US1957368A - Paper manufacture - Google Patents

Description

May l, 1934 J. H. SWAN, 3D

PAPER. MANUFACTURE 2 Sheets-Sheet 1 INVENTUR ATTORNEY Filed'Aug. 30 1929 May 1, 1934. J. H. SWAN, 3D

PAPER MANUFACTURE Filed Aug. 5O 1929 2 Sheets-Sheet 2 INVENTOR A TTORNE Y5 fiatented May 1, 1934 UNITED sures PAPER MANUFAfiTURE Joseph H. Swan, 3d, Middletown, Ohio, assignor to The Gardner-Richardson ilompany, Middletown, Ohio, a corporation of Ohio Application August 30, 1929, Serial No. 389,424

8 Claims. (01. 91-68) This invention'relates to the manufacture of paper, and particularly to the manufacture of board adapted for use in the tainers and the like.

One of the principal objects of this invention is to provide a paper or board which is grease proof and moisture proof, is sufiiciently flexible and elastic to permit bending, is substantially odorless and tasteless, stands up well in use and does not objectionably deteriorate on standing for considerable intervals'of time, and is commercially economical.

Another object of the invention is to provide a methodof forming such a grease'proof paper or board, which is simple; economical and highly effective, and which permits the continuous application of a composite coating with the formation of a product of good character.

Still another object of the invention is to provide an apparatus for carrying out the above method.

Other objects and advantages of the invention will be apparent from the following description, from the accompanying drawings and appended claims.

In the drawings in'which'like characters of reference designate like parts throughout the'several views thereof,-

Fig. 1 is a partial diagrammatic side elevational view of apparatus constructed-for carrying out the method of this invention;

Fig. 2 is a view similar to Fig. 1 disclosing another portion of the apparatus;

Fig. 3 is a plan view of the apparatus shown iii-Fig. 1, certain parts being broken away and in section to illustrate the construction thereof;

Fig. 4 is a vertical sectional view taken on the plane of the line 44 of Fig.2; and

Fig. 5 is a vertical sectional View on an enlarged scale of a container board made in accordance with this invention.

This invention is particularly applicable to the rendering of paper or board, such as container board, impervious to grease so that containers made therefrom may be used for packaging greasy or oily substances which would otherwise penetrate through the package. When such a product is used for packaging foodstuffs, it is particularly desirable that the surface of the container board be substantially tasteless and odorless. The coating should be of such characher as to form an impervious layer on the surface of the board without pin holes which destroy the effectiveness of the coating, and it should be sufi'iciently flexible and elastic to permit bending making of con-.

of the board, such as is necessary in the formation of the box or container, Without cracking. The coating should also be of a durable nature and one that will stand up well in use and will not objectionably deteriorate upon standing for considerable intervals of time. In accordance with the present invention, a coated paper product is formed which is unusually eflicacious in satisfying the above requirements.

Referring to the drawings which disclose a preferred embodiment of apparatus constructed in accordance with this invention, a roll of paper to be coated is indicated at 10 carried by asuit able reel which is journaled at 11 upon a framework 12. The paper to be coated passes in a travelling web indicated at 13 over suitable guide rolls 14 and 15 and thence passes in, contact with the upper surface of roll 16 of a coating press. This coating press comprises also a lower roll 17 dipping within a trough 18 to which the coating solution is uniformly supplied in any suitable manner. Rolls 16 and 17 are positively driven, and are mounted in adjustable bearings so that they can be vertically adjusted relatively to each otherso as to contact at the nip with the desired pressure. In operation, rotation of the lower roll 17 within the coating solution serves to pick up a film of the coating material upon the surface of the roll. A portion of this film is transferred to the surface of the upper roll 16, the amount or thickness of the film being regulated by adjusting the pressure of contact of the rolls 16 and 17, and this film is then transferred to the travelling web 13.

The coating composition applied at this point comprises a rubber latex, a water solution of an oil insoluble adhesive such as sodium silicate, and an alkaline compound such as ammonia or sodium hydroxide adapted to maintain the coating in an alkaline condition. The rubber latex is a relatively concentrated water solution or emulsion of the pure sap of the rubber tree in colloidal state. The addition of an oil insoluble adhesive, such as sodium silicate, to the rubber latex imparts superior characteristics of adhesiveness, thereby providing an excellent composi- 5 or fish glues or gelatine, may be used for this J viously described and purpose. Other alkali metal silicates suchas potassium silicate can be used in place of sodium silicate; but from the standpoint of economy the latter is preferred. The presence of an alkali in the coating prevents deterioration of the same on standing and serves toincrease the effective life of the coating;

the oil insoluble adhesive is made up in a relatively concentrated solution. Thus where sodium silicate is used, a. water solution containing in excess of about 20% sodium silicate is preferred. Satisfactory results may be securedwitha solution containing from about 15% to sodium silicateby weight. The alkaline compound suchv as ammonia is added to either the rubber latex or the sodium silicateorboth; and the solutions are then mixed. Satisfactory results have been secured with compositions containing from 10% to by volume of latex, the balance being primarily a water solution of sodiumsilicate of the above strength, this composition containing about 1% to 2% by weight on the total solids of an alkalinecompound adapted to preserve the alkalinity of the coating- 'Where the coating is used for a lower or base coat it is found preferable to provide in excess of 50% rubber latex by volume in order to give a base coating which has high flexibility and covering power.

As an example of a very satisfactory coating composition for the base coat which is applied to the paper or board, the following is mentioned: Sodium silicate solution of about "38% strength, and rubber latex containing about 38% by weight of rubber hydrocarbons and the balance water and ammonia, are mixed in about 60% or more by volume of rubber latex and 40% or less by volume of sodium silicate solution to form the liquid coating composition.

In accordance with the present invention, a composite grease proofing coating is provided on the surface of the, paper or board, which composite coating is made up of upper andv lower coats having different characteristics and which are found to combine to give a superior resultant coating. bility and the upper coating provides high greaseproofness and moistureproofness, the composite coating resulting in a very satisfactory greaseproof and moistureproof sheet which can be formed on a forming machine for manufacture into containers or the like.

The web 13with the coating applied to the undersurface thereof at the coating press 1617 then passes with the uncoated surface in contact with the guide roll 20, and thence with the coated surface in contact with the surface of upper roll 21 of a second coating press. This coating press is constructed similarly to thecoating press prehas a lower rotatable roll 22 dipping within trough 23,'whereby a film of coating of the desired thickness is transferred from the lower roll 22 to the upper roll 21 and thence to the previously coated surface of the travelling web 13.

The upper layer of the composite grease proofing coating applied at this point comprises a polyliydric alcohol. such as glycerine, an oil insoluble adhesive such as sodium silicate, and a suitable binder.

the proportions of The lower coating provides high flexi-' The oil insoiuble adhesive, such as sodium silicate, has high grease proofing qualities, and also assists in securely binding the coating to the sheet. The addition-ofgglycerine to the sodium silicate imparts characteristics of resiliency to the upper coating and tends to prevent cracking thereof when the board is bent in the formation of the container without impairing the greaseproofing character thereof, and also improves the spreading and covering power of the coating. Other polyhydric alcohols, for example glycols such as ethylene glycol, can be used 1 .fwith satisfactory results'in substantially the same In the preparation 'of the coating composition,

silicate is preferably incorporated a binder, such for example as an oxidized starch, starch acetate or ground talc, flour, chalk and the like. A water soluble starch compound. such as an oxidized starch or starch acetate, are preferred due to ease of handling and superiority of results. Such starch compounds may be formed into a water solution and then added to the coating composition to provide a uniform andfree-fiowing coating which is readily applied at the coating press. Such a binder is found to improve the top coating, to make it more durable, and to prevent the possibility of the coating flaking in a dry atmosphere. In the preparation of the coating composition for this top coat, the alkali metal silicate is made up in a relatively concentrated water solution as is the case withthe base coat above described. The oxidized starch isalso made up into a suitable water solution by heating the starch compound in water such as by the introduction of steam. Satisfactory results have been secured with compositions'containing from 15% to 40% by volume of glycerine, the balance being made up of a water solution of sodium silicate and the binder.

As an example of a very satisfactory coating composition for "the upper coat, the following is mentioned: Sodium silicate solution of about 38% strength is mixed with glycerine and an oxidized starch solution in-the proportions by volume of about 35% sodium silicate solution, 20% glycerine, and 45% starch solution containing'about one pound of the soluble starch compound to a gallon of water.

The composite. grease proofing coating thus produced has superior characteristics toa ,coatto prevent the upper layer or coat from sinking into the sheet. The base coat provides unusual flexibility which is quite important in container board which is subjected to severe bending in the manufacture of the ultimate containers. This coating forming a flexible background for the overcoat, thus assists in-preventing cracking of the overcoat upon bending of the board. The highpercentage of a rubber compound such as rubber latex in the base coat acts as a water proofing and moisture proofing agent; and the spreading or covering power of this material together with its flexibility enables a substantially impervious coating to be formed with only a relatively thin, film. This is materially assisted by the fuzz laying'quality of the base coating. The upper layer or overcoat acts as a deodorizer of the base vcoat, and fills in any pores'or pin holes which may have been left by the base coating. The relatively high percentage of the oil insoluble adhesive, such as sodium silicate, gives an overcoat having high grease proofing qualities.

As many coatings as desired may be applied to the traveling web 13. Thus as shown, a third coating press comprising an upper roll 28 and a lower roll 29 dipping within a trough 30 is provided. If it is desired to apply only two grease proofing coats as above described, coating solution is not supplied to the trough 30. For the purpose of drying the coated web, drying blasts such as hot air blasts, are supplied to the coated surface of the web. As shown, a conduit 32 extends longitudinally beneath the coating machine from a point somewhat in advance of the first coating press to a point sufficiently removed therefrom to secure the proper drying of the web. This conduit is supplied with a drying fluid such as air by means of a pump indicated diagrammat-' ically at 33, the pump forcing air under pressure over suitable heating coils 34.

Intermediate the respective coating presses are upstanding ducts 35 and 36 which serve to direct blasts of the heated air against the traveling web so as to dry the coating sufliciently to permit the next coat to be applied. The duct 35 discharges the heated air against the web opposite the area at which the web is supported against guide roll 20, while the duct 36 discharges against the web at the area where it is supported by guide roll 3'7. This arrangement gives the proper tensioning and surface contact of the web at the coating presses and also serves to support the web and hold it adjacent the discharge of the ducts .to secure satisfactory drying while minimizing danger of breaking the web. Beyond the coating presses a plurality of upstanding extending ducts 38 are provided which branch off from the conduit 32.

Each of the ducts 35, 36 and 38 is constructed similarly to that shown more particularly in Fig. 4. The conduit 32 is provided with a rectangular opening 39 over which is mounted the respective duct, the end walls of which diverge as indicated at 40 so that an upper outlet opening'41 is provided which extends across the full widthof the web. The openings 39 in the respective ducts progressively increase in cross section from the duct 35 throughout the series to the duct at the end of the conduit 32 to thereby equalize the distribution of air discharged from the respective ducts. The duct closest to the pump 33 and at the point along the conduit 32 where the pressure is highest thus has the smallest effective opening,

.and the ducts farther along have progressively supported above the discharge ports of the various ducts to subsequent treating apparatus; The pressure fluid notonly serves to dry the web during itstravel but also sustains it suitably spaced from the discharge of the ducts so that the coated side of the web does not contact with solid objects untilit is substantially dry. The upper ends of each of the ducts are provided with a flat rim or flange 46 of smooth metal so as to provide'a under grease proof coating and to provide a substantially odorless and tasteless outer surface. Very satisfactory results are secured with paraffin, beeswax, montan wax, or other well known in soluble waxes. From the standpoint of economy and ease of application parafiin is preferred for this purpose. The overlying wax coat not only protects the under grease proofing coat from exposure and deterioration, but also adds to the water proofness and moisture proofness of the coating, which is particularly advantageous in the packaging of deliquescent substances, such as crackers for example.

For the purpose of applying the top wax coat a coating press is positioned beyond the driers. This coating press comprises an upper rotatable roll 50 and a lower rotatable roll 51, the rolls being mounted in bearings which are vertically adjustable in a suitable frame work 52 so as to adjust the pressure of contact at the nip. The web 13 passes directly through the nip of rolls 50 and 51 with the undercoated surface in contact with the surface of roll 51 which in turn 'ps within a suitable trough 53 provided in the rame work 52. This trough may be supplied with a paraffin size solution, or may be supplied with paraflin or other wax which is maintained in a molten condition by suitable heating coils. Rotation of rolls 50 and 51 causes a thin film of paraffin to be picked up on the surface of roll 51 and thus transferred to the coated web, the thickness of the film being limited by the pressure at the nip.

The presence of a suitable binder, such as a soluble starch compound, in the top layer of the grease proof coating causes the top paraffin coat to adhere firmly to the coated web. The use of such a binder has a further advantage in assisting in the control of the amount of parafiin or other wax which is taken up by the sheet during the application of this top wax coat. Thus it is found that the higher the percentage of soluble starch in the upper layer of the grease proofing coating, the more parafiin the sheet will take for the same roll pressure at the nip, and vice versa.

press through pressure rolls 55 and 56 carried in vertically adjustable bearings by the frame 52. These rolls are preferably constructed in the manner of calender rolls and are steam heated. A high degree of pressure is used at these rolls, and the pressure together with heat serves to render the top wax coat fiuid and spread it uniformly over the surface of the coated paper. The pressure roll's 5556 also serve as a driving means for drawing the paper through the machine. The coated paper than passes to further treating apparatus, or is wound upon a reel 57, or may be passed to suitable cutters and cut into sheets of desired size for the manufacture of containers.

If desired, the paper or board previous to the coating as above described. maybe first subjected to a sizing treatment. The sizing treatment is useful in that it tends to prevent curling of the drop test, which means that water will not penetratethe sheet at'that time, is satisfactory. Or the sheet may be given a surface sizing by an application of a size to the surface of the formed web, using suitable conventional sizing materials such as above specified. The surface sizing may be applied during the formation of the sheet prior to the application of the grease proofing coating. The sized paper is then supplied in roll form as indicated at 10 to the coating machine and the grease proofing coating is applied to the sized sheet.

- Referring to Fig. 5, a section through a preferred sheet or board is disclosedwhich is found to be highly efiective for use in containers for the packaging of greasy materials, and which protects the materials from water and damp atmospheric conditions. The sheet comprises inner layers of ordinary board stock 60, with an intermediate layer 61 of asphalt material, such as an emulsion of asphalt and clay. The outer surfaces of the board are formed of good grade liner stock, there being a bottom-liner 62 and a top liner 63. One of the outside liners, such as the top liner 63, which is adaptedto form the interior of the container and to receive the grease proof coating, may be a hard sized sheet.

This board as above described may be formed on a conventional cylinder mold machine having a number of molds to form the various layers or plies of the sheet, these plies being brought together and united in the ordinary manner. Thus a conveying felt of the forming machine passes first across a cylinder mold containing the bottom liner stock and forms a web, and then passes successively across cylinder molds provided with board stock, asphalt emulsion, board stock, and finally top liner stock to form the complete builtup sheet of container board. The board as thus formed is then passed to the coating machine where the composite grease proofing coating is applied, there being a lower or base coat of high flexibility-indicated at 64 and an upper or overcoat of high grease proofing quality indicated at .65. A final overlyingwater insoluble wax coat 66 is then applied over the grease proofing coating. A container formed from this sheet is protected from water and moisture tending to penetrate from the outside into the interior of the container by the intermediate asphalt layer and by the base coat 64, and is made effectively grease proof, water proof and moisture proof on the interior by the coating applied to the interior surface of the container.

While the forms constitute preferred embodiments thereof, it is to be understood that the'invention is not limited to these precise forms, and that changesmay be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A paper product of the character described comprising a sheet having a composite greaseproofing surface, said sheet and composite surface being flexible to maintain the continuity of said surface material against disruptive effects I ,to bending and the of inventiwn disclosed herein during use, said surface comprising a lower layer including rubber latex and anoil insoluble adhesive, an upper layer including an oil insoluble adhesive and a binder, and an overlying top coat of a water insoluble wax, the binder being of such character as to modify the retention and adhering properties of the coated sheet for the water insoluble wax.

2. A paper product of the character described comprising a sheet having a composite greaseproofing surface applied thereto, said greaseproofing surface comprising a lower layer having high flexibility and including rubber latex and an alkali metal silicate, and an upper layer having high greaseproofness and including a polyhydric alcohol and an alkali metal silicate, said sheet and composite coating being flexible to maintain the continuity ofsaid composite coating against disruptive effects in use due to bending and. the like.

3. A paper product of the character described comprising a sheet having a composite greaseproofing surface applied thereto, said greaseproofing surface comprising a lower coat which isthe dried deposit of a solution containing in excess 'of 50% rubber latex by volume, the balance being primarily a water solution of an alkali metal silicate of a strength in excess of 20%; and. an upper coat which is the dried deposit of a so-' lution containing in excess of 15% by volume of glycerine, the balance having a substantial pro portion by volume of a water solution of an alkali metal silicate of a strength in excess of 26%, said sheet and composite coating being flexible to maintain the continuity of said composite coating against disruptive efiects in use due to bend! ing and the like.

4. A paper product adapted for formation into containers comprising a sheet having a composite greaseproofing surface applied thereto capable of withstanding bending operations *incident to formation into containers without destruction of the impervious character of said surface, said greaseproofing surface comprising a lower layer of high flexibility including a rubber material,

coating layer of high greaseproofcomprising a lower layer of high flexibility ineluding a rubber material,

and an upper coating layer of high greaseproofness comprising a polyhydric alcohol, an oil insoluble adhesive, and a binder, said sheet and compositecoating being flexible to maintain posite coating against disruptive effects in use due like.

alcohol and a soluble the continuity of said com- 6. A paper product of the character described comprising a sheet having a composite greaseproofing surface applied thereto, proofing surface comprising a lower layer of high flexibility including a rubber material, and an upper coating layer of high greaseproofness in-' cluding a polyhydric alcohol, an alkali metal silicate, and a soluble starch compound, saidsheet and composite coating being flexible to maintain the continuity of said composite coating against said greasedisruptive effects in use due to bending and the like.

'1. A paper product of the character described comprising a sheet having a composite greaseproofing surface" applied thereto, said greaseproofing surf ace comprising a lower layer of high flexibility including a rubber material, and an upper coating layer of high greaseproofness including" an alkali metal silicate and a soluble starch compound, said sheet and composite coating being flexible to maintain the continuity of ,''said composite coating against disruptive efiects in use due to bending and the like.

8. A paper product of the character described comprising a sheet having a composite grease-

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