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Abstract: The production of composite structural products having high sound-proofing characteristics by impregnating a mat of fibers of substantial length with an organic thermoplastic resin containing an expanding agent, and thereafter heating the treated mat. The resin is partially jelled during the initial stage of heating and the expanding agent is dissociated during the later stage of the heating, which results in a controlled swelling of resin while the resin completes the jelling thereof while the product attains its predetermined density. Upon the cooling of the material it is transformed from a plastic to an elastic state, especially in the direction of thickness of the product.

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Description: It is the object of the present invention to provide a method of obtaining products having high sound-proofing qualities, particularly against shock or impact noises and which have good dimensional stability, except in the direction of thickness, in which case they are flexible.

The inventive method contemplates the use of mineral or organic fibers having high resistance to traction, particularly glass fibers, immersed in a thermoplastic resin, in particular, a polyvinyl resin such as plasticized polyvinyl chloride.

It is an essential characteristic of the invention that one begins with a pad or mat of entangled or matted fibers which are not joined together and which are uniformly impregnated with resin containing an expanding agent. This mat is then subjected to heating, whereupon the mat expands freely under the swelling action of the resin at atmospheric pressure, and the material is cooled after it has acquired its predetermined density, said material then passing from the plastic to the elastic state.

According to another characteristic of the invention, the initially fabricated mat is constituted of entangled fibers in superposed planes, these fibers not being joined to one another during heating, while permitting a controlled expansion in the direction of thickness while limiting all expansion in transverse directions. These fibers are preferably at least 50 cm. long.

According to another characteristic of the invention, the first heating operation takes place, in the course of which the resin is partially jelled, then a second heating operation serves to cause the dissociation or decomposition of the expanding agent and the termination of the jellification of the resin.

Other characteristics and purposes of the invention will appear from the following description thereof, taken in conjunction with the accompanying drawings, wherein:

FIGS. 1 to 4 are front elevations of different layouts for impregnating the fiber mats with the resin compositions in accordance with the invention and the subsequent treatments thereof;

FIG. 5 is a graph showing the pliable compressibility characteristics of fiber mats in accordance with the invention; and

FIGS. 6 to 8 are graphs showing the improvements in sound insulating characteristics of fiber mats in accordance with the invention.

The products obtained by the method in accordance with the invention all have the common characteristic of possessing high sound-proofing qualities and great dimensional stability while being flexible in the direction of their thickness. The appearance and mechanical properties of these products may be varied by modifying the following parameters: weight of the fibers, weight of the plastic materials, concentration of the expanding agent, and the concentration of the plasticizer.

According to one mode of executing the invention, the predetermined density of the product is caused to vary by varying the quantity and nature of the expanding agent. According to another working method, the degree of elasticity or suppleness of the product is made to vary by modifying the quantity of the plasticizer which is incorporated in the resin. The impregnation of the fibers by the resin can be accomplished by any appropriate method, and in particular by immersion, by spraying or atomizing, by flowing over weirs, or by a combination of these.

1. Impregnation by immersion or dipping

The mode of execution of this method is illustrated in FIG. 1 of the drawings. A sheet of fibers 1, for example, glass fibers which are not connected, is unwound from a roll 2 and passes into a vat or tank 3 containing the resin, such as polyvinyl chloride, and the additional expanding agent. Upon leaving this vat, the impregnated sheet is dried and calendered by passage between calendering rolls 4. It is then advanced into a continuous oven or drying chamber comprising two consecutive parts 5a,5b. In the first part 5a of this oven, the sheet is brought to a temperature close to 140.degree.C. and the polymer begins to jellify. The time of passage of the sheet in the first part is about 2 minutes. In the second part 5b of the drying chamber, the temperature is raised to a range of 180.degree.C. to 200.degree.C. At this stage and the time required for the passage of the sheet therethrough is substantially the same, namely, approximately 2 minutes. The expanding agent is dissociated or decomposed and the resultant gas forms pores in the body of the mass while the jellification is completed. Upon leaving the drying chamber, the composite structure, which has reached its definitive dimensions, is cooled either by natural heat exchange with the surrounding air, or by a forced convection device 6. It is then wound on roll 7 or cut into plates.

In order to fabricate special products, it is possible to stop the heat-drying of the composite structure immediately after the first phase of jellification. The expansion agent not being decomposed and the resin being incompletely jellified, the expansion and the completion of the jellification may be realized in a repeated operation, for example, after the addition of a surface coating.

2. Impregnation by atomization or spraying

In the method of executing the invention illustrated in FIG. 2, the sheet of fibers 1 passes in front of one or more spray guns 8 which spray or atomize the resin on said sheet with the expansion additives. A suction device 9 assures the distribution of the resin solution through the body of the fibers and regulates its surface mass. Calendering rolls 10 may complete the distribution of the resin in the fibrous mass. The treatment of the composite structure then proceeds as in the immersion process described above.

In the variant embodiment shown in FIG. 3, the spraying of the resin and the expansion additives is effected by means of spray guns 14 acting directly on the fibers 13 issuing from the fibering device 11. The fibers thus impregnated are received on a travelling net or band 12 passing over a suction device 15, to form a pad or mat 1 which is subjected to the same treatments as described above.

3. Impregnation by overflowing across weir or spillway

This method of executing the invention, illustrated in FIG. 4, is analogous to that shown in FIG. 2 with this difference, that the one or more spray guns are replaced by an overflow tank 16 with a screen or curtain 17, over which the plasticized resin with the expansion agent flows onto the sheet of fibers 1.

Below are given two examples of compositions for executing the process according to the invention:

EXAMPLE 1

    ______________________________________
    Polymerized polyvinyl chloride in emulsion
                           100 parts by weight
    Ethyl phthalate - 2 hexyl
                           100 parts by weight
    Azodicarbonamide       1.7 parts by weight
    Potassium stearate and zinc stearate
     (with, partially, tribasic lead sulfate)
                           1.5 to 2 parts by
                            weight
    Dyes or coloring matter (possibly)
                           in sufficient
                            quantity
    ______________________________________

EXAMPLE 2

    ______________________________________
    Polymerized polyvinyl chloride in emulsion
                           100 parts by weight
    Ethyl phthalate - 2 hexyl
                           60 parts by weight
    Azodicarbonamide       1.7 parts by weight
    Potassium and zinc stearate
     (with, partially, tribasic lead stearate
                           1.5 to 2 parts by
                            weight
    Dyes or colorants      in sufficient
                            quantity, as
                            required
    ______________________________________

The viscosity of the principal mixtures can be adjusted, as needed, with the help of a solvent such as kerosene KSO:

    ______________________________________
    Density at 15.degree.C.
                 0.780
    Flash point 80.degree.C.
                 Aniline point 81.5.degree.C.
    Distillation:
                 beginning 195.degree.C. - final point 255.degree.C.
    ______________________________________

Such products as described above have, at one and the same time, a high resistance to elongation and rupture in the direction of length and breadth, and a great elasticity in the direction of thickness. Thus, when the product is produced with 200 grams of glass fibers per square meter and 874 grams of polyvinyl chloride expanded according to Example 1, it has a resistance to rupture by traction of 8 kg. per cm. for a relative elongation .DELTA.L/L of 2.5%. On the other hand, this product remains very pliable and elastic during compression.

FIG. 5 shows a graphical representation of the property of this same product in curve X, which portrays the percentage decrease in thickness of the product as a function of the loading. By way of proof, a comparison curve Y is shown which portrays the percentage loss in thickness of a sheet of polyvinyl chloride foam without fibrous reenforcement of the same density as the above-mentioned product. It is evident that the elasticity of the product according to the invention remains very close to that of the comparative product represented by curve Y.

The products obtained by the procedures of the invention are capable of numerous applications, particularly the following: as coverings or sheathings for floors, walls, ceilings, in the form of panels, bands or the like assuring sound-proofing of buildings. As underlayers, in association with coverings of floors, walls, or ceilings. These coverings may be of a textile nature, for example, needled velvet pile upholstery fabric in the form of small squares, tiles or diamonds. The use of these underlayers contributes to the improvement in comfort in walking, and increases in high proportion the insulation against impact noises. The junction between the underlayers and coverings may be effected by countergluing or by gluing the juxtaposed surfaces.

FIG. 6 portrays the comparative improvements in sound-proofing or acoustic insulation against impact or shock noises of different materials as a function of the acoustic frequencies in cycles per second, which are represented as absiccas on the graph. The ordinates represent gains or improvements in noise levels resulting from the use of these different materials when compared with the noise resulting from the shocks when the machine producing such is placed on a slab of bare concrete. Thus, curve A shows the difference in noise levels resulting from the use of a needled covering of super-polyamide with felt alone, as against curve B which results from the same covering glued to an underlayer in accordance with the invention, this underlayer having a surface mass of 1 kg. per square meter with 200 grams per square meter of Verranne type glass fibers. Thus, as may be seen from FIG. 6, the gain in the muting or deadening of shock noises of 800 cycles per second, for example, by the use of the composite structures in accordance with the invention over sheathings without such structures in approximately 19 decibels.

The products according to the invention may be associated, in particular, with the composite structures of mineral fibers and thermoplastic materials disclosed in U.S. Pat. No. 3,658,633, Apr. 25, 1972.

The products of the invention may be used as underlayers in association with coverings, particularly rigid flooring, such as ceramic sandstone, glass block, parquet flooring, etc. Thus, floors having resilient properties are attained. Gluing of the rigid covering is effected by means of mastic, or pliable or rigid adhesives.

The curve C in FIG. 7 illustrates the gain in sound-proofing against impact noises of a ceramic facing glued to an underlayer in accordance with the invention having a surface mass of 1.5 kg. per square meter with 200 grams per square meter of Verranne type glass fibers.

The products of the invention may be used as underlayers in association with vinyl coated facings. The vinyl facing may be applied on an underlayer by counter-gluing or direct coating. The resulting product then presents excellent properties from the point of view of insulation against impact noises, as is shown by curves D and E in FIG. 8. Curve D illustrates the muted gains derived from a vinyl coating applied to an underlayer of felt, and curve E shows the gains obtained when the same coating is glued to an underlayer in accordance with the invention, having a surface mass of 1 kg. per square meter with 200 grams per square meter of Verranne glass fibers.

The products according to the invention may also be utilized as expansion joints for buildings, as insulators for pipes or conduits, for the production of packing, antivibrating or cushion layers, etc. They may also be utilized for sound-proofing vehicles. In the latter case, they can be molded as needed to attain the desired shapes. They also may be associated with layers having decorative surfaces, as in the case of floors, walls, and ceilings.

Title: Manufacture of products having high acoustic insulating characteristics