JPS6397618A - Production of polyurethane molding - Google Patents

Abstract

PURPOSE:To obtain the title molding at a decreased rate of rejects due to short shots, loose skins, voids, sink marks, etc., by reaction-injection-molding a specified polyol mixture in the presence of an organic polyisocyanate and a catalyst. CONSTITUTION:A polyol mixture is obtained by mixing 100pts.wt. polyetherpolyol of an MW of 2,000-8,000 with 2-40pts.wt. ethylene glycol, 1-10pts.wt. aromatic diamine (e.g., 4,4'-diphenylmethanediamine) as a chain extender and 2-15pts.wt. aniline/ethylene oxide (1-4mol) adduct. This mixture and an organic polyisocyanate (e.g., 4,4'-diphenylmethane diisocyanate) at an NCO to OH ratio of 100/70-140 are reaction-injection-molded in the presence of a catalyst such as triethylenediamine.

Description

[Detailed Description of the Invention] Industrial Application Fields> The present invention provides polyurethane molded products by reaction injection molding (RIM).
), and particularly relates to a manufacturing method suitable for manufacturing automobile bumpers and the like by RIM.

<Conventional technology> Conventionally, when manufacturing relatively hard polyurethane molded products with a microcellular structure, such as automobile bumpers, using RIM, a long chain polyol is generally mixed with ethylene glycol as a chain extender and further to accelerate the reaction. A polyol mixture in which an aromatic diamine is added to a polyisocyanate component is reacted at high speed in the presence of a catalyst (added to the polyol or polyisocyanate component), that is, instantaneously mixed in a mixing chamber of a high-pressure foaming machine, This was done by injecting it into a closed cavity.

<Problems to be solved by the invention> However, filling defects may occur, which may be caused by poor material flow (fast reaction) during the injection process.
On the other hand, loose skin was likely to occur, which may be due to the material flow being too good (reaction was slow). Note that loose skin occurs when the mold portion is relatively low, as heat is absorbed on the skin side and the reaction on the skin side becomes slow.

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

When manufacturing polyurethane molded products by RIM, a polyol mixture consisting of a long-chain polyether polyol, ethylene glycol, an aromatic diamine, and an ethylene oxide adduct of aniline is reacted with an organic polyisocyanate in the presence of a catalyst. It is characterized by

<Embodiment> Each component of the present invention will be described in detail below. "Part j" indicating the number of parts to be blended means "part by weight" unless otherwise specified.

The polyol mixture used is one in which 100 parts of the following (a) is mixed with various parts of each of the compounds (b) to (d).

(a) Molecule J12000-8000 (7) Polyether polyol.

The reason why polyether-based polyols are used is that they have a lower viscosity (500 to 150 viscosity at 25°C) than polyester-based polyols.
0 cpg) and excellent hydrolysis resistance. Here, the polyether polyol is obtained by reacting a cyclic ether such as ethylene oxide, propylene oxide, butylene oxide, or styrene oxide with a low-molecular-weight polyol such as ethylene glycol, diethyleglycol, glycerin, or trimethylolprosine. If the molecular weight of the polyol is less than 2,000, the molded article will not have the desired toughness, and if it exceeds 8,000, the viscosity will be high and stability will be poor (undesirable).

(b) Ethylene glycol...2 to 40 parts (preferably 15 to 25 parts).

It is used as a chain extender, but the reactivity of isocyanate is not very high. If the amount of ethylene glycol 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. At the same time, the ratio with respect to the diamine described below becomes large, and the reaction rate does not increase, which is undesirable.

(c) Aromatic amine...1 to 10 parts (preferably 2 to 6 parts).

Used as a chain extender, the reactivity of incyanate is very high. If the amount of aromatic diamine is less than 1 part, the reaction rate is too slow, and if it exceeds 10 parts, the reaction rate becomes too fast, and each Undesirable, specifically 4.
Examples include 4''-diphenylmethanediamine, 2.4-)luenediamine, and the like.

(d) Ethylene oxide adduct of aniline (addition mol f
i1-4)...2-15 parts (preferably 5NlO parts).

It has the effect of promoting dispersibility and compatibility in the polyether polyols (b) and (c) above, and also functions as a chain extender. If the number of moles of ethylene oxide added is outside the above range, there will be no effect of promoting dispersibility, etc., and if the amount of the compound is less than 2 parts,
It does not have the effect of promoting dispersibility, etc., and if it exceeds 15 parts, there is a risk that SWS will be affected in the heat resistance, etc. of the molded product.

The above polyol mixture is mixed with the following CD polyisocyanate component and NGOlo in the presence of the catalyst illustrated in (e) below.
A reaction injection molded product is produced by reacting with a recipe of H-100/To to 100/140.

(e) Amine-based catalysts such as triethylenediamine, N-methylmorpholine, pentaethyldiethyltriamine, dimethylethanolamine, diethylethanolamine, and tin-based catalysts such as dibutyltin diurarate, dibutyltin fumarate, and dibutyltin diacetate. I can give an example, but usually,
It is desirable to use an amine type and a tin type in combination from the viewpoint of increasing the catalytic activity.

m Polyisocyanate component usually 4,4゛-diphenylmethane diisocyanate)
(MDI), ) lylene di incyanate (TDI), a
, aromatic ones such as t-diphenyl ether diisocyanate, xylylene diisocyanate, polymethylene phenyl isocyanate, or 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate, Although aliphatic compounds such as xylene diisocyanate are used, MDI compounds are particularly desirable because they have high monoreactivity and the reactivity of the two incyanate groups is the same.

In the above reaction injection molding, an inorganic filler and a paint are added to the polyol mixture or incyanate component.

Add additives such as face weight, anti-aging agent, ultraviolet absorber 9 and foaming agent as appropriate.

<Operations and Effects of the Invention> As described above, the method for producing a polyurethane molded article of the present invention involves adding ethylene glycol as a chain extender to a long-chain polyether polyol, and aniline to an aromatic diamine during reaction injection molding. By reacting a polyol mixture containing an ethylene oxide adduct with an organic polyisocyanate in the presence of a catalyst, reaction injection molding with good material flow and reactivity is possible, as shown in the examples below. The incidence of molded product defects (particularly poor appearance) such as short shots, loose skin, voids, and sink marks is reduced. The reason for this is not clear, but by including the ethylene oxide adduct of aniline in the polyol mixture, the dispersibility and compatibility of ethylene glycol and aromatic diamine in the long chain polyol improve, and It is presumed that this is because the reactivity of each component with respect to the polyisocyanate component is stabilized.

In addition, in order to delay the reactivity of aromatic diamine contained as a chain extender with NCO in the polyol mixture that is the reaction injection molding material for polyurethane molded products, that is, NG
In order to approach the reactivity of O with long-chain polyols, a halogen group is introduced into the aromatic ring of aromatic diamine (see Japanese Patent Publication No. 51-45316), or an alkyl group is introduced (Japanese Patent Publication No. 54-45316). 17359) is known, and it is presumed that the problems of the present invention can be solved to some extent by using this specific aromatic diamine. It is generally difficult to stably introduce a group or an alkyl group, and the particular aromatic diamine lacks versatility.

<Examples> In order to confirm the effects of the present invention, examples will be listed 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 each molded article.

Molding conditions: (a) Molding machine Niigata Iron Works! I Mo 50/38
(a) Injection speed 400 g/5ea (1) Injection pressure 130 kg/am' (1) Injection time 1.40
5ec (e) Mold cavity 400 x 400 x 2.
5 mm (force) Mold temperature 70° C. (g) Demolding temperature 30 sec Tests were conducted on each of the two molded products for each item shown in Table 2. The loose skin and material filling state were determined as follows.

(1) Loose skin (skin layer peeling off thinly): 0...none, Δ...slightly observed, ×...
Significant.

(2) Material filling form S (gold yJ!! into cavity) 20...The mold cavity is all filled and the material flows to the air vent.

Δ: The material almost fills the cavity, but there is a slight chipping.

×・・・The material does not fully fill the cavity, and 1 of the total area
05 or more chipping occurs.

From the test results shown in Table 2, when polyurethane molded products were reaction injection molded using the method of the present invention, that is, in the case of the examples, loose skin and material filling defects did not occur, and material flow and reactivity were good. I understand that there is something. On the contrary,
In the comparative example in which the polyol mixture does not contain an ethylene oxide adduct of aniline, loose skin and/or material filling defects occur, indicating that either or both of material flow and reactivity are not good. .

Claims (1)

[Scope of Claims] A method for producing a polyurethane molded article, which comprises reacting the following polyol mixture with an organic polyisocyanate in the presence of a catalyst when producing the polyurethane molded article by reaction injection molding. (a) Polyether polyol with a molecular weight of 2,000 to 8,000...100 parts by weight, (b) Ethylene glycol...2 to 40 parts by weight, (c
) Aromatic diamine...1 to 10 parts by weight, (d) Ethylene oxide adduct of aniline (additional mole number 1 to 4)...
- 2 to 15 parts by weight.