JPH0221918A - Production of filter element - Google Patents

Abstract

PURPOSE:To obtain a filter element having a long service life by cutting a heat-adhering conjugate fiber into short fibers of a specified length, forming the short fibers into a web by a wet paper making method or an air laying method, heating and winding the web around a winding core. CONSTITUTION:A heat-adhering conjugate fiber such as a high density PE/ crystalline PP fiber is cut into short fibers of 5-20mm length and the short fibers are formed into a web by a wet paper making method or an air laying method. This web is heated to a temp. between the m.ps. of the low m.p. and high m.p. components of the composite fiber, wound around a winding core and cooled. The core is then pulled out and a cylindrical filter element is obtd. Since the short fibers are three-dimensionally arranged at random, the filter element has enhanced bulkiness, reduces pressure drop and prolongs the service life.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a filter element, and more particularly to a method for manufacturing a filter element formed by molding fiber into a thick cylinder.

[Conventional technology]

As a method for manufacturing a thick cylindrical filter element using fibers, a method of heating a carded web containing thermally adhesive fibers and winding it around a core (4! Publication No. 56-4133
9), a method of winding spun yarn or multifilament around a porous core, and a method of winding a nonwoven fabric using a spunbond method or the like around a porous core.

[Problem to be solved by the invention]

In conventional cylindrical filter elements, the fibers are arranged in a plane parallel to the cylindrical surface, so gaps between the fibers also exist parallel to the cylindrical surface, and filtration is mainly performed in the surface layer of the filter. However, the inner layer of the filter only has the effect of reinforcing material, and therefore has a short service life.

[Means to solve the problem]

The inventors of the present invention have conducted intensive research to produce a fibrous filter element that effectively exhibits fJ overaction even in the inner layer and has a long flow life. Mixed fibers containing 30% (weight) or more of The present invention was completed after discovering that the desired objective can be achieved by heating the thermoadhesive conjugate fiber to a temperature higher than the bonding temperature and winding it around a winding core.

The heat-adhesive composite fiber used in the present invention uses a low-melting point thermoplastic resin and a high-melting point thermoplastic resin having a melting point 20°C or more higher than the lower melting point thermoplastic resin, so that the low-melting point thermoplastic resin is present on the surface of the fiber. The fibers are spun in a parallel type or sheath-core type. Examples of such heat-adhesive composite fibers include high-density polyethylene/crystalline polypropylene, ethylene-vinyl acetate copolymer/crystalline polypropylene, and high-density polyethylene/polyester (PET).

In the present invention, it is possible to use only the above thermoadhesive conjugate fiber as the raw material fiber, but a mixture with other fibers containing 30% (weight) or more of thermoplastic fiber can also be used. Other fibers that can be used in combination with the heat bonding fibers may include any fibers that do not melt or deteriorate under the heating conditions for heat bonding described below, such as natural fibers such as cotton, wool, and hemp. A fiber suitable for the object to be filtered may be selected from among fibers, synthetic fibers such as nylon, polyester, and polyolefin.

These fibers are cut into 5 to 20 pieces and then made into a web by a known wet papermaking method or airlay method. If the fiber length is less than 5 mm, the web will have a small porosity and a filter element using this will also have a large filtration resistance, which is not preferable. In addition, if the fiber length exceeds 20 m, most of the fibers in the web will be deposited in parallel on the web surface, and like carded webs, filter elements using this will have a short f-length. Undesirable. Fiber length is 6-20! In a web made of 11 short fibers produced by a wet papermaking method or an airlay method, the fibers that fall down due to free fall fall not only in the direction of the surface of the web, but also in the direction of the surface of the web.
It is also oriented in the direction of the web thickness to form a bulky web. The short fibers having a fiber length of 5 to 20 fibers used in the present invention may be those obtained by washing and removing the oil applied in the spinning process before or after the step of cutting into short fibers.

It is preferable to attach 10 to 60% water to the short fibers from which the oil agent has been removed in order to prevent charging during the air-laying process. Further, it is preferable that the short fibers have crimps, since this further improves the bulkiness of the web.

A web of the above-mentioned short fibers obtained by the air-laying method was heated at a temperature between the melting points of the low melting point component and the high melting point component of the heat-adhesive composite fiber (simply referred to as the bonding temperature) according to the method of Japanese Patent Publication No. 56-A9AO5@T4. A filter element is obtained by heating the filter element to a certain temperature, winding it around a winding core, and removing the winding core after cooling.

〔effect〕

In the filter element of the present invention, the fibers are randomly arranged three-dimensionally not only in the direction parallel to the surface of the filter element but also in the thickness direction, so the pressure loss is small and the filtration life is long. Furthermore, since fibers to which no spinning oil is attached can be used as the raw material fibers, a sanitary and safe filter element can be provided in fields where contamination with foreign matter is averse, such as in the food field and the pharmaceutical field.

[Example] The present invention will be further explained by Examples and Comparative Examples. The physical property evaluation methods used on each side are as follows.

Pressure loss: ] filter elements are installed in the housing, and the water in the aquarium is circulated at a filtration speed of 301/min.
JI filter. Add 20 f of cake (described below) every 5 minutes to this circulating water, and read the pressure difference between the inlet and outlet of the filter element 25 minutes after the start of filtration (total amount of cake added: 100 r) and use it as the pressure loss.

Filtration accuracy: After measuring pressure loss (1 unit of cake added 0Of)
Sampling the f liquid yuooffI/grain & JIL
Filter with a membrane filter that can collect particles of rn or more, measure the particles collected on the membrane filter with a particle size distribution analyzer, and take the maximum particle size as the filtration accuracy.

*Cake: Carborundum" 1200 (average particle size Co-1
゜5~14.5μm) 50% by weight and carborundum 6
00 (average particle size 26-31 μm) 50% by weight mixture.

Example 1-4, Comparative Example 1.2 Composite fibers a to f of each type shown in Table 1 were used, but the oil agent was removed.For example b1d1f, the moisture content was adjusted to 22% by weight, and each was air laid. By law, the basis weight is 3oy7. The web was made into a web of The outer diameter is 6811x
Wind it up while applying pressure with its own weight until it becomes , and after cooling, remove the core to make a product with an inner diameter of 3011 m, an outer diameter of 68 mm, and a length of 250 s.
A filter element with a porosity of 61% was obtained. The performance of these filter elements is shown in Table 2.

From the results shown in Table 2, the filter element according to the present invention (Examples 1-4) has low pressure loss and can withstand long-term use regardless of the presence or absence of oil, but there are cases where the fiber length is too small or too long. It can be seen that in (Comparative Example 112), the increase in pressure loss was large.

Example 5.6 Comparative Example 3 Using the fibers S, d and g (all oil-free products) shown in Table 1, the moisture content was adjusted to 22% by weight and the fabric weight was 28 y/m' by the air-lay method. This web was heated to 145° C. (heating time: 25 seconds) with an infrared heater while being conveyed by a conveyor, and cooled to form a nonwoven fabric.

Using the above nonwoven fabric in place of the web in Example 1, it was heated at 145°C for 2 minutes and 25 seconds with an infrared heater in the same manner as in Example 1, wound up, cooled, and the core was removed. A filter element having a diameter of 68n1, a length of 230m, and a porosity of 57% was obtained. The performance of these filter elements is shown in Table 3.

From the results shown in Table 3, the pressure loss is small when the fiber length is 5 u+ or 10 u+, and when the fiber length is 32 iu
It can be seen that for filters as long as m, even if the filtration accuracy is the same, the pressure loss is large and the filtration life is short.

Table 1: Heat-adhesive composite fibers S/C: Sheath/Core S/S: Parallel HDPE: High density polyethylene/ PP; Polypropylene PET: Polyester for textiles PETl: Polyester for low melting point fiber Table 2 Filter element evaluation Table 3

Claims (3)

[Claims] (1) Short fibers with a fiber length of 5 to 20 mm made of heat-adhesive conjugate fibers or mixed fibers containing 30% (weight) or more of heat-adhesive conjugate fibers are made into a web by a wet paper-making method or an air-lay method. A method for manufacturing a filter element, which comprises heating the web to the bonding temperature of the thermoadhesive conjugate fiber and winding it around a winding core, cooling it, and then removing the winding core. (2) A short fiber web produced by wet papermaking or air-laying is heated in advance to the bonding temperature of heat-adhesive composite fibers to form a non-woven fabric, and this non-woven fabric is heated to the bonding temperature of heat-adhesive composite fibers and wound around a winding core. A method for producing a filter element, which comprises cooling the filter element after cooling and removing the winding core. (3) The method for manufacturing a filter element according to claim 1 or 2, wherein short fibers are used as short fibers after cleaning and removing an oil agent applied in a process such as spinning or drawing.