US 3808164 A
Description (OCR text may contain errors)
United States Patent 3,808,164 PREFORMED SOUND CONTROL SHAPES James A. Gulino, Lockport, 11]., and William J. Woodring, Highland Park, N.J., assignors to GAF Corporation, New York, NY. No Drawing. Filed Oct. 20, 1971, Ser. No. 190,821 Int. Cl. C08f 45/52; C08g 51/52 US. Cl. 26028.5 AS 4 Claims ABSTRACT OF THE DISCLOSURE An asphalt mastic composition for use as a vibration damping medium comprising: (a) an asphalt; (b) shaperetaining agents; (c) a mineral filler; and (d) a heat-resistant fibrous material. The present invention is most advantageous where preformed shapes of irregular configurations are required.
The present invention relates to a composition of matter suitable for use in the manufacture of a moldable shape capable of retaining a contour of the body onto which it will be used in order to reduce vibration and sound transmission from such body.
Applicants, in researching the prior art, have found that two general types of sound-control material have been used where automotive applications were involved.
The first is concerned with a flexible flat sheet of filled asphalt mastic having a density of about 1 lb. per square foot. This material is treated in a manner enabling it to be surfaced with a variety of paper film and/or felted or non-woven mats. Once applied to a metallic surface, this particular asphaltic composition has been able to minimize vibration noises by damping and simultaneously reducing the transmission of sound.
A second type or class of product that has been used as a dash liner or head liner is composed of a non-woven felt or fibrous mat compression molded to a specific shape. In this particular instance, the end product functions as a sound absorbent material. This is quite different to that of aforementioned asphaltic sheet product which serves to reduce noise generation and noise transmission from the surface to which it is attached.
The present invention is more concerned with the first class of product, namely, an asphaltic sheet product, rather than the latter product which is outside of the scope of the present invention.
A modification of the fibrous product is found in US. Pat. 3,429,728. According to this reference, a sound-in sulating barrier is formed by impregnation of a preformed fibrous mat with asphaltic material. While such product is good, it is costly and the fibrous mat is unnecessary for sound-damping characteristics.
While applicants have endeavored to evaluate and establish parameters on the composition of matter used in the present invention, with particular emphasis on automotive applications, it is to be understood that the present invention is not intended to be so limited. It has also been found that the composition of matter has useful applications in most every area of manufacturing and endproduct usage where it is desired to control vibration and sound transmission, such as in different types of metal cabinets.
A main object of the present invention is to provide a composition of matter not subject to one or more of the disadvantages attributable to the prior art.
Another main object of the present invention is to provide a composition of matter having improved sounddamping qualities.
Another object of the present invention is to provide a method of utilization of a composition of matter for manufacturing preformed molded shapes which require less fitting than the present type of materials.
Still another object of the present invention is to provide a composition of matter which has the ability to substantially retain its shape after being formed into a molded form.
Still another object of the present invention is to provide an easy-to-install, low-cost composition of matter which is moldable to a pre-selected shape.
Other objects and advantages will be apparent from the following description of the invention, particularly in the appended claims.
The attainment of the above objects is made possible by the provisions of the present invention which include an asphalt mastic composition suitable for use as a vibration-damping medium comprising:
(a) an asphalt;
(b) shape-retaining agents;
(c) a mineral filler; and
(d) a heat-resistant fibrous material.
The present invention is the result of numerous empirical approaches to finding an asphaltic composition that is capable of being produced in a preshaped manner to improve the ease of installation especially where a complex shape is required and in so doing, applicants have endeavored to eliminate the heretofore necessary steps of cutting and fitting of flat mastic sheets and forms to obtain a reasonably close fit with the body onto which it is placed.
For an example, in a particular use, such as a rear wheelhouse cover (to be found over the Wheel attached to the auto body) in the manufacture of automobiles, such mastic products were usually fitted by hand and had to be slit and cut since the shape upon which the mastic was to be fit was quite irregular.
Testing procedures utilizing the present composition indicated that the specimen with the preformed mastic membrane provided sound levels two zones below the control level used with heretofore available fiat sheet mastic material. These tests were performed on two test automobiles and were evaluated for sound and noise levels. The improved sound level reduction resulted basically from the nearly perfect fit which yielded improved vibration damping characteristics of the molded product. Of noteworthy importance was the fact that there was substantial elimination of the necessary fitting and slitting function normally required when using flat sheet mastic material.
The presently preformed shaped mastic material eliminates slits and cuts into the spaces between part openings previously required for proper fitting of the mastic material. Through such openings sound could have been transmitted to the surrounding areas.
The present invention, including the composition of matter, has a particularly useful characteristic in automotive use in that it acts as a sound deadener and especially saves in direct labor costs during installation of the particular part molded from the composition of matter of the present invention. In effect, there is provided an essentially perfect fit with resultant sound properties that are noticeably favorable compared to the prior art. The positive fit and self-indexing characteristics, that is, the ability to immediately sit upon the substrate base material to which it is being fitted reduces or substantially eliminates the problems usually associated with assembly line operations, for an example, access or mounting holes which require special alignment. The preformed mastic shape developed through the use of applicants composition maintains its shape after installation. This characteristic is noteworthy when compared to prior art flat mastic, since the fiat material must be forced into position during the assembly operation and sometimes tends to return to its flat condition unless in some manner restrained.
Applicants have also employed a method of manufacturing a premolded shape employing the inventive asphalt mastic composition including the steps of: introducing said asphalt mastic into a female mold, cooling the mastic composition at the surface of said mold, inverting and rotating said mold by hand or mechanical means to pour off any excess fiuid mastic, circulating water or fluid through the mold to effect further cooling and permit easy withdrawal of the finished product from the mold, and then withdrawing the product from the mold.
According to the present invention, the composition of matter used to mold the preformed shape includes an asphalt, in amounts of about 15-30%, preferably about 18-28%, mineral filler material, shape-retaining agents and fibrous materials for reinforcement. The shape-retaining agents may include thermoplastic resins such as low-density polyethylene, polyamides, polypropylene, polyvinyl acetate, polyvinyl chloride, ethylenevinyl acetate copolymers, in amounts ranging from about 3.0% to about 12%, preferably 5.0% to 7.0%; hydrocarbon resins such as styrene indene terpolymers and homologs thereof, alkyl and alicyclic aliphatic hydrocarbons such as dichloropentadiene and homologs thereof, and polymerization products of aliphatic C type diolefins and solidified hydrocarbons and natural occurring asphalts such as gilsonite in amounts ranging from about 1% to about 6%, preferably about 2 to about 4%; copolymers including piperylene and isoprene unsaturates and polymerization products of high-boiling aromatic fractions produced as a by-product from the thermal cracking of petroleum streams cut from crude oil such as naphthenic and anthracenic-containing polymers; any one or combination of which may be employed in amounts ranging from about 3.0% to about 11.0% preferably about 5.0% to about 7.0%; also: indene or coumarone-indene resins and monovinyl aromatic resins such as styrenated resins, polystyrene, vinyl naphthalenes and the like in amounts ranging from about 3.0% to about 9.0% preferably about 5.0% to about 7.0%; also, natural or synthetic Waxes having the general formula RCONHR -NHCOR, wherein R=an alkyl or alkenyl having 12 to 1-8 carbon atoms and R =an alkylene group having 1 to 6 carbon atoms, such as the ethylene bis(stearamide) and propylene bis(oleylamide), polyamide types and like waxes in amounts ranging from about 2.0% to about 7.0% preferably about 4.0% to about 6.0%. Many of the shaperetaining agents also function as viscosity control agents which is of importance during the molding operation.
Suitable filler materials have been found to include ground limestone, rock dust, clay, sand or other suitable mineral fines and the like in amounts ranging from about 60% to about 80% preferably about 65% to 75%.
The heat-resistant fibrous material may be chopped, shredded, etc. fiberglass, asbestos fiber or heat-resistant organic fibers such as sulphate cellulosic fibers preferably bleached, and other fibers having a basis of silicones or mineral-filled silicones and resins such as phenol-formaldehyde resins, polytrifluorochloroethylene resins, polytetrafluoroethylene resins, mixtures thereof and like resins in amounts ranging from about 0.5% to about 3.0%, preferably about 0.5% to about 1.5%.
The size of the particles, rods, pellets or fibers can vary from about 0.5 micron to about 20.0 microns.
All of the aforementioned materials when used in appropriate amounts and in correct combination with one another are basically formulated to provide stiffness for shape-retention in conformance with a predetermined form, while at the same time, retaining a high degree of viscoelastic behavior for the GQIIect vibration damping characteristic.
The following examples are shown for purposes of illustration and provide a typical preferred formulation of the molded mastic composition of matter as it is used in the present invention. All parts and proportions mentioned herein and in the claims are by weight unless otherwise indicated.
EXAMPLE 1 Percent Asphalt ll85 F. softening point (S.P.) 20.0 A non-reactive, non-saponifiable, thermoplastic petroleum hydrocarbon resin made from a highboiling aromatic petroleum fraction 6.0 a-Methyl styrene polymeric resin 1 240-255 F.
Limestone 71.0 Chopped fiberglass 0A") 1.0
1 A Friedel-Crafts catalyzed reaction product with a molecular weight of less than 1500.
Example 1, the hydrocarbon resin and the polymeric u-methyl styrene, are believed to function as stifiening and shape-retaining components and the limestone provides most of the mass of the overall material in producing an end product that is capable of providing the sound-control characteristics according to the present invention. The fiberglass is added to impart the necessary tensile strength, tear-resistance and the like.
EXAMPLE 2 Percent Asphalt 180-195 F. (S.P.) 20.0 A non-reactive, non-saponifiable, thermoplastic petroleum hydrocarbon resin made from a high- 1 A natural occurring asphalt.
In the above formulation, it will be noted that the wax component (Example 2) provides viscosity control and improved shape retention at elevated temperatures, while at the same time there may be some loss in the ability to handle the end shape as is evidenced by a lower tensile strength as compared to that of the first example. In this same illustration, the actual molding of the preformed shape was carried out in the manner described previously.
The formulations given and shown in Examples 1, 2 and 3 include ranges for the critical components. However, variations within the limits indicated have been found not to materially affect the finished product performance and the actual choice of formulation can be based upon the complexity of the specific parts being molded, the severity of handling, cost and use considerations and the like.
During the preparation of the composition of matter, normal mixing techniques were employed, that is, asphalt was charged into a suitable mixer and maintained at a t mp rature of about 300 to 400 F. The hydrocarbon resin and the styrene components were then added while the temperature was maintained at the aforementioned level. Thereafter, limestone and fiberglass were added. Agitation of the mixture in accordance with the techniques known in the art was maintained throughout the entire addition process to facilitate substantially uniform mixing of the entire composition.
Once the composition of matter is developed, thereafter, it is employed in a molding operation for conforming the composition to a preformed shape suitable for production use. In the foregoing example, the forming of the complex molded shape was used, for example, on a wheelhouse cover of an automobile. The process employed in the actual casting operation is one that is mentioned for illustrative purposes only. In this particular instance, a slush casting process was employed. A layer of mastic at the inner mold surface cools sufiiciently to resist the flow of material. Thereafter, the mold is inverted through suitable means in order to pour off the excess molten mastic material. Cooling of the mold to about 150 to about 100 F. takes place to allow the article being formed to be removed from the mold. It has been found that the cycle for the molding operation is in the neighborhood of about 30 to about 90 seconds, the preferred time being about 60 seconds. Cooling of the preformed shape may be accomplished by circulating water or other fluid at about 48 F. through the mold while the mastic temperature is about 360 F. For purposes of evaluating the present invention, a number of duplicate parts were molded in a like manner and tested for sound and shape-retention properties. The sound testing, as previously described, included providing a two-zone reduction in a test automobile when compared over conventional mastic product which is usually available in a flat sheet and which has to be cut by an operator to a selected shape. The physical properties of the resultant products are depicted in Table 1 below.
TABLE 1 Control I II III Caliper (in.) 0.125 0.120 0. 120 0.120 Tensile strength (average) (Scott, 1bs./
nc width) 34 25 34 Stiffness (Tinius Olsen) 0.75# total load, 2" span, 30 angle AMD 5 29 21 32 Direct reading, average WMD 6 37 27 46 Heat distortion temp. F.) 1 1" sag across 2" span both ends supportecL- 170 215 260 215 Heat deflection temp. F.) 1 1 sag across 2" span one end free, one clamped 70 122 126 114 Impact resistance (inch-pounds) 1" x 1 exposed, clamp one edge 0.5# weight dropped in center of exposed portion 0. 75 3. 2. 0 3.
1 Rate of temperature rise for heat distortion and heat deflection tests was approximately 1 F. per minute.
When studying Table 1 above, it can be seen that the shape-retention characteristics as measured under control heat test is quite superior for Examples 1 to 3 (see pages 10 and 11) as compared to a control formulation. The control formulation is composed solely of asphalt and limestone and is a standard formulation used commercially to produce non-molded sound control membranes.
This invention has been disclosed with respect to certain preferred embodiments, and it will be understood that modifications and variations thereof will become obvious to persons skilled in the art and are intended to be included within the spirit and purview of this application and the scope of the appended claims.
What is claimed is:
1. A vibration-damping mastic composition comprising approximately by weight:
(a) 15 to 30% of an asphalt having an S.P. of about (b) 1 to 6% of gilsonite,
(c) 3 to 11% of a non-reactive, non-saponifiable thermoplastic petroleum hydrocarbon resin made from a high boiling aromatic petroleum fraction,
(d) 60 to of ground mineral fines, and
(e) 0.5 to 3% of chopped fiberglass or asbestos fiber.
2. A composition as defined in claim 1 wherein component (d) is limestone.
3. A composition as defined in claim 1 wherein component (e) is fiberglass.
4. A composition as defined in claim 1 comprising approximately by weight (a) 26.0% of an asphalt having an S.P. of about (b) 3.0% of gilsonite,
(c) 3.0% of a non-reactive, non-saponifiable, thermoplastic petroleum hydrocarbon resin made from a high boiling aromatic petroleum fraction,
(d) 67.0% of limestone, and
(e) 1.0% of chopped fiberglass.
References Cited UNITED STATES PATENTS 3,418,402 12/1968 Grissom 106282 3,615,803 10/1971 Draper 26028.5 AS 3,556,819 1/1971 Koons 26028.5 AS 3,345,316 10/ 1967 Nielsen 26028.5 AS 3,312,157 4/1967 Coscia 26028.5 AS 3,144,423 8/ 1964 Belak 26028.5 AS 2,688,005 8/1954 Clayton 260-285 AS OTHER REFERENCES A. H. Warth: The Chemistry and Technology of Waxes, 2nd edition, 1956, Reinhold Pub., pp. 484-485.
MORRIS LIEBMAN, Primary Examiner P. R. MICHL, Assistant Examiner US. Cl. X.R.