The present invention relates to a thermally insulating batt that can be used in a thermally insulated composite suitable for use in an exterior portion, such as a wall or roof, of residential and commercial buildings.
A batt suitable for thermal insulation preferably contains staple fibers that are strong, small in diameter and pack together in an open or loose manner. Undrawn melt spun staple fibers have large diameters. Drawn melt spun staple fibers have smaller diameters and are strong but are difficult to open or to spread the fibers apart during carding resulting in non-uniformity issues. Melt blown fibers have small diameters but are weak and tend to pack together too tightly resulting in sub-optimum thermal insulation.
It would be desirable to have a thermally insulating batt that contains staple fibers that are strong, small in diameter and pack together in an open or loose manner.
In a first embodiment, the present invention relates to a thermally insulating batt comprising: (i) 10 to 70% by weight of first staple fibers that comprise staple flash spun plexifilamentary fibers, wherein the staple flash spun plexifilamentary fibers comprise a polyolefin polymer; (ii) 10 to 70% by weight of the total batt of second staple fibers, wherein the staple fibers comprise a polyester polymer, polyolefin polymer, polyamide polymer or viscose rayon; and (iii) 5 to 30% by weight binding agent, wherein the binding agent comprises at least one polymeric component with a melting point below the melting point of the staple flash spun plexifilamentary fiber melting point and the staple fiber melting point.
In another embodiment, the present invention relates to a thermally insulating composite comprising: (a) a thermally insulating batt comprising: (i) 10 to 70% by weight of first staple fibers that comprise staple flash spun plexifilamentary fibers, wherein the staple flash spun plexifilamentary fibers comprise a polyolefin polymer (ii) 10 to 70% by weight of the total batt of second staple fibers, wherein the staple fibers comprise a polyester polymer, polyolefin polymer, polyamide polymer or viscose rayon and (iii) 5 to 30% by weight binding agent, wherein the binding agent comprises at least one polymeric component with a melting point below the melting point of the staple flash spun plexifilamentary fiber melting point and the staple fiber melting point; and (b) a moisture vapor permeable, substantially liquid impermeable, substantially air impermeable substrate on one surface of the thermally insulating batt. The substrate has a Gurley Porosity between 250 and 5990 sec/100 cubic centimeters /inch2 a moisture vapor transmission rate (MVTR) of between 250 and 1870 grams/meter2/24hours and a hydrostatic head of between 200 and 400 centimeters of water.
In still another embodiment, the present invention relates to an exterior portion of a building comprising the aforementioned thermally insulating batt or thermally insulating composite.
The term "batt" as used herein means single or multiple sheets of fibers used in the production of a nonwoven.
The term "nonwoven" or "web" as used herein means a structure of individual fibers or threads that are positioned in a random manner to form a planar material without an identifiable pattern, as in a knitted fabric.
The term "plexifilamentary fibers" as used herein means a three-dimensional integral network or web of a multitude of thin, ribbon-like, film-fibril elements of random length and with a mean film thickness of less than about 4 microns and a median fibril width of less than about 25 microns. The average film-fibril cross sectional area if mathematically converted to a circular area would yield an effective diameter between about 1 micron and 25 microns. In plexifilamentary structures, the film-fibril elements intermittently unite and separate at irregular intervals in various places throughout the length, width and thickness of the structure to form a continuous three-dimensional network.
The term "polymer" as used herein, generally includes but is not limited to, homopolymers, copolymers (such as for example, block, graft, random and alternating copolymers), terpolymers, etc., and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term "polymer" shall include all possible geometrical configurations of the material. These configurations include, but are not limited to isotactic, syndiotactic, and random symmetries.
The term "polyolefin" as used herein, is intended to mean any of a series of largely saturated polymeric hydrocarbons composed only of carbon and hydrogen. Typical polyolefins include, but are not limited to, polyethylene, polypropylene, polymethylpentene, and various combinations of the monomers ethylene, propylene, and methylpentene.
The term "polyethylene" as used herein is intended to encompass not only homopolymers of ethylene, but also copolymers wherein at least 85% of the recurring units are ethylene units such as copolymers of ethylene and alpha-olefins. Preferred polyethylenes include low-density polyethylene, linear low-density polyethylene, and linear high-density polyethylene. A preferred linear high-density polyethylene has an upper limit melting range of about 130°C to 140°C, a density in the range of about 0.941 to 0.980 gram per cubic centimeter, and a melt index (as defined by ASTM D-1238-57T Condition E) of between 0.1 and 100, and preferably less than 4.
The term "polypropylene" as used herein is intended to embrace not only homopolymers of propylene but also copolymers where at least 85% of the recurring units are propylene units. Preferred polypropylene polymers include isotactic polypropylene and syndiotactic polypropylene.
The present invention is directed to a thermally insulating batt comprising: (i) 10 to 70% by weight of first staple fibers that comprise staple flash spun plexifilamentary fibers, wherein the staple flash spun plexifilamentary fibers comprise a polyolefin polymer, (ii) 10 to 70% by weight of second staple fibers, wherein the staple fibers comprise a polyester polymer, polyolefin polymer, polyamide polymer or viscose rayon and (iii) 5 to 30% by weight binding agent, wherein the binding agent comprises at least one polymeric component with a melting point below the melting point of the staple flash spun plexifilamentary fiber melting point and the staple fiber melting point. Described herein are also staple melt spun fibrillated fibers, which can be included in the first staple fibers. Preferably, the present invention is directed to a thermally insulating batt comprising: (i) 25 to 60% by weight of first staple fibers that comprise staple flash spun plexifilamentary fibers and -if present- staple melt spun fibrillated fibers; (ii) 25 to 60% by weight of second staple fibers; and (iii) 15 to 25% by weight binding agent.
The staple flash spun plexifilamentary fibers of the thermally insulating batt can be made according to the flash spinning process described in
The staple melt spun fibrillated fibers can be made according to any general process known to those skilled in the art. For example, melt spun fibrillated fibers can be made by melt spinning bicomponent polymer fibers with fiber cross sections such as round pie shape with pie wedges of alternating polymers or islands in the sea with the islands made from one polymer and the sea made from another polymer. The melt spun bicomponent polymer fibers can then be cut to a length of at least about 2.5 cm to make staple melt spun unfibrillated fibers. The staple melt spun unfibrillated fibers are later converted into staple melt spun fibrillated fibers via a carding process. The staple melt spun fibrillated fibers can be made of polyolefin polymer, polyester polymer, polyamide polymer or mixtures thereof.
The staple fibers can be made according to any general process known to those skilled in the art. The staple fibers preferably are stiff to provide some support and loft to the batt. The staple fibers comprise a polyester polymer, preferably polyethylene terephthalate, polyolefin polymer, polyamide polymer or viscose rayon.
The binding agent comprises at least one polymeric component with a melting point below the melting point of the staple flash spun plexifilamentary fiber melting point and the staple fiber melting point. The binding agent can take the form of staple binder fibers or small particles. The staple binder fibers can comprise multiple polymeric components with (a) at least one polymeric component with a melting point below the melting point of the staple flash spun plexifilamentary fiber melting point or the staple melt spun fibrillated fiber melting point and the staple fiber melting point and occupying at least a portion of a surface of the staple binder fibers and (b) at least one polymeric component with a melting point above that of the melting point of the at least one polymeric component with a melting point below the melting point of the staple flash spun plexifilamentary fiber melting point or the staple melt spun fibrillated fiber melting point and the staple fiber melting point. A common example of this type of staple binder fiber is a bicomponent fiber wherein a low melting point polymer on at least a portion of the surface of the fiber melts and adheres to another fiber while a high melting point polymer does not melt keeping a portion of the fiber intact.
The staple flash spun plexifilamentary fibers and -if present- staple melt spun unfibrillated fibers, staple fibers and a binding agent are mixed and fed to a carding machine to form a carded web. The carding process splits the larger diameter staple flash spun plexifilamentary fibers into microfibers or splits the staple melt spun unfibrillated fibers into staple melt spun fibrillated fibers by breaking the fibers apart along the interfacial boundary between the different polymers. The carded web is fed, for example, onto a conveyor belt or apron to a crosslapper, where lapper aprons crosslap the carded web by traversing a carrier means such as an intermediate apron in a reciprocating motion, to produce a thermally insulating batt of fibers that are oriented primarily in the transverse direction. The number of laps used to form the thermally insulating batt depends upon variables such as the
desired weight of the base layer, and the final weight of the thermally insulating batt. The thermally insulating batt is then, optionally, fed into an oven at a temperature that will activate the binding agent to adhere fibers together and impart strength to the batt.
The staple flash spun plexifilamentary fibers or staple melt spun unfibrillated fibers, staple fibers and a binding agent may optionally be mixed and pre-opened in a card opener (For example a Dell'orco Villani co/1500 machine.) The blend may then be fed through a chute feeder (such as disclosed in
In one embodiment the thermally insulating batt of the invention has a thermal conductivity/basis weight ratio, at 0.0318 m thickness, of less than 7.5 x 10-5 (W/m•K)/(g/m2), preferably less than 6.0 x 10-5 (W/m•K)/(g/m2).
Between 5 to 50% of the second staple fibers can have a weight of less than 3.0 denier per filament.
In another embodiment the present invention is directed to a thermally insulating composite comprising: (a) a thermally insulating batt comprising: (i) 10 to 70% by weight of first staple fibers that comprise staple flash spun plexifilamentary fibers, wherein the staple flash spun plexifilamentary fibers comprise a polyolefin polymer, (ii) 10 to 70% by weight of second staple fibers, wherein the staple fibers comprise a polyester polymer, polyolefin polymer, polyamide polymer or viscose rayon, and (iii) 5 to 30% by weight binding agent, wherein the binding agent comprises at least one polymeric component with a melting point below the melting point of the staple flash spun plexifilamentary fiber melting point and the staple fiber melting point; and (b) a moisture vapor permeable, substantially liquid impermeable, substantially air impermeable substrate on one surface of the thermally insulating batt. The substrate has a Gurley Porosity between 250 and 5990 sec/100 cubic centimeters/inch2 a moisture vapor transmission rate (MVTR) of between 250 and 1870 grams/meter2/24hours and a hydrostatic head of between 200 and 400 centimeters of water.
The moisture vapor permeable, substantially liquid impermeable, substantially air impermeable substrate can be a nonwoven comprising flash spun plexifilamentary fibers. Flash spun plexifilamentary fibers can be made for example according to the process described in
5 to 50% of the staple fibers can weigh less than 3.0 denier per filament.
One surface of the thermally insulating batt is adhered to the moisture vapor permeable, substantially liquid impermeable, substantially air impermeable substrate via any method known to one of ordinary skill in the art. For example, the thermally insulating batt and the moisture vapor permeable, substantially liquid impermeable, substantially air impermeable substrate can be adhered together by a spray-on adhesive.
Another embodiment of the present invention is an exterior portion, such as a wall or roof, of a building comprising the thermally insulating batt or the thermally insulating composite of the invention.
In the non-limiting Examples that follow, the following test methods were employed to determine various reported characteristics and properties. ASTM refers to the American Society of Testing Materials.
Basis Weight was determined according to ASTM D-3776 and reported in g/m2.
Thickness was obtained from the thermal resistance test and is reported in meters.
Surface Area of the plexifilamentary fiber was measured by the BET nitrogen absorption method of
Crush Value was determined using the following procedure. Three plexifilamentary fiber strands of different sizes were manually pulled from an unbonded plexifilamentary web. The three samples weighed about one, two and three grams. The reported crush values are the averages of the values measured on the three samples. Each sample plexifilamentary strand was formed into a ball shape with minimum application of pressure to avoid crushing and the sample was then weighed in grams. A crush tester comprised of an acrylic sample holder and crusher was used to measure the crush value of each sample. The sample holder comprised a cylindrical section having an inner diameter of 2.22 inches (5.64 cm) and an outer diameter of 2.72 inches (6.91 cm). The center of the cylinder was located at the geometric center of a square base measuring 6.00 inches by 6.00 inches (15.24 cm by 15.24 cm). The crusher comprised a cylindrical plunger rod (diameter = 0.75 inches (1.91 cm)) having a first disk-shaped face (the disk having a thickness of 0.25 inches (0.64 cm) and a diameter of 2.20 inches (5.59 cm)) located at one end of the plunger rod and a second disk on the plunger rod spaced back 1.50 inches (3.81 cm) from the first disk. The second disk also had a thickness of 0.25 inches (0.64 cm) and a diameter of 2.20 inches (5.59 cm). The disks were sized slightly smaller than the inner diameter of the cylindrical sample holder in order to allow air to escape from the sample during crushing. The plexifilamentary samples were placed, one at a time, in the sample holder and a thin piece of paper having a diameter of about 2.2 inches (5.59 cm) was placed on top of the plexifilamentary sample prior to crushing. The plunger rod was then inserted into the cylindrical sample holder such that the first disk-shaped face contacted the piece of paper. The second disk served to maintain the axis of the plunger rod in alignment with the axis of the cylindrical sample holder. Each plexifilamentary strand sample was crushed by placing a 2 lb (0.91 kg) weight on the plunger rod. The crush height (mm) was obtained by measuring the height of the sample from the bottom of the cylindrical sample holder to the bottom of the crusher. The plunger and weight were removed from the sample after approximately 2 minutes, leaving the piece of paper in place to facilitate measurement of the restored height of the sample. Each sample was allowed to recover approximately 2 minutes and the restored height (mm) of the sample was obtained by measuring the height of the paper from the center of each of the four sides of the sample holder and averaging the measurements. The crush value (mm/g) is calculated by subtracting the average crush height from the average restored height and dividing by the average of the weights of the samples. The crush value is a measure of how much the sample recovers its original size after being crushed, with higher values indicating greater recovery of original sample height.
Thermal Conductivity was determined according to ASTM C-518. The test sample or specimen is located between two flat plates in a heat flow meter, and the plates are maintained at known, but different, temperatures. As heat flows through the test sample from the hot side to the cold side, a heat flux transducer measures the amount of heat transferred and thermocouples measure the temperatures of each of the two plates (i.e., of the so-called hot and cold plates). Fourier heat flow relation is used to calculate thermal conductivity. The thermal conductivity is reported in W/m•K.
Thermal Resistance is calculated using measured thermal conductivity and the thickness of the sample. Thermal resistance was reported in units of m2•K/W.
Thermal Conductivity/Basis Weight ratio was calculated by dividing the thermal conductivity by the basis weight and was reported in units of (W/m•K)/(g/m2).
Moisture Vapor Transmission Rate (MVTR) was determined by ASTM E398-83 (the "LYSSY" method) and is based on a pressure gradient of 85% relative humidity ("wet space") vs. 15% relative humidity ("dry space"). The LYSSY method measures the moisture diffusion rate for just a few minutes and under a constant humidity delta, which measured value, is then extrapolated over a 24 hour period. MVTR is reported in g/m2/24 hr
Hydrostatic Head (HH) was determined by ATTCC 127 and is a measure of the resistance of the sheet to penetration by liquid water under a static load. A 17.78 cm x 17.78 cm sample is mounted in a SDL 18 Shirley Hydrostatic Head Tester (manufactured by Shirley Developments Limited, Stockport, England). Water is pumped against one side of a 102.6 cm section of the sample at a rate of 60+/-3 cm/min until three areas of the sample are penetrated by the water. The hydrostatic pressure is measured in inches, converted to SI units and reported in centimeters of water. The test generally follows ASTM D 583 (withdrawn from publication November, 1976).
Gurley-Hill Porosity was measured in accordance with TAPPI T-460 using a Lorentzen & Wettre Model 121D Densometer. This test measures the time of which 100 cubic centimeters of air is pushed through a one-inch diameter sample under a pressure of approximately 12.4 cm of water. The result is expressed in seconds and is usually referred to as Gurley Seconds.
Hereinafter the present invention will be described in more detail in the following examples and the resultant data presented in the Table.
Example 1 represents a thermally insulating batt of the present invention. The staple flash spun plexifilamentary fibers of the thermally insulating batt were made by using the flash spinning technology as disclosed in
Fifty(50)% of the staple flash spun plexifilamentary fibers were then mixed with 35% staple polyester fibers with a cut length of about 3 cm and 15% of a low melting bicomponent sheath/core binder fiber of a polyester copolymer as the sheath and polyethylene terephthalate as the core. The staple mixture was fed to a carding machine. The carding process split the larger diameter plexifilamentary fibers into microfibers and further produces a fibrous structure or carded web. The carded web was fed onto a conveyor belt or apron to a crosslapper, where lapper aprons crosslapped the carded web by traversing a carrier means such as an intermediate apron in a reciprocating motion for 13 laps, to produce a thermally insulating batt of fibers that are oriented primarily in the transverse direction. The resulting thermally insulating batt had a basis weight of 534 g/m2, a thickness of 0.0318 m, a thermal conductivity of 0.036 W/m•K, a thermal resistance of 0.883 m2•K/W and a thermal conductivity / basis weight ratio of 6.7 x 10-5 (W/m•K)/(g/m2).
Example 2 represents a thermally insulating composite of the present invention. The thermally insulating batt from Example 1 was used to prepare the thermally insulating composite. The moisture vapor permeable, substantially liquid impermeable, substantially air impermeable substrate used was Tyvek® Homewrap™ (available from the DuPont Company, Wilmington, DE). The substrate was moisture vapor permeable with a moisture vapor transmission rate of 370 g/m2/24 hr, substantially liquid impermeable with a hydrostatic head of 250 cm, and substantially air impermeable with a Gurley Hill porosity of 1200 s. One surface of the thermally insulating batt was adhered to the Tyvek® Homewrap™ by a spray-on adhesive of 77 Multi-purpose (available from 3M, St. Paul, MN).
Example 3 represents a thermally insulating batt of the present invention. The staple melt spun fibrillated fibers (T-502 Fiber Innovation Technology, Johnson City, Tn.) were 6 DPF and 0.006 m long. 50% of the staple melt spun fibrillated fibers were then mixed with 35% staple polyester fibers with a cut length of about 3 cm and 15% of a low melting bicomponent sheath/core binder fiber of a polyester copolymer as the sheath and polyethylene terephthalate as the core. The staple mixture was fed to a carding machine. The carding process split the larger diameter melt spun fibrillated fibers into microfibers and further produced a fibrous structure or carded web. The carded web was fed onto a conveyor belt or apron to a crosslapper, where lapper aprons crosslapped the carded web by traversing a carrier means such as an intermediate apron in a reciprocating motion for 13 laps, to produce a thermally insulating batt of fibers that are oriented primarily in the transverse direction. The resulting thermally insulating batt had a basis weight of 646 g/m2, a thickness of 0.0318 m, a thermal conductivity of 0.034 W/m•K, thermal resistance of 0.935 m2•K/W and a thermal conductivity/basis weight ratio of 5.3 x 10-5 (W/m•K)/(g/m2).
85% of the staple polyester fibers with a cut length of about 3 cm were mixed with 15% of a low melting bicomponent sheath/core binder fiber of a polyester copolymer as the sheath and polyethylene terephthalate as the core. The staple mixture was fed to a carding machine. The carded web was fed onto a conveyor belt or apron to a crosslapper, where lapper aprons crosslapped the carded web by traversing a carrier means such as an intermediate apron in a reciprocating motion for 13 laps, to produce a thermally insulating batt of fibers that are oriented primarily in the transverse direction. The resulting thermally insulating batt had a basis weight of 528 g/m2, a thickness of 0.0318 m, a thermal conductivity of 0.043 W/m•Ka thermal resistance of 0.739 m2•K/W and a thermal conductivity/basis weight ratio of 8.1 x 10-5 (W m•K)/(g/m2).
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.