Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1990-08-15
1992-03-03
Welsh, Maurice J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521160, 521174, 521176, C08G 1814
Patent
active
050933809
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. TECHNICAL FIELD
The present invention relates to a polyurethane flexible foam and a method for its production. Particularly, it relates to a polyurethane flexible foam having excellent physical properties as a seat cushion for automobiles, and a method for its production.
2. BACKGROUND TECHNIQUE
In recent years, various new studies have been made to improve the properties of polyurethane flexible foam. For example, reflecting a trend for grading up of e.g. automobiles, improvement of the vibration characteristics of seat cushions, is desired. The relation between the vibration of the car body and the human being is not uniform. However, it is suggested that it is effective for the improvement of the comfortable ride to take a particularly large attenuation of the frequency region (e.g. from 4 to 8 Hz or from 6 to 20 Hz) to which human being is particularly sensitive. Accordingly, it is considered possible to substantially improve the comfortable ride if the seat cushion is made of a polyurethane flexible foam having a resonant frequency lower than this frequency region. However, heretofore, no polyurethane flexible foam has been known which has a resonant frequency of less than 4 Hz.
SUMMARY OF THE INVENTION
The present invention provides a polyurethane flexible foam having a resonant frequency of less than 4 Hz. Further, the present invention provides a method for producing a polyurethane flexible foam, whereby such a polyurethane flexible foam can be produced. The polyurethane flexible foam of the present invention can be obtained by using a polyoxyalkylene polyol having a particularly low hydroxyl value and a low total unsaturation degree. Namely, it can be obtained by using as the polyoxyalkylene polyol a high molecular weight polyol which is a polyoxyalkylene polyol containing oxyalkylene groups of at least 3 carbon atoms as the main component, particularly a polyoxyalkylene polyol having at least 70% by weight of oxypropylene groups derived from 1,2-propyleneoxide and wherein the hydroxyl value (X mgKOH/g) and the total unsaturation degree (Y meq/g) are in the relation of the following formula (1), and Y .ltoreq.0.07 and X is from 5 to 38: polyol is preferably from 2 to 8, more preferably from 2 to 6. Further, a polymer-dispersed polyol having this polyoxyalkylene polyol as the matrix and a mixture of such a polymer-dispersed polyol and this polyoxyalkylene polyol, are also preferred polyols.
Further, it is also preferred to use a polyfunctional compound having a relatively low molecular weight which is called a crosslinking agent, together with the above polyoxyalkylene polyol. It is essential to use a polyisocyanate compound as a starting material for the polyurethane flexible foam. Further, a catalyst, a foaming agent and a foam stabilizer are usually essential assisting agents. Thus, the polyurethane flexible foam of the present invention is produced by using these materials as the starting materials.
For the polyurethane flexible foam of the present invention, it is essential that its resonant frequency is less than 4 Hz, particularly not higher than 3.5 Hz. In addition, the impact resiliency of the core is preferably at least 70%, and further, the wet heat permanent strain is preferably not higher than 10%.
Now, each starting material component in the present invention will be described.
Polyoxyalkylene polyol
The polyoxyalkylene polyol used as a starting material for polyurethane, is usually produced by ring-opening addition polymerization of an alkylene oxide such as propylene oxide to an initiator such as a polyhydric alcohol by means of an alkali catalyst such as an alkali metal hydroxide. In such a process, a monool having an unsaturated group is formed as a byproduct, and the production rate of this unsaturated monool increases with an increase of the molecular weight of the polyol (with a decrease of the hydroxyl value). The presence of this unsaturated monool is not in such a serious amount in the case of a polyoxyalkylene polyol having a hydroxyl value of about 56
REFERENCES:
patent: 3829505 (1974-08-01), Herold
patent: 4326047 (1982-04-01), Yates
patent: 4687851 (1987-08-01), Laughner
Doi Takao
Sonobe Tsunehisa
Takeyasu Hiromitsu
Yamaguchi Yoshiyuki
Asahi Glass Company Ltd.
Welsh Maurice J.
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