JPH02147644A - Production of air-permeable sheet - Google Patents

Abstract

PURPOSE:To make it possible to form an air-permeable polyurethane layer in which fine pores are stably distributed by mixing a specified organic solvent solution of a polyurethane with a thermoplastic resin which, when freed from the solvent, deposits before the polyurethane does. CONSTITUTION:A polyurethane solution is obtained by reacting a long-chain glycol an organic isocyanate and a low-MW diol in an organic solvent. In this reaction, a solvent of a water solubility of 1-50g/100g at 20 deg.C is used as the organic solvent. This solution is mixed with 10-95wt.%, based on the critical water amount, water and 0.1-30wt.%, based on the polyurethane, thermoplastic resin (e.g. vinyl chloride/urethane copolymer) which, when freed from the solvent, deposits before the polyurethane does to form a slurry. A fiber aggregate sheet is coated or impregnated with this slurry, freed from the solvent and dried to obtain an air-permeable sheet.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to artificial leather, an artificial leather substrate, etc., in which polyurethane is attached to the surface or inside of a fiber aggregate sheet made of a nonwoven fabric, a mW material, or a laminate thereof. The present invention relates to a method for manufacturing a breathable sheet used.

[Conventional technology]

A polyurethane solution is obtained by reacting long-chain glycols, organic isocyanates, low-molecular diols, etc. with an average molecular weight of 1,500 to 5,000 in an organic solvent. Water is added to liquid 8 to make a water-in-oil type (-10 type) water-containing slurry, and after applying or impregnating the fiber aggregate sheet with the slurry,
The method of drying to obtain a breathable sheet is a conventional method. This method uses methyl ethyl ketone (NHK
), whose boiling point is sufficiently lower than that of water, and drying must be carried out at two temperatures: one above the boiling point of the organic solvent but below the boiling point of water, and the other above the boiling point of water. In particular, when obtaining a sheet having a polyurethane layer on the surface of the fiber aggregate sheet, there is a problem that the obtained sheet tends to have poor air permeability.

In addition, if the water distribution in the slurry is not uniform, it will be difficult to form a polyurethane layer with a uniform porous structure, and variations in process conditions may cause the water distribution to become uneven, making it easy to form a polyurethane layer with a non-porous surface. He said that if a large amount of surfactant is used to stabilize water distribution uniformly, the physical properties of the polyurethane layer may deteriorate, resulting in poor yields when producing sheets with a polyurethane layer on the surface. There are also problems.

[Problems to be Solved by the Invention] The present invention was made with the aim of solving the above-mentioned problems, and even if the water distribution in the slurry becomes somewhat uneven,
To provide a method for producing a highly breathable sheet having a polyurethane layer on the surface with a high yield even when a fiber aggregate sheet coated with a slurry is dried in one step at an atmospheric temperature higher than the boiling point of water, which is highly productive. With the goal.

[Means to solve the problem]

The present inventor has developed a polyurethane that can stably form a porous, breathable polyurethane layer with excellent physical properties using a dry method.
As a result of repeated research on Type 10 water-containing slurry, we found that thermoplastic resins that solidify and precipitate earlier than polyurethane when dissolved in water-containing slurry and desolventized to remove the organic solvent from the water-containing slurry were found to 30% by weight
By adding and mixing, you can avoid using a lot of surfactant.
It has been found that even when drying is performed at one temperature step, it is possible to stably form a breathable polyurethane layer in which fine pores are distributed.

The present invention was made based on this knowledge, and the solubility of water at 20°C is 100°C when the boiling point is 120°C or lower.
A solution of polyurethane obtained by reacting long-chain glycols, organic isocyanates, low molecular diols, etc. in an organic solvent containing 1 to 50 g per gram, and at least 10 to 95% of the critical water amount dissolved in the solution. and adding and mixing 0.1 to 30% by weight of a thermoplastic resin of the polyurethane, which solidifies and precipitates before the polyurethane when desolvation is performed to remove the organic solvent from the solution, to form a slurry;
The present invention provides a method for producing a breathable sheet, which comprises applying or impregnating a fiber aggregate sheet with the slurry, followed by solvent removal and drying.

(Function) The method of the present invention uses a slurry containing a thermoplastic resin that solidifies and precipitates before the polyurethane solidifies when the solvent is removed by evaporation of the organic solvent. When the slurry coated or impregnated on the body sheet is desolventized by dry method by drying or wet method by coagulation bath using water, the thermoplastic resin solidifies and precipitates before the polyurethane solidifies, which becomes a core and forms a core in the polyurethane layer. Because micropores are generated in the slurry, even if the water distribution in the slurry is somewhat uneven, even if dry method drying is performed at one temperature, the polyurethane layer formed will have micropores evenly distributed. The sheet has excellent air permeability, and therefore a sheet with excellent air permeability can be obtained at a high yield. Of course,
If a slurry is applied to a fiber aggregate sheet by a dipping method or by coagulating polyurethane etc. by a wet method, a breathable sheet can be obtained relatively stably even with conventional methods. The method of the present invention shows a remarkable difference in results from conventional methods, particularly when a sheet having a polyurethane layer on the surface is obtained by a dry method.

In the present invention, if the boiling point of the solvent is higher than 120'C, when the solvent is removed by dry method, the water will evaporate first and the resulting sheet will have poor air permeability. become something. The boiling point of the organic solvent is preferably lower than the boiling point of water, similar to the conventional polyurethane type 0 water-containing slurry, and if the solubility of water at 20°C of the organic solvent is lower than Ig per 100g, the sheet obtained (If the water solubility exceeds 50 g per 100 g, the solvent and water will easily evaporate together when removing the solvent using a dry method. Therefore, if the polyurethane layer is not made slowly and evaporated, the polyurethane layer It tends to have a rough porous structure with poor physical properties, and it is difficult to remove the solvent wetly.The amount of water added is the critical water amount. If the amount of water is less than 10% of the critical amount of water that does not disperse, the air permeability of the resulting sheet will decrease, and if it is more than 95%, the polyurethane layer formed tends to have a rough porous structure with poor physical properties. The amount of thermoplastic resin added is 1
If it is less than 0.1% by weight of 7tan, it is no different from using a conventional polyurethane 11 θ type water-containing slurry, and if it is more than 30% by weight, the physical properties of the polyurethane layer formed by the thermoplastic resin will be inferior. Become.

From the above, when using the slurry of the present invention,
The reason for the formation of micropores with thermoplastic (M) cores in the formed polyurethane layer is that water collects around the thermoplastic resin that has solidified and precipitated, and after the polyurethane begins to solidify, it evaporates and becomes thermoplastic. The first possibility is that voids are created around the resin, and the second possibility is that the polyurethane that solidifies later contracts and creates voids around the thermoplastic resin.

〔Example〕

The organic solvent used in the present invention is one that has a boiling point of 120°C or lower, preferably 100°C or lower, and a water solubility of 1 to 50% per 100g at 20°C, such as those used in conventionally known solution polymerization or slurry polymerization of polyurethane.
g organic solvents can be used, for example MEX,
Methyl isobutyl keto 7 (MIBM).

Preferred examples include methyl butyl ketone (iBK), tetrahydrofuran (TIIF), and acetone.

Also, long chain glycols reacted in organic solvents.

As the organic isocyanate and low-molecular diol, long-chain glycols, organic isocyanates, and low-molecular diols having an average molecular weight of 500 to 5,000, which are conventionally used in solution polymerization or slurry polymerization, can be used. That is, as long chain glycols, polyalkylene ether diols such as polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, polyethylene adipate, polybutyl L
Polyester diols such as /N adibate and polyhexamethylene adipate can be used as organic isocyanates such as diphenylmethane to 4,4'-diisocyanate, tolylene-2,4-diisocyanate, phenylene diisocyanate, xylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate. Hexamethylene diisocyanate, etc. are used as low molecular weight diols such as enalene glycol, 1.4-butanediol, cyclohexane 4-diol, α.α-p-xylene diol, 1
・4~bis(β-hydroxyethoxy)benzene, 2・
Examples include 2-bis(4-(β-human[Jxyethquin)phenyl]propane, propylene diamine, hexamethylene diamine, and the like.

Furthermore, the polyurethane production reaction in a solvent can be carried out in the same manner as conventionally known solution polymerization or slurry polymerization, and includes surfactants, coloring agents, W antistatic agents, and flame retardants that are stable against heat and light. Similarly to conventional methods, it is also possible to add additives such as agents, and to appropriately adjust the viscosity of the resulting polyurethane solution by adjusting the concentration of polyurethane. In addition, it is preferable to add a surfactant after or before the reaction in order to obtain a polyurethane solution with a large amount of critical water, but if the polyurethane to be produced has a hydrophilic group in its main chain, it is not necessary to add It is not necessary to do so.

As the thermoplastic resin that dissolves in a polyurethane solution and solidifies and precipitates earlier than polyurethane, a vinyl chloride/urethane copolymer or a cellulose derivative is preferably used, or an acrylonitrile/styrene copolymer or the like is also used. Examples of vinyl chloride/urethane copolymers include polyvinyl chloride (PVC) and polyurethane 7 (pH) (7
) Examples include those having a weight ratio PVC/pH in the range of 70/30 to 40/60, and examples of cellulose derivatives include cellulose acetate, cellulose butyrate, cellulose propionate, and the like. Adding 0.1 to 30% by weight of such a thermoplastic resin to the polyurethane is not limited to after the polyurethane forming reaction, but can also be done before the reaction.
It's okay.

The slurry obtained by the above process can be coated or impregnated onto a fiber aggregate sheet using methods such as roll coater, graphia roll, printing, knife coater spray, and dipping and squeezing, in the same way as conventional polyurethane version 0 water-containing slurry. . The solvent can be removed by a dry method in which the organic solvent is evaporated, or by applying water to a fiber aggregate sheet that has been coated and impregnated with slurry so as to form a water film on the surface of the slurry, and then evaporating in the same way as in the dry method. As mentioned above, the difference in effectiveness between the conventional method and the conventional method is most noticeable when using the highly productive dry method, which may be carried out by a wet method in which the organic solvent is removed from the slurry in a coagulation bath using water. It is as follows. As with the conventional method, desolvation in the dry method may be performed at a different atmospheric temperature from that for drying, but from the viewpoint of productivity it is preferable to perform it at the same atmospheric temperature as for drying using a temperature higher than the boiling point of water and organic solvent. is preferred. This allows solvent removal and drying to be performed at the same time. Drying when performed separately from solvent removal is performed in the same manner as conventionally.

As a result of the above, it is possible to obtain a sheet with excellent air permeability in which a polyurethane layer with excellent air permeability is formed on the surface or inside of the fiber aggregate sheet with uniform distribution of fine pores with thermoplastic resin as the core, and with a good yield.

Further specific examples of the present invention will be shown below.

In addition, parts in the following examples are parts by weight.

Example 1 Polytetramethylene glycol (molecule ff12190)
300 parts, polycaprolactone diol (molecular weight 181
0) Dissolve 296 parts of diethylene glycol, 30 parts of diethylene glycol, and 315 parts of diphenyl 4,4' diisocyanate in 235 parts of methyl ethyl ketone, and dissolve 0.2 parts of triethylene diamine.
After reacting at 60°C for 90 minutes, 710 parts of a mixed solvent with a methyl ethyl ketone/toluene mixing ratio of 9/1 was added, and then 60 parts of tetramethylene glycol was added while controlling the temperature at 65 to 70°C. Stirring is performed, and as the viscosity increases, the methyl ethyl ketone/toluene mixing ratio becomes 9.
A mixed solvent of 1/1 was poured in and reacted for about 4 hours to obtain a polyurethane solution with a viscosity of 1800 cps/70'C/20% by weight of polyurethane. For 100 parts of this solution, the average molecule having two hydroxyl groups at the end is 1t3400
After addition reaction of polypropylene oxide to dimethylpolysiloxane under a caustic alkali catalyst, a surfactant consisting of polyalkylene oxide modified polysiloxane obtained by further addition reaction of polyethylene oxide was added, and the mixture was stirred with a homomixer. Tsutsumizu 28 parts and PVC
A slurry was prepared by adding 5 parts of a vinyl chloride/urethane copolymer having a Ptl/Ptl ratio of 60/40.

- After applying needle punching to a laminate of carded webs of polyethylene terephthalate fibers of 4,1,8de, 51n*, it was shrunk to 55% of its original area in hot water at 68°C, and then squeezed to a water content of 1300%. Pressurized and dried in a drum pressure dryer at 130℃ to a thickness of 1.301 mm.
11. A nonwoven fabric with an apparent density of 0.30 g/IIIz was obtained, and this nonwoven fabric was immersed in a dimethylformamide solution (resin concentration 15%) of polyurethane resin (Lisbon 8766 manufactured by Dainippon Ink ■), squeezed, and then coagulated by water immersion. The sample was then pulled up to drain water from the surface, and the same solution was cast on one side, placed on a 1N inclined conveyor net, and coagulated in a 40°C coagulation bath containing 10% dimethylformamide. Most of the solvent was removed by washing with water and then dried to obtain an artificial leather substrate.

One side of the obtained artificial leather substrate was coated with the above-mentioned slurry using a roll coater method so that the solid content was approximately 30 g/m'', and after drying at 100°C, the coated surface was coated with
Artificial leather was made by embossing a natural leather pattern with an embossing roll at 0°C.

The obtained artificial leather showed a uniform distribution of micropores on the surface and exhibited good breathability.On the other hand, no vinyl chloride/urethane copolymer was added to the artificial leather base. Artificial leather made in the same manner by coating with the slurry had no uniform distribution of micropores on the surface and had almost no air permeability.

Example 2 An artificial leather made in the same manner as in Example 1 using cellulose acetate instead of the vinyl chloride/urethane copolymer had the same surface and breathability as the artificial leather of Example 1.

Example 3 An artificial leather made in the same manner as in Example 1 using an acrylonitrile/styrene copolymer instead of a vinyl chloride/urethane copolymer was almost the same as the artificial leathers of Examples 1 and 2.

[Effects of the Invention] According to the method of the present invention, a polyurethane layer in which fine pores are evenly distributed and whose core is a thermoplastic resin stabilizes a highly breathable sheet attached to the surface or inside of a fiber aggregate sheet. can be produced with high productivity.

Claims (1)

[Claims] The boiling point is below 120℃ and the solubility of water at 20℃ is 10
A solution of polyurethane obtained by reacting long-chain glycols, organic isocyanates, low-molecular diols, etc. in an organic solvent of 1 to 50 g per 0 g, and at least 10 to 95% of the critical water amount dissolved in the solution. When desolvation is performed to remove the organic solvent from the solution, a thermoplastic resin of 0.1 to 30% by weight of the polyurethane, which solidifies and precipitates before the polyurethane, is added and mixed to form a slurry. A method for producing a breathable sheet, which comprises applying or impregnating a fiber aggregate sheet, followed by solvent removal and drying.