US2441492A

US2441492A - Moldable plastics composition and method of preparing same

Info

Publication number: US2441492A
Authority: US
Publication date: 1948-05-11
Anticipated expiration: 1965-05-11

Description

May 11, 1948. A. w. KOON ET AL MOLDABLE PLASTICS COMPOSITION AND METHOD OF PREPARING SAME Filed Feb. 27, 1946 a. 2 TH T CHE-R Patented May 11, 1948 UNITED; RATE-NT .o-FFIcE ---MOLDABLE,PLAS:TICS COM-POSITION AND METHOD OF PREPABINGMSAME 'Archie Koonand Jack P. Thatcher; Auburn, N'. Y'., assignors to'Columbia'n Rope-Company, Auburn N'. Y., 'aworporation of:N'e'w York .Application'February 27, 1946, Serial No. 650,618

' This invention relates .to themolded plastics art and particularly to' a molded'plastics composition and method of producing the same.

It has heretofore been the practice, in some instances, in the plastics art to prepare bodies of moldable plastics composition, consisting of the binder and filler material, in sheet-form; For in'- stance, one type of mol'dable plasticseomposition which may be usedjfor purposes of'illustration, is prepared from a web ofcomparatively long vegetable fibers whichserve as filler material, the web of fibers being stabilized by passing itthrough a so-called needling machine which results in small groups or tufts *of'fibers beingformed in vtheweb to stabilize the latter without .too densely'compacting the web so asto-produce an intersticed sheet of fibers to which the binder can be applied either in the form of a solution or in dry pow dered form. Howeven-where the-needledweb 'of fibers has been combined with the binder in' dry powdered form difiicultyhas been encountered in preventing loss of the-binder particles from the web, particularly where the powdered treated web is subjected to'vibration as in the case of being roughly handled in manipulating it in connection with actual molding operations and in the case of being transported'or shippedover appreciable distances. The primary object of the present invention; therefore, is to provide a sheet or web of moldable plastics composition where the binder is used in powdered form in combinationwith loosely compacted filler elements; for instance, the needled -fibers, but in whicn-the powdered binder'will be securely-retained so as to prevent loss thereof if the 'sheet' or webof com position is unduly jarred or vibrated. a

More particularly,-the invention contemplates the production of mol'dablei plastics com-position in sheet or web form wherein thesurfaces ofrt'he web of vegetable fibers or filler elementsare sub stantially sealed with 'bindermateriahso as to prevent loose powdered binder in the interior' of the web sifting out of. the -web-while being handled or shipped. 7

In its preferred form, the invention'consists forming a stable intersticed web of -'-vegetab1 'e' fibers and first applying toone surfaceofthat web a covering of powdered: bind6l' 'WhiCh.b'- comes attached to ands'eals said surface after which the web is. inverted and' a-seeond appl-ica tion of powdered-binder-.deposited on its optic site side while it is being vibrated so as totacilitate or augment entry of the powderedzparticlesweb and finally.- applying :a: covering of powdered '4-Claiinsw (Cl. 11'Z140) of the second application:into-theinteriorsof the binder to said opposite surface of the web which covering-also becomesattached to and substantially'seals said second surface. Thus; the-powderedbinder which has-freely entered theinterstices through the'interior of the web and-which would otherwise be free to sift out of the web if the surfaces of the web were not sealed will be securely retained in the interior or the web by reason of the surfaces of the latter'beingsealed as described. I Consequently, webs'of composition produced according to the present invention can be shipped over longdistances without'danger of losing any appreciable ortion of their binder content, 1 Similarly, there is little danger of the binder content escaping or sifting out of the web while it isbeing handled in connection with loading it" inthe mold or other manipulations in handl-in-git'in connection with actual molding operations.

1 In the accompanyingdrawing:

- Figural illustrates more or less schematically one form of apparatus for carrying out the present 'method and producing the present moldable composition; and ---Figs. 2 to 4 constitute a series of views illustrating diagrammatically the severalsteps involved in the preferred method of produ'cingthe present composition. 1

"While various forms of filler material may be used in connection with the present'invention it is preferred to use a filler material of filamentaryforin, for instance; vegetable fibers and these filamentsor-fibers should be comparatively long. That is, -when'-fil-le'rs offilamentary form, or ve etable fifbers, are used thefibers or filaments shOiIId'becompa-ratively long or atleast long enough -to permit needling. This so-called' needlingoperation; which is more fully disclosed in United States- Letters Patent No; 2349.888,

consists essentially in iorming a bat or web of vegetable fibersand passing the web through the socalled' needling machine which isprovided' enter when the binder is used 7 in 7 drypowdered form} 'A full disclosure of the use ofdiypowdered binder resin may be had by referring lto V United States hetter's Pa tent' No;;2;372;433;

a i aaccordance witlr the present fmvention the needled web of fibers indicated at 10 in the accompanying drawing is passed beneath a dusting mechanism consisting of a hopper II and a dusting nozzle [2, the web being supported on a, traveling conveyor [3 so that the particles of binder discharged from the nozzle 12 can be applied in the form of a covering to the upper surface of the web. Various types of binders may be used although the most common examples are probably phenolic condensation products generally referred to as synthetic thermo-setting resinous binders. Thermo-plastic binders, for instance, vinyl compounds may also be used, so that, in a broad sense, binders susceptible of use in connection with the present invention may be described as therm0-re sponsive binders.

After the upper surface of the web [0 has been covered with the powdered binder, as just described, the particles constituting the covering, indicated at M in Fig. 2, are caused to adhere to and seal said web surface. In the case of thermo-setting binders, this may be accomplished by passing the covered web through a heating compartment l (Fig. 1) so as to raise thetemperature of the binder slightly and render it tacky whereby the particles will attach themselves to the fibers at the surface of the web. It will be appreciated that some care should be exercised to prevent any appreciable portion of this covering of binder particles entering the interior of the web as it is the intent to substantially seal the web surface. It will also be appreciated that the temperature of the binder should not be raised to that point which will unduly advance or set the binder. In the art this slight raising of the temperature of the binder for rendering it tacky is usually spoken of as sintering.

After one surface of the webhas thus been sealed by sinterin the covering of powdered binder thereon, the web is again placed on the conveyor l3 but inverted so that the powdered binder dusted on the opposite surface of the Web can be caused to enter the interior of the web by vibrating the latter. For instance, the web can be passed to a vibrating mechanism after this second application of the powdered binder to cause the binder particles to enter the interstices in the interior of the web, as indicated at H5 in Figs. 3 and 4. One form of vibrating mechanism, as illustrated in Fig. 1, may comprise a platform or table [1 on which the inverted web is placed, said platform being suitably supported on crank shafts l8 so that rotary motion of the shafts [8 will impart a vibratory motion to the table. Preferably a traveling slatted belt I9 is suitably supported above table I! to retain the web on the table and feed it along the table. However, the web should not be depressed so tightly against the vibrating table as to cause the table and web to vibrate as a unit while, on the other hand, the web should not be held down too loosely so as to dampen the vibration or jarring of the web itself because under either of these circumstances the effectiveness of the vibrating mechanism is minimized.

After the second application of powdered binder has been caused to enter the interior of the web, as shown in Fig. 3, the web is again placed on conveyor l3 while still inverted so as to apply a covering of powdered binder to the opposite face of the web, as indicated at 20 in Fig, 4. 'Ihis last coveringof binder then becomes, at-

tached to, and. seals, the opposite surface of the web, as also indicated in Fig. 4. Here, again, Where a thermo-setting binder is used and its temperature is raised for rendering it tacky. care should be taken to guard against undue advancement of the binder as previously stated, as it is intended that this second covering merely be sintered so that it will become tacky and attach itself to the web surface. Thus. the present invention in its preferred form may be said to consist in first sealing one surface of the web with a covering of powdered binder, then applying additional powdered binder to the opposite surface of the web and causing these particles to enter the interior of the web after which still another application of powdered binder is deposited on said opposite surface to cover the latter and this last covering is also attached to said opposite surface to seal the same whereby all the free particles of powdered binder in the interior of the web are securely retained therein and cannot sift out in subsequent handling of the Web.

The method described is preferred particularly where a comparatively thick web is to be treated or impregnated with the powdered binder and it is desired to be certain that the web is thoroughly impregnated substantially throughout its thickness. However, where the binder is being combined with a comparatively thin web of fibers or other filler material the intermediate step which involves the second application of binder and the vibrating of the web to cause this application of binder to enter the interior of the web might be omitted. In other Words, where a thin sheet or web is being processed it is possible to simply apply a covering to one surface and sinter and then apply and sinter a second application of binder on the opposite side of the web. This is true because a limited amount of binder will sift into the interior of the web when the two covering applications are deposited on the opposite surfaces and this limited amount will usually sufflce for thin webs.

It will be understood that the effect of the so-called sintering operation in connection with the covering applications of binder is largely superficial and free powdered binder in the interior of the web is enveloped or encased by the sintered crusts which are formed at the surfaces ofthe web, the primary purpose of the present method being to prevent loss or migration of binder from the web when being shipped and during subsequent handling and manipulation, which, as will be understood, includes the actual moldable composition. In this connection it might be added that it will also be understood that when the composition is actually molded the severalapplications of powdered binder flow and merge into one another when fiuXed so as to produce a molded article of substantially uniform density and strength.

It has been previously stated that the invention is not specifically limited to vegetable fibers although they are the preferred form of filler material and that binders of different types may also be used. A further possible modification of the preferred method may be indulged in in connection with the attachment of the powdered binder to the web surfaces. For instances, the surfaces of the web may be coated with mucilaginous or adhesive substances preliminary to application of the two coverings of binder particles or the surface filaments of the web may be dampened-with liquids which are solvents for the binder preliminary to the application of the two surface coverings of powdered binder. Specific examples of mucilaginous or adhesive substances are starch, glue, natural or synthetic resins, oils, tars, and dispersions of rubber or other elastomers. Examples of solvents that may be used, especially in connection with resinous binders such as the phenolic resins, are alcohol and acetone.

What is claimed is:

1. The method of preparing moldable plastics compositions of dry powdered thermo-responsive resinous plastics and filler material in the form of a web of loosely compacted filler elements which consists in depositing a first application of the powdered plastics to one surface of said web, rendering the applied plastics particles tacky to attach the same to the filler material and substantially seal said surface of the web, inverting said web and depositing a second application of the dry powdered plastics to the opposite surface of said web while vibrating thelatter to augment infiltration of said second application into the interior of the web, depositing a third application of the dry powdered plastics to said opposite surface and rendering said third application tacky to attach the same to the filler material and to substantially seal said opposite surface of the web whereby loose unattached particles of the dry binder in the interior of the web are retained therein by said sealed surfaces.

2. The method of preparing moldable plastics compositions of a synthetic thermo-setting resinous binder in the form of a dry powder and filler material in the form of an intersticed web of vegetable fibers which consists in applying the dry powdered binder to substantially cover one surface of said web of fibers, preventing any substantial penetration by the powder into the interior of the web by maintaining the web substantially free of vibration, raising the temperature of the applied covering of powder to render the same tacky and attach it to said surface of the web, whereby said surface of the web is substantially sealed, inverting said web and depositing a second application of dry powdered binder on the opposite surface thereof while vibrating said web, depositing a third application of dry powdered binder on said second surface of the inverted web without vibrating the latter to substantially cover said opposite surface, and raising the temperature of said third application of binder to render it tacky and attach it to and substantially seal the opposite surface of the web whereby unattached particles of binder in the interior of the web are retained in the web by said sealed surfaces.

3. The method of producing a sheet of moldable plastics composition of powdered synthetic thermo-responsive resinous binder and vegetable fiber filler which comprises forming a stabilized, intersticed web of fibers, covering one surface of said web with powdered resin, attaching said covering to said surface by rendering the binder particles of the covering tacky, said attached covering substantially sealing said surface, inverting said web and applying powdered binder to the opposite surface of the web while vibrating the latter to cause the particles of the second application of binder to enter the interstices in said web, applying a covering of powdered resin to said opposite surface of the inverted web and attaching the same to said opposite surface by rendering the particles of the same tacky, said covering on said opposite surface substantially sealing the latter whereby unattached particles of binder in the interior of the web are retained in the web by said sealed surfaces.

4. A web of moldable plastics composition of powdered synthetic thermo-setting resinous binder and comparatively loosely associated filler filaments, said powdered binder being present in said web in the form of sealing layers of partially advanced particles attached to the filaments at the two opposite surfaces of the web and detached, free particles in the interior of said web, said detached particles being retained in the web by the sealed surfaces of the latter.

ARCHIE W. KOON. JACK P. THATCHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,372,433 Koon Mar. 27, 1945 2,373,033 Kopplin Apr. 3, 1945