Method of making fibrous mats and fibrous mats

[0001] The present invention relates to a method of producing non-formaldehyde, fiber nonwoven mats from glass fibers, intended for use in lining ceiling panels and for other applications where similar requirements exist, and such mats.

[0002] Ceiling panels are commonly used to create ceilings in buildings and can be made of a variety of materials, including mineral fibers, cellulose fibers, fiberglass, wood, metal and plastics. It is usually preferred that such ceiling panels have good structural properties such as rigidity and flexibility as well as fire resistance. In some applications, it may also be beneficial for the ceiling panel to have acoustic absorption properties. [0003] It would be beneficial to develop a ceiling panel whose structural properties, fire resistance and sound absorption are excellent, and which is furthermore very light. It would be even more beneficial, in order to reduce storage and forwarding costs, for the ceiling panels to be compressed to a fraction of their normal size for packaging, and then returned to their normal size for installation and use. Such a ceiling panel was designed by other inventors using a fibrous nonwoven mat, see US Patent Application Publication No. 20020020142 filed April 23, 2001. US-A-5,772,846 discloses a fibrous nonwoven mat containing glass fibers with a length of 25 mm and a diameter between 9 and 16 pm, which are joined together by a binder.

[0004] Unfortunately, traditional non-woven fibrous mats have not been able to meet all the requirements and needs of this design, which are formaldehyde-free and non-toxic gas release when exposed to fire. Mat made of DU RAG LASS ™ 8802 from Johns Manville, which is a bonded acrylic, wet-laid polyester fiberglass mixture, failed to perform its function satisfactorily in the ceiling tile due to excessive flammability and excessive bending at ambient temperatures. The present invention solves these problems and satisfies the need for a mat suitable for making the ceiling tile forming the subject of the aforementioned US Patent Application Published.

[0005] The present invention includes a method of making a formaldehyde-free fibrous non-woven mat from glass fibers. This method involves dispersing glass fibers having preferably a fiber diameter of on average 13 +/- 1.5 to 13 +/- 3 microns to obtain an aqueous dispersion, draining a large amount of water from the dispersion through a movable permeable shaping tape to form a wet fibrous web. The wet web is saturated with an aqueous resin binder and excess binder is removed in a conventional manner to obtain a wet web with the desired binder content. An aqueous binder is a mixture consisting of water and a resin formed from a homopolymer or copolymer of polyacrylic acid and polyalcohol. The wet web is then heated to remove water and to at least partially cure the resin in the binder to form a bonded resinous fibrous nonwoven mat.

441544 352 Bl [0006] A preferred binder is called TSET® and is available from Rohm & Hass of Phiiadelphia, Pennsylvania. The binder content may vary and may constitute up to about 35 wt. ready-made dry mat and down to about 10% by weight, with content ranging between about 15-25% by weight is preferred, and 20 +/- 3 wt. is the most advantageous. Mats made by the method described above are also included as part of the present invention. An alternative source of similar resin is Acronal® 2348 from BASF.

[0007] It has been found that using a combination of glass fibers with a diameter of about 13 +/- 3 microns, preferably 13 +/- 2 microns, and most preferably 13 +/- 1.5 microns, bonded with a binder formed from a homopolymer and a copolymer of polyacrylic acid and polyalcohol, a fibrous non-woven mat with high tensile strength, adequate smoothness and unexpectedly high fire resistance is obtained, given the amount of oxygen in the binder. The mats of the present invention pass the flame test method # 701 of the National Fire Protection Association (NFPA). Taber rigidity of such mats is preferably above 40, more preferably above about 50, and most preferably above about 55. The air permeability of the mats is preferably between about 14.1584 m³/ min / 0.0929 m² and 22.3635 m³/ min / 0.0929 m² (from · 500 to about 800 cubic feet per minute per square foot). The term "substantially phenol-free, formaldehyde-free and urea-free" as used herein means that the content of phenolic formaldehyde and urea formaldehyde and any formaldehyde compound is low enough that the mat passes the NFPA flammability test.

[0008] The mats of the invention, or the binder used to bond the mat together, may also contain a small but effective amount of one or more of fillers, pigments, biocide, fungicide and hydrophobic agent, of which there are many known chemical compounds and commercially available products, either on the entire mat or focused on one or both surfaces. For example, the mat may contain effective amounts of fine particles of limestone, glass, clay, coloring pigments, biocide, fungicide, fire protection or mixtures thereof. Preferably, the mats of the present invention have very low or zero cellulose fiber content, usually present only as impurities from other components, [0009] The mat of the invention can be used as an exposed surface on ceiling panels and as a cladding or substrate for other products requiring good strength, good fire resistance and formaldehyde free. Preferably, about 65 to 90 percent by weight of such a mat are fibers and about 10 to about 35 percent of its weight is a binder.

[0010] The glass fibers preferably have a length of about 1.91 cm (0.75 inches) and a fiber diameter of about 13 +/- 3 microns, preferably being E-type glass fibers carrying a chemical adhesive, as is well known. Fiber products preferably used in the present invention are 1.91 cm (0.75 inch) Wet Chop K117 and K137 fibers available from Johns Manville Corporation based in Denver, Colorado, but any type of glass fiber, typically used or suitable for wet laying processes. Any types of stable glass fibers can be used, such as A, C, S, R and E, as well as other types of glass fibers. Preferably, the glass fibers have an average fiber diameter in the range of between about 10 and about 16 microns (13 +/- 3 microns). Preferably, the fiberglass fiber length is in the range between about 0.635 cm

5 1 544 352 BI (0.25 inches) and about 3.175 cm (1.25 inches), preferably between 1.02 cm (0.40 inches) and 3.05 cm (1.2 inches), more preferably between about 1 , 27 cm (0.5 inch) and about 2.54 cm (1 inch), and most preferably about 1.778 cm (0.7 inch) +/- 0.381 cm (0.15 inch).

[0011] The fibers are bonded together by means of an aqueous binder composition applied by means of a curtain coater, by dipping and extruding, roller coating or other known saturation method, and the resultant binder coated, saturated wet web lying on a supporting mesh or the screen is passed through one or more suction boxes to remove enough binder to achieve the desired binder content in the mat. The weight level of binder content of the mats of the invention may be in the range of between about 10 and about 35 percent of the finished dry mat, preferably between about 15 and about 25 percent, and most preferably between about 20 +/- 4 and about 30 percent. The binder composition is heat curable, i.e. the binder composition is a thermosetting composition.

[0012] The binder composition includes a polyacrylic acid homopolymer or copolymer. Preferably, the average molecular weight of the polyacrylic acid polymer is less than 10,000, more preferably less than 5,000, most preferably about 3,000 or less, and preferably about 2,000. The use of a low molecular weight polyacrylic acid polymer in a low pH binder composition may result in a final product which exhibits excellent structural reconstruction and rigidity features. The binder formulation may also include at least one additional polycarboxylic polymer, such as, for example, the polycarboxylic polymer disclosed in US Patent No. 6,331,350, the content of which is incorporated herein by reference in its entirety.

[0013] The binder composition also includes a polyol containing at least two hydroxyl groups. This polyol is preferably sufficiently volatile that it can remain substantially available for reaction with the polyacid in the composition during its heating and curing. The polyol may be a chemical compound with a molecular weight of less than about 1000 carrying at least two hydroxyl groups, such as, for example, ethylene glycol, glycerol, pentaerythritol, trimethylolpropane, sorbitol, sucrose, glucose, resorcinol, catechol, pyrogallol, glycolated ureas, 1,4 -cyclohexanediol, diethanolamine, triethanolamine and certain reactive polyols, such as, for example, hydroxyalkylamides, such as, for example, adipine bis [N, Ndi (hydroxyethyl)] amide, which may be prepared according to US Patent Nos. 6,331,350 and 4,076,917, the contents of which are herein incorporated by reference. The polyol may be an addition polymer containing at least two hydroxyl groups, such as, for example, polyvinyl alcohol, partially hydrolyzed vinyl acetate and homopolymers or copolymers of hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate and the like. Most preferably, the polyol is triethanolamine (TEA).

[0014] The ratio of the number of carboxyl equivalents, anhydride or their polyacid salt to the number of hydroxyl equivalents in the polyol may be from about 1 / 0.01 to about 1/3. Preferably, there is an excess of carboxyl equivalents, anhydride, or a polyacid salt thereof relative to the hydroxyl equivalents in the polyol of from about 1 / 0.4 to about 1/1, more preferably from about 1 / 0.6 to about 1 / 0.8, and most preferably from about 1 / 0.65 to about 1 / 0.75. A low ratio, for example 0.7: 1, is advantageous in combination with a low molecular weight poi carboxy polymer and a low pH binder.

[0015] The binder composition may also include a catalyst. Preferably, the catalyst is a phosphorus-containing accelerator, which may be a chemical compound with a lower molecular weight

ΕΡ 1 544 352 Bl than about 1000. For example, the catalyst may include alkali metal polyphosphate, alkali metal dihydrogen phosphate, polyphosphoric acid, alkylphosphinic acid and mixtures thereof.

[0016] Furthermore, or optionally, the catalyst may comprise an oligomer or polymer carrying phosphorus-containing groups, such as, for example, addition polymers of acrylic and / or maleic acids formed in the presence of sodium hypophosphite, addition polymers prepared from ethylenically unsaturated monomers in the presence of chain transfer agents and phosphoric acid salts, addition polymers containing acid functional monomer residues, such as, for example, copolymerized phosphoethyl methacrylate and similar phosphonic acid esters, and copolymerized and vinylized sulfonic acid monomers and their salts, as well as mixtures thereof.

[0017] The catalyst may be used in an amount of from 1% to about 40% by weight based on the combined weight of the polyacrylic acid polymer and polyol. Preferably, the catalyst is used in an amount of from about 2.5% to about 10% by weight based on the combined weight of the polyacrylic acid polymer and polyol.

[0018] The binder formulation may also contain processing ingredients such as, for example, emulsifiers, pigments, fillers, anti-migration agents, hardeners, co-agents, wetting agents, biocides, plasticizers, organosilicon compounds, anti-foaming agents, dyes, waxes and antioxidants. The binder composition can be prepared by mixing the polyacrylic acid polymer and polyol together. Such mixing may be carried out by known mixing techniques.

[0019] Preferably, the pH of the binder composition is low, for example about 3 or less, preferably about 2.5 or less, and most preferably about 2 or less. The pH of the binder can be adjusted by adding a suitable acid, such as sulfuric acid. Such a low pH of the binder can provide processing benefits, while also providing a product that exhibits excellent restoration and rigidity properties. Examples of processing advantages include reducing the time and cure temperature. Reducing the curing temperature may result in a reduction in the amount of energy needed to cure the binder, and thus may allow, if necessary, the use of more water in the binder to achieve processing benefits.

[0020] To increase the fire resistance of the ceiling panel, flame retardant material may be used. The flame retardant material can be incorporated into the ceiling panel by, for example, mixing it into a water binder. Any flame retardant material that is suitable for use in a fibrous mat may be used, including, for example, organic phosphonate. Such organic phosphonate is available from Rhodia, based in Cranburry, New Jersey, under the trade name Antibiaze NT, [0021] Preferably, a dilute aqueous suspension of glass fibers can be formed and deposited on an inclined mobile screen forming a conduit to dehydrate the suspension and form a wet fibrous non-woven mat. For example, a Hydroformer available from VoithSuizer based in Appleton, Wisconsin aibo Deitaformer available from Valmet / Sandy Hill based in Glenn Faiis, New York may be used. Other similar machines for wet mats can also be used. [0022] After the wet, uncured web has been formed, it is preferably transferred to a second mobile screen through the binder application station, where the aqueous binder described above is applied to the mat. The binder may be applied to the structure in any suitable manner, including, for example, by air or airless spraying, padding, saturation, roller coating,

EP 1 544 352 B1 curtain coating, beater deposition, coagulation or application by dipping and extrusion. The use of a curtain coater is preferred.

[0023] If there is excess binder, it is removed to obtain the desired level of content in the mat. The web is formed and the binder content level is controlled so as to obtain such binder content in the final dry mat as defined above and to obtain a dried mat having a grammage preferably ranging between about 453.59 g / 9.29 m² (1 pound / 100 square feet) a about 1360.78 g / 9.29 m² (3 pounds / 100 square feet), preferably from about 907.19 g / 9.29 m² (2 pounds / 100 square feet) to about 1247.38 g / 9.29 m² (2.75 pounds / 100 square feet), such as about 1,133.98 g (2.5 pounds) +/- 90.72 g / 9.29 m² (0.2 pounds / 100 square feet). The wet mat is then preferably transferred to a moving oven belt which will rub the wet mat through a drying and curing oven, such as, for example, a blow oven, air float oven or air flow oven. Before curing, the wet mat can optionally be slightly compressed if necessary to give the finished product a predetermined thickness and surface finish.

[0024] In the oven, the binder coated web can be heated to dry / cure to form a dry mat bonded with a cured binder. For example, heated air can be passed through the mat to remove water and cure the binder. For example, the heat treatment may take place at a temperature of about 204.44 ° C (400 ° F) or higher, but preferably the mat is at or near the temperature of the hot air for only a few seconds downstream of the oven. The duration of the heat treatment may be any suitable period of time, such as, for example, from about 3 seconds to 5 minutes or more, but it is usually less than 3 minutes, preferably less than 2 minutes, and most preferably less than 1 minute. Considering the present disclosure, it is within the scope of average specialization to change the curing conditions to optimize or modify the mat so that it has the desired properties.

[0025] Drying and curing can be carried out in two or more different stages. For example, the binder formulation may first be heated at a sufficient temperature and for a sufficient period of time to substantially dry the composition, but not substantially cure, and then heat it a second time at a higher temperature and / or for a longer period of time to cure. This action, called B grading, can be used to obtain an adhesive-treated non-woven mat, for example in the form of a roll, which can be cured at a later stage, shaping or forming it or not, to a particular shape, simultaneously with the curing process.

[0026] The following examples are provided for illustrative purposes and are not intended to limit the scope of the present invention in any way.

[0027] The mats of the present invention also have surprisingly high fire resistance, considering the oxygen content of the binder used in these mats. These mats pass the NFPA flammability test method # 701.

[0028] By modifying the above method in the drying / curing step, a mat with other characteristics can be obtained. This modification is to reduce the temperature in the furnace so that the binder in the mat is cured only to the state of "B". This can be done by heating the mat in the oven to only about 121.11 ° C (250 ° F). The residence time at such a lower maximum temperature can be

ΕΡ 1 544 352 Bl is different, but usually around 30 seconds or less. Mats made with this modification can be thermoformed to the desired shape or pleated, and then heated to complete curing of the binder. The mat will then keep the desired shape. Such molded shapes can have many applications, for example as intermediates for SRIM and laminating processes, pleated filters and many other applications.

[0029] The above mats of the invention may also be coated in-line or off-line as disclosed in US Patent No. 6,291,011 to provide facing mats with the desired pattern. Coating can be carried out before applying the mat to the ceiling panel, or after making it part of the ceiling panel, or a hydrophyte coating can be applied to selected areas of the mat before applying the mat to the ceiling panel, and the final coating can be applied after the cladding has been applied to the ceiling panel.

[0030] Although the invention has been described with preferred embodiments, it should be understood that changes and modifications may be made thereto, as will be apparent to those skilled in the art. For the sole purpose of illustrating the variations included in the present invention, carbon black, titanium (IV) oxide, limestone or kaolin clay particles if a white mat is desired, or a coloring pigment if a color mat is desired to affect the color. Some of the particularly effective whitening agents are NovaCote ™, a pigmented white primer available from Georgia-Pacific based in Atlanta, Georgia, SUPER SEATONE® Titanium White available from Noveon based in Cincinnati, Ohio, ROPAOUE® polymer latexes for paper coating available from Rohm and Haas and Polyplate ™ P, which is a stratified kaolin clay available, from JM Huber Corporation based in Macon, Georgia. In addition, flame retardants such as organic phosphates may be included in the aqueous binder formulation, exemplified by ANTI-BLAZE ™ NT from Rhodia based in Cranburry, New Jersey and other functional or bulking additives as mentioned above. Such changes and modifications should be considered as falling within the scope of the reservations annexed to this document.

EXAMPLE 1 [0031] The fibers were dispersed in conventional sieve water in a known manner to obtain a slurry in which E-type glass fibers 2.54 cm long (Τ ') have an average fiber diameter of about 16 microns. The slurry was traditionally formed of a wet web with Voith Hydroformer®. Then, the wet web was saturated with a traditional modified urea-formaldehyde resin binder composition using a curtain coating machine, and the excess water binder was removed to obtain a binder content in the finished mat of about 25%, based on the weight of the finished dry mat. The adhesive coated mat was then heat treated at a peak temperature of about 204.44 ° C (400 ° F) to dry the mat and cure the binder. This mat had a basis weight of about 907.19 g / 9.29 m² (2 pounds / 100 square feet) and the following properties:

Thickness - 0.1016 cm (40 mils)

Tensile Strength - Machining Direction (MD - Direction Machine) - 47,627.23 g / 7.62 cm (105 pounds / 3 inches) wide

Cross-Machine Direction (CMD) - 34019.45 g / 7.62 cm (75 lb / 3 inches) wide

ΕΡ 1 544 352 Bl [0032] This mat is a typical mat in the prior art. It is undesirable by the manufacturers of ceiling panels due to the roughness of its surface and the presence of formaldehyde in the binder, which can lead to formaldehyde emissions at high temperature and high humidity.

EXAMPLE 2 [0033] The mat was made in the same manner as in Example 1, except that the modified urea-formaldehyde binder was replaced with the TSET ™ binder, which is an aqueous binder from polyacrylic acid / polyalcohol resin available from Rohm and Haas based in Phiiadelphia, Pennsylvania. The mat had a weight of 1120.37 g / 9.29 m² (2.47 pounds / 100 square feet) and the following other physical characteristics:

Average thickness - 0.1372 cm (54 mils)

MD + CMD tensile strength - 109.7694 kg / 7.62 cm (242 lb / 3 inches) wide Taber stiffness - 72.5 [0034] This mat did not satisfactorily fulfill the function of a facing or pad on a ceiling panel disclosed in a published patent application US No. 20020020142, because the exposed surface was too rough and visually unacceptable.

EXAMPLE 3 [0035] Fibers having an average fiber diameter of about 13 microns and a length of 1.91 cm (0.75 inches), being a commercial fiber product called K137 available from Johns Manville Corporation based in Denver, Colorado, have been dispersed in such traditional sieve water alone used in Example 1 and in the same manner to obtain a suspension. Several wet webs with different weights were formed from the slurry using Voith Hydroformer®. The wet webs were then impregnated with TSET ™ binder, an aqueous binder composition of polyacrylic acid / polyalcohol resin, using a curtain coating machine. Excess binder has been removed in a traditional manner to obtain different binder contents in finished mats, on the order of about 15 +/- about 3% by weight, based on the weight of the finished dry mat. The coated mats were then heat treated at a peak temperature of 170 ° C for 5 to 15 seconds to dry the mat and cure the binder. This mat had a basis weight of about 2.3 to 2.6 pounds / 100 square feet and the following other properties:

Thickness - 0.11194 cm (47 mils) +/- 0.0127 cm (5 mils)

Tensile strength in the machining direction - 40823.34 g / 7.62 cm (90+ pounds / 3 inches) wide Towards the direction of the face - 27215.56 g / 7.62 cm (60+ pounds / 3 inches) wide, MD tensile / CMD stretch squareness ratio, -1.2 to 1.8

Air permeability 14,1584 m³/ min / 0.0929 m² up to 19.8218 m³/ min / 10.0929 m² (500 to 700 cubic feet per minute / square foot) [0036] This mat satisfactorily fulfilled the function of an exposed mat and backing mat in the production of ceiling panels made according to published US Patent Application No. 20020020142.

Used as exposed lining, it hid the ribbons in the panel. This mat also satisfactorily served as a cladding for a traditional glass wool ceiling panel.

EP 1 544 352 B1

EXAMPLE 4 [0037] The same type of fibers as those used in Example 3 were in a known manner dispersed in conventional sieve water to obtain a suspension. A wet web was formed from the slurry with Voith Hydroforni er®. Then, the wet web was impregnated with TSET ™ binder, which is an aqueous binder composition of polyacrylic acid / pofiaikohol, with a curtain coater, and excess water binder was removed in the traditional manner to obtain a binder content in the finished mat of about 16.5%, based on the weight of the finished dry mat. The adhesive coated mat was then heat treated at a peak temperature of about 204.4 ° C (400 ° F) for about 3 seconds to dry the mat and cure the binder. Such a mat had a basis weight of about 1079.55 g / 9.29 m² (2.38 pounds / 100 square feet) and the following characteristics:

Thickness-0.1118 cm (44 mils)

MD + CMD tensile strength - 107.9551 kg / 7.62 cm (238 lb / 3 inches) wide

Taber stiffness - 52

Permeability - 16.6503 m³/ min / 0.0929 m² : and is useful as a facing for other types of traditional ceiling panels.