JPS5940949B2 - Synthetic leather manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing synthetic leather, and relates to a synthetic leather having a smooth macroporous layer on the surface of the synthetic leather and microporous pores provided throughout the resin layer. It is intended to manufacture.

Synthetic leather is made by providing a layer of foamed resin such as polyurethane on a base fabric, and in this case, if the cells in the resin layer are macroporous, synthetic leather with a good feel can be obtained.

However, although synthetic leather with such a low-density resin layer has a good texture and appearance, it has the disadvantage of low strength and poor moisture permeability due to its low density, and is particularly suitable for products that require strength and moisture permeability. could not be manufactured.

For this reason, synthetic leather with a smooth surface and a macroporous foam layer, and a microporous foam layer on the base fabric side is ideal in terms of texture, strength, etc. be able to.

Conventionally, when producing synthetic leather with a foam layer using a dry method, there is a method in which the solvent of a synthetic resin liquid coated on a base fabric is evaporated to form a microporous foam layer, or a method is used in which a microporous foam layer is formed by forming a microporous foam layer. A method is known in which a foaming agent and an auxiliary agent are mixed into a foam, and the mixture is heated and foamed to form a macroporous foam layer.

However, in the former method, that is, the method of stirring the solvent of the synthetic resin liquid to form a foam layer, most of the bubbles generated are minute pores, and even if macroporous is generated, the bubbles are of constant size. Synthetic leather is produced uniformly and asymmetrically throughout the layer, making it impossible to provide synthetic leather with a very good feel.

Furthermore, in a method in which a foaming agent is mixed into the resin liquid and foamed by heating, it is difficult to adjust the foaming agent, resulting in bubbles having non-uniform dimensions, and moreover, bubbles are generated asymmetrically throughout the foam layer.

Therefore, even if the synthetic leather has macroporous bubbles, traces of the macroporous bubbles will remain on the surface of the synthetic leather, causing unevenness and poor texture. has the disadvantage of being inferior in terms of strength.

The present invention aims to eliminate the drawbacks of such conventional synthetic leather manufacturing methods, and provides a synthetic leather with ideal properties that is microporous inside the foam layer and macroporous on the surface of the foam layer. This is what I am trying to do.

Therefore, in the method for producing synthetic leather according to the present invention, two or more solvents having different boiling points are added to a polyurethane polymer at 50 to 1
A polyurethane resin solution basically consisting of 00 parts by weight is applied to a release paper, and then a base fabric is laminated to the formed coating layer, and the base fabric is heated to evaporate the low-boiling solvent, and the low-boiling solvent is evaporated in sequence. The method is characterized in that it includes the steps of evaporating a high boiling point solvent and peeling off the release paper.

According to the method for producing synthetic leather of the present invention, the low boiling point solvent and the high boiling point solvent are evaporated in two or more stages,
Moreover, since the base fabric side is heated, the base fabric side hardens first to form a microporous foam layer, and the air expelled with the formation of the foam layer concentrates near the semi-hardened release paper, and then When the boiling point solvent is evaporated, a macroporous foam layer is formed near the release paper.

Therefore, the resin layer on the base fabric side becomes a microporous foam, and the resin layer near the release paper becomes a macroporous foam, making it possible to produce synthetic leather with extremely excellent texture, appearance, and strength. .

Furthermore, after the resin layer is heated and cured, the release paper is peeled off to produce a product, so the synthetic leather surface is smooth and feels very good to the touch.

To explain the present invention in more detail, the present invention first applies a polyurethane resin liquid onto a release paper.

The release paper is preferably one that is resistant to the polyurethane resin liquid and that can be easily peeled off after curing.

For example, a material coated with a polyurethane film is preferable, but there is basically no limitation as long as it fulfills the above-mentioned function.

The urethane polymer which is the main component of the polyurethane resin liquid may basically be any polymer that is used for producing synthetic leather.

The polyurethane resin liquid is basically made by adding two or more solvents having different boiling points to the urethane polymer as the main component.

These solvents are heated from the base fabric side in at least two stages, first the low-boiling point solvent is stirred, and then the high-boiling point solvent is sequentially stirred, so that at least the above two steps can be performed separately. Therefore, it is necessary to select two or more solvents whose boiling points are sufficiently different from each other.

Of course, it is also possible to select three or more types of solvents and perform the heating process in three stages. Depending on the selection of solvents, the heating process can also be performed in multiple stages exceeding three stages.

In this case, it is possible to produce a foam that has layers with different density distributions depending on the number of heating steps, that is, the density of the upper layer is gradually lower than that of the lower layer.

As described above, the solvents used in the present invention vary depending on the relationship between the solvents, and two or more types can be selected functionally within the range. ~
One or more solvents having a boiling point of 110 to 145°C such as doluol, butyl acetate, butyl methyl ketone, and xylene may be used in combination as high boiling point solvents.

These two or more solvents have a 50%
It is added in a proportion of ~100 parts by weight.

If it is less than 50 parts by weight, the density of the foam will be too high,
This is because if the amount is more than 100 parts by weight, the density of the resulting foam will be low, making it impossible to obtain ideal synthetic leather.

The amount is preferably 70 to 80 parts by weight.

This is because a synthetic resin with an ideal density distribution can be obtained.

Furthermore, the weight ratio of the high boiling point solvent and the low boiling point solvent is 2:3 to 4.
: 1 degree is preferable.

The optimal ratio is around 3:2.

Too much low boiling point solvent is undesirable because it tends to form a dry film only on the surface layer, leading to non-uniform cell structure.

Moreover, if too much high boiling point solvent is added, the density becomes high and it is difficult to form a cell structure.

Organic and/or inorganic fibrous powder can be added to such a polyurethane resin liquid.

The powder in these fibers acts as a nucleator for the air bubbles that occur in the foam, making the air bubbles smooth and uniform, and also prevents air from being drawn in and creating large air bubbles when applying polyurethane resin onto the release paper using a doctor knife. , which is added to help produce uniform bubbles.

The fibrous powder to be added preferably has a high porosity and excellent heat resistance.

This is to reduce the apparent specific gravity and to act as a texture control agent.

For example, Kokichi can be made of one or more of cellulose powder, pulp flock, asbestos, glass fiber, etc.

This organic and/or inorganic fiber powder is preferably added in an amount of 20 to 100 parts by weight based on the polyurethane polymer.

If it is less than 20 parts by weight, the addition effect will not be sufficient;
This is because if it exceeds the weight part, it becomes difficult to ensure the required physical strength, and the feel of the synthetic leather is also difficult to satisfy.

More preferably, it is added in an amount of 40 to 60 parts by weight.

Next, a base fabric is laminated onto the polyurethane resin coated on the release paper.

At this time, the base fabric used is basically not limited, and for example, non-woven fabric, knitted fabric, etc. can be used.

The base fabric laminated in this way is heated from the side, and at this time, at least two kinds of solvents contained in the polyurethane resin liquid are sequentially dispersed from the low boiling point solvent to the high boiling point solvent. Do it like this.

For example, when using methyl ethyl ketone as a low boiling point solvent and doluol as a high boiling point solvent, first stir the methyl ethyl ketone at around 90°C to form a dense layer, then heat it to 100 to 130°C and stir the doluol. The particles are dispersed to form a low-density layer.

When the solvent is dispersed in at least two stages from the base fabric side, as mentioned above, the base fabric hardens first, forming a microporous high-density layer, and as the foam layer is formed. When expelled air and fibrous powder are mixed, the air adsorbed to the powder concentrates in the semi-hardened portion, that is, near the release paper.

When a high boiling point solvent is stirred therein, a macroporous foam layer is formed.

If the release paper is peeled off from the resin layer formed in this way,
Synthetic leather can be obtained which has a smooth surface, a macroporous surface, a good texture and appearance, and a microporous foam layer from the center to the lower part of the resin layer, which also has excellent strength.

Examples will be described below.

Example polyurethane resin (Rezamin ME65: Dainichiseika (silk) 100% by weight 3 dimethylformamide 20 〃Methyl ethyl ketone 60 〃Dolol
30 〃Leveling agent (5th grade doluol solution) 4 〃Pigment
20 Apply a polyurethane resin liquid with the above composition onto paper using a doctor knife, roll coater, etc.
A release paper coated with a polyurethane film was produced by heating and drying at a temperature of 100 to 130°C.

On the polyurethane film side of this release paper, polyurethane resin (contains 3 touge doluol) 100% by weight 5 crosslinking agent 1211 Vulcanization accelerator 7゜5〃Methyl ethyl ketone 20〃Tackifier
2011 pigment
5 //Pulp flock
A polyurethane resin liquid consisting of 35 is uniformly applied, a polyester nonwoven fabric is laminated on top of the polyurethane resin liquid, and the base fabric is heated at 90°C for 30 seconds to 1 minute.
Heated at 30°C for 1-2 minutes.

After that, it was aged at 70℃ for more than 48 hours, and the release paper was peeled off.
Finish painting was applied as necessary.

For comparison, as Comparative Example 1, 100 parts by weight of a polyurethane resin (Rezamin UD-603: manufactured by Inu Nisseika), a crosslinking agent (Rezamin UD), was placed on a release paper coated with a polyurethane film obtained in the same manner as in Example 1. Crosslinking agent (manufactured by Dainichiseika) 12 parts by weight Accelerator (Rezamin UD accelerator: manufactured by Dainichiseika) 7.5 parts by weight
5 parts by weight methyl acetate
A polyurethane resin liquid of 20 parts by weight was uniformly applied, a polyester nonwoven fabric was laminated thereon, and the mixture was heated at 130°C for 3 minutes, then aged at 70°C for over 48 hours, and the release paper was peeled off. Synthetic leather was manufactured using the same method, and its mechanical properties were measured.

Furthermore, as Comparative Example 2, sponge paste A2 (manufactured by Ohmukai Shinko) was added to the polyester resin liquid of Comparative Example 1 as a foaming agent.
Synthetic leather was produced in the same manner as in Comparative Example 1 by adding 15 parts by weight of.

The results of Examples of the present invention and Comparative Examples 1 and 2 are summarized in the table below.

As is clear from the above table, the synthetic leather produced by the method of the present invention was superior in strength to the synthetic leather produced using a foaming agent (Comparative Example 2).

Although it is inferior in strength to synthetic leather produced by conventional solvent agitation, it has macroporous pores on its surface, so the synthetic leather produced by the method of the present invention (
Example) had excellent smoothness, and even when tension was applied, wrinkles on the leather surface were less likely to cause cracks (white streaks).

Furthermore, the texture was almost the same as or better than that of Comparative Example 2, and compared to Comparative Example 1, the texture and smoothness were significantly improved.

In terms of cost, it is also cheaper than Comparative Example 1.

As described above, according to the method of the present invention, it is possible to eliminate the disadvantages of conventional comparative examples 1 and 2 and provide a good synthetic leather that extracts only the advantages of both.

Claims (1)

[Scope of Claims] 1. A polyurethane resin liquid that basically consists of adding 50 to 100 parts by weight of two or more solvents with different boiling points to a polyurethane polymer is applied to a release paper, and then a base fabric is applied to the resulting coating layer. A method for producing synthetic leather, comprising the steps of laminating, heating from the base fabric side to evaporate a low boiling point solvent, sequentially evaporating a high boiling point solvent, and then peeling off the release paper. . 2. The method for producing synthetic leather according to claim 1, wherein the solvent is divided into at least two steps and is comprised of two or more types of solvents having different boiling points to the extent that they can be evaporated. 3. The low boiling point solvent is one or more selected from the group of ethyl acetate, methyl ethyl ketone, and acetone, and the high boiling point solvent is one or more selected from the group of doluol, butyl acetate, butyl methyl ketone, and xylene. A method for producing synthetic leather according to claim 2, characterized in that: 4 The weight ratio of high boiling point solvent and low boiling point solvent is 2:3 to 4:
1. A method for producing synthetic leather according to any one of claims 1 to 3, characterized in that: 5 The above two or more solvents are added to the polyurethane polymer at 5
The method for producing synthetic leather according to any one of claims 1 to 4, characterized in that 0 to 100 parts by weight is added. 6 Add organic and/or inorganic fiber powder to the polyurethane resin liquid at a ratio of 20 to 70% of the polyurethane polymer.
Claims 1 to 5 characterized in that parts by weight are added.
The method for producing synthetic leather according to claim 6, wherein the organic and/or inorganic fiber powder is one or more of cellulose powder, pulp flock, asbestos, and glass fiber. Manufacturing method. 8. The method for producing synthetic leather according to any one of claims 1 to 7, wherein the release paper is coated with a polyurethane film.