JPS63137917A - Production of molded polyurethane article - Google Patents

Abstract

PURPOSE:To obtain a molded urethane, article, having excellent weather resistance and suitable as automotive bumpers, side moldings, etc., by reacting a specific polyol mixture with an aromatic polyisocyanate in the presence of a catalyst and reaction injection molding the reaction product. CONSTITUTION:(A) A mixture of (i) 100pts.wt. polyether polyol having 2,000-8,000 molecular weight with (ii) 2-40pts.wt. low-molecular polyol having 62-1,000 molecular weight and (iii) 2-4pts.wt. alkylene oxide adduct of phenylenedialkyldiamine (1-4 number of added mol) is reacted with (B) an aromatic polyisocyanate, e.g. 4,4'-diphenylmethane diisocyanate, etc., in the presence of (C) a catalyst, e.g. triethylenediamine, etc., to afford the aimed molded polyurethane article by reaction injection molding.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides polyurethane molded products by reaction injection molding (RIM).
), and particularly relates to a method suitable for manufacturing urethane molded products that require weather resistance, such as automobile bumpers and side moldings.

<Prior art> The polyisocyanate component in the materials for polyurethane molded products as described above is MDI (4,4'-diphenylmethane diisocyanate) and TDI (tolylene diisocyanate) from the viewpoint of molded product strength and material cost.
Aromatic isocyanate is used.

<Problems to be Solved by the Invention> However, when aromatic isocyanates are used, the aromatic rings are affected by ultraviolet rays and turn into quinoids, which tends to cause tallying in urethane molded products. In order to improve weather resistance, it is possible to add anti-aging agents such as ultraviolet absorbers and antioxidants, but it is not expected to have much of an improvement effect (see Comparative Example 3 in Table 2).

Means for Solving the Problems> In order to solve the above problems, the present inventors made earnest efforts in development, and as a result, they were able to come up with a method for manufacturing a urethane molded product having the following configuration.

When producing polyurethane molded products by RIM, a polyol mixture consisting of a long-chain polyether polyol, a low-molecular polyol, and an alkylene oxide adduct of phenylene dialkyl diamine is reacted with an aromatic polyisocyanate in the presence of a catalyst. It is characterized by doing.

<Embodiment> Hereinafter, each component of the present invention will be explained in detail. Note that "parts" indicating the number of parts to be blended means "parts by weight" unless otherwise specified.

(2) As a polyol mixture, a mixture of 100 parts of the following (a) and each part of each of the compounds (b) to (c) is used.

(a) Polyether polyol with a molecular weight of 2000 to 8000 Polyether polyols are used as polyols because they have a lower viscosity (500 to 1500 at 25°C) than polyester polyols.
cps) and has excellent hydrolysis resistance.

Here, polyether polyols refer to those obtained by reacting cyclic ethers such as ethylene oxide, propylene oxide, butylene oxide, and styrene oxide with low-molecular-weight polyols such as ethylene glycol, diethylene glycol, trimethylolpropane, and glycerin, and those obtained by reacting such polyols. If the molecular weight of this polyol, including those obtained by graft polymerization with a vinyl monomer, is less than 2,000, the desired toughness cannot be obtained in the molded product, and if it exceeds 8,000, the viscosity will be high and the stability will be poor, which are both undesirable.

(b) Low-molecular polyol...2 to 40 parts (preferably 15 to 25 parts) Although used as a chain extender, its reactivity with isocyanates is not very high. Examples of the low-molecular polyol include those already mentioned, 1,3-propanediol, 1,4-butanediol, and the like. If the amount of the low-molecular-weight polyol is less than 2 parts, the desired rigidity cannot be obtained in the molded product, and if it exceeds 40 parts, the green strength will decrease, which is undesirable.

(c) Alkylene oxide adduct of phenylene dialkyl diamine (number of moles added 1 to 4)...2 to 40 parts (
Preferably 15 to 25 parts).

It has the effect of improving weather resistance and also functions as a chain extender. Here, if the active hydrogen of the phenylene dialkyl diamine is not substituted with alkylene oxide, the compatibility with the polyether polyol will be poor and the addition effect will not be obtained. In addition, the alkyl carbon number of phenylene dialkyl diamine is 1 to 3, and phenylene is ortho-carbon number.
Regardless of whether it is meta or para, meta-xylene diamine can be mentioned as a specific example. Examples of the alkylene oxide include ethylene oxide and propylene oxide.

The above polyol mixture is prepared by adding an aromatic polyisocyanate component NGO10H=100/70 to 100/14 as shown in (e) below in the presence of a catalyst shown in (d) below.
0 to form a reaction injection molded product.

(d) Amine-based catalysts such as triethylenediamine, N-methylmorpholine, pentaethyldiethyltriamine, dimethylethanolamine, diethylethanolamine, and tin-based catalysts such as diptyltin dilaurate, dibutyltin fumarate, and dibutyltin diacetate. Examples can be given, but usually
It is desirable to use an amine type and a tin type in combination from the viewpoint of increasing the catalytic activity.

(e) Polyisocyanate component MDI, TDI, 4,4'-diphenyl ether diisocyanate, xylylene diisocyanate, polymethylphenylisocyanate and the like can be mentioned. In particular, MDI-based prepolymers are desirable from the viewpoint of physical properties and reactivity.

During the reaction injection molding, additives such as inorganic fillers, paints, pigments, anti-aging agents, ultraviolet absorbers, and blowing agents are added to the polyol mixture or isocyanate component as appropriate.

<Actions and Effects of the Invention> As described above, in the method for producing a polyurethane molded article of the present invention, during reaction injection molding, a long-chain polyether polyol is added to a low-molecular-weight polyol as a chain extender and an alkylene of phenylene dialkyl diamine. By mixing a polyol mixture with an oxide adduct in the presence of an aromatic polyisocyanate and a catalyst, the weather resistance is significantly improved as shown in the Examples below.

The reason for this is not clear, but it is presumed that the aliphatic aminopolyol has an aromatic ring, so the aromatic ring is not converted into quinoid.

<Example> In order to confirm the effects of the present invention, Examples will be given below along with Comparative Examples, and the results of physical property tests will also be shown.

(A) Molding method Using the polyol mixture/polyisocyanate component and catalyst shown in Table 1, reaction injection molding was carried out under the following conditions to obtain molded articles.

■Molding machine...Niigata Iron Works MG50/3B ■Injection speed・
...4oOg/sec, ■Injection pressure Curl 3 Q kg/crn'', ■Injection time...1.40 seconds, ■Mold cavity...4.00 x 400 x2.
5mm.

■Mold temperature...70℃, ■Demolding time: 30 seconds.

Then, each molded article was tested for each item shown in Table 2. Weather resistance was determined by microscopic observation (x100 magnification) of the occurrence of surface turrets after 1200 hours of exposure using a sunshine weather meter, and was judged based on the criteria shown in FIG.

From the results shown in Table 2, each example of the present invention using a polyol mixture containing an alkylene oxide adduct of phenylene dialkyl diamine was compared with a comparative example without an anti-aging agent, especially a comparative example containing an anti-aging agent. It can be seen that it exhibits much better weather resistance compared to No. 3.

[Brief explanation of the drawing]

FIG. 1 is a reference diagram of the occurrence of tarasing for determining weather resistance in Examples and Comparative Examples of the present invention. Patent application Toyoda Gosei Co., Ltd.

Claims (1)

[Claims] When producing polyurethane molded products by reaction injection,
A method for producing a polyurethane molded article, which comprises reacting the following polyol mixture with an aromatic polyisocyanate in the presence of a catalyst. (a) Polyether polyol with a molecular weight of 2,000 to 8,000...100 parts by weight, (b) Low molecular weight polyol with a molecular weight of 62 to 1,000...
2 to 40 parts by weight, (c) alkylene oxide adduct of phenylene dialkyl diamine (number of moles added 1 to 4)...2 to 40 parts by weight,