Active polymer modification of bitumen for use in roofing materials

Abstract

A modified bitumen consisting of a polyurethane wherein the polyisocyanate or polyisocyanate-dominated polyurethane prepolymer (or prepolymers) is first reacted with the bitumen to take advantage of the bitumen's hydroxyl and amine functionality and form an isocyanate-bitumen adduct to form a weatherproofing product.

Claims

1. An actively modified polymer-modified bitumen formulation comprising: 25-75 wt. % of a first component that consists of bitumen, coal tar, or combinations thereof; 2-45 wt. % of a second component that consists of polyurethane, or blend of polyurethane and rubber, said polyurethane including isocyanate end groups, said polyurethane formed from at least one polyisocyanate compound and two or more polyols, at least two of said polyols selected from the group consisting of propylene glycol, polycarbonate diol, polybutadiene glycols and polybutadiene polyols, said two or more polyols include a 1000-5000 molecular weight compound, a content of said two or more polyols creating a NCO/OH equivalent ratio of about 1.2-15:1 in said bitumen formulation, said polyurethane content is no more than 25 wt. % of said bitumen formulation, a weight ratio of said polyurethane to said first component is 0.1-0.5:1, said polyols include both diols and triols, a weight ratio of said diols to said triols is about 1-5:1; 1-66 wt. % of a filler, said filler including two or more compounds selected from the group consisting of potassium polyphosphate, calcium carbonate, ammonium polyphosphate, alumina trihydrate and Mg(OH).sub.2; wherein a weight percent of said first component is greater than a weight percent of said second component, said isocyanate end groups in said polyurethane reacting with hydroxyl end groups in said bitumen, said coal tar, or combinations thereof, said formulation can be used to create a membrane having improved mineral retention and weatherability.

2. The formulation as defined in claim 1, wherein said filler includes three or more compounds selected from the group consisting of calcium carbonate, ammonium polyphosphate, and alumina trihydrate, said filler constituting 5-40 wt. %.

3. The formulation as defined in claim 1, wherein said second component includes said polyurethane and said rubber, said rubber including one or more compounds selected from the group consisting of SBS, SEBS, SIS, and nitrile rubber, a weight ratio of said rubber to said polyurethane is 1:0.2-15.

4. The formulation as defined in claim 1, wherein said first component includes said bitumen having a softening point of 43.3-65.6 C. (ASTM D3461) and a penetration of 40-75 dmm (ASTM D5).

5. The formulation as defined in claim 1, wherein said first component includes said coal tar having a softening point of 40-80 C. (ASTM D3461).

6. The formulation as defined in claim 1, wherein said first component includes a blend of said coal tar and said bitumen, a weight ratio of said coal tar and said bitumen is 1:0.1-10.

7. The formulation as defined in claim 1, further including an antioxidant.

8. The formulation as defined in claim 1, further including a process oil.

9. The formulation as defined in claim 1, further including a catalyst.

10. The formulation as defined in claim 1, comprising by weight percent: TABLE-US-00008 Bitumen and/or coal tar 30-70% Polyurethane 4-20% Filler 10-66%.

11. The formulation as defined in claim 1, comprising by weight percent: TABLE-US-00009 Bitumen and/or coal tar 50-55% Polyurethane 8-20% Filler 30-41%.

12. The formulation as defined in claim 1, comprising by weight percent: TABLE-US-00010 Bitumen and/or coal tar 50-55% Polyurethane 8-20% Filler 30-41% Process oil 1-5%.

13. The formulation as defined in claim 1, comprising by weight percent: TABLE-US-00011 Bitumen and/or coal tar 50-55% Polyurethane 8-20% Filler 30-41% Process oil 1-3%.

14. The formulation as defined in claim 1, comprising by weight percent: TABLE-US-00012 Bitumen and/or coal tar 25-75% Polyurethane 2-49% Filler 1-66% Process Oil 1-20% Rubber 1-30% Modifier 0.01-5% Antioxidant 0.01-5% Catalyst 0.01-1%.

Description

Example 1Based on FORMULA 1

(1) TABLE-US-00003 Component Component Weight Percent PG 64-22 (or other Bitumen 50-55% bitumen) Rubinate 9433 4,4-MDI 8-20% R45HTLO Hydroxy-terminated polybutadiene Krasol LBH 2000 Linear Hydroxy- terminated polybutadiene Poly CD220 2000 MW Polycarbonate diol CaCO.sub.3, Aluminum Filler, Flame 30-41% trihydrate (ATH), retardant Potassium polyphosphate

Example 2Based on FORMULA 1

(2) TABLE-US-00004 Component Component Weight Percent PG 64-22 (or other Bitumen 50-55% bitumen) Hyperlast LP 5610 Linear 8-20% butadiene/MDI based diisocyanate terminated prepolymer R45HTLO Hydroxy-terminated polybutadiene Poly CD220 2000 MW Polycarbonate diol CaCO.sub.3, Aluminum Filler, Flame 30-41% trihydrate (ATH), retardant Potassium polyphosphate

(3) One non-limiting method for creating the composition of Formula 1 and Example 1 is to add the monomeric, polymeric, or prepolymeric diisocyanate to the molten bitumen or a blend of bitumen and fillers at a process temperature of about 160-179.4 C. (320-355 F.) for about 10-60 minutes (e.g., 25-35 min., etc.). Then, after determination of residual % NCO using potentiometric titration or other method familiar to those skilled in the art, enough polyol is added to react with the remaining isocyanate pendant groups. The blend of polyols will help determine the physical properties of the final product, so choice of blend is important. Another non-limiting method for creating the composition of Formula 1 and Example 1 is to first extend the prepolymeric diisocyanate further using processes familiar to those in the art with additional polyol or polyol blends such that the extended prepolymer increases in molecular weight, but still maintains some NCO functionality, but said NCO functionality is lower than the initial prepolymer's NCO content. Said extended NCO-dominated prepolymer is then added to molten bitumen or a blend of molten bitumen and fillers at 160-179.4 C. (320-355 F.). After allowing the reaction of the NCO-terminated prepolymer and hydroxyl pendant groups of the asphaltine molecules within the bitumen, titration can be used to determine if any residual NCO exists, which in turn can be used to calculate the equivalents of an optional amount of chain extender or other polyol and/or amine structure to increase viscosity, but is not necessary.

(4) Formula 2: Active Modification of SBS-Modified Asphalt

(5) TABLE-US-00005 Component Weight Percent Bitumen 50-55% Rubber (SBS, SEBS, SIS, 4-20% and blends thereof) Loading Total at Diisocyanate (monomeric, Various Ratios polymeric, or prepolymeric) Polyol (diol, triol, diol/triol blend) Filler 10-66% Process Oil 1-5%

Example 3Based in FORMULA 2

(6) TABLE-US-00006 Component Component Weight Percent PG 64-22 Bitumen 50-55% SBS, SIS, SEBS (or Rubber In various weight blends thereof) ratios such that the Polymeric MDI NCO-terminated overall weight % is polymeric less than or equal to diisocayante 20% PPG 2000 2000 MW polyol Voranol 220-530 500 MW diol CaCO.sub.3, Aluminum Filler, flame 30-41% trihydrate, Ammonium retardant polyphosphate Naphthenic process oil Process oil 1-3%

(7) One non-limiting method for creating the composition of Formula 2 and Example 3 is to first blend the SBS, SIS, and/or SEBS or blend thereof into molten asphalt, followed by the fillers. Once the rubber/asphalt blend is fully associated, the polymeric diisocyanate follows, but the prepolymer can be extended ahead of time with a polyol blend, but is not necessary. Reaction temperature should remain between 160-179.4 C. (320-355 F.); higher temperature increases the risk of gelation.

(8) Table 1 shows physical properties observed in modified bitumen roofing membranes made with the aforementioned formulations compared to a control produced using conventional processes.

(9) TABLE-US-00007 TABLE 1 Physical Properties Observed With Invention vs. Control Component Control Example 1 Example 2 Example 3 Softening Point 272 F. 400 F. 400 F. 290 F. (ASTM D3461, F.) Penetration 20 dmm 21 dmm 31 dmm 22 dmm (ASTM D5, Units) Compound Stability Pass 225 F. Pass 225 F. Pass 225 F. Pass 220 F. (ASTM D5147) Granule Loss (%, Dry, 4% 0.7% 0.9% 2% ASTM D4977) Aged Appearance Some cracking, No cracking, No cracking, No cracking, 4000 hours in Q-Sun shrinkage, sagging. shrinkage, shrinkage, shrinkage, Weathering Some blisters sagging, sagging, sagging, blisters blisters blisters Low Temperature Pass 50 F. Pass 10 F. Pass 20 F. Pass 30 F. Flexibility Granule Loss after 6% 1% 1% DNT 4000 h Exposed in Georgia (%, Dry, ASTM D4977) Granule Loss after 7% 1% 1% DNT 4000 h Exposed in California (%, Dry, ASTM D4977) DNT: Did not test

(10) Table 1 shows that for the membrane made using Example 1, wherein only polyurethane comprised the total polymer content, the softening point increased to 400 F., which translates to improved high temperature sag resistance. In fact, even when exposed to 300 F., the membrane made with Example 1 did not show any signs of sag or mineral loss, while the control softened to the point where flow occurred. However, the membrane retained its flexibility at low temperature. The mineral roofing membrane created with Example 3 had properties closer to that of the Control. This is to be expected as the asphalt will take on properties of both polymers.

(11) ASTM D412 Stress-Strain Testing of QUV-Aged Films

(12) To demonstrate the resistance to aging of the invention made by the Examples (specifically Example 1), films of just the modified bitumen were placed into a QUV chamber for 3000+ hours and tested at 500 hour intervals to determine peak stress values. At these intervals, 1 wide strips were cut and pulled on a tensile tester until failure. Graph 1 shows the results.

(13) The data in FIG. 1 shows that prior to 2000 hours there is a steady increase in strength which occurs as a result of UV-induced crosslinking reactions that can occur in both traditional rubber and urethanes. Significantly, beyond 2000 hours there is a 13% decrease in strength in the urethane compared to a nearly 40% decrease in strength with the conventional modified bitumen as the films are continually exposed in the intense UV-rich environment. This trend continues with little change to 3000 hours.

(14) ASTM 4977 Scrub TestingMineral Loss

(15) The mineral retention properties of the membrane made by the Examples (specifically Example 1), show significant improvement over the conventionally produced roofing membrane. When the substrates were aged over 4000 hours in California and Georgia, mineral retention in Example 1 was 6-7 times better than the conventional roofing membrane. To further test the invention's mineral retention, specimens of mineral roofing membranes made with Example 1 were soaked for 72 hours in water, and then a granule loss test was performed on the wet aged samples alongside a control similarly conditioned. The results are shown in FIG. 2.

(16) Wet vs. Dry Scrub Test Results

(17) Wet scrub testing was not performed on Example 2. The data in FIG. 2 clearly shows that Example 1 has an eight-fold improvement in mineral retention vs. the conventional mineral cap sheet. When tested dry, Examples 1 and 2 still show a three-fold improvement in mineral loss.

(18) ASTM D4798 Cycle A-1 Weathering

(19) As a demonstration of the improved weatherability of the invention, environmental aging was performed in a Q-Sun Model XE-3-HS (Q-Lab). Exposures of the non-limiting examples of the invention verses a similarly prepared convention mineral cap sheet show that, after more than 4000 hours subjected to ASTM D4798 Cycle A-1, wherein the prepared panels were subjected to a continuous hourly cycle consisting of a 51-minute light only exposure of noon day sun at 60 C. at equilibrium, followed immediately by a 9-minute period of light/water spray, Examples 1 and 2 show no signs of blistering or surface defects, while the conventional mineral cap sheet had begun to show signs of small blisters on the surface.

(20) It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the constructions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. The invention has been described with reference to preferred and alternate embodiments. Modifications and alterations will become apparent to those skilled in the art upon reading and understanding the detailed discussion of the invention provided herein. This invention is intended to include all such modifications and alterations insofar as they come within the scope of the present invention. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.