JPH04185657A - Production of molded polyurethane foam - Google Patents

Abstract

PURPOSE:To obtain a molded polyurethane foam excellent in strengths, etc., in good productivity by mixing a compound having a plurality of active hydrogen atoms with a compound having a plurality of isocyanate groups and two specified catalysts, foaming the mixture by agitation, molding the formed foam and curing the molding by heating. CONSTITUTION:A mixture of a compound having a plurality of active hydrogen atoms (e.g. hydroxyl-terminated polyether polyol), a compound having a plurality of isocyanate groups (e.g. tolylene diisocyanate), a catalyst comprising an aromatic sulfonic acid salt of 1,8-diazabicyclo[5.4.0]-undecene-7 and an organometallic catalyst (e.g. tin acetate) is foamed by mechanical mixing, and the formed foam is molded and cured by heating to obtain a molded polyurethane foam. This foam can be desirably used in the production of sealing materials, roller materials, etc.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a method for forming a foam obtained by foaming a mixture containing a polyol, a polyisocyanate, and a catalyst by mechanical stirring without adding a special blowing agent. This invention relates to an improvement in a method for producing polyurethane foam (thermosetting polyurethane foam molded product) by heating and curing the same.

[Prior Art] Conventionally, as a method for producing polyurethane foam, a foaming raw material mixture to which a blowing agent that generates gas by chemical reaction or heat is added is used, and during foaming, the generated gas is quickly captured to form a foam. For this purpose, a method in which foaming and curing are performed almost simultaneously is widely adopted.

However, in the conventional method where foaming and curing proceed almost simultaneously,
When making long sheet-like products, in order to adjust the thickness of the form and obtain smoothness, it is necessary to constrain the top and bottom surfaces to the desired thickness, which requires special equipment. Ta. In addition, when making complex molded products, when the foaming raw material mixture (undiluted solution) expands and flows through the mold, the cells of the foam may become soaked, forming voids or, in extreme cases, causing the foam to collapse. There was also the problem that some unfilled portions were left unfilled.

In order to solve these problems, a method has been adopted in which polyurethane foam is manufactured by separately performing foaming and curing. This method uses mechanical beating to substantially uniformly disperse an inert gas throughout the mixed solution of polyurethane foam raw materials at room temperature to form a structurally stable foam for polyurethane foam moldings, and this foam is then This method involves molding the material into a shape and then heating and hardening it.

In this method, when a conventional formulation for manufacturing polyurethane foam is used, the viscosity of the raw material mixture increases when the inert gas is dispersed into the mixture by mechanical beating, resulting in uneven dispersion of the inert gas. In extreme cases, solidification may occur during beating. Furthermore, the short pot life makes molding difficult.

In order to prevent such an increase in viscosity, the amount of catalyst in the mixture can be reduced, and a uniform foam can be obtained by doing so.
If the amount of catalyst added is reduced, curing will not proceed sufficiently even when heated after molding the foam, making it impossible to obtain a foam with good quality and satisfactory physical properties.

In other words, in the method of obtaining polyurethane foam by uniformly dispersing an inert gas at room temperature into a mixed solution of polyurethane foam raw materials by mechanical beating, and then molding and curing this foam by heating, the reaction is difficult. Control, or catalyst selection, is a very important issue.

From this point of view, in Japanese Patent Publication No. 53-8735,
It is proposed to use nickel acetylacetonate or the like as a catalyst for such a method.

[Problem to be solved by the invention] However, when nickel acetylacetonate or the like is used as a catalyst, the foam formed by mechanical stirring at room temperature has a sufficient pot life, but it hardens rapidly when heated. Therefore, there is a need for a catalyst that has a sufficient pot life at room temperature and can quickly harden the foam by heating, thereby producing polyurethane foam molded products with good workability and productivity. There was a demand for a manufacturing method.

[Means and effects for solving the problem] As a result of intensive studies in order to meet the above demands, the present inventors have developed a compound containing two or more active hydrogens, a compound having two or more isocyanate groups, and a catalyst. 1,8-diaza-bicyclo[5,4,
0] By using an aromatic sulfonate of undecene-7 in combination with an organometallic catalyst, a polyurethane foam that is foamy at room temperature and has a stable pot life, and also quickly hardens when heated and has good physical properties. A molded body is obtained,
The inventors discovered that the catalyst system described above improves workability and productivity, leading to the present invention.

The present invention will be explained in more detail below.

The method for producing a polyurethane foam molded article of the present invention includes 2
A mixture containing a compound containing two or more active hydrogens, a compound having two or more isocyanate groups, and a catalyst is foamed by mechanical stirring, the resulting foam is molded, and then heated and cured to form a polyurethane foam molded product. It is manufactured.

Here, the compound containing two or more active hydrogens (polyhydroxyl compound) includes polyols used in the production of general flexible polyurethane foams and urethane distomers, such as polyether polyols, polyester polyols, and polyester polyols having hydroxyl groups at the terminals. In addition to polyether polyester polyol, which is a copolymer of both, common polyols such as so-called polymer polyols obtained by polymerizing ethylenically unsaturated monomers in polyols can be used.

Further, as the compound having two or more isocyanate groups (polyisocyanate compound), polyisocyanates used in the production of general flexible polyurethane foams and urethane elastomers can be used. Namely, tolylene diisocyanate (TDI), crude TDI, 4,
4°-diphenylmethane diisocyanate (MDI),
Crude MDI, aliphatic polyisocyanates having 2 to 18 carbon atoms, cycloaliphatic polyisocyanates having 4 to 15 carbon atoms, aromatic polyisocyanates having 8 to 15 carbon atoms, and mixtures and modified products of these polyisocyanates, e.g. Prepolymers obtained by reacting with polyols are used. These can be in normal usage amounts.

In the present invention, 1,8-diaza-
It is characterized by the combined use of an aromatic sulfonate of bicyclo[5,4,0]undecene-7 (DBU) and an organometallic catalyst, and the combination of both catalysts stabilizes the pot life. It was possible to achieve both of this and the rapidity of heat curing.

In this case, when the aromatic sulfonate of DBU is used alone, the heat curing property is poor and a polyurethane foam molded article with good physical properties cannot be obtained.On the other hand, when the organometallic catalyst is used alone, The purpose of the present invention cannot be achieved in either case because the pot life is short.

Examples of aromatic sulfonic acids that form salts with DBU include sulfonic acids having a benzene nucleus such as benzenesulfonic acid, toluenesulfonic acid, and xylene sulfonic acid, and naphthalene skeletons such as naphthalene sulfonic acid and propylnaphthalene sulfonic acid. Examples include sulfonic acids having the following: and further, aromatic sulfonic acid esters such as methyl toluenesulfonate can also be used.

On the other hand, as the organometallic catalyst, an organotin compound is particularly preferably used. Preferred organotin compounds include tin(II) salts of carboxylic acids, such as tin(II) acetate, tin(II)
) octoate, tin (II) ethylhexoate, silver (n) laurate, etc., and further tin (IV) compounds,
Examples include dibutyltin oxide, dibutyltin dichloride, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, dioctyltin diacetate, and the like.

The amount of the aromatic sulfonate of DBU and the organometallic catalyst to be used is appropriately selected, but the aromatic sulfonic acid of DBU is Salt is 0.01-5 parts, especially 0.1-1
The organometallic catalyst is preferably 0.0001 parts.
~1 part, particularly preferably 0.001 to 0.2 part. Further, the ratio of the aromatic sulfonate of DBU and the organometallic catalyst is preferably 1:100 to 50,000:1, particularly 1:2 to 1,000:I.

The present invention involves foaming a mixture containing a compound containing two or more active hydrogens, a compound having two or more isocyanate groups, and a catalyst by mechanical stirring, and molding the resulting foam. However, the formation of this foam can be carried out by uniformly dispersing the mixture with an inert gas according to known methods. Note that the inert gas used here includes air, CO, gas, N2 gas, and the like.

Moreover, normal conditions can be used for heat curing, for example, conditions of heating at a temperature of 100 to 150°C for 2 to 5 minutes can be used.

In addition, if necessary, the above mixture may contain silicone foam stabilizers, flame retardants, organic fillers, inorganic fillers, pigments, plasticizers, and auxiliary blowing agents such as freon and methylene chloride, which are used in ordinary polyurethane foams. can be blended.

The polyurethane foam molded product thus obtained can have various densities by selecting the amount of foam during foam formation, but the method of the present invention has a relatively high density (0.1-0. It is a polyurethane foam molded product with a weight of 8 g/cm"), and is suitably used when forming a continuous sheet or molding to obtain gaskets, sealing materials, cushioning materials, roller materials, etc.

EXAMPLES Hereinafter, the present invention will be specifically explained by showing examples and comparative examples, but the present invention is not limited to the following examples.

[Example and Comparative Examples As a copolyol, polyether polyol (Excenol 8 manufactured by Asahi Glass Co., Ltd.) with a molecular weight of 5000 by adding propylene oxide and ethylene oxide to glycerin
28) 100 parts, 7.5 parts of 1.4-butanediol,
Silicone surfactant (5Z161 manufactured by Nippon Unicar Co., Ltd.)
8) 1.5 parts of urethane-modified MDI as polyisocyanate (Sumidur P manufactured by Bayer Urethane GmbH)
Using 50 parts of F), stir for 2 minutes with a household whisk (Toshiba hand mixer HM-300) to incorporate air to make a foam. ], 8-Diaza-bicyclo[
0.5 parts of toluenesulfonate of 5,4,O]undecene-7 (DBU) and 0.001 parts of dibutyltin dilaurate
5 parts of toluene sulfonate of 1,8-diaza-bicyclo[5,4,0oundecene-7 (DBU) (DBU) and dibutyltin dilaurate were added alone (comparative example). 1 to 3) or when nickel acetylacetonate was added (Comparative Example 4), the pot life, the hardening state when heated at 130° C. for 10 minutes, and the physical properties of the final foam were investigated. The results are shown in Table-1.

Note that the pot life is expressed as the time until sheeting with a doctor knife becomes impossible.

Table 1 From the results in Table 1, the foaming raw material mixture of the example using DBU toluene sulfonate and dibutyltin dilaurate has a pot life of 20 minutes and can ensure sufficient stirring and working time. Moreover, when heated at 130° C., it was cured in 5 minutes, showed a good hardening state in 10 minutes, and the obtained foam also had good physical properties.

On the other hand, when DBU toluene sulfonate is used alone (Comparative Example 1) and when nickel acetylacetonate is used (Comparative Example 4), pot life can be secured, but curing at 130°C The process was slow and the resulting foam was untidy and unusable. Furthermore, when dibutyltin dilaurate is used alone (
Comparative Example 3), the pot life was shortened and sufficient workability could not be ensured.

[Effects of the Invention] According to the present invention, it is possible to form a stable foam with a long pot life, and this foam can be rapidly cured by heating to provide a polyurethane foam molded product with good physical properties. The method of the present invention has good workability and productivity.

Applicant: Brideston Co., Ltd.

Claims (1)

[Claims] A mixture containing a compound containing one or more active hydrogens, a compound having two or more isocyanate groups, and a catalyst is foamed by mechanical stirring, the resulting foam is molded, and then heated and cured to form a polyurethane foam. Polyurethane foam molding, characterized in that, in the method for producing a molded article, an aromatic sulfonate of 1,8-diaza-bicyclo[5.4.0]undecene-7 and an organometallic catalyst are used in combination as the catalyst. How the body is manufactured.