US2291586A - Method of making laminated products - Google Patents

Description

Patented July 28, 1942 Harry ,Galber and Theodore W. Dike, Wash assignors to I. F. Laucks, Inc.,

Wash.

CTS

Seattle, Seattle,

No Drawing. Application June 20, 1940, Serial No. 341,587

4 Claims. (Cl. 144-309) This invention is a process for making plywood. By plywood," we mean laminated bodies composed of thin sheets or plies of wood veneer united by glue, usually to an intermediate or core" ply.

The process comprises applying restricted amounts of a seedmeal gluehaving a low viscosity to the ply surfaces followed by hot-pressing at moderate temperature m a short time.

The invention is an improvement over the process described in our Patent No. 2,178,566 which continues to meet with wide commercial application. However, we find that there are some manufacturers of plywood to whom the process of the present application may be more acceptable either because of their smaller volume of production or the diversity of their products, one of the important advantages of the present invention being its economical applicability to small volume and diverse production.

Seedmeal flour glues, as heretofore employed in the manufacture of plywood, have been substantially restricted to the so-called cold-press process, except when used in the very high viscosity range described in our above-mentioned issued patent. There are various reasons for the previous unsuccessful efforts to use seedmeal glues in a hot-press method of assembly, among these being the use of excessive amounts of glue, as well as improperly regulated heat and pressure.

Our present invention is based upon our discovery that seedmeal flour glues made from soy bean, peanut, cottonseed or other bases of the character described in our aforesaid issued patent, may be practically and efllciently employed in a hot-press method, and without using the high viscosities described in our issued patent,

provided certain herein described critical factors are controlled. As stated in our issued patent, the consistency of ordinary fluid glues as measured by a No. 26 gauge wire, .of a MacMichael viscosimeter, is'from 25 to 150. While glues of suchviscosity made from bases other than seedmeal have been-widely used in hot-press methods in Europe, and to a limited extent in the United States, they have been objectionable for various reasons. Among these objections are the higher cost of such glue bases as compared to seedmeals, the excessive amount of water which must be employed in the case of the blood glues, with the attendant moisture penetration of the wood and. in the instance of casein, the long setting periods and undesirably high-press tempera-' ture.

v We have discovered that seedmeal glues may be produced within the viscosity range above specified with materially less water "than is required for production of glues from blood,'for example, within the same viscosity range, and that seedmeal glues of such viscosity range may be effectively and economically employed in a hot-press method of short duration and consequent large press output, provided the glue spread is substantially less than is ordinarily employed in the'cold process, wherein seedmeal glues of such viscosity have heretofore been employed. By substantially less spread, we mean a reduction of about one-half in applied volume. For example, in the conventional cold-press process, it is customary to apply from 110 to 140 pounds of wet glue per 1000 square feet of three-ply panels, 1. e., from to pounds per 1000 square feet of single glue line. In accordance with the process of the present invention, we apply only from about 12 to 45 pounds, generally about 32% pounds per 1000 square feet of single glue line.

In conjunction with the low spreading rate we also employ a low range of press temperature, preferably from about 215 to around 250 F. and a range of mechanical pressure of about pounds to less than 200 to 225 pounds, i. e., preferably somewhat less than that used in the process of our prior invention which with that heavy glue employes also a heavy pressure. For instance, in pressing fir plywood in the present process we use a press temperature of about 230 F. with lbs. pressure applied foronly 3 minutes when pressing two fir panels in a single press opening. As in our former process, we also prefer to remove the panels from the press as soon as the bond is strong enough to resist spontaneous separation of the piles and complete the heat treatment of the adhesive by close piling of the panels so that they retain their heat and cool down slowly in the pile. This, of course, tends to shorten the actual pressing period and increases the press output.

Aside from merely avoiding the danger of steam blisters, the low heat seems to perform an unexpectedly useful function in assisting the low .volume of thin seedmeal flour glue to form a strong bond quickly and our experience indicates that a moderate mechanical pressure also contributes favorably towards this result. While the causes of the quick formation of a bond in our -process are not known to us with certainty, and previously, sharp heating 'with heavy pressure has been commonly thought to bring quick development of adhesion, we are of the opinion that in our process permits the seedmeal glue to rea main or: the glue line, and we restrict the applied volume of glue to an amount that is thus able to change quickly into a strong adhesive layer. This permits a pressing time (which, of

. course, varies with the thickness of plies in the press opening) that is of short duration, as for example 3 minutes in the above instance and corresponding time periods for other assemblies.

At any rate, we find that the very substantial reduction in the applied volume of the glue is not only possible, but is, in fact, necessary ina hot process when using seedmeal glue having a viscosity within the range above indicated. On the other hand, in a cold-press process, the use of seedmeal glue in an applied volume of this reduced order will not afiect commercial adhesion, and conversely the old heavy spreads are inoperative in our present process.

So far as we are aware, we are the first to discover a commercially useful method of using seedmeal glues within the viscosity range above mentioned in a hot-press process, and that such glues may be used within this viscosity range in a hot-press process with a low applied volume of glue spread of the order above set forth.

A further marked improvement made available by our invention and one which contributes substantially to its successful use by that section of the press by hand methods before the adhesive has dried up too much to give proper adhesion. It will thus be, seen that by reason of this extended tolerance of assembly time, automatic or semi-automatic equipment desirably employed with our former process for conveying the assemblies to and loading them into the press may be dispensed with. Furthermore, the present invention also avoids having to provide the special equipment found necessary for mixing, conveying, and spreading the heavy consistency glues of our previous invention and permits the use of the regular glue mixers and Spreaders now available in cold process plants. It also enables the small or diversified producer to still enjoy the low stain, low moisture-input, and accompanying features hitherto only available to large mass productionplants when using the heavy consistency glues of our former invention.

In this connection the process of our former patent also requires relatively high mechanical pressure to obtain the best results, and this involves the use of a more costly heavily constructed v resides in the method of uniting plies into a plywood structure by applying a low viscosity glue at a low glue spread and then uniting the plies by a hot-press process characterized by a low temperature and short pressure application. This method is distinguished from the procedure of uniting plies by means of blood glues of low viscosity and low glue spread. Such blood glues have involved various hampering restrictions, such, for example, as the requirement that after the plies have been hot-pressed, they must be removed from the press and stood on edge individually until they lose sufficient water and weight from the very watery blood glue to become saleable and be economically shipped. Further, the method is distinguished from procedures in which the plies are united by casein glues in that these casein glues, notwithstanding that they may be made up, to have a low viscosity and be applied at a low glue spread, nevertheless have been found to require a less eflicient and more expensive treatment, such as either a nearly complete drying out of the applied glue film and then a short pressing at a press temperature of about 265 F. or above, thususing casein practically as a thermoplastic material, or else if pressed while the glue is still wet, a similar high temperature is used with a pressing, so long as to practically entirely dry out the assembly in the press so that the press can be opened without steam blisters rupturing the plies. The resulting overdried panel must then be remoistened and is also very apt to warp.

These restrictions seem to be due to a tendency of casein to hold glue water very tenaciously. This is probably due to its inherent character as a nearly pure protein capable of forming solutions of marked viscosity in contradistinction to the seedmeal flours which only contain about half as much protein and which include a considerable content of not completely soluble hemicellulose and crude fiber. It is perhaps due to these features that the seedmeal glues give up their water so readily, which feature seems to be a factor in their usefulness in the present process. Thus, neither blood nor casein are found to be adapted to the present process except when used as blending components in the presence of a predominant amount of seedmeal flour, as will be described subsequently.

In contrast to these glues the seedmeal adhesives which we employ under the conditions of our process, give up their water to the plies very rapidly at desirably moderate pressing temperature and by means of our low spread in con- Junction with their moderate water content, produce strong bonds quickly and economically, and with such low injection of water into the plies that the moisture content of the panels is kept within bounds so that they are fit for prompt shipment without the cost or delay of either a redrying or a remoistening while the press capacity is also kept to a high level by the short pressing.

seedmeal glues have been principally employed .in cold pressing, and when used in low viscosity and low glue spread under such cold pressing conditions, they are a complete failure. In other words, in a cold process, a heavy spread of seedmeal adhesive gives satisfactory results while in the hot process, as we have found, a heavy spread is unsatisfactory. But to our surprise, a light spread of low viscosity seedmeal glue, such as would be useless in the cold process, is highly effective in the hot process and renders our discovery of great commercial importance.

We find that by following the method of the present invention not only are excellent results obtained with straight seedmeal flour glues, but

that the same advantages continue in blend glues,

provided a predominant amount of seedmeal flour is incorporated in the blend. The other glue bases most desirable in such blends are soluble blood, casein, and animal glue. Blood is useful to raise the water resistance of the bonds and increase the water requirement, while casein tends to increase dry strength, and both casein and animal glue are useful both for lowering the water requirement and improving spreading consistency. Thus, since the amount spread on the plies is very low, thesemore expensive glue bases may be used along with the inexpensive seed flour to produce a wide range of formulae adapted to meet a variety of conditions. However, where these non-seedmeal glue bases are used in excessive amounts, particularly above about fifty per cent of the total of glue base, then their previously mentioned undesirable characteristics seem to predominate. We, therefore, find that the blend glues should at least contain a predominant proportion of seedmeal flour.

The following examples illustrate but do not limit the practice of our invention.

Example I Soy bean (or cottonseed or peanut) flour-" 94 Disodium phosphate 2.5 Soda ash 2 Sodium fluoride .5 I Pine oil -L l 100 I The wet glue is mixed as follows:

. Parts The above dry mix 100 Water; 370 I Hydrated lime in suspension in a small part or the above water 1O Caustic soda dissolved in a small part of the water N" brand sodium silicate 25 Mixture of equal volumes of carbon disulfide and carbon tetrachloride 2 This gives a glue of about 40 viscosity #26 wire Maclviichael.

65 lbs. per 1000 square feet of double glue line (i. e., 32 lbs. per 1000 square feettof single glue line) of the above glue are spread on ti Douglas flr three ply panels and the assembly hotpressed 3 minutes, with two panels per press opening, with 1'15 lbs. pressure at 230 F. after an assembly time varying from one to fifteen minutes. The panels are piled closely upon removal from the press and are allowed to cool slowly in the pile.

Dry shears averaged-270 lbs.

failure Wet shears averaged-160 lbs. with 3% wood failure This glue can also be used as a cold process glue forfir plywood, but only when used with spreads of between about 110 and 140 lbs. per

with 70% wood "1000 square feet or three ply panels. Below 100 lbs. the cold process results are not commercial and below about 90 lbs. the adhesive is a total failure.

Example II e following ingredients constitute the dry mix ' Percent Soy bean (or cottonseedor peanut) flour 65 Case 20 Blond 9 Disodium phosphate 5 Pine ni l The wet glue is mixed as follows:

Parts Dry mix 100 Water 3'70 Hydrated lime in suspension in a small part of the above water Caustic soda dissolved in a small part of the water 8 N brand sodium silicate 25 Mixture of equal volumes of carbon bisulfide and carbon tetrachloride 2 This glue also has a viscosity of about 40 #26 wire MacMichael.

It is spread and pressed as in Example I and gives similar results, but due to the casein and blood, the water resistance is considerably higher.

Example III The following ingredients taken by'weight are dry mixed:

l Percent Soy bean'(or cottonseed or peanut) flour"- 60 Casein 15 Blood 5 Animal g 10 Wood flour 4 Disodium phosphate 3 Sodium fluoride 2 Pine nil 1 100 The wet glue is mixed as follows:

Parts Dry mix 100 Water 340 Hydrated lime in suspension in a small part of the above water l2 Caustic soda dissolved in a small part of the water "N" brand sodium silicate 25 Mixture of equal volumes of carbon bisulflde and carbon tetrachloride This glue also has a viscosity of about 40 #26 wire MacMichael.

It is spread and pressed as in Example I and gives similar results, but due to the casein and and chemicals to produce a glue having a viscosity of about 40 #26 wire MscMichael, it is weilunderstoodbythoseskilledintheartof making seedmeal flour glues that individual samples of the same kind of seedmeal, tor instance soy bean, vary somewhat in their ability to take up water and likewise flour made from different seeds, such as soy bean, peanut, cottonseed, flax seed, castor bean, and the like, also often show some characteristic differences in their ability to take up water when they are treated with chemicals. Therefore, while in each of our three examples we have stated the amount of water required to make a glue with the cgrrect viscosity with the material which we actually used, slight adjustments will have to be made, according to the available materials, but any one skilled in the art will find no diifi-culty in adjusting the water or chemicals in order to obtain the required viscosity. Furthermore, as previously mentioned, where blend glues are prepared, the desired water content to obtain the required viscosity can be adjusted considerably, notwithstanding the inherent water requirement of the preponderant seedmeal flour, for as indicated,

by using a higher proportion of blood in the blend, the water requirement can be raised while both casein and animal glue can be used to lower it. Thus, the present invention is not limited as to the particular variety or individual character of the seedmeal flour or in the case of blends of the added glue base, since the water content of the glue can be controlled by known methods to produce the proper viscosity.

We claim:

1. The process of making laminated bodies such as plywood which comprises coating at least one or theplies with a disposed adhesive comprising an aqueous alkaline oil seed adhesive having a viscosity between substantially and 150, No. 26 wire MacMichael between the range.

of substantially 12 and 45 pounds 01 wet glue Per square inch.

2. The process of making laminated bodies such as plywood which comprises coating at least one of the piles with a dispersed adhesive comprising an equeous alkaline oil seed' adhesive having a viscosity between substantially 25 and 150, No. 28 wire MacMichael between the range of substantially 12 ,6 and pounds or wet glue per 1000 square'ieet of single glue line, assembling the plies, and hot pressing the assembly at a temperature substantially between 215 F. to 2,501". and at a pressure between substantially and 225 pounds per square inch.

3. The process of making laminated bodies such as plywood which comprises coating at least one 01 the plies witha dispersed adhesive comprising an aqueous alkaline oil seed adhesive and an adhesive selected from the group consisting of blood, casein and animal glue, said adhesive having a viscosity between substantially 25 and 150, No. 26 wire MacMichael between the range of substantially 12 and 45 pounds or wet glue per 1000 square feet of single glue line, assembling the plies, and hot pressing the assemblyat a pressure between substantially 125 and 225 pounds per square inch. I

4. The process of making laminated porous bodies such as plywood which comprises coating at least one of the plies with a dispersed adhesive comprising an aqueous alkaline oil seed adhesive having a viscosity between. substantially 25 and 150, #26 wire MacMichael, between the range of substantially 12V; and 45 pounds of wet glue per thousand square feet of single glue line. assembling the piles and hot pressing the assembly at a pressure between substantially 125 and 225 pounds per square inch and at a press temperature from about 215 F. to around-250 F. and for a time insufficient to cause steam blisters and effective to quickly convert the restricted spread of adhesive into a strong binder for the piles whereby excess-penetration of the adheive into the porous piles and consequent starving of the glue Joint is avoided.

- HARRY GALBER.

THEODORE W. DIKE,

'- I CERTIFICATE OF commcnon.

- mm GALBER, 'ET' A-L.

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M uwuQ' rpm "aqueousand that fine said Let'tera Pgitnt should be read with this correction therein that the same may co nrom to the record of the ca, in theratent orriqe;

Signed. and sealed this 29th dw ofse ptembor, A. D.-1+2.

Henry Vm pedals,

(Seal) Actihg Commissibner of Patents.