CA1173340A - Plastic embossing caul and method for forming same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The method comprises: sealing a textured wood panel by applying at least one coat of a sealer to the surface of the panel; providing the sealed panel with a release agent; placing an assembly comprising the sealed panel, a backing panel, and a plurality of high temperature resin non-cellulosic prepreg plies each including a heat insensitive web in a hot press, the prepreg plies being disposed between the two panels; compressing the assembly under heat and pressure conditions until the prepreg plies form a laminated caul which is substantially cured and has assumed the relief configuration of the textured wood panel;
removing the assembly from the hot press; and separating the sealed panel and backing panel from the caul, whereby the configuration of the textured wood panel assumed by the caul is permanently maintained and usable for embossing a grain pattern onto a wood panel.

Description

Case FDN-261-CIP
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~ ~733~0 This application involves a further development of the invention disclosed and claimed in our Carladian Patent 1115631 granted January S, i982.
Our copending application concerns a rnethod of forming - 5 a plastic embossing caul. That method comprises sealing a textured wood panel by applying at leas~ one coat of varnish to the surface of the panel, providing the sealed panel with a release agent, placi.ng an assembly comp.ri.sing the sealed panel, a backing panel and a plurality of resinous prepreg plies in a hot. press, the prepreg plies being clisposed between the sealed panel and the backirlg panel, compressing ~:he assembly under heat and pressure condit:Lons until the prepre~ plies form a laminated caul which is substantially cured and has assllmed the relie configuration of the textured wood pane:L, rernoving the assembly from the hot press, and separating the secllecl panel and the backing panel from che caul.
The present invention concerns a method which is similar to that of our copending application and differs there-fram in that the prepreg plies used to form ~he caul advantageously comprise a plurality of high temperature res:in non-cellulosic prepreg plies each including a heat insens-.it:i~e web. The heat insensitive web may be a fiberglass or graph:ite web. By use oE
lamina~es including a plurality of high temperature resin non-lr~se~S~ ~v~
cellulosic prepreg plies, each including a heat~e~ ~ web, . -2 . . ,~

~ 1733'~0 the resulting cauls are not subject to cellulosic thermal degra-dation. Also, for a given caul thickness, the prepreg plies have ; relatively good thermal conductivity for acceptably rapid cure of wood panel adhesives and a thermal expansion which is capable of minimizing thermal stress and potential delamination, particularly in a m~tal containing composite caul.
More specifically, and in accordance with the invention ,, we provide a method for forming a plastic embossing caul comprising: sealing a textured wood panel by applying at least one coat of a sealer to the surface of said panel; providing said sealed panel with a release agent; placing an assembly comprising said sealed panel, a backing panel, and a plurality of high temperature resin non-cellulosic prepreg plies each including ` a heat insensitive web in a hot press, said prepreg plies being disposed between the two panels; compressing said assembly under heat and pressure conditions until the prepreg plies form a laminated caul which is substantially cured and has assumed the relief configuration of the textured wood panel; removing the assembly from the hot press; and separating the sealed panel and backing panel from the caul, whereby the configuration of the tèxtured wood panel assumed by the caul is permanently maintained and usable for embossing a grain pattern onto a wood panel.
By virtue of our invention, cauls may be formed that are relatively light weight and easy to handle, this being possible by the use of metal sheets for either the caul core or the caul back. In a preferred embodiment the metal sheet is preferably steel or aluminum.
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The high temperature resin non-cellulosic prepregs suitable for use in carrying out this invention are available commercially or may readily be made. These non-cellulosic prepregs are ~hin (usually less than 1/2" thick) sheets - 5 composed of a fabric such as fiberglass or woven graphite which has been impregnated with a high temperature resin; i.e.
epoxy, phenol formaldehyde, polyester~ or polyimide and then partially cured to a flexible state. Although solid, in a normal sense, they are still deformable. Also, they are self-bonding where subjected to sufficient heat to complete curing.
These sheets are preferably of a size appropriate for use in embossing conventional paneling-sized wood. This means that they (and any metal sheet included for reinforcement) are ordinarily essentially rectangular and planar in form with dimensions of at least about eight feet by four feet~ This shape and size may vary, however, with different modes of use.
For example, where smaller panels are to be textured by an embossing roll, the caul would be formed as a tube for the roller and in suitably reduced dimensions of circumference and length.
- To provide the desired rigidity and strength to the product caul,a plurality of high temperature resin non-cellulosic prepreg sheets are laminated. Although the mlmber o~ sheets may yary dependent upon the depth of texture and the stress to which the caul will subsequently be exposed, from about six to twenty sheets ~preferably enough to produce a caul having a thickness of about 0.05 to 0.3 inch) are commonly employed.

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Where a sheet of metal is included within the laminate, equal numbers of sheets of prepreg are usually placed on either side of the metal~ Such a metal core reduces the number or prepreg plies necessary for good rigidity and also improves the thermalconductivity of the composite~
A metal sheet, usually steel, also can be utilized in a method of one-step fabrication of a caul plate involving the plurality of high temperature resin non-cellulosic prepreg plies bonded with and without film adhesive) to only one side of the metal sheet. While bonding between the metal and prepreg sheet may be obtained simply by curing the prepreg, one or ; more layers of adhesive may also be provided to enhanc:e the strength of the bond between these dissimilar sheet materials.
In forming the embossing caul of the subject inven-tion, a texture panel surface (usually a natural wood surface) is sealed with one or more coats of, for example, varnish.
The varnish may be, for example, a urethane varnish, (RexthaneTM
~44V20 from Sherwin-Williams Co.), or a water reducible, imine catalyzed acrylic varnish with urethane additive, (T75CH10 from Sherwin-Williams Co.). The varnish on the panel is then cured and provided wi-th a conventional release agent such as a release coating - e.g. Vydax of DuPont, Wilmington, Delaware-`and/or a release paper to prevent sticking that could occux later in the procedure. A plurality of the prepreg plies of the invention is placed on the treated surface of the wood panel. This assembly is then compressed under heat and pressure ? conditions for a sufficient period of time so that the prepreg `~ forms a caul which is at least substantially cured and which has assumed the configuration of the textured wood panel.

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, These desired curing conditions are readily obtained in a conventional hot press. The assembly (ordinarily also including a smooth backing panel of, for example, wood used with the textured panel to sandwich the prepreg sheets and facilîtate application oE pressure) may simply be compressed.
Particular conditions vary in conventional manner dependent upon the specific prepreg sought to be cured; however~ they ordinarily range upward of minimums of about one hour at 320F. and fifty pounds per square inch.
Following the compression step, the assembly is removed from the hot press and the wood panels are separated from the caul which then bears a relief of the design configura-tion of the textured wood panel. The prior application of the release agent to the textured wood panel aids in preventing , 15 sticking between the wood panel and the caul. The prepreg caul of the invention may then be baked, if not sufficiently cured in the compression step to ensure that the configuration of the textured wood panel assumed by the caul is permanently maintained.
The final cure, however, can be ultimately achieved from heating the caul during use.
The conditions for-baking are again conventional and vary in accordance with the specific prepreg utilized. In addition, their minimums obviously depend upon the degree to which cùring is effected during the compression step. It can be done in the compression step to sufficient completion or substantially so. Ordinarily, however, intermediate curing is performed after separation of the caul in a distinct baking ~33~0 : oven where the caul may be held for at least one hour at 35~F., and final curing i5 accomplished during use in the heated press.
Figure 1 is an exploded elevational cross-section of the element used in forming an embossing caul in accordance with the method of the su~ject invention~
Figure 2 is an elevational view, partly broken away, of the same elements being compressed in accordance with the method of the subject invention, Figure 3 is an elevational cross~section of the embossing caul formed in accordance with the. method of the subject invention.
Figure 4 is a perspective plan view of the embossing caul ~ormed in accordance with the subject inventionl said view taken facing the textured surface of the embossing caul.
: Figure S is an exploded elevational cross-section of t~e elements used in forming an em~ossing caul in accordance with an alternate embodiment of the method of the subject invention .
Figure 6 is an elevational cross~se.ction o~ the em~ossing caul formed in accordance w~th said alternate em~odi-~en't of the method of the sub.ject inventions In accordance wit~ the subject invention, a plastic caul and method fo~ producing same are provided. Such cauls are used to improve the appearance of paper overlaid wood panel sur~aces by em~ossing with a natural wood grain or other desired texture, '; .

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The wood panel surface ls most desirably convention-ally overlaid - i.e. covered with an adherent resin-impregnated paper. In this case, it is the overlay that will be primarily embossed with the natural wood grain or other desired texture.
Wood panel surfaces commonly upgraded in this fashion include plywood, particle board, hardboard and medium density fiber-board.
Suitable overlays for the preferred purposP of this invention are conventional. Most desirably~ however, these materials are those recognized as "medium density overlays" by the wood products industry. Such paper overlays consist of cellu]ose - fiber sheet or sheets containing not less than about 17% resin solids for a beater-loaded sheet, or abou~ 22%
for an impregnated sheet, both based on the volatile free weight of resin and fiber exclusive of glueline. The typical resin type used to impregnate such sheets is thèrmosetting phenol-formaldehyde, but other high temperature resins provided equivalent performance with respect to durability are also acceptable. Examples of other high temperature resin ~amilies which are suitable are acrylics and melamines. The resin impregnated paper usually weighs not less than 58 pounds per 1,000 square feet of single face, including both resin and fiber but exclusive of glueline. After application, such materials usually measure not less than 0.012 inch in thickness.
Referring to Figure 1, the elements used in forming an embossing caul in accordance with the method of the subject invention include a wood panel 21 having textured surface 31, a smooth backing panel 23, and a plurality of high temperature resin non-cellulosic prepreg plies 22. Prior to the caul ~ ~33~0 construction, the textured wood panel 21 (preferably a one-quarter to five eighths inch plywood or hardboard panel~ is sealed with one or more coats of varnish, such as a urethane varnish, (RexthaneTM B44V20) or a water reducible, imine catalyzed acrylic varnish with urethane additive (T75CH10), both available from Sherwin-Williams Co., Cleveland, Ohio.
After the varnish has dried, the textured panel 21 is coated with a conventional release agent which minimizes sticking problems that might otherwise occur la~er during the formation of the caul. The smooth backing panel 23 is preferably a one-quarter to five-eighths inch sanded plywood or hardboard panel.
The plastic material 22 comprises a plurality of high temperature resin non-cellulosic prepreg sheets. Three such prepreg ; materials that have been found to be quîte effective are CordopregTM E-293, sold by Ferro Corporation of Norwalk, Connecticut; E-712A Rov-MatTM, sold by U.S. Polymeric of StamfordJ Connecticut; and F-439 sold by Hexcel Corp., Dublin, California. Woven graphite may also be used.
Referring to Figure 2, an assembly comprisin~ the textured wood panel 21 and a sanded wood panel 23 with the high temperature resin non-cellulosic prepreg 22 disposed therebetween is placed between the platens 11 and 12 of a hot press and compressed under heat and pressure conditions for a period of time so that the prepreg 22 forms a caul which is at least sub-stantially cured and which has assumed the configuration ofthe textured panel 21. The assembly is then removed from the hot press, and the panels 21 and 23 are separated from the caul - -~ - -, ~ - - . .

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22, which has textured surface 41 corresponding in relief configuration to surfaces 31 of panel 21.
The caul 22 may then be baked until ully cured, if necessary, whereby the textured surEace 41 of the caul is permanently maintained.
Figures 3 and 4 illustrate the caul 22 produced in accordance with the subject invention. It can be appreciated that because ~he caul 22 is formed against the surface of an actual textured wood panel, the resultant caul is a very realistic reproduction thereo, having a fine decorative relief textured wood grain design.
In order to more fully appreciate the subJect inven-tion, reference is made to the following examples of specific caul constructions:

An assembly comprising the following elements is placed in a hot press: a 1/4 inch textured plywood panel, six high temperature resin non-cellulosic plies of CordopregTM
E-293, and 1/4 inch sanded plywood panel. This assembly is compressed for one hour at 320F. (platen temperature~ and 50 pounds per square inch. The plywood panels are then removed from the press and the caul baked and fully cured according to the following schedule: approximately one hour at a temperature on the order of 350F., approximately one hour at a temperature on the order of 375F., and approximately four hours at a temperature on the order of 400F. The intended application for this caul is for embossing medium density over-laid plywood at 300F. and 200 pounds per square inch.

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An assembly comprising ~he following elements is placed in a hot press: a 1/4 inch textured plywood panel, three high temperature resin non-cellulosic plies of E-712A Rov-MatT~, and a lt4 inch sanded plywood panel. The curing schedule and application for this caul are identical to those of Example 1.
The methods illustrated in Examples 1 and 2 relate to the construction of what is known as a "traveling caul".
~` A "traveling caul" is one which is matched with individual wood panels (plywood, particle board, etc.) prior to hot-pressing, pressed against the wood panels ~mder heat and pressure, and then separated rom the wood panels (after each ~ot press cycle) for re-use. Thicker such cauls of from about 12 to 20 plies of prepreg, however, are sufficiently more rigid to serve as "hanging" cauls as discussed below.
In an alternate method for forming the plastic caul of the subject inven-tion, the caul comprises an assembly con-; taining an internal metal core sheet, which may be steel or aluminum. This metal sheet should be of essentially the same length or width as the prepreg sheet; it is usually about 0.1inch thick. Plies of the high temperature resin non-cellulosic prepreg are ordinarily adhered to each face of an aluminum or steel sheet. Approximately equal numbers of plies of each side of the metal core acilitate curing without warpage. The prepreg plies may be self-bonded to the metal sheet incident to curing.
Alternatively, epoxy or other suitable adhesives may improve the bond. As indicated above, CordopregTM E-293 and E-712A Rov-MatTM have been found to be particularly effective epoxy prepregs.

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Embossing cauls formed from such prepreg-aluminum combination are particularly useful in forming what are known as stationary or "hanging" cauls. A "hanging" caul is one which is mechanically suspended wi~hin a hot press opening.
In this manner of operation, the need for matching with and then separating the cauls from the individual wood panels for each hot press cycle is eliminated. Because typical hot press designs restrict the methods available for suspending the caul within the press openings, "hanging" cauls ordinarily have excellent stiffness at relatively high (300F. - 350F.) press temperatures. Metal such as aluminum or steel, pre~erably aluminum, has been found to provide the structural rigidity required for "hanging" caul use.
Referring to Figures 5 and 6, the elements employed in the:alternate embodiment of the method o the subject invention are illustrated. An assembly comprising: first, the release coated textured panel 21'; second, a first set of plies of high temperature resin non-cellulosic prepreg 51; third, an adhesive film 53; fourth, an aluminum sheet 52; fifth, a second adhesive f-llm 53; sixth, a second set of plies of high tèmperature resin non-cellulosic prepreg 51; and seventh, a ~acking wood panel 23~, is placed in a hot press (not shown).
The assembly is then compressed under heat and pressure candi-tions until the plies of prepreg 51 are adhered to the aluminum sheet 52, forming a caul 22', which is su~stantially cured, and which has assumed the configuration 31' of the textured panel 21~
~ The assembly is then removed from the hot press and panels 23' and 21' are separated from the caul 22~. Note in ... .. . . , ,.. .. .. ... .... . . ~ .. . ... . . . . . ... .. . ... ... . ..

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Figure 6 the caul 22' has surface 41' which corresponds in relief to surface 31' of textured wood panel 21'.
; The caul 22' may ~hen be baked, if required, until :~ fully cured whereby the surface 41' is permanently maintained, . 5 In order to better appreciate the alternate embodi-ment of th~ method of the subject invention reference is made ;` to the following examples:

An assembly comprising the ollowing elements i5 placed in a hot press: a 1/4 inch textured plywood panel, four plîes of high temperature resin non-cellulosic prepreg (CordopregTM E-293~; one ply of film adhesive (EA-9605 sold ;: by the Hysol Division of Dexter Corporati.on, Pittsburgh, Pa.);
.~ a 1/8 inch aluminum sheet; one ply of EA-9605; four high tempera-ture resin non-cellulosic plies of CordopregTM E-293; and a 1/4 inch sanded plywood panel. This assembly is compressed at 75 pounds per square inch for one hour at 300~F., followed by one hour at 350F. The plywood panels are then removed from : the press and the caul is ba~ed and fully cured according to ~ 20 the following schedule: one hour at 375F. and four hours at : 400F. The intended use for this caul is for embossing mediumdensity overlaid plywood at 300F. and 200 pounds per square inch.
EXAMPLE_4 An assembly comprising the following elements is placed in a hot press: a 1/4 inch textured plywood panel;
four plies of high temperature resin non-cellulosic prepreg OEerro ~ -293); a 1/8 inch sheet of aluminum metal, four plies of the same prepreg (FerroTM E-293); and a 1/4 inch panel of .
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~ 1 ~3~0 smooth-sanded plywood. This assembly is compressed for 1 1/2 hours at a temperature of 350F~ under a pressure of 75 pounds per square inch. After separation, the caul is further cured by baking for one hour at 350F., one hour at 375F., and then four hours at 400F.
Other examples of caul production methods utilizing the principles of the invention are as follows:

A one inch textured plywood panel is sealed with a urethane varnish (RexthaneTM B44V20 from Sherwin-Williams Co., Cleveland, Ohio), the varnish cured, and the sealed textured surface coated with a release agent (VydaxTM from Du:Pont, Wilmington, Delaware).
An assembly comprising the following elements is placed in a hot press to form a textured caul face: a one inch textured plywood panel (sealed and released); six plies of a high temperature resin non-cellulosic prepreg (FerroT~ E-293);
and a one inch smooth-sanded plywood panel. This assembly is compressed for 2 hours at a temperature of 360F. under a ` 20 pressure of 100 pounds per square inch. After separation, the textured caul face is further cured by baking for sixteen hours at 360F.
An assembly comprising -the following elements is placed in a hot press to form a smooth caul back: a one inch ; 25 smooth-sanded plywood panel; six plies of the same prepreg ~FerroTM E-293); and a one inch smooth-sanded plywood panel.
This assembly is compressed for 2 hours at a temperature of 360F. under a pressure of 100 pounds per square inch. After separation the smooth caul back is further cured by baking for sixteen hours at 360F.

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Once cured, -the textured caul face (specifiall~, the smooth - rather than textured - side) and the smooth caul back are sanded to promote adhesion. Then, an assem~ly comprising the following elements is placed in a hot press to form a textured embossing caul: a one inch smooth-sanded plywood panel; a cured, textured caul face; one ply of film adhesive ~Hysol TM EA~9605); a 1/8 inch aluminum sheet (sand blasted both sides); one ply of film adhesive (HysolTM EA-9605);
a cured, smooth caul back; and a one inch smooth-sanded plywood panel. This assembly is compressed at a pressure of 100 pounds per square inch as follows: 1/2 hour a~ 275F., 1/2 hour at 300F,, and 1 1/2 hours at 350F. The assembly is then removed from the hot press and the caul plate separated from the plywood panels.

A five-eighths inch textured plywood panel is sealed with a varnish (Sherwin-Williams T75C~10 - a water reducible, imine catalyzed acrylic varnish with urethane additi~e)l the varnish cured, and the sealed textured surface coated with a 20 ~ release agent (DuPont Vydax).
An assembly comprising the following elements is placed in a hot press to form a textured embossing caul: a five-eighths inch textured plywood panel (sealed and released);
five plies of the prepreg of Example5(Ferro E-293); one ply of film adhesive ~HysolTM EA-9605); an ll-gauge (0.120") steel sheet (sand ~lasted one side); and a five eighths inch smooth-sanded plywood panel. This assembly is compressed at a pressure of 200 pounds per square inch as follows: 1/2 hour at 275F.;
1/2 hour at 300F.; 1/2 hour at 325F.; and 1 hour at 350F.

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This assembly is ~hen removed from the hot press and the caul plate separa~ed from the plywood panels.

An assembly comprising the following elements is placed in a hot press to form a textured embossing caul:
a five-eighths inch textured plywood panel (sealed and released per Example 6); four plies of the prepreg of Example 5 (FerroTM
E-293); an ll-gauge steel sheet (sand blasted one side); and a five-eights inch smoo~h-sanded plywood panel. This assembly is compressed under the same time, temperature and press-ure condi~ions described in Example 6.

An assembly comprising the following elements is placed in a hot press to form a textured caul face: a one-half ' 15 inch textured plywood panel (sealed and released per Example ; 6); six plies of a high temperature resin non-cellulosic prepreg (F-439 from Hexcel Corp., Dublin, California); and a on~-half inch smooth-sanded plywood panel. This assembly is compress~d for 2 hours at a temperature of 350F. under a pressure of 100 pounds per square inch.
` Once cured, the textured caul face (specifically, ; the smooth - rather than textured - side) is sanded to promote adhesion. Then, an assembly comprising the following elements is placed in a hot press to form a textured embossing caul:
, 25 a one-half inch smooth-sanded plywood panel; a cured, textured caul face; one ply of an epoxy film adhesive (FM-400 from American Cyanamid, Havre de Grace, Maryland); an ll-gauge . ~, .
~ steel sheet (sand blasted one side); and a one-half inch ., '.
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.. . ~ --~ 1~33~0 smooth-sanded plywood panel. This assembly is compressed at a pressure of 40 pounds per square inch as follows: 1/2 hour at 250F.; 1/2 hour at 300F.; and 1 1/2 hours at 350F.
In summary, the subject invention provides a new and improved caul for embossing overlaid wood surfaces with a textured surface, and a method for forming said caul.
The various plastic caul configurations of the subject invention are all significantly less expensive to manufacture (with respect to both material used and actual processing) than metal cauls produced by aforementioned techniques. As a result of the cheaper costs, manuacturers may aEford many different cauls, thus exploiting the many designs that are available for use. Aside from the economic standpoint, the cauls formed in accordance with the subject invention are very realistic reproductions of wood surfaces because they are formed directly against actual textured wood surfaces. This is in contrast with most types of metal cauls which are formed indirectly from textured wood surfaces. In addition, all the cauls formed in accordance with the subject invention, even the plastic-metal composites, are significantly lighter than the metallic cauls currently available. This results in easier and safer handling, especially during installa-tion and removal from the hot press.
Finally, the surface composition of the subject cauls - 25 permits them to be recycled for further use. This may be done ` by removlng the applied texture (by sanding or similar mechan-ical means) and then reapplying a new texture design. This reapplication is performed in a manner similar to the method :

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11733~0 already discussed. Thus, one or more plies of prepreg sheeting are placed on the s~ooth surface of the old caul. Then this ~! caul assembly is re-compressed against a new textured surface in a hot press, removed and (if necessary) baked.
In essence, therefore, the present cauls are susceptible to replacement of their texture-containing surface (or alternatively, the opposite side of the caul could be provided with a new texture-containing surface). This characteristic still further increases the utility of the present cauls while reducing their cost by permitting conserva-tion of their material through re-use.
- Since the high temperature resin non-cellulosic pre-pregs used in all of the cauls of the invention are relatively heat insensitive, and therefore not thermally degradable at normal press temperatures, and have better thermal conduction and therefore shorter press cycle times, the invention is a distinct advance over prior techniques such as those taught by Hale et al.
Although the foregoing invention has been described chiefly in terms of forming a caul ha~ing a relief texture taken from a natural wood surface, it is understood that reli~fs of other surfaces may also be made. As long as the surface sought to be duplicated in relief is sealed and provided wi~h release agent, a suitable caul may be made Erom it. Thus, for example, plastic cauls of the present invention could be formed from metal or cast surfaces having a desirable design texture.

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for forming a plastic embossing caul comprising:
a) sealing a textured wood panel by applying at least one coat of a sealer to the surface of said panel;
b) providing said sealed panel with a release agent;
c) placing an assembly comprising said sealed panel, a backing panel, and a plurality of high temperature resin non cellulosic prepreg plies each of the plies including a heat insensitive web in a hot press, said prepreg plies being disposed between the two panels;
d) compressing said assembly under heat and pressure conditions until the prepreg plies form a laminated caul which is substantially cured and has assumed the relief configuration of the textured wood panel;
e) removing the assembly from the hot press; and f) separating the sealed panel and backing panel from the caul, whereby the configuration of the textured wood panel assumed by the caul is permanently maintained and usable for embossing a grain pattern onto a wood panel.

2. A method according to claim 1, wherein there is placed in said hot press said assembly which includes a metal backing sheet to which the plies of prepreg are adhered under heat and pressure conditions.

3. A method according to claim 1, wherein there is placed in the hot press a metal sheet on one side of which is disposed said assembly and on the other side of the metal sheet a second plurality of high temperature resin non-cellulosic prepreg plies, the plies of prepreg being adhered to the metal sheet on compressing under heat and pressure.

4. A method according to claim 1, wherein the plurality of prepreg plies are composed of sheets of woven graphite impregnated with a resin selected from the group consisting of phenol formaldehyde polyester or polyimide.

5. A method for forming a plastic embossing caul according to claim 1, wherein a step of further curing the caul is included according to the following schedule:
baking the caul for about one hour at approximately 350°F., followed by about one hour at approximately 375°F., followed by about four hours at approximately 400°F.

6. A method according to claim 2, wherein a step of further curing the caul is included according to the following schedule:
baking the caul for approximately one hour at a temperature on the order of 375°F. followed by approximately four hours at a temperature on the order of 400°F.

7. The method of claim 1, 2 or 3, in which the sealer is a urethane varnish.

8. The method of claim 1, 2 or 3, in which the sealer is a water reducible, imine catalyzed acrylic varnish with a urethane additive.

9. The method of claim 1, 2 or 3, in which the high temperature resin non-cellulosic prepreg plies include a heat insensitive web of fiberglass.

10. A method for forming a plastic embossing caul comprising:
a) sealing a textured wood panel by applying at least one coat of a sealer to the surface of said panel;
b) providing said sealed panel with a release agent;
c) placing in a hot press an assembly comprising said sealed panel, a backing panel, and a plurality of high temperature resin non-cellulosic prepreg plies, each of the plies including a heat insensitive web selected from the group consisting of fiberglass and woven graphite impregnated with a high temperature resin, said prepreg plies being disposed in said hot press between the two panels;
d) compressing said assembly under heat and pressure conditions until the prepreg plies form a laminated caul which is substantially cured and has assumed the relief configuration of the textured wood panel;
e) removing the assembly from the hot press; and f) separating the sealed panel and backing panel from the caul, whereby the configuration of the textured wood panel assumed by the caul is permanently maintained and usable for embossing a grain pattern onto a wood panel.