JP7484208B2 - Urethane resin composition and method for producing porous body - Google Patents

Description

The present invention relates to a urethane resin composition and a method for producing a porous body by a wet film-forming method.

Polishing pads using urethane resin compositions are widely used in fields that require high surface flatness, such as liquid crystal glass, hard disk glass, silicon wafers, and semiconductors. In particular, for the final finishing polishing, soft porous bodies are used that are processed by a wet film formation method in which urethane resin diluted with a solvent such as DMF (dimethylformamide) is solidified in water (see, for example, Patent Document 1).

The properties required for this porous polishing pad include, for example, a high bulk modulus (= low compressibility) to maintain the flatness of the workpiece surface, flexibility as a material to prevent scratches on the surface, and fineness and uniformity of the porous cells (wet film-forming ability) that are responsible for retaining the slurry (polishing liquid) and stable polishing.

However, the above-mentioned low compression ratio, flexibility, and wet film-forming properties are contradictory physical properties. For example, if an attempt is made to reduce the compression ratio of a polishing pad in order to emphasize flatness, the urethane resin will harden, and scratch resistance will deteriorate. Furthermore, if the hardness of the urethane resin is reduced in order to emphasize scratch resistance, coagulation in water will not proceed quickly, resulting in a loss of uniformity in the porous cells and instability in polishing. As such, it has been difficult to achieve a high level of balance between all of these physical properties.

JP 2004-256738 A

The problem that the present invention aims to solve is to provide a method for producing a porous body that has excellent wet film-forming properties and a low compression ratio.

The present invention provides a urethane resin composition containing a urethane resin (A), a solvent (B), and a film-forming aid (C), characterized in that the film-forming aid (C) contains a hydrocarbon (c1) having 8 to 18 carbon atoms.

The present invention also provides a method for producing a porous body, which is characterized by wet-forming the urethane resin composition.

According to the present invention, by using a specific film-forming assistant, a fine and uniform porous body can be produced with a low compression ratio by a wet film-forming method. Therefore, the present invention can be particularly suitably used for the production of polishing pads, artificial leather, and synthetic leather.

In the present invention, the "porous body" refers to a body having a large number of pores that can be obtained by solidifying a urethane resin composition using a wet film-forming method, and for example, a body having a spindle-shaped or teardrop-shaped porous structure that is long in the thickness direction of the surface.

The present invention is a method for producing a porous body by wet film formation of a urethane resin composition containing a urethane resin (A), a solvent (B), and a specific film-forming aid (C).

In the present invention, it is essential that the film-forming auxiliary (C) contains a hydrocarbon (c1) having a carbon number in the range of 8 to 18. The hydrocarbon having the specific carbon number is moderately hydrophobic, and therefore adjusts the coagulation speed of the urethane resin in water, reduces the replacement of DMF with water, and suppresses surface coagulation, thereby realizing fine and uniform porous cells by wet film formation, and also obtaining a porous body with a low compression ratio. If a hydrocarbon having less than 8 carbon atoms is used as the hydrocarbon, it is not effective in suppressing the speed of surface coagulation, and a porous body with excellent low compression ratio cannot be obtained, and if a hydrocarbon having more than 18 carbon atoms is used, the hydrophobicity is too strong and the uniformity of the porous cells is poor. Furthermore, if a film-forming auxiliary with high hydrophilicity is used instead of the hydrocarbon (c1), the porous cells will become enlarged, the wet film-forming property will deteriorate, and the compression ratio will increase. The number of carbon atoms of the hydrocarbon (c1) is preferably in the range of 9 to 16, more preferably in the range of 10 to 14, from the viewpoint of achieving a higher level of both wet film-forming property and low compression ratio.

The hydrocarbon (c1) is one that is composed only of carbon atoms and hydrogen atoms and has a number of carbon atoms within the specific range. Examples of the hydrocarbon (c1) include normal paraffins, isoparaffins, aromatic compounds, naphthenic compounds, and the like. These compounds may be used alone or in combination of two or more. Among these, isoparaffins are preferred because they can achieve a higher level of both wet film-forming properties and low compression ratio.

The density of the hydrocarbon (c1) at 15° C. is preferably in the range of 0.7 to 0.83 g/ ^cm3 , and more preferably in the range of 0.7 to 0.8 g/ ^cm3 , from the viewpoint of achieving both wet film-forming properties and a low compressibility at a higher level.

The film-forming auxiliary (C) may be used in combination with other film-forming auxiliary in addition to the hydrocarbon (c1). The content of the hydrocarbon (c1) in the film-forming auxiliary (C) is preferably 30% by mass or more, and more preferably 70% by mass or more, in order to achieve a higher level of both wet film-forming property and low compression ratio.

The content of the hydrocarbon (c1) is preferably in the range of 0.1 to 30 parts by mass, and more preferably in the range of 1 to 25 parts by mass, per 100 parts by mass of the urethane resin (A).

The urethane resin (A) used in the present invention may be, for example, a reaction product of polyol (a1) and polyisocyanate (a2).

As the polyol (a1), for example, polyester polyol, polyether polyol, polycarbonate polyol, etc. can be used. These polyols may be used alone or in combination of two or more kinds.

The number average molecular weight of the polyol (a1) is preferably in the range of 500 to 10,000, more preferably in the range of 700 to 8,000, from the viewpoint of the mechanical properties and flexibility of the porous body. The number average molecular weight of the polyol (a1) is a value measured by gel permeation chromatography (GPC).

The polyol (a1) may be used in combination with a chain extender (a1-1) having a number average molecular weight of less than 500, if necessary. As the chain extender (a1-1), for example, a chain extender having a hydroxyl group, a chain extender having an amino group, etc. may be used. These chain extenders (a1-1) may be used alone or in combination of two or more kinds.

Examples of the chain extender having a hydroxyl group include aliphatic polyol compounds such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexamethylene glycol, saccharose, methylene glycol, glycerin, and sorbitol; aromatic polyol compounds such as bisphenol A, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfone, hydrogenated bisphenol A, and hydroquinone; and water. These chain extenders may be used alone or in combination of two or more.

Examples of the chain extender having an amino group include ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, 4,4'-diphenylmethanediamine, 3,3'-dichloro-4,4'-diphenylmethanediamine, 1,2-cyclohexanediamine, 1,4-cyclohexanediamine, aminoethylethanolamine, hydrazine, diethylenetriamine, and triethylenetetramine. These chain extenders may be used alone or in combination of two or more.

Examples of the polyisocyanate (a2) that can be used include aromatic polyisocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenylene diisocyanate, toluene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate and lysine diisocyanate; and alicyclic polyisocyanates such as cyclohexane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate. These polyisocyanates may be used alone or in combination of two or more.

The urethane resin (A) can be produced, for example, by reacting the polyol (a1), the polyisocyanate (a2), and, if necessary, the chain extender (a1-1). These reactions are preferably carried out at a temperature of 50 to 100°C for approximately 3 to 10 hours. The reaction may also be carried out in a solvent (B) described below.

The molar ratio of the sum of the hydroxyl groups of the polyol (a1) and the hydroxyl groups and amino groups of the chain extender (a1-1) to the isocyanate groups of the polyisocyanate (a2) [(isocyanate groups)/(hydroxyl groups and amino groups)] is preferably in the range of 0.8 to 1.2, and more preferably in the range of 0.9 to 1.1.

The weight average molecular weight of the urethane resin (A) obtained by the above method is preferably in the range of 5,000 to 1,000,000, and more preferably in the range of 10,000 to 500,000, from the viewpoint of the mechanical strength and flexibility of the porous body. The weight average molecular weight of the urethane resin (A) is a value obtained by measuring in the same manner as the number average molecular weight of the polyol (a1).

The content of the urethane resin (A) is, for example, in the range of 10 to 90 parts by mass in the urethane resin composition.

As the solvent (B), for example, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N,N,2-trimethylpropionamide, N,N-dimethylacrylamide, N,N-dimethylpropionamide, N,N-diethylacetamide, N,N-diethylacrylamide, N-ethylpyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, etc. can be used. These organic solvents may be used alone or in combination of two or more. In addition, organic solvents such as ethyl acetate, methyl acetate, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropyl alcohol, isobutanol, sec-butanol, and tertiary butanol may be used in combination, if necessary.

The content of the solvent (B) is, for example, in the range of 10 to 90 mass % in the urethane resin composition.

The urethane resin composition contains the urethane resin (A), the solvent (B), and the film-forming aid (C) as essential components, but may contain other additives as necessary.

Examples of the other additives that can be used include pigments, flame retardants, plasticizers, softeners, stabilizers, waxes, defoamers, dispersants, penetrants, surfactants, fillers, antifungal agents, antibacterial agents, UV absorbers, antioxidants, weathering stabilizers, fluorescent brighteners, antiaging agents, thickeners, etc. These additives may be used alone or in combination of two or more.

Next, we will explain how to manufacture a porous body using the urethane resin composition by a wet film-forming method.

The wet film-forming method is a method in which the urethane resin composition is applied to or impregnated into the surface of a substrate, and then the applied or impregnated surface is brought into contact with water, water vapor, or the like to solidify the urethane resin (A) and produce a porous body.

As the substrate to which the urethane resin composition is applied, for example, a substrate made of nonwoven fabric, woven fabric, or knitted fabric; a resin film, etc. can be used. As the material constituting the substrate, for example, chemical fibers such as polyester fiber, nylon fiber, acrylic fiber, polyurethane fiber, acetate fiber, rayon fiber, and polylactic acid fiber; cotton, hemp, silk, wool, and blends thereof can be used.

The surface of the substrate may be subjected to antistatic treatment, release treatment, water repellency, water absorption, antibacterial and deodorizing treatment, bacteriostatic treatment, ultraviolet blocking treatment, etc., as necessary.

Methods for applying or impregnating the urethane resin composition onto the surface of the substrate include, for example, a gravure coater method, a knife coater method, a pipe coater method, and a comma coater method. In this case, the amount of organic solvent (B) used may be adjusted as necessary to adjust the viscosity of the urethane resin composition and improve coating workability.

The thickness of the coating film made of the urethane resin composition applied or impregnated by the above method is preferably in the range of 0.5 to 5 mm, and more preferably in the range of 0.5 to 3 mm.

Examples of a method for contacting water or water vapor with the coating surface formed by coating or impregnation with the urethane resin composition include a method of immersing a substrate provided with a coating layer or impregnation layer made of the urethane resin composition in a water bath, and a method of spraying water onto the coating surface using a spray or the like. The immersion can be performed, for example, in a water bath at 5 to 60°C for 2 to 20 minutes.

The porous body obtained by the above method is preferably washed on its surface with water at room temperature or hot water to extract and remove the solvent (B), and then dried. The washing can be carried out, for example, with water at 5 to 60°C for 20 to 120 minutes, and it is preferable to replace the water used for washing at least once, or to replace it continuously with running water. The drying is preferably carried out for 10 to 60 minutes, for example, using a dryer adjusted to 80 to 120°C.

As described above, according to the present invention, by using a specific film-forming assistant, it is possible to produce a fine and uniform porous body with a low compression ratio by a wet film-forming method. Therefore, the present invention is particularly suitable for use in the manufacture of polishing pads, artificial leather, and synthetic leather.

The present invention will be explained in more detail below using examples.

Synthesis Example 1 Synthesis of Urethane Resin (A-1) 100 parts by mass of polyester polyol (reaction product of 1,4-butanediol and adipic acid, number average molecular weight: 2,000), 12 parts by mass of ethylene glycol, 519 parts by mass of N,N-dimethylformamide (hereinafter abbreviated as "DMF"), and 61 parts by mass of 4,4'-diphenylmethane diisocyanate were added to a reaction apparatus equipped with a stirrer, a reflux condenser, and a thermometer, and reacted at 60°C for 6 hours with stirring. Subsequently, 1 part by mass of isopropyl alcohol was added, and the mixture was further stirred at 60°C for 1 hour to obtain a urethane resin (A-1) composition.
The obtained urethane resin (A-1) composition had a solid content of 25% by mass, a viscosity of 600 dPa·s, and a weight average molecular weight of the urethane resin of 188,100.

Synthesis Example 2 Synthesis of Urethane Resin (A-2) 65 parts by mass of polyester polyol (a reaction product of ethylene glycol and adipic acid, number average molecular weight: 2,000), 35 parts by mass of polytetramethylene glycol (number average molecular weight: 2,000), 20 parts by mass of 1,4-butanediol, 564 parts by mass of DMF, and 68 parts by mass of 4,4'-diphenylmethane diisocyanate were added to a reaction apparatus having a stirrer, a reflux condenser, and a thermometer, and reacted at 60°C for 6 hours with stirring. Subsequently, 1 part by mass of isopropyl alcohol was added, and the mixture was further stirred at 60°C for 1 hour to obtain a urethane resin (A-2) composition.
The obtained urethane resin (A-2) composition had a solid content of 25% by mass, a viscosity of 550 dPa·s, and a weight average molecular weight of the urethane resin of 168,000.

[Method of measuring number average molecular weight and weight average molecular weight]
The number average molecular weight of the raw material polyol and the weight average molecular weight of the urethane resin (A) used in the synthesis examples are values measured by gel permeation chromatography (GPC) under the following conditions.

Measurement device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were used, connected in series.
"TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 "TSKgel G2000" (7.8mm I.D. x 30cm) x 1 Detector: RI (differential refractometer)
Column temperature: 40°C
Eluent: tetrahydrofuran (THF)
Flow rate: 1.0 mL/min Injection volume: 100 μL (sample concentration 0.4% by mass in tetrahydrofuran solution)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

[Example 1]
To 100 parts by mass of the urethane resin (A-1) composition obtained in Synthesis Example 1, 40 parts by mass of DMF and 1 part by mass of isoparaffin having 12 carbon atoms ("Merveille 30" manufactured by Toa Oil Co., Ltd., density: 0.77 g/cm ³ , hereinafter abbreviated as "c1-1") as a film-forming aid were added to prepare a blended liquid, which was then applied to a polyethylene terephthalate (PET) film to a thickness (wet) of 1 mm. Next, the applied substrate was immersed in a coagulation bath (water at 25°C) for 10 minutes to coagulate the urethane resin. Thereafter, the substrate was immersed in water at 50°C for 60 minutes to wash off the solvent. After washing, the substrate was dried with hot air at 100°C for 30 minutes to obtain a porous body.

[Example 2]
In Example 1, the type of the film-forming auxiliary was changed to isoparaffin having 12 carbon atoms ("IP Solvent 1620" manufactured by Idemitsu Kosan Co., Ltd., density: 0.76 g/cm3 ^, hereinafter abbreviated as "c1-2"). A porous body was obtained in the same manner as in Example 1.

[Example 3]
A porous body was obtained in the same manner as in Example 1, except that the type of film-forming auxiliary was changed to isoparaffin having 12 carbon atoms ("IP Clean LX" manufactured by Idemitsu Kosan Co., Ltd., density: 0.74 g/cm3 ^, hereinafter abbreviated as "c1-3").

[Example 4]
In Example 1, the type of the film-forming auxiliary was changed to isoparaffin having 16 carbon atoms ("IP Solvent 2028" manufactured by Idemitsu Kosan Co., Ltd., density: 0.79 g/cm3 ^, hereinafter abbreviated as "c1-4"). A porous body was obtained in the same manner as in Example 1.

[Example 5]
A porous body was obtained in the same manner as in Example 1, except that the urethane resin (A-1) composition in Example 1 was replaced with a urethane resin (A-2) composition.

[Comparative Example 1]
A porous body was obtained in the same manner as in Example 1, except that the type of film-forming auxiliary in Example 1 was changed to hexane (hereinafter referred to as "cR1-2").

[Comparative Example 2]
In Example 1, the type of the film-forming auxiliary was changed to isoparaffin having 20 carbon atoms ("IP Solvent 2835" manufactured by Idemitsu Kosan Co., Ltd., density: 0.82 g/cm3 ^, hereinafter abbreviated as "cR1-1"). A porous body was obtained in the same manner as in Example 1.

[Method for evaluating wet film-forming properties]
The cross-sectional state of the porous bodies obtained in the examples was observed with a scanning electron microscope "JSM-IT500" (magnification: 100x) manufactured by JEOL Ltd. to confirm the cell shape (thinness, uniformity). If the cells had a maximum width of 70 μm or less, which accounted for 60% of the total, the cell was evaluated as "○", otherwise it was evaluated as "×".

[Method of evaluating compression ratio]
The porous bodies obtained in the examples were evaluated for compressibility in accordance with JIS L-1021-6. Specifically, the "thickness under standard pressure: t0" was measured after applying an initial load of 2 kPa for 30 seconds, and then the "thickness under constant pressure: t1" was measured after applying a final load of 98 kPa for 30 seconds, and the compressibility was calculated by applying this to the following formula.
Compression ratio (%) = 100 × (t0 - t1) / t0
If the compression rate thus obtained was 20% or less, it was evaluated as "◯", otherwise it was evaluated as "×".

It was found that the porous body obtained from the urethane resin composition of the present invention has fine and uniform cells and also has excellent low compressibility.

On the other hand, Comparative Example 1 uses a hydrocarbon with fewer carbon atoms than the number specified in the present invention as a film-forming aid, but the porous cell formation is poor and the low compressibility is also poor.

Comparative Example 2 uses a hydrocarbon with a carbon atom number exceeding the number specified in the present invention as a film-forming aid, but the porous cell formation is poor and the low compressibility is also poor.

Claims (4)

A urethane resin composition comprising a urethane resin (A), a solvent (B), and a film-forming auxiliary (C),
The urethane resin (A) contains polyol (a1) and polyisocyanate (a2) as essential reaction raw materials,
the polyol (a1) comprises a polyester polyol,
The polyisocyanate (a2) contains 4,4'-diphenylmethane diisocyanate,
The solvent (B) contains N,N-dimethylformamide,
The urethane resin composition, wherein the film-forming auxiliary (C) contains a hydrocarbon (c1) having 8 to 18 carbon atoms. 2. The urethane resin composition according to claim 1, wherein the content of the hydrocarbon (c1) is in the range of 0.1 to 30 parts by mass per 100 parts by mass of the urethane resin (A). The urethane resin composition according to claim 1 or 2, wherein the hydrocarbon (c1) is isoparaffin. A method for producing a porous body, comprising wet-forming a film of the urethane resin composition according to any one of claims 1 to 3.