Acoustic Nonwoven Fabric For Perforated Ceiling Elements

Abstract

A ply has a base weight of not more than 45 g/m.sup.2 for use in a ceiling element and includes a fiber blend in a proportion of not more than 30 g/m.sup.2 a flame retardant in a proportion of not more than 10 g/m.sup.2.

Description

[0001] This application is a U.S. National Phase Application under 35 U.S.C. .sctn.371 of International Application No. PCT/EP2008/003759, filed on May 9, 2008, which claims benefit to German Application No. DE 10 2007 044 906.4, filed Sep. 19, 2007. The International Application was published in German on Apr. 2, 2009 as WO 2009/039900 under PCT Article 21 (2).

[0002] The invention relates to a ply for producing an acoustical nonwoven.

BACKGROUND

[0003] Acoustical nonwovens and plies of the kind mentioned at the beginning are already known from the prior art. These are frequently used in perforated, viz., holed or slotted, metal or wood ceiling elements.

[0004] With regard to their reaction to fire behavior, such acoustical nonwovens and ceiling elements used to be assessed in accordance with German Standard Specification DEN 4102-1 by means of the "Brandschacht" test furnace. The acoustical nonwoven would be tested on its own and in the assembly with the ceiling element. The market required that the assembly of ceiling element and acoustical nonwoven achieve a classification in fire class "A2" ("noncombustible"). The acoustical nonwoven as such was required to achieve fire class "B1" (="low flammable").

[0005] Since July 2007, a revised, EU-wide regulation with regard to certification and classification of suspended ceilings is in force, viz., a CE marking regime. The regulation requires ceiling elements to meet demands which are laid down in DIN EN 13964, which cites DIN EN 13501-1 for the classification of the reaction to fire behavior.

[0006] The reaction to fire behavior is no longer tested in accordance with DIN 4102-1 ("Brandschacht"), but in accordance with DIN EN 13823. This standard describes a single burning item (SBI) test on a complete ceiling element construction and defines the parameters which are classification-relevant according to DIN EN 13501-1. In contradistinction to the previous test for reaction to fire behavior under DIN 4102-1, the testing as per DIN EN 13823 focuses increasingly on the evaluation of smoke release in the event of a fire. DIN 13501-1 applies tougher criteria to the assessment of smoke release than hitherto.

[0007] Prior art acoustical nonwovens are prone to a relatively severe production of smoke and thereby make it impossible for ceiling elements to be classified as "noncombustible" (classification "A2/s1/d0") as per the revised requirements of DIN 13501-1. This classification is stipulated particularly for buildings, and parts of buildings, having heightened safety requirements, for example public buildings, escape routes, etc.

[0008] In addition, the acoustical nonwoven shall have a high acoustical efficacy, viz., a weighted sound absorption coefficient .alpha..sub.w of at least 0.75, the weighted sound absorption coefficient .alpha..sub.w being obtained from measurement in accordance with EN ISO 354 and conversion in accordance with EN ISO 11654.

[0009] Further desiderata simplicity of processing, more particularly space-saving handling or automated incorporation in ceiling elements. Finally, the acoustical nonwoven must have no adverse effects on hygiene, health and environmental aspects.

[0010] Accordingly, there is an appreciable market need for efficiently processible acoustical nonwovens which assembled with ceiling elements meet the "A2/s1/d0" classification as per DIN EN 13501-1.

SUMMARY OF THE INVENTION

[0011] An aspect of the present invention is to provide an acoustical nonwoven which after trouble-free processing gives very little smoke production in the event of a fire.

[0012] A sheetlike ply having a basis weight of not more than 45 g/m.sup.2 comprises a fiber blend in a proportion of not more than 30 g/m.sup.2 and a flame retardant in a proportion of not more than 10 g/m.sup.2.

[0013] The inventors recognized that it is specifically the combination of an astute choice of the overall basis weight and of a proportionate reduction in flame retardant which brings about an appreciable reduction in smoke production. The ply of the present invention is particularly useful, once an adhesive material has been provided thereon, for arrangement in a metal ceiling element. As a result, the problem mentioned at the beginning is solved.

[0014] The impregnating mixture could include diammonium hydrogenphosphate as a flame retardant because it is both halogen- and heavy metal-free and hence is environmentally friendly. However, it is also conceivable to use other nitrogen-phosphorus-based flame retardants, for example ammonium polyphosphates or nitrogenous phosphonic acid salts.

[0015] The fiber blend could include fibrous or fibrillated cellulosic components. These components serve to adjust the acoustical efficacy of the ply. It is conceivable against this background for the fiber blend to comprise two different types of cellulosic pulp which are adjusted to each other with regard to fineness. However, it is also conceivable to use finely ground synthetic pulps, produced from viscose, polyolefin or aramid fibers for example.

[0016] fiber blend could further include glass fibers in a proportion of not more than 10 g/m.sup.2. This proportion of glass fibers endows the ply with high structural stability and low thermal shrinkage. This suitabilizes the ply for automated incorporation in ceiling elements. However, it is also conceivable to use other inorganic fibers, for example fibers of basalt or alumina. Lastly, polyester fibers could also be used.

[0017] The fiber blend could be prebonded with an acrylate-based binder at a proportion of less than 5 g/m.sup.2. Prebonding endows the ply with sufficient stability for homogeneous incorporation of an impregnating mixture. It is conceivable against this background for prebonding to be effected by means of a low-formaldehyde acrylate binder. This satisfies heightened requirements in respect of the formaldehyde content of the ply as per DIN EN 13964 (formaldehyde class "E1"). Also conceivable is prebonding by means of a mono- or bicomponent binder fiber, for example with an undrawn polyester fiber or a PET/PBT or PET/copolyester bicomponent binder fiber.

[0018] An acoustical nonwoven for metal ceilings having a basis weight of less than 60 g/m.sup.2 could include a ply of the herein described kind and an adhesive material in a proportion of less than 15 g/m.sup.2. The adhesive material makes it possible to fix the acoustical nonwoven by moderate heating in a metal ceiling element without damaging the constituents of the ceiling element such as paintwork, for example, in the process. It is conceivable against this background for the adhesive material to consist of a thermoplastic, substantially amorphous polyester, copolyester or copolyamide having a melting point below 100.degree. C.

[0019] The acoustical nonwoven could have a weighted sound absorption coefficient .alpha..sub.w of at least 0.75, the weighted sound absorption coefficient .alpha..sub.w being obtained from measurement in accordance with EN ISO 354 and conversion in accordance with EN ISO 11654. Such an acoustical nonwoven is a particularly good absorber of sound.

[0020] An assembly comprising a ply or an acoustical nonwoven of the herein described kind and also an uncoated perforated metal ceiling element could in a measurement in accordance with DIN EN 13823 exhibit a SMOGRA value of not more than 30 m.sup.2/s.sup.2 and also a TSP(600s) value of not more than 50 m.sup.2. Such an assembly is particularly useful for fire protection as well as for sound protection.

[0021] There are now various ways to implement and develop the teaching of the present invention in an advantageous manner. Reference for this is made to the dependent claims and also to the following elucidation of the invention by means of the drawing.

BRIEF DESCRIPTION OF THE DRAWING

[0022] In the drawing,

[0023] The single FIGURE shows a diagram which compares the DIN EN 13823 smoke production of a ceiling element construction comprising an acoustical nonwoven of the prior art with the smoke production of an analogous ceiling element construction comprising an acoustical nonwoven of the present invention.

DETAILED DESCRIPTION

[0024] The single FIGURE shows a diagram in which a ceiling element construction comprising a specimen of an acoustical nonwoven of the prior art is compared with a ceiling element construction comprising a specimen of an acoustical nonwoven of the present invention. The following observations may be made in this regard:

[0025] The curves relating to the prior art specimen are characterized by the interrupted lines and the symbol of a square. The curves relating to the specimen according to the invention are characterized by the solid lines and the symbol of a circle.

[0026] The SPR.sub.av curves and the individual SPR.sub.av(t) values ("Smoke Production Rate", left-hand y-axis, in [m.sup.2/s]) represent the current smoke production of the specimens at time t of the measurement (or within a differential time interval [t, t-3s]). An SPR.sub.av value is the ratio of a smoke gas volume stream in [m.sup.3/s] to the length in [m] of the optical path through the tube of a photometric measuring device, resulting in the unit [m.sup.2/s].

[0027] The TSP curves and the individual TSP(t) values ("Total Smoke Production", right-hand y-axis, in [m.sup.2]) represent the total smoke production of the specimens up to the time t of the measurement. A TSP(t) value corresponds to the sum total of the individual SPR.sub.av(t) values in the time interval from the start of the measurement to the time t, and corresponds to the associated area under the SPR curve. A TSP value represents the product of a sum total of SPR.sub.av values in [m.sup.2/s] and the asssociated time interval in [s], resulting in the unit [m.sup.2].

[0028] The SPR.sub.av and TSP values of a specimen, measured in the time window from 300 s to 900 s within the overall test length which includes a period before and after the time window, are used for assessment. Therefore, the time axis is scaled from 300 s to 900 s. The zero point of the actual measurement is thus at 300 s in relation to the overall length of the test.

[0029] The TSP(600s) values ("Total Smoke Production", in [m.sup.2]) represent the total smoke production of the specimens in the first 600 s of measurement. In accordance with the above remark concerning the scaling of the time axis, they correspond to the symbol-identified points on the TSP curves at the time t=900 s in relation to the overall length of the test.

[0030] The SMOGRA values ("SMOke GRowth RAte index", in [m.sup.2/s.sup.2]) represent the maxima of the ratios of the SPR.sub.av(t) values of the specimens to the associated times t of the measurement. They characterize to some extent the gradients of the SPR.sub.av curves at the start of the measurement ("slope triangles"). The SMOGRA value is the ratio of an SPR.sub.av(t) value in [m.sup.2/s] to the associated time t in [s], and hence has the unit of [m.sup.2/s.sup.2].

[0031] According to DIN EN 13823, to determine the SMOGRA value, a ratio of an SPR.sub.av(t) value to the associated time t of the measurement shall be taken to be 0 by definition when the following criteria are met:

[0032] (a) the SPR.sub.av(t) value is less than or equal to 0.1 m.sup.2/s, or

[0033] (b) the associated TSP(t) value is less than or equal to 6 m.sup.2.

[0034] This means: provided the SPR.sub.av curve does not go beyond 0.1 m.sup.2/s, or if it temporarily does, and the associated TSP(t) values in this time interval are not above 6 m.sup.2, all the ratios of SPR.sub.av(t) values to the associated times t of the measurement shall be deemed to be 0 and hence the SMOGRA value should also be deemed to be 0 by definition.

[0035] However, for low-smoke specimens to be sensibly or comparatively assessed, the SMOGRA values were determined while disregarding the criterion (a).

[0036] To be able to assess exclusively the influence of the specimens of acoustical nonwoven on smoke production, it was generally constructions of ceiling elements formed from perforated sheets of steel without coating or other smoke-relevant constituents which were measured in accordance with DIN EN 13823. This is intended to eliminate disruptive influences due to other constituents of the ceiling element, such as a paint layer for example.

[0037] In relation to smoke behavior, DIN EN 13501-1 stipulates that it is the SMOGRA value and the TSP(600s) value which are crucial as parameters for determining a "smoke class" (s1, s2 or s3). To achieve the "noncombustible" classification "A2/s1/d0" mentioned at the beginning, which includes the "smoke class" s1 and hence imposes the highest requirements on smoke behavior, the following limits for the abovementioned smoke-relevant parameters shall be observed: SMOGRA value less than or equal to 30 m.sup.2/s.sup.2 and TSP(600s) value less than or equal to 50 m.sup.2.

[0038] Measurements of the herein described type of ceiling element constructions demonstrate that a specimen of the acoustical nonwoven representing the prior art gives a SMOGRA value of about 30 m.sup.2/s.sup.2 and a TSP(600s) value of about 40 m.sup.2. This is shown by the diagram of the single FIGURE.

[0039] By contrast, a specimen of the acoustical nonwoven representing the invention only gives a SMOGRA value of about 15 m.sup.2/s.sup.2 and a TSP(600s) value of about 30 m.sup.2, i.e., an approximately 50% reduced SMOGRA value and an approximately 25% reduced TSP(600s) value.

[0040] Reference measurements on similar ceiling element constructions without acoustical nonwoven but with a coating show that commercially commonplace coatings make an, to a first approximation, additive contribution to the SMOGRA value of at best about 10 m.sup.2/s.sup.2, typically about 15-20 m.sup.2/s.sup.2, and a contribution to the TSP(600s) value of at best about 15 m.sup.2, typically about 20-30 m.sup.2.

[0041] Hence commercially available ceiling element constructions with coating and an acoustical nonwoven as per the prior art give SMOGRA values of at best about 40 m.sup.2/s.sup.2 and TSP(600s) values of at best about 55 m.sup.2/s.sup.2. These high values prevent a "noncombustible" classification "A2/s1/d0" under DIN EN 13501-1.

[0042] By contrast, ceiling element constructions with an acoustical nonwoven of the present invention and with optimum execution of the coating give SMOGRA values of only about 25 m.sup.2/s.sup.2 and TSP(600s) values of only about 45 m.sup.2/s.sup.2. These values permit a "noncombustible" classification "A2/s1/d0" under DIN EN 13501-1.

[0043] Example representing the prior art:

[0044] An acoustical nonwoven representing the prior art consists of a ply and an adhesive material. The basis weight is altogether 63 g/m.sup.2. Of this, the ply accounts for 48 g/m.sup.2 and the adhesive material accounts for 15 g/m.sup.2.

[0045] The ply includes a fiber blend composed of fibers of cellulosic pulp and fibers of glass. The fiber blend contributes altogether 25 g/m.sup.2 to the basis weight of the ply.

[0046] The ply further includes fiber prebonding of acrylate binder having a basis weight contribution of 4 g/m.sup.2.

[0047] The ply additionally includes an impregnating mixture comprising a flame retardant which accounts for a basis weight contribution of 14.5 g/m.sup.2. The impregnating mixture further comprises colorant grade carbon black and also an ethyl vinyl alcohol binder which together make a basis weight contribution of 4.5 g/m.sup.2.

[0048] The adhesive material consists of epsilon-polycaprolactone.

[0049] Embodiment representing the invention:

[0050] An acoustical nonwoven representing the invention consists of a ply and an adhesive material. The basis weight is altogether 54 g/m.sup.2. Of this, the ply accounts for 42 g/m.sup.2 and the adhesive material accounts for 12 g/m.sup.2.

[0051] The ply includes a fiber blend composed of fibers of two types of cellulosic pulp and fibers of glass. The fiber blend contributes altogether 26 g/m.sup.2 to the basis weight of the ply. The cellulosic pulp fibers contribute 20 g/m.sup.2 to the basis weight of the ply, the glass fibers 6 g/m.sup.2.

[0052] The ply further includes fiber prebonding of acrylate binder having a basis weight contribution of 4 g/m.sup.2.

[0053] The ply additionally includes an impregnating mixture comprising a flame retardant which accounts for a basis weight contribution of 7.5 g/m.sup.2. The impregnating mixture further comprises colorant grade carbon black and also an ethyl vinyl alcohol binder which together make a basis weight contribution of 4.5 g/m.sup.2.

[0054] The adhesive material selected was epsilon-polycaprolactone.

[0055] With regard to further advantageous implementations and developments of the teaching of the present invention, reference is made to the general part of the description and to the claims.

[0056] It may finally be particularly emphasized that the previously purely arbitrarily selected embodiment merely serves to discuss the teaching of the present invention, but does not restrict it to this embodiment.

Claims

1-9. (canceled)

10. A ply having a base weight of not more than 45 g/m.sup.2 for use in a ceiling element comprising: a fiber blend in a proportion of not more than 30 g/m.sup.2; and a flame retardant in a proportion of not more than 10 g/m.sup.2.

11. The ply as recited in claim 10, wherein the flame retardant includes diammonium hydrogenphosphate.

12. The ply as recited in claim 10, wherein the fiber blend includes cellulosic fibers.

13. The ply as recited in claim 10, wherein the fiber blend includes fibers of two different types of cellulosic pulp.

14. The ply as recited in claim 10, wherein the fiber blend includes glass fibers in a proportion of not more than 10 g/m.sup.2.

15. The ply as recited in claim 10, further comprising an acrylate-based binder in a proportion of less than 5 g/m.sup.2.

16. An acoustical nonwoven having a basis weight of less than 60 g/m.sup.2 for metal ceilings comprising: a ply having a base weight of not more than 45 g/m.sup.2 and including a fiber blend in a proportion of not more than 30 g/m.sup.2 and a flame retardant in a proportion of not more than 10 g/m.sup.2; and an adhesive material in a proportion of less than 15 g/m.sup.2.

17. The acoustical nonwoven as recited in claim 16, wherein the flame retardant includes diammonium hydrogenphosphate.

18. The acoustical nonwoven as recited in claim 16, wherein the fiber blend includes cellulosic fibers.

19. The acoustical nonwoven as recited in claim 16, wherein the fiber blend includes fibers of two different types of cellulosic pulp.

20. The acoustical nonwoven as recited in claim 16, wherein the fiber blend includes glass fibers in a proportion of not more than 10 g/m.sup.2.

21. The acoustical nonwoven as recited in claim 16, wherein the ply includes an acrylate-based binder in a proportion of less than 5 g/m.sup.2.

22. The acoustical nonwoven as recited in claim 16, further comprising a weighted sound absorption coefficient .alpha..sub.w of at least 0.75, the weighted sound absorption coefficient .alpha..sub.w being obtained from measurement according to EN ISO 354 and conversion according to EN ISO 11654.

23. An assembly comprising: a ply having a base weight of not more than 45 g/m.sup.2 and including a fiber blend in a proportion of not more than 30 g/m.sup.2 and a flame retardant in a proportion of not more than 10 g/m.sup.2; and an uncoated perforated metal ceiling element, wherein the assembly exhibits in a measurement according to DIN EN 13823 a SMOGRA value of not more than 30 m.sup.2/s.sup.2 and a TSP(600s) value of not more than 50 m.

24. An assembly comprising: an acoustical nonwoven having a basis weight of less than 60 g/m.sup.2 for metal ceilings including a ply having a base weight of not more than 45 g/m.sup.2 and including a fiber blend in a proportion of not more than 30 g/m.sup.2 and a flame retardant in a proportion of not more than 10 g/m.sup.2 and an adhesive material in a proportion of less than 15 g/m.sup.2; and an uncoated perforated metal ceiling element, wherein the assembly exhibits in a measurement according to DIN EN 13823 a SMOGRA value of not more than 30 m.sup.2/s.sup.2 and a TSP(600s) value of not more than 50 m.