Patent Application
20110024933
The present invention relates to an expandable filler insert comprised of a polymer matrix, methods of making the expandable filler insert, and the use of the expandable filler insert to fill or seal cavities such as the hollow structural members of vehicles.
Foamable materials, generally aided by carriers, are currently used to fill and/or seal hollow structures or cavities, such as pillars of vehicles. Such materials foam and expand upon applying external heat of about 120 degrees Celsius to about 210 to 220 degrees Celsius (° C.) to the automobile body in the electrodeposition or baked finish process, thereby providing sound insulation, soundproofing and vibration suppression and improving the quietness within the vehicle by blocking the transmission of road and wind noise during driving. Additionally, foamable materials are commonly used to strengthen or stiffen vehicle cavities by providing structural reinforcement of the hollow structure.
Generally, an expandable (also referred to as foamable) material is supported and fixed to predetermined sites in the cavity of a hollow structure until it is foamed and expanded by external heat. Support/fixation of the expandable material is typically necessary because otherwise the expandable material is susceptible to being dislodged from the desired position within the cavity prior to or during activation of the expandable material. As a result, the unsecured expandable material may not necessarily or reproducibly block or seal the cavity to an acceptable extent.
Holding jigs (also known as carriers or supports) were developed to hold the foamable materials in place until external heating was accomplished so that the desired space or cavity was filled or sealed. These carriers are made of materials such as metal or heat resistant rigid synthetic resins which have very different properties than the foamable material. The use of such carriers presents certain problems in that the foamable materials may not adhere strongly to the carrier, before and/or after activation of the foamable material. The foamable/foamed material thus may separate from the carrier, thereby interfering with consistent, uniform and durable filling or sealing of the cavity. Additionally, assembly or manufacture of a part comprised of a carrier and a foamable material may be relatively complicated and hence expensive due to the use of different materials for the components.
WO 01/054936 A1 describes a stiffening part in the form of a self-supporting body that expands upon heating to an expansion temperature. The body contains a first and a second group of ribs that are arranged at a distance from one another. During heat activation, heated air can flow through between the ribs arranged at a distance, so that a larger surface area of the stiffening material is exposed to the heat.
US 2005/0249916 describes another insert for filling the hollow space or cavity of a structure is a foamable sheet that is manufactured as a continuously formed sheet using continuous molding processes. The sheets are then processed into strips and the ends of the strips are overlapped and held together using an attaching device. These foamable or expandable materials can be capable of uniformly expanding to fill the hollow space or cavity when sufficiently heated. However, there are practical limits to the thickness of such sheets. This may make it difficult to introduce a quantity of the foamable material into the cavity which is sufficient to fully seal or fill the cavity, especially when the cavity is irregular in shape or has acute corners.
EP 383 498 describes support-less, foamable shaped parts for insertion into vehicle cavities and subsequent foaming. The shaped parts can be manufactured by extrusion, their cross section being adapted to the cross section of the cavity to be filled up.
Many hollow structures, such as a pillar of a vehicle, are constructed by combining two or more side metal sheets and the transverse cross-sectional shape of its cavity has corners where the side sheets are joined. These corners are often narrow and complicated and simply foaming and expanding the foamable material in the central area of the cavity or directionally expanding the foamable material is not enough to fill the entire cavity or the corners adequately.
Accordingly, there is still a need in the art for heat-expandable components adapted for use in hollow structures or cavities such as in pillars of automobiles and the like, which can be readily designed and controlled, which are inexpensive to manufacture, and which solve one or more problems of the prior art designs, such as those described above.
The present invention provides an expandable filler insert for filling or sealing a hollow space or cavity (e.g., a vehicle pillar) without the use of a carrier or support component. In one embodiment of the present invention, the insert comprises a self-supporting continuous structure with an interior space and an outer surface that substantially parallels the cross-sectional shape of the cavity but does not (in its unactivated state) contact the interior surface of the cavity. The self-supporting continuous structure is fabricated from a polymer matrix comprised of at least one polymer or polymer precursor and at least one latent blowing agent. At least one fixing element protrudes from, and is integral with, the self-supporting continuous structure for securing the insert to at least one interior surface of the cavity. The expandable filler insert can have one or more protrusions extending into the interior space of the self-supporting continuous structure providing additional polymer matrix to assure complete sealing or filling of the cavity. The insert may also have one or protrusions extending from the outer perimeter of the self-supporting continuous structure in the direction of corners of the cavity having acute angles, thereby assisting in complete sealing or filling of such corners. The expandable filler inserts of the present invention are surprisingly effective in achieving full blockage or sealing of cavities, despite their lack of a carrier or holding jig. At the same time, such inserts are relatively simple and inexpensive to manufacture.
In yet another aspect, there is provided a method for producing such expandable filler inserts wherein the polymer matrix is contour extruded into an extruded strand, in special embodiments into an extruded closed tube having a cross-sectional shape corresponding to the desired dimensions of the self-supporting continuous structure, with the extruded strand or tube then being cut into the desired thickness.
The present invention provides for an expandable filler insert for filling or sealing a hollow space or cavity. Additionally, the present invention provides for an expandable filler insert for filling or sealing the hollow space or cavity of a vehicle pillar. The present invention also provides for a method for making an expandable filler insert by contour extrusion molding (also referred to as profile molding).
The present invention provides for an expandable filler insert for filling a cavity having an interior surface, the insert comprising a self-supporting continuous structure having an outer surface that substantially parallels the interior shape of the cavity but is spaced apart from the interior surface of the cavity, and a fixing element which is selected from the group consisting of:
In some embodiments, the insert has an interior space, preferably realized by the self-supporting continuous structure being a ring.
In one embodiment the present invention provides for an insert having a main body made of a reactive cross-linking material including the polymer matrix comprising at least one polymer or polymer precursor and at least one latent blowing agent, that is expandable by at least 20% at a temperature in the range of 120 to 220° C., which body comprises at least one fixing element having respectively a front side and a back side which are defined in that the entire expandable filler insert, including the fixing element or elements, is delimited by two parallel flat surfaces, the front side of each fixing element lying in one of the parallel surfaces, and the back side lying in the other of the parallel surfaces.
In one embodiment, in the non-expanded state the insert extends farther in a first direction, perpendicular to a longitudinal axis that is perpendicular to the parallel surfaces, than in a second direction perpendicular to the longitudinal axis and perpendicular to the first direction, the first direction being the direction of farthest extension and being designated the horizontal direction, while the second direction perpendicular respectively to the longitudinal axis and to the horizontal direction is designated the vertical direction.
In some embodiments, upon heating to 120 to 220° C., the expandable filler insert expands in such a way that the expansion in the vertical direction is relatively greater than the expansion in the direction of the longitudinal axis.
In some embodiments, upon heating to 120 to 220° C., the expandable filler insert expands in such a way that the expansion in the vertical direction is relatively greater than the expansion in the horizontal direction.
The expandable filler insert may have at least one fixing element comprising a cavity that extends parallel to the longitudinal axis from the one to the other of the parallel surfaces, and opens into the surfaces.
In some embodiments of the expandable filler insert, the expandable material is not tacky at a temperature in the range of 10 to 40° C. and it comprises at least one outer surface that extends from the one to the other of the parallel surfaces and is covered, at least in a selected region of the outer surface, by a material that is tacky at 10 to 40° C., this selected region being delimited on two sides by the two parallel surfaces.
In some embodiments, the outer surface of the self-supporting continuous structure is dimensioned so as to form a substantially uniform gap between the outer surface and the interior surface of the cavity around the perimeter of the self-supporting continuous structure of from 1 to 10 mm.
The polymer matrix after heat activation may expand by at least about 1000 percent. In some embodiments, the polymeric matrix is comprised of at least one thermoplastic and at least one chemical blowing agent.
In one embodiment the expandable filler insert may fill a cavity having a cross-sectional shape comprising at least one acute angle and having an interior surface, the insert comprising a self-supporting continuous structure having an interior space and an outer surface that substantially parallels the cross-sectional shape of the cavity but does not contact the interior surface of the cavity, wherein the outer surface of the self-supporting continuous structure has at least one protrusion that extends towards the at least one acute angle of the cavity, a fixing element protrudes from the self-supporting continuous structure for securing the insert to the interior surface of the cavity, and the polymer matrix comprises at least one polymer or polymer precursor and at least one latent blowing agent.
The expandable filler insert may comprise a protrusion comprised of the polymer matrix extending into the interior space of the self-supporting continuous structure.
The invention is also directed to a method for filling or sealing a cavity having an interior surface, the method comprising attaching an expandable filler insert in accordance with the invention as described herein to an above described interior surface and heating the expandable filler insert to a temperature effective to activate the at least one latent blowing agent.
In some embodiments of the method for manufacturing an expandable filler insert, the expandable material is extruded through a die into a strand, and the strand is sliced so that the aforesaid parallel surfaces are produced as cut surfaces.
In an embodiment of the present invention, an expandable filler insert is provided which is used for filling and/or sealing a cavity such as, for example, the cavity or hollow structure of a pillar of a vehicle such as an automobile. The expandable filler insert comprises a self-supporting continuous structure having an interior space, the structure being comprised of a polymer matrix containing a) at least one polymer and/or polymer precursor and b) at least one latent blowing agent.
The continuous structure is a structure that is fabricated as a single continuous piece optionally having an interior space (i.e., an opening, which in certain embodiments represents at least about 50% or at least about 60% or at least about 70% or at least about 80% of the total area of the expandable filler insert as viewed from the direction which is perpendicular to the plane defined by the self-supporting continuous structure). The continuous structure in this case has an inner surface (which faces towards the interior space) and an outer surface (which faces towards the interior surface of the hollow member within which the insert will be placed) and is self-supporting (i.e., the expandable filler insert does not contain a separate carrier, holding jig or other support to which the polymer matrix is attached, other than the fixing element in one embodiment of the invention). The outer surface of the structure has a shape that in outline corresponds to and generally follows or parallels the cross-sectional shape of the cavity to be filled. In one embodiment, the continuous structure is resilient. By resilient, it is meant that the continuous structure (at room temperature, e.g., 15-30 degrees C.) is capable of being temporarily flexed, deformed or distorted to at least some extent without breaking or cracking when subjected to an external force such as twisting or squeezing, but returns to its original shape when such external force is released. This characteristic facilitates handling and placement of the expandable filler insert within a cavity of a structural member such as a vehicle pillar or the like. The continuous structure is preferably fabricated of a polymer matrix that is sufficiently rigid so as to render the continuous structure dimensionally stable and self-supporting.
In certain embodiments of the invention, the self-supporting continuous structure takes the form of a ring. The dimensions and shape of the ring in cross-section (i.e., a cross-section in a plane perpendicular to the plane defined by the self-supporting continuous structure) are not believed to be particularly critical, but generally should be selected so as to provide sufficient polymer matrix such that when the latent blowing agent contained therein is activated by heating, complete or essentially complete sealing of the cavity is attained. Additionally, the dimensions and shape of the ring in cross-section should be selected so as to render the continuous structure self-supporting. In cross-section, the ring may, for example, be in the form of a circle, oval, square, rectangle, polygon, triangle, cross, “U”, “V”, “D”, “T”, “X”, “C” or the like or may be irregular in shape. Typically, the average thickness of the ring (as viewed from the direction that is perpendicular to the plane defined by the self-supporting continuous structure) is less than 50% or less than 40% or less than 30% or even less than 20% of the average overall radius of the self-supporting continuous structure.
The expandable filler insert may be secured within the hollow space or cavity of, for example, a vehicle pillar by a fixing element that protrudes from and which is integral with the outer surface of the continuous structure. “Integral with”, as used herein, means that the fixing element is part of the continuous structure and cannot be removed or separated therefrom without damaging the continuous structure of the expandable filler insert. In another embodiment described further below, the expandable filler insert is fixed onto the inner cavity wall by a piece of a tacky substance.
In one embodiment of the invention, the expandable filler insert is formed entirely from the polymer matrix. The fixing element(s) may be in the form of engaging projections or the like that are capable of being inserted through openings in the cavity walls but are designed to resist being withdrawn through such openings (for example, by engagement of hooks or ridges on the projections with the exterior surface of the structural member wall in the vicinity of the opening), thereby securing the expandable filler insert in place. The fixing element is comprised of polymer matrix so that upon activation by heating the fixing element expands and helps to fill and seal off the opening in the cavity wall into which it has been inserted.
Any of the devices known in the art to be capable of securing a carrier bearing an expandable material to the interior wall of a structural member cavity may also be adapted for use as a fixing element in the expandable filler inserts of the present invention. For example, the fixing element may include two or more resiliently deflectable barbs configured for secured receipt in an opening in the structural member. Each barb may comprise a shank bearing a retaining piece that protrudes at an angle to the shank so as to form a hook. Such a fixing element is inserted into the wall opening with application of minor force, causing the barbs to reversibly bend together and towards each other. After the barbs have passed through the opening, they return to their normal position apart from each other. This allows the retaining pieces to engage with the outer surface of the structural member wall around the periphery of the opening. Affixing the insert in this manner so as to prevent it from being easily displaced is highly desirable, since otherwise the handling that the structural member will normally encounter during assembly of a vehicle prior to heating and activating the polymer matrix is likely to cause the expandable filler insert to no longer be properly positioned in the desired location within the cavity. Alternatively, the fixing element may be comprised of a post portion and a pair of resilient retaining leg members, each diverging from a respective side of the post portion at an acute angle and extending from the tip of the post portion towards the self-supporting continuous structure. When inserted into an opening in an interior wall of a pillar or other hollow structural member, the leg members are initially compressed and, upon full insertion, extend out beyond the opening and thereby engage the exterior surface of the pillar or other hollow structural member. Other types of fixing elements may also be used for this purpose, including for example a “Christmas tree”-type fastener having an elongated portion with multiple angled flanges. The expandable filler insert may have one fixing element or a plurality of fixing elements, of the same type or different types.
Typically, the fixing element projects radially from the self-supporting continuous structure. For example, the fixing element may project from the outer surface of the self-supporting continuous structure.
When the expandable filler insert is to be attached to a wall of a structural member, for example, at least a portion of the fixing element is inserted into an opening of the wall that is sized to substantially match the portion of the fixing element. The shape of the opening is not particularly critical, provided it is capable of receiving the fixing element and interacting with the fixing element so as to hold the expandable filler insert in the desired position. Typically, the expandable filler insert will be mounted within the cavity such that the plane defined by the self-supporting continuous structure is substantially perpendicular to the longitudinal axis of the vehicle pillar or other hollow structural member.
The fixing element has the same composition as the polymer matrix and is formed from the polymer matrix when the expandable filler insert is fabricated. The expandable filler insert after being attached within a vehicle cavity using the fixing element(s) is activated by heating for a period of time sufficient to foam and expand the polymer matrix, thus blocking or sealing the cavity so as to leave no spaces or holes therein.
The polymer matrix utilized in the expandable filler insert of the present invention may be selected from any of the materials known in the art that contain one or more polymers and/or polymer precursors and one or more latent blowing agents and that have sufficient dimensional stability at ambient temperatures so as to permit a continuous structure prepared therefrom to be self-supporting. It is also highly desirable for the polymer matrix (or at least its outer surface) to be substantially non-tacky at ambient temperatures and yet capable of being softened or melted at an elevated temperature so that it can be shaped or formed into the desired configuration by contour extrusion molding without activating the latent blowing agent(s). In a desirable embodiment of the invention, the polymer matrix is resilient. The latent blowing agent is selected to provide the property of foaming and expanding the polymer matrix by application of external heating (e.g., temperatures of from about 120° C. to about 220° C., the range of temperatures typically encountered by an automobile body when the finish coatings are baked onto the body) for from about 10 minutes to about 150 minutes. The polymer may be a thermoplastic polymer, rubber (elastomer, including crosslinkable or curable elastomers), and/or thermoplastic elastomer. Suitable thermoplastic polymers include, for example, ethylene-vinyl acetate copolymers, copolymers of ethylene and alkyl (meth)acrylates, polyethylenes, polypropylenes, polyesters. Suitable rubbers and thermoplastic elastomers include, for example, styrene-butadiene rubbers (SBR), ethylene-propylene rubbers, ethylene-propylene-diene monomer rubbers (EPDM), polybutadienes, styrene-isoprene-styrene block copolymers, styrene-butadiene-styrene block copolymers, styrene-ethylene/butylene-styrene block copolymers, styrene-ethylene/propylene block copolymers, nitrile rubbers, chlorinated polyethylene rubbers, and the like. Polymer precursors, i.e., materials or substances including prepolymers, resins and the like that are monomeric or oligomeric in character that are capable of being cured, cross-linked and/or chain extended upon heating, may also be used, both by themselves as well as in combination with one or more polymers. Examples of suitable polymer precursors include, without limitation, epoxy resins, polyurethane prepolymers, and the like. The polymer matrix thus may be thermoplastic, thermosettable, or, in one especially desirable embodiment, both thermoplastic and thermosettable (i.e., capable of being shaped or molded at a moderately elevated temperature but also capable of being cured or crosslinked at a higher temperature).
The latent blowing agent or agents present in the polymer matrix causes expansion or foaming of the polymer matrix when heated to an elevated temperature. The latent blowing agent can be any known blowing agent known in the art, such as, for example, “chemical blowing agents” which liberate gases by decomposition upon heating and/or “physical blowing agents”, i.e., expanding hollow beads that expand in volume upon heating (also referred to as expandable microspheres). Combinations of different blowing agents may be used, for example, a blowing agent having a lower activation temperature (e.g., about 100° C.) may be used together with a blowing agent having a higher activation temperature (e.g., about 180° C.). The amount of latent blowing agent is selected so as to provide the desired volume expansion of the polymer matrix when heated to a temperature effective to activate the blowing agent. The amount of latent blowing agent typically is from about 5 weight percent to about 20 weight percent of the total polymeric matrix.
Examples of latent blowing agents that are considered “chemical blowing agents” can include, but are not limited to, azo, hydrazide, nitroso and carbazide materials such as, for example, azobisisobutyronitrile, modified or unmodified azodicarbonamide (ADCA), di-nitroso-pentamethylenetetramine, 4,4′-oxybis(benzenesulfonic acid hydrazide) (OBSH), azocyclohexyl nitrile, azodiaminobenzene, benzenesulfonyl hydrazide, calcium azide, 4,4′-diphenyldisulfonylazide, diphenyl-sulfone-3,3′-disulfohydrazide, benzene-1,3-disulfohydrazide, trihydrazinotriazine, p-toluene sulfonyl hydrazide and p-toluenesulfonyl semicarbazide. “Chemical blowing agents” may be used in combination with additional activators or accelerators such as zinc materials (e.g., zinc oxide, zinc stearate, zinc di-toluene sulfinate), magnesium oxide, (modified) ureas and the like. Various acid/(bi)carbonate mixtures may also be utilized as the latent blowing agent.
Examples of latent blowing agents that are considered “physical blowing agents” include, but are not limited to, expandable hollow microspheres wherein the hollow microspheres are based on polyvinylidene chloride copolymers or acrylonitrile/(meth)acrylate copolymers and contain encapsulated volatile substances such as, for example, light hydrocarbons or halogenated hydrocarbons.
Depending on the amount and type(s) of blowing agent(s) used in the polymer matrix as well as other factors (e.g., the presence of foaming accelerators/activators, the properties of the polymer(s)/polymer precursor(s)), the polymer matrix can be formulated to expand when heated at least about 500 percent, or at least about 1000 percent, or at least about 1500 percent, or at least about 2000 percent in volume, as compared to the initial volume of the polymer matrix.
Additionally, additives known in the art such as, for example, cross-linking agents, curatives, and the like may be added to the polymer matrix to promote curing and/or cross-linking of the polymers or polymer precursors. Such cross-linking agents and curatives are selected based on the type(s) of polymers or polymer precursors that are utilized in the polymer matrix. In preferred embodiments of the invention, the cross-linking agent(s) and/or curative(s) are latent, i.e., stable/unreactive at ambient temperatures but activated when the polymer matrix is heated to an elevated temperature. In such embodiments, the polymer matrix is both expanded and cross-linked/cured as a result of such heating. The types of cross-linking agent(s)/curative(s) employed are generally selected so as to be compatible with the other components of the polymer matrix, in particular the polymer(s) and polymer precursor(s).
Additives known in the art, such as, for example, stabilizers, stiffeners, fillers, softeners, plasticizers, waxes, age resisters, antioxidants, pigments, colorants, fungicides, tackifiers, waxes and/or flame retardants may also be added to the polymer matrix.
Suitable waxes include paraffinic waxes having melting temperatures of from about 45° C. to about 70° C., microcrystalline waxes with melting temperatures of from about 60° C. to about 95° C., synthetic Fisher-Tropsch waxes with melting temperatures of from about 100° C. to about 115° C., and polyethylene waxes with melting temperatures of from about 85° C. to about 140° C.
Any antioxidants and stabilizers as known in the art can be added to the polymer matrix such as, for example, sterically hindered phenols and/or thioethers and/or sterically hindered aromatic amines.
Any fillers as known in the art can be present in the polymer matrix, such as, for example, talc, calcium carbonate, clay, silica, alumina, glass beads, glass fibers, polymeric fibers, barium sulfate, mica, carbon black, calcium-magnesium carbonates, barite and silicate fillers, potassium aluminum silicate, calcium metasilicates, pumice, and organic fillers. The amount of filler may, for example, be from about 1 weight percent to about 20 weight percent of the polymer matrix.
Formulations that may be adapted for use in fabricating the self-supporting continuous structure of the present invention include, for example, the formulations described in various patents and published patent applications such as, for example, US 2005-0096401; U.S. Pat. No. 6,830,799; U.S. Pat. No. 6,281,260; US 2004-0221953; U.S. Pat. No. 5,266,133; U.S. Pat. No. 5,373,027; U.S. Pat. No. 7,084,210; U.S. Pat. No. 5,160,465; U.S. Pat. No. 5,212,208; U.S. Pat. No. 6,573,309; US 2004-0266898; U.S. Pat. No. 6,150,428; U.S. Pat. No. 5,708,042; U.S. Pat. No. 5,631,304; U.S. Pat. No. 5,160,465; US 2004-0266899; US 2006-0188726 and U.S. Pat. No. 5,385,951, each of which is incorporated herein by reference in its entirety.
The assembly of the vehicle pillar (1) and expandable filler insert (10) illustrated in
The expandable filler insert of the present invention may be produced by a contour extrusion molding process. An extrusion machine (extruder) extrudes the polymer matrix in molten or softened form through a die assembly. In the case that an expandable filler insert having an interior space is desired, the die assembly includes a member to which an end plate is secured by fasteners. A profile plate having a desired cross-sectional shape is disposed between the member and the end plate. The shape of the opening in the profile plate defines the cross-section of the closed tube of polymer matrix that will be extruded. For example, a die with an annular exit cross section may be utilized to mold the extruded polymer matrix into the desired hollow shape. Any of the techniques and equipment known in the art of extrusion molding of hollow tubes, pipes and other such shapes may be adapted for use in the present invention. For example, the die assembly may comprise a center-fed mandrel-support die (also sometimes referred to as a spider-supported mandrel die or supporting ring die) wherein the molten polymer matrix is divided in the region of the mandrel support into separate streams. The molten polymer matrix flows around the spider legs. A screen-pack die (also referred to as a breaker-plate die) may also be used wherein the mandrel is held by a tubular perforated body screen pack. Yet another type of die assembly that can be used is a side-fed mandrel die (also called a cross-head die). When a side-fed mandrel die is employed, the molten polymer matrix is passed around the mandrel by way of a manifold. Spiral-mandrel dies may also be utilized in which spiral-shaped mandrels wind around the mandrel in the form of a multiple thread. A cooling fixture may be used in conjunction with the extrusion machine to lower the temperature of the hot extruded closed tube of polymer matrix until it is sufficiently solidified to retain the desired shape. The extruded closed tube is cut to the desired length/thickness to provide the self-supporting continuous structure of the expandable filler insert. Generally speaking, the extruded closed tube may be cut in a direction substantially perpendicular to the longitudinal axis of the extruded closed tube using any suitable method such as a hot knife, saw or other such device. Furthermore, the profile plate may be changed to produce a tube of different diameter or cross-sectional shape. In one embodiment of the invention, for example, the cross-sectional shape includes one or more protrusions having the desired cross-sectional shape of the fixing elements so that when the extruded closed tube is cut one or more fixing elements integral with the self-supporting continuous structure are provided. As an alternative to a hollow tube, a massive strand of the expandable material may be contour extruded and then cut into the desired pillar filler inserts.
Other embodiments of the present invention may be described as follows. In these embodiments, the term “shaped part” is used synonymously with the term “expandable filler insert” used herein before.
Thus, in a further embodiment, the present invention relates to a shaped part having a main body made of a reactive cross-linking material as described above, which body comprises at least one fixing element having respectively a front side and a back side which are defined in that the entire shaped part, including the fixing element or elements, is delimited by two parallel flat surfaces, the front side of each fixing element lying in one of the parallel surfaces, and the back side lying in the other of the parallel surfaces.
It is provided according to this embodiment of the present invention that the entire shaped part, including all fixing elements, be delimited by two parallel flat surfaces. For manufacturing reasons, however, slight deviations from the parallelism of the two surfaces may exist. The two surfaces are, however, intended at least to lie in approximately parallel fashion to the extent that they form an angle of at most 10°, by preference at most 5°, with one another. These two (approximately) parallel surfaces therefore delimit not only the main body of the shaped part, but also all fixing elements that are present. In other words: viewed in a direction parallel to the two parallel delimiting surfaces, the entire shaped part, including fixing elements, exhibits neither projections nor setbacks with respect to the two parallel delimiting surfaces.
The direction that extends perpendicular to the two parallel surfaces will be referred to hereinafter as the longitudinal direction, and a corresponding axis as the longitudinal axis. This is independent of the extension possessed by the shaped body in the direction of the longitudinal axis.
In directions perpendicular to the longitudinal axis, the shaped part can be delimited by arbitrarily shaped surfaces, with the restriction that all surfaces other than the two delimiting surfaces located perpendicular to the longitudinal axis run parallel to the longitudinal axis. Once again, small deviations from parallelism may occur for manufacturing reasons, although these deviations are to be no greater than 10°, by preference no greater than 5°. Alternatively, the shaped part according to the present invention, including fixing elements, can be described in such a way that it substantially comprises two parallel delimiting surfaces, and that all other delimiting surfaces can be arbitrarily shaped, but are substantially perpendicular (with maximum deviations of 10°, by preference of 5°) to the aforesaid parallel surfaces. This further includes the fact that the delimiting surfaces other than the two aforesaid parallel surfaces extend in flat fashion in the direction of the longitudinal axis, i.e. exhibit no elevations or depressions in that direction. This can also be expressed by saying that any line that lies on a delimiting surface other than the aforesaid two parallel surfaces and extends in the direction of the longitudinal axis is a straight line. All edges that are formed by delimiting surfaces that extend perpendicular to the two aforesaid parallel surfaces correspondingly extend as straight lines parallel to the longitudinal axis.
At temperatures below 70° C., the shaped part according to the present invention is solid and self-supporting, i.e. its shape does not change under the influence of its own weight. The shaped part does not comprise a support element on which the reactive material abuts. Reinforcing elements, selected from fibers, fabrics, or nets, can nevertheless be embedded into the reactive material. These reinforcing elements can be made, for example, of glass, plastic, metal, rock wool, or carbon fibers. For manufacturing reasons, fabrics or nets are embedded into the shaped part so that they lie largely parallel to the longitudinal axis of the shaped body. Fibers can also run obliquely with respect to the longitudinal axis, but exhibit a definite preferred orientation in the direction of the longitudinal axis.
When looking in plane view onto the two parallel delimiting surfaces, i.e. in the direction of the longitudinal axis, the main body of the shaped part generally exhibits an irregular cross section, which results from the fact that the cross section is adapted to the cross section of the component cavity that is to be insulated or reinforced. The shaped part therefore generally has different extensions in the various directions perpendicular to the longitudinal axis. It is possible in this context to define an axis that lies perpendicular to the longitudinal axis and points in the direction of the greatest extension of the shaped body. This axis is hereinafter referred to as the horizontal axis, and the corresponding direction as the horizontal direction. That axis that runs perpendicular to both the longitudinal axis and the horizontal axis is referred to as the vertical axis. A direction parallel to the vertical axis is referred to as the vertical direction. By definition, the non-expanded shaped part has less of an extension in the vertical direction than in the horizontal direction. Viewed in the direction of the longitudinal axis, the shaped body can be thicker or thinner than in the horizontal or vertical direction. In particular, the shaped part can be relatively flat and disk-shaped in the longitudinal direction. For example, the shaped part can be at least three times as wide in the horizontal direction as it is thick in the direction of the longitudinal axis.
The geometrical limit case can, however, also exist in which the horizontal direction cannot be distinguished from the vertical direction, since two directions of greatest extension are present that are perpendicular to one another. This geometrical limit case will, however, seldom occur in practice.
As
As explained herein before, a filler insert or shaped part according to the present invention can be manufactured in particularly favorable fashion by extruding the reactive material through a correspondingly shaped die to produce a strand, and by slicing the strand, perpendicular to the extrusion direction, in such a way that approximately parallel cut surfaces are produced. This extrusion operation imparts to chain-shaped molecules of the reactive material a statistical preferred direction in the direction of the longitudinal axis of the shaped body. As a consequence of the packing of the chain-shaped molecules that is thereby produced, a shaped part according to one embodiment of the present invention shrinks by no more than 10% in the horizontal direction and the vertical direction when heated to a temperature in the range of 70 to 100° C. This shrinkage is by preference less than 5%, in particular less than 3%, based in each case on the extension in the corresponding direction prior to heating from 20° C. to 70-100° C. This behavior is desirable, since as a result the shaped body remains largely geometrically stable upon heating, before foaming and crosslinking begin at even higher temperature.
The same mechanism of the preferred orientation of chain-shaped molecules in the extrusion direction further causes the shaped part according to the present invention to expand, upon heating to 120 to 220° C., in such a way that the expansion in the vertical direction is greater than the expansion in the direction of the longitudinal axis, considered in each case relative to the material thickness in the corresponding direction. This also applies to the expansion in the vertical direction as compared with the horizontal direction, so that a shaped part according to the present invention expands, upon heating to 120 to 220° C., in such a way that the expansion in the vertical direction is greater than the expansion in the horizontal direction, once again considered, in each case, relative to the material thickness in the corresponding direction.
The relatively greater expansion in the direction perpendicular to the longitudinal axis is particularly desirable, since the expansion in the direction perpendicular to the longitudinal axis extends in a direction toward the walls of the cavity to be reinforced or insulated.
The shaped part is dimensioned so that in the non-expanded state, it does not completely fill up the cavity cross section. Leaving aside those locations at which the shaped part must have contact with the cavity walls for immobilization, a flow gap approximately 1 to approximately 10 mm wide remains between the outer surface of the shaped part and the inner delimiting walls of the cavity. As long as the shaped part is not expanded, treatment and coating fluids can flow freely through this flow gap. Only as a result of thermal expansion does the volume of the shaped part increase in such a way that the shaped part abuts conformingly everywhere against the inner walls of the cavity and thus completely seals the cavity or stiffens the cavity walls. This expansion is accomplished by heating to a temperature in the range of 120 to 220° C. for a time period in the range between 10 and 150 minutes.
As depicted in
In a further embodiment, the main body itself can comprise an interior space or cavity or several cavities that extend(s) parallel to the longitudinal axis from the one to the other of the parallel surfaces, and open(s) into the surfaces. This embodiment is depicted by way of example in
In this embodiment, the reactive material is confined to a wall 5a that is delimited internally by the delimiting surfaces of cavity 4a and externally by the external delimiting surfaces of the shaped body. This wall can be of identical thickness in every direction perpendicular to the longitudinal axis. In this case the internal and external delimiting surfaces of wall 5a extend in parallel fashion. FIG. 7, however, depicts a generalized embodiment according to which cavity wall 5a has a different thickness in different directions perpendicular to the longitudinal axis. The cavity-side delimiting surfaces of wall 5a then do not extend parallel to the external delimiting surfaces of the shaped body. This embodiment has the advantage that the quantity of reactive material can be distributed differently over the cross section of the component cavity to be reinforced or insulated. In the specific example of
In a preferred embodiment, the expandable material of the shaped part according to the present invention is not tacky in the non-expanded state at a temperature in the range of 10 to approximately 40° C. This facilitates transport and handling of the shaped parts. Provision can also be made, however, for a portion of the surface of the shaped part to be tacky in the aforesaid temperature range, so that the shaped part can be adhesively fastened, with the tacky surface segment, onto the inner wall of the cavity that is to be reinforced or insulated. Mechanical fixing elements such as clips are then not necessary. This embodiment is therefore characterized in that the otherwise non-tacky shaped part comprises at least one outer surface that extends from the one to the other of the parallel surfaces and is covered, at least in a selected region of the outer surface, by a material that is tacky at 10 to 40° C., this selected region being delimited on two sides by the two parallel surfaces. This embodiment is depicted schematically in
Possible compositions of the expandable material (comprising at least one polymer or polymer precursor and at least one latent blowing agent) have been described herein before. In order to establish a desired viscosity for the extrusion process, the reactive material can contain reactive thinners. Reactive thinners for the purpose of this invention are low-viscosity substances (glycidyl ethers or glycidyl esters) containing epoxy groups and having an aliphatic or aromatic structure. These reactive thinners serve on the one hand to lower the viscosity of the binder system above the softening point, and on the other hand they control the pre-gelling process in injection molding. Typical examples of reactive thinners to be used according to the present invention are mono-, di- or triglycidyl ethers of C6 to C14 monoalcohols or alkylphenols, as well as the monoglycidyl ethers of cashew-shell oil, diglycidyl ethers of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, and cyclohexanedimethanol, triglycidyl ethers of trimethylolpropane, and the glycidyl ethers of C6 to C24 carboxylic acids, or mixtures thereof.
If the thermally expandable, hot-curable shaped bodies are to be used to manufacture specifically lightweight structures, they preferably contain, in addition to the aforementioned “normal” fillers, so-called lightweight fillers, which are selected from the group of the metal hollow spheres such as, for example, hollow steel spheres, hollow glass spheres, fly ash (finite), hollow plastic spheres based on phenol resins, epoxy resins, or polyesters, expanded hollow microspheres having wall material made of (meth)acrylic acid ester copolymers, polystyrene, styrene-(meth)acrylate copolymers, and in particular of polyvinylidene chloride, as well as copolymers of vinylidene chloride with acrylonitrile and/or (meth)acrylic acid esters, hollow ceramic spheres, or organic lightweight fillers of natural origin such as ground nut shells, for example the shells of cashew nuts, coconuts, or peanut shells, as well as cork flour or coke powder. Those lightweight fillers that are based on hollow microspheres are particularly preferred; they ensure, in the cured shaped-body matrix, a high level of compressive strength for the shaped body.
The present invention further relates to a method for manufacturing a shaped part having the features and properties described above, the premixed expandable material preferably being extruded into a strand at a temperature above room temperature, and the strand being sliced so that the aforesaid parallel surfaces are produced as cut surfaces. The temperature of the expandable material during extrusion through the die is by preference in the range of approximately 70 to approximately 110° C. The expandable material can be extruded at a rate in the range of 1 to 15 m/minute. The reactive expandable material is extruded through a die whose opening is shaped so that a portion of the extruded strand of the material exhibits the cross section of the fixing elements and, if present, of the spacers. Upon slicing of this strand into the shaped parts according to the present invention, a portion of the extruded material then has the shape of the fixing elements, and, if present, the spacers.
If it is desired that the shaped parts according to the present invention comprise the reinforcing elements recited previously, selected from fibers, fabrics, or nets, it is preferable to proceed as follows: The expandable material is extruded into a strand as described above, and the reinforcing elements, selected from fibers, fabrics, or nets, are pressed into the strand before it is sliced; the strand is then sliced in such a way that the parallel surfaces are produced as cut surfaces. Rollers, for example, can be used to press the reinforcing elements into the extruded strand.
A shaped part in which a selected region of its surface is covered with a material that is tacky at 10 to 40° C. was described previously as a further embodiment of the shaped part according to the present invention, the selected region being delimited on two sides by the two parallel surfaces. A method for manufacturing a shaped body having these features preferably proceeds in such a way that the tacky material is co-extruded with the reactive material in such a way that a strip of the tacky material is formed on an outer surface of the extruded strand. Upon slicing of this strand in a fashion such that parallel cut surfaces are produced, the correspondingly embodied shaped body is obtained. Alternatively thereto, however, only the reactive material can be extruded into a strand, and after extrusion into a strand but before it is sliced, a strip of the tacky material is applied onto the strand. This can be accomplished by a kind of laminating process using rollers.
The present invention furthermore encompasses a method for reinforcing, insulating, damping, and/or sealing hollow components, wherein a shaped part or expandable filler insert according to the present invention is fastened, before completion of the hollow component, to an inner wall of the hollow component, and the hollow component is closed and heated to a temperature in the range of 120 to 220° C., by preference for a time period in the range of 10 to 150 minutes.
The usual production process for elongated hollow structures in vehicle construction, for example for the frames that surround the passenger cell, is utilized for this method. These hollow structures are usually produced by manufacturing two correspondingly shaped half-shells from metal, and joining these half-shells together to yield the hollow frame structure or a portion thereof. Hollow structures or hollow supports of this kind are, for example, the A-, B-, or C-pillar of an automobile body that support the roof structure, or roof frames, sills, and parts of the wheel housings or engine supports. As is usual in the existing art with the use of so-called “pillar fillers” or “baffles” in hollow structures of this kind, the shaped part according to the present invention can be fastened, with the aid of a fixing element or a tacky surface portion, onto that surface of the one half-shell which will later become the inner wall of the cavity, before the half-shell is joined to the other half-shell to constitute the hollow structure. The shaped part is preferably shaped in such a way that its cross section (viewed perpendicular to the longitudinal axis) corresponds to the cross-sectional shape of the cavity. The shaped part is, however, dimensioned so that prior to foaming, it is in contact with the inner wall of the hollow part at only one or a few points. Aside from these points, a flow gap having a width of approximately 1 to approximately 10 mm, by preference approximately 2 to approximately 4 mm, remains between the delimiting surfaces located parallel to the longitudinal axis of the shaped part and the inner walls of the hollow part. This flow gap ensures that the various process fluids with which the basic auto body is treated can wet every part of the inner sides of the cavity walls. The flow gap closes up only upon thermal expansion of the shaped body, with the result that the latter fulfils its purpose of reinforcing, insulating, damping, and/or sealing the hollow components. Spacers on the shaped parts can guarantee that this flow gap is reliably produced before foaming of the shaped body, and is maintained until foaming.
Lastly, in a further aspect, the invention relates to a vehicle having a hollow frame structure that contains the filer inserts or shaped parts described above after expansion and hardening thereof.
The herein described expandable filler inserts (or “shaped parts”) of the present invention can be used in any location within an automotive vehicle frame. For instance, such locations include, but are not limited to, pillars (including A, B, C and D pillars), rails, pillar to door regions, roof to pillar regions, mid-pillar regions, roof rails, windshield or other window frames, deck lids, hatches, removable top to roof locations, other vehicle beltline locations, motor (engine) rails, lower sills, rocker panel rails, support beams, cross members, lower rails, and the like. In general, the expandable filler insert will be placed within a hollow structural member having a longitudinal axis so that the plane defined by the self-supporting continuous structure is substantially perpendicular to the longitudinal axis of the hollow structural member.
Although the expandable filler insert of the present invention has been described for use in the hollow spaces or cavities of vehicles such as automobile pillars, it also understood that the expandable filler insert offers advantages in any other applications where it is desired to seal or fill a hollow space or cavity (especially where the article of manufacture is subjected to a heating step during at least one assembly step). For example, the expandable filler insert can be used in products having hollow structural members other than vehicles, including, without limitation, aircraft, domestic appliances, furniture, buildings, walls and partitions, and marine applications (boats).
| Number | Date | Country | Kind |
|---|---|---|---|
| 102007038659.3 | Aug 2007 | DE | national |
This application is a continuation under 35 U.S.C. Sections 365(c) and 120 of International Application No. PCT/EP2007/062746, filed Nov. 23, 2007 and published on Jun. 5, 2008 as WO 2008/065049, which claims priority from U.S. Provisional Patent Application Ser. No. 60/867,203 filed Nov. 27, 2006 and German Patent Application No. 102007038659.3 filed Aug. 15, 2007, which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60867203 | Nov 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2007/062746 | Nov 2007 | US |
| Child | 12473093 | US |
