Semi-rigid polyurethane foam

Details Semi-rigid polyurethane foam Semi-rigid polyurethane foam

1999-08-31

2001-10-23

Cooney, Jr., John M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

C521S118000, C521S155000, C521S167000, C521S174000

Reexamination Certificate

active

06306918

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semi-rigid polyurethane foam. More specifically, the present invention relates to a semi-rigid polyurethane foam which can be suitably used for interior materials of automobiles such as headrests and armrests, particularly headrests which are produced by high-speed foam molding with surface material.
2. Discussion of the Related Art
Semi-rigid polyurethane foams have appropriate impact absorptivity, elasticity and compression recovery. Therefore, the foams have been used for interior materials of automobiles as disclosed in Japanese Patent Laid-Open Nos. Hei 8-143637 and Hei 8-217847.
When the semi-rigid polyurethane foams are used for the interior materials of automobiles, however, there may arise a clouding phenomenon on the window glass of automobiles, so-called “fogging” due to an amine catalyst used in the preparation of the semi-rigid polyurethane foam at the time the room temperature inside the automobile becomes high.
An object of the present invention is to provide a semi-rigid polyurethane foam which would not cause fogging under high-temperature conditions, and which can be suitably used for interior materials of automobiles.
This and other objects of t he present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
The present invention pertains to the following:
[1] a semi-rigid polyurethane foam having a strength retention of not less than 70% when allowing it to stand at 120° C. for 24 hours, and a Haze value of not more than 2 as determined by Fogging test, prepared by mixing a polyol mixture comprising a polyol, water and a catalyst with a polyisocyanate, and foaming the resulting mixture; and
[2] a process for preparing a semi-rigid polyurethane foam having a strength retention of not less than 70% when allowing it to stand at 120° C. for 24 hours, and a Haze value of not more than 2 as determined by Fogging test, comprising mixing a polyol mixture comprising 100 parts by weight of a polyol, 2 to 8 parts by weight of water, and 0.5 to 6 parts by weight of a catalyst with a polyisocyanate, and foaming the resulting mixture.
DETAILED DESCRIPTION OF THE INVENTION
The term “strength retention when allowing it to stand at 120° C. for 24 hours” mentioned in the present specification refers to a value obtained by allowing a produced semi-rigid polyurethane foam to stand at room temperature for 24 hours, thereafter cutting out 10 test pieces from the semi-rigid polyurethane foam for “No. 2 tensile test” prescribed in JIS K 6301obtaining an average value of strength (initial strength) when subjecting 5 test pieces to a tensile test at room temperature at a tensile speed of 125 mm/min with a tensile tester [autograph commercially available from Shimadzu Corporation under Article No. DCS-50M], also obtaining an average value of strength (high-temperature strength) when allowing the remaining 5 test pieces to stand in an atmosphere of 120° C. for 24 hours, thereafter subjecting the remaining 5 test pieces to a tensile test in the same manner as above, and calculating the strength retention according to the following equation:
[Strength Retention (%)]=[High-Temperature Strength]/[Initial Strength]×100
When the semi-rigid polyurethane foam has a strength retention of not less than 70%, the semi-rigid polyurethane foam can be suitably used for interior materials of automobiles. Also, from the viewpoint of preventing the lowering of foam strength in accordance with the passage of time, it is preferable that the strength retention is not less than 80%.
The term “Haze value as determined by Fogging test” mentioned in the present specification refers to a value obtained by allowing the produced semi-rigid polyurethane foam to stand at room temperature for one day, thereafter cutting out a test piece (50 mm×50 mm×100 mm) from its core portion, placing this test piece in a 500 ml-glass bottle charged with 0.1 ml of 2 N hydrochloric acid, sealing the aperture with a transparent glass plate, immersing about two-third of this glass bottle in a water bath kept at 80° C. for 100 hours, thereafter measuring the Haze value of the glass plate with a Hazemeter (color difference meter) commercially available from Nippon Denshoku Kogyo Kabushiki Kaisha under Article No. NDH-20D. The smaller the Haze value is, the lower the degree of cloudiness is.
The semi-rigid polyurethane foam of the present invention has a Haze value of not more than 2. Accordingly, the foam exhibits some excellent effects such that no fogging is generated on the window glass when the foam is used as interior materials of automobiles and allowed to stand under high temperatures in a sealed space such as inner space of automobiles. The Haze value is not more than 2, preferably not more than 1, from the viewpoint of preventing fogging.
It is desired that the foam density (hereinafter referred to as “core density”) of the semi-rigid polyurethane foam is 25 to 100 kg/m
3
, preferably 30 to 80 kg/m
3
, from the viewpoints of foam strength, cushioning property, and light weight.
The semi-rigid polyurethane foam can be prepared by mixing a polyol mixture comprising a polyol, water and a catalyst with a polyisocyanate, and foaming the resulting mixture.
The polyol includes polyester-polyols, polyether-polyols, and the like. It is desired that the average hydroxyl value of the polyol is 14 to 100 mg KOH/g, preferably 17 to 75 mg KOH/g, more preferably 17 to 70 mg KOH/g, from the viewpoints of viscosity and imparting elasticity to the foam.
The dicarboxylic acid which can be used in the polyester-polyol includes saturated aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid; saturated alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid and isophthalic acid; unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid; halogenated dicarboxylic acids such as tetrabromophthalic acid; ester-formable derivatives thereof; acid anhydrides thereof, and the like. Those dicarboxylic acids can be used alone or in admixture thereof. The dicarboxylic acid may contain a tri or more functional polybasic acid, such as trimellitic acid and pyromellitic acid, as occasion demands.
The diol constituting the polyester-polyol includes ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, methylpentanediol, 1,6-hexanediol, trimethylolpropane, glycerol, pentaerythritol, diglycerol, dextrose, sorbitol, and the like. Those diols can be used alone or in admixture thereof.
Representative examples of the polyether-polyol include polyoxypropylene polyols (hereinafter referred to as “PPG”); polyoxytetramethylene glycol (hereinafter referred to as “PTMG”), and mixtures thereof. Among them, the PPG to which ethylene oxide is added at its terminal is preferable. The weight ratio of polyoxypropylene/polyoxyethylene of the PPG is preferably 50/50 to 95/5 more preferably 60/40 to 80/20, from the viewpoints of hydrolysis, and reactivity and foam strength.
The PPG can be prepared by a process comprising subjecting a compound having at least two active hydrogens as a starting material to ring-opening addition of a usual alkylene oxide, and further adding ethylene oxide in a block form to its end.
The compound having at least two active hydrogens includes polyhydric alcohols, polyhydric phenols, polyamines, alkanolamines, and the like. Concrete examples thereof include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, pentaerythritol, diglycerol, dextrose, sucrose, bisphenol A, ethylenediamine, and modified products thereof, and the like. Those compounds can be used alone or in admixture thereof.
The alkylene oxide includes, for instance, ethylene oxi

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