Blown asphalt compositions

The invention relates to a method of making a compatible, block copolymer modified bituminous composition. The invention also relates to bituminous compositions comprising selectively hydrogenated block copolymers and their use in roof shingles.

BACKGROUND

In shingle applications, there is a need for increased flexibility to improve wind damage resistance and increased impact resistance to improve hail damage resistance. Previous improvements involving styrene block copolymer / asphalt blends have made advances in this area. U.S. Patent 4405680 teaches polymer modified shingles where a blend of unblown, compatible asphalt and an SBS-styrene block copolymer has been prepared. The glass mat substrate of the clapboard was impregnated with this mixture. In order to achieve the required resistance, however, the shingle was covered with a relatively high penetration index (PEN) blown asphalt.

In the blowing process, asphalt is oxidized by passing an oxygen-containing gas through the asphalt. This process serves to increase the asphaltene content, introduce ester functionality and increase molecular weight. These are all factors that lead to incompatibility with styrene block copolymers. Thus, while the blowing process increases the stiffness and softening point of the asphalt, it also makes the asphalt less suitable for blending with styrene block copolymers. Blends of styrene block copolymers and blown asphalt generally have poor storage stability, with the block copolymer separating from the blend over time. Furthermore, the conditions for blowing are harsh in that high temperatures and high oxidative conditions are used. This leads to severe degradation of SBS-like polymers.

However, methods have been developed, as taught in U.S. Patents 5,939,474 and 6,060,542, in which blends of styrene block copolymers and asphalt are blown. These processes require a blow catalyst to run the blow under conditions suitable for block copolymers. Even with mild conditions and blown catalysts are nonetheless

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hydrogenated SEBS-like block copolymers have been found to be unsuitable as taught in U.S. Patent 5342866. ·

There is still a need for stable, blown, polymer [modified, high polymer bituminous compositions and methods of making them which do not require blown catalysts. Such an improvement would result in shingles with excellent field performance and resistance to mechanical damage such as abrasion during roof installation and repair using simple and economical methods. The present invention provides a method and material suitable for block copolymer modified shingle making comprising a blown mixture of asphalt and a SEBS-like block copolymer which has a high PEN and maintains its flexibility and impact resistance. |

SUMMARY OF THE INVENTION l

The present invention relates to a method for producing a bituminous composition comprising 1

i) Heating 100 parts by weight of bitumen to at least |

375 ° F (190.56 ° C) I ii) Adding 6 to 25 parts by weight of a selectively hydrogenated block copolymer having at least one A block from a polymerized monoalkenyl arene and at least one B block from | a polymerized and hydrogenated conjugated diene, b iii) stirring the mixture using a low shear mixer; and iv) bubbling an oxygen-containing gas through the mixture at a gas flow rate of at least 5 liters per minute (lpm) for a time of at least 75 minutes in the absence of a blowing catalyst.

Another embodiment of the present invention is a stable, polymer-modified bituminous composition made by the invention process having a softening point of at least 190 ° F (87.78 ° C).

Another embodiment of the present invention is a shingle comprising the stable, polymer-modified, bituminous composition made by the invention.

DESCRIPTION OF THE FIGURES

FIG. 1 shows a predictive contour diagram of the softening point (° F) at various polymer contents and blowing times. The prediction is for the examples of the invention blown at 500 ° F (260 ° C) and an air flow of 14 lpm.

FIG. 2 shows a predictive contour diagram of the penetration (units) at different polymer contents and blowing times. The prediction is for the examples of the invention blown at 500 ° F (260 ° C) and an air flow of 14 lpm.

Figure 3 shows a predictive contour plot of viscosity (cps) at 400 ° F (204.44 ° C) at various polymer levels and blowing times. The prediction is for the examples of the invention blown at 500 ° F (260 ° C) and an air flow of 14 lpm. DETAILED DESCRIPTION OF THE INVENTION

In the process of the present invention, bitumen (alternatively referred to as asphalt) is heated to at least 375 ° F (190.56 ° C). Below this temperature the bitumen is too viscous to work with and does not easily include added block copolymer. In a preferred embodiment, the bitumen is heated to a temperature from 375 ° F (190.56 ° C) to 525 ° F (273.89 ° C).

From 6 to 25 parts by weight of a block copolymer are added to the heated bitumen based on 100 parts by weight of bitumen. Only low shear mixing is required. Surprisingly, it has been found that the action of blowing results in easy entrapment of the relatively high molecular weight block copolymers. While high shear mixing could be used, it is not necessary to achieve the modified bituminous compositions. Typical low shear mixers are screw-type or paddle-type mixers. More preferred amounts of block copolymer are 7 to 15 parts by weight based on 100 parts by weight of bitumen.

The present invention does not require the use of a blow catalyst or additive to increase entrapment of the block copolymer. The process does not use a blown catalyst.

In the blowing process, an oxygen-containing gas is forced through the bitumen block copolymer mixture. The oxygen-containing gas is preferably air, but can be any other gas mixture or pure oxygen. The degree of blowing achieved depends in one respect on the speed of the gas flow. In one embodiment of the present invention the gas is air and the flow rate is at least 5 lpm per kg of the bitumen block copolymer mixture. In a preferred embodiment, the air throughput rate is from 5 to 50 and in a particularly preferred embodiment from 5 to 25 lpm per kg of the bitumen block copolymer mixture.

The degree of blowing also depends on the time that the bitumen block copolymer mixture spends at elevated temperature and under the flow of oxygen-containing gas. In one embodiment of the present invention, the blowing occurs for at least 75 minutes. In a preferred embodiment, the blowing occurs for from 75 to 360 minutes. In a most preferred embodiment, the blowing takes place for 75 to 240 minutes.

If either the temperature, gas flow, time, or the combination of these effects is excessive, then undesirable degradation of the block copolymer results. The conditions demarcated by the present inventive method result in block copolymer modified bituminous compositions which experience minimal degradation and beneficial properties for shingle applications.

One of the advantageous properties of bituminous compositions produced by the process of the invention is the homogeneity of the mixture. In the context of the present invention, homogeneity means that the block copolymer is so finely dispersed in the bitumen that the mixture appears smooth and uniform. The block copolymer can be dissolved in the bitumen or can be held as a microscopically dispersed mixture, depending on the temperature and the degree of blowing.

If the bituminous composition is not homogeneous, it will have a grainy or lumpy appearance. In extreme cases, which are not desired in the present invention, the mixture can form separate layers or areas of block copolymer and bitumen.

Another advantageous property of bituminous compositions produced by the process of the invention is the stability of the mixture. In the context of the present invention, stability means maintaining the state of homogeneity during the roofing shingle manufacturing process. If ··

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• ·· ··· * ·· ·· · • · · · · · · · · · · · · ··· ···· ··· ·· φφ

If a block copolymer-modified bituminous composition is designated as "compatible, it is meant that the composition has these characteristics of homogeneity and stability.

The monoalkenyl arene monomers of the selectively hydrogenated block copolymer can be selected from styrene, alphamethyl styrene, paramethyl styrene, vinyl toluene, vinyl naphthalene and parabutyl styrene, or mixtures thereof. Of these, styrene is most preferred and is commercially available from a variety of manufacturers and is relatively inexpensive. The conjugated dienes for use herein are 1,3-butadiene and substituted butadienes such as isoprene, piperylene, 2,3-dimethyl-1,3-butadiene and 1-phenyl1,3-butadiene, or mixtures thereof. Of these, 1,3-butadiene is most preferred. As used herein and in the claims, "butadiene specifically refers to" 1,3-butadiene.

Polymerization conditions to prepare the novel copolymers of the present invention are typically similar to those used for anionic polymerizations in general. In the present invention, polymerization is preferably carried out at a temperature of about -30 ° to about 150 ° C, more preferably about 10 ° to about 100 ° C, and particularly preferably about 30 ° to about 90 ° C in view of industrial restrictions. It is carried out in an inert atmosphere, preferably nitrogen, and can also be carried out under pressure within the range from about 0.5 to about 10 bar. This copolymerization generally takes less than about 12 hours and can take from about 5 minutes to about 5 hours, depending on the temperature, the concentration of the monomer components, the molecular weight of the polymer, and the amount of

Means of distribution that is employed can be accomplished.

Production of radial (branched) polymers requires a post-polymerization step, called “coupling,” In the above radial (radical) formula, n is an integer from 2 to about 30, preferably from about 2 to about 15 and particularly preferably from about 2 to about 4 and X stands for remnants or residues of a coupling agent. A variety of coupling agents are known in the art and include, for example, dihaloalkanes, silicon halides, siloxanes, multifunctional epoxides, silicon dioxide compounds, esters of monohydric alcohols with carboxylic acids, and epoxidized oils. Star-shaped polymers who ·· • · ·· ··

-βάθη made with polyalkenyl coupling agents, as in, for example, US Pat. Nos. 3,985,830; 4391949 and 4444953; Canadian Patent Number 716645. Suitable polyalkenyl coupling agents include divinylbenzene and preferably m-divinylbenzene. Tetraalkoxysilanes such as tetraethoxysilane (TEOS), aliphatic diesters such as dimethyl adipate and diethyl adipate and diglycidyl-aromatic epoxy compounds such as diglycidyl ether, derived from the reaction of bisphenol A and epichlorohydrin, are preferred.

The monoalkenyl arene blocks of the present invention range in molecular weight from 5,000 to 30,000. The preferred range is from 5,000 to 20,000, and the most preferred range is from 5,000 to 10,000. The total molecular weight of the block copolymer, whether linear or coupled, is from 50,000 to 300,000. The preferred range is from 60,000 to 200,000, and the most preferred range is from 70,000 to 100,000.

As used herein, the term "molecular weights" refers to the actual molecular weight in g / mol of the polymer or block of the copolymer. The molecular weights referred to in this specification and claims can be measured by gel permeation chromatography (GPC) using polystyrene calibration standards as performed in accordance with ASTM 3536. GPC is a well known process in which polymers are separated according to their molecular size, with the largest molecule eluting first. The chromatograph is calibrated using commercially available polystyrene molecular weight standards. The molecular weight of polymers measured using GPC thus calibrated are styrene-equivalent molecular weights. The styrene equivalent molecular weight can be converted to actual molecular weight if the styrene content of the polymer and the vinyl content of the diene segment are known. The detector used is preferably a combination of an ultraviolet and a refractive index detector. The molecular weights expressed herein are measured at the peak of the GPC trace, converted to actual molecular weights, and are commonly referred to as "peak molecular weights."

The monoalkenyl arene content of the present invention is from 15 to 50% by weight. The preferred bandwidth is from 20 to 40 «· · ·· · ♦ ·· ········· · • · · · · ··· ·· * • t · · · · · · · • · · ♦ ······· 009 ···· 999 90 99

- Ί wt% and the most preferred range is from 25 to 35 wt%.

An important aspect of the present invention is the microstructure of the block copolymer. The microstructure relevant to the present invention is a high amount of vinyl in the conjugated diene blocks. In the case of 1,3-butadiene, a vinyl configuration of 1,2-addition results during polymerization. In the case of isoprene, a vinyl configuration of 3.4 addition results during polymerization. The vinyl structure of other conjugated dienes can be understood as analogous to these two examples. The vinyl configuration can be achieved through the use of a microstructure control agent during the polymerization of the diene. A typical agent is diethyl ether. See US Patent No. Re 27145 and US Patent No. 5777031, the disclosures of which are hereby incorporated by reference. Any microstructure control agent known to those skilled in the art of making block copolymers can be used to make the block copolymers of the present invention.

In the practice of the present invention, the block copolymers are made to have from about 20 to about 80 mole percent vinyl in the conjugated diene blocks prior to hydrogenation. In a preferred embodiment of the present invention the vinyl content is from 30 to 75 mol% and in a particularly preferred embodiment the vinyl content is from 35 to 70 mol%.

The preferred embodiment of the present invention comprises a hydrogenated block copolymer. The preferred hydrogenation is selective hydrogenation of the diene portions of the final block copolymer. Hydrogenation can be carried out by any of several hydrogenation or selective hydrogenation processes known in the art. For example, such hydrogenation has been accomplished using methods such as those described in, for example, U.S. Patents 3,595,942; 3634549; 3670054; 3700633 and Re. 27145, the disclosures of which are incorporated herein by reference.

Hydrogenation can be carried out under conditions such that at least 90 percent of the conjugated diene double bonds have been reduced and between zero and 10 percent of the arene double bonds have been reduced. Preferred bandwidth ·· * · • · ·

·· ·&lt;· ···· ·· ·· • 9

999 9··

9 · 9 • · · ·

99 At least about 95 percent of the conjugated diene double bonds are reduced, and more preferably about 98 percent of the conjugated diene double bonds are reduced. Alternatively, it is possible to hydrogenate the polymer so that aromatic unsaturation is also reduced beyond the above-mentioned 10 percent level. Such exhaustive hydrogenation is usually achieved at higher temperatures. In that case, the double bonds of both the conjugated diene and arene can be reduced by 90 percent or more.

The bituminous component, also known as asphalt, which is present in the bituminous compositions according to the present invention can be a naturally occurring bitumen or derived from petroleum. Petroleum pitch and coal tar obtained by a cracking process can also be used as the bituminous component, as can mixtures of various bituminous materials. Examples of suitable constituents include distilled or straight-run bitumen, precipitated bitumen, eg propane bitumen, blown bitumen, eg catalytically blown bitumen or “Multiphalt” and mixtures thereof. Other suitable bituminous constituents include mixtures of one or more of these bitumens with extenders (fluxes) such as petroleum extracts, for example aromatic extracts, distillates or residues, or with oils. Suitable bituminous constituents (either "straight run bitumen or" flux bitumen) are those with a penetration in the range of 50 to 300 units (equivalent to decimillimeters, dmm) at 25 ° C. In applications where the flexibility, tack or adhesion of the product is of great importance, such as in roofing shingle applications, flux bitumens with penetrations in the range of greater than 300 units at 25 ° C are particularly useful.

The polymer modifier is suitably present in the bituminous composition in an amount ranging from 6 to 25 parts by weight based on 100 parts by weight for bitumen. Inclusion of block copolymers causes the bitumen to change from viscous to viscoelastic. This change in properties generally takes place with polymer contents in the range from about 0.5% to about 8%. With higher polymer contents, which range up to about 25%, substantial increases in flexibility and elastic strength can be achieved

4 · 4 • 4 4 4

44 will. This is particularly interesting for roofing shingles, roofing felt, asphalt adhesives and waterproofing membranes.

The bituminous composition may also optionally contain other ingredients as required for the intended end use. Thus fillers can be included, for example talc, calcium carbonate and carbon black, or other ingredients including resins, oils, stabilizers or flame retardants can be included. The content of such fillers and other ingredients can range from 0 to as much as 99 percent by weight. Of course, if advantageous, other polymer modifiers can also be included in the bituminous composition of the invention.

The penetration indices of the bituminous composition of the present invention suitable for shingle manufacture are critical in determining shingle performance. Typical shingle grade asphalt has a penetration of less than 20 units at 25 ° C, a ring-and-ball softening point of less than 200 ° F (93.33 ° C), and a viscosity of less than 1500 cps at 400 ° F (204.44 ° C). Typical shingle grade asphalts with penetration indices less than 20 units are stiff and prone to breakage. As a result, they are more likely to fail tests conducted in accordance with UL 2218 regulations. Softer asphalts or modified asphalts can be used which have penetration indices greater than 30 units at 25 ° C. However, they are generally too soft to be practical and are likely to suffer abrasion damage during use. In the present invention, the bituminous composition comprising a block copolymer is blown in a controlled manner to achieve a preferred penetration of 20 to 30 units at 25 ° C and a softening point of at least 190 ° F (87.78 ° C).

The shingles of the present invention comprise from 30 to 50% by weight of the polymer modified bituminous composition, from 50 to 65% by weight of an inert filler, and from 1 to 10% by weight of a nonwoven glass mat. In the manufacturing process, the filler is added to the bituminous composition and this mixture is used to coat the non-woven glass mat. The shingle surface is also coated with inert granules to ensure durability, ability to represent • 4 © · ··· 444 · 4 «• 4 · 4 ·· ·· ·· ♦ · • · • · • 4444

- 10 to run on, provide an attractive finish and prevent blockage during storage and shipping.

EXAMPLES

Test procedure

Penetration of the pure bitumen and polymer modified bitumen was measured according to ASTM D 5. The ring and ball softening point of the polymer modified bitumen was measured according to ASTM D36. Viscosities were measured using a Brookfield viscometer.

materials

SEBS was a linear styrene-ethylene / butylene-styrene block copolymer with a total molecular weight of 80,000 and a polystyrene content of 30%.

SBS was a coupled, linear styrene-butadiene-styrene block copolymer with a total molecular weight of 120,000, a coupling efficiency of 84%, and a polystyrene content of 28%.

The tarmac was Hunt AC5. Unmodified, AC5 has a viscosity of 500 poise at 140 ° F (60 ° C), a PEN of approximately 150 units, a ring-and-ball softening point in the range of 40 to 50 ° F (4.44 to 10 ° C) .

Example 1 and Comparative Examples CI and C2

900 Grams of asphalt were heated to 400 ° F (204.44 ° C). Polymer (SEBS or SBS) was then added at 7% by weight and stirred manually using a paddle. The polymer / asphalt mixture was then added to a 2 gallon (9.1 L) blowing still, preheated to 500 ° F (260 ° C). The mix temperature was stabilized at 500 ° F (260 ° C) and air bubbling was started at 20 liters per minute (lpm). The mixture was stirred using an air driven low shear impeller while sparging continued at 500 ° F (260 ° C) for 120 minutes. The polymer modified asphalt was then drained from the still. In both cases of Inventive Example 1 and Comparative Example C1, the resulting mixture was homogeneous and the block copolymer was completely dispersed in the asphalt.

Table 1 shows the composition and process conditions.

Table 2 shows the resulting physical properties · • · • · • ft • ftftft • ·· ·· • ft «· • ··· ··· • · · · · • · · · · • ft · ·· ··

- 11 shafts of bituminous composition.

It was used for both example 1 and comparative example

Cl achieved similar softening points. However, the PEN of the SBS sample is far too low for good impact resistance and as such is unsuitable for roofing shingles. Analysis by GPC showed that the SBS polymer was completely degraded by the blowing process. In contrast, GPC analysis of the samples containing SEBS polymer showed minimal degradation of the block copolymer. The blowing process included the selectively hydrogenated polymer under conditions of only mild mechanical mixing to form a homogeneous bituminous composition with properties suitable for roofing shingles.

TABLE 1

<td>example</td><td>polymer</td><td>Temp ° F (° C)</td><td>Time Min.</td><td>Polymer content, wt .-%</td><td>Airflow, lpm</td>

<td> 1</td><td>SEBS</td><td> 500 (260)</td><td> 120</td><td> 7</td><td> 20</td>

<td>Cl</td><td>SBS</td><td> 500 (260)</td><td> 120</td><td> 7</td><td> 20</td>

<td>C2</td><td>no</td><td> 500 (260)</td><td> 210</td><td> 0</td><td> 20</td>

TABLE 2

<td>sample</td><td>PEN, units</td><td>R&amp;K ° F (° C)</td><td>Vis. at 400 ° F (204.44 ° C), cps</td><td>Vis. at 425 ° F (218.33 ° C), cps</td><td>Vis. at 475 ° F (246.11 ° C), cps</td>

<td> 1</td><td> 26</td><td> 226 (107,78)</td><td> 1390</td><td> 932</td><td> 445</td>

<td>Cl</td><td> 8</td><td> 220 (104,44)</td><td> 1370</td><td> 748</td><td> 290</td>

<td>C2</td><td> &lt;12</td><td> 220 (104,44)</td><td> —</td><td> —</td><td> —</td>

Examples 2-7 and Comparative Examples C3-C6

Block copolymer modified asphalt mixes were prepared according to the procedure of Example 1 with the variations shown in Table 3. In all cases the resulting mixture was homogeneously dispersed throughout the asphalt with the polymer.

··

9

99 9 99 99 ·«···©· 9

9 9 9 9 999 999

9 9 9 9 9 ^9

9 9 9 9 9 *99

999 9999 999 99 99

- 12 TABLE 3

<td>example</td><td>Temp. ° F (° C)</td><td>Time, min.</td><td>SEBS salary, Wt%</td><td>Airflow, lpm</td>

<td> 2</td><td> 525 (273,89)</td><td> 90</td><td> 10</td><td> 8</td>

<td> 3</td><td> 525 (273,89)</td><td> 210</td><td> 10</td><td> 20</td>

<td> 4</td><td> 475 (246,11)</td><td> 90</td><td> 10</td><td> 20</td>

<td> 5</td><td> 475 (246,11)</td><td> 210</td><td> 10</td><td> 8</td>

<td> 6</td><td> 500 (260)</td><td> 150</td><td> 7</td><td> 14</td>

<td> 7</td><td> 500 (260)</td><td> 150</td><td> 7</td><td> 14</td>

<td>C3</td><td> 475 (246,11)</td><td> 90</td><td> 4</td><td> 8</td>

<td>C4</td><td> 475 (246,11)</td><td> 210</td><td> 4</td><td> 20</td>

<td>C5</td><td> 525 (273,89)</td><td> 90</td><td> 4</td><td> 20</td>

<td>C6</td><td> 525 (273,89)</td><td> 210</td><td> 4</td><td> 8</td>

The series of experiments in Table 3 represents a partial factorial scientific design. The resulting physical properties are listed in Table 4. Simple linear regressions with an R-squared correlation greater than 90% were obtained for correlations of penetration, softening point, and viscosity. Figures 1, 2 and 3 show the predictive contour graphs obtained.

The Inventive Examples demonstrated that polymer levels greater than 4% by weight were required to produce suitable block copolymer modified compositions with softening points of at least 190 ° F (87.78 ° C). These examples of the invention had penetrations in the range of 22 to 29 units at 25 ° C and viscosities in the range of 390 to 1250 cps at 400 ° F (204.44 ° C).

TABLE 4

<td>sample</td><td>PEN, units</td><td>R&amp;K ° F (° C)</td><td>Vis. at 400 ° F (204.44 ° C), cps</td><td>Vis. at 440 ° F (226.67 ° C), cps</td><td>Vis. at 480 ° F (248.89 ° C), cps</td>

<td> 2</td><td> 27</td><td> 205 (96,11)</td><td> 578</td><td> 315</td><td> 197</td>

<td> 3</td><td> 22</td><td> 213</td><td> 1250</td><td> 625</td><td> 360</td>

··

4

4

4

4

4444

44

4

444 444

4 · 4

4 · 4

44

<td></td><td></td><td> (100,56)</td><td colspan="2"></td><td></td>

<td> 4</td><td> 27</td><td> 212 (100)</td><td> 578</td><td> 330</td><td> 197</td>

<td> 5</td><td> 25</td><td> 211 ( (99, 44)</td><td> 427</td><td> 230</td><td> 138</td>

<td> 6</td><td> 29</td><td> 203 (95)</td><td> 573</td><td> 317</td><td> 188</td>

<td> 7</td><td> 28</td><td> 192 (88,89)</td><td> 390</td><td> 215</td><td> 130</td>

<td>C3</td><td> 42</td><td> 168 (75,56)</td><td> 110</td><td> 65</td><td> 40</td>

<td>C4</td><td> 26</td><td> 189 (87,22)</td><td> 340</td><td> 183</td><td> 105</td>

<td>C5</td><td> 21</td><td> 176 (80)</td><td> 190</td><td> 105</td><td> 65</td>

<td>C6</td><td> 29</td><td> 175 (79,44)</td><td> 200</td><td> 112</td><td> 68</td>

Examples - impact resistance

Block copolymer modified asphalt mixes were prepared according to the procedure of Example 1. The impact resistance of the blends was measured according to ASTM D 5420: 3 mm panels were cast from molten blends, the samples were allowed to cool to room temperature, sample disks were cut, impact was tested using a 1.2 lb (544.32 g) dart and the Height required to break the sample was recorded. Table 5 presents the results. The control sample, which did not contain any polymer modifier (C2), failed at a 3 inch throw. Addition of SEBS in accordance with the inventive method gave strike heights as large as 40 inches (101.60 cm).

TABLE 5

<td>sample</td><td>Polymer content, wt .-%</td><td>Stroke height, In. (cm)</td>

<td>C2</td><td> 0</td><td> 3 (7,62)</td>

<td>C5</td><td> 4</td><td> 25 (63,50)</td>

<td> 6</td><td> 7</td><td> 15 (38,10)</td>

<td> 3</td><td> 10</td><td> 40 (101,60)</td>

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