US2285526A - Method for producing cavitied rubber sheeting - Google Patents

Description

June 9, 1942. .1. U. MANN 2,285,526

METHOD FQR PRODUCING CAVITIED RUBBER SHEETING Filed May 15, 1959 I INVENTOR JAM/f6' 0. AMA/Af ATTORNEYS the number and arrangement of the pits pre| Patented June 9, i942 METHQD FOR. PRODUCING CAVITIED RUBBER SHEETING .lames U. Mann, Arlington, N. J., assignor to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application May- 13, 1939, Serial No. 273,470

(ci. 154-2) l 4 Claims.

This invention relates to methods of producing cavitied rubber sheet material and more particularly to methods of making rubbersheet material having a desired number and arrangement and dimensions of pits or cavities in the surface thereof. This invention is especially advantageous in making any number of replicas of a master cavitied deposition backing or blanket in which the size andarrangement of pits or cavities in each replica are identical with all the others.

g According` to United States Letters Patent No.y

2,032,942, a latexcomposition is-spread onto an Y air impermeable deposition backing or blanket having cavities or pits in its uppermost surface so as to entrap air within the cavities or pits of the deposition blanket. By the application of' heat to the blanket, the thus entrapped air ls caused to expand and force its way through the Wet latex. coating, While at the same time the latex coating is caused to dry or gel so as to render permanent the perforations in the spread film of latex composition. These spreading and heating operations may be repeated until the desired total thickness of perforate rubber sheet has been builtup. After the final drying, the

perforate rubber sheet is stripped from the blanket and then vulcanized.

While various deposition blankets and methods of making them are described in the above cited patent; the preferred backing' is made by coating a woven fabric, such as 4.75 cotton sheeting@ withrubber latex in such a manner that the meshes of the fabric are closed on one side of the fabric and are open onthe other side, and the individual interstices are also sealed on. each from the other. bythe coating of the .threads-to provide a multitude of pockets opening on the deposition surface of the fabric. A deposition blanket so made ,hasv proven satisfactoryV for making a limite'dquantity ofrubber `films or sheets, but upon its wearing out or being de'- faced'the blanket must be replaced by another blanket preparedjfrom another and different piece of fabric. .As a consequence it is diflicult ent in the surface of a master deposition blanket which may have been made according to the. process described in the above previously cited patent, or by any other suitable process. Any desired number of identically cavitied deposition backings may be vproduced without the disadvantages and dimculties mentioned. In practicing the invention, a cavitiedldeposition surface is spread with a film of .latex composition,

and the latex film thereby deposited is at least partially dried or gelled and concurrently therewith is' pierced with1 a plurality of fluid jets to form permanent perforations therein. A perforate rubbersheet of the desired thickness may be built up by carrying out the above operations the requisite number of times. On the upper surface of this sheet, one or more films of latex composition are then spread sofas to bridge and seal on the perforations formed; in the lower strata, and this final film (or filmsl is dried to form a fluidimpervious continuous sealing filmy or layer. A sheet of woven fabric or other equivalent inextensible reinforcing material may then be ad hered to the sealing film or films either by rolling the fabric down into a wet film of freshly spread latex or rubber cement or by passing the fabric through 'a bank of latex and under either'a doc- `tor blade or -a helically grooved cylindrical to prepare a replacement vblanket which is ldentical with the previous one. described preparation of such blankets is a difilcult process, entailing a great dealof careto avoldthe preparation ofimperfect blankets which must. of course, be discarded.

The present invention provides a method of manufacturing, at relatively/low cost, replica deposition blankets which reproduce faithfully Furthermore, the

spreader bar. Other suitable methods of doubling a fabric to a spread sheet of latex rubber may be used conveniently.- After the fabric reinforcement has been adhered to the deposition surface one or more additional films of latex rubber may,- if desired, be spread thereonand dried to complete the production of an lnextensiy ble cavitiedsheet. The cavitied sheet may then be removed from the deposition surface upon which it was formed and vulcanized, and the cavitied' surface thereof mayk be treated, as -by chlorination or oxidation, to render latex subsequently deposited thereon easily removable therefrom after it has dried orgelled, The rev4sultant cavitied rubber sheet provides an initial master deposition blanket for the production of others identical to it, andthe procedure may berepeated as many times as desired, so that the cavities in each rubber sheet deposited thereon will be substantially identical in site and arrangement to those in every other peri'orat'e sheet formed therefrom.

By the present invention the possibility of er-` ror in reproducing replica blankets identical with the originals is reduced to a minimum. Af'terthe perforate pliesof the blanket 4have been produced, and the imperforate ply has been deposshowing partial removal Fig. 2 -from the backing on which it is produced.

layer l. 0n the backing may be produced as follows: A hlm or 'cation of sufficient heat ited thereon, it may readily be determined merely by inspection whether the imperforate plies have succeeded in sealing off all the perforations in the outermost perforate ply. In the manufacture of cavitied deposition blankets heretofore in the fact that the entire deposition blanket is built` up in a continuous series of operations without the necessity of removing the perforate sheet material from the backing and thereby subjecting it to folding or stretching. VThe applicaltion of an inextensible ply of reinforcing material reduces the possibility of distortion during removal.

The drawing illustrates diagrammatically, on a greatly enlarged scale, a series -of steps in the Another render the vulcanized surface non-adherent to rubber deposited thereon from latex.

For the production of a series of replica samples, the process may be carried out as shown in Figs. 2 and 3. Accordingly,l a layer Il of latex composition is deposited on the upper surface t bridge over and seal oil the perforations I5, and 1 is dried without being perforated. The replica production of identically cavitied rubber sheets y according to the present invention, in which:

Fig. l is a greatly enlarged cross-sectional view of a master cavitied sheet produced according to the invention on a conventional deposition backing;

Fig. 2 is a greatly enlarged cross-sectional view of replica cavitied sheet produced from the master: and

Fig. 3 is a greatly enlarged cross-sectional view Referring tothe drawing,vFig. 1 shows the formation of a cavitied rubber sheet on a conventional backingl comprising woven threads 2 individually impregnated-and/or coated with a rubber fllm 3 and secured to a rubber backing backing I a similar master layer i of latex is spread onto the backing I to entrap air inthe pits or cavities between the threads 2, and the backing I and film 6 are f heated to expand the thus entrapped air sufficiently to form perforations 1 while at the same time the rubber inthe film 6 is caused to gel or dry. This process is 'repeated until a perforate rubber layer 8 of the desired thickness is built up and dried. Before or after' completion of the drying of the layer I, the upper surface 9 thereof-is coated with one or more films I0 which may be of the samelatex composition as that in the j layer 8. This ilnalnlm (or films) is dried under conditions which d o not effect piercing of the rubber covering over perforations 1. For example, f the drying or gelling ofthefilm III maybeaccomplished at to appreciably expand the entrapped air. The film Il provides a fluidimpervious -and continuous rubber seal which n closes ofi' the perforations. A reinforcing or stiifening base ply II comprising, for example, one or more fabric layers I2 bonded with rubber, may beA secured to the outer surface of the backing l. After drying 4the replica' blanket I may be stripped from the deposition blanket I and vulcanized. This vulcanized surface of the initial layer 8 may be haiogenated and hardened by treatment with, for example, a 'W2% solution of sulphur chloride in carbon tetrachloride, followed by a treatment with a 2 to 3% solution of bromine, in the carbon tetrachloride; or with the bromine solution alone; or in any desired manner, of which many are known in the; art, to

of the sheet formed in room temperature without the'appli blanket I3 may then be withdrawn from the blanket 5, as shown in Fig. 3, before or after application of a reinforcing ply, and may be vulcanized and treated as above described. Inl this manner as many identical blankets as maybe desired can be produced either from the original blanket 5 or from any of the replica blankets I3.

While a particular method of producing ,the original blanket has been described, it may be produced upon an original perforate base instead of the air impermeable cavitied base employed in the method described. In this embodiment, a film of latex is spread in the ordinary manner to bridge the perforations, and a Jet of uid is forced through each perforation in the base to pierce the spread film. Asthe film is pierced to form perforations therein, the latex immediately surrounding the perforations may be set by heating if no coagulant is used, or by employing, as the jet.of uid, a coagulant for latex. The gelling or drying ofthe remainder of the pierced nlm may thenbe completed in any desired manner. A convenient method for carrying out this' stage in the process is described in United States Letters Patent 2,032,923. After the desired number of superimposed perforate films have been produced in this way, the nal sealing film or films are deposited thereon, as above described, that is, under conditions which gel or dry the final film orffilmsbut do not produce perforations therein. In this particular embodiment of the invention, heat may be employed to gel or dry the final layers without danger of expanding the air in the perforations-therebelow, since that air in this case is not confined or entrapped.

I'he term latex as employed in this speciflcation and the appended claims designates broadly coagulable dispersions of rubber or rubber-like materials as well as natural latex, which may be preserved or compounded or` otherwise treated as desired, as by vulcanization, and which may be in normal, concentrated, diluted, or purified condition produced by methods well known in the art.

While certain present preferred methods of practicing the invention have been described, it

may be understood that it may be otherwise prac.- V

ticed as will occur to those skilled .in the artand within the spirit of the inventio and is to be limited only by the'scope of the appended claims.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

l. The method of making a rubber sheet havving cavities in the surface thereof which comprises depositing a lm of latex composition onto a deposition blanket, concurrently drying or gelling said vfilm and piercing said film with a plurality of fluid jets to form permanent perforations therein, depositing a lm of latex :onto said film and concurrently drying or gelling and piercing said second named 4film, repeating said 2,285,526 operations until a perforate rubber sheet is built itied, built-up blanket from the first-named.

deposition blanket.

2. A process for manufacturing a rubber sheet having cavities in the surface thereof which comprisesspreading a coating of latex composition onto an air-impermeable deposition `blanket having cavities or pits in the deposition surface thereof so as to entrap air between the latex coating and the backing in the said'cavities or pits, and heating the backing to cause the entrapped air to expand and force its Way through the latex coating while it is drying or gelling to form permanent perforations therein, depositing a lm of latex onto said coating and concurrently drying or gelling and piercing said second named lm, repeating said operations until a perforate rubber sheet is built up, and thereafter spreading a i'llm of latex composition upon said perforate sheet to bridge over and thereby seal exteriorly, without filling up, an opening of each perforation, drying or gelling said film so that it remains imperforate, and removing the cavitied,

built-up blanket from the first-named cavitied deposition blanket.

3. The method. of making a rubber sheet having cavities in the surface thereof which comprises depositing a nlm of latex a deposition blanket, concurrently drying' or gelling said nlm and piercing said nlm with a plurality offluid jets to form permanent perforations therein, depositing a iilmof latex onto said film and concurrently drying or gelling and piercing said second named film, repeating said operations until aperforate rubber -sheet is built up, and thereafter depositing a sealing lm of latex composition onto said perfora e rubber composition onto sheet to bridge over and thereby seal exteriorly, withoutlling up, an opening of each perforation, drying or gelling said sealing lm so that i it remains imperforate, removing the cavitied sheet from the blanket, and rendering the cavitied surface of said sheet -non-adherent to an in situ solids deposit of a latex composition; substantially in the manner set forth.

4. The method of making a rubber sheet having cavities in thesurface thereof which comprises the step of deposizing a. film of latex composition onto a deposition blanket, the step of concurrently drying or gelling said iilm and piercing said film with a plurality of uidjets to form permanent perforations therein, the step of depositing a film of latex onto said film and concurrently drying or gelling and piercing said second named film, repeating said operations until a perforate rubber sheet is built up, and the step of depositing a sealing lm of latex composition onto said perforate rubber sheet to bridge over and thereby seal exteriorly', without lling up, 'an opening of each perforation, and the step of securing a ply of reinforcing material to vsaid sealing layer, said steps being performed in the order named as a continuous series of operations while the built-up sheet remains in place upon the deposition blanket, and -thereafter removing the reinforced cavitied sheet from said deposi.

tion blanket.

JAMES U. MANN.

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