US2754236A

US2754236A - Composite paper sheet

Info

Publication number: US2754236A
Application number: US283307A
Authority: US
Inventors: William A Hermanson
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-04-21
Filing date: 1952-04-21
Publication date: 1956-07-10
Anticipated expiration: 1973-07-10

Description

July 10, 1956 w. A. HERMANSON COMPOSITE PAPER SHEET Filed April 21, 1952 IN VENTOR Mam A. Ham/M00 BY W ATTORNEY United States Patent COMPOSITE PAPER SHEET William A. Hermanson, Brookline, Mass. Application April 21, 1952, Serial No. 283,367 5 Claims. (Cl. 154-54) The present invention relates to a composite cellulose sheet used as soft flexible padding for various purposes. The present invention is particularly useful in the protecting of highly polished and highly finished surfaces both in shipment and in use and it may also be used in protecting such merchandise as glass, pottery, furniture and other items from scratching, chipping, denting, cracking or from damage in many other ways.

The present invention is an improvement over the composite sheet shown in my prior Patent No. 2,200,171, and also in the copending application in which I am a co-inventor, Serial No. 166,826, filed June 8, 1950, issued December 16, 1952, as United States Letters Patent No. 2,622,051.

While in the copending application mentioned above,

the pad therein described is provided with spaced areas which are raised above other areas cemented to a backing sheet, in the present invention the backing sheet and the other sheets may be continuously cemented over their entire area, or the other sheets may be fluted, corrugated or arranged to be adhered to the backing intervals. One of the difficulties which is encountered in manufacturing composite protective pads or sheets of the present invention is that the adhesive used for cementing the sheets or Webs together pentrate too rapidly and completely the group of sheets so that they lose some sheet at spaced of their soft, flexible, yielding and protective characterisi tics in the finished product.

It is one of the purposes of the present invention to control the action of the adhesive so that the composite sheet retains all of the qualities of the individual sheets as if they were laid together without any adhesive being.

used. This is accomplished in the present invention by using diflerent types of sheets in face contact with the backing sheet from the type of sheet which comes in contact with the surface to be protected. These intermediate sheets are latently absorbent and permit smaller adhesive particles or only a percent of the adhesive to penetrate through the latently absorbent sheets in suflicient space distribution to provide the cementing of the highly absorbent cellulosic top sheets together and to the latently absorbent sheet or sheets lying against the back of the sheet. By controlling the penetration of the adhesive from the surface of the back sheet through the latently absorbent sheets and through the highly absorbent cellulosic sheets the resultant composite pad remains soft, pliable, flexible, yieldable without any indication of hardness usually caused at the places of cementation.

A latently absorbent sheet may be defined as one which is partially sized in such a way that the absorption through the material is gradual in time and not particularly rapid so that liquid adhesive will penetrate the web while drying thereby having an appreciably smaller area covered by the adhesive on the side of the sheet opposite to that where the adhesive was applied than on the side where it was applied. Such sizing which may be slack sizing may be accomplished by the use of rosin,

ice

wax emulsions, starch, hydroxyethylcellulose, carbozymethylcellulose, halogenated-siloxanes and other suitable types of slack sizing. These intermediate sheets are also preferably manufactured'from a different product than the top sheets both for cheapness and for the purpose for which they are used. The intermediate sheets next to the backing sheet may be blended of waste paper stock with a small fraction of absorbent sulphate or sulphite fiber pulp. The top sheets should be highly absorbent and soft.

In the ordinary course of producing a composite sheet, the sheets are run through a pressure roller after the backing sheet has had adhesive applied to it. The squeezing between the pressure rollers of the sheets usually force adhesive from the backing sheet through to the top sheets so that the structure of the composite sheet is not uniform in surface texture and not suitable for the intended purpose.

With sheets composed as briefly set forth above, it is possible to run the sheets with the adhesive applied to the backing sheet through the pressure rolls and produce a composite sheet which has all the desired char acteristics of a perfect sheet for the intended purpose.

Without further describing the merits and advantages of the present invention, the invention will be more fully described in connection with the drawings illustrating an embodiment thereof, in which:

Figure 1 shows in exploded form the composition of the composite sheet forming the subject of the present invention, and,

Figure 2 shows somewhat in diagrammatic form a section taken through the composite sheet when the composite sheet is made up as a parallelly corrugated sheet adhered along spaced intervals to the backing sheet.

Both figures are somewhat diagrammatic since they are upon an enlarged scale due to the difiiculty of showing the elements clearly in proportionate sizes.

In Figure 1, 1 indicates a backing sheet which may be any type of paper or paper composition material such for instance as kraft paper, fabric, thin cardboard or ordinary strong paper. This backing sheet is preferably of a closed formation and may be treated to provide Wet strength and other durable properties. Next to the backing sheet 1 are

sheets

2 and 3 which are latently absorptive of partly closed formation, sized with rosin or other suitable sizing or slack sizing materials, which sheets are preferably made of a blend of a waste paper stock with a small fraction of absorbent sulphite or sulphate cellulose fibers. For low cost it is preferable to use such a blend of waste paper stock with a small fraction 10%20% of sulphite or sulphate. The latent absorbency of the sheet may be controlled by a combi nation of such materials since if more sizing is used this will offset the absorbent action of the sulphite or sulphate fibers and the sizing may also be used, to effect the desirable partly closed formation. By partly closed formation is meant a formation in which the openings in the sheet are comparatively small and will not pass large size adhesive particles which are applied to the backing sheet. Such adhesive particles pass through the latently absorbent sheet either by pure mechanical action of being squeezed through a partially open formation or by true absorbency of the latently absorbent sheets in penetrating by capillary action and adsorbtion the fibers and structure of the sheet. Using a waste paper stock with low sulphite and sulphate content, this absorbency is materially delayed so that while the particles of adhesive are pressed and forced through the partly closed formations of the sheet the adhesive is not soaked up by the sheet and therefore the surfaces of the sheet lying against the light thin creped cellulose sheets 4, 5 and 6, are only spotted at spaced intervals with the adhesive which form a suliicient bond to hold the sheets together but not to effect the charcateristics of the web. While only three such top sheets are shown in Figure l, more than three such sheets are used. Figure 2 shows five such sheets indicated by numerals 4, 5, 6, 7 and 8. On

, the surface of sheet 1 there is applied preferably a paste adhesive 9, composed preferably of starch or other suitable material. Such adhesive is formed of various size particles, some of see Figure 2, and some large, as illustrated by 11. The top sheets 4-3 inclusive are composed of cellulose material of thin low tensile strength, extremely absorbent, creped, flexible, unhydrated, unsized fibers of very open formation having a percentage of creping in excess of 25%. These sheets are formed and creped prior to making the composite sheet. Such creped sheets are fed from rolls to the pressure rollers simultaneously with the latently

absorbent sheets

2 and 3 which may be slightly creped as for instance less than 25% and the backing sheet 1 to which the adhesive is applied. These webs may be combined into a flat sheet or as shown in Figure 2, they may be combined in a corrugated sheet in which both the latently absorbent sheets, slightly creped, if desired, and creped sheets are'corrugated just prior to the time they are applied to the backing sheet. The adhesive lying between the faces of the backing sheet and the latently absorbent sheets is forced by pressure and by the latently absorbent action of the latently absorbent sheets through the sheets and provide a substantial spot cementation as indicated by the spots 12, 12, 12 dispersed and spaced in the sheets 4, 5, 6, 7 and 8. These sheets are so highly absorbent and of such open web construction that the particles of adhesive which penetrate the latently absorbent sheets are almost instantaneously dispersed among the creped highly absorbent cellulose webs forming the top of the composite sheet or pad.

When the composite sheet is made in corrugated form as indicated in Figure 2, the adhesive in the area not in contact with the latently absorbent sheets, dry and'simply form a film or coating on the backing sheets in these areas, but since the sheet is covered, this has no effect upon the composite sheet.

As an example of the materials forming the composite sheet, I have used for the top creped open formation, a cellulosic sheet of a 12 pound weight based on 500 sheets, 24" x 36" dimension. For the latently absorbent sheets I have used a 32 pound sheet on the basis of 500 sheets, 24" x 36" dimension. The top open web highly absorbent sheet will absorb approximately -20 times their weight of water. Latent absorbency is usually which are small as illustrated by 10,

measured on a time basis. In the present instance it is necessary that the adhesive does not penetrate through the top sheets of the composite sheet during the time that it is passing through the rolls which join the sheets together.

Having now described my invention, I claim:

1. A composite sheet comprising a backing sheet of relatively closed formation heavier than the other sheets forming the composite sheet, an intermediate sheet lying in face contact with the backing sheet and a plurality of thin, low tensile strength, extremely absorbent creped, flexible, unhydrated, unsized, cellulosic webs, forming the top sheets of very open formation having a percentage of creping of approximately 25% lying over said intermediate sheet, said interrnediate sheet being of higher tensile strength, heavier and having a less open formation than said webs and being latently absorbent and sufficient adhesive applied to the face of the backing sheet whereby only enough of it will penetrate the intermediate sheet to spot cement the open webs together and tothe intermediate and backing sheets without afiecting the visible characteristics of the web. 7

2. A composite sheet as in claim 1 in which two similar intermediate sheets are laid together between the backing sheet and the open formation top sheets. 7

3. A composite sheet as in claim 1 in which the top sheets are sulphate cellulose pulp webs and the intermediate sheet has from 10% to 30% sulphate cellulose pulp.

4. A composite sheet as in claim 1, in which the top sheets are sulphite cellulose pulp webs and the intermediate sheet has from 10% to 30% pulp.

5. A composite sheet, comprising a multiple set of thin, low tensile strength, extremely absorbent, creped, flexible, unhydrated, unsized, cellulosic webs of very open formation, having a percentage of creping in excess of 25%, in combination with at least one Web of higher tensile strength, latently absorbent creped, flexible, cellulosic webs of partially closed formation, having a percentage of creping less than 25%, means forming said set of webs in parallel fluting with said set of webs being bonded in parallel lines between said flutings, to a cellulosic, hydrated, sized backing sheet of closed formation.

sulphite cellulose References Cited in the file of this patent UNITED STATES PATENTS 1,556,575 Armstrong Oct. 13, 1925 2,226,553 Cross Dec. 31, 1940 2,622,051 Hermanson et al Dec. 16, 1952

Claims

1. A COMPOSITE SHEET COMPRISING A BACKING SHEET OF RELATIVELY CLOSED FORMATION HEAVIER THAN THE OTHER SHEETS FORMING THE COMPOSITE SHEET, AN INTERMEDIATE SHEET LYING IN FACE CONTACT WITH THE BACKING SHEET AND A PLURALITY OF THIN, LOW TENSILE STRENGTH, EXTREMELY ABSORBENT CREPED, FLEXIBLE, UNHYDRATED, UNSIZED, CELLULOSIC WEBS, FORMING THE TOP SHEETS OF VERY OPEN FORMATION HAVING A PERCENTAGE OF CREPING OF APPROXIMATELY 25% LYING OVER SAID INTERMEDIATE SHEET, SAID INTERMEDIATE SHEET BEING OF HIGHER TENSILE STRENGTH, HEAVIER AND HAVING A LESS OPEN FORMATION THAN SAID WEBS AND BEING LATENTLY ABSORBENT AND SUFFICIENT ADHESIVE APPLIED TO THE FACE OF THE BACKING SHEET WHEREBY ONLY ENOUGH OF IT WILL PENETRATE THE INTERMEDIATE SHEET TO SPOT CEMENT THE OPEN WEBS TOGETHER AND TO THE INTERMEDIATE AND BACKING SHEETS WITHOUT AFFECTING THE VISIBLE CHARACTERISTICS OF THE WEB.