Plexifilament-like sheet

Abstract

This product provides a protective wrap that improves energy efficiency and provides protection against air intrusion and moisture buildup within buildings. [Solution] 0.002~0.2(m 3 / m 2 A sheet having a plexifilamentous structure with a standardized fragile permeability of .min @ 50gsm and a standardized water head of 150-250 cm @ 50gsm.

Description

[Technical Field]

[0001] The present invention relates to flash-spun plexifilament sheets or fabrics suitable for home wraps, protective clothing, and other end uses where the sheets or fabrics must exhibit both good barrier properties and low breathability. [Background technology]

[0002] House wrap is used to wrap the exterior of a house or other building during its construction, more specifically, after the installation of the plasterboard and before the installation of the side walls / exterior cladding.

[0003] House wraps generally include a barrier layer that provides a moisture barrier against water or humidity from the outside, and also allows water vapor to pass through from the inside of the house. In this way, the passage of liquid water and air (e.g., rain and wind) into the building is restricted, thereby preventing water damage to insulation and structural members and minimizing air movement within the walls. At the same time, water vapor entering the walls from the inside of the building can escape without condensing within the walls and potentially damaging the insulation and structural members. Typical house wrap barrier materials include spunbonded high-density polyethylene fibers sold by EIDu Pont de Nemours and Company, Wilmington, DE under the trade name "DuPont® Tyvek® HomeWrap®", nonwoven barrier materials sold by EIDu Pont de Nemours and Company, Wilmington, DE under the trade name "DuPont® Tyvek® CommercialWrap®", high-density, orthogonal-laminated microperforated polyethylene sheet material sold by Raven Industries, Inc., Sioux Falls, SD under the trade name "Rufco-wrap", and cross-woven microperforated polyolefin sheet material sold by Amoco Foam Products Company, Atlanta, GA, and Fabrene Inc., Mississauga, Ontario, Canada, under the trade names "Amowrap Housewrap" and "Air-Gard® Housewrap", respectively. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] House wraps require low frazil permeability and, furthermore, high head. Therefore, there is a need to provide a protective wrap that improves energy efficiency and protection against air infiltration and moisture generation within a building while meeting newly implemented industry-wide energy and building standards. There is also a need to use a protective wrap that meets or exceeds newly implemented code requirements for existing frameworks or openings and / or does not increase the building wall cross-section.

Means for Solving the Problem

[0005] The present invention relates to a sheet having a standardized frazil permeability of 0.002 to 0.2 m 2 , ,

[0010] , 2 ,

[0011] , , / m 2 .min@50 grams per square meter (gsm) and a standardized head of 150 to 250 cm@50 gsm.

[0006] A further embodiment of the present invention has a BET surface area of at least 9 m 2 / g.

[0007] In yet another embodiment, the sheet has a standardized frazil permeability of 0.09 m 3 / m 2 .min@50 gsm or less. Also, the sheet may have a standardized frazil permeability of 0.0075 m 3 / m 2 .min@50 gsm or more.

[0008] In yet another embodiment, the sheet has a standardized head of 165 to 208 cm@50 gsm.

[0009] In yet another embodiment, the sheet has a BET surface area of 9 to 25 m 2 / g, or further a BET surface area of 9 to 20 m 2 / g.

[0010] Also, the sheet may have a basis weight of 30 grams per square meter or more.

[0011] The present invention further provides that at least one sheet has a standardized fragility air permeability of 0.002 to 0.2 m 3 / m 2 .min @ 50 gsm, I. a standardized head of 150 to 250 cm @ 50 gsm, and II. a basis weight of 30 gsm or more The present invention relates to a multi-layer structure including two or more sheets which are sheets including a plexifilamentous structure having the above properties.

[0012] A further embodiment of the multi-layer structure of the present invention has a BET surface area of at least 9 m 2 / g.

Brief Description of Drawings

[0013] [Figure 1] A schematic cross-sectional view, not to scale, of a spinning cell showing a method for producing a flash-spun plexifilamentous sheet is shown.

Embodiments for Carrying Out the Invention

[0014] The applicant specifically incorporates the entire contents of all cited documents in this disclosure. Further, when a quantity, concentration, or other value or parameter is given as either a range, a preferred range, or a list of a preferred value on the higher side and a preferred value on the lower side, this is to be understood as specifically disclosing all ranges formed from any pair of any range upper limit or preferred value and any range lower limit or preferred value, regardless of whether the ranges are separately disclosed. When a numerical range is recited herein, unless otherwise stated, the range includes its endpoints and all integers and fractions within the range. It is not intended to limit the scope of the present invention to the specific values recited when defining the range.

[0015] As used herein, the term “polymer” generally encompasses, but is not limited to, homopolymers, copolymers (e.g., block, graft, random, and alternating copolymers), terpolymers, etc., as well as blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” encompasses all possible geometric configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic, and random symmetry.

[0016] As used herein, the term "polyethylene" is intended to include not only homopolymers of ethylene but also copolymers in which at least 85% of the repeating units are ethylene units, such as copolymers of ethylene and alpha-olefins.

[0017] As used herein, the terms “nonwoven fabric,” “nonwoven sheet,” or “nonwoven web” mean a structure of single fibers or threads arranged in an irregular manner to form a planar material without a discernible pattern, as seen in knitted fabrics.

[0018] As used herein, “longitudinal direction” refers to the lengthwise direction of the sheet in the plane, i.e., the direction in which the sheet is manufactured. “Transverse direction” refers to the direction in the plane of the sheet that is perpendicular to the longitudinal direction.

[0019] As used herein, the term “plexifilamentous” refers to a three-dimensional, integrated network structure of multiple thin, ribbon-like, film fibril elements having irregular lengths and median fibril widths of less than approximately 25 micrometers. In a plexifilamentous structure, the film fibril elements are generally aligned coaxially with the axis of the structure and are joined and separated discontinuously at irregular intervals at various locations throughout the length, width, and thickness of the structure to form a continuous three-dimensional network structure.

[0020] The term "spinning fluid" refers to the entire composition spun using the spinning apparatus described herein. The spinning fluid contains a polymer and a spinning agent.

[0021] The term "spinning agent" refers to a processing medium or mixture of mediums used to initially dissolve a polymer and form a spinning fluid.

[0022] In this specification, "consisting essentially of" means that the item described in the claim contains a dominant component, but may also contain other items added to improve or enhance the functional performance of the item described in the claim. For example, an item consisting essentially of polyethylene may also contain fillers, antioxidants, and other additives that improve its performance or function.

[0023] Test method In the description, examples, and claims, various reported characteristics and properties were verified using the following test methods. ASTM refers to the American Society for Testing and Materials, and TAPPI refers to the Technical Association of the Pulp and Paper Industry.

[0024] The BET surface area of ​​plexifilamentous film-fibril web products is another measure of the degree and fineness of fibrilization in flash-spun products. The surface area is measured by the BET nitrogen absorption method described in S. Brunauer, PHEmmett and E. Teller, J. Am. Chem. Soc., V. 60 pp. 309-319 (1938), m 2 It is recorded as / g. BET surface area is measured using the Quantachrome model NOVA 3000e.

[0025] The base weight was measured according to ASTM D-3776 (the contents of which are incorporated herein by reference), g / m 2 Alternatively, it is recorded in gsm units. The base weights recorded for each of the following examples are based on the average of at least 12 measurements performed on the sample.

[0026] Gurley-Hill (or simply "Gurley") porosity is a measure of the permeability of a sheet material to a gaseous material. Specifically, it measures how long it takes for a large volume of gas to pass through a region of the material where a particular pressure gradient exists. Gurley-Hill porosity is measured using a Lorentzen & Wettre Model 121D Densometer according to TAPPI T-460 OM-88. This test measures the time required for 100 cubic centimeters of air to pass through a 28.7 mm diameter sample (with an area of ​​1 square inch) under a pressure of approximately 1.21 kPa (4.9 inches) of water. The results are expressed in seconds, often referred to as Gurley seconds.

[0027] Fragile air permeability is a measure of the air permeability of porous materials, ft 3 / min / ft 2 It is recorded in units of ft. Fragile permeability is measured according to ASTM D737-04. It measures the volume of airflow through the material at a differential pressure of 0.5-inch water column (equal to 124.5 Pa). An orifice is placed in the vacuum apparatus to restrict the airflow through the sample to a measurable amount. The size of the orifice depends on the porosity of the material. Also called Fragile porosity, Fragile permeability is measured in ft. 3 / (ft 2 The measurements were taken using a Sherman W. Frazier Co. dual manometer in units of calibration orifice (min), and it is recorded here in mins. 3 / (m 2It was converted to min). The Fragile permeability is stated here as standardized to a base weight of 50 grams / square meter (gsm). When only the Gurley porosity was measured for the sample, the Fragile permeability was calculated according to the following formula. Fragile (m 3 / m 2 min) × Gurley porosity (seconds) = 0.945

[0028] To facilitate comparison of the Fragile permeability of sheets with different base weights, it is convenient to standardize the Fragile permeability for sheets with a base weight of 50 grams / square meter. The standardized Fragile permeability for a base weight of 50 grams / square meter is determined by the following relationship:

number

[0029] Hydrostatic head (or hydrostatic head) is a measure of a sheet's resistance to permeation by liquid water under static load. A 7-inch x 7-inch (17.78 cm x 17.78 cm) sample is placed on an SDL 18 Shirley hydrostatic head tester (manufactured by Shirley Developments Limited, Stockport, England). Water is pumped at a rate of 60 + / - 3 cm / min towards one face of a 102.6 cm profile of the sample, supported by a 30-mesh scrim with wires approximately 0.28 mm in diameter, until three areas of the sample are permeated with water. The hydrostatic pressure is measured in inches, converted to SI units, and expressed as hydrostatic head in centimeters. The test generally follows ASTM D583 (November 1976 publication).

[0030] The hydrohead is described herein as being standardized to a base weight of 50 grams / square meter according to the following formula.

number

[0031] Embodiments of the present invention This invention relates to 0.002 to 0.2 m 3 / m 2 The objective is to create a sheet containing plexifilamentous structures having a standardized Fragile permeability of .min @ 50gsm and a standardized water head of 150-250 cm @ 50gsm for a base weight of 50 grams / square meter. The term "@ 50gsm" refers to the standardization procedure shown above, in which any base weight measurement is standardized to 50gsm.

[0032] In a further embodiment, the sheet is essentially made of polyethylene.

[0033] In yet another embodiment, the BET surface area of ​​the sheet is at least 9 m² 2 It is / g.

[0034] In a further embodiment, the sheet is 0.09 m 3 / (m 2 It has a standardized Fragile breathability of 50gsm or less per minute. Also, the sheet is 0.0075m 3 / m 2 It may have a standardized Fragile air permeability of 50gsm or more per minute.

[0035] In yet another embodiment, the sheet has a standardized head of 165-208 cm at 50 gsm.

[0036] In yet another embodiment, the sheet is 9-25m 2 BET surface area per gram, or further 9-20 m² 2 It has a BET surface area of ​​ / g.

[0037] Furthermore, the sheet may have a basic weight of 30 grams / square meter or more.

[0038] In further embodiments, flash-spun plexifilament fiber strands of any of the embodiments described herein may be solidified into a sheet structure. This sheet structure may then be optionally bonded together by heat or mechanical means.

[0039] The present invention further includes at least one sheet, 1.0.002~0.2m 3 / m 2 Standardized Fragile air permeability of .min@50gsm, II. Standardized hydrostatic head of 150-250 cm @ 50 gsm, and III. Basic weight of 30 grams / square meter (gsm) or more The objective is to create a multi-layer structure comprising two or more sheets, which are polyethylene sheets containing plexifilamentous structures having [a specific characteristic].

[0040] A further embodiment of the multi-layer structure of the present invention is at least 9m 2 Includes a plexifilamentous sheet having a BET surface area of ​​1 / g.

[0041] A method for producing flash-spun plexifilamentous sheets, specifically Tyvek® spunbonded olefin sheet materials, was first described in U.S. Patent No. 3,081,519 to Blades et al. (granted to DuPont). U.S. Patent No. 3,081,519 describes a method for producing plexifilamentous film-fibril strands by spinning a solution of a polymer in a liquid spinneret that is below the standard boiling point of the liquid spinneret and not a solvent to the polymer, at temperatures above the standard boiling point of the liquid spinneret and above the autogenous pressure, to a range of lower temperatures and substantially lower pressures. Plexifilamentous film-fibril strands are best obtained using the method disclosed by Blades et al. when the pressure of the polymer and spinneret solution is slightly reduced in a letdown chamber immediately before flash spinning.

[0042] A typical flash spinning apparatus selected for describing the present invention is similar to the flash spinning apparatus disclosed in U.S. Patent No. 3,860,369 to Brethauer et al. (incorporated herein by reference). Apparatus and methods for flash spinning spinnable polymers are fully described in U.S. Patent No. 3,860,369 and are shown in Figure 1. The flash spinning method typically takes place in a chamber 10, sometimes referred to as a spinning cell, having a spinneret removal hole 11 and an opening 12 for removing the nonwoven sheet material produced in the method. A spinning fluid containing a mixture of polymer and spinneret is supplied to a spinning orifice 14 through a pressurized supply conduit 13. The spinning fluid passes from the supply conduit 13 to the chamber 16 through a chamber opening 15. In certain spinning applications, the chamber 16 may function as a pressure-reducing chamber, where a pressure reduction causes phase separation of the spinning fluid, as disclosed in U.S. Patent No. 3,227,794 to Anderson et al. A pressure sensor 22 may be provided to monitor the pressure inside the chamber 16.

[0043] The spinning fluid in chamber 16 then passes through the spinning orifice 14. It is believed that the pressurized polymer and spinning agent passing from chamber 16 to the spinning orifice generates an extensional flow near the inlet of the orifice, which helps to align the polymer. As the polymer and spinning agent flow out of the orifice, the spinning agent rapidly expands as a gas, leaving behind a fibrillated plexifilamentous film-fibril. The gas exits chamber 10 through the pore 11. Preferably, the gaseous spinning agent is concentrated for reuse in the spinning fluid.

[0044] Polymer strands 20 released from the spinning orifice 14 are conventionally guided toward a rotating deflector baffle 26. The rotating baffle 26 spreads the strands 20 toward a more planar structure 24, which the baffle alternately guides to the left and right. As the spread fiber strands descend from the baffle, they become electrostatically charged, holding them in a spread-out, open configuration until they reach the moving belt 32. The fiber strands 24 accumulate on the belt 32 to form a sheet 34. The belt is grounded to help ensure proper fixation of the charged fiber strands 24 on the belt. The fiber sheet 34 may be fed toward a roller 31, thereby compressing the sheet into a lightly solidified sheet 35 formed of a plexifila-like film-fibril network aligned in an overlapping, multi-directional configuration. The sheet 35 exits the spinning chamber 10 through an outlet 12 and is then collected toward a sheet recovery roll 29.

[0045] A "heat-solidified" or "heat-bonded" sheet is a sheet manufactured by the heat-solidification of the web of the present invention. Some examples of heat bonding methods include gas bonding, steam entanglement, ultrasonic bonding, stretch bonding, high-temperature calendering, high-temperature roll embossing, and high-temperature surface bonding.

[0046] To obtain a rigid bonded surface, thermal surface bonding can be performed by the method described in U.S. Patent No. 3,532,589 to David. In this method, the plexifilamentous sheet is then passed over a heated drum-cooling drum-heating drum-cooling drum to thermally bond both sides of the material. The heated drum is maintained at a temperature that results in partial melting of the plexifilamentous structure, including the bonding of the sheet. The cooling drum is intended to reduce the temperature to a value that prevents the sheet from shrinking or deforming when unrestrained. During the bonding process, the sheet is slightly compressed by a flexible belt, resulting in controlled shrinkage.

[0047] Alternatively, a plexifilament sheet may be bonded to one or two sides of the sheet by bonding it with an embossing roll and a rubber-coated backup roll. The embossing roll may be smooth or may have different patterns, not limited to those shown in the following documents, namely, dot patterns (U.S. Patent No. 3,478,141, U.S. Patent No. 6,610,390, U.S. Patent Application Publication 2004 / 241399A1), rib patterns (U.S. Patent Application Publication 2003 / 0032355A1), random patterns (U.S. Patent No. 7,744,989), or different patterns (U.S. Patent No. 5,964,742). The sheet may pass through one or more parts of the embossing roll and the rubber-coated backup roll. Furthermore, the sheet may be in contact with a preheating roll or a cooling roll before and after the pair of embossing rolls and backup rolls, as described in U.S. Patent No. 5,972,147. Finally, the material may be softened by a bonding process, for example, by a button-breaking device as described in U.S. Patent No. 3,427,376 by Dempsey. [Examples]

[0048] The spinning fluid was prepared according to U.S. Patent No. 3,860,369 and the method described above, flash-spinned, and formed into a solidified sheet. The polymer concentrations reported in the examples are calculated as weight percentages of the polymer based on the total weight of the spinning fluid, where the total weight of the spinning fluid includes the weights of the polymer and the spinning agent.

[0049] Unless otherwise specified, the plexifilamentous webs and sheets produced in this embodiment were flash-spun using a spinning agent consisting of 81 wt percent dichloromethane and 19 wt percent 2,3-dihydrodecafluoropentane. Comparative examples were produced using a spinning agent containing n-pentane. The sheets of the present invention are at least 15 cm long. 3 The fibers were obtained by a flash spinning method performed from an upstream pressure reduction chamber and a discharge pressure of 75 bar (gauge minimum), resulting in fibers of 300-400 denier.

[0050] The polymers used in all the examples had melt indexes of 2.35 g / 10 min (measured according to EN ISO 1133 at 190°C and a 5 kg load) and 24.5 g / 10 min (measured according to EN ISO 1133 at 190°C and a 21.6 kg load), and 0.96 g / cm³ (measured according to EN ISO 1183). 3 The polymer used in the comparative example was high-density polyethylene with a density of 0.96 g / 10 min (measured according to ASTM D1238 at 190°C and a 2.16 kg load) and a melt index of 34.4 g / 10 min (measured according to ASTM D1238 at 190°C and a 21.6 kg load).

[0051] Table 1 lists the spinning conditions for the examples and comparative examples.

[0052] [Table 1]

[0053] Table 2 describes the properties of the obtained flash-spun plexifilament sheets. Comparative Examples 7-9 describe the standardized Fragile permeability and standardized water head @ 50 gsm for further basic weight values. BET surface area was not measured (nm).

[0054] [Table 2]

[0055] None of the comparative examples achieved the head performance of the embodiment of the present invention, which exhibits a unique combination of performance with respect to the selected comparison criteria in Table 2.

Claims

1. 0.002~0.2m 3 / m 2 A sheet comprising plexifilamentous structures having a standardized Fragile permeability of min @ 50 gsm and a standardized water head of 150–250 cm @ 50 gsm.

2. The sheet according to claim 1, which is essentially made of polyethylene.

3. The plexifilamentous structure is at least 9 m 2 The sheet according to claim 1, having a BET surface area of ​​1 / g.

4. The plexifilamentous structure is 0.09 m 3 / m 2 The sheet according to claim 1, having a standardized Fragile air permeability of 50 gsm or less per minute.

5. The plexifilamentous structure is 0.0075 m 3 / m 2 The sheet according to claim 1, having a Fragile air permeability of 50 gsm or more per minute.

6. The sheet according to claim 1, wherein the plexifilamentous structure has a standardized water head of 165 to 208 centimeters at 50 gsm.

7. The plexifilamentous structure is 9 to 25 m 2 The sheet according to claim 6, having a BET surface area of ​​ / gm.

8. The pre - plexiform structure is 9 to 20 m 2 / gm of BET surface area, the sheet according to claim 6.

9. The sheet according to claim 1, wherein the plexifilamentous structure has a basic weight of 30 grams / square meter or more.

10. A multi-layer structure comprising two or more sheets, at least one of which is the sheet described in claim 1.

11. The plexifilamentous structure is at least 9 m 2 The multi-layer structure according to claim 10, having a BET surface area of ​​1 / g.

12. A heat-solidified sheet manufactured from the sheet described in claim 1.

13. A multi-layer structure comprising two or more sheets, at least one of which is the sheet described in claim 12.

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