JPH0660260B2 - Method for producing polyurethane foam - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a polyurethane foam, and more specifically, a polyurethane foam from a polyurethane emulsion, which is soft and has a good texture, particularly polyurethane foam for artificial leather. A method of manufacturing a body.

(Prior Art and Its Problems) [Prior Art] A conventionally known method for producing a polyurethane foam is a wet coagulation method using a solution of a polyurethane resin in an organic solvent, which is a non-solvent for the polyurethane resin and an organic solvent. Is passed through a coagulating liquid (usually water) compatible with the above to coagulate, followed by washing with water and drying to form a porous foam.

[Problems of the prior art] The foam obtained by the wet coagulation method as described above is the only method commonly used in the field of high-grade artificial leather, because it gives a unique suede-like texture. However, this wet coagulation method requires an apparatus for collecting an organic solvent that elutes in water from the standpoint of pollution prevention, in addition to a production machine and peripheral equipment, and for these reasons, a huge capital investment is required.

In recent years, the application of a polyurethane emulsion containing no organic solvent to the artificial leather field has been studied, for example,
A foaming agent and a thickener are added to polyurethane emulsion, and the foaming liquid obtained by mechanically foaming is coated on a base cloth,
A method of drying: a method of adding a chemical foaming agent and a heat-sensitive coagulant to a polyurethane emulsion, dipping the base cloth using the same, and then drying it is known.

However, in the former case, a constant thickening is required to maintain the stability of the foam, and as a result, the processing method is limited to the coating method, so that the base cloth is not appropriately impregnated. In the latter case, it is difficult to obtain a stable and uniform structure because it is difficult to balance the foaming temperature of a normal chemical foaming agent and the solidification temperature of a urethane emulsion, so it is still established as an industrial manufacturing method. I haven't.

(Object of the Invention) In view of the above situation, the present invention does not contain an organic solvent,
An object of the present invention is to provide a method for producing a polyurethane foam, which is suitable for application to the artificial leather field using a polyurethane emulsion.

(Means for Achieving Object) [Outline] The present inventors have conducted a study on a method for producing a polyurethane foam that does not contain an organic solvent and is suitable for application to the artificial leather field by using a polyurethane emulsion. We succeeded in forming a stable and uniform foam structure without mechanical foaming.

That is, the present invention, a heat-sensitive coagulable and heat-expandable polyurethane emulsion composition having a heat-sensitive coagulable polyurethane emulsion and a heat-expandable plastic ma microballoon as essential components, in water or steam of 40 ℃ ~ 190 ℃. A method for producing a polyurethane foam, which is characterized in that it is treated.

[Heat-sensitive coagulable polyurethane emulsion] The heat-sensitive coagulable polyurethane emulsion of the present invention has a cloud point of 35 to 95 ° C with respect to 100 parts by weight of a hydrophobic polyurethane resin.
A nonionic polyurethane emulsion containing 2 to 30 parts by weight of the nonionic surfactant of 1.
It may contain 5 to 10 parts by weight of a heat-sensitive coagulant. The method for producing this nonionic polyurethane emulsion is not particularly limited, and a method of forcibly emulsifying and dispersing by adding a nonionic surfactant to a hydrophobic polyurethane resin;
A method in which a hydrophobic urethane prepolymer containing a free isocyanate group is dispersed in water in the presence of a nonionic emulsifier and then chain-extended with a polyamine compound; and the like can be mentioned, but according to the method of Japanese Patent Application No. 62-174376. Are particularly preferred.

The nonionic surfactant used in the present invention includes polyoxyethylene alkyl ether type, polyoxyethylene alkylphenol ether type, polyoxyethylene propylene ether type, higher alcohol polyethylene glycol ether type, aliphatic polyethylene glycol ether type,
Polyoxyethylene arylphenol ether type, etc. having a cloud point of 35 to 95 ° C. and having a cloud point of 35 ° C. or lower and 95 ° C. or higher cannot give a stable urethane emulsion or a uniform foamed product which is an object of the present invention. Does not form.

The amount of nonionic surfactant added is 100% polyurethane resin.
2 to 30 parts by weight is suitable with respect to parts by weight, a stable emulsion cannot be obtained with 2 parts by weight or less, and the performance of the obtained foam is insufficient with 30 parts by weight or more.

The nonionic polyurethane emulsion of the present invention itself has a heat-sensitive coagulation property due to the cloud point of the nonionic surfactant, but if necessary, a heat-sensitive coagulant is added to adjust it to a desired heat-sensitive coagulation temperature. The preferred heat-sensitive coagulation temperature of the emulsion of the present invention is 35 to 100 ° C. Here, as the heat-sensitive coagulant optionally added, cellulose methyl ether, a compound having a methyl ether group such as polyvinyl methyl ether, a polymethylsiloxane compound,
Well-known substances such as sodium salts of potassium and potassium fluoro, nitric acid, sulfuric acid, ammonium salts of hydrochloric acid, soluble salts of polyvalent metals such as calcium, magnesium, zinc, cadmium, nickel, barium and aluminum can be used.

[Heat-Expandable Plastic Microballoon] The heat-expandable plastic microballoon used in the present invention comprises a thermoplastic resin as a shell, and an encapsulating organic compound having a specific boiling point as an expanding agent.
It is a small hollow sphere having a size of 0 μm, and the outer shell of the plastic is softened by heating, the encapsulated organic compound is gasified and expanded, and normally expands to a volume of about 50 times.

Examples of this type of microballoon include those obtained by encapsulating and encapsulating isobutane with a vinylidene chloride-acrylonitrile copolymer as a shell. There are various grades such as fine powder or water-containing cake that have different expansion start temperature and maximum expansion point depending on polymer type, shell thickness, balloon diameter, etc., heat-sensitive coagulation temperature of polyurethane emulsion and treatment bath with water or steam. It can be appropriately selected in relation to the temperature. In this case, the expansion initiation temperature of the microballoon is preferably at least equal to or slightly higher than the heat-sensitive coagulation temperature of the polyurethane emulsion. If the temperature is significantly lower or higher than the heat-sensitive coagulation temperature, the desired foam cannot be obtained.

The mixing of the heat-sensitive coagulable polyurethane emulsion and the heat-expandable plastic microballoon is easy. The amount of microballoons added is the expansion ratio of the desired foam,
Depending on the heat-sensitive coagulation temperature of the emulsion, treatment bath conditions, etc., it is 1 to 100 parts by weight, preferably 2 to 50 parts by weight, based on 100 parts by weight of the solid content of the heat-sensitive coagulation polyurethane emulsion.

The heat-sensitive coagulable and heat-expandable polyurethane emulsion composition includes a cross-linking agent such as methylol melamine-based, aziridine-based, epoxy-based, blocked isocyanate-based, a colorant such as a water-dispersible pigment, calcium carbonate, and aluminum hydroxide. If desired, a filler, a thickener such as polyvinyl alcohol, an antioxidant, an antiaging agent such as an ultraviolet absorber, and various other commonly used additives may be added. It is also possible to add other water-based resins having heat-sensitive coagulability, for example, natural rubber, synthetic rubber tex, ethylene vinyl acetate copolymer emulsion, acrylate emulsion and, if desired, other water-based resins that do not impair heat-sensitive coagulability. is there.

[Foaming Treatment] The heat-sensitive coagulable and heat-expandable polyurethane emulsion composition of the present invention instantaneously coagulates and foams to form a polyurethane foam by being treated in water or steam at 40 to 190 ° C. . In general, the present emulsion composition is impregnated or applied to a base fabric such as a non-woven fabric or a raised fabric, and is immersed in the hot to hot water or is passed through hot steam to form a foam coagulated heat sensitively between fiber tissues. It can be formed in a block shape. The temperature of the treatment bath varies depending on the heat-sensitive coagulation temperature of the emulsion composition, but it is necessary to be at least 10 ° C. higher than the heat-sensitive coagulation temperature, and usually hot water or hot steam treatment at 80 ° C. or higher is suitable. The hot steam treatment here is the usual pressurized steam (0 to 6 kg / cm ² ) treatment and 17
Includes superheated steam treatment at 0-190 ° C. The treatment time is usually several seconds to several minutes. After the treatment, if necessary, excess water is squeezed and dried at 80 to 120 ° C by dry heat.

When the temperature of the treatment bath is equal to or lower than the heat-sensitive coagulation temperature of the emulsion composition, sufficient foamed coagulated product is not generated or is not coagulated at all and is eluted in hot water. Further, even if the emulsion composition of the present invention is impregnated or applied and then dried by heat, a desired foamed product cannot be obtained regardless of the treatment temperature. The reason why the desired foam can be obtained only by warm to hot water or hot steam treatment is not clear from now on, but a strong solidified film of urethane emulsion is formed under dry heat. On the other hand, one reason may be that the film strength is appropriate under the wet heat condition and does not hinder the thermal expansion of the microballoons.

(Function) The polyurethane foam formed by the method of the present invention is
The present invention provides an excellent industrial production method that has a feeling equal to or better than that of a conventional wet coagulation method and does not contain an organic solvent at all, and thus does not cause environmental pollution and has a low total cost.

In short, the method for producing a polyurethane foam of the present invention is a method which can be called, so to speak, a wet coagulation method using a water-based urethane resin, and is conventionally impossible except for a wet coagulation method using a solvent-based polyurethane resin. This is an epoch-making thing that can be applied to leather.

The polyurethane foam according to the present invention can be applied to not only the above-mentioned artificial leather but also a non-clothing field such as clothing or shoes, bags, wall coverings, etc. as a base fabric and an intermediate layer of synthetic leather.

(Examples) Hereinafter, details and effects of the present invention will be more specifically described with reference to Reference Examples, Examples, and Comparative Examples, but the exemplification is naturally for explanation, and is not intended to limit the inventive idea. Absent.

Reference example 1. Preparation of heat-sensitive coagulable polyurethane emulsion; Polyptyrene adipate diol (average molecular weight 1,000) 1
80 parts, polyoxyethylene propylene random copolymer glycol (average molecular weight 3,400, oxyethylene chain content 8
0 wt%) 20 parts, 1,4-butanediol 3.8 parts, trimethylolpropane 3.8 parts and methyl ethyl ketone 143.8 parts in a mixture of zinc hexyl methane diisocyanate 79.9
Parts were added and reacted at 75 ° C. for 90 minutes to obtain a methyl ethyl ketone solution of a urethane polymer having a free isocyanate group content of 1.03%. To this solution, 14.4 parts of polyoxyethylene arylphenol ether type nonionic surfactant (HLB 15, cloud point 86.2 ° C), which is an ethylene oxide adduct of distyrenated phenol, was added and mixed, and then 301.9 parts of water was added to emulsify. Disperse and add 5% aqueous solution of ethylenediamine 4
After adding 2.4 parts and stirring for 60 minutes, methyl ethyl ketone was distilled off at 40 to 50 ° C under reduced pressure with an evaporator to obtain an average particle size.
A milky white urethane resin emulsion having 1.2 μm and a solid content of about 43% was obtained. The heat-sensitive coagulation temperature of this emulsion is 80
It was ~ 85 ° C.

Reference example 2. Preparation of heat-sensitive coagulable polyurethane emulsion; Polyoxyethylene arylphenol ether type nonionic surfactant of Reference Example 1 (HLB 15, cloud point 86.2 ° C) was replaced with polyoxyethylene arylphenol ether type nonionic surfactant (HLB 13, Except that the cloud point was changed to 64.5 ° C)
The same operation as in Reference Example 1 was carried out to obtain a milky white urethane resin emulsion having an average particle size of 1.5 μm and a solid content of about 49.5%. The heat-sensitive coagulation temperature of this emulsion was 60 to 65 ° C.

Reference example 3. Preparation of heat-sensitive coagulable polyurethane emulsion: 100 parts by weight of the urethane resin emulsion of Reference Example 2
% Magnesium sulfate aqueous solution 10 parts by weight was added to the solid content
A 47.5% milky white emulsion was obtained. The heat-sensitive coagulation temperature of this emulsion was 50 to 55 ° C.

Reference example 4. Preparation of heat-sensitive coagulable polyurethane emulsion; polyoxytetramethylene glycol (average molecular weight 1,00
0) 180 parts, polyethylene glycol (average molecular weight 600) 1
74.8 parts of diphenylmethane diisocyanate was added to a mixture of 4.8 parts, polyoxyethylene / propylene random copolymer glycol (average molecular weight 3,400) 14.8 parts, 1,4-butanediol 3.0 parts, trimethylolpropane 5.1 parts and methyl ethyl ketone 147.6 parts, and 75 ° C was added. Was reacted for 60 minutes to obtain a methyl ethyl ketone solution of a urethane polymer having a free isocyanate group content of 0.36%. To this solution, 14.8 parts of polyoxyethylene arylphenol ether type nonionic surfactant (HLB 13, cloud point 64.5 ° C), which is an ethylene oxide adduct of distyrenated phenol, and polyoxyethylene which is an ethylene oxide adduct of distyrenated phenol, are added. After adding 14.8 parts of ethylene arylphenol ether type nonionic surfactant (HLB 15, cloud point 86.2 ° C) and 324.7 parts of water to emulsify, add 15.2 parts of 5% aqueous solution of ethylenediamine, stir for 60 minutes, and then distill off the solvent. Average particle size 1.2μ
A urethane resin emulsion having a solid content of about 50% and an emulsified color was obtained. The heat-sensitive coagulation temperature of this emulsion is 70-75 ℃
Met.

Reference example 5. 100 parts by weight of the urethane resin emulsion of Reference Example 4 was added with a polymethylsiloxane-based heat-sensitive coagulant (TP manufactured by Toshiba Silicon Co., Ltd.
A-1380) 5 parts by weight was added to obtain a milky white emulsion having a solid content of about 49%. The heat-sensitive coagulation temperature of this emulsion was about 50 ° C.

Examples 1-13. Preparation of heat-sensitive coagulable and heat-expandable polyurethane emulsion composition; Heat-expandable plastic microcapsule obtained by encapsulating vinylidene chloride-acrylonitrile copolymer as a shell and isobutane as an expanding agent in the heat-sensitive coagulable polyurethane emulsions of Reference Examples 1 to 5. Balloon (Expansell DU # 551, expansion temperature 100-140 ° C and Expansell WU # 642: expansion temperature 90-120 ° C)
The heat-sensitive coagulable and heat-expandable polyurethane emulsion of the present invention was prepared by blending as shown in the table.

Examples 14-26. Impregnation treatment of non-woven fabric: Polyester non-woven fabric (Spunbond E-1040 manufactured by Asahi Kasei Kogyo Co., Ltd.) was dipped in the heat-sensitive coagulable and heat-expandable polyurethane emulsion compositions of Examples 1 to 13 to 70% with mangle. Squeezed into Then, the impregnated cloth was immersed in hot water of 95 to 100 ° C. for 1 minute to foam and coagulate, and then excess water was centrifugally dehydrated and dried and dried at 100 ° C. for 5 minutes. Each of the impregnated non-woven fabrics after drying (solid content adhesion amount: about 35%) was a flexible foamed sheet, and the sheet thickness was about 3 to 5 times that before treatment.

Comparative Example 1. Polyester nonwoven fabric (Asahi Kasei Co., Ltd.) was added to the heat-sensitive coagulable and heat-expandable polyurethane emulsion compositions of Examples 1 to 13.
Impregnated with Spunbond E-1040 manufactured by K.K.
Squeezed to 70%. Next 80 ℃ 100 ℃ 120 ℃ 140 ℃ 160
Dry heat drying was carried out for 1 to 10 minutes in each oven at ℃ and 180 ℃.

Regardless of the length of the drying time, the impregnated treated cloths after drying each became a hard paper-like sheet, and the sheet thickness was about 1.0 to 1.5 times that before treatment, and almost no foaming was observed. .

Comparative example 2. The polyester nonwoven fabric was immersed in the heat-sensitive coagulable and heat-expandable polyurethane emulsion compositions of Examples 1 to 4, squeezed to 70% with a mangle, and then immersed in hot water at 80 ° C and 60 ° C.

At 80 ° C, a solidified product was gradually formed, but it was hardly fixed to the nonwoven fabric. At 60 ° C, the emulsion was only eluted in hot water.

Example 27. The polyester nonwoven fabric was dipped in the heat-sensitive coagulable and heat-expandable polyurethane emulsion composition of Example 12, squeezed to 70% with a mangle, and then dipped in hot water at 80 ° C. and 60 ° C. for 2 minutes. After removing excess water, it was dried at 100 ° C. 80 ° C
The one treated with hot water foamed to a sheet thickness about 3 times, and the one treated with hot water at 60 ° C. foamed to a sheet thickness about twice.

Example 28. The heat-sensitive coagulable and heat-expandable polyurethane emulsion compositions of Examples 1 to 4 were impregnated with a polyester nonwoven fabric and squeezed to 70% with a mangle. Then, it was continuously steamed for 1 minute by using superheated steam at 140 to 150 ° C. Each of the impregnated non-woven fabrics after dry heat drying became a flexible foamed sheet-like material, and the sheet thickness was foamed to about 4 to 6 times that before the treatment.

(Effects of the Invention) As described above, the present invention has an excellent texture equal to or higher than that of the conventional wet solidification method, and has a low total cost.
Moreover, since no organic solvent is used at all, it is possible to provide a method for industrially producing a polyurethane foam that is free from environmental pollution, which can contribute to related industries.

Claims (1)

[Claims] 1. A heat-sensitive coagulable and heat-expandable polyurethane emulsion composition comprising a heat-sensitive coagulable polyurethane emulsion and a heat-expandable plastic microballoon as essential components is treated in water or steam at 40 ° C. to 190 ° C. The heat-sensitive coagulable polyurethane emulsion is a nonionic polyurethane emulsion having 100 parts by weight of a hydrophobic polyurethane resin and 2 to 30 parts by weight of a nonionic surfactant having a cloud point of 35 to 95 ° C. as an emulsifier. Microballoon is used for 100 parts by weight of solid content of heat-sensitive coagulable polyurethane emulsion,
1 to 100 parts by weight of the method for producing a polyurethane foam.