US3505436A - Production of foam article - Google Patents

Description

April 7, 1970 HANS-DIETRICH KRUG ET PRODUCTION OF FOAM ARTICLE Filed May 17, 1966 FIG. I.

FIG. 2.

FIG. 4.

FIG. 5.

INVENTORS HANS-DIETRICH KRUG PETER RUTSCH ATTORNEYS.

United States Patent 3,505,436 PRODUCTION OF FOAM ARTICLE Hans-Dietrich Krug, Heidelberg, and Peter Rutsch, Unter Abtsteinach, Germany, assignors to Carl Freudenberg, Weinheim, an der Bergstrasse, Germany, a corporation of Germany Filed May 17, 1966, Ser. No. 550,720 Claims priority, application Germany, July 1, 1965, F 46,487 Int. Cl. B29d 9/00 US. Cl. 264-45 3 Claims ABSTRACT OF THE DISCLOSURE Process of producing a composite foam containing article by positioning in a mold of suitable shape which mold has freely accessible shoulders on both sides thereof, a film draped between and laying on said shoulders, a non-woven fabric and a foamable polyurethane mass, and permitting the polyurethane to become foam-form, whereby embedding such foam through said non-waven fabric and on to said film, adhering said foam to said film without the necessity of extraneous adhesives, and filling out the mold cavity with the foam whereby to extend the film to mate with the peripheral portions of the mold cavity.

This invention relates to the production of foamed articles. It more particularly refers to the production of reinforced foam articles.

In the production of shoes, it has often been found desirable to utilize an inner sole and an outer sole. The outer sole material is especially chosen for its wear characteristics as well as for its customer appeal in the esthetic sense. The inner sole is also required to be esthetically pleasing to the customer. In addition, the inner sole also serves a utilitarian purpose in that it provides support and cushioning whereby the comfort of the shoe wearer is increased.

It is often the case that inner soles are made of cork, plastic foam or other resilient material in which case it has been found desirable to coat that surface of the inner sole adjacent the wearers foot with a flexible, relatively impervious material. The inner sole is usually produced by pasting or gluing the resilient layer to the impervious coating therefor.

It is apparent that it is time consuming and cumbersome to produce the cushioning material as a separate part and the impervious coating as a separate part and then glue the two together. Further this type of operation does not lend itself to economical operation in that the coating film must be exactly fit to the shape of the resilient member. If the film is pulled too tightly over the edge of the resilient member, it tends to stretch in elastically and in some cases even tear. If the film is glued too loosely to the resilient member, it buckles and forms creases which impair its appearance as well as impart uncomfortable spots to the final product. In addition, these creases are places of little or no adhesion between the resilient member and its coating film and therefore represent points at which delamination and tearing can initiate.

It has been proposed to remedy this situation by placing the resilient coating film in a bipartite mold and to create a foam of the proper physical characteristics and shape on top of this film in the mold cavity. It has been proposed to accomplish this by providing a first layer of film in a suitably shaped mold, disposing a foamable material on this first film in the mold and providing a second film on top of the foamable material. The ends of the two films are juxtaposed between the two half molds such that when the bipartite mold is closed, the ends of the two resilient films are pressed together by the meeting faces or flanges of the mold halfs.

After the mold is closed the foamable paste is allowed to foam whereby pressure is exerted upon the resilient films causing them to assume the shape of the mold cavity. The foaming process inherently causes the resilient films and the contained foam to adhere to each other by means of the heat of foaming as well as the tacky nature of the foam during its creating. During the foaming process the film and the foam actually partially merge together partially dissolving each other or fusing together and thus belcoming intermingled whereby excellent adhesion resu ts.

As can be appreciated from the above description, it has generally been believed that it was necessary to completely envelop the foam in a pouch of resilient film. Therefore there were always used the two films joined at their edges in the manner described. This joining of the edges of the two films not only creates a pouch for the foam to be created in but also holds each film tightly whereby creasing of the films due to slackness is substantially eliminated as is the possible tendency of the coating film to slip with relation to the foam and thus obtain only partial coverage thereof.

This described improvement is not the complete answer to problems existing in this art since the films tend to be stretched in an irregular and non-controllable manner. Further, particularly severe stresses are created in the edge of the film at the line where the mold cavity joins the mold-half meeting faces. This situation tends to tear the film or at least to stretch it inelastically whereby a weakness is imparted thereto. Even more disadvantageous is the fact that composite film-foam articles prepared in this manner tend to delaminate and literally fall apart when subjected to stress, particularly to bending or creasing stress.

It is therefore an object of this invention to provide a film-foam article which does not suffer from the disadvantages of the prior art.

It is another object of this invention to provide an improved process for the production of film-foam composite articles.

It is a further object of this invention to provide an improved process for the manufacture of shoe inner soles.

Other and additional objects of this invention will become apparent from a consideration of this entire specification including the drawing and claims appended hereto.

In accord with and fulfilling these objects, this invention resides, in one of its aspects, in a process for the production of film-foam articles having only a single film layer coating the foam member thereof. In the process of this invention, a bipartite mold is used as in the prior art. This mold has a cavity containing longitudinal shoulders therein upon which is placed the film coating member such that this film drapes between the shoulders and rests upon the bottom of the mold cavity.

A batt of non-woven fabric is placed up on the draped film member. This batt may be constructed of substantially any fiber desired such as nylons, polyesters, polyacrylics, modacrylics, cellulosics, wools, etc. It is preferred to utilize relatively long fibers in producing the batt such as for example about 3 to 6 cm. long, preferably about 4 cm. It is also preferred to use fairly rough staple fibers such as for example about 15 to 30 denier, preferably about 20 denier. It is essential to the practice of this invention that the batting used be needled. Needling imparts strength to the batt and makes such resistant to delamination. It has been found that when a non-needled batt of non-woven fabric is used, the subsequent foaming process, which will be described below, tends to cause the batt to separate from the coating film whereby is created a composite article having film on one side, non-woven fibrous batt on the other side and foam in between. Needling tends to increase the rigidity of the batt as well as the bulk density thereof whereby it remains properly positioned adjacent to the coating film.

A foam-forming composition is placed on the nonwoven batt and the mold halves closed taking care to insure that neither the film nor the batting edges are disposed between the meeting surfaces of the mold halves. The foam forming material is then permitted to foam whereby it impregnates the non-woven fabric by reason of the pressure exerted by the foam filling the mold cavity. The expanding foam forces the film coating member to fill out the mold cavity by slipping off the aforementioned shoulders and being pressed into the cavity recesses.

In another aspect of this invention vacuum may be applied to the recesses of the mold cavity in order to aid in filling out the cavity by the foam and insuring that the film coating member conforms to all shapes of the mold cavity. This vacuum may be drawn through appropriately positioned and sized channels through the mold body as is known in the vacuum forming art. It is preferred to position at least some of the vacuum channels in the deepest and most remote recesses of the mold in order to insure filling of the most inaccessible areas.

As is known in the prior art, the expanding foam is self-adherent both to the non-woven fibrous batt and to the film coating member under the conditions of foaming. Thus there is created a flexible article having excellent dimensional stability, strength and good continued integrity.

The coating film used in this invention may be of any of the known film forming resilient materials such as for example polyvinyl chloride, polyvinylidene chloride, polyethylene, expanded polystyrene, ethylenevinylacetate copolymer, polypropylene, acrylate homo and copolymers etc. It is preferred to use polyvinylchloride or expanded polyvinylchloride film in this use.

The foam material used in this invention may be any of those known in the art such as polyurethane, flexible polyvinylchloride, flexible styrene-acrylo-nitrile-butadiene, polyisoprene, polychloroprene, etc. which can be manufactured by known processes using internally produced blowing agents or externally added artificial blowing agents. The nature of the foam is to a great extent determined by the particular end use to which the composite product will be put. It is preferred for most general applications to use an arylene di-isocyanate-polyester derived polyurethane flexible foam.

It should be kept in mind that all of the constituents of the instant described composite article must be compatible such that the presence of any of the constituents will not be detrimentally aifected b the processing conditions required by reason of the presence of the other conditions. Thus, for example, it would not be par ticularly effective to use a coating film having a melting point below the foaming temperature of the foamforming material utilized.

It is still another aspect of this invention to produce a still more useful composite article, particularly well suited to use in the shoe industry. Thus it is possible to provide the shoe outer sole at the top of the mold such that the foam will adhere thereto upon filling of the mold cavity. In this manner the composite inner-outer sole can be produced in a single operation if desired. Positioning of the outer sole can be accomplished by insertion thereof between the meeting faces of the half molds and use this member to form the mold seal gasket.

This invention will be better understood with reference to the drawing in which FIGS. 1 through are all front elevations in section of the process of this invention showing the sequential process steps.

Referring now to this drawing, FIG. 1 shows the lower half 1 of a bipartite mold having a cavity 2 and meeting faces 3 and 3. This mold is so constructed that shoulders 4 and 4 are provided about the periphery of the cavity 2 thereof. These shoulders preferably have sloping upper faces 5 and 5'. An appropriately shaped film 6 is draped between the shoulders 4 and 4 and the bottom 7 of the mold.

FIG. 2 shows the second step in the process wherein a non-woven textile fabric 8, of the type described above, is disposed upon the film.

FIG. 3 shows the third step in the process wherein a foam-forming material is disposed upon the non-woven textile fabric 8. and the top half 10 of the bipartite mold is closed so that its meeting faces 11 and 11 close upon the meeting faces 3 and 3 of the bottom half 1 of the bipartite mold. Car must be taken to insure that neither the film 6 nor the non-woven fabric 8 are trapped between the meeting faces 3, 3', 11 and 11' of the mold halves 1 and 10. In FIG. 4 there is indicated that the foam-forming material is starting to expand into a foam 12 forcing expansion of the coating film 6 to fill the mold cavity 2. Filling of the mold cavity by the foam fabric-film composite is aided by the presence of channels 13 through which a vacuum is drawn whereby insuring that the film and its associated components reach all areas of the mold.

In FIG. 5 there is shown a completed composite article 14 in accord with this invention having a coating film 6,. non-woven textile fabric 8, impregnated and coated with foam 12 which composite completely fills the mold cavity as set forth above.

After the foaming has been completed and the mold cavity substantially or completely filled with the foamed composite article, it has been found desirable to permit the article to remain in the mold for a short time to permit the foam to set and stabilize itself. It is preferred to permit up to about 15 minutes residence time for stabilization and setting of the foam whereupon the composite article can be removed from the mold and used.

It has been discovered that it is preferred to practice the process of this invention in such manner that the mold is substantially gas tight. In the prior art, no particular emphasis has been placed upon the gas tightness of the mold since it is known that a foaming process generally works substantially equally as well in a gas tight or open mold cavity. In accord with the practice of the invention wherein suction is applied through the channels referred to above, it has been found that the increasing pressure applied to the top of the foam by reason of residual air being compressed in the space above the foam aids in securing good mold feature reproducibility since this excess pressure tends to force the coating film down tightly against the mold.

An alternate processing technique according to this invention envisions applying vacuum through the above referred to channels prior to closing of the mold halves whereby the coating film, and if desired the deposited non-woven textile fabric, whereby the film conforms to the contours of the bottom mold prior to foaming of the foam-forming material. Either alternative has been found to be satisfactory.

It is within the spirit and scope of this invention to provide that the coating film conforms to the contours of the mold by a cold drawing process since it hasbeen found that where this film is heated to too high a degree and then suitably formed, it looses its elasticity in addition to becoming weakened due to stretching and the thinning that accompanies such stretching.

EXAMPLE The bottom half of a mold has a cavity which corresponds to the contour of a sole. The length of the cavity amounts to 23.5 cm., the depth up to 2 cm. A slanted shoulder, measuring 1 cm., runs along the side wall of the cavity. A polyvinylchloride film which is commercially available under the name Hella, is placed into this hollow mold. The contours of this film correspond approximately to the side walls of the cavity in the bottom half-mold. However, the film is cut in such a way that it protrudes approximately 1 cm. beyond the outside of the cavity. It thus covers the shoulders entirely. A needled non-woven fabric made of nylon fibers, is placed upon this film. After needling, the weight of the fabric material is, for instance, 100 g./m. The individual fiber length exceeds 4 cm., and the fiber is 20 den.

A piece, whose contours correspond exactly the measurements of the indentations in the bottom mold-half is cut out of the needled non-woven fabric material and is inserted. The shoulder is not covered by the fabric only covering film lies there. Subsequently, 50 g. of a paste is poured on it. The paste is prepared by mixing together 60 parts of a polyester prepolymer produced by the reaction of adipic acid and 1,6 hexanediol, and 40 parts of tolylenediisocyanate.

Then, the upper mold-half is closed taking care not to jam in the film between the upper and lower mold-halves along the contact points. The mold is closed so tightly that it may resist a pressure of approximately 5 atm. The paste now starts to foam in the mold, and the foam is evenly distributed within the needled fabric. Thus, the foam also adheres to the fiber structure of the needled fabric. At the same time, the customary fervent adhesion between the foam and the covering film takes place.

After approximately 5 to minutes, the mold can be opened. The finished, fiber-reinforced insole, which is partially covered with a protective foil, is still warm to the touch, after removal from the mold. After a cooling off period, the same can be rolled or exposed to other heavy duties (stresses), without the danger of breaking which has persisted up to now. At the same time, the edges of the sole are exact and distinct.

What is claimed is:

1. A method of forming a composite foam containing article which comprises providing a mold having a cavity in the shape of the desired article, which cavity has freely accessible shoulders protruding from the side wall thereof; positioning a film in said cavity with the ends thereof resting on said shoulders said film is at least one member selected from the group consisting of polyvinyl chloride, polyvinylidene chloride, polyethylene, expanded polystyrene, ethylenevinylacetate copolymer, polypropylene and acrylate homoand copolymers and the remainder draped between said shoulders; providing a needled, non-woven textile fabric on said draped film; providing a foamable polyurethane composition on said fabric and said cavity; closing said mold such that said film ends are free of said closure; and causing said polyurethane to foam whereby said foam impregnates said fabric, adheres to the fibers of said fabric and adheres to said film, and whereby said foam fills out said cavity and forces said film into the peripheral shape of said cavity.

2. Process as claimed in claim 1 wherein said mold is gas tight when closed.

3. Process as claimed in claim 1 wherein said mold has provided in the recesses thereof channels and wherein suction is drawn through said channels.

References Cited UNITED STATES PATENTS 2,728,702 12/1955 Simon et al. 264- 2,879,197 3/1959 Muskat et al. 264-45 2,976,577 3/1961 Gould 264-45 3,258,511 6/1966 MCGregor 264-45 3,215,764 11/1965 Haworth 264-244 JULIUS FROME, Primary Examiner L. GARRETT, Assistant Examiner US. Cl. X.R. 264-54

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