CN115279961A

CN115279961A - Bituminous films with biodegradable binders

Info

Publication number: CN115279961A
Application number: CN202180021007.XA
Authority: CN
Inventors: L·阿苏玛; M·康弗索; L·德安德里亚
Original assignee: Kedebao High Performance Materials Group
Current assignee: Kedebao High Performance Materials Group
Priority date: 2020-03-30
Filing date: 2021-03-25
Publication date: 2022-11-01
Also published as: EP3966379B1; WO2021197999A1; EP3966379A1

Abstract

The subject matter of the present invention relates to 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 that may comprise up to 5mol.% of other monomer units, wherein (c) the adhesive does not comprise a crosslinker, and (d) the adhesive does not comprise a filler. The subject of the invention is also the use of the nonwoven carrier, a method for producing the same, a bitumen membrane and a building material.

Description

Bituminous films with biodegradable binders

The present 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 crosslinking agent or a filler. The subject of the invention is also the use of the nonwoven carrier, a method for producing the same, a bitumen membrane and a building material.

Background

Bituminous membranes with water-repellent and barrier properties are used in building applications, particularly as roofing materials. The asphaltic membrane comprises a textile support impregnated with asphalt. The asphalt is applied to the textile carrier in a bath of molten asphalt at about 180 ℃ to 200 ℃, and then cooled and solidified. The main function of the carrier is to impart mechanical stability, in particular mechanical resistance and dimensional stability in this respect, to the bitumen membrane and to "hold the bitumen together".

The textile fabric may be a nonwoven consolidated with an aqueous binder such as acrylic, SBR, polyurethane or natural polymer binder. The binder should increase the mechanical resistance and dimensional stability of the nonwoven. Optionally, the stability of the nonwoven is further increased by reinforcements such as fiberglass yarns or scrims. The nonwoven is impregnated with an aqueous binder solution and then dried and cured to obtain a nonwoven support for pitch impregnation. Nonwoven carriers and bitumen membranes are usually provided in the form of relatively thin flexible sheets, usually having a thickness of a few millimetres, which can be rolled up and unrolled.

Such binder-consolidated nonwoven carriers for bituminous membranes should have special properties which make them suitable for producing bituminous membranes. Ideally, the nonwoven carrier should not dimensionally shrink or stretch when subjected to temperature or mechanical forces. It should easily follow all the stresses during the asphalting process (at about 180 to 200 ℃) and thus have a high initial modulus and a high dimensional stability (low deformation). Further, the nonwoven carrier should have high tear resistance and elongation at break (as determined by tensile testing at room temperature). This requirement is important because it determines the specifications of the film, such as tear resistance and elongation at break.

Bitumen membranes for construction applications are produced in large quantities. It is therefore usually mass produced in an automated production line, in which a roll of nonwoven fabric carrier is continuously unwound and guided through a bath of molten asphalt. The product is then cooled until the bitumen solidifies and the bitumen film product is rolled up. In such processes, it is important that the nonwoven carrier be dimensionally stable, so that deformation is as small as possible. The nonwoven carrier should not deform at about 180 ℃ when it is processed and guided through a hot bath. Otherwise, the sheet material may be damaged or a non-uniform product may be obtained. The adhesive must remain stable at around 180 ℃. However, many polymeric binder properties deteriorate at high temperatures, thereby reducing bond strength and nonwoven stability. Thus, many binder-consolidated nonwoven supports that may have mechanical stability at low temperatures are not suitable for producing bituminous membranes. In general, it is generally desirable that nonwoven carriers be capable of producing asphalt films in an efficient automated large-scale process without damaging the material.

Further, the bituminous membrane must meet high quality standards for construction applications. Typically, they are used as building and roofing membranes, such as shading membranes (sometimes referred to as underlayment membranes), barrier membranes, or waterproofing membranes. In such applications, the bitumen membrane must protect roofs and buildings from moisture for many years. It is therefore very important that the bitumen film is homogeneous and free from defects such as cracks and punctures, or even structural irregularities that may lead to damage over time. Even small defects can result in moisture leaks or other problems at the building site over time. Thus, the relatively thin asphalt roofing membrane and the nonwoven fabric carrier embedded therein should have good mechanical properties and high dimensional stability so that it can be conveniently applied to a building or roofing site without damage. High stability is also required after application to a construction site, as a building site or roof may be subjected to stress and strain over many years.

In general, it is desirable that such nonwoven supports for bituminous membranes be flexible while having good mechanical properties and high dimensional stability at cold and hot temperatures. Even a slight improvement in the mechanical stability of the nonwoven carrier at cold or hot temperatures can significantly reduce damage, resulting in a more accurate and reliable material.

Various synthetic binders are used in the art to consolidate nonwovens such as acrylic, SBR, or polyurethane polymers. For environmental reasons, it is also desirable to use natural and biodegradable materials. Thus, starch-based binders for consolidating nonwoven carriers for asphalt films have been described in the art. Starch is available in large quantities as a binder and is relatively inexpensive. Conventional starch-based binders for nonwovens are usually provided in a mixture with another binder polymer. Such compositions also comprise a crosslinker covalently linked to the binder molecule, thereby forming a three-dimensional polymer matrix. The art also hypothesizes that high dimensional stability is achieved by crosslinking the polymeric binder.

EP 0 354 023 A2 relates to a binder composition for a fibre mat, wherein the binder comprises starch, a starch cross-linking agent and an anti-wicking agent. The cross-linking agent may be melamine formaldehyde or urea glyoxal condensate. The adhesive may contain a polymeric strength additive such as polyvinyl alcohol or an acrylic polymer. Anti-wicking agents are typically surfactants.

WO 2006/120523 A1 discloses a curable aqueous adhesive composition comprising polyvinyl alcohol, starch or sugar, a multifunctional crosslinker and a catalyst. It is recommended to impregnate the glass fiber product with a binder.

WO 2015/084372 A1 discloses an aqueous binder for impregnation of nonwovens comprising a polyol in colloidal form such as starch and a cross-linking agent. The adhesive may comprise additional polymers. The cross-linking agent is a multifunctional small molecule, such as glyoxal or citric acid.

WO2019/050439A2 relates to a thermal and acoustic insulation material made from mineral fibres. The product is a mat made of mineral fibres and a binder, which mat is cross-linked with a heavy metal or a boron compound and a heavy metal salt.

DE 1 619 127 relates to a method for impregnating a fibrous product with a resin. In a first step, the fibrous substrate is impregnated with an intermediate first binder (a), which is washed off after subsequent impregnation with binder (B). The intermediate product is unstable and not suitable for producing bituminous membranes.

EP 3 299 A1 relates to textile fabrics impregnated with a binder system comprising ≥ 30% polyvinyl alcohol, ≤ 70% starch, crosslinking agent, filler and additives. However, no specific adhesive composition or working examples are disclosed.

Starch-based binder compositions and nonwovens consolidated therewith that have been described in the art may still be improved. Generally, the adhesive composition requires various additives and is therefore relatively complex. All concrete binder compositions contain a crosslinking agent and, typically, also a catalyst for controlling the crosslinking reaction. The reaction between the starch, polyvinyl alcohol and the cross-linking agent must be initiated, controlled and monitored. An insufficient degree of crosslinking may result in a low stability of the product, whereas an excessively high degree of crosslinking may result in an excessively rigid product. It is therefore generally desirable to consolidate such nonwoven carriers with a simpler and more reliable adhesive system.

Further, the mechanical properties of nonwoven supports impregnated with such binders may still be improved. There is a great need for binder-consolidated nonwoven supports that are flexible and have good mechanical properties at cold and hot temperatures; and is therefore suitable for the production of bituminous membranes. However, most of the prior art documents do not address this problem, especially the mechanical properties at high temperatures.

Another problem is that known binders for nonwoven fabrics often contain formaldehyde based cross-linking agents, such as melamine formaldehyde. This is undesirable for safety and environmental reasons, as aldehyde-based binders, such as those derived from formaldehyde and glyoxal, can cause health problems.

It is also a problem that known adhesive compositions are often relatively expensive, because components or additives are not readily available in large quantities. Since bituminous membranes are industrial products and are used in large quantities in building applications, lower cost binders are desired.

Another problem with known adhesive compositions is that they comprise components or additives that are not obtainable from natural sources and/or are not biodegradable. It would be desirable to provide a readily available adhesive composition that can be obtained from natural sources or that is biodegradable.

First layer problem of the invention

The underlying problem of the present invention is to provide a nonwoven fabric, use, method and bituminous membrane that overcome the above-mentioned problems. A particular problem is to provide a nonwoven carrier that is impregnated and consolidated with a binder in a relatively simple, efficient and inexpensive manner. The adhesive composition should be simple and reliable to provide and process. The binder should be free of formaldehyde and/or should be as obtainable from natural sources as possible or be biodegradable. Overall, the nonwoven carrier should be as sustainable as possible.

A further problem of the present invention is to provide a nonwoven carrier consolidated with a binder, which is well suited for the production of bituminous membranes. The nonwoven supports should have good mechanical properties at room temperature, in particular in terms of maximum tensile strength and toughness before fracture. Furthermore, the nonwoven carrier should have high dimensional stability at elevated temperatures of about 180 ℃. Therefore, the nonwoven carrier should be suitable for producing rolled bitumen membranes in an automated process with standard machinery.

Disclosure of Invention

The subject of the invention relates to a nonwoven carrier for bituminous membranes, wherein the nonwoven comprises organic polymer fibres and is consolidated with an aqueous binder, wherein the binder comprises

(a) The starch is added to the mixture of starch and starch,

(b) Polyvinyl alcohol which may comprise up to 5mol.% of further monomer units, wherein

(c) The adhesive does not contain a crosslinking agent, and

(d) The adhesive does not contain a filler.

The subject of the invention is also a method, use, bituminous membrane and building material as defined in the claims. Additional embodiments are disclosed in the specification.

The nonwoven carrier comprises a nonwoven consolidated with a binder. According to ISO 9092, a nonwoven is a sheet of staple fibers or continuous filaments that have been formed into a web by any means and bonded together by any means other than weaving or knitting. Preferably, the fibers forming the nonwoven are randomly oriented. Preferably, they are joined by friction, cohesion and/or adhesion.

Nonwoven carriers are substrates for producing bituminous membranes. Bitumen membranes are commonly used in construction applications, especially roofing applications. In a typical production process, the nonwoven fabric support is impregnated with molten pitch.

The binder-consolidated nonwoven supports of the present invention are porous. Preferably, the porosity of the nonwoven carrier and/or the nonwoven before binder impregnation is between 60% and 95%, more preferably between 75% and 93%, especially between 80% and 90%. Porosity can be calculated from the weight and density of the product and components. Thus, the molten pitch can penetrate the pores from one side of the nonwoven carrier sheet to the other, so that a compact and stable composite can be obtained after the pitch has solidified. Preferably, the average pore diameter is between 50 μm and 300 μm, preferably between 80 μm and 200 μm, preferably determined by ISO 15901-1.

The nonwoven carrier is a sheet material. Preferably, the nonwoven carrier is flexible and/or crimpable. The subject matter of the invention also relates to a roll of nonwoven fabric support and/or bituminous membrane. Such rolls may be conveniently unrolled and rolled up again by a user. The flexible and roll form of the nonwoven carrier facilitates efficient processing in an automated, continuous process. The flexibility and roll form of the asphalt membrane facilitates 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 polymer and optionally additives in water, which is applied to the nonwoven, usually by dipping in a bath, drying and curing, and binds the nonwoven fibers together. The nonwoven binder enhances the stability of the nonwoven.

The adhesive of the present invention comprises starch and polyvinyl alcohol. Nonwoven binders comprising starch and polyvinyl alcohol have been described in the art. However, the adhesive according to the invention is different in that it does not comprise a cross-linking agent. Surprisingly, it was found that a crosslinker-free binder comprising starch and polyvinyl alcohol as structuring polymer is suitable for producing nonwoven carriers for bitumen films which meet the high requirements for mechanical resistance and dimensional stability in cold and even at high temperatures around 180 ℃. Surprisingly, such nonwoven carriers have sufficient stability even at elevated temperatures without crosslinking agents used in conventional adhesives to form a three-dimensional matrix of covalently linked adhesive polymers. Even more surprisingly, it has also been found that adhesives without crosslinking agents can have even better mechanical properties at cold and hot temperatures, in particular better dimensional stability than the corresponding adhesives with crosslinking agents.

As used herein, the term crosslinker refers to a compound that is specifically added to an aqueous binder and forms covalent bonds of the binder polymer in the binder composition upon consolidation. According to the present invention, there is no such compound that would form a covalent bond between the starch and the polyvinyl alcohol molecule. Polyvinyl alcohol and starch are polyols characterized by repeating hydroxyl functional groups on the polymer backbone. In the art, cross-linkers for adhesives comprising starch and/or polyvinyl alcohol are typically compounds having two or more functional groups that can react with hydroxyl groups, typically carboxyl groups, but also amine or aldehyde groups. The starch may also be chemically modified, for example by partial oxidation, in which some of the hydroxyl groups are converted to carboxyl groups. Such modified starches may be crosslinked with a crosslinking agent having hydroxyl and carboxyl groups. The aqueous binder used according to the invention does not contain a crosslinker compound which would covalently link the specific starch to the polyvinyl alcohol during binder consolidation.

The aqueous binder of the present invention does not contain a crosslinking agent. Typical crosslinkers used in the art for corresponding binders are formaldehyde or formaldehyde resins, such as urea-formaldehyde resins, melamine-formaldehyde resins or acetone-formaldehyde resins, glyoxal or glyoxal resins, urea or urea resins, or non-polymeric polycarboxylic acids or non-polymeric polycarboxylic acid anhydrides comprising two, three or more carboxyl groups, such as citric acid. In a preferred embodiment, the aqueous binder does not comprise a further compound comprising two or more functional groups for cross-linking the specific starch and polyvinyl alcohol in the binder, in particular for cross-linking the hydroxyl groups of the starch and polyvinyl alcohol; such as a functional group selected from the group consisting of: carboxyl, isocyanate, amine, aldehyde, epoxy or ketone groups. The binder also does not contain a crosslinking agent in the form of a heavy metal or boron salt or compound. Preferably, the adhesive does not contain a catalyst, especially a crosslinking catalyst, as no catalytic chemical reaction is required.

Preferably, the nonwoven is not consolidated with an aqueous binder in a manner that causes the binder to crosslink. The binder without cross-linking agent does not cross-link the starch and polyvinyl alcohol under standard conditions, in which the nonwoven is impregnated, dried and the binder is cured. However, under certain severe conditions, crosslinking occurs at least to some extent despite the absence of a crosslinking agent. Thus, it is preferred that the nonwoven carrier not be subjected to conditions under which crosslinking may occur during or after binder consolidation. For example, it is preferred not to adjust very high or very low pH, pressure, temperature and/or water depletion; the aqueous binder does not contain a high reactivity additive; or the nonwoven fabric support is not subjected to highly reactive environments such as reactive radiation or plasma.

Preferably, in the nonwoven carrier of the present invention, the starch and polyvinyl alcohol are not crosslinked, or at least substantially uncrosslinked. In this respect, "substantially" means that although the conditions are adjusted so that crosslinking should not occur, an inevitable and negligible small amount of covalent bonds may be formed, for example, due to impurities or structural abnormalities of the raw materials. For example, substantially uncrosslinked may 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 cross-linking can be determined by removing the binder from the nonwoven carrier, molecular analysis (e.g., by MALDI TOF), and comparison to an aqueous binder solution.

The starch may be a modified starch or a native (native/native) starch. Native starch is obtained directly from natural sources without any physical or chemical treatment. Preferably, the source of the modified or native starch is native. Preferably, the source is a plant, preferably a vegetable. Preferably, the starch source is a tuber such as potato, tapioca, arrowroot, sweet potato, etc., a cereal such as wheat, corn (corn/maize), rye, rice, barley, millet, oats, sorghum, etc., a fruit such as chestnut, acorn, bean, pea, and other legumes, bananas, or plant pulp, e.g., sago palm, etc. Preferably, the starch is corn starch, which is preferably modified.

In a preferred embodiment, the starch is not native starch. Thus, the starch is a modified starch. It is highly preferred that the starch is physically and/or chemically modified. Modified starches can be obtained by physical and/or chemical treatment of native starch, usually in order to modify its properties. According to the present invention, it was found that modified starches can impart high stability to nonwoven carriers. In contrast, in the absence of a cross-linking agent, it may be more difficult to provide a uniform binder with native starch, which may result in low stability of the nonwoven carrier.

In a preferred embodiment, the starch is chemically modified. In this respect, the term "chemically modified" refers to partially hydrolyzed starches and starches having chemically modified side chains and/or functional groups. For example, the chemically modified starch may be an alkali modified starch, a bleached starch, an oxidized starch, an acetylated starch, a hydroxypropylated starch, a starch ether, a hydroxyethyl starch, a cationic starch, or a carboxymethylated starch.

In further embodiments, the starch may be a dextrin, such as maltodextrin or cyclodextrin. Dextrins are low molecular weight carbohydrates obtained by hydrolysis of starch, characterized by a dextrose equivalent between 3 and 20. In another embodiment, the starch is not dextrin. Since the molecular weight of dextrin is relatively low, it may be preferable to use starch having a higher molecular weight to obtain a highly stable product.

In a preferred embodiment, the chemically modified starch is a partially hydrolyzed starch. Partially hydrolyzed starches are characterized by shorter polysaccharide chain lengths compared to the corresponding native starches. It was found that partially hydrolyzed starch can impart advantageous properties to the nonwoven carrier.

In one embodiment, the average molecular weight of the starch may be between 500g/mol and 25,000g/mol, in particular between 2,500g/mol and 20,000g/mol, as determined by MALDI-TOF.

Preferably, the starch, in particular the chemically modified starch, does not comprise chemically modified side chains, i.e. hydroxyl groups which have been converted into other functional groups by a chemical reaction. Preferably, the starch comprises hydroxyl groups as its starch precursors from natural sources. Native starch, physically modified and partially hydrolyzed starch 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, e.g., less than 2%, less than 0.5%, or less than 0.2% of the total hydroxyl groups and/or total non-terminal hydroxyl groups. It was found that the stability of the nonwoven carrier at cold and hot temperatures can be particularly high when the starch hydroxyl groups are not chemically modified.

In a preferred embodiment, the mean size of the starch particles in the aqueous binder dispersion is at least 0.1 μm, preferably at least 1 μm, more preferably at least 2 μm or at least 5 μm. The average size may be in the range of 0.1 μm to 50 μm, preferably 1 μm to 50 μm, especially between 5 μm and 25 μm. The average particle size may be determined by Dynamic Light Scattering (DLS), for example according to ISO 22412. In this regard, the term "starch granule" refers to the observed starch aggregates, which may also include some PVOH. It was found that such relatively high particle sizes can be correlated with high dimensional stability of the nonwoven carrier at high temperatures and higher mechanical resistance at low temperatures.

The starch may have a viscosity of 50mpa s to 800mpa s, preferably 150mpa s to 600mpa s, or more preferably 250mpa s to 600mpa s, as determined according to ISO 2555 at a concentration of 25wt.% and 23 ℃. The viscosity of the starch may be at least 50mpa · s, preferably at least 150mpa · s, or more preferably at least 250mpa · s. It was found that the mechanical stability of the nonwoven carrier at cold and hot temperatures can be significantly increased if the viscosity of the starch is adjusted accordingly. Without being bound by theory, it was found that viscosity can be a more suitable parameter for selecting the type of starch in the adhesive composition than molecular weight, since viscosity depends not only on molecular weight, but also on other characteristics, such as the three-dimensional structure of the starch molecules.

Starch is a polysaccharide, consisting mainly 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 relative to the total amount of amylose and amylopectin). It has been found that such starches, such as corn starch, which contain relatively high amylopectin content can impart high dimensional stability to the nonwoven carrier.

In a preferred embodiment, the starch is of the type to be cooked. Preferably, the starch is insoluble in water and/or does not pregelatinize at 23 ℃. Preferably, when 5wt.% starch is added to cold water and stirred for 2 minutes, the starch is insoluble. Starch is commercially available in either soluble or insoluble form. For various practical and industrial applications, soluble starches such as pregelatinized starch are more convenient to use. Soluble starches are readily soluble in water at low temperatures. In the starch industry, native starch is made soluble by physical treatments such as heating, mechanical shearing, drying and grinding. Soluble starches can be provided in dry powder form, are instantly soluble in cold water and have thickening/gelling capabilities. The pregelatinized, soluble starch granules exhibit a lack of birefringence and retain little, if any, of the original native granular structure. According to the invention, it was found that starches of the type to be cooked can provide high stability to nonwoven carriers at cold and hot temperatures. Since the starch to be cooked cannot simply be dissolved in cold water, the binder of the invention should be pretreated before it is applied to the nonwoven. Typically, the pre-treatment comprises heating and stirring, for example to at least 80 ℃, preferably at least 90 ℃. After cooling, the homogeneous starch dispersion obtained can be added to the binder.

Preferably, the starch is physically modified. The starch may be subjected to physical treatment, for example under heat and/or mechanical shear, which changes the physical structure. Here, if no chemical reaction such as cleavage of the polysaccharide chain occurs, the modification is considered to be physical. Physical modification can make the starch more uniform, which can improve adhesive properties.

In a highly preferred embodiment, the starch is a partially hydrolyzed starch from natural sources, preferably comprising 10% to 50% amylose (dry weight relative to the total amount of amylose and amylopectin) and having an average molecular weight between 1000g/mol and 2500g/mol, and/or the average size of the starch particles in the starch dispersion and/or the aqueous binder dispersion is at least 0.1 μm, preferably at least 1 μm, and/or the viscosity is at least 150mpa s, preferably at least 250mpa s, determined at a concentration of 25wt.% according to ISO 2555 at 23 ℃. It was found that the stability of the nonwoven carrier at high temperatures can be particularly high when using starches having such properties.

In another embodiment, the starch is a chemically modified starch, wherein the functional group is chemically modified. The hydroxyl groups of the starch substrate may be at least partially converted into different functional groups, for example by etherification, esterification, amidation or oxidation. Chemically modified starches include starch esters such as xanthates, acetates, phosphates, sulfates, nitrates; starch ethers, such as methyl or ethyl ether, nonionic starch ethers, anionic starch ethers or cationic starch ethers; and oxidized starches, such as carboxyl starches. In a preferred embodiment, the starch comprises at least 90%, preferably at least 95%, more preferably at least 98%, or even at least 99% of hydroxyl groups, which have not been chemically modified. Most preferably, the starch does not contain chemically modified hydroxyl groups. High levels of hydroxyl groups may be beneficial for the stability of the binder, which may be mediated at least in part by hydrogen bonds. In another embodiment, the starch is partially oxidized. Preferably, the degree of oxidation of the hydroxyl groups is low, for example between 0.1% and 10%, or between 0.5% and 5%. Partially oxidized starch may contain more than 90% amylopectin. In an embodiment, the starch comprises about 99% amylopectin and has a degree of oxidation of about 0.5% to 2%.

The aqueous binder comprises polyvinyl alcohol, which may comprise up to 5mol.% of other monomer units. Polyvinyl alcohol is a linear polymer consisting of building blocks of monomers with hydroxyl groups. It is assumed that starch has good compatibility with polyvinyl alcohol, also because both polymers contain hydroxyl groups and are capable of forming intramolecular hydrogen bonds. Another advantage of polyvinyl alcohol is that it is biodegradable, although relatively slow.

Preferably, the polyvinyl alcohol has a viscosity of at least 25mpa · s, more preferably at least 30mpa · s. Preferably, the viscosity is in the range of 25mpa · s to 100mpa · s, more preferably between 30mpa · s and 75mpa · s. It was found that the mechanical properties of the nonwoven carrier are particularly good at cold and hot temperatures if the viscosity of the polyvinyl alcohol is adjusted accordingly. If the viscosity is too low, the mechanical stability of the nonwoven is reduced. If the viscosity is too high, processability may be reduced and the formation of an intimate mixture of starch and polyvinyl alcohol may be impaired. Here, the viscosity of the polyvinyl alcohol is determined according to ISO 2555 at a concentration of 4wt.%, at 23 ℃.

Preferably, the polyvinyl alcohol has a saponification degree (degree of hydrolysis) of at least 90mol%, more preferably at least 95mol% or at least 98mol%. The degree of saponification indicates the degree of conversion of the acetate group from the precursor polymer to a hydroxyl group. A high degree of saponification is advantageous because the binder is more homogeneous and can thus impart higher stability to the nonwoven carrier.

The polyvinyl alcohol may comprise up to 5mol.%, preferably up to 2mol.%, of other monomer units. These other monomer units are intentionally incorporated into the polymer chain during polymerization. Thus, the other monomer is part of a 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 hydrolyzed when converting polyvinyl acetate to polyvinyl alcohol. Polyvinyl alcohol derivatives having other monomer units are known in the art and are commercially available. For example, small amounts of other monomer groups, such as ethylene or carboxyl groups, may be incorporated into the polymer to impart the desired functionality to the polymer. In a preferred embodiment, the polyvinyl alcohol contains no further monomer units and/or groups, except for residual acetate groups. This may be advantageous because the polymer is homogeneous and may impart high stability to the nonwoven carrier.

In one embodiment, the polyvinyl alcohol has a degree of polymerization of at least 600, more preferably at least 1000. The relatively high degree of polymerization associated with the relatively high polymer chain length can provide good mechanical stability to the nonwoven carrier.

In a preferred embodiment, the starch and/or polyvinyl alcohol are produced from natural raw materials. Starch may be produced from natural sources, and polyvinyl alcohol may be produced from natural building blocks, e.g. based on bioethanol. Thus, a sustainable adhesive can be produced, which is also biodegradable. Preferably, the nonwoven fibers are from recycled PET, such as from used PET bottles. Thus, a sustainable nonwoven carrier can be provided.

In preferred embodiments, the amount of polyvinyl alcohol in the adhesive is less than 30wt.%, less than 25wt.%, or less than 20wt.%. The advantage is that the proportion of starch in the composition can be significantly higher than that of polyvinyl alcohol, since commercially available starch is cheaper than polyvinyl alcohol. Since no crosslinker is included, the additive (if present) does not include a crosslinker.

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 imparted to the nonwoven carrier by means of a binder which consists entirely or predominantly of starch and polyvinyl alcohol. In industrial applications, it is highly advantageous if such adhesives consist of small amounts of components. First, it can be easily prepared and is inexpensive. Further, both polymer components are biodegradable. Another advantage of binders without cross-linking agents is that no chemical reaction takes place during or after impregnation of the nonwoven. In contrast, reactive adhesives used in the art require control of the chemical reaction. If the reaction is incomplete or excessive, the product may have undesirable characteristics. Overall, a simple binder composition can improve product uniformity, reproducibility, and quality control. Another advantage of binders without cross-linking agents is that excess aqueous binder can be reused in the production process. In contrast, crosslinked aqueous adhesives cannot be reused and must be discarded. Thus, the present invention can reduce waste and provide a more sustainable nonwoven carrier. Surprisingly, it has also been found that adhesives without a crosslinking agent can impart even better mechanical properties, including dimensional stability, to a substrate than comparable adhesives with a crosslinking agent. For example, it was found that binders without cross-linking agents can have a lower heat distortion, which is particularly important for the asphalting process. This is unexpected because it is generally assumed in the art that cross-linking agents increase dimensional stability by forming a polymer network.

In a preferred embodiment, the adhesive does not contain a structuring polymer other than starch and polyvinyl alcohol. Preferably, the binder does not contain additional structural polymers commonly used in nonwoven binders, such as acrylic polymers, SBR, polyurethane, polyamide, polyester or copolymers thereof, or other natural polymers such as proteins, gelatin or alginates. Preferably, the adhesive contains no other polymers at all and therefore does not act as a functional additive. Since a nonwoven carrier with high mechanical stability can only be obtained using starch and polyvinyl alcohol as structuring polymer, it is not necessary to include an additional structuring polymer. This is also advantageous for reasons of simplicity of the production process, quality control and cost.

The adhesive may comprise additives. Preferably, the total amount of additives is relatively low. Preferably, it is less than 15wt.%, more preferably less than 10wt.%, or less than 5wt.%, all wt.% relating to the total binder dry weight. It is particularly preferred that the amount of additive is less than 2wt.%, less than 1wt.% or no additive at all. It is therefore preferred that the binder consists entirely or substantially of starch and polyvinyl alcohol as solid components.

The additive may be a functional additive that imparts desired properties to the adhesive. Such functional additives are known in the art and include UV stabilizers, adhesion promoters, colorants, and processing aids. Preferably, the additive is not a polymer. In a preferred embodiment, only the additives are those in the aqueous binder solution which do not become part of the consolidated binder on the nonwoven carrier, such as salts and buffer substances.

It is highly preferred that the total amount of additives is low. According to the present invention, it has surprisingly been found that very simple binder compositions based essentially or only on starch and polyvinyl alcohol can impart highly advantageous properties to nonwoven carriers. Thus, the binder solution can be very simple, which facilitates mass production and processing. Small amounts of additives may also be advantageous for environmental reasons. In general, adhesives containing no additives or only small amounts of additives can be more efficiently recycled. Such adhesives may be recovered from an adhesive bath and/or may be peeled and recovered from the nonwoven carrier. In contrast, crosslinked adhesives or adhesives containing high levels of synthetic additives cannot be efficiently recycled.

The adhesive does not contain a filler. This may be advantageous because fillers are generally applied in relatively high amounts and may significantly impair the stability of the polymer matrix formed from starch and polyvinyl alcohol. In particular, since the binder is not crosslinked, the stability of the nonwoven carrier may be reduced by the filler.

According to the present invention, it was found that the usual functional additives used in such binders in the art negatively influence the mechanical properties of the nonwoven carrier. In a preferred embodiment, the binder does not contain surfactants, detergents, wetting agents, emulsifiers, protective colloids and/or dispersants, preferably does not contain any of these additives. Preferably, the adhesive does not contain an additive which is an amphiphilic molecule or a non-ionic surfactant. More preferably, the adhesive does not contain a hydrocarbon containing from 8 to 18 carbon atoms attached to a polar or ionic moiety, and/or an ethoxylated surfactant, such as an ethoxylated sorbitan ester. Without being bound by theory, such functional additives may compromise internal hydrogen bonds between binder molecules, thereby reducing the stability of the nonwoven carrier. However, the binder may contain unavoidable impurities such as salts which have no relevant effect on the consolidated binder structure.

Preferably, the polyvinyl alcohol is provided to the binder in the form of an aqueous solution. Preferably, the polyvinyl alcohol is not provided in the form of a dispersion. In this example, no additives, such as emulsifiers or protective colloids, are provided as are required for the preparation of such dispersions.

In another embodiment, the adhesive is free of additives comprising hydrophilic groups, such as hydroxyl, carboxyl, amine, aldehyde, or ketone groups and/or ionic groups. More preferably, the adhesive is free of hydroxyl containing additives. Without being bound by theory, the hydrophilic groups may affect hydrogen bonding in the adhesive structure, thereby reducing the stability of the nonwoven carrier.

In a preferred embodiment, the binder comprises

5 to 95wt.%, preferably 10 to 90% starch,

5 to 95wt.%, preferably 10 to 90% of polyvinyl alcohol, and

0 to 15wt.%, preferably 0 to 2% of additives,

wherein the sum of all percentages is 100wt.%. Herein, all percentages of the binder component refer to dry weight unless otherwise indicated. It was found that the amount of starch and polyvinyl alcohol can be varied widely, even in the absence of a cross-linking agent, to provide various nonwoven carriers with high dimensional stability at high or low temperatures.

In a preferred embodiment, the adhesive comprises 50 to 95wt.%, preferably 72 to 95wt.% starch, 5 to 50wt.%, preferably 5 to 28wt.% polyvinyl alcohol, and 0 to 15wt.%, preferably 0 to 2wt.% additive, wherein the sum of all percentages is 100wt.% (dry weight). Binder compositions comprising such relatively high amounts of starch have been found to impart high dimensional stability to nonwoven carriers.

In another preferred embodiment, the adhesive comprises 5 to 69wt.% starch, 31 to 95wt.% polyvinyl alcohol and 0 to 15wt.%, preferably 0 to 2wt.% additives, wherein the sum of all percentages is 100wt.% (dry weight). It has been found that binder compositions comprising such relatively high amounts of polyvinyl alcohol can impart high mechanical resistance to the nonwoven carrier.

In another preferred embodiment, the adhesive comprises 30 to 70wt.% starch, 30 to 70wt.% polyvinyl alcohol and 0 to 15wt.%, preferably 0 to 2wt.% additives, wherein the sum of all percentages is 100wt.% (dry weight). It has been found that binder compositions comprising relatively similar amounts of polyvinyl alcohol and starch can impart high dimensional stability to nonwoven carriers, especially at elevated temperatures.

In a preferred embodiment, the adhesive comprises 60 to 90wt.% starch, 10 to 40wt.% polyvinyl alcohol and 0 to 5wt.% additives, wherein the sum is 100wt.% (dry weight). In another preferred embodiment, the adhesive comprises 70 to 90wt.% starch, in particular 72 to 90wt.% starch, 10 to 30wt.% polyvinyl alcohol and 0 to 5wt.% additives, wherein the sum is 100wt.% (dry weight).

The nonwoven may be a spun, spunlaced, melt spun or staple fiber nonwoven. As used herein, the term fiber includes staple fibers and filaments. The staple fibers have a defined length and the filaments may be "endless" filaments. The staple fibers may be processed and laid out by conventional methods such as carding. Preferably the length of the staple fibres is between 20mm and 200mm, more preferably between 60mm and 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 contain nonwoven inorganic and/or mineral fibers such as nonwoven glass fibers. Nonwovens from organic and polymeric fibers are advantageous because they are lighter than glass fibers, and binders can provide high stability to such nonwovens. In a preferred embodiment, the organic polymer is a polyester. The polyester may be selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, and polyester copolymers. Preferably the polyester is polyethylene terephthalate (PET). This polymer is particularly suitable for use as a support for bitumen membranes because of its high melting temperature, low cost and good mechanical properties. It is also assumed that the starch and polyvinyl alcohol-based adhesive used in the present invention has 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, in particular PET fibers, it may optionally contain reinforcements which are not made of nonwoven fibers.

In an embodiment, the nonwoven fibers are a mixture of organic and inorganic fibers. The nonwoven may comprise a mixture of polyester fibers and other nonwoven fibers, for example less than 50wt.%, less than 20wt.%, or less than 10wt.% for all fibers. The nonwoven may comprise other fibers that are relatively stable at high temperatures, such as natural fibers or inorganic nonwoven fibers.

Preferably, the linear density of the nonwoven fibres is from 0.5dtex to 20dtex, more preferably from 1dtex to 10dtex, especially in the range of from 2dtex to 6 dtex. Nonwovens of such fibers may provide strength and flexibility to the asphalt film. Preferably, the diameter of the nonwoven fibers is in the range of 5 μm to 50 μm, preferably 10 μm to 30 μm. Preferably, the fiber titer is at least 2.5dtex.

In a preferred embodiment, the nonwoven comprises reinforcement. As used herein, reinforcement refers to any fibrous structure, i.e., fibers, filaments, yarns, threads, or other elongated structures. The reinforcing fibers are different from the nonwoven fibers in that they are not randomly arranged in the pile fabric (nonwoven precursor) during nonwoven production as are other nonwoven fibers. Instead, the reinforcing fibers are added in a different manner during or after the nonwoven production process. Typically, the reinforcement is directional, i.e. it reinforces the nonwoven especially in a specific direction. For example, the reinforcement may be a linear yarn or a discrete layer, such as a scrim. The reinforcing fibers are not part of the raw fiber material that is arranged to form the nonwoven or fleece precursor. Preferably, the reinforcement is embedded within the interior of the nonwoven carrier.

The reinforcement may be multifilament and/or monofilament. The reinforcement may be derived from aramid, preferably so-called high modulus aramid, carbon, glass roving, mineral fibres (basalt), high strength polyester mono-or multifilament, high strength polyamide mono-or multifilament, and yarns, such as hybrid multifilament yarns (yarns containing reinforcing filaments and low melting binder fibres), or threads made of metal or metal alloys (monofilaments). Preferably, the reinforcement is made of inorganic fibers, such as glass fibers or glass fiber yarns.

In a preferred embodiment, the reinforcement is a yarn, preferably a glass fiber yarn. Preferably, the amount of fiberglass yarn in the nonwoven carrier is from 2wt.% to 20wt.%, preferably from 5wt.% to 15wt.%. Such levels are generally sufficient to increase strength without compromising the properties of the nonwoven. Preferably, the yarns are aligned with each other, preferably parallel. The glass fiber yarns may increase the mechanical strength of the nonwoven carrier.

Preferably, the nonwoven carrier consists of a nonwoven which is consolidated with a binder and optionally contains reinforcement. In another embodiment, the nonwoven fabric support is a composite substrate comprising an additional, separate layer of inorganic fibers. The additional layer may be a nonwoven, woven, net or scrim, or a layer of fibers and/or yarns. In another embodiment, the nonwoven does not contain additional layers.

In a preferred embodiment, the nonwoven has a basis weight of 50g/m prior to impregnation with the binder²To 500g/m²More preferably 100g/m²To 300g/m²In particular 150g/m²To 250g/m². Such basis weights are particularly suitable for bituminous membranes. The nonwoven can be consolidated beforehand, in particular mechanically, for example by hydroentangling or preliminary needling, before being impregnated with the binder. Preferably, the binder (additional) loading is 1 to 50wt.%, preferably 5 to 40wt.%, more preferably 10 to 30wt.% of the nonwoven (binder free dry weight). Preferably, water is the only solvent in the aqueous binder.

Preferably, the thickness of the nonwoven carrier is between 0,25mm and 6mm, more preferably between 0,5mm and 4mm, especially between 0.8mm and 2mm, as determined according to ISO 9073-2,1997, paragraph 5.1 "common nonwoven".

In a preferred embodiment, the nonwoven carrier has a thermal tensile set at 180 ℃ and 120N of less than 1.8%, more preferably less than 1.5%, preferably at 180g/m²Is determined at the basis weight of (c). Due to this high dimensional stability, the nonwoven carrier can be advantageously used for producing bitumen membranes with standard machinery. Further, high stability at high temperatures indicates that the bitumen membranes remain stable for long periods of time in building and roofing applications. Even in mild climates, the roof temperature can rise to 100 ℃, for example when sunlight is directed onto the metal components of the roof. In hot geographical areas and for certain applications, the temperature may rise even higher. Thus, high dimensional stability at high temperatures is also beneficial for building and roofing applications。

In a preferred embodiment, the nonwoven carrier has a maximum glass tensile strength at 180 ℃ of at least 150N/50mm, more preferably at least 200N/50mm, especially when comprising reinforcing glass fiber yarns. The maximum glass tensile strength is related to dimensional stability. Which defines the threshold for collapse of the nonwoven due to breakage of the reinforcement (usually glass fibers). This is defined by the peak defined in the tensile strength versus elongation plot. A high maximum glass hot tensile strength is desirable because it indicates that the material can withstand higher tensions and pulls on the bitumen production line at 180 ℃, especially at higher speeds. When a force higher than the maximum glass tensile strength is applied to the nonwoven carrier, it loses its shape (collapses) and cannot be reprocessed. Thus, a high maximum glass tensile strength indicates that the nonwoven support is suitable for efficient production of high quality asphalt films in industrial processes.

At low temperatures, bituminous membranes are used in construction applications and are subjected to mechanical forces, such as bending to cover irregular building components, nailing or being subjected to stress and strain. Therefore, it is important that the material is mechanically stable at low temperatures to avoid puncture, rupture, etc.

Preferably, the nonwoven carrier has an overall maximum tensile strength of at least 600N/5cm, more preferably at least 625N/5cm, at room temperature (23 ℃), as determined according to ISO 9073-3. Preferably, the peak toughness at room temperature is at least 0.28daN/5cm/g/m². Preferably, the elongation at break is at least 40% determined according to ISO 9073-3 at room temperature.

Unless otherwise stated, the above-mentioned parameters relating to mechanical stability are determined in the longitudinal direction, preferably in the longitudinal and transverse directions. Preferably, the characteristic is for 180g/m with an additional 20% adhesive addition²The basis weight of the spunbond(s) was determined.

Preferably, the nonwoven carrier has an air permeability of 250 ÷ 2500l/m²As determined by ISO 9037-15.

The subject matter of the invention is also a method for producing the nonwoven carrier of the invention, comprising the following steps:

(a) There is provided a non-woven fabric which,

(b) Impregnating the nonwoven with an aqueous binder comprising starch and polyvinyl alcohol, wherein the binder does not comprise a cross-linking agent, and

(c) Drying and curing the binder to obtain the nonwoven carrier.

Curing may be achieved by drying during the production process. Because no crosslinking agent is present, there is no need to induce, monitor, and/or terminate the crosslinking reaction.

The invention also relates to the use of the inventive nonwoven carrier as a substrate for producing bitumen membranes. The subject of the invention is also an asphalt film comprising the nonwoven carrier of the invention. The subject of the invention is also a process for producing an asphalt membrane, comprising the following steps:

(A) Providing a nonwoven carrier of the invention, and

(B) The nonwoven carrier is impregnated with pitch.

Typically, impregnation of the nonwoven fabric support with pitch is carried out in a bath containing molten pitch, the nonwoven fabric support being immersed in the bath. The pitch-attached nonwoven carrier is then removed from the bath and dried. Preferably, the process is carried out as an automated, preferably continuous process, wherein an "endless" roll of nonwoven fabric carrier is fed into the process and a roll of bitumen film is obtained as the final product.

In order to produce asphalt membranes efficiently from nonwoven carriers, the nonwoven carriers and asphalt membranes should be flexible. Thus, the nonwoven fabric support and/or the asphaltic film are rollable. In contrast, nonwoven carriers and/or bituminous membranes are not rigid.

The bituminous membrane may be obtained by a conventional process in which a nonwoven carrier bonded with a binder is impregnated with molten bitumen in a bath. Typically, the nonwoven carrier is supplied to the production line in roll form, where it is unwound and directed through a hot asphalt bath by standard machinery, drawn from the bath, and subsequently cooled and solidified to adhere the asphalt to the carrier. After curing, the asphalt film is rolled up so that it can be stored, transported and provided to a building site.

Bitumen membranes can be used in building and roofing applications. Typically, the bituminous membrane is unrolled at the building site, optionally cut into a desired shape, subjected to temporary heating by combustion to soften at least one bituminous surface, placed at the application site, and optionally deformed and thus aligned with the surface of the application site. Subsequently, additional layers, such as insulation layers or tiles, are disposed on the asphaltic membrane. The process of applying bituminous membranes in construction applications is standardized in DIN V20000-201. In the bituminous membrane, the proportion of bitumen to nonwoven carrier is preferably from 60% by weight to 97% by weight to 3% by weight to 40% by weight.

The subject matter of the invention also relates to a roof, a building material or a building comprising the bituminous membrane of the invention. For example, an asphalt film may be used as a masking film, a sealing film, or a waterproof sheet.

The nonwoven carriers of the invention may also be used in other applications such as reinforcing inserts, optionally in combination with additional textile fabrics, in masking films, as textile backings or textile reinforcements, in flooring, especially for fitting carpets and PVC flooring, as wall coatings or decorative surface finishes for the interior and exterior of buildings.

The nonwoven fabric support, the bituminous membrane, the uses and the method of the present invention solve the potential problems of the present invention. A nonwoven fabric carrier for producing asphalt membranes is provided which is readily available, easy to produce, inexpensive and has excellent mechanical properties. Surprisingly, the nonwoven carrier has a high mechanical resistance, in particular a dimensional stability at room temperature and elevated temperature, which is even better than a comparable binder comprising a crosslinking agent, despite the fact that no crosslinking agent is added to stabilize the binder system. This is unexpected because the stability of many thermoplastic polymer binders deteriorates at high temperatures. Due to the high mechanical resistance (as indicated by tensile strength, toughness) and dimensional stability (as indicated by heat distortion), nonwoven carriers are suitable for producing high quality asphalt films in an efficient, high speed automated process. The high dimensional stability at high temperatures and the very good mechanical properties at room temperature make nonwoven carriers particularly suitable for building and roofing applications. The present invention also provides guidance on how to provide specific cross-linker-free starch/polyvinyl alcohol adhesives with particularly advantageous properties. A further advantage is that the binder is biodegradable and formaldehyde free and can be based on natural sources, which can provide a sustainable product.

Examples of the invention

In the working examples below, bottle Recycled Polyester (RPET) nonwovens were consolidated with various starch/polyvinyl alcohol binder compositions without a crosslinking agent.

Materials and methods

Dynamic light scattering-size distribution analysis

The average particle size of the solution was determined by Dynamic Light Scattering (DLS) at 25.0 ± 0.1 ℃ using a 90Plus particle size analyzer (Brookhaven Instruments Corporation, US). The autocorrelation function was measured at 90 deg. while the laser beam was operating at 658 nm. The mean particle size and standard deviation (± s.d.) were obtained directly from the instrument fit data by the inverse Laplace transform (Laplace transformation) method and Contin. All analyses were performed in triplicate and expressed as mean ± standard deviation. The s.d. was found to be 10nm.

Starch

Four different corn starches were used to prepare the binder. Starch a is composed of 99% amylopectin, which is partly low-oxidized. Starch B and starch C contain about 20% to 25% (dry weight) amylose and are partially hydrolyzed to reduce M_w. Starch D contains about 20% to 25% (dry weight) amylose, is pregelatinized and water soluble. It has been pretreated by the supplier by cooking and removing water to make the starch soluble in water so that no cooking step is required before use.

The viscosity of the starch was measured according to ISO 2555 at 23 ℃ with a 25% (w/w) aqueous dispersion or solution. The properties of the starch determined are summarized in table 1 below.

TABLE 1: characteristics of starch

Starch	A	B	C	D
					Viscosity (mPas)	450	370	100	200

Polyvinyl alcohol (PVOH)

Polyvinyl alcohols are used in various grades and are characterized by different molecular weights. The higher the molecular weight, the higher the viscosity of the polymer in aqueous solution. All grades were characterized by 98% hydrolysis (acetate groups). The pH of the aqueous PVOH solution was 6 as determined according to ISO 976. The viscosity was determined according to ISO 2555 at 23 ℃ with a 4% (w/w) aqueous solution, summarized in Table 2.

TABLE 2: viscosity of PVOH grades

Type (B)	PVOH 498	PVOH 698	PVOH 1098	PVOH 2098
					Viscosity (mPas)	22	26	32	50
Degree of hydrolysis (saponification)	98–98.8	98–98.8	98–98.8	98–98.8

Method

Preparation of the Binder

The adhesive was prepared by mixing a starch dispersion (20% solids content) with a PVOH solution (10% solids content). In a typical procedure, a starch dispersion (500 g-20% solids content) is prepared by dispersing 100g of dry starch in 400g of water. The starch dispersion was heated to 90 ℃ and held at this temperature for 15 minutes, with the system kept under mechanical agitation. Finally, the system was cooled to 60 ℃. An aqueous PVOH solution (10% solids content) was prepared by introducing 60g of PVOH and 540g of water into a three-necked flask equipped with a mechanical stirrer. The mixture was then heated to 95 ℃ and held at this temperature for at least 40 minutes. After that, the temperature was cooled to 60 ℃. 500g of an adhesive formulation with a solids content of 12.5% was prepared by mixing 219g of the starch dispersion, 187g of the PVOH solution and 94g of water. If indicated, 1g of wetting agent was added. Finally, the mixture was stirred at 60 ℃ for 10 minutes and used for nonwoven impregnation.

Impregnation of nonwovens

The nonwoven substrate was a spunbonded nonwoven fabric (4.4 dtex; reinforced with 68tex glass yarns, basis weight 180 g/m) made from recycled polyethylene terephthalate (PET) fibres²By needle punching and thermosetting pre-consolidation). The nonwoven fabric substrate was impregnated with the adhesive formulation using a Mathis Fouland setup (speed: 2.5 m/min; cylinder pressure: 3.5 bar). A sample (33 cm. Times.44 cm) of the nonwoven was immersed in a bath containing the adhesive formulation. After oven drying, a final addition of 20% on a dry basis was adjusted. The adhesive applied to the nonwoven fabric samples was dried in an oven at 200 ℃ for 3 minutes 45 seconds.

Test method

A set of 15 specimens was obtained from the produced samples, which were subjected to mechanical tensile testing with a dynamometer (Instron). At low temperature (23 ℃), 5 samples of 50mm × 300mm were used in MD and CD, respectively. At high temperature (180 ℃), 5 specimens of 50mm × 180mm were used. Hot tensile set is the elongation at a specific tensile strength. The lower the value, the more dimensionally stable the material and therefore the better the product. Tensile stress testing at 180 ℃ was performed based on US2008/0214716 under modified conditions. The heat distortion resistance of PET nonwovens was characterized by tensile stress experiments using a stretcher (dynamometer) with an integrated thermostatic chamber at T =180 ℃. The clamping length was 80mm and the unwinding speed was 100 mm/min. The elongation of the nonwoven and thus also the maximum tensile strength in the Machine Direction (MD) was determined with increasing tension under loads of 80N, 100N and 120N.

Examples 1 to 5: effect of different types of corn starch on mechanical Properties

In a first series of experiments, the nonwoven was consolidated with a binder comprising a different type of starch and the same PVOH (grade 1098). The product is a thin porous sheet that is flexible and rollable. The adhesive compositions and results are summarized in table 3. In comparative example 1, a conventional binder for a nonwoven fabric carrier for asphalt roofing membranes was used, consisting 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 being in dry wt.%).

TABLE 3: effect of different types of corn starch on mechanical Properties

The results show that the starch/PVOH adhesive has advantageous properties compared to a conventional crosslinked acrylic acid/melamine formaldehyde adhesive, although no crosslinker is included.

First, starch/PVOH adhesives are formaldehyde free, which is advantageous for safety and environmental reasons. Further, the cost of starch/PVOH adhesives is significantly reduced, which is associated with commercial products on a large scale. Third, starch/PVOH adhesives can be produced without a crosslinking agent and a crosslinking catalyst. Thus, the composition and the production process are much simpler than for crosslinking compositions in which the reactive components have to be adapted to each other and reaction control is required.

Furthermore, the results provide evidence that the starch/PVOH adhesive, although not crosslinked, can impart improved mechanical properties to the product, making it well suited as a carrier for bituminous films. For the production of bituminous membranes, it is of utmost importance that the nonwoven carrier is dimensionally stable at 180 ℃. The results show that the deformation of the starch/PVOH binder consolidated nonwoven is much lower and the maximum glass tensile strength is higher than the comparative standard nonwoven with the crosslinked melamine acrylic binder. This represents a great advantage when impregnating a nonwoven carrier with pitch in an industrial process. The low thermal stretch deformation indicates that the nonwoven carrier can maintain its shape while passing through the production line under significant tension and loaded with a large amount of pitch. The high maximum glass tensile strength indicates that the nonwoven support can withstand the considerable maximum forces in the asphalt-impregnated wire. The maximum force is significantly higher for the nonwoven carrier of the present invention than for the comparative nonwoven with standard binder. Thus, the pitch film can be produced from the nonwoven fabric carrier of the present invention at higher speeds and production rates, and with higher product quality, i.e., less failure, product abnormalities and damage. A particularly high dimensional stability at high temperatures is observed in example 3 using starch B. Only example 4 provided a level of deformation at elevated temperatures comparable to standard adhesives. However, this is still a good and unexpected result for adhesives without cross-linking agents.

Further, the results indicate that mechanical properties at low temperatures are advantageous. As shown in examples 2 and 3, the starch/PVOH consolidated nonwovens had a comparable cold toughness as comparative example 1 using a standard binder. The adhesives of examples 4 and 5 did not provide the same tensile strength and toughness as the conventional adhesives, but the results were still good and unexpected for natural adhesives that did not contain a crosslinker. The nonwoven carrier may also be stretched and elongated as required for building and roofing applications. The results at low temperatures indicate that the nonwoven fabric support also imparts good mechanical properties to the bitumen membrane in the final construction or roofing application.

Example 6: size of starch granule

The size of the starch aggregates in the starch-only dispersion and the starch/PVOH adhesive dispersion was determined by DLS. As shown in table 4, the size of the starch aggregates present in the dispersion was different for different aqueous starch dispersions and aqueous starch/PVOH dispersions. In particular, starch B and starch B/PVOH dispersions are characterized by relatively large particles. Further, the average particle size of the starch B/PVOH dispersion was significantly higher than the dispersion containing only starch B. In contrast, dispersions of starch a or C mixed with PVOH showed similar aggregate sizes as starch a or C alone. Without being bound by theory, PVOH appears to exert a self-assembling effect on starch molecules in starch B. This may explain the advantageous properties of the starch/PVOH adhesive system in example 3 above.

TABLE 4: starch particle size (in nm) determined by DLS

Conclusion

In general, the working examples show that a high efficiency crosslinker-free aqueous binder composed of starch and PVOH can be used to consolidate the nonwoven carrier of the asphaltic film. Analysis of cold mechanical properties, in particular tensile strength and toughness, starch a and starch B showed optimal values, comparable or even slightly better than the melamine/acrylic adhesive standard (overall toughness and tensile strength). With respect to thermo-mechanical properties, starch B provides the lowest MD deformation at 120N. These values are supported by physicochemical studies. In fact, rheological characterization indicated the highest G value of the mixture starch B/PVOH (data not shown), indicating that this adhesive had a stronger biopolymer network. Aggregate size as measured by DLS was highest compared to other binders. The largest aggregates may result in better fiber adhesion and better thermo-mechanical properties.

The presence of a small amount of carboxylated groups in the starch of example 2 does not appear to have a significant effect on the adhesive properties due to chemical oxidation. The pregelatinized starch used in example 5 was water-soluble and could be instantly dissolved in cold water. The results show that these modifications of the starch structure may lead to a reduction of the binding properties compared to the starch to be cooked.

Example 7: adhesive analysis

In a further experiment, the aqueous binder was heated to 200 ℃ for 3 minutes and the size of the binder molecules was analysed by MALDI-TOF. It was observed that the size of the binder molecules was not affected by the heat treatment. Thus, the esterification reaction between starch and PVOH can be excluded. This confirms that the good mechanical properties of the binder-consolidated nonwovens of examples 2 to 5 were obtained despite the binder not being crosslinked.

Examples 8 to 12: effect of different types of PVOH

In a second series of experiments, the nonwoven was consolidated with a binder comprising starch a and four PVOH's with different viscosities. In comparative example 8, the same conventional binder as in comparative example 1 was used. The results are summarized in table 5.

TABLE 5: effect of different grades of PVOH

The viscosity of polyvinyl alcohols with linear polymer chains is directly related to the average molecular weight. PVOH 498 and 698 are characterized by low molecular weight and viscosity. PVOH 698, 1098, and 2098 has lower thermal tensile set than traditional adhesives. Hot glass tensile strength is always significantly higher than standard adhesives. These products are therefore very suitable as nonwoven carriers for the production of bituminous membranes. Overall, the results show that if PVOH has a higher molecular weight, the bonding properties can be improved.

Examples 13 to 16: effect of wetting agent (surfactant) on mechanical Properties of starch/PVOH Adhesives

In a further experiment, the effect of wetting agents (surfactants) on starch/PVOH adhesive compositions was examined. Some starch/PVOH adhesives are prepared with additional wetting agents that are used in the art as additives to improve the processability and nonwoven properties of the adhesive. A non-silicon containing nonionic ethoxylated surfactant (example 14) was used which was characterized by a low tendency to foam and was efficient in reducing the surface tension of water-based solutions and dispersions. By adding 0.2% (v/v%) of this substance to the aqueous dispersion, the surface tension can be lowered to below 30 mN/m. Polyethoxylated monoesters of 3, 6-sorbitan (example 16) which are hydrophilic and soluble or dispersible in dilute solutions of water and electrolyte have also been used. The solubility in aqueous solution increases with increasing degree of ethoxylation. The adhesive with wetting agent was compared with the adhesive of the invention without additives (examples 13, 15), respectively. A significant decrease in cold tensile strength (MD and CD) and cold glass tensile strength was observed when the sorbitan polyethoxylate wetting agent was added (example 14). A decrease in cold drawing properties was also observed when the ethoxylated wetting agent was added (example 16). Both wetting agents also influence the hot-stretch deformation in an undesirable manner, since higher deformations are observed in comparison with adhesives without additives. Without being bound by theory, the high tensile strength of the starch/PVOH adhesive may be due to the high number of hydrogen bonds between the molecules and/or the high compatibility between the two polymers. Thus, when a wetting agent is added, the hydrogen bonding network may be at least partially disturbed, resulting in potential delamination of the two polymers. In addition, surfactants have a tendency to migrate at the interface, resulting in reduced adhesion between the adhesive and the surface of the PET fibers. This can be confirmed by electron microscopy images of the product. Wetting agents adversely affect the adhesive microstructure because undesirable phase separation is observed in the adhesive film. In contrast, a uniform adhesive film was observed in comparative example 15. This may explain the lower tensile strength of the nonwoven samples in examples 14 and 16. Overall, these examples show that standard additives such as surfactants can significantly reduce the stability of the nonwoven carrier.

Examples 17 to 21: effect of different types of crosslinking Agents on mechanical Properties

In examples 19-21, the nonwoven was consolidated with a binder as described in example 2 above, which additionally included a crosslinking agent. Three specific types of crosslinking agents preferred in the art, such as EP 3 299 514A1, were selected for crosslinking starch-based adhesives for nonwoven substrates (see table 6). An adhesive was prepared as described in example 2 above, wherein 5% (solids content) of starch B was replaced by 5% (solids content) of cross-linking agent, respectively.

Table 6: crosslinking Agents added in examples 19 to 21

	Crosslinking agent 1	Crosslinking agent 2	Crosslinking agent 3
				Chemical name	Melamine formaldehyde	Polyacrylic acid + sodium hypophosphite (catalyst)	Polyamine epichlorohydrin
Concentration of	70% (aqueous solution)	50% (aqueous solution)	20% (aqueous solution)

Impregnating the nonwoven as described above. The product is a thin porous sheet that is flexible and rollable. The adhesive compositions and results are summarized in table 7. Comparative example 17 is a conventional binder for a nonwoven fabric carrier for asphalt roofing membranes consisting of 70% acrylic/melamine/formaldehyde binder (63% acrylic resin, 7% melamine formaldehyde crosslinker 1) and 30% starch C, all percentages being in dry wt.%. The results were compared with those obtained for the corresponding adhesive without crosslinker and the melamine/acrylic standard adhesive.

TABLE 7: examples 17 to 21

The results in table 7 show that:

(A) The starch/PVOH adhesive mixture without crosslinker (example 18) provided the same toughness of cold PET as the comparative standard formulation based on melamine formaldehyde crosslinker (example 17). Furthermore, the adhesive of example 18 provided the lowest hot tensile set at 120N and the highest hot glass tensile strength of all examples, which is the reason for the best runnability during bitumen impregnation in a continuous production line.

(B) starch/PVOH + crosslinker 1 (comparative example 19) imparts the same cold toughness to PET as the starch/PVOH adhesive mixture, but the MD and CD cold PET elongation (%) is low. This is a disadvantage because higher cold elongation is preferred to prevent roof tearing. The hot tensile set at 120N is higher than without the crosslinker (example 18), making the product less processable during bitumen impregnation.

(C) The starch/PVOH + crosslinker 2 and crosslinker 3 adhesive mixture (comparative examples 20, 21) imparts lower cold PET toughness to the substrate compared to starch B/PVOH without crosslinker (example 18) and the standard formulation (comparative example 17). The thermal tensile set (1.84% and 1.92%) was much higher than without the crosslinker, similar to the standard formulation.

In summary, the starch/PVOH adhesive without crosslinker showed the best properties for the substrate:

very good thermomechanical stability (lowest tensile set and highest tensile strength of glass)

Very good cold mechanical properties (PET toughness and PET elongation)

FA-free, simpler in composition, low in cost, capable of providing 100% biodegradable adhesives from natural raw materials, and capable of recycling the original components.

As evidenced by DLS measurements, PVOH can aggregate starch granules very efficiently due to the very good cold and hot stretching properties of the starch granules. Without being bound by theory, the cross-linking agent may interfere with the aggregation phenomenon, which results in a decrease in tensile properties.

Examples 22 to 25: industrial-Scale production of nonwoven carriers

Nonwoven carriers (98% degree of hydrolysis, pH 6, viscosity 32mpa · s at 23 ℃, determined according to DIN EN ISO 2555 with 4% (w/w) aqueous solution) were mass produced using a binder comprising starch B and PVOH.

The adhesive was mass produced by mixing a starch dispersion (25% solids content) with a PVOH solution (15% solids content). In a typical procedure, a starch dispersion (500 Kg-25% solids content) is prepared by dispersing 125Kg of dry starch in 375Kg of water. The starch dispersion is heated to 90 ℃ to 100 ℃ by a jet cooking system. Finally, the system was cooled to 60 ℃. An aqueous PVOH solution (15% solids content) was prepared by introducing 90Kg PVOH and 510Kg water into a heated tank equipped with a mechanical stirrer. The mixture was then heated to 95 ℃ and held at this temperature for at least 40 minutes. After that, the temperature was cooled to 60 ℃. 500Kg of an adhesive formulation having a solids content of 15% was prepared by mixing starch, PVOH and water in the amounts detailed in Table 8. Finally, the mixture was stirred at 60 ℃ for 10 minutes and used for nonwoven impregnation. Nonwoven impregnation was performed on a typical follard for binder liquid impregnation and the mechanical properties were determined as described above.

TABLE 8: adhesive composition examples 23 to 25

Examples of the invention	Adhesive formulations	Starch amount [ kg]	Amount of PVOH [ kg]	Water [ kg]
					23	69% starch-31% PVOH	210	150	140
24	50% starch-50% PVOH	150	250	100
					25	33% starch-66% PVOH	99	330	71

The product is a thin porous sheet that is flexible and rollable. The adhesive compositions and results are summarized in table 9. In example 22, the comparative adhesive was applied as described above.

TABLE 9: large-Scale production according to examples 23 to 25

The results provide evidence that the starch/PVOH adhesive can impart mechanical properties to the product that make it well suited as a carrier for bituminous films. Although the binder does not contain a crosslinking agent, the nonwoven carriers of the present invention have improved properties compared to standards with conventional crosslinked acrylic acid/melamine formaldehyde binders. In particular, adhesive formulations comprising at least 50% pvoh can have advantageous mechanical properties.

For the production of bituminous membranes, the mechanical stability of the nonwoven carrier at 180 ℃ is very important. In this regard, the results show that the starch/PVOH binder consolidated nonwovens had lower distortion and significantly higher glass tensile strength than the standards. This represents a great advantage in the customer line, since lower hot stretch deformation means less deformation during bitumen impregnation and therefore higher speed and productivity, and fewer breakdowns, product irregularities and damages. Especially low distortion at high temperatures was observed in examples 24 and 25 having at least 50% pvoh. With respect to cold mechanical properties, in particular tensile strength and toughness, starch/PVOH adhesive formulations may in particular show better values than standard adhesives, in particular when the amount of PVOH is above 30% wt.

Claims

1. A nonwoven carrier for a pitch membrane, wherein the nonwoven comprises organic polymer fibers and is consolidated with an aqueous binder, wherein the binder comprises

(a) Starch, and

(c) The adhesive does not contain a crosslinking agent, and

(d) The adhesive does not contain a filler.

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

3. The nonwoven carrier of at least one of the preceding claims characterized in that the starch is partially hydrolyzed.

4. The nonwoven carrier according to at least one of the preceding claims, characterized in that the binder contains less than 2% of additives, preferably 0% of additives (based on the total dry weight).

5. The nonwoven carrier according to at least one of the preceding claims, characterized in that the starch particles in the aqueous binder dispersion have an average size of at least 0.1 μm, as determined by Dynamic Light Scattering (DLS), and/or

The viscosity of the starch is at least 150mPas, the viscosity being determined according to ISO 2555 at a concentration of 25wt.%, at 23 ℃.

6. The nonwoven carrier according to at least one of the preceding claims, characterised in that the starch is insoluble in water and/or does not pregelatinize at 23 ℃ and/or the starch comprises 10 to 50% amylose (dry weight relative to the total amount of amylose and amylopectin).

7. The nonwoven fabric carrier according to at least one of the preceding claims, characterized in that the starch and the polyvinyl alcohol are essentially uncrosslinked and/or the viscosity of the polyvinyl alcohol is at least 25mpa-s, the viscosity being determined at a concentration of 4wt.% according to DIN EN ISO 2555 at 23 ℃.

8. The nonwoven carrier according to at least one of the preceding claims, characterized in that the binder comprises 5 to 95wt.% starch, 5 to 95wt.% polyvinyl alcohol and 0 to 15wt.% additives, all percentages referring to dry weight and the sum of all percentages being 100wt.%.

9. The nonwoven carrier according to at least one of the preceding claims, characterized in that the binder does not contain a structuring polymer other than starch and polyvinyl alcohol and/or the binder does not contain an additive comprising hydroxyl groups.

10. The nonwoven carrier according to at least one of the preceding claims, characterized in that the nonwoven consists of organic polymer fibers, preferably polyester fibers, and/or the nonwoven comprises reinforcements, such as inorganic fiber yarns.

11. A method for producing a nonwoven fabric carrier according to at least one of the preceding claims, comprising the steps of:

(a) There is provided a non-woven fabric which,

(c) Drying and curing the binder to obtain the nonwoven carrier.

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

13. A method of producing a bituminous membrane, said method comprising the steps of:

(A) Providing a nonwoven fabric carrier according to any of claims 1 to 10, and

(B) Impregnating the nonwoven carrier with pitch.

14. An asphalt film comprising the nonwoven carrier according to at least one of claims 1 to 10.

15. A roof, building material, or building comprising the asphaltic membrane of claim 14.