US3265555A

US3265555A - Adhesive coated sheets and method of manufacture

Info

Publication number: US3265555A
Application number: US186386A
Authority: US
Inventors: Harold R Dalton
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-04-10
Filing date: 1962-04-10
Publication date: 1966-08-09
Anticipated expiration: 1983-08-09

Description

Aug. 9, 1966 H. R. DALTON 3,265,555

ADHESIVE COATED SHEETS AND METHOD OF MANUFACTURE Filed April 10, 1962 INVENTOR" Z6 flaw/.2: R. $44 TON TT RNEY required usable tackiness.

United States Patent O 3,265,555 ADHESIVE COATED SHEETS AND METHOD OF MANUFACTURE Harold R. Dalton, Rydal Road, Jenkintown, Pa. Filed Apr. 10, 1962, Ser. N 0. 186,386 18 Claims. (Cl. 161-161) This invention relates to the coating art and more especially it relates to the coating of sheet or web material whose dimensional stability is subject to change during, or as a result of, the coating operation.

In certain of the arts, particularly in the art of adhesive coating upon paper, the adhesive film upon drying tends to shrink in greater proportion to the paper. Consequently, when the coating material is subjected to the usual drying heat to form it into a film, and since the coating material usually has a different shrinking characteristic from that of the paper, the differential characteristics of the paper and coating tend to cause the paper to curl or otherwise dimensionally distort. This problem is particularly noticeable where the coating material is a gum, glue or similar moistenable adhesive. Ordinarily, when such glue coating is applied in liquid form to a paper or similar porous backing, the coating when dried is a continuous film and the surface continuity thereof increases the tendency of the paper to curl.

This problem of curling is so pronounced in the gum coating art that it has been necessary heretofore to subject the gum or glue coating to a mechanical breaking operation. Thus, in the manufacture of gummed paper in continuous lengths or sheets which are subsequently to be cut into sealing tapes, labels, stamps, etc., it is customary to process the gummed sheet in a breaking machine before it is subjected to the subsequent processing operations such as slitting, cutting, printing, punching, etc. In other words, it has been found necessary to break or crack the glue or gum layer into sections so as to effect a discontinuous film and thereby reduce the curling effect. The fihn breaking operation is employed to produce a finishedgummed sheet that has as closely as possible the same handling properties as the original uncoated paper, fabric or foil, and also to modify the gummed film so that it will readily accept water or other softening liquid when the gum coating is to be moistened to give it the The equipment for mechanically accomplishing the film breaking is well known in the art, and for that purpose reference may be had to the periodical publication entitled Paper, Film and F-oil Converter, May 1957, page 27. This machine, which is used quite generally, consists essentially of unwind and rewind stands between which are located two sharp-edged breaker bars or edges placed at an angle of approximately 45 degrees to the length of the sheet and at approximately 90 degrees to each other. The ungummed surface of the paper, fabric or foil is forced against the sharp edges of the breaking bars to crack the adhesive coating, which for example may be bone glue, hide glue, dextrine, gum arabic, polyvinyl alcohol prany other well known adhesive which is intended to be subsequently moistened to render it tacky.

The film breaking operation entails considerable waste of paper or other material that is to be gummed, especially since the sheet material is usually coated in a relatively high speed sheet feeding operation. Since the paper or similar sheet material must be held taut against, or otherwise pressed against and deflected around, the sharp edges of the breaking bars, there is always the possibility of the sheet rupturing or tearing, and a considerable length of paper is ruined before the coating machine can be brought to rest. Furthermore, since the sharp-edged breaker bars are in tight pressing engagement with the uncoated side "ice of the sheet, the mechanical rubbing or scraping may affect the surface characteristics of that uncoated side so as to render it unsatisfactory for subsequent printing, drawing or other operations to be performed on the un coated side. The above difficulties are, of course, greatly increased in proportion to the thinness or fragility of the sheet which is being gummed or coated, thus limiting the use of the coating and breaking equipment to sheets in excess of a predetermined minimum thinness.

I have found that the above noted and other difficulties can be averted by eliminating the usual mechanical fihn breaking and by efiecting the breakage of the film by what may be termed a physio-chemical action within the fihn itself. Accordingly, one of the principal objects of the present invention is to provide a backing sheet with a novel coating which is broken to render the coating discontinuous but without requiring external mechanical breaking force. Another object is to produce a broken or discontinuous film without marring or physically disturbing the uncoated surface of the backing sheet which carries the fihn on its opposite surface.

Another object is to provide a broken or discontinuous surface film which has fracture or breakage lines of greater number per unit area than has been possible with fihns broken with the usual mechanical breaking operations.

Another object is to provide a broken or surface discontinuous adhesive film wherein the fracture or breakage lines are produced in a greater non-statistical array than is possible with the breaking effected by physical breaker bars or the like.

A further object is to provide a process of coating a backing sheet of paper, film, foil or the like with a broken adhesive film whereby lighter weight stock can be used for the backing than has been practicable heretofore.

A feature of the invention relates to a novel coating batch for producing a fractured or broken surface film on a flexible backing sheet, which batch has incorporated therein a material that effects the film breakage by an inherent explosive or disruptive action, but without destroying or reducing the interfacial adhesive force between the backing sheet and film.

Another feature relates to a gummed paper or the like which is particularly free from curling or similar dimensional distortion, while at the same time possessing a high order of receptivity to water or similar moistening agent when the paper is subsequently being treated to render it tacky.

. A "further feature relates to an improved laminated paper or cardboard product and also to an improved such product of the corrugated kind.

Other features and advantages not particularly enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

In the drawing,

FIG. 1 is a top plan view in schematic form showing the mechanical fihn breaking equipment heretofore considered necessary for fihn breakage;

FIG. 2 is a side perspective view of FIG. 1;

FIG. .3 is a drawing of a photomicrograph taken of an adhesive coated paper showing the film fracture lines produced by the conventional mechanical breaking mechanisrn;

FIG. 4 is a drawing of a photomicrograph of an adhesive coated paper wherein the broken adhesive film is prepared according to one embodiment of the invention;

FIG. 5 is a drawing of a photomicrograph of an adhesive coated paper wherein the broken adhesive film is prepared according to another embodiment of the invention;

3 FIG. 6 shows an improved laminated product embodying the invention;

FIG. 7 shows an improved cocrugated product embodying the invention.

Referring to FIGS. 1 and 2, the basic parts of the conventional mechanical film breaking equipment are schematically shown, comprising, for example, the un-- wind roll 10 from which the previously dried gummed.

paper 11 is unrolled and rewound on the rewind roll 12. Located between the two rolls are the usual adhesive

film breaker bars

13, 14 which are usually at an angle of 45 degrees to each other and which are held in pressed engagement with the ungummed surface of the paper 11, as indicated schematically by'the offset rollers 15, 16 adjacent the

bars

13, 14 as shown. In other words, the paper is held taut against the breaker bars. As a result of this mechanical breaking, the previous gum coating on the paper 11 which had a continuous surface is mechanically broken or fractured. In some cases, a third breaker bar 17 and offset roller 17a extends parallel to the sheet width. FIG. 3 shows a magnification (fifty times) of a portion of such a sheet after breakage of the gummed film. It will be observed that the fracture lines are in all cases roughly linear and define roughly triangular areas of comparatively regular statistic shape; Because of the physical nature of the breaking operation, it is not practicable to decrease the size of the areas bounded by the fracture lines even though such a reduction has decided advantages. One of the advantages in decreasing the bounded area between fracture lines is the improvement in water absorption properties of the dried film.

I have found that the breakage of the gum film can be effected by incorporating into the gumming material, prior to its application to the paper 11, a finely divided solid chemical having the property of producing gas when heated to a certain temperature within the usual drying range to which the gummed paper is subjected, more specifically within the range of temperatures used in commercial drying ovens which is from 220 degrees F. to 500 degrees F. While the present invention is not limited to any particular solid chemical gassing agent for the above breakage purpose, the following nitrogenous agents have been found satisfactory for that purpose:

4,4 Oxybis (benzenesulfonyl semicarbazide) 4,4 Oxybis (benzenesulfonyl hydrazide) Azodicarbonamide Trihydrazino-sym-triazine N,N' dimethyl N,N dinitrosoterephthalamide Barium azodicarboxylate Bis-benzenesulfonyl hydrazide Of the above, the azodicarbonamide is particularly advantageous since, after the decomposition and gas releasing, no trace of the'chemical is left in the gum coating. While the above are given as illustrative of suitable chemical gassing agents, other such agents may be used, the prerequisite being that they be solid at room temperature, decompose at a temperature within the working range of the gumming equipment, produce a suflicie nt amount of gas when used in small percentages to accomplish the desired film breakage, and that both the gassing agent and the decomposition products be nontoxic and non-hazardous to handle.

If any one of the above gassing agents is dispersed with a water remoistenable adhesive in an amount of from approximately 0.5 percent to 10 percent of the dry weight of the adhesive, applied to paper or other sheet material by any one of the well known methods such as roll coating, doctor blade coating, knife coating, etc., in an amount to give the usually applied weight or thickness common in industry, i.e. from two pounds totwenty pounds (24" x 3 "500), and dried in an oven at the proper temperature and lineal speed, it is found that the entire dried adhesive film will be broken with random 3 comparative similar results.

fracture lines, the breaking seemingly being caused by the individual dispersed solid particles of gassing agent decomposing and producing a gas which will crack the film before leaving the area within which it was entrapped.

The dextrine and water were mixed with a high speed mixer until the dextrine was dissolved. T-he azodicarbonamide was then added and .mechanical agitation continued for about fifteen minutes. The liquid adhesive mixture was applied to a sixteen pound bond paper with a roll coater to give a dried coating weight of fifteen pounds (24" x 36500). The coated paper was dried at a temperature of 350 degrees F. The-sheet laid flat after cooling and its surface was Well broken, as shown in FIG. 4. The same solution was applied to kraft paper (sixty pound 24" x 3 "-500) and drafting cloth with Example 2 This example utilizes dimethyl dinitrosoterephthalamide as a gassing agent using mechanical dispersion.

Pounds Stein Hall gumming grade dextrine 200.0 Water 160.0 Dimethyl dinitrosoterephthalamide 5.0

The dispersion was prepared and coated as indicated in Examplel. The coated paper was partially dried at a temperature of 200 degrees F. and then passed over a polished sheet drum, gummed face out, heated to 350 F. The sheet laid fiat after cooling and its surface was well broken similar to that of FIG. 4.

Example 3 This example utilizes azodicarbonamide chemically dispersed in a dextrine solution, using physio-chemical dispersion.

Triton X-l00 (Rohm & Haas dispersing agent;

alkyl aryl polyether alcohol) 2.0

' The dextrine and water were mixed with a high speed mixer until the dextrine was dissolved. The Triton X.- 100 was added to the azodicarbonamide, a little water added (1 pound) and mixed until a smooth paste was formed:- another pound of Water was added, and then the dispersion transferred to the dextrine solution while the latter was being agitated. The agitation was continued for about fifteen minutes. The mixture was applied to paper as in Example 1. The sheet laid flat after cooling and its surface was well broken; a finer structure of the broken adhesive layer was obtained compared to Example 1, as shown in FIG. 5.

Example 4 This example utilizes azodicarbonamide mechanically dispersed in an animal glue solution.

Pounds Darling animal glue, g 120.0

Naphtha bone glue 80.0

Pounds Water a 185.0 Azodicarbonamide 4.0

, Soak the glue in water until swollen and then heat to 150 degrees F. Add the azodicarbonamide and agitate for fifteen minutes with a high speed mixer. The liquid adhesive was applied to a fifth pound (24" X 36"500).

clay coated paper with a blade coater to give a direct coating weight of eighteen pounds (24" X 36-500). The coated paper was dried at a temperature of 350 degrees F. The sheet laid flat after cooling and its surface waswell broken. The same, solution was applied to ametal foil laminated paper with similar results.

Example 5 This example utilizes dimethyl dinitrosoterephthalamide with a synthetic adhesive polyvinyl alcohol.

Pounds Polyvinyl alcohol (Dupont 52-22) 100.0 Water 800.0 Dimethyl dinitrosoterephthalamide 4.0

Example 6 This example utilizes bis-benzenesulfonyl hydrazide mechanically dispersed in a kraft sealing tape gumming solution.

Pounds Darling glue, 120 g 180.0 Water 175.0 Bis-benzenesulfonyl hydrazide 14.0

The dispersionwas prepared and coated as indicated in Example 2 and the results were similar to those obtained in that example.

. While the examples given contain only water as a solvent, various other materials may be used along with the water to modify the film properties of the adhesive during the drying process to develop the desired random breakage lines, certain fineness of grain or crackle, certain cellular structure, etc. Materials that are suitable for this purpose are the glycol ethers, high boiling alkylene amines, alkanolamines and alcohols, etc. Also, the adhesive film itself may. consist of more than one type of adhesive and certain softening agents like glycerine,

' glycols, sorbitol, etc., or other additives, such as pyrophosphates, gluconic acid, pigments, fillers, etc., may be a part of the formulation. Other'modifying agents to impart anti-blocking properties such as polyvinyl methyl ether, polyvinyl acetate, polyacrylic acid, polyvinyl acetatemaleic anhydride copolymer, polyethylene glycols, etc., may also be used in the gumming formulation.

While particular chemicals, temperatures and drying times have been mentioned hereinabove, it will be understood that such' are given purely by way of illustration and-not by way of limitation. Furthermore, while the invention finds its primary utility in the manufacture of gummed or glued sheets, in certain of its aspects the invention is equally well adapted to other kinds of coatings where it is desired to avoid mechanical breaking of the coating while producing such a coating with .a multiplicity of fracture lines arranged in a substantially non-statistical array so that the chances of forming a number of individually continuous fracture lines across the coated sheet are greatly reduced.

While the invention has been described hereinabove as applied to the gumming of a single sheet or web, the invention also finds utility in the manufacture of laminated sheets, composed of a plurality of sheets of fibrous stock bonded together at adjacent faces by an intermediate, i.e. intervening, dried adhesive layer. In such laminated product the intermediate dried adhesive layer has a multiplicity of fracture lines occurring in random array. Thus, FIG. 6 shows the invention applied to two sheets of paper or cardboard which are laminated through the intermediary of glue or gum film which has been applied to either or both of the opposed surfaces of the two liminated sheets 18, 19. This glue film 20 is prepared in accordance with the above disclosure. After being applied to one or both of the sheets, it is subjected to the drying heat .above mentioned to cause the solid gas releasing particles to disintegrate and fracture the bonding gum film between the sheets. This fracturing of the film increases the flexibility of the laminated sheets without materially affecting the laminated bond therebetween.

FIG. 7 shows the invention applied to .a corrugated laminated product wherein the intermediate corrugated cardboard or paper portion 21 is bonded at its crests to the flat cardboard or

paper sheets

22, 23. These

sheets

22, 23 are provided with a

film

24, 25 of the glue or gum above described, and when the sheets have been assembled in laminated array with the

fiat sheets

22, 23 in contact with the crests of the corrugated sheet 21, the assembly is subjected to the above noted drying heat to cause the film to become fractured as above described. This fracturing of the glue or gum film increases the resilient compressability of the corrugated assembly without materially affecting the bond between the fiat sheets and the corrugated sheets.

One of the advantages of the fracturing method, according to the invention, is that the gas releasing action is derived directly from the fracturing agent of the solid particles, these particles being individually and directly decomposed by the drying heat as distinguished from the release of gas by chemical interaction of two or more chemicals which release such gas by ionic action. By such direct heat disintegration of the solid particles, the production of the randomly occuring fracture lines in relatively close array is readily achieved. The invention is not limited to any particular degree of fineness of these particles, their fineness, of course, being correlated with the psysical effect desired. Most of the gasing agents disclosed consist of fine powder having a particle size of from 1 to 5 microns. However, when mixedwith a water solution of a glue or gum, they form large .agglomerates which must be broken down by agitation or otherwise, as by milling, into the individual particles or into small agglomerates to give the results desired. Thus, it will be noticed that mechanical agitation for a short time produces fracture lines as in FIG. 4, whereas dispersing the particles more completely produces many more fracture lines per unit area as shown in FIG. 5.

It' will be understood that the term gum, .as used herein, is merely illustrative of any well known moistenable adhesive which becomes usefully tacky when moistened with water or similar moistening agent. It will also be understood that the fracture lines referred to herein are of extremely thin or hairline form and are not visible except under relatively high magnification.

7 What is claimed is: p

1. The method of providing over a flexible backing material a dry adherent film of a dryable, moist flowable adhesive coating composition, a coating of which has the undesirable tendency to shrink on drying and which is tacky when wetted and adherent when dry, and substantially to eliminate said tendency toward shrinkage, which method comprises applying to said backing material a moist, flowable adhesive of said'coating composition containing dispersed therein a gas-providing substance which is stable therein at ordinary ambient conditions during application and under elevated temperature employed to dry the applied moist film decomposes therein with release of gaseous decomposition products therefrom; and then subjecting the moist coating to an elevated drying temperature sufiicient to dry it under the drying conditions employed and so simultaneously to decompose said gas-providing substance and to enable the released gaseous products thereof to produce a multiplicity of fracture lines in the resulting dried adherent film of the adhesive material.

2. The method according to claim 1 in which said gas-providing substance used has a decomposition temperature between 200 degrees F. and 500 degrees F.

3. The method according to claim 1 in which said gasproviding substance is incorporated in the coating composition as a comminuted solid.

4. The method according to claim 1 in which said gasproviding substance is a member of the class consisting of oxybis benzenesulfonyl semicarbazide, oxybis benzenesulfonyl hydrazide, azodicarbonamide, trihydrazino-symtriazine, dimethyl dinitrosoterephthalamide, barium azodicarboxylate, and bis-benzenesulfonyl hydrazide.

5. The method as claimed is claim 1, wherein said gasproviding substance is azodicarbonamide.

6. The method according to claim 1, wherein said adhesive coating composition contains as its adhesive constitutuent a member of the class consisting of bone glue, hide glue, dextrine, gum 'arabic, and polyvinyl alcohol.

7. The method of making a sheet coated with dried moistenable-adhesive, which method comprises preparing a dryable, moist, fiowable gumming batch comprised of a moistenable-adhesive ingredient in a solvent vehicle therefor and including dispersed therein solid particles of a gas-providing substance whichis stable therein at ordinary ambient conditions and under elevated temperature used to dry a coating of said batch decomposes therein with release of gaseous decomposition products therefrom; applying a suitable moist coating of said batch over a backing sheet; and then subjecting said moist coating on said sheet to an elevated drying temperature sufficient to dry it under the drying conditions employed and so simultaneously to decompose said gas-providing substance to enable the released gaseous products thereof to form said composition on the backing sheet into a dried moistenable-adhesive film having a multiplicity of fracture lines.

8. The method as claimed in claim 7, wherein the solid particles of said gas-providing substance are mechanically dispersed throughout the gumming batch before applying it to the backing sheet.

9. The method as claimed in claim 7, wherein a chemical dispersing agent is incorporated in the gumming batch.

10. The method according to claim 7, wherein the coated sheet is passed through a drying oven and said gas-providing substance has a decomposition temperature within the drying temperature range of said oven.

11. The method of breaking a dried gum coating on a backing sheet, which comprises incorporating into the starting gum coating composition prior to applying it to said sheet a heat-decomposable coating-fracturing ingredient, and after applying said coating composition to the.

sheet, heating it to decompose said ingredient thereby to fracture said coating by the resulting heat decomposition of said ingredient.

12. The method as claimed in claim 11, wherein said coating-fracturing ingredient is a gas-providing substance which is stable at ordinary ambient conditions during application of said coating composition and under elevated temperature decomposes therein with release of gaseous decomposition products therefrom, and said heating of the coating is at a temperature sufficient to decompose said gas-providing substance to release from it gas to effect said fracturing of the coating.

13. A coating batch for the manufacture of gummed sheets and the like, comprising a dispersion of a gum, a

solvent for the gum, and a gas-providing substance stable therein at ordinary ambient conditions and which substance decomposes With release of gaseous decomposition product therefrom when said sheet is heated to dry the gum coating thereon and whereby the released gas effects fracturing of the dried gum coating on the sheet.

14. A coating batch according to claim 13, wherein said gas-providing substance is a member of the class consisting of oxybis benzenesulfonyl semicarbazide, oxybis benzenesulfonyl hydrazide, azodicarbonamide, trihydrazino-sym-triazine, dimethyl dinistrosoterephthalamide, barium azodicarboxylate, and bis-benzenesulfonyl hydrazide.

15. A coating batch as claimed in claim 14, wherein the gas-providing substance is azodicarbonamide.

16. A gummed sheet comprising a backing of porous material and adhesively attached thereto a fractured dried coating of a moistenable adhesive, which coating of said frangible dried moistenable adhesive has a multiplicity of fracture lines in an irregular array exhibiting substantially negligible recurrent pattern; said gummed sheet being substantially free of any tendency to become dimensionally distorted when moistened and subjected to drying heat and in contrast to, and which tendency so to be distorted is manifested by, a corresponding gummed sheet having such backing and attached to it a continuous dried coating of said adhesive, with said coating being free of fracture lines.

17. A gummed sheet according to claim 16, in which the number of fracture lines in the dried coating is many times greater per unit area than the fracture lines produced by a conventional mechanical breaking operation. 18. A laminated fibrous stock sheet product comprising a plurality of sheets of fibrous stock bonded together at their adjacent faces by an intervening dried adhesive layer having a multiplicity of fracture lines occuring in random array exhibiting substantially negligible recurrent pattern.

References Cited by the Examiner UNITED STATES PATENTS 1,148,783 8/1915 Knappstein 117-11 1,958,721 5/ 1934 Scott 117-11 2,770,406 11/ 1956 Lane.

2,815,297 12/ 1957 Herrlinger 117-11 2,849,332 8/1958 Smith et a1 117-41 2,947,647 8/ 1960 Hart et a1 117-11 2,973,295 2/1961 Rogers.

3,041,193 6/1962 Hamway et al. 117-11 EARL M. BERGERT, Primary Examiner.

J. F. BURNS, T. R. SAVOIE, Assistant Examiners.

Claims

18. A LAMINATED FIBROUS STOCK SHEET PRODUCT COMPRISING A PLURALITY OF SHEETS OF FIBROUS STOCK BONDED TOGETHER AT THEIR ADJACENT FACES BY AN INTERVENING DRIED ADHESIVE LAYER HAVING A MULTIPLICITY OF FRACTURE LINES OCCURING IN RANDOM ARRAY EXHIBITING SUBSTANTIALLY NEGLIGIBLE RECURRENT PATTERN.