|
BACKGROUND OF THE INVENTION
The present invention pertains primarily to integral skin foams, and more particularly to color or light stable integral skin polyurethane foams.
The following cited references are believed to be representative of the state of the art:
______________________________________
U.S. Pat. No.
Inventor(s) Issued
______________________________________
3,182,104 Civik May 4, 1965
3,422,036 Ellegast et al
January 14, 1969
3,473,951 De Rossi et al
October 21, 1969
3,476,933 Mendelsohn November 4, 1969
3,645,924 Fogiel February 29, 1972
3,655,597 Strassel April 11, 1972
3,769,244 Hashimoto October 30, 1973
3,775,350 Juhas November 27, 1973
3,814,707 Moller June 4, 1974
3,925,526 Haas December 9, 1975
3,993,608 Wells November 23, 1976
4,006,124 Welte et al February 1, 1977
4,025,466 Jourquin et al
May 24, 1977
4,150,206 Jourquin et al
April 17, 1979
______________________________________
Canadian Patent No. 580,788 to Parker et al, issued August 4, 1959.
United Kingdom
Patent No. Inventor(s) Issued
______________________________________
891,007 Lowe et al March 7, 1962
900,392 Cowdrey et al July 4, 1962
1,009,965 -- November 17, 1965
______________________________________
Generally, integral skin polyurethane foam is used on articles which must be elastic, flexible, relatively impermeable, have good resistance to tear and plastic deformation, a compact surface or skin, and a cellular internal structure. Typical of such articles are many of the parts used in automobiles such as arm rests, crash pad covers, and steering wheels. The one step molding operation for integral skin polyurethane foam replaced to some extent the two step process in which a separate skin was first molded, and then a non-skinning urethane foam was molded inside the skin to form the finished product.
The surface or skin of an integral skin foam article comprises a substantially nonexpanded elastomer layer which is both compact and impervious, while internally, the article comprises a flexible and elastic cellular mass forming a protective padding which provides insulation against shocks and vibrations. For example, a steering wheel comprising integral skin urethane foam would have a skin that may have the appearance of leather, have a pleasant feel, be relatively resilient when handled, provide vibration absorption and thermal isolation, and also be somewhat flexible in the event of an accident.
Originally, most integral skin polyurethane foam parts were produced in just a few colors, namely black, brown, or gray; and then if some other surface color was desired, the part would be painted. However, painted wheels are considerably more expensive to produce than unpainted wheels for reasons that should be readily apparent. Further, there is very often some problem with paint adhesion and paint wear in actual use due to abrasion and other effects of repeated handling. As a result of these problems, efforts have been directed at producing integrally colored integral skin foam parts, that is, parts in which the color is molded right into the part so that the entire part bears the same color inside and out.
Normal integral skin polyurethane foams, because of the presence of aromatic diisocyanates in the reacting mixture, have poor color stability and usually will yellow severely when exposed to ultraviolet light or other visible radiation. Efforts at preparing such foams using aliphatic diisocyanates have met with rather limited success since although the foams produced are relatively color stable, they are slow reacting and thus are difficult to incorporate into commercial manufacturing processes and also are economically unattractive or prohibitive.
It is a principal object of the present invention therefore to provide a color stable integral skin polyurethane foam.
Another object of the present invention is to provide a color stable integral skin foam formulation which uses aliphatic diisocyanates and which reacts at a reasonable rate.
It is thus a further object of the present invention to provide a foam which because of its reasonable reaction rate is economically attractive to produce. Other objects, features and advantages of the present invention will become apparent from the subsequent description and examples, and the appended claims.
SUMMARY OF THE INVENTION
In accordance with the present invention, a color stable integral skin foam and method of producing the same are provided wherein stannous octoate and dimethyltin dilaurate are used as catalysts to drive the urethane or urea reaction between the hydroxyl or amine and the alphatic or cyclo-aliphatic isocyanate. The particular ingredients in the composition used to make the foam, such as the specific polyol, specific aliphatic or cyclo-aliphatic isocyanate, and specific crosslinker should be a relatively simple matter of choice for one skilled in this art. Also, the addition of optional ingredients such as blowing agents, pigments, ultraviolet absorbers, anti-oxidants, anti-ozonants, and the like are left to the discretion of one skilled in the art.
The use of stannous octoate and dimethyltin dilaurate (DMTDL) as an effective catalyst to produce color stable integral skin foam at a reasonable reaction velocity has proven to be very surprising and unexpected, especially in view of the fact that a combination of the same stannous octoate with dibutyltin dilaurate (DBTDL), an adjacent homolog of DMTDL, does not sufficiently catalyze a reaction with aliphatic isocyanates. Further evidence of this surprising result is found in the fact that both DMTDL and DBTDL are used as catalysts for aromatic isocyanates, whereas only the former works satisfactorily with aliphatic or cyclo-aliphatic isocyanates.
The composition used to prepare the color stable integral skin polyurethane foam of the present invention may be comprised of the following main ingredients:
The polyol used in the invention should be selected from the group of polyether polyols, which are polymer products of organic oxides. An active hydrogen compound such as a glycol, acid, or amine serves as an initiator for the oxide polymerization. The two organic oxides used for most polyether polyols are ethylene oxide and propylene oxide. In particular, it has been found that such materials as Pluracol Polyol 380, 538, 581, and 816 (manufactured by BASF-Wyandotte Corp.) perform satisfactorily. The amount of polyol should broadly be present within the range of between about 40 to about 80 percent by weight of the composition, and preferably should be between about 50 to about 70 percent by weight of the composition, with best results being obtained within the range of about 50 to about 60 percent by weight of the composition.
The isocyanate utilized in accordance with the present invention should be selected from the group consisting of aliphatic or cyclo-aliphatic isocyanates. In particular, such materials as DuPont Hylene-W, a saturated aliphatic isocyanate; Desmodur W, a hydrogenated MDI manufactured by Mobay Chemical Co.; IPDI, an isophorone diisocyanate manufactured by Veba-Chemie AG; and xylene diisocyanate have been found to perform satisfactorily. The amount of isocyanate should broadly be present within the range of between about 10 to about 40 percent by weight of the composition, and preferably should be between about 15 to about 35 percent by weight of the composition, with best results being obtained within the range of about 20 to about 30 percent by weight of the composition.
The crosslinker or chainextender used in the present invention should generally be a short chain polyol or polyamine having an equivalent weight of between about 30 and about 90. It has been found that ethylene glycol; 1, 4-butanediol; glycerine; and diproplylene glycol all perform satisfactorily. The amount of crosslinker or chainextender should broadly be present within the range of between about 2 to about 10 percent by weight of the composition, and preferably should be between about 3 to about 7 percent by weight of the composition, with best results being obtained within the range of about 4 to about 6 percent by weight of the composition.
The catalyst utilized in the present invention comprises stannous octoate in combination with dimethyltin dilaurate, with M & T Chemicals Inc. T-9 stannous octoate and Witco Chemical Co. UL-28 dimethyltin dilaurate (DMTDL) being found to perform satisfactorily. The catalyst may comprise equal parts of stannous octoate and DMTDL and should broadly be present within the range of between about 1 to about 5 percent by weight of the composition, and preferably should be between about 2 to about 4 percent by weight of the composition, with best results being obtained within the range of about 3 to about 4 percent by weight of the composition.
In addition to the above ingredients, the following materials may also be present in the integral skin polyurethane foam composition and method of the present invention:
A blowing agent such as E. I. DuPont deNemours Chemical Co. F-11B, trichloro-fluoromethane (Freon), performs satisfactorily. It may be broadly present within the range of between about 5 to about 15 percent by weight of the composition, and preferably should be between about 8 to about 13 percent by weight of the composition, with best results being obtained within the range of about 9 to about 12 percent by weight of the composition.
With regard to pigments which may be used in the composition and method of the present invention, any commercially available pigment compatible with polyurethane ingredients should be acceptable. Verona Red, Verona Green 609, and Verona Blue pigments such as those available from Mobay Chemical Co. have been found to be satisfactory. Although the amount of pigment used is generally related to the intensity of the desired color, it has been found that the pigment should be broadly present within the range of between about 1 to about 4 percent by weight of the composition, with best results being obtained within the range of about 2 to about 4 percent by weight of the composition.
It has surprisingly been found that long term stability of the foam produced in accordance with the present invention can be enhanced by including a small amount of UV stabilizer and anti-oxidant in the composition. A UV stabilizer such as Tinuvin 327, 328, or 777 as supplied by Ciba-Geigy Corp., and an anti-oxidant such as Irganox 1010 also supplied by Ciba-Geigy Corp. have been found to so enhance the performance of the foam of the present invention after exposure to ultraviolet, Weatherometer, and Fadeometer tests. These materials should both be broadly present within the range of between about 0.5 to about 3 percent by weight of the composition, with results being obtained within the range of about 1 to about 2 percent by weight of the composition.
An anti-ozonant may also be used in the present invention. The Irganox 1010 material referred to above has also been found to function well as an anti-ozonant in the quantities referred to above. Thus, the use of between about 0.5 to about 3 percent by weight of this particular material provides both anti-oxidant and anti-ozonant properties with best results being obtained within the range of about 1 to about 2 percent by weight of the composition.
In order to further illustrate the invention, the following examples are provided. It is to be understood, however, that the examples are included for illustrative purposes only and are not intended to be limiting of the scope of the invention as set forth in the subjoined claims.
EXAMPLE 1
______________________________________
Ingredient Parts
______________________________________
Pluracol 581 100
Ethylene Glycol 12.0
T-9 3.0
UL-28 3.0
F-11B 20.0
Tinuvin 328 1.0
Irganox 1010 1.0
Hylene-W 43.9 per 100 parts
of above resin
mixture
______________________________________
______________________________________
Physical Test Results
______________________________________
Tensile, psi 950
Elongation, % 100
Hardness, Shore A 70
Tear, ppi (w/skin) --
Tear, ppi (no skin) 7.4
Compression Set, % 24.5
U.V. - 250 hours 1*
Weatherometer - 250 hours
1*
Fadeometer - 250 hours
1*
______________________________________
*The following subjective ratings were used for the U.V. Weatherometer,
and Fadeometer tests:
1No cracks, negligible discoloration
2No cracks but more discoloration than #1 rating
3Some cracks and discoloration
4Cracked, crumbled, broken, and/or badly discolored
EXAMPLE 2
______________________________________
Ingredient Parts
______________________________________
Pluracol 581 100
Ethylene Glycol 14.0
T-9 3.0
UL-28 3.0
F-11B 20.0
Tinuvin 328 1.0
Irganox 1010 1.0
Hylene-W 48.9 per 100 parts
of above resin
mixture
______________________________________
______________________________________
Physical Test Results
______________________________________
Tensile, psi 820
Elongation, % 110
Hardness, Shore A 71
Tear, ppi (w/skin) --
Tear, ppi (no skin) 9.1
Compression Set, % 23.8
U.V. - 250 hours 1
Weatherometer - 250 hours
1
Fadeometer - 250 hours
1
______________________________________
EXAMPLE 3
______________________________________
Ingredient Parts
______________________________________
Pluracol 380 100.0
Ethylene Glycol 10.0
T-9 3.0
UL-28 3.0
Tinuvin 328 1.0
F-11B 20.0
Hylene-W 37.1 per 100 parts
of above resin
mixture
______________________________________
______________________________________
Physical Test Results
______________________________________
Tensile, psi 520
Elongation, % 185
Hardness, Shore A 40
Tear, ppi (w/skin) 7.2
Tear, ppi (no skin) 7.0
Compression set, % 13.1
U.V. - 250 hours 1
Weatherometer - 250 hours
1
Fadeometer - 250 hours
2
______________________________________
EXAMPLE 4
______________________________________
Ingredient Parts
______________________________________
Pluracol 380 100.0
1,4-Butanediol 10.0
T-9 3.0
UL-28 3.0
Irganox 1010 1.0
F-11B 20.0
Hylene-W 27.0 per 100 parts
of above resin
mixture
______________________________________
______________________________________
Physical Test Results
______________________________________
Tensile, psi 390
Elongation, % 165
Hardness, Shore A 69
Tear, ppi (w/skin) 9.9
Tear, ppi (no/skin) 6.7
Compression set, % 8.7
U.V. - 250 hours 1
Weatherometer - 250 hours
1
Fadeometer - 250 hours
3
______________________________________
EXAMPLE 5
______________________________________
Ingredient Parts
______________________________________
Pluracol 380 100.0
Ethylene Glycol 8.0
UL-28 3.0
T-9 3.0
F-11B 20.0
Verona Red 1.0
Isocyanate (comprised of 42.9 parts
34.1 per 100 parts
Dipropylene glycol and 957.1
of above resin
parts Hylene-W) mixture
______________________________________
______________________________________
Physical Test Results
______________________________________
Tensile, psi 340
Elongation, % 290
Block Tear, ppi (no skin)
6.0
Block Tear, ppi (with skin)
7.9
Compression Set, % 54.9
U.V. - 250 hours 3
Weatherometer - 250 hours
3
Fadeometer - 250 hours
3
______________________________________
EXAMPLE 6
______________________________________
Ingredient Parts
______________________________________
Pluracol 380 100.0
Ethylene Glycol 8.0
UL-28 3.0
T-9 3.0
F-11B 20.0
Verona Red 1.0
Isocyanate (comprised of 72.9 parts
37.9 per 100 parts
Dipropylene glycol and 927.1
of above resin
parts Hylene-W) mixture
______________________________________
______________________________________
Physical Test Results
______________________________________
Tensile, psi 360
Elongation, % 270
Block Tear, ppi (no skin)
6.6
Block Tear, ppi (with skin)
8.8
Compression Set, % 73.1
U.V. - 250 hours 3
Weatherometer - 250 hours
3
Fadeometer - 250 hours
3
______________________________________
EXAMPLE 7
______________________________________
Ingredient Parts
______________________________________
Pluracol 380 100.0
Ethylene Glycol 8.0
UL-28 3.0
T-9 3.0
F-11B 20.0
Verona Red 1.0
Isocyanate (comprised of 103.0 parts
42.6 per 100 parts
Dipropylene glycol and 897.0
of above resin
parts Hylene-W) mixture
______________________________________
______________________________________
Physical Test Results
______________________________________
Tensile, psi 406
Elongation, % 300
Block Tear, ppi (no skin)
7.0
Block Tear, ppi (w/skin)
11.5
Compression Set, % 85.0
U.V. - 250 hours 3
Weatherometer - 250 hours
3
Fadeometer - 250 hours
3
______________________________________
EXAMPLE 8
______________________________________
Ingredient Parts
______________________________________
Pluracol 380 100.0
Ethylene Glycol 8.0
UL-28 3.0
T-9 3.0
F-11B 20.0
Verona Red 1.0
Isocyanate (comprised of 136.5
49.4 per 100 parts
parts Dipropylene glycol and
of above resin
863.5 parts Hylene-W) mixture
______________________________________
______________________________________
Physical Test Results
______________________________________
Tensile, psi 360
Elongation, % 450
Block Tear, ppi (no skin)
9.0
Block Tear, ppi (w/skin)
17.1
Compression Set, % 94.4
U.V. - 250 hours 3
Weatherometer - 250 hours
3
Fadeometer - 250 hours
3
______________________________________
With regard to the formulation set forth in Example 1 above, the following procedure is intended to be an illustrative example of one of the ways of practicing the method of the present invention:
A mixture of: 100 parts (0.04993 equivalents) of a polyoxypropylene-ethylene-polymer modified glycol, in this case Pluracol Polyol 581 from BSAF Wyandotte Corp.; 12 parts of ethylene glycol (0.38710 equivalents); 3 parts of stannous octoate, T-9 from M&T Chemical Corp.; 3 parts of dimethyltin dilaurate; UL-28 from Witco Chemical; 20 parts of trichloromonofluoromethane, F-11B of Du Pont Chemical Co.; 1 part of Tinuvin 328, an ultraviolet absorber from Ciba-Geigy Corp.; and 1 part of Irganox 1010, an antioxidant from Ciba-Geigy Corp., was prepared at room temperature.
To 100 parts of the polyol or resin mixture above (320 equivalent weight), 43.9 parts of Hylene-W, 4,4'-methylene-bis-cyclohexylisocyanate, from Du Pont Chemical Co. (equivalent weight of 132) was added with thorough agitation. Within about 20 seconds, the entire mixture was immediately poured into a mold at about 50.degree. to 70.degree. C. in which it spread and formed the integral skinned foam product.
After a short time of about 3 to 5 minutes, the part was demolded and allowed to age at room temperature for at least one hour before subjecting it to physical tests. There was no need to post cure at elevated temperatures.
The color stable integral skin foam of the present invention has as one of its principal advantages the fact that it can be formulated to meet a wide range of physical properties such as hardness, density, etc. Other advantages include the facts that the end product can be made to have a feel very similar to leather, and is lower in weight than PVC (polyvinyl chloride), CAB (cellulose acetate butyrate), or PP (polypropylene), its typical material competitors. From an equipment standpoint, the present invention can be made using low cost tooling, and equipment costs are lower than for injection molding.
As one of its most basic advantages, the present invention does away with the problems associated with painted foam products. Parts made using the present invention need not be painted to match colors, since the entire part is precolored. There are no problems with paint adhesion or paint wear in actual use due to abrasion or other effects of repeated handling. The parts offer excellent color stability and will not yellow or change color severely when exposed to ultraviolet or other visible radiation. In addition, since the formulations used in the present invention are relatively fast reacting compared to the prior art, they are easy to incorporate in commercial manufacturing processes, plus are economically attractive in other ways.
While it will be apparent that the preferred embodiments of the invention disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.
|
|
