JPS5926708B2 - Synthetic leather manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing soft and microporous synthetic leather.

Generally, pseudo-leather sheets are made by applying a polymer solution to a base material such as woven fabric, non-woven fabric, or knitted fabric, and then immersing it in a coagulating liquid (insoluble in the polymer but compatible with the polymer solvent). The polymer was produced by extracting and displacing the solvent to solidify the polymer into a porous structure, completely removing the solvent in a water bath, and then drying.

However, in the above method, when a highly elastic material such as stockinette fabric is used as a base material, it is technically difficult to apply the polymer solution directly to the surface of the base material and form fake leather. It has been known.

In addition, if the polymer solution is directly applied to the base material, the base material will be fixed with the fibers and resin firmly bonded as the polymer solution soaks into the base material, resulting in a hard texture and a soft texture. It has the disadvantage that its properties are significantly impaired.

Furthermore, a water tank for removing the solvent and a large amount of equipment for separating and recovering the solvent and non-solvent are required, which is not economical.

The present invention has been achieved as a result of research into an economically advantageous manufacturing method that eliminates such drawbacks, and an example of its implementation will be described with reference to the drawings. A soft polymer such as urethane elastomer is coated with dimethylformamide (DMF) on the surface of the moldable strip 1.
, a polymer solution 2 dissolved in a solvent such as tetrahydrofuran (THF) is applied. The polymer solution can be applied to the releasable strip by using a doctor blade 101 shown in FIG. 1 or by any other suitable method such as a reverse roll method. Next, on the coated surface of the polymer solution, a base material 3 made of a base fabric such as a double-sided stockinette knitted fabric, woven fabric, or nonwoven fabric having air permeability and hygroscopicity is impregnated in advance with a coagulating liquid such as water, preferably. After immersing the base material in the coagulation liquid, it was squeezed with a mangle to impregnate an appropriate amount of the coagulation liquid, and the base material was sprayed and impregnated with the coagulation liquid from one side of the base material using a sprayer (not shown) (impregnated amount of the coagulation liquid). (approximately 100 to 2007/Rrl) is pasted using a pressure roll 102 and a backup rubber roll 103.

The amount of coagulation liquid impregnated as described above is suitable for preventing excessive penetration of the polymer solution into the substrate, but is insufficient for coagulating the polymer solution layer. Therefore, after pasting the base material, a sprayer 104 is used to spray/impregnate the base material with a sufficient amount of coagulating liquid 5 to solidify the coating layer from the back side of the base material, or a sponge roll such as a PVA sponge roll is coated. A roll filled with coagulation liquid is used to transfer the coagulation liquid to the substrate. In addition, when immersed in a water tank for a short time (a few seconds is sufficient as the purpose is not to achieve a complete solidification state in the water tank), the amount of coagulation liquid impregnated into the base material is approximately 400%.
- Impregnate to 6007/A. Of course, it is sufficient to coagulate the coating film in the base material in advance without impregnating the coagulating liquid in two stages as described above, that is, 400 to 6007/
It may be applied in a state where it is impregnated with a certain amount of coagulation liquid. As soon as the base material 3 and the coating layer 2 come into contact, a whitening phenomenon and coagulation occur.

This phenomenon occurs when the polymer solvent in the coating film and the coagulating liquid impregnated in the base material are extracted and replaced, rapidly reducing the solubility of the polymer solution, and causing the polymer to coagulate and become porous at the same time. It shows that the quality is being improved. When the coagulation further progresses and the coating layer is in a morphologically fixed state (that is, in a gelled state), this coating film laminate (consisting of the coating layer and the base material) is removed by a peeling roll 105. Backup Prowl 1
06 to peel it off from the releasable strip (Fig. 3)
. When the polymer solvent and coagulation liquid are extracted and replaced to solidify the coating layer, a mixed liquid film consisting of the solvent and coagulation liquid is formed at the interface between the coating layer and the release strip. Peeling work can be performed extremely easily.

At this point, the porosity of the coating layer has been completed, and even if some pressing force is applied, the deformation is extremely small, so the solidification state can be determined. Next, on the coating surface 2 that has been released from the release strip 1, a smooth, breathable and water-absorbent surface is coated with a nonwoven fabric, felt, cardboard, etc. made of unnecessary fibers in the solvent of the polymer solution. Roll 1 pressing body 5
07. While being lightly abutted and pressed by the back-up roll 108, it is wound into a roll onto the winding shaft 109 as shown in FIG.

In this case, care should be taken to ensure that the winding tension is not excessive. If the tension is too strong, the interposer 5 may shrink due to moisture absorption, which may cause deformation such as waving in the coating layer, so care must be taken. By winding with this interposer 5 interposed, the solvent and coagulating liquid remaining in the coating film laminate are sucked up into the interposer by the capillary action of the interposer fibers.

After curing for 12 to 24 hours, the coating laminate is peeled off from the interposer, lightly pressed between metal press rolls, and dried to create a soft, smooth surface that takes advantage of the texture of double-sided stockinette. Finely porous synthetic leather can be obtained.

The above porous reaction can be carried out quickly by adding and mixing fillers such as calcium carbonate and pulp fibers that are insoluble in solvents into the polymer solution as a means of creating porosity. Transparency can be increased. FIG. 5 shows an enlarged view of each portion indicated by a circle in FIGS. 1 to 4, that is, A, B, C, D, and E. FIG. 5A shows that the coating film 2 of the polymer solution applied on the releasable strip 1 is homogeneous and bubble-free.

Figure 5-B shows a state in which the base material 3 impregnated with the coagulating liquid 4 is laminated on the coating film 2 applied on the releasable strip 1, and the coagulation and porosity have progressed to some extent. The state is shown in which the coating film 2 has been transformed into a porous coating film (or gelled coating film) 2' by extraction and displacement of the coagulating liquid and the solvent.

Figure 5-C shows that the coating film has become porous (or gelatinized),
This shows the state in which the releasable strip 1 has been peeled off and removed after the coating film has been morphologically fixed, and the base material 3 is filled with a mixed liquid 4' of a coagulating liquid and a solvent. A thin mixed liquid film 42 of a coagulating liquid and a solvent is present on the surface of the porous coating film 2 .

FIG. 5-D shows a state in which an air-permeable and highly water-absorbent interposer 5 such as a non-woven fabric is in contact with the porous coating film z, following FIG. 5-C. The figure shows that the coagulating liquid-solvent mixture 42 present in a thin film form is absorbed into the interposer 5 as shown by the arrow.

Of course, in this case, the coagulating liquid-solvent mixture present in the porous coating layer is also sequentially moved and absorbed in the direction of the arrow. Figure 5-E shows the overlapping state of the interposer 5 and the coating film laminate 2 when the interposer 5 is in contact with the winding shaft 109 and the interposer of the coagulating liquid-solvent mixture. This figure shows the state of movement of the coagulating liquid and solvent into the interposer 5 on D1, and at the same time the coagulating liquid and solvent mixture 47 moves and absorbs from the porous coating film 27 of D1, the interposer 5 is placed on D1 in a close state. It is shown that the mixed liquid 4' of coagulating liquid and solvent contained in the base material 3 of D2 being wound up is moved and absorbed by the interposer in the direction of the respective arrows.

The effect of using the interposer 5 is that in addition to absorbing the coagulating liquid-solvent mixture as described above, it also absorbs the absorbed mixed liquid during curing for 12 to 24 hours while wound on the winding shaft. By gradually volatilizing it from both ends of the interposer (this is where the effects of the breathable material come into play), coagulation and fixation are further progressed.

As mentioned above, since the present invention uses a transfer method and the base material is impregnated with a coagulating liquid as a pretreatment, there is little excessive penetration of the polymer solution into the fabric grains, and the base material and porous body are The adhesive is bonded to the extent that it does not affect the texture of the base material.
Flexible synthetic leather can be obtained even if a flat, highly stretchable knitted fabric is used as a base material, which is difficult to achieve using conventional methods. , the method of the present invention is characterized in that the polymer solution of the coating film is coagulated with a coagulation liquid impregnated into the base material, and the coagulation liquid is uniformly diffused into the coating layer through the base material and coagulated uniformly. urge

As a result, the coating layer is formed into a microporous shape. In addition to the polyurethane elastomers mentioned above, the polymers used in the present invention include acrylic resin elastomers, thermoplastic polyester elastomers, chlorinated polyethylene elastomers, chlorosulfonated polyethylene elastomers, or acrylonitrile-butadiene elastomers and ethylene monoacetic acid. Vinyl copolymer elastomers, etc.
It is suitable that the polymer itself is flexible at room temperature and has appropriate extensibility and strength, and a soft vinyl chloride resin or the like that is compatible with these elastomers can be used in combination with the above elastomers.

The solvent necessary to dissolve these polymers and obtain a polymer solution includes the above-mentioned DMF. ．． In addition to THF, various solvents are used such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MlBK), cyclohexanone (anone), ethyl acetate, butyl acetate, toluene, xylene, cellosolve, and trichlene, but the optimal solvent is Since it differs depending on each polymer, it will be necessary to select it carefully.

The solid liquid for the polymer solution varies considerably depending on the polymer used and its solvent, but water, a mixed solution of ethyl alcohol and water, and petroleum solvents such as solvent naphtha are generally used. As mentioned above, the type of coagulating liquid used as a coagulating liquid differs greatly depending on the combination, so it should be selected carefully.

Dimethyl formaldehyde, the solvent for urethane elastomers, has an exothermic solubility with water, so when dimethyl formaldehyde and water are extracted and replaced, heat is generated and some of the solvent is scattered in the form of mist, making the base material breathable. Knitted fabrics, low-density nonwoven fabrics, and the like are preferred.

Since coagulation is promoted by the exothermic effect, if the coating layer thickness is about 0.6 mm or less, it coagulates into a morphologically fixed state in about 10 minutes.

In addition, the present invention does not remove the solvent by extracting and replacing the solvent remaining in the coating layer with water by immersing it in a water tank as in the conventional method.
A hygroscopic support is placed in contact with the coating surface of the coating structure, and the solvent remaining on the coating structure is absorbed together with the coagulation liquid using the capillary action of the support. In other words, it is characterized by removing the solvent using a dry method.

At this time, the solvent remaining in the coating layer is mixed with the coagulating liquid, so the solubility of the solvent in the polymer decreases, and the porous structure is destroyed as it remains morphologically fixed. Absorbed without being affected.

Furthermore, since a highly water-absorbing support is used, the solvent and coagulating liquid can be uniformly and quickly absorbed and diffused, so that the time required for removing the solvent can be shortened. The saturated impregnation amount of the support is preferably greater than the saturated impregnation amount of the base material.

Furthermore, it is economical because the solvent can be treated in the drying process without requiring a large amount of equipment to separate and recover the solvent and non-solvent.

Next, examples of the present invention will be shown.

Example The above composition was stirred, mixed and defoamed to obtain a uniform urethane elastomer solution.

This solution was applied to a thickness of 0.55 mm on the surface of release paper, and the coated surface was impregnated with water.
After adhering 0 (a) and (a), spray the back side of both sides of the knitted fabric with water to fill it up. The water impregnated into the double-sided knitted fabric performs extraction displacement with the solvent of the urethane elastomer solution to coagulate the urethane elastomer.

It solidifies into a morphologically fixed state in about 10 minutes, so peel off the release paper, then place a dry nonwoven fabric on it, roll it up while pressing lightly, and hold for 10 minutes to ensure that it remains on the coating structure. Absorb the solvent and coagulation liquid.

Then, the nonwoven fabric is peeled off and dried at 80 to 90°C. The resulting product is flexible and water vapor permeable (water vapor transmission rate 3750
It was a highly microporous synthetic leather with a rating of 7/I (24 hours).

[Brief explanation of the drawing]

The drawings show an example of the implementation of the synthetic leather manufacturing method of the present invention, and FIGS. 1 to 4 are cross-sectional views showing the process order, and FIGS. These are enlarged views of the parts indicated by circles in Figs. be.

Claims (1)

[Claims] 1. A polymer solution is applied to the surface of a releasable strip, and a coagulating liquid that is insoluble in the polymer and compatible with the polymer solution is applied to the applied surface. The impregnated base material is attached, and if necessary, the base material is further impregnated and filled with a coagulation liquid, and the coagulation liquid coagulates the polymer solution into a morphologically fixed state. The releasable strip is peeled off, an intercalator such as a breathable and water-absorbing nonwoven fabric is brought into contact with the peeled surface, and the material is rolled up while being lightly pressed. A method for producing synthetic leather, which comprises holding the material until it is absorbed, peeling off and removing the interposer, and then drying the base material and the polymer layer. 2. A method for producing synthetic leather, characterized in that the base material according to claim 1 is made of double-sided knitted material. 3. A method for producing synthetic leather, characterized in that the polymer according to claim 1 is a polyurethane elastomer.