Air filter material

Abstract

An air filter material has spun bond nonwoven fabric and melt blown nonwoven fabric. The spun bond nonwoven fabric includes conjugate polyester continuous filaments having a Y4-like cross sectional shape. The Y-4 shape of the continuous filament is composed of plural nearly V-shape portions formed from low melting point polyester, joined by a nearly + shape portion formed from high melting point polyester. The continuous filaments are heat-bonded with each other by the low melting point polyester. The spun bond nonwoven fabric is bonded with the melt blown nonwoven fabric with a powder type or spider web type hot melt adhesive agent.

Claims

1. A process for producing an air filter comprising: applying a powder type or spider web type hot melt adhesive agent in solid form on ultrafine fiber nonwoven fabric formed from ultrafine fibers having a fiber diameter of 1 to 5 micrometers; and placing polyester nonwoven fabric on the powder type or spider web type hot melt adhesive agent, the polyester nonwoven fabric formed from polyester continuous filaments having a fineness of not less than 10 dtex, a shape of the polyester continuous filament in a cross section has four parts, each part having: a first portion with a first end and a second end, and two convex portions that each extend from the first end of the first portion, the convex portions extending in different directions such that a concavity is formed between the convex portions, wherein the second ends of the four parts are interconnected, and the four parts are connected together such that a concavity is formed between each adjacent pair of the parts, and the polyester continuous filaments are heat-bonded with each other; and bonding the ultrafine fiber nonwoven fabric and the polyester nonwoven fabric by the powder type or spider web type hot melt adhesive agent, with the polyester nonwoven fabric being on the hot melt adhesive agent, wherein the powder type or spider web type hot melt adhesive agent has a melting point lower than the melting points of the ultrafine fiber and the polyester continuous filament.

2. The process according to claim 1, wherein the polyester continuous filament is a conjugate polyester continuous filament in which the convex portions are formed from low melting point polyester and the first portions are formed from high melting point polyester.

3. The process according to claim 1, wherein the conjugate polyester continuous filaments are bonded to each other by heat bonding of the low melting point polyester.

Description

EXAMPLES

(1) Next, the present invention will be explained in detail based on working examples of the present invention. Physical properties in the examples are determined as follow:

(2) (1) Melting point ( C.):

(3) A melting point was determined to be a temperature indicating a maximum value of a melting endothermic peak measured at a rising temperature speed of 20 C./min using a differential scanning calorimeter DSC-7 manufactured by Perkin Elmer Co., Ltd.

(4) (2) Relative viscosity [rel]:

(5) A sample of 0.5 g was dissolved in 100 ml of a mixture solution of phenol and ethane tetrachloride in an equal amount ratio and a relative viscosity was determined by a conventional method at a temperature of 20 C.

(6) (3) Air permeability (cc/m.sup.2/sec):

(7) An air permeability was determined by a Frazier Type Air Permeability Tester, according to JIS L 1096-1979 Testing methods for woven and knitted fabrics, keeping at 1.27 cm of an inclined type barometer.

Production Example A of Polyester Nonwoven Fabric

(8) A low melting point polyester was prepared by copolymerizing 92 mol % of terephthalic acid and 8 mol % of isophthalic acid, as a dicarboxylic acid, with 100 mol % of ethylene glycol, as a diol. The low melting point polyester had a melting point of 230 C. and a relative viscosity [rel] of 1.44. Four % by mass of titanium oxide as a nucleating agent was added into the low melting point polyester, which was employed as the low melting point polyester component.

(9) A high melting point polyester was prepared by copolymerizing 100 mol % of terephthalic acid as a dicarboxylic acid with 100 mol % of ethylene glycol as a diol. The high melting point polyester had a melting point of 260 C. and a relative viscosity [rel] of 1.38, which was employed as the high melting point polyester component.

(10) The low melting point polyester component was provided and melt spun in V parts shown FIG. 3 of the nozzle orifice and the high melting point polyester component was provided in a + part shown FIG. 3. The melt spinning was performed by providing the two types of polyester at the rate of 8.33 g/min. per nozzle orifice and at 285 C. A mass ratio of the low melting point polyester component/the high melting point polyester component was 1/2.

(11) The continuous filaments spun from the nozzle orifices were passed in an air sucker device located 2 m below the nozzle orifices and drawn into 17 dtex in fineness to form conjugate continuous filaments which had a cross section as shown in FIG. 1. The conjugate continuous filaments were opened by an opening device, and accumulated on a moving net conveyor to obtain a continuous filamentous web. The filamentous web was passed between an embossing roll and a flat roll as a heat embossing device to obtain a polyester nonwoven fabric A. The embossing roll had convex tips which had the area of 0.7 mm.sup.2, and a total area of the convex parts was occupied 15 percent of the entire surface of the embossing roll. The embossing conditions were a surface temperature of 213 C. and a linear pressure of 300 N/cm. The polyester nonwoven fabric A had a weight of 40 g/m.sup.2.

Production Example B of Polyester Nonwoven Fabric B

(12) A polyester nonwoven fabric was obtained as generally described in Production Example A, with the exception that the weight of the final polyester nonwoven fabric A was changed to 70 g/m.sup.2.

Production Example of Ultrafine Fiber Nonwoven Fabric

(13) Polypropylene having a melting point of 162 C. was introduced into a melt blown die from which heated air was blown, to form ultrafine fibers having a diameter of about 3 micrometers. The ultrafine fibers were accumulated on a moving conveyor to obtain an ultrafine fiber nonwoven fabric having a weight of 20 g/m.sup.2.

Example 1

(14) The ultrafine fiber nonwoven fabric was spray-coated with powder type hot melt adhesive agent (powder formed from low density polyethylene having a melting point of about 100 C.) in a spray-coating amount of 5 g/m.sup.2, and then laminated thereon with the polyester nonwoven fabric A to obtain a layered laminate. The laminate was put on a lower conveyor combined with an upper conveyor in a heat treatment device, both conveyors being covered with Teflon coating on the surfaces, and heated with moving. A temperature of the space between the upper conveyor and the lower conveyor was controlled to 100 C. and the space was gradually narrowed from an entrance to an exit to set a width of the space of 1 mm at the exit.

(15) After the heat treatment device, the layered laminate was cooled to obtain an integrated air filter material composed of the ultrafine fiber nonwoven fabric and the polyester nonwoven fabric. The air filter material had an air permeability of 26.5 cc/m.sup.2/sec. Since the ultrafine fiber nonwoven fabric was firmly integrated with the polyester nonwoven fabric A, the ultrafine fiber nonwoven fabric was damaged when it was peeled off from the polyester nonwoven fabric.

Example 2

(16) An air filter material was obtained as generally described in Example 1, with the exception that the polyester nonwoven fabric A was changed to the polyester nonwoven fabric B. The resulting air filter material had an air permeability of 25.7 cc/m.sup.2/sec. The ultrafine fiber nonwoven fabric was firmly integrated with the polyester nonwoven fabric B.

Example 3

(17) An air filter material was obtained as generally described in Example 1, with the exception that a spray-coating amount of the powder type hot melt adhesive agent (powder formed from low density polyethylene having a melting point of about 100 C.) was changed to 10 g/m.sup.2. The resulting air filter material had an air permeability of 25.3 cc/m.sup.2/sec. The ultrafine fiber nonwoven fabric was firmly integrated with the polyester nonwoven fabric A.

Example 4

(18) An air filter material was obtained as generally described in Example 2, with the exception that a spray-coating amount of the powder type hot melt adhesive agent (powder formed from low density polyethylene having a melting point of about 100 C.) was changed to 10 g/m.sup.2. The resulting air filter material had an air permeability of 25.0 cc/m.sup.2/sec. The ultrafine fiber nonwoven fabric was firmly integrated with the polyester nonwoven fabric B.

Example 5

(19) An air filter material was obtained as generally described in Example 1, with the exception that the powder type hot melt adhesive agent (powder formed from low density polyethylene having a melting point of about 100 C.) was changed to a spider web type hot melt adhesive agent (available from Kurehatech Ltd. as Item Stock Number LNS0020, based on copolymerized polyamide, melting point 115 C., coating amount 20 g/m.sup.2). The resulting air filter material had an air permeability of 23.7 cc/m.sup.2/sec. The ultrafine fiber nonwoven fabric was firmly integrated with the polyester nonwoven fabric A.

Example 6

(20) An air filter material was obtained as generally described in Example 2, with the exception that the powder type hot melt adhesive agent (powder formed from low density polyethylene having a melting point of about 100 C.) was changed to a spider web type hot melt adhesive agent (available from Kurehatech Ltd. as Item Stock Number LNS0020, based on copolymerized polyamide, melting point 115 C., coating amount 20 g/m.sup.2). The resulting air filter material had an air permeability of 23.9 cc/m.sup.2/sec. The ultrafine fiber nonwoven fabric was firmly integrated with the polyester nonwoven fabric B.

(21) As is apparent from the above Examples 1 to 6, the ultrafine fiber nonwoven fabric and the polyester nonwoven fabric A or B are laminated and integrated using powder type or spider web type hot melt adhesive agent to obtain an air filter material having excellent air permeability.

BRIEF DESCRIPTION OF DRAWINGS

(22) FIG. 1 is a cross sectional view of a continuous filament used in the invention.

(23) FIG. 2 is one nearly Y part in the nearly Y4 shape which is the cross sectional view of the continuous filament used in the invention.

(24) FIG. 3 is the Y4 figure of the nozzle orifice.

(25) FIG. 4 is one Y part in the Y4 figure of the nozzle orifice.

REFERENCE SIGNS LIST

(26) 1 Bottom end of the nearly Y shape in a cross sectional shape of the continuous filament, 2 Concave portion formed in the nearly Y4 shape, 3 Convex portion formed in the nearly Y4 shape, 4 Small concave portion formed in the nearly Y4 shape, 5 Nearly+shape portion formed in the nearly Y4 shape, 6 Nearly V shape portion formed in the nearly Y4 shape, 7 Bottom end in the Y4 shape being a nozzle orifice when melt spinning, 8 part of the Y shape, 9 parts of the Y shape, 10 V part in the Y shape, 11 + part in the Y shape.