US2170655A - Laminated crepe cellulosic product - Google Patents

Description

Aug. 22, 1939. c. A. FOURNESS LAMINATED CREPE CELLULQSIC PRODUCT \QQB Filed Sept. 5, 1936 Patented Aug. 22, 1939 UNITED STATES LAMINATED oasra cnLLULosrc raonoo'r Charles A. Fourness, Appleton, Wia, aslignor to Paper Patents Company, Neenah, Wia, a corporation of Wisconsin Application September 5, 1936, Serial No. 99,520

2 Claims.

which may be arranged into multi-ply pads or bats for use as a sound or heat insulating medium or the like. The present application is in part a continuation of my abandoned application Serial No. 668,205 which was filed on April 27, 1933, and which is assigned to the assignee of the present application.

Generally stated, the objects of the present invention are to provide an improved, low density, bulky, cellulosic product of great porosity which inherently accomplishes intimate contact between the individual fibers making up the product and the surrounding air or other medium so as to produce a resultant product of very high thermal and very high sound insulating ability; to produce a bulky, porous, low density, cellulosic product wherein the individual fibers shall be unequally weighted or loaded with a thermo-plastic material or like substance in the form of small discrete particles which are individually attached to the individualv fibers or groups of fibers of the product, so as to cause the sound reflecting properties of the individual fibers of the product to vary within wide limits and thereby accomplish effective and eflicient sound absorption by the product over a wide range of sound frequencies; to produce a porous, low density product of the subject type, the properties of which may be varied from stiff through resilient to soft and dead by changes in the kind, arrangement, and distribution of the weighting or loading material, thus permitting control of the sound absorption and other properties of the product over a wide range; and

to provide a multi-ply, bulky, water resistant product of the subject type which shall be stronger, more resilient, and capable of sustaining greater loads without material diminution of bulk than any of the products heretofore known to the art.

Other objects of the invention are to provide an improved cellulosic sheet suitable for use in products of the previously described type which is itself inherently water resistant and which can be readily manufactured at low cost upon existing paper making machines; to provide an improved cellulosic sheet of this type which shall be. lighter and more bulky while at the same time being stronger, sturdier, more resilient, and must more permanent than the products heretofore known to the art; to provide a cellulosic sheet in accordance with the above stated ob- Jects which can be readily creped to increase its bulk and resilience; to provide an improved water resistant cellulosic sheet of the subject type which can be fireproofed without injury to the desirable physical properties and characteristics thereof; and in brief, to provide an improved cellulosic sheet product.

A preferred form of the invention is illustrated in the accompanying drawing wherein- Figure 1 is a perspective view showing a plurality of cellulosic sheets according to the present invention combined into a pad or bat; and

Figure 2 is an enlarged, fragmentary perspective view of a portion of one of the sheets making up the pad or bat illustrated in Figure 1.

It is to be understood that the use of multiply pads or bats consisting of a plurality of thin, superposed cellulosic sheets is not in itself new. In fact, rnulti-ply pads or bats of such sheets have been extensively used as packing material and to some extent for heat and sound insulating purposes prior to the present invention. For example, multi-ply wadding comprising a plurality of plies or layers of creped cellulosic sheets of gossamer-like thinness held together with or without embossing has been and is being used most extensively as packing material.

In contrast with packing materials, heat and sound insulating materials'are ordinarily used under extremely adverse conditions and must possess a long useful life. Such materials are frequently exposed to moisture and insects, and to satisfactorily accomplish their function over a long period of time, the individual plies must not only be very permanent but mlst possess considerable mechanical strength and resiliency in addition to high insulating ability. The products heretofore known to the art have failed to fully satisfy these requirements, and their use as insulating materials for sound and heat insulating purposes has been accompanied with serious disadvantages in part due to the inherent lack of strength and permanence of those products, their inability to withstand moisture, etc. These disadvantages are entirely overcome by the present invention.

Reduced to its simplest form, the present invention consists in the provision of a multi-ply product comprising a plurality of superposed, very thin, gossamer-like, creped, cellulosic sheets having a basis weight (1. e. weight in the flat or uncreped state) of from 4 to 9 pounds for 480 sheets 24 x 36 inches and containing from 10% to 50% by weight of an asphalt or other thermoplastic material which is in the form of small discrete particles of widely differing dimensions attached to the individual fibers of the sheet preferably by fusion thereon. By virtue of the differing sizes of these particles and their more or less indiscriminate attachments to the fibers, the individual fibers of the sheet are differently weighted or loaded, and as a result have widely differing sound reflection and absorption characteristics. The resultant product, seemingly due to this variable weighting or loading of the fibers cient thermal insulator, and has a number of most desirable physical properties, outstanding among which is the remarkable low stable density of the product, which likewise appear to result from the presence of this weighting or loading material.

Various thermo-plastic materials within the classification of bitumens, pyro-bitumens, pyrogenous distillates, and pyrogenous residues may be used for accomplishing this desired weighting or loading of the individual fibers of the sheet. The important considerations in the selection of the weighting or loading material, as will appear more clearly in subsequent paragraphs, are that the material shall be capable of being introduced into the furnish for the paper making machine so as to cause small discrete particles of widely varying size to adhere to the individual fibers of the web during its formation, that the material shall not foul the machine during the manufacture of theweb, that the material shall be relatively brittle and not sticky at ordinary room temperatures, and that the material shall be of sufficiently low viscosity at the temperature of the drier to adhere thereto. In brief, these considerations are primarily concerned with the manufacture of the article, although various properties 01 the resultant sheet, such as stifi'ness, may be varied very substantially by a proper selection of the weighting or loading medium.

Tests indicate that most of the thermo-plastic materials within'the above described classifications which have a ball and ring melting point within the range of F. to 200 F. and which are relatively brittle at room temperatures, i. e. are relatively hard and have good penetration resistance at such temperatures, are suitable for accomplishing the desired weighting or loading of the individual web fibers. It is to be understood, however, that this classification is of a very general nature and that all thermo-plastics having the above defined physical properties may not be satisfactory for the purposes of the invention. It is believed, however, that the further description of the principles and features of the invention appearing herein will clearly indicate to those skilled in the art which materials are suitable for the purposes of the invention and the course to be followed in selecting such materials.

Following considerable experimentation, it has been ascertained that particularly desirable results are accomplished if the weighting and loading material constitutes an asphalt having the above specified properties, i. e. is relatively brittle at room temperatures (of low penetration), and which has a ball and ring melting point within the range of 140 F. to 200 F. Particularly, asphalt of this type may readily be caused to subdivide into the small discrete particles which accomplish the loading of the web fibers during the manufacture of the sheet. Further, cellulosic sheets containing asphalt of this type can be readily manufactured upon existing paper making equipment and are found to possess remarkable mechanical strength and resilience superior to many of the other known thermoplastics. At the same time the sheets are very porous and bulky and can be readily combined into relatively sturdy, multi-ply pads or bats which have very desirable physical characteristics, such as prolonged resistance to compression and very low stable density.

In fact, under ordinary manufacturing conditions the completed pad or bat product made by superposing a plurality of the above described cellulosic sheets (i. e. sheets having a basis weight of from about 4 to 9 pounds for 480 sheets 24 x 36 inches and containing from 10% to 50% by weight of an asphalt which is relatively hard or brittle at room temperatures and which has a melting point within the range of 140 F. to 200 F., the asphalt being in the form of very small, discrete particles of widely varying dimensions attached to the individual fibers or groups of fibers constituting the sheet) will have a stable density within the range of about 1.25 to 2.00 pounds per cubic foot. The attainment of this very low stable density is a most important feature of the present invention, for the reason that the lowest stable density obtainable in a similar pad or bat product made from similar creped cellulosic sheets which do not contain asphalt, or which do not contain asphalt of the particular type and in the particular amounts and in the particular particle form specified above, is in excess of about 3.0 pounds per cubic foot.

Moreover, multi-ply bats or pads of sheets containing asphalt of the type and in the amounts hereinbefore specified may be embossed without the use of additional adhesive, and even when the product is not embossed, the presence of the great numbers of discrete particles of asphalt istics of the product, as compared with non-- weighted sheets, probably due to the fact that the number of fiber to fiber contacts in the weighted product is materially reduced, and insulating contacts are substituted therefor. Variation in the dimensions of the particles of as-- phalt or other thermo-plastic material and in the amount, kind, and type of such materials permits the accomplishment of considerable variation in the sound absorbing properties of the product.

The thermo-plastic weighting or loading mate-.

rial constitutes a convenient medium for impregnating the product with water insoluble germicides, bactericides, insecticides or fungicides.

If the basis weight of the sheet is materially increased over the amount above stated, many ofthe advantages of the present invention are lost, the sheet becomes unduly expensive to manufacture, and there is a very marked decrease in the heat and sound insulating characteristic, probably due to the fact that the unequal weighting. or loading of the individual fibers of the web cannot conveniently be accomplished in such heavier sheets.

As mentioned previously, cellulosic sheets according to the present invention may be manufactured upon paper making machines such as are ordinarily employed for manufacturing the complishes the creping thereof. The thermoplastic material which may be of the particular type of asphalt discussed above is added to the furnish to the paper making machine and so processed that it is introducedinto the web as small discrete particles of widely varying dimensions which adhere to the individual fibers of the web during the manufacturing operation. The processes described in Stevenson and Buron Patent No. 1,771,150 issued July 22, 1930 and the processes disclosed in Kirschbraun Patent No. 1,606,427, issued November 9, 1926 can be successfully used for introducing the thermo-plastic materials such as asphalt of the above described type into the furnish, either process being capable of forming the large number of small, separate particles of the thermo-plastic material which accomplishes the desired unequal loading of the web fibers. To attain maximum permanency of the finished product, it is desirable that the incorporation of the material into the web fibers be accomplished prior to the felting of the fibers on the paper making machines.

Sufficient of the thermo-plastic material is added to the furnish to produce a finished product which shall contain from to 50% thereof by weight. For certain uses, as mentioned previously, the material is preferably asphalt of a type which is relatively brittle, i. e. has low penetration, at ordinary temperatures and which has a ball and ring melting point within the range of 140 F. to 200 F., this particular type asphalt assuring the atttainment of all of the novel and beneficial characteristics of the subject invention.

Percentages of the thermo-plastic material between 10% and 50% by weight of the finished sheet are capable of rendering such sheets highly water resistant. At the same time if the weighting and loading material is relatively brittle at room temperatures, its presence in the sheet serves to effect a remarkable increase in the strength, weight carrying ability, and inherent resilience of that sheet as compared with sheets not containing such material, and thereby serves to maintain the sheet in its normal creped condition throughout the useful life thereof.

To accomplish satisfactory creping, the thermoplastic material must be of sufliciently low viscosity and sufficiently tacky at the temperatures encountered at the surface of the drying cylinder to secure good adhesion between the web and the surface of the drying roll, and hence good creping, as the web is removed by the creping doctor.

The melting point of the thermo-plastic material is generally a fairly good index of the viscosity and adhesiveness of the material at the temperature of the drier. Hence this characteristic of the material is of great importance, for the reason that unless it is within the specified range, 140 F. to 200 F., the sheet probably cannot be manufactured upon conventional paper making machines without possible serious contamination of the felt and rolls or unsatisfactory creping of the web as it is removed from the drying cylinder.

From this it follows that if the melting point of the thermo-plastic material is above the specified range, satisfactory creping of the sheet is extremely difficult of attainment, and if the melting point is below the specified range with an accompanying reduction in viscosity, the sheet does not possess the desirable resilience, strength and body at ordinary room temperatures, and during the formation of the web serious contamination of the felts and rolls may occur. Asphalt having the characteristics hereinbefore specified meets all of these requirements most satisfactorily.

The amount of thermo-plastic material is likewise of considerable importance, the optimum amount probably being in the neighborhood of to by weight. Amounts up to may be used, however, with good results, particularly when extremely high moisture resistance is required, but if an attempt-is made to go much beyond this amount, it will be found that the sheet loses its desirable qualities of strength and resilience. It would appear that a certain optimum balancing of the amounts of asphalt and fiber is attained within this specified range, and to use either materially more or materially less asphalt disturbs this balance wit most undesirable results.

The use of the particular type asphalt defined above for rendering the sheet material water resistant and for imparting sound absorption characteristics thereto has certain other advantages, for the reason that a web containing asphalt of the type and in theamounts hereinbefore specified, may be fireproofed during the drying operation through the simple expedient of spraying suitable fireproofing solutions upon the web. A satisfactory method for accomplishing this is disclosed in Patent No. 2,132,016 to Horace A. Du Bois, which is assigned to the assignee of the present invention. Ordinary nonasphalt containing cellulosic sheets containing sufiicient rosin size to render those sheets water resistant cannot be fireproofed by the conventional salt solutions without destroying the water resistance of such sheets, i. e. in effect, destroying the size characteristic. Further, alkaline adhesive solutions such as sodium silicate may be applied to the asphalt containing products of the present invention without seriously affecting the water resistant characteristics of such products. Such adhesives cannot be used without disastrous effect upon the water resistant characteristics of sheets containing resin or like sizes.

In one commercial process for manufacturing cellulosic sheets of the subject type, two parts of a commercial asphalt which is relatively brittle at room temperatures, and has a melting point not less than 140 F. nor greater than 200 F., is intimately mixed with one part of ground wood and one part of unbleached sulphite fiber substantially in accordance with the method described in Stevenson and Buron Patent No. 1,771,150 to form what is termed a thermoplastic mix. To make cellulosic sheets containing 20% asphalt by weight the furnish used for supplying the heater is substantially as follows:

Pounds Thermo-plastic mix 400 Unbleached sulphite pulp 300 Ground wood 300 To make cellulosic sheets containing 10% asphalt, the beater is supplied with the following:

Pounds Thermo-plastic mix 200 and Unbleached sulphite pulp 800 In either case suflicient water is mixed with the furnish in the beaters to produce pulp suspension of about 3%, which mixture is pumped directly to the paper making machine. Here the mixture may be thinned with additional circulating water and fed onto the wire as a very thin suspension of fiber in the usual manner. The

resultant web is carried by the felt or felts from the wire to the drying cylinder from which it is removed as a creped sheet by the creping doctor. The asphalt will be found to intimately adhere to individual fibers of the web in the form of minute discrete particles of widely varying size which are apparently fused to the web fibers.

Any number of sheets may, of course, be superposed toform a bat or pad suitable for the purposes of the invention. As stated previously, under ordinary manufacturing conditions the completed pad or bat product ready for use as an insulating material will have a stable density within the range of about 1.25 to 2.00 pounds per cubic foot. Single bats comprising 20 to separate sheets will be found of sufllcient bulk for most ordinary uses.

' Various modifications may be made in the invention without departing from the novel principles disclosed in the foregoing. It is my intention, therefore, that the accompanying claims shall be accorded the broadest reasonable construction consistent with the state of the art.

I claim the following as my invention:

1. A bulky, porous, multi-ply pad or bat particularly suitable for use as an insulating material, comprising a plurality of superposed, thin, creped, cellulosic sheets each of which contains from 10% to 50% by weight of ab asphalt which is relatively brittle at room temperatures, and which has a melting point within the range of F. to 200 F., said asphalt being in the form of small, discrete particles of widely varying dimensions, and substantially all of said particles being individually attached to individual fibers or groups of the fibers making up each of said sheets, whereby the individual fibers in said pad or bat are unequallyloaded or weighted, said pad or bat having a stable density under ordinary manufacturing conditions within the range of 1.25 to 2.00 pounds per cubic foot.

2. A bulky, porous, multi-ply pad or bat particularly suitable for use as an insulating material, comprising a plurality of superposed, creped, cellulosic sheets, each of which has a basis weight of from 4 to 9 pounds for 480 sheets 24 x 36 inches, and each of which contains from 10% to 50% by weight of an asphalt which is relatively brittle at room temperatures and which CHARLES A. FOURNESS.

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