CA3169143A1

CA3169143A1 - Bituminous membranes with biodegradable binder

Info

Publication number: CA3169143A1
Application number: CA3169143A
Authority: CA
Inventors: Luca ASSUMMA; Maria CONVERSO; Laura D'ANDRIA
Original assignee: Individual
Current assignee: FREUDENBERG PERFORMANCE MATERIALS GMBH & CO. KG
Priority date: 2020-03-30
Filing date: 2021-03-25
Publication date: 2021-10-07

Abstract

Subject of the invention is a nonwoven carrier, wherein the nonwoven comprises organic polymer fibers and is consolidated with an aqueous binder, wherein the binder comprises (a) starch (b) polyvinyl alcohol, which may comprise up to 5 mol.% of other monomer units, wherein (c) the binder does not comprise a crosslinker, and (d) the binder does not comprise a filler. Subject of the invention are also uses of the nonwoven carrier, production methods, bituminous membranes and building materials.

Description

Bituminous membranes with biodegradable binder The invention relates to a nonwoven carrier comprising a nonwoven consolidated with a binder, wherein the binder comprises starch and polyvinyl alcohol, wherein the binder does not comprise a crosslinker or a filler. Subject of the invention are also uses of the nonwoven carrier, production methods, bituminous membranes and building materials.
State of the art Bituminous membranes having waterproofing and shielding properties are used in building applications, especially as roofing materials. Bituminous membranes comprise a textile carrier, which is impregnated with bitumen. The bitumen is applied to the textile carrier in a bath of molten bitumen at approximately 180 C to 200 C, followed by cooling and solidification. The main function of the carrier is to confer mechanical stability, and in this regard especially mechanical resistance and dimensional stability, to the bituminous membrane and to "keep the bitumen together".
The textile fabric can be a nonwoven, which is consolidated with aqueous binder, such as an acrylic, SBR, polyurethane or natural polymer binder. The binder shall increase the mechanical resistance and dimensional stability of the nonwoven. Optionally, the stability of the nonwoven is increased further by a reinforcement, for example glass fiber yarns or a scrim. The nonwoven is impregnated with the aqueous binder solution, followed by drying and solidification, thereby obtaining a nonwoven carrier for bitumen impregnation.
The nonwoven carriers and bituminous membranes are generally provided in the form of relatively thin flexible sheets, typically with a thickness of a few millimeters, which can be rolled up and unrolled.
Such binder consolidated nonwoven carriers for bituminous membranes should have special properties, which render them suitable for producing bituminous membranes.
Ideally, the nonwoven carrier should not develop dimensional shrinking or stretching when subjected to temperature or mechanical forces. It should easily follow all stresses in the bituminization process (at about 180 C to 200 C), thereby having a high initial modulus and high dimensional stability (low deformation). Further the nonwoven carrier should have a high tearing resistance and elongation at break (determined from tensile test at room temperature). This requirement is important because it is determinant for the technical specification of the membrane like tearing resistance and elongation at break.
Bituminous membranes are produced in large amounts for building applications.
Therefore, they are often produced at large scale in an automated production line, wherein a roll of nonwoven carrier is continuously unwound and guided through a bath of molten bitumen. Subsequently, the product is cooled until the bitumen solidifies and the bituminous membrane product is rolled up. In such a process, it is important that the nonwoven carrier is dimensionally stable, thus being deformed as little as possible. The nonwoven carrier should not be deformed at about 180 C, when it is processed and guided through the hot bath. Otherwise, the sheet material could be damaged or a non-uniform product could be obtained. The binder must remain stable at around 180 C.
However, the properties of many polymer binders deteriorate at hot temperature, such that adhesive strength and nonwoven stability could be reduced. Therefore, many binder-consolidated nonwoven carriers, which may have mechanical stability at low temperature, are not suitable for producing bituminous membranes. Overall, there is a general desire for nonwoven carriers, from which bituminous membranes can be produced in an efficient automated large scale process without damaging the material.
Further, bituminous membranes must meet high quality standards for the building applications. Generally, they are used as building and roofing membranes, such as sarking, shielding or waterproofing membranes. In such applications, they must shield the roof and building from moisture over many years. Therefore, it is very important that bituminous membranes are homogenous and have no defects such as cracks and punctures, or even structural irregularities which could lead to damages over time. Even minor defects can lead to leakage of moisture or other problems at a building site over extended time periods. Therefore, the relatively thin bituminous roofing membranes and nonwoven carriers embedded therein should have good mechanical properties and high dimensional stability, such that they can be applied to a building or roofing site conveniently without being damaged. High stability is also required after application to the construction site, because a building site or roof can be subjected to stress and strain over the years.

- 2 -Overall, it is desirable that such nonwoven carriers for bituminous membranes are flexible, and at the same time have good mechanical properties and high dimensional stability at cold and hot temperature. Even minor improvements of mechanical stability of the nonwoven carriers at cold or hot temperature can provide a significant reduction of damages, such that a more accurate and reliable material is obtained.
In the art, various synthetic binders are used for consolidating nonwovens, such as acrylic, SBR or polyurethane polymers. For environmental reasons, there is also a desire to make use of natural and biodegradable materials. Therefore, starch-based binders for consolidating nonwoven carriers for bituminous membranes have been described in the art. Starch as a binder is available in large amounts and relatively inexpensive.
Conventional starch based binders for nonwovens are often provided in a mixture with another binder polymer. Such compositions also comprise a crosslinker which covalently links the binder molecules, such that a three dimensional polymer matrix is formed. It is also assumed in the art that a high dimensional stability is achieved by crosslinking the polymer binder.
EP 0 354 023 A2 relates to a binder composition for fiber mats, wherein the binder comprises starch, a starch crosslinking agent and an anti-wicking agent. The crosslinker can be melamine-formaldehyde or urea-glyoxal condensate. The binder may comprise a polymer strength additive, such as polyvinyl alcohol or acrylic polymer. The anti-wicking agent is typically a surfactant.

3 Al discloses a curable aqueous binder composition comprising polyvinyl alcohol, starch or sugar, a multi-functional crosslinking agent and a catalyst. It is suggested to use the binder for impregnating glass fiber products.
WO 2015/084372 Al discloses aqueous binders for impregnating nonwovens, which comprise a polyol in colloid form, such as starch, and a crosslinker. The binder may comprise additional polymers. The crosslinker is a polyfunctional small molecule, such as glyoxal or citric acid.

W02019/050439A2 relates to a heat and sound-insulating material made from mineral fiber. The product is a mat obtained from mineral fibers and a binder, which is crosslinked with heavy metal or boron compounds and heavy metal salts.
DE 1 619 127 relates to methods for impregnating fiber products with resins.
In a first step, a fibrous substrate is impregnated with an intermediate first binder (A), which is washed away after subsequent impregnation with a binder (B). The intermediate products are instable and not suitable for producing bituminous membranes.
EP 3 299 514 Al relates to textile fabrics impregnated with a binder system comprising 30cYo polyvinyl alcohol, 70% starch, a crosslinker, fillers and additives.
However, specific binder compositions or working examples are not disclosed.
The starch-based binder compositions and nonwovens consolidated therewith, which have been described in the art, could still be improved. Often, the binder compositions require various additives and are thus relatively complex. All concrete binder compositions include a crosslinker, and frequently also a catalyst for controlling the crosslinking reaction. The reaction between starch, polyvinyl alcohol and crosslinker has to be initiated, controlled and monitored. An insufficient degree of crosslinking may result in lead low product stability, whereas an overly high degree could render the product too rigid.
Thus, it would generally be desirable to consolidate such nonwoven carriers with more simple and reliable binder systems.
Further, the mechanical properties of nonwoven carriers impregnated with such binders could still be improved. There is a high need for binder-consolidated nonwoven carriers, which are flexible and have good mechanical properties at cold and hot temperature; and which are thus suitable for producing bituminous membranes. However, most prior art documents do not address this problem, and especially not mechanical properties at hot tern perature.
It is another problem that known binders for nonwoven fabrics often comprise formaldehyde-based crosslinkers, such as melamine-formaldehyde. Since aldehyde based binders, such as those derived from formaldehyde and glyoxal, can cause health problems, this is not desirable for safety and environmental reasons.

- 4 -It is also a problem that known binder compositions are often relatively expensive, because components or additives are not easily available in large amounts.
Since bituminous membranes are industrial products, which are used in large amounts in building applications, less costly binders would be desirable.
It is another problem of known binder compositions that they comprise components or additives, which are not obtainable from natural sources and/or which are not biodegradable. It would be desirable to provide easily available binder compositions which are obtainable from natural sources or biodegradable.
Problem underlying the invention The problem underlying the invention is to provide nonwoven fabrics, uses, methods and bituminous membranes which overcome the above mentioned problems. A specific problem is to provide nonwoven carriers which are impregnated and consolidated with binders in a relatively simple, efficient and inexpensive manner. The binder compositions shall be provided and processed simply and reliably. The binder should be formaldehyde-free and/or shall be available, as much as possible, from natural sources or biodegradable. Overall, the nonwoven carrier shall be produced as sustainable as possible.
It is a further problem of the invention to provide nonwoven carriers consolidated with a binder, which are highly suitable for producing bituminous membranes. The nonwoven carriers shall have good mechanical properties at room temperature, especially with regard to maximum tensile strength before break and tenacity. Moreover, the nonwoven carriers shall have high dimensional stability at hot temperature of about 180 C.
Accordingly, the nonwoven carrier shall be suitable for producing bituminous membranes in roll form with standard machinery in an automated process.
Disclosure of the invention

- 5 -Subject of the invention is a nonwoven carrier for bituminous membranes, wherein the nonwoven comprises organic polymer fibers and is consolidated with an aqueous binder, wherein the binder comprises (a) starch (b) polyvinyl alcohol, which may comprise up to 5 mol.% of other monomer units, wherein (c) the binder does not comprise a crosslinker, and (d) the binder does not comprise a filler.
Subject of the invention are also methods, uses, bituminous membranes and building materials as defined in the claims. Further embodiments are disclosed in the description.
The nonwoven carrier comprises a nonwoven consolidated with a binder.
According to ISO 9092, the nonwoven is a sheet of staple fibers or of continuous filaments that has been formed into a web by any means and bonded together by any means with the exception of weaving or knitting. Preferably, the fibers forming the nonwoven are randomly orientated. Preferably, they are bonded by friction, cohesion and/or adhesion.
The nonwoven carrier is a substrate for producing bituminous membranes.
Bituminous membranes are often used for building applications, especially roofing applications. In a typical production process, the nonwoven carrier is impregnated with molten bitumen.
The nonwoven carrier of the invention, which is consolidated with the binder, is porous.
Preferably, the void fraction of the nonwoven carrier and/or of the nonwoven before binder impregnation is between 60% and 95%, more preferably between 75% and 93%, especially between 80% and 90%. The porosity can be calculated from the weight and density of the product and components. Thus, the molten bitumen can permeate the pores from one side of the nonwoven carrier sheet to the other, such that an intimate and stable composite is obtainable after bitumen solidification. Preferably, the average pore diameter is between 50 pm and 300 pm, preferably between 80 pm and 200 pm, as preferably determined by ISO 15901-1:2016.
The nonwoven carrier is a sheet material. Preferably, it is flexible and/or rollable. Subject of the invention is also a roll of the nonwoven carrier and/or of the bituminous membrane.

- 6 -Such a roll can be unrolled and rolled up again conveniently by a user.
Flexibility and roll form of the nonwoven carrier are advantageous for efficient processing in an automated, continuous process. Flexibility and roll form of the bituminous membrane are advantageous for application and processing at a building site or the like.
The nonwoven carrier is consolidated with an aqueous binder. This is a solution or dispersion of the polymers and optionally additives in water, which is applied to the nonwoven, typically by impregnation in a bath, dried and solidified, and bonds the nonwoven fibers together. The nonwoven binder enhances the stability of the nonwoven.
The inventive binder comprises starch and polyvinyl alcohol. Nonwoven binders comprising starch and polyvinyl alcohol have been described in the art.
However, the binder according to the present invention is different, because it does not comprise a crosslinker. Surprisingly, it was found that crosslinker-free binders comprising starch and polyvinyl alcohol as structural polymers are applicable for producing nonwoven carriers for bituminous membranes, which meet the high requirements regarding mechanical resistance and dimensional stability at cold and even at hot temperature around 180 C. It was unexpected that such nonwoven carriers would have sufficient stability even at hot temperature in the absence of a crosslinker, which is used in conventional binders for forming a three-dimensional matrix of covalently linked binder polymers. More surprisingly, it was also found that the crosslinker free binders can have even better mechanical properties at cold and hot temperature, and especially better dimensional stability, than respective binders with crosslinker.
As used herein, the term crosslinker refers to a compound which is specifically added to the aqueous binder, and which forms covalent linkages of binder polymers in the binder composition upon consolidation. According to the invention, no such compound is present which would form covalent bonds between starch and polyvinyl alcohol molecules.
Polyvinyl alcohol and starch are polyols, which are characterized by repetitive hydroxyl functional groups on the polymer backbones. In the art, crosslinkers for binders comprising starch and/or polyvinyl alcohol are often compounds having two or more functional groups, which can react with hydroxyl groups, often carboxylic groups, but also amine or aldehyde groups. Starch can also be chemically modified, for example by partial oxidation in which some hydroxyl groups are converted into carboxyl groups.
Such

- 7 -modified starch may be crosslinked with crosslinkers having hydroxyl and carboxyl groups. The aqueous binder used according to the present invention does not comprise a crosslinker compound, which would covalently link the specific starch to the polyvinyl alcohol during consolidation of the binder.
The aqueous binder of the present invention does not comprise a crosslinker.
Typical crosslinkers for respective binders in the art are formaldehyde or formaldehyde resins, such as urea-formaldehyde resin, melamine-formaldehyde resin or acetone-formaldehyde resin, glyoxal or glyoxal resins, urea or urea resins, or non-polymeric polycarboxylic acids or non-polymeric polycarboxylic acid anhydrides comprising two, three or more carboxylic groups, such as citric acid. In a preferred embodiment, the aqueous binder does not comprise an additional compound which comprises two or more functional groups for crosslinking the specific starch and polyvinyl alcohol in the binder, and especially for crosslinking hydroxyl groups of the starch and polyvinyl alcohol; such as functional groups selected from carboxyl, isocyanate, amine, aldehyde, epoxide or keto groups.
The binder also does not comprise crosslinkers in the form of heavy metal or boron salts or compounds. Preferably, the binder does not comprise a catalyst, especially a crosslinking catalyst, because no chemical reaction needs to be catalyzed.
Preferably, the nonwoven is not consolidated with the aqueous binder in a manner such that the binder is crosslinked. Crosslinking of starch and polyvinyl alcohol does not occur in a crosslinker-free binder under standard conditions, at which a nonwoven is impregnated, dried and the binder is solidified. However, under specific harsh conditions, at least some degree of crosslinking may occur although no crosslinker is present.
Therefore, it is preferred that the nonwoven carrier, during or after binder consolidation, is not subjected to conditions at which crosslinking would occur. For example, it is preferred that a very high or very low pH, pressure, temperature and/or water depletion is/are not adjusted; that the aqueous binder does not comprise highly reactive additives;
or that the nonwoven carrier is not subjected to a highly reactive environment, such as reactive radiation or plasma.
Preferably, in the nonwoven carrier of the invention, the starch and polyvinyl alcohol are not crosslinked, or at least not substantially crosslinked. In this regard, "substantially"
means that although conditions are adjusted such that no crosslinking should occur, an

- 8 -

9 unavoidable and negligible small number of covalent bonds may be formed, for example due to impurities or structural anomalies of the raw materials. For example, not substantially crosslinked could mean that less than 2% or less than 0.5 % of the starch and/or polyvinyl alcohol molecules are covalently bonded to each other. The amount of crosslinking can be determined by removing the binder from the nonwoven carrier, molecular analysis, for example by MALDI TOF, and comparison to the aqueous binder solution.
The starch can be modified starch or native (natural) starch. Native starch is directly obtained from natural origin without any physical or chemical treatment.
Preferably, the origin of the modified or native starch is natural. Preferably, the origin is plants, preferably vegetables. Preferably, the starch origin is tubers, such as potatoes, manioc, maranta, batata, grain such as wheat, corn (maize), rye, rice, barley, millet, oats, sorghum, fruits such as chestnuts, acorns, beans, peas, and other legumes, bananas, or plant pulp, e.g.
sago palm. Preferably, the starch is corn starch, which is preferably modified.
In a preferred embodiment, the starch is not native starch. Thus, the starch is modified starch. It is highly preferred that the starch is physically and/or chemically modified.
Modified starch is obtainable by physical and/or chemical treatment of natural starch, typically in order to change its properties. According to the invention, it was found that modified starch can confer high stability to the nonwoven carriers. In contrast, it can be more difficult to provide a uniform binder with native starch in the absence of a crosslinker, which can result to lower stability of the nonwoven carrier.
In a preferred embodiment, the starch is chemically modified. In this regard, the term "chemically modified" refers to partly hydrolysed starch and starch with chemically modified side chains and/or functional groups. For example, the chemically modified starch can be alkaline-modified starch, bleached starch, oxidized starch, acetylated starch, hydroxypropylated starch, starch ether, hydroxyethyl starch, cationic starch or carboxymethylated starch.
In a further embodiment, the starch can be a dextrin, such as maltodextrin or cyclodextrin.
Dextrins are low-molecular-weight carbohydrates obtained by hydrolysis of starch, which are characterized by a dextrose equivalent between 3 to 20. In another embodiment, the starch is not dextrin. Since molecular weights of dextrins are relatively low, it can be preferred to use starch having a higher molecular weight for obtaining a highly stable product.
In a preferred embodiment, the chemically modified starch is partly hydrolysed starch.
Partly hydrolysed starch is characterized by lower polysaccharide chain lengths compared to the corresponding natural starch. It was found that partly hydrolysed starch can confer advantageous properties to the nonwoven carriers.
In an embodiment, the starch may have an average molecular weight between 500 g/mol and 25,000 g/mol, especially between 2,500 g/mol and 20,000 g/mol, as determined by MALDI-TOF.
Preferably, the starch, especially the chemically modified starch, does not comprise chemically modified side chains, i.e. hydroxyl groups which have been converted into other functional group by chemical reaction. Preferably, the starch comprises the hydroxyl groups as its starch precursor from natural origin. Native starches, physically modified and partly hydrolysed starches have a characteristic structure, in which all functional groups on the polymer backbone are hydroxyl groups. In these starches, the amount of other functional groups is negligible, for example less than 2%, less than 0.5% or less than 0.2% of the total hydroxyl groups and/or total of non-terminal hydroxyl groups. It was found that the stability of the nonwoven carrier at cold and hot temperature can be especially high when the starch hydroxyl groups are not chemically modified.
In a preferred embodiment, the average size of the starch particles in the aqueous binder dispersion is at least 0.1 pm, preferably at least 1 pm, more preferably at least 2 pm or at least 5 pm. The average size can be in the range of 0.1 pm to 50 pm, preferably 1 pm to 50 pm, especially between 5 pm and 25 pm. The average particle size can be determined by dynamic light scattering (DLS), for example according to ISO 22412:2017. In this regard, the term "starch particles" refers to the starch aggregates observed, which may also include some PVOH. It was found that such a relatively high particle size can correlate with high dimensional stability to the nonwoven carrier at hot temperature and higher mechanical resistance at cold temperature.

- 10 -The starch may have a viscosity of 50 mPa*s to 800 mPa*s, preferably 150 mPa*s to 600 mPa*s, or more preferably 250 mPa*s to 600 mPa*s, as determined according to ISO 2555 at a concentration of 25 wt.% and 23 C. The starch viscosity may be at least 50 mPa*s, preferably at least 150 mPa*s, or more preferably at least 250 mPa*s. It was found that the mechanical stability of the nonwoven carrier at cold and hot temperature can be improved significantly, if the viscosity of the starch is adjusted accordingly. Without being bound to theory, it was found that viscosity may be a more suitable parameter for selecting the type of starch in the binder composition than molecular weight, because viscosity depends not only from molecular weight, but also other properties such as the three dimensional structure of the starch molecules.
Starch is a polysaccharide, which consist essentially of amylose and/or amylopectin. In a preferred embodiment, the ratio of amylose in the starch is between 10% and 50%, more preferably between 15% and 30% (dry weight, of total amount amylose and amylopectin).
It was found that such a starch comprising a relatively high degree of amylopectin, such as corn starch, can confer high dimensional stability to the nonwoven carrier.
In a preferred embodiment, the starch is to-be-cooked type. Preferably, the starch is insoluble in water at 23 C and/or is not pre-gelatinized. Preferably, the starch is not soluble when 5 wt.% is added to cold water at and stirred for 2 minutes.
Starch is commercially available in soluble or insoluble form. For various practical and industrial applications, soluble starch such as pre-gelatinized starch is more convenient to use.
Soluble starch can be dissolved easily in water at cold temperature. In starch industry, native starch is rendered soluble by physical treatment, such as heating, mechanical shearing, drying and grinding. Soluble starch can be provided in dry powder form, is instantaneously soluble in cold water and has thickening/gelling capability.
Pre-gelatinized soluble starch particles exhibit a lack of birefringence and retain little, if any, of the original native granule structure. According to the invention, it was found that to be cooked type starch can provide high stability to the nonwoven carrier at cold and hot temperature.
Since starch to be cooked cannot be simply dissolved in cold water, it should be subjected to a pretreatment before applying the binder of the present invention to the nonwoven.
Typically, the pre-treatment comprises heating and stirring, for example to at least 80 C, preferably at least 90 C. After cooling, the uniform starch dispersion obtained can be added to the binder.

-11 -Preferably, the starch is physically modified. Starch can be subjected to a physical treatment, for example under heat and/or mechanical shearing, which changes the physical structure. Herein, a modification is considered physical, if no chemical reaction occurs, such as cleavage of polysaccharide chains. Physical modification can render the starch more homogeneous, which can improve the binder properties.
In a highly preferred embodiment, the starch is a partly hydrolyzed starch from natural origin, which preferably comprises 10% to 50% amylose (dry weight, of total of amylose and amylopectin), and which has an average molecular weight between 1000 and 2500 g/mol, and/or an average size of the starch particles in the starch dispersion and/or aqueous binder dispersion of at least 0.1 pm, preferably at least 1 pm, and/or a viscosity of at least 150 mPa*s, preferably at least 250 mPa*s, determined according to at a concentration of 25 wt.% at 23 C. It was found that stability of the nonwoven carrier at hot temperature can be especially high when using starch having such properties.
In another embodiment, the starch is chemically modified starch, wherein functional groups are chemically modified. Hydroxyl groups of the starch substrate can be converted at least in part to different functional groups, for example by etherification, esterification, amidation or oxidation. Chemically modified starches include starch esters, such as xanthogenates, acetates, phosphates, sulfates, nitrates; starch ethers, such as methyl- or ethyl- ethers, nonionic, anionic or cationic starch ethers, and oxidized starches such as carboxylic starch. In a preferred embodiment, the starch comprises at least 90%, preferably at least 95%, more preferably at least 98%, or even at least 99%
hydroxyl groups, which are not chemically modified. Most preferably, the starch does not comprise chemically modified hydroxyl groups. A high level of hydroxyl groups could be advantageous for binder stability, which could be mediated at least in part by hydrogen bonds. In another embodiment, the starch is partly oxidized. Preferably, the oxidation degree of the hydroxyl groups is low, for example between 0.1 and 10%, or between 0.5 and 5%. The partly oxidized starch could comprise more than 90% amylopectin.
In an embodiment, the starch comprises about 99% amylopectin and has an oxidation degree of about 0.5 to 2%.

- 12 -The aqueous binder comprises polyvinyl alcohol, which may comprise up to 5 mol.% of other monomer units. Polyvinyl alcohol is a linear polymer consisting of monomeric building blocks with hydroxyl groups. It is assumed that starch has good compatibility with polyvinyl alcohol, also because both polymers comprise hydroxyl groups and are capable of forming intramolecular hydrogen bonds. It is a further advantage of polyvinyl alcohol that it is biodegradable, although relatively slow.
Preferably, the viscosity of the polyvinyl alcohol is at least 25 mPa*s, more preferably at least 30 mPa*s. Preferably, the viscosity is in the range of 25 to 100 mPa*s, more preferably between 30 and 75 mPa*s. It was found that the mechanical properties of the nonwoven carrier are especially good at cold and hot temperature, if the viscosity of the polyvinyl alcohol is adjusted accordingly. If the viscosity is too low, the mechanical stability of the nonwoven can decrease. If the viscosity is too high, the workability may be lower and formation of an intimate mixture of starch and polyvinyl alcohol may be impaired.
Herein, viscosities of polyvinyl alcohol are determined according to ISO 2555 at a concentration of 4 wt.% at 23 C.
Preferably, the polyvinyl alcohol has a saponification degree (degree of hydrolysis) of at least 90 mol%, more preferably of at least 95 mol% or at least 98 mol%. The degree of saponification indicates which degree of acetate groups from a precursor polymer is converted into hydroxyl groups. A high degree of saponification is advantageous, because the binder is more uniform and can thereby confer higher stability to the nonwoven carrier.
The polyvinyl alcohol may comprise up to 5 mol.% of other monomer units, preferably up to 2 mol.%. Such other monomer units are incorporated intentionally into the polymer chain during polymerization. Thus, the other monomers are part of the monomer mixture from which the polyvinyl alcohol or polyvinyl alcohol precursor, typically polyvinyl acetate, is polymerized. Thus, the monomer is not vinyl alcohol or residual vinyl acetate, which has not been hydrolysed when converting polyvinyl acetate to polyvinyl alcohol.
Polyvinyl alcohol derivatives with other monomer units are known in the art and commercially available. For example, a small amount of other monomer groups, such as ethylene or carboxylic groups, can be incorporated into the polymer in order to confer a desired functionality to the polymer. In a preferred embodiment, the polyvinyl alcohol does not comprise other monomer units and/or groups, except for residual acetate groups. This can

- 13 -be advantageous, because the polymer is homogenous and may confer high stability to the nonwoven carrier.
In one embodiment, the polyvinyl alcohol has a polymerization degree of at least 600, more preferably at least 1000. A relatively high polymerization degree, which correlates to a relatively high polymer chain length, may provide good mechanical stability to the nonwoven carrier.
In a preferred embodiment, the starch and/or the polyvinyl alcohol are produced from natural raw materials. Starch can be produced from natural origin and polyvinyl alcohol from natural building blocks, for example based on bioethanol. Accordingly, a sustainable binder can be produced, which is also biodegradable. Preferably, the nonwoven fibers are from recycled PET, for example from used PET bottles. Thereby, a sustainable nonwoven carrier can be provided.
In preferred embodiments, the amount of polyvinyl alcohol in the binder is less than 30 wt. 70, less than 25 wt.% or less than 20% wt.%. It is an advantage that the ratio of starch in the composition can be significantly higher than the ratio of polyvinyl alcohol, because commercially available starch is less expensive than polyvinyl alcohol. Since crosslinkers are excluded, the additives, if present, do not comprise crosslinkers.
In a preferred embodiment, the binder comprises only starch and polyvinyl alcohol as solid components. According to the invention, it was found that highly advantageous properties can be conferred to the nonwoven carrier by a binder, which consists completely or predominantly of starch and polyvinyl alcohol. In industrial applications, it is highly advantageous if such a binder consists of a low number of components. At first, it can be prepared easily and is inexpensive. Further, both polymer components are biodegradable.
It is another advantage of a binder without crosslinker that no chemical reaction is carried out during or after impregnation of the nonwoven. In contrast, reactive binders used in the art require control of the chemical reaction. If the reaction is incomplete or excessive, the product can have undesired properties. Overall, a simple binder composition can improve product uniformity, reproducibility and quality control. Another advantage of binders without crosslinker is that excessive aqueous binder from the production process can be reused. In contrast, an aqueous binder which is crosslinked cannot be used again and has

- 14 -to be discarded. Thus, invention can reduce waste and provides a more sustainable nonwoven carrier. Surprisingly, it was also found that binder without crosslinker can confer even better mechanical properties, including dimensional stability, to a substrate than a comparable binder with crosslinker. For example, it was found that a binder without crosslinker can have lower hot deformation, which is especially important for the bituminization process. This was unexpected, because it is generally assumed in the art that crosslinkers increase the dimensional stability by formation of a polymer network.
In a preferred embodiment, the binder does not comprise structural polymers different from starch and polyvinyl alcohol. Preferably, the binder does not comprise an additional structural polymer which is commonly used in nonwoven binders, such as acrylic polymers, SBR, polyurethane, polyamides, polyester, or copolymers thereof, or other natural polymers, such as proteins, gelatin or alginate. Preferably, the binder does not comprise other polymers at all, and thus also not as functional additives.
Since nonwoven carriers with high mechanical stability can be obtained only with starch and polyvinyl alcohol as structural polymers, it is not necessary to include additional structural polymers.
This is also advantageous for ease of the production process, quality control and cost reasons.
The binder may comprise additives. Preferably, the total amount of additives is relatively low. Preferably, it is less than 15 wt.%, more preferably less than 10 wt.%, or less than 5 wt.%, all wt.% relating to total binder dry weight. It is especially preferred that the amount of additives is less than 2 wt%, less than 1 wt.%, or that no additives are present at all. Accordingly, it is preferred that the binder consists fully or substantially of starch and polyvinyl alcohol as the solid components.
The additives can be functional additives, which confer a desired property to the binder.
Such functional additives are known in the art and include UV stabilizers, adhesion promoters, colorants and processing aids. Preferably, the additives are not polymers. In a preferred embodiment, only additives are additives in the aqueous binder solution, which do not become part of the consolidated binder on the nonwoven carrier, such as salts and buffer substances.

- 15 -It is highly preferred that the total amount of additives is low. According to the invention, it was surprisingly found that a very simple binder composition based essentially or solely on starch and polyvinyl alcohol can confer highly advantageous properties to the nonwoven carrier. Thus, the binder solution can be very simple, which is advantageous for large scale production and processing. A low amount of additives can also be advantageous for environmental reasons. Generally, a binder without additives or with only low amount of additives can be recycled more efficiently. Such a binder can be recycled from the binder bath and/or can be stripped from the nonwoven carrier and recycled. In contrast, crosslinked binders or binders comprising high levels of synthetic additives cannot be recycled efficiently.
The binder does not comprise a filler. This can be advantageous, because fillers are often applied in relatively high amounts and can significantly impair the stability of the polymer matrix formed from starch and polyvinyl alcohol. Especially since the binder is not crosslinked, nonwoven carrier stability could be decreased by a filler.
According to the invention, it was found that common functional additives, which are used in such binders in the art, can have a negative impact on the mechanical properties of the nonwoven carrier. In a preferred embodiment, the binder does not comprise a surfactant, detergent, wetting agent, emulsifier, protective colloid and/or dispersant, preferably none of these additives. Preferably, the binder does not comprise an additive, which is an amphipathic molecule or a non-ionic surfactant. More preferably, the binder does not comprise a hydrocarbon containing 8 to 18 carbon atoms, which is attached to a polar or ionic portion, and/or an ethoxylated surfactant, such as an ethoxylated sorbitan ester.
Without being bound to theory, such functional additives can impair the internal hydrogen bonds between binder molecules, thereby reducing the stability of the nonwoven carrier.
However, the binder may comprise unavoidable impurities, such as salts, which have no relevant impact on the consolidated binder structure.
Preferably, the polyvinyl alcohol is provided to the binder in form of an aqueous solution.
Preferably, the polyvinyl alcohol it is not provided in the form of a dispersion. In this embodiment, it is provided without additives required for preparing such a dispersion, such as emulsifiers or protective colloids.

- 16 -In another embodiment, the binder does not comprise an additive which comprises hydrophilic groups, such as hydroxyl groups, carboxyl groups, amine groups, aldehyde or keto groups and/or ionic groups. More preferably, the binder does no comprise an additive which comprises hydroxyl groups. Without being bound to theory, hydrophilic groups may affect hydrogen bonds in the binder structure and thus reduce the stability of the nonwoven carrier.
In a preferred embodiment, the binder comprises 5 to 95 wt.%, preferably 10 to 90% starch, 5 to 95 wt.%, preferably 10 to 90% polyvinyl alcohol, and 0 to 15 wt.%, preferably 0 to 2% additives, wherein the total of all percentages is 100 wt.%. Herein, all percentages of binder components refer to dry weight, unless noted otherwise. It was found that even in the absence of a crosslinker, the amounts of starch and polyvinyl alcohol can be varied broadly in order to provide various nonwoven carriers having high dimensional stability at hot or cold temperature.
In a preferred embodiment, the binder comprises 50 to 95 wt.%, preferably 72 to 95 wt.%
starch, 5 to 50 wt.%, preferably 5 to 28% wt.% polyvinyl alcohol, and 0 to 15 wt.%
preferably 0 to 2 wt.% additives, wherein the total of all percentages is 100 wt.% (dry weight). It was found that binder compositions comprising such relatively high amounts of starch can confer high dimensional stability to the nonwoven carrier.
In another preferred embodiment, the binder comprises 5 to 69 wt.% starch, 31 to 95 wt.%
polyvinyl alcohol and 0 to 15 wt.%, preferably 0 to 2 wt.% additives, wherein the total of all percentages is 100 wt.% (dry weight). It was found that binder compositions comprising such relatively high amounts of polyvinyl alcohol can confer high mechanical resistance to the nonwoven carrier.
In another preferred embodiment, the binder comprises 30 to 70 wt.% starch, 30 to 70 wt.% polyvinyl alcohol and 0 to 15 wt.%, preferably 0 to 2 wt.% additives, wherein the total of all percentages is 100 wt.% (dry weight). It was found that binder compositions comprising relatively similar amounts of polyvinyl alcohol and starch can confer high dimensional stability to the nonwoven carrier, especially at hot temperature.

- 17 -In a preferred embodiment, the binder comprises 60 to 90 wt.% starch, 10 to 40 wt.%
polyvinyl alcohol and 0 to 5 wt.% additives, wherein the total is 100 wt.%
(dry weight). In another preferred embodiment, the binder comprises 70 to 90 wt.% starch, especially 72 to 90 wt.% starch, 10 to 30 wt.% polyvinyl alcohol and 0 to 5 wt. /0 additives, wherein the total is 100 wt.% (dry weight).
The nonwoven can be spunlaid, spunlace, melt-spun or staple fiber nonwoven. As used herein, the term fiber includes staple fibers and filaments. Staple fibers have a defined length, whereas filaments can be "endless" filaments. Staple fibers can be processed and laid by conventional means, such as carding. Preferably, the length of staple fibers is between 20 mm to 200 mm, more preferably between 60 mm to 100 mm.
The nonwoven comprises organic polymer fibers. In a preferred embodiment, the organic fibers are synthetic fibers. Preferably, the nonwoven consists of organic polymer fibers, preferably synthetic fibers. Preferably, the nonwoven does not comprise nonwoven inorganic and/or mineral fibers, such as nonwoven glass fibers. Nonwovens from organic and polymer fibers are advantageous, because they are lighter than glass fiber and the binder can provide high stability to such nonwovens. In a preferred embodiment, the organic polymer is polyester. The polyester can be selected from polyethylene terephthalate, polybutylene terephthalate and polyester copolymers. It is preferred that the polyester is polyethylene terephthalate (PET). This polymer is especially suitable for carriers for bituminous membranes, because it has high melting temperature, low cost and good mechanical properties. It is also assumed that binders based on starch and polyvinyl alcohol, as used in the present invention, have good adhesion to polyester fibers, especially PET fibers. In a preferred embodiment, the nonwoven fibers are only polyester fibers. The nonwoven may comprise monocomponent and/or multicomponent fibers, such as bicomponent fibers. The nonwoven may optionally comprise additional reinforcing inorganic fibers. If the nonwoven consists of organic polymer fibers, preferably synthetic fibers, preferably polyester fibers, especially PET fibers, it may optionally comprise a reinforcement, which is not made from nonwoven fibers.
In an embodiment, the nonwoven fibers are a mixture of organic fibers and inorganic fibers. The nonwoven may comprise a mixture of polyester fibers and other nonwoven

- 18 -fibers, for example less than 50%, less than 20% or less than 10% by weight of all fibers.
The nonwoven may comprise other fibers which are relatively stable at hot temperature, such as natural fibers or inorganic nonwoven fibers.
Preferably, the linear density of the nonwoven fibers is from 0.5 to 20 dtex, more preferably from 1 to 10 dtex, especially in the range of 2 to 6 dtex.
Nonwovens of such fibers can provide strength and flexibility to bituminous membranes.
Preferably, the diameter of the nonwoven fibers is in the range of 5 pm to 50 pm, preferably 10 to 30 pm.
Preferably, the fiber titer is at least 2.5 dtex.
In a preferred embodiment, the nonwoven comprises a reinforcement. As used herein, the reinforcement relates to any fibrous structure, i.e. fibers, filaments, yarns, wires or other elongated structures. Reinforcing fibers are different from the nonwoven fibers, because they are not randomly laid into the fleece (nonwoven precursor) in the nonwoven production process, as the other nonwoven fibers. In contrast, the reinforcing fibers are incorporated in a different manner during or after the nonwoven production process.
Often, a reinforcement is directional, i.e. it especially reinforces the nonwoven in a specific direction. For example, the reinforcement can be linear yarns or a discrete layer, such as a scrim. The reinforcing fibers are not part of the fiber raw material, which is laid to form the nonwoven or fleece precursor. Preferably, the reinforcement is embedded in interior of the nonwoven carrier.
The reinforcement can be multi- and/or monofilaments. The reinforcement can be from aramids, preferably so-called high-module aramids, carbon, glass, glass ravings, mineral fibers (basalt), high-strength polyester monofilaments or multifilaments, high-strength polyamide monofilaments or multifilaments, as well as yarns, such as hybrid multifilament yarns (yarns containing reinforcing filaments and lower melting binder fibers), or wires (monofilaments) made of metals or metallic alloys. Preferably, the reinforcement is made from inorganic fiber, such as glass fibers or glass fiber yarns.
In a preferred embodiment, the reinforcement is yarns, preferably glass fiber yarns.
Preferably, the amount of glass fiber yarns in the nonwoven carrier is 2 to 20 wt.%, preferably 5 to 15 wt.%. Such levels are normally sufficient for increasing the strength without impairing the nonwoven properties. Preferably, the yarns are aligned to each

- 19 -other, preferably in parallel. Glass fiber yarns can increase the mechanical strength of the nonwoven carrier.
Preferably, the nonwoven carrier consists of the nonwoven, which is consolidated with the binder and which optionally comprises the reinforcement. In another embodiment, the nonwoven carrier is a composite substrate which comprises an additional, separate layer of inorganic fibers. The additional layer can be a nonwoven, a woven, a net or scrim, or a layer of fibers and/or yarns. In another embodiment, the nonwoven does not comprise an additional layer.
In a preferred embodiment, the base weight of the nonwoven, before impregnation with the binder, is from 50 to 500 g/m2, more preferably from 100 to 300 g/m2, especially from 150 to 250 g/m2. Such base weights are especially suitable for bituminous membranes.
The nonwoven can be pre-consolidated before impregnation with the binder, especially mechanically, for example by hydroentangling or pre-needling. Preferably, the load of binder (add-on) is from 1% to 50 wt.%, preferably from 5% to 40 wt.%, more preferably from 10% to 30 wt.%, of the nonwoven (dry weight without binder). Preferably, water is the only solvent in the aqueous binder.
Preferably, the thickness of the nonwoven carrier is between 0,25 mm and 6 mm, more preferably between 0,5 mm and 4 mm, and especially between 0.8 mm and 2 mm, as determined according to ISO 9073-2, 1997, section 5.1, normal nonwovens.
In a preferred embodiment, the nonwoven carrier has a hot tensile deformation at 180 C
and 120 N of less than 1.8%, more preferably less than 1.5%, preferably determined at a base weight of 180 g/m2. Due to this high dimensional stability, the nonwoven carrier can be advantageously used for producing bituminous membranes with standard machinery.
Further, the high stability at hot temperature indicates that the bituminous membranes remain stable for long time periods in building and roofing applications. Even in moderate climate, roof temperatures can raise up to 100 C, for example when the sun shines directly on metal parts of a roof. In hot geographical regions and for specific applications, temperatures may raise even higher. Therefore, high dimensional stability at hot temperature is also advantageous for building and roofing applications.

-20 -In a preferred embodiment, the nonwoven carrier has a maximum glass tensile strength at 180 C of at least 150 N/50 mm, more preferably at least 200 N/50 mm, especially when comprising reinforcing glass fiber yarns. The maximum glass tensile strength is correlated to dimensional stability. It defines the threshold, at which the nonwoven collapses because of the breaking of the reinforcement, typically the glass fibers. This is defined by a defined peak in the tensile strength vs. elongation diagram. High maximum glass hot tensile strength is desirable, because it indicates that the material can withstand higher tension and pulling forces at 180 C on the bitumen production line, especially at higher speed. When a higher force than the maximum glass tensile strength is exerted on the nonwoven carrier, it loses its shape (collapses) and cannot be processed any more. Thus, the high maximum glass tensile strength indicates that the nonwoven carrier is suitable for efficiently producing high quality bituminous membranes in an industrial process.
At low temperature, Bituminous membranes are used for building applications and are subjected to mechanical forces, for example bent to covering irregular building parts, nailed or subjected to stress and strain. Thus, it is important that the material is mechanically stable at low temperature to avoid punctures, ruptures and the like.
Preferably, the total maximum tensile strength of the nonwoven carrier at room temperature (23 C) is at least 600 N/5 cm, more preferably at least 625 N/5 cm, determined according to ISO 9073-3. Preferably, the peak tenacity at room temperature is at least 0.28 daN/5 cm/g/m2. Preferably, at room temperature the elongation at break is at least 40%, determined according to ISO 9073-3.
Unless noted otherwise, the above parameters regarding mechanical stability are determined in machine direction, preferably in machine direction and cross-direction.
Preferably, the properties are determined for a base weight of 180 g/m2 spunbond with additional 20% binder add-on.
Preferably, the air permeability of the nonwoven carrier is 250 2500I/m2, as determined by ISO 9037-15.
Subject of the invention is also a method for producing the nonwoven carrier of the invention, comprising the steps of

-21 -(a) providing a nonwoven, (b) impregnating the nonwoven with an aqueous binder comprising starch and polyvinyl alcohol, wherein the binder does not comprise a crosslinker, and (c) drying and solidifying the binder to obtain the nonwoven carrier.
In the production process, the solidification may be achieved by drying. Since no crosslinker is present, it is not necessary to induce, monitor and/or terminate a crosslinking reaction.
Subject of the invention is also the use of the nonwoven carrier of the invention as a substrate for producing bituminous membranes. Subject of the invention is also a bituminous membrane, comprising the nonwoven carrier of the invention. Subject of the invention is also a method for producing a bituminous membrane, comprising the steps of (A) providing a nonwoven carrier of the invention, and (B) impregnating the nonwoven carrier with bitumen.
Typically, the impregnation of the nonwoven carrier with bitumen is performed in a bath comprising molten bitumen in which the nonwoven carrier is immersed. The nonwoven carrier with the bitumen attached to it is subsequently removed from the bath and dried.
Preferably, the method is carried out as an automated process, preferably a continuous process, in which "endless" rolls of the nonwoven carrier are fed into the process and rolls of the bituminous membrane are obtained as the final product.
For an efficient production of bituminous membranes from the nonwoven carrier, the nonwoven carrier and the bituminous membranes should be flexible. Accordingly, the nonwoven carriers and/or bituminous membranes are rollable. In contrast, the nonwoven carriers and/or bituminous membranes are not rigid.
The bituminous membrane is obtainable in a conventional process, in which nonwoven carrier, which is bonded with the binder, is impregnated with molten bitumen in a bath.
Typically, the nonwoven carrier is provided in roll form to a production line where it is unrolled and directed through the hot bitumen bath by standard machinery, led out of the bath, followed by cooling and solidification of the bitumen adhered to the carrier. After

-22 -solidification, the bituminous membrane is rolled up, such that it can be stored, shipped and provided to the building site.
The bituminous membrane can be used in building and roofing applications.
Typically, the bituminous membrane is unrolled at the building site, optionally cut to a desired shape, subjected to temporary heat by flaming in order to soften at least a bituminous surface, laid on the application site, and optionally deformed and thus aligned with the surface of the application site. Subsequently, additional layers, such as insulating layers or tiles, are laid over the bituminous membranes. Methods for applying bituminous membranes in building applications are standardized in DIN V 20000-201. In the bituminous membrane, the proportion of bitumen to the nonwoven carrier is preferably 60 to 97% by weight to 3 to 40% by weight.
Subject of the invention is also a roof, building material or building, which comprises a bituminous membrane of the invention. For example, the bituminous membrane can be used as a sarking membrane, sealing membrane or waterproofing sheet.
The nonwoven carrier of the invention can also be used for other applications, such as a reinforcing insert, optionally in combination with further textile fabrics, for sarking membranes, as a textile backing or textile reinforcement, in flooring, in particular fitted carpets and PVC flooring, as a facer in wall coatings for the interior and exterior of buildings, or in decorative surfaces.
The nonwoven carrier, bituminous membranes, uses and methods of the invention solve the problem underlying the invention. A nonwoven carrier for producing bituminous membranes is provided which is easily available, easy to produce, inexpensive and has excellent mechanical properties. Surprisingly, although no crosslinker is added which would stabilize the binder system, the nonwoven carriers have high mechanical resistance and especially dimensional stability at room temperature and also at hot temperature, which can be even better than for comparable binders which comprise a crosslinker. This was unexpected, because the stability of many thermoplastic polymer binders deteriorates at hot temperature. Due to the high mechanical resistance (as indicated by tensile strength, tenacity) and dimensional stability (as indicated by hot deformation), the nonwoven carriers are suitable for producing high quality bituminous membranes in an

-23 -efficient high-speed automated process. The high dimensional stability at hot temperature and also the very good mechanical properties at room temperature render the nonwoven carriers especially suitable for building and roofing applications. The invention also provides guidance how to provide specific crosslinker-free starch/polyvinyl alcohol binders having especially advantageous properties. It is a further advantage that the binder is biodegradable and formaldehyde-free, and can be based on natural sources, such that a sustainable product can be provided.
Examples In the following working examples, bottle recycled polyester (RPET) nonwovens were consolidated with various starch / polyvinyl alcohol binder compositions without crosslinker.
Materials and Methods Dynamic Light Scattering ¨ Size Distribution Analysis The average particle size of solutions were determined by dynamic light scattering (DLS) using a 90 Plus Particle Size Analyzer (Brookhaven Instruments Corporation, US) at 25.0 0.1 C. The autocorrelation function was measured at 900, while the laser beam was operating at 658 nm. The mean size and standard deviation ( S.D.) were directly obtained from the instrument fitting data by the inverse "Laplace transformation"
method and by Contin. All analyses were done in triplicate and expressed as mean standard deviation.
The S.D. was found to be 10 nm.
Starches Four different corn starches were used for preparing the binders. Starch A is constituted by 99% of amylopectin, which is partly oxidized at low degree. Starch B and starch C
comprise about 20 to 25% (dry weight) amylose and are partly hydrolyzed to decrease the M. Starch D comprises about 20 to 25% (dry weight) amylose, is pre-gelatinized and water soluble. It has been pre-treated by the supplier by cooking and water removal, which renders the starch water soluble such that no cooking step is required before use.

-24 -The viscosities of the starches were measured according to ISO 2555 at 23 C
with

25% (w/w) aqueous dispersion or solution. The properties determined for the starches are summarized in table 1 below.
Table 1: Properties of starches Starch A
viscosity (m Fes) 450 370 100 Polyvinyl Alcohol (PVOH) Polyvinyl alcohols were used in various grades, which are characterized by different lo molecular weights. The higher the molecular weight, the higher is the viscosity of the polymer in aqueous solution. All grades are characterized by 98% of hydrolysis (of acetate groups). The pH of PVOH aqueous solutions is 6, as determined according to ISO
976.
Viscosities were determined according to ISO 2555 at 23 C with 4% (w/w) aqueous solution and are summarized in table 2.
Table 2: Viscosity of PVOH grades Type PVOH 498 PVOH 698 PVOH 1098 PVOH

Viscosity (mPa*s) 22 26 32 Degree of hydrolysis 98 ¨ 98.8 98 ¨ 98.8 98 ¨ 98.8 98 ¨ 98.8 (saponification) Methods Binder preparation Binders were prepared by mixing the starch dispersion (20% solid content) and PVOH
solution (10% solid content). In a typical procedure, the starch dispersion (500 g ¨ 20%
solid content) was prepared by dispersing 100 g dry starch in 400 g water. The starch dispersion was heated to 90 C and left at this temperature for 15 minutes keeping the system under mechanical stirring. Finally, the system was cooled to 60 'C. The PVOH
water solution (10% solid content) was prepared by introducing 60 g PVOH and 540 g water into a three-necked flask equipped with mechanical stirrer. Then the mixture was heated up to 95 C and kept at this temperature for at least 40 minutes.
Afterwards, the temperature was cooled down to 60 C. 500 g binder formulation with a solid content of 12.5% was prepared by mixing 219 g of the starch dispersion, 187 g of the PVOH
solution and 94 g water. 1 g wetting agent was added if indicated. Finally, the mixture was stirred at 60 C for 10 minutes and used for nonwoven impregnation.
Nonwoven Impregnation The nonwoven substrate was a spunbond nonwoven fabric from recycled polyethylene terephthalate (PET) fibers (4,4 dtex; reinforced with glass yarns 68 tex, base weight 180 g/m2, pre-consolidated by needle-punching and thermosetting). The nonwoven substrates were impregnated with the binder formulation using Mathis Foulard settings (speed: 2.5 m/min; cylinder pressure: 3.5 bar). Specimens (33 cm x 44 cm) of the nonwoven were impregnated in a bath containing the binder formulation. A final add-on of 20% on a dry basis following oven drying was adjusted. The binder applied on nonwoven fabric samples was oven dried at 200 C for 3 minutes and 45 seconds.
Test methods A set of 15 specimens was obtained from the samples produced, which were subjected to mechanical tensile tests with a dynamometer (Instron). At cold temperature (23 C), 5 specimens of 50 mm x 300 mm were used in MD and in CD, respectively. At hot temperature (180 C) 5 specimens of 50 mm x 180 mm were used. The hot tensile deformation is the elongation at a specific tensile strength. The lower the value, the more dimensionally stable is the material, and thus the better is the product. The tensile stress test at 180 C was performed based on US2008/0214716 under modified conditions.
The heat distortion resistance of PET nonwovens is characterized by tensile stress experiments with a tensile machine (dynamometer) with integrated thermostated chamber at T=180 C. The clamping length is 80 mm and the take-off speed is 100 mm/min.
The elongation of the nonwoven was determined in machine direction (MD) with increasing tensile force at loads of 80 N, 100 N and 120 N, whereby the maximum tensile strength was also determined.
Example 1 to 5: Impact of different types of corn starches on mechanical properties In a first series of experiments, nonwovens were consolidated with binders comprising different types of starch and the same PVOH (grade 1098). The products were thin porous

-26 -sheets, which were flexible and rollable. The binder compositions and results are summarized in table 3. In comparative example 1, a conventional binder for nonwoven carriers for bituminous roofing membranes was used, which consists of 70%
acrylic/melamine/formaldehyde binder (63% acrylic resin, trademark Acronal S888S, BASF, DE, 7% melamine-formaldehyde crosslinker, trademark Saduren 163, BASF, DE) and 30% starch C, all percentages dry wt.%).
Table 3: Effect of different types of corn starches on mechanical properties Example 1 (comp.) 2 3 4 starch 30% 70% 70% 70%
70%
starch C starch A starch B starch C
starch D
PVOH
30% PVOH 30% PVOH 30% PVOH 30% PVOH

Other 70% acrylic/ - - --melamine FA
starch viscosity 100 450 370 100 (m Pa*s) start nonwoven 182 180 181 180 grammage (g/sqm) binder add-on (%) 20 20 20 20 cold tensile tests MD max tensile 660 650 684 600 strength (N/50mm) MD elongation (%) 22 29 29 25 MD tenacity 0,30 0,30 0,31 0,27 0,25 (daN/gsqm/50mm) CD max tensile 450 438 445 380 strength (N/50mm) CD elongation (%) 28 40 41 38 CD tenacity 0,19 0,20 0,20 0,17 0,17 (daN/gsqm/50mm) total cold tensile 1110 1088 1129 980 strength (N/50mm) total cold tenacity 0,49 0,50 0,51 0,45 0,42 (daN/gsqm/50mm) hot tensile tests

-27 -MD deformation at 1,46 1,12 0,84 1,24 0,90 80N (%) MD deformation at 1,59 1,36 1,05 1,53 1,11 100N (%) MD deformation at 1,91 1,61 1,27 1,90 1,32 120N (%) MD max glass hot 123 219 226 161 tensile strength (N/50 mm) The results demonstrate that starch/PVOH binders, although no crosslinker is comprised, have advantageous properties compared to the conventional crosslinked acrylic/melamine formaldehyde binder.
At first, the starch/PVOH binder is formaldehyde free, which is advantageous for safety and environmental reasons. Further, the starch/PVOH binder is significantly less costly, which is relevant for industrial products which are produced at large scale.
Thirdly, the starch/PVOH binder can be produced without crosslinker and crosslinking catalyst. Thus, the composition and production process is much simpler than a crosslinking composition, in which reactive components have to be adapted to each other and reaction control is required.
Moreover, the results provide evidence that the starch/PVOH binder, although not crosslinked, can confer improved mechanical properties to the product, which render it highly suitable as a carrier for bituminous membranes. For the production of bituminous membranes, it is extremely important that the nonwoven carrier is dimensionally stable at 180 C. The results show that the starch/PVOH binder consolidated nonwovens can have a much lower deformation and higher maximum glass tensile strength than the comparative standard nonwoven with crosslinked melamine acrylic binder. This represents a great advantage when the nonwoven carrier is impregnated with bitumen in an industrial process. The low hot tensile deformation indicates that the nonwoven carrier can maintain its shape when being pulled through the production line under significant tensile force and loaded with high amounts of bitumen. A high maximum glass tensile strength suggests that the nonwoven carrier can withstand a comparably high maximum

-28 -force in the bitumen impregnation line. It is significantly higher for the inventive nonwoven carrier than with for the comparative nonwoven with standard binder.
Therefore, bituminous membranes can be produced from inventive nonwoven carriers at higher speed and productivity, but also with higher product quality, i. e. less failures, product irregularities and damages. Especially high dimensional stability at hot temperature was observed in example 3 with starch B. Only example 4 provides a level of deformation at hot temperature, which is comparable to the standard binder. However, this is still a good and unexpected result for a binder without crosslinker.
Further, the results indicate that the mechanical properties at low temperature are advantageous. As shown in examples 2 and 3, the cold tenacity of the starch/PVOH
consolidated nonwovens was comparable to comparative example 1 with the standard binder. The binders in example 4 and 5 were not able to provide the same tensile strength and tenacity as the conventional binder, but the results are still good and also unexpected for a natural binder which does not comprise a crosslinker. The nonwoven carriers can also be stretched and elongated, as required for building and roofing applications. The results at cold temperature demonstrate that the nonwoven carriers also confer good mechanical properties to bituminous membranes in the final building or roofing application.
Example 6: Dimension of starch particles The size of starch aggregates in starch only dispersions and in starch/PVOH
binder dispersions was determined by DLS. As seen in table 4, the size of starch aggregates present in the dispersion was different for different aqueous starch dispersions and aqueous starch/PVOH dispersions. Specifically, starch B and starch B /PVOH
dispersion are characterized by relatively large particles. Further, the average particle size of starch B/PVOH dispersion is significantly higher than in the dispersion with starch B only.
In contrast, the dispersions of starch A or C mixed with PVOH show similar aggregates dimension as starch A or C only. Without being bound to theory, it seems that PVOH
could exert a self-assembling effect on starch molecules in starch B. This could explain the advantageous properties of the starch/PVOH binder system in example 3 above.
Table 4: Size of starch particles in nm as determined by DLS

-29 -Starch A
starch only 185 2150 220 mean particle size (nm) starch / PVOH 122 9359 85 mean particle size (nm) Conclusion Overall, the working examples demonstrate that highly efficient crosslinker-free aqueous binders, which consist of starch and PVOH, can be used for consolidating nonwoven carriers for bituminous membranes. Analyzing cold mechanical performances and in particular tensile strength and tenacity, starch A and starch B displayed the best values, comparable or even slightly better than the melamine/acrylic binder standard (total tenacity and tensile strength). Regarding hot mechanical performance, starch B
provides the lowest MD deformation at 120 N. These values are supported by the physico-chemical study. In fact, the rheological characterization demonstrated the highest G*
value for the mixture starch B/PV0H (data not shown), which is an indication of a stronger bio-polymer network for this binder. The size of aggregates measured by DLS was the highest compared to the others binders. The largest aggregates could lead to a better adhesion to the fibers and better thermo-mechanical properties.
The presence of a low amount of carboxylated groups in the starch in example 2, due to the chemical oxidation, does not seem to have a significant impact on the binding properties. The pre-gelatinized starch used in example 5 is water soluble and can be instantaneously solubilized in cold water. The results demonstrate that these modifications of starch structure may cause a decrease in binding properties compared to the to-be-cooked starch.
Example 7: Binder analysis In a further experiment, the aqueous binder was heated to 200 C for 3 minutes and the size of the binder molecules was analyzed by MALDI-TOF. It was observed that the size of binder molecules is not affected by the heating treatment. Thus, it can thus be excluded that an esterification reaction between starch and PVOH occurs. This confirms that the good mechanical properties of the binder consolidated nonwovens of examples 2 to 5 are obtained although the binders are not crosslinked.

- 30 -Example 8 to 12: Impact of different types of PVOH
In a second series of experiments, nonwovens were consolidated with binders comprising starch A and four PVOH having different viscosities. In comparative example 8, the same conventional binder was used as in comparative example 1. The results are summarized in table 5.
Table 5: Effect of different grades of PVOH
Example 8 (comp.) 9 10 11 Starch 30% 70% 70% 70%
70%
starch C starch A starch A starch A
starch A
PVA -30% PVOH 30% PVOH 30% PVOH 30% PVOH

Other 70% acrylic, melamine FA
PVOH viscosity 32 50 22 start nonwoven 181 181 182 181 grammage (g/sqm) add-on (%) 20 20 20 20 cold tensile tests MD max tensile 660 650 700 610 strength (N/50mm) MD elongation (%) 22 29 28 30 MD tenacity 0,30 0,30 0,32 0,28 0,27 (daN/gsqm/50mm) CD max tensile 450 438 430 390 strength (N/50mm) CD elongation (c)/0) 28 40 38 40 CD tenacity 0,19 0,20 0,20 0,17 0,18 (daN/gsqm/50mm) total cold tensile 1110 1088 1130 1000 strength (N/50mm) total cold tenacity 0,49 0,50 0,52 0,45 0,46 (daN/gsqm/50mm) hot tensile tests MD deformation at 1,46 1,12 1,10 1,28 1,18 MD deformation at 1,59 1,36 1,30 1,58 1,45

- 31 -MD deformation at 1,91 1,61 1,58 1,90 1,73 MD max glass hot 113 219 210 165 tensile strength (N/50 mm) The viscosity of polyvinyl alcohol having linear polymer chains is directly related to the average molecular weight. PVOH 498 and 698 are characterized by low molecular weight and viscosity. The hot tensile deformations for PVOH 698, 1098 and 2098 are lower than for the conventional binder. The hot glass tensile strength is always significantly higher than with the standard binder. Thus, the products are highly suitable as nonwoven carriers for producing bituminous membranes. Overall, the results show that the binding properties can be improved, if the PVOH has a higher molecular weight.
Examples 13 to 16: Impact of wettinq acients (surfactants) on mechanical properties of starch/PVC H binders In further experiments, the impact of wetting agents (surfactants) on starch /
PVOH binder compositions was examined. Some starch / PVOH binders were prepared with additional wetting agents, which are used in the art as additives for improving workability of the binder and properties of nonwovens. A silicon free non-ionic ethoxylated surfactant was used (example 14), which is characterized by low tendency to create foam and high efficiency in decreasing the surface tension of water based solution and dispersion.
Adding 0.2% (v/v %) of this substance to an aqueous dispersion allows decreasing the surface tension to below 30 mN/m. A polyethoxylated monoester of 3,6-sorbitan (example 16) was also used, which is hydrophilic and soluble or dispersible in water and dilute solutions of electrolytes. The solubility in aqueous solution increases with the degree of ethoxylation. The binders with the wetting agents were compared to inventive binders without the additive, respectively (examples 13, 15). When adding a sorbitan polyethoxylate wetting agent, a strong decrease in cold tensile strength (MD
and CD) and cold glass tensile strength was observed (example 14). When adding an ethoxylated wetting agent, a decrease in cold tensile properties was also observed (example 16). Both wetting agents also affected hot tensile deformation in an undesired manner, since higher deformation was observed compared to the binders without the additive, respectively.
Without being bound to theory, the high tensile strength of a starch/PVOH
binder could be due to the high number of hydrogen bond between the molecules and/or the high

- 32 -compatibility between both polymers. Thus, when a wetting agent is added, the network of hydrogen bonds could be at least partially disturbed, causing a potential demixing of two polymers. Moreover, surfactants have the tendency to migrate at the interfaces, causing a decreasing in adhesion force between the binder and the surface of the PET
fibers. This could be confirmed by electron microscopy images of the products. The wetting agent has an adverse effect on binder microstructure, since an undesired phase separation in the binder film was observed. In contrast, a homogenous binder film was observed in comparative example 15. This could explain the lower tensile strength of the nonwoven samples in examples 14 and 16. Overall, the examples suggest that standard additives such as surfactants can significantly reduce the stability of the nonwoven carriers.
Example 17 to 21: Impact of different types of crosslinkers on mechanical properties In examples 19 to 21, nonwovens were consolidated with binders as described in example 2 above, which additionally comprised a crosslinker. Three specific types of crosslinker were selected which are preferred in the art, such as EP 3 299 514 Al, for crosslinking starch based binders for nonwoven substrates (see table 6). The binders were prepared as described above for example 2, whereby 5% (solid content) of starch B
was replaced by 5% (solid content) crosslinker, respectively.
Table 6: Crosslinkers added in examples 19 to 21 crosslinker 1 crosslinker 2 crosslinker 3 chemical melamine formaldehyde polyacrylic acid + polyamine name sodium hypophosphite epichlorohydrine (catalyst) concentration 70% (aqueous solution) 50% (aqueous solution) 20% (aqueous solution) Nonwovens were impregnated as described above. The products were thin porous sheets, which were flexible and rollable. The binder compositions and results are summarized in table 7. Comparative example 17 is the conventional binder for nonwoven carriers for bituminous roofing membranes, which consists of 70%
acrylic/melamine/formaldehyde binder (63% acrylic resin, 7% melamine-formaldehyde crosslinker 1) and 30% starch C, all percentages dry wt.%). The results were compared

- 33 -with those obtained for respective binder without crosslinker and melamine/acrylic standard binder.
Table 7: Example 17 to 21 Example 17 (comp.) 18 19 (comp) 20 (comp) 21 (comp) starch 30% 70% 65% 65%
65%
starch C starch B starch B starch B
starch B
PVOH
30% PVOH 30% PVOH 30% PVOH 30% PVOH

crosslinker melamine FA - 5% 5%
5%
+ acrylic resin crosslinker 1 crosslinker 2 crosslinker 3 starch viscosity 100 370 370 100 (mPa*s) start nonwoven 182 181 181 180 gram mage (g/sqm) binder add-on (%) 20 20 20 20 cold tensile tests MD max tensile 660 650 665 616 strength (N/50mm) MD elongation (%) 22 29 17 28 MD tenacity 0,30 0,30 0,30 0,28 0,27 (daN/gsqm/50mm) CD max tensile 450 438 440 423 strength (N/50mm) CD elongation (%) 28 40 18 42 CD tenacity 0,19 0,20 0,20 0,19 0,16 (daN/gsqm/50mm) total cold tensile 1110 1088 1105 1040 strength (N/50mm) total cold tenacity 0,49 0,50 0,50 0,47 0,43 (daN/gsqm/50mm) hot tensile tests MD deformation at 1,46 0,84 1,07 1,16 1,24

- 34 -80N (c)/0) MD deformation at 1,59 1,05 1,31 1,46 1,54 100N (%) MD deformation at 1,91 1,27 1,56 1,84 1,92 120N (%) MD max glass hot 123 226 184 150 tensile strength (N/50 mm) The results in table 7 demonstrate:
(A) The starch / PVOH binder mixture without crosslinker (example 18) provides the same cold PET tenacity as comparative standard formulation (example 17) based on melamine formaldehyde crosslinker. Moreover, the binder of example 18 provides the lowest hot tensile deformation at 120 N and highest hot glass tensile strength from all examples, which are responsible for the best runability during bitumen impregnation in a continuous production line.
(B) The starch / PVOH + crosslinker 1 (comp. example 19) confers the same PET
cold tenacity to the substrate as the starch / PVOH binder mixture, but MD and CD
cold PET elongation (%) are low. This is a disadvantage, because higher cold elongation is preferred in order to preventing tearing on the roof. The hot tensile deformation at 120 N is higher than without crosslinker (example 18), such that the product has inferior workability in the bitumen impregnation process.
(C) The starch / PVOH + crosslinker 2 and crosslinker 3 binder mixtures (comp.
examples 20, 21) confer low cold PET tenacity to the substrate, as compared to starch B
/ PVOH
without crosslinker (example 18) and the standard formulation (comp. example 17).
The hot tensile deformation (1.84 and 1.92%) is much higher than without crosslinker, and similar as for the standard formulation.
In conclusion, the starch / PVOH binder without crosslinker displays the best properties to the substrate:
- very good hot mechanical stability (lowest tensile deformation and highest glass tensile strength) - very good cold mechanical properties (PET tenacity and PET elongation) - FA free, simpler composition, low cost, possibility to provide 100%
biodegradable binder from natural raw materials, possibility to recover the original components.

- 35 -As demonstrated by DLS measurement, PVOH can be very effecting in aggregating starch particles that are responsible for the very good hot and cold tensile performances.
Without being bound to theory, it is possible that the crosslinker interferes with the aggregation phenomena, which leads to a decline of tensile properties.
Example 22 to 25: Industrial scale production of nonwoven carriers Nonwoven carriers were produced at large scale with binders comprising starch B and PVOH (98% hydrolysis degree, pH 6, 32 mPa*s viscosity at 23 C, determined according to DIN EN ISO 2555 with 4% (w/w) aqueous solution).
Binders were prepared at large scale by mixing the starch dispersion (25%
solid content) and PVOH solution (15% solid content). In a typical procedure, the starch dispersion (500 Kg ¨ 25% solid content) was prepared by dispersing 125 kg dry starch in 375 kg water. The starch dispersion was heated to 90 C ¨ 100 C through a jet cooker system.
Finally, the system was cooled to 60 C. The PVOH water solution (15% solid content) was prepared by introducing 90 Kg PVOH and 510 kg water into a heated tank equipped with a mechanical stirrer. Then the mixture was heated up to 95 'C and kept at this temperature for at least 40 minutes. Afterwards, the temperature was cooled down to 60 C. 500 Kg binder formulation with a solid content of 15% was prepared by mixing starch, PVOH and water as described in the quantity detailed on Table 8.
Finally, the mixture was stirred at 60 C for 10 minutes and used for nonwoven impregnation.
Nonwoven impregnation was performed on a typical Foulard for binder liquid impregnation and the mechanical properties were determined as described above.
Table 8: Binder compositions examples 23 to 25 Example Binder Recipe Starch quantity PVOH quantity Water [kg] [kg]
[kg]
23 69% Starch ¨ 31% PVOH 210 150 24 50% Starch ¨ 50% PVOH 150 250 25 33% Starch ¨ 66% PVOH 99 330

- 36 -The products were thin porous sheets, which were flexible and rollable. The binder compositions and results are summarized in table 9. In example 22, the comparative binder was applied as described above.
Table 9: Large scale production according to examples 23 to 25 example 22 (comp.) 23 24 starch 30% 70% 50%
33%
PVOH - 30% 50%
66%
other 70% Acrylic! - - -melamine FA
cross linker dry concentration binder 15% 15% 15%
15%
mass per unit g/m2 195 200 201 dry Binder on Nonwoven (%) 13 13 13 Cold Tensile Tests MD max tensile strength 637 631 772 (N/50mm) MD elongation (%) 27.5 27.2 26.9 29.4 MD tenacity (daN/gsqm/50mm) 0.326 0.313 0.378 0.365 CD max tensile strength 414 382 471 (N/50mm) CD elongation (c)/0) 35.4 29.6 29 34.7 CD tenacity (daN/gsqm/50mm) 0.212 0.190 0.231 0.261 total cold tensile strength 1051 1013 1243 (N/50mm) total cold tenacity 0.538 0.503 0.609 0.626 (daN/gsqm/50mm) Hot tensile tests MD deformation at 80 N (%) 1,70 0.82 0.83 0.80**
MD deformation at 100 N (%) 2,80 1.54 1.40 1.29**
MD deformation at 120 N (%) 3.8 2.1 1.9 1.7 max glass tensile strength 121 125 127

- 37 -The results provide evidence that the starch/PVOH binder can confer mechanical properties to the product, which render it highly suitable as a carrier for bituminous membranes. Although the binder does not comprise crosslinker, the inventive nonwoven carriers have improved properties compared to the standard with conventional crosslinked acrylic/melamine formaldehyde binder. Especially binder formulations comprising at least 50% PV0H can have advantageous mechanical properties.
For the production of bituminous membranes, it is very important that the nonwoven carrier is mechanically stable at 180 C. In this regard, the results show that the starch/PVOH binder consolidated nonwovens have a lower deformation and significantly higher glass tensile strength than the standard. This represents a great advantage at the customer line, because lower hot tensile deformation means lower deformation during bitumen impregnation and therefore higher speed and productivity, but also less failures, product irregularities and damages. Especially low deformation at hot temperature was observed in examples 24 and 25 with at least 50% of PVOH. Regarding cold mechanical performances and in particular tensile strength and tenacity, starch/PVOH
binder formulation can display especially better values than standard binder, especially when the quantity of PVOH is higher than 30% wt.

- 38 -

Claims

PCT/EP2021/057696

1. A nonwoven carrier for bituminous membranes, wherein the nonwoven comprises organic polymer fibers and is consolidated with an aqueous binder, wherein the binder comprises (a) starch, and (b) polyvinyl alcohol, which may comprise up to 5 mol.% of other monomer units, wherein (c) the binder does not comprise a crosslinker, and (d) the binder does not comprise a filler.

2. The nonwoven carrier of claim 1, wherein the starch is physically and/or chemically modified starch from natural origin.

3. The nonwoven carrier of at least one of the preceding claims wherein the starch is partly hydrolysed.

4. The nonwoven carrier of at least one of the preceding claims, wherein the binder comprises less than 2% additives, preferably 0% additives (based on total dry weight).

5. The nonwoven carrier of at least one of the preceding claims, wherein the average size of the starch particles in the aqueous binder dispersion is at least 0.1 pm, as determined by dynamic light scattering (DLS), and/or wherein the viscosity of the starch is at least 150 mpa*s, determined according to ISO 2555 at a concentration of 25 wt.% at 23 C.

6. The nonwoven carrier of at least one of the preceding claims, wherein the starch is insoluble in water at 23 C and/or not pre-gelatinized, and/or wherein the starch comprises 10% to 50% amylose (dry weight, of total of amylose and amylopectin).

7. The nonwoven carrier of at least one of the preceding claims, wherein the starch and polyvinyl alcohol are not substantially crosslinked, and/or wherein the viscosity of the polyvinyl alcohol is at least 25 mpes, determined according to DIN EN ISO 2555 at a concentration of 4 wt.% at 23 C.

8. The nonwoven carrier of at least one of the preceding claims, wherein the binder comprises 5 to 95 wt.% starch, 5 to 95 wt.% polyvinyl alcohol and 0 to 15 wt.%

additives, wherein all percentages refer to dry weight and the total of all percentages is 100 wt.%.

9. The nonwoven carrier of at least one of the preceding claims, wherein the binder does not cornprise structural polymers different from starch and polyvinyl alcohol, and/or wherein the binder does not comprise an additive, which comprises hydroxyl groups.

10. The nonwoven carrier of at least one of the preceding clairns, wherein the nonwoven consists of organic polymer fibers, preferably polyester fibers, and/or wherein the nonwoven comprises a reinforcement, such as inorganic fiber yarns.

11. Method for producing a nonwoven carrier of at least one of the preceding claims, comprising the steps of (a) providing a nonwoven, (b) impregnating the nonwoven with an aqueous binder comprising starch and polyvinyl alcohol, wherein the binder does not comprise a crosslinker, and (C) drying and solidifying the binder to obtain the nonwoven carrier.

12. Use of a nonwoven carrier of at least one of claims 1 to 10 as a substrate for producing bituminous membranes.

13. A method for producing a bituminous membrane, comprising the steps of (A) providing a nonwoven carrier of any of claims 1 to 10, and (B) impregnating the nonwoven carrier with bitumen.
14. A bituminous membrane, comprising a nonwoven carrier of at least one of claims 1 to 10.
15. A roof, building rnaterial or building comprising a bituminous membrane according to

claim 14.