Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-10-21
2001-09-18
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S174000, C521S176000
Reexamination Certificate
active
06291538
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing a polyurethane foam. More specifically, the present invention relates to a process for preparing a polyurethane foam which can be suitably used as shoe soles and the like.
2. Discussion of the Related Art
Polyether-based polyurethanes have been employed in soles of men's shoes which would be used for a long period of time since the polyether-based polyurethanes are excellent in hydrolysis resistance as compared with polyester-based polyurethanes. However, the polyether-based polyurethanes are poor in mechanical characteristics such as abrasion resistance and flexing properties at ambient temperature.
To improve the mechanical characteristics of the polyether-based polyurethanes, it has been proposed to replace all or a part of polyoxypropylene-based polyols with polyoxytetramethylene glycol as a polyol component. In general, however, it is difficult to apply a sole made of a polyether-based polyurethane, particularly a sole having a low density to practical uses since the strength of the soles is generally insufficient not only in its foaming process but also as a final product.
Japanese Patent Laid-Open No. Sho 61-268716 discloses a process for preparing an inflexible polyurethane foam excellent in air-permeation properties and dimensional stability, wherein a low-molecular weight polyol and a high molecular weight polyol are used in combination, and not less than 1 part by weight of urea and not less than 2 parts by weight of water are simultaneously used based on 100 parts by weight of the polyols. However, this document does not disclose or suggest the use of a specific amount of urea to improve the strength of a polyurethane foam.
Japanese Unexamined Patent Publication No. Hei 4-502926 discloses that an alkoxylated polyol containing urea in a content of about 5 to about 15% by weight is used in the production of an improved flame-retardant polyurethane foam, wherein the alkoxylated polyol is prepared by subjecting an urea-dissolved mixture obtained by dissolving urea in the mixture of a polyether-polyol or a polyester-polyol with a sugar such as sucrose or lactose to alkoxylation using an alkylene oxide. However, in the alkoxylated polyol, a relatively large amount of urea is used. Also, this document does not disclose or suggest the use of urea in a specific amount to improve the strength of a polyurethane foam.
An object of the present invention is to provide a process for preparing a polyurethane foam having a high strength in spite of having a low density, and is excellent in demolding properties.
Another object of the present invention is to provide a process for preparing a polyurethane foam which can be suitably used as shoe soles.
These and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a process for preparing a polyurethane foam, comprising the step of:
reacting a polyol composition comprising a polyol component containing a polyoxypropylene polyol having an unsaturation degree of not more than 0.06 meq/g (hereinafter referred to as PPG), a catalyst and water with a polyisocyanate compound.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, there is one of great characteristics in that the PPG having an unsaturation degree of not more than 0.06 meq/g is contained in the polyol component. Accordingly, there can be provided a polyurethane foam having high strength such as foam strength and core strength.
The PPG has many oxypropylene recurring units. Accordingly, the PPG effectively acts as a soft segment in a polyurethane foam obtained, and also imparts excellent elongation properties and flexing properties to the polyurethane foam. The molecular weight of the PPG per its hydroxyl group is preferably 1,500 to 20,000, and more preferably 1,800 to 10,000 in order to give sufficient elasticity as a soft segment of the oxypropylene chain and improve its handling.
The PPG can be prepared from a compound having not less than two active hydrogen atoms as a starting material by a process which comprises carrying out a usual ring-opening addition reaction of an alkylene oxide to the above compound, and adding ethylene oxide to the resulting compound at its terminal in a block copolymerization way, and the like.
The compounds having two hydroxyl groups include glycols, phenols having two hydroxyl groups, amines having two hydroxyl groups, alkanolamines having two hydroxyl groups, and the like. The specific examples include alkylene glycols having 2 to 9 carbon atoms such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,9-nonanediol; aromatic glycols such as xylylene glycol, hydroquinone and bisphenol A; diethanolamine; dimethylol urea; and modified compounds thereof. These can be used alone or in admixture thereof.
The compounds having not less than three hydroxyl groups include polyhydric alcohols having not less than three hydroxyl groups, polyphenols having not less than three hydroxyl groups, and the like. The specific examples include glycerol, trimethylolpropane, pentaerythritol, sucrose and triethanolamine, and the like. Among them, glycerol and trimethylolpropane are preferred, and also those which give a PPG having a hydroxyl value of 10 to 300 are preferred.
The alkylene oxide which is added to the compound having two hydroxyl groups and the compound having not less than three hydroxyl groups by ring-opening addition reaction includes ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, styrene oxide, and the like. Among them, it is desirable that propylene oxide is employed alone or used together with the other alkylene oxide so that the propylene oxide can be a main component (the content of which being not less than 50% by weight, preferably not less than 65% by weight, and particularly preferably not less than 80% by weight) to give a random copolymer or a block copolymer of the propylene oxide and the other alkylene oxide, preferably the block copolymer.
It is preferable to use the PPG in which a compound having two hydroxyl groups has been used as a starting material (hereinafter referred to as PPG-A), since there can be obtained a polyurethane foam being excellent in abrasion resistance and flexibility as well as having high strength such as foam strength.
The content of the PPG-A in the polyol component is preferably 50 to 100% by weight, more preferably 80 to 100% by weight, and particularly preferably 90 to 100% by weight from the viewpoint of obtaining an inexpensive polyurethane foam being excellent in strength, flexibility, and abrasion resistance.
Further, it is preferable that (A) the PPG-A having an unsaturation degree of not more than 0.06 meq/g, in which a compound having two hydroxyl groups has been used as a starting material is used alone or together with (B) a polyoxypropylene-polyol B in which a compound having not less than three hydroxyl groups has been used as a starting material (hereinafter referred to as PPG-B) as the PPG within the weight ratio (PPG-A/PPG-B) of not less than 4. When the PPG-A and the PPG-B are used in combination, there are imparted to a foam, high strength such as foam strength, high abrasion resistance and high flexibility, and excellent appearance on the basis of the use of the PPG-A, and excellent dimensional stability and excellent solvent resistance on the basis of the use of the PPG-B. The polyol component contained in a polyol composition means a compound having a high molecular weight, which forms a soft segment in a urethane foam.
The PPG-A and the PPG-B have many oxypropylene recurring units, respectively. Accordingly, they effectively act as soft segments in a polyurethane foam obtained, and also impart excellent elongation properties and high elasticity to the polyurethane foam. Each molecular weight of the PPG-A and the PPG-B per hydr
Nomura Takayuki
Okubo Makoto
Suzuki Ken'ichi
Bagwell Melanie D.
Birch & Stewart Kolasch & Birch, LLP
Gorr Rachel
Kao Corporation
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