WO2004096916A1

WO2004096916A1 - Composition which contains bitumen and polyethylene

Info

Publication number: WO2004096916A1
Application number: PCT/NL2004/000266
Authority: WO
Inventors: Wilhelmus Gerardus Marie Bruls; Johannes Fredericus Repin
Original assignee: Dsm Ip Assets B.V.
Priority date: 2003-05-02
Filing date: 2004-04-22
Publication date: 2004-11-11
Also published as: NL1023333C2

Abstract

Composition which contains bitumen and polyethylene and also a functionalized polyolefin polymer and less than 5 wt% of an atactic polyolefin. The polyethylene is preferably a metallocene polymerized polyethylene and the functionalized polyolefin polymer is a functionalized polyethylene. The composition is very suitable for application in a membrane for roofing material, in which at least a layer containing the composition is present.

Description

COMPOSITION WHICH CONTAINS BITUMEN AND POLYETHYLENE.

The invention relates to a composition which contains bitumen and polyethylene.

Such a composition is known from 'Blends of bitumen with polyethylenes', Polymer 40 (1999) 6337-6349. Applications of this composition include membranes for roofing material. In these compositions polyethylene is an alternative for the widely applied but increasingly less produced atactic polypropylene and for the styrene-butadiene-styrene block copolymers or the more costly hydrogenated styrene-butadiene-styrene block copolymers.

For bituminous roofing material and also for other applications of the known composition high requirements are specified in relation to both low- temperature flexibility and stability at higher temperatures. Low-temperature flexibility is understood to mean that the composition at low temperatures, in particular from 0 to -30 °C, can be bent without cracks developing. Stability at higher temperature is here understood to mean that the desired structure of the composition, in particular the relative distribution of the polyethylene and the bitumen present therein, does not essentially change upon exposure to elevated temperature so that low-temperature flexibility is retained at low temperature thereafter.

The known composition has the disadvantage that in the course of time both properties deteriorate, in particular flexibility deteriorates after exposure of the composition to elevated temperatures. This means that roof coverings manufactured from the composition would need to be replaced fairly soon because they no longer comply with the requirements for use.

The invention aims to provide a composition of bitumen and polyethylene that retains the desired flexibility and stability for a longer time.

This object is achieved according to the invention by the composition also containing a functionalized polyolefin polymer and also containing less than 5 wt.% of an atactic polyolefin.

It has been found that the presence of the functionalized polyolefin polymer substantially delays the deterioration over time of said properties. In particular it was found that the composition according to the invention retains its flexibility at significantly lower temperatures than the known composition even after exposure to temperatures as high as 80°C.

The presence of a greater quantity of atactic polyolefin than the aforementioned 5 wt% appears to result in lower stability assumedly on account of the mediocre miscibility of the atactic polyolefin, in particular atactic polypropylene, with the polyethylene.

The composition contains as an important constituent bitumen in a quantity of for example 40-80 wt%. Bitumen is a by-product of crude oil from for example cracking operations and mainly consists of a mixture of aromatics, paraffins, asfaltenes and resins. The ratio of the components in the bitumen may vary depending on the starting product and the applied cracking or distillation process. For various applications it is advantageous to modify or oxidize the bitumen. In particular oxidized bitumens find application as a material for roofing material. Bitumens that are suitable for the intended application, such as roofing material, are known per se to one skilled in the art and are commercially available. Furthermore, the composition contains a polyethylene polymer.

As a polyethylene polymer in the composition all current homopolymers and copolymers of ethylene with one or more a-olefins, preferably C3-C10 monomers, are suitable, including ethylene propylene rubbers and blends of the said polyethylene polymers. The polymers can be manufactured using Ziegler-Natta and Phillips catalysts but also metallocene and other metallocene and other single site catalysts. The density of these polyethylenes may be between 850 and 970 kg/m³ and is preferably between 850 and 920 kg/m³ and more preferably between 850 and 890 kg/m³. The composition preferably contains at least a polyethylene preferably in the form of copolymers with a C3-C8 α-olefin comonomer. The latter are preferable on account of their rubbery behaviour, which is conducive in particular to the required low-temperature flexibility of the composition. The composition may additionally contain a polyethylene, for example a high density polyethylene (HOPE) or a very low density polyethylene (VLDPE) with a crystallinity of at least 50 %, preferably greater than 60 %. The presence hereof has been shown to improve ageing resistance, which is accompanied by loss of mechanical properties, of the composition upon exposure to elevated temperatures.

In addition to the bitumen and the polyethylene as main components, the composition may contain other polymers, additives such as oils and customary additives such as 5-40 wt% fillers, for example chalk and/or fibers. Suitable polymers are those which can be finely distributed in polyethylene but cannot be mixed molecularly therewith. An example hereof is isotactic polypropylene.

The composition according to the invention also contains a functionalized polyolefin polymer. This includes a polyolefin polymer grafted with an ethylenically unsaturated functionalized compound or a polyolefin polymer in which monomers with a functional group are applied during polymerization. As such are suitable homopolymers and copolymers of one or more olefin monomers grafted with an ethylenically unsaturated functionalized compound or in which an ethylenically unsaturated functionalized compound is incorporated. Examples of suitable polyolefin polymers are ethylene polymers, propylene polymers and styrene-butadiene-styrene block copolymers or the hydrogenated form thereof. Examples of suitable ethylene polymers are all thermoplastic homopolymers of ethylene and copolymers of ethylene and copolymers of ethylene containing as a comonomer one or more a-olefins with 3-10 C-atoms that can be manufactured with the known catalysts such as for example Ziegler-Natta, Phillips and metallocene catalysts or other single-site catalysts, in particular propylene, isobutene, 1 -butene, 1 -hexene, 4-methyl-1 -pentene and 1 -octene. As a rule, the quantity of comonomer is between 0 and 50 wt. %, preferably between 5 and 35 wt. %. Such ethylene polymers are also known as high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), linear very low-density polyethylene (VL(L)DPE), plastomers and elastomers. Suitable polyethylenes have a density of between 850 and 970 kg/m³. Examples of suitable propylene polymers are homopolymers of propylene and copolymers of propylene with ethylene, in which the proportion of ethylene amounts to at most 30 wt% and preferably at most 25 wt%. The Melt Flow Index (measured for polyethylene at 190°C, 2.16 kg and for polypropylene at 230 °C, 2.16 kg) of the functionalized polyolefin polymer is between 0.1 and 100 g/10min, preferably between 0.5 and 50 g/10min, and more preferably between 1.0 and 30 g/10min. Functionalised polyethylene is preferred on account of good miscibility with the polyethylene in the composition. Suitable ethylenically unsaturated functionalized compounds are those which can be grafted on at least one of the aforesaid suitable polyolefin polymers. Such compounds contain a carbon-carbon double bond and can form a side branch to a polyolefin polymer by grafting thereon or which may be incorporated in the polymer chain during the polymerization process. The compounds are functionalized, which means that they possess a first functional group. Examples of functional groups are carboxylic acids and esters, anhydrides and salts. The functionalized compounds thereof may contain an epoxy ring, an amine group, an alkoxy silane group or an alcohol group. The compound may also be an ethylenically unsaturated oxazoline.

Examples of suitable ethylenically unsaturated functionalized compounds are the unsaturated carboxylic acids and esters and anhydrides and metallic or non-metallic salts thereof. Preferably the ethylenic unsaturation in the compound is conjugated with a carbonyl group. Examples thereof are acryl, methacrylic, maleic, fumaric, itaconic, crotonic, methyl crotonic, and cinnamic acid and esters, anhydrides and possible salts thereof. Among the compounds with at least one carbonyl group maleic acid anhydride is preferable.

Examples of suitable ethylenically unsaturated functionalized compounds with at least one epoxy ring are for example glycidyl esters of unsaturated carboxylic acids, glycidyl ethers of unsaturated alcohols and of alkyl phenols and vinyl esters and allyl esters of epoxy carboxylic acids. Glycidyl methacrylate is especially suitable.

Examples of suitable ethylenically unsaturated functionalized compounds with at least one amine functionality are amine compounds with at least one ethylenically unsaturated group, for example allyl amine, propenyl amine, butenyl amine, pentenyl amine and hexenyl amine, amine ethers, for example isopropenylphenyl ethylamine ether. The amine group and the unsaturation should be positioned relative to each other in such a manner that they do not unduly affect the grafting reaction. The amines may be unsubstituted but also substituted with for example alkyl and aryl groups, halogen groups, ether groups and thioether groups. Examples of suitable ethylenically unsaturated functionalized compounds with at least one alcohol functionality are all compounds with a hydroxyl group, whether or not etherified or esterified, and an ethylenically unsaturated compound, for example allyl ethers and vinyl ethers of alcohols such as ethyl alcohol and higher branched and unbranched alkyl alcohols as well as allyl esters and vinyl esters of alcohol substituted acids, preferably carboxylic acids and C₃ -C₈ alkenyl alcohols. Furthermore, the alcohols may also be substituted with for example alkyl and aryl groups, halogen groups, ether groups and thioether groups that do not unduly affect the grafting reaction. Examples of oxazoline compounds which are suitable as ethylenically unsaturated functionalized compounds in the framework of the invention are for example those with the following general formula

where each R, independently of the other hydrogen, is a halogen, a CrC₁₀ alkyl radical or a C₆-C₁₄aryl radical. The quantity of the ethylenically unsaturated functionalized compound in the functionalized polyolefin polymer is between 0.1 and 10 wt%, preferably between 0.25 and 5 wt%, more preferably between 0.5 and 2.5 wt%.

The functionalized polyolefin polymer may be prepared by reacting the polyolefin polymer with the ethylenically unsaturated functionalized compound by methods known per se for the purpose, for example as described in US patent 3.236.917, US patent 5.194.509 and US patent 4.950.541. The functionalized polyolefin polymer may also be prepared in a high or low pressure polymerization process according to methods known per se.

In the composition the quantity of polyethylene relative to the total of polyethylene and bitumen is between 5 and 30 wt%, preferably between 5 and 25 wt% and more preferably between 7.5 and 20 wt%.

The quantity of functionalized polyolefin polymer is between 0.5 and 30 wt % relative to the total of polyethylene and functionalized polyolefin polymer, preferably between 1 and 20 wt% and more preferably between 2.5 and 10 wt%.

The favourable properties of the composition according to the invention are manifested in particular in membranes for roofing material. The invention therefore also relates to a membrane for roofing material, in which at least one layer is present that contains the composition according to the invention. Such membranes appear to have a long life in comparison with membranes manufactured with the known composition.

Such a membrane consists of at least one layer of the composition according to the invention. In addition, other layers may be present in the membrane, for example PET or fiberglass fabric. When applied as a roofing material, the membrane may be provided with a finish layer of for example grit or sand on the side that is exposed to the environment, in particular to weather.

Methods for manufacturing such bituminous membranes are known per se and the composition according to the invention may be processed according to these known methods to form a membrane according to the invention.

The invention is elucidated on the basis of the following examples.

Example I and Comparative Experiment A.

In a metal mixing tank that was heated with a heating jacket and controlled with a temperature controller by means of a thermocouple and equipped with a propeller stirrer (Heidolph variable-speed stirrer ) 60 parts by weight of Nytop B190 bitumen were heated up to 180 °C. To the molten hot bitumen were added 20 parts by weight of polymer and mixed with the bitumen, initially at low speed and then at high speed, to form a homogeneous mixture. Subsequently, 20 parts of chalk were added as a filler and after this had been mixed in the bitumen-polymer mixture the whole was intensively mixed at an increased speed for 30 minutes.

For Comparative Experiment A there were applied as polymer 20 parts by weight of Exact 8201 as polyethylene and for Example I a mixture of 18 parts by weight of Exact 8201 as polyethylene and 2 parts of Exact 8210 on which 1 wt% of MAA as functionalized polyolefin had been grafted via a melt grafting process. The mixture was cooled off. Test strips of 100x30x3 mm were punched out of the cooled mixture at 80°C. In a thermostatted room a test strip was placed on two parallel support beams that were 42 mm apart. Once the test strips had assumed the desired temperature, a mandril with a radius of curvature of 16 mm was lowered midway between the support beams on to the test strips until a load of 0.5 N was reached. Next the mandril was pressed down at a speed of 500 mm/min over a distance of 40 mm. In that process the test strip was folded about the mandril. The bent surface of the thus folded test strips was visually inspected for the presence of cracks or fractures.

This procedure for determining the low-temperature flexibility was carried out first at various temperatures from 0 to -25 °C. To determine the stability, i.e. retention of flexibility after exposure to higher temperatures, the flexibility was also determined of test strips that had been exposed for a certain time to a temperature of 80 °C. If no cracks or fractures could be seen, 'OK' was stated as the result. The results of the described experiments are presented in Table 1. Table 1 : Results of flexibility measurements

These results indicate that, in comparison with the comparative compound, the composition according to the invention exhibits distinctly improved flexibility at low temperatures down to well below freezing point. Furthermore, the stability of the composition according to the invention after ageing at 80°C for 1 to 4 weeks is found to be excellent: The flexibility is not adversely affected over the whole measuring temperature range, in contrast to the results for the comparative composition.

Claims

1. Composition which contains bitumen and polyethylene, characterized in that the composition also contains a functionalized polyolefin polymer and also contains less than 5 wt% of an atactic polyolefin.

2. Composition according to claim 1 which contains at most 4 wt% of an atactic polyolefin.

3. Composition according to claim 1 or 2, in which the polyethylene is a metallocene polymerized polyethylene.

4. Composition according to any one of claims 1 -3, in which the functionalized polyolefin polymer is a functionalized polyethylene. S. Membrane for roofing material, in which at least one layer is present that contains the composition according to one of the preceding claims.