Solid material comminution or disintegration – Processes – With heating or cooling of material
Reexamination Certificate
1999-06-10
2001-06-05
Woodward, Ana (Department: 1711)
Solid material comminution or disintegration
Processes
With heating or cooling of material
C241S024180, C241S025000, C264S037170, C264S143000, C521S040500, C525S064000, C525S066000, C525S166000, C525S179000
Reexamination Certificate
active
06241168
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to a recycling method for preparing a polymeric blend formed from carpet scrap through the use of ultralow density polyethylene and useful products produced therefrom. More particularly, the invention relates to a method of forming a useful product having desired properties from polymeric carpet scrap which contains a polyamide and/or a polyester and a polyolefin which are normally incompatible in molten or solid states, through the use of ultralow density polyethylene (ULDPE).
BACKGROUND OF THE INVENTION
Plastics are now used in every segment of American business and are found in all aspects of daily life. Carpets are now substantially made of plastics. One problem relating to carpets is what to do with them after their service life is exhausted. Furthermore, since a considerable amount of waste is involved in the process of making carpets, the problem also exists of what to do with it once it is generated. For instance, automobile carpet in most instances has a face of fiber forming polymer such as polyamide and/or a polyester and a backing polymer such as a polyolefin or copolymer thereof. Automotive carpet scrap is generated during the cars' fitting process and as post-consumer waste. During the fitting process, a quantity of carpet remnant is generated as the carpet is formed and cut into various irregular shapes. As a result, millions of pounds of carpet waste are generated every year as part of the automobile manufacturing process. It has been difficult to reuse this carpet scrap in the primary manufacturing process, due to problems with separation, and the like. Furthermore, when an automobile is disposed of after its years of useful life, the carpet installed ends up in the waste stream as post-consumer waste.
Besides the carpet waste generated by automobile manufacturing, carpet waste is also generated during residential and non-residential building construction as well as during renovation. The volume of this carpet scrap generated each year is also expected to continue to increase worldwide. Considerable effort has been devoted to recycling carpet waste. Furthermore, the interest in secondary recycling of carpet or other commingled waste continues to increase due to increasing costs of storage and/or land fill space, more stringent regulations for disposal, and incineration, among other things.
A number of methods have been developed for the recycling of carpet scrap. For example, U.S. Pat. No. 5,852,115 discloses the addition of compatibilizing agents to mixtures of carpet scrap. In particular, carpet scrap mixtures of nylon, polyester, polypropylene, polyethylene, ethylenevinyl acetate (EVA), and filler, were compatibilized with a compatibilizing agent selected from the group of a polypropylene having acrylic acid grafted thereon, a maleic anhydride modified polypropylene, a maleic anhydride modified poly(ethylene-co-vinyl acetate), and a poly(ethylene-co-vinylacetate). Substantially homogeneous thermoplastic blends of the carpet scrap and these compatibilizing agents have produced products possessing very useful properties, for instance, tensile strengths, elongations at break, and hardness. Further improvements have been sought in the field of recycling carpet scrap.
SUMMARY OF THE INVENTION
This invention is directed to a method of recycling carpet scrap and to substantially homogeneous thermoplastic blends resulting therefrom. In particular, the method of this invention involves granulating carpet scrap to obtain an incompatible mixture of polyamides and/or polyesters in combination with polyolefins or copolymers thereof. Ultralow density polyethylene (ULDPE) is added as a compatibilizing agent to the heterogeneous mixture for compatibilization of the polymers. Upon heating the granulated scrap in admixture with the compatibilizing agent, substantially homogeneous thermoplastic blends are produced.
It has been found that the addition of ULDPE to carpet scraps having a mixture of polyamide and/or polyester in combination with polyolefins produces very desirable properties. In particular, for example, when 50% by weight mixtures of ULDPE and 50% carpet scrap are blended, elongations at break for the resulting blend are comparable to elongations of the ULDPE alone. The ability to recycle such carpet waste and obtain desirable properties is advantageous. These advantageous results are also considered unexpected since high-density polyethylene (HDPE), linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) when added to the carpet scrap in the same or similar amounts did not produce a blend having advantageous properties such as elongation at break. Accordingly, this invention is predicated in part upon the use of ULDPE as a compatibilizing agent in carpet scrap to produce homogeneous thermoplastic blends that are useful products. Moreover, this invention is also predicated in part upon the unexpected results achieved with ULDPE in contrast to apparently similar polyolefins such as HDPE, LLDPE, and LDPE.
Homogeneous thermoplastic blends of the compositions of this invention may be injection molded or extruded. Injection molding of the compositions produce shaped articles with desirable properties. For example mats and sheets made using the compositions produced properties in the range of general-purpose commodity thermoplastics. The thermoplastic blends were easily processed both for extrusion and injection molding.
In another aspect of this invention, when extruding blends of carpet scrap and ULDPE, a plateout or precipitate on the extrusion die lips may occur. Over time, this build up may break off and mar the surface of the sheets or article being extruded. It has been found by replacing an amount of the ULDPE with an anhydride modified polyolefin or an acrylic acid modified polyolefin that the plateout problem is eliminated with minimal change in physical properties. In particular, minor amounts of about 1% to about 10% of the anhydride modified or acrylic acid modified polyolefin eliminated the plateout problem with minimal change in physical properties.
In a preferred form of the invention, the ULDPE is contained in an amount of about 40% to about 50% by weight of the carpet scrap. When the anhydride modified or acrylic acid modified polyolefin is used to eliminate or reduce the plate out problem, amounts on the order of about 1% up to about 10% by weight of the carpet scrap are employed.
The advantages and the objectives of this invention will be further understood with reference to the following detailed description and operating examples.
DETAILED DESCRIPTION
An automotive carpet scrap used in the following examples has the following general component ranges:
Scrap Carpet Component
Ranges (% by weight)
Polyamide (nylon)
about 10-35
Polyester (polyethylene terephthalate)
about 1-6
Polyolefins (polyethylene and polypropylene)
about 8-18
Ethylene vinyl acetate (EVA)
about 15-36
Filler
about 35-60
In general, the automotive carpet scrap compositions comprise various amounts of nylon 6, or nylon 6.6, polypropylene, polyethylene, polyester (such as polyethylene terephthalate), ethylene vinyl acetate (EVA), and filled EVA. The EVA employed contains between about 9% and 36% vinyl acetate. The carpet face fibers may comprise polyamides and/or polyesters, typically nylon. A primary backing of polyolefin such as polypropylene, and a mass back of EVA precoated with a filled EVA back coat, is typically provided. More specifically, the back coating contains a filler such as barium sulfate or calcium carbonate with a polymer matrix of EVA containing processing oils. These compositions are well known and comprise a typical North American carpet scrap for automotive purposes. Other typical carpet scrap compositions are disclosed in U.S. Pat. No. 5,852,115 and that disclosure is incorporated herein by reference.
In accordance with the compounding method of the present invention, formulations were usually compounded at temperatures of about 200° C. to about 230° C., and injection molded at abo
Chlystek Stanley J.
Rice Jeffrey Lynn
Young Dennis C.
Lear Corporation
Wood Herron & Evans L.L.P.
Woodward Ana
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