Technical field

The invention relates to the field of waterproofing of building constructions by using sealing devices comprising a waterproofing layer. Particularly, the invention relates to roofing membranes comprising a waterproofing layer based on plasticized polyvinylchloride having an improved tear resistance.

Background of the invention

In the field of construction polymeric sheets, which are often referred to as membranes, panels, or sheets, are used to protect underground and above ground constructions, such as basements, tunnels, and flat and low-sloped roofs, against penetration water. Waterproofing membranes are applied, for example, to prevent ingress of water through cracks that develop in concrete structures due to building settlement, load deflection, or concrete shrinkage. Roofing membranes used for waterproofing of flat and low-sloped roof structures are typically provided as single-ply or multi-ply membrane systems. In a single-ply system, the roof substrate is covered using a roofing membrane composed of a single waterproofing layer. In multi-ply membrane systems, roofing membranes comprising multiple waterproofing layers having similar or different composition are used. Single-ply membranes have the advantage of lower production costs compared to the multi-ply membranes, but they are also less resistant to mechanical damages caused by punctures of sharp objects.

Commonly used materials for the roofing membranes include plastics, in particular thermoplastics such as plasticized polyvinylchloride (p-PVC), thermoplastic olefins (TPE-O, TPO), and elastomers such as ethylenepropylene diene monomer (EPDM). The roofing membranes are typically delivered to a construction site in form of rolls, transferred to the place of installation, unrolled, and adhered to the substrate to be waterproofed. The substrate on which the roofing membrane is adhered may be comprised of variety of materials. The substrate may, for example, be a concrete, metal, or wood deck, or it may include an insulation board or recover board and/or an existing membrane.

The plastics used in roofing membranes have a relatively high CO2 footprint due to the petroleum based origin of the raw materials and energy intensive production process. According to a recent study, the greenhouse gas emissions generated across the life cycle of plastics has doubled since 1995, reaching 2 billion tons of CO2 equivalent (CO2e) in 2015 representing 4.5 % of the global greenhouse gas emissions. Increase plastics production in coalbased, newly industrialized countries such as China, India, Indonesia, and South Africa has also been recognized as the main cause of the growing carbon footprint of plastics.

Although several carbon capture and storage (CCS) methods have been proposed, they have turned out to be economically inefficient due to their high energy and/or land use requirements. Current carbon capture concepts are based on physical or chemical absorption, and membrane or cryogenic separation, all of which are very energy intensive and have a low efficiency. The storage of the captured carbon may then be carried out by geological or marine sequestration, both of which are again very cost- and energy intensive and carry some risk regarding the environment

Bio-sequestration of carbon, i.e. , conversion of CO2 into biomass via photosynthesis, seems to provide an elegant way for sustainable CSS. Furthermore, the biomass could in turn be used for the production of bioenergy or other value-added products. Bio based CCS is most easily implemented by trees. However, trees grow relatively slowly and need a large area, since a single tree (e.g. beech tree) requires 80 years capture and store 1 ton of CO2, or 12.5 kg per year. Efficient biological carbon capture is mostly feasible with fast growing plants, such as algae. Consequently, using microalgae has emerged as a promising new approach to provide a versatile and efficient way for biological carbon capture. Particularly, open pond algae growth systems are very easy to implement and can serve to capture CO2 directly at the source, for example, next to a CO2 producing factory. Algae also offer the option for generating raw materials for subsequent use in long living or recyclable products.

Despite its enormous potential, the production of microalgae for low-value bulk products, such as biofuels or plastics, is currently economically not attractive. Particularly, energy-intensive downstream processing (drying, extraction etc.) far outweighs the ecological benefits obtained through the replacement of fossil fuels and raw materials with renewable alternatives. Thus, in order to achieve economic viability and sustainability, major hurdles in both, the upstream and downstream processes have to be overcome. Furthermore, from sustainability point of view, using the produced biomass for providing long living products should be favored over returning the captured CO2 to the environment by burning for production of bioenergy.

While biofuel or bioplastic extraction from algae is not efficient and requires further processing, direct use of dried algae mass is an attractive option. The use of algae with a plant polymer (starch or protein) in a thermoplastic composition for plastic applications, such as personal care products, agriculture films, containers, building materials, electrical apparatus, and automobile parts has been proposed in EP 2424937 B1 . As another example, an algae derived flexible or rigid foam composition is disclosed US 20170142978 A1.

Generally, it would also be highly desirable to combine the benefits of the carbon capture and storage with increased performance of the product. At least the use of a renewable raw material should not result in deterioration of the application relevant properties of the product. PVC compounds are generally considered to be well suitable for blending with biomass fractions due to their polarity, broad performance and application spectrum, and longevity as well as recyclability of products based on PVC formulations.

When it comes to roofing membranes made from plasticized PVC, tear resistance is one of the most important features regarding longevity. In contrast to tensile strength, tear resistance describes the resistance of the material against growth of an existing crack. This is insofar relevant since small damages (hail impacts, installation damages etc.) are very common, and the material has to resist growth of such initial damages (“crack seeds”) under stresses (thermal stress, wind load, etc.). No compounding measure to systematically increase the tear resistance of plasticized PVC formulation without affecting other properties is known.

It would thus be desirably to provide a PVC-based sealing element, particularly a roofing membrane, having a lower CO2 footprint and at least equivalent performance compared to State-of-the-Art PVC-sealing elements.

Summary of the invention

The object of the present invention is to provide a sealing element, particularly a roofing membrane, having a lowered CO2 footprint and having at least equal mechanical properties when compared to the sealing elements of prior art.

Surprisingly, it has been found that the features of claim 1 achieve this object.

Particularly, it was surprisingly found out that adding dried algae biomass to a plasticized PVC formulation not only results in reduction of the CO2 footprint but that the modified formulations also exhibit improved tear strength. These PVC formulations are especially suitable for use in providing of sealing elements, such as roofing membranes, that due to their application environment are prone to mechanical damages and subsequent crack growth. Thus, the core of the present invention is related to a sealing element comprising a waterproofing layer comprising: a) 25 - 65 wt.-% of a polyvinylchloride resin, b) 15 - 50 wt.-% of at least one plasticizer, and c) 0 - 30 wt.-% of at least one mineral filler, all proportions being based on the total weight of the waterproofing layer (2), wherein the waterproofing layer (2) further comprises: d) dried algae biomass comprising at least one type of microalgae.

Additional aspects of the present invention are presented in further independent claims. Particularly preferred embodiments are outlined throughout the description and the dependent claims.

Brief description of the Drawings

Fig. 1 shows a cross-section of a sealing element (1) comprising a waterproofing layer (2) and a layer of fiber material (3) fully embedded into the waterproofing layer (3).

Fig. 2 shows a cross-section of a sealing element (1) comprising a waterproofing layer (2) and a second waterproofing layer (4) adhered to the upper major surface of the waterproofing layer (4).

Detailed description of the invention

A first aspect of the present invention is directed to a sealing element comprising a waterproofing layer comprising: a) 25 - 65 wt.-% of a polyvinylchloride resin, b) 15 - 50 wt.-% of at least one plasticizer, and c) 0 - 30 wt.-% of at least one mineral filler, all proportions being based on the total weight of the waterproofing layer (2), wherein the waterproofing layer (2) further comprises: d) dried algae biomass comprising at least one type of microalgae.

Substance names beginning with "poly" designate substances which formally contain, per molecule, two or more of the functional groups occurring in their names. For instance, a polyol refers to a compound having at least two hydroxyl groups. A polyether refers to a compound having at least two ether groups.

The term “polymer” designates a collective of chemically uniform macromolecules produced by a polyreaction (polymerization, polyaddition, polycondensation) where the macromolecules differ with respect to their degree of polymerization, molecular weight and chain length. The term also comprises derivatives of said collective of macromolecules resulting from polyreactions, that is, compounds which are obtained by reactions such as, for example, additions or substitutions, of functional groups in predetermined macromolecules and which may be chemically uniform or chemically non- uniform.

The “amount or content of at least one component X” in a composition, for example “the amount of the at least one plasticizer” refers to the sum of the individual amounts of all plasticizers contained in the composition.

Furthermore, in case the composition comprises 20 wt.-% of the at least one plasticizer, the sum of the amounts of all plasticizers contained in the composition equals 20 wt.-%. The term “room temperature” designates a temperature of 23 °C.

The waterproofing layer is preferably a sheet-like element having upper and lower major surfaces, i.e., top and bottom surfaces. The term “sheet-like element” refers in the present document to elements having a length and width at least 25 times, preferably at least 50 times, more preferably at least 150 times greater than the thickness of the element.

Preferably, the sealing element is selected from a roofing membrane, a waterproofing membrane, and a tape, preferably from a roofing membrane and a waterproofing membrane. According to one or more embodiments, the sealing membrane is a roofing membrane.

The term “roofing membrane” refers in the present disclosure to the conventional meaning of the term roofing membrane, i.e., a membrane that is a water impermeable sheet of polymeric material that is use for covering an outer surface of a roof deck. Roofing membranes and method for their production are known to a person skilled in the art.

According to the invention, the waterproofing layer comprises: a) 25 - 65 wt.-%, preferably 30 - 60 wt.-% of a polyvinylchloride resin, b) 15 - 50 wt.-%, preferably 20 - 40 wt.-% of at least one plasticizer, c) 0 - 30 wt.-%, preferably 0 - 20 wt.-% of at least one mineral filler, and d) dried algae biomass comprising at least one type of microalgae, all proportions being based on the total weight of the waterproofing layer.

Preferably, polyvinylchloride resin has a K-value determined by using the method as described in ISO 1628-2-1998 standard in the range of 50 - 85, more preferably 65 - 75. The K-value is a measure of the polymerization grade of the PVC-resin and it is determined from the viscosity values of the PVC homopolymer as virgin resin, dissolved in cyclohexanone at 30° C. The type of the at least one plasticizer is not particularly restricted in the present invention. Suitable plasticizers for the PVC-resin include but are not restricted to, for example, linear or branched phthalates such as di-isononyl phthalate (DINP), di-nonyl phthalate (L9P), diallyl phthalate (DAP), di-2- ethylhexyl-phthalate (DEHP), dioctyl phthalate (DOP), diisodecyl phthalate (DIDP), and mixed linear phthalates (911 P). Other suitable plasticizers include phthalate-free plasticizers, such as trimellitate plasticizers, adipic polyesters, and biochemical plasticizers. Examples of biochemical plasticizers include epoxidized vegetable oils, for example, epoxidized soybean oil and epoxidized linseed oil and acetylated waxes and oils derived from plants, for example, acetylated castor wax and acetylated castor oil.

Particularly suitable phthalate-free plasticizers to be used in the waterproofing layer include alkyl esters of benzoic acid, dialkyl esters of aliphatic dicarboxylic acids, polyesters of aliphatic dicarboxylic acids or of aliphatic di-, tri- and tetrols, the end groups of which are unesterified or have been esterified with monofunctional reagents, trialkyl esters of citric acid, acetylated trialkyl esters of citric acid, glycerol esters, benzoic diesters of mono-, di-, tri-, or polyalkylene glycols, trimethylolpropane esters, dialkyl esters of cyclohexanedicarboxylic acids, dialkyl esters of terephthalic acid, trialkyl esters of trimellitic acid, triaryl esters of phosphoric acid, diaryl alkyl esters of phosphoric acid, trialkyl esters of phosphoric acid, and aryl esters of alkanesulphonic acids.

According to one or more embodiments, the at least one plasticizer is selected from the group consisting of phthalates, trimellitate plasticizers, adipic polyesters, and biochemical plasticizers.

Suitable mineral fillers for use in the waterproofing layer include, for example, sand, granite, calcium carbonate, clay, expanded clay, diatomaceous earth, pumice, mica, kaolin, talc, dolomite, xonotlite, perlite, vermiculite, Wollastonite, barite, magnesium carbonate, calcium hydroxide, calcium aluminates, silica, fumed silica, fused silica, aerogels, glass beads, hollow glass spheres, ceramic spheres, bauxite, comminuted concrete, and zeolites.

The term “sand” refers in the present document to mineral clastic sediments (clastic rocks) which are loose conglomerates (loose sediments) of round or angular small grains, which were detached from the original grain structure during the mechanical and chemical degradation and transported to their deposition point, said sediments having an SiO2 content of greater than 50 wt.- %, in particular greater than 75 wt.-%, particularly preferably greater than 85 wt.-%. The term “calcium carbonate” as mineral filler refers in the present document to calcitic fillers produced from chalk, limestone, or marble by grinding and/or precipitation.

The waterproofing layer further comprises dried algae biomass comprising at least one type of microalgae.

The term “microalgae” refers in the present disclosure to a eukaryotic microbial organism that contains a chloroplast, and optionally that is capable of performing photosynthesis, or a prokaryotic microbial organism capable of performing photosynthesis.

Furthermore, the term “dried microalgae biomass” refers to a dried biomass obtained by subjecting a raw microalgae biomass separated, for example, from a cultivation process to various post-treatment steps, such as centrifugation, washing, and drying steps. A major proportion of the dried microalgae biomass is typically composed of cells with or without their intracellular contents.

According to one or more embodiments, the dried algae biomass has median particle size dso of not more than 200 pm, preferably not more than 150 pm.

The term “median particle size dso“ refers in the present disclosure to a particle size below which 50% of all particles by volume are smaller than the dso value. The particle size distribution can be determined by sieve analysis according to the method as described in ASTM C136/C136M -2014 standard (“Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates).

Algae biomass with a median particle size falling within the above cited ranges have been found out to be especially suitable for use in a plasticized PVC formulation for providing sealing elements.

Preferably, the waterproofing layer comprises at least 0.5 wt.-%, preferably at least 1 .5 wt.-%, based on the total weight of the waterproofing layer, of the dried algae biomass.

According to one or more embodiments, the waterproofing layer comprises 0.5 - 15 wt.-%, preferably 1.5 - 10 wt.-%, more preferably 1 .5 - 7.5 wt.-%, even more preferably 2 - 6.5 wt.-%, still more preferably 2.5 - 6 wt.-%, based on the total weight of the waterproofing layer, of the dried algae biomass.

The at least one type of microalgae is preferably selected from Chlorella sp. and Spirulina sp.

According to one or more embodiments, the dried algae biomass comprises Chlorella sp., preferably in an amount of at least 15 wt.-%, more preferably at least 35 wt.-%, even more preferably at least 50 wt.-%, still more preferably at least 75 wt.-%, based on the total weight of the dried algae biomass.

Chlorella sp. has been found to be especially suitable for use in the waterproofing layer due to its near spherical shape and strong cell walls, and significant positive impact to the tear resistance properties of the waterproofing layer.

According to one or more embodiments, the at least one type of microalgae is Chlorella sp.

The waterproofing layer can further comprise one or more additives, for example, UV- and heat stabilizers, antioxidants, flame retardants, dyes, pigments such as titanium dioxide and carbon black, matting agents, antistatic agents, impact modifiers, biocides, and processing aids such as lubricants, slip agents, antiblock agents, and denest aids.

According to one or more embodiments, the waterproofing layer has a thickness determined by using the measurement method as defined in DIN EN 1849-2 standard of 0.5 - 5.0 mm, preferably 0.7 - 3.5 mm, more preferably 1 - 3 mm, most preferably 1 - 2.5 mm.

According to one or more embodiments, the sealing element further comprises a layer of fiber material, which is fully embedded into the waterproofing layer or adhered to a lower major surface of the waterproofing layer. By the expression “fully embedded” is meant that the layer of fiber material layer is fully covered by the matrix of the waterproofing layer.

The layer of fiber material may be used to ensure the mechanical stability of the waterproofing layer when exposed to varying environmental conditions, in particular to large temperature fluctuations.

The term “fiber material” designates in the present document materials composed of fibers comprising or consisting of, for example, organic, inorganic or synthetic organic materials. Examples of organic fibers include, for example, cellulose fibers, cotton fibers, and protein fibers. Particularly suitable synthetic organic materials include, for example, polyester, homopolymers and copolymers of ethylene and/or propylene, viscose, nylon, and polyamides. Fiber materials composed of inorganic fibers are also suitable, in particular, those composed of metal fibers or mineral fibers, such as glass fibers, aramid fibers, wollastonite fibers, and carbon fibers. Inorganic fibers, which have been surface treated, for example, with silanes, may also be suitable. The fiber material can comprise short fibers, long fibers, spun fibers (yarns), or filaments. The fibers can be aligned or drawn fibers. It may also be advantageous that the fiber material is composed of different types of fibers, both in terms of geometry and composition. Preferably, the layer of fiber material is selected from the group consisting of non-woven fabrics, woven fabrics, and non-woven scrims.

The term “non-woven fabric” designates in the present document materials composed of fibers, which are bonded together by using chemical, mechanical, or thermal bonding means, and which are neither woven nor knitted. Nonwoven fabrics can be produced, for example, by using a carding or needle punching process, in which the fibers are mechanically entangled to obtain the nonwoven fabric. In chemical bonding, chemical binders such as adhesive materials are used to hold the fibers together in a non-woven fabric.

The term “non-woven scrim” designates in the present document web-like nonwoven products composed of yarns, which lay on top of each other and are chemically bonded to each other. Typical materials for non-woven scrims include metals, fiberglass, and plastics, in particular polyester, polypropylene, polyethylene, and polyethylene terephthalate (PET).

According to one or more embodiments, the layer of fiber material is a nonwoven fabric, preferably a non-woven fabric having a mass per unit weight of not more than 300 g/m ² , preferably not more than 250 g/m ² . According one or more embodiments, the layer of fiber material is a non-woven fabric having a mass per unit weight of 15 - 300 g/m ² , preferably 25 - 250 g/m ² , more preferably 35 - 200 g/m ² , most preferably 45 - 150 g/m ² .

Preferably, the non-woven fabric of the layer of fiber material comprises synthetic organic and/or inorganic fibers. Particularly suitable synthetic organic fibers for the non-woven fabric include, for example, polyester fibers, polypropylene fibers, polyethylene fibers, nylon fibers, and polyamide fibers. Particularly suitable inorganic fibers for the non-woven fabric include, for example, glass fibers, aramid fibers, wollastonite fibers, and carbon fibers.

According to one or more embodiments, the non-woven fabric of the layer of fiber material has as the main fiber component synthetic organic fibers, preferably selected from the group consisting of polyester fibers, polypropylene fibers, polyethylene fibers, nylon fibers, and polyamide fibers. According to one or more further embodiments, the non-woven fabric of the layer of fiber material has as the main fiber component inorganic fibers, preferably selected from the group consisting of glass fibers, aramid fibers, wollastonite fibers, and carbon fibers, more preferably glass fibers.

The sealing element of the present invention may be a single- or a multi-ply roofing membrane. The term “single-ply roofing membrane” designates in the present document membranes comprising one single waterproofing layer whereas the term “multi-ply roofing membrane” designates membranes comprising more than one waterproofing layers. In case of a multi-ply roofing membrane, the waterproofing layers may have similar or different compositions.

Single- and multi-ply membranes are known to a person skilled in the art and they may be produced by any conventional means, such as by way of extrusion or co-extrusion, calendaring, or by spread coating. According to one or more embodiments, the roofing membrane is a single- ply membrane comprising exactly one waterproofing layer, as shown in Figure 1.

According to one or more further embodiments, the sealing element is a multiply membrane comprising at least two waterproofing layers, preferably exactly two waterproofing layers, as shown in Figure 2. In these embodiments, the roofing membrane further comprises a second waterproofing layer having lower and upper major surfaces, wherein the lower major surface of the second waterproofing layer is directly or indirectly bonded to at least portion of the upper major surface of the waterproofing layer.

According to one or more embodiments, the second waterproofing layer is a polyvinylchloride-based waterproofing layer. Preferably, the second waterproofing layer has substantially similar composition as the waterproofing layer. The second waterproofing layer may further comprise a layer of fiber material, which is fully embedded into the second waterproofing layer. It may, however, be also possible or even preferred that the second waterproofing layer does not contain a layer of fiber material.

The sealing element of the present invention is typically provided in a form of a prefabricated membrane article, which is delivered to the construction site and unwound from rolls to provide sheets having a width of 1 - 5 m and length of several times the width. However, the sealing element can also be used in the form of strips having a width of typically 1 - 20 cm, for example so as to seal joints between two adjacent membranes. Moreover, the sealing element can also be provided in the form of planar bodies, which are used for repairing damaged locations in existing adhered waterproofing, roofing, or facade systems.

Another aspect of the present invention is use of dried algae biomass comprising at least one type of microalgae to increase tear resistance of a plasticized polyvinylchloride formulation comprising: a) 25 - 65 wt.-% of a polyvinylchloride resin, b) 15 - 50 wt.-% of at least one plasticizer, and

0 - 30 wt.-% of at least one mineral filler, all proportions being based on the total weight of the plasticized polyvinylchloride formulation.

According to one or more embodiments, the plasticized polyvinylchloride formulation comprises: a) 25 - 65 wt.-%, preferably 30 - 60 wt.-% of a polyvinylchloride resin, b) 15 - 50 wt.-%, preferably 20 - 40 wt.-% of at least one plasticizer, and c) 0 - 30 wt.-%, preferably 0 - 20 wt.-% of at least one mineral filler.

Preferences given above for the polyvinylchloride resin, the at least one plasticizer, and to at least one mineral filler contained in the waterproofing layer are also applicable for the plasticized polyvinylchloride formulation. According to one or more embodiments, the dried algae biomass has median particle size dso of not more than 200 pm, preferably not more than 150 pm.

Preferably, the plasticized polyvinylchloride formulation comprises at least 0.5 wt.-%, preferably at least 1 .5 wt.-%, based on the total weight of the plasticized polyvinylchloride formulation, of the dried algae biomass.

According to one or more embodiments, the plasticized polyvinylchloride formulation comprises 0.5 - 15 wt.-%, preferably 1 .5 - 10 wt.-%, more preferably 1 .5 - 7.5 wt.-%, even more preferably 2 - 6.5 wt.-%, still more preferably 2.5 - 6 wt.-%, based on the total weight of the plasticized polyvinylchloride formulation, of the dried algae biomass.

The at least one type of microalgae is preferably selected from Chlorella sp. and Spirulina sp.

According to one or more embodiments, the dried algae biomass comprises Chlorella sp., preferably in an amount of at least 15 wt.-%, more preferably at least 35 wt.-%, even more preferably at least 50 wt.-%, still more preferably at least 75 wt.-%, based on the total weight of the dried algae biomass.

Chlorella sp. has been found to be especially suitable for use in the plasticized polyvinylchloride formulation due to certain properties, particularly near spherical shape and strong cell walls, which makes it suitable for processing using similar techniques as with fillers and pigments.

The plasticized polyvinylchloride formulation can further comprise one or more additives, for example, UV- and heat stabilizers, antioxidants, flame retardants, dyes, pigments such as titanium dioxide and carbon black, matting agents, antistatic agents, impact modifiers, biocides, and processing aids such as lubricants, slip agents, antiblock agents, and denest aids. Examples

The followings materials shown in Table 1 were used in providing the polymer formulations.

Table 1

Preparation of sealing elements

The polymer compositions were melt-processed in a two roll mill and then pressed into sheets having a thickness of 2.0 mm, using a laboratory curing press at a temperature of 190 °C and using a pressing time of 3 minutes at 120 bar.

Mechanical properties

Tensile strength and elongation at break were measured according to ISO 527- 3:2018 standard at a temperature of 21 °C using a Zwick tensile tester and a cross head speed of 100 mm/min. Elastic modulus was measured according to ISO 527-2/5/1 under identical conditions. Tear resistance was measured according to DIN EN 12310-2 using pre-cut samples having a trapezoidal shape under identical conditions.

The tested polymer compositions and the measured mechanical properties as shown in Table 2. Table 2