hours gives very high figures on plywood glued with this new glue, the same may also be true of other glues, but I have found by practical tests such as weathering tests, exposure to the elements, repeated alternate soaking and drying tests, long continued soaking tests, freezing tests and alternate heating and soaking tests, that plywood made by my process and glue withstands these practical tests and is for all practical purtests is a thing'which'is notdetermined b'y'the ordinary wet shear test and it is in this endurance to these practical tests that I consider that my "process and glue give new, unique and very valuable practical results forplywood. Prior known glues, even' though giving high wet shear tests, have suffered a deterioration in strength when exposed to moisture or weather for some time and for this reason such panels have not been of practical use foroutdoor purposes.

After the cold pressing of the plywood, the panels contain a considerable percentage of moisture, and when such moist panels are heated a very severe strain is set up. Published figures show that the transverse strains set up in even the weakest native woods during change of moisture content amount to over 200 pounds per square inch. To hold the panels during this second operation, that is, heating, it is necessary that the glue line be strong enough to withstand this severe strain, and to make finally a panel without pressure which will bestronger than the unheated panel, requires a glue which will increase in strength during heating, such increase being greater than the strain set up.

When plywood is to be hot pressed, using a blood-base glue, a low degree of alkalinity heretofore has been used or even no alkalinity at all. Thus ammonia, or small amounts of alkaline salts such as sodium silicate, or very small percentages of caustic soda will furnish suflicient alkalinity for hot pressing. The case is radically different however, in my process. I must use a positive alkalinity to secure the necessary adhesion in the cold press, so that the cold pressed panels will withstand the after heating operation.

To secure this positive alkalinity I prefer to use caustic soda as such, and in amounts over 3% referred to the adhesive base. When thus using caustic soda as such I am free from all the uncertainties of producing caustic soda by double decomposition chemicals. (By double decom-' position I mean whatever reaction takes place in an aqueous colloidal dispersion of proteinous substances and other colloids, between lime and sodium salts such as sodium fluoride, sodium silicate, etc.)

While I prefer to use caustic soda as such, I find that I can get good results by using double decomposition chemicals such as the ones named, and I consider, in this invention, the combinations lime and sodium silicate, lime and sodium fluoride, etc. the equivalents, so far as alkalinity is concerned, of caustic soda as such, with this reservation however, which I can best explain by an example, viz: Sodium fluoride has a molecular weight of 42, and by reaction with excess lime in water (i. e., in the absence of colloids) 42 parts sodium' fluoride will give theoretically 40 parts caustic soda. The case is entirely different, however, in the presence of colloids. find that a combination of excess lime and 42 parts sodium fluoride is nowhere near as effective for my purpose as 40 parts caustic soda as such. Furthermore, the effectiveness of double decomposition combinations varies greatly with the kind of sodium salt used, so that in general I consider that a double decomposition combination for my purposes is less than as effec- In such case I ,poses waterproof. "Endurance to these practical nova-res i to be marketed in sacks as a glue composition, for

example lime, sodium metasilicate and the chemicals which react to form caustic soda by double decomposition in aqueous medium, and terpin'eol.

In general I find best resultswhen using from 8% to 15% caustic soda as such, (i. e., 8% to 15% of thedry adhesive base) or correspondingly larger amount of double decomposition chemicals. Above 20% caustic soda as such I find that deterioration sets in, so that I consider 20% the upper limit.

Along with caustic soda I prefer also to use lime as 'I find that this increases the water resistance, 'and in some formula: also the dry strength. or course when using double decomposition combinations, lime is present, and in such case I prefer to add an excess of lime, by

which I mean an excess over the amountthat would be theoretically required to combine with whatever sodium salt or potassium salt is used, in the absence of colloids. I find that lime in amount of 7% gives excellent results, while 15% I also gives very good water resistance.

When I use lime, I also may use sodium silicate to give increased water resistance, e. g.,'30% water glass with 7% lime gives very great water resistance, To a certain extent the combination lime plus sodium silicate may substitute for caustic soda. That is, when I use this combination, I may not use as much caustic soda as I would without the combination. Silicate thus plays a dual role. e

In carrying out my invention, or discoveries, I

have developed many formulae of which examples .will be set forth with actual experimental tests,

results and explanation. A typical formula with blood is as follows:

; Parts I. Dried bloo 100 NaOH 8 Lime '7 Sodium silicate 30 Water 675 to 725 When this is spread using 18 lbs. of dried blood per thousand square feet of plywood, three-ply i. e., two glue lines with 10 minutes time of assem- -bly and pressed cold with 150 pounds pressure,

with inch fir plywood, it gives a dry strength of 283 and a. wet strength of 243.

.After they are removed from the'press, I- then place the panels in any convenient apparatus forheating. This may be,'for example,.a veneer dryer, as used for drying the single plies, or better still a tunnel drier such as used for redrying panels. The panels may even be placed in racks in a hot room. By whatever means is used for the heating, I bring the glue line to a temperature .of approximately 212 F. and 'hold it at this temready to use without further seasoning. Because of the high, dry strength of the bond before heating, I run no risk of blistering,'which is one of the disadvantages of hot' pressing. It should be noted that this is not a drying operation, as drying is not essential, although some drying may take place unavoidably or even intentionally, as the panels can be turned out at any desired moisture content by controlling the humidity in the heating apparatus. Obviously, moisture may be add ed to the panel if desired. Such control of moisture. content is impractical to realize with the hot press. The purpose of the heating" is to increase the water resistance, and weather proofness.

A typical procedure inheating is as follows: Time 15 minutes, and temperature 300 F. These panels gave the following results expressed in pounds per square inch shear strength:

Before After heating heating Dry strength 283 304 Wet strength 243 318 I find that considerable amounts of proteins, such as casein or isolated vegetable proteins, can be admixed with the blood and the combination base then subjected to the same chemical treat These added proice cottonseed, castor, etc., also I include in this class i of alkali-dispersibles. and may be used instead of casein or the isolated proteins or used with these materials. On the other hand, if the alkalidispersible proteins are usedv without 'blood in my process, they give considerable lower results as far as wet strength is concerned. The combination of some substantial amount, at least 10% of the glue base, of blood appears necessary in my. process. Although the alkali-dispersibles by themselves do not give good results in my process, they can be mixed with blood in large proportions, up to 90% of the glue' base, and still obtain many of the benefits of my process.

With certi n woods, for example, birch, I find that the chemical treatment of blood alone as described herein; is not sufficient to give the requisite dry strength for some purposes with cold pressing. Onsuch woods, I have found that 'I can incorporate a protein such as casein, or isolated vegetable proteins, or both, with the blood;

and then treat the combintion base with the same chemical treatment as described above, and can obtain a glue better suited for these woods with my process. I have found good results with mixtures of 10% blood and 90% casein or chemically isolated protein with birch.

A typical formula is as follows:

Parts II. Blood 50 Terpineol 1 Casein 50 Lime 7 NaOI-I 10 Silicate 30' Water 460 Spread on birch wood, cold pressed, then heated to 220 F this gave the following results in Dry Wet Soya bean protein can be substituted for casein in the above formula although more water must be added, which in this process, is not a detriment. Also, the thinning tendency of soya bean protein is counteracted in this mixture.

It will be noted that my process so far has been intended to furnish plywood of maximum water resistance, as well as high, dry strength. However, it will be seen by the above results that even without the after heating it gives very good results, and this is true on a number of diiferent woods. I may therefore stop short of the heating step and produce a thoroughly commercial plywood, especially where water resistance of the very highest order is not desired.

I have also found that the various seed flours may be admixed with either blood alone, or even with the combinations, blood-casein or blood-isolated vegetable protein, and may be thus used to constitute a considerable percentage, even seventy-five percent of the base of the glue used in my process, so long as blood constitutes 10% of the base. The glue made from such admixture has advantages in working properties, in particular, it tends to lump very much less than the glue does made without the seed flours. Also, the viscosity and consistency-of the glue made by admixture of seed flours is much more constant with time. I have used amounts of seed flours up to 75% of the base and find that my process can be effectively carried out with such an adhesive. The amount which I use varies with different woods. For example, on fir I find that a mixture of 50 parts of soya bean fiour with 50 parts of blood gives excellent results. By thus using these considerable amounts of seed fiours, I am enabled to make a much more economical adhesive for use in my process and at the same time realize all the necessary requirements to fit into my process. In fact, I find that although casein gives relatively inferior wet strength when used alone as the glue base in my process, yet a glue made from a mixture of 50 parts casein and 50 parts blood as a base, gives much better wet strength than is obtained with blood alone.

When using seed flours admixed, I use substantially the same chemical treatment as specified for the blood. The use of caustic soda as such is particularly desirable with seed fiour combinations.

Typical formulae of such seed flour-blood glues are as follows:

the highly water resistant result I have described will not be realized. I have experimented with many agents in an endeavor to find one which will eliminate the foam and I find that the terpineols are particularly eifective in this respect on this particular glue. Instead of using pure terpineol, I may also use, for example, pine oilwhich contains terpineol in a considerable percentage and there are also other oils of like nature which contain terpineol, all of which I consider as equivalents for this step of my method. I find that 2% of terpineol on the basis of the glue base gives good practical Working results.

Plywood made from my process and using the glue made as above described, is characterized by a remarkable absence of foam. It has been known for a long time that blood glues were particularly liable to foam and while a water resistant plywood was obtained by prior known glues 'when hot pressed, yet the water resistance of such hot pressed blood plywood sufiered considerably because of the foam in the glue. To obtain the highest water resistant plywood, it is essential that foam be eliminated as completely as possible. This I have succeeded in doing by the use of terpineol as described above. The result is that I get a plywood which is characterized by absence of any evidence of foam onthe glue line and it is this homogeneous glue line which contributes in a large measure to the highly water resistant results or even waterproof results that I have obtained.

I have found that a convenient and efficient way to use terpineol is to add it to the dry glue base. I have found that it can be stored with the dry glue base for a long period of time without losing its effectiveness and without afiecting objectionably the glue base. It is also effective when added at any other point in the mixing operation of producing the finished glue. I have also found that terpineol increases to some extent the water resistance of the glue.

I have found the following procedure a convenient method of preparing my glue for use in my process:

Add the dry adhesive base, whether it be blood alone or mixture of blood and alkali-dispersibles, to a portion of the water to be used. By adding the dry adhesive to the water slowly and by efiicient mixing, lumping can be avoided and a smooth mixture obtained. The chemicals such as lime, caustic soda and sodium silicate are then added to this mixture in solution or suspension in water, and mixed in thoroughly. Terpineol may be added either to the dry glue base or to the wet glue mixture. When the right amount of water is added to give the glue a suitable consistency for spreading, the glue is ready for use.

H P Unheated fir Heated fir Soyaempea I bean seed nut Casein Blood Lime g gg g 2% Water I flour flour flour Dry Wet Dry Wet All of the glues above described tend to foam considerably in the spreader. In order to make the highly resistant plywood that I have described, it is particularly essential that this foam be eliminated or kept at a minimum. Otherwise, a sufiicient spread can not be obtained, and

A typical mixing formula follows:

VII. To 135 lbs. of water, add 100 lbs. of a mixture of parts soya bean flour and 50 parts blood and 2 parts of alpha terpineol, stir 10 minutes, add 330 lbs. of water, stir 2 minutes, add 7 lbs. of lime suspended in 25 lbs. of water; stir 1min- 'ute, add 8 lbs. of caustic soda dissolved in lbs.

of water, stir 1 minute, add lbs. of water glass,

soda, a considerable amount of water. can be used in the glue, and still maintain a. spreadable consistency, thus affording an economical glue to use. Also, the use of caustic soda gives the high dry strength needed in my process, whereas ammonium hydroxide, when used in'my process does not give sufiicient dry strength. This in itself is a very unexpected result for it has commonly been found that the greater is the con centration of the glue solution, the greater is the strength of the bond obtained therefrom. Manu= facturers of glue when faced with the problem of increasing the strength of the bond to be obtained from any glue base, have heretofore striven to reduce the amount of water required to bring the glue to a proper working consistency, for

it has been the common experience of workers in this. art that concentration of the glue solution tends to increase the strength of the bond, whereas dilution of the glue solution weakens the bond. obtained. It is therefore. a most unexpected and surprising thing to discover thata. glue made bythe treatment of blood with considerable amounts of caustic soda, which requires about seven parts of water to one part of blood in order to bring the glue to proper working consistency should be capable of giving a bond far superior in strength to that obtained with the blood glues commonly in use which contain only comparatively mildly.alkaline reagents and are very concentrated, containing only about 1 to 2 parts of water to each part of dry blood.

Blood glues made by heating during the mixing are quite different than glues made without heat. Blood in the presence of water and heat coagulates rapidly, and glues made hot have a higher water requirement than glues made cold, but the adhesion suffers by the heating.

In hot pressing procedure, the usual procedure is to apply a thin coating. of blood glue and immediately place in hot press and apply pressure.

'There is little lapse of timesothat the glue does not have opportunity to penetrate or dry out to any great extent. However, in cold pressing, considerable time in ordinary manufacturing procedure elapses between the time of assembly and the time when pressure is applied. Hence 'the relatively large amount of glue base used in hot 1 pressing with blood would necessarily be increased by the step of cold pressing of my process. I overcame this objection by discovery that blood could be treated with a large percentage of chemicals which imparted a positive alkalinity and ing can be safely carried out not only without adversely aflfecting strength, but, markedly increasing wetstrength. a

I may also use sodium silicate, that is, water glass, with caustic soda and without lime. fI find that the silicate greatly increases the water resistance of the glue. A typical formula with blood and sodium silicate is as follows:

1 Parts VIII. Dried blood 100 v Caustic soda 12 Sodium silicate 30 Water 600-650 It is to .be understood that I do not confine myself to sodium sLlicate, commonly known as waterglass, but may use other soluble silicates as well. I find also that sodium metasilicate can be used with blood in my process and give very good results. A typical formula with blood and sodium metasilicate is as follows: v

' Parts IX. Dried blood 100 Sodium metasilicate 42.5 Water 700- 750 The construction unit resulting from the use of the glue and process herein set forth may be identified by the physical and/or'chemical properties of the same.

The advantages of mypro'cess are:

1. That I am enabled to secure a highdegreecan be admixed, and still realize the benefits of heat treatment of blood.

5. On some woods, such as coniferous, thehot press is impractical because of checking, etc; But I can secure all the benefits of the hot'press in my process, without its disadvantages, and with many positive advantages, both in low cost and superior quality.

It is to be understood that I can'also use, blood that has been heated in a dry state. I have found that dried blood can be heated to temperatures much higher than those at which the blood coagulatesin the presence of moisture, without causing the dry blood to become non-dispersible in a1- kali. I have raised the temperature of dry blood to 270 F. without causing it to become non-dispersible in alkalies. I have found that the heat treatment of blood is in many cases beneficial to the water resistance of the resulting glue.

By the term blood" I mean to include fresh blood as well as spray dried or film dried bloods, which have not been rendered non-disper'sible in alkaliesin'the drying. I also include blood from which fibrin has not been separated.

-A's equivalents ofcaustic soda, I include potas-.

sium hydroxide, but not ammonia; as equivalents of sodium salts the corresponding potassium salts; as-equivalents of lime, baryta and strontia. This of course includes caustic soda or potash developed by double decomposition-as described herein.

By glue I mean ordinary aqueous dispersed glue, spread wet.

By dry adhesive base I mean. dry blood mixture of dry blood and other protein containing material. When fresh blood is used I mean the solid contents of such blood.

I claim:

1. A glue for use in a cold press comprising the reaction products in aqueous 'medium at normal temperature of blood treated with not less than approximately 3%, nor more than approximately 20% of caustic alkali, said percentage being based upon the blood constituent.

2. A glue for use in a cold press comprising the reaction products in aqueous medium at normal temperature of blood treated with not less than approximately 3%, nor more than approximately 20% of caustic alkali; and hydrated lime, said percentage being based on the blood constituent.

3. A glue for use in a cold-press comprising the reaction products in aqueous medium at normal temperature of blood treated with not less than approximately 3%, nor more than approximately 20% of caustic alkali; hydrated lime; and sodium silicate, said percentage being based on the blood base, the step of treating blood with terpineolfor overcoming the foaming tendency of blood glue.

7. A.glue for use in a cold press comprising the reaction products of a base consisting of not less than 10% blood, and not more than 90% of an alkali-dispersible protein containing material, which base is acted upon in aqueous medium at normal temperature by not less than approximately 3%, nor more than approximately 20% of caustic alkali, said percentage being based upon saidbase.

8. A glue for use in a cold press for plywood comprising the reaction product of a base consisting of not less than 10% blood and not more than 90% of an alkali-dispersible protein containing material, which base is acted upon by not less than approximately 3%, nor more than approximately 20% of caustic alkali; hydrated lime; and sodium silicate, said percentage being based upon the said base 9. A glue for use in a cold press for plywood consisting of the reaction product of a base consisting of not less than 10% blood and not more than 90% of an alkali-dispersible protein containing material, which base is acted upon by not less than approximately 3%, nor more than approximately 20% of caustic alkali; hydrated lime; and sodium silicate, said percentage being based upon the said base.

10. A glue for use in a cold press for plywood comprising the reaction products of a base consisting of not less than 10% 01 blood and not more than 90% of an alkali-dispersible protein containing material in aqueous medium; which base is acted upon by not less than approximately 3%, nor more than approximately 20% of caustic alkali; and terpineol. v

11. A glue for use in a cold press for plywood comprising the'reaction products of a. base consisting of not less than 10% of blood and not more than 90% of soya bean flour, which base is acted upon in aqueous medium at normal temperature by not less than approximately 3%, or more than approximately 20% of caustic alkali, said percentage being based upon said base.

12. A glue for use in a cold press for plywood comprising the reaction products of a base consisting of not less than 10% blood and not more than 90% soya bean flour, which base is acted uponin aqueous medium at normal temperature by not less than approximately 3%, nor more than approximately 20% of caustic alkali; and hydrated lime, said percentage being based upon said base.

13. A glue for use in a cold press for plywood comprising the reaction products of a base consisting of not less than 10% blood and not more than 90% soya bean flour, which base is acted upon in aqueous medium at normal temperature by not less than approximately 3%, nor more than approximately 20% of caustic alkali; hydrated lime; and sodium silicate, said percentage being based upon said base.

14. A glue for use in a cold press for plywood comprising the reaction products of not less than 10% blood and not more than 90% soya bean flour, which base is acted upon in an aqueous medium by not less than approximately 3%, nor more than approximately 20% of caustic alkali; and terpineol, said percentage being based upon the dry adhesive base.

15. An adhesive for use in a cold press comprising the reaction products of blood acted upon in aqueous medium at normal temperature by 8% caustic soda, 7% lime and 30% silicate, said percentage being based upon the blood constituent.-

16. An adhesive for use in a cold press comprising the reaction products of blood acted upon in aqueous medium by 8% caustic soda, 7% lime, 30% silicate; and terpineol, said percentage being based upon the blood constituent.

17. A glue for use in a cold press comprising the reaction products of blood and alkali-dispersible protein containing material acted upon in aqueous medium at normal temperature by i.

8% caustic soda, 7% lime, 30% silicate, said percentage being based upon the dry adhesive base.

18. A glue for use in a cold press comprising the reaction products in an aqueous medium at normal temperature of 100 parts dried blood; 12 parts caustic soda; 30 parts sodium silicate; and 600 to 650 parts water.

19. A glue for use in a cold press comprising the reaction products in an aqueous medium at normal temperature of'100 parts dried blood; 42.5 parts sodium metasilicate; and 700 to 750 parts water.

20.. A glue for use in a cold press consisting of the reaction products in an aqueous medium at normal temperature, of blood, and sodium metasilicate.

21. A glue for use in a cold press comprising the reaction products, in an aqueous medium at normal temperature, of blood, sodium metasilicate, and caustic soda, the latter in the proportion of not less than 3% nor more than 20% of the blood constituent.

22. A glue for use in a cold press consisting of the reaction products, in an aqueous medium at normal temperature, of blood, sodium silicate, and caustic soda, the latter in the proportion of not less than 3% nor more than 20% of the blood constituent.

' CHARLES N. CONE.