阅读说明：本技术 一种滤料 (Filter material ) 是由 费传军 张振 郭晓蓓 徐涛 匡新波 尹奕玲 吴涛 于 2021-09-24 设计创作，主要内容包括：本发明公开了一种滤料。所述滤料至少由三层组成,其中上下层由耐高温机织布或非织造布组成,中间层为过滤层,所述的过滤层由96％～99％玻璃微纤维和1％～4％耐高温异形合成纤维复合而成,上下层与中间层通过耐高温胶经热压复合而成。本发明滤料可在150℃液压油温度下长期稳定地使用,具有优异的耐高温性能。其过滤比β-((5μm))不小于75,适用于车辆、飞机等领域的液压系统中。(The invention discloses a filter material. The filter material is composed of at least three layers, wherein the upper layer and the lower layer are composed of high temperature resistant woven fabric or non-woven fabric, the middle layer is a filter layer, the filter layer is formed by compounding 96% -99% of glass microfiber and 1% -4% of high temperature resistant profiled synthetic fiber, and the upper layer and the lower layer are compounded with the middle layer through high temperature resistant glue through hot pressing. The filter material can be stably used for a long time at the temperature of 150 ℃ hydraulic oil, and has excellent high-temperature resistance. Filtration ratio beta thereof (5μm) Not less than 75 percent, and is applicable to hydraulic systems in the fields of vehicles, airplanes and the like.)

1. A filter material is characterized by at least comprising three layers, wherein the upper layer and the lower layer are made of high-temperature-resistant woven fabric or non-woven fabric, the middle layer is a filter layer, the filter layer is formed by compounding 96% -99% of glass microfiber and 1% -4% of high-temperature-resistant profiled synthetic fiber, and the upper layer and the lower layer are compounded with the middle layer through high-temperature-resistant glue through hot pressing.

2. The filter material of claim 1, wherein the upper and lower layers are made of the same or different materials; the material of the high-temperature resistant woven or non-woven fabric is selected from one or more of polytetrafluoroethylene, polyimide, aramid fiber, polysulfonamide, polyphenylene sulfide and polyethylene terephthalate.

3. The filter material according to claim 1, wherein the original weave of the high temperature resistant woven fabric is plain weave, twill weave or satin weave; the non-woven fabric is prepared by adopting a needle punching method, a spun-bonding method or a spunlace method.

4. Filter material according to claim 1,the gram weight of the upper layer and the lower layer is 10-50 g/m²(ii) a The gram weight of the middle layer is 60-100 g/m²(ii) a The gram weight of the filter paper is 80-200 g/m²。

5. The filter material according to claim 1, wherein the high temperature resistant shaped synthetic fibers are shaped synthetic fibers having a high temperature resistance of 150 ℃ or higher; the high-temperature resistant profiled synthetic fiber is one or more than one of trilobal polyimide fiber, elliptical polyimide fiber, waist-shaped polyimide fiber, trilobal polyphenylene sulfide fiber, elliptical polyphenylene sulfide fiber and waist-shaped polyphenylene sulfide fiber.

6. The filter material according to claim 1, wherein the high temperature resistant profiled synthetic fibers have a length of 0.5 to 5mm and a fineness of 0.5 to 3 denier; the length of the glass microfiber is 0.5-5 mm, and the beating degree is 44-59 degrees SCR; the high-temperature-resistant glue is adhesive glue with the characteristic of resisting high temperature of more than 150 ℃, and is selected from organic silica gel, polyurethane resin, phenolic resin or acrylic resin.

7. A method of making a filter material according to any one of claims 1 to 6, comprising the steps of:

step 1, preparing an intermediate layer: pulping the high-temperature resistant profiled synthetic fiber and a dispersant in a pulping tank with an ultrasonic function; pulping the glass microfibers in a sulfuric acid solution, conveying the two types of pulped fibers to a pulp mixing tank, uniformly mixing the two types of fibers, then forming the fibers on a net, drying the fibers, and then rolling the fibers to form the fibers, wherein the production line speed is 20-100 m/min;

step 2, synthesis of filter paper: and hot-pressing and compounding the upper layer and the lower layer with the middle layer to form the filter paper for the hydraulic oil.

8. The method according to claim 7, wherein in step 1, the dispersant is selected from the group consisting of methylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, polyethylene oxide, and polyacrylamide; the addition amount of the dispersing agent is 0.2-2% of the high-temperature resistant profiled synthetic fiber, and preferably 0.3-0.6%; the ultrasonic power for beating the high-temperature-resistant profiled synthetic fibers is 200-1000W, and the frequency is 10-60 kHz; the pulping time is 15-30 min, and the pulping concentration is 0.1-5%.

9. The preparation method according to claim 7, wherein in the step 1, the pH value of the sulfuric acid solution is 1-4, preferably 2-3.5; pulping for 15-30 min, wherein the pulping concentration is 0.1-5%; the middle layer adopts an ultra-low concentration inclined net forming technology, and the net feeding concentration is 0.1-5 per mill, preferably 0.3-0.6 per mill.

10. The preparation method according to claim 7, wherein in the step 2, glue spraying or glue pouring is adopted when the upper layer, the lower layer and the middle layer are compounded; the concentration of the glue solution is 1-10%, preferably 3-7%; the composite pressure is 0.05-0.4 MPa, and the speed is 5-50 m/min.

Technical Field

The invention belongs to the field of filter materials, relates to a filter material, and particularly relates to high-temperature-resistant filter paper for hydraulic oil and a preparation method thereof.

Background

Hydraulic oil filtration is one type of liquid filtration, and the cleanliness of the hydraulic oil filtration is important to the stability of a hydraulic system. The cleaning of hydraulic oil is an important guarantee for the normal operation of the hydraulic transmission system. The medium material for filtering hydraulic oil is usually glass fiber paper, so as to achieve the aims of high precision, low resistance and long service life. The filtration accuracy is generally expressed in terms of the beta ratio of particulate contaminants of a given size (upstream contaminant concentration divided by downstream contaminant concentration in the filtration system), with the greater the beta ratio, the better the filtration. The steady or rising beta ratio during the filtering process of the hydraulic oil means that the downstream important parts can be effectively protected. In the use process of the hydraulic oil filter, glass fibers (particularly glass microfibers) are likely to fall off due to the drag force of oil, the phenomenon of hair falling occurs, secondary pollution is easily caused to the filtered oil, and the gradual breakage of the fiber structure of the filter paper also affects the filtering precision and the service life of the filter, so that the beta ratio is continuously reduced in the filtering process. Spunbond nonwovens are commonly used on the outflow face or sides of fiberglass paper to increase its strength. The spun-bonded non-woven fabric is usually prepared from PE, PP, PET and other materials, the temperature resistance of the spun-bonded non-woven fabric is generally not more than 150 ℃, part of hydraulic systems frequently work, the frequent temperature can reach 150 ℃ or even more than 180 ℃, and the spun-bonded non-woven fabric can be influenced by pressure pulses, so that the common glass fiber paper can not meet the requirements, and the filtering material composed of the metal fiber net can not meet the requirements in general, the filtering precision can not meet the requirements, the dirt receiving capacity is weak, and the service life is short.

CN109183279A discloses a non-woven fabric for being compounded with a polytetrafluoroethylene film, a preparation method thereof and a formed polytetrafluoroethylene composite material. The non-woven fabric comprises a front surface and a back surface, wherein the front surface and the back surface are both made of thermoplastic resin with the melting temperature of 120-300 ℃, and the comprehensive melting temperature of the thermoplastic resin for preparing the front surface is higher than that of the thermoplastic resin for preparing the back surface. In this method, the polytetrafluoroethylene film is present, and thus the filtration accuracy is high, but the dirt-receiving capacity is weak.

CN100485123C discloses a fiber paper made of basalt fiber, aramid fiber and polyphenylene sulfide fiber by wet process. The synthetic fiber paper has the advantages of good mechanical property, good high temperature resistance, acid and alkali resistance, strong ultraviolet resistance, low hygroscopicity, better environment resistance, good insulating property, good high temperature filtering property, radiation resistance, good wave-transmitting property and the like. But the filter paper prepared by the method has lower filtering precision.

Disclosure of Invention

The invention provides a filter material, which at least comprises three layers, wherein the upper layer and the lower layer are made of high-temperature-resistant woven fabric or non-woven fabric, the middle layer is a filter layer, the filter layer is formed by compounding 96% -99% of glass microfiber and 1% -4% of high-temperature-resistant profiled synthetic fiber, and the upper layer and the lower layer are compounded with the middle layer through high-temperature-resistant glue through hot pressing.

In the invention, the high temperature resistance is the temperature resistance of more than 150 ℃.

The upper layer and the lower layer can be made of the same material or different materials. The upper and lower layers mainly play two roles: firstly, the glass microfiber layer plays a supporting role and protects the middle part; secondly, the uniform distribution of the fluid is facilitated and the primary filtration function is played.

The material of the high temperature resistant woven or nonwoven fabric is a synthetic fiber material with a high temperature resistance of more than 150 ℃ common in the art, and includes but is not limited to one or more of Polytetrafluoroethylene (PTFE), Polyimide (PI), aramid, Polysulfonamide (PSA), polyphenylene sulfide (PPS) and polyethylene terephthalate (PET). The original structure of the high-temperature resistant woven fabric is not particularly limited, and plain, twill or satin can be adopted.

The nonwoven fabric of the present invention is prepared by a method commonly used in the art, for example, a needle punching method, a spunbond method, and a spunlace method.

The gram weight of the upper layer and the lower layer is 10-50 g/m²。

The gram weight of the intermediate layer is 60-100 g/m²。

The gram weight of the filter paper is 80-200 g/m²。

The high-temperature resistant profiled synthetic fiber is a profiled synthetic fiber with the characteristic of resisting high temperature of more than 150 ℃ common in the field, and the high-temperature resistant profiled synthetic fiber comprises one or more than one of trilobal Polyimide (PI) fiber, elliptical Polyimide (PI) fiber, waist Polyimide (PI) fiber, trilobal polyphenylene sulfide (PPS) fiber, elliptical polyphenylene sulfide (PPS) fiber and waist polyphenylene sulfide (PPS) fiber.

The length of the high-temperature resistant special-shaped synthetic fiber is 0.5-5 mm, and the fineness of the high-temperature resistant special-shaped synthetic fiber is 0.5-3 denier.

The glass microfiber has the length of 0.5-5 mm and the beating degree of 44-59 degrees in SCR.

The high-temperature-resistant glue is common in the field and has the characteristic of resisting high temperature of more than 150 ℃, and can be organic silica gel, polyurethane resin, phenolic resin or acrylic resin.

The preparation method of the filter material comprises the following steps:

step 1, preparing an intermediate layer: pulping the high-temperature resistant profiled synthetic fiber and a dispersant in a pulping tank with an ultrasonic function; pulping the glass microfibers in a sulfuric acid solution, conveying the two types of pulped fibers to a pulp mixing tank, uniformly mixing the two types of fibers, then forming the fibers on a net, drying the fibers, and then rolling the fibers to form the fibers, wherein the production line speed is 20-100 m/min;

step 2, synthesis of filter paper: and hot-pressing and compounding the upper layer and the lower layer with the middle layer to form the filter paper for the hydraulic oil.

In the preparation method of the filter material, in the step 1, the fibers are easy to flocculate due to low affinity between the synthetic fibers and polar water molecules and small repulsion between the fibers, so that a dispersing agent needs to be added for dispersion. The dispersant used may be Methylcellulose (MC), sodium carboxymethylcellulose (CMC-Na), Hydroxyethylcellulose (HEC), polyethylene oxide (PEO) and Polyacrylamide (PAM). The addition amount of the dispersing agent is 0.2-2% of the high-temperature resistant profiled synthetic fiber, and preferably 0.3-0.6%. The method is more favorable for the dispersion of the synthetic fibers in the ultrasonic environment, and a hydrapulper with an ultrasonic effect is adopted for pulping. The ultrasonic power for beating the high-temperature-resistant profiled synthetic fibers is 200-1000W, and the frequency is 10-60 kHz; pulping for 15-30 min; the pulping concentration is 0.1-5%.

In the preparation method of the filter material, in the step 1, the glass microfiber is pulped in a sulfuric acid solution with the pH value of 1-4, and the pH value is preferably 2-3.5. The beating adopts a high-frequency fluffer, and the main reason is that proper gaps are arranged between movable and static discs of the high-frequency fluffer, and the fibers are only purely dispersed without damaging the fibers. Pulping for 15-30 min; the pulping concentration is 0.1-5%.

In the preparation method of the filter material, in the step 1, the middle layer adopts an ultra-low concentration inclined net forming technology, and the net-feeding concentration is 0.1-5 per mill, preferably 0.3-0.6 per mill.

According to the preparation method of the filter material, in the step 2, glue spraying or glue sprinkling mode is adopted when the upper layer and the lower layer are compounded with the middle layer, preferably the glue spraying mode, so that a reticular binder layer can be generated on the surface of the filter paper, and the air permeability loss rate caused by the binder is greatly reduced; the concentration of the glue solution is controlled to be 1-10%, and preferably 3-7%.

In the preparation method of the filter material, in the step 2, the composite pressure is 0.05-0.4 MPa, and the speed is 5-50 m/min.

The filtering mechanism of the filter paper for the hydraulic oil mainly has two aspects, namely interception and adsorption. The interception means that solid particles in the oil are directly intercepted on the surface of the filter paper or the necking part of a pore channel in the filter paper; adsorption mainly means that solid particles are adsorbed on the fiber surface of the filter paper under the action of the surface force of the fibers.

In the initial stage of filtration, the filter paper does not retain the pollutants, the filtration resistance is generated by the oil flowing through the filter paper, and the pressure difference is called as initial pressure difference. With the injection of the contaminants, the contaminant particles are continuously trapped on the surface and inside of the filter paper, causing the pore structure inside the filter paper to change, and gradually forming a filter cake on the surface of the filter paper, thereby causing the increase of the pressure difference. The air permeability of the filter paper is inversely proportional to the differential pressure, and according to darcy's law, the lower the air permeability, the greater the differential pressure of the filter paper. When the filter paper reaches a limit pressure difference or a termination pressure difference, the service life of the filter paper is terminated, and the filter paper needs to be replaced.

The evaluation of the performance of the filter paper mainly includes absolute filtration accuracy, filtration efficiency (filtration ratio), and contamination holding capacity. The diameter of the largest spherical particle that can pass through the filter is defined as the absolute filtration precision, expressed in μm. The filtration ratio (beta) refers to the number N of pollutant particles with a certain size x (mu m) in the unit volume of oil liquid at the upstream of the filter material_uxThe number of pollutant particles N which are larger than the same size in unit volume of downstream oil_dxThe ratio of (a) to (b). The dirt holding capacity is the weight of the filter material per unit area capable of holding dust particles, in g/m, when the filter material reaches its limit pressure value or end life²And (4) showing.

Pure glass fiber filter paper has high filtration precision but is very fragile. The invention adds the special-shaped synthetic fiber into the glass microfiber. The profiled fiber has large specific surface area, and can increase the interception capability and the adsorption capability in terms of a filtration mechanism. Meanwhile, due to the existence of the special-shaped synthetic fibers, the pollutant carrying capacity and the fatigue performance of the composite fiber can be improved, and the service life of the composite fiber is prolonged. In addition, the synthetic fiber adopted in the invention has higher temperature resistance, so that the high-temperature service performance at 150 ℃ can be ensured. In addition, because the specific gravity of the synthetic fiber is smaller than that of the glass fiber, the synthetic fiber of the intermediate layer filter paper in the invention is distributed in a gradient way when the inclined net is formed, namely, the proportion of the synthetic fiber is lower from top to bottom, and the gradient filtration from fine to fine can be generated.

In conclusion, the filter paper can be stably used for a long time at the temperature of 150 ℃ hydraulic oil, and has excellent high-temperature resistance. Filtration ratio beta thereof_(5μm)Not less than 75, can be used in hydraulic systems in the fields of vehicles, airplanes and the like.

Drawings

Fig. 1 is a schematic structural diagram of the filter material of the present invention, wherein 1 and 5 are high temperature resistant woven or nonwoven fabrics, 2 and 4 are high temperature resistant glue, and 3 is an intermediate layer.

FIG. 2 is a diagram of the morphology of a PPS trilobal fiber.

FIG. 3 is a topographical map of PI trilobal fibers.

FIG. 4 is a morphology chart of PPS round fiber.

Detailed Description

The present invention will be described in further detail with reference to the following examples and the accompanying drawings.

Example 1

Preparation of the intermediate layer: pulping trilobal PI fiber with fineness of 0.5 denier and length of 0.5mm in aqueous solution of Methyl Cellulose (MC) with concentration of 0.3% in a hydrapulper with ultrasonic function, wherein the pulping speed is 2000 rpm, the ultrasonic power is 200W, and the frequency is 10 kHz; pulping for 30 min.

Putting SCR glass microfibers with the beating degree of 59 degrees into a sulfuric acid solution with the pH value of 2.5, and beating in a high-frequency fluffer at the rotating speed of 2000 r/min for 15 min; the pulping concentration is 0.1%.

Conveying the two pulped fibers to a pulp mixing tank, uniformly mixing the two fibers, adding water to adjust the pulp concentration to 0.3 per mill, conveying the pulp to an inclined net for forming, drying and rolling for forming, wherein the production line speed is 100m/min, and the gram weight of a product is 60g/m²。

Synthesizing a filter material: adopts 15g/m of upper and lower layers²The PET spun-bonded non-woven fabric and the middle layer are compounded by acrylic resin glue through hot pressing after glue spraying, the concentration of the glue solution is 3%, the compounding pressure is 0.05MPa, and the speed is 50 m/min. The gram weight of the finally formed filter material for the hydraulic oil is 90g/m²。

The ratio of the PI fibers to the glass microfibers in the intermediate layer is shown in Table 1.

TABLE 1 proportion of PI fibers to glass microfibers

Sample number	PI fiber content (%)	Glass microfiber content (%)
			P-1	20	80
P-2	15	85
			P-3	10	90
P-4	5	95
			P-5	2	98

The properties of the filter media produced are shown in table 2.

TABLE 2 Filter Material Properties

Example 2

Preparation of the intermediate layer: pulping elliptic PPS fiber with fineness of 1.5 denier and length of 5mm in 0.6% of polyethylene oxide (PEO) aqueous solution in a hydrapulper with ultrasonic function, wherein the pulping speed is 1400 rpm, the ultrasonic power is 500W, and the frequency is 50 kHz; pulping for 30 min.

Putting SCR glass microfibers with the beating degree of 54 degrees into a sulfuric acid solution with the pH value of 3.5, and beating in a high-frequency fluffer at the rotating speed of 1400 revolutions per minute for 30 min; the pulping concentration is 0.5 percent.

Conveying the two pulped fibers to a pulp mixing tank, uniformly mixing the two fibers, adding water to adjust the pulp concentration to 0.6 per mill, conveying the pulp to an inclined net for forming, drying and rolling for forming, wherein the production line speed is 20m/min, and the gram weight of a product is 100g/m²。

Synthesizing a filter material: adopts 50g/m of upper and lower layers²The PET spun-bonded non-woven fabric and the middle layer are compounded by hot pressing after being sprayed with phenolic resin glue, the compounding pressure is 0.4MPa, and the speed is 5 m/min. The gram weight of the finally formed filter material for hydraulic oil is 200g/m²。

The ratio of PPS fibers to glass microfibers is shown in Table 3.

TABLE 3 proportioning of PPS fibers and glass microfibers

Sample number	PPS fiber content (%)	Glass microfiber content (%)
			PPS-1	20	80
PPS-2	15	85
			PPS-3	10	90
PPS-4	5	95
			PPS-5	4	98

The properties of the prepared composite filter material are shown in table 4.

TABLE 4 composite Filter Properties

Example 3

Preparation of the intermediate layer: pulping waist-shaped aramid fiber with fineness of 3 deniers and length of 2mm in an aqueous solution of Polyacrylamide (PAM) with concentration of 0.1% in a hydrapulper with an ultrasonic function, wherein the pulping speed is 900 revolutions per minute, the ultrasonic power is 300W, and the frequency is 30 kHz; pulping for 20 min.

Putting SCR glass microfibers with the beating degree of 49 degrees into a sulfuric acid solution with the pH value of 4, and beating in a high-frequency fluffer at the rotating speed of 900 r/min for 20 min; the pulping concentration is 0.1%.

Conveying the two pulped fibers to a pulp mixing tank, uniformly mixing the two fibers, adding water to adjust the pulp concentration to 0.1 per mill, conveying the pulp to an inclined net for forming, drying and rolling for forming, wherein the production line speed is 50m/min, and the gram weight of a product is 80g/m²。

Synthesizing a filter material: the upper layer and the lower layer are all 30g/m²The PET spun-bonded non-woven fabric and the middle layer adopt polyurethane resin adhesiveAfter glue pouring, hot-pressing and compounding are carried out, the compounding pressure is 0.2MPa, and the speed is 10 m/min. The gram weight of the finally formed filter material for the hydraulic oil is 140g/m²。

TABLE 5 compounding ratio of aramid fiber to glass microfiber

Sample number	Aramid fiber content (%)	Glass microfiber content (%)
			F-1	20	80
F-2	15	85
			F-3	10	90
F-4	5	95
			F-5	1	98

The properties of the prepared composite filter material are shown in table 6.

TABLE 6 composite Filter Properties

Sample number	Absolute Filter precision (μm)	Beta value (5 μm)	Resistance (Pa)	Soil receptivity (g/m)2)
					F-1	4.97	3.01	185	198
F-2	4.74	6.34	243	176
					F-3	4.04	17.32	261	156
F-4	3.79	70.58	291	135
					F-5	3.66	236.2	343	127

Example 4

Preparation of the intermediate layer: pulping trilobal polyphenylene sulfide (PPS) with fineness of 2.2 denier and length of 3mm in an aqueous solution of 5% sodium carboxymethylcellulose (CMC-Na) in a hydrapulper with an ultrasonic function, wherein the pulping speed is 1800 rpm, the ultrasonic power is 400W and the frequency is 40 kHz; pulping time 25 min.

Putting SCR glass microfibers with the beating degree of 44 degrees into a sulfuric acid solution with the pH value of 1, and beating in a high-frequency fluffer at the rotating speed of 1800 rpm for 25 min; the beating concentration is 5%.

Conveying the two pulped fibers to a pulp mixing tank, uniformly mixing the two fibers, adding water to adjust the pulp concentration to 5 per mill, conveying the pulp to an inclined net for forming, drying and rolling for forming, wherein the production line speed is 90m/min, and the gram weight of a product is 70g/m²。

Synthesizing a filter material: the upper layer and the lower layer are 35g/m²The PET spun-bonded non-woven fabric and the middle layer are compounded by hot pressing after polyurethane resin glue is sprayed, the compounding pressure is 0.3MPa, and the speed is 20 m/min. The gram weight of the finally formed filter material for the hydraulic oil is 140g/m²。

TABLE 7 blend ratio of trilobal polyphenylene sulfide fibers to glass microfibers

Sample number	Trilobal polyphenylene sulfide fiber content (%)	Glass microfiber content (%)
			PY-1	20	80
PY-2	15	85
			PY-3	10	90
PY-4	5	95
			PY-5	1.5	98

The properties of the prepared composite filter material are shown in table 8.

TABLE 8 composite Filter Properties

Sample number	Absolute Filter precision (μm)	Beta value (5 μm)	Resistance (Pa)	Soil receptivity (g/m)2)
					PY-1	4.46	3.51	183	213
PY-2	4.24	6.23	241	193
					PY-3	4.04	16.82	253	178
PY-4	3.77	73.04	267	152
					PY-5	3.06	245.6	326	139

Comparative example 1

Preparation of the intermediate layer: respectively pulping trilobal PI fiber and round PI fiber with fineness of 0.5 denier and length of 0.5mm in aqueous solution of Methyl Cellulose (MC) with concentration of 0.3% in a hydrapulper with ultrasonic function, wherein the pulping speed is 2000 r/min, the ultrasonic power is 200W, and the frequency is 10 kHz; pulping for 30 min.

Putting SCR glass microfibers with the beating degree of 59 degrees into a sulfuric acid solution with the pH value of 2.5, and beating in a high-frequency fluffer at the rotating speed of 2000 r/min for 15 min; the pulping concentration is 0.1%.

Respectively conveying the beaten trilobal PI fiber and the beaten circular PI fiber and the beaten glass microfiber to a pulp mixing tank, uniformly mixing the two fibers, adding water to adjust the pulp concentration to 0.3 per mill, conveying the pulp to an inclined wire for forming, drying, rolling and forming, wherein the production line speed is 100m/min, and the product gram weight is 60g/m²。

Synthesizing a filter material: adopts 15g/m of upper and lower layers²The PET spun-bonded non-woven fabric and the middle layer are compounded by acrylic resin glue through hot pressing after glue spraying, the concentration of the glue solution is 3%, the compounding pressure is 0.05MPa, and the speed is 50 m/min. The gram weight of the finally formed filter material for the hydraulic oil is 90g/m². The ratio of the two PI fibers to the glass microfiber is shown in tables 9 and 10.

TABLE 9 blend ratio of trilobal PI fibers to glass microfibers

TABLE 10 proportion of round PI fibers to glass microfibers

Sample number	Round PI fiber content (%)	Glass microfiber content (%)
			PG-1	20	80
PG-2	15	85
			PG-3	10	90
PG-4	5	95
			PG-5	2	98

The properties of the prepared composite filter material are shown in table 11.

TABLE 11 composite Filter Properties

Sample number	Beta value (5 μm)	Resistance (Pa)	Soil receptivity (g/m)2)
				P-1	2.15	170	195
PG-1	1.52	187	185
				P-2	5.46	197	168
PG-2	3.19	201	157
				P-3	13	215	147
PG-3	12.13	239	132
				P-4	66	275	128
PG-4	52.63	285	119
				P-5	142	288	116
PG-5	75.54	304	104

As can be seen from table 11, the filter material with the addition of the shaped synthetic fibers performed better than the filter material with the addition of the round fibers.