Modified bituminous composition for roof membranes

• US 6,579,921 B1
• Filed: 09/24/2001
• Issued: 06/17/2003
• Est. Priority Date: 01/27/1999
• Status: Expired due to Fees

• Current Assignee: Polyphalt Inc.
• Original Assignee: Polyphalt Inc.
• Inventors: Zhang, Yan-Ping, Liang, Zhi Zhong
• Primary Examiner(s): SZEKELY, PETER A
• Application Number:
  US09/890,107
• Time in Patent Office: 631 Days
• Field of Search: 524/68, 524/71, 428/147
• US Class Current: 524/68
• CPC Class Codes: C08L 2666/24 Graft or block copolymers according to groups C08L51/00, C08L53/00 or C08L55/02; Derivatives thereof
• CPC Class Codes: C08L 53/00 Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
• CPC Class Codes: C08L 95/00 Compositions of bituminous materials, e.g. asphalt, tar, pitch
• CPC Class Codes: D06N 5/00 Roofing materials comprising a fibrous web coated with bitumen or another polymer, e.g. pitch compositions of bituminous materials C08L95/00, roof covering E04D5/00, roofing underlays E04D12/002
• CPC Class Codes: E04D 5/02 of materials impregnated with sealing substances, e.g. roofing felt
• CPC Class Codes: Y10T 428/24405 Polymer or resin [e.g., natural or synthetic rubber, etc.]

Abstract

Roofing membranes are provided with both high stiffness at high temperature (greater than 110 ° C.) and good flexibility at low temperature (less than −20 ° C.). Bituminous compositions may be more effectively used in such membranes at lower elastomer concentration than currently practiced, using conventional cross-linking reagents to prepare the modified bituminous compositions with a range of viscosities that are readily processed as compared with conventional non-cross-linked systems.

Claims

1. A roofing membrane having cold flexibility below about −

20°

C. and high flow resistance above about 110°

C., comprising a matrix-filled fibrous substrate and a filled elastomer-modified bituminous composition comprising about 10 to about 30 wt % of said composition of a mineral filler and a bituminous composition comprising bitumen and about 8 to 13 wt % of said bitumen of an elastomer having a conjugated diene structure cross-linked to an extent to permit a reduction of about 10 to 20 wt % in the amount of elastomer in the bituminous composition for the same low and high temperature properties or a concomitant improvement in low and high temperature properties at the same amount of elastomer.

2. The roofing membrane of claim 1 wherein said elastomer is employed in an amount of about 10 to 12 wt %.

3. The roofing membrane of claim 1 wherein said filler is employed in an amount of about 15 to about 25 wt %.

4. The roofing membrane of claim 1 wherein said elastomer is a styrene-butadiene-styrene polymer.

5. The roofing membrane of claim 1 wherein said elastomer is cross-linked using a cross-linking agent in a minimum amount such that the desired high temperature stiffness level is achieved at the lower amount of elastomer and in a maximum amount with the low temperature flexibility is not impaired at the lower amount of elastomer.

6. A method of forming a roofing membrane comprising a filled bituminous composition, which comprises:

(a) fully dispersing into bitumen an elastomer having a conjugated diene structure in an amount of about 8 to about 13 wt % of the bitumen,

(b) dispersing a cross-linking reagent for said elastomer in a predetermined amount depending on the reagent used,

(c) permitting said cross-linking reagent to cross-link said elastomer while minimizing the incorporation of air into the composition,

(d) blending a mineral filler in an amount of about 10 to about 30 wt % of the composition to provide a filled bituminous composition, and

(e) forming a roofing membrane from said filled bituminous composition having about 10 to 20 wt % less elastomer in the bitumen for the same low and high temperature properties or a concomitant improvement in low and high temperature properties for the same amount of elastomer.

7. The method of claim 6 wherein said cross-linking agent is elemental sulfur and is used in an amount of about 0.05 to about 0.2 wt %.

8. The method of claim 7 wherein the amount of elemental sulfur employed is about 0.1 to about 0.15 wt %.

9. The method of claim 6 wherein said cross-linking agent is phenol-formaldehyde and is used in an amount of about 0.1 to about 0.25 wt %.

10. The method of claim 9 wherein the amount of phenol-formaldehyde used is about 0.15 to about 0.20 wt %.

11. The method of claim 6 wherein said elastomer is used in an amount of about 10 to about 12 wt %.

12. The method of claim 6 wherein said filler is employed in an amount of amount of 15 to about 25 wt %.