US3483025A

US3483025A - Film coalesced latex impregnated paper and process therefor

Info

Publication number: US3483025A
Application number: US566816A
Authority: US
Inventors: Philip K Isaacs
Original assignee: WR Grace and Co
Current assignee: WR Grace and Co
Priority date: 1966-07-21
Filing date: 1966-07-21
Publication date: 1969-12-09
Anticipated expiration: 1986-12-09

Description

K. ISAACS 3,483 025 FILM COALESCED LATEX IMPREGNATED PAPER AND PROCESS THEREFOR Dec. 9, 1969 Filed July 21, 1966' PHILIP K. ISAAOS BY 7W 7 ATTORNEY United States Patent U.S. Cl. 117-155 5 Claims ABSTRACT OF THE DISCLOSURE The invention disclosed is directed to an impregnated paper comprising a cellulosic pulp paper impregnated with coalesced synthetic polymer latex solids With substantially all of the solids being coalesced on the surface of fibers in the paper so that the interior of the fibers are substantially free of latex solids. The paper is impregnated in a process which comprises contacting a synthetic polymer latex with an organic cation/free base organic anion exchange resin and thereafter applying the latex to a cellulosic pulp paper. In a preferred embodiment of the present invention, the latex contains from about 5% to about 70% synthetic polymer and more preferably from about 15% to about 50%.

The present invention relates to a novel and useful product and a process for preparing the product. More particularly, it relates to an impregnated paper and a process for impregnation.

It is known in the art that various latex impregnated papers may be used in the manufacture of pressure sensitive tapes, shoe insoles, artificial leather bases and the like". In the preparation of the latex for paper impregnation, two distinct systems are utilized. The first system utiilzes a monomer, water, soap and an initiator which are mixed with heat and pressure. The second system utilizes the polymer, water, a quite large quantity of surfactant and energy which is generally imparted in the form of mixing to disperse the particles. The latex resultingfrom each of these systems, when applied to a paper, usually results in a bridging of polymer strings between thepaper fibers and some actual penetration of the polymer into the fibers. The bridging results in a waste of polymer since the bridges add little, if any, to the strength of the paper. The penetration of the polymer into the fibers also results in a loss of polymer since it actually detracts from the strength of the fibers it has penetrated. In addition, the surface active agent used impair the physical properties of the paper and the resulting tapes are generally not suitable for electrical Work since the surfactant increases the conductivity in the finished product. Quite obviously, if a system could be developed which did not utilize a surface active agent and resulted in the fiber being uniformly coated with substantially no bridging or penetration, it would receive widespread acceptance in the art.

It is an object of the present invention to provide a process for preparing an improved latex. A further object is to provide an impregnated cellulosic pulp paper. A still further object is to provide a more uniformly impregnated cellulosic pulp paper. Other objects will become apparent as the description of the invention proceeds.

These objects are accomplished by the present invention which provides a process for impregnating paper which comprises contacting a synthetic polymer latex with an organic cation/free base organic anion exchange resin and thereafter applying the latex to a cellulosic pulp paper.

In a preferred embodiment of the present invention,

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the latex contains from about 5% to about 70% synthetic polymer and more preferably from about 15% to about 50%.

The present invention also provides an impregnated paper comprising a cellulosic pulp paper impregnated with a coalesced synthetic polymer latex solids with substantially all of the said solids being coalesced on the surface of the fibers in the paper so that the interior of the fibers are substantially free of said latex solids.

In a preferred embodiment of the present invention the impregnated paper contains at least about 20% synthetic polymer latex solids and more preferably from 30 to In a still more preferred embodiment, the impregnated paper contains from 40 to 60% synthetic polymer latex solids.

The term latex is used in its conventional sense to mean a dispersion of solid synthetic polymer particles in water which is capable of forming a film from the dispersion. The synthetic polymers which can be utilized in the latex includes, without limitation, polymers and copolymers of butadiene, isoprene, chloroprene, acrylates, vinyl halides, vinyl esters and the like. Specific examples include the homopolymers polyethyl acrylate, plasticized polyvinyl chloride and the copolymers styrene-butadiene (40%60%) and styrene-acrylonitrile-butadiene-acrylic acid (35 %14%50%1% Other polymers are likewise suitable.

The expression organic cation/free base organic anion exchange resin is used to signify all the conventional organic resins which are utilized for the removal of anions and cations from solutions. The solution may be passed sequentially through the cation exchange resin and then the anion exchange resin (or vice versa) or the resins may be utilized as a mixed bed. Preferably, the anion exchange resin is a strong base resin since a longer contact time is required with the weaker resins. In many instances, the anion exchange resin is furnished in the form of the chloride since it is more stable in this form. In such cases, the chloride should be changed to the free base before being used as the free base does not add ions to the solution. Anion and cation exchange resins are well known in the art and are described in numerous publications, books and patents. A partial list of suitable organic anions and cations resins is given in the Encyclopedia of Chemical Technology (1952), volume 8, page 13. Other organic resins are also suitable and may be found in any standard textbook on ion exchange.

The terminology cellulosic pulp paper is used to mean any conventional paper such as that made from Wood pulp, cotton linters and the like. It also includes paper which contains some synthetic filaments as reinforcement. The term coalesce merely signifies that the polymer has been heated sufficiently so as to fuse the particles together.

The invention will now be described by reference to the drawings. In the drawings:

FIGURE 1 is an artists conception of an enlarged cross sectional view of a sheet of impregnated paper produced in accordance with the prior art; and

FIGURE 2 is an artists conception of an enlarged cross sectional view of a sheet of impregnated paper produced in accordance with the present invention.

In FIGURE 1 the paper fibers 1 have been penetrated by the polymer 2 and strings of the polymer 3 bridge the individual filaments. The figure demonstrates that the prior art procedures result in a waste of polymer by the bridges being formed and by the polymer penetrating into the fibers.

In FIGURE 2 the paper fibers 4 are substantially uniformly coated with the polymer 5. The figure demonstrates that very little polymer is Wasted when the impregnated paper is made in accordance with the present invention since the polymer is quite uniformly coated onto the filaments.

The following examples are given to illustrate the invention and are not intended to limit it in any manner. All

4 tore. The tear strength is reported in grams/mil. A fixture comprising a triangular (904545) plate, attached by a pivot (at the 90 angle) to a A inch rod, is set into the hole in the paper, rod first. The apex of the triangle just touches the paper at the start of the test.

parts are given in parts by weight unless otherwise ex- The electrical resistance tests are carried out using pressed. the ASTM-Dl000 test procedure.

In the following examples, the tests are carried out as follows. EXAMPLE 1 The percent total solids in the latex is determined by To 1000 grams of a latex containing 50% of solids accurately Weighing a sample of the latex: drylhg h (40% styrene-60% butadiene copolymer) is mixed with sample to constant weight and reweighing. The total solids 200 grams of a mixed bed ion exchange resin and 00 a n Calculated fIOIIl the following formula: grams of water. The cation portion of the mixed bed is Dry weight a styrene/divinyl benzene sulfonic acid resin. The anion m 100 perceht total so Ids 5 portion of the bed is a quaternary base of a styrene/ divinyl benzene copolymer having a tetramethylamino- Tensile properties, i.e., tensile strength at failure, permethyl group attached to the benzene rings (free base cent elongation at failure and 1 percent tensile modulus form of resin) The resin is described in I. A. Kitchener are measured in accord with ASTMD41264T. The Exchanoe' Resin Methuen and Ltd London copolymer latex is dried in film form (3 mils thick), cut (1957), mixture is Stirred at O for 3 to /4" sample strips, placed in the aws, (2" ap of hours and then filtered to remove the resin. Ash content tensile strength tester (Instron, Model TT, available from Shown that Over 95% of the ions are removed The final Ihstron Engineering h Quincy Mas?) and Separated at solids content is 35 to 40%. A standard size sheet (8 /2 a F of Per mlhute and strain fa of 50% Per inch by 11 inches) of cotton linters paper (12 mils thick) mmute at Cgand 9 Telahve hum1d1ty- 25 is impregnated with the latex by dipping the base into The dclamination resistance is measured by preparing the latex to give an impregnatfid paper having 40% Poly test specimens which are cut to a length of approximately mer solids (dry weight) The Sheet is dried at room 4 /2 inches in machine direction and a width of approxitfimpemwm mately 2 inches in the cross direction of the paper. The. When the impregnated sheet is examined under a high test specimens are conditioned 48 hours at 23 C. and 50% powemd microscope it can be Seen that the fib r h relative hUIhidhX-AS'iHChIOhg Strip of'rug binding P been quite uniformly coated with the latex solids with Placed on each slde of the Paper Specimen so that the substantial absence of any strings or bridges conextends beyond the ends of the paper. The pecimen 18 meeting the fibers. By taking /2 of the paper sheet before thenplaced 011 h bottom platen of a Press 50 that 1 drying, the latex on the exterior of the sheet can be PFOXImateIY lheh of the p eXtehdS beyond the ehd removed by washing with water leaving only that latex of the p The Specimens are Pressed 30 seconds at which has penetrated into the fibers. A comparison of the 2750 at Pressure of Pounds P Square inch on weight of the washed dried sheet with the weight of the ihe binding P The Specimens Cooled to room original sheet, shows that substantially no latex has penel The Specimens are Cut in strips aPPTOXlIIIateIY 1 trated into the fibers. In contrast, when a control latex is inch Wide- The two ends of the rug binding p are Pulled carried through the same procedure without the treatment, apart into tWO pp y equal P The ends of the a great deal of bridging takes place between the fibers binding p are P into the l of the Instfoh Tensile of the paper. Also, by the removal of the latex solids from tester after the first inch of Separfioh, the average the sheet, it can be determined that about 15% of the force required to Separate the P p is recorded at a CTOSS- latex solids has penetrated the interior of the fibers. head speed to 10 inches/min. The delamination resistance of the paper is reported in pounds based on the average EXAMPLES 2 5 Values of 3 specimens- The procedure of Example 1 is repeated utilizing a The fold endurance is tested in accordance to the commercial mixed bed anion and cation exchange resin. 7 testing Procedure. The commercial resin wherein the cation exchange resin The teal" Strength is tested y the following Procedure: consists of a sulfonated copolymer of styrene and divinyl Samples are Cut into PieceS 1 inch y 41/2 inch and Condibenzene combined with an anion exchange resin of a honed 48 hours Prior to testhllg- A 141 inch hole is Phnehed styrene-divinyl benzene copolymer matrix containing a in the center of the sample with a Punch 0f the yp used quatinized base of dimethyl amino methacrylate. 111- to prepare sheets for loose leaf binders. The thickness of coway TM-l is marketed by the Illinois W te Tr tthe sample is measured to the nearest 0.1 mil on each merit Company. In Example 2, the latex polymer is the side of the hole (along the 1 inch dimension of the sarnsame as that utilized in Example 1. In Example 3 the ple). The fixture is clamped in the upper jaw of an Instron latex polymer is a copolymer containing 35% styrene, tensile tester. The bottom jaw of the tester is positioned 14% acrylonitrile, 50% butadiene and 1% acrylic acid. 0.15 inch below the bottom of the test fixtures. The two In Example 4 polyethyl acrylate is utilized and Example 5 ends of the sample are clamped in the lower jaw of the uses a plasticized vinyl chloride marketed under the name Instron tester and the test run (at 10 inches/min.) until of Geon 450X23 (Goodrich Chemical Company). In the sample tears. The maximum force developed in teareach example the properties resulting from the deionized ing the sample is recorded. The edge tearing resistance. is latex are compared to those of the same latex without calculated by dividing the force recorded in grams by the such treatment. The properties for the products are given thickness of the sample on the side at which the sample in the following table:

Delamina- Elongation Fold Tear Example Tensile tion Resistance Endurance Strength 2 Untreated 1,000 14 0.50 Deionized 1, 17 0. 55 3 Untreated... 900 11 0.47 1,000 13 0. 45 720 20 0. 45 740 32 0. 03 1,100 19 0.37 1,200 19 0. 42

When the impregnated papers prepared in accordance with the present invention are examined under the microscope the results are substantially the same as in Example 1. When the latex is removed from the product as in Example 1, it shows there is substantially no penetration of the latex into the fibers of the paper just as in Example 1.

EXAMPLE 6 The procedure of Example 4 is repeated employing a latex having a solids content of 60%. After deionization, however, the latex is concentrated to a solids content of 40%. After impregnating the sheet, the product has substantially the same properties as that produced in Example 4.

EXAMPLES 7-11 The first part of the procedure of Example 3 is repeated using 150 grams of water rather than 200 grams of water. The resulting latex contains 40% by weight of synthetic polymer solids. In Example 7 the resulting latex is diluted to 5% solids to give an uptake on the paper of 6%. In Example 8 the resulting mixture is diluted to solids to give an uptake on the paper of 20%. In Example 9 the resulting mixture is diluted to 20% solids to give an uptake on the paper of 40%. In Example 10 the resulting mixture is diluted to 30% solids to give an uptake on the paper of 60% and in Example 11 the resulting mixture 40% solids is used to give an uptake on the paper of 90%. The properties of the resulting impregnated paper are given in the following table.

What is claimed is:

1. A process for coating the surface of fibers of paper which comprises, applying a synthetic polymer latex containing from about 5% to about 70% synthetic polymer having over 95% of ions removed therefrom by contacting with an organic cation/free base organic anion exchanged resin, thereafter applying the said latex to a cellulosic pulp paper, and drying the impregnated paper sufliciently so as to substantially coalesce the synthetic polymer on the surface of the fibers of the paper whereby the interior of the fibers is substantially free of said synthetic polymer.

2. The process of claim 1 wherein the latex contains from about 15% to about 50% synthetic polymer.

3. A fiber-coated paper which comprises a cellulosic pulp paper fiber-coated with at least 20%, based on the weight of the paper, of coalesced synthetic polymer latex solids having over 95% of ions removed therefrom by contacting with an organic cation/ free base organic anion exchange resin, substantially all of the said latex solids being coalesced on the surface of the fibers of the paper whereby the interior of the fibers is substantially free of said synthetic polymer.

4. The fiber-coated paper of claim 3 wherein the synthetic polymer latex solids are present in an amount from about to about 100% based on the weight of the paper.

5. The fiber-coated paper of claim 3 wherein the synthetic polymer latex solids are present in an amount from Delamina- Percent on Fold Tear Polymer Tensile resistance endurance strength 0 004 0. 30 18 0.28 6 676 0. 20 0. 27 20 73s 0. 5s 68 0.31 20 904 0. 130 0. 3s 40 909 0. 94 223 0. 47 Deionoized 40 1022 1020 795 0. 45 10 Untreated 971 1.40 530 0. 57 Deionized--- so 1240 1. 1968 0. 04 11 Untreated..- 1046 1. 93 412 0. 63 Deionized 90 1200 2. 58 1422 0. 74

EMMPLE 12 about 40% to about 60% based on the weight of the In order to show the advantages in electrical properpaper ties with the paper produced in accordance with the pres- References Clted ent invention, the process of Example 3 is repeated em- 45 UNITED STATES PATENTS ploying a crepe paper- Fo comparison Purposes, the 3,262,811 7/1966 Sellet 117 X electrical reslstlvity is given for the paper, the untreated 2,912,349 11/1959 Videen et a1 117 161 resin impregnated paper and the deionized resin ln'l- 2,912,350 11/1959 Videen et aL 117 161 pregnated paper. The properties are given In the table 2,961,417 11/1960 small below: 50 3,017,295 1/ 1962 Outterson et al 117-155 Electrical ,29 6/ 1962 Hatch 260-2.1 Percent resistivity 3,114,485 11/1963 Kunin 21038 X polymer afia? 1%? 3,205,184 9/ 1965 Hatch 21038 X Latex Paper mpaper (A 595m; 3,300,416 1/1967 Hatch 260-21 0 12 55 3,303,155 2/1967 Peterson et a1. 117-155 X gfffz fiii aijj 40 2 3,332,890 7/1967 Hatch Deionized ..d0---.- 40 26 3,335,100 8/1967 Geyer 117201 X While in the above examples unmodified latex systems FOREIGN PATENTS are utilized, it is obvious that latex systems containing 1,131,013 6/ 1962 Germany.

anti-oxidants, fillers, pigments, oils, thickeners and the like can be employed.

Many equivalent modifications will be apparent to those skilled in the art from a reading of the foregoing without a departure from the inventive concept.

WILLIAM D. MARTIN, Primary Examiner M. R. LUSIGNAN, Assistant Examiner