CA1181908A - Treatment for improving saturability in normal saturating furnish - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Improved resin saturating paper is produced by a mechanical treatment of various types of pulp resulting in twisting, kinking, curling and collapse of the fibers in the saturating furnish. The improved saturating paper has reduced bulk and decreased resin penetration time and increased resin pick up at a given Williams slowness for all the normal components of saturating furnish as well as a typical mixture of the components.

Description

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TREATMENT E~OR IMPROVING SATURABILITY
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IN NOI~AL SATURATING FURNISH

; This invention rela-tes to resin saturating papers which are more economic to manufacture and which are pene-tra-ted with resin more rapidly and more complete]y. More particularly, this inven-tion relates to resin satura-tinc3 paper having reduced bulk, decreased resin penetration times and increased resin pickup and a process for producing the improved sa-turating paper.
Saturating paper is designed to be impregna-ted wi-th resin. Several shee-ts of resin-imprec3nated paper are converted into a laminate by consolidation and curing in a hea-ted press.
Conventional decorative laminates, for example, involve print and overlay sheets impregnated with melamine-formaldehyde resin combined wi-th several core stock shee-ts impregnated with phenol-formaldehyde. In a heated press the mul~-ply assembly is converted to a monolithic panel by polymerization and cross-linking of the resins.
To perform sa-tisfactorily in this service, a sa-turating paper must possess a special combination of carefully-controlled ~0 properties. First of all, the basis weight must be con-trolled within tight specifications. Not only must it be controlled across and throughou-t a roll, it mus-t also be controlled on a quarter-inch to two-inch scale. This lat-ter property is generally referred to as forma-tion and is judged by the show-through of ligh-t through the shee-t. In this case, thin places transmit more light than the heavier weight clumps and fiber knots. For , J ~ 9 0 ~
a good saturatlng paper, this formation or show-throu~h shoul,d be of low contrast wi-th little clifference in light transmission from the da,rkest to the ligh-test places.
Good saturating sheets are also relatively clean withou-t sizeable shives or unfiberi,zed pieces of wood. Such material constitutes nonuniformities in the structure causing surE~Ice roughness and points of stress concentration. This material i.s not readily i~pregnated with resin and thus can become~ the site of blister in:itiation.
The important propertles of saturating papers, however, are those that control the ra-te of resin imbibition and its dis-tribution -throughout the sheet. These depend on the size and number oE the interfiber voids or pores in the sheet~ Two special terms are used to refer to these properties:
"saturabili-ty" and "penetrabilityO"
Saturabi]ity describes those paper-related properties which control the dynamic short term phenomena associated with the imbibition of resin. It includes all the sheet properties -that control the quanti-ty of resin picked up during the interval

2~ between contacting the sheet with resin and the removal of excess resin. Because of the short time interval involved, only the larger pores on the sheet play a significant role in determining saturability.
Penetrability describes those sheet proper~ies which contrvl the distribution of resin within the sheet as equilibrium is approached. Penetrability involves those sheet-related proper-ties which act to move the resin imbibed by the larger voids or pores of the paper into -the smaller diameter pores and distribute it throughout the paper. This process begins when the resin first (3 ~
contac-ts the sheet and continues until the resin is solidified in the press. The number and size disbri~u-tion of the smaller pores play the major role in determining penetrability.
Since both these properties are very complex and only partially understood, practical papermaking requires the use of more readily measured a-ttrlbutes to guide the manufacturing process. Apparent density or its reciprocal, bulk, is often used. Since the density oE the papermaking fibers are relatively constant, the difference in the apparent density of the sheet and that of the fibers i5 an indication of the total void or pore volume present.
A paper with low apparent density (high bulk) will possess a hiyh total pore volume, i.e., many large diameter pores, and hence will have hiyh saturability. Conversely, a high apparent density sheet possesses more small pores. This will result in less saturability and more penetrability. The apparent den~ity of the sheet is generally controlled by increasing or decreasing the degree of pulp refining and/or pressing and calendering.
In practice it has been found desirable to use a furnish consis-ting of a mixture of softwood and hardwood pulps.
The shorter, thinner, hardwood fibers make it easier -to produce paper with the required uniformity of shee-t formatlon. Because -the hardwood Eibers are smaller they result in a greater number of smaller-sized pores wl~ich enhance penetrability. Pine fibers are necessary to give the sheet adequate strength to enable its processing on the paper machine and in the resin impregnating operation. The pine fiber being larger and stiffer tends to give bulk to Ihe sheet thus enhancing saturability.

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In fabricating panels from resin-impregnated papers r it has been found necessary to use sufficien-t resin to insure tha-t, after pressing, all inter-:Eiber voids have been filled with resin. If this is not achiev~d, the physical proper-ties and water absorption characteriskics of the panels will be impaired. 5ince resin is more ~expensive than an equal volume of paper fiber, it is desirable to minimize the quantity of resin used. Saturating papers with high penetrabilities are, therefore, preferred. In these, capillary forces ensure that all the finer pores are wet with resin and microscopic voids are thus eliminated.
U.S. Patent 3,8~7,934 does teach a process for producing high strength, high yield hardwood pulp which involves modifying the alkaline chemical pulping treatment and subsequen-tly mechanically -trea-ting the pulp to cause fiberiza-tion along the fiber surfaces without substantially fracturing ; the ~ibers. The saturating sheet prepared from the high yield hardwood pulp did imbibe resin at a rate comparable to a convPntional, hardwood and pine pulp-containing sheet.
U.S. Patent 4,060,450 describes a high yield saturating paper characterized by a high yield hardwood component of 65% or higher and up to 35~ of a lower yield softwood component. The pa-tent further specifies that the paper contain from 8% to 15~ lignin, which must be primarily hardwood lignin, to avoid rapid tool deterioration. The saturating paper described does not exhibit the desired characteristics of reduced bulk and decreased resin penetration times and resin pick up over conventional saturating sheets containing lower lignin contents.

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ThereEore, it is a genera~ object of this invention to produce a resin saturating paper with improved penetra~
bility. More particularly, it is an object of the invention to provide a resin saturating paper produced from various types of pulp which exhibits reduced bulk, decreased resin penetration time and increased resin pick up at a given Williams slowness. Another object of the invention i9 to provide a saturating paper with reduced shives and improved ~irt dispersion. A further object is to provide a process for producing the improved saturating paperO
It has been found that a saturating paper with exceptional penetrability can be produced from various types of pulps which have been subjected to mechanical treatment at high pulp consistencies which results in twisti.ng, kinking~ curling, and lumen collapse of the fibers~ The saturating paper made from pulp that has been so treated also exhibits significantly fewer shives and improved dirt dispersion. Saturating papers with adequate resin saturability and penetrability can be formed with more rapid drainage on the fourdrinier thus generally permitting more rapid rate of manufacture, i.e., higher machine speed. Alternatively, this property may permit the manufacture of sheets of higher basis weight than is otherwise possible. According to the present invention, then, there is provided an improved resin saturable paper made from hardwood or softwood pulps or mixtures thereof produced by the alkaline pulping processes for impregnation with a phenolic resin wherein the improvement comprises . ~i 9 ~ ~

including in -the paper a-t least 10~ by weiyht of Eibers produced by subjecting wood pulp -to a first mechanical treatmen-t -to raise the wood pulp from a lower consistency of below 20% to a higher consistency of Erom 20g~ to 60%
and Eurther subjecting the higher consistency wood pulp to a second mechanical treatment at an energy lnpu-t level of from 0.2 to 8.0 hpd/ton producing twisted, kinked, curled and collapsed fibers, the paper exhibiting reduced bulk and higher density, decreased resin penetration time and increased resin pickup characteristics over conventional resin saturable paper.
According to another aspect of the present inven-tion, there is also provided in a method for treating wood pulps produced by alkaline pulping processes to produce a resin saturable paper exhibiting reduced bulk and higher density, decreased resin penetration ti.me and increased resin pickup characteristics relative to conventional resin saturable paper, the improvement which comprises including in the paper at least 10% by weight of fibers produced by subjecting wood pulp to a first mechanical treatment to raise the wood pulp from a lower consistency of below 20% to a higher consistency of from 20~ to 60%, and sub~ecting the higher consistency wood pulp to a second mechanical treatment at an energy level input of from 0.2 to 8.0 hpdlton producing twisted, kinked, curled and collapsed fibers.
Embodiments of the invention will now be described in greater detail and will be better understood when read in conjunction wi-th the following drawings in which:

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FIGURE 1 is a graph of the eEfect of the invention treatment on bulk as a function of Wi].liams slowness for untreated pulps and pulps treated at an energy level of 4.0 hp-daysiton.
FIG~RE 2 is a graph of the effect of the invention treatrnen-t on bulk as a :Eunction oE ~illiams slowness -Eor untreated pulps and pulps trea-ted at an energy level of 8.0 hp-days/ton~

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FIGURE 3 is a graph of the effect of the inven-tion treatmen-t on bulk as a func-tion of Williams slowness for untreated mixtures of pulps which represent the normal components of saturating furnish and mixtures treated at an energy level of 6.0 hp-days/-ton.
E'IGU~E ~ is a graph of the effect of the invention treatment on the time required for a standard resin to penetra~e through 5% of the sample area as a function of bulk for samples of untreated pulps and puLps trea-ted at an energy level of 8.0 hp-days/ton.
FIGURE 5 i5 a graph of -the effect of the invention treatment on the 5% resin penetration time as a function of bulk for untreated mixtures of normal saturating furnish component pulps and mix-tures treated a-t 6.0 hp-days/ton.
FIGURE 6 is a graph oE the effect of adding hardwood pulp treated by the invention process to uiltreated hardwood pulp on the resin penetration time.
The superior and unexpected properties of the saturating paper of this invention result from treating hardwood or softwood high consistency pulp produced by an alkaline pulping process, such as sulfate processes, either continuous or batch, or mixtures of sllch pulps, with a subsequent mechanical treatment step or steps which result in twisting, kinking and curling of the fibersO
Inasmuch as the invention lies in the discovery that pulp~ treated according to the process described result in substantially improved resin pene~rability, the particular type of mechanical defibration or specifi.c equipment employed is not essential ~o the invention. It is essential that the result of the mechanica:L defibration is the twisted, kinked, curled and collapsed cellulose fibers .in orde.r for the saturating paper of this invention to achieve the enhanced characteris-tics claimed herein .
To achieve -the desired effect of the mechanical treatment on the fibers, -the pulp should be of relatively hiyh consistency, i.e., 20~ to 60% solids, when subjected to the mechanical txeatment. The preferred pulp consistency is from 30% to 3S%.
A more detailed description of the invention can be ~leaned from the following examples.

~ o demonstratethe method of the invention, four different types of pulp, representing the normal componen-ts of saturating furnish, were treated by the invention process. The pulp samples were 11~ softwood pulp, ~2) hardwood pulp, 13) sawdust pulp and (4) saturating broke (saturating furnish which has been ormed from a mixture of hardwood and softwood pulps and dried and then repulped ~or mixing with the virgin pulp~.
The pulp samples ranged in consi~tency from about 7%
to about 28%. Therefore, the pulp was first di.luted to about 5~ consi.stency in a low energy repulper. The temperature was adjustecl to about 45C using direct steam, and samples were removed as tile un-treated controls.
The pu].p sample slurry was next pumped to a screw press for the first treatment stage where the consistency was raised to from 30~ to 35~. Some twisting and curling did occur.
The particular screw press employëd in the examples was a Sudor loOR press, but there are other acceptable means of achieving the increased consistency. Samples were removed for ~0 evaluation after screw pressing E'rom -the screw press, the pulp was -transferred by mea~s oE a feed screw directly into a twin screw machine for ~urther mechanical deEibration, or a second treatment stage. The twin screw apparatus employed in the examples is that described in Swedish Patent 210,862, July 1967, and Swedish Paten-t 314,288, November 11, 1~69. This stage of mechanical treat~ent serves to twist, compress, curl, knead and shear the pulp be-tween very closely spaced, counter ro-tating, intermeshing screws without actually shortening the fibers further. Each pulp sample was subjected to three different energy inputs in -this second stage treatment corresponding -to app~oximately 70, 110 and 140 kwh/ton pulp (~, 6 and 8 hp-days/ton pulp). After -treatment, the pulp was immediately quenched in 25C water to cool the pulp. The actual running conditions are given in Takle I. (see next page) EX~PLE 2 A series of standard handsheets were run to determine the effect of the invention process on the normal strength properties of the pulps. Also, a large number of 10 x 12 inch handsheets were made for Williams Pene-trescope evaluations. The pulp samples of Example 1 were prepared in a five pound Valley beaterr and the charge in every case was 2500 grams of O~D. (oven dried3 pulp made up to 90 liters giving a consistency of 2.77% in the beater.
The norma]. procedure was to adjust the pH in the beater to 7.0 and to make standard sheets at zero minutes beating time after determining the slowness. The pulp was then beaten to obtain slowness of 20, 30 and 70 seconds. Standard handsheets were made at all slowness levels. Fi~teen of the 10 x 12 inch heavy sheets (200 g/m ) were made at both 20 and 30 seconds Williams slowness on the Williams sheet mould. The heavy sheets were _ ) O U~ U) ~D CO
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pressed and -then dried individually on an electrically heated p]a-te dryer. The results (interpolatecl to 25 seconds Williams slowness~ :Eor -the standard handsheets are presented in Table II.
(see next page) In general, for all the pulps, the invention process caused a decrease in bulk, a decrease in tensile, and an increase in bo-th s-tretch and work to b.reak at constant slowness.
Specifically, the most significan-t effect o~ the invention process is to greatly decrease the bulk of sheets made from pulps at a given slowness level. Conversely, at a given bulk, the slowness ti.e., drainage resistance) is lower for treated pulps. This effect i.s shown quite vividly in Figures 1, 2 and 3.

All of the resin penetration data was determined on the 10 x 12 inch handsheets which have a basis weight in the range of 200-220 g/m2. The instrurnent used for this study was the Williams Penetrescope in which the time in seconds was determined for a standard resin to penetrate through 5~ of the sample area and 95%
of the sample arPa. This instrument measures a combination of ~o saturability and penetrability since an excess of resin is present throuyhout the test. The shorter the Penetrascope time, the more readily the sheet imbibes resin. Also, the percentage resin pickup was determined by freezing a sample at the 5% show-through level in liquid nitrogen, and compared to an unpenetrated sheet.
rrhe res n utilized in ~his evaluation was phenol-formaldehyde resin of 71.4~ solids. It was undiluted and had a viscosity of 180-205 centipoise at 23C. The data at 25 seconds Willir~ls slownes~ is presented in Table III. (see page 12) , .. .. .. .... . . . ... .

1 ~8:~go~
TA BLE II
E~$~r ON ~-~PN~S~E~' PRDPF~'rES P~ 25 S~CNDS WILLI~S SL~WNESS
~60 g/rn> Ba~sis Weiyht) Pulp ',ample Beating Wbrk to (hpd/t~n Time Burst Bulk Tensile S-tretch Brec~k pulp _ Min Tear Factor Fb~ cm3/g 100 M ~ ft-lb!in2 Softwcx~ lp __ Untreat~d 21.4 173 55737 1.89 76 2.9 49 1st St:age~3.5 165 S6583 1.83 78 2.8 44 2nd St:~ge (4)21.l 17654 564 1.84 77 3.1 49 (6)18.0 1994~ 337 1.85 6~ 3.0 41 (~)21.8 19356 711 1.77 76 3.5 57 HaIdw~ ~
Untrealted 6.9 102 2412 1.84 46 2.3 24 1st Stage 10.8 97 2614 1.73 44 3.0 33 2nd Stage (4) 7.0 9623 14 1.63 39 306 38 (6~ 3.2 10526 19 1.59 44 3.~ 31 ~8~ 8.5 8718 7 1.67 34 3.4 34 S~wdust Pu1p Untreated 9.0 73 15 7 1.77 31 2.0 16 1st Stage 10.3 74 17 8 1.69 34 2.6 23 2n~ Sta~e (4) 5.5 8719 10 1.62 37 2.7 28 (6~ 5.7 7717 7 1.68 31 2.6 21 (8~ 6.2 7~1~ 8 1.6~ 32 2.9 26 Broke P~~
Untreated 2.0 121 28 16 1.76 50 2.7 29 1st Stage 4.3 97 26 14 1.73 46 2.9 30 2nl St~ge (4) 2.2 114 29 27 1.61 46 3.3 37 (6)3.0 10~ 22 13 1.65 40 3.2 34 ~ .1 93 20 ~ 1.69 35 3. ~ 30 Mixtunes**
Untreated 5.0 115 28 19 1.79 49 2.4 23 2nd St,a~e (6) 3.8 110 2Ç 25 1.69 47 3.0 36 ~ _ . . . ..
* Bro'ke data at 50 seoonds Williams slowness.
** Mixtures are: 60-65~ ha~ od pulp 8-12~ softwo~d pulp 8-12% sawdust pulp 10-20~ broke pulp.

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TA~E III

EFFECT ON BULK AND RESIN PENETR~ION P~DPEXrIES ~T 25 SECCNVS hnII,IAMS
SIOWNESS FOR ~DEAVY SIE~S (212 g/m2) Williams Penetrescope, Pelt ~ide At 25 Sec. 5% 95%
Slowness Pene- Pene-Beating -tration tration Resin Pulp Energy Time Bulk Time, TL~e,Pick-up Samplehpd/ton ~in~ cm3/g Sec. Sec.
~oftw~od .
Untreated 21.4 2.07 16.0 52.0 57.7 1st StaCJe 23.5 2.01 12.2 43u8 --21~ S-tacJe 4.0 21.1 1.78 17.1 79.8 -~
6.l 1~.0 1.8~ 10.1 3~.2 --8.6 2108 1.72 13.8 60.9 38.8 Hardwo3d Untreated 6.9 1.94 20.5 48.4 62.5 1st Stag~ 10.8 1.86 16.1 36.2 --2nd Stage 4.1 7.0 1.70 9.4 21.7 --6.3 3.2 1.70 4.2 11.5 --8.4 8.5 1.68 4.6 15.3 46.0 Sa~ s~
Pulp Untreat~d 9.0 1.86 10.9 38.6 49.5 1st Stage 10.3 1.85 11.2 41.1 --2nd Stage 3.6 5.5 1.69 7.1 24.1 --5.7 5.7 1.77 4.4 20.1 ~-7.S 6.2 1.71 4.9 1~.5 ~4.8 Broke Pulp*
Vntrea~ed 2.0 1.94 16.8 40.5 57.5 1st Stag 4.3 1.83 12.3 33.1 --2nd S~age 4.0 2.2 1.62 19.0 32.1 --5.8 3.0 1.72 6.9 15.5 ~
8.1 4.1 1.68 9.0 1~.5 52.0 Mixt~e I** 6.6 1.94 ~15.8 35.7 59.2 Mixture II** 6.0 4.0 1.71 8.8 21.5 53.0 ~ _ ..
* Broke data is at 50 seconds Willians slo~less.
** ~xtures are: 60-65% hardwood pulp; 8-12% soft~ocd pulp;
10-20% br~ke pulp; 8-12~ saw~ust pulp.

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Table :ILI and ~E~ic3ures 4 and 5 show that the resin pene-tration time is greatly decreased in all except the softwood pulp by the treatment. The softwood pu]p shows so~le decrease in resin penetra-tion time although not of the mayni-tude shown for the other pulps.
Another advanta-Je of the sa-tuxatiny paper of the invention i5 reduced shives and dispersed dirt. In -the cases of the hardwood, sawdust and broke sa~ples, there were no shlves remaining after treatment even at the low energy input and the 1~ resulting handsheets were extremely clean in appearance. The softwood pulp was apparent].y more difficul-t to work on; and although considerable reduction in shives was apparent at the low energy input, it required the highest level of energy input (g.0 hp-days/ton pulp~ -to remove most of the shives.
The improved saturating paper of the present invention can be prepared from pulps se]ected .from the group consisting of softwood pulp, sawdust pulp, hardwood pulp and saturating broke pulp and mixtures thereof. The paper trea-ted in the manner disclosed with the fiber properti~s described exhibits reduced bulk, and, therefore, higher density, decreased resin penetrat.ion time and decreased resin pick up at a given Williams slowness, as well as reduced shives and improved dirt dispersion.

In order to determine how many fibers treated by the invention process mus-t be present to cause a significant improve-ment i.n the sa-turating properties of saturating finish, a series of mixtures of untreated and treated hardwood pulps were made.
Handshe~ts were prepared from these mixtures cont.aining 0, 5, 10, 20, 40, 80 and 100 percent treated pulp. The resin penetration ... . ~ . . ... . . ... .

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times were de-terminecl using -the Willic~ms penetrescope and a phenolic resi.n o~ 59~ solids. The results are given in Table IV
and Figure 6r T~BLE IV
E~ESIN PENETRATION TIMES FROM WILLIAMS PENETRESCOPB

5% R~sin 95~Re~.in PenetratlonTime _ _ Penetration Time _ 95~ 95%
ConEi.dence Confidence Sam~le(sec.) Limits (sec.1 Limits 100~ Untrea~ed 8.7 ~ 0.9 7~5 9.8 20.G + 1.1 19.1 - 22.1 95~ Untreat~d/
5% Treated7.4 + 1.1 6.0 ~ B.8 18.4-~ 2.6 1501 - 21.7 90~ Un~reated/
10% Treated7.4 + 0.4 7~0 - 7.9 16~5 + 1.0 15.3 - 17.7 80~ Untreated/
20% Treated6.9 ~ 0.7 6.0 - 7~8 15~8 + 1.3 14.2 - 17a4 60~ Untreated/
40% Treated6.4 + 1.3 4.8 - 8.0 16.3 + 1.7 14.3 - 18.5 20% Untreated/
80% Treated4.0 + 1.4 2.3 - 5.8 11.0 + 3.9 6.0 - 16.0 on% Treated 2.1 + 0.3 1.8 - 2.4 5.0 + 1.1 3.6 - 6.3 - - - ..

The resin penetration times shown in Table IV and depieted in Figure 6 show a linear relationship exists between the amount of treated pulp and -the resin penetration time. Stat.istically, the amount of treated fiber necessary to give a significant difference in resin penetration time is around 10%.

EX~MPLE 5 To determine whether lower energy inputs (than approximately 4 hpd/ton) would produce the significant changes in the pulp and in the properties of the final paper observed in .:

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-the foregoing examples, a trial was conducted with hardwood pulp at various power inpu-ts up -to approximately 4.0 hpdtton.
The harclwood pulp was suhjected to the two-stage treatment described in Example 1 wi-th the exception of the following running conditions in Table V.

TABLE V
OPERATING DATA

Experiment Number 1 2 3 4 5 Feed Flow Rate~ gpm* 37S 375 375 375 375 Consistency out of 1st Treatment~ ~30.0 29.7 29.9 28.9 28.8 Cons~tency out of 2nd Treatment, %27.5 28.3 30.2 28.9 29.7 Energy Input in 2nd Treatment, hpd~ton0.4 1.2 4.1 0.2 1.8 . ., *Equivalent to approximately 83 ton/day.

~ he pulp was sampled after the first treatment, and a s~mple was then obtained after the second treatment. 5everal feed samples to the first treatment stage were taken during the trial, and this was considered to be untreated pulp. Valley Beater evaluations were carried out on all eleven samples (1 untreated, 5 after the first treatment, and 5 after the second treatment~
using 360 grams O.D. charges of pulp. The sheets were all made ts be nominally 3.0-gram sheets with a basis weight of 150 g/m2 (92.Z lb/3000 ft2 o.D.j; a filter paper was placed between the sheet and the polished pla-te before pressing and air-drying in restxaining rings. The sheet evaluations included breaking length and strength. The sheets were also tested for 5~ resin penetration time using a phenol~formaldehyde resinO Table VI
contains the results at various density levels.

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TABLE VI
PUI.P AND PAPER PROPERTIES BY GRAPHICAL
INTERPOLATION AT VARIOUS BULKS

~eating Willi~ns Brea~ing 5~Resin Bulk Time Slowness Length Stretch Penetration Sample cm3/g l~n. sec. 100 min. ~Time, sec.
Control 2.05 6.1 19.8 41.5 2.5~ ---17.6 (untreated) 2.00 8.0 21.8 44.0 2~519.6 1.95 9.9 25.9 46.0 2.621.5 l.gO12.0 30.6 48.5 2.623~4 1st Trea~t 2.05 4.8 16.3 39.9 3.016.2 2~00 6.1 lg.9 43.0 3.118.1 1.95 7.~ 22.0 46.5 3.3~0.6 l.gO10.0 26.5 49.9 3~524.0 2nd Trea~nent 2.05 4.3 14.9 37.5 2.5 15.0 (0.2 hpdtton) 2.00 6.1 17.4 41.0 ~.7 16.7 1.95 7.g 20.5 4~.4 3.018.9 1.~0 9.6 26.5 ~l8.0 3.221.6 2n~ Treatment 2.05 4.3 14.9 37.5 2.S 15.0 (0.4 hFd/ton) 2.00 6.1 17.4 41.0 2.7 16.7 1.95 7~9 20.5 44.4 3.01~.9 1.90 9.6 26.5 48.0 3.221.6 Treatment 2.05 1.3 11.5 29.0 2.3 9.8 (1.2 hpd/ton) 2.00 3.5 1400 31.6 2.5 11.2 1.95 5.~ 17.3 35.8 2.913.0 1.90 8.0 21.4 ~1.2 3.315.2 2r~ Trea~ment 2.05 1.0 11.5 29.0 2.2 11.0 ~1.8 hpd/ton~ 2.00 3.2 14.0 31.6 2.3 13.4 1.95 5.7 17.3 35.~ 2.616.0 1.90 8.0 21.4 41.2 2.818.4 2nd Trea ~ nt 2.05 1.0 11.5 29.0 2.9 7.6 (4.1 hpd/bon) 2.00 3.2 14.0 31.6 3.0 10.0 1.95 5.3 17.3 35.8 3.211.8 1.9G 7.5 21.4 41.2 3.514.0 . .

The pulps treated throuyh the second stage require signifi-cantly less bea-ting -time in the Valley Beater to reach any density.
It is also obvious, tha-t the first stage treatment also significantly reduces the bea-ting time ~o a given bulk. The most striking effect of the various treatment levels is shown in the 5% resin penetration time. There is a dramatic decrease in resin penetration times for the 1.2~4~1 hpd/ton treated sheets when compared to the untreated shee-t. These results indica-te a definite correlation between energy input and resin penetra-tion time.
Thus, while a decrease in resin penetration can be achieved at second stage treatment levels of from 0.2 to 8.0 hpd/ton, the preferred range is from 1.2 to 4.1 hpd/ton.
While the lnvention has been described and illustrated herein by references to various specific materials, procedures and examples, it is understood -that the invention is not restricted to the particular materials, combinations of materials, and procedures selected or that purpose. Numerous variations of such details can be employed, as will be appreciated by those skilled in the art.

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Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

1. An improved resin saturable paper made from hardwood or softwood pulps or mixtures-thereof produced by the alkaline pulping processes for impregnation with a phenolic resin wherein the improvement comprises including in said paper at least 10% by weight of fibers produced by subjecting wood pulp to a first mechanical treatment to raise the wood pulp from a lower consistency of below 20% to a higher consistency of from 20% to 60% and further subjecting the higher consistency wood pulp to a second mechanical treatment at an energy input level of from 0.2 to 8.0 hpd/ton producing twisted, kinked, curled and collapsed fibers, said paper exhibiting reduced bulk and higher density, decreased resin penetration time and increased resin pickup characteristics over conventional resin saturable paper.

2. The improved resin saturable paper of claim 1 wherein the wood pulp is softwood pulp comprising pine pulp or sawdust pulp or a mixture thereof.

3. The improved resin saturable paper of claim 1 wherein the wood pulp is saturable broke pulp.

4. The improved resin saturable paper of claim 1 wherein the wood pulp is 60-65% hardwood pulp, 8-12%
softwood pulp, 8-12% sawdust pulp and 10-20% saturable broke pulp.

5. The improved resin saturable paper of claim 1 wherein the lower consistency wood pulp is raised to a consistency of from 30% to 35%.

6. The improved resin saturable paper of claim 1 wherein the higher consistency wood pulp is subjected to the mechanical treatment to produce the treated fibers at an energy level input of from 1.2 to 4.1 hpd/ton.

7. In a method for treating wood pulps produced by alkaline pulping processes to produce a resin saturable paper exhibiting reduced bulk and higher density, decreased resin penetration time and increased resin pickup character-istics relative to conventional resin saturable paper, the improvement which comprises including in said paper at least 10% by weight of fibers produced by subjecting hardwood or softwood pulp or a mixture thereof to a first mechanical treatment to raise the wood pulp from a lower consistency of below 20% to a higher consistency of from 20% to 60%, and subjecting the higher consistency wood pulp to a second mechanical treatment at an energy level input of from 0.2 to 8.0 hpd/ton producing twisted, kinked, curled and collapsed fibers.

8. The method of claim 7 wherein wood pulp is a softwood pulp comprising pine pulp or sawdust pulp or a mixture thereof.

9. The method of claim 7 wherein the mixture of hardwood and softwood pulps is saturable broke pulp.

10. The method of claim 7 wherein the wood pulp is 60-65% hardwood pulp, 8-12% softwood pulp, 8-12% sawdust pulp and 10-20% saturating broke pulp.

11. The method of claim 7 wherein the lower consistency wood pulp is raised to a consistency of from 30% to 35%.

12. The method of claim 7 wherein the higher consistency wood pulp is subjected to the second mechanical treatment at an energy level input of from 1.2 to 4.1 hpd/ton.