Modified asphalt with partitioning agent

Abstract

A modifier material and method for making the same is characterized by the addition of a partitioning agent to a polymer material such as synthetic rubber to prevent reagglomeration of the rubber. The partitioning agent reduces the time required to disperse the modifier material in a material to be modified and also reduces the viscosity of the modified material so that the modified material is easier to handle.

Description

BACKGROUND OF THE INVENTION

The use of polymers to make polymer modified asphalt (PMA) is growing nationally and internationally. The increased use of polymers to modify asphalt is because most base or virgin asphalts are not suitable for use in different environments owing to different geographical and temperature conditions around the country. In order to satisfy the demand for more polymers, manufacturers are seeking to increase production, especially of less expensive polymers which are suitable for asphalt modification. Polymers are also suitable for use in the shoe industry and particularly for making shoe soles.

One type of economical polymer which is readily available at a reasonable price is synthetic rubber or butadiene back bone polymer because of its high volume of consumption. Block copolymers are also readily available. Most of these commodity type polymers reagglomerate after grinding into crumb rubber, which is a major drawback to their acceptance by the asphalt modification and footwear industries. The present invention relates to a method for treating a polymer such as synthetic rubber which prevents reagglomeration of the rubber. This reduces the dispersion time of the polymer into the asphalt or other material with which it is mixed and also decreases the viscosity of the resulting product.

BRIEF DESCRIPTION OF THE PRIOR ART

Modified asphalts including polymer and crumb rubber are well-known in the patented prior art, as evidenced by the Memon U.S. Pat. No. 6,444,731. This patent discloses the use of furfural or vegetable oil as a dispersion agent for the modifier material which comprises butadiene back bone polymers or crumb rubber to form a treated modifier material which disperses quickly into asphalt. The rapid dispersal of the modifier material reduces the production time of the modified asphalt, thereby reducing its cost. In addition, the modified asphalt has improved low and high temperature rheological properties.

While the prior polymer modified products operate satisfactorily, there is one drawback to the efficient production thereof. This is the tendency of the polymer and crumb rubber to reagglomerate which reduces the homogeneity of the resulting product. This in turn increases the cost of manufacturing and handling the product.

SUMMARY OF THE INVENTION

The present invention was developed in order to overcome these and other drawbacks of prior polymer modified products by providing improved treatments of the modifier material before it is mixed with another product such as asphalt or fillers used for manufacturing shoe soles. Specifically, the modifier is treated with a partitioning agent such as a polyethylene wax and phenyl formaldehyde resin so that the modified product resists reagglomeration. The resulting product has reduced viscosity and improved distribution of the modified polymer therein.

The invention further utilizes a butadiene back boned polymer as the modifier for the asphalt and block copolymers for shoe soles. These polymers include Soloprene 1205 and 1502 elastomer which are found in pulverized or crumb rubber. The most popular block copolymers are styrene butadiene styrene (SBS), styrene butadiene rubber (SBR), and styrene butadiene (SB). The major difference in SBS, SBR, and SB for the asphalt and footwear industries is the amount of styrene in the polymer.

BRIEF DESCRIPTION OF THE FIGURE

Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawing, in which:

FIG. 1 is a flow diagram showing the method steps for treating polymer with a partitioning agent according to the invention;

FIG. 2 is a flow diagram showing the method steps for making modified asphalt according to a preferred embodiment of the invention; and

FIG. 3 is a flow diagram showing the method steps for making modified polymer according to the invention.

DETAILED DESCRIPTION

The preferred polymers which are modified according to the invention are synthetic rubbers such as butadiene back boned polymers. Specific examples of such rubbers are Soloprene 1205, from Dynasol, which is a butadiene back boned styrene butadiene (SB) block copolymer and 1502 elastomer, also from Dynasol, which is a butadiene back boned styrene butadiene rubber (SBR). Both of these synthetic rubbers are commodity polymers which are readily available and inexpensive. A further rubber which is suitable for use according to the invention is a styrene butadiene styrene (SBS) polymer.

Referring to FIG. 1, the polymers are preferably ground or crushed into smaller particulates. The particulates are treated with a partitioning agent, preferably by spraying the agent onto the polymer particles and then mixing the same to form a treated modifier material. A preferred partitioning agent is a polyethylene wax, a polymethylene wax (such as EnHance™ polymethylene hydrocarbon manufactured by Plastic Technology Service Ltd.) or a linear aliphatic hydrocarbon polymer. In addition, a phenyl formaldehyde resin is mixed with the wax or polymer prior to mixing with the synthetic rubbers. Synthetic polymer is preferred over natural polymer because it has different properties which assist with the manufacturing process. Specifically, the combination of synthetic linear aliphatic hydrocarbon polymer and phenyl formaldehyde resin acts as a good partitioning agent for synthetic rubbers in that they prevent reagglomeration of the synthetic rubber modifier.

The treated polymer modifier material is mixed so that the partitioning agent is thoroughly distributed throughout the synthetic rubber. If desired, the mixture is also heated while mixing. Heating is conducted in the range of between 90° C. and 1500° C., but preferably in the range of 160° C. and 210° C. Mixing occurs for up to 10 minutes, but less time is normally required because of the properties of the partitioning agent.

Referring to FIG. 2, the treated polymer material according to the invention is added to hot asphalt, preferably having a temperature of 160° C.-210° C., and mixed, preferably by stirring. The resulting modified asphalt resists reagglomeration of the synthetic rubber and is characterized by reduced viscosity and improved Theological properties of both high and low temperatures.

Modified polymer according to the invention and the corresponding unmodified polymer were tested for reagglomeration by a conventional industrial protocol using Instron's Tensile Instrument. The test results are shown in Table I.

	TABLE I
	Electro-	Electro-
	mechanical	mechnical		Viscosity @
	Force for	Force for		135° C. cP
	Untreated	Treated	Dispersion	Using 10%
	Polymer	Polymer	Time	of Polymer
Soloprene	30 Kilo Force		40 minutes	4700
1205 (SB0
Un-
Treated
Soloprene		8 Kilo Force	5 minutes	2730
1205 (SB)
Treated
1502 (SB)	150 Kilo Force		45 minutes	6100
Elastomer
Un
Treated
1502 (SB)		19 Kilo Force	7 minutes	3310
Elastomer
Treated
SBS 411	20 Kilo Force		35 minutes	5710
Un-
Treated
SBS 411		4 Kilo Force	5 minutes	3140
Treated

An acceptable number for reagglomeration is 20 Kilo force or lower. Table I establishes that the partitioning agent according to the invention is extremely beneficial to prevent reagglomeration of the synthetic rubber modifier. After use of the partitioning agent, styrene butadiene (SB) type polymer acts just like a styrene butadiene styrene (SBS) type polymer.

Another benefit attendant with the invention is the reduction in dispersion time of polymer in asphalt. Dispersion times which are almost eight times faster than those of prior asphalt modification techniques can be achieved. This is because once the partitioning agent enters the polymer modifier material, the partitioning agent melts when added to hot asphalt due to its low melting point. The change in state creates a new hydraulic pressure which breaks the particles of polymer in the modifier.

A further benefit of polymer modified asphalt including a partitioning agent is the reduced viscosity of the asphalt. Such an asphalt may be highly concentrated and transported via a pump which facilitates the construction of roadways, parking lots and the like from the modified asphalt.

Table II shows the continuous performance grade (PG) of neat, untreated polymer modified asphalt (PMA) and treated polymer modified asphalt.

	TABLE II
				Untreated	Treated
	Asphalt	Polymer	Neat PG	PMA PG	PMA PG
		Dynasol
		Soloprene
		1205
	BP	4% Polymer	65-23	80-20	82-23
	Asphalt	Treated or
		Untreated
	Irving	4% Polymer	53-35	69-33	70-34
	Asphalt	Treated or
		Untreated
		Dynasol
		1502
		Elastomer
	BP	4% Polymer	65-23	81-21	83-23
	Asphalt	Treated or
		Untreated
	Irving	4% Polymer	53-34	70-33	71-35
	Asphalt	Treated or
		Untreated

As shown in Table II, the partitioning agent impacts the polymer and shows slight improvement for both high and low temperature rheological properties over untreated polymer. The performance grades for the treated polymer are higher than those for untreated polymer.

Referring now to FIG. 3, a method for using the modified polymer material in the manufacture of soles for footwear will be described. The polymers used in this embodiment of the invention are preferably block copolymers having a higher amount of styrene in the polymer. The polymer is formed into particulates and the partitioning agent is formed from a mixture of wax or polymer and resin as in the embodiment of FIG. 1. The partitioning agent is sprayed onto the particulates which are then mixed and, if desired, heated to between 90° C. and 1500° C., but preferably between 160° C. and 210° C. so that the polymer is modified to incorporate the partitioning agent. The resulting modified polymer prevents reagglomeration of the polymer. The modified polymer is mixed with fillers known to people in the footwear art to form a composite material suitable for use in forming the soles for shoes.

While the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those of ordinary skill in the art that various changes and modifications may be made without deviating from the inventive concepts set forth above.

Claims

1. A method for making a modified polymer, comprising the steps of: (a) mixing a resin with a wax or a linear aliphatic hydrocarbon polymer to form a partitioning agent; and (b) mixing the partitioning agent with particles of synthetic rubber material to produce a modified polymer which resists reagglomeration.

2. A method as defined in claim 1, wherein said wax comprises a polyethylene wax or a polymethylene wax.

3. A method as defined in claim 2, wherein said resin comprises a phenyl formaldehyde resin.

4. A method as defined in claim 2, wherein said synthetic rubber comprises a butadiene back bone polymer or a block co-polymer.

5. A method as defined in claim 4, wherein said synthetic rubber comprises styrene butadiene styrene, styrene butadiene, or styrene butadiene rubber.

6. A method as defined in claim 2, wherein said mixing step is performed at a temperature of between 90° C. and 1500° C.

7. A method as defined in claim 6, wherein said mixing step is performed at a temperature of between 160° C. and 210° C.

8. A method for making a footwear sole material, comprising the steps of: (a) mixing a resin with a wax or a linear aliphatic hydrocarbon polymer to form a partitioning agent; (b) mixing the partitioning agent with particles of synthetic rubber material to produce a modified polymer which resists reagglomeration; (c) adding the modified polymer to a filler material; and (d) mixing the combination of modified polymer and filler material to produce a composite material which resists reagglomeration of the synthetic rubber and which has reduced viscosity.

9. A method as defined in claim 8, wherein said wax comprises a polyethylene wax or a polymethylene wax.

10. A method as defined in claim 9, wherein said resin comprises a phenyl formaldehyde resin.

11. A method as defined in claim 9, wherein said synthetic rubber comprises a butadiene back bone polymer or a block co-polymer.

12. A method as defined in claim 11, wherein said synthetic rubber comprises styrene butadiene styrene, styrene butadiene, or styrene butadiene rubber.

13. A method as defined in claim 9, wherein said mixing step is performed at a temperature of between 90° C. and 1500° C.

14. A method as defined in claim 13, wherein said mixing step is performed at a temperature of between 160° C. and 210° C.

15. A modifier material, comprising (a) a synthetic rubber material; and (b) a partitioning agent mixed with said rubber material to resist reagglomeration of the synthetic rubber material, said partitioning agent including a resin mixed with a wax or a linear aliphatic hydrocarbon polymer.

16. A modifier material as defined in claim 15, wherein said wax comprises a polyethylene wax or a polymethylene wax.

17. A modifier material as defined in claim 16, wherein said resin comprises a phenyl formaldehyde resin.

18. A modifier material as defined in claim 16, wherein said synthetic rubber comprises a butadiene back bone polymer or a block co-polymer.

19. A modifier material as defined in claim 18, wherein said synthetic rubber comprises styrene butadiene styrene, styrene butadiene, or styrene butadiene rubber.

20. A footwear sole material, comprising (a) a modifier material, including (1) a synthetic rubber material; and (2) a partitioning agent mixed with said rubber material, said partitioning agent including a resin mixed with a wax or a linear aliphatic hydrocarbon polymer; and (b) a filler material mixed with said modifier material to produce a composite material which resists reagglomeration of the synthetic rubber and which has reduced viscosity.

21. A footwear sole material as defined in claim 20, wherein said wax comprises a polyethylene wax or a polymethylene wax.

22. A footwear sole material as defined in claim 21, wherein said resin comprises a phenyl formaldehyde resin.

23. A footwear sole material as defined in claim 21, wherein said synthetic rubber comprises a butadiene back bone polymer or a block co-polymer.

24. A footwear sole material as defined in claim 23, wherein said synthetic rubber comprises styrene butadiene styrene, styrene butadiene, or styrene butadiene rubber.