CA1241506A

CA1241506A - Flocced mineral materials and water-resistant articles made therefrom

Info

Publication number: CA1241506A
Application number: CA000484759A
Authority: CA
Inventors: Thomas M. Tymon
Original assignee: Armstrong World Industries Inc
Current assignee: Armstrong World Industries Inc
Priority date: 1984-10-18
Filing date: 1985-06-21
Publication date: 1988-09-06
Also published as: AU4425485A; AU573011B2; SE8504856D0; IT8521768A0; GB2166127A; BE903446A; IN165345B; JPH0255396B2; SE8504856L; JPS6197155A; FR2572068A1; FR2572068B1; CH670081A5; IT1207500B; GB8525561D0; NL8502815A; CN85108496A; LU86125A1; ES8700287A1; GB2166127B

Abstract

FLOCCED MINERAL MATERIALS AND WATER-RESISTANT
ARTICLES MADE THEREFROM

Abstract Disclosed are flocced mineral materials which may be utilized to prepare high temperature resistant, water resistant articles. These materials are prepared by utilizing, as a starting material, a gellable layered swelled silicate that has an average charge per structural unit that ranges from about -.5 to -1 and which contains interstitial cations which promote swelling with a source of at least one species of guanidine derive cations.

Description

- 2 ~1506 FLOCCED MINERAL MATERIALS AND WATER-RESISTANT
ARTICLES MADE THEREFROM
Backqxound of the Invçntion It is known that non-asbestos papers and~or sheets may be produced from water-swellable inorganic materials and, in particular, swelled silicate gels. For example, United States Patent No. 4,239,519 is directed to the preparation of inorganic crystal-containing gella~le, water-swelling sheet silicates and certain articles, such as papers, fibers, films, boards, and coatings, produced therefrom. These non-asbestos papers and/or sheets exhibit good high temperature stability and good chemical resistance. Furthermore, since asbestos fibers are not utilized in their manufacture, such articles will not have the health hazards which are associated with asbestos containing articles.
U.S. Patent 4,239,519 teaches the method for making the precursor gellable silicates used to produce said paper6 or sheet articles, as involving three fundamental steps: (a) a fully or predominantly crystalline body is formed which contains crystals consisting essentially of a lithium and/or sodium water-swelling mica selected from the group of fluorhectorite, hydroxyl hectorite, boron flurophlogopite fluorphlogopite, hydroxyl boron phlogopite, and solid 601utions between those and other structurally compatible species 6elected from the group of talc, fluortalc, polylithionite, fluorpolylithionite, phlogopite, and fluorphlogopite; (b) that body is contacted with a polar liquid, normally water, to cause swelling and disintegration of the body accompanied with the formation of a gel, and (c) the solid:liquid ratio of the gel is adjusted to a desired value depending upon the applicationtherefor. Glass-ceramicsarethepreferred

- 3 06 crystalline starting bodies. Those products are then contacted with a source of large cations, i.e., with an ionic radius larger than that of the lithium cation, to cause macro flocculation of the gel and an ion exchange reaction to take place between the large cations and the Li+ and/or Na+ ions from the interlayer of the crystals.
Alternatively, U.S. Patents No. 3,325,340 and 3,434,917 teach producing aqueous di6persions of vermiculite flaked crystals which have been caused to swell due to the introduction therein of interstitial ions such a6 (1) alkylammonium cations having between 3 and 6 carbon atoms inclusive in each carbon group such as methylbutylammonium, n-butylammonium, propylammonium and iso-amylammonium, (2) the cationic form of amino-acids, such as lysine and ornithine, and/or (3) lithium.
While the articles, such as papers, sheets and films, prepared via the prior art processes set forth above exhibit excellent heat resi6tance and are very useful in a wide variety of applications, it has been discovered that they exhibit a certain amount of water sensitivity which is generally exhibited by the articles having a considerable 1066 of 6trength and general deterioration of mechanical and electrical properties when exposed to high humidity environments or submerged in water or other polar liquids. This sensitivity to water correspondingly curtails the utility of these articles in certain applications, such as, for example, head gaskets, electrical insulators, environmental protective coatings, and washable and environmentally stable building materials.
Summarv of the InYention It has now been unexpectedly discovered that high temperature, fire-re6istant, non-asbesto6, water-re6i6tantarticle6,sucha6sheet, papar, board, film, ';

~2~S06 fiber and coating articles, can be made from a swelled, layered flocced silicate gel material that is prepared by utilizing an exchange cation that is selected from guanidine derivatives. Such article6 surprisingly have been found to exhibit, in general, much improved results in tensile strength and puncture resiRtant tests that are conducted whan the articles are wet than do materials that are prepared utilizing prior art exchange cations.
Furthermore, the articles made according to the present invention generally display superior electrical and mechanical properties over those materials made by prior art method.
With reference to heat resistance, the articles that are produced according to the present invention are completely stable to temperatures of approximately 350-400 C.
Detailed description of the Invention The articles and the flocced mineral suspensions of the present invention are, in one embodiment of the invention, prepared by utilizing, as a starting material, a water-swelling silicate that has an average charge per struetural unit of from about -.5 to about -1 and which contains interstitial exchangeable cations that promote swalling. The specific exchange cations in the starting material will depend on the silicate being utilized. For example, if a synthetically derived gellable silicate, which is made according to the procedures of U.S. Patent

4,239,519, is utilized as a starting material, the exchange cations will generally be Li+ and/or Na+ ions.
If a natural vermiculite dispersion, such as made according to U.S. Patent 3,325,340, is utilized, the exchange cations will generally include alkylammonium cations and the other cations specified in U.S. Patent 3,325,340. The silicate, whether synthetic or natural in ~2~1~0~

origin, will generally have morphologies that are represented by thin flakes which are generally disc, strip, and/or ribbons. The flake6 will have typical measurements which are from about 500 A to 100,000 A, and preferably 5,000 A to 100,000 A in length, 500 A to 100,000 A in width, and less than 100 A thick. The term "charge per structural unit" as used in the specification and claims refers to an average charge density as specified by G. Lagaly and A. Weiss, "Determination of Layer Charge in Mica - Type Layer Silicates," Proceedings of International Clay Conference, 61-80 (1969) and G.
Lagaly, "Characterization of Clays by Organic Compounds,"
Clay Minerals, 16, 1-21 (1981).
The starting 6ilicate can be made according to the afore-mentioned procedures of U.S. Patent 4,239,519;
3,325,340; or 3,434,917 or other methods which result in dissociated layer materials with charge densities in the desired ranges.
The silicate is then contacted with a source of at least one specie6 of guanidine derived cations to thereby effect an ion exchange reaction to occur between the cations and the interstitial ions. This ion exchange reaction may be carried out between the cations and the silicate material to thereby from a floc which is then utilized to form the articles of the present invention.
In another embodiment of this invention, the starting silicate can be directly formed into a product, 6uch as a lithium fluorhectorite fiber or film by using the procedures of U.S. Patent 4,239,519, and a cationic exchange reaction utilizing the guanidine derived cations can be carried out with the product, such as by immersing the product into a solution of guanidine derived cations.
Thus, the ion exchange reaction may be carried out in during the actual forming process for the product.
Exchange cations that maay be utilized in the present invention will be derived from compounds that correspond to the Formula C~R2 ) , wherein R~ Rl and ~2 are individually selected from -NH2 and -CH3, with the proviso that at least two of R, R1 and R2 are -NH2 and, furthermore, wherein one or more of the hydrogens on R, R1, and/or R2 can be replaced by substituents such as C1-C5 alkyl, C1-C5 alkenyl, Cl-C5 alkynyl and, whsrein further one or more groupings of two of such substituents can join to form rings which may be optionally aromatia.
The flocced mineral su6pensions of the present invention are prepared, for example, by reacting, generally with agitation, a suitable silicate gel with a source of exchange cations derived from the guanidine compounds jet forth in the Formula above in order to effect an ion exchange between the guanidine derived cations and the interstitial cations in the silicate gel to form exchanged macro flooculated particles. For example, if the exchange cation of choice is guanidinium or melaminium, the silicate will be reacted with the correæponding hydrochloride.
s stated above, one or more exchange cations that are derived from the Formula above can be utilized in the cationic exchange reaction. Since the various cations will give floc, and eventually end products, with differing physical properties, the specific cation or combination of cations will be chosen by the practitioner of this invention based on the desired end use.
The flocced mineral suspension will be used to form the desired end productæ. The specific treatment steps applied to the floc will depend on the particular article being formed. For example, if the articles of the _ 7 _ S O

present invention are to be formed into sheet materials, the resultant exchanged floc will be agitated with sufficient shear to produce a particle size distribution which leads to suitable particle packing in the sheet forming operation. Following this process the floc is optionally washed to remove any excess salt solution and the consistency of the flocced slurry is adjusted to from about 0.75~ to about 2% solids. To promote better drainage rates on a fourdrinier wire, polyelectrolyte flocculating agents can then be added to the slurry at a level of from about 0.1% to about 1%, and preferable 0.2~-0.3% of floc 601ids. One example of a suitable polyelectrolyte flocculating agent is Polymin P, which is a trademark of BASF Corporation for a polyethylene imine.
This slurry is then fed to a papermaking apparatus where it i6 dewatered by free drainage and/or vacuum drainage followed by pressing and drying on drum driers.
The thus formed sheet material can be used in applications such as gaskets and the like.
If desired, and depending on the intended end use of the product, additional inert materials may be added to the flocced mineral suspen6ion. For example, if desired one or more fibrous material6 from the group of natural or 6ynthetic organic fibers or inorganic fibers may be added to the floc to improve its drainage rate and to provide an end product that has improved strength and/or handleability. For example, when the desired end products are gaskets, the fibers of choice are cellulose fibers, glass fibers, and/or Kevlar fibers (Kevlar is a trademark of DuPont Corporation for an aromotic polyamide fiber).
In addition, latex or other binders may be added to the floc to provide for a product with improved strength characteristic6.
Ifthecationicexchangereactionis conducted or directly on a product formed from the silicate starting material, any de6ired additional inert material6 would be added to the slurry of the silicate starting material prior to the formation of the product and, of course, the subsequent cationic exchange reaction.
The term "water resistant" as used in the specification and claims is not meant to imply that the articles of the present invention are waterproof or are completely impervious to water. By contrast, the term is used to indicate that the material6 do not substantially degrade, at least in their tensile strength and puncture resistant properties, when exposed to water.
In these following Examples, unless otherwise specified, the starting material utilized was a lithium fluorhectorite made according to procedures taught in U.S. Patent No. 4,239,519.
Example 1 This example illustrates a method of producing both a guanidinium exchanged fluorhectorite flocced silicate and a formed sheet that was prepared therefrom.
A slurry of guanidinium fluorhectorite was prepared by adding 475 grams of a 10% dispersion of lithium fluorhectorite to 1.4 liters of lN guanidine hydrochloride solution. The 61urry was then agitated with a high shear mixer to reduce the particle size of the resultant floc, was washed and then was analyzed for water content and diluted to result in a 2% solids slurry. The slurry was transferrea to a 11.5" x 11.5"
hand sheet mold (manufactured by Williams Apparatus Co.) and dewatered. The resultant formed sheet was then wet pressed and dried on a drum direr. The sheet had good flexibility and performed well in the gasket sealing test.

Example 2 This example illustrates a method of producing films of the present invention wherein the cationic exchange is made in flu A 10% solids lithium fluorhectorite gelled dispersion was prepared according to procedures taught in U.S. Patent No. 4,239,519. A film was made of this material by using a 4.5 mil Byrd applicator, which was 5 inches wide, to draw down a 4~ mil thick wet film of the dispersion on a gla6s plate. The glass plate, with the film attached, was then immersed in a .25M guanidinium hydrochloride 601ution to cause a cation exchange between the guanidinium cations and the fluorhectorite's interlayer cations. A skin was formed, seemingly instantaneously, on the film which indicated such an exchange was taking place, In 10 minutes the film was removed from the plate, washed in deionized water to remove residual salts, and dried. The film had good flexibility and strength retention when wet.
Examples 3-9 For each of these examples, the procedure of Example 2 was substantially repeated with the exchange cation as specified to form the corresponding film. In Example 7, a O.lN solution of melamine hydrochloride was employed.
In all the other examples, a .25N solution of the respective exchange source was employed:
Example Exchange Cation 3 Diaminoguanidine hydrochloride 4 Aminoguanidine hydrochloride Tetramethylguanidine hydrochloride 6 Methylguanidine hydrochloride 7 Melamine hydrochloride 8 2,6-diaminopyridine hydrochloride 9 2-aminopyridine hydrochloride 3L2~15~6 Com~axative Examples 1-3 These comparative examples illustrate ~luorhectorite films that axe made with various prior art exchange cations. Four and one half mil thick films of potassium fluorhectorite (KFH) and ammonium fluorhectorie (NH4FH) were separately prepared by the process specified in U.S.
Patent No. 4,239,519. A film was then cast of both the KFH and a NH4FH slurry. A kymene (a trademark of Hercules, Inc. for a cationic, polyamide-epichlorohydrin resin) fluorhectorite film was also prepared by the procedure of Example 2, except that (1) a 3.0% Kymene solution was used and (2) the lithium fluorhectorite film had to be immersed in the Kymene solution for 2 hours until the resultant exchanged film was sufficiently self supporting to be removed from the glass plate. These films, along with the films made in Examples 2-9, were then 6ubjected to tensile strength and puncture resi6tance tests which were conducted as follows:
Tensile Strenqth Measurements Dry tensile strength measurements were determined using an Instron at l jaw separation and 0.2"/min.
crosshead æpeed. Wet strength measurement6 were made by bringing water-6aturated 6ponges in contact with both sides of the film sample for 10 second6 while the sample ~5 was positioned in the Instron clamps just before the strength te6t was conducted.
juncture Resistance Measurements Sample of film was secured in a retaining device which held the film securely. A stylu6 which could be loaded was impinged on the film in the direction normal to the 6urface of the film and loaded with increasing weight until the 6tylus penetrated the film. In the wet test the film in the retaining device was 6ubmerged in deionized water for 10 second6 immediately proceeding the .~

L2415~6 puncture resistance test.
The data from these tests is shown in the table below. TABLE
Tensile juncture Strength Resistance Film of Exchange (~6 i) ~gr/mml Example # Cation Dry wet Dry wet 2 Guanidin~um 14,000 9,000 7,100 4,600 3 Diaminoguanid-inium 13,000 11,000 14,000 4,200 4 Aminoguanidinium 13,000 11,000 8,900 3,500 Tetramethyl-guanidinium11,00011,000 13,000 4,400 6 Methylguanidin-ium 5,2002,800 6,600 3,400 7 Melaminium19,00020,000 10,000 3,300 8 2,6-Diamino-pyridine (protonated)13,0005,300 7,900 3,600 9 2-Aminopyridine (protonated)11,0007,000 7,800 3,600 Comparative Example #
1 Kymene (protonated)7,0002,700900 260 2 Ammonium 3,300l,4003,500 680 3 Potassium 1,1002003,300 440 The data indicates that the films made according to the procedures of the present invention have markedly superior wet tensile strength and/or superior wet puncture re6istance when compared to prior art compositions.
Fire and Smoke Resistance A film prepared according to Example 2 was, after being dried, subject to fire and smoke resistant tests in ' :

.Y-' ! i .

- 12 - ~'~4~0~>

accordance to the procedures specified in ASTM-E-662-79.
Three separate tests were made and the results are set forth below. The numerical values correspond to the maximum specified optical density as per N.B.S. Technical 5Note #708.
Flaming Smoldering Test # DM Corr PM Corr Electrical Properties Films of Examples 2 and 7 and Comparative Example 3 were, when dried, tested for dielectric strenqth using the procedures of ASTM D149. The results are set forth below.
Films of Dielectric Strenath (v/mil) Example 2 5,000 Example 7 9,000 Comparative Example 3 2,920 Com~arativs Examples 4 and 5 Thece examples illuætrate using, as a starting material, silicate materials which fall outside the æcope of the present invention in their charge per structural unit and their phy6ical meaæurements.
For comparative Example 4, a 10% aqueous dispersion was made from a natural hectorite obtained from the source clay minerals depository of the Clay Mineral6 Society, Bloomington, Indiana. For Comparative Example

5, a 10~ aqueous dispersion utilizing sodium montmorillonite, which was obtained form the same source.
In each example, a film was drawn down using the procedures set forth in Example 2. The glas6 plates were then immersed for 10 minutes in a 0.25 M guanidine hydrochloridesolution. Inbothinstances, acoherent - 13 5~

film was not produced.
Example lO
This example illustrates a method of preparing a film of the present invention utilizing a vermiculite starting material:
A 10% solids suspension of n-butylammonium vermiculite, which was prepared according to the procedures specified in U.S. Patent 3,325,340, was cast a a film on a glass plate according to the procedure set forth in Example 2. The gla6s plate, with the film attached, was immersed for 10 minutes in a 0.25 M
guanidinium hydrochlcride solution. The resulting film was removed from the plate, washed, and dried. The film displayed wet strength in the tensile 6trength and puncture resistance tests that a comparable unexchanged vermiculite film aoes not display.
Example 11 This example illustrates preparing fibers utilizing the method of the invention. A 15% solids suspension of lithium fluorhectorite prepared as above) was extruded through an 11 mil opening needle into a 2N solution of guanidine hydrochloride. The extruded fiber was carried by a porous belt and delivered to a second bath of 2N
guanidine hydrochloride. The fiber BO produced was washed via submersion in deionized water and dried. The resultant fiber was strong and flexible.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of preparing a flocced mineral material that can be utilized to form a non-asbestos high temperature article that exhibits water resistance, which method comprises contacting a swelled layered silicate gel that has an average charge per structural unit that ranges from about -.5 to about -1 and which contains exchangeable interstitial ions with at least one species of guanidine derived cations to thereby effect an ion exchange reaction between at least some of the exchangeable interstitial ions and at least some of the guanidine derived cations.

2. The method of claim 1 wherein the gelled layered silicate is a synthetic gellable silicate and the interstitial ions are Li+
and/or Na+.

3. The method of claim 2 wherein said synthetic silicate is prepared by contacting a body consisting essentially of crystals of a water-swelling mica selected from the group of fluorhectorite, hydroxyl hectorite, boron fluorphlogopite, hydroxyl boron phlogopite, and solid solutions among those and between those and other structurally compatible species selected from the group of talc, fluortalc, polylithionite, fluorpolylithionite, phlogopite and fluorphlogopite, with a polar liquid for a time sufficient to cause swelling of the crystals accompanied with the formation of a gel.

4. The method of claim 3 wherein the crystals are fluorhectorite.

5. The method of claim 3 wherein the polar liquid is water.

6. The method of claim 1 wherein the silicate is vermiculite and the interstitial ions are alkylammonium cations, the cationic form of amino-acids and/or Li+.

7. The method of claims 2 or 6 wherein the guanidine derived cations are 8 elected from the group of diaminoguanidine, tetramethyl guanidine, guanidine, aminoguanidine, methyl guanidine and melamine derivatives.

8. A flocced mineral material which comprises a swelled layer silicate gel that has an average charge per structural unit that ranges from about -.5 to about -1, said silicate containing at least some interstitial cations that are guanidine derivates.

9. The material of claim 8 wherein the silicate is synthetically derived.

10. The material of claim 9 wherein said silicate is prepared by (1) contacting a body consisting essentially of crystals of water-swelling mica containing interstitial lithium and/or sodium cations, said mica selected from the group of fluorhectorite hydroxyl hectorite, boron fluorphlogopite, hydroxyl boron phlogopite, and solid solutions among those and between those and other structurally compatible species selected from the group of talc, fluortalc, polylithionite, fluorpolylithionite, phlogopite and fluorphlogopite, with a polar liquid for a time sufficient to cause swelling of the crystals accompanied with the formation of a gel, and (2) contacting the thus formed gel with at least one species of a cationic guanidine derivative to thereby effect an ion exchange reaction between at least some of the lithium and/or sodium cations and at least some of the guanidine derived cations.

11. The material of claim 10 wherein the crystals are fluorhectorite.

12. The material of claim 10 wherein the polar liquid is water.

13. The material of claim 8 wherein the silicate is vermiculite.

14. The material of claims 9 or 13 wherein the interstitial cations that are guanidine derivatives are selected from the group of diaminoguanidine, tetramethyl guanidine, guanidine, aminoguanidine, methyl guanidine, and melamine derivatives.

15. A high temperature, water resistant article that is prepared from a swelled layered silicate that has an average charge per structural unit that ranges from about .5 to about -1, said silicate containing at least some interstitial cations that are guanidine derivates.

16. The article of claim 15 that is prepared from a silicate floc.

17. The article of claims 15 or 16 which further is a sheet material.

18. The article of claims 15 or 16 which further is a fiber.

19. The article of claims 15 or 16 which further is a film.

20. A method of preparing a high temperature silicate article that exhibits water resistance, which method comprises contacting an article formed from gellable layered water-swelling silicate that has a charge per structural unit that ranges from about -.5 to -1 and which contains exchangeable interstitial ions with a source of at least one species of guanidine derived cations to thereby effect anion exchange reaction between at least some of the guanidine derived cations and at least some of the interstitial ions.