US20040231814A1

US20040231814A1 - Enhancement of a cellulose-based paper product with glass fibers

Info

Publication number: US20040231814A1
Application number: US10/445,098
Authority: US
Inventors: Tejendra Singh
Original assignee: Evanite Fiber Corp
Current assignee: Evanite Fiber Corp
Priority date: 2003-05-23
Filing date: 2003-05-23
Publication date: 2004-11-25
Also published as: WO2004106629B1; WO2004106629A1

Abstract

Enhancement of cellulosic paper products with coarse diameter glass wool fibers (average diameter of from about 5.5 μm to about 11 μm) results in stronger, more air resistant, and less hygroexpansive paper products. Paper products comprising cellulose pulp and coarse diameter glass wool fibers are disclosed. Additionally disclosed are methods for making coarse diameter glass wool fiber enhanced cellulosic paper products.

Description

FIELD

The compositions, methods, and products provided herein relate to glass-fiber enhanced, cellulose-based, paper products.

BACKGROUND

In conventional papermaking, raw cellulosic material, such trees, are broken down into small fragments or chips. These fragments are heated under pressure with water and chemicals and beaten to separate their fibers and extract cellulose from their non-fibrous material, such as lignin. This process is known as pulping and results in a product called cellulose pulp. The cellulose pulp can be dried at this point for later use in papermaking. This is preferred if the papermaking facility is not adjacent to the pulping facility in order to reduce shipping costs. Alternatively, if the pulping and papermaking facility are integrated or close, the wetted pulp may simply be transported to the next stage of the papermaking facility. In either case, the cellulose pulp is then refined into a slurry (known as a furnish) through additional beating and the addition of an aqueous solution. This process is known as stock preparation. During stock preparation certain additives may be added to the pulp. After stock preparation, the furnish is pumped into a papermaking machine, such as a Fourdrinier machine, to dewater the slurry into a web and form it into paper or board. A basic papermaking machine comprises a wire mesh screen that receives the slurry and begins the dewatering process to create a web, a press section to consolidate the web and continue dewatering the web to produce a paper product, and a drying section to remove residual water from the paper product. A paper product is known as board if it has a weight, expressed in grams per square meter (gsm), of more than 150, and is known as paper is it has a gsm of 150 or less.

Paper products are used in countless applications including: containers, such as boxes, sacks, drums, crates, cans, and buckets; printing and publishing applications, such as books, newspapers, magazines, catalogs etc; electronics applications, such as plugs, speaker cones, panel boards, telephone sets, instrument cases, fiber conduits; mechanical applications, such as gaskets, packing, tire cord, oil filters; construction applications, such as pressboard, insulation, sheathing papers; textiles and apparel applications, such as clothing, shoes, arch supports, blankets, bed sheets, and diapers; household applications, such as towels, tissues, cups, furniture (pressboard), plates, and trays; farming applications, such as seed starters, egg containers, poultry feeders, and produce crates; and special applications, such as air filters, absorbent waddings, surgical gowns, fluorescent papers, gas and flameproof paper, and washable paper maps.

Certain applications for paper products require or are enhanced by a paper product having special characteristics. For example, high tearing resistance, high air resistance, low flammability, and low hygroexpansivity are desired characteristic in many applications, such as paper containers, printing applications, maps, and many other applications.

Certain of these attributes can be enhanced by the use of additives to the cellulose pulp. For example, adding asbestos to the pulp can reduce the flammability of the resulting paper product. However, the use of asbestos has significant health-related disadvantages.

Glass fibers also have been added to cellulose pulp to enhance desired paper characteristics. For example, U.S. Pat. No. 2,653,090 describes reinforcing paper with strands of glass yarn. U.S. Pat. No. 2,919,221 describes a method of making paper entirely from very fine diameter glass fibers having average diameter of 1 micron (μm) or less. U.S. Pat. No. 3,749,638 describes the use of chopped strand glass fibers to make either entirely glass paper or to reinforce paper containing other synthetic or natural fibers.

Chopped strand fibers are significantly different from glass wool fibers. Chopped strand fibers are produced through a process in which molten glass is passed through a spinner and rolled over a spool before it is cut to a specific length. Glass wool fibers, on the other hand, are produced by techniques such as rotary spinning, flame attenuation, and controlled attenuation technology (CAT) in which glass fibers are produced at an unspecified length. Chopped strand fibers are held within close limits to the specified length. Glass wool fibers, on the other hand, have varying diameter to length (aspect) ratios, for example from 1/500 to 1/4000. Additionally, chopped strand fibers are relatively long compared to glass wool fibers. The shortest chopped strand fibers are about 6500 μm, while the shortest glass wool fibers are about 1600 μm, and can even be shorter.

Cellulose pulp enhanced with fine diameter (average diameter less than 5.2 μm) glass wool fibers has been used to make paper for air and liquid filtration applications because desirable pore size characteristics can be achieved. Additionally, the patentee has used fine diameter glass wool fibers to enhance paper for applications such as printer paper.

It is generally believed in the paper industry that the smaller the diameter of glass fibers that are used, the greater the tearing resistance, the greater the air resistance, and the lower the hygroexpansivity of the resulting paper product (as one of ordinary skill in the art would expect). For example, in U.S. Pat. No. 3,749,638, the smaller the diameter of the chopped strand glass fibers used, the higher the strength of the resulting paper (i.e., paper made with chopped strand fibers having an average diameter of 3.8 μm exhibited greater tearing resistance than paper made with chopped strand fibers having an average diameter of 8.9 μm). Additionally, those skilled in the art expect paper products made with fine diameter glass fibers to also have a lower hygroexpansivity than paper products made with larger diameter fibers because the smaller diameter glass fibers should be able to interlock to a greater degree. Moreover, one would expect paper products made with smaller diameter glass fibers to have a higher air resistance than paper products made with larger diameter glass fibers due to a tighter pattern.

SUMMARY

The inventors surprisingly discovered that enhancement of cellulosic paper products with coarse diameter glass wool fibers (e.g., an average diameter ranging from about 5.5 μm to about 11 μm) resulted in stronger, more air resistant, and less hygroexpansive paper products than cellulosic paper products enhanced with fine diameter glass wool fibers (an average diameter of 5.2 μm or less). These novel paper products were heretofore unknown in the art because all indications suggested that glass fiber paper products made from coarse diameter glass wool fibers would perform poorly relative to paper products made with finer diameter glass wool fibers.

Accordingly, compositions for making glass fiber paper products comprising cellulose pulp and coarse diameter glass wool fibers are provided. Also provided are methods of making glass fiber paper products comprising coarse diameter glass wool fibers. Additionally provided are glass-fiber-enhanced, cellulosic paper products comprising coarse diameter glass wool fibers

In particular examples compositions for making coarse diameter glass wool fiber paper products include coarse diameter glass wool fibers having an average diameter ranging from about 5.5 to about 11 μm. In certain cases the course diameter glass wool fibers have an average diameter from about 6.0 μm to about 10.0 μm. In still other cases the course diameter glass wool fibers have an average diameter from about 6.5 μm to about 9.5 μm. An average diameter of about 7.0 μm is particularly useful. In particular instances the coarse diameter glass wool fibers comprise between about 1% and about 25% of the paper product by weight, which percentage is calculated by comparing the dry weight of the glass wool fibers to the total dry weight of the glass wool fibers together with the cellulose pulp. In certain cases the coarse diameter glass wool fibers comprise between about 1% and about 15% of the paper product by weight. Examples in which glass wool fibers comprise about 3% to about 5% of the paper product by weight are particularly useful.

The average glass wool fiber diameter can be determined using a BET (Brunauer, Emmett and Teller method) specific surface area (SSA) analyzer. The BET method works on the principle that the adsorption and desorbtion of rare gases, such as argon, is proportional to the SSA of a material. For the examples in this application, a Gemini 2375 BET SSA analyzer by the Micromeretics Instrument Co., of Norcross, Ga. operating with Micromeretics 5 ^thversion of its software was used with argon as the absorbtive gas to determine the average diameter of samples of glass wool fibers (each about 0.321 grams). The SSA analyzer was used to determine the SSA of the glass wool fiber sample. The average diameter of the glass wool fibers was determined by the formula: diameter=4/(SSA×P) where P is the density of the of the glass of which the glass wool fibers are comprised.

In some cases coarse diameter glass wool fiber paper products are made on a papermaking machine, such as a Fourdrinier machine. However, in other cases, coarse diameter glass wool fiber paper products are made by hand, or on any other type of papermaking machine.

The coarse diameter glass wool fiber paper products disclosed herein include any paper products made with the disclosed methods or compositions. Such products are useful in any application where dimensional stability is desired. That is, the coarse diameter glass wool fiber paper products are useful in most any paper application, especially for applications where paper curling, shrinking, or expansion would be a disadvantage. In particular examples the coarse diameter glass wool fiber paper products are for use in printers, such as a laser printer. In other examples, however, the paper products are for use in other applications, such as containers, card stock, or speaker cones.

The coarse diameter glass wool fiber compositions, methods, and paper products described herein are advantageous because coarse diameter glass wool fibers are less expensive than fine diameter glass wool fibers. Additionally, coarse diameter glass wool fibers are non-respirable, whereas glass wool fibers having average diameters less than 3 μm are respirable.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the average tearing resistance in grams of force for cellulose-based handsheets weighing 160 grams per square meter (gsm), which were made with varying diameters of glass wool fiber and varying percentages of glass wool fiber by weight. The 411 handsheets comprise fine glass wool fibers having an average diameter of about 3.26 μm. The 716 handsheets comprise fine glass wool fibers having an average diameter of about 4.80 μm. The “coarse diameter fiber” handsheets, which are examples of the novel coarse diameter glass wool fiber paper products, include coarse diameter glass wool fibers having an average diameter of about 7.0 μm. [0017]
FIG. 2 shows the average air resistance in seconds for 300 cubic centimeters of air to pass through 19.2 square centimeters of handsheets having the same glass fiber percentages and diameters as the sheets described in FIG. 1. [0018]
FIG. 3 shows average hygroexpansivity as measured by the percentage increase or decrease in handsheet length when moved from standard conditions (73° F., 50% relative humidity (RH)) and placed in high humidity conditions (80° F., 80% RH) for 24 hours for handsheets having the same glass fiber percentages and diameters as the sheets described in FIG. 1.[0019]

DETAILED DESCRIPTION

Disclosed herein are glass-fiber enhanced, cellulosic paper products including, in part, coarse diameter glass wool fibers. Also disclosed are compositions for making glass fiber paper products including cellulose pulp and coarse diameter glass wool fibers. Additionally, methods of making glass fiber paper products including cellulose pulp and coarse diameter glass wool fibers are disclosed. The coarse diameter glass wool fiber paper products disclosed herein, or made from the compositions or methods disclosed herein, are useful in most any paper application, especially applications in which dimensional stability is desired. That is, the paper products are particularly useful in applications in which limited curling, shrinking, or expanding is desired. [0020]
Coarse diameter glass wool fibers refer to glass wool fibers having average diameters ranging from about 5.5 to about 11 μm. In particular examples the average diameter of the coarse diameter glass wool fibers ranges from about 6 to about 10 μm. In other examples the average diameter of the course diameter glass wool fibers is from about 6.5 to about 9.5 μm. Good results have been obtained using average glass wool fiber diameters of about 7 μm. In particular cases, glass wool fibers having an average diameter of about 7.0 μm with a minimum diameter of about 6.15 μm, and a maximum diameter of about 8.34 μm are used. Coarse diameter glass wool fibers also have significant variation in their diameter to length ratios. For example, in particular cases the coarse diameter glass wool fibers have diameter to length ratios varying from about 1/500 to about 1/4000. [0021]
The glass wool fibers include glass made from any material capable of being made into glass wool fibers. For example, in some cases the glass wool fibers are made from glass compositions comprising boric oxide. In other cases the glass wool fibers are made from compositions comprising low boron concentrations and high barium concentrations, such as the compositions described in U.S. Pat. No. 6,358,871, which is herein incorporated by reference. Good results have been obtained using general-purpose soda/borosilicate glass. In particular cases coarse diameter glass wool fibers were obtained from the Evanite Fiber Corporation of Corvallis, Oreg. [0022]
Coarse diameter glass wool fibers are formed by any process that results in the coarse diameter glass wool fibers described above. In some cases, the coarse diameter glass wool fibers are produced by conventional methods, such as by rotary spinning flame attenuation, or controlled attenuation technology (CAT). These methods are described in detail in U.S. Pat. No. 6,358,871 and one of ordinary skill in the art would be able to determine these and other methods of producing coarse diameter glass wool fibers. Alternatively, such fibers are available for purchase commercially, such as from the Evanite Fiber Corporation. [0023]
Cellulose pulp refers to pulp produced from any cellulosic material. A cellulosic material is any material containing cellulose and which is capable of use in papermaking. In particular examples the cellulosic material comprises wood, such as from a tree. In other examples the material comprises straw, grass, cane, reed, bamboo, woody stalks, such as jute or flax, bast fibers, such as linen, leaf fibers, such as hemp, and/or seed fibers, such as cotton or combinations thereof. In still other cases the material comprises recycled paper or other cellulose based products. [0024]
Cellulose pulp is produced by extracting cellulose from raw, cellulosic material. This involves separating the cellulose from the non-fibrous materials, such as lignin, in the raw, cellulosic material. In particular cases, raw, cellulosic materials, such as logs from trees, are broken down into smaller fragments, such as chips. The cellulose from the chips is separated or extracted by beating or fibrillation of the chips in a digestor. In other cases the pulp is extracted through chemical processes, such as the kraft process or the sulfite process. In some instances kraft pulp from Smurfit-Stone Container Corporation is used. In certain cases pulp is produced through combined mechanical and chemical processes. In some instances the pulp is bleached, while in other instances unbleached pulp is used. In still other examples cellulose based waste products are recycled to produce pulp. One of ordinary skill in the art would be able to determine these and other methods of producing or obtaining cellulose pulp suitable for use in the paper products, compositions, and methods disclosed. For example, Smook, G. A., H[0025] ANDBOOK FOR PULP AND PAPER TECHNOLOGIES, 7^thPrinting (1989), which is incorporated by reference herein, explains numerous mechanical, chemical, thermal, and combination processes for producing pulp for papermaking. The cellulose pulp produced by these methods, or otherwise obtained, is subsequently used to make the enhanced cellulose paper products disclosed herein.
Compositions for making paper products comprising cellulose pulp and coarse diameter glass wool fibers are disclosed herein. In some cases the compositions for making coarse diameter glass wool fiber paper products include coarse diameter glass wool fibers having an average diameter ranging from about 5.5 to about 11 μm. In certain cases the course diameter glass wool fibers have an average diameter from about 6.0 μm to about 10.0 μm. In still other cases the course diameter glass wool fibers have an average diameter from about 6.5 μm to about 9.5 μm. In some examples an average diameter of about 7.0 μm is particularly useful. In particular instances the composition includes cellulose pulp and between about 1% and about 25% coarse diameter glass wool fiber by weight, relative to the total dry weight of the pulp and glass wool fibers. In other examples the composition includes cellulose pulp and between about 1% and about 15% coarse diameter glass wool fiber by weight. Good results have been obtained with compositions including cellulose pulp and between about 3% and about 5% coarse diameter glass wool fiber by weight. [0026]
In certain cases the composition includes an aqueous solution having a pH between about 2 and about 6. In particular examples the aqueous solution has a pH of from about 3 to about 4.5. In other particular examples the aqueous solution has a pH of about 2.5. The aqueous solution can help to disperse the coarse diameter glass wool fibers in the cellulose pulp. In certain cases the aqueous solution includes water and an acid. Any acid or combination of acids can be used. In some cases the acid is sulfuric acid. In other cases the acid is hydrochloric acid, nitric acid, or phosphoric acid. In particular examples the aqueous solution includes about 1% to about 40% acid by volume. In other examples the aqueous solution includes about 10% to about 20% sulfuric acid by volume. [0027]
In some examples additives, such as ceramics, clay, plastics, and/or metallic fibers, that enhance particular properties or the appearance of the resulting paper are included in a composition including cellulose pulp and coarse diameter glass fibers. [0028]
Methods for making coarse diameter glass wool fiber paper products include methods for making paper products using any papermaking technique. Conventional papermaking techniques are explained in Smook, supra, and are well known to those of skill in the art. In some cases a papermaking machine, such as a Fourdrinier machine, is used to make the coarse diameter glass wool fiber paper products described herein. In other cases coarse diameter glass wool fiber paper products are made by hand. Conventional hand-made papermaking techniques are described in the Technical Association of the Pulp and Paper Industry's (TAPPI) “Forming handsheets for physical tests of pulp,” T 205 om-88 (1988), which is incorporated by reference herein. In some cases paper products are made in conformance with such conventional hand sheet-making methods. [0029]
The coarse diameter glass wool fibers are added to the cellulose pulp at any point in the papermaking process before the furnish is discharged onto the screen used to initially form the web. In particular cases the coarse diameter glass wool fibers are added to the cellulose pulp as the raw cellulosic material is processed into cellulose pulp in a pulper/digestor. In other cases the glass fibers are added to the cellulose pulp during stock preparation. In still other cases the glass fibers are added to the furnish just before the headbox of a papermaking machine. [0030]
No special technique is needed to add coarse diameter glass wool fibers to cellulose pulp. For example, in particular instances, coarse diameter glass wool fibers are added by hand, such as from a bucket. In other cases the fibers are dropped into the pulp from a reservoir. In still other cases the coarse diameter glass wool fibers are added to an aqueous solution separate from the pulp, which is subsequently added to the pulp. [0031]
After adding the coarse diameter glass wood fibers to the pulp, the coarse diameter glass wood fibers are dispersed. Dispersion of the glass fibers in the cellulose pulp requires only a small amount of energy or agitation. In some examples a composition including cellulose pulp and coarse diameter glass wool fiber is beaten for about 20 seconds after addition of the coarse diameter glass wool fibers to the pulp. In other examples a composition including cellulose pulp and coarse diameter glass wool fibers is beaten longer, such as from about 5 minutes to about 30 minutes. In still other examples the glass fibers are dispersed without further beating. For example, the movement of the furnish into a stuffbox and thereafter into the headbox of a papermaking machine disperses the coarse diameter glass wool fibers. In certain cases the pH of the furnish is raised in the headbox by the addition of water. [0032]
Once the coarse diameter glass wool fibers are dispersed, the stock or furnish is applied to a screen. In some cases the screen is a wire mesh screen. In other cases a plastic mesh screen is used. In particular examples the screen is part of a papermaking machine, such as a Fourdrinier machine. In other examples the screen is part of a handsheet machine. In still other cases the screen is not a part of any machine. The screen receives the furnish and begins the dewatering/drying process to create a web. In some instances a vacuum is applied to web on the screen to accelerate the dewatering process. In some other cases the web is simply allowed to dry on the screen to produce a paper product. In other examples additional steps are performed to produce a paper product. In some examples a press, such as the press of a papermaking machine, for example a Fourdrinier machine, is used to consolidate and continue dewatering the web to produce a paper product. In some cases the press is cylindrical rolls. In certain instances additional drying steps are performed. In some cases a dryer, such as an oven, multi-cylinder dryer, or heat lamp apparatus is used to remove residual water from the paper product. [0033]
The coarse diameter glass wool fiber paper products disclosed herein include cellulose pulp and coarse diameter glass wool fibers. In some cases the coarse diameter glass wool fibers have an average diameter of about 5.5 to about 11 μm. In particular instances the average diameter of the coarse diameter glass wool fibers ranges from about 6 to about 10 μm. In other instances the average diameter of the coarse diameter glass wool fibers ranges from about 6.5 to about 9.5 μm. Good results have been obtained using an average glass wool fiber diameter of about 7 μm. In certain examples coarse diameter glass wool fibers having an average diameter of about 7.0 μm with a minimum diameter of about 6.15 μm, and a maximum diameter of about 8.34 μm are used. [0034]
The coarse diameter glass wool fibers make up from about 1% to about 25% of the paper product by weight, which percentage is determined by comparing the dry weight of the coarse diameter glass wool fibers to the total dry weight of the coarse diameter glass wool fibers and cellulose pulp. In some cases the coarse diameter glass wool fibers make up from about 1% to about 15% of the paper by weight. In other cases the coarse diameter glass wool fibers make up from about 3% to about 5% of the paper by weight. [0035]
In some cases of the coarse diameter glass wool fiber paper product the paper product further includes additives, such as ceramics, clay, plastics, and/or metallic fibers that enhance particular properties or the appearance of the paper product for particular applications. [0036]
The coarse diameter glass wool fiber paper product has physical properties, such as weight (expressed in grams per square meter (gsm)), tearing resistance, air resistance and hygroexpansivity. In some cases the paper has a gsm of about 90 to about 160. Tests for measuring tearing resistance, air resistance, and hygroexpansivity are explained below in Example 1. The physical properties of the paper product depend in part upon the percentage of coarse diameter glass wool fiber used in making the paper product. For example, for a 160 gsm coarse diameter glass wool fiber enhanced paper product with 1% coarse diameter glass wool fibers, the average air resistance is about 120 s/300 cm[0037] ³, the average tearing resistance is about 158 grams of force, and the average hygroexpansivity is about 0.125, with 3% coarse diameter glass wool fiber the average air resistance is about 108 s/300 cm³, the average tearing resistance is about 146 grams of force, and the average hygroexpansivity is about 0.08, and with 5% coarse diameter glass wool fiber the average air resistance is about 97 s/300 cm³, the average tearing resistance is about 151 grams of force, and the average hygroexpansivity is about 0.18. Of course, these properties depend upon the thickness of the paper product, other additives that can be present in the paper, and the environment in which the physical properties are measured. Example 1, below, describes certain physical properties of particular embodiments of the coarse diameter glass wool fiber paper product provided herein.
The coarse diameter glass wool fiber paper product is useful in any paper product application, especially applications where dimensional stability is desired. In certain examples the coarse diameter glass wool fiber paper product disclosed herein is for use with a conventional printing device, such as an inkjet or dot-matrix printer. In other examples the paper product is paper or board for use as magazine paper, label/card stock, containers, sheathing, or speaker cones. In still other examples the paper product also is packaging paper. [0038]
The following are non-limiting examples of the products, compositions, and methods disclosed herein. [0039]

EXAMPLE 1

In this example coarse diameter glass wool fiber paper products were made with various examples of the disclosed compositions using various examples of the disclosed methods. In this particular example, the coarse diameter glass wool fiber/cellulose composition included coarse diameter glass wool fibers having an average diameter of about 7.0 μm. Paper also was made with finer diameter glass wool fibers having average diameters of 3.26 and 4.80 μm. Tests of the physical properties of the paper products were performed to compare the physical properties of the paper product made with the finer diameter glass wool fibers to the paper product including cellulose and coarse diameter glass wool fibers. This example demonstrates the surprisingly superior physical properties of the coarse diameter glass wool fiber paper product. [0040]
Handsheets were prepared by conventional techniques in order to compare the coarse diameter glass wool fiber paper product to paper products made with finer diameter glass wool fibers as well as ordinary cellulose paper products. Each handsheet compared was produced by first placing cellulose pulp into a pulper jar. Glass wool fibers were then added to the pulp to form a composition of pulp and glass wool fiber. The amount of pulp and glass fiber used in the composition depended on the type of paper product desired. For example, the 5% glass fiber paper product contained 0.7 grams (g) of glass fiber and 11.8 g of cellulose pulp, while the 1% glass fiber paper product contained 0.2 g of glass fiber and 12.3 g of cellulose pulp. [0041]
To the pulper jar was added about 2000 milliliters (mL) of an aqueous solution of water and sulfuric acid at a pH of about 2.5 to form a slurry. The slurry composition was blended (beaten) for five minutes in the pulper jar. This slurry was transferred to a bucket containing an additional 2000 mL of an aqueous solution at a pH of about 2.5. This diluted slurry was stirred for about 20 seconds. Depending on the handsheet weight desired, a particular amount of this slurry was then transferred an automatic handsheet mold as described in Technical Association of the Pulp and Paper Industry's (TAPPI) “Forming handsheets for physical tests of pulp, T 205 om-88 (1988). The handsheet was then couched off the mold and dried in an oven at about 180° F. for about one hour. [0042]
The amount of slurry used to make each sheet was determined by first making a handsheet using 500 mL of slurry and determining the gsm of the handsheet. Dividing the gsm of this handsheet by 500 mLs and multiplying by 100 gave the consistency percentage of the slurry. Dividing the desired handsheet weight by the consistency percentage of the slurry and multiplying by 100 gave the number of mLs of slurry needed to create a handsheet for any given handsheet weight. Handsheets were produced with [0043] fine diameter 411 glass wool fibers (about 3.26 μm average diameter), fine diameter 716 glass wool fibers (about 4.80 μm average diameter), and coarse diameter glass wool fibers (in this specific example having an average diameter of about 7.0 μm) at 1%, 3%, and 5% glass fiber content by weight, and at a handsheet weight of approximately 160 gsm. Additionally, handsheets having no glass wool fibers were produced at a handsheet weight of approximately 160 gsm.
For each of the several handsheets described above, several physical comparison tests were performed. The handsheets were tested for tearing resistance, air resistance, and hygroexpansivity. Tearing resistance was tested with an Elmendorf tearing tester as described in TAPPI's “Internal tear resistance of paper,” T 414 om-88 (1988), which is incorporated by reference herein. This is a standard paper industry test for determining the tearing resistance of paper. This method was used to measure the force perpendicular to the plane of the handsheet required to tear multiple handsheets once a tear had already been started. The Elmendorf tester used in the examples in this application was from the Thwing Albert Instrument Co., of Philadelphia, Pa. The Elmendorf tester was of the pendulum and pointer type and had an analog gram-force scale. For each tearing resistance number reported, four plies of 5.3×6.3 cm sections of the handsheets were torn through a tearing distance of 4.3 cm. The tearing resistance was calculated by reading the gram-force from the analog scale and dividing this energy by the tearing distance and the number of sheets to give the tearing resistance per sheet. [0044]
Air resistance was tested as described in TAPPI's “Air resistance of paper,” T 460 om-88 (1988), which is incorporated by reference herein. This method was used to determine the air resistance of the handsheets by measuring the time required for 300 cubic centimeters of air to pass through a 19.2 cm[0045] ²handsheet sample.
Hygroexpansivity was tested using an optical comparator technique as described in TAPPI's T 402 om-88 (1988), which is incorporated by reference herein. This method was used to measure the changes in the length of handsheets (to the nearest 0.1 mm) over time after the handsheets were transferred from standard conditions (73° F., 50% relative humidity (RH)) to high humidity conditions (80° F., 80% RH). [0046]
Because handsheets do not have a machine and a cross direction, the hygroexpansivity of the handsheets was measured only in one direction. In the examples described in this application the hygroexpansivty was measured using an optical comparator by Menasha Corp of Neenah, Wis. that included a base plate having a scale marked in millimeters with two moveable optical lenses set in a groove running the length of the instrument. Using a pencil or pen, the sample was divided in half by drawing from one end through the middle and to the other end of the handsheet. Incisions were made across the line approximately 1” from each side of the handsheet. The optical comparator was placed so that the reference line running the length of the instrument is directly on top of the line drawn on the handsheet. The left eyepiece of the optical comparator was placed so that the “0” mark was at the point where one incision crosses the drawn line. This is the reference point. [0047]
The right eyepiece was moved so that the cross hair lined up with the opposition incision along the drawn line and number on the scale was determined to the nearest 0.1 mm to determine the initial length. The handsheet was then moved into the high humidity environment. After at about 24 hours the handsheet was again measured as described above to determine the final length and accordingly the hygroexpansivity, which is the percent change determined by the final length of the handsheet less the initial length of the handsheet divided by the initial length of the handsheet. [0048]
When hygroexpansivity is measrured for commercial paper products made on a machine, the hygroexpansivity is determined in both the machine and cross directions in the same manner as described above (but instead of measuring changes in only one direction, two lines and four incisions are made with the initial and final lengths determined for both directions). [0049]

The results of these tests are summarized in the table below and illustrated in FIGS. 1-3.

TABLE I


			Average
		Average Tearing	Hygroexpansivity
	Average Air Resistance	Resistance	as percentage change in
	in seconds per 300 cubic	in grams of force, for 6	length over 24 hours at high
% Glass wool fiber	centimeters, for 6 samples	samples	humidity for two samples

0%	141.6	182.28	0.225
1% 411 fiber	116.33	152.61	0.115
3% 411 fiber	79.5	145.6	0.315
5% 411 fiber	68.83	134.51	0.22
1% 716 fiber	103.17	139.52	0.245
3% 716 fiber	82.17	134.67	0.16
5% 716 fiber	66.83	142.75	0.7
1% coarse diameter	119.83	158.33	0.125
fiber
3% coarse diameter	107.67	145.67	0.08
fiber
5% coarse diameter	96.5	150.73	0.18
fiber

With reference to FIG. 1, the results for the 0% glass fiber handsheets and the 411 and 716 fine diameter glass wool fiber handsheets illustrate an expected downward trend in tearing resistance as fiber diameter increases. Surprisingly, handsheets including coarse diameter glass wool fibers exhibited higher tearing resistance for each percentage of glass fiber as compared to handsheets including the fine diameter, 411 and 716 glass wool fibers (i.e. average diameters of about 3.26 and about 4.80 μm). For example, at 1% glass wool fiber content, handsheets including [0051] fine diameter 411 glass wool fibers (about 3.26 μm average diameter) had a tearing resistance of 152.61 grams of force and handsheets including fine diameter, 716 glass wool fibers (about 4.80 μm average diameter) had a tearing resistance of 139.52 grams of force. Surprisingly, handsheets including coarse diameter glass wool fibers (about 7.0 μm average diameter) had a tearing resistance of 158.33 grams of force. One of ordinary skill in the art would have expected handsheets including coarse diameter glass wool fibers to tear more easily than handsheets including fine diameter 411 or 716 glass wool fibers.
With reference to FIG. 2, the results for the 0% glass fiber hand sheets and the 411 and 716 glass wool fiber handsheets illustrate an expected downward trend in air resistance as glass wool fiber diameter increases. Surprisingly, handsheets including coarse diameter glass wool fibers exhibited higher air resistance for each percentage of glass fiber as compared to handsheets including the [0052] finer diameter 411 and 716 glass wool fibers. For example, the measured volume of air passed through handsheets including 3% 411 glass wool fibers in 79.5 seconds, while the same volume of air passed though the handsheets including 3% coarse diameter glass wool fibers in 107.67 seconds.
With reference to FIG. 3, the hygroexpansivity of handsheets including 411 or 716 glass wool fibers was generally equivalent to or greater than cellulose only handsheets. Interestingly, handsheets including coarse diameter glass wool fibers exhibited lower hygroexpansivity as compared to both cellulose only handsheets and handsheets including fine diameter glass wool fibers, such as 716 glass wool fibers. [0053]

EXAMPLE 2

In this example the coarse diameter glass wool fiber paper product is made from a composition including cellulose pulp and coarse diameter glass wool fibers, on a large scale, by commercial papermaking methods. [0054]
Commercial papermaking methods are well known in the art. In this example raw cellulosic material in the form of wood chips is supplied to a chemical/thermal/mechanical digestor. The digester produces cellulose pulp by heating the chips and by digesting the chips in a kraft cooking solution. This pulp is subsequently used for stock preparation. Alternatively, pulp may be purchased for use in stock preparation. Stock preparation includes additional beating or refining of the pulp in a pulper with an aqueous solution to prepare a furnish for making paper. The aqueous solution comprises water and sulfuric acid, having a pH of approximately 2.5. A higher or lower pH, such as from 2-6 is sometimes used. [0055]
Coarse diameter glass wool fibers (having average diameter of about 5.5 to about 10 μm) are dispersed in the cellulose pulp that has been beaten to a degree of freeness (prerefined) in the pulper at any time during stock preparation to form a composition including cellulose pulp and coarse diameter glass wool fibers. The coarse diameter glass wool fibers are added to the cellulose pulp by simply dropping them from a reservoir of glass fibers stored above the pulper. After adding the coarse diameter glass wool fibers, the stock is beaten or refined for an additional ten minutes, although longer or shorter periods are also used depending on the rate of beating and the amount of glass wool fiber to disperse. The amount of coarse diameter glass wool fiber dispersed in the stock is an amount equal to from about 1% to about 25% of the total dry weight of the glass fibers and cellulose. [0056]
Once the furnish is prepared it is supplied to a constant head tank (stuffbox). The furnish is fed from the stuffbox through a control valve to the headbox of a Fourdrinier papermaking machine. The headbox discharges the furnish onto a continuous wire screen. There the furnish begins to dewater and forms a web through the action of gravity and the application of a vacuum. The web is transferred to the press section of the machine where cylindrical rolls compress the web to remove additional water and to consolidate the web into paper. After pressing, the paper is transferred to the dry end of the machine where residual moisture in the paper is evaporated in an oven or multicylinder dryers or cans. In certain cases the paper is dried with infrared lights. In particular cases, the web is surfaced-sized before drying, or example, by application of a starch solution to reduce the paper's rate of liquid penetration. Once dry, the paper is rolled or cut into sheets depending on the particular application for which the paper is to be used. [0057]
The above-described examples merely provide particular examples of coarse diameter glass wool fiber paper products, and compositions and methods for making such paper products. They are not intended to be limiting in any way. Moreover, although these examples have been described herein in detail, it will be understood by those of skill in the art that variations may be made thereto without departing from the spirit or scope of the appended claims. [0058]

Claims

We claim:

1. A paper product comprising:

cellulose pulp; and

coarse diameter glass wool fibers.

2. The paper product of claim 1, wherein the coarse diameter glass wool fibers have an average diameter between about 6.0 and about 10.0 microns.

3. The paper product of claim 2, wherein the coarse diameter glass wool fibers comprise a low-boron, high-barium composition.

4. The paper product of claim 2, wherein the coarse diameter glass wool fibers have an average diameter between about 6.5 and about 9.5 microns.

5. The paper product of claim 4, wherein the coarse diameter glass wool fibers comprise a low-boron, high-barium composition.

6. The paper product of claim 4, wherein the coarse diameter glass wool fibers have an average diameter of about 7.0 microns.

7. The paper product of claim 1, wherein the coarse diameter glass wool fibers comprise about 1% to about 25% by weight of the total dry weight of the cellulose pulp together with the coarse diameter glass wool fibers.

8. The paper product of claim 7, wherein the coarse diameter glass wool fibers comprise about 1% to about 15% by weight of the total dry weight of the cellulose pulp together with the coarse diameter glass wool fibers.

9. The paper product of claim 8, wherein the coarse diameter glass wool fibers comprise about 3% to about 5% by weight of the total dry weight of the cellulose pulp together with the coarse diameter glass wool fibers.

10. The paper product of claim 9, wherein the paper product has a weight of about 160 grams per square meter, and wherein the paper product has a tearing resistance of about 145 to about 150 grams of force.

11. The paper product of claim 10, wherein the paper product has an average air resistance of from about 108 to about 97 s/300 cm³.

12. The paper product of claim 11, wherein the paper product has an average hygoexpansivity of about 0.08 to about 0.18.

13. The paper product of claim 9, wherein the coarse diameter glass wool fibers comprise about 5% by weight of the total dry weight of the cellulose pulp together with the coarse diameter glass wool fibers.

14. The paper product of claim 13, wherein the paper product has a weight of about 160 grams per square meter, and wherein the paper product has a tearing resistance of about 150 grams of force.

15. The paper product of claim 14, wherein the paper product has an average air resistance of about 97 s/300 cm³.

16. The paper product of claim 15, wherein the paper product has an average hygoexpansivity of about 0.18.

17. A method of making a paper product comprising:

preparing a stock comprising cellulose pulp, coarse diameter glass wool fibers, and an aqueous solution;

applying the stock to a screen to form a web; and

drying the web to form a paper product.

18. The method of claim 17, wherein the coarse diameter glass wool fibers have an average diameter between about 6.0 and about 10.0 microns.

19. The method of claim 18, wherein the coarse diameter glass wool fibers comprise about 3% to about 5% by weight of the total dry weight of the cellulose pulp together with the coarse diameter glass wool fibers.