Stock material or miscellaneous articles – Structurally defined web or sheet – Physical dimension specified
Reexamination Certificate
1998-08-05
2001-02-13
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Physical dimension specified
C428S323000, C428S332000, C428S304400, C428S500000, C428S515000, C428S904400, C525S240000
Reexamination Certificate
active
06187424
ABSTRACT:
FIELD OF INVENTION
This invention relates to sheet materials suitable for use as floor, wall or ceiling coverings, and processes and intermediates for making the same. The present invention particularly relates to floor, wall or ceiling coverings made of one or more non-polyvinyl chloride (non-PVC) polymeric layers.
BACKGROUND OF THE INVENTION
Materials for floor, wall and ceiling coverings should possess a wide variety of properties which are sometimes not compatible. An important property of materials for floor, wall and ceiling coverings is a good conformability to uneven or contoured surfaces to allow efficient application of the material to floors and walls. Particularly important for materials used for floor coverings are good wear, abrasion, scratch and indentation resistance and good indentation recovery to reduce visible scratches and indentations of furniture and rolling objects, such as office chairs.
Well known floor coverings are based on polyvinyl chloride (PVC). PVC-based materials have many desirable properties, such as good filler acceptance, flexibility and scratch resistance. However, in more recent years attention has focused on the disadvantages of PVC-based flooring.
Typical PVC covering construction includes a PVC-plastisol based covering. The plastisol typically consists of PVC particles, plasticizer, heavy metal additives and inorganic filler. The covering layer is formed in a spreading process by laying-down the plastisol on a fabric or release paper substrate and subsequently curing the plastisol. The PVC covering layer is typically manufactured using a calendering or roll mill process. In such processes, rigid PVC requires plasticizers and heavy metal stabilizers. Plasticizers have a tendency to migrate, which results in a gradual deterioration in resiliency and build up of a sticky residue that can lead to dirt accumulation, and the plasticizers can form pathways in the polymer for dye migration which can render printed patterns less distinct. The hydrogen chloride and heavy metal ash from decomposition of the heavy metal stabilizers are undesired consequences from the incineration of scrap associated with manufacturing and installation of PVC-based covering materials.
PVC-based coverings are known to be more difficult to recycle than polyolefin polymers, but attempts to produce covering materials from recyclable, or at least safely incineratable, thermoplastic polyolefin polymer compositions have been limited by currently available manufacturing technology. They have been more difficult to process on conventional equipment used to make PVC coverings. Whether manufactured using a spreading process or a calendering process, in order to avoid an excessive number of seams or joints when installed, PVC coverings are typically manufactured as endless webs having widths up to 4 or 5 meters. This width requirement is generally considered to significantly limit the possible products and/or processes available for providing suitable alternatives for PVC coverings. See, for example, the disclosure by Oppermann et al. in U.S. Pat. No. 5,407,617 at Col. 1, lines 32-36. In particular, known processes for manufacturing crosslinked thermoplastic floor covering materials are said to be limited to widths of about 2 meters due to die width limitations. See, U.S. Pat. No. 5,407,617 at Col. 2, lines 8-28.
Another difficulty with the use of thermoplastic polymers as substitutes for PVC is that they lack a good balance of flexibility to mechanical strength and controlled softening ability at the elevated temperatures often used by installers to thermoform a large sheet of covering material around tight-fitting spaces and other obstacles, so that such materials tend to break or tear during such installation.
No present single material can entirely fulfill the wide range of required and incompatible properties. Therefore, the desired properties are prioritized based on the desired end-use of the floor, wall and ceiling coverings and the materials are accordingly selected. To increase the variety of materials and material properties which are suitable for floor, wall and ceiling coverings, it would be highly desirable to provide floor, wall and ceiling coverings based on other polymers than those used in the prior art. It would be particularly desirable to provide floor, wall and ceiling coverings which have a good balance of desired properties, particularly sufficient flexibility and conformability to uneven or contoured surfaces for efficient application to floors, walls or ceilings, sufficient scratch resistance, sufficient indentation recovery, sufficient abrasion resistance, and sufficiently low coefficients of friction to avoid excess dirt build-up.
SUMMARY OF THE INVENTION
One aspect of this invention is sheet material suitable for use as a floor, wall or ceiling covering material comprising
1) a polymer mixture having:
(A) at least one homogeneously branched ethylene Polymer (A) having a molecular weight distribution, M
w
/M
n
, less than about 3 and a short chain branching distribution index (SCBDI) equal to or greater than about 50 percent obtainable by polymerization of ethylene with at least one C
3
-C
20
&agr;-olefin in the presence of a single site or constrained geometry catalyst;
(B) at least one ethylene Polymer (B) having a density at least 0.005 g/cm
3
greater than the density of ethylene Polymer (A) and a TREF elution temperature at least 5° C. greater than the TREF elution temperature of ethylene Polymer (A) and, optionally,
(C) at least one ethylene Polymer (C) having a density at least 0.005 g/cm
3
greater than the density of ethylene Polymer (B) and a TREF elution temperature at least 5° C. greater than the TREF elution temperature of ethylene Polymer (B), and
2) optionally a filler at least partially dispersed with a compatibilizer in the polymer mixture,
wherein the weight ratio of ethylene Polymer (B) to the total amount of ethylene Polymers (A) and (C) in the polymer mixture is at least 0.5, the weight ratio of any ethylene Polymer (C) to ethylene Polymer (A) does not exceed 2.0, and the total amount of ethylene Polymer (A) and any ethylene Polymer (C) in the polymer mixture is at least about 25 wt % based on the total amount of polymers in the polymer mixture, and when less than about 10 wt % filler is dispersed in the polymer mixture, than the melt index of Polymer (A) is preferably less than or equal to about 1.5 g/10 min., the melt index ratio of Polymer (B) to Polymer (A) is preferably less than or equal to about 5.0, and/or Polymer (B) is preferably a homogeneously branched ethylene polymer.
Another aspect of this invention is polymer resin-based floor, wall and ceiling coverings comprising at least one layer of the above-described sheet material.
In another aspect, the present invention relates to the use of a mixture of the above-mentioned ethylene Polymers (A), (B) and, optionally, (C) for producing floor, wall or ceiling coverings. Such use includes, but is not limited to, use in a process for the production of a sheet material suitable for use as a floor, wall or ceiling covering which comprises:
(1) providing the above-mentioned ethylene Polymers (A), (B), and optionally (C);
(2) mixing the ethylene polymers of step (1) at an elevated temperature sufficient for melting those polymers, but below a temperature which causes substantial degradation of those polymers, to form a fluid mixture;
(3) forming the fluid mixture of step (2) into a sheet; and
(4) allowing the sheet of step (3) to cool and solidify.
A further aspect of this invention is intermediates for making a sheet material suitable for use as a floor, wall or ceiling covering material comprising a pelletized polymer mixture of the above-mentioned ethylene Polymers (A), (B) and, optionally, (C).
DETAILED DESCRIPTION OF THE INVENTION
By the term “floor, wall or ceiling covering” as used herein is meant an article with a length and width which are substantially greater than its thickness, such as a sheet, tile or board, which is useful to cover at least a portion of a floor,
Kjellqvist Jerker B. I.
Quack Wolfgang
Thoen Johan A.
Wevers Ronald
Ahmed Sheeba
The Dow Chemical Company
Thibodeau Paul
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