WATER-REPELLENT AND LIPOPHILIC COMPOSITE NEEDLE-PUNCHED NONWOVEN FABRIC AND PREPARATION METHOD THEREOF

Abstract

The invention relates to a water-repellent and lipophilic composite needle-punched nonwoven fabric and a preparation method thereof. The method comprises the following steps: blending a PET fiber and a polyolefin-based fiber in a mass ratio of 3:1-1:3, and performing needle punching to obtain a composite needle-punched nonwoven fabric; carrying out hot-drying treatment on the composite needle-punched nonwoven fabric at 110-160° C. for 40-90 min; and carrying out water-repellent finishing on the hot-dried fabric using 50-70 mL/L of an aqueous solution of a modified resin-based fluorine-free waterproofing agent, and drying to obtain the water-repellent and lipophilic composite needle-punched nonwoven fabric, wherein the water-repellent finishing is dip rolling, the air pressure is 1.8 kPa and the liquid carrying rate is 160-230%. The preparation method of the invention is simple, and the prepared composite needle-punched nonwoven fabric has significantly improved water repellency, lipophilicity and tensile strength compared with the fabric before treatment.

Claims

1. A preparation method of a water-repellent and lipophilic composite needle-punched nonwoven fabric, comprising the steps of: (1) blending a PET fiber and a polyolefin-based fiber in a mass ratio of 3:1-1:3, and performing needle punching to obtain a composite needle-punched nonwoven fabric; (2) carrying out hot-drying treatment on the composite needle-punched nonwoven fabric at 110-160° C. for 40-90 min; and (3) carrying out water-repellent finishing on the hot-dried fabric using 50-70 mL/L of an aqueous solution of a modified resin-based fluorine-free waterproofing agent, and drying to obtain the water-repellent and lipophilic composite needle-punched nonwoven fabric, wherein the water-repellent finishing is dip rolling, the air pressure of dip rolling is 1.8 kPa and the liquid carrying rate of dip rolling is 160-230%.

2. The preparation method according to claim 1, wherein in step (1), the polyolefin-based fiber is selected from the group consisting of a polyethylene fiber, a polypropylene fiber, an ES fiber and any combination thereof.

3. The preparation method according to claim 1, wherein in step (1), the blended fibers are processed by a needle punching process, and the needle punching process comprises the following steps: opening and mixing the PET fiber and the polyolefin-based fiber, carding, lapping and pre-needle punching, then folding the pre-needle-punched fabric in half to perform main needle punching.

4. The preparation method according to claim 1, wherein in step (3), the modified resin-based fluorine-free waterproofing agent is a cationic modified resin-based fluorine-free waterproofing agent, and the modified resin-based fluorine-free waterproofing agent has a pH of 3.5-4.5.

5. The preparation method according to claim 1, wherein in step (3), the modified resin-based fluorine-free waterproofing agent is a HOLPOSON ECO-OC fluorine-free waterproofing agent.

6. The preparation method according to claim 1, wherein in step (3), the liquor ratio of the modified resin-based fluorine-free waterproofing agent to the fabric is 10:1-20:1.

7. The preparation method according to claim 1, wherein in step (3), the water-repellent finishing is two-dip two-rolling.

8. The preparation method according to claim 1, wherein in step (3), the drying temperature is 60-90° C.

9. A water-repellent and lipophilic composite needle-punched nonwoven fabric prepared by the method according to claim 1, wherein the water-repellent and lipophilic composite needle-punched nonwoven fabric has a water contact angle of 120-150° and an oil absorption rate of 3.2-4.4 g/g.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is an electron micrograph of a product prepared after water-repellent finishing without hot-drying at different magnifications;

[0033] FIG. 2 is an electron micrograph of a product prepared after hot-drying treatment and water-repellent finishing at different magnifications;

[0034] FIG. 3 is a contact angle picture of a material before and after finishing a fabric that is not hot-dried with 70 mL/L of a fluorine-free waterproofing agent;

[0035] FIG. 4 shows a test result of the effect of the finishing concentration of a fluorine-free waterproofing agent on the contact angle;

[0036] FIG. 5 shows a test result of the contact angle of a nonwoven fabric after the fabric is hot-dried and then is subjected to water-repellent finishing with a fluorine-free waterproofing agent;

[0037] FIG. 6 shows a test result of the oil absorption rate of a needle-punched nonwoven fabric prepared by hot-drying treatment; and

[0038] FIG. 7 shows a test result of the oil absorption rate of a water-repellent nonwoven fabric with hot-drying treatment and without hot-drying treatment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] The invention will be further illustrated in more detail with reference to the accompanying drawings and embodiments. It is noted that, the following embodiments only are intended for purposes of illustration, but are not intended to limit the scope of the present invention.

[0040] In the following examples of the present invention, the PET fiber and the ES fiber are commercially available, and the non-fluorine waterproofing agent (HOLPOSON ECO-OC) is produced by Zhejiang Holposon New Materials Co., Ltd., and has a pH of 3.5-4.5. The oily wastewater is specifically prepared as follows: 1,000 mL of deionized water was poured into a beaker, and 250 mL of kerosene was slowly poured into the beaker, and stirred by a magnetic stirrer at 60 r/min for 10 min, and then the resulting solution was allowed to stand for 30 min such that water was mixed with oil to obtain the oily wastewater.

[0041] The instrument models used in the invention are as follows:

[0042] needle punching production line (Wanlong Machinery Co., Ltd., Changshu, China), universal material testing machine (Instron5967 testing machine, Instron Corporation, U.S.A), full-automatic video contact angle meter (OCA50, Dataphysics, Germany), desktop electron microscope (TM3030, Hitachi, Japan), magnetic stirrer (84-1, Shanghai Meiyingpu Instrument Manufacture Co., Ltd., China), electronic balance (Adventurer, Ohaus Instrument Co., Ltd., Germany), and oven (model WGLL-125BE, Tianjin Taisite Instrument Co., Ltd.)

Example 1

[0043] (1) Preparation of PET/ES needle-punched nonwoven fabric: a PET fiber and an ES fiber were thoroughly mixed at a mass ratio of 3:1, and then the blended fibers were processed by a needle punching process. The needle punching process were as follows: PET/ES opening and mixing.fwdarw.carding.fwdarw.lapping machine.fwdarw.pre-needle punching.fwdarw.main needle punching, to obtain a PET/ES needle-punched nonwoven fabric. To increase the strength of the nonwoven fabric, the pre-needle-punched material was folded in half and then subjected to main needle punching. The power frequency was set as 13 Hz.

[0044] (2) A part of the PET/ES needle-punched nonwoven fabric prepared in step (1) was subjected to hot-drying treatment. The sample was placed in the oven and hot-dried at a temperature of 120° C. for 60 min.

[0045] (3) Then, the hot-dried sample was subjected to water-repellent treatment with 50 mL/L of an aqueous solution of the fluorine-free waterproofing agent, and a liquor ratio of the aqueous solution of the fluorine-free waterproofing agent to the sample was 10:1-20:1. The water-repellent finishing process was as follows: PET/ES needle-punched nonwoven fabric.fwdarw.two-dip two-rolling (the sample was soaked in the aqueous solution of the fluorine-free waterproofing agent for 30 s to fully wet the sample, the air pressure for a dip rolling machine was set as 1.8 kPa and the liquid carrying rate was 230%).fwdarw.drying in the oven at 60° C., to obtain a water-repellent and lipophilic composite needle-punched nonwoven fabric.

Example 2

[0046] A water-repellent and lipophilic composite needle-punched nonwoven fabric was prepared according to the method of Example 1, except that in step (1), the mass ratio of the PET fiber to the ES fiber was 1:1.

Example 3

[0047] A water-repellent and lipophilic composite needle-punched nonwoven fabric was prepared according to the method of Example 1, except that in step (1), the mass ratio of the PET fiber to the ES fiber was 1:3.

Example 4

[0048] Three water-repellent and lipophilic composite needle-punched nonwoven fabrics were prepared according to the methods of Examples 1-3, except that in step (3), the concentration of the aqueous solution of the fluorine-free waterproofing agent was 60 mL/L.

Example 5

[0049] Three water-repellent and lipophilic composite needle-punched nonwoven fabrics were prepared according to the methods of Examples 1-3, except that in step (3), the concentration of the aqueous solution of the fluorine-free waterproofing agent was 70 mL/L.

Comparative Example 1

[0050] For comparison, five control samples were prepared according to the methods of Examples 1-5, except that the ES fiber used in step (1) was replaced with the PET fiber of equal mass, that is, ES:PET=0:4.

Comparative Example 2

[0051] For comparison, five controls were prepared according to the methods of Examples 1-5, except that the PET fiber used in step (1) was replaced with the ES fiber of equal mass, that is, PET:ES=0:4.

Comparative Example 3

[0052] For comparison, control samples were prepared according to the methods of Examples 1-5, except that the hot-drying treatment of step (2) was omitted.

[0053] The water-repellent and lipophilic PET/ES needle-punched nonwoven fabrics prepared in the foregoing examples have a gram weight of 390-750 g/m.sup.2 and a thickness of about 6 mm. The fiber morphology of the prepared samples is observed by the desktop electron microscope, and the sample prepared (PET:ES=1:1) is selected as the observed object. FIGS. 1a and 1b are electron micrographs of products prepared after water-repellent finishing without hot-drying at different magnifications, respectively. FIGS. 2a and 2b are electron micrographs of products prepared after hot-drying treatment and water-repellent finishing at different magnifications. As shown in FIGS. 1 and 2, the PET and ES fibers are effectively entangled together, and the fiber morphology is clear and complete, with some breakage; there is no significant difference in the surface of the nonwoven fabric treated by hot drying at 120° C. The fluorine-free waterproofing agent is adhered to the fibers and there are still large pores between the fibers, and the well-dispersed fluorine-free polymer appears as a covering and prevents the fibers from absorbing water. Due to the influence of product thickness, density, hot air temperature, etc., it can be seen in FIGS. 1 and 2 that bonding occurs in some of the ES hot-melt fibers.

[0054] In real life, industrial waste water and oil, printing wastewater, petroleum oil spillage, etc. are the main sources of environmental pollution. The main task of oil-water separation materials is to solve such pollutants. However, it is necessary to further improve the mechanical stability, durability, etc. of the oil-water separation materials, so that the oil-water separation materials are suitable for use in various harsh environments. Therefore, the tensile properties of the sample are critical.

[0055] Tensile tests are carried out on the products prepared in the foregoing examples and comparative examples. The results are shown in Table 1. The unit of the breaking strength in Table 1 is N, and the gray shaded portions in the table are values of the breaking strength (N) of the PET/ES needle-punched nonwoven fabrics subjected to hot-drying and then water-repellent finishing.

[0056] As can be seen from Table 1, after the PET/ES needle-punched nonwoven fabric is hot-dried, it is found from the comparison of the strength of the hot-dried material and the strength of the untreated material that the tensile strength of the nonwoven fabric that is hot-dried and then subjected to water-repellent finishing is significantly different from the tensile strength of the nonwoven fabric that is only subjected to water-repellent finishing, and the tensile strengths all are improved when PET:ES=3:1, 1:1, and 1:3. When the proportions of the PET fiber and the ES fiber are the same, the breaking strength and the elongation at break of the nonwoven fabrics that are hot-dried and then subjected to water-repellent finishing are generally greater than those of the nonwoven fabrics that are only subjected to water-repellent finishing. The different proportions of the PET fiber and the ES fiber have no significant effect on the strength of the nonwoven fabrics. The hot drying improves the mechanical properties of the nonwoven fabrics with the ES fiber, and the fiber strength is enhanced. Moreover, hot drying has a significant effect on the strength when the PET/ES ratio is 1:1. The tensile properties of the nonwoven fabrics with the ES fiber are more significantly improved due to the unique characteristic of the ES fiber that the strength is increased after the ES fiber is heated.

TABLE-US-00001 TABLE 1 Effects of different ratios of PET/ES and different concentrations of the waterproofing agent on the breaking strength of the PET/ES needle-punched nonwoven fabric Waterproofing agent finishing Fiber blending ratio(PET/ES) concentration(ml/L) 4/0 3/1 2/2 1/3 0/4 0 128 ± 0.42 136 ± 0.26 128 ± 0.25 123 ± 0.32 122 ± 0.22 132 ± 0.37 139 ± 0.46 144 ± 0.23 132 ± 0.25 122 ± 0.14 50 132 ± 0.37 123 ± 0.52 122 ± 0.18 121 ± 0.41 112 ± 0.28 154 ± 0.26 148 ± 0.63 156 ± 0.37 162 ± 0.24 113 ± 0.15 60 127 ± 0.38 132 ± 0.32 123 ± 021  129 ± 0.44 126 ± 0.19 132 ± 0.15 140 ± 0.25 160 ± 0.19 134 ± 0.31 147 ± 0.36 70 154 ± 0.29 145 ± 0.23 125 ± 0.36 134 ± 0.23 118 ± 0.21 171 ± 0.32 150 ± 0.38 147 ± 0.39 148 ± 0.19 136 ± 0.35

[0057] In general, a surface having a water contact angle of greater than 150° and having small contact angle hysteresis is called a super-hydrophobic surface, and the contact angle is an index for determining the wettability of a nonwoven fabric. The larger the contact angle is, the worse wettability of the nonwoven fabric is, that is, the water repellency is enhanced when the water absorbency of the nonwoven fabric is worse. The nonwoven fabric has good water repellency when the water contact angle reaches 135°.

[0058] FIGS. 3a and 3b are contact angle pictures of materials before and after finishing fabrics that is not hot-dried with 70 mL/L of a fluorine-free waterproofing agent (PET:ES=1:1). It can be seen from the pictures that when the water droplets fall on the water-repellent treated nonwoven fabrics, the contact angles all are large and the fabrics do not absorb the water droplets (FIG. 3b). However, when the water droplets fall on the untreated nonwoven fabrics, the contact angles are significantly smaller than the contact angles of the water-repellent treated nonwoven fabrics (FIG. 3a). FIG. 4 is shows a test result of the effect of the concentration of a fluorine-free waterproofing agent on the contact angle (after hot-drying treatment). It can be found that during the water-repellent finishing with the same concentration of the fluorine-free waterproofing agent, when the proportions of the PET fiber and the ES fiber are different, the contact angles of the nonwoven fabrics are also different. The contact angle of the material is the smallest when the raw materials of the nonwoven fabric are all PET fibers, that is, the water repellency of the material is the worst. When the proportions of the PET fiber and the ES fiber are the same, the contact angle of the fiber is large, that is, the water repellency of the nonwoven fabric is stronger. The contact angle of the PET/ES needle-punched nonwoven fabric changes with the concentration of the fluorine-free waterproofing agent, and increases with the increase of the concentration of the fluorine-free waterproofing agent, that is, when the concentration of the fluorine-free waterproofing agent is set as 70 mL/L, the PET/ES needle-punched nonwoven fabric has the largest contact angle and the best water repellency.

[0059] FIG. 5 shows a test result of the contact angle of a nonwoven fabric after the fabric is hot-dried and then subjected to water-repellent finishing with the fluorine-free waterproofing agent (at the concentration of 70 mL/L). After the hot-drying treatment and then the water-repellent finishing, the contact angle of the fabric is 148°, which is significantly increased. To some extent, the hot-drying treatment has a certain influence on the water contact angle of the nonwoven fabric, and the water repellency of the nonwoven fabric is increased.

[0060] Further, the oil absorption rate of the prepared fabrics is measured, and the effects of the amount of the fluorine-free waterproofing agent, the raw material ratio of the PET fiber to the ES fiber, and the hot-air drying on the nonwoven fabrics are investigated. After the water contact angle of each sample is investigated, since the untreated nonwoven fabrics and the nonwoven fabrics that are only hot-dried have a small contact angle and have a certain water absorbency, in the oil absorption experiment, the absorbed part may contain two components, i.e., water and oil, and the weight determination of the nonwoven fabrics after oil absorption is not accurate, the water-repellent nonwoven fabrics that are only subjected to water-repellent treatment and the water-repellent nonwoven fabrics that are hot-dried and then subjected to water-repellent treatment are mainly focused in investigating the oil absorption rate.

[0061] FIG. 6 shows a test result of the oil absorption rate of a needle-punched nonwoven fabric prepared by hot-drying treatment. It can be seen from FIG. 6 that when the raw material only consist of the PET or ES fiber, the prepared needle-punched nonwoven fabrics, after being subjected to the water-repellent finishing, have a significantly lower oil absorption rate than the PET/ES blended needle-punched nonwoven fabrics. That is, when the ratio of the PET fiber to the ES fiber is 4:0 or 0:4, the oil absorption rate of the nonwoven fabrics is the smallest, and when the proportions of the PET fiber to the ES fiber are the same, the oil absorption rate of the materials reaches a large value. Therefore, the nonwoven fabric prepared by the mixed raw material of the PET fiber and the ES fiber has better oil absorption performance than the single-fiber raw material.

[0062] FIG. 7 shows a test result of the oil absorption rate of a water-repellent nonwoven fabric with hot-drying treatment and without hot-drying treatment when the ratio of PET/ES is 1:1. It can be seen from FIG. 7 that the oil absorption rate curve of the nonwoven fabric that is hot-dried and then subjected to water-repellent treatment is higher than the oil absorption rate curve of the nonwoven fabric that is only subjected to water-repellent treatment, that is, under the same conditions and with the same concentration of the fluorine-free waterproofing agent, the oil absorption rate of the nonwoven fabric that is hot-dried in advance is higher than that of the nonwoven fabric that is only subjected to water-repellent treatment.

[0063] In the present invention, the PET and ES fibers are selected in the preparation of the composite needle-punched nonwoven fabric. The ES fiber may be replaced with the PP fiber and/or PE fiber, and the water-repellent and lipophilic composite needle-punched nonwoven fabric having similar properties are also obtained. The hot-drying temperature may be adjusted in the range of 110-160° C., preferably 120-130° C. The hot-drying time is preferably 60-70 min.

[0064] The above description is only preferred embodiments of the present invention and not intended to limit the present invention, it should be noted that those of ordinary skill in the art can further make various modifications and variations without departing from the technical principles of the present invention, and these modifications and variations also should be considered to be within the scope of protection of the present invention.