WO2022158507A1

WO2022158507A1 - Porous layer structure, and method for producing porous layer structure

Info

Publication number: WO2022158507A1
Application number: PCT/JP2022/001901
Authority: WO
Inventors: 祥汰綿貫; 寛女奥泉; 亮河村; 一弥佐々木
Original assignee: 大日精化工業株式会社
Priority date: 2021-01-22
Filing date: 2022-01-20
Publication date: 2022-07-28
Also published as: TW202243869A; JP2022112712A; JP6911215B1

Abstract

Provided are: a porous layer structure in which satisfactory adhesion between a base material and a foamed layer produced by foaming a urethane prepolymer can be exhibited even when the range of density at which the formation of a foamed layer can be achieved is expanded to a lower range (i.e., a range in which a foamed layer can become softer), and can exhibit an excellent texture (softness); and a method for producing a porous layer structure.　The porous layer structure comprises a base material 10, an under layer 20 provided on the base material 10 and formed from a blend solution containing a water-soluble resin, and a foamed layer 30 provided on the under layer 20 and produced by foaming a urethane prepolymer having an isocyanate group at an terminal thereof, in which the basis weight of the under layer 20 is 3 to 60 g/m2·dry, and the film rupture strength of the under layer 20 after being dried is 5 MPa or more.

Description

Porous layer structure and method for producing porous layer structure

The present invention relates to a porous layer structure and a method for manufacturing a porous layer structure.

Methods for producing synthetic imitation leather made of polyurethane resin are broadly classified into wet methods and dry methods. Among them, the synthetic imitation leather made of polyurethane resin using the wet method is characterized by being softer to the touch and finished with a high-class feeling compared to that of the dry method.
Polyurethane resins used in the wet process generally use N,N'-dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) as organic solvents, and in recent years, they have become harmful to the human body. The use of DMF and the like is being regulated or prohibited due to environmental problems, and environmentally friendly synthetic leather that does not use organic solvents such as DMF is desired as a substitute.

As an environmentally friendly synthetic leather that does not use organic solvents, a base material and a skin layer are bonded using a reactive hot-melt adhesive (RHM), which is a urethane prepolymer having an isocyanate group at the end. There is
A urethane prepolymer having an isocyanate group at the terminal of the urethane prepolymer reacts with moisture (humidity) in the air and develops a function as a moisture-curable adhesive as a cross-linking reaction proceeds. Therefore, reactive hot-melt adhesives (RHM) made of urethane prepolymers with isocyanate groups at their ends are 100% solids adhesives that do not use organic solvents, and are currently in demand as environmentally friendly adhesives. It has increased.

In addition, in synthetic imitation leather, in order to increase the adhesion between the base material and the adhesive layer, the base material is coated or impregnated with a formulation containing an aqueous polyurethane resin (PUD), and after drying the formulation, the base is It has been proposed to provide a layer containing PUD between the material and the adhesive layer (for example, Patent Documents 1 and 2).
In Patent Documents 1 and 2, by providing a layer containing PUD, the adhesive strength between the base material and the adhesive layer can be increased, but the moisture in the PUD layer does not contribute to foaming at all, and generally It has the same texture (flexibility) as synthetic imitation leather (foam layer density: about 0.05 g/cm ³ to 0.4 g/cm ³ ) made by the wet method using DMF, which is evaluated to be extremely soft. I couldn't.
In addition, in general, when trying to improve the softness by lowering the foam density of the foam layer, the adhesive strength with the base material tends to decrease, resulting in a problem of lack of practicality as a leather.

Japanese Patent No. 4123418 JP-A-2005-206970

The present invention was made in order to solve such problems. The object of the present invention is to provide a porous layer structure capable of exhibiting good adhesion to a foamed layer formed by the method and exhibiting excellent texture (flexibility), and a method for producing the porous layer structure. do.

As a result of intensive studies to solve the above problems, the present inventors have found that by forming an undercoat layer with a compounded liquid containing a water-soluble resin on a base material, the undercoat layer has a good anchoring action with the base material. Since the urethane prepolymer provided on the base layer can be evenly and sufficiently foamed by the water content of the compounded liquid, the foamed shape of the foamed layer can be made uniform and stable, and the problem can be solved. After discovering that it can be done, the present invention was conceived. That is, the present invention is as follows.

[1] A substrate, an underlayer formed by a liquid mixture containing a water-soluble resin provided on the substrate, and a urethane prepolymer having an isocyanate group at the end provided on the substrate and foamed. A porous layer structure comprising a foamed layer comprising: a base layer having a basis weight of 3 to 60 g/m ² ·dry; and a film breaking strength of 5 MPa or more after drying of the base layer.
[2] The porous layer structure according to [1], wherein the viscosity of the blended liquid containing the water-soluble resin is 500 to 50,000 mPa·s at 25°C.
[3] The porous layer structure according to [1] or [2], wherein the water-soluble resin is at least one selected from the group consisting of water-based polyurethane resin, water-based polyethylene glycol resin and water-based polyvinyl alcohol resin.
[4] The porous layer structure according to [3], wherein the water-soluble resin is an aqueous polyurethane resin.
[5] The porous layer structure according to [3], wherein the water-soluble resin is a water-based polyethylene glycol resin, and the number-average molecular weight of the water-based polyethylene glycol resin is 500,000 or more.
[6] The porous layer structure according to any one of [1] to [5], wherein the base layer and the substrate have a thickness ratio of 1:10 to 1:1,000.
[7] The porous layer structure according to any one of [1] to [6], which has a skin layer on the surface of the foam layer opposite to the surface on which the base layer is laminated.
[8] A base layer lamination step of applying a liquid mixture containing a water-soluble resin onto a base material to form a wet base layer on the base material, and an isocyanate group at the end of the wet base layer. and a foam layer laminating step of forming a foam layer by foaming the urethane prepolymer with the moisture of the base layer, wherein the basis weight of the base layer is 3 to 60 g / m ² - A method for producing a porous layer structure, wherein the underlayer is dry and the film breaking strength of the underlayer after drying is 5 MPa or more.
[9] The method for producing the porous layer structure according to [8], further comprising a skin layer laminating step of laminating a skin layer on the surface of the foam layer opposite to the surface on which the base layer is laminated.
[10] The method for producing a porous layer structure according to [8] or [9], further comprising an aging step of performing an aging treatment to promote foaming of the foam layer after the foam layer laminating step.

According to the present invention, even if the density range that can be realized as a foam layer is expanded to a lower region (a region where the foam layer becomes softer), good adhesion between the substrate and the foam layer formed by foaming the urethane prepolymer is achieved. It is possible to provide a porous layer structure and a method for producing a porous layer structure that can exhibit excellent texture (softness).

1 is a schematic cross-sectional view (part 1) showing a porous layer structure according to the present embodiment; FIG. 4 is a cross-sectional photograph taken by a scanning electron microscope (SEM) of the porous layer structure according to the present embodiment. FIG. 2 is a schematic cross-sectional view (part 2) showing the porous layer structure according to the present embodiment;

Although the embodiment (this embodiment) of the present invention will be described in detail below, the present invention is not limited to this embodiment.

[Porous layer structure]
As shown in FIG. 1, the porous layer structure according to the present embodiment includes a substrate 10, a base layer 20 formed of a liquid mixture containing a water-soluble resin provided on the substrate 10, and a base layer 20 A foam layer 30 formed by foaming a urethane prepolymer having an isocyanate group at the end provided thereon is provided.

(Base material)
As the base material 10, a conventionally known synthetic imitation leather base material can be used. Examples include nylon cloth, polyester cloth, Kevlar cloth, non-woven fabrics (polyester, nylon, various latexes), various films, sheets, and the like.

The thickness of the base material 10 is not particularly limited as long as the base layer 20 can be formed from a liquid mixture containing a water-soluble resin. It is preferably 01 to 2.0 mm, more preferably 0.02 to 1.5 mm.

(Underlayer)
The base layer 20 is formed by coating the base material 10 with a liquid mixture containing a water-soluble resin, and providing the base layer 20 with a specific coating amount (basis weight) and a substantially uniform thickness. The base layer 20 may be partially impregnated into the base material 10 as shown in FIGS. 1 and 2 .
The base layer 20 is provided substantially uniformly and evenly over the entire surface of the base material 10 with a basis weight described later, so that the contact with the foam layer 30 provided on the base layer 20 is uniform, and the foam layer The amount of water supplied to 30 becomes constant in the planar (interface) direction.
Since the distribution of the amount of moisture per unit area supplied from the base layer 20 is constant, the foamed shape of the foamed layer 20 formed of the moisture-curable urethane prepolymer is uniform and stable (that is, excessive foaming can be prevented). It is possible to reliably prevent the occurrence of different parts and the occurrence of variations in foam shape and size), and it is possible to demonstrate excellent texture (flexibility), as well as between the base material and the foam layer Improves adhesion.

The basis weight of the underlayer 20 is 3 to 60 g/m ² ·dry.
If the basis weight of the base layer 20 is less than 3 g/m ² ·dry, the foaming of the foam layer 30 provided on the base layer 20 tends to be insufficient, and the adhesion between the base material 10 and the foam layer 30 is poor. becomes. In addition, if the base layer 20 has a basis weight of more than 60 g/m ² ·dry, the foaming of the foam layer 30 becomes excessive, making it difficult to make the foam shape and size uniform and stable. Since the physical properties of the film tend to adversely affect the tactile feel of the synthetic imitation leather, excellent texture (flexibility) cannot be exhibited.
The basis weight of the base layer 20 should be 5 to 50 g/m ² ·dry from the viewpoint of uniform and sufficient foaming of the foam layer 30 provided on the base layer 20 and uniform and stable foam shape. is preferable, 6 to 45 g/m ² ·dry is more preferable, and 7 to 40 g/m ² ·dry is even more preferable.

The film breaking strength of the underlying layer 20 after drying is 5 MPa or more.
If the film breaking strength of the underlayer 20 after drying is less than 5 MPa, the peel strength between the substrate 10 and the foam layer 30 will be insufficient, and the adhesion between the substrate 10 and the foam layer 30 will be poor.
The film breaking strength of the underlayer 20 after drying is preferably 8 MPa or more, more preferably 10 MPa or more, more preferably 12 MPa or more, from the viewpoint of improving the peel strength between the substrate 10 and the foam layer 30. It is even more preferable to have There is no particular upper limit for the film breaking strength of the underlying layer 20 after drying.
The film breaking strength of the underlayer 20 after drying can be measured by a method using an autograph. As a specific measurement of the film breaking strength of the underlying layer 20, it can be measured by the method described in the "film breaking strength test" in the examples.

The thickness ratio between the base layer 20 and the substrate 10 is preferably 1:10 to 1:1,000, more preferably 1:30 to 1:30, from the viewpoint of exhibiting excellent texture (flexibility) of the porous layer structure. 1:750 is more preferred, and 1:70 to 1:500 is even more preferred.
The thickness ratio between the base layer 20 and the base material 10 is the ratio between the thickness t of the base layer 20 and the thickness T of the base material 10. As shown in FIG. 1, the base material 10 is impregnated with In this case, the thickness t of the base layer 20 includes the thickness of the portion impregnated into the base layer 10, and the thickness T of the base layer 10 is obtained by subtracting the thickness of the portion impregnated with the base layer 20.

The thickness t of the underlying layer 20 can be calculated by measuring 10-point average from a cross-sectional image obtained by SEM (see FIG. 2).
On the other hand, when the base layer 20 cannot be confirmed in the cross-sectional image by SEM, on release paper (“DNTP-FL” manufactured by Dai Nippon Printing Co., Ltd.) is coated with a compounded liquid containing a water-soluble resin to be measured, and the drying process is performed at 60 ° C for 4 minutes, 100 ° C for 3 minutes, and 120 ° C for 3 minutes. The measured thickness of the underlayer is regarded as the thickness t of the underlayer 20 to be measured.
As a basis for setting the thickness of the base layer formed on the release paper to the thickness t of the base layer 20 to be measured, a water-based polyurethane resin ("Rezamin D-6065NP" manufactured by Dainichi Seika Kogyo Co., Ltd.) was used as a water-soluble resin. Table 1 shows the specific relationship between the weight per unit area of the mixed liquid containing the above-mentioned formulations when dried, the viscosity of the mixed liquid, and the thickness of the base layer 20 formed on the release paper. As shown in Table 1, it can be seen that the basis weight of the base layer 20 is not greatly related to changes in viscosity, but correlates with the thickness of the base layer formed on the release paper.

<Combination liquid containing water-soluble resin>
The compounded liquid containing the water-soluble resin that forms the base layer 20 of the present invention is a compounded liquid in which the water-soluble resin is dispersed in water. Examples of water-soluble resins include water-based polyurethane resins, water-based polyethylene glycol resins, water-based polyvinyl alcohol resins, and water-based acrylic resins. One type is preferred. Among them, water-based polyurethane resin is preferable as the water-soluble resin. An aqueous polyurethane resin is produced by reacting a polyol component with a polyisocyanate compound. There is no particular limitation as long as it forms the base layer 20, but examples include those in which a hydrophilic group is introduced into the molecule of a polyurethane resin in order to improve dispersibility in water. The hydrophilic group may be an anion, a cation, or a nonion. For example, (α) an anionic group having one or more active hydrogen groups in the molecule and having a carboxyl group, a sulfonic acid group, and a salt thereof and (β) a group having one or more active hydrogen groups in the molecule and consisting of repeating units of ethylene oxide, or a nonion containing a group consisting of repeating units of ethylene oxide and other repeating units of alkylene oxide chemical compounds, and the like.
The content of the water-soluble resin (paint solid content) relative to the entire liquid mixture is not particularly limited. It may be up to 60% by mass, preferably 10 to 50% by mass, more preferably 15 to 40% by mass.

《Aqueous Polyurethane Resin》
The polyurethane resin constituting the aqueous polyurethane resin according to the present invention mainly contains a polyol component and an isocyanate component.

<Polyol component>
The polyol that is used as the polyol component in the present invention is not particularly limited, but examples thereof include polycarbonate polyol, polyether polyol, polyester polyol, polylactone polyol, polyolefin polyol, and polymethacrylate diol.

Although the number average molecular weight of the polyol is not particularly limited as long as it is 500 or more, it is preferably about 500 to 4,000, more preferably about 1,000 to 3,000. These polyols can be used alone or in combination of two or more, but from the viewpoint of long-term durability, it is preferable to include a polycarbonate diol.
The number average molecular weight is a polystyrene-equivalent number average molecular weight, and can be usually determined by gel permeation chromatography (GPC).

<Isocyanate component>
The isocyanate used as the isocyanate component in the present invention is not particularly limited, but bifunctional polyisocyanates such as aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates are preferred.
Specific examples of polyisocyanate include tolylene diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-butoxy-1 ,3-phenylene diisocyanate, 2,4-diisocyanate-diphenyl ether, mesitylene diisocyanate, 4,4′-diphenylmethane diisocyanate, dulylene diisocyanate, 1,5-naphthalene diisocyanate, benzidine diisocyanate, o-nitrobenzidine diisocyanate, 4,4-diisocyanate dibenzyl, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylene diisocyanate, 4,4' -methylenebis(cyclohexyl isocyanate), 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate and the like.
When the porous layer structure is used for applications requiring flexibility, mechanical properties, and resistance to discoloration, it is preferable to mainly use an aliphatic diisocyanate or an alicyclic diisocyanate.

The ratio of the isocyanate group equivalent of the polyisocyanate component to the hydroxyl group equivalent of all components is preferably 0.8 to 1.9, more preferably 0.9 to 1.5. When the NCO/OH is within the above range, both flexibility and durability are improved.

<Additive>
The liquid mixture containing the water-soluble resin of the present invention may contain additives as necessary. Additives include, for example, thickeners, cross-linking agents, antioxidants (hindered phenols, phosphites, thioethers, etc.), light stabilizers (hindered amines, etc.), ultraviolet absorbers (benzophenones, benzotriazole system, etc.), gas discoloration stabilizers (hydrazine system, etc.), metal deactivators, and the like.

<Crosslinking agent>
The cross-linking agent preferably contains, for example, at least one selected from the group consisting of an isocyanate-based cross-linking agent, a carbodiimide-based cross-linking agent, an oxazoline-based cross-linking agent and an epoxy-based cross-linking agent. More preferably, it contains at least one selected from the group consisting of cross-linking agents.
If the amount of the cross-linking agent used is too large, problems such as embrittlement of the underlying layer 20 and plasticization due to unreacted cross-linking agent may occur. ) is preferably 10 parts by mass or less, more preferably 0.5 to 8.0 parts by mass, in terms of the solid content of the cross-linking agent per 100 parts by mass.

<<Viscosity of liquid containing water-soluble resin>>
The viscosity at 25° C. of the liquid mixture containing the water-soluble resin can be appropriately adjusted by adding a thickener or the like. Specifically, it is preferably from 500 to 50,000 mPa·s, more preferably from 550 to 45,000 mPa·s, even more preferably from 600 to 40,000 mPa·s.
Since the viscosity of the compounded liquid containing the water-soluble resin at 25° C. is equal to or higher than the lower limit, impregnation of the base layer 20 is suppressed when the compounded liquid is applied onto the base material 10. can form a coating film. In addition, since the viscosity of the compounded liquid containing the water-soluble resin at 25° C. is equal to or less than the above upper limit value, when the compounded liquid is applied onto the base material 10, the coating film of the base layer 20 is prevented from becoming patchy. can be prevented. That is, when the viscosity at 25° C. of the compounded liquid containing the water-soluble resin is within the above range, the coatability is improved, and the coating film of the base layer 20 is uniformly and evenly formed on the base material 10. can be done.

《Aqueous polyethylene glycol resin》
The water-based polyethylene glycol resin according to the present invention is a polymer of ethylene glycol that becomes a water-based polyethylene glycol resin having the following number average molecular weight.

<Number average molecular weight of water-based polyethylene glycol resin as water-soluble resin>
The number average molecular weight of the water-based polyethylene glycol resin as the water-soluble resin is preferably 500,000 or more, more preferably 600,000 or more, from the viewpoint of forming the base layer 20 well and obtaining the optimum foam density. more preferred. Also, if the number average molecular weight is too high, the ease of formation of the base layer 20 and the foam density may decrease. More preferably:
The number average molecular weight is a polystyrene-equivalent number average molecular weight, and can be usually determined by gel permeation chromatography (GPC).

<<Method for producing compound liquid containing water-soluble resin (aqueous polyurethane resin)>>
As a method for producing a mixed liquid containing an aqueous polyurethane resin as the water-soluble resin in the present invention, for example,
(1) A reaction step of reacting a polyol, a compound (α) having an anionic hydrophilic group, a compound (β) serving as a hydrophilic alkylene oxide component, and an isocyanate, and adding a surfactant or the like after the reaction to obtain an ion A method of emulsifying and polymerizing by adding a mixed solution of exchanged water and diamine, etc., and emulsifying it, and adding a surfactant or the like in the emulsifying and polymerizing step. A method of gently stirring at about 300 rpm and strongly stirring at about 4,000 to 6,000 rpm when adding a mixed solution of ion-exchanged water and diamine, and (2) a stirring blade for circulation in the tank. and a stirring vessel having a stirring blade for imparting a shearing force, at least a polyol, an isocyanate, and a compound serving as a hydrophilic alkylene oxide component are reacted and emulsified.
By this production method, it is possible to efficiently produce the water-based polyurethane resin having the above-described volume average particle size at the above-described high non-volatile component concentration. Moreover, it can be set as a desired viscosity.

<<Method for Producing Mixed Liquid Containing Water-soluble Resin (Aqueous Polyethylene Glycol Resin, Aqueous Polyethylene Glycol Resin, Aqueous Polyvinyl Alcohol Resin)>>
As a method for producing a mixed solution containing an aqueous polyethylene glycol resin, an aqueous polyethylene glycol resin and an aqueous polyvinyl alcohol resin as the water-soluble resin in the present invention, for example, as the main ingredients of the mixed solution, an aqueous polyethylene glycol resin, an aqueous polyethylene glycol resin and an aqueous A mixed liquid having a desired viscosity can be obtained by appropriately selecting a polyvinyl alcohol resin, mixing an appropriate amount of a thickening liquid, water, and the like, and stirring the mixture.

(Foam layer)
The foam layer 30 is provided on the base layer 20 and is a layer formed by foaming a urethane prepolymer having an isocyanate group at its end. That is, the foam layer 30 is a layer made of a urethane prepolymer foam having an isocyanate group at its end.

The density of the foam layer 30 is preferably 0.03 to 0.30 g/cm ³ and preferably 0.05 to 0.3 g/cm 3 from the viewpoint of achieving both excellent texture (flexibility) and peel strength of the porous layer structure. It is more preferably 25 g/cm ³ and even more preferably 0.07 to 0.20 g/cm ³ . The density of the foam layer 30 can be measured by the method described in Examples.

The thickness of the foam layer 30 is not particularly limited because it varies depending on the thickness of the polyurethane prepolymer to be coated and the type of leather to be produced. For example, from the viewpoint of achieving both excellent texture (flexibility) and peel strength of the porous layer structure, the thickness may be about 0.05 to 1.0 mm, preferably about 0.1 to 1.0 mm.

Since the foam layer 30 is laminated on the base material 10 with the base layer 20 interposed therebetween, the adhesion between the base material 10, the base layer 20 and the foam layer 30 is improved. Demonstrates durability. In addition, the porous layer structure has excellent peel strength and durability because the foam layer 30 is foamed at a low density without excessive foaming and variations in foam shape and size. It has a good texture (flexibility) while maintaining the

The peel force for peeling the foam layer 30 from the substrate 10 is preferably 1.0 kgf/inch or more, more preferably 1.2 kgf/inch or more, and 1.5 kgf/inch or more. is more preferred. Since the peeling force for peeling the foam layer 30 from the base material 10 is at least the above lower limit, for example, the adhesiveness (peel strength) with the base material 10 exceeding a level that has no practical problem as a foamed synthetic imitation leather can be obtained. The upper limit of the peel force for peeling the foam layer 30 from the substrate 10 is not particularly limited.
The peel strength for peeling the foam layer 30 from the base material 10 can be measured by the method described in "Peel Strength Test" in Examples.

Moreover, the urethane prepolymer according to the present embodiment does not substantially contain volatile components. That is, since the porous structure is produced without using an organic solvent, there is no problem of toxicity or environmental problems.
Here, in the present invention, "substantially free of volatile components" means that volatile components such as organic solvents are not intentionally contained, more specifically, the absence of organic solvents. .

<Urethane prepolymer>
A urethane prepolymer is composed of a polyol component, an isocyanate component, and other components as appropriate. That is, the urethane prepolymer having an isocyanate group at the end of the present embodiment is a urethane prepolymer obtained from a polyol component and a polyisocyanate component. In particular, the urethane prepolymer is a moisture-curable urethane prepolymer, and the porous layer structure of the present invention can be obtained by utilizing the fact that the base layer 20 foams when moisture-cured by moisture.

<Polyol component>
The polyol that becomes the polyol component of the urethane prepolymer is not particularly limited, but examples thereof include polycarbonate polyol, polyether polyol, polyester polyol, polylactone polyol, polyolefin polyol, and polymethacrylate diol.

As the polyol component, a polycarbonate polyol component may be included in order to improve hydrolysis resistance and obtain better durability. When the polycarbonate polyol component is contained, it is preferably contained in an amount of 50% by mass or more, more preferably 70 to 90% by mass, based on the total polyol component.

<Isocyanate component>
Although the isocyanate used as a synthetic component of the urethane prepolymer according to the present embodiment is not particularly limited, bifunctional polyisocyanates such as aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates are preferred.
Specific examples of polyisocyanates that serve as isocyanate components include tolylene diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4 -butoxy-1,3-phenylene diisocyanate, 2,4-diisocyanate-diphenyl ether, mesitylene diisocyanate, 4,4'-diphenylmethane diisocyanate, dulylene diisocyanate, 1,5-naphthalene diisocyanate, benzidine diisocyanate, o-nitrobenzidine diisocyanate, 4 ,4-diisocyanate dibenzyl, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate and the like. Among them, it is preferable to contain at least 4,4'-diphenylmethane diisocyanate (MDI).

When light resistance is required, such as for vehicle applications and light-colored applications, it is preferable to use an aliphatic diisocyanate or an alicyclic diisocyanate together with 4,4'-diphenylmethane diisocyanate.

The ratio of the polyol to the polyisocyanate when making the urethane prepolymer according to the present embodiment is preferably a ratio of the isocyanate group equivalent of the polyisocyanate component to the hydroxyl group equivalent of all the polyol components of 1.33 to 5.0. More preferably 1.5 to 3.0. When the NCO/OH is within the above range, both flexibility and peel strength to the substrate 10 are improved.

The method for producing the urethane prepolymer according to this embodiment is not particularly limited. For example, the polyisocyanate can be mixed with the above-described polyol so that the NCO/OH ratio is 1.33 to 5.0, and reacted at 80 to 120° C. for about 60 to 120 minutes.

In addition, in the urethane prepolymer, an appropriate amount of polyfunctional polyisocyanate, thermoplastic polymer, tackifier resin, etc. may be blended as needed.

(skin layer)
As shown in FIG. 3, the porous layer structure according to the present embodiment may have a skin layer 40 on the surface of the foam layer 30 opposite to the surface on which the base layer 20 is laminated.
The skin layer 40 is not particularly limited, and examples thereof include those formed of a skin layer-forming paint such as solvent-based polyurethane, water-based polyurethane, and TPU.

As described above, the porous layer structure according to the present embodiment can be suitably used as synthetic imitation leather and artificial leather, and can be used for shoes, clothing, bags, furniture, vehicle interior materials (for example, instrument panels, doors, consoles, seats), heat insulating materials, sound absorbing materials, shock absorbing materials, etc.

[Manufacturing method of porous layer structure]
The manufacturing method of the porous layer structure of the present embodiment includes a base layer lamination step of applying a liquid mixture containing a water-soluble resin onto the base material 10 to form the base layer 20 on the base material 10; and a foam layer laminating step in which a urethane prepolymer having an isocyanate group at its end is disposed thereon, and the urethane prepolymer is foamed by moisture in the base layer 20 to form the foam layer 30 .
Each step will be described below.

(Base layer lamination step)
First, one surface of the prepared base material 10 is coated with a liquid mixture containing a water-soluble resin contained in a coating machine to form a wet base layer 20 on the base material 10 . The weight per unit area of the base layer 20 by the blended liquid containing the water ^- soluble resin depends on the coating weight and viscosity of the blended liquid. Apply liquid.

(Foam layer lamination process)
Next, a urethane prepolymer having terminal isocyanate groups is disposed on the wet underlayer 20 . As a method of disposing the urethane prepolymer, for example, there is a method of coating the base layer 20 with the urethane prepolymer housed in a coating machine such as a melter.
In order to foam the foam layer 30 with water, it is important to arrange the urethane prepolymer so as to be in contact with the base layer 20 before the base layer 20 dries. As a result, the urethane prepolymer disposed on the base layer 20 is foamed by the moisture in the base layer 20 to form the foam layer 30 .

The thickness of the urethane prepolymer coating film (immediately after coating, ie, before foaming) depends on the viscosity and composition of the urethane prepolymer, but is preferably 50 to 500 μm, more preferably 60 to 400 μm. It is preferably 70 to 300 μm, more preferably 70 to 300 μm.

(Skin layer lamination process)
The method for manufacturing the porous layer structure of the present embodiment may further include a skin layer lamination step of laminating the skin layer 40 on the surface of the foam layer 30 opposite to the surface on which the base layer 20 is laminated. In order to laminate the skin layer 40 in close contact with the foam layer 30, the skin layer 40 is placed in contact with the foam layer 30 before the foaming of the foam layer 30 is completed, that is, before the base layer 20 dries. set up.

When the skin layer laminating step is included, it is preferable to apply a urethane prepolymer having an isocyanate group at the end to one surface of the skin layer 40 to provide a urethane prepolymer coating. Then, the urethane prepolymer coating film provided on the skin layer 40 and the base layer 20 provided on the base material 10 are attached together by lamination or the like, so that a urethane prepolymer having an isocyanate group at the terminal is formed on the base layer 20. can be arranged. At this time, in order to foam the foam layer 30 well, the foam layer 30 should be placed in contact with the base layer 20 before the base layer 20 dries, that is, while the base layer 20 is in a wet state. is important.

(Aging process)
The manufacturing method of the porous layer structure of the present embodiment may further include an aging step of performing an aging treatment for promoting foaming of the foam layer 30 after the foam layer laminating step. In the aging process, the porous layer structure after the foam layer lamination process is aged at 15 to 80° C. and 40 to 95% RH for 48 to 120 hours. This aging treatment promotes foaming to produce the porous layer structure of the present embodiment.

(Water vapor contact step)
In addition, in the present production method, a steam contacting step of contacting steam with the porous layer structure after the foaming layer laminating step can be included between the foaming layer laminating step and the aging step. In the steam contact step, the atmosphere is 30 to 60 ° C. (preferably 35 to 55 ° C.) and 80% RH or more (preferably 85% RH or more), and the time in the atmosphere depends on the temperature and humidity conditions. is preferably 20 seconds or more (preferably 25 to 60 seconds).
Since the moisture content of the porous layer structure can be improved by the steam contact step, a favorable expansion ratio can be easily obtained in the subsequent aging treatment step. That is, the degree of foaming can be well controlled.

Through the steps described above, the base layer 20 is uniformly and evenly provided on the base material 10, and the urethane prepolymer disposed on the base layer 20 is in uniform contact with the base layer 20. Therefore, the amount of water supplied from the base layer 20 becomes constant, and the foam layer 20 having a uniform and stable foam shape can be formed. By forming the foamed layer 20 with a uniform and stable foamed shape, it is possible to obtain a porous layer structure exhibiting excellent texture (flexibility) while maintaining high adhesion.

Although the porous layer structure can be used as it is as a synthetic imitation leather, it may be appropriately treated, for example, by coating it with a surface treatment agent or bonding it to another base material.

Next, the present invention will be described in further detail with examples and comparative examples. However, the present invention is not limited by the examples and the like.

(Preparation of base layer liquid mixture (part 1: water-based polyurethane resin))
Lezamin D-6065NP, Lezamin DN-0445, and Lezamin D-1063 (aqueous polyurethane resin, manufactured by Dainichi Seika Kogyo Co., Ltd.) were selected as the main ingredients of the formulation liquid for applying the underlayer, and xanthan gum (DSP Gokyo Food & Chemical Co., Ltd.) was selected. Company) 2% aqueous solution (thickened liquid A) or D-87 (manufactured by Dainichiseika Kogyo Co., Ltd., thickened liquid B) is blended little by little until the viscosity shown in Tables 2 and 3 for Examples and Comparative Examples. and thickened to obtain an underlayer liquid mixture (B-1).
With respect to the liquid mixtures using a cross-linking agent (Examples 5 and 6), Lezamin D-52 (a carbodiimide-based cross-linking agent (solid content: 40%), Dainichisei Kakogyo Co., Ltd.) or Lezamin D-65 (isocyanate-based cross-linking agent (solid content: 70%), Dainichiseika Kogyo Co., Ltd.) was blended in the amounts shown in Table 2 to prepare a base layer formulation solution (B -2). The parts by mass of the carbodiimide-based cross-linking agent in Example 5 are parts by mass with respect to 100 parts by mass of the aqueous dispersion in which the solid content of the aqueous polyurethane resin is 50%. Also, the parts by mass of the isocyanate-based cross-linking agent in Example 6 are parts by mass with respect to 100 parts by mass of the aqueous dispersion in which the solid content of the aqueous polyurethane resin is 43%.
Tables 2 and 3 show the solid content concentration (% by mass) of each of the base layer formulation solutions (B-1 and B-2).

(Preparation of base layer formulation (part 2: water-based polyethylene glycol resin))
L-11 (number average molecular weight: about 110,000), E-45 (number average molecular weight: 600,000 to 1,000,000), E-75 (number average molecular weight: about 2,000,000) are used as the main ingredients of the compound liquid for applying the underlayer. , E-300 (number average molecular weight: about 7 million) (aqueous polyethylene glycol (PEG), manufactured by Meisei Chemical Industry Co., Ltd.) is selected, and water is added as a viscosity modifier in Table 4 until it reaches the viscosity shown in Table 4. Then, an underlayer liquid mixture (B-3) was obtained.
Regarding the formulations using a cross-linking agent (Examples 18 and 19), Lezamin D-65 (an isocyanate-based cross-linking agent (solid content: 70%), Dainichisei (manufactured by Kakogyo Co., Ltd.) were blended in the respective amounts shown in Table 4 to prepare an underlayer blend solution (B-4). The parts by mass of the isocyanate-based cross-linking agent in Examples 18 and 19 are parts by mass with respect to 100 parts by mass of the aqueous dispersion containing 6% solids of aqueous polyethylene glycol.
Table 4 shows the solid content concentration (% by mass) of each of the base layer formulation solutions (B-3, B-4).

(Preparation of base layer liquid mixture (Part 3: water-based polyvinyl alcohol resin))
PVA105 (aqueous polyvinyl alcohol (PVA), manufactured by Kuraray Co., Ltd.) was selected as the main ingredient of the liquid composition for applying the underlayer, and water was added as a viscosity modifier little by little until the viscosity shown in Table 5 was reached. A formulation solution (B-5) for
Regarding the formulations using a cross-linking agent (Examples 23 and 24), Lezamin D-65 (an isocyanate-based cross-linking agent (solid content: 70%), Dainichisei (manufactured by Kakogyo Co., Ltd.) were blended in the respective amounts shown in Table 5 to prepare an underlayer blend solution (B-6). The parts by mass of the isocyanate-based cross-linking agent in Examples 23 and 24 are the parts by mass for 100 parts by mass of the aqueous dispersion in which the solid content of the water-based polyvinyl alcohol resin is 20%.
Table 5 shows the solid content concentration (% by mass) of each of the underlayer liquid mixtures (B-5 and B-6).

(Preparation of base layer liquid mixture (part 4: water-based polyurethane resin))
D-87 (aqueous urethane resin, manufactured by Dainichiseika Kogyo Co., Ltd.) used as a thickener in Example 6 is selected as the main ingredient of the liquid composition for applying the underlayer, and water is listed in Table 6 as a viscosity modifier. were blended little by little until the viscosity reached , to obtain an underlayer blend solution (B-7).
Regarding the formulations using a cross-linking agent (Examples 31 and 32), Lezamin D-65 (an isocyanate-based cross-linking agent (solid content: 70%), Dainichisei (manufactured by Kakogyo Co., Ltd.) were blended in the respective amounts shown in Table 4 to prepare an underlayer blend solution (B-8). The parts by mass of the isocyanate-based cross-linking agent in Examples 31 and 32 are parts by mass based on 100 parts by mass of the aqueous dispersion in which the solid content of the aqueous polyurethane resin is 20%.
Table 6 shows the solid content concentration (% by mass) of each underlayer liquid mixture (B-7, B-8).

(Preparation of base layer liquid mixture (Part 5: water-based acrylic resin))
XK-12 and XK-36 (water-based acrylic resin, manufactured by Covestro Japan Co., Ltd.) were selected as the main ingredients of the compounded liquid for applying the base layer, and A-7100 (acrylic thickener, manufactured by Toagosei Co., Ltd., thickened liquid C) was blended little by little until the viscosity shown in Table 7 was reached, and the viscosity was increased to obtain a liquid mixture for underlayer (B-9).
Table 7 shows the solid content concentration (% by mass) of each underlayer liquid mixture (B-9).

(Preparation of epidermis)
Rezamin NE-8875-30M (Dainichiseika Kogyo Co., Ltd.), which is a solvent-type urethane resin for synthetic imitation leather, and Seika Seven BS-780 (Dainichiseika Kogyo Co., Ltd.), which is a coloring agent for synthetic imitation leather, Methyl ethyl ketone and dimethylformamide are mixed as a diluent solvent, and a coating amount of 250 μm/wet is uniformly applied on release paper with a bar coater, and then dried at 120° C. for 5 minutes to provide a skin layer 40 with a thickness of 40 to 50 μm. A skinned film was obtained.

(Production of synthetic imitation leather)
[Examples 1 to 34, Comparative Examples 2 to 4]
On the skin layer 40 of the film with the skin, Lezamin F-916 (urethane prepolymer, moisture-curing adhesive, manufactured by Dainichiseika Kogyo Co., Ltd.) heated to 100° C. is applied. coated to form.
In addition, a layer (underlayer 20 ) was applied so as to be formed at the weight (g/m ² ·dry) described in each of Examples and Comparative Examples.
Then, the urethane prepolymer coating film formed on the skin layer 40 is arranged so as to be in contact with the base layer 20 formed on the base material 10, and immediately pressure-bonded at a laminate roll temperature of 40 ° C. The urethane prepolymer foamed to form a foam layer 30 .
As an aging process, after aging for 5 days in an environment of a temperature of 35° C. and a relative humidity of 65%, the synthetic imitation leather was obtained by peeling from the release paper.

[Comparative Example 1]
On the skin layer 40 of the film with the skin, Lezamin F-916 (urethane prepolymer, moisture-curing adhesive, manufactured by Dainichiseika Kogyo Co., Ltd.) heated to 100° C. is applied. coated to form.
Also, a polyester base fabric (substrate 10) having a thickness of 1.0 mm, which is circular knitted polyester, was impregnated with water in an amount of 50% with respect to the weight of the polyester base fabric.
Then, the coating film of the urethane prepolymer formed on the skin layer 40 is disposed so as to be in contact with the base material 10 impregnated with water, and immediately press-bonded at a laminate roll temperature of 40° C. to obtain a urethane prepolymer. The polymer foamed to form foam layer 30 .
As an aging process, after aging for 5 days in an environment of a temperature of 35° C. and a relative humidity of 65%, the synthetic imitation leather was obtained by peeling from the release paper.

(Applicability of liquid mixture for base layer)
A layer (base layer 20) composed of the base layer formulation solutions (B-1) to (B-9) in a wet state is formed on a polyester base fabric (base material 10) having a thickness of 1.0 mm, which is a polyester circular knit. , and evaluated the coatability when coated so as to be formed at the weight (g/m ² ·dry) described in each of Examples and Comparative Examples. "Good" indicates that the coating film of the base layer 20 could be formed uniformly and evenly on the base material 10, and that the coating film of the base layer 20 could not be formed uniformly and evenly. was determined as "Bad".

(Film breaking strength test)
The film breaking strength of the base layer 20 used in each of the obtained synthetic imitation leathers was measured by the following method.
Each base layer formulation solution (B-1) to (B-9) was placed on a release paper (“DNTP-FL” manufactured by Dai Nippon Printing Co., Ltd.), and the weight (g /m ² ·dry), and the film obtained by drying was punched into a width of 1.5 cm and a length of 5.0 cm using a dumbbell to prepare a sample.
Then, a cellophane tape ("CT-12S" manufactured by Nichiban Co., Ltd.) was attached to each 1.5 cm part from both ends of the sample, fixed to a gripper of Autograph AGS-J manufactured by Shimadzu Corporation, and at a speed of 200 mm / min. The breaking strength of the film was obtained by dividing the tensile strength at which the sample broke by the cross-sectional area of the sample.

(Peel strength test)
A urethane-based HM tape with a width of 17 mm was thermocompression bonded to each of the obtained synthetic imitation leathers, and then a strip-shaped measurement sample with a width of 25 mm was prepared. was measured.
In general, it is judged that adhesion (peel strength) to the base material 10 exceeding a practically acceptable level for foamed synthetic imitation leather is obtained when it is 1.5 kgf/inch or more.

(Evaluation of degree of foaming: Density of foam layer)
Each obtained synthetic imitation leather was cut into 10 cm×10 cm squares and weighed. Separately, the weights of the substrate 10 on which the base layer 20 composed of the base layer formulation solutions (B-1) to (B-6) of 10 cm×10 cm was formed, and the skin layer 40 obtained by peeling the release paper from the film with skin were measured. Then, the density of the foam layer 30 was calculated by the following formula.
(1) Weight measurement and calculation of synthetic imitation leather:
The weight of the entire synthetic imitation leather: a, the weight of the base material 10: b, the weight of the skin layer 40: c, the weight of the base layer 20: d. The weight of the foam layer 30 was obtained by the following formula. .
Weight of foam layer 30: Ho-I-Ro-Hani (2) Thickness measurement and calculation of synthetic imitation leather:
The thickness of the foam layer 30 was obtained from the following formula: thickness of the entire synthetic imitation leather: f; thickness of the base material: g;
Thickness of foam layer 30: Le = Haet-line (3) Calculation of density of foam layer 30: Density of foam layer 30 was obtained by the following formula.
Density of foam layer 30 = ho / (ru x 10 x 10) (g/cm ³ )
It can be determined that good flexibility and high peel strength can be achieved at the same time when the foam layer 30 has a density of 0.03 g/cm ³ to 0.30 g/cm ³ .

(Texture (flexibility) evaluation)
The softness of each synthetic imitation leather thus obtained was compared with the standard synthetic imitation leather based on the feeling of touch with the hand, and the evaluation indexes were as follows. If the evaluation is A to C, it is acceptable.
A: Softer than standard synthetic imitation leather B: Equivalently soft as standard synthetic imitation leather C: A little harder than standard synthetic imitation leather D: Significantly harder than standard synthetic imitation leather

《Production of standard synthetic imitation leather》
100 parts by mass of Rezamin UD-8351NT (polyurethane resin adhesive, manufactured by Dainichiseika Kogyo Co., Ltd.), C-50 cross-linking agent ( An adhesive prepared by mixing 10 parts by mass of an isocyanate cross-linking agent (manufactured by Dainichiseika Kogyo Co., Ltd.) was coated so as to form an adhesive layer having a thickness of 100 μm.
After that, pre-drying is performed at 80° C. for 2 minutes, and the obtained adhesive layer is arranged so as to be in contact with a 1.0 mm-thick polyester base fabric (base material 10), which is circular knitted polyester, and laminated rolls. Pressure bonding was performed at a temperature of 40°C. Thereafter, aging was performed under the conditions of 50° C./48 hours to obtain a standard synthetic imitation leather (common dry leather using MEK) for texture (flexibility) evaluation.

[Regarding pass/fail judgment]
In each table, a peel strength of 1.5 kgf / inch or more and a texture (flexibility) evaluation of A to C are judged as "Pass", and those that do not meet this standard are judged as "Fail". did.

In Tables 2 and 3, the coating film thickness of the underlayer composition liquid is coated with a certain distance from the die slot for those other than the bar coater. Since this is due to die coating, the distance between the die slot and the base material was used as a reference value for the coating film thickness in the wet state immediately after coating.
In Tables 2 and 3, the bar coater indicated as the coating film thickness of the base layer formulation liquid indicates that the coating was performed using the bar coater of the indicated count. The standard film thickness in the wet state quoted from the manufacturer's data (Daiichi Rika Co., Ltd.) is also written in parentheses as a reference value for the coating film thickness in the wet state.

The (dry) thickness of the base layer in Tables 2 and 3 was calculated by measuring 10-point averages from cross-sectional images obtained by SEM for Examples 3, 8, 10 and Comparative Example 3.
On the other hand, in Examples 1, 2, 4 to 7, 9 and Comparative Examples 2 and 4, since the base layer 20 could not be confirmed in the cross-sectional image by SEM, release paper (“DNTP-FL” manufactured by Dai Nippon Printing Co., Ltd.) ), a blended liquid containing the water-based polyurethane resin to be measured is applied so as to be equivalent to the basis weight of the underlying layer 20 when dry, and the drying process is 60° C. for 4 minutes and 100° C. for 3 minutes. , and 3 minutes at 120° C., the thickness of the base layer formed on the release paper was used as the thickness of the base layer 20 to be measured.

From Tables 2 and 3, this example reduces the foaming density to less than 0.3 g/cm ³ and has an excellent texture comparable to that of conventional leather, for example, synthetic imitation leather made by a wet method using DMF ( It was found that good adhesion was exhibited even when flexibility) was expressed.
Moreover, in this example, a higher peel strength was obtained than in the case where the base material was impregnated with water as in Comparative Example 1. This is because in Comparative Example 1, the distribution of the amount of water per unit area tends to vary due to dehydration due to the use of mangles, and the moisture-curable adhesive that can be a foam layer locally foams excessively, and excessively It is presumed that it was impregnated.

REFERENCE SIGNS LIST 10 base material 20 base layer 30 foam layer 40 skin layer

Claims

a substrate;
A base layer formed of a liquid mixture containing a water-soluble resin provided on the base material;
A foam layer formed by foaming a urethane prepolymer having an isocyanate group at the end provided on the base layer,
The base layer has a basis weight of 3 to 60 g/m 2 ·dry,
The porous layer structure, wherein the film breaking strength of the underlayer after drying is 5 MPa or more.
The porous layer structure according to claim 1, wherein the viscosity of the blended liquid containing the water-soluble resin is 500 to 50,000 mPa·s at 25°C.
The porous layer structure according to claim 1 or 2, wherein the water-soluble resin is at least one selected from the group consisting of water-based polyurethane resin, water-based polyethylene glycol resin and water-based polyvinyl alcohol resin.
The porous layer structure according to claim 3, wherein the water-soluble resin is an aqueous polyurethane resin.
The porous layer structure according to claim 3, wherein the water-soluble resin is a water-based polyethylene glycol resin, and the number-average molecular weight of the water-based polyethylene glycol resin is 500,000 or more.
The porous layer structure according to any one of claims 1 to 5, wherein the thickness ratio between the underlayer and the substrate is 1:10 to 1:1,000.
The porous layer structure according to any one of claims 1 to 6, which has a skin layer on the surface of the foam layer opposite to the surface on which the base layer is laminated.
A base layer lamination step of applying a liquid mixture containing a water-soluble resin onto a base material to form a wet base layer on the base material;
a foam layer lamination step of disposing a urethane prepolymer having an isocyanate group at the terminal on the wet base layer, and foaming the urethane prepolymer with the moisture of the base layer to form a foam layer;
The base layer has a basis weight of 3 to 60 g/m 2 ·dry,
A method for producing a porous layer structure, wherein the film breaking strength of the underlayer after drying is 5 MPa or more.
The method for producing a porous layer structure according to claim 8, further comprising a skin layer lamination step of laminating a skin layer on the surface of the foam layer opposite to the surface on which the base layer is laminated.
The method for manufacturing the porous layer structure according to claim 8 or 9, further comprising an aging process for promoting foaming of the foam layer after the foam layer lamination process.