CA2459191A1 - Ground elastomer or plastic or composite materials with substantially homogenous properties - Google Patents

Abstract

The present invention relates to a method for converting an elastomer, plastomer or composite to a decreased size in a grinding apparatus is disclosed. In accordance with the present invention there are provided materials that may originate from multiple sources wherein the product produced has substantially homogenous chemical and/or physical properties throughout the whole of the material. Methods disclosed include optionally soaking the at least two elastomers in a first additive. A carrier is added to the elastomers to form an elastomer slurry, and optionally providing a second additive to the slurry. The elastomers are then converted to a smaller particle size wherein the elastomers become a homogenous mixture with substantially homogenous properties throughout the whole. The final intermixed, interpenetrated particles are recovered for use in various applications.

Description

GROUND ELASTOMER OR PLASTIC OR COMPOSITE MATERIALS WITH
SUBSTANTIALLY HOMOGENOUS PROPERTIES
CROSS-REFERENCE TO RELATED APPLICATION
0001 The present application is related to U.S. Patent Nos. 6,333,373 filed on February 10, 1999 entitled "Ground Elastomer and Method", 6,238,448 filed August 16, 1999 entitled "Grinding Stones", 6,426,136 filed on January 30, 2000 entitled "Method of Reducing Material Size" and U.S. Patent Application Nos. 60/331,537 filed November 19, 2001; 60/334,097 filed November 30, 2001; 60/331,538 filed November 19, 2001; 60/178,130 filed January 26, 2000; 10/164,426 filed June 10, 2002;
09/984,961 filed October 31, 2001; 10/294,897 filed November 15, 2002; 09/984,961 filed October 31, 2001; 09/658,678 filed September 8, 2000; 10/177,161 filed June 24, 2002 and 09/768,497 filed January 25, 2001, the content of which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
Technical Field of the Invention [0002] The present invention relates generally to elastomers and methods involving at least two different materials, and in particular, to methods and materials that can be employed with both virgin and recycled or scrap products.
Description of Related Art [0003] In recycling and reusing rubber materials, it is generally known to decrease the size of such rubber materials to small ground rubber particles (i.e., particles of irregular outline that pass through a minus 80 mesh or through a minus 50-mesh or finer). Such particles can be chemically more reactive and mechanically easier to dissolve into various mixes.

[0004] A variety of rubber products (e.g., natural rubber, synthetic rubber, vulcanized rubber, automotive tire scrap, etc.) may be reduced to ground rubber particles. Known methods for producing rubber of a decreased size include cryogenic cracking of the rubber. Other known methods include the milling of the rubber between horizontal la Atty l7ocket No. 22132.00028 ."
grinding stones in a horizontal grinding mill. Such milling techniques have been developed in the flour, paper pulp industry and the paint pigment compounding industries. Such milling techniques include grinding the rubber between opposed milling wheels, such that one wheel is fixed and the other wheel rotates relative to the fixed wheel. Such known milling techniques include pressing the two wheels against a rubber slurry, such that the rubber is ground to a fme state (i.e., powder) in a single pass.
However, such known milling methods have the disadvantage of creating friction and introducing energy to the slurry, which may increase the temperature of the slurry.
Increased slurry temperatures may cause "flash over" in which the slurry becomes a largely dry rubber mass that inhibits grinding. Such known milling methods further have the disadvantage of not producing a uniformly fine rubber powder that passes through a minus 50-mesh.

[0005] Processes of reducing material size of elastomers are generally known such as described in U.S. Patent No. 6,133,373. However, it has been found that the chemical and physical properties of the final products produced thereby may not be uniform enough to be used in many industries. Such lack of uniformity would therefore drive down the market price for these materials and make them less desirable in industries such as the automotive industry where specifications and reproducible standards are not only encouraged, they are mandatory in almost every situation.

[0006] Accordingly, it would be advantageous to have methods and products whereby two or more different materials could be commingled together in an effort to prepare a single unitary product with common properties throughout. It would also be desirable for such common properties to be reproducible.
SLITyIMARY OF THE INVENTION

[0007] The present invention, therefore, is directed to ground elastomeric and thermoplastic materials having substantially homogenous physical and chemical properties as well as to related methods and their uses. Ground elastomeric materials of the present invention preferably include multiple materials from multiple sources, ~,. z...~._,.~"-*.. ~>uw~wwry-s:s~z,a~~.~~~u,,~y~y .~~~~~.~e~mx,sm~a~>.~..~,~.~p~..."."",-.,....-,_,.......__.,_w_._.........
..._, Atty Docket No. 22132.00028 particularly recycled materials that are treated by grinding so that the material becomes a homogenous mixture with common properties throughout the entirety of the material.

[0008] Additional objects, features and advantages of the invention will be set forth in the description which follows, and in part, will be obvious from the description, or may be learned by practice of the invention. The objects, features and advantages of the invention may be realized and obtained by means of the instrumentalities and combination particularly pointed out in the appended claims.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0009] Preferably, the elastomers employed in connection with the present invention are originate from the same elastomeric "family." For example, fluoroelastomers (such as fluorosilicones), nitrites, SBR, silicones and so on. The size of an elastomer (e.g., natural rubber, synthetic rubber, recycled rubbers containing polyethylene and/or polypropylene, vulcanized rubber, carbon black, waste from tire production, various polymers, various plastics, thermoplastic elastomers, thermoplastic vulcanates, polyethylene plastics, etc.) may be decreased using a variety of mechanisms. According to an exemplary embodiment, the elastomer is soaked in a fluid. According to a preferred embodiment, the fluid is soapy water and/or an aromatic oil. Soaking the elastomer, among other things, causes the elastomer to swell, removes oils a from the elastomer and dissolves adhesives in the elastomer.

[0010] According to an exemplary embodiment, a variety of water-soluble additives may be added to the soaking fluid. The additive, when used during soaking of the elastomer, decreases the swelling time of the elastomer as compared to elastomers soaked in the absence of the additive. According to an alternative embodiment, the additive may be a chemical that swells the rubber, but is not a tackifier, such as tetrahydrofuran (THF) or dimethyl formamide (DMF). According to other alternative embodiments, a variety of additives (as described below) may be used when soaking the elastomer.
According to a preferred embodiment the additive used when soaking the elastamer is a fatty amine, such as DELAMINTM commercially available from Hercules, Inc. What is important is that Atty Docket No. 22132.00028 whatever additive is employed; it is added in order to compatibilize the two or more elastomers that are desired to be homogenized.
[0011 J In fact, is is possible that even uncured elastomers (known as "spru"
in the industry) can be cogound with at least one other elastomer of the same elastomeric family. It has unexpectedly been found that the uncured material when coground with other scrap material or other elastomers, will coat the other elastomer, i.e., especially with silicone, and makes for better adhesive properties of the cured elastomer when it is utilized in downstream applications. Moreover, the spru coground with another elastomer (scrap or not scrap) can also be added to virgin materials for many applications with a huge degree of success. Since 10% of scrap material in many plants is the uncured material, the ability to reuse this material successfully amounts to an unexpected advantage of the present invention, particularly because the uncured material can be added in the degree desired to impart certain properties to the final coground material with homogenous properties. It is also possible to employ many thermoplastics such as polypropylenes, polyethylene, chlorinate PE, ultra high molecular weight PE, polycarbonate can be reduced to plastic particles. Other materials such as Nylon 6, Nylon 6.6, Nylon 12 and other composites can be reduced to particles in the present invention.
This could also include carbon, vegetable matter, and biological materials.
[0012] In the present invention, at least two plastomers and/or elastomers (designated at "P") are employed wherein the final product may be Pl-~-PZ or P1+PZ+P3 or P1+P3+P" and so on. The number of elastomer (vulcanized and unvulcanized) can be any desired number and should be selected for the desired Tg and other physical properties such as TPA.
[0013) The size of the soaked elastomer may be decreased in a grinding apparatus, such as a set of milling stones. According to an alternative embodiment, the size of the soaked elastomer may be decreased by freezing the elastomer and cracking or hammering or extruding the elastomer into small sized particles. According to other alternative embodiments, the soaked elastomer is shredded by a series of blades or an Archimedes screw apparatus. According to still other alternative embodiments, the size of a soaked or non-soaked elastomer may be decreased by brute force (i.e., by two counteracting ,....._.."...... ,_"... ""..,. .m.....<. .r...-.a~...S.V N W'G9".:n"M~'t,.~...
..Famw.9f;,... W ,..~a?4~cp.6~.xa.;.~-~~~yaa8~~.yu-~...~.~..".m...".............,...-..~,.~",~"""",~"",_",~""n..,.~......,....,~_"~....._-._...-~_.... ,........, _....

Atty Docket No. 22132.00028 surfaces). According to a preferred embodiment, grinding of the soaked elastomer material is achieved using the grinding apparatus as disclosed in U.S. Pat.
No. 5,238,194 issued Aug. 24, 1993 to Rouse et al. for "METHOD OF PRODUCING FINE
ELASTOMERIC PARTICLES" and incorporated herein by reference. The grinding apparatus expediently includes a horizontal grinding machine providing a fixed stator and a rotating rotor, on which disc-shaped grinding stones having hollow centers can be mounted. The grinding stones provide flat, opposing abrasive surfaces (i.e., flat annulus surface), and each grinding stone is opposed to the other. The abrasive surfaces provide periodically spaced openings in the annulus for introducing the elastomers to be ground between the closed, cooperating abrading surfaces.
[0014] Impurities (e.g., metals, cords, reinforcing materials; etc.) may be removed from the ground elastomer. According to an alternative embodiment, a magnet may be used to remove certain metallic impurities from the ground elastomer. According to a preferred embodiment, the impurities can be removed by passing the ground elastomer through a screen that allows 1/4-inch to 518-inch particles to pass through.
[0015] An elastorner slurry may be formed by adding a carrier to the ground elastorner.
According to an alternative embodiment, the carrier may be a gas (e.g., air) that may carry a wet or dry stream of elastomer particles. According to other alternative embodiments, the carrier is a fluid (e.g., water). According to other alternative embodiments, the carrier may be provided through the grinding apparatus before the slurry is provided through the grinding apparatus. According to any alternative or preferred embodiment, a uniform set point fluid flow rate through a properly spaced set of grinding stones is determined as disclosed in U.S. Pat. No. 5,238,194 issued Aug. 24, 1993 to Rouse et al. for "METHOD OF PRODUCING FINE ELASTOMERIC
PARTICLES" and incorporated herein by reference.
[0016] According to an exemplary embodiment of the present invention, the additive may be added to the slurry. The additive provides for faster grinding of the slurry as compared to a slurry in which the additive is absent. According to an alternative embodiment the additive is a water miscible dispersing agent for carbon black, such as DAXADTM
commercially available form R. T. Vanderbilt Company, Incorporated of Norwalk, Conn.

Atty Docket No. 22132.00028 According to a particularly preferred embodiment about 25% DAXADTM is added to an elastomer slurry of 15% to 60% solids. According to an alternative embodiment, the additive is a surfactant, such as TRITON-XTM commercially available from Rohm &
Haas Company. According to a particularly preferred embodiment, the additive is added to the slurry in the amount of about 1% to 20% based on the amount of elastomer in the slurry, and about 10% to 15% by total weight of the elastomer in the slurry.
[0017] The additive provides a higher yield at the first pass of grinding of the slurry as compared to a slurry in which the additive is absent. Use of the additive produces a higher quantity (i.e., more uniformly fine ground and having less shear) particle as compared to a the particles produced from a slurry in which the additive is absent. A
slurry having an additive yields a significant increase in throughput of ground particles of the desired smaller size, and a smaller percentage of particles passed through the mill without adequate reduction in size. This alone is beneficial, as the economic losses occasioned by the necessity of screening out insufficiently reduced particles and re-grinding them can be reduced. Further, use of the additive provides decreased grinding times of the slurry as compared to a slurry in which the additive is absent. Generally, optimizing the proper additive will affect the desired properties and/or consistency of the slurry.
Decreased grinding times may reduce wear and damage to the wheels of the grinding apparatus.
[0018] The additives provide a lower temperature to the slurry as compared to a slurry in which the additive is absent. A slurry in which the additive is absent reaches high temperatures, whereas the slurry having the additive may have lower maximum tempertatures. Decreased temperature of the slurry is beneficial, in part, because high temperatures may destroy some polymers, less insulation is required in the grinding apparatus, heat damage to the grinding apparatus is decreased and the temperature of the grinding operation is better controlled to achieve the desired viscoelastic effects in milling the elastomer.
[0019] The additives chemically react with the elastomer to produce a more desirable uniform homogenous elastomer particle. The glass transition temperature (Tg) of the elastomer-additive product is more uniform as compared to elastomer particle product in which the mixtures and optional additives are not employed. A uniform Tg value over Atty Dacket No. 22132.00028 the entirety of the product produced is beneficial in producing downstream materials from the elastomer-additive product because uniformity of glass transition temperature is necessary for down stream applications. That is, the Tg should not vary more than 15%
over the entire "batch" produced, preferably not more than 10%, most preferably no more than 5%. A lower temperature is often required for the elastomer-additive product to change from a brittle state to a plastic state, which reduces energy costs.
Uniformity is often difficult to achieve, even when an additive is used. Further, the additives chemically react with the elastomer to produce a more tacky elastomer-additive particle product as compared to the elastomer particle product in which the additive is absent.
Thus, the Tg can vary widely with many additives.
[0020] According to an alternative embodiment, the additive is a resin (natural or synthetic). According to other alternative embodiments, the additive is a rosin (i.e., a mixture of monocarboxylic acids having a hydrophenanthrene nucleus) such as gum rosin or wood rosin. Rosins are of particular interest because they tend to act as dispersing agents in the elastomer slurry and affect the tackiness of the elastomer-additive product.
According to a preferred embodiment of the present invention, the rosin is tall oil rosin (i.e., a by-product of the paper manufacturing process). According to a particularly preferred embodiment, the tall oil rosin has a low acid number, such as XP56TM
commercially available from Arizona Chemical Company.
[0021 ] According to an alternative embodiment, the additive is a resin acid (i.e., abietic-type acids that contain an isopropyl group pendent from carbon 13 as numbered using the Chemical Abstracts system, or pimaric-type acids that include a methyl and vinyl group pendent from the same carbon atom). According to other alternative embodiments, the resin acid is abietic acid or rosin soap (i.e., rosin leached with sodium hydroxide). The rosin is made water-soluble by neutralizing the rosin with a suitable base, such as ammonia, ammonium hydroxide, an amine (i.e., a Frisch amine). Other additives of interest include any rosin acid, polymerized rosin acid, esters of rosin acid, dispersions of rosin acid, dispersions of esters of rosin acid, copolymers of rosin acid, disproportionated rosin acid, hydrogenated rosin acid, 9-anthracene carboxylic acid, 2-ethylhexanoic acid, acetal R-type acids, or any organic acid that could be soluble in water by neutralizing the acid.

Atty Docket No. 22132.00028 [0022] According to an alternative embodiment, the additive is oleic acid (i.e., (CH3 (CH2)~ CH:CH(CH2)~ COOH derived from animal tallow or vegetable oils). Oleic acid may not substantially modify the tackiness of the elastomer-additive product.
[0023] According to an alternative embodiment, the additive is an oligimer (i.e., a low molecular weight polymer molecule consisting of only a few monomer units (e.g., dimer, trimer, tetramer)). According to a preferred embodiment, the oligimer has a viscosity of about 100,000 CP and tends to act as a dispersing agent in the elastomer slurry.
According to a preferred embodiment the oligimer is short chain copolymers of styrene and malefic anhydride that offer typical anhydride functionality in a polymeric material such as SMA~ resin commercially available from Sinclair Petrochemicals, Incorporated.
According to a preferred embodiment, the oligimer is ethylene-malefic anhydride copolymers such as EMA~~'i resin commercially available from Monsanto Industrial Chemicals Co.
[0024] According to an alternative embodiment, the additive is an ester, such as di(2-ethylhexyl) adipate (also known as dioctyl adipate or DOA), DOS, DOD or plasticizers in PVC.
[0025] A filler may optionally be added to the slurry. The filler may be added to the slurry (i.e., elastomer slurry or elastomer-additive slurry) to combine with the slurry to form an elastomer-additive product or an elastomer product having reinforcing properties, temperature modifying properties, increased high surface area, and/or increased tensile strength. A filler (e.g., nylon) combines with the final elastomer product to give the final product reinforcing properties, temperature modifying properties, increased high surface area, and/or increased tensile strength. According to a particularly preferred embodiment of the present invention, the filler is a nylon material. Also silica, Talc or any other desired partition agents can be used.
[0026] The slurry (i.e., elastomer-additive slurry or elastomer slurry) is provided within a grinding apparatus and the elastomer and the additive can be co-ground (or the elastomer is ground) to decrease the elastomer particles to a decreased size. According to an alternative embodiment, the slurry is provided between the two wheels of the grinding apparatus as disclosed in U.S. Pat. No. 5,238,194 issued Aug. 24, 1993 to Rouse et aI. for Atty Docket No. 22132.00028 "METHOD OF PRODUCING FINE ELASTOMERIC PARTICLES" and incorporated herein by reference. The grinding stones can be brought into contact with (or spaced a distance apart from) each other. Choosing or maintaining the fixed position of the grinding stones with respect to each other is known in the art of colloid mills. Persons of skill in the art will readily understand how the slurry is input, at a feed pressure, to such grinding stones and how the spacing between the stones is to be adjusted and set. The grinding action generates heat, which may be controlled, modified or reduced by the particular additive in the slurry.
[0027] The earner and the slurry (i.e., elastomer-additive slurry or elastomer slurry) can be separated. According to an alternative embodiment, the liquid from the slurry is removed to a capture region positioned outside the outer perimeter of the opposed grinding stones. According to a preferred embodiment, the carrier is removed by a centrifuge action, such that the carrier is driven off from the slurry and the elastomer-additive particles or the elastomer particles remain. Floatation methods can also be employed if desired as known in the industry.
[0028] The grinding of the slurry (i.e., elastomer-additive slurry or elastomer slurry) may be conducted in a single pass or a multiple pass operation. According to an alternative embodiment, the grinding operation may be conducted in a single pass where the coarse particles that do not pass a screening operation can be feed to a slurry (i.e., elastomer-additive slurry or elastomer slurry) for re-grinding. According to any alternative or preferred embodiment, the grinding operation may be conducted in a multiple pass where two interconnected grinding mills sequentially grind the slurry to a final fine grind state as disclosed in U.S. Pat. No. 5,411,215 issued May 2, 1995 to Rouse for "TWO
STAGE
GRINDING" and incorporated herein by reference. According to the multiple pass grinding operation, a first grinding mill produces an intermediate feedstock of decreased size. The feedstock is re-wet with water or another carrier to form a feed slurry that is then sequentially fed into a second mill. The multiple pass grinding operation, by selecting optimum size of the grinding stones for production of the intermediate feedstock and then for the production of the final minus 80-mesh to 200-mesh product, requires less energy than, for example, the single pass grinding operation.

.~ .. ~__ ,_. ~,~.~,,,~~ ,~~ ~m ~~;~:.:~~m,.a~.~~._m~,..~.~,r.~..~."~.."~...... -.-...,-___.._.__-__.___.._._...__ ___ .._ Atty Docket No. 22132.00028 [0029] The elastomer mixture plus optional additive if needed or desired which can optionally form a composite may be dried by heat or air.
[0030] According to an alternative embodiment, the earner "flashes off' when the ground particles in slurry exit from between the grinding stones to a decreased pressure (i.e., atmospheric pressure). The flash avoids the necessity of having a separate processing step of drying the ground particles, which saves energy costs of running a separator. The elastomer product is recovered.
[0031] The elastomer or plastomer, which preferably chemically bonds with the additive to form the mufti-elastomer-additive and/or plastomer product, has certain functional characteristics. According to an exemplary embodiment, the elastomer-additive product is a very fme powder having a consistency similar to cooking flour. According to an alternative embodiment, the elastomer-additive product is in the original vulcanized state.
The top and bottom variation of the softening point of the rosin-modified elastomer-additive product varies by about 1°Celsius. This range of softening variation is advantageous compared to the elastomer product that is not rosin-modified, which has a top and bottom softening point that various by about 10°Celsius.
[0032] By using one or more additives with the ground elastomer as described herein, a finely ground product is obtained that is unexpectedly superior in terms of many of its properties, particularly when used in many products such as roofing, paving, building materials, sealants, automotive products, plastic skins, etc. The final product obtained when using one or more additives as described herein will generally have a bulk density of 26-28 lbs./sq. ft., have a specific gravity of from 1.13 +.backslash.-0.02;
have 100% of the particles finer than 17S microns or minus 80 mesh. Ground elastomer, or thermoplastic, products prepared as described herein will typically resist phase separation, are storage stable, provide superior low temperature properties and have excellent high temperature stiffness. When the ground elastomer is mixed at a ratio of from 10-1S%
with asphalt such as WY Sour AC-20, AC-10, Venezu. AC-20, Saudi AC-20 and the like, by any known method, the storage stability of the asphalt product per ASTM

(incorporated herein by reference) also known as the "Cigar Tube" storage stability test will typically range for the top (SP, top, °F.) from 133-144 and at the bottom (SP, bottom, Atty Docket No. 22132.00028 °F.) from 134-156. The change in storage stability between the top and bottom sections generally remains substantially unchanged, that is, the ~1F. from top to bottom will preferably be from 0-2 degrees. This is beneficial, inter alia, because the small change in storage stability of the asphalt will minimize cracking due to temperature changes since the layers of asphalt applied for example on a road, will generally age at the same rate.
Asphalt including a ground elastomer with one or more of the instantly described additives will also be easier to store and ship. However, asphalt is but one possible use;
many others are envisioned and are highly adventageous.
[0033] The additive can be added in any desired amount. Preferably the additive is added in an amount from 0.5% to 95%, more preferably from 5% to 40% advantageously from 5% to 20% but in a preferred embodiment is added in an amount of about 10% or 10%, in each case being based on the total weight of the elastomer.
(0034] In accordance with the present invention, the final material produced by the process involves a situation whereby the at least two elastomers are ground for a time sufficient to commingle the polymeric backbone of both materials to form a new polymeric material that is chemically uniform throughout the whole of the material. If necessary, an additive can be provided that causes the polymeric backbones of the materials to breakdown when being ground in at such a force to impart a new polymeric material with substantially uniform glass transition temperature, and a substantially uniform particle gradation TPA when subjected to a gravonometric analysis as well as a uniform melt flow index, when any part of the final material is tested.
EXAMPLES
[0035] In a two roll mill as disclosed in US Patent No. 5,411,215, and 5,238,194, the contents of which is incorporated herein by reference, two different silicone materials (one prepared by peroxide oxide or and one by catalysis system) are coground according to the method disclosed therein to -40 mesh and the Tg (glass transition temperature) and particle gradation (TPA) are analyzed. It was found throughout the entirety of the ground material, the Tg, and TPA and melt flow index varied by as much as 45%. This was used as a baseline comparison.

Atty Docket No. 22132.00028 [0036] In the same two roll mill, the same two silicone materials peroxide and catalysis q made polymers were coground with uncured silicone. During the mixing and cogrinding, the mixture was monitored to ensure that the polymeric backbones of the two silicones were broken down. The materials were ground to the same -40 mesh size.
However, when the Tg, TPA and melt flow index were measured of this inventive material, it wsa found that these physical properties did not vary more than 5% throughout the entirety of the material.
[0037] Additional advantages, features and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, and representative devices, shown and described herein.
Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
[0038] All documents referred to herein are specifically incorporated herein by reference in their entireties.
[0039] As used herein and in the following claims, articles such as "the", "a"
and "an"
can connote the singular or plural.

Claims (4)

1. A method for blending at least two polymers, all of which are heterogenous with respect to each other so as to form a single uniform new polymer blend matrix, wherein said blend matrix has a substantially uniform melt flow index, Tg and particle gradation, said method comprising;
cogrinding said at least two polymers in a liquid slurry to a reduced particle size and monitoring the Tg, and/or melt flow index particle gradation of said reduced size polymers so that said Tg and particle gradation do not vary more than 15% aver the entirety of the coground blend matrix.

2. A method according to claim 1, further comprising adding at least one chemical additive to enhance the blend matrix.

3. A method of claim 1, wherein said polymers comprise elastomers, plastomers, composites, vegetation materials and/or biological materials.

4. A method of claim 1, wherein said polymers comprise polyethylene and polypropylene.