CA1183986A - Bitumen, atactic polypropylene and propylene/ethylene copolymer compositions and water-proofing membranes using the same - Google Patents

Abstract

A B S T R A C T

This invention relates to a novel bitumen mixture and a high performance prefabricated waterproofing membrane useful for roofing which is obtained by impregnating differ-ent layers of reinforcing material with the bitumen mixture.
More particularly, the invention relates to a novel bitumen mixture and a waterproofing membrane comprising a series of reinforcing layers including a polyester mat, a mat of fiberglass and a fiberglass net. Each reinforcing layer is impregnated with bitumen mixed with a thermoplastic polymer wherein the polymer is selected from the group consisting of an amorphous copolymer of ethylene/propylene, atactic polypropylene, polyisobutylene and styrene-butadiene-styrene block copolymer. The mixture has a ring and ball softening point of at least 105°C and preferably about 155°C.

Description

This invention relates to a novel bitumen mixture and a high performance prefabricated waterproofing membrane useful for roofing which is obtained by impregnating differ-ent layers of reinforcing material with the bitumen mixture.
More particularlyl the invention relates to a novel bitumen mixture and a waterproofin~ membrane comprising a series of reinforcing layers including a polyester ma~, a mat of fiberglass and a fiberglass netO Each reinforcing layer is im~regnated with bitumen mixed ~ith a thermoplastic polymer wherein the polymer is selected from the group consisting of an amo~phous copolymer of ethylene/propylene, atactic polypropylene, polyisobutylene ar.d styrene-butadiene-stvrene block copolymer. The mixture has a minimum ring and ball softening point of about 105C and preferablv 155C.
Preferably the bitumen contains amorphous ethylene/propylene copolymer, a mixture of atactic polypropylene polymer and ethylene propylene copolymer containing mineral acid and isotactic polypropylene.
For almost a century bituminous roofing membranes have been used in the United States to protect buildings, their contents and the occupants from the weather. The most common type of bituminous roofing membranes consist of two to five layers of felt or fabric which during application to the roof are made to adhere together with bituminous material, such as tar, pitch or asphalt. The fabrics or felts may contain organic material, asbestos or ~lass. In general, these types of roofing membrane have been the source of problems for manufacturers of the membrane r roof designers, appliers and users. The incidence of failures in flat roof waterproofing membranes has increased in the order of 30 percent in that time period. The problems have been ~0 attributed in part to poor design, inadequate materials and improper workmanship! but many believe that the problem is more fundamental.
Conventional roofing membranes were originally developed in order to cover concrete and wood roofs which formed a relatively stable rigid base for the roofing mem-brane. Today roofs are be;ng made of more flexible light-weight material and are often formed from prefabricated sheets or panels many of which have highly e~ficient thermal insulationO These changes in the thermal properties of the building materials have completely altered the temperature environment of the roofing membrane. This thermal change coupled with resulting movement in the joints of the roof and the insulation, places substantial local stress on con-ventional roofing membranes which were originally designedwith relatively low tensile strength and elasticity.
An additional problem associated with traditional roo~ing material is that it requires about 12 lbs/m2 of bitumen or other petroleum based products. Due ~o the high cost of petroleum and the efforts to conserve petroleum, it is also desirable to decrease the amount of petroleum based products used in roofing membranes.
Some attempts by others in the roofing field to produce an improved roofing material are described in U.S.
Patent Nos. 3,741,856; 3,753,938 and 3,937,640. U~S. Patent No. 3,741,856 to Hurst issued January 26, 1973, describes a bitumen waterproofing sheet which has a polyethylene support layer and a pressure sensitive adhesive backing. The Montague patent, U.S. 3t753r938, issued August 21, 1973, descri~es a special roofing material which contains a mixture of bitumen, a synthetic elastomeric material which is predominantly chlorosulphonated polyethylene and fibrous material such as filaments of fiberglass or other synthetic bituminous roofing membrane comprising a base sheet of a synthetic polymer and one or more layers of bitumen. Tn addition, another roofing membrane has been developed in Europe in an attempt to meet the new requirements of modern roof construction and is the subject of patents in Luxembourg (No. 69480), France (NoO 7505703) and Italy (20554A/75).

(See also Impermeabilizzazione Delle Construzioni, Romolo Gorgati, 1974 pp. 63-64). The preEabricated roofing membrane developed in Europe contains a polyester mat and a fiber-glass mat both impregnated with polymer modi~ied bitumen.
Although this roofing material has performed satisfactorily in some applications, it does not have the necessary tensile strength, dimensional stability, resistance to puncture, oxidation and aging needed for demanding modern roofing applications.
It would be desirable to provide a bitumen mixture having superior mechanical and physical-chemical characteristics which meet the preliminary performance criteria for bituminous membrane roofing published by the United States Department of Commerce/National Bureau of Standards and to achieve these superior characteristics without substantially increasing the total weight, cost of the roofing membrane or the amount of petroleum based product used.
It is an object of this invention to provide a novel bitumen mixture and a novel waterproofing membrane which may mitigate at least some of the disadvantages previously encountered.
Accordingly, the invention provides a prefabricated waterproofing membrane which comprises a series of super-posed reinforcing layers including a fiberglass mat, a polyester mat and a fiberglass net, the layers being impregna-ted with bitumen mixed with at least one thermoplastic polymer selected from the group consisting of an amorphous copolymer of ethylene/propylene, atactic polypropylene, _. 4 polyisobu-tylene and styrene-butadiene-styrene block co-polymer, the bitumen polymer mixture having a ring and ball soEtening point of at least 105C wherein the bitumen poly-mer mixture is further modified by the addition of at least one polymeric material selected from the group consisting of a mixture of atactic polypropylene and ethylene propylene copolymer and a mixture of atactic polypropylene and ethylene propylene copolymer containing mineral oil.
Preferably the ring and ball softening point is at least 155C.
The invention also provides a novel bitumen mix-ture which comprises bitumen mixed with amorphous copolymer of ethylene and propylene modified by addition of at least one of a mixture of atactic polypropylene polymer and ethylene propylene copolymer and a mixture of atactic poly-propylene polymer and ethylene propylene copolymer contain-ing mineral oil.
A further aspect of the invention provides a prefabrica-ted waterproofing membrane which comprises a series of superposed reinforcing layers including a fiber-glass mat and a bonded fiberglass net/polyester mat, the layers being impregnated with bitumen mixed with at least one thermoplastic polymer selected from the group consist-ing of an amorphous copolymer of ethylene/propylene, atactic polypropylene, polyisobutylene and styrene-butadiene-styrene block copolymer, the bitumen polymer mixture having a ring and ball softening point of at least 105~C.
The improved waterproofing membrane is formed by the conventional method which is employed in Europe to manufacture European type roofing membranes. The polymeric i~

materials are melted and stirred in a heated au-toclave and the bitumen is added and blended for about 1-2 hours. In a second agita-ted autoclave additional bitumen and fillers are mixed for about 5-10 minutes at about 100-150C~ At the end of the mixing period the two mixtures are combined and homogenized to form the bitumen polymer mixture. The reinforcing layers are impregnated with the bitumen polymer mixture by passing the reinforcing layers through the bitumen !
polymer mixture, at about 175C, whereby the reinEorcing 10. layers and the bitumen polymer mixture adhere and interact with each other to form a single waterproofing membrane with superior mechanical and physical-chemical - 5a -I"

24141-~

characteristics over known waterproofing membranes~ The reinforcing layers are preferably positioned together at a point above the median point of the membrane close to the upper surface of the membrane in order that the bulk of the bitumen polymer mixture in the membrane which acts as the adhesive for the membrane is below the reinforcing layers and is thereby shielded from the sun's ultraviolet rays.
The bitumen polymer layer under the reinforcing layers is at least 1.5-2.5 mm thick. The preferred order of the re-in~orcing layers within the membrane is to have the fiber-glass mat closest to the surface, the fiberglass net in ~he center and the polyester mat beneath it.
The polyester mat, the inner most reinforcing layer weighs from about 50-250 y/m2 and (1) distributes internal tensions in the membrane and (2) improves the impact resistance of the membrane. Moreover, the polyester mat permits the membrane to remain impermeable to water even if the outer fiberglass mat and fiberglass net are ruptured by an external force. The fiberglass mat weighs about ~0~
125 g/m and, as the top reinforcing layer, provides thermal stability to the membrane both during manufacture and in application. It also serves to screen the membrane from ultraviolet rays and minimizes tearing due to the foo~
traffic associated with installation and maintenance.
The middle fiberglass net weighs about 60-100 y/m2 and adds additional stability to the waterproofing membrane without significantly increasing the thickness or weight of the membraneO The additional stability provided by the fiberglass net is needed in order to mlnimize movemen~ in 24141~A

the membrane due to thermal changes. The open weave of the net is from about 1 mm to 5 mm, and preferably about 3 mm, which allows the bitumen polymer mixture to flow through the net and provide good contact between the polyester mat below and the fiberglass mat above~ The addition of the fiber-glass net which has definite structure and rigidity as compared to the fibergla s mat improves tensile strength, but does not decrease the elongation at the break of the resulting membrane. Rather surprisingly, the presence of the fiberglass net tends to increase the elongation at break of th~ membrane.
In a preferred embodiment, the fiberglass net is made with fiberglass fibers containing about 20-25% poly-vinyl chloride threads and the glass net is heat fused directly to the polyester mat at a temperature of about 100C to form a single fiberglass net/polyes~er mat layer.
The polyvinyl chloride threads melt and serve to fuse the layers together. The resulting single layer is thinner than the combined thickness of the unfused polyester mat and fiberglass net. The single fused fiberglass net/polyester mat layer is then used as described above witEl the fiber-glass mat to form the waterproofing membrane.
Regardless of how the reinforcements are pre-pared, the resulting waterproofing membrane is about 4 cm thick. However, since the fused fiberglass net/polyester mat is thinner than when each layer is combined separately~
the resulting waterproofing membrane can contain more of the bitumen mixture below the reinforcing layers and still be about 4 mm thick. In addition the use of the fuse~ fiber-glass net/polyester mat allows for faster manufacturing speeds since the fusion step helps to eliminate the forma-tion of air bubbles between the fiberglass mat and the polyester mat during impregnation with bitumen.
Bitumen as used in making the novel waterproofing membrane is a solid or viscous semisolid mixture of hydro-carbons which is obtained from petroleum by distillation of the lighter hydrocarbons at atmospheric pressure. The ring and ball softening point of the bitumen can vary, but the most common range is between 30C and 110C. The ring and ball softening test is a standard test described in Impermeabilizzazione Delle Costruzione, Romolo Gorgati, 1974, pp. 13-14. The ring and ball softening poin~ of bitumen is the temperature at which a standard steel ball placed on a standard ring filled with bitumen penetrates into the bitumen. It is also known as asphalt and may also be obtained from the acid sludge produced by treating the heavy distillates of asphalt based petroleum with concen-trated sulfuric acid~
In or~er to improve the elasticity, flexibility, homogeniety, cold cohesion and aging of the resulting water proofing membrane, the bitumen is modified by mixing with a thermoplastic polymer such that the bitumen polymer mixture has a ring and ball softening point of at least 105C, and preferably about 155C.
Examples o~ suitable polymers or modifying bitumen are amorphous ethylene/propylene copolymers, atactic polypropylene, polyisobutylene and styrene-butadiene-styrene block copolymer~ Preferably, amorphous ethylene/propylene ;3~

block copolymer is used because of its high resistance to oxidation and its elasticity. Ethylene/propylene copolymer is usually, but not necessarily, a by-product of the produc-tion of polypropylene~ The preferred copolymer ha~ a S viscosity o~ about 0.3-25 million CPS (centipoise) at about 180C and contains from 0-40~ ethylene, preferably 20-30%, and may contain some atactic and isotactic polypropylene.
Prior to this invention, amorphous ethylene/propylene co-polymer had been considered to be of no industrial value because of the high viscosity and resulting fusion problems.
This invention takes these previously undesirable properties and utilizes them to prepare a bitumen mixture and a water-proofing membrane with superior mechanical and physical characteristics.
In the preferred embodiment, additional modifiers selected from the group consisting of atactic polypropylene, powdered rubber, isotactic polypropylene, a mixture of atactic polypropylene polymer and ethylene propylene co-polymer and a mixture of atactic polypropylene polymer and ethylene propylene copolymer containing mineral oil are added to the bitumen polymer mixture to further improve its characteristics. The mixture of atactic polypropylene polymer and ethylene polypropylene copolymer containing mineral oil, a by-product of the process for separating atactic and isotactic polypropylene, is the preferred additional modifier and is often used in the bitumen in combination with isotactic polypropylene. The mineral oil in the preferred modifier can be, for example, paraffin or one of its homologs. Powdered rubber which can also be used as an additional modifier in this invention is obtained from natural or synthetic rubber, or a mixture thereo~, and has a particle size of about 20-50 microns. Atactic polypro-pylene, another modifier, is obtained as a by-product of the process for producing isotactic polypropylene.
The preferred bitumen polymer mixture may also contain a plasticizer, for example, a paraFfin lubricating oil having an Engler viscosity lower than 10 at 50C. If the mixture of atactic polypropylene polymer and ethylene copolymer containing mineral oil is used, the plasticizer is not needed.
The preferred bitumen mixture also contains fillers to decrease oxidation and slow the aging of the waterproofing membrane. Suitable fillers have a particle size of about 10 to 75 microns, and may include, for example, spent lime (calcium hydroxide oxide), talc tmagnesium silicate Mg3Si4OlO(OH2), ground sand, ground slate, ground cement, diatomaceous earth, clay and titanium dioxide. Preferably, the filler is any inert absorbant material such as spent lime.
The novel bitumen mixture used to impregnate t.he reinforcement layers, and thereby to form the waterproofing membrane, contains about 50-70% bitumen, about 10-50%
- polymer and about 0-20~ fillers. The preferred bitumen mixture contains about 67% bit~men, about 24% polymers, and about 9~ fillers and additives~
The composition of the bitumen mixture can be adjusted in order to adapt to local climate conditions. In colder climates, for example, the bitumen mixture preferably contains about 65% bitumen, about 28% polymer and about 7~
other fillers and additives. In warmer climates the mixture preferably contains, for example, about 62~ bitumen, about 22% polymer and about 16% other additivesO
S The wa~erproofing membrane which results from the impregnation of a fiberglass mat, a fiberglass net and a polyester mat with the bitumen polymer mixture is abou~
4-7 mm thick, preferably 4-5 mm, and weighs about 4~3-5.4 Kg/m . In the embodiment containing the single layer fused fiberglass net/polyester mat, the thickness and weights are normally the same.
The surface of the resulting waterproofing mem-brane is dusted lightly with talc or some other suitable material to prevent sticking, covered with a protective film lS such as polyethylene and rolled up and packaged in rvlls about 100-110 cm high and 7-10 meters long. The water~
proofing membranes are placed loose on the roof surface or are fused in place on the roof using a gas burner or similar equipment. In applyin~ the membrane to the surface, the membrar.es are overlapped at the edges and fused to insure complete waterproofing.
In general, the una9ed waterproofing membrane of about 4 mm thickness has superior physical-mechanical characteristics as listed in Table I and can be expected to give at least 20 years of service under normal conditions.

, 5~

TABLE I
Physical Mechanical Properties of an unaged 4 mm waterproofing membrane PropertY Value Creep due to heat (DIN 53.123/181gO) (AIB 4687.02) 120C
Low temperature flexibility (AIB 4224) -10C
Permeability to water under pressure (DIN 16935~ none (131' column of water) Vapor permeation Index (23C) 11.2934 g~m2/24 hrs) (24 hrs) 10.2714 g/m /24 hrs) t72 hrs) Permeance = 0~0246 meters perms Solubility in water (25C) 0.019 mg/cm2 Tensile Strength (ASTM 2523) 200 lbs/in Elas~icity modulus 0.13 Coefficient of thermal expansion (30-O~F) 20 x 10 6 Longitudinal elongation at break* 0F (ASTM 2523) 3 Transver~al Elongation at break 0F (ASTM 2523) 3%

* Percent elongation at break is equivalent to the percent strain.

The waterproofing membrane also has high impact strength when tested according to ASTM D-2643 6O7~
At 3.9C no damage to the membrane was observed and at -13C only a slight crack at the point of impact was observed when the sample was bent. Visible crackin~ occurred at the point of impact when a standard weight was dropped :
from a height of seven feet.

DETAILED DISCUSSION OF THE INVENTION

This invention will be more fully understood through the following examples which are used only for illustration and are not meant to limit this invention in S any way.

Example 1 A waterproofing membrane was prepared by impreg-nating three reinforcing layers, that is a fiberglass mat which weighed 70 g/m2, a fiberglass net whic~ weighed 80 g/m2, and polyester mat which weighed 150 g/m2 with a bitu-men polymer mixture which contained 66.7 bitumen, 1~.7%
ethylene/propylene copolymer, 9.5~ atactic polypropylene,

2.4% isotactic polypropylene and 8.7% fillers (spent lime and talc). In order to prepare the bitumen polymer mixture, ~00 kg of copolymer of ethylene/propylene, 600 kg atactic polypropylen~ and 150 kg isotactic polypropylene were melted in an agitated autoclave at 190C allowing a minimum time for the operation. 2100 kg of bitumen were added keeping the blend at 150C for one and one-half hours~ The temper-ature should not be allowed to exceed 195C~ In another stirred autoclave, 2100 kg bitumen, 150 kg talc and 400 kg lime were mixed for lG minutes at 150C. At the end of the operation, the second blend was homogenized with the first blend at about 175C for 6 hours~ At this point, the bitumen polymer mixture had acquired the characteristics of an entirely new substance having a ring and ball softening point of 150C and good flexibility down to -8C.

The reinforcing layers were passed through the bitumen polymer mixture and allowed to adhere togethre to form the waterproofing membrane which had a total weight of 4.4 Kg/m2, a thickness of 4 mm. The bitumen polymer layer under the reinforcing layer was 1.5 mm thick.
The superior physical properties of the water-proofing membrane described in Example 1 were tested ac-cording to Recommended Practice for Testing Load-Strain Properties of Roof Membranes, ASTM-D-2523-70, Part 11, ASTM
Annual Book of Standards, 1973 which is incorporated herein by reference. Each test was performed six times, three times on transverse samples and three times on longitudinal samples. The results of those tests appear in Tables II
and III, respectively.

TABLE I I I
LONGITUDINAL SAMPLES

Average Test Value Average coefficient oflxlO ~3xlO` 66xlO 6 3.3xlO 6 5. expansion (73~30~F) Average coefficient of24xlO 626xlO 626xlO 625.3xlO 6 expansion (30-0F) Tensile strength 210 238 232 226.6 lbs~in (0F) Percent elongation at3.~6 3.10 3.31 3~22 break (0F) Load Strain modulus 0~3217 0.3836 0.3502 .3518 x 104 lbs/in (0F) Modulus of Elasticity - - - 0~13 (lb~/in) I~ can be se~n from these test results that the novel waterproofin~ membrane as described in Example 1 has a superior thermal expansion coefficient and high elasticity.
The average modulus of elasticity of ~he improved water-proofing membrane described in Example 1 is 0.13 in both thelongitudinal and transverse directions of the membrane.
Comparisons have shown that the longi~udinal mod-~lus of elasticity for Example 1 is about 1.8 times higher ~ than the average modulus of elasticity obtained for three leading roofing materials and about 2.7 times higher than the value for th~ least popular of the three materials and about l.S times higher than the leading material.
Comparisons have also shown that the transverse modulus of elasticity for the material described in Example 1 ~ ; 24141-A

was about 2.2 times higher than the average value for the three leading materials; about 2.7 times higher than the value for the least popular materials and about 1.86 times higher than the leading material.

Example 2 ~ waterproofing membrane was prepared by impreg-nating three reinforcing layers, tha~ is a fiberglass mat which weighed 95 g/m2, a fiberglass net which weighed 80 g/m2, and polyester mat which weighed about 120 g/m2 with a bitumen polymer mixture which contained 66.7~ bitumen, 11.5% ethylene/propylene copolymer, 11.5% of a mixture of atactic polypropylene polymer and ethylene propylene copolymer containing mineral oil obtained from separa~ing atactic and isotactic polypropylene, 1.5~ isotactic polypropylene and 8.7% fillers ~spent lime and talc). In order to prepare the bitumPn polymer mixture, 72~ kg of co-polymer of ethylene/propylene, 725 kg atactic polypropylene and 95 kg isotactic polypropylene were melted in an agitated autoclave at 190C allowing a minimum time for the operation. 2100 kg of bitumen were added keeping the blend at 150C for one and one-half hours. The temperature should not be allowed to exceed 195C. In another stirred autoclave, 2100 kg bitumen, 150 kg talc and 400 kg spent lime were mixed for 10 minutes at 150C~ At the end of the operation, the second blend was homogenized with the first blend at about 175C for 6 hours. At this point, the bitumen polymer mixture had acquired the characteristics of an entirely new substance having a ring and ball softening point of 155C and good flexibilit~ down to -10Co ~ ; 24141-A

The three reinforcing layers were passed through the bitumen polymer mixture and allowed to adhere together to form the waterproofing membrane which had a total weight of 4.4 Kg/m2 and a thickness o~ 4 mm. The bitumen polymer layer under the reinforcing layer was 1.5 mm thick.
The superior physical properties of the water~
proofing membrane described in Example 2 were tested as de-scribed ~or Example 1. Three samples were tested. The average of those three test results appear in Tables IV
and V.

TABLE IV
TRANSVERSE SAMPLES

Average Test Value Average coefficient of 1.34 x 10 6 expansion (73-30F) Average coefficient of 5.3 x 10 6 expansion (30-0F) Tensile strength 244 ~0 lbs/in (0F) Percent eLongation 2.8 at break ~0F) Load Strain modulus 0.879 x 104 lbs/in (0F) Modulus of Elasticity 0.14 (lbs/in) TABLE V

LONGITUDINAL SAMPLES

Aver age Test Value Average coefficient of 1.48 x 10 6 expansion (73-30F) Average coefficient of 3.0 x 10 6 expansion (30-0F) Tensile strength 252.5 lbs/in (0F~

Percent elongation at 2.8 break (0F) Load Strain modulus O.gl6 x 104 lbs/in (0F) Modulus of Elasticity 0.14 (lbs/in) It can be seen from these test results that the novel waterproofing membrane as described in Example 2 has a lower and, therefore, superior thermal expansion coefficient as well as high elasticity. The average modulus of elas-ticity of the improved waterproofing membrane described inExample 2 is 0.14 in both the longitudinal and transverse directions of the membrane.
Comparisons have shown that the longitudinal mod-ulus of elasticity for Example 2 is about 1.9 times higher ~5 than the average modulus of elasticity obtained for three leading roofing materials and about 2.7 times higher than the value for the least popular of the three materials and about 1.6 times higher than the leading material.
Comparisons have also shown that the transverse modulus of elasticity for the material described in Example 2 was about 2.4 times higher than the average value for the ` 24141-A

three leading materials; about 2.9 times higher than the value for the least popular materials and about 2.0 times higher than the leading material.

Example 3 A waterproofing membrane was prepared as described in Example 2 except that a fiberglass net is made with fiber-glass fibers containing about 25% polyvinyl chloride threads and which weighed 80 g/m was fused at about 100C with a polyester mat which weighed about 50 g/m2. The fused poly-ester mat/fiberglass net single layer and a fiberglass mat which weighed 95 g/m2 were passed through the bitumen poly-mer mixture and allowed to adhere together to fQrm a water-proofing membrane which has a total weight of about 4.3 kg/m2 and a thickness of about 4 mm.
In preliminary testing, the membrane was found to permit excellent tensile strength and percent elongation at break when proper impregnation was achieved, as shown below in Table VI.

TABLE VI
Longitudinal Tensile Strength (lbs/in) 288 318 205 191* - 183*
Pescent elongation at break 3.5 3.9 ?.3 2.2 - 1.9 Transversal _ Tensile strength (lbs/in) 171* 225 177* 172* 165* 226 Percent elongation at break 2.2 2.9 2.3 2.2 2.1 3~0 * samples not adequately impregnated 24141~A

As will be seen from Table VI, the material must be properly impregnated with the mixture to achieve homogeneity and optimum properties on a consistent basis.

Exam~e 4 A conventional waterproofing membrane was prepared by impregnating a ~iberglass mat which weighed 50 y/m2 and a polyester mat which weighed 150 g/m2 with a bitumen mixture which contained 65.0% bitumen, Z3.5% atac~ic polypropylene, 2.5% isotactic polypropylene and 9.0% fillers (talc and spent lime).
The bitumen mixture was prep~red as in Example 1 and the reinforcing layers were passed through the bitumen mixture to form the conventional waterproofing membrane.
The tensile strength and the percent strain at 0F of this membrane were measured by the same procedure used in Example 1 The sample had a longitudinal tensile strength of 132 lbs/in and a percent strain of 3. The transverse tensile strength was 94 lbs/in and the transverse percent strain was 2%. It should be noted that not only are tbe 2Q tensile strengths and percent strain values for Examples 1, 2 and 3 significantly better than those for Example 4, but there is greater consistency in the transverse and longi-tudinal values for Examples 1, 2 and 3 than for Example 4.
These results demonstrate that not only do the novel mem-branes described in Example 1, 2 and 3 give superior values over conventional membranes, but those values are also more consistent throughout the membrane regardless of test direction.

Claims (18)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A prefabricated waterproofing membrane which com-prises a series of superposed reinforcing layers including a fiberglass mat, a polyester mat and a fiberglass net, said layers being impregnated with bitumen mixed with at least one thermo-plastic polymer selected from the group consisting of an amor-phous copolymer of ethylene/propylene, atactic polypropylene, polyisobutylene and styrene-butadiene-styrene block copolymer, the bitumen polymer mixture having a ring and ball softening point of at least 105°C wherein the bitumen polymer mixture is further modified by the addition of at least one polymeric material selected from the group consisting of:

1) a mixture of atactic polypropylene and ethylene propylene copolymer; and 2) a mixture of atactic polypropylene and ethylene propylene copolymer containing mineral oil.

2. The waterproofing membrane as described in claim 1 wherein the fiberglass mat weighs about 50-125 g/m2, the poly-ester mat weighs about 50-250 g/m2 and the fiberglass net weighs about 60-100g/m2.

3. The waterproofing membrane as described in claim 2 wherein the fiberglass net contains about 25% polyvinyl chlor-ide threads and the fiberglass net is heat fused to the polyester mat prior to being impregnated with bitumen.

4. The waterproofing membrane as described in claim 2 wherein the fiberglass net is positioned between the fiber-glass mat and the polyester mat, the fiberglass mat being the closest to the surface.

5. The waterproofing membrane as described in claim 1 wherein the bitumen is mixed with an amorphous copolymer of ethylene propylene atactic polypropylene and isotactic poly-propylene.

6. The waterproofing membrane as described in claim 1 wherein the bitumen is mixed with an amorphous copolymer of ethylene propylene, atactic polypropylene, isotactic polypropy-lene and ethylene propylene copolymer containing mineral oil.

7. The waterproofing membrane as described in claim 1 wherein the bitumen polymer mixture has a ring and ball soft-ening point of about 155°C.

8. A bitumen polymer mixture which comprises bitumen mixed with amorphous copolymer of ethylene and propylene modi-fied by addition of at least one of 1) a mixture of atactic polypropylene polymer and ethylene propylene copolymer and 2) a mixture of atactic polypropylene polymer and ethylene propylene copolymer containing mineral oil.

9. A prefabricated waterproofing membrane which comprises a series of superposed reinforcing layers includ-ing a fiberglass mat and a bonded fiberglass net/polyester mat, said layers being impregnated with bitumen mixed with at least one thermoplastic polymer selected from the group consisting of an amorphous copolymer of ethylene/propylene, atactic polypropylene, polyisobutylene and styrene-butadiene-styrene block copolymer, the bitumen polymer mixture having a ring and ball softening point of at least 105°C.

10. The waterproofing membrane as described in claim 9 wherein the bitumen polymer mixture is further modified by the addition of at least one polymeric material selected from the group consisting of isotactic polypropy-lene, a mixture of atactic polypropylene polymer and ethylene propylene copolymer and a mixture of atactic poly-propylene polymer and ethylene propylene copolymer con-taining mineral oil.

11. The waterproofing membrane as described in claim 10 wherein the fiberglass mat weighs about 50-125 g/m2, the polyester mat weighs about 50-250 g/m2 and the fiberglass net weighs about 60-100 g/m2.

12. The waterproofing membrane as described in claim 11 wherein the fiberglass mat is the closest to the surface.

13. The waterproofing membrane as described in claim 12 wherein the bitumen is mixed with an amorphous copolymer of ethylene propylene and the bitumen polymer mixture is modified with at least one of the materials se-lected from the group consisting of atactic polypropylene and isotactic polypropylene.

14. The waterproofing membrane as described in claim 12 wherein the bitumen is mixed with an amorphous copolymer of ethylene propylene and the bitumen polymer mixture is modified with a mixture of atactic polypropylene polymer and ethylene propylene copolymer containing mineral oil and isotactic polypropylene.

15. The waterproofing membrane as described in claim 9 wherein the bitumen polymer mixture has a ring and ball softening point of about 155°C.

16. The waterproofing membrane as described in claim 9 wherein the bitumen polymer mixture is further modified by the addition of powdered rubber.

17. The waterproofing membrane as described in claim 9 wherein the fiberglass mat weighs about 50-125 g/m2, the polyester mat weighs about 50-125 g/m2 and the fiberglass net weighs about 60-100 g/m2.

18. A waterproofing membrane as described in claim 10, wherein the polyester mat contains a polyester net bonded to the polyester mat.