JP3487968B2 - Sulfonated composite fibers and nonwovens - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sulfonated composite fiber and a sulfonated non-woven fabric used for battery separators, separators, cement reinforcing materials and the like.

[0002]

2. Description of the Related Art Nonwoven fabrics can be manufactured directly from fibers without undergoing a spinning process or a twisting process, so that the manufacturing operation thereof is simpler than that of a woven fabric or a knitted fabric. Nonwoven fabrics having such advantages are currently widely used as sanitary materials such as paper diapers and clothing materials. Then, as the fibers to be the material of the non-woven fabric, single fibers such as polypropylene fibers, heterogeneous polymer composite fibers such as polyethylene-polypropylene composite fibers and polyethylene-polyethylene terephthalate composite fibers, copolymerized polyester-polyethylene terephthalate composite fibers and co-fibers. Homogeneous polymer composite fibers such as polymerized polypropylene-polypropylene composite fibers have been developed.

As a separator for batteries such as nickel-cadmium batteries, a non-woven fabric made of synthetic fibers is used for applications other than the above-mentioned hygiene materials and clothing materials. Strength, good gas permeability, electrolyte retention capacity, electrolyte durability and oxidation resistance are required. Nonwoven fabric made of polyamide fiber, which is commonly used at present, has hydrophilicity,
Although it has excellent electrolyte retention capacity, it is poor in electrolyte durability and oxidation resistance, and begins to decompose from amide bonds during repeated charge and discharge, and the decomposed product dissolves in the electrolyte, causing self-discharge. Become.

On the other hand, a non-woven fabric made of polyolefin fibers such as polypropylene and polyethylene is excellent in electrolytic solution durability and oxidation resistance, but is hydrophobic,
Poor electrolyte retention capacity. For this reason, it has been attempted to use the polyolefin-based fiber after treating the polyolefin-based fiber with a hydrophilic property to make it hydrophilic, but when the surfactant is eluted by a large number of charging / discharging times and the self-discharge characteristic deteriorates. at the same time,
There is a drawback that the hydrophilicity gradually deteriorates.

Therefore, it is conceivable that a hydrophilic functional group is introduced into the surface of the polyolefin fiber by a chemical reaction to maintain permanent hydrophilicity.

For example, in JP-A-57-141862, a hydrophilic non-woven fabric is prepared by graft-polymerizing a hydrophilic monomer by using a non-woven fabric made of fibers having a polyethylene resin arranged on the surface of a polypropylene resin fiber as a substrate. Is getting However, in the method described in this publication, a hydrophilic monomer is attempted to be graft-polymerized to polyethylene, which is poor in reactivity among polyolefins, and the graft-polymerization time becomes long, and even if the polymerization time is lengthened, grafting is not possible. It has the disadvantages that it becomes non-uniform and the hydrophilic functional groups are easily eliminated.

In Japanese Patent Laid-Open Nos. 1-132042 and 1-132044, polypropylene short fibers are opened and dispersed, and then uniformly sprinkled in an organic solvent in which polyethylene is dispersed to form polypropylene fibers. The fibers are heat-bonded to each other by giving a binding property and further passing between hot rolls to obtain a nonwoven fabric having polypropylene inside and polyethylene near the surface layer, and immersing the nonwoven fabric in fuming sulfuric acid. A method of imparting hydrophilicity by sulfonation of a polyethylene portion is disclosed.

However, in the methods described in these publications, operations such as application of a binder and desolvation work are complicated in the steps up to the production of the non-woven fabric, and the conventional heat-adhesive conjugate fiber is used. It is not possible to adopt a simple non-woven fabric manufacturing method. Further, there is a portion that is not sulfonated, and the sulfonation is non-uniform.

By the way, Japanese Patent Application Laid-Open No. 59-9255 discloses a heat-adhesive non-woven fabric obtained by heat-bonding a composite fiber containing linear low-density polyethylene as a sheath component and polyethylene as a core component. It is disclosed. However, the non-woven fabric described in this publication is intended to be used as a hygienic material while maintaining a high non-woven fabric strength with the least possible non-woven fabric weight and having a soft texture as much as possible. No attention has been paid to the hydrophilicity of.

Regarding the reactivity of the polyolefin resin,
For example, "Polymer Reaction", pages 8 to 17 (Polymer Experimental Studies, vo
l 6. Edit: As described in The Society of Polymer Science, Japan Society for Polymer Experiments, Kyoritsu Shuppan 1978), polyethylene generally has poor reactivity because radicals due to hydrogen abstraction are difficult to generate, and sheath / core = With conventional composite fibers having a polyethylene / polypropylene structure, it has been accepted that it is difficult to carry out a uniform sulfonation or grafting reaction on the fiber surface.

Therefore, in order to carry out the hydrophilic treatment uniformly, the treatment conditions are made severe, but there is a disadvantage that the strength of the non-woven fabric is lowered. On the other hand, if the treatment conditions are gentle such as low concentration, there is a drawback that the treatment time becomes long in terms of reaction rate and the productivity is lowered.

Therefore, the object of the present invention is (i) can be obtained by a simple method, (ii) the sulfonation is uniform, (ii)
i) To provide a sulfonated composite fiber and a sulfonated nonwoven fabric, which have advantages such as less reduction in strength as compared with before sulfonation.

[0013]

Means for Solving the Problems As a result of intensive studies conducted by the present inventor to achieve the above object, a linear low density polyethylene is used as a sheath component and has a higher melting point than the linear low density polyethylene. Surprisingly, when a sheath-core type composite fiber (a) containing a polymer as a core component or a nonwoven fabric (b) obtained from the sheath-core type composite fiber is subjected to a sulfonation treatment with an ordinary sulfonating agent such as fuming sulfuric acid. The linear low-density polyethylene in the sheath-core type composite fiber (a) and the non-woven fabric (b) is easily sulfonated despite being included in the category of polyethylene, and is uniformly sulfonated, and The present invention was completed by finding that the decrease in strength of the sheath-core type composite fiber (a) and the nonwoven fabric (b) after sulfonation is small.

Therefore, the present invention comprises a sheath-core type composite fiber comprising a linear low-density polyethylene as a sheath component and a polymer having a melting point higher than that of the linear low-density polyethylene as a core component. The gist is a sulfonated composite fiber, which is characterized in that chain low-density polyethylene is sulfonated.

The present invention also comprises a non-woven fabric obtained from a sheath-core type composite fiber having a linear low density polyethylene as a sheath component and a polymer having a melting point higher than that of the linear low density polyethylene as a core component. A sulfonated non-woven fabric is characterized in that a linear low-density polyethylene as a sheath component is sulfonated.

First, the sulfonated composite fiber of the present invention will be described. The sheath component constituting the sulfonated conjugate fiber of the present invention is linear low density polyethylene (hereinafter referred to as L-LDPE). L-LDPE used is etc. Ho those low density is improved reactivity of the scan sulfonated. Therefore, the density is preferably 0.945 or less, but if the density is less than 0.90, the softening point becomes too low, and it becomes difficult to form fine fibers having a denier of 1 or less. Therefore, the preferable density range of L-LDPE is 0.90 to 0.945. Specific examples of L-LDPE include those obtained by copolymerizing ethylene and an α-olefin having 4 to 8 carbon atoms in the presence of an ionic polymerization catalyst, wherein a linear polymer is an ethyl group, a butyl group, or a hexyl group. Group, a structure in which a side chain such as a 2-methylpropyl group is formed, and can be selected from commercially available products generally called linear low-density polyethylene.

The sheath component L-LDPE has a density of 0.9.
Homopolymers such as low-density polyethylene, medium-density polyethylene, or high-density polyethylene that have hitherto been commercially available within a range not exceeding 45, and copolymers containing polypropylene as a main component (ethylene-propylene random copolymer, ethylene-propylene- Copolymers such as butene-1 random copolymers) can be mixed.

On the other hand, the polymer of the core component is the above L-LDP.
A polymer having a melting point higher than that of E is used, and preferably a polymer having a melting point of 15 ° C. or higher is used. Examples of such a polymer include polypropylene and polypropylene-
Melt-spinnable polymers such as polyethylene copolymers, polyesters and polyamides can all be used.

The structure of the composite fiber composed of the sheath component and the core component can be any conventionally known structure such as concentric type or eccentric type structure. The sheath component is at least the surface of the composite component. It must be arranged so that a part is formed continuously in the longitudinal direction. The range of the sheath / core cross-sectional area ratio is preferably 30/70 to 70/30.

This composite fiber is obtained by spinning and drawing according to the usual method for producing a sheath-core type composite fiber, and cutting it into a desired length. For example, a melt spinning temperature of 1
The temperature is 80 to 250 ° C., and the spun undrawn yarn is 0.5 to
The composite fiber can be obtained by heat drawing usually 2 to 6 times in the range of 30 denier.

Although the non-sulfonated conjugate fiber has been described above, the sulfonated conjugate fiber of the present invention is
The sheath component L-LDPE in the composite fiber is sulfonated. Sulfonation is fuming sulfuric acid,
It is carried out using a known sulfonating agent such as chlorosulfuric acid or concentrated sulfuric acid. The preferred degree of sulfonation of L-LDPE is 3.
-10%. The reason is that if the degree of sulfonation is less than 3%, sufficient hydrophilicity cannot be obtained, and if it exceeds 10%, the strength of the conjugate fiber is reduced.

The sulfonated composite fiber of the present invention is a fiber that has been subjected to hot-drawing by a factor of about 2 or more after melt spinning, and needs to have contradictory characteristics such as a fiber for FRC (fiber reinforced cement) such as alkali resistance and hydrophilicity. Although it may be used for the reinforcing fiber application, after obtaining a nonwoven fabric by a usual means as described below, a battery separator, an electrodialysis membrane, an electrolytic isolation membrane, an electroosmosis membrane, a gas separation membrane, a liquid-liquid. It is preferably used for various applications requiring alkali resistance, hydrophilicity, high strength, antistatic property, etc., such as separation membranes, fuel cell membranes and antistatic printing sheets.

Next, the sulfonated nonwoven fabric of the present invention will be described. The non-woven fabric constituting the sulfonated non-woven fabric of the present invention is usually the above-mentioned sheath-core type composite fiber having L-LDPE as a sheath component and a polymer having a higher melting point than L-LDPE as a core component. After processing by a conventional method using a card machine such as a roller card and a flat card to prepare a web, a hot air fusion method, a heat roll fusion method, a needle punch method, and a water stream according to the intended use of the nonwoven fabric. It is obtained by joining or entanglement of webs by a conventional method such as an entanglement method. Further, the non-woven fabric constituting the sulfonated non-woven fabric of the present invention may be obtained by short-cutting the above-mentioned sheath-core type composite fiber and then making a paper by a wet paper making method.

Although the non-sulfonated non-woven fabric has been described above, the sulfonated non-woven fabric of the present invention is L-LDPE which is the core component in the sheath-core type composite fiber constituting the non-woven fabric.
Is sulfonated. The sulfonation is carried out using a known sulfonating agent such as fuming sulfuric acid, chlorosulfuric acid and concentrated sulfuric acid as described above. L-LD
The preferred degree of sulfonation of PE is 3 to 10%. The reason is that if the degree of sulfonation is less than 3%, sufficient hydrophilicity cannot be obtained, and if it exceeds 10%, the strength of the conjugate fiber is reduced.

In the sulfonated nonwoven fabric of the present invention, the basis weight of the nonwoven fabric is preferably more than 30 g / m ² and 100 g / m ² or less. The reason is that if the amount is 30 g / m ² or less, sufficient nonwoven fabric strength cannot be obtained when considering applications such as battery separators, while if it exceeds 100 g / m ² , applications such as battery separators and gas separation membranes are not possible. This is because sufficient air permeability cannot be obtained when thinking.

The sulfonated nonwoven fabric of the present invention comprises a battery separator, an electrodialysis membrane, an electrolytic isolation membrane, an electroosmotic membrane,
It is preferably used for various applications requiring alkali resistance, hydrophilicity, high strength, antistatic property, etc. such as gas separation membranes, liquid-liquid separation membranes, fuel cell membranes and antistatic printing sheets.

[0027]

[Function] L-LDPE is a linear high-density polyethylene
The reason why the sulfonation reaction rate is high in comparison is as follows.
Be inferred. L-LDPE is an α-o having 4 to 8 carbon atoms.
Coordination of ethylene monomer with reffin as copolymerization component
Nion-polymerized, long linear polyethylene
It has a structure with many short side chains in the chain. With the main chain
The carbon atom at the branch point of the side chain is an asymmetric carbon.
The bonding hydrogen atom is extracted compared to other hydrogen atoms.
It tends to be easy, so it is easy to cause a radical reaction
Yes. Also, due to the presence of this short side chain, linear high-density poly
It has a lower density than ethylene and has excellent permeability for reaction reagents.
It Due to these two effects, sulfonation of L-LDPE
It seems that the reaction rate becomes faster.

According to the present invention, as described above, by using the composite fiber containing L-LDPE having a fast sulfonation reaction rate as the sheath component and the nonwoven fabric obtained from the composite fiber as a raw material, a simple method can be obtained. It is possible to obtain a sulfonated composite fiber and a sulfonated non-woven fabric whose surface layer is uniformly sulfonated, without lowering the fiber strength.

[0029]

The present invention will be further described with reference to the following examples.

Example 1 The sulfonation rates of various polyethylenes were tested and compared.

The polyethylene raw materials tested are as follows:

(A) Esplen SPO No.377 (L-LDPE manufactured by Sumitomo Chemical Co., ρ = 0.89) (b) GA-801 (L-LDPE manufactured by Sumitomo Chemical Co., ρ = 0.92) (c) NeoZex 45200 (Mitsui Petrochemical L-LDPE, ρ = 0.945) (d) J-310 (Asahi Kasei Kogyo HDPE (high density polyethylene) ρ = 0.962) 100 kg / cm ² by heating the above four kinds of raw materials to 200 ° C. The film was molded under the pressure condition of 1 to prepare a film having a thickness of about 0.2 mm, which was used as a test film.

80 ml of fuming sulfuric acid (SO ₃ concentration: 20%) was placed in a sample bottle (capacity: 100 ml), a test film of 50 × 100 mm size was placed therein, and immersed at 25 ° C. for a predetermined time. Immediately after the treatment, it was dipped in concentrated sulfuric acid for 3 minutes, successively dipped in 50% sulfuric acid and 10% sulfuric acid for 3 minutes each, and then washed with water.

The degree of sulfonation in the test film obtained after sulfonation was measured as follows. After the sulfonated test film was dried, FT-IR analysis was performed (ATR method; incident angle 45 °). In the obtained IR spectrum, the S = 0 stretching vibration (about 1180c) of the sulfone group with respect to the absorption spectrum height of the C-H symmetric bending vibration (about 1460 cm ^-1 ) of the saturated aliphatic hydrocarbon
The height ratio of the absorption spectrum by m ^-1 ) was calculated, and this value was used as the peak ratio. Then, the degree of sulfonation of the sulfonation-treated test film was measured by XPS measurement (X-ray photoelectron spectroscopy) to prepare a calibration curve. The sulfonation degree of each test film was calculated from the peak ratio obtained by FT-IR analysis and the prepared calibration curve.

The relationship between the sulfonation treatment time and the sulfonation degree of various polyethylene test films is shown in FIG. From this figure, it is clear that ρ = 0.962
= −0.945, ρ = 0.92 and ρ = 0.89 L−
It can be seen that LDPE is more easily sulfonated.

Example 2 (1) Production of sheath-core type composite fiber As a sheath component, MFR value is 20 g / 10 min, ρ = 0.9
A uniaxial extruder using 2 g / cc of L-LDPE (product name: GA801, manufactured by Sumitomo Chemical Co., Ltd.) and polypropylene (product name: 130 MV, manufactured by Ube Industries, Ltd.) having a MFR value of 20 g / 10 min as a core component. With a composite spinning equipment equipped with two units and a circular nozzle for composite fibers with a hole diameter of 0.4 mm,
At a spinning temperature of 200 to 240 ° C., a take-up speed of 500 m /
And the cross-sectional area ratio of the sheath and the core is 50/5.
A composite fiber (undrawn yarn) having a single yarn denier of 3.1 de was obtained at 0.

The obtained undrawn yarn was drawn 3.1 times to obtain a sheath-core type composite fiber composed of fibers having a fiber length of 5 mm and a single yarn denier of 1.0 de.

(2) Manufacture of non-woven fabric by wet method 2.6 g of the above fiber was added to a water 10 containing a surfactant.
Dispersed evenly in the liter, dimensions 250 mm x 200 mm
Paper was made on the No. 3 mesh to make a wet web.
The obtained web was held between two heating plates and the temperature was adjusted to 12
While pressing and drying at 0 to 125 ° C. for 10 minutes, the sheath portion of the composite fiber was melted and the fibers were joined together to produce a nonwoven fabric.

(3) Production of Sulfonated Nonwoven Fabric The obtained nonwoven fabric is dipped in methanol to remove adhering oil, and then dipped in fuming sulfuric acid (SO ₃ concentration 20%) and sulfonated at 25 ° C. for 5 minutes. Processed. Thus, the sulfonated nonwoven fabric of the present invention was obtained.

The water absorption test of the obtained sulfonated nonwoven fabric was conducted as follows. The sulfonated non-woven fabric was gently dipped in water and allowed to stand for 15 minutes. After that, this non-woven fabric was taken out, suspended in the air for 30 seconds, and then weighed to determine the water absorption rate by the following formula.

Water absorption rate (%) = [(weight after water absorption−weight before water absorption) / weight before water absorption] × 100 The sulfonated nonwoven fabric obtained in the present invention immediately sinks from the water surface when floated in water, The water absorption rate was 210%, and it was possible to clear the target value of 200% of hydrophilicity when used as a battery separator.

(Example 3) As a raw material for the sheath component, MFR
L-LDP with a value of 20 g / min and a density of 0.945 g / cc
E (Product name: Neo-Zex 45200, manufactured by Mitsui Petrochemical Co., Ltd.)
Was used, and a sulfonated nonwoven fabric was obtained in the same manner as in Example 1 except that the sulfonation treatment time was 10 minutes, and the water absorption rate was measured in the same manner as in Example 1.

The sulfonated nonwoven fabric obtained in this example is
Immediately when it floats in the water, it sinks from the surface and the water absorption rate is 205.
%, And the target value of 200% for hydrophilicity could be cleared.

Comparative Example 1 MFR was used as a raw material for the sheath component.
A sulfonated nonwoven fabric was obtained in the same manner as in Example 1 except that high density polyethylene (product name: J310, manufactured by Asahi Kasei Corporation) having a value of 20 g / min and a density of 0.962 g / cc was used. Water absorption was measured in the same manner as in Example 1.

The obtained sulfonated nonwoven fabric floated even when immersed in water and had a water absorption rate of 130%, which was insufficient as a hydrophilic nonwoven fabric.

(Examples 4 to 6) A sulfonated nonwoven fabric was produced in the same manner as in Example 1 by using the following L-LDPE as a raw material for the sheath component.

Example 4 ... Esplen SPO No.377 (L-LDPE manufactured by Sumitomo Chemical Co., ρ = 0.89) Example 5 ... CS5005 (L-LDPE manufactured by Sumitomo Chemical Co., ρ = 0.91) Example 6 ... GA-801 (L-LDPE manufactured by Sumitomo Chemical Co., ρ = 0.92) The sulfonated nonwoven fabrics obtained in Examples 4 to 6 immediately sink into the water when floated in water, and the water absorption rate is 200%.
It was possible to clear the target value of 200% for hydrophilicity.

(Relationship between Sulfonation Treatment Time and Water Absorption) Table 1 shows the relation between the sulfonation treatment time and water absorption in Examples 2 to 6 and Comparative Example 1.

[0049]

[Table 1]

From Table 1, L-LD having a density of 0.945 or less
In the nonwoven fabrics of Examples 2 to 6 in which PE was used as the sheath component, the sulfonation treatment time was 5 to 10 minutes and the target value of the hydrophilicity (200
%, Whereas the conventional product of Comparative Example 1 requires 30 to 40 minutes or more.

(Mechanical Strength of Sulfonated Nonwoven Fabric) From the sulfonated nonwoven fabrics obtained in Example 2 and Comparative Example 1, a width of 5 was obtained.
A sample having a length of 0 mm and a length of 140 mm was cut out, and the tear strength (Kg) was measured for each sulfonation time under the conditions of a chuck interval of 100 mm and a pulling speed of 100 mm / min. The results are shown in Table 2.

[0052]

[Table 2]

From Table 2, in Example 2 and Comparative Example 1, the decrease in the mechanical strength of the non-woven fabric is not so different when the sulfonation treatment time is 10 minutes, but from Table 1 above, Comparative Example 1 shows the sulfonation treatment time. However, the water absorption rate is as low as 168% at 10 minutes, and it is 60
It requires a sulfonation treatment time of a minute, which reduces the mechanical strength of the nonwoven fabric from 16.2 kg to 13.0 kg. On the other hand, in Example 2, as shown in Table 1, even if the sulfonation treatment time was 5 minutes, the water absorption was 20% of the target value.
It is 210% which exceeds 0%, and the mechanical strength of the nonwoven fabric at this time is 17.4 kg, which is almost the same as the value before the sulfonation treatment.

From the results shown in Tables 1 and 2 above, it was revealed that the sulfonated nonwoven fabric of the present invention is significantly superior to the conventional products in terms of sulfonation degree and mechanical strength.

(Example 7) (1) Production of sheath-core type composite fiber As a sheath component, MFR value was 20 g / 10 min, ρ = 0.9.
A uniaxial extruder using 2 g / cc of L-LDPE (product name: GA801, manufactured by Sumitomo Chemical Co., Ltd.) and polypropylene (product name: 130 MV, manufactured by Ube Industries, Ltd.) having a MFR value of 20 g / 10 min as a core component. With a composite spinning equipment equipped with two units and a circular nozzle for composite fibers with a hole diameter of 0.4 mm,
At a spinning temperature of 200 to 240 ° C., a take-up speed of 500 m /
And the cross-sectional area ratio of the sheath and the core is 50/5.
A composite fiber (undrawn yarn) having a single yarn denier of 3.1 de was obtained at 0.

The obtained undrawn yarn was drawn 3.1 times to obtain a sheath-core type composite fiber composed of fibers having a fiber length of 5 mm and a single yarn denier of 1.0 de.

(2) Production of Sulfonated Composite Fiber The obtained composite fiber was dipped in methanol to remove adhering oil, and then dipped in fuming sulfuric acid (SO ₃ concentration 20%) at 25 ° C. for 5 minutes. Sulfonated. Thus, the sulfonated composite fiber of the present invention was obtained. The degree of sulfonation of the obtained sulfonated composite fiber was 4%.

[0058]

As described above, according to the present invention,
(i) Sulfonated composite fiber and sulfonated non-woven fabric, which have the advantages that they can be obtained by a simple method, (ii) uniform sulfonation, and (iii) less reduction in strength compared to before sulfonation. Was provided.

These are used in applications requiring hydrophilicity, acid resistance and alkali resistance such as battery separators, separation membranes and cement reinforcing materials.

[Brief description of drawings]

FIG. 1 is a graph showing the sulfonation rate of various polyethylenes.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI D21H 13/12 D21H 13/12 15/10 15/10 H01M 2/16 H01M 2/16 P // D06M 101: 20 D06M 101: 20 (58) Fields surveyed (Int.Cl. ⁷ , DB name) D06M 11/55 B01D 39/16 D01D 5/34 D01F 8/06 D04H 1/42 D21H 13/12 D21H 15/10 H01M 2/16 D06M 101: 20

Claims (5)

(57) [Claims] 1. A sheath-core type composite fiber comprising a linear low-density polyethylene as a sheath component and a polymer having a melting point higher than that of the linear low-density polyethylene as a core component. A sulfonated composite fiber characterized in that density polyethylene is sulfonated. 2. The sulfonated composite fiber according to claim 1, wherein the degree of sulfonation in the linear low-density polyethylene is 3 to 10%. 3. A non-woven fabric obtained from a sheath-core type composite fiber comprising a linear low-density polyethylene as a sheath component and a polymer having a melting point higher than that of the linear low-density polyethylene as a core component. A sulfonated non-woven fabric characterized in that the linear low-density polyethylene of 1. is sulfonated. 4. The sulfonated nonwoven fabric according to claim 3, wherein the degree of sulfonation in the linear low-density polyethylene is 3 to 10%. 5. The basis weight of the non-woven fabric exceeds 30 g / m ² and 10
The sulfonated non-woven fabric according to claim 3, which is 0 g / m ² or less.