US 3362869 A
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Description (OCR text may contain errors)
Jan. 9, 1968 H. s. WELSH 3,362,869
METHOD OF FORMING MACHINE GLAZED EXTENSIBLE PAPER Filed Jan. 12, 1965 3 Sheets-Sheet l FLOW- DIAGRAM FORMATION OF A PAPER WEB IMPARTI-NG EXTENSIBILITY TO THE FORMED WEB APPLICATION OF A WATER-THIN SOLUTION OF ADHESIVE TO THE WEB SURFACE DRYING THE PAPER WEB ON A MACHINE GLAZING CYLINDER FIG. I
INVENTOR HEW TT 8. WELSH BYKV Jan. 9, 1968 H. WELSH. 3,362,869
METHOD OF FORMING MACHINE GLAZED EXTENSIBLE PAPER Filed Jan. 12, 1965 3 Sheets-Sheet 2 FIG. 2
HEWITT S. W ELSH Jan. 9, 1968 H. s. WELSH $362,869
METHOD OF FORMING MACHINE GLAZED EXTENSIBLE PAPER Filed Jan. 12, 1965 3 Sheets-Sheet 5 v INVENTOR. 4 HEWITT s. WELSH United States Patent 3,362,869 METHOD OF FORMING MACHINE GLAZED EXTENSIBLE PAPER Hewitt S. Welsh, Short Hills, N.J., assignor to Clupak, Inc, New York, N.Y., a corporation of Delaware Filed Jan. 12, 1965, Ser. No. 424,895 3 Claims. (Cl. 162-175) ABSTRACT OF THE DISCLOSURE Process for producing a machine glazed extensible web by applying an aqueous solution of adhesive to one face of the web and subsequently drying the web against the surface of a polished glazing cylinder. This invention includes forming a wet laid web, compacting the web by mechanically pushing and crowding the fibers of the web together in the space between the Web faces by forces ap plied in a direction parallel to the web faces and opposed to the direction of its movement, then plasticizing the surface fibers of the web by applying a water thin solution of adhesive to one surface of the web, and then urging the surface of the web to which the adhesive has been applied, against the surface of a heated glazing cylinder under sufiicient pressure to cause a total adhesion of the web to the surface of the cylinder, and thereafter drying the web on the cylinder.
The present invention relates to machine glazed extensible paper and to a method and apparatus for glazing of extensible paper. More particularly, the present invention relates to the making of extensible paper having a high specular gloss.
In the ordinary machine glazing of conventional paper, the paper in a highly moist condition is placed against a heated, smooth surfaced rotating roll and dried while in contact therewith. This roll is the machine glazing cylinder or Yankee roll. The drying of the paper sheet or web against the polished surface of the roll, causes the contacting side of the web to take on a fine glazed, glossy surface due to the plastic condition of the surface of the web which conforms to the polished surface of the roll. The resulting fiat web, which has been put through the Yankee machine, is known in the trade as machine glazed paper or simply M.G. M.G. paper has a high specular gloss and is generally in the range of 25 gloss as measured by the L.R.L. Gloss Meter, Serial No. 1. Paper makers recognize that the best condition for adhesion of the paper to the glazing cylinder is where the paper has a moisture content by weight in the range of approximately 50% to 55% at the point where the web is placed on the cylinder. As the moisture content is reduced, the resulting gloss is progressively lessened and may reach a point where the web is allowed to break away from the roll prematurely and cause spotting.
At the point where the web is removed from the glazing cylinder, it is substantially dry. In this dry state, the paper cannot now be made substantially extensible by any known method without impairing or destroying the gloss.
Although the specification will concern itself primarily with machine compacted extensible kraft paper, it should be understood that the present invention should be beneficially applicable to many types of extensible webs such as non-Wovens which types may be made extensible by any of the various known methods.
The manufacture of extensible paper requires a treatment of the paper web while the web is in a moist, plastic condition. Where the paper web is made extensible by machine compaction, ability to stretch without rupture is 3,362,869 Patented Jan. 9, 1968 imparted to the web by means of a mechanical compressive shrinkage technique. When machine compaction is used, it has been found preferable to compact the web at a time during its manufacture when its moisture content by weight is in the range of approximately 30% to 40%. The compacted paper Web can be subsequently placed against a heated dryer roll for the purposes of removing water; however, the process of glazing cannot be readily efiected because the moisture content of the Web is too low to obtain sufiicient adhesion to a dryer roll surface. On the other hand, if a moisture content level sufficient to obtain adhesion of the web to the cylinder is present, substantial compaction will not take place since the moisture in large quantities in the body of the web fills the interstices of the web and in effect makes a relatively incompressible solid which is incapable of substantial shortenlng.
The problems inherent in machine glazing of extensible paper arise from the above limitations encountered both by the available methods of manufacturing the extensible paper and the machine glazing of the paper. For example, extensible paper cannot be properly machine glazed after compaction because its moisture content is too low for proper adhesion to the glazing cylinder. Compaction after machine glazing is not practical because the moisture content of the paper web at this time is too low to allow extensibility to be imparted to the web; and any attempt to compact a dry, glazed paper web would result in limited extensibility being imparted to the web and would impair the glazed finish.
The present inventor knew that friction glazing does not impart a gloss comparable to M.G. He knew that super-calendering would produce a high gloss; but subjecting the relatively dry extensible web to super-calendering would be a costly operation and would, to some extent, destroy extensibility and impair the strength imparted previously to the web. He knew that a web of paper once dried of moisture can be later rewet throughout its fibrous network but that the moisture content throughout the thickness of the web is not uniform unless a lengthy period of time is provided in which the moisture content can come to equilibrium. Paper which is not uniformly rewetted will not have a uniformly glazed finish after being placed on a machine glazing cylinder. In dealing with extensible paper, if the paper is rewet throughout and enough time is allowed to let the moisture content come to equilibrium, the resulting relaxation and straightening of the entire fibrous network of the web will destroy much of the extensibility of the web and furthermore, the time necessary to achieve equilibrium would seriously limit practical use of such a process.
To overcome the problems such as those noted in the foregoing, the present inventor comprehended that a water-thin solution of adhesive might be applied to the relatively dry traveling web just prior to the placing of the web against the Yankee roll to produce a glazed extensible paper equivalent to that obtained by the usual commercial machine glazing of conventional paper.
Therefore, it is an object of the present invention to provide an apparatus for imparting a machine glazed finish to extensible paper.
A further object is to provide an apparatus and method for imparting a high gloss to a moving web of extensible paper.
Another object is to provide a method and apparatus for imparting a machine glazed surface to a mechanically compacted web by surface treating such web and subsequently drying the web on a polished roll without substantial loss of extensibility.
A further object is to provide a method of making machine glazed extensible paper which is compatible with and adaptable to modern paper making processes.
A further object is to provide as an article of manufacture, a machine glazed extensible paper.
In accordance with one aspect of the present invention, the foregoing and other objects of the present invention are accomplished by preparing a paper web so that it has extensibility in excess of its primitive extensibility, surface treating the web with a water-thin solution of adhesive without any substantial disturbing or relaxing of the fibre network of the web, and subsequently drying the web so treated on a dryer roll so that a high gloss is imparted to the treated web surface. For a more complete understanding of the present invention, reference should be made to the drawings wherein:
FIGURE 1 is a flow diagram setting out the method of the present invention;
FIGURE 2 is a diagrammatic side elevation of the apparatus employed in the practice of the present invention;
FIGURE 3 is a detail of application means, in side elevation; and
FIGURE 4 is a detail of application means in frontal elevation.
The drawings are to be understood to be more or less of a diagrammatic character for the purposes of illustration. Like characters identify the same elements in the several views.
FIGURE 1 shows a flow diagram setting out an embodiment of the method of the present invention. The paper Web is formed in any conventionad manner, for example, a water-laid furnish of cellulose. The web is then partially dried to a coherent structure. The web is then made extensible. Any apparatus such as the Cluett mechanical compaction apparatus would be applicable to impart extensibility to the web. In the Cluett compaction apparatus, a paper with sufficient water removed to create a coherent fibrous structure, is submitted to a process which pushes and crowds the fibres of the web together in the space between the opposed faces of the web as laid by forces applied in the direction parallel to the faces of the web and opposed to the direction of its lengthwise movement continuously and uniformly over the web. Upon subsequent drying by conventional means, the modified orientation of fibres and fibrils is retained in the dry state and the sheet takes on firmness and strength due to the mutual adherence of the finely entangled structures within the Web. A resistance to deformation is produced which allows continuous deformation in the direction of extensibility until rupture occurs.
Means are available for imparting extensibility to a web in multiple crossing directions so that continuous re sistance to deformation is exhibited in more than one direction. The elongation is characterized by no substantial decrease in thickness of the web.
The extensible web is then passed through an applicatormeans which applies a water-thin solution of adhesive to one surface of the web. The treated surface is then placed against the polished surface of a machine glazing cylinder before the water has an opportunity to penetrate substantially into the body of the web. The web is removed from the roll after removal of all but a residual amount of moisture and is found to have a high gloss on the surface which was adhered to the cylinder. Since less total water is present in the web at the point of contact with the glazing cylinder, less drying during the glazing period is required than in conventional commercial operations. Thus the lineal speed of the web can be increased or, in the alternative, 21 small cylinder can be used without loss of capacity. This is an advantage since larger cylinder diameters necessitate an increase in dryer shell thickness which retards heat transfer and largely nullifies gains realized from larger drying areas. Furthermore, associated problems of fabrication, spacing and shipping make utilization of the smallest possible cylinder desirable.
FIGURE 2 illustrates one embodiment of an apparatus constructed in accordance with the present invention. This figure shows a mechanical compaction apparatus 1 into which the web 2 is introduced after having been dried to approximately 30% to 40% moisture by weight. The compaction apparatus imparts extensibility to the moving web. Extensibility of zero to 25% or more can be imparted to the web by a single unit. Further operations on the web may be carried out for even greater extensibility.
The web is moved along suitably mounted rollers 3 and 4. After compaction, the Web has approximately 25% to 35% moisture by weight. The method of imparting extensibility by mechanical compaction is set out in United States Patent No. 2,624,245 and reference can be made to that patent for the technical details of mechanical compaction.
In the present invention, a flexible blade 5 is mounted by mounting means 6 so that it rides in tension against one surface of the moving web. A water-thin solution of adhesive 7 is applied to the trailing surface 8 of the blade which then transports it to the surface of the Web and applies it thereon in a uniform fashion. A storage tank 9 is located in proximity to the applicator blade 5. A pipe or conduit 10 connected to the tank transports the water-thin solution to the upper portion of the trailing surface of the blade. The solution is carried from the tank to the blade by a gravity feed as shown in FIG- URE 2; but a pump located in the feed line from the storage tank would allow placement of the tank at any convenient point. A metering valve 11 is disposed in the line from the tank so that the amount of solution applied to the surface of the web per linear foot can be precisely controlled. A steam coil 12 is disposed within the storage tank to provide a means for controlling the temperature of the solution. The temperature is not critical, but it is desirable to heat the solution to reduce the amount of heat required for drying of the paper web. It can be readily seen that any heating device which would not contaminate the solution could be readily employed such as electric heaters.
After being surface treated, the web is moved along by rollers 13 and 14 to a rotatably mounted steam heated glazing cylinder 15. Roll 14 is a pressure rol-l. This roll is loaded in a conventional manner so that it applies enough pressure to cause the moving web to adhere to the polished surface of the glazing cylinder. The nip pressure produced by roll 14 and the drum 15 must be sufficient to adhere initially the plastic surface of the Web to the polished contour of the glazing cylinder. Excessive pressure will impair extensibility and produce other undesirable effects. Pressures in the range of approximately 300 to 400 lb. per linear inch have been found most satisfactory. A felt backing 16 may be utilized in a conventional manner during the drying process, although its use is optional.
In general the distance between the applicator means and the point of adhesion to the dryer roll should be kept at a minimum. The proper distance in a given operation will depend on absorptivity of the web and the speed of the web.
The glazing cylinder is a large metal drum 15 having a polished chrome plating or other smooth finish on its peripheral surface. A cylinder temperature of about 200 F. has been used but the appropriate temperature is easily determined depending on the grade of paper being processed. The cylinder is mounted rotatably.
In a pilot operation, a Web of unbleached kraft paper of the sort used in wrappings having approximately 28% moisture by weight was treated With a solution of starch of a mixture of about 5% starch by weight. This repre sents about 1% of starch when pounds of starch is com.- pared with pounds of paper. A typical water-thin solution would contain approximately 2% to 6% solid content of starch by weight. The Yankee dryer roll was maintained at approximately 215 F. and the nip pressure, that is,
the pressure produced by the roller 14 and the drum 15 was about 350 pounds per linear inch. The resulting gloss was 23 as measured on the L.R.L. Gloss Meter, Serial No. 1. Control samples of paper of about 28% moisture content by weight were run in the pilot operation without surface treatment to demonstrate the effectiveness of the method of the present invention. After drying on the Yankee cylinder, a gloss from 6 to 7 was produced. This is as compared with the gloss of 23 obtained as noted above. A web surface treated according to the method of the present invention with pure water having little or no starch in solution therewith, had a gloss of about 10. It will be understood by those familiar with the art that this treatment is not of the type utilized in coating of paper to produce high gloss and high brightness paper for specialized uses such as printing where waxes, pigments and the like are used.
The solution used is water-thin and accordingly has a low viscosity. It has been found that for best results the web should have above approximately 22% moisture by weight when the Water-thin solution is applied. The amount of starch in solution can be varied. Starch solutions of approximately 1.4% to approximately 5.5% were successfully utilized to produce a high gloss surface. Using more than approximately 10% starch should be unnecessary since the starch is used successfully in very low quantities only to enhance the surface tension of the solution so that the treated surface of the web adheres firmly to the surface of the glazing cylinder. The Water content of the solution plasticizes the surface of the web to an extent greater than that which is produced by the moisture content of the web which has been established during the making of the web and the imparting of extensibility to the web. The web surface, due to the plastic condition, conforms to the surface contours of the glazing cylinder while the web is adhered to the cylinder by reason of the surface tension between the drier surface and the surface of the treated web.
It is not a purpose of this invention to use large amounts of starch or any other solid ingredient to fill up the superficial interstices of the Web surface. It is not necessary that pigment be added to the water-thin solution to produce the desired gloss. The adhesive is used in small quantities and adds little to the resulting gloss by reason of its ability to fill in surface voids when it solidifies. The adhesive acts with the water to provide enough surface tension to hold properly the web against the glazing cylinder so that the web surface can take on a gloss.
Referring to the description of the pilot operation, a web of about 28% moisture by weight was surface treated with about 13.7 pounds of water per hundred pounds of paper which gives a total moisture by weight of about 37%. This is still low when compared with the usual 50% or more which is generally considered necessary for proper machine glazing. Furthermore, it should be noted that the glazing was carried out without substantial loss of extensibility.
The glazed extensible paper made according to the present invention, is not substantially impaired in its extensibility or flexibility. The method of this invention can be used to glaze paper whether extensible in only one direction or in multiple crossing directions.
FIGURE 3 is a detail of one type of applicator blade arrangement used to accomplish the surface treating of the web. The blade supporting means 6 carries a thin, flexible curved blade 5. The blade is supported in tension against the paper web 2. The blade supporting means must be laterally adjustable and also rotatable in order that the tension and the angle that the blade makes with the plane of the surface of the moving web can be regulated. One form for accomplishing this is to mount the supporting means on a journal for rotation and to base the journal on a member which is movable in a plane toward or away from the surface of the web. Excessive tension will tend to tear the web. The fluid supply pipe 10 communicates with the rearward or trailing surface 8 of the blade and the water-thin solution is applied to the blade at a point away from the nip formed by the blade and the paper web. The solution runs down by gravity and capillary action into the nip and is evenly spread across the surface of the paper by the action of the blade. It was found more desirable to apply the solution to the trailing surface of the blade because applying the solution from the leading surface of the blade produced considerable streaking.
FIGURE 4 shows a front view of the applicator blade 5. The blade extends across the full width of the web so that the water-thin solution is applied to the entire web surface. Multiple supply pipes 10 are utilized to produce a uniform flow down the blade surface and into the nip formed by the blade and the paper web.
There are other methods available for applying the water-thin solution such as a roll applicator, an air knife applicator, or a gravure drum. It is desirable that the means used be suitable to control the passage of the waterthin solution to the surface of the paper and to spread the solution evenly over the surface of the paper in continuous controlled amounts. The moisture content of the body of the web remains relatively constant throughout the operation since the solution is applied to the surface of the web and is not allowed to penetrate substantially into the body of the web. The water-thin solution may be applied to the glazing cylinder and then in turn to the surface of the web as the web is brought into contact with the surface of the cylinder. In such an embodiment, the solution would be applied to the web surface by utilizing the glazing cylinder as an applicator means. Here the application of the solution and the placing of the web against the cylinder would be substantially simultaneous. The present inventor anticipates that such an embodiment may prove useful in treating certain types of webs.
When the present inventor talks about an extensible web, he is referring to a web which has been subjected to mechanical compaction or similar processes which operate to produce in the web, an ability to stretch without rupture which would not be present in the web where the wet fibres of the web laid and then dried by conventional means such as is done where extensibility is not a determinative consideration. A web which is formed and then dried without compaction has some amount of inherent extensibility. This has been termed primitive extensibility to differentiate it from the extensibility produced by mechanical compaction and similar processes. This primitive extensibility may vary with different types of webs and with direction in a given web.
Several commercial grades of starch were used as an adhesive in the pilot operation, including hot and cold swelling, and tapioca starches. Essentially the same results, as far as gloss is concerned, were obtained.
Although the present invention has been described with reference to specific apparatus, it will be appreciated that a wide variety of changes may be made both in the apparatus and method without departing from the scope of this invention. For example, some of the components of the apparatus may be reversed, certain features of the ap paratus may be used independently of others, and equivalents may be substituted for the apparatus and methoc steps, all within the spirit and scope of the invention a: defined in the appended claims.
1. The process of producing a web of water laid adherent fibers having substantially parallel opposed face: and having a machine glazed finish on one of said faces and said web being characterized by having extensibilit; in excess of the primitive extensibility of said web, com prising the steps of:
(a) slowly removing a part of the moisture from th: web as it leaves the papermaking machine until llllt web has an established moisture content throughou in the range of approximately 30% to 40% by weight;
(b) moving the web with its established moisture content in a lengthwise direction;
(:1) mechanically pushing and crowding the fibers of the web together in the space between the faces of the web as laid by forces applied in the direction parallel to the faces of the web and opposed to the direction of its lengthwise movement continuously and uniformly over the Web;
(d) then plasticizing the surface fibers of the web to an extent greater than that produced by the established moisture content of the web by applying a continuous film of a water-thin solution of adhesive to one surface of the web after extensibility has been imparted to the web;
(e) and then urging the surface of the web to which the adhesive solution has been applied against the surface of a heated, revolving glazing cylinder under sufiicient pressure to cause a total adhesion of the Web to the surface of the glazing cylinder so that the plasticized surface fibers of the web conform to the surface contours of the cylinder;
(f) drying the Web while adhered to the revolving cylinder until the web is substantially dry throughout; and
g) removing the web from the glazing cylinder.
2. The process of claim 1 wherein the solution is an aqueous solution of adhesive comprising approximately 1.4 to 5.5% solid content by weight.
3. The process of producing a web of water laid adherent cellulose fibers having substantial extensibility in excess of the primitive extensibility of the Web and no substantial decrease in thickness when elongated by stretching, and having substantially parallel opposed faces one of which faces exhibits a high gloss, comprising the steps of:
(a) slowly removing a part of the moisture from the web as it leaves the papermaking machine until the web has an established moisture content throughout in the range of approximately 30% to 40% by weight;
(b) moving the web with its established moisture content in a lengthwise direction;
(c) mechanically pushing and crowding the fibers of the web together in the space between the faces of the web as laid by forces applied in the direction parallel to the faces of the web and opposed to the direction of its lengthwise movement continuously and uniformly over the web;
(d) then plasticizing the surface fibers of the web to an extent greater than that produced by established moisture content of the web by applying a continuous film of an aqueous solution of starch comprising approximately 1.4% to 5.5% solid content by weight to one surface of the web after extensibility has been imparted to the web;
(e) and then urging the surface of the web to which the starch solution has been applied against the surface of a heated, revolving glazing cylinder under sufiicient pressure to cause a total adhesion of the Web to the surface of the glazing cylinder so that the plasticized surface fibers of the web conform to the surface contours of the cylinder; and
(f) drying the web while adhered to the revolving cylinder; and
(g) removing the web from the glazing cylinder.
References Cited S. LEON BASHORE, Primary Examiner.