Polyurethane material for decorative parts

A polyurethane material for decorative parts is disclosed which is a tow-liquid type material comprising a polyol component and an isocyanate component and having a stabilizer incorporated in the polyol component. The stabilizer is a ternary system of a specific hindered amine type ultraviolet stabilizer, a specific hindered phenol type antioxidant, and a specific benzotriazole type ultraviolet absorbent or acrylontrile type ultraviolet absorbent. A transparent synthetic resin part formed by potting this polyurethane material on the upper surface of a base excels in weatherability and lightfastness. Thus, the present invention provides decorative parts which retain good appearance for a long time.

BACKGROUND OF THE INVENTION 
This invention relates to a polyurethane material for decorative parts. 
More particularly, this invention relates to a material suitable for the 
formation of a transparent synthetic resin part possessing a positive 
meniscus on a base of synthetic resin in interior and exterior decorative 
parts of automobiles requiring exacting lightfastness such as, for 
example, steering wheels, ornaments and marks for incorporation in 
interior wall materials, and various moldings including side moldings, 
bumper moldings locker moldings, and interior ornamental strips. 
As a typical representative of the decorative marks enumerated above, a 
mark 1 illustrated in FIG. 1 which is intended for incorporation in a 
steering wheel will be described below. It should be noted that the mark 
is selected purely for illustration and is never meant as a limitation on 
the invention. 
This mark 1 is produced by a method which comprises casting a liquid 
transparent synthetic resin material of suitable viscosity on an upper 
surface 3a of a disc-shaped base 3 made of synthetic resin or metal and 
provided with an edged periphery and then allowing the cast resin to set 
thereby giving rise to a transparent synthetic resin part 5 possessing a 
positive meniscus (so-called potting method) (Japanese Patent Application 
Disclosures SHO No. 58(1983)-221,741 and SHO No. 61(1986)-207,249). As the 
material for the transparent synthetic resin part 5 mentioned above, it 
has been customary to employ a two-liquid type polyurethane material using 
a polyol component and an isocyanate component with a view to ensuring 
resistance to abrasion and resistance to shock, for example. The 
aforementioned polyol component generally incorporates a combination of 
various stabilizers therein for the main purpose of preventing the 
produced mark from yielding to discoloration or development of cracks 
under the influence of solar rays and ozone in the air. 
As stabilizers mentioned above, hindered amine type ultraviolet light 
stabilizers represented by bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate 
and hindered phenol type antioxidants represented by 
pentaerythrityl-tetrakis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] 
have been generally used in combination. 
The inventors' test performed on the aforementioned combination of 
stabilizers, however, has revealed that long retention of good appearance 
with this combination of stabilizers is difficult to achieve (Comparative 
Experiment, Table 2). To be specific, products using such stabilizers show 
signs of discoloration and surface fusion (ready impartation of finger 
prints on the surface of a test piece) after the test of exposure to 
weather conditions or the test of exposure to light. 
SUMMARY OF THE INVENTION 
The polyurethane material for decorative parts contemplated by this 
invention is a two-liquid type material using a polyol component and an 
isocyanate component separately and having stabilizers incorporated in the 
polyol component, which decorative material is characterized by using as 
stabilizers a ternary system composed of a specific hindered amine type 
ultraviolet stabilizer and a specific hindered phenol type antioxidant in 
combination with a specific benzotriazole type ultraviolet absorbent or an 
acrylonitrile type ultraviolet absorbent. Owing to the construction 
described above, the polyurethane material of the present invention 
produces on the upper surface of a base made of a specific material a 
transparent material which shows no sign of discoloration or surface 
fusion after the test for weatherability or the test for lightfastness as 
demonstrated in the working examples cited later. This invention, 
therefore, permits production of decorative parts enjoying retention of 
good appearance for a long time.

DETAILED DESCRIPTION OF THE INVENTION 
I. The polyurethane material of this invention for decorative parts 
comprises a polyol component and an isocyanate component and has a 
specific ternary stabilizer incorporated in the polyol component. 
A. As examples of the aforementioned polyol component, there can be cited 
those of (1) the polyether type, (2) the polyester type, (3) the 
polycarbonate type, and (4) the polymer polyol type to be enumerated 
below. From the standpoint of resistance to hydrolysis, the polyether type 
proves to be particularly desirable among other types mentioned above. 
(1) Polyether polyol 
There are bifunctional, trifunctional, and tetrafunctional polyether 
polyols which are obtained by the reaction of such cyclic ethers as 
ethylene oxide, propylene oxide, butylene oxide, and styrene oxide with 
such low molecular polyols as ethylene glycol, diethylene glycol, 
glycerin, trimethylol propane, and bis-phenol A. Generally, polyether 
polyols having molecular weights in the range of 2,000 to 7,000 are used 
in this invention. 
(2) Polyester polyol 
There are polyester polyols which are obtained by causing such diols as 
ethylene glycol, polyoxyethylene glycol, dipropylene glycol, and 
polyoxypropylene glycol to react in an excess amount upon such 
dicarboxylic acids as succinic acid, glutaric acid, adipic acid, and 
piperic acid. Generally, polyester glycols having molecular weights in the 
range of 3,000 to 8,000 are used in this invention. 
(3) Polycarbonate polyol 
There are polycarbonate polyols which are obtained by the reaction of the 
reaction of 1,6-hexanediol with such compounds as ethylene carbonate and 
caprolactan. Generally, polycarbonate polyols having molecular weights in 
the range of 1,000 to 2,000 are used in this invention. 
(4) Polymer polyol 
There are polymer polyols which are obtained by the graft polymerization of 
acrylonitrile and/or such a vinyl monomer as styrene to polyether polyols. 
Generally, polymer polyols having molecular weights in the range of 4,000 
to 7,000 are used in the present invention. 
B. As examples of the aforementioned isocyanate component, there can be 
cited those of (1) the aliphatic type and (2) the aromatic type to be 
enumerated below. From the standpoint of resistance to yellowing, the 
aliphatic type is more desirable than the aromatic type. 
(1) Aliphatic type isocyanate 
There are alicyclic isocyanates as well as aliphatic isocyanates. Examples 
of these types of isocyanates include hexamethylene diisocyanate (HMDI), 
xylene diisocyanate (XDI), hydrated xylene diisocyanate (hydrated XDI), 
4,4'-methylenebisdicyclohexyl diisocyanate (H12MDI), methylcyclohexyl 
diisocyanate (hydrated TDI), and isopholone diisocyanate (IPDI). Further, 
as examples of aliphatic type isocyanate which prove to be particularly 
desirable from the standpoint of convenience of handling, there can be 
cited dimers, trimers, trimethylol propane adducts, and prepolymers of 
aliphatic type isocyanates which have increased molecular weights. 
(2) Aromatic type isocyanate 
Examples of the aromatic type isocyanate, there can be cited 4,4'-diphenyl 
methane diisocyanate (hereinafter referred to as "MDI" for short), crude 
MDI, liquid MDI, trilene diisocyanate, and phenylene diisocyanate. As 
examples of the aromatic type isocyanate which prove to be particularly 
desirable from the standpoint of convenience of handling, there can be 
cited dimers, trimers, trimethylol propane adducts, and prepolymers of 
aromatic type isocyanates which have increased molecular weights. 
C. The combinations of three members for the ternary stabilizer to be added 
to the aforementioned polyurethane material (generally to the polyol 
component thereof)fall under the first combination and the second 
combination as follows. 
The amount of each of the components thus added is generally in the range 
of 0.1 to 2.0 parts by weight, based on 100 parts by weight of the amount 
of the urethane polymer. 
First Combination of Stabilizers 
(a) A hindered amine type ultraviolet stabilizer represented by the 
following chemical formula. 
As a concrete example of this stabilizer, there can be cited 
2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butyl-malonic acid 
bis(1,2,2,6,6-pentamethyl-4-piperidyl). 
##STR1## 
(wherein R.sub.1 stands for a t-butyl group, R.sub.2 for a n-alkyl group 
of 3 to 5 carbon atoms, and R.sub.3 for a hydrogen atom or a methyl 
group). 
(b) A benzotriazole type untraviolet absorbent represented by the following 
chemical formula. 
As concrete examples of this absorbent, there can be cited 
2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole and 
2-[2-hydroxy-3,5-bis(.alpha.,.alpha.-dimethylbenzyl)phenyl]-2H-benzotriazo 
le. 
##STR2## 
(wherein R stands for an ethyl group or a phenyl group). 
(c) A hindered phenol type antioxidant represented by the following 
chemical formula. 
As concrete examples of this antioxidant, there can be cited triethylene 
glycol-bis[(3-(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] and 
1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate). 
##STR3## 
(wherein R.sup.1 stands for a branched alkyl group of 3 to 6 carbon atoms, 
R.sup.2 for R.sup.1, CH.sub.3 or C.sub.2 H.sub.5, and R.sup.3 for CH.sub.2 
or OCH.sub.2). 
Second combination of Stabilizers 
(a) A hindered amine type ultraviolet stabilizer represented by the 
following chemical formula. 
As concrete examples of this type of ultraviolet stabilizer, there can be 
cited bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate and 
bis(1,2,2,6,6,-pentamethyl-4-piperidyl) sebacate. 
##STR4## 
(wherein n stands for an integer in the range of 6 to 10 and R for a 
hydrogen atom or a methyl group). 
(b) An acrylonitrile type ultraviolet absorbent represented by the 
following chemical formula. 
As concrete examples of this type of ultraviolet absorbent, there can be 
cited .alpha.-cyano-.beta.-phenyl-(2-ethylhexyl) cinnamate and 
.alpha.-cyano-.beta.-phenylethyl cinnamate. 
##STR5## 
(wherein n stands for an integer in the range of 2 to 8). 
(c) The same hindered phenol type antioxidant as (c) used in the first 
combination described above. 
D. The aforementioned polyurethane material generally incorporates therein 
(a) a heavy metal type catalyst or (b) an amine type catalyst indicated 
below and other additives such as, for example, surfactant (for 
improvement of leveling property), pigment, and dye. 
(a) Heavy metal type catalyst: Examples of this type include dibutyl tin 
dilaurate, dibutyl tin fumarate, dibutyl tin acetate, stannous octylate, 
cobalt naphthenate, zinc naphthenate, and cobalt octylate. 
(b) Amine type catalyst: Examples of this type of catalyst include triethyl 
amine, N-methyl morpholine, N,N-dimethylcyclohexyl amine, 
N,N-dimethylethanol amine, N,N'-diethylethanol amine, pentamethyl 
diethylene triamine, and triethylene diamine. II. Now, the method by which 
a mark (decorative part) illustrated in FIG. 1 is produced by the use of 
the polyurethane material described above will be explained. 
A polyol component and an isocyanate component, each of the foregoing 
description, are mixed in a substantially stoichiometric ratio. The 
resultant mixture is deaerated under a vacuum to obtain a polyurethane 
material. By potting this polyurethane material on the upper surface of a 
base 3, there is formed a transparent synthetic resin part 5. 
The base 3 is formed by extrusion or injection molding such a synthetic 
resin material as acrylonitrile-butadiene-styrene terpolymr (ABS), 
polyvinyl chloride (PVC), nylon (polyamide), polycarbonate, 
acrylonitrile-styrene copolymer (AS), or ionomer which excels in 
resistance to heat and resistance to shock. Otherwise, the base 3 may be 
formed with a metallic material such as aluminum. 
EXAMPLES 
Now, the present invention will be described more specifically below with 
reference to working examples. 
Examples I: 
A polyol component mixed with a catalyst and a stabilizer and an isocyanate 
component selected by the formula of Table 1 were separately deaerated 
under a vacuum (under the conditions of 60.degree. C..times.5 mmHg.times.1 
h) and mixed. The mixture was gain deaerated under a vacuum (under the 
conditions of 60.degree. C..times.5 mmHg.times.5 min.) to obtain a potting 
material. This potting material was deposited in the form of a bulb on a 
base of PVC preheated to 70.degree. C. and then caused to set under the 
conditions of 80.degree. C..times.30 min. to form a mark possessing a 
transparent synthetic part. As the stabilizer in the aforementioned 
formula, a varying combination of stabilizers shown in Table 2 was used. 
(a) Hindered amine type ultraviolet stabilizer: 
(1) Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate 
(2) 
Poly[6-[(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl][(2,2,6,6- 
tetramethyl-4-piperidyl)imino 
hexamethylene][(2,2,6,6-tetramethyl-4-piperidyl)imino,]] 
(3) 2-(3,5-Di-t-butyl-4-hydroxybenzyl)-2-n-butyl-malonic acid 
bis(1,2,2,6,6-pentamethyl-4-piperidyl) 
(b) Benzotriazole type ultraviolet absorbent: 
(4) 
2-[2-Hydroxy-3,5-bis(.alpha.,.alpha.-dimethylbenzyl)phenyl]-2H-benzotriazo 
le 
(5) 2-(3,5-Di-t-butyl-2-hydroxyphenyl)benzotriazole 
(6) 2-(3,5-Di-t-amyl-2-hydroxyphenyl)benzotriazole 
(c) Hindered phenol type antioxidant 
(7) Triethylene 
glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate] 
(8) 
2,4-Bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine 
(9) Pentaerythrityl-tetrakis[3-(3,5-di-6-butyl-4-hydroxyphenyl)propionate] 
(Test for evaluation) 
The test pieces (marks) obtained in working examples I and comparative 
experiments as described above were subjected to 1,000 hours' test for 
lightfastness with a hot Fade-O-Meter, using a blackpanel at 
83.degree..+-.3.degree. C. After the test, they were visually examined to 
determine whether or not they sustained discoloration or surface fusion. 
The results were rated on the three-point scales, wherein .circle. 
stands for absence of change, .DELTA. for a slight sign of change, and x 
for a conspicuous sign of change. 
From the results of the evaluation shown in Table 2, it is noted that the 
test pieces using combinations of stabilizers not falling within the 
ranges contemplated by the present invention were incapable of retaining 
good appearance of the decorative parts for a long time. 
Examples II: 
Molds were produced by faithfully following the procedure of Examples II. 
In this case, a varying combination of stabilizers shown in Table 3 was 
used. 
Hindered amine type ultraviolet stabilizer: 
(1) Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate 
(2) Polycondensate of succinic acid and 
dimethyl-1-(2-hydroxyethyl)-4-hydroxyl-2,2,6,6-tetramethyl piperidine 
(b) Benzotriazole type ultraviolet absorbent 
(3) 2-(5-Methyl-2-hydroxyphenyl) benzotriazole 
(4) 
2-[2-Hydroxy-3,5-bis(.alpha.,.alpha.-dimethylbenzyl)phenyl]-2H-benzotriazo 
le 
(5) 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole 
(c) Acrylonitrile type ultraviolet absorbent: 
(6) .alpha.-Cyano-.beta.-phenyl-(2-ethylhexyl) cinnamate 
(d) Hindered phenol type antioxidant 
(7) Triethylene 
glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate] 
(8) Pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl]propionate 
(e) Organic sulfur type antioxidant 
(9) Ditridecyl-3,3'-thiodipropionate 
(Test for evaluation) 
The test pieces (molds) obtained in working examples II and comparative 
experiments as described above were subjected to 1,000 hours' test for 
weatherability with a sunshine Weather-O-Meter, using a black panel at 
63.degree. C. After the test, they were visually examined to determine 
whether or not they sustained discoloration, surface crack, or surface 
fusion (stickiness). The results were rated on the three-point scales, 
wherein O stands for absence of change, .DELTA. for a slight sign of 
change, and x for a conspicuous sign of change. 
It is noted from the results of the test given in Table 3 that the test 
pieces using combinations of stabilizers not falling within the ranges 
contemplated by this invention were incapable of retaining good appearance 
of moldings for a long time. 
TABLE 1 
______________________________________ 
(Units: parts by weight) 
Proportion 
for 
Combination 
Description combination 
______________________________________ 
Polyol Propylene oxide adduct of 
10 
component 
bis-phenol A 
Ethylene oxide-propylene oxide 
10 
adduct of bis-phenol A 
Isocyanate 
Prepolymer of hexamethylene 
17 
component 
diisocyanate 
Catalyst Dibutyl-tin-dilaurate 
0.01 
Stabilizer 
See Table 2 and Table 3. 
______________________________________ 
TABLE 2 
__________________________________________________________________________ 
Examples I Comparative Experiments I 
Stabilizer 
1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 
__________________________________________________________________________ 
Ultraviolet stabilizer 
.circle.1 No 0.037 
0.185 
0.185 
0.185 
.circle.2 stabilizer 0.185 
0.185 
0.185 
.circle.3 
0.037 
0.185 
0.037 
0.185 0.185 
0.185 
0.185 
Ultraviolet absorbent 
.circle.4 
0.037 
0.185 0.185 0.185 
.circle.5 0.185 0.185 0.185 0.185 
.circle.6 
0.037 
0.185 0.185 0.185 
Antioxidant 
.circle.7 
0.037 
0.185 
0.037 
0.185 0.185 
0.185 0.185 0.185 
0.185 
.circle.8 0.185 0.185 
0.185 
.circle.9 0.037 
0.185 
Discolor- 
o o o o x x x .DELTA. 
o x .DELTA. 
.DELTA. 
.DELTA. 
.DELTA. 
o 
ation 
Surface 
o o o o x .DELTA. 
o o .DELTA. 
x x x o .DELTA. 
.DELTA. 
fusion 
__________________________________________________________________________ 
TABLE 3 
__________________________________________________________________________ 
Unit: Parts by weight 
Examples II Comparative Experiments II 
Stabilizer 
1 2 1 2 3 4 5 6 7 8 9 10 11 12 
__________________________________________________________________________ 
.circle.1 
0.037 
0.185 
No 0.037 
0.185 
0.185 
0.185 
0.185 
0.125 
0.185 
0.185 
0.185 
.circle.2 stabilizer 0.185 
0.185 
.circle.3 0.185 
.circle.4 0.185 0.125 
0.185 
.circle.5 0.185 0.185 
.circle.6 
0.037 
0.185 0.185 0.185 
0.185 
.circle.7 
0.037 
0.185 0.125 
0.185 0.185 
0.185 
.circle.8 0.037 
0.185 
.circle.9 0.185 0.185 
Discolor- 
o o .DELTA. 
x x x x x x .DELTA. 
x x .DELTA. 
.DELTA. 
ation 
Surface 
o o -- x x .DELTA. 
x x x x x x -- -- 
crack 
Surface 
o o x o o o o o o o o o x x 
fusion 
__________________________________________________________________________