DE1240383B - Process for the production of asbestos paper - Google Patents

Description

GERMAN 'WTW> PATENT OFFICE

EDITORIAL

German KL: 55 F-11/10

Number: 1240 383

File number: G 35 370 VI b / 55 f

1 24 0 383 filing date: July 3, 1962

Open date: May 11, 1967

The aim of the present invention is to provide an improved method for producing asbestos paper with improved, excellent tensile and tear strength that is easily manufactured in an economical manner and that is much better and cheaper than the previously known bound asbestos papers.

The excellent properties of asbestos, especially for such uses, contribute to where heat and flame resistance are important are known. As an insulation material in Form of textile products used either as woven cloth or as ribbed paper fabric no other product can match asbestos. For the production of asbestos wipes Asbestos yarns and threads are used essentially the usual textile machines, and the fibers used for this correspond to the long fibers, such as. B. the raw fibers, and those of Group 3 (Quebec Asbestos Producers Association Quebec Screen Test). They are many different Types of asbestos fibers known. The most commonly produced asbestos with the highest utility value, in particular in the manufacture of woven textile asbestos products, the "chrysotile asbestos" is a simple magnesium silicate that is easily made into fibers and spun and a has high tensile strength and extensive heat resistance. Even with such a high quality one Fiber it is usually necessary to add cotton or other fiber material that gives the asbestos increased strength and serves as a support on the scraper. Such fibers are a lot too expensive and processing into cloths is uneconomical for many areas of application for asbestos products. Because of this, there is an exceptionally large demand for asbestos in the form of asbestos paper products. In the preparation of Such paper products made from asbestos are essentially used conventional paper-making processes, wherein a slurry of the asbestos fiber in an aqueous medium is placed on a sieve and then processed into a dry sheet in the usual way. From an economic point of view From the point of view of this, it is advisable to use the cheapest asbestos raw material available on the market. These are, of course, the shorter fibers that are unsuitable for use in textile spinning processes are. The shorter fibers are classified into groups 4 to 7 according to the Quebec screen test, with higher numbers mean shorter fiber lengths. Despite the great advances in resin and plastic processes for the production of asbestos paper

Applicant:

General Aniline & Film Corporation,
New York, NY (V. St. A.)

Representative:

Dr. W. Schalk, Dipl.-Ing. P. Wirth,
Dipl.-Ing. GEM Dannenberg
and Dr. V. Schmied-Kowarzik, patent attorneys,
Frankfurt / M., Große Eschenheimer Str. 39

Named as inventor:

Samuel Jacob Cukier, Montreal (Canada)

Claimed priority:

V. St. v. America July 6, 1961 (122 070)

production one has not yet found a satisfactory substitute for starch as a binder for Asbestos products found in the manufacture of asbestos paper, both in terms of the economy as well as the properties that come with the use of the various materials occur with asbestos.

According to the present invention, it has been found that an excellent asbestos paper product can be produced can, which is far superior to the product using starch as a binder, and where in addition, the production is cheaper. It was further found that significant improvements in the Properties of the manufactured asbestos paper can be obtained if the strength previously used by a copolymer of alkyl vinyl ether and maleic anhydride described in more detail below is replaced. In particular, there are considerable improvements in the tensile and tear strength of the so produced Papers scored.

As mentioned above, the objects of the present invention are achieved in that as Binder for the asbestos fibers a smaller amount of a copolymer of alkyl vinyl ether and maleic anhydride is used. The in

709 579/397

The scope of the present invention provided alkyl vinyl ether monomers are those in which the Alkyl group contains 1 to 4 carbon atoms, e.g.

Methyl vinyl ether,

Ethyl vinyl ether,

n-propyl vinyl ether,

Isopropyl vinyl ether,

n-butyl vinyl ether,

Isobutyl vinyl ether and

tertiary butyl vinyl ether.

It has been found that the alkyl vinyl ethers with maleic anhydride are stoichiometric in a ratio of 1: 1 even if one of the reactants is during the interpolymerization is present in excess.

Therefore, in all cases in which reference is made to the monomeric constituents of the copolymers, each of the specified amounts is present in equimolar amounts. Copolymers with different viscosity properties can be produced, which depends on the conditions of the copolymerization. The different viscosities result from the different distributions of the average molecular weight. Higher viscosity substances are those that have a higher average molecular weight. Another characteristic of the average molecular weight of a polymeric material is the K value, which can be calculated from the viscosity values. The determination of the K-value is described in detail in "Modern Plastics", Vol. 23, No. 3, on pages 157 to 161, 212, 214, 216 and 218 (1945) and is described as a thousand times the viscosity coefficient in the the following empirical equation given by k :

Iogjire _l _ 75 k ²

C ~ 1 + 1.5 kc ^ '

in which C is the concentration in grams per 100 ecm of polymer solution and η _{Γίί stands} for the ratio of the viscosity of the solution to that of the pure solvent. The K values are given as a thousand times the calculated viscosity coefficient in order to avoid the use of decimal places. In the context of the present invention, polymeric substances whose K value is approximately 10 to 200, preferably approximately 15 to 100, can be used.

K values and the specific viscosity values (// _S p) are mutually convertible and are related to one another via the relative viscosity (η _{$ ρ} ).

The copolymers used in the context of the present invention are now characterized that they have a specific viscosity between 0.1 and 2.5. The corresponding K values of such copolymers are between about 10 to about 100. Those used with the asbestos Copolymers can be used in a concentration between about 0.05 and about 5 percent by weight, based on the weight of the asbestos, but preferably about 0.1 to about 1.0 percent by weight copolymer, based on the weight of the asbestos fibers, is used. It is be-

it is worth noting that even the use of such low amounts as about 0.2% gives an asbestos product, that is of higher quality than an asbestos product made using over 5% starch it should be noted that the use of starch is about two and a half times as expensive is than the use of the copolymers according to the invention.

In addition to the advantages and improvements already mentioned that result from the use of the copolymer can be obtained from alkyl vinyl ether and maleic anhydride, it was further established that in the papermaking process when using the product according to the invention a more favorable one Processing is possible than when using starch, which is much better Outflow of the aqueous medium is due when the product is in the usual way to sheets, webs is processed.

The Quebec Standard Test includes a method of dry classification of chrysotile asbestos fibers to be divided into commercial qualities by length distribution. A Quebec standard asbestos test machine, Model # 2 used which, according to the National Research Council, Canada, also designed and operated a 0.454 kg scale scoop with graduations of 5.7 g and a sensitivity of 2.8 g as well as a control desk with a smooth surface.

The sample to be tested is placed on the table and dried to normal room temperature and humidity. The moisture content of the sample should not exceed 3%. It is then carefully mixed and a portion of 0.54 ± 2.8 g weighed exactly on the weighing pan and dropped into container 1 of the test machine. The bowl should be kept between 15.2 and 25.4 cm from the throw-through cloth. The fiber should not be constricted when the lid of the test machine is closed. When attaching the containers to the machine, they should be properly aligned with the platform and their ends should always point in the same direction. The machine is started and runs until it stops automatically. You remove each container and let the fibers of each container fall in individual piles on the control desk and also add the loose fibers that stick to the cloth to the piles. The fibers are weighed individually from each container.

When carrying out the method according to the invention, the best results are obtained, when working at pH values below 7. It is preferred to work at a pH of 3.5. The following examples serve to illustrate the present invention. The ones specified in these Unless otherwise specified, parts are parts by weight.

example 1

13 g of "Chrysotile" asbestos (fiber classification group 5; Quebec screen test) were dispersed in 21 pieces of water and the pH adjusted to about 3.5 using IOVoiger hydrochloric acid. To the watery one A 5% strength aqueous solution of a copolymer of vinyl methyl ether was then dispersed and maleic anhydride (specific viscosity 0.5, measured at 25 ° C, 1 g per 100 ecm benzene) added, until a concentration of the copolymer

solids of 0.19%, based on the weight of the asbestos, was achieved. The aqueous slurry was then beaten for 1 minute and then on a sieve in the usual way by hand Sheets formed which, after being removed from the sieve, were dried. The tensile strength of the obtained Arch was determined by the weight required to make a 15 mm strip tear. In this example this weight was about 500 g.

Example 2

Example 1 was repeated, with the exception that the asbestos dispersion was 0.38 percent by weight Copolymer, based on the weight of the asbestos, were added. According to example 1 measured tensile strength was 1160 g.

Example 3

Example 1 was repeated, but using 5.5 percent by weight instead of the copolymer Wheat starch based on the weight of the asbestos were added. The measured according to Example 1 The tensile strength of the sheet thus obtained was only 395 g.

From the above examples it can be seen that the use of the copolymer in one An amount that was only 7% of the weight of the starch used, a 300% improvement in tensile strength is achieved. It is also achieved that the sheets produced according to Examples 1 and 2 dry faster and better than those of Example 3, thereby significantly speeding up the process is made possible.

Examples 4 to 6

Examples 1, 2 and 3 were repeated, but the pH of the asbestos dispersion to about 7.0 was set and also held at this value. Here were with the copolymer obtained similar improvements in tensile strength from vinyl methyl ether and maleic anhydride.

Example 7

Example 2 was repeated, except that a copolymer of vinyl ethyl ether and maleic anhydride was used with a specific viscosity of 0.35 was used. The corresponding example 1 the measured tensile strength was 1000 g.

Example 8

Example 2 was repeated again, but the following copolymers were used:

Vinyl alkyl ethers Specific viscosity 1. Vinyl methyl ether 0.2 2. vinyl ethyl ether 0.2 3. Vinyl n-propyl ether. 0.4 4. Vinyl n-butyl ether ... 0.3 5. Vinyl isobutyl ether ... 0.1 6. Vinyl methyl ether .... 0.7 7. Vinyl methyl ether 0.9 8. Vinyl methyl ether 1.2 9. Vinyl methyl ether 1.5 10. Vinyl methyl ether 1.8 11. Vinyl methyl ether .... 2.3 12. Vinyl methyl ether 2.5

A significant improvement in tensile strength was observed in each of the above examples; the Values in the individual examples, which were measured according to Example 1, ranged from about 1000 to 1200 g.

Example 9

Example 8 was repeated, but with concentrations of the copolymer of 0.5,

ίο 0.7, 1.0, 2.5 and 5.0% was worked. The tensile strength increased with an increasing amount of copolymer used, but the increase in tensile strength between 1 and 5% copolymer slowly decreased. For economic reasons, an amount of about 1 to 2 percent by weight of copolymer is preferred in most cases.

Example 10

Example 9 was repeated. However, it was worked with a pH of 7, according to Example 4, and excellent results were obtained.

Example 11

Examples 1, 2 and 4 to 10 were repeated, but instead of "Chrysotile" asbestos, "Crocidolite" asbestos (fiber classification group 4 - Quebec screen test) was used. With this Asbestos-type improvements were made similar to that used in the previous examples Scored asbestos.

Example 12

Examples 1, 2 and 4 to 10 were repeated, but using "Chrysolite" asbestos, type 6D became. As in the previous examples, significant improvements have been made to the Tensile strength achieved.

Example 13

Example 10 was repeated, but using an asbestos mixture instead of the "chrysotile" asbestos was used, which consisted of 50% Johns-Manville Grade 4 R 04 and 50% Grade 7 D15. Here were obtained excellent tensile strengths.

Example 14

A dispersion of the asbestos mixture was produced by adding 15 g of asbestos according to Example 13 to 21 water. 0.25% of a copolymer of vinyl methyl ether and maleic anhydride with a specific viscosity of 1.8 was added to this dispersion. Sheets were produced according to Example 1 and tested for their tear strength (folding strength) (Mullen burst test). The values are given in kg / cm ² per 2.54 cm of the thickness of the sheets. The sheets produced in this example had a tear or fold strength of 14.8 according to the Mullen burst test. A similar sheet using 5% wheat starch as a binder had a Mullen rating of 12.6.

Example 15

Example 14 was repeated, but using a copolymer with a specific viscosity of 0.31 was used. The Mullen value here was 10.3. A comparison sample in which 5%

Claims (6)

Wheat starch were used as a binder, in contrast, had a Mullen Burst value of 133. Example 16 Example 14 was repeated, but using a copolymer with a specific viscosity of 1.5. Here too, the Mullen burst value was 10.3, while the Mullen value of the comparative sample, which contains 5% wheat starch as a binder, was 9.3. Patent claims: 1. The use of an aqueous dispersion of a copolymer known per se from an alkyl vinyl ether with 1 to 4 carbon atoms in the alkyl substituent with maleic anhydride in an amount of about 0.05 to 5 percent by weight, based on the weight of the asbestos fibers, in the manufacture of asbestos paper or the like on a wet road. 2. Embodiment according to claim 1, characterized in that the copolymer in in an amount of from about 0.1 to about 1 percent by weight. 3. Embodiment according to claims 1 and 2, characterized in that a vinyl ethyl ether maleic anhydride, Vinyl methyl ether-maleic anhydride, vinyl propyl ether-maleic anhydride or vinyl butyl ether-maleic anhydride copolymer is used. 4. Embodiment according to claims 1 to 3, ίο characterized in that chrysotile asbestos is used as asbestos. 5. Embodiment according to claims 1 to 4, characterized in that a copolymer with a K value of about 10 to about 100 is used. 6. Embodiment according to claims 1 to 5, characterized in that a pH of about 3.5 is set. ao Considered publications: German Patent No. 540101;
Römpp, Chemie-Lexikon, Vol. II (1953), p. 1925.