JPH02145877A - Synthetic leather manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in a method for producing synthetic leather by a wet process.

(Conventional technology) Synthetic leather made using the wet process is very soft and has a leathery texture, so it is used for shoe materials, bags, clothing, etc. (softness)
Synthetic leather is used in fields where design is important, and the production of synthetic leather by conventional wet manufacturing methods has generally been carried out by the method according to Prior Art I, which will be described later. Furthermore, as a related matter, a technique related to prior art (1) (Japanese Unexamined Patent Publication No. 160480/1983) has been disclosed.

Conventional technology I refers to ``a wet compound solution such as a dimethylformamide (hereinafter referred to as DMF) solution in which a polyurethane resin is dissolved is applied to a raised cloth, and then coagulated and washed to discharge the DMF together with water. As a result of the above-mentioned coagulation, washing, and drying process, many marks are formed on the polyurethane resin where DMF has escaped along with water. Synthetic leather has a microporous polyurethane sponge layer that gives it a soft texture.

In addition, the invention of prior art (ii) relates to a method for manufacturing a coated fabric using a wet manufacturing method, and involves ``coating a fabric with a mixture of a polyurethane solution containing an acrylic compound and an inorganic or organic fine powder, and then wet coagulating it. (Problems to be Solved by the Invention) As mentioned above, the synthetic leather produced by the wet process of Prior Art I has many microporous sponge layers, so it has a soft feel. Since it is a structure containing air in polyurethane, the cohesive failure strength is low and the glabella strength is low. Therefore, it is possible to increase the solid content in the polyurethane solution by reducing the amount of DMF added to make the microporous layer denser, but in this case, the coagulation speed of the polyurethane will be slow, resulting in poor processability.
In addition, there may be a problem that the surface becomes noticeably rough due to insufficient coagulation, resulting in poor appearance.

Further, the purpose of Prior Art H is to provide a method for manufacturing synthetic leather with excellent water resistance and moisture permeability, and its purpose is different from that of the present application. Therefore, in prior art (2), a fabric is coached with a polyurethane solution containing an acrylic compound to form a large number of micropores, and organic or inorganic fine powder is interposed in the micropores, thereby degrading the moisture permeability. The aim is to improve water resistance without sacrificing water resistance. However, the presence of such fine powder deteriorates the strength of the polyurethane coating, which is contrary to the purpose of the present application.

In view of the above, an object of the present invention is to provide a method for producing synthetic leather that is soft and has a leathery feel, has high glabella strength, and has an excellent appearance using a wet production method.

(Means for Solving the Problems) In order to solve the above problems, the gist of the present invention is to coat a woven fabric, Akebono fabric, or a nonwoven fabric with a DMF solution of polyurethane containing a polyacrylic acid ester or a derivative thereof. A method for producing wet synthetic leather, characterized by wet coagulation after dipping.

(Function) Is polyacrylic acid ester or its derivative the DMF of polyurethane? By adding it to solution a, the solid content in the solution increases, so the cell walls of the polyurethane sponge layer become thicker, the microporous layer becomes denser, and the glabella strength can be improved.

In addition, polyacrylic acid ester or its derivative is DMF
Since it is stable in liquid and has good compatibility with water, water easily enters the cells, promoting coagulation of polyurethane by water, increasing the polyurethane film formation rate, improving workability, and creating a smooth surface. Synthetic leather with improved properties and excellent appearance can be obtained.

(Example) Examples 1 and 2 of the present invention will be described below in order of steps. The base fabric used in this example is a single-sided raised fabric with a blend ratio of Tetron to rayon of 65 to 35. The difference between Examples 1 and 2 is that the composition of the polyurethane resin of the wet sponge layer is different.

■After impregnating the one-sided raised fabric with water, it was squeezed with a squeezing roll to bring the moisture content to 80%. In addition, in this application, the moisture content refers to the following.

(Weight of attached water)/(Weight of raised fabric))X100%
■ Apply appropriately colored polyurethane resin (Example 1 = Formulation A, Example 2 = Formulation B) to the raised side of the above raised fabric using a bar coater so that the total thickness is 1.5111 m, A wet sponge layer was formed.

(2) The above-mentioned raised fabric was immersed in a 20°C coagulation solution (mostly water and may contain DMF) for 5 minutes.

(2) The above-mentioned raised fabric was sequentially immersed in five baths of Washing M (water) at 50°C, pulled up from each layer, and the DMF in the microporous layer was removed using a squeezing roll, which was repeated.

■Put the above-mentioned raised cloth into a drying oven with a tenter and dry it for 120 minutes.
Dry at °C for 5 minutes. Through the above steps 1 to 2, a wet raw fabric was completed.

■The thickness after drying is 20μ using a bar coater on the release paper.
A skin layer was formed by applying a polyurethane resin (Formulation F) suitably colored so as to have a color of m.

■ Apply a suitably colored polyurethane resin (Formulation C) on the above skin layer using a bar coater so that the thickness after drying is 20 μm to form an adhesive layer, and then heat at 100°C.
and dried for 1 minute.

■The above adhesive layer and the wet sponge layer of the wet original fabric were bonded together.

■The above adhesive layer and wet raw fabric were laminated together at 40℃ for 24 hours.
After aging for an hour, the release paper was peeled off.

The product according to the present invention has now been completed.

Comparative Examples 1 to 3 are polyurethane resins of the wet sponge layer (Comparative Example 1 = Formulation C1, Comparative Example 2 = Formulation D, Comparative Example 3 = Formulation E
) is different from this example, and the process is the same as that of Example 1 above.
and 2.

In addition, in the above explanation, polyurethane resin formulation A-
C refers to the composition shown below.

Next, the physical property values of the products of Examples 1.2 and Comparative Examples 1 to 3 of the present invention obtained as a result of the above manufacturing process are shown in the table on the next page. In addition, the symbols in the table on the next page (◎, O1Δ
, ×) are roughly as follows.

In the table showing the physical property values above, the measurement of the glabella strength is based on JI
Performed according to 180' peeling test of S K 6772, sample width was 1 cm, speed was 50 ma.
/min.

As mentioned above, one of the objects of the present invention is to provide a wet-processed synthetic leather with high interlaminar strength. It is said that it can also be used in fields where high-rise strength is required. Therefore, in order to obtain synthetic leather with glabellar strength of 2.0 kg/cm or more, in Examples 1 and 2 according to the present invention, methyl methacrylate resin (polymethacrylate ester resin) was added to the polyurethane solution, so that the solid content was reduced. As a result, the cell walls become thicker, the microporous layer becomes denser, and the interlayer strength improves, and the glabella strengths of the products of Examples 1 and 2 were as high as 2.3 and 2.6, respectively. The reason why the glabellar strength of Example 2 is slightly higher than that of Example 1 is because the DMF ratio in the polyurethane solution of Example 2 is lower than that of Example 1, and as a result, the solid content of Example 2 is lower than that of Example 1. As the ratio increases, the density of the microporous layer increases, and the interlayer strength also becomes slightly higher. In addition, methyl methacrylate resin is stable in DMF liquid and has good compatibility with water, making it easier for water to enter the cells and promoting coagulation of polyurethane with water, resulting in improved processability (curing speed). As a result, it was possible to obtain synthetic leather with improved surface smoothness and an excellent appearance.

The amount of methyl methacrylate resin added in Comparative Example 1 was twice that of Example 2, and the solid content was further increased than in Example 2.
As a result, the interlaminar strength was 2.9, which was higher than the value of the synthetic leather product of Example 2. However, in Comparative Example 1, the amount of methyl methacrylate resin added was too large, so the solid content was too high, and the product was inferior to Examples 1 and 2 in terms of texture (softness) and appearance, and the overall All I could get was something unsatisfactory.

In addition, Comparative Examples 2 and 3 are examples in which methyl methacrylate resin is not added, and the glabella strength in both cases is low.
The glabella strength that is the goal of this application has not been achieved. In addition, in Comparative Example 3, an attempt was made to relatively increase the solid content by reducing the amount of DMF added in order to ensure a solid content ratio commensurate with the addition of methyl methacrylate resin, but the resulting product still The intensity between the eyebrows is only 1.7, which is an insufficient level compared to the target value of this application.

In addition, in Comparative Example 3, the solidification rate of polyurethane was slow due to the low ratio of DMF in the polyurethane solution.
Only unsatisfactory results were obtained in terms of cutting speed and surface smoothness.

In addition, in Examples 1 and 2 above, methyl methacrylate resin, which is a derivative of polyacrylic ester, was added to the polyurethane resin mixture, but in addition to the above substances, ethyl methacrylate, n- Propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate and i
-Butyl methacrylate can also be used. Also,
Even when polyacrylic ester is added to a polyurethane resin formulation, it exhibits the same actions and effects as polyacrylic ester derivatives, and as a polyacrylic ester,
Methyl acrylate, ethyl acrylate, n-acrylate
Propyl, propyl acrylate, n-butyl acrylate, i-butyl acrylate, and the like can be used.

The drawing is a sectional view showing an example of a synthetic leather product according to the present invention manufactured through the steps of Examples 1 and 2 described above, and 1 is a skin layer, 2 is an adhesive layer, 3 is a wet sponge layer, and 4 is a Raised, 5 is the weft, and 6 is the warp.

(Effects of the invention) By adding polyacrylic acid ester or its derivative (methyl methacrylate resin) while keeping the amount of DMF added to the polyurethane resin compounded liquid, the solid content is increased and the coagulation rate of polyurethane is reduced. It is possible to produce wet synthetic leather with high glabella strength by densifying the microporous layer without any problems. Furthermore, since polyacrylic acid ester or its derivative promotes coagulation of polyurethane in water, processability is improved, surface smoothness is improved, and wet-processed synthetic leather with excellent appearance can be obtained.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of a synthetic leather product manufactured according to the present invention.

Claims (1)

[Claims] A method for producing wet synthetic leather, which comprises coating or dipping a woven fabric, knitted fabric, or non-woven fabric with a dimethylformamide solution of polyurethane containing a polyacrylic acid ester or a derivative thereof, and then wet-coagulating the solution.