JPS5940948B2 - Method for manufacturing suede-like artificial leather - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing suede-like artificial leather.

More specifically, the present invention relates to a method for producing suede-like artificial leather made of a nonwoven fabric made of ultrafine fibers and a specific polyurethane.

It is conventionally known to produce suede-like artificial leather by applying an elastic polymer, particularly a polyurethane polymer, to a nonwoven fabric made of ultrafine fibers.

For example, Tokuko Sho 37-2489 and Tokusho 47-2438
discloses suede-like artificial leather obtained by applying a polyurethane elastomer to a nonwoven fabric composed of 0.5 tenier poly-11 ethylene terephthalate fibers and then buffing the surface of the nonwoven fabric.

Still special public service No. 44-24699 and special public service No. 46-27392
The deerskin-like fabric is obtained by adding polyurethane to a nonwoven fabric made of a bundle of polyethylene terrescrete fibers with a single fiber denier of 0.047 denier, which is obtained by removing the sea component from sea-island composite fibers. Artificial leather is disclosed.

In all of these prior art solutions or emulsions of polyurethane polymers in organic solvents are used.

When polyurethane polymers are used in organic solvent solutions, difficult problems arise in environmental control and disposal of solvent waste, and when polyurethane polymer emulsions are used, the stability of the emulsions is poor and long-term problems occur. It has the disadvantage that it is difficult to store for a long period of time, and that so-called gum-up, in which the polyurethane polymer adheres in lumps to the mangle roll or the treated fabric during processing of the fabric, is likely to occur.

Furthermore, when producing suede-like artificial leather by impregnating a nonwoven fabric with a polyurethane polymer, there are serious problems in terms of the performance of the resulting product.

That is, due to the high molecular weight of polyurethane polymers, it is difficult to uniformly impregnate the inside of nonwoven fabrics, and the impact resilience and wrinkle recovery properties of nonwoven fabrics are not necessarily improved. % emulsion concentration or higher), the surface of the nonwoven fabric becomes paper-like and the lighting effect, which is a characteristic of suede-like artificial leather, is significantly deteriorated.

On the other hand, JP-A-50-108395 and JP-A-50-15
No. 5794 discloses a urethane prepolymer in which free incyanate groups are blocked with bisulfite.

This urethane prepolymer has good solution stability in aqueous systems and does not cause gum up, and ordinary woven or knitted fabrics or nonwoven fabrics processed with this prepolymer have good rebound resilience.
It is disclosed that wrinkle resistance, shrink resistance, etc. are improved.

However, this specification does not describe or suggest that the urethane prepolymer is used for processing nonwoven fabrics made of ultrafine fibers.

The present inventors have developed a method for processing nonwoven fabrics composed of ultrafine fibers by using the methods described in JP-A-50-108395 and JP-A-5
If the aqueous solution of the urethane prepolymer disclosed in No. 0-155794 is used and deposited in a specific amount under specific conditions, there will be no process troubles such as gum up, and in addition, The present invention was achieved by discovering that the use of polyurethane polymers provides excellent effects that could not be expected at all.

That is, the present invention includes (1) a step of creating a nonwoven fabric containing fine fibers having a single fiber denier in the range of 0.0001 to 0.8 denier; (2) a step of forming a nonwoven fabric containing free incyanate groups in the nonwoven fabric A step of applying an aqueous liquid having a pH in the range of 50 to 70 of a bisulfite-blocked hydrophilic and heat-reactive urethane prepolymer.

(3) Nonwoven fabric with urethane prepolymer added to 10
This is a method for producing suede-like artificial leather, comprising the steps of: forming a polyurethane polymer in a nonwoven fabric by heat treatment at a temperature of 0 to 180°C; and (4) buffing the surface of the nonwoven fabric containing the polyurethane polymer.

Other embodiments of the present invention include (1) a single fiber denier of 0.
Following the step of creating a nonwoven fabric containing composite fibers or mixed fibers capable of forming ultrafine fibers in the range of 0.0001 to 0.8 denier, the step of (2) applying an aqueous solution of urethane prepolymer is performed. (4) By treating the nonwoven fabric containing the polyurethane polymer with an organic solvent, ultrafine fibers having a single fiber denier in the range of 0.0001 to 0.8 denier are formed from the composite fibers or mixed fibers. and (5) a buffing process.

To prepare the nonwoven fabric of the present invention, for example, the following composite fibers or ultrafine fibers are used.

■ As disclosed in JP-A-51-70366, a component made of fiber-forming polyester, a component made of fiber-forming polyamide, and a component made of fiber-forming polyamide are alternately adjacent to each other and at least Hollow composite fibers (ultrafine fibers are formed by mechanical action) that are arranged in a ring in four pieces, extend in the longitudinal direction of the fibers, and constitute a tubular body as a whole.

■ Microfiber-containing fibers obtained by mixing at least two incompatible fiber-forming polymers and spinning and drawing as disclosed in U.S. Pat. No. 3,382,305 (one of the polymers is ultrafine fibers are formed by dissolving and removing the

■ Wet-processing a mixture of two or more high molecular weight polymers as disclosed in U.S. Pat. No. 3,424,604;
Mixed spun fibers obtained by dry or melt spinning (ultrafine fibers are formed by extracting away at least one polymer).

■ Island-in-the-sea highly oriented composite fibers obtained by simultaneously spinning at least two different polymers, as disclosed in U.S. Pat. No. 3,562,374 (
Ultrafine fibers are formed by dissolving and removing sea components).

■ Consisting of a first polymeric component and a second polymeric component, each component having at least one sharp edge in the form, as disclosed in U.S. Pat. filaments that are joined along the entire length of the fibers so as to form a contact surface (by mechanical action or removal of one component a microfiber with a sharp edge morphology is formed).

■ U.S. Patent Specification No. 2578899 C Special Publication No. 28-
Ultrafine fibers obtained by the method of spardraw or known high-speed spinning methods, as disclosed in No. 617).

■ As disclosed in Japanese Patent Publication No. 52-30629, one ultra-fine single fiber A whose cross-sectional shape has at least three radial parts and the same number of radial cross-sectional shapes as the number of radial parts of A have the radial shape of A. A peelable composite fiber consisting of an ultrafine single fiber B having a shape that complements the parts (the ultrafine fiber is formed by mechanical action).

Examples of the nonwoven fabric manufacturing process include the following methods.

After the composite fibers or ultrafine fibers described above are crimped, they are cut to a length of, for example, 1.5 to 7.5 CTL, and then cut to a weight of 5 to 2 CTL by a carding machine.
00f/m" web.

Then, multiple sheets of this web are overlapped and passed through a locker room with needles at a rate of 200 to 2000 webs/cm.
t needle punching is performed.

The web thus obtained is shrunk to 30 to 60% of its original area in hot water at 60 to 80°C, for example, and then reduced to 0.05 to 0.3 kg/kg using a belt press dryer.
It is dried at 110 to 170° C. while being pressurized at a pressure of cT11 to form a nonwoven fabric.

The nonwoven fabric has a weight of 100 to 400 g/m2, a thickness of 0.5 to 2 mm, and an apparent density of 0.2 to 0.36 P/m2.
cIIN is preferred.

When the composite fibers of (1), (2) or (3) are used, these composite fibers are made into extremely fine fibers due to the mechanical action during the manufacturing process of the nonwoven fabric, but if this is insufficient, F11- The surface of the nonwoven fabric may be brushed with a napping machine, a thistle napping machine, a needle cloth napping machine, a roller sander equipped with sandpaper or sand cloth, or the like.

In this way, a nonwoven fabric containing the ultrafine fibers of the present invention is formed.

When using the composite fibers of ■, ■, ■, or ■ above,
After producing the nonwoven fabric, the nonwoven fabric is treated with an organic solvent capable of dissolving at least one kind of polymer in the composite fibers to dissolve and remove the polymer.

In this way, a nonwoven fabric containing the ultrafine fibers of the present invention is formed.

In the case of using the ultrafine fibers described in (1) above, a nonwoven fabric containing the ultrafine fibers of the present invention is directly formed.

In another embodiment of the present invention, a nonwoven fabric is created using the conjugate fibers of (1), (2), (2), or (3), and after passing through a step of applying a urethane prepolymer and a step of forming a polyurethane polymer, The nonwoven fabric is treated with an organic solvent capable of dissolving at least one kind of polymer, and this polymer is dissolved and removed.

Polymers for forming ultrafine fibers include polyesters such as polyethylene terephthalate, nylon 6 and nylon 66.
Particularly preferred are polyamides such as.

The denier of the ultrafine fiber is o, o o o ~ 0.8, preferably o, ooi ~ 0.6, more preferably 0.01
~0.5 denier.

If the denier is less than 0.0001, the surface abrasion and pill resistance of the nonwoven fabric will be poor, and if the denier is greater than 0.8, the texture of the nonwoven fabric will be rough, making it difficult to obtain a suede-like touch. .

In the present invention, next, an aqueous solution of urethane prepolymer is applied to the nonwoven fabric.

The nonwoven fabric may be dyed or printed by a conventional method before applying the aqueous solution of the urethane prepolymer, and if necessary, the dyed or printed nonwoven fabric may be sheared.

In some cases, after treating the nonwoven fabric with a urethane prepolymer to form a polyurethane polymer in the nonwoven fabric,
Dyeing or printing may also be performed.

The urethane prepolymer used in the present invention is a hydrophilic and thermally reactive urethane prepolymer whose free isocyanate groups are blocked with bisulfite.

In particular, a urethane prepolymer containing 10 to 40% by weight of oxyethylene chains is preferred in terms of ease of production and performance after the polyurethane polymer is formed.

Bisulfite as a blocking agent for incyanate groups is
Compared to other known blocking agents such as phenols, alcohols, and amides, its dissociation temperature is very low, and it quickly forms polyurethane polymers when heated, making it very suitable as a processing agent for textile products. There is.

Moreover, since the bisulfite-blocked urethane prepolymers are hydrophilic, they have the additional advantage that they can be used as aqueous liquids, ie, aqueous solutions or emulsions.

A method for producing an aqueous liquid of a hydrophilic and heat-reactive urethane prepolymer in which free incyanate groups are blocked with bisulfite used in the present invention is disclosed in JP-A No. 50-15
5794 and Japanese Patent Application Laid-Open No. 50-108395.

The outline of the manufacturing method is as follows.

■ Number average molecular weight is 20 with active hydrogen atoms at both ends.
0 to 20,000, an excess amount of polyisocyanate with respect to the compound, and optionally a low molecular weight chain extender, a substantially A low molecular weight urethane prepolymer containing no gel content is produced.

Examples of compounds having active hydrogen atoms at both ends include known polyester polyols, polyester polyols, and polyester ester polyols.

Among these, those containing 10 to 40% by weight of oxyethylene chains in the molecule are particularly preferred.

Examples of the polyisocyanate include known aliphatic polyinsyanates such as hexamethylene diisocyanate;
Aromatic polyisocyanates such as 4'-diphenylmethane diisocyanate, araliphatic polyisocyanates such as xylylene diisocyanate, and alicyclic polyisocyanates such as 4,4'-dicyclohexylmethane diisocyanate can be used.

As chain extenders, known ethylene glycol, 1,4
- Glycols such as butanediol and 1,6-hexanediol, polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol, diamines such as ethylenediamine, hexamethylenediamine, and piperazine, monoethanolamine, jetanolamine, etc. amine alcohols can be used.

Active hydrogen atoms (including active hydrogen atoms with chain extenders)
The ratio of the number of moles of incyanate group to the number of moles of is 1
Although the content of free isocyanate groups in the prepolymer obtained is preferably 10% by weight or less, it is desirable that % is less than 7% by weight.

■ The urethane prepolymer produced in (■) is mixed with an aqueous bisulfite solution at 60℃ either as it is or after diluted with a solvent.
The reaction is carried out by mixing and stirring at the following temperature for 5 minutes to 1 hour.

As the bisulfite, ammonium bisulfite, sodium bisulfite, and potassium bisulfite are preferably used.

The bisulfite aqueous solution preferably contains bisulfite in an amount not more than 3 times the equivalent of free incyanate groups and has a concentration of 15 weight percent or more.

As a solvent for diluting the prepolymer, dioxane, methyl ethyl ketone, M ethyl, toluene, dimethylformamide, etc. are used.

(2) A water-in-oil emulsion or an oil-in-water emulsion of the urethane prepolymer is obtained by the reaction (2).

The emulsion thus obtained is diluted as it is or after removing the solvent with water to an appropriate concentration to form an aqueous solution (aqueous solution or oil-in-water emulsion) of the urethane prepolymer.

From the viewpoint of stability of the aqueous liquid, it is preferable to then add hydrogen peroxide and an organic acid and store the aqueous liquid in an acidic state, preferably in a state where the pH is 5 or less.

On the other hand, if the aqueous liquid is applied to the nonwoven fabric while the pH is below 5, the repellency of the polyurethane polymer formed in the nonwoven fabric will not be sufficient, and the water fastness of the dyed product will also deteriorate, which is not preferable.

Therefore, the pH of the aqueous solution of urethane prepolymer applied to the nonwoven fabric is 5.0 to 7.0, particularly 6.0 to 6.
It is preferable to use it by adjusting it to a range of 5.

Inorganic alkalis such as sodium bicarbonate, sodium carbonate, and caustic soda are preferably used to adjust the pH.

The urethane prepolymer of the present invention is applied in an amount in the range of 10 to 100, preferably 20 to 80% by weight, based on the dry weight of the nonwoven fabric containing ultrafine fibers.

If it is less than 10 weight ratio, sufficient rebound resilience will not be imparted to the nonwoven fabric containing ultrafine fibers, and if it exceeds 100 weight ratio, the writing effect will deteriorate, which is not preferable.

In another embodiment of the invention, the urethane prepolymer is
It is applied in an amount in the range of 5 to 50%, preferably 10 to 40% by weight, based on the dry weight of the nonwoven fabric containing composite fibers or mixed fibers capable of forming ultrafine fibers.

A method for applying the aqueous liquid of urethane prepolymer is to impregnate a nonwoven fabric with the aqueous liquid.

There are coating methods, spraying methods, etc.
The method of impregnating the nonwoven fabric with an aqueous liquid is preferable because it allows the urethane prepolymer to be uniformly applied to the inside of the nonwoven fabric.

The aqueous solution of urethane prepolymer is preferably used with a weight coefficient of 1 to 30.

The nonwoven fabric to which the aqueous solution of urethane prepolymer has been applied is dried to remove moisture.

Although the drying temperature is not particularly limited, it is usually carried out at a temperature of 60 to 120°C for 1 to 15 minutes.

Then, in the present invention, the nonwoven fabric provided with the urethane prepolymer is heated to a temperature of 100 to 180°C - preferably 110°C.
When heat treated at a temperature of ~140°C, the urethane prepolymer in the nonwoven fabric dissociates the bisulfite blocks, regenerates the reactive incyanate groups, and becomes a polyurethane polymer through a self-crosslinking reaction.

A heat treatment time of 10 seconds to 15 minutes is sufficient.

If the heat treatment temperature is less than 100°C, the crosslinking rate of the urethane prepolymer will be slow, and if it exceeds 180°C, the mechanical performance of the nonwoven fabric will tend to deteriorate, which is not preferred.

In the case of a dyed nonwoven fabric, it is particularly preferable to heat treat it at a temperature of 110 to 140°C in order to maintain good color fastness.

In the present invention, a catalyst can also be used to promote the crosslinking reaction of the prepolymer.

Catalysts include tertiary amines such as diazabicyclooctane and organometallic compounds such as dibutyltin dilaurate.In the present invention, at least one surface of the nonwoven fabric containing the polyurethane polymer is buffed by a conventional method. be done.

Buffing can be carried out using known means such as a sand roll with 40 to 400 mesh sandpaper, a sand belt, or a sand cloth.

By buffing the surface of the nonwoven fabric, the fluffs of the ultrafine fibers on the surface of the nonwoven fabric, which are bundled in a certain direction by the polyurethane polymer, are randomized and the lengths of the fluffs are made uniform.

The result is a texture and appearance similar to natural suede, as well as excellent lighting effects.

Thereafter, if necessary, the non-woven fabric can be subjected to a brushing operation and/or
Or a decatizing operation is performed.

Furthermore, in the present invention, it is also possible to perform treatments such as water repellency, oil repellency, waterproofing, stain resistance, antistatic, slimy imparting, flame retardant, flame retardant, etc. simultaneously with or after the treatment with the urethane prepolymer. .

The method of the present invention using a urethane prepolymer has the following features compared to the conventional method using a polyurethane polymer emulsion or an organic solvent solution.

■ Since the urethane prepolymer of the present invention has a relatively low molecular weight, it can penetrate uniformly into the interior of the nonwoven fabric, and the effects of polyurethane are significantly exhibited, giving the nonwoven fabric excellent rebound and wrinkle recovery properties. can.

■Since the urethane prepolymer of the present invention is used as an aqueous liquid, it has a relatively low viscosity, and even when a relatively high concentration of an aqueous liquid is contained in the nonwoven fabric, the surface part does not become paper-like, and it has an excellent lighting effect. can get.

(2) The aqueous solution of the urethane prepolymer of the present invention has very good solution stability, so problems such as gum-up do not occur during processing.

The suede-like artificial leather obtained by the present invention has a texture and appearance similar to natural suede, has an excellent lighting effect, and is also excellent in repulsion and wrinkle resistance.

Therefore, the artificial leather of the present invention can be used for jackets, for example.
Jumpers, blazers, skirts, pants, shorts,
It has a wide range of uses, including clothing such as slacks, dresses, suits, waistcoats, coats, and gloves, as well as bags, boots, and chair covers.

The following shows examples of the invention.

Note that all parts in the examples mean parts by weight.

Example 1 [Preparation of non-woven fabric] Polyethylene terephthalate with an intrinsic viscosity of 0.62 (measured at 35°C in orthochlorophenol) and an intrinsic viscosity of 130 were prepared according to the method disclosed in JP-A-51-70366.
Using poly-ε-caproamide (measured in metacresol at 35°C), 16 polyester component parts and 16 polyamide component parts are arranged adjacent to each other alternately in a ring as shown in FIG. A hollow composite fiber was produced which stretches in the direction and constitutes a tubular body as a whole.

In FIG. 1, 1 is a hollow composite fiber, 2 is a polyamide (poly-ε-caproamide) component, 3 is a polyester (polyethylene terephthalate) component, and 4 is a hollow portion.

In the hollow conjugate fiber shown in Figure 1, the weight ratio of all polyamide components to all polyester components is 1:1, the denier of each component is 0.23 denier, and the denier of the hollow conjugate fiber is 37 denier. Ta.

Further, the hollowness ratio - the ratio of the volume of the hollow part to the total volume of all the polyamide constituent parts, all the polyester constituent parts, and the hollow part - was 8%.

The hollow composite fiber obtained as described above was crimped at 12 threads/inch and then cut into a length of 25 CTL to form a stable.
A web having a weight of 20 Of/m2 was prepared.

This web was passed through a needle locker room, needle punched at 800 needles/cnf, and then immersed in warm water at 68° C. for 5 minutes to shrink to 62% of its original area.

This shrink web was dried using a belt press dryer.
Dry at 130℃ under pressure of kg/crA, weighing 2
9097m - thickness is 1.1mm, apparent density is 0.26
A nonwoven fabric of f/cnf was obtained.

When the inner layer and surface of this nonwoven fabric were observed under a microscope, most of the hollow composite fibers were split and the single fiber denier was 0.2.
The fibers were ultrafine fibers of 3 to 0.69 deniers.

[Production of urethane prepolymer]

■ 21 parts of block copolymerized polyether diol with a number average molecular weight of 2,400 obtained by adding ethylene oxide to polypropylene glycol with a number average molecular weight of about 1,200, ■ Adipic acid, 1,6-hexanediol, and neopentyl glycol. A mixture consisting of 56 parts of polyester diol obtained by reaction at a molar ratio of 10:4, (1) 3 parts of 1,6-hexanediol, and (2) 20 parts of hexamethylene diisocyanate (inocyanate group relative to active hydrogen atom). The molar ratio of is 206
) were reacted at 100 to 105°C for 1 hour under a nitrogen stream to produce a urethane prepolymer having free incyanate groups.

The content of free incyanate groups in the obtained urethane prepolymer was 5.02%, and the content of oxyethylene chains was 10%.
．． It was 2%.

The obtained urethane prepolymer was cooled to 40°C,
Diluted with 20 parts of dioxane.

Then, 65 parts of a 25% by weight aqueous solution of sodium bisulfite was added to the diluted urethane prepolymer and
The mixture was thoroughly stirred for 0 minutes.

Thereafter, 202 parts of water was added to the reaction system, and an appropriate amount of hydrogen peroxide was further added to obtain an aqueous solution of urethane polymer having a pH of 3 and a concentration of about 30% by weight.

[Manufacture of suede-like artificial leather]

The nonwoven fabric obtained as described above was immersed in a 25% by weight aqueous solution of the aforementioned urethane prepolymer (pH was adjusted to 6.0 with sodium bicarbonate), and then
The liquid was squeezed out to a pickup rate of 90% based on the weight of the nonwoven fabric.

After drying at 100℃ for 3 minutes, drying at 140℃ for 30 minutes.
Heat treated for seconds.

Thereafter, the surface of the heat-treated nonwoven was buffed once by a roller sander with 100 mesh sandpaper7 and then flushed.

The obtained artificial leather was suede-like artificial leather having excellent rebound resilience, wrinkle recovery properties, and lighting effect.

The measurement results of various physical properties of this artificial leather are shown in Table 1.

In particular, the repellency, wrinkle resistance, and lighting effect are superior to those of Comparative Example 1, which will be described later.

Comparative Example 1 In place of the urethane prepolymer of Example 1, a 25-wt ice-water emulsion of a polyurethane polymer (a reaction product of methylene-diphenyl-diisocyanate, polyethylene glycol and 1°4-butanediol) was used, and the same as that of Example 1 was used. Suede-like artificial leather was produced in a similar manner.

The measurement results of various physical properties of this artificial leather are shown in Table 1.

This suede-like artificial leather had low rebound resilience and poor wrinkle resistance.

Examples 2 to 4 Using the nonwoven fabric and urethane prepolymer produced in Example 1, artificial leather was produced in the same manner as in Example 1, except that the amount of urethane prepolymer added to the nonwoven fabric was varied. .

The measurement results of various physical properties of these artificial leathers are shown in Table 1.

Examples 2 (applied polymer weight: 30% by weight), Example 3 (45% by weight) and Example 4 (within the scope of the present invention)
60% by weight), suede-like artificial leather having excellent rebound resilience, wrinkle recovery properties, and lighting effect was obtained.

Example 5 According to the method disclosed in U.S. Pat. ,00
A sea-island type conjugate fiber as shown in FIG.

In FIG. 2, 5 is a sea-island type composite fiber, 6 is an island component (polyethylene terephthalate), and 7 is a sea component (polystyrene).

In the sea-island type composite fiber shown in Figure 2, the number of island components is 8, the weight ratio of the whole island component to the sea component is 6:4, the denier of one island component is 0.24 denier, and the sea-island type composite fiber has a weight ratio of 6:4. The denier of the composite fiber was 3.8 denier.

The sea-island type composite fiber obtained as described above was clipped with 12 threads/inch, heat-set at 120° C. for 30 minutes, and then cut into 51 mm pieces to obtain staples.

400 copies m2 of this staple using a cross-lapper.
Webb.

Pass this web through the needle locker room and
A nonwoven fabric was prepared by needle patching of this/crA.

Thereafter, in the same manner as in Example 1, an aqueous urethane prepolymer solution was applied to this nonwoven fabric and heat treatment was performed.

The obtained nonwoven fabric containing the polyurethane polymer was washed five times with trichlorethylene to dissolve and remove the polystyrene as a sea component.

Thereafter, the nonwoven fabric was buffed and brushed in the same manner as in Example 1.

The obtained artificial leather was suede-like artificial leather having excellent rebound resilience, wrinkle recovery properties, and lighting effect.

The measurement results of various physical properties of this artificial leather are shown in Table 1.

Example 6 [Preparation of nonwoven fabric] Poly-ε-caproamide was spun at a temperature of 260°C and
High-speed spinning at a spinning speed of 0 m/min, 40 denier 15.
7 filament (single fiber denier is 0.77')
A multifilament yarn was obtained.

A nonwoven fabric was made from this multifilament yarn under the same conditions as in Example 1.

[Production of urethane prepolymer]

■ 36 parts of polyester diol obtained by reacting adipic acid, 1,6-hexanediol and neopentyl glycol in a molar ratio of 4:3:2; ■ 41 parts of polyethylene glycol having a number average molecular weight of approximately 1000; and (1) A mixture consisting of 23 parts of xylylene diisocyanate (molar ratio of incyanate groups to active hydrogen atoms is 1.60) was reacted at 95 to 100°C for 1 hour under a nitrogen stream to remove free incyanate groups. A urethane prepolymer having the following properties was produced.

The content of free isocyanate groups in the obtained urethane prepolymer was 3.76%, and the content of oxyethylene chains was 39%.
．． It was 6%.

The obtained urethane prepolymer was cooled to 40°C,
50 parts of a 30% by weight aqueous solution of potassium bisulfite was added and thoroughly stirred at 40°C for 20 minutes.

Thereafter, 233 parts of water was added to the reaction system, and appropriate amounts of hydrogen peroxide and tartaric acid were added to obtain an emulsion of urethane prepolymer having a pH of 2 and a concentration of about 30% by weight.

[Manufacture of suede-like artificial leather]

The above nonwoven fabric was mixed with a 25Ii weight % emulsion (pH: carbonic acid) of the urethane prepolymer obtained as above.
65) and then the nonwoven was squeezed to a pick-up rate of 90% based on the weight of the nonwoven.

After drying at 100°C for 3 minutes, drying at 120°C for 2 minutes.
Heat treated for minutes.

The surface of the heat-treated nonwoven was then buffed and brushed once by a roller sander with 100 mesh sandpaper.

The obtained artificial leather was suede-like artificial leather having excellent rebound resilience, wrinkle recovery properties, and lighting effect.

The measurement results of various physical properties of this artificial leather are shown in Table 1.

[Brief explanation of drawings]

FIG. 1 is a reproduction of a hollow composite fiber, FIG. 2 is a reproduction of a sea-island type composite fiber, and FIG. 3 is an explanatory diagram showing a method for measuring bending hardness and bending elasticity.

Claims (1)

[Claims] 1. (1) A step of producing a nonwoven fabric containing ultrafine fibers having a single fiber denier in the range of 0.0001 to 0.8 denier; a step of applying an aqueous liquid having a pH in the range of 5.0 to 7.0 of a bisulfite-blocked hydrophilic and heat-reactive urethane prepolymer; (3) a nonwoven fabric provided with the urethane prepolymer; 10
A method for producing suede-like artificial leather, comprising the steps of: heat-treating at a temperature of 0 to 180°C to form a polyurethane polymer in the nonwoven fabric; and (4) buffing the surface of the nonwoven fabric containing the polyurethane polymer. 2. The method for producing suede-like artificial leather according to claim 1, wherein the urethane prepolymer contains 10 to 40 weight percent oxyethylene chains in the molecule. 3. The method for producing suede-like artificial leather according to claim 1, wherein the amount (dry weight) of the urethane prepolymer is 10 to 100% by weight based on the weight of the nonwoven fabric. 4. The method for producing suede-like artificial leather according to claim 1, wherein the heat treatment temperature is 110 to 140°C. 5(1) A step of creating a nonwoven fabric containing composite fibers or mixed fibers capable of forming ultrafine fibers having a single fiber denier in the range of 0.0001 to 0.8 denier; A step of applying an aqueous liquid having a pH in the range of 5.0 to 7.0 to a hydrophilic and heat-reactive urethane prepolymer in which incyanate groups are blocked with bisulfite; (3) applying the urethane prepolymer; made of non-woven fabric. (4) forming a polyurethane polymer in the nonwoven fabric by heat treatment at a temperature of 100 to 180°C; (4) treating the nonwoven fabric containing the polyurethane polymer with an organic solvent to convert the composite fiber or mixed fiber to a single fiber denier of 0. A method for producing suede-like artificial leather, comprising the steps of: forming ultrafine fibers having a denier of 0.0001 to 0.8 denier; and (5) buffing the surface of the obtained nonwoven fabric. 6. The method for producing suede-like artificial leather according to claim 5, wherein the urethane prepolymer contains 10 to 40 weight percent oxyethylene chains in the molecule. 7. The method for producing suede-like artificial leather according to claim 5, wherein the amount (dry weight) of the urethane prepolymer is 5 to 50% by weight based on the weight of the nonwoven fabric. 8. The method for producing suede-like artificial leather according to claim 5, wherein the heat treatment temperature is 110 to 140°C.