Patent Application
20080081875
This invention includes a flooring product having at least one layer including a polymeric binder comprising a homo-polymer PVC resin and a thermoplastic, high molecular weight polyester resin, wherein the polyester resin comprises at least one renewable component. The flooring product can comprise sheet or tile products. The layer in these structures may be solid or foamed, and filled or unfilled. In some embodiments the layer comprises a transparent wear layer or wear layer component.
One particular well known example of a prior art flooring product is vinyl composition tile (VCT), as described by ASTM Specification 1066-04. While the present invention is intended for use in such tile, as the Specification and Examples describe, it will be obvious to one skilled in the art that the invention is also applicable to various other types of flooring, including tile products such as Type III solid vinyl tile, surface applied tile, and to sheet flooring products.
In one embodiment, the at least one layer comprises consolidated chips or particles having a binder comprising a homo-polymer PVC and a thermoplastic, high molecular weight polyester resin. In another embodiment, the layer is a homogeneous, melt processed layer having a binder comprising a homo-polymer PVC and a thermoplastic, high molecular weight polyester resin.
In one embodiment, the at least one layer comprises consolidated chips or particles having a binder comprising a homo-polymer PVC and a highly viscous polyester resin. In another embodiment, the layer is a homogeneous, melt processed layer having a binder comprising a homo-polymer PVC and a highly viscous polyester resin.
Unless the layer is transparent, it typically comprises a filler in addition to the polymeric binder. Limestone, talc, or other minerals are utilized as filler in PVC flooring. Interest in using recycle materials as fillers has increased due to “green” issues. Such recycle or renewable filler materials include those obtained from wood or plants. These include pecan shells, wood flour, saw dust, walnut shells, rice hulls, corn cob grit, and others. Additionally, ground shells from animals such as clams, coral, etc. are renewable inorganic fillers. Such renewable fillers contain biobased carbon in the form of carbonates. These can be considered post-industrial or renewable materials under the LEED System. Mineral fillers generated from post-industrial processes include limestone, quartz, ceramic powders, glass, fly ash and concrete powder.
Recycle thermoset resin based fillers can also be employed. For example, powders produced by grinding thermoset polyester materials, such as products made from bulk molding compounds (BMC) or sheet molding compounds (SMC) can be post-industrial, as well as post-consumer materials. Another thermoset material of interest is recycled fillers made from Urea Formaldehyde thermoset resins. Depending upon the source, these materials can also be post-industrial or post-consumer. Another example includes ground, cured (cross-linked) rubber materials such as used in tires. These rubbers materials can be based on natural or synthetic rubbers, polyurethanes, or other well known thermoset rubber compositions.
Additionally, recycle thermoplastic resin based materials may be employed as fillers if they are incompatible with the PVC/polyester resin binder. For example, polyethylene, polypropylene, polystyrene, polycarbonate, acrylonitrile butadiene styrene and thermoplastic rubbers maybe incompatible with the PVC/high molecular weight polyester binder. Such materials, if added as particulate will essentially function as fillers in these compositions. If the recycled thermoplastic resin is compatible with the binder, it may function as a binder and not as a filler in the composition. Compatibility may be dependent upon the processing conditions employed. Depending upon the source, these materials can be post-industrial or post-consumer.
In one embodiment, the layer comprises a recycle or renewable filler in addition to the PVC/high molecular weight polyester binder or highly viscous binder.
The thermoplastic, high molecular weight polyester resin has a number average molecular weight (Mn) of at least 5,000, and in some embodiments the polyester resins have a molecular weight (Mn) of at least 10,000. The polyesters may be biodegradable, and/or may contain renewable components. In one embodiment, the polyester comprises at least 50% by weight of renewable components. In another embodiment, the polyester comprises greater than 80% by weight of renewable components. In yet another embodiment, the polyester comprises essentially 100% by weight of renewable components (Example 4).
In one embodiment, the polyesters may comprise aliphatic diacid and aliphatic diol components. Although a wide range of aliphatic diacids and aliphatic diols may be used, it is preferred that these components come from renewable sources. Renewable aliphatic diacid and aliphatic diol components may include but are not limited to Bio-PDO (1,3-propanediol), 1,4-butanediol, sebacic acid, succinic acid, adipic acid, azelaic acid, glycerin and citric acid.
The polyesters may be pre-reacted with epoxidized natural oils, or the reaction can occur during the melt processing into flooring layers. Such reaction during melt processing is a type of dynamic vulcanization. Dynamic vulcanization is the process of intimate melt mixing of two or more reactive components, such as an acid-terminated polyester and epoxidized natural oil, and the reaction occurs between at least two of these components during the melt mixing.
Other diacid and diol components from renewable resources will become available as the need for renewable materials continues to grow. The diol components may also include diols which are branched or hindered to limit crystallinity in the final polyester binder. These can include neopentyl glycol, glycerin, and others.
Renewable components based on plants, animals, or biomass processes have a different radioactive C14 signature than those produced from petroleum. These renewable, biobased materials have carbon that comes from contemporary (non-fossil) biological sources. A more detailed description of biobased materials is described in a paper by Ramani Narayan, “Biobased & Biodegradable Polymer Materials: Rationale, Drivers, and Technology Exemplars”, presented at American Chemical Society Symposium, San Diego 2005; American Chemical Society Publication #939, June 2006. The Biobased Content is defined as the amount of biobased carbon in the material or product as fraction weight (mass) or percent weight (mass) of the total organic carbon in the material or product. ASTM D6866 (2005) describes a test method for determining Biobased Content.
Theoretical Biobased Content was calculated for the resultant polyester resins in Table 2 and Table 3. In one embodiment the Biobased Content is at least 5% by weight of. In another embodiment the Biobased Content is at least 50% by weight of. In still another embodiment the Biobased Content is at least 80% by weight of.
In another embodiment, the thermoplastic, high molecular weight polyesters or the highly viscous polyesters can comprise aromatic diacid components and aliphatic diol components. The aromatic acid components may include but are not limited to phthalic acid (anhydride), isophthalic, or terephthalic acids. In some cases an amount of trimellitic anhydride can also be used.
In another embodiment, the thermoplastic, high molecular weight polyesters may comprise aliphatic diacid and aromatic diacid components reacted with various aliphatic diols.
The thermoplastic, high molecular weight polyesters may also be branched. For example utilizing aliphatic alcohols that have more than two functional groups, such as glycerin, or aromatic acids having more than two functional groups such as trimellitic anhydride may be used to produce branched polyesters.
Although, the above diacid components are described, it is understood that their simple diesters such as from methanol or ethanol can be used to prepare the thermoplastic, high molecular weight polyesters or highly viscous polyesters via known transesterification techniques.
Depending upon the diacid and diol selected, polyesters can be amorphous or crystalline/semi-crystalline materials. In one embodiment, the polyester is amorphous. Table 2 shows some examples of amorphous polyester binders of the invention and their wt % renewable components.
In another embodiment, the polyester is crystalline and comprises a Tg below about 25° C. and a crystalline melting temperature Tm greater than about 25° C. In yet another embodiment, the polyester has a Tg at or below about 25° C. and a Tm between about 25° C. and about 200° C. Table 3 shows some examples of polyesters having a Tg at or below about 25° C. and Tm above about 25° C. Tg and Tm were determined by standard Differential Scanning Calorimetry (DSC) techniques. The polyester compositions include modifying 100% renewable aliphatic polyesters by the addition of an amount of aromatic diacid, such as terephthalic acid, to help control crystalline regions and Tm.
The high molecular weight polyesters may be prepared by several known methods. One method involves esterification of a diacid and a diol components at elevated temperature. Typically, a slight excess of diol is employed (see Procedure 1). After the acid functional groups have essentially reacted, a high vacuum is applied and excess diol is stripped off during transesterification, thereby increasing molecular weight. In some embodiments, 1,3-PDO is the diol of choice to build high molecular weight in this step of the process.
It has been found that high molecular weight polyester resin can be made by esterification of a diacid and diol at elevated temperature using a very slight excess of diacid (See Procedure 1B). After all the hydroxyl groups are reacted, a high vacuum is applied to build molecular weight. The mechanism by which high molecular weight is achieved is not clear. Table 4 shows some examples of polyesters comprising renewable components and the number average molecular weights obtained from these processes of Procedure 1.
Another method for obtaining high molecular weight polyesters involves the co-reaction of a renewable polyester with recycle polyesters such as PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PPT (polypropylene terephthalate) or other recycle polyester resins. In these co-reactions an aliphatic polyester comprising renewable ingredients was first prepared as described in Procedure 1. The recycle polyester resin was then mixed with the aliphatic polyester and transesterification between the two polyesters was accomplished at high temperature and preferably under high vacuum. In one embodiment, the co-reacted polyester had a Tm at or below about 150° C. that could be processed in low intensity mixers. See Example 2.
Molecular weight of the polyester resins was determined by Gel Permeation Chromatography (GPC) using the following procedure. The polyester resin was dissolved into tetrahydrofuran (THF), quantitatively diluting to ˜30 mg/ml and filtering with a 0.45 micron filter. Two drops of toluene were added to each sample solution as an internal flow rate marker.
Samples soluble in THF were run by the following conditions. GPC analysis was run on the TriSec instrument using a four column bank of columns with pore sizes: 106, 2 mixed D PLGel and 500 Angstroms. Three injections were made for the sample and calibration standards for statistical purposes. Universal Calibration (UC) GPC was used to determine MW. UC is a GPC technique that combines Refractive Index (RI) detection (conventional GPC) with Intrinsic Viscometry (IV) detection. Advantages of UC over conventional GPC are:
1. MW is absolute (not relative only to standards).
2. Yields information about branching of molecules.
The mobile phase for the THF soluble samples was THF at 1.0 ml/min. The data was processed using the Viscotek OmniSec UC software. The instrument is calibrated using a series of polystyrene narrow standards. To verify calibration, secondary standards were run. They include a 250,000 MW polystyrene broad standard, and a 90,000 MW PVC resin. The calculated molecular weight averages are defined as follows:
Highly crystalline or some high molecular weight samples insoluble in THF were dissolved in a 50/50 (wt.) mixture of tetrachloroethylene (TTCE)/phenol. The column set is 104 and 500 Angstrom 50 cm Jordi columns. The mobile phase was 50/50 (wt.) mixture of TTCE/phenol at 0.3 ml/min. flow rate. The slower flow rate is due to the greater back pressure of the solvent system on the columns. The data was processed using the Viscotek UC OmniSec software.
Since MW data must be compared from one column set to the other, standards and selected samples were run on both column sets in THF for comparison. A calibration curve was made for each column set. There is good agreement of the standards between the two sets.
Flooring products may be prepared by combining the homopolymer PVC resin and high molecular weight polyester resin or highly viscous polyester resin and heating to melt mix the resins and other formulation ingredients. The melt mixed formulation can then be formed into layers to create flooring structures using processing methods known in the art, including but not limited to calendaring, extruding, casting, consolidating, and laminating. In some flooring structures the layer may be homogeneous, and filled or unfilled depending upon its location and function within the flooring structure. In other cases, the melt mixed formulation can be formed into chips or particles. These chips or particles can be further processed in many different ways to provide flooring products. For example, they can be used to prepare layers comprising consolidated ships or particles, as known in commercial sheet and tile flooring product structures.
The examples described below describe the formation of tile flooring products utilizing traditional low intensity, “dough type” mixers. It is understood that the homo-polymer PVC and high molecular weight polyesters or highly viscous polyesters may be mixed using high intensity, “extruder type” mixers to process the formulations into flooring products. The examples described below describe the formation of Vinyl Composition Tile (VCT) type products, but are not intended to limit the scope of the invention to these type flooring products. The binder system comprising homo-polymer PVC resin and high molecular weight polyester resin or highly viscous polyester resin eliminates the need for co-polymer PVC resins, and low molecular weight, volatile plasticizers in these flooring structures.
1A: This describes the general procedure utilized to make thermoplastic, high molecular weight polyesters from diacids and diols. A desired polyester formulation was developed based upon mole equivalent weight of the diacid and diol functional groups. An excess of diol of the most volatile diol component of the formulation was employed in the formulation. In one embodiment, 1,3-propanediol was the excess diol of choice. The diacid and diol ingredients were added into a stainless steel vessel of a RC1 automated reactor (Mettler-Toledo Inc, 1900 Polaris Parkway, Columbus, Ohio), stirred and heated under a continuous flow of pure, dry nitrogen. Typically, the ingredients were heated to 200° C. for 2 hours and temperature increased to 230° C. for an additional 4 to 6 hours until essentially all acid end groups were reacted and theoretical amount of water removed. Subsequently, the nitrogen was stopped and a high vacuum was applied. The mixture was heat and stirred under high vacuum for an additional 4 or more hours at 230° C. to 300° C. In some cases the temperature of the transesterification step was increased to 250° C. or higher. Depending upon the experiment, a vacuum in the range of 5 mm of mercury was utilized. Subsequently, the polymer was allowed to cool to 150° C. to 200° C. and physically removed from the reactor under a flow of nitrogen and allowed to cool to room temperature.
It is understood that removal of the volatile diol component during transesterification leads to high molecular weight. High molecular weight may be obtained faster if higher vacuum is utilized (below 1 mm of mercury). It is also known that as the melt viscosity increases due to increased molecular weight, the removal of diol becomes more difficult. The increase in molecular weight can become diffusion dependent because of the high viscosity of the molten polyester. This means that the released volatile diol from the transesterification reaction reacts back into the polymer before it can diffuse out of the melt, and be removed. Renewing the surface of the melt can facilitate the loss of diol and increase molecular weight. The polyesters obtained by this procedure generally have terminal hydroxyl end groups.
Although, diacid components are described above, it is understood that their simple diesters such as from methanol or ethanol can be used to prepare the thermoplastic polyester resin via known transesterification techniques. The polyesters from this procedure generally have ester terminated end groups.
1B: The same general procedure as in 1A is employed. A desired polyester formulation was developed based upon mole equivalent weight of the diacid and diol functional groups. An excess of about 0.01 to 0.5 mole excess of diacid was typically employed in the formulation. The ingredients were mixed and heated as in 1A above, except that the temperature was generally held below 200° C. to keep acid/anhydride from being removed until all hydroxyl groups were reacted. Subsequently, a high vacuum was applied as in 1A and the mixture heated to between 230° C. and 280° C. and stirred as in Procedure 1A. The resultant high molecular weight polyester was removed from the reactor and cooled as in 1A.
The mechanism of achieving high molecular weight is not clear. In some formulations containing phthalic anhydride, the phthalic anhydride was identified as being removed from the mixture under high vacuum.
Tables 5A to 5E provide additional examples of high molecular weight polyesters having renewable components made according to the procedure of Procedure 1.
The following formulation was processed as per Procedure 1 to prepare the aliphatic polyester EX43 comprising 100% renewable components and a Biobased Content of 100%.
The aliphatic polyester EX43 was mixed with PET bottle recycle resin obtained from Nicos Polymers & Grinding of Nazareth, Pa., and catalyst added as listed below.
The mixture was heated under nitrogen at 265° C. for a period of about 3 hours, and a high vacuum applied as in Procedure 1 for an additional 3 hours at 265° C. Subsequently, the resultant polyester having 50% by weight of renewable content and 50% by weight of recycle content was shown to have a molecular weight Mn of 17,200 with a Tg of −9° C. and a Tm of 114° C. Molecular weight Mn of the starting PET recycle bottle resin was determined by GPC techniques described above and found to be 14,000. A sample of PET film obtained from Nicos Polymers & Grinding was also analyzed by GPC and molecular weight Mn determined to be 17,300.
High molecular weight polyesters comprising the compositions of Table 6A were made according to Procedure 1.
The polyesters of Table 6A, were each mixed with recycle PET bottle resin obtained from Nicos Polymers & Grinding of Nazareth, Pa., and 0.1% T-20 catalyst added and transesterification conducted as per Example 2. In some examples, transesterification was also carried out on PBT resin Celanex 1600A obtained from Ticona (formerly Hoechst Celanese Corp.), Summit, N.J. Table 6B shows some of the resultant polyester co-reaction products and their Tm. It is obvious that these transesterification reactions may be carried out on virgin PET or PBT type resin.
The melting points listed in Table 6B were determined using an “Optimelt” automated unit. Higher Tm co-reacted polyesters may be produced by using less aliphatic polyester than described in the Table 6B above.
This is an example of VCT flooring product prepared with a binder comprising homopolymer PVC and an amorphous, thermoplastic, high molecular weight polyester resin. The following VCT formulation, comprising homopolymer PVC and high molecular weight polyester resin Ex-6 of Table 2, was mixed using a low intensity Baker Perkins heated mixer. The ingredients were added to the mixer which was heated to 325° F. The formulation was mixed and heated for approximately 7 to 11 minutes in the Baker Perkins mixer to a drop temperature of approximately 280° F. Depending upon the formulation, mixing time varied between 4 to 16 minutes on average and drop temperature varied between approximately 280° F. and 290° F.
The hot, mixed formulation was then dropped into the nip of a two roll calendar. The rolls of the calendar were set a different temperatures—one roll hotter than the other. Typically, the hot roll was set at about 290° F. and the cold roll set at about 250° F. The nip opening between the calendar rolls were set to provide a final sheet thickness of about 125 mils. The processability of the formulations were evaluated using the key described in Table 7A. As can be seen from the formulation and processing data sheet Table 7B, the formulation based upon homopolymer PVC and the high molecular weight polyester or highly viscous polyester processed very similar to a standard PVC formulation containing PVC copolymer and low molecular weight plasticizer.
The final calendered sheet was removed from the calendar and cut into tile and physical properties determined. The tile comprising PVC homo-polymer and highly viscous polyester binder met the VCT ASTM 1066 standards for indentation, static load and impact resistance.
This is an example of a flooring product having a binder comprising homopolymer PVC resin and a totally aliphatic, thermoplastic, high molecular weight polyester resin. The following formulation was processed as per Procedure 1 to prepare the aliphatic polyester EX-80 comprising 100% renewable components. The polyester had a Tg of −16° C. and a Tm of 62° C.
The following VCT formulation, comprising homopolymer PVC and high molecular weight polyester resin EX-80 was mixed using a low intensity Baker Perkins heated mixer as described in Example 4. The following formulation and processing data sheet Table 7 documents that the formulation processed acceptably. The final calendered sheet was removed from the calendar and cut into tile and physical properties determined. The Tile comprising PVC homo-polymer and thermoplastic, high molecular weight polyester EX-80 binder met the VCT ASTM 1066 standards for indentation.
