BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a process for preparing light weight automotive interior trim components and products produced thereby. More particularly, the present invention relates to a process in which a multi-layered composite article is produced using isocyanurate or trimer linkages, and to the products produced thereby.

2. Description of Related Art

In the past, light-weight panels having self- supporting cores having been made by methods requiring several steps. One such prior art disclosure is U.S. Patent No. 5,089,328 to Doerer et al. (hereinafter referred to as Doerer et al. '328 and incorporated herein by reference) which describes a method of making a lightweight multi-layered panel having a cover sheet attached to a self-supporting foam core impregnated with an isocyanate compound which cures when activated to stiffen the impregnated foam core. The cover sheet is bonded to the foam core under heat and pressure in a compression molding operation at a temperature at which activation of the isocyanate compound is accelerated and the foam core layer is rendered self-supporting and less compressible. The isocyanate compound used to impregnate the foam core is typically MDI (4-4'- diphenylmethane di-isocyanate) . The MDI is reacted with water and a tertiary amine to accelerate polymerization

and to reduce the reaction time of the isocyanate compound.

U.S. Patent No. 4,451,310 to Lairloup (hereinafter referred to as Lairloup '310 and incorporated herein by reference) discloses a similar process for preparing light-weight, insulating, and semi-rigid or rigid elements. The Lairloup '310 process essentially comprises impregnating a porous open-celled foam core material with an isocyanate and reacting the isocyanate with water thereby forming urea or biuret linkages, rendering the final products thermosetting.

The prior art methods which utilize urea or biuret linkages to cure or rigidize the foam core. These reactions typically occur at relatively low temperatures and thereby shorten or limit the amount of time the multi-layered panel can remain outside the temperatures of a die mold, since the polymerization or curing can begin in the interim period at temperatures lower than mold temperatures. Therefore, it is desirable to have a process for manufacturing multi-layered, lightweight articles in which the catalyzation or curing step occurs at a higher temperature, thereby increasing the amount of time

("open time") between formation of the multi-layered panel and its subsequent molding in a die mold. This increase in "open time" prior to molding provides for more economical and flexible manufacturing and assembly processes.

SUMMARY OF THE INVENTION AND ADVANTAGES

In accordance with the present invention, a rigid multi-layer composite article (20) comprises a sheet of an open cell foam material (22) , one or more layers of a reinforcing material (24) disposed on the surfaces of the foam material (22) , a trimerized

isocyanate having at least one -NCO group dispersed throughout the foam material (22) and the reinforcing material (24) and adhering the foam material (22) and the reinforcing material (24) together in fixed rigid relationship, and at least one surface layer (26) adhesively affixed to a surface of the reinforcing material (24) . The present invention also provides for a process for preparing the multi-layered composite article (20) .

FIGURES IN THE DRAWINGS

Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIGURE 1 is a diagrammatic view of a layered assembly of the parts of which the article is constructed prior to being compressed and molded; and FIGURE 2 is a schematic representation of the process of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to Figure 1, an article 20 embodying the present invention and made according to the method of the present invention is shown in Fig. 1. The article 20, a panel, is relatively lightweight and flexible. It comprises a foam core 22 having reinforcing layers 24 located on each surface or side of the foam core 22.

The reinforcing layers 24 are preferably made of glass fibers. An adhesive layer or film 28 is applied over the reinforcing layers 24 and is used to bond outer layers of foam/scrim 26 to the reinforcing layers 24. The foam/scrim layers 26 comprise the

exterior surface of the composite article 20 of the present invention.

The foam core 22 can be of uniform thickness and can be made from soft, flexible sheets of any suitable expanded, reticulated or open cell plastic material such as a polyether, polyolefin, polyester, polyurethane, or any combination thereof.

The foam core 22 is impregnated or saturated with a heat-activated liquid hardening compound/binder which enters and fills the cells of the foam, coating the cell walls.

Referring to Fig. 2, in the method of the present invention, the foam core 22 is fed from a stock reel 40 which contains foam stock which has been previously sized to the desired thickness. In the present invention the thickness of the foam material is approximately 7mm; however, the foam core 22 can be of any thickness and can be varied to meet manufacturing specifications from 2mm to 30mm. The foam which makes up the foam core 22 is unrolled from the stock reel 40 and passes through a binder bath 42 which contains the heat activatable compound/binder. In the preferred embodiment, the heat activatible liquid compound/binder is preferably polymeric MDI (4-4 '-diphenylmethane di- isocyanate) . However, other isocyanates such as TDI (toluene di-isocyanate, IPDI (isophoronediisocyanate) , IPDI, phenyl isocyanate, and H ₁₂ MDI may be used as substitutes for the MDI.

The isocyanates should have at least one -NCO group, polymers of isocyanates with at least one terminal -NCO group, and any compound having at least one terminal -NCO group in its formula in order to form a tri er.

A typical trimer is formed by the reaction:

O

II catalysis C 3RNCO ► R-N N-R

I I

0=C C=0

N where RNCO is MDI: NCO NCO NCO

CH CH.

N=0 1+

The MDI saturates the foam and through a process of tri erization of the MDI rigidizes the cell walls of the foam core 22 by forming isocyanurate linkages.

The MDI saturated foam 22 exits the binder bath 42 and is compressed between a set of calender rolls 44 which are used to control the amount of MDI retained in the foam core 22. The amount of MDI saturation is commonly referred to as the saturant level. By controlling the saturant level (amount), it is possible to vary the rigidity of the article 20 produced. Since the degree of rigidity (soft < ► hard) of the composite article 20 is a function of both the type and the amount of saturant present, i.e., %MDI, varying the type or the amount of saturant directly effects the rigidity of the composite article 20. That is, by controlling the amount of saturant in the foam 22 by either squeezing the saturant out of the foam 22 using the calender rolls 44 or by diluting or thinning

the concentration of saturant in a suitable solvent such as trichloroethane, methylene chloride, propylene carbonate, or similar solvents, a composite article 20 can be produced having any desired degree of resilience or yieldability. Therefore, a composite article 20 can be produced wherein the foam core 22 provides structural rigidity ranging from very soft (little or no structural support, very resilient) to very rigid (good structural support, not resilient) . The saturant concentration can range from about 100 grams/m ² to 1000 grams/m ² with approximately 500 grams/m ² being the preferred concentration.

The temperature of the MDI can range from approximately 70°C to 150°C with the preferred temperature being approximately 75°C.

The rigidity or strength of the resultant composite article 20 can further be modified by the addition of certain polymers. Polyols are one such polymer. Polyols can be used to enhance the strength and integrity of the composite article 20 by addition of a prepolymerized long chain polyol with the isocyanate prior to trimerization. Examples of suitable polyols include 1000-4000 molecular weight polyether diols and triols, 1000-2000 mw THF-based diols and glycols, and 2000-10,000 mw low monol diols and triols. In addition to modifying the rigidity or stiffness of the resultant composite article 20, the addition of the prepolymerized long chain polyol improves both impact resistance and toughness of the resultant composite article 20 while retaining excellent heat stability. The prepolymers are produced by combining the long chain polyols with an excess amount of the isocyanate in order to yield long isocyanate terminated polymers which react as isocyanates due to the terminal isocyanates but, which

impart toughness and durability to the composite due the incorporation of the long chain polymer.

Isocyanurate linkages contribute to brittleness characteristics of the foam and yields a foam with a constant crush rate. In addition, foams having isocyanurate linkages are inherently flame resistant; and when combined with the prepolymerized long chain polyol, use of flame retardant additives are optional. Isocyanurate foams are also extremely stable with very little change in properties over time or with changes in environment.

The foam core 22 with the desired amount of MDI is then treated in a catalyst applicator 46 with a trimerization catalyst which catalyzes the cyclization of the isocyanate. The catalyst can be applied directly onto the MDI impregnated foam core 22 utilizing methods and apparatus known to those skilled in the art. The catalysts employed are referred to in the art as trimer catalysts and include various oxides, alykoxides, amines, carboxylates, hydrides, and hydroxides of quaternary nitrogen, phosphorous, arsenic, antimony, or mixtures thereof as shown in Table 1 as set forth below. Other catalysts which may be used in preparing the foam of the present invention include acids, organo- metallics, and combinations of such as shown in Table 2 set forth below. Common catalysts used in the present invention include potassium octoate (Air Products K-15) , potassium acetate (Air Products Polycat-46) , tertiary amines such as DABCO™ TMR (Air Products Proprietary A ine) , or any of the many other catalysts known to the art. The amount of the catalyst employed depends on the catalyst type, mold temperature, required "open time", and the desired cure time. Catalyst concentrations can range from approximately two percent to twelve percent with the preferred catalyst concentration being

approximately eight percent. A typical formulation would include 100 parts MDI to 4 parts trimerization catalyst. The catalyst spray may also contain other components such as water, dye, surfactant, and other minor ingredients. The water concentration can range from approximately 88% to 98% with the preferred percentage being approximately 92%.

Following exit from the MDI application, the multi-layered composite 20 is assembled. The foam core 22 receives a layer or mat 24 of reinforcing fibers. The foam core 22 can receive one or more layers or mats 24 of reinforcing fibers. Each surface of the foam core 22 typically receives a reinforcing layer or mat 24. The reinforcing layer 24 consists of a fibrous material having discrete, distinct fibers. The fibrous material which comprises the reinforcing layer 24 can be of natural or synthetic material. Natural fibrous materials suitable for use in the reinforcing layer 24 include animal or vegetable fibers. Suitable synthetic fibers can include glass fibers, synthetic fibers such as Kevlar®, or other synthetic fibers known to those skilled in the art. The preferred material for use in the reinforcing layer 24 is glass fiber.

The fibrous reinforcing layer 24 is necessary in order added strength and stiffness to the composite article 20. Additionally, because the reinforcing layer 24 is typically constructed of woven or interlaced fibrous material, voids or intersticial spaces are created within the weave of the reinforcing layer 24. These voids or intersticial spaces allow the heat activatable binder compound, i.e., MDI, to flow through the voids or intersticial spaces and permeate and saturate the fibers of the reinforcing layer 24. Saturation of the fibers of the reinforcing layer 24 with the binder compound allows, upon catalyzation, for

formation of a mechanical bond between the foam core 22 and the reinforcing layer 24. That is, when the binder compound is catalyzed, the same curing reaction that stiffens the foam core 22 mechanically bonds the reinforcing layer 24 to the foam core forming an essentially integral layer.

After the reinforcing layer 24 is applied to the foam core 22, an exterior or surface layer 26 can then be applied to the reinforcing layer 24. The surface layer 26 can be any suitable material such as scrim or foam. The surface material 26 is chosen with a particular application in mind. That is, should a multi-layered composite panel 20 be required to have impact or energy absorbing characteristics, a foam exterior layer can be applied.

The scrim material can be any suitable material such as a polyester fabric, vinyls, olefins, thermoplastic urethanes, and other thermoplastics.

The exterior or surface layer 26 can be adhesively bonded directly to the reinforcing layer 24 with the same MDI which bonds the reinforcing layer 24 to the foam core. However, if the exterior or surface layer 26 is bonded using MDI, surface characteristics such as resilience or impact resistance may be affected. That is, because the MDI, used to bond the exterior or surface layer 26 directly to the reinforcing layer 24, will undergo the same trimerization and curing thereby altering the surface characteristics of the exterior or surface layer 26. However, in the preferred embodiment, an additional adhesive layer 28 (intermediate layer) is used to bond the exterior or surface layer 26 to the reinforcing layer 24. The adhesive can be a film or sheet of a thermoplastic material such as a polyester, polyamide, polyethylene, polypropylene, and other

olefins which melts or forms bonds at die molding and trimerization reaction temperatures. The adhesive layer 28 is applied to the reinforcing layer 24 in between the reinforcing layers 24 and the exterior or surface layer 26. Under the heat of molding, the adhesive layer 28 melts and forms a bond between the reinforcing layer 24 and the exterior or surface layer 26.

In addition to bonding the exterior or surface layer 26 to the reinforcing layer 24, prior to melting, the adhesive layer 28 also serves as an occluεive barrier, preventing migration of the MDI (hardening solution) to the exterior or surface layers 26. By preventing the migration of the MDI to the exterior or surface layers 26, i.e., a foam exterior layer, the surface characteristics of the foam exterior layer 26 can be maintained without the influence of the MDI hardening solution.

The adhesive layer or film 28 is positioned over the reinforcing layers 24, and finally the surface layer 26 of foam/scrim is applied to complete the formation of the composite article 20. Each of the constituents which comprise the multi-layered composite article 20, i.e., the reinforcing layer 24, the adhesive layer 28, and the surface layers 26 are fed from continuous stock reels (shown in Figure 2) . The multi- layered composite 20 is ^' then passed through a second set of calender rolls 48 which impregnate the reinforcing layers 24 with the MDI, trimerization catalysts, and any other ingredients. The continuous length of the multi-layered composite 20 is then conveyed through a shearing apparatus 50 which cuts the multi-layered composite 20 to desired length. The sheared lengths of the multi- layered composite 20 are then placed into a tenter frame

(holding frame) (not shown) . The tentered composite is then transported to a die press/mold 52.

The die press/mold 52 is maintained at a temperature between 200°F and 400°F. It is at this temperature that the trimerization reaction occurs, and the foam core 22 becomes a rigid thermosetting plastic. The multi-layered composite 20 is pressed between male and female die halves at a pressure between approximately 2-25 psi for twenty second to two minutes to reproduce the configuration of the final article to be made such as automotive interior trim components e.g., headliners, dashboards, armrests, etc. The die pressed or molded multi-layered composite article 20 is then allowed to cure for between 15 to 90 seconds and is then removed the press/mold 52 for trimming and other post assembly processing.

The period of time «between the formation of the multi-layered composite 20 and its subsequent molding is referred to in the art as "open time". In order to enhance manufacturing flexibility and to reduce waste, the present invention allows for the amount of "open time" to be increased because the trimerization reaction occurs at temperatures much greater than typical ambient, or room temperatures. Therefore, should it become necessary to stop the manufacturing process prior to the final heating and compression molding steps, the multi-layered composite 20 material does not undergo significant curing or polymerization during this period of time. Since the multi-layered composite 20 will not cure at the lower temperatures, the manufacturing process can be interrupted without having to discard the unmolded but fabricated composite material.

Additionally, impact strength and overall toughness (impact resistance) of the multi-layer

composite article 20 can be improved by incorporating a solid polyol material into the surface layers 26 of the composite. Incorporation of the solid polyol into one or possibly both of the surface layers 26 provides for formation of urethane linkages in the surface layer 26 which are quite flexible.

The solid polyol can be incorporated into the surface layers 26 by sprinkling (salting) the multi¬ layer composite 20 with ground or powdered solid polyol material just prior to introduction of the multi-layer composite 20 into the die mold. The temperatures of the die mold allow the solid polyol to melt and react with the isocyanate forming the urethane linkages in or on the surface layers 26. Suitable solid polyols include amine or hydroxyl terminated polyols with relatively low melting points such as polytetramethylene ether (PTMEG) , 1,4- cyclohexanedimethanol (CHDM) , and hydrogenated bis- phenol A (HBPA) . The molecular weight of these polyols ranges from 250 to 2000. The solid polyols can also be applied to the composite 20 by melting the polyol and a spraying the molten polyol onto the reinforcing layer(s) 24. The polyol is allowed to cool thereby forming a solid and the surface layers 26 are then applied. Alternatively, the surface toughness and impact resistance of the prior art polyurea multi-layer composite articles (such as those disclosed in the Lairloup patent incorporated herein by reference) can be improved by the incorporation of the solid polyol materials into the surface layers of the composite. Incorporation of the solid polyol into the surface layers provides for formation of urethane linkages in the surface layer. The traditional polyurea method of forming multi-layer composites utilizes the reaction of

isocyanate and water leading to derivatives of urea and biuret urethane linkages.

Additionally, impact strength and overall toughness (impact resistance) of the multi-layer composite article can be improved by incorporating a solid polyol material into the surface layers of the composite. Incorporation of the solid polyol into one or possibly both of the surface layers provides for formation of urethane linkages in the surface layer which are quite flexible.

The solid polyol can be incorporated into the surface layers by sprinkling (salting) the multi-layer composite 20 with ground or powdered solid polyol material just prior to introduction of the multi-layer composite into the die mold. The temperatures of the die mold allow the solid polyol to melt and react with the isocyanate forming the urethane linkages in or on the surface layers.

Suitable solid polyols include amine or hydroxyl terminated polyols with relatively low melting points such as polytetramethylene ethylene glycol (PTMEG) , 1,4-cyclohexanedimethanol (CHDM) , and hydrogenated bis-phenol A (HBPA) . The molecular weight of these polyols ranges from 250 to 2000. The solid polyols can also be applied to the composite by melting the polyol and a spraying the molten polyol onto the reinforcing layer(s). The polyol is allowed to cool thereby forming a solid and the surface layers are then applied. The polyurea multi-layer composites are essentially constructed by the same method as described above for the polyisocyanurate composites. The method includes impregnating a sheet of open cell material, such as foam, with an isocyanate having at least one terminal -NCO group. Water is then applied to the

isocyanate impregnated open celled material to cause the formation of the urea and biuret urethane linkages and impart rigidity to the composite article. Layers of reinforcing material can be applied over the open celled material to add additional strength to the composite article. As described above, surface layers such as scrim or foam can be applied over the reinforcing material either with or without the use of an additional adhesive material. The composite material can then be molded under heat and pressure to cure the urethane reaction and form the rigid composite article.

The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

TABLE 1

CATALYSTS FOR ISOCYANATE TRIMERIZATION

TABLE 2

CATALYSTS FOR ISOCYANATE TRIMERIZATION

Acids Combinations Organoraetallics

HC1 Amines/epoxides R ₃ Si-SR'

(C0 ₂ H) ₂ Amines/alcohols R ₃ Sn-SR'

AlCl ₃ and Friedel- Amines/alkylene carbonates R-.Sn-S-SnR _j Crafts catalysts

Amines/alkylene imides R ₃ Sn-OR'

Amines/carboxylic acids R ₃ Pb-NR' ₂

Amines/peroxides R ₃ Sb-(OR' ) ₂

Ammonium hydroxides/carbamates R ₃ Sb-(OCOR" ) ₂

Tetraethylammonium iodide/phenyl glycidyl ether RZn-OR'

RZn-NR' ₂