CA1222606A - Method of forming beater-saturated sheet using carbonate ion - Google Patents

Abstract

METHOD OF FORMING BEATER-SATURATED SHEET USING
CARBONATE ION

Abstract of the Disclosure Method of forming a beater-saturated non-woven sheet by treating a slurry of papermaking fibers with alum and either sodium carbonate or a mixture of sodium bicarbonate and sodium hydroxide to achieve a pH
in the range of about 7-9 followed by adding a binder latex which deposits on the fibers, and finally forming a sheet from the resulting slurry.

Description

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METHOD OF FORMING BEATER-SATURATED SHEET USING
CARBONATE ION

BACKGROUND OF TH~ ~INVENTION
F'ield of-th'e Inventi'on The invention relates to a method of forming non-woven flooring backing by the beater-saturated method in which the white water does not accumulate ammonium sulfate or multivalent cations which interfere with the precipitation process.
Des'c'ription o'f the Prior Art U.S. Patent No. 2,375,245-Pretzel teaches the pretreatment of a papermaking Eibrous slurry with alum and ammonia to ~orm aluminum hydroxide in and around the papermaking fibers so that a subsequently added binder latex will without ~urther precipitation agent addition, precipitate and act as a binder during the sheet-laying process. U. S. 2,599,092-Craig teaches the addition of calcium chloride to a slurry of cellulosic fiber stock followed by the addition of sodium carbonate to precipitate calcium carbonate within the fibers in order to form a stiffer board. U. S. 3,082,145-Kao teaches a process of simultaneously coa-ting cork granules and fibers with a coating material which may be a rubber latex. The process calls for pretreating with a salt wh.ich may be alum and adding an alkali which may be sodium carbonate or sodium hydroxide to a pH of approximately 5; no aluminum hydroxide appears to be Eormed. A latex is then added followed by the addition of a latex coa~ulant such as alum. U. S. 3,549,485-Eckert teaches a method of forming a mineral Eiber-clay ceramic board by adding aluminum sulfate to a slurry of the mineral fiber and clay and then adding a deElocculant such as sodium carbona-te or sodium hydroxide. And then there is U.S. Patent No. 123747-~26~lE;

Tiemann which issued February 13, 1872~ Here a papermaking slurry is pretreated with alum and followed by a treatment with "freshly-burned lime which has been previously slacked" in order to form a precipitate of "hydrate of alumina", doubtless aluminum hydroxide.
Summary of the Invention The aqueous slurry of papermaking fibers, along with any fibrous or nonf;.brous fillers, is treated with papermaker's alum and sodium carbonate in indifferent order to achieve in the slurry a pH in the range of about 7-9. A mixture of sodium hydroxide and sodium bicarbonate may replace the sodium carbonate. A
suitable binder latex is then added to the carbonate-treated slurry. On agitation, the latex-containing slurry begins to form small clumps as thelatex particles precipitate on the fibers. Additionally, any multivalent cations, particularly Ca ' will precipitate as carbonate. This system prevents the formation of ammonium sulfate in the white water as occurs when the alum-ammonia process is used as described above in connection with the Pretzel patent.
While it has not yet been established, ammonium sulfate may be deleterious to aquatic life in rivers, streams and lakes to which the white water ultimately finds its way. Additionally, multivalent cations slowly accumu-late in recycled white water as the water slowly extracts those cations from clays and other fillers In time, the accumulated multivalent cations interfere with the precipitation of the binder latex thus making it necessary to discharge and replace the white water with Eresh water mcre often than is economically desirable.

~222~06 - 3 - TLT-7~18 Description of the Preferred Embod'iment The slurry of papermakiny fibers will comprise those fibers, fillers, and additives normally used in making a non-woven flooring backing. Among the cellulosic fibers may be mentioned sulfite pulp, kraft, soda pulp, cotton aids, cotton linters, rags, and newsprint. Inorganic fibers such as glass, mineral wool, asbestos, wollastonite, may be used along with organic polymeric fibers of polyethylene; polypropylene, polyester, polyvinyl chloride, and others. The stock is formed by adding the fibers to water along with desirable fillers such as the clays, some silicates, carbon black, and other suitable fillers. Swelling agents for the cellulosic fibers may be added along with antioxidants, colorants, and additives such as titanium dioxide to increase the opacity of the final sheet. The consistency of the slurry will be in the range of about 0.5-5%. The stock of a suitable consistency may be sub-jected to mechanical refinement until the desired degree of freeness is obtained. The freeness of the paper-makiny slurry to be used in the present invention will generall~ be in the range of about 200 to 400.
The slurry will then be treated with either papermaker's alum or sodium carbonate. ~he amount of alum to be added -to a slurry will generally be in the range of about 10% to 90%, based on the weight of the dry latex solids. One o~ the points of control of the present precipitation process is the amount of alum lnitially added; using smaller amounts within the range stated give a larger precipitated floc size and usually exhibit a longer latex precipitation time while greater amounts give a smaller precipitated floc size and usually exhibit a shorter latex precipitation time. A
latex precipit,ation time in the range of about 2 to 5 minutes is generally preferred.
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Once the alum has been added in the form of a solid or water solution and thoroughly dissolved in the slurry, the sodium carbonate will be added in one embodiment. Sodium carbonate may be added in the form of a solid or aqueous solution and will be added until the pH of the papermakin~ slurry is in the range of about 7-9. The preferred embodiment is to achieve a pH
of 8. The reaction of the sodium carbonate with the previously added alum produces aluminum hydroxide and sodium sulfate. The aluminum hydroxide precipitates on and around the fibers and fillers in the papermaking slurry and brings about the smooth even deposition of the latex particles upon addition to the binder latex emulsion. Additionally, the carbonate ions from the sodium carbonate will react with multivalent cations, particularly calcium, and produce a precipitate of calcium carbonate which then serves as an additional finely divided ~iller in the ultimate sheet. The advantage of using sodium carbonate instead of the ammonium hydroxide of the Pretzel process is that ammonium sulfate may be objectionable in waterways containiny fish while sodium sulfate is not. Further, the removal o~ the calcium ions from the white water allows the white water to be recycled more often than would otherwise be the case where ammonium hydroxide is added to the alum-treated slurry. Ammonium hydroxide allows the unreacted calcium ions and other ions in the white water to accumulate to undesirable levels. Other divalent ions present in the white water are those of iron, ma~nesium, manyanese, nickel, copper, and zinc.
As these collective ions accumulate in the white water, all of them will produce an increasiny detrimental ef~ect on the subse~uent precipi-tation of the latex particles.
It is possible to use sodium bicarbonate as ;,~, ~2~

_ 5 _ TLT-7418 the treating agent for the alum treated slurry instead of sodium carbonate. However, the addition of sodium bicarbonate alone will never achieve a pH of greater than about 7. While the latex and cation precipitation will occur at a pH of 7, it is not -the preferred embodiment. The addition of sodium hydroxide to the sodium bicarbonate will allow achieving the desired pH
of about 8, and so the mixture of sodium bicarbonate-sodium hydroxide can be used, again, in indifferent order of addition relative to the alum addi-tion. In such case, sufficient sodium bicarbonate should be used to convert all the multivalent cations to carbonates.
The sodium hydroxide function is merely to reach the desired pH.
Use of the sodium carbonate makes it possible to maintain consistent latex deposition times and floc size. The retention o fiber and fillers is increased and the ultimate sheet has a higher tensile strength.
pH control of the slurry is improved as opposed to the alum/ammonia process of the Pretzel pa-tent. Elimination of the multivalent cations enables use of binder latices which are too ion sensitive for use in the alum/ammonia process.
Some rubber latexes are signiEicantly more stable than others, resulting in increased precipitation time in the present process. This increased stability may be due to the surfactants in the latex or the manner in which any carboxyl groups are introduced into the polymer chain. The precipitation time may be brought back to normal by adding the sodium carbonate first.
This achieves a pH of about lO. The alum is then added to reach a pH of about 7 to form the appropria-te aluminum hydroxide. The process then proceeds normally.
Having achieved the desired pH in the carbonate-treated slurry, -the appropriate binder latex ~:22Çi0~

is merely added to the slurry with agitation. Over a period of several minutes the particles in the ~inder latex will deposit on and around the fibers and fillers, producing a larger, more uniform composite floc and a clear supernatant.
The binder latex may be any of the tacky synthetic latices well known in the paper- and felt-making art. Copolymers of butadiene and styrene, copolymers of butadiene and acrylonitrile, many of the neoprenes which are polymers of 2-chloro-butadiene-1,3, homopolymers of butadiene, the acrylic latices, and others may be employed. The binder latex is merely poured into the slurry with agitation to bring about the precipitation. The amount of latex to be added will be dependent upon the amount of binder desired in the final sheet. This will normally range in the amount of about 3 to 30% by weight binder based on the dry weight of the fibers and fillers.
The final step in the method is the forming of the resultin~ mixture into a sheet. The sheet may be formed in a conventional way by feeding the mixture to any paper-forming machine, such as a Fourdrinier, cylinder machine, wet machine, or the like for forming into fibrous sheets. The sheet will be dried in normal fashion.
The following examples illustra-te several embodiments of the invention.
EXAM~LE 1 Two hand sheets were made, designated 4535 and 5048, each having the ingredients lis-ted below. All parts are by weight unless otherwise stated. The calcium chloride was added to simulate a slurry containing a rather large amoun-t of calcium ion.
Following are the data:

t .,, :~22Z Ei06 Ingredients 4535 5048 Unbleached Kraft 4.6 4.6 Newsprint 2.3 2.3 1/8" DE670-6 Glass Fiber 1.39 1.39 1/8" Polyester Fiber 1.3~ 1.39 Pulpex E-A, polyethylene fiber 0.83 0.83 Wollastonite P-1 14.5 14.5 Klondyke KWW Clay 14.5 14.5 Celite 321, diatomaceous eaxth 10.5 1~.5 Kymene 2064, an amine polymer/epichlorohydrin adduct 0.345 0.345 TINOX antioxidant, a substituted cresol 0.066 0.066 Carbon Black 0.0125 0.0125 Water 2500 cc 2500 cc Polysar PL-255 Latex, a carboxylated styrene/butad.iene latex 7.5 7.5 Alum 0.5 2.75 NH40H to 7 pH
Na2CO3 - to 8 pH
CaC12 (0.1 M~ 100 cc 100 cc Precipitation Time 45 sec 2.5 min Canadian Standard Freeness 510 660 Sheet Wei~ht 51.9 55.3 Tensile Strength (73.4F) 29.5 lbs 3 7.4 lbs (350F) 12.4 lbs 20.5 lbs Ca level in white water 204 PPM 10 PPM

Four hand sheets were made containing the in~redien-ts below. Except ~or increasing calcium ion concentrations, all four sheets are the same. The purpose of this example is to show the ef~ect on the Canadian ~'reeness, precipitation -time, and calcium ion * Trademark ~22Z6~)~

remaining in the white water of the prior art alum-ammonium process. The addition of extra ammonia to a pH greater than 7 causes no change in any of the parameters.
Ingredients 5143 5144 5145 5146 Unbleached Kraft 2.75 do. do. do.
Newsprint 2.76 do. do~ do.
Glass OC-670-6 1/8" 1.12 do. do. do.
Pulpex E-a polyethylene ~iber 1.76 do. do. do.
Wollastonite P-l 11.6 do. do. do.
Klondyke clay 11.6 do. do. do.
Celite 321 (diatomaceous earth~ 8.4 do. do. do.
15 K~mene 2064 (epichlorohydrin adduct~ 0.~76 do. do. do.
TINOX (antioxidant) 0.0528 do. do. do.
Carbon Black 0.01 do. do. do.
Polysar PL-255 (carboxylated SBR) 6.0 do. do. do.
H2O (2~ consistency) 2000 cc do. do. do.
Alum 3.0 do. do. do.
CaC12 (0.1 M) - 20 cc 40 cc 80 cc NH3 to pH 7 do. do, do.
Canadian Freeness 660 62n 630 520 Precipitation time 2 min14 min 13 min 1 min Ca~ concentration level in white water 47.3 PPM 84.2 PPM 109.0 PPM 182.8 PPM

A series of four hand sheets was made having the same inyredients except for increasing amounts of calcium ion in the slurry. This example shows the resul-ts of using sodium carbonate to a pH o~ 7. While -the precipitation of -the binder la-tex remains controllable, the amount o~ calcium ion in the white water increases, '`' I

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- g - TLT-7418 although not as much as the attendant increase in using the alum ammonia process illustrated by Example 2.
Ingredients 51475148 5149 _150 Unbleached Kraft 2.76do. do. do.
Newsprint 2.76do. do. do.
Glass OC-670-6 1.12do. do. do.
Pulpex E-A 1.76do. do. do.
Wollastonite P-l 11.6 do. do. do.
Klondyke Clay 11.6 do. do. do.
Celite 321 8.4 do. do. do.
Kymene 2064 0.276 do. do. do.
TINOX 0.0528 do. do. do.
Carbon Black 0.01do. do. do.
Polysar PL-255 6.0 do. do. do.
H2O (2~ consistency) 2000 cc do. do. do.
Alum 3.0 do. do. do.
CaC12 (0.1 M) ~ 20 cc 40 cc 80 cc

2 3 1.9 2.0 2.0 2.1 Canadian Freeness 690 680 680 660 Precipitation Time 22 min 2 min 14 min 12 min to pH 7 do. do. do.
Ca~concentration level in white water 40.5 PPM 70.5 PPM 91.4 PPM 145~9 PPM

This example illustrates the preferred embodiment in that the sodium carbonate is added to achieve a pH of 8 in the slurry prior to the addition of the binder latex. Precipitation time remains constant despite increase in calcium ion since a substantial amount of the calcium ion has been removed by precipitation as calcium carbonate.

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- 10 - TL'~-7418 Ingredients 5155 5156 5157 5158 Unhleached Kraft 2.76 do. do. do.
Newsprint 2.76 do~ do. do.
Glass OC-670-6 1.12 do~ do. do.
Pulpex E-A 1.76 do. do. do.
Wollastonite P-l 11.6 do. do. do.
Klondyke Clay 11.6 do. do. do.
Celite 321 8.4 do. do. do.
Kymene 2064 0.276do. do. do.
TINOX 0.0528 do. do. do.
Carbon Black 0.01 do. do. do.
Polysar PL-255 6.0 do. do. do.
H2O (2% Consistency) 2000 cc do. do. do.
Alum 3.0 do. do. do.
CaC12 (0.1 M) ~ 20 cc 40 cc 80 cc N 2C 3 2.3 2.4 2.5 2.7 Canadian Freeness 700 670 710 680 Precipitation Time 2 2 min 2 4 min 2 2 min 2 4 min to pH 8 do. do. do.
C~a++ concentration level in white water 19.6 PPM 37.3 PPM 36.9 PPM 54.5 PPM

A hand sheet having the ingredients of Example 4 was prepared. AEter the addition o~ the alum, and su~ficient CaC12 to give a CA ~ontent of 160 PPM, sodium hydroxide in amount of 0.63 parts was added to achieve a pH of 8. There was then added 3 parts of sodium bicarbonate. The Canad~an Freeness of the resulting slurry was 700, the precipitation time was 2 minutes, and the remaining calcium ion concentration was 43 PPM.

. ., ~2~6~116 ~ rLT-7418 EX~MPLE 6 A hand sheet, designated 5487, was made having the ingredients listed below.
Ingredients 5487 Unbleached Kraft fiber 5.0 Newsprint 2.2 Glass fiber, OC-670-6 1.4 Polyester fiber 1.4 Polyethylene fiber 2.2 Klondyke clay 22.5 Wollaston.ite 11.5 Diatomaceous earth 6.0 Kymene 2064 (epichlorohydrin adduct) 0.25 Flectol H (antioxidant, a hydroquinoline type) 0.3 Carbon black 0.013 Alum 3.0 Water ~2% consistency) 2500 cc Sodium carbonate 2.34 Carboxylated styxene/butadiene ].atex (Pow 283~ 10.0 Canadian freeness 610 Precipitation time 32 min.
The sodium carbonate was added first to the slurry. The pH was about 10. The alum addition then brought the pH to 7. Sheet formation was normal.

Claims (8)

I CLAIM:

1. The method of forming a beater-saturated, non-woven flooring backing comprising forming in water a slurry of papermaking fibers, in indifferent order (1) adding alum to said slurry, and (2) adding sodium carbonate or sodium hydroxide and sodium bicarbonate to form aluminum hydroxide, the pH of the slurry after addition of both alum and carbonate being in the range of 7-9, adding a binder latex to the carbonate-treated slurry, agitating the latex-containing slurry to precipitate the binder onto the fibers and to precipitate any multivalent cations as carbonates, and forming a sheet from the resulting slurry.

2. The method of claim 1 in which said papermaking fibers comprise cellulosic fibers, glass fibers, and polyolefin fibers.

3. The method of forming a beater-saturated, non-woven flooring backing comprising forming in water a slurry of papermaking fibers, adding alum to said slurry, adding sodium carbonate or sodium hydroxide and sodium bicarbonate to the alum-treated slurry to a pH in the range of 7-9 and to form aluminum hydroxide, adding a binder latex to the carbonate-treated slurry, agitating the latex-containing slurry to precipitate the binder onto the fibers and to precipitate any multivalent cations as carbonates, and forming a sheet from the resulting slurry.

4. The method of claim 3 in which said papermaking fibers comprise cellulosic fibers, glass fibers, and polyolefin fibers.

5. The method of claim 3 in which particulate fillers are included in said papermaking slurry.

6. The method according to claim 3 in which said binder latex consists of a carboxylated styrene-butadiene rubber.

7. The method according to claim 3 in which said pH is 8.

8. The method according to claim 1 in which said fibers comprise cellulose, glass, and polyolefin fibers, said carbonate is sodium carbonate, said pH is 8, and said binder latex is a carboxylated styrene butadiene rubber.