JPS6050752B2 - Method for manufacturing film or sheet shaped articles from vermiculite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for producing film or sheet shaped articles from vermiculite, which belongs to the phyllosilicate mineral family.

It is known that phyllosilicate minerals can be swollen by aqueous solutions of various salts. Vermiculite (defined below) is an example of a phyllosilicate mineral, consisting of individual particles or lamellae that make up swollen vermiculite.
It has already been proposed to make flexible sheets of swollen vermiculite after delamination to colloidal dimensions such that the size of the e'Eae (scales) is reduced. Such technology is described, for example, in British Patent No. 101
No. 6385 and No. 1119305. The term vermiculite as used herein refers to a substance mineralogically and commercially known as vermiculite, which includes hydropiotite or a certain proportion of vermiculite-like layers. Contains and swells in the same or similar manner. It is also intended to include other silicic silicate minerals such as vermiculite, which can be chlorinated.

One problem encountered in making suitably flexible, high strength articles from delaminated vermiculite is that the vermiculite does not delaminate properly and therefore the vermiculite does not delaminate properly. The presence of significant amounts of granular material may impair the strength or flexibility of the final article formed from the lamellae. Here, careful control of the swelling and milling steps during the processing of vermiculite; subsequent formation of vermiculite lamella layers prepared to appropriate dimensions and, if blended, film or sheet formation. It has been found that a particle size screening step can be advantageously performed to separate particles of large size that may impair the physical properties of the article.

The gist of the present invention is to prepare a shiku-miculite mineral by contacting it with an aqueous solution of at least one salt of sodium or lithium or an organic substituted ammonium cation, followed by washing with water to remove at least 20% of its initial volume. Step (1) of swelling the vermiculite to double its original size, and subjecting the swollen vermiculite particles in the aqueous suspension obtained in this step (1) to shearing action to delaminate the swollen vermiculite and suspend it. step (Ii) of carrying out the delamination until an aqueous suspension of vermiculite particles in which the three-dimensional dimension of the delaminated vermiculite particles in the liquid is 50 microns or less can be selected;
Furthermore, by depositing the vermiculite particles from the obtained aqueous suspension of vermiculite particles onto a solid surface, a film or a sheet-like molded article of vermiculite particles is formed, and the suspension is (iii) forming a film or sheet-like molded article by removing water from the suspension;
step (Iv) of erasing all or substantially all of the vermiculite particles having a maximum (longest) dimension of greater than 50 microns from the aqueous suspension of vermiculite particles obtained in step i); A method for producing a film or sheet-like molded article from vermiculite, which is carried out before the step (Iiii) for forming the film or sheet-like molded article. It is in.

In the swelling step (1) of the method of the present invention, the swelling of the vermiculite mineral is preferably allowed to proceed to at least four times its initial volume, and it is best when the swelling ratio is greater than 6:1. Results are often obtained.

The anion of the salt of lithium, sodium or substituted ammonium is preferably an inert anion commonly found in stable salts of these cations and is an anion that does not decompose chemically during the swelling step (1). is preferable.

For example, halogen ions, preferably chloride ions.
Swelling can be carried out by immersing the vermiculite mineral in an aqueous solution of salt at various temperatures, and since it usually proceeds more rapidly at temperatures above room temperature, the aqueous salt solution is refluxed with the mineral. is preferable.

The maximum degree of swelling can be achieved by washing the vermiculite mineral with pure water.
and optionally only by immersion in water after contact with the salt solution.

successively treating the mineral with separate solutions of two different salts;
It is often preferred to immerse or wash the vermiculite mineral in pure water in between the two treatments. Delamination of swollen vermiculite particles in suspension occurs fairly easily when subjected to some shearing action.

The shearing action can be provided by a mill, mixer or macerator, which has, for example, shearing members such as rotating paddles or blades acting within a limited constant volume, or counter-rotating rollers of a multi-roll mill. be. Alternatively, a shearing action can be imparted to the suspension by a suitable vibratory treatment, such as, for example, ultrasonic agitation. The desired products in the delamination step (Ii) are small lamellae of vermiculite (hereinafter referred to as
(sometimes simply 1 thin layer) or 3 as shown by the plate crystal.
The dimension σ in one direction of the dimensions corresponds to the dimension σ in the other two directions (corresponds to the lateral diameter or the longitudinal diameter in the plane perpendicular to the thickness r). It is an aqueous suspension of vermiculite particles that are much smaller than the corresponding vermiculite particles, and therefore there is a risk that the three-dimensional dimensions of the particles will be approximately the same in all three directions. It is undesirable to subject the suspension to some severe abrasive or impacting action.

The preferred milling or maceration of the suspension is
High-speed rotating mixer such as RGreaves HS M-■
It can be carried out in a laboratory mixer with a rotating paddle, such as in a laboratory mixer, or in a home or pharmaceutical juicer. Some high temperature mills such as colloid preparation mills or RpOlytrOn. The J-mixer should be used with caution as it tends to destroy the thin layers quickly after the desired delamination has occurred. The step (1i) of delaminating the layers in the method of the invention is carried out until the aqueous suspension of vermiculite particles subjected to the delamination treatment exhibits a cohesive viscosity of at least 100 centipoise, particularly preferably 400 centipoise or more. Preferably.

In this specification, the above-mentioned cohesive viscosity means a viscosity value measured by the following method. In other words, the first cohesive viscosity is obtained by taking a number of samples of a predetermined amount from an aqueous suspension of vermiculite particles, all of which are 50 microns or less, which have undergone delamination treatment, and calculating the vermiculite content in each sample. After adjusting the amount to 3.5% by weight, this is mixed with, for example, 1 N to 1 powder of 1 N dilute hydrochloric acid while varying the amount of dilute hydrochloric acid used to cause agglomeration of vermiculite particles. For the flocculated liquid, 58
The viscosity is measured at a shear rate of /sec, and the maximum value of the various viscosity measurements thus obtained is taken as the cohesive viscosity. A test is carried out to measure the cohesive viscosity and the delamination step (il)
progress can be monitored.

A preferred method of measuring cohesive viscosity consists of the following operations.
A portion of the vermiculite suspension that has undergone delamination treatment is taken out, particles of 50 microns or more are separated from this sample, and after adjusting the vermiculite solid particle content, 1N or 1 powder is added to the vermiculite suspension. 1N dilute hydrochloric acid is added to cause flocculation, and the flocculated suspension sample is measured using a viscometer (e.g., HaakeR).
Transfer to OtOviskORV3). Furthermore, a large number of samples were simultaneously taken out of the suspension during the delamination process, and the amount of dilute hydrochloric acid added to each sample was increased by changing the amount.
The viscosity of each sample is measured, and among the various viscosity measurements obtained, the maximum achievable viscosity value is determined as the cohesive viscosity. For example, for each 50ml sample taken from a vermiculite suspension, add 20-30ml of 1/10N hydrochloric acid or 1-5ml of 1N hydrochloric acid, measure the maximum viscosity, and draw a graph. By finding the maximum value, we were able to determine the value of r-cohesive viscosity. In an oversize particle elimination step (Iv), particles with a maximum dimension dimension greater than 50 microns are separated from the entire suspension, the larger particles being subjected to a swelling step (1) if desired.
for further swelling or a delamination step (I
Return to step i) for further milling. Preferably, all or substantially all particles with a maximum dimension dimension (diameter) greater than 20 microns are erased, but this may suitably (but not necessarily) ), preferably by a second particle classification operation that is the same as or similar to the first particle classification operation. Particles with a maximum dimension dimension greater than 50 microns must necessarily be separated out in the oversized particle elimination step (1v), but all or substantially all particles with a maximum dimension dimension greater than 20 microns are also suspended. When erasing from the surface, it is not preferable to try to erase both particles with a particle size of more than 50 microns and particles with a particle size of 20 to 50 microns in one operation.

Particle size selection can be performed more efficiently in two stages than in one stage. For better physical properties of the molded article it is preferred to eliminate all particles with a diameter greater than 5 microns. Furthermore, it is desirable that the size distribution of particle diameters in the final suspension is not too broad. The sizing screening carried out in the oversized particle elimination step (Iv) is usually carried out on unagglomerated suspensions that have been milled to the required standard.

Suitable milling standards can be determined by viscosity tests performed on agglomerated suspensions, as described above. Elimination of particles with a maximum dimension size greater than 50 microns (or 20 microns) can be accomplished by any of the conventional dimension-specific separation methods, such as sedimentation, filtration, sieving, centrifugation, and cyclone. There is a separation method.

Alternatively, the entire aqueous suspension of vermiculite particles may be sheared again to eliminate particles larger than 50 microns in size. Preferred methods for determining this are overnight and sedimentation methods. (a) Sedimentation method The suspension (agglomerated or non-agglomerated as described above) is stirred well to make it homogeneous, and then left to stand.

Did it settle to the bottom of the container after a certain period of time? Allow the suspension above to flow away. If desired, the resulting homogeneous decantation liquid can be processed in the same manner as many times as required. In this way, coarse particles (those that settle) are separated from fine particles (those that remain in suspension)! can be done.

Although experimental determination is often satisfactory for this operation, calculations based on Stokes' law (eg considering particles of equivalent spherical diameter) are also often useful. The important variables for a given suspension are:
4 (1) the settling time, and (Ii) the height at which a given particle falls.

The flocculation state of the suspension influences both of the above variables.

The reason is that agglomeration of vermiculite particles affects effective particle size and suspension viscosity. For the operation of the present invention, a completely unagglomerated suspension gives the best results, since all but the very fine particles (colloidal) settle out.

Thus, if small particle sizes are desired, the suspension is allowed to stand for an extended period of time (eg, many hours or even days if necessary) until equilibrium is approached. Upon standing for such an extended period of time, electron microscopy reveals that the resulting suspension contains only particles with a maximum dimension size substantially less than 20 microns. (b) Filtration Methods Although the sedimentation method described above allows the concentration of particles to be spread over a wide particle size range, it is not the preferred method when a fraction with one well-defined particle size range is required.

However, such a well-defined size range of fractions can be obtained by using filters of precise known pore size. This is because particles of any size larger than the pore size cannot pass through. In some cases, filtration methods are useful to supplement sedimentation methods for specific purposes. Since the vermiculite plate crystals tend to clog the filter pores, it is not always easy to filter the unagglomerated vermiculite suspension.

In order to promote filtration, various auxiliary means can be used to avoid clogging the pores of the filter. For example, mechanical or vibrational. Mechanical cleaning of the filter pores can be done by brushing or scraping, with rotary flushing being convenient. Vibratory cleaning can be accomplished by mechanically vibrating the entire filter assembly. Alternatively, the filter network itself may be vibrated, for example ultrasonically. For the delamination step (Ii), the vermiculite particle concentration (measured by weight of vermiculite in a given volume of suspension) is suitably between 1 and 50 wt%, most preferably between 5 ~2
It is 5wt%.

For the oversized particle elimination step (1v), a vermiculite particle concentration of 1 to 25%, preferably 5 to 10% is used.

Film or sheet-like molded product forming process by this method (Ii
Although i) can be carried out using a suspension containing 5-10% vermiculite, it is preferred to concentrate the suspension prior to step (iii).

Higher concentrations of vermiculite, such as in the range 5-60% (or 70%), preferably in the range 10-40%, are advantageous for sheets. This is because water removal can be performed more quickly (and therefore using less energy) on sized films or sheet shaped articles from highly concentrated suspensions. The particles retained in the suspension have a three-dimensional dimension of 50
Particles that are smaller than microns, and here 50 microns or smaller means that the maximum (longest) dimension of the dimension in three directions of the particle is 50 microns or smaller.
Refers to being smaller than a micron. Since the vermiculite particles in suspension are in the form of fine plates or lamellae, all particles have a very small dimension in one of the three dimensions (the so-called 1 plate). This dimension value corresponds to the maximum (longest) dimension of the particle (corresponds to the transverse diameter or longitudinal diameter in a plane perpendicular to the thickness). In many cases, it is on the order of 1/1000 to 1/1000. A dried film or sheet shaped article made from vermiculite lamellae by the method of the present invention is an article consisting essentially entirely of vermiculite lamellae bonded together by mutual attraction. be.

Laminates or sandwich structures of sheets or films of vermiculite and other materials (eg, paper, plastic) may also be produced using the method of the present invention. Molded articles in the form of films or sheets produced by the method of the invention are susceptible to liquid water, but these articles can be made water resistant by post-molding ion exchange treatment (such ion exchange For example, the treatment method is described in British Patent No. 1016385.
(as stated in the specification).

Corrugated sheets can be produced by depositing a vermiculite suspension on a suitably shaped substrate or by stamping a dry sheet between stamped press plalens or rollers. .

The corrugations can be applied in two directions (eg machine direction and transverse direction) and such sheets are not only decorative but also have improved mechanical properties (eg elongation at break). Additionally, sheets so creeped have improved handling and drapability. Multiple corrugated sheets can be joined together to create a honeycomb-like three-dimensional structure. When a film or sheet-like article is formed using this method, moisture is removed by heating or evaporating without heating, or by using a molding mold using a method similar to the pour molding method used in the ceramics industry. surface (e.g.
It can be removed by absorbing it into the absorbent material of the mold.

When rapid removal of water is required, a thin layer of vermiculite can be deposited electrophoretically from the suspension. Once most of the water has been removed by any of the above methods, the vermiculite layer may be stripped from the mold surface on which it was formed;
or it can remain as a non-flammable coating on the mold surface (such a coating also has the added advantage of low water vapor permeability). It has been found that vermiculite from the United States can be delaminated more efficiently than vermiculite from South Africa and exhibits lower permeability to water vapor when sheeted.

For example, water vapor permeability values twice as good as those typically found in polypropylene films have been obtained for vermiculite. The vermiculite suspension can be applied to a substrate (eg, a plastic material) by any surface coating method, such as a spray method.

For materials such as wood, hardboard and fibreboard, coating vermiculite sheets by using suitable adhesives or by forming vermiculite sheets in-situ on the material. I can do it.

Materials with such vermiculite coatings give good ratings in the British Standard Fire Test, e.g. Class I in the Small Scale Surface Expansion Flame Test, but
Materials without Novamiculite coating are class ■～■
It only shows that. According to the method of the invention, sheets with excellent physical properties, in particular tensile strength and flexibility, can be produced if particle size selection in the suspension is carried out in the oversized particle elimination step (Iv). .

More specifically, as in the method of the present invention, an aqueous suspension of vermiculite lamellae freed of particles with a maximum dimension size greater than 50 microns is used, which is formed into a sheet by dehydration. Sheet moldings can then be produced which have excellent physical properties, in particular tensile strength and flexibility. As an effect of the process of the invention, film or sheet moldings produced by the process of the invention from vermiculite lamellar suspensions free of vermiculite particles with a maximum dimension dimension greater than 50 microns: It has good appearance and considerable strength, generally exhibiting a breaking strength of greater than 8000 KNm-2.

For example, when a suspension containing only vermiculite lamellae with a particle size slightly smaller than 50 microns is used, a film exhibiting a breaking strength of about 25,000 KNm-2, and a film with a particle size of 5 microns or less is produced. Vermiculite・
When using a suspension containing only lamellae, 60
A film is obtained which exhibits a breaking strength of 000 KNm-2.

Moreover, these films withstand repeated folding and refluxing well without cracking or tearing. On the contrary, a suspension of vermiculite particles which is similarly prepared without the method of the present invention still contains vermiculite particles having a maximum dimension dimension greater than 50 microns without being removed. The resulting film or sheet molded product has a poor appearance with coarse vermiculite flakes protruding on its surface, and is brittle and has a lot of dust. It is difficult to measure because of poor performance. If you dare to measure it, the breaking strength of the film is only about 4000 to 5000 KNm-2 at the most, and if you fold it back, you can avoid the drawback of cracking. I can't do it. The vermiculite sheets or papers produced by the method of the invention can be applied as facings or liners to organic polymer foam panels (e.g. polyurethane foam panels) to improve flame resistance. It is useful for

Such a panel is described in British Patent Application No. 33918/77. The vermiculite sheet was found to be able to withstand temperatures of at least 1000'C without cracking, and the sheet maintained its physical integrity although certain physical properties changed. The vermiculite ♦ sheet produced according to the present invention has the following uses, for example.

A. Providing a flame barrier to suppress the combustion of organic foam or wood or other flammable materials; B. As such,
or other materials (e.g. polymeric films or paper)
To provide a flexible flame-resistant packaging material that can prevent the spread of flame when laminated to a flame-resistant and moisture-resistant barrier (e.g., the outer surface of a building material).

D As a flexible container for powder or fibrous insulation to prevent the insulation from spreading at high temperatures or after long periods of use, E Flexible to not collapse when exposed to flame or other high temperature conditions providing an electrically insulating layer (e.g. cable jacket).

F. Use as a flexible flame-resistant membrane to provide a protective enclosure to limit the spread of smoke, gases, and other contaminants during a fire.

Use as a separator between articles being processed in a G-furnace or rotary furnace or as a spacer for important documents (e.g. to reduce the risk of complete loss due to fire).

H For use as a flexible protective blanket or shield against sparks and flames (e.g. from welding torches).

I. Use as a base material for transcription that is resistant to high temperatures and relatively inert to chemicals.

As mentioned above, all or all of the vermiculite particles obtained starting from vermiculite minerals through the above steps (1), (Ii) or (Iv) and having a maximum dimension dimension of greater than 50 microns The aqueous suspension of vermiculite particles, which has been substantially depleted, is then subjected to the dehydration molding process described above (i. , it is possible to provide a high-strength film or sheet-like molded article consisting essentially entirely of vermiculite lamellae.

and an aqueous solution of vermiculite lamellae containing vermiculite lamellae having a maximum dimension dimension of 50 microns or less, but substantially free of vermiculite particles having a maximum dimension dimension of greater than 50 microns. It is obvious that all suspensions, regardless of how they are prepared, can be used to produce vermiculite lamellar film or sheet shaped articles by removing the water. The vermiculite sinite produced by this method exhibited good flexibility under normal atmospheric conditions (i.e., could be folded repeatedly many times without creasing or tearing).

The fracture strength measurements reported here were taken at a pull rate of 0.5 cm/min and are for sheets vacuum dried on silica gel for 2 hours.

Example 1 Vermiculite from South Africa (MandOv
A sample of 1k9 (referred to as all micron grade) was refluxed for 8 hours in a saturated saline solution 5e.

Excess salt was then washed from the product with water. Next, vermiculite was dissolved in n-butylammonium chloride solution 5e (1250 mt of 1N hydrochloric acid (5n-butylamine 12
The mixture was refluxed again in a diluted 0 mt mixture.
After washing out the excess salt, the product was swollen in water. The fully swollen material (swell ratio = 6.0) was divided into two equal parts A and B. Add part A to 4' with water and JGre
Milling was carried out for 1 hour using an aveso high speed mixer (6000 r'Pm).

Oversized material (greater than 50 microns) was then removed from the product by a sedimentation method as described below. Its cohesive viscosity was determined to be 500 centipoise (measured similarly to the measurement method described in Example 8 below). The resulting homogeneous suspension was left in an aspirator bottle for 5 minutes (liquid height 22.1
cm), and then the upper suspension was separated by decantation from the lower settled solids. The decantation solution was stirred well to make it homogeneous and processed in the same manner as above (an additional 3
Processed twice. A settling time of 10 minutes was used each time). The wave height before final settling was 15.3 cm. The final decantation liquid (3290TrL1) obtained in this way was
It is called suspension (A)J. This had a solids content of 4.3%. All excluded residues were saved (see below)
. Part B of the swollen vermiculite was then treated in the same manner as part A to form a zero suspension BJ (35
30 ml) and a rejected residue were obtained.

Combine the residues from A and B above and add 4 ml of water.
e and was milled and sedimented as described for suspension A. The resulting suspension was made into 4470ml. This is called 1 suspension CJ. The solids content of suspension (C) was 3.6%. Suspension C under electron microscope
Testing showed that there were (1) particles less than 1 micron in diameter, (1i) particles between 1 and 10 microns in diameter, and (iii) a small number of particles up to about 40 microns in diameter.

When a sample of this suspension was evaporated, the breaking strength was 22,
251KNm-2 and tensile modulus 4149MNm
-2 vermiculite sheet was obtained.

This sheet shows good flexibility under normal indoor conditions and
Folded at least 20 times without tearing in repeated creasing folding test. Sheets produced by evaporation from suspension A are similarly flexible and have a breaking strength of 23,19
5KNm-2 and tensile modulus 1430fΔm-2
It was hot. For comparison, after milling Part A for 1 hour, the oversized particles (larger than 50 microns) were removed by sedimentation immediately from the milled suspension. When a sheet of vermiculite was formed by evaporation and removal of water, the sheet molded product obtained was extremely brittle and broke after being bent once, making it difficult to measure its breaking strength. When measured, the breaking strength was found to be about 4000 to 5000 KNm-2. "Example 2 1 kg of the South African vermiculite sample used in Example 1 was added to 5 f of a saturated salt solution.
The mixture was refluxed in a vacuum chamber for 3 minutes, and then thoroughly washed with distilled water.

After draining off the excess water, the vermiculite was refluxed in the n-butylammonium chloride solution 5' prepared as in Example 1 for 2 hours. The vermiculite is then washed in distilled water until sufficient swelling occurs (swelling ratio 4
．． 8) Left in water. The swollen vermiculite was converted into a suitably small thin layer suspension using an RGreaves J mixer (see Example 1).

Upon completion of the milling operation, oversized particles (greater than 50 microns) were removed by passing the suspension through a 50 micron stainless steel sieve.

The cohesive viscosity was 500 centipoise (measured in the same manner as described in Example 8 below). The solids content of the classified suspension was 4.12% W/v. This suspension was dried overnight at room temperature in a ventilated room to a thickness of 0.13 mm.
I made a wt sheet. Breaking strength 24,480KNm-
2. Tensile modulus was 1929r1V4Nm-2. The flexibility of the sheet under normal atmospheric conditions is good,
It was possible to repeatedly bend it over 20 times without tearing it. For comparison, after the above milling operation was completed, the milled suspension was immediately processed in the same manner as the sheet forming method of Example 2 without removing oversized particles (>50 microns) by filtration. It was molded into a sheet with a thickness of 0.13 Tf$L.

This sheet molded product was extremely fragile and broke after being folded once, making it difficult to measure its breaking strength.
The value of was obtained. Example 3 Vermiculite from North America (ZenOlite NO.4)
1k9 was subjected to the same treatment conditions as in Example 2.

The swelling ratio was 5.6. The solids content of the filtered suspension (less than 50 microns) was 3.5% w/v).
The vermiculite sheet made as in Example 2 had a breaking strength of up to 50,592 KNm-2 and a
The tensile modulus was up to 9 MN m-2. The flexibility of the sheet was comparable to that of Examples 1 and 2. Example 4 Vermiculite from South Africa (MandOvaLl
Micron grade Jl5Og was soaked in a 26.4% (w/w) lithium chloride solution for 3 weeks with occasional stirring.

At the end of this period, the minerals were thoroughly washed with distilled water and left in distilled water until fully swollen (swelling ratio 93.0).

The suspension of the swollen mineral was then made up to 31% with distilled water, and Grea
Milling was carried out in a VES mill for 1 hour (at 6000 rpm). Coarse particles larger than 50 microns were sedimented and removed using the method of Example 1.

In this case, the liquid height before the final sedimentation treatment was 12.0 cm. The solids content of the final decantation liquid is 22.2
% (w/v). The vermiculite sheet made as in Example 2 had a breaking strength of 8,892 KNm-2 and a tensile modulus of 2,012 mm.

It broke after 14 repeated folds under normal room conditions. For comparison, after completing the milling operation mentioned above,
Without removing oversized particles (>50 microns) by sedimentation, the suspension after milling was immediately molded into sheets with a thickness of 0.13 mm by the same method as the sheet forming method of Example 2. It was formed into a sheet.

This sheet molded product breaks after being folded once,
It was extremely fragile and it was difficult to measure its breaking strength, but when we dared to measure it, it was approximately 4000 to 5000 KNm-
A value of 2 was obtained. Example 5 1k9 American vermiculite, 30% (w/w)
The mixture was refluxed for 2 hours in a lithium chloride solution.

Excess salt was first washed away with tap water, and the final washing and swelling treatment was carried out in distilled water. The final swelling ratio was 9.0 in this example. The swollen mineral was milled as in Example 1 in an RGreaveso mill. and 5
Passed through a 0 micron sieve. The solids content of the sake suspension was 4.2% (w/v). The breaking strength of the vermiculite sheet made as in Example 2 was 10.20.
9KNm-2, and the tensile modulus is 1283MNm
It was -2.

For comparison, after the above milling operation was completed, the milled suspension was immediately processed in the same manner as in the sheet forming method of Example 2 without removing oversized particles (>50 microns) by filtration. A sheet having a thickness of 0.13 Wf1 was formed by this method. This sheet molded product broke after being folded once and was extremely brittle, making it difficult to measure its breaking strength.
A value of KNm-2 was obtained. Example 6 Aqueous suspension C of n-butylammonium vermiculite with a solids content of 3.6% as in Example 1 Suspension C
I created a

Next, 300 mt of this suspension was allowed to stand at a wave height of 9 cm for 8 hours. At this time, the upper suspension (190 mL) was removed from the sediment.
) was collected by decantation. This decantation liquid contained 24% of the total solids initially present and upon evaporation formed a sheet with a breaking strength of 30,424 KNm-2 and a tensile mossulus of 4,866 rV1 Nm-2. Electron microscopic examination of the decantation suspension revealed that it contained only particles less than 1 micron in diameter. Similar results can be achieved more quickly by using a low speed centrifuge (eg 4000 rpm) to accelerate the sedimentation process.

Example 7 An aqueous suspension of n-butylammonium vermiculite (Suspension A) with a solids content of 4.6% was prepared as in Example 1.
) was created.

This suspension was then passed successively through filters with pore sizes of 20 micron, 10 micron and 5 micron. At this time, the flow through each filter was maintained using an ultrasonic needle. Samples of each Oki filtrate and Mioki filtrate suspension were evaporated to form sheets. The tensile strength properties of these sheets were as shown in the table below. In another experiment, it was found that ultrasound irradiation itself had no effect on tensile strength properties. After forming a sheet of vermiculite, the tensile strength can be increased (eg, by up to 30%) by applying compressive force with parallel plate braces.

For example, it is effective to apply a pressure on the order of 10 MNm-2 for about 1 min. Example 8 Two 3 kg batches of South African vermiculite (Mandvalr micron grade) were prepared as in Example 1 after refluxing in saturated saline solution 15e and then washing in distilled water. The mixture was further refluxed for 2 hours in n-butylammonium chloride solution 15e.

The vermiculite mineral was washed well again in distilled water and swelling started. When left in the 201 solution, each batch reached a final swelling volume of 5.5 times the initial mineral volume.

The two batches were then milled together. The solids content of the combined batch was adjusted to 9% (w/w). The swollen vermiculite was converted into a suspension using three different mill apparatuses as described below.

(a) Batch of 4' was mixed with RGreavesJ mixer (6
Milling was carried out at 000r'Pm).

(b) A batch of 2e was milled in a similar rotor-in-stator mill (referred to as the 11ad0 mill) to approximately 15,000
Milling was carried out at T'Pm.

(C) A batch of 1e was milled in a pharmaceutical KenwOOd liquefier.

The rotational speed was 14,000 r'Pm. The milled suspension in each case was sieved through a 50 micron sieve.

Claims (1)

Claims: 1. Vermiculite mineral is prepared by contacting it with an aqueous solution of at least one salt of sodium or lithium or an organic substituted ammonium cation, followed by washing with water to at least twice its initial volume. step (i) of swelling the vermiculite particles in the aqueous suspension obtained in step (i) to a shearing action to delaminate the swollen vermiculite; step (ii) of carrying out said delamination until it is possible to select an aqueous suspension of vermiculite particles in which the three-dimensional dimension of the delaminated vermiculite particles is 50 microns or less; A film or a sheet-like molded article of vermiculite particles is formed by depositing the vermiculite particles onto a solid surface from an aqueous suspension of vermiculite particles, while forming the suspension. (iii) forming a film or sheet shaped article by removing moisture from the
Moreover, a step (iv) of erasing all or substantially all of the vermiculite particles having a maximum dimension dimension greater than 50 microns from the aqueous suspension of vermiculite particles obtained in step (ii) above. )of,
A method for producing a film or sheet-like molded article from vermiculite, which is carried out before the step (iii) of forming the film or sheet-like molded article. 2. The method of claim 1, wherein the swelling of the vermiculite mineral proceeds to at least four times its initial volume. 3. The method of claim 1, wherein all or substantially all particles having a maximum dimension dimension greater than 20 microns are eliminated from the suspension after the delamination step. 4. The method of claim 1, wherein all or substantially all particles having a maximum dimension dimension greater than 5 microns are eliminated from the suspension after the delamination step. 5. The method according to claim 1, wherein in the step of forming a molded article by removing water, water is removed by evaporation, absorption or electrophoresis.