JPS58214570A - Absorbable dry forming fibrous web - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to fibrous absorbent webs, and more particularly to dry formed fibrous webs with improved wipe drying properties.

It is well known in the papermaking art to form a high quality paper web by mechanically beating the wood pulp 7" fibers prior to forming the web. This beating operation improves the freeness of the fibers. In order to reduce and, in many cases, achieve a strong web structure, the fibers are actually fibrillated to form interconnected fiber segments. A typical method of
U.S. Patent No. 3,582.14, which became another patent
It is disclosed in No. 0.

When wood pulp 7° fibers are beaten to a significant degree of seedness, thereby reducing freeness, the webs formed therefrom are generally very dense. This type of web provides an excellent substrate from which high gloss papers are formed, as disclosed in U.S. Pat. No. 2.999.7B6 to Downs et al.

In summary, it is well known to prefibrillate aqueduct pulp fibers to form strong, dense, wet-laminated sheets. These sheets are known to be desirable for use as printing papers, papermaking, and other end uses requiring high strength and/or high density; It was considered undesirable to form such dense, strong sheets for subsequent use as feed mats. In particular, the high strength structure of such mats results in the ability, in fiberizing operations, to substantially separate or separate the fibers therefrom, which must be achieved to form a substantially cohesive web. is known to interfere with Therefore, those skilled in air lamination techniques have not considered reducing the freeness of the wood pulp 7°m fibers used to form feed mats intended for use in air lamination techniques. (I didn't want it). To the applicant's knowledge, feed mats formed from highly beaten wood pulp fibers have not been used in any air lamination or similar dry forming process to form absorbent fibrous web structures.

In the present invention, the predominant amount of heavy electric fiber is approximately 6.35 m.
m (1/4 inch) or more paper making length (papermak
length) and 20m1F'/
Absorbent dry-formed fibers, characterized in that they are fine wood pulp fibers having a roughness of less than 100 m, said fine wood pulp 7″ fibers having experienced a reduction in freeness of at least 150 by machining. It is believed that this magnitude of reduction in the freeness of the wood pulp fibers is necessary to achieve the advantageous results of the present invention.

The present inventors have discovered that, contrary to prior teaching, dry formed fibrous webs of reduced moisture content can be used with great advantage. determine their freeness, most preferably
It has been discovered that machining the fibers to a degree less than 500 significantly increases wipe dry properties.

However, contrary to the coarseness of machined wood pulp fibers, when
The increase in sex is the most obvious.

For the purposes of this invention, the term fine wood pulp fibers is defined as
It means fibers with a coarseness of less than 0 m / 100 m. These are preferably gold leaf trees.

In the present invention, freeness (Freeness 1el+1
or freeneee) is the Kanagaian standard for pulp freeness, TAPP method T227M-5
Measured according to 8.

The absorbent dry-formed webs of the present invention have significant benefits for forming blankets for domestic and industrial use, and more generally for pond end uses where wipe dryness is considered important. have. The dry formed webs of the present invention have a run of less than 4 oz/sq yd, and most preferably [J, 0678~
0.1556 kg/m2 (2-4 ounces/square yard)
is within the range of

# It is critical that the predominant amount of the fiber composition by weight in the dry-formed web is the finely machined wood pulp fibers since the finely machined wood valves are responsible for increasing the overall wipe drying properties of the web. However, a small percentage of the fiber composition, i.e. about 25-60% by weight,
It is believed that long steno length fibers can be incorporated into the web for the purpose of increasing strength. Webs containing such long fibers are disclosed in U.S. Pat. No. 4,145;
No. 464 [McOnnell et al.] and No. 4.154.948 Baker, Jr.
ker.

It is known in the prior art as exemplified by the description in J.J. These recent patents are incorporated herein by reference.

In the most preferred embodiment of the invention, an acrylic binder, or other suitable adhesive, can be applied to stabilize the web. Most preferably, the binder should constitute less than 5% of the total weight of the final web structure. It is desirable to keep the binder weight as low as possible while maintaining the desired web strength so that the binder does not significantly interfere with the absorbency of the web. Adding too much binder to the web actually interferes with or negates the effects that can be achieved by machining operations.

Other objects and advantages of the invention will become apparent from the description of the best mode thereof.

BEST MODE OF THE INVENTION This invention relates to absorbent dry formed fibrous webs, most preferably webs formed by conventional air laminated web forming operations.

Preferably the air laminated web includes a low amount of binder, ie, less than 5% of the total weight of the adhesive bonded structure.

In the present invention, one or more wood pulp wraps or mats are fed to a fiberizing roll to separate the individual fibers from the mat, and then a foraminoue fo.
rmingF3surface) in an air stream. Such fiberization techniques include Trance O, Addy and Davit P.
.

Patented by David P. Gutman, Scott Paper Company (5co.
No. 4,118,832 issued to TT Paper Company. This patent is incorporated herein by reference.

It is contemplated that the air laminated webs of the present invention may include small amounts by weight of long staple length fibers such as rayon, polyester, and the like.

A typical technique for forming such a web is that of John H.
Baker, Jr. (John H, Baker, J
No. 4,134,948 issued to Scott Paper Company. This patent has already been incorporated herein by reference.

Regardless of the type of air-laminated web formed, in the present invention the wood pulp wrap processed through the fiberizing equipment has a
．． Made of fine wood pulp 7° fibers with a papermaking length of 35 mm or less. Additionally, the fine wood pulp fibers used in the present invention have experienced a reduction in freeness of at least 150 by mechanical processing and are preferably reduced in freeness by treatment in a conventional mill as part of the parno razzo forming operation. experienced a decrease in the degree of

As previously explained, the pulp mats or wraps formed by the above techniques are extremely strong and dense and extremely difficult to form into fibers. To combat this problem, we used a release agent (Aebondθr) before forming the wrap.
) was added to the paper stock. This is a mutual fiber bond (1n
terfiber bonding) and have been found to sufficiently disrupt terfiber bonding to enable the desired separation of individual fibers from the wrap in the fiberization operation. The release agent can be of any suitable type that does not significantly interfere with the absorbency of the web. In a preferred embodiment of the invention, penzyl chromilam chloride debonder is used.

In forming an air laminated web, after the individually separated fibers are attached to the forming surface, the web can be sprayed with an adhesive on opposing surfaces of the web to stabilize the structure. The method disclosed in the above-referenced Becker patent allows the web to be embossed prior to application of the adhesive, if desired.

The inventors have found that it is quite surprising that the air seed layer webs formed according to the present invention, whether embossed or not, are of the same type of fine wood pulg fibres, but are formed from fibers in an unbeaten state. compared to similar webs, and also compared to air phase webs formed from beaten oily fibers having a coarse density greater than 20 WJ/i 00 m. I discovered that This is clearly explained by the data shown in Table 1.

The spilled liquid wiping drying ability of the present invention was measured by the following method.

First, a sample of the web to be tested is sledded (10
It was attached to a padded surface of 6.5 cm x 6.5 art.

Second, the sled was attached to an arm designed to traverse the sled by 4% off the rotating disk.

Third, weigh the sled, and measure the total weight of the sled and sample.
The sled and Tachibana arm were placed on a horizontally rotating disk with the sample being pressed against the surface of the disk by a weighted sled. The leading edge of the sled (6, 30 side) and 10 cm of the sled installed along the radial line of the disc, along with the center line, so that the tracking 6.6 brocade end is located near the periphery of the rotating plate. ].

Fifth, 0.5 ml of water was placed in the center of the disc in front of the leading end of the sled (sufficient amount of surfactant was added to the water so that when wiped, it formed into discrete droplets). rather, it remains as a film). A 0.1% Tergitol 15-8-15 solution (a nonionic surfactant available from Union Carbide) was used in this test.

Sixth, a disc with a diameter of about 60 cm has a speed of about 65 rpm
, while the transverse arm moves the sled across the disk at a speed of about 2.5α until the trailing end of the sled crosses and leaves the outer edge of the disk, at which point the test is stopped. (approximately 15 seconds from start to stop of the test).

Seventh, during the test where the sled wiped across the disc, the wiping effect of the test sample was observed for the aqueous solution. (Observing the wet surface, a wiped dry area appeared in the center of the disc and expanded radially on the disc).

Eighth, the test was stopped (when the tracking end of the sled passed the edge of the disc) and the size of the area that had been wiped dry and soaked was observed (if any). .

The test was carried out under conditions of constant temperature and relative humidity (70
below ±2°F1 relative humidity 65% ±2%). The test was repeated and the average of 11α (step 8), expressed as the square of the wiped dry area, was defined as the wipe dryness index of the sample tested. To help observe the size of the area on the dry disk wiped by the test sample (steps 7 and 8), the concentric score line was set to 50.10 (1,200, filter 0
Prepare the surface of the disk corresponding to a circle of 0.400.500.750 and i, o o o squared, so that the side of the dry area is marked with a reference score line indicating the known area and the dry area visually. can be compared and measured quickly.

The wipe dryness index measured by the above test is considered accurate to a value of ±50. Despite this range of error, from a technical standpoint, a significant difference in wiping dryness between compared webs is reflected in a difference in wiping dryness index greater than ±50.

Table 1 shows the difference between beaten and unbeaten Brown's Wick.
llNvick) Pine (oil fiber 204/100m
The tested differences in wiping drying index (with larger crude density) are within experimental error (±50). Therefore, when rough Brown's Wick pine was beaten to a freeness of 450, reducing the freeness of the originally purchased or manufactured bulb from about 700 to about 250, the change in wiping drying was even However, it is considered not technically significant.

However, when wiping drying was tested on webs formed from unbeaten and beaten northern kraft fibers, significant wiping drying improvements were found in the beaten samples.

Northern Cloud fibers are considerably less thick than Brown's Wink pine and have a roughness of about 18 mg'/100 m. Note that the difference in wipe drying is statistically significant for both embossed and unembossed web variants.

Green Picto (greθr1 pic), a northeastern softwood fiber with a roughness of about 13 mg/l
Further comparison was made using Again, a comparison of webs formed from beaten Picto fibers and webs formed from unbeaten Picto fibers shows that beating the fine wood pulp fibers has a significant and strong effect on wipe drying. .

In the present invention, the machined fine wood pulp 7° fiber is about 6-55
It has a weaving length of mm or less. Preferably, these fibers are of a grade down to lengths of about 1 or less and include a significant portion of the fiber supply, i.e.
Bauer-Mack net (
Bauer-Me Nett) Includes what is retained on a 48 mesh screen when sorting using the wet sorting technique. In particular, 7'l of fine wood pulp (approximately 16-25% by weight of the miscellaneous) is separated by the Bauer-Macknet sorting technique through a series of screens having mesh sizes 14, 28, 48 and 100 in a regular series of At the time, it was kept on the mesh screen for 4 days.

To explore the mechanism responsible for the improved wipe drying provided by the present invention, separate air-laminated fibrous webs were formed from fine wood pulp fibers collected at each of the screens used in the Bauer-Macknet fractionation operation. They were formed from both beaten and unbeaten fibers collected on each screen and compared. The results are shown in Table ■.

Within the range of experimental error, it can be argued that the effect of beating various parts, except for the part collected with the 48-mesh screen, is extremely small. The portion collected with this 48 mesh screen showed more than a 5x increase in wipe dry weight for the embossed air laminated web and a 4x increase for the unembossed web.

From the above observations, it can be seen that the length of fine wood pulp 7° fibers used to form the web of the present invention must contain a fiber portion that can pass through a 28 mesh screen but remain on a 48 mesh screen. I think it must be done. The use of the feature N' in the claims for "length" wood pulp fibers refers to wood pulp fibers having portions of such fibers, preferably such wood pulp fibers having a length of 15 It means that it consists of more than one component.

Claims (9)

[Claims] (1) The predominant amount by weight of the fibers is paper-length fine wood pulp fibers, and the fine wood pulp 7° fibers exhibit a reduction in freeness of at least 150 upon machining. Absorbent dry-formed fibrous web. (2) An absorbent web according to claim 1, characterized in that a binder is included on the opposing surfaces of the web to stabilize the structure. (3) Claim 1, characterized in that the fine wood pulp 7° fiber has a freeness of less than 500.
Absorbent web as described in Section. (4) Fine wood pulp 7° fiber of papermaking length is TAPPI
14-2 when fractionated using the Baawomacnet wet fractionation technique described in standard T2530θ-75.
The absorbent web according to claim 1, characterized in that the absorbent web contains 4,815% or more of the mesh that passes through the mesh screen. (5) The absorbent web according to claim 1, 2, or 6, wherein the fine wood pal 7° fibers include Northeast Kraft fibers. (6) The absorbent web of claim 1, 2, or 6 characterized by a velocity of less than 4 ounces per square yard. (7) Claim 1, characterized by embossing to form a large number of spaced compressed high bulk regions with low density high bulk regions arranged here and there;
The absorbent web according to item 2 or 3. (8) The absorbent web according to claim 1, claim 2, or claim 6, wherein the fiber content is 100% of wood pulp fibers. (9) The absorbent web according to claim 5, wherein all of the wood pulp fibers are the fine wood pulp 7° fibers.