DE9207368U1 - Laminate made of fleece and scrim - Google Patents

Description

HOECHSTAKTIENGESELLSCHAfTf HOE /F i-58 G Dr.VA/

Laminate made of fleece and scrim.

The present invention relates to a flame-retardant laminate made of at least two fleece layers and at least one scrim layer, which serves in particular as an insert for bitumen sheets.

A similar material is known from GB-PS-1 517 595, in which a web of glass fibers is incorporated into a nonwoven fabric made of organic fibers and the resulting structure is then consolidated by applying an acrylate binder.
EP-B-110 039 also discloses a laminate with at least three layers, which is made up of fleece and gel layers. In one embodiment, this known laminate contains two fleece layers made of organic fibers, between which a mesh made of mineral fibers, e.g. glass fibers, is enclosed. In this known material, the bond between the fleece layers and the mesh is achieved by means of a hot melt adhesive.

From the German utility model G-74 24 706 a filter material is known which consists of a fleece onto which a fabric or scrim is needled in such a way that a fibrous pile is formed on the side of the fabric or scrim facing away from the fleece.

The materials known from the above-mentioned publications GB-PS-1 517 595 and EP-B-110 039 are recommended for the production of bitumen roofing membranes.
However, in this application they show the serious defect that they tend to form waviness and cracks under thermal stress.
This defect can lead to production difficulties when the known laminates are impregnated with hot bitumen, but it can also lead to leaks in the manufactured roof covering when the bitumen sheets are laid hot on the roof or later when the sunlight changes.

These difficulties are addressed in DE-A-39 41 189, where it is stated that these deficiencies of the known materials are due to the very different reactions (e.g. stretchability, modulus changes, shrinkage) of the fiber materials used in the fleece and in the reinforcement (polyester fibers in the fleece and glass fibers in the reinforcement) under mechanical and/or thermal stress. It is therefore proposed in this publication, in order to eliminate the aforementioned deficiencies of the known materials consisting of nonwovens and scrims, to reinforce nonwovens not with scrims but with individual reinforcing threads, which are spaced apart and parallel in the

Nonwoven fabric is incorporated. These structures are bonded using chemical binders, needles and/or thermal bonding.

The materials obtained according to this method do indeed show improved thermal stability. However, they do not have the high mechanical stability of nonwovens reinforced with mesh. In particular, strong mechanical stresses can lead to a shift in the nonwoven mass, resulting in local increases and decreases in the thickness of the nonwoven.

In addition to the basic requirements of good workability when bituminizing and laying the finished roofing membrane and good long-term stability of the roof covering, the demand for flame-resistant roofing membranes is repeatedly raised.

Although good flame-retardant properties can be achieved by combining metal foils with nonwovens, as described, for example, in DE-A-28 27 136 or DE-A-38 21 011, there is often a desire for metal-free but still flame-retardant bitumen sheets.

An object of the present invention is therefore to provide laminates that can be used to produce metal-free, flame-retardant bitumen roofing membranes with high stability against mechanical stress.

One subject of the present invention is a flame-retardant laminate made of at least two layers of spunbonded nonwovens, preferably two layers of spunbonded nonwovens, and at least one scrim layer, preferably a scrim layer made of reinforcing yarns, wherein the scrim layers or the scrim layer are each located between two spunbonded nonwoven layers and the scrim or scrims have a thread density of more than 3 threads/cm, preferably more than 5 threads/cm, and that the spunbonded nonwovens and scrims are connected to one another by needling with approximately 20-70 stitches/cm ² , preferably 20-50 stitches/cm ² .

The laminate according to the invention thus consists of a number N of spunbond layers and a number G = N-1 of scrim layers. N is generally a number from 2 to 4, but can also be higher for certain requirements. N=2 is preferred, which means that preferred laminates according to the invention consist of two layers of spunbond and a scrim layer in between.

Figure 1 shows a schematic section through such a preferred laminate (1) with the two fleece layers (2, 2'), the intervening scrim layer (3), the filaments (4) that extend from the outer fleece layer through the layer structure and bring about a firm connection between the layers, and with the reinforcing threads (5) that make up the scrim layer (3).

The basis weight of the laminates according to the invention is 80 to 400 g/m ² , preferably 100 to 250 g/m ² .

Of this, 15 to 70, preferably 25 to 50 g/m ² are allocated to the clutch.

The spunbonds are preferably so-called spunbonds, which are produced by randomly laying freshly melt-spun filaments.

They consist of continuous synthetic fibers made of melt-spinnable polymer materials. Suitable polymer materials are, for example, polyamides, such as polyhexamethylene diadipamide, polycaprolactam, aromatic or partially aromatic polyamides ("aramids"), partially aromatic or fully aromatic polyesters, polyphenylene sulfide (PPS), polymers with ether and keto groups, such as polyether ketones (PEK) and polyether ether ketone (PEEK), or polybenzimidazoles.

The spunbonded nonwovens are preferably made of melt-spinnable polyesters.
In principle, all known types suitable for fiber production can be used as polyester material. Such polyesters consist predominantly of building blocks derived from aromatic dicarboxylic acids and aliphatic diols. Common aromatic dicarboxylic acid building blocks are the divalent residues of benzene dicarboxylic acids, in particular terephthalic acid and isophthalic acid; common diols have 2-4 C atoms, with ethylene glycol being particularly suitable. Particularly advantageous are laminated webs according to the invention whose fleeces consist of a polyester material that consists of at least 85 mol% polyethylene terephthalate. The remaining 15 mol% are then made up of dicarboxylic acid units and glycol units, which act as so-called modifiers and allow the expert to specifically influence the physical and chemical properties of the filaments produced. Examples of such dicarboxylic acid units are residues of isophthalic acid or of aliphatic dicarboxylic acids such as glutaric acid, adipic acid, sebacic acid; Examples of modifying diol residues are

of longer-chain diols, e.g. of propanediol or butanediol, of di- or triethylene glycol or, if present in small quantities, of polyglycol with a molecular weight of approx. 500 - 2000.

Particularly preferred are polyesters containing at least 95 mol% polyethylene terephthalate, especially those made from unmodified PET.

The flame-retardant effect can be further enhanced by using spunbonded nonwovens made from flame-retardant modified polyesters. Such flame-retardant modified polyesters are well known. They contain additives of halogen compounds, in particular bromine compounds, or, which is particularly advantageous, they contain phosphorus compounds that are condensed into the polyester chain.

Particularly preferred flame-retardant laminates according to the invention contain spunbonded nonwovens made of polyesters which contain units of the formula

0 0

T l|

O-P-R-C (I)

wherein R is alkylene or polymethylene having 2 to 6 C atoms or phenyl and R ^{1 is} alkyl having 1 to 6 C atoms, aryl or aralkyl.
Preferably, in the formula IR is ethylene and R ¹ is methyl, ethyl, phenyl, or ω-, m- or p-methyl-phenyl, in particular methyl.
Such spunbonded nonwovens are described, for example, in DE-A-39 40 713.

The polyesters contained in the nonwovens according to the invention have a molecular weight corresponding to an intrinsic viscosity (IV), measured in a solution of 1 g of polymer in 100 ml of dichloroacetic acid at 25 ^° C, of 0.7 to 1.4.

In the sense of this invention, scrims are thread grids formed from sets of parallel yarns lying at an angle to one another, with the threads being fixed to one another at their intersection points.

The angle at which the threads cross is usually between 10° and 90°. A clutch can of course contain more than just two threads

The number and direction of the thread sets depends on any special requirements.

Preference is given to fabrics that consist of two sets of threads that intersect at an angle of preferably 90°. If a particularly high level of mechanical stability is required in one direction, e.g. the longitudinal direction of the laminate, it is recommended to install a fabric that has a set of threads with a smaller thread spacing in the longitudinal direction, which is stabilized, for example, by a transverse set of threads or by two sets of threads that form angles of approximately +40° to +70° or -40° to -70° with the first. Figures 2 and 3 show, for example, schematically the arrangement of the reinforcing threads (5) in such fabrics (3) and

Special stability requirements in all directions can be met by a scrim with 4 or 5 sets of threads that lie on top of each other in different directions and are connected to each other at the thread crossing points.
An example of such a special scrim (13), which has three sets of threads (15; 15a; 15b) running in different directions and additionally a set of threads (15c) running parallel to one of these sets of threads but in a fourth plane, is shown in an oblique view in Figure 4.

The thread density specified above is measured perpendicular to the respective thread running direction. As already mentioned, the thread density can be the same for all existing thread groups or, depending on the expected stress, different thread densities can be selected within the scope of these limit values.

The fixing of the crossing reinforcing threads at the crossing points can be done by autogenous fusion at elevated temperatures and, if necessary, by applying pressure to threads that soften without decomposing. However, the fixing can in any case be done by commercially available chemical binders, such as polyvinyl alcohol or butadiene-styrene copolymers or by hot-melt adhesives. For flame-retardant laminates according to the invention, the fixing can also be done by a flame-retardant binder, e.g. a polyester containing phosphoric acid or phosphonic acid groups, which is used as a hot-melt adhesive.

Commercially available clutches that correspond to the description above can of course also be used.

The reinforcement yarns DG can in principle be staple fiber yarns or filament yarns (= continuous fiber yarns), provided that they have the desired combination of maximum tensile strength and maximum tensile elongation.

The filaments of the reinforcing yarns can also have non-circular cross-sections, such as multilobal, dumbbell-shaped or ribbon-shaped cross-sections.
Filament yarns made of glass are preferred due to their advantageous mechanical properties and heat resistance.

In addition to fabrics made of glass filaments, fabrics made of aromatic polyamides that are modified by incorporating building blocks containing meta-positioned functional groups (e.g. isophthalic acid) or fully aromatic polyamides that are statistically composed of various diamine and/or dicarboxylic acid building blocks can also be used for special applications.

Yarns made from other high-modulus fibers such as carbon fibers or fibers made from polyphenylene sulfide, PEEK (polyetheretherketone), PEK (polyetherketone) or polybenzimidazole can also be contained in the fabrics of the laminates according to the invention.

The reinforcing yarns DG of the laminates according to the invention have a maximum tensile elongation of about 2.5 - 25%.

Within these relatively wide limits, the desired elongation can be set by the selection of the yarn material. A very low elongation of around 2.5 to 3.5% can be achieved by choosing glass fibers or aramid fibers, and a medium to high elongation can be achieved by choosing modified aramid fibers (e.g. (R)NOMEX).

The tenacity-related strength is approximately 40 to 180 cN/tex, preferably 40 to 70 cN/tex. Here, glass fibers cover the strength range of approximately 40 to 50 cN/tex

The linear density of the reinforcement yarns DG is preferably 70 to 1200 dtex for organic fiber materials and approx. 30 to 130 tex for inorganic fiber materials. In special cases where a lower or particularly high mechanical strength is desired, a lower or higher linear density of the reinforcement yarns may of course also be indicated.

In preferred fabrics made of glass fiber reinforcement yarns, the yarns have titres of approx. 30 to 130 tex.

Preferably, the hot air shrinkage of the reinforcing yarns made of polyesters at 160 ^° C is preferably 0.5 to 6% measured according to the test standard DIN 53 866 .

Preference is given to laminates according to the invention whose spunbonded nonwovens consist of polyester fibers, in particular of polyethylene terephthalate, and whose reinforcing fabrics consist of one of the above-mentioned thermally stable raw materials, but in particular of glass.

Furthermore, such a laminate is particularly preferred if it has two fleece layers and a scrim layer in between.

Particularly preferred is also a laminate according to the invention which is constructed from two nonwoven layers and a scrim layer in between, wherein both nonwoven layers have approximately the same basis weight.
For special requirements, a laminate according to the invention is particularly preferred which is constructed from two nonwoven layers and a scrim layer in between, wherein one of the nonwoven layers is at least 20% thicker than the other.

In addition to needling, the laminates according to the invention can also be strengthened by a chemical binder.

As additional binders, the laminates according to the invention can contain, for example, the usual polymers that are applied in the form of dispersions. These are expediently dispersions of polyvinyl alcohol (PVA) or butadiene-styrene copolymers.

However, flame-resistant binders, such as those described in DE-A-39 01 152, are preferred.

In nonwovens according to the invention which are consolidated in addition to needling, the binder is preferably a melt binder.

Particularly suitable melt binders are modified polyesters with a melting point that is 10 - 50 ^° C, preferably 30 - 50 ^° C, lower than that of the nonwoven raw material. Examples of such a binder are polybutylene terephthalate or polyethylene terephthalate modified by condensing longer-chain diols and/or isophthalic acid or aliphatic dicarboxylic acids, but in particular polyethylene terephthalate modified by incorporating chain links of the formula I given above.

The melt binders are preferably introduced into the nonwovens in fiber form

and are then preferentially enriched in the nonwoven layers facing the gel layers.

Also particularly preferred are filament-reinforced nonwoven webs according to the invention which have a combination of preferred features.

The laminates according to the invention are produced by depositing the fiber material forming the fleece layers on a moving depositing surface. For depositing the continuous fibers, spinning beams are expediently used, from which a fiber curtain is spun into a spinning and stretching shaft in which the fibers are simultaneously cooled and accelerated by a fluid flow and thus stretched.

The reinforcement fabrics are conveniently inserted by a delivery device from which the yarns enter between two fleece layers, which are then deposited on the same deposit by two rows of deposit devices arranged one behind the other in the transport direction.

Of course, it is also possible to produce laminates according to the invention by combining the prefabricated fleece and gel layers on assembly machines and then needling.

The selection of the fabrics used to produce the filament-reinforced nonwovens according to the invention is carried out according to the criteria given above.

The nonwoven laminate is solidified by needling the laid nonwoven and gel layers with the number of stitches specified above. If desired, additional solidification can be carried out in a conventional manner by applying, e.g. spraying, binding agent solutions or dispersions or preferably by introducing hot melt binders and subsequent heat treatment at a temperature at which the hot melt binder melts and connects the supporting filaments of the nonwoven at their crossing points.

The melt binder is particularly advantageously introduced into the fleece in the form of binding filaments. These can be present as separate filaments, for example if they are spun out of separate openings in the spinning beams and evenly distributed in the running fiber curtain, or they can be present as a sheath or side of the supporting filaments or part of the supporting filaments if

appropriate nozzle openings for spinning core-shell filaments or side-by-side two-component filaments must be provided in the spinning beam.

If the binder is a melt binder, the laminate is subjected to a heat treatment after needling and the binder application at a temperature at which the melt binder melts.

The flame-retardant laminate sheets according to the invention show no tendency to delaminate and no formation of waves and cracks, even under high thermal-mechanical stress.

In addition to the good flame-retardant properties when bituminized, the laminated sheets according to the invention exhibit a surprisingly low width shrinkage, which is only 2 to 4 mm for a sheet about 1000 mm wide, compared to about 12 mm for conventional sheets. It is also shown that the laminated sheet according to the invention produces flat, surface-stable, bubble-free bitumen sheets even under rough bituminizing conditions. The puncture resistance also increases, as shown in the stamp puncture test according to DIN 54 307. This results in significantly improved processability and increased work safety when laying the bituminized roofing sheets according to the invention on the roof. The good flame retardancy even when using very light glass fabrics with 3 threads/cm in the laminated sheet according to the invention is also surprising.

These advantages of the reinforcing sheet according to the invention result, surprisingly, from needling the fleece layers with the reinforcement yarn.

The glass fabric layer is covered by the two polyester spunbond layers. This proves to be very advantageous when needling the laminate and when bituminizing.

A further subject matter of the present invention is a bituminized roofing membrane and a bituminized roof underlay membrane which contains a fabric-reinforced laminated sheet according to the invention as a carrier.

These bituminized roofing membranes or roof underlay membranes are produced by impregnating and/or coating the reinforcing membranes according to the invention with molten bitumen in a manner known per se.

Claims (4)

HOE92/F 158 Protection claims 1. Flame-retardant laminate made of at least two layers of spunbonded fabrics and at least one scrim layer made of reinforcing yarns, characterized in that the scrim layers or the scrim layer are each located between two spunbonded fabric layers and the scrim has a thread density of more than 3 threads/cm, and that the spunbonded fabrics and scrim are connected to one another by needling with about 20 - 70 stitches/cm ² . 2. Laminate according to claim 1, characterized in that the spunbonded fabrics consist of polyester fibers, in particular polyethylene terephthalate, and the reinforcing threads consist of glass or other thermally stable raw materials. 3. Laminate according to at least one of claims 1 and 2, characterized in that the laminate is additionally strengthened by a chemical binder, preferably by a flame-retardant binder. 4. Use of a laminate of claim 1 for the production of roofing membranes and roof underlay membranes.