JP2008151980A - Filter material for toner filter, and cassette filter using the filter material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter material suitable as a filter for toner correction capable of satisfying flame retardant standards though a harmless flame retarder is used without deterioration in its filtering performance. <P>SOLUTION: A nonwoven fabric layer 2 on the upstream side composed of an upper layer 3 and an intermediate layer 4 and also having a fiber density gradient is composed of a heat-fusible fiber with a core-sheath structure using a PP (polypropylene) fiber subjected to flame retardant treatment with a phosphorous or nitrogen based flame retarder as a core and PE (polyethylene) as a sheath part. On the other hand, the lower layer 5 as a nonwoven fabric layer on the downstream side is composed of a heat-fusible fiber with a core-sheath structure using a PET fiber as a core and PE as a sheath part. The respective layers 3, 4, 5 are laminated and integrated with the heat fusion of the heat fusible fibers, to form a filter material 1. Further, the whole of the filter material 1 is subjected to electret treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner filter medium for collecting toner contained in exhaust air from an apparatus and a cassette filter using the filter medium in an electrostatic copying printing type copying machine or printer.

As a general-purpose air filter medium, non-woven fabrics subjected to electret treatment have been proposed in Patent Document 1 and Patent Document 2, etc., but for the purpose of collecting toner contained in the exhaust of a copying machine or the like as described above. Therefore, it is necessary to satisfy the flame retardant standard (for example, UL standard) as a required specification of the filter medium, and for that purpose, it is effective to add a small amount of flame retardant (for example, halogen-based one) to the filter medium. It is said that.
Japanese Utility Model Publication No. 58-51929 JP-A-62-83017

  However, the use of halogen-based flame retardants is not always preferred from the viewpoint of quantitative restrictions on harmful substances. Instead, the flame retardant standards must be met without degrading filtration performance and using harmless flame retardants. The production of filter media that can be made is desired.

  The present invention has been made to meet such a demand.

  The invention according to claim 1 is a filter material for a toner filter having at least a two-layer structure for collecting toner used for electrostatic copying printing, wherein the upstream nonwoven fabric layer is a non-halogen flame retardant. In addition, a non-woven fabric layer on the downstream side is made of polyethylene terephthalate (polyethylene terephthalate (PP) fiber having a core-sheath structure in which a flame-retardant polypropylene (PP) fiber is used as a core and a sheath part is made of polyethylene (PE)). PET) is composed of heat-sealable fibers with a core-sheath structure in which the sheath part is polyethylene (PE) and the sheath part is polyethylene (PE), and the upstream and downstream nonwoven fabric layers have heat-sealable heat-sealable fibers. While being laminated and integrated, the whole nonwoven fabric layer is subjected to electret treatment.

  In this case, in order to prolong the life of the filter medium, the upstream portion of the upstream nonwoven fabric layer is formed of thick fibers and a low fiber packing density as described in claims 2 and 3. On the contrary, it is desirable that the downstream portion is formed of fine fibers and has a high fiber packing density, and the upstream nonwoven fabric layer has a fiber density gradient.

Further, as described in claim 4, it is desirable that the total basis weight of the entire filter medium is 100 to 140 g / m ² and the total thickness is 0.8 to 1.2 mm in order to satisfy the flame retardancy standard. This is because if the total basis weight exceeds 145 g / m ² , the amount of non-flame retardant PE increases and the flame retardant standard cannot be satisfied.

In this case, the basis weight of the nonwoven fabric layer on the downstream side is 1/5 to 1/7 of the total basis weight as a result of intensive studies, and numerically, 20 g / m ² is the upper limit. This is because when the basis weight of the PET nonwoven fabric layer is increased, the moldability (including the bondability with the frame) is improved, but the flame retardancy standard cannot be satisfied in the same manner as described above.

  Furthermore, as described in claim 5, the polypropylene (PP) fiber is subjected to flame retardant treatment with harmless phosphorus or nitrogen-based flame retardant.

  The invention according to claim 6 is specified as a cassette filter using the filter medium according to any one of claims 1 to 5, wherein the filter element is formed by folding the filter medium into a filter element, and then the filter element. And a non-woven fabric layer on the downstream side of the filter element is integrally formed with a resin frame by an insert molding method.

  The frame is made of, for example, ABS resin as described in claim 7.

  Therefore, at least the inventions of claims 1 and 7 can satisfy the flame retardant standard as a filter medium or a filter without causing deterioration of filtration performance due to pressure loss or the like and without using harmful substances. Become.

  According to the first and fourth aspects of the present invention, the flame retardant standard as a filter medium or a filter can be satisfied without deteriorating the filtration performance and without using harmful substances. it can. In addition, since the downstream nonwoven fabric layer is formed with heat-fusible fibers with polyethylene terephthalate fibers as the core and the sheath as polyethylene, the rigidity of the filter medium is improved, for example, the workability when pleat folding is good It will be something.

  According to the second and third aspects of the invention, since the upstream nonwoven fabric layer has a fiber density gradient, it is possible to prolong the life of the filter medium without causing early clogging.

  FIG. 1 shows an enlarged cross-sectional view of a filter medium 1 as a more specific embodiment of the present invention.

  As shown in the figure, the filter medium 1 has substantially three layers of an upstream nonwoven fabric layer 2 formed of an upper layer 3 and an intermediate layer 4 and a lower layer 5 as a downstream nonwoven fabric layer so as to have a fiber density gradient. Each layer 3, 4 and 5 is composed of a non-woven fabric of heat-fusible fibers (thermal bond fibers) having a core-sheath structure.

More specifically, as shown in FIG. 2 in addition to FIG. 1, the upper layer 3 is a polypropylene fiber (hereinafter referred to as PP fiber) that has been subjected to a flame retardant treatment with a flame retardant other than a halogen-based flame retardant, such as phosphorus or a nitrogen-based flame retardant. Is a core 6 and a sheath 7 is made of polyethylene (hereinafter referred to as PE) with a heat-sealable fiber having a core-sheath structure. Thickness of the fiber is 3.3 dtex (Show decitex in Figure 1 and dt), basis weight in the range of 30 to 80 g / m ^2, wherein one as 50 g / m ^2. In addition, the weight ratio of the core 6 and the sheath part 7 is 50%: 50%.

Further, the intermediate layer 4 is also composed of heat-fusible fibers having the same core-sheath structure as the upper layer 3. However, thickness of the fiber was 1.7 dtex, weight per unit area in the range of 30~90g / m ^2, wherein one as 70 g / m ^2. In addition, the weight ratio of the core 6 and the sheath part 7 is 50%: 50%.

On the other hand, as shown in FIG. 3 in addition to FIG. 1, the lower layer 5 has a polyethylene terephthalate fiber (hereinafter referred to as PET fiber) that has not been subjected to flame retardant treatment as a core 8 and a sheath portion 9 as polyethylene (hereinafter referred to as PE). The core-sheath structure has a heat-fusible fiber. The thickness of the fiber is 2.2 dtex, and the basis weight is 20 g / m ² . In addition, the weight ratio of the core 8 and the sheath part 9 is 50%: 50%.

Here, if attention is paid only to the filtration performance, the total basis weight as a whole of the filter medium 1 may be 100 g / m ² or more. However, if the total basis weight exceeds 145 g / m ² , the PE fiber having no flame retardancy is used. The amount increases, the flame retardancy decreases and the flame retardance standard is not met. Similarly, when the basis weight of the PET fiber nonwoven fabric layer, which is the lower layer 5, is increased, the moldability (including the bondability with the frame) is improved, but the flame retardance standard cannot be satisfied as described above. . Therefore, after limiting the basis weight of the lower layer 5 to 1/5 to 1/7 of the overall weight of the filter medium, here 20 g / m ² , the total weight of the entire filter medium 1 is in the range of 100 to 140 g / m ² . The basis weight of the upper layer 3 is adjusted in the range of 30 to 80 g / m ² , and the basis weight of the intermediate layer 4 is adjusted in the range of 30 to 90 g / m ² while determining the performance.

  Then, after the upper layer 3 and the intermediate layer 4 and the lower layer 5 are overlapped with each other, they are laminated and integrated by so-called thermal fusion by applying pressure from both sides of the front and back, so that the thickness is 0.8-1. The filter medium 1 is about 2 mm. In addition, since it is only fused at the contact portion between the fibers forming the respective layers 3, 4, 5, there is actually no boundary between the layers 3, 4, 5.

  Furthermore, the filter medium 1 obtained in this way is subjected to a charging process, for example, by corona discharge, so that the entire filter medium 1 is formed into a so-called electret.

  According to such a filter medium 1 of the present embodiment, it is confirmed that a predetermined flame retardance standard can be obtained without using harmful substances, and that the filtration performance is not lowered due to pressure loss or the like. did it. Moreover, the rigidity of the filter medium 1 is improved by providing a PET fiber nonwoven fabric layer as the lower layer 5, and for example, the workability at the time of pleat folding is also improved.

  In addition, the upper layer 3 on the upstream side of the upstream nonwoven fabric layer 2 is formed with thick fibers and a low fiber packing density, while the intermediate layer 4 on the downstream side is formed with thin fibers and a high fiber packing density. Since the upstream nonwoven fabric layer 2 is formed to have a fiber density gradient, the lifetime is not shortened by early clogging, which is advantageous in extending the lifetime.

  4 and 5 show an example of a cassette filter 11 using the filter medium 1 as a filter element 10.

  The cassette filter 11 is obtained by subjecting the filter medium 1 to pleat folding (processing to bend into an accordion pleat shape with a relationship between peaks and valleys) to form a filter element 10 and, for example, a frame made of ABS resin by an insert molding method. It is integrated with the body 12.

  The filter element 10 formed of the filter medium 1 subjected to pleat folding is fixed as an insert to a mold for forming the frame body 12 with comb teeth, and then the ABS resin material is injected to mold the frame body 12 while filtering It is integrated with the element 10. In this case, the adjacent protrusions are positioned by forming the minute protrusions 13 on the inner side of the peak part on the both ends in the longitudinal direction of the peak part or the valley part of the filter element 10, and the adhesion prevention effect between the pleats and the pleats is achieved. On the other hand, the PET fiber nonwoven fabric layer, which is the lower layer 5 of the filter medium 1, is firmly bonded as the contact surface 14 with the frame body 12 at both end surfaces in the longitudinal direction orthogonal to the peaks or valleys.

  That is, the melting point of the ABS resin, which is the material of the frame body 12, is 220 ° C., and the fiber core 8 of the PET fiber nonwoven fabric layer 5 also has a melting point of 260 ° C. Therefore, the PET fiber core 8 melts at the resin temperature. Instead, the ABS resin enters the PET fiber nonwoven fabric layer 5 which is the lower layer 5, and the two are joined.

  By the way, when the PP fiber nonwoven fabric layer side which is the upper layer 3 is used as the joint surface with the frame body 12, the melting point of the core 6 of the PP fiber is 160 ° C. (the melting point of PE in the sheath portion 7 is 130 ° C. is lower). Since it is lower than that of the ABS resin, the PP fiber nonwoven fabric layer as the upper layer 3 is melted at the ABS resin temperature to form a film, and a clear boundary surface is formed between the two, so that bonding cannot be performed.

  The cassette filter 11 obtained in this way is detachably mounted, for example, on the exhaust port of an electrostatic copying printing type copying machine using toner, and is periodically replaced.

The typical expanded sectional view of the filter medium concerning the present invention. The expanded sectional view of the heat-fusible fiber which forms the upper layer 3 of FIG. The expanded sectional view of the heat-fusible fiber which forms the lower layer 5 of FIG. The perspective view which shows an example of the cassette filter which used the filter medium of FIG. 1 as a filter element. The expanded sectional view which follows the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Filter medium 2 ... Upstream nonwoven fabric layer 3 ... Upper layer 4 ... Intermediate layer 5 ... Lower layer (downstream nonwoven fabric layer)
6 ... core 7 ... sheath 8 ... core 9 ... sheath 10 ... filter element 11 ... cassette filter 12 ... frame

Claims (7)

A filter material for toner filter having at least a two-layer structure for collecting toner used for electrostatic copying printing,
The upstream nonwoven fabric layer is composed of a core-sheathed heat-fusible fiber with a polypropylene (PP) fiber treated with a flame retardant other than a halogen-based flame retardant and a sheath part made of polyethylene (PE). While
The downstream nonwoven fabric layer is composed of heat-fusible fibers with a core-sheath structure in which polyethylene terephthalate (PET) fibers are the core and the sheath is polyethylene (PE),
A filter material for a toner filter, wherein the upstream and downstream nonwoven fabric layers are laminated and integrated by thermal fusion of heat-fusible fibers, and the entire nonwoven fabric layer is electretized.   2. The toner filter medium according to claim 1, wherein the upstream nonwoven fabric layer has a fiber density gradient.   3. The toner filter according to claim 2, wherein the upstream portion of the nonwoven fabric layer on the upstream side is formed of thicker fibers and a lower fiber packing density than the downstream portion. Filter media. The toner filter medium according to any one of claims 1 to 3, wherein the total weight of the filter medium is 100 to 140 g / m ² and the total thickness is 0.8 to 1.2 mm.   5. The filter material for toner filter according to claim 1, wherein the polypropylene (PP) fiber is subjected to a flame retardant treatment with a phosphorus or nitrogen flame retardant. A cassette filter using the filter medium according to claim 1,
After filtering the pleats to make a filter element, the resin frame was integrally molded with the downstream nonwoven fabric layer on the outer periphery of the filter element by an insert molding method using the filter element as an insert. Features a cassette filter.   The cassette filter according to claim 6, wherein the frame is formed of an ABS resin.

Images