US3494527A

US3494527A - Web stretching devices having silicone resin surfaces

Info

Publication number: US3494527A
Application number: US705951A
Authority: US
Inventors: Ignaz Bauer; Rudolf Riedle; Siegfried Nitzsche
Original assignee: Wacker Chemie AG
Current assignee: Wacker Chemie AG
Priority date: 1967-02-21
Filing date: 1968-02-16
Publication date: 1970-02-10
Anticipated expiration: 1987-02-10
Also published as: FR1555998A; BE710992A; GB1186828A; DE1635364B1

Description

Feb. 10, 1970 AUER ETAL 3,494,527

WEB STRETCHING DEVICES HAVING SILICONE RESIN SURFACES Filed Feb. 16, 1968 INVENTORS 7 5 IGNAZ BAUER RUDOLF RIEDLE SIEGFRIED NITZSCHE wai -v ATTORNEY United States Patent Office Patented Feb. 10, 1970 US. Cl. 22688 4 Claims ABSTRACT OF THE DISCLOSURE This application covers a web-stretching device, such as those used in textile coating equipment, in which the surfaces which contact the web are coated with a silicone resin constituting a cured organopolysiloxane resin having a content of between 35 and 900 percent by weight of fillers or reinforcing agents and may also include a glass cloth as reinforcing agent. The metal surfaces are roughened, as by sand blasting, and a layer of reinforced resin, preferably between 0.5 and 3 mm. in thickness is applied. The resin is then cured.

Background of the invention The present invention related to textile coating equipment or other web feeding equipment wherein widths of the web are stretched by wedging contact with the edges of the web, and more particularly relates to prevention of build-up of deposits on the web contacting surfaces.

In the textile industry webs of woven, knitted, or nonwoven fabrics are frequently subjected to heat treatment especially during drying, finishing, thermofixing, or thermosetting. During these procedures the widths of fabrics must be clamped and stretched with stretching apparatus at both selvages so that at the completion of this step they will have the desired width, as well as being smooth and even. Such stretchers include those which operate by wedging or pinching. This application concerns mechanical clamping devices which grasp the edge of the widths of fabric like a pliers and hold it by pinch- It is impossible to manufacture light-colored material, such as yellow for instance, if the clamps in use are not free from dye residues remaining from previous use and which will affect the yellow tone which is desired. This is particularly true when the web has been previously treated with a dark color such as blue. Furthermore, supplementary textile materials such as sizings or impregnating agents can form undesirable, firmly adhering, generally colored residues on the clamps, especially at the usually high fixing temperatures. It is therefore necessary to have clamps available which have not been soiled by previous use with materials which will cause trouble upon subsequent use. Because of the increasingly large numbers of treatments to which widths of fabric are subjected, the variety of the chemicals employed, and the increasingly high temperatures at which heat treatments of textiles running through a stretched frame are conducted, the solution to this problem has become more and more difficult.

The mechanical removal of dye residues and other deposits by brushing, for example, requires substantial cost in both money and labor and is frequently combined with a lengthy halt in production. Running the clamps through cleaning baths containing organic solvents which will dissolve the deposits or at least soften them enough so that they are more readily removed mechanically, also requires high expenditure of time and labor. The cost of the additional equipment is also often quite substantial.

An attempt to avoid the formation of deposits on the clamps by coating these parts which come in contact with the web of fabric with aqueous diorganopolysiloxane emulsions, known as release agents, or other agents for preventing deposits, does not lead to satisfactory results. As the widths of textile traverses the clamps, such emulsions are rapidly carried away. The absorption of the release agents by the webs of fabric results in uneven dyings and finishing.

Summary of the invention Accordingly, it is an object of the present invention to eliminate, insofar as possible, the above-mentioned disadvantages.

In accordance with the present invention, at least the portion of the clamp surfaces which come into contact with the web of material passing through the clamps, consists of a cured organopolysiloxane resin such as those known for the preparation of molded articles, and which has a content of between 35 and 900 percent by weight calculated on the weight of the organopolysiloxane resins, of fillers which term includes reinforcing agents. Preferably, the layer of organopolysiloxane resin is between 0.5 and 3 mm. in thickness.

The present invention avoids the above disadvantages. No deposits, or at least none that are difficult to remove, can form on the stretching devices of the present invention even when these devices are run at temperatures of up to 220 C. Furthermore, the resin does not rub off on the web and thereby create problems with further processing, nor is it eliminated from the surfaces of the clamping devices during operation.

Brief description of the drawings The invention along with other objects and advantages thereof will become understood to those skilled in the art by reference to the following detailed description when read in conjunction with the accompanying drawings wherein:

FIG. 1 is a somewhat diagrammatic view in perspective of a web being fed through a treating roller and being held taut by clamping devices according to the present invention;

FIG. 2 is a fragmentary view of a portion of the system shown in FIG. 1 showing the position of one of the clamping devices made according to the present invention; and

FIG. 3 is a fragmentary view partly in cross-section showing an elevation of one of the clamping devices shown in FIG. 1 or 2.

Description of the preferred embodiments Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the figures thereof, there is shown in FIG. 1 a web 11 which may be, for example, a textile being fed through a treatment roller 12 driven by a motor 13. The web 11 is held stretched in a width-wise direction by a plurality of pinchers or clamping devices 14 positioned at the edges of the web.

As may be seen more clearly from FIG. 2 the web 11 is provided with a selvage 16 at each edge, which selvage is kept in position by a presser foot 17 of the clamping device 14 in contact with the web. Biasing means such as a spring 18 are provided to maintain the presser foot 17 in constant wedging contact wtih the web 11. A pivot pin 19 is preferably provided to allow the presser foot 17 to be raised for insertion of a new web whenever such is desired.

As may be seen more clearly from FIG. 3 the web 11 passes over a table 21 which serves to support the web 11 and offer counterpressure to the presser foot 17. Both the presser foot 17 and the table 21 are conventionally made of metal material.

According to the present invention, the web contacting surfaces, at least, are provided with a layer of organopolysiloxane resin having a filler therein, the layer being shown in the drawing as 22. Similarly, a layer of like material 23 is applied to the opposing surface of the table 21.

As heretofore stated, the organopolysiloxane resin should have a filler or reinforcing agent content between 35 and 900 percent by weight, calculated on the weight of the organopolysiloxane resins. The shape or form of the stretching devices can be any of those used in known clamps on present machines. It is generally sufficient if only those portions of the presser foot 17 by which the web is contacted and the portions of the table, lying in juxtaposition thereto, are coated with the resin containing fillers. Preferably such layer is between 0.5 and 3 mm. thick, although thicker layers may also be provided. If desired, the presser foot or portions thereof may be molded entirely of the resin-filler combination.

Preferably, the known organopolysiloxane resins which are used for preparing the stretching devices of the present invention are those known for the preparation of molded articles and which are cured at temperatures above 100 C. when they are employed for preparing pressure molded articles. Those organopolysiloxane resins consisting of (a) 0.1 to mol percent units of the formula R SiO wherein each R is a methyl or phenyl radical, (b) 99.9 to mol percent units of the formula R SiO, wherein each R is a vinyl, methyl or phenyl radical, and optionally, (c) units of the formula RSiO wherein R is as above defined, and wherein 2.0 to 3.5 mol siloxane units with vinyl groups are present per kilogram of organopolysiloxane, having a viscosity of 200 to 20,000 cs./25 C. are especially suitable. (The quantity of (0) units in mol percent is taken from the difference of the sums of the (a) and (b) units present in mol percent to 100.) These organopolysiloxane resins are cured with radical formers such as dicumylperoxide, cumene hydroperoxide, 2,2-bis (tert-butylperoxy)-butene, tert-butyl perlaurinate, tert-butylperbenzoate and tert-butylhydroperoxide by heating to between 140 and 250 C.

Another group of organopolysiloxane resins which may be used within the framework of the present discovery may be represented by the general formula In this formula R is as above defined, R" is an alkyl radical with 1 to 4 carbon atoms, generally methyl or ethyl, x, y, z are 0, 1, 2, or 3, the sum of x+y+z is not greater than 3, the average value of x is 0.9 to 1.7, the average values of y and z are 0.00 to 0.20, where y and z must, of course, not be 0.00 at the same time. Expediently, these vinyl-group-free organopolysiloxane resins contain not more than mol percent of units wherein x is 2 or 3, and preferably their viscosity in 50 percent toluene solution does not exceed 1000 cs./ 25 C. These organopolysiloxane resins are cured by heating to between 90 and 25 0 C., optionally with the use of condensation catalysts, as they are commonly used for curing vinyl-group-free organopolysiloxanes, for example, triethanolamine titanate, lead and/or zinc naphthenate, and/ or superatmospheric pressure.

The preparation and curing of the organopolysiloxane resins described here is already known to those skilled in the art. organopolysiloxane resins of the type described here are commercially available.

All those fillers and reinforcing agents which heretofore have been or could have been used for the preparation of molded organopolysiloxane resin articles can also be used for the present discovery. This includes use of known fillers (which term is used herein to include reinforcing agents) for organopolysiloxanes which will cure to non-elastomeric articles. Examples of suitable fillers are silicon dioxide obtained pyrogenically in the gas phase, silicic acid hydrogel dehydrated while maintaining the structure, precipitated silicon dioxide, quartz flour, mica flour, pure, white fibrous magnesium silicate occurring in nature, asbestos in the form of, for example, powders, fibers, cloths or foils; zirconium silicate, titanium dioxide, aluminum oxide, glass in the form of powders, threads, fibers, yarns, cloths or foils; ground porcelain dishes, i.e., the so-called shard flour; iron powder and aluminum powder.

If desired, the organopolysiloxane resins used within the framework of the present invention may contain solvents conventionally used for the processing of organopolysiloxane resins before curing. Examples of such solvents are hydrocarbons such as toluene, xylene, and trimethylbenzene; chlorohydrocarbons such as trichloroethylene; ethers such as di-n-butylether; alcohols, such as ethanol; and ketones such as methyl ethyl ketone. However, since the expense which is connected with the processing of solvent-containing resins is usually undesired, resins which can be processed without the use of solvents are preferred. This is one of the reasons why the above-described vinyl-group-containing organopolysiloxane resins are preferred to other organopolysiloxane resins. Finally, the organopolysiloxane resins used within the framework of the present discovery can also contain conventionally used additives such as heat stabilizers and soluble dyes.

Before molding, such as by pouring and pressing and curing, the fillers, the optional or requisite hardeners which are used and all of the optionally used other additives, are incorporated in the organopolysiloxane resins.

The following examples are illustrative of the invention:

Example 1 The surfaces of the metal clamp and juxtaposed metal table surface for a stretching frame which are designed to face the textile web are roughened in the known manner by sand blasting. A linear organopolysiloxane of 40 mol percent diphenyl, 20 mol percent dimethyl, 36 mol percent vinyl methyl and 4 mol percent trimethylsiloxane units having a viscosity of ca. 5000 cs./ 25 C., which has been mixed with 2 percent by weight, calculated on the weight of the organopolysiloxane, of dicumyl peroxide at C., is then thinly applied to these roughened surfaces with a brush (about 0.2 g. organopolysiloxane per clamp). Heat cleaned glass cloth, is cut into pieces of the same size as the areas of the clamp and table which will be in contact with the textile. These pieces weigh 1.5 g. each. One of these pieces is placed on the organopolysiloxane coated side of the clamp table and the abovedescribed mixture of organopolysiloxane resin and dicumyl peroxide is poured over it (again about 0.2 g. resin per clamp table). After covering with a polyglycol terephthalate foil and removing the air bubbles from the cloth with a rubber roller, the applied material is cured by heating for 3 hours to C. and further heating to 200 C. for 3 hours.

A smooth layer is obtained which is very stable to mechanical strain, and to which neither dyes nor textile finishing agents will adhere. The nominal residues of dyes and other deposits can be readily and rapidly removed by washing with water containing a wetting agent or simply by rubbing, after having been in use for some time in a textile stretching frame, operating at temperatures between and 200 C.

Example 2 33 parts by weight of the organopolysiloxane described in Example 1 are mixed while heating to 70 C. with 1 part by weight of dicumyl peroxide and 66 parts by weight of shard (ground porcelain) flour. The mixture thus obtained is formed into clamping surfaces of the clamp and table by pouring and is cured as described in Example 1.

The clamp-table thus obtained is similar in characteristics to that set forth in Example 1. Similar results are obtained when a clamp-table is prepared as described above, with the exception that in place of the 66 parts by weight of shard flour, 100 parts by weight of zirconium silicate are used. The resulting clamp-table can be kept clean without difficulty.

Example 3 An organopolysiloxane resin is prepared as follows: A mixture of 90 parts by weight of methyltrichlorosilane and parts by weight of dimethyldichlorosilane is added, while stirring, to 70 parts by weight ethanol. To the mixture thus obtained, 15 parts by weight of Water are added slowly while stirring is continued. After 10 minutes, 90 parts by weight of toluene and 50 parts by weight of water are added while still stirring. The stirrer is shut off, the aqueous phase is discarded and the toluene phase is cleared of hydrogen chloride by washing with water. The toluene is distilled 01f. The organopolysiloxane remaining as a residue after this distillation is mixed with 1.4 parts by weight of a paste containing 0.5 part by weight of boric acid and 0.9 part by weight of methanol and heated to 150 C. until a 50 percent by weight of a toluene solution of this resin has a viscosity of ca./ 80 cs./ C. (75:10 sec. with a DIN cup having an opening of 2 mm). The organopolysiloxane is then dissolved in an equal quantity by weight of toluene and filtered.

Heat cleaned glass cloth is saturated with the above prepared weight percent solution of organopolysiloxane resin in toluene, until it has absorbed about percent by weight, calculated on the weight of the cloth, of organopolysiloxane. The cloth is then dried at to C. in a drying tower. Four layers are placed over each other, with the warp thread alternating at an angle of 90 to each other in adjacent layers. The glass cloth thus impregnated is heated to C. for 2 hours at a pressure of 50 kg./cm. it is then allowed to cool to 60 C. and removed from the press. Finally, the laminate is heated for another 2 hours to 250 C.

After cooling, the laminate is cut into pieces, with which the portions of the metal clamp are covered. The laminate is attached to the clamp and table with screws. After 600 hours in a textile dryer its properties are still unchanged, and it can easily be cleaned,

Example 4 20 parts by weight of the organopolysiloxane described in Example 1 are mixed while heating to 80 C. with 79 parts by weight of iron powder and 1 part by weight of dicumyl peroxide. The mixture thus obtained is cured by pouring in the form of a contact ledge of a clamp and cured as described in Example 1.

After placing the contact ledge of the present discovery thus prepared in a clamp instead of the metal contact ledge, the functionality of this machine part remained fully identical. The contact ledge of the present invention, however, is much more easily cleaned of all deposits than the metal contact ledge.

The above examples are, of course, merely illustrative of the present invention. It will be understood by those skilled in the art that the invention may be practiced otherwise than as heretofore described.

That which is claimed is:

1. In equipment for treating a moving web wherein clamping devices are provided for stretching the edges of the web in a width-wise direction, the improvement which comprises: A surface on those portions of the clamping device which are designed to be contacted by the moving web made of a cured organopolysiloxane resin having a filler content of between 35 and 900 percent by weight based on the weight of the organopolysiloxane resin.

2. The improvement as defined in claim 1 wherein: the filler includes a glass cloth reinforcement.

3. The improvement as defined in claim 1 wherein: substantially all of the clamping portions are constructed of said filler containing cured organopolysiloxane resin.

4. The improvement as defined in claim 1 wherein: said filler containing organopolysiloxane resin comprises a layer between 0.5 mm. and 3 mm. in thickness over those portions of the clamping device which are to be contacted by the moving web.

References Cited UNITED STATES PATENTS 1,703,586 2/1929 Jahnke 226-88 2,774,593 12/1956 Lewis et al 226- 3,110,439 11/1963 Drake 22639 X ALLEN N. KNOWLES, Primary Examiner US. Cl. X.R, 226195, 198